A conjecture about numbers of the form $10^{m}(2^{k}−1)+2^{k-1}−1$, where $m$ is the number of decimal digits of $ 2^{k-1}$.

Question     Numbers $n$ of the form $10^{m}(2^{k}−1)+2^{k-1}−1$, where $m$ is the number of decimal digits of $ 2^{k-1}$. For example:         $k=1$ then $n=10$.   $k=2$ then $n=31$.    $k=3$ then  $n=73$.   $k=4$ then $n=157.$      Conjecture:   the number $(2^k-1)\cdot 10^m+2^{k-1}-1$ where $m$ is the number of decimal digits of $2^{k-1}$ is never prime when it is of the form $7s+6$, that is when it is congruent to $6$ $\pmod 7$. Examples: $n=1023511$ ($k=10$)$\equiv 6 \pmod 7$ and thus it is composite $(1023511=19\times103\times523)$, $n=20471023$ ($k=11$) $\equiv 6 \pmod 7$ and thus it is composite ($20471023=479\times42737)$. With PFGW we arrived to $k=565000$ and all the $n's$ congruent to $6 \pmod 7$ are composite. According to Giovanni Resta's calculations in a post which has been canceled, there should be no probable prime congruent to 6 $\pmod 7$ upto k=800.000. The residue $6$ $\pmod 7$ occurs when either $m=6t+3$ and $k=3l+1$ or $m=6t+4$ and $k=3l+2$ with $k$ and $l$ some non-negative integers, but amazingly when it occurs the number is not prime. Can you find a counter-example or give a proof for the conjecture? Here a link to other interesting questions:  and  For primes of this form see:  The following vector contains all the exponents k<=366800 leading to a prime  $[2, 3, 4, 7, 8, 12, 19, 22, 36, 46, 51, 67, 79, 215, 359, 394, 451, 1323, 2131, 3336, 3371, 6231, 19179, 39699, 51456, 56238, 69660, 75894, 79798, 92020, 174968, 176006, 181015, 285019, 331259, 360787, 366770]$  Exponent $541456$ leads to another probable prime with residue 5 mod 7 and 325990 digits, but it need not be the next in increasing order.  Remark: we found five-in-a-row probable primes with res 5 mod 7. Probable primes with residue 5 are now twice frequent than expected. Exponents of these primes seem to be NOT random at all. Another thing I noticed, i don't know if it has some importance: the exponents leading to a probable prime $215, 69660, 92020, 541456$ are multiples of $43$. I noticed that $\frac{215}{41}, \frac{69660}{41}, \frac{92020}{41}, \frac{541456}{41}$ all have a periodic decimal expansion equal to $\overline{24390}=29^3+1$. This is equivalent to say that when k is a multiple of 43 and the number $10^{m}(2^{k}−1)+2^{k-1}−1$ is prime, then k is of the form $41s+r$ where r is a number in the set (1,10,16,18,37). Is there some mathematical reason for that?


How to deal with downvotes on an answer I posted that is accepted?

Some person is downvoting my answer.  This answer is the accepted answer, but they cast downvotes on my answer. How to deal with such kind of users? How to complain to the admin of Stack Overflow?


For what value of $p$ would the series $\sum_{n=2}^\infty \frac{1}{n^p\ln(n)}$ converge?  I have tried using the series convergence test, and limit comparison test, which does't help. So i am considering using the divergence test, and finding all values for p for which the limit is not $0$


Mounting shares with Login Items at login, Finder windows popup

I have some shares that are mounted during login. I used Users & Groups' "Login Items" panel to do this. When I login, all of the shares pop up in their own Finder windows.  How can I keep the Finder windows from popping up at login? I've already tried checking the Hide checkbox.


I hope to show that $$\mathbb{Z}[i]/(a+bi) \cong \mathbb{Z}_{a^2+b^2}$$ for $(a,b)=1$.  I made an effort to find a homomorphism but I failed.  Can you give a hint?


Let $X$ be a complex vector space with inner product and $T \, : \, X \rightarrow X$ a bounded linear operator.   Show that if $\langle Tx,y \rangle = 0$ for all $x,y \in X$, then $T$ is the zero operator.     My current suggestion: Since $T$ is a bijective mapping I now that for all $Tx$ there is some $y$, that is $Tx = y$ for some $x$ and $y$. Since this should be true for all $x,y \in X$ i can just write  $$\langle Tx,y \rangle = \langle Tx,Tx \rangle$$ This is only true if $Tx = 0$ if we should have this equality for all $x$, hence $T$ is the zero operator.


One particular permutation $\sigma $ of $5$ elements such that $\sigma ^{-1} (j) \le \sigma (j)$

As  for  options  $1.$  and  $2.$  I  have  taken  a  few  examples  randomly and  found  them  to  be  correct  but  could  not  generalize  and I am  clueless  about options $3.$  and  $4.$ The  answer   keys  that  came  with   it  says  all  the  options   are  correct.


In the last episode of Aincrad arc of Sword Art Online, how did Asuna survive even though her avatar disintegrated after being attacked by Kayaba? Also Kirito was stabbed by Kayaba as well. How did he survive?  Was it in the novel on how they really survived?


How can you calculate  $$\lim_{x\rightarrow \infty}\left(1+\sin\frac{1}{x}\right)^x?$$  In general, what would be the strategy to solving a limit problem with a power?


I live in Italy (Emilia Romagna), and my house, seasonally in spring, is full of these guys, someone knows their name and if they could represent a problem? They are very tiny slightly less than 0,5 cm including the antennae.


applescript: commands to maximize (green button) an iTerm window

Assuming I am opening an iTerm window with the following AppleScript:  tell application "iTerm"             set win1 to (create window with default profile)         repeat until exists win1             delay 0.01         end repeat         tell current session of current tab of current window             write text "watch -n1 " & "'"  & "kubectl get pods | grep -i " & input & "'"             split horizontally with default profile             split vertically with default profile         end tell   What code snippet should I use so that win1 gets maximized (as in clicking on the green window button)?  edit: regarding the proposed solution indicated in the question that is supposed to be duplicate, I have changed my snippet as follows:      tell application "iTerm"             set win1 to (create window with default profile)         repeat until exists win1             delay 0.01         end repeat         tell application "System Events"             perform action "AXZoomWindow" of (first button whose subrole is "AXFullScreenButton") of (first window whose subrole is "AXStandardWindow") of (first process whose frontmost is true)         end tell         tell current session of current tab of current window             write text "watch -n1 " & "'"  & "kubectl get pods | grep -i " & input & "'"             split horizontally with default profile             split vertically with default profile         end tell   However this now opens a new terminal window and no further command executes.


A triangle with vertices on the sides of a square, with one at a midpoint, cannot be equilateral

Let A, B, C, D, L, M, N be distinct points in the plane such that A, B, C, D are the vertices of a square with sides AB, BC, CD, DA and L, M, N lie on the sides AB, CD, BC respectively. If M is the mid-point of CD, then show that △LMN is not an equilateral triangle.  I cannot get anywhere with it. I tried to find a contradiction by assuming 60 degree angles, but no luck.   Source: Geometry proof contest math 2b


Installations going to folder with less space

Whenever I install any software, it goes to shlok-Lenovo-Legion-Y530-15ICH and soon the free memory becomes so low that I cancel installation.   However when I check the storage of my home directory from Files Properties, it shows over 73GB free memory:   So I tried to install softwares in home\documents but still shlok-Lenovo-Legion-Y530-15ICH is used up.   How can I utilize the free space and install softwares at my desired directory?


What can be done with a blatantly wrong answer to a popular question?

Today I came across a very popular question with 153,899 views. One of the answers suggested something which I knew was not possible (I was in doubt, but a quick test proved I was right):   The answer is plain wrong:   It adds a second parameter to a function that only takes one (this is legal in JavaScript, but the parameter is ignored) It suggests the second parameter can be used to specify the format. (again, it does nothing) It only works because the sample string in the answer is already in the supported format - which ignores the OP's real problem. Any other string and any custom format will fail.   Normally, I'd add my comment and walk away, but here we have a very popular question, a very bad answer, and the poster is gone (has not been seen since May - which to me suggests he is dead). If that is not bad enough, the answer has 27 upvotes, for a made-up feature. I can't even edit the answer to correct it - it really has nothing...  What should be done here? Can the answer be deleted?


I read that the correct way of  removing elements while iterating the Collection, is this way (using iterator):  List<Integer> list = new ArrayList<Integer>(); list.add(12); list.add(18);  Iterator<Integer> itr = list.iterator();  while(itr.hasNext()) {     itr.remove(); }   But, I receive Exception in thread "main" java.lang.IllegalStateException and I don't know why. Can someone help me?


Problem with getting out of an answer ban

I've been answer-banned today because of 3 poor answers, which I admit is my fault.  I read , and  of  on Meta, and I think I understand how to get out of the answer ban.  I edited 1 of 3 poor answer which got me banned and made the deleted answer flagged, hoping someone would undelete it.  I also edited , because the questioner wants a better solution than I have.     I have also searched for alternative means for detection, but with no positive result. Perhaps some light-weight parser becomes available in the future. In the mean time, your answer at least helped solving my issue, so for now, it's accepted. Thanks. – Marten Koetsier Dec 4 '15 at 21:49   But the  was rejected by , the reason being:     This edit was intended to address the author of the post and makes no sense as an edit. It should have been written as a comment or an answer.   Yes, maybe he is right, but I can neither comment nor answer.  Should I have to find another question and try to edit an answer, hoping someone will accept it? If not, should I try again?


EDIT after closing question: the referenced answers say how to install the themes by putting theme in an appropriate tex folder. But this is not what I am asking, I want to be able to "pack and ship" my theme together with other tex files so that other users are able to use them without doing anything. Like custom packages.  I have created a custom Beamer theme. This is defined in the file beamerthemeMYTHEME.sty. As usual, this file calls three more files namely  beamercolorthemeMYTHEME.sty, beamerinnerthemeMYTHEME.sty and beamerouterthemeMYTHEME.sty.  If my .tex is in the same directory as the theme files, I can use the theme only by \usetheme{MYTHEME}.   Next, if I put these files in a directory (Theme) I must use \usepackage{Theme/beamerthemeMYTHEME.sty}. HOWEVER it seems that the other files cannot be found as I get the error  beamerinnerthemeMYTHEME.sty' not found. \useinnertheme{MYTHEME}.  I want to use this approach as I expect other people to use these theme.  Is there any way to make this work?  Addition  Besides handling the theme files, it would also be interesting how to best incorporate graphics from subfolders with things like \pgfdeclareimage


It seems that panel shadow is somehow hardcoded in KDE 4 and devs do not have any plans to change it and/or make it customizable. So, what I'm actually asking is some kind of hack (if there is any) which will remove the shadow of the panel in KDE 4.x completely (but without need to disable all desktop effects in the process).  Possible application: When a user wants a completely transparent panel, no top/bottom borders at all, the shadow is completely out of place and destroys the experience.


