Why is the definition of inertial mass circular?

On , the definition of inertial mass is:       Inertial mass is the mass of an object measured by its resistance to   acceleration. And, can be evaluated using $F = ma$, Newton's second   law.   And, in the answer of  question, the viewer has also answered in terms of Newton's second law of motion.  However, I think that both these answers are circular in nature, as Newton didn't derive mass $m$ in terms of force $F$ , he derived $F$ in terms of $m$.  Another confusion I have is related to the law of conservation of momentum. I read that it was experimentally found by Newton that momentum is a "conserved" quantity, which led him to define momentum as $p = mv$ ( is the link to one of my questions regarding momentum).  But now, when I again think of this, I wonder how did he calculated "mass". To experimentally find that momentum is conserved, he must be knowing the values of mass $m$. And even if he used a scale or a weighing machine of some sort, how was he able to calculate $m$ from $F$, even when $F$ is not defined yet?  I am asking this question because I am not able to find the explanation to this anywhere. Most people just answer this in terms of $F$, which is circular. Am I making any mistake in thinking this way, I mean is there any other theory that I don't know?


I have already made a JList below a JTextField. It shows the information that I want coming from MySQL database. But when I choose from the list and gets the item to be on the text field, and then type backspace in gives me java.lang.NullPointerException. So I'll just click okay to remove the error dialog box. But then when I type something again on the text field, it repeats the same error. I don't know how to fix it. I think it can be fixed with some key events or mouse events. But I don't know how to do it. Can someone give me an example of what to code in KeyEvent to stop the error? Or any suggestion will do.


How to convince stakeholders to invest in proper UX?

I'm working on a web app with a team of 5, including me. One database administrator, one project manager, two programmers and me the front-end designer. This project is an internal reporting system.  Anyways, I've struggling a little bit with my team, the DBA and two programmers seem to control our meetings with what Data we are going to pull and the best way to work it into an object model.  And then look to me to design some pretty interface.  Truth is, we've never measured the objectives of this application and what strategy will best meet them from a front-end design/UX standpoint. We've done no wire frames, no planning of content, no planning of pages, no conversations on specific interface components, nothing like that. It seems my team is content with designing and building the entire UX/UI based on a couple of ideas we've spit-balled in meetings.  Forgive me if this sounds too much like a gripe, but I'm at a loss. How do I get my team to understand, we can't just throw the front-end together based on back-end data and the interface HAS to be well planned out and organized?


How to apply multiple modifiers as one shape key?

I'd like to know if there is a direct, or at least more efficient way (see 2. below) to go from "mesh with multiple modifiers" to "one shape key".  I was offered the solution to merge shape keys (from multiple modifiers) which I tried and it works. It's just too many steps in my opinion. My current solution works slightly better, but not much.   Detailed description: I have two meshes: human base mesh and clothing. My clothing mesh has two shrinkwrap modifiers. One regular which fits the clothing tightly to the selected shape key on my base mesh and one with "VertexWeightProximity" applied to bring back all the wrinkles the clothing has. Works perfectly, but saving "what I see" (all modifier results) into one shape key seems impossible to do in a fast and easy way.   When you apply a second/third... modifier as shape key it ignores what the first modifier(s) did, so you'd have to apply all of them. But I need a non destructive solution. "Display in edit mode" and "Adjust edit cage" do not help.   My most efficient solution so far: Make copies of my clothing mesh for every shape key I want to have, Activate the desired shape key on my base mesh, apply all modifiers on the clothing mesh copy and apply the last one as shape key, transfer this shape key back to the original clothing mesh, delete the copy, repeat.


I've recently discovered snapsort.com and use it to compare other cameras with the one I own. When comparing Pentax k10D with the K-x model I learned that the K-x has a CMOS sensor and that     CMOS-family sensors often produce better quality images   The  for that is     [CMOS sensors] also permit more integrated designs which can cut down on noise gain and provide the opportunity for a cleaner image.   which I take to mean that lower noise is due to better IC designs made possible with CMOS, not the sensor type itself.   Is this a meaningful  distinction? All things being equal, do CMOS sensor produce better quality images that CCD?


How do I split a long equation with equal sign on new line?

I have a long equation that must fit in a two-column journal. I know how to break up the right-hand terms nicely, but even so it won't fit and I need the equal signs to start on a new line, but I can't figure out how to do it nicely.  Here is what I've tried:  \begin{align*} p(\{K_{\text{pre}},\theta_{\text{b,pre}},\sigma_{\text{pre}},K_{\text{post}},\theta_{\text{b,post}},\sigma_{\text{post}}\}\mid D)\\ \begin{split}=\phantom{} & p(\{K_{\text{pre}},\theta_{\text{b,pre}},\sigma_{\text{pre}}\}\mid D)\\  & \times p(\{K_{\text{post}},\theta_{\text{b,post}},\sigma_{\text{post}}\}\mid D) \end{split} \\ \begin{split}=\phantom{} & p(\{K_{\text{pre}},\theta_{\text{b,pre}},\sigma_{\text{pre}}\}\mid D_{\text{pre}})\\  & \times p(\{K_{\text{post}},\theta_{\text{b,post}},\sigma_{\text{post}}\}\mid D_{\text{post}}) \end{split} \end{align*}   and the result:    Ideally I guess the right-hand lines should be "moved" to the left, but I'm not sure how to do that. I've seen the answers to  but here the first equal sign must come on a new line.


Highlighting text with citations and references

I was using the package soul to highlight text. It is pretty good, except for the fact that I get errors when I try to highlight a block of text with references or a citation. For example:  \hl{\citet{stuff} some text...}   gives  ! Argument of \@citex has an extra }.


Rhodes able to use armor without Arc Reactor?

Correct me if I'm wrong. Before Tony created a new element, or maybe before Iron Man 3, from what I understand, the Iron man suits are powered via the Arc Reactor in his chest. How was Rhodes able to use the Mark II?  Or to further my question: When did Tony build Arc Reactors in his suits? Because from what I remember they still use the one in his chest from Iron Man movie.


showing a sequence is Cauchy in a normed space

Suppose I have a sequence in a normed space.  In this space, the Cauchy-ness and convergence of the sequence is determined completely by the specific norm defined on the space, correct?  So when showing that a given sequence is Cauchy on this normed space, one would not be able to use any information about the sequence from an outside context (for example, that the sequence convergences under the standard absolute value norm in $\mathbb{R}$)?    As you can see, I am a little confused about non-standard norms on vector spaces.  If we have one, is that the ONLY norm we can have there?  Or can we have many different norms, including the standard one, on the space simultaneously?  I hope that makes sense.


Proof: Series converges $\implies $ the limit of the sequence is zero

I've been using the sentence:     If a series converges then the limit of the sequence is zero   as a criterion to prove that a series diverges (when $\lim \neq 0$) and I can understand the rationale behind it, but I can't find a formal proof.  Can you help me?


I have been thinking about this  recently but have found no good solution so I thought I might post it here to see what other people think:  Consider a cylinder made of iron that is magnetised so that the two poles are on the two opposite circular ends. Now suppose we bend this magnet. Bending the magnet does not change where the poles are ( alternate: or consider a bent version of the cylinder magnetised with the two poles on opposite circular ends ).  Suppose we bend this magnet into a torus, so that the north/south poles are brought into direct contact with each other (as they are opposite they should attract so repulsion is not a problem here) to form a torus. (alternate: or consider a series of progressively more bent cylinders whose limit is the torus).  What I can't seem to figure out is where would the North/South poles of this  magnet be or even whether the torus would have a magnetic field!  Any help is much appreciated.


When people take a rest in/on the bed, do they lie ON or IN the bed?   (In my native language both are optional)


Apart from a US visa what do I need for travel from state to state?

I'm from Trinidad and Tobago and I possess a valid US visa. I'm travelling to Minnesota and have have several connection flights to get there. Do I need anything other than the visa?


Why can't my `date` deal with timezones?

I'm having some weird issues with GNU coreutils date v8.4 (CentOS) that aren't occurring in v8.21 (Ubuntu/Mint).  On v8.4, I get the following output (I'm in PST):  $ date --version | head -n 1 date (GNU coreutils) 8.4 $ date -d '2014-11-08' Sat Nov  8 00:00:00 PST 2014 $ date -d '2014-11-08T00:00:00' Fri Nov  7 09:00:00 PST 2014   I'm assuming it's trying to timezone-correct for UTC, even though I didn't request it and this behavior doesn't occur on my local Linux Mint machine.  Okay, so I'll add a timezone specifier, as specified by . On my machine:  $ date --version | head -n 1 date (GNU coreutils) 8.21 $ date -d '2014-11-08T00:00:00-0800' Sat Nov  8 00:00:00 PST 2014 $ date -d '2014-11-08T00:00:00-08:00' Sat Nov  8 00:00:00 PST 2014   Great. But on CentOS:  $ date --version | head -n 1 date (GNU coreutils) 8.4 $ date -d '2014-11-08T00:00:00-0800' date: invalid date `2014-11-08T00:00:00-0800' $ date -d '2014-11-08T00:00:00-08:00' date: invalid date `2014-11-08T00:00:00-08:00'   EDIT: Another one that doesn't work, using date's own output:  $ date -d "$(date -Ihours)" date: invalid date `2014-11-08T13-0800'   The following does work:  $ date -d '2014-11-08 00:00:00 -08:00' Sat Nov  8 00:00:00 PST 2014   but, due to completely unrelated requirements, I can't have any spaces in my date string.  I'm quite perplexed. I looked for  but didn't see anything that looks promising.  My question: How can I get date to either not change my timezones at all (preferable), or accept timezone input from a human-readable string without spaces?


"Please insert disk into removable drive" error with pen drives in Vista

Whenever I insert a pen drive, I am not able to open it.  Vista shows me this error:     Please insert disk into removable drive   I have tried changing the drive letter, but it didn't help.


Why did Zobrist leave the trail to the virus in the first place?

So the billionaire in Inferno leaves a crumb trail all the way to the inferno virus so his followers can find it e.g. Siena. And Siena even says she's going to protect the virus to ensure it goes off because people are looking for it. However, the people looking for it are only able to find it, as is Siena, because of the trail Zobrist left.  Why did he leave a crumb trail? It doesn't make sense. Nobody would have found it if he didn't. Just time the device to go off. Most likely, the WHO characters in the film wouldn't have even known without the Faraday pointer...   Am I missing something?


Remove taskbar and time displayed in right corner and move to upper middle of the screen

I'm new to Ubuntu. I'm using Ubuntu 17.10, gnome-tweak-tool .  I want to remove the bar which is showing at the bottom of the screen and in the upper bar I don't want that "places" option to be shown. I also want time to be shown in the middle of the upper bar.


