We roll a 6-sided die n times. What is the probability that all faces have appeared on top face?

i tried it like this:  we need 6 places to put the $ 1,2,3,4,5,6 $ numbers on top face and in rest of the places we don't care.  So number of favorable cases is   $$ ^nC_6*6!*6^{n-6}$$  My total number of cases are $6^n $  So my probability is $$ ^nC_6*6!*6^{n-6}/6^n$$  but it's wrong. where am i wrong?


Is it possible to set session in wordpress. If yes can you please tell how to do it? My sample code is.  <?php session_start();  if(!isset($_SESSION['impression'])) {     $_SESSION['impression'] = 100;   }else {     if($_SESSION['impression']<=0)         $_SESSION['impression'] = 100; }  echo $_SESSION['impression']    = $_SESSION['impression'] -1;  ?>


I don't completely understand KL divergence yet, and how the breakdowns are completely different for similar looking distributions. In  it says: $$KL(q_\lambda(z|x) || p(z|x)) = E_q[log \space q_\lambda(z|x)] - E_q[log \space p(x,z)] + log \space p(x)$$ The two distributions in the comparison look similar, both stating the probability distribution of $z$ given $x$, but in the first case it's the cross entropy ($q$ relative to $q$?), in the second case we're subtracting the cross entropy of $p(x,z)$ relative to $q$ plus $log \space p(x)$. Could someone explain why this problem should be solved like this?


MWE for externalize + automatic recompilation after tikz figure modification

I am using the external library to avoid recompiling tikz figures unnecessarily in a large document. Every now and then I have to change some details of some selected pictures. After the modifications it is necessary to recompile only those figures that have been modified. My aim is to do that automatically.   From Christian Feuersänger's answer to , I have interpreted that pictures whose content change can be remade automatically. I have not found however a simple MWE in which a tikz figure is recompiled only when its content is changed. It would be useful to have one.  The following MWE does not work, in the sense that changes in figure.tikz do not trigger re-compilation of the figure.  \documentclass{article} \usepackage{pgfplots} \usetikzlibrary{external} \tikzexternalize[prefix=tikz2pdf/]  \begin{document} \begin{figure}   \tikzsetnextfilename{figure}   \input{figure.tikz} \end{figure} \end{document}   figure.tikz  \begin{tikzpicture}  \draw (0,0) -- (1,0); \end{tikzpicture}   From the logs of pdflatex I can see  ===== Image 'tikz2pdf/figure' is up-to-date. ======   which tells that the file checked against being up-to-date is the generated pdf, not the original tikz. Obviously I am missing something.  How do I specify that the file to be checked is the original tikz?  For the background, I use pdflatex and tikz/pgf 2.10.


How can the Community user review a Low Quality post?

I was reviewing an old post I flagged and saw that the Community user reviewed this post as "Looks OK."  I know the Community user can , but in what scenario can the Community user review Low Quality posts?


How does one cluster multiple machines to act as one to run multiple virtual machines on this single-seeming machine?

How does one take multiple computers and make them act as one, such that all their processors and memory are combined now and you are running any application such that yo are running them on a single very fast computer. Such that it can be used to run virtual machines (on software like vmware).  What operating system(s) can this be accomplished with? Or what software is needed?


Should I move the world or move the player?

I'm about to start developing a sidescrolling game where the player's goal is to travel as far as he can in the horizontal axis before touching down. Note that I do not need to ever travel back on the horizontal axis.   I'm developing this with the AndEngine for Android which uses OpenGL and Box2d.  Before starting, I need to decide on something important: should I use the world around the player to simulate movement or actually move the player and follow him with the camera features of the game engine?  Both approaches seems to have different strengths and fallbacks, so I don't know which one is considered best. For example, what would make it easier to add power ups along the way and have a nice animated background?  Thanks!


Smallest positive element of $ \{ax + by: x,y \in \mathbb{Z}\}$ is $\gcd(a,b)$

Let $S = \{ax + by: x,y \in \mathbb{Z}\}$  and let $e > 0$ be the smallest element in $S$. Prove that $e \mid a$, and hence prove that $e = \gcd(a,b)$  I'm afraid I can't provide much of my initial working here because I'm at a loss of how to start.  I suppose that to show $e\mid a$ I would have to show that $eg = a$ for some $g \in \mathbb{Z}$. But I have no idea how I would do this.


I wanted to install snap-store, but got this error message: error:unable to contact snap store  I decided to reinstall snapd, so I ran these commands: sudo apt-get purge snapd sudo apt-get autoremove   After that I lost my software center. Is there a way to bring it back? I tried: sudo apt install software-center  but I got this error message: E: Package 'software-center' has no installation candidate


c++ difference between reinterpret cast and c style cast

Code:  char keyStr[50]={ 0x5F, 0x80 /* bla bla */ }; uint32_t* reCast  = reinterpret_cast< uint32_t* >( &keyStr[29] ); uint32_t* reCast2 = ( uint32_t* )&keyStr[29]; if( reCast == reCast2 ){     cout << "Same Thing!"; }   Output:     Same Thing!   I wonder what's the difference between the two casting methods. Also if you could specify ( with examples ) difference between static_cast, dynamic_cast, and other types of casting you know ( i.e. while staying as low level and as close to assembly language as possible ).  static_cast dynamic_cast const_cast reinterpret_cast C-style cast (type)value Function-style cast type(value)   Thanks.  Please read the P.S. I know from the example above that reinterpret_cast assigns to the int pointer the address of keyStr[29] In assembly that would translate into:  lea eax, [keyStr+1D] mov [reCast], eax   So in other words reinterpret_cast, in a low level prospective, is not dangerous at all as it does not modify the original data.  I wanted to know how the other casting methods behave in a low level way. So, for example, an object, in a low level way, is just a variable which holds an address. And the type if that object is how the compiler then interprets that address and how it offsets it.( this is exactly what I'm not interested in, in assembly, i could care less if that variable holds a value, a pointer or an object ( i.e. another pointer ) ). Another thing that could be just the same, is the difference between int and int* or unsigned int and int; all 4 declarations generate the same assembly instruction. ( push value ) or (sub esp-(length of int) && mov esp, value) I hope this clarifies the question and why I tagged it "low-level-code" and "assembly"  P.S. In this program I'm trying to create I don't care for non portability or other high level stuff. I'm trying to be as low level as possible and as close to assembly language as possible. That means that, for this program, memory is just memory ( i.e. 0 and 1 bits ) and types are not important ( e.g. I don't care if mem address: 0x123 is an "int" type or "float" type, it's just "data")


what does the ldapadd error: "additional info: objectClass: value #2invalid per syntax mean?

I'am tryin to migrate from active directory windows server to Openldap i found a problem while importing .ldif database exported from AD to my new Openldap ! when  i try to do : ldapmodify -Y EXTERNAL  -H ldapi:/// -f exportuser.ldf i got : dn:dc=si,dc=infra changetype: add objectClass: top objectClass: domain objectClass: domainDNS distinguishedName: DC=si,DC=infra instanceType: 5 whenCreated: 20140903112404.0Z whenChanged: 20200710114957.0Z subRefs: DC=ForestDnsZones,DC=si,DC=infra subRefs: DC=DomainDnsZones,DC=si,DC=infra subRefs: CN=Configuration,DC=si,DC=infra uSNCreated: 4099 dSASignature:: AQAAACgAAAAAAAAAAAAAAAAAAAAAAAAAFZdkFLMGb0aPv8u9xkFAiw== repsFrom::  AgAAAAAAAADwAQAAoQQAAEk0WhMDAAAArh8ZFQMAAADZBgAA2AAAABgBAABwAAAAERERERERERERER  ERERERERERERERERERERERERERERERERERERERERERERERERERERERERERERERERERERERERERERER  ERERERERERERERERERERAAAAAKpXAQAAAAAAAAAAAAAAAACqVwEAAAAAAK5eK8JSo2VLj8lZCMtB4q  W2BWGS+bZXS5Ih2qP3nk/NAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAGAEAABgAAAAAAAAAkAAAAAAA  AAAAAAAAYwAyADIAYgA1AGUAYQBlAC0AYQAzADUAMgAtADQAYgA2ADUALQA4AGYAYwA5AC0ANQA5AD  AAOABjAGIANAAxAGUAMgBhADUALgBfAG0AcwBkAGMAcwAuAHMAaQBmAGEAcwB0AC4AaQBuAGYAcgBh  AAAAAAAAAAAAYwAyADIAYgA1AGUAYQBlAC0AYQAzADUAMgAtADQAYgA2ADUALQA4AGYAYwA5AC0ANQ  A5ADAAOABjAGIANAAxAGUAMgBhADUALgBfAG0AcwBkAGMAcwAuAHMAaQBmAGEAcwB0AC4AaQBuAGYA  cgBhAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA== repsFrom::  AgAAAAAAAADwAQAAblMAAJkvBQ8DAAAAWh8ZFQMAAAC6BgAA2AAAABgBAABwAAAAERERERERERERER  ERERERERERERERERERERERERERERERERERERERERERERERERERERERERERERERERERERERERERERER  ERERERERERERERERERERAAAAALrDDAAAAAAAAAAAAAAAAAC6wwwAAAAAANGWjIQnKUVChkMTYKaH0u  6nIrWbtxGPSZF02Z788HncAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAGAEAABgAAAAAAAAAkAAAAAAA  AAAAAAAAOAA0ADgAYwA5ADYAZAAxAC0AMgA5ADIANwAtADQAMgA0ADUALQA4ADYANAAzAC0AMQAzAD  YAMABhADYAOAA3AGQAMgBlAGUALgBfAG0AcwBkAGMAcwAuAHMAaQBmAGEAcwB0AC4AaQBuAGYAcgBh  AAAAAAAAAAAAOAA0ADgAYwA5ADYAZAAxAC0AMgA5ADIANwAtADQAMgA0ADUALQA4ADYANAAzAC0AMQ  AzADYAMABhADYAOAA3AGQAMgBlAGUALgBfAG0AcwBkAGMAcwAuAHMAaQBmAGEAcwB0AC4AaQBuAGYA  cgBhAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA== uSNChanged: 88191049 name: si objectGUID:: L2ettnpuxEaavgfWpC5gUQ== replUpToDateVector::  AgAAAAAAAAACAAAAAAAAALYFYZL5tldLkiHao/eeT83zVwEAAAAAAEk0WhMDAAAApyK1m7cRj0mRdN  me/PB53MzDDAAAAAAAiiEFDwMAAAA= creationTime: 132388553973680553 forceLogoff: -9223372036854775808  Some help please .???


