Probability of touching

Question: For a vanilla option, I know that the probability of the option expiring in the money is simply the delta of the option...  but how would I calculate the probability, without doing monte carlo, of the underlying touching the strike at some time at or before maturity?
Comment: @WilliamS.Wong - the OP is about probability of touching, *before expiration*.  Read it again.
Comment: It seems like for a vanilla there should be a non-simulation way to calculate this.
Comment: This question is entitled the "probability of touching", but the OP was asking for the probability of an option **expiring** in the money.  The two are not the same.

Note how many folks mentioned "stopping time" and "barriers" in their answers.
Answer: Assume the price follows a lognormal process. We can convert it, by taking the natural logarithm of the price, into a problem of finding the probability of a standard Brownian motion particle starting from $0$ and hitting $x\ge0$ before time $t$, or its first passage time $\tau_x$ being less than $t$. This can be derived through the reflection principle. The paths crossing $x$ are exactly paired up by the segment post crossing through mirror reflection about $x$.
Case 1) No drift.
By the strong Markov property, at the moment a path first touches $x$, the probabilities of the particle taking on either of two path mirror reflecting about the line $x$ are the same, therefore the total probability of touching $x$ is twice of that of particle reaching above $x$
$$P(\tau_x<t) = \frac{2}{\sqrt{2\pi t}}\int_x^\infty e^{-\frac{y^2}{2t}} {\rm d}y=\sqrt{\frac{2}{\pi}}\int_{\frac{x}{\sqrt t}}^\infty e^{-\frac{y^2}{2}} dy={\rm erfc}\Big(\frac{x}{\sqrt{2t}}\Big).$$
Case 2) The drift is $vt$, where $v$ is a constant.
The probability measure is
\begin{align}
dP(y) &= \frac{1}{\sqrt{2\pi}}\exp\Big(-\frac{(y-vt)^2}{2t}\Big)\frac{{\rm d}y}{\sqrt t} \\
&= \frac{1}{\sqrt{2\pi}}\exp\Big(vy-\frac{1}{2}v^2t\Big)\exp\Big(-\frac{y^2}{2t}\Big)\frac{{\rm d}y}{\sqrt t}.
\end{align}
The set of paths crossing $x$ can be partitioned into two disjoint subsets, one ends at $t$ above $x$ and the other ends below. The probability $P_1$ of the first set is obtained directly using the first expression above
\begin{align}
P_1 &= \frac{1}{\sqrt{2\pi}}\int_x^{\infty}\exp\Big(-\frac{(u-vt)^2}{2t}\Big)\frac{{\rm d}u}{\sqrt t} \\
&=\frac{1}{\sqrt{2\pi}}\int_{\frac{x}{\sqrt t}-v\sqrt t}^\infty e^{-\frac{y^2}{2}} dy \\
&= \frac{1}{2}{\rm erfc}\Big(\frac{1}{\sqrt 2}\Big(\frac{x}{\sqrt t}-v\sqrt t\Big)\Big).
\end{align}
In the second set, the paths that end in $[y-dy,y],\, y<x$ is a subset of the set of all the paths that start from $0$ and end in $[y-dy,y],\, y<x$. That former set one-to-one corresponds to the set of paths starting from $0$ ending in $[2x-y,2x-y+dy]$. The second expression for the probability measure indicates we can treat the first exponential as a factor or a random variable dependent only on the final time $t$ and the second a new probability measure. The first factor can also be interpreted as a Radon-Nikodym derivative or Jacobian between two probability measures. This new measure makes any two path sets reflectively symmetric about $x$ have the same measure just as in the driftless case, which allows us to compute the probability of second set  using that of the first set when driftless. So the probability $P_2$ of the second set is
\begin{align}
P_2 &= \frac{1}{\sqrt{2\pi}}\int_{-\infty}^x\exp\Big(vu-\frac{1}{2}v^2t\Big)\exp\Big(-\frac{(2x-u)^2}{2t}\Big)\frac{{\rm d}u}{\sqrt t} \\
&=\frac{e^{2vx}}{\sqrt{2\pi}}\int_{\frac{x}{\sqrt{t}}+v\sqrt t}^\infty e^{-\frac{y^2}{2}} {\rm d}y \\
&= \frac{e^{2vx}}{2}{\rm erfc}\Big(\frac{1}{\sqrt 2}\Big(\frac{x}{\sqrt t}+v\sqrt t\Big)\Big).
\end{align}
Therefore the probability of the particle passing $x$ or the first passage time $\tau_x$ of $x$ less than $t$ is the sum of the above two probability
$$P(\tau_x<t)=P_1+P_2.$$
Comment: Sounds positive. Can anyone else verify the solutions?
Comment: An interesting reference using similar arguments seems to be "How Likely is it to Hit a Barrier? Thoretical and Emperical Estimates" by Lujing Su and Marc Oliver Rieger.
Comment: @philippe: Thank you for the reference. Their theoretical argument is indeed the same as mine. The empirical work is interesting.
Answer: There is a simple solution if there is no drift, as the probability $p(x,t)$ obeys a simple diffusion equation: $\mathrm{d}(p)/\mathrm{d}t = \frac{1}{2} \sigma^2 \frac{\mathrm{d}(\mathrm{d}(p))}{\mathrm{d}x^2}$, here $x$ is the price difference $\text{price}(t) - \text{price}(t=0)$.  Of course there is a simple solution to the diffusion equation (using scaling as a method to solve the PDE):
$$
p(x,t) = (4\pi \frac{\sigma^2}{2}  t)^{-\frac{1}{2}} \text{e}^{(-x^2/(4 \frac{\sigma^2}{2} t) )}
$$
 to find the probability of hiting a barrier $x$ on or before $T$ simply ( :} ) integrate,
$$
\text{prob of hitting ($t \le T$)} = \int\limits_{t=0}^{T} p(x,t)\mathrm{d}t
$$
Comment: This formula is definitely wrong. @mchangun, your instinct is right. See my solution below.
Comment: @glyphard: This answer is wrong. You should unaccept this answer and instead accept the correct answer by Hans below.
Comment: that's what I was looking for,
Comment: I am trying to use this in Sage to approximate the probability of touching on a vanilla option. However, I don't think I am getting the correct results. I am using the volatility of the underlying (for example .30 for 30%) for sigma (not sigma squared) and then using the price of strike minus the current price for x. Is that the correct interpretation?

For example, inputting the current price of 123.97, strike of 130, volatility of .30, and 30 days .. I am getting a .00107 which is much much less than the 50+% I get on online calculators that do the same thing.
Comment: I think something is wrong with the answer, I'm surprised so many people upvoted it.  The original answer (before the edit) doesn't have the correct number of brackets so I'm not sure how the Editor has rewritten it into Latex.  Would appreciate if someone could clarify / check this
Answer: Allow me to disagree with Jaydles' proposal ; his methodology is valid only if the events of touching the barrier on each were independent.
If you are working within the standard Black-Scholes framework, you're looking for the probability of a drifted Brownian motion hitting a fixed level before a fixed time ; this probability is derived in most stochastic calculus texts, see for example Karatzas-Shreve or Chesney-Jeanblanc-Yor.
Another way of seeing it : you're trying to price a knock-in digital option with 0 interest rate, or knock-in zero bond. You can find formulae for these in Peter Carr's work on barrier options.
Comment: OK. An approach without tedious computations is as follows : first find a nonzero real number $\gamma$ such that $X_t=S_t^{\gamma}$ is a martingale. This process $X$ now satisfies a "multiplicative reflection principle" : for any stopping time $T$, $X_{T+s}$ has the same law as $X_T^2/X_{T+s}$. Use this at $T_H$ (first hitting time of $H$) and mimic the classic reasoning for standard Brownian motion to find an expression of $P(T_H < t)$ as a function of $P(X_t > H)$, and finally, go back to $S$.
Comment: the stocastic calculus approach is called 'first hitting time' or 'stopping time'.  Shreve does not talk about actually calculating it.  He just says, 'use monte carlo'  There is a non-monte carlo method of calculating it, and that is what I am looking for.
Comment: Shreve (in "Stochastic calculus for finance") does talk about calculating the distribution of the stopping time for Brownian motion. See chapter 4 or 5.
Comment: With all that discussion and references, why don't you write out the derivation and the final expression? Is your diffusion process more general than the Brownian motion? It is not that complicated and "tedious". See my answer below for standard Brownian motion.
Answer: First of all, the delta is not the probability of the option in the black scholes model,
it is instead the closely related N(d2) (binary probability)
Secondly, the black scholes model gives risk neutral probabilities - for a binary event this is ok, but it gives no correct measure of, say, how far you would be through
Thirdly, the options you are interested in are traded in the market - they are called binary no touch or one touch options ... there are several mechanisms to price, depending on your model for volatility ... black scholes pricers for them are available online, eg here
http://www.volopta.com/Matlab.html
Answer: This surely isn't the most efficient way, but if you want something quick and dirty:
You could run a vanilla model that calcs delta for each expiration date between now and expiration, and grab the delta for each.  That would give you the likelihood that it's in the money at the close on any day.
From that, you can pretty easily calculate the odds that it's not in the money each day (just subtract the delta from one), multiply them all together, and subract the product from one to determine the likelihood that it closes above the strike between now and expiration.
This does require running the formula to calc delta many times, and it ignores the risk of an intra-day touch, but it doesn't require writing something to calc the exotic you're describing.
Comment: This answer hardly seems like it could be correct, as the closing prices on each day are not independent events. If an option is OTM on day 1, it is more likely than not to be OTM on day 2.
Answer: For in-the-money options the probability of ever getting in-the-money
(hitting the strike) before maturity naturally equals unity. The risk neutral probability for an out-of-the-money option ever getting in-the-money is equal to the barrier hit probability used for computing the value of a rebate, developed by Reiner/Rubinstein (1991):
$$p_c = (X/S)^{\mu+\lambda}N(-z) + (X/S)^{\mu-\lambda}N(-z + 2\lambda \sigma\sqrt{T})$$
$$p_p = (X/S)^{\mu+\lambda}N(z) + (X/S)^{\mu-\lambda}N(z - 2\lambda \sigma\sqrt{T})$$
with
$$z=\frac{ln(X/S)}{\sigma\sqrt{T}} + \lambda\sigma\sqrt{T}$$
$$\mu = \frac{b-\sigma^2/2}{\sigma^2}$$
$$\lambda=\sqrt{\mu^2+\frac{2r}{\sigma^2}}$$

Reiner, E., & Rubinstein, M., (1991), Breaking Down the Barriers,
Risk Magazine, 4(8).
Comment: The probabilities calculated from this formula is comparable to those produced by the other formula (reflected Brownian Motion). Both are approximately twice the probability of option being in the money at expiry, i.e. N(d2).  The results from formula by reflected Brownian Motion seem to be more exactly twice the value of N(d2), the above formula generated results are off by few percentage points.
Answer: Shreve's book chapter exotic option, the probability of maximum Brownian Motion does not exceed a threshold is as follows.

