Do the trunks have special compartments or something? How do they fit all of their school supplies, casual clothes and personal belongings in them? They have big school supplies like a cauldron and a telescope.  How do they fit all of their stuff in their trunks?

Is Harry's trunk magically oversized (like Hermione's bag in book 7, or the Weasley car in book 2) to allow him to store his Firebolt in it? Is Harry able to hide, pack his broom so the Dursley's can't see it? the broom, almost more than anything, would repulse the Dursleys.   I don't recall there being a mention of his broom specifically being at the Dursely's or being transported to Platform 9 3/4, specifically in book 4 when the Weasley's come to collect Harry from the Dursleys. One of the twins climbs into the fireplace with Harry's trunk, but no mention of the Firebolt is made, yet, Harry has it at the Burrow after the World Cup.


#include <stdio.h> struct test {     unsigned int x;     long int y: 33;     unsigned int z; }; int main() {     struct test t;     printf("%d",sizeof(t));     return 0; }   output     24  size of long int is 8 byte but here it is taking 16 byte why?

Why does the sizeof operator return a size larger for a structure than the total sizes of the structure's members?


On Wednesday my wife came across the word atavism in Out of Africa that she did not know the meaning of. I did not recognise the word and did not know what it meant. So we looked it up and found out.  Then on Thursday I was reading an article on the Guardian () and saw the word atavistic. I cannot for the life of me recall seeing this word ever before, and here it pops up shortly after finding out what it meant.   I am sure this phenomenon has happened before - where I learn something new (usually the meaning of a word that I have never seen before, or name of a place or person) and then the very shortly afterwards see it being used. (This also happened to me this year with quinoa.)  Is there a name for this phenomenon? Or is it just me that this happens to?

Most of us have had the experience of stumbling over a new fact or bit of knowledge and then finding several more references to it in the near future.  For example, you see a strange word which you're forced to look-up and then the next day the same word appears in the headline of your local paper.  There's a term for this phenomenon but I've been unable to track it down.  Can anyone help?


I understand it's not the present tense, else it would be "goes". Is the sentence grammatically correct? If so, does it mean "you are seeing that it is going away"?

"Heard me [infinitive]" vs. "heard me [present participle]"             At that time, you wouldn't have heard me talk about it.   At that time, you wouldn't have heard me talking about it.         At that time, you wouldn't have heard me condemn it.   At that time, you wouldn't have heard me condemning it.         Which one of the above sentences are incorrect and why?


What is correct sentence to ask,    How much money How many money  How many dollars   In case of singular noun we use much, but is money singular? I'm a bit confused need help here.

page suggests that we use much with only uncountable nouns whereas the use of many/several is limited to countable nouns only. So I conclude that money is uncountable noun as I've heard people saying phrases like      So much money!   But, We do count the money in our daily life then why is it that money is considered an uncountable noun instead of countable? What if I say      I have $500 to spend   Wouldn't the money be considered countable in this case?  Edit The question may be considered duplicate of the suggested question but, in my opinion, the question on that link itself is not answered properly.


for $x \in \mathbb{R}$, consider $f(x) = x(1-x)$, using traditional methods of finding global extremas, we can show that the derivative has a unique zero at $x= \frac12$ and $f''(\frac12) < 0$, thus $x(1-x) \leq \frac14 = f(\frac12)$  is there a more elegant way ?

Let $p,q \in \mathbb R$, and $p+q=1$. Prove that $$pq \le \frac{1}{4}.$$   The first thing I did was define 3 possibilities that we can have from $p+q=1$:  1º  $p$ or $q$ is negative. Example:   $p=-10$, $q=11$   $-10+11=1$  $(-10)(11)=-110$  So if $p$ or $q$ are negative the inequality $pq$ $\le$ $\frac14$ holds.  2º $p$ or $q$ is $0$, that makes the inequality $pq$ $\le$ $\frac14$ be $0$ $\le$ $\frac14$, the inequality holds.  3º The final possibility I saw  was $0$ $\lt$ $p,q$ $\lt 1$, here i just see that the max value from $p,q$ can be $p,q = 1/2$ making $\frac12 + \frac12 = 1$ and $(\frac12) (\frac12) \le \frac14$, but i do not see the elegant way of proving that with other values the inequality holds.  I apologize in advance if I made any mistake or missed something.


In the following example, should I use a, any, the, it, or one?   Yesterday my friend told me someone had parked a truck in our playground but when I reached there I did not see a truck/it/any trucks/the truck/one.

In the following example, can I use the truck, it, and one interchangeably? Are they all correct?        Yesterday my friend told me someone had parked a truck in our playground but when I got there I could not see the truck.    Yesterday my friend told me someone had parked a truck in our playground but when I got there I could not see it.   Yesterday my friend told me someone had parked a truck in our playground but when I got there I could not see one.


I am trying to read a properties file from a package within my program without having to copy it to the plugin directory. I can read from a properties file which is in the plugin directory:  private String displayProperties() {     Properties props = new Properties();     InputStream is = null;      try      {         File f = new File(getDataFolder()+"/test.properties");         is = new FileInputStream(f);         props.load(is);         return props.getProperty("Test1");     }      catch (IOException e)      {         e.printStackTrace();     }      return null; }   This is all good and works BUT the user is able to edit the properties file. I have done some 'googling' and what i have found is people saying its not possible to write to a properties file in the .jar file. I am not trying to write to it, I just want to read from it.  Is this possible? and if so how can I change my code to accomplish this?  (If you know of a tutorial that would be great too)  Edit: I have now solved the problem, all I had to do was to change the input stream from file to this:  is = getClass().getResourceAsStream("test.properties");   Now it works perfectly.

I'm trying to access an XML file within a jar file, from a separate jar that's running as a desktop application.  I can get the URL to the file I need, but when I pass that to a FileReader (as a String) I get a FileNotFoundException saying "The file name, directory name, or volume label syntax is incorrect."  As a point of reference, I have no trouble reading image resources from the same jar, passing the URL to an ImageIcon constructor.  This seems to indicate that the method I'm using to get the URL is correct.  URL url = getClass().getResource("/xxx/xxx/xxx/services.xml"); ServicesLoader jsl = new ServicesLoader( url.toString() );   Inside the ServicesLoader class I have   XMLReader xr = XMLReaderFactory.createXMLReader(); xr.setContentHandler( this ); xr.setErrorHandler( this ); xr.parse( new InputSource( new FileReader( filename )));   What's wrong with using this technique to read the XML file?


I saw some code in C header like this:  //a.h  typedef struct name name;  //a.c  struct name {    int number;    int age; };   what is the reason why typedef struct in header file?  and kind of implement it in source file?  Why not just define the struct in header file? what is the propose of doing this?

I have seen many programs consisting of structures like the one below  typedef struct  {     int i;     char k; } elem;  elem user;   Why is it needed so often? Any specific reason or applicable area?


let $x^{/1/}=x+x$ (addition)   $x^{/2/}=x.x$ (multiplication)  $x^{/3/}=x^x$ (exponentiation)  $x^{/4/}={}^xx$ (tetration)  and so on.....  I have the following questions:     $(1)$ Can we define an operation between two known operations (Ex.addition and multiplication), where $n$ in $x^{/n/}$ is fractional (Ex. $x^{/1.5/}$)?      $(2)$ Is there a closed form for $x^{/x/}$?      $(3)$ Is infinitation ($x^{/\infty/}$) equal to infinite tetration $\left( x^{x^{x...}}\right)$?   I think the answer to the last question is true as infinite tetration is equal to infinite pentation (as both of them equal to $x^{x^{x^{.^{.^.}}}}$ when we convert them to their exponentiation form.) Following the same logic, any $n$-ation is equal to $x^{x^{x^{.^{.^.}}}}$, and therefore infiniation is also equal to infinite tetration.     Edit: Does this notation seem useful for defining operations?

I noticed this  which attempts to find the shades of grey between a linear and log scale where results are between zero and one.  However, I was looking for the more general case where we find the continuum between the operators themselves - add, multiply, and exponentiation or even higher.  The function could be a hyperoperation$(n,x,y)$, where $x$ and $y$ are the numbers to operate on, and $n$ is allowed to be a non-integer number for the type of operator. So $n=1$ would be 'addition', $n=2$ would be multiplication, and $n=3$ would be exponentiation. But one would also have $n=2.5$ to be the shade of grey BETWEEN multiplication and exponentiation, or $n=3.5$ or $4$ for beyond exponentiation and tetration).  I want the formula to work with real numbers, not just integers. Any thoughts?  These related posts may also be of interest:


Let $f$ be a holomorphic function on the unit disk. If $|f(z)|=1$, show that $f$ must be a constant function.  I am a little confused how to start this.

How can I prove the following assertion?    Let $f$ be a holomorphic function such that $|f|$ is a constant.  Then $f$ is constant.    Edit: The more elementary the proof, the better. I'm working my way through a complex analysis workbook, and by this exercise, the only substantial thing covered has been the Cauchy-Riemann equations.


After I made desired shape with subdivision modifier, how do I turn it into a mesh, there is no apply button in modifier.

Why I can't apply mirror modifier? Here's screen


i am trying to install s-nail and i am getting this error..  tried it to google it but there is no luck  the packages are already updated "sudo apt-get update" i am using Ubuntu 16,  sudo apt-get install s-nail Reading package lists... Done Building dependency tree    Reading state information... Done E: Unable to locate package s-nail   please help thank you

When I try to install any package through the command line, I get an error.   $ sudo apt-get install <package> Reading package lists... Done Building dependency tree        Reading state information... Done E: Unable to locate package <package>   Can anyone help me on this?


