Uniform convergence on two separate intervals

Test the sequence of functions for uniform convergence       $$f_n(x)=\frac{nx}{1+n^2x^2}$$      $a) \text{on} \ [0,1]$      $b) \text{on} \ [1,{\infty})$   a)  If we differentiate this with respect to x we get the following :  $$(\frac{nx}{1+n^2x^2})'=\frac{n(1-n^2x^2)}{(1+n^2x^2)^2}$$  This is equal to $0$ for $x=^{+}_{-}\frac{1}{n}$  From here we can either check these two values in the original function and take the larger one as the supremum or we can find the second derivative and check whether it's negative. In either case we find that for $x=\frac{1}{n}$ we get the value $f_n(x)=\frac{1}{2}$ and for $x=-\frac{1}{n}$ we get $f_n(x)=-\frac{1}{2}$. Note that $x=-\frac{1}{n}$ doesn't even belong in our interval. Now we can finish the problem.  $$\lim_{n\to \infty}{\frac{nx}{1+n^2x^2}}=0$$  So it is piecewise converging to $f(x)=0$  $$\lim_{n\to \infty}\sup{\left \lvert{f_n(x)-f(x)}\right \rvert}=\lim_{n\to \infty}{\frac{n\frac{1}{n}}{1+n^2 \frac{1}{n^2}}}=\frac{1}{2}$$  So $f_n(x)$ does not convergence uniformly on $[0,1]$ to $f(x)=0$  b)  Now we need to test the on the interval $[1,\infty)$.From the first derivative we notice that if $x\in [1,\infty)$ then the numerator seems to be negative for all $x>1$. So $f_n(x)$ is monotonically decreasing. That means that the supremum will be at the first point of the interval or $x=1$. Taking the limit :  $$\lim_{n\to \infty}{\frac{n}{1+n^2}}=0$$  We can see that the function convergences uniformly on this interval.  Is there something wrong with either of these solutions?  I'm having doubts mostly about the second interval since $x=\frac{1}{n}$ is a supremum but only for $n=1$. However I believe that we need to have the supremum that's satisfied for all $n \in N$. Pointing even the tiniest mistake in my solutions would be very helpful. Thank you.


Does GregorianCalendar constructor check invalid input?

constructor have signature:  GregorianCalendar(int year, int month, int dayOfMonth) GregorianCalendar(int year, int month, int dayOfMonth, int hourOfDay, int minute, int second)    What happen if I pass month or dayOfMonth out of constructor contract?  It is easy to check if month in 0-11 range. But it is impossible to check valid day (which should be  28/28/30/31?) without writing own Calendar implementation.  It should be nice if Java Platform checks user date input. I don't like to check if 2015-13-32 is valid ISO date in own code.


I' using Debian 9 Cannot install libgstreamer-0.10.so I tried   sudo apt-get install libgstreamer0.10-0  Reading package lists... Done Building dependency tree        Reading state information... Done E: Unable to locate package libgstreamer0.10-0 E: Couldn't find any package by glob 'libgstreamer0.10-0' E: Couldn't find any package by regex 'libgstreamer0.10-0'   When I search   sudo apt-cache search libgstreamer libgstreamer-plugins-bad1.0-0 - GStreamer development files for libraries from the "bad" set libgstreamer-plugins-bad1.0-dev - GStreamer development files for libraries from the "bad" set libgstreamer-plugins-base1.0-0 - GStreamer libraries from the "base" set libgstreamer-plugins-base1.0-dev - GStreamer development files for libraries from the "base" set libgstreamer1.0-0 - Core GStreamer libraries and elements libgstreamer1.0-0-dbg - Core GStreamer libraries and elements libgstreamer1.0-dev - GStreamer core development files libgstreamermm-1.0-1 - C++ wrapper library for GStreamer (shared libraries) libgstreamermm-1.0-dev - C++ wrapper library for GStreamer (development files) libgstreamermm-1.0-doc - C++ wrapper library for GStreamer (documentation) libgstreamer-ocaml - OCaml interface to the gstreamer library -- runtime files libgstreamer-ocaml-dev - OCaml interface to the gstreamer library -- development files libgstreamerd-3-0 - GStreamer media framework - D bindings libgstreamerd-3-0-dbgsym - Debug symbols for libgstreamerd-3-0 libgstreamerd-3-dev - GStreamer media framework - development files for D   I created a /etc/apt/sources.list.d/unstable.list  deb http://ftp.nl.debian.org/debian/ unstable main deb-src http://ftp.nl.debian.org/debian/ unstable main   and  /etc/apt/preferences.d/unstable      Package: * Pin: release a=unstable Pin-Priority: 200   But when I run apt-cache policy libgstreamer0.10-0 I get same error   apt-cache policy libgstreamer0.10-0   After I typed apt-get update      sudo apt-get update Hit:1 http://security.debian.org/debian-security stretch/updates InRelease Hit:2 http://ftp.nl.debian.org/debian unstable InRelease                        Ign:3 http://mirrors.edge.kernel.org/debian stretch InRelease                   Hit:4 http://mirrors.edge.kernel.org/debian stretch-backports InRelease Hit:5 http://mirrors.edge.kernel.org/debian stretch-updates InRelease           Hit:6 http://mirrors.edge.kernel.org/debian stretch Release                     Reading package lists... Done


Why do I Get a Blank Output When echoing $variable?

I'm just trying to echo a variable stored in a file. When issuing the echo $variable command I'm getting a black area with no output. I don't understand why.  Content of file1:   name="Jhon"   My output    Solutions tried:  source /home/ec2-user/file1  After this I get the correct answer. But if I log out from the instance and come back again, it doesn't work.  I tried different type of instances with the same results.   In most of the tutorials on Linux when they execute a variable it pick up from multiple file. Why do I have issue the source command?


Primary replica set server goes secondary after secondary fails

I have a 2 servers replica set that, after the secondary fails the primary goes into secondary mode while the secondary is in STARTUP2 (recovering). The problem with this is that I can't use the collection stored in that replica set freely, I'm getting errors trying to use the collection:  pymongo.errors.OperationFailure: database error: ReplicaSetMonitor no master found for set: rs2   Sometimes if I restart the mongod instances, the server rs2-1 is the primary for a while, but after some time (while the secondary is recovering) I see this in the logs of rs2-1 (the primary):  Tue May  7 17:43:40.677 [rsHealthPoll] replSet member XXX.XXX.XXX.XXX:27017 is now in state DOWN Tue May  7 17:43:40.677 [rsMgr] can't see a majority of the set, relinquishing primary Tue May  7 17:43:40.682 [rsMgr] replSet relinquishing primary state Tue May  7 17:43:40.682 [rsMgr] replSet SECONDARY Tue May  7 17:43:40.682 [rsMgr] replSet closing client sockets after relinquishing primary   Is there an easy way to make the primary keep being primary after the secondary fails? Am I doing something wrong?  Thanks in advance!


Bug on topbar showing pending suggested edits while I am done with edits for today

I was reviewing some suggested edits and some other posts on SO today.  Aftera short while I have exhausted by contigent of reviews for the suggested edits queue. As I still wanted to do some other reviews, I stumbled upon a minor bug.  Despite not being allowed to do any reviews, I got the topbar indicating that there is pending reviews. I took a screenshot (and edited it to decrease the size by removing all the other review queues from the image).    This did not happen all the time, but could be reproduced by using the review link in the topbar now and then.


How can I get randomly generated numbers between 0 to 99 with 0 and 99 included?

Use a random number function to randomly generate 10 integers between 0 and 99 with 0 and 99 included


These are a defining and a non-defining relative clause :-     (A)  He deleted the picture that upset me.       (B)  He deleted the    picture, which upset me.   Could you please explain the difference in meaning of these sentences?


what is the close form expression for the update of $x_i$ in coordinate descent?

I am trying to derive the close form expression for the update of $\omega_i$ in coordinate descent for lasso, but I find it hard to proceed. Could you give me some hints?  $min_\omega\sum_{i=1}^m(y_i-X_i\cdot\omega)^2+\lambda\|\omega\|_1$ I need to find $\omega_i = ?$


Should protected questions prevent the comment privilege from the association bonus?

At 1 rep, a user can post, i.e. ask a question or post an answer to a question. They must earn sufficient rep to be able to comment.  Users with the association bonus get 100 points added, so a new user can post and comment.  Protected questions prevent users with only the association bonus from posting. They have to earn sufficient rep on that site. However, they are still allowed to comment, and post answers as comments, defeating the purpose of protecting the question.  Should protected questions block commenting with only the association bonus?


How do I create a random alpha-numeric string in C++?

I'd like to create a random string, consisting of alpha-numeric characters. I want to be able to be specify the length of the string.  How do I do this in C++?


Does borrowing from my 401(k) make sense in my specific circumstance?

I know the standard answer and understand that I will be losing out on that compound interest, but I am young and only need to borrow a few thousand. here are some more details:   Need to borrow $6500 to pay off a car and two student loans ($300/month in payments combined) I am 22 and work full time, making about $70K annually I contribute 8% of my income with a 4% company match I increase that by 2% every year The loan would be over 48 months ($140/month) I live very frugally and have almost no discretionary spending that can be cut (don't eat out all the time, no gym membership/ Netflix/ Apple music etc.) I'm cash-poor: 90% of my salary is going to mortgage, groceries, students loans, car payment, newborn baby medical expenses, and commute. These are not my only debts, just the ones I am seeking to pay off in the short term. I work two jobs, one full and one part time. I started a business, and my wife has two jobs. Working more is not a good answer to the original question.   It seems to me that I would be reducing middle to high interest debt while also saving myself $150 per month.   Loans:     Student loan 1: $1200 @ 5%   Student loan 2: $1100 @ 4.25%   Car Loan: $4000 @ 6%


My grandma hadn't finished her schooling, so I wanted to know when she stopped going to school or more specifically "the grade after which she stopped going to school". Actually she completed her tenth grade.     Till what grade did you go to school?      I went  to school till 10th grade. (I finished my tenth grade)   Do you think that these sentences sound natural? I made them up, but I don't know why but they sound a bit off to me. Can you please suggest something better instead?  My question is mostly about the use of "till" (not "10th") and therefore isn't like these related questions:


Prove that $3^{2n-1} + 2^{n+1}$ is always a multiple of $7$.

I'm trying to prove the following statement: $P(n) = 3^{2n-1} + 2^{n+1}$ is always a multiple of $7$  $\forall n\geq1$. I want to use induction, so the base case is $P(1) = 7$ so that's okay.  Now I need to prove that if $P(n)$ is true then $P(n+1)$ is true. So there exists a $d \in \mathbb{N}$ such that  $$ 3^{2n-1} + 2^{n+1} = 7d $$ From this I need to say that there exists a $k \in \mathbb{N}$ such that: $$ 3^{2n+1} + 2^{n+2} = 7k $$ With a little algebraic manipulation, I have managed to say: $$ 2 \cdot 3^{2n+1} + 9 \cdot 2^{n+2} = 7\cdot(18d) $$ But now I am stuck. How should I keep going?


I have an idea for an april fool's prank on SO. How would I go about pitching it to someone who could implement it?  Also, before I email them and clutter their inbox with what could possibly be an ineligible prank, what are the guidelines governing the eligibility of an April Fool's prank?