The probability of touch, i.e. the probability of an option moving from OTM to ITM any time before expiry, is based on the above. The derivation is based on change of measure under Girsanov's Theorem.
For an out-of-the-money call option with strike K, the probability of the option falling in-the-money any time before expiry is given by the above formula as 1-P ̂{M ̂(T)≤m} where

r is the risk free rate.
For an out-of-the-money put option with strike K, the probability of the opton falling in the money any time before expiry is
Answer: The required probability is equivalent to asking: what is the probability that the geometric brownian motion of the underlying touches the strike for the first time before the given time $T$?
A strategy for solving this related to Brownian motion - first passage time.
After transforming from geometric brownian motion to brownian motion via the log, the full distribution of the first passage time of a random walker (with a given drift and vol) to a boundary (which should be $log(K/S_0)$ where $K$ is the strike and $S_0$ is the initial stock price), is given by the Inverse Gaussian Distribution.
The explicit form for the distribution is given here http://goo.gl/lzGZ9Y.  Using the notation in that link, the parameters of the IG distribution would be $\mu=log(K/S_0)/d$ and $\lambda=(log(K/S_0))^2/\sigma^2$ where $d, \sigma$ are the drift and volatility of the geometric brownian motion.
So, you will want to compute the probability that this random variable, the first passage time of ordinary brownian motion with drift $d$ and volatility $\sigma$ to a fixed boundary at $log(K/S_0)$,  is $<= T$, by straightforward integration.
I believe the CDF is known in closed form (see e.g. http://goo.gl/DUK9fh)
Comment: I have accepted your "a bit of a challenge", as you put it, and edited my answer above to include the derivation for drift. Now I pose my "bit of challenge" to you to show the inverse Gaussian distribution is indeed the right density function for the first passage time. If it comes from time differentiating the final probability in my answer above, then the integration process is redundant. That was what I meant by "absurd", albeit not a good choice of word. I would be very intrigued to see your derivation, were it not derived via time differentiation.
Comment: This is wrong. The first passage time density function is NOT inverse Gaussian. The two look similar, but are not the same. The probability is shown in my answer above. The time derivative of that probability is the first passage time probability density, specifically, $p(\tau_x=t) = \frac{x}{\sqrt{2\pi t^3}}\exp\big(-\frac{x^2}{2t}\big).$
Comment: No I think the density function of the first passage time of brownian motion to fixed barrier is well known to be the Inverse Gaussian.  There are certainly more authoritative references in existence than Wikipedia (including the Springer link I linked to), but here is Wikipedia on the question: http://en.wikipedia.org/wiki/Inverse_Gaussian_distribution#Relationship_with_Brownian_motion
Comment: You are right. I realized that and was just about to edit my previous comment. But my main point still remains that the derivation of the first passage time density comes from the derivative of the integral which is what is sought after. The integral can be easily derived from the reflection principle. Now your approach is essentially to time differentiate the integral then time integrate it again. It is a bit absurd. Rather than taking all that time listing all the references, why don't you just derive the "closed form" explicitly yourself? It is not that hard.
Comment: Your comment is puzzling (if not actually absurd itself).  The point of this site is to provide correct answers.  I happened to know the answer to this question and tried to supply the poster with the answer.  My "approach" as you put it is to integrate a function, nothing more.  I agree the derivation is probably not too difficult, though it seems it was a bit  of a challenge for you.
Answer: The answer requires reflected Brownin motion
$w=(\ln (p/b)+rt+ \frac{\sigma^2}{2} t)/(\sqrt{t}\sigma) $
$z=(\ln (p/b)-rt- \frac{\sigma^2}{2} t)/(\sqrt{t}\sigma) $
$g=2(\frac{\sigma^2}{2}+r)/\sigma^2$
probability of hitting=  $N(w)+(b/p)^gN(z)$
for $b>p$
$N$ cumulative normal distribution
Answer: I understand that a useful approximation for prob of touch is 2 * delta, though I don't recall which authority that is from.
Answer: An asymptotic answer is
$$
p(t > \tau) \sim \mathrm{e}^{(-t/\tau)} \qquad \text{where $\tau = x^2/(\frac{\sigma^2}{2} \pi^2)$};
$$
However, as in much of statistics, asymptotic answers = "In the long-run" are not usually helpful to traders, or even investors.  Example: say initial price $x_0=\$20$, and you wish the probability of reaching say, $x= \$25$ before $x = \$15$ with an annual $\sigma$ of say $0.2$.  Convert $X$ to fractions, $X=(\$25-\$15)/\$15$, and calculate $\tau = 1.126$ years.  That is without some drift and for reasonable values of the volatility, you are going to have to wait a long time.
Comment: This is wrong. By asymptotics, do you mean, when $t$ becomes very large, or the strike becomes large? It is really vague. I think you want the former. If that is the case, the probability of reaching the strike or any price becomes certainty, or approaches $1$.

Probability of touching


What teaching techniques can be used, in teaching students from a medical background, to improve their programming?

Question: Students from premedical background feel difficulty in programming. They have no basic concepts of programming, so they are unable to do good programming. I have searched but didn't get any solution which help me to improve the programming skills of medical background student.
Comment: Why are premed students taking programming in the first place?  What is the *goal* of the course?
Comment: Is this a self-learning situation, or are you faced with teaching a group of such students? Also, what is your own background if you are the teacher of such a group?
Comment: @BenI., maybe it is a research oriented program for the medical sector. I'd like more information, of course.
Comment: The good news is that it only takes about 10,000 hours to become proficient at anything. Start now and you can get there in a few years of all-out effort. Otherwise, get used to being a dabbler. Is there value in that? Yes. I used to be a Teaching Assistant in a "101" college course in programming for non-majors. Many students came away with helpful experience, some did not. I didn't try to figure out which would be which.
Answer: To get the premedical students involved you can tell them that by the end of the course they will be able to dissect a program. It may not be as gross as a frog, but it will be more interesting. Unlike the frog, when done dissecting the program they can bring it back to life.
The next thing requires that you mean what you say, and follow through with actions that match. Tell the class that their marks in the course will be based on their performance in the course and their apprehension of the course material, not upon their major or program of study.
Final thing is to forget which students are pre-med, chemistry majors, fine arts students, or comp-sci majors, and teach the class as if all the students are willing and able to learn.
The one thing that did catch my eye in the question was that the students in question have no basic concepts of programming. That causes me to wonder if some students are taking a course which should have a prerequisite course and does not, or if the course has been designed, unintentionally perhaps, based on the premise that incoming students have those basic concepts even though it is listed as an entry course.
Perhaps it has been the history of the course that students arrived with prior experience even though it was an entry course, and the faculty has grown accustomed to that and adjusted the course accordingly.
Comment: I like the statement "forget which students are pre-med..." Etc. I used to tell my students that programmers are not paid to have opinions. Teachers are not either.


Why dont' nodes change the block version number when the nonce overflows?

Question: After computing 4 billion nonces, the miner is supposed to update the merkle root.
Why don't they choose a new nonce and assign it to the block version number and begin again?
It would save time and improve an ASIC.
Answer: Block versions are modified as part of other use cases, such as BIP 9, which use specific bits in the block version to signal for specific proposed updates to the protocol. Incrementing the block version and treating it as a nonce would prevent this kind of use.
Moreover, using a version field as a source of randomness (not really, but similar enough when talking about nonces) is generally a bad idea - version fields serve an important role in helping other nodes on the network determine how to decode and process a block, or other entity within the blockchain. Turning this into an effectively random number for the sake of saving a handful of cycles would just be a plain bad design choice.
Recomputing the merkle tree by just modifying a single tx within is a relatively fast operation regardless, since you only have to recompute the nodes affected by that tx.
Comment: Moreover, incrementing the extraNonce and recomputing the Merkle root can be done by the miner controller while the ASIC itself is hashing, and queued up so that the ASIC can switch to the new header immediately when the nonce overflows.  So this really doesn't slow down mining at all.
Answer: Miners do do this, but not so simply. It is actually a recent controversial issue called ASICBoost. The version number is assigned different values as part of this algorithm.
It's a bit more complex than just using the version number as an extended nonce, though. Remember that SHA256 is actually multiple mathematical operations rolled into one name. I believe the way it works is due to the SHA256 algorithm's first few operations, which involve leftshifting bits from the rightmost side side of the blockheader. If you can keep the right side of the blockheader (the last 4 bytes of the merkle root, the nonce, and the timestamp) mostly constant, then it allows you to skip these first few computations of the SHA256 function (because you're inputting the same thing every time from these bits). To change the final hash value though, you have to be able to change the leftside bits, which includes the version number. So in that sense the version number becomes the thing you use to change block hashes almost entirely (with the left side of the merkle root working in the traditional way).
This apparently saves mining power by about 20%.


How to find a large factorial in scientific notation?

Question: For example, given $8952!$, how do I write this in scientific notation?
Comment: You can use [Stirling's approximation](http://en.wikipedia.org/wiki/Stirling%27s_approximation).
Answer: Use Stirling's approximation to as many terms as you need:
$$n!\approx\sqrt{2\pi n}\left(\frac{n}e\right)^n\left(1+\frac1{12n}+\frac1{288n^2}-\frac{139}{51840n^3}-\frac{571}{2488321n^4}+\ldots\right)\;.$$
The factor $\left(\frac{n}e\right)^n$ is already very large, so it's easier to work with the approximation for $\ln n!$:
$$\ln n!\approx n\ln n-n+\frac12\ln(2\pi n)+\frac1{12n}-\frac1{360n^3}+\frac1{1260n^5}-\frac1{1680n^7}+\ldots\,.$$
I get $\ln 8952!\approx 72,513.37666589$; dividing by $\ln 10$, I get $\log_{10} 8952!\approx 31,492.15935017$, so $8952!\approx 10^{0.15935017}\times 10^{31492}\approx 1.443278591\times 10^{31492}$.
Answer: Without using Stirling's formula, it is easy enough to use
$$
\ln n! = \sum_{i=1}^{n} \ln i$$
and, as long as $n$ isn't too large (depending on how soon you want your answer), one can evaluate this sum directly with Mathematica, Maple, GP, etc.
With $n=8952$, GP tells me ( with the command "sum(i=1,8952,log(i))")
$$
\ln 8952! = 72513.37666589335322455704104
$$
so 8952! $\approx 1.44327859093238883310 \times 10^{31492}$.
In fact, with GP, one can calculate 8952! exactly, and then simply apply a logarithm to put it into scientific notation.  The results agree to the level of precision I gave above.


