Surface where number of coordinate charts in atlas has to be infinite

In the definition of a parametrised surface $S$, for every point in the surface, $p \in W \subseteq S$, where $W$ is open, there exists a coordinate chart or patch , $F :U\to \mathbb{R}^n$ that maps to $p$ from an open subset $U \in \mathbb{R}^n$  Is that right? If anyone knows of a more general definition, I'm willing to learn. It sounds a lot like a manifold, which I'm not entirely familiar with.  In this definition, the number of surface patches in the atlas is not stipulated. Given a parametrisable surface, is a finite number of charts sufficient to describe the surface? Can we find a surface that requires infinitely many patches to fully chart? If so, in which $\mathbb{R}^n$ does the first such surface occur?   In which dimensions is it always possible to find a finite number of patches for any given surface?  EDIT: Added requirement that such a surface (manifold) be connected. One made from infinitely many disconnected subsets would have to be charted infinitely.


I'm trying to create a buffer   I'm using QGIS 2.4.0  layers and have street departments and rivers with coordinate system EPSG: 4326 - WGS 84   I need to create a buffer layer 500 meter rios    This is my rivers layer    but my result look like this


How to fix time lapse issues in Fallout Shelter

I've had Fallout shelter on my android phone from release on the 13th of Aug and all worked well. That was until I went to a mates wedding in Greece and changed the time on my phone to +3 and then back when I returned.   All the timers on the rooms, rush options and training times went screwy.  I have managed to reset the timers, the majority of which were fixed by rushing in each room or sending dwellers to train elsewhere or like the countdown for the radio room which went up to around 5 or 6 hours, they simply timed out and reset... But I have been left with a one remaining issue.  Now whenever I send a dweller out to explore nothing happens. They just head out into the wilderness and report nothing. I've sent every dweller in my vault out to explore for hours and hours and still they all report nothing.  Any ideas how I might resolve this issues? Clearing the Cache didn't help.


Python solving matrix simultaneous equation incorrectly


Can an IRA recharacterization be unrecharacterized?

Here's what happened:   I made the maximum contribution to a Roth IRA this year. I thought about how my marginal tax rate now is a lot higher than I expect it to be in retirement, so I decided a traditional IRA would have been a better idea. I recharacterized this year's contributions to a traditional IRA. I realized my income is too high to qualify for a traditional IRA deduction.     Here's what I did not do, and why this question is not a duplicate of similar questions already asked:   I have not made any conversions at all. I have not taken any distributions, and thus have not received a 1099-R. I did not previously go from a traditional to a Roth, and now want to go back to a traditional. I am not rolling over any 401k or other non-IRA account.    seems like a good duplicate, but alas it's very old and has no answers.    My understanding is that (for married, filing jointly taxpayers for 2015) that someone with a MAGI above $118,000 is not eligible for a traditional IRA deduction. Below $183,000, the full Roth IRA contribution is still allowed.  I'm in this range (between $118,000 and $183,000), so a Roth IRA seems like the only rational choice. Please correct me if I'm wrong.  So, I would like to unrecharacterize (rerecharacterize?) this year's IRA contribution back to a Roth IRA. I've not yet filed a return for the contribution year, so I'm hoping I can do that.  Can I? Would I report to the IRA two recharacterizations? Or would I file as if no recharacterization ever happened?


I was hoping you guys could recommend reading material on quantum information. I have a good background in quantum mechanics, including in foundational issues, as covered in Ballentine's Quantum Mechanics.  I am interested in the intersection of quantum information and quantum foundations, such as in the works of C. Fuchs and in the research of the Perimeter Institute. While I prefer a more rigorous text, I'm trying to be as open as possible and would enjoy any suggestions or recommended reads.  Currently, I am reading the book by Busch, Lahti and Grebowski, notes on ArXiv by Keyl and also the notes by Preskill.


What's the proof that $\sqrt {AB} = \sqrt A \times \sqrt B$

Sorry for simple questions, just trying to understand the basics. I suppose since  $\sqrt x = x^{\frac12}$ the proof must be the same as: $$(AB)^x =A^x \times B^x $$ But then how do you prove that?


Can I transfer installation directory of a particular package to another computer to avoid the installation step?

I installed one package in my Linux machine and I want to install the same package on another Linux machine. Can I directly copy the installed directory from one computer to another computer? I mean cloning the installation directory.


I am trying to make a connect 4 board that is of any size, here is the code: row = []  board = []  empty = "-"     numOfRows = int(input("Rows: "))  numOfCs = int(input("Columns: "))     for i in range(0, numOfCs):      row.append(empty)        for i in range(0, numOfRows):      board.append(row)      print(board)  board[4][1] = "R"  print(board)   And it prints (if the board is big enough) the list, but in for some reason it replaces "R" for all of the columns in the list, how can I make it only replace the singular value?


How to turn off chrome's annoying auto-fill?

For example: If I type reddit.com, it autofills it to reddit.com/r/fffffffuuuuuuuuuuu based on my history.  I wanted to go to reddit.com, not F7U12. Any way to turn this off?


How to forward X over SSH to run graphics applications remotely?

I have a machine running Ubuntu which I SSH to from my Fedora 14 machine. I want to forward X from the Ubuntu machine back to Fedora so I can run graphical programs remotely. Both machines are on a LAN.  I know that the -X option enables X11 forwarding in SSH, but I feel like I am missing some of the steps.  What are the required steps to forward X from a Ubuntu machine to Fedora over SSH?


How many entries into this contest before a win is guaranteed.

I thought of a sort of "game" that illustrates a situation where a person's probability of "winning" ranges from 0 to 1. I'm sure there's a name for it, or a better way to put it, but anyway, it goes like this:  There are N entries allowed in a contest. Every time someone submits an entry, one of the existing entries is swapped out (at random) and the new entry is added. Each person can submit more than 1 entry, but only 1 at a time. There's a glitch in the system where all the entries are in and ready to pull, but Tom, who currently has no entries in the contest, is still allowed to submit. What is the average number of times Tom has to submit to ensure all of the entries are his, resulting in a 100% chance of winning?  Obviously, if Tom submits 0 entries, he has a 0% chance of winning. The entries are swapped out at random, so he will at least have to submit 100 entries; however, every time he submits he might swap out an entry he already has. If he keeps swapping one of his entries for a new one of his entries, he stays at a 1/N probability of winning no matter how many entries he submits. So obviously the expected value of number of turns to guaranty a win ranges from 100 to Infinity.  For N=100, the average appears to be ~520, which I determined empirically. I am looking for a mathematical way to determine what this average, expected value would be based on N.  For various values of N: N      Apparent Ave 10     29 50     220 100    520 500    3360 800    5820   I scripted up a little R code to determine what the value might be, and that should help illustrate what I'm asking. Obviously not going for code-golf here.    tres <- 1000 ress <- vector("numeric",tres) bigN <- 100 for (i in seq_along(ress)){   sdf <- rep(0,bigN)   counts <- 0   while (any(sdf==0)) {     sdf[sample(length(sdf),1)]<-1     counts=counts+1   }   ress[i] <- counts } summary(ress)


Are features in Random Forest sampled with replacement

My understanding from the sklearn random forest classifier documentation is that at every node, a new sample of m features are sampled from a total of M. Some criterion is computed for each of them and the best one is selected to split on. My question is, are these features sampled with replacement?  Here they say they do Random forest tree growing algorithm and to stop at some number of samples in a leaf to be able to detect some relationships, but the default value for the min samples leaf parameter in the sklearn implementation is 1. If this is the case why would you split on the same feature twice?  My guess would be that they are not, such that at every node a new feature sample of size m is taken from M removed with all features previously split on, hence every tree wil either grow to depth of max M or stop once every leaf node is pure.  Which one of the two is it?


Understanding Cylinders expressed as Inequalities

I am currently studying for the MEXT exam (an underdrag math exam for people seeking to studying in Japan with a MEXT Scholarship) and meanwhile I understand most questions I do not know how to approach this one at all. Can someone give me some tips or advice on how to approach this question or what to study in order to answer it? I do not need the answer as I was given the answer in a seprate document, yet I want to learn how to solve it. Thanks.


What's the big deal with the first FTL jump in the Battlestar Galactica miniseries?

In the miniseries the first time we hear about FTL jumps (Adama ordering the jump to Ragnar Anchorage), there's an exchange on how dangerous it is ("we could end up in the middle of a sun") and after the jump they actually clap. So it seems like jumping is a big deal, but not much later it turns out that random civilian ships jump all around, and giving the impression that it is very routine to jump for a lot of ships. So what's the deal with that first jump?


VirtualBox Guest OS gets IP address in different subnet range

I installed a Debian-based Linux distro on a virtual machine with VirtualBox on an iMac. The private IP of the iMac is in the subnet range of 192.168, where as the Guest OS' IP is in the subnet range of 10.0. How do I make sure that the Guest OS gets the same IP range as the Host OS?


Is there such a thing as charge density in quantum mechanics?

Is there such a thing as a time-varying charge density in quantum mechanics? I am looking at the tungsten filament in a light bulb. Am I allowed to say that there is a wave function which describes that filament, and that in some sense there is a time-varying charge density (which some people call a probability) associated with the square of that wave function? There are electrons which have a probability distribution, and there are nuclei which are vibrating within the lattice, but all in all is there, or is there not, a time-varying charge distribution associated with that glowing filament? And if not, why not?  EDIT: There seems to be some question as to just what kind of charge-density fluctuations I am talking about. Let me clarify: in a hydrogen atom in the ground state, I would say there are NO charge density fluctuations. But if there is a superposition of the ground state and a 2p state, I would say the charge distribution fluctuates sinusoidally at the difference frequency of the two states. THAT is the kind of charge density fluctuation I am asking about for in the tungsten filament. Does it or doesnt' it?  I hope this clarifies the intent of my question.   RE-EDIT: In a separate (and rather hard-fought) discussion, it appears that people who know more than me agree that there is indeed an oscillating charge distribution in the hydrogen superposition as described above (see  ).  So if there is an oscillating charge in the hydrogen atom, why wouldn't there be oscillating charge in a heated tungsten filament?


Misc. Q's for installing Ubuntu Phone/Tablet on the Galaxy S5

I want to install Ubuntu on my Galaxy S5 with 16 GB and I had many things that are way over my head:      -Can It be dual booted? -Is it possible to boot from the micro-sd card slot?      -Is it possible to install ubuntustudio?      -How can the warranty be retained?      -What software is available for calling/texting through Verizon's network? -What would make more sense to install: Ubuntu Phone or Ubuntu Tablet? Answers to any of these questions are greatly appreciated  :)


Why is the plural pronoun **them** used here?

Look at the following sentence that I just saw while viewing a profile:  Apparently, this user prefers to keep an air of mystery about them.   As it looks, them refers to this user, right? This user refers to one person; however, the pronoun them is used which refers to many people and seems incompatible.  Can somebody explain why this sentence is right and why him/her aren't used?