Is there any tool in Solaris UNIX (so no GNU tool available) to subtract dates? I know that in Linux we have gawk that can subtract one date from another. But in Solaris the maximum we have is nawk (improved awk) which cannot perform date calculations. Also I cannot use perl.  Is there any way to do date calculations like 20100909 - 20001010?  UPDATE: Is bc able to perform dates calculations?


How do I sync contacts with my online account?

I've just got my new Ubuntu Touch, how do I import my contacts if I have them saved in my Google account?


I installed Kubuntu 18.04 as a dual boot with Windows 10, recently, on my Dell Inspiron 3543. Bluetooth is working fine, but Wi-Fi is not working. I have tried almost every possible fix available in the internet, but still could not have it up and running. Ethernet is working fine. And wifi works fine in Windows 10.  I have Broadcom Wi-Fi card.


running python script with limited command privileges (help)

i added a user a new user and would like them to be able to execute a file, when entering "python3" it works and i can enter code but when trying to execute python script i get this  python3: can't open file 'bot.py': [Errno 13] Permission denied


Hello everyone i would like to know if the PHP code used by me for registration in my Android App is vulnerable to Mysql Injection or not.  I would also like to know if the Android Apps are vulnerable or not to Mysql Injection and if anyone has any advice to give me on how to defend myself from these attacks.    <?php      if($_SERVER['REQUEST_METHOD']=='POST'){   // echo $_SERVER["DOCUMENT_ROOT"];  // /home1/demonuts/public_html //including the database connection file        include_once("config2.php");             $idAKr = $_POST['idAKr'];     $cell = $_POST['cellulare'];     $nome = $_POST['nome'];     $cognome = $_POST['cognome'];     $data = $_POST['data_nascita'];     $sesso = $_POST['sesso'];     $ristorante = $_POST['ristorante'];         if($nome == '' || $cognome == '' || $data == '' || $ristorante =='' ){             echo json_encode(array( "statusr" => "false","message" => "Inserisci tutti i dati") );      }else {                           $query= "SELECT * FROM Ristoratori WHERE nome='$nome' AND cognome='$cognome' AND data_nascita='$data' ";             $result= mysqli_query($con, $query);                       if(mysqli_num_rows($result) > 0){                  echo json_encode(array( "statusr" => "false","message" => "Utente già registrato!") );             }else if{             $query= "SELECT * FROM Ristoratori WHERE ristorante='$ristorante'";             $result= mysqli_query($con, $query);                       if(mysqli_num_rows($result) > 0){                  echo json_encode(array( "statusr" => "false","message" => "Nome ristorante già in uso") );                          }             else             {               $query = "INSERT INTO Ristoratori (idAKr,cellulare,nome,cognome,data_nascita,sesso,ristorante) VALUES ('$idAKr','$cell','$nome','$cognome','$data','$sesso','$ristorante')";              if(mysqli_query($con,$query)){                                   $query= "SELECT * FROM Ristoratori WHERE nome='$nome' AND cognome='$cognome' AND data_nascita='$data' AND ristorante='$ristorante' ";                          $result= mysqli_query($con, $query);                      $emparray = array();                          if(mysqli_num_rows($result) > 0){                            while ($row = mysqli_fetch_assoc($result)) {                                      $emparray[] = $row;                                    }                          }                 echo json_encode(array( "statusr" => "truer","message" => "Registrazione completata!" , "datar" => $emparray) );              }else{                  echo json_encode(array( "statusr" => "false","message" => "Errore") );             }         }                 mysqli_close($con);      }      } else{             echo json_encode(array( "statusr" => "false","message" => "Errore") );     }    ?>     thank you.


I have just installed bash in windows 10 insider preview. But gedit is not working. I also use software R for my statistical work, its lot of options like 'plot' also not working. Is it the fact that no program like gedit can be opened through bash I mean wont that support any GUI ?


Ball $X^*$ is weak-star metrizable iff X is separable in Conway's book.

This is a Theorem in Conway's book     I don't understand in the third paragraph why there are open sets $\{U_n:n\geq1\}$ in $(ball X^*,wk^*)$ such that $0\in U_n$ and $\bigcap^{\infty}_{n=1}U_n=\{0\}$. By the definition of the relative weak-star topology on ball $X^*$, for each $n$, there exists a finite set $F_n$ contained in $X$ such that $$\{x^*\in\text{ball }X^*:|\langle x,x^*\rangle|<1 \text{ for all }x\in F_n\}\subseteq U_n.$$  Can someone explain this for me？ Thank you so much!!


biblatex: extrayear only if full date is equal?

I have a bunch of bib entries of the same author which are labeled by the full date. The problem is that some of them have the same date and so need an extrayear label. But extrayear works by year not by full date. So it looks as if I can only either label all entries or none. Has someone an idea how in the following example the two middle entries could get the labels "a" and "b" while the other have no label?  \documentclass[fontsize=11pt,parskip=half]{scrartcl} \usepackage[T1]{fontenc} \usepackage[utf8]{inputenc} \usepackage[ngerman]{babel} \usepackage[backend=biber,             style=authoryear-ibid,             datelabel=short,             ]{biblatex}  \addbibresource{testextra.bib}  %\AtEveryBibitem{\iffieldundef{day}{}{\clearfield{extrayear}}{}} %\AtEveryCitekey{\iffieldundef{day}{}{\clearfield{extrayear}}{}}   \begin{document} abc\nocite{*}  \printbibliography  \end{document}   Bib (edited to contain two unrelated entries which should not be affected).  @article{authorA1,  author={authorA},  title={blaa},  date={2014-03-03}  }  @article{authorA2,  author={authorA},  title={blab},  date={2014-03-04}  }   @article{authorA3,  author={authorA},  title={blac},  date={2014-03-04}  }  @article{authorA4,  author={authorA},  title={blad},  date={2014-03-05}  }  @article{gambol, author={Gambolputty, Johann}, title={Titel}, year={1970}}  @book{authorB, author={authorB}, title={Titel}, date={2010-10}}


I have two buttons:  $('#prev').click(function() {    // some code });  $('#next').click(function() {    // some other code });   what I now want to do is adding a .keypress() handler to the site which triggers on arrow-left the #prev click and for arrow-right it triggers #next. Problem is how can I add this handler?


For the command   sudo apt-get update   I get following error:  W: Failed to fetch http://ch.archive.ubuntu.com/ubuntu/dists/maverick-updates/multiverse/binary-i386/Packages.gz   407  Proxy Authentication Required (The ISA Server requires authorization to fulfill the request. Access to the Web Proxy filter is denied. )   I am running Ubuntu 10.10 installed on Windows XP using VirtualBox. For Internet connections I am using proxy server with an authentication. I tried to use gnome-network-proxy tool to set proxy settings system-wide.   After that /etc/environment has been updated by http_proxy variable with the format http://my_proxy:port/, there were no authentication data.  I checked this with Firefox. Browser asked my for login and password and everything was working fine. It was unfortunately not the case for apt-get. I have also tried to do as described . Unfortunately it does not work.  May it be somehow related to the fact that a proxy is in a Windows domain, any ideas?  My proxy name is http-proxy. Is '-' a special character here?


Landscape-like tool to distribute security upgrades to OS?

i'm looking for an alternative to Landscape, Spacewalk (for RHEL), or CTL to perform a specific job. I need to control and apply OS upgrades on ubuntu systems, for 100+ servers, and so far i wasn't that lucky. I've tried Approx tool (similar to apt-proxy), but it just caches the content, and what i really need to do is set update milestones, apply the upgrades to QA servers, validate, then Stage environment, and so on to Production. I hope I was clear enough, any answer will be much appreciated.


Finitely Presented Modules and Exact Sequences

I came across this passage in Rotman's Advanced Modern Algebra:     If $M$ is finitely presented, there is a short exact sequence       $\begin{equation*}0 \rightarrow K \rightarrow F \rightarrow M \rightarrow 0,\end{equation*}$      where $F$ is free and both $K$ and $F$ are finitely generated. Equivalently, $M$ is finitely presented if there is an exact sequence      $\begin{equation*}F' \rightarrow F \rightarrow M \rightarrow 0,\end{equation*}$      where both $F'$ and $F$ are finitely generated free modules (just map a finitely generated free module onto $K$).   It's not obvious to me why the second statement must be true. Is it really trivial enough to just claim in passing? Any insight would be much appreciated. Thank you.


In "The Hobbit", where did goblins come from?

I was wondering if goblins were somehow just created like humans and elves, or if they were a cross-breed of some other creatures.


Show that if $n$ is not divisible by $2$ or by $3$, then $n^2-1$ is divisible by $24$.   I thought I would do the following ... As $n$ is not divisible by $2$ and $3$ then $$n=2k+1\;\text{or}\\n=3k+1\;\text{or}\\n=3k+2\;\;\;\;$$for some $n\in\mathbb{N}$. And then make induction over $k$ in each case.$$24\mid (2k+1)^2-1\;\text{or}\\24\mid (3k+1)^2-1\;\text{or}\\24\mid (3k+2)^2-1\;\;\;\;$$This question is in a text of Euclidean Division I'm reviewing, and I wonder if there is a simpler, faster, or direct this way.


I just configured Ubuntu Snappy Core on my Raspberry Pi 3 and now it is now asking for a user name and password in the terminal (I think). It says:  Ubuntu Core 16 on <my ip address> (ttyl) localhost login: Password:   I'm not sure whether these fields are for your Ubuntu account username and password or email and password or whatever. I've tried my Ubuntu account username and password and I also tried it with my email and password. Neither worked so I tried leaving them blank which also didn't work.  Is there some default password or did I put it in earlier and if so when or where? If I knew that I might be able to remember what I put.


For example:  S ::= “Sales will go up.” E ::= “Expenses will go up.”  Express the following: Both sales and expenses will fall.  Why is it  ¬ (S ∧ E)  instead of ¬S ∧ ¬E ?


Is there any stylish/colorful CV writing package?

.    I can make CV in LaTeX using the moderncv package. I also saw the . But I don't see yet above type of CV writing in LaTeX. Is there any package on this?


Optimal URL structure for directory-like site

I'm building a site where organic SEO is very important for me. It's a niche, there's very little competition, and any edge I can get will help me out tremendously. That being said, which URL structure would you suggest is best, for both technical reasons, and SEO?   example.com/dining (HUB for all dining) example.com/dining/restaurants (HUB specifically for restaurants) example.com/dining/cafes (HUB specifically for cafes) example.com/dining/restaurants/red-onion-club (actual page for that venue)   Or   example.com/dining (HUB for all dining) example.com/dining/restaurants (HUB specifically for restaurants) example.com/dining/cafes (HUB specifically for cafes) example.com/venues/red-onion-club (actual page for that venue)   Note I will also have hotels, bars, etc., with the same structure (give or take sub categories).    Which of these is best?   Someone made an argument for the the second set, as the flat URLs are shorter, don't tie any location to a specific category (if a bar was also a restaurant, and vice versa), and if I change any naming conventions, the URLs never change, because they're all at /venues/the-location. However, the first set of URLs contains keywords in the URL that let users and search engines know exactly what they are. If it's a restaurant, it's in the URL, if it's a bar, it's in the URL.   As I said, I have both of these working on the technical side, I just need to know which I should go forward with.


