Source for # times chai?

Question: I often see donation requests with amounts in multiples of $18. I would like to know the source for giving charity of the numeric value of the Hebrew word chai (18) and its multiples.
Comment: Our Sources says: "Great is peace, for it outweighs everything." [Num. R. 6:7]  So donations should really be made in multiples of $376, the gematria of "shalom". :-)
Answer: When charity is given as a form of merit, as opposed to a general tithing obligation, it is seen as an intercessor before G-d. This is termed a sanegor.
Angels also play a part in this role, especially the angel, Michoel. To attest to this symbolically or perhaps to request that this angel intercede and serve as a sanegor on our behalf there is a custom to give charity with the numerical equivalent of Michoel - 101.
This follows the allegory told by Hillel to Bar Hei Hei of the wagon driver who charges his fare a specified fee for driving 10 parasangs, but doubles the fee for driving 11. Because 1 parasang beyond his habit goes completely beyond his nature, it has double the value of acting only according to ones habitual nature.
It is worth noting that this concept is also associated to 101 as found in regard to the difference in reviewing what one has learned in Torah 100 times versus 101 times like is found in Chagigah 9b. Hillel explains that the individual who goes beyond their natural habit (for example, their natural habit of giving, like the required tithe) is one who serves G-d.
So the idea of 101 is connected to the doubling of payment or blessing. This custom is still prevalent among Sefardic Jews.
Since giving 101 of a particular currency may not be feasible because of excessive cost to the individual, other numeric equivalents which were connected to angels were found.
18 stems from a kabbalistic understanding of a story in Chagigah 15b: Rebbi Mayer found a pomegranate (רמון) he ate the inside and cast away the husk.
The kabbalists understood this to be a veiled reference to the angel מטטרון שר הפנים [MaTat, the leader of the entire Angelic court as alluded to by the leading letters to his full title which spell Moshe, משה, who is the leader of the Jewish people]. Just as the Shechinah (G-d's revealed presence in the lowers worlds) spoke from the midst of Moshe's throat, so to the inner aspect of Metatron is equated with the Shechinah in his realm.
The idea alluded to with the story of Rabbi Mayer is that the letters of the word רמון are the outer letters of the name מטטרון. When those are removed you are left with ט-ט, the inner substance or פנימיות, which is what Rebbi Mayer "consumed". In other words, the inner essence of the Angel Metatron is the Shechinah. This is alluded to by the gematria value of ט-ט which is 18 or life.
Hence, the giving of charity in multiples of 18 (doubling 18 for example like with the Angel, Michoel). And this is derived from the the posuk from Bemidbar 14:28 which says:

אֱמֹ֣ר אֲלֵהֶ֗ם חַי־אָ֙נִי֙ נְאֻם־יְהֹוָ֔ה אִם־לֹ֕א כַּאֲשֶׁ֥ר דִּבַּרְתֶּ֖ם בְּאׇזְנָ֑י כֵּ֖ן אֶֽעֱשֶׂ֥ה לָכֶֽם׃

I am life, says G-d...
Comment: Do you have a source for this?
Comment: קטיגור = prosecuter. You meant סניגור
Comment: (a) This has nothing to do with Chai; it is specific to 18. Multiples would not count.
Comment: (b) Referenced gemara has nothing to do with *tzdaka*; throwing away the peel, even if it were to refer to *ט-ט*, says nothing about charity.
Answer: While not directly answering this question, there is an incident recorded in R. Hayyim Joseph David Azulai's diary that shows that the gematria of the sum of charity was taken to be significant. Once you have that premise, it is not a huge leap to specifically the value of chai, as I think most people would readily acknowledge "life" to be the the most fundamental blessing. Multiples of chai is surely just a way of amplifying the message of "life", (as opposed to an entirely separate rationale). Here is the text of the diary entry for November 21st, 1753:

'And the reply came back' from the eldest among them that they had reached agreement, 'and a spirit of goodwill supported them' for the sum of two hundred and seventy five Corinthian ducats [= escudos]. I answered that 'I went through the sum' mentioned, and 'there is a hint of the number' of evil, and it is not fitting to repay evil for so much good – 'for they had rendered me only good'. And when they heard me present this pleasantry it found favour in their eyes, and they added another five! So I left there with 'behold! it is good.
(Cymerman translation)
Comment: "Multiples of chai is surely just a way of amplifying the message of "life", (as opposed to an entirely separate rationale)." - are you sure it's not just because $18 is not that much and people want to give more?  That was my assumption.
Answer: In his work, The Book of Ruth: Paradise Gained and Lost Benjamin Segal makes the observation that in the book of Ruth God's name appears 18 times (as it does in Tehillim 29)
I would like to suggest, based on Chazal who say that the book of Ruth teaches the importance of chessed, perhaps the notion of donating 18 or a multiple thereof is related to this

Source for # times chai?


Simulation of radio in LTspice

Question:

I simulated a radio-receiver circuit, where I have actually build a part of the circuit which helps to amplify a AM carrier 550 kHz frequency of microvolts (antenna voltage) into several volts, however, I do not see any amplification on the output voltage as highlighted above. I am not sure what have I done wrong. I have attached my LTspice file at google drive here for edit and just click on download and if possible, edit and simulate it in LTspice to prove that there is amplification.
Comment: https://youtu.be/CJi93dBBUJ0
Here's an AM radio I built on a breadboard. I believe this schematic has a number of issues. In the book I told you about, there's a very similar design (also based on the LM386) without those issues, plus you don't need a special germanium diode in the book design, but only a simple silicon one. You could choose a different book of course, but in general I'd recommend a book over internet schematics.
Comment: You could draw the schematic a little bit more readable. Otherwise, you're lucky for the default `Rser=1m` for theinductor, otherwise you'd be getting voltage loop errors. Also, `L1, C1` are absolutely useless here (they're in parallel with a voltage source, which has zero internal resistance). If you meant to simulate an antenna then a current source would have been better.
Answer: You need a resistor from the output of D1 to ground for the demodulator to work.
A value of 10k or so is a reasonable starting point.
Th resistor is necessary or the node from the diode will just charge up to the max voltage of the RF then stay there. (It may even have difficulty simulating Spice often doesn't like nodes without a DC path to ground).
C2 is rather large to get a reasonable audio bandwidth - 1000pF would be better.
In your simulation you should couple the voltage generator B1 loosely to the inductor. That loose coupling could be a small capacitor, maybe 10pF.
Comment: To better simulate the AA119, which is a germanium diode, one could put a resistance in parallel with it.  Per the data sheet, somewhere around \$200\mathrm k \Omega\$ to \$1 \mathrm M \Omega\$ may be about right.  Or use a Shottkey, or find a SPICE model of a germanium diode.

Simulation of radio in LTspice


Disable access request for all SharePoint online Sites

Question: When users create SharePoint sites, By default access requests and Sharing are enabled. I would like to disable this feature globally on my SharePoint online Tenant.
Answer: You can refer to the powershell in the article below:
To change access request Emails of all sites in a site collection or tenant:
SharePoint Online: PowerShell to Change Access Request Email for All Sites
To disable access request, simply clear the Email value.
Please note:
Microsoft provides third-party contact information to help you find technical support. This contact information may change without notice. Microsoft does not guarantee the accuracy of this third-party contact information.
Comment: It won't disable it for all SharePoint sites. I am looking for a solution to disable it completely for all sites.
Comment: I've updated my reply.


Breaking a rectangle into smaller rectangles with small diagonals

Question: Say I am given a rectangle with dimensions $a \times b$ and an integer $n$.  I'd like to break this rectangle into $n$ smaller rectangles $R_i$, and I'd like to make the maximum diagonal of any of these rectangles $R_i$ as small as possible.  I don't need a provably exact solution, just a heuristic that works well.  Is there a common way that one does this?  As an extreme example, if $a$ and $b$ happen to both be integers and $n$ happens to be equal to $ab$, then we can of course divide the rectangle into unit squares.  Even if $n$ is not exactly equal to $ab$, we should be able to get a "good" division by stretching this grid slightly.
Comment: That statement of the problem neither requires that the subrectangles have integer sides nor that they have equal diagonals. Indeed, s and b might happen to be integers but  need not be. I'd try $n=2,3,4,5,6,7$ first.
Comment: Near duplicate: http://mathoverflow.net/questions/137287/tiling-the-square-with-rectangles-of-small-diagonals .
Comment: $k$ should be $n$.
Comment: Tilings of a rectangle by smaller rectangles are nicely described by planar graphs, as described here:
http://www.squaring.net/sq/ss/ss.html
Comment: That's not a solution, but at least allows one to describe potential solutions.
Answer: UPDATED
This is a very interesting question. Here is a motivating example followed by a conjectured solution.
Consider the problem of dividing the unit square into $28$ rectangles so as to minimize the maximum diagonal of any of the rectangles.

Using $28$ rectangles of shape $\frac14 \times \frac17$  gives a diagonal of $\sqrt{\frac1{16}+\frac1{49}} \approx\sqrt{0.0829}$
Using $25$ squares of side $\frac15$ then subdividing three to get $28$ rectangles gives maximum diagonal $\sqrt{\frac2{25}}=\sqrt{0.08}$
Since $28=10+18,$ another option is the configuration below. It seems clear that it is optimal to have equal diagonals which gives the system of equations $$3u+2v=1 \text{ and }\frac1{36}+u^2=\frac1{25}+v^.2$$ Here the two equal sides of the second equation are the square of the diagonal. The solution turns out to be $u=\frac{45-13\sqrt{5}}{75} $ and $v=\frac{-20+13\sqrt{5}}{50}$ with diagonals $\sqrt{\frac{269-130\sqrt{5}}{500}}\approx \sqrt{0.0729}.$ I think, but do not claim, that this is optimal. I do think it can be shown to be optimal among solutions made up of rows running side to side.

