Prove $-(-a)=a$ using only ordered field axioms

I need to prove for all real numbers $a$, $-(-a) = a$ using only the following properties:     I tried by starting with P12 written using symbolic logic:  $\begin{align} \forall a,b \in P \to & a \cdot b \in P \Leftrightarrow True \\ \forall a \in P \land \forall b \in P \to & a \cdot b \in P \Leftrightarrow True \\ \lnot \left[ \left( \forall a \in P \right) \land \left( \forall b \in P \right) \right] \lor & a \cdot b \in P \Leftrightarrow True \\ \exists a \notin P \lor \exists b \notin P \lor & a \cdot b \in P \Leftrightarrow True \\ \end{align} \\ $  and played with evaluating it with $b = -1$, $-a$ and so on. But, felt this wasn't really a solution because the last symbolic logic statement above is ambiguous.  Not to mention--other than P12--I haven't used any of the axioms listed above whatsoever. ( And I've not bothered to prove any of the theorems of symbolic logic I have used. )  Can anyone give me a start on this problem?  Many thanks in advance.  Edit  Thank you, everyone! .  Best regards!


A potentially dangerous Request.Form value was detected from the client

Every time a user posts something containing < or > in a page in my web application, I get this exception thrown.  I don't want to go into the discussion about the smartness of throwing an exception or crashing an entire web application because somebody entered a character in a text box, but I am looking for an elegant way to handle this.  Trapping the exception and showing     An error has occurred please go back and re-type your entire form again, but this time please do not use <   doesn't seem professional enough to me.  Disabling post validation (validateRequest="false") will definitely avoid this error, but it will leave the page vulnerable to a number of attacks.  Ideally: When a post back occurs containing HTML restricted characters, that posted value in the Form collection will be automatically HTML encoded. So the .Text property of my text-box will be something & lt; html & gt;  Is there a way I can do this from a handler?


It would be nice if sites had a link to StackExchange's main site. I find myself regularly editing my address bar's contents just to do something websites used to do as a unwritten rule.


Prove the Integral of $\frac{1}{x}$ is not a Rational Function

The title is pretty self explanatory, I'd like to prove that \begin{align*} \int\frac{1}{x}\,dx \end{align*} cannot be a rational function. I have attempted a proof by contradiction, but it doesn't seem to lead anywhere. If it is assumed that $F(x)=\frac{p(x)}{q(x)}$,  where $p(x)$ and $q(x)$ are polynomials, then using logarithmic differentiation, \begin{align*} \frac{1}{x}=\frac{p(x)}{q(x)}\left(\frac{p'(x)}{p(x)}-\frac{q'(x)}{q(x)}\right) \end{align*} I don't see how this leads to a contradiction. I get similar results using the quotient rule  \begin{align*} \frac{1}{x}=\frac{p'(x)q(x)-p(x)q'(x)}{[q(x)]^2} \end{align*} Writing out the terms of $p(x)$ and $q(x)$ seems too messy. Any help or suggestions would be greatly appreciated.


Display each sub-directory size in a list format using one line command in Bash?

I want to get a list of the directories and their sizes in a list format like how you get when you do a ls -l.  The thing is that is there a one line command that can do this? I see others have long commands just to output this. That's just too long.  What command can do this or combination of commands that can be easily typed? du -h gives it, but it displays all of the sub-folders which is not what I want. just the current directories folders.


Can quarks be considered real and elementary?

In our current theories all hadrons are made up of quarks and gluons.  This view reduces considerably the big family of hadrons by providing a very logical structure in which all quantum properties values of the hadrons are originated from the valence quarks' quantum properties. But since they cannot be observed isolated, in the sense that electrons or positrons can be, the theory assumes color confinement is just part of the game.  However actual calculations of QCD use a view where they are quarks and gluons are distributed in a space-time volume, which is needed to describe much of the rich phenomena of high energy physics.  But all of this makes me wonder:   Are quarks real and elementary? I mean, is there more evidence supporting that they are more than just a model that works?  Since hadronic matter cannot by split into pieces smaller than the smallest hadron, couldn't reality be explained also by a model where all observable hadrons are the elementary ones, which follow rules for transforming into other ones, etc.?  By the way, this last idea was already presented by Hagedorn on his very famous known paper, in the end where he tries to give a phylosofical point of view to his model, so I wonder why was it discarded.


I want to see if I can charge my netbook with solar panels. With 16 smalls solar panels(they are from Westinghouse Turbo Rocket Solar Path Light with a 1.2v 150mAh a piece) the voltage and amps come out to be 19.2V and 2.4A. The power strip that came with the netbook has an output of 19V and 2.1A. Will charging it with a slightly higher volt and amp mess it up or anything? Thanks


Tutorial on how to back up my full Ubuntu desktop and files?

I would like to be able to back up all my settings and files to a dedicated external hard drive in a way that makes (1) all the backup files accessible and (2) would allow me to restore my system is there is a crash.   Is there an app for this or any pointers?  Thank so much.


How can I dissuade my players from attacking a deadly foe who isn't meant to be attacked?

I will be taking over as DM of our group in a few weeks.  Our party right now has a large number of magic items, and while I don't have a problem balancing that, I would rather replace lesser ones with greater ones.  The plot device I have chosen to do this, as part of the Hoard of the Dragon Queen adventure, is to have a dragon wyrmling attack the group as part of a medium challenge encounter.  When the wyrmling is killed, an ancient dragon appears to demand reparations from the group in the form of relinquishing one of each of their magic items.  What I want NOT to happen is for the group to decide they can kill the ancient dragon - because they can't.  The ancient dragon I plan to use is the Silver, and mainly because it can paralyze with its breath attack.  The party being a band of murderous heathens makes this problematic — I honestly believe they would attack almost any foe and ask questions later. How do I ensure that the party doesn't go kamikaze on the ancient dragon?  If it makes a difference, the group is composed of six 7th-level characters. Only one of them is a melee attacker.


Proof that there are infinite primes $p$ such that $p+2$ is not prime.

Let $p\in\mathbb N$ be a prime. I want to prove that there is an infinite amount of primes $p$ with the property $p+2$ is not a prime. I am stuck on how to do this, though. I have tried an alternation of Euclids proof of the infinitude of primes but I cannot seem to find a construction that implies the desired result. Any help would be appreciated.


Basically I want to pass a image file with ajax on submitting a form and retrieve the image and send it by email as an attachment file:  Here's the form :  <form role="form" action="" name="devis" id="devis" method="post" enctype="multipart/form-data" class="form-horizontal">     <fieldset>
             Company
                 <input type="text" class="form-control input-md col-md-8" name="societe" value="" maxlength="" id="societe">

             * Message
                 <textarea rows="5" name="message" class="form-control input-md col-md-8" maxlength="" required="" style="resize:none;" id="message"></textarea>

             Logo

                                                               Parcourir <input type="file" id="image_input_field" name="file">                                                       <input type="text" class="form-control" readonly="">

         <input type="submit" value="Envoyer" name="" class="btn btn-primary" id="submit">         <input type="reset" value="Annuler" name="" class="btn btn-default" id="reset">

     </fieldset> </form>   I can't seem to find what's the error in my code ! Here's the AJAX call :  jQuery(document).on("click", "#submit", function(e) {       e.preventDefault();       var fileInput = document.getElementById('image_input_field');       var file = fileInput.files[0];       var formData = new FormData();       formData.append('file', file);       // console.log(file);        var societe = $("input#societe").val();       var message = $("textarea#message").val();       jQuery.ajax({         url: "ajax.php",         type: "post",         data: {            'file': file,            'module' : 'ajax_data_form',            'societe': societe,            'message': message         },         cache: false,          success: function(reponse) {           if(reponse) {             alert(reponse);             // console.log(reponse);             // jQuery('#devis').trigger("reset");           } else {             alert('Erreur');           }         }       });      });   And here's the ajax.php:  <?php if( isset($_POST['module']) && $_POST['module'] == "ajax_data_form" ) {      var_dump($_FILES); }


MS Word: preserve hyperlinks when exporting to PDF

How can I convert a Word document to PDF and preserve all hyperlinks?  I have Word 2011 and Acrobat XI available on OS X.  Save As -> PDF from Word doesn't preserve hyperlinks.  Acrobat's File -> Create -> PDF... from the .docx file also doesn't preserve hyperlinks.  When testing this, please use a link whose text is not identical to the URL it is pointing to.  Many PDF readers will recognize URLs and automatically make them clickable, even if the PDF doesn't actually contain hyperlinks.


Every airline I've been on has an ashtray in the bathrooms, ironically right below the sign that says no smoking in the bathrooms.     If it's prohibited to smoke on airlines, and (in theory) you can't bring a lighter on the plane anyway, what's the point of the ashtray? If it's for cigarettes smoked before security, there are plenty of garbage cans and ashtrays outside of airports.


Why cardinalities inequality defined that way?

This is the definition of $|A| <= |B| $: there exists an injective function from $A$ into $B$. Why it is defined that way and not like the following proposal, which is equivalent under the assumption of the axiom of choice: there exists a surjective function from $B$ into $A$.


Let $R$ be a UFD and $a,b,c \in R$ be nonzero. If $c \mid ab$ and $\gcd(a, c) = 1$, then $c \mid b$.

Here is the problem If $c\ |\ ab$ and $\text{gcd}(a,c)=1$ then $c\ |\ b$ Here's my approach. There exists $x,y$ such that $ax+cy=1$, so $c\ |\ axb+cyb=b$ I'm pretty sure my first step is wrong. Any help would be appreciated!


Can't log in after a shutdown apparently deleted my user account

Last night, I wanted to shutdown my PC after using it, but when I clicked the power icon, a tiny empty box showed with nothing in it (i.e. there's not Shutdown option)  So I thought rebooting will fix it, so I typed in my Terminal:     shutdown -P 1   After one minute, the PC got hung for few seconds, and then it suddenly shutdown, without closing any programs or anything, it did shutdown abnormally  Later, I turned my PC on and I was surprised that my user account was deleted! Plus the background and other settings were set back to their defaults, however the Wi-Fi connected automatically without asking for the password, seems like it was saved  There's the login button with Username/Password fields, I am sure that I typed them correctly but it says invalid credentials  I can sign in as Guest, but I can't do anything administrative, my user folder is still in place, but I can't access it due to being Guest  I have Ubuntu 13.04, dual-boot with windows 8


I have the following problem: (1) I get a package with many samples with values (2) I have reasonable time to calculate whatever i want and keep in memory any info i want, but not all of the samples (the samples are very large, I can keep a few MB of data) (3) I drop the package and go to step (1) with a new package, unless no more packages (4) Use all kept information to calculate the 10% percentile \ median \ 90% percentile Can it be done? Thx


I am working on a re-design for  a eCommerce site and they have a section where they offer a free gift card if the user makes a purchase over $1000. The idea of the gift card is to get users to purchase more on the site and since the products are generally expensive (its a jewelry site) chances are they will spend the gift card plus some more money on the site.  So the question I have is should the radio button group which asks user if they want a free gift card be pre-selected ?         – Wireframes created with   There are two aspects to it which I am trying to consider and I would appreciate it if answers consider those a parameters   The user experience if the radio button is pre-selected as yes and the user is wondering when did he sign up for a gift card even though its free The aspect of conversion from a e-commerce perspective


Ubuntu 13.04 won't boot after new AMD catalyst center

I am far from an experienced linux user.  I uninstalled the latest catalyst center and installed the new AMD beta driver.  The installation seemed to go fine then it said I should restart to avoid instability.  I restarted and then the purple screen comes up for a second, some message flashes too quickly for me to read.  Then it goes into a black screen with the blinking cursor.  Nothing I type on the keyboard registers.  I've looked up and down for solutions but everything I've found about boot problems says I need to get into the terminal and type commands.... I can't even get there.  I tried holding shift while computer was booting as I saw that in a thread saying it will help load some sort of safe mode.  What do I do?