Multiple choice exam solution: emphasising math

I am designing a multiple choice question exam and I would like for the correct answer to be emphasized in the standardized bold way. The issue is that some of the answers contain only mathematics.  Here is a MWE:  \documentclass[addpoints]{exam} \printanswers  \begin{document}  \begin{questions} \question Which of these guys invented time?     \begin{choices}         \choice Stephen Hawking          \choice Albert Einstein         \choice Isaac Newton         \correctchoice This makes no sense     \end{choices}      \question     What is the way to write down the function for cubic power?     \begin{choices}         \choice  $f(x) = x$         \choice  $f(x) = x^2$         \correctchoice  $f(x) = x^3$         \choice  $f(x) = x^4$     \end{choices} \end{questions}  \end{document}   This, however, leads to the math option not being bolded:   I've tried to redesign the appearance of the correct option using \CorrectChoiceEmphasis{\boldmath}, but this does not provide the appropriate solution for two reasons: 1) I have to redefine it before every question with mathematical answer and then return back to the original definition, 2) The option mark (in this case "C.") is not bolded:    Is there a way to set the emphasis automatically so that both text and math are bolded in the correct solution?


How does the Higgs Boson gain mass itself?

If the Higgs field gives mass to particles, and the Higgs boson itself has mass, does this mean there is some kind of self-interaction?  Also, does the Higgs Boson have zero rest mass and so move at light-speed?


How to make a circle with grid on the outside ring

I made something like this:    I did this with the Ellipse Tool and the Line Tool.  Now the circle is accurate, but the lines inside are very inaccurate. Is there another tool that does the same thing but with a lot more accuracy?


Why does it keep saying the capacity of my dynamic array is 2 even though I keep changing it so it is not 2?

I want to print out the capacity of my dynamic arrays, but no matter how I change it, it keeps saying that the capacity of both the arrays are 2.  The code (tmp.c)  #include <stdio.h> #include <stdlib.h>  int main(){    int *ptr1 = (int *)malloc(sizeof(int) * 3);   int capacity_ptr1 = sizeof(ptr1)/sizeof(int);   printf("capacity of ptr1 is: %d\n", capacity_ptr1 );    int *ptr2 = (int *)realloc(ptr1, sizeof(int) * 5);   printf("capacity of ptr2 is: %ld\n", sizeof(ptr2)/sizeof(int) );      return 0; }   What I execute in terminal  gcc -std=c99 tmp.c -o tmp ./tmp   The output in terminal  capacity of ptr1 is: 2 capacity of ptr2 is: 2   I get this output no matter what capacity parameter I enter for malloc() and realloc()


How to avoid bad box with long words with no hyphenation?

I know there are planty of similar questions, but I haven't found the answer to this particular one.   I have a long word (say some long acronym like ABCDEFGH). It happens to be at the and of the line in the text, going over the margins and creating a bad box.  How can I avoid this, and force the acronym into the new line, but without breaking it ?  The concreete example is displayed in the attached image.


What is the measure of the set of numbers in $[0,1]$ whose decimal expansions do not contain $5$?

I just came across an exercise that asks to show that set of numbers in $[0,1]$ which possess decimal expansion not containing the digit $5$ has measure zero. How do I approach this? I tried thinking of relating this to Cantor set but, I see that numbers whose decimal expansion contains the digit $5$ are both contained in the Cantor set as well in its complement too, I thought if it was in the Cantor set and since measure of Cantor set is zero, so it's measure will be zero but this does not happen. In fact how is this set measurable? Any idea?


How can I sit in on a stream without getting in the way, while capturing and testing it?

How can I test whether a command's output is an empty string while not   interfering with buffering?  Example:  command | ??? if [ $? = 0 ] && [ -n "$output_from_command"]; then    ...   I want the output from the code above to be the same as when running command.


prove that $f(A) \backslash f(B) \subseteq f(A\backslash B)$

Let $A,B$ be two subsets of a set $X$,and let $f:X \to Y$ be a function.Prove that $f(A) \backslash f(B) \subseteq f(A\backslash B)$   So I first show what these sets are. The set $f(A) \backslash f(B) =\{y \in Y \mathtt{\ and \ } \exists x \in B (\ y=f(x)) \mathtt{\ and \ } \neg(\exists u \in B (\ y=f(u)))\}=\{y \in Y \mathtt{\ and \ } \exists x \in B (\ y=f(x)) \mathtt{\ and \ } (\forall u \in B (\ y\ne f(u)))\}$  And the set $f(A \backslash B)=\{y \in Y \mathtt{\ and \ } \exists x \in A\backslash B (y=f(x)) \} =  \{y \in Y \mathtt{\ and \ } \exists x (x \in A \mathtt{\ and \ } x \notin B  \  y=f(x)) \}  $  and  to prove every $y \in f(A)\backslash f(B) \implies y \in  f(A\backslash B) $.  Suppose $y \in f(A)\backslash f(B) $,then exists an $x \in A$ such that $y=f(x)$,and $x$must $ \notin B$ for if $x \in B$ then $f(x)\neq y $ leads to contradition.This means  $y=f(x)$ and $x \in A $ and $x \notin B $ then $y$ is an element of $f(A\backslash B)$.And this complete the proof.  I'm a self-study guy and I feel my statement quite strange.Although I got some intuition about the question,I'm not sure whether I'm doing right. Any help to correct or improve my statement is welcome.  Thanks.


Suggestion for someone who talks a lot but says little

I know many politicians that avoid interview questions by talking a lot but not really communicating anything.  You could say that what they were saying was full of banalities or canned answers or that they were waffling, but is there a better word for this behaviour?  I'd like to say some thing like That response was a _____ or he\she is ___ing?


I need to prove that :  $$\binom{m+M}{n}= \sum_{i=0}^n \binom{m}{i}\binom{M}{n-i}$$  without expanding.  I started by seperating the left hand side to get:  $$\binom{m+M}{n} = \binom{m}{n}\binom{M}{n}$$, and am trying to open up the right hand side with Pascal's identity but I am not sure how to make it work out to the required equality.


My method readFromFiles can't find the source files

I have a method readFromFile like this:  private static ArrayList<ArrayList<Integer>> readFromFile(String name) { ArrayList<ArrayList<Integer>> inputs = new ArrayList<ArrayList<Integer>>();  try {     InputStream in = ReadWriteFile.class.getClass().getResourceAsStream(name);     BufferedReader reader = new BufferedReader(new InputStreamReader(in));     String line;      while ((line = reader.readLine()) != null) {         ArrayList<Integer> input = new ArrayList<Integer>();          for (int i=0; i<line.length(); i++) {             int value = 0;             try {                 value = Integer.parseInt(String.valueOf(line.charAt(i)));             } catch (Exception e) {                 input.add(value);             }         inputs.add(input);         }     reader.close();     } } catch (IOException e) {     e.printStackTrace(); } return inputs; }   and I use this method here to read a folder of txt files. I need it to put the names of files in an arraylist (the files are an alphabet):  public static ArrayList<TrainingSet> readTrainingSets() { ArrayList<TrainingSet> trainingSets = new ArrayList<TrainingSet>();  for (int i=0; i<26; i++) {     char letterValue = (char) (i+26);     String letter = String.valueOf(letterValue);      for (ArrayList<Integer> list : readFromFile("C:\\Users\\hp\\Desktop\\resources\\" + letter + ".txt")) {         trainingSets.add(new TrainingSet(list, GoodOutputs.getInstance().getGoodOutput(letter)));     } } return trainingSets; }   The source folder includes files like: A.txt, B.txt, etc. When I try to run the code I get an error.   Exception in thread "main" java.lang.NullPointerException at java.io.Reader.<init>(Unknown Source) at java.io.InputStreamReader.<init>(Unknown Source) at data.ReadWriteFile.readFromFile(ReadWriteFile.java:34) at data.ReadWriteFile.readTrainingSets(ReadWriteFile.java:22) at network.Train.<init>(Train.java:16) at gui.MainGui.<init>(MainGui.java:38) at gui.MainGui.main(MainGui.java:32)   I guess the method can't find the files on my computer. But I don't know why. Is the form wrong? Can you help me?


For an intranet server would you buy a ssl cert or use a self signed cert?

We have a webservice that our application uses and the developers require https connections to the webservice.  Since this is an internal webservice would you use a self signed cert?


Why use "of" in the phrase "delivered of a baby"?

With all the "Royal baby" craze comes something that really confuses me. All the news media used pretty much the same sentence to make the announcement:      The Duchess of Cambridge has been delivered of a son.   A couple of questions:   Why not "The Duchess of Cambridge gave birth to a son" or "delivered a baby", or something along those lines? Why is "of" used in this structure, and what purpose does it serve?   From a non-native English speaker's perspective, this sentence doesn't seem to make any sense at all to me.


Question view count error in profile page

One of my question in SO  has only 1532 view counts, But when i look into my profile where all my questions are listed it is shown as 2k Views, even when i hover on this 2k the tooltip shows 1532 views


Express $\partial f/\partial x$ and $\partial f/\partial y$ in terms of $\partial f/\partial r$ and $\partial f/\partial \theta$, and vice versa.

I wrote down the following:  \begin{align}     \frac{\partial f}{\partial x} = \frac{\partial f}{\partial r} \frac{\partial r}{\partial x} =  \frac{\partial f}{\partial r} \cos(\theta) \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, (1) \end{align} \begin{align}     \frac{\partial f}{\partial x} = \frac{\partial f}{\partial \theta} \frac{\partial \theta}{\partial x} =  - \frac{\partial f}{\partial \theta} \frac{\sin(\theta)}{r} \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, (2) \end{align} \begin{align}     \frac{\partial f}{\partial y} = \frac{\partial f}{\partial r} \frac{\partial r}{\partial y} =  \frac{\partial f}{\partial r} \sin(\theta) \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, (3) \end{align} \begin{align}     \frac{\partial f}{\partial y} = \frac{\partial f}{\partial \theta} \frac{\partial \theta}{\partial y} =  \frac{\partial f}{\partial r} \frac{\cos(\theta)}{r} \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, (4) \end{align} \begin{align}     \frac{\partial f}{\partial r} = \frac{\partial f}{\partial x} \frac{\partial x}{\partial r} =  \frac{\partial f}{\partial x} \left [-r\sin(\theta) \frac{\partial \theta}{\partial r} + \cos(\theta) \right ] \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, (5) \end{align} \begin{align}     \frac{\partial f}{\partial \theta} = \frac{\partial f}{\partial x} \frac{\partial x}{\partial \theta} =  \frac{\partial f}{\partial x} \left [ -r \sin(\theta) + \cos(\theta) \frac{\partial r}{\partial \theta}\right ] \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, (6) \end{align}   It is possible to write $\frac{\partial f}{\partial x}$ purely in terms of $\frac{\partial f}{\partial r}$ and $\frac{\partial f}{\partial \theta}$? And same for $\frac{\partial f}{\partial y}$  Also, I think $\partial \theta / \partial r = \partial r / \partial \theta = 0$ so $(5)$ and $(6)$ become:  \begin{align}     \frac{\partial f}{\partial r} = \frac{\partial f}{\partial x} \frac{\partial x}{\partial r} =  \frac{\partial f}{\partial x} \left [ \cos(\theta) \right ] \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, (5') \end{align} \begin{align}     \frac{\partial f}{\partial \theta} = \frac{\partial f}{\partial x} \frac{\partial x}{\partial \theta} =  \frac{\partial f}{\partial x} \left [ -r \sin(\theta) \right ] \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, (6') \end{align}    Comparing $(5')$ with $(1)$ and comparing $(6')$ with $(2)$ is really confusing to me. Can anyone explain what am I doing incorrect?


