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The SELEX collaboration Gough Eschrich, Ivo M. ; Kruger, H. ; Simon, J. ; et al.
Phys.Lett. B522 (2001) 233-239, 2001.
The Sigma^- mean squared charge radius has been measured in the space-like Q^2 range 0.035-0.105 GeV^2/c^2 by elastic scattering of a Sigma^- beam off atomic electrons. The measurement was performed with the SELEX (E781) spectrometer using the Fermilab hyperon beam at a mean energy of 610 GeV/c. We obtain <r^2> = (0.61 +/- 0.12 (stat.) +/- 0.09 (syst.)) fm^2. The proton and pi^- charge radii were measured as well and are consistent with results of other experiments. Our result agrees with the recently measured strong interaction radius of the Sigma^-.
Total systematic errors are given.
The SELEX collaboration Pogodin, P. ; Alkhazov, G. ; Atamantchouk, A.G. ; et al.
Phys.Rev. D70 (2004) 112005, 2004.
Measured values of the SIGMA+ polarization as functions of PT and XL for proton CU collisions.
Measured values of the SIGMA+ polarization as functions of PT and XL for proton BE collisions.
The SELEX collaboration Kaya, M. ; Alkhazov, G. ; Atamantchouk, A.G. ; et al.
Phys.Lett. B558 (2003) 34-40, 2003.
The production of $D_s^-$ relative to $D_s^+$ as a function of $x_F $ with 600 GeV/c $\Sigma^-$ beam is measured in the interval $0.15 < x_F < 0.7$ by the SELEX (E781) experiment at Fermilab. The integrated charge asymmetries with 600 GeV/c $\Sigma^-$ beam ($0.53\pm0.06$) and $\pi^-$ beam ($0.06\pm0.11$) are also compared. The results show the $\Sigma^-$ beam fragments play a role in the production of $D_s^-$, as suggested by the leading quark model.
Acceptance corrected yields for the SIGMA- beam.
Production asymmetry for the SIGMA- beam.
Integrated asymmetry (with XL > 0.15) for the PI- and SIGMA- beams.
The SELEX collaboration Garcia, F.G. ; Alkhazov, G. ; Atamantchouk, A.G. ; et al.
Phys.Lett. B528 (2002) 49-57, 2002.
We present data from Fermilab experiment E781 (SELEX) on the hadroproduction asymmetry for anti-Lambda_c compared to Lambda_c+ as a function of xF and pt2 distributions for Lambda_c+. These data were measured in the same apparatus using incident pi-, sigma- beams at 600 GeV/c and proton beam at 540 GeV/c. The asymmetry is studied as a function of xF. In the forward hemisphere with xF >= 0.2 both baryon beams exhibit very strong preference for producing charm baryons rather than charm antibaryons, while the pion beam asymmetry is much smaller. In this energy regime the results show that beam fragments play a major role in the kinematics of Lambda_c formation, as suggested by the leading quark picture.
The number of events reconstructed in the signal mass region of LAMBDA/C+ production. Statistical errors only.
The number of events reconstructed in the signal mass region of LAMBDA/CBAR- production. Statistical errors only.
Fit to XL distributions of the form (1-XL)**POWER for 3 different XL regions.
The SELEX collaboration Dersch, U. ; Akchurin, N. ; Andreev, V.A. ; et al.
Nucl.Phys. B579 (2000) 277-312, 2000.
Total cross sections for Sigma- and pi- on beryllium, carbon, polyethylene and copper as well as total cross sections for protons on beryllium and carbon have been measured in a broad momentum range around 600GeV/c. These measurements were performed with a transmission technique adapted to the SELEX hyperon-beam experiment at Fermilab. We report on results obtained for hadron-nucleus cross sections and on results for sigma_tot(Sigma- N) and sigma_tot(pi- N), which were deduced from nuclear cross sections.
Results for nuclear total cross sections.
Average total cross sections for nucleon targets deduced from the nuclear target data, at the average beam momentum. | CommonCrawl |
Let $X$ be a set.
A $\sigma$-algebra $\mathcal R$ is a $\sigma$-ring with a unit.
A $\sigma$-algebra $\mathcal R$ over $X$ is an algebra of sets which is closed under countable unions.
This is also seen as $\sigma$-algebra, from $\sigma$ being the Greek letter sigma.
Results about $\sigma$-algebras can be found here.
$\sigma$-Algebra as Magma of Sets, proving that $\sigma$-algebras instantiate the general concept of a magma of sets.
The $\sigma$ in $\sigma$-algebra is the Greek letter sigma which equates to the letter s.
$\sigma$ stands for for somme, which is French for union. | CommonCrawl |
Does this concept in Fourier analysis which eliminates Gibbs' phenomenon and also introducing some new concepts, possibly have applications in any areas of physics, like QM or in any applied areas?
How do I enforce the no-slip boundary condition in time dependent incompressible pipe flow?
I would be very grateful if you could help me with some insight into the concepts of time translation and dynamic evolution in QM and QFT.
Any relativistic quantum system must be Poincare covariant. Cf. Wigner, the Poincare transformations are represented by unitary operators in the system's Hilbert space. The infinitesimal generators of the unitary operators are Hermitian operators corresponding to basic observables. The very definition of the way the time translation operator acts in either Schroedinger or Heisenberg picture is formally equivalent with the Schroedinger and Heisenberg equations of motion (in integrated form), respectively. For example, $\psi (t+a) = U(a)\psi (t)$, etc.
Question 1: Is it sufficient to postulate Poincare covariance instead of postulating the Schroedinger or Heisenberg eqs. of motion? That is, are the Schroedinger or Heisenberg eqs. of motion really consequences (byproducts) of postulating Poincare invariance?
Question 2: I've read a bit axiomatic qft (AQFT) and saw that there is no axiom (postulate) for dynamics among Wightman's postulates. Why is it so? Is it not needed due to an yes answer to Question 1?
I understand that it's hard to come up with a nice Hamiltonian $H$ for a realistic system in AQFT, but the equations of motions should exist at least formally, with an yet to be found $H$. Am I wrong? What are the dynamical equations for a general system (field or otherwise)?
Question 3: Is there a difference between time translation and dynamical evolution? If yes, which is that from the math and physics point of view? Are they described by different operators? Could you provide a simple example for illustration?
1: yes, yes. - 2. yes, yes. - 3. no,no. -- It is too late now to give a detailed answer.
@ArnoldNeumaier In 1970, while presenting Wightman's axioms at a physics school (see Haag's lecture, p.14 in Stanley Deser, Marc Grisaru, and Hugh Pendleton, "Lectures on Elementary Particles and Quantum Field Theory", vol.2, 1970), Haag states: "It has, however, so far not been possible to incorporate a formulation of a specific dynamical law into the framework of axiomatic field theory." How does this square with an "yes, yes" answer to my question 2)?
1. The dynamical law (Schroedinger resp. Heisenberg equation) is simply the statement that time translations form a unitary representation of the 1-dimensional Lie group $U(1)$. Its infinitesimal generator $H$ automatically has all the required properties (densely defined action on states satisfying the Schroedinger equation, self-adjointness, and adjoint action on observables satisfying the Heisenberg equation of motion). Thus restricting a unitary representation of the Poincare group to time translations provides the dynamics.
2. In case of a QFT satisfying the Wightman axioms, the states are the linear combinations of $N$-point states; the latter are obtained from the distributional (improper) states $|x_1,\ldots,x_N\rangle:=\Phi(x_1)\cdots\Phi(x_N)|vac\rangle$ by integration with suitable weight functions. Spacetime translations (and in particular the dynamics) are now easily seen to be given by $U(x)|x_1,\ldots,x_N\rangle:=|x_1-x,\ldots,x_N-x\rangle$. In particular, once one has a realization of the Wightman axioms, the Hamiltonian is very explicitly given by $H=i\hbar \sum_j \partial/\partial x_j$.
Haag's comment refers not to the lack of an explicit dynamics but to a lack of an explicit construction of an interacting 4D relativistic QFT in which given nonlinear field equations (e.g., equations related to the Lagrangian of QED) are realized. The latter constitute the ''specific dynamical law'' in his quote. In modern terminology, what is missing is a rigorous construction in which a nontrivial operator product expansion (Wilson's replacement of the notion of nonlinear field equations) can be proved.
3. The answer is already in the formula for the Hamiltonian given above.
@ArnoldNeumaier Thank you so much for your very illuminating answer! Now it's clear to me what Haag meant by his statement. | CommonCrawl |
Motivated by gauge theory, we develop a general framework for chain complex valued algebraic quantum field theories. Building upon our recent operadic approach to this subject, we show that the category of such theories carries a canonical model structure and explain the important conceptual and also practical consequences of this result. As a concrete application we provide a derived version of Fredenhagen's universal algebra construction, which is relevant e.g. for the BRST/BV formalism. We further develop a homotopy theoretical generalization of algebraic quantum field theory with a particular focus on the homotopy-coherent Einstein causality axiom. We provide examples of such homotopy-coherent theories via (1) smooth normalized cochain algebras on $\infty$-stacks, and (2) fiber-wise groupoid cohomology of a category fibered in groupoids with coefficients in a strict quantum field theory. | CommonCrawl |
Yang Yang (S'11–M'14-SM'17) was born in Bayan Nur, Inner Mongolia, China and received MEng, MSc, Ph.D degrees from Monash University, Melbourne, Australia, in 2007, 2008 and 2013, respectively. From 2012 to 2015, he was an Asia-Pacific GSP Engineer at Rain Bird and a Global GSP Success Award holder of the year 2014. He served as a Senior Research Associate with Department of Engineering, Macquarie University, Sydney, during April 2015 to April 2016. From April 2016 to December 2016, he was a Research Fellow with State Key Laboratory of Millimeter-Waves, City University of Hong Kong. In December 2016, Dr Yang Yang joined School of Electrical and Data Engineering, University of Technology Sydney. His research interests include RFIC, microwave, millimeter-wave and terahertz devices/circuits, reconfigurable antennas, wearable antennas, wearable medical devices, sensors and remote sensing techniques. Dr Yang has published over 100 peer-reviewed publications. To date, he has published 1 book, 2 book chapters, 8 invited papers and 45 SCI journal papers, including 30 top-tier JCR-Q1 IEEE journals. He is an IEEE Senior Member and a current Associate Editor of IEEE ACCESS.
Best student paper nomination in 2018 Australia Microwave Symposium, Brisbane, Australia, Feb. 2018 (supervised PhD student).
Best student paper nomination (24 out of 390) in 2017 IEEE MTT-S International Microwave Symposium, Honolulu, Hawaii, Jun 2017 (supervised PhD student).
Advanced Practice Competition nomination in 2017 IEEE MTT-S International Microwave Symposium, Honolulu, Hawaii, Jun 2017(supervised PhD student).
IEEE EDL Editor's Picks (top three) in Issue May 2017. Y. Zhong, Y. Yang, X. Zhu, E. Dutkiewicz, K. M. Shum and Q. Xue, "An On-Chip Bandpass Filter Using a Broadside-Coupled Meander Line Resonator with a Defected-Ground Structure," IEEE Electron Device Lett., vol. 38, no. 5, pp. 626–629, May 2017 (supervised PhD student).
Reviewer of IEEE Transactions on Antennas and Propagation (TAP), IEEE Transactions on Microwave Theory & Techniques (TMTT), IEEE Antennas and Wireless Propagation Letters (AWPL), IEEE Microwave and Wireless Components Letters (MWCL), IEEE Electron Device Letters (EDL), IEEE Sensors Journal, IEEE Access, Sensors and Actuator, IET Electronics Letters (EL), IET MAP, etc.
This book presents the design, development and field trials of radio frequency based wireless monitoring system for sleep apnoea patients. It contains 4 major areas including general background of wireless monitoring technology and MIMO in wireless body area network (WBAN), microwave hardware designs, virtual MIMO in WBAN and hardware system level implementation and field trials. At components level, this book presents the design theory, process and examples of bandpass filters, lowpass filters, low profile patch antennas, power amplifiers and oscillators which are the key elements in transducer designs in the body area network and cooperative communication wireless sensor network system. At system level, this book features the hardware integration, field trial and network coding techniques. This book also gives a presentation of virtual MIMO applications, e.g. MIMO implementation using FPGA, correlation coefficient measurement and correlation coefficient measurement. The book will create impact in the fields of wireless monitoring technology in biomedical engineering, which have been growing exponentially.
© 2019 Elsevier B.V. Graphene based three-layer compound film on the silicon substrate is formed by gold deposition of electron beam evaporation (EBE) and graphene transfer. Processed with different high temperature annealing in nitrogen, the film with residual tensile stress of 52.58 MPa at 500 can be achieved by using an X-ray diffraction (XRD) method. Based on this low stress film, a series of long lifecycle MEMS double-clamped beams (DCBs) are fabricated by the standard MEMS manufacturing technology. The achieved beam can be turned on/off for up to 100 million times at the pull-in voltage of 30 V, which is compatible with the conventional, complementary metal-oxide-semiconductor (CMOS) circuit requirements.
© 2019 IEEE. In this paper, a novel design approach is proposed for on-chip bandpass filter (BPF) design with improved passband flatness and stopband suppression. The proposed approach simply uses a combination of meander-line structures with metal-insulator-metal (MIM) capacitors. To demonstrate the insight of this approach, a simplified equivalent LC-circuit model is used for theoretical analysis. Using the analyzed results as a guideline along with a full-wave electromagnetic (EM) simulator, two BPFs are designed and implemented in a standard 0.13-m (Bi)-CMOS technology. The measured results show that good agreements between EM simulated and measured results are achieved. For the first BPF, the return loss is better than 10 dB from 13.5 to 32 GHz, which indicates a fractional bandwidth (FBW) of more than 78%. In addition, the minimum insertion loss of 2.3 dB is achieved within the frequency range from 17 to 27 GHz and the in-band magnitude ripple is less than 0.1 dB. The chip size of this design, excluding the pads, is 0.148 mm 2 . To demonstrate a miniaturized design, a second design example is given. The return loss is better than 10 dB from 17.3 to 35.9 GHz, which indicates an FBW of more than 70%. In addition, the minimum insertion loss of 2.6 dB is achieved within the frequency range from 21.4 to 27.7 GHz and the in-band magnitude ripple is less than 0.1 dB. The chip size of the second design, excluding the pads, is only 0.066 mm 2 .
IEEE The well-known Internet-of-things is recently being considered for critical missions, such as search and rescue, surveillance and border patrol. One of the most critical issues that these applications are currently facing is how to correctly distinguish between human and animal targets in a cost-effective way. In this work, we present a relatively low-cost but robust approach that uses a combination of device-free sensing and machine-learning technologies to tackle this issue. In order to validate the feasibility of the presented approach, a variety of data is collected in a cornfield using impulse-radio ultra-wideband transceivers. These data are then used to investigate the influence of different statistical properties of the RF signal on the accuracy of human/animal target classification. Based on the probability density function of different statistical properties, two distinguishing features for target classification are found, namely standard deviation and root mean spread delay spread. Using them, the impact on the classification accuracy due to different classifiers, number of training samples and different values of signal-to-noise ratio is extensively verified. Even with the worst case, the classification accuracy of the system is still better than 91targets (including goats and dogs), which indicates that the presented approach has a great potential to be deployed in the near future.
© 2018 IEEE. The quasi-elliptic multi-mode bandpass cavity filters and duplexer with slot mixed-coupling structure are proposed in this paper. A single metal cavity embedded with a rectangular-shaped slot-cut metal plate is utilized to constitute a multi-mode bandpass filter with a few features including wide passband, low profile and controllable transmission zeros (TZs). In this paper, the slot-cut metal plane serves as the multi-mode resonators. In detail, the slot on the metal plane functions as the circuit element to move the higher order modes within the reasonable frequency-band, while serving as a mixed-coupling structure to generate out-of-band transmission zeros. To demonstrate the multiple-mode capability in filter design, the dual-mode, triple-mode, and quadruple-mode filters are developed by appropriately allocating a few TZs in the upper stopbands using the proposed slot mixed-coupling approach, namely, Type-I filters. Next, a quadruple-mode cavity filter with both lower and higher TZs is designed, namely, Type-II filter, which is further applied for the exploration of a duplexer. Finally, the filter and duplexer prototypes are fabricated and measured. The measurement results are found in good agreement with the simulated ones.
© 1963-2012 IEEE. This communication presents new designs of dual-circularly polarized (CP) planar aperture antenna and array for 60 GHz applications. First, a four-port planar aperture antenna with its feeding network is developed that exhibits wide impedance bandwidth, dual-CP radiation as well as high gain. Then, based on the proposed antenna, a new scheme of building a dual-CP array is proposed. With this new scheme that combines the power splitting network and series feeding method, four sequentially fed antenna elements are successfully combined to form a CP radiation array. The experimental results show that the -10 dB impedance bandwidths of the antenna and the array are more than 18.2% (55-66 GHz). While the 3 dB axial ratio bandwidths are from 54.2 to 64.3 GHz (17.2%) for the antenna and from 54.8 to 65 GHz (17%) for the array. The maximum gains achieved are 13.7 and 17.85 dBic for the antenna and array, respectively.
IEEE Load-variation insensitivity, for impedance matching between power amplifiers (PAs) and transmitting antennas, contributes to challenging the design of millimeter-wave wireless systems. In this paper, a W-band two-way balanced PA based on a compact quadrature coupler with a broadside coupled strip-line (BCSL) as the core is presented to enhance the load-variation insensitivity and stability. The proposed coupler is truly broadband with low amplitude and phase imbalance. The proposed $W$-band balanced PA achieves higher power-added efficiency (PAE) and unsaturated output power Psat over wide frequency bandwidth. The W-band balanced PA is implemented in a 0.13- & #x03BC;m SiGe BiCMOS process and achieves a measured Psat of 16.3 dBm and a peak PAE of 14.1 & #x0025; at 100 GHz (with 1.6-V power supply). The measured Psat with 1-dB bandwidth is from 91 to 102 GHz. The measured results present the feasibility of the compact quadrature coupler. The total chip surface area (with pads) is 0.64 mm & #x00B2;, where the size of the proposed quadrature coupler area is only 0.04 mm & #x00B2;.
© 1963-2012 IEEE. A novel 360° beam steering patch antenna with parasitic elements is presented in this paper. The designed antenna consists of a radiating patch and six parasitic elements, each of which is connected through a group of shorting vias controlled by p-i-n diode switches. By switching on the desired groups of the shorting vias, the electric field distribution inside substrate cavity appears at the desired beam direction. Rotationally switching on the groups of the shorting vias, the performance of 360° beam scanning is realized. To further understand operating mechanism, the antenna is modeled with equivalent circuit in terms of the on and off status of a sector of the antenna, which can be used as a design guide for shorting-vias-controlled reconfigurable microstrip patch antennas. The fabricated antenna achieves a bandwidth of 14.5%, a peak gain of 10 dBi, and the efficiency of 80.5%. The achieved beamwidths are 42° and 97° in azimuth and elevation planes, respectively. With an ability of being steered around zenith axis at six directions, the scanned beam range covers the entire 360°. The physical dimension is only 2.5 g for the size and 0.5 g for the profile. This antenna operates from 5.1 to 5.9 GHz and has significant meaning in the IEEE 802.11ac wireless local area network applications due to its capabilities of generating 360° steered beams.
© 1963-2012 IEEE. A novel concept for the two-in-one design with the integration of filters and antennas, using a single cavity, is presented in this communication. Basically, a triple-mode resonator (TMR) is utilized as a common feeder to achieve filtering and radiating functions at three different frequency bands. Each of the three bands adopts one of the three fundamental modes, namely, TE011, TE101, and TM110, in a single TMR to realize the relevant functions. Owing to the modal orthogonality of these fundamental modes, high isolation can be effectively realized among these three channels. Based on the proposed TMR, three different prototypes are designed for different applications. For the first prototype, the structure of a dual-band filter plus an antenna is presented using a second-order TMR. Based on the combination of a duplexer plus an antenna, the second prototype is attained. To further explore the function of the proposed TMR, the structure of a filter plus a dual-polarization antenna is depicted as the third prototype. For verification, the third prototype is fabricated and tested. Good agreement between the simulated and the measured results is achieved, which proves the feasibility of the proposed design methodology.
© 1963-2012 IEEE. In this paper, design of an ultracompact bandpass filter (BPF) in GaAs technology without compromising its electrical performance is investigated by means of both theoretical analysis and electromagnetic simulation. In particular, the relationship between the external quality factor and the coupling coefficient of the second-order BPF is formulized to better understand the principle of the mutual coupling effect. To prove the concept, the designed filter is implemented in a commercial 0.1-m GaAs technology. A step-by-step design guideline is elaborated. The BPF has not only the merits of ultracompactness, but also remarkable insertion loss (IL) compared with other state-of-The-Art on-chip designs. The measurement results show that the 1-dB bandwidth of the BPF is from 28 to 36 GHz, while the IL is less than 1 dB at 29.5 GHz. In addition, more than 40-dB rejection is achieved from 56 to 69 GHz. The size of the filter is only 230 × 280 m2, excluding the pads, which is equivalent to 0.074 × 0.09 g m2} at 28 GHz. To the best of our knowledge, the proposed design is known to be the most compact one in the open literature using GaAs technologies.
© 2018 The Author(s). Periodic corrugated metal structure is designed to support and propagate spoof surface plasmon polaritons (SSPPs) wave in the microwave frequencies. In this paper, firstly a plasmonic waveguide consisting of oval-ring shaped cells is proposed with the performance of high transmission efficiency in a wide frequency range. The coplanar waveguides (CPWs) with 50 impedance are adopted to feed the energies or extract signals at both ends of the plasmonic waveguide. Then a well-isolated power divider is constructed based on the SSPPs waveguides aiming to equally split the energy of the SSPPs wave into two equal parts. The stepped-impedances are co-designed with the three input/output ports of the power divider to achieve the impedance-matching between the SSPPs waveguides and the coplanar waveguides. Besides, a single resistor is placed in the middle of two symmetrical half oval-rings to realize the isolation between the two output ports over the spectrum of 4.5-7.5 GHz. Finally, both plasmonic waveguide and the power divider are fabricated and tested to verify the predicted characteristics.
© 2018 Elsevier B.V. A new and simple design of photo-excited broadband to dual-band tunable terahertz (THz) metamaterial cross polarization converter is proposed in this paper. The tunable converter is a sandwich structure with the center-cut cross-shaped metallic patterned structure as a resonator, the middle dielectric layer as a spacer and the bottom metallic film as the ground. The conductivity of the photoconductive semiconductor (Silicon) filled in the gap of the cross-shaped metallic resonator can be tuned by the incident pump power, leading to an easy modulation of the electromagnetic response of the proposed converter. The results show that the proposed cross-polarization converter can be tuned from a broadband with polarization conversion ratio (PCR) beyond 95% (1.86–2.94 THz) to dual frequency bands (fl=1.46 THz & fh=2.9 THz). The conversion peaks can reach 99.9% for the broadband and, 99.5% (fl) and 99.7% (fh) for the dual-band, respectively. Most importantly, numerical simulations demonstrate that the broadband/dual-band polarization conversion mechanism of the converter originates from the localized surface plasmon modes, which make the design simple and different from previous designs. With these good features, the proposed broadband to dual-band tunable polarization converter is expected to be used in widespread applications.
© 1980-2012 IEEE. This letter proposes a compact and broadband quadrature coupler with a center frequency of 55 GHz, which consists of a 90° broadside coupled-line to support the differential signal propagation and two T-type L-C networks to support the common signal propagation. To analyze the proposed coupler, an equivalent circuit model is provided for estimation of the distributed and lumped component values. The measured results of the proposed on-chip quadrature coupler show that the return loss and isolation are greater than 20 dB with a bandwidth of 105%, while the insertion loss is about -0.85 dB. The magnitude imbalances are less than 1 dB within the bandwidth of 56% and the phase differences are with ±1° errors within the bandwidth of 96.9%. The chip size, excluding the test pads, is only 0.31 × 0.22 mm2.
© 1963-2012 IEEE. A highly integrated three-state diplexer (TSD) on a single planar elliptical structure is for the first time presented in this paper. Three resonant modes are investigated in a planar elliptical resonator, e.g., two TM11 degenerate modes and one TM21 mode. These three resonant modes are designed to form three filtering channels, which are further combined to generate three states of a diplexer, namely, TSD. The planar elliptical triple-mode resonator is fed by three microstrip lines to form a triple-mode TSD. In order to validate the concept, the designed planar TSD is fabricated and measured. The measured results are in good agreement with the simulated ones.
© 1963-2012 IEEE. A new approach to realize robust, flexible, and electronically tunable wearable antennas is presented. Conductive fabric is used to form the conducting parts of the antenna on a polydimethylsiloxane (PDMS) substrate. Then the antenna and the lumped (active and passive) elements, required for electronic tuning and RF choking, are fully encapsulated with additional layers of PDMS. As a concept demonstration, a new frequency-reconfigurable antenna has been designed and fabricated. The details of the prototype manufacturing process are described. Two UWB human muscle equivalent phantoms were also fabricated for testing purposes. Furthermore, the antenna was subjected to several investigations on its RF performance (both in free space and on a flat phantom) and mechanical stability. The latter includes bending tests on several locations on a human-body shaped phantom and washing in a household washing machine. Good agreement between predicted and experimental results (both in free space and on the phantom) is observed, validating the proposed concept. The tests demonstrated that lumped components and other antenna parts remained intact and in working order even under extreme bending (to a bending radius of 28 mm) and after washing, thus maintaining the overall antenna performance including good frequency reconfigurability from 2.3 to 2.68 GHz. To the best of our knowledge, all these features have never been demonstrated in previously published electronically tunable antennas.
IEEE This letter proposes a compact and low-loss on-chip bandpass filter (BPF) design in (Bi)-CMOS technology. The proposed BPF consists of a self-coupled folded-line resonator (SCFLR) and a pair of metal-insulator-metal (MIM) capacitors. The proposed resonator has a property of flexible self-resonant-frequency (SRF) to form a transmission zero (TZ), which is analyzed in details by a simplified LC equivalent circuit. Moreover, the parametric studies of the feeding capacitance for the proposed BPF design have been performed to demonstrate the tenability of the resonant frequency. For verification, the proposed BPF is fabricated in a standard 0.13-μm (Bi)-CMOS technology. The measured results show that the proposed BPF has a notch with 25.4 dB suppression at 65 GHz and an insertion loss of 1.66 dB in the passband. The chip size of the device, excluding the test pads, is only 0.009mm2 (0.11 × 0.086mm2).
© 2018 IEEE. A novel concept and approach for integration of a three-state diplexer (TSD) by utilizing the triple-mode cavity resonators is proposed in this paper. The proposed TSD has the inherent nature of three frequency channels, two of which can be utilized for duplexing channels by exciting one port as the input in each state. Meanwhile, three fundamental modes, namely, TE 011 , TE 101 , and TM 110 , are excited in the triple-mode resonators (TMRs) to control these three frequency channels. Without utilizing any junction networks for impedance matching, the required values of the external quality factors and coupling coefficients can be extracted to meet the relevant Chebyshev responses in the three bands of the TSD, simultaneously. Owing to the modal orthogonality among the three fundamental modes, high isolation among these three frequency channels can be effectively achieved. For proof of concept, two design examples of the TSD structures are presented with different topologies. For both examples, four and six TMRs are adopted, respectively, where the predicted three frequency channels of the TSD can be successfully excited with excellent channel isolations. The fabricated prototype shows good agreement between the simulated and measured results verifying the feasibility of the proposed design methodology.
© 1963-2012 IEEE. This communication presents a new design of a quadri-polarization-agile aperture-coupled patch antenna array for 60 GHz applications. Four polarization states, namely, vertical linear polarization, horizontal linear polarization, left-hand circular polarization (LHCP), and right-hand circular polarization (RHCP) can be flexibly reconfigured by dynamically switching the excitation of the corresponding port. More importantly, as the LP and CP radiations are achieved by using differential feeding and sequential-rotation feeding, respectively, the array exhibits wide impedance and axial ratio (AR) bandwidths, high polarization purity as well as symmetrical pattern with the main beam fixed at boresight. The-10 dB impedance bandwidths are better than 11.6% (57-64 GHz) for the four polarization states. The measured AR bandwidths are from 58 to more than 64 GHz for both the LHCP and RHCP. The good radiation performance together with the quadri-polarization-agile capability of this new array, as demonstrated in the communication, underlines its suitability for the future 5G communication systems, especially in a multipath propagation environment.
© 2013 IEEE. We present our study on polydimethylsiloxane (PDMS)-embedded conductive fabric, which we propose as a simple yet effective solution to the challenging issue of poor PDMS-metal adhesion, allowing for a relatively easy realization of robust flexible antennas for wearable applications. The method combines the use of conductive fabric as a radiator with PDMS, which acts as the substrate and a protective encapsulation simultaneously. For the first time, a holistic study on the mechanical and electrical properties of the proposed combination of materials is presented thoroughly using a number of fabricated samples. As concept demonstrations, a microstrip patch and a reconfigurable patch antenna are fabricated using the proposed technique to validate the idea. The inclusion of a PDMS-ceramic composite as part of the antenna's substrate, which leads to over 50% reduction in the size compared with a pure PDMS, is also demonstrated to showcase further the versatility of the proposed technique. The fabricated antennas are tested in several wearable scenarios and consistent performance including reconfigurability is obtained even after the antennas are exposed to harsh environments, i.e., extreme bending and machine-washing.
© 2018 IEEE. In this paper, a novel on-chip circuit design approach is proposed using hybrid coupling technique. Taking advantage of this technique, a microwave bandpass filter (BPF) is proposed as a design example for proof of concept. Based on stub-loaded stepped-impedance transmission lines and folded stepped-impedance meander line from different metal layers, the proposed BPF can generate three transmission zeros (TZs) and two transmission poles (TPs), which are excited through the hybrid mutual couplings between the inductive and capacitive metals. To understand the principle of this configuration, an equivalent LC-circuit model is presented and simplified, of which the TZs and TPs of the proposed BPF are estimated by the extracted transfer function. The calculated results exhibit good agreements with the simulated and measured ones. In addition, the bandwidth and center frequency of the proposed BPF can be tuned flexibly. Finally, to further demonstrate the feasibility of this approach in practice, the structure is implemented and fabricated in a commercial 0.13- m SiGe (Bi)-CMOS technology. The measurement results show that the proposed BPF, whose chip size is 0.39 mm × 0.45 mm (excluding the test pads), can realize a wide bandwidth from 19.7 to 33.2 GHz with a return loss of 15.8 dB and insertion loss of 3.8 dB at the center frequency of 26.5 GHz.
© 1980-2012 IEEE. In this Letter, a flexible approach for low-loss on-chip bandpass filter (BPF) design in CMOS technology is presented. The proposed approach takes the advantages of a combination of an edge-coupled electromagnetic structure, namely resonator, and a pair of metal-insulator-metal capacitors for BPF implementation. To demonstrate the insight of the approach, the designed resonator is analyzed in details by means of a simplified equivalent LC-circuit model. Then, the impact on the BPF design due to the variations of the feeding capacitance is investigated. To prove the concept, both the resonator and BPF are fabricated in a standard 0.13- m CMOS technology. The measured results show that the designed resonator can generate a notch with 20-dB attenuation at 59.4 GHz, while the BPF has a center frequency of 35.4 GHz with an insertion loss of 1.7 dB. The chip size of both devices, excluding the test pads, is only 0.039 mm2(0.15 × 0.26 mm2).
© 2018 IEEE. This paper introduces a unique approach for the implementation of a miniaturized on-chip resonator and its application for the first-order bandpass filter (BPF) design. This approach utilizes a combination of a broadside-coupling technique and a split-ring structure. To fully understand the principle behind it, simplified LC equivalent-circuit models are provided. By analyzing these models, guidelines for implementation of an ultra-compact resonator and a BPF are given. To further demonstrate the feasibility of using this approach in practice, both the implemented resonator and the filter are fabricated in a standard 0.13-m (Bi)-CMOS technology. The measured results show that the resonator can generate a resonance at 66.75 GHz, while the BPF has a center frequency at 40 GHz and an insertion loss of 1.7 dB. The chip size of both the resonator and the BPF, excluding the pads, is only 0.012mm2 (0.08 × 0.144 mm2).
© 2001-2012 IEEE. In this letter, a C-band compact wideband bandpass filter (BPF) with high selectivity and improved return loss (RL) is proposed. Two pairs of short-circuited stubs are employed on a transmission-line model to generate three transmission poles and two transmission zeros (TZs), where the odd-and even-mode analysis is used to analyze the resonant frequencies of the BPF. By applying the transversal signal-interference technique, two additional TZs can be generated in the upper and lower stopbands, respectively. The measured results show that the 3-dB fractional bandwidth is 62.8% at the center frequency of 5 GHz. The RL and the insertion loss within the passband are better than 22 and 0.6 dB, respectively. Moreover, the roll-off rate is up to 100 dB/GHz.
© 2018 IEEE. In this paper, two third-order bandpass filters (BPFs) designed for millimeter-wave applications are presented. Unlike previously published ones, the proposed designs use a "cell-based" approach, which utilizes identical broadside-coupled resonators (BCRs) with series and shunt capacitors. The capacitors are mainly used as J -inverters to achieve the desired frequency responses. To fully understand the operational mechanism of the presented approach, both the BCR and BPFs are analyzed using the simplified LC-equivalent circuit models. To prove the concept, both BPFs are implemented in a standard 0.13- m silicon-germanium bipolar complementary metal-oxide-semiconductor technology. According to the on-wafer measurement results, the BPFs exhibit the excellent performance including flat in-band responses with relatively large harmonic suppression. The first design has a 1-dB bandwidth from 23.9 to 39.7 GHz with an insertion loss of 3.9 dB at the center frequency of 31 GHz. The stopband attenuation is better than 45 dB at 58 GHz. The 1-dB bandwidth of the second design covers from 26.7 to 44.3 GHz with an insertion loss of 3.1 dB at the center frequency of 35 GHz, and stopband attenuation up to 35 dB is achieved at 59 GHz. Both designs occupy an identical area of 0.073 mm 2 (0.248×0.294 mm 2 ), excluding the G-S-G testing pads.
© 2016 IEEE. Advanced micromachining technology has made magnificent progress for fabrication of non-planar circuits. Using this technology, circuits and systems can be implemented in a more cost-effective way. Unlike the conventional planar circuit, low-cost and highly sensitive misalignment sensor is required to detect imperfect placement of different micro-devices, which may be of the order of sub-micrometers. Currently, this is hardly to be achieved by using the existing approaches. In this letter, we present a novel sensor design approach utilizing the parasitic capacitance of an integrated coupled-line resonator for misalignment sensing. Due to vertical misalignment between two metal strips, the parasitic capacitance of the sensor varies, which results in a resonance shift from 53 to 68 GHz, while a reasonably strong transmission notch is still maintained. Taking advantage of this principle, misalignment can be effectively detected. To prove the concept, several devices are fabricated in a standard silicon technology. Three samples with the same structure are used to evaluate the reliability, while eight different structures are used to verify the concept. All results are extensively validated through both simulation and measurements.
© 2017 IEEE. In this letter, the possibility of using device-free sensing (DFS) technology for personnel detection in a foliage environment is investigated. Although the conventional algorithm that based on statistical properties of the received-signal strength (RSS) for target detection at indoor or open-field environment has come a long way in recent years, it is still questionable if this algorithm is fully functional at outdoor with the changing atmosphere and ground conditions, such as a foliage environment. To answer this question, a variety of the measured data have been taken using different targets in a foliage environment. Applying these data along with support vector machine, the impact on detection accuracy due to different classification algorithms is studied. An algorithm that based on the extraction of the high-order cumulant (HOC) of the signals is presented, while the conventional RSS-based one is used as a benchmark. The measurement results show that the classification accuracy of the HOC-based algorithm is better than the RSS-based one by at least 17%. Moreover, to ensure the reliability of the HOC-based approach, the impact on classification accuracy due to different numbers of training samples and different values of signal-to-noise ratio is extensively verified using experimentally recorded samples. To the best of our knowledge, this is the first time that a DFS-based sensing approach is demonstrated to have a potential to distinguish between human and small-animal targets in a foliage environment.
© 2017 IEEE. An on-chip bandpass filter (BPF) is designed and fabricated in a 0.13-m SiGe (Bi)-CMOS technology. This BPF consists of a broadside-coupled meander-line resonator (BCMLR) in conjunction with a defected-ground structure (DGS). By simply grounding a BCMLR, the resonator can be converted into a BPF. Further applying a DGS to this BPF, an additional transmission zero can be generated in the high-frequency band. To understand the fundamentals of this design, an $LC$-equivalent circuit is given for investigation of the transmission zeros and poles. The measured results show that the BPF has a center frequency at 33 GHz with a bandwidth of 18%. The minimum insertion loss is 2.6 dB, while the maximum stopband attenuation is 44 dB. The chip size, excluding the pads, is only 0.038 mm 2 ( 0.126×0.3 mm 2 ).
© 2017 IEEE. A novel compact dual-band cavity-backed substrate integrated waveguide (SIW) array antenna using high-order radiation modes has been proposed in this paper. The first high-order hybrid mode (superposition of TM 310 and TM 130 ) and the second high-order mode (TM 320 ) of K-band in the SIW cavity are excited by an inductive window for dual-band application. The operation mechanism of high-order modes is analyzed and then verified through simulations by inserting metallic vias in different positions of the resonant SIW cavity. The designed subarray antenna has the advantages of high gain, high front-to-back ratio, and low cross-polarization level. To further validate the design idea, a dual-frequency band $2 \times 2$ array antenna has been fabricated and measured including reflection coefficients, realized gains, and radiation patterns. The measured results show that the 10-dB impedance bandwidths at resonant frequencies of 21 and 26 GHz are 800 MHz (3.7%) and 700 MHz (2.6%), and the realized gains at boresight direction are around 16 and 17.4 dBi, respectively. Moreover, the proposed array antenna also possesses both advantages of metallic cavity-backed antennas and planar patch antennas, such as low cost, easy fabrication with the printed circuit board technology, and integration with other planar circuits.
© 2017 Wiley Periodicals, Inc. A novel continuously tunable lowpass filter (LPF) with compact size, sharp roll-off and low insertion loss is presented in this paper. The filter employs two varactor diodes, a pair of open-ended coupled lines and a U-shape step impedance line (SIL) with an open-ended stub loaded at the center of the SIL to form a very compact layout. The odd- and even-mode analysis and equivalent circuit model are demonstrated for estimation of the transmission characteristics. Tuning the DC voltage applied on the varactor diodes, the varactor capacitance accordingly changes leading to a varying cutoff frequency f c . The measured results show that the achieved 3-dB f c tuning range is 60.6% (1.15–2.15 GHz). The measured insertion loss (IL) and roll-off rate are 0.2-0.4 dB and 50–73 dB/GHz, respectively. The overall size of the LPF is only 0.005 g 2 , which shows a competitive advantage comparing with the state-of-the-art work.
© 2013 IEEE. This paper presents a new class of second-order individually and continuously tunable dual- and triple-band bandpass filters in a single metal cavity. Each passband is realized by two identical metal posts. These dual- and triple-band tunable filters are achieved by putting two or three identical sets of metal-post pair in a single metal cavity. Metal screws are co-designed as a part of the metal posts to control their insertion depth inside the cavity. In this way, the resonant frequencies can be continuously controlled and designed at the desired frequency bands. Moreover, the distance between the two metal posts in a post pair can be freely tuned. Thus, the external quality factor (Q e ) and coupling coefficient (k) between the adjacent modes can be easily adjusted to meet the specified requirement in synthesis design. At the bottom of the cavity, some grooves are used to extend the tunable frequency range and make the resonant frequency linearly varied with the height of the metal post. The center frequency of each passband can be independently tuned with a frequency range of 0.8-3.2 GHz and tunable ratio of 4. Finally, the continuously tunable dual- and triple-band bandpass filters prototypes with second order response are designed and fabricated, of which each passband can be individually tuned with a large tuning range.
© 2017 Elsevier B.V. The explosion of different types of wireless communications is leading to an impending spectrum famine. As a result, spectrum sensing has gained increasing interest from governments, industry and regulators. In this paper, a novel approach for cooperative spectrum sensing is proposed based on a modified shuffled frog leaping algorithm (SFLA). This approach is to fuse the perceived results of multiple nodes, and to improve the detection reliability. Simulations are used to compare the performance of the modified SFLA to the conventional one. The performance of the proposed cooperative spectrum sensing method based on the modified SFLA and that of the cooperative spectrum sensing method using modified deflection coefficient (MDC) are also compared. Results show that the proposed SFLA outperforms the traditional SFLA, and the proposed cooperative spectrum sensing method based on the modified SFLA gives higher miss detection probability than the MDC-based method, which validates the effectiveness of the modified SFLA-based cooperative sensing method.
A novel design of boresight and conical pattern reconfigurable antenna with the capability of 360° polarization scanning is presented in this paper. At boresight mode, the antenna produces a continuously reconfigurable polarization over 360° in the azimuth plane, which provides adaptive-polarization reception between a transmitter and a receiver. The antenna is analyzed in terms of the electric field with an explanation of the generation of TM11 and TM02 resonant modes, which provides an innovative method of designing pattern reconfigurable antennas for the WLAN applications. The proposed method is validated by a good agreement between simulation and experimental results for an antenna designed to provide boresight and conical pattern switching at 2.4 GHz. The gain of 6.05 dBi and efficiency of 86.7% are measured in the boresight mode, corresponding to 4.39 dBi and 82.4% at conical mode.
© 2013 IEEE. On the basis of doublet and its properties, a class of multiple-mode narrow band bandpasss filter is designed and fabricated by simultaneously exploiting the three resonant modes in a single rectangular cavity: TE 101 , TE 011 , and TM 110 modes. The input/output ports of the proposed filter are fed by coupling a microstrip line to a slot on the side wall of a rectangular cavity. Different modes are excited by changing the position and shape of the two slots at input and output of the rectangular cavity without any intra-cavity coupling. Besides three poles within the passband, a pair of transmission zeros (TZs) is achieved, which can be controlled independently by setting the positions of the two TZs at the lower and/or upper stopband. High stopband attenuation and high filtering selectivity are achieved by considerably allocating three transmission poles and two zeros. In order to verify the proposed theory, two filter prototypes are fabricated and measured.
© 2017 IEEE. A dual-band antenna for off- and on-body communications in the 2.45- and 5.8-GHz Industrial, Scientific, and Medical bands is presented. The two radiation characteristics, i.e., patch-like radiation for the off-body link and monopole-like radiation for the on-body link, are achieved by utilizing inherently generated TM11 and TM02 modes of a circular patch antenna. A shorting pin and two arc-shaped slots are employed to tune both modes to the desired operating frequencies. This approach allows a realization of a dual-band dual-mode antenna with a very simple structure, i.e., a single radiator with a simple feed. A further advantage of the proposed antenna is its realization using a silver fabric integrated onto a flexible polydimethylsiloxane substrate that makes it more practical for wearable applications. An experimental investigation of the antenna performance has been carried out in free space and on a semisolid human muscle equivalent phantom, which shows a robust performance against the human body loading effect. When placed on the phantom, the measured bandwidths of 84 and 247 MHz in the 2.45- and 5.8-GHz bands, respectively, are achieved with the corresponding peak gains of 4.16 and 4.34 dBi, indicating a promising candidate for body-centric communications.
