Thomson's Lamp and the possibility of supertasks

The Thomson's Lamp paradox:  A mad scientist owns a desk lamp. It begins in the toggled on position. The scientist toggles the lamp off after one minute, then on after another half-minute. After a quarter-minute the lamp is toggled off, then the scientist waits an eigth-minute and turns the lamp on again. The scientist continues toggling the lamp, waiting one-half of the previously waited time between toggles. After a total sum of two minutes of toggling, what is the state of the lamp (on or off)?  The  states that supertasks are impossible and the lamp is neither on nor off after the two minutes. This does not make sense to me, as this would mean that the lamp is in a superposition of two states.  Proof (1 is on, 0 is off):  $S = \sum \limits_{i=0}^n {(-1)^i}$  $S=1-1+1-1+1...$  $S=1-(1-1+1-1+1...)$  $S=1-S$  $S=\frac1 2$  How can a macroscopic object like a lamp exist in such a state?


How to use the Alt + right click in edit mode in Ubuntu 17.xx?

How can I use the Alt + right click shortcut in Ubuntu 17.xx and higher without installing additional software?


Disable Secure Boot to install Windows 8.1 in UEFI mode via USB stick

I'm trying to install Windows 8.1 using a USB stick from UEFI mode. I used  to format the USB stick as "GPT for UEFI".   The problem is that my PC can boot in UEFI mode only if I turn Secure Boot off. Secure boot in the BIOS is enabled and grayed out. Is there a way to boot from the USB stick in UEFI mode when Secure Boot is enabled?  Alternately, is there a way to disable secure boot?  PC:


What's to stop the Weasleys from simply creating money? Can't they create gold, silver, or bronze? Why not make muggle money and exchange it at Gringotts? Old clothes? Or just use a doubling charm when purchasing an item for infinite "new" clothes?


I am following Rob Conery MVC Storefront tutorial series and I get an Inconsistent accessibility error from the following constructor public SqlCatalogRepository(DB dataContext) :  public class SqlCatalogRepository : ICatalogRepository {     DB db;      public SqlCatalogRepository()     {         db = new DB();         //turn off change tracking         db.ObjectTrackingEnabled = false;     }       public SqlCatalogRepository(DB dataContext)     {         //override the current context         //with the one passed in         db = dataContext;     }   Here is the error message : Error   1   Inconsistent accessibility: parameter type 'SqlRepository.DB' is less accessible than method 'Data.SqlCatalogRepository.SqlCatalogRepository(SqlRepository.DB)'


Problem with installing wine through "Ubuntu Software"

I was trying to install wine through the Ubuntu software as seen in the screenshot below:    but got a error saying that it has unmet dependencies.  I am running Ubuntu 18.04 LTS on my desktop with AMD Ryzen 5 (1600), 1050ti Nvidia graphics card  what should I do to resolve this problem?


$$I=\int_{0}^{\dfrac\pi4}\log(\cos(x))\mathop{\mathrm{d}x}$$ I can solve it if the limit is from $0$ to $\frac\pi2$. How to do it? I have done like this, tried not to use any knowledge of series but just simple integration rules. $I_1=\int_{0}^{\frac{\pi}{4}} \ln(\sin x)+\ln (\cos x) dx \\ =\int_{0}^{\frac{\pi}{4}}\ln\left(\frac{\sin 2x}{2}\right) dx \\ =-\frac{\pi}{4}\ln 2 -\frac{\pi}{4}\ln 2 \\ =-\frac{\pi}{2}\ln 2$  Now ,  $I_2=\int_{0}^{\frac{\pi}{4}} \ln(\cos x)-\ln(\sin x) dx \\ =\int _{0}^{\frac{\pi}{4}} \ln(\cot x) dx \\ =-\int_{-\infty}^{0} \frac{(e^z)^2}{1+(e^z)^2} dz$  Say $$[\cot x=e^z \implies dx=-\frac{e^z}{1+(e^z)^2} dz]$$  Now from above, $$=-\int_{0}^{\infty} \frac{1}{1+(e^z)^2} dz \\ =-\int_{0}^{\infty} \frac{e^{-z}}{e^z+e^{-z}} dz \\ =-\frac{1}{2} \int_{0}^{\infty} 1-\frac{e^z-e^{-z}}{e^z+e^{-z}}dz \\ =-\frac{1}{2}\left[z-\ln (e^z+e^{-z})\right]^\infty_0 \\ =-\frac{1}{2}\ln 2$$


Deriving of formula for finding the length of median

In the below image    $AD$ is the median of $\triangle ABC$  We know that $m_A = \frac 1 2 \sqrt{2b^2 + 2c^2 - a^2} $    But can someone tell me how it's derived !! I am just unable to think of it !!   But I assume it muste be linked with the Appolonius Theorem !!


How to use WiFi and Ethernet at the same time

Brief Description:  I need my Ethernet card (en0) to see all traffic under 192.168.2.xxx.  However I also need to use WiFi card (en1) for all other traffic.  OS: OS X Lion    I am using a separate network location to deal with this specific use (since this is a for a robotics project that communicates via Ethernet). Ethernet (en0) had to be set up as a static IP (192.168.2.10) per the requirements for the device I am connecting to. All connections on the Ethernet card (en0) should be 192.168.2.xxx as specified above. WiFi (en1) is set up as DHCP to a router since their is no point in assigning it as a static for general purpose traffic. Ethernet (en0) is set up as priority over WiFi (en1).  I would also like to keep this under the network location preferences if at all possible since I do not require this feature to be on all the time.  I would really appreciate your help on this. No one I have talked to knows how to solve this.