Evidence of family members remaining in your home country whilst you travel for Standard visiting visa

I am from Indian. My parents are staying in India but I am working in China. I need to apply for UK Visa from China. Do I need to submit any documents as a support for "evidence of family members remaining in your home country whilst you travel"? If so what kind of document I suppose to ?


android - launch different activities depending on edittext values

I want to launch different activities depending on the values of 2 EditText fields on the start activity, one should start for admins, the other for all other users.  I think you 'll understand better seeing the code I 've done so far:  package com.example.xxx;  import android.app.Activity; import android.content.Intent; import android.os.Bundle; import android.widget.Button; import android.widget.EditText; import android.view.View;  public class MainScreenActivity extends Activity {      EditText USERNAME, PASSWORD;     String username, password;     Button btnLogin;      @Override     protected void onCreate(Bundle savedInstanceState) {         super.onCreate(savedInstanceState);         setContentView(R.layout.activity_login);         USERNAME = (EditText) findViewById(R.id.username);         PASSWORD = (EditText) findViewById(R.id.password);          // Button         btnLogin = (Button) findViewById(R.id.btnLogin);           // login click event         btnLogin.setOnClickListener(new View.OnClickListener() {              @Override             public void onClick(View view) {                 // Launching next activity                 if (USERNAME="admin" && PASSWORD="1234") {                     Intent i = new Intent(getApplicationContext(), admin.class);                     startActivity(i);                  } else {                  Intent i = new Intent(getApplicationContext(), user_form.class);                 startActivity(i);                 }             }         });     } }   The error is at the if statement, on PASSWORD="1234" says "Incompatible operand types EditText and String". I also tried password="1234" and password.toString="1234" but no luck.  I'm not even sure if I'm to use 'USERNAME' and 'PASSWORD' or 'username' and 'password'. How can I make this work?  EDIT: Ok now the code is correct, having if (USERNAME.getText().equals("admin") && PASSWORD.getText().equals("1234")), but the application always opens the user_form activity, and not the admin, even though I input the specific values. Where is the mistake?


Tried to move a file and now i cant find it

I am using Ubuntu 15.10 and I had a file name __app.zip and I was wanting to move that inside the folder name testing  To move the file i used the following command after which I cant find the file anymore, from searching online I understand now that i did not need to put / before the folder name.  sudo mv __apps.zip /testing   Is there anyway to get the lost file back?


Installing Ubuntu alongside Windows on 3TB HDD "exceeds the msdos-partition-table-imposed maximum"

I'm trying to install Ubuntu alongside Windows. I have a 3TB hard drive, but when I installed Windows 7 it only allowed me to use 2.2TB.  I want to install Ubuntu in my free hard drive space (which isn't formatted). I supposed I should use the Something else option, but I really don't know what to do. I tried the Install alongside Windows option and it gave me an error message     starting sector number, 4294967296 exceeds the msdos-partition-table-imposed maximum of 4294967295   What should I do?   motherboard : Asus Maximus IV // Hard drive    : Western Digital Caviar Green 3TB


Extending a class in the method signature

Can someone explain what this does? This is a generics question but since I'm learning in Java I tagged it as Java.  public static <T extends Comparable<? super T>> void quickSort(T[] list) {...}  What I don't understand is this part: <T extends Comparable<? super T>>  I have tried looking at  but it doesn't seem to explain it in a clear way.  My guess is: the genetic type T extends the Comparable interface which itself requires a generic type to be a superclass of a generic type. But I don't really understand this.


Sometimes I think, for example, that a mathematician cannot be religious. I mean, the idea of belief in a God is very antiquated and not coherent for a scientist like a mathematician. But I know that Gödel said he believed in a superior being. He was a deist, not a theist. He declared this. And this makes me curious because it let me believe that religion and science have really something in common – but I can't explain what.   I think, a scientist should accept only logical statements and the point of view of an atheist is more logical than others, I believe.   What do you think?


How to move "n" to the top, "i" to the bottom for this symbol $\prod_{i=1}^n$

this command   \prod_{i=1}^n   could generates this symbol    How to move "n" to the top, "i" to the bottom, like this


Prove $E((X+Y)^p)\leq 2^p (E(X^p)+E(Y^p))$ for nonnegative random variables $X,Y$ and $p\ge0$

Suppose $X \geq 0$ and $Y \geq 0$ are random variables and that $p\geq 0$   Prove $$E((X+Y)^p)\leq 2^p (E(X^p)+E(Y^p))$$  Proof   Since $(X+Y)^p \leq (2 \> \max\{X,Y\})^p=2^p \> \max \{X^p,Y^p\}\leq 2^p(X^p+Y^p)$ $ \implies E((X+Y)^p)\leq 2^p (E(X^p)+E(Y^p))$   If $p>1$ the factor $2^p$ may be replaced by $2^{p-1}$ If $0 \leq p \leq 1$ the factor $2^p$ can be replaced by $1$   Need help with part 2 and 3 any suggestions


How to use \s16o2 as a newcommand in latex and bibtex?

I would like to use the \s16o2 newcommand for S$^{16}$O$_2$. How to define it? Thank you for your help!


I'd like to attach a light to a specific object. I used "ctrl j" but it's not permanent. For example a car or street light that I can move around the scene etc. I change my mind a lot.


Backing up disk images to network shares with empty space removed?

I'd like to use dd to create some disk image backups to S3 buckets, however the extra space that's included from empty space is not tolerable. I have thought I could pass it through xz to compress out the zeros, however when this happens, it seems that it's not really losing the empty space padding.  Any ideas on how to properly to pass a dd stream on through a compression algorithm so as to create minimum sized images directly on S3 mounts?  These images will range from tens of MB to tens of GB of data with very little local working space for the upper bounds and so it's necessary to remove the 0s as early as possible (ie, perhaps reducing the buffer or chunk size for the compression tool).


How to fix missing characters from font after awakening from suspend?

I find that often after awakening from suspend on Ubuntu GNOME 16.04 with GNOME 3.20 (I have only found this issue on the latest version, though I have not tried with GNOME 3.18 on 16.04) that I get this strange font issue which can't be fixed by restarting gnome-shell and seemingly only by restarting my entire machine:            I do not believe that this is a theme issue as I have tried all the built-in themes (including the dark and light versions) and it is the same for them all. Though it does not seem to affect gnome-shell areas, that is the top-bar, the Activities Overview, etc, are not affected for some reason. So what could this issue be caused by and how can I fix or workaround it?  Information Update:  I have had a look at  but the only options in the gnome-tweak-tool for Antialiasing are Rgba, None, and Grayscale, but none of them seem to have any affect on the issue. Is there something I'm missing?


Force / Encourage Answers with explanation

Lately i have seen many answers to "trivial" questions being just a block of code, which is, I must admit, most of the times very self-explanatory and obvious, but only to people with a bit  more knowledge than the newly created 10 rep whatever-beginner.  please compare  and revision two. it is not much of a problem to write three lines of explanation, instead of providing a solution, and having OP return for a simple variation of the problem.  Thus I would like to discuss the introduction of a feature:  Dialog-Box with "please consider adding further explanation to you answer", when a submitted answer consists only of a code-block


Please, give-me a hint to prove this proposition:     Let $\mathcal A$ be the ring of all continuous real functions (with the usual operations of sum and multiplication) defined on the interval $[0,1]$, and $I= \{f \in \mathcal A;f(0)=0 \}$. Prove that $I$ is a maximal ideal of $\mathcal A$.   My approach to this problem was the following: consider $I \subset Y \subset \mathcal A$, with $Y \neq I$. Then I must prove that $Y=\mathcal A$. Since $I \subset Y$, there exists a continuous function $g$ such that $g \in Y$ and $g \notin I$, i.e., $g(0) \neq 0$, or $g(0)=a, a \neq 0$. Now, if I manage to show that $1 \in Y$,  then I am done. So I ask: What should be the next step? Thanks in advance!


I trying to echo  this line:  $mother_name = "סבטלנה ואסילבנה";  echo strrev($mother_name);   result is: �נבליסאו� �נלטבס�  What is wrong? Where from I getting this � symbol.  and when I trying to echo single char from the string I getting also � for example $mother_name[0]


Why might right aligned field labels be better?

For the longest time, I've used left-aligned labels in my forms, like this:    I did this because I thought having the labels left aligned made it easier for readers to scan the list of labels.  However, I found my axiom challenged recently while watching  from , in which Billy asserts that right-aligned labels are simply better, like this:    I've done a bunch of research and found a lot of discussion, including , which compares and contrasts the approaches, but nothing definitive.  In particular, I haven't been able to find anything to indicate why Billy Hollis changed his opinion from left- to right- alignment for labels (apparently he switched around 2007).   I figure Billy's too smart to have made the change without evidence - so I'm interested in seeing that evidence for myself.


Overriding Tkinter "X" button control (the button that close the window)

When the user presses a close Button that I created, some tasks are performed before exiting. However, if the user clicks on the [X] button in the top-right of the window to close the window, I cannot perform these tasks.   How can I override what happens when the user clicks [X] button?


Real Analysis Continuous Function Problem

Show that the only continuous function on $(-1,+1)$, which is not identically zero and satisfies the equation $f(x + y) = f(x)f(y)$ for all $x,y \in \mathbb{R}$, is the exponential function $f(x) = a^x$ with $a = f(1) > 0$.


I installed Ubuntu 14.04 (clean install). I like it a lot, but the system would freeze and computer sometimes would even restart by itself. Does anyone else have the same issue and how it can be resolved? The crashes would happen about every 30 minutes, but mostly when I watch youtube videos (but this could be coincedence). I installed 12.04, and everything is fine now, but I would really like to upgrade.


When I entered the -al attribute with the  command, I got the following:  anupam@JAZZ:~/blog$ ls -al total 76 drwxrwxr-x 13 anupam anupam 4096 Aug 28 21:45 . drwxr-xr-x 34 anupam anupam 4096 Aug 28 20:52 .. drwxrwxr-x  8 anupam anupam 4096 Aug 28 12:19 app drwxr-xr-x  2 anupam anupam 4096 Aug 28 12:19 bin drwxrwxr-x  5 anupam anupam 4096 Aug 28 12:19 config -rw-rw-r--  1 anupam anupam  154 Aug 28 12:19 config.ru drwxrwxr-x  3 anupam anupam 4096 Aug 28 12:37 db -rw-rw-r--  1 anupam anupam 1339 Aug 28 12:19 Gemfile -rw-rw-r--  1 anupam anupam 2871 Aug 28 12:19 Gemfile.lock drwxrwxr-x  7 anupam anupam 4096 Aug 28 21:45 .git -rw-rw-r--  1 anupam anupam  466 Aug 28 12:19 .gitignore drwxrwxr-x  4 anupam anupam 4096 Aug 28 12:19 lib drwxrwxr-x  2 anupam anupam 4096 Aug 28 12:29 log drwxrwxr-x  2 anupam anupam 4096 Aug 28 12:19 public -rw-rw-r--  1 anupam anupam  249 Aug 28 12:19 Rakefile -rw-rw-r--  1 anupam anupam  478 Aug 28 12:19 README.rdoc drwxrwxr-x  8 anupam anupam 4096 Aug 28 12:19 test drwxrwxr-x  6 anupam anupam 4096 Aug 28 12:33 tmp drwxrwxr-x  3 anupam anupam 4096 Aug 28 12:19 vendor   What does each column mean, and what does the total 76 signify here?