I would like to test wether there's a significant difference in the mean between this two samples:  withincollaraccuracyknn<-c(0.960, 0.993,0.975,0.967,0.968,0.948) withincollaraccuracytree<-c(0.953,0.947,0.897,0.943,0.933,0.879)   The data is normally distributed as you can see after running a Shapiro-Wilk test:  > sh<-c(0.960,0.993,0.975,0.967,0.968,0.948,0.953,0.947,0.897,0.943,0.933,0.879) > shapiro.test(sh)      Shapiro-Wilk normality test  data:  sh W = 0.91711, p-value = 0.2628   However, using t.test() or wilcox.test() yield different p-values:  > t.test(withincollaraccuracyknn,withincollaraccuracytree)      Welch Two Sample t-test  data:  withincollaraccuracyknn and withincollaraccuracytree t = 3.1336, df = 7.3505, p-value = 0.01552 alternative hypothesis: true difference in means is not equal to 0 95 percent confidence interval:  0.01090532 0.07542802 sample estimates: mean of x mean of y  0.9685000 0.9253333   > wilcox.test(withincollaraccuracyknn,withincollaraccuracytree)      Wilcoxon rank sum test  data:  withincollaraccuracyknn and withincollaraccuracytree W = 35, p-value = 0.004329 alternative hypothesis: true location shift is not equal to 0   Could somebody please let me know why? On the Wikipedia page of Mann-Whitney U test, it is stated: "It is nearly as efficient as the t-test on normal distributions".  Note also a Warning when the data is not normally distributed:  > withincollarprecisionknn<-c(0.985,0.995,0.962,1,0.982,0.990) > withincollarprecisiontree<-c(1,0.889,0.96,0.953,0.926,0.833) >  > sh<-c(0.985,0.995,0.962,1,0.982,0.990,1,0.889,0.96,0.953,0.926,0.833) >  > shapiro.test(sh)      Shapiro-Wilk normality test  data:  sh W = 0.82062, p-value = 0.01623  >  >  > wilcox.test(withincollarprecisionknn,withincollarprecisiontree)      Wilcoxon rank sum test with continuity correction  data:  withincollarprecisionknn and withincollarprecisiontree W = 30.5, p-value = 0.05424 alternative hypothesis: true location shift is not equal to 0  Warning message: In wilcox.test.default(withincollarprecisionknn, withincollarprecisiontree) :   cannot compute exact p-value with ties   Any help is appreciated. Note that I need to run similar analysis for other datasets having not normally distributed data, so using wilcox.test() instead of t.test() would be an advantage!

This is a repost from the R forum, as I was told to post here instead.  I would like to test whether there's a significant difference in the mean between this two samples:  withincollaraccuracyknn<-c(0.960, 0.993,0.975,0.967,0.968,0.948) withincollaraccuracytree<-c(0.953,0.947,0.897,0.943,0.933,0.879)   The data is normally distributed as you can see after running a Shapiro-Wilk test:  > sh<-c(0.960,0.993,0.975,0.967,0.968,0.948,0.953,0.947,0.897,0.943,0.933,0.879) > shapiro.test(sh)      Shapiro-Wilk normality test  data:  sh W = 0.91711, p-value = 0.2628   However, using t.test() or wilcox.test() yield different p-values:  > t.test(withincollaraccuracyknn,withincollaraccuracytree)      Welch Two Sample t-test  data:  withincollaraccuracyknn and withincollaraccuracytree t = 3.1336, df = 7.3505, p-value = 0.01552 alternative hypothesis: true difference in means is not equal to 0 95 percent confidence interval:  0.01090532 0.07542802 sample estimates: mean of x mean of y  0.9685000 0.9253333   > wilcox.test(withincollaraccuracyknn,withincollaraccuracytree)      Wilcoxon rank sum test  data:  withincollaraccuracyknn and withincollaraccuracytree W = 35, p-value = 0.004329 alternative hypothesis: true location shift is not equal to 0   Could somebody please let me know why? On the Wikipedia page of Mann-Whitney U test, it is stated: "It is nearly as efficient as the t-test on normal distributions".  Note also a Warning when the data is not normally distributed:  > withincollarprecisionknn<-c(0.985,0.995,0.962,1,0.982,0.990) > withincollarprecisiontree<-c(1,0.889,0.96,0.953,0.926,0.833) >  > sh<-c(0.985,0.995,0.962,1,0.982,0.990,1,0.889,0.96,0.953,0.926,0.833) >  > shapiro.test(sh)      Shapiro-Wilk normality test  data:  sh W = 0.82062, p-value = 0.01623  >  >  > wilcox.test(withincollarprecisionknn,withincollarprecisiontree)      Wilcoxon rank sum test with continuity correction  data:  withincollarprecisionknn and withincollarprecisiontree W = 30.5, p-value = 0.05424 alternative hypothesis: true location shift is not equal to 0  Warning message: In wilcox.test.default(withincollarprecisionknn, withincollarprecisiontree) :   cannot compute exact p-value with ties   Any help is appreciated. Note that I need to run similar analyses for other datasets having not normally distributed data, so using wilcox.test() instead of t.test() would be an advantage!


I have two byte arrays. I want to merge these two byte arrays into one byte array.  Usually, I just create a new byte array with length = byte array #1 + byte array #2. Then copy byte array #1 and #2 to the new byte array.  Is there a more efficient way to merge two byte arrays using VB.NET and .NET 4?

I have 3 byte arrays in C# that I need to combine into one. What would be the most efficient method to complete this task?


I have successfully done a 301 from example.com to newexample.com/example but Google Webmaster Tools will ONLY let me submit a change of address for root level domains e.g. from example.com to newexample.com. So, should I instead value the Webmaster Tool more and just redirect the old domain to the new root directory instead of it's sub folder, even though it is not as relevant, or stick to my more relevant 301s and just not use webmaster for change of address. Will this hurt my PR from the old site or will Google still be nice to me?

Is it possible to tell Google's Webmaster Tools that our site hosted on www. has moved to a sub folder, sub domain or a new domain with sub folder?


I didn't really understand this proof to begin with, and I really don't understand what this question is asking. Do I just let n equal some number and then try to prove it from there, how do I begin the proof?

I'm trying to prove that ${n \choose r}$ is equal to ${{n-1} \choose {r-1}}+{{n-1} \choose r}$ when $1\leq r\leq n$.  I suppose I could use the counting rules in probability, perhaps combination= ${{n} \choose {r}}=\frac{n!}{r!(n-r!)}$.  I want to see an actual proof behind this equation.  Does anyone have any ideas?


Basically I was just struck with the term 'attorney at law' as being a somewhat odd English construction. I can't think of any other time where we refer to another profession this way. In other words, can one be an Attorney at Butchery, or perhaps an Attorney at Plumbing? Aren't all attorney's "at law"? Which also made me wonder is there any difference between Attorney and Lawyer? I know that they are colloquially used to mean the same thing, but perhaps they were originally more (or less) specific? Or is it simply a redundancy?

I have wondered from time to time about the phrase "attorney at law." Are there other kinds of attorneys? Attorneys at arms? If not, why do we specify?


I asked a freelancer to migrate the website from staging to live server and they perform the migration, but now I want to back up the files and DB I need a pem file, which the freelancer never gave me.  What do I do? I don't know the FTP details also. How can I backup my website files and DB? The website is hosted on aws Ec2-Linux?

I am working with some Amazon EC2 servers that are up and running, and I need to SSH into the servers. I don't have any keys that were generated when the servers were first set up (someone else did it long before I got here). Can I still get into the servers without the key files?  FWIW I've tried a lot of things to SSH into the box so far, including generating new key pairs in the EC2 dashboard, and nothing seems to be working.  and  seem to indicate that I'm out of luck unless I want to make an AMI of my current server and then use it to instantiate a whole new EC2 server instance (just to get the .pem file generated at that time). Is that really the only way I can get into the box at this point?!


Here is my story... I had a dual booted PC with Ubuntu and Windows 7. It worked fine. But I forgot my admin password of Ubuntu. So I decided to uninstall my older version and reinstall a newer version of Ubuntu. But what I got what was a   grub rescue error    Then I installed Ubuntu with my USB without trying get Windows back. Now my PC automatically boots Ubuntu. So I downloaded a Windows 7 ISO and used my USB to repair it. But when I load my USB in boot option menu, instead of asking me to install Windows, it shows the  0xc0000225 error   and asks me to insert a disk(which I've done using my USB). What should I do to get Windows 7 back (or course, without losing Ubuntu)?

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


I am a GIS guy and do not know much about deep learning and AI. How can I start using ArcGIS Python API to do GeoAI ?

I am new to the world of ArcGIS and I come from a data science background. I recently installed ArcGIS Pro with a Single User license from my organization. I would like to use it with the Python API for deep learning.  Can anyone tell me how to get my setup properly working. I am confused as to how to login with the GIS() object in Python.  I would like to be able to perform tasks similar to this example:


Consider a group of size 40. What is the probability that at least three members of the group were born in the same month and in the same day (same birthday)? Ignoring leap years.

I have been looking at the birthday problem (http://en.wikipedia.org/wiki/Birthday_problem) and I am trying to figure out what the probability of 3 people sharing a birthday in a room of 30 people is. (Instead of 2).  I thought I understood the problem but I guess not since I have no idea how to do it with 3.


When do we use the word pressure instead of force? I think pressure and force are same. Please explain without including the formula. In the example of nail penetrating into the wall whereas if we invert the nail and then it will be hard to penetrate this example doesn't help me. I think here there is only requirement of force nothing else.

I have looked around, and I will admit that I'm a bit lost on the definitions.  's opening reads:     Pressure (symbol: P or p) is the ratio of force to the area over which that force is distributed.   That's a bit hard to understand at first, I'll have to say. Is vaguely saying "pressure" relative to "air resistance", or drag? Because they seem to be mixed around often.        refers to forces acting opposite to the relative motion of any substance moving in a fluid.   Sounds unrelated to pressure, so let's move on.  If pressure is the ratio of force to an area which the force is distributed, wouldn't anything be force then? Wind's force is covered over an area that it's distributed from. A punch would count too, based on how I understand pressure. I have always envisioned pressure as a uniform body of gaseous force or energy acting versatilely upon everything, such as below illustrates:    Higher pressure of the atmosphere is like a tighter "squeeze" on everything within it.  People often say pressure in exchange for force, such as when someone shakes someone's hand very hard (with a strong grip), one will say that the force is pressure. Is this correct? If so, why, and how do force and pressure coincide?


I m trying to change some characters in a file, like this:  //this is a thest of how this works #include <stdio.h>  int main() { // declare some variables here int num1 = 4; float num2 = 3.5;  // print the result  printf("The result is %f\n", num1 * num2); // this does it  /* does it work? */ return 0; }   I want to change all the // character for commenting in c++ to the c comment characters /* */ making the file then look like this:  /*  This is a test of how this works */ #include <stdio.h>  /*this is a thest of how this works */ #include <stdio.h>  int main() { /* declare some variables here */ int num1 = 4; float num2 = 3.5;  /* print the result  */ printf("The result is %f\n", num1 * num2); /* this does it */  /* does it work? */ */ return 0; }   I do not know much bash at all and this is what i came up with sed 's/////* *//g' myprog.c  it did not work, what am i doing wrong or what do i need to do to make these changes? Im trying to make it a one line command

I have a line as follows   // Testing this   I am trying to use a sed command to replace the // with a /* (sentence or word in between) */ on each line.  so it should look something like this  /* Testing this */   The first part is easy with calling  sed 's#//#/*#'   however, with the second part, I tried this solution    I tried with -e which gave me an error of 'unterminated s command'. Then, I tried with a semi colon to make it one so it was something along the lines of   's#//#/*#;#//#s#/$#*/#'   but all that seems to do is the first part (replacing // with /*)and not the second (putting a */ at the end of the same line).  What am I not doing correctly? Any pointers would be appreciated.


Electrical systems have neutral besides live and ground. Electronic systems have only VCC and gnd. I read that having neutral is necessary for safety in electrical systems because of the higher voltage and current involved.   How does having neutral make electrical systems safer?