A novel wireless transducer that uses analog-based technology at 2.4 GHz is presented in this letter. The transducer consists of an electrocardiography (ECG) detection circuit and a novel three-stage amplitude modulation transmitter that up-converts the ECG signal to a 2.4-GHz carrier frequency. To minimize the effects due to local oscillator leakage as well as the interference at the image frequency, the intermediate frequency is carefully selected, and a bandpass filter with a very sharp selectivity is designed. As demonstrated by the experimental results, the full-wave ECG signals can be successfully demodulated from the transmitted signal using the presented transducer. This enables the possibility of using analog-based technology for remote patient monitoring in real time.
An on-chip resonator is designed and fabricated using a standard 0.13-m SiGe technology for millimeter-wave applications. The designed resonator is based on a unique structure, which consists of two broadside-coupled meander lines with opposite orientation. The equivalent LC circuit of the resonator is given, while the impact of the structure on the resonance frequencies is investigated. Using this structure along with capacitors, a compact bandpass filter (BPF) is also designed and fabricated. The measured results show that the resonator can generate a resonance at 57 GHz with the attenuation better than 13.7 dB, while the BPF has a center frequency at 31 GHz and a insertion loss of 2.4 dB. The chip size of both the resonator and the BPF, excluding the pads, is only 0.024 mm2 (0.09×0.27 mm2).
In RFID reader systems, power amplifier plays a critical rule for efficiency enhancement. A high efficiency power amplifier may not only increase the life expectancy of portable RFID devices but also reduce the reliance on heat sinks. Heat sinks usually occupy plenty of space and lead to packing difficulties. A well-designed power amplifier with high efficiency and output power may also increase the reading range of RFID and system reliability, especially for the applications requiring long reading range (e.g. vehicle tagging in complicated traffics) or in a lossy environment (e.g. in sensing in rainy weather). This chapter systematically introduces the typical power amplifiers classified as Class A, AB, B, E, and F. The principles of Class F are emphasized due to its outstanding performance in efficiency enhancement. A practical design example is also presented, and also some recent typical techniques for improving the performances of Class F power amplifier are summarized. © 2012, IGI Global.
Sleep apnea is a severe, potentially life-threatening condition that requires immediate medical attention. In this chapter, a novel wireless sleep apnea monitoring system is proposed to avoid uncomfortable sleep in an unfamiliar sleep laboratory in traditional PSG-based wired monitoring systems. In wireless sleep apnea monitoring system, signal propagation paths may be affected by fading because of reflection, diffraction, energy absorption, shadowing by the body, body movement, and the surrounding environment. To combat the fading effect in WBSN, the MIMO technology is introduced in this chapter. In addition, the presented active RFID based system is composed of two main parts. The first is an on-body sensor system; the second is a reader and base station. In order to minimize the physical size of the on-body sensors and to avoid interference with 2.4 GHz wireless applications, the system is designed to operate in the 5.8 GHz ISM band. Each on-body sensor system consists of a physiological signal detection circuit, an analogue-to-digital convertor (ADC), a microcontroller (MCU), a transceiver, a channel selection bandpass filter (BPF), and a narrow band antenna. © 2013, IGI Global.
© 2018 IEEE. In this paper, a low phase noise VCO employing tunable stubs loaded nested split-ring resonator (SLNSRR) has been proposed By loading anti-pair varactors at each side of the SLNSRR, the center frequency of the SLNSRR filter can be tuned from 1.82 GHz to 2.18 GHz. In the oscillator design, the tunable SLNSRR filter is used as a frequency stable element to select the oscillation frequency while keeping the low phase noise performance. To validate the method, an L-band to S-band VCO is designed, fabricated and measured. The measured results show that the proposed VCO has a frequency tuning range from 1.787 GHz to 2.117 GHz with a 16.9 % bandwidth. Over this frequency range, the phase noises measured at 1 MHz frequency offset are better than -113.49 dBc/Hz.
© 2013 IEEE. A wideband and high gain cavity-backed 4 × 4 patch antenna array is proposed in this paper. Each patch antenna element of the array is enclosed by a rectangular cavity and differentially-fed by the slot underneath. By optimizing the geometry of the radiating patch and the cavity, a very uniform E-field distribution at the antenna aperture is achieved, leading to the high array aperture efficiency and thus the gain. Taking advantages of the higher-order substrate integrated cavity excitation, the elements of the array are efficiently fed with the same amplitude and phase in a simplified feeding mechanism instead of the conventional bulky and lossy power-splitter-based feeding network. Measured results show the antenna bandwidth is from 56 to 63.1-GHz (16.1%) with the peak gain reaching 21.4 dBi. The radiation patterns of the array are very stable over the entire frequency band and the cross-polarizations are as low as -30 dB. These good characteristics demonstrate that the proposed array can be a good candidate for the future 60-GHz communication system applications.
© 2018 IEEE. In this paper, a novel frequency-tunable filter based low noise voltage-controlled oscillator (VCO) is proposed. The proposed tunable filter consists of a T-type resonator with four varactors and a pair of short-ended stubs connected with feedlines. High-Q can be achieved by introducing a transmission zero on the upper stopband, which can reduce the phase noise of the VCO. The whole size of the tunable filter is 0.0022g. The proposed VCO was fabricated and measured indicating a promising frequency-tuning range from 2.2 to 3.2 GHz with the second harmonic suppression level of better than 22 dB. The measured phase noise is -88-91.44dBc/Hz at 100KHz offset.
© 2018 IEEE. A triple-mode cavity filter with narrow passband realized in a single rectangular metal cavity without any tune crews, coupling apertures, iris, and corner cuts is proposed in this paper, while three resonant modes are classified as a TM mode and a pair of TE modes, which are excited by two metal probes in one single cavity. At both the upper and lower stop-bands, two transmission zeros are created to achieve a considerable out-of-band suppression. To prove the concept, a prototype is fabricated by using the silver plated aluminum technology demonstrating a measured fractional bandwidth of 3.6% at the center frequency of 2.53 GHz. The measured and simulated results are presented in good agreement.
© 2018 IEEE. Design of a broadband on-chip bandpass filter (BPF) using grounded ring resonator with capacitive loading technique is presented in this paper. To prove the concept, a standard 0.13-m (Bi)-CMOS technology is selected for implementation. To understand how to effectively optimize the designed BPF, parametric studies against some critical parameters are given by means of EM simulation. Finally, the implemented filter is fabricated. The measured results show that the BPF has a center frequency at 33 GHz with a bandwidth of 42.4%. The minimum insertion loss is 2.6 dB, while the stopband rejection is maintained to be better than 20 dB beyond 58 GHz. The chip, excluding the pads, is very compact at only 0.03 mm2 (0.11 × 0.28 mm2).
© 2018 IEEE. This paper presents a low phase noise oscillator with high harmonic suppression employing a pair of substrate integrated waveguide (SIW) quarter-wavelength resonators (QWR) in the feedback loop of the oscillator. By tuning the width of the SIW-QWR based filter, the stopband bandwidth can be extended while maintaining the high group delay in the passband. Taking advantages of the proposed SIW-QWR, an X-band low phase noise oscillator with the second and third harmonic suppression is designed, fabricated and tested. The measured results show that the oscillator operates at 8.08 GHz with -2.14 dBm output power. The second and third harmonic suppression of the presented oscillator can reach to 39.23 dB and 67.64 dB, respectively, with a single SIW-QWR filter. The phase noise performance of the proposed oscillator are -109.94 dBc/Hz at 100 kHz frequency offset and - 130.36 dBc/Hz at 1 MHz frequency offset, respectively.
© 2018 Institution of Engineering and Technology.All Rights Reserved. A novel reconfigurable antenna with the capability of 360-degree polarization scanning and the diversity of boresight and conical radiation patterns switching is presented in this paper. Each shorting-post is connected and controlled by a PIN diode to achieve the desired distribution of electric field null(s) in the substrate, where transverse magnetic (TM) modes switching between TM11 and TM02 can be accordingly realized corresponding to boresight and conical patterns. The antenna is analyzed in a cavity model, which, in terms of electric field, theoretically explains the generation of TM11 and TM02 resonant modes, and provides the audience with an innovative method of designing pattern reconfigurable antennas for the applications such as multiple-input and multiple-output (MIMO), wireless body sensor network (WBSN), Wi-Fi and WiMAX. The proposed antenna is with a competitive radius of 0.32 g. The antenna structure is very easy to be fabricated. The measurement shows that the antenna can realize a boresight and conical pattern reconfiguration at 2.4 GHz with a gain of 6 dBi and efficiency of 86.7% (boresight mode), and 4.39 dBi and efficiency of 82.4% (conical mode).
© 2018 IEEE. This paper presents a recently proposed novel approach for pattern reconfigurable antenna designs. Individually associating a shorting post with an RF switch, the shorting post can be simply connected to the ground by turning the switch on or disconnected to the ground by turning the switch off. This approach has been successfully validated through two recently reported designs, for the implementations of transverse magnetic TM mode reconfiguration and 360° beam-steering.
Simorangkir, RBVB, Yang, Y & Esselle, KP 2018, 'Robust implementation of flexible wearable antennas with PDMS-embedded conductive fabric', IET Conference Publications, London, UK.
© Institution of Engineering and Technology.All Rights Reserved. In this paper, a new approach to fabricate a robust flexible body-worn antenna is introduced. It combines conductive fabric, used as the radiator, with polydimethylsiloxane (PDMS) utilized as the substrate as well as the encapsulation of the antenna. The mechanical and electrical characteristics of PDMS-embedded conductive fabric structures are firstly investigated, followed by the general steps of the antenna fabrication process. As concept demonstrations, two designs, dual-band dual-mode and frequency-reconfigurable patch antennas, have been fabricated. Experimental investigations on the antennas' RF performance (both in free space and on a muscle phantom) and mechanical stability are also demonstrated. The latter includes bending on human's arm-shaped phantom and machine-washing tests. The results demonstrated that the proposed method is applicable for realization of robust, flexible, not only passive but also active, wearable antennas.
© 2018 IEEE. A new and simple fabrication method to realize robust flexible wearable antennas by combining conductive fabric and polydimethylsiloxane (PDMS) is proposed. The conductive fabric acts as the conductive part of the antenna, while PDMS acts as the substrate as well as the encapsulation layers. The method takes advantage of the porous structure of the conductive fabric and the initial liquid form of PDMS to attain a significantly strong integration between the two, leading to a robust PDMS-based wearable antenna. A number of patch antennas have been designed, fabricated, and tested to validate the proposed concept and the results are presented, showing robust performance. The fabricated prototypes have a resonance frequency approximately at 2.46 GHz with a 10 dB return-loss bandwidth ranging from 3.3 to 5.7%.
© 2018 IEEE. The study of temperature rise distribution in the human eye under plane electromagnetic wave exposure up to 10 GHz is presented in this paper. The effects of different frequencies and different blood perfusion rates of sclera to thermal calculations are investigated by finite difference method. The results reveal that the changes in the thermal parameter produce a maximum relative standard deviation of ~15% in the temperature rise in lens.
© 2018 IEEE. This paper introduces an on-chip third-order bandpass filter (BPF) for millimeter-wave (mm-wave) applications. The proposed BPF is composed of three identical broadside-coupled meander-line resonators (BCMLR) which are jointly connected by three MIM capacitors through aT-shape network. The MIM capacitors are used as J-inverters for the implementation of the third-order BPF in order to achieve the desired multiple transmission poles and zeros across the passband and stopband, correspondingly. To fully understand the operational mechanism of the proposed high-order structure, the resonator and the proposed BPF are analyzed using an LC- equivalent circuit model for further investigation of the distribution of the transmission poles and zeros in terms of the metal inductance and MIM capacitance. To prove the concept, the proposed BPF prototype is implemented in a commercial 0.13-l.lm SiGe (Bi)-CMOS process. According to the results obtained from on-wafer measurement, three transmission poles and three transmission zeros are clearly observed. Noticeably, the proposed BPF exhibits excellent performances including a flat in-band response (less than 1 dB attenuation) from 26.7 GHz to 44.3 GHz with a measured insertion loss of 3.1 dB at the center frequency of 35.5 GHz and stopband attenuation up to 35 dB at 59 GHz. The chip size is 0.016 mm2(0.066 × 0.236 mm-), excluding the GSG pads.
Simorangkir, RBVB, Yang, Y & Esselle, K 2017, 'Active and Passive Antennas Based on Unconventional Materials, for Next Generation Wearable Wireless Devices (Invited Paper)', 2017 IEEE MTT-S International Microwave Symposium, Honolulu, Hawaii.
In this paper, the millimeter-wave circuit miniaturization techniques using BCMLR and interdigital resonators are introduced. Using these structures, the physical size of the on-chip filter can be dramatically reduced. The designed BPFs are implemented in standard 0.13-m SiGe and 0.1-m GaAs technologies for concept approval. Compared with other state-of-the-art work at millimeter-wave frequencies, our proposed designs have the merits of ultra-compact size as small as 0.038 mm 2 , competitive insertion loss (1 dB in GaAs BPF) and harmonic suppression of more than 44 dB.
A 320 GHz on-chip 2 × 2 antenna array employing a compact feeding network is presented in this paper. The feeding network is designed based on the conducted-back coplanar waveguide (CBCPW) transmission line with a compact size, which has the full shielding performance providing good isolation from circuits around or below the CBCPW transmission lines. The proposed on-chip feeding network and antenna array are fabricated using standard 0.13-m SiGe process. The antenna array is measured using a specially designed backside radiation measurement system. The simulated and measured results show that the backside radiation on-chip antenna array has a measured peak gain of 7.9 dBi at 320 GHz.
© 2017 IEEE. This paper presents a design of a miniaturized resonator for millimeter-wave applications. The resonator is implemented in a standard 0.13m (Bi)CMOS technology. Its performance is verified using an EM simulator from NI-AWR. The designed resonator is based on a unique structure, a combination of spiral loop and meander line structure. The ground plane is characteristically altered with a ring defected ground structure (DGS) to enhance the overall performance. The resonator design exhibits tuning flexibility at its resonance frequency within the mm-wave spectrum that is proportional to its design dimension. By using capacitive feeding, the designed resonator generates one transmission zero at 60 GHz with insertion loss of -2.7 dB and -29.4 dB return loss respectively. The chip size of the resonator excluding the pads is only 116 m × 236 m (0.027mm2).
© 2017 IEEE. In this paper, design of miniaturized on-chip quadrature hybrid branch-line coupler is investigated. The motivation of this work is to minimize the footprint of the designed coupler while maintaining high performance of the circuit in the mm-wave band spectrum. Three examples are implemented in a standard (Bi)-CMOS process for millimetre wave applications. Excluding the pads, the chip size of the conventional design is 0.35 mm2, and the proposed two other designs structures are 0.26 mm2and 0.21 mm2, respectively, which indicates an area reduction by 13% and 30% respectively.
© 2018 Electromagnetics Academy. All rights reserved. Design of a miniaturized resonator and its application for dual-band bandpass filter design for millimeter-wave application is presented in this paper. Both the resonator and filter are implemented in a standard 0.13-m (Bi)-CMOS technology. The performance is extensively verified using an EM simulator from NI-AWR. Using the presented resonator structure, two transmission zeros can be generated and effectively controlled. By feeding the resonator using a capacitive coupling technique, a dual-band bandpass filter that operated at 40 GHz with insertion loss of 0.7 dB and at 71 GHz with insertion loss of 1.5 dB, respectively. The proposed design achieves a reduced layout size of 302 m × 131 m.
© 2017 IEEE. The full potential of active device in current Si-based technology has almost reached its limit. However, the passive devices that are integrated with transistors in the same technology have yet been fully explored. Improving the quality of on-chip passive devices is not only beneficial for energy efficiency, but also has significant meaning in cost reduction for a system-on-chip (SoC) solution while the passive circuits are miniaturized. A review of on-chip circuit miniaturization techniques for bandpass filter (BPF) design is demonstrated in this paper. Although the recently presented broadside-coupled meander line resonator (BCMLR) is very compact, the stopband attenuation is quite limited. To solve this issue, a ring-based structure is studied in this work. Using this approach, the size of the proposed millimeter-wave on-chip BPF can be significantly reduced due to the multi-mode characteristics of the proposed resonators, of which the equivalent circuits can be effectively modeled through the accurately extracted lumped components values. Our works exhibit excellent performance comparing with the state-of-the-art designs.
© 2017 IEEE. A variety of multiple-mode narrow-band bandpasss filer is designed, analyzed, and fabricated based on doublet and its properties. Three resonant modes: TE101, TE011and TM110 modes in a single cavity are excited. The proposed filters use a microstrip line as a feeder then couple to a slot on one side of a single rectangular cavity. By rotating and offsetting two slots at the input port and output port of the rectangular cavity, three fundamental modes are implemented without any cross-coupling. The proposed structure also create two transmission zeros (TZs), by adjusting the positions of the two TZs near the passband, e.g., at lower or upper stopband, high rejection is achieved. Due to emergence of the three resonant modes and realization of a pair of TZs, a high attenuation and sharp filtering selectivity is achieved. Good agreement between measurement and simulation is achieved.
© 2017 Euraap. In this paper the performance of TM21 resonance-mode circular patch antennas embroidered with different stitching patterns is discussed and compared. The goal is to investigate the difference in the performance when the antenna is embroidered with stitches following the antenna current paths as opposed to some simple patterns such as horizontal and vertical ones. This creates an alternative solution for embroidering prototypes of wearable antennas with complicated current distributions. The results reveal that by embroidering the antenna in line with the complex TM21 current distribution a good monopole-like radiation pattern is achieved, which is close to an etched copper prototype's used as the reference. However, with a dense horizontal stitching pattern an acceptable monopole-like radiation pattern can also be achieved with quite good gain and efficiency. While simplifying the embroidery process, the use of the simple horizontal pattern with high density suffers from high cross-polarization and thread consumption as compromises.
© 2016 IEEE. This paper proposed a novel broadside-coupled meander-line resonator (BCMLR) for millimeter-wave (mm-wave) passive and active circuit designs. This on-chip resonator is designed and fabricated using a 0.13m SiGe technology. The proposed BCMLR consists of two broadside-coupled meander lines with opposite orientation. Applying this resonator with on-chip capacitors, a compact first-order and a second-order on-chip bandpass filters (BPFs) are designed. The measured results illustrate that the resonator can generate a resonance at 57 GHz with attenuation of 13.7 dB. The BCMLR based BPFs with excellent measured results are also presented in the paper as an example of applying the BCMLR in MMIC circuits designs. The chip size of both the BCMLR and the BPF, excluding the pads, is only 0.024 mm2 (0.09 × 0.27mm2).
© 2016 IEEE. Design of an inductor-less wideband variable-gain amplifier (VGA) using a cell-based strategy is presented. The VGA has a measured gain range of 24 dB, of which 17.3 dB is dB-linear with less than ±0.3 dB gain error. The -3 dB bandwidth is from 2 GHz to 2.2 GHz for the entire dB-linear range. An output 1 dB compression point of 1.8 dBm and a noise figure of 24 dB are measured. Due to the simple structure, the current consumption of the VGA core is only 2.9 mA from a 1.2 V supply, and the size is only 225 m × 45 m, excluding pads.
© 2016 IEEE. This paper presents an Integrated on-chip balun design for millimeter-wave applications. The balun is designed and fabricated in a standard silicon-germanium technology. The designed balun is based on a coupled-line structure, which consists of two edge-coupled meander lines along with a solid ground plane. The simulation shows that the proposed balun covers the bandwidth from 30 GHz to above 100 GHz. Within this frequency range, the magnitude error and phase error are 0.3 dB and 4°, respectively. The insertion loss of the balun is better than 5 dB at the center of the band. The size of the balun is only 500 m × 400 m, excluding the pads.
© 2016 IEEE. This paper proposed a novel internally pre-matching network for high power and high efficiency power amplifier design. Based on this matching network, a push-pull GaN power amplifier with the high saturated output power of 805 W and peak PAE of 74.5% is realized. The proposed power amplifier can provide a relatively stable output power above 58.5 dBm (707 W) in the band of 400 MHz to 500 MHz while maintain a stable gain above 17.5 dB.
© 2016 IEEE. This paper proposed a novel modeling method of bonding wires array for internally matched network for high power and high efficiency power amplifier design. Based on this modeling method, a 120 W X-band internally-matched AlGaN/GaN PA under continues wave (CW) condition is presented. The proposed power amplifier can provide a relatively stable output power above 50.6 dBm (115 W) and power added efficiency above 42% from 7.7 GHz to 8.7 GHz, while maintain a stable gain above 10.1 dB. This work is relatively competitive comparing with other state-of-the-art works.
© 2016 European Association of Antennas and Propagation. By utilizing inherently generated TM11 and TM02 modes of a patch antenna, a new dual-band dual-mode antenna is proposed for off-/on-body centric communication. The antenna consists of a simple probe-fed circular patch with a shorting pin and two arc-shaped slots, which are added to tune the resonances of the corresponding modes to the desired frequencies of 2.45 and 5.8 GHz. A broadside radiation pattern suitable for off-body communication and a monopole-like radiation pattern for on-body communication are thereby provided at each frequency, respectively. To determine the human body's effect on the antenna performance, a study has been conducted through simulations in both free space and on a human body-equivalent phantom. The results reveal a robust performance of the antenna against the human body loading, which indicates that the proposed antenna is a very promising candidate for body centric communications.
© 2015 IEEE. A novel idea of applying a proposed radio frequency transducer architecture for wireless monitoring of sleep apnoea patients has been presented in this article. The architecture has been realized on a primary prototype and tested from baseband to 2.5 GHz band. The experimental results prove that this architecture can be used for wireless sleep apnoea monitoring for the design of each portable transducer. The architecture will be finally realized on a system-on-chip prototype.
A novel portable wireless monitoring system for sleep apnoea diagnosis is presented in this paper. The presented system is composed of two main parts. The first is an on-body sensor system; the second is a reader and base station. In order to minimize the physical size of the on-body sensors and to avoid interference with 2.4 GHz wireless applications, the system is designed to operate in the 5.8 GHz ISM band. Each on-body sensor system consists of a physiological signal detection circuit, an analogue-to-digital convertor (ADC), a microcontroller (MCU), a transceiver, a channel selection bandpass filter (BPF) and a narrow band antenna. The reader uses 6 narrow band antennas, 6 channel selection BPFs, a transceiver and a MCU. Instead of dealing with channel selection at baseband, multiple passive BPFs at the RF front-end are adopted to select the desired signals, in order to minimize the power consumption and cost of the overall system. Moreover, a 5.8 GHz circular patch antenna is simulated and measured. Both the simulated return loss of 21 dB and the measured one of 26 dB have a 10 dB bandwidth of 140 MHz which satisfies the requirements for the reader system. The measured antenna gain from 5.725 GHz to 5.875 GHz is more than 7.5 dBi. Furthermore, the 3 dB beam-width is about 60° and the front to back ratio is 14 dB. © 2011 Engineers Australia.
UWB chipless RFID receivers require compact and low cost integration solutions aiming at improving the signal integrity. A wide stopband, high selectivity and compact microstrip lowpass filter (LPF) is therefore needed. A combination of compact microstrip resonant cells (CMRCs) and uniquely shaped defect ground structures (DGS) are used in present LPF design to optimize the filter performances. The stopband with an attenuation level lower than 20 dB is obtained from 3.1 GHz up to 20 GHz. Both simulated and measured results are presented, showing a good agreement between simulation and measurement. © 2011 Engineers Australia.
In this paper, a novel high selectivity compact dual planar microstrip bandpass filter (BPF) with compact ring resonator and two uniquely designed defected ground structures (DGSs) is proposed. By employing the inter-digital and spiral DGSs, the filter selectivity can be significantly enhanced with a wide suppression of higher order harmonics. The filter has a selectivity of 220 dB/GHz, passband insertion loss (IL) of 1.55 dB and bandwidth of 61 MHz at 2.53 GHz. Moreover, the proposed compact ring resonator saves 70.5% area compared to a conventional ring resonator. The significance of this BPF to be applied in wireless telemetry monitoring systems has been introduced in this paper. © 2011 Engineers Australia.
This paper proposes a parameter-dependent approach to robust fault detection and estimation problem for linear time-invariant (LTI) systems. The unknown input, actuator faults, sensor faults and disturbances are considered in our design. Through Projection lemma, we provide a sufficient affine matrix inequality for the integrated system in order to achieve robust performance criterion. In stead of obtaining the optimal solution by quadratic approach, we have used a parameter-dependent lyapunov approach which aimed at eliminating the involved coupling between system matrices and the lyapunov matrices; hence the conservativeness due to quadratic approach can be dramatically reduced. We present a design example in which we apply our method to a helicopter model. © 2008 IEEE.
Simorangkir, RBVB, Yang, Y, Esselle, K & Diao, Y 2017, 'A Varactor-Tuned Frequency-Reconfigurable Fabric Antenna Embedded in Polymer: Assessment of Suitability for Wearable Applications (TU3C)'. | CommonCrawl |
"The oloid is one of the only known objects, along with some members of the sphericon family, that while rolling, develops its entire surface."
Link to video of oloid rolling.
Link to video of sphericon rolling.
Q1. The phrasing of the Wikipedia sentence quoted above seems to allow the interpretation that it is unknown if there are other objects with the same rolling property. Is this the case? Or is there a proof that these are the only such objects?
Q2. Does anyone know where I can find a proof of this rolling property for either of these objects?
Here is a more general construction, which contains both the sphericon and the oloid as particular cases.
Take two intersecting planes, $\alpha$ and $\beta$.
Take two compact convex regions $A\subset\alpha$ and $B\subset\beta$.
Make sure that $A$ is split in two non-empty regions by the plane $\beta$, and $B$ by the plane $\alpha$.
Let $a=A\cap\beta$, and $b=B\cap\alpha$. Both sets $a-b$ and $b-a$ are nonempty.
The desired object is the convex hull of the union of the two planar convex regions, $A\cup B$. Let $S$ be its boundary.
Of course, because we the convex hull, in condition 2 we can drop the condition that the two planar regions are convex, but this doesn't increase generality.
Let $\partial A$ be the boundary of $A$ in the plane $\alpha$, and $\partial B$ the boundary of $B$ in the plane $\beta$.
A. Condition 3 implies that for any point $P$ on $\partial A$, there are two points $Q_1$ and $Q_2$ on $\partial B$, which are separated by the plane $\alpha$, hence the segments $PQ_1$ and $PQ_2$ are also separated by $\alpha$. This also holds for $B$.
B. From A, follows that if $P\in\partial A\cap S$, there are two points $Q_1,Q_2\in\partial B\cap S$, so that the segments $PQ_1,PQ_2\subset S$.
C. From condition 3, and remarks A and B, and the definition of convex hull, it follows that $S$ is the union of segments $PQ$, where $P\in\partial A\cap S$, and $Q\in\partial B\cap S$. If both $P$ and $Q$ would belong to $\partial A\cap S$, then by condition 3, the segment $PQ$ would be in the interior of the convex hull, so we can rule this possibility out.
D. From condition 4, $\partial A\cap S$ and $\partial B\cap S$ are open curves.
E. From D, and since the curves $\partial A\cap S$ and $\partial B\cap S$ don't intersect, the surface $S-(\partial A\cup\partial B)$ is connected.
F. By using my answer to another question, When is the hull of a space curve composed of developable patches?, the surface $S$ is made of developable patches. To apply that result, join the two open curves $\partial A\cap S$ and $\partial B\cap S$ by two curves which lie on $S$, so that the union is not self-intersected.
G. From C, E and F, the surface $S-PQ$ is developable, where $PQ$ is as in C.
H. During complete rolling cycle, the curve $\partial A\cap S$ is covered twice, once from one end to the other on one side, and once back, but on the other side. Similarly for $\partial B\cap S$.
Therefore, $S$ has the property that, when rolling, it develops its entire surface.
For both the sphericon and the oloid, we take $\alpha\perp\beta$.
For oloid, take $A$ and $B$ two disks, so that each disk has its center on the boundary of the other disk.
For sphericon, take $A$ and $B$ two identical hemidisks, each being symmetric w.r.t. $\alpha\cap\beta$, and so that their centers coincide with their intersection.
The generalization made by Manfred Weis in his comment is also included here.
It is easy to morph the oloid and the sphericon. Take $A',B'$ two identical disks, each being symmetric w.r.t. $\alpha\cap\beta$. Take a plane $\gamma$ through their mass center, perpendicular on $\alpha$ and $\beta$. Cut the circles by $\gamma$, and take $A$ as the part of $A'$ which contains the center of $A'$, and similarly for $B$. It is easy to see that the oloid and sphericon are particular cases of this construction, and by varying the distance between the centers of the disks, we can morph one into the other.
Q1. No, the sphericon and the oloid are not unique with these properties, there is an infinity of such objects. Perhaps not many were known.
Q2. In this answer, hopefully.
If the curves $\partial A\cap S$ and $\partial B\cap S$ are line segments, we obtain a tetrahedron. If they are each made of two segments, they can be chosen so that we get an octahedron.
In general, a convex polyhedron whose faces admit a Hamiltonian path, can be rolled so that it develops its entire surface, but is not necessarily obtained by the method I proposed.
One may want to rule out such cases, in which, after the rolling starts, the rolling is not unique, hence for which the contact between the object and the plane surface on which it is rolled is a (sur)face. One may want that at any point, the contact is along a segment. In this case, we have to add the condition that the curves $\partial A\cap S$ and $\partial B\cap S$ don't contain line segments.
Not the answer you're looking for? Browse other questions tagged reference-request dg.differential-geometry mg.metric-geometry classical-mechanics or ask your own question.
When is the convex hull of two space curves the union of lines?
Is there a sideways-walking rolling convex body?
When is the hull of a space curve composed of developable patches?
Which convex bodies roll along closed geodesics?
Is there a convex three-dimensional body with constant width and only finitely-many equilibria? Or: do spheroform gömböcök exist? | CommonCrawl |
"Systoles of arithmetic hyberbolic surfaces and 3-manifolds" by Benjamin Linowitz, D.B. McReynolds et al.
Our main result is that for any positive real number $x_0$, the set of commensurability classes of arithmetic hyperbolic 2- or 3-manifolds with fixed invariant trace field $k$ and systole bounded below by $x_0$ has density one within the set of all commensurability classes of arithmetic hyperbolic 2- or 3-manifolds with invariant trace field $k$. The proof relies upon bounds for the absolute logarithmic Weil height of algebraic integers due to Silverman, Brindza and Hajdu, as well as precise estimates for the number of rational quaternion algebras not admitting embeddings of any quadratic field having small discriminant. When the trace field is the rationals, using work of Granville and Soundararajan, we establish a stronger result that allows our constant lower bound to instead grow with the area/volume. As an application, we establish a systolic bound for arithmetic hyperbolic surfaces that is related to prior work of Buser-Sarnak and Katz-Schaps-Vishne. Finally, we establish an analogous density result for commensurability classes of arithmetic hyperbolic 3-manifolds with a small area totally geodesic surface.
Linowitz, Benjamin, D.B. McReynolds, P. Pollack, and L. Thompson. 2017. "Systoles of arithmetic hyberbolic surfaces and 3-manifolds." Mathematical Research Letters 24(5): 1497-1522. | CommonCrawl |
where $V$ is the volume of the solid, $\bar x$ is the coordinate of the centroid of the resulting solid, and dV is the element of volume, usually a disk, ring or shell. Because of symmetry of the solid that lies on its axis, we only need one coordinate to find its centroid.
We can imagine that we could create a solid figure by using very small cylindrical shells, so we will use the cylindrical shell method to get the whole volume.
The volume of the cylindrical shell element $dV$ is expressed as $2\pi x$ $\times$ $y$ $\times$ $dx$. | CommonCrawl |
A ring on which all finitely generated projectives modules are free but not all projectives are free?
Sorry if the question is naive: any nice example of such a ring or, better, of a class of such rings?
Cher Michel, these rings are uncommon.
1) Over a local ring ALL projective modules are free : this is a celebrated theorem due to Kaplansky.
And now for the good news: the rings you are after are uncommon but they exist. Bass in the article just quoted shows that the ring $R=\mathcal C([0,1])$ of continuous functions on the unit interval has all its finitely generated projective modules free. Nevertheless the ideal consisting of functions vanishing in a neighbourhood of zero (depending on the function) is projective, not finitely generated and not free. Bass attributes the result to Kaplansky.
Not the answer you're looking for? Browse other questions tagged projective-modules or ask your own question.
A finitely generated, locally free module over a domain which is not projective?
What is the insight of Quillen's proof that all projective modules over a polynomial ring are free?
Nonfree projective module over a regular UFD?
Must a finitely generated projective module over a group ring with vanishing coinvariants be trivial?
Is projectivity preserved by invariants?
When is countable direct-product of projective modules again projective ?
Finitely generated submodules of projectives lie inside f. g. projectives? | CommonCrawl |
Must the calculation of such matrix norm be NP-hard?
You claim that usual matrix norms do not work because of the $|f(x_1)-f(x_2)|$ criterion, but if $f$ is differentiable, then given any $x_1$ it is Lipschitz in some neighborhood of $x_1$ (with a constant that may depend on $x_1$), and hence $|f(x_1)-f(x_2)|\leq C \|x_1(:)-x_2(:)\|_1$. Did I miss something?
Not the answer you're looking for? Browse other questions tagged na.numerical-analysis matrix-analysis matrix-theory norms np or ask your own question.
What are the upper bound and stability conditions for the following simple linear system?
How to find moment condition for generalized method of moments?
Is there a matrix that converts the gradient of every possible function to gradient of other function?
How to show that a continuous family of symmetric matrices is uniformly positive? | CommonCrawl |
Brothers, cousins, and foes - what am I?
I am one of many siblings in a great family.
Because each of us has a clear worst enemy.
We never hide our hatred for each other.
Wave at my eldest brother and he becomes me.
She too can turn into me, in her gentle way.
So smooth and perfect that he'll always outstrip me.
Often he even steals my words, confusing all concerned.
1) As @KeithS worked out, the answer is something in pure maths, and more abstract than anything anyone has tried so far. You need to know a bit of undergraduate-level maths, at the level of basic topology and group theory.
2) Every line has a thought-out meaning, so you need to find a solution that matches everything from "we never hide our hatred for each other" to "he'll always outstrip me". I could give you a word for each of the "family", "siblings", "cousin", "eldest brother", and "younger brother". About the only red herring is "in her gentle way", which is just a nod to Thomas Hardy.
The answer is a mathematical object which someone has mentioned (not proposing it as an answer, but just mentioning it in passing) in one of the responses below. I won't say which one!
I am the only one who can go directly to Leipzig from a well-policed city.
a homeomorphism. i.e. an isomorphism between two topological spaces. I am continuous and so is my inverse.
the set of invertible functions. Our clear worst enemy is the inverse function.
a homomorphism. When she "finds the end of her life" (the letter e), and adds it to herself, it forms my name.
A diffeomorphism. i.e. an isomorphism over a differentiable manifold. It is a smooth function whose inverse is also smooth. Because smoothness is a higher restriction than continuousness, the younger brother outstrips me. However, people are often confused about the difference between smooth and continuous.
We are the most perfect of our race, Because each of us has a clear worst enemy.
My foe - I know him well - is much like me, But we continually fight each other; We never hide our hatred for each other.
When my dear cousin finds the end of her life, She too can turn into me, in her gentle way.
My younger brother thinks too highly of himself, So smooth and perfect that he'll always outstrip me. Often he even steals my words, confusing all concerned.
an Electron? in a high energy orbital?
I am one of many siblings in a great family. We are the most perfect of our race, Because each of us has a clear worst enemy.
Worst enemies: Sine -> Cosecant, Cosine -> Secant and Tangent -> Cotangent. Perfect: describe a circle.
Wave at my eldest brother and he becomes me. When my dear cousin finds the end of her life, She too can turn into me, in her gentle way.
Sine turns to cosine or Secant and Cosecant.
foe/enemy is much like me: inverse functions have very similar properties to that of the original function. But we continually fight each other: inverse functions are the same graph but with the axis changed.
Wave at my eldest brother and he becomes me. When my dear cousin finds the end of her life, She too can turn into me, in her gentle way. My younger brother thinks too highly of himself, So smooth and perfect that he'll always outstrip me.
I think this is talking about the integral and derivative.
Same family. could both be called exponential functions?
An integer is a whole number ('perfect') with a clear worst enemy, its negative value.
For every integer, the opposite integer exists, 'fighting' each other.
A 'waving' motion in real life looks similar to a '-' or minus sign, so it could just simply be saying 'subtract from my older brother and he becomes me', which would be true, assuming the 'older brother' is just a higher integer. For the cousin one, the character mentions he is one of many siblings (a brother or sister) in a great family, so the cousin may be referring to a non-integer floating point number. She 'turns into' an integer by rounding up or down.
The younger brother is the integer 0 ('smooth and perfect'), and thinks highly of himself because he is his own opposite. He steals the 'words' of other integers by taking their beginning numbers (1, 3) and adding to them (10, 30), 'stealing' part of their values.
The narrator is x -> e ^ x (e is the Euler–Mascheroni constant), and the family is the set of all exponential functions, x -> a ^ x, a is real.
Race means the set of all functions. Perfect because of the nice properties about derivatives also being exponential functions.
Worst enemy means inverse, in this case (natural) logarithic function.
x -> log(x) has many similar properties to the exponential function.
Both the exponential and logarithm functions are continuous.
I think the eldest brother is x -> a ^ x where a < e. There is a transformation from the eldest brother function to the narrator function. The word wave is a reference to the fact that the exponential function can be constructed from sine and cosine "wave" functions.
I think the cousin is x -> e ^ -x. As x increases towards positive infinity, this function decreases towards zero.
There is a transformation from one function to the other.
By the same logic as the younger brother, this must be x -> a ^ x where a > e. (Probably a = 10; see below.) This function will return values greater than the narrator function for all x > 0.
The exponential functions are infinitely differentiable (smooth). Outstrip me means the same as "thinks too highly of himself".
"Exponential function" can refer specifically to x -> e ^ x, or to the more general family of functions. In particular, x -> 10 ^ x is often confusingly referred to as the exponential function.
well, this one I am not sure, factorial maybe?
Family is the universal set, and siblings probably means those in the same class.
Race refer to all relations. We are perfect because we are equivalence, and being equivalence, we have an inverse relation that are "perfect" too. That, my friend, is my worst enemy.
He is indeed a perfect creature, just like me.
Indeed, one can easily find the inverse relation when given an equivalence, nothing to hide.
Yeah of course, we are equivalent, so if I am x, and my brother is y, x ~ y. Awesome.
I'm not so sure, maybe some clousure under certain operator. Strictly speaking, I did not have any education in sets and relations yet, so my knowledge is limited here. Tried my best.
Well, we can represent a certain partition with just a single element. Like maybe the n ≡ k modulo 3 operator, we can represents all multiple of 3, which includes 6, 9, ... 3k by . It's really stealing my identity as the holy go-to person for all questions, 42.
Pretty sure this isn't correct. I feel like there is too many holes that I only breifly dealt with. Just post this because it might be one interesting answer.
I know this isn't going to be the answer, but just wanted to share my thoughs.
Positive Infinity vs Negative Infinity. Which one is stronger ? Impossible to tell.
(positive) infinity - 1 ?
So smooth and perfect that he'll always outstrip me. Often he even steals my words, confusing all concerned.
(positive) infinity - 1 is not really infinity, but is so great that it can be assumed as infinity aswell... or so. XD.
Young stars often burn through their energy quickly. Young being relative.
Because each of us has a clear worst enemy. My foe - I know him well - is much like me, But we continually fight each other; We never hide our hatred for each other.
The sine function is a periodic one. It can not overcome the +1 / -1 limits.
The cousin is the cosine: sin($\alpha$ +$\pi/2$ ) = - cos($\alpha$ ).
The dear cousing is a McLaurin /Taylor series If n$\rightarrow$ $\infty$, the series is really the same as sin.
my own integral, he is a higher order function, he is also a smoother function, he also includes all of my own terms and adds some more of his own.
0's applied to a matrix remove data that can never be recovered. this is the same as him stealing my words confusing all concerned.
I'm not sure why he thinks so highly of himself though.
The intersection function function which corresponds to a union function would either be defined in terms of it, it would have the same parameters. Or you might be getting at the fact the symbols for these operations are vertically symmetrical opposites?
This is the summation function, which can incrementally add set elements until reaching the same set membership as the union function would create.
The younger brother would be the recursion function, who would be able to defining himself in terms of the original union function. Recursion functions are just generally quite confusing!
I believe that the Leipzig reference is a reference to Leibniz (not because they sound similar, rather than Leibniz being born in Leipzig, the Uni at Leipzig, etc.). So following this train of thought, we arrive at a lot of philosophy and maths. Topology and calculus, to be precise.
I have two suggestions, first - fractals, defined with functions that can have their inverse. Fractals are self-similar, which explains why age difference is a thing in the family. As each member becomes older, they get more-complex (higher-definition of sorts). That is why the smaller brother is smoother.
The second suggestion is about manifolds. A manifold can have different spatial properties depending on "scale". For example the area around each point on a sphere resembles Euclidean space when the area is small enough. Each manifold is defined by a function and the enemies are the inverse?
Not the answer you're looking for? Browse other questions tagged mathematics riddle or ask your own question.
That which I am 2 - who are we?
Help me beat my friend at hide-n-seek! | CommonCrawl |
Kim, N. (2004). Multi-spin strings on AdS5 x T1,1 and operators of N=1 superconformal theory. Physical Review D, 69(12): 126002.
Abstract: We study rotating strings with multiple spins in the background of $AdS5 times T1,1, which is dual to a $\cN=1$ superconformal field theory with global symmetry $SU(2)\times SU(2)\times U(1)$ via the AdS/CFT correspondence. We analyse the limiting behaviour of macroscopic strings and discuss the identification of the dual operators and how their anomalous dimensions should behave as the global charges vary. A class of string solutions we find are dual to operators in SU(2) subsector, and our result implies that the one-loop planar dilatation operator restricted to the SU(2) subsector should be equivalent to the hamiltonian of the integrable Heisenberg spin chain. | CommonCrawl |
Abstract: The standard Hopfield model for associative neural networks accounts for biological Hebbian learning and acts as the harmonic oscillator for pattern recognition, however its maximal storage capacity is $\alpha \sim 0.14$, far from the theoretical bound for symmetric networks, i.e. $\alpha =1$. Inspired by sleeping and dreaming mechanisms in mammal brains, we propose an extension of this model displaying the standard on-line (awake) learning mechanism (that allows the storage of external information in terms of patterns) and an off-line (sleep) unlearning$\&$consolidating mechanism (that allows spurious-pattern removal and pure-pattern reinforcement): this obtained daily prescription is able to saturate the theoretical bound $\alpha=1$, remaining also extremely robust against thermal noise. Both neural and synaptic features are analyzed both analytically and numerically. In particular, beyond obtaining a phase diagram for neural dynamics, we focus on synaptic plasticity and we give explicit prescriptions on the temporal evolution of the synaptic matrix. We analytically prove that our algorithm makes the Hebbian kernel converge with high probability to the projection matrix built over the pure stored patterns. Furthermore, we obtain a sharp and explicit estimate for the "sleep rate" in order to ensure such a convergence. Finally, we run extensive numerical simulations (mainly Monte Carlo sampling) to check the approximations underlying the analytical investigations (e.g., we developed the whole theory at the so called replica-symmetric level, as standard in the Amit-Gutfreund-Sompolinsky reference framework) and possible finite-size effects, finding overall full agreement with the theory. | CommonCrawl |
The table below gives some information about the points scored by Arjun in AHC (All Hastin Championship), in each of five different mind games-Dice, Dance, Dupe, Digit and Dynasty.
for every successful attempt Anon gets one point and for every unattempted problem he loses 1/6th of a point and for every failure he loses 1/3rd of a point.
the number of failures of Arjun in Digit is 1/6th of his total number of failures and twice his number of failures in Dance.
