The scenario is as follows.  I am working on a paper using the  latex class.  I am generating some figures using the  plotting library in Python.  Matplotlib lets the user adjust the font and compile figures with the help of tex so that you can get nice looking fonts in your figure labels which match the font used in the document the figures are going into.  What I would like to know though, is what font is the IEEEtran class actually using so that I can configure Matplotlib to use the same font?    I guess this problem generalizes beyond IEEEtran which I happen to be using.  Short of eyeballing a font, is there a reliable way to determine which font is being used at a given point in a document?  I'm guessing the font can be overridden in any one of a million possible places, so I'm really interested in knowing whether there is a generalized solution that isn't "read through the manual of whatever class files/other files you're using until you figure it out".  Is there a command I can put inline in the middle of a paragraph or something that will tell me the font details in the current context?

Is it possible to identify the font used in a specific document/picture?  Answers to this question should identify:   Possible methods to do this (perhaps one answer per method) and adequately describe how to use it (as opposed to merely stating it); Ways of finding the identified fonts, if possible (free or not); and Any prerequisites associated with the method used, if required (for example, "In order to use method X, your document has to be in format Y").   This question is meant as an FAQ, based on an . Its aim is to facilitate the community with the general procedures involved in font identification. Similar cases are solved on a per-usage basis on 's  tag.


Let $V$ be the vector space of all functions $f \colon \mathbb{R} \to \mathbb{R}$ over $\mathbb{R}$, is the set of functions which are continuous a subspace?  I think if you add functions which are continuous, the resultant function should also be continuous, but I'm not sure about it

I'll go ahead and give you the problem first, and then explain my trouble with it.  Which of the following subsets are subspaces of the vector space C(-$\infty$,$\infty$) defined as follows: Let V be the set of all real-valued continuous functions defnined on $\mathbb{R}^1$. If $f$ and $g$ are in $V$, we define $(f + g)(t) = f(t) + g(t)$. If $f$ is in $V$ and $c$ is a scalar, we define $c$ · $f$ by $(c · f)(t) = cf(t)$. Then $V$ is a vector space, which is donatedby C(-$\infty$,$\infty$).  (a) All nonnegative functions (b) All constant functions  There are more, but I have a feeling that after the (a) I'll be able to get the rest myself. Anyay, my problem is that the problem says it required calculus, and I don't understand how calculus even comes into it.  As far as I can tell, (b) would be a subspace (because it's are closed under operations of V), but (a) would not because V could make a negative value positive.  I may be completely wrong though; any suggestions?


I have enjoyed the second edition of the title's book (Nouveaux jeux de l'esprit et divertissements mathématiques) and now I have bought the first edition. To set some context, the book has some "games" (problems), some of them require a few skills (or none) on logic and math, and other ones need more time and more knowledge on mathematical concepts. I am interested in books like this, or other books with problems of logic, puzzles, etc (Obviously, related to mathematics, mathematical concepts and logic).  I'm not interested in books of sudoku, and puzzles like that (just because there are a lot of books with that content).    Thanks for your answers and have a nice day!

So my partner and I thought it would be great if we could do some maths problems over Skype while we are apart (long distance). We'd like some recommendations on problem books that are ideal for working on together. We know there are quite a few questions online for best puzzle books in general but we'd like to know of any that have been written for or are suited for couple solving.   We are both fairly proficient in general but are not experts in any one topic. Ideally, the book should cover multiple fields with fairly difficult logic/maths problems.  As a starter list, what do people think of:   Raymond M. Smullyan - The Godelian puzzle book Peter Winkler - Mathematical puzzles a connoisseur's collection Raymond M. Smullyan - What is the name of this book?   I'm aware this is a rather strange request but thought it was worth asking just in case.


I have encountered an issue with the current live installer for Ubuntu 18.04.1 server.  Whenever I run an integrity check on the drive there is always 3 errors. I have tried multiple drives and writing them multiple times. I have also verified the iso.  Now where do I report this?  Is there a package that is concerned with making the iso image where I can report this?  Something must have gone wrong in build the ISO, since the ISO it self passes the checksum, but the files packed in it does not.  Also: Can someone please confirm or refute this issue?  Also, it doesn't show me which files has errors, and pressing any key after the check will reboot. Update: I found out which files fail.

I found a problem with an application on Ubuntu.   Questions :   How do I best report the issue?  What sort of information should I provide?


I've got this problem:   Here, if $Z,W$ are independent random variables, and $Z$ has normal standart distribution and $W$ has $\chi^2$ with $n$ degrees of freedom, $T=\frac{Z}{\sqrt{\frac{W}{n}}}$. I don't expect to find any problems in $b$ and $c$ parts, but in $a$, I don't know how to find the conditional density. How could I?

Using the student t-distribution with $k > 0$ degrees of freedom, location parameter $l$ and scale parameter $s$ having density  $$\frac{\Gamma \left(\frac{k+1}{2}\right)}{\Gamma\left(\frac{k}{2}\sqrt{k \pi s^2}\right)} \left\{ 1 + k^{-1}\left( \frac{x-l}{s}\right)\right\}^{-(k+1)/2},$$  how to show that the Student $t$-distribution can be written as a mixture of Gaussian distributions by letting $X\sim N(\mu,\sigma^2)$, $\tau = 1/\sigma^2\sim\Gamma(\alpha,\beta)$, and integrating the joint density $f(x,\tau|\mu)$ to get the marginal density $f(x|\mu)$? What are the parameters of the resulting $t$-distribution, as functions of $\mu,\alpha,\beta$?  I got lost in calculus by integrating the joint conditional density with the Gamma distribution.


If we have vertical linearly polarized light and if we put it through a polarizing filter oriented at 45 to the vertical, then only half of the light passes through.   I am able to intuitively grasp this fact as photons of vertically polarized light may exist in a superposition of being in two diagonally polarized and mutually perpendicular states, for which the amplitudes interfere. Thus upon interacting with the filter half of the photons pass through.   But if we subsequently pass this light through another filter which is oriented horizontally, still half of this light will pass through.   Why does this happen? Doesn't the fact that it passed through the first filter mean that it is oriented diagonally without uncertainty? How can it, after passing through the first filter, still exist in superposition of two states? Wouldn't the act of passing it through a filter disturb this superposition and force it to occupy one definite state?

If light is passed through two polarizing filters before arriving at a target, and both of the filters are oriented at 90° to each other, then no light will be received at the target. If a third filter is added between the first two, oriented at a 45° angle (as shown below), light will reach the target.  Why is this the case? As I understand it, a polarized filter does nothing except filter out light--it does not alter the light passing through in any way. If two filters exist that will eliminate all of the light, why does the presence of a third, which should serve only to filter out additional light, actually act to allow light through?


I have a directory that contains 800 subdirectories named disp-001 ... disp-800. All these sub-directories need to contain a specific file say stdout. One among them does not contain the file and I need to find the folder that does not have the file. If I try  find . -name "stdout"   it returns me the values of all files, but they are not ordered from 001 to 800, which makes it very difficult for me to identify the folder. Is there a way to order the output such that they are ordered numerically?  NOTE:  I'm leaving this question unedited to demonstrate  (atleast to myself) a classic . All I needed was to identify directories not containing a particular file, but instead this question was about a particular attempted solution to the problem. The solution for finding a directory that does not contain a particular file is provided .

How would I go into listing all directories that do not have a file with a given file name inside? e.g. given this tree  /   /a      README      file001      file002   /b      README      file001   /c      file003   I want to list the directories that do not have a file named README, in this case it would be directory /c. How would I do that? I can't think of any syntax using e.g. find.


What is foo? I have seen it in many CSS and Web designing examples usually as a CSS class.

I hope this qualifies as a programming question, as in any programming tutorial, you eventually come across 'foo' in the code examples. (yeah, right?)  what does 'foo' really mean?  If it is meant to mean nothing, when did it begin to be used so?


(*Question edited for clarification)  Does the lower bound of the unstandarized beta distribution always have to be bigger than 0?

What is the difference between standard beta and unstandard beta distributions? How to understand in an article if it is not described if it is standard or not?


I am using SQL Server 2008 R2  This is the value that I have :  DECLARE @DBB varchar(200) = 'A2gg3h.B2g3ghh3.Cggh3663.D1jhg23.Eh2hjj2g'   Returning the 2 outer values are easy enough :  SELECT LEFT(@DBB, CHARINDEX('.', @DBB)-1) SELECT RIGHT(@DBB, CHARINDEX('.', @DBB)-1)   How would I alter script in order to select values :  1. 'Bg2g3ghh3' 2. 'Chggh3663' 3. 'Dh1jhg23'   Using CHARINDEX would only bring back (LEFT) 7 and (RIGHT) 9.  Thanks

Using SQL Server, how do I split a string so I can access item x?  Take a string "Hello John Smith". How can I split the string by space and access the item at index 1 which should return "John"?


can one travel back in time and if not so, what laws prevent time travel to the past. this is quite a challenge to understand.

I read somewhere that according to relativity, it is possible - involving black holes and other stuff - to jump into the past. Is it possible for anything to go back in time either continuously or by jumping?


I want to create a new div tag via  $(this).prepend("

");   and onclick it should close  $(function() {     $(".test_close").click(function() {         console.log("clicked");         $(this).remove();     }); });   but it doesn't work for me...  do you have an idea how i can do this?  thanks in advance and sorry for my bad english

I have a bit of code where I am looping through all the select boxes on a page and binding a .hover event to them to do a bit of twiddling with their width on mouse on/off.  This happens on page ready and works just fine.  The problem I have is that any select boxes I add via Ajax or DOM after the initial loop won't have the event bound.  I have found this plugin (), but before I add another 5k to my pages with a plugin, I want to see if anyone knows a way to do this, either with jQuery directly or by another option.


In my PC,  the @ and " need to be interchanged on keyboard. As they are printed according to that in the key board.  Please advice.  Thanks

I want to switch between English and another language.  I have tried Lubuntu and it was easy, I figured it out from the friendly menus. But in Ubuntu everything is so cryptic.