Solution of $\frac{a}{b}=\frac{a'}{b'}$ if $a,b,a',b' \in \mathbb{N}$

Let $\dfrac{a}{b}=\dfrac{a'}{b'}$ , $a,b,a',b' \in \mathbb{N}$ s.t. $a$ and $b$ have no common factors. How can we show that the only solution to this equality is $a'=na$ and $b'=nb$, $n$ is a natural number. I know that $a'=na$ and $b'=nb$ is a valid solution of equation-1, because $(an)b=(bn)a$. But how can we prove that this is the only solution?     What I have tried is this:       Version 1.   We know the two fractions $\dfrac{a}{b},\dfrac{a'}{b'}$ are equal iff $ab'=a'b\tag{1}.$   Let $ab'=a'b=c$. Now, $a$ and $b$ have no common factors means that they are coprime, so we have, $a=p_1p_2\cdots p_m$ and $b=q_1q_2\cdots q_n$. $p's$ and $q's$ are prime numbers and no $p$ is equal to any $q$. Equation 1 becomes $$(p_1p_2\cdots p_m)b'=(b_1b_2\cdots b_n)a'$$   By the Fundamental theorem of Arithmetic, both the sides should have same prime numbers, so $b'$ should contain $(b_1b_2\cdots b_n)$ and $a'$ should contain $(p_1p_2\cdots p_m)$, i.e. $b'=r(b_1b_2\cdots b_n)=rb$ and $a'=(p_1p_2\cdots p_n)s=sa$, where $r,s \in \mathbb{N}$. Now equation 1 becomes, $a(rb)=(sa)b$. This leaves the only possibility, $r=s$.      Version 2.    The idea is basically the same as of version 1, but now I use Euclid's lemma in place of FTA. We know the two fractions $\dfrac{a}{b},\dfrac{a'}{b'}$ are equal iff $ab'=a'b\tag{1}.$   Let $ab'=a'b=c$. $a$ and $b'$ are the factors of $c$, so both of them divide $c$, i.e. $a|c$ and $b'|c$. Now $a|c \implies a|{(a'b)}$, by Euclid's lemma, $a$ divides at least one of $a'$ and $b$, but we know that $a$ doesn't divide $b$, so $a$ has to divide $a'$.      Similarly we can show that $b$ divides $b'$. So we have $a'=\alpha a$ and $b' = \beta b$, where $\alpha, \beta \in \mathbb{N}$. Substituting these in equation 1 gives $\alpha = \beta$.   Question   Is my method correct?    Is there any other method to prove that $a'=na$ and $b'=nb$ is the only solution of $\dfrac{a}{b}=\dfrac{a'}{b'}$; If yes then please explain.   Also if $a$ and $b$ have common factor then for what condition there does not exist any $n$ s.t. $a'=na$ and $b'=nb$ where $n$ is a natural number. E.g. $\dfrac 39 = \dfrac 26$     P.S:  I've just improved my question. Barry's comment points a crucial error in my previous proof. I needed to justify $a|a'$ and $b|b'$. In previous proof I proceeded with proof by contradiction. The proof by contradiction was ok, but unnecessary, so I've replaced it with a direct proof. At the time of asking the question I lacked the knowledge of some introductory number theory concepts. Now I've learned them and soon I will ask in comments for further clarifications. Thank you.


Let $f:\mathbb{R}\rightarrow\mathbb{R}$ Lebesgue integrable. Prove $\int{f(x)dx}=\int{f(x+t)}dx$

Let $f:\mathbb{R}\rightarrow\mathbb{R}$ Lebesgue integrable. Prove  $$\int{f(x)dx}=\int{f(x+t)}dx$$  My attempt: Suppose $f\geq 0$, Let $\varphi$  an increasing sequence $0\leq\varphi_{n}\leq f$ of simple functions such that $\varphi_{n}\uparrow f$ and we have by Monotone Convergence Theorem(Beppo-Levy) that  $$\int f=\lim_{n}\int\varphi_{n}$$  here i'm stuck. can someone help me?


I have a HTML variable an it contains characters like "●","❒","◉","⭕","■". And i have to store these in MYSQL database. I am using Capsule for this without laravel. There is no problem with printing these characters but when put them into database they show up like this "â—","Ã¢Â—Â". I dont want to remove these characters.  I have tried all html escape functions.  Edit: My database's charset is utf8_general_ci.


Suppose I have two latex files file1 and file2 with the same preamble and so on. Then I want to create a file called bigfile which just puts the two files together. This is not working for some reason. Therefore I first tried to include just file1, this is what I have done:  \documentclass .... %% same as file1 ... same preamble as file1 \begin{document} \input{file1} \end{document}   The result is that I not only get file1, but also the preamble and so on. This is my first experience with putting files together in 1 file. Kindly provide me a solution :)


BM01 2011/12 Question 6 Geometry Problem

Let $ABC$ be an acute-angled triangle. The feet of the altitudes from $A,B$ and $C$ are $D, E$ and $F$ respectively. Prove that $DE +DF \le BC$ and determine the triangles for which equality holds. The altitude from A is the line through A which is perpendicular to BC. The foot of this altitude is the point D where it meets BC. The other altitudes are similarly defined.   Thanks in advance for any contributions.


If unit A attacks unit B (which was attacking unit C) does the attack on B by A stop the attack on C by B?

Let's say an English fleet has orders to attack Denmark from Skagarac, with plenty of support to take it. However, a Russian fleet attacks the English fleet from the Baltic Sea, with plenty of support to take Skagarac.  Would the Russian fleet's attack take priority, preventing the English fleet from taking Denmark? Or would both moves be successful, putting Denmark in English control and Skagarac in Russian control?


I'm working with Beamer and I would like to create boxes with round corners. I use \ovalbox, but I would like to control the thickness of the line. How can I do this? I also tried \thinlines, but I still not understand the sintax since I didn't find a minimal example.


Chance of getting into engineering PhD if I have good references and research experience but don't satisfy 3.0 GPA requirement?

I graduated with 2.7 undergrad, and currently pursuing a masters degree and will graduate with 3.3. I plan to apply for PhD programs in engineering for 2017 Fall.   Here is my question: Many schools state that they require 3.0 GPA or so, but how do I know that whether they intend undergrad GPA?  Do you think should I apply to such school that states that     Minimum GPA: The MS and PhD program has a minimum GPA requirement of   3.0 on a 4.0 scale.    ?  Is it waste of my time if I have stellar letters of references and cool research experiences?


WOL over Internet success for a while but fail after a period of time

I have a computer in my home LAN, and i have successfully set up my computer and router to use wol over Internet.  The problem is, after a period of time(say, a night), the next day i want to start my computer over Internet it failed, but it can be waken up from home LAN.  I have the correct public IP of my router. I use  for WOL over Internet  The answer for  seems good, but i don't think it explains why WOL over Internet fail but WOL success.


Why BSD grep is not returning all the results, but GNU does?

Given the file with numbers from 1 to 100 (seq 1 100 > dataset.txt),  and the pattern file with numbers from 1 to 20 (seq 1 20 > patterns.txt),  I would like to to print all exact matches from the dataset file given the list of patterns.  Here is my command using BSD grep:  $ \grep --version grep (BSD grep) 2.5.1-FreeBSD  $ \grep -w -F -f patterns.txt dataset.txt 1 2 3 4 5 6 7 8 9   but the output is missing the numbers from 10 to 20.  However all patterns are printed when running the same command in GNU grep, e.g.  $ \ggrep --version ggrep (GNU grep) 3.1 Packaged by Homebrew  $ \ggrep -w -F -f patterns.txt dataset.txt 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20   When tested with , all are returned as well.  Why is that? Is there any different approach to make them both return the same result?


I have a set of external hard disks I'm using for backups, so except for the backup in the middle of the night they shouldn't show any activity. Now on one of the drives the LED has been blinking for hours, indicating some activity.    Is there a way to find which program/process is accessing the drive?  I'm using Windows 7 Home Premium.


How much power can be drawn from the lightning connector by a external device?

How much power can be drawn from the iPhone/iPad lightning connector by a external device?  Update: The use case is a audio-related device for iPhone/iPads. It would require around ~100 mA at 3,3 volts, so I'm trying to find out if we could draw this from the iPhone/iPad. (That would allow us to skip an external battery –> smaller size...)  (This question has been asked for the old 30-pin connector , but a new connector might imply new power constraints.)


performance issue with System.Linq when subdividing a list into multiple lists

I wrote a method to subdivide a list of items into multiple lists using System.Linq.  When I run this method for 50000 of simple integers it takes about 59.862 seconds.  Stopwatch watchresult0 = new Stopwatch(); watchresult0.Start(); var result0 = SubDivideListLinq(Enumerable.Range(0, 50000), 100).ToList(); watchresult0.Stop(); long elapsedresult0 = watchresult0.ElapsedMilliseconds;   So I tried to boost it, and wrote it with a simple loop iterating over each item in my list and it only needs 4 milliseconds:  Stopwatch watchresult1 = new Stopwatch(); watchresult1.Start(); var result1 = SubDivideList(Enumerable.Range(0, 50000), 100).ToList(); watchresult1.Stop(); long elapsedresult1 = watchresult1.ElapsedMilliseconds;   This is my Subdivide-method using Linq:  private static IEnumerable<List<T>> SubDivideListLinq<T>(IEnumerable<T> enumerable, int count) {     while (enumerable.Any())     {         yield return enumerable.Take(count).ToList();         enumerable = enumerable.Skip(count);     } }   And this is my Subdivide-method with the foreach loop over each item:  private static IEnumerable<List<T>> SubDivideList<T>(IEnumerable<T> enumerable, int count) {     List<T> allItems = enumerable.ToList();      List<T> items = new List<T>(count);     foreach (T item in allItems)     {         items.Add(item);          if (items.Count != count) continue;         yield return items;         items = new List<T>(count);     }      if (items.Any())         yield return items; }   you have any idea, why my own implementation is so much faster than dividing with Linq? Or am I doing something wrong?  And: As you can see, I know how to split lists, so this is not a duplicated of the related question. I wanted to know about performance between linq and my implementation. Not how to split lists


Different operations if operator is pressed with "Ctrl", "Alt" or "Shift" within the UI?

I saw multiple add-ons that are using alternative operator action when pressing Shift, Alt or Ctrl within the operator interface (I think it's only one of the 3).  I created an operator and draw it in in properties>Object and it'd like to batch use this operator with my selection while pressing Alt as it is a default blender behavior when changing properties.   I was hoping that this feature could do the trick? maybe? Are any templates available?