I define a number of aliases for my git work flow.  alias gs='git status' alias ga='git add -u' alias gaa='git add -A' alias gc='git commit' alias gr='git checkout --' alias gu='git reset HEAD' alias gch='git checkout' alias gst='git stash save' alias gmm='git fetch && git merge origin/master' alias glf="git log --color --graph --pretty=format:'%Cred%h%Creset -%C(yellow)%d%Creset %s %Cgreen(%cr) %C(bold blue)<%an>%Creset' --abbrev-commit" alias gl='glf | head'   The problem with this is that using the aliases disables bash's git tab completion.  For example, with the following:  $ gs On branch master Your branch is up-to-date with 'origin/master'.  Changes not staged for commit:   (use "git add <file>..." to update what will be committed)   (use "git checkout -- <file>..." to discard changes in working directory)      modified:   bar     modified:   foo  no changes added to commit (use "git add" and/or "git commit -a")   If I type git add and then hit tab, it will display only the modified files:  $ git add  bar  foo        If I type b and tab, it will complete bar  However, if I try use my alias, tab completion no longer works.  $ ga  bar  baz  foo  etc..  etc..  etc..   Is it possible to enable git tab completion with my aliases?


C++ Issues creating class objects and circular inclusion

This is my first question, so I apologize in advance for any things about stack overflow that I may not be aware of!  The issue I am having is that I am making a simple SDL program, currently it is just supposed to draw a PNG image (Assets/Board.png) to the screen, but I am being faced with many errors to do with the two classes communicating with each other, I think that I have circular inclusion errors. But I have been trying to fix the problem for days and I haven't been able to solve it.  Here are the errors that I am getting:    (Here is a text version of it, but the formatting is bad sorry)  1>d:\code\c++\games\chess\chess\manager.h(41): error C2079: 'Manager::Tex' uses undefined class 'Render' 1>d:\code\c++\games\chess\chess\render.h(32): error C2146: syntax error : missing ';' before identifier 'manager' 1>d:\code\c++\games\chess\chess\render.h(32): error C4430: missing type specifier - int assumed. Note: C++ does not support default-int 1>d:\code\c++\games\chess\chess\render.h(32): error C2146: syntax error : missing ';' before identifier 'manager' 1>d:\code\c++\games\chess\chess\render.h(32): error C4430: missing type specifier - int assumed. Note: C++ does not support default-int   (I have used an image because the formatting of the image is easier to read.) (Also click on the image in imgur to see the zoomed in version)  You can download the entire code project here (ZIP FILE):     But here is the code that I think is causing the issues:  (Manager.h file)  //Include guards. #pragma once  //Headers. #include "Render.h"  //Librarys. #include <SDL_image.h> #include <string> #include <SDL.h>  //Namespaces. using namespace std;  //Enumerator. enum State { Play, Exit };  class Manager { public:     Manager(); //Constructor.     ~Manager(); //Destructor.      //Rendering.     SDL_Window* Window;     SDL_Surface* Screen;     SDL_Renderer* Renderer;      //Functions.     void Run();     void Init();     void Close();     void Input();     void Update();     void Error(string);      //Game variables.     State state;     Render Tex;  private:      //Constant values.     const int WINDOW_POS_X = SDL_WINDOWPOS_CENTERED;     const int WINDOW_POS_Y = SDL_WINDOWPOS_CENTERED;     const int INIT_FLAGS = SDL_INIT_VIDEO;     const int SCREEN_HEIGHT = 600;     const int SCREEN_WIDTH = 600; };   (And here is the Render.h file)  //Include guards. #pragma once  //Headers. #include "Manager.h"  //Librarys. #include <SDL_image.h> #include <string> #include <SDL.h>  //Namespaces. using namespace std;  class Render { public:     Render(); //Constructor.     ~Render(); //Destructor.      //Functions.     void Draw(int, int); //Draws texture at position.     void Load(string); //Loads texture from path.     void Deallocate(); //Destroy texture.      //Getter functions.     int GetHeight() { return Height; };     int GetWidth() { return Width; };  private:     SDL_Texture* Texture; //Actual image.     Manager manager; //Manager class.      int Height; //Height of image.     int Width; //Wdith of image. };   So in conclusion, I am having errors related to the class objects, which I believe are being caused by circular inclusion, despite my research I have not been able to fix these issues. I would greatly appreciate any help with this issue.  P.S I know I am not supposed to use the std namespace, instead I must write std::foo, I am aware, so please don't comment about it!  --Thanks in advance, Cameron Bell.


QGIS 2.18: Configure edit widget of a editable layer with Python with "value map" from CSV

I want to configure the edit widget (in qgis: "Properties" of a layer, "Fields", column "edit widget") for a field of a editable layer (shapefile) using a Python plugin. I want set the edit widget with a "Value Map" using a CSV file for the values.  In the documentation  i find the method setEditorWidgetV2Config, but when i try a code like this:  layToEdit.setEditorWidgetV2Config(indField, {...} )   QGIS returns this error for any configuration value in the second parameter:  (qgis.bin:6585): Gtk-CRITICAL **: IA__gtk_widget_get_direction: assertion 'GTK_IS_WIDGET (widget)' failed   what parameters should I use to configure the edit widget as a "value map" that uses the values of a CSV?


lets say we have two person A and B. Person A is holding a light source (lets call this light source 'S1') which is pointed towards north. Now person A starts moving at speed 0.86c WRT (with respect to) Person B in the direction of north. Now Person A turn on the S1. what will be the speed of light emitted from S1:  1- WRT Person A.  2- WRT Person B.  This question can also be asked as an excited electron traveling at 0.86c emits a photon in the same direction in which it is moving. what will be the speed of that photon WRT to the electron and WRT to the observer (here the observer is the one from whom's respect electron is moving at 0.86c).  Please consider this hypothetical experiment that may help under the question better. I have a metal cylinder which is 1m long. it absorbs all the light. now on its both ends i have light sensors which gives the signal to a very accurate micro-controller that can record the signal and detect the time between two events. An event is described as light being detected by a sensor. I then place this cylinder in my home horizontally and put a light source on one end. light first hit one sensor and after some time (i guess) the other sensor. My micro controller records this time as 1/299792458 seconds accurately. now i put the same experiment on a train that is moving at 0.86c. the cylinder is now placed in the direction of the train. lets say its end 1 face the engine and end 2 faces the tail and i put the light source at end 2. now i run the experiment again. now what time will be recorded by my micro controller. In this case i think it should be greater then 1/299792458 seconds. In both cases, the one at my home and the one in the train uses the same clocks and have same distance between the two sensors so this dictates that speed of light should remain same (299792458 m/s). But as both sensors are moving at speed near the speed of light, after hitting one the other is farther apart (i think due to doppler effect) the speed would change.  what will be actual time i will find in this experiment and can i use it to find my speed relative to the observer standing on the platform?  PS the above apparatus is in a vacuum chamber.


After setting a new drive to be the home partition, where can I find the old /home files?

I recently bought a new hard drive and set it to be my /home partition. The old one used to be on the root partition, so I just added /dev/sdXX to my fstab file. The drive where the root partition lives is quite small, so I was wondering where the old /home files are now. I just want to remove them to free some disk space (I had already backed up any important stuff into my new ~). Is there a way to access these files without commenting my /home line in the fstab file and rebooting to manually delete the files in the old home directory?


Is there an online national repository of marriage documents?

I found an index on ancestry.com for my person that says it came from the U.S. and International Marriage Records, 1560-1900. The index only gives limited information from the document such as both names, marriage date, and marriage place but leaves out most other information. Why wouldn't Ancestry let me access the actual record and is there some other on-line place (preferably free) where I can find such records?


Javascript, copying properties and arrays versus a pointer

So I just ran into this issue, and while i've been working Javascript a while now, I didn't realize what seems to be an innate behavior and I'm hoping you guys can help explain when in this is the case. Consider this:  let a = {key1: [1,2,3]}; let b = a.key1; b.pop(1); console.log(a); // { key1: [ 1, 2 ] }   It appears that instead of b becoming a copy of a.key1 it is infact passing a pointer to the original data. This causes any changes that I make to b reflect up to a.key1. So my question is where can I read more about this behavior, does this apply for copying solely objects, or does it apply to other things (e.g.arrays, strings).  This is somewhat alarming to me considering code I've written in the past not being aware of this and leaving landmines for myself to find later...


I have two dates in javascript:  var first = '2012-11-21'; var second = '2012-11-03';   i would like make:   if(first > second){    //...  }   how is the best way for this, without external library?


I'm working on a bash script that appends to /etc/profile but instead of appending, I accidentally wrote over it, losing all of its content. How can I restore the file?  I did search here but being new to Ubuntu, I don't know if the posted /etc/profile content I see in other questions is the default content.


What's the term for design ala "object.method1().method2().method3()"?

What's the term for this design?  object.method1().method2().method3()   ..when all methods return *this?  I found the term for this a while ago, but lost it meanwhile. I have no clue how to search for this on google :) Also if anyone can think of a better title for the question, feel free to change it.  Thanks  Update-Gishu: After reading about it, I feel that your question is misleading w.r.t. code snippet provided.. (Feel free to rollback)  Method Chaining  object.method1().method2().method3()   Fluent Interfaces  private void makeFluent(Customer customer) {         customer.newOrder()                 .with(6, "TAL")                 .with(5, "HPK").skippable()                 .with(3, "LGV")                 .priorityRush();     }


Prevent SSH from advertising its version number

The server I am using is Ubuntu 10.10. To ensure security I want to edit the banner the server sends to the client.   If I telnet to my host on port 22 it tells me the exact version of SSH I am running (SSH-2.0-OpenSSH_5.3p1 Debian-3ubuntu4). The situation is the same with MySQL and Cyrus.  Any suggestions? At least for SSH?  Thanks


WiFi auto discovery works in Window 10 but does not in Ubuntu 14.04

I have successfully installed ubuntu 14.4 LTS alongside with Window 10 in my new Aspire E15 E5-573G-779S. WiFi auto detection in Window 10 is ok but not in Ubuntu 14.04. Appreciate if anyone can help to advise. Thanks.  Results of lspci -nnk | grep 0280 -A2 shows   03:00.0 Network controller [0280]: Qualcomm Atheros Device [168c:0042] (rev 30)     Subsystem: Lite-On Communications Inc Device [11ad:0806] 04:00.0 3D controller [0302]: NVIDIA Corporation Device [10de:1299] (rev a1)


I'd like to know if there is something I should know about when making a decision to use/not to use the article with most when it modifies the verb. For example,     My main passion are the horses that's what I love the most about   the sport.      Each of us has to find what we love most about our profession.      It's having your family and your friends alive, and that's what   matters the most.      Put yourself in your partner's shoes to gain perspective on what   matters most.   Is this again one of those cases of personal preference, or is there a better explanation?  I read on another forum that when love most is followed by about, the is often ommitted and, from my research, it really seems to be the case. So does it depend on what words go next?  I thought it was the case with formality/informality as the  states, but it doesn't sound very convincing to me. Also, both the Corpus of Contemporary American English and google books give more results for "love most/matter most" versus "love the most/matter the most".


Comments not showing time of posting under some circumstances

Looking at , I noticed the times for the comments are missing:    When I reload the page, I see the times on the comments for a fraction of a second, and then they are gone.  On shorter comment threads, I sometimes do see the comments.  Initially I thought that they seemed to disappear if and only if the comments thread gets collapsed due to a large number of comments.  When I click on "show 14 more comments", all comments are shown, including the times, but for shorter comment threads, I sometimes do, sometimes do not see them all; I cannot fully reproduce this.   on Linux (Ubuntu xenial 16.04), no user scripts.