Wouldn't it be simpler if electrical systems take away the neutral and just have live and ground similar to electronic systems?


I created a 2d array of type string, which stores name, marks of 3 subjects and total marks. I need to display the records on basis of the rank i.e the student with higher total marks should be shown first. How can i achieve this in C#? Please help.....  class Program     {         static void Main(string[] args)         {             int noOfStudents, totalMarks, position = 1;             string studentName, engMarks, mathMarks, computerMarks;              Console.Write("Enter Total Students: ");             noOfStudents = Convert.ToInt32(Console.ReadLine());             string[,] studentInfo = new string[noOfStudents, 5];              studentInformation(studentInfo);              for(int i = 0; i < studentInfo.GetLength(0) + 1; i++)             {                 int temp, count = 0;                 for(int j = 0; j < studentInfo.GetLength(1); i++)                 {                     if (int.Parse(studentInfo[i,4]) < int.Parse(studentInfo[i+1, 4]))                     {                         temp = int.Parse(studentInfo[i, 4]);                         studentInfo[i, 4] = studentInfo[i + 1, 4];                         studentInfo[i + 1, 4] = temp.ToString();                     }                     else                     {                         count++;                     }                 }                     Console.WriteLine("Student Name: {0}, Position: {1}, Total: {2}/300", studentInfo[i,0], position, studentInfo[i, 4]);                     position++;              }              Console.ReadKey();                 void studentInformation(string[,] a) {                 for(int i = 0; i < noOfStudents; i++)                 {                     Console.Write("Enter Student Name: ");                     studentName = Console.ReadLine();                     studentInfo[i, 0] = studentName;                      Console.Write("Enter English Marks(Out of 100): ");                     engMarks = Console.ReadLine();                     studentInfo[i, 1] = engMarks;                      Console.Write("Enter Maths Marks(Out of 100): ");                     mathMarks = Console.ReadLine();                     studentInfo[i, 2] = mathMarks;                      Console.Write("Enter Computer Marks(Out of 100): ");                     computerMarks = Console.ReadLine();                     studentInfo[i, 3] = computerMarks;                      Console.WriteLine("************************************");                     totalMarks = (int.Parse(engMarks) + int.Parse(mathMarks) + int.Parse(computerMarks));                     studentInfo[i, 4] = totalMarks.ToString();                 }              }         }     } }

I have a two-dimensional array (of Strings) which make up my data table (of rows and columns).  I want to sort this array by any column.  I tried to find an algorithm for doing this in C#, but have not been successful.  Any help is appreciated.


Let $f(x)=x^4-6x^2+4 \in \mathbb{Q}[x]$ and $L$ a splitting field of $f(x)$ over $\mathbb{Q}$.  How to determine the Galois group?  My idea was:  $x^4-6x^2+4=(x^2)^2-6x^2+4$  So $x^2 \in \lbrace \frac{6}{2} \pm \sqrt{(\frac{6}{2})^2-4} \rbrace = \lbrace 3+\sqrt{5},3-\sqrt{5} \rbrace$  Then $x \in \lbrace \sqrt{3+\sqrt{5}}, \sqrt{3-\sqrt{5}} \rbrace$  These are two roots of the polynomial. Now I'm not sure what to do next. I thought about finding the other two roots, but I don't know how.  How to continue? Or is there a better method to find the Galois group here?

From Hungerford, section V, chapter 4 exercise 9:     Let $x^4+ax^2+b$ in  $K[x]$ (with char $K\neq $2) be irreducible with   Galois group $G$.      (a) If $b$ is a square in $K$, then $G =  \mathbb{Z}_2\times\mathbb{Z}_2$.       (b) If $b$ is not a square in $K$   and $b(a^2-4b)$ is a square in $K$, then $G = \mathbb{Z}_4$.       (c)   If neither $b$ nor $b(a^2-4b)$ is a square in $K$, then $G = D_4$   (dihedral group).   What I've tried  With (a):  Let be $u_1,u_2,u_3,u_4$ the roots of the quartic, then $b=u_1u_2u_3u_4$ is in $K$ and there exists $a\in K$ with $a^2=b$. On the other hand, $G = \mathbb{Z}_2\times\mathbb{Z}_2$ if and only if $\alpha=u_1u_2+u_3u_4$, $\beta=u_1u_3+u_2u_4$, $\gamma=u_1u_4+u_2u_3$ are in $K$, but I don't find the way to rely those results.   With (b) I know that $b=u_1u_2+u_1u_3+u_1u_4+u_2u_3+u_2u_4+u_3u_4$ but again I dont know how to continue.  Any help? Thanks.


Over the course of the Winter Bash, I have encountered a lot of spam questions here on MSE, the common pattern among them being the keyword "keto diet" or simply "keto".  No doubt they are deleted as soon as they are posted (thanks to the active community), but isn't there a method already in place which helps prevent such cases? If not, is there a plan to introduce/try one?  To begin with, one can check the user's history of questions to see if they have been asking questions with similar keywords earlier, and whether those questions were closed/deleted. This can then be expanded to consider posts made by that user across the SE network to prevent spam.  Thoughts?

Of course spam posts should be flagged, and if they come up in review, rejected.  Over on Mi Yodeya during the past 24 hours I’ve helped delete and reject four spam posts through the review queue, and I can only imagine that others were posted over the course of the night. To clarify, I’m referring to edits and answers that were about 99.274% words that I don’t think any decent person would use in everyday discussions, even if someone got them really angry.   Thing is, if the only thing we can do as a community is delete his posts/reject his edits, and as moderators to ban his account, can’t he just create a new account? Further, some of these posts . Maybe the mods can ban his IP address? I’m not one, so I have no idea what kind of power they wield in that respect. But he can always just get a new computer.   I don’t have the numbers to see what this is like on other sites, but I know this doesn’t happen often on Mi Yodeya. I wonder, then, whether this is the optimal solution, or whether an automatic spam filter be put into place - say, a new review queue that automatically deletes posts or rejects edits that can then be voted on whether to be reposted if it’s a false alarm. Perhaps it can be automatically triggered by certain keywords (like ****, %$#^, or @$+^).   Now, all of these posts that I voted to delete/reject came up in Suggested Edits and First Posts. Maybe such edits would show up in Low Quality in general, and that just wasn’t the case here because of precedence rules. I don’t know. But perhaps the above would be a better solution, if this is even as big of a problem as I’m making it out to be.


we need to know about simple message header accessor in web-socket spring boot. how to pass the database value to websocket using simple message header accessor.

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


I have several directories and sub-directories include text files. I need to change particular line of these text files for all directories and sub-directories. I used below sed command to perform this task;  find ./ -type f -exec sed -i -e 's/old_line/new_line/g' {} \;   It is working if there is no space in old_line and new_line. But it doesn't work for below example;  old_line=5704550660          SPP91564_2                              ANT # / TYPE  new_line=5704550660          SPP91564_2      NONE                    ANT # / TYPE   when I append these lines within above sed command, I receive;   sed: -e expression #1, char 56: unknown option to `s'   How can I modify above command to work properly for above example?

I am trying to replace a string inside a text file with a variable.  I am using this code:   sed -i "s/search text \/TAG\//replace text ${variable}/" ${textfile}   The content of the variable is /newTAG/. And the content of the variable is the problem, more accuratelyte the / at the beginning and the end.   When both / are removed so the content is only newTAG everything works fine.  I already tried the following  sed -i "s/search text \/TAG\//replace text "${variable}"/" ${textfile} sed -i 's/search text \/TAG\//replace text "${variable}"/' ${textfile}   Can anybody help me? Thanks


So I recently did my PhD project approval which is the process where I agree my objectives with my supervisor and present a short overview to a review panel. All that went well and my project has been approved and I can finally make a start on the work I need to do. I'm feeling a bit swamped and unsure about how to proceed tackling the objectives we need to achieve and this has left me feeling quite overwhelmed and overworked. My supervisor sent me a one line email last week basically saying "do objective 1 now" but I wanted to spend some time with them discussing the theory and devising a suitable way to do this objective. I know it's all about independent work but I feel I could benefit from a short meeting just to straighten up my work plan and ensure we're both on the same page. To clarify, the problem isn't that I don't understand the theory- I just need to clarify what my workplan should look like. Would I be dumb if I asked for a sit down to talk through the objectives and clarify what I should be working on? I feel very out of my depth

When needing to ask a professor about something important and potentially delicate, what is an appropriate way to phrase the question or write the email?  Examples include:   Requesting a recommendation letter Asking for exceptions to policy (e.g., ignoring a course prerequisite, rescheduling an exam) Asking if you can do research with them, join a group, get into a program Scheduling a meeting, exam, or defense Letting them know about a change of plans Letting them know about a life event affecting your work or studies (e.g., wedding, funeral, sickness, vacation)


At the time of Harry Potter and the Chamber of Secrets we have 2 conscious and functioning Horcruxes - young Tom Riddle from the Diary and the "main piece" hiding somewhere in Albania.   Young Tom Riddle reveals that he is not aware of the future - it's Ginny who told him that Voldemort was defeated when trying to kill Harry.     “Well, you see, Ginny told me all about you, Harry,” said Riddle. “Your whole fascinating history.“ His eyes roved over the lightning scar on Harry’s forehead, and their expression grew hungrier. “I knew I must find out more about you, talk to you, meet you if I could. So I decided to show you my famous capture of that great oaf, Hagrid, to gain your trust—”      [...]      “Haven’t I already told you,” said Riddle quietly, “that killing Mudbloods doesn’t matter to me anymore? For many months now, my new target has been—you.”      [...]      “So I made Ginny write her own farewell on the wall and come down here to wait. She struggled and cried and became very boring. But there isn’t much life left in her… She put too much into the diary, into me. Enough to let me leave its pages at last… I have been waiting for you to appear since we arrived here. I knew you’d come. I have many questions for you, Harry Potter.”      “Like what?” Harry spat, fists still clenched.      “Well,” said Riddle, smiling pleasantly, “how is it that you a skinny boy with no extraordinary magical talent—managed to defeat the greatest wizard of all time? How did you escape with nothing but a scar, while Lord Voldemort’s powers were destroyed?” There was an odd red gleam in his hungry eyes now.      — Harry Potter and the Chamber of Secrets, chapter 17, The Heir of Slytherin   It is quite clear, that the Diary only has a memory of 16 years old Tom Riddle.  If he were to win that fight and consume Ginny, what would happen with his memory? What would be his memory state at the moment?   addresses whether there would be 2 Voldemorts and how would they interact. For the sake of this question, I set that aside and actually ask in what state exactly will Voldemort's memory be and why. I see three possible outcomes:   The memory of Tom Riddle from the diary will merge with the original Voldemort's memory (though I'm not sure in this one since Voldemort doesn't seem to have any connection to his Horcruxes as he doesn't even notice them being destroyed) Riddle's 16 y.o. identity will dominate and be more or less single source of memory since that is Horcrux's condition vice versa original Voldemort's identity will prevail since he's the original one and have higher ground on this. He can't die while there's at least a single Horcrux, while Horcruxes can be destroyed, which places his original part higher.