I want to install both windows 7 and ubuntu 15.10 on my acer gateway ne-572 notebook. How can i do that?

I have 1TB hard drive and 4GB RAM. I want to know the whole procedure from scratch i.e. which OS to be installed first and how to make the partitions. I'll be installing both OS from bootable usb drives. Please help me out.


catalan numbers - counting sequances with sum of 0

I need help in prooving that the cardinal number of the following set is $C_{n}$:  The set of all sequences   $a_{1}, a_{2}, .., a_{n} \in \mathbb{Z} \\ s.t \\ a_{1}+a_{2}+....+a_{n} = 0$  and for every $1 \leqslant i \leqslant n$ , $ a_{i}\geq -1$ and $a_{1}+a_{2}+....+a_{i}\geq 0$  For example, if $n =3$:  the series in the set will be: $(0, 0, 0),(0, 1, −1),(1, 0, −1),(1, −1, 0),(2, −1, −1)$  EDIT: I thought of presenting the problem using parenthesis. Every sequence as a total equal number of "(" and ")". Every sub-sequence has more "(" than ")".  $0$ is presented by "$\color{blue}(\color{blue})$",   $1$ by "$\color{red}($"   $-1$ by "$\color{green})$"  The problem is that the number of parentheses isn't fixed for a given $n$. For example when $n=2$ the series could be $\color{blue}(\color{blue})\color{blue}(\color{blue})$ or $\color{red}(\color{green})$   Also, I don't know how to "translate" the term $ a_{i}\geq -1$  And for $n=3$ the representation of the sequences $(0,1,-1)$ and $(1,-1,0)$ is the same - "$()()$"


I want to delete the swap partition to free up space to increase the root partition, but accidentally when I restarted Ubuntu I got this:    I have made a live Ubuntu to solve this, but I can't close grub rescue. How to close grub rescue and solve this problem?  This is the output of GParted:


"Question: Show that $n^5 - n$ is divisible by 30; for all natural n"

Show that $n^5 - n$ is divisible by $30;$ $\forall n\in \mathbb{N}$   I tried to solve this three-way. And all stopped at some point.  I) By induction: testing for $0$, $1$ and $2$ It is clearly true. As a hypothesis, we have $30|n^5-n\Rightarrow n^5-n=30k$. Therefore, the thesis would $30|(n+1)^5-n-1\Rightarrow (n+1)^5-n-1=30j$. By theorem binomial $(n+1)^5-n-1=n^5+5n^4+10n^3+10n^2+5n+1-n-1$ $=30k+5n^4+10n^3+10n^2+5n.$ It was a little messy and not given to proceed.  II)I tried by Fermat's Little Theorem: $$30|n^5-n\Rightarrow 5\cdot3\cdot2|n^5-n $$ Analyzing each case, we have; clearly $5|n^5-n$ (Fermat's Little Theorem). Now cases $3|n^5-n$ and $2|n^5-n$ I could not develop.  III)In this I wanted your help especially like to solve using this because this exercise on this handout (Properties of the Greatest Common Divisor). Would show that $$gcd(n^5-n,30)=30$$ Are detailers, please, because'm coursing Theory of the numbers the first time. In the third semester of the degree course in mathematics What would be the idea to solve this by using the Greatest Common? This problem in this handout GCD?


Sort and count number of occurrence of lines

I have Apache logfile, access.log, how to count number of line occurrence in that file? for example the result of cut -f 7 -d ' ' | cut -d '?' -f 1 | tr '[:upper:]' '[:lower:]' is  a.php b.php a.php c.php d.php b.php a.php   the result that I want is:  3 a.php 2 b.php 1 d.php # order doesn't matter 1 c.php


Homework question:     Let $G$ a finite group with order of $2p$, where $p > 2$ is prime. given that there's $a \in Z(G)$ such that $o(a) = 2$. Prove: $G$ is abelian.    Can you give me some hints and help to solve it? Thanks in advance.


How to find and delete identical points?

I recently performed  on a merged point feature class in ArcGIS 10.1.  I specified "1 meter" XY tolerance for the Integrate command.  The resulting point feature appears to be what I want except points that were integrated are now stacked on top of each other, which will be problematic in future processing steps.  The attributes for my dataset consist of an OID, Shape, x, y, z.  Where x and y = UTM coordinates and z = buffer distance.  The command  does not appear to work for my dataset (i.e based on Fields: OID, Shape, x, y, z and XY tolerance = 1m) as the output still has stacked points.  I am also working with big data--the integrate output has 37 million points.    There is a related thread, titled , although I would like to open the question up to python solutions too.  What is the best way to find and delete (spatially) duplicate points?  Is there a better solution to integrating such that the output does not contain overlapping points?


How do I re-install Windows 10 after upgrade

I have Windows 10, as I upgraded from Windows 7  Everything works fine, but it's quite possible I will need to re-install the OS at a later date.  When I upgraded, I was not provided with a new key.  When I visit  I get an a.exe which gives me 2 options. Upgrade or create installation for a new PC. Neither is what I want as the page cited suggests I can create an ISO for this PC.  If I were to reformat my PC today, how can I re-install Windows 10 as I have no key and no ISO?


Did Voldemort know what would happen when he died?

There's plenty of info about the process that Voldemort used to  and even more info about how he ultimately  but a simple question occurred to me;  Prior to Voldemort, is there any canon evidence of what would actually happen to a wizard who died with a horcrux in place? From this, did Voldemort know he would become...     "...less than the meanest ghost"   ...and if so, why didn't he plan accordingly (presumably returning to power much more quickly)?  Clearly it would be much more useful to know that when you died, you were going to turn into this sort of spirit; you could probably pre-arrange to have your body restored to you within a week or two. Since Voldemort did not do this, I'm assuming he didn't know would happen to him, but I wanted to know if there was proof either way.


We recently purchased an LSI MegaRAID 9266-8i SAS RAID card to replace a failed card in our NAS.  Setup of the card went smoothly, I updated the firmware, set up RAID6 with hotswap, and let it initialize.  Every so often (once a week or so?) we get flooded with the following error:  Controller ID:  0  Patrol Read aborted on PD:   -:-:0   This error repeats for each of the drives (12 total.)  After all of the errors are sent to us (via email as well as an alert on the device), we get this error:  Consistency Check inconsistency logging disabled, too many inconsistencies on VD:       0   Also, something new that happened today, the MegaRAID software is reporting the array is 'optimal', but looking at the disks shows that one of the drives has a very high media error count (the rest have 0).  Anyone have any idea if this is just a failed drive despite the status being 'optimal?


What's the difference between the work function and ionisation energy?

In a particular textbook, the work function of a metal (in the context of the photoelectric effect) is defined as:     the minimum amount of energy necessary to remove a free electron from the surface of the metal   This sounds similar to ionisation energy, which is:     the amount of energy required to remove an electron from an atom or molecule in the gaseous state   These two energies are generally different. For instance, Copper has a work function of about 4.7eV but has a higher ionisation energy of about 746kJ mol-1 or 7.7eV.  I've sort of figured it's because the work function deals with free electrons whilst ionisation is done with a valence electron still bound within the atom. Is the difference due to the energy required to overcome the attraction of the positive nucleus?


How can I find all possible coordinates from a list of x and y values using python?

Beginner here. I am writing a basic algorithm that involves taking a list of x-values and a list of  y-values and then storing all possible combinations of coordinates.   Here are the x and y value lists:  x_line = [6,5,9,3,7,5,9] y_line = [10,3,5,7,1,7,3,1]   I would ideally want to store all possible coordinates in variable xy because I will be comparing the coordinates in this variable to other sets of coordinates.  I tried to use zip() to do this but I am unsure if I can zip() iterators. Here is that code:  for i in x_line:    for j in y_line:        xy = zip(i,j)    This yields an "int object not iterable" error.   I tried even this:  xy = zip(x_line,y_line)   but obviously this does not get every possible combination.   Again, I want to store all possible coordinates given a list of x and y value lists in one variable. I would appreciate any help or guidance. Thanks


Prove that $G$ has a subgroup of order $p^k$ using the third isomorphism theorem and induction on $k$

Let $G$ be a group of order $p^kq$ with $p$ and $q$ distinct primes and $k \geqslant 1$. I have to prove that $G$ has a subgroup of order $p^k$ using the third isomorphism theorem and induction on $k$. I have tried to play around a bit with definitions and theorems but I can't seem to figure it out. I found some help on other posts but none use the third isomorphism theorem. Thanks in advance!


Does every point in a system has equals moment (Torque)?

Is there some special condition for this to be true or is this always true?


jQuery selectors for dynamically generated HTML elements?

In my page, I use this block of code to generate :  $.ajax({         url: '...' }).done(function (model) {     for (var i = 1; i <= model.numberOfPages; i++) {         html += ''+i+'&nbsp;';     }     $(".page_numbers").html(html); });   But when I try to add a click event on these a tags, nothing happen. Where did I go wrong?  $(document).ready(function (event) {     $('.page_number').click(function (event) {         //Some code here     }); });


I have a laptop with Windows 7 Pro and a Core 2 duo processor. (Lenovo SL510 Laptop) My Lpatop has 6Gb ram. What version of ubuntu do i need? And will it work at all? P.S. I have integrated graphics...


How to prove $b=c$ if $ab=ac$ (cancellation law in groups)?

I want to prove for a group $G$, that if  $$a\circ b =a\circ c$$ then this is true $$b=c$$ I started with $b=b\circ e$, but this didn't help me at all.   Next I tried with this: $$(a\circ b)\circ c=a\circ (b\circ c)$$ but I don't know/understand how to go further. How can I prove this equation?


Why is the speed of light considered as a fundamental constant if its speed changes with medium resulting in refraction?

I know that the speed of light, the universal constant of gravitation and the Planck's constant are considered to be the three fundamental constants of the universe. But, why is speed of light considered as a fundamental constant? The speed of light changes from medium to medium for satisfying Fermat's principle then, how can it be a constant?


This may seem trivial, so my apologies, I've searched for a quantitative answer and couldn't find anything explicitly.  If a moving object has some velocity, and experiences a decrease in mass will the object lose velocity? My thoughts: Example, a cart is rolling and I take a box off the cart while it's in motion does the cart lose velocity due to the decrease in mass, or maybe it can be shown that the momentum decreases which equates to a decrease in velocity.


Why scientific articles do not include year/date?

I noticed that (most?) articles do not include the date of publishing/writing.  For example see .  If I click for a citation on that page, I see there the year listed as "2018". But in the article itself, there is no indication when it was written.  Why is that? Or did I miss something?  PS: To clarify, I am not asking about the duration of the work, but the information when the work was done (realizing that a single point in time can not be picked). For example if there is a paper about "Method for better battery capacity", then it is a substantial information whether it was written or published in 1899, 1989 or 2018.


Is there harm in editing grammatical errors?