Why beta sign is different than correlation sign?

I am trying to interpret the sign of my 5 x-variables against y-variable. The sign of some coefficients in the regression output (command: reg) are different than the signs under correlation matrix (command: correlate). Which one defines the relation sign/direction?


In PHP 4 you would enter a form to a MySQL db like this:  <form  action="script.php" method="post">  <fieldset>   <input id="name" name="name" type="text" placeholder="Insert your name" />   <input type="submit" value="Opslaan" />             </fieldset> </form>       script.php:  $name= $_POST['name'];   $name = stripslashes($name);   $name = mysql_real_escape_string($name);  mysql_connect($host,$username,$password); @mysql_select_db($database) or die( "Unable to select database"); $query = "INSERT INTO names (id, name) VALUES ('','$name')"; mysql_query($query); mysql_close();   Now PHP 5 is out, what is the correct notation to put this form in a MySQL db by the latest standards using PDO?


How to resize Ubuntu partition without re installing Ubuntu

I am using Ubuntu 13.10. When I type df -h, the terminal shows the following information  Filesystem      Size  Used Avail Use% Mounted on /dev/sda7        28G   26G     0 100% / none            4.0K     0  4.0K   0% /sys/fs/cgroup udev            3.9G  4.0K  3.9G   1% /dev tmpfs           794M  872K  793M   1% /run none            5.0M     0  5.0M   0% /run/lock none            3.9G  224K  3.9G   1% /run/shm none            100M   48K  100M   1% /run/user /dev/sda8        35G  102M   33G   1% /boot /dev/sda5        69G   18G   51G  27% /media/user/Chinnu /dev/sda2       130G   40G   90G  31% /media/user/CCCA371ACA37006E /dev/sda1        70G   50G   21G  72% /media/user/76E66C99E66C5AFF  /dev/sda3       130G   12G  118G  10% /media/user/jinju   I hope 28G is the size given to Ubuntu.  When I took "About this computer" menu item. it shows that     DISK : 66.2 GB    But I need some more GBs in Ubuntu. Is it possible to resize my Ubuntu partition without reinstalling?


Why does a bigger sensor lead to a shallower depth of field?

It has been mentioned at    that a larger sensor results in images with a shallower depth of field. Example image:          I understand how sensor size would relate to, for example, field of view, but the relationship with depth of field does not seem straightforward.  It actually seems contradictory - I have more wells on my sensor, and I am able to focus on less number of points.  What is the reason for this effect?


Why can I access any linux /home/user files booting from a live distro?

Is it not a security risk, that someone could access all the documents of a user just by booting a distro live cd?


As the title says, What is the difference between validity and satisfiability? Suppose I have a sentence If the sun is made of blue cheese, then cats fly. How do I tell if its valid or satisfiable?


Expectation inequality for a set and its subset.

Given that a function $g(x)$ is a monotone increasing function. Its domain is an interval [c,d]. There are two sets $a_j \in A, j= 1,...,J$ and $b_k \in B,k=1,...,K$  on this interval, which satisfy $c_z \in C = B$\A and $c_z \geq a_j$ for all $a_j \in A$. For example, the interval $[c,d]=[0,8]$,$A=\{0,1,2,3,4,5\}$ and $B=\{0,1,2,3,4,5,6,7\}$. In this case, does the following inequality hold? If yes, could you give me some hints to prove that?  $$\frac{1}{K} \sum_{k=1}^{K}g(b_k) \geq \frac{1}{J} \sum_{j=1}^{J}g(a_j)$$


Where should I post follow-up questions?

I recently posted a question that quite promptly got a number of decent answers. One of those answers led me to a closely related but slightly different question. What's the best way to bring up that additional question? I could..   ask the new question in an "answer" to my original question (this is what I did, but it's kind of colder and, I suspect, less likely to be seen by people), edit my original question to include the second one, or post a new question.   Any thoughts?


Add default syntax highlighting for the [dart] tag

I just approved several edits from a user adding  to questions with the  tag. Apparently , Google Code Prettify has added support for Dart.  I suggest it's time to follow suit and update the default syntax highlighting associated with the  tag. Adding it manually to every question sounds like way too much work, even if I all I have to do is click the "Approve" button.


How can I add thickness to a polygonal chain?

I'm really new to blender and I'm trying to add thickness to a fairly complex polygonal chain. I've seen a lot on how to do it with Bezier curves but nothing on how to do it with polygonal chains. Does anybody know how to?  That orange dot in the middle is what I'm talking about the big mess on the left is my polygonal chain getting sucked towards it:    UPDATE: My problem was fixed thanks to this question and answer -


How can a user undownvote posts after the votes are locked?

Yesterday, some of  But today, three of those downvoted questions were undownvoted. But    were edited after the downvotes. My question is how can a user undownvote posts after the votes are locked?  Not sure whether it's related or not but my today's reputation on the top bar is .  PS: I am not discussing anything about serial voting


How can I remove the peel and pit of an avocado without the whole thing turning into mush?

Making solid pieces out of a ripe avocado is a difficult business (for me, anyway). What is the best way to remove the peel and pit without ending up with a pile of green mush? I can sometimes remove the peel without too much difficulty, but that pit always gives me grief.


Android SharedPreferences: non static method referenced from static context

Hi everybody and sorry if i did not find the answer myself yet - i think i fooled myself but cannot find where. Idea is to adapt an example i found here for a shared preferences class:  public class spHelper {      private final Context context;     private final SharedPreferences sharedPrefs;     private String strTest;      public spHelper(Context context) {         this.context = context;         sharedPrefs = context.getSharedPreferences("demo", Context.MODE_PRIVATE);     }      public String getStrTest() {         strTest = sharedPrefs.getString("keyTest","yet empty");         return strTest;     } }   Then i tried to use it, but i get the error above in the last line of code - why? Maybe i should have a break.. i feel its something quite stupid.. but i don't see it - please open my eyes..  public class MainActivity extends AppCompatActivity {      @Override     protected void onCreate(Bundle savedInstanceState) {         super.onCreate(savedInstanceState);         setContentView(R.layout.activity_main);           TextView t = (TextView) findViewById(R.id.txtInfo);         spHelper sph = new spHelper(this);         t.setText(spHelper.getStrTest());      } }


Given two numbers $A$,$B$. Let $G$ be the GCD of two numbers. I need to tell the values of $X$ and $Y$ such that   $$ G = X A + Y B $$  How to approach this problem ? Like if we have $A=25$ and $B=45$ then GCD , $G=5$.  So $5 = 2 \times 25 - 1 \times 45$. Hence here $X=2$ and $Y=-1$.  So how to tackle this problem for given $A$ and $B$?  My try :  int a=25; int b=45; int s=0; int old_s=1; int t=1; int old_t=0; int r=b;     int old_r=a; while(r!=0){     int quotient = old_r / r;     old_r = r;     r = old_r-quotient * r;     old_s = s;     s = old_s - quotient * s;     old_t = t;     t = old_t - quotient * t; } cout<< old_s << " " << old_t<<endl; cout<< old_r <<endl; cout<< t << " " << s <<endl;   Whats wrong with this code ?


What is the proper way to re-throw an exception in C#?

I have a question for you that stems from my partner doing things a different way than I do.  Is it better to do this :  try {     ... } catch (Exception ex) {     ...     throw; }   or this:  try {     ... } catch (Exception ex) {     ...     throw ex; }   Do they do the same thing? Is one better than the other?


How to downgrade Ubuntu Hirsute Hippo (21.04) to Focal Fossa (20.04) LTS? Or that's not actually an option?


I imported a .dae file but there seems to appear line like objects (and circles at the end of it) starting out from the center of the world. Can you tell me what they are and can it be removed?  But when I open the same environment (.dae file) in another application, I get a proper environment.


Strange behavior in simple command line program

I'm trying to create a Java guessing game, but the first part I'm working on is having issues and I would like some help. The program first asks a user to input a number, then the program asks them to confirm whether their number is what they inputted. If they enter yes to whether they inputted the correct number, it currently just outputs "bru". If no is inputted then they re-enter the input number and the cycle will go on until the user correctly inputs their number and confirms it. I'm trying to accomplish this with a while loop. Unfortunately when I run the program everything works fine until I'm asked to enter yes or no to confirm my number. If I enter yes it still asks for me to re-enter the number. But if I enter no and then I say no again confirming my number it gives me the output for when I confirm that I inputted the correct number. import java.util.Scanner; import java.util.Random;  public class Assignment6 {      public static void main(String args[]) {         Scanner input = new Scanner( System.in );         System.out.print ( "Please enter the upper bound of the secret number.");         int UpperBound = input.nextInt();         System.out.print ( "The UpperBound you entered is" + " " + UpperBound + "." + "Is that correct?" + "" + "If yes please enter yes, if not please enter no.");         String TrueOrFalse = input.next();         while (TrueOrFalse == "no" | TrueOrFalse == "No");         {             System.out.print ( "Please enter the new upper bound of the secret number.");             UpperBound = input.nextInt();             System.out.print ( "The UpperBound you entered is" + " " + UpperBound + "." + " " + "Is that correct. If yes please enter yes, if not please enter no.");             TrueOrFalse = input.next();         }         System.out.print ("Bru");     } }


Difficulties in understanding basic energy equation in quantum mechanics

While reading a text book about basics of Quantum Mechanics, I came across a situation in which it is said that   $E=\hbar\omega$ and also  $E = \frac12mv^2=p^2/2m$  where   $h$ Planck's constant  $\hbar=\frac{h}{2\pi}$ Planck's reduced constant  $\omega=2\pi f$ angular frequency   $m$ mass  $v$ velocity  $p$ momentum  But if I take the first definition,E=(h/2pi)*w,then  E=(h/2pi)*2*pi*f (because w=2*pi*f)   = h*f   = h*(v/λ)       (because v=fλ)   = p*v           (de-Broglie's wave-particle duality p=h/λ )   = mv*v          (because p=m*v, the momentum)  E = m*v^2   This is not same as definition $E=\frac12mv^2$.  What am I missing in the derivation above?


I'd like to use a relative div to fill it up with inline-block-elements aligned next to each other that all got the same width & same height (= squares).   So if there are n elements the relative div should get scrollable in x-direction. This is working so far as you can see in the example code below:    .outer {   position: absolute;   width: 100%;   height: 100%; }  .parent {   position: relative;   width: 90%;   height: 40%;   overflow-y: hidden;   overflow-x: scroll;   text-align: center;   white-space: nowrap;   background: red; }  .item {   background: yellow;   display: inline-block;   width: 4%;   margin: 0% 3%; }  .item::after {   content: "";   display: block;   padding-bottom: 100%; }

     But now I'd like the item-elements (yellow squares) to vertical align into the red parent-div (relative div) so that the distance from top to center and from bottom to center is identical. Please have a look at this image:    Note: I do not want to change the hierarchy (keep the parent elem relative & the outer elem absolute, etc...)  How can I achieve this?