How to print only editor and title of parent entry in a child entry in the bibliography

In my bibliography, I want  to print only the editor's name and the title of the parent work in the child entry if the parent has at least two children, while what I now get is the full parent entry within each single child entry. The parent entry should then be printed in full under the editor's name. So instead of  Test Author. “Testing the second Title”. In: My Proceedings. Ed. by Senor Editor and Senora Editora. Any Publisher, 2013, pp. 10–20.  Test Author. “Testing the Title”. In: My Proceedings. Ed. by Senor Editor and Senora Editora. Any Publisher, 2013, pp. 1–10.  Senor Editor and Senora Editora, eds. My Proceedings. Any Publisher, 2013.   what I would like to get is:  Test Author: “Testing the second Title”. In: Senor Editor and Senora Editora, eds., *My Proceedings*, pp. 10–20.  [Test Author. “Testing the Title”. In: Senor Editor and Senora Editora, eds., *My Proceedings*, pp. 1–10.  Senor Editor and Senora Editora, eds. *My Proceedings*. Any Publisher, 2013.   I am aware that a similar question has been answered , but I just can't figure out how I can manipulate the code suggested there so that it prints editor and title. I managed to replace the alphabetic label by the title of the collection (or proceedings or book) by using  \printfield{labeltitle}   instead of   \printfield{labelalpha}   but neither  \printfield{labelname}   nor   \printlist{labelname}   seems to work to get the editor's name. Any idea what's going wrong here? I add a MWE:  \documentclass[]{scrartcl}  \usepackage[backend=biber,style=authortitle-icomp]{biblatex} \usepackage{filecontents}  \begin{filecontents}{my.bib} @incollection{inproc1,     Author = {Test Author},     Crossref = {proc},     Pages = {1--10},     Title = {Testing the Title}}  @incollection{inproc2,     Author = {Test Author},     Crossref = {proc},     Pages = {10--20},     Title = {Testing the second Title}}  @collection{proc,     Editor = {Senor Editor and Senora Editora},     Publisher = {Any Publisher},     Title = {My Proceedings},     Year = {2013}}  @inproceedings{inproc3,     Author  = {Nother Author},     Publisher = {Nother Publisher},     Title   = {In Some Other Proceedings},     Maintitle = {Main Title of Other Proceedings},     Year     = {2001}, } \end{filecontents}   \DeclareBibliographyDriver{incollection}{%   \usebibmacro{bibindex}%   \usebibmacro{begentry}%   \usebibmacro{author/translator+others}%   \setunit{\labelnamepunct}\newblock   \usebibmacro{title}%   \newunit   \printlist{language}%   \newunit\newblock   \usebibmacro{byauthor}%   \newunit\newblock   \usebibmacro{in:}%   \iffieldundef{crossref}     {\usebibmacro{crossref:full}}     {\usebibmacro{crossref:label}}   \newunit\newblock   \usebibmacro{chapter+pages}%   \iffieldundef{crossref}     {\usebibmacro{crossref:extrainfo}}     {}   \setunit{\bibpagerefpunct}\newblock   \usebibmacro{pageref}%   \usebibmacro{finentry}}  \newbibmacro{crossref:full}{%     \usebibmacro{maintitle+booktitle}%   \newunit\newblock   \usebibmacro{event+venue+date}%   \newunit\newblock   \usebibmacro{byeditor+others}%   \newunit\newblock   \iffieldundef{maintitle}     {\printfield{volume}%      \printfield{part}}     {}%   \newunit   \printfield{volumes}%   \newunit\newblock   \usebibmacro{series+number}%   \newunit\newblock   \printfield{note}%   \newunit\newblock   \printlist{organization}%   \newunit   \usebibmacro{publisher+location+date}}  \newbibmacro{crossref:label}{%   \entrydata{\strfield{crossref}}      {\printtext{         {\printfield{labeltitle}\printfield{extratitle}}}}}  \addbibresource{my.bib}  \begin{document}  Test \cite{inproc1} and \cite{inproc2} and \cite{inproc3} \printbibliography \end{document}   And, one more little thing (too connected and minor a point for an extra question), how can I make the title of the collection appear in italics in the child entry?  Thanks for your help - as it is my first post on TeX Stack Exchange, please don't hesitate to correct me in case I didn't make myself clear, or violated any convention!


Suppose you have a computer with a password of length $k$ in an alphabet of $n$ letters.  You can write an arbitrarly long word and the computer will try all the subwords of $k$ consecutive letters. What is the smallest word that contains all combinations of $k$ letters as subword? (i.e. the fastest way to hack the computer :) )  The smallest word that contains $n^k$ subwords of size $k$ has length $k-1+n^k$ and based on some easy cases, we would like to prove that it is in fact possible to find a word of such length that contains all possible passwords. The problem can be translated into a problem in graph theory, by taking as vertices all words of length $k$.  We tried $k=2$, where you can prove the conjecture by induction. For $n=2$ and small $k$ it also works.


Is it possible to change the toolbar icons in gVim?

Is it possible to change the toolbar icons in gVim (without patching the exe)?  It seems like you can change everything else, and they are so ugly...


How to calculate (by hand) trig functions?

I asked a similar question in high school and people started laughing as they thought like it's trivial.  We only learn to memories the values cosine function but not even in college we're we taught how exactly it works.  Trig functions as far as I was taught in college were defined as infinite series. But if I plugged pi in that infinite series I see no reason why it would converge to - 1 for the cosine function trig series or why that series definition would be equivalent to the geometric one.   The relation to the geometric definition is not the central point but if you will talk about it I would appreciate AVOIDING COORDINATES IN YOUR ANSWERS AND COMMENTS, I find them extremely detrimental to conceptual reasoning.   I think it probably the easisent explanation lies in complex numbers, but I don't know if that would be satisfactory.


Is it possible to prove that $\cos(\pi/3)=1/2$ without using any trigonometric identities?  To be specific, my calculus-book simply states that with an angle of $\pi/3$ on the unit-circle the points (0,0) and (1,0) are the vertices of an equilateral triangle with edge length 1. But how can one reach such conclusion?  Thanks!


Is my proof of $\sqrt{2} + \sqrt{3} + \sqrt{5}$ is an irrational number valid?

The question is prove $\sqrt{2} + \sqrt{3} + \sqrt{5}$ is an irrational number.  I started by assuming the opposite that $\sqrt{2} + \sqrt{3} + \sqrt{5}$  is a rational number. I stated that a rational number is a number made by dividing two integers. So I set $\sqrt{2} + \sqrt{3} + \sqrt{5} = i_1/i_2$, where $i_1$ and $i_2$ are two integers. I multiplied $i_2$ onto both sides and got $i_2\sqrt{2} + i_2\sqrt{3} + i_2\sqrt{5} = i_1$. I then said that in order to turn an irrational number such as $\sqrt{2}$ into a rational number you can multiply, $\sqrt{n}\sqrt{n}=n$. Meaning $i_2$ would have to hold the value of $\sqrt{2}$, $\sqrt{3}$ and $\sqrt{5}$ which is impossible. So it is an irrational.  I think I made a mistake somewhere but I am not sure.


For what values will f(x) be necessarily one-one?

Let $g:\mathbb{R}\to\mathbb{R}$ be a differentiable function such that   $|g'(x)|\le M$ for all $x\in \mathbb{R}$. For what values of   $\epsilon$ will the function $f(x)=x+\epsilon g(x)$ will be   necessarily one-one?   Not getting any idea how to proceed, maybe Mean value theorem will work.


Does a Galois group being $S_3$ correspond to the extension being the splitting field of a cubic?

If $f(x)$ is an irreducible cubic, then $\operatorname{Gal}(f(x))\cong S_3$ or $A_3$. But what about the converse? That is, if $\operatorname{Gal}(K/F)\cong S_3$, is it necessarily true that $K$ is the splitting field of some irreducible cubic in $F[x]$?


When I do man passwd, it opens the manual for PASSWD(1). So what is PASSWD(5) and how to open its man page?


Retrieve Opportunity Data in marketing cloud

I have created an dynamic email template using AMP Script so that i can send emails to all records which are present in my salesforce report.  AMP Script:  %%[     Var @fname,@AccountName,@PictureDay,@AccountPhone,@BookingOwner,@BookingOwnerEmail     Set @fname=FirstName     Set @AccountName=AccountName     Set @PictureDay=PictureDay     Set @AccountPhone=Account:Phone     Set @BookingOwner=BookingOwner     Set @BookingOwnerEmai=BookingOwnerEmail ]%%  Dear %%=v(@fname)=%%,  We are looking forward to taking photographs at %%=v(@AccountName)=%% on %%=v(@PictureDay)=%%. The phone number we have on file for you is %%=v(@AccountPhone)=%%.  Your Account Manager is %%=v(@BookingOwner)=%% and you can reach them at %%=v(@BookingOwnerEmail)=%%   Notes:   I don't want to import data using Salesforce Data Extension. I have Opportunity columns in my report so i am unable to fetch from normal Data Extension (They can fetch only Contact,Lead & Opportunity columns) Trying to use AMP Script for Dynamic Email Content. Tried using RetrieveSalesforceObject function but no luck.


can not login to terminal after upgrade to 18.04

I can log in to GUI but not to any terminal (CTRL+ALT+F1-6). As soon as I hit enter after I type the user Login system display "Password:" and the prompt jump to the beginning of next line just as if I had hit "enter" without entering any password.  After this, system enter in a loop displaying "Login incorrect" without my intervention. I've recorded a 12 seconds movie for those who did not understand the issue, but it is not allowed to attach movies, so I attached a photo. Seems that the system don't let me to type the password...or it behaves as I hit enter without typing a password.


Exporting 3GB ArcGIS Raster to KML without losing resolution?

I have a 3GB raster layer, and I'd like to export it to KML for use with Google Earth.  When I use the "Layer to KML" conversion tool in ArcMap, I end up with a low-resolution overlay: looks like one 2000x2000 pixel image (give or take). I've tried messing with the "layer output scale" parameter, but it isn't having any effect.


Maximum Likelihood Estimation (MLE) in layman terms

Could anyone explain to me in detail about maximum likelihood estimation (MLE) in layman's terms? I would like to know the underlying concept before going into mathematical derivation or equation.


Portable hard drive - bad sectors blocks fails on backup

I have a 2TB portable hard drive from Western Digital that I have used over the years.  I use it on my home server to for NFS streaming. I have noticed recently while streaming some content it fails to play and first thought it was my server configuration but after further investigating the issue I have found it is my NTFS partition on the hard drive that was faulty.  I have used rsync, and cp to copy the content but I get read/write io failure when trying to copy over the content. I thought about making a disk image with dd but as the hard drive is 2TB thats a very large image and all I have are 2TB hard drives out here with me.  What is my best option for backing up all this content without having files skipped over because of read write io fails?


why should I use tar.xz instead of tar.gz? xz is a lossless data compression program and file format

Today first time in my life I saw tar.xz download. I searched the internet and found Wikipedia articles ( and )  Interesting quote about the users of xz     xz has gained notability for compressing packages in the GNU coreutils   project,[7] Debian family of systems deb (file format), openSUSE,[8]   Fedora,[9] Arch Linux,[10] Slackware,[11] FreeBSD,[12] Gentoo,[13]   GNOME,[14] and TeX Live,[15] as well as being an option to compress a   compiled Linux kernel.[16] In March 2013, kernel.org announced the use   of xz as the default compressed file format for distributing kernel   archive files.[17]   I always use tar.gz. When and why should I use tar.xz? What's the use case?  I found out after first comment that a  already posted. I often compress mongodump/mongoexport (BSON/JSON) and mysqldump (SQL text). Is there an advantage to use tar.xz for those backups?