I love the ease of correcting misspellings, typos, and grammatical errors in SO.  Certain errors catch my eye and annoy me - and the wikiness of SO is a great blessing; I don't have to live with the errors, I can simply fix them.  But...  It can be useful to know how sloppy the OP is.  A question that reads, "plz hlep me fix this" can be safely ignored - safely, in the sense that if it wasn't worth the OP's time to express him/herself, it may not be worth our time to help out with answers.  It can also be useful, say, when it's clear the OP isn't a native English speaker - we can calibrate our answers to make them more readable.  And a healthy edit obscures all that useful information.  So, where's the balance?  Personally, I'm on the side of "Fix it!", but I can certainly see the case for leaving it alone.


Where does Skype Desktop 8.x for Windows store its messages, it stopped using main.db

On my machine, since 24 July 2018, Skype Desktop 8.x for Windows 7 (Skype version 8.29.0.50) does not store its messages anymore in C:\Users\UserNameHere\AppData\Roaming\Skype\SkypeUserNameHere\main.db (timestamp is 24 July 2018).  When I export messages (the , but there's still an export function that says "Export chat history from Skype 7.x"), it only exports up until that date to HTML.   How can I export more recent messages for offline viewing? In the absence of such option, what is the new location of the *.db SQLite file in Windows 7?   I may be able to get messages from my Windows 10 laptop, where it is well documented, but not all Skype instances are in-sync, hence I prefer to get all history in my backups and for offline viewing / analysis.  (Note: other threads on this subject only seem to list the UWP location and/or the old Skype 7.x location)  (Also note that tools like NirSoft Skype Log Viewer and BitRecover Skype Chat Viewer all use the historical location of Skype 7 and don't find the new messages)


Extracting EPSG from a raster using gdal bindings in Python

My goal is to check that a shapefile and raster have the same projection and datum using EPSG number.  One can easily extract EPSG number from a shapefile by the following:    ds=ogr.Open(r'....satates48.shp') utm_sr=ds.GetSpatialReference() utm_sr.GetAttrValue('AUTHORITY',1)   This works great but how does one do the same for a raster file, you cannot, to my knowledge get a spatial reference of a raster.  One can get projection, or projecitonref (I am not sure if there is any difference), but you cannot do more, like:  fn_raster=gdal.open(r'raster_file.tif') raster_sr=fn_raster.GetProjection().GetAttrValue('AUTHORITY',1)   This does not work. Perhaps there is an alternative way to do this?


Why does my GFCI circuit breaker trip with any small load, even after replacing the breaker?

I have a 20A 240V GFCI breaker in my main breaker box going to a conduit to another breaker box outside. All worked well last summer. Now, when I put any load (weed-eater, light, etc.) on an outlet connected to the outside breaker box, the indoor breaker immediately trips.  I've tried replacing the indoor breaker with a 30A model (it's 10AWG wire) but it still trips under any load.  I've also replaced the outdoor breakers.  I am confused. If this were a short circuit, the breaker would trip regardless of whether there was a load.  Does anyone have ideas on why this is happening and how I can fix it?


I'm having trouble providing code coverage for my Apex Class.  Apex Class  public class CSMetricsDashboardController {     public CS_Metrics_Dashboard__c dashboard {get;set;}      public CSMetricsDashboardController() {         List<CS_Metrics_Dashboard__c> results = [             SELECT                 Antic_Needs_Avg__c,                 Antic_Needs_Target__c,                 Expenses_Color__c,                 KLAS__c,                 KLAS_Target__c,                 Investment_Projects_Led__c,                 Investment_Projects_Supported__c,                 Product_Release_Training_Color__c,                 Project_NPS_Avg__c,                 Project_NPS_Target__c,                 Project_On_Budget__c,                 Project_On_Budget_Target__c,                 Time_Entry_Color__c,                 Time_Entry_Missed__c,                 Time_Entry_Missed_Percentage__c,                 Time_Entry_Rating__c,                 Utilization_MTD_Actual__c,                 Utilization_YTD_Target__c,                 Utilization_YTD_Actual__c             FROM CS_Metrics_Dashboard__c             WHERE User_Name__c =: UserInfo.getUserId()             AND Inactive__c = false         ];         if (results.size() > 0) {             this.dashboard = results[0];         }     } }   Test Class:  @isTest public class CSMetricsDashboardContollerTest {      public static testmethod void testRunAs(){         // Setup test data         // Grap Profile         Profile p = [SELECT Id FROM Profile WHERE Name ='Standard User'];         // Create new user         User u = new User(Alias = 'standt',                            Email = 'standarduser@stratadecision.com',                           EmailEncodingKey = 'UTF-8',                            LastName = 'Tester',                            LanguageLocaleKey = 'en_US',                           ProfileId = p.Id,                           TimeZoneSidKey = 'America/Chicago',                           UserName = 'standarduser@stratadecision.com');         insert u;         // Create new account          Account a = new Account(Name = 'Test Account',                                 DBA_Name__c = 'Test Account', // Legal Entity Name                                 Type = 'Prospect');          insert a;         // Create new contact, master to CS Metrics Dashboard         Contact c = new Contact(LastName = 'Tester',                                 AccountId = a.Id,                                 Status__c = 'Active');         insert c;         // Create new CS Metrics Dashboard record related to new contact         CS_Metrics_Dashboard__c cs = new CS_Metrics_Dashboard__c(Contact__c = c.Id,                                                                  User_Name__c = u.Id,                                                                  Project_NPS_Avg__c = 90,                                                                  Inactive__c = false);         insert cs;          // start test         test.startTest();              System.runAs(u){                 // The following code runs as user 'u'             List<CS_Metrics_Dashboard__c> results = [SELECT Id,                                                             Inactive__c,                                                             Project_NPS_Avg__c,                                                             User_Name__c                                                       FROM CS_Metrics_Dashboard__c                                                       WHERE User_Name__c =: u.Id];                  System.assert(u != null);                 System.assertEquals(false, results[0].Inactive__c);                 System.assertEquals(90, results[0].Project_NPS_Avg__c);                 System.assertEquals(u.Id, results[0].User_Name__c);          // stop test          test.stopTest();         }       } }


How do I attract attention to a new answer to an old question?

I've answered a question asked several years ago, and my answer is half-contradictory of the accepted answer (which I believe overlooked many things). Not much time has passed yet, but let's assume for the sake of discussion that the OP will not pay attention to this new answer. Also assume that this is a reasonable question which has a few upvotes.  What can I do (if I should be doing anything at all) to attract attention to my new answer?


Why is Ubuntu inflating the file /var/log/kern.log.1 to dozen GB?

I have installed Ubuntu on a 128GB drive, but I ran out of space. Got a few warnings in form of notifications of out of space, me knowing that I used probably 20GB max or even less than that.   Decided to dig in and saw that for some reason /var/log is huge, more precisely kern.log and kern.log.1. In my case:  /var/log$ sudo ls -laSh | grep "kern" -rw-r-----   1 syslog            adm              47G iul  6 23:42 kern.log.1 -rw-r-----   1 syslog            adm              63K iul 11 14:42 kern.log   How can this be? How can a log file, even kernel related can get this big this fast? And more importantly how can I stop it, Permanently? Sure I can remove it but it will grow again fast and chubby.  Also why does Ubuntu behave like this?


How to disable Windows 10 lock screen password on IDLE only

I would like to configure this windows 10 machine to not ask for a password when resuming from IDLE, but still ask for a password when resuming from STANDBY or HIBERNATE.  The screen needs to turn off after 5 minutes and NOT use a screen saver.  The only information I can find is about disabling the lock screen password entirely - which is not what I want. Whether the lock screen continues to show or not is relevant as long as it doesn't require a password.  Version is Windows 10 Pro. It is also connected to a SBS2011 domain.


How do I install NVIDIA GPU drivers properly?

Having found a lot of different questions on Ask Ubuntu regarding NVIDIA graphics drivers installation generating various issues and problems on Ubuntu systems - I do want to know:    What do Ubuntu users have to care about when installing the NVIDIA graphics drivers?    Explanation:  Being aware that this topic already has many good questions and answers it actually always stays up-to-date. One example : Many new notebooks come with hybrid graphics and Optimus support so they depend on proprietary NVIDIA drivers being installed to function properly but most of all existing posts point to  which doesn't provide the drivers anymore since ubuntu  was introduced, so many old answers are mostly obsolete or wrong.


Is the sequence of sum of $\binom{n}{k}^{-1}$ bounded?

Is there a real number $M >0$ such that $$S_n \leq M, \forall n \geq 1$$  where    $$  S_n = \sum_{k=0}^{n-1}\binom{n}{k}^{-1}, n\geq 1.$$   Thank you in advance


How can I see the true, non-adaptive histogram for my photograph?

Given that both Lightroom and (as far as I know) Photoshop use adaptive histograms, is there any way to look at my photos using a true histogram?  By true I mean showing a true distribution of greyscale values across the x axis.


Why is discrimination based on citizenship allowed in PhD funding in the UK?

This question is specifically aiming at the UK PhD admission system.   Having spent roughly 6 years in the UK - 2 years A-Level and 4 years undergraduate, I am now moving forward into applying for PhD programs. To my surprise, I discovered that I would have to face a lot of difficulties regarding my eligibility for funding.   Most of the funding I applied for were strictly 'UK/EU citizens only', and it is rare to have full funding for international students. I have applied to a lot of places, and received a lot of responses in the form of "... you are a good match, but I don't have funding for overseas students...".  Having chosen the UK to study with the belief that 'as long as I am competent I should be qualified for the job', the reality has really slapped back at me.   Why such discriminations are allowed in a developed country like the UK? I made this claim knowing little to nothing about the US or other countries' systems, but lots of my friends having applied to EU PhDs received their offers without being asked whether they are 'caucasians' or not.


How can I make a transparent lock screen for Windows 7?

Okay I am wondering if there is a solution I can use that incorporates itself into the Windows log off, shutdown, restart, etc... menu.   I am looking for this solution to add in the lock screen option. Not lock screen as in log off but lock screen as in lock the screen and have a password prompt on the screen but you can still see what everything is doing in the background (Useful when scanning the computer).  This would be especially useful on my shared computer because then my family can see my screen when I am scanning but not snoop through my account. Obviously, this solution would need to have an option to also switch users in-case the other user really needs to use the computer and the screen is locked but they don't want to shut it off/restart it.  Is there a solution someone can point me to that can do just this???  Oh yeah btw I would like it to be free (Not a trial)...


I want to reduce the size of the vertical space in matrix environment and have a result something like this     But at present I manage something like below     with the following code    $\begin{bmatrix}     00 & 08 & 10 & 18 & 20 & 28 & 30 & 38 \\     01 & 09 & 11 & 19 & 21 & 29 & 31 & 39 \\     02 & 0a & 12 & 1a & 22 & 2a & 32 & 3a \\     03 & 0b & 13 & 1b & 23 & 2b & 33 & 3b \\     04 & 0c & 14 & 1c & 24 & 2c & 34 & 3c \\     05 & 0d & 15 & 1d & 25 & 2d & 35 & 3d \\     06 & 0e & 16 & 1e & 26 & 2e & 36 & 3e \\     07 & 0f & 17 & 1f & 27 & 2f & 37 & 3f   \end{bmatrix}$   I can change the font using \mathsf{}, but other than that, how I reduce the vertical space between the rows? I did find things like  to increase vertical space between rows in matrix, but not something that can decrease the space.