As teenager Tom Riddle is speaking to Harry Potter in the Chamber of Secrets, both he and Harry are refering to the real Voldemort in the third person. If Tom Riddle had succeeded in sucking all the life energy out of Ginny and had come back alive, wouldn't that have meant there were two Voldemorts in the world? The wraith one which had lived in Quirrell, and the newly constituted one?  This Tom Riddle clearly doesn't have the memories of the wraith version.   As a bonus: If they both existed, would they have competed against each other?


Do I need transit visa for 8 hrs 5 mins transit time at Sydney for flight to London Heathrow?

Is there a website or some other way to find out if I need a transit visa for a short stop in the UK on my way somewhere else? Ideally this should give me the answer for all nationalities, and take into account any other visas I may have.


We finished preparing a manuscript and there is a researcher who helped and advised us on many aspects of the research. I know this may sound trivial but I would like to ask if it is required from me to ask him if I can mention him in the acknowledgment or not. Can I mention him without taking his permission to do so? Thank you in advance...

I had the impression that obtaining written permission before including someone in acknowledgements was required. Therefore, I just wrote to someone asking for written permission to include him in the acknowledgements of a paper, and he said he didn't think it was necessary. I don't recall where I got this notion from - perhaps the rules of a specific journal? So, I was wondering if there are any general rules about this or not, or are they perhaps journal specific?


Not sure if heap or stack is just in a Java, but why have two separate things to hold memory? Why not just have an unlimited stack, or just have a an unlimited heap? What’s the purpose of having them separate, or the reasoning to design it like that? I think I understand the difference between the two at a beginner level.

Programming language books explain that value types are created on the stack, and reference types are created on the heap, without explaining what these two things are. I haven't read a clear explanation of this.  I understand what a stack is. But,    Where and what are they (physically in a real computer's memory)? To what extent are they controlled by the OS or language run-time? What is their scope? What determines the size of each of them? What makes one faster?


Let $R = \mathbb{Z}[i]\ /\ (1+3i)$ (a) Conclude that R is a ring and $|R|=10$. (b) Define $\phi:\mathbb{Z} \rightarrow R$ by $\phi(n) = 1_R + \ldots + 1_R$ ($n$ times) if $n>0$ and $\phi(-n) = -\phi(n)$. Show this is a ring homomorphism. (c) Show that $\mathbb{Z}/10\mathbb{Z} \cong  \mathbb{Z}[i]\ /\ (1+3i)$  (a) I think I need to use $(1+3i)(1-3i)=10$ but not sure how. (b) I'm not sure how to show this. (c) Maybe I need to use the kernel but I'm not sure how to start.

A very basic ring theory question, which I am not able to solve. How does one show that    $\mathbb{Z}[i]/(3-i) \cong \mathbb{Z}/10\mathbb{Z}$. Extending the result: $\mathbb{Z}[i]/(a-ib) \cong \mathbb{Z}/(a^{2}+b^{2})\mathbb{Z}$, if $a,b$ are relatively prime.   My attempt was to define a map, $\varphi:\mathbb{Z}[i] \to \mathbb{Z}/10\mathbb{Z}$ and show that the kernel is the ideal generated by $\langle{3-i\rangle}$. But I couldn't think of such a map. Anyhow, any ideas would be helpful.


I'm trying to determine if it is possible to embed the Docusign Signature and Date tags into apex code that dynamically generates a PDF file using XMLStreamWriter. The PDF file is generated from the Quote by clicking a button that runs apex code and builds the PDF content using XMLStreamWriter and sends the XML using a callout to an external service endpoint (managed package) which returns the PDF and attaches the PDF to the Quote. At that point, it is the normal process of sending the Quote PDF via Docusign, however, the Signature and Date tags are missing from the PDF document for signing, which requires the user to drag the signature and date tags onto the PDF form the Docusign interface before hitting send. Ideally, having the signature and date tags automatically included in the PDF is the goal. I'm trying to determine if this is even possible and, if so, what approach would need to be taken to accomplish this. Has anyone encountered this type of use case? If so, what approach was taken? Thanks.

Is it possible to generate a PDF using Apex and then embed the 'Signature tab' of DocuSign into the PDF?  For example: in the Contract Object we have a text area in which the user could add legal agreements, such as:  Agreements (Text Area):     I agree that this and that are true and correct...      Signature: signature_tag   We would like that when a user clicks on a custom button, called 'Send to Docusign', an Apex code is run that will convert the agreements text area above into a PDF, then it converts the tag into a 'Signature tab' that DocuSign interprets as the location where the client needs to sign.  Is this possible?  Thanks.


I installed windows 10 and then dual booted my laptop by Ubuntu 18.04 Now I can't copy files (while using ubuntu) to the partitions which were created using windows as the partitions are Read-only. Properties show that the filesystem are of fuse type. I have tried solutions given

I am an infrequent Ubuntu / Linux user, only use it in case of major disaster (in this case Ransom-ware nuclear, but that's another story).  So i booted up another laptop using Ubuntu from a USB-drive; inserted my external ntfs drive, and it gets recognized automatically, but if i try to create a new folder / drive anywhere, the "file manager" interface just closes down, and i have to launch it again (try again, rinse and repeat).  This leads me to guess my ext.drive was mounted in read-only mode by default.  Q1. How / where can i verify it is mounted in read-only mode?  Q2. What's the best way to make it mount in read-write mode?


create unix alias for "ssh username@", and I would like to use it for any ip address.   for example,  alias go="username@" usecase: $go 10.1.1.1 ; implement => ssh username@10.1.1.1  Currently if i do $go 10.1.1.1, it is taking extra white space between @ and ip address. how can i remove it?

It's taken me almost 10 years of Linux usage to ask this question. It was all trial and error and random late-night internet surfing.  But people shouldn't need 10 years for this. If I were just starting out with Linux, I'd want to know: When to alias, when to script, and when to write a function?  Where aliases are concerned, I use aliases for very simple operations that don't take arguments.   alias houston='cd /home/username/.scripts/'   That seems obvious. But some people do this:  alias command="bash bashscriptname"   (and add it to the .bashrc file)   Is there a good reason to do that? I'm trying really hard, but I genuinely can't think of any circumstances in which I'd want to do that. So, if there is an edge case where that would make a difference, please answer below.  Because that's where I would just put something in my PATH and chmod +x it, which is another thing that came after years of Linux trial-and-error.  Which brings me to the next topic. For instance, I added a hidden folder (.scripts/) in the home directory to my PATH by just adding a line to my .bashrc (PATH=$PATH:/home/username/.scripts/), so anything executable in there automagically autocompletes.  If I needed to.  I don't really need that, though, do I? I would only use that for languages that are not the shell, like Python.  If it's the shell, I can just write a function inside the very same .bashrc:  funcname () {   somecommand -someARGS "$@" }   As I stated, I found a lot of this out through trial and error. And I only truly saw the beauty of functions when my computer died and I was forced to use the computers of the people around me when they weren't using them.   Instead of moving a whole directory of scripts from computer to computer, I ended up just replacing everyone else's .bashrc with my own, since they had never even made a single modification.  But did I miss anything?   So, what would you tell a beginning Linux user about when to alias, when to script, and when to write a function?   If it's not obvious, I'm assuming the people who answer this will make use of all three options. If you only use aliases, or only use scripts, or only use functions—or if you only use aliases and scripts or aliases and functions or scripts and functions—this question isn't really aimed at you.


My question is regarding a SQL server query.  Assume a user types a text "text1 text2 text3...textn" in a search textbox. Now I want to send this to a SELECT's  WHERE clause using a parameter.    cmd.Parameters.AddWithValue("@colname", textSearch.Text).    I want to write in this way    SELECT ... WHERE (colname LIKE text1 OR colname LIKE text2 OR colname LIKE text3 OR ....... colname LIKE textn)  OR (colname LIKE 'text1 text2 text3 ...textn')   How can I do this in SQL?

How do I parameterize a query containing an IN clause with a variable number of arguments, like this one?  SELECT * FROM Tags  WHERE Name IN ('ruby','rails','scruffy','rubyonrails') ORDER BY Count DESC   In this query, the number of arguments could be anywhere from 1 to 5.  I would prefer not to use a dedicated stored procedure for this (or XML), but if there is some elegant way specific to , I am open to that.


A body in free fall "feels" no gravitational force (equivalence). Why does it continue to accelerate. Why is your program refusing my question?

Note: For the purposes of my question, when I refer to free fall assume it takes place in a vacuum.   From my (admittedly weak) understanding of the equivalence principle, falling in a gravitational field is physically indistinguishable from floating in interstellar space. This would make sense to me if gravity simply caused an object to move at a constant velocity. Moving at a constant speed, or floating in space, are just two different ways of describing an inertial frame, and are fundamentally no different. But free falling in a gravitational field means accelerating continuously, and doesn't an accelerating body experience a force? Then isn't free falling fundamentally different from floating in space?


I've read that PyPDF can have issues while cropping PDF's with python.  Anyone able to help me understand why my script crops and leaves the files blank?  def cropPDF(filenamePDF):     top = 57      ###############################     right = 26    #   Margin's to be trimmed    #     bottom = 75   #          in pixels          #     left = 26     ###############################     pdfIn = PdfFileReader(open(filenamePDF,'rb'))     pdfOut = PdfFileWriter()     for page in pdfIn.pages:         page.mediaBox.upperRight   =  (page.mediaBox.getUpperRight_x() - right, page.mediaBox.getUpperRight_y() -top)         page.mediaBox.lowerLeft    =  (page.mediaBox.getLowerLeft_x() - left, page.mediaBox.getLowerLeft_y() -bottom)         pdfOut.addPage(page)         ous = open(filenamePDF, 'wb')         pdfOut.write(ous)         ous.close()

I was wondering if anyone had any experience in working programmatically with .pdf files. I have a .pdf file and I need to crop every page down to a certain size.  After a quick Google search I found the pyPdf library for python but my experiments with it failed. When I changed the cropBox and trimBox attributes on a page object the results were not what I had expected and appeared to be quite random.  Has anyone had any experience with this? Code examples would be well appreciated, preferably in python.