Is there an onSelect event or equivalent for HTML ?

I have an input form that lets me select from multiple options, and do something when the user changes the selection. Eg,  <select onChange="javascript:doSomething();">   <option>A</option>   <option>B</option>   <option>C</option> </select>   Now, doSomething() only gets triggered when the selection changes.  I want to trigger doSomething() when the user selects any option, possibly the same one again.  I have tried using an "onClick" handler, but that gets triggered before the user starts the selection process.  So, is there a way to trigger a function on every select by the user?  Update:  The answer suggested by Darryl seemed to work, but it doesn't work consistently. Sometimes the event gets triggered as soon as user clicks the drop-down menu, even before the user has finished the selection process!


Why variable inside function is being used outside the JavaScript function?

I am new and learning JavaScript from Udemy        Question is  age variable is declared globally so the second console.log should be 23 which is outside the function what am i doing wrong ? but the console.log is taking the variable from the function !


I am writing an article, and I am having some trouble making my equations large enough to stand out on the page.  Does anyone have a suggestion on how to best resize this?  Thanks  \documentclass[11pt]{article} \usepackage[margin=1in]{geometry} \usepackage{amsfonts, amsmath, amssymb,} \usepackage[none]{hyphenat} \usepackage{fancyhdr} \usepackage{tikz} \usepackage{pgfplots} \usepackage{pst-eucl} \usepackage[nottoc, notlot, notlof]{tocbibind} \usepackage{bm,nicefrac}  \begin{document}  \subsection{My Text Begins Below} Text Here Text Here Text Here Text Here Text Here Text Here Text Here Text Here Text Here Text Here Text Here Text Here Text Here Text Here Text Here Text Here Text Here Text Here Text Here Text Here Text Here Text Here Text Here Text Here Text Here Text Here Text Here Text Here Text Here Text Here Text Here Text Here.     \begin{center}      \boldmath          \[     \underbrace{ \mathit{}   \frac{x_n({A^{x+y}})}{b} }\unboldmath_{\text{{\begin{huge}$=c$\end{huge}}}} \]     \unboldmath      \underbrace      Figure 1: My equation above.      \unboldmath      \end{center}  \end {document}


Checkbox property set to visbility:hidden acts like display:none

When i set the checkbox property "visibility: hidden" it acts like "display: none". Meaning it's is not visible and not accessible. For example in the code below i overlayed my checkbox over the text creating the effect that when the text is clicked the checkbox should be checked. Setting the "opacity:0" will create the effect for me. I just want an explanation why "visible:hidden" kinda removes the checkbox.  To test this you can remove the visibility property to show the checkbox    div {   position: relative;   width: 200px;   border: 1px solid red; } input {     position: absolute;     left: 0;     right: 0;     bottom: 0;     top: 0;     width: 100%;     visibility: hidden;     height: 100%;     cursor: pointer;     /**opacity: 0;**//**I can use this instead tho**/ }
   <input id="units" type="checkbox" value="13">TEST


Present simple form for City/group of people

Let's say we have a group of people who starts an activity together.  The name of group can be: York speaks English! - as York is 3rd person singular.  But at the same time: York speak English! - as York could be understood as a group of people, thus 3rd person plural.  The group is suppose to practice English together.  What is a correct form?


Showing that $\bar{\mathbb{B}}^n$ is a manifold with boundary (Lee ITM Probelm 3-4)

"Show that every closed ball in $\mathbb{R}^n$ is an $n$-dimensional manifold with boundary, as is the complement of every open ball. Assuming the theorem on the invariance of the boundary, show that the manifold boundary of each is equal to its topological boundary as a subset of $\mathbb{R}^n$, namely a sphere. Hint: for the unit ball in Rn, consider the map  $\pi \circ \sigma^{-1}: \mathbb{R}^n \rightarrow \mathbb{R}^n$, where $\sigma$ is the stereographic projection and $\pi$ is a projection from $\mathbb{R}^{n + 1}$ to $\mathbb{R}^n$ that omits some coordinate other than the last."  So, I've got (the first part, anyways) of the question done, but my technique was a little different than what Prof. Lee suggested: I considered the ball as infinitely many foliated spheres, mapped each one to a plane using the stereographic projection, and then put the last coordinate as a function of the distance from the north/south pole. However, my solution seemed to neatly avoid any use of $\pi$ as mentioned, and I'm curious if anyone knows how that solution runs.


Change the URL in the browser without loading the new page using JavaScript

How would I have a  action that may have some effects on the current page but would also change the URL in the browser so if the user hits reload or bookmark, then the new URL is used?    It would also be nice if the back button would reload the original URL.  I am trying to record JavaScript state in the URL.


Can I charge my MacBook with a phone charger?

Can I use a phone USB-C charger (e.g. the ) to charge my 2016 MacBook Pro? How about a USB-A charger with a USB A->C cable?  Physically it fits, but  says that it is not a good idea, without elaborating why.


How do you disable the window switch animation when switching spaces with Mission Control?

In Snow Leopard, I had the window switch animation disabled when I quick-key between spaces. Now that it's Mission Control in Lion, there's a long animation during which all my desktop icons disappear and I can't use anything. I'd really like to disable this, but .  How can I disable this needless animation in OS X Lion or later?


I am having a problem trying to set the active vertex in blender. I have a list of vertices but I cannot set the active vertex. I am able to retrieve the active vertex through select_history of the bmesh, but I cannot set it, says its not writable  #get bmesh bm=bmesh.from_edit_mesh(bpy.context.active_object.data)  #print active vert print(bm.select_history.active)  #if I do something like this, error not writable bm.select_history.active = bm.verts[5]


Window air conditioner exhaust temperature

I'm planning to put a window air conditioner in an apartment awning window. The window part that swings open cannot be removed so,the exhaust from the air conditioner would be blowing against the window. Would the exhaust be very hot and,if so could it cause damage to the window parts? Any suggestions?


Reputation Graph X Axis Bug in Edge and IE

The small reputation graph on the profile page is broken in Edge and IE:     While in Chrome it looks like this:    Firefox also shows it correctly. I have not tested Safari.  I know the Edge rendering engine is going to go away at some point, so this issue will disappear in the long run, but it'd be nice if Stack Exchange worked on all browsers, not just the main ones.  Seeing as you are redesigning the profile page, seems like an ideal time to fix it. 🙂  Tested versions: Chrome 71.0.3578.98, Firefox 64.0, Edge 44.17763.1.0, IE 11.195.17763.0, all on Windows 10 1809 (17763).


What should one do if they've discovered a "breakthrough" but lack academia credentials?

Let's assume someone has a very thorough knowledge of a particular field of science but they have absolutely no formal education in this background.  This individual one day realizes a very novel approach to solving a somewhat complex problem.  After developing independent tests and coming up with rock-solid evidence that her method is groundbreaking, and consistently produces test results that would be impossible without a legitimate solution, what can she do with her research to both share the information with the world and retain some form of credit for the discovery?  In other words, how can one be both a hobbyist contributing to a field of scientific study and yet also retain the respect they deserve for their work if it is of great use and benefit?  To be clear, this isn't about having one's name appear in a Science Journal without the necessary credentials.  I think it's respectable to maintain certain sets of rules and standards for journalistic publications.  However, it also isn't fair for such a person to have to divulge this information to someone who is "qualified" and have them receive all or most of the credit for someone elses work, just because that other person hasn't earned a piece of paper.  How can hobbyist both share, and maintain, the recognition they deserve if they make a legitimate scientific breakthrough?


dimensional analysis - how to find the dimensions of a variable inside an angle

Take this equation  $$v^2 = 2 a \sin(2\pi b t)$$ where $v$ is a velocity and $t$ is a time. Find the dimensions of $a$ and $b$.   Finding the dimensions of $a$ is easy as the $\sin$ has no dimension  so it will have the same dimensions as $v^2$.  But the problem is finding the dimensions of $b$ because the $\sin$ takes an angle as a parameter, and angles have no dimension we can simply say that $b$ should be $1/[\mathrm{T}]$ which will make the entire argument dimensionless. But isn't that just wrong?   Because there are some physical laws that have $\sin(t)$ for example where $t$ is a time, so it isn't a condition that the angle's value should be dimensionless.  This is really confusing.


Which macs are compatible with OS X 10.11 El Capitan?

Is there a list of officially supported Macs for OS X El Capitan?  I ask to get ready if any hardware which is supported on Yosemite is not supported by El Capitan?


How to append a percent sign % to a some columns/rows only using siunitx

I have two questions related to the MWE shown:   How to append a percent sign to only cells of a column, or of a row by using siunitx package whether the tabular is defined by row or by columns. ? (I know I can put it only in the header but it's not the point). How to add a vertical space, it doesn't work with the commented \vspace*{2cm}?   PS: I am not familiar with this package yet.  Here is a simplified MWE picked from :  \documentclass[preview,border=5pt]{standalone} \usepackage{booktabs} \usepackage{siunitx}     \newcommand\mc[1]{\multicolumn{1}{c}{#1}}  \begin{document}     \begin{table} \centering %defined by rows \begin{tabular}{ l*{5}{S[input-symbols = {()},                               table-space-text-post=\ ,                               table-format=-1.2]}} \toprule \multicolumn{4}{c}{Panel A: $\beta_{\sigma,t}$} \\ \midrule & \mc{Low}  & \mc{Med}  & \mc{High} \\  \midrule MV  & 1.64  &  1.14  &  1.58  \\     & 1.17  &  0.97  &  0.87  \\ TA  & 1.90  &  1.03  &  0.88   \\ \bottomrule \end{tabular} %\vspace{2cm}  %defined by columns \begin{tabular}{ c*{4}{S[input-symbols = {()},                               table-space-text-post=\ ,                               table-format=-1.2]}} \toprule \multicolumn{4}{c}{Panel A:  $\beta_{\sigma,t}$} \\ \midrule & \mc{Low}  & \mc{Med}  & \mc{High} \\  \midrule MV  & 1.64  &  1.14  &  1.58  \\     & 1.17  &  0.97  &  0.87  \\ TA  & 1.90  &  1.03  &  0.88   \\ \bottomrule \end{tabular} \end{table}         \end{document}


Repeated roots in exponential ansatz method of solving second order differential equations

Consider the differential equation, $$ y'' - 10y' + 25y=0$$ Suppose $ y = e^{rx}$, we will find $r=5$ as solution. THis suggests: $$ y = A e^{5x}$$ But it can also be found that the family of functions of form $Bxe^{5x}$ also solves this differential equation. What exactly is the intuition behind this happening? i.e: repeated root equations having $xe^{rx}$ also as solution?