I have a flow that goes MainActivity -> StoriesActivity -> StoryBodyActivity.  Each passes variables to the next using Intents.  I'm trying to implement a back button from StoryBodyActivity to StoriesActivity, but it's throwing a NullPointerException on authorID = extras.getInt("author_id"); in StoriesActivity.  I know what a NullPointer is. I just don't know how to fix this one! Could it be because it no longer has access to the data that was passed from the MainActivity?  Note: This works fine when clicking the back button on the device, just not the icon on the ActionBar.  Snippet from StoryBodyActivity:  @Override     protected void onCreate(Bundle savedInstanceState) {         super.onCreate(savedInstanceState);         setContentView(R.layout.activity_story_body);          getSupportActionBar().setDisplayHomeAsUpEnabled(true); }  @Override     public boolean onOptionsItemSelected(MenuItem item) {         switch (item.getItemId()) {             // Respond to the action bar's Up/Home button             case android.R.id.home:                 NavUtils.navigateUpFromSameTask(this);                 return true;         }         return super.onOptionsItemSelected(item);     }   Snippet from StoriesActivity:  private int authorID;      @Override     protected void onCreate(Bundle savedInstanceState) {         super.onCreate(savedInstanceState);         setContentView(R.layout.activity_stories);          Bundle extras = getIntent().getExtras();          authorID = extras.getInt("author_id"); // NullPointerException here         final String authorName = extras.getString("author_name");         Log.i("click", Integer.toString(authorID)); }   Snippet from MainActivity:  Intent intent = new Intent(MainActivity.this, StoriesActivity.class); intent.putExtra("author_id", author.getID()); intent.putExtra("author_name", author.getName()); startActivity(intent);   Snippet from AndroidManifest:  <application         android:allowBackup="true"         android:icon="@mipmap/ic_launcher"         android:label="@string/app_name"         android:roundIcon="@mipmap/ic_launcher_round"         android:supportsRtl="true"         android:theme="@style/AppTheme">          <activity             android:name=".MainActivity" android:theme="@style/AppTheme.NoActionBar" >             <intent-filter>                 <action android:name="android.intent.action.MAIN" />                 <category android:name="android.intent.category.LAUNCHER" />             </intent-filter>         </activity>          <activity             android:name=".StoriesActivity"             android:theme="@style/AppTheme.NoActionBar" />          <activity             android:name=".StoryBodyActivity"             android:theme="@style/AppTheme"             android:parentActivityName="com.example.apple.bookshelf.StoriesActivity">         <meta-data             android:name="android.support.PARENT_ACTIVITY"             android:value="com.example.apple.bookshelf.StoriesActivity" />         </activity>      </application>

What are Null Pointer Exceptions (java.lang.NullPointerException) and what causes them?  What methods/tools can be used to determine the cause so that you stop the exception from causing the program to terminate prematurely?


So, I am creating a LorenzSZ40 simulator. And I'm still in early stage of creating it. The thing is the fact that I am using byte[] arrays in order to store plain text and key data.  For example I have this  byte[] plainText = {1, 0, 1, 0, 0}; and  byte[] key = {1, 1, 1, 0, 1}; When XOR'ing that, the result should be 0, 1, 0, 0, 1 But the problem is that I cannot use ^ operator on byte[].      public static byte[] xor(byte[] plainText, byte[] key) {     byte[] result = new byte[Math.min(plainText.length, key.length)];      for (int i = 0 ; i < result.length ; i++) {         result[i] = (byte) (((int) plainText[i]) ^ ((int) key[i]));     }      return result; }  public static void main(String[] args) {      String pt = "10100";     String key = "11011";     byte[] som = pt.getBytes();     byte[] k = key.getBytes();     //0, 1, 1, 1, 1      String nm = new String(xor(som, k));     System.out.println(xor(som, k)); }    This is the code I have tried. When I run it I only get [B@3d494fbf and if I was to use   String nm = new String(xor(pci, key));     System.out.println(new String(nm));   Instead of   String nm = new String(xor(som, k));     System.out.println(xor(som, k));   I wouldn't get anything at all.  My question is, how should I make it right?

In Java, arrays don't override toString(), so if you try to print one directly, you get the className + '@' + the hex of the  of the array, as defined by Object.toString():  int[] intArray = new int[] {1, 2, 3, 4, 5}; System.out.println(intArray);     // prints something like '[I@3343c8b3'   But usually, we'd actually want something more like [1, 2, 3, 4, 5]. What's the simplest way of doing that? Here are some example inputs and outputs:  // Array of primitives: int[] intArray = new int[] {1, 2, 3, 4, 5}; //output: [1, 2, 3, 4, 5]  // Array of object references: String[] strArray = new String[] {"John", "Mary", "Bob"}; //output: [John, Mary, Bob]


$\lim \limits_{x \to 0} f(x)=\lim \limits_{x\to a} f(x-a)$   My strategy (based off an answer to one of my previous questions) has been to set the two limits equal to some number c, so that $\lim \limits_{x \to 0}$ $f(x)=c$ and $\lim \limits_{x\to a}$ $f(x-a)=c$, and then to show both limits equal each other. So given an $\epsilon >0$, there is a $\delta >0$ such that,  if $0<|x-a|<\delta$, then $|f(x-a)-c|<\epsilon$  and  if $0<|x-0|=|x|<\delta$, then $|f(x)-c|<\epsilon$  How do I proceed from here to show that the two limits are equal?

$$ \lim_{x\to a} f(x) = \lim_{h\to 0} f(a+h) $$   How do I write a formal proof of it?


Why doesn't Stack Exchange delete posts that have no comments, answers, or activity for a long period of time. The number of unanswered questions continues to grow on each community (Stack Overflow: 2,710,786) , and it seems questions that are worthwhile to answer are already answered and were within a short period of time.   I understand many questions are answered in the comment section, so it seems viable to leave unanswered questions that have comments, but there are many that have never had activity (probably because they are badly worded questions, already answered before, or too individualized such that the question would not benefit the entire community).  My old question fits under all of these and has no comments or answers. It seems like it should be deleted.   I have some strange goal that one day all questions will have answers, and the questions with no activity stand in the way.

Related to Meta Super User efforts:  and Meta Server Fault efforts:  We already auto-remove negatively voted unanswered old questions automatically after 30 days, network wide, with no human intervention required. I was thinking we might extend that to remove old, unanswered zero score questions... based on the following criteria:  fewer than (question age in days * 1.5) views 0 score or lower, or 1 score or lower if the original author is deleted no answers 1 comment or fewer asked more than 1 year ago (thus based on creation date, not last activity date, so , or a user editing it, does not give a doomed question 365 more days of zombie "life")  See the results of this query on:  (10509) |  (787) |  (650) This query has been refined based on the comments, and this is the final version that will roll out tonight. Every site in the network (except metas) will automatically delete old questions that meet this criteria from this point forward.


For example I want to install Google Chrome via deb file. Will it be added to my repository list for apt-get update and apt-get upgrade?  If not, how would I go about updating it and other software installed through deb files?

I'm having some difficulties exactly understanding how the the whole update thing work in Ubuntu and good practice for installing software.  I understand I have a  /etc/apt/sources.list file where all my repositories are listed, and that these repositories are queried when I use apt-get update - to later be used with e.g. apt-get upgrade.  This makes perfect sense and I recently installed spotify by adding deb http://repository.spotify.com stable non-free to this "sources" list.    But then I got confused...  When I went to download Google Chrome I merely had to download and grab a .deb file, and Chrome installed with no problem... but I don't see any new entry in /etc/apt/sources.list...  So how does apt-get update know where to query concerning Chrome updates?  Has it somehow been added to one of the already listed repositories in the sources file?  I would like all my installed software to be encompassed by the update function.


when I do sudo apt-get update I get these errors,  Err http://ppa.launchpad.net trusty/main amd64 Packages 404  Not Found Err http://ppa.launchpad.net trusty/main i386 Packages  404  Not Found W: Failed to fetch http://ppa.launchpad.net/adilson/experimental/ubuntu/dists/trusty/main/binary-amd64/Packages  404  Not Found W: Failed to fetch http://ppa.launchpad.net/adilson/experimental/ubuntu/dists/trusty/main/binary-i386/Packages  404  Not Found E: Some index files failed to download. They have been ignored, or old ones used instead.   I have no idea what launchpad is. what this error is? what this error points to?  How can I remove this error?  Thanks.

PPA seems to be constantly offline. Whenever I use sudo apt-get update, this error is shown:  W: Failed to fetch http://ppa.launchpad.net/ 404  Not Found   How do I fix these errors?


i am wanting to unlock the bootloader on my Samsung Galaxy A5 2017. The problem that I have encountered is that fastboot doesn't actually detect my device but adb does!  I have tried 'adb devices' and that finds my device but when i try 'fastboot devices' it doesn't appear with anything.  If you have any solutions please tell me!

I was trying to do some fastboot commands on my Galaxy devices (Galaxy S4, 9515, 4Tab4), I start with fastboot devices and I am getting nothing (after adb reboot bootloader), is there any problem with samsung devices?


As a non-root user, when I run top or ps aux, I only see processes with my user name.   $ ps aux USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND mahmood 31398  0.1  0.0 117152  3948 pts/10   Ss   19:27   0:00 -bash mahmood 32468  0.0  0.0 148964  1872 pts/10   R+   19:31   0:00 ps aux $   How can I fix that in a way to show all processes?

Using ps -aux or top, I can list other users running processes, but I'm neither running as root nor making use of sudo, why?


I'm using an HDRI () And the objects are not casting any shadows but if I don't use the HDR, objects are casting shadows Hope that makes sense

Blender 2.8 supports the same world node setup that Cycles does. This correctly puts the HDR image in the world background.  But EEVEE doesn't light the scene properly. Everything looks flat and washed out. Is there a way to properly light an EEVEE scene with an HDR?


I am trying to take kernel logs but so far have only got errors like 'permission denied', 'path does not exist' or 'kernel log does not exist'. I have tried , , ,, , and several other links. List of commands tried:  cat /proc/last_kmsg dmesg cat /proc/kmsg cat /dev/kmsg cat /sys/fs/pstore/console-ramoops *#9900# (Samsung only)  I am doing this in response to a comment on . Any suggestions? Edit: So I have been able to get logs using *#9900#. The kernel log option didn't work but I set debug mode to high, let the reboot happen and then used the inbuilt option to copy logs to storage. The device restarted and showed 'watchdog reset' after which I force restarted. Along with many other files, texts, logs, it has mention of /proc/last_kmsg in a txt file. I will see if it is useful and share in the original post.

I have a rooted Samsung device(system-as-root). When I open adb shell and run the dmesg  then it behaves differently for su and normal user. It throws      dmesg: klogctl: Permission denied   error when I run it without su shell.  Please suggest how can I fix this?


I downloaded vim-Latex from , and installed vim-Latex by hand (without Vundle or similar). I followed the instructions on the page:    However, upon opening an already existing (la)tex-file with vim I don't get the menu bar as it is shown on the page:    So I cannot choose a particular template type. But it is even worse. Upon typing \ll at the beginning it did not work at all, but after simplifying my .vimrc file it finally worked, however, it spits out a lot of error messages which apparently have nothing to do with my (la)tex-file (in particular because a call of latex (la)tex-file at the commandline prompt works perfectly without any error):   Error detected while processing function Tex_RunLaTeX..Tex_SetupErrorWindow..Tex_GetMainFileName:   line   23: E121: Undefined variable: v:true E116: Invalid arguments for function glob('*.latexmain',v:true) == ''  E15: Invalid expression: glob('*.latexmain',v:true) == '' line   34: E121: Undefined variable: v:true E116: Invalid arguments for function glob('*.latexmain',v:true)  E15: Invalid expression: glob('*.latexmain',v:true) line   35: E121: Undefined variable: lheadfile E15: Invalid expression: lheadfile != '' line   51: E121: Undefined variable: lheadfile E15: Invalid expression: lheadfile   I am using vim 7.4 on a KDE OpenSuse Linux system (version number at least 14). I've never used a vim-plugin, so actually my experience in the field is still limited. But as I use Latex a lot, I thought it would be useful to give vim-Latex a try. Thank you for any help.