Looking for a bibstyle for biblatex I have never encountered

A journal I like to submt to requires a bibliography style that appear do require lots of hacking. Before I start, I looked at the biblatex manual and it appears the style mingles different styles. Maybe somebody recognizes a known bibstyle from biblatex that corresponds to the examples:  Journal article     Hamburger, C.: Quasimonotonicity, regularity and duality for nonlinear systems of partial differential equations. Ann. Mat. Pura Appl. 169, 321–354 (1995)   Article by DOI     Sajti, C.L., Georgio, S., Khodorkovsky, V., Marine, W.: New nanohybrid materials for biophotonics. Appl. Phys. A (2007). doi:10.1007/s00339-007-4137-z   Book     Geddes, K.O., Czapor, S.R., Labahn, G.: Algorithms for Computer Algebra. Kluwer, Boston (1992)   Book chapter     Broy, M.: Software engineering — from auxiliary to key technologies. In: Broy, M., Denert, E. (eds.) Software Pioneers, pp. 10–13. Springer, Heidelberg (2002)   The citestyle is authoryear, no worries there. But the stuff above gives me a headache, especially that year all the way at the end and abbreviated journal names.  Any ideas?


Where does $(A\Delta B)\Delta C = ((A\Delta B)\cup C)\cap ((A\Delta B)^c \cup C^c)$ come from?

I am working with operations and sets, and have been reading about the symmetric difference of AΔB. The textbook has explained some equivalences of this difference, such as:  $$(A\setminus B)\cup(B\setminus A)$$  $$(A\cap B^c)\cup(B\cap A^c)$$  $$(A\cup B) \setminus (A\cap B)$$  The textbook has also explained satisfactorily why the complement of $A\Delta B$ is $(A^c\cup B)\cap (A\cup B^c)$.  I am reading now the proof of the associativity of the symmetric difference for three elements, and can follow the argument except for the first equality, which seems to have been produced out of the blue (I don't see anything in the textbook previously that verifies it):  $$(A\Delta B)\Delta C = ((A\Delta B)\cup C)\cap ((A\Delta B)^c \cup C^c)$$  How is this warranted?  Thanks in advance for your ideas.


What is the difference between "don't care" and "don't mind"?

From an :     “don’t mind” sounds very polite and gentle. It’s like the person is   saying “It’s ok with me.”; however, “don’t care” sounds stronger and   it’s like the person is saying, “It doesn’t matter to me”.`   I'm curious: is it really just a matter of stronger emphasis, or is there more to it?


I made an edit to a post and a editor stole it

A couple of days ago I made an edit to a post, after a few minutes, I guess a reviewer, edited the post precisely how I edited the post and did not say I edited the post.   Is there anything that can be done from people stealing edits?


How to Manage Multiple Gmail Accounts on the Same PC/Browser?

I have a Gmail address with my employer, a personal Gmail address, and a Gmail address for my personal business.  My girfriend also has a Gmail address she uses on the same PC. Currently this requires much logging in/out to switch between everything because besides Gmail I use Google Docs, App Engine, and other sites that use the same credentials.  Is there a way to keep all of these accounts open in the same browser at the same time without constantly having to log in/out?


Shape of confidence interval for predicted values in linear regression

I have noticed that the confidence interval for predicted values in an linear regression tends to be narrow around the mean of the predictor and fat around the minimum and maximum values of the predictor. This can be seen in plots of these 4 linear regressions:    I initially thought this was because most values of the predictors were concentrated around the mean of the predictor. However, I then noticed that the narrow middle of the confidence interval would occur even if many values of were concentrated around the extremes of the predictor, as in the bottom left linear regression, which lots of values of the predictor are concentrated around the minimum of the predictor.  is anyone able to explain why confidence intervals for the predicted values in an linear regression tend to be narrow in the middle and fat at the extremes?


Let $A$ be a $  2 \times  2 $ matrix and  a positive integer $k \geq 2$. Prove that $A^k = 0 $ iff $A^2 = 0$.  I can make it to do this exercise if I have $ \det (A^k) = (\det A)^k $. But this question comes before this.  Thank you very much for your help!


Remove Actions/Filters added via Anonymous Functions

That's a freaking bad practice I must say. Spent last two hours finding a solution to remove actions and filters added via Anonymous functions.    This is the code used on a Parent Theme, and I need to remove it.  /**  * Add custom columns to admin comments grid  *  * Rate that user set.  */ add_filter( 'manage_edit-comments_columns', function( $default ) {     $columns['smr_comment_rate']  = __( 'Rate', 'txtdmn' );      return array_slice( $default, 0, 3, true ) + $columns + array_slice( $default, 2, NULL, true ); });   Got , played with it heavily, but no help. So, is there any other alternative that will remove actions/filters added via anonymous functions?  Thanks


Why do potential supervisors not reply to my emails?

I have contacted so far 5 supervisors for my master program that I want to enroll in ( applications open late September and admission January 2017) .   I emailed various faculty in the most polite way possible. Introduced myself, showed that I am interested in pursuing a research career in their field, talked briefly about my achievements  but only one supervisor replied. I am not sure why is this happening ? I have attached my transcript ( I am not a high GPA student but I received excellent grades for my thesis and seminar courses).     I emailed them this week ( and one hardcore researcher last Friday)   what could be the reason ?  note : I am intending to apply for the biomedical engineering program (one I really want to pursue) , most students have engineering undergrad however , I have a biotechnology degree. Could that be the reason? the department said my biotechnology degree is acceptable for that admission purposes.


For what conditions on sets $A$ and $B$ the statement $A - B = B - A$ holds?

The obvious response is $A = B$. But I came up with another response. I can't figure out what's my bias.  Lets say    $S = A - B$ $T = B - A$   Proving $S=T$ means proving $S \subseteq T$ and $T \subseteq S$  Let's start with $S \subseteq T$  For any $x \in S$ :   $x \in A$ $x \notin B$   if $S \subseteq T$, $x \in T$ and :    $x \in B$ $x \notin A$   There is no $x$ giving satisfaction, so $A$ and $B$ are empty.  I prove $T \subseteq S$ by symmetry  My solution is : $A = B = \emptyset$  What's wrong ?


I have a VPS that keeps getting shut down because of excessive inbound or outbound traffic. I thought I had a virus on my server and with it shut down so was my email server. So I got a new VPS running clean install of Axigen Mail Server. Migrated all our emails over to it and shortly later it gets shut down again. Keep in mind, the old server I just used Postfix with Roundcube to handle emails. Not an actual email server solution like Axigen.  Here's what my hosting company says:  I've restored the VPS.  Looks like excessive inbound or outbound traffic.  Thu, 05 Feb 2015 21:43:16 -0500  VPS 4273 (192.227.159.235) has 41554 conntrack sessions Thu, 05 Feb 2015 21:43:22 -0500  VPS 4273 (192.227.159.235) has 41566 conntrack sessions Thu, 05 Feb 2015 21:43:26 -0500  Possible DoS VPS 4273 (192.227.159.235): 170862 pps during 5 second interval Thu, 05 Feb 2015 21:43:32 -0500  VPS 4273 (192.227.159.235) has 41499 conntrack sessions Thu, 05 Feb 2015 21:43:32 -0500  Possible DoS VPS 4273 (192.227.159.235): 162520 pps during 5 second interval Thu, 05 Feb 2015 21:43:36 -0500  VPS 4273 (192.227.159.235) has 41507 conntrack sessions Thu, 05 Feb 2015 21:43:48 -0500  VPS 4273 (192.227.159.235) has 56126 conntrack sessions Thu, 05 Feb 2015 21:43:56 -0500  SUSPENDING VPS 4273 (192.227.159.235); it has 56126 conntrack sessions   They said at one time that there was a script on MY server initiating something out there causing the inbound traffic. I can't get to any logs because as soon as they start the VPS it gets automatically shut down from excessive traffic.   ITS THAT BAD.  Anyways, I need a course of action to tell them what I can do to clean it up. If I can get SSH'd into the server, I'll block ALL traffic except SSH and try to figure it out there. But I'm not sure what to look for.  I thought it was an email someone opened on the server. They said something suspicious looking was in one of the email files. But Axigen doesnt have files for email like postfix does. I can't just go to /var/vmail/....to get to them


Are the lightsaber battles in the original trilogy slower and less acrobatic than those in the prequel trilogy?

Obviously as filmed the lightsaber battles in the original trilogy are slower and less acrobatic than those in the prequel trilogy. Is this canon? There's a popular question that basically asks why this is and most of the answers are out of universe explanations about lightsabers originally being meant to be heavy, improvements in CG, and that the choreographer in the original trilogy was an Olympic fencer while the choreographers in the prequel trilogy were stuntmen. This implies that the lightsaber battles as shown are not meant to be taken literally.    On the other hand, the lightsaber battles tend to be taken more literally in questions comparing the lightsaber skills of Anakin and Darth Vader and various explanations are given for why Darth Vader doesn't do flips.  I've always figured that when a lightsaber battle happens it should just be understood that <epic battle takes place> and the exact movements are unimportant. If that weren't the case, it would be sensible to ask silly questions like "Why are Qui Gon Jinn and Obi-Wan playing around in the battle with Darth Maul at the end of Episode I? Why are they flipping around instead of trying to kill each other? Who are they trying to impress?"


Show that for any measurable function $f$ in a measure space, we have: $$ ||f||_p \leq \max\{||f||_r ,||f||_s \} $$ whenever $0<r<p<s$. Now by splitting the integrals into parts where $f>1$ and $f\leq 1$, we could easily show that $$ ||f||_p \leq ||f||_r+||f||_s \ $$ But I have no idea how to show the stronger inequality as above.


I hope I don't regret this vs I hope I won't regret this

What is the difference between these two?  From my understanding:  I hope I will not regret this - this means he has hope that in the future he will not regret something he has done (or will do).  I hope I do not regret this - because of using "hope" before "don't" it seems he is referring to future as well (if I understand that correctly). I can't see a difference in meaning from the first one.  So do they actually mean the same or there is a difference?


For which $k\in \Bbb N$ does $x^2+x+1$ divide $ (x + 1)^{2k}+x^{2k} + 1$?

I tried many attempt to solve this problem but failed every time.  The polynomial $x^{2k} + 1 + (x + 1)^{2k}$ is not divisible by $x^2 + x + 1$. Find the value of $k \in \mathbb{N}$  My question is: can this be solved with using remainder/factor theorem only?  I haven't learned Number Theory yet so maybe I don't know sufficient number of lemmas.


How can I get lines to break automatically using the LaTeX listings package?