Adonis net score in Dance is double that in Dupe.
Q3. What is the number of problems attempted by Arjun in Dance?
Q4. What is the net score of Arjun in Dynasty?
Arjun attempted 125 problems and got 67 points i.e., he already lost $60 \times 1 / 6 = 10$ points for unattempted problems and for every failure he loses another 4/3 (1 mark of the question and 1/3 rd negative marks) points of this 115 points.
Now, sum of number of unattempted problems and successful attempts in Digit is 34 and as the total score in Digit is a integer. the number of unattempted problems must be a multiple of 6. | CommonCrawl |
Abstract: We study regular, static, spherically symmetric solutions of Yang-Mills theories employing higher order invariants of the field strength coupled to gravity in $d$ dimensions. We consider models with only two such invariants characterised by integers $p$ and $q$. These models depend on one dimensionless parameter $\alpha$ leading to one-parameter families of regular solutions, obtainable by numerical solution of the corresponding boundary value problem. Much emphasis is put on an analytical understanding of the numerical results. | CommonCrawl |
Wherever there is large-scale construction, you will find cranes that do the lifting. One hardly ever thinks about what marvelous examples of engineering cranes are: a structure of (relatively) little weight that can lift much heavier loads. But even the best-built cranes may have a limit on how much weight they can lift.
The Association of Crane Manufacturers (ACM) needs a program to compute the range of weights that a crane can lift. Since cranes are symmetric, ACM engineers have decided to consider only a cross section of each crane, which can be viewed as a polygon resting on the $x$-axis.
Figure 1 shows a cross section of the crane in the first sample input. Assume that every $1 \times 1$ unit of crane cross section weighs 1 kilogram and that the weight to be lifted will be attached at one of the polygon vertices (indicated by the arrow in Figure 1). Write a program that determines the weight range for which the crane will not topple to the left or to the right.
The input consists of a single test case. The test case starts with a single integer $n$ ($3 \le n \le 100$), the number of points of the polygon used to describe the crane's shape. The following $n$ pairs of integers $x_ i, y_ i$ ($-2\, 000 \le x_ i \le 2\, 000, 0 \le y_ i \le 2\, 000$) are the coordinates of the polygon points in order. The weight is attached at the first polygon point and at least two polygon points are lying on the $x$-axis.
Display the weight range (in kilograms) that can be attached to the crane without the crane toppling over. If the range is $[a,b]$, display $\lfloor a \rfloor $ .. $\lceil b \rceil $. For example, if the range is $[1.5,13.3]$, display 1 .. 14. If the range is $[a,\infty )$, display $\lfloor a \rfloor $ .. inf. If the crane cannot carry any weight, display unstable instead. | CommonCrawl |
Sage is capable of executing most vector operations, including dot products, cross products, and Euclidean norms.
We can calculate the cross product $\mathbf u \times \mathbf v$ of $\mathbf u = (1, 3/2, -1)$ and $\mathbf v = (1, 8, -2)$.
We can calculate the Euclidean norm of $\mathbf v$ of $\mathbf v = (1, 8, -2)$.
Primary Tags: Linear Algebra: Vector geometry; Multivariable Calculus: Vector geometry.
Secondary Tags: Vector geometry: Dot product, length, and unit vectors; Cross product.
Vectors in Sage. Vectors in Sage. | CommonCrawl |
Abstract: This is the first in a series of papers devoted to the theory of decomposition spaces, a general framework for incidence algebras and Möbius inversion, where algebraic identities are realised by taking homotopy cardinality of equivalences of $\infty$-groupoids. A decomposition space is a simplicial $\infty$-groupoid satisfying an exactness condition, weaker than the Segal condition, expressed in terms of active and inert maps in Delta. Just as the Segal condition expresses composition, the new condition expresses decomposition, and there is an abundance of examples in combinatorics. After establishing some basic properties of decomposition spaces, the main result of this first paper shows that to any decomposition space there is an associated incidence coalgebra, spanned by the space of 1-simplices, and with coefficients in $\infty$-groupoids. We take a functorial viewpoint throughout, emphasising conservative ULF functors; these induce coalgebra homomorphisms. Reduction procedures in the classical theory of incidence coalgebras are examples of this notion, and many are examples of decalage of decomposition spaces. An interesting class of examples of decomposition spaces beyond Segal spaces is provided by Hall algebras: the Waldhausen S-construction of an abelian (or stable infinity) category is shown to be a decomposition space. Note: The notion of decomposition space was arrived at independently by Dyckerhoff and Kapranov (arXiv:1212.3563) who call them unital 2-Segal spaces. Our theory is quite orthogonal to theirs: the definitions are different in spirit and appearance, and the theories differ in terms of motivation, examples and directions. | CommonCrawl |
Is it possible to put the scale factor in youre best cp plugin ?
Very handy that scale factor !
But when I put CP in front of nr , all get mixed up !
can not get this plugin to clear at score.
so it looks realy messy !
$xml.='<quad scale="'.$scale.'" posn="' .$x_quad_cp. " "
The xml config from the download of v1.5 is still needed with this.
The above : copy and past and save as plugin. thats all ?
Ok I will try it , and let you know if it works .
Do you have time to look into a cp plugin ?
I found a realy nice one , but it's very small.
I can not get it bigger, may I pm you about that ?
Oke Ant , I installed like you said.
It's working !!! Thanks man.
Btw can this shutdown ( dissapear ) at score also done with fufimenu ?
I have fufimenu at standard place , and at score it overlaps: Top rank. | CommonCrawl |
Abstract. Let $f(\varphi)$ be a positive continuous function on $0\leq\varphi\leq\Theta$ , where $\Theta\leq2\pi$ , and let $\xi$ be the number of two-dimensional lattice points in the domain $\Pi_R(f)$ between the curves $r=(R+c_1/R)f(\varphi)$ and $r=(R+c_2/R)f(\varphi)$ , where $c_1<c_2$ are fixed. Randomizing the function $f$ according to a probability law $\bold P$ , and the parameter $R$ according to the uniform distribution $\mu_L$ on the interval $[a_1L,a_2L]$ , Sinai showed that the distribution of $\xi$ under $\bold P\times\mu_L$ converges to a mixture of the Poisson distributions as $L\to\infty$ . Later Major showed that for $\bold P$-almost all $f$ , the distribution of $\xi$ under $\mu_L$ converges to a Poisson distribution as $L\to\infty$ . In this note, we shall give shorter and more transparent proofs to these interesting theorems, at the same time extending the class of $\bold P$ and strengthening the statement of Sinai. | CommonCrawl |
Abstract: Let $G\subset\mathbb C\times\mathbb R$ be a domain such that $G\times\mathbb R\subset\mathbb C^2$ is strictly pseudoconvex and let $U\subset bG$ be an open subset. We define the hull $\mathscr E(U)$ with respect to the algebra $\mathscr A(G\times\mathbb R)$ and study its properties. It is proved that every continuous function on $U$ can be extended to a continuous function on $\mathscr E(U)$ whose graph is locally foliated by holomorphic curves. | CommonCrawl |
Is it possible to unify the strong, weak, electric and magnetic field just by Maxwellian type equations? (Maxwell by adding a small change - unified electric and magnetic field, then Einstein's equations - use it to create special and general theory of relativity, now maybe all we need is a little more change to unify all fields,) When $B$ and $E$ are known magnetic and electric fields, then $W$ and $S$ are weak and strong fields, what are their units?
I dont understand your question, Perhaps you are referring to the standard model.
You've got some catching up to do! Look up "Yang-Mills Theory". From Wiki: Yang–Mills theory seeks to describe the behavior of elementary particles using these non-Abelian Lie groups and is at the core of the unification of the Weak and Electromagnetic force (i.e. U(1) × SU(2)) as well as Quantum Chromodynamics, the theory of the Strong force (based on SU(3)). Thus it forms the basis of our current understanding of particle physics, the Standard Model.
What do you mean by "strong field" and "weak field" ...? This question looks very confused to me.
What Alfred Centauri said. The weak and strong theories are generalisations of ordinary electromagnetism. So for the strong force their are chromo-electric and chromo-magnetic fields (actually eight of each) and for the weak force there are weak-electric and weak-magnetic fields (actually three of each). These follow a close analogy to ordinary E&M (although the theories are much more complicated). It is less common to work with the electric & magnetic fields than the vector potentials for technical reasons, but they exist.
I'm guessing at what you're asking - ignore this answer if I've misunderstood you.
Maxwell's equations describe the classical behaviour of electromagnetism. They can only do this because the EM forces are long range so at macroscopic distances they behave classically. By contrast, the weak and strong forces are short range and cease to act over anything like the classical limit of distance. There is no classical approximation to describe the weak and strong forces, so there is no analogy to Maxwell's equation.
Above the electroweak transition the electroweak force will become long range. Whether there is some classical limit in the spirit of the Maxwell's equations is a good question and I don't know the answer. I would guess that there is no such limit for the strong force even about the EW transition because the force will still be confined.
At high enough temperature and energy density, the strong force stops confining. This plays a role in the standard stories of the early universe.
Ah yes, as in the quark gluon plasma. I bet there's still no (useful) classic long distance description though.
Depends on what you mean by "unify" If you just mean "describe", then it's simple. We have the Standard Model with it's exceedingly simple Lagrangian Density formed by adding Yang - Mills & Dirac fields to Klein - Gordon fields.
Here, it is easy to identify the Yang Mills field for gluons et al, the Dirac Fields for the quwarks et al, the Klein - Gordon for the Higgs, a scalar field.
If you mean "unify" in the sense of grand unification and such, then it's a bit more complicated.
Refers to the unification (meaning: having a simple group as the gauge group, as opposed to the Standard Model whose gauge group is $SU(3)\times SU(2)\times U(1)$; yet describe the Standard Model, since it's experimentally verified to a pretty high degree).
$E(6)$ GUT Gauge group $E(6)$.
Better than GUTs; unify (quantised) gravity too. Examples include string-theory. | CommonCrawl |
I have a set of sample time-series data below of monthly prices for two companies.
Q1. I want to calculate monthly and quarterly log returns.what is the most expedient way to do this? TimeSeriesAggregate only has the standard Mean, etc.
Q2. With the returns from Q1, what is the most expedient method to calculate the correlation of the monthly returns between the two companies?
Q3. How would it be possible to calculate six-monthly log returns and then create a series of overlapping $6m \log$ returns so I can derive $7\times 6M$ outcomes from the limited dataset below; i.e. [1m-6m, 2m-7m, 3m-8m, ...] (and then calculate a correlation between these)?
The code below was written with the assumption that you want to keep your data within TimeSeries objects. (Since you mention "time-series data" and TimeSeriesAggregate.) That is not necessary with the regular grid of dates in the data you provided; you could use simple lists of numbers instead.
You can redefine LogReturn accordingly.
Q1. TimeSeriesAggregate works with any function, it maps over non-overlaping windows.
Q3. Use MovingMap to map over overlapping windows.
Not the answer you're looking for? Browse other questions tagged time-series or ask your own question.
How to slice TimeSeries data?
How to prevent TimeSeries adding TimeObject parameter and TimeZone option to DateObjects?
Inconsistent arithmetic of TimeSeries with non-equally spaced data? | CommonCrawl |
Audio normalization and noise reduction is a vital part for robust speech recognition in various environment. Unfortunately Julius has no modern normalization or noise reduction techniques in it, just offers some basic methods.
Note that the recognition results may not be the same between live audio input and file input, even for equivalent audio data. It is due to the approximation of cepstral mean normalization at live audio input as described below.
Here is a brief summary of currently implemented methods.
Julius has two different implementation of DC offset removal.
-zmean enables input-wise offset removal. For buffered processing (i.e. file input), the offset is estimated for each input by computing the mean of the whole input. For stream proccessing (live audio input and network input), the offset will be determined from the mean of the first 48,000 samples (3 seconds in 16kHz sampling), and removal will be performed for the rest samples. This process is performed prior to all audio processing.
-zmeanframe enables frame-wise offset removal. The offset is estimated per windowed samples and subtracted within the frame. This behavior is equivalent to HTK's ZMEANSOURCE, and performed at the first stage of feature extraction.
In most cases -zmeanframe is sufficient. This works the same in both buffered processing and stream processing.
A simple spectral subtraction can be used to reduce effect of stationary noise. No dynamic update of the noise spectrum is implemented, i.e., the noise spectrum should be estimated statically before speech process. There are two ways.
Compute the average spectrum of first 300 msec of every input and subtract it from the rest input as noise spectrum (-sscalc). Available for buffered processing only.
Compute average spectrum from noise-only audio beforehand by the tool mkss, and apply it with -ssload. Available for both buffered and stream input.
Tweaking options of spectral subtractions are -sscalclen, -ssalpha and -ssfloor.
Note that spectral subtraction is performed inside AM instance: those options are categorized as AM. When using multiple acoustic model, the spectral subtraction should be set up at each module.
Cepstral mean normalization (CMN) and variance normalization (CVN) are standard techniques to compensate long-term spectral effects caused by different microphones and audio channels. CMN subtracts the mean vector from each input frame. Additionally, CVN will normalize the variance. When CMN and CVN are enabled, features are normalized to $N(0, 1)$. Note that mean normalization will be performed for static coefficients, whereas variance normalization will be for all vector dimensions. Of course, when using CMN/CVN you should have acoustic model trained with CMN/CVN.
The CMN will be enabled automatically when using acoustic model trained with CMN, i.e., the feature parameter of acoustic model has CMN qualifier "_Z".
Variance normalization should be enabled manually by option -cvn. Note that CVN alone is not supported, use CVN with CMN. At Julius, CMN only or CMN+CVN is allowed.
At buffered processing like file input, both mean normalization and variance normalization will be performed per input: all samples of an input file are read into memory first, and then their mean and variance of the whole input are computed. Then normalization will be applied using the values.
The weight $w$ can be changed by option -cmnmapweight. Note that only mean is updated at each frame, and variance will be kept within an input.
At stream processing, after each input has been processed and recognition result was obtained, the generic mean/variance values will be re-computed to fit the current environment by calculating the mean/variance of the recent five seconds of the input by default. The re-computed generic mean/variance will be then applied as the initial values for the next input. Option -cmnnoupdate disable this generic mean/variance updates.
When -cmnload is set on stream processing, Julius performs MAP-CMN using the given values as the first initial generic mean. If the file contains variance, it will be applied for CVN. Please note that for variance normalization the given value will be streated as static: it will be kept during recognition and not updated while recognition.
When -cmnload is not set, Julius start with zero mean and variance, so the first utterance will not be recognized correctly. When -cmnsave is specified, the generic mean and variance, being computed from the last 5 seconds, will be saved to file at every input ends.
If you do not want to update the general mean while recognition and keep the starting values from -cmnload for the initial values at each stream input, set -cmnnoupdate.
You may want to use a static mean and variance unchanged for all frames. The static CMN can be performed by setting option -cmnstatic together with -cmnload. In that case, at both stream processing and buffered processing, the given mean and variance will be applied for all input frames. Another option -cvnstatic can be used to apply static normalization for variance only but leave mean as normal behavior (MEAN ignored in the loaded file).
Here is the summary of CMN / CVN algorithm being applied when the options are specified. Note that parameter qualifier "_Z" in the given acoustic model is required in all situation to enable CMN and/or CVN.
- self mean CMN / self var CVN MAP-CMN, no init, update / CVN, no init, last 5 sec.
Option -vtln enables a frequency warping function, so called vocal tract length normalization (VTLN). This can be applied as a simple speaker normalization that compensates speaker's vocal tract size.
It is a simple linear function, controlled by a warping factor $\alpha$ and warping frequency boundaries. The algorithm and parameter values are the same as HTK's VTLN feature. HTK's configuration variables WARPFREQ, WARPHCUTOFF and WARPLCUTOFF can be applied as is.
Unfortunately Julius has no searching scheme to find a working warping factor for given input. | CommonCrawl |
Given the polynomial $f = (xy-yx)z \in \mathbb R[x,y,z]$, how can I evaluate it on matrices?
Given the polynomial $f = (xy-yx)z \in \mathbb R[x,y,z]$, Q[x,y,z]$, how can I evaluate it on matrices?
Given the polynomial $f = (xy-yx)z \in \mathbb Q[x,y,z]$, how How can I evaluate it on matrices?construct a map $M_2(\mathbb Q)^3 \to M_2(\mathbb Q), (A,B,C) \to (AB-BA)C$ where $M_2(\mathbb Q)$ denotes the space of 2x2 matrices.
How can I construct a map $M_2(\mathbb Q)^3 \to M_2(\mathbb Q), (A,B,C) \to (AB-BA)C$ where $M_2(\mathbb Q)$ denotes the space of 2x2 matrices.
How can I construct a map $M_2(\mathbb Q)^3 \to M_2(\mathbb Q), (A,B,C) \to \mapsto (AB-BA)C$ where $M_2(\mathbb Q)$ denotes the space of 2x2 matrices. | CommonCrawl |
Please help by writing tag wikis for your favorite tags!
Use answers to this post to suggest tag synonyms.
Finally, if you're a 10k+ user, note how easy it is for you to edit tags now!
From Redesigned Tags Page on SE Blog.
We just got a question tagged icm-2014 and we have icm-2010 (with two closed questions tagged with it).
I think it is not necessary to have separate tags here and one ICMs tag should suffice.
Actually, I do not even think this ICM tag is necessary, conferences should suffice.
There are tags lattices and lattice-theory, both being used for the two unrelated meanings "partial order with binary suprema and infima" and "discrete subgroup of $\mathbb R^n$". I'm not sure it's feasible to sort out the ~300 questions involved, but maybe we could try at least to alleviate the problem for future by deciding which tag is supposed to denote which meaning, renaming them unambiguously, and supplying tag summaries. If not, the tags should be merged.
In addition to that, duality is a word which is used in several different - although related - meanings.
I suggest to create a separate tag dual-spaces for questions about dual spaces of vector spaces, linear normed spaces, etc.
Tag 'kahler': I was wondering if the tag 'kahler' should be renamed 'kahler-manifolds' (or something like it), so as to make it more descriptive and less prone to confusion. I have browsed through all the questions with the tag 'kahler' and all of them are indeed about Kähler manifolds. This means the renaming would be an easy process, but it may also mean that it is not necessary. Any opinions?
Update: The tag 'kahler' no longer exists and 'kahler-manifolds' now exists in its place.
Tag 'differential-graded-lie-a': Here is another suggestion that may or may not be desired. Due to the character limit for tags, some long tags may become hard to understand. The worst offender I have found so far is 'differential-graded-lie-a' (with only two questions). This could very well be made a synonym of 'dg-lie-algebras' if people think there is a benefit.
I suggest to rename the tag divisors in a way which distinguishes it more clearly from divisors-multiples.
For questions related to divisors in the sense of algebraic geometry (Cartier divisors, Weil divisors and so on). For question on divisors in the number theoretic sense please use the tag divisors-multiples.
I am not really sure what would be a good name for the tag. So I'd be grateful if you have some reasonable suggestions in comments.
I would probably suggests simply divisors-algebraic-geometry following the title used in Wikipedia article Divisor (algebraic geometry). I have seen that Ricardo Andrade suggested scheme-divisors in chat. Joe Berner mentioned the (already existing) tag algebraic-cycles, but immediately added also that algebraic cycles and divisors are not the same thing, so these two tags should stay separate. See also his comment below this post.
A few years ago a separate question about divisors tag was posted: What subject specific tags could replace the tag 'divisors'? However, it did not generate much discussion (only two comments).
Maybe generalized-functions and schwartz-distributions should be made synonyms? I think technically the latter is a subset of the former, since the former can also cover Coloumbeau distributions.
Resolved: The tag synonym has been created.
The tag history has been created a few days ago. This tag has been created a couple of times in the past and usually replaced by ho.history-overview.
I think that the synonym history $\to$ ho.history-overview would be useful. If not for other reason, just to save the effort going into repeated removal of the tag.
Based on the reception of the question Pronunciation questions (currently at score 22) it seems that questions about pronunciation are on-topic on this site (within some reasonable limits).
I suggest creating pronunciation tag for questions asking about pronunciation of mathematical terms, mathematical symbols and notation, names of mathematicians, etc. If we have a tag for such questions, this would make easier for the poster of a new question to check whether his question has been asked before.
I will add that (pronunciation) tag exists on Mathematics site.
I'd like to propose creation of continuum-theory tag.
Quick search reveals several questions on the main with the word continuum or continua - of course, sometimes this word might be used in different meanings, but if you browse a bit among the search results you can see that several of those question are from this area or closely related to this topic.
The tag called (continuum-theory) also exists on Mathematics site. (See also the tag-info.) Since it's creation in September it attracted 11 questions.
For some time there was concavity tag, see here. The tag was later deleted by an automated process which removed the tags which removes the tags used on single questions after certain time (unless the tag has a tag-wiki). As a result, the question where the tag was created is currently tagged untagged - since it was the only tag there.
Mathematical questions related to mathematical software systems such as Sage, Mathematica, Maple, Pari/GP, and GAP. Note that troubleshooting questions are generally considered off-topic.
If there are reasons to keep them separate, editing the tag-info for both tags to make the distinction clearer would be useful.
I will also mention that some programs have separate tag. For example, gap, sage, coq, magma, and maybe some others I did not notice.
Resolved: Both the suggested tag and the suggested tag-synonym have been created.
Maybe on-topic tag could be created on meta and made a synonym of allowed-questions.
I think that it is quite probable that users asking about question which are on topic might look for a tag with a similar name. Several metas in SE network have a tag called (on-topic).
If the consensus is that the tag small-uncountable-cardinals would be too specific and it is better not to create such tag, I would be grateful also for comments suggesting which tags can be used for questions where small uncountable cardinals are the main topic. In the past I have sometimes added infinite-combinatorics to such questions - was it a reasonable choice?
I think stone-cech should be a synonym of compactification (and the latter might be pluralized); at least I think stone-cech should be renamed to stone-cech-compactification (minus some characters to fit the limit).
There was tag open-problems-list for questions asking list of open problems in certain area or more generally satisfying certain criteria.
But it disappeared recently. I do not think it is good. Can we revert it?
There is tag "open-problems" but that tag is very general and there too many questions on specific open problems, so it is not convenient to find "open problem LISTs" questions.
Create a closing tag on meta.
If there is some agreement that we should have both questions about closed questions and the process of closing questions under the same tag, this should be also added to the tag-excerpt/tag-wiki. And I think that on-hold questions could be included under the same tag.
I will add a comparison with other meta site - the one which I am most familiar with. On Mathematics Meta there are three separate tags closing, closed-questions and on-hold-questions. This sometimes makes users unsure which of the three tags to use.
I have previously asked about usefulness of potential on-hold-questions tag in MO editors' lounge. Todd Trimble replied that it's better to have them under the same tag as closed question.
I have noticed that there is a tag called interesting-tags on meta. It is actually one of the default tags - these are the tags that are automatically created on every new meta site and are not deleted even if they have zero questions.
On meta there are two tags searching and search. The latter is one of the default tags - these are the tags that are automatically created on every new meta site - which essentially means that it cannot be removed.
I would suggest creating a synonym search $\to$ searching. Having two tags for the same topic could lead to confusion which tag to choose and also to inconsistent usage of tags - and, consequently, this would make searching using tags a bit difficult.
I have mentioned this a few times in chat (October 2016, April 2018). Since I have not received any feedback there, I've decided to try my luck here on meta.
I suggest to create a tag synonym analysis-and-odes $\to$ ca.classical-analysis-and-odes.
The tag analysis-and-odes has only five questions and empty tag info - so it does not seem to have any distinction from ca.classical-analysis-and-odes. Four of the five questions in this tag were asked by the same user, but since thy no longer have account on MathOverflow, we cannot even ask them whether their intention was to create something different from the existing top-level tag. For the list of questions, see here and here.
A reasonable alternative would probably be also to remove the tag manually, but a synonym solves the problem without bumping old question. And another advantage is that if somebody tries to create this tag in the future, it will automatically be changed to the ca.classical-analysis-and-odes tag.
Not the answer you're looking for? Browse other questions tagged support tags 10k-tools . | CommonCrawl |
In this paper we consider approximations à la Sacks-Uhlenbeck of the harmonic energy for maps from $S^2$ into $S^2$. We continue the analysis in 6 about limits of $\alpha$-harmonic maps with uniformly bounded energy. Using a recent energy identity in 7, we obtain an optimal gap theorem for the $\alpha$-harmonic maps of degree $-1, 0$ or $1$. | CommonCrawl |
Does there exist a space filling curve which sends every convex set to a convex set ?
Does there exist a surjective continuous function $f:[0,1]\to [0,1]^2$ which maps every convex set to a convex set ?
Partial answer: Here is a discontinuous surjective function $f:[0,1]\rightarrow[0,1]^2$ that maps convex sets to convex sets. We can make sure every interval maps to the entire (convex) set $[0,1]^2$.
Let's say that two real numbers are in the same equivalence class if their unique decimal expansion (with no infinite tail of 9s) differs only in a finite number of digits. For example $0=0.0000...$, $1=1.0000...$, $1/2=0.50000...$ are all in the same equivalence class.
Let $A$ be the set of all equivalence classes. The cardinality of $A$ is the same as that of the reals, which is the same as that of $[0,1]^2$. So there is a surjective function $g:A\rightarrow [0,1]^2$. For each $x\in[0,1]$ let $a(x) \in A$ denote its equivalence class. Define $f:[0,1]\rightarrow[0,1]^2$ by $$ f(x) = g(a(x))$$ Let $I\subseteq[0,1]$ be an interval (containing more than one point). Then $I$ contains points from all equivalence classes in $A$, so $f(I)=[0,1]^2$.
All convex subsets $C \subseteq [0,1]$ that contain at least two distinct points must contain the interval between those points, so $f(C)=[0,1]^2$. And of course all single-point sets map to single-point sets.
Note: I originally overlooked the continuity requirement, as zhw notes below. So I have edited to emphasize that.
When does a continuous function defined on a closed and bounded convex set has a fixed point?
Given any non compact set $A \subset \mathbb R^n$ does there exist a continuous function $f: A \to \mathbb R$ which is not uniformly continuous?
A-noncompact, Does there always exist a continuous function $f: A \to \mathbb R$ which is bounded but does not assume extreme values?
Does there exist a continuous injection from $[0,1)$ to $(-1,1)$?
Does there exist an open map satisfying the following properties which is continuous?
Does there exist a convex function which is not strictly differentiable almost everywhere?
does there exist a smooth function which is nowhere convex/concave?
Does subdifferential function with non-convex dom exist? | CommonCrawl |
Transcript What are Quadratic Functions?
"You've seen the posters. You've seen the billboards. Now drink the drink. The question of the summer is about to be answered. The Quadratic Functions are proud to present a refreshing line of new drinks, Parabolica! Parabolica XTRA Strong is just amazing. It makes gravity work better!"
A quadratic equation, written in standard form, is equal to y=ax²+bx+c for all 'a's not equal to zero.
"Wanna be a quadratic function, too? Then the 2nd degree is the way to be! Tame your inner beast, just look at that beautiful parabola! Also from quadratic functions: Parabolica Chill! Try it! Feel the thrill of Parabolica Chill! This drink will give you energy, but not quite so much."
Ok, enough math, back to the energy drinks.
The sign of the 'a' value affects a parabola's direction. When the 'a' value is negative, the parabola is shaped like a frown. But when the 'a' value is positive, we can turn that frown upside down!
A quadratic function is represented by the standard form, y = ax2 + bx + c.
In order for such an equation to be a quadratic function, and not a linear one, we must have that the coefficient a is not equal to zero; i.e. a ≠ 0.
The graph of a quadratic function is a parabola. The larger the absolute value of a is, the thinner the shape of the parabola becomes. The smaller the absolute value, the wider the parabola becomes.
The coefficient a is also an indicator of the direction of the shape of the parabola. If the value of a is positive, the parabola opens upwards. If the value of a is negative, the parabola opens downwards.
Graph linear and quadratic functions and show intercepts, maxima and minima.
Du möchtest dein gelerntes Wissen anwenden? Mit den Aufgaben zum Video What are Quadratic Functions? kannst du es wiederholen und üben.
Decide if the given shape is a parabola.
A parabola looks like a rainbow or a smile.
A parabola doesn't have an angle.
Three of the given examples are parabolas.
A parabola is shaped like a rainbow.
Depending on the sign of $a$ you can determine the direction of the parabola; the parabola can look like a rainbow itself or smile.
The rollercoaster isn't a parabola at all.
Determine which functions are quadratic functions.
A quadratic function means that the hightest power is $2$.
For example, $y=mx+b$ is a linear function, where the highest power $1$.
So the highest power is $2$ and $a\neq 0$. Otherwise we would have a linear function $y=mx+n$.
$y=6x^2$ with $a=6$ and $b=c=0$.
$y=\frac12 x^2$ with $a=\frac12$ and $b=c=0$.
Describe a quadratic function and the role of $a$.
$y=3x^2-2$ is an example of a quadratic function.
Depending on $a$ you can decide the width of the parabola.
For example, let's see when the parabola $y=ax^2$ is thinner than $y=x^2$, and when $y=ax^2$ is wider than $y=x^2$.
The greater the absolute value of $a$, the thinner the parabola.
So when $a>1$, the parabola $y=ax^2$ is thinner than $y=x^2$.
And when $0<a<1$, the parabola $y=ax^2$ is wider than $y=x^2$.
Explain how to find the corresponding quadratic function.
The sign of $a$ determines if the corresponding parabola is opened upwards or downwards.
The larger the absolute value of $a$, the thinner the parabola. Similarly, the smaller the absolute value of $a$, the wider the parabola.
Here you see a parabola, the graph of a quadratic function.
How can you determine the corresponding equation?
Keep the standard form in mind: $y=ax^2+bx+c$.
The vertex of the parabola is the origin, so we have $b=c=0$ and thus that our equation is of the form $y=ax^2$.
The parabola is opened upwards. Thus we know that $a$ must be positive.
The parabola is thinner than the parabola corresponding to $y=x^2$ (i.e. the red parabola in the picture to the right). You can recognize this, for example, by looking at the point $(1,1)$ on $y=x^2$, and $(1,2)$ on the blue parabola in question. Thus $a$ must be greater than $1$.
To determine $a$, plug a point on the parabola into $y=ax^2$. For example, the point $(2,8)$ gives us $8=a\times 2^2$. Dividing by $4$ results in $a=2$.
And so the resulting quadratic function is $y=2x^2$.
Identify the value of the coefficient $a$ of each parabola.
One of the parabolas is the graph of $y=x^2$.
Each quadratic function has the form $y=ax^2$, with $b=c=0$.
Check the $(x,y)$ pairs lying on the parabola.
The parabola to the right is the graph of $y=x^2$. So $a=1$.
How can this be determined? Look at some $(x,y)$ points lying on the parabola: $(1,1)$, $(2,4)$, $(-1,1)$. All these points satisfy $y=x^2$.
The smallest $a$ is given by $a=\frac14$. The parabola corresponding to $y=\frac14x^2$ could be determined by the points $(2,1)$ and $(4,4)$.
Next we have $a=\frac12$, which can be determined via the points $(2,2)$ and $(1,0.5)$.
Then we have $a=1$, which is pictured here to the right.
Then we have the parabola which is the graph of $y=1.5x^2$; so $a=1.5$. This can be detected by the points $(1,1.5)$ or $(2,6)$.
The last parabola corresponds to $y=3x^2$; $a=3$ and $(1,3)$ satisfies $y=3x^2$.
Find the corresponding quadratic function.
Each quadratic function has the form $y=ax^2$.
If $a>0$, then the parabola looks like a rainbow.
If $a<0$, then the parabola looks like a smile.
Each pair $(x,y)$ on a parabola must satisfy $y=ax^2$.
Each of the parabolas above belongs to a quadratic function of the form $y=ax^2$.
First we look at the sign of $a$: the yellow as well as the red parabola are opened downwards, or are "rainbow shaped". The blue and the green parabola are opened upwards, or are "smile shaped". | CommonCrawl |
The definition of a symmetry is this: You close your eyes, then I perform a transformation on an object/system and if you can't tell that I changed anything at all, the transformation I performed is a symmetry of the object/system.
Symmetry is the pattern that tells you how to generate one part of an object from another. It condenses information. Saying that a human face is symmetrical is another way of telling you that you do not need to draw both sides of it; instead, you can generate the left side from the right. Said differently, a truly symmetric human face is indistinguishable from its mirror image, which flips the left and right sides.
Mathematically, we describe symmetries using group theory.
The symmetry of Classical Mechanics is the Galilei group. The canonical structure of the phase space is characterized by the symplectic groups $Sp(2N)$.
The symmetry of Electrodynamics and Special Relativity is the Poincare group. (However, take note that the Maxwell equations are also invariant under the larger conformal group.) The Poincare group becomes the Galilei group in the limit when everything moves slow compared to the speed of light. In addition, electrodynamics has an $U(1)$ gauge symmetry.
The symmetry of Quantum Mechanics and Relativistic Field Theory is the double cover of the Poincare group.
The symmetry of particle physics is the $SU(3)_C\times SU(2)_L \times U(1)_Y$ gauge symmetry.
The symmetry of general relativity is the diffeomorphism group.
most simply, what representations of the group appear in the system?
is the symmetry preserved by the groundstate? If not, this is called 'spontaneous symmetry breaking'.
is it 'on-site'? Alternatively, is it 'anomalous'? What are its anomaly coefficients?
Symmetry is the magic word that distinguishes theory from coincidence.
In physics we use many different types of symmetries, but they have one thing in common: they are potent unifying principles because they explain how things that once appeared very different actually belong together, connected by a symmetry transformation.
"Symmetry pervades the inner world of the structure of matter, the outer world of the cosmos, and the abstract world of mathematics itself. The basic laws of physics, the most fundamental statements we can make about nature, are founded upon symmetry" L. M. Lederman and C. T. Hill, Symmetry and the Beautiful Universe (Prometheus Books, Amherst, 2004).
Physicists are mostly agreed that the ultimate laws of Nature enjoy a high degree of symmetry. By this I mean that the formulation of these laws, be it in mathematical terms or perhaps in other accurate descriptions, is unchanged when various transformations are performed. Presence of symmetry implies absence of complicated and irrelevant structure, and our conviction that this is fundamentally true reflects an ancient aesthetic prejudice - physicists are happy in the belief that Nature in its fundamental workings is essentially simple. Moreover, there are practical consequences of the simplicity entailed by symmetry: it is easier to understand the predictions of physical laws. For example, working out the details of very-many-body motion is beyond the reach of actual calculations, even with the help of computers. But taking into account the symmetries that are present allows one to understand at least some aspects of the motion, and to chart regularities within it.
Local symmetries are especially important in modern physics in the form of gauge symmetries. Global symmetries are believed to be accidental.
Continuous symmetries are important as internal symmetries but also as spacetime symmetries like, for example, rotational symmetry. Discrete symmetries are also important, mainly in the form of charge-conjugation and parity symmetry.
It is believed that no global symmetries exist in a quantum theory of gravity . This suggests that global symmetries are not ingredients of the fundamental theory. Global sym- metries can only be approximate and accidental. In other words, they are emergent properties at low energy. A simple example is the rotational symmetry that emerges in the spherical-cow approximation. Examples more pertinent to particle physics are baryon and lepton number in the SM, custodial symmetry of the Higgs model in the limit of vanishing hypercharge and quark mass difference, flavour symmetry in the limit of vanishing Yukawa couplings, isospin symmetry in nuclear forces, chiral symmetry in the pion Lagrangian, and many oth- ers. These examples show that global symmetry is a useful concept in the IR. It is useful as a classifier in low-energy theories, both in linearly realised versions (establishing selection rules for forbidden local operators) and non-linear versions (characterising the structure of the Lagrangian of light scalar particles). However, in spite of their practical usefulness in the IR, they are probably inconsequential in the UV, where the truly fundamental theory is expected to live.
The same "folk theorem" that rules out continuous global symmetries at the fundamental level applies to discrete (non-gauge) symmetries as well. The Standard Model vouches for this assertion since discrete symmetries like C, P, and T can be explained as the result of Lorentz invariance and the structure of the interactions. Whenever possible, the Standard Model breaks maximally C and CP, both in weak and Yukawa interactions. Surprisingly, this is not true for strong interactions, where the topological structure of the gauge theory allows for a large violation of CP, which is not observed in nature. This anomalous behaviour is taken seriously by most physicists, who believe it cannot be just a fluke of strong interactions, but the indication for some new dynamics yet to be discovered (e.g. the axion). | CommonCrawl |
Time for another classic post from the old site, while I'm at it… As we have seen in a bunch of previous posts, the notion of configuration space has held a prominent place in my mathematical explorations, because, I can't emphasize enough, it's not just the geometry of things that you can directly see that are important; it's the use of geometric methods to model many things that is.
Consider all possible straight lines in the plane (by straight line I mean those that are infinitely long). This collection is a configuration space—a catalogue of these lines. What does that mean? Of course, in short words, it's a manifold, and we've talked about many of those before. But it always helps to examine examples in detail to help develop familiarity. Being a manifold means we can find local parametrizations of our collection by $n$-tuples of real numbers. How do we do this for lines in the plane?
\] The variable m if you recall is the slope of a line, and b is the y-intercept which means where the line crosses the y-axis. However few people realize that what they're doing, really, is indexing every non-vertical line in the plane with some point in another plane (called, say, the mb-plane rather than the old traditional xy-plane). That is, we have a correspondence between points in one abstract mb-plane to the lines in the xy-plane, where m is the slope, and b the y-intercept. It doesn't get all lines, though—vertical lines have infinite slope, and you can't have a coordinate on any plane with an infinite value. That is, you have charted out the space of all possible nonvertical lines with points in a different plane.
\] It's essentially obtained by reflecting everything about the diagonal line x = y and finding the usual slope and intercept. In other words we can chart out all non-horizontal lines on this new kc-plane. So you could represent the collection of all lines in the plane by having two charts... an atlas or catalogue of all lines, with these two sheets, the mb-plane and the kc-plane.
\] that is, if $k = 1/m$ and $c = -b/m$, then $(m,b)$ and $(k,c)$ represent the same line in the two sheets. So to "glue" the sheets together, we glue every $(m,b)$ in the mb-plane to $(1/m,-m/b)$ in the kc-plane. Obviously the sheets need to be made of some very stretchable material, because it is going to be awfully hard to glue points together. Actually it's pretty hard to physically do this so don't try this at home, but just try to imagine it (don't you just love thought experiments?). For example, points in the mb-plane $(1,1)$, $(2,2)$, $(3,3)$, and $(4,4)$ get glued to the corresponding points $(1,-1)$, $(1/2,-1)$, $(1/3,-1)$, and $(1/4,-1)$. You glue them in a very weird way, but if you suppose for a moment, that you allow all sorts of moving, rotating, shrinking, stretching in this process (topological deformations), but without tearing, creasing, or collapsing, you can preseve the "shape" of this space, and yet make it look like something more familiar. This would be our new catalogue of lines. In addition, the catalogue has an additional property: nearby points in the catalogue translate to very similar-looking lines.
One should wonder what kind of overall "shape" our nice spiffy catalogue has, after gluing together the two possible charts we've made for it. As it turns out, its shape is the Möbius strip! That's right, the classic one-sided surface (without, as it turns out, its circle-boundary).
That is to say, if you give me a point on the Möbius strip, it specifies one and only one line in the plane. One would not, initially, be able see why non-orientability enters the picture. But a little interpretation is in order. First, if we take a particular line and rotate it through 180 degrees, we get the same line back. Everything in between gives every possible (finite) slope. It so happens that as far as slopes of lines is concerned, $\infty=-\infty$, and if you go "past" this single projective infinity, as they call it, you go to negative slopes. In other words, if you start on a journey on rotating a line through 180 degrees, from vertical back to vertical, you come back to the same line, except with orientation reversed (because what started out as pointing up now points down).
If you fix an origin and declare that it correspond to a certain special line in the plane, and then select a "core circle" for the Möbius strip, then as you travel around this circle, the distance traveled represents rotation angle for this special line. Traveling from the origin along the core circle and making one full loop should correspond to rotating the special line by 180 degrees. If you instead move up or down on the core circle, you instead end up sliding the line along a perpendicular direction, without changing its angle. So moving up and down the strip corresponds to parallel sliding of lines, and moving around the strip along a circle corresponds to rotating a line.
\] We'll show how we got this in an update to this post, or perhaps a "Part 2." This can be readily checked by simply substituting the transition charts for $(m,b)$ and $(k,c)$. However, the extra case for $k=0$ here is simply gotten by taking the limit as $k$ goes to zero from above in the other case. What proves that it is a Möbius strip is that, if we take the limit as $k$ goes to zero from below, it will approach $(\pi,c)$ instead of $(0,-c)$. This would make it discontinuous, unless we decide to identify $(\pi,c)$ with $(0,-c)$: the $c$ going to $-c$ means we take the strip at $\pi$ and flip it around to glue it to the strip at $0$ (see this post for another example of defining a Möbius strip this way). Technically, we need an infinitely wide Möbius strip for this, but we can always scrunch it down into a finite-width strip without its boundary circle (using something like arctangent). It's just that the closer you get to the edge, the quicker things go off to infinity.
The more general object here we are describing is closely related to the notion of Grassmannian manifold, which are all $k$-dimensional subspaces in an $n$-dimensional vector space (the only difference is that Grassmannians only consider spaces through the origin). | CommonCrawl |
(A) I will not leave the place until the minister does not meet me.
(B) I will not leave the place until the minister doesn't meet me.
(C) I will not leave the place until the minister meet me.
(D) I will not leave the place until the minister meets me.
Answer : (D) I will not leave the place until the minister meets me.
The sentence above is an example of a ___________ statement.
A shaving set company sells 4 different types of razors, Elegance, Smooth, Soft and Executive. Elegance sells at Rs. 48, Smooth at Rs. 63, Soft at Rs. 78 and Executive at Rs. 173 per piece. The table below shows the numbers of each razor sold in each quarter of a year.
Which product contributes the greatest fraction to the revenue of the company in that year?
Indian currency notes show the denomination indicated in at least seventeen languages. If this is not an indication of the nation's diversity, nothing else is.
Which of the following can be logically inferred from the above sentences?
(A) India is a country of exactly seventeen languages.
(B) Linguistic pluralism is the only indicator of a nation's diversity.
(C) Indian currency notes have sufficient space for all the Indian languages.
(D) Linguistic pluralism is strong evidence of India's diversity.
Answer : (D) Linguistic pluralism is strong evidence of India's diversity.