Render Camera sees only what it wants to part 2

I created a dashboard for car model, then used it to build the instrument panel proportionately, completed the build, then clicked on Render Image and only the Dashboard was visible. what would cause this? This is what it looks after the supposed render No instrument panel even though it's there before I click on Render Image


SQL: How to get a column's values of all rows as a single value?

I am working with SQL Server 2008 R2.   This is my table:  CREATE TABLE step (    id int IDENTITY(1,1) NOT NULL PRIMARY KEY,    step_value nvarchar(max) NOT NULL )   Currently there are 197 rows in step table. I want to get all values of step_value column as a single value with a semi-colon delimiter. How can I do that?  Some sample data:  Insert Into step(step_value) Values ('a'),('b'),('c'),('d'),('<workflow name="DISCIPLINE_LETTER">'), ('   <target>MEETING_INITIAL_MEETING_LETTER</target> ')   Thanks


Finding a nontrivial normal subgroup of a group of rank 36

Let $G$ be a group such that $|G| = 2^2 \cdot 3^2$. I want to show that there exists a nontrivial normal subgroup of $G$.  My tries: By the Sylow theorem I find out that te number of $2$-Sylow subgroups is equal to 1,3 or 9. On the other side the number of $3$-Sylow subgroups is equal to $1$ or $4$. Now I don't have any ideas what to do.


Lost indian passport with Austrian schengen visa, How to continue travelling?

I lost my Indian passport with a three-month Schengen visa (Austrian) while travelling in France.   I have a new passport, but does anyone know the way in which I can continue to legally travel in the Schengen area? ( I have a passport, a copy of my visa and the police report along with my “Meldezettel”)


Should paginated content have unique meta tags?

I have a category page that leads to an additional 100 pages. For example:  www.example.com/category <- this is my category page   www.example.com/category-2.html <- this is paginated content  My question is, do I need unique meta tags for each and every page, or is there any way that my category page's meta tags can be used by all the numbered pages?


What scope does a using statement have without curly braces

I inherited the following code:      using (var dataAccessConnection = da.GetConnection()) //no opening curly brace here     using (var command = new SqlCommand(sql, dataAccessConnection.Connection))     {         command.CommandType = CommandType.Text;         using (var sqlDataReader = command.ExecuteReader(CommandBehavior.CloseConnection))         {             while (sqlDataReader.Read())             {                 rueckgabe.Add(new Myclass                                   {                                       Uid = Guid.NewGuid(),                                       ImportVersionUid = versionUid,                                       MyProperty = Convert.ToInt32(sqlDataReader["MyProperty"])                                         });                    }         }         command.Connection.Close();         dataAccessConnection.Connection.Close();     }   Looking at the code I expexted an opening curly brace after the using clause.  The code compiles  and does what it is expected to do.  The application behaves unpredictable. At some time it cant access the Database server.  Does this code make sense? Does  dataAccessConnection have the rigth scope?


I read that big bang caused all the matter to spread in the universe and it happened by a gigantic bang from a tiny ball of matter. But where was matter before it? From where did all the stuff came and contracted into a ball?


One can use the command such as \textcolor[rgb]{1.00,0.00,0.00}{boundary} to color the word "boundary" in a document.   Here is my question:  How to color the math symbols in $$? For example, can one turn $C^{2}$ into red in LaTeX?


I'm trying to implement a search widget in my app . I found a useful tutorial from .    But my app crashed.  Activity A       @Override         public boolean onCreateOptionsMenu(Menu menu) {             MenuInflater inflater = getMenuInflater();             inflater.inflate(R.menu.create_menu, menu);             // Associate searchable configuration with the SearchView             SearchManager searchManager =                     (SearchManager) getSystemService(Context.SEARCH_SERVICE);             SearchView searchView =                     (SearchView) menu.findItem(R.id.search).getActionView();             searchView.setSearchableInfo(                     searchManager.getSearchableInfo(getComponentName()));             return true;         }   @Override     public boolean onOptionsItemSelected(MenuItem item) {         // Handle action bar item clicks here. The action bar will         // automatically handle clicks on the Home/Up button, so long         // as you specify a parent activity in AndroidManifest.xml.         switch (item.getItemId()) {              case R.id.add: // create new file                 View menuItemView = findViewById(R.id.add);                 PopupMenu po = new PopupMenu(HomePage.this, menuItemView); //for drop-down menu                 po.getMenuInflater().inflate(R.menu.popup_menu, po.getMenu());                 po.setOnMenuItemClickListener(new PopupMenu.OnMenuItemClickListener() {                     public boolean onMenuItemClick(MenuItem item) {                         //  Toast.makeText(MainActivity.this, "You Clicked : " + item.getTitle(), Toast.LENGTH_SHORT).show();                         if ("Create New File".equals(item.getTitle())) {                             Intent intent = new Intent(HomePage.this, Information.class);  // go to Information class                             startActivity(intent);                          } else if ("Edit File".equals(item.getTitle())) {                             Intent intent = new Intent(HomePage.this, Edit.class);                             startActivity(intent);                         }                         return true;                     }                 });                 po.show(); //showing popup menu          }         return super.onOptionsItemSelected(item);     }   searchable in xml folder  <?xml version="1.0" encoding="utf-8"?>  <searchable xmlns:android="http://schemas.android.com/apk/res/android"     android:label="@string/app_name"     android:hint="Search by date" />   create_menu  <menu xmlns:android="http://schemas.android.com/apk/res/android"     xmlns:app="http://schemas.android.com/apk/res-auto">      <item android:id="@+id/search"         android:title="Search by date"         android:icon="@mipmap/search"         app:showAsAction="collapseActionView|ifRoom"         android:actionViewClass="android.widget.SearchView" />      <item         android:icon="@mipmap/menu"         android:id="@+id/add"         android:orderInCategory="100"         android:title="Main Menu"         app:showAsAction="always" />  </menu>   declare this in mainfest    <meta-data android:name="android.app.searchable"             android:resource="@xml/searchable" />   Error LogCat  01-18 18:31:09.298    9215-9215/com.example.project.myapplication E/AndroidRuntime﹕ FATAL EXCEPTION: main     Process: com.example.project.myapplication, PID: 9215     java.lang.NullPointerException             at com.example.project.myapplication.GUI.HomePage.onCreateOptionsMenu(HomePage.java:104)             at android.app.Activity.onCreatePanelMenu(Activity.java:2646)             at android.support.v4.app.FragmentActivity.onCreatePanelMenu(FragmentActivity.java:298)             at android.support.v7.internal.view.WindowCallbackWrapper.onCreatePanelMenu(WindowCallback   This is the line where error pointed to   searchView.setSearchableInfo(