The general problem is: given a rectangle of dimensions $a \times b$ (where we may assume $a \le b$) and an integer $n$, find a division of the rectangle into $n$ sub-rectangles in such a way as to minimize the longest diagonal of any sub-rectangle. I think that the optimal solution will have all diagonals equal. However let us specify that among solutions with the shortets longest diagonal,  we prefer the one with diagonals as close to equal as possible, say ones  which minimize $$\sum_{1 \le i_1 \lt i_2 \le n}(d_{i_1}-d_{i_2})^2$$ where $d_i$ is the diagonal of the $i$th sub-rectangle.
The idea (presented dynamically) is to start with a division of the rectangle into $j$ rows of $k$ rectangles, all of dimensions $\frac{a}{j} \times \frac{b}{k}$ where $j$ and $k$ are integers to be specified with $jk \ge n.$ Then remove  $jk-n$ rectangles leaving either

$j$ rows, $jk-n$ with $k-1$ rectangles and the rest with $k$ rectangles OR
$k$ columns, $jk-n$ with $j-1$ rectangles and the rest with $j$ rectangles.

Let us assume it is the first case, the other being the same mutatis mutandis. Then we make all the rectangles in the deficient rows have width $\frac{b}{k-1}$ and then adjust the rows to have each of the two kinds of rectangles have equal diagonal. That is we  use rectangles of sizes $u \times \frac{b}{k}$ and $v \times \frac{b}{k-1}$ where

$u^2+(\frac{b}{k})^2=v^2+(\frac{b}{k-1})^2$
$(j-(jk-n))u+(jk-n)v=a$.

It remains to specify $j$ and $k$. If the task was to find $n$ disjoint rectangles with total area $ab$ and minimize the maximum diagonal, then the solution would be $n$ squares of side $s=\sqrt{\frac{ab}{n}}$ and diagonal $\sqrt{\frac{2ab}{n}}.$ We can certainly not do better than that for the given problem and can only do that well exactly when $a$ and $b$ are both integer multiples of $s.$ To dispose of an extreme case which does not exactly fit the later description: if $a \lt s$ then use a single row of rectangles $a \times \frac{b}{n}.$ Otherwise, let $$j'=\Big\lfloor\frac{a}{s} \Big\rfloor \text{ and }k'=\Big\lfloor\frac{b}{s} \Big\rfloor.$$  Consider the choices $j=j'+1,k=k'$ and $j=j',k=k'+1$. If both satisfy $jk \ge n,$ then try both (I'll guess that the one minimizing $jk$ is better). If only one does, use it. Finally, if neither does, then use $j=j'+1,k=k'+1.$
This description has one try as many as $4$ cases. A certain amount of experimentation, which I have not done, might allow one to conjecture , and then possibly prove,  rules for what choices to make for $j,k$ and which choice (rows or columns) to truncate. It would also provide a check if the description given works. For example I am implicitly assuming (in the first case) that $j \ge jk-n.$  If both this and $k \ge jk-n$ can fail at the same tie, then something is wrong with the description.
Answer: Without loss of generality you may assume that the horizontal spacing and vertical spacing are homogeneous.  If the side of length $a$ is split into $n_1$ parts and the side of length $b$ is split into $n_2$ parts, a direct application of the arithmetic mean vs geometric mean shows that the subrectangle diagonal is maximised if $n_1 = \sqrt{\frac{an}b}$ and $n_2 = \sqrt{\frac{bn}{a}}$.  Thus, you should try the two divisors of $n$ closest to the optimal value of $n_1$ and the one that gives you the smallest subrectangle diagonal is your optimal solution.
EDIT: You can try $n_1 = \left\lfloor \sqrt{\frac{an}b} \right\rfloor$ and $n_2 = \left\lfloor \sqrt{\frac{bn}{a}} \right\rfloor$ and then subdivide some of the small rectangles in order to have $n$.  This would give an approximation that is not terrible.
Comment: This doesn't always produce a good solution; for example if $n$ is the prime number $100000000000000000039$, I doubt you will get a good solution by dividing the rectangle into a $1\times n$ grid.
Comment: You are right, fixed in the edit.


Can i recover ethereum sent to and invalid address?

Question: i've mistakenly pasted "2.5" in address field submitted a withdrawal request. can i get my coins back since the address is an invalid or the coin will be sent? I'm afraid i may loose my coins.
Answer: If I understand you correctly, you inputted wrong address ("2.5") to a withdrawal form somewhere.
In general if this request triggers a transaction then it can't be reverted anymore. But if it was just some online form and the data goes to a company processing the information you may ask them to stop the process. It really depends on where you input the information.
Depending on where and how you submitted this request it may vary how "2.5" will be interpreted - if the request went through it's probably parsed into some unaccessible address. Perhaps into 0x2500000000000000000000000000000000000000 and if that's the case you could check its transactions for example here: https://etherscan.io/address/0x2500000000000000000000000000000000000000 (there are no transaction currently).


How can a person move with non-uniform centripetal acceleration along a circle?

Question: I am just confused how a person or a particle can move with non uniform centripetal acceleration along a circle. Take the case of non uniform circular motion. The magnitude of centripetal acceleration is given by $a=\frac{v^2}{r}$. So if $v$ is changing, $a$ must also change, but $a$ is the rate of change of direction of velocity. If the rate is not constant, how can the object form circular path? Please explain.
Comment: I am trying to say that the path should be a circle only when direction of velocity vector is changing at a constant rate. Then how can a particle or a person can move in a circular path if magnitude of centripetal acceleration vector is not constant?
Answer: The critical thing here is something you've said, in fact: $a$ is the magnitude of the acceleration, and $v$ is the magnitude of the velocity.  But velocity and acceleration are vectors: their magnitudes do not capture everything about them.
For uniform circular motion, up to a constant added to $t$,
$$\vec{v} = (-r\omega \sin \omega t)\vec{i} + (r\omega \cos \omega t)\vec{j}$$
where $\vec{i},\vec{j}$ are unit vectors in the $x,y$ directions respectively.  It's easy to compute the magnitude, $v$, of $\vec{v}$:
$$
\begin{align}
  v &= \sqrt{\vec{v}\cdot\vec{v}}\\
    &= \sqrt{r^2\omega^2\cos^2\omega t + r^2\omega^2\sin^2\omega t}\\
    &= r\omega
\end{align}
$$
This is constant:  $\vec{v}$ is not constant, but $v$, its magnitude, is.
The same holds for $\vec{a}$: it is not constant, but its magnitude, $a$, is.
In the case of non-uniform circular motion, $v$ is not constant, and neither in general is $a$.
As an example consider an object moving on a path such that $\vec{p}(t) = (r\cos t^2)\vec{i} + (r \sin t^2)\vec{j}$.  This is a circle but the motion is not uniform.  For this motion:
$$
\begin{align}
  \vec{v}(t) &= -(2rt\sin t^2)\vec{i} + (2rt\sin t^2)\vec{j}\\
  v(t)       &= \sqrt{4r^2t^2}\\
             &= 2rt\\
  \vec{a}(t) &= (-4rt^2 \cos t^2 - 2r\sin t^2)\vec{i} + (2r\cos t^2 - 4rt\sin t^2)\vec{j}\\
  a(t)       &= 2r\sqrt{1 + 4t^4}
\end{align}
$$
Well, in this case none of $\vec{v}, v, \vec{a}, a$ are constant.
Comment: r is constant the radius
Comment: @Teaislife: yes.
Answer: If you work in polar coordinates ($\bf \hat r,\hat{\theta}$) then the position is defined by:
$$ {\bf \vec r}(t) = r(t){\bf \hat r} $$
The velocity is:
$$ {\bf \vec v}(t) = \dot r(t){\bf \hat r} + r(t)\omega(t){\bf \hat{\theta}}$$
The acceleration is:
$$ {\bf \vec a}(t) = (\ddot r(t)-r(t)\omega(t)^2){\bf \hat r} + (r(t)\dot{\omega}(t) +2\dot r(t)\omega(t)){\bf \hat{\theta}}$$
So the criterion for circular motion is $\dot r(t)=0$, or:
$$ {\bf \vec r}(t) = R{\bf \hat r} $$
then
$$ {\bf \vec v}(t) = R\omega(t){\bf \hat{\theta}}$$
which is tangential to the circle, while:
$$ {\bf \vec a}(t) = -R\omega(t)^2{\bf \hat r} + R\dot{\omega}(t){\bf \hat{\theta}}$$
is not radial for $\dot{\omega} \ne 0$.
Answer: Suppose you have a vector $\vec{a}$ having magnitude $a$. If you want to rotate it by $\theta$ without changing its magnitude then you would have to add to it a vector having magnitude
$$
\sqrt{2a^2 - 2a^2\cos{\theta}} = \sqrt{2a^2(1 - \cos{\theta})}
$$
Note that this depends on the magnitude of $\vec{a}$. So to rotate two vectors having different magnitudes by the same angle you need to add a longer vector to rotate the longer of the two.
Now suppose this vector is the velocity vector. If you want to rotate it by an amount $\Delta\theta$ then you would add to it a vector having magnitude $\Delta v = v\sqrt{2(1 - \cos{\Delta\theta})}$. Dividing by $\Delta t$, the time over which this rotation occurred, we get,
$$
\frac{\Delta v}{\Delta t} = \frac{ v\sqrt{2(1 - \cos{\Delta\theta})}}{\Delta t}
$$
And if you take limits, the left hand side becomes the magnitude of acceleration responsible for this rotation and the right hand side becomes the familiar $\frac{v^2}{r}$,
$$
a_c = \lim_{\Delta t \to 0} \frac{v\sqrt{2(1-(1-\frac{(\Delta\theta)^2}{2!} + \frac{(\Delta\theta)^4}{4!}.....))}}{\Delta t}
$$
$$
a_c = \lim_{\Delta t \to 0}\frac{v\Delta\theta}{\Delta t} = \frac{v^2}{r}
$$
Answer: You are having the same doubt that I had a while back.
In  circular motion, there are two types of acceleration :

$a_{centripetal}$ - which gives rate of change of direction in velocity
$a_{tangential}$  - which gives rate of change of magnitude of velocity

We can also define a net change in acceleration which is noting but vector sum of above two accelerations.
Now to answer your question (and I am quoting my professor's words):

It depends on what controls the radial distance. If you have a body at the end of a rigid rod, pivoted at one end, then the radial distance cannot change so tangential acceleration just makes it circle faster/slower with the same radius but, if you have a body moving in a gravitational field, then the tangential acceleration will make it spiral in or out.