Level progression starting from target total XP

I'm sort of a newbie here, so pardon me if I don't get any of the lingo right.   But I'm trying to create a level progression that charts with the "10,000 hr" rule such that, basically, each hour worked will equal 1 XP and level 99 (xx, if you will) charts with having accumulated 10,000 XP.   I understand how I can make a straight progression of levels, but what I really want to do is create a sloped progression, where you level up more often early and then it requires more and more effort to level up as the progress goes on. (The only targets, I guess, are level 1 being 0 and level 99 being 10,000.)  Any ideas? Can anyone help? (I'm sure this is simple, but if you can show me the way toward the answer, I'll gift you by first-born sword.)


$F_\sigma$-subsets in a normal space can be separated

Let $X$ be a normal Hausdorff space and let $C,D$ be two $F_{\sigma}$ subsets of $X$ such that $\overline{C} \cap D = \emptyset$ and $C \cap \overline{D} = \emptyset$.  Prove there exists disjoint open subsets $U,V$ such that $C \subset U$ and $D \subset V$.  No idea how to show this. Can you please help?


What is the difference between PIR and OT?

A private information retrieval (PIR) protocol is a protocol that allows a user to retrieve an item from a server in possession of a database without revealing which item is retrieved. An oblivious transfer (OT) protocol is a type of protocol in which a sender transfers one of the potentially many pieces of information to a receiver, but remains oblivious as to what piece (if any) has been transferred.   As the Wikipedia said, PIR is a weaker version of 1-out-of-n oblivious transfer, but I do not really know why is a weaker version.


How can I individually scale the voronoi color chunks?

I'm trying to make sort of a granite slab material for flooring. And i've tried a lot of things, but none seem to make it look good, and using the image doesn't help either since there's changes in brightness. My main idea was to use a voronoi texture as a base from where to build up. I get sort of close, but not really there. It doesn't seem that hard in theory, but making all the layers from big chunks to small details makes it all the more difficult. Could anyone tell me a way to start off? Maybe not even procedurally Edit: I'll just ask a simple question where I can go on from, how can I decrease the size of the chunks individually in the voronoi color socket?


Browser asks for confirmation when submitting a question or answer

Every time I try to post a question or answer, my browser pops up a confirmation dialog:                               I need to choose "leave page" to continue. If I chose "stay on this page" and hit "submit" again, I am told that my post is a duplicate. In other words, the post was successfully submitted the first time, before the confirmation dialog.   I can confirm this by opening the page in a new tab and I can see my answer there despite being told that I haven't actually posted it. This happens on both firefox (40.0 and previous versions) and chromium (45.0.2454.85) and on all sites of the network.   Both browsers running on a 64 bit Debian. This may or may not be related to .  This is what I see in the Network tab of chromium's dev tools when submitting:    and after clicking on "leave page":    I just checked and this doesn't occur with another account on the same machine, which would suggest that it is somehow a problem on my end. Any ideas what could cause this? It can't be an extension issue since it occurs in both firefox and chromium. What would those two share that could produce this issue?


I want to produce this matrix:    For the vertical line I can use \begin{array}{cc|c} and for the matrix operation I use environment gmatrix from the  package. But I can't use these options at the same time.  Does anyone have a solution?    Update:  What I actually have:  \begin{gmatrix}[p]     1 & 2 & \vline & 3 \\      4 & 5 & \vline & 6 \\     7 & 8 & \vline & 9     \rowops     \swap{0}{1}     \mult{0}{\cdot 7}     \add[5]{1}{2} \end{gmatrix}   and result:


I have a script that works when called:  /usr/local/bin/myscript #this works fine   Permissions for the file are:  -rwxr-xr-x 1 root root 155 Jan 27 09:34 myscript   I've added a line to /etc/crontab:  * * * * * root /usr/local/bin/myscript   But cron doesn't seem able to run this.  The crontab has the PATH variable set:  PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin   The script is a mysqldump to the /var/tmp/ directory:  #!/bin/bash  DAY=`date +%y%m%d` TIME=`date +%k%M` mysqldump test -u john -pxxxxxxx > /var/tmp/$DAY.$TIME.test.sql   I can't think what is wrong with this, but the script isn't running.  Edit: /var/log/syslog shows the following entries:  Jan 27 10:20:01 hector CRON[8286]: (root) CMD (/bin/bash /usr/local/bin/myscript) Jan 27 10:20:01 hector CRON[8285]: (CRON) info (No MTA installed, discarding output)   So I guess it's trying to run the script, but it must be failing somewhere because I don't get the same output as if I ran it with /usr/local/bin/myscript.


Question posted twice despite following the question posting process only once

I followed the question posting process, and at the end saw that it posted 2 questions:    [removed because it is a duplicate question]  I don't know how to reproduce. Rare, but not the first time this happened with me.


Change the way folders are displayed in terminal

I moved over from Xubuntu to Fedora.   In a colored Xubuntu terminal the folders appear in bold blue wheras in Fedora they appear as normal blue.  I'm familiar with ANSI codes for colors and style but I don't know which file to edit.  How can I make folders appear as bold blue when I type ie: ls in my terminal?


Sharepoint 2010 - Deploy webpart as Feature scope = web

I want to create and deploy a web part as web-scoped feature.  In Visual Studio 2010, when I make the feature scope=web, I cannot add the webpart to that feature as I am able to do when scope=site.


Title of short story about two men in a spaceship running out of air

In this short story, two men -- one more by the book and the other less so -- are the crew on a cargo ship. An accident takes out their oxygen reserves, leaving only enough for one of them to make it back. One detail I can recall: the more easygoing one allows himself the occasional cigarette, infuriating his crewmate. Only the easygoing one survives, and it's one of those mystery reveal type stories where we find out the end of the story before we learn what happened. It possibly may be by Arthur C. Clarke, but just as possibly not. It's driving me nuts not being able to remember! Thank you in advance!


DDos attack ToS Violation - Outbound DoS

Fount ddos attack on ubuntu server  netstat -nputw  given outout  Local Address       Foreign Address        State        PID/Program name  55.57.72.37:59792   123.166.137.95:25000    SYN_SENT    2890/ip6tablesu.sh   I found on internet that 123.166.137.95 is China's ip address  How should I block outbound traffic to that address?


Lately I tried to change the path after installing pycharm. They recommend to logout. After that I'm not able to login. I'm using ubuntu 20.04lts.


How to calculate a missing middle digit of a multiplication between 2 big numbers using modular arithmetic?

What elementary number theory methods can I use for solving this type of questions? One of these kind of problems is to find $x$ where $985242x6565 = 172195\cdot 572167$ without multiplying the numbers again. I tried doing, let's call $985242x6565$ $N$, $N\text{mod}10^5$ to somehow get to the $5th$ digit but this is doesn't get me anywhere and in hindsight it doesn't make any sense. How should I proceed?


My device is stuck in bootloop and my USB debugging is disabled. When I type adb devices in CMD, it says adb is not recognized as an internal or external command operable program or batch file. Please help


I've got a  file, and I can't figure out how to open it. How can I open it?


There is the notion of Generalized RBF Kernels, for example in "Towards Optimal Bag-of-Features for Object Categorization and Semantic Video Retrieval" from Jiang (1) or in formula (2.72) in  (2).  They define: Gen. RBF Kernel: $e^{-pd(x,y)}$, where (1) says d can be any distance function and (2) requires it to be a metric.  I now have been wondering for a long time: Is a function defined by $e^{-pd(x,y)}$ where d is a metric always a Mercer's Kernel? I think in (2) it sounds like it, but if it were true, not many people know of it, since they are still looking to prove that $e^{-EMD(x,y)}$ is a kernel, where EMD = Earth Mover's Distance, which is a metric.  If its not a Mercer's Kernel - do you know of any counter example?


I recently installed Ubuntu 20.04. I am trying to run Win 10 on Oracle Virtual Box  6.1.8(last version) but I get error  "Kernel driver not installed (rc=-1908)"  It suggests to run 'modprobe vboxdrv' on the terminal  but when I do (adding sudo ) I get back this:  modprobe: ERROR: could not insert 'vboxdrv': Operation not permitted  Does anyone know how to sort it out please?


How to detect the anomaly in a time series data with trend and seasonality present?

I want to detect the outliers in a time series data which contains the trend and seasonality components. I want to leave out the peaks which are seasonal and only consider only the other peaks. As I am new to time series analysis, Please assist me to approach this problem.  The coding platform am using is Python.


I'm reading How to Prove It: A Structured Approach (Velleman) Second Ed.  Doing all the end of chapter exercises for chapter 1 and having trouble on problem 5a which reads     Show that $P \leftrightarrow Q$ is equivalent to $(P \wedge Q) \vee (\neg P \wedge \neg Q)$   Clearly they're equivalent to each other based on the truth tables. But is that really the best way to 'show' it? I was able to derive the second form from the first in all the other questions that asked to show two forms are equivalent so far.  Here's what happens when I try to derive it:     $$P \leftrightarrow Q$$   $$ \text{Form of biconditional} $$   $$(P \rightarrow Q) \wedge (Q \rightarrow P)$$   $$ \text{Form of conditional}$$   $$ (\neg P \vee Q) \wedge (\neg Q \vee P)$$   From here it appears to match the form of a distributive law but with mismatched negations. I just don't know where to go from here...


I got an e-mail notification of three comments to a question I posted. Now going to look, I see one of the comments, but the other two are not there. Presumably, they were deleted. Since a record is available of revisions to questions and answers, I wonder if there's any way to see comments that have been deleted?


How can I render text as HTML on a page?

I am currently working within a Lightning Component where I have returned the contents of a rich text field from a knowledge article to a <div> section of the page. Instead of the browser rendering the rich text contents as HTML, it is being rendered only as text, which also displays all of the HTML markup on the page.   Since I am working in a Lightning component I do not seem to have access to functions such as {!HTMLENCODE}, but I'm not sure if that is what I would be looking for anyway. I not sure if there is some way I can convert the rich text content to HTML characters either in the Apex controller or on the client side before displaying it to the page?  Thank you everyone. I look forward to any information you can provide.  I have attached a screenshot for reference.


Question using induction to prove an inequality

Could someone help me to prove this inequality using the induction method?  $n \in\mathbb{N}$ (Naturals)  $$\frac{1}{\sqrt{1}}+\frac{1}{\sqrt{2}}+\frac{1}{\sqrt{3}}+\ ...\ +\frac{1}{\sqrt{n}}\geq\sqrt{n}$$  I did the basis step ($n=1$), but I got stuck at the second step (induction step).  All help is appreciated!