A single word or phrase when someone pretends to be so close to you

I know that I came from a country where inventing words or phrase for something is common. I always hear this phrase when they say it:     you're so feeling close   to denote that someone pretends to be your close friend or vice versa. I'm not just that confident that the usage of this phrase is valid. I believe that we're the only one who used this.  A singled word or phrase will do.


Nearby electronic devices turn off laptop's display

My Toshiba laptop turns it's display off when I put my smartphone or my soundbar next to it. If I remove them, the display turns back on. How can I fix this?


How can I talk to my game-master about his self-insert character without offending him?

I have been in this long-term game where the group has been in a semi-railroaded adventure. However, there has been something that has been bugging me for a while.  The game-master has this person following us who is the father of the gods. He resurrects us when we get a party wipe or gives us quests, which made him appear as a typical NPC at first; however, as the game progressed, the guy has started appearing everywhere, watching us fight and occasionally mocking us while flaunting his powers that cannot be explained by the book (like stopping time for everyone except him and the group while also disabling all of the group's spells).  It has reached a point where several players along with me are disturbed by this character appearing everywhere and mocking us, or getting mad at us saying we owe him for doing something he was against and then sending us to the next quest with us having no choice but to obey him or risk his wrath. All the while, the game-master constantly states that we are free to follow any lead we want.  I am planning to talk to the game-master and ask him to dial back with that character a bit or something similar. I am afraid that he will take it as a personal insult, as he seems to really associate with the character; the character says what he (the GM) wants to say to the party, and speaks and acts the same way he does.   How can I talk to the GM and tell him my problem with his character without actually offending him?


could anyone tell me how exactly to do this via a batch file:   The x86 version. Much appreciated.


How to connect two sales force org using REST web service?

We are trying to migrate data from one sales force org to other using REST web service. Created REST service in one org trying use that service from other org but getting error "System.HttpResponse[Status=Unauthorized, StatusCode=401]".  Http Callout :  String username = correct usernme; String password = Correct password;  Blob headerValue = Blob.valueOf(username + ':' + password);      String authorizationHeader = 'Basic' +      EncodingUtil.base64Encode(headerValue);  HttpRequest req = new HttpRequest(); req.setEndpoint('https://ap4.salesforce.com/services/apexrest/Accounts/'); //req.setHeader('Authorization', authorizationHeader); req.setMethod('GET'); //req.setHeader('content-type', 'application/json');   req.setTimeout(120000); //req.setBody(jsonBody);                 Http htp = new Http(); HttpResponse resp = htp.send(req);  System.debug('resp:'+resp);   HOw should i call one sales force rest web service from another salesforce org?


I currently read a java book and I am stuck at an example including this line :  Bird titi = new Swan();   where Swan is a subclass of Bird.  I could explain this as follow:     when java executes this line, it stores memory for the value titi, and the memory stored can contain an information for an object of type Bird. next, the second part of the line call the Swan constructor without any argument, which initializes the titi value.   if I am right, I can't explain why a Swan instance can be stored in a Bird type because Swan, as a subclass, contains more information than Bird. so I think I am something wrong. where?  and, extra-question : in which case this type of statement is useful?  thank you


How do you find the vector of length 2 in ℝ2 making an angle of 30∘ with the x-axis?


Removing apk of inbuilt apps completely (without rooting)

I'm working on Samsung Galaxy On7, Android 6.0.1-Marshmallow.  My internal memory is 8 GB, due to which I have disabled several inbuilt apps which I do not need at all.  The problem is that, these disabled apps are still taking up space, even though they are disabled and replaced by their factory versions.  Is there any way I can completely free up the space the Google apps are using up (like Facebook and its Manager, which are taking up almost no space):  (Click the image to enlarge it)     Please note that I do not want to root my phone. I had previously rooted my other phone with kingo root, but could never unroot it.


How do I troubleshoot high 'svchost.exe' usage in Windows 7?

I'm having a problem with Windows 7 64-bit. I thought it was slow and all, but then I saw that the CPU usage was always around 80% and started searching for a solution.  There are two svchost.exe's consuming around 30% each and in the resources monitor there's a system interrupts consuming 45% all the time. I tried closing the applications, but it makes no difference.  I tried some other things that I've found on Google, like disable system updates, but it didn't work.  I don't know if it will help but here's my specifications:  Core 2 Duo 4400 ATI Radeon 4850 4 GB DDR2 RAM     EDIT  I ran the suggested program and got this information; did I get it right?      EDIT  As you asked here it is, did I get it right now? The other TCP/IP there's nothing.    EDIT  I ran msconfig and took the services that one of the svchost.exe processes was using out of the startup and now my CPU is around 50%, but I still would like to improve it further. I can't lose that much CPU power just because of Windows...    EDIT  Yeah, there's nothing I can do here. I am going to reinstall Windows XP soon, it's really weird...


Proof that total derivative is the only function that can be added to Lagrangian without changing the EOM

So I was reading this:  and while the answers for the first question are good, nobody gave much attention to the second one. In fact, people only said that it can be proved without giving any proof or any.  So, if I have a Lagrangian and ADD an arbitrary function of $\dot{q}$, $q$ and $t$ in such a way that the equations of motion are the same, does this extra function MUST be a total time derivative?   EDIT Ok, I changed my question a little bit:  Question: If I have a function that obeys the Euler-Lagrange equation off-shell, this implies that my function is a time derivative? (This was used in Qmechanic's answer of this other question: , equation 14.)  Also, why people only talk about things that change the Lagrangian only by a total derivative? If this is not always the case that keeps the equation of motion the same, so why is it so important? And why in the two questions I posted about the same statement on Landau&Lifshitz's mechanics book only consider this kind of change in the Lagrangian?


Not able to update/upgrade to latest Ubuntu, since "Your Ubuntu release is not supported anymore."

I need help on upgrading my ubuntu from 19.04 to 19.10. When I tried to run sudo do-release-upgrade, the message is "Your Ubuntu release is not supported anymore." How could I upgrade my ubuntu if it's not supported anymore? Any help will be appreciated, thanks in advanced.


I have a function that has an std::istream argument and uses the member functions read() and eof() on it. Someone may pass in a subclass ifstream,ofstream,fstream,etc and I don't know if it is in binary mode.  My questions:    Is there any way to determine whether or not the istream is an ifstream,ofstream,fstream,etc and has been opened in binary mode?    Do read() or eof() have any differences on the istream depending on the subclass? Let's say an ifstream in text mode is the argument, if I call the istream read() and eof() am I in binary or text mode, and is this covered by the standard?    #include <string> #include <fstream> #include <iostream>  using namespace std;  int main( int argc, char *argv[] ) {     ofstream out("test", ios::trunc|ios::binary);     char a[] = "before \x1a after";     out.write( a, (sizeof a) - 1);     out.close();      ifstream in("test");     char buffer[(sizeof a) - 1];     // read one less than the actual file size     in.istream::read(buffer, (sizeof buffer) - 1);     buffer[in.gcount()]=0;     cout << "gcount: " << in.gcount() << endl;     cout << "eof: " << in.istream::eof() << endl;     cout << buffer << endl;      return 0; }


Do creatures that are hit with poison attacks (or take poison damage) become Poisoned?

Appendix: POISONED:    A poisoned creature has disadvantage on attack rolls and ability checks.   Would this condition ever be applied to a creature that's stung by giant scorpion's tail-sting attack, or bitten by a poisonous snake (both found in the Monster Manual), or shot with a poisoned arrow? I can see several instances where poison damage is applied to a creature, but very few where the poisoned condition is applied (so far just the magical poison dagger).   Even poison you can purchase only inflicts poison damage and makes no mention of applying the poisoned condition. There seem to be a great many anti-poison measures but little to no poisoning methods.


Do I need to check for Autocorrelation, Heteroskedasticity and Normality when building a model with data that are not time series?

I want to build a simple regression model with non-time series such as Client ID Number. when testing the validity of this model, do I need to check for autocorrelation, Heteroskedasticity and Normality?


Determine whether the set $W= \{(2a-2,3b,2a-3b)\}$ is a subspace in $\mathbb R^3$  Describe the set.   I know that in order for a set to be a subspace, it must be closed under multiplication and addition.. How would I go about showing this? Thanks


In the first or second book, when Daenerys is in a city, she wants to enter a building ( I think) and she thinks:     [...] and there was a eunuch guarding the door [...].   How could she understand that the person she saw (that she haven't seen before) was a eunuch? Do eunuchs have something distinctive so people can tell them apart?   Are they like Varys? Shaven head and no beard?


I'm interested in removing one object's geometry from another. I should be able to do this with a boolean modifier on the larger object (the "car") targeting another object (the "window"). I would then like the window not to show when rendering. I expected to find this option in the outliner view (based on ), but maybe this has changed in blender 2.80? In the outliner window, I see the "Hide in Viewport" option, but where is the option to hide it in the final render?


Is there a limit to how many power armor frames can be obtained?

In Fallout 4, you can obtain  (the base for the armor - not the workstation) in a few ways. The ones I know of are:   Fixed/Quest related ones (such as the ones placed at vertibird crash sites) From vendors From pickpocketing fusion cores from armored enemies, causing them to step out of their frames   Are any of these sources renewable? If so, which ones?  If they are, I wouldn't feel so bad killing enemies rather than stealing their cores. I basically want to know if any of these sources respawn.


I was doing first post reviews, and saw a question that I assumed must have been answered before, so I went through the flag process of looking for dupes. However instead of showing me search results where I could assess whether it was a dupe, I was informed I had failed a review audit. Had I been unable to find a dupe I would have actually voted the question up for being high quality, but because I searched first, that search triggered an audit failure.  It seems the search results need to be shown before revealing the question to be an audit. Otherwise doing thorough research is deemed a failure.


Example of subgroup $H$ with the property $g H g^{-1}$ is properly contained in $H$.

After learning the definition of normal subgroup, I would like to find an example of a group $G$ which has a subgroup $H$ such that there exists an element $g \in G$ such that $gHg^{-1} \subsetneq H$, namely, $gHg^{-1}$ is a proper subgroup of $H$.   Can anyone provide an example? Thank you very much!


HEX Code in Color Chooser for Mavericks?

How can I get a HEX code entry into the Color Chooser for Mavericks?