I hope it helps.
Comment: But it didn't answer my question
Comment: @ayushsharma what's the problem?
Comment: I am saying that circular motion is possible only when the direction of velocity vector changes at a constant rate. So if speed is not constant, how can the motion be circular in mathematical sense? Ok you answered my question. But I am not able to figure out where you have answered this query. Can you please illustrate in a more clear way?
Comment: @ayushsharma  If velocity vector only changes it's direction or as per u if its speed is constant it will be a case of uniform circular motion. Now read quoted part in my answer for the case  when the speed is not constant.
Comment: @ayushsharma, "circular motion is possible only when the direction of velocity vector changes at a constant rate." is not correct.  That would be true for uniform circular motion.
Answer: While all the other answers are correct (+1 to all), they appear not to address the source of your confusion.

the path should be a circle only when direction of velocity vector is changing at a constant rate.

This is incorrect. It is true for the simplest case, when the speed is constant.
Suppose you and I are in a car with no steering wheel on a circular track. You control the gas and brake, the force parallel to the direction the car is traveling. I control a rocket mounted on the side of the car. Its force is perpendicular to the direction the car is traveling. My goal is to keep the car on the track no matter what you do.
I can do this because I control the curvature of the path. If I turn the rocket up, the car turns more sharply.
For any constant speed, I can of course stay on the track. If you let the car travel at a constant speed $v_1$, I adjust the rocket so the sideways force is $v_1^2/r$.
If you smoothly accelerate from $v_1$ to $v_2$, at any instant you are traveling at some speed $v$. So I can adjust the rocket so the acceleration is $v^2/r$. I will have to smoothly increase the power so the acceleration changes from $v_1^2/r$ to $v_2^2/r$ in sync with your change.

So if v is changing, a must also change, but a is the rate of change of direction of velocity. If the rate is not constant, how can the object form circular path?

If you go around a circle at a constant speed, the velocity vector changes direction at a constant rate. A constant sideways acceleration provides this change in direction.
If you step on the gas and the car travels in circles at an ever increasing velocity, the velocity vector changes direction at an ever increasing rate. An increasing sideways acceleration is needed to provide this change in direction.


Windows server 2008 r2 rdp causes lags

Question: I'm running a server with Windows 2008 r2 OS.
The server is used as a Web server.
I'm logging to the server remotely using rdp.
I've noticed that when I have Internet connection problems, and I'm logged in to the server, it causes serious lags to the website. (of course that I checked with another users and they're having lags too).
Is it rational that my connection causes problems on the server through the rdp?
Thank you.
Comment: whats the internet upload/download rates?
Comment: @infografig of the server, 100mbit simetric.
Of the client, 15mbit download 1 upload
Answer: This could be if your server's connection to the internet is very slow and limited. It could also be whatever you are running during that RDP session which could, possibly though uncertain due to lack of data provided, take server resources and leave the web server with not enough resources, or you are causing your server to swap.
Basically, there are a lot of options. A web server is normally best left without users logged onto them (or any servers for that matter) as GUI generally use up a lot of useful resources and users (even admin) can easily "take down" a server by using it as a workstation (like opening a 5GB log file in Notepad).
All in all, there is not enough data to give a conclusive "answer" but above are general points that apply to your question.
Comment: There is always a user logged in, as there is a program running in the background that is acting as the server and getting connections. There is also always someone connected to that session through rdp, but I've noticed that when the user that is connected has network issues, the whole server and users are suffering too.

Windows server 2008 r2 rdp causes lags


Would my question about pdf rendering quality be on-topic for GD.se?

Question: I asked the question Why does transparency disable subpixel rendering in Adobe Reader? on superuser.com. Because I haven't gotten any answers or even comments there, and because I see technical issues are being discussed on GD.se, too, I asked a moderator to move my post there. He doubted whether the question would be on-topic here, and he has a point. So I thought I'd ask: Would my question be welcome here?
Comment: Well, that can't be generally true, seeing that about 50% of the questions listed are of a more-or-less technical nature. Your top question, "What should you ask the printer?", is a good example.
Answer: I think only someone with expert knowledge of the under-the-hood inner workings and architecture of Adobe Reader could answer that. You might get lucky, but I'd be very surprised - we're good for tips or tricks in using software as tool, but we're not technicians.
When it's more "fixing the under-the-hood workings" than "tips and tricks for creating things", we recommend the manufacturer's own forums and tech support, which for Adobe is usually the best option, or superuser since it's the SE world's equivalent of tech support -but unfortunately, as you've found, I think they don't have  many Adobe specialists.

I saw your comment:

"people on Graphic Design discuss technical issues, too, they
  routinely work with pdfs, and they are highly concerned with quality"

While this is true, when it comes to things like Adobe bugs and quirks, it means we designers are great at spotting and complaining about bugs, quirks and frustrations in Adobe software... but aren't necessarily qualified to fix them... This one doesn't sound like the kind of thing where there might be a workaround, so if you want a fix, I'd ask the under-the-hood Adobe software experts directly on the Adobe forums.
I'd suggest targeting Acrobat as well as or instead of Adobe Reader - in my experience, the forum people take Acrobat much more seriously than Reader, but I think the PDF rendering is the same.
Comment: Thank you, that's helpful.
Answer: Sorry for not explaining last night we were having a very bad storm here.  We try to focus on design and artistic questions, if you reference our help center it has great information under "What topics can I ask about here?"
To your comment:

"Well, that can't be generally true, seeing that about 50% of the
  questions listed are of a more-or-less technical nature. Your top
  question, "What should you ask the printer?", is a good example.

and in response to not explaining my comment:

technical questions are outside the scope on GD.

Every question could at some degree be considered a technical question but this community, based on the question's contexts, will close technical software questions.  As stated by user568458 it may not be a good fit here and you should address the issue at the manufacture's forum.  We have in the past been visited by some experts that can address issues that pertain to them, such as What is Pantone Cyan used for?.
Another point to consider is technical questions in regards to software needed to be worded in a careful manner that they can be helpful to someone else, dont have to be diagnosed or appear to be "I have to see this" to be able to fix it.
Comment: Any extra information you can provide in a question will always be helpful and I would suggest wording it and looking at it like a "quality issue" and not a "software based issue".
Comment: Maybe the title of my question, "Why…" is wrong. I'm not so much interested in an explanation but in a way to make it go away. :-) A practical work-around. Would it help if I included links to the pdfs?


If Then Constraint Linear Programming

Question: I want to write the following constraint:
If A=1 and B <= m then C=1 ( where A and C are binary, m is a constant and B is continuous).
Answer: My solution requires some kind of hack in the model, a Big-$M$ value, which is pretty common, but also a tolerance $\varepsilon$, which is not very desirable. I hope that I do not miss something easy here but reckon there is no way around it.
To model a condition of the form $(X \wedge Y) \to Z$ for binary $X, Y, Z$, you can use $$\tfrac12(X + Y) \leq Z + \tfrac12.$$
We can verify this by inserting: $X=Y=1$ yields to $1$ on the left hand side, thus, $Z$ has to be at least $\frac12$, and since it is binary, it must be $1$. If either $X$ or $Y$ is $0$ (or both), we have at most $\frac12$ on the left hand side and in this case $Z$ might be either $0$ or $1$.
We also need to transform the constraint $B \leq m$ as a binary variable in order to use the template above. This can be done by introducing a new binary variable $B'$ which must assume the vaue $1$ iff $B \leq m$. We also need a Big-$M$ value which must be greater than any value that $B$ can assume (note that for numerical reasons in practice, $M$ should be not too large). Moreover, we have $\varepsilon$, a small tolerance value to get a strict $>$-inequality (in practice you would choose the difference to the next greater number from $m$ that can be represented exactly on your machine). We now add the constraints $$B \leq m + (1-B')M\tag{1}$$ $$B \geq m + \varepsilon - B'M\tag{2}$$
$(1)$ guarantees that $B' = 0$ if $B > m$, $(2)$ guarantees that $B' = 1$ if $B \leq m$. We verify this again: If $B \leq M$, $(1)$ and $(2)$ can be satisfied with $B' = 1$, but not with $0$. If $B > m$, we need $B' = 0$ to satisfy $(1)$ and then $(2)$ is satisfied since $B$ is at least $\varepsilon$ larger than $m$.
Putting it all together, we obtain your constraint
$$
\tfrac12(A + B') \leq C + \tfrac12,\\
B \leq m + (1-B')M,\\
B \geq m + \varepsilon - B'M.
$$
Comment: Thanks for your reply. So is B' an auxiliary binary variable?
Comment: Yes $B'$ is a new binary variable that does not occur anywhere else in your IP.

If Then Constraint Linear Programming


How add  tag android manifest

Question: How to add a tag <supports-screens> in the android manifest from file build.settings?
Answer: You need to use apktool to open the Corona APK, and then edit the manifest, and then repack again...
There are a very good tutorial on how to fiddle with apktool and Corona
Unfortunately, this tutorial seemly only apply to build up to 840, the newest build does not work with it...