Consider the following statements relating to the level of poker play of four players P, Q, R and S.
If $ \mathrm f\left(x\right)=2x^7+3x-5 $, which of the following is a factor of fx ?
Consider the plane truss with load P as shown in the figure. Let the horizontal and vertical reactions at the joint B be HB and VB, respectively and VC be the vertical reaction at the joint C.
Which one of the following sets gives the correct values of VB, HB and VC? | CommonCrawl |
We elucidate the connection between different notions of differentiability in $\mathcal P_2(\mathbb R^d)$: some have been introduced intrinsically by Ambrosio--Gigli--Savar\'e, the other notion due to Lions, is extrinsic and arises from the identification of $\mathcal P_2(\mathbb R^d)$ with the Hilbert space of square-integrable random variables. We mention potential applications such as uniqueness of viscosity solutions for Hamilton-Jacobi equations in $\mathcal P_2(\mathbb R^d)$, the latter not known to satisfy the Radon--Nikodym property. (This talk is based on a work in progress with A Tudorascu). | CommonCrawl |
Problem. Let $X$ be a Polish space, $\mathcal I$ be a $\sigma$-ideal with Borel base, and $\mathcal A\subset\mathcal I$ be a point-finite cover of $X$. Is it true that $\mathcal A$ conatins a subfmaily $\mathcal B$ whose union $\bigcup\mathcal B$ is completely $\mathcal I$-nonmeasurable in the sense that any Borel subset $B\notin\mathcal I$ intersects both sets $\bigcup\mathcal B$ and $X\setminus\bigcup\mathcal B$.
(This problem (attributed to Jacek Cichoń) was written 27.07.2018 by Szymon Żeberski from Wrocław on page 28 of Volume 2 of the Lviv Scottish Book).
Browse other questions tagged set-theory gn.general-topology measure-theory descriptive-set-theory or ask your own question.
Can each non-open analytic subgroup of a Polish abelian group be covered by countably many closed Haar null subsets? | CommonCrawl |
We consider the task of obtaining the maximum a posteriori estimate of discrete pairwise random fields with arbitrary unary potentials and semi-metric pairwise potentials. For this problem, we propose an accurate hierarchical move making strategy where each move is computed efficiently by solving an st-MINCUT problem. Unlike previous move making approaches, e.g. the widely used $\alpha$-expansion algorithm, our method obtains the guarantees of the standard linear programming (LP) relaxation for the important special case of metric labeling. Unlike the existing LP relaxation solvers, e.g. interior-point algorithms or tree-reweighted message passing, our method is significantly faster as it uses only the efficient st-MINCUT algorithm in its design. Using both synthetic and real data experiments, we show that our technique outperforms several commonly used algorithms. | CommonCrawl |
I am running a non-parametric paired samples analysis.
I've been reading about calculation of the effect size r for this analysis and most literature referes to the formula proposed by Rosenthal (1991). The formula is: r = Z/sqrt(N). In the case of JASP, the way the same coefficient r is computed seems to be quite different: W / ((n*(n+1))/2) * 2 - 1 (thank you Johnny van Doorn for the clarification).
If we assume N as the number of subjects (e.g., 10 subjects evaluated in two moments), the calculation of this effect size is (in my example) varies from r=.693 to r=.782, depending on whether the calculation is based on the Rosenthal formula or as it is implemented in JASP.
To add even more noise to this, Field (2009) and Pallant (2007) propose that when dealing with related samples, N should refer to the number of observations (i.e., 10x2 in my example) and thus this difference is even more pronounced (r=.490). I am reporting such analysis in a revision of a manuscript and I would like to have more certainty in how I should compute this ES, given the impact that this has for the magnitude of the effect.
Do you have any thought on the most accepted way of computing this?
The matched-pairs rank-biserial correlation can also be expressed as the difference between the proportion of data pairs where $x_i > y_i$ versus $x_i < y_i$. "
Basically, the formula we use is just a way to standardize the W statistic to cover the range [-1, 1]. I really like the straightforward and intuitive interpretation that it provides in terms of difference in proportions of data pairs where $x_i > y_i$ versus $x_i < y_i$.
Could you tell me what Z you are talking about? Is the the normal approximation/transformation of the W statistic?
The formula that I am referring to is computed as follows: https://www.statisticshowto.datasciencecentral.com/wilcoxon-signed-rank-test/. The lowest sum of ranks (i.e., the lowest value between the sum of positive ranks and the sum of negative ranks) is used together with n to compute the Z-statistic.
It is one of the outputs obtained with SPSS (and other commercial software) and is widely reported when researchers present the results of this test. | CommonCrawl |
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We analyze the class of universal Markov processes on $R^d$ which do not depend on random. For this, as well as for several subclasses, we prove criteria whether a function $f:[0,\infty[ \to R^d$ can be a path of a process in the respective class. This is useful in particular in the construction of (counter-) examples. The semimartingale property is characterized in terms of the jumps of a one-dimensional deterministic Markov process. We emphasize the differences between the time homogeneous and the time inhomogeneous case and we show that a deterministic Markov process is in general more complicated than a Hunt process plus `jump structure'. | CommonCrawl |
The topic of my Master's thesis, "Divergence-measure fields: generalizations of Gauss-Green formula with applications", which I wrote under the supervision of Prof. K. R. Payne, concerns the study of$L^p$-summable vector fields whose divergence is a Radon measure, in order to achieve a generalization of the classical divergence theorem in the context of sets of finite perimeter. These fields were introduced some years ago in order to study nonlinear hyperbolic systems of conservation laws by Chen and Frid, and also the fundaments of continuum mechanics by Degiovanni, Marzocchi, Musesti and Šilhavý. We explored especially the case $p=\infty$. The method of the proof of the Gauss-Green formula for essentially bounded divergence-measure fields is however different from the previous ones, since we adapted the techniques already developed for BV functions in Vol'pert's work. | CommonCrawl |
The method of martingale approximation consists in approximating the partial sums of a strictly stationary sequence by those of a martingale differences sequence with stationary increments. Gordin and Peligrad (2011) gave a necessary and sufficient condition for martingale approximation. This condition can be used to establish an invariance principle. After having reviewed the main results in dimension one, we will present the extension to processes indexed by $\mathbb Z^d$, $d\geqslant 1$. | CommonCrawl |
One of the key motivating factors for free software is so that a user or interested third party can see how a program works, how it was created, verify it for bugs and security, and can easily modify it including to fix bugs. To some degree this philosophy can be carried across to other works covered by copyright, yet the Creative Commons licenses don't yet offer a license for this. For instance, say I do a drawing with a pencil on paper. There isn't really any source, only a binary (the final drawing). If you want to change it, all you can do is draw over the top of it or use an eraser (just like modifying binary encoded machine code).
However, works covered by copyright are no longer solely creative, and no longer a single final binary. Just like software code which although could have creative thought put into it, it is mostly functional. I have the same thought process for creative works, I want to be able to see how it was created, and how I can modify it. Take for instance a digital painting, where every brush stroke is stored as a brushstroke. This way a third party could come along later, select the single brush stroke in question, select it and change the paint color.
The RTA supports and encourages open access information, and is determined to grow its range of traffic resources to provide developers with access to live updates and traveller information feeds. Request for licensing agreements are assessed against the following considerations: - Consumer benefit - Legal constraints - Road safety - Branding - Technical capacity - Cost - Availability of data If you would like to apply for a license agreement for the RTA's Live Traffic content, please submit a proposal for your service and how you would like to use the RTA's content, including the above considerations. Your proposal will then be assessed by the RTA.
What a load of garbage, if you trully "support and encourage open access information" then you would release these data feeds under a public domain like license. Saying "we will make a case by case decision once you tell us your proposal" is just going to hinder the innovative use of that data. People will create their own datasets independent of you, which of course this could go either way. The peoples dataset could be either better or worse quality than yours, but either way you would save people some work if you helped out by releasing your data under a free and open license. You are a government department, not a company.
I've taken some time to look at the NearMap licenses (Community License, Free Commercial License) more closely. Here is some of my commentary of them. I'll use the terminology used in the licences so please excuse me for using their language and jargon. When I say free I mean free as in "free software", "free culture" and "free as in freedom". Also this is just my interpretation from reading them, I am not a lawyer. Hopefully I've interpreted them as NearMap intended.
Previously I had thought that any derived works that came from NearMap PhotoMaps used in OpenStreetMap needed to be attributed to NearMap. I guess I just incorrectly thought that all the information was CC BY-SA licensed by NearMap, but that is not the case. These works actually need to be attributed to the user who observed that information and turned it into a work by, for example, adding it into the OSM database. The works do not need to be attributed in any way to NearMap.1 This also means that any copyright that arises from any creativity in deciding what to trace, and any copyright that arises from the tracing being a derivative work can be treated as CC BY-SA licensed by that person or user. That person is the copyright holder but they are only allowed to distribute the work under a CC BY-SA license. This is a good thing! I'm glad that NearMap have not chosen to change the wording to make it compatible with the public-domain-like OpenStreetMap contributor terms, as (unless of course one has some other license from NearMap) it guarantees that this information remains free2.
The discussion and use of Yahoo imagery as a source of tracing for OpenStreetMap was before my time, but from http://wiki.openstreetmap.org/wiki/Yahoo it seems that strong legal foundations are lacking. In this respect I feel much safer tracing from NearMap. I know that my contributions can be licensed under the free CC BY-SA license and nothing can be done to unfree these works. Whereas the legalities of Yahoo imagery is, at least from my reading, very questionable and potentially a huge problem in the future.
Another reason I took a closer look at the licenses was to make sure that the works I posted earlier which were modified PhotoMaps complied with all licensing requirements, both the NearMap and OpenStreetMap requirements. I have come to the conclusion that unfortunately I am most likely unable to satisfy both the Mapnik share-alike requirement and the NearMap share-alike requirement in coexistence.
The NearMap "free community licence" gives me the "right to use, copy, modify and distribute our PhotoMaps". The distribution to others clause says that I must give NearMap attribution for the distribution of any original or modified PhotoMaps, however the license also says "You may sublicense your rights to the Licensed PhotoMaps, Modified PhotoMaps or APIs to others on the same terms as this licence or our free commercial licence." I interpret this as if I modify a PhotoMap I need release it under the "NearMap free community license", that is it is share-alike.
On the other hand though, I also used the default OpenStreetMap Mapnik-style map images. My understanding is that like the data used to create these maps, the actual map images are copyrighted by all the OpenStreetMap contributors and released under the CC BY-SA license. The share-alike means that any derivative works (like overlaying NearMap terrain maps) must the released under a CC BY-SA compatible license, so you cannot impose non-commercial or non-government on it. However although the NearMap free community licence plus the NearMap free commercial license almost allow anyone to use or modify the work they don't meet CC BY-SA because they exclude government and exclude commercial use made in a "competing manner" and use that is "material to their business". This leaves me to believe that I cannot legally distribute any work that is a mash-up of OSM data/maps and NearMap PhotoMaps. Unless of course that it is only the default Mapnik tiles that are CC BY-SA, and that anyone can copyright map images made from OSM data. Because NearMap uses OSM data to create Mapnik tiles using their own map style. I assume then that it is only the OSM data that is CC BY-SA and someone is free to make a non-free map using their own style from this data. Then they would own the copyright to that map and hence you would be free to combine this with NearMap's PhotoMaps and release the product under their free community license. This could also explain why NearMap can overlay their transparent tiles based on OSM data over their non CC BY-SA imagery.
It is a shame, but I can totally understand NearMap restricting use of their PhotoMaps in a specific field of endeavor, namely the government. The government is central to their current revenue stream, without it they probably could not produce the volume of work they currently do under their almost free, community license. It is almost CC BY-SA, except they exclude three fields of endeavor, "Competing Manner", "Material to their business" and "Government Entities that use our PhotoMaps for their own governmental purposes". The first two exclusions make the PhotoMaps near CC BY-NC-SA, but the last clause means they cannot be compatible with any of the Creative Commons licenses.
Let me use the example case of distribution of original NearMap PhotoMaps. For instance say I download a bunch of imagery tiles and distribute them through BitTorrent, the key question here is do I need to enforce that this distribution is to non-government entities. If I am only allowed to distribute it to non-government, I cannot do that, so the freedoms that the license grants are not as broad as I thought. If on the other hand if I can distribute the works to government entities along with the free community license as a LICENSE file, but leave the responsibility and liability on the government to not use the works I make available, then this would be much better. Hopefully the latter is the case. This was almost touched on here, but which party the liability lies on was not mentioned.
This is why I hate reading all this legal jargon, every word is important but has different interpretations. Code on the other hand has just one interpretation, and that is defined in the compiler... Anyway, at first I thought this termination clause meant NearMap could terminate the license grant at any time, however I missed the words "if the other party breaches this licence". I view this to mean that NearMap cannot terminate the license grant unless you breach the license. But even if such a case arose, derived information is safe. So NearMap can do nothing to prevent the CC BY-SA distribution of derived information. Although it appears all the other parts of the license grant can be subject to this clause.
1 However I still think that one should attribute NearMap regardless. In the OSM case, attribution using the source tag should be done for other reasons as well; like so people know where the data came from, hinting some clues of the quality of the data.
2 Without turning this into a copyleft v permissive debate, I think that CC BY-SA is the most common license in use (there is a whole OSM database under it), so to avoid incompatibilities with other works under different share-alike licenses, CC BY-SA is probably the best choice at the moment. Some people say CC BY-SA is not for data, this is true, but that doesn't stop the Australian government releasing data under the license, but more to the point, CC BY-SA has a clause that allows derivative works to also be licensed under a "Creative Commons Compatible License" that is listed at http://creativecommons.org/compatiblelicenses. One would hope that if someone creates an attribution share-alike license suited for data that would protect that data in jurisdictions that copyright data, and leave it free to use without restriction in jurisdictions that don't copyright data (so don't try to force attribution share-alike in these jurisdictions with contracts), Creative Commons could add this as a Creative Commons Compatible License, and all works like the current CC BY-SA OSM database could be relicensed under that data attribution share-alike license.
Tags: copyright, law, nearmap, osm.
"Please note: Any organisation or individual wanting to use the Gazetteer data in a similar capacity to the Online Place Name Search or any other online application, will require an Internet user licence. (See the Licence Fees and Order Form below)."
So much for the CC-BY license. The latter notice is an "otherwise noted" which says, this data is NOT CC-BY because if you want to use it for such an such purpose you need to get another license to allow you to do that.
I've run into a little legal problem. By a problem I mean that if I were convicted for this I could face "a fine of not more than 550 penalty units or imprisonment for not more than 5 years, or both." Apparently one penalty unit is $110. So that means in the worst case a $60, 500 fine and 5 years imprisonment.
(1) A person commits an offence if: (a) the person makes a device, intending it to be used for making an infringing copy of a work or other subject‑matter; and (b) copyright subsists in the work or other subject‑matter at the time of the making of the device. (2) A person commits an offence if: (a) the person possesses a device, intending it to be used for making an infringing copy of a work or other subject‑matter; and (b) copyright subsists in the work or other subject‑matter at the time of the possession. .... (11) In a prosecution for an offence against this section, it is not necessary to prove which particular work or other subject‑matter is intended to be, or will be, copied using the device.
And herein lies the problem. As a regular citizen this is too ambiguous, because people have different interpretations of what a "device" is. Case law can help here as it can give concrete examples of what is illegal and what is not, but someone always is going to be the first one to have to step up to the court to make the case law. Statute law should be clear enough on its own to be understood by the general public.
The term "infringing copy" could also be interpreted different ways, but the law actually explains what it means here (unlike for device which is to be interpreted as "includes a plate" where a "plate includes a stereotype, stone, block, mould, matrix, transfer, negative or other similar appliance." (The Act)).
Back to the actual problem that I'm referring to, I read the "Time-shifting" fact sheet from the Attorney-General's Department, http://www.ag.gov.au/www/agd/rwpattach.nsf/VAP/(CFD7369FCAE9B8F32F341DBE097801FF)~Copyright+Fact+Sheets+-+Time-shifting.pdf/$file/Copyright+Fact+Sheets+-+Time-shifting.pdf (wow what an ugly URL!). It says that it is now legal to record a television or radio broadcast to watch or listen to at a more convenient time. However broadcast does not cover streaming of content online. As such ABC's iView and friends fall outside this scope. When you stream content from ABC's iView using an Adobe Flash player I'm not sure if any content is actually written to disk or not but it is definitely saved on various memories, however this "copy" would fall under SECT 111B of The Act and is legal.
What would probably not fall under SECT 111B is there are tools, or what a court may call "devices", that are "intending it to be used for making an infringing copy of a work" (SECT 132AL, The Act). You can use these tools to store a permanent copy of material that ABC's transmits to you. My problem is I wrote a script which "helps" users make infringing copies of material published by SBS. Its not the part that actually copies the material (flvstreamer does that) but I can just imagine some lawyer convincing a judge and jury that they should send me to prison. Its way too confusing because you don't even need these scripts you just need your OS. tcpdump can be used to capture the traffic just like these tools do. Then there is the word "intending" which is open to interpretation to much.
The computer is a copying machine, its not going to stop and check if the copy will be infringing or not. Sorry this has turned into a bit of a rant, but The Act really annoys me. Maybe its because I interpret it different to the people who wrote it, or the people who will use it to send me to prison or give me huge fines.
Then there is the whole other thing of who is held liable. I wrote about the script on wordpress.com, and linked to its location on pastebin.com. Will they come after Automattic (the owner of wordpress.com) or me or the owners of pastebin.cem? But I'm (or maybe its not really me at all but Automattic) publishing all this in the US (I presume wordpress.com is hosted on servers in the US), so that makes all this Australian Copyright Act garbage useless.
Oh and the other thing, under the current act, if you visit a web site most browsers will cache that to disk (I wouldn't call that a temporary copy "as part of a technical process of use", but I would call the copying of the data for the HTML document to registers, the processor cache and RAM a temporary copy, but this is not defined in The Act.). Are then web browsers a "device, intending it to be used for making an infringing copy of a work" because they ask for content from a web server, get given it and then save it to disk? (but it's no defence to say heaps of other people are breaking the law and you have singled me out so you can't charge me) Does it matter that the web server can send a "Cache-Control: no-cache" response header, if they don't does that mean that we are allowed to cache all this to disk? But that HTTP header and even the whole HTTP spec is just a W3C recommendation.
This is just a little bit on my reasons why I have no respect at all for the Copyright Act. I don't want to have to worry about any of this legal stuff, but I must because if I don't the government can send me to prison or impose huge fines and I don't want to take a risk there.
Oh and in my defence, the script that I linked to in this post, I would not classify as "device, intending it to be used for making an infringing copy of a work" if anything it would be flvstreamer, but then you cannot single those out. If publishing that script I linked to, or flvstreamer is illegal in this country then publishing an HTTP web browser, tcpdump, or an OS that interfaces with a network must also be devices that are intending it to be used for making an infringing copy of a work.
Also something I've been wondering for ages, how can anyone ever be convicted of downloading copyright infringement mealy by downloading it over the internet? One cannot know if such material is protected by copyright (they don't even know what the data is until they have downloaded it), and one cannot know if the entity they are receiving the data from is the copyright holder who permits this use. A lawyer may come along and say that this is all true, but I wouldn't want to bet my life on the fact that the court will also agree (given the track record of the courts, see Cooper v Universal Music Australia Pty Ltd FCAFC 187).
Anyway back to studying for my COMP courses.
We want to hear the arguments, information and stories that you have to tell us. The rest of this document is simply our way of helping you do that. It is not a template that you should feel obliged to follow, though we hope that this paper helps. There may be questions you wish to address that are not here, just as there may be questions we have raised you do not wish to address.
Also, please note, our focus in this Issues Paper is on your making a written submission. You can find details about how to make a submission at Appendix 1. We also offer the option to make online submissions through our Consultation page at http://gov2.net.au/consultation.
As you may be aware, there are other channels by which you can communicate with us. You can comment on our blog at http://gov2.net.au and members of both the Taskforce and its secretariat are attending various conferences and other activities where Government 2.0 will be discussed. You are welcome to attend.
You can provide the Taskforce with feedback at any time, for instance through our blog, but we cannot promise to consider submissions on this paper which we receive after start of business Monday 24 August 2009.
The Taskforce would like to thank those people, both from Australia and offshore, who contributed to this Issues Paper both by making comments on our blog and by making specific comments on this Issues Paper when it was issued in 'Beta' format a few days before finalisation.
The Taskforce is charged with finding ways of accelerating the development of Government 2.0 to help government consult, and where possible actively collaborate with the community, to open up government and to maximise access to publicly funded information through the use of Web 2.0 techniques. We will do this with recommendations for government policy and also by funding projects which offer promise in accelerating the coming of Government 2.0.
The Taskforce will be looking at the use of Web 2.0 both within government as well as in the government/public interface.
The Terms of Reference of the Taskforce are at Appendix 2.
The aim of Government 2.0 is to make government information more accessible and useable, to make government more consultative, participatory and transparent, to build a culture of online innovation, and to promote collaboration across agencies in online and information initiatives.
There are obvious benefits in moving in this direction to support, complement and strengthen existing engagement and consultation practices. Online engagement means citizens should be able to collaborate more readily with government and each other in developing and considering new policy ideas. It can give citizens greater insight into the policy making process and greater appreciation of the complexities of policy decisions. It makes possible an ongoing conversation amongst all who wish to participate in considering the effectiveness of existing government programs, laws and regulations and the scope for improvement. Government can use collaborative technologies to draw on the skills, knowledge and resources of the general community when developing policies or delivering services. Government agencies can receive feedback more rapidly, from more people at less cost. This in turn provides an opportunity for government to improve the way it delivers services to citizens.
How will we achieve Government 2.0?
Governments around the world and certainly our own governments have been relatively good at seizing many of the opportunities provided in the first incarnation of the internet, now often called Web 1.0, that is the use of the internet as a platform to distribute public material and solicit information from stakeholders by way of online 'feedback forms'. Indeed in 2008 the internet became the most common way citizens last made contact with government .
However a range of possibilities are emerging on the internet which have been dubbed Web 2.0. The revolutionary potential of Web 2.0 is apparent in websites like Google, Flickr, Facebook and Wikipedia. The central theme of Web 2.0 is moving away from point to point communications and towards many to many communication and collaboration.
There is a buzz of Web 2.0 in the community and amongst enthusiasts who post to blogs and sites like Flickr and join online discussions.
Governments across Australia have taken some interest in the applications of Web 2.0 to government. However compared with the speed of adoption of Web 2.0 tools and modes of operating in some quarters, progress in embracing Web 2.0 within government has been modest.
This comes down to a fundamental view of what Government is for.
If one is of the view that the purpose of Government is to shape society into some kind of ideal, where everyone is on the same page working to some kind of utopian goal, then Web2.0 has very little to offer. In that world view, the Government has already worked out what it's going to do and the job of the citizen is to either help it get there (usually by means of constructive "submissions", but only when "consulted") or get out of the way and let the Government do its thing.
If one is of the view that the role of the Government is to act as a kind of social lubricant to enable citizens to employ their own ideals in furtherance of their own goals, then that's where Web2.0 is strong. Enabling that outcome requires the Government to be part of the conversation, so that it can see where obstacles are and apply its resources appropriately to smoothing the way for citizens without creating more problems than it solves. Government can be a remarkably blunt instrument, which needs to be wielded with care.
I suspect that the slowness of Web2.0 adoption comes from the fact that those of us who support this initiative are in the latter mindset, while much of the Government and its accompanying bureaucracy are in the former mindset. Resolving this schism is, IMHO, one of the paramount challenges of Government 2.0.
How can we build a culture within government which favours the disclosure of public sector information?
What government information should be more freely available and what might be made of it?
What are the major obstacles to fostering a culture of online engagement within government and how can they be tackled?
How can government capture the imagination of citizens to encourage participation in policy development and collaboration between citizens and government?
iv) using the wrong kind of engagement tool; it's not about fashion, it's about choosing the right tool for the policy stage and audience.
A number of reviews and processes have pointed to the importance of greater dissemination and reuse of public sector information and greater online engagement with citizens/between governments/between governments and citizens. At the Australian Government level, for example, these include the Cutler Review into Innovation , and the Gershon Review into ICT use and management . Some State governments have also been making important strides. Most recently the Victorian Government has released its Report of the Economic Development and Infrastructure Committee on the Inquiry into Improving Access to Victorian Public Sector Information and Data, Parliamentary Paper No. 198 Session 2006-2009, June 2009.
Proposed legislative change, including proposals for the establishment of an Office of the Information Commissioner and amendments to Freedom of Information legislation to impose a publication scheme on all agencies underpin an agenda of greater public access to government information.
The proposed Office of the Information Commissioner will incorporate the existing Office of the Privacy Commissioner. Handling privacy well is important to generating the trust and confidence in the community necessary to optimise community engagement in Web 2.0 initiatives.
Many government agencies are currently involved in aspects of information policy development. Many are also exploring the use of new tools and techniques to improve the way they work. The Taskforce seeks to build on this work and to accelerate this process of change to allow more open access to, and use of, the information created and/or funded by government. Equally important, the Taskforce will explore the issue of effective consultation, engagement and collaboration with citizens. This work will inform the framework for an Information Policy that can be applied across the Australian Government.
In this paper we elaborate on issues relating to public sector information. We have covered these at greater length than other issues under reference because there has been greater policy development in this area compared with innovation and online engagement. The relatively smaller space devoted to the latter themes in this Issues Paper does not signal that we view them as being of lesser importance.
The Taskforce acknowledges these principles and intends to use them as a starting point for that part of our work relating to public sector information. Our focus then becomes how we realise those principles as fully as possible in the practical operations of government.
1. Openness. Maximising the availability of public sector information for use and re-use based upon presumption of openness as the default rule to facilitate access and re-use. Developing a regime of access principles or assuming openness in public sector information as a default rule wherever possible no matter what the model of funding is for the development and maintenance of the information. Defining grounds of refusal or limitations, such as for protection of national security interests, personal privacy, preservation of private interests for example where protected by copyright, or the application of national access legislation and rules.
2. Access and transparent conditions for re-use. Encouraging broad non-discriminatory competitive access and conditions for re-use of public sector information, eliminating exclusive arrangements, and removing unnecessary restrictions on the ways in which it can be accessed, used, re-used, combined or shared, so that in principle all accessible information would be open to re-use by all. Improving access to information over the Internet and in electronic form. Making available and developing automated on-line licensing systems covering re-use in those cases where licensing is applied, taking into account the copyright principle below.
3. Asset lists. Strengthening awareness of what public sector information is available for access and re-use. This could take the form of information asset lists and inventories, preferably published on-line, as well as clear presentation of conditions to access and re-use at access points to the information.
4. Quality. Ensuring methodical data collection and curation practices to enhance quality and reliability including through cooperation of various government bodies involved in the creation, collection, processing, storing and distribution of public sector information.
5. Integrity. Maximising the integrity and availability of information through the use of best practices in information management. Developing and implementing appropriate safeguards to protect information from unauthorised modification or from intentional or unintentional denial of authorised access to information.
6. New technologies and long-term preservation. Improving interoperable archiving, search and retrieval technologies and related research including research on improving access and availability of public sector information in multiple languages, and ensuring development of the necessary related skills. Addressing technological obsolescence and challenges of long term preservation and access. Finding new ways for the digitisation of existing public sector information and content, the development of born-digital public sector information products and data, and the implementation of cultural digitisation projects (public broadcasters, digital libraries, museums, etc.) where market mechanisms do not foster effective digitisation.
7. Copyright. Intellectual property rights should be respected. There is a wide range of ways to deal with copyrights on public sector information, ranging from governments or private entities holding copyrights, to public sector information being copyright-free. Exercising copyright in ways that facilitate re-use (including waiving copyright and creating mechanisms that facilitate waiving of copyright where copyright owners are willing and able to do so, and developing mechanisms to deal with orphan works), and where copyright holders are in agreement, developing simple mechanisms to encourage wider access and use (including simple and effective licensing arrangements), and encouraging institutions and government agencies that fund works from outside sources to find ways to make these works widely accessible to the public.
8. Pricing. When public sector information is not provided free of charge, pricing public sector information transparently and consistently within and, as far as possible, across different public sector organisations so that it facilitates access and re-use and ensures competition. Where possible, costs charged to any user should not exceed marginal costs of maintenance and distribution, and in special cases extra costs for example of digitisation. Basing any higher pricing on clearly expressed policy grounds.
9. Competition. Ensuring that pricing strategies take into account considerations of unfair competition in situations where both public and business users provide value added services. Pursuing competitive neutrality, equality and timeliness of access where there is potential for cross-subsidisation from other government monopoly activities or reduced charges on government activities. Requiring public bodies to treat their own downstream/value-added activities on the same basis as their competitors for comparable purposes, including pricing. Particular attention should be paid to single sources of information resources. Promoting non-exclusive arrangements for disseminating information so that public sector information is open to all possible users and re-users on non-exclusive terms.
10. Redress mechanisms: Providing appropriate transparent complaints and appeals processes.
11. Public private partnerships. Facilitating public-private partnerships where appropriate and feasible in making public sector information available, for example by finding creative ways to finance the costs of digitisation, while increasing access and re-use rights of third parties.
12. International access and use. Seeking greater consistency in access regimes and administration to facilitate cross-border use and implementing other measures to improve cross-border interoperability, including in situations where there have been restrictions on non-public users. Supporting international co-operation and co-ordination for commercial re-use and non-commercial use. Avoiding fragmentation and promote greater interoperability and facilitate sharing and comparisons of national and international datasets. Striving for interoperability and compatible and widely used common formats.
13. Best practices. Encouraging the wide sharing of best practices and exchange of information on enhanced implementation, educating users and re-users, building institutional capacity and practical measures for promoting re-use, cost and pricing models, copyright handling, monitoring performance and compliance, and their wider impacts on innovation, entrepreneurship, economic growth and social effects.
The remainder of this paper discusses OECD principles and additional principles as they relate to online innovation and engagement.
Open access to public sector information is generally agreed to be beneficial to our economy and society and to be the preferred approach. By openness and access, we refer to the making available of appropriate categories of public sector information on terms and in formats that permit and enable use and reuse of that information by any member of the public. However, we recognise that there are limits to this principle of open access, namely to respect privacy, confidentiality, security and possibly cost recovery concerns.
For the purposes of this issues paper public sector information is taken to exclude personal information that would not be available for publication or reuse under Australian privacy laws, or other legislation. It might include such information if it were adequately transformed to address any concern, for instance by anonymising it.
Another issue is how widely policies to optimise the openness of public sector information should apply across government. The recent Victorian Parliamentary inquiry proposed that public sector information policy should apply to government departments only, at least for an initial period, although it suggested that it may be appropriate to expand this coverage over time. We would be interested to hear arguments for and against restrictive and more expansive application of policies to optimise the openness of public sector information and, where a broader definition is supported, how this might relate to information that is commercially sensitive.
Question 1: How widely should policy to optimise the openness of public sector information be applied? Should it be applied beyond government departments and, if so, to which bodies, for instance government business enterprises or statutory authorities?
The OECD recommends that the presumption of openness should be the default rule, and this has been backed by recent moves in the Australian Government. Proposed changes to the Freedom of Information Act 1982 (FOI Act) aim to make it easier to obtain documents under FOI legislation, in part by emphasising the presumption of openness. FOI Act changes also aim to encourage the release of information through a publication scheme and otherwise outside that Act. Proposed changes to the Archives Act 1983 bring forward the time at which government records come available under that Act from 30 to 20 years. These changes are backed by the proposed creation of an Information Commissioner and Freedom of Information Commissioner.
These legislative changes are a significant move in the direction of accessibility of government information.
One of the major barriers to achieving greater accessibility has been the lack of a pro-disclosure culture within government. Privacy, national security and confidentiality issues will properly prevent the release of some information, but this should not inhibit the release of other non-sensitive government information.
Question 2: What are the ways in which we build a culture within government which favours the disclosure of public sector information? What specific barriers exist that would restrict or complicate this and how should they be dealt with?
Question 3: What government information would you like to see made more freely available?
Question 4: What are the possible privacy, security, confidentiality or other implications that might arise in making public sector information available? What options are there for mitigating any potential risks?
I believe that Question 2 is one of the most important problems we face in adoption of this goal. Broad cultural change is required across government that encourages innovation whilst providing a safety-net for those who try and fail. Leadership from the highest levels and generational change is required to make this a reality. The key is not to expect too much too soon as transparency is a terrifying concept for most government agencies and their officers.
All of the technical, legal and logistical problems will be solvable, but worthless without real cultural change at all levels of government.
Government agencies currently make a large amount of information available on their websites, and much more could be made available freely on the internet. However, technological, copyright and licensing issues tend to restrict the way that this information can be made available and used by the public.
Making government information accessible online, particularly in standard formats such as XML, CSV, ODF, RDF or RDFa etc allows those outside government, whether they are citizens, firms or third sector organisations, to combine, present and analyse this information in different ways, creating both public and private benefits.
Question 5: What is needed to make the large volume of public sector information (a) searchable and (b) useable? And in each case, what do we do about legacy information in agencies? How might the licensing of on-line information be improved to facilitate greater re-use where appropriate?
The Semantic Web is a series of World Wide Web Consortium (W3C) standards that provides a framework to describe information about data. This information is called metadata. Providing sets of raw data without accompanying context may limit the ability of people to meaningfully re-use any information provided. For example, what does the data element '60' represent? Is it someone's age? A speed limit? When was the information collected? By whom? What are the units of measurement?
In Australia the Australian Government Locator Service (AGLS) Metadata Standard (AS 5044) has been endorsed by all Australian Governments as the standard for describing government resources (information and services) to support their discovery in a Web environment. AGLS is based on and extends the international resource discovery metadata standard, the Dublin Core Metadata Element Set. AGLS metadata can be expressed using RDF (Resource Description Framework) syntax and modelling, which is one of the recommendations of the Semantic Web.
There are other relevant metadata standards as well for things like rights management, geospatial data, recordkeeping, digital preservation, etc, all of which can potentially be useful in a semantic web environment, but discoverability is the key requirement for which you need standardised metadata for the Semantic Web to work.
There are of course costs associated with marking up data with semantic annotations. These costs increase with the degree of metadata provided for each element. A difficult-to-answer issue what be at what point do the costs of providing extra information exceed the benefits?
How could information be made more accessible?
Question 6: How does government ensure that people, business, industry and other potential users of government information know about, and can readily find, information they may want to use, for example, the use of a consolidated directory or repository for public sector information?
Publication in proprietary formats can represent a barrier to participation for citizens if the owner of intellectual property in the standard refuses to make it freely available. In addition, a requirement for government to maintain information in multiple formats represents a cost to government.
Some national and sub-national governments have mandated that all information must be accessible and stored in formats that are publicly open standards. Thus such formats like Open Document Formats (ODF) have been preferred to proprietary formats such as DOC.
Question 7: Should governments mandate that information should be only kept and stored in open and publicly documented standards? Could such a stipulation raise costs or reduce flexibility?
It should be possible to share the benefits and knowledge gained from online and information initiatives across government. However, this largely depends on the interoperability of information and business architectures between government agencies and between them and their users.
Interoperability in turn depends on a range of factors including the adoption of standards and definitions for recording information to enable it to be shared.
Question 8: What approaches should the Government use to allow information to be easily shared?
In addition, there are many online and information initiatives being trialled across government agencies. A variety of online tools, technologies and platforms are being tested and used. In the Web 2.0 sphere, these include the use by agencies of blogs, YouTube, Flickr and Facebook.
Question 9: How can the initiatives and ideas of agencies be harnessed for the benefit of agencies across government? How can duplication of effort be avoided?
The US Government has recently established the Data.gov website to increase public access to high value, machine readable datasets generated by the Executive Branch of the Federal Government.
Data.gov includes searchable data catalogues providing access to data in three ways: through the "raw" data catalogue, the tool catalogue and the geo-data catalogue. The raw data and the Geo-data catalogues are provided in CSV, XML, KML or SHP formats. The Tools Catalogue includes pre-packaged data sets such as look-up tables.
The stated goal of Data.gov is to improve access to Federal data and expand creative use of those data beyond the walls of government by encouraging innovative ideas (e.g., web applications). Another objective is to make government more transparent by creating an unprecedented level of openness.
To ensure these principles are implemented sensibly we need effective mechanisms for hearing complaints about and redressing government's inaction in the release of information.
Conversely, making government information available online may increase the risk of unintentional or inappropriate release of information that may damage an individual or business. If that information is then re-used, it may lead to proliferation of the harm.
Formal complaints and appeals processes already apply across the Australian Government. Depending on the specific circumstances, a person has redress, for example, to appeal mechanisms in the FOI Act, the complaints mechanisms in the Ombudsman Act 1976 or Privacy Act 1988, or judicial mechanisms in the Administration Decisions (Judicial Review) Act 1977.
Question 10: Are these complaints and appeals processes sufficient? Are additional processes needed for government as it engages in the Web 2.0 world?
All government agencies are engaged in the creation and collection of information and government's online engagement with citizens is subject to the same information laws, such as the Freedom of Information Act 1982, the Archives Act 1983 and the Privacy Act 1988, as are the records of other interactions with citizens. The fundamental importance of good recordkeeping to ensure transparent and accountable government has been widely recognised, as has the part played by failures in recordkeeping in many inquiries and audit reports.
Question 11: What should government do to foster a culture of compliance with information and records management policies and best practice?
Question 12: What recordkeeping challenges are posed by both the re-use of government information, and in the mechanisms of development of government policy and practice through interactive citizen engagement?
There is rich potential in this area for perverse outcomes. Agencies frequently cite concerns about the integrity of their information as a reason for their reluctance to release it. And the perfect can be the enemy of the good. On the one hand mandating the release of information might be one way of ensuring that agencies have an incentive to maintain its quality and integrity. On the other hand the release of some information (with an appropriate disclaimer as to quality) may often, but not necessarily always, be better than not releasing it at all.
Question 13: How does government manage the costs and risks of publication of inaccurate information?
An important aspect of quality (and integrity) is the provision of information ('metadata') that describes the quality of information, so that users can determine whether it is 'fit for purpose' in terms of their proposed use of the information. For example, knowing the source of the information, the checks the information has been subject to, and any other factors that might affect accuracy, can help users know how the information might be used appropriately and equally important, the hazards in using it improperly.
Users may be able to interact with government information providers to better understand the information (and therefore increase the likelihood that the information will be used appropriately) or to express concerns about aspects of the information.
Citizens expect government information to be of high quality and integrity but will also have an expectation of the responsiveness of government to deliver information.
Timeliness is a particularly important matter. From at least the late 1970s the ICT revolution has been driven by firms that have made felicitous tradeoffs between the quality of their offering and getting their product to market. Too early and the market could turn against a product for the number of bugs and other errors which frustrate users. Too late and the market has moved on.
This was the case even before 'Web 1.0' as summarised in Steve Jobs arresting comment "True genius ships". But it is particularly so in the world of Web 2.0 where it is now quite normal to provide users with comprehensive access to beta products and indeed to leave them designated as beta products for many years. Gmail only recently moved out of beta after five years as a mainstream consumer product.
The issue raises its head particularly in the area of data where government agencies delay publication to ensure data integrity anxious either from a natural desire to do their job properly, or to minimise risk, or to meet standards internally mandated within government. In the meantime, as we saw in the case of the Victorian fires, valuable information however imperfect goes unpublished.
Question 15: It often takes quite some time to compile and create consistent and reliable data – especially for large data sets. When is it appropriate to release limited and possibly less accurate data and where is it appropriate to wait for higher quality and more extensive data? Where various principles are in some tension with each other, for instance quality and cost or timeliness, how should trade-offs be made?
As part of the National Continence Management Strategy, the Australian Government funded the development of the National Toilet Map website . The website shows the location of more than 14,000 public and private public toilet facilities across Australia. Details can also be found along major travel routes and for shorter journeys as well. Useful information is provided about each toilet, such as location, opening hours, availability of baby change rooms, accessibility for people with disabilities and the details of other nearby toilets.
A number of organisations, commercial and not-for-profit, large and small, have requested access to the data in order to provide a range of innovative services. To date, such access has not been granted. The wider availability of this information, through sources other than the National Toilet Map website, appears to promote the objectives of the National Continence Management Strategy and is consistent with the OECD principles enunciated earlier in this Issues Paper.
It is hoped that, through strategic management of copyright and new Web 2.0 licensing tools like Creative Commons and similar open licensing mechanisms for database material, we can more easily provide the necessary permission to promote better access to and reuse of public sector information. In the short term this means using current copyright law and practice to do a better job and in the longer term assessing the appropriateness of existing copyright law for a digital environment and any changes that should be made to address problems.
Question 16: What can we do to better promote and co-ordinate initiatives in this area? How can we draw key departments together?
Question 17: What sort of public sector information should be released under what form of copyright license? When should government continue to utilise its intellectual property rights?
The 2008 Apps for Democracy competition was an initiative of the District of Columbia's Office of the Chief Information Officer. The competition involved members of the public making an application using data from the 277 datasets made available by the District of Columbia.
There was a total of $US20,000 in prize money on offer, spread over 60 cash prizes ranging from $US100 to $US2000. The competition ran for 30 days and received 47 entries including web, Facebook and iPhone applications. Entries were divided into two categories: entries by professional agencies, and "indie" entries by individuals and groups of individuals.
Entries included a large number of geospatial mash-up applications making use of available datasets. The competition was viewed as an unqualified success by the D.C. government, as it cost $US50,000 to run, but provided a claimed $US2.6 million in value to the city through the created applications.
Government is subject to additional obligations which seek to ensure that all levels of our community are able to access its services, whether online or offline. For online engagement, government must consider those citizens who are excluded for various reasons, e.g. lack of access to technology, disability, health barriers, lack of computer-literacy, lack of English, lack of literacy, etc. Many of these issues are currently not adequately addressed by commercially available and popular online platforms.
Pricing and Competition (OECD principles 8-9) There is currently a mixed approach across government to the pricing of information. In the electronic world, the marginal costs of providing information are lower than in a paper-based environment, which could suggest that different pricing approaches might be appropriate. Furthermore, information is often considered as a 'public good', which also might impact on thinking about appropriate pricing policies.
Question 18: When should agencies charge for access to information? Should agencies charge when they are providing value-added services? What might constitute 'value added services' (eg customisation of information)? In what circumstances should agencies be able to recover the costs of obtaining the information or providing access? A common model in the private sector is 'freemium' distribution whereby many, often most, users are supplied with some product or service for free whilst others pay for use in large scale commercial enterprise (for instance AVG anti-virus) or for some premium product (for instance Word Web). Are there similar models for public sector information and/or do they merit further consideration?
Pricing should also take into account the economic value of information if released.
There are many cases where there is significant positive economic or social value in making data freely available – such as the sharing of emergency data between government agencies (which currently is often costed at a level that discourages usage and therefore reduces the effectiveness of emergency responses).
Charging for maintenance and distribution costs can cost significantly more in lost economic or social benefit than it achieves in cost recovery.
Public private partnerships (OECD principle 11) Public-private partnerships might provide a way to make public sector information more readily available, for example by financing the costs of digitisation.
Question 19: How can government take advantage of public private partnerships to increase access to public sector information without unduly constraining opportunities for third parties to use and reuse the information?