Skip last leg, but get on different flight in layover city

Disregarding the morals of hidden-city ticketing, I've got a question.  Are there any issues from flying and skipping the last leg and hopping onto a different airline's flight to get to my wanted final destination?  So, I would go from DFW, layover in ORD and skip the final leg to GSO and go from ORD to KEF.  DFW-ORD-GSO-KEF     DFW: Dallas / Fort Worth (USA) ORD: O'Hare International Airport (USA) GSO: Piedmont Triad International Airport (USA) KEF: Keflavík International Airport (Iceland)


Which IDE or Tool can I use to code ASP.NET applications on Ubuntu 15.10?

I want to code in ASP.NET but I don't know which IDE to use


Ubuntu Boot From Flash Drive Out of Range

Seems to be booting from the flash drive and screen turns black and a small box appears with "Out Of Range" appears. I have been able to get to the grub menu and boot without graphics. I tried to change the display resolution, but the only 2 options were 800 x 600 and 1280 x 768. How do I get other resolutions and graphics? I also tried to change to the native resolution (1920 x 1080) before attempting to boot and got the same out of range box.


java.lang.NullPointerException in my JDBC app - Do I need to use resultSet or something?

I am attempting to create a database connection and update using a prepared statement with JDBC to MYSQL.  I have tried changing the connection a bit and had to change the preparedStatement class to static in order to not get errors.  However, when running the app I got a NullPointerException error and I can't see where exactly I need to create a new object.  Currently, I get an error:     Exception in thread "main" java.lang.NullPointerException           at Alter.main(Alter.java:12)      import java.sql.PreparedStatement; import java.sql.SQLException;  public abstract class Alter {      public static void main(String[] args) throws SQLException {                   String query = "INSERT INTO school.students (First_Name, Last_Name, Gender, Grade_Level, IEP, Disruptive_1to5_LowtoHigh, OffTask_1to5_LowtoHigh, Not_Responsible_1to5_LowtoHigh, Not_GetAlong_1to5_LowtoHigh) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?)";                  PreparedStatement myStmt = Connection.prepareStatement(query);                           myStmt.setString(1, "Chris");                     myStmt.setString(2, "Johnson");                     myStmt.setString(3, "Male");                     myStmt.setString(4, "K");                     myStmt.setString(5, "N");                            myStmt.setInt(6, 1);                     myStmt.setInt(7, 3);                     myStmt.setInt(8, 5);                     myStmt.setInt(9, 2);                     myStmt.addBatch();                      int[] result = myStmt.executeBatch();                      System.out.println(result + " were added to the database.");      } }   import java.sql.*;  public class Connection extends Alter {     {     try {          Class.forName("com.mysql.cj.jdbc.Driver").getDeclaredConstructor().newInstance();      }          catch (Exception ex) {          }     try {          batchInsertRecordsIntoTable();      } catch (SQLException e) {          System.out.println(e.getMessage());      } }      final static void batchInsertRecordsIntoTable() throws SQLException {         {             try {           DriverManager.getConnection(                      "jdbc:mysql://localhost:3306/school?allowPublicKeyRetrieval=true&useSSL=false&serverTimezone=UTC",                        "root", "");           System.out.println("Connection Successful"); }       catch (SQLException ex) {          ex.printStackTrace();      }         } }      public Statement createStatement() {         return null;     }      public static PreparedStatement prepareStatement(String query) {         return null;     } }


How does the hyperparameter lambda affect L2 norm

Let's say I have L2 regularization in ridge regression:  How would I go about giving a formal mathematical proof that  I know that the larger the lambda the smaller the L2 norm. But, I don't know how to give a mathematical proof


I have a problem with flipping pose, I try to do the same thing as in . On 3:25, he flips the pose by Ctrl+C, Ctrl+Shift+V. In my case, it only flips some rotations, but legs stay in the same place:    I did everything exactly like in this video. I've tried to changing from "ZYX Euler" to "Quaternion" (saw this in some other question here) but it didn't helped.  Here is my blend file:


How to read integer content in xml response using volley?

I have response as <int xmlns="http://tempuri.org/">3</int>. When I try to fetch using StringRequest in volley i get exception as Attempt to invoke virtual method 'int java.lang.String.length()' on a null object reference. Is there any way that I can get the integer value from xml using volley. This is my code   StringRequest volleyReq = new               StringRequest(Request.Method.POST, url,                 new Response.Listener<String>() {                     @Override                     public void onResponse(String response) {                         try {                              Toast.makeText(getActivity(), finalMsg,Toast.LENGTH_SHORT).show();                           } catch (Exception e) {                             e.printStackTrace();                             Crashlytics.logException(e);                              showErrorlayoutwithBtn(Global.SERVER_OUT_OF_REACH);                          }                     }                 },                  new Response.ErrorListener() {                     @Override                     public void onErrorResponse(VolleyError err) {                         Log.e("Error in time json", err.getMessage());                         err.printStackTrace();                         //pbInOut.setVisibility(View.GONE);                         ShowCustomToast(errorToast, Global.FAILURE_RETROFIT);                     }                 }) {             @Override             protected Map<String, String> getParams() {                 Map<String, String> map = new HashMap<>();                 map.put("UserID", usrId);                 map.put("latitude", latitude);                 map.put("longitude", longitude);                 return map;             }         };         volleyReq.setRetryPolicy(new DefaultRetryPolicy(                 2000,                 5,                 DefaultRetryPolicy.DEFAULT_BACKOFF_MULT));          MyApplication.getInstance().addToRequestQueue(volleyReq);   and here is my stack trace     2019-04-02 11:01:13.650 6595-6649/com.hrdelight.android.hrdelight   E/Volley: [288] NetworkDispatcher.processRequest: Unhandled exception   java.lang.NullPointerException: Attempt to invoke virtual method 'int   java.lang.String.length()' on a null object reference       java.lang.NullPointerException: Attempt to invoke virtual method 'int java.lang.String.length()' on a null object reference           at java.net.URLEncoder.encode(URLEncoder.java:204)           at com.android.volley.Request.encodeParameters(Request.java:491)           at com.android.volley.Request.getBody(Request.java:477)           at com.android.volley.toolbox.HurlStack.addBodyIfExists(HurlStack.java:245)           at com.android.volley.toolbox.HurlStack.setConnectionParametersForRequest(HurlStack.java:219)           at com.android.volley.toolbox.HurlStack.executeRequest(HurlStack.java:97)           at com.android.volley.toolbox.BasicNetwork.performRequest(BasicNetwork.java:131)           at com.android.volley.NetworkDispatcher.processRequest(NetworkDispatcher.java:120)           at com.android.volley.NetworkDispatcher.run(NetworkDispatcher.java:87)   Is there any way that I can get the integer value from xml using volley


I have a pair of users on an ssh Server. lets call them UserX & UserY. UserX has the home Dir /home/userX UserY has the home Dir /home/userX Both are members of the userX group.  UserX has no problems, everything is cool, and working fine. UserY may read Files in his home directory, but cannot write files.  How can I give full access permissions (rwx) to UserY?


Conditional statement truth table reasoning.

Let P be the Hypothesis and Q be the conclusion.    I believe I understand the logic of If P then Q in the two case where,   A.  P is True and Q is false.  B.  P is True and Q is true.   the two cases where I'm having a trickier time fully understanding what is going on are,   C. P is False and Q is True. D. P is False and Q is False.   A line of reasoning that I've heard expressed are that, if P is False it cannot be said whether or not Q is True.   If this is the case, why is it that C. and D. return values of True rather than values of Undetermined?  How can you know the truth of the statement if when P is false, you cannot make a conclusion?  Thank you for your valuable time!


I can't trash files anymore, but only delete them directly

When I want to delete a file in Finder or in the Desktop a popup appears and it says it will be deleted immediately, and I need to confirm.  The trash is always empty, and I can't use it anymore.   What's going on with Snow Leopard and not having a working trash can?


How to I stop Chrome from updating when it is first installed?

There are a lot of answer here describing how to disable chrome update AFTER it is installed. What I couldn't figure out is how to stop Chrome from updating DURING installation. For example, I was trying to install 30.0.1599.10 for debugging but it always update me to the latest version.


Sorry to bother you all but I'm new two programming and I'm really stuck on this task. I have to add code to the class to print numbers from this array in order to make a for-loop.  This is what I have so far:   public class ArrayExercise {   public static void main(String[] args)   {     String[] numbers = {"one", "two", "three", "four", "five"};     String numbers = number[i];     String nextnumber = number[i + 1];   } }   How can I do this?


A story about an expedition to a nearby star, on arrival finding out humans are already there

I can't remember the title of this story. It was about an expedition in a low-tech spacecraft to a nearby star with a potentially habitable planet. The journey would take several hundred years.   Along the way, each astronaut would wake up from cryogenic sleep from time to time, to perform some duties. One of them wakes up just as the craft is passing an asteroid, takes a few photos, and I vaguely remember him finding out that the man who invented their cryogenic pods... died in one.      The asteroid happens to be a passenger ship going from that system to Earth, or back, pulled out of warp with catastrophic results to avoid crashing with an unknown object (the primitive spacecraft)   In the end, the crew makes it to the planet, find out humans are already there, there's a lush civilization, commerce with Earth, and that humans have become very "posh". They also learn about the plot twist from earlier.


$1+\sqrt{2}$ seems special: its powers quickly approach integers

$ \alpha = 1+\sqrt{2}$ has some interesting properties. One of which is that if you look at powers \begin{align*} \alpha^2 &= 3+2\sqrt{2} \approx 5.8284 \\ \alpha^3 & \approx 14.0710 \\ \alpha^4 & \approx 33.9705 \\ & \vdots \\ \alpha^{10} & \approx 6725.9998 \\ \alpha^{11} & \approx 16238.0000 \\ \vdots &  \end{align*} (values truncated, not rounded) then the sequence $\{ \alpha^n \}$ is "almost" an unbounded integer sequence. What is going on here? Is this property secondary to $\alpha$ being a unit in $\mathbb{Z}[\sqrt{2}]$? Can $\alpha$ be interpreted as a type of approximate eigenvalue? Does this behavior have to do with the continued fraction representation? Other numbers such as $1+\sqrt{3}$ have a similar property, but they don't appear to "become integer" as quickly.


How do I load an org.w3c.dom.Document from XML in a string?