Let $f(z)$ be an entire function satisfying $|f(z)|\leq k|z|$ for some positive constants $k$ and all $z$. Show that $f(z)=az^2$ for some constant $a$.


Can we have some tools to handle link rot?

There are many links posted in answers, and some in questions, that are either stale or broken.  An example is the change to  on-line documentation this year to do away with separate 'Optional' and 'Core' tasks areas in the documentation - the old links 404 now.  I've fixed a bunch of 'optionaltasks' broken links, but searching for 'coretasks' in Stack Overflow questions returns over 300 matches...  Are there any tools for us to review and fix these - with an emphasis on the fixing - without sifting through completely manually?  Is it time for some refactoring tools for Stack Overflow content, in particular, for links?  Also, I'd be interested to know if there is an analysis of links (as found in the Stack Overflow data dumps) out there. Answer: there is a  of a sample of links and images, but it's getting a bit out-of-date.


Let $X_1, \cdots ,X_n$ be independent and identically distributed random variables.

Find $E[X_1|X_1 + \cdots +X_n=x] $  This is pretty new concept for me so any help would be very helpful.


Definition of "Universe of Discourse" and Definition of "Set"

I want to axiomatize "the concept of set" in my head, but every time I face some circular definition or intuition.   In predicate logic, we quantify over some "Universe of Discourse". Intuitively Universe of Discourse is a set, a collection. But then, in naive set theory or axiomatic set theory, we define "set" by using quantifiers (over Domain of Discourse)... Isn't it circular?  I mean, we assume that "Universe of Discourse" is some kind of "set", then by using first order predicate logic we define set again?


How to develop the static and kinetic friction formula?

How do you end up with the formula for ? ($F_s = \mu_s \times N$) or ($F_k = \mu_k \times N$). I know how to use the formula. Now I need to know how to get to it.


I am having trouble seeing why Cantor set has uncountably many elements. A cantor set $C$ is closed. So $[0,1] - C = \bigcup\limits_{n=1}^{\infty} I_n$ is open and is countable union of disjoint open intervals. I can further assume that I can order the $\{I_n\}$ by their left endpoints since there are only countably many of them. So between $I_n=(a_n,b_n)$ and $I_{n+1} = (a_{n+1},b_{n+1})$, we must have $a_n < b_n \leq a_{n+1} < b_{n+1}$. If $b_n < a_{n+1}$, then the Cantor set $C$ consists of an interval, which is a contradiction, so $b_n = a_{n+1}$ for all $n$, and thus Cantor set can have at most countably many points.


Pigeonhole principle: prove that any set of $n+1$ integers from $\{1,2,...,2n\}$ has two consecutive integers differ by one.

Let $n \ge 1$ be an integer. Use the Pigeonhole Principle to prove that in any set of $n + 1$ integers from $\{1, 2, . . . , 2n\}$, there are two integers differ by one. I've attempt and come up with this: Let S be $\{1,2,...,2n\}$, $T_0$ be a subset of S with $n$ elements, $T_1$ is a subset of S with $n+1$ elements. We form $T_1$ by adding a number to $T_0$. If $T_0$ already has two integers differ by one, then we're done. If $T_0$ has no integers differ by one, how do we know $T_1$, having 1 more number, has two integers differ by one?


90s SciFi TV show, pilot/marine searches for his sister who landed on an alien planet before him

I have looked everywhere but can't find a TV show I am having flashbacks of! Here is what I remember  Based in space on an alien planet there is conflict with any alien race the main character is a pilot? Marine? the big thing I remember is the main character's sister is missing, she landed on the planet before him. Finding her is the long-running story arc late nineties, aired on a major network the whole series felt like it was filmed at night


How do I find if a package is installed by default for each Ubuntu release?

I know how to check if a package is installed and if its available for install but I cannot find any list of packages that are installed with a release from Ubuntu.  Sometimes I am trying to answer something and I cannot remember if the tool I will refer was installed by default of if I installed in a later point and cant remember. What if its something I have and a user using another desktop environment does not?  I know I can recommend to install the package prior to asking him to use it but I would like to know if its installed by default or not.  Is there such list? Where can I find it?


How does LIGO detect accurate time differences if gravitational waves are also compressing and stretching the light waves-specific confusion below

I was watching this veritaserum which explains my question at 5:55  saying that the speed of light is much faster so will pass through the arms multiple times during each compression/stretch and the changingintensity of light in the interference pattern overtime can be detected but I thought gravitational waves travelled at the speed of light?


I've seen many memes employing this scene of Batman slapping Robin:    Where is this taken from?


The "Esc" key in my bluetooth keyboard doesn't work, how to fix it?

I'm using Mac mini, and bought this new bluetooth keyboard. It's not Apple production, but has Apple layout. The other keys all work except "Esc" in the left up corner. Obviously it won't be handy if this important key didn't work. How to fix it, please?


Find $x$ and $y$ such that   $$ \binom{100}{0}+2\binom{100}{1}+4\binom{100}{2}+\cdots+2^{100}\binom{100}{100}=x^{y} $$   I started out by letting $n$ be a small number.  Let $n=3$: $$ 2^{0}\binom{3}{0}+2^{1}\binom{3}{1}+2^{2}\binom{3}{2}+2^{3}\binom{3}{3}=1(1)+2(3)+4(3)+8(1)=27=3^{3} $$  Let $n=4$: $$ 2^{0}\binom{4}{0}+2^{1}\binom{4}{1}+2^{2}\binom{4}{2}+2^{3}\binom{4}{3}+2^{4}\binom{4}{4}=1(1)+2(4)+4(6)+8(4)+16(1)=81=3^{4} $$  However, I cannot for the life of me figure out how to use this and solve the original question. More specifically, I know the answer is $3^{n}$, but I don't know how to do a combinatorial proof.


Remove a old indexed keyword from google search for a website

A webpage X had a text : old-text and it got indexed with this keyword old-text Now that content is removed from the page X but page is still active with different content. Still if user is searching for old-text in google search, page X with which it indexed earlier comes up while on page X old-text is not available at all. Following are the questions:  Is there any way to remove this index using some tool like webconsole Does google keep keyword level index permanent If it auto clears this irrelevant index automatically and then after how much time ?  This is creating severe problem for us where this old-text is sensitive information that needs immediate removal from google search.


Im getting 100% disk usage on only 1 of 2 disks

I have windows 10 so i put in a second hard drive to try to aid with my 100% disk usage but noe it just has on at 100% and the new second one at 0% how do i get the two to work together?


Why does (insert favorite search engine here) get better search results than SO, SF, or SU's own search function?

I've lost count of the number of times I've either asked a question or been answering a question only to have it closed as an exact duplicate. But searching for the question turns up  a list of seemly unrelated results using the sites builtin search. Then if I switch to a general web search engine and limit its scope to just SO, SF or SU I find the question within the first two or three results.  Why is this?  I'm pretty sure this isn't an exact duplicate of another question though I did find some that were at least somewhat related (using google).  Update:  I also have gotten (somewhat) better results by simply typing a question and browsing the generated list of related questions. Still a search feature that doesn't return good results isn't going to be used by most people.  Common sense would suggest (though common sense isn't always the best indicator) that a targeted solution to a specific problem domain should be superior to a generalized solution. In most cases this appears to hold true.


What is the best way to manage user accounts for Windows servers in a DMZ? We are expanding our web presence and adding several IIS servers to our DMZ. I would prefer not to manage a bunch of local accounts or, on the other hand, expose our internal Active Directory servers directly to the DMZ either. Is there a standard approach to this problem?


How can I avoid this NullPointerException?

I have the following situation, where my program terminates with a NullPointerException during the function. What can I do to make this function work?  UPDATE  else if (str == null)     emptyLinks.add(newPageLinks.get(i).getText() + "at link: " + str);


Is it possible to reference a cell in Google Sheets so that cell where it gets displayed also displays it using the same text and cell colour formatting?  =A1   Will only reference cell's value. But if that particular cell has red background and white text I'd like that to be copied as well.  I'm leaning toward existing formula solutions rather than scripts. If applicable of course.


Word for someone who tries to manage, or oversee everything

I know a couple of people who have determined that they, for whatever reason, need to help guide other people through their lives. They always do things or suggest things to multiple people, usually disingenuously, in order to reach a desired outcome. This isn't necessarily to their benefit, but usually a mutual benefit or to the benefit of the "victim".  Looking for something other then overseer, if possible.


I installed linux and replace with window 7 ? how to recover drives data back

i just installed LINUX in my laptop.i had window 7 , i replace UBUNTU with window 7. the drives data(D:, E:) in window is not showing in LINUX. how to recover my drives data. i didn't use LINUX yet. how to get my data back.in this(LINUX) it shows 490 GB free. my Hard disk is 500 GB.how to get back my 150 GB data now. Please describe me the way to get all the deleted data.please help me.i need your suggestion.thanks a lot for helping me.


Do I need to remove/modify a journal's Latex template style before submitting a paper to arXiv?

I want to submit a paper to a SIAM journal. Before submitting it I want to put the paper on arXiv. I've written the paper using SIAM's Latex template files. Is it ok to upload the current version of the paper to arXiv as it is or do I need to remove the templating or modify the paper in some way?


TV series from 70s or 80s - 1 female pilot was cloned from the other pilot's fingernail

This was a tv show that aired in the US in the '70s or early '80s, possibly on Saturday mornings. Since I was a child, I'm assuming it was a kids program? It was comic science fiction and set on a spaceship. The only 3 specific details I remember are:   The crew traveled between ship levels by using open "jump tubes" that were similar to a giant vacuum tube message system, only without any "container" for the passenger. They just stepped into an alcove with a big hole in the floor and ceiling, then shot up or down. Frequently the show would use this as a source of slap-stick comedy.  The captain was male. The 2 pilots were female, and 1 had been cloned from the other's fingernail cell. They often disagreed about which one was the clone.


Desktop design still similar to Ubuntu 16.04 even after upgrading to Ubuntu 19.04

I upgraded my system from Ubuntu 16.04 to 18.04 then to 19.04, but it still looks like the 16.04 version:   What should I do to make it look like the 19.04?