International access and use (OECD principle 12) Many government agencies are involved in cooperative international programs and liaison. There are advantages to government in guiding interoperability and compatibility in dataset formats so as to ensure the most efficient and effective use of information.
Question 20: What international activities relevant to this Taskforce should the Taskforce be considering and what needs to be done to improve cross-border use and interoperability of information?
Question 21: How can best practice be facilitated, identified, rewarded, and further propagated?
There are obvious benefits to government in using collaborative technologies to draw on the skills, knowledge and resources of the general community when developing policies or delivering services. In many situations, much of the expertise, experience and deep knowledge that governments need to make good decisions about increasingly complex or 'wicked' problems exists outside government. New possibilities are emerging to link highly distributed networks of knowledge and expertise quickly and securely to focus on shared opportunities or problems to be solved.
In harnessing the opportunities arising from Web 2.0 technologies there is a potential for individuals to hesitate or avoid contributing where they sense that the technology isn't 'safe'. For example, people may fear that information about them will fall out of their control or they may avoid situations where they have to fully identify themselves before engaging with collaborative technologies. In this regard, embedding good privacy practices into collaborative technologies will play an important role in garnering the trust and confidence of individuals who wish to participate.
But beyond that, online engagement creates at least the potential to 'democratise' public administration and policy development by offering a much richer mix of spaces in which people can talk, listen, debate, argue and contribute their ideas and aspirations to the public conversation.
Moderated online engagement offers the potential for people to learn from each other and to constructively find common ground.
Question 22: Have you engaged with the Australian government via a Web 2.0 channel? Which one/s? If so, why and what was your experience? If not, why not? What can be improved?
A major finding of the UK Power of Information reports is that Government consultation efforts can be greatly enhanced by consulting with existing interest groups in their online communities, such as netmums.com. A similar approach involves employing social networks and existing forums and blogs to target a different audience than would normally respond to a traditional government consultation. In Australia a recent example of this was the use of the Open Forum blog by Father Frank Brennan , the Chair of the Human Rights Consultative Committee to engage netizens on questions relating to the consultation.
Different combinations of public interaction methods suit different requirements and different audiences.
• including RSS feeds on the consultation site.
Having responded to one consultation, a user may be more likely to respond to another consultation. A related consultation should be easily visible at the point of completion or commencement of a user's response.
The benefits of online engagement will be realised best if as wide a range of citizens as possible are involved. However, some people may be uncomfortable with this type of interaction with government.
Question 23: How can government capture the imagination of citizens to encourage participation in policy development and collaboration between citizens and government?
Question 24: What sort of privacy issues might dissuade individuals from engaging with government via collaborative technologies? What sort of steps can we take to ensure that personal information is used appropriately? What options are there for mitigating any potential privacy risks?
Governments have generally mandated minimum accessibility standards which can create obstacles to using some of the leading Web 2.0 platforms where they do not conform with those standards.
Question 25: How can government make it easier for people to engage on policy and other issues and make sure the opportunities are as open and accessible as possible?
Question 26: What trade-offs must be considered between government using commercially available and popular online platforms and ensuring inclusive participation with all members of society and how should those tradeoffs be made?
It is significant that the Government is in the process of introducing legislation that proposes to incorporate the Office of the Privacy Commissioner, together with a Freedom of Information Commissioner, in a proposed Office of the Information Commissioner. These initiatives illustrate the complex relationship and tension between protecting the privacy of individuals and opening access to public sector information.
A great deal of public sector information (PSI) is not on its face "personal information" as defined in the Privacy Act 1988. On the other hand there can still be privacy issues or risks associated with open access to PSI. Information from which only name and address has been removed, may still fall under the definition of "personal information," as an individual's identity may still be reasonably ascertainable from the information.
Re-identification of personal information is usually context-sensitive. An organisation's capacity to re-identify data may depend critically on its particular resources, or changing priorities. Factors which may impact on the capacity for data to be re-identified include available data, new technologies, resources, and social or political imperatives for access to new or different types of data. Combining unrelated datasets, now or in the future, may create the environment for more intrusive profiling, data-linking or data-matching of individuals' personal information.
There are also privacy risks and issues relating to digital engagement, particularly around moderation, consent to publish and anonymity. For example, in respect to post-moderation, there is the risk that a participant may identify and provide information about another individual, which is published without that individual's knowledge or consent. This may constitute a breach of privacy by the relevant agency and provide grounds for a complaint to the Privacy Commissioner by the individual whose personal information has been disclosed. This risk is not different in kind to existing risks, but the immediacy and ubiquity of the internet increases its likelihood considerably.
Australian Government efforts in online engagement have been crafted to comply with the Australian Public Service values, set out in section 10 of the Public Service Act 1999. These require that public servants to act in an apolitical, impartial and professional way.
The Australian Public Service Commission also recently released interim protocols for online media participation by public servants . There are a number of other legislative restrictions on what information can be disclosed by public servants. This has an impact on how free government agencies and public servants are to experiment with online consultation, since agency websites must be impartial and apolitical. This may affect the extent to which they can enter into meaningful discussion with the public.
Question 27: How can public servants comply with the APS values and other protocols whilst still participating in online engagement? Should existing rules including legislation be changed and/or adapted to facilitate greater online engagement?
Moderation Government collaborative websites such as blogs generally require moderation. This involves time and labour cost. Third-party moderation tools and services are available. The process of moderation should be transparent, with the principles and parameters of the editorial control specified. This is good practice in all online jurisdictions.
Online consultations seeking input from the public can be at risk of agenda hijacking and the derailment of discussion although other forms of engagement are not immune from such possibilities. Thus for instance when the Obama Administration held online consultations on what the new Administration's new priorities should be, the legalisation of marijuana was voted the most important priority. More recently one of the most prominent priorities has been the release of Barack Obama's birth certificate.
While it is appropriate that views about which people feel strongly are aired, it is also important for there to be an ability to 'agree to disagree' and get on with the process of using the strengths of online engagement to improve policy development without being diverted by the attention given to symbolic issues or to lowest common denominators in policy.
Question 28: How does government provide sufficient room for personal debate and passionate dissent but still ensure appropriate levels of moderation in online forums? Should moderation be 'outsourced' and if so in what circumstances and how? How might volunteers from the commenting community be selected to moderate?
… If legalization of marijuana comes out of Obama's online consultations, perhaps he should have a legalization-of-marijuana policy that stakes out a position on the issue. Personally I couldn't care less, but if it's an issue that some folks think is important enough to get organized over, why shouldn't it be on the agenda? Would it hurt to put out a position paper?
New collaborative technologies are emerging all the time. These new technologies can improve the efficiencies of Government internally and can also alter and (hopefully) improve external-facing relations, particularly government-citizen engagement.
• awareness of the new technologies and the opportunities that they offer may delay their adoption.
Cultural barriers may constrain the adoption of collaborative tools and the newness of the approach may generate trepidation and dissuade uptake within the public sector.
Question 29: What are the barriers to fostering a culture of online innovation within government? Which of those barriers should be maintained in any Government 2.0 initiatives? Which of those barriers should be removed? How should this be achieved? What different norms can or should apply to Government 2.0 efforts?
Question 30: To what extent can government assist the uptake of Government 2.0 by centrally providing standard business management guidance and tools to avoid agencies having to 'reinvent the wheel' when considering their own online engagement guidelines?
Question 31: How can government engage with individuals and stakeholders to support the development of innovative policies, programs, practices and service delivery? Are there good examples of where this is happening?
For profit firms often use the rich data they harvest from their existing information assets and their ongoing presence on the web to guide their own innovation, measuring consumer reactions to many small scale experiments and optimising operations, for instance the design of a website, in response to this feedback.
Question 32: To what extent can we promote such an approach in the public sector and are there any examples of emerging practice?
It is a cliché that public sector managers – and possibly the Ministers to whom they report -- are risk averse. But often they are not so much risk averse as innovation averse. That is, there is a high 'burden of proof' against doing something differently even where it involves relatively low risks.
Sometimes this is because it is simply more comfortable to do things the way they've always been done. In other circumstances, some argue that specific professions can be set in their ways. There may be some wisdom in this given the complexity of existing systems and the possibility of unanticipated consequences, particularly where these consequences may be political. These decisions are often heavily influenced by experts.
Question 33: How can such expertise be governed so as not to unduly stifle innovation?
In comparison to many large commercial enterprises, public sector agencies in the main adopt quite restrictive practices in allowing staff access to Web 2.0 tools, social networking sites and even webmail. Most agencies simply ban access to these sites. One of the reasons often used to justify this position is the need to protect internal IT systems from exposure to threats from the internet. Highly prescriptive and centrally mandated security policies are often rigorously applied. Given the low risk culture of the public sector, it is difficult to see how agencies wishing to enter into the Web 2.0 world will be able to argue that the benefits to citizens, and to the operations of the agency, are of sufficient value to offset an exposure which cannot easily be assessed. Clearly the risks to agencies will vary depending on the nature of their business. It is unlikely that technology alone will solve this challenge.
Question 34: To what degree is the opportunity for Government agencies to participate in the Web 2.0 world inhibited, or severely compromised, by issues such as security? How might this problem be overcome, in general and by individual agencies, within current legal and policy parameters and how might these parameters be changed to assist in overcoming these problems?
The use by government agencies of social networks and Web 2.0 applications and services may raise contractual and procurement issues for governments such as unacceptable indemnity clauses.
The United States Government, through the General Services Administration, negotiated whole of government agreements with Flickr, YouTube and other Web 2.0 providers with waivers of objectionable provisions. Similar agreements with Web 2.0 providers may be needed in Australia.
The Australian Government has proposed legislative reforms with the principal objects of promoting a pro-disclosure culture across the Government and building a stronger foundation for more openness in government. These reforms involve changes to the Freedom of Information Act 1982 and Archives Act 1983 and the establishment of an Office of the Information Commissioner (OIC).
The functions of the Information Commissioner are set out in Clause 9 of the exposure draft and require the Information Commissioner to report to the Minister on a broad range of policies and practices relating to the administration and management of government information.
This Taskforce, in its Terms of Reference , has been given the task of identifying policies and frameworks to assist the Information Commissioner (and other agencies) in encouraging the dissemination of government information.
The Information Commissioner functions set out in the proposed Exposure Draft will obviously encompass issues that touch on questions raised in this Issues Paper. One of these is which aspects of Government information could fall within the purview of the proposed OIC.
These include, but are not limited to, the information management standards, policies and guidelines that are the responsibility of the National Archives, the IT system issues that are the responsibility of the Australian Government Information Management Office, and the administration of copyright that is the responsibility of the Attorney-General's Department.
These areas all have some impact on recommendations the Taskforce might make.
Question 35: What role could the proposed OIC play in encouraging the development of Government 2.0? Are there practical recommendations the Taskforce might make about how the OIC might best fulfil its functions in relation to optimising the dissemination of Government information?
We welcome your written submissions. There is no set format required and submissions need not be formal documents.
Submissions in electronic format are preferred and can be emailed to us at [email protected].
We also offer the option to make online submissions through our Consultation page at http://gov2.net.au/consultation.
As a general principle all written submissions will be placed on the Government 2.0 website, as will discussion papers and other material developed as the Taskforce progresses.
Confidential submissions will be accepted from individuals where individuals can argue credibly that publication might compromise their ability to express their view freely. Pseudonymous submissions will also be accepted. Should you make a pseudonymous submission, it may not receive full consideration unless you remain contactable by e-mail should we wish to seek clarification or elaboration.
Please note that any request made under the Freedom of Information Act 1982 for access to any material marked confidential will be determined in accordance with that Act. Submissions must be received by start of business Monday 24 August 2009.
If you do not want to make a written submission but would still like to give us some feedback, you can communicate with us on our blog at http://gov2.net.au.
• identify and/or trial initiatives that may achieve or demonstrate how to accomplish the above objectives.
The Taskforce will advise government on structural barriers that prevent, and policies to promote, greater information disclosure, digital innovation and online engagement including the division of responsibilities for, and overall coordination of, these issues within government.
The Taskforce will work with the public, private, cultural and not for profit sectors to fund and develop seed projects that demonstrate the potential of proactive information disclosure and digital engagement for government. More information can be found on the Taskforce's Project Fund page.
• encouraging effective online innovation, consultation and engagement by government, including by drawing on the lessons of the government's online consultation trials and any initiatives undertaken by the Taskforce.
The Taskforce will meet regularly, consulting in an open and transparent manner and use online solutions for its engagement wherever possible.
The Taskforce will provide a final report on its activities to the Minister for Finance and Deregulation and the Cabinet Secretary by the end of 2009. The Taskforce will disband on completion of its final report.
Unless otherwise specified, posts are licensed under the Creative Commons Attribution licence, Australian variant 2.5.
We do not hold copyright for comments, however, except where we make it clear that other licensing arrangements are contemplated, your submission of content to this site is taken as an assertion by you that your own content falls under the same Creative Commons license as posts. If you have made a comment unaware of this policy and you are unhappy about it, please contact us and we can remove your comment from our system.
The Taskforce does not hold copyright for the Government 2.0 logo which was designed by Ben Crothers of Catch Media but as a condition of entry to the design competition, the creator of the logo consented to its use under a Creative Commons Attribution Non Commercial Use license Australian variant 2.5 .
All rights reserved and Creative Commons together?
Just noticed that a book I was reading over is apparently "Copyright All rights reserved." and Creative Commons licensed at the same time, I thought that they conflicted? There is probably some legal reason, but it seems a bit weird and confusing to me. Its also not the first time I've come across something like this.
EDIT: Maybe it means that we start off with all rights reserved, and from there give you some exceptions or exclusions to these reserved rights. But, well at least in Australia you have "All rights reserved" unless you state otherwise, making it redundant.
It's sad but I'm not surprised. Not only does this reinforce that the Government does not want you republishing what they say in Parliament sessions (as per their copyright statement on their web site), but they are not even willing to grant specific rights to specific groups for specific intentions.
Patents are a business tool.
I think that is the most important thing I gathered from this lecture by two Freehills attorneys (Stuart Irvine & Ronelle Geldenhuys) about IP and software patents. Lecture slides here.
Monopoly vs. Secrecy. In order to get the monopoly you must give up the secrecy.
Patents can be used as a sword (legal action to get royalties or force the infringer to stop), shield (dissuade others from infringing), war chest (trade and negotiation).
A patent gives the patent owner an exclusive right to exclude others from exploiting (manufacturing or importing a patented product or using or importing a product made by a patented process) an invention in a particular country.
To enforce a patent, the patent owner must take the infringer to court.
"A method of determining the length of a road (L) in metres by applying the formula $latex L = \cos \theta \times N \times g^2$ where $latex \theta$ is the gradient of the road, N is the number of litres of fuel used by a car travelling on the road, and g is the acceleration due to gravity", According to APO, Manual of Practice and Procedure, Volume 2. Sounds a bit silly to me.
US Pat. 5356330 (via google) - Apparatus for simulating a "high five"
Self publication prior to filing does class as prior art, meaning you cannot get the patent.
To invalidate a patent you just need to find prior art. That is, find the idea published prior to the filing date of the patent. Lesson here, if you know you don't want to get a patent for something and you want it to remain free to the world publish your idea/concept. Remember you don't need something working in order to patent it. Just detail how it would work (that's easier than getting it to work right?).
US patent 5490216 (or via google) is interesting. Filed in 1993, its a System for software registration. Basically there is a demo mode and a full mode. To get the full mode you need a registration key. Thats the general gitz. I didn't read the whole thing.
I don't know what to think. They seem trivial, simple and obvious, but they weren't published today. As most people would say, you need to ensure that trivial patents are not granted (problem here is how do you define trivial?), and that the term is not too long (20 years is too long in my opinion).
Patenting of illegal methods in not allowed, though you may patent a things which may be used illegally such as gun (heh, otherwise nothing would be patentable).
Interesting example. A safe design was patented and then a thief used the patents to work out how to break it.
In terms of software, copyrighting software only stops others from using the same implementation as you. They are free to use an alternate implementation to do the exact same thing.
You can copyright compiled machine code.
I have a lot to say about this (creative/computational universe, and the clouds that span derivative works). So much that I'll have to leave it till later.
Registered designs are interesting. There is a nice brochure from an Australian Law firm here.
A registered design provides a monopoly of a limited duration (max 10 years in Australia) granted by the government to an entity of a "concept" which determines the appearance of a product. I'm a little confused here as I though (its such a shame that the audio recoding from that lecture is corrupt) Geldenhuys said that registered designs are for a specific device. So if you register a design for an electronic device, anyone can use that design for say a paperweight. However in their lecture slides it says that registered designs protect appearance not functionality.
You will all probably recognise AU Registered Design 307210. Currently owned by Apple Inc. and must expire by Nov 23, 2015.
All registered designs must have a "Statement of Newness and Distinctiveness". AU RD 307210 says, "Newness and distinctiveness is claimed in the visual features shown in solid lines in the representations."
Registered designs must be renewed to stay protected. Though they have a max of 10 years, renewal fees get larger near the end of the designs protected life, either Irvine or Geldenhuys then added to this "governments don't like monopolies". Sorry but I strongly disagree with you there. If governments didn't like monopolies they would abolish crown copyright.
I won't say too much here. But here is a sample trade mark "thing"(?).
You don't publish, you just swear everyone to secrecy (contracts). Does not protect against reverse engineering or independent formulation.
From Cory Doctorow and the start of Little Brother (pg 5).
Finally, let's look at the moral case. Copying stuff is natural. It's how we learn (copying our parents and the people around us). My first story, written when I was six, was an excited retelling of Star Wars, which I'd just seen in the theater. Now that the Internet the world's most efficient copying machine is pretty much everywhere, our copying instinct is just going to play out more and more. There's no way I can stop my readers, and if I tried, I'd be a hypocrite: when I was 17, I was making mixtapes, photocopying stories, and generally copying in every way I could imagine. If the Internet had been around then, I'd have been using it to copy as much as I possibly could. There's no way to stop it, and the people who try end up doing more harm than piracy ever did. The record industry's ridiculous holy war against filesharers (more than 20,000 music fans sued and counting!) exemplifies the absurdity of trying to get the foodcoloring out of the swimming pool. If the choice is between allowing copying or being a frothing bully lashing out at anything he can reach, I choose the former.
It got me thinking, patent law was really designed for a different age where you invented things such as the telephone and the Rubik's Cube. Patents documented the inner workings of the invention and how to build it. Thus after the patent owner has made some money from their invention and it falls into the patent equivalent of the public domain anyone else can make it and build upon it. Enter the digital age where generally copyright is used to protect computer software rather than patents (I've heard of software patents, but they don't require submission of source code). Copyright was intended to protect creative works where there are no "inner workings" or "instructions" needed in order to build it. Given the fact that most (maybe not most, but lots of) software is written in programming languages that get compiled into machine code, computer software needs these "inner workings" and "instructions" i.e. the source code in order to build upon it once the original creators have made some money.
There are two problems here with the fact that software falls under copyright rather than patents.
secondly copyright laws currently last life + 70 years. In some cases this could be 160 years it takes for the copyright to expire. By then the technologies would have most certainly changed and the software would be of no use (even if the physical storage medium has survived that long (though I think laws now allow copying for backup)). As suggested in the quoted article above a reasonable protection length would need to be less. I think 2-3 years, but really an experienced team of worldwide economists would be able to come up with this figure much better than I could. This would, I think, push innovation forward as software creators would need to come up with new things in order to continue the income stream.
that creators will just say "okay we don't need protection from the law, we won't use patents, we'll just implement our own DRM and skip your patent laws". This is even worse as it locks up the program for as long as it takes to crack the DRM.
Another key thing is that even in the time of patents if you bought a product that was protected under patent law, you were still allowed to make changes to it. For example if you bought a Rubik's Cube and if it was protected by a patent, the law could not stop you for example pulling it apart to see what it looks like on the inside, or writing some numbers on the outside squares. However now in the digital age and particularly with the DMCA you cannot even do this (though I don't think Australia has any law that is equivalent to the DMCA that restricts you circumventing DRM). In these time it is apparently illegal for you to open up and change your own products that you have purchased and own.
I've just read this article http://smh.com.au/news/technology/biztech/youtube-yanks-freeview-parody-clip/2009/03/09/1236447116498.html and viewed this video (though that link may not work in the future) http://www.youtube.com/watch?v=Q9JGdE-p4dQ.
On one side of the argument, companies are yet again using Copyright laws (which were originally designed to create incentive to create the work in the first place (though I'm not saying that that is true for our current laws, nor it should or should not be true (I'm not an academic...)) to hinder or stop speech. This is the opposite of free speech, this is censorship. I think that in this case this derivative work should be legal. I don't think that simply because one side does not like or agree with the views of another they should be allowed to censor the others argument. If this were so, then we could not debate an issue very easily.
Despite this I do understand the other side of the argument. They have copyright in a video, and they have not authorised this reproduction of the video. Full stop.
This is where I think the current copyright laws fail. But I can't see a simple solution in sight. Creative Commons helps, but only for works that creators have chosen that (or a similar) license. On one hand this sort of derivative work should be allowed, on the other if this use were legal what would then be stopping some one taking a full length feature film, adding a small logo to the bottom (similar to what TV networks do) and then claiming it is a derivative work and hence distributes it freely to all, counter with the copyright owner of the original work who is trying to get some money back to cover their expenses of the creation of the work. This is a tricky question because its a very subjective line that splits these two examples, so it would be difficult to have a law that works for both these cases.
Should this derivative work simply be allowed because the original work was freely distributed? I think not.
A concept I explored in this post, in my view would allow both parties to win, though unfortunately I don't see this type of economy becoming the main any time soon.
Though probably not a valid argument, but the video (not the audio) in question was a commercial. It was made in an aim to get as many people as possible to watch it. Pushing organisations to stop re-distributing it seems a bit against what the ad was made for doesn't it?
So I just read the article over at ZDNET.com.au. Sadly this sounds all to common. I recommend you read the article for yourself.
I don't know the legal status of whether RailCorp would win if they went to court, but either way this in more evidence of Australia's poor Copyright laws. The fact that government created facts that are not creative works can be protected by copyright is absurd. Dispite numerous reviews (Crown Copyright Law Review 2005, Review of The Nation Innovation System (though the Government is still reviewing the findings of this one)) nothing has changed.
As the article states, "A 2005 inquiry by the Copyright Law Review Committee recommended relaxation of Crown copyright provisions to allow for more easy access to public interest information, but those changes have yet to be implemented and RailCorp is standing by its challenge.". This inquiry was done in 2005, it is now 2009 so its safe to assume that the Government is not willing to change the laws in light of the recommendations.
They say that they are using copyright laws to protect people from information that may be false. That is a poor argument. The public know this, they know that this is a service provided by a third party and that it may not be accurate. This works because if there are too many problems with it for what the consumer is happy to accept they will simply not use this. This is no excuse to stop people using/republishing/remixing facts.
I always thought that copyright laws were there in order to create incentive for the original creation of a creative work. Thought I think that this is more of a US constitutional or outdated view. I do not necessarily agree with this, and I don't think that is the sole reason we need copyright laws. But obviously that is not what the copyright laws are doing in this case.
I'm just hoping that the Department of Broadband, Communications and the Digital Economy fixes crown copyright soon before this mess continues.
Remark 1. It seems that from the offical source you can only stream live, you cannot download past videos.
Remark 2. On another note I checked the licensing of the official parliamentary videos.
I'm interested if "[y]ou may ... reproduce this material in unaltered form only..." grants you the right to reproduce it as part of a larger derivative work, whilst not altering the copied segment. I think it should, but this is not clear enough in my opinion. Secondly "personal use" is a bit ambiguous. There are no references made to "personal use" in the Copyright Act 1968, so I'm wondering if this implies that one cannot republish this material for others to use. Again I think this should be allowed but it is unclear.
"On 26 November 2008, the Federal Attorney General, Hon Robert McClelland MP, launched the report Making the intangible tangible: the economic contribution of Australia's copyright industries at Parliament House, Canberra. The report by PricewaterhouseCoopers, commissioned by the Australian Copyright Council, assesses the contribution to the economy of Australia's copyright industries."
Core – industries that exist only because of copyright and are primarily involved in the creation, manufacture, production, broadcast and distribution of copyrighted works."
I wouldn't go so far as saying these industries (Motion picture and video production and distribution, Authors, writers, Magazines/periodicals, etc.) would not exist without copyright laws. Though they would not doubt be less profitable, but that is not my worry here. I am not commenting on these industries (film, music).
My concern is that this report claims that Newspapers, Libraries, Artists, would not exist were it not for copyright laws. I fail to see this. I'm not an economist, but don't newspapers make money from selling the news. Its only valuable right when its breaking. Libraries would still be there to store information, people will still borrow books. Artists would still exist, I'm guessing most people make art for fun as a way to express yourself, not for the money. Picture framers; people will still take digital photos or produce art that they want framing, if anything the picture framing industry would go up if there were no copyright laws because anyone could take someone else's image that they like and can manage to copy and print it/frame it without worrying about legal consequences.
I'm not saying we should abolish copyright laws, nor have I given this a full economic analysis, but think yourself, use some common sense. Do you really think these industries would be non-existent? But surly a multi-million dollar economic firm would know best, much better than just some kid like me who knows little about economics, wouldn't they?
I have just come to light on some of the views and information that the Australian Copyright Council has published on the Australian Creative Commons licenses. They published an Information Sheet (HTML), an article and another article. In all of these they present almost entirely reasons why not to use Creative Commons licenses with maybe just one or two arguments for the licenses. I acknowledge that they are entitled to their opinion and are free to say this even as an independent body. Despite their views it was interesting to read and made me aware that I should think more carefully about copyright licenses. It may also be appropriate to note that most (if not all) of the board members of ACC are people who make a living from a strict permission culture as opposed to a free culture. For instance the board members include people from the Australasian Performing Right Association, the Australian Society of Authors, Banki Haddock Fiora Solicitors, Copyright Agency Limited, etc. I'm guessing that most of these organisations benefit from strict copyright laws, anyway I'll put that matter aside and go on.
I'll begin with the article by Ian McDonald (who is a Senior Legal Officer for the Australian Copyright Council), titled "Creative Commons licences for visual artists: a good idea?".
One of the reasons I use and like Creative Commons licenses is that the law is too restrictive for my liking but Creative Commons is (at least to me) the only well known widespread license that breaks down this restrictiveness.
"Indeed, the one licence which a community-arts-oriented practitioner might be willing to grant—a licence to permit copying and modification only if their work is transformed or utilised in some new, creative way—is simply not available as a CC licence."
Yes, I can see occasions where an artist or creator may want to allow use of their works only for remixing whereby something new with additional value is created. But short of writing up your own license I am unaware of any respected licence which grants this. For reasons I argue later on we need to try to avoid duplicate license and try to limit them to a few common ones. The way I see it is Australians cannot license material in this way because there exists no license to do it (why doesn't the ACC write a set up?)―we are not all lawyers. We have to choose between all rights reserved and the few CC ones. I'm sure many will oppose this view but that is how I see it.
"Under US law, copyright owners have a separate right to authorise the making of derivative works, but under Australian law, they do not: owners of copyright in musical, dramatic and literary works do have a tightly defined right of 'adaptation', but there is no equivalent right relating to artistic works. In other words, having given people permission to use your work under a CC licence, you couldn't generally stop them making 'derivative' versions even if you chose one of the 'NoDerivs' licences."
Well then, according to this, if they use a CC license or not it will not change the underlying derivative right for artistic works. Hence in this respect all rights reserved and CC NoDerivs are the same, so what's the big deal? Sure some people may have a false sense of security but they would be no better off with all rights reserved in this respect. At least now the ACC has pointed this out. Its good to know but from what I just read it doesn't change anything.
"Further, when it comes to the 'NonCommercial' licences, the prohibition relates only to uses of the relevant work 'in a manner that is primarily intended or directed toward commercial advantage or private monetary compensation' (my emphasis). This wording still allows—without payment—any business or corporation to use your work in items such as corporate gifts, calendars, publications and websites, and in any other way that might only secondarily achieve a commercial advantage. Nonetheless, in each of these situations, I can see no reason in principle why, as a general rule, practising artists would want to volunteer effectively to subsidise such commercial uses of their work."
Again, thank you for pointing this out, its good to know. It would be good if there was a licence that covered this.
Many of the issues raised in the article I think could be solved by creating a set of licenses which cover all the combinations of the common usage types. Whilst CC licenses are great for some things I can see times where you might want something a little more in the middle. But it is important too not have to many and provide human readable versions because the license legal code is too much for some people. I raise some points in this article about why I favour licensing the work with a copyright license when the work is published as opposed to opting for "All rights reserved." and granting rights on a case by case basis when contacted.
Not all creators are layers. In fact (in almost certainty) every living person on this earth is a creator, even if it were only a drawing they did in kindergarten. However not everyone has experience and knowledge in copyright law. So someone may write a license but it may have legal loopholes that they are unaware of. There needs to be solid licenses that normal people who don't speak in legal terms can understand, both for the creator and the user of the work.
They then become less machine readable. For instance if I want to search works that allow verbatim copying, if every work had a different license I would have to read through each license to work out if it did allow this. However if there were a set of common well known licenses I could just search for the set that allow this, eg. "Creative Commons Attribution 2.5 Australia, ...".
What makes the CC licenses work in my opinion is much like what trademark laws do. When people see "Creative Commons Attribution 2.5 Australia", they instantly know what they can do. But if however everyone makes their own licenses people will have to try to decipher the legal mumbo jumbo.
Now to the information sheet published by ACC.
"For example, if you offer written material under a CC licence, you won't be entitled to receive any of the payments made by governments and the education sector to collecting societies for use of your material; if you offer music or songs under a CC licence, you won't be entitled to a share of the payments made to APRA by broadcasters and, for example, businesses using background music."
People who license under CC should already know this, it's good for letting them know. Not that this information sheet implies otherwise, but most people would be aware of this and they license CC because they want to make it easier for their work to be spread. They may not want money generated from their work going to a collecting society which you may not have bothered to join just for one photograph you put on the web. As a side note, I did not know what "collecting societies" like CAL (together with NEALS) were before now (though I had heard of them), but I'll look into it and write a post about it.
"You should also note that the CC licences generally take away your ability to actively manage your copyright, because they allow people to use your works in all sorts of ways without having to contact you. Of course, this is also the case where you allow a collecting society, or an agent, a publisher or a producer to deal with your work on your behalf."
This can also be a benefit, as you don't have to reply to usage requests, it also means that your work can be used how you wanted it to be used after you are no longer contactable or passed away. Also I'm guessing people are more willing to use your work if it is licensed then and there, rather than going to the effort of telling you their planned usage and asking for permission. This is better for society on a whole, see the Free Culture movement (I'll leave my arguments for this to another article).
At the end of the day, CC license are great for anyone who wants to release their work to the public allowing anyone to build upon it freely. The deed or human readable summary is just that a summary. I still love Creative Commons for both it's licenses and for its vision in what it aims to achieve. Minus the negative views thank you ACC for shining some light on the technical details of the legal code, but that won't stop me from using CC license all together.
I have used all quotes for the purposes of review and criticism.
I see two ways (they can even be combined so that both methods are used) to allowing use or granting rights to a copyrighted work. Those two being licensing the work with a copyright license when the work is published, and/or opting for "All rights reserved." and granting rights on a case by case basis when contacted.
Let's say an organisation uses the latter method for licensing a work. If you were an individual who wanted to use say a small portion for non-commercial purposes then that organisation may for instance grant you those usage rights for free. But if you were a commercial company who wanted to use the work say as part of a commercial feature film the organisation may for instance charge a fee for the usage rights. This is the approach that anyone who wanted to use a copyrighted work which does not have a license would need to take (or if the license does not meet their needs).
What if the original copyright was vested in a company that goes out of business. The work becomes an orphan work. (I'm not exactly sure what provisions in the laws allow for this though) A license allows these decisions that the organisation once made to continue to be made.
It leaves all discrimination transparent to the public and hence more reachable to the Anti-Discrimination Act. For example the latter effective allows an organisation to grant rights to say a girls school to exhibit a film to its students for free but may demand a similar boys school to pay. This kind of discrimination would be difficult to notice. However with the former approach of a license at creation time it is clear from the license what can and cannot be done and by who.
Sure I can see why a company, organisation or individual would want to do it, because it gives them more control over how their work is used, and the latter method is probably better suited where the copyright owner would charge money for any use. I personally haven't used the latter approach, though I do favour the former more. | CommonCrawl |
Spivak Calculus 4-th Ed., Chapter 2, Exercise 13a, Understanding the proof of $\sqrt3$ being irrational.
Prove that $\sqrt3$ is irrational. Hint: To treat $\sqrt3$, for example, use the fact that every integer is of the form $3n$, $3n+1$ or $3n+2$.
Supose $\sqrt3$ were rational, and let $\sqrt3 = p/q$, where $p$ and $q$ have no common factor. Then $p^2=3q^2$, so $p^2$ is divisible by 3, so $p$ must be. Thus, $p=3p'$ for some natural number $p'$ and consequently $(3p')^2=3q^2$, or $3(p')^2=q^2$. Thus, $q$ is also divisible by 3, a contradiction.
I have a hard time linking the first part where he states that "$k^2$ being divisible by 3 leads to $k$ being divisible by 3" and the second part. Where does the first conclusion come from?
NOTE: Problem statement in the book in the same manner requests the proof of $\sqrt5$ and $\sqrt6$ being irrational. However, in this question I'm interested in the proof for the case of $\sqrt3$.
Let $k$ be an integer. It can take one of the following forms: $3n$ or $3n+1$ or $3n+2$ where $n$ is simply the quotient in the euclidean division of $k$ by $3$.
if $k=3n+2$, then $k^2 = 3\times ... +1$, thus $k^2$ isn't multiple of $3$.
Thus, if $k^2$ is multiple of 3, then $k$ can't be of the form $3n+1$ or $3n+2$. Hence, it must be of the form $3n$, that is, $k$ must be multiple of 3.
Hence, if $k^2$ is multiple of $3$, then $k$ is also multiple of $3$.
If $k^2$ is divisible by $3$ then so is $k$.
holds for all integers $k$. He uses this fact below for $k=p$ and for $k=q$.
In the first part, Spivak proves that of a number is not a multiple of $3$ (that is, if it is of the type $3n+1$ or $3n+2$), then its square is not a multiple of $3$. Therefore, if the square is a multiple of $3$, then the number itself must be a multiple of $3$ too.
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Spivak Calculus Chapter 13 Question 28.
Proof that $\sqrt6 - \sqrt2 - \sqrt3$ is irrational.
Is there a way to prove numbers irrational in general? | CommonCrawl |
109 How to learn from proofs?
87 Is "women men girls love meet die" a valid sentence?
87 Does C++ compiler remove/optimize useless parentheses?
73 Are $10\times 10$ matrices spanned by powers of a single matrix?
71 Is there any concrete relation between Gödel's incompleteness theorem, the halting problem and universal Turing machines? | CommonCrawl |
SUMMARY Given the probability measure $\nu$ over the given region $\Omega\subset \R^n$, we consider the optimal location of a set $\Sigma$ composed by $n$ points $\Om$ in order to minimize the average distance $\Sigma\mapsto \int_\Om \dist(x,\Sigma) d\nu$ (the classical optimal facility location problem). The paper compares two strategies to find optimal configurations: the long-term one which consists in placing all $n$ points at once in an optimal position, and the short-term one which consists in placing the points one by one adding at each step at most one point and preserving the configuration built at previous steps. We show that the respective optimization problems exhibit qualitatively different asymptotic behavior as $n\to\infty$, although the optimization costs in both cases have the same asymptotic orders of vanishing. | CommonCrawl |
During long milking sessions, Bessie the cow likes to stare out the window of her barn at two huge rectangular billboards across the street advertising "Farmer Alex's Amazingly Appetizing Alfalfa" and "Farmer Greg's Great Grain". Pictures of these two cow feed products on the billboards look much tastier to Bessie than the grass from her farm.
One day, as Bessie is staring out the window, she is alarmed to see a huge rectangular truck parking across the street. The side of the truck has an advertisement for "Farmer Smith's Superb Steaks", which Bessie doesn't quite understand, but she is mostly concerned about the truck potentially blocking the view of her two favorite billboards.
Given the locations of the two billboards and the location of the truck, please calculate the total combined area of both billboards that is still visible. It is possible that the truck obscures neither, both, or only one of the billboards.
The first line of input contains four space-separated integers: $x_1$ $y_1$ $x_2$ $y_2$, where $(x_1, y_1)$ and $(x_2, y_2)$ are the coordinates of the lower-left and upper-right corners of the first billboard in Bessie's 2D field of view. The next line contains four more integers, similarly specifying the lower-left and upper-right corners of the second billboard. The third and final line of input contains four integers specifying the lower-left and upper-right corners of the truck. All coordinates are in the range -1000 to +1000. The two billboards are guaranteed not to have any positive area of overlap between themselves.
Please output the total combined area of both billboards that remains visible.
Here, 5 units of area from the first billboard and 12 units of area from the second billboard remain visible. | CommonCrawl |
This is a basic course of the Berlin Mathematical School and will be held in English. Depending on the audience one of the tutorials may be held in German.
Introduction to projective, spherical, hyperbolic, Möbius and Lie geometry.
Update: Further oral exams will be offered on 26 June. Please see Prof. Sullivan's webpage.
The signatures for the first two pencils of circles were reversed.
and the normals should be normalized to satisfy $\langle n_1, n_1 \rangle = \langle n_2, n_2 \rangle = 1$.
The angle $\alpha_n$ in (ii) is the interior angle of a regular Euclidean $n$-gon as determined in (i).
First lecture on Wednesday, October 18.
First tutorials on Wednesday, October 25.
The exercises are to be handed in in groups of two people. Depending on the number of students it might be possible to form groups of three.
The homework is due weekly during the tutorials on Wednesday.
Prasolov & Tikhomirov, Geometry, TMM 200, Amer. Math. Soc.
Coxeter, Non-Euclidean Geometry, Math. Assoc. Amer. | CommonCrawl |
Given a (hereditary) finitary abelian category $\mathcal C$, one can associate to it the Hall algebra $H_ \mathcal C $, which encodes the combinatorial information about extensions between objects in $\mathcal C$. When $\mathcal C$ is the category of finite-dimensional representations of a quiver over a finite field, these algebras are rather well understood and provide a useful viewpoint on quantum groups. Much less is known when $\mathcal C=\operatorname Coh X$ is the category of coherent sheaves over a smooth projective curve $X$, even though they seem to encode interesting geometric and arithmetic data associated to curves, such as the number of cuspidal functions. In particular, there is no comprehensive representation theory of such algebras.
My talk will consist of two parts. The first hour will primarily serve as a motivation for the second part, and will be dedicated to an overview of the classical theory of Hall algebras. We will recall their relation to quantum groups as evidenced by Ringel's theorem, and some structural results in the case when $\mathcal C=\operatorname Coh X$. In the second hour, I will shift the gears somewhat and introduce the cohomological version of Hall algebras (so-called CoHAs). I will then discuss some recent results providing an action of CoHA of Higgs torsion sheaves on homology groups of certain moduli spaces. These moduli spaces are heavily inspired by Nakajima quiver varieties, and are closely related to Hilbert schemes of points and moduli of sheaves on $T^*X$. If time permits, I will speculate about possible analogs of these CoHAs for an arbitrary smooth surface $S$ and/or extension of these results to Higgs bundles. | CommonCrawl |
Abstract: In the example of a weakly imperfect Bose gas, we discuss the mechanism of establishing thermodynamic equilibrium for a chaotic set of quantum vortex filaments. We assume that the dynamics of the Bose condensate is described by the Gross–Pitaevsky equation with an additional noise satisfying the fluctuation-dissipation theorem. In considering a vortex filament as the intersection line of surfaces on which the real and imaginary parts of the order parameter $\psi(\mathbf x,t)$ vanish, we obtain an equation of the Langevin type for elements of the vortex filament with an appropriately transformed random force. The Fokker–Planck equation for the probability density has a solution given by the Gibbs distribution at the temperature of the Bose condensate. In other words, when the Bose condensate is in thermal equilibrium and no other random actions exist, the system of vortices is also in thermal equilibrium. | CommonCrawl |
Herman and Alex play a game on a $5 \times 5$ board. On his turn, a player can claim any open square as his territory. Once all the squares are claimed, the winner is the player whose territory has the longer border. Herman goes first. If both play their best, who will win, or will the game end in a draw?
I will call the players $A$ and $B$.
The game is made trivial by the following observation. Let $s_A$ and $s_B$ be the final scores of the two players. Let $x_A$ be the number of outer perimeter segments that $A$'s region touches, and the same for $x_B$ with $B$.
No matter how the game is played, $s_A-s_B=x_A-x_B$.
This is because in $s_A-s_B$, all interior segments cancel out.
Therefore, all that matters is grabbing up the outside perimeter segments. The best strategy is to claim a corner if possible, claim an edge square otherwise, and then play arbitrarily once the outer squares are all gone. $A$ and $B$ will each claim two corners and six edge squares, and therefore tie.
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What is the optimal losing move?
Is there a generic algorithm to solve m,n,k games? | CommonCrawl |
We use this to prove yet another important inequality called Minkowski's inequality.
Theorem 1 (Minkowski's Inequality (General)): Let $(X, \mathfrak T, \mu)$ be a measure space and let $1 \leq p \leq \infty$. Then for all $p$-integrable functions $f, g \in \mathcal L^p (X, \mathfrak T, \mu)$ we have that $\| f + g \|_p \leq \| f \|_p + \| g \|_p$.
Proof: Let $f, g \in \mathcal L^p (X, \mathfrak T, \mu)$. Observe from the main theorem on the Lebesgue Spaces page, that for $1 \leq p \leq \infty$ we have that if $f, g \in \mathcal L^p(X, \mathfrak T, \mu)$ then $(f + g) \in \mathcal L^p (X, \mathfrak T, \mu)$. So we indeed may consider the $p$-norm of $f + g$.
There are a few cases to consider. | CommonCrawl |
Events matching "Plurisubharmonic subextensions as envelopes of dis"
I will describe new joint work with Evgeny Poletsky. We prove a disc formula for the largest plurisubharmonic subextension of an upper semicontinuous function on a domain $W$ in a Stein manifold to a larger domain $X$ under suitable conditions on $W$ and $X$. We introduce a related equivalence relation on the space of analytic discs in $X$ with boundary in $W$. The quotient is a complex manifold with a local biholomorphism to $X$, except it need not be Hausdorff. We use our disc formula to generalise Kiselman's minimum principle. We show that his infimum function is an example of a plurisubharmonic subextension.
It is well-known that orbifolds can be represented by a special kind of Lie groupoid, namely those that are étale and proper. Lie groupoids themselves are one way of presenting certain nice differentiable stacks. In joint work with Ray Vozzo we have constructed a presentation of the mapping stack Hom(disc(M),X), for M a compact manifold and X a differentiable stack, by a Fréchet-Lie groupoid. This uses an apparently new result in global analysis about the map C^\infty(K_1,Y) \to C^\infty(K_2,Y) induced by restriction along the inclusion K_2 \to K_1, for certain compact K_1,K_2. We apply this to the case of X being an orbifold to show that the mapping stack is an infinite-dimensional orbifold groupoid. We also present results about mapping groupoids for bundle gerbes.
