What is an example of a Lie algebra L and its non-semisimple representation? I need this for study so any help would be appreciated.

I am slightly confused over the semantics of the definition of complete reducibility of a representation of a Lie algebra. Here's what I understand it to mean:  First, A representation $\phi:g \rightarrow gl(V)$ of a Lie algebra $g$ is irreducible if the vector space $V$ has no invariant subspaces.  Where we say a subspace $W$ of $V$ is invariant if it is invariant under $\phi(x)$ for all $x$ in $g$.  Now, it is said that a representation is completely reducible if it decomposes into a direct sum of irreducible representations (Wikipedia).  I struggle to understand what the last sentence means. What I think it means is that $V$ decomposes into a direct sum of vector spaces $V_i$ which are all irreducible (IE have no invariant subspaces).  This makes sense to me, but I also am not quite sure that I understand why it's not trivial. Should it not be the case that for any representation we will always be able to decompose $V$ into a direct sum of subspaces which are irreducible? I mean, the answer is obviously not (unless $g$ is semisimple), but I'm struggling with an intuitive understanding of that. Any help is appreciated.


I am requested to create an Android app that have to connect to an external Bluetooth GPS and read the NMEA output and visualize the location on ad digital map. I am a new comer in this aspect. Grateful if anyone can suggest how can i connect the GPS and read the NMEA file? Please suggest any good reference materials / source code if available.  I am instructed to simply import the coordinates from the non-professional grade GPS receiver (i.e. GoPass GPT-810 Bluetooth GPS Trip Recorder), and visualize them on top of a geotiff. How can the android "locationlistener" get the coordinates from the GNSS receiver?

I'm looking to integrate a GNSS receiver with a Smartphone app. I've found only GNSS receivers that are meant to communicate only with their mobile interface, they don't provide any documentation for integrating smartphone apps in the workflow of using GNSS receivers.  Any ideas about communicating with existing GNSS receivers? If not, what are the available options ?


Let's say I have the following JS Object  data = {     name: "John",     dataOfBirth: "",     externalId: 2548,     email: "john@email.com",     mobile: "" }   I will receive an object like this with many more properties that can be either String, Integer or undefined. For me to update my database, I cannot override a valid information with an empty one.  I could try if (data.email === "") delete data.email with all of them, but that seems unpractical to maintain.  Is there any way I can scan all properties without having to name every single one of them and remove all empty/undefined ones?

How do I remove all attributes which are undefined or null in a JavaScript object?  (Question is similar to  for Arrays)


Good evening,  I'm writing my thesis in Latex, with which I already had the pleasure to work for some other projects, but I'm now facing a problem I don't know how to solve. I'll try to get to the point as straight as possible: let's say I have a chapter of simulation results, which includes a huge set of images. This chapter is subdivided itself in some sections, among which the images are distributed. Now, what I would like to have is a way to have all the images related to section A inseted before section B starts and so on. I don't mean I want to precisely insert them where I want (the most of them are set of subfigures, difficult to be fit anywhere), it would be enough to be able to tell the compiler to put them all before the next section starts.  Do someone of you have any suggestion on the matter ?   Thanks a lot in advance  Michele

Often floats may land quite a bit later in the document than the point they are created, sometimes after a section break.  Is there a way to force a new section to start on a new page, after any unplaced floats?


Blender resizes and moves my objects when I close the file, and I open it again. Also when I try it to render it, it gives a different picture than in the object mode. Why and how could I solve this problem?  For example  In Object mode:   Rendering:   It is doing it all the time.

I am new to blender, and I have just created a island using ANT landscapes, and I have build two boats for this.    Two boats on island  They are in this place when I am in object mode, but when I render it they appear here:    I check the position of where they end up, and it is both where they were imported and 0,0,0. Although, all the other objects I have imported have not changed position. Does anyone know about how to fix this or have experienced this problem?


I have designed a website a few years back, and it ranks pretty well, customer is happy, no problems there. I took one of the pages and replaced manually all the tables with <div>, used structured data and got the website to look exactly the same.  I would like to know what other steps should I take to improve or at least not hurt this page's rank, or if perhaps I should just not bother altogether.  What are best practices here?  By the way, the page is not live yet.

What are the best ways to improve a site's position in the Google search results?


I have tried to approach this problem in a variety of ways, like triyng to construct a solution, looking at telescoping series, geometrically... But I have been unable to solve it. I would appreciate any hint. Thanks.

I have a hard induction problem here that I feel completly lost on.  For every $n\ge3$ there is n different positive integer $a_1,...,a_n$ so that $\frac{1}{a_1}+\frac{1}{a_2}+...+\frac{1}{a_n}=1$.  There is only one possible solution for $n=3 $  $\frac{1}{2}+\frac{1}{3}+\frac{1}{6}=1$  for $n=4$ there is 2 possible solutions and they both start with $\frac{1}{2}$.  $\frac{1}{2}+\frac{1}{3}+\frac{1}{8}+\frac{1}{24}$ and $\frac{1}{2}+\frac{1}{4}+\frac{1}{5}+\frac{1}{20}$.  I think the first one is the one.  For $n=5$ there is alot of different possible solutions but it have to start with at least $\frac 13$  I think it have to start with $\frac 12+\frac13$ and then be some kind of sum answer for the last $\frac16$ based on $n$. But I don't know  I have tried finding a pattern but not getting anywhere anymore. Any tips on how to tackle a problem like this?


Whenever I use a pager like less or an editor like nano in the shell (my shell is GNU bash), I see a behaviour I cannot explain completely and which differs to the behaviour I can observe with other tools like cat or ls. I would like to ask how this behaviour comes about.  The —not easy to explain— behaviour is that normally all output to stdout/stderr ends up being recorded in the terminal-emulators backbuffer, so I can scroll back, while (not so normally to me) in the case of using less or nano, output is displayed by the terminal-emulator, yet upon exiting the programs, the content "magically disappears".  I would like to give those two examples:   seq 1 200 (produces 200 lines in the backbuffer) seq 1 200 | less (lets me page 200 lines, yet eventually "cleans up" and nothing is recorded in the backbuffer)   My suspicion is that some sort of escape codes are in play and I would appreciate someone pointing my to an explanation of this observed behavioural differences.  Since some comments and answers are phrased, as if it was my desire to change the behaviour, this "would be nice to know", but indeed the desired answer should be the description of the mechanism, not as much the ways to change it.

Today I was using glance tool in my office to monitor CPU utilization.When I run glance from terminal ,the command clears the screen and after all the work when I quit back to the terminal,the previous prompts are still there on my screen.I mean that I can see all the previous lines.My question is how is this effect of clearing screen achieved.If they had used command like clear,It should have cleared the whole screen,how did they manage to get back all the previous prompts ? I want to implement the same feature for some of my scripts.  Similarly when using vi command ,the screen is fully occupied and after exiting,we are able to view previous prompts as well.


Since quantum entangled particles can transfer the data of their spin properties faster than the speed of light and without any problem of weak signal, can we use quantum entanglement to transfer phone calls and internet connection? Why are we not building up a telecommunication structure based on this technology? What is stopping us? What are the practical difficulties in this process?

recently i was watching a  on quantum computing where the narrators describes that quantum entanglement information travels faster than light!  Is it really possible for anything to move faster than light? Or are the narrators just wrong?  Regards,


import java.io.*;  class Main0 {     public static void main(String args[])     {         String onoma, epitheto, key01;         short AriMit, EtosEis, AM, key02;         int i, pos;         Foititis pinakas[] = new Foititis(3);         for (i = 0; i < pinakas.length; i++)         {                    System.out.println("Ola ta stoixeia na einai taksinomimena symfwna me ton Arithmo Mitroou." + "\n" + "Dwste Onoma.");             do             {                 onoma = FUserInput.getString();                 if (onoma == "x")                     System.out.println("Mh egkyrh timh. Epanalagete");             } while (onoma == "x");              System.out.println("Dwste Epitheto.");             do             {                 epitheto = FUserInput.getString();                 if (epitheto == "x")                     System.out.println("Mh egkyrh timh. Epanalagete");             } while (epitheto == "x");              System.out.println("Dwste Arithmo Mitrwou.");             do             {                 AriMit = FUserInput.getshort();                 if (AriMit == -1)                     System.out.println("Mh egkyrh timh. Epanalagete");             } while (AriMit == -1);              System.out.println("Dwste Etos Eisagwghs.");             do             {                 EtosEis = FUserInput.getshort();                 if (EtosEis == -1)                     System.out.println("Mh egkyrh timh. Epanalagete");             } while (EtosEis == -1);              pinakas[i] = new Foititis(onoma, epitheto, AriMit, EtosEis);         }         pos = 1;         System.out.println(Foititis.toString(pos, pinakas));     } }  class Foititis       {     private String onoma, epitheto;     private short AriMit, EtosEis;      public Foititis (String on, String ep, short AM, short EE)     {         onoma = on;         epitheto = ep;         AriMit = AM;         EtosEis = EE;     }      public String getEpwnymo()      //alles klaseis     {         return epitheto;     }      public String toString(int j, Foititis b[])     {         String emf;         emf = b[j].onoma;     } }  class FUserInput          /*dedomenwn kateli3a na xrisimopoihsw thn "FUserInput" gia ola ta dedomena, anti na kanw "catch" to "exception" gia kathe scanner ksexwrista, kathws eixa skopo na xrisimopoihsw mono scanner)*/ {     static String getString()      {          String line;         InputStreamReader eisodosDouble = new InputStreamReader(System.in);         BufferedReader br = new BufferedReader(eisodosDouble);         try         {             line = br.readLine();             return line;         }         catch(Exception e)          {                return "x";         }     }      static short getshort()      {          String line;         InputStreamReader eisodosDouble = new InputStreamReader(System.in);         BufferedReader br = new BufferedReader(eisodosDouble);         try         {             line = br.readLine();             short i = Short.parseShort(line);             return i;         }         catch(Exception e)          {                return -1;         }     } }   This is not a duplicate of anything, I am not asking about my string equations but about the toString method that I want to use!!!!  So I have this code... all it does is to create an array of objects of type Foititis, named pinakas and having the four attributes. If you look at class named Foititis you will notice a toString method, all I want to do is to use the toString method to show something on the screen (at this example it is simplified to the onoma attribute of the array-object). Note that I also want to send the certain position of the array that I want to be seen(pos -> j), at this example the position is fixed (set to 1) but in the actual code it won't.  I try to compile it and I get these 2 errors, the second one is probably justified because I haven't written the code in the proper way, but what about the first? I have done the same thing again and I had no problem (at creating an array of objects).