Freya crashes when exiting full-screen from youtube

Question: As I exit out of full-screen from youtube, the picture on the computer is frozen. I can still hear the audio and the cursor can move but I cannot interact with the OS and the screen seems to be frozen. This has happened several times, it does not happen every time but enough to frustrate me.
Comment: me too its crash every time i want to watch youtube and other things now i use opera but please fix it ps.... iam so exited about elemantary os 0.4 loki :D
Answer: I think both Chrome and Firefox use PPAPI, the pepper flash plugin so could be a compatibility issue with that. I would try looking in ~/.xsession-errors or ~/.xsession-errors.old if you have had to reboot.
Also if you have an Intel display adapter then try enabling "sna" as the Acceleration Method, it fixes a lot of video issues with some Intel chipsets in Ubuntu based distro's. Here's a link on how to do it.
http://www.apolitech.com/2016/01/how-to-solve-video-tearing-on-intel.html


Is there a name for the standard 7-die set?

Question: I'm curious if there is a formal name for the standard 7-die set (d4, d6, d8, d10, d10*10, d12, d20), and is there any backstory or history associated with it?
Answer: There is no name for the full set other than "a set of polyhedral dice."
If I need to distinguish it from  another set of polyhedral dice:
I would say a Set of polyhedral dice suitable for playing DnD,
as compared to a Set of dice for playing L5R (10d10)
or a Set of dice suitable for playing Dilettante (10 d8s and 10 d4s)
History
The d4, d6, d8, d12, and d20 are the Platonic Solids. They are the only polyhedrons that have all sides the same shape and area, and have the same number of faces meeting at each corner. Platonic solids are ideal dice.
The d10 and the d% are not Platonic Solids. While the most common diamond d10 shape (pentagonal trapezohedron) does have faces the same size and shape, it does not have same number of faces meeting at each corner. (The top and bottom points have 5 faces meeting; the other corners have 3 faces meeting.)
d10s, while not being Platonic Solids, are super useful because of modern humanity's decimal thought process. (Base 10 number system, 10 fingers-plus-thumbs.)
The two d10s for a d% is great because people are used to thinking of percentage probabilities, so can judge things well.
To get to the d10 diamond shape we know today actually took quite a lot of development.
I have an old d10 that looks more like a d12 but with some faces rounded off.
Original D&D had no 10 sided die, and instead had a d20 number 0–9 twice.
The modern pentagonal trapezohedron (diamond like profile) shape was developed in 1980 according to this history.
Its benefit over the double numbered icosahedron (d20 shape) is that is is easy to tell apart from the normal 20.
Calling them a full set of dice can be misleading, you can get a actual d100 (looks like a golf ball), as well as d16s and d32s that look like d10s .
And a huge variety of other weird ones.
Wizards of the Coast published an article on the history of the dice.
They offer no name for the set that was included in early DnD (and later), other than referring to them as "a full set of  polyhedral dice."
Comment: I was doing a search for D&D dice sets recently and found that [many distributors](http://www.dicegamedepot.com/polyhedral-sets/) use the term [Polyhedral set](http://www.artisandice.com/faq/), so this seems to be the emerging convention.
Answer: History
The reason for the set mix as it exists is that, originally, the dice available were a set of platonic solids, sold by an educational company and repurposed by TSR. Namely, a tetrahedron (d4), cube (square hexahedron, d6), equilateral octohedron (d8), dodecahedron (d12), icosahedron (d20). This was a "platonic solids" set.
D20's were routinely read as d10's in wargaming, and used for generating percentiles, which made use of the d20 as a d10 or pair as a d100 a standard practice, going back as early as 1972.
A 1938 dodecahedron with 2 rounded faces opposite each other was available in 1938 for stock simulations. ➀ It wasn't used by TSR, but shows the probable origins of the pentagonal dipyramid we now think of as the d10.
Names
As to names - the earliest modern set (with trapezohedron d10) I can readily find documented by name is the "Dragon Dice" set from 1981 (as evidenced on the packaging copyright notice), as photographed at Dice Collector. ➁
I can, however, cite TSR "catalogue" from a ©1979 TSR product - Swords & Spells lists the older set as "Multi-Sided Dice Set" in the catalogue extract on the back flyleaf. ➂ It reads:

Multi-Sided Dice Sets — Each set contains one 20-, 12-, 8-, 6-, and 4-sided die

The same title and text was used in the 1975 product list in Strategic Review Vol 1. Issue 3 (1975). ➃
So:
Multi-Sided Dice Set - the original d20 d12 d8 d6 d4 platonic set.
Dragon Dice - the "mud dice" set with d10's.

➀ Dice Collector - Mason & Co Stock Exchange Dice - www.dicecollector.com/MINT39_MASON_&_CO_STOCK_EXCHANGE_DICE.jpg
➁ Dice Collector - TSR - www.dicecollector.com/THE_DICE_THEME_TSR.html
➂ Gygax, [E.] Gary,  Swords & Spells, 6th printing, Tactical Studies Rules,  1979. Original copyright 1976.
➃ Tactical Studies Rules, Strategic Review, Vol. 1, No. 3, Autumn 1975, Ed. [E.] Gary Gygax. TSR advert on page 8. From the Dragon Archive CD.
Answer: The manufacturers (Chessex, Gamescience, etc.) just refer to them as 7 die sets.
Answer: A term I have read, heard, and used in conversation (which to my mind indicates a fairly broad understanding in the community) is just, "seven-set."
As in, "Joe got a cool new seven-set with steampunk gears."
Comment: Using a word in conversation only indicates that the people in your local region are familiar with it. I for one have never heard that phrasing, and would probably need to ask for clarification, rather than using context.
Answer: The D4, D6, D8, D12  and D20 collectively are known as the Platonic Solids, however there is no commonly accepted name for a set of these dice plus the two percentile D10s other than a "Dice Set" or "Polyhedral Dice".  See this Wikipedia entry for more information.
Answer: The common name I always knew them by is "Dragon Dice" but I think that may have been a reference to an old TSR game rather than the dice themselves.
Comment: Aramis' answer sheds some light on this confusion: it was an early TSR brand name for the set at one point but it was later reused for the collectible dice game.
Comment: Yes, I remember Dragon Dice being a specific brand/style also, never generic.
Comment: [Dragon Dice](http://en.wikipedia.org/wiki/Dragon_Dice) is a different product.
Answer: For what it is worth - the Blue covered "Basic D&D" Box in 1978 (mine was a fourth printing containing B1 - In Search of the Unknown) contained the following dice:
1d4 - Yellow
1d6 - Orange
1d8 - Green
1d12 - Blue
1d20 - White
1d20 - Pinkish Red
The d20s were both numbered with 2 sets of 1-0 numbers and you had to color one set into to make them work as D20's.
But it also allowed you to use the two dice to make percentile rolls.
Sets that do not contain two d20's are probably either incomplete or may have been produced in 1979 during the beginning or ending of the dice shortage that led to the use of paper chits and provision of an ordering coupon.
None of the sets currently (December 19, 2018) available for sale on ebay contain both.
They are commonly called Mud Dice due to the soft plastic used in their construction.
Comment: Hello & Welcome! RPG Stack Exchange is not a forum, it is a Q&A and your post does not actually answer the question. See "[How do I write a good answer?](https://rpg.stackexchange.com/help/how-to-answer)"
Comment: The question is asking about the history behind them though, so I'm not sure how to weigh that up.
Comment: @doppelgreener: It seems to ask about the history of the name of the 7-die set, not about the history of dice in gaming themselves (which would be a little too broad a question). The last line of the answer mentions a term, but the rest of the answer is mostly a tangent.


Is an IBEP/EBF course also possible with a recurve bow?

Question: I wanted to take a bow-hunter course (DBJV) following the guidelines provided by IBEP and EBF. However, all the regulations seem to be for compound bows. Is it even possible to take the exam with a recurve bow? If yes, where are the regulations for such written down?
Answer: yes, it is possible, at least for the Alabama curriculum it is.  Alabama doesn't require the course, but other states do and you can take it online.  The course specifically talks about recurves and longbows.  Check you state laws concerning minimum poundage and equipment, and assuming the state your hunting in allows the weapon, give it a go.
You can see where it talks about 'traditional' archery stuff in the alabama study guide on this page:  https://www.bowhunter-ed.com/alabama/studyGuide/The-Longbow/301002_776


"courant juillet prochain" and "fin juillet dernier"

Question: I often see these phrases in Le Monde and other news articles. Is it fine to use them as part of the everyday, street language, too?
Answer: Disclaimer : In French, relative date references usage can be tricky. The mean depends on both context and author and current date.
"Courant juillet prochain" is quite heavy. I don't use it and I never hear it in everyday french, only in more formal context (like news and written support). In everyday, you should prefer "courant juillet" or "juillet prochain" ( usage can be both tricky, see below for more explanations)
"Courant juillet" is common used. It refer to the immediate previous or next July. It can be use as fallback value if the mean of "juillet prochain" is equivocal. It can be equivocal in very few case ... but is is not the most used. It is less used in June and July.
"juillet prochain" is more common used. In the second part of the year (from July to December) it mean July in immediate next year. In the first part of the year (from January to June) ... try to avoid to use it alone. For half of people it mean July from current year, for others mean July from immediate next year... and there are exactly the same trouble with weekdays.
In the first part of the year I almost never use it. Only to target the immediately next July and if July of the next year is a nonsense. (Exemple: "J'ai un contrat d'intérim qui commence en juillet prochain." and "On fini les travaux dans trois mois, donc juillet prochain sera la dernière ligne droite.").
If there no nonsense I paraphrase it. To target July from current year I don't use it but "courant juillet", "en juillet" or "au mois de juillet". To target July from the next year, I explicit it and say "en juillet de l'an(née) prochain(e)" or "au mois de juillet de l'an(née) prochain(e)"
In the second part of the year I can use it alone or in explicit version.
"juillet dernier" is also used. It's little less tricky (more uniform) but differ for months and weekdays:

from January to July it is July from immediate previous year (obvious no ?)
from August to December it seem to be July from immediate previous year for huge majority of people
from August to December it seem to be July from current year for little minority of people
for weekdays this seem to always be the day from the previous week. And that for almost all people and all target weekdays, independent from current day.

You can take a break after that ;)
Answer: Courant juillet prochain seems a little bit formal to be commonly used in everyday language. That would rather be:

en juillet
ce mois de juillet

or

en juillet de cette année (or de l'année prochaine).

Similarly, fin juillet dernier would compete with

à/vers la fin du mois de juillet de l'année dernière

and

à la fin du mois de juillet (dernier).


Can I be bulky and fast at the same time?