Let Diff(D^k) be the space of diffeomorphisms of the k-disc fixing the boundary point wise. In this talk I will show for k > 5, that the homotopy groups \pi_*Diff(D^k) have non-zero 8-periodic 2-torsion detected in real K-theory. I will then discuss applications for spin manifolds M of dimension 6 or greater: 1) Our results input to arguments of Hitchin which now show that M admits a metric with a harmonic spinor. 2) If non-empty, space of positive scalar curvature metrics on M has non-zero 8-periodic 2-torsion in its homotopy groups which is detected in real K-theory. This is part of joint work with Thomas Schick and Wolfgang Steimle.
Publications matching "Plurisubharmonic subextensions as envelopes of dis" | CommonCrawl |
Today, Connor asked the following question involving a system of linear equation with an additional parameter: Given that $x_1 + hx_2 = 4$ and $3x_1 + 6x_2 =8$, find all pairs of the form $(x_1,x_2)$ satisfying both equations. OK…What do we do with that additional $h$? Well, read on! | CommonCrawl |
This topic contains 2 replies, has 2 voices, and was last updated by sona2017 2 years, 2 months ago.
I have the date in a CSV file, I am reading in php, I am not able to convert date (Ex: 05/01/2016) to a format readable by canvas JS. The Date function is PHP is not working. Can someone please help?
In your case, changing $x_axis = date('D M d Y H:i:s O', strtotime($csv[$i])); to $x_axis = new Date('D M d Y H:i:s O', strtotime($csv[$i])); should work fine.
Thank you! I forgot to add xValueType: "dateTime". | CommonCrawl |
Davis, Burgess and Song, Renming 2011. Selected Works of Donald L. Burkholder. p. 724.
Chilin, Vladimir and Litvinov, Semyon 2011. A Banach Principle for <mml:math altimg="si1.gif" overflow="scroll" xmlns:xocs="http://www.elsevier.com/xml/xocs/dtd" xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://www.elsevier.com/xml/ja/dtd" xmlns:ja="http://www.elsevier.com/xml/ja/dtd" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:tb="http://www.elsevier.com/xml/common/table/dtd" xmlns:sb="http://www.elsevier.com/xml/common/struct-bib/dtd" xmlns:ce="http://www.elsevier.com/xml/common/dtd" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:cals="http://www.elsevier.com/xml/common/cals/dtd"><mml:msup><mml:mi>L</mml:mi><mml:mo>∞</mml:mo></mml:msup></mml:math> with semifinite measure. Journal of Mathematical Analysis and Applications, Vol. 379, Issue. 1, p. 360.
QUAS, ANTHONY and WIERDL, MÁTÉ 2010. Rates of divergence of non-conventional ergodic averages. Ergodic Theory and Dynamical Systems, Vol. 30, Issue. 01, p. 233.
Карагулян, Григорий Арташесович and Karagulyan, Grigori Artashesovich 2009. Суммы Римана и максимальные функции в $\mathbb R^n$. Математический сборник, Vol. 200, Issue. 4, p. 53.
Akcoglu, Mustafa Baxter, John Bellow, Alexandra and Jones, Roger L. 2001. On restricted weak type (1,1); the discrete case. Israel Journal of Mathematics, Vol. 124, Issue. 1, p. 285.
Petersen, Karl 1996. Ergodic theorems and the basis of science. Synthese, Vol. 108, Issue. 2, p. 171.
In this paper we establish conditions on a sequence of operators which imply divergence. In fact, we give conditions which imply that we can find a set B of measure as close to zero as we like, but such that the operators applied to the characteristic function of this set have a lim sup equal to 1 and a lim inf equal to 0 a.e. (strong sweeping out). The results include the fact that ergodic averages along lacunary sequences, certain convolution powers, and the Riemann sums considered by Rudin are all strong sweeping out. One of the criteria for strong sweeping out involves a condition on the Fourier transform of the sequence of measures, which is often easily checked. The second criterion for strong sweeping out involves showing that a sequence of numbers satisfies a property similar to the conclusion of Kronecker's lemma on sequences linearly independent over the rationals.
[B1]Bellow, A.. On bad universal sequences in ergodic theory (II), Springer Verlag Lecture Notes in Math, 1033, 1983.
[B3]Bellow, A.. Two problems. Proc. Oberwolfach Conf. Measure Theory (June 1981), Springer Lecture Notes in Math. 945, (1982).
[F]Furstenberg, H.. Recurrence in Ergodic Theory and Combinatorial Number Theory. Princeton University Press, Princeton, 1981.
[K1]Krengel, U.. Ergodic Theorems, de Gruyter, Berlin-New York, 1985.
[R2]Rosenblatt, J.. Universally bad sequences in ergodic theory. Almost Everywhere Convergence II. ed. Bellow, A. and Jones, R.. Academic Press, 1991, pp. 227–245.
[S]Smorodinsky, M.. Ergodic Theory, Entropy. Springer-Verlag, New York, 1971.
[W]Wierdl, M.. Almost everywhere convergence and recurrence along subsequences in ergodic theory. Ph.D Thesis, Ohio State University, 1989. | CommonCrawl |
If we form a triangle with sides $b, c$ and angle $\alpha$ in-between then, according to the Law of Cosines, the side opposite $\alpha$ will be exactly $a.$ This means that $a,b,c$ form a triangle and the Law of Cosines applied twice implies the required two inequalities.
Leo Giugiuc has kindly messaged me this problem from the 2017 Caucasus Mathematics Olympiad (#6), and a fancy solution of his (Solution 1).
Computer assisted Solution 3 is by N. N. Taleb. | CommonCrawl |
Abstract: When modelling inflaton fluctuations as a free quantum scalar field, the initial vacuum is conventionally imposed at the infinite past. This is called the Bunch-Davies (BD) vacuum. If however an asymptotically Minkowskian past does not exist, this requires modifications. We derive corrections to the scalar spectral index $n_s$ and the tensor tilt $n_t$ descending from arbitrary mixed states or from explicit non-BD initial conditions. The former may stem from some pre-inflationary background and can redshift away whereas the latter are induced by a timelike hypersurface parametrising a physical cut-off. In both cases, we find that corrections scale in parts or fully as $\mathcal O(\epsilon)$ where $\epsilon$ is the first slow-roll parameter. The precise observational footprint is hence dependent on the model driving inflation. Further, we show how the inflationary consistency relation is altered. We thus provide an analytic handle on possible high scale or pre-inflationary physics. | CommonCrawl |
We analyze elemental abundances of the common proper motion pair HD 134439 and HD 134440 to understand their formation history. This pair of metal-poor ([Fe/H]$\sim -1.50$) halo dwarfs are known, from previous studies, to exhibit abnormally low [$\alpha$/Fe] ratios compared to typical Galactic halo stars. Some have attributed this to planetesimal accretion; others believe these stars formed in the dusty part of a dwarf spheroidal galaxy and were later captured by our Galaxy. To investigate this anomaly, we measure carbon, nitrogen, and oxygen abundances for HD 134439 and HD 134440 from near-UV molecular features using high-resolution spectra obtained with Keck HIRES spectrograph. The [C, N, O/Fe] ratios range from $\sim -0.30$ to $\sim -0.60$ dex. We confirm a previously suggested correlation between the elemental abundances and condensation temperature at the $\sim$5\% confidence level. A comparison of HD 134439 and HD 134440 with stars of similar metallicity in the Galactic halo suggests very different formation histories; though, the abundances of dwarf spheroidal stars seems less different from our stars. Chemical yields of low mass Type II supernovae provide an explanation for most of the abundance patterns observed for the common proper motion pair. Finally, the peculiar abundances of neutron-capture elements (Y, Ag, Ba, Eu) are put in context with various nucleosynthetic sources.
Chen, Yu, "A Spectroscopic Analysis of HD 134439 and HD 134440" (2008). All Theses. 466. | CommonCrawl |
This paper addresses the problem of provably efficient and practically good on-the-fly determinacy race detection in task parallel programs that use futures. Prior works on determinacy race detection have mostly focused on either task parallel programs that follow a series-parallel dependence structure or ones with unrestricted use of futures that generate arbitrary dependences. In this work, we consider a restricted use of futures and show that we can detect races more efficiently than with general use of futures.
Specifically, we present two algorithms: \MultiBags and \MultiBagsPlus. \MultiBags targets programs that use futures in a restricted fashion and runs in time $O(T_1 \alpha(m,n))$, where $T_1$ is the sequential running time of the program, $\alpha$ is the inverse Ackermann's function, $m$ is the total number of memory accesses, $n$ is the dynamic count of places at which parallelism is created. Since $\alpha$ is a very slowly growing function (upper bounded by $4$ for all practical purposes), it can be treated as a close-to-constant overhead. \MultiBagsPlus is an extension of \MultiBags that target programs with general use of futures. It runs in time $O((T_1+k^2)\alpha(m,n))$ where $T_1$, $\alpha$, $m$ and $n$ are defined as before, and $k$ is the number of future operations in the computation. We implemented both algorithms and empirically demonstrate their efficiency. | CommonCrawl |
Abstract: Following our result that for the final state of continued spherical gravitational collapse, the gravitational mass of the fluid, $M_f\to 0$, we show that for a physical fluid the eventual value of $2GM_f/R_f\to 1$ rather than $2GM_f/R_f <1$, indicating approach to a zero-mass black hole. We also indicate that as the final state would be approached, the curvature components tend to blow up, and the proper radial distance $l$ and the proper time $\tau \to \infty$. This indicates that actually the singularity is never attained for the collapse of an isolated body. We also identify that, the final state may correspond to the local 3-speed $v\to c$, eventhough the circumference speed $U\to 0$. However, at a finite observation epoch, such Eternally Collapsing Objects (ECOs) may have a modest local speed of collapse $v \ll c$, and the lab frame speed of collapse should practically be zero because of their extremely high surface gravitational red-shifts. | CommonCrawl |
We consider the triple L-function $L(1/2,f\times g\times \phi_i)$ for fixed Maass forms f and g as the eigenvalue of $\phi_i$ goes to infinity.
We deduce a subconvexity bound for this L-function from the uniqueness principle in representation theory and from simple geometric properties of the corresponding invariant functional. Joint with J. Bernstein. | CommonCrawl |
Abstract: The Lieb-Liniger model describes one-dimensional bosons interacting through a repulsive contact potential. In this work, we introduce an extended version of this model by replacing the contact potential with a decaying exponential. Using the recently developed continuous matrix product states techniques, we explore the ground state phase diagram of this model by examining the superfluid and density correlation functions. At weak coupling superfluidity governs the ground state, in a similar way as in the Lieb-Liniger model. However, at strong coupling quasi-crystal and super-Tonks-Girardeau regimes are also found, which are not present in the original Lieb-Liniger case. Therefore the presence of the exponentially-decaying potential leads to a superfluid/super-Tonks-Girardeau/quasi-crystal crossover, when tuning the coupling strength from weak to strong interactions. This corresponds to a Luttinger liquid parameter in the range $K \in (0, \infty)$; in contrast with the Lieb-Liniger model, where $K \in [1, \infty)$, and the screened long-range potential, where $K \in (0, 1]$. | CommonCrawl |
Abekawa, T., Ito, K., Nakagawa, S., & Koyama, T. ( 2007).
Abi-Dargham, A., Laruelle, M., Aghajanian, G. K., Charney, D., & Krystal, J. ( 1997).
The Journal of Neuropsychiatry and Clinical Neurosciences, 9( 1), 1-17.
Aika, Y., Ren, J. Q., Kosaka, K., & Kosaka, T. ( 1994).
Experimental Brain Research, 99( 2), 267-276.
Albéri, L., Lintas, A., Kretz, R., Schwaller, B., & Villa, A. E. P.( 2013).
Journal of Neurophysiology, 109( 11), 2827-2841.
Ali, A.B., & Thomson, A.M . ( 2007).
Cerebral Cortex, 18( 6), 1260-1271.
Barr, M. S., Farzan, F., Tran, L. C., Chen, R., Fitzgerald, P. B., & Daskalakis, Z. J. ( 2010).
Schizophrenia Research, 121( 1-3), 146-152.
Bartos, M., Vida, I., & Jonas, P. ( 2007).
Nature Reviews Neuroscience, 8( 1), 45-56.
Abstract Gamma frequency oscillations are thought to provide a temporal structure for information processing in the brain. They contribute to cognitive functions, such as memory formation and sensory processing, and are disturbed in some psychiatric disorders. Fast-spiking, parvalbumin-expressing, soma-inhibiting interneurons have a key role in the generation of these oscillations. Experimental analysis in the hippocampus and the neocortex reveals that synapses among these interneurons are highly specialized. Computational analysis further suggests that synaptic specialization turns interneuron networks into robust gamma frequency oscillators.
Beasley, C.L., & Reynolds, G.P . ( 1997).
Schizophrenia Research, 24( 3), 349-355.
Recent studies have provided evidence for a functional impairment of γ-aminobutyric acid (GABA)-containing interneurons in the prefrontal cortex of schizophrenics. This evidence includes reported deficits of basket and chandelier cells, which are known to contain the calcium-binding protein parvalbumin. Using a monoclonal antibody against parvalbumin we investigated possible changes in this subpopulation of neurons in the prefrontal cortex of schizophrenic cases and controls. Significantly reduced numbers of parvalbumin-immunoreactive neurons were observed in laminae III and IV, while no difference was detected in cortical width. Our findings are consistent with damage following a toxic insult, occurring during a developmental 'window of vulnerability' and specifically affecting this subpopulation of GABAergic neurons.
Belforte, J. E., Zsiros, V., Sklar, E. R., Jiang, Z., Yu, G., Li, Y., ... Nakazawa, K. ( 2010).
Nature Neuroscience, 13( 1), 76-83.
Behrens, M. M., Ali, S. S., Dao, D. N., Lucero, J., Shekhtman, G., Quick, K. L., & Dugan, L. L. ( 2007).
Abuse of the dissociative anesthetic ketamine can lead to a syndrome indistinguishable from schizophrenia. In animals, repetitive exposure to this N-methyl-D-aspartate--receptor antagonist induces the dysfunction of a subset of cortical fast-spiking inhibitory interneurons, with loss of expression of parvalbumin and the 纬-aminobutyric acid--producing enzyme GAD67. We show here that exposure of mice to ketamine induced a persistent increase in brain superoxide due to activation in neurons of reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase. Decreasing superoxide production prevented the effects of ketamine on inhibitory interneurons in the prefrontal cortex. These results suggest that NADPH oxidase may represent a novel target for the treatment of ketamine-induced psychosis.
Behrens, M.M., & Sejnowski, T.J . ( 2009).
Does schizophrenia arise from oxidative dysregulation of parvalbumin-interneurons in the developing cortex?
Bezaire, M.J., & Soltesz, I.( 2013).
Billingslea, E. N., Tatard-Leitman, V. M., Anguiano, J., Jutzeler, C. R., Suh, J., Saunders, J. A., ... Siegel, S. J. ( 2014).
Bitanihirwe, B. K. Y., Lim, M. P., Kelley, J. F., Kaneko, T., & Woo, T. ( 2009).
BMC Psychiatry, 9( 71), 1.
Background The underlying nature of negative symptoms in psychosis is poorly understood. Investigation of the relationship between the different negative subsymptoms and neurocognition is one approach to understand more of the underlying nature. Apathy, one of the subsymptoms, is also a common symptom in other brain disorders. Its association with neurocognition, in particular executive functioning, is well documented in other brain disorders, but only studied in one former study of chronic patients with schizophrenia. This study investigates the association between apathy and neurocognitive functioning in patients with first episode psychosis (FEP), with the hypothesis that apathy is more associated with tests representing executive function than tests representing other neurocognitive domains. Methods Seventy-one FEP patients were assessed with an extensive neuropsychological test battery. Level of apathy was assessed with the abridged Apathy Evaluation Scale (AES-C-Apathy). Results AES-C-Apathy was only significantly associated with tests from the executive domain [Semantic fluency (r = .37, p < .01), Phonetic fluency (r = .25, p < .05)] and working memory [Letter Number Span (r = .26; p =< .05)]; the first two representing the initiation part of executive function. Confounding variables such as co-occuring depression, positive symptoms or use of antipsychotic medication did not significantly influence the results. Conclusion We replicated in FEP patients the relationship between apathy and executive functioning reported in another study for chronic patients with schizophrenia. We also found apathy in FEP to have the same relationship to executive functioning, as assessed with the Verbal fluency tests, as that reported in patients with other brain disorders, pointing to a common underlying nature of this symptom across disorders.
Schizophrenia Research, 14( 3), 187-202.
A rapidly growing body of data suggests that dysfunction in serotonergic (5-HT) function may be involved in the pathophysiology of schizophrenia, and that pharmacologic agents for this illness have their therapeutic effects mediated through serotonergic mechanisms. The purpose of this paper is to critically review data relevant to 5-HT's role in the pathophysiology and drug treatment of schizophrenia. Pathophysiologic evidence includes the psychotomimetic effects of lysergic acid (LSD), postmortem studies, single-dose 'challenge' studies and investigations of CSF and peripheral levels of 5-HT and its metabolites. The current nomenclature, potential therapeutic effects and importance of 5-HT receptor subtype antagonism will be examined. In addition, relatively novel strategies of 5-HT uptake blockade and direct acting 5-HT agonists will be assessed. A hypothesis of cortical-subcortical imbalance with an increase in subcortical 5-HT function responsible for positive symptoms and a decrease in prefrontal 5-HT function responsible for negative symptoms is proposed. Future implications of these data are discussed.
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Cortical gamma oscillations (20-80 Hz) predict increases in focused attention, and failure in gamma regulation is a hallmark of neurological and psychiatric disease. Current theory predicts that gamma oscillations are generated by synchronous activity of fast-spiking inhibitory interneurons, with the resulting rhythmic inhibition producing neural ensemble synchrony by generating a narrow window for effective excitation. We causally tested these hypotheses in barrel cortex in vivo by targeting optogenetic manipulation selectively to fast-spiking interneurons. Here we show that light-driven activation of fast-spiking interneurons at varied frequencies (8-200 Hz) selectively amplifies gamma oscillations. In contrast, pyramidal neuron activation amplifies only lower frequency oscillations, a cell-type-specific double dissociation. We found that the timing of a sensory input relative to a gamma cycle determined the amplitude and precision of evoked responses. Our data directly support the fast-spiking-gamma hypothesis and provide the first causal evidence that distinct network activity states can be induced in vivo by cell-type-specific activation.
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Neuroscience Letters, 211( 2), 93-96.
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Weak inhibition within visual cortex early in life prevents experience-dependent plasticity. Loss of responsiveness to an eye deprived of vision can be initiated prematurely by enhancing$\gamma-aminobutyric$acid (GABA)-mediated transmission with benzodiazepines. Here, we use a mouse "knockin" mutation to 伪 subunits that renders individual GABA type A (GABAA) receptors insensitive to diazepam to show that a particular inhibitory network controls expression of the critical period. Only$\alpha 1-containing$circuits were found to drive cortical plasticity, whereas$\alpha 2-enriched$connections separately regulated neuronal firing. This dissociation carries implications for models of brain development and the safe design of benzodiazepines for use in infants.
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Biological Psychiatry, 74( 6), 400-409.
Background: Schizophrenia is associated with impaired antioxidant defense, including abnormal serum, plasma, and red blood cell (RBC) oxidative stress parameters. We performed a meta-analysis of these associations, considering the effect of clinical status and antipsychotic treatment after an acute exacerbation of psychosis.Methods: We identified articles by searching PubMed, PsychInfo, and Institute for Scientific Information, and the reference lists of identified studies.Results: Forty-four studies met the inclusion criteria. Total antioxidant status seemed to be a state marker, because levels were significantly decreased in cross-sectional studies of serum and plasma in first-episode psychosis (FEP) and significantly increased in longitudinal studies of antipsychotic treatment for acute exacerbations of psychosis (p Conclusions: Oxidative stress abnormalities in FEP suggest an effect that might be independent of antipsychotic medications. Although some parameters (total antioxidant status, RBC catalase, and plasma nitrite) might be state markers for acute exacerbations of psychosis, others (RBC superoxide dismutase) might be trait markers; however, more longitudinal studies are needed. Our findings suggest that oxidative stress might serve as a potential biomarker in the etiopathophysiology and clinical course of schizophrenia.
Flynn, G., Alexander, D., Harris, A., Whitford, T., Wong, W., Galletly, C., ... Williams, L. M. ( 2008).
Schizophrenia Research, 105( 1-3), 262-271.
Recent studies have explored a model of the disconnection hypothesis of schizophrenia through the demonstration of abnormal stimulus induced gamma phase synchrony (GPS). These studies have principally examined synchrony in the 4002Hz band elicited in post-stimulus time periods, relative to a pre-stimulus baseline. In this study we examined the absolute magnitude of GPS elicited by a selective attention task, in first-episode psychosis (FEP). We hypothesized that FEP would be associated with abnormalities in absolute GPS, particularly when required to selectively attend to task-relevant stimuli. Fifty-five first-episode psychosis (FEP) subjects and one hundred and ten matched healthy control subjects underwent an auditory oddball selective attention task during EEG recording. The absolute magnitude of GPS was extracted for the range 35–4502Hz, and time-locked to stimulus onset. GPS averaged were computed for oddball 'target' (task-relevant) and 'non-target' (task-irrelevant) stimuli, for each subject. FEP subjects showed a significant elevation in absolute GPS relative to controls, apparent across the 35–4502Hz range. This elevation was most marked in the left centro-temporal region, across the 80002ms post-stimulus period. In FEP subjects, the elevation in GPS was also greater for target compared to non-target stimuli, while healthy controls did not show a stimulus effect. These findings complement previous evidence for reductions in peak gamma synchrony, calculated relative to a pre-stimulus baseline, in schizophrenia. The results an excess of absolute GPS in schizophrenia may contribute to an inability to effectively integrate task-relevant information, which underlie psychotic symptoms.
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Journal of Neurodevelopmental Disorders, 1( 2), 172-181.
One unifying explanation for the complexity of Autism Spectrum Disorders (ASD) may lie in the disruption of excitatory/inhibitory (E/I) circuit balance during critical periods of development. We examined whether Parvalbumin (PV)-positive inhibitory neurons, which normally drive experience-dependent circuit refinement (Hensch Nat Rev Neurosci 6:877鈥888, 1), are disrupted across heterogeneous ASD mouse models. We performed a meta-analysis of PV expression in previously published ASD mouse models and analyzed two additional models, reflecting an embryonic chemical insult (prenatal valproate, VPA) or single-gene mutation identified in human patients (Neuroligin-3, NL-3 R451C). PV-cells were reduced in the neocortex across multiple ASD mouse models. In striking contrast to controls, both VPA and NL-3 mouse models exhibited an asymmetric PV-cell reduction across hemispheres in parietal and occipital cortices (but not the underlying area CA1). ASD mouse models may share a PV-circuit disruption, providing new insight into circuit development and potential prevention by treatment of autism. The online version of this article (doi:10.1007/s11689-009-9023-x) contains supplementary material, which is available to authorized users.
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Gamma activity in schizophrenia: evidence of impaired network binding?
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Phencyclidine (PCP, "angel dust") induces a psychotomimetic state that closely resembles schizophrenia. As opposed to amphetamine-induced psychosis, PCP-induced psychosis incorporates both positive (e.g., hallucinations, paranoia) and negative (e.g., emotional withdrawal, motor retardation) schizophrenic symptoms. PCP-induced psychosis also uniquely incorporates the formal thought disorder and neuropsychological deficits associated with schizophrenia. The purpose of the present paper is to review recent advances in the study of the molecular mechanisms of PCP action and to describe their implications for the understanding of schizophrenic pathophysiology. Twenty-five papers were identified that described the clinical dose and serum and CSF levels at which PCP induces its psychotomimetic effects. The dose range of PCP-induced effects were compared to the dose range at which PCP interacts with specific molecular targets and affects neurotransmission. It was found that PCP-induced psychotomimetic effects are associated with submicromolar serum concentrations of PCP. At these concentrations PCP interacts selectively with a specific binding site (PCP receptor) that is associated with the N-methyl-D-aspartate (NMDA)-type excitatory amino acid receptor. Occupation of its receptor by PCP induces noncompetitive inhibition of NMDA receptor-mediated neurotransmission. Other NMDA antagonists such as the dissociative anesthetic ketamine induce PCP-like neurobehavioral effects in proportion to their potency in binding to the PCP receptor and inducing NMDA receptor inhibition. These findings suggest that endogenous dysfunction of NMDA receptor-mediated neurotransmission might contribute to the pathogenesis of schizophrenia. The relative implications of the PCP and amphetamine models of schizophrenia are discussed in relationship to the diagnosis and etiology of schizophrenia.
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Autism is a disabling neurodevelopmental disorder characterized by social deficits, language impairment, and repetitive behaviors with few effective treatments. New evidence suggests that autism has reliable electrophysiological endophenotypes and that these measures may be caused by n-methyl-d-aspartic acid receptor (NMDAR) disruption on parvalbumin (PV)-containing interneurons. These findings could be used to create new translational biomarkers. Recent developments have allowed for cell-type selective knockout of NMDARs in order to examine the perturbations caused by disrupting specific circuits. This study examines several electrophysiological and behavioral measures disrupted in autism using a PV-selective reduction in NMDA R1 subunit. Mouse electroencephalograph (EEG) was recorded in response to auditory stimuli. Event-related potential (ERP) component amplitude and latency analysis, social testing, and premating ultrasonic vocalizations (USVs) recordings were performed. Correlations were examined between the ERP latency and behavioral measures. The N1 ERP latency was delayed, sociability was reduced, and mating USVs were impaired in PV-selective NMDA Receptor 1 Knockout (NR1 KO) as compared with wild-type mice. There was a significant correlation between N1 latency and sociability but not between N1 latency and premating USV power or T-maze performance. The increases in N1 latency, impaired sociability, and reduced vocalizations in PV-selective NR1 KO mice mimic similar changes found in autism. Electrophysiological changes correlate to reduced sociability, indicating that the local circuit mechanisms controlling N1 latency may be utilized in social function. Therefore, we propose that behavioral and electrophysiological alterations in PV-selective NR1 KO mice may serve as a useful model for therapeutic development in autism. Autism Res 2013, 6: 69 77. 2013 International Society for Autism Research, Wiley Periodicals, Inc.
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The early visual-evoked gamma oscillation (VGO) elicited by Gestalt stimuli is reduced in schizophrenia patients compared with healthy individuals, but it is unknown whether this effect is specific to these particular stimuli and task. In contrast, the early auditory-evoked gamma oscillation (AGO) was reported to be unaffected in a sample of unmedicated, mostly first-episode schizophrenics, but it is unknown whether this oscillation is abnormal in chronic, medicated patients. We investigated these issues by examining the VGO and AGO in chronic schizophrenic (SZ) and matched healthy control (HC) subjects. Subjects (21 HC, 23 SZ) performed visual and auditory oddball tasks. Visual stimuli were letters, and auditory stimuli were simple tones. Event-related spectral measures (phase locking factor and evoked power) were computed on Morlet wavelet-transformed single epochs from the standard trials. VGO phase locking at occipital electrodes was reduced in SZ compared with HC. In contrast, AGO phase locking and evoked power did not differ between groups. The VGO deficit may be a general phenomenon in schizophrenia, whereas the AGO evoked by simple tone stimuli does not appear to be abnormal in chronic, medicated schizophrenia patients.
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Tremblay et聽al. review our current knowledge of the diversity of neocortical GABAergic inhibitory interneurons and discuss how the intrinsic properties of interneuron subtypes contribute to specific computational properties within various circuit motifs formed between inhibitory and excitatory neurons.
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Schizophrenia (SZ) is a brain disorder that has been intensively studied for over a century; yet, its etiology and multifactorial pathophysiology remain a puzzle. However, significant advances have been made in identifying numerous abnormalities in key biochemical systems. One among these is the antioxidant defense system (AODS) and redox signaling. This review summarizes the findings to date in human studies. The evidence can be broadly clustered into three major themes: perturbations in AODS, relationships between AODS alterations and other systems (i.e., membrane structure, immune function, and neurotransmission), and clinical implications. These domains of AODS have been examined in samples from both the central nervous system and peripheral tissues. Findings in patients with SZ include decreased nonenzymatic antioxidants, increased lipid peroxides and nitric oxides, and homeostatic imbalance of purine catabolism. Reductions of plasma antioxidant capacity are seen in patients with chronic illness as well as early in the course of SZ. Notably, these data indicate that many AODS alterations are independent of treatment effects. Moreover, there is burgeoning evidence indicating a link among oxidative stress, membrane defects, immune dysfunction, and multineurotransmitter pathologies in SZ. Finally, the body of evidence reviewed herein provides a theoretical rationale for the development of novel treatment approaches.
Zhang, Y., Behrens, M. M., & Lisman, J. E. ( 2008).
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Schizophrenia research, 55( 1-2), 1-10. | CommonCrawl |
For $G_2$ a six term relation is valid which converts a factorisation $x_1(a)x_2(b)x_1(c)x_2(d)x_1(e)x_2(f)$ into a product of the form $x_2(A)x_1(B)x_2(C)x_1(D)x_2(E)x_1(F)$ where $A$, $B$, $C$, $D$, $E$, and $F$ are subtraction-free rational expressions in the complex parameters $a$, $b$, $c$, $d$, $e$, and $f$ --- see the paper "Total positivity in Schubert varieties" by Arkady Berenstein and Andrei Zelevinsky.
These relations correspond to coxeter relations of length $2d$ within the group of dihedral symmetries of a regular $2d$-gon.
Question: Is there a length five relation of this kind ? If so, is there a nice representation of the corresponding nilpotent group ?
Now solve for $A$, $B$, $C$, $D$, and $E$ to obtain the conjectured "dihedral" relation.
--- Call this system of identities ($\dagger$).
which of course violates the independence of $a$, $b$, $c$, $d$, and $e$.
Not the answer you're looking for? Browse other questions tagged rt.representation-theory lie-groups algebraic-groups or ask your own question. | CommonCrawl |
Gigapixel videography, beyond the resolution of single camera and human visual perception, aims to capture large-scale dynamic scene with extremely high resolution. Restricted by the spatial-temporal bandwidth product of optical system, the size, weight, power and cost are central challenges in gigapixel video. More explicitly, as shown in Fig. 1(a), the most popular single lens camera is composed by one stage optical imaging system, suffering from the inherent contradiction between high resolution and wide field-of-view. The single-scale multi-camera/camera-array system in Fig. 1(b) solves the contradiction through panoramic stitching pipeline, such as Microsoft ICE , Autopano Giga , Gigapan , Pointgrey ladybug 360 camera, etc. Such stitching based scheme always requires for a certain overlapping regions among nearby images/cameras, leading to the redundant usage of CCD/CMOS in the camera array system.
Fig.1: Illustration of representative imaging systems. (a) single camera imaging system faces the contradiction between wide FOV and high resolution, (b) single-scale camera array imaging relies on image stitching, (c) structured multi-scale camera array (AWARE2) adopts two-stage optical imaging design, (d) unstructured multi-scale camera array (denoted as UnstructuredCam).
While the recent multiscale optical design [4, 8] adopts a spherical objective lens as the first-stage optical imaging system, and the secondary imaging system uses multiple identical micro-optics to divide the whole FOV into small circular overlapped regions, as shown in Fig. 1(c). It substantially reduced the size and weight of gigapixel scale optical systems, the volume and weight of camera electronics in video operation is more than 10 times larger than the optics [4, 9]. More importantly, it usually adopts the delicately structured camera array design, which is faced with the challenges of complicated optical, electronic and mechanical design, laborious calibration, massive data processing etc.
As a matter of fact, typical natural scenes are highly compressible, where the static background usually contains large sections of sky, foliage or building while owns limited corridors of action such as roadways or playing fields. Consequently, 'scalable sampling' strategies are of great importance to practical implementation of gigapixel-scale broadcasting systems. Here the 'scalable' indicates that: 1) the overall number of cameras in the camera array, and the relative location/pose among cameras can be varied for different scenes, 2) each camera itself is allowed to have different focal length, field of view, resolution, frame rate etc., such that the whole camera array can work in a highly unstructured, scalable and economized way to reduce the redundancy.
Aiming for the aforementioned scalable, efficient and economized gigapixel videography, a novel gigapixel videography system with unstructured multi-scale camera array. design, denoted as 'UnstructuredCam' is presented in Fig. 1(d), i.e., reference/global camera (with wide-angle lens to capture the global scene) works together with local camera (with telephoto lens to capture local details). 'Unstructured' indicates that the overall structure of this camera array does not follow fixed or particular designs thus without precise assembling and careful calibration in advance. `Multi-scale' means not only the parameters of global-view camera varies from local-view camera, but also the parameters of local-view cameras can be different. Such setting enables gigapixel videography by warping each local-view video to the reference video independently and parallelly, without the troublesome camera calibration among local-view cameras, which further allows flexible, compressible, adaptive and moveable local-view camera setting during data capture.
Standing on the novel unstructured camera array design, there remains a big challenge that how to make the multi-camera array work just as a 'single camera', given that the single camera always owns superior characteristics that it does not require for pre-calibration, and the captured result from single camera is seamless. Therefore, an online unstructured embedding scheme is contributed to the novel unstructured camera array, i.e., cross resolution matching and warping approach to automatically embed each local-view video in the global video. Recall that the global video owns wide field-of-view yet is lack of high resolution details, which degrades the accuracy and robustness of feature extraction significantly. Inspired by the observation that a more uniformly distributed feature map may lead to a more robust feature correspondence, a new feature detection and keypoint pooling method based on structure edge map is proposed to identify the uniformly spaced features in reference video for zncc matching. Then a multi-scale quadtree mesh structure to represent the non-rigid warping field, as well as a two-pass non-iterative outlier removal algorithm, is contributed to speed up the mesh-based homography warping step while maintaining embedding robustness. Finally, to maintain salience structures such as straight lines in the scene, structure-feature based mesh refinement strategy is proposed to remove visual artifacts.
The UnstructuredCam enables several unique capabilities over the prior works, and works just like a single camera: 1) it bypasses the need for careful camera alignment, tedious geometry and color calibration [10, 11], as well as the requirement for image overlaps among local-view cameras in available methods [4, 12]; 2) it allows local-view camera movements such that the gigapixel video is captured in an adaptive and efficient way by allocating more sensor resources to the regions of interest; 3) it enables parallel stitching of the final high resolution video and optimized for real time synthesis even with online camera movements. 4) the generated result tends to be a seamless video, where existing computer vision algorithms can be simply applied with very little modification.
As the warping method in requires for iterative optimization during feature matching, it can not run in realtime so as to enable online local view camera movements. The present work makes the following contributions compared with the preliminary version. First, a new embedding algorithm is proposed which bypasses the complex iterative warping strategy by introducing a novel feature pooling and a multi-scale quadtree warping strategy. Second, the proposed gagapixel camera system has the ability for online synthesis of gigapixel video even with the dynamically movement of local-view cameras. Third, this system has compelling performance for various computer vision applications, including large-scale human/vehicle tracking, face detection, skeleton detection, and crowd counting etc.
In short summary, the UnstructuredCam, an end-to-end unstructured multi-scale camera system, shows the ability of realtime capture, dynamically adjusting local-view cameras, and online warping for synthesizing gigapixel video. For the first time, this system shows the ability of capturing a seamless gigapixel video with adaptive and online pixel allocation for important or desired scene regions. This new ability benefits from not only the new unstructured camera array design, but also the new algorithm for embedding (warping) the local videos into the global video. In fact, such design poses new challenges for the video embedding algorithm, including parallaxes, abundant and various complex scene appearances, color inconsistency among cameras, and, there exists significant resolution gap (usually more than $8\times$) between the global and the local-view videos. More importantly, all the computations are expected to run efficiently for dynamically adjusting local camera viewpoints online. This scalable gigapixel videography system fully explores the flexibility, scalability and efficiency enabled by the unstructured multi-scale camera array mechanism, alleviating the bottleneck of hardware design to the computational algorithm development. We believe that this system and algorithm will open up new research on more adaptive and efficient gigapixel video capture and synthesis using capture setups with smaller size and lower cost.
Wilburn, B., Joshi, N., Vaish, V., Talvala, E.V., Antunez, E., Barth, A., Adams, A., Horowitz, M. and Levoy, M., 2005, July. High performance imaging using large camera arrays. In ACM Transactions on Graphics (TOG) (Vol. 24, No. 3, pp. 765-776). ACM.
Perazzi, F., Sorkine‐Hornung, A., Zimmer, H., Kaufmann, P., Wang, O., Watson, S. and Gross, M., 2015, May. Panoramic video from unstructured camera arrays. In Computer Graphics Forum (Vol. 34, No. 2, pp. 57-68).
Brown, M. and Lowe, D.G., 2007. Automatic panoramic image stitching using invariant features. International journal of computer vision, 74(1), pp.59-73.
Brady, D.J., Gehm, M.E., Stack, R.A., Marks, D.L., Kittle, D.S., Golish, D.R., Vera, E.M. and Feller, S.D., 2012. Multiscale gigapixel photography. Nature, 486(7403), p.386.
Cossairt, O.S., Miau, D. and Nayar, S.K., 2011, April. Gigapixel computational imaging. In Computational Photography (ICCP), 2011 IEEE International Conference on (pp. 1-8). IEEE.
Nichols, J.M., Judd, K.P., Olson, C.C., Novak, K., Waterman, J.R., Feller, S., McCain, S., Anderson, J. and Brady, D., 2016. Range performance of the DARPA AWARE wide field-of-view visible imager. Applied optics, 55(16), pp.4478-4484.
Tommaselli, A.M.G., Marcato Jr, J., Moraes, M.V.A., Silva, S.L.A. and Artero, A.O., 2014. Calibration of panoramic cameras with coded targets and a 3D calibration field. The International Archives of Photogrammetry, Remote Sensing and Spatial Information Sciences, 40(3), p.137.
Golish, D.R., Vera, E., Kelly, K., Gong, Q., Jansen, P., Hughes, J., Kittle, D.S., Brady, D.J. and Gehm, M.E., 2012, June. Challenges in gigapixel multiscale image formation. In Computational Optical Sensing and Imaging (pp. JW3A-4). Optical Society of America.
Kopf, J., Uyttendaele, M., Deussen, O. and Cohen, M.F., 2007, August. Capturing and viewing gigapixel images. In aCm Transactions on Graphics (TOG) (Vol. 26, No. 3, p. 93). ACM.
Yuan, X., Fang, L., Dai, Q., Brady, D.J. and Liu, Y., 2017, May. Multiscale gigapixel video: A cross resolution image matching and warping approach. In Computational Photography (ICCP), 2017 IEEE International Conference on (pp. 1-9). IEEE. | CommonCrawl |
January 30, 1966, 1000AM–1050AM. Jaume Pujol Capdevila, (Universidad Autónoma de Barcelona), Tópicos en Códigos Algebraicos.
March 13, 1996, 1000AM–1050AM. Victor García Muñiz, (Universidad de Puerto Rico), El Sistema Original de las Coordenadas Cartesianas.
March 27, 1996, 1000AM–1050AM. Dr. Guoliang Yu, (University of Colorado at Boulder), Large Scale Geometry, Positive Scalar Curvature and Higher Signature.
March 28, 1996, 1000AM–1050AM. Dr. Jorge M. López Fernández, Universidad de Puerto Rico, De la Geometría de Descartes al Análisis de Leibniz.
April 8, 1996, 1000AM–1050AM. Dr. Liangqing Li, (Fields Institute for Research in Mathematical Sciences), Cellular Cohomology for Noncommutative Spaces.
April 10, 1996, 1000AM–1050AM.Alexander Rosa, (McMaster University), Large Sets of Steiner Triple Systems.
April 11, 1996, 1000AM–1050AM. Jorge Urrutia, (Universidad de Ottawa), Illumination of the Plane with Reflectors.
April 12, 1996. Franya Franek, (McMaster University), Ramsey-Like Properties of Steiner Systems.
April 12, 1996. Dr. Larry Shepp, (AT & T Bell Laboraries), Lectures on Probabilistic Modeling in Finance.
April 12, 1996. Dr. Carlos Toro-Vizcarrondo, (Universidad de Puerto Rico), Una Aplicación de los Modelos Lineales al Mercado.
April 12, 1996. Dr. Hardeo Sahai, (Escuela de Salud Publica,Universidad de Puerto Rico), Estimation of Variance Components for Unbalanced Data.
April 12, 1996. Dr. Julio Quintana, (Universidad de Purto Rico), Sampling of Sensitive Questions.
April 12, 1996. Dr. Carlos Castillo-Chávez, (Universidad de Cornell), Importancia de los Factores Epidemiológicos y Sociológicos en la Dinámica de Transmisión del HIV.
April 12, 1996, 1000AM–1050AM. Dr. Wolfgang Rolke, (Universidad de Puerto Rico), Statistical Methods in High Energy Physics.
April 12, 1996, 1000AM–1050AM. Dr. Dieter Reetz, (Universidad de Puerto Rico), Multiple Stopping Processe.
April 23, 1996, 1000AM–1050AM. Jorge Urrutia, (Universidad de Ottawa), 3-Triangulaciones de Polígonos y Familias de Puntos en el Plano.
May 15, 1996, 1000AM–1050AM. Donald Silberger, (SUNY, New Paltz), The Relevance of Spikes for Monoids.
May 7, 1996, 1000AM–1050AM. Curt Lindner, (Auburn University, Alabama), The Euler Officer Problem.
May 9, 1996, 1000AM–1050AM. Curt Lindner, (Auburn University, Alabama), How to Embed a Partial Steiner Triple System.
June 26, 1996, 1000AM–1050AM. Huaxin Lin, (University of Oregon) Extensions of C* Algebras.
September 4, 1996, 0400PM–0450PM, Martin Kindt, (University of Utrecht), Calculus Teaching in Holland.
October 16, 1996, 1030AM–1130AM, Gunter Lumer, (University of Mons), Interaction Problems, Complex Analysis and Higher Order Non Detectable Signals.
October 18, 1996, 0330PM–0450PM, Curt Lindner, (Auburn University), Every n \times n Latin Square has at Least One Partial Transversal of Size $n \sqrt(n)$. | CommonCrawl |
And the objective is to both maximize profit and minimize cost. First of all, if the problems are dual, does that mean the result will be the same in variables such as demands?
For profit maximization, either $x_1$ or $x_2$ (but not both) must be zero. If not, say $x_1^*>x_2^*>0$ at the optimum, then one could increase profit by lowering cost by reducing $x_2^*$ without affecting output and thus revenue.
Solve $(1)$ for the condition determining the optimal level of $z$, and compare the costs of achieving this level using either $x_1$ or $x_2$. Use the one that entails the lower cost.
Not the answer you're looking for? Browse other questions tagged production-function cost profit-maximization cost-functions or ask your own question.