I have a complete XML document in a string and would like a Document object. Google turns up all sorts of garbage. What is the simplest solution? (In Java 1.5)  Solution Thanks to , I have settled on this implementation. It has the right level of input flexibility and exception granularity for me. (It's good to know if the error came from malformed XML - SAXException - or just bad IO - IOException.)  public static org.w3c.dom.Document loadXMLFrom(String xml)     throws org.xml.sax.SAXException, java.io.IOException {     return loadXMLFrom(new java.io.ByteArrayInputStream(xml.getBytes())); }  public static org.w3c.dom.Document loadXMLFrom(java.io.InputStream is)      throws org.xml.sax.SAXException, java.io.IOException {     javax.xml.parsers.DocumentBuilderFactory factory =         javax.xml.parsers.DocumentBuilderFactory.newInstance();     factory.setNamespaceAware(true);     javax.xml.parsers.DocumentBuilder builder = null;     try {         builder = factory.newDocumentBuilder();     }     catch (javax.xml.parsers.ParserConfigurationException ex) {     }       org.w3c.dom.Document doc = builder.parse(is);     is.close();     return doc; }


I have a problem using dynamic types to instantiate a custom class. Example, I have the following class:  public class myClass<T> {     public myClass(String header); }   If I use the following code, everything works fine:  var myInstance = new myClass<int>("myHeader");   However, I am in a position I don't have the int type defined, so I need to dynamically cast it from a generic type parameter. What I tried so far:  1.      Type myType = typeof(int);     var myInstance = new myClass<myType>("myHeader");   2.      int myInt = 0;     Type myType = myInt.GetType();     var myInstance = new myClass<myType>("myHeader");   In all examples I get the following error:     The type or namespace name 'myType' could not be found (are you missing a using directive or an assembly reference?)   The reasons I cannot use int directly is because I am loading the types from specific assemblies at runtime, so they will not be "int" at all times.


Why was $\vec{A}\cdot\vec{B}$ defined as $|\vec{A}||\vec{B}|\cos \theta$? Historically what is the underlying idea?


Computing rotation index of $(\cos t, \sin(3t))$

I'm trying to compute the rotation index of the curve $\vec x\colon [0,2\pi]\to\mathbb R^2$ defined by $$ \vec x(t) = (\cos t, \sin(3t)). $$ I know that \begin{align*} x'(t) & = -\sin t & y'(t) & = 3\cos(3t) \\ x''(t) & = -\cos t & y''(t) & = -9\sin(3t) \end{align*} so the curvature is \begin{align*} \kappa_g(t) & = \frac{x'(t)y''(t) - x''(t)y'(t)}{\lVert{\vec x'(t)}\rVert^3} \\ & = \frac{9\sin t\sin(3t) + 3\cos t \cos(3t) }{\lVert{\vec x'(t)}\rVert^3}. \end{align*} Then I tried to compute the rotation index as \begin{align*} \frac{1}{2\pi} \int_0^{2\pi} \kappa_g \, ds & = \frac{1}{2\pi} \int_0^{2\pi} \kappa_g(t) s'(t) \, dt \\ & = \frac{1}{2\pi} \int_0^{2\pi} \frac{9\sin t\sin(3t) + 3\cos t \cos(3t) }{\lVert{\vec x'(t)}\rVert^2} \, dt \\ & = \frac{1}{2\pi} \int_0^{2\pi} \frac{9\sin t\sin(3t) + 3\cos t \cos(3t) }{\sin^2 t + 9\cos^2(3t)} \, dt. \end{align*} When I try to approximate the integral at the end, it looks like the rotation index comes out close to $1$, but I'm not sure how to simplify that integral. Is there a better way of finding the rotation index or a way to simplify the integral?


Serial numbers generated copy to clip board button

Im selling serial numbers the customers and they get in trouble to copy manually the text while mostly they are mobile users , i want to add the copy button to the serial number generated from database to data table so the customer can copy it with click on button only This is my code: <?php defined( 'ABSPATH' ) || exit(); ?> <?php global $serial_numbers; ?> <?php echo sprintf( '
%s
', esc_html( $heading ) ); ?>

         <?php echo sprintf( '%s
', html_entity_decode( $product_column ) ); ?>         <?php echo sprintf( '%s
', html_entity_decode( $content_column ) ); ?>

     <?php foreach ( $serial_numbers as $serial_number ): ?>
                              <?php                 $product_column_content = html_entity_decode( $product_column_content );                 $product_column_content = str_replace( '{product_url}', esc_url( get_permalink( $serial_number->product_id ) ), $product_column_content );                 $product_column_content = str_replace( '{product_title}', get_the_title( $serial_number->product_id ), $product_column_content );                 echo $product_column_content;                 ?>             	                               <?php                 $serial_column_content = str_replace( '{serial_number}', \PluginEver\SerialNumbers\Helper::decrypt( $serial_number->serial_key ), html_entity_decode( $serial_column_content ) );                 $serial_column_content = str_replace( '{activation_email}', $order->get_billing_email(), $serial_column_content );                 $serial_column_content = str_replace( '{expired_at}', \PluginEver\SerialNumbers\Helper::get_expiration_date( $serial_number ), $serial_column_content );                 $serial_column_content = str_replace( '{activation_limit}', \PluginEver\SerialNumbers\Helper::get_activation_limit( $serial_number ), $serial_column_content );                 echo $serial_column_content;                 ?>
     <?php endforeach; ?>


I am trying to output the values of array element but I am getting weird output. Please have a look at it and help me solve it. Thank you.  n=2 declare -a myarray[$n] myarray[0]=hey myarray[1]=hello myarray[2]=bye for i in ${myarray[@]} do         echo $i done   Output:  robin@robin-VirtualBox:~/lx$ sh array.sh array.sh: 2: array.sh: declare: not found array.sh: 3: array.sh: myarray[0]=hey: not found array.sh: 4: array.sh: myarray[1]=hello: not found array.sh: 5: array.sh: myarray[2]=bye: not found array.sh: 6: array.sh: Bad substitution


In other words, what counts as "First Rollback"?


resolution is undefined in XeTeX so the following code will produce different values when compiled with pdfTeX and XeTeX.  \documentclass{article} \usepackage{graphicx}  \newsavebox\IBox \savebox\IBox{\includegraphics[scale=1]{koala.jpg}}  \begin{document} \the\wd\IBox \end{document}   How to force pdfTeX and XeTeX to produce the same measurement for the imported image?


Check array for string that starts with given one (ignoring case)

I am trying to see if my string starts with a string in an array of strings I've created. Here is my code:  string x = "Table a"; string y = "a table"; string[] arr = new string["table", "chair", "plate"] if (arr.Contains(x.ToLower())){     // this should be true  } if (arr.Contains(y.ToLower())){     // this should be false  }   How can I make it so my if statement comes up true? Id like to just match the beginning of string x to the contents of the array while ignoring the case and the following characters. I thought  to do this but I could be mistaken. I'm a bit of a newbie with regex.


Equivalent Condition for Being a Division Ring

Let $R$ be a ring with at least two elements and suppose that for any non-zero $a\in R$ there exists a unique $b\in R$ such that $aba = a$. Prove that $R$ is a division ring.  Given the assumptions and $a\in R$ we have $aba = a$, then $aba - a = 0 = a(ba - 1) = (ab-1)a$. If $ab-1$ and $ba-1$ are both not zero divisors, then $ab - 1 = 0$ and $ba - 1 = 0$ so that $ab = ba = 1$ and $b = a^{-1}$. I'm not sure what to do in the case when there are zero divisors. I've seen that in general, division rings don't have zero divisors, but I don't know a priori that $R$ is a division ring (as that's what I'm trying to prove haha).


Book: World covered in trees that are miles high

The world is covered in trees that are miles high. A resident of the planet climbs to the highest tree top to find a crashed ship. He has never been to that level before. This leads him on a journey to the lowest depths which no one has seen before, which is full of strange creatures. I think the cover showed the resident climbing down into the dark lower areas with tree roots and glowing creatures.  It was a very small book, and a very quick read. I stayed up all night to finish it. I borrowed it from a friend who was into Dune in about 1986.


Windows 7 command line: request MS Security update

I am trying to eliminate the SMBv1 vulnerability from a Windows 7 box.  I do keep the machine patched with Windows updates, however, I would like to install the proper update because I was unable to confirm it was installed.  One can query which MS updates have been applied with:  wmic qfe   Results were piped into a file and a search for update 4013389 was negative.  If this is not the correct technique to determine if the vulnerability patched please state this.   If it is a valid technique, is there a command to specifically to retrieve and install security update 4013389?


What is the caster level for the spells granted by Spell Sniper?

Cantrips generally get more powerful as you progress in your spellcasting class.  The Spell Sniper feat allows casting a cantrip.  If you pick a Spell Sniper cantrip from another class will the damage increase? E.g.   A level 6 Fighter takes the Spell Sniper feat and chooses Produce Flame. Would the damage be 1d8 or 2d8?


Find equation of two tangent lines to ellipse $x^2+4y^2=36$ drawn from $(12,3)$

Find the equation of the two tangent lines to the ellipse $x^2+4y^2=36$ that pass through the point $(12,3)$.   I tried using implicit differentiation, and then I didn't know where to go from there.


How to generate randomly colors that is easily recognizable from each other?

I want to generate random colors for a graphic chart but what I tried is not recognizable and generated color are similar to each other generally. Is it possible to create such colors?  My method:      public Color[] GenerateColors(int n)     {         Color[] colors = new Color[n];         for (int i = 0; i < n; i++)         {             int R = rnd.Next(0, 250);             int G = rnd.Next(0, 250);             int B = rnd.Next(0, 250);              Color color = Color.FromArgb(R, G, B);             colors[i] = color;         }         return colors;     }


Let functions $ f: A \to B$ and $g: B \to A$, suppose that $ g \circ f = i_A$. Prove that if $f$ is onto, then $g$ is one-to-one

For nonempty sets $A$ and $B$ and functions $ f: A \to B$ and $g: B \to A$, suppose that $ g \circ f = i_A$. Prove that if $f$ is onto, then $g$ is $1-1$.   Here is what I started, I don't think it's correct.   Suppose $f$ is onto  i.e for each element $b \in B$ there is an element of $a\in A$, $f(a)=b$. (definition of onto).   Let $y,\ z$ be any two elements of $B$.Then $y=f(a)$ and $z=f(b)$ for some $a,b \in A$.   If $g(y)=g(z)$, then $g(f(a)) = g(f(b))$,which implies that $a=b$, so $f(a)=f(b)$, so $y=z$.   Thus, whenever $g$ maps $y$ and $z$ to the same element in $A$, $y=z$, so $g$ is one-to-one.   PS: New to proof writing, any constructive criticism is much appreciated.


Public and temporary files error in my "Status Report"

I just upgraded to 7.25 from 7.19, and now in my Status Report I have a red X on my "Public Files" and "Temporary Files".     See  for information about the   recommended .htaccess file which should be added to the   sites/default/files directory to help protect against arbitrary code   execution.   I go to the address above, but I don't have any user friendly explanation of what to do to fix this. Thanks in advance.  Update: (1/8/14)  The answer below fixes the Public files problem 100%.  It does not fix the Temp files. To fix temp files, I go to admin/config/media/file-system and change the path from /tmp to ../tmp  I will update this if this is fixed in a newer version of drupal, or if there is another fix available. I'm not sure if the ../tmp is the correct solution, but it works.


How to remove page numbers behind acronyms?