Question: Is it true that bulky people can't be fast like Bruce Lee or flexible like "Superfoot" Wallace or tall like the great Khalil? I want to be big, fast, and able to fight all at the same time.
Comment: Have you ever watched American football, or heavyweight Olympic lifting? It's absolutely possible to be simultaneousl big, strong, fast, and flexible.
Comment: Because it is science.
Answer: Sure, you can be big and fast.  That said, there's some important ideas to keep in mind about what your training is going to look like.  There's basically going to be 4 factors you are training (as far as conditioning) - power, speed, endurance, and, size.
To quote Wikipedia on Bodybuilding:

Weight training aims to build muscle by prompting two different types of hypertrophy: sarcoplasmic hypertrophy and myofibrillar hypertrophy. Sarcoplasmic hypertrophy leads to larger muscles and so is favored by bodybuilders more than myofibrillar hypertrophy which builds athletic strength. Sarcoplasmic hypertrophy is triggered by increasing repetitions, whereas myofibrillar hypertrophy is triggered by lifting heavier weight.[16] In either case, there is an increase in size and strength of the muscles (compared to if that same individual does not lift weights at all). However, the emphasis is different.

Right here you can see power and size are trained for differently.   Then there's the issue of endurance (which varies on how you expect to use your martial arts and in what conditions).
Finally, speed.   The usual adage of the slow bulky guy isn't a matter of too much muscle as much as result of bad training.
Here's where we go into neuromuscular science... your body has a natural reflex reaction when a part of your body is moved too fast - it tightens the muscles around the joint to serve as a braking action to stop the joint from getting injured.   The extreme result of this is a muscle pull or muscle tear - the body decides to let a muscle take damage rather than a joint because muscle heals easier.
When it comes to resistance training, the advice to stretch after a workout is so that you can reset your muscle spindles back to normal full ranges - otherwise they will set their "default" at a shorter range - and when you try to move fast, your own muscles serve as a braking factor to your speed.
So it's not that more muscle slows you down, it's that muscle training that ALSO sets the muscle spindles to a smaller range of motion, done over long periods of time, slows you down.  Stretching after resistance training isn't about getting more range of motion, it's about keeping what you have and making sure it's available when you move at speed.  Reset the muscle spindles and you can keep your fast movement.
Beyond that, then it's really about developing your flow and ability to read the movements of an opponent in martial arts.  There's plenty of folks who aren't fast, if you watch them, but when you're facing them they're a step ahead and sometimes you can't track their movements well - because they've figured out how to read you and not telegraph their own movements in return.
Answer: Have you ever watched American football, or heavyweight Olympic lifting? What about the heavyweight and light-heavyweight divisions of the UFC? It's absolutely possible to be simultaneously big, strong, fast, and flexible.
The key elements are getting big and strong, then incorporating a lot of power training into your strength and conditioning program, and maintaining that weight while working on mobility and explosiveness.
Comment: What about punching power or gymnastic training.
Comment: @cameron Punching power is developed with technique plus general power training such as the Olympic lifts like the power snatch, power clean, and push press. I'm not sure what you're asking gymnastic training. I mean, yeah, gymnastics is great, but it won't make you very big except in the shoulders, lats, and upper arms. (Which are great places to be big.)
Answer: One would need a picture to see exactly what you mean by bulky.
The more volume you have the more mass you have and thus the slower you are.
The more volume you have the less space (and tendon) you have for flexibility.
Look at the bodies of those who are the strongest, the fastest or the most flexible.
Look at animals in nature it's even more speaking.
You simply can't encompass all extremes, it's a physical limitation.
You can however reach an optimum where you develop the maximum strength in the minimum volume (lean muscles) that allows you to be fast and flexible enough.
Martial arts isn't about force, as in brute explosive force, as you don't try to lift your opponent over your head or snap his bones in two. Excluding the actual fighting techniques, a fighter needs to have stamina (lean muscles) to keep up a long fight, speed to attack before being seen and flexibility to execute extreme movements without injuries.
Comment: "The more volume you have the more mass you have and thus the slower you are." Preposterous. Bulky NFL linemen can out-sprint most people who aren't accustomed to sprinting. A 1-ton bull can leap and rotate in the air. All it requires is sufficient muscle to move that mass at the desired velocity. Strong = fast (for that specific muscle group).
Comment: Ridiculous. Any sprinter will out sprint any bulky person. A tiger (not a cat) will jump 3 times its length in height and climb trees. Strong = Slow. You don't understand what you're seeing.
Comment: "Any sprinter will out sprint any bulky person." - Come on now, you can't state absolutes like that and expect to be taken seriously. Bo Jackson ran the fastest 40-yard dash EVER RECORDED (4.12 seconds) and he was over 200lbs at the time. If you take Usain Bolt's record 100M run (9.63 seconds) and scale it down to a 40 yard dash, he'd clock in at about 3.97 seconds, only about 1/7th of a second ahead of Jackson, and most pro's don't even think a sub-4.0 40yd dash is even humanly possible anyway.
Comment: Based on pictures Bo Jackson is bulkier and based on your data Usain Bolt is faster, so you've proven my point. The strongest aren't the fastest and vice versa, it's a law of physics, nature proves it.
Answer: YES, so much yes!
I have seen big bulky people contend in races. I have also seen bulky people out-spar their skinnier opponents in a dojo. It is possible
The above answers your question but I would go on a bit, if I may.
To achieve this,

You would have to understand the difference between bulky and overweight. Someone who is overweight has excess fat which which pulls them down; and by excess fat I mean extra body mas with neither function nor utility. However, someone who is bulky is made of larger muscle mass—may not necessarily be built or toned. Assess yourself and get into the bulky zone.
Your training should have lots of running, with your full form in check: arms swinging, knees perpendicular and footsteps keeping a cadence. Pay attention to form more than anything else—once you break form, there's no need utility in continuing the training, take a break. And try to decrease your snap time.
Master your weight. The bulkiness is yours. Know it, accept it, love it, master it. Once it's no longer a burden on your thoughts, despite your size, you could be lighter than a feather.

p.s: A little informal physics... velocity is caused by acceleration which is caused by jerk which in turn is caused by snap <— this is what you want to decrease. I should add, "it ain't easy". You mentioned Bruce Lee who, in my books, was the master of minimal snap time. His acceleration posed a problem for video cameras of his time. Try to beat yours.
Answer: Yes you can. But in general you need to train your muscles in a balanced way so that you don't overdo one and thus de-emphasize the others.
There are different types of muscles in the body. There are muscles for strength, power and speed, the latter is generally known as fast twitch muscles.
Those that are bulky in a muscular way, such as a very large body builder, tend to be slower because they've over emphasized one type of muscle over another. But of course it all depends on how bulky you are talking about.
Van Damme is a pretty muscular guy and also quite fast. My second Master was a very big guy and was faster even than Bruce Lee while his arms and muscles were over twice the size of Bruce and he was over six feet tall and come in at 280-300lbs.
So you can do it but you have to do some research and become educated on different types of working out and exercises for different effects and maintain a balance otherwise one type of muscle fiber will suffer over the others.
Comment: Interesting as in this article it describes on how Bob wall and chuck Norris easily did pull ups when van dammed had trouble, it seems that people who do different things on physiques, size, everything biological has its advantages and disadvantages. Here is the article: Bill "Superfoot" Wallace on Chuck Norris, Dolph Lundgren, Bob Wall and Jean-Claude Van Damme


Tax implications of dispersing trust to my child's 529 plan vs directly to me

Question: I will be inheriting a portion of my father's trust. My child is in college now, and I contribute the full amount to the trust every year. Are there tax advantages to disperse proceeds from the trust directly to the 529 plan? Second question: Since my name is on the trust, can both of us (me and the trust) contribute $5000 each to the 529 plan?
Comment: Something to consider is the time frame of the 529. If the child is in college the time frame may be so short that the tax savings may not mean much. The state tax savings may already being maximized if the taxpayer and the 529 are from the same state.
Comment: You are inheriting money from your father's trust. Ok. You "contribute the full amount to the trust every year." What does this mean? Where does $5000 come in to play? Without more details, this question makes no sense.
Comment: $5k per person/trust? is the most that can be contributed per year. The 529 plan is in one state and the trust in another state. I am a beneficiary of the trust set up for my father's estate. He recently died.
Answer: You should probably talk to an estate attorney (a lawyer duly licensed in your State) and a licensed tax adviser (EA/CPA licensed in your State) about this, as this may become tricky. It depends greatly on how the trust is defined and who are the beneficiaries.
Answer: You definitely need an estate lawyer and maybe a CPA.   My estate lawyer was generally knowledgable about estate tax.
The gift tax exclusion is $14,000 per year.   Your 529 contributions are considered gifts.  There is also something called a generation skipping transfer tax, the details of which I'm not familiar with.
The best advice would be dependent on how your father's will and trusts were set-up, and the rules of your state.


setup PPPoE over ethernet card

Question: How to setup PPPoE connection over wired DSL connection (Ethernet)?
I'm using Ubuntu 12 dual-booting with windows. It runs OK. on windows
Comment: Similar question: http://askubuntu.com/questions/83869/setting-up-a-pppoe-connection-in-ubuntu
Answer: If you have a decent router, the PPPoE connection is (or should be) handled in the router and is stored in it, unaffected by power down resets. The connection to your computer becomes a VPN to the router (LAN). Very few routers (only very old ones) need the PPPoE to be reset for every computer or operating system. If they do, you have very little firewall protection between you and the web, in which case I'd recommend a new one, SMC, Netgear etc. ....
You can boot in windows and check the connection settings there, make a note of them including any passwords, then boot back into Ubuntu and make sure the connection is the same. Ubuntu nearly always finds the correct settings for a LAN entirely on its own, unlike some others!

setup PPPoE over ethernet card


What type of wire and load center for subpanel in detached pole garage?