Is a production function bilinear? | CommonCrawl |
Abstract: A great deal of research into the theory of random processes is concerned with the problem of constructing a process that has certain properties of regularity of the trajectories and has the same finite-dimensional probability distribution as a given stochastic process $x_t$. It is a complicated theory and one that is difficult to apply to those properties that we most need for the study of Markov processes (the strict Markov property, standardization, and the like.) The problem can be usefully reformulated. In an actual experiment we do not observe the state $x_t$ at a fixed instant $t$, but rather events that occupy certain time intervals. This is the motivation behind the Gel'fand–Itô theory of generalized random processes. Kolmogorov, in 1972, proposed an even more general concept of a stochastic process as a system of $\sigma$-algebras $\mathscr F(I)$ labelled by time intervals $I$. Developing this approach, we introduce the concept of a Markov representation $x_t$ of the stochastic system $\mathscr F(I)$ and prove the existence of regular representations. We construct two dual regular representations (the right and the left), which we then combine into a single Markov process by two methods, the "vertical" and the "horizontal" method. We arrive at a general duality theory, which provides a natural framework for the fundamental results on entry and exit spaces, excessive measures and functions, additive functionals, and others. The initial steps in the construction of this theory were taken in . The note deals with applications to additive functionals (detailed proofs are in preparation). We consider random processes defined in measurable spaces without any topology: the introduction of a reasonable topology allows of a certain arbitrariness. The relation between our definitions of regularity and more traditional properties stated in topological terms (continuity from the right, the existence of a limit from the left, etc.) are considered in the Appendix, which is written by S. E. Kuznetsov. | CommonCrawl |
S Weisberg, R Leibel and D V Tortoriello.
Proteasome inhibitors, including curcumin, improve pancreatic $\beta$-cell function and insulin sensitivity in diabetic mice.. Nutrition & diabetes 6:e205, January 2016.
Abstract BACKGROUND: Type 2 diabetes stems from obesity-associated insulin resistance, and in the genetically susceptible, concomitant pancreatic $\beta$-cell failure can occur, which further exacerbates hyperglycemia. Recent work by our group and others has shown that the natural polyphenol curcumin attenuates the development of insulin resistance and hyperglycemia in mouse models of hyperinsulinemic or compensated type 2 diabetes. Although several potential downstream molecular targets of curcumin exist, it is now recognized to be a direct inhibitor of proteasome activity. We now show that curcumin also prevents $\beta$-cell failure in a mouse model of uncompensated obesity-related insulin resistance (Lepr(db/db) on the Kaliss background). RESULTS: In this instance, dietary supplementation with curcumin prevented hyperglycemia, increased insulin production and lean body mass, and prolonged lifespan. In addition, we show that short-term in vivo treatment with low dosages of two molecularly distinct proteasome inhibitors celastrol and epoxomicin reverse hyperglycemia in mice with $\beta$-cell failure by increasing insulin production and insulin sensitivity. CONCLUSIONS: These studies suggest that proteasome inhibitors may prove useful for patients with diabetes by improving both $\beta$-cell function and relieving insulin resistance.
Lucia Chico, Elena Ienco, Costanza Bisordi, Annalisa Gerfo, Erika Schirinzi and Gabriele Siciliano.
Curcumin as an ROS Scavenger in Amyotrophic Lateral Sclerosis. Reactive Oxygen Species, 2016.
Abstract O xidative stress, a deleterious process resulting from an imbalance between pro-oxidants and anti-oxidative defenses, plays a key role in several neurodegenerative disorders, such as amyotrophic lateral sclerosis (ALS). Curcumin has been studied for its anti-inflammatory, anti-cancer, and antioxidant effects. Curcuminoids exhibit a protective effect by accelerating antioxidant defense mechanisms and attenuating mitochondrial dysfunction. As a result of epidemiological, clinical, and animal studies, several molecular mechanisms, such as the activation of Nrf2 pathway and the decrease of aberrant proteins aggregation, are emerging to account for the multiple biological effects of curcumin and provide a basis for its potential use in the treatment of ALS. This review focuses on oxidative damage, with particular reference to ALS pathogenesis, and antioxidant defense mechanisms to limit such damage, and summarizes the most interesting in vitro and in vivo studies on the effects of curcumin as an antioxidant and its implications in ALS.
Nidhi K Bhatia, Ankit Srivastava, Nidhi Katyal, Nidhi Jain, Ashhar M I Khan, Bishwajit Kundu and Shashank Deep.
Curcumin binds to the pre-fibrillar aggregates of Cu/Zn superoxide dismutase (SOD1) and alters its amyloidogenic pathway resulting in reduced cytotoxicity.. Biochimica et biophysica acta, February 2015.
Abstract Amyotrophic Lateral Sclerosis (ALS) is a fatal neurodegenerative disease that affects motor neurons. Unfortunately, effective therapeutics against this disease is still not available. Almost 20% of familial ALS (fALS) is suggested to be associated with pathological deposition of superoxide dismutase (SOD1). Evidences suggest that SOD1-containing pathological inclusions in ALS exhibit amyloid like properties. An effective strategy to combat ALS may be to inhibit amyloid formation of SOD1 using small molecules. In the present study, we observed the fibrillation of one of the premature forms of SOD1 (SOD1 with reduced disulfide) in the presence of curcumin. Using ThT binding assay, AFM, TEM images and FTIR, we demonstrate that curcumin inhibits the DTT-induced fibrillation of SOD1 and favors the formation of smaller and disordered aggregates of SOD1. The enhancement in curcumin fluorescence on the addition of oligomers and pre-fibrillar aggregates of SOD1 suggests binding of these species to curcumin. Docking studies indicate that putative binding site of curcumin may be the amyloidogenic regions of SOD1. Further, there is a significant increase in SOD1 mediated toxicity in the regime of pre-fibrillar and fibrillar aggregates which is not evident in curcumin containing samples. All these data suggest that curcumin reduces toxicity by binding to the amyloidogenic regions of the species on the aggregation pathway and blocking the formation of the toxic species. Nanoparticles of curcumin with higher aqueous solubility show similar aggregation control as that of curcumin bulk. This suggests a potential role for curcumin in the treatment of ALS.
Pragati P Nahar, Angela L Slitt and Navindra P Seeram.
Anti-Inflammatory Effects of Novel Standardized Solid Lipid Curcumin Formulations.. Journal of medicinal food, December 2014.
Abstract Abstract Inflammation and the presence of pro-inflammatory cytokines are associated with numerous chronic diseases such as type-2 diabetes mellitus, cardiovascular disease, Alzheimer's disease, and cancer. An overwhelming amount of data indicates that curcumin, a polyphenol obtained from the Indian spice turmeric, Curcuma longa, is a potential chemopreventive agent for treating certain cancers and other chronic inflammatory diseases. However, the low bioavailability of curcumin, partly due to its low solubility and stability in the digestive tract, limits its therapeutic applications. Recent studies have demonstrated increased bioavailability and health-promoting effects of a novel solid lipid particle formulation of curcumin (Curcumin SLCP, Longvida(\textregistered)). The goal of this study was to evaluate the aqueous solubility and in vitro anti-inflammatory effects of solid lipid curcumin particle (SLCP) formulations using lipopolysaccharide (LPS)-stimulated RAW 264.7 cultured murine macrophages. SLCPs treatment significantly decreased nitric oxide (NO) and prostaglandin-E2 (PGE2) levels at concentrations ranging from 10 to 50 $\mu$g/mL, and reduced interleukin-6 (IL-6) levels in a concentration-dependent manner. Transient transfection experiments using a nuclear factor-kappa B (NF-$\kappa$B) reporter construct indicate that SLCPs significantly inhibit the transcriptional activity of NF-$\kappa$B in macrophages. Taken together, these results show that in RAW 264.7 murine macrophages, SLCPs have improved solubility over unformulated curcumin, and significantly decrease the LPS-induced pro-inflammatory mediators NO, PGE2, and IL-6 by inhibiting the activation of NF-$\kappa$B.
H Dong, L Xu, L Wu, X Wang, W Duan, H Li and C Li.
Curcumin abolishes mutant TDP-43 induced excitability in a motoneuron-like cellular model of ALS. Neuroscience 272:141–153, July 2014.
Yali Zhang, Xin Jiang, Kesong Peng, Chengwei Chen, Lili Fu, Zhe Wang, Jianpeng Feng, Zhiguo Liu, Huajie Zhang, Guang Liang and Zheer Pan.
Discovery and evaluation of novel anti-inflammatory derivatives of natural bioactive curcumin.. Drug design, development and therapy 8:2161–71, January 2014.
Abstract Curcumin is a natural active product that has various pharmacological activities such as anti-inflammatory effects. Here, we report the synthesis and evaluation of 34 monocarbonyl curcumin analogs as novel anti-inflammatory agents. Among the analogs, the symmetrical heterocyclic type displayed the strongest inhibition of lipopolysaccharide (LPS)-stimulated expression of pro-inflammatory cytokines in macrophages. Analogs S1-S5 and AS29 reduced tumor necrosis factor-$\alpha$ (TNF-$\alpha$) and interleukin-6 (IL-6) production in a dose-dependent manner and also displayed excellent stability and low cytotoxicity in vitro. In addition, analog S1 dose-dependently inhibited LPS-induced extracellular signal-regulated kinase (ERK) phosphorylation. Furthermore, analogs S1 and S4 displayed a significant protective effect on LPS-induced septic death in mouse models, with 40% and 50% survival rates, respectively. These data demonstrate that the heterocyclic monocarbonyl curcumin analogs have potential therapeutic effects in acute inflammatory diseases.
Amira Zaky, Mariam Mahmoud, Doaa Awad, Bassma M El Sabaa, Kamal M Kandeel and Ahmad R Bassiouny.
Valproic acid potentiates curcumin-mediated neuroprotection in lipopolysaccharide induced rats.. Frontiers in cellular neuroscience 8:337, January 2014.
Abstract The etiology of neuroinflammation is complex and comprises multifactorial, involving both genetic and environmental factors during which diverse genetic and epigenetic modulations are implicated. Curcumin (Cur) and valproic acid (VPA), histone deacetylase 1 inhibitor, have neuroprotective effects. The present study was designed with an aim to investigate the ability of co-treatment of both compounds (Cur or VPA, 200 mg/kg) for 4 weeks to augment neuroprotection and enhance brain recovery from intra-peritoneal injection of (250 $\mu$g/kg) lipopolysaccharide-stimulated neuroinflammatory condition on rat brain cortex. Cortex activation and the effects of combined treatment and production of proinflammatory mediators, cyclooxygenase-2 (COX-2), APE1, and nitric oxide/inducible nitric oxide synthase (iNOS) were investigated. Neuroinflammation development was assessed by histological analyses and by investigating associated indices [$\beta$-secretase (BACE1), amyloid protein precursor (APP), presenilin (PSEN-1), and PSEN-2)]. Furthermore we measured the expression profile of lethal-7 (let-7) miRNAs members a, b, c, e, and f in all groups, a highly abundant regulator of gene expression in the CNS. Protein and mRNA levels of neuroinflammation markers COX-2, BACE1, APP, and iNOS were also attenuated by combined therapy. On the other hand, assessment of the indicated five let-7 members, showed distinct expression profile pattern in the different groups. Let-7 a, b, and c disappeared in the induced group, an effect that was partially suppressed by co-addition of either Cur or VPA. These data suggest that the combined treatment induced significantly the expression of the five members when compared to rats treated with Cur or VPA only as well as to self-recovery group, which indicates a possible benefit from the synergistic effect of Cur-VPA combination as therapeutic agents for neuroinflammation and its associated disorders. The mechanism elucidated here highlights the particular drug-induced expression profile of let-7 family as new targets for future pharmacological development.
Dong-Chan Kim, Sae-Kwang Ku, Wonhwa Lee and Jong-Sup Bae.
Barrier protective activities of curcumin and its derivative.. Inflammation research : official journal of the European Histamine Research Society ... [et al.] 61(5):437–44, May 2012.
Abstract AIM AND OBJECTIVE: Curcumin, a poly-phenolic compound, possesses diverse pharmacologic activities. However, the barrier protective functions of curcumin or its derivative have not yet been studied. The objective of this study was to investigate the barrier protective activities of curcumin and its derivative (bisdemethoxycurcumin, BDMC) on lipopolysaccharide (LPS) barrier disruption in human umbilical vein endothelial cells (HUVECs) were investigated. METHODS: The barrier protective effects of curcumin and BDMC such as permeability, expression of cell adhesion molecules, monocytes adhesion and migration toward HUVECs were tested. RESULTS: Curcumin and BDMC inhibited LPS-induced barrier permeability, monocyte adhesion and migration; inhibitory effects were significantly correlated with inhibitory functions of curcumin and BDMC on LPS-induced cell adhesion molecules (vascular cell adhesion molecules, intracellular cell adhesion molecule, E-selectin). Furthermore, LPS-induced nuclear factor-$\kappa$B (NF-$\kappa$B) activation and tumor necrosis factor-$\alpha$ (TNF-$\alpha$) release from HUVECs were inhibited by curcumin and BDMC. Surprisingly, the barrier protective activities of BDMC were better than those of curcumin, indicating that the methoxy group in curcumin negatively regulated barrier protection function of curcumin. CONCLUSION: Given these results, curcumin or its derivative, BDMC, showed barrier protective activities and they could be a therapeutic candidates for various systemic inflammatory diseases.
Yan Jiao, John Wilkinson, Xiumin Di, Wei Wang, Heather Hatcher, Nancy D Kock, Ralph D'Agostino, Mary Ann Knovich, Frank M Torti and Suzy V Torti.
Curcumin, a cancer chemopreventive and chemotherapeutic agent, is a biologically active iron chelator.. Blood 113(2):462–9, January 2009.
Abstract Curcumin is a natural product currently in human clinical trials for a variety of neoplastic, preneoplastic, and inflammatory conditions. We previously observed that, in cultured cells, curcumin exhibits properties of an iron chelator. To test whether the chelator activity of curcumin is sufficient to induce iron deficiency in vivo, mice were placed on diets containing graded concentrations of both iron and curcumin for 26 weeks. Mice receiving the lowest level of dietary iron exhibited borderline iron deficiency, with reductions in spleen and liver iron, but little effect on hemoglobin, hematocrit, transferrin saturation, or plasma iron. Against this backdrop of subclinical iron deficiency, curcumin exerted profound 2 effects on systemic iron, inducing a dose-dependent decline in hematocrit, hemoglobin, serum iron, and transferrin saturation, the appearance of microcytic anisocytotic red blood cells, and decreases in spleen and liver iron content. Curcumin repressed synthesis of hepcidin, a peptide that plays a central role in regulation of systemic iron balance. These results demonstrate that curcumin has the potential to affect systemic iron metabolism, particularly in a setting of subclinical iron deficiency. This may affect the use of curcumin in patients with marginal iron stores or those exhibiting the anemia of cancer and chronic disease.
Ajay Goel, Sonia Jhurani and Bharat B Aggarwal.
Multi-targeted therapy by curcumin: how spicy is it?. Molecular nutrition & food research 52(9):1010–30, September 2008.
Abstract Although traditional medicines have been used for thousands of years, for most such medicines neither the active component nor their molecular targets have been very well identified. Curcumin, a yellow component of turmeric or curry powder, however, is an exception. Although inhibitors of cyclooxygenase-2, HER2, tumor necrosis factor, EGFR, Bcr-abl, proteosome, and vascular endothelial cell growth factor have been approved for human use by the United States Food and Drug Administration (FDA), curcumin as a single agent can down-regulate all these targets. Curcumin can also activate apoptosis, down-regulate cell survival gene products, and up-regulate p53, p21, and p27. Although curcumin is poorly absorbed after ingestion, multiple studies have suggested that even low levels of physiologically achievable concentrations of curcumin may be sufficient for its chemopreventive and chemotherapeutic activity. Thus, curcumin regulates multiple targets (multitargeted therapy), which is needed for treatment of most diseases, and it is inexpensive and has been found to be safe in human clinical trials. The present article reviews the key molecular mechanisms of curcumin action and compares this to some of the single-targeted therapies currently available for human cancer.
Rui Wang, Ying-Bo Li, Yu-Hua Li, Ying Xu, Hong-li Wu and Xue-Jun Li.
Curcumin protects against glutamate excitotoxicity in rat cerebral cortical neurons by increasing brain-derived neurotrophic factor level and activating TrkB. Brain Research 1210:84–91, May 2008.
Abstract Curcumin is a major active component isolated from Curcuma longa. Previously, we have reported its significant antidepressant effect. However, the mechanisms underlying the antidepressant effects are still obscure. In the present study, we explored the effect of curcumin against glutamate excitotoxicity, mainly focusing on the neuroprotective effects of curcumin on the expression of Brain-Derived Neurotrophic Factor (BDNF), which is deeply involved in the etiology and treatment of depression. Exposure of rat cortical neurons to 10 microM glutamate for 24 h caused a significant decrease in BDNF level, accompanied with reduced cell viability and enhanced cell apoptosis. Pretreatment of neurons with curcumin reversed the BDNF expression and cell viability in a dose- and time-dependent manner. However, K252a, a Trk receptor inhibitor which is known to inhibit the activity of BDNF, could block the survival-promoting effect of curcumin. In addition, the up-regulation of BDNF levels by curcumin was also suppressed by K252a. Taken together, these results suggest that the neuroprotective effect of curcumin might be mediated via BDNF/TrkB signaling pathway.
Hyun-Woo Suh, Seongman Kang and Ki-Sun Kwon.
Curcumin attenuates glutamate-induced HT22 cell death by suppressing MAP kinase signaling.. Molecular and cellular biochemistry 298(1-2):187–94, April 2007.
Abstract Glutamate induces cell death by upsetting the cellular redox homeostasis, termed oxidative glutamate toxicity, in a mouse hippocampal cell line, HT22. Extracellular signal-regulated kinases (ERK) 1/2 are known key players in this process. Here we characterized the roles of both MAP kinases and cell cycle regulators in mediating oxidative glutamate toxicity and the neuroprotective mechanisms of curcumin in HT22 cells. c-Jun N-terminal kinase (JNK) and p38 kinase were activated during the glutamate-induced HT22 cell death, but at a later stage than ERK activation. Treatment with a JNK inhibitor, SP600125, or a p38 kinase inhibitor, SB203580, partly attenuated this cell death. Curcumin, a natural inhibitor of JNK signaling, protected the HT22 cells from glutamate-induced death at nanomolar concentrations more efficiently than SP600125. These doses of curcumin affected neither the level of intracellular glutathione nor the level of reactive oxygen species, but inactivated JNK and p38 significantly. Moreover, curcumin markedly upregulated a cell-cycle inhibitory protein, p21cip1, and downregulated cyclin D1 levels, which might help the cell death prevention. Our results suggest that curcumin has a neuroprotective effect against oxidative glutamate toxicity by inhibiting MAP kinase signaling and influencing cell-cycle regulation.
Vittorio Calabrese, Eleonora Guagliano, Maria Sapienza, Mariangela Panebianco, Stella Calafato, Edoardo Puleo, Giovanni Pennisi, Cesare Mancuso, D Allan Butterfield and Annamaria Giuffrida Stella.
Redox Regulation of Cellular Stress Response in Aging and Neurodegenerative Disorders: Role of Vitagenes. Neurochemical Research 32(4-5):757–773, December 2006.
Abstract Reduced expression and/or activity of antioxidant proteins lead to oxidative stress, accelerated aging and neurodegeneration. However, while excess reactive oxygen species (ROS) are toxic, regulated ROS play an important role in cell signaling. Perturbation of redox status, mutations favoring protein misfolding, altered glyc(osyl)ation, overloading of the product of polyunsaturated fatty acid peroxidation (hydroxynonenals, HNE) or cholesterol oxidation, can disrupt redox homeostasis. Collectively or individually these effects may impose stress and lead to accumulation of unfolded or misfolded proteins in brain cells. Alzheimer's (AD), Parkinson's and Huntington's disease, amyotrophic lateral sclerosis and Friedreich's ataxia are major neurological disorders associated with production of abnormally aggregated proteins and, as such, belong to the so-called "protein conformational diseases". The pathogenic aggregation of proteins in non-native conformation is generally associated with metabolic derangements and excessive production of ROS. The "unfolded protein response" has evolved to prevent accumulation of unfolded or misfolded proteins. Recent discoveries of the mechanisms of cellular stress signaling have led to new insights into the diverse processes that are regulated by cellular stress responses. The brain detects and overcomes oxidative stress by a complex network of "longevity assurance processes" integrated to the expression of genes termed vitagenes. Heat-shock proteins are highly conserved and facilitate correct protein folding. Heme oxygenase-1, an inducible and redox-regulated enzyme, has having an important role in cellular antioxidant defense. An emerging concept is neuroprotection afforded by heme oxygenase by its heme degrading activity and tissue-specific antioxidant effects, due to its products carbon monoxide and biliverdin, which is then reduced by biliverdin reductase in bilirubin. There is increasing interest in dietary compounds that can inhibit, retard or reverse the steps leading to neurodegeneration in AD. Specifically any dietary components that inhibit inappropriate inflammation, AbetaP oligomerization and consequent increased apoptosis are of particular interest, with respect to a chronic inflammatory response, brain injury and beta-amyloid associated pathology. Curcumin and ferulic acid, the first from the curry spice turmeric and the second a major constituent of fruit and vegetables, are candidates in this regard. Not only do these compounds serve as antioxidants but, in addition, they are strong inducers of the heat-shock response. Food supplementation with curcumin and ferulic acid are therefore being considered as a novel nutritional approach to reduce oxidative damage and amyloid pathology in AD. We review here some of the emerging concepts of pathways to neurodegeneration and how these may be overcome by a nutritional approach.
Surendra S Ambegaokar, Lauren Wu, Kaneshka Alamshahi, Jennifer Lau, Lila Jazayeri, Sharon Chan, Pavan Khanna, Emily Hsieh and Paola S Timiras.
Curcumin inhibits dose-dependently and time-dependently neuroglial cell proliferation and growth.. Neuro endocrinology letters 24(6):469–73, December 2003.
Abstract OBJECTIVES: Curcumin (CUR), the active chemical of the Asian spice turmeric, has strong anti-oxidant and anti-inflammatory properties. CUR inhibits proliferation and growth of several cell types, e.g. cancer cells. While CUR inhibitory effects on microglial cells are demonstrated, little is known of its effects on neuroglia, astrocytes (AST) and oligodendrocytes (OLG). Our work focuses on CUR's effects on neuroglial proliferation and growth in vitro, utilizing C-6 rat glioma 2B-clone cells, a mixed colony of both neuroglial cells, in 6 day trials. METHODS: The doses studied included 4, 5, 10, 15, and 20 microM - concentrations slightly smaller than those shown to stimulate protein expression in ASTs. Automated particle counter was used to determine proliferation, and marker enzyme assays were used to determine AST and OLG activity. RESULTS: CUR inhibited neuroglial proliferation, with the degree of inhibition correlated directly with the CUR concentration. Proliferative inhibition was observed after a concentration as low as 5 microM by day 6, while inhibition of 20 microM doses occurred by day 2 of culture. Proliferative inhibition is associated with morphological changes, e.g. cell elongation and neurite prolongation, and increased activity of a marker enzyme corresponding to differentiation of OLG and with a reduced activity of the marker enzyme for AST. CONCLUSIONS: Our data suggests CUR acts continuously over a period of time, with low doses being as effective as higher doses given a longer period of treatment. It has been suggested that CUR's anti-inflammatory and anti-oxidant actions may be useful in the prevention-treatment of neurodegenerative diseases, e.g. Alzheimer's and Parkinson's Diseases. Given neuroglial involvement in these diseases, and CUR's observed actions on neuroglia, the data presented here may provide further explanations of CUR's preventative-therapeutic role in these diseases.
G Shoba, D Joy, T Joseph, M Majeed, R Rajendran and P S Srinivas.
Influence of piperine on the pharmacokinetics of curcumin in animals and human volunteers.. Planta medica 64(4):353–6, May 1998.
Abstract The medicinal properties of curcumin obtained from Curcuma longa L. cannot be utilised because of poor bioavailability due to its rapid metabolism in the liver and intestinal wall. In this study, the effect of combining piperine, a known inhibitor of hepatic and intestinal glucuronidation, was evaluated on the bioavailability of curcumin in rats and healthy human volunteers. When curcumin was given alone, in the dose 2 g/kg to rats, moderate serum concentrations were achieved over a period of 4 h. Concomitant administration of piperine 20 mg/kg increased the serum concentration of curcumin for a short period of 1-2 h post drug. Time to maximum was significantly increased (P \textless 0.02) while elimination half life and clearance significantly decreased (P \textless 0.02), and the bioavailability was increased by 154%. On the other hand in humans after a dose of 2 g curcumin alone, serum levels were either undetectable or very low. Concomitant administration of piperine 20 mg produced much higher concentrations from 0.25 to 1 h post drug (P \textless 0.01 at 0.25 and 0.5 h; P \textless 0.001 at 1 h), the increase in bioavailability was 2000%. The study shows that in the dosages used, piperine enhances the serum concentration, extent of absorption and bioavailability of curcumin in both rats and humans with no adverse effects.
Curcumin was recently shown to prevent LPS-induced intestinal permeability in an experimental model, while green tea reduces LPS-induced sickness behavior and BBB permeability [138-140]. | CommonCrawl |
$V$ is an inner product space, and a is a linear transformation from $V$ to $V$. Prove that for any unit vector $v$ belongs to $V$, we have $\langle av, v\rangle \langle v, av\rangle \le \langle av, av\rangle$.
The textbook I am reading on talks nothing about the product of two inner products. But I assume that $\langle v, v\rangle \langle v, v\rangle = |\langle v, v\rangle|^2$, is that right?
I think this problem has to discuss two circumstances, one is where $\langle av, v\rangle = 0$, so both sides equal to $0$, that is an equivalent, but what about the other case when $\langle av, v\rangle$ is not equal to $0$, where the left hand side less than the right hand side?
Browse other questions tagged linear-algebra inner-product-space or ask your own question.
$T: \mathbb R^n \to \mathbb R^n$, $\langle Tu,v\rangle=\langle u,T^*v\rangle$, is $T^*=T^t$ regardless of inner product?
Does $\langle f+h,g\rangle=\langle f,g\rangle+\langle h,g\rangle$ hold for all elements $f, g, h$ of an inner product space?
Prove $\langle u,v \rangle = uAv^* $ defines an inner product. | CommonCrawl |
Аннотация: Let $R$ be a topological ring and $E$ be a unitary topological $R$-module. Denote by $C_p(X,E)$ the class of all continuous mappings of $X$ into $E$ in the topology of pointwise convergence. The spaces $X$ and $Y$ are called $l_p(E)$-equivalent if the topological $R$-modules $C_p(X,E)$ and $C_p(Y,E)$ are topological isomorphisms. Some conditions under which the topological property $\mathcal P$ is preserved by the $l_p(E)$-equivalence (Theorems 8–11) are given.
Ключевые слова и фразы: function space, topology of pointwise convergence, support, linear homeomorphism, perfect properties, open finite-to-one properties. | CommonCrawl |
In this second talk, I will continue to describe the relation between differentiable stacks and Lie groupoids, focusing this time on Lie groupoids. I will provide explicit examples and, if time permits, I will explain the relation to C*-algebras.
We will conclude our discussion of the work of Carchedi and Roytenberg on the foundations of super Fermat theories, the natural superalgebraic generalizations of Fermat theories. In this talk, we will continue our discussion of super Fermat theories and show that every ordinary Fermat theory may be extended canonically to a super Fermat theory.
The theory of presentable and especially presentable and stable ∞-categories provides a very powerful framework. For instance, stable presentable categories form a monoidal category, there is also an adjoint functor theorem and a version of Brown representability theorem for such categories. In this talk, I will present, following Lurie, a brief overview of the theory of stable and presentable categories from the viewpoint of the user. If time permits, I will also discuss spectra and stabilization.
In this introductory talk, I will introduce differentiable stacks and show how they are presented by Lie groupoids. I will describe generalized morphisms between Lie groupoids and the resulting notion of Morita equivalence. I will then explain in which precise (bicategorical) way isomorphic differentiable stack correspond to Morita equivalent Lie groupoids.
We will continue our discussion of the work of Carchedi and Roytenberg on the foundations of super Fermat theories, the natural superalgebraic generalizations of Fermat theories. In this talk, we will discuss nilpotent extensions in the context of Fermat theories, superalgebras, and super Fermat theories.
We will continue our discussion of the work of Carchedi and Roytenberg on the foundations of super Fermat theories, the natural superalgebraic generalizations of Fermat theories. In this talk, we will continue to discuss the development of differential calculus in the context the Fermat theories of Dubuc-Kock.
We will continue our discussion of the work of Carchedi and Roytenberg on the foundations of super Fermat theories, the natural superalgebraic generalizations of Fermat theories. In this talk, we will present further background material on the Fermat theories of Dubuc-Kock, and the development of differential calculus in the context of such theories.
Dubuc and Kock developed the concept of Fermat theories, theories of commutative algebras for which infinitely differentiable functions may be evaluated on elements. These theories arose in the development of models for synthetic differential geometry, but have more recently played a key role in the development of models for derived differential geometry.
In this series of talks, we will discuss the work of Carchedi and Roytenberg on the foundations of super Fermat theories, the natural superalgebraic generalizations of Fermat theories. In this first talk, we will present background material on Lawvere algebraic theories, and the Fermat theories of Dubuc-Kock.
This is the second part of last week's talk. We will combine the Koszul-Tate and Longitudinal differentials to construct the BRST complex.
In my last talk, I defined the longitudinal differential. I will now show that its zero homology is equal to the space of observables. I will then define the Koszul-Tate resolution as a semifree resolution of $C^\infty(\Sigma)$, where $\Sigma$ is the constraint surface. Combining Koszul-Tate and Longitudinal differential, I will construct the BRST complex.
This is the third talk in our series. After reviewing the symplectic structure on the phase space induced by the Poisson bracket, we will show that zero vector fields of the induced two form on the constraint surface are generators of infinitesimal gauge transformations. Moreover, such vector fields satisfy Frobenius' theorem on the constraint surface. This allows us to define the de Rham complex mentioned previously.
This is the second part of last week's talk.
In gauge theory, equations of motion contain arbitrary functions of time. This leads to relations (constraints) between the canonical variables $p$ and $q$ in the Hamiltonian formalism, restricting the motion to a submanifold of the phase space (the constraint surface). Constraints are divided into first and second class. The existence of first class constraints corresponds to the existence of gauge symmetries, which is the case when more than one set of canonical variables describe the same physical state. Vector fields generating infinitesimal gauge transformations satisfy Frobenius' theorem on the constraint surface. This enables us to define something similar to de Rham complex over their "duals". At the end, I will establish a 1-1 correspondence between these vector fields and first class constraints, that will be crucial for the antighost-ghost correspondence needed in the BRST formalism. | CommonCrawl |
Why are antibonding molecular orbitals formed?
When two atomic orbitals make one molecular orbital there must be an antibonding orbital also. Why should they make also an antibonding molecular orbital, such as the $2\mathrm b_2$ orbital in the scheme below?
Why should they make also an antibonding molecular orbital?
Orbital symmetry must be conserved. Thus, when you mix orbitals, the number of orbitals must also be conserved. As a consequence, when two orbitals are operated on to produce new orbitals, two new orbitals must be created.
Think about it conceptually this way: When two orbitals that have the same symmetry and appropriately matched energy come together, a bonding orbital is formed. This bonding orbital contains all of the "good orbital stuff" from that pair of orbitals. But, because there were two orbitals originally, there has to be "orbital stuff" left over. This leftover "orbital stuff" forms the antibonding orbital.
Now, the screwy part is that orbitals are not real. They are mathematical constructs to describe the wave-like probabilistic properties of electrons. If there are no electrons in the orbital, then the orbital is not really "there". So, while an antibonding orbital is formed, it is not real unless it has electrons in it. In the case of water above, the antibonding orbitals are not populated, so they don't exist.
Not the answer you're looking for? Browse other questions tagged inorganic-chemistry molecular-orbital-theory or ask your own question.
Why do n AOs only form n MOs?
Why do two atomic orbitals form two molecular orbitals?
Will bonding molecular orbital be formed?
Why are there as many molecular orbitals as atomic orbitals? | CommonCrawl |
A freshman of SNU CALS at Korea.
I code to learn, and learn to code. I've programmed for 6 years. I am interested in Brain-Computer Interface.
Programming: Android, Bluetooth, Reverse engineering, cross compiling, etc.
Please answer this(Generalization of Carleman coefficients to multivariable functions - Carleman tensor?)! Thank you!
8 What does 초고수 mean?
7 Why don't fish get hurt with so many sharp fish bones?
7 Is there any $a, b \in \mathbb R, b \ne 0$ such that $\Gamma(a+bi)$ can be evaluated manually?
6 Can we process infinite matrices with a quantum computer?
5 How does API call work on Android (NDK)? | CommonCrawl |
Problem: QM/MM study of the Urea Zwitterion in water by means of a QM/MM Hamiltonian.
For this tutorial some input and output files are given in order to present a complete procedure to solve the given problem. Some hints are also given to help in the analysis of the results. In order to be able to run these examples, some paths need to be correctly set in the input files (i.e. set the variables ROOT for instance).
In order to have a reasonable QM/MM starting structure, we need to prepare a fully functional classical setup. In order to do so, we need to prepare a classical force field for both UREA (Zwitterionic form) and water. In this tutorial we will not cover specifically this aspect, which has been fulfilled using the ambertools. For people willing to understand and dominate these operative procedures, the link provided above contains tons of information. For your convenience, I have copied in the main distribution of the source input/output files, everything related to the preparation of the forcefield.
RUN02_QMMM_MTD2 contains the sampling (by means of metadynamics) of the elimination reaction: i.e. elimination of NH3 and formation of cyanic acid.
Study the chemical reactivity of the Zwitterion in solution: by inspecting the possibility of having a reversal reaction with formation of neutral urea or alternatively the elimination reaction, with formation of NH3 and cyanic acid.
Urea is formed in large quantities as a product of catabolism of nitrogen-containing compounds. Owing to its resonance stabilization, urea is highly stable in aqueous solutions. For example, urea spontaneously eliminates ammonia to form cyanic acid with a half life of 3.6 years at 38 Celsius degrees.
Cyanate ion further readily undergoes conversion to CO2 and ammonia. In contrast, when catalyzed by ureases, urea is generally believed to undergo hydrolysis rather then ammonia elimination producing either HCO3- and NH4+ or ammonium carbamate, depending on the buffer system. Activation energies for urea decomposition in water at different pH have been obtained experimentally. For neutral pH, the reported activation energy ranges from 28.4 Kcal/mol to 32.4 Kcal/mol. There have been also numerous theoretical investigations of the decomposition of urea and related systems. In all of them the explicit representation of the solvent was found to be essential for detailed resolution of the mechanism, identification of the rate determining step and evaluation of the barrier. In particular in a very recent paper by Jorgensen et al. the hydrogen bonded water molecules were found to act as hydrogen shuttle for the first step of the elimination reaction. The forming zwitterionic intermediate, H3N(+)CONH(-), participates in 8-9 hydrogen bonds with water molecules and its decomposition is found to be the rate-limiting step. The overall free energy of activation for the decomposition of urea in water is computed to be 37 Kcal/mol while the barrier for hydrolysis by an addition/elimination mechanism is found to be 40 Kcal/mol.
The goal of this exercise will be to inspect the chemical reactivity of the zwitterion surrounded by water molecules. In this exercise, in a very simplicistic way, only urea will be considered QM while the rest of the system will be described with a classical Hamiltonian. By some high level calculations, performed in literature, it is know that the elimination mechanism, leading to cyanic acid and ammonia, happens with barrier of 5.0 Kcal/mol.
The first task to complete is the NPT equilibration of the entire system (UREA+water) with a classical force-field. In principle, one could start, for very difficult molecular cases hard to parametrize, directly with a QM/MM equilibration. Due to the larger cost of QM/MM calculations, compared to classical, whenever possible is always better to equilibrate with a classical Hamiltonian at the beginning.
The force-field, as said in the introduction, has been optimized using the AMBERTOOLS: refer to the link provided above in order to aquire the proper knowledge on how to perform a classical force-field optimization.
In the directory Files, you will find two files Files/mol_solv.crd and Files/mol_solv.top as generated from leap, with the AMBER format. Feel free to open them, to inspect the structure of the two files. These two files can be as well opened with VMD, in order to inspect how the initial systems look like.
The classical equilibration is performed in the directory RUN01_EQUIL_MM. Let's have a look more in details at the input file used to perform the NPT equilibration.
The initial cell size was provided by LEAP and in the topology we specify both the starting coordinates Files/mol_solv.crd and the connectivity (mandatory for meaningful classical systems) Files/mol_solv.top, specifying it as AMBER type.
In the FORCE_EVAL/MM/FORCEFIELD section we specify the same AMBER topology file, specified for the connectivity, since it stores the force-field information as well. In FIST (which is the classical module) the non-bonded potential is mapped on splines and in the spline section above, we specify the cutoff for these interactions (in this case 9 Å).
The core of the evaluation in a classical run, is the evaluation of the electrostatic. We can adjust these parameters in the FORCE_EVAL/MM/POISSON section (similarly to the DFT calculations). For classical runs we can employ either standard EWALD summations, Particle-Mesh Ewald (PME) sums or Smooth-Particle-Mesh Ewald ones (SPME).
For this exercise we emply the SPME with a grid mesh of 54 for all 3 dimensions and the $\alpha$ parameter for the reciprocal space contributions is equal to 0.4.
For the equilibration we employ an isotropic ensemble (NPT_I), using a time step of 0.5 fs for 50 ps overall. The thermostat used is a Nosé-Hoover thermostat with a timeconstant of 100 fs. The barostat is using a manostat with a timeconstant of 100. fs and an external pressure of 1 Atm.
It is important to notice as well the output frequency of files and other additional information, since it may significantly affect the performance of you calculations at home. So be always careful on the amount of output in your calculations.
At this level you can launch the run: for the provided setup it takes almost 5:00 hours on a single processor (3 GHz). Upon completion of the equilibration we need to inspect whether 50 ps where enough to equilibrate the system. Check the convergence of the cell parameters, by simply plotting (gnuplot or your preference plot manager) the content of the file RUN01_EQUIL_MM/UREA-ZW.cell. Take the averages of the parameters of the cell lattices, we will employ them for the next run: the isothermal equilibration of the classical ensemble.
Using the average parameters of the cell lattice, as determined in the previous run, we setup an input file to run an NVT equilibration, restarting all information but the FORCE_EVAL/SUBSYS/CELL, form the previous run.
All the files generated in this task can be found in the directory RUN01_EQUIL_MM_AVG. For the purpose of equilibrating the system in the NVT ensemble we will run 5 ps. Check the RUN01_EQUIL_MM/UREA-ZW-1.ener for the conservation of the energy, the temperature fluctuations and the potential energy.
Starting from the MM system, equilibrated at the right pressure and temperature, we will start now an equilibration at the QM/MM level in the directory RUN01_EQUIL_QMMM. Compared to previous input files, we need to specify everything related to the QM/MM Hamiltonian. In particular, for this system, in order to keep the computational load small, I decided to treat at the QM level only the zwitterion. We need to specify which atoms will be treated QM and also the atomic kinds of these atoms. In this tutorial example we will use SE as quantum Hamiltonian, but the extension to the DFT is immediate, since the only difference are the specification of the basis set and pseudo potential and of the proper DFT section (all these specs are not related to the QM/MM itself).
All the informations about a QM/MM run are specified in the QMMM section being part of the FORCE_EVAL/QMMM. In particular, we need to specify first the QM CELL. This is mandatory and important for DFT calculations (performance, correctness, efficiency) while in principle for SE runs one may use a cell as large as the MM one.
For this specific example, we need also to introduce an additional modification in the force-field. In fact, in the classical force-field, there is no direct Lennard-Jones interaction between the hydrogens of water and the oxygen and nitrogens of UREA. The possible collapse of the hydrogens on the Oxygen,Nitrogens is avoided by the presence of Lennard-Jones terms between Oxygen and Nitrogens of UREA and the Oxygen of water (inspect the force-field file). When performing QM/MM calculations, we may face an additional problem mainly known as electron spill-out. In fact it is possible, especially for COULOMB coupling scheme, that the electrons tend to interact in an unphysical way with the classical charges. This leads to strong attraction of classical charges inside the QM electron density. In order to avoid that, we need to implement an additional force-field term, to avoid that the hydrogens of water (extremely light) may be attracted on the Oxygen or Nitrogens of UREA, leading to a system explosion.
No other modification are necessary to perform this task. Run the MD equilibration and inspect the temperature, potential energy and total conserved quantity.
Try to convert this input to use GPW. Hints: when setting-up a correct FORCE_EVAL/DFT section, keep in mind that the QM/MM multigrid approach requires the usage of FORCE_EVAL/DFT/MGRID#COMMENSURATE grids in the FORCE_EVAL/DFT/MGRID section. Moreover, instead of using the COULOMB interaction scheme for QM/MM coupling, use the GAUSS coupling. Do not forget to provide reasonable basis sets and pseudo potentials in the subsys for the QM kinds, as defined in the QMMM section.
The two above defined CV, represent the coordination of each Nitrogen with all QM Hydrogens.
Inspec the RUN02_QMMM_MTD1/UREA-ZW-COLVAR-1.metadynLog until you see the exploration of a second basin. Inspecting the trajectory file is always strongly recommended.
To determine the free energy profile employ the fes.sopt program. How deep is the basin?
Similarly to the previous mechanism, inspect the COLVAR files, the trajectory and determine the barrier for the elimination process.
Evaluate the free-energy for both processes: from Zwitterionic to Neutral form and for the elimination pathway. How do these numbers compare with the 5 kcal/mol predicted in several published works? Inspect carefully the metadynamics trajectory in order to find a solution (what is the first attempt of the hydrogen of NH3(+) before moving towards the NH(-) group? what would happen if the nearby water molecules would be treated QM?).
Take into account a primary solvation shell of water molecules as a part of the QM subsystem, using a FLEXIBLE_PARTITIONING scheme to prevent the diffusion of the QM water molecules. Re-run the equilibration steps and perform the Zwitterionic-Neutral metadynamics. Do you see any change in the barrier energy? Why? | CommonCrawl |
I think that MathOverflow is a very interesting and useful web site. I try to answer those questions which I can answer without devoting to this significant time. Exceptions are given to those questions which I consider as interesting research problems.
27 Do there exist infinite-dimensional Banach spaces in which every bounded linear operator attains its norm?
22 Who proved that $l^1$ and $L^1[0,1]$ are not isomorphic?
11 Is $\ell_p$ $(1<p<\infty)$ finitely isometrically distortable? | CommonCrawl |
Determine all possibilities for the number of solutions of each of the system of linear equations described below.
(a) A system of $5$ equations in $3$ unknowns and it has $x_1=0, x_2=-3, x_3=1$ as a solution.
(b) A homogeneous system of $5$ equations in $4$ unknowns and the rank of the system is $4$.
See the post Summary: possibilities for the solution set of a system of linear equations to review how to determine the number of solutions of a system of linear equations.
Let $m$ be the number of equations and $n$ be the number of unknowns in the given system.
Note that the information $m > n$ tells us nothing about the possibilities for the number of solutions.
The system has at least one solution $x_1=0, x_2=-3, x_3=1$, hence it is consistent.
Thus, the system has either a unique solution or infinitely many solutions. Since $m > n$, we cannot narrow down the possibilities further. Thus, the possibilities are either a unique solution (which must be $x_1=0, x_2=-3, x_3=1$) or infinitely many solution.
Since the system is homogeneous, it has always the zero solution, hence it is consistent.
The fact $m > n$ gives no new information. But since the rank $r$ of the system is equal to the number of unknowns $n$, there is no free variable. ($n-r=0$.) Thus, the system must have a unique solution, which is the zero solution.