How add  tag android manifest


can leafy greens push up through woodchips

Question: I'm growing spinach, and swiss chard, but they don't seem to be sending up new shoots. Can these plants along with other leafy greens push up through wood chips?
Comment: How thick are these wood chips, Black?  If they are over an inch those seeds will not get sunshine, warmth, forget getting chemistry out of the cold compacted soil for growth.  Who is dumping chips on top of germinating seeds?  Even without chips you bury your seeds 2 to 3 times the largest dimension of the seed.  So lettuce which is TINY tiny seed is buried too deeply by ANY size wood chip.  Ugh.  This wood chip gig is not impressing me in the least.  Thank you for bringing this stuff up because I have long ago poo pooed bogus gardening practices.  This is a new perspective for me.
Comment: 1-2 inches from starts
Comment: So 1 to 2 inches thick and you plant starts?  You plant the starts in soil and then dump chips?  Black thumb, I am sorry I see absolutely no benefit using wood chips.  Scrape that stuff off and compost it, then use it on the surface of the soil.  Only THEN is that compost usable to the life in the soil.  There are many types of fungus, right?  Some fungi are part of the decomposer crowd.  There is fungi EVERYWHERE.  The fact is these chips cause any nitrogen to be used up because non decomposed stuff HAS to be decomposed.  Fact of life and death.  I refused to use wood chips in landscapes...
Comment: i planted starts that were small, and gave them some growth then they started to get bigger, and i'm wondering about new leaf growth not old leaf growth
Comment: You planted your starts in soil and THEN you put chips around them or OVER them? I am thinking you put chips OVER them, right?  No sunlight, no photosynthesis.  New leaves might make it out from under the chips.  I dump regular dirt over weeds.  Never see those weeds again.  1 to 2 inches will block out the light and kill.  Black Thumb, please send ONE picture.  What exactly did you do and why?  Growing plants is not rocket science.  You are making rocket science...I adore those who want to test everything.  Meanwhile, just give your plants the basics.  I would shuck this wood chip thing.
Comment: i didn't cover them, but put the chips around them so they could do their jobs.
Comment: Why are you worried about the plants growing up through the chips then?  Please tell me what those 'jobs' are, that chips do...I am again telling you I don't see one bit of benefit mulching with non decomposed wood chips.  NONE.  I went to school for this stuff to make sure I could responsibly handle ALL landscapes.  Please tell me what you learned and I can help redirect your thinking or I can maybe change my thinking.  You ARE a born gardener...I want to help a little bit!  Remember, I've been gardening heavy duty for over half a century.  I just want to help...
Answer: New small leaves of tender plants like spinach don't have the strength to lift a wood chip.  Neither does the new growth often make enough sideways progress underneath a piece to snake its way up between chips.  A good weed like bindweed sure will, but not the wonderful wimpy plants we like to eat.  That's why it's not good to plant seeds under chips.
On the other hand, chips even an inch or two away from established plants, while one can argue about their overall benefits or lack thereof, won't cause new spinach leaves to fail to emerge.  That's because new leaves in spinach emerge from the center of the plant, like lettuce or carrot leaves but not like rhubarb or peonies.  So as long as the wood chips aren't right on top of the spinach but are an inch or two away like you describe, that isn't why they aren't producing new leaves.  As to what IS causing them not to grow I can't tell.  But it sounds like the wood chips aren't to blame.
There's an argument, to my mind excessively clinical, that wood chips bind nitrogen in the short run, robbing the plants they surround.  Eventually as the chips rot from below, the nitrogen gets released again, together with wonderful new humus for a net long-run benefit.  I use lots of chips, mostly around ornamentals, and I don't worry about it.  But some people do.  In that extreme instance, your existing spinach leaves would be yellowing etc.  And there are many other possible causes of yellowing leaves even if they are.
Spinach hates heat.  Is it getting summer-hot in your area, and what spinach that is growing shooting straight up?
Comment: Yes, through thin and/or mostly rotten chips.
Comment: have you seen grass struggle to push up through wood chips if it's in the post winter emersion stage?


How can I tell whether my computer is Harvard or von Neumann architecture?

Question: I understand the difference between the two architectures is the separation of instructions from data in the Harvard architecture. But how do I know which type of system I'm on? Is it possible to write a program such that the program determines whether the system is von Neumann or Harvard? Could there be another architecture or are these architectures the only ones known?
Comment: [Modern Uses of Harvard Architecture](http://en.wikipedia.org/wiki/Harvard_architecture#Modern_uses_of_the_Harvard_architecture).  Everything else in typical use is Von Neumann.
Comment: While modern systems aren't strictly von-Neumann either . thinking about GPUs and all those other things :)
Comment: There are other architecture types. [Dataflow architecture](http://en.wikipedia.org/wiki/Dataflow) is my favorite. But you are unlikely to see it out in the wild.
Comment: Unless you are doing something really really low level I am not sure why you would need to know the difference (are you writing self modifying code?). Even though most modern machines are von-Neumann the OS usually marks code pages differently from data pages to prevent accidental (malicious) modifications to the code.
Answer: Your computer is a von Neumann machine.  All general purpose computers are.  The only exceptions are specialized co-processors like GPUs.  It's not that you can't have a Harvard machine (or any other architecture).  It's just that nobody builds them, especially not for sale (modulo co-processors, of course).
Comment: This surely depends on the definition. If you replace the rather obsolete dichotomy by [a trichotomy](http://en.wikipedia.org/wiki/Modified_Harvard_architecture#Comparisons), most current general purpose computers are Modified Harvard Architecture.
Comment: Many embedded microcontrollers use Harvard architectures.  They generally run code from some kind or ROM or flash memory, and little would be gained by using a common bus for code and data.
Answer: Most current general purpose CPUs use Modified Harvard Architecture. The CPU cores can access program and data independently in their separate L1 caches. At the outside, there are no separate program and data memories (nor the other cache levels are separated).

Could there be another architecture or are these architectures the only ones known?

All the other architectures are rather restricted in their use. Because of the extreme complexity and costs associated with processor development, I don't think anybody would try it seriously again.
However, while modern CPUs are basically von Neumann, they incorporate a lot of ideas like Dataflow Architecture internally.
Answer: Both Von Neumann and Harvard architectures belong to the Control flow paradigm.
There is another paradigm, which is Data flow.
A common example of dataflow computing, though implemented on control flow computers, is the spreadsheet (from Visicalc and Multiplan to Excel).
Neural networks also belong to this category.
FPGA are another example of dataflow architecture. They are programmed with hardware description languages such as VHDL.
Answer: Harvard Architecture is typically only used in embedded microprocessors where the program is stored in on-board eeprom memory. The only one you are likely to see is an Atmel AVR as used in the Arduino
Answer: When you program it: Modify a memory region and then jump there and execute it.
If it is Havard you can not do it.
Comment: Or it might be a Von Neumann machine with a W^X memory manager.


How to limit memory usage by application in linux?

Question: I have a closed source software with some memory leaks problems. Is there a tool or solution to "sandboxe" processes in a fixed amount of memory without using "ulimit" (to generic, I need a per-application memory control)
Comment: related: https://unix.stackexchange.com/questions/44985/limit-memory-usage-for-a-single-linux-process
Answer: On systemd-based distros you can also use systemd-run (which indirectly uses cgroups). For example:
systemd-run --scope -p MemoryLimit=1G firefox

Note: this gonna ask you for a password but the app gets launched as your user. Do not allow this to mislead you into thinking that the command needs to run with sudo, because that would cause the command to run under root, which hardly was your intention.
If you want to not enter the password (indeed, why would you need a password to limit memory you already own), you could use --user option, however for this to work you gonna need cgroupsv2 support enabled, which right now requires to boot with systemd.unified_cgroup_hierarchy kernel parameter.
Answer: 'ulimit' is a 'per-application' control… per process in fact. The ulimit shell command is a shell built-in setting the limit for the shell process and its children.  Put the 'ulimit' command in the script starting your application and the limit will be set for this application only.
Comment: As Jacek said, that's what ulimit's for.  If a binary application, you could wrap it in a script.
Answer: You could use a process management daemon like monit to monitor the amount of memory in use by your proceses and restart it when it grows over your defined limit.
This does sound drastic, but given your application is known to leak, restarting it regularly based on its usage is just putting off the inevitable, when the process size grows larger than the smaller of, your machines physical memory, or any address space limitations imposed by your operating system.
Answer: Use cgroups.
https://man7.org/linux/man-pages/man7/cgroups.7.html
Note the difference between memory.limit_in_bytes and memory.memsw.limit_in_bytes. Also note memory.soft_limit_in_bytes.
Further information can be found in the kernel source file
Documentation/admin-guide/cgroup-v1/memory.rst (or
Documentation/cgroup-v1/memory.txt in Linux 5.2 and
earlier).


Awk script to run a command based on condition using 'if'

Question: I have a piece of code here that basically takes a file called 'srcip' (which is just a list of IP addresses) and compares it to my '~/db' file which is just a tab delimited IP HOSTNAME database of servers we have in our environment. The objective is to take the 'srcip' file and match it with what's in the ~/db file to get the hostname. It works fine but there are a lot of IP addresses that are intentionally not in the ~/db file because of DHCP issues, so we need a real host lookup using the host command. What I'd like is to basically put an if statement in this awk code that will check if the IP does not match in the db, then run the host command on that ip and give me the output. How can I do that here?
awk 'FNR==NR {a[$1]=$2; next} $1 in a && a[$1]!=$2 {print $1, a[$1], $2}' OFS="\t" srcip ~/db

I am aware that awk can use if statements such as this below to check if any system users have a /bin/bash shell:
awk -F':' '{ if ($3 < '500' && $7 != "/bin/bash" ) print $0 }' /etc/passwd

As stated, I need to use something that parses this data fast such as awk or sed and not rely on any loops. Please keep in mind I can already do this with a while loop but given the nature of a while loop, it is parsing it line by line and slow for our use since we have nearly 100,000 IPs to parse at a time if not more. For 2000 lines, I can run this piece of code but again this is not what I want to do:
#!/bin/bash

while read this_IP_address
do
    db_host=$(grep "^$this_IP_address" ~/db | awk -F ' ' '{print $2}')
    if [ "$db_host" = "" ]
    then
        host $this_IP_address | head -n 1 | awk -F ' ' '{print $5}'
    else
    echo $db_host
    fi
done

Answer: It sounds like you need something like this:
awk '
    NR == FNR {ip[$1]=1; next}
    $1 in ip {print; delete ip[$1]}
    END {
        for (i in ip) {
            system("host " i)
        }
    }
' srcip ~/db

Comment: It works but it must stay in order of the IP addresses. It cannot END and begin the for loop afterwards. Any ideas on how to re-structure this awk code?