Question: I am installing a 60 AMP subpanel in a detached pole garage 150 feet from the house. Garage subpanel will be supplied from an existing 100 AMP subpanel in the basement of the house (running from the 200 AMP main is not an option).
What size of wire and type of wire is required?  Can it be direct burial with just short runs of conduits as it exits/enters the structures?
Is a NEMA 1 load center suitable for mounting on the inside surface of the pole garage?
Comment: Do the other answers on this topic not answer your question? For example, https://diy.stackexchange.com/questions/41235/how-to-determine-what-type-and-gauge-of-wire-should-used-for-underground-wiring?rq=1
Comment: Garage is 24x36. Was thinking I would need 3-20A circuits and 1-15A lighting circuit.  Would it be OK by code to use a 100A subpanel in the garage, fed from 100A subpanel in the basement?  I would only need maybe 40 amps at a time, but having a larger subpanel would be more convenient than trying to squeeze 4 circuits into a 60A subpanel.  I could still use a 60A breaker in the basement panel, couldn't I?  Either way, looks like #2 Al feeder is needed (URD in conduit underground, then switching to SER when it enters the unfinished basement area)....
Comment: Are you planning for a minimum spec garage (1 SABC + 1 lighting circuit), or for the full 60A load, or something in between? Is underground the only option, or is an overhead run possible?  How many square feet is the garage?
Answer: Ditch the URD
Underground Residential Distribution cables are really uni-taskers: all they're good for is buried residential service from the utility.  Most of the commonly available ones lack a ground wire (hot/hot/neutral), and they're often made from AA-1350/EC aluminum, which is picky about proper termination.
Instead, especially since you're considering using conduit anyway, I'd use individual XHHW-2 AA-8000 alloy conductors in a generously sized schedule 80 PVC conduit -- 2" would not be at all out of place for this run.  A box can be used to make the transition to SER cable once you get into the basement, or you can simply keep going with the conduit run.  Make sure to leave enough access points (pull elbows, conduit bodies, boxes) to make the run practical, and use expansion fittings in aboveground PVC runs subject to temperature changes!
As to conductor sizing, 2AWG aluminum should be fine for your purposes -- voltage drop will still be acceptable even at the full 60A you propose for this feeder.  Given the amount of it you'll need (over 450') and that it's large enough for phase taping to be permissible for wire identification, it may be cheapest simply to buy a full 500' spool of the stuff instead of buying it by the foot.  You'll also want some 6AWG bare copper for the grounding electrode conductor at the garage, and 10AWG bare copper for the equipment grounding conductor in the feeder run.
Keep 'em separated!
Speaking of grounding, you'll need to be careful on this point.  Past practice with outdoor feeders treated them like services, bonded via the neutral, but this is no longer allowed -- instead, your feeder will be a full 4-wire feeder (hot/hot/neutral/ground) with neutrals and grounds separated onto their own bars and the loadcenter's bonding screw/strap removed.
Furthermore, you'll need to provide a grounding electrode at the garage and tie that to the grounding system: a concrete-encased (Ufer) electrode is ideal, or if your garage is steel-framed, you can tie into that.  If neither of those are practical, a pair of ground rods driven at least 6' apart will do the trick.
Go big, or go home!
There is no shame in getting more loadcenter than one strictly needs -- it  is often cheaper now to buy a somewhat larger loadcenter up front than to replace an undersized loadcenter later.  Given that, the fact you'll need a main breaker loadcenter to provide the structure with a local disconnecting means (it's OK if the subpanel main is oversize as all it needs to be is a disconnecting means), and that a NEMA 1 cabinet will suffice for going inside the garage (all the space needs is four walls with doors that close and a roof that won't leak), I'd recommend a Siemens P3030B1100CU for this application as a minimum specification -- it provides plenty of spaces for an outbuilding application (30 spaces for a 100A panel is quite a bit), and ships with all the terminal bars needed (including separate ground bars).  Of course, you are more than welcome to drop a few extra bucks on a larger panel (but you'll have to go up to 200A bussing to do so, most likely) -- a 42 space/200A loadcenter would not be at all out of place here.
TORQUE ALL CONNECTIONS TO SPEC
Last but not least, get an  inch-pound torque wrench and torque all breaker and panelboard lugs you are connecting to up to manufacturer specified torque when you're doing this -- it's a new Code requirement for 2017 (see 110.14(D)), and just a darn good idea from a reliability standpoint, unless you want to pull a Greg Biffle with your garage's electrical system, that is.
Comment: Thanks for your suggestion on the underground run.  I'll probably stick with SER in the basement.  There will be a section that will run aboveground below a deck before it enters the basement. Should the transition from individual conductors in conduit to SER be done inside the basement, or under the deck?
Comment: Does the 60 Amp breaker in the basement for the garage panel need to be a GFI breaker?
Comment: If I do run URD unground, how is it picky regarding termination?
Comment: @Chris -- re: the feeder breaker: it *can* be a GFCI if you want every garage outlet to be GFCI protected, or you can provide GFCI protection to the individual branch circuits instead.  As to the URD?  It's picky because it's made from AA-1350/EC aluminum, the same stuff that gave aluminum wiring its bad rap back in the 60s and 70s, as opposed to the aluminum alloy (AA-8000 series) conductors required for modern aluminum building wiring.
Comment: @Chris -- also, *why* are you wanting to run URD within conduit?  Can you not find XHHW-2 singles at the electrical supply houses (note: NOT big-box stores) in your area?
Comment: I can find XHHW-2 at the local electrical supply.  It is most economical to buy a 500-foot role of black wire rather than by the foot in white/black/red.  Can I buy a full spool of black wire and label each conductor at all exposed locations for hot-hot-neutral (black/red/white) using tape or paint around the circumference of the insulation?
Comment: @Chris -- since you're using 2AWG conductors for this, yes you can! (It is only very recently that conductors 4AWG and larger have become available in colors other than black, so the Code allows remarking of wire ends at-will for them)


Can I do Chow Mein without rice wine nor substituting it?

Question: I mistakenly bought "rice wine vinegar" instead of "rice wine". Now I am missing this ingredient from the recipe but I still want to do it. I could replace with red wine but I guess it's not a good substitute. I don't have any of the common substitutes for rice wine (gin, sherry, apple juice...).
Answer: I would say, yes, you can make chow mein without wine of any kind. I say that without hesitation because the first four recipes that come up on a Google search for chow mein (all highly rated) don't call for wine.


Beginner certification to enter into project management

Question: I am looking for project management entry level certification. I searched online and I found CAPM and PRINCE 2. I am bit confused which one should I go for.  Which one is worth doing??
Answer: Here are 2 articles that describe the differences so that you can to make sensible choices.

Should I take CAPM or PRINCE2?
PMP vs CAPM vs PRINCE2 - Which One's Right for you? and you can see that you have a third choice also of PMP.

I think a summary would be the quote:

The main difference between CAPM/PMP and PRINCE2 Foundation/Practitioner is project experience. Having said that, it's not compulsory to have project management experience under your belt for CAPM, as long as you can demonstrate 23 hours of formal project training instead. There are no pre-requisites for applying for the PRINCE2 exams (although it will be certainly easier to understand the concepts if you have spent at least some time working on projects).
Because PMI requires pre-requisites either in the form of training or work experience and PRINCE2 doesn't, I don't think they are seen as equivalent (or competing, for that matter).

And there is  the issue of cost - both are a similar price.
Also, CAPM certification expires after 5 years and you have to do it again, but PRINCE2 is forever.


How to find small short programming freelance job or project

Question: I would like to become a freelancing programmer and web developer. I am now studying computer science in university, so my programming skills and the number of language that I know will improve and increase over the times. Since I am still studying, I would like to find some small short programming or web development freelance job to do. But some freelancing website I found on the web requires bidding, or the jobs are long term.
I would like if someone can recommend some freelance website for small programming or web development projects.
And also, is there any tips for getting started in freelancing?
Thanks
Comment: see the multitude of similar questions elsewhere on the site, http://freelancing.stackexchange.com/questions/101/how-do-i-get-my-first-job-at-a-freelancing-site?rq=1, http://freelancing.stackexchange.com/questions/871/how-do-i-start-my-own-freelancing-company?rq=1, etc.
Comment: @user3244085 Freelancing SE would really benefit from a canonical question & answer for this due to the multiple questions on the topic. One that also aims to address a wide range of starting points, as I rarely see pro-bono, charitable or open source suggestions from answers, for complete beginners who still want to scope out their skills and abilities. Also many don't fully address the difficulty of getting a first freelancing project, they may touch upon it with "I've been in this situation and understand . . ." but tend not to provide solid, useful tips on overcoming the difficulty.
Comment: Fiverr, UpWork...
Answer: For that kind of thing I suppose you will still looking and looking and probably won't find anything at all, I use freelancer.com and there was a few months I was looking for small jobs that I can finish in less than 15 days but didn't work, my best advice is: Start a small project yourself while still looking, as is web I'm not that familiar with it, but I'm mainly a mobile dev and when I can't find a freelancer job I continue my project or start a new one if I'm free, Even if they don't get to the market it works as an experience & learning ways of improvements of my coding skills, and platform I'm developing in. This can help you to speed up any medium/large project that you may get because you already have a design :D.
Answer: There are numerous topics about this all over Internet.
Short-term options:

Ask friends and family if you can help them in some way by developing web app for their need
Ask fellow students that aren't doing so well to help them with their studies for a fee
Offer web development tuition services in local classifieds
Go through web development forums and search for a topic with no good answers and then offer to solve a problem for a fee

Long-term options:

Make profile on freelancing sites such as UpWork, Freelancer, Fiverr etc... and be active in applying for jobs and improving your profile (this can take months)
Make online portfolio with links to your previous work and recommendations of previous clients (letters with links to their LinkedIn profile or even better link to YouTube video in which your clients recommend you)
Write a professional blog (post about web development and similar) and promote it any way you can all the time
Comment on other developers's blogs
Comment on web development forums and portals (don't forget to include link to your blog, especially to service page)
Ask previous clients to recommend you
If you don't have any experience then ask to volunteer on a project that you think would be a good reference
Answer: I'm editing the answer because the comment below asked me to.  When it comes to programming as a freelance career you've come to the right place to get answers and resources on how to earn a living.  What I would like to do is point you in the direction where many people have succeeded in finding exactly what it is you're looking for.  Try:
freelancer.com
upwork.com
guru.com
djangojobs.com
linkedin.com
truelancer.com
When you bid for projects don't get discouraged if you don't at first succeed.  Rememeber, it takes time to build a reputation for good programming skills.
Let us know how you get along with your search.  Good luck.
Comment: While this link may answer the question, it is better to include the essential parts of the answer here and provide the link for reference.  Link-only answers can become invalid if the linked page changes. - [From Review](/review/low-quality-posts/5736)
Comment: In this case, the answer is the link.  I've seen many questions here on finding resources; most questions (not answers) were flagged or marked for deletion.  I find it surprising that my precise and useful answer was not enough before the edit.


What's the origin of "I'm down with it"?

Question: I understand it's an expression of agreement. What exactly does it mean and where did it originate from?
Comment: @FumbleFingers I'm certain this is the phrase, and I heard it being used by different communities. Sometimes people say simply "I'm down" to mean "Count me in".
Comment: It's certainly not a common idiom (I've never heard it). Perhaps you misheard ["I'm **done** with it"](http://www.thefreedictionary.com/done), meaning *"I've finished with it / I want nothing more to do with it"*.
Comment: That's a different context, which is really just a truncation of *"I've put myself down [on the list of people willing to participate]"*. But if you hear *"I'm down with it"* on a regular basis, you move in "non-standard" linguistic circles. Accordingly I've voted to close this question as "Too Localised".
Answer: "I'm down with it" or more often "I'm down with that" is confirmation, acceptance as in "that's fine by me", or commitment. It's originally African American jazz slang from around 1935.
It was popular during the 1990s especially in rap and hip hop, also in the 1970s, and in jazz from the 1930s to at least the 1960s.
Definitions
Webster's New World American Idioms Handbook (2011) says:

I'm down with that: slang; means "I'm agreeable to that"

A poster on Wordreference.com (2006) said:

In AAVE [African American Vernacular English] "I'm down" or "I'm down with that" can mean "I am in", I will commit to that action or position, or I am on your side.