What is the best way to handle a lot of misused tags?

So today I noticed a question that had the  tag. As the question was not about JSFiddle, and only included a link to the site, I thought somebody has just created this for the sake of it. So I decided the best action would be to remove it, and try to stop it from getting out of control.  But then I searched (clicked the tag) for other questions that used it and I was amayonaised to see over 500 questions had the very same tag! Most of which were incorrectly tagged. So I cleaned up a couple and then quickly got bored.  So I am wondering, aside from going through them all by myself, is there a more efficient way?  I think it would be a great idea if there was some feature (probably an admin feature) that allowed a new tag queue to be added to the review list. I think this could work well as follows:   Somebody brings up the problematic tag in question (e.g. Me on here) An admin reviews my concern, and decides that the tag is very misused That admin adds the tag for review in a (temporary) new review queue. All users that can review can then go through existing tags, and vote for "No action" or "Remove tag" The world becomes a slightly better place   ...or not?    By the way, I tried to add some new tags to this post but I don't have the rep. So if someone could create them for me that would be swell: "musefan", "today", "sunny-spells", "pointless-tags"


LaTeX allows me to write a matrix up to 10 columns only. But I want to write a matrix of dimension 13. Can anyone help me to write it?


If $f$ is a continuous function and $f(a + b) = f(a) + f(b)$, how do I prove that $f(x) = mx$ where $m=f(1)$?

If $ f $ is a continuous function and $ f ( a + b ) = f ( a ) + f ( b ) $, how do I prove that $ f ( x ) = m x $ for any $ x $ in real numbers, where $ m = f ( 1 ) $? I know that I have to start by showing $ f ( x ) = m x $ for any rational $ x $ and then extend that to any real number with continuity. However, I do not know how to go about it.


Does anyone know of a Module for Google Tag Manager?   I found something under development here:


Getting "out of memory" errors when around 65% used in Windows 10

Since upgrading to Windows 10, I've noticed I get out-of-memory warnings (leading to out-of-memory app crashes if I don't address it) when my actual memory usage is only around 60% according to Task Manager. It wasn't an issue at first, but after the major update they did about a month ago, it seems to be happening more frequently.  I did occasionally run out of memory on Windows 7, but only when I was actually hitting 95+ percent usage, which was quite rare.     of task manager immediately before a crash, and it's typical of what I normally see - around 60-65% usage being flagged as "out of memory" territory. Where's my other one-third gone?  Current setup is Windows 10, with 4x4GB sticks of Corsair memory for 16GB total. Any advice is appreciated.


What I want to do is simply read a input (Char/String , preferably char), its a single char and then print some outputs based on the inputs. My problems faced is that, if i convert my input 'choice' into a char, my error messages are:  Type mismatch: cannot convert from String to char Incompatible operand types char and String  any idea whats wrong? Thanks!   *If I leave it like this it just gives me "Invalid Choice"  import java.util.*;  public class P1 {      public static void main(String[] args) {          // Create a scanner         Scanner userInputScanner = new Scanner(System.in);         String choice = userInputScanner.nextLine();          System.out.println("Your choice is " + choice);          if ((choice == "A") || (choice == "a"))             System.out.println( " Action Movie Fan");               else if ((choice == "C") || (choice == "c"))                   System.out.println( " Comedy movie fan ");             else if ((choice == "D") || (choice == "d"))                   System.out.println(" Drama movie fan ");               else                   System.out.println( "Invalid choice" );       }  }


Which is greater, $98^{99} $ or $ 99^{98}$?  What is the easiest method to do this which can be explained to someone in junior school i.e.  without using log tables.  I don't think there is an elementary way to do this. The best I could find was on Quora, in an answer by Michal Forišek on a similar question , which is to consider $\frac{98^{99}}{99^{98}}=98.(\frac{98}{99})^{98}=98.(1-\frac{1}{99})^{98} \approx\ \frac{98}{e} >1$ and hence $98^{99} >  99^{98}$. But the approx sign step does use definition of $e$ in terms of limits and thus cannot be considered elementary. Any other way?    Edit- I was hoping something that does not involve calculus, that is why I tagged it in number theory, but as it seems it is almost impossible to avoid calculus when exponentials are involved.  All the answers are fine, and can be explained to students in classes above seventh or eigth. My aim for this qustion was to check with you all, if I have missed some elementary trick or not,I guess I did not. I was looking for the easiest solution someone can come up with. Thanks!


How many integral triplets ($x, y, z$) satisfy the equation $x^2 + y^2 + z^2 = 1855$?

How many integral triplets $(x, y, z)$ satisfy the equation $x^2 + y^2 + z^2 = 1855$ ?  solution:- Note that 1855 = 7 mod 8 while all perfect squares are 0, 1 or 4 mode8. So it is impossible for 3 squares to sum up to 7 mod8. So no solutions are there.  Could anyone please explain how we choose number to take mod with, on both the sides.Here for example, we took mod 8..why not, mod 4?   How we chose 8 here.