I have a couple of questions for prediction and tolerance intervals.  Let's agree on the definition of the tolerance intervals first: We are given a confidence level, say 90%, the percentage of the population to capture, say 99%, and a sample size, say 20. The probability distribution is known, say normal for convenience. Now, given the above three numbers (90%, 99% and 20) and the fact that the underlying distribution is normal, we can compute the tolerance number $k$. Given a sample $(x_1,x_2,\ldots,x_{20})$ with mean $\bar{x}$ and standard deviation $s$, the tolerance interval is $\bar{x}\pm ks$. If this tolerance interval captures 99% of the population, then the sample $(x_1,x_2,\ldots,x_{20})$ is called a success and the requirement is that 90% of the samples are successes.   Comment: 90% is the a priori probability for a sample to be a success. 99% is the conditional probability that a future observation will be in the tolerance interval, given that the sample is a success.  My questions:  Can we see prediction intervals as tolerance intervals? Looking on the web I got conflicting answers on this, not to mention that nobody really defined the prediction intervals carefully. So, if you have a precise definition of the prediction interval (or a reference), I would appreciate it.   What I understood is that a 99% prediction interval for instance, does not capture 99% of all future values for all samples. This would be the same as a tolerance interval that captures 99% of the population with 100% probability.   In the definitions I found for a 90% prediction interval, 90% is the a priori probability given a sample, say $(x_1,x_2,\ldots,x_{20})$ (size is fixed) and a single future observation $y$, that $y$ will be in the prediction interval. So, it seems that both the sample and the future value are both given at the same time, in contrast to the tolerance interval, where the sample is given and with a certain probability it is a success, and under the condition that the sample is a success, a future value is given and with a certain probability falls into the tolerance interval. I am not sure if the above definition of the prediction interval is right or not, but it seems counterintuitive (at least).   Any help?


I wanted to do a multithreaded ChatServer, which is based on telnet and I thought I got it but after I type in 1 message in telnet it gives the following error  "Exception in thread "Thread-0" java.lang.NullPointerException at Server.sendAll(Server.java:20) at ServerThreads.run(ServerThreads.java:33)"  I know where it causes the problem but I don't know how I can fix it specifically in my code. I think all the other stuff is working fine. This is my ServerThread Class import java.io.BufferedReader; import java.io.IOException; import java.io.InputStreamReader; import java.io.PrintWriter; import java.net.InetAddress; import java.net.ServerSocket; import java.net.Socket;   public class ServerThreads extends Thread {      private String prefix;     private Socket socket;     PrintWriter pw;      public ServerThreads(String prefix, Socket s){         this.prefix = prefix;         this.socket = s;         this.start();     }      public void run(){          try {             PrintWriter pw = new PrintWriter(socket.getOutputStream(),true);             BufferedReader br = new BufferedReader(new InputStreamReader(socket.getInputStream()));             Server.list.einfuegen(0, this);             pw.println("Client verbunden mit: "+prefix);                          while(true){                 //System.out.println("User: "+ socket.getInetAddress() + " Nachricht: " + line);                 String line = br.readLine();                 Server.sendAll(line, prefix);                 pw.flush();             }         }catch (IOException e){             e.printStackTrace();         }     } }  This is my Server Class import java.io.IOException; import java.io.PrintWriter; import java.net.ServerSocket; import java.net.Socket;   public class Server {     static EinfachListe list = new EinfachListe();     static int zaehler = 1;     private int port;     ServerSocket socket;      public Server(int port) throws IOException{         this.port = port;         socket = new ServerSocket(port);     }      static public void sendAll(String s, String prefix){         for(int a = 0; a<list.getAnzahl(); a++){             ((ServerThreads) (list.get(a))).pw.println(s);         }     }      public void starteServer(){         System.out.println("Der Server wurde gestartet");          while(true){             try {                 Socket s = socket.accept();                 //ServerThreads user = new ServerThreads("User:Anzahl Nachrichten "+zaehler++, 1000, s);                 String client = "Client"+zaehler++;                 new ServerThreads(client, s);                 //user.start();             } catch (IOException e) {                 e.printStackTrace();             }         }     } }  I don't think that the mistake is in my LinkedList but if you think it is I can also copy the code of my LinkedList in here. Thank you for the help!


Calling PHP functions within HEREDOC strings

In PHP, the HEREDOC string declarations are really useful for outputting a block of html.  You can have it parse in variables just by prefixing them with $, but for more complicated syntax (like $var[2][3]), you have to put your expression inside {} braces.  In PHP 5, it is possible to actually make function calls within {} braces inside a HEREDOC string, but you have to go through a bit of work.  The function name itself has to be stored in a variable, and you have to call it like it is a dynamically-named function.  For example:  $fn = 'testfunction'; function testfunction() { return 'ok'; } $string = <<< heredoc plain text and now a function: {$fn()} heredoc;   As you can see, this is a bit more messy than just:  $string = <<< heredoc plain text and now a function: {testfunction()} heredoc;   There are other ways besides the first code example, such as breaking out of the HEREDOC to call the function, or reversing the issue and doing something like:  ?> <!-- directly output html and only breaking into php for the function --> plain text and now a function: <?PHP print testfunction(); ?>   The latter has the disadvantage that the output is directly put into the output stream (unless I'm using output buffering), which might not be what I want.  So, the essence of my question is: is there a more elegant way to approach this?  Edit based on responses: It certainly does seem like some kind of template engine would make my life much easier, but it would require me basically invert my usual PHP style.  Not that that's a bad thing, but it explains my inertia..  I'm up for figuring out ways to make life easier though, so I'm looking into templates now.


Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException bouncing ball

I have a java program that contain four classes, but I'll post two just to show my object interaction. After I run it I receive AWT-EventQueue-0" java.lang.NullPointerException  I believe it because of my objects interaction. How to fix it?  public class myFrame extends JFrame {     public PanelOne P1 = new PanelOne();     public PanelTwo P2 = new PanelTwo();     public myFrame mf;      public myFrame() {         super("MyFrame");         setLayout(new BorderLayout());         add(P1,BorderLayout.CENTER );         add(P2,BorderLayout.EAST);         setSize(600,500);         setVisible(true);     }     public static void main(String args[]) {         myFrame mf = new myFrame();         mf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);     } }     public class PanelTwo extends JPanel {     private myFrame mf;      private JButton quit = new JButton("quit");     private ButtonHandler bh = new ButtonHandler();      private JRadioButton start = new JRadioButton("Start", true);     private JRadioButton stop = new JRadioButton("Stop");     private ButtonGroup group = new ButtonGroup();      public PanelTwo(){         super();         setLayout(new GridLayout(9,1));         setBackground(Color.RED);         add(new JLabel("PanelTwo"));         add(quit);         quit.addActionListener(bh);         add(start);         add(stop);         group.add(start);         start.addActionListener(bh);         group.add(stop);         stop.addActionListener(bh);     }     public PanelTwo(myFrame mf){         super();         this.mf=mf;     }     public class ButtonHandler implements ActionListener {          public void actionPerformed(ActionEvent ac){             if(ac.getSource()==quit){                 System.exit(0);             }             if(ac.getSource()==stop){                 mf.P1.timer.stop();             }             if(ac.getSource()==start){                 mf.P1.timer.start();             }         }     } }     And this is what I got: Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException     at Sep16and2014.PanelTwo$ButtonHandler.actionPerformed(PanelTwo.java:45)     at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2018)     at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2341) .........     So, it said that my mistake starts in line with mf.P1.timer.stop(); I believe I somewhere assigned a null value. How to fix it?


My interest is just to test a small website hosted on my own computer that a friend of mine will access remotely from another state, I don't know how it works so I don't need dns I can just use the ip as an address, the server is an apache and  my question is how to make the site accessible in addition to localhost?


Creating a line separated gradient bar in Tikz

I am trying to create something similar to this in Tikz:    I have been looking at using the \shadedraw macro, but have not found a way to create the color spectrum.  It seems possible if I stack multiple gradient-shaded rectangles on top of each other, but I would rather not use such a lengthy and ugly solution.  Is there a way to recreate this PH-scale image in Tikz, ideally using few rectangles?  (Note: the number labels are not necessary, as they will be replaced with horizontal lines anyway.)


Process: com.example.vicevirus.myapplication, PID: 13471       java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String com.google.firebase.auth.FirebaseUser.getUid()' on a null object reference               at com.example.vicevirus.myapplication.RegisterActivity$1.onComplete(RegisterActivity.java:48)               at com.google.android.gms.tasks.zzc$1.run(Unknown Source)               at android.os.Handler.handleCallback(Handler.java:751)               at android.os.Handler.dispatchMessage(Handler.java:95)               at android.os.Looper.loop(Looper.java:154)               at android.app.ActivityThread.main(ActivityThread.java:6119)               at java.lang.reflect.Method.invoke(Native Method)               at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)               at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)   This is on android monitor. How do I solve this?  package com.example.vicevirus.myapplication;  import android.app.ProgressDialog;          import android.support.annotation.NonNull;          import android.support.v7.app.AppCompatActivity;          import android.os.Bundle;          import android.view.View;          import android.widget.EditText;          import android.widget.Toast;          import com.google.android.gms.tasks.OnCompleteListener;          import com.google.android.gms.tasks.OnSuccessListener;          import com.google.android.gms.tasks.Task;          import com.google.firebase.auth.AuthResult;          import com.google.firebase.auth.FirebaseAuth;          import com.google.firebase.database.DatabaseReference;          import com.google.firebase.database.FirebaseDatabase;  public class RegisterActivity extends AppCompatActivity {     private EditText email,name,password;     DatabaseReference databaseReference;     FirebaseAuth mAuth;     private DatabaseReference userIdRef;     ProgressDialog registerDialog;     @Override     protected void onCreate(Bundle savedInstanceState) {         super.onCreate(savedInstanceState);         setContentView(R.layout.activity_register);         email=(EditText)findViewById(R.id.email);         name=(EditText)findViewById(R.id.name);         password=(EditText)findViewById(R.id.password);         databaseReference= FirebaseDatabase.getInstance().getReference().child("chat_users");         mAuth=FirebaseAuth.getInstance();         registerDialog=new ProgressDialog(this);         registerDialog.setMessage("Registering..");     }     public void submit(View view) {         registerDialog.show();         mAuth.createUserWithEmailAndPassword(email.getText().toString(),password.getText().toString()).addOnCompleteListener(this, new OnCompleteListener<AuthResult>() {             @Override             public void onComplete(@NonNull Task<AuthResult> task) {                 if(task.isComplete())                 {                     registerDialog.dismiss();                     Toast.makeText(getApplicationContext(),"Registered successfully",Toast.LENGTH_SHORT).show();                     userIdRef=databaseReference.child(mAuth.getCurrentUser().getUid());                     userIdRef.child("name").setValue(name.getText().toString());                     finish();                 }                 registerDialog.dismiss();             }         });     } }


Disable stack protection on Ubuntu for buffer overflow without C compiler flags

I'd like to try some shell codes and I want to disable linux protections.  I know I could compile using flags but I know another way exists to disable these protections in general I just can't remember. Can you help me?


gdal_polygonize converts whatever rasters values into vector integers as it is based on the GDALPolygonize() function ().  It is suggested that the GDALFPolygonize() function () should be employed in case floating points are to be transferred.  However, it is absolutely obscure to me how to implement or call such function instead of the standard one. No clue is available anywhere.  I'm calling gdal using both OSGeo4W shell as well as QGIS2.6 python interface (I'm on Windows 7 and 8.1).