Many Nintendo devices often come with , which means if you purchase a device in one country, you won't be able to play games from another (generally).  Is the Nintendo Switch also region locked like many of its predecessors such as the Wii U and Wii?


Calculating new velocities of $n$-dimensional particles after collision

I am working on a particle simulation where there is no gravitational force exerted on particles, they simply travel through space and, upon collision, change trajectories accordingly. There isn't a set number of dimensions the simulation can be run on, with the minimum being 2. Each particle has three attributes: radius (each particle is an  $n$-ball of  $n$ dimensions corresponding to the simulation's dimensions), coordinates (a tuple describing its position), and velocity (another tuple describing how quickly it moves in any given direction, determining where it will be on the next iteration). With the coordinates one can determine exactly the angle at which it strikes another particle, and that should be enough to determine the new velocities of both particles, or so I think. However, I'm not sure how to do this for an unknown amount of dimensions. I would presume a sigma function could describe this behaviour well, but I'm not sure how to write it. How might I go about doing so? Any necessary information can be added upon request.


Why doesn't StackExchange Do Something About ExpertsOverflow.com?

I can't find a better place to ask this question -    if there is one, please suggest it and I will repost there.   expertsoverflow.com is a blatant screen scrape of stackoverflow.com.  Everything is copied - graphics, the name (Stack Overflow), everything.  It's a blatant violation of copyright.  Why don't the Powers That Be at SO shut them down?


How many types of distinct Binary Tree can be formed with a height of h? if we only know the height of binary tree, and we regard root-left and root-right as the same tree structure, this means if the height of binary tree equal to 1, we can formed 2 different trees structure:  root - leftchild/rightchild; root - leftchild - rightchild


Evaluate $$\sum_{n=0}^\infty (n+1)\left(\frac13\right)^n.$$   $$1 + 2\left(\frac{1}{3}\right) + 3\left(\frac{1}{3}\right)^2 + 4\left(\frac{1}{3}\right)^3 + 5\left(\frac{1}{3}\right)^4 +\cdots$$  Show using ‘Techniques of Convergence of Geometric Series’ only that it converges to 9/4?


Meaning of the word "cut" in "cut me some slack"

Roughly what purpose does the word "cut" serve in the sentence "cut me some slack"?  I have a guess as to what this word means in that sentence. English is actually my second language; my first was Polish.   So in literal translation from a common Polish phrase "to cut yourself a nap" means that you basically have yourself a nap.   So coming from that, I assume that to "cut" in the  sentence in question means to just give/have yourself some slack (If you give yourself slack, you're gonna have slack is what I mean by "have yourself some slack").   Would this be an acceptable interpretation?


How can I use amsmath package and mathptmx package together?

I use the below method. But this method doesn't work for this situation. Why? I have the same results. This is my minimal file and I use texlive 2015. This problem is about \prod too. Thanks for your responsibility.  \documentclass[12pt,a4paper]{report} \usepackage{amsmath} \let\amssum=\sum \usepackage{mathptmx} \let\ptmxsum=\sum \let\sum\amssum \begin{document} I want this one in ams style:        \[ \sum \] text text text text text text text text text text text text   and this one in mathabx style:   \let\sum\ptmxsum \[ \sum \]   But both of them are the same and I don't like it ..... \end{document}


Is it possible to encrypt a message with two different keys (or maybe a public key) such that ciphertext will be decrypted with either of the keys?

I have an app that I store sensitive user data which requires user to set a password to login the app and I use this password as key to encrypt the data.  Now, I want to add an option to login the app with PIN. My problem is if user adds a PIN obviously I can't use it to decrypt the data. The only solution comes to my mind is to encrypt the password with PIN and store it locally. So when user enters the PIN, I can decrypt the password by using PIN then decrypt the data with this password.   Is it secure? Is there another way to achieve this problem? Is it possible to encrypt the data such that I can decrypt it with password or PIN only?


Command line code to pin program to taskbar Windows 10?

I'm trying to reimage several computers, and am making a batch file to run the basic commands. Is there a command line code that will allow me to pin programs to the task bar? For instance, Internet Explorer.


Do “noopener noreferrer” links count as backlinks?

I have bought ad links in some websites with a link, but when I saw the sites, they add an attribute noopener noreferrer on my website link.   Does Google count this as backlink?


I've cloned my repository via git clone, and now I want to checkout a folder.  Source folder: /opt/XYZ/foldertochecout  and it should be checked out to  /var/www/foldertochecout    Is that possible and how?


Does it make sense to give upvotes before I have 15 reputation points?

Short of the question:  Does it do any good to provide an up-vote if you have less than 15 reputation points?  They are not displayed to help others identify answers that worked.  Do they show up after I gain 15 reputation points?  Longer explanation  I have multiple stackexchange accounts but I only have over 15 reputation points in the one I use most.  In that forum I am in the habit of giving up-votes when a question and/or answer has helped me, but I am not sure if it does any good elsewhere.  Because of my work situation up-voting is my best method of giving back to the community - taking time to monitor the site for opportunities to answer questions isn't appropriate, though I do attempt to contribute when, by chance, I see an opportunity.  I also rarely have a question that hasn't already been asked. Because of this my reputation grows very slowly.  So, when I find a question/answer in an Exchange forums where I have less than 15 reputation points it is frustrating to see the notification that my vote is counted but not posted; I wonder if my up-votes will ever contribute in any way.  Do I just wait until I have 15 reputation points to vote?  Or, when I reach that level in some distant future, will they suddenly start contributing, and help to guide later questioners to good answers?


\section{Results} In the figures attached in \textbf{Section 0.6} and in this section, two options are show that can be accessed by the user.   \begin{figure}[!h] \centering \includegraphics[width=0.75\textwidth]{bookin2.jpg} \caption{A User entering Specific Data to book a room.} \end{figure} \begin{figure}[!h] \centering \includegraphics[width=0.75\textwidth]{data.jpg} \caption{User can view his data, if he commands the system.} \end{figure}  It has made it much simpler for the user, to simultaneously access his previous booking details, and make a new booking for further use.   I am trying to put these both pictures vertically in one section, but only the first picture is being placed there. the second one is being placed at the end of document after two sections. i am writing a report. Any help with it?


What is the probability that if you break a stick at $2$ points the three sides form a triangle?  Is there a technique that avoids calculus?


regex expression to accept ENTER key in string

Issue    I am having an issue creating a regex to accept any string and the ENTER key, at the moment i have this:  ^$|^.+$   I have looked around and people have said to add \n but this does not work.  An example of the string is should allow is as follows:  Hello this is a test string   and i want this to be accepted


I have already uploaded some files in the free web host I chose and created a database there using phpMyAdmin v2.11.4  Also, I have Googled first this question before posting this here but I don't understand some rules and I need a clarification.  The exact error I get from viewing my uploaded file(index.php) is this:  Warning: mysqli_connect() [function.mysqli-connect]: (HY000/1130): Host '31.170.160.98' is not allowed to connect to this MySQL server in /home/a6400350/public_html/subdomains/index.php on line 7   Domain name of free web host I'm using is   And my php code for connecting to host is:  <?php  $host = "sql10.000webhost.com"; //or "31.170.160.98" $username = "a6400350xxxxxx"; $password = "••••••••";  $con = mysqli_connect($host, $username, $password);  ?>    I also check if the server is down  or it's just me There was also no previlege section in phpMyAdmin page as other suggest   Don't I have any permission to connect programmatically to this host as I am just a free user?  Edit     I'm also thinking of uploading the whole XAMPP in the server so I   could do the things I'm imagining.   Edit 2     Also one more thing, I imported the database by means of .sql file   locally through that server, maybe this has something to do about it?


We have ArcGIS Enterprise in SQL and I see a lot of iNumber tables. I can't find information about what is the purpose, how they got created and do I need to delete them?


How do I download a Facebook messenger audio file?

A loved one recorded an audio message on Facebook messenger for me; it looks like the image below. I'm trying to download it, but nearly all of the ways to capture it don't see that the file exists, and the one exception to that downloaded a file that nothing can open.  Can someone please tell me how to download this file such that it can be played? I have 10.9.5, if that makes a difference. Thanks!


How to recover deleted .zip files through TWRP?

I deleted internal storage and forgot that my .zip backups was there. I have no OS installed, only access via TWRP. How can I restore my .zip files?


After Win10 2004 update can no longer connect to my samba server

I run an openSUSE 15.1 server with samba shares. I've always been able to connect to my shared folders using Windows 10. However, after the Win10 2004 (May 2020) update I now get this:  Error code: 0x80070043 The network name cannot be found.  I can ping the server and even connect to it using another PC w/o the update, so it appears something is now broken. Has anyone else experienced this? EDIT: My smb.conf file contains win protocol = SMB2. Changing to SMB3 had no effect. Purpose of this post is to see if anyone else who upgraded to 2004 is also running into this problem. EDIT #2: I verified that other Windows 10 computers on my network (same version) can still access the server shares so not sure what's up with this one PC. It's doing some other strange things as well, like not connecting to port 80 on this same server when using its public DNS.


predefined input in a nohup shell script

i am trying to write a shell script that i can then nohup as it is supposed to run for hours. i am a shell novice so I'm struggling with it a lot.  the script should first open some software (ACE data mining suite), which usually prompts the user for some input (choosing one of many possible input files; this can potentially be avoided by only placing one input file in the directory from which the script is called). i then need to start the algorithm by typing its name in (warmr).  in summary I need the script to:  1) open ACE 2) input file name into ACE (optional, can be avoided)  3) start the algorithm by inputting its name   input in steps 2-3 should be predefined -- i do not want to be prompted for it as i know what i want to run.  so far i have ace_script:  #!/bin/sh  /home/nfg/ACE-ilProlog-1.2.20/linux/bin/ace   adding echo "warmr" or read "warmr" avails to nothing. running ace_script fires up ACE which then complains of an error reading from the stream and shuts down.


How use cd command for a folder which has two words

I have a folder name like this :         Eccc App   when I use the cd command like this:      cd  Eccc App   I am getting an error like this:        -bash: cd: too many arguments   how can I solve this?


Degrees of freedom for diatomic molecules

I have a doubt in understanding about the degrees of freedom (dof) ......as I have learned dof is nothing but the necessary parameters to specify the location and configuration of a system.....if that's so then why is there only two extra dof for diatomic molecules to account for the rotation of its molecules? The molecule can rotate about any axis which passes through the line joining the two atoms....when freely moving in space. So why we account dof as two only to uniquely specify it's configuration ? It should be greater than two


Why am I constantly being redirected to stackexchange.com/promos?

I have to close my browser to make it stop. If I try to go to  it redidects me to  What's going on??


A better answer was posted long after accepting another. Should I accept the new one?

I've accepted an answer in 2010. In 2011 new options came to hand, and a better answer was posted. Should I move the accepted answer to the new one?


Could I play online on two different consules with the same account

If I was to buy a PSN online membership card and activate it on my brother's PS4, could I play online on my PS4? (It's two different consoles).  And would all account on the ps4 that is activated play online  I have my account on there ps4 but want to know if it would allowed me to play online on mine .