Proof of the identity: $c\sin \frac{A-B}{2} \equiv (a-b) \cos \frac{C}{2}$

Trigs is not my strongest apparently...  I need to prove  $c\sin \frac{A-B}{2} = (a-b) \cos \frac{C}{2}$ for a general triangle $ABC$.  Here is what I do, or rather, here is how I fail at proving it:  $\cos \frac{C}{2} \equiv \sin \frac{A+B}{2}$, so $\displaystyle{\frac{\sin \frac{A-B}{2}}{\sin \frac{A+B}{2}} \equiv \displaystyle{\frac{a-b}{c}}}$.   This implies: $\displaystyle{\frac{\tan \frac{A}{2}-\tan \frac{B}{2}}{\tan \frac{A}{2}+\tan \frac{B}{2}} \equiv \frac{a-b}{c}}$.   Now, imagine graphing an angle bisector from angle $A$ and then from angle $B$, the point where they intersect, let's call it $K$. From that point drop a perpendicular on $AB$, let's call that point $L$. Hence, $\tan \frac{A}{2} = \frac{KL}{AL}$ and $\tan \frac{B}{2} = \frac{KL}{LB}$. Plugging those in, gives us: $$\frac{LB-AL}{c} \equiv \frac{a-b}{c}$$ And now I have no clue how to show that $LB-AL = a-b$.  If you could let me know how to show that and/or you know a better way of proving the identity, please share.


Reason for vanishing of the covariant derivative of energy-momentum tensor of matter in general relativity

Einstein assumed in the derivation of his field equations that the covariant derivative (defined through the metric) of the energy momentum tensor of matter is zero, i.e. $$\nabla_{\mu}T^{\mu\nu}=0,$$  no matter how distorted the spacetime is.  It seems such a conclusion cannot be reached at via Nöther's theorem (since the metric is itself changing over spacetime). So my question is how did he have this insight then, and how would one justify the correctness of this assumption in retrospect from a Lagrangian point of view now?   If it's based on the existence of infinitesimal coordinate transformations that fix the boundary of some volume in spacetime, then would this also imply that the energy momentum tensor of any field will always have zero covariant derivative with or without gravity?    Edit: Previous form of the question had an abuse of language, viz., that I referred to the "vanishing of the covariant derivative of the energy-momentum tensor" as "energy momentum tensor is covariantly conserved". This was rightly pointed out by Ben Crowell in his answer and, I've edited the question and made it mathematically precise for the sake of clarity.


Approximating magnetic field at center of current loop by solenoid of 1 turn

It's well known that by application of biot-savart law, the magnetic field at the center of a loop of current is $\frac{\mu_0 I}{2r}$.  Now when we consider a solenoid, isn't the resulting magnetic field at the center inside essentially just formed from a superposition of many current loops?  The magnetic field at the center of a solenoid is $\mu_0 N I$ where N is the number of turns per unit length. If we consider the case where there is only 1 turn, however, this doesn't seem to give the same result that manual integration via biot-savart did.  Similarly, a toroid with only 1 loop should be equivalent to a current loop, but we don't get the same result then either.  Why is it wrong to find the magnetic field at the center of a current loop in this way?


Show that $(R \times R) \setminus A$ is path connected

Let $R$ be the usual topological space and $A$ be a countable subset of $R \times R$.   How to show that $(R \times R) \setminus A$ is path connected?


Did this character even qualify for being Azor Ahai or The One Who Was Promised?

In the books and to some degree in the show as well there is a prophesy about the legendary figure Azor Ahai. But in the latest Game of Thrones episode (S08E03) we see Arya      killing the Night King.   However in a  we discussed all possible candidates but nobody thought about Arya. Does she even fulfill the prophecy? If she does, how?


When will GCC be updated in 16.04 and 18.04?

The current version of supported GCC on Ubuntu 16.04.3 LTS is 5.4 version and the latest GCC version is already at 7.0. So can we expect a newer version of GCC in Ubuntu 18.04 LTS?


Using Ubuntu 10.04, is developing sites in my home folder instead of /var/www a significant security risk?

Using advice from this , (using a LAMP on Ubuntu 10.04) I have edited the  /etc/apache2/sites-available/default file and originally changed both the Document Root and Directory lines from  /var/www to /home/me/sites  in my home folder, with no sudo or root privileges.   I've always just developed my sites here in this home folder, and create multiple sites and point apache to the active one using the same settings.    Is this a notable security risk?  How could I make my development process more secure using this method?


If $0< \alpha, \beta< \pi$ and $\cos\alpha + \cos\beta-\cos (\alpha + \beta) =3/2$ then prove $\alpha = \beta= \pi/3$   How do I solve for $\alpha$ and $\beta$ when only one equation is given? By simplification I came up with something like  $$ \sin\frac{\alpha}{2} \sin\frac{\beta}{2} \cos \frac {\alpha +\beta}{2}=\frac{1}{8}. $$ I don't know if this helps. How to do this?