I would like to remove the page numbers behind my acronyms. Is there a way to do this?     I create my acronyms the following way:  \makenoidxglossaries \setacronymstyle{long-short}  ...  \begin{document}      ...      \printnoidxglossary[type=acronym]


Question while reading Learning PHP, MySQL & JavaScript by Robin Nixon RE: Sanitizing Input PHP

I'm currently reading and learning PHP from a book that offers this as the proper way to sanitize input from forms:  function mysql_entities_fix_string($connection, $string)  { return htmlentities(mysql_fix_string($connection, $string)); }  function mysql_fix_string($connection, $string) {   if (get_magic_quotes_gpc()) $string = stripslashes($string);   return $connection->real_escape_string($string); }   Which is great, except I know that get_magic_quotes_gpc() is deprecated in the current version of PHP. From looking at a few different resources I learned that instead of using get_magic_quotes_gpc() I should just use an sql prepared statement. That confuses me though because I would presume that we still need to do some functional cleaning of the string.   Unless I'm wrong(it happens, I'm relatively new at this) this is a big no-no, regardless of the prepared statement:  $username = $_POST['username']; $stmt = $conn->prepare("SELECT password FROM users WHERE username=?"); $stmt->bind_param("s", $username"); $stmt->execute(); ...   but if that's the case, is this an acceptable sanitation process:  function get_post($conn, $var) { return $conn->real_escape_string($_POST[$var]); } ... $username = get_post($conn, 'username'); $stmt = $conn->prepare("SELECT password FROM users WHERE username=?"); $stmt->bind_param("s", $username); $stmt->execute(); ...   or do I need to add some other escaping function on top of it?


Blank screen after opening a notification in iOS8

In my device (iPhone 6, iOS v8.0.2, app v1.2.0.138) whenever I receive a notification and I tap it in order to open the application, the screen that is displayed is blank.  I need to quit the app, re-open it, go to my 'inbox' and tap the last notification in order to see the question screen, focused on the comment.  This is not new (for me) in v1.2.0.138; it has been happening for at least the last ~7 updates that I've done.


Is it possible to get multiple Fanatic/Enthusiast badges?

Can I get multiple Fanatic/Enthusiast badges?  I don't really care if I can or not, I'm just curious... after all we are talking about a colored dot on a computer screen :)


The sentence I was writing is: "I thought tubes and bike ... synonymous" is it: "are" or "were"? Thought process is, I am reporting what I thought at the time, which is that they are synonymous, but as a native English speaker it sounds wrong. edit: I think I answered my question in the first sentence but I'll wait for an official answer...


i Have a Computer with Old Configuration and want to install ubuntu

I have a computer with this configuration  Processor: Intel(R) Core(TM)2 CPU 6300@ 1.86GHz  RAM: 2GB Hard disk : 500GB  Please suggest me which ubuntu is working good in my computer i have ubuntu 16.4 with 32bits and 64bits  Please tell me which bit is better for my computer.  Thanks


Python 2.7: List declaration, difference between initialization using "*" operator and initialization in a for loop

I want to declare a list in python 2.7 and initialize it with 10 lists, each containing 10 elements, all initialized to 0. So its a list which contains 10 lists. I do it as shown below.  l = [[0] * 10] * 10   After doing this, when I try to assign a value to any element within any of the 10 lists, the assignment is reflected across all other lists. i.e  l[0][0] = 1 print l[0] --> 1, 0, 0, 0, 0, 0, 0, 0, 0, 0 print l[1] --> 1, 0, 0, 0, 0, 0, 0, 0, 0, 0   As seen above, the assignment of 1 to the first element of list at index 0 is reflected in the list at index 1 too. This is case for all the other 10 lists.  However, if I do the below  for i in range(10):     l.append([0] * 10)   This does not happen. I think this has got to do with the "*" operator, but I do not know the exact reason. I would appreciate it if anybody can help me understand this behavior.


What is the term for using an adjective in the place of a noun?  It seems to come up a lot in fantasy fiction, generally used as a proper noun to describe a group ("the Twisted", "the Hunted"), but it also comes up in everyday use ("the mentally ill").


Windows 10 Ubuntu Bash Shell: How Do I Mount Other Windows Drives?

I'm using Windows 10's Ubuntu Bash shell. It maps the C drive fine as /mnt/c.  I have other local physical hard drives, mounted in Windows as E: and F:  How do I tell Bash to mount these drives too (ideally automatically at /mnt/e and /mnt/f, but manual mounting is fine)? "sudo fdisk -l" doesn't seem to work (cannot open /proc/partitions), so I'm not sure how to find their names, otherwise I'd just use a regular mount command.


Where does Time Machine store its settings?

I'm looking for the file that contains all the Time Machine exclusions entered in its Options dialogue. I know that (some of?) the scheduling related settings are stored in the com.apple.backupd-*.plist files at /System/Library/LaunchDaemons but I haven't been able to find the exclusions.


Sometimes, right in the middle of a project, when I'm trying to zoom in on an object, the zoom just halts at a certain point as if I'm reached some kind of limit, even though I earlier was able to go much closer. What is the deal with this and how can I solve it?


$\lim_{x \rightarrow 0}\left(\frac{1}{\sin^2(x)} -\frac{1}{x^2}\right)$ and the problem of $\infty-\infty$

I'm trying to calculate  $$\lim_{x \rightarrow 0}\left(\frac{1}{\sin^2(x)} -\frac{1}{x^2}\right)$$  but I'm having the problem of getting   $$\infty - \infty$$  which I read to be indeterminate.  I cannot figure out how could I manipulate the above to get rid of the indeterminacy.


Shellshock - not vulnerable with bash version 4.1?

We have several Amazon servers. It has bash version 4.1.2.  that all bash versions up to 4.3 are unsafe. When I do this test...  env x='() { :;}; echo vulnerable' bash -c 'echo hello'   ... it returns: hello, and even though  that I should get an error back: bash: warning: x: ignoring function definition attempt bash....., I guess the simple "hello" is good enough. Still I'm in doubt.   Can you explain what info I can trust?


Number Theory: How to prove this statement (Lucas's theorem?)

Assume $1\le k \le p-1$ and $p$ is a prime number.      Prove:      a) ${p \choose k} \equiv 0$ (mod p)       b) ${p-1 \choose k} \equiv (-1)^k $ (mod p)   Probably the statement can be proved using Lucas's theorem. But I'm not sure about the right way to use if so. So any hints how to prove the statement?


What makes a Decimal datatype higher precision for decimal numbers than the datatype Double?

Why can a decimal number always be accurately represented in a Decimal datatype whereas in a Double it cannot. Does a Decimal datatype have more bits in the Mantissa? Is a Decimal datatype normalised?


I’d like to prove:     Let $G$ be a group and $m,n$ two relatively prime numbers. If $x^my^m=y^mx^m$ and $x^ny^n=y^nx^n$ for all $x,y\in G$, then $G$ is abelian.   Thanks for help in advance.


Minimum Uncertainty Wavefunction derivation

Can anyone point me to a reference (preferably either something online or something a small liberal arts school would be likely to have in its library) that goes through a derivation of the minimum uncertainty wavefunction in more detail than in the Griffiths?  Edit I've moved the second part of my original question to a separate post:


After Javascript function ends, its internal variables are still accessible by closure?

function create(){     var ret=new Array();     for(var i=0;i<10;++i){         ret[i]=function(){return i;};     }     return ret; }; var a1=create(); console.log(a1[2]());   The code above will print "10".  I know the inside "create()", the variable "i" in for loop, has execution context of "create()", so the 10 elements of "ret" are all functions that will return "10". So inside "create()", ret2 will return 10. No problem.  But outside "create()", there's no more "i". If I try "console.log(i)" it will give exception like below:  console.log(i);             ^  ReferenceError: i is not defined   Why, closure can still visit "i" as a reference, while outside blocks cannot? The life cycle of "i" is ended!


What is the maximum size of an HTML file that Google will crawl through?

I have a 10MB HTML file. Will Google crawl through the entire file, or does it only look at the first X MB?


New navigation doesn't appear to alert of question changes when watching a tag

I am watching the  tag on Stack Overflow. My filter looks like this:    I do not receive notification of new questions. Previously I'd get notifications like this:    This notification does work when watching the  page of Meta.   Are notifications only active for a certain set of filter options? If so, what are they? If not, can we get them back when watching pages other than the main page?


UK Immigration and EU and Non EU Passport Couple

We are a same sex married couple, my husband has a Singaporean passport and I have an EU/UK passport... Can he join me in the EU line at immigration when we visit in September ? The last time we visited the UK it took 4 hours for him to go through and we do not want the same thing to happen again


Java map with values limited by key's type parameter

Is there a way in Java to have a map where the type parameter of a value is tied to the type parameter of a key? What I want to write is something like the following:  public class Foo {     // This declaration won't compile - what should it be?     private static Map<Class<T>, T> defaultValues;      // These two methods are just fine     public static <T> void setDefaultValue(Class<T> clazz, T value) {         defaultValues.put(clazz, value);     }      public static <T> T getDefaultValue(Class<T> clazz) {         return defaultValues.get(clazz);     } }   That is, I can store any default value against a Class object, provided the value's type matches that of the Class object. I don't see why this shouldn't be allowed since I can ensure when setting/getting values that the types are correct.  EDIT: Thanks to cletus for his answer. I don't actually need the type parameters on the map itself since I can ensure consistency in the methods which get/set values, even if it means using some slightly ugly casts.


I have a table and I want to extract the row in reverse order of columns in shell script

The table looks like this:  1|Hunk|First|London 2|Hero|Second|London 3|Will|First|Pow 4|Thomas|Second|Pow 5|Venus|First|Berlin   I want to print the output as:  Berlin|First|venus|5   i want to print only the final line.


Chrome Browser open bookmarks in a new tab

Is there a way to set Chrome to open bookmarks into new tabs instead of loading into the window I am working in? I just lost an assignment because I was typing, and I opened another bookmark to research another article and when the bookmark opened it deleted my progress. I clocked "back" and my information was gone! I had to start my research paper over! I know. I should have written in Word and then pasted... Consider THAT a lesson learned. Is there an extension to get around this default?


Camera direction and `view_frame()` - How to calculate the direction vectors that describe the corners of the camera frame

The camera origin is:  scene = bpy.data.scenes["Scene"] camera_origin = scene.camera.location   The camera direction is calculated with  camera_direction = scene.camera.matrix_world.to_quaternion() @ Vector((0.0,0.0,-1.0))   The view_frame i.e. camera_corners are:  camera_corners = scene.camera.data.view_frame(scene=scene)  # camera corners   At this point camera_corners contains 4 vectors.  Question: From the camera_origin, how do I calculate the direction of the view_frame/camera_corners similar to the camera_direction?


Does the Sorting Hat speak only to the person wearing it?

My question is straightforward. Does the Sorting Hat speak only to the person wearing it, or to the Great Hall? Did all of the students hear it say,      "Not Slytherin, eh?"   when Harry used it?


There are many lengths in LaTeX. For instance, \enskip, \enspace, \quad, \parskip, \smallskip, ...  Some of them are mostly used for vertical spacing, some others are mostly used for horizontal spacing, and perhaps some of them are used in both cases. I wonder whether there is a list that indicates the meaning and intended use of each length in LaTeX.  By "intended use" I mean not only whether the length is vertical or horizontal, but in which circumstances it is a good practice to use that specific length.