I am using the listings package to include sample Perl source code in LaTeX. I included the package with \usepackage{listings}, and used the following code:  \lstset{language=Perl} \lstset{commentstyle=\textit} \lstset{frame=shadowbox} \begin{lstlisting}[numbers=left] $subject = "<owamp:subject xmlns:owamp=\"http://ggf.org/ns/nmwg/tools/owamp/2.0/\" id=\"subject\">\n"; \end{lstlisting}   The resulting output is:    The line doesn't seem to breaking, but I read that lines break automatically when using the listings package. This line is the entire PDF snapshot of the code.  Am I doing anything wrong as far as the code is concerned?


Is angular displacement a vector? How is work defined in rotation if it isn't?

Is angular displacement has a direction as well ie is it a vector because angular velocity has a direction and it is defined as rate of change of angular displacement hence it must also be a vector .  Eg consider rotation about a fixed axis it has many similarity with linear one dimensional motion. Like work done by force is force times dx similarly here work done by torque is torque times angular displacenment and must be dot product of two vectors so am I correct is angular displacement a vector as well along the axis of rotation  It isn't according to the answer so how can we define work for rotation about a fixed axis ? Work by definition is scalar product of two vectors then shouldn't it be not defined or is conventionally Work defined in some other way in this case ?


There is Graph which is connected with Submultiples. (I am sorry but I don't know what this is called.)  For example,  10-node Graph has 10 nodes, 18 edges. node 1 connect all the other nodes. node 2 connect node number 2,4,6,8,10. node 3 connect 3,6,9. node 4 connect 4,8. etc.  This is Planar graph of 10-node graph.    Question 1.  It is easy to check if 11-node graph is planar or not. (Just put the node no.11 and connect with no.1) But, Is 12-node Submultiple graph planar? And how can I prove it? (I saw  But I cannot find the graph of $K_{3,3}$ If there is, please show me with picture.  Question 2.  If 12-node Submultiple graph is possible, How many node are possible? (I mean, 14 or 15 nodes graph is planar? or not?)


I have to make an app where the user inputs and then the AI responds but when I input some text and press send it gives me the message "Unfortunately, app has stopped".  Here is my code:  Here is the code for sending:  <Button         style="?android:attr/buttonStyleSmall"         android:layout_width="wrap_content"         android:layout_height="wrap_content"         android:text="@string/Button"         android:id="@+id/Send_btn"         android:layout_alignParentBottom="true"         android:layout_alignParentRight="true"         android:layout_alignParentEnd="true"         android:onClick="Zdenka"   />...   Here is the start of the .java file:      EditText Text, OdgBox;     String odg;      @Override     public void onCreate(Bundle savedInstanceState) {         super.onCreate(savedInstanceState);         setContentView(R.layout.activity_my);          EditText Text = (EditText) findViewById(R.id.Txt); //User input         Button Btn = (Button) findViewById(R.id.Send_btn); //Send button         TextView Output = (TextView) findViewById(R.id.TextView); //AI output      }...   And the last part of the java file:  ... public void Zdenka (TextView Output, EditText Text, String odg) {      String Text1 = Text.toString().toLowerCase();       if (Text1 == "živjo") {          odg = "Živjo";      }     else if (Text1 == "zivjo") {         odg = "oj";     }     else{ odg = "Ne razumem."; }        Output.setText(odg);   Thanks for the help!


How to log-in to ssh without password? Note I do not have root previledge of server

I can only login to server as a non-root user. How can I make ssh login password-less?


Are any of my mods not cross-compatible?

I want to play Minecraft (modded) with my brother but I do not know if they will be Survival Multiplayer (LAN) compatible or if they will be compatible with each other. The mods are:    Rei's minimap Industrial craft Optifine Balcons Weapons Backpacks mod Timber mod Millenaire More arrows mod Recipe book  Death chest Flashlight mod   Do any of these mods have known incompatibilities with one another? How would I workaround it if that is the case?


I'm writing some mathematical formulas and I wonder if I can autoformat them. Here is an example:  \( {n(1+\frac {1} n)n(1+\frac {2} n)...n(1+\frac {10} n) \over n(1-\frac {1} n)n(1-\frac {2} n)...n(1-\frac {10} n)} =  \frac{n^{10}}{n^{10}} = 1 \)   Do you know what this thing means? I have no idea also, I have to compile it, to see the content. What I want is to recognize it from source code for fast editing. Any chance that I can have this kind of feature for offline editor? I'm using TeXworks right now.


I'm having some fun writing simple applications that use pthreads. Is it possible for a thread to get information about which core it is running on? I'm trying to play around with the thread affinity of a thread, so it would be really useful to know the details of which core a thread would be running on.


Physical reasons for metric definition in special relativity

I am working through "General Relativity" by Wald, and am currently going through the brief section on Special Relativity. The spacetime metric is defined as $\eta_{ab} = \sum\limits_{\mu, \nu=0}^3 \eta_{\mu,\nu} (dx^\mu)_a(dx^\nu)_b$ where $\eta_{\mu, \nu} = \mathrm{diag}(-1,1,1,1)$. My question is, what is the physical motivation for this? The last three terms in the summation I understand - they give the physical distance between two events. But what about the negative sign infront of the "time term"?


The commath package use the TeX command \ifinner to select between inline math mode and display math mode. Because of this, it fail to work properly with some display math environments.  In the breqn package, we find:     The test \ifinner is unreliable for distinguishing whether we are in a displayed formula or an inline formula: (...) So we provide a more reliable test. But it might have been provided already by the amsmath package.   The more reliable test should be \if@display but only replace \ifinner with  \if@display in commath.sty not work. Any suggestion?


What determines whether a unit is a base unit?

I've had base units explained to me as units that cannot be broken down into a combination of other units. The Ampere is considered a base unit, however it can be written as coulombs per second.  Is there a better explanation of SI base units?


I am a Ph.D. student in pure mathematics and I am in my final year of graduate studies. I found that academia is not suited for me: unstable job, low salary, and a self-sacrifice culture that it is based on the motto "Publish or Perish". I want to ask you what are the odds to get a good job with a Ph.D. in pure mathematics? I am truly lost. I consider myself a big failure. I have expended three years of my life in pursuing a thing that it is useless and purely theoretical. Currently, I only want to make some good money in the industry. I want to ask you: what can a pure mathematician do in the real world? Is there any kind of investment banking or hedge funds interested in hiring mathematicians holding a Ph.D. in pure mathematics and a master´s degree in big data and business analytics? Thank you very much for any response.


Problem  According to , the Gamma function is computed as  $$ \Gamma(z)=\int_{0}^{\infty} x^{z-1} e^{-x} d x $$ where $z$ is a complex number.  Using integration by parts, it is easy to verify that $\Gamma(z)=(z-1)\Gamma(z-1)$ and therefore I have $$\Gamma(z) = (z-1)!$$ However, I am not sure how do I compute something like $4.7!$ (or value of any real number). I tried $4.7\cdot 3.7\cdots \cdot 0.7$, but it does not give the correct result as verified by scipy.math.gamma function.


What colors to choose for colorblind people?

I'm creating a game. Color coding is its main gameplay feature. What colors should I choose so the game will be colorblind-friendly? (I need 4 colors)


Is it important to dress in formal clothing for a postdoc interview?

Just curious is it crucial?  It's one of the reasons I like academia that I don't need to care too much the boring stuff like wearing suits.


The refered . The commands used in order: 1)wget https://desktop-download.mendeley.com/download/apt/pool/main/m/mendeleydesktop/mendeleydesktop_1.19.4-stable_amd64.deb 2)sudo dpkg -i /mendeleydesktop_1.19.4-stable_amd64.deb 3sudo apt -f install It fails as soon as I input my password as required in the second step. This is what the terminal shows me: dpkg: error: cannot access archive '/mendeleydesktop_1.19.4-stable_amd64.deb': No such file or directory  Also, in the Mendeley website the current versions of the software seem to be incompatible with 20.4.


I've noticed mains voltage tends to be 120V +/- 10% for 108-132VAC.  How would you go about building a regulated AC-to-AC power supply which works off of mains and outputs 120VAC with a much lower (less than 1%) variation?  The output must be a sine wave at 120Vrms.  Edit: For those asking, the output would be fairly low, 1.5A - 2A, 2.25A max.  Circuit to be powered:  Expected input: 0V-5.5KVrms sine wave at 60Hz  Simulated output: +/- 0-100KV DC.  The objective here would be to connect components in the order:  mains --> power conditioner --> variac --> 1:46 center-tapped transformer insulated for high voltage --> Cockcroft Walton Multiplier outlined above.  To achieve a variable 0-100KV DC (effectively 0-200KV DC with both channels factored in) power supply.  I am not certain the power conditioning stage is the way to go but assumed it would be since it is much easier to stabilize low voltage (120Vrms) than it is to stabilize high voltage (5.52KVrms.)  Relatively minor ripple of 5% will grow into +/- 10% by the end of the CW stage at full power, yielding around 20KV off of the expected value - not an insignificant amount.


Prove that if $ \gcd(a,m) = 1 $ and $ a b \equiv a c ~ (\operatorname{mod} ~ m) $, then $ b \equiv c ~ (\operatorname{mod} ~ m) $.

Problem. Prove that if $ \gcd(a,m) = 1 $ and $ a b \equiv a c  \pmod m $, then $ b \equiv c \pmod m $.   I have $ m | a b - a c $, or $ m | a (b - c) $, and I know that if $ \gcd(a,m) = 1 $, then $ n | b - c $. I just don’t know what lemma I can use here.


I'm trying to compile a latex file from coq on Mac and get the following error:  File utf8x.def not found.  Where can I find utf8x.def?  Most of the other answers pertain to ubuntu and don't work on mac.


C# dynamically set property using lambda?

I have a tree constructed using a TreeNode class where each node has an Amounts object. The Amounts object is a simple class that houses some decimal values. E.g.  public class Amounts {     public decimal Amount1 { get; set; }     public decimal Amount2 { get; set; }     ... }   I need to be able to perform some code for each individual property independently, and what I'd like to do is somehow pass one of the Amounts properties to this method using a lambda or similar but I can't quite work out how to do this (I've been a while off the tools unfortunately). I don't particularly like the idea of passing a property name string so I can use reflection SetPropertyValue method.  I want the traversal method to look something like the below. I'm aware that Linq supports a Sum method but I have just used this as a simplified example, with the actual calculation performed being more complex.  public void Traverse(Func<ContributionAmounts, decimal> getter) {     foreach (var child in this.Children)     {         getter(this.Amounts) += getter(child.Amounts);     } }   Rather than having a separate method for each amount, I'd like to do be able to call it something like below:  Traverse(a => a.Amount1); Traverse(a => a.Amount2);   The code above does not work as the value returned by the Func is a read-only decimal value, rather than the decimal property (e.g. Amount1).  I'm not sure if I have explained the requirement very well, but hopefully enough to get a pointer in the right direction.  Thanks, John


Unable to install an OS on Mac (prohibited sign)

I had an issue with my MacBook Air "Core i5" 1.6 13" (Early 2015) (MacBookAir7,2) and after repeated problems I decided to wipe the computer and give it a clean slate.   I downloaded a copy of Mavericks and Yosemite off the internet and created a bootable external hard drive with an iMac. I've tried both Mavericks and Yosemite but always get the prohibited sign.   I tried cmd + S while booting with the hard drive and it said "This version of Mac OS X is not supported on this platform" for both versions of OS X. The funny thing is I tried the bootable hard drive with the old iMac I have in the house and it booted into the installer just fine.   What can I do to fix this issue?