Questions should be deleted or not when get closed by moderators?

Question: If any question gets closed due to be duplicate or off-topic or unclear etc. should it not be deleted? Sometimes users do not delete those questions. Some questions may be useful and some are not. What should be done with them?
Comment: [Duplicates are useful](http://blog.stackoverflow.com/2010/11/dr-strangedupe-or-how-i-learned-to-stop-worrying-and-love-duplication/) because they may help more people find the canonical answers by widening the search terms that lead to them. Other questions are put on-hold, not closed, because **we hope that the OP will improve them** so that they can be reopened and answered. If this doesn't happen, they're usually [autodeleted after a while](http://meta.stackexchange.com/a/5222/248731).
Comment: @JonasCz per the link I just provided *"closed (not as a duplicate), unlocked questions with zero or negative score having no upvoted or accepted answers or pending reopen votes, that were closed 9 or more days ago and haven't been edited in the past 9 days"* are automatically deleted.
Comment: Closed questions are deleted after a week anyway, if they have -1 score or lower. (I believe.) I don't think a mod would delete something, since it might not be a dupe after all, and it might get reopened.
Comment: What about the answers which gets lot of downvotes but not deleted by user?
Comment: @sgtBOSE what about them? They appear greyed out at the bottom of the list, but they aren't automatically removed as far as I'm aware.
Comment: related: [Which edits push closed questions to the reopen review queue?](http://meta.stackoverflow.com/q/256567/839601) See also: [reopen review triggers](http://meta.stackexchange.com/a/256071/165773) "There are three ways a question can end up in Reopen Review..."
Answer: Duplicates often should not be deleted, since they serve as a trail of breadcrumbs that people can follow to find the original question. Unless a question is nearly identical to the original (meaning it doesn't offer anything new for search engines to find), then it should be preserved.
Other questions can be deleted after a time if they aren't improved. There is an automated process that deletes old questions that are negatively upvoted and have no answers, since these weren't helpful to anyone. Users with sufficient privileges can cast votes to delete closed questions as well.


How to trim multiple paths within a clipping mask?

Question: the image below was created from a clipping mask; is there a way to trim what is outside of the mask? I want to keep the paths separate and preserve their individual stroke colours. I have tried using the crop pathfinder option but this deletes everything and if i try to expand the image it converts the paths to shapes. Any help would be amazing! Thanks
Comment: There's no easy automated solution for this, but it is possible using the Shape Builder tool. First you need to release the mask, select all. Then using the Shape Builder hold down (Alt) to remove pieces, then you will probably have to zoom in to remove the connecting strokes that are left behind. [see simplified example](https://imgur.com/BFMRjXx)
Comment: Shape builder has done the job, thanks! Was just being hopeful that there may have been a quicker option
Answer: Try this:
Release the clipping mask. Let it have no fill, but insert a well visible stroke.
Select all.
Wipe the unwanted parts off with the Shape builder. Hold the Alt key continuously to keep "wipe off" active instead of building new closed areas. Click with the shape builder just the paths which you want to remove. Do it one by one, do not drag nor click empty area between the paths.
This may not work if the paths have effects or tricky multilevel groupings or nested masks. A single group doesn't harm.
In the next image the blue-red shapes are a single group of separate paths. The green rectangle is the released clipping mask;

The result after Alt+clicking with the shape builder every unwanted segment. The green rectangle is only moved aside. The group is released after wiping the unwanted parts only to show the remaining paths are free. The shortest one is selected:

Warning: If you happen to drag or Alt+click the areas between the paths you get easily unwanted extras which must be deleted separately or something can vanish totally. Work with a copy to avoid irreversible damages.


Centripetal force for a rotor or centrifugal force?

Question: From basic physics any object experiencing a uniform circular motion, experiences a centripetal force. However in electric machines at high speed the rotor would be deformed outward as if a centrifugal force acting on its outer surface. How mathematicaly we can convince ourselves the force is centrifugal although we learned it is centripetal because of the centripetal acceleration?
Answer: An rotating object will deform if it isn't resilient enough to provide the required centripetal force.
Take for example the manual skill of spreading out pizza dough by tossing it in the air with a lot of rotation. A wooden disk would keep its shape. The dough does have elasticity (making it tedious to try and spread it out with a roller) but the dough does not have the strength to maintain its shape when it is rotating fast.
There are no exceptions: it is always the structural integrity of the material. The higher the rotation rate that you want to design for, the stronger the material needs to be in order to be able to provide the required centripetal force to sustain the overall co-rotating motion.
Another example: reducing the water content of textile by spinning it in a centrifuge. Adhesion between the fibres of the fabric and the water makes the textile retain water. Spinning the textile in a centrifuge subjects the water to a high G-load. There is not enough adhesive force between the water and the fabric to sustain the circular motion of the water, so rather than co-rotating with the textile the water moves along an outward spiral. This makes the water in the textile move closer to the wall of the centrifuge drum. Eventually the water exits the drum.
Note that in the case of a centrifuge for drying textile the only centrifugal force being exerted is force exerted by the textile on the wall of the drum. That's because the wall of the drum is exerting a centripetal force upon the textile. These opposing forces are not in equilibrium; there is a surplus of centripetal force, sustaining the circular motion. The structural integrity of the drum wall is sufficient to provide all the required centripetal force.
Later edit:
Another example:
the tires on dragster cars are designed to be very, very elastic. When the run starts the fast spinning tires undergo elastic deformation. The diameter of the tire expands until the tension force along the circumference is so large that it provides the required centripetal force. At the end of the run the tire spins down again, and in this phase there is a surplus of centripetal force, causing the tire to contract again. This is the counterpart of the expansion process: when the exerted centripetal force is larger than the required centripetal the rotating object will contract.
Note that in the case of elastic deformation there is a self-adjusting process going on. As an elastic material is stretched the elastic force increases. During spin-down: as the rotating object contracts the elastic force decreases again. Due to the self-adjusting character of the process the actually exerted centripetal force will always be close to the required centripetal force.
Incidentally, the pizza dough undergoes mainly plastic deformation. That is, when the rotation of the tossed pizza dough is stopped tt contracts back a little, but most of the stretching is permanent.
Comment: Thanks @Cleonis For the pizza  example, when the dough spreads out can we say it does not experience the uniform circular motion because if it does the dough wouldn't spread and would be stretched toward the axis of rotation due to the centripetal force?


Ender Dragon spawn egg?

Question: I know that in a previous version of Minecraft, you could get a Ender Dragon spawn egg (a white egg, like it has no texture). Is that still possible, and if how do i get it?
Comment: I don't believe the newer versions have it anymore, but you may be able to obtain it by using console commands.
Comment: If you still want to spawn in the Ender Dragon, just type in this command: /summon EnderDragon
Answer: There's no Ender Dragon Spawn Egg since 1.2
Reading the page on Spawn Eggs on the Wiki, it does not seem possible to get an Ender Dragon Spawn Egg since version 1.2.
Specifically,

Any entity not in the list above, such as paintings, entity blocks, or primed TNT, cannot be created with spawn eggs, even if set to the relevant entity ID value by commands. The egg is colored gray (Spawn Null.png) and will only work in version 1.1.

(emphasis mine)
As far as I can tell, the list is identical with the spawn eggs you can get in creative mode. Ender Dragon is not listed, and can not be spawned using spawn eggs.
Answer: There is an update now which allows you to spawn it. Just simply use the command
<code>/summon EnderDragon
</code>
That's all. Hope I helped
Answer: As of 1.19.3, you can now obtain them with the <code>/give</code> command.
Answer: You can also type '/give  383 1 63'. It'll give you the white egg with grey spots.
It is avaliable on any version below 1.7.5
Example:
 /give Popcorn98 383 1 63
Comment: Does it actually spawn an Ender Dragon though?

Ender Dragon spawn egg?


Direct2D --- Why are Brush resources bound to individual Direct2D render targets?

Question: Why did Microsoft decide to bind Brush resources to individual Direct2D render targets, rather than the overall Direct2D context. What should we do if we have a Direct3D texture, which is mapped to a Direct2D render target (for a HUD) which needs to be resized to the full width and height of the screen when the user changes between fullscreen and windowed mode, or resizes the window? Is the only thing to do recreate all of the brushes when this happens; or is there another way, such as somehow binding brushes to the ID2D1Factory, rather than the Direct2D surface?
Comment: Meant Direct2D -- big difference apparently
Answer: Brushes require the allocation of resources on the GPU. Since Direct2D is a "policy-less" API, which means they want to make sure you can have direct control over memory usage, the brush factory methods hang off the render target instead of the root factory. Otherwise they'd need to have some policy in place that decides when to free the hardware resources, and that policy will always be wrong in some scenarios (it would negatively impact performance or memory usage).
Factory methods for geometries and stroke styles hang off the root factory because they are stored in main memory, and any processing they affect is done on the CPU. You can "compile" a geometry object w/ stroke style into a hardware resource via ID2D1Mesh, which basically just tessellates it straight into a vertex buffer. While it will be much faster (at render time, not at tessellation time!), it can also use a lot more memory depending on the complexity of the geometry.
Answer: I am not sure if this can help, since you didn't describe what will happened when user switch between full-screen mode and window mode, so I assume the only change is the size of the render target, if this is the case, you can just resize your render target by calling the ReSize function, and use the brush as usual, nothing need to change with the brush.


How do I set Views Bulk Operations Fieldset Collapsed by default?