Misplaced \omit. \multispan with \newcommand

I'm trying to build my own cookbook-style, which has an ingredient makro. Sometimes the ingredients should be separated and have a headline, so I tried with an optional argument. A minimum example looks like this:  \documentclass{scrartcl} \newcommand{\ingredient}[3][]{     #1 #2 & #3 \\ } \begin{document}     \begin{tabular}{r|l}                 \ingredient[\multicolumn{2}{l}{Head} \\]{test1}{test2}         \ingredient[test3]{test4}{test5}         \ingredient{test6}{test7}     \end{tabular} \end{document}   What's wrong with this code? I get the following error message:  ! Misplaced \omit. \multispan -&gt;\omit                     \@multispan  l.7 ...[\multicolumn{2}{l}{Head} \\]{test1}{test2}


Functions satisfying $f\left( f(x)^2+f(y) \right)=xf(x)+y$

Find all functions $f:\mathbb{R} \rightarrow \mathbb{R}$ such that $f\left( f(x)^2+f(y) \right)=xf(x)+y$ for all real numbers $x$ and $y$.   Clearly $f(x)=x$ is a solution, check by substitution.  I'm at a loss as to how to show this is the only one or find others.  Any help would be very much appreciated.


How to get inverted colour arrow on the username in the terminal?

Please refer the attached image. I want an inverted colour arrow on the username part in the terminal.  This screenshot is taken from a Mac Terminal.   For the below image, i want an arrow on top the of the whole left side text(as in above image), starting from  dp0522 till the $(in the below image),


So i'm thinking of getting the Asus Transformer Infinity TF700 and I was wondering if it could run ubuntu.  Also I have heard that there are not many good apps for tablet android OS, if I did get ubuntu would it have more apps? What other benefits does ubuntu have over android?


I try to modify @Mico  as follows:  \documentclass{article}  \begin{document} \[ V = \int_0^2(4-x^2)\,dx = 4\int_0^2\!dx - \int_0^2\!x^2\,dx = 4\left[x\middle]_0^2 - \middle[\frac{1}{3}x^3\right]_0^2 \] \end{document}   but to my surprise I got the following result:    Is this a bug?   I expect that at both term indices will be on the same position regarding bracket. The same result is also if instead x is for example if in brackets is \frac{1}{x}.


Internet Explorer playing ads in background, possible malware

I think I may have a virus. The audio of ads keep blasting in the background and I found the source to be internet explorer. Task Manager shows Internet Explorer open in the applications tab but there are no visible windows. When I right click on IE and click Go to process nothing happens. In the processes tab, I see 3 iexplore.exe processes. Whenever I end them, an hour later the background ads return with IE windowless. I have tried the following AV's and tools but none of them succeeded:   Trend Micro Maximum Security Malwarebytes Anti-Malware Junk Ware Removal Tool by Thisisu Hitman Pro AdwCleaner   I'm running Windows 7 Ultimate 64-bit.  While I was writing this: I noticed a program in the programs and features list called "agederar by ryofward". Could this be the culprit?


Including a stackexchange account in graduate school applications

I'm writing this with a throwaway account, for obvious reasons; if this is inappropriate or runs counter to the rules of the site in some way, please let me know. I'm an undergraduate student in the UK, and am planning on applying to PhD programs next year. For context, I'm looking primarily at programs in the US, and am hoping to specialize in applications of model theory to algebra and geometry. For the past year or so, I have been a reasonably active contributor on ; at present I am self-studying some material, and so have been asking occasional questions when getting stuck on a proof or exercise in the textbook I'm reading, but for the most part I enjoy answering questions on the site, generally in algebra or logic. (I'll avoid specificity, again for obvious reasons.) Most of the questions I've answered are pretty standard, with a handful of (at least for me) less obvious ones, but my activity on the site has been largely well-received, at least as far as I can tell. So, in short, my question is whether a stackexchange profile can be a worthwhile inclusion in graduate school applications. I see a few pros and cons; on the one hand, I'm (embarrassingly) a bit proud of my contributions here! I really enjoy sharing my love of math and helping people resolve questions (teaching is one of the things I'm most excited for in the future), especially questions that are particularly interesting or thought-provoking. I also enjoy mathematical writing, and one of my favorite parts of the site is that it's an excellent venue for sharpening one's expository abilities. These are important things to me, and I feel that including the math.SE profile in an application would be a good way of indicating this. I also believe (read: hope) that the questions I've posted are worthwhile, and indicate a good understanding of and level of thought about the material I'm studying. On the other hand, I'm concerned an application committee might see the time spent on the site as frivolous or wasted, somehow; the site is certainly a source of procrastination for me, and my involvement may give an undesirable impression of being too vested in virtual things. Furthermore, while I'm generally happy with my contributions to the site, I'm also aware that one's own view of such things may be very different than the view of an experienced mathematician; what if my answers seem overcomplicated or my questions seem silly? In any case, these are some of the things I've been thinking about; any thoughts would be greatly appreciated.


Switching Micro-controller from Adapter power to Battery

Currently I am running my micro-controller boards with power adapter(AC to DC).  Now I am developing a system which senses AC power and sends me some signal when AC power is gone.  The problem is I am running my board with the AC power(through adapter) which I am sensing. So, I need to switch to battery power( as backup ) instantly when AC power is gone making sure my board doesn't turn off while switching.   I am not sure how it should be done.


URL of Meta Stack Exchange chat room transcript (which I opened from inbox) contains 2 slashes after "chat.meta.stackexchange.com". Why?

I was chatting in a chat room and I went offline after some time. When I came back online, I checked my inbox and there was a chat reply in the chat room. The URL of the transcript (which I opened from inbox) had two slashes after "chat.meta.stackexchange.com". Like this:   Even if I remove one of the slashes, it's still the same website. So what's the need of two slashes when we can use one? Is this a bug?


How can I see deleted comments on my question?

In my notification bar at the top of the page, there's a pretty rude comment about my question, but when I try to look at it, it's already been deleted. I'd really like to be able to respond to that comment (in a polite, professional manner, of course.) Is there any way I can see comments that have been deleted?


Does constant charging harm my Android cellphone?

I usually disconnect my cellphone from the charger some time after it's fully charged because I'm afraid the battery could lose capacity over time if I don't. However, I believe modern electronics should be able to handle this kind of scenario and automatically stop charging the battery once it's full. Does this apply to modern Android phones? Or do I need to continue disconnecting it all the time?


Unable to start VMWare player after upgrade to 13.04

Am unable to start VMWare player after upgrade to 13.04. Error: Before you can run Vmware several modules must be compiled and loaded into the running kernel. if i click on install nothing happens, kindly assist.


Auto.arima with daily data: how to capture seasonality/periodicity?

I am fitting an ARIMA model on a daily time series. Data are collected daily from 02-01-2010 to 30-07-2011 and are about newspaper sales. Since a weekly pattern in sales can be found (the daily average amount of copies sold is usually the same from Monday to Friday, then increases on Saturday and Sunday), I am trying to capture this "seasonality". Given the sales data "data", I create the time series as follows:  salests<-ts(data,start=c(2010,1),frequency=365)   and then I use the auto.arima(.) function to select the best ARIMA model via AIC criterion. The result is always a non-seasonal ARIMA model, but if I try some SARIMAs model with the following syntax as example:  sarima1<-arima(salests, order = c(2,1,2), seasonal = list(order = c(1, 0, 1), period = 7))   I can obtain better results. Is there anything wrongs in the ts command / arima specification? The weekly pattern is very strong so I would not expect so many difficulties in capturing it.  Any help would be very useful. Thank you, Giulia Deppieri  Update:  I have already changed some arguments. More precisely, the procedure selects ARIMA(4,1,3) as the best model when I set D=7, but AIC and the others good of fit indexes and forecasts as well) do not improve at all. I guess there's some mistakes due to confusion between seasonality and periodicity..?!   Auto.arima call used and output obtained:  modArima<-auto.arima(salests,D=7,max.P = 5, max.Q = 5)     ARIMA(2,1,2) with drift         : 1e+20  ARIMA(0,1,0) with drift         : 5265.543  ARIMA(1,1,0) with drift         : 5182.772  ARIMA(0,1,1) with drift         : 1e+20  ARIMA(2,1,0) with drift         : 5137.279  ARIMA(2,1,1) with drift         : 1e+20  ARIMA(3,1,1) with drift         : 1e+20  ARIMA(2,1,0)                    : 5135.382  ARIMA(1,1,0)                    : 5180.817  ARIMA(3,1,0)                    : 5117.714  ARIMA(3,1,1)                    : 1e+20  ARIMA(4,1,1)                    : 5045.236  ARIMA(4,1,1) with drift         : 5040.53  ARIMA(5,1,1) with drift         : 1e+20  ARIMA(4,1,0) with drift         : 5112.614  ARIMA(4,1,2) with drift         : 4953.417  ARIMA(5,1,3) with drift         : 1e+20  ARIMA(4,1,2)                    : 4960.516  ARIMA(3,1,2) with drift         : 1e+20  ARIMA(5,1,2) with drift         : 1e+20  ARIMA(4,1,3) with drift         : 4868.669  ARIMA(5,1,4) with drift         : 1e+20  ARIMA(4,1,3)                    : 4870.92  ARIMA(3,1,3) with drift         : 1e+20  ARIMA(4,1,4) with drift         : 4874.095   Best model: ARIMA(4,1,3) with drift           So I assume the arima function should be used as:  bestOrder <- cbind(modArima$arma[1],modArima$arma[5],modArima$arma[2]) sarima1<-arima(salests, order = c(4,1,3))   with no seasonal component parameters and period specifications. Data and exploratory analysis show that the same weekly pattern can be approximatively considered for each week, with the only exception of August 2010 (when a consistent increase in sales is registered). Unfortunately I have no expertise in timeseries modeling at all, in fact I am trying this approach in order to find an alternative solution to other parametric e non-parametric models I have tried to fit for these problematic data. I have also many dependent numeric variables but they have shown low power in explaining the response variable: undoubtedly, the most difficult part to model is the time component. Moreover, the construction of dummy variables to represent months and weekdays turned out not to be a robust solution.


Are creatures attack stats based on attributes / proficiency?

The Brown Bear seems to be equivalent to a fourth level character with D10 as hit dice. It has STR +4, and thanks to its 'level' a proficiency bonus of +2.  Based on those stats, its to-hit should be +6, not +5.   The often compared Dire Wolf (same level, about the same) has only STR +3, but still to-hit +5. So the proficiency bonus is not based on CR, as I first thought.  Is this a typo? Or just minor balancing applied without correcting the attributes?  Are there any official comments on this?  PS: The Brown Bear is just one example, this comes up multiple times in MM.


Cannot post question about tag on per-site meta, due to "quality standards" filter

, I was unable to post my simple and brief and relevant question to the meta page.  This response stood between me and posting it:  "The question body does not meet our quality standards. Please make sure that it completely describes your problem - including what you have already tried - and is written using proper grammar."  This is totally bogus.  Why does this exist in Stack Exchange and what can be done about it?