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?


Thank you for clicking. Trying to print a numbered list. Have a for loop for printing list. Ie.  print("COMPOUND:EMBED=okay but not right") # for num in range(1,6+1): #   for error in errors_list: #       num=str(num) #       print(num + ".", error, end=", ") # print()   My wanted output is say:   list_item_1 list_item_2 three,..   Given an exact number of 6 elements, the output is instead:  1. list_item_1 1. list_item_2 1. three,.. 2. list_item_1 2. list_item_2 2. three,.. 3. list_item_1,..list_item_1   Individually, the print is okay. Ie. for item and for range. I've tried embedding the opposite way, list[i] and compounding the two for statements with and. The last of which retrieves: "num is not defined"?

How do I access the index in a for loop like the following?  ints = [8, 23, 45, 12, 78] for i in ints:     print('item #{} = {}'.format(???, i))   I want to get this output:  item #1 = 8 item #2 = 23 item #3 = 45 item #4 = 12 item #5 = 78   When I loop through it using a for loop, how do I access the loop index, from 1 to 5 in this case?


Commonly backup needs for stupidity. In Ubuntu when I run default Backups application it creates a new folder. If I accidentally delete this folder also(very stupid) then is it possible to recover my lost data?

Are there any tools, methods, incantations to recover recently deleted files on Ubuntu?  If it makes any difference, I want to recover a  2.x database file. But would be better to have a method/tool that works on any kind of file.


In set theory, we have {x, y, z}, which is the same as {z, y, x} which is the same as ... {y, x, z}, {z, x, y} ... Now, in Lisp (Scheme etc.) a list doesn't allow such juxtaposition. Order matters. Question: Is there a Lisp/Scheme equivalent to an order-doesn't-matter set?  Just guessing, I might simply construct a list, say (x y z), then have some sort of member? i.e., Are you a member of? mechanism.  ...I bet I'm not the only person who's wondered about this...

I need something like , a collection of elements which contains no duplicates of any element. Does Common Lisp, specifically SBCL, have any thing like this?


My problem ist, that the filled Area overlays a part of the x-axis. Is there a possibility to fill the area without hiding a part of the x-axis?  \begin{figure}[H] \centering \begin{tikzpicture} \begin{axis}[          scale only axis,          axis x line=middle,          axis y line=middle,          inner axis line style={=>},                  width=15cm,height=6cm,                      ymin=0,ymax=0.45,                      xmin=-3.5,xmax=3.5,                      axis line style = thick,                      xtick={-3,-2,-1,1,2,3},                      ytick={0.1,0.2,0.3,0.4},                  every axis x label/.style={at={(current axis.right of           origin)},anchor=west},          every axis y label/.style={at={(current axis.north)},above=0.5mm},                  xlabel={$x$},                  ylabel={$f(x)$}         ]       \addplot[fill=blue!25,draw=none,domain=1.63:3.5] {gauss(0,1)}        \closedcycle;]       \addplot [domain=-3.5:3.5,samples=500,red,thick] {gauss(0,1)};         \node[below] at (1.63,0)  {\Large \textcolor{black}{$\mu_{3}$}};        \end{axis}        \end{tikzpicture}         \caption{Graph der Dichtefunktion $f_X(x)$ mit $X\sim\mathcal{N}        (0,1)$}% \end{figure}

I have a plot with a pass/fail metric, and wish to show this clearly by having to seperate colors in the plot. To make the data stand out, I have a background grid to the axis tick marks. However, this does not affect the fill I use to color the area under the plot, as this seems to be the top layer.   An example of what I have now is shown below:    The code used to generate this is:  \documentclass{article}  \usepackage{pgfplots, amsmath} \pgfplotsset{compat=newest} \pgfplotsset{major grid style={color=black}} \pgfplotsset{every  tick/.style={black,}} \pagestyle{empty} \begin{document} \begin{tikzpicture} \begin{axis}[       xmin=5,      xmax=55,      ymin=0,      tick align=outside,      tickpos=left,      xtick=data,      ytick={0,0.2,...,2.5},      enlargelimits=false,      axis background/.style={fill=green!30},      grid=both,      xlabel=Frequency (MHz),      ylabel=V$_{\text{DD}}$ (V)] \addplot [const plot, fill=red!30]  coordinates { (5,0.7) (10,0.8) (15,0.9) (20,1) (25,1.1) (30,1.2) (35,1.3) (40,1.4) (45,1.5) (50,1.6)  (55,1.7) }  \closedcycle;  \end{axis} \end{tikzpicture} \end{document}   I want the gridlines to overlap the whole plot (meaning the fill as well). How can I achieve this?


When working with Threads, it is fairly common to write something like this:  Runnable r = new Runnable() {     public void run() { /* ... */ } }; new Thread(r).start();   This is all nice and correct, but I believe the same could be achieved in a more performant and easy way:  new Thread() {     public void run() { /* ... */ } }.start();   However, I almost never see anything like this in code examples using Threads and Runnable. Is there any technical or style-related reason to use the first example instead of the second?

From what time I've spent with threads in Java, I've found these two ways to write threads:  With implements Runnable:  public class MyRunnable implements Runnable {     public void run() {         //Code     } } //Started with a "new Thread(new MyRunnable()).start()" call   Or, with extends Thread:  public class MyThread extends Thread {     public MyThread() {         super("MyThread");     }     public void run() {         //Code     } } //Started with a "new MyThread().start()" call   Is there any significant difference in these two blocks of code ?


class AA {         void run()           {              System.out.print("In AA");           }        }    class B extends AA{           void run()          {              System.out.print("In B");          }        public static void main(String z[])         {          //upcasting        AA a= new B();       a.run();     }   }    Upcasting here working fine but now i m trying to call Parent class method like this..  B b=new AA();   It gives compile time error so cast it.   B b=(B) new AA();   However, I'm not sure why it's not working how I expect. Any thoughts?

Upcasting is allowed in Java, however downcasting gives a compile error.   The compile error can be removed by adding a cast but would anyway break at the runtime.   In this case why Java allows downcasting if it cannot be executed at the runtime? Is there any practical use for this concept?   public class demo {   public static void main(String a[]) {       B b = (B) new A(); // compiles with the cast,                           // but runtime exception - java.lang.ClassCastException   } }  class A {   public void draw() {     System.out.println("1");   }    public void draw1() {     System.out.println("2");   } }  class B extends A {   public void draw() {     System.out.println("3");   }   public void draw2() {     System.out.println("4");   } }


I created an arcgis custom tool for converting an excel file to both kml and shapefile . Now I want to include radio button or checkbox to select according user interest for either kml or shapefile.

I am working on creating an ArcGIS tool from a Python script I am writing.  I am wondering if it is possible to have a checkbox parameter.    I want to have a parameter where the user selects a feature class, then from the feature class the user will choose the field for the upper most layer in their model, then I want the user to be able to choose what layers they want the script to run on with a checkbox structure derived from the upper most layer field.    Is this possible with python, and ArcGIS Desktop?


At noon the sun and the earth pull the objects on the earth's surface in opposite directions. At midnight, the sun and the earth pull these objects in same direction. Is the weight of an object, as measured by a spring balance on the earth's surface more at midnight as compared to it's weight at noon? As if I draw the gravitational  force vectors of sun & earth it seems that the statement must be true. Also does the answer is affected if I use equal-beam balance instead of spring balance.

Using $g = \frac{Gm}{r^2}$, the force on a point mass located at 1 AU from the Sun ($m = 2 \cdot 10^{30} \text{ kg}$) is about ~0.006 N/kg.  Does that mean that, e.g., a 70 kg person is ~42g lighter during the day, and ~42g heavier at night? That seems like it could make a big difference for things like measuring gold bars or other weight-sensitive items. (Gold arbitrage: buy your gold during the day and sell it during the night! Risk-free profit!)  This makes me suspect that I'm overlooking something obvious, because a ~0.05% weight difference seems like something everyone would have noticed long ago. So what am I missing?    Edit: A few answers below indicate that there shouldn't be any weight difference, because the Earth orbits the Sun in free-fall. But if that's the reason, does that mean that a 1:1 tidally-locked Earth-Sun system wouldn't experience differential gravity from the Sun on opposite sides? That doesn't seem right.


I am unable to assign style to a dynamically created column in a table. On selecting a cell in the table, both the row and column are highlighted. this however does not work if the element is added later on. I used delegated binding by using on() but without the desired result. A search on the internet didn't give me a solution. Any ideas?    $("td").on("click", function(event) {   var table = 'table'   var styleA = {'-webkit-box-shadow':'inset 10px 10px 0px 200px rgba(213, 228, 237, 1)',               '-moz-box-shadow':'inset 10px 10px 0px 200px rgba(213, 228, 237, 1)',               'box-shadow':'inset 10px 10px 0px 200px rgba(213, 228, 237, 1)'};   var styleB = {'-webkit-box-shadow':'inset 10px 10px 0px 200px rgba(220, 231, 237, 1)',               '-moz-box-shadow':'inset 10px 10px 0px 200px rgba(220, 231, 237, 1)',               'box-shadow':'inset 10px 10px 0px 200px rgba(220, 231, 237, 1)',               'outline':' 3px solid #086aa7'};      $(table).find("td,tr").removeAttr('style');    $(table).find("td").removeAttr('style');   $(this).parent('tr').css(styleA);   $('td:eq(' + this.cellIndex + ')','tr').css(styleA);   $(this).css(styleB); });  $(document).mouseup(function(e){     var container = $("table");     if (!container.is(e.target) && container.has(e.target).length === 0)      {       $("table").find("tr,td").removeAttr('style');       $("table").find("td").removeAttr('style');     } });  $(window).on("load", function () {     $( 'table tr th:nth-child(1)').after('');   $( 'table tr td:nth-child(1)').after('	'); }); table {   font-family: arial, sans-serif;   border-collapse: collapse;   width: 500px;   margin: 50px 0 0 50px; }  td,th {   border: 1px solid #cacaca;   text-align: left;   padding: 8px;   background-color: #f5f5f5; } th {   background-color: #dce0e3; }

     Company	     Contact	     Country

     Alfreds Futterkiste	     Maria Anders	     Germany

     Centro comercial	     Francisco Chang	     Mexico

     Ernst Handel	     Roland Mendel	     Austria

     Island Trading	     Helen Bennett	     UK

     Laughing Bacchus 	     Yoshi Tannamuri	     Canada

     Magazzini Alimentari 	     Giovanni Rovelli	     Italy

I have a bit of code where I am looping through all the select boxes on a page and binding a .hover event to them to do a bit of twiddling with their width on mouse on/off.  This happens on page ready and works just fine.  The problem I have is that any select boxes I add via Ajax or DOM after the initial loop won't have the event bound.  I have found this plugin (), but before I add another 5k to my pages with a plugin, I want to see if anyone knows a way to do this, either with jQuery directly or by another option.