What should be the approach to draw the graph of the above inequality with modulus? Should I need to begin like this? $$|y| = 1 - |x|$$


Show that $x^n -1 \mid x^k -1 \Leftrightarrow n \mid k$

Problem: Show that $x^n -1 \mid x^k -1 \Leftrightarrow n \vdots k$   My solution: For the inverse statement we have $n \vdots k \Rightarrow n=kt \Rightarrow x^n = x^{kt} \Rightarrow x^n-1 = (x^k)^t-1 = (x^k-1)((x^k)^{t-1} + \dots + 1) \vdots (x^k-1)$.  How to show that the $``\Rightarrow"$ statement?


Indian green card holder traveling from NY to India with a layover of 11 hours in London. Do I need a transit visa to go and sightsee London?


I you have photon polarized in a given orientation going through a BBO crystal... what orientation will have the entangled photons going out?


Help me answer this Number Theory question on GCD (involves exponents)

Basically I need a good hint how to solve the problem.I have solved it partly.     $gcd(2^a-1,2^b-1)=2^{gcd(a,b)}-1$.   I have reached till:     $gcd(2^a-1,2^b-1)=gcd(2^{a-b}-1,2^b-1)$   How to proceed from here.  Please give detailed answer if you are using special manipulation or property please do explain how do you use it in this problem to solve it.  Thanks.


Can tag gold-badge holders take off their golden hat when casting close votes?

It was  that when a tag gold-badge (TGB) holder casts a close vote for dupes, the question gets closed immediately. It  in what order a TGB holder casts their vote.  I have gold tag badges only on Sci-fi & Fantasy Stack Exchange, which I mostly refrain from using due to my tendency to avoid the arguments which nearly always occur when one user hammers a question instead of a community consensus via a review (unless I am up for an argument, which is very rare).  But yesterday, on Stack Overflow, . The fourth voter there holds a gold badge in the iOS tag. Yet, the question wasn't closed until it got a fifth vote. So that got me thinking: Is it possible for TGB holders to take off their golden hat and vote as a normal user? Or do gold-badge closing privileges vary based on where they are coming for i.e. A review requiring five people to agree, irrelevant to the badges they hold while a direct close vote outside the review queue would instantly close the post?  If they can take off the golden hat, how does one do that?


Difference between Random forest vs Bagging in sklearn

I know that Random forest uses Bagging, but how does ensemble give a single prediction in sklearn Bagging vs Random forest? Also, I do not understand why in Bagging you not need to choose a tree estimator, while not in RF?  other than this, are the other steps the same? wht are main implementation differences in sklearn Bagging vs Random forest?  bonus points if you have "explain like I'm 5 years old" simple example using sklearn please.


Correlation of beta coefficients from linear regression

Suppose that I have a linear regression: $ y = \beta_{0} + \beta_{1}x_{1} + \beta_{2}x_{2} + \epsilon $ I would like to demonstrate that one regression coefficients is significantly greater than the other:  $H_{0} = \beta_{1} > \beta_{2}$ or $H_{0} = \beta_{1} - \beta_{2} > 0$. Therefore, I would conduct a t-test: $t = \mu_{d} / \sigma_{d} $  with $\mu_{d} = \beta_{1} - \beta_{2} $ and $\sigma_{d} =  \sqrt{\sigma_{\beta_{1}}^2 + \sigma_{\beta_{2}}^2 - Cov(\beta_{1}, \beta_{2})}$ and $Cov (\beta_{1}, \beta_{2}) = \sigma_{\beta_{1}} * \sigma_{\beta_{2}} * \rho_{\beta_{1}, \beta_{2}} $ As $\beta_{1}$, $\beta_{2}$, $\sigma_{\beta_{1}}$ and $\sigma_{\beta_{2}}$ are known from the regression results, the only mising part is the correlation of $\beta_{1}$ and $\beta_{2}$. However, I don't know how this can be computed and would be really thankful for any help!


So I'm trying to get this:    And I've calculated $z^4=16 \left( \cos (\frac{- \pi}{3})+ \sin ( \frac{- \pi}{3}) \right)$  So I'm trying to find the roots using the formula:  $ r^{1/n} = \left( \cos ( \frac { \theta + 2 \pi \cdot k}{n}) + i \cdot \sin ( \frac{ \theta + 2 \pi \cdot k}{n}) \right) $  But my result does not equal. Take a look:    This is for $k=0$.  What am I doing wrong?


This is the code in my template.php file.  function studiga_theme_theme($existing, $type, $theme, $path) {         $items['add_property_form'] = array(         'render element' => 'form',         'template' => 'node--14',         'path' => drupal_get_path('theme', 'studiga_theme') . '/templates/node',     );      return $items; }    function custom_add_property_form($form, &$form_state) {     $form['first_name'] = array(         '#type' => 'textfield',         '#attributes' => array('placeholder' => t('First name')),     );     $form['last_name'] = array(         '#type' => 'textfield',         '#attributes' => array('placeholder' => t('Last name')),     );     $form['address'] = array(         '#type' => 'textfield',         '#attributes' => array('placeholder' => t('Address')),     );     $form['city'] = array(         '#type' => 'textfield',         '#attributes' => array('placeholder' => t('City')),     );     $form['state'] = array(         '#type' => 'select',         '#options' => array(             'default' => 'State',             '...' => '...',         ),     );     $form['zip'] = array(         '#type' => 'textfield',         '#attributes' => array('placeholder' => t('Zip')),     );     $form['email'] = array(         '#type' => 'textfield',         '#attributes' => array('placeholder' => t('Email')),     );     $form['phone'] = array(         '#type' => 'textfield',         '#attributes' => array('placeholder' => t('Phone')),     );     $form['submit'] = array(         '#type' => 'submit',         '#value' => 'Submit',     );      return $form; }   This is the code in node--14.tpl.php.                                          Contact Information

         <?php print render($form['submit']); ?>

     But no fields are appearing - what am I doing wrong? You can't have a straight forward  in a tpl.php file can you?


: Old English butan, buton "unless, except; without, outside," [...]  I don't know Old English. From the étymons overhead, how did but  to mean    |adverb| = 1. No more than; only  ? What can explain the semantic shift? I didn't understand , because English is not my first language  :   In sense: Only. An elliptic development of the conjunction: see .  a. By the omission of the negative accompanying the preceding verb (see ), but passes into the adverbial sense of: Nought but, no more than, only, merely.    I understand Shakespeare's use in . Thank you all.


I am pretty sure this is a common beginner mistake and it is already answered, but i couldn't find anything helpful. So since this happened to me twice, I would like to know where my mistake is and what i can do to prevent this. Also it would be awesome if there was a way of fixing this without losing my data.  What happened is, I created another ext4 partition alongside my existing Xubuntu system (consisting of a EFI and a ext4 partition) and then installed Peppermint on it (the first time this happened it was Windows 7, so i don't think the OS matters at all). Both OS worked perfectly fine, but when I decided to delete the new partition (the one with Peppermint), i couldn't boot it any more, instead it would show me a grub console where I could enter commands. I can still boot from a live Disc tho.  Thank you for helping and being an awesome community allaround. Johannds


Possible Duplicates:             Voting on questions played a big role in the site when we didn't have the option to comment on, close, migrate, flag, or edit questions which did not fit the site or required modification to be useful and usable.  As it is, question votes are not much more than a popularity contest, and a lot of bandwidth is taken up on Meta regarding question votes.  Notably:        In most cases a downvote is being given where a good edit should be used instead, or a comment indicating that the question user needs to provide more information.  People are also downvoting in the case of duplicates (or suspected duplicates) when they don't want to do the work of finding the duplicate.  There is no need to downvote to 'alert' other users that a question isn't worth spending time on - if it's bad enough that it can't be fixed, and so bad that you want to be sure others avoid it then it's not worth keeping open.  These are all situations where the person downvoting should be taking a different action.  , and several questions have thrown ideas at how to increase question upvoting artificially, and a  was even implemented to encourage this behavior.  Given all this, I am now convinced that voting on questions is an unnecessary distraction.  Voting no longer provides any useful information about a question, and there are more than adequate means of fixing or removing questions that need work.  Voting makes more sense for sites like Meta where questions aren't really questions, but suggestions and discussions.  For purely Q/A sites such as SO, SF, SU, the voting is superfluous.  The only two possible positive things voting now provides are:   A way for users at lower rep levels to have a voice when they are unable to perform many of the other functions that are needed to fix a question (I contend this is useless, but perhaps they need some sort of outlet) A 'hook' to get new users into the reputation game (which fails frequently because questions aren't getting upvotes, especially questions from new users)   If that is truly the case, then we should consider removing question voting altogether, or removing the effect of question votes on reputation.   Am I wrong? What obvious and explicitly important role does question voting play in our community?


How do I prove that a subspace of a vector space $X$ is the null space of some linear functional on $X$? Say $\dim(X) = n$ and $Z$ is the subspace and $\dim(Z)=n-1$. Further, how to show that the functional is always uniquely determined to within a scalar multiple?  I'm having a difficult time coming up with a functional $f$ and don't understand how I would have to go about proving it unique to within a scalar multiple. Any help will be greatly appreciated.


Iphone App Rejected by apple App Store for 1.0 Binary Rejected

They are saying This app duplicates the content and functionality of other apps submitted by your but this is my first app to be submitted and I never submitted apps before. From Apple:   3 Design: Spam Guideline 4.3 - Design  This app duplicates the content and functionality of other apps submitted by you or another developer to the App Store, which is considered a form of spam. Apps that simply duplicate content or functionality create clutter, diminish the overall experience for the end user, and reduce the ability of developers to market their apps. The next submission of this app may require a longer review time, and this app will not be eligible for an expedited review until this issue is resolved. Next Steps  Review the Design section of the App Store Review Guidelines. Ensure your app is compliant with all sections of the App Store Review Guidelines and the Terms & Conditions of the Apple Developer Program. Once your app is fully compliant, resubmit your app for review.  Submitting apps designed to mislead or harm customers or evade the review process may result in the termination of your Apple Developer Program account. Review the Terms & Conditions of the Apple Developer Program to learn more about our policies regarding termination"  What should I do?