Do I need an airport transit visa for Amsterdam

I am a Philippines passport holder working in Kazakhstan. From Kazakhstan I would like to fly to USA but I will have a 2 hour and 30 minute layover in Amsterdam AMS Airport.    Do I need an airport transit visa?


Given $g$ is continuous on $[0,1]$ and differentiable on  $(0,1)$,   $g(0)=0$, and $g(1)=1$.        1) Prove that there exist $0<c_1<c_2<1$ such that   $$\frac{1}{g'(c_1)}+\frac{1}{g'(c_2)}=2.$$       2) Prove that there exist $0<c_1<c_2<1$ such that    $$g'(c_1)g'(c_2)=1.$$   I am thinking if Mean Value Theorem would help, but Mean Value theorem could only prove that in interval (0,1) there exists $g'(c)=1$.


Assumptions behind simple linear regression model

Let's say we have a simple linear regression model, that is, $y = X\beta + r$ where $y$ is a vector of size n x 1, $X$ a matrix of size n x p, $\beta$ the regression coefficient vector of size p x 1 and $r$ is a residual error of size n x 1.  Most of papers I read consider that $y$ follows a multivariate normal distribution. My question is whether $y$ can follow a distribution different from normal, for example elliptical, etc. Is it necessary that in linear regression, for $y$ to be assumed Gaussian?   I discussed with a researcher and he told me that linear regression models are only suitable (or efficient) for Gaussian assumption. Is this true?


how to get a list of all FCurves in a scene

for the addon I'm working on, I need a list of all fcurves (a list of all selected/visible fcurves would be enouph) Do I really have to loop through all animation_data objects to get this list?  Thanks in advance, Jacques Lucke


Installing Previous Firmware in iPhone | New Firmware keeps Rebooting iPhone

After upgrading to iOS 14.4.2 my iphone keeps rebooting every 5 mins! I would like to restore my iphone to iOS 14.3.7. After finding signed firmware I tried using iTunes but kept getting error 9 . I found the solution in  stated that (in short) this is Apples way of giving trouble by removing signed firmware! However he suggested a solution that utilizes paid version of the software to flash earlier version of firmware (ISPW) into iphone, using Reiboot Now my iphone is completely unlocked, with my account signed in and everything is legit, yet if I restore earlier ISPW, then iTunes keep giving me error that I cant install old firmware! I need to know if there are any free tools online or Github project that can flash old firmware into iPhone? or anyway to check what is causing kernel panic. When I say old firmware i mean just one step earlier revision where my iphone didnt keep rebooting!  (update 1) iOS 14.4.2 is known to have heating issue which is perhaps why my iphone is rebooting -


Why the stock price is rising when company is growing well

I mean, you have a company with shares of 20 dollars and they have 10 million of it (market cap 0.2 B), not paying dividends. What makes other people buy their stocks, when they see that they were doing great e.g. in Q1 and they expect growth? Company doesnt pay dividends. Suppose they can earn 100 millions/y and they have two classes of stocks and they sell only B stocks (with much less votes) so that they cannot lose their majority and someone cant just buy them and take over the company. Why should the price go higher? Why should the demand go higher, when the company is doing amazingly well?  Why the stock price rises, when someone is doing great and growing? Do people buy stocks just because they think that other people will do the same and according to supply and demand law, the price will go higher? That seems just a bit odd. What do they expect? They expect to get more money than they invested, but how exactly (why the demand and therefore price goes higher)? They expect that the price will go higher for example, but why should it go higher? Why should the demand be higher and make the price rise?


How to calculate a weighted center of a set of zip codes

I have the zip codes for the US and their population. I need to calculate the weighted center. I have tried finding the zip code with the minimum   sum(distance_to_zip * zip_population)   This works but is slow. With 30,000 zip codes there are two loops, so 900 million calculations. I've tried to optimize by sorting based on distance from the middle, and stopping the inner loop once the value hits the current lowest value. This helps, but it's still too slow.  Is there a faster algorithm for calculating the weighted center?   Note: I am writing my own code, I'm not looking to do this in a GIS package.


I have been reading on  OnCalendar=   Sadly, I found no info on how to schedule an event on a day other way than defining a day of the week, which would make it run every week at the rarest.  I need it to run every, say, 14 days. And at a specified hour (say, 4am). Is this possible with systemd?


Reviewer Stats shows incorrect number of Suggested Edit rejections

I have reviewed 1786 Suggested Edits on Super User, as shown on the  page:            If I go to the approval/rejection status page for a suggested edit immediately after casting my approve/reject vote (before anybody else has voted) and click on “(more)”, I see something like:                    showing that I have approved 919 edit suggestions and rejected 585 edit suggestions.  This sounds about right, although the numbers add up to far less than the 1786 total.  (OK,  suggests that “Improve” actions count as reviews, but do not contribute to either the “Approve” or “Reject” counts.)  And these numbers are updating; yesterday they were 913 and 583.  But, if I look again after the edit has gotten its final vote, I see                    (“Scott has approved 919 edit suggestions and rejected 7 edit suggestions”), which is clearly, grossly wrong.  Note that the above two screenshots came from , about an hour apart.  Here’s :                    (and later)                    Even though I rejected a suggested edit today, the “7” is not incrementing; it was “7” yesterday.  And, BTW, the rejection numbers for  and  are clearly wrong, too; they are among Super User’s most prolific contributors.


Determine when $\sum_1^\infty \frac{(2n)!x^n}{n(n!)^2}$ converges. By ratio test, when $|x|<1/4$, the sum converges, $|x|>1/4$ diverges. But I'm not sure about $|x|=1/4$. By Stirling's approximation $\frac{(2n)!(1/4)^n}{n(n!)^2}\sim\frac{4^n}{n{4^n}\sqrt{ \pi n}}\sim\frac{1}{\sqrt{\pi}n^{3/2}}$, so when $|x|=1/4$, the sum converges. But I haven't learned Stirling's approximation yet, so how to prove that when $|x|=1/4,$ the sum converges, without using it?


I've been seeing a few failed tests when I vote to close questions on SO. Apparently others thought the questions were valid enough, but they lacked (for instance) code, or were not code-related.  One example I just failed was , which in my opinion is not a proper question for SO (as it is not code-related, but caused by setting a specific option in VS).    Similarly, I recently voted to close some question that showed some kind of a flow diagram and asking how to achieve it, but without any code or other effort shown in it. I've noticed it happening with a few other questionable questions as well, at ended up getting blocked from reviewing for 2 days as a result.  Is there a way to somehow flag or otherwise object to the test result? I'm perfectly fine with being told I was wrong, but some of these questions still do not seem like a good fit. Perhaps they shouldn't be used as test questions, as they do lack some of the (what I consider to be) essentials (I.e. code, or what the user tried to solve their issue).   Edit: I think this is the link to the review mentioned:


If I am banned from entering the US can I still land at an airport there, for a flight transfer?

I'm legally banned from the US and I need to get to Cost Rica or at least close to it. I can't find any direct flights from Ottawa or Montreal.   Will they arrest me if I land in the US for a flight transfer? Will they see that I am banned? Do they scan the passports?


Is it 'can you please send me the the files?' or 'please can you send me the files?'

My instinct feels the second one is more polite but I'm not sure if it is grammatically correct. Can someone answer this and explain which is the correct and polite way to frame this question?


Is it possible to use Python with the Ubuntu SDK?

wrote in  to a question I posted that:      ...the recommended way to develop apps for Ubuntu is the Ubuntu SDK.   So I installed it, but looks like the supported programming language is C++. Does it mean I will need to know C++ to develop a new application for Ubuntu? Is C++ the recommended programming language for Ubuntu application now?  What about Python, I started learning it hoping to develop applications for Ubuntu.


I am able to run my node server on an EC2 instance by SSH-ing into the server and running the command node index.js when inside of the src file. The server works fine, but the issue is that I have to persist the SSH connection to the EC2 instance, otherwise it terminates the server process. I'm sure I'm doing something wrong, but I couldn't find a clear cut and dry solution online without getting too much into the weeds. Also for anyone wondering, I SSH-ed into my github and installed git on the EC2 instance in order to pull the code from the repository to the instance, instead of using CodeDeploy. The reason is that I was getting vague errors with CodeDeploy like "there was an issue deploying your revision", so I decided to go the manual route for uploading the code. So I could use some solutions to common "gotchas" in this area as well. Thanks.


How do I test for a symmetric distribution?

I collect numbers from generators that yield different ranges of whole numbers with an unknown distribution. I want to estimate the mean of the numbers outputted by this generator. I'm convinced the distributions are symmetric (more specifically, uniform) though, so I can just average the min and max after I have a decent sample size. What would be the best way to test that the distribution of numbers is symmetric or uniform?  Things I've tried: -Checked that the mean, median, and midpoint converge to the same values, but I can't quantify how close the values would have to be. -Histogram, but my sample sizes (n<100 because I must manually collect) are too low for me to tell -Chi-square test with the frequencies of each number in the range and testing them against the expected value for a uniform distribution, but I've read there are problems with this in other posts -Pearson's skewness coefficient and comparing that with the standard error of skewness, but I think there are limits to this kind of approach -Comparing kurtosis of data with that of a uniform distribution  I've also read about the Kolmogorov-Smirnov tests and Shapiro-Wilk tests but these seem too complicated for such a simple seeming task..  Thanks


Why does Gmail no longer offer the 'Send through Gmail option' for aliases?

In the past, I could add any email address that I own via Settings → Accounts → Add another email address you own.  .  On that wzard, there were 2 options:    But now it only lets you specify the SMTP server directly and it doesn't accept the standard settings of smtp.gmail.com    Did they change policies?  Or am I missing something here?  I tried this on two different accounts.


How can a wire be called the "hot" wire and another the "neutral" wire when ac current reverses itself 60x/sec? For first half of a given cycle it flows from the "hot" wire to the load and back out to the source through the  "neutral" wire. Since ac reverses itself in the second half of the cycle, it flows from the "neutral" to the load and back to the source through the "hot" wire. So they are alternately the "hot" and "neutral" wire depending on which half of the cycle we are in?


What "time travel" story required the traveller to mentally reconstruct his world in order to return to it?

Here's what I remember about it:   The protagonist is sent a relatively short distance into the future (maybe a year? I've forgotten). When he arrives in this "future" he finds himself in a completely different world, with non-human inhabitants. The inhabitants use a machine to teach him their torturous language. He tries to return home, and (eventually) finds himself in a realm of chaos/nothingness. He laboriously reconstructs in his mind everything he can remember about his home and finds himself back there somehow. The twist is      that in his "home" reality everyone speaks the language he was taught by the non-human inhabitants at his first stop.


Charged metal sphere- electric potential

Why is the electric potential on the surface of a charged metal sphere always constant?


how to find the source where the spam is originating from

Is there anyway I can trace the sender profile through email headers?  We have received spam emails as undeliverable sent from our mail id.  We would like to find out where they are originating from  Thank you


How to run .desktop files from command line

I am configuring a box with openbox (with GNOME under the scenes), and I want to run the .desktop files in /etc/xdg/autostart/ from a script at login.  But xdg-open and gnome-open do not seem to do what I want (unless I use them in the wrong way).  I am looking for a standard command, and don't want to parse the desktop files looking for the Exec line.  Also welcome would be an indication on how to tell openbox to start those desktop files in some other way, and without an ad hoc script.