Best Approach to Render a PDF from External Source Without Storing File and Preventing User Download On Mobile

I am working on a requirement to display a PDF that is returned from an external application. I've written the Apex class that will authenticate and then return the PDF document in a HTTP Get response. Given these documents contain sensitive information, we do not want to store the PDF in Salesforce (e.g. create a ContentVersion or File record using the PDF). Also, if viewing from the Salesforce mobile app, we want to avoid users' being able to open the PDF in other apps or downloading them. I've started my approach of using a Lighting Web Component that will call the Apex class to return the PDF. However, I'm not sure this is a viable option to continue to pursue. I've read about the PDF.js library, as well as many examples posted online for LWC or Aura Components. Plenty of them rely on the document being stored in Salesforce, or are Aura Components instead of LWC. We are in Lightning and would need a working approach for Desktop too. Preferably, I'd be able to use the same component for both desktop and mobile, and not have to pursue different frameworks for each device type (i.e. Aura for mobile and LWC for desktop). What approach would be recommended for this? I'm not certain a Lightning Web Component is going to work. Should I double back to Aura Components? Pursue embedding a Visualforce page as PDF? I have limited time so I want to avoid building something then learning I won't be able to meet one of the requirements outlined above. This older question was answered before Lightning Web Components existed:  The answers are limited to using Aura Components. Here is an explanation which highlights differences between Aura and LWC:


So, I am trying to update Ubuntu on my external HDD, but it doesn't update, and it shows this. I tried to find something on Google, but no efficient results. This is what sudo apt-get update -y returns:


When teaching trigonometry, sometimes it is useful to represent angles greater than 360º with some kind of "spiral arc". For example:    the angle of -440º in the figure.  My question is:     How can I do this in nicely TikZ?   I can do it by using several consecutive arcs, but I wish to know if is there a more elegant solution to this.


Java change array data isn't shown in output

I'm trying to change certain index values of this boolean array to false and it does change but when re-displayed in another method it doesn't print properly.   This is for an assignment at school. I've check memory locations and they are the same.  import java.util.Scanner; import java.util.Arrays; public class Lab11avst {     public static void main(String[] args)     {         Scanner input = new Scanner(System.in);         final int MAX = 100;         boolean primes[];         primes = new boolean[MAX];         computePrimes(primes);         displayPrimes(primes);     }      public static void computePrimes(boolean list[])     {         Arrays.fill(list, true);         for (int i = 1; i < list.length ; i++)         {             if (list[i] = true)             {                 for (int j = (i+1); j < 20; j+=(i+1))                 {                     list[j] = false;                     System.out.println( j+" "+list[j]);                 }             }         }     }     public static void displayPrimes( boolean x[])     {         for(int y = 1; y< (x.length); y+=1)         {             if(x[y] =true)             {                 System.out.print(y+ " ");             }         }     } }


Use regex to replace lower case values to title Case JavaScript

I want to use regex to replace the lowercase letter of every word within a string of words, with an uppercase, ie change it to title case such that str_val="This is the best sauce ever"  becomes "This Is The Best Sauce Ever". Here is my code  function (str_val) {    let reg_exp = /\s\w/g;    let str_len = str_val.split(' ').length;     while (str_len){       str_val[x].replace(reg_exp, reg_exp.toUpperCase());       x++;       str_len--;    }    return str_val; }   How do I solve this with regex?


Get error when install Oracle JDK 8 on Ubuntu 18.04

I am trying install Oracle Java 8 on Ubuntu 18.04 LTS.  $ java --version  Command 'java' not found, but can be installed with:  sudo apt install default-jre             sudo apt install openjdk-11-jre-headless sudo apt install openjdk-8-jre-headless     According  i added ppa:  sudo add-apt-repository ppa:webupd8team/java   and after that i updated my os:  $ sudo torsocks apt-get update Hit:1 http://ppa.launchpad.net/webupd8team/java/ubuntu bionic InRelease         Ign:2 http://dl.google.com/linux/chrome/deb stable InRelease                    Hit:3 http://us.archive.ubuntu.com/ubuntu bionic InRelease                Hit:4 http://dl.google.com/linux/chrome/deb stable Release               Hit:6 http://us.archive.ubuntu.com/ubuntu bionic-updates InRelease       Hit:7 http://us.archive.ubuntu.com/ubuntu bionic-backports InRelease Hit:8 http://us.archive.ubuntu.com/ubuntu bionic-security InRelease Reading package lists... Done   and then I ran:  sudo apt-get install oracle-java8-installer   But I got :  $ sudo torsocks apt-get install oracle-java8-installer Reading package lists... Done Building dependency tree        Reading state information... Done Package oracle-java8-installer is not available, but is referred to by another package. This may mean that the package is missing, has been obsoleted, or is only available from another source  E: Package 'oracle-java8-installer' has no installation candidate   I found this  but it is not working and I got same error


The Cycles render engine can render both on the CPU and the GPU. I often render over-night so I do not need my computer to be responsive.  Is it possible to render with Cycles using both the CPU and GPU? If not, are there any other workarounds that maximize the hardware's potential?       This question here:  focused on single frames optimisation.


Getting MTP enabled devices to work with Ubuntu?