Question: Using VBO, I am trying to set the Operations Fieldset to collapsed by default. Is there a setting to do this? or a theme override that I can use per view?
Answer: Use hook_views_bulk_operations_form_alter()
<?php
function mymodule_views_bulk_operations_form_alter(&$form, &$form_state, $vbo) {

 if($form['#form_id'] =='views_form_block_id'){

  $form['operations_fieldset']['#collapsed'] = TRUE;

 }

}
?>

Comment: You deserve the bounty for taking the time to give him the proper form ID, the more efficient function call, and the fieldset element's ID :)
Answer: You can do this in a hook_form_alter():
<?php
mymodule_form_alter(&$form, &$form_state, $form_id) {
  if ($form_id == 'views_bulk_operations') { // inspect your form in your browser to get the actual ID; it's in a hidden element at the bottom of the form.
    $form['operations_fieldset']['#collapsed'] = TRUE;
  }
}
?>

This assumes the fieldset's name is "operations_fieldset". You should install the devel module (drupal.org/project/devel) and then do a dpm($form) inside the if() statement in the code above to see what the form's elements are named.
More info on the 'fieldset' form element: http://api.drupal.org/api/drupal/developer!topics!forms_api_reference.html/7#fieldset
Answer: I had to use this to get this to work in 7.x-3.2
<?php
function mymodule_views_bulk_operations_form_alter(&$form, &$form_state, $vbo) {
  if($form['#form_id'] =='views_form_[view_machine_name]_[view_display_type]'){
    $form['select']['#collapsible'] = TRUE;
    $form['select']['#collapsed'] = TRUE;
  }
}
?>

If you want it to apply to all bulk operations forms then just remove the $form['form_id'] condition.
Answer: For all who googled this with a similar question: We have an issue to change the fieldset to *un*collapsible in VBO which might need some help.
Until we have that i rolled a sandbox module for this, based on Ryan G's snippet, but incorporating the API changes which happened since then.


Fantasy novel involving mythical creatures on a farm and two children staying with a relative for the summer

Question:
Mythical Creatures on a farm (unicorns, basilisks, etc.).
Relative having two children come to stay for summer.
Children's book.
Pre-2010.
Comment: If someone posts the correct answer, you can accept by clicking on the checkmark by the voting buttons, as per the [tour].
Comment: Was the relative you mentioned the owner of the farm with the mythical creatures? And can you tell us anything else about the plot or characters?
Comment: I read this book when I was about 8 so I'm very much struggling for accurate details, If anything comes to me i will update            - the relative was the owner and was either their grandfather or uncle
Answer: The book is called The Dragons at Ordinary Farm by Tad Williams.

Tyler and Lucinda have to spend summer vacation with their ancient uncle Gideon, a farmer. They think they're in for six weeks of cows, sheep, horses, and pigs. But when they arrive in deserted Standard Valley, California, they discover that Ordinary Farm is, well, no ordinary farm. The bellowing in the barn comes not from a cow but from a dragon. The thundering herd in the valley? Unicorns. Uncle Gideon's sprawling farmhouse never looks the same twice. Plus, there's a flying monkey, a demon squirrel, and a barnload of unlikely farmhands with strange accents and even stranger powers. At first, the whole place seems like a crazy adventure. But when darker secrets begin to surface and Uncle Gideon and his fabulous creatures are threatened, Lucinda and Tyler have to pull together to take action. Will two ordinary kids be able to save the dragons, the farm—and themselves?
Comment: You can self-accept by clicking on the checkmark by the voting buttons, but as a self-answer, it won't let you complete the process (although it will tell you how long you have before you can accept) for 48 hours after you asked the question.
Answer: Might this be Fablehaven by Brandon Mull as per Book: Girl can see magical creatures, finds secret passages at her grandparents'?

The series begins as 13-year-old Kendra and 11-year-old Seth Sorenson are traveling to their Grandpa and Grandma Sorenson's house while their parents are away on a 17-day cruise. When they get there, they also meet Dale, the groundskeeper, and Lena, the housekeeper. Grandma Sorenson is "mysteriously" missing. Grandpa Sorenson does not tell Kendra and Seth about Fablehaven being a secret preserve for magical creatures at first, but instead sets up a rather complex puzzle involving six keys and a locked journal for Kendra to solve. Once Kendra unlocks the mostly blank journal, she discovers the words "Drink the milk." She and Seth drink the magical milk Dale sets outside in their yard every morning, opening their eyes to a whole new, mystical world full of the magical beings of Fablehaven. Then Kendra and Seth must face challenges such as defeating an evil witch and a powerful demon, defending the preserve from an evil society, stopping a plague that changes creatures of light into creatures of darkness, accidentally turning Lena into a naiad, and, ultimately, protecting the world from a horde of imprisoned demons.

The first book came out in 2006, which matches your timeframe.
Comment: Thanks for the suggestion, I have managed to find it, it's called "The dragons at ordinary farm" and sounds quite similar to that, I will have to reader the one you suggested too, thanks
Comment: @Alex: Glad you found it. I gussied up your answer a bit with a Goodreads link, image, and summary. Don't forget to accept in the next two days.


Where should I ask a question about my career?

Question: I need to ask a question about what path to follow and what knowledge must be acquired to land a job in a certain big company? (Knowing the requirements of the job position aren't enough to tell you how to go about acquiring them.)
Comment: Can you explain a little about the field it is in? If it's an academic or research field, it could go on Academia.SE, otherwise it might fit in with a site with the same subject area.
Answer: Some questions about careers are welcome at The Workplace. However, I fear they would close your question as it stands;

Questions asking for advice on a specific choice, such as what job to take or what skills to learn, are difficult to answer objectively and are rarely useful for anyone else. Instead of asking which decision to make, try asking how to make the decision, or for more specific details about one element of the decision.

From their Meta:

When people ask us for personalized advice, a lot of the specific details will not apply to other people who come across the question since their details may be slightly different and they can't determine whether or not the answer is appropriate for their situation. It's also hard to answer these questions objectively; we're not looking for collections of unsupported opinions.
Comment: Thank you for your answer. Although it is a bit unfortunate that the question might be closed there, given that I already made up my mind as of which company i want to join but still need advice on what steps to follow, given that the world of technology is ever changing, same as the company's goals


Story in which a man gets executed because of a bureaucratic mix-up

Question: Trying to identify a story: I once read an anthologized short story in which a man is scheduled to be executed for a minor offence. I believe the narrative was conducted entirely in letters back and forth between people like his lawyer, relevant authorities, and other such figures. As the situation progresses his fate remains unavoidable for one absurd reason or other (holidays, rules, automatic mechanisms.) Does this ring a bell for anyone? Thanks!
Comment: Almost sounds like a thematic prequel (inspiration) to Gilliam's BRAZIL.
Comment: Sounds very similar to this [one](http://scifi.stackexchange.com/questions/41518/short-science-fiction-story-told-in-a-series-of-letters) already on the site.  Give it a look.  With that said, based on your description, what about the story would make it sci-fi or fantasy ?
Comment: That's the one! Thank you. I believe a story set decades into the future in which human lives are lost based on computer algorithms might quality as Sci-Fi, but better judges than me have already originally published it in the Sci-Fi publication Analog and anthologized it in Sci-Fi volumes. Thanks for the link! I'm not too familiar with the software on this site; can I mark your comment as an accepted answer somehow?
Comment: Wouldn't be fair for me to get credit :)  I'm going to VTC as duplicate.  Glad we could assist and welcome to the site.  Hope you'll continue to participate.
Comment: The post that this was closed as a duplicate of does not have an accepted answer; **this should be reopened**.
Comment: Marking it as a Duplicate to an actual accepted answer. As seen above, *firasd* accepted the answer by comment.
Answer: As per this answer, this is "Computers Don't Argue" by Gordon R. Dickson.
Summary from Wikipedia:

The story is told in the form of correspondence.
Walter A. Child of Panduk, Michigan has a disagreement with his book club in Chicago, Illinois over a damaged copy of Kim by Rudyard Kipling (cost $4.98) that was sent to him. He returned it, asking for a replacement. Instead, he is sent a copy of Kidnapped by Robert Louis Stevenson. He returns it, requesting that the matter be settled. Instead, he receives a second, automated notice.
He replies saying that the book club now owes him money. He receives a third letter and his reply to it is not read. His account is then turned over to a third party collection agency, increasing the amount owing to $6.83. A second letter ups it to $7.51 and a third to $10.01. Child responds with a letter explaining the matter, but the agency does not believe him and threatens legal action.
The matter goes to small claims court in Illinois, the amount having increased to $15.66. A duplicate judgment is passed the next day in Michigan. However, the amount owing ($15.66) and the statute number (Statute 941) are transposed on the punch card.
Child sends a letter that he will visit the book club offices personally and settle the matter himself. Meanwhile the transposed amount is interpreted as Statute 1566, relating to criminal matters. Since no such statute exists, it is changed to 1567 (Kidnapping). The changed punch card is then incorrectly interpreted to relate to the kidnapping of a child named Robert Louis Stevenson by a person named A. Walter and an arrest and hold warrant is issued.
Child is arrested at the book club offices. The judge requests more information, since a trial transcript is missing from the record. He specifically requests if the victim, Robert Louis Stevenson, was harmed. The request returns that RLS is deceased, having died at age 44. The reply omits the age of death, simply replying that the victim is dead. A personal reply to the judge mentions that the victim was slain and mentions a possible gang connection.
Child's lawyer believes him, but Child is sentenced to execution, for first-degree murder in connection with the death of a kidnap victim. Since no previous trial transcripts were available, the judge was forced to rely on the computerized records.
Since all records have been computerized, appeal time has been cut to 5 days, and ten for it to be acted upon. Instead of appealing, he appeals to the governor for a pardon. The governor is out of the country and slow in responding. Child refuses an offer by the warden to let him escape, believing that the pardon will arrive in time.
The pardon is issued by the governor, but a post office routing number error stalls it and it arrives too late.