Creating an array of JLabels - Why do I get this weird error?

JLabel[] labels=new JLabel[10];     ImageIcon[] image = new ImageIcon[10];          labels[0].setForeground(Color.BLACK);     image[0] = new ImageIcon(this.getClass().getResource("/White.jpg"));     labels[0].setIcon(image[0]);     labels[0].setBounds(12, 124, 31, 18);     frame.getContentPane().add(labels[0]);  I'm trying to create a simple array of JLabels and print an array of ImageIcons on it. But I get this weird error which says it is null:  How can labels[0] be null? Does someone have any idea why may this be happening? Thank you so much in advance!


postfix - how to prevent users from sending with another users name

Even though my postfix server cannot be used without authentification (open relay), sending mail in another users name after logging in is still possible like this:  EHLO domain.org auth plain eW91IGxpdHRsZSBkaXJ0eSBiYXN0YXJkIDstKQ== 235 2.7.0 Authentication successful mail from: otheruser@domain.org 250 2.1.0 Ok rcpt to: recipient@otherdomain.org 250 2.1.5 Ok data 354 End data with <CR><LF>.<CR><LF> Please send me your account info. . 250 2.0.0 Ok: queued as D40692A61AA quit   How can this be prevented?


Custom Setting vs. Custom Object vs. Custom Metadata Type for Multiple Environment Credentials

I am looking to confirm the best practice of storing client / secret credentials for multiple environments for multiple external webservices within salesforce.   Below is the analysis I have done using custom objects, custom settings, custom metadata types, and named credentials for this objective.   Analysis:  Custom Settings are controlled by Profile or by User.   Whereas Custom Objects are controlled with object and field level security and access is controlled by sharing settings.   I have seen some users use custom settings for credential storage, I'm assuming the reasons for this is by using the .get methods on the custom setting it will not count against your SOQL query limits and due it being stored in the application cache it is faster to access. In addition, you don't have to worry about users accessing / modifying the credentials unless they have the system permission to view and modify custom settings.   If I have various credentials to the various endpoints for the same service. Ex: dev.mycompany.com/data/, uat.mycompany.com/data/, prod.mycompany.com/data/ that are not specific to the user or profile, I find it excessive to add each environment, its subdomain, and its credentials (client secret) to a new field on the custom setting. In this example, if I would have 3 x 2 fields (client and secret) + 3 x 1 field (subdomain) + 1 field to determine which endpoint to hit depending on type of salesforce instance I'm on (dev, partial, prod).   Whereas with the custom object, I would have four fields (client, secret, active(boolean for whether or not this should the endpoint to request data from), and subdomain) and 3 records.   In addition, there is Custom Metadata types, which seem to be more or less like custom settings, but are stored as metadata as opposed to a table structure like custom settings / objects for simpler migration from environment to environment.   As for security I could encrypt the custom object fields as I can encrypt custom settings fields, however Salseforce seems to advise against the use of custom settings or custom metatypes to store credentials and recommends named credentials (which don't fit my use case of client/secret) or encrypted custom fields, due to custom metadata and custom settings being public.   I noted that other stack articles, such as: , suggest using protected custom settings to accomplish this, however I believe this answer was before custom metadata types existed.   Summary / Question:   Knowing this, based on my understanding of these three options, I believe it makes the most sense to store the credentials in a custom object from a security perspective and custom metadata / custom settings from a deployment perspective.   Given that security concerns would be my first priority, I'm leaning towards custom objects visible and editable only by system admins.   Is my understanding correct, is there other considerations that I have not made but need to weigh in making this decision?


Find unmatched results obtained by two different queries on two different tables


System.Drawing in Windows or ASP.NET services

According to , it is not a particularly good idea to use classes within the System.Drawing namespace in a Windows Service or ASP.NET Service. Now I am developing a class library which might need to access this particular namespace (for measuring fonts) but it cannot be guaranteed that the host process is not a service.  Now there is a less optimal method I can fall back to if System.Drawing is unavailable, but if it is possible, I would rather use classes in System.Drawing. So what I would like to do is to determine at runtume if System.Drawing is safe or not, and if it is, use it, otherwise fall back to the suboptimal option.  My problem is: How could I possibly detect if System.Drawing is safe to use?  I think I should either   Detect if the current process is a Windows Service or ASP.NET service Detect if GDI is available Or maybe there is a way to ask System.Drawing.dll itself if it is safe to use   Unfortunately, I cannot come up with a way to implement any of these approaches. Does anyone have any idea?


Where can I get guidance on a specific OOP style issue?

I know that Stack Overflow is the wrong place to ask for opinions, so instead I'm wondering where I can ask a question about a specific OOP issue. You can ignore the summary below beyond suggesting where I can ask for guidance.     I apologise for being callow enough to mess around with designing a game.  But I'm messing around with it anyway. And I'm not sure whether this structure makes sense:  class Character:      self.name...     self.offense_value     self.defense_value     self.resources_value      def set.offence(self):          self.offence = [algorithm]     ...  class Combat(Character):      ...init class and parent     def attack(self, modifier):          return self.offence + modifier      ...  ...    Are there any Stack Exchange sites where such a question would be on-topic?


Advance someone in a Journey based on an event in Salesforce

We're injecting records into a journey using a Salesforce data event.  I also want to advance the people in the journey based on updates that happen in Salesforce (e.g., as an Opportunity record advances through the sales process), but I can't figure out how to do that.  I've read all the documentation I can find, but there doesn't seem to be a Journey Builder widget that will wait to be prompted by an event in Salesforce before continuing someone on a journey.  At the moment, I'm completely stuck.    I'd greatly appreciate any advice or information on how I can make journeys event-driven in this way.  Thanks very much!


Can I transfer games from my friends steam account to mine?

I bought Garry's Mod, and it's currently a 2 gb download. I have poor wifi, so I want to know if I can transfer Gmod from my friend's account to mine. He has Gmod on Steam as well. Is it possible with the backup and restore method and a pen drive?


Ok, I've always, for some reason, thought that my cpu had 32 bit registers... so I always installed the 32bit version of all OSs that I've used. Now though I ran a lscpu, and I get:  fer@fer-lap:~$ lscpu Arquitectura:          i686 CPU op-mode(s):        32-bit, 64-bit   Does this mean I can use 64 bit OSs?  Running these I get:  fer@fer-lap:~$ grep flags /proc/cpuinfo  flags       : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe nx lm constant_tsc arch_perfmon pebs bts aperfmperf pni dtes64 monitor ds_cpl est tm2 ssse3 cx16 xtpr pdcm lahf_lm dtherm   And I have read that the lm flag means long mode, which stands for 64 bit cpus. Also, as a last test, running lshw gives, for the cpu section:   *-cpu:0               descripción: CPU               producto: Intel(R) Core(TM)2 Duo CPU     T5800  @ 2.00GHz               fabricante: Intel Corp.               id físico: 4               información del bus: cpu@0               versión: 6.15.13               serie: 0000-06FD-0000-0000-0000-0000               ranura: U2E1               tamaño: 2GHz               capacidad: 4096MHz               anchura: 64 bits   It's in spanish and the last line stands for width (I guess register width). So... can I install the 64 bit of the OS? Will it be a big diference in performance? Because that's what I'm looking for (doesn't need to be a BIG difference)  Thanks in advance.


Suppose an object A is traveling towards black hole. For an observer outside it looks like A almost reached even horizon and is still trying to reach it.  So from point of view of an observer all the matter is on even horizon (we don't see all of it due to severe severe redshift making black holes invisible in all EM spectrum that we can detect). And all observers being equal, this view is also correct.  So which one is true, did A cross horizon or not? Or somehow both is true? Which leads to this question do blackholes contain matter? Or they are just a void out in both time and space. Because for all practical and theoretical purposes all curved spacetime ends at event horizon. We simply don't know what lies beyond.


How do I free up more space (increase partition size) in /boot on a VPS?

My boot partition is full. I cannot apply system updates. How can I resize partitions? I don't want to remove old files, I only want to resize. I can not install gparted because I do not have desktop access. Is it possible to do it from webmin ?  I tried these methods:        [root@mail ~]# sudo apt-get install gparted Reading package lists... Building dependency tree... Reading state information... You might want to run 'apt-get -f install' to correct these: The following packages have unmet dependencies:  gparted : Depends: libatkmm-1.6-1 (>= 2.22.1) but it is not going to be installed            Depends: libglibmm-2.4-1c2a (>= 2.36.2) but it is not going to be installed            Depends: libgtk2.0-0 (>= 2.14.0) but it is not going to be installed            Depends: libgtkmm-2.4-1c2a (>= 1:2.24.0) but it is not going to be installed            Depends: libpangomm-1.4-1 (>= 2.27.1) but it is not going to be installed  linux-image-extra-3.13.0-119-generic : Depends: linux-image-3.13.0-119-generic but it is not going to be installed  linux-image-extra-3.13.0-133-generic : Depends: linux-image-3.13.0-133-generic but it is not going to be installed  linux-image-generic : Depends: linux-image-3.13.0-133-generic but it is not going to be installed E: Unmet dependencies. Try 'apt-get -f install' with no packages (or specify a solution).   If I try apt-get -f install then I get "disk full" error.  Screenshots from webmin.


Is the Playstation 4 backwards-compatible?

Does the PS4 have backwards compatibility of some form? The majority of forums/sites suggest not, or posters are adamant it doesn't yet. Others imply that some form of backwards compatibility will include a cloud service and PS3 titles? I've even heard on some forums that PS4 does actually play PS3 games but those posts seem to be a minority compared to those that say it's not...


Can I tile my shower in stages on different days?