This is a setup I have on my site photo directory pages:    On the desktop site, Users can choose to select one from a maximum of 100, 200 or 500 photo thumbnails per page.   I feel now at the rate technology is moving and because the pages load very fast, I'm tempted to eliminate the choices and allow users to select one from up to 500 photo thumbnails per page.  While this pleases a large number of guests on the site, I'm not sure how much it pleases Google because as of the first decade of the year 2000, they indicated that websites should have no more than 100 links per page and the 500 thumbnails means 500 links. I think they also indicated back then that a page that exceeded 100kb won't get processed.  How do all the major search engines respond to 500 links per page today? would they still happily accept it or would that exceed their internal link or page size limits?


DELL INSPIRON 1100 15" LAPTOP with no os

How do i  install ubuntu on a DELL INSPIRON 1100 15" LAPTOP with no Preloaded OS?


I am a student of class 9. When I was going through magnetism and read that an earth is a magnet I got some doubts. My question is: is earth really a magnet? Doesn anyone have any proof that earth is a magnet? Is there a magnetic core at the center of the earth? Has anyone reached the core of the earth?


I'm running Windows 7 Pro 64bit on a Dell Precision M4400 laptop and whenever I boot it it takes ages ( >5mins average).  This doesn't seem right as it's a fairly beasty piece of kit, It get's a 5.9 on the WEI with the lowest score being the Hard disk.  Core 2 Duo P8600 @ 2.4GHz 4GB RAM 150GB 7200RPM Hard Disk with 16MB buffer    How can I tell which part(s) of the boot sequence it taking so long so I might disable / avert the issue and improve the boot time?  The machine is part of a Windows Active Directory and I regularly use it outside the corporate network. Neither situation improves performance.  In my user profile on the AD have a login script which mounts 12 network drives using the following commands  net use I: /delete net use I: \\machine\share /persistent:no   In the startup folder on the start menu I have Sophos and Dropbox. I do have a bunch of services as I'm a developer. There are 2 versions of SQL server, Microsoft Azure developer tools and a few other bits and pieces. Ideally I'd like not to have to disable these; I'd like to see exactly how long each item is taking during boot and make educated decisions from there.


How can Cho Chang be afraid to fail her O.W.L.s if she's a year ahead?

In numerous Harry Potter books, Cho Chang is described as a year older than Harry. And, in OotP, Harry and the other 5th years are taking their O.W.L.s. Then why did Hermione say in the movie, "And she's so frightened that she'll fail her O.W.L.s because she's so worried about everything else"? She should have completed her O.W.L.s and gotten her results!


Galois group of $X^6-2$ over $\mathbb{Q}$

Hello I would like to calculate all subfields of the field in which $f$ splits in linear factors (I just don't know the right english word for this field :) )  $f:=X^6-2$ is irreducible with Eisenstein criterion. Define $a:=2^\frac{1}{6}$ and $\xi:=\exp(\frac{2\pi i}{6})$. Then $$X^6-2=(X-a)\cdot\ldots\cdot(X-a\xi^5).$$  Now $[\mathbb{Q}(a):\mathbb{Q}]=6$, since $f$ is the minimal polynomial of $a$.  and $[\mathbb{Q}(a)(\xi):\mathbb{Q}(a)]=2$, since $a\in\mathbb{R}$, so $X^2-X+1$ is still the minimal polynomial of $\xi$.  Therefore $[\mathbb{Q}(a,\xi):\mathbb{Q}]=12=ord(Gal(f,\mathbb{Q}))$, since $K:=\mathbb{Q}(a,\xi)$ is the field in which $f$ splits in linear factors.  Now calculate the automorphisms:  First there are automorphisms:  $$\phi:\mathbb{Q}(a)\rightarrow\mathbb{Q}(\xi a), \phi|_\mathbb{Q}=id_\mathbb{Q}, \phi(a)=\xi a$$  and the extension  $$\varphi:K\rightarrow K, \varphi|_\mathbb{Q}=id_\mathbb{Q}, \varphi(a)=\xi a, \varphi(\xi)=\xi.$$  There is also an extension with $\overline{\varphi}(\xi)=\overline{\xi}$, since $\xi$ and $\overline{\xi}$ are roots of the minimal polynomial of $X^2-X+1$, but one can get this by using the product of $\varphi$ and the following automorphism  $$\psi:K=\mathbb{Q}(a)(\xi)\rightarrow\mathbb{Q}(a)(\overline{\xi}),\psi|_\mathbb{Q}=id_\mathbb{Q}, \psi(a)=a, \psi(\xi)=\overline{\xi},$$  since $X^2-X+1$ is still the minimalpolynomial of $\xi$ and $\overline{\xi}$ over $\mathbb{Q}(a)$.  So $G:=Gal(f,\mathbb{Q})=\{id,\varphi,\ldots,\varphi^5,\psi,\psi\varphi,\ldots,\psi\varphi^5\}$.  So one gets the subgroups of $G$ of order $2,3,4$ or $6$.  But now I am having problems to calculate the subfield. For example for $\psi\varphi^3$ one has:  $$[K:K^{<\psi\varphi^3>}]=ord(<\psi\varphi^3>)=2$$ and $$[K^{<\psi\varphi^3>}:\mathbb{Q}]=6$$.  ($K^{<\psi\varphi^3>}$ denotes the usual fixgroup) Now the usual approach I know would be to find an linear combination $c$ of elements of the fixgroup and show by using the degree formula that $K^{<\psi\varphi^3>}=\mathbb{Q}(c)$ but I cannot find such $c$. So what is the usual approach to solve this?  Thanks for your help!


I am currently working on update 3 to my app, I wanted to add the ability to shake the iPhone and have it go to a random cell in my UITableView. I know Apple recommends against doing this kind of gesture, but I want to add it or at least try it out.   Any help would be appreciated!


I have a bookmark folder labeled "Stack Exchanges" for the trilogy plus all of the Area 51 exchanges that are either in public beta or private beta that I'm interested in - a total of 10 sites. Every morning, before work, I sit down, open up all of them in tabs, and read through the first page or two of questions and see if there's any that I can answer. But this morning, I got a notice that my IP address had made too many requests. A quick refresh of the page loaded the site.  What's going on here? As more exchanges open, this list is going to grow to more than 10. I really don't want to cause problems, but I also don't want to trigger the next level of this error. If I routinely open 10-15 exchanges every morning simultaneously, is this going to be a problem?


I have no idea why is it grainy on the left side. But on the right side it is ok. I added additional lights on the left side but the problem is still there. Any tips? I am struggling about lighting the rooms.


Update: Maybe we can convert this question into an FAQ-style question? I didn't find a place where the style and type of questions for meta are described (as it is the case e.g. in the  or in ).     Original question:  Can someone please explain what happened to the discussion threads about the new/removed "recent" feature?  For the ones not knowing what I am talking about you will still find  in Google's cache:        Should this topic no longer be discussed? How is the discussion of UI changes generally considered? Which topics can be freely discussed?   So far I thought that meta was the place to discuss and vote about all things related to StackOverflow and the other SE sites. However, it seems that there are some hidden rules what can/should be discussed and what shouldn't?  Sorry, but I am highly confused and be glad if someone please could shed some light on the general culture of discussions here.


Binding single key (such as 'F1') to multiple keys (such as 'Ctrl+C') in Gnome

I know how to map a single key to a command using the gconf settings. I also know how to map a single key to another key (F1 -> ctrl) using Xmodmap. My question is how can I map a single key such as F1 to a multi-key operation such at ctrl+c. I am basically trying to set up a single key to simulate copy. I can think of two ways to possibly do this:   Map single key to multiple keys so that when the single key is pressed it is essentially pressing ctrl+c. Use gconf settings to execute the copy “command” upon the single key press. I am not sure if there is a “command” to copy text.


Time loop or time travel in an aeroplane, where the main character disappears to save the others

When: I recall seeing this when I was young so could have been early to mid 1990s. Setting: It is either based primarily in an aeroplane around the passengers and may also involve the airport but those details are a bit hazy. From what I can remember it wasn't futuristic but set at the current time. Details: the only real clear details I can recall are at the end the passengers need to go to sleep in their original positions on the plane to get out of their predicament (time loop?), however one passenger needs to stay awake in the cockpit and ends up disappearing once all the others wake up. I believe the problem facing the characters was either time travel or time loop related.


Prove the inequality: $(y+z)*x^4+(x+z)*y^4+(x+y)*z^4\le((x+y+z)^5)/12$ for positive reals.

The inequality is homogeneous, but I am not sure if that helps. Also, I was thinking about considering a concave function and apply Jensen or Karamata on LHS.


How to change the volume name of a FAT32 filesystem?

I know I can set the volume name when I format the partition with the -n option of mkfs.vfat. But how to just change the name without formatting?  I especially want to be able to use lower and uppercase letters. In worst case, I can use a windows tool, but windows by default transforms all letters to uppercase (but works fine with lowercase letters in volumes created with mkfs.vfat).


How to solve these two problems with Beamer?

This is the two problems I'm trying to solve: 1. A title, which I don't want here, appears in my TOC. How to remove it? 2. The command \cite{} does not work: any of my references appear in the dedicated section. I request your help. This is my MWE: \documentclass{beamer}     \usetheme{default}     \usepackage{soul}     \usepackage{framed,color}     %\definecolor{shadecolor}{rgb}{1.0, 0.8, 0.3}     \definecolor{shadecolor}{rgb}{0.74, 0.83, 0.9}     %\definecolor{shadecolor}{rgb}{0.95, 0.83, 0.86}     \useoutertheme[subsection=false]{smoothbars}     \usepackage[frenchb]{babel}     \usepackage[T1]{fontenc}     \usepackage[utf8]{inputenc}     \usepackage{helvet}     %%%%%%%%%%%%%%%%%paragraphes justifiés%%%%%     \usepackage{ragged2e}     \apptocmd{\frame}{}{\justifying}{} % Allow optional arguments after frame.     %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%     \setbeamertemplate{caption}[numbered]     \usepackage[labelsep=period]{caption}     %%%%%%%%%%%%%%%%%%%%%footline%%%%%%%%%%%%     \addtobeamertemplate{footnote}{}{\vspace{2ex}}     \setbeamertemplate{footline}[text line]{%       \parbox{\linewidth}{\vspace*{-8pt}Title\hfill\insertshortsubtitle\hfill\strut\insertframenumber/\inserttotalframenumber}}       %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%     \setbeamertemplate{navigation symbols}{}     %%%%%%%%%%%%%%%%%NUMÉROTATION TOC%%%%%%%%     \setbeamertemplate{section in toc}{\hspace*{1em}\inserttocsectionnumber.~\inserttocsection\par}     \setbeamertemplate{subsection in toc}{\hspace*{2em}\inserttocsectionnumber.\inserttocsubsectionnumber.~\inserttocsubsection\par}     %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%     %\useinnertheme{circles}     \makeatletter     \patchcmd{\beamer@sectionintoc}{\vskip1.5em}{\vskip0.5em}{}{}     \makeatother     \usepackage{graphicx}     \usepackage{hyperref}     %\usepackage{apacite}     %%%%%%%%%%%%%%%%PLAN%%%%%%%%%%%%%%%%%%%%     \AtBeginSubsection[]     {     \begin{frame}<beamer>     \frametitle{Plan}     \tableofcontents[       currentsection,       sectionstyle=show/show,       subsectionstyle=show/shaded/hide     ]     \end{frame}     }     %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%     \title{\textbf{Title}}     \subtitle[]{Colloque}     \author{My name}          \date{}               \begin{filecontents}{\jobname.bib}         @Book{Anzieu1993,     author = {Anzieu, Didier and Haag, Geneviève and Tisseron, Serge and Lavallée, Guy and Boubli, Myriam and Lassègue, Jean},      title = {Les contenants de pensée},      volume = {},      pages = {},      editor = {},      publisher = {Dunod},      address = {Paris},      year = {1993},      abstract = {},      keywords = {contenance; pensée; penser},     }          @Book{Anzieu1994,     author = {Anzieu, Didier},      title = {Le Penser. Du Moi-peau au Moi-pensant},      volume = {},      pages = {},      editor = {},      publisher = {Dunod},      address = {Paris},      year = {1994},      abstract = {},      keywords = {},     }          \end{filecontents}     \usepackage[]{apacite}               \begin{document}     \maketitle          \begin{frame}{\normalsize{Déroulement}}     \tableofcontents         \end{frame}               \section{Introduction}     \begin{frame}         \cite{Anzieu1993}                      \cite{Anzieu1994}     \end{frame}               \section{Développement}     \begin{frame}              \end{frame}                    \section{Conclusion}     \begin{frame}              \end{frame}          \begin{frame}     \bibliographystyle{apacite}     %\renewcommand{\bibliographytypesize}{\tiny}     \bibliography{\jobname}     \end{frame}     \end{document}