As seen in the comments above, this was accepted by the querent:

That's the one! Thank you. I believe a story set decades into the future in which human lives are lost based on computer algorithms might quality as Sci-Fi, but better judges than me have already originally published it in the Sci-Fi publication Analog and anthologized it in Sci-Fi volumes. Thanks for the link! I'm not too familiar with the software on this site; can I mark your comment as an accepted answer somehow? – firasd Nov 1 '13 at 17:59


create an ecdsa key

Question: Is it possible to create an ECDSA key using the jdk 1.6 keytool?
I have tried with the <code>-genkey</code> command, but it doesn't seem to be supported.
Any ideas of how can I resolve this?
Answer: AFAIK Java 6 has some limited support ECDSA regarding to TLS however it does not include any ECDSA implementation - it can make use of a third party JCE like BouncyCastle. It may be possible to use keytool with BouncyCastle to generate ECDSA keys but I have never tried that.
I would suggest to update to Java 7. But even using Java 7 there seems to be some problems in the early versions. According to the bug entry 6870812 : enhance security tools to use ECC algorithms you have to use 1.7.0_07 or higher for ECC support.
Furthermore a related question here on Stackoverflow Java 7 keytool Elliptic Curve Encryption points out that you have to install the unlimited strength policy files for JCE to make use of ECC.

create an ecdsa key


Are there any tools to make text labeling faster?

Question: I saw the labelme tool and was wondering if there is a similar tool for labelling short documents? Preferably in Python.
Comment: Could you provide some more explanation about the tool and what you are searching for?
Answer: There are many. A couple of the most popular:

ML-Annotate - Supports binary, multi-label and multi-class labeling.
TagEditor - A  Windows application that uses spaCy
Answer: Yes, there are several tools available for annotating short documents in Python. Some popular options include:

Prodigy: Prodigy is an annotation tool that allows you to label short documents and other text data quickly and easily. It is written in Python and has a simple, user-friendly interface. You can use Prodigy to label text data for tasks such as named entity recognition, sentiment analysis, and topic classification.

Brat: Brat is an open-source annotation tool that is widely used for annotating short documents and other text data. It is written in JavaScript and has a web-based interface, but you can also use it from Python using the brat_client library.

Doccano: Doccano is another open-source annotation tool that is written in Python and has a web-based interface. It is designed specifically for labeling text data and supports a wide range of annotation tasks, including named entity recognition, part-of-speech tagging, and sentiment analysis.

scribe: scribe is a Python library that provides tools for labeling text data. It includes a command-line interface and a web-based annotation tool, and it is designed to be easy to use and customize.

Hope this helps!
Answer: Prodigy: Prodigy is a powerful annotation tool that can be used to label short documents and other text data. It has a user-friendly interface and a range of features that make it easy to label text data quickly and accurately. Prodigy can be used in Python through its API.
spaCy: spaCy is a popular natural language processing library that includes tools for labeling and annotating text data. It has a range of functions for tokenizing, tagging, parsing, and visualizing text data, and it can be used in Python to label short documents and other text data.
NLTK: The Natural Language Toolkit (NLTK) is a comprehensive library for working with human language data. It includes tools for tokenizing, tagging, and labeling text data, as well as functions for working with a wide range of linguistic data. NLTK can be used in Python to label short documents and other text data.
GATE: GATE (General Architecture for Text Engineering) is a powerful platform for building and deploying text processing systems. It includes tools for annotating and labeling text data, and it can be used in Python to label short documents and other text data.


How can we find representatives from specific cities?

Question: I would like to know U.S. House of Representatives from Houston, Atlanta, and Los Angeles in 1980. I know districts and city boundaries do not overlap, but is there any way to know them?
Answer: Los Angeles
Wikipedia's page for California's Congressional districts will tell you the historical boundaries from 2002-2010.  You can then work backwards from those to find districts from Los Angeles in 1980.
For example, if you look at the map, you will see that the 31st district was in Los Angeles in 2002.  The Wikipedia page says that the 31st was redistricted from the 30th.  The 30th district was from Los Angeles in 1980.  George E. Danielson.  You can see that if you look at the historical list of representatives for the 30th.
Atlanta
Atlanta is simpler.  Wikipedia has the map in effect in 1980.  It shows that Atlanta covered the 4th (Elliott H. Levitas) and 5th (John Lewis).
Houston
Texas also has a historical map from 1980.  It looks like Houston was covered by the 7th (Bill Archer), 8th (Bob Eckhardt), and 18th (Mickey Leland) in 1980.
Summary
I picked out the districts by eye.  I'm not so familiar with any of these cities that I could not have made a mistake.  I'm confident that these districts each had a slice of the listed city.  I'm not confident that I didn't miss any.  And of course, I hardly tried with California.  That's more just to get you started.
Comment: Thanks! I also checked Wikipedia, but don't we have to consider redistricting? Are districts in 2000's the same in 1980?
Comment: @user51966  Sorry, for some reason I decided that you wanted the 2000 data rather than the 1980 data.  Adjusted.
Comment: For Houston (city of Houston proper, not just Greater Houston), in 1980 the districts also included 22 and possibly 9. Source: District maps for 96th Congress from https://cdmaps.polisci.ucla.edu/ , loaded into Google Earth Pro. Also applying knowledge of Houston to the historical map from 1980 linked in the answer. You can see where district 22 reaches up inside the loop at highway 90 / S. Main, which is definitely within Houston boundaries. You can also see where district 9 reaches down from the northeast corner, which may or may not have been within the city boundaries in 1980.


Unwanted rotation behavior

Question: The Cube should rolle like a cube should roll^^. In some cases the rotation goes wrong in case of a gimbal lock? How to avoid that?
Comment: I don't know Animation nodes, but can it do [axis-angle](https://en.wikipedia.org/wiki/Axis%E2%80%93angle_representation) or [quaternions](https://en.wikipedia.org/wiki/Quaternions_and_spatial_rotation). Those don't gimbal lock.
Comment: Yes, it has axis-angle and quaternions. But I don't know how to set this up. It's pretty new to me.
Answer: This rotation behavior occurs because the first rotation causes a rotation in the axes as well. This would require you to recalculate the axis to use for the second rotation. Unfortunately this problem isn't the result of gimbal lock and won't go away if you're switching to quaternions.
A quick and dirty solution would be to change the order of your rotations depending on whether the cube is rolling in the x or y direction. I don't know if it's possible to change the rotation order for one node, but if you multiply the rotation matrices you end up with the same result. If you're sticking to nodes, use two Matrix Math and a Matrix Mix node. I just decided to switch to a script to reduce the amount of wiring.

This approach would require you to keep track of the cube's direction and manually add keyframes for the script input which changes the matrix multiplication order.
The fact that the orientation of the cube might change whenever you switch could lead to problems if you replace the cube with an object with less symmetry. But then it might be better to search for another approach as the x and y position of an empty alone isn't sufficient to determine the desired orientation of the final object.
Comment: Thank You for helping me. I can't test the script because of an TypeError in [Line:3 - can't multiply sequence by non-int of type 'float' (TypeError)]
Comment: @DanielGlebinski The input types for the script should be *Float* for both *x* and *y* and *Boolean* for the third value. I assume you picked *Float List* and tried to pipe *Location* directly into the script.
Comment: Sorry, was my fault. I used the Script Node incorrectly.
Comment: Still dirty but beautiful^^ Maybe I could automate the boolean with a case function. In one case the whole geometry flips and if the cube were detailed or textured asymmetrical it would flip and the flip would be recognizable. Works fine, thank you @binweg.

Unwanted rotation behavior


use SUM() or caching

Question: I don't have much experience with databases, so I don't know which is better for long-term performance, better practice, etc.
Here is my (hypothetical) case: imagine you have a database of customer information and history of purchase orders for each. You want to keep track of how much each customer is buying. I can think of two ways of calculating this:
1) Just do a SUM() every time it is needed. This is an easy solution, but the concern is that this database could be 20 years old with tens of thousands of rows for each customer. As more customers purchases are added to the database, the SUM() operation will take longer to calculate.
2) Keep the sum cached in the customer information table, and every time a new purchase is made (updated, deleted, etc), update this cache. That way no matter how many purchase orders there are, there won't be an increase in the calculation time. The downside is that, this is a less flexible solution (only the sum over all rows, what about per month sum? other intervals? etc); this cached value could get out of sync with the actual total somehow (technically shouldn't happen, but it might)
So what should I be doing for this? I know I shouldn't be storing anything I can calculate from what's already in the database, but part of me doesn't like the fact that this type of calculation will get worse in time, and that there is some kind of elegance to option 2.
Comment: As an aside, "tens of thousands of rows" are far too few for modern database engines, try hundreds of millions.
Answer: In database terms, there is no elegance in option 2 - it would be considered a hack that you might use as a last resort if your database gets to be truly humongous - not likely to happen for a novice setting it up for the first time (but possible).
There would be a lot of work maintaining the totals; and you'd be forever dealing with the question: "Why doesn't the detail add up to the total?"
Go for option 1 until you've proven you can't. Which will in most cases be a long time.
Comment: You can use Oracle's materialized views or DB2's indexed views.  They do the caching exactly as you described seamlessly, silently and automatically.
Comment: Yup, when the time comes. BUt baby-steps first.
Answer: What you're describing in option #2 is a case of premature optimization.  Using the SUM() of all purchases is going to work for a really long time (years).  When (if) you start to see this function degrade, you can add indexes or a totals table to your database to speed things up.  Don't complicate things when a simple solution exists.
Of course, the real solution is to try both solutions with 20 years of made-up data and see if there's any real difference.  I suspect there isn't.
Answer: Almost always 1.
How often will you be querying for the total for 20 year's worth of history? If the answer is often, and the performance is poor, then you can think about optimisation or OLAP.
I suspect you're worrying about optimisation too early. This is the sort of thing databases are designed for - let them worry about caching.
Answer: I'll just add that another possibility is to create roll-up tables.  For instance, when tracking page hits, it's not very useful necessarily to know that IP such-and-such accessed page1.php at 14:42:04 on 11/19/2008; but you might want to track daily stats for page1.php.  In this case, at the end of each day you might run a procedure to sum up the hits for each page and create a record in a summary table, which can in turn be heavily indexed.  Your reporting then can run against that table.  In addition to speeding up reporting, it can also speed up writing the original records, as you don't need to worry about table locking or building indexes.
That said, good indexes can go a long way with reporting; and like others here have admonished, it's best to go with the easier, even if less optimal, solution until (if ever) it becomes a problem.
Answer: Kudos for thinking ahead, but the question that begs asking, is your sales data going to stay in the transactional database for 20 years?
There comes a point where it's going to be a lot easier to move that data into a data warehouse, and just keep your frontline database current.
If this is a new project, be more concerned with making it work, and getting people to use it. Worry about scalability when you've crossed those bridges.
Answer: Use option 1.  Later, if performance becomes poor, you can identify specific bottlenecks and resolve them with options like #2, or materialized views, or several other possibilities.

use SUM() or caching


How long does it take to validate transactions?