I've started to learn about GCM. In the  I read on page 4 there is the equation: $$ T = \text{MSB}_t(\text{GHASH}(H, A, C) \oplus E(K, Y_0)) $$  It's clear to me that the function $\text{MSB}_t(S)$ returns the bit string containing only the most significant (leftmost) $t$ bits of $S$ (defined on the same page). But I couldn't find any info on the value of $t$.   mentions several possible sizes of $t$ with advantages and disadvantages.  So, can the implementer choose $t$?  Which value of $t$ is used in TLS's AES-GCM cipher suites?  EDIT:  I can see that  is determining $t = 128$, but how can I see that  is part of TLS 1.2?

The MAC size is reduced to 80 bits in  , which says "forging of MAC values cannot be done off-line: in TLS, a single failed MAC guess will cause the immediate termination of the TLS session."  Question 1 (main question): So can I reduce MAC size to something even smaller, say 32 bits?  Question 2: The truncated_hmac extension does not effect AEAD. Can I reduce the tag's size in AEAD, e.g. GCM or CHACHA-POLY?


I was installing Chrome using apt-get and after that I'm not able use command sudo apt-get install  or sudo apt-get update anything which I am doing with my package manager is not working, is always showing this error:  Reading package lists...Error!  E: Problem parsing dependency Recommends     E: Error occurred while processing foomatic-filters (NewVersion2)     E: Problem with MergeList /var/lib/dpkg/status     E: The package lists or status file could not be parsed or opened.   Can you please tell me how to fix this problem? I am using Ubuntu 11.10. I am not even able to upgrade to Ubuntu 12.04 because of this problem.

Recently I have installed an older version of Ubuntu on my old machine. Whenever I try to install any software, I get an error saying it couldn't be found:  $ sudo apt-get install vlc Reading package lists... Done                Building dependency tree        Reading state information... Done     E: Couldn't find package vlc


For any integer n greater than 1, show that $4^n+n^4$ is never a prime number.  My approach: I tried to use mathematical induction. But somehow couldn't manage to prove it. Is it to be done by induction or can it be done by another method?

My coach said that for all positive integers $n$, $n^4+4^n$ is never a prime number.  So we memorized this for future use in math competition.  But I don't understand why is it?


I just need to download ubuntu onto a disk. How do i do it? I can't seem to figure it out. I feel funny asking but I need help. Thanks!

I have an old computer that can't handle a boot stick install, so i have to create an actual, old fashioned boot CD.  However, the image size for Ubuntu 12.04 is 732MB, which is too large for a CD, which can hold only 700MB.  The maintainers of Ubuntu 12.04 say the image size will never go over 700MB, and indeed, the download size seemed to be 689MB.  Brasero says it won't burn the CD because the file is too big, what's going on?


I saw a question here with the same title but it was not answered properly, or I just couldn't extract the solution from the comments/answers. This is an exercise from Beachy and Blair: Abstract algebra. A positive integer is called $\textbf{square-free}$ if it is a product of distinct primes. Prove that every positive integer can be written uniquely as a product of a square and a square-free integer.  Here is my try:  Let $n\in\mathbb{N}^+$, by the Fundamental theorem of arithmetic we can write $n$ uniquely as  $$ n=p_1^{\alpha_1}\cdot p_2^{\alpha_2}\cdot\ldots\cdot p_n^{\alpha}. $$ with $p_n$ being distinct primes. Now $\alpha_i$ is either even or odd, lets rename the odd ones as $\beta_j$, then we have $$ \alpha_i=2k_i\qquad \beta_j=2l_j+1\qquad k_i,l_j\in\mathbb{Z}^+, \ \text{and} \ i+j=n. $$ Since multiplication is commutative we can rearrange the factors so all the even exponents come first so $$ n=p_1^{2k_1}\cdot p_2^{2k_2}\cdot\ldots\cdot p_i^{2k_i}\cdot p_{n-j+1}^{2l_{n-j+1}+1}\cdot p_{n-j+2}^{2l_{n-j+2}+1}\cdot \ldots\cdot p_n^{2l_n+1}= $$ $$ n=p_1^{2k_1}\cdot p_2^{2k_2}\cdot\ldots\cdot p_i^{2k_i}\cdot p_{n-j}^{2l_{n-j+1}}\cdot p_{n-j+1}\cdot p_{n-j+2}^{2l_{n-j+2}}\cdot p_{n-j+2}\cdot \ldots\cdot p_n^{2l_n}\cdot p_{n}. $$ Again by commutativity we can arrange so all the factors with exponent "$1$" get to the end of the expression so  $$ n=p_1^{2k_1}\cdot p_2^{2k_2}\cdot\ldots\cdot p_i^{2k_i}\cdot p_{n-j+1}^{2l_{n-j+1}}\cdot p_{n-j+2}^{2l_{n-j+2}}\cdot \ldots\cdot p_n^{2l_n}\cdot p_{n-j+1}\cdot p_{n-j+2}\cdot\ldots\cdot p_{n}. $$ finally $$ n=\underbrace{(p_1^{k_1}\cdot p_2^{k_2}\cdot\ldots\cdot p_i^{k_i}\cdot p_{n-j+1}^{l_{n-j+1}}\cdot p_{n-j+2}^{l_{n-j+2}}\cdot \ldots\cdot p_n^{l_n})^2}_{a^2}\cdot \underbrace{p_{n-j+1}\cdot p_{n-j+2}\cdot\ldots\cdot p_{n}}_{b}. $$ And we are done since this factorisation was unique from the beginning. Now one of my problems is that this doesn't look too nice. In my head it looks simpler ("bringing down" the ones from odd exponents) but the final product looks like a mess. Is there any easier way to describe this? (maybe I could have renamed the primes with odd exponents as $q$?) I mean if it is correct at all. And I have a further question, can I get any HINTS how to do this by induction? Thank you in advance!

Possible Duplicate:          I am trying to prove that for every $n \ge 1$ there exist uniquely determined integers $a \gt 0$ and $b \gt 0$ such that $n = a^2b$ where $b$ is square-free.  The fact that such $a$ and $b$ exist is easy to prove.  From the fundamental theorem of arithmetic, $n$ can be uniquely represented as $p_1^{a_1} p_2^{a_2} \cdots p_s^{a_s}$ where $s$ is a positive integer. Thus  \begin{align*} n & = \prod_{i=1}^s p_i^{a_i} \\\\   & = \prod_{i=1}^s p_i^{\left(2 \left\lfloor \frac{a_i}{2} \right\rfloor + a_i \bmod{2}\right)} \\\\   & = \prod_{i=1}^s p_i^{\left(2 \left\lfloor \frac{a_i}{2} \right\rfloor\right)} \cdot \prod_{i=1}^s p_i^{a_i \bmod{2}} \\\\   & = \left(\prod_{i=1}^s p_i^{\left\lfloor \frac{a_i}{2} \right\rfloor}\right)^2 \cdot \prod_{i=1}^s p_i^{a_i \bmod{2}}. \end{align*}  Clearly, $\left(\prod_{i=1}^s p_i^{\left\lfloor \frac{a_i}{2} \right\rfloor}\right)^2$ is a perfect square and $\prod_{i=1}^s p_i^{a_i \bmod{2}}$ is square free. Hence, we have shown that such $a$ and $b$ exist.  Now, how do we show that such a pair of $a$ and $b$ is unique?  I know how to start proving such a theorem. Let us assume that $n = a^2b = a'^2b'$ such that $a' \ne a$ and $b' \ne b$. Now since this is not possible this should lead us to some contradiction. But, I'm unable to reach a contradiction from this assumption. Could you please help me?


So, I have some knives with handles that I'd like to 3d laser-engrave pockets for the knives into wooden cutting boards, using bump maps that I generate with Blender.  I have traced the side view and the top view of the knife, and from those two dimensions, I should be able to create a 3D model that I can export as a bump map.  Any ideas on how to do this? I'm pretty new to this.  Thank you!

I have a cartoon character (a lion) that is part of my business logo that I want to put into Blender and animate it somehow. Is there any way I can take a flat picture (JPEG) and transform it into a 3D image and then animate it in Blender?


I was on the beach with my best dino, he was set to neutral and to not follow, however I don't remember where I died. He's still alive but I can't find him. Any help?

I went on a resource run with a Quetz, perched it on a cliff, and (I assume) it got attacked while I was exploring. It had a lot of health and melee damage, so I think it probably survived the fight and just landed somewhere in the forest. I've tried scouting the area with another flying mount, whistling and using a telescope as I search, but no luck so far. Sadly, it did not have a transponder attached.  With the recent advent of admin commands on console, I started wondering if there was a way to teleport that missing Quetz to my location, or reveal it on the map somehow. Is there any command or technique you can use to locate a nearby, but hidden, tamed dino? Or bring it to your location automatically?  EDIT:  To clarify, I want this dino back. I am aware that dinos can be spawned via commands. I want to find out how to recover this dino, with all its inventory.


I'm new to Swift! I'd like to know how I can use custom fonts in my swift application in Xcode 6.

I would like to have an app include a custom font for rendering text, load it, and then use it with standard UIKit elements like UILabel. Is this possible?


I'm playing a 5e D&D homebrew campaign and we are all new to D&D, we don't know all the rules.  So I'm wondering: can you make a multiple rolls for one task? For example: I'm trying to spot something unusual on a ring and I get a low roll, then my DM says I didn't notice anything unusual then I say I try again then I get a higher roll and my DM says I saw that I saw. That seem a little odd, also when you fail a check and another player in the party tries to do that it doesn't seem realistic.