I'm implementing OLS linear regression without using the built-in functions in Matlab with normal equation:    I know this is probably very basic, but I want to double check, the input X yields a unique solution, right? I just figured that there could only be one solution because 1) it's a straight line and 2) because the term $\bf X_{ext}\bf X_{ext}^{T}$ doesn't give me a singular matrix warning when I perform inv() in Matlab, and 3) when I perform rank() on it in Matlab it says rank=2.   Is this correct, is there a more important reason, and is there any generalization to this that I should remember?   Also small side question, should I always subtract the mean to center my data?


How do I print the correspond key of a value of dictionary in Python?

I have already build a dictionary.Here is my dictionary:  mydict = {'to': 12, 'and': 35, 'Python': 26, 'for': 49}   I want to sort this dictionary by value (from max to min) and print result like this:  for 49 and 35 Python 26 to 12   I don't know how to do it.Any help will be appreciated! I have tried:    (1)  for key,value in mydict.items():         print(key,sorted(mydict.values(),reverse=True))  #int is not iterable   (2)use dict.keys() and dict.values(), but I don't know how to print correspond keys.  (3)I tried to build a list for value and build a new dictionary from value's list.But I don't know how to do it.  (4)try to convert int to string,but it can't be converted! Thank you so much!


Is there an application to log component temperatures to file?

I purchased a computer a month or two ago (core i7,  24gb ram, geforce gtx 590, windows 7 ultimate).  Within the last week it began to bluescreen regularly.  I tried lots of things (check hds, check memory, reinstall windows etc..) but it still bluescreened.   At the time my temps were as follows...  CPU - aprox 40/50c. GPU - arpox 60 idle,  aprox 90 during heavy use. HDDs  - aprox 55c after the PC had been on a while.  I thought the 55c was ok,  but I have since realized it was probably too high and may have been the direct cause of the bluescreening.  I've installed a spare fan I had in the front of the PC blowing air in, (so there's airflow from front to back)  Since then, obviously, all my temps are down.  Especially the HDDs - three of them reach 30c and one has been up to 47c (it is some distance away from the airflow, in one of the 5.25inch drive bays)  I haven't had the PC on for as long as it would normally take to bluescreen yet,  but If it does I want to know what all the temps were right before the bluescreen.  I have tried Everest but it only shows me realtime temps or gives me the ability to create one-off reports.  I want something that can record all the temps to a file at 30 seconds intervals.  If the computer bluescreens I can load it up again and check the last entry in the file.  Side question:  Am I right in thinking 55c was far too hot for a HDD?  (It might have got higher than that before the bluescreens.. I don't know)  Another side question:  Is 47c too high?  This is actually why I am asking the main question - I am concerned that this one drive that isn't getting the benefit of the extra fan may still cause the computer to bluescreen.


Reading package lists... Done Building dependency tree        Reading state information... Done E: The package libwacom2 needs to be reinstalled, but I can't find an archive for it.   Running Ubuntu 16.04


Now it is proven that that medicine is harmful to people.  Now it is proved that that medicine is harmful to people  Here, are proved and proven interchangeable? .


Let $x,y,z$ be positive integers such that $x^2+y^2+1=xyz$.   Show that $z=3.$


Is this possible to modifying the .sty file?

Interested to modifying the fontawesome.sty file?


To get to the point - what's the defining differences between them? Alas, my current understanding of a spinor is limited. All I know is that they are used to describe fermions (?), but I'm not sure why?   Although I should probably grasp the above first, what is the difference between Dirac, Weyl and Majorana spinors? I know that there are similarities (as in overlaps) and that the Dirac spinor is a solution to the Dirac equation etc. But what's their mathematical differences, their purpose and their importance?  (It might be good to note that I'm coming from a string theory perspective. Plus I've exhausted Wikipedia here.)


Define $ f:\mathbb C\rightarrow \mathbb C$ by  $$f(z)=\begin{cases}0 & \text{if } Re(z)=0\text{ or }Im(z)=0\\z & \text{otherwise}.\end{cases}$$ Then the set of points where $f$ is analytic is:     (a) $\{z:Re(z)\neq 0$ and $Im(z)\neq 0\}$,   (b) $\{z:Re(z)\neq 0$ or $Im(z)\neq 0\}$,   (c) $\{z:Re(z)\neq 0\}$,   (d) $\{z:Im(z)\neq 0\}$.   my think all the options are correct. because if consider option a) then the function $f$ will be $f(z)=z$ and it is a polynomial function. hence analytic. but for option b) if let $Re(z)\neq 0\}$ but $\{z:Im(z)= 0\}$ then the function $f$ will be $f(z)=0$ and it is also analytic. similarly we can say every option is correct. Am I right? please help me.


Android NullPointerException when trying to display an intent message for an activity

I see a run time error at this line of code   TextView textView = (TextView) findViewById(R.id.textView);  textView.setText(message);   exception I am getting,  error:Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference


How to process console application closing

We do have console application:   namespace MyApplication {      public void Main()     {         try         {             AppDomain.CurrentDomain.ProcessExit  += (sender, eventArgs) => Stop();              Start();             Console.ReadLine();         }         finally         {             Close();         }     }      public void Start()      {         //...     }      public void Stop()      {         //...     } }   So if application is stopped proper (by pressing Enter in console window) Close() method is called from finally & AppDomain.CurrentDomain.ProcessExit  But when application is closed by Close button or terminated from Task Manager Close() method is not called at all.  Questions are:   Why finally block doesn't work? How to handle console closing by Close button?   UPD Even object's destructor is not called:  public class Watcher {     Action _start;     Action _stop;     public Watcher(Action start, Action stop)     {         _start = start;         _stop = stop;     }      ~Watcher()     {         _stop();     }      public void Start()     {         _start();     } }  // And using as: var w = new Watcher(Start, Stop); w.Start();   Destructor is not called!


Why is the current constant in a series circuit? I am confused as I thought that the charges closer to the negative terminal move with a greater velocity than the charges closer to the positive terminal at the moment the voltage is applied?


What permissions should a udev rule have?

What permissions should a udev rule have for a USB device? 644? 755?  For example on Ubuntu I'm looking at this file: /etc/udev/rules.d/99-lpcscrypt.rules


Every user should be allowed to put/read files in directory, but ONLY the FILE OWNER can delete their files

I'm doing an assignment for school and we have to create a directory where users are allowed to create, read and excecute files. So if user1 creates a file named 'file.txt' user2 should not be allowed to delete this file; however he can read the contents.


Where do I ask questions from the intersection of software engineering, translations, and linguistics?

This is a repost of a quickly closed question to make it clear that it has nothing to do with naming conventions. Naming conventions are, well conventions: following simple patterns and using simple terms referring to design patterns. This question deals with searching for an appropriate word (or words) which describes, or at least mentally associates with some abstract concept. When programming, I use thesaurus (and dictionaries) more than Google and Stack Overflow combined, especially in the case of frameworks and libraries expected to be used by many other developers and with longer lifetimes. If you are a programmer, you know how a concise name suggestive of the implemented contract is almost impossible and, in situations where a good name comes to mind, there are several connected classes which could be named the same, due to the deficiency of natural languages. Differentiating between them is the most frustrating part of the job for me. I do not subscribe to the Java school of 'long descriptive names' as they tend to not work that well in strongly typed functional languages (due to types of higher kinds and type bounds on type parameters) and for abstract concepts, at least not in the API. As a non-native speaker, despite a fair understanding of English, the mind associations and sums of usage that form the subtle differences between synonyms can elude me. I sometimes ask such questions on linguistic fora (or Facebook), but they almost always are far too abstract for non-programmers to fully understand and attract interest. On the other hand, some questions are quite simple, but require some programming knowledge (design patterns, algorithms and data structures, databases, etc.). An example of one would be:  I need a word describing a tag marking where a Thing came from which binds with a specific preposition, so X <preposition> Y strongly suggests Y as that term.  I used Origin and it was good: it has the proper association and is not a common word, but this caused conflict with ...". Another:  What do you call a generalization of a from clause of an SQL select which includes a where clause and, possibly, a group by clause, but is not yet a complete select?  They obviously don't belong on Stack Overflow, but the way I see them, they do not invite open discussions and are less opinionated than a lot of questions that do get asked and answered on these sites (setting the topic aside for a moment). A good answer can be argued for successfully, just as with choices done by book translators which encounter the same kind of problems, although even if for made-up words and fantastic entities, they rarely venture far into the abstract.


HTML: Adding OnClick event ignored if element is not visible

On my web page I have panels which contain various input widgets, some of which are Bootstrap button groups. The basic HTML for these looks similar to this:

         <button type="button" class="btn">Option A</button>

         <button type="button" class="btn">Option B</button>

         <button type="button" class="btn">Option C</button>

   The panels of inputs are generated via Knockout templates, and are shown or hidden depending on which menu item the user selects in a main menu tree. This is done using jQuery's addClass() and removeClass() to add or remove the hide class that's present in Bootstrap/AdminLTE. In both cases this class is just defined as display: none !important.  I have jQuery code that performs tasks when the user provides input. For the buttons, it looks like this:  $(".param-widget-buttongroup .btn-group button").on("click", function() {     // Do some stuff here - send messages to the device I'm controlling, etc. });   This is done after the Knockout data bindings are applied. It definitely used to work, and still does for my other non-buttongroup inputs - however, at some point in the last month or so of development it's stopped working, and I'm currently trying to work out why.  If I place a console.log() in the click handler function, nothing is printed when the button is clicked. However, reporting $(".param-widget-buttongroup .btn-group button").length at the point when I'm attempting to add the click handler returns a count of 152 (ie. all the buttons across all the panels), so the buttons are definitely being found.  I've eventually determined that if I execute $(".param-widget-buttongroup .btn-group button").on("click", function(){ console.log("Button pressed"); }) in the Chrome web console, I only actually see this on click if the button's panel is visible at the time I attach the handler. Buttons whose panels are not visible do not get that handler set on them, even though the number of buttons found by the selector is still reported as 152. Once the handler is attached, however, I can show a different panel and come back to the original one later, and the expected output will still be printed on click.  Is there any reason jQuery would decide not to attach the click handler if the item is hidden at the time? I've not had this issue with any of the other inputs I'm using (single buttons, text boxes, select boxes, ion range sliders, ...).  Alternatively, is there a way I can definitively check what click handler an element currently has? I've tried checking the $(...)[0].onclick value of the element, but regardless of whether the jQuery handler was attached successfully or not, this value is always null.


Microsoft licensing in a virtualized environment questions

I plan on deploying two physical servers which will run VMware ESXi and have a number of questions regarding Microsoft licensing. To note, all the VMs on the servers will be configured to run in ESXi's fault tolerance mode. This means that all the VMs on the secondary server will run in lock step with the primary server.   Would I need to buy Windows Server CAL licenses for each VM on one server? For instance 1 ESXi server has 2 virtual Microsoft servers running on it. Each virtual server has 25 devices (or users) connecting to it. The devices (or users) connecting to each VM would be the same. Would I need 25 or 50 CALs for the physical server? Would I need to buy additional Windows 2012 Datacenter Server licenses and the associated CAL licenses for the redundant ESXi server? Would I need to buy additional SQL 2012 Standard (or Business Intelligence) server licenses and associated CAL licenses for the redundant ESXi server? And although this doesnt pertain to a virtualized environment, when/how do CALs come in to play with IIS?   Thanks!