Our Souls to Keep: Black/White Relations in America (1999) by George Henderson equates "I agree" with black English "right on" and "I'm down with that".
Law Enforcement Vocabulary (1973) by Julian A. Martin:

I'm Down With You. Juvenile slang: I'll fight on your side.

This version was used in Buffy The Vampire Slayer in 1998, showing overlap between being friends with someone or generally agreeable with them, and and described as mainstream slang in the book Slayer Slang: A Buffy the Vampire Slayer Lexicon (2004) by Michael Adams (first published online in 1999):

If Faith's Goth-chick slang veers towards the obscure, other characters favor the teen mainstream: ... "So, you're not down with Angel," she acknowledges of Spike, Angel's rival among Sunnydale vampires; ...

The American Heritage Dictionary of Idioms (1997) shows a slightly different use:

4. be or get down with. Be close friends with, as in I'm down with that crowd. [Slang; late 1900s]

From the introduction to A Jazz Lexicon (1964) by Robert S. Gold:

A few terms, perhaps because of their simplicity and
  widespread applicability, have survived from the early jazz
  life... The jazz slang speaker's
  aloofness is tacitly justified by his feeling that only those
  who are down with the action (aware of what is going on)
  should have access to the speech of those who have paid
  their dues (suffered an apprenticeship in life generally and
  in the jazz life in particular).

And its own entry (read online):

down with, [poss. from gambling slang to be down
  (i.e., to have one's bet placed) and poss. from general
  colloquial down to his toes (or socks); current esp.
  among Negro jazzmen since c. 1935] See 1957 and
  second 1959 quots. — 1944 Dan Burley's Original Handbook of Harlem Jive, p. 15. "I'm down with the action."
  — p. 41. Othello, the spade stud, pops in port, "down
  with it, cause he can't quit it." — p. 47. Iago is down with
  the action. — 1946 Really the Blues, p. 369. down with it:
  top-notch, superlative. — 1955 Down Beat, 5 Oct., p. 51.
  I don't know who the singer is, 'cause I'm not down with
  all the singers now. — 1957 The Book of Negro Folklore,
  p. 483. down with it: to get acquainted with, to understand. — 1959 Diggeth Thou?, p. 23. Let's see what's
  down with the deal. — 1959 Esquire, Nov., p. 70I. down
  with something, to be: to know something thoroughly.
  — 1960 Beat Jokes Bop Humor & Cool Cartoons, p. 57.
  The Ham wasn't down with the action.

Early examples
From an interview with rapper Guru from Gang Starr in Blues & Soul magazine (1990):

"You see I'm down with anything that's about uplifting and giving self-esteem to the black man. You see the black man in cities in America, over here and around the world . . . they need self-esteem because a lot of them see it as society's so hard on them they can't get it together. What these religions are based on is building pride, awareness and knowledge of culture and self, and that is important. So, anything like that I'm down with. That's why I say 'I'm down with the Nation [of Islam]"

Ebony magazine (January 1976):

Buffalo's Randy Smith, a former NSSFNS recipient, said he was determined to make the tournament, with or without his club's blessings. "That's how most of the players felt," said Smith. "The tournament is designed to help black youngsters, and anytime there is something I can do to help the cause, hey, I'm down with it."

New Black voices: an anthology of contemporary Afro-American literature (1972):

"Don't bet on that. Chumps like to deal with a winner, if you know what I mean. I'ma stone hustler. I'm down with it, dig? And he threatened me, even if it was with ...

From Mezz Mezzrow's autobiography Really the Blues (1946) , in a reference to jazz slang of the 1930s:

first cat: Hey there Poppa Mezz, is you anywhere?
  me: Man I'm down with it, stickin' like a honky.

A translation of terms appears in the glossary:

Down with it: top-notch, superlative
Comment: @Memming: You're welcome! I also found the term's roots in 1930s jazz slang, see edit.
Comment: The gambling origin is interesting to hear; I've always just taken it to mean that rather than being above or apart from someone, you're *down with* them, where they are.
Comment: I wish there was an interesting explanation for figure "down" -'with it'. For instance on a war front one soldier to another assure I am going down with you - as to say I commit to fight till death with you. There must be some story/literal-meaning  behind it which seems to be lost.
Answer: To supplement Hugo's excellent answer, I offer a couple of fairly early in-the-wild examples of "I'm down with it" as used by black American scenesters of the 1940s and 1950s.
First, from "'Harlem Jive Solid'; So Dan Burley's 'Loaded'," in the Indianapolis [Indiana] Recorder (December 2, 1944), a historically black newspaper:

Dan Burley, managing editor of a Harlem weekly and author of "Harlem Jive," was one of the most sought after men in town this week following publication of his widely publicized handbook.
To the amazement of "serious thinkers and jive artists," alike, Burley's book which he is publishing himself sold more than 3,000 copies in five days.
Burley, one of the most popular newspapermen in the city, took it all in stride and promised something better next time. "Meanwhile," he said, "I'm down with it, ole man, found with it, bound with it, around with it and gowned with it. In other words, I'm a hip kitty from New York City."

The sense of "down with it" here seems to be "hip to it."
And from Bob Womack, "Musical Upbeat," again in the Indianapolis Recorder (November 30, 1957):

Hi friends, the jive is wild as an untrained colt, and I'm down with it and can't quit it, so I'll unload the whole deal on you cool cats and the slick chicks. I'll take off on the local news first.

Womack's meaning seems identical to Burley's 13 years earlier.
J.E. Lighter, Random House Historical Dictionary of American Slang (1994) lists two quotations from Burley's 1944 Handbook of Jive as the earliest instances of "down with" in two distinct senses:

6. Black E[nglish] a. ready and eager for action; (also) formidable in a fight; tough. [First cited occurrence:] 1944 Burley Hndbk Jive 137: Down with It...to be ready for action. ...
b. knowledgeable or conversant, esp. thoroughly.—constr[ued] with with; (hence) smart; canny; sophisticated; HIP. ...[First cited occurrence:] 1944 Burley Hndbk Jive 15: I'm with it....I'm down with the action to my own satisfaction. Do you dig? Ibid. 47: That square, Iago, is down with the action. Ibid. 137: Down with it—To understand, know.

In short, if you have to ask what "I'm down with it" means, you're not down with it.


Does the feature level affect multisampling?

Question: I'm using DirectX 11 with the feature level 9_3 even though my computer could run 11_0, but I want to support older hardware as well.
I'm using CheckMultisampleQualityLevels to check whether multi sampling with the given samplecount is supported or not. However it returns 1 for quality with 4samples. And with 8samples it returns 0 (so its not supported). With feature level 11_0 CheckMultisampleQualityLevels returns 1 for 8samples. I'm using a AMD/ATI Radeon HD5830. In the most DirectX9 games I can still use 8x antialiasing. So why is it not supported in DX11 with a lower feature level.
Another point is it seems like 4samples doesnt really affect the output:

With mutlisampling disabled the result is the same. I'm sure that I configurated ms correctly.. even in the Depthbuffer.
Whether I enable AntialiasedLineEnable in the RasterizerDesc or not the output is still the same.
I searched in MSDN but I couldn't find any more information about multisampling.
EDIT: The blacklines in the picture are outlines made in the pixelshader
Answer: A breakdown of capabilities by feature level is available here. You'll note there is no explicit mention of MSAA support. However, the documentation does point out that for the 9.3 feature level, no guarantee is made for MSAA support.


Origin of a Jewish quote about fools

Question: There is a quote about fools that I have heard, which is attributed to the Talmud.  It goes as follows, "Never tell a fool he is a fool.  All you'll have is an angry fool."
I know that there are a number of Talmudic statements about fools.  I've asked a number of people if they have ever heard of or read this quote.  No one that I have asked recalls this statement in the Talmud.  I wonder if it is a Yiddish saying, or if it has roots in some Jewish text, or if it isn't of Jewish origin at all.
Comment: Don't forget though that even from a fool we can learn.
Answer: A possible source is Proverbs (9:8)
אַל תּוֹכַח לֵץ פֶּן יִשְׂנָאֶךָּ הוֹכַח לְחָכָם וְיֶאֱהָבֶךָּ
"Criticize not the scoffer lest he hate you; criticize the wise and he will love you."
Another close one (26:4)
אַל תַּעַן כְּסִיל כְּאִוַּלְתּוֹ פֶּן תִּשְׁוֶה לּוֹ גַם אָתָּה
"Answer not the fool with his foolishness lest you too resemble him."
Comment: Barry,
Thank you for your response. They are close. I've seen these proverbs before in my initial search for an answer to my question.

At this point I'm wondering if there is a Yiddishist (someone who studies the Yiddush language) out there who may have read or heard a Yiddish witticism similar to my quote.

To All. Have a happy and Kosher Pesach!
Answer: A possible source of this saying is, perhaps, by establishing a connection between two quotes:
"A fool is not aware of his folly" (Gemara in Shabbos 13b), therefore if you tell him he is fool, he will be angry, because "Anger rests in the heart of fools" (koheles 7:9)

Origin of a Jewish quote about fools


What does Myers-Briggs Type Indicator tell about a person?

Question: Does Myers-Briggs Type Indicator tell something objective and predictive about the persons decision making tendencies?  In other words, can a Myers-Briggs score give you useful information about what decisions a person is likely to make in future scenarios, or about his/her abilities?
Comment: @Russell Steen: You mean it is impossible to decide by scientific method if MBTI tells something or not, or that you do not want this particular question to be discussed here from some other reasons?
Comment: Voted to close, it's really just an opinion topic.
Comment: I mean that it's impossible to decide conclusively what makes sense for employers at large regarding the use of this test.  If you asked if Myers-Briggs measures what it claims to measure (and explained what that was), then I would have no problem with the question.  As it stands, that's not what was asked however.
Comment: By the way, this is not a bad question. You just need to elaborate more.
Comment: I have tried to improve it. I am afraid this is more or less the best I can do, therefore if you still do not consider it a good question, and cannot suggest some particular way ho to improve it, I guess I will rather delete it.
Comment: @Suma -- I tried to help with an edit.  See if that is a reasonable re-phrasing for you.
Comment: Brian Dunning of Skeptoid has devoted [an episode](http://skeptoid.com/episodes/4221) to MBTI, I recommend it.
Comment: The MB is based on Jungian archetypes - thus it is on shaky ground to begin with. It also tends to produce less reliable results over time. When it comes to personality research and tests as a general rule tests based on the "big 5" dimensions (Extraversion, Agreeableness, Conscientiousness, Neuroticism and Openness to experience. (OCEAN or CANOE)) are most reliable and other personality tests more flawed.
Answer: Actually, there is little evidence to support that the Myers-Briggs gives us much useful information, at all. The M-B was based on Jungian ideas, but the people who developed it were not even psychologists. They based the questions on a variety of things, only some of which can be linked to Jungian ideas on psychology. Jungian ideas have not necessarily been supported, consistently, when tested. The test, itself, has shown to be problematic in determining behavior simply because people's results are often inconsistent.
Basically, the MB test is a very widely used measuring tool which hasn't been proven to be either consistent or even very useful.
There's a decent breakdown of the history of the test and its flaws at skepdic, here.
Answer: I was able to find this study which seems to indicate that the MBTI was predictive for the Extravert/Intravert and Sensing/Intuition dimensions. People who ranked high on these tended to be in jobs which aligned with their scores.
I could not find any studies which focused on the abilities of the person versus the MBTI score, so I'm not sure a correlation would make sense as the test focuses on personality and not skill.