I'm making a very simple "guessing game" in Java. At the end of my game, I ask the user if he/she wants to play my game again as follows:       System.out.println("Would you like to play again? (Type 'yes' or 'no' into the field)");      Scanner scanner2 = new Scanner(System.in);      String again = scanner2.nextLine();       if (again=="yes") {         local = false;         loopAgain = true;      }       else if (again=="no") {         loopAgain = false;         local = false;      }       else {         System.out.println("Invalid input. Please type 'yes' or 'no' into the field.");         local = true; }   Theoretically, if I type "yes" into the console, the if statement should execute, setting the variable loopAgain to true which activates a while statement earlier in my code. The other variable local also references an earlier while statement.  However, when I do type "yes" (or "no" for that matter) into the console I receive the invalid input message. I know that the variable again is a string, as is the "yes" that I'm implying it should be equal to, so I'm quite confused as to why the first if statement is not executing as it should. This is likely something very simple, but this is my first time ever programming in Java, so I apologize if I missed something really obvious!!  Any help would be greatly appreciated.

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


I am trying to connect to internet via a server in local network. I don't have permissions to change server configuration.  I want to do a ssh tunnel to that server and via that using socks proxy, I want to use internet.  When I try using:  ssh -D 2222 user@server   and setting socks proxy accordingly in firefox, and opening google.com in firefox shows:     channel 3: open failed: administratively prohibited: open failed   several times for each request.  I googled it, tried many solutions, but I am not able to get it working. It may have happened that because of being new, I have not applied the solution properly.  I can ssh into the server easily and everything works fine.    I have seen other questions that this question is possible duplicate of. I am not able to resolve my problem from the answers to those questions  Some additional questions,  The port 2222 is on my localhost. I don't need permission on server to open the port 2222. It creates tunnel via ssh (port 22). Is my understanding wrong?  If not, why would I need access to server admin?

When I open this ssh tunnel:  ssh -nXNT -p 22 localhost -L 0.0.0.0:8984:remote:8983   I get this error when trying to access the HTTP server running on localhost:8984:  channel 1: open failed: administratively prohibited: open failed   What does this error mean, and on which machine can you fix the problem?


A sequence is given by $a_{n+1}=\dfrac{1}{2}\left(a_n + \dfrac{5}{a_n}\right)$ for each integer $n \geq 0$.  Does the limit of $a_n$ as $n$ goes to infinity equal $\sqrt{5}$ for $a_0 =2$?  What if $a_0=3$?

a) Let $a>0$ and the sequence $x_n$ fulfills $x_1>0$ and $x_{n+1}=\frac{1}{2}(x_n + \frac{a}{x_n})$ for $n \in \mathbb N$. Show that $x_n \rightarrow \sqrt a$ when $n\rightarrow \infty$. I have done it in two ways, but I guess I'm not allowed to use the first one and the second one is incomplete. Can someone please help me?  We already know $x_n \rightarrow \sqrt a$, so we do another step of the iteration and see that $x_{n+1} = \sqrt a$.  Using limit, $x_n \rightarrow x, x_{n+1} \rightarrow x$ (this is the part I think it's incomplete, don't I have to show $x_{n+1} \rightarrow x$, how?), we have that   $$x = \frac x 2 (1 + \frac a {x^2}) \Rightarrow 1 = a/x^2 \Rightarrow x = \sqrt a$$ b) Let the sequence $x_n$ be defined as $x_{n+1}= 1 + \frac 1 {x_n} (n \in \mathbb N), x_1=1$. Show that it converges and calculate its limit. "Tip: Show that sequences $x_{2n}$ and $x_{2n+1}$ monotone convergent to the limit." I didn't understand the tip, how can this help me? Does it make a difference if the number is odd or even? Thanks in advance!


Here I want to merge unallocated space to ext4 partition. But during running in Ubuntu it is not allowed. Am I right? It has key picture. I must do that Ubuntu DVD booting from it and selecting try Ubuntu there with GParted, I must merge this unallocated part by right clicking on ext4 partition and then selecting shrink. Am I right?   Then for swap area I want to take 5GB from extended partition (which is now called D on Windows). Can I format this partition in Windows or should I use GParted? But in GParted it has key picture. Or in the same way should I do this during trying Ubuntu to merge unallocated space to ext4? Thank you for your answers.

Previously, I have installed Windows 7 on my 320 GB laptop with three partitions 173, 84 and 63 GB each. The 63 GB partition was where the Windows was installed. The rest were for file containers.  Now I changed my OS to Ubuntu 12.04 LTS. I installed Ubuntu by replacing the entire Windows 7 on the 63 GB partition. The rest of the partitions remain as an NTFS Windows partition and I can still access them both (the 173 and 84 GB partitions).  Now I want to change the two partitions of Windows into an Ubuntu format partitions plus most importantly, I want to extend the 63 GB partition to more than a 100 GB because at the moment I am running out of disk space. Whenever I try to install any application, especially using wine, it always complains for a shortage of disk space.  How do I do the extending activity before I entirely format my laptop again and lose all the important files on my partitions?


My son received an asus tablet for his birthday last year and has now told me the screen does not work completely (some areas are dead to the touch). I have told him we will send it for repair but he is worried that when it comes back they will have reset it and he will have lost all his apps, videos, photos, programs etc. Can anyone tell me how I back it up so that when it comes back I can just put all the information back on so that it is exactly as it is now. Please can any answers be as easy to understand as possible

I know I'm asking for the close-to-impossible -- as a real full-backup certainly requires root permissions. But still there are many folks around not wanting to root their devices -- afraid of voiding their warranties or bricking their devices, or just not having their devices supported by any rooting method.  I also know there were a lot of questions asked already on this topic, and I checked all of them having the backup tag -- none covers the entire topic, all just have pieces, and especially people new to Android (but other non-power-users as well) would have a hard time figuring out the best way.  So I want a detailed canonical answer to the question:  Not involving root-solutions, how to achieve a backup as close as possible to a full backup?  Please do not give simple one-liner answers like "Use app xyz [full-stop]." If mentioning an app (and I doubt a single app would be the answer here), include what parts are covered by it -- as well as ideas on how to fill the gaps it leaves. (And to make it absolutely clear: I know the first thing coming to mind is Titanium Backup -- I use it myself, but this does not apply here: This question is strictly about methods for non-rooted devices!) Moreover, the answer should be as generic as possible in terms of applying to a wide range of devices (i.e. it should not be restricted to one device or manufacturer).  I already mentioned having investigated all questions here tagged backup. These will certainly be helpful providing details for answers here, so I will list up the topmost ones concerning my question:            All these provide some details for my question (so feel free to get inspired by them) -- but I feel there are still details missing. Also it would be helpful to have a summary -- say, an answer including the full description of "the maximum possible".  A last criterium: While I'd consider cloud-based solutions legit, I'd favour local solutions. If you can provide both: all the better. But some people value privacy quite high (I'm one of them), and thus would not trust their data to some cloud service.    Thanks to Ryan, we now have a solution for a really complete backup of all apps and their data -- which I didn't dare to hope for! The only disadvantage: His solution only works for less than 10% of all Android users; namely those whose devices are running at least with Android 4.x.  So again, I ask the close-to-impossible: Any solutions applicable at least on Gingerbread (2.3.x) or, better, even Froyo (2.2.x) -- so they cover the majority of current devices? These solutions may involve multiple tools (try to keep it as simple as possible though; think of your mother to follow your instructions ;)  And keep in mind: NO ROOT!    To further motivate high-quality answers (and hopefully avoid low-quality ones), I will be a harsh one here: As I rarely do, I will down-vote answers not fitting the mentioned criteria on one end -- but on the other end, I will setup a bounty for the best answer (which cannot be done immediately, but earliest after 2 days).


I've observed that the spring constant of a spring with a smaller radius is higher than that of a spring with a larger even though they are made of the same material , their thickness and all other factors are same but the radius. Does this mean that the spring constant of a spring made of a given substance is not its property and is there a relation that governs such behaviour of a spring?

For certain springs we have been taught that Hookes law, $F=-kx$ works. For such springs, what factors determine k. For instance, k is proportional to length. Can k be expressed in terms of dimensions, mass and other fundemental quantities, or is k a fundemental property of the spring itself?


My $6$ friends and I tried buying tickets to a popular event. Everyone who wanted a ticket got a random number and if your number is less than or equal the number of tickets available, you can buy a ticket.  None of us $7$ was selected to buy tickets. How can I estimate the probability of successfully buying a ticket? Using maximum likelihood on a binomial model the answer is $0$, but I know tickets were sold, so it can't be $0$.

I was wondering if there is a way to tell the probability of something failing (a product) if we have 100,000 products in the field for 1 year and with no failures? What is the probability that one of the next 10,000 products sold fail?


The reviewer has the copy for manuscript and they are generally top notch in the field in which the paper was written. What prevents the reviewer from exploiting his/her power? As in, rejecting it and publishing a slightly modified version himself?   I am new to this, so forgive me it is a foolish question.

Suppose some author provides his original research article to a journal for publication. In this way, he is disclosing or revealing his confidential research work to that journal. Now, consider the case that his article gets rejected. So, is it not possible that whoever reviews that article can publish that kind of work and say that it's theirs? Since the original author's work has not been published and he is disclosing his confidential work to somebody, how could the author get assurance that if his article is rejected, his work will not be leaked by the journal staff in any form? What happens if this kind of thing happens?


Take the proof that $\sqrt{5}$ is irrational. Starting with the assumption that $\sqrt{5}=\frac{p}{q}$ and that p and q are coprime, we get that both p and q are both divisible by 5 and hence are not coprime and hence a contradiction has occurred. But can the same not be done for say $\sqrt{4}=\frac{p}{q}$ ? Following the same procedure we get that both p and q are divisible by 4 and are not coprime. Obviously $\sqrt{4}=\frac{2}{1}$ but the above procedure doesn't tell us that. It leads us to ''both p and q are divisible by 4''. Where am I going wrong in my argument ?

The most common way to prove the irrationality of a number is to do it by  contradiction. However, in this proof the contradiction arises from having two numbers, say p\q that are assumed to not have any common factors but are later proved to share the number under the radical as a factor. But for instance if the question so arises:  Is √4 rational or not? Answer with a proof.  At first glance, it is obviously rational, but assuming I do not know that √4 can be simplified to 2, what would stop me from arriving at irrationality as my conclusion?   This question seems quite trivial and probably stupid. Is this meant to be by definition or am I missing something fundamental to the aforementioned fallacy?


My son and I are playing Borderlands 2 in co op play. Is there a way that he or I can play a separate game on our own that will not affect our on line game? The other day he played for a while on his own and the next time we entered the game together it moved me further ahead in the game than I originally was.

Can we have multiple save files in this game? I mean, can I start a new game while keeping my last character's save?  Or is it a game with only 1 save file and you have to live with it?


I am new to running a linux server and wanted to know the difference between the total memory shown with the top command (which appears to be 78GB)  and the free command which shows that I have 743GB of memory  Thank you in advance!

I use free to get the amount of free space on some of my servers. Its output is something like:  $ free -m              total       used       free     shared    buffers     cached Mem:           374        366          8          0         58         98 -/+ buffers/cache:        209        165 Swap:         1906        120       1785   How much free space do I really have?