The use of nominative "whom" (as in “persons whom it is foreseeable are likely to...”)

From  page 48 of Law: A Very Short Introduction, by Raymond Wacks:     In other words, you owe a duty to persons whom it is foreseeable are likely to be harmed by your conduct.   To try to parse this, temporarily overlook 'it is foreseeable'. Then persons is the subject of the verb phrase are likely to be harmed. So , should the relative pronoun for persons be who instead? Is my parse wrong?   Are the (deleted) comments right: that this style predominates in law texts? If this is correct grammar, what is the general rule? Is it commonly used in other contexts?


"Quite" is probably the most ambiguous word in the English language. Merriam-Webster defines it three ways:  1:  completely, wholly, totally (quite mistaken)  2:  to an extreme :  positively (quite drunk)   3:  to a considerable extent :  pretty, rather (quite near, quite ill quite rich)  So if someone tells you someone else is "quite drunk", how do you know this person is: a) completely drunk? b) very drunk? c) pretty drunk?  Or how about "quite difficult?" Does it mean rather difficult? Or extremely difficult?


I made a small java program with a Frame showing a small ImageIcon. I'm using IntelliJ to make my programs. When I click on "Run", it shows me the Frame with the picture. Then I made a JAR file out of it, and now it just shows me the Frame but not the Image. What can I do?


While loop is not recognizing white space array value?

I created this function that is supposed to replace all the white space within a string with the string "%20". ie: "Mr John Smith" becomes "Mr%20John%20Smith". To accomplish this, I placed all the characters of the string into an array and attempted to loop through, replacing any instance of " " with "%20". For some reason, the code I wrote doesn't seem to recognize the " " value within the list and skips over this part of my loop. So instead of getting a new String with the white spaces replaced, I simply get back the same string with the white spaces intact. Can anyone help correct my error? I ran it through the Java Tutor to visualize my code and it reflected this same error  import java.util.ArrayList;  public class Interview {      public static void main(String[] args) {          Interview theFunc = new Interview();          String d = "Mr John Smith   ";          System.out.print(theFunc.URLify(d, 13));      }     public String URLify(String str, int x){         String result = "";         String real = str.substring(0,x);         String [] list = new String[real.length()];         int i = 0;         while (i != real.length()) {             list[i] = real.substring(i,i+1);             i = i +1;            }         int b = 0;         while (b < list.length) {             if (list[b] == " ") {                 list[b] = "%20";                 b = b + 1;             }else{                 b = b + 1;             }         }         int d = 0;         while (d != list.length) {             result = result + list[d];             d =d + 1;         }      return result; }   The error is occurring in the second while loop. Thanks!


Can anybody help me with this logarithm problem?

If $(\log_4 x)^2= (\log_2 x)(\log_a x)$ (the $4$ is the little number next to log by the way) , find the value of $a$.


How to interpret logistic regression output?

I have the R output for the logistic regression model. It seems that only the intercept and psa are statistically significant. Does that mean I should remove sorbets_psa and cinko from my model and create a new model as new.model = glm(status ~ psa,family = binomial(link ="probit"))  Call: glm(formula = status ~ psa + serbest_psa + cinko, family = binomial(link ="probit"), data = data)  Deviance Residuals:  Min       1Q   Median       3Q      Max   -2.3285  -0.6773  -0.6261  -0.5604   1.9500    Coefficients:       Estimate Std. Error z value Pr(>|z|)     (Intercept) -0.9697009  0.2409856  -4.024 5.72e-05 *** psa          0.0444376  0.0094368   4.709 2.49e-06 *** serbest_psa -0.0440718  0.0250486  -1.759   0.0785 .   cinko       -0.0006923  0.0016984  -0.408   0.6835     --- Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1  (Dispersion parameter for binomial family taken to be 1)  Null deviance: 534.27  on 477  degrees of freedom Residual deviance: 477.07  on 474  degrees of freedom AIC: 485.07  Number of Fisher Scoring iterations: 6


Am not able to install other debian packages after installing google chrome. what could be the issue?

$ sudo apt-get install cryptkeeper Reading package lists... Error! E: Encountered a section with no Package: header E: Problem with MergeList /var/lib/apt/lists/dl.google.com_linux_chrome_deb_dists_stable_main_i18n_Translation-en E: The package lists or status file could not be parsed or opened.


$n$ divides a product of $n$ consecutive integers (by $n$ divides one of them)

If $x$ is positive integer, prove that for all integers $a$, $(a+1)(a+2)\cdots(a+x)$ is congruent to $0\!\!\!\mod x$.  Any hints? What are the useful concepts that may help me solve this problem?


Is there a way I can change the way files are currently "sorted by name", to include common non-alphabetical characters like +-_?  I don't mind getting my hands dirty if someone can point me to the script that's responsible for sorting the files (probably a python script?).    @muru helpfully pointed to  as being responsible for sorting filenames in Nautilus' sources. I can't see anything wrong with it given that it uses strcmp, so maybe the problem happens before that because of some string sanitization?  To be clear with the question: I would expect the order {"_name 1", "_name 3", "name 2"} but Nautilus currently sorts these names as {"_name 1", "name 2", "_name 3"}.


Package draftwatermark: no watermark on the first page

I need to add a watermark on all pages of a latex document but the first.  Currently, I'm using , but I haven't suceeded yet.  Any advice or suggestion?  I tried the xwatermark package, as suggested , but it came out that it is not compatible with other packages I'm using.


Combinatorial proof for $\sum_{k = 0}^n \binom {r+k} k = \binom {r + n + 1} n$

I'm trying to figure out a combinatorial proof for:  $$\displaystyle \sum_{k \mathop = 0}^n \binom {r+k} k = \binom {r + n + 1} n$$  I've tried the committee counting thing, but that didn't work.


Practical hyperparameter optimization: Random vs. grid search

I'm currently going through Bengio's and Bergstra's Random Search for Hyper-Parameter Optimization  where the authors claim random search is more efficient than grid search in achieving approximately equal performance. My question is: Do people here agree with that claim? In my work I've been using grid search mostly because of the lack of tools available to perform random search easily. What is the experience of people using grid vs. random search?


How to save a bookmark in Firefox with POST data?

I would like to save as a Firefox bookmark a page which is not accessible using GET. The only way to retrieve the page is to send some POST data.  For example, I would like to bookmark a , which only allows POST for entering parcel numbers.  Does anyone know a Firefox extension, or some other technique, which would allow me to do this?


The intersection of maximal subgroups of abelian group is not trivial.

I want to find the sufficient and necessary condition of intersection of maximal subgroup of abelian group is not trivial. I showed intersection of maximal subgroup of a group $G$ is normal subgroup of $G$. I know fundamental theorem of abelian group. Thank you for your help.


Clash between newtxmath and amsthm packages

I'm writing a document with a book structure using only these few packages:  \documentclass[letterpaper, 10pt, oneside]{book} \usepackage{XCharter} \usepackage[xcharter]{newtxmath} \usepackage[cal=boondox,scr=boondox,bb=boondox,frak=euler]{mathalfa} \usepackage[utf8]{inputenc} \usepackage[T1]{fontenc}  \usepackage{amsthm} \usepackage{mathtools} \usepackage{enumerate}   I wanted to use the proof environment from the amsthm package, but it produces the following error: Command \openbox already defined. \vrule\hfil}}. I noted that, although my LaTeX editor didn't throw any preview of the document, there is in fact a .pdf file generated, and it compiled just fine.  I began to comment some of the previous packages I use, just to debug and see what caused the problem. If I comment \usepackage[xcharter]{newtxmath}, then the warning disappears.  By the error and the answer given in , it is clear that both newtxmath and amsthm are defining a command called \openbox at the same time. What can I do to solve this error? I really don't want to get rid of the newtxmath package nor the XCharter fonts, I love them.  Thank you very much in advance. I provide a MWE:  \documentclass[letterpaper, 10pt, oneside]{book} \usepackage{XCharter} \usepackage[xcharter]{newtxmath} \usepackage[cal=boondox,scr=boondox,bb=boondox,frak=euler]{mathalfa} \usepackage[utf8]{inputenc} \usepackage[T1]{fontenc}  \usepackage{amsthm} \usepackage{mathtools} \usepackage{enumerate}  \newcommand{\Ccal}{\mathcal{C}} \newcommand{\Pcal}{\mathcal{P}}  \begin{document}     Suppose $\Omega = \{0,1\}$ and $\Ccal = \{\{0\}\}$. Enumerate $\aleph$, the class of all $\sigma$-fields containing $\Ccal$.     \begin{proof}         There are just two $\sigma$-fields on $\Omega$: the trivial one $\{\emptyset, \Omega\}$ and the discrete one $\Pcal(\Omega) = \{\emptyset, \{0\}, \{1\}, \Omega\}$. So, $\aleph = \{\Pcal(\Omega)\}$.     \end{proof} \end{document}


when I install Ubuntu with a USB-disk, following message occurred:    task swapper/0:1 blocked for more than 120 seconds.   And my computer have an CPU of core-i7-4710MQ and 12 GB memory.  But, if I install Ubuntu on a very old computer, I can success.It is a double core Intel CPU with a 2 GB memory.  The SSD I used on both computer is the same one. After I installed Ubuntu on that old computer with my SSD, I replace the hard disk of my computer with that SSD witch installed Ubuntu 16.04 successful already, it can't run.  My bios is legacy at first. When I change to UEFI mode, I can enter  . But, no matter what I choose, my screen becomes to be grey, and a cursor twinlkling. about 2 or 3 minutes later,  following message occurred:    task swapper/0:1 blocked for more than 120 seconds.   What I should do? or what information I should provide? thanks!


I'm about to publish a paper with my previous group.   I'm not in a permanent position, and my boss doesn't care if I mention or if I don't mention my current institution in the paper.  For me, a researcher who wishes to have a permanent faculty position, would it be helpful or not at all to do that?


Were there mind reading devices in 1984?

How was it that O'Brien could read Winston's mind so well in 1984? Is it possible the Party had a mind reading device?


What is the difference between a C# property with a getter and a property with an equals sign?

What is the difference between these two properties: public int Foo = 6; public int Bar {get;} = 6  Here is a link to a working program that shows the output is the same:  using System;  class Program {     static void Main(string[] args) {              var someClass = new SomeClass();              Console.WriteLine(someClass.PropertyWithEquals);       Console.WriteLine(someClass.PropertyWithGetter);            } }  public class SomeClass {     public int PropertyWithEquals = 6;     public int PropertyWithGetter {get;} = 6; }  The output of this is 6 and 6. If the output is the same, are there any other reasons to prefer one over the other?


For $a,b,c>0$ and $abc=1$. Find max: $\frac{a}{b+2a}+\frac{b}{c+2b}+\frac{c}{a+2c}$


Didn't Voldemort also survive the killing curse?