How to translate/understand "还不" in "还不是因为爱"

Question: Just realized that the 还不 part of speech in phrases such as "还不是因为爱", "还不都怪你" is quite tricky. How do you translate it into English?
Comment: It's **nothing but** love.
Comment: I think I'm even more confused after studying all the answers... o_O
Answer: It's translated as "actually", "really", "just"; it is used to show your emphasis. It's a very tricky expression because it has no negative meaning, while it has a negative look (不).You usually use this word in a sentence as a response to show your disagreement with the speaker.
You and your friends go hiking in a big mountain, and you get lost. Fortunately, you have a GPS device, and it helps you get out of the adversity. When you are safe, one of your friends says, "Thank goodness!". You would say,

这还不是因为我带了GPS导航仪。= It is really because I took the GPS navigator along.

Here, You imply that he should thank you!Not thank goodness!.
And another one would say

还不是我叫你带上的。=It's I who asks you to take it along.

Now,he wants everyone to know that they should thank him :)

还不是因为爱。= (It is) really because of love.

I also want to show you the negative form of this expression, you would say:

这还真不是因为爱。= This is really not because of love.
Comment: This is wrong comparison. 还真不 != 还不.
Comment: I kind of "heavily" edited your answer correcting wording and changing the formatting. I think I didn't change anything regarding the meaning, but just check it to be sure. :)
Comment: @Alenanno I noticed you changed my answer too. Mostly just re-formatting. Is there a standard way to present translations when English & Chinese sentences side by side? Or is it just personal preference?
Comment: @StarCub I don't think so, but I think translations on the side are better readable than translations under the original sentence. It's just a matter of "visual order". Of course people can rollback, though. :)
Comment: @StarCub I think you mean "not equal to" by "!=", so what's the problem? I said "还真不" was the negative form of "还不"
Answer: I think 还不=还不是,it might be translated into 'it's all'. Because in Chinese you could express the same meaning with "全都是。。。".
还不是因为爱 = 全都是因为爱 = It's all because of love
还不(是)都怪你 = 全都(是)怪你 = It's all your bad
Answer: I think StarCub has a good answer.
With an example of a person explaining why or why not he is inclined to help another person, I'd possibly translate it as
还不是因为爱 = If it wasn't for love...(I wouldn't help you)

Example meaning: I will help you, because I love you
还不都怪你 = If it wasn't all your fault...(I'd feel more inclined to help you)

Example meaning: I would help you, if only you weren't solely responsible
Answer: Although it's not quite, you can think 还不 as double negation. The character 还 contains a 不 too. :)
I would translate 还不 as "isn't it". For example:

还不是因为爱 = Isn't it because of love.
还不都怪你 = Isn't it because of you to blame.
Comment: Just note that this is simply a mnemonic device as the traditional character (還) does not contain the 不 element nor any other elements that connote negation. I suspect the 不 element in the simplified character is merely a phonetic component.
Comment: I like this structure a bit better than "It's all/really because of love" because one usually says this phrase with a sort of half-questioning tone, rather than a flat declarative tone.
Answer: 还不是 can be translated to English literally as isn't.
Actually, sometimes we can add a 吗 to the end of that sentence without changing its meaning like "还不是因为爱吗?".
So the answer is obvious,
还不是因为爱 means "isn't it because of love?" or "it is because of love, isn't it?"
In the same way, '还不都怪你?' can be translated as "It's your fault, isn't it?"


What determines the best glide speed?

Question: I found the best glide speed of cessna 152 is 60 kts. My question is why it is not more or less than 60 kts? What are the factors upon which the best gliding speed is determined?
Comment: do these posts answer your question? https://aviation.stackexchange.com/q/606/1467 https://aviation.stackexchange.com/q/3610/1467
Comment: The weight doesn't "control" the best glide speed, it dictates it. Best glide speed means the most distance traveled per distance dropped. The lower the weight, the lower the speed. See [this FAA document](https://www.faa.gov/news/safety_briefing/2016/media/SE_Topic_16-01.pdf) for some more information.
Comment: Because that gives the most distance per unit drop. A lower speed will have a steeper descent and a higher speed will also have a steeper descent. Remember when you are gliding, your only speed control is pitch, and pitch also affects your descent rate. Its also not that simple as you state, best glide is dependent on the weight of the aircraft, usually the POH states "best glide" at maximum weight.
Comment: I understand a higher speed will steeper may descent more than a lower speed. But how that controls the best gliding speed? Does it only depend on the weight? If my weight is less/more how that will control the best gliding speed?
Answer: Basically, the faster you go, the more lift and drag a wing will produce. These two values are not proportional, though. When speeding up, the amount of drag produced is higher than the extra amount of lift - which is why you need additional power to maintain level at higher speeds.
When you go slower, the amount of drag will reduce more than the amount of lift produced - at least for a while. That's why going slow is better in terms of gliding distance. The amount of "drag per lift" is very low. However, slowing down beyond a certain point, the wing will rapidly start producing less lift, because airflow separates from the wing. This is what's known as a stall. The best glide speed is the speed as which the drag is as low as possible while the wing is still producing a relatively large amount of lift.
This is illustrated on a speed polar, like this one:

The black line indicates the rate of sink for a given airspeed. The optimum glide speed is the speed corresponding to the point where the red line touches the black line (Vbg).
The red line is a straight line going from (0,0) and touching the speed polar at exactly one point.
A change in aircraft mass will shift the curve along the vertical axis, which is why a heavier aircraft has a higher best glide speed than a lighter one. The intersecting point between the black and red line would shift to the right as the black line is shifted down, and vice versa.
Comment: At Vmd you are indeed sinking slower, but you are also moving forward slower. Your air time will be higher, but you will cover a shorter distance because your forward speed is slower. Vmd/Minimum sink is the speed that will keep you in the air for the longest time. The Vbg/best glide is the speed that will let you cover the greatest distance.
Comment: Now I have one question,  according to graph at Vmd the sink rate is less and by this I can remain up in the air for more time. And at Vbg sink rate is greater. Then why my best glide speed is not at the speed of Vmd? Why it is a higher speed at which sink rate is more?
Comment: This is kind of a fine point, but in general, slowing down does not actually cause a reduction in Lift.  See my recent answer for a different view.
Comment: @quiet flyer that's very much a valid point - unless accelerating upwards or downwards the lift must equal the weight of the aircraft.  However, it does depend on which variables you change and which you don't - if the airspeed is reduced and the attitude is unchanged then you're right, but if the angle of incidence is maintained then the aircraft will accelerate downwards (initially at least).
Answer: The most important factors for the best glide speed are the aircraft's wing loading, the air density, the wing's aspect ratio, and the aerodynamic quality of the aircraft.
The aircraft must create lift equal to its own weight. The drag for doing so varies with airspeed, and to find the point where the glide ratio has its maximum, drag must be minimal. To find this speed, we describe drag mathematically as the sum of two components:

Parasitic drag, which goes up with the square of airspeed. We express this as the zero-lift drag, a drag component which is independent of lift: $D_0 = \frac{\rho}{2}\cdot v^2\cdot S\cdot c_{D0}$
Lift-dependent or induced drag which goes down with the inverse of the square of airspeed: $D_i = \frac{\rho}{2}\cdot v^2\cdot S\cdot \frac{c_L^2}{\pi\cdot AR\cdot\epsilon}$

Now it helps to find the lift coefficient to create the needed lift at a given speed:
$$c_L = \frac{m\cdot g}{\frac{\rho}{2}\cdot v^2\cdot S}$$
Which, when inserted into the formula for induced drag, produces
$$D_i = \frac{(m\cdot g)^2}{\frac{\rho}{2}\cdot v^2\cdot S\cdot \pi\cdot AR\cdot\epsilon}$$
Now it should be obvious that induced drag is indeed proportional to the inverse of flight speed squared. We can simplify this a little by inserting $AR = \frac{b^2}{S}$ and express the total drag as the sum of both components:
$$D = \frac{\rho}{2}\cdot v^2\cdot S\cdot c_{D0} + \frac{(m\cdot g)^2}{\frac{\rho}{2}\cdot v^2\cdot \pi\cdot b^2\cdot\epsilon}$$
Next, we differentiate with respect to speed $v$ and need to set the result to zero to arrive at an equation for the speed of lowest drag:
$$\frac{∂ D}{∂ v} = \rho\cdot v\cdot S\cdot c_{D0} - \frac{(2\cdot m\cdot g)^2}{\rho\cdot v^3\cdot \pi\cdot b^2\cdot\epsilon} = 0$$
$$\rho\cdot v^4\cdot S\cdot c_{D0} = \frac{(2\cdot m\cdot g)^2}{\rho\cdot \pi\cdot b^2\cdot\epsilon}$$
$$v = \sqrt[4]{\frac{(2\cdot m\cdot g)^2}{\rho^2\cdot\pi\cdot b^2\cdot\epsilon\cdot S\cdot c_{D0}}}$$
$$v = \sqrt{\frac{2\cdot m\cdot g}{\rho\cdot S\cdot\sqrt{\pi\cdot AR\cdot\epsilon\cdot c_{D0}}}}$$
There you have it: The best glide speed is proportional to the square root of both the wing loading $\frac{m\cdot g}{S}$ and the inverse of air density $\rho$, and the fourth root of the inverse of the aspect ratio $AR$, the Oswald factor $\epsilon$ and the zero-lift drag coefficient $c_{D0}$. The Oswald factor is a measure of the quality of lift production and is close to unity in most cases.
Thankfully, quiet flyer reminds me in the comments that I need to point out that I always talk about true air speed here. If you want to set your speed using the speed indicator, reduce the value by the applicable density correction.
Nomenclature:
$c_{D0} \:$  zero-lift drag coefficient
$c_L \:\:\:$ lift coefficient
$S \:\:\:\:\:$  reference area (wing area in most cases)
$v \:\:\:\:\:$  airspeed
$\rho \:\:\:\:\:$  air density
$\pi \:\:\:\:\:$  3.14159$\dots$
$AR \:\:$  aspect ratio of the wing
$\epsilon \:\:\:\:\:$  the wing's Oswald factor
$m \:\:\:\:$  the aircraft's mass
$g \:\:\:\:\:$  gravitational acceleration
$b \:\:\:\:\:$  wingspan
Comment: @MaxvonHippel: Yes. Minimum drag at constant lift means that L/D is at its maximum.
Comment: Is this the same as the L/D max speed (Vldmax)?
Comment: Re "There you have it: The best glide speed is proportional to the square root of both the wing loading m⋅gS and the inverse of air density ρ..."  -- since you have brought air density into it, it might be helpful to specify that you are speaking of TAS (if you are).
Comment: @quietflyer Yes, I am. Good point!
Answer: (it's simpler than it may looks)
If you are at a certain height, you have a certain amount of potential energy (or height energy). The only thing you can do is to convert it to kinetic energy (or speed, which then creates lift). The problem: drag takes up energy too. So all the energy you loose due to drag means a loss in kinetic energy (=speed) and therefore a loss in lift.
The question actually is: how to reduce drag to a minimum?
It's actually quite simple:
there are roughly two different kinds of drag:

induced drag, induced by the angle of attack of the airplane. The more your nose goes up (so the lower your airspeed is), the higher the induced drag. This is an exponential relation.

parasitic drag, comes from the air and is the "usual" drag you also feel with a car or bike. It depends exponential on the airspeed.