I have a tileset as seen on the right and they make the images seen on the left:   In game I have placed the full grass and full stone tiles for each chunk (infinitely generated) using perlin noise as seen in the image below:  I am trying to find a way to determine what corner tiles to use and then place them.  As you can see there is so many possibilities that I don't know how to do it.  Using Lua with love2d engine by the way.  This question is different.  Everything I read about bitmasking with corners says that you need at least 48 tiles or more in a set to do corners.  I am wondering how and if it is possible to use the tile set at the right which doesn't need this many tiles to make any possible shape.  It only uses 14 original plus 2 existing tiles.  Here is a image of what tiles are used in bitmasking.

I am working on a tiled map editor, and I need to choose tiles automatically, based on the adjacent tiles. For example, when placing a road tile, next to another road tile, the two need to be oriented so that they form a continuous road. If there are other roads around them, we may need to use corner or intersection tiles.  Can anyone recommend some algorithms for doing this? The game uses an 8-directional square tiled map.


The question about the correct use of there is vs there are pops up quite often.  However I couldn't find any reference to a case similar to the one below. My wife is writing a crochet pattern with the following sentence:  Count the stitches all around - make sure there is an odd number of stitches.  Word's grammar correction tool suggests: make sure there are an odd number of stitches.  I myself find the "there are" version more pleasing to the ear. However I think my wife is correct in stating that the subject should be considered to be odd number of stitches and not just stitches.  Which is correct?

Formally, is it correct to write:     A number of questions has been asked here.   or:     A number of questions have been asked here.   As a non-native speaker of English, I would prefer the former: the subject seems to be "number", therefore the verb ought to be singular, I'd say. However, the latter seems more common, and therefore I believe that my gut feeling is just plain wrong — but I would really like to have a definite answer.  Moreover, is it the same for "a myriad of", "a plethora of", and so on?


“The U.S. is too immature a society to be allowed to play with guns. It has never shed its Wild West mythology.”   Why is not "a" put in front of "too immature"?What is the explanation for this?  I would write this sentence as "The U.S. is a too immature society ...."

Is there any alternative to this construction?      It was too stupid a question.    I mean, can we somehow put the 'a' in a different position and is it used in English (maybe informal) or the version I've given is the only possible?  Also, I feel as if something's wrong in my previous sentence, it would be very nice if anybody corrected it.


I've been trying to solve this limit without application of L'Hospital's rule for some time now, but with no success, tried a couple of approaches but all end up in dead end.   $$\lim_{x\to0} \frac{\ln(e+x)-e^x}{\cos^2x-e^x}$$  any kind of hint would be appreciated.

Without using L'Hopital's rule find: $$\lim_{x\rightarrow 0}{\frac{\ln{(e+x)}-e^x}{\cos^2{x} -e^x}}$$ I found the first derivative because I planned to use Taylor series:  \begin{align} \frac{d}{dx}{\left(\frac{\ln{(e+x)}-e^x}{\cos^2{x} -e^x}\right)} &=\frac{\left(\frac{1}{x+e}-e^x\right)\left(\cos^2{x} -e^x\right)-\left(\ln(x+e)-e^x\right)\left(\sin{2x}-e^x\right)} {(\cos^2{x} -e^x)^2}\\ &=\frac{\frac{1}{x+e}-e^x}{\cos^2{x}-e^x}-\frac{\left(\ln(x+e)-e^x\right)\left(\sin{2x}-e^x\right)}{(\cos^2{x} -e^x)^2} \end{align}  However, it seems I haven't gone so far. Should I start from the beginning and try a different method?  Source in Croatian: 2.kolokvij, matematička analiza


I'm filling out a form but 1 part takes a longer time, and it messes up the whole thing. I'm using splinter in python 2.7 on mac. I need help and any help would be helpful.

I would like to know how to put a time delay in a Python script.


An apple and the Moon are both attracted to Earth. So why does the Moon have circular motion while an apple has one-dimensional motion?

Why doesn't the Moon fall onto the Earth? For that matter, why doesn't anything rotating a larger body ever fall onto the larger body?


Let it be my main phase: I got  on the field and one  in my graveyard and another one in my hand.  Could I then play forever? Because I would never run out of cards, so these  would never apply, right?   MTG Arena: If I continue to do this combo over and over again, would at some point my timer start to run out?

What happens in a game of magic if neither player can win or lose?  Examples:   Both players have empty libraries and control  on an otherwise empty board. One player controls  and  and neither player has a way to remove either from the battlefield. Both players have empty libraries and control some lands and  on an otherwise empty board. Both players have some lands and a copy of , but no other way to win. One player has an empty library but is using  to prevent themselves from being milled.


I just need a simple way to calculate inventory. Say we have 100 items to sell, I need it to count down each time an order is submitted.

I want to limit inventory quantities on a sales form, so that it can start at say 100 and count backwards as applicants submit orders and then shut down that particular option when it reaches 0.    Is this possible with Cognito?


We are given a sequence : $[1,2,...N]$. Let's consider all the permutations of the above sequence.   Say, $a[1]=1, a[2]=2,\dots,a[N]=N$.  Now, a good permutation is defined as the one in which there is at least one pair of numbers such that $a[i]+1=a[i+1]$ (where $1\leq i \leq N-1$). How to count the number of good permutations?   Example: For $n=3$, the good permutations are $\{1,2,3\}$, $\{2,3,1\}$ and $\{3,1,2\}$.

I've been grading exams for most of the day. Once I finished grading, I started entering the grades into my gradebook -- one by one, from top to bottom on the stack. About halfway through, I entered one students grade and the next student on the stack was also the next person alphabetically in the gradebook. What is the probability of this happening with $n$ students, all of whom have unique names?  Equivalent question:  For a random permutation $\left(a_1,a_2,\ldots,a_n\right)$ of the list $\left(1,2,\ldots,n\right)$, what is the probability that there exists at least one entry $k$ of the permutation that is followed immediately by $k+1$ (that is, $k = a_i$ and $k+1 = a_{i+1}$ for some $i \in \left\{1,2,\ldots,n\right\}$) ?  For small $n$, it's not hard to exhaustively calculate the probability. But my combinatorics skills are rusty, and I don't think I can easily calculate this for my 30 students.


How can I easily implement "formData" in this ajax call?  HTML:  <form id="insertDocument" action="#" enctype="multipart/form-data">     <input type="file" id="file" name="file" />     <select name="type_d" id="type_d">         <option value="1">something</option>         <option value="2">something</option>         <option value="3">something</option>         <option value="3">something</option>         <option value="3">something</option>     </select>     <input type="text" name="description_d">     <input type="date" name="date_d">     <input type="date" name="valid_d">     <input type="submit" value="Upload document" id="insert_d"> </form>   jQuery:  $("#insert_d").click(function() {     event.preventDefault();     var data = $("#insertDocument").serialize();     $.ajax({         type: 'POST',         url: 'insertDocument.php',         data: data,         success: function(html){             console.log(html);         }     }); });   My problem is, that I need to post all the data - file and other inputs. Do I have to combine formData with serialize?

I would like to upload a file asynchronously with jQuery.     $(document).ready(function () {     $("#uploadbutton").click(function () {         var filename = $("#file").val();          $.ajax({             type: "POST",             url: "addFile.do",             enctype: 'multipart/form-data',             data: {                 file: filename             },             success: function () {                 alert("Data Uploaded: ");             }         });     }); });  File <input type="file" id="file" name="file" size="10"/> <input id="uploadbutton" type="button" value="Upload"/>     Instead of the file being uploaded, I am only getting the filename. What can I do to fix this problem?


As I'm planning to buy an SSD and replace my old mechanical hard drive, I've heard rumors that having swap partition can decrease the life of SSD. So is this true? Or can I still have a swap partition on my SSD?

I have a Samsung 960 Pro SSD with Ubuntu 18.04  is it safe to put the swap file on there or would it hurt it in the long run,  I heard some people saying that new SSDs don't suffer from that issue anymore, is this true?


I want to prove that if $f$ is continuous at $c$ and $f(c)<y$, then $\exists \delta >0$ such that $\forall x \in Dom(f)$ and $x \in (c- \delta , c + \delta)$ implies $f(x) < y$.   I know that $f$ is continuous at $c$ and $f(c) < y$. So I should choose a $\delta$. But I am not sure how to progress after that.

Pretty much the problem asks if a function is continuous at the point $c$ and $f(c) > 0$ then there exists a $d > 0$ such that $\forall x$, $f(x) > 0$ with $|x-c| < d$.   I can understand what the problem means. That if a function is positive at a point then there is another point that's really close that'll also be positive. I can not prove this in a formal way though. I've tried using the intermediate value theorem and I do not know hot to implement it. Any ideas?


I would like to place some (PHP)functions in a helper files, which requires across modules and themes.  Do I have to create a new module or I can place a simple helper file with list of common functions, what is the best practice for these kind of functions in drupal 8 ?

Let's say I use a  with a lot of code inside. To improve readability and reusability I'd like to use helper/private methods. However, a Drupal .module file is not a class.  The idea is to split big methods from this file into more readable and reusable smaller methods.  What is the correct way to call helper/private methods from a Drupal .module file?


I can easily prove the inverse, however I cannot prove this. We know that $\operatorname{ord}_{n}(a)\mid\phi(n)$, so I have been trying to prove that $x \equiv y \pmod{\phi(n)}$ and it follows that $x \equiv y \pmod{\operatorname{ord}_{n}(a)}$. I have also noted some relevant properties that might be of help: $$a^{\operatorname{ord}_{n}(a)}\equiv 1 \pmod n $$ $$\gcd(a,n)=1$$ $$\operatorname{ord}_{n}(a)\mid\phi(n)$$ $$a^{\phi(n)} \equiv 1\pmod n$$

I've read about Fermat's little theorem and generally how congruence works. But I can't figure out how to work out these two:   $13^{100} \bmod 7$ $7^{100} \bmod 13$   I've also heard of this formula:  $$a \equiv b\pmod n \Rightarrow a^k \equiv b^k \pmod n $$  But I don't see how exactly to use that here, because from $13^1 \bmod 7$ I get 6, and $13^2 \bmod 7$ is 1. I'm unclear as to which one to raise to the kth power here (I'm assuming k = 100?)  Any hints or pointers in the right direction would be great.


I just ran across a bug in chat.  If you are the room owner, you have the ability to pin/unpin messages.  However, recently I ran a test (in my own private chat-room, don't worry! :) ) to see how many messages I could pin and what happens if I ran over the limit.  However, I ran across a bug which we verified in another room.  When you remove the pin from the message, it remains starred, even if the pinner was the poster of the message.    A friend tried the same thing, but with a single message in a chatroom he owns, and it appears that it is a reproducable bug.  Would appreciate some help on it!