is there anyway to know if your supposedly fully dedicated server is really a virtually resource-shared machine?

sometimes I feel my server not responding as smoothly as I would expect (i have a Intel(R) Xeon(TM) CPU 2.80GHz Quad Core), given that for example, the 'top' commands reports a low load < 0.5, CPU are almost completely idle ...  I maybe have internet connectivity issues, so I don't really know if it's me or if it's the server itself.  Is there anykind of benchmarking script (or something analogous) I could run and see the actual performance of the server ?


Is there a harder way to prove that if an integral curve's derivative vanishes then the curve is constant?

In the context of differential geometry, we have a smooth vector field $X$ and an integral curve of $X$ called $\gamma$ such that $\exists\ t_0 \in \mathbb{R}$ with $\gamma'(t_0) = 0$. The exercise asks to prove that under those conditions, $\gamma$ is constant.  Invoking the Picard-Lindelöf theorem of existence and uniqueness of differential equations that can easily be proved.  I was wondering if there was another, more indirect and "by hand" way.  Thanks!  PS: I don't think this is a duplicate question, as it's not the same to have an integral curve into an arbitrary manifold as it is to have one to $\mathbb{R^n}$. Of course, given Anthony's answer, I can see that this specific question can be answered by reducing it to the other case. But there could also be another answer that takes a different approach.


Somewhat of a noob here. How might one go about creating this salt flat material in blender? I'm assuming you'd start with the voronoi texture but that's as far as I've gotten. Thanks!


Ubuntu ufw Lightsail not opening port 80

I have port 80 open from AWS lightsail console, and ufw status shows that port 80 should be open.   And yet, I cannot curl into port 80 nor can I telnet or ping or launch a server.   I've checked iptables and I can confirm that the rules from ufw apply there. However, when I run lsof -i -P -n it does not show any open port 80. Is there another firewall that is blocking 80?   Any help to troubleshoot this would be greatly appreciated!  Below is the result of ufw status  5432/tcp                   ALLOW IN    Anywhere                   22/tcp                     ALLOW IN    Anywhere                   80                         ALLOW IN    Anywhere                   80/tcp                     ALLOW IN    Anywhere                   443/tcp                    ALLOW IN    Anywhere                   5432/tcp (v6)              ALLOW IN    Anywhere (v6)              22/tcp (v6)                ALLOW IN    Anywhere (v6)              80 (v6)                    ALLOW IN    Anywhere (v6)              80/tcp (v6)                ALLOW IN    Anywhere (v6)              443/tcp (v6)               ALLOW IN    Anywhere (v6)   And when I run sudo lsof -i -P -n | grep :80 I get nothing returned.


Integer $x$ for which $x^4+x^3+x^2+x+1$ is perfect square.

Integer values of $x$ for which $\bf{x^4+x^3+x^2+x+1}$ is a Perfect Square.  $\underline{\bf{My\; Try}}$:: Let $\bf{x^4+x^3+x^2+x+1 = k^2}$, where $k\in \mathbb{Z}$  $4x^4+4x^3+4x^2+4x+1 = 4k^2 = (2k)^2$  Now How can I proceed after that  Help Required,  Thanks


How to remove Volume slider from Control Center

When I swipe my home screen from bottom to top, I see below screen :  However I want to customise this screen like I want to remove the volume icon from this screen. Is there any way to achieve this. Thanks for any pointer.


Custom JQuery script in page template won't work

i created custom page template where i inserted followed JQuery script.  <script type="text/javascript"> $( document ).ready(function() { console.log( "ready!" ); }); </script>   But it wont work. I get Object expected error.  Jquery is inserted on page header so it should be loaded.  Why is that not working?


I'm trying to remove all tags other than italics, bold, or span tags, and can't seem to get it to work.  Currently, I have:   /[^i|b|span]/g   I understand that [] is range, and that [span] will match s,p,a,n, rather than the whole word.  So my question is how to state: not: "tag1" or "tag2"?  EDIT I found the 'duplicate' question earlier, and it did not solve my issue.


QGIS 2.16 - Missing menu Vector > Research Tools > Vector Grid

I just upgraded to QGIS 2.16 on Xubuntu Ubuntu 14.04.4 and I'm missing the "Research Tools" under the Vector menu. I'm specifically looking for the Vector Grid option.  I didn't notice any error messages during the startup, or the error logs. Would anyone know how to resolve this?


What is the correct choice for the sentence below?

The sentence is  "I'd like a cake and a cup of tea, please." Waiter: "............" A. Here it is. B. Here they are.  what is the correct answer to put in the space for the waiter? Should it be singular or plural?


Are ultra-cold neutrinos an option for cold dark matter?

Nobody hass seen cold dark matter. Are ultra-cold (non-relativistic) neutrinos, below 1 fK (femtokelvin), an option for dark matter? This is a question about normal neutrinos - electron neutrinos and muon neutrinos and tau neutrinos - and not any additional, invented neutrino types. This is a question about neutrinos that are not in the cosmic neutrino background, which have a temperature of 1.95K. The question is about cosmological dark matter, not about galactic dark matter. Their density could be large enough to produce the observed cosmological dark matter density. Due to their low temperature and low kinetic energy they would be undetectable. They would be continuously emitted by the cosmological horizon in the same way as black hole radiation is continuously emitted by a black hole. Alternatively, they would arise automatically throughout the universe, whenever space grows in size. Why is this not possible? Or why is it possible? -- Given that the answers below imply that ultra-cold neutrinos cannot be dense enough because of their fermion character, could fermion condensation (via Cooper pairs, as in superconductors) solve the problem?


How much Elven ancestry does Aragorn have?

I know Aragorn is descended from Elros the half-Elf, and from what I've been able to find, there are somewhere between 64 and 99 generations separating Elros from Aragorn.  I can't do the math, I don't know how many generations actually separate them, and I don't know if Aragorn had any other Elves in his family tree.    So how much Elven blood flows through Aragorn's veins?  What percentage of his total DNA comes from Elves?


I have been building out an app and to save important time information I have been using System.currentTimeMillis() to get the timestamps in ms.  All my algorithms use this ms data and dates are saved with this ms data.  Also duration of cache is determined and object dates are formatted from this millisecond timestamp. I am unsure if this is a good practice though.  Is it better to use Calendar.getinstace() I have gathered that currentTimeMillis() could be a bad practice as it can lead to inconsistencies in the time data but I don't understand why this is.


I've an object as below:   default = {     name: "",     details: {         age: "",         place: ""         country: ""     },     contact: {         email: null,         phone: null     } }   Now, I've another object as:   data = {     name: "Abc",     details: {         age: "27,     },     contact: {         email: "abc@xyz.com"     } }   Want to achieve:   result = {     name: "Abc",     details: {         age: 27,         place: ""         country: ""     },     contact: {         email: "abc@xyz.com",         phone: null     } }   Now, I want to get the values from data and put it in default. Currently I'm checking if the key exists, then assign value, else keep default. But it's a long process. Is there a JS helper function or something that I can use for this?   Object.assign(default, data) is only copying the property values and not going deep.


Using "which" instead of "that", one out of two : could a reader see this?

I am trying to write a scientific paper in English, with a colleague, but we can not agree on the usage of "which" with respect to "that": he systematically used "which" in place of "that"! When reading the paper, I admit it is understandable, but at the same time the repetition seems strange (while "that" sounds OK to me).   What is the difference that makes me uncomfortable with "which"? What is the underlying intention of an author when he uses "which"?  As an example:     We present a model which shows...    (correct but "that" sounds simpler for me, and better).  Am I wrong? Any idea? And what if I suddenly decide to apply "which" in one sentence out of two ? Could a reader see this ?


How do I cross validate daily time series data

I want to cross validate various models to understand which one performs best. I have been referring to Rob J Hyndman's post  here     But I am a little lost as to how to use it on daily data.   my daily time series data starts at 2015-01-01 and ends at 2017-03-31.   Specific questions include:   What should k be in my case?  In mae1 <- mae2 <- mae3 <- matrix(NA,n-k-12,12) instead of 12 will I use 365? In for(i in 1:(n-k-12)) will I use 365?    I have a very high level understanding of the code and I believe that is another reason why I cannot translate this to a daily usecase. Any help in clarifying the problem would be greatly appreciated!


What is a good, simple way to compute ISO 8601 week number?

Suppose I have a date, i.e. year, month and day, as integers. What's a good (correct), concise and fairly readable algorithm for computing the   of the week the given date falls into? I have come across some truly horrendous code that makes me think surely there must be a better way.  I'm looking to do this in Java but psuedocode for any kind of object-oriented language is fine.


amsthm not working correctly with unicode-math

I'm trying to use unicode-math with amsthm. I'm using the following code:  \documentclass{article}  \usepackage{amsthm} \usepackage[math-style=TeX]{unicode-math}  \newtheorem{question}{Question}  \begin{document}     \begin{question}         My question     \end{question} \end{document}   The output produced looks like this:  ? My question   Any idea how to fix this? Thanks!


Does it matter if IV is used as the first block of data before the encryption and then some fixed value is used for the actual IV?

Usually the IV for the crypto operations is chosen randomly and is sent together with the encrypted data [at the first block]. For decryption, the IV is first extracted from data and set separately in the crypto components (functions or HW peripherals) and then feed the crypto operation with data.    The other case is to set the IV always to fixed value but the first block of data is chosen randomly. In this case after decryption the first block will be just ignored!    In terms of result, I understand that the encrypted text are different but in terms of security does anybody know if it matters or not?