Picking a lock typically requires a DC 15 Dexterity check (Basic rules, p. 49). Likewise for manacles (p. 50), which can alternately be escaped with a DC 20 Dexterity check or broken with a DC 20 Strength check. But what happens if you fail?  The general rules for ability checks state (p. 58):     If the total equals or exceeds the DC, the ability check is a success—the creature overcomes the challenge at hand. Otherwise, it’s a failure, which means the character or monster makes no progress toward the objective or makes progress combined with a setback determined by the DM.   As a DM, how can I handle this in practice? In our last session, the players wanted to get inside a locked building to rescue people trapped inside. Picking the lock seemed like an easy enough task for the rogue, but unluckily he failed the check, and I wasn’t prepared for the consequences. There wasn’t much time pressure and no obvious reason why he couldn’t try again, so I allowed another attempt, but it just didn’t feel right.  I’m sure that similar situations will come up again, so I’d like some advice on how to deal with checks so that they don’t just turn into a tedious exercise of rolling until you succeed. I presume that  was left out of the game for good reason, but I’m not sure what to do instead. I suspect that this was a good occasion to use “progress with a setback” but that’s a fairly new thing for D&D and I’m not sure how to go about it. I’m unsure when I should use setbacks versus lack of progress, and in the latter case I’m unsure when I should allow players to try again versus requiring a different approach.  For example, suppose that a manacled player tries to pick the lock and fails the DC 15 Dexterity check. Now, the player could try to pick it again, or he could try one of the other escape methods, or he could wait for somebody else to rescue him, or he could simply succeed with some setback like a minor injury. How do I choose how to proceed? Or do I let the players choose?


Let $K$ be a finite field with $|K|=p^n$ for a prime $p$ and $n\in\mathbb{N}$.   Now I have to show that the characteristic of $K$ is $p.$  So I know that $(K,+)$ is a $p$-Group and therefore there exists a $m\in\mathbb{N}$ such that $p^m\cdot 1_K = 0_K$. This means that char$(K)=p^m$ because $ker(\varphi)=(p^m)$, where $\varphi: \mathbb{Z}\rightarrow K, n\mapsto n\cdot 1_K$.  Now I don't know how to show $m=1$.  Help is very much appreciated!

So the question is simply.      If $D$ is an integral domain and has finite characteristic prove that the characteristic of $D$ is a prime number.    This is my proof.  Assume $p$ is the characteristic of $D$. Let $a$ be a non zero element of $D$. Seeking a contradiction assume $p$ is not prime.  Then $p$ can be written as a factor: $rs=p$ for some $r$ and some $s$. By definition $pa=0$, so $(rs)a=0$. We know that $r,s$ are non-zero, so by definition of integral domain the only way this equation can equal zero is if $a=0$ however this is a contradiction as we chose a to be a non-zero element of $D$. Therefore $p$ is a prime.   Is this proof correct? The answer I have for this problem is slightly longer and I thought I might have missed something in my proof.


I keep doing classes and typing away at learning programming and in a few different lesson they say this is how you declare a null variable(java and Kotlin if i remember right python is a "none" not exactly the same).   But everything I read or learn says don't do it.  Why do it or is there a legitimate use for one?  REV 1.0 Below  I edited and rolled this question back some because a none after some more digging into the subject acts very similar as a null.  Instead of changing my question please make comments on how i can look at it differently or reframe or ask better questions.

We noticed that lots of bugs in our software developed in C# (or Java) cause a NullReferenceException.  Is there a reason why "null" has even been included in the language?  After all, if there were no "null", I would have no bug, right?  In other words, what feature in the language couldn't work without null?


I have been trying to find the sum of the series $$\sum_{n=1}^{\infty} \frac{1}{n^{2}2^{n}}$$ but I couldn't find any methods (such as a fourier series) that seem to get me anywhere.   WolframAlpha gave $ \dfrac{\pi^2}{12}-\dfrac{ln^2(2)}{2},$ but how would one get to this?

There is an infinite sum given: $$\sum_{n=1}^{\infty}\frac{1}{n^22^n}$$ It should be solved using integration, derivation or both. I think using power series can help but I don't know how to finish the calculation. Any help will be appreciated!


As an example, I know a leaf looks green because it absorbs red and blue light, but reflects green light*. My question is how the red and blue light are absorbed, not reflected. And conversely why the green light is reflected, and not absorbed. (I know that transmission of light can also occur, and if you can explain transmission as well that would be great, but not necessary for the answer.)   My first assumption was that the absorbed light is being converted to thermal energy, since objects that appear black to us absorb most (or at least relatively more) visible light, and these surfaces become the warmest in sunlight. So one potential answer to my question will explain how EMR in the range of visible light is converted to thermal energy. However, maybe this isn't the process, and maybe coincidentally the black surface also happen to absorb a lot of IR light, and that's why the surfaces warm up.  Maybe the process can be explained in terms of filtering: red and blue light are filtered out, and green light isn't, so it's reflected....? But that seems too simple, and 'filtering' is a very vague word. If the red and blue wavelengths are absorbed, conservation of energy must happen, so that energy needs to go somewhere. Where? And if this is the case, then how does the filtering occur?  I've done a lot of searching on this topic, and have found many explanations of absorbtion and emission of light with gasses such as neon, as per Niels Bohr's work. I don't believe this example applies to the leaf, which reflects light, not emits. However the example with neon gives the style of answer I am looking for, because a physical process is described, resulting in the perceived color (electrons absorb photons with specific amounts of energy, and then emit at that wavelength of light, and the combination of those wavelengths stimulate the retina and result in the perceived color).  *I'm using 'green light' (for example) as a shorthand to mean 'the wavelengths of EMR that stimulate M cones in the retina, and result in the perception of green.' I know that the light itself physically isn't green, but the 'greenness' arises from our perception of it.

This well-observed phenomenon has, besides several others, always been a fascination to me. We are well aware of several theories, experiments, and practical applications of this well-known phenomenon, but is it established what goes on at the grassroots of reflection?  My high school teacher once told me that whenever light is incident on any reflecting surface, its electrons absorb the energy of the photon and release back the same energy. If this is actually true, then I have plenty of questions to continue, but if it is not, then what is reflection, and how and why does it take place?


Suppose we have a list, where every item has its frequency: 1, 2, 3 , etc. Then,  from this list, I would like to get another list where every item has a frequency 1.   For example, the original list is:  A = [1, 2, 3, 1, 2, 5, 6, 7, 8, 5]   The idea is to get another list such as:  B = [1, 2, 3, 5, 6, 7, 8]   How can I do it?  This is what I implemented in Python:  for i in range(10):     k = i     item1 = A[k]     for j in range(k):         l = j         item2 = A[l]         if (item1 != item2):             B.append(item1)             break   But I get:  B = [1, 2, 5]   Can someone  please help me? Thanks in advance.

Is there a built-in that removes duplicates from list in Python, whilst preserving order? I know that I can use a set to remove duplicates, but that destroys the original order. I also know that I can roll my own like this:  def uniq(input):   output = []   for x in input:     if x not in output:       output.append(x)   return output   (Thanks to  for that .)  But I'd like to avail myself of a built-in or a more Pythonic idiom if possible.  Related question:


I'm doing principal components analysis (PCA) on quite a bit of data (3000 variables, 100079 data points). I'm doing this mostly for fun; data analysis is not my day job.  Normally, to do a PCA I would calculate the covariance matrix and then find its eigenvectors and corresponding eigenvalues. I understand very well how to interpret both of these, and find it a useful way to get to grips with a data set initially.  However, I've read that with such a large data set it's better (faster and more accurate) to do the principal components analysis by doing singular value decomposition (SVD) on the data matrix instead.   I have done this using . I don't really understand SVD, so I might not have done it right (see below), but assuming I have, what I end up with is (1) a matrix U, which is of size $3000\times 3000$; a vector s of length $3000$, and a matrix V of size $3000\times 100079$. (I used the full_matrices=False option, otherwise it would have been $100079\times 100079$, which is just silly.)  My questions are as follows:   It seems plausible that the singular values in the s vector might be the same as the eigenvalues of the correlation matrix. Is this correct? If so, how do I find the eigenvectors of the correlation matrix? Are they the rows of U, or its columns, or something else? It seems plausible that the columns of V might be the data transformed into the basis defined by the principal components. Is this correct? If not, how can I get that?   To do the analysis, I simply took my data in a big $3000 \times 100079$ numpy array and passed it to the svd function. (I'm aware that one should normally center the data first, but my intuition says I probably don't want to do this for my data, at least initially.) Is this the right way to do it? Or should I do something special to my data before passing it to this function?

Principal component analysis (PCA) is usually explained via an eigen-decomposition of the covariance matrix. However, it can also be performed via singular value decomposition (SVD) of the data matrix $\mathbf X$. How does it work? What is the connection between these two approaches? What is the relationship between SVD and PCA?  Or in other words, how to use SVD of the data matrix to perform dimensionality reduction?


Suppose $(a,b)=1$. If $a$ divides $c$ and $b$ divides $c$ prove that $ab$ divides $c$.  Use theorem $1.4$: If $a$ divides $bc$ and $(a,b)=1$, then $a$ divides $c$.  $a$ divides $c \implies c=ak$ $b$ divides $c \implies bt=c=ak$ $(a,b)=1$, $au+bw=1$ I tried moving things around and plugging things in but I can't figure out how to finish the proof from here.

Prove: If $a\mid m$ and $b\mid m$ and $\gcd(a,b)=1$ then $ab\mid m$  I thought that $m=ab$ but I was given a counterexample in a comment below.  So all I really know is $m=ax$ and $m=by$ for some $x,y \in \mathbb Z$. Also, $a$ and $b$ are relatively prime since $\gcd(a,b)=1$.   One of the comments suggests to use , i.e., $aq+br=1$ for some $q,r\in\mathbb{Z}$. Any more hints?  New to this divisibility/gcd stuff. Thanks in advance!


On the S3 it was easy to find. I clicked on everything under Settings.  I can't find it. Where do I access it?

I wanted to access the developer options to enable adb access on Android 4.2 but cannot find it.  How can I enable that?  Once I've activated the menu, how can I hide it again?