Since Ubuntu 13.04 storage access to external devices via MTP is supposed to work out of the box via a GVFS-MTP module.      While this question is about the Galaxy Nexus, other Android devices as well as Windows Phones and MTP enabled media players are also supported.      For troubleshooting see .     I am having quite a bit of problems getting file-transfers working over MTP with the Galaxy Nexus. I am using Kubuntu 11.10 64-bit, and this is what I have done and the results I get:   Added rule for device in /etc/udev/rules.d/51-android.rules. The rule is the following and works for adb:  SUBSYSTEMS=="usb", ATTRS{idVendor}=="04e8", ATTRS{idProduct}=="6860", MODE="0666", OWNER="leob" #Galaxy Nexus  Restarted udev (and computer just to make sure).   Adb works, and all methods for reading from the device via MTP seems to work (I have tried mounting with mtpfs, gmtp and using the mtp-tools package directly). When I try to write to the device however, nothing I have tried works.  As an example, running mtp-newfolder test_dir 0 0 gives the following output:  libmtp version: 1.1.0 Device 0 (VID=04e8 and PID=6860) is a Samsung GT-P7510/Galaxy Tab 10.1. Folder creation failed. ERROR: Could not close session!   If I run mtp-folders after a failed mtp-newfolder without re-plugging the device, I get the following output:  Attempting to connect device(s) Device 0 (VID=04e8 and PID=6860) is a Samsung GT-P7510/Galaxy Tab 10.1. PTP_ERROR_IO: failed to open session, trying again after resetting USB interface LIBMTP libusb: Attempt to reset device mtp-folders: Successfully connected Friendly name: (NULL) Error 1: Get Storage information failed. Error 2: PTP Layer error 02fe: get_all_metadata_fast(): could not get proplist of all    objects. Error 2: (Look this up in ptp.h for an explanation.) Error 2: PTP Layer error 02fe: get_handles_recursively(): could not get object handles. Error 2: (Look this up in ptp.h for an explanation.) LIBMTP_Get_Storage() : Resource temporarily unavailable OK.   Accompanied by the following in dmesg:  [ 1000.912082] usb 2-4: reset high speed USB device number 7 using ehci_hcd [ 1001.045877] usb 2-4: usbfs: process 3166 (mtp-folders) did not claim interface 0 before use   Does anyone have any idea about what to do?  EDIT:  I also tried the PTP mode. Again, reading works fine, but I cannot write anything to the device.


I wonder about the foundations of set theory and my question can be stated in some related forms:   If we base Zermelo–Fraenkel set theory on first order logic, does that mean first order logic is not allowed to contain the notion of sets? The axioms of Zermelo–Fraenkel set theory seem to already expect the notion of a set to be defined. Is there are pre-definition of what we are dealing with? And where? In set theory, if a function is defined as a set using tuples, why or how does first order logic and the axioms of Zermelo–Fraenkel set theory contain parameter dependend properties $\psi(u_1,u_2,q,...)$, which basically are functions?


Find which session is holding which temporary table

We have a SQL Server 2005 database the temp database has become full. By going into SQL Server Management Studio I can see all the temporary tables in the tempdb. Is it possible to tell which session is holding which temp table? Ideally a query which would list temp tables used by each session.  Thanks,


non-parametric tests for repeated observations

I am looking for an RM-ANOVA alternative that fits with non-normal data that may not satisfy sphericity assumption. My dataset: Through a mark and recapture study, I trapped turtles, and collected fecal seed samples from these turtles (number of seeds present in per fecal sample varied between 0-~1500-- with most fecal samples having no seeds). About 20% of the fecal seed samples I have are from recaptured (same turtle captured more than ones on different instances) turtles-- therefore, my fecal seed samples are not necessarily independent samples.  I need to figure out a statistical tests to see (1) whether no-seed fecal samples were significantly greater than seed-containing fecal samples AND (2) identify predictor variables (contagious and discrete variables-- such as turtle body wt, sex, sampling location) that influence number of seeds present in fecal samples.  Had this been a case of independent observations, for my question 1, a chi-squared test of a Wilcoxon rank sum test (M-W type) would've worked easily. for question 2, a permutation ANOVA or a variations of GLMs could have been used. But, in this case, the samples are not really independent. Tests such as McNemar's are for before-after comparisons, Friedman does not work either as not all of my samples are repeated. So, what would be the best test to use?


Using Selenium webdriver with chrome browser - Junit or java - how to upload a file from desktop(or any folder in pc) to application

Using Selenium webdriver with chrome browser for automation - Junit or java programming - how to upload a file from desktop(or any folder in pc) to application


I have a 17" Macbook Pro from late 2011 and recently it's been shutting down randomly, but almost always when I try to move the machine. Nowadays it's happening once every few hours and it makes it very hard to use the machine.   Model Name: MacBook Pro  Model Identifier: MacBookPro8,3  Processor Name: Intel Core i7  Processor Speed: 2.4 GHz  Number of Processors: 1  Total Number of Cores: 4  L2 Cache (per Core): 256 KB  L3 Cache: 6 MB  Memory: 4 GB   I'm hoping people can tell me what to do. I have AppleCare till March 19th, 2015


How to access form methods and controls from a class in C#?

I'm working on a C# program, and right now I have one Form and a couple of classes. I would like to be able to access some of the Form controls (such as a TextBox) from my class. When I try to change the text in the TextBox from my class I get the following error:     An object reference is required for the non-static field, method, or property 'Project.Form1.txtLog'      How can I access methods and controls that are in Form1.cs from one of my classes?


The roots of the equation $z^n=(1+z)^n$...

The complex roots of the equation      $$z^{n}=(1+z)^{n}$$   $A.$ are vertices of a regular polygon  $B.$ lie on a circle  $C.$ are collinear  $D.$ none of these  Don't know where to start.. Please help.!  NOTE:  $z$ is a complex number.


Can I equate the solutions $\arcsin\frac{x^2+y^2-a^2/2}{a^2/2}=2\arctan\frac{y}{x}+C$ to $\arcsin\frac{\sqrt{x^2+y^2}}{a}=\arctan\frac{y}{x}+C$