Whenever I try to compile my LaTeX on vim using vim-latex and \ll I get the following error  vDoc.tex || I can't find file `0'. 0 || Emergency stop. 0  [Quickfix List] :latex -interaction=nonstopmode -file-line-error-style 0                                  1,1             All  How to fix this? I have the latex version of Mac OS X. Also I have tried to fix by typing in latex -interaction=nonstopmode -file-line-error-style 0    to no avail. Please help.  Thanks.  EDIT: When I type in the command  :!latex -interaction=nonstopmode % it compiles but whenever I do \ll it doesn't Furthermore when I use :!latex -interaction=nonstopmode % it doesn't go over the errors when I hit enter...Any help is appreciated.


There are a lot of questions asking what happens if you change the current, but keeping the same voltage. If more current is flowing to me it means you can damage the device. But what if it is the other way around? What happens if you increase the voltage, but have the same current?  Let's say I power on a device with an adapter that outputs 5 volts @ 2 amperes. If I would like to connect that same device to an adapter that outputs 20 volts @ 2 amperes, will I burn it? I think you burn a device by passing too much current, no? Could increasing the voltage also burn it if you are passing the same current?

Power supplies are available in a wide range of voltage and current ratings.  If I have a device that has specific voltage and current ratings, how do those relate to the power ratings I need to specify?  What if I don't know the device's specs, but am replacing a previous power supply with particular ratings?  Is it OK to go lower voltage, or should it always be higher?  What about current?  I don't want a 10 A supply to damage my 1 A device.


I am just learning about recurrence relations and restricted compositions, can someone help me solve this problem

How can you find count of the total combinations possible if you have the count of unique combinations? Suppose I need to form a sum of $3$ using $\{1,2\}$ Unique combn. $(1+1+1)$, $(1+2)$ hence '$2$' unique but total is '$3$' i.e, $(1+1+1)$, $(1+2)$, $(2+1)$ I know the elements used to make the combination Note: Number of unique combinations (ie. 2 here) is known. How can I find the total number of combination given the unique combinations?


I was told by my professor that homeomorphisms are continuous maps with continuous inverse, but do those conditions also imply that the map is bijective?

Here is my question:  Is a homeomorphism, that is, a continuos function whose inverse function is also continuous, always bijective?


I'm trying to resize bitmap............on click its working bt in idle time when click on view..." 'int android.graphics.Bitmap.getWidth()' on a null object reference " this error occurs. here is resize code for my bitmap...........how to solve this ??      public static Bitmap resizeImage(Bitmap source, int w, int h) {     int width = source.getWidth();     int height = source.getHeight();     float scaleWidth = ((float) w) / width;     float scaleHeight = ((float) h) / height;     Matrix matrix = new Matrix();     matrix.postScale(scaleWidth, scaleHeight);     return Bitmap.createBitmap(source, 0, 0, width, height, matrix, true); }   code :      public static int getScreenWidth() {     WindowManager wm = (WindowManager) FusionMusicApplication.getInstance().getSystemService(Context.WINDOW_SERVICE);     return wm.getDefaultDisplay().getWidth(); }   here is usage code:  bitmap = resizeImage(bitmap, getScreenWidth()/2, getScreenWidth()/2);   how to fix this ?

What are Null Pointer Exceptions (java.lang.NullPointerException) and what causes them?  What methods/tools can be used to determine the cause so that you stop the exception from causing the program to terminate prematurely?


Every time I boot my computer, I get the auto pop-up in the upper right notifying me that Ubuntu One is closing June 1, 2014.  I can't figure out how to get it to stop showing that message.  I have disconnected all of my devices from Ubuntu One, and clearly June 1 has already past, and I still get the pop-up.  Any advice?

Good day, people It's been 8 days since the announced discontinuation of Ubuntu One, which I've never used at all, but I'm still receiving the notice for "June 1st discontinuation" every time I boot up my 12.04. Will that message ever go away?  Thanks.


Let G be the Galois group of a field with nine elements over its subfield with three elements. Then find the number of orbits for the action of G on the field with 9 elements.

Let $G$ be the Galois group of a field with nine elements over its subfield with three elements. Then the number of orbits for the action of $G$ on the fields with nine elements is   3 5 6 9   I have no idea how to compute the numbers of orbits for a group action. Anyone please help me. Thanks.


I have a simple cosine wave: $y=\cos(\pi x/2)$. This equation passes through the points $(0,1), (1,0), (3,0)$ and so on (the black line in the picture). I want to keep these points, but "inflate" the graph more to look like the green graph in the illustration.  How would I go about doing this? EDIT: I have tried using roots of 2 through 3 (including square roots, cube roots, and even the  2.3rd root). However, it appears that none of them seem to line up with the green equation (made up of portions of circles. Is there any way to have a "perfectly circular" cosine equation (in terms of radius of the circle for general use) like the green graph? If so, what method or root should I use to achieve this? To clarify: I am looking for the equation of an "inflated" graph, and the equation of a graph that has been "inflated" to its fullest while still being a function (a "perfectly round" cosine equation).

A perfect arc is $y=\sqrt{|1-(x-1)^2|}$. A sin wave is $y=\sin({\pi x\over2})$  I am curious how I can amplify the sin wave so that it's a perfect alternating arc.  In the link below you can see graphed each of these two equations, as well as the delta between them.  So in the sage code there's function $i(x) = $SOMETHING $\times f(x)$, where $f(x) = \sin({\pi x\over 2})$, but I want to replace the 'SOMETHING' with an expression that transforms the wave to  $$y=\sqrt{|1-(x-1)^2|}+\sqrt{|1-(x-3)^2|}+\sqrt{|1-(x-5)^2|}... + \sqrt{|1-(x-n)^2|}$$     In other words, I want $g(x):g(x)\sin({\pi x\over 2}) = \sqrt{|(1-(x-1)^2|}$ where $0<x<2$   I have no particular goal, I am just curious how I would go about solving that as currently I'm a bit stumped...    thank you kind internet maths wizards!


Problem:  Getting the error message Undefined control sequence. (\end{document}..). This occurs when I include the following code that prints out formatted programming code. If I remove this code the issue goes away.  Minimal Working Example (MWE):  \documentclass{studentlitteratur}  \usepackage{lipsum}  \usepackage{listings}  \mdfdefinestyle{mdlistingstyle}{}  \mdtheorem[style=mdlistingstyle]{sourcecode}[chapter]{Kodexempel}  \begin{document}  \part{Title}  \begin{sourcecode}  \end{sourcecode}  \lipsum[1-3]  \begin{sourcecode}  \end{sourcecode}  \end{document}   .cls content available here:   .sty content available here:   Error message:  ./studentlitteratur.tex:13: Undefined control sequence. <argument> \protect \bbl@restore@actives delz                                          i\protect \hspace  {0.5em} title l.13 \end{document}   Desired outcome:  To remove the error message and achieve correct code.

Consider the following MWE:  \documentclass{scrreprt}  \usepackage{textcase}  \RequirePackage{listings} \usepackage[american]{babel}  \begin{document}     \MakeTextLowercase{A~B} \end{document}   LaTeX fails with the error  ! Undefined control sequence. <to be read again> az                      b l.9     \MakeTextLowercase{A~B}  ?    The error seems to lie in the combination of MakeTextLowercase, the listings package and the tilde. Whenever I remove any of these three components, everything works fine. Does anyone have a clue where the problem is?


Let $P_1 P_2 \dotsb P_{18}$ be a regular 18-gon. Show that $P_1 P_{10}$, $P_2 P_{13}$, and $P_3 P_{15}$ are concurrent.    When positioned on the unit circle, I know that $P_1 P_{10}$ is the diameter.  I also know that if $p$ and $q$ are points on the unit circle such that the line through $p$ and $q$ intersects the real axis and if $z$ is the point where this line intersects the real axis, then $z = \dfrac{p+q}{pq+1}$.  So I should let $P_1 P_{10} be on the real axis.  Where should I go from now?  Thanks.

Let $X_1 X_2 \dotsb X_{18}$ be a regular 18-gon. Show that $X_1 X_{10}$, $X_2 X_{13}$, and $X_3 X_{15}$ are concurrent.   What would be the best way to prove this? I am actually struggling understanding 'concurrent' as I am not sure how they are concurrent in a regular 18-gon


I like to relay on my own forged armor and custom enchants it giving it a more personal touch since i spent all that cash/time buying/collecting the items needed to make the armor  I got Deadric and Dragonbone smithing perks and looking at the initial stats of the armors Deadric has a greater value despite that Dragonbone needed a Blacksmithing skill of 100 to unlock the perk.  My Flawless Platemail has been beating initial Orcish armor for a while so knowing that i can further improve Dragonbone and Deadric Armor, with a Blacksmithing skill of 100, no potions to boost and being able to improve armor/weapons right after i forge them, i am wondering which armor/weapon set is more powerful to forge, Deadric and Dragonbone  NOTE 1: i use a one-handed sword (ie. Blades katana) so for comparison between Deadric and Dragonbone sets only compare one-handed swords, not maces or axes   NOTE 2: the enchantments on my armor don't boost resistances to attacks (they mainly boost Mana regeneration and Carry Weight) and my sword always has a 1 second Soul Trap so answers should avoid possible increases to attack/armor rating done via enchantments  NOTE 3: an answer doesn't need to be all Deadric/Dragonbone or even include them (as i am just going by the last 2 perks in the Blackmithing Skill), it just need to include Armour i can make in any forge and further improve at the armor bench/grind stone

There seems to be 3 general categories of gear in Skyrim: Heavy Armor, Light Armor, and Clothing. These seem to (roughly) correspond with the three class archetypes of warrior, thief, and mage.  In Elder Scrolls games, finishing quests to get rare artifacts is generally a good way to get uber-powerful equipment. Another very effective way is to enchant armor and weapons yourself, and as a bonus you generally don't need to leave town for more than a few materials. In Skyrim, crafting your own now seems to be a very viable option.  What is the most powerful (by AR or damage) user-crafted gear, and how would one obtain it? I assume crafting skill bonuses would be required for smithing and enchanting; how would you attain these bonuses?


I am going to be away from my rMBP for 2 weeks, I powered it off and left it with around 56% of battery charge, anything I should do differently / didn't do? in order to keep the battery in a good condition without causing damage (losing capacity or getting it in too deep discharge state).

Will my MacBook's battery be damaged if I do not use for next couple of months?  I bought a new Macbook Pro (March 2015) a month back. So far I have not started using it yet. It's charged and box packed as I do not currently have time to set it up for my development work.  Update: It's charged 90%+ but not being used.