There is . Is the site appropriate for stuff related to requesting frameworks and libraries? Or should we have another site for that (e.g. name it Frameworks Recommendations or stuff alike)?  I can ask stuff there like: I need a software satisfying W, X, Y, and Z, but I'd like -some day- ask like: I need a Python library satisfying W, X, Y, and Z. The audience may be (and perhaps will be) different.    Is that website on-topic for stuff like that? Or should we open another proposal for that?  No: It's not about asking for a giga-dump for subjectivish questions. The linked-to-dupe question was written and answered with an old mindset and without Software Recommendations in mind. Also it does not consider this specific kind of questions but all the crap in one place. So, no,  is not an appropriate dupe mark for this question.

Stuff like polls, recommendations based on subjective constraints, puzzles, webcomics etc. do not belong on the serious main SE sites, where professionals should be considered at work and having just a few spare minutes ("code's compiling") to answer questions, so they should not be distracted by such things. However, I'd also like to have a home for these things still using the SE engine. For the reason I mentioned before, this needs to be a separate place though. Let's call it four.[sitename-here].com.


If we have a number which represents the number of images, do you call that the images count or the image count?  If you take the example with the images you could say:     The '15' is the image count for this album   But you could also say:     What is the minimum images count to take part in the photography competition   Which one is correct? Do you use the pluralized noun or not?

Is it correct to say user accounts or users account when referring to the accounts any user has on a site like this one?  In general, in the case of a noun that is used as adjective for the noun that follows, is it better to use <plural-noun> <singular-noun> or <singular-noun> <plural-noun>?


I am implementing an R-type summary() function in python with the restriction to exclude use of scientific libraries. (assignment) I found this  material explaining the calculation of standard errors of coefficients. As I already had a multiple linear model coded with gradient descent, I was able to code the standard error of coefficients, except the intercept. I just do not understand how to calculate $S{_b}_0$ based on the below equation:   I can calculate $R^{2}{_X}_k{_G}_k$ for k>0, but not for k=0  The following code piece works already, but I need something for the (z=-1) below, which would fill the coeff_stderr[0] element:          for z in range(len(X[0])):             xk_vector = get_matrix_column(X, z)             var_xk = variance(xk_vector)             RRxk = coefficient_of_determination_Xk(X, z, num_iters, alpha)             coeff_stderr[z+1] = RSE / sqrt((1-RRxk)*var_xk*(len(X)-1))   what is $X_0$? The intercept term - the column with 1s? Then it's variance is 0, and I would divide with 0...

I want to calculate standard error of y-intercept or constant term in the multiple regression equation $Y = b_0 + b_1X_1 + b_2X_2$  I found the formula for standard error estimation of co-efficient $b_1$ and $b_2$ as given in the link    But I am not getting any formula for estimating the standard error of b0. Could anyone help me out? Regards Koushik


I'm struggling with the once function. The once callback function is not called. I'm trying to use like this:  (function ($, Drupal){   Drupal.behaviors.my_module = {     attach: function (context, settings) {       console.log('this runs');        $('.my_selector', document).once('special-mark', function() {         console.log('this never called');       });        console.log('this also called');     }   } })(jQuery, Drupal);   In the library file I use the following:  dependencies:   - core/jquery   - core/jquery.once   - core/drupal   There's no a single error in the console. It's just simply not called the callback... How can I make it work?  Drupal: 8.8.4 jQuery: 3.4.1

I created a custom theme (a sub-theme of  base theme).   I am loading a custom Javascript file (radix_sub.script.js) using the module libraries.yaml file like below:  style:   version: VERSION   css:     theme:       assets/css/radix_sub.style.css: {}   js:     '//cdnjs.cloudflare.com/ajax/libs/popper.js/1.14.7/umd/popper.min.js': { type: external }     '//stackpath.bootstrapcdn.com/bootstrap/4.3.1/js/bootstrap.min.js': { type: external }     assets/js/radix_sub.script.js: {}   dependencies:     - core/drupal     - core/jquery     - core/jquery.once     - core/drupalSettings   In that file, I want to register some JavaScript events (Bootstrap modal).  (function ($, Drupal) {    Drupal.behaviors.portfolio = {      attach: function (context) {        console.log('CONTEXT', context);        $('#portfolioModal', context).once('bootstrap-modal-shown', console.log('*** REGISTER SHOWN.BS.MODAL')).each(function () {         $(this).on('shown.bs.modal', function () {           console.log('SHOWN BS MODAL EVENT TRIGGERED');         });       });        $('#portfolioModal', context).once('bootstrap-modal-hidden', console.log('*** REGISTER HIDDEN.BS.MODAL')).each(function () {         $(this).on('hidden.bs.modal', function () {           console.log('HIDDEN BS MODAL EVENT TRIGGERED');         });       });     }   } }(jQuery, Drupal));   It works. I see both SHOWN BS MODAL EVENT TRIGGERED and HIDDEN BS MODAL EVENT TRIGGERED logs when I show/hide the modal.  First, am I doing that the correct way?  This is what my developer console looks like when I load my page.        This happens only when I am logged in (as admin). When I am anon, I see the REGISTER logs only once but here my code seems to be executed 11 times.  Is this normal behavior? And/or why is it doing that?


Clipboard.GetText() always empty, I want to copy the text in my clipboard inside my app  var str = Clipboard.GetText();   but it's always empty! why is that? where it has data.

My clipboard is populated with text, but when I run  string clipboardData = Clipboard.GetText(System.Windows.Forms.TextDataFormat.Text);   I get back an empty string. I've toyed with various forms of the call including:  string clipboardData = Clipboard.GetText(); string clipboardData = Clipboard.GetText(System.Windows.Forms.TextDataFormat.UnicodeText);   But with the same result.  Am I missing something obvious?


While trying to install lsb-core, I get the following error:  Err:1 http://us.archive.ubuntu.com/ubuntu zesty/universe i386 libfreeimage3 i386 3.17.0+ds1-5build1   404  Not Found [IP: 91.189.91.26 80]    Additional errors appear about not finding the page. I ping the IP address and it is real.  Have the files been removed? If so, the installation scripts or must be updated.  Any suggestions on how I can proceed?

Recently I have installed an older version of Ubuntu on my old machine. Whenever I try to install any software, I get an error saying it couldn't be found:  $ sudo apt-get install vlc Reading package lists... Done                Building dependency tree        Reading state information... Done     E: Couldn't find package vlc


I have a 4x6x16 to use for the header of a swing set. I was going to span 12 ft between supports and cantilever 4 ft but I now would prefer to put the supports at each end. I would hang 4 swings over the 16-ft span. Assuming 200 pounds per swing, would this be safe. I plan to use 12-ft splayed legs.

I need to create a 15 feet span beam for kid swing (300 lbs load / 150 lbs and 2 swings assumption). One end will bolt to the tree (just for convenience).  What "treated lumber" lumber size and material I should use? Or is it better / cheaper to use metal pipe (from the plumbing department)?  I guess 4x8x16 or two (2) 2x8x16 would do it according to this website . But I do like a clean look of metal. My wife would concern about big piece of lumber running on top of the kid (that looks heavy visually).


There is no postgresql option in the autorun menu, but it starts when the system starts. Searches have failed. Can you help?

I have postgresql 8.4 installed on my desktop. It keeps starting on bootup because I think I used default settings.   so I issue /etc/init.d/postgresql stop everytime and sometimes i keep forgetting  It has folder paths as,  /etc/postgresql/8.4/main /usr/lib/postgresql/8.4   There are a lot of configuration files and if someone can tell me where to look and what to change, that will be great.   Thanks.


How do we know that a wave of light has electric field? Maxwell proved that light is an electromagnetic wave. Can you give me a reference of an experiment which proves light as an EM wave?

For example, has anyone has directly observed charges oscillating due to standing EM waves? I am particularly interested because it'd demonstrate that radiation has a transverse electric component to it. Anything else (historical or modern) that shows that light has a transverse electric component would also be gladly invited.


I'm trying to return the dml error messages to the lightning component.  According to this  I can throw an aurahandledexception. But i keep getting this error message.  System.AuraHandledException: Script-thrown exception

It seems like when I call getMessage on a thrown AuraHandledException, I see "Script-thrown Exception" instead of the message that I have set. Any idea why this may be happening?  Controller:       @AuraEnabled     public static Conversation__c makeConversation(String tonum, String objid)     {         if (tonum.length() != 10)             throw new AuraHandledException('ToNumber length invalid.');     }   TestController:  @isTest     static void testMakeConversationInvalidTo()     {         Boolean testPass = false;         String fromNumber = '1234567890';         String toNumber = '1';          List<ConversationController.ConversationWrapper> test =    ConversationController.getConversations();         System.assertEquals(0, test.size());         try {             ConversationController.makeConversation(toNumber, '0');         } catch (AuraHandledException e) {             System.debug(e.getMessage());             System.debug(e.getTypeName());             System.assert(e.getMessage().contains('ToNumber length invalid'));             testPass = true;         }     }   Return:  16:26:28:477 USER_DEBUG [320]|DEBUG|Script-thrown exception 16:26:28:477 USER_DEBUG [321]|DEBUG|System.AuraHandledException


Because linear velocity is a vector  which I can agree as it's because of the direction of the displacement but in case of angular velocity it's angles covered in certain time but angles got no direction then how come it got any direction  P.S  I came to know it's something of a pseudo vector but didn't understand it so explain it in simple terms.Thanks

I apologize if this question is dumb, but I've looked all over for a straightforward answer, and either I can't find one or either the terms are too complex for me to understand. I have only a rudimentary knowledge of Mechanics, but I do understand basic Linear Algebra. So torque, mathematically, is the cross product of the radial distance vector and a force vector. This cross-product gives another vector that is orthogonal to both vectors and it points either outside or towards the "page" (in the context of a two-dimensional diagram). Assuming this is correct, I do not understand what it pointing in or out means. Does it even have a physical, intuitive meaning? The best answer I've been able to come up with is that it's just a mathematical convention with no actual physical meaning, meant to provide a framework within which operations between torque vectors, such as addition and subtraction, make sense. Am I correct or way off the mark here?


We have that $0<b\le a$ are two positive real numbers. Their arithmetic mean is defined as  $a_1=(a+b)/2$ and their geometric mean is $b_1=\sqrt{ab}$.  Firstly we have to show an that $b_1\le a_1$ iff $a=b$, so we must show both directions algebraically.  Then we define two sequences by setting $a_{n+1}=(a_n+b_n)/2$ and $b_{n+1} = \sqrt{a_nb_n}$. Using mathematical induction to show : $a\ge a_1\ge\dots \ge a_n\ge b_n\ge\dots\ge b_1\ge b$.  Prove that both series converge and show their limit.  I'm having trouble with the first step in proving the iff statement in the forward and backward direction, as well as showing the proof by induction. Also how would one determine the convergence and limit of this series?