I am trying to decide if I want to tile my shower myself. Can I tile in sections on different days? Say if I can only get a few walls done and have to stop, is that ok? I have built an L shaped shower with a bench seat in the short leg. I am pretty confident I can do a good job but it may take me longer than it would a more experienced tile setter. I don't want to compromise the integrity of the shower. Thanks in advance.


How to get rid of the "Oxford comma" in a listing of three or more authors?

The following bib entry hat three authors but the last one is separated with , and instead of just and. Is it possible to remove that comma?  \documentclass[a4paper,10pt]{article} \usepackage[utf8]{inputenc} \usepackage[T1]{fontenc} \usepackage[english]{babel} \usepackage{csquotes} \usepackage[style=alphabetic,maxnames=10]{biblatex} \addbibresource{references.bib} \usepackage{filecontents} \begin{filecontents}{references.bib} @book{key,   author = {Baur, S and Schmid, A and Schur, B.},   year = {2001},   title = {Title},   publisher = {Publisher}, } \end{filecontents} \begin{document} \nocite{*} \printbibliography[heading=bibintoc] \end{document}


iMac Pro microphone doesn't work and camera is not detected

I have an iMac Pro. No camera shows in the system report under Camera, just under USB. My microphone is also not working. I tried resetting the NVRAM but it didn't solve the problem.    What should I do to fix it?


Ubuntu 18.04 boot error: syntax error: unexpected end of file when loading .profile

I can't figure out what is wrong with my Ubuntu 18.04. I was trying to set a path for an application in my .profile and restarted the machine. Since then, I've been getting this error on the screen. I tried rebooting Ubuntu changing configuration from the boot menu via the DVD but yet nothing is happening.  What's the problem and how can I fix it?


Hide processes from other users based on groups (under Linux)?

Is it possible to configure process hiding for certain user groups under a linux system?  For example: Users from group X should not see processes owned by users from group Y in ps/top or under /proc.  Is it possible to configure such a setup with SELinux?  (I vaguely remember a similar feature in the funny grsecurity patch set - but IIRC, it was more generic - and besides, I want to configure a stock linux distro without having to maintain a custom kernel.)  Edit: For better illustration, . The example is not that generic, but one can configure that a user or some users can only see information of their own processes in ps etc.


Why does heisenberg uncertainty principle work?

Hiesenberg's Uncertainty Principle states that inaccuracy in momentum and position will always be there and we will never ever be able to get it 100% accurate. Suppose in future millions of years from now, we have equipments that can measure potential and kinetic energy of any object without having to measure it at two different point of time and at only one point of time then simply we can have the position and momentum at the same time of an object. The formula doesn't makes any sense so why and how does it work ?


What does the notation of $2^{\mathbb{N}}$ mean?

I've learned over the course of the last years that some mapping $\lambda$ denoted :   $$ \lambda : \mathbb{N} \rightarrow 2^{\mathbb{N}}.$$  essentially means that for every natural number, you assign (or map) some set of natural numbers to it. At multiple times, I've wondered if there's some meaning behind this notation (more precisely the $2^{\mathbb{N}}$ part) that I'm not understanding, as it does not seem as straightforward as say :  $$ f : n \rightarrow 2n$$  (also just noted as $f(n) = 2n$), where you clearly map any $n$ to $2n$. Is this $2^{\mathbb{N}}$ just some notation that one has to get used to, or does it make sense somehow to note it this way? If it does make sense, why the choice of exponentiation, and why the $2$?


Laptop power adapter output compatibility

I've lost my original power adapter, and I can't find the proper one in any of the stores currently available.  I've HP Compaq 6730b, and as per  it outputs 18.5V 3.5A. However, I've found an older power adapter I have which outputs 19.5V 4.62 A.  So, my question is: how much of a difference between those two it really is, and more importantly, how much of a risk would it be if I tried the power adapter I already have.  P.S. I know pretty much nothing about electricity/electronics.


how to take arrays to another subprogram?

I have an array in a sub program and I want to re-use that data in a new subprogram. how would I do this?  I have heard about using a dictionary but i am not sure about how to proceed on doing so. The simpler the code the better, thank you.  def optiona():  playernames = ['A', 'B', 'C', 'D', 'E', 'F']  numjudges = 5  playerscores = [] scoresfile = open('scores.txt', 'w')  for players in playernames:     string = []     for z in range(5):         print("Enter score from Judge", z+1, "for Couple ", players, "in round 1:")         data = input()         playerscores.append(int(data))         string.append(data)     scoresfile.write(','.join(string) + '\n')     print() print('Registration complete for round 1') scoresfile.close() round2()  def round2(playerscores):            print(playerscores)   now after this, i get this error TypeError: round2() missing 1 required positional argument: 'playerscores'


Transfer content from one Apple ID to another?

My daughter was using my Apple ID with her Ipad mini. I want her to use her own Apple ID now that she is old enough. How can we transfer the content of her ipad mini, ( music, photos, apps) particularly game apps WITH THEIR DATA onto her new account? She doesn't want to start from scratch with all her games.


Is there any evidence Jon was legitimized?

Ned Stark has five legitimate children (in order of age) Robb, Sansa, Arya, Bran, and Rickon. Up through the events of A Dance With Dragons we end up with the following:       Robb - dead      Sansa - Alive, at the Eyrie, under the protection of Littlefinger who is plotting something.      Arya - Alive, off in Bravos, but even if she does return would still be behind all the others.      Bran - Alive, may or may not return, but given his situation it highly unlikely he would be laying a claim.      Rickon - Alive, MIA (Davos has been sent to see if he is hiding on Skagos)    Sansa and Rickon would have the best claims based on the above information. This would also mean that the Boltons will have to be stripped of their titles over the North as well. I do not see this as a major problem as the other Lords of the North believe only a Stark can rule Winterfell.   Sansa seems to be in a position to claim sooner, but Rickon is liable to just pop out of nowhere (much like Aegon VI). Littlefinger will not have wanted all his hard work to go to waste, so I would imagine he will do anything to install Sansa. The other Lords of the North may back Rickon as he is male... given the general rules of succession in Westeros, male heirs are given priority over females. However, with the state of turmoil most of these rules are subject to all kinds of interpretations and ignorance.    However, there is final option... Jon Snow. If Jon was able to secure a royal decree making him a true Stark his claim would be better than both Sansa (Jon is male) and Rickon (Jon is older). Is there any evidence that this has happened?    I am looking for evidence from the books only. The show is outpacing and has gone in different directions in many instances.


Is there any way to restart the Tiny Death Star Holiday Decoration Event?

The Holiday Decoration Event may have started a month ago, but, it only showed up yesterday in my game.  And, it says there are 0 days left. The app was updated as soon as it was released, but there was no sign of it in-game. Is this a bug? If so, are there any fixes that I can apply?


density of $\mathbb{Q}$ and $\mathbb{R}$ in $\mathbb{R}^2$

suppose i define $$C=\{ (x,y)\in \mathbb{R}^2 | x^2+y^2=1\}$$ $$A=\{ (x,y)\in \mathbb{R}^2 | x,y\in \mathbb{Q} \wedge x^2+y^2<1\}$$ and i define a graph $G= \langle C,E \rangle$ when $E$ is the set edges, and 2 vertices are connected iff the chord between them does not contain any points in $A$ (every point on the chord has at least one irrational coordinate).  i want to prove that for every countable set $B\subseteq C$ there is a point $(x,y)\in C-B $ that has an edge to any point in $B$. It feels like transfinite induction but im not really sure on how to start it  thank you!


How to make a bootable flash drive with multi OSes including Windows and linux distros on the same flash?

Is there any way I can make a bootable flash drive with multiple OSes like windows 10 , Ubuntu etc in only one flash drive.  I tried using winsetupfromusb. But I'm not sure which file system do I format my flash drive to, NTFS?  Fat32?  I just want windows 10 and Ubuntu as compulsory and both bootable. Thank you in advance!


Are there any cookbooks specifically designed for restaurant-level chefs/cooks?

It's fair to say most cookbooks are designed for the home cook. Not just in terms of quantities but also in terms of technique; it's very common to see recipes - even those written by giants in the catering world - edited "so you can prepare them at home".  Even a high-level book such as Thomas Keller's The French Laundry Cookbook boasts that "all [recipes] have been thoroughly tested in home kitchens".  Do recipe books for restaurant-level chefs exist? I'm not talking about  which focus on event cooking but rather books where the author assumes that you have access to professional-level equipment, unusual/exotic/technical ingredients. Books which actually document the way a restaurant chef would prepare and cook their own food every day.


How to execute su in the middle of a shell script and continue the rest of the script?

#!/bin/bash USERNAME=abcds HOSTS="abcde fghij klmno pqrst aksjd ajsdf" SCRIPT="su - admin;hostname;ulimit -u;ulimit -n" for HOSTNAME in ${HOSTS} ; do     ssh -l ${USERNAME} ${HOSTNAME} "${SCRIPT}" done   su in above script does not work and displays an error: standard in must be a tty  Any workaround?


Finding  value of $\lim_{n\rightarrow \infty}\sin(\sin(\sin(.......(\sin \left(\frac{\pi}{2}\right))))$  Attempt: $\displaystyle \sin(\frac{\pi}{2})=1$  so $\displaystyle \sin(\sin \frac{\pi}{2})= \sin(1)$  could  some help me how to  solve it,thanks


I installed Debian 8, I would like to install Java JRE and JDK. I use  and it works.  But, I am afraid because it's a script hosted in a repository. I would like to understand why it doesn't work when I put the extract of  in /usr/java/jre1.8.0_73 directory as . I added the path variable with PATH=/usr/local/jdk1.8.0/bin:$PATH export PATH as explained in  but it doesn't work.  Even if I try to install OpenJDK, the package isn't found. I don't understand why it's so complicated to install Java on Debian; it is very simple on Ubuntu. I would like someone give me step-by-step instructions to install it.


apt update/apt upgrade won't work after using GNOME Software

I have to kill aptd everytime I use GNOME Software in order to get sudo apt update or sudo apt upgrade to work. If I dont kill aptd then I get this:  E: Could not get lock /var/lib/dpkg/lock - open (11: Resource temporarily unavailable) E: Unable to lock the administration directory (/var/lib/dpkg/), is another process using it?   Is there something I can do to make aptd stop automatically when I quit GNOME Software?


Let $K$ be a number field and let $\mathcal O_K$ be its ring of integers. Let $I$ be a non-zero ideal in $\mathcal O_K$.      If $I$ is free as a $\mathcal O_K$-module then is it a principal ideal?    I know that any (fractional) $\mathcal O_K$-ideal is generated by at most two elements since $\mathcal O_K$ is Dedekind but is there an easy way to show the above?   Many thanks.