In Harry Potter and the Philosopher's Stone, Harry and his parents were attacked by Voldemort and Harry's parents died. But Harry survived because his mother had died to save him and as a result Voldemort's killing curse had rebounded upon him. But that is weird because if Harry is the only one to have survived the killing curse then Voldemort should have been dead. This leads me to think that Voldemort was able to survive the killing curse as well and so Harry wasn't the only one to survive it.


How to create a tetrakaidecahedron and keep only the edges?

The idea I have is to start from the tetrakaidecahedron, have the edges and create something organical as the photomicrograph below.


How do I remove kubuntu-full and all it's applications?

I'm running 12.04 - I installed kubuntu to try it out and realized that with all the bloatware applications that I didn't want it anymore - I was able to uninstall the kubuntu-desktop but there are still packages left over... How can I make sure I get rid of EVERYTHING Kubuntu installed - even the kde leftovers?  Here's some of what's left when I ran sudo apt-get autoremove kde then "tab" it displayed this:     kdeaccessibility              kdepim-runtime kdeadmin   kde-runtime kde-baseapps                  kde-runtime-data   kde-baseapps-bin              kdesdk-dolphin-plugins kde-baseapps-data   kde-style-oxygen kde-config-cron               kdesudo kde-config-gtk    kdeutils kde-config-touchpad           kde-wallpapers   kdegames-card-data            kde-wallpapers-default   kdegames-card-data-extra      kde-window-manager kde-icons-mono   kde-window-manager-common kdelibs5-data                 kde-workspace   kdelibs5-plugins              kde-workspace-bin kdelibs-bin   kde-workspace-data kdemultimedia-kio-plugins   kde-workspace-data-extras kdenetwork   kde-workspace-kgreet-plugins kdenetwork-filesharing   kde-zeroconf kdepasswd                     kdf kdepim-kresources   kdm kdepimlibs-kio-plugins        kdoctools   Those are all installed by kubuntu... correct?  I just want to go back to my Ubuntu 12.04LTS with Gnome2-classic and without all the kubuntu extras.  I started it off by just removing unnecessary apps that came with kubuntu-full - then realized I didnt want the whole thing at all and uninstalled kubuntu-full but it still says I have these as well:     alex@griever:~$ sudo apt-get --purge remove kubuntu-   kubuntu-debug-installer           kubuntu-netbook-default-settings   kubuntu-default-settings          kubuntu-notification-helper   kubuntu-firefox-installer         kubuntu-web-shortcuts


Integration proof: sin(1/x) is integrable

Question:     Let $f : [a,b] \mapsto \mathbb{R}$ be a bounded function. Suppose $f$ is integrable on $[a,r]$ for all $a<r<b$. Show that $f$ is integrable on $[a,b]$ and prove that $$a) \;\; \int_{a}^b f(x) dx = \lim_{r\rightarrow b^-}\int_{a}^r f(x)dx$$ Use this result to justify that the function $f:[0,1]\mapsto\mathbb{R}$ defined by: $$b) \;\; f(x) = \begin{cases}\sin \left(\frac{1}{x}\right) & 0 < x \leq 1\\0 & x = 0\end{cases}$$ is integrable.   I have proven that $f$ is integrable on $[a,b]$ by showing that there exist a partition $P'$ of $[a,b]$ with $U(P′,f)−L(P′,f)< \epsilon$ ($\epsilon$ arbitrary) and now I don't know where to start to prove the problem a) ...  please refer to the image :


How do we know the Riemann Sum gives us the area under the curve?

I'm currently learning calculus (high school senior), and I am not comfortable with the idea that the limit of the sums of rectangles actually converges to the area under the curve. I know it looks like it does, but how do we know for sure?  Couldn't the tiny errors beneath/over the curve accumulate as we add more and more rectangles? What's troubling me is the whole Pi = 4 thing with the staircase approximating a circle pointwise, and how it's wrong and the perimeter of the staircase shape does not approach the circumference of the circle, even though pointwise it does approach a circle. So how are the increasingly many, increasingly small errors in Riemann sums any different? How do we know the error in each step decreases faster than the number of errors increases? I would really like to see a proof of this.  Thanks so much!


Composite Foreign key to single primary key

How do I create a composite foreign key to a table with a single primary key? For example suppose I have the following tables:  CREATE TABLE Branches (     BranchId UniqueIdentifier DEFAULT NewSequentialID(),      CONSTRAINT pk_BranchId PRIMARY KEY (BranchId) );  CREATE TABLE Expectations (     ExpectationId UniqueIdentifier DEFAULT NewSequentialID(),      BranchId UniqueIdentifier NOT NULL,       CONSTRAINT fk_Expectations_BranchId FOREIGN KEY (BranchId) REFERENCES Branches(BranchId),      CONSTRAINT pk_ExpectationId PRIMARY KEY (ExpectationId) );  CREATE TABLE ClassSections (     ClassId UniqueIdentifier NOT NULL,     BranchId UniqueIdentifier NOT NULL,       CONSTRAINT fk_ClassSections_ClassId FOREIGN KEY (ClassId) REFERENCES Classes(ClassId),      CONSTRAINT fk_ClassSections_BranchId FOREIGN KEY (BranchId) REFERENCES Branches(BranchId),      CONSTRAINT pk_ClassSections PRIMARY KEY (ClassID, BranchId) );  CREATE TABLE ClassExpectations (     ClassId UniqueIdentifier NOT NULL,      BranchId UniqueIdentifier NOT NULL,      ExpectationId UniqueIdentifier NOT NULL,       CONSTRAINT fk_ClassExpectations_ClassId FOREIGN KEY (ClassId) REFERENCES Classes(ClassId),      CONSTRAINT fk_ClassExpectations_BranchId FOREIGN KEY (BranchId) REFERENCES Branches(BranchId),      CONSTRAINT fk_ClassExpectations_ExpectationId FOREIGN KEY (ExpectationId) REFERENCES Expectations(ExpectationId),      CONSTRAINT fk_ClassExpectations_ExpectationIdBranchId FOREIGN KEY (ExpectationId, BranchId) REFERENCES Expectations(ExpectationId, BranchId),      CONSTRAINT pk_ClassDueDates PRIMARY KEY (ClassId, ExpectationId) );   I'm trying to add the following constraint, but it won't allow me:  ALTER TABLE ClassExpectations ADD CONSTRAINT fk_ClassExpectations_ExpectationIdBranchId FOREIGN KEY (ExpectationId, BranchId) REFERENCES Expectations(ExpectationId, BranchId);   I keep getting the error:      There are no primary or candidate keys in the referenced table   'Expectations' that match the referencing column list in the foreign   key   How else do I ensure that an ExpectationId is never added to ClassExpectations without its corresponding BranchId (from the Expectations table)?


I searched before asking, and there are indeed similar questions, however I could not find one that matches exactly my situation. Feel free to point me to the right question answer / close this one, if you have better luck finding one.  I'm posting here, and not on meta.gaming.stackexchange, because I believe that the rules are the same for all sites, again, if that assumption is wrong, please feel free to let me know.  I asked . This question turned out to be a not so good question and was closed by the community. Because the question was not useful, and I could not improve it, I decided that I might as well delete it. When I choose "delete" I was prompted if I was really-really sure and that's usually a bad thing to delete questions with answers, but hey, what I'm deleting is a trash question that is also mine, why could this be bad? So I choose to proceed.  In response I got unspecific "the question cannot be deleted" message without any reason and an advise to flag for moderator attention.  So I flagged for moderator attention, and the flag was declined with the reason "it would be unfair to people who answered to delete it".  Now I'm completely confused. Could you please explain me   1) As a community do we care more about peoples rep then about site content and refuse to delete bad questions, only because some one answered them? 2) As a community do we want reward people who answer bad questions? 3) Can a message that a question cannot be deleted be made more user friendly and give a reason why the question cannot be deleted?


Why is this command deleting all entities?

I'm trying to remove a specific, named, item if it is dropped on the floor. I have the following on my command block:  kill @e[type=Item] {Item:{tag:{display:{Name:"RedFlag"}}}   But it's removing all items, not just the one I want. What am I doing wrong?  I also tried  kill @e[type=Item] {Item:{id:"red_flower",Damage:2}}   But that didn't work either, it's still removing all items, even things that aren't red flowers!


I could not prove that "Every Boolean ring is commutative", but I found it on the Internet. I am giving the idea of the proof that I "learned".  Let $R$ be the Boolean ring.  We can easily prove that $x+x = 0 \; \forall \; x \in R$. Then, we again use the same idea that $(x+y)^2 = (x+y), \; \forall \; x,y \in R$ to get that $xy=-yx$ and use the fact that $xy= -xy$ to get the result.  We had to find the new property for the Boolean ring that $x+x =0 $ to solve that it is commutative. Even with this solution, I cannot understand what makes  a Boolean ring commutative. Is there any intuitive way to understand that Boolean ring is commutative? I am not looking for just a computational answer (if possible, there should be some idea behind the computation). I am hoping for any sort of intuition or idea (mathematical or in plain English) that tells us why Boolean ring is commutative.    P.S.: A Boolean ring $R$ is a ring in which $a^2 = a, \; \forall \; a \in R $.


Is it possible for certain library packages which have been packed for an ubuntu normal release to be installed into an ubuntu LTS?

I am running the Ubuntu 20.04 LTS I need certain packages as dependencies for an opensource project I want to contribute to, however the required package versions are only available for 20.10 normal release. I realize that this isn't recommended but is there way to make apt remove that restriction and take them from the universe package registry into my ubuntu LTS?


Most of the material when heated turn red or orange or yellow, why materials don't have a tone green or blue when heated high.


Linear Diophantine eq. in three variables

I'm solving this equation in integers: $6 \, x + 10 \, y + 15 \, z = 1$. I can find many solutions, by combining two two-variable equations into $x = u \, p$, $y = v \, p$, $z = q$, where $u = 2 + 5 \, t$, $v = -1 - 3 \, t$, and $p = 8 + 15 \, s$, $q = -1 - 2 \, s$, with $s$ and $t$ integers. (see ) But I'm obviously missing some solutions. How does Mathematica arrive at this elegant general solution?


Combinatorial approach to a binomial sum identity?

So I'm trying to prove the following:  $$ \sum\limits_{k=0}^{n} {k \choose a} {n-k \choose b} = {n+1 \choose a+b+1}$$  And I'm a little caught on how to get started. It doesn't seem like a straightforward manipulation of the binomial theorem, so I was wondering if there was a nice way to visualize this in a combinatorial way -- i.e. I see that we'd be multiplying the ways of finding a subset of size a from a set of size $k$ and the ways of finding a subset of size $b$ from a set of size $n-k$, and this should equal the ways of finding a subset of size $a+b+1$ from a set of size $n+1$. I was wondering if this type of story could be extended to prove this, or if another approach was more advantageous.   This is a homework problem, tried to put as much of my thought process down as possible.


All $f$ such that $(\exists k)(f^\prime(x) = f(x+k))$

I was wondering if there is a general way to solve the functional equation  $$(\exists k)(f^\prime(x) = f(x+k))$$  I know that this is true for certain functions:  $$(e^{cx})^\prime = e^{c(x+\frac{\ln c}{c})}$$ $$\sin(x)^\prime=\sin(x+\tfrac{\pi}{2})$$  but I was wondering if these functions take a general form or are related to the eigenvalues of the second derivative, because both of these are.


abstract class constructor practical use

Can we have constructor in abstract class ?  If yes, what the use of that because we can't instantiate the Abstract class and constructor will never call.