I am given this problem: let $a\ge0$,$b\ge0$, and the sequences $a_n$ and $b_n$ are defined in this way: $a_0:=a$, $b_0:=b$ and $a_{n+1}:= \sqrt{a_nb_n}$ and $b_{n+1}:=\frac{1}{2}(a_n+b_n)$ for all $n\in\Bbb{N}$    To prove is that both sequences converge and that they have the same limit. I don't know how to show this. I have spent 2 hours on this, no sign of success


(The original title of this post was "Boot Repair doesn't work after April 2014 Windows 8.1 Update" since I wanted to highlight that this is not about the 8.0 -> 8.1 update, but the update for 8.1 that came out in April 2014.)  I'm dual booting Ubuntu 13.10 and Windows 8.1. Today I got the "big" Windows 8.1 Update and now my PC doesn't show GRUB anymore, but boots straight into Windows. I've tried running  from Ubuntu on a USB stick, but that doesn't seem to do anything. The system still boots directly into Windows every time.  I'm sure I just need to change some setting in Boot Repair, but I don't want to do that without knowing what I'm doing. :)  Here's my Boot Repair Ubuntu Pastebin thingy:    Thanks!  Update:  Now I effed everything up completely.  Since I didn't get an answer here, I tried fiddeling with the Boot Repair options. Now the following message flashes for a second when I start the PC:  Could not open "\EFI\BOOT\fallback.efi": 14 Failed to open \EFI\BOOT\grubx64.efi - 800000000000000E Failed to load image Failed to open \EFI\BOOT\MokManager.efi - 800000000000000E Failed to load image   ...just before stopping at this line:  Operating System Not Found   Here's my updated Boot Repair report:

I have an Ubuntu 13.10 and Windows 8 dual-boot working properly, and upgrading to Windows 8.1 breaks grub2 as expected. However, this time boot-repair was not able to bring grub back for me. My laptop jumps right into windows.  I double checked that Windows 8.1 re-enabled fast startup, so I've disabled it. And in my BIOS, UEIF is used for boot and secure-boot is disabled.  I have a 500GB GPT partition, in which, sda1 is the efi partion, sda2 is the /boot, sda3 is the / for ubuntu, and sda7 is the swap area. For Windows, sda4 is the msft reserve, sda5 is c://, and sda6 is Windows recovery. Those are (at least) my original setup.  Here's the boot info:   I also tried mount my hard drive from a live ubuntu session, then re-install grub on /dev/sda, which didn't work either.  Is there any other thing I could try to bring my Ubuntu back?


How do I get the restoname from the db that has apostrophe on it? using the mysql or php.   The code: public function searchRestaurant($searchinfo){ $sql = "SELECT * FROM restaurants WHERE restoname = '$searchinfo' OR restocuisines = '$searchinfo'"; $result = $this->db->query($sql); $result = $result->result('array');      return $result; }   The error:

If user input is inserted without modification into an SQL query, then the application becomes vulnerable to , like in the following example:  $unsafe_variable = $_POST['user_input'];   mysql_query("INSERT INTO `table` (`column`) VALUES ('$unsafe_variable')");   That's because the user can input something like value'); DROP TABLE table;--, and the query becomes:  INSERT INTO `table` (`column`) VALUES('value'); DROP TABLE table;--')   What can be done to prevent this from happening?


My friend likes to repeatedly shake his leg up and down when idle. In Chinese, there is a specific term for this action that, if loosely translated, would be "vibrating leg."   Is there a more general or commonly accepted term in English for this specific habit? This habit is quite common and as a child I would do it, too. But I was reprimanded by my mother for doing so and that is why I know the Chinese term and now I am wondering what the English term is.

There are persons who keep jiggling their legs sitting on the chair during conversation or being interviewed. This motion is annoying and seen as the indication of the speaker’s tension, weakness to pressure, timidity, and lack of self-confidence.   We call it derogatorily ’貧乏ゆすり/ binboyusuri - poor man’s (leg) shake’ in Japanese, and were told not to jiggle legs when sitting on chair before people, even during a meal from the childhood by parents.   Kenkyusha’s English Japanese Dictionary translates ‘binboyusuri’ as ‘tap one’s foot nervously.”  When you do ‘binboyusuri’ in front of interviewer(s) while job interview in Japan, you are 150 % sure to flunk. Is this 'leg-specific motion' seen as negatively in western world too? Are there short words to express  ‘Binboyusuri’ as a noun or verb, say in two words?


I downloaded an Ubuntu 14.10 64-bit iso, then put it on my 8GB USB. I closed my laptop then plugged the USB in and opened the laptop, I pressed F12 to get the "Boot Menu", then I clicked "USB Flash Drive" (Something like that), then it said "Boot Error"

I am trying to install linux on my laptop, a Toshiba Satellite C6550-S5200. I did it once but something happened so I removed it then I had to destroy all data on hard drive so now I have nothing on it. Well I got a iso file burned to a CD and to a flash drive. With the flash drive I get.   SYSLINUX 4.06 EDD 4.06-pre7 Copyright (C) 1994-2012 H. Peter Anvin et al  With the CD it will start booting it but somewhere loading it up, the dots turn all orange and stay that way and my CD drive turns quiet.  Oh and some more info the images work because I tried loading them up on another pc and it worked just fine.  I manage to get the CD to boot I just had to let me pc boot up first then insert the CD and have it boot the CD then. Once I get done installing ubuntu it works fine but I have to leave the PC on 24/7 for if I turn it off the PC will freeze 5-10 seconds after booting back up no matter how I install it.


I downloaded Ubuntu 14.04 64-bit .iso from official Ubuntu site. While installing it from a bootable USB drive I selected to replace Windows 8. The installer removed all my partitions and replaced it with an Ubuntu one.  I then installed Windows 8 by making a separate partition out of the Ubuntu space. I did not get any option to boot Ubuntu.  Why can't I boot Ubuntu and how do I fix this? And is there any way to get back my files(a whole lot collection of Programmes, Movies, Games and Music?

I installed Windows 7, which ate Ubuntu's boot file. When starting up the computer, it now goes straight to Windows, without giving me the option of booting Ubuntu.   How can I get Ubuntu back?


Can anyone help me out finding the number of solutions i.e. $(x,y,z)$ for the inequality $x+y+z\leq n$ where, $n$ is a constant positive value and $x,y,z$ are non-negative?

How to use the  method?  Say I want to find number of combinations I can get with $x_1+x_2+x_3+x_4=22$,  where $x_i\in\mathbb{N}$.  Is this the correct time to apply the method?  This is being repurposed in an effort to cut down on duplicates, see here:     and here:


On Windows 10 (64-bit), I have a file that I want to open with an app that I installed from the Microsoft Store. I just want to open it with it once, I do not want to set the default app. I right-click the file and choose Open With. The app doesn't happen to be in the list (that's fine), so I select Look for another app on this PC and it opens a file dialog in the Program Files directory. Normally that'd be fine and I'd pick the application, except I guess apps from the Store aren't installed into Program Files, and I have no idea how to choose the app I want. How do I choose a Store-installed app on the Open With dialog if it's not in the initially displayed list of apps?  Specific Example: In this case the file I want to open is a .3MF file, and the app I want to use is Zip Extractor, which is installed but doesn't appear in the list in the dialog. Now, just out of curiosity, I used Process Explorer to find the executable for an open Zip Extractor window, it appears to be: C:\Program Files\WindowsApps\38526MediaLife.ZipPlus_2.0.4.0_x86__1crh1k73ty8mg\ZP.exe  I tried navigating there in the Open With dialog, but received a couple of hard "access denied" errors when attempting to open WindowsApps. Plus, even if that did work, it's not exactly convenient and definitely doesn't feel like the right way to do that. I feel like I'm missing something obvious here...  Note: I know there's other ways to open that file (e.g. renaming it to .zip, dragging it into a Zip Extractor window, using a different non-Store application, etc.), but I'm not asking about how to open the file, I'm asking about how to choose Store apps from Open With if they're not in the initial list. :)

I want to open a certain file extension with a Windows 10 UWP (Microsoft Store) app. I right-click on the file in File Explorer, select Open With, then Chose another app and I get the menu below, which does not include the app I want. At this point, I can click Look for another app on this PC, but the app I need is an UWP one, which is not in the Program Files or Program Files (x86) folders, so I cannot just navigate to the path of the executable file. How can I associate my extension to the UWP app? (Nota that this is not a duplicate of the same question for non-UWP programs)


I wanted my variable play to change whenever the turn changes so I made a function. If turn is even play will be variable O="O", vice versa for odd then I used the function even(turn) with turn=1, it displays O even though it should be X. Is my code below wrong in some way or it just doesn't work like that?  I'm making a tic tac toe program on repl.it, I've tried using manual change as in making 9 different copies to change the turns but its just too much work, I wanted to make a simpler code.   play=0 X="X" O="O"  turn=1   def even(turn):   if turn%2==0:     play=O    else:     play=X    even(turn) print(play)   I expect the output to be either O or X according to if the number is even or odd respectively.

How can I create or use a global variable in a function?  If I create a global variable in one function, how can I use that global variable in another function? Do I need to store the global variable in a local variable of the function which needs its access?


I've got a USB3 external hard drive connected to my laptop running 14.04. Every time I want to disconnect it, using "safely remove", the hard drive turns off, but then immediately turns on again.   I don't want to unplug it, while it's still running. So I'd really appreciate tips on how to solve this.   Thanks.

I have an external HDD with a USB 3.0 connection. When I connect it to the USB 3.0 port on my laptop, it works fine but when I eject it, it gets remounted immediately.  This doesn't happen when I connect the same drive to a USB 2.0 port.  At the moment I'm unmounting (clicking the "eject" button in Nautilus) instead.   Is there a way to avoid this issue?


I don't have access to the internet on my Samsung Tab 3 and don't have wifi either. Only my PC has internet access through a landline and non wireless modem. How can I download apps from Google Play to my tab? I got the USB cable that connects my tab to the PC.

I can't download apps from the Play Store on my Android device (maybe due to a network issue), so I'm wondering how could I download the APK file of an app on my PC from ?