Any tools to generate an XSD schema from an XML instance document?

I am looking for a tool which will take an XML instance document and output a corresponding XSD schema.  I certainly recognize that the generated XSD schema will be limited when compared to creating a schema by hand (it probably won't handle optional or repeating elements, or data constraints), but it could at least serve as a quick starting point.


i'm a new user at Ubuntu, and i think i've lost my boot to Windows. I'm using Ubuntu 18.04 and i'm not an expert of this issues (but i can move through the console). Please, would you mind to help me? I only want to have Windows at my bootmenu working (now it is but it doen't work).  My pastefile is:   Thanks a lot, i'm desperated and about to remove Linux and have only Windows, please help me :(


I have remember that my friend told me that I can just click a line in the *.pdf, then latex will direct me to the corresponding line in the latex code. I have tried this function when I am using WinEdt 10. When I press the key Ctrl shift + X, I can compile my code and read it in dvi. format, when I click the content in dvi, it can not direct me to the latex code but the Texwork file come out. How can I fix it?


QGIS reclassification - calculate colors back into values

I have a raster layer in QGIS that is stored as a three color image. I want to do some analyses on it and would like to have it just as values 1,2,3 (and then I can leave the presentation to later)   The raster is red, yellow, green and the band values are  255,0,0 0,245,0 240,240,0   So I should be able to use either the red band or the yellow band to extract my information.  This could easily be coded as  value=redband.value if value==255:     return(3) if value==240:     return(2) if value==0:     return(1)   To return red yellow and green as 3,2 and 1 respectively.  But in the field calculator, I can only see how to do mathematical expressions. Is it possible to run a script in the field calculator or do I have to rewrite this as a python script to run in the python console?  (I know it possible to turn a raster with only three distinct values into a polygon layer, but due to the structur of the raster, the polygon gets quite unwieldy and the analysis I am going to do on this later requires a raster)


I was playing on my main world when my laptop ran out of power.  I found a charger and woke it up, but Minecraft had crashed.  Now, it doesn't appear in the world selection screen!  I have verified that it still exists in the Minecraft folder, and the directory contents look to be in order.  Does Minecraft save an internal flag somewhere when it crashes hard?  If so, how do I reset it?


How to use use Regular Expression (RegEx) within Azure logic app

I want to verify a value in my azure logic app which follows a pattern which can be identified by Regular Expressions.  My Value is KUL-M-X-Y, here KUL is fixed value but value of M can be "KG", "TON" etc., also Value of X and Y can be numeric.  I searched for RegEx related expression in Logic apps but didn't find any.  Can any one suggest possible way to work with this?


webupd8 oracle-java-7-installer failing with 404

I am attempting to install java7 in a docker image. This was working till a few days ago. Commands are:      apt-get --fix-missing update     apt-get -y upgrade      apt-get -y install software-properties-common     add-apt-repository ppa:webupd8team/java     apt-get -y upgrade     apt-get -y update      echo oracle-java7-installer shared/accepted-oracle-license-v1-1 select true | /usr/bin/debconf-set-selections     apt-get install -y oracle-java7-installer   Output is:         Setting up oracle-java7-installer (7u80+7u60arm-0~webupd8~1) ...        debconf: unable to initialize frontend: Dialog        debconf: (TERM is not set, so the dialog frontend is not usable.)        debconf: falling back to frontend: Readline        debconf: unable to initialize frontend: Readline        debconf: (This frontend requires a controlling tty.)        debconf: falling back to frontend: Teletype        Downloading Oracle Java 7...        --2017-05-29 16:54:29--  http://download.oracle.com/otn-pub/java/jdk/7u80-b15/jdk-7u80-linux-x64.tar.gz        Resolving download.oracle.com (download.oracle.com)... 104.96.220.162, 104.96.220.106        Connecting to download.oracle.com (download.oracle.com)|104.96.220.162|:80... connected.        HTTP request sent, awaiting response... 302 Moved Temporarily        Location: (REMOVING H-T-T-P-S BECAUSE I DON'T HAVE ENOUGH REP POINTS)://edelivery.oracle.com/otn-pub/java/jdk/7u80-b15/jdk-7u80-linux-x64.tar.gz [following]        --2017-05-29 16:54:29--  (REMOVING H-T-T-P-S BECAUSE I DON'T HAVE ENOUGH REP POINTS)://edelivery.oracle.com/otn-pub/java/jdk/7u80-b15/jdk-7u80-linux-x64.tar.gz        Resolving edelivery.oracle.com (edelivery.oracle.com)... 23.196.115.62, 2600:1408:10:184::2d3e, 2600:1408:10:185::2d3e        Connecting to edelivery.oracle.com (edelivery.oracle.com)|23.196.115.62|:443... connected.        HTTP request sent, awaiting response... 302 Moved Temporarily        Location: (REMOVING H-T-T-P BECAUSE I DON'T HAVE ENOUGH REP POINTS)//download.oracle.com/otn-pub/java/jdk/7u80-b15/jdk-7u80-linux-x64.tar.gz?AuthParam=1496076904_47c6805122b1f8131f00e210452116ca [following]        --2017-05-29 16:54:29--  http://download.oracle.com/otn-pub/java/jdk/7u80-b15/jdk-7u80-linux-x64.tar.gz?AuthParam=1496076904_47c6805122b1f8131f00e21                                                0452116ca        Connecting to download.oracle.com (download.oracle.com)|104.96.220.162|:80... connected.        HTTP request sent, awaiting response... 404 Not Found        2017-05-29 16:54:31 ERROR 404: Not Found.         download failed        Oracle JDK 7 is NOT installed.        dpkg: error processing package oracle-java7-installer (--configure):        subprocess installed post-installation script returned error exit status 1        Setting up gsfonts (1:8.11+urwcyr1.0.7~pre44-4.2ubuntu1) ...        Setting up x11-common (1:7.7+1ubuntu8.1) ...        debconf: unable to initialize frontend: Dialog        debconf: (TERM is not set, so the dialog frontend is not usable.)        debconf: falling back to frontend: Readline        debconf: unable to initialize frontend: Readline        debconf: (This frontend requires a controlling tty.)        debconf: falling back to frontend: Teletype        invoke-rc.d: policy-rc.d denied execution of start.        Processing triggers for ureadahead (0.100.0-16) ...        Setting up xfonts-encodings (1:1.0.4-1ubuntu1) ...        Setting up xfonts-utils (1:7.7+1) ...        Setting up gsfonts-x11 (0.22) ...        Processing triggers for libc-bin (2.19-0ubuntu6.9) ...        Errors were encountered while processing:         oracle-java7-installer        E: Sub-process /usr/bin/dpkg returned an error code (1)        The command '/bin/sh -c apt-get install -y oracle-java7-installer'            returned a non-zero code: 100


Why is the Gamma function defined the way it is?

The Gamma function $\Gamma(n)$ is defined as $$\Gamma(n)=\int_{0}^{\infty}x^{n-1}e^{-x}dx$$ $$\Gamma(n)=(n-1)!$$ Why isn't it defined as $$f(n)=\int_{0}^{\infty}x^{n}e^{-x}dx$$ $$f(n)=n!$$ This seems a lot more intuitive and easier to apply, or is there something I'm missing in terms of uses for the function?


What is the difference between normal distribution and standard normal distribution?

Two terms normal distribution and standard normal distribution are used in statistics. Does standard term contribute to the normal distribution anything? Please give a simple-however a substantive reasoning in the back of these terms.


Generate (not so)random string with particular string occurences

I have a requirement where I have the alphabet 'ACGT' and I need to create a string of around 20,000 characters. This string should contain 100+ occurrences of the pattern "CCGT". Most of the time the generated string contains it around 20-30 instances.       int N = 20000;     std::string alphabet("ACGT");     std::string str;     str.reserve(N);     for (int index = 0; index < N; index++)     {         str += alphabet[rand() % (alphabet.length())];     }   How do I tweak the code so that the pattern would appear more often?   Edit - Is there a way of changing the alphabet, i.e - 'A', 'C', 'G', 'T', 'CCGT' as characters of the alphabet?  Thank you.


I regularly use a hat under my helmet and a neck warmer.  This keeps me relatively warm in the winter but leaves a bit to be desired.  What are the best options to keep your face warm?  Some people in NYC particularly those riding electric devices wear full face motor cycle style helmets.  I’ve never tried that but it must keep you warm...


Are there any open source network analysis tools?

A researcher in my field* recently created an "", an ArcGIS extension built upon Network Analyst. It calculates a number of measures on urban networks, such as betweenness and reach.   He was criticized for relying on ArcGIS, a commercial tool not available to many researchers, especially outside the US. But ArcGIS was a convenient platform, since it contains the Network Analyst extension, simplifying the work required for the analysis.  Are there open source network analysis tools that do the work of the Network Analyst extension? Are there other methods for creating the network datasets required as input for the toolbox? My understanding of the toolbox is that it uses the network dataset to calculate a distance matrix for a given set of points on the network. The toolbox does not use any of the higher level problem solving tools in Network Analyst.  *Quantitative Urban Morphology, perhaps? No one seems settled on a name for the broader field. The particular brand of research I do is with Space Syntax.


I  and then continued to clarify things for the asker, both by editing my answer and by answering directly in the comments.  Now the original asker has deleted his questions, perhaps as he learned a bit more, thinking they looked like stupid questions, so the conversation is broken and my comments don't make much sense. They were actually good questions and cast light on the problem, the conversation might have been useful to a later reader.  So my question is, should I now go back and re-format my comments to make them general clarifications, or delete them and embellish my answer, or just leave them?


Why can I see the camera gizmo in the 3D View but not the actual camera itself?

I am new to Blender. The camera widget in my viewport only displays as a dot and yellow rectangle, while in the tutorials it has a pyramid shaped bounding box and arrow indicating which way is up. How do I correct this?


Evaluation of $\int^{1}_{0}\bigg(\frac{1}{1-x}+\frac{1}{\ln x}\bigg)dx$

Evaluation of $$\int^{1}_{0}\bigg(\frac{1}{1-x}+\frac{1}{\ln x}\bigg)dx$$   Let $$I = \int^{1}_{0}\bigg(\frac{1}{1-x}+\frac{1}{\ln x}\bigg)dx = \int^{1}_{0}\frac{(1-x)+\ln x}{(1-x)\ln x}dx$$  Now How can i solve after that , Help required, Thanks


What are longest extension names functioning in actual programs?