Is there any case where one would use, snap, crackle or pop?

As we all know, if you differentiate distance with reference to time, you get speed, and likewise, differentiating speed you get acceleration. However, if you keep differentiating, to the rate of change of acceleration and so forth (more emphasis on the so forth): is there any point to this? Does it have any useful application in any industrial or practical industry, as opposed to theoretical physics?  Also, what could we possibly learn about a situation by understanding the rate of the rate of the rate of change of the objects distance?


Is it possible to leave the Schengen area a day before my flight will leave?

I was issued a Schengen visa from the German embassy. I gave all the right documents and dates, and while the date validity matches my trip, the duration of stay is 1 day less than it should be based on my tickets. (I have a 8 day duration of stay, and my flight out is on the 9th day after I land. My visa is valid until the 10th day after I land)  Is there any way I can get away with not changing my tickets? (It is super expensive to change). For example, can I get to the airport and get out of the Schengen area a day before my flight and stay "airside" for ~14 hours?


Ubuntu 18.04 HP Laptop Realtek 8821CE WiFi Adapter not working

I’m a brand new Linux user, made the switch from Windows 10 last night. I have a HP 15-db0030AU laptop that has a Realtek 8821ce wireless lan 802.11ac pci-e NIC.   Currently, the wifi section in the settings app shows that no “No Wi-Fi Adapter Found”. I have been tethering via USB to my phone.  After running commands in the terminal while following a tutorial, my adapter is being recognised and is listed, but it is not operational.  Does anyone now how to fix this?  Thank you so much in advance


Java: Searching an array by a variable in an instance of object

Overall goal is to create a library simulation that allows searches for books as well as transactions eg to borrow a book. I've only included the parts I think are relevant.   I have the array stock in the Biblio class as follows:     public class Biblio{     private ArrayList<Book> stock;   and the Book class with the constructor:      public Book(String author , String title)     {         this.author = author;         this.title = title ;         code = null;//this is a String      }   In the main method I am trying to search for a Book object using the code (which is String), I am using the findCode method in the Biblio class:      public Book findCode(String searchedCode){         Book foundBook = null;         for(Book bookObj : stock){              if(bookObj.getCode().equxals(searchedCode)){                  bookObj= foundBook;}//         return foundBook;     }   and here is the code in the main method I currently have:   Biblio libSim;  libSim = generateLib();                                                                ... System.out.println(libSim.findCode(scan.next()));   but the output is coming up as null and I think it is because the foundBook equals null. However I can't return bookObj.  I do not know how I can find an object in an array by searching for the code variable. The books are added to the library in another method and using a setter method I have set any code that equals null to a string with the format LIB0001, this is done before I call the findCode method.   How do you find an object by searching the array for a specific instance variable?


"I'm putting you on notice." Proper phrase?

I'm trying to construct a phrase that has the meaning of informing someone they are deficient and hereby directed to correct the deficiency. They type of thing a supervisor would say to a chronic screw-up after a particularly significant mistake. Not a dismissal or reprimand, but a declaration of intent toward such, or worse, without immediate correction.  I've zeroed in on "I'm putting you on ______" or "Consider yourself on ______" as phrases I've heard used for this situation, but can't decide if 'notice' is what belongs there as it has an awkward feel to me. I've considered reworking the structure to "I'm giving you notice..." which gets roughly the same message across while feeling a bit less awkward, but I keep returning to the initial structure as the base of what I'm looking for.  Is "I'm putting you on notice"/"Consider yourself on notice" the common phrase for expressing this situation or is it some other very close variant that I'm grasping at and just missing?


Intuition behind $k$-algebra, $k$-algebra morphisms?

I will state the definition of a $k$-algebra and $k$-algebra morphisms.  A ring $A$ equipped with a ring homomorphism $k \to Z(A)$ is called a $k$-algebra. More explicitly, this means that $A$ has a structure of vector space over $k$ and also a ring structure such that: (1) The operations "$+$" coming from the vector space structure and the ring structure, respectively, are the same. (2) The ring multiplication $\cdot$: $A \times A \to A$ is a $k$-bilinear map. One defines $k$-algebra morphisms as $k$-linear ring morphisms.  I understand these definitions formally, but I have quite a poor grasp on the intuition behind the definition of $k$-algebra and $k$-algebra morphisms. Could someone provide me with their intuitions on such?


Not every open set in $\mathbb{R}^n$, for $n\geq2$, is a disjoint union of countable open balls.

I know that every open set in $\mathbb{R}$ can be decomposed as the union of countably many disjoint open intervals and I'm trying to show that this property no longer holds in higher dimensions. For this I'm trying to show that there is no countable, pairwise disjoint open balls whose union is the open square $(0, 1)^2 ⊂ \mathbb{R}^2$. I know that it is because of the corners, but I don't know how to write this in mathematical terms. Thanks for any help.


SQLServer 2016 SP1 connection error with Server\Instance name via .Net

After SQLServer 2016SP1 installation, installation of ODBC Driver 13.1 resolves problem to start SQLAgent and to read Errorlog in SSMS.  However, another connection exists for .NET connection. The following connection string does not work :  $Connection = New-Object System.Data.SQLClient.SQLConnection    $Connection.ConnectionString = "server=SERVER\INSTANCE;Database=master;..."    $Connection.Open()    Connection.close()   The error message is:     A network-related or instance-specific error occurred while establishing a connection to SQL Server. ...   What is a solution or workaround to this issue?


Why do particles moving in circular motion emit em radiation?

For example particles moving in a synchrotron . Which energy of the particle is converted to the energy of the radiation ? What is the relation between this energy and the change in direction of the particle?.  Thankyou for the help .


On Kubuntu 14.04, Muon doesn't work after update and upgrade via terminal

I ran:  sudo apt-get update sudo apt-get upgrade   on my terminal.  After that, neither the "muon update manager" nor the "muon software center" work, when run, they both give an error:  Initialization Error  The Package system could not be initialized, your configuration may be broken.   Details  Encountered a section with no package: header   I tried restarting the computer, update, upgrade a few times continually, and didn't help.  Then I tried:  sudo apt-get dist-upgrade   on a terminal and got a set of these errors:  Reading package lists... Error!  **E:** Encountered a section with no Package: header  **E:** Problem with MergeList /var/lib/apt/lists/archive.ubuntu.com_ubuntu_dists_trusty-security_main_i18n_Translation-en  **E:** The package lists or status file could not be parsed or opened.   Then I tried:  sudo dpkg --configure -a     sudo apt-get install -f    sudo apt-get update     sudo apt-get install muon --reinstall   but received the same errors quoted above for the lines 2 and 4  Does anyone know why I am having all of these problems or what I have done wrong?


Exporting a single project from an SVN repository

I'm storing several projects under the same SVN repository. I've followed the manual and did this: I svnadmin dump c:\repository | svndumpfilter include <my project> > myproject.dump.  My problem is, svndumpfilter chokes with the error "Invalid copy source path", because we moved that particular project from branches back to another folder a while ago.  Has anyone dealt with this particular problem successfully?  I am currently thinking of dumping the main repository in chunks, skipping the revisions that may cause errors. I will then load each chunk into the new repository, each chunk under a folder, and merge them using Eclipse. Does this sound sane to you? Do you see any problems with it?


Searching for a sci fi story from the 50's or 60's, of snail like creatures on another planet spend their lives eating

It may be called The Gleanors, or something.  They each have a strip of land to glean, with neighbors doing the same. the story is hard to remember, but it was totally interesting. When I think back, I can only say that they must have been an excellent writer, to be able to do so much with so little in the story.


I accidentally deleted all bootloaders (Windows Boot Manager and GRUB)

I accidentally deleted all bootloaders (Windows Boot Manager and Grub). If I start my laptop it doesn't found any bootloaders. How can I reinstall at least Windows 10 boot manager and/or GRUB afterwards?


Nautilus not generating thumbnails in 13.10

Like the title says, Nautilus is not generating thumbnails for any file types (pictures, documents, pdf, etc) after a clean install of 13.10.  I have checked the preferences and it is set to always generate thumbnails.  Help please!


When I open , the padlock icon in my Firefox has a yellow warning triangle icon, clicking on it, the message says:     Connection is Not Secure      Parts of this page are not secure (such as images).   F12 console contains many messages like (all of them about gravatar.com URLs):     Loading mixed (insecure) display content “” on a secure page   Since the HTTPs version of that URL seems to work fine, I think they should be changed.


installing .deb file without internet connection without software centre

i want to install OS uninstaller i have its .deb file and the two other dependency files(.deb) required for it but when i try to install the dependency file in the liveUSB the software center opens and the install button is grayed out, is there any other way?


C# double/decimal always have two decimals

I need 45.7 to be 45.70  Math.Round(d, 2) have no effect. Have tried with decimal and double type.   I would appreciate any kind of help.


Missing number, treated as zero when renewing enumerate \item and using hyperref

When I tried to integrate the answer for my question  on my thesis document, latex throwed this error:  main.tex:26: Missing number, treated as zero main.tex:26: Missing \endcsname inserted main.tex:26: Missing number, treated as zero   After two hours, I managed to create a minimal example reproducing this error:  \documentclass[12pt]{article} \errorcontextlines 10000 \usepackage[shortlabels]{enumitem} \usepackage{hyperref}  \def\renewenumerateoptionalitem{%   \let\itemenumerateoptional\item   \renewcommand{\item}[1][]{%       \refstepcounter{enumerateoptionali}% increment the counter       \itemenumerateoptional[\bfseries##1~\theenumerateoptionali]%   }% }  \newlist{enumerateoptional}{enumerate}{1} \setlist[enumerateoptional]{     before=\renewenumerateoptionalitem,     label=\arabic*,     nosep,     labelindent=20mm,     leftmargin=*,     after=\let\item\itemenumerateoptional, }  \begin{document} \begin{enumerateoptional}[1.]    \item[Some first] item one    \item[Some second] item two \end{enumerateoptional} \end{document}   If you run this, you will get the error main.tex:26: Missing number, treated as zero. The line 26 is the first \item[Some first] item one on the enumerateoptional list.  If you comment the line \usepackage{hyperref}, everything works fine. You can also comment the line before=\renewenumerateoptionalitem, and keep enabled the hyperref package and everything will also work fine too.  After looking into the  I found this:  \let\H@item\item \newcounter{Item} \def\theHItem{\arabic{Item}} \def\item{%   \@hyper@itemfalse   \if@nmbrlist\@hyper@itemtrue\fi   \H@item }   It seems hyperref is also redefining \item to something. How can I integrate the  answer with the hyperref package?    Related questions


Finding limit when limit approches to infinity

Finding $\displaystyle \lim_{y\rightarrow \infty}\bigg[\frac{y}{e}-y\bigg(\frac{y}{y+1}\bigg)^y\bigg]$   Attempt: Put $\displaystyle y=\frac{1}{z}$ . Then $\displaystyle \lim_{z\rightarrow 0}\bigg[\frac{1}{ze}-\frac{1}{z}\bigg(\frac{z}{z+1}\bigg)^{\frac{1}{z}}\bigg]$  Could some help me to solve it, thanks


Can I count the number of times each reference is cited?