I need to export final files with at max 128mb for print on fabric.  My initial canvas size is 16.383px x 10.000px (the 16383 is the max allowed by illustrator).  I've noticed that even working in 300dpi, when uploaded in jpg format, even if my canvas size is bigger that the final application, my dpi drops to 190.  That's why I'm making a huge canvas with 400dpi.  As my Illustrator says that the jpg is too large to be exported, I'm opening the .ai file in Photoshop and Save As jpg from there.  The jpg file is 17mb while a PNG file is 600mb.  What I can do to have the best quality? What I should do?  Thank you very much if someone can help me.

For wall-sized graphics and large banners (e.g. 3m × 5m), what is an acceptable PPI for print? As I understand it 300 ppi is the typical for 'small' artworks (esp. for clean text resolution). However, for small artworks, the audience usually engages at a much closer distance. Therefore, in the interests of keeping a bitmap file down to a reasonable size, can you get away with a much-reduced PPI for a large format/banner print?


I am trying to add biber to QuickBuild in Kile and I tried following the instructions in  post. However, seems like the instructions are for a different version of Kile. Could someone help me understand what to include for in the blank spaces of the screenshots I've attached. Thank you!

Running the minimal example  \documentclass{article} \usepackage{filecontents} \begin{filecontents*}{\jobname.bib} @ARTICLE{example,   author  = {Other, Anthony Norman},   title   = {Some things I did},   year    = {2014},   journal = {J.~Irrep. Res.},   volume  = {1},   number  = {1},   pages   = {1-10} } \end{filecontents*} \usepackage[backend=biber]{biblatex} \addbibresource{\jobname.bib} \begin{document} Hello\cite{example}. \printbibliography \end{document}   I get the warning There were undefined references.  I have read  and know that I need to run:   LaTeX Biber LaTeX   However, my editor is only set up to run BibTeX. How do I go about setting up my editor/IDE to be able to run Biber, and how do I run the LaTeX/Biber/LaTeX cycle?  Answers (sorted alphabetically by editor name)                    Answer guidelines   Each answer should be for one editor. If the editor is cross-platform, if possible give a single answer with notes covering the minor platform variations. Please edit the question to include new answers in the 'link list' Each answer should be 'stand alone', i.e. don't say 'It's almost the same as editor Y but ...' for the editor part Instructions for 'build tools' such as arara or latexmk are welcome but should explain how to set up the editor in question as not all editors allow simple addition of arbitrary tools


I think there should be a way for the user to review and accept the Edit from someone else.  If I am willing to ask a question for example, if somebody else hasn't understood it, edited the question and thereby diverted the topic, I should be allowed to review the 'suggested' edit and accept it or decline it if need be, right?

It is possible for users to edit an existing post.   How do edits work? Who may edit a question or answer? How can you tell what has been changed between edits?      For more information, see "" in the .     Related:


He is very lazy. I have never seen  him working.   He is very lazy. I have never seen him work.      Are both of them grammatically correct? What is the difference in meaning between them?    Update:  I read the duplicate question, but I couldn't understand which one is correct in the above context. work or working?  I think work is correct, because it follows the verb tense in the first clause.  I think working is useful in another context. when the situation is temporary e.g.      It seem he is frustrating, I haven't seen him working recently.

I know using the bare infinitive after verbs such as hear, see, watch, etc. conveys  a different meaning from using the present participle (verb+ing):        I watched him climbing over the fence ( Climbing wasn't finished at the moment of speaking)   I watched him climb over the fence ( Climbing was finished at the moment of speaking)       I noticed the majority of the Grammar books use past tense to explain the aforementioned difference. Personally, I think that is quite rational because the bare infinitive implies a completed or finished occurrence. This means that event belongs to the past. However, I have a problem conceiving similar sentences in the present tense. For example:   .   The questions is:     If the bare infinitive implies a completed action, then why should we use the present tense to talk about that event? (the event is in the past).      We can say that:      An uneasy feeling came over me as I watched him walk towards the revolving doors     Added info 1  If you think my "climbing" examples are irrelevant, you can check Cambridge Advanced Grammar In Use, page 60, Unit 30, Section D or just check this     Added info 2  My question is from the logical point of view. I think the act of "seeing" is instantly. Therefore, it is not rational to say "see" a "completed process" but, "saw" a "completed process".


I have a date field in my site and I want it to hide/be invisible when the date I have set is now or matches the sites date. I hope there is a way to do this using Rules.

I want to know if I can hide the values of a date field if the values are older than a certain time. The website is built with Drupal 7, and Display Suite.


I have two friends living with me and they only pay bills (no rent) and I wondering if I would be liable for CGT on the period they live there?  I don't take any rent from them at all and they are just friends staying in my house.  So, in HMRC's eyes, what is the definition of a lodger and specifically does it ever differ from a friend staying rent free in my house?  Also, in the definition of a lodger, if I let a room to a couple on one room lodger agreement does that count as one lodger or two?  (This has extremely large implications on CGT because having two lodgers makes the time they live there liable to CGT)

I have been letting my home to lodgers on and off for a few years to friends for no profit or a considerably lower profit (30% -50% of market value).  I don't consider it a business or a money making scheme but I want to know if HMRC would before I find another place and go bankrupt after I get a huge unexpected bill from them!  For those years I shared my house would I be liable for capital gains tax?    I've owned the property for 7 1/2 years, I would say I've been on my own for about three years, one lodger for about two years and three lodgers for about two years.  During the period of lodgers I lived there on and off (mostly lived there though) and I have always considered it my only home with all my things and mail going there (I haven't rented anywhere else).  I would share when I had friends who needed somehwere to stay or when I have travelled for work purposes and two two month backpacking holidays.  It feels ludicrous if I had to pay because I would have been paying CGT for the only privilege of sharing my house!


My Database has Full BackUp Plan on Every Morning on 01:00 Am. Today I came to work and Deleted all of the Records in a table by mistake in sql server management Studio by running this command  delete * from Table1 where 10=10   instead of  delete * from Table1 where Id=10   this happened around  13:00 pm. worktime starts from 8:00 am . is it possible to undo the deleted Records? if I want to recover it from the backup file, I loses the records entered between 8:00 and 13:00. what is the best solution for this problem?  I read this post  but it was not the same as mine. and I read it was a duplicate post. but again i couldn't find the the main post for this problem.

I mistakenly deleted around 2,000,000 records from a remote SQL Server 2008 table.  The server is not granting me access to the backup files on the server side.   Is there any way to get back these records?


Im doing a project at university where i need to replace the names of people in a chat log we have.  The problem is, i have over 900 unique names i need to replace, and manually doing so would take a lot of time, time i do not have. I have the names extracted and a list of the replacement names, i just need a smart way of mass replacing them. Again, this is not replacing in many different files, its replacing many different things in the same document.  I've been working in Notepad++ trying to do this, but cant seem to find the answer.   Edit: I have looked earlier at the answer provided in  however as mentioned its 900 unique names, and creating a script described there would also be very time consuming. The person is asking for 2 instances of find and replace, i need over 900

I have a file with multiple instances of Text_1 and Text1 and I need to replace both those strings with Text_A and TextB respectively.    Currently I'm doing two Find and Replace functions on each file one that finds Text_1 and replaces it with Text_A and the other that finds Text1 and replaces it with TextB.    Is there any way to do this all at once instead of having to run "Find and Replace" twice?  I am using Dreamweaver CS3, but I also have Notepad++, regular Notepad, OO Writer, MS Word if those will be easier.  Ideally I could do this in Dreamweaver or Notepad++ but I'm open to downloading something else to get the job done.  I'd prefer not to have to do any command line stuff or create a batch file (while I'm aware of it, I don't understand it really).  In case the above description isn't clear, let me explain it this way...  I want to run Find & Replace 1 time in 1 document and I want it to do ALL of the following during that one Find & Replace instance:   Find Text_1 and Replace with Text_A Find Text1 and Replace with TextB   I am not trying to do a Find and Replace across several documents.


I am new to Linux and I have created a dual boot with windows 10 inside a SSD, in the start I did a partition of 20 gb believing that it would be just for the system and it would be possible to use the memory leftover without needing to do anything else, so now my system is almost full and I've tried to extend the partition through the gparted unallocating 50 gb of my SSD, but even with the new unallocated space it is not possible to extend through the resize option, what should I do to extend it? And is it possible for me to use the memory from an HD too?

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?


How does one prove that $(1+\frac{1}{x})^x$ is monotonic increasing for any $x \in [1,\infty)$?  Thanks a million!

Let $F(x)=(1+\frac{1}{x})^x$.  How do we prove $F(x)$ is increasing when $x>0$?


I have Ubuntu 18.04.2 LTS on my laptop. Got a new USB Stick (Samsung) for storing extra files and I am unable to access it.  When I insert it, the folder shows up but when I click on it, it says:  Unable to access Samsung USB  - Error mounting ... Samsung USB: Unknown file system Type 'Exfat'   What do I need to do to be able to access it? Please give advice that an absolute IT beginner can handle :)

When trying to mount an exfat filesystem, I get the following error:  Error mounting /dev/sda6 at /media/gkp/Backup: Command-line  `mount -t "exfat" -o "uhelper=udisks2,nodev,nosuid" "/dev/sda6" "/media/gkp/Backup"'  exited with non-zero exit status 32: mount: unknown filesystem type 'exfat'   Exfat is used on some USB sticks and camera sd cards. What can I do to mount this type of filesystem?


I am using the following regex   '/\@(.*)\((.*)\)/'   And I am trying to get @ONE(TWO) one and two from the expression. Which works as long as it's the only time that it can be found before an end of line (I think)   I am quite green with regex and I really cannot understand what I am doing wrong.   What I need is to be able to get all the ONE/TWO couples. Can you please help me.   I am working with PHP and the following function   $parsed_string = preg_replace_callback(     // Placeholder for not previously created article     // Pattern example: @George Ioannidis(person)                  '/\@(.*)\((.*)\)/',      function ($matches) {         return $this->parsePlaceholders( $matches );     },     $string );   The results I am getting from

I have this gigantic ugly string: J0000000: Transaction A0001401 started on 8/22/2008 9:49:29 AM J0000010: Project name: E:\foo.pf J0000011: Job name: MBiek Direct Mail Test J0000020: Document 1 - Completed successfully  I'm trying to extract pieces from it using regex. In this case, I want to grab everything after Project Name up to the part where it says J0000011: (the 11 is going to be a different number every time). Here's the regex I've been playing with: Project name:\s+(.*)\s+J[0-9]{7}:  The problem is that it doesn't stop until it hits the J0000020: at the end. How do I make the regex stop at the first occurrence of J[0-9]{7}?