In the virtual particles FAQ here , under "How can they be responsible for attractive forces?" I didn't follow this step:  "If the wave packet is small enough in position space, a Coulomb potential and a sinusoidal one are both effectively a constant-force potential, so I can do this.  Neglecting all magnetic effects and taking the nonrelativistic limit, the amplitude for transfer of a given momentum by a single virtual photon […] has to have an imaginary part odd in p_x because the potential is real,…"  How is this oddness derived? Or, what do I need to know/study to derive this? Added: More precisely, I would like to understand first of all, what is the right equation to write down from QM theory, and what are the modifications (neglecting magnetic effects, taking limit, etc.) we should make for this simplified model? And secondly, if it's not already clear, how do I get from there, to an approximation by an odd function (whose sign depends on parity) such as is necessary to follow the rest of the thought experiment in the FAQ? (My real goal here isn't to pick apart this FAQ, but to understand how attractive force comes from QM first principles, I'm just not knowledgeable enough to fill in the gaps of the FAQ. If there is another more detailed treatment of this topic to recommend that would also be helpful.)

How can two particles be drawn together by exchanging other (force carrier) particles. Both reactive components of exchange and absorption logically seem to support repulsion. How are these particle exchanges responsible for attraction of the exchanging parent particles? Unable to find an online answer after considerable effort. Help


im using this: system("netsh wlan show profiles");  That command output the profiles on interface WLAN on the console and what i want to know is if there's a way to copy a user profile name from the console into a varibale.

I am looking for a way to get the output of a command when it is run from within a C++ program.  I have looked at using the system() function, but that will just execute a command. Here's an example of what I'm looking for:  std::string result = system("./some_command");   I need to run an arbitrary command and get its output. I've looked at , but I have not found anything that will give me what I need.


I can't find this integral around here,  does anybody suggest how to calculate this integral?  $$ I = \int x^x dx. $$  Thanks in advance

I'm trying to find $\int x^x \, dx$, but the only thing I know how to do is this:  Let $u=x^x$.  $$\begin{align} \int x^x \, dx&=\int u \, du\\[6pt] &=\frac{u^2}{2}\\[6pt] &=\dfrac{\left(x^x\right)^2}{2}\\[6pt] &=\frac{x^{2x}}{2} \end{align}$$  But it's certain that this isn't the correct way to evaluate that, and the answer must be wrong.


How to read the coordinate system of an input feature class in python script. How we can use "Describe()" function and tool validator for that purpose

I developed one tool  in arcgis using python code, in the process i used Describe(feature class) function to know the coordinate system of input feature class. I got success while compiling code, But i couldn't get how to set parameters for this function in tool(arcgis 10.0) designing.  I tried parameters as follow  Display  name:input feature class Data type : coordinate system. Type   : optional Direction : input.   My problem is  while i'm selecting input feature class, i didn't get coordinate system of that feature class.  Please Suggest..


Say we have $f(x+y) = f(x) + f(y) \quad \forall x,y \in \mathbb R$ and $f$ is continuous at one point at least. I wish to show there must be some $c$ such that $f(x)=cx$ for all $x$. Think I can do so by first showing $f$ is continuous everywhere I'm not sure how then let $f(q) = 1$ somehow and show that $f(q)  = cq$ where $q$ is rational. But then the aim is to show for all real $x$ so I am not sure~

Suppose that $f$ is continuous at $x_0$ and $f$ satisfies $f(x)+f(y)=f(x+y)$. Then how can we prove that $f$ is continuous at $x$ for all $x$? I seems to have problem doing anything with it. Thanks in advance.


If $f'(x)$ is decreasing, is it always true that $f''(x)$ is also decreasing?  I want to make sure I understand this concept thoroughly.  Thanks.

If a function is differentiable and monotone on the interval $(a, b)$, then its derivative is also monotone on $(a, b)$.   How do you prove this statement is wrong?   Can you please provide an example?


I'm trying to verify the correctness the following sentence:     Game time is Sunday.   Is it correct or should it be "game-time"?

Some compound words are written without hyphens (nonaggression, nonbeliever), some with hyphens (well-intentioned), and others with spaces (post office).  Is there a rule or good guide as to which option should be used?


What will happen to the Ubuntu in this situation?  The Windows is Windows 7.  Thank you.

For some reason I can't install Ubuntu from CD or USB, so that I had to installed Ubuntu via Wubi. But I install Ubuntu into partition 'D' and partition of Win 7 is 'C'. If I re-install win 7, how can I use pre-installed Ubuntu ?


I have an array out of bound exception with the following program. The problem comes from the fact that my first if statement (expression == "") doesn't catch the case where my expression is empty. Why is it not catched and how can I properly write this condition?    public static boolean isWellFormed(String expression, int braces, int brackets, int parentheses){     if (expression == ""){       if (braces == 0 && brackets == 0 && parentheses == 0){         return true;       }       else{         return false;       }     }     System.out.println("expression " + expression + " " + expression.length());     char firstChar = expression.charAt(0);     if (firstChar == '['){       return isWellFormed(expression.substring(1),braces, brackets+1, parentheses);     }     else if(firstChar == '{'){       return isWellFormed(expression.substring(1),braces+1, brackets, parentheses);           }     else if(firstChar == '('){       return isWellFormed(expression.substring(1),braces, brackets, parentheses+1);     }     else if(firstChar == ']'){       return isWellFormed(expression.substring(1),braces, brackets-1, parentheses);     }     else if(firstChar == '}'){       return isWellFormed(expression.substring(1),braces-1, brackets, parentheses);     }     else if(firstChar == ')'){       return isWellFormed(expression.substring(1),braces, brackets, parentheses-1);     }       else{       return isWellFormed(expression.substring(1),braces, brackets, parentheses);     }   }

I've been using the == operator in my program to compare all my strings so far. However, I ran into a bug, changed one of them into .equals() instead, and it fixed the bug.  Is == bad? When should it and should it not be used? What's the difference?


Let $A$ and $B$ be sets.  Is there a set $C$ such that $|B|=|C|$ and $A\cap C=\emptyset$?

I was recently thinking about the fact (in ZFC) that, given a (first-order) structure $A$ that embeds into another structure $B$, there is some structure $C$ isomorphic to $B$ such that the domain of $A$ is a subset of the domain of $C$. This is trivial if we can prove the following:     Given any injection from $S$ into $T$, there is some set $U$ disjoint from $S$ that bijects with $T$.   I can prove this within either ZC (using AC) or ZF (using Foundation). My ZC proof uses transfinite induction to pick $U$ out from $(P(T)×2)∖S$. My ZF proof constructs $U = \{ \{S,x\} : x∈T \}$. But I don't see a way to prove it within just Z. In one attempt, I tried to use one of $k$ disjoint copies of $T$ where $k$ is a well-ordered set that does not inject into $S$, but if every copy intersects $S$ then I seem to need a choice function on $S$ to obtain a contradiction. At least this means that I can prove it for countable $S$, but what about uncountable $S$?  I may be missing something easy, because intuitively it cannot be possible that every set that bijects with $T$ has a non-empty intersection with $S$, even in the absence of choice...


I have a site which will print the whole page in chrome browser.  function do_print(){       window.print();   }

I want to remove the URL that gets printed on the bottom of the page.   like:  yomari.com/.../main.php?sen_n   How can it be omitted or prevent from getting printed?  To be more specific, is there any way I can prevent the page URL, date and the page title being printed along, while printing the web page?


Is there a way that I could reference the same path from one command to the next? For example, I may want to list the contents of a specific folder:  $ ls ~/Documents/some/dir  Then, once I've done that, I may want to perform some action in that same directory:  $ mv ~/Documents/some/dir/file.txt ~/Documents/other/dir  Is there a way to, essentially, invoke that path without typing it again (or using some sort of auto-suggestion or auto-fill that I can do with .zsh)?   I vaguely remember reading about something along these lines but I don't remember what the technique is?

This is a situation I often find myself in:  mkdir /Some/really/long/path/to/a/directory/ cd /Some/really/long/path/to/a/directory/   I know that ideally you would cd /Some/...etc.../a/ and then mkdir directory, but I've often performed mkdir first and then had to cd to the end of the same lengthy file path I just created.  Short of doing...  var="/Some/...etc.../a/" mkdir $var/directory; cd $var   ...which is even worse, is there some way to reuse the parameter passed to the previous command? I'm aware of course of tab completion, but in a series of nested directories with similar names this doesn't always help that much. Ideally, I'm hoping for a shortcut like $# or $@.  Failing this, the next best time-saving solution would be equally appreciated!


Vandermonde matrix is widely used in many fields, e.g. Fast Fourier Transform.  Does this matrix always have inverse matrix?

A Vandermonde-matrix is a matrix of this form:  $$\begin{pmatrix}  x_0^0 & \cdots & x_0^n \\ \vdots & \ddots & \vdots \\  x_n^0 & \cdots & x_n^n \end{pmatrix} \in \mathbb{R}^{(n+1) \times (n+1)}$$.  condition ☀ : $\forall i, j\in \{0, \dots, n\}: i\neq j \Rightarrow x_i \neq x_j$  Why are Vandermonde-matrices with ☀ always invertible?  I have tried to find a short argument for that. I know some ways to show that in principle:   rank is equal to dimension all lines / rows are linear independence determinant is not zero find inverse   According to , the determinant is  $$\displaystyle V_n = \prod_{1 \le i < j \le n} \left({x_j - x_i}\right)$$  There are two proofs for this determinant, but I've wondered if there is a simpler way to show that such matrices are invertible.