I was able to star my own message by pinning it and unpinning it.  Pinning a message adds a star, even to your own messages, but when the pin is removed, the star remains.


So I am trying to implement an object as a set in javascript, where there are no duplicate elements or specific order of elements in the collection. Here is my implementation with the regular for loop:  var Set = function(elements) {     for(i=0;i<elements.length;i++) {         this[elements[i]] = true;     } };   And this works as intended:     y = new Set([4, 5, 6, 3, 2]) => { '2': true, '3': true, '4': true, '5': true, '6': true }   However, if I used the for in loop, something really strange happens:  var Set = function(elements) {     for(var elem in elements) {         this[elem] = true;     } };     t = new Set([9, 8, 7]) => { '0': true, '1': true, '2': true }   Why does the for in loop cause the elements 0, 1, and 2 to be in my set, and not the numbers I had in my array originally?

I've been told not to use for...in with arrays in JavaScript. Why not?


x+x+x+x+x+...... Up to finite x times= x^2   Differentiating both sides  we get 1+1+1+1+1......=2x  What is wrong in this?? Attempt: I'm thinking that the above statement written is only for natural numbers..

Consider the following:   $1 = 1^2$ $2 + 2 = 2^2$ $3 + 3 + 3 = 3^2$   Therefore,   $\underbrace{x + x + x + \ldots + x}_{x \textrm{ times}}= x^2$   Take the derivative of lhs and rhs and we get:   $\underbrace{1 + 1 + 1 + \ldots + 1}_{x \textrm{ times}} = 2x$   Which simplifies to:   $x = 2x$   and hence    $1 = 2$.     Clearly something is wrong but I am unable pinpoint my mistake.


Ubunbtu 18.04 I started getting the notice that not all updates can be installed - which led me to the following post:  I ran the two commands mentioned - sudo apt-get update && sudo apt-get upgrade Then re-booted, and re-ran software updater, and got the same notice I ran the 2 commands again, and nothing was installed, but I still get the same notice when using software updater.  If I click on continue, I see this:  Can anyone shed any light on this?  How can I prevent seeing the partial upgrade notice?

Sometimes when I am running a development version of Ubuntu, the Software Updater will tell me that a partial upgrade is needed when I check for updates.  What is a partial upgrade, and why are they necessary? Sometimes users run into problems when doing them, so when should I run a partial upgrade, if ever?


I would like to prove this by induction.  How can I approach this, or maybe give me an answer and show me how you did this in detail? I'm struggling with using induction and would like to expand my knowledge. Would really appreciate your help, Thanks

Given $$1\cdot 2^1 + 2\cdot 2^2 + 3\cdot 2^3 + 4\cdot 2^4 + \cdots + d \cdot 2^d = \sum_{r=1}^d r \cdot 2^r,$$ how can we infer to the following solution? $$2 (d-1) \cdot 2^d + 2. $$   Thank you


I bought a TV (Panasonic 55 inch NON-Smart TV) like 3 years back and using it. The airline says, extra baggage will be $200 which I can do, but I'm not sure how much will be the custom duty at Chennai airport (or India in general). If anyone took similar TV before to India/Chennai, let me know please. I have the receipt of the TV purchase with me.

I am planning to travel to India (COK airport, Kerala) from United States. I want to take my laptop as well as my tablet (iPad). Am I allowed to take both in my backpack with my documents related my work. I think I am allowed to take only one computer as per the rule. Will the customs consider my iPad as a computer?  What all I can take?   One of my friends took 2 laptops (1 work and 1 personal) and had trouble at the airport.  Also I am planning to take some wristwatches (7 of them, each avg price is 45 $). I read in a website that I can take stuff up to max 35000 INR. Is that true? In that case, how will I manage my stuff?


Let $ \vec u = \begin{bmatrix} u_1\\ u_2 \end{bmatrix}$ and $\vec v =  \begin{bmatrix} v_1\\ v_2  \end{bmatrix}$  Doesn't the number of columns in u have to equal number rows in v?  Why are they multiplied directly across?  EDIT: I feel that my question is unique to the one proposed () b/c it succinctly addresses confusion arising from multiplication of two column-vectors, and the definition of $\vec u \cdot \vec v$.

I understand how to calculate the dot product of the vectors. But I don't actually understand what a dot product is, and why it's needed.  Could you answer these questions?


, but I didn't have evidence of it, so it was dismissed. I'm not crazy though, and here's proof!:    When clicking on a HNQ in the side-bar, the link appears to open within the ad itself (an iframe? I'm not a web-dev so I'm not sure the terminology).  This happens consistently. I can't reproduce it often because the ads don't appear very often. Every time I try to reproduce it though, I'm able.  This was done on Edge 44.18362.329.0, but as the link above shows, a year ago I did it in Chrome.

Today I came across an ad on this question on SO:  (I don't expect it to stay very long).   There was a community promotion ad on the right hand side of the site, I think for one of our English sites. It had a sentence that I only partially remember:     Idiom ... poor or even poorer   I found it interesting, so I clicked that ad. Which caused a new instance of SO to open within the ad space. Unfortunately I failed to take a screenshot. I've been refreshing the page like crazy, but can't get the ad to appear again.  Edit: I managed to get a new community add, for the photography site, and captured a screenshot:   Edit2: This bug still persists, I saw it today with an OOP add from CodeReview, and an area 51 add.


The problem:  There are n different kinds of coupons, and we need to get every kind of coupon at least once to win. Each time we get new coupons we get them in a batch of k coupons where k ≤ n (the same coupon can appear multiple times in the batch of k coupons).  Let Xk,n be a random variable that denotes the number of batches we need to buy to collect all the n different coupons.  I already know and understand how to calculate the expected value when k=1 (that is the classic coupon collector problem), but have difficulty calculating E[Xk,n] for k > 1.  If it helps, I've also made some simulations and estimations, and came up with this table:

I am trying to solve a variation on the .  In this scenario, someone is selecting coupons at random with replacement from n different possible coupons. However, the person is not selecting coupons one at a time, but instead, in batches.  Here's an example problem formulation: There are 100 distinct coupons. A person makes selections in 10-coupon batches at random (each coupon with replacement). What is the expected number of batches necessary to have selected 80 unique coupons?  I have been able to determine the expected number of selections necessary to have selected k unique coupons when selecting one at a time (much like Henry's ), but I'm a bit stumped as to how to go about solving it with this particular wrinkle.  Any tips/guidance would be greatly appreciated.


I'm using a continous integration system (CruiseControl.NET) as a service on our Windows 2008 64-bit server.  Now I would like to run Delphi 2006 from CruiseControl.NET (which runs as a service).  The point where I'm stuck is that Delphi 2006 requires a folder with licensing information in the users home folder. It won't run if it can't find the licensing information.  Where is that folder for the LOCAL SYSTEM account? I've looked in C:\Users but no luck.  I could also run the service using the LOCAL SERVICE account but there is no folder for that account either under C:\Users\.

I'm using a service which stores data on disk. The service is running as "local system account".  Where is the stored data for that system user?  I'm thinking about C:\Documents and Settings\Default User but I'm not sure about that.  Can someone confirm that?


I have two different sets of  commands working that I would like to try to combine.  The first command is a basic "concat" command:  ffmpeg -i "concat:file01.mpg|file02.mpg|file03.mpg" -c copy -target pal-dvd newfile.mpg   The second adds a watermark:  ffmpeg -i newfile.mpg -i full_page_watermark.png -filter_complex "overlay=0:0" -target pal-dvd newfilewatermark.mpg   Question:  How would I combine these two commands? Or is it necessary to first create the intermediate file as I am presently doing?

I want to combine two ffmpeg commands to a single command. I am using ready made ffmpeg binary in my Android application. I want to concat .ts files and overlay an image.  I am using following commands:   To concat .ts files:  String[] ffmpegcommand = {"ffmpeg", "-i","concat:"+input_file_path+"|"+input_file_path1, "-c", "copy", "-bsf:a", "aac_adtstoasc", output_file_path};  Apply image overlay effect:  String[] ffmpegcommand = {"ffmpeg","-y" ,"-i", input_file_path,"-strict","experimental", "-vf","movie="+AppStaticData.BASE_FOLDER_PATH + File.separator + "watermarklogo.png"+" [watermark]; [in][watermark] overlay=main_w-overlay_w-10:10 [out]", AppStaticData.BASE_FOLDER_PATH+"/" + output_file_path};


Let S$^2$ := $\lbrace$ x $\in$ $\mathbb{R}$$^3$ : $\Vert x\Vert$$_2$ $\rbrace$ $\subset$ ($\mathbb{R}$$^3$, $\Vert .\Vert$$_2$) and T: S$^2$ $\to$ ($\mathbb{R}$, $\vert x\vert$ ) a continuous function.  a) Is there a point x$_0$ $\in$ S$^2$ such that T(x$_0$) = T(-x$_0$) ?  b) Is there a value T $\in$ (Tmax,Tmin), which exactly one x $\in$ S$^2$ takes, with Tmax = sup $\lbrace$ T(x) : x $\in$ S$^2$ $\rbrace$ and Tmin = inf $\lbrace$ T(x) : x $\in$ S$^2$ $\rbrace$ ?  I think I have a example of a function in a) : Let T(x) = cos (x$_1$) with x = (x$_1$, x$_2$, x$_3$)$^T$, so take for example x$_0$=(1,0,0)$^T$, so is T(x$_0$)=T(-x$_0$), however I don't know how to start b)

Can you help me with this?     Let $S^2 := \{x\in \mathbb R^3:||x||_2 = 1\} \subset (\mathbb R^3, ||\cdot||_2)$  and $T:S^2 \to (\mathbb R, |\cdot|)$ be a continuous map.   a) Why does T assume its maximum ($T_{max}$) and its minimum ($T_{min}$)?   b) Is there a point $x_0 \in S^2$ with $T(x_0) = T(-x_0)$?   c) Is there a value $T\in]T_{min},T_{max}[$ that is assumed at only one $x\in S^2$?     a) is easy, it is compact since it's closed and bounded (Heine-Borel).  For b) I know it can't be injective since it maps from a higher to a lower dimension, but I don't know if I can use that to show what I need.  For c) I assume I can use non-injectivity again, but don't know either how. Any hints?


Each of my projects is a directory in which I have the following folders:  Data/.. (contains .shp files, tables, and rasters in various formats)  Maps/.. (contains .mxd files that depend on the files in Data/)  I reuse some feature classes extensively between projects. Most of them I would probably never update, so I keep copies of them in each projects Data/ folder. My supervisors/colleagues depend on this data organization as well, so that they don't have to dig around to find the supporting shapefiles for a given project.  This system has worked decently for our purposes, but it has problems. Some files are large, yet need to be available in multiple Data/ folders. This is an inefficient use of space. In addition, on occasion changes have to be made to commonly used files that we wish to persist for all versions. This results in many headaches and a lot of extra work for me.  What if instead of maintaining separate versions of each of these large datasets between each project we had a "file shortcut" like what people frequently put on their Desktops, but as a sort of proxy or pointer to the actual shapefile that would be stored in a common File Geodatabase.  Does such a "shortcut" method exist for managing various geospatial data formats, especially shapefiles?