Unix replace all lines in a file starting with a string,by a variable

I have a requirement to replace all the lines in a file that start with a certain string to be replaced by a variable.   Contents of te file -      SDI=/u05/rdbms/admin     NONSDI=/u07/rdbms/admin1     NONNON=/u01/rdbms/     SDI=/u05/rdbms/admin3   I have a variable SDI_N="SDI=/u01/data/admin/instance"  $echo $SDI_N SDI=/u01/data/admin/instance   Expected output -    $cat file      SDI=/u01/data/admin/instance      NONSDI=/u07/rdbms/admin1      NONNON=/u01/rdbms/      SDI=/u01/data/admin/instance   I am trying the following -  sed -e "s/^SDI=.*/${SDI_N}/g" file ERROR - sed: -e expression #1, char 16: unknown option to `s'  sed -i 's/^SDI=.*/\${SDI_N}/' file   It does not replace with the value of SDI_N         $cat file         ${SDI_N}        NONSDI=/u07/rdbms/admin1        NONNON=/u01/rdbms/        ${SDI_N}   Nor is this helping   sed -i 's/^SDI=.*/"${SDI_N}"/' file  sed -e "s/^SDI=.*/${SDI_N}/g"  file        sed: -e expression #1, char 16: unknown option to `s'   Please let me know what changes I will have to make to my existing code to get the desired output.The issue could be with " or '. But I am unable to get through. I used all the possible combination of Single and Double quotes but with no success.


Prove the probability that X takes on an even value for a Poisson R.V.?

We have a random variable $X$ that is distributed according to the Poisson distribution with $ \lambda$, such that $P[X=k]=e^{-\lambda}\frac{ \lambda^k}{k!}$ for $k=0,1,\dots$.  We want to show that probability that $X$ takes on an even value is $\frac{1+e^{-2\lambda}}{2}$.  I am thinking that the identities $e^{t}=\sum_{k=0}^{\infty}\frac{t^k}{k!}$ and $e^{-t}=\sum_{k=0}^{\infty}\frac{-t^{k}}{k!}$ could be used, namely through a system of equations, but I need help figuring out how to productively do this.


How does a website that accesses my salesforce metadata/data authorize against my org?

I am attempting to create a web app (ruby on rails) that requires access to a user's Salesforce environment to perform some REST api calls (SOQL queries) and in doing so I've implemented the . On a dev org I have access to I have created a connected app and am able to successfully connect to that connected app, authorize against it with a user from that environment and then with the returned authorization code I'm able request an access token and make REST calls. However my goal is to allow a salesforce user to authorize access to their org without having a connected app installed in their environment? How is this done?  To look at this same issue from a different perspective, how does a website such as  or  allow a salesforce user to authorize access to their environment?


I am having hard time figuring out how the CX (controlled-NOT) gate is represented in the matrix representation.  I understood that tensor product and the identity matrix are the keys, and I understood how the matrix representation works for single-qubit matrices. For example, if we have a circuit with a quantum register q composed of 3 qubits, the operation X q[1] has the matrix representation 1 $$I_2 \otimes X \otimes I_2 = \begin{pmatrix}  0&0&1&0&0&0&0&0 \\ 0&0&0&1&0&0&0&0 \\ 1&0&0&0&0&0&0&0 \\ 0&1&0&0&0&0&0&0 \\ 0&0&0&0&0&0&1&0 \\ 0&0&0&0&0&0&0&1 \\ 0&0&0&0&1&0&0&0 \\ 0&0&0&0&0&1&0&0 \\ \end{pmatrix}.$$  Obviously, I am aware of the matrix representation of the CX gate: $$\begin{pmatrix} 1&0&0&0\\ 0&1&0&0\\ 0&0&0&1\\ 0&0&1&0\\ \end{pmatrix}$$  Taking back our quantum register q, applying CX to the second (control) and third register (target) (CX q[1], q[2]) gives us the matrix representation 2 $$I_2 \otimes CX = \begin{pmatrix} 1&0&0&0&0&0&0&0\\ 0&1&0&0&0&0&0&0\\ 0&0&0&1&0&0&0&0\\ 0&0&1&0&0&0&0&0\\ 0&0&0&0&1&0&0&0\\ 0&0&0&0&0&1&0&0\\ 0&0&0&0&0&0&0&1\\ 0&0&0&0&0&0&1&0\\ \end{pmatrix}$$  The problem comes when we try to apply the CX gate to other pairs of qubits:   I suspect the matrix representation of CX q[2], q[1] (applying a CX gate with the third qubit of the system as control and the second qubit of the system as target) to be $I_2 \otimes CX^r$ where $$CX^r = \begin{pmatrix} 0&1&0&0\\ 1&0&0&0\\ 0&0&1&0\\ 0&0&0&1\\ \end{pmatrix}$$ but I am not sure. I really don't know how CX q[0], q[2] (applying a CX gate with the first qubit of the system as control and the third qubit of the system as target) would be represented.    To summarise, my question is "how does the CX (or more generally multi-qubit gates) is represented as a matrix when there are more than 2 qubits in the system?".  1 Computed with Python and numpy:  import numpy as np X = np.array([[0, 1], [1, 0]]) ID2 = np.identity(2) print(np.kron(np.kron(ID2, X), X))   2 Computed with Python and numpy:  import numpy as np CX = np.array([[1, 0, 0, 0], [0, 1, 0, 0], [0, 0, 0, 1], [0, 0, 1, 0]]) ID2 = np.identity(2) print(np.kron(ID2, CX))


Initialization of list of empty dictionaries in python

I was expecting below ways of initialization to result in same output:  a = [{}, {}] b = [{}] * 2 a[0]["assigned"] = 1 b[0]["assigned"] = 1 print(a) print(b)   but the output is as follows:  [{'assigned': 1}, {}] [{'assigned': 1}, {'assigned': 1}]   Looks like in case of b, a single dictionary instance is being created and referenced in all the list elements.  Can someone help me with reason behind this implementation?   Thanks.


I'm trying to understand what cp --preserve=links does when used by itself,  from my tests it seems that it copies a normal file normally and dereferences symlinks, but it seems like it just has the same effect as cp -L when used on a single file.  Is that true or is there something I'm missing?


Integer coefficient polynomial - values as powers of 2

Does there exist a polynomial $f$ with integer coefficients such that for every natural number $n$, $f(0) , f(1) ... f(n) $ are all distinct powers of 2 ?   I have no clue about how should I start thinking about this problem but I felt that it is very interesting.


Compute $\sum_{n=1}^{\infty}\frac{1}{n^4}$ using Parseval identity

Starting with Fourier cosine series for $f(x)=x^2$ in the interval $(0,l),$ use Parseval identity to compute $\sum_{n=1}^{\infty}\frac{1}{n^4}$.  Attempt: I have that the coefficient $A_n$ for cosine series is $$A_n=(1/(n^3 \pi^3))2 l^2 (2 n \pi \cos(      n \pi) + (-2 + n^2 \pi^2) \sin(n \pi))$$  By other hand I have that $\int_0^lx^2dx<\infty$ so the convergence is in $L^2$ sense, so I have the parseval identity, i.e.  $\frac{l^5}{5}=\int_0^l|x^2|^2dx=\sum_{n=1}^\infty A_n^2\Vert \cos\frac{n\pi x}{l}\Vert^2=\sum_{n=1}^\infty A_n^2 (l (n \sin(2 \pi n) +       n \sinh(2 \pi n)))/(4 \pi n^2)$  Now I have to take out the $\frac{1}{n^4}$ term from the series, which is definetely not an easy task.  Am I correct so far?   Is there a easy way to proceed? If not, Is there an alternative (easier) solution to this exercise?    Edit  Noticing the cosine multiples of $\pi$ I get   $\frac{\pi^5}{20}=\sum_{n=1}^{\infty}\frac{\sinh(2\pi n)}{n^5}$  but this doesn't looks like $\sum_{n=1}^{\infty}\frac{1}{n^4}$ at all... Unless $\frac{\sinh(2\pi n)}{n}=1$  What am I doing wrong?   Please help me.


Responding with "OK" & "Welcome" to "Thank you"

Please, let me make it clear that my question is not asking how native speakers usually respond to "Thank you". Before posting this question I did some research and I also read this discussion:   In my opinion none of the suggested answers apply to my question.  This is a specific question on the appropriateness of two specific responses.  Let's take a situation when I ask my colleague to briefly explain me something. And after he has done it, I say, "Thank you".   Is it polite to respond with an "OK" to my "Thank you"? (That's how a native English speaker replied to me today.)     Is it acceptable in an informal situation to respond with "You welcome" (without "are") or even with "Welcome"? Responding, "You are welcome" sometimes feels too long to me :)   UPDATE. Today two different people responded with "OK"  to my "Thank you" and "Thanks", so it seems it's not that rare.


I want to show that $$ \int\limits_0^\pi \ln\left(1-\cos\left(t\right)\right)\text{d}t=-\pi\ln\left(2\right) $$ I wanted to use the integral $\displaystyle \int\limits_0^\pi \ln\sin\left(t\right)\ dt$ which I know the value but I struggle finding a judicious change of variable. Is there a way to do it ?


I've gotten my Enchantment up to 100, and my smithing up to 100, So I was wearing Vampire armour which allowed 125% magicka regen, which I thought was pretty awesome.  Anyway,  I thought well wouldn't it be nice to look cool and also have the armour AND regen, but it turns out I can't do that?  After all this work to level up, I disenchant my Vampire Armour, make daedric armour, enchant it with greater soul, and only get 37%!! What kind of crap is that?  How can I make enchantments like the enchantments that are found in the game items?


How can I stop the updates notifier box from appearing?

note to future users who come across this question  this question has been tagged as a possible duplicate of          That question is about the whole process of having the OS apt-get update and apt-get upgrade packages automatically - not the popup manager window. However this question is a duplicate of this:      It turns out the update manager popup cannot be managed through apt's configuration files, it acts as an independent daemon and needs to be managed separately.    Every morning when I log into my install of Ubuntu 16.04.1 I get this:    I don't want this box to appear, as I would rather handle the updating process manually.    I have the following configuration:  file: /etc/apt/conf.d/10periodic  APT::Periodic::Update-Package-Lists "0"; APT::Periodic::Download-Upgradeable-Packages "0"; APT::Periodic::AutocleanInterval "0"; // Try and turn off autoupating APT::Periodic::Enable "0";   file: /etc/apt/conf.d/20auto-upgrades  APT::Periodic::Update-Package-Lists "0"; APT::Periodic::Unattended-Upgrade "0";   My attempt to discover what is responsible for firing the automatic update system  man apt.conf states:     PERIODIC AND ARCHIVES OPTIONS          APT::Periodic and APT::Archives groups of options configure behavior of          apt periodic updates, which is done by the /etc/cron.daily/apt script.          See the top of this script for the brief documentation of these          options.   It looks like this has been replaced by /etc/cron.daily/apt-compat which mixes times abit so everyones Ubuntu doesn't try update at once then it calls:  /usr/lib/apt/apt.systemd.daily   /usr/lib/apt/apt.systemd.daily is a shell script that starts with a comment:     This file understands the following apt configuration variables:    Values here are the default.    Create /etc/apt/apt.conf.d/10periodic file to set your preference.   so following this advice I entered this      // Try and turn off autoupating     APT::Periodic::Enable "0";   into /etc/apt/apt.conf.d/10periodic as you can see from my config listing above. yet I am still getting the notification...  Possible solutions I can think of   the comment // Try and turn off autoupating may be causing a parse error of the config file, causing apt to ignore the entire file?  unlinking or commenting out /etc/cron.daily/apt-compat ?   How can I disable the update notifier box?