What is a good word to describe someone who is talking down to you and thinks your decisions/actions are wrong?

So if someone is giving you an attitude when you are telling them about certain life decisions you made.  And that person really doesn't understand the situation, not to mention they are ignorant... how would you describe what he or she is being?


How do I delete a board from a Trello account?

I wish to permanently "delete" a board from my account.  There is one entry in the forum asking this question already, but the reply states that you should "close" the board. I am looking for the answer to the question if a board can be permanently removed from the account?  I've just started to play around with Trello and created several boards that are not relevant any more, will never be relevant and I never want to see them again. So, is it possible to "delete" a board? I cannot find a way to do it.


Properly discontinous actions and orientation of a mainfold

Let $G×M→G$ be a properly discontinuous action of a group $G$ on a differentiable manifold $M$. Prove that the manifold $M/G$ is orientable if and only if there exists an orientation of $M$ that is preserved by all the diffeomorphisms of $G$. (Each group element $g∈G$ gives a diffeomorphism of M, namely the map $\phi_g:M→M$ sending $x∈M$ to $g⋅x$. These are the diffeomorphism the exercise is talking about) My attempt: since the action is properly discontinous it induces a smooth manifold structure on $M/G$.Let $π:M→M/G$ be the quotient map. If $M/G$ is orientable, then I can choose an oriented atlas $(U_i, x_i)$ on $M/G$. $π^{ -1}(U_i)$ is a cover of M. And here I'm stucked.


Suppose I have a sample of $N$ numbers $a_1,\dots,a_N$ from $1,\dots,k$. How can I test whether they are equidistributed?  I'm not interested in a full randomness test as the order does not matter to me, so  is not relevant to me, neither are its dupes. For me, a sequence $1,2,3,\dots k,1,2,3,\dots,k,\dotsc$ is perfectly fine.  I would like to have a test just from the frequencies/counts, i.e., my input data really is the vector of number of occurrences $c_j=\#\{n\leq N:a_n=j\}$ for $j=1,\dots,k$. I was unable to google the way how to proceed.


how to filter a list to remove the element with duplicated attribute in java?

I want to filter a list to remove the element with duplicated attribute, see code snippet below:     public class People{       string name;       string priority;       //...getter setter     }     list<People> peopleList = //...get a list of people    Here I want to show a list of people with unique name attribute , how to operate the peopleList  ? and also if there are several People object with same name, i want to check the priority to decide which one should be in the final unique list. hope i am clear.


How do I make Portable Document Format -- portable?

I prepared a document in XeLaTeX in Linux, fonts embedded, then I went to a printing guy on windows + lots of Adobe tools, and pdf looks the other way on his machine: some fonts get scaled which results in a slightly deformed layout.  How do You get a portable pdf?  My first thought is to convert pdf to ps with a virtual printer (CUPS in case of linux).  One other possible solution is to embed fonts in the ps resulted:  ps2pdf14 -dPDFSETTINGS=/prepress document.ps   Edit:  MWE:  \documentclass{article}  \usepackage{fontspec}  % fonts: \defaultfontfeatures{Scale=MatchLowercase,Mapping=tex-text} \setmainfont{DejaVu Sans} \setsansfont{DejaVu Sans} \setmonofont{DejaVu Sans Mono}  \usepackage{fontawesome}  \begin{document}  \faBullhorn test.  \end{document}   In okular:    In Adobe Reader:    You see in Adobe the glyph is larger. How do I process pdf so that it is displayed in the same way in any major pdf viewer?  Edit 2:  The problem with scaled font is solved if I open the pdf and export it to pdf with  -- but its free version warns me about the watermark (which I actually can't find).  Export to pdf in  doesn't help.  Printing to pdf in virtual CUPS printer doesn't help. Moreover after piping pdf through CUPS adobe reader doesn't see the glyph at all.


Accepting your own answer with alternative answers to be worth +2 reputation?

Today, when you accept an answer you did not provide, you get a +2 reputation, however, if you accept your own answer, you get +0.  I expect the reason for this is to stop people gaming the system by asking and answering their own questions repeatedly.  However, this has the downside of providing a disincentive of accepting your own answer when it seems the best and instead accepting an inferior one in order to get the reputation bonus.  Therefore, I propose that the accept your own answer is only worth zero when there are no answers provided by anyone other than yourself.  I feel this keeps the intent of preventing gaming the system for reputation, while removing disincentive from picking the best answer, even if it is your own.


A friend asks me all the time to pick up money for her (Western Union, Moneygram)

A friend of mine trades Bitcoin and often asks me to pick up money for her, i.e., someone sends money to me (on my name) and I just pick it up and give it to my friend. The amounts are usually around $500.   Is this legal? Can I get into trouble doing this?   I have no idea who the senders are. Thank you.


How do I implement a get() method for a quadtree without it throwing a nullPointerException?

I'm trying to put together a quad tree for a homework assignment, similar in function to a binary tree, and I got down to implementing the get() method, where it returned a key's value if the value existed, otherwise it returned null. However, with my given test cases, I keep receiving a nullPointerException, and I can't seem to figure out why. Any and all help is appreciated.  Here's my get() method:  public V get(Coord<X,Y> key) throws IllegalArgumentException {     checkKey(key);     Position<Entry<Coord<X, Y>, V>> p = treeSearch(tree.root(), key);     if(tree.isExternal(p)) { return null; }     return p.getElement().getValue();   }   Now, my homework file says that this should be almost identical to this get method(also in the homework file):  public V get(K key) throws IllegalArgumentException {     checkKey(key);                          // may throw IllegalArgumentException     Position<Entry<K,V>> p = treeSearch(root(), key);     rebalanceAccess(p);                     // hook for balanced tree subclasses     if (isExternal(p)) return null;         // unsuccessful search     return p.getElement().getValue();       // match found   }   with some exceptions for the types.  In the test cases, it makes a temporary tree with random integers as an entry's value, and these:  assertEquals(null, m.get(new Coord<>(0,2))); assertEquals(null, m.get(new Coord<>(-6,-5))); assertEquals((int)3, (int)m.get(new Coord<>(-5,-6))); assertEquals((int)6, (int)m.get(new Coord<>(7,7))); assertEquals((int)0, (int)m.get(new Coord<>(0,0)));   would always return a nullPointerException for my get() method, whereas if used on the example, it would return the key's value.


An automated sandbox refresh caused the loss of data

Our sandbox got refreshed friday afternoon by an "automated process". Is there any way to recover the lost data ? Also, the integration to Clarizen is gone and I no longer can connect it.   Thanks,   Regards,   Amir


All I know is that for $x>0$ we have that $f(x)>0$. I do not have any experience with this kind of equations and do not know how to start attacking this problem.


Let $V : \mathbb{R}^n \rightarrow  \mathbb{R}$ be (strictly) convex and continuously differentiable on $\mathbb{R}^n$. Show that for any $y \in \mathbb{R}^n$ and any $x \in \mathbb{R}^n$ $$ V(y) \geq V(x) + \nabla V(x)^\top(y-x) $$ For $n=1$ this implies that for any $x \in \mathbb{R}$ and for any $y \in \mathbb{R}$, $V(y)$ lies above the tangent line to $V$ at $x$.


Looking at  privilege, I find this to be a surprising requirement:  Try to make the post substantively better when you edit, not just change a single character. Tiny, trivial edits are discouraged.  What motivated this, or rather, what does this mean exactly? Does that, for example, include removing stuff like "Hi, all", and "thanks in advance"? [update] I was led to a  talking about this topic, but it has a million Comments, and doesn't really justify the rule (unless it's hidden in those million Comments). However, looking at Jeff's Comments gives me an idea that this was meant as a general guideline, instead of a hard-and-fast rule: If you edit a post, check elsewhere on that post if there are other improvements that can be made.


Is "Do your data bear this out?" correct?

While reading , if found the following expression:     Since the Fermat test has O(log n) growth, how would you expect the   time to test primes near 1,000,000 to compare with the time needed to   test primes near 1000? Do your data bear this out?   Is it correct? Shoudn't it be "Does your data bear this out?"


Force between two finite parallel current carrying wires

Remark: This is not a homework question...It is pure out of theoretical interest. I asked this the mathematics-community a couple days ago and got no answer, so I figured I'd try here.  Most standard physics textbooks compute the force two infinite wires exert on each other, but they remain silent about the case where the wires are finite. Let's say we have two parallel wires carrying a current of equal magnitude in the same direction, both of which have a length $d$ and also seperated by a distance $d$. I now want to find out the force one wire exerts on another, using the Biot-Savart Law.  Let the left wire be positioned at the origin of the $xy$-plane, going along the $y$-axis, and let the other wire be a distance $d$ to the right. We assume the currents are flowing in the positive $y$-direction. Then we first choose a source element (on the left wire) of infinitesimal length $dy$ described by the position vector $\mathbf{r_0} = y_0 \hat{j}$. This constitutes a current source of $I d\vec{l} = (Idy) \hat{j}$.  We then pick an arbitrary field point $P$ on the other wire with position vector $\mathbf{r_p} = x\hat{i} + y \hat{j}$. Then the position vector $\mathbf{r}$ pointing from the source point to the field point is given as  \begin{align*}  \mathbf{r} = \mathbf{r_p} - \mathbf{r_0} = x\hat{i} + (y - y_0) \hat{j}, \end{align*} with $\sqrt{x^2 + (y-y_0)^2}$ being the length of this vector. If we now calculate the crossproduct $d\vec{l} \times \mathbf{r}$, we can write it as \begin{align*} dy \hat{j} \times (x\hat{i} + (y - y_0)\hat{j}) = -dy x \hat{k} \end{align*} Now comes the tricky part. I think I need to setup a double integral, because we are working with infinitesimal force elements $d\mathbf{F}$, each which is given as  $d\mathbf{F} = I d\vec{l} \times \mathbf{B}$. But we also have that \begin{align*} d\mathbf{B} = \frac{\mu_0 I}{4 \pi} \frac{d \vec{l} \times \hat{r}}{r^2}  = \frac{\mu_0 I}{4 \pi} \frac{d \vec{l} \times \mathbf{r}}{r^3} = -\frac{\mu_0 I}{4 \pi} \frac{dyx}{\sqrt{x^2 + (y-y_0)^2}} \hat{k} \end{align*} Hence I need to somehow integrate over $d\mathbf{F}$ and $d\mathbf{B}$. Does anyone have an idea how to do this?


Guidelines for duplicating tag text in a question title

Suppose we have a question like:     How to check if an object is a string in JavaScript?   Obviously, we should tag the question with the javascript tag.  But do we need that 'in JavaScript' part in the question title then?  It looks redundant, since tags seem to be the best mean to put a context of the question. I believe short, concise and key-wordish titles are more preferrable, so I'd rather make the title like this and let tags say the rest:     Check if object is string   Moreover, I noticed that often a question title in Google Search gets automatically prepended with the left-most SO tag text like this:     javascript: How to check if an object is a string in JavaScript?   Which makes the 'in JavaScript' part even more questionable.  Could someone clarify this or point me to a question asking guidelines on this, if any?