Back in the days when I was in the university I had a "Organization and tidiness" problem – I was unorganized and kept my layers in different folders without distinct names and hence had multiple copies of each layer.   Ever since I  started working, I've improved a lot – I keep special folders with special subfolders. I name my layers according to  a system which lets me be a bit more neat, but as I still have to manage multiple copies of layers (As Autocad and ArcGIS have their differences when dealing with non-Latin languages, I have to keep a copy adjusted for each program), I'd like to hear from your experiences and maybe learn a few tips from you:   How do you organize your layers? How do name them? By name, date, contents, customer?   How do you organize or deal with multiple copies (more acute: how do you update several copies at once)?   Note: I'm talking from the analyst/DBA POV and not from a web-developer's/web-manager's POV (I'm talking about organizing the layers for myself and maybe two more GIS workers, not more).


I need to converte NULL values to 0 values with the overall goal of sum up two columns in attribute table in QGIS. Since one of these colums has NULL values, the new column with the sum also appears with NULL value (instead of preserving numeric value of other column).  I have tried Selecting column by all NULL value and putting 0 in Expression Field but that does not work.   Any ideas on how to do it?

In QGIS 1.8 I have a new column in my attribute table with a lot of NULL values and I want to replace all them to zeros. How can I do that in field calculator?


What is the common sense for the time to accept a user answer? For example, I usually think that I need to wait, for example, 1 week or more, because some questions have more than one answer and I like to hear different answers than accept the first one that appears. I want to read more answers about this subject. Another point I want to discuss: is there a option where I can pass the decision for the community chooses what is the best answer in my questions? Thank you!

What does it mean to accept an answer? How do I accept an answer, and what are the rules? Can I accept my own self-answer? What are the reputation benefits? Which answer should I accept? Should I upvote the accepted answer? What should I do if none of the answers are suitable?      For more information, see "" in the .


I do not want to install a few jars into a Maven repository (both local/remote). In particular I have a few jar files located in   c:\work\projects\myapp\src\main\webapp\WEB-INF\lib\test.jar  c:\work\projects\myapp\src\main\webapp\WEB-INF\lib\test2.jar   How to include them into my project when open/edit with NetBeans?

Maven 2 is driving me crazy during the experimentation / quick and dirty mock-up phase of development. I have a pom.xml file that defines the dependencies for the web-app framework I want to use, and I can quickly generate starter projects from that file. However, sometimes I want to link to a 3rd party library that doesn't already have a pom.xml file defined, so rather than create the pom.xml file for the 3rd party lib by hand and install it, and add the dependency to my pom.xml, I would just like to tell Maven: "In addition to my defined dependencies, include any jars that are in /lib too." It seems like this ought to be simple, but if it is, I am missing something. Any pointers on how to do this are greatly appreciated. Short of that, if there is a simple way to point maven to a /lib directory and easily create a pom.xml with all the enclosed jars mapped to a single dependency which I could then name / install and link to in one fell swoop would also suffice.


In bash, I use arguments that look like  paste <(cat file1 | sort) <(cat file2 | sort)   or  comm <(cat file1 | sort) <(cat file2 | sort)   When I check man comm or man paste, the documentation says the args are indeed FILES.  Question:     Are intermediate temporary files get created (on TEMP filesystem or elsewhere on slower disk) for <(cat file1 | sort) and <(cat file2 | sort)?  What is the name for this <( ) magic? (to lookup its documentation) Is it specific to bash or does it work across other shells?

I am trying to understand named pipes in the context of this particular example.  I type <(ls -l) in my terminal and get the output as, bash: /dev/fd/63: Permission denied.  If I type cat <(ls -l), I could see the directory contents. If I replace the cat with echo, I think I get the terminal name (or is it?).  echo <(ls -l) gives the output as /dev/fd/63.  Also, this example output is unclear to me.  ls -l <(echo "Whatever") lr-x------ 1 root root 64 Sep 17 13:18 /dev/fd/63 -> pipe:[48078752]   However, if I give,ls -l <() it lists me the directory contents.   What is happening in case of the named pipe?


I'm very much a rookie with Linux and recently installed Ubuntu 12.04.  Now I'm trying to stall a wireless adapter, RT5370, but the instructions are completely over my head (plus certain steps like copying a file to etc/Wireless aren't working because I get a permission denied error).  Is there a simple step-by-step guide on how to install a wireless adapter???

Just bought a new TP-LINK tl-wn727n usb thumb drive.  I'm running Ubuntu 12.04 32-bit. When I plug the stick in, nothing happens.  This may be normal for Linux veterans but as a new Linux user coming from Windows it seems weird.   I used the lsusb command and the device appears in the terminal as:  Bus 002 Device 007: ID 148f:5370 Ralink Technology, Corp. RT5370 Wireless Adapter  It is not showing up in the network connections list and I have no idea where to go from here.


A metal sphere of radius $R$ carries a total charge $Q$. What is the force of repulsion between the northern hemisphere and southern hemisphere?    In this problem you consider the force per unit area on the surface of the northern hemisphere and then add it up basically: You get the average electric field as$$ \frac{1}{2}(E_{\text{outside}} + E_{\text{inside}})  ~=~ {E_{\text{average}}} ~=~ \frac{1}{2}\frac{1}{4 \pi \epsilon_0}\frac{Q}{R^2}\hat{r} \,,$$because of the symmetry the horizontal components cancel for the force per unit area you get $f_{z} = {\sigma \left(E_{\text{average}}\right)}_{z}$ where $\sigma = \frac{Q}{4 \pi R^2}$. Then the total force on the northern hemisphere is$$ F_{z} ~=~ \int f_{z} \, \mathrm{d}a ~=~ \int_{0}^{2 \pi} \int_{0}^{\frac{\pi}{2}} \left(\frac{Q}{4 \pi R^2}\right)\frac{1}{2}\left(\frac{Q}{4 \pi \epsilon_0 R^2}\right) \cos{\theta} \, R^2 \sin{\theta} \, \mathrm{d} \theta \, \mathrm{d} \phi ~=~ \frac{Q^2}{32 \pi R^2 \epsilon_0}. $$  Question:  Are the forces of repulsion on the northern hemisphere a result of only the charges from the southern hemisphere while there is symmetric cancellation from charges in the northern hemisphere, or is the force on each unit area in the northern hemisphere due to the whole sphere?  The way the question is worded seems to suggest that the answer is the first case, i.e. that the force on the northern hemisphere is due completely to the southern hemisphere.

This is Griffiths, Introduction to Electrodynamics, 2.43, if you have the book.      The problem states Find the net force that the southern hemisphere of a uniformly charged sphere exerts on the northern hemisphere. Express your answer in terms of the radius $R$ and the total charge $Q$. Note: I will say its uniform charge is $\rho$.   My attempt at a solution:   My idea is to find the field generated by the southern hemisphere in the northern hemisphere, and use the field to calculate the force, since the field is force per unit charge.   To do this I start by introducing a Gaussian shell with radius $r < R$ centered at the same spot as our sphere. Then in this sphere,   $$\int E\cdot\mathrm{d}a = \frac{1}{\epsilon_0}Q_{enc}$$  Now what is $Q_{enc}$? I feel like $Q_{enc} = \frac{2}{3}\pi r^3\rho$ , since we're just counting the charge from the lower half of the sphere (the part thats in the southern hemisphere of our original sphere). (Perhaps here is my error, should I count the charge from the entire sphere?, if so why?)   Using this we get $$\left|E\right|4\pi r^2 = \frac{2\pi r^3\rho}{3},$$ so $$E = \frac{r\rho}{6\epsilon_0}.$$ Using these I calculate the force per unit volume as $\rho E$ or $$\frac{\rho^2 r}{6\epsilon_0}$$  Then by symmetry, we know that any net force exerted on the top shell by the bottom must be in the $\hat{z}$ direction, so we get $$ F = \frac{\rho^2}{6\epsilon_0} \int^{2\pi}_0\int^{\frac{\pi}{2}}_0\int^R_0 r^3\sin(\theta)\cos(\theta) \mathrm{d}r\mathrm{d}\theta\mathrm{d}\phi$$  integrating we get $F = \frac{1}{4}\frac{R^4\rho^2\pi}{6\epsilon_0}$.   Now Griffiths requests us to put this in terms of the total charge, and to do so we write $\rho^2 = \frac{9Q^2}{16\pi^2R^6}$  Plugging this back into $F$ we get $$F = (\frac{1}{8\pi\epsilon_0})(\frac{3Q^2}{16R^2})$$  Now the problem is that this is off by a factor of $2$ ...   I tried looking back through and the only place I see where I could somehow gain a factor of $2$ is the spot I mentioned in the solution, where I could include the entire charge, however, I can't see why I should include the entire charge, so if that's the reason I would be very grateful if someone could explain to me why I need to include the entire charge.   If that is not the reason, and perhaps this attempt at a solution is just complete hogwash, I would appreciate if you could tell me how I should go about solving this problem instead. (but you don't need to completely solve it out for me.)


What is the X11 equivalent of GNU Screen for X11 applications? I know there is VNC, possibly RDP and other candidates, but last week when tuning up my VNC config I've stumbled upon a project, that was basically screen for X11 applications, i.e. you could start remote app wrapped in it, log out of the X11 session and later return to the application. Unluckily this wasn't a direct google hit and I cannot find it in the google history now. Any idea, what the name/url of the project might be ?

Under unix/linux, there is this extremely useful program screen: it's for bash, text-only, and I can detach a session, log out (the session is still running though), log in later (even from a different computer) and resume the session exactly as I left it.  My question is, is there an equivalent to screen for X?  So what I want to do is: work remotely with ssh -X in an X-session on a remote linux machine, log out, then later log in from a different computer again with ssh -X and then re-attach the X-session; practically resuming work from the moment when I logged out before. Is this possible?


I can't figure out how to prove this one. Help please how to prove $(A\setminus B)\setminus C ⊆ A\setminus(B\setminus C)$ in which prove system to choose?

If $A, B, C$ are sets prove that $(A\setminus B)\setminus C\subseteq A\setminus(B\setminus C)$. Find a description of when it is that we have equality, and give an example where the inclusion is strict.   I'm not sure how to do this one I know that to prove that two sets $X$ and $Y$ are equal, we need to show that if $x$ is any element of $X$, then $x\in Y$, and that if $x$ is any element of $Y$, then $x\in X$: the first of these means that $X\subseteq Y$ and the second that $Y\subseteq X$, so the two together establish that $X=Y$. I'm not sure how to use this for a question and how to finish it.