Calculation of surface of external walls of buildings from a cadastral footprint shapefile

I need to calculate the surface (m2) of external walls of all the buildings in a town. By external walls I mean all the walls of a building or parts of a wall which are not in contact with another building. I have a 2D shapefile of polygons with the cadastral footprint of the buildings, which includes information of the building’s height in the attribute table.  I don’t really know how can I do it… My idea is to convert the 2D file to 3D and use the 3D shapefile to distinguish the external walls from the shared walls (parts of a building that are shared with other buildings) of all buildings, and from there, calculate the total area but I’m not sure whether this can be done with ArcScene.  Anybody knows how could it be done and if there is an automate way to do it?


Desktop shortcut to create a new desktop shortcut doesn't do anything

It's weird that creating desktop shortcuts is currently so primitive.  I found the following:   That helps.  However, if there's something wrong with the shortcut, it just doesn't do anything.  For instance, I tried to create a shortcut for this command line to create a shortcut.  When I double-click it, it just does nothing.  This is the resulting text of my "Create Desktop Shortcut.desktop" file on the desktop:  [Desktop Entry] Version=1.0 Type=Application Terminal=false Icon[en_CA]=gnome-panel-launcher Exec=/usr/bin/gnome-desktop-item-edit ~/Desktop/ --create-new Name[en_CA]=Create Desktop Shortcut Name=Create Desktop Shortcut Icon=gnome-panel-launcher   As I said, when I double-click this, or right-click it and select Open, nothing happens.  Is there a log file where something about this would be written to?


Proof that $2^{10}+5^{12}$ is a composite number

A hint or full answer will help a lot, because I have no idea what to do.


Having troubles finding Regular Solids with blender 2.78

I am new to Blender and I have been watching a video tutorial on how to create a soccer ball. So this guy went to Addons then Add Mesh and he enabled Regular Solids. I am using blender v2.78 and I don't have this option. I am trying to create a Truncated Icosahedron shape.


Keeping dead beta sites as "archive sites"

This is not a duplicate of  because the main point of that is to allow for a process in Area 51 to "reopen" a closed site, while this one merely asks for closed sites to remain alive and read-only, without a special procedure for "reopening".  When a beta site is closed, the questions that can be migrated are given to other sites. But what about the questions that aren't relevant on other sites?   Let's say you have a question, that was fairly high voted, and has an accepted answer. That question may be useful to someone else in the future, even if it will not be useful to as many people as a StackExchange site requires. If that question is deleted, than in the future, people who are searching for answers on a question that happened to be covered by a closed beta, will not be able to get it.  What I propose, is that when a beta site dies, instead of deleting it, it should be turned into an "archive site".  The archive site would basically be the same as the regular site, except there would be a big "Archive" at the top of the site (it would look just like the meta site, except with "archive" instead of "meta", and it would be colored even more gray), and it would be read-only. People would be able to view the questions and answers, but no one would be able add anything, or vote.  Also, I would suggest that Stack Exchange keep track of the traffic that comes into that site. If, for some reason, the topic of that dead beta become of interest to enough people, the site could be recreated.  Any questions, comments, suggestions?


I'm Syrian Citizen and i want to go to USA

My Sister is already in the USA and she has a green card. She has a baby that is born in US so he is an American citizen. My question is, can I get a visa to visit  her and her son?  note : i applied for a visit visa before she had a green card and baby so I got refused  Thanks for reading.


Seeking podcasts related to geospatial technologies?

I would like to make a list of podcasts related to geospatial technologies.  Do you listen to any that you find interesting and informative?


I have a 1000 piece puzzle it's rectangular 99cm x 33cm

I don't know if its possible to find out how many pieces are the boarder?


How to create an expectation symbol that behave similarly to \sum?

Introduction  This question is already asked . If you want you could consider this one a duplicate. However, even if the proposed solution satisfied the one that posted the question, it doesn't completely satisfy me (and this is the reason for this duplicated question).  My aim is to declare a new operator for the expected value that behave like the summation symbol. The proposed solution is to declare it with \DeclareMathOperator*{}{} command (note the presence of the asterisk). This solution satisfies the feature of \sum like operators that put superscripts and subscripts in a different way depending on the current math mode. However, in \sum like operators, the size of the symbol itself change accordingly to the current math mode.  In the following a visual example that shows the difference between \sum and the new math operator.    And this is the code to generate it:  \documentclass{article} \usepackage[utf8]{inputenc} \usepackage{amsmath} \usepackage{amssymb} \DeclareMathOperator*{\expec}{\mathbb{E}}  \begin{document} $\sum_a x_a$ vs $\displaystyle \sum_a x_a$ ~~~ $\expec_a x_a$ vs $\displaystyle \expec_a x_a$ \end{document}   Real question  How could I define the new operator in order to scale it differently based on the current math mode?  Bonus question: I'm interested only in scaling the symbol. However, in some cases, one may want to use a different symbol (I'm thinking about the \int command, that in a lot of fonts use two different symbols for inline and display math). So, a solution that takes into account also this feature would be appreciated.    Of course, it could be that I miss something really obvious like that already exist a math operator for the expected value. In this case, I will appreciate if you notify me. However, the question remains valid for other new defined operators.


If $f(x)=\int_{x-1}^x f(s)ds$, is $f$ constant? Periodic?

I was thinking of periodic functions, and in particular the following type of condition:     If a function $f:\mathbb{R}\to\mathbb{R}$ always "tends to its average", then it should be periodic.   To make things more formal, by "tending to the average" we could say something like $f(x)=\int_{x-1}^x f(s)ds$. This is only the average depending on a previous time interval of length $1$, but it seems an interesting enough property. However, the only type of functions which I could find that satisfies this property are the constant ones!     Question: If $f:\mathbb{R}\to\mathbb{R}$ is continuous (or more generaly measurable) and $f(x)=\int_{x-1}^x f(s)ds$ for (almost) every $x\in\mathbb{R}$, then is $f$ constant (a.e.)? Periodic (a.e.)?   Here is a first try for $C^1$ functions (see edit below!): If $f$ is $C^1$ and $x$ is fixed, we can use Taylor expansion $f(s)=f(x)+O(s-x)$ (and similarly for $x-1$) to obtain \begin{align*} f(x+t)-f(x)&=\int_x^{x+t}f(s)ds-\int_{x-1}^{x-1+t}f(s)ds\\ &=\int_x^{x+t}f(x)+O(s-x)ds-\int_{x-1}^{x-1+t}f(x-1)+O(s-x+1)ds\\ &=t(f(x)-f(x-1))+O(t^2), \end{align*} so $f'(x)=f(x)-f(x-1)$. This is obviously true if $f$ is constant, but the converse is not clear to me at the moment.    Edit: From a comment and answer below, the equation $f'(x)=f(x)-f(x-1)$ has non-periodic solutions on $\mathbb{R}\setminus\mathbb{Z}$, so this should not be the way to go for $C^1$ functions. However, even in this case it is not clear that any solution of this equation will satisfy $f(x)=\int_{x-1}^x f(s)ds$, which is the question: All I can obtain, in principle, is $f(x)-f(x-1)=\int_x^{x-1}f(s)ds-\int_{x-2}^{x-1}f(s)ds$.


Quick question: what is the compiler flag to allow g++ to spawn multiple instances of itself in order to compile large projects quicker (for example 4 source files at a time for a multi-core CPU)?


Why “help” doesn’t show all available Windows commands?

I’m trying to understand how the commands are grouped in the Windows command line. I can not find all of them when I type help. Why there isn’t eg. the net command, and no explanation of what are the signs > <| & etc.   I found the official documentation on the , where all commands are listed alphabetically but I wonder why some of them are not available directly from the command line.


Find the sum to n terms as well as the sum to infinity of the series:

Find the sum to $n$ terms as well as the sum to infinity of the series:  $$\frac{1}{3} + \frac{1}{4\cdot 2!} + \frac{1}{5\cdot 3!} +\cdots.$$  I was trying this question many times but I didn't get the answer. I was using geometric series formula, but it was not applicable here...I don't know where I have to start, and I don't know any hint about this series....  If anybody helps me, I would be very thankful to him.


Error "syntax error near unexpected token `('?"

What's in my terminal  bash: settings64.csh: line 35: syntax error near unexpected token `(' bash: settings64.csh: line 35: `foreach i ( $xlnxInstLocList )'   Portion of the script  set xlnxInstLocList="${xlnxInstLocList} common" set xlnxInstLocList="${xlnxInstLocList} EDK" set xlnxInstLocList="${xlnxInstLocList} PlanAhead" set xlnxInstLocList="${xlnxInstLocList} ISE" set XIL_SCRIPT_LOC_TMP_UNI=${XIL_SCRIPT_LOC} foreach i ( $xlnxInstLocList )   Location of syntactical error at the bottom  line 35 foreach i ( $xlnxInstLocList )   I'm not a scripter; I'm trying to fix an error in the scripting for my ISE DESIGN SUITE installation. I just need a quick set of code to replace "foreach i ( $xlnxInstLocList )" to perform its intended function. I think it's a Bash script.


Econometrics Problem. Proving Regressions have both R squared

I am working on a problem that requires proving both regressions have the same R^2. The question is: Suppose you run a regression of Yi and Xi and obtain parameter estimates beta hat 1 and beta hat 2. Then using the same data, you decide to run a regression of Ybar 1 on Xi, where Ybar = 2yi. How do I prove this>


$A,B\in M_{n}(\mathbb{R})$ so that $A>0, B>0$, prove that $\det (A+B)>\max (\det(A), \det(B))$

Let $A,B\in M_{n}(\mathbb{R})$ be symmetric, with $A>0$ and $B>0$.  I need to prove that $\det (A+B)>\max (\det(A), \det(B))$.  I want to use Sylvester theorem of having a matrix $D$ so that $D=\operatorname{diag}(1,1,\ldots, 1,-1,-1, \ldots-1,0,0,\ldots,0)$.  Do I need to use it? How do I use it here?  Thank you.


Preventing Brute Force Logins on Websites

As a response to the recent  and , what is the best way to secure your website against brute force login attacks?  Jeff's post suggests putting in an increasing delay for each attempted login, and a suggestion in the comments is to add a captcha after the 2nd failed attempt.  Both these seem like good ideas, but how do you know what "attempt number" it is?  You can't rely on a session ID (because an attacker could change it each time) or an IP address (better, but vulnerable to botnets).  Simply logging it against the username could, using the delay method, lock out a legitimate user (or at least make the login process very slow for them).  Thoughts? Suggestions?


What is the best obtainable gear in Heavy Armor, Light Armor and Clothing?

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