Question: It seems to be a common sense that validation process on the blockchain is very fast. I wonder how fast the process could be? How long does it usually take to validate a transaction? What will be done to validate a transaction?
Answer: There are different factors that affect the time to consider a transaction as validated.

Gas price: the lower it is defined in the transaction, the more time to be picked up by miners. You can check that in ETH Gas Station.
Network congestion: if there is a high number of transactions to be processed during a certain period, this will affect also the gas price (newer transactions might increase the gas price to go faster, so the rest will have to wait more).
Number of block confirmations: the more you set, the more you wait, being 12 blocks as an overall safe value (this is to avoid potential forks or uncle (orphaned) blocks).

If the average time to mine a block is around 14 seconds (nowadays), then you can estimate the time to validate a transaction depending on the decisions you make on the above points.
Comment: I think validation is irrelevant to gas price, network congestion and number of block confirmations. When a node receives a new transaction, it needs to validate the transaction firstly(check the balance, the nonce, etc.). I just wonder how long it will take to do that. I think maybe it is related to cpu time. But I want to know an estimated time.
Comment: I think you are mixing the concept of mining vs. validated transaction. If you are only referring to the mining process by a node, it all depends on the hash power of that node (so there is no straight answer, because you can't compare a GPU at your home vs. a professional mining farm). A validated tx has a wider scope in which the conditions I mentioned influence in the time to consider a transaction as validated.


How can heat turn into light

Question: I am confused about how hot surfaces can radiate light to their surroundings. When I shine a light on a surface the light turns to heat spontaneously, and when I leave that hot surface it  radiates light spontaneously. To me this suggests that the process isn't driven by entropy increasing because it is two directional. Could anyone explain how this process complies with the second law of thermodynamics?
Comment: Please keep in mind that the second law holds for isolated systems. ("shine light" and "absorb light" )are one system and the entropy increases because of all the microstates of photons absorbed and emitted. If you isolate a hot object, it is a different system, and its entropy increases by the radiation and all the microstates of all those photons emitted, which should be counted in the isolation.
Comment: The light that you get back will be at a longer wavelength in general.  The process is not reversible.
Answer:
Could anyone explain how this process complies with the second law of thermodynamics?

The Stefan-Boltzmann law.
I'll start with an ideal black body. Black bodies absorb all incoming radiation. They also emit radiation as a function of temperature. The peak frequency and the intensity increase as temperature increases. The emitted power is given by the [Stefan-Boltzmann law](Stefan–Boltzmann law), $P=A\sigma T^4$, where $A$ is the surface area of the black body, $\sigma$ is the Stefan–Boltzmann constant, and $T$ is the body's temperature. Now let's put the body in empty space, well-removed from any other radiating object. The body loses energy thanks to this radiation and hence suffers a dropping temperature. It also receives incoming energy from the cosmic microwave background radiation. The incoming and outgoing energy balance when the object finally cools to 2.73 Kelvin, the temperature of the CMBR.
Now let's look at a pair of flat plates, each one of which is a perfect white body (or perfect mirror) on one face, a perfect black body on the other. White bodies and perfect mirrors neither absorb nor emit heat radiation. We'll arrange the bodies so their black body faces face each other. This arrangement means they aren't radiating into space. Suppose the plates have different temperatures. Per the Stefan-Boltzmann law, the hot plate will radiate more energy than will the cold plate. The hot plate will cool down and the cold plate will warm up. The process stops when the two plates are at the same temperature.
Those were spherical cows, but even with realistic bodies, thermal radiation always operates in concordance with the second law.
Update:
I never said why that final sentence is the case. Objects coming into thermal equilibrium with one another is the second law of thermodynamics in action. The entropy of an isolated system reaches its maximum value when all elements of the system are in thermal equilibrium with one another.
One of the many statements of the second law is that heat cannot spontaneously flow from a colder body to a warmer one. If heat can flow between two objects, the heat flow will always be from the warmer object to the cooler one. Radiative heat transfer is but one of many mechanisms by which heat spontaneously flows from a warmer object to a cooler object.
Answer: Heat, in the context of something "giving off heat" that we use in everyday conversation, is a term we use often to describe emission of a specific part of the electromagnetic spectrum (namely the infrared spectrum). As you start to pour more and more energy into an object, the electrons can get more and more excited (which is the process of absorbing photons), until they emit a photon to return to a lower energy state. As you get hotter the electron can jump up further and further until when it returns to the ground state it emits visible (or UV/x-ray) photons.
In terms of entropy and the second law, when shining the light on a surface, the electrochemical processes occurring in the flashlight results in a greater amount of entropy since the chemical concentrations of the battery cells increase in the number of micro-states. Similar would be true of whatever is driving the light emission from your source. When the energy is emitted from the surface, heat is flowing from a hot source to a colder one, increasing the number of potential states (multiplicity) and thus entropy of the entire system. Throughout the entire process entropy is having a net increase if you observe the entire system.
Comment: "Heat is a term we use often to describe a specific part of the electromagnetic spectrum..." this is not the standard thermodynamical definition of heat.
Comment: i meant heat in terms of the colloquial definition of something "giving off" heat, which the context he used in the beginning of the problem. I'll clarify that now.

How can heat turn into light


How to get the generative counterpart of a discriminative CNN

Question: Say we train a (discriminative) CNN to predict age from images of faces. Is there a direct way of obtaining the homologous generative network (ie, from a scalar age to an image of a face) ?
The backward pass during training should be doing something similar in order to propagate the gradients from age to the face.
Answer: There is probably no good way to do this, since it is possible to discriminate age without modeling the whole space of faces. If you also happened to have a density model of faces $X$ as well, perhaps you could use MCMC to sample from $P(X|y) \propto P(y|X)P(X)$.


Is there a web app that provides a terminal emulator / secure interface to the bash shell?

Question: Is there a website where I can use the bash shell with support for xwindows, e.g. so that I can ssh -Y into my Linux desktop?
Comment: Why would you want to do that? The 3rd party site would have to see your credentials in order to log in into your Linux box on your behalf and create a ssh emulation. This way not only you would have to trust (I'm guessing) public terminal you want to log in from but also the site. Better to start an ssh session directly from the workstation in question.
Comment: @Andris that is a good point. But how can I ssh in the scenario where I am on a public computer (e.g. I can't or don't want to install Cygwin) and would like to use bash?
Comment: I see your point. You could carry Cygwin with your [on a USB stick](http://sites.google.com/site/devinsezer/Home/software/portable-cygwin) if the public computer allows you to use it. I haven't tested this though. On the other hand if you trust the 3rd party website more then the public computer and this website would allow some form of one-time-passwords or multi factor authentication then it would be a better solution from the security standpoint.
Answer:
Apparently HTML5 enables your browser to be used as a terminal, and this is available in the Chrome web-app secure-shell.
It is described in the FAQ as similar to Putty, but embedded in your browser:

"HTML Terminal", or hterm, is an xterm-compatible terminal emulator
  written   entirely in JavaScript.
It is intended to be fast enough and correct enough to compete with
  native   terminals such as xterm, gnome-terminal, konsole and
  Terminal.app.
hterm is only a terminal emulator.  It does not provide SSH access
  (or any   other text-based command) on its own.

This is even better than any of my previously posted solutions, any of which answered the OP.

Old answer below

Here is a CW list of options:
Web based SSH apps
consoleFISH is probably closest to what you are looking for
There is a list of both software on the Wikipedia Web based SSH page, including the following hosted option consoleFish at serfish.com
weblive
This doesn't give a great answer because it is not secure, but there is a way to access a live ubuntu session using the weblive interface.
Perhaps the software that runs this, nomachine has a solution.
rstudio
Another option is to install R-studio server, on a desktop or server (binaries available for Ubuntu > 10.04 or Debian > 6).
Rstudio can be accessed at http://localhost:8787 and provides access to a shell terminal; Ctrl + Shift + H or Tools > Shell
Answer: You can also just use tightVNC
http://www.tightvnc.com/ssh-java-vnc-viewer.php


Post apocalyptic book - ruins of a city

Question: I read a book set in a post-apocalyptic world who crossed the river to see what the audience knows are city ruins. He thinks they are filled with ghosts. I remember him going into an office building and sitting at a desk and I think there were pictures of a family on the desk. Does anyone know the name of this book?
Comment: possible duplicate of https://scifi.stackexchange.com/questions/83093/youth-ya-boy-with-telepathic-panther
Comment: If your memory is a little fuzzy and there's any possibility this was a short story instead of a book, you might also check out Stephen Benet's "By the Waters of Babylon" (1937).
Answer: "Daybreak 2250 AD" by Andre Norton?
This copy on Amazon has the same cover I remember: a guy on a raft going down a river, amid a ruined city: http://www.amazon.com/Daybreak-2250-A-D-Andre-Norton/dp/B000O8KU76
I read this back in junior high in the 60s - 'guess teens liking dystopian futures isn't unique to this new generation. :-)
Anyway, IIRC, the protagonist thinks the city is filled with ghosts, but it's really inhabited by what he calls "Beast Things" which are sort of like large, bipedal, sentient rats.
Now I'm wanting to dig up my ancient copy and read it again. Norton was a fantastic author.
Comment: Also published as *Star Man's Son* or *Star Man's Son, 2250 A.D.* Recognize any of [these covers](http://www.isfdb.org/cgi-bin/titlecovers.cgi?2944)?

Post apocalyptic book - ruins of a city