For rounding to the nearest 0.05, I am just dividing it by 0.05 and then multiply by 0.05. As described in other similar questions.  In [119]: (127.651//0.05)*0.05 Out[119]: 127.65  In [120]: (127.6501//0.05)*0.05 Out[120]: 127.65  In [121]: (127.65000001//0.05)*0.05 Out[121]: 127.65  In [122]: (127.65000000001//0.05)*0.05 Out[122]: 127.65  In [123]: (127.6500000000001//0.05)*0.05 Out[123]: 127.65   Till here its doing as expected. However for this special case:  In [124]: (127.650000000000000001//0.05)*0.05 Out[124]: 127.60000000000001   I would have expected 127.65 here.  Tried rounding off before dividing, but again.. strange. Not only i am getting unexpected result(expecting 127.65), but also it is giving results that is beyond 2 decimal places, which will result into failure in my further processing functions.  In [125]: (round(127.650000000000000001,5)//0.05)*0.05 Out[125]: 127.60000000000001   If i execute just the inner round,  o/p is 127.65...   In [126]: round(127.650000000000000001,5) Out[126]: 127.65   But on adding the divide and multiply logic.. the result becomes unexpected.  In [125]: (round(127.650000000000000001,5)//0.05)*0.05 Out[125]: 127.60000000000001   Should there be any datatype issue? or internal precision limitations of python?  how do i overcome it in an elegant way?  PS:   1) I am using python 2.7  2) I am eventually using it in a function. Which is giving unexpected results for this special case. I cannot control the input data quality and its data precision, as it is coming from reading a csv file to dataframe.  def RP(price):# Round down to the nearest price quotable ...i.e. multiple of 0.05         return(round(price//0.05*0.05,2))

Consider the following code:   0.1 + 0.2 == 0.3  ->  false   0.1 + 0.2         ->  0.30000000000000004   Why do these inaccuracies happen?


i tried a lot of solutions but none seems work. For example this  two links:   The second link  suggest this solution: sudo add-apt-repository ppa:thopiekar/mt7601 The answer is:     Source code: (c) Copyright 2002-2013, MediaTek Inc. (released under GPLv2) GitHub: https://github.com/porjo/mt7601 Patches: @poma at linux-wireless mailing list  More info: https://launchpad.net/~thopiekar/+archive/ubuntu/mt7601 Press [ENTER] to continue or Ctrl-c to cancel adding it.  Ignorato:1 http://ppa.launchpad.net/thopiekar/mt7601/ubuntu focal InRelease Trovato:2 http://archive.ubuntu.com/ubuntu focal InRelease                      Errore:3 http://ppa.launchpad.net/thopiekar/mt7601/ubuntu focal Release           404  Not Found [IP: 91.189.95.83 80] Trovato:4 http://archive.canonical.com/ubuntu focal InRelease                   Lettura elenco dei pacchetti... Fatto E: Il repository "http://ppa.launchpad.net/thopiekar/mt7601/ubuntu focal Release" non ha un file Release. N: L'aggiornamento da tale repository non può essere eseguito in modo sicuro ed è quindi disabilitato come impostazione predefinita. N: Consultare la pagina man apt-secure(8) per la creazione di un repository e la configurazione utente.  At the end is written that the repository is note sicure and i have to go to the page "man apt-get secure" to make a repository and the id configuration Can someone help me? Thanks

When updating, I get the following error message:   W: The repository 'http://ppa.launchpad.net/mc3man/trusty-media/ubuntu xenial Release' does not have a Release file.   Here, I find another statement on this error:   This recommends removing certain PPAs; and, I'm not sure if I should do that since it might mean not getting the updates that I need.    Is this what I should do?


is it OK for the battery if you keep using the tablet while it's charging? And should you stop charging when it's fully charged.

I understand using phone while it is being charged by a normal charger is not advised. What about using phone while it is being charged by a portable charger (powerbank)?  I own a HTC one and i was told by a mobile technician HTC’s own portable charger only should be used for HTC one. How much truth is there to it as HTC powerbank is not available in my city and i am thinking of using Sony portable charger for charging my HTC One?


Recommendations are a recurring topic on multiple Stack Exchange (SE) sites. Some sites allow recommendations (ex: ), some do not (ex: ). There are many reasons for that and I can still remember animated discussions on this subject on the Gaming meta. Then there is that existential problem with Sci-Fi SE, "What problems does answering a question on this site solve?"  The only common problem I can think of is What to read/watch next?, which obviously led to a big number of recommendation questions, later slightly disguised as list question. And the main trouble with these questions isn't objectivity at all, some of them aren't even subjective. It's the fact that they don't have an answer - they are open ended. -  Those questions are monstrously popular because:  There's an actual problem to be solved,  or  This problem is quite common.  In view of the  blog post, a recommendation question fails the "real questions have answers, not items or ideas or opinions." criteria. But it's still a "practical, answerable questions based on actual problems that you face. " and it requires expertise to answer. The problem is that there are multiple acceptable answers, and the asker is not the best person to evaluate the best answer because he doesn't know which one is the best compared to the others, and he cannot test it in short term. Even the need to accept an answer is questionable. So, is a recommendation question an acceptable kind of list-type question or should it be closed just like any other list-type questions?

Stuff like polls, recommendations based on subjective constraints, puzzles, webcomics etc. do not belong on the serious main SE sites, where professionals should be considered at work and having just a few spare minutes ("code's compiling") to answer questions, so they should not be distracted by such things. However, I'd also like to have a home for these things still using the SE engine. For the reason I mentioned before, this needs to be a separate place though. Let's call it four.[sitename-here].com.


I installed easybcd app to change grub bootloader but accidentally deleted windows boot entry , now in the grub option ubuntu and windows boot manager appears. When i try to boot windows by Windows boot manager option it says to repair the pc. Can i fix it without repairing?

I installed Windows on my computer, followed by an installation of Ubuntu. However, now I'm unable to boot into my Windows install.  What can I do to fix this?


Similar to how in python you can do 'if letter in string:', I'm trying to imitate this in bash. The code is below:   SYMBOLS="ABC" msg="alskdfjAasdksdfh!?asdflkjhghrg"  # Loops through each letter in the variable msg individually for (( i=0; i<${#real_message}; i++ )); do     # Assigns the current letter to the variable     letter="${msg:$i:1}"      # This is the part I have a question about     if [[ $msg == *"$SYMBOLS"* ]]; then         echo "Found."     fi done   However, the if statement doesn't work.  What's supposed to happen is anytime it grabs a character to be stored in the variable 'letter', it should check if that character exists in the variable 'SYMBOLS'.    For example, msg has the character 'A' in it, so when 'letter' iterates through and gets to 'A', it should echo "Found." indicating the if statement works.  However, this doesn't work obviously because I'm not understanding something correctly.  Just for clarification: it isn't looking for substrings containing "ABC", it's looking for either "A", "B", or "C" when it's stored in the 'msg' variable.

I have a string in Bash: string="My string"  How can I test if it contains another string? if [ $string ?? 'foo' ]; then   echo "It's there!" fi  Where ?? is my unknown operator. Do I use echo and grep? if echo "$string" | grep 'foo'; then   echo "It's there!" fi  That looks a bit clumsy.


Is there a difference between doing  if(something === undefined) {     //handle }   and  if(typeof(something) === "undefined") {     //handle }   please? Which is better to use and why? Are there any risks involved?

What's the best way of checking if an object property in JavaScript is undefined?


I want to convert an number (integer) to a hex string  2 (0x02) to "\x02"   or  62 (0x0062) to "\x62"   How can I do that correctly?

How do you convert decimal values to their hexadecimal equivalent in JavaScript?


Because I am quite new to programming and I am discovering Bootstrap right now, I am doing an exercise with containers and rows and col-XX etc., to know how what are their CSS properties.  Therefore, I am looking for getting the CSS values that devs put in the CSS files with Javascript. Not jQuery, but vanilla JS. Not the CSS values computed, but the CSS values written. Like the one we have in the console. I want to get them in order to put them back in a the HTML this way :
margin-right: 5%
, for example.  So a lot of people are talking about window.getComputed(element).getPropertyValue("property"), but I am not interested. I heard somewhere cssText, but I am not sure that it's the good one.  Is there a solution ? Is there actually a place somewhere where all the property-values-written of a selector are stored, in parallel to the property-values-computed ?  Thanks Arnaud  PS: I know the subject is already open  but it opened 7 years ago, and the only self-answer is not satisfying I think...

I would like to return a string with all of the contents of a CSS rule, like the format you'd see in an inline style. I'd like to be able to do this without knowing what is contained in a particular rule, so I can't just pull them out by style name (like .style.width etc.)   The CSS:  .test {     width:80px;     height:50px;     background-color:#808080; }   The code so far:  function getStyle(className) {     var classes = document.styleSheets[0].rules || document.styleSheets[0].cssRules     for(var x=0;x<classes.length;x++) {         if(classes[x].selectorText==className) {             //this is where I can collect the style information, but how?         }     } } getStyle('.test')


I have got a Single Player World that I want my friend to play with me on. However we aren't in the same LAN, how do we play together?

I've had this problem a lot lately because me and my friend would like to play a map together, but the thing is we can't use LAN. She lives in California and I live 700 miles away, so we are definitely not connected to the same wifi. If you could please answer this it would be a lot of help to me because I have been searching this for a while and nothing that works have come up so far. Thanks


I made more than 10 robots. all of them had not less than 4 materials, and some had 12 materials. I can't go back and fix this. How this will effect on the game performance later ?

I have learned that a Mesh with 4 Materials each 1024x1024 in Size is somewhat slower than a Mesh with 1 Material 2048x2048 in Size? In my usual workflow I tend to seperate different Materials into different Materials so an Object tends to have around 2-8 Materials. I have created more than a hundred Assets like this.  Is the performance dramatically affected by this? Is it acceptable to upload such Objects to sites like turbosquid or sell them on Unity Asset Store or will the buyer behead me after noticing?    Window Textures need to be transparent, Metal / Wood / Concrete need different smoothness settings. As far as I know Unity doesn't support Gloss maps.


Possible Duplicate:          I am wanting to generate a random string of 20 characters without using apache classes. I don't really care about whether is alphanumeric or not. Also, I am going to convert it to an array of bytes later FYI.  Thanks,

I've been looking for a simple Java algorithm to generate a pseudo-random alpha-numeric string.  In my situation it would be used as a unique session/key identifier that would "likely" be unique over 500K+ generation (my needs don't really require anything much more sophisticated).    Ideally, I would be able to specify a length depending on my uniqueness needs. For example, a generated string of length 12 might look something like "AEYGF7K0DM1X".


I was trying to edit my sources.list in order to add local mirror information. I am not comfortable with command line editors, so I tried using sudo mousepad /etc/apt/sources.list.  I got the following error report.  No protocol specified  (mousepad:4942): Mousepad-ERROR **: Cannot open display:    I tried several other editors such as gedit, kwrite etc. but I get similar error reports.  No protocol specified  ** (gedit:4957): WARNING **: Could not open X display No protocol specified Unable to init server: Could not connect: Connection refused  (gedit:4957): Gtk-WARNING **: cannot open display: :0   I am on a local 64 bit system running Debian Jessie.

System: .    Objective: To define  aliases to launch various  and  text editors while opening a file in  mode from  emulator.    Progress  For example, the following aliases seem to work as expected:  For , in this example I used Nano ():  alias sunano='sudo nano'   For , in this example I used Xed ():  alias suxed='sudo xed'   They both open a file as .    Problem  I have an issue with  in conjunction with :  alias susubl='gksudo /opt/sublime_text/sublime_text'   Sometimes it works. It just does not do anything most of the time.  How do I debug such a thing with inconsistent behavior? It does not output anything. No error message or similar.    Question  gksudo has been deprecated in Debian and also no longer included in Ubuntu 18.04 Bionic, so let me re-formulate this question to a still valid one:  How to properly edit system files (as root) in GUI (and CLI) in Linux?  Properly in this context I define as safely in case, for instance, a power loss occurs during the file edit, another example could be lost SSH connection, etc.