I need to view the saved WiFi passwords on my non-rooted Android phone

I have an LG Optimus 7 (not-rooted), and all my WiFi passwords are there. I want to view the saved WiFi passwords to transfer thm to my new Samsung Galaxy S3, but I don't know how.  I tried to search on the Internet and Google play for an application that would allow me to view this information, but I can't find one. Is there any way for me to accomplish this?


My Daughter Has Claimed to Change Gender, How Do I Address This As a Father

I have a daughter who is in the grips of a social media encouraged self identity crisis.  For the past 15 years nothing has ever made me, her mother, or herself double think her gender identity.  However, recently social media and a club at school have caused her to be socially engaged into dabbling in a gender identity that doesn't match her biological sexual identity.  This has historically never been an issue and I fully believe this is not an internal situation but rather a social situation. As a concerned and caring father how can I address this and bring my daughter back to the identity I truly believe she has and truly believe she herself holds internally despite temporary social influence which is pushing her away from that? Please do not frame challenge me.  That is against the rules of this site.


Review Rating not being displayed on Google

We have recently added a review section on our website with rich snippets. Structured Data Tool indicates no problem, but the star rating doesn't appear in Google search results. Could someone help me identify a possible reason and improve on it?


How to model non-negative zero-inflated continuous data?

I'm currently trying to apply a linear model (family = gaussian) to an indicator of biodiversity that cannot take values lower than zero, is zero-inflated and is continuous. Values range from 0 to a little over 0.25. As a consequence, there is quite an obvious pattern in the residuals of the model that I haven't managed to get rid of:   Does anyone have any ideas on how to solve this?


Proof that $(AA^{-1}=I) \Rightarrow (AA^{-1} = A^{-1}A)$

I'm trying to prove a pretty simple problem - commutativity of multiplication of matrix and its inverse.  But I'm not sure, if my proof is correct, because I'm not very experienced. Could you, please, take a look at it?     My proof:   We know, that $AA^{-1}=I$, where $I$ is an identity matrix and $A^{-1}$ is an inverse matrix. I want to prove, that it implies $AA^{-1}=A^{-1}A$   \begin{align} AA^{-1}&=I\\ AA^{-1}A&=IA\\ AX&=IA \tag{$X=A^{-1}A$}\\ AX&=A \end{align} At this point we can see, that $X$ must be a multiplicative identity for matrix $A \Rightarrow X$  must be an identity matrix $I$.  \begin{align} X = A^{-1}A &= I\\ \underline{\underline{AA^{-1} = I = A^{-1}A}} \end{align}


I opened snippet of the NSAssert and found this:  do {                \     __PRAGMA_PUSH_NO_EXTRA_ARG_WARNINGS \     if (!(condition)) {     \          [[NSAssertionHandler currentHandler] handleFailureInMethod:_cmd \          object:self file:[NSString stringWithUTF8String:__FILE__] \          lineNumber:__LINE__ description:(desc), ##__VA_ARGS__]; \       }             \     __PRAGMA_POP_NO_EXTRA_ARG_WARNINGS \ } while(0)   Why do ... while(0) was used? It will be allways performed one time.


Add MathJax rendering to chat on all MathJax sites

In StackExchange sites that support MathJax the inline markup is rendered in comments but not chat rooms -- at least I noticed this is the case on .  This is awkward, particularly for comment discussions that are moved to chat.


How do ridge, LASSO and elasticnet regularization methods compare? What are their respective advantages and disadvantages? Any good technical paper, or lecture notes would be appreciated as well.


Wondering how to create our own CentOS 5 based yum repository? Basically, we want to make rpm packages and then be able to do things like:  yum install our-custom-package yum remove our-custom-package yum update our-custom-package   Thanks.


$p \in \mathbb{N^*}$,  $u_n = \frac{1}{n(n + 1)...(n + p)}$ Determine $\sum_{n=1}^{+ \infty}u_n$ Hint: write $pu_n$ in the form $v_n - v_{n+1}$  I couldn't see how to use the hint, I tried to use $ln$ but I did not proceed much to write it in the from of $v_n - v_{n+1}$


Any recommendations for good books on general topology?

I am looking for books that are on general set theory. So open sets, closed sets, Boundarys complements etc. I sort of understand most of the logic but I would love to go deeper into it.


Is there any terminology or wording to describe the type of fundamental change of a system that is not the result of a single cause, but rather caused by many influences at interplay pushing from several directions that jointly make the status quo unsustainable, reaching a tipping point to force change?  So in a way, the opposite of a simple cause and effect relationship in say physics, and more the sort of causation in society or politics.


Is there a way to restrict certain tables from the mysqldump command?  For example, I'd use the following syntax to dump only table1 and table2:  mysqldump -u username -p database table1 table2 > database.sql   But is there a similar way to dump all the tables except table1 and table2? I haven't found anything in the mysqldump documentation, so is brute-force (specifying all the table names) the only way to go?


Do "No A or B" and "No A and B" mean the same thing?

Hopefully my question is not the same as  as I am asking about the English in writing a prohibition. Do "No A or B" and "No A and B" mean the same thing, where A and B are present participle of some verb?  For example: Is there any difference between     No eating and drinking   and     No eating or drinking   ?  Which one of these two, if any, should one say if he/she wishes to express the idea "either A or B is allowed", but not both A and B (such as drinking alcohol and driving)?


How many combinations of groups are there where no member of a group has been with another member before?

I found this hard to word in the title, so let me give an example. I have 16 students, and I want to split them up into 4 groups of 4. However, I want to make sure that every time I have a new combination of groups, that a student has never been with any of their new groupmates before. I found info on how to separate objects into groups, but not in only unique ways as I've described above. I think I figured this out the rote way, by assigning each student a number and then finding the unique combinations, and got 3. But I'd like to know the math behind it, and how it could be applied to other configurations (20 students w/ 4 groups of 5?). Thanks for any help you can give!


Kernels and reduced row echelon form - explanation

The following text is written in my textbook and I don't really understand it:     If $A = (a_{ij}) \in$ Mat$(m x N, F)$ is a matrix in reduced row echelon form with $r$ nonzero rows and pivots in the columns numbered $j_1 < ... < j_r$, then the kernel ker$(A)$ is generated by the $n-r$ elements $ w_k = e_k - \sum\limits_{1 \le i \le r, j_i \le k} a_{ik}e_{j_i}$ for $k \in {1, \cdots , n} \ {j_1, \cdots, j_r}$, where $e_1, \cdots, e_n$ are the standard generators of $F^n$.    There are no computational examples and the notation is a bit overwhelming so I don't know how I can use it. Can somebody give an example of this in practice?


Angular momentum of electrons in orbitals

Why do angular momentum of electrons in atoms are discrete value rather than being continuous ? I understand angular momentum needs to be fixed in a closed system but why I don't understand why they take value in accordance to the formula: $$L^2 = \ell(\ell+1)\hbar.$$ Why quantum mechanics allow only certain values of angular momentum? Is there any non mathematical explanation for it that can be visualized?


What's the distance between two circumcenters

This problem was came to a Facebook post of mathigon ......the problem seems trickier than I expected...can you help me to find the distance??


Novel in which alien (Martian?) is trapped on Earth in prehistory

What I seem to remember is that the Martian is stranded by the destruction of his civilization. Also, there is an odd detail that sticks in my brain: the Martian drops a bracelet (or a watch?) in a river, where the implication is that it could be found centuries later. The Martian may have intended to influence the development of humans. Quite poignant at the end.


Multilevel Inheritance, trying to access super classes

class A { public int a = 100; } // End of class A class B extends A { public int a = 80; } // End of class B class C extends B { public int a = 60; } // End of class C class D extends C { public int a = 40; } // End of class D  class E extends D{     public int a =10;      public void show(){         int a =0;          // Write Java statements to display the values of         // all a’s used in this file on System.out     } // End of show() Method }// End of class E   I am trying to access the variable a of the superclasses A,B,C from E but I don't understand how to do it. I tried something like this  System.out.println(super.a+" "+super.super.a+" "+super.super.super.a+" "+                    super.super.super.super.a);


Sorry it's not typeset, but hopefully it's readable. I've recently been making a Geogebra file to show linear regression and correlation coefficient.     I included some elements to help show things geometrically and learnt and few things in the process which got me wondering further.  For the covariance of $x$ and $y$, as $$\sum xy-\frac{\sum x\sum y}{n}$$   I realised that this can be written as $$\sum xy-n\frac{\sum x}{n}\frac{\sum y}{n}$$ which is $$\sum xy-n\bar x \bar y$$    Visually I showed this as the sum of the rectangles formed by each point with the origin, and subtracting $n$ times the area of the rectangle formed by the double mean point and origin.  Subsequently I've also realised this could more easily seen by actually representing  $\sum xy-n\bar x \bar y$ as $\sum(xy-\bar x \bar y)$, which could be graphically shown as the sum of the areas of each point with it's opposite vertex at the double mean point.    This leads to me wonder, is this process similar with 3 variables, ie. the volumes formed by the triple mean point. Is covariance of 3 variables 3D and if so how does this scale to more dimensions?  @WHuber Your link is very interesting, and I can see how you've avoided using the double mean point but computationally to connect all points using rectangles seems like a lot of work.  Both of my geometric interpretations are equivalent but my main question is how this generlizes to the covariance of 3 variables and beyond.


The use of the relative pronoun "whose" in a sentence

How is "whose" used as relative pronoun and is it possible to use it when we're specifying things?   I built up a sentence with "whose":      I have a book whose story is about chaina town.


Prove 1 + a + a^2 + a^3 + .... a^n-1 = 1-a^n/1-a by mathematical induction

ANS: Not sure how to do this. I wrote Induction: Prove P(K) = P(k+1) so assume P(k) is true. Statement = P(k+1) 1 + a + a^2 + a^3 + .... a^n-1 = 1-a^n/1-a = a + a + a^2 + a^3... a^k-1 = 1-a^k/1-a a + a + a^2 + a^3... a^k-1 + k + 1 = 1-a^k(k+1)/1-a ? I think I did this completely wrong


Newton's 3rd law... hitting drywall (which I break) vs hitting a brick (which breaks me)?

According to the Third Newton's law of motion:        For every action there is an equal and opposite reaction.   So, I understand that if I hit a brick wall with $50\, \mathrm{lbs}$ of force, the brick wall also hits me with $50\, \mathrm{lbs}$ of force (usually painfully). In this instance, Newton's third law makes sense. What I'm confused about is, if I hit a patch of drywall with $50\, \mathrm{lbs}$ of force, it's probably going to break, and due to the lack of pain in my hand, I can tell it did not hit me back with $50\, \mathrm{lbs}$ of force.   How does Newton's third law apply to situations when one object or the other is destroyed? It certainly seems like at that point it is incapable of delivering the full force of my blow back to me. What happens with the energy?