I use the highlight mode in vim to copy a few characters.  I then want to paste more than once.  My current technique does not work well.  Sample text: Linux Solaris Irix HP-UX  Suppose I want to copy the word Linux, then paste over Solaris and Irix.   Place cursor at L in Linux Command v (for visual hilite), then e (for end-of-word), then y (for yank/copy) Now Linux is on my "vim clipboard" Move cursor to S in Solaris (first instance) Command v (for visual hilite), then e (for end-of-word), then p (for paste) Text is now: Linux Linux Irix HP-UX, but now Solaris is on my "vim clipboard" Move cursor to I in Irix (second instance) Command v (for visual hilite), then e (for end-of-word), then p (for paste) Text is now: Linux Linux Solaris HP-UX which is not what I expected.   I resort to using highlite/paste with the mouse (via X Terminal).  Surely, I can do this better.  How?


A rearrangement of an absolutely convergent complex series is also absolutely convergent

I just completed the following proof.  Is it valid?   Let $\sum_{k=1}^{\infty} a_k$ be an arbitrary convergent series that also converges absolutely.  Then $\sum_{k=1}^{\infty} a_k \in \mathbb{C}$ and $\sum_{k=1}^{\infty} |a_k| \in \mathbb{R}$. Let $\{b_k\}$ denote a rearrangement of the $\{a_k\}$.  That is, we have that $\{a_k\} = \{b_k\}$ yet $a_i = b_i$ needn't hold. We will first show that $\sum_{k=1}^{\infty} b_k$ converges absolutely (immediately implying it converges non-absolutely).  We will use the Cauchy Criterion on the partial sums of $\sum_{k=1}^{\infty} |b_k|$ to demonstrate this. First let $\epsilon > 0$. Consider that since $\sum_{k=1}^{\infty} |a_k| \in \mathbb{R}$, we have that $\exists N_1 \in \mathbb{N}$ s.t. for all $N_1 < m < n$ we have   $$ \sum_{k=m}^n |a_k| \le \epsilon. $$ Now let $0 < N_2$ be large enough s.t $\{a_1, \ldots , a_{N_1}\} \subseteq \{b_1, \ldots , b_{N_2}\}$.  Let $M > max\{N_1, N_2\}$.  Let $M < m' < n'$.  Then since $\{b_k\} - \{b_1, \ldots , b_{m'}\} \subseteq \{a_{N_1}, a_{N_{1}+1},  a_{N_{1}+2} \ldots\}$, we will have that   $$ \sum_{k=m}^n |a_k| \le \epsilon \implies \sum_{k={m'}}^{n'} |b_k| < \epsilon. $$ Then we have that   $$ \left| \sum_{k={m'}}^{n'} |b_k| \right| = \sum_{k={m'}}^{n'} |b_k| < \epsilon $$  so that since $\epsilon$ was arbitrary, we have obtained that   $$ \left| \sum_{k=1}^n |b_k| - \sum_{k=1}^m |b_k|  \right| = \left| \sum_{k=m}^n |b_k|  \right| \rightarrow 0 $$  so that via the Cauchy Criterion for Convergence  we have that $\sum_{k=1}^{\infty} |b_k|$ converges to some  value in $\mathbb{R}$ as desired. Then it follows that $\sum_{k=1}^{\infty} b_k$ is absolutely convergent (and hence also just convergent).   $\square$


I chose wrong license during submission on arXiv, what shall I do?

I am a PhD student from computer science and try to submit a paper to IEEE transactions. In addition, I also submitted it to arXiv under the CC0 license (Creative Commons Public Domain Dedication), where it was already published. This might be unacceptable for IEEE.   My question is: Can I just withdraw the current version, and resubmit it to arXiv under non-exclusive license? It seems like that there will be a record in arXiv. Will it affect my IEEE publication?


Inner products and notations of orthogonality

Let $v\in\textbf{R}^3$ have norm one. If $\{v_{1},v_{2},v_{3}\}$ is an orthonormal basis for $\textbf{R}^{3}$ and $v = a_{1}v_{1} + a_{2}v_{2} + a_{3}v_{3}$, can we have $|a_{1}| > 3$? Justify the answer.  I think the answer should be no because they are in $\textbf{R}^3$, is that right?


What does the dot mean after -rwxr-xr-x in the ls -l output?

What is the meaning of the  dot '.' after last (the rightest one ) 'x' in the second line ? This is the output of       [igor@localhost ~]$ ls -l /usr/local/bin   -rwxr-xr-x  1 root root  113797 Aug 20 05:30 gpib -rwxr-xr-x. 1 root root   30283 Jul 16 22:48 ibtest   No, this is not the only dot in the output from 'ls -l'. There are many ... but NOT on every line. (CentOS 6.4 32-bit)


I am getting error while using sudo apt-get upgrade stating:  dpkg: error processing libgfortran3:amd64 (--configure):   package libgfortran3:amd64 is not ready for configuration   cannot configure (current status `half-installed') Errors were encountered while processing:   libgfortran3:amd64 E: Sub-process /usr/bin/dpkg returned an error code (1)   It does not seem to block the installation/upgrade other applications. I believe this problem arose due to direct shutting down of my PC while the application was being upgraded.  How can I fix this?


Use 2 HDRI at once, one to light the scene and one as background

I was working on a project and then i got stuck on this problem. I want to use 2 HDRI at once. One HDRI to affect the lighting of the scene while other to affect the background. I am using cycles to render.I know its not photoreal to do that but there are no much shiny parts in the scene so it shouldn't affect all that much. Is there any way to do this? Sorry,it says this question is already answered but the answer its suggesting does not help in my case. Any other Answer??


Notify others if a question is already solved on Stack Overflow

I posted a question on Stack Overflow. And already solved it with the help of another user. How to notify everyone that the question is already solved?


How to calibrate the monitor on an Ubuntu system?

What is the procedure to calibrate the monitor and what software to use?  Edit: I think what I mean is "colour profile" if that's what it is called. I happened to notice that the same photos look very differently indeed on my home laptop and on other computers…


How do i make a button with delayed reactivation time?

I have a button which i want it to activate something. But i don't want it to be constantly activated, as i want it to be with a 10 - 20 seconds delay before you can activate it again.


In the previous version the logout button is under your username, which it can be found by clicking the down arrow. However, in the new version, after a couple minutes of searching, it is under the "site-switcher" button:        This is really illogical since the logout button is usually under your username, including Google and Yahoo! services.  I suggest bringing back the  which will definitely benefit new users and even old users.


Proof of an elementary property of Projection Operators

I'm asked to show the following:  Let $X$ be a linear space, and let $P : X \rightarrow X$ be a projection operator. Restricted to the linear space $range(P)$, the projection $P$ is the identity operator, that is, $Px = x$ for all $x \in range(P)$.  If anyone could offer a hint for how to show this. I'm rusty with linear algebra so don't really know what I'm supposed to bring in outside of what's specified in the lemma/definition of projection. What is so special about the range of P that would make this so?


How do I prove if $\lim a_{2n}=L$ and $\lim a_{2n+1}=L$ then $a_n$ converges and $\lim a_n =L$?

This seems obvious as its just saying that if the sequence has $L$ for limit when $n$ is odd and even then the sequence has $L$ for its limit. Yet, I am not quite sure how to prove this


Cannot boot system due to start job running for hold

I've installed ubuntu-desktop on Ubuntu 16.04 Gnome and I picked lightdm and now once I restart, I get this error message when I press CTRL + ALT + F2:  A start job is running for Hold until boot process finishes up (Xmin Xs/no limit)   This goes on for 20 minutes+. What do I do to fix this problem or even troubleshoot?


ESTA controls when travelling within two states in the US

I understand that ESTA travellers are allowed to travel and can also go the Automated Passport Control (APC) in certain airports. But once I have arrived in a state (e.g. NY) and then would like to go to another state e.g. IL - How does this work? Do I need to treat this as an international travel i.e. do the ESTA based checks again?


What is the significance of the name Bleach?

The name "Bleach" seems to be having no relevance to the plot unlike most other series. Was it just chosen at Kubo-sensei's whim or does it have some significance? Maybe some cultural significance associated with shinigami, etc. that I am now aware of?


I ran into this  that looks like its been copied over from another site.  I'm not really sure how to deal with it. I mean, there's an actual question burried in there somewhere, but as it stands I wouldn't call it a good post.  Should I just edit it and remove all the junk or flag it and pass it up the chain?


I intuitively understand proof with limits, but I'm not sure on how to write a formal proof for this example.  For each $n \in \mathbb{N}$, let $a_n$, $b_n$ be real numbers. Also, let $a_{\infty}$, $b_{\infty}$ be real numbers. Suppose that $\lim_{n\to \infty} a_n = a_{\infty}$ and $\lim_{n\to \infty} b_{n} = b_{\infty}$.  Prove that $\lim_{n\to  \infty} (a_n b_n) = a_\infty b_\infty$.


Views exposed filter error "An illegal choice has been detected. Please contact the site administrator."

I am having a very odd problem with an exposed filter in one of my Views. The page I am talking about is here:   When I select one of the last 2 options in the menu (EPS Packaging Recyclers or Loose Fill Recycling Drop-off) I get an error that says An illegal choice has been detected. Please contact the site administrator. This is really weird to me because it only happens with these 2 options. I don't believe they are set up any differently than the other taxonomy terms. There's nothing all that special about them, its just a term that the admin selects when creating a location for the map.  Any ideas as to why this is happening or how to fix it?


rerender section of page when field is inline edited without saving

Is there a way to re-render my VF page when a field is modified via inline editing without anything being saved? Right now I have the following snippet in my VF page:  <apex:outputField value="{!qli.Quantity}">                         <apex:inlineEditSupport event="ondblclick"/> </apex:outputField>   I can double click on this field to change its value, then click outside of it to set that new value. At that point, nothing has actually been saved, but the new value I typed in is displayed in that outputField.  As soon as that field is modified, I would like to rerender a section of the page.  I tried using apex:actionsupport in my outputField with an "onchange" event, but it didn't work.  <!-- this does not work --> <apex:outputField value="{!qli.Quantity}">     <apex:actionSupport rerender="qliList" event="onchange" immediate="true"/>     <apex:inlineEditSupport event="ondblclick"/> </apex:outputField>   Is there a way to do this? I tried a few different hacks to make this work such as trying to attach an event listener to the field in Javascript, but Salesforce make this basically impossible since they change the id and class attributes of the element. I don't know of a reliable way to pull these elements in javascript to attach an event listener to them, and theres the further challenge of actually triggering a page re-render from JS which I'm not entirely sure how to do...  My problem cannot be solved by the solution offered by Shailendra Singh in    Inline editing can only be done with outputfields. I specifically need an outputfield to use this feature. Inputfields are always editable, whereas outputfields are not editable by default unless they have inline editing enabled, at which point the user can double click on them to enable editing and change them. The solution Shailendra Singh offered in that other question involves changing the field from an outputfield to an inputfield, which is not what i need.