I'm writing piece of code detecting file extensions and I was getting quite a lot of garbage like . Jones - Some Document Title just because file name was starting with Dr. Jones. So I decided to put some additional filters like isalnum(c) to filter out only strings that contain alphanum characters but I'm still getting names like .65aab294d987659953343e8da131b2091c0c81c8 because some filenames happen to end with sha1 checksum. So what are the longest extension names used in actual applications? I know DOS used to have 3 characters extension names but it's long gone since a lot of modern applications actually use 4 letters extensions namely jpeg, .mpeg, .webm, docx and so on so I'm rather asking about real world experience. Has anyone ever seen real extension longer than lets say 16 characters?


Cosmic gravitational background and its temperature

There is a cosmic microwave background, according to the Big Bang theory. There is also a cosmic neutrino background, at 1.945 K, yet to be discovered, according to the Big Bang theory. My question is: what is the cosmic graviton/gravitational background temperature?  If any, how could it be related to the neutrino or photon background temperatures?  Remark: Sometimes, some people distinguish between the stochastic gravitational wave background and the so-called primordial gravitational wave events. The answer to this question should also clarify what are these two GW and how could they be related to the hypothetical cosmic gravitational wave background.


How to subtract a day from datetime format in python?

I'm trying print the day ranges from today up to a year ago. So i can apply this to a sql query in my other code. I know my algorithm works but i need to subtract 1 day from the format '2014-05-15' Here is the code  from datetime import date, timedelta import datetime current_date = datetime.date.today() datecounter = 0 while datecounter != 365:     print current_date     date_start = current_date     print date_start     # current_date = current_date.timedelta(days=1)     print current_date     print 'the date is between', date_start, 'and', current_date     datecounter += 1   im looking for this code to output  the date is between 2014-05-16 and 2014-05-15 the date is between 2014-05-15 and 2014-04-14   etc  i wrote a contrived example based on the logic, if you would like to run it yourself, you may better understand what i am trying to do.  x = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] curdate = 5 for i in x:     print curdate     date_start = curdate     curdate = curdate - 1     # print curdate       print ' the date is between', date_start, 'and', curdate     print ' ---------- '


How to get parent process in .NET in managed way

I was looking a lot for method to get parent process in .NET, but found only P/Invoke way.


What does mysql error 1025 (HY000): Error on rename of './foo' (errorno: 150) mean?

I tried this in mysql:  mysql> alter table region drop column country_id;   And got this:  ERROR 1025 (HY000): Error on rename of './product/#sql-14ae_81' to './product/region' (errno: 150)   Any ideas? Foreign key stuff?


Why wouldn’t I invest in NYSE:UPRO over something like NYSE:IVV?

I recently came across this 3x leveraged etf of the S&P 500 (NYSE:UPRO). I understand that it’s a risky investment, but I still see way more reason to buy it over any other thing that tracks the S&P 500. Since it’s 3x the S&P 500 (also 3x NYSE:IVV), then how about you throw a third of the money you normally would into it? The Pros of NYSE:UPRO: So,   profit potential is the same AND investing in A allows us to spend leftover money on other things (less money at risk)   The Cons: Expense ratio seems to be the only reason not to buy (0.93% for NYSE:UPRO vs. 0.03% for NYSE:IVV) ok, this is a big difference... but even still, let’s account for the expense ratios. Similar to what I said before, we’re going to invest one-third (since it’s 3x the volatility) that of NYSE:IVV, so we’ll just say $10 for NYSE:UPRO vs $30 for NYSE:IVV. Well, our expense at the end of the year for UPRO would be 0.0093(10)=$0.093 and our expense for IVV would be 0.0003(30)=$0.009, meaning our expense for UPRO is just over 10x that of IVV assuming we spend 1/3 of what we would on IVV. So,   our expenses will be a bit over 10x larger   Even knowing this, the S&P 500 is almost guaranteed to increase in value in the long run, so NYSE:UPRO should be too, but 3x more! All we have to do to account for the larger expense ratio is (yes, go against what I said before) spend a bit more than a third of what we would on IVV. Are there any other reasons that NYSE:IVV is a better investment? Yes, it’s less risky, but spending a bit over a third of what you would on IVV on UPRO allows you better profit potential, with slightly more risk. In the long run, I’d expect UPRO to be a far better investment that the S&P 500. Also, is there any other etfs that multiply the S&P 500 by more than 3, (yes I know there’s NYSE:SPXU which is -3x, but I’m talking even more volatile)?


I'm making an A/B test (Injecting code onto a page) to increase the images of products in your shopping cart.  When you select a different shipping method - the whole table appears to be refreshed.   and my code will only execute the first time.  So when i select a different shipping method the second time. my code is lost.  Except the  tags stay.  You'll need to have a random product in your cart to see it first.


Standard deviation of quantities with errors

Suppose I have taken 5 measurements, each with an associated error, let's call these values $\eta_i\pm\sigma_i$, where $i$ is an integer from 1 to 5.  I would like to find the mean and standard deviation of these quantities, $\bar{\eta}\pm\bar{\sigma}$.  The mean can be calculated simply:  $\bar{\eta}=\sum_{i=1}^{5}\eta_i$.  How is the standard deviation $\bar{\sigma}$ calculated, including the contribution from the deviation of $\eta_i$ about $\bar{\eta}$, and also the contribution from the errors $\sigma_i$?  EDIT To give some more context, the $\eta_i$ are a function of the number of counts $N$ of a Poisson distributed variable. Due to the high number of counts, $\sigma_i$ is a function of $\sqrt{N}$, which is the standard deviation of the count number.  Thus, I definitely know the errors $\sigma_i$. However, I would like to combine my repeated measurements to find a mean and deviation.  EDIT#2 My reading into the topic thus far has led me to this page on propagating errors ().  The example formulas tab has an example for the function $f=aA+bB$, which should be applicable in my case where I would like to find the mean. For my purposes (finding the mean) $a=1, b=1$. Using this entry in the table, $\sigma_f=\sqrt{\sigma_A^2+\sigma_B^2+2\sigma_{AB}}$, where $\sigma_{AB}$ is the covariance.  If I were to apply this reasoning to my problem, I should get:   $\bar{\sigma}=\sqrt{\sum_{i=1}^5\sigma_i^2 + 2cov}$, where $cov$ is the covariance.  I am rather unfamiliar with the covariance, but I think that in my example, it is equal to the variance of my 5 different $\eta_i$.  In other words, $cov=\frac{\sum_{i=1}^5(\eta_i-\bar{\eta})^2}{5}$  My question, is this interpretation right for the propagation of my errors, and if not, where has my reasoning gone wrong?


Is it possible to retrieve data off of a (possibly) damaged flash drive?

I plugged in my USB flash drive into a port that sticks out of the front of the computer and put my files onto it. I didn't immediately take it out, but instead left it in there while I continued using the computer. When I went to stand up, though, my knee bumped against the underside of the flash drive causing to jerk upward and I'm pretty sure damage it (the metal connector bit bends at a slightly more upward angle now than the plastic part).  I thought maybe it would be fine still, but when I plug it into a computer the computer still detects it is there and will install the driver software but won't allow me to access the removable storage. On Windows XP it will show up like normal in "My Computer," but double-clicking to open it results in the pop-up message "Please insert a disc into drive X." On Windows 7 it will recognize that the flash drive was inserted, but it won't show up in Windows Explorer. It does come up in the Device Manager, though.  So since the computer still recognizes that the device is there is it possible to retrieve the data off the flash drive somehow?    P.S. this is not a repost of , and I also have pretty much no experience with soldering so I would like to avoid that option.


How do Star Fleet officers command the computer? Sometimes they just speak commands, other times they also add a code like "Picard epsilon 7 9 3".  I presume the computer authenticates commands by voice recognition (now a real world technology). However that's vulnerable to replay attack (someone could record a command voiced by Picard, then play it back later).   Is that why they use the keys? If they were single use, that would thwart a replay attack. I guess they must be one-time only, else Picard wouldn't say his key loudly on the bridge.  In Ship in a Bottle Moriarty conducts a man in the middle attack. Picard believes he is giving his code to the Enterprise's computer, but he is really in conversation with the sim-Enterprise created by Moriarty. Moriarty then using Picard's code to take command of the real Enterprise.  Does Star Fleet ever introduce a defence against that?


Time dilation as an observer in special relativity

I've been having a discussion regarding time dilation relating to special relativity and how it should be observed from the FoR (Frame of Reference) of "the person moving" :  I assert- If we have a time is slower in the moving FoR than when I observe the stationary frame of reference (earth) then I should perceive events as occurring faster, i.e., if I observe 15 years passing and 90 years pass in the stationary frame then I should observe events on earth happening at a rate of 6:1. So if I observe a 1 min event on earth I watch that entire event occur in 10 seconds.   My thought process is similar to the idea that if I was near a massive object and looked out I would observe events further away as moving faster. My teacher seems to believe this line of reasoning is incorrect but will not (or cannot) give me the correct thought process.  Hence my question is, "is my logic correct, and if not why?"


How to separate declaration and definition into header and source of non-member operator for known template values of a class template?

The following is a great simplification of my code:  data.h  #include "id.h"  namespace n1 {     struct data     {         /* Relies on struct id */     }; }   id.h  namespace n1 {      struct data; // Forward declaration      template <int dims>     struct id     {         id(unsigned n);         data operator*(unsigned n) const;     };      template <int dims>     data operator*(unsigned n, id<dims> i);  } // namespace n1   id.cpp  #include "id.h" #include "data.h"  using namespace n1;  // Force instantiation of struct id for template values 1, 2, and 3 template struct id<1>; template struct id<2>; template struct id<3>;  template <int dims> id<dims>::id(unsigned n) {}  template <int dims> data id<dims>::operator*(unsigned n) const {     return data(); }  // warning C4667: no function template defined that matches forced instantiation template data operator*<1>(unsigned n, id<1> i);  template <int dims> data operator*(unsigned n, id<dims> i) {     return i * n; }   I'm using Visual Studio 2013. The first problem I encounter with this approach is the warning C4667. An alternative is to declare friend data operator*(unsigned n, id i) inside struct id and not forcing instantiation of this operator, which gets rid of the warning, but nothing else.  The real problem occurs when I decide to actually use this operator, e.g. in main():  using namespace n1; id<1> i(7);      // Works fine data d1 = i * 5; // Works fine data d2 = 4 * i; // error LNK2019: unresolved external symbol                  // struct n1::data __cdecl n1::operator*<1>(unsigned int,struct n1::id<1>   , however it does not have an answer. My hoping is that my example is much simpler to identify the problem.  I tried all the suggestions from there, trying all combinations that I could find that were able to compile, but none of them were able to link. I guess an alternative would be to split structs id and data into multiple structs and files, however that may prove messy at this point.  Edit: The question is definitely not a duplicate of . As you can see from my code, I'm asking about explicit specialization for known data types, which I have been successful in implementing in a separate source file for everything except non-member operators. I have to admit that forced instantiation is a new trick for me, which I do not know how to use in this particular example.