I'm trying to write a script to append an Object or a Collection from a blend file to a new file. Can someone please point what I'm doing wrong?  import bpy  filepath  = "/home/lucas/Desktop/Auto_Eye/02_versions/auto_eye_v03.blend" directory = "\\Object\\" filename  = "auto_eye_v03"  bpy.ops.wm.append(filepath=filepath, directory=directory, filename=filename)   This code gives me this error:   Error: '\Object\auto_eye_v03': not a library Traceback (most recent call last):   File "/Text", line 7, in <module>   File "/home/lucas/Programs/blender-2.80/2.80/scripts/modules/bpy/ops.py", line 201, in __call__     ret = op_call(self.idname_py(), None, kw) RuntimeError: Error: '\Object\auto_eye_v03': not a library  Error: Python script failed, check the message in the system console     And the other method that I've found .  import bpy scn = bpy.context.scene filepath = "/home/lucas/Desktop/Auto_Eye/02_versions/auto_eye_v03.blend"  #append object from .blend file with bpy.data.libraries.load(filepath) as (data_from, data_to):     data_to.objects = data_from.objects  #link object to current scene for obj in data_to.objects:     if obj is not None:         scn.objects.link(obj)   And this code is given me this error.  Traceback (most recent call last):   File "/Text.001", line 6, in <module> OSError: load: /home/lucas/Desktop/Auto_Eye/02_versions/auto_eye_v03.blend failed to open blend file  Error: Python script failed, check the message in the system console     I run this two commands on the Blender Console.  >>> bpy.data.libraries <bpy_collection[0], BlendDataLibraries>  >>> bpy.data.objects <bpy_collection[5], BlendDataObjects>   So I didn't have anything on the libraries of the file, but I can't find a way do add then to the libraries.  In the "bpy.data.objects" it lists the objects that I have on the scene, so I need to learn how to append the objects from there.

I'm searching a way to append a group in Python.  It should behave exactly like the Append function (ShiftF1) works, all objects should be local and editable. The idea is to append a character (with rig etc.) via Python and not Link it (to be able to modify it without making everything local one by one).  Thanks


I see a lot of solutions to validate a phone number by Regex... But I want some characters in my phone number such as +31(0)12 for example.  If you have string with the value +31(0)12-1234567. This is a correct notation of a phone number. How could you validate by using Regex?   I have tried this:   Regex phonePattern = new Regex(@"\+\d{3}?(\0)\d*\-\d*");    What do I wrong?   Other examples are: +31(0)6-12345678 or +31(0)123-123456

I'm trying to put together a comprehensive regex to validate phone numbers. Ideally it would handle international formats, but it must handle US formats, including the following:   1-234-567-8901 1-234-567-8901 x1234 1-234-567-8901 ext1234 1 (234) 567-8901 1.234.567.8901 1/234/567/8901 12345678901   I'll answer with my current attempt, but I'm hoping somebody has something better and/or more elegant.


Prove that $\cot^220^\circ + \cot^240^\circ + \cot^280^\circ = 9$.   I tried bringing them all to $\cot^220^\circ$ but it didn't work. How do I proceed?

Evaluate $\tan^{2}(20^{\circ}) + \tan^{2}(40^{\circ}) + \tan^{2}(80^{\circ})$.  Can anyone help me with this? Thank You!


I did study the whole idea of functors, unfortunately I can't understand the real advantage of functors over typical functions.   According to some academic scripts, functors can hold state unlike functions.  Can anyone elaborate on this one with some simple, easy to understand example ?   I really can't understand why typical, regular function are not able to do the same. I'm really sorry for this kind of novice question.

I keep hearing a lot about functors in C++. Can someone give me an overview as to what they are and in what cases they would be useful?


In this  they said that a vulnerability has been discovered in samba.  In this same article, they said that the maintainer of samba had already patched the vulnerability in the versions 4.6.4/4.5.10/4.4.14. And they also said in the article that Ubuntu and Redhat has already released patched versions.  The problem is : the samba version that is installed on my Ubuntu 17.04 is 4.5.8 (I used the command samba --version to get this information).   So did Ubuntu release a patched version of samba ? and if yes, how does it come that I have the version 4.5.8 and not the 4.5.10 which is patched.  PS : I updated my computer today with sudo apt update && sudo apt upgrade.

I read these two threads:         And I got a little bit worried, is my Ubuntu machine safe? Or am I vulnerable to this vulnerability?  The second article mentioned that:     The flaw actually resided in the way Samba handled shared libraries.   The other thing that they say is all versions from versions 3.5.0 onwards since 2010 are vulnerable.     At that time, nearly 485,000 Samba-enabled computers were found to be exposed on the Internet, and researchers predicted that the SambaCry-based attacks also have potential to spread just like WannaCry ransomware widely.   .   I don't have a samba server however I've got samba-libs package installed.  What, if anything, should I do?  I'm running Ubuntu 16.04.


I have read in Griffith's Introduction to Electrodynamics that Maxwell's correction on Ampère's original law, $\nabla \times \mathbf{B}=\mu_{0}\mathbf{J}$, fixes the problem that arises from applying $\nabla ·$ to the equation:  $$0=\nabla \cdot(\nabla \times \mathbf{B})=\mu_{0}(\nabla \cdot \mathbf{J})$$  The RHS is not necessarily zero, as it happens in the cases of non-steady currents. So, using the principle of conservation of charge and Gauss's law, it can be found that adding the extra term $\epsilon_0\mu_0\frac{\partial\mathbf{E}}{\partial t}$ overcomes the problem.  However, Griffith says that Maxwell's reasons had not to do with the principle of conservation of charge but with the concept of "ether".   Which were these reasons he followed in order to make the correction?

What was the improvement that Maxwell did to the  and why?  I understand that he combined the main equations so that you could get a wave equation for the vectors of $\bf E$ and $\bf B$ but is there anything else?


I am trying to train a simple neural network for regression, where the underlying function is a quadratic. Training data is generated by this underlying function, and I am just trying to get a network to learn this function.  This underlying function is $y = (x - 0.5)^2$, and I have generated 100 samples with $x$ from 0.0 to 1.0. Then, I train the network to take $x$ as input, and regress to the corresponding $y$. Training is done in batches, until the training loss converges.  However, my network cannot learn this function, even though it is very simple. These graphs show what is going on:    The top graph is the training data (one circle per datum), showing the underlying quadratic function. The second graph is the final network's predictions with the same inputs as the training data (i.e. 100 samples with $x$ from 0.0 to 1.0). The third graph overlays these two, and the fourth graph shows the training loss over time.  It is clear that the network is not learning the underlying function, and seems to be fitting a linear function to the best of its ability. However, my network has two hidden layers, with non-linear ReLU activations, and so should certainly be able to learn a quadratic function.  Here is the code for setting up and training the network:  # Create the neural  network model = Sequential() model.add(Dense(16, input_shape=(1,))) model.add(Activation('relu')) model.add(Dense(16, input_shape=(1,))) model.add(Activation('relu')) model.add(Dense(1)) sgd = SGD(lr=0.001) model.compile(loss='mean_squared_error', optimizer=sgd)  # Create the training data inputs = np.zeros((100, 1), dtype=np.float32) targets = np.zeros((100, 1), dtype=np.float32) for i in range(100):     inputs[i] = 0.01 * i     targets[i, 0] = np.power((inputs[i] - 0.5), 2)  # Training loop while True:     # Perform one weight update     loss = model.train_on_batch(inputs, targets)

I'm training a neural network but the training loss doesn't decrease. How can I fix this?  I'm not asking about overfitting or regularization. I'm asking about how to solve the problem where my network's performance doesn't improve on the training set.    This question is intentionally general so that other questions about how to train a neural network can be closed as a duplicate of this one, with the attitude that "if you give a man a fish you feed him for a day, but if you teach a man to fish, you can feed him for the rest of his life." See this Meta thread for a discussion:   If your neural network does not generalize well, see:


Prove That  $\lim_{n\to\infty}\left(\sum_{k=1}^{n}\frac{1}{2k-1}-\sum_{k=1}^{n}\frac{1}{2k}\right).$   My Approach I was solving:  $$\sum_{n=1}^{\infty}\frac{\left(-1\right)^{n-1}}{n}= \left(1+\frac 1 3 + \frac 1 5 +\ldots \right)-\left(\frac 1 2 + \frac 1 4 +\ldots  \right)  =\sum_{n=1}^{\infty}\frac{1}{2n-1}- \sum_{n=1}^{\infty}\frac{1}{2n}$$ Searching On Mathstack i found   I know that $ \sum_{n=1}^{\infty}\frac{\left(-1\right)^{n-1}}{n}$ = $\ln2$ But i don't know how to prove it using this method.

What are the argument(s) that I can use proving that   $$1+\frac{1}{3}+\frac{1}{5}+\frac{1}{7}+\cdots-(\frac{1}{2}+\frac{1}{4}+\frac{1}{6}+\cdots)$$  does not exist.    The question was:  Find a arrangement of $\sum\frac{(-1)^{n-1}}{n}$ for which the new sum is not exist(even not $+\infty$ or $-\infty$)


Respected All  I was trying to prove that  $$\sum_{n\geq 0}(-1)^{n} \frac{1}{2n+1}=\frac{\pi}{4}$$ What I tried to show like this.  We know  $$\frac{1}{1+x^2}=(1+x^2)^{-1}=\sum_{n\geq 0}(-1)^nx^{2n}, |x^2|<1$$ Integrating term by term with in interval of convergence we get  $$\int_0^{x_0}\frac{dx}{1+x^2}=\sum_{n\geq 0}(-1)^n\frac{x_0^{2n+1}}{2n+1}$$ Taking $x_0=1$ we have  $$[\arctan(x)]_0^1=\sum_{n\geq 0}(-1)^n \frac{1}{2n+1}$$ i.e. $$\frac{\pi}{4}=\sum_{n\geq 0}(-1)^n \frac{1}{2n+1}$$  Am I right?

Why is $\arctan(x)=x-x^3/3+x^5/5-x^7/7+\dots$?  Can someone point me to a proof, or explain if it's a simple answer?  What I'm looking for is the point where it becomes understood that trigonometric functions and pi can be expressed as series.  A lot of the information I find when looking for that seems to point back to arctan.


I need to make use of an array of unsigned bytes. I need to send certain characters over the network to a server and some of these characters are greater that 127.   I have a simplified version of the code below to try and understand the concept:  int i= 160; byte j = (byte) i; System.out.println((byte)i); System.out.println(j);   and this gives an output of: -96 -96  I need to print 160. As the server is expecting a byte of 160 and if it receives -96 it does not accept the value. The reason I used an int is that when I was reading how to get around the problem, I often came across the suggestion to just use an int, but I don't quite understand that, as I need my array to be of type byte.  This is the part of my code where I send the array:  public boolean send(byte[] data) {     try {      out.write(data); // Write the data to the outStream      out.flush();     } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); return false; // Return false if the TCP Transmit failed  // } return false; }   I would really appreciate it if some one could help me.

In Java, there is no such thing as an unsigned byte.  Working with some low level code, occasionally you need to work with bytes that have unsigned values greater than 128, which causes Java to interpret them as a negative number due to the MSB being used for sign.  What's a good way to work around this? (Saying don't use Java is not an option)


How can I create some ambient particles in Cycles, as showed in the following images:     If I need to use the particle system, please be very specific, because I don't know how to use it.  Thanks!