Expressing polar complex numbers in cartesian form

I need to express $z = 4e^{-i\pi/3}$ in the form of $x + yi$ and represent it on the Argand diagram.  I think that $4 = \sqrt{x^{2} + y^{2}}$ and that $\tan (\pi/3) = y/x$ but I haven't been able to do anything useful with this information...  Is this solvable via simultaneous equations?  Thanks!


Why does the liquid metal Terminator T-1000 have a default human face / shape?

Why does the T-1000 Terminator almost always go back to the same appearance of a policeman?  By often reusing the same face and body shape, it gives itself away. Sarah Connor and John Connor would learn to recognize that face and avoid it.  It could choose many other shapes and faces that Sarah and John never recognized. It saw, touched, or interacted with a bike gang member, employees at the steel foundry, other cops, a scientist, waitresses at the cafe, and a guard at the mental hospital. It could have used any of those. (Or maybe create a whole new face? Or mix and match features and clothes from different people it met.) Seems counter-productive to use the same face every time when it is tracking down Sarah and John at the steel foundry.  The out-of-universe explanation is that Robert Patrick played the villain and the producers wanted the same actor for most scenes in order to get a consistent  acting style for the T-1000. Is there an in-universe explanation?


Do access token expiration times reset/get updated every time they are used?

I have my access token session set to expire every 24 hours, but if someone uses that token (say through a rest API call) at some point, does it last for another 24 hours or does the session not restart?


Getting hash of a list of strings regardless of order

I would like to write a function GetHashCodeOfList() which returns a hash-code of a list of strings regardless of order. Given 2 lists with the same strings should return the same hash-code.   ArrayList list1 = new ArrayList()     list1.Add("String1"); list1.Add("String2"); list1.Add("String3");      ArrayList list2 = new ArrayList()     list2.Add("String3");     list2.Add("String2");  list2.Add("String1");  GetHashCodeOfList(list1) = GetHashCodeOfList(list2) //this should be equal.   I had a few thoughts:    I can first sort the list, then combine the sorted list into 1 long string and then call GetHashCode(). However sorting is a slow operation. I can get the hash of each individual string (by calling string.GetHashCode()) in the list, then multiplying all hashes and calling Mod UInt32.MaxValue.  For example: "String1".GetHashCode() * "String2".GetHashCode * … MOD UInt32.MaxValue. But this results in a number overflow.   Does anyone have any thoughts?  Thanks in advance for your help.


What did I do wrong? Inverting amplifier 1:1 ratio

I'm getting a non inverted output. The resistors I used were two 100ohm 1/4watts. Signal was 4v peak to peak 600hz.


Does anyone know what might be causing this to happen with my renders? It's like part of the material doesn't want to show but I'm using a very basic setup.  It looks even worse with cycles:  My rock looks perfectly fine though on the viewport.  Here are the files for it


How to resolve the null pointer exception when entering elements from user to store in an array?

In the following program, I am trying to get values in an array from user.  However, I am getting NullPointerException after entering only two values. Can someone explain why I am getting this exception?  import java.util.*; import java.io.BufferedReader; import java.io.IOException; import java.io.InputStreamReader;  public class MemoriseMe{      static int arr1[],count;      public static void main(String[] args) throws IOException      {         BufferedReader brObj = new BufferedReader(new InputStreamReader(System.in));          int firstQuery =Integer.parseInt(brObj.readLine());         System.out.println("Enter the elements : ");           String line = brObj.readLine(); // to read multiple integers line         String[] strs = line.trim().split("\\s+");          for(int i =0;i<firstQuery;i++)         {             arr1[i]=Integer.parseInt(brObj.readLine());         }     } }


I am using a Compaq Presario C700. Before upgrading from Ubuntu 12.10 everything was fine, but since I switched to Ubuntu 13.04, I can't shutdown my system in any way. The only thing I could do is hold the power button until it shuts down on its own.  I have tried using the terminal to shutdown, but it's no use. When I click on the shutdown button on the title bar, there is no option for shutdown. The only thing I could see is Lock Screen and Log Out. What should I do?


Bones: Connect moving spheres with strechable pipe

I want to connect some of the spheres below with pipes/lines. These spheres should move around a center with varying distance. How can i add bones to them and the pipes so that:  the spheres can be controlled by the bones the pipes stretch according to distance the spheres keep their form the start/end of the pipes stay in the center of the spheres


What to call the area where the hair directions all change on the head? In Russian that term is макушка, and looking for the translation I find it to be top.   However, that is not a satisfactory answer, since some people have two areas on their head where the hair changes its direction.  Also, sometimes these areas are not on the top of their head.


Show that the set $ [-1, \infty )$ has cardinality $ c \ \ $

Show that the set $ [-1, \infty )$ has cardinality of the continuum. Draw the bijection.    Answer: If I consider the map $ f: [-1, \infty ) \rightarrow (-\infty, \infty) $ by $ f(x)=\log(1+x) $.   This is one-one  and onto.   Hence the proof.  But I have doubts using $ f(x)= \log(1+x) $ because it is not defined at $ x=-1 $.  Any help is there ?


Schengen area entry point rules when no visa is needed

It is said that when requesting a short stay Schengen visa you must follow this rule:     You must apply for a visa in the representation of the Schengen   country in which lies the main reason/purpose of your trip or the   representation of the Schengen country where you will remain longer.   If the length of stay is the same for many countries, you need to   apply in the representation of the Schengen country where you will   arrive first.   However, if my country starts to take part of the visa waiver program, do I need to follow the same rule from above and even if a visa is not needed anymore?   It seems that embassies are very picky with this (at least with visa applicants) but I wonder what to expect when no visa is needed you arrive in one of these Schengen countries.


Syntax of Using Math Mode: Empty Lines (Beginner Question)

I'm just starting to learn LaTeX. I tried typing \begin{equation*}  (math goes here)  \end{equation*}  and I got a whole bunch of errors. It seems LaTeX interpreted the empty line as the equation: when it saw nothing there, I guess it just ended math mode? It then said my other commands needed $'s so I assume that's what happened. When I typed \begin{equation*} (math goes here) \end{equation*}  everything was fine. So I'm confused. If LaTeX sees an empty line in an environment, does it just interpret this as me changing my mind, and deciding not to use the declared environment?


Show that if $a$ is a divisor of $bc$ and $(a, b) = 1$, then $a$ is a divisor of $c$.

Suppose I set $ax+by=1$ such that $x, y$ are integers and $a$ and $b$ are elements.   The greatest common divisor of $a, b$ is $1$.   If $a=bc$, then $bcx+by=1$.   But then what do I do?


Avoiding being blocked for suggesting new ideas

On SO meta a while back I complained about the way downvoting worked because many people were downvoting legitimate, high-quality questions, for other reasons. Usually they didn't either like the idea being proposed, or they didn't like the subject of the post even being discussed because it deviated from the status quo.  The response to this was that I shouldn't take it personally, and that the votes in no way reflected the quality of the post, but were just indicative that the readers disagreed in one way or another with the question or suggestions in the question. They seemed to think this was perfectly normal and ok and conducive to further discussion.  Well, now after proposing an idea, which I thought merited discussion, that was disliked to the tune of -22, I am getting a warning "you are in danger of being blocked from asking anymore".  I thought the purpose of meta was to discuss things and consider new ideas. If everyone who proposes new ideas, gets dozens of downvotes from the status quo crowd, then I would think that would have the effect of discouraging new ideas, or simply banning people who propose new ideas, as appears to be happening to me. The effect of this may be that by a Darwinian process meta participation will be limited to people who like the status quo, and outsiders with new ideas will be greated with hostily and rejection.  Anyway, as this post falls into the category of "things disturbing the status quo" it will probably be given another twenty downvotes, so I will be banned. Thanks for letting me participate while it lasted, and goodbye.


I just installed Ubuntu 16.04 on a Gigabyte PC. Installation went without any issues. This OS is fantastic. I just have one problem, it freezes often usually while browsing the Internet.Can someone please steer me in the right direction?


transition from multiplicative order to Fermat's little theorem

I am reading a paper and they write that Fermat derived his little theorem from this observation: If $p$ is a prime, and $a$ is any number not divisible by $p$, then the order of a modulo $p$ divides $p−1$. In terms of divisiblity and this is the theorem that Fermat found the theorem looks like this: If $p$ is prime and $a$ is coprime to p, then $p$ divides $a^{p−1}−1\implies p \mid a^{p-1}-1$ The multiplicative order in terms of divisibility looks like this: the order of $a$ mod $p$ is the smallest $e > 0$ so that $p$ divides $a^e−1\implies p \mid a^{e}-1$ I am trying to obtain Fermat's theorem by having a look on his observation: So I want to show that: "If $p$ is a prime, and $a$ is any number not divisible by $p$, then the order of a modulo $p$ divides $p−1$" leads to "If $p$ is prime and $a$ is coprime to p, then $p$ divides $a^{p−1}−1$". My approach is, taking the definition of order: p | $a^e-1$ and using the observation $=>$p | $a^{e|p-1}-1$. This already looks pretty similar to  $ p $ | $a^{p-1}-1$, but not quite and I am not sure if I am on the right track. Thanks for your help


How to change subdivisions after adding a grid

I'm following this , when I use Add > Mesh > grid and then scale it, I get a grid with 9x9 squares:    To make the maze, I want the grid to have more squares (15x15 for e.g) however, no mater how big I scale it it remains 9x9 squares.  Is there a way to control the number of squares this grid has?


XML Schema: Element with attributes containing only text?

I'm having difficulty searching for this. How would I define an element in an XML schema file for XML that looks like this:  <option value="test">sometext</option>   I can't figure out how to define an element that is of type xs:string and also has an attribute.   Here's what I've got so far:  <xs:element name="option">     <xs:complexType>         <xs:attribute name="value" type="xs:string" />     </xs:complexType> </xs:element>


If you want to buy a house but you also think value will drop… is there something you can do to alleviate the risk?

Disclaimer: yours won't be fiscal advice. People involved will consult a professional before doing anything. This is just to gather some preliminary information.  Situation:   you want to buy a house or a flat, in UK you will get a mortgage in GBP, but you'd pay the down payment in EUR you think that there are fairly high chances that the value of houses in UK and GBP will drop the whole point of this question is actually buying the house/flat, renting is not an option by definition   What can you do to mitigate that risk?


What causes this corkscrew-shaped object to rise up in a stream of water falling down?

A corkscrew-shaped object is floating in a tub of water. When water is poured into the tub from some height, the object starts rising up vertically in the stream of water. The water stream is falling down in a spiral fashion. What is the Physics behind this? Is it the turning effect on the object caused by the spiral motion of the water falling on it? Or is it some other phenomenon?


Electric field created from time varying current in solenoid

I know how to calculate the magnetic field due to current inside the solenoid.  Obviously, when the current is varying, then the magnetic field will be time dependent.  By the 3rd Maxwell's equation, an electric field will be created.  I'm wondering that, why can I still use Ampere's law to calculate the magnetic field within the solenoid? (in fact, can i?)  I thought that the time varying electric field will also produce a magnetic field, meaning that the total magnetic field is not just that calculated from Ampere's law, but the sum of that calculated from Ampere's law and that produced by time varying electric field.