If $p\in R[X_1,\dots,X_n]$ is irreducible, is it still irreducible in $R[X_1,\dots,X_n,\dots,X_N]$?

It is a known fact that if $R$ is a UFD, then $R[X_1,X_2,\dots]$ is also a UFD, but there is a subtlety that is making me uncomfortable.  The standard approach essentially goes something along the lines of...let $f$ be a polynomial, so it only involves finitely many variables, say up to $X_1,\dots,X_n$. Then since $R[X_1,\dots,X_n]$ is a UFD, $f$ has a factorization into irreducibles. Then $f$ cannot have a factorization involving indeterminates $X_N$ not in $R[X_1,\dots,X_n]$. If it did, then $f$ would have two factorizations in the UFD $R[X_1,\dots,X_n,\dots, X_N]$, a contradiction.  This seems to assume that the prime factorization in $R[X_1,\dots,X_n]$ is still a prime factorization in $R[X_1,\dots,X_n,\dots,X_N]$. But how can you see that irreducibles in $R[X_1,\dots,X_n]$ are still irreducibles in $R[X_1,\dots,X_m]$ for $m>n$? This does not seem obvious.  Let $R_k=R[X_1,\dots,X_k]$. The explanantion I found is this: Suppose $p\in R[X_1,\dots,X_n]$ is irreducible in $R_n$. Suppose $p=ab$ for $a,b\in R_m$. Evaluating $X_1,\dots,X_n$ at $1$, you get  $$ \bar{p}=\overline{ab}\in R[X_{n+1},\dots,X_m] $$ But $\bar{p}\in R$, which implies that $a$ and $b$ do not involve any variables $X_{n+1},\dots,X_m$. So $a,b\in R_n$, and thus one is a unit, hence a unit in $R_m$.   The part I don't follow is how evaluation at $1$, implies $a$ and $b$ do not have indeterminates other than $X_1,\dots,X_n$. Isn't it possible that some of the higher indexed indeterminates disappear when you evaluate? Suppose for instance $p\in R_1$, and $a\in R_2$ is $a=-X_1X_2+X_2$. Then evaluting at $1$ gives $\bar{a}=0$ so we may not get the desired contradiction since $\overline{ab}=0\in R$?


Starting a new line below a certain word

I would like to start a new line directly below a certain word in previous line. For example, let the first line begins by 'Let A denote ...' and I want to have 'B denote ...' for the second line. However I want 'B' to be exactly below 'A'. Is there a technical method of doing this in Latex? If you have any other suggestions, please let me know.


I have an image (PNG or JPG) inside which there is at least one pixel of a certain RGB color I know in advance.  I want to find the pixel(s) of that color  For example, I may have image.jpg, inside which I know some pixel has the RGB value 255,100,200. I want a program that will give me the list of pixels (if any) of that color in the image.  Anyone know of a tool to help me with that?  Thanks!


Changing files names of more than 100 files

So there's a folder in my directory which contains around 400-500 files (java, cpp, xml & etc) each with one name common for e.g xml_1_ubuntu.xml java_1_ubuntu.java cpp_1_ubuntu.cpp ...  I wanna change the ubuntu in their name (irrespective of their extension/file type) to notubuntu so the work dir will have files like xml_1_notubuntu.xml java_1_notubuntu.java cpp_1_notubuntu.cpp ...  is there anyway I can do this?


Custom CSS and JS that would load only for a content type's view mode

I am trying to load a custom css and js on my content type's view mode. Can this be achieved in drupal 8?


How to define white color scientifically?

I'm sorry some of you may mark this question as duplicate, but  even though I searched over about this I couldn't get satisfacory answer. Also I think this question is more related to biology, but I dont think I would get a satisfactory answer on biology forum.  I have had much intesest in color perception. I learned that color is just illusion of human brain to interpret electromagnetic spectrum. But though I'm physics grad student, I never questioned myself why there is no white color in visible ray spectrum. I realized that today. Sure thing, I learned when I was young that white color is    what we see when we see an object that reflect all the light.  But what do we mean by 'all the light' here? every illuminant has different spectral power distribution so even if an object reflects them all what we see would depends on illuminant. And what does it means that it reflects every light? surely not all the electromagnetic spectrum. Only visible rays? reflects 400nm but not 390nm? I'm not sure about that. Equal composition of RGB, three primary colors.  If you see the CIE color space picture with sRGB gamut on it, you would question whether we can call these colors 'primary'.      Yes we humans have three types of cones, but they don't correspond exactly to each color of RGB.   I thought white should be a extreme on certain measure (like lightness in 'conventional' term) but Im not sure which is corresponding scientific term. Or isnt white such a special color? just some 'appropriate' mixture of colors like RGB?  I read some articles about this on Wikipedia but I'm not sure I understood them because they use many technical terms in color science.


What's the difference between the following examples:   I noticed that the clock had stopped.  I noticed that the clock has stopped.    Some of them say that if the emphasis is laid on the subordinate clause then present perfect tense can be used, while some say if the emphasis is laid on 'noticing' then past perfect tense is to be used. How correct is this explanation?


I have previously asked  the following integral:$$\int \frac{6x^{3}+7x^2-12x+1}{\sqrt{x^2+4x+6}}dx.$$ In the meantime I have received an answer from Achille Hui , but there are still some points that I don't understand from his answer.  At some point there is:   Set $B(y)$ to $ay^2 + by + c$, RHS($*1$) becomes $(6-3a)y^3 + \cdots$. We should fix $a$ to $2$.  Repeat this procedure once more, we find $c$ should be fixed to $24$.    I don't understand how does he fix these numbers? Does he let them equal $0$ to obtain the final result?


Doodling in wolfram, I found that $$ \sum^{k}_{n=1}1=k $$ The formula is pretty obvious, but then you get $$ \sum^{k}_{n=1}n=\frac{k(k+1)}{2} $$ That is a very well known formula, but then it gets interesting when you calculate $$ \sum^{k}_{n=1}n(n+1)=\frac{k(k+1)(k+2)}{3}\\ \sum^{k}_{n=1}n(n+1)(n+2)=\frac{k(k+1)(k+2)(k+3)}{4} $$ And so on. There is an obvious pattern that I really doubt is a coincidence, but I have no idea how to prove it in the general case. Any ideas?


Reading and writing components from multiple systems in ECS

As a learning exercise, I'm building my own ECS. I've got a situation where two separate systems want to query and possibly update a Transform component - input handling and collision detection.  Given that each system operates in isolation, as if it were running in its own private thread, I'm effectively doing a concurrent update, but don't really want to block. I'm also concerned that one system might update the transform and then the next system is operating on different data.  Are these valid concern, or are the periods between updates so small that this is negligible and not worth worrying about? If valid, what are some other possible options for solving?


Altering window.print() Javascript functionality

This question is mostly out of academic interests(and partly because I faced an issue like this before and simply found a workaround, but I want to know the proper way to do it).   How does the window.print() JavaScript function decide which parts of a page to print? My end goal is to add new fields to the 'print' dialog which is not there in the original page and also be able to prevent some content in my page from being printed(for eg: prevent some plaintext links on my webpage being printed onto paper).   Can I edit the function to suit my requirements? Where are the JS files located?


What are you allowed to run on a Free Hyper-V 2012 host?

I have been looking for a "layman" version of the license for the Free Hyper-V 2012, and more precisely, what services you are allowed to run on the host.  The OS itself does not prevent you from installing a variety of applications and services, but I wonder how legal this is.  You can install 3rd party virtualization managers or servers (anything based on http.sys will run f.i, and so will 3rd party FTP or mail server). For that matter you can even install alternative desktop shells, explorers, browsers and utilities etc. so the OS itself does not prevent installation of any 3rd party software, only the OS components are missing.  My particular purpose would be to know if the license allows to use the Free Hyper-V 2012 as a "bare-metal" OS for hosting simple web services (based on http.sys or raw sockets rather than IIS), that would otherwise require a full Windows 2012 server. Virtualization functions would not even be used.


With constant travel, is it possible to not have a tax residence?

We're in the EU (EU passports) and planning on spending the next couple years traveling. Income is coming through a company I have set in a country I was never a resident of.  The only taxes I'm normally liable for is my personal income, at my place of residence.  During the travel period, we will not stay longer than 2-3 month in a specific country, therefore we don't establish tax residence in any of them.  In that situation, can I avoid paying income tax during that time?


D:\>rmdir /S default default, Are you sure (Y/N)? y default\default\default\default\default\default\default\default\default\default\default\default\default\default\default\default\default\default\default\default\ default\default\default\default\default\default\default\default\default\default\default - The system cannot find the path specified.   I've also tried Unlocker and various other tools. Can't get rid of this folder. I also tried moving it to another drive then format, no luck.


apt-get upgrade is producing a GUI interaction and is prohibiting an interaction-free upgrade

So I am writing a script that changes various aspects of an Ubuntu 16.04.4 machine and one of the tasks is upgrading all packages. To do this I useapt-get -y upgrade. (-y for auto yes on dialogue and provide automation) This works fine and is automated for nearly all packages but once every so often I will get the interaction pane depicted below.    I'm assuming there is no easy way to handle and answer these dialogues in a uniform way across all packages but is there a way to disable such an interaction and provide a truly automated, interaction-free upgrade?


Unity 2D graphical glitch cuts sprite diagonally

While making a game in unity, we found a graphical glitch that only happens on one of our mobile devices (a htc) where the screen will be oddly sliced by a triangle as shown in this image;    I've searched online but found no problem. We're using unity 2D, it only does it on the HTC but we have no idea why.  The background is a 3D quad with a texture wrapped around it (so we can make it move with the character when the character is running, without having one large background).  Any help would be greatly appreciated.  Thanks


How can I install Google Earth in Ubuntu minimal from command line?

I'm trying to install google earth pro in ubuntu from command line to implement Liquid Galaxy, following the HOWTO ()  sudo apt install gdebi-core wget wget https://dl.google.com/dl/earth/client/current/google-earth-pro-stable_current_amd64.deb sudo gdebi google-earth-pro-stable_current_amd64.deb   and it returns errors:  Error: could not find xdg-icon-resource when installing google-earth-pro-stable dpkg: error processing package google-earth-pro-stable (--install)  installed        google-earth-pro-stable package post-installation script subprocess returned error exit status 1 Errors were encountered while processing: google-earth-pro-stable   Can anybody help me to understand how to install Google earth for LiquidGalaxy?


How to merge particular cells into a single-row cell?