I am writing a paper, and I would like to be able to find out automatically how many times each reference is cited. This could either be appended to the references in a printed version, or outputted as a separate file.  I've seen , but it focusses on checking each reference at the point of citation, while I want to do an overall count.  The reasons are twofold. Firstly, to see if any references are being 'overcited'. Secondly, if space becomes an issue, to be able to see easily which references are only being cited once and could potentially be removed with minimum fuss.


Rational values of trigonometric functions

I am using extensively trigonometric functions when an angle is given in degrees. Some of these functions like sine or cosine have rational values, for example, the well   known example is that $\cos(\theta) =0.6 $ and $\sin(\theta) =0.8 $.       However besides the case of multiplicity of $90^\circ$ it seems there are no rational numbers $\theta$  with simultaneously rational  values of  sine and cosine.      Is it possible somehow to prove that for rational values of an angle given in degrees there are  no values simultaneously rational of sine and cosine functions, beside obvious case of multiplicities of $90^\circ$?


Does path-connected imply simple path-connected?

Let $X$ be a path-connected topological space, i.e., for any two points $a,b\in X$ there is a continuous map $\gamma\colon[0,1]\to X$ such that $\gamma(0)=a$ and $\gamma(1)=b$. Note that beyond continuity little is required about $\gamma$.     Is it always possible to make $\gamma$ a simple (=injective) curve? (Of course we consider only the case $a\ne b$).    If the answer depends on $X$, what are some mild sufficient conditions on $X$?   If $X$ is sufficiently nice, e.g., an open subset of $\Bbb R^n$, the answer is "yes";  more generally, what one would call "locally simplepath-connected" suffices (the set of points reachable from $a\in X$ by a simple curve is both open and closed). Also, for arbitrary $X$ it is clear that a single instance of self-crossing can be short-cut. But for infinitely many possible short-cuts the situation may become somewhat hairy, I'm afraid.  EDIT: To avoid Mike Miller's counterexample (indiscrete topology on $X$ with $|X|<|\Bbb R|$), let's at least assume that $X$ is Hausdorff. At any rate, $|X|\ge|\Bbb R|$ is a necessary condition - I am still looking for "as mild as possible"  sufficient conditions ...


Let $R$ be a Noetherian ring and $x\in R$ an $R-\mathrm{regular}$ element. Show that $\mathrm{Ass}_R(R/(x^n))=\mathrm{Ass}_R(R/(x))$ for every $n\geqslant 1$.  Let $M$ be an $R-\mathrm{module}$. An element $a\in R$ is called a non-zero-divisor on $M$ or $M-\mathrm{regular}$ if whenever $x\in M$ and $ax=0$, then $x=0$.


When do I apply Significant figures in physics calculations?

I'm a little confused as to when to use  for my physics class. For example, I'm asked to find the average speed of a race car that travels around a circular track with a radius of $500~\mathrm{m}$ in $50~\mathrm{s}$.  Would I need to apply the rules of significant figures to this step of the problem? $$ C = 2\pi (1000~\mathrm{m}) = 6283.19 $$  Or do I just need to apply significant figures at this step? $$ \text{Average speed} = \frac{6283.19~\mathrm{m}}{50~\mathrm{s}} = 125.664~\mathrm{m}/\mathrm{s} $$  Should I round $125.664~\mathrm{m}/\mathrm{s}$  to  $130~\mathrm{m}/\mathrm{s}$ since the number with the least amount of significant figures is two?


Lagrangian, metric and geodesics: obtention of equation of motion in GR

I would like to check my global understanding on G.R: how we determine the trajectories of particles.  Everything starts from the equations of Einstein.   We have to find a metric that satisfies thoose equation: this is the first step (which is generally really hard). Once it is done we have two different ways to proceed.    First method  We want to find the trajectories of particles. We know that thoose trajectories will be geodesics. It mean that they will minimise the length:  $$ L=\int ds = \int \sqrt{g_{\mu, \nu} \frac{dx^{\mu}}{dt} \frac{dx^{\nu}}{dt}} dt.$$  Little question: how do we know that the particles will follow geodesics? Is it a postulate of GR?  To find the minimum of this quantity is equivalent as finding the minimum of:  $$ \int g_{\mu \nu} \frac{dx^{\mu}}{dt} \frac{dx^{\nu}}{dt} dt. $$  Thus, we can say that the Lagrangian describing our moving particle is in fact:  $$ \mathcal{L}=g_{\mu \nu} \frac{dx^{\mu}}{dt} \frac{dx^{\nu}}{dt}.$$  Of course this Lagrangian has "no link" with the lagrangian of GR. The last one describes the equation of the fields and lead to the einstein equation, whereas this one is the lagrangian of a moving particle in the theory of general relativity.    Second method :  We also could use the Levi-Civita connexion. This connexion ensure the conservation of scalar product for 2 parallel vectorial field along a given curve.  Using this connexion, a geodesic is a curve which tangent vector is parallel along the curve.  Then we have a differential equation for the geodesics (which will be the same as the one derived from the lagrangian written above).    Am I right with everything I  wrote?  In fact I have a general relativity class this year which is supposed to be a part II and I haven't followed the part I so I need to catch up fast. This is why my questions are probably basics ones.


How can i Bypass the owners Google account verification on Android v10

My friend bought a used LG Android v10 T-Mobile phone and she factory reset it immediately because she didn't know the screen lock password. Unaware of the new security lock option for Google account. It says connect to Wi-Fi. Then press next. It says 'checking connection' and  'verifying Google account'. Then it directs me to the sign in requirement page for the phone set up and asks for my e-mail address.   When I put my e-mail and password in, Google security account verification calls phone to give code. I then have to type in the 6 digit code provided. It checks information and accepts my account info but before next step it redirects me to "please sign in using the owners account that was previously synced to device" and I don't have any way of knowing a name or e-mail of original owner.   Is there a way for me to bypass this Google security verification so I can use this phone?


Downcast an Object in a generic but not anywhere else?

I'm new to Java and I just started learning about generics. I learned how to write a very simple GenericList: public class GenericList<T> {      private T[] items = (T[]) new Object[10];     private int count;      public void add(T item) {         items[count++] = item;     }      public T get(int index) {         return items[index];     } }  The line that particularly troubles me is the first field: private T[] items = (T[]) new Object[10];  I'm curious why this is allowed. I don't see how this is any different from something like this: private String[] items = (String[]) new Object[10];  The second statement satisfies the compiler because it sees we're trying to cast to a string, but breaks at runtime because downcasting doesn't work like that. The type "T" will of course always be a descendant of Object, so I don't understand how generics don't break at runtime for the same reason. I guess what I'm trying to ask is what exactly happens at: a) compile time, when GenericList.java is compiled b) runtime, when an instance of GenericList is instantiated Are instructions for creating a new Object[10] array compiled into GenericList.class? And then at runtime when an instance of that class is instantiated, that Object[] gets cast to whatever T[] is? Again, that's where I get confused because that should break the program. Any help/resource is appreciated! Thanks


Favicon of Earth Science and Spanish are too similar (exactly the same in HNQ list)

The favicon is used in various places around the Stack Exchange (SE) network, to identify the site. Currently, Earth Science has  for main and  for meta. The problem I see is that these are awfully similar (i.e. exactly the same, as demonstrated here) to those for Spanish.SE, which are  for main and  for meta. The larger versions offer slight differences, but it's still hard to tell quickly which is which. Power users on this site, did you guess right, even after some time to think about it? (Answers under spoiler tag).   for main and  for meta.  for main and  for meta.    The first one is Earth Science and the second is Spanish.  Should SE visually distinguish between the two very different sites?


How do you generate correlated ARMA(1,1) models?

I am interested in generating two ARMA(1,1) time series with a pre-defined cross-correlation p between x(t) and y(t).  If you could please provide the mathematical framework and the code in R for generating it would be perfect!  I have looked at the question  which is not a duplicate, since that question (despite the title) looks for a given correlation between the errors, while I am looking for a given correlation between the series themselves.


Allow wildcards in ignored/interesting tags

I'd like to be able to specify an interesting or ignored tag via a wildcard.  May tags which cover similar topics have common roots.  For example  windows windows7 windows-vista windows-xp windows-errors windows-xp-sp3   would all match the wildcard windows*.  Someone who finds one of these tags "interesting" would probably find all of them to be "interesting" (or vice versa, if they want to ignore all the windows related stuff, they would need to ignore all of these tags).  I realize that technically everything tagged windows-xp should also be tagged windows, but that's not the case.  ()


My file test2.tex  \documentclass{article} \usepackage[utf8]{inputenc}  \begin{document} \section{Hello} Testing Bibs from Jabref \cite{einstein}  \bibliography{mybib} \bibliographystyle{plain}   \end{document}   and my mybib.bib file  @article{einstein,     author =       "Albert Einstein",     title =        "{Zur Elektrodynamik bewegter K{\"o}rper}. ({German})         [{On} the electrodynamics of moving bodies]",     journal =      "Annalen der Physik",     volume =       "322",     number =       "10",     pages =        "891--921",     year =         "1905",     DOI =          "http://dx.doi.org/10.1002/andp.19053221004" }   Compile using pdflatex -interaction=nonstopmode -synctex=1 test2.tex  I always get an error :  Citation einstein is undefined and No file test2.bbl   What am I missing?


I'm occasionally have my keyboard switch mode switch from British English to American English while I am typing (or more generally have the system loadedd up doing normal things) and I'm unable to identify the cause.  This can be fixed by clicking on the scrabble tile language (top right) and reclicking on EN (it still says English before you click) - but I'm curious as to what is going on. Has anyone encountered (and solved) this before?


Make chocolate with a high melting point?

Is there something that can be done to chocolate which will raise its melting point?  I ask because  wanted a way of getting space dust into a cake, which might be able to be done by encasing it in chocolate chips, but to have the best chance of success the chocolate needs to have a higher melting point.  So can this be affected, and if so by what?


In a dual boot system, how does the BIOS choose which bootloader to run?

I have a dual boot of Windows and Ubuntu. When I switch on the machine, the BIOS does POST and after that the bootloader starts.  I want to understand how the BIOS chooses which bootloader to run. I want to know the process going on between the BIOS and the bootloader in a dual boot computer.


Determine the exact date of creation of an Apple ID

Is it possible to determine the exact date and time (if possible) of creation of an Apple ID?   Is there any official or unofficial way to establish this if you don't have the initial sign up information recorded?


Can the Mavericks install binary be shared between two different apple accounts?