This is one of the midterm exam 1 problems of linear algebra (Math 2568) at the Ohio State University.
Some students wrongly concluded from the condition $m >n$. Again, note that the condition $m > n$ gives no new information at all.
The following list is the problems and solutions/proofs of midterm exam 1 of linear algebra at the Ohio State University in Spring 2017.
Are the Trigonometric Functions $\sin^2(x)$ and $\cos^2(x)$ Linearly Independent?
Prove that every plane in the $3$-dimensional space $\R^3$ that passes through the origin is a subspace of $\R^3$. | CommonCrawl |
Is there something similar to the Kourovka Notebook for graph theory (or anyway an organized, possibly commented, collection of conjectures and open problems)?
The largest section in the open problem garden is about graph theory. The book Erdös on Graphs with its living version might be interesting as well.
A list of about 60 algorithmic problems pertaining to trees are given in the paper by Stephen T. Hedetniemi. Some of the discussion in the paper can be extended to questions on graphs of bounded treewidth.
Here is a nice problem about graphs: it is true that every Cayley graph of every finitely generated cancellative semigroup must have either $1$, or $2$, or $\infty$-many ends (number of connected components looked from the infinity perspective, roughly speaking). But yet, no analog of Stallings Theorem for finitely generated cancellative semigroups is known. It would be fun to know.
Not the answer you're looking for? Browse other questions tagged reference-request graph-theory soft-question big-list open-problems or ask your own question.
What are the big problems in probability theory?
Open problems/questions in representation theory and around?
What are some open problems regarding elliptic curves in finite fields? | CommonCrawl |
Clearly if a sequence converges then also it will also have a convergent subsequence (take for example the whole sequence). However, I have been told the the opposite it not true. Could someone give an explicit example on a sequence which have a convergent subsequence but which do not converge?
Also we know that on a compact set, any bounded sequence has a convergent subsequence. Is there any criteria so that bounded sequences converges on compact set? Or more generally, is there a criteria so that if $x_n$ has a convergent subsequence then it will also converge?
You could take the sequence $a_n = (-1)^n$. What are the convergent subsequences?
It is necessary that a convergent sequence be a Cauchy sequence. Conversely, a Cauchy sequence with a converging subsequence converges.
Two convergent sequences with different indices, can I make them the same index for a subsequence?
How to know if a space has a convergent subsequence? | CommonCrawl |
Let R be the triangle with vertices at ($x_1$, $y_1$) , ($x_2$, $y_2$), ($x_3$,$y_3$).
Im not sure how to even start. can someone help me?
Browse other questions tagged linear-algebra determinant triangles area or ask your own question.
Why this representation of circle is valid?
Prove that the determinant of a given matrix is proportional to the area of the triangle whose corners are the three points.
Can the determinant of an integer matrix with a given row be any multiple of the gcd of that row?
What does the determinant form of triangle area imply "transformation-wise"? | CommonCrawl |
Friday January 18, 2019, 8:00 a.m.-10:50 a.m.
Continued fractions for the golden L, and billiards in the pentagon.
Hybrid subgroups of complex hyperbolic lattices.
Geodesic submanifolds of hyperbolic hybrids.
Presentations for cusped arithmetic hyperbolic lattices.
Families of Division Algorithms: Structure for Multidimensional Continued Fraction Algorithms.
Friday January 18, 2019, 1:00 p.m.-5:50 p.m.
$\alpha$-continued fractions for infinitely many triangle groups.
Iwasawa continued fractions and higher-dimensional hyperbolic spaces.
Coding geodesic flows and various continued fractions.
$\alpha$-expansions with odd partial quotients.
The Lagrange and Markov Spectra of Pythagorean triples.
Dimension Spectrum for Complex and Real Continued Fractions with Restricted Entries.
Badly approximable numbers over imaginary quadratic fields.
Is one-dimensional Diophantine approximation all about continued fractions? | CommonCrawl |
The matrix given as below where you are supposed to put number from 1 to 25 in it. But the condition is that, the difference between the neigbours (horizontal and vertical) will be at least $x$.
What is the maximum value of $x$?
Is it possible to generalize the maximum value of $x$ in terms of the dimension of the matrix ($n\times n$)?
Note: The first part is answered correctly, still looking for the general equation for $n$ in terms of $x$.
Numbers increase by 10 as you go right, and by 11 as you go down, wrapping around when this would make them exceed 25.
Suppose we have a labeling where adjacent numbers differ by at least eleven. Divide into cases based on where 13 is in the grid.
Note: I will repeatedly use the fact that diagonally adjacent numbers cannot differ by 22. This is because if $d=a+22$ in the below picture, then both $b$ and $c$ would be forced to be $a+11$.
13 has only four possible neighbors: 1, 2, 24 and 25. You can't put 2 diagonally next to 24, so 2 is across from 24, leading to some rotation/reflection of the left picture. You are now forced to put 12 between 1 and 24, and 14 between 2 and 25.
Now, 12 has only four possible neighbors: 1, 23, 24 and 25. But 25 was already placed away from 12. With only three available neighbors, 12 must be on the border of the grid. Same goes for 14, leading to one of the two pictures on the right. In the left case, a 3 is forced above 14, leaving no options for *. The right grid has a similar contradiction.
Say 13 is on the left edge. After possibly replacing each number $n$ in the grid with $25-n$, the number to the right of 13 is either 24 or 25.
2b. Otherwise, there is a 25 to the right of 3. There are now to further subcases: either (i) one of 13's vertical neighbors is a 2, or (ii) it isn't.
2b(i). The first possibility is illustrated below. A 14 is forced between 2 and 25. There must be a 1 to the right of 14: if it was 3 to the right of 14, nothing could go above the 3. This forces a 12 above the 1, then a 23 or 24 to the right of 12, leaving a contradiction at *.
2b(ii) Otherwise, there must be a 1 vertically next to the 3, and a 24 on the other side. Following similar logic to case 2a leads to the picture below, which has no place to legally put an 11.
Case 3: 13 is in a corner.
Everything is similar to one of the three pictures below (omitting the case where the two neighbors are 2 and 24).
Anyone following along diligently should be comfortable making deductions in this grid by now, so I'll just show all the forced decisions in the first two grids (the first one also has similar variation where 14 is replaced with 12).
For the last case, consider the location of the 14. If 14 is placed on a square marked #, then its other two sides must contain a 3 and 25, which differ by 22. Same goes if 14 is in one of the other corners. If 14 is placed anywhere else, then it will have 3 neighbors, which can't be covered by 3 and 25 alone.
While doing this, the distance between the numbers should be as close as possible.
This is just an example, you could have put these differently but to get the maximum distance, this methodology seems optimal where you do not need to worry about the close numbers might get close to each other.
Since you put the numbers in the same order as before, the maximum difference happens between numbers which is $10$ as @MikeEarnest solved, but this time this methodology is applicable any size of matrix!
To form the formula, we can use the example above. as you will notice the maximum difference between numbers in $5\times5$ case is $(13+1)-4$ where $13$ is the last value you can put without any neighbor and $4$ is the first value on the second row where it has to be neigbour the next value after $13$ which is $14$. How do we get $13$ and $4$, if we can figure that out, the rest is just forming the formula!
$13$ case: It is simply $\left \lceil25\div2 \right \rceil$ which is the maximum value you can put into a $5\times5$ matrix without any neigbor.
$4$ case: It is simply $\left \lceil5\div2 \right \rceil+1$ which is the maximum value you can put on the row with the size of $5$ plus 1, first value on the second row. | CommonCrawl |
In this thesis we describe intermediate Jacobians of threefolds obtained from singular cubic threefolds. By this we mean two things. First, we describe the intermediate Jacobian of a desingularization of a cubic threefold with isolated singularities. Second, we describe limits of intermediate Jacobians of smooth cubic threefolds, as the family of cubic threefolds acquires isolated singularities. In regards to the first question, generalizing a result of Clemens--Griffiths we show specifically that the intermediate Jacobian of a distinguished desingularization of a cubic threefold with a single singularity of type $A_3$ is the Jacobian of the normalization of an associated complete intersection curve in $\mathbb P^3$, the so called $(2,3)$-curve. In regards to degenerations, we describe how the limit intermediate Jacobian, under certain conditions, can be described as a semi-abelian variety as the extension of a torus by the finite quotient of the product of Jacobians of curves, where one of the curves is the normalization of the $(2,3)$-curve associated to the cubic threefold and a choice of singularity, and the other curves are so-called tails arising from stable reduction of plane curve singularities.
Havasi, Krisztián, "Geometric Realization of Strata in the Boundary of the Intermediate Jacobian Locus" (2016). Mathematics Graduate Theses & Dissertations. 42. | CommonCrawl |
The goal is to tile rectangles as small as possible with the given heptomino, in this case number 6 of the 108 heptominoes. We allow the addition of copies of a rectangle. For each rectangle $a\times b$, find the smallest area larger rectangle that copies of $a\times b$ plus at least one of the given heptomino will tile.
I found 14 more. I considered component rectangles of width 1 through 11 and length to 31 but my search was not complete.
Most of these could be tiled by hand using logic rather than just trial and error.
I like how this one and Jaap's attempt are fundamentally different; this one is 'chaos' and the other one 'order'. It's asymmetric but it can be turned in a symmetric one; there are two ways to tile the irregular shape formed (twice) by the darker shaded polyominos. If you use the same one for both, you get a symmetric solution.
Here are a few more solutions.
Here is a $1\times8$ solution that is surely non-optimal. | CommonCrawl |
The picture illustrates the sum $1 + 2 + 3 + 4 = (4 \times5)/2$. Prove the general formula for the sum of the first $n$ natural numbers and the formula for the sum of the cubes of the first n natural numbers. See the problem Picture Story .
Number theory. Mathematical reasoning & proof. Visualising. Arithmetic sequences. Inequalities. Generalising. Quadratic equations. Games. Creating and manipulating expressions and formulae. Networks/Graph Theory. | CommonCrawl |
Exotic Mott insulators are excellent candidates to study quantum magnetism and strongly correlated phases. First, we study one specific example for an exotic strong-interacting phase in a bosonic system, the fully gapped chiral Mott insulator (CMI). Using a perturbative approach we show the existence of a low-lying exciton state on several lattice geometries obeying the correct symmetry-behavior for a formation of the CMI. The binding of the exciton mainly arises from dynamical bosonic processes. In a second step we perform large-scale numerical density matrix renormalization group simulations and find two quantum phase transitions surrounding a very narrow window for the CMI in the intermediate interaction regime, which can be extended by introducing a repulsive nearest neighbor interaction or changing density and anisotropy. That means, that it is harder than previously assumed to experimentally find this exotic phase in a quasi-one dimensional and especially in two dimensional systems. Next, we turn to fermionic Mott insulators with highly symmetric spin degrees of freedom, described by the special unitary group, $SU(N)$. By implementing an $SU(N)$-invariant Exact Diagonalization (ED) code, and using the message-passing-interface (MPI) for the parallelization, we calculate the thermodynamics and correlation functions for a series of $SU(N)$ Heisenberg models in one and two dimensions. Supported from high-temperature series expansions and numerical linked-cluster expansions (NLC) on top of ED we find an universal high-temperature regime with dominating short-ranged two-flavor antiferromagnetic correlations. The phase exhibits real-space correlation patterns subject to Manhattan shells. On the one-dimensional chain we find strong evidence for a continuous Lifshitz transition around $T\sim 0.6J$ for several $N$. For $SU(3)$ and $SU(4)$ on the square lattice we find further signs for a Lifshitz transition in the low temperature regime $T<J$. In the last part we address the thermodynamics of the Shastry-Sutherland model, which represents another instance of a Mott insulator and is an effective description for the material $\mathrm Below the transition a small finite temperature induces a change of the structure, characterized by another wave vector. | CommonCrawl |
Farmer John has decided his home needs more decoration. Visiting the local china shop, he finds a delicate glass cow figurine that he decides to purchase, knowing that it will fit perfectly on the mantel above his fireplace.
The shape of the cow figurine is described by an $N \times M$ grid of characters like the one below ($3 \leq N, M \leq 500$), where lowercase letter characters are each part of the figurine (indicating different colors) and '.' characters are not.
Unfortunately, right before FJ can make his purchase, a bull runs through the shop and breaks not only FJ's figurine, but many of the other glass objects on the shelves as well! FJ's figurine breaks into 3 pieces, which quickly become lost among $K$ total pieces lying on the ground ($4 \leq K \leq 100$). Each of the $K$ pieces is described by a grid of characters, just like the original figurine.
Please help FJ determine how many sets of 3 pieces (out of the $K$ on the floor) could be glued back together to mend his broken figurine.
The pieces on the ground might have been flipped vertically or horizontally, or rotated by some multiple of 90 degrees. Therefore, given the original grid as well as $K$ grids describing pieces, you want to find sets of 3 pieces that can be joined together to form the original picture, allowing the pieces to be translated, flipped, or rotated multiples of 90 degrees. When then superimposed, the 3 pieces should exactly form the original picture, with each colored square in the original picture represented in exactly one of the pieces.
The first line contains a single integer $K$. Following that will be $K + 1$ piece descriptions. The first description will describe the original glass cow, the following $K$ descriptions will be of the broken pieces.
Each description begins with a line containing two integers $R$ and $C$ ($1 \le R, C \le 100$). The following $R$ lines contain $C$ lowercase alphabet characters describing the color of each cell. Each piece will be horizontally/vertically connected and have at least one non-empty cell.
Output the number of triples $i, j, k$ ($i < j < k$) such that pieces $i$, $j$, and $k$ can be arranged to form the original glass cow.
The three solutions use pieces $(0, 1, 2)$, $(0, 2, 4)$, $(1, 3, 4)$.
Note that this problem has a time limit of 6 seconds per test case (and twice that for Java and Python submissions). | CommonCrawl |
which yields the same result, 2.
Could someone prove mathematically(or otherwise) why this works? OR provide an example where it won't work? I'm pretty sure it works all the time but don't have a proof..
Edit 1: @Mark Bennet. Thanks for your answer. I was able to fill in the gaps and understand why the answer can be derived directly from the initial positive number using modulo 9. I will write out the proof after telling what I didn't understand.
However, what I didn't understand is, why when going by the less efficient way of repetitively summing the digits of the numbers, the order of adding the digits does not matter.
Let n be original number, s1, s2, s3, ..., sk be the sums formed by adding the digits. Let sk be single digit. We know what n-s1, s1-s2, s2-s3 are all divisible by 9 because of your explanation. So we can add them all up, cancelling s1,s2, ..., sk-1j, until we are left with just n-sk which is also divisible by 9.
So, we can write n = 9p+sk where p >=0. By definition, sk is n%9.
What I didn't understand, (or rather connect this proof to) what my question is initially seeking an answer for: If I still went by my way of adding digits repetitively, why does the order of adding digits not matter?
Think about just one digit. In the original number it appears as $a\times10^r$ because of its "place value". In the sum of digits it appears just as $a$.
The difference between the two is $a\times (10^r-1)$, and you will see that $10^r-1$ has every digit $9$ (or is zero if $r=0$) and is therefore divisible by $9$.
The difference between the original number and its sum of digits is therefore divisible by $9$, and this can be used to show that when you start with a positive integer the single digit you get at the end is $9$ if the number is divisible by $9$ or is otherwise the remainder you get when you divide the original number by $9$.
It doesn't matter how this sum is calculated - beginning with a single digit shows that this can be done digit by digit. The difference at every stage between the number you started with and the one you finish with is divisible by $9$. That is the key point.
I have left some gaps for you to fill in. There are plenty of slick proofs out there ("casting out nines" is an old name for this, which was a check on arithmetic in the days before electronic calculators), but you will do best to work it through for yourself.
Not the answer you're looking for? Browse other questions tagged proof-verification summation or ask your own question.
what is a numbers cross sum? | CommonCrawl |
Using the digits $1, 9, 9$ and $8$ in that order, and the operations $+$, $-$ and/or $\times$ in any order between pairs of digits, create an expression that equals $81$. Normal precedence rules apply.
As an example, here is one solution: $1 \times 9 + 9 \times 8 = 81$. Find three or four more solutions that fit the criteria.
If truly only + - X are accepted, no parenthesis or concatenations, and the numbers must stay in this order, all I can see for now are those.
Not sure if this is considered cheating or not but would these solutions count?
To get 81, we need to get any of the following: 80, 81, or 82 with 9,9,8; 9, 72, or 90 with 1,8,9; or 73 or 89 with 9,9,1. Let's start with 9,9,1. The closest we can come to 73 is 9*(9-1) = 72. Likewise, we also miss 89 by one, with 9*(9+1) = 90. Any other combination either gives a number in the 80s or number that is too small. Continuing with 1,8,9, it is possible to get 72 in one of the two ways (that we have already said.) Getting 9 is impossible; your numbers are either too high or too low (9+1-8) = 2, 9+8-1 = 16). The highest possible number to get by using 1,8,9 with your rules is 9*(8+1) = 81, so 90 is out of the question. Finally, 9, 9, 8. At first glance, it seems possible to get 81 (9*8+9), but this solution is the same as the solutions from 72 with 1,8,9. Also, it's not possible to get 80 or 82, because the only way to get close is 9*9 or 9*8. 9*9 is 81, which + or -8 doesn't help; and 9*8 + 9 is 81, which we've covered. So, the only two (eight with negative numbers) possible solutions with your rules are 9*8*1+9 and 9*8+9*1. | CommonCrawl |
Abstract: Let $(X,\mu,T)$ be a measure preserving system. A factor is a system $(Y,\nu,S)$ so that there exists $F$ with $SF=FT$ and so that $F$ pushes $\mu$ forward to $\nu$. A measurable dynamical system is prime if it has no non-trivial factors. A classical way to prove a system is prime is to show it has few self-joinings, that is, few $T \times T$ invariant measures that on $X \times X$ that project to $\mu$. We show that there exists a prime transformation that has many self-joinings which are also large. In particular, its ergodic self-joinings are dense in its self-joinings and it has a self-joining that is not a distal extension of itself. As a consequence we construct the first known rank 1 transformation that is not quasi-distal and show that being quasi-distal is a meager property in the set of measure preserving transformations, which answers a question of Danilenko. This talk will not assume previous familiarity with joinings or prime transformations. This is joint work with Bryna Kra. | CommonCrawl |
Alexandre Mouton. Two-scale semi-Lagrangian simulation of a charged particle beam in a periodic focusing channel. Kinetic & Related Models, 2009, 2(2): 251-274. doi: 10.3934\/krm.2009.2.251.
Philippe G. LeFloch, Seiji Ukai. A symmetrization of the relativistic Euler equations with severalspatial variables. Kinetic & Related Models, 2009, 2(2): 275-292. doi: 10.3934\/krm.2009.2.275.
Jishan Fan, Tohru Ozawa. Regularity criteria for the magnetohydrodynamic equations with partial viscous terms and the Leray-$\\alpha$-MHDmodel. Kinetic & Related Models, 2009, 2(2): 293-305. doi: 10.3934\/krm.2009.2.293.
Bertrand Lods. Variational characterizations of the effective multiplicationfactor of a nuclear reactor core. Kinetic & Related Models, 2009, 2(2): 307-331. doi: 10.3934\/krm.2009.2.307.
Gilberto M. Kremer, Filipe Oliveira, Ana Jacinta Soares. $\\mathcal H$-Theorem and trend to equilibrium of chemically reacting mixtures of gases. Kinetic & Related Models, 2009, 2(2): 333-343. doi: 10.3934\/krm.2009.2.333.
J-F. Clou\u00EBt, R. Sentis. Milne problem for non-grey radiative transfer. Kinetic & Related Models, 2009, 2(2): 345-362. doi: 10.3934\/krm.2009.2.345.
Jos\u00E9 A. Carrillo, M. R. D\u2019Orsogna, V. Panferov. Double milling in self-propelled swarms from kinetic theory. Kinetic & Related Models, 2009, 2(2): 363-378. doi: 10.3934\/krm.2009.2.363.
Thibaut Allemand. Derivation of a two-fluids model for a Bose gas from a quantum kinetic system. Kinetic & Related Models, 2009, 2(2): 379-402. doi: 10.3934\/krm.2009.2.379. | CommonCrawl |
Now denote the addition in th group $\mathcal M$ by "$+$" as usual, and the addition and multiplication in the ring $\mathcal R$ by "$\hat+$" and "$\hat*$", respectively. Now denote the addition in th group $\mathcal M$ by "$+$" as usual, and the addition and multiplication in the ring $\mathcal R$ by "$\hat+$" and "$\hat*$", respectively.
"$*$" is an action of the ring on the group from the left. If the ring is commutative, then one need not distinguish between left- and right module. "$*$" is an action of the ring on the group from the left. If the ring is commutative, then one need not distinguish between left- and right module.
One generally speaks of an $R$-left-module over $M$. Here $R$ and $M$ are just sets. One generally speaks of an $R$-left-module over $M$. Here $R$ and $M$ are just sets. | CommonCrawl |
Abstract: Langevin diffusion processes and their discretizations are often used for sampling from a target density. The most convenient framework for assessing the quality of such a sampling scheme corresponds to smooth and strongly log-concave densities defined on $\mathbb R^p$. The present work focuses on this framework and studies the behavior of Monte Carlo algorithms based on discretizations of the kinetic Langevin diffusion. We first prove the geometric mixing property of the kinetic Langevin diffusion with a mixing rate that is, in the overdamped regime, optimal in terms of its dependence on the condition number. We then use this result for obtaining improved guarantees of sampling using the kinetic Langevin Monte Carlo method, when the quality of sampling is measured by the Wasserstein distance. We also consider the situation where the Hessian of the log-density of the target distribution is Lipschitz-continuous. In this case, we introduce a new discretization of the kinetic Langevin diffusion and prove that this leads to a substantial improvement of the upper bound on the sampling error measured in Wasserstein distance. | CommonCrawl |
A Dirichlet character is a function $\chi: \mathbb Z\to \mathbb C$ together with a positive integer $q$, called the modulus of the character, such that $\chi$ is completely multiplicative, i.e. $\chi(mn)=\chi(m)\chi(n)$ for all integers $m$ and $n$, and $\chi$ is periodic modulo $q$, i.e. $\chi(n+q)=\chi(n)$ for all $n$. If $(n,q)>1$ then $\chi(n)=0$, whereas if $(n,q)=1$, then $\chi(n)$ is a root of unity. | CommonCrawl |
Bebiano, N. ; Providência, J. da ; Teixeira, R.
The point equation of the associated curve of the indefinite numerical range is derived, following Fiedler's approach for definite inner product spaces. The classification of the associated curve is presented in the $3\times 3$ indefinite case, using Newton's classification of cubic curves. Illustrative examples of all the different possibilities are given. The results obtained extend to Krein spaces results of Kippenhahn on the classical numerical range.
Ball, W. W. R.: On Newton's classification of cubic curves. Proc. London Math. Soc. 22 (1890), 104-143 \JFM 23.0778.05. | CommonCrawl |
I got this problem from Rustan Leino, who was told it by Clark Barrett.
Given is a (possibly enormous) rectangular chocolate bar, divided into small squares in the usual way. The chocolate holds to a high quality standard, except for the square in the lower left-hand corner, which is poisonous. Two players take turns eating from the chocolate in the following manner: The player whose turn it is points to any one of the remaining squares, and then eats the selected square and all squares positioned above the selected square, to the right of the selected square, or both above and to the right of the selected square. Note that, although the board starts off rectangular, it may take on non-rectangular shapes during game play. The object of the game is to avoid the poisonous square. Assuming the initial chocolate bar is larger than $1 \times 1,$ prove that the player who starts has a winning strategy.
Hint: To my knowledge, no efficient strategy for winning the game is known. That is, to decide on the best next move, a player may need to consider all possible continuations of the game. Thus, you probably want to find a non-constructive proof. That is, to prove that the player who starts has a winning strategy, prove just the existence of such a strategy; in particular, steer away from proofs that would construct a winning strategy for the initial player.
Suppose there's a rectangle for which the starting player doesn't have a winning strategy. Then, any move he makes must allow the non-starting player to win. In particular, the move of "eat only the upper-right square" must let the non-starting player win.
This means that, when presented with the rectangle with the upper-right square removed, the non-starting player has some winning strategy. In particular, there is some square $S$ he can point to that will let him win. After he eats that square and every square above and/or to the right of it, the chocolate bar will be in some state $C$ from which the next player to go (the starting player) cannot win.
Now, imagine that, at the beginning of the game, the starting player had pointed to square $S$ instead of the upper-right corner. He would leave the chocolate bar in state $C,$ which we know is a losing position for the next player to go, in this case the non-starting player. In other words, the starting player will win! This contradiction shows that our earlier supposition was false. In other words, there is no rectangle for which the starting player doesn't have a winning strategy. | CommonCrawl |
Augustine, Jacob and Feng, Wen and Jacob, James (1995) Logic Minimization Based Approach for Compressing Image Data. In: 8th International Conference on VLSI Design, 4-7 January 1995, New Delhi, India, pp. 225-228.
We propose a novel approach for the lossless compression of binary images using logic minimization. The image is divided into windows or blocks of size $r\times c$ pixels and each block is transformed into a Boolean switching function in cubical form, treating the pixel values as output of the function. Compression is performed by minimizing these switching functions using ESPRESSO, a cube-based two-level logic minimizer. To reduce the bits required to encode the minimized cubes (product terms), a code set which satisfies the prefix property is used. If this technique fails to produce compression for a window, the pixels are stored as such. The main motivation of the work has been to investigate the potential of logic minimization as a tool for image data compression. Our technique outperforms UNIX compress in terms of compression ratio on most of the test images. The compression scheme is relatively slower while the decompression time is comparable to that of UNIX compress.
Copyright 1995 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE. | CommonCrawl |
Separation of melt from residual solid and its migration from beneath a mid-ocean ridge to Earth's surface require a transition from porous to channelized flow in order to preserve chemical and radiogenic disequilibrium. Chemically isolated, high-permeability melt conduits in Earth's mantle develop as a consequence of instabilities in the deformable and dissolvable porous media. Models for the formation of such flow instabilities include stress-driven and reaction-driven melt channelization.
Melt rising from depth becomes under saturated in pyroxene with respect to the surrounding upper mantle; thus, pyroxene dissolves into the melt as it migrates toward the surface. Tabular rocks rich in olivine and depleted in pyroxene found in peridotite massifs serve as channels for rapid melt extraction from the mantle. Formation of such dunite channels involves dissolution-precipitation reactions between mantle rock and percolating reactive melt. Dunite channels also coincide with shear zones, indicating that deformation together with reaction plays an important role during melt channelization.
Understanding stress-driven and reaction-driven melt segregation processes requires a close coupling of experiment with theory. My talk focuses on results from laboratory investigations of the formation and evolution of melt-enriched channels in mantle rocks. (i) The first part examines the formation of stress-driven, melt-enriched channels predicted by theory. Here, the experimentally observed alignment of channels motivated further development in theory. (ii) The second part considers experimental investigations of reaction infiltration instabilities in mantle rocks. In partially molten rock samples composed of olivine and pyroxene sandwiched between a source of reactive (pyroxene under-saturated) melt and a porous sink, finger-like melt-enriched channels composed of olivine + melt propagated into and often through the rock in response to a gradient in fluid pressure.
Better constraints on rates of melt migration within the partially molten regions of the upper mantle are required to advance our current understanding of various dynamic processes at ocean ridges. In this study, we synthesized texturally equilibrated mono- and polymineralic aggregates containing various amounts of partial melt and characterized the 3-dimensional (3-D) distribution of melt using synchrotron-based x-ray microtomography. With the availability of the high-resolution 3D melt distribution, we developed digital rock physics models to calculate the physical properties of partially molten rocks. We focus on the characteristic change in melt geometry as a function of melt fraction and lithological variation, and how they affect the transport and elastic properties. Our results indicate that 1) the permeability and melt fraction are related by a power-law relation with an exponent of ~2.7 and geometric factor of 57±28 (Miller et al., 2014); 2) the bulk electrica l conductivity also follows a power-law relationship with melt fraction, with the exponent is ~1.3 and the geometric factor 0.66±0.06 (Miller et al., 2015); 3) in a partially molten rock, in general, the fluid pathways differ from, and are more tortuous than the electric current pathways; 4) lithological melt partitioning is observed: the presence of pyroxene causes melt focusing in olivine-rich regions of partially molten harzburgite. We quantified the effect of lithological partitioning on transport properties.
Earth's sea ice packs are key players in the climate system and critical indicators of climate change, as evidenced by the recent precipitous losses of summer Arctic sea ice. As a material, frozen sea water is a polycrystalline composite of a pure ice matrix containing brine inclusions - the melt phase - whose volume fraction and connectivity depend strongly on temperature. The brine phase undergoes a percolation threshold at a critical temperature where the inclusions coalesce to form channels through which the melt phase can flow. Fluid transport through sea ice mediates key climatological and biological processes, and can enhance thermal transport via convection in the porous microstructure.
During the Arctic melt season, the sea ice surface is transformed from vast expanses of snow covered ice to complex mosaics of ice and melt ponds. Sea ice albedo, a key parameter in climate modeling, is largely determined by melt pond evolution. As the ponds grow and coalesce, the melt phase undergoes a percolation threshold and the fractal dimension of the pond boundaries transitions from 1 to about 2 around a critical pond size.
In the two lectures, I will discuss mathematical models of composite materials and statistical physics that we have been using to describe the effective fluid, thermal, and electromagnetic transport properties of sea ice, and to address other problems in sea ice physics such as melt pond evolution. I will cover a range of mathematical techniques, some of which may possibly shed light on similar questions for partially molten rock. They include percolation theory, multiscale homogenization, integral representations for effective transport coefficients of composite media, spectral measures and random matrix theory, homogenization for advection diffusion processes, and Ising models. These models have been developed in conjunction with our field experiments in the Arctic and Antarctic. A short video on a recent Antarctic expedition will be shown.
Mechanical and transport properties of a partially molten rock strongly depend on the grain scale melt geometry. To quantify the microstructural effects, constitutive mechanical relations for elasticity (Takei, 1998) and diffusion creep viscosity (Takei and Holtzman, 2009) are derived theoretically by considering a realistic microstructural model. The essential geometrical factor which determines these properties was found to be the ``grain boundary contiguity'' which represents the area of grain-to-grain contacts relative to the total surface area of each grain. One of the most striking results is that while contiguity affects both elasticity and viscosity, the effect on viscosity is about 100 times larger than that on elasticity. When partially molten rock is texturally equilibrated, contiguity is determined as a function of melt fraction and dihedral angle. However, when it is deformed under a deviatoric stress, contiguity deviates from the equilibrium value an d evolves, resulting in a significant change in the matrix viscosity. Possible consequences of these microstructural evolution on the macroscopic dynamics can be studied within the framework of continuum mechanics by solving the governing equations of two phase flow together with the viscous constitutive relation which includes contiguity as an internal state variable. By applying this approach to the formation of stress-driven, melt-enriched channels, I will demonstrate the important role of microstructural processes in the macroscopic dynamics.
Bulk properties of partially molten rocks are significantly affected by the melt distribution and geometry. Surface energy minimisation determines the melt geometry, both locally at the junction of two grains and melt (dihedral angle), and for the aggregate as whole, in the form of grain growth. Grain growth is a continuous process and partially molten rocks therefore constitute a dynamic system. This contrasts with the assumptions of the model melt distribution in a static system with isotropic grains of a single size that can be fully characterised by measuring dihedral angles. In the dynamic system the local melt geometry is not always in its minimum energy configuration, as grain growth continuously creates new neighbours that need to adjust their grain boundary plane orientations. In this dynamic system, the melt distribution can not be characterised by only measuring dihedral angles.
As a somewhat more comprehensive assessment of the melt distribution, we measure the proportion of grain boundaries wetted by melt (grain boundary wetness/contiguity). While deformation experiments in the diffusion creep regime by necessity need to be carried out on fine-grained samples, the melt distribution can be determined on significantly more coarse-grained samples, hot-pressed at high temperatures up to two weeks in a piston cylinder apparatus. The wetness data from these samples, obtained at suitably high resolution, allows augmentation of the experimentally measured diffusion creep rheology.
For the direct experimental determination of the effect of small amounts of melt on both large-strain rheology and seismic properties it is important to characterise genuinely melt-free materials for reference. For this reason we use synthetic Fo90 olivine aggregates that contain no melt or trace elements, unless deliberately added. Experiments with melt-bearing samples show that both the large strain rheology and seismic properties are substantially affected by small amounts of melt, consistent with the observations of the melt distribution described above. For seismic properties the presence of melt affects both the shear modulus and attenuation in the seismic frequency band. Important for the effect of melt on seismic properties are wetted grain boundaries with sufficiently low aspect ratio for local fluid flow to take place (i.e. on the scale of a single grain, 'melt squirt').
Similar materials are also used to determine the effect of water (hydroxyl) on the rheology and seismic properties of olivine. This allows comparison of the relative effects of water and melt in the upper mantle.
The migration of melt over length scales of hundreds of kms takes place through grain edge tubules and films with typical dimensions of a few hundred nanometers to a few microns. The volume fraction, shape, and distribution of these tubules and films exert a strong influence on the effective physical properties, anisotropy, and the trajectory of melt migration in the mantle. In this talk, I will outline new techniques for modeling the microstructure in partially molten rocks,their influence on the effective physical properties, and the implications for large scale magma flow.
Grain size is a critical parameter for the understanding of our planet's mantle since it has considerable impact on seismological properties, on the permeability of mantle rocks and therefore on melt migration characteristics of Earth's interior. Grain growth therefore becomes an important process that should be meticulously determined in order to better understand the dynamics of our planet's interior.
By combining the existing database on olivine grain growth and our experimental data, we have succeeded in modeling (i) genuinely dry olivine grain growth aggregates, through grain boundary diffusion-controlled processes, (ii) H2O-oversaturated olivine aggregates and (iii) melt-bearing olivine aggregates, from nominally melt-free to ∼ 50 wt.% melt. Different important parameters have been constrained by using our model, namely the dry effective grain boundary thickness (δ ∼ 6 nm), melt contents in nominally melt-free samples (Φ ≤ 0.5 wt.%) as well as the wetting properties (Ψ) of melt as a function of melt content, pressure and temperature. We expect that our results will not only have considerable implications on the grain size-dependent deformation mechanisms of mantle rocks but also reconcile macroscopic observations to microscopic-scale key processes governing the mantle behavior, particularly in intergranular zones impregnated by low melt content s.
The modeling of seismic elastic wave full waveform in a limited frequency band is now well established with a set of efficient numerical methods like the spectral element, the discontinuous Galerking or the finite difference methods. The constant increase of computing power with time has now allow the use of seismic elastic wave full waveforms in a limited frequency band to image the elastic properties of the earth. Nevertheless, inhomogeneities of scale much smaller the minimum wavelength of the wavefield associated to the maximum frequency of the limited frequency band, are still a challenge for both forward and inverse problems. In this work, we tackle the problem of elastic properties and topography varying much faster than the minimum wavelength. Using a non periodic homogenization theory and a matching asymptotic technique, we show how to compute effective elastic properties and local correctors and how to remove the fast variation of the topography. The implications on the homogenization theory on the inverse problem will be presented.
An elliptic-parabolic system of partial differential equations describes the flow of a single-phase incompressible fluid and the transport of a dissolved chemical by advection and diffusion through a heterogeneous porous medium. The objective is to develop an upscaled model of this system which represents the full range of scales observed. After a review of homogenization results for the traditional low contrast and the $\epsilon^2$-scaled high contrast cases, the new discrete upscaled model based on local affine approximations is constructed. It reproduces the full range of scale contrasts observed in experiments.
Icicles are a common ice formation, familiar to anyone who lives in a cold climate. The shape of an icicle emerges from a delicate dance between solidification, hydrodynamics and heat transport. Many, but not all, natural icicles are observed to be decorated around their circumference by ribs or ripples. These features are presumed to be the result of a morphological instability in the growth process of the ice. The sides of an icicle are covered by a thin supercooled water film which flows down their nearly vertical surface. The wavelength of the ripples, which is always found to be near 1~cm, is surprisingly constant, even under diverse growing conditions. A recent detailed study in which hundreds of icicles were grown in controlled laboratory experiments revealed that trace amounts of impurities are required for the formation of the ripples. Icicles grown from distilled water have no ripples. Ripples appear at a remarkably low concentration of impurity, becoming me asurable above a concentration of just 10 −3 weight \% of salt. Thereafter, they grow at a rate which is roughly logarithmic in the concentration of the impurity. These effects are not explained by linear stability theory which does not account for impurities.
In this talk, we will discuss our recent experiments in which the concentration and molecular species of the impurity were varied, as well as our progress toward a generalized linear stability analysis of the growing ice surface, which includes the effects of impurities. The theory crucially depends on the boundary conditions on the ice-water interface and the possible presence of a mushy layer near this interface.
Progressive deformation of upper mantle rocks via dislocation creep causes their constituent crystals to take on a non-random orientation distribution (crystallographic preferred orientation or CPO) whose observable signatures include shear-wave splitting and azimuthal dependence of surface wave speeds. Comparison of these signatures with mantle flow models thus allows mantle dynamics to be unraveled on global and regional scales. However, existing self-consistent models of CPO evolution are computationally expensive when used in 3-D and/or time-dependent convection models. We propose a new method, called ANPAR, which is based on an analytical parameterization of the crystallographic spin predicted by the second-order (SO) self-consistent theory. Our parameterization runs ≈2–6\times 10^4 times faster than the SO model and fits its predictions for CPO and crystallographic spin with a variance reduction >99 per cent. We illustrate the ANPAR model predictions fo r the deformation of olivine with three dominant slip systems, (010), (001) and (010), for three uniform deformations (uniaxial compression, pure shear and simple shear) and for a corner-flow model of a spreading mid-ocean ridge.
Co-authors: Chao Qi (University of Pennsylvania), David Wallis (University of Oxford), Benjamin Holtzman (Lamont-Doherty), David Kohlstedt (University of Minnesota)Seismic anisotropy is a key indicator of the kinematics of flow in the upper mantle. Much insight has been gained into seismic anisotropy that results from the crystallographic alignment of olivine during deformation. This anisotropy is primarily characterized by alignment of the seismically fast axis with the flow direction. This relationship between olivine anisotropy and the macroscopic kinematics allows detailed comparison between simulations of global mantle flow and seismic tomography. However, relatively little is known about the development of seismic anisotropy in partially molten rocks. Some experimental studies on partially molten rocks suggest that the seismically fast direction tends to lie at high angles to the flow direction, leading to a vastly different relationship between anisotropy and kinematics. Thus, the presence of a melt phase appears to fundamentally alter the grain-scale processes leading to crystallographic rotation of the solid phase.
Here we present a new experimental data set detailing the evolution of anisotropy during deformation of partially molten peridotite. Torsion experiments were conducted on samples composed of San Carlos olivine and basaltic melt at a temperature of 1473 K and a confining pressure of 300 MPa. Seismically fast axes of olivine tend to lie at a high angle to the flow direction in a manner similar to previous experiments. The anisotropy in these samples is weak compared to that in dry, melt-free olivine deformed to similar strains. The anisotropy also exhibits relatively little change in strength and orientation with progressive deformation. Detailed microstructural analyses allow us to distinguish between competeing models for the grain-scale deformation processes, favoring one in which intergranular processes control grain rotations. Based on our observations, we extrapolate our results to flow in the oceanic upper mantle, demonstrating good correlation between predicted and obse rved seismic anisotropy.
In a melt-free mantle, development of crystal preferred orientations (CPO or texture) in response to deformation is the major source of anisotropy of physical properties. Measurement of seismic (elastic) anisotropy is indeed the best available tool to unravel flow patterns at various depths in the mantle. Though it cannot be easily measured in situ, anisotropy is even more marked for thermal diffusion and viscosity. These anisotropies probably induce a memory-effect on the thermo-mechanical evolution of the upper mantle. In this presentation, we will address how the presence of melts may change the anisotropy of physical properties in the upper mantle. The presence of melts may: (1) induce an additional (probably stronger) component of anisotropy if the melt is concentrated in aligned pockets or lenses, (2) change the olivine texture evolution and (3) the mineralogical composition. Anisotropy due to melt alignment, though strong, is only effective while melts are present in t he system. The two latter processes induce weaker, but long-term changes in the anisotropy, which remain effective even after melt extraction or crystallization. Observations in naturally deformed peridotites suggest all three processes occur in the upper mantle. Analysis of the spatial arrangement of products of melt-rock reactions in mantle peridotites provides evidence for melt organization in planar lenses or layers parallel to the shear plane at both the grain boundary and larger (cm to tens of meters) scales. Such an arrangement may induce significant decrease in the shear viscosity parallel to the shear plane. Comparison of olivine crystal preferred orientations within and outside melt-focusing domains records changes in the deformation processes and hence on the resulting CPO-induced anisotropy, which depend on the nature of the melt-rock reactions. The latter also controls the crystallization of new minerals, which most often dilutes the anisotropy. | CommonCrawl |
I have heard that the worst case for the euclidian algorithm is in the case of Fibonacci numbers. Can this be proven, and can it be proven only n-2 divisions are required (where euclidian algorithm is performed on naturals a, b <= fib(n))?
Browse other questions tagged abstract-algebra induction fibonacci-numbers euclidean-algorithm or ask your own question.
Euclidean Algorithm : Confusion with how many divisions needed?
Why are Fibonacci numbers bad for Euclid's Algorithm and how to derive this upper bound on number of steps needed in general?
What is the worst case for the Euclidean algorithm in $\mathbb Z[i]$? | CommonCrawl |
the sum of two and three gamma variate with argument 2. Due to the fact Due to the fact that the sum of n independent gamma variates with shape parameter c i is... Abstract. We give expressions for the distribution and density of a product of gamma or equivalently chi-square random variables. In particular, we give the distribution of the product of two independent gamma variables of mean k in terms of the Bessel functions K 1, … , K k.
Steece, B.M. (1976) On the exact distribution for the product of two independent beta-distributed random variables. Metron 34 , 187 – 190 . Stuart , A. ( 1962 ) Gamma-distributed products of independent random variables .
When p 1 = p 2 = 1 the pdfs , reduce to those of the product and quotient of two independent Weibull random variables. When a = 1 the pdfs (2.1) , (3.1) reduce to those of the product and quotient of two independent gamma random variables (these results agree with those given in Gupta and Wong (1984) ).
Printer-friendly version The Beta Distribution. Let $X_1$ and $X_2$ have independent gamma distributions with parameters $\alpha, \theta$ and $\beta$ respectively.
26/01/2010 · If X and Y are gamma distributed random variables, then the ratio X/Y, I was told follows a beta distribution, but all I can find so for is that the ratio X/(X+Y) follows a beta distrinbution. | CommonCrawl |
Is this a pseudodifferential operator?
a pseudodifferential operator? More precisely, is there a pseudodifferential operator $P:C_c^\infty(M)\rightarrow C_c^\infty(M)$ of order $-1$ such that $P$ extends to $A$?
Browse other questions tagged dg.differential-geometry fa.functional-analysis operator-theory elliptic-pde pseudo-differential-operators or ask your own question.
Why is this operator compact?
Does adding a compact operator change the symbol of a pseudodifferential operator? | CommonCrawl |
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