Quite impressed by all of Gleb Alexandrov's scenes with some amazing dust floating around.   (To see what I'm talking about > )  And I started working last night on a scene that is going to need the same sort of atmospheric dust in the air. But when I looked around on how to create dust particles in the air there was nothing there. Not even anything I could adapt from a tutorial. Everything was from 2009 before volumetrics was even introduced.  Someone in an older tutorial did use a particle system and used a scaled down icosphere as a mesh for each particle, but experimenting with that made everything look really tacky.  Is there a way to do dust particles that I'm not thinking of?


I'm try install and configure Mod_Security on Amazon EC2 Linux 64 bits, but one error happens  Syntax error on line 23 of /etc/httpd/conf.d/modsecurity.conf: ModSecurity: Found another rule with the same id  Need help to solve this, I tried to find in many search engines, but found nothing.  Can someone help me?

I have installed httpd 2.2.15 on CentOS 6.5 (minimal installation with no cPanel) with modsecurity 2.8. When I am starting httpd I am getting this error:  Starting httpd: Syntax error on line 23  of /etc/httpd/conf.d/modsecurity.conf:  ModSecurity: Found another rule with the same id   The line 23 is:  "id:'200000',phase:1,t:none,t:lowercase,pass,nolog,ctl:requestBodyProcessor=XML"


I need to prove that  $\lim_{n\rightarrow \infty} \int_0^{n^2} n\sin(x/n) e^{-x^2}dx=1/2$  I tried substituting $t=\frac{x}{n^2}$, but it was not very useful because I can't find a bounding function for the integrand which does not depend on $n$ in order to apply the Dominated convergence Theorem. It would not help anyway as the limit of the integrand is zero which would give the wrong result.  I think I need a good substitution, if anyone could give a hint about that it would be very appreciated!

I am trying to compute this integral/limit, I don't feel like I have any good insight...   $$\lim_{n \to \infty} \int_0^{n^2} e^{-x^2}n\sin\frac{x}{n} \, dx.$$  I have tried to make a change of variable to get rid of the $n^2$, I changed to $X=\frac{x}{n^2}$ but got something even worse, I've tried to reach a situation where I could use a convergence theorem for Lebesgue Integrals,... I'm not sure I'm even on the right track!  Could you give me a hint on how to start this?  Thank you very much!


I've seen this font several times (in Springer books for instance) and would like to use it in my documents if possible. I've tried What The Font to no avail. Can anyone give me some pointers on what it is and how to use it with pdfLaTeX?    (picture taken from )

Is it possible to identify the font used in a specific document/picture?  Answers to this question should identify:   Possible methods to do this (perhaps one answer per method) and adequately describe how to use it (as opposed to merely stating it); Ways of finding the identified fonts, if possible (free or not); and Any prerequisites associated with the method used, if required (for example, "In order to use method X, your document has to be in format Y").   This question is meant as an FAQ, based on an . Its aim is to facilitate the community with the general procedures involved in font identification. Similar cases are solved on a per-usage basis on 's  tag.


I am watching  and noticed that "fucking" (or other variations of "fuck" - I did not notice that with other words) is scrambled to "fng" (more or less). The viewer is expected to recognize the dirty word.  Why would Syfy do that? They created the series so they could have gone with "freaking" or something like that instead of a bleeping if they wanted to go for a younger rating.  I do not even think that the rating is the reason - extracted eyeballs or other violent elements would surely require a higher rating. This is not sure, though, as nudity or profanity is usually more problematic in the US than violence (I do not have sources for that).

The Magicians is a SyFy original series based on a fantasy book of the same name. It's essentially a deconstruction of the young-adult fantasy genre, aimed squarely at grown ups (it includes obvious send-ups of Narnia and Hogwarts).  The show has some pretty adult themes: there's an absurd amount of sex between all variety of participants, lots of death, depression, addiction, etc. Plus, there's a lot of swearing. Every episode contains multiple lines of dialogue where characters use obscene language, and the worst of it (primarily the "f-word") gets censored out.   It's that last part that confuses me. As far as I can tell, the show was written and produced specifically for the SyFy channel. Unlike many of SyFy's shows, it's not an Australian or Canadian import. It was produced by a US company, by people who have extensive experience with American network TV (one of the EPs worked on Supernatural for 6 years).  Why would they write and film dialogue that they knew would never be allowed to air on the network they sold the show to?


I use Ubuntu 16.04 under VirtualBox. Today I updated VirtualBox to 5.0.26. After it I updated the Ubuntu using GUI, but the update has frozen during grub update. After reset, it started normally and I finished the update manually from command line.  Now, after logging in the Unity does not start. I can reach the terminal via popup menu and start the Unity manually via the terminal using "unity -v" command. Interestingly without the "-v" option the unity does not start. I tried to reinstall unity and  without success. Any idea?

When I login, nothing happens.   I am presented with my desktop wallpaper.    No Dash, no Launcher, nothing.


Petersen graph is this graph:       Petersen graph can not be a Cayley graph.   How to prove that?  Can someone give a general method to judge a graph is or not a Cayley graph?

How can I show that the Petersen graph is not a Cayley graph?  I don't know very much about Cayley graphs, I know that they are vertex-transitive, but so is the Petersen graph. It probably has to do with the group structure of $\Gamma$ in $Cay(\Gamma,S)$ (which is a group of order $10$, i.e., it is either the cyclic group $C_{10}$ or the dihedral group $D_{10}$). Then I am guessing we go for some sort of contradiction(?). My group theory is a bit rusty, I would very much appreciate someone showing me how to do this one!


I have a command in a script to do a 'backup database [name] to [file]  and all the other parameters. Now, we have a problem where we run out of disk space, the script keeps on trucking, just issuing the message: BACKUP DATABASE is terminating abnormally. As if there is no problem... no exception is tossed, or anything... so the next command in the series, to do a restore of that database to another database... fails... and the script keeps on running... Why doesn't it throw an exception when there is a catastrophic failure like either of these? I've seen some suggestions that we should query log files to see if there was a database backup failure, but good grief, it should just DIE when you run the script. Do I need to catch the exception, and throw the exception with a higher severity (I'd assume that the other one is thrown with the max severity, but maybe someone thought that a complete failure of a backup is just minor?) I've seen other code / questions where people are doing a try/catch around the backup, but I have no interest in catching the exception, I want it to Abort right there, die, and report the error up the chain.. Instead, it just keeps going..

When issuing a backup command within a stored procedure that uses a try catch and dynamic sql, the error messages are very general when compared to running the backup command directly.  Try/Catch within SP:         begin try         execute sp_executesql @sql;  -- a backup command     end try     begin catch           print ERROR_MESSAGE();  -- save to log, etc.     end catch   Results in      50000:usp_Backup:117:  BACKUP DATABASE is terminating abnormally.   wheareas issuing the raw command:      backup DATABASE someDb to disk...   Results in better details:         Lookup Error - SQL Server Database Error: A nonrecoverable I/O error     occurred on file "H:\FolderName\Filename.bak:" 112(There is not enough     space on the disk.).   Is there a way to catch these details into variables within the stored procedure (to log, pass back to caller, for retry logic)?  It seems the details are coming through on the message channel but I would like them available within the SP.


It is shown in a book (Essential grammar in used: unit 22)  "Football matches are often played at the weekend, but no matches are being played next weekend."  In my opinion it should be:  "Football matches are often played at the weekend, but no matches will be played next weekend."  Edit: Just to point out that my wonder is in the present form are being when referring to a future event next weekend. So in my opinion it should be will be instead of are being.

I know we can use both Present Simple and Present Continuous to describe future actions. But I don't know when to use the correct form.   For example:  We fly to Paris next week.  We are flying to Paris next week.   These sentences both seem correct to me.  Can anyone explain me how to correctly use these tenses?


This is a question for the   Let's say that I have a directory with five files..  for i in $(seq 1 5); do touch "$i.jpg"; done; mkdir subdir   How would I move 1.jpg, and 4.jpg, and 5.jpg, into subdir?  I need something like a mark and move, or bulk move. Because these are images I need to to be able to render the previews in Ranger (already got that working), before I know which ones I want to move. For this reason I can not simply use mv. I need to interactively pick the batch.

When I select multiple files within ranger (using <Space> or V), how do I move these selected files to another directory?  I've tried to use dd and pp, but this only moves the file that's currently highlighted.


I teach high school physics and I'm trying to put together a correct explanation for the levitation of a superconductor above a magnet without a high level of quantum mechanics (but consistent). I have seen several explanations online and in text books. Many of them say Lenz's law is not part of the explanation for the situation. I'll propose an explanation and hopefully someone can comment on what is correct and incorrect about it.   A superconductor is sitting on top of a magnet and the superconductor is cooled below its critical temperature. The Meissner effect results in the exclusion of the external magnetic field from the superconductor. The exclusion of the internal magnetic field creates a changing magnetic field on the surface of the superconductor which induces a current in accordance with Lenz's law (many sources I have found say that a surface current is created on the superconductor). The induced magnetic field from the surface of the superconductor repels the magnetic field of the magnet and the superconductor rises above the magnet until the force of gravity is balanced by the magnetic repulsion.   Note: I know that flux pinning is at play to contribute to the stability of the situation but I am just interested in clearing up the basic physics of how the levitation is possible.  So, are there surface currents? Is my explanation above consistent with current understanding of the situation? If anyone knows someone who I should contact directly who could help me that would be wonderful.  Thanks.

I just saw  demonstration by someone from a Tel Aviv University lab.  What they achieved there is mind blowing. I myself own a levitron that uses the Hall effect to levitate a magnet, the problem with that is the magnet must always be flat facing the Hall effect base, any unbalance will wreck the levitation. But in the case of the video you can see that he isn't constrained by such things, the disk can levitate and stay still at whatever angle and orientation. Instead of being levitated, the disk is simply being held still.   How does this happen? He referred to this as quantum trapping, but I've little idea about what that is....  Also, what material is the base in these demos? Is the circular track in the demonstration magnetic? I assume this is so. Is there any conceivable way for this technology to make objects levitate on any surface?


After reading , xargs waits for receiving the stdin input before processing any of the input, such as splitting it into arguments.   How does xargs know when a stdin input ends, so that it can start processing it?  Is -E used for specifying the end of a stdin input?   Without it, how does xargs knows when it ends? Is there some timeout?

How does a program detect the end of stdin input?  There are several ways of providing stdin input to a program.   When using here-document, we specify a delimiter to signal the end of stdin input:  <<[−]word here-document delimiter   Why do we need to explicitly specify the end of stdin input? When using here string, there is no extra effort to signal the end of stdin input:  <<< word   How does the program knows the end of stdin input? When using redirection from a file to stdin, there is no extra effort to signal the end of stdin input. How does the program knows the end of stdin input? When using pipe to direct stdout output from another program to the stdin input of the program,  there is no extra effort to signal the end of stdin input? How does the program knows the end of stdin input? In some programs, such as bc, whenever you enter an arithmetic expression and hit return, it will takes in the expression as stdin input and output the evaluated result. In such case, is each line ended by return considered a whole stdin input, or are all the lines typed from starting bc till exiting bc considered a stdin input? What is the general principle that a program knows how to detect the end of stdin input?   When do we need to specify the end of stdin input explicitly like for here-document, and when do we need not?  Are they program-dependent, or program-independent?