I always get the analogy of the pretend sun on a piece of cloth pulling everything down such as the image attached below: But What I never really understood is what IS that piece of cloth. Like is it some sort of invisible force field or something? Sorry if I sound a little crazy, I only recently started reading a little bit of popular physics (fabric of the cosmos).

I've seen many science popularisation documentaries and read few books (obviously not being scientist myself). I am able to process and understand basic ideas behind most of these. However for general relativity there is this one illustration, which is being used over and over (image from Wikipedia):    I always thought that general relativity gives another way how you can describe gravity. However for this illustration to work, there needs to be another force, pulling the object down (referring to a direction in the attached image). If I put two non-moving objects in the image, what force will pull them together?  So where is my understanding incorrect? Or is general relativity not about explaining gravity and just describes how heavy objects bends spacetime (in that case the analogy is being used not correctly in my opinion)?    UPDATE Thank you for the answers and comments. Namely the XKCD comics is a spot on. I understand that the analogy with bent sheet of fabric pretty bad, but it seems that it can be fixed if you don't bent the fabric, but just distort the drawn grid.   Would you be so kind and answer the second part of the question as well - whether general relativity is explaining gravitational force. To me it seems that it is not (bending of spacetime simply can not affect two non-moving objects). However most of the time it is being presented that it does.


This question is highly related to  main question but with one key difference I just want to check:  I'd PREFER to have the old version use my profile, firefox sync, etc, to stay current with bookmarks AND i'm not bothered about having both open at the same time, the only reason I want it is because FF52 supports 2 old extensions which still haven't been updated to run quantum and I need them for a specific occasional task.  So: will I run into any problems just installing ? Or will it overwrite default current FF and/or cause other problems, does anyone know?  Edit: given I only really need the bookmarks to be synced, would it be better to create a separate profile then use a bookmark sync extension?  Thanks!  Edit2: re: possible duplicate: I'd argue that the main question is distinct from the question cited by N0rbert, so while one approach to solving my issue is shared with the other poster, there are alternative solutions to both of our questions. Conceptually this distinction strengthens the cause to leave this question up, as I suspect there will be a similar or greater number of people who want to run side-by-side than simply downgrade.

What is the most straight forward way to downgrade Firefox 57 to Firefox 56?   This is to have more time to wait for working replacements for legacy extensions.


Does a viewfinder cover really make a difference? I've heard opinions from people that they are essential for scenarios such as shooting long exposure pictures. I'm just wondering if it is only a slight difference or a major one.

A rubber viewfinder cover is connected to my camera strap.  What's it for, and when do I use it?  What happens to a photo if I don't use it?


I have the coordinates : North = 861597.4129 , East = 1063313.808 All I know is that they should belong somewhere in the city of Cali, Colombia. I have tried different Colombian EPSG codes but I still do not know which format they are in.

I have a Shapefile but its coordinate system is Unknown, and there is no *.prj file.   How can I identify it now?


I installed Ubuntu on a second hard drive inside the computer by booting with the CD.  I now want to switch back to my main hard drive but I don't know how. When I unplug the Linux HD it goes into this black grub thingy and I don't know if my Windows got deleted because I didn't touch that HD. I don't have a Windows disk, my computer came with Windows 8. I need help please...

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?


Windows Explorer (win7) keeps crashing when I select some files. It's several different file extensions (.png, .pdf).  This does not happen when I use XY explorer (a thirdparty explorer) So I suspect it's some third party app integrated with WE.  How can i disable such?

I have reason to believe that I may have malware on my system in the form of an Explorer extension. I suspect this because Procmon shows that Explorer.exe keeps re-writing a certain Registry key that is intended to run a certain EXE at startup.  How do I find out what Explorer extensions are installed, and how do I remove them?


I am little confused and not sure, how to add the cat << EOF style to my script. Would really appreciate a little feedback and help.  Here is my script  !/bin/sh #This is a disk mailer script for hdfs     DU_RESULTS_HOME=$(sudo -u hdfs hadoop fs -du -s /user/* | sort -r -k 1 -g | awk '{ suffix="KMGT"; for(i=0; $1>1024 && i < length(suffix); i++) $1/=1024; print int($1) substr(suffix, i, 1), $3; }'| head -n 22 |awk '{ print $1"\t\t\t" $2 }')  DF_RESULTS_HOME=$(sudo -u hdfs hadoop fs -df -h /user) HOSTNAME=$(hostname -s)  MESSAGE_SUBJECT="Disk usage" MESSAGE_SENDER="xyz" MESSAGE_EMAIL="abc"  DU_RESULTS_HEADER_USER="Dir size             User"  MESSAGE_BODY="Team:  High level Disk Usage Report for: /user  Please take a moment to clean out any old data, and write temp files to an appropriate filesystem, such as /tmp.  Thanks  if [[ --debug == "$1" ]]; then     echo debug on      printf '%s\n\n\n\n%s\n\n%s\n%s\n\n\n\n\n%s\n%s\n%s' "$MESSAGE_BODY" "$DF_RESULTS_HOME" "$DU_RESULTS_HEADER_USER" "$DU_RESULTS_HOME" else                      echo debug off      printf '%s\n\n\n\n%s\n\n%s\n%s\n\n\n\n\n%s\n%s\n%s' "$MESSAGE_BODY" "$DF_RESULTS_HOME" "$DU_RESULTS_HEADER_USER" "$DU_RESULTS_HOME" | /bin/mail -s "$MESSAGE_SUBJECT" -r "$MESSAGE_SENDER" "$MESSAGE_EMAIL"                         fi

I often see tutorials online that connect various commands with different symbols. For example:  command1 |  command2 command1 &  command2 command1 || command2     command1 && command2   Others seem to be connecting commands to files:  command1  > file1 command1  >> file1   What are these things? What are they called? What do they do? Are there more of them?    .


In this program I am trying to create a user and add them to a data base which occurs in the first case of my switch statement. Second I am trying to validate that the user exists in the database. This is done in the seconds case in the switch. In my second case on my switch I am trying to validate that the user exists,but when I compare the string pulled from the data base to the one entered from the user the if statement is not passed. Any idea on how to solve this issue?  import java.sql.*; import java.util.*; public class client {  public static void main(String args[])throws SQLException {      Scanner keyboard = new Scanner(System.in);      try {         Class.forName("org.postgresql.Driver");         System.out.println("Connected");     }     catch(ClassNotFoundException e) {         System.out.println("error class not found");     }     //Connecting to the database     Connection con = DriverManager.getConnection("jdbc:postgresql://localhost:5432/postgres","postgres","????????????");     PreparedStatement st;     Statement stmt = con.createStatement();     ResultSet rs;     String user = "";     String password = "";     String cuser = "";     int num1 =0;     System.out.println("Press 1 to create account and 2 to check if account already exists: ");     num1 = keyboard.nextInt();     keyboard.nextLine();     switch(num1){     case 1:         System.out.print("Please Enter in a username: ");         user = keyboard.nextLine();         System.out.print("Please Enter in a password: ");         password = keyboard.nextLine();         user u1 = new user(user,password);         System.out.println(u1);         st = con.prepareStatement("INSERT INTO user1 VALUES(?,?)");         st.setString(1,u1.getUser());         st.setString(2,u1.getPassword());         st.executeUpdate();     case 2:         System.out.print("Please enter in Username: ");         cuser = keyboard.nextLine();         System.out.print("Please Enter in a Password: ");         String cpassword = keyboard.nextLine();         user u2 = new user(cuser,cpassword);         rs = stmt.executeQuery("SELECT username FROM user1 where username = username");         System.out.println("Selected from the table");         while(rs.next()) {             System.out.println("Entered into the loop");             String firstname = rs.getString("username");             //This is statement right here             if(u2.getUser() == firstname) {              System.out.println("The username "+ u2.getUser() +" Exists");             }         }         con.close();      } }   }

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?


In the linear model    we make the assumption that the vector of errors follows a multivariate normal distribution:   I want to test this assumption for a given data set. How can I do this? I was thinking about estimating the vector of errors by    where beta hat is the least squares estimator of beta.  And then use a test on e. Is this the right way to do this? And if so, which test should I use then.

I'm sorry if this is a broad question but can someone explain to me how to interpret these regression diagnostic plots? I understand the Normal Q-Q show's how normal the spread of the data is, but the other three I am confused by. For the Residuals vs Leverage, what does it mean for a point to be outside of the bounds? What does it mean if the red lines are parabolic and curved like in the first two? Why do we care about residuals, and what do they tell us? I've searched the web multiple times for some guide to interpret these and I can't get any straight forward answers. Any help is appreciated, thank you.


I have searched long and far for a way to have a function change a given global variable using the function's arguments and local variables inside as the "shortcut" to it. Because I can't find the right words to explain this well, I will be adding 2 scripts bellow, the first being what it looks like and the second being what it should act like.  Note: The examples given are meant to replace all matching characters/text of a location to a new value.  Example 1:  function ReplaceAll(loc,old,new_text) {     while (loc.includes(old)) {         var new1 = loc.replace(old,new_text);     }     loc = new1; }   This script [Example 1] is how I wish to set up my script yet it does not work because it only catches the value of the location and not setting the original value when changed.    Example 2:  var example = "What is? Where is? Why is? Who is?"; ReplaceAll(example,"is","was"); console.log(example);   Preferred Output: "What was? Where was? Why was? Who was?"  This script [Example 2] is the effect that I am attempting to achieve to be able to make this and other scripts of mine work.    PS: I am not trying to ask for people to do the work for me thus going against the rules of Stack Overflow, I just want to know, if possible, how this can be done.  Thank you.  ☺

The primitive types (number, string, etc.) are passed by value, but objects are unknown, because they can be both passed-by-value (in case we consider that a variable holding an object is in fact a reference to the object) and passed-by-reference (when we consider that the variable to the object holds the object itself).  Although it doesn't really matter at the end, I want to know what is the correct way to present the arguments passing conventions. Is there an excerpt from JavaScript specification, which defines what should be the semantics regarding this?