$$ \frac{xdx+ydy}{xdy-ydx}=\sqrt{\frac{a^2-x^2-y^2}{x^2+y^2}} $$   This is asked many times and attmpted to solve particularly at  by @Simon S by seting $u=x^2+y^2$ and $v=\dfrac{y}{x}$ $$ LHS=\frac{du}{2x^2dv}=\frac{du}{2dv}.\frac{1+v^2}{u}\\ RHS=\sqrt{\frac{a^2-u}{u}}\\ \frac{du}{2dv}.\frac{1+v^2}{u}=\sqrt{\frac{a^2-u}{u}}\implies\boxed{\int\frac{du}{\sqrt{u(a^2-u)}}=\int\frac{du}{\sqrt{-[u^2-a^2u}]}=2\int\frac{dv}{1+v^2}}\\ \int\frac{du}{\sqrt{-[u^2-2\frac{a^2}{2}u+\frac{a^4}{4}-\frac{a^4}{4}]}}=\int\frac{du}{\sqrt{\Big(\dfrac{a^2}{2}\Big)^2-\Big(u-\dfrac{a^2}{2}\Big)^2}}=2\int\frac{dv}{1+v^2}\\ \implies \sin^{-1}\bigg[\frac{u-\dfrac{a^2}{2}}{\dfrac{a^2}{2}}\bigg]=2\tan^{-1}v+C\\ \color{red}{\sin^{-1}\bigg[\frac{x^2+y^2-\dfrac{a^2}{2}}{\dfrac{a^2}{2}}\bigg]=2\tan^{-1}\frac{y}{x}+C}\\ $$  But my reference and the post that I mentioned give the solution $\sqrt{x^2+y^2}=a\sin\Big[C+\tan^{-1}\frac{y}{x}\Big]\implies\color{red}{\sin^{-1}\frac{\sqrt{x^2+y^2}}{a}=\tan^{-1}\frac{y}{x}+C}$, so are both the same or am I missing something here ?  Note: This isn't about exactly how to solve the differential equation, which is what is asked in the mentioned post(already specified by me in the first place), I am having trouble equating the form of solution given there, kindly look into it before marking it duplicate.


UTF-8 wont work when PHP read from mysql

I have an code which read from mysql and if I use special characters i get back this �, I am using UTF-8 on PHP file and on MYSQL. If I change PHP file to UTF-8 wihtout BOM it shows me but it wont show special characters from html in this PHP.  This is a problem which has to be solved and i tryed many solutions none wont work. (I'm using mysqli)  $sql1 = " SELECT * FROM news ORDER BY id DESC ";  if ($result1 = $mysqli->query($sql1)) { while($row = mysqli_fetch_array($result1)) { echo "
 {$row['name']}
"; echo "{$row['text']}
"; echo " {$row['date']}
"; }   }


In this sentence :     It was a dream come true .   What's the grammatical rule used here ?  Is this sentence structure common ? If so , could you please give me an example ?


Java - NullPointerException with graphics

I was trying to draw a simple rectangular on a JFrame but when I tried to draw it it gave me a NullPointerException. I could not find the problem because it is one of my codes that I already used. The object that is Null is a Graphics object that I got from the super class. Can someone help me with this?  Error:  Exception in thread "Thread-2" java.lang.NullPointerException at com.daansander.game.Game.render(Game.java:83) at com.daansander.game.Game.run(Game.java:76) at java.lang.Thread.run(Thread.java:745)   Full Code:  package com.daansander.game;   import javax.swing.*; import java.awt.*; import java.awt.image.BufferStrategy;  /**  * Created by Daan on 12-9-2015.  */ public class Game extends Canvas implements Runnable {      public static final int WIDTH = 500;     public static final int HEIGHT = WIDTH / 12 * 9;     public static final int SCALE = 2;     public static final String NAME = "2DGame";      private JFrame frame;     private volatile boolean running;      public Game() {         setMinimumSize(new Dimension(WIDTH * SCALE, HEIGHT * SCALE));         setMaximumSize(new Dimension(WIDTH * SCALE, HEIGHT * SCALE));         setPreferredSize(new Dimension(WIDTH * SCALE, HEIGHT * SCALE));          frame = new JFrame(NAME);          frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);         frame.setLayout(new BorderLayout());          frame.add(this, BorderLayout.CENTER);         frame.pack();          frame.setResizable(false);         frame.setLocationRelativeTo(null);         frame.setVisible(true);      }      public static void main(String[] args) {         new Game().start();     }      public synchronized void start() {         running = true;         new Thread(this).start();     }      public synchronized void stop() {     }      @Override     public void run() {         long lastTime = System.currentTimeMillis();         long current;         long delta = 0;          int frames = 0; //        int ticks = 0;          while (running) {             current = System.currentTimeMillis();             delta += current - lastTime;             lastTime = current;             frames++;              if (delta > 1000) {                 delta -= 1000;                 System.out.println("FRAMES " + frames);                 frames = 0;              }              try {                 Thread.sleep(2);             } catch (InterruptedException e) {                 e.printStackTrace();             }              render();         }     }      public void render() {         BufferStrategy bs = getBufferStrategy();          Graphics g = bs.getDrawGraphics(); // <----- Line of error  //        g.setColor(Color.black); //        g.drawRect(0, 0, 5, 5); // //        g.dispose(); //        bs.show();     }      public void tick() {      }      public void init() {      } }


Given distances from two locations how to accurately find geographic coordinates

I am working on a research problem which requires me to calculate a geographic location accurately (with error distance of few meters), given distances from two geographic locations. For instance:     Since the points are static I know their location already. Flipping of the triangle is avoided by adding one more known location. I have calculated the distances using great circle distance formulae.  double theta = lon1 - lon2; double dist = Math.sin(deg2rad(lat1)) * Math.sin(deg2rad(lat2))              + Math.cos(deg2rad(lat1)) * Math.cos(deg2rad(lat2)) * Math.cos(deg2rad(theta)); dist = Math.acos(dist); dist = rad2deg(dist); dist = dist * 60 * 1.1515; // in miles   How to find the coordinates of C?  The correct answer is 39.98, -83.03, but I am getting 8 miles off the track. Am I doing anything wrong?


What are some tools available for drawing good figures for computer science research papers and presentations

What are good choices to create figures in computer science research papers? Not talking about graphs here, just block diagrams and simple illustrations. For example, what is the tool that can be used to produce this figure?