I created the tag proxybroker on Stack Overflow and then tried to add the excerpt and description, but I got:     An error occurred submitting the post   while trying to Save Edits.  I also tried removing the description, but it isn't working either.

I've been editing some wiki entries on the new Expatriates site, and started to get the following error:    When I go to a normal post, I see what is presumably the proper explanation:    Can the Wiki Tag edit error be updated to show a more meaningful error message?


We are asked to prove the following theorem found in page 88 of Differential Geometry: Curves, Surfaces, Manifolds by Wolfgang Kühnel.  Using standard parameters, calculate the Gaussian curvature and the mean curvature of a ruled surface as follows:  $K = -\dfrac {{\lambda}^2} {{{\lambda}^2 +v^2}^2}$   and   $H = -\dfrac {1} {2({\lambda}^2 +v^2)^{3/2}} (Jv^2 + \lambda' v + \lambda (\lambda J + F))$    In standard parameters, a ruled surface is $f(u,v) = c(u) + v X(u)$ and $||X|| = ||X'|| = 1$ and $\langle c', X' \rangle = 0$.  Thus, using standard parameters, a ruled surface is, up to Euclidean motions, uniquely determined by the following quantities:  $F = \langle c', X\rangle$  $\lambda = \langle c' \times X, X' \rangle = \det (c', X, X')$  $J = \langle X'', X \times X' \rangle = \det (X, X', X'')$  Also, the first fundamental form is given as follows:  $I = \begin {pmatrix} \langle c',c' \rangle + v^2 & \langle c', X \rangle \\ \langle c', X \rangle & 1 \end {pmatrix} = \begin {pmatrix} F^2 + {\lambda}^2  + v^2 & F \\ F & 1 \end {pmatrix}$ with $\det (I) = \lambda^2 + v^2$.  So far, I have that  $f_u (u,v)  = c' + vX'$  and  $f_v (u,v) = X$  But I don't know how to proceed from there to get the first fundamental form, the normal vector, and the second fundamental form.

We are asked to prove the following theorem found in page 88 of Differential Geometry: Curves, Surfaces, Manifolds by Wolfgang Kühnel.  Using standard parameters, calculate the Gaussian curvature and the mean curvature of a ruled surface as follows:  $K = -\dfrac {{\lambda}^2} {{{\lambda}^2 +v^2}^2}$   and   $H = -\dfrac {1} {2({\lambda}^2 +v^2)^{3/2}} (Jv^2 + \lambda' v + \lambda (\lambda J + F))$    In standard parameters, a ruled surface is $f(u,v) = c(u) + v X(u)$ and $||X|| = ||X'|| = 1$ and $\langle c', X' \rangle = 0$.  Thus, using standard parameters, a ruled surface is, up to Euclidean motions, uniquely determined by the following quantities:  $F = \langle c', X\rangle$  $\lambda = \langle c' \times X, X' \rangle = \det (c', X, X')$  $J = \langle X'', X \times X' \rangle = \det (X, X', X'')$  Also, the first fundamental form is given as follows:  $I = \begin {pmatrix} \langle c',c' \rangle + v^2 & \langle c', X \rangle \\ \langle c', X \rangle & 1 \end {pmatrix} = \begin {pmatrix} F^2 + {\lambda}^2  + v^2 & F \\ F & 1 \end {pmatrix}$ with $\det (I) = \lambda^2 + v^2$.  So far, I have that  $f_u (u,v)  = c' + vX'$  and  $f_v (u,v) = X$  Also,  $f_{vv} (u,v) =0$  I know the formula for the first fundamental form, the normal vector, and the second fundamental form. However, I don't know how to obtain the dot products and the cross products without having to isolate the components.


How to set the transparency of the background image of the frame in beamer? I have tried this.  \documentclass[bigger]{beamer} \usepackage[utf8]{inputenc} \usepackage[T1]{fontenc}  \usepackage{graphicx}   %Global Background must be put in preamble \usebackgroundtemplate% {%     \includegraphics[width=\paperwidth,height=\paperheight]{Doc8}% }     \begin{document}  \begin{frame}{Introduction} \begin{itemize} \item 1 \item 2 \item 3 \end{itemize} \end{frame}   % Local background must be enclosed by curly braces for grouping. { \usebackgroundtemplate{\includegraphics[width=\paperwidth]{GPGC}}% \begin{frame}{Kitten} \begin{itemize} \item 1 \item 2 \item 3 \end{itemize} \end{frame} }  \begin{frame}{Summary} \begin{itemize} \item 1 \item 2 \item 3 \end{itemize} \end{frame}  \end{document}

I want to add a background image in my beamer presentation. The thing is that when I use  \usebackgroundtemplate{ \includegraphics[width=\paperwidth, height=\paperheight]{cern-logo.jpg} }   in my preamble, the image has its true colors, meaning that it is not opaque or transparent. Is there  a way to achieve that?


I believe that the question of which this was marked a duplicate seems to be one about the actual HTML tag's max length. I know there is no such max length and instead want to know about how the number of keywords affects SEO   I know that search engines like Google try to detect which webpages are lying by putting in too many keywords in the <HEAD>, but what if I have a webpage where very many keywords apply? Specifically, I noted that in my online résumé I have the following tag:  <META NAME="keywords"    CONTENT="Ben Leggiero,Ben,Leggiero,programmer,programming,developer,Java,C,C++,C#,Objective-C,JavaScript,Ruby,Python,HTML5,CSS3,PHP,XML,XSL,Haskell,Lisp,Prolog,COBOL,Android,Android 4.0,Ice Cream Sandwich,Android 4.1,Jellybean,Android 4.4,KitKat,Android 5.0,iOS,Windows 8,Windows Store,Browser extensions,browser apps,PSP software engineering,TSP software engineering,multiplatform,multiple languages,artist,graphic artist,Graphic Design,Vector,Raster,Photo touchup,photomanipulation,Adobe,Photoshop,Illustrator,CS3,CS4,CS5,CS6,Autodesk,Revit,Maya,3DS Max,Blender,Terragen,Inkscape,GIMP,Ulead,Corel,PhotoImpact,UI,UIX,GUI,TUI,User interface,enthusiast,professional,resume,cv" />   which is 75 keywords. All of these reflect what I consider the most important information in the page, especially since some of it (photo touchup, the full list of CS#, etc) is implied in English but probably not inferred by a crawler. Is this too many? Where's the limit?  Additionally, I heard through the grapevine that modern search engines actually ignore keywords in favor of fancy intelligent parsers. If this is true, how to I attach meta information to text on the page like "CS3,CS4,CS5,CS6" for "CS3-6", or "Android,Android 4.0,Ice Cream Sandwich,Android 4.1,Jellybean,Android 4.4,KitKat,Android 5.0" for "Android 4.0+"?

Could you please tell me that what is the maximum length for meta keywords?


Currently, moderators get an inbox message for each new post submitted to a per-site meta they moderate, SO excluded.  I would like to have that, please.  The reason is, I like to know what's going on. I usually read all of meta anyway, when I notice that there's something new, so I figure I might as well get notified about it as soon as it happens.  And there's already a system that delivers new meta posts to certain inboxes.  (This might not be a good idea for MSO in particular though, at least until .)

I'm currently helping out on . One of the most valuable things on new beta sites, especially private/early public betas, is Meta participation - see :  Treat Meta Questions Like Gold It’s not unusual for your meta site to receive significantly less traffic than the main site. The problems begin when you meta starts to get ignored by the community and ignored by the moderators. It is particularly disturbing when users reach out in meta and starts talking about improving the site or asking for help… only to be ignored; No follow-up, only deafening silence  Because of this, Diamond mods get a notification in their inbox for each new question on their Meta, helping ensure that each meta post is addressed. However, wouldn't it be great if Diamond mods weren't the only ones that could do this? The post does say that the community needs to be seeing these questions too. As an involved user, I would really like to be notified of these new questions - it would increase the good I could do the site. How about this?:  Of course, it would be opt-in, not opt-out, and per-site. A feature like this would greatly improve the good that enthusiastic site-builders can do for the site, and would, most likely, increase the overall chances of a site's success.


I need to write files in a specific directory on the file system where I have access to. But even if I can write files in the current working directory or any sub-directories, it seems that I am stock there.  For example, let's say that my test.tex file is located in this directory:  c:\SomeDirectory\test.tex   Is it possible to create a file in a directory I have access to (I created it myself), for example this one?  c:\AnotherDirectory\results.txt   Currently, I am using this code, and it doesn't work:  \newwrite\file %\immediate\openout\file="results.txt"  % This works when uncommented \immediate\openout\file="c:/AnotherDirectory/results.txt"  % Does not work... \immediate\write\file{Line 1} \immediate\write\file{Line 2} \immediate\write\file{Line 3} \closeout\file   I get this error message:  I can't write on file `"c:/AnotherDirectory/results.txt"'   Am I restricted by my LaTeX editor? Maybe I am not using the proper syntax?  Thanks!  Dave

Reading  got me thinking about the potential of .tex files for harbouring malicious code.  The filecontents package is used to write external files from within a LaTeX document. According to my tests, it can be used to write external files in an existing path down the directory tree. In other words, it can create a file in the directory in which the input .tex file is located, or in any of its subdirectories. For instance, the following code works as expected,   \documentclass{article}  \usepackage{filecontents}  \begin{filecontents*}{./myfolder/myfile.txt} Hello World \end{filecontents*}  \begin{document} test \end{document}   as long as     ./myfolder   is a valid path (i.e. the "myfolder" subdirectory already exists):  Is writing an external file up the directory tree possible?  All of my attempts so far have been unfruitful. I'm guessing that it's not possible; otherwise, that would represent a potentially very malicious exploit, without even requiring --shell-escape; malevolent people would have used that exploit long before I asked myself this question, and LaTeX would have become infamous for it.  So, is writing an external file up the directory tree possible or not? If the answer is yes, how do you do it? If the answer is no, what exactly forbids it?


The following experiment is performed: An observation is made of a Poisson random variable $N$ with parameter $ \lambda $. Then $N$ independent Bernoulli trials are performed, each with probability $p$ of success. Let $Z$ be the total number of successes observed in the $N$ trials. What is the distribution of $Z$?   My attempt:  So I managed to work out $E(Z) = \lambda p$ and $V(Z) = \lambda p(1-p) + p^{2} \lambda$. I'm not sure how to proceed to get the distribution of $Z$. Assistance would be appreciated.

Suppose you have:  $X|N \sim \text{MN}(N,p_1,p_2...p_J)$  $N \sim \text{Poisson}(\lambda)$  Where is the marginal distribution of $X$?