The total drag consists of the sum of both.
The minimum is the best gliding speed.
Comment: Wouldn't the best glide speed be a bit faster than the minimum drag speed (since, by definition, the airplane covers more distance per unit time at higher speeds?)
Comment: Sure. But your goal is not to fly the longest distance in the *shortest* time, which means speed is *irrelevant*, only the *efficiency* matters. If you loose, say, 500 feet, you better need 2 minutes for that with a speed of 50 knots instead of 1 minute with a speed of 70. We only look for the best height-loss versus distance covered ratio. We do not care about the time at all, it is completely irrelevant.
Comment: @reirab --no.  We can show that the best glide angle occurs at the highest ratio of L to D.  We can also show that this occurs exactly at the point of minimum D.  (By the way, L is *nearly* constant and *nearly* equal to Weight; more precisely, L = Weight * cosine glide angle.)
Comment: This is kind of a fine point, but in general, slowing down does *not* actually cause a reduction in Lift.
Comment: Also, if we were really trying to minimize the rate of energy loss, I think we'd end up at the airspeed for min sink rate, not max glide ratio. So, generally good answer but some room for improvement--
Comment: @quietflyer, I read your comments but I actually miss somehow what can be improved in the answer. What exactly is the point that you are trying to make? I think the answer states clearly that it is not about the speed but about the efficiency, right?
Answer: I've never heard of the term maximum gliding speed, there's no special limitation to how fast you can fly a c152 without an engine as opposed to with it working. I think what you are talking about is best glide speed, also known as Vbg, which is the speed that gives you the farthest horizontal distance travelled per unit of height lost. If I remember correctly 60kts is the best glide with flaps extended, 65kts was best glide with no flaps.
The best glide speed actually varies based on weight, as do most of the V-speeds. A heavier airplane would mean a faster Vbg and a lighter one a slower Vbg. On a c152 the difference is pretty small, maybe 2 kt either way, so giving a 1 speed answer makes sense as it's easy to remember. Best glide speed on a big airplane will vary much more and would need to be calculated based on weight estimate at that point in the flight.
Answer: In this answer, we'll confine ourselves to steady linear flight with the wings level.
We can show that the highest glide ratio (i.e. smallest or flattest glide angle) occurs at the highest ratio of L (Lift) to D (Drag).  In fact we can show that the glide ratio is exactly the same as the ratio of L to D.  We can also show that the highest ratio of L to D occurs exactly at the point of minimum D. (L is nearly constant and nearly equal to Weight; more precisely, L = Weight * cosine glide angle.)

I found the best glide speed of cessna 152 is 60 kts. My question is why it is not more or less than 60 kts? What are the factors upon which the best gliding speed is determined?

Because that is where D (Drag) is at a minimum.  Nothing else matters.
Keep in mind that Drag is proportional to the product of the drag coefficient-- which increases as we increase the angle-of-attack-- and the square of the airspeed.
Other answers give additional insight as to why the point of minimum Drag occurs where it does-- it is the point where Induced Drag and Parasite Drag are exactly equal.
By the way, the ratio of L/D is exactly equal to the ratio of Cl / Cd, where Cl and Cd are the coefficients of Lift and Drag.  Unlike Lift, Cl is not nearly constant across a wide range of angles-of-attack or airspeeds.  It is always much  greater at high angles-of-attack (low airspeeds), at least until we get very close to the stall angle-of-attack.  Cd is also always much greater at a high angle-of-attack (low airspeed) than at a low angle-of-attack (high airspeed). So we can also say that the  maximum glide ratio occurs at the maximum ratio of Cl to Cd.  Lest there be any confusion, we should also observe that this is the point of minimum Drag, but not the point of minimum drag coefficient.  If we were flying at the angle-of-attack for the maximum glide ratio, and we then moved the stick or yoke forward to reduce the angle-of-attack (and increase the airspeed), this would reduce the drag coefficient (as well as the lift coefficient), but this would also increase Drag, and would decrease L/D and Cl / Cd.
In comments you indicate that you want to know how best glide speed varies with weight.  A good approximation is that it scales up or down in proportion to the square root of any change in your wing loading.  In gliders where we don't have drag from a windmilling prop to complicate things-- or in any airplane where we've stopped the prop-- this should be exactly true, except for effects due to changes in Reynolds number.
For completeness, we should say something about where the minimum power-off sink rate occurs. That turns out to happen at the angle-of-attack that gives the maximum value of (Cl cubed) / (Cd squared).  This always occurs at a higher angle-of-attack (lower airspeed) than does the best glide ratio.

What determines the best glide speed?


SPD 2007 Custom Calendar NewForm.aspx broke DispForm.aspx

Question: Hello I edited NewForm.aspx in a Calendar List now every time someone clicks on an event in any calendar view for the list, it takes the user to NewForm.aspx instead of DispForm.aspx, I changed GUIDs in both pages, and everything is correct in Properties / Supporting Files via SPD, but I can't get it to work. When you switch views to All Items and click an event it takes you to DispForm.aspx correctly so I know it works, any suggestions?
Answer: What changes did you make to NewForm.aspx? Obviously it's best practice to never touch the OOTB NewForm, EditForm and DispForm files. It's far better for you to copy the contents into a new file, modify that file, then change the list properties to point to the appropriate file.
My suggestion would be to do that; ie: copy the source of your modified files to new files, then reset the definition on the original files--this will reset them to their OOTB configuration. Then edit the list properties to point to your modified ones. My assumption here is that once you do that it "may" tweak itself back to life.
Answer: I ended up just creating a new list and exporting the original data and pasting it in


How do you design a cricket sound?

Question: Does anyone have any tricks for designing a sound like a cricket or crickets? I live in Scotland and recording actual crickets obviously isn't an option!
Comment: There are really no crickets in Scotland? That's fascinating.
Comment: @graeme should i send you some?
Answer: Hi Graeme,
I like crickets and I'm designing a cricket machine on puredata.
I've made a good cricket so far but it still lacks some frequencies.
My puredata bible for sound design is here: http://obiwannabe.co.uk/tutorials/html/tutorials_main.html
First I made a recording with some real crickets so I studied the waveform and the harmonic spectrum. A chirp is made by 4 impulses (20ms each every 30ms). The dominant frequency is
4170Hz with some 8340, 12480, 16680Hz (a flat C note).  Now I'm working on the resonance.
I didn't try it but I'm sure you can do a great cricket with the Operator (Ableton Live instrument) and with many other vst synths. The advantage with pd is that you can simulate the strange tempo/nontempo of the nature.
I can give you the puredata patch if you like but I don't know how to attach files here.
Comment: How long have you been using PD?  Do you have previous experience with languages?
Comment: When I started with pd two years ago I already knew some max/msp stuff, not very much though. Now I'm using pd a lot and I love it.
Answer: If you're any good with your own voice try this: http://www.ehow.com/how_4702844_chirp-like-cricket.html
and if you're not try a synth! Base the sound on a  white noise hiss and fiddle around with other pre-sets (those that sound like a ringing phone) until you have something clear and resonant. There's plenty of free cricket sound effects on-line if you need inspiration/a reference point.
Failing that- go to your local reptile supply shop and buy a box of crickets!
Happy noise making!
Helen @LenSound
Answer: answering a question with a question: If you live in a country that does not have crickets are you aware of when/how/why their presence occurs?
Answer: I'm pleased to announce that I've just published a new tool called the Cricket Chirp Tool, as well as some videos on this topic of Cricket Chirp SFX. An extensive written tutorial is found here on my blog, which includes some background and analysis techniques.
To introduce a very basic technique:

Apply Ring modulation to a Sine Wave. Tune the main Osc to a high Octave like C7, which is 2khz.
If you can change the Ring Mod wave, change it to a Triangle, and tune it in a low octave so that it's between 35hz - 70hz. This creates a nice buzzing, with sidebands in a very narrow frequency range.
Then modulate the chirp syllables how you like, I prefer to use a pulse-wave LFO, but custom Envs also work, they just need to be very fast.

A number of other techniques are demonstrated in the following video:

And thank you Andy Farnell, I love your work!
Answer: If you like I have two cricket recordings from Australia that I could send your way. First is a shotgun mic on a single cricket chriping loudly and constantly with lttle variation. The other is a stereo recording which features a group of crickets chriping at regular intervals. Into the recording a second group of crickets joins in. Send me an email to kyle [at] cannedgeek.com if those are useful to you.
I really should have more. There have been some great varieties of crickets I have been hearing this summer in my area. I am happy to just send those to you fo free - although if you have something to trade from Scotland in return that would be even better. ^^
Answer: I know it's not a cricket, but to get a good synthesized cicada sound I'd try taking a recording of a baseball card being flipped by the spokes of a bike tire and pitch it up like 2 octaves to get that cool cicada sound effect. I'd also experiment with different types of material - like an old plastic credit card or plastic spoon.
Answer: Just noticed this on Music of Sound:
http://www.musicofsound.co.nz/blog/cicadas-meet-pitch-shift

How do you design a cricket sound?


Helm grep is too slow

Question: Whenever I use helm-grep, helm-ag, or helm-ack, some results show up faster than others. In some cases the search completes after several minutes. Is it because I have to create some sort of index? If yes, how do I do it?
Answer: try ivy-mode, here is a grep example written by ivy-mode's developer.
http://oremacs.com/2015/04/19/git-grep-ivy/
I turn to ivy-mode because helm is too slow.
Answer: I had many griefs with helm-git-grep and helm-ack but I did like the basic interface.  I've since switched to helm-grepint.
https://github.com/kopoli/helm-grepint

Helm grep is too slow