Prove that if $f(1) = 0$, then $f(xy) = f(x) + f(y)$ for all $x, y > 0$.

Suppose that $f$ is a function such that $f'(x) = \frac{1}{x}$ for all    $x > 0$. Prove that if $f(1) = 0$, then $f(xy) = f(x) + f(y)$ for all    $x, y > 0$   I've tried applying the Mean Value Theorem, such that $f'(x) = \frac {f(b) - f(a)}{b - a} = \frac {1}{x}$, where $y = f(x)$ if continuous on $[a,b]$ and differentiable on $(a,b)$ such that there exists at least one point $c ∈ (a,b)$.   I'm probably wrong, but i don't know how do i really approach this question and what they are really asking for (e.g. $f(xy) = f(x) + f(y)$)


How can I even out a set of uneven vertices to form a vertical surface?

Hey so I'm a Blender newbie who figured out that somewhere during my modelling, I got some parts uneven as seen on this picture from the side:    .  That vertical part is supposed to be 90 degrees straight. It consists of several vertices. **How can I straighten out these vertices to form a shape parallel to the z axis, completely vertical?


I have tried on many different browsers and computers to format my SO questions, but they always end up showing up as unformatted paragraph text, and someone else formats them. I indent by text four spaces for code, but it does not work. Original edit screenshot:   Source of edit:


Linux equivalents of Windows / DOS terms

I am trying to adjust to Linux terms after many years of DOS and Windows. I have been wanting to switch from Windows to Linux for years now, but couldn't decide on a flavor. Today I got fed up with Windows 7 and just picked one--Ubuntu.  I know Linux has different terms and the file system is a little different. Right now I am trying to find the Linux equivalent of the root directory. My external drives all have their proper names, but the C: drive's name apparently was changed. I would like to change it back, if possible.  Is there a glossary or something that can be used?


I have some text in my document in primary font what is in LaTeX but I would like to get some text in font Times New Roman but just some text between primary text, as a local command (something as \textit{}, \textbf{} etc.), an example below.  My cat has black skin. % in primary font My second cat has white skin. % I would like to get in Times New Roman  Thanks for help.


What sanitization should be done to form inputs before inserting them into a database?

What sanitisation should be done to form inputs before inserting into a MySQL database?  I have just 2 user-entered inputs in my PHP web application which will be sent to a series of successive pages (both via GET and via POST), before they are eventually stored into a MySQL database.  Both are text inputs (e.g., <input type="text />").  The first is a field which should be filled by a Google maps api javascript, but which I nevertheless obviously can't trust; the second is a freely entered username field, which at the moment only has a restriction on the string length.  What server-side checks or transformations should I perform on the values of these two fields before inserting them into the database, to prevent malicious actions, or other errors perhaps with special characters?  I am using PDO prepared statements for all my database operations, like:  $id = '1234567'; $username = 'John Smith'; //Could be weird characters like "Seán Óg Ó hAilpín"! $Query = $db->prepare("INSERT INTO `MyTable` (`id`, `username`) VALUES (?,?)"); $Query->execute(array($id, $username));   If the values should be encoded or transformed, how should they be unencoded before displaying in HTML?  (All my other form variables are the result of choices from drop-down select menus, and I thought of validating & sanitising their values by simply exiting the receiving script if any of them was not (!===) any of the limited number of variables I am expecting.  I'm hoping this 'whitelisting' method would be sufficient for those.)


Instantiate DateTime with localized time

I'm trying to migrate some data from MySQL DateTime format. Here's one:  $old_date = "2019-05-06 08:00:00" My content type has a custom field using DateTime.   Using the info from SO links below, I can do this:  $date_object = DateTime::createFromFormat("Y-m-d H:i:s", $old_date);  which gives me a lovely object in my current timezone.  date: 2019-05-06 09:00:00.0 US/Central (-05:00)  MySQL is looking for a string in the UTC format. When I attempt to format this new object, it dutifully returns   $date_object->format(DATETIME_DATETIME_STORAGE_FORMAT); "2019-05-06T08:00:00"  But this is not helpful. Using the Drupal 8.7 admin interface, when I enter the date and time values, I see in MySQL table when I save the node, that I get:  2019-06-06T03:00:00  So, apparently Drupal Entity has a handler to automatically instantiate a localized DateTime value in MySQL that is UTC friendly. I ask because I haven't found what this method might be and I have not found it in DrupalDateTime or related classes. Happy to be shown what I've overlooked. Or how to discern how Entity handles all of these functions that I can use in my custom modules.   Or should I do the math for each of these strings and hope I get the correct timezone differential depending on the time of the year?


What is best way to mention that a document has been typeset with TeX?

Is there any common way to mention that a document has been typeset by TeX? So non-TeXnicians (TeXperts) may become a little familiar with the TeX world.  Update: It would be nice if one hero make a package that insert such information in a beauty and concise manner in a given language, so even lazy TeXnicians will credit TeX . For example:  ... \usepackage{colophon} ... \colophon[language=fa,packages=bibtex,xepersian] ...


How does the uncertainty product $\Delta x \Delta p$ behave for the bound states of the triangular potential?

As has been , if you take an unbounded potential $V(x)$ (so that all the eigenstates are bound) and you look at the uncertainty product $\Delta x\Delta p$ as a function of the index $n$ of the eigenstate, then for the two usual unbounded potentials (the simple harmonic oscillator and the infinite square well) $\Delta x\Delta p$ grows linearly with $n$.  How does this product behave for other solvable potentials, such as the linear cone potential $V(x)=|x|$?


Show that the set of algebraic numbers is countable

Is this proof correct to show that the set of algebraic numbers is countable?  Show as a lemma that the infinite disjoint union of countable sets is countable show