My question is similar to , but instead of re-using the Mavericks install file on my own Macs, I would like to make a copy for a friend (so he doesn't have to download such a huge file over his slow connection).   Is this legal?   A side thought; Does this question even make sense if the binarys have the same checksum?  Is there anything unique to the install file? (e.g.: My app store account details.)   I was thinking if we dropped it in place in the /Applications dir and then he went to the app store and "bought" it, it would detect the file was already in place and proceed as if it had been downloaded.  (Not trying to do anything dodgy, just trying to save him from downloading a file that I already have.)


RHEL 7.5 Cannot Yum install from text file

I cannot figure out why installing packages listed in a text file with Yum wouldn't work but for some reason it does not. Yum cycles through all the listed package names and and lists them as available but at the end it shows the last package as installed with "Nothing to do". There has to be a way of doing this.  I tried the following:  yum -y install $(/tmp/installs.txt) yum install -y $(awk '{printf("%s ",$1)}' /tmp/installs.txt) for i in $( /tmp/installs.txt);do yum install $i -y;done yum install `cat /tmp/installs.txt | tr '\n' ' '` yum install $(cat /tmp/BSTNinstalls.txt)   Is this not allowed in Redhat or is there another way to go about this?


Strange applications of the Axiom of Choice

I've heard a lot of differing opinions about the Axiom of Choice (AOC): some don't mind it, some hate it. Yet, so far every time I've seen the axiom of choice being applied, it doesn't seem too crazy to be able to apply a result like that. What are some strange/overreaching results we can reach with AOC? I know AOC is used in proving the Banach-Tarski paradox, but the usage isn't too strange.   For the sake of completeness:  The axiom of choice  states that for any non-empty collection of sets $\{X_{\alpha}\}_{\alpha}$, we can pick $x_{\alpha} \in X_{\alpha}$ for each $\alpha$. For finite sets, this can be deduced from other axioms of set theory, but for infinite sets, it needs to be an axiom and cannot in fact be deduced from more basic axioms.


Title says it all (I think). I'm betting it's something to do with Standard Integrals though. What is this symbol "$\int$" called?


It was an interview question that a List contains 5 objects like Organisation, Employee, Address,Country etc. How will you know which object is the heaviest one without running through java agent. There is one condition that all the objects available inside Arraylist are not serializable. Basically interviewer wants know how to write code know the size of the objects available inside ArrayList so that you can now that a particular object is heavier. Please provide me help. Once again let me put the conditions once again.   You can not use any profiler tool. All the objects are not serializable. You can run though java agent.   You have to write code to test and run as normal java program.


Making an Ubuntu 16.04 64 bit bootable USB drive using the startup disk creator utility on an Ubuntu 12.04 32 bit computer

I made a bootable Ubuntu 16.04 64 bit USB drive using the startup disk creator utility on an Ubuntu 12.04 32 bit computer. The final message of the startup disk creator utility said that the bootable drive is successfully created and I can use it. When I boot my other 64 bit computer using this Ubuntu 16.04 64 bit USB drive I get the following message:   What could be the problem?


What is the meaning of the axes in t-SNE?

I'm currently trying to wrap my head around the  math. Unfortunately, there is still one question I can't answer satisfactorily: What is the actual meaning of the axes in a t-SNE graph? If I were to give a presentation on this topic or include it in any publication: How would I label the axes appropriately?  P.S: I read  Reddit question but the answers given there (such as "it depends on interpretation and domain knowledge"), don't really help me to understand this.


As a normal user, how should I act on posts showing a severe level of paranoia or signs of other mental problems?

As a normal, unprivileged user, I wonder what I should do if I encounter a post on any SE site which contains signs of severe mental health problems like paranoia or persecution mania, but not necessarily any suicide notes.  Last time when I stumbled over such a post, I left a custom moderator flag explaining that I think the user has mental problems. It was marked helpful later and the post got deleted.  However, I would like to ask whether that was the right way to react or whether I could/should have done something else. I didn't really dare to leave a comment regarding their mental state, as I feared it might worsen the situation. What about technical comments, e.g. if I can explain that something they see as threat is actually normal and why - should I post that? Or just flag it and leave?


Number of real roots of $\sum_{k=0}^{n}\frac{x^{k}}{k!}=0$

Prove the following, without induction. Is it possible?         The equation $\sum_{k=0}^{n}\frac{x^{k}}{k!}=0$ has no real root if $n$ is even.   And if $n$ is odd, it has only one real root.       I also tried searching the proofs many times with search key words "number of real root" or "exponential function" or "$\sum_{k=0}^{n}\frac{x^{k}}{k!}$". But failed. What is the way to search the related topics?


I want to create threads that will add something to an array, but, if they don't do that in less than 2 seconds, I want to terminate them. This is a prof of concept, so the code is simple. Every second I want a thread to add that item in the list, so a thread runs after 0, 1, 2, 3 and 4 seconds. The idea is to not let the thread 3 and 4 run. import threading, time  myList = []  def foo(value):     global myList     time.sleep(value)     print("Value: {}".format(value))     myList.append(value)  threads = []  for i in range(5):     th = threading.Thread(target=foo, args=(i,))     threads.append(th)  for th in threads:     th.start()  What do I do now? I tried using some other logic like using th.join(timeout)  But that doesn't seem to work.


Changing a row's color depending on the value ( TEXT ) of a cell

In a cell, I have the choice of YES and NO for values. I would like to know how to change the background color for other cells in the same row depending on the value of the first without changing the values in the other cells.  How can I do this?


I accidentally enter to gmai.com trying to enter to gmail. I saw a moving image that seems to be loading and immediately I closed firefox. Do you know if that site is safe? And in case it's not.I What should I do? I use that PC for working, because of that I fear. Thanks.


Possible Duplicate:          Multiple networks I can connect to have the following set up. There is a single node that can be accessed with ssh from the internet, and from there you can ssh to the inside network.  Is there a way, that on my ubuntu box (no sudo rights), I somehow can configure that the command ssh internal.host is first setting up an connection to external.host and from there to internal.host? In the ideal situation it would be something very transparent, so that I even would be able to do scp myfile internal.host:  All authentication is done with certificates.  Btw. I am aware of ssh tunnels. I'm only searching something more transparent, I don't want to have to always manually open an ssh tunnel to reach a host.


Find all primes $p$ such that $(2^{p-1}-1)/p$ is a perfect square. I tried brute-force method and tried to find some pattern. I got $p=3,7$ as solutions. Apart from these I have tried for many other primes but couldn't find any other such prime. Are these the only primes that satisfy the condition? If yes, how to prove it theoretically and if not, how to find others? Thanks in advance!


can we check if a key exists in a map in vf page

is it possible to check for a specific key in a map i.e., whether it exists or not in VISUALFORCE page?  Based on this i need to render a pageblocktable.


How to show that any separable space is CCC

I thought I had the proof of this in my head, but it doesn't sound right on paper. Can someone see if my argument could be improved.  Let $(X,\tau)$ be a topological space that is separable, then it contains a countable dense subset $\{D_n\}_{n \in \mathbb{N}}$. Then $X$ is CCC if it does not contain any uncountable collection of disjoint open sets.  My argument:      By contradiction, suppose $X$ is separable but is not CCC.       Since a countable dense subset could only intersection countably many   open sets, there exists some open sets $U$ that $D_n$ fails to   intersection.      Therefore, $X$ is not separable as claimed.    My problem with this statement is that: Since a countable dense subset could only intersection countably many open sets...  Is there to make the middle paragraph rigorous? The whole proof feels wrong, please assist!


How can black holes have infinitely small mass?

This is my question. Black holes have infinite density right? (At least that is the leading theory), but if they have infinite density, and a finite amount of mass, then they must be infinitely small with means they can't have any volume. But that can't be possible because the definition of matter is anything with mass AND VOLUME. So that means black holes can't be made of matter because they are infinitely small, but they still some how have mass. I can't figure this out.


Where does Windows store its wallpapers?

I run Windows XP and the wallpaper I used to have got lost. I have backups of the system itself, so if I knew where to look, I could find a copy of the old wallpaper.  I have some idea of the original filename (searching now), and I recall it saves it as a bitmap, but an exact location would be helpful.  It was a photo/JPEG that used to be on the filesystem, and I don't have backups, so the Firefox, and Internet Explorer wallpaper locations are unlikely. I checked %SYSTEMROOT%\system32 as well - so I'm assuming it's somewhere else.


$X$ and $Y$ are continuous random variables. Find $E(X\vert Y=y)$ given $f_{X,Y}(x,y)=1$ for $0<x<1$ and $2x<y<2$ and $0$ otherwise.    I have computed $f_X(x)=\int_{2x}^{2} 1dy=2-2x$  and $f_Y(y)=\int_0^{y/2} 1dx=\frac{y}{2}$  then $E(X\vert Y=y)=\int_0^1 xf_{X\vert Y}(x\vert y)dx$  $$\int_0^1 x\frac{f_{X,Y}(x,y)}{f_Y(y)}dx$$  $$=\int_0^1 x \frac{1}{\frac{y}{2}} dx$$ $$=\int_0^1 \frac{2x}{y}dx$$ $$=\frac{1}{y}\int_0^1 2x dx$$ $$=\frac{1}{y}(x^2)\vert^1_0$$ $$=\frac{1}{y}$$  Answer is supposed to be $\frac{y}{4}$


Any relevant knowledge/studies about voluntary goose bumps

I'm not entirely sure how normal this is, but since I was a child, I've been able to produce myself voluntarily a "chill" sensation that seems to start on my head and traverse the rest of my body, being least intense in the feet. Looking around the internet and forums, looks like other people but not everybody also describe this ability. However, unlike other people's reports, I don't see "goose bumps" on my skin, at least there aren't any visibly; it's just the sensation.  Does anybody know if there are any relevant studies or knowledge out there about "voluntary goose bumps"? Is there even a proper name for that?


I would like to tweet a message using terminal.  I tried something like:  curl -u 'TwitterUsername':'TwitterPassword' -d status=”Your Message Here” https://twitter.com/statuses/update.xml   but seems this isn't working anymore.  I get a error like this one:  <?xml version="1.0" encoding="UTF-8"?>     <errors>     <error code="53">Basic authentication is not supported</error> </errors>   So, how could we tweet from the terminal?  PS.: my motivation to this is because I use the Yakuake terminal a lot, and it would be awesome to tweet from there.


How can I return an object from a ArrayList? (JAVA)

I would like to return the Host thats have the same domain as the Host in the List. But it gives me and error: "This method have to return a type of Host".  How I have to return the object Host?  public class Manager {  private List<Host> hosts = new ArrayList<Host>();  public Host getHost (String domain) {        for(int i = 0; i < hosts.size(); i++) {           if(domain == hosts.get(i).getDomain()) {               return hosts.get(i);           }}         }     Thanks.


I am trying to add new layers into a specific group which I can get to work if I know the index, but how can I get Python to find the index of a group so it can load the new layer into the group wherever it is in the TOC?  qgis.utils.iface.legendInterface().moveLayer( layer, index )


Example, assassin rogue with the charlatan background, both the class and background specify the disguise kit as a proficiency. What do you do about that to even it out? With the second proficiency do you turn it into expertise? Or do you choose another kit to become proficient in? Or do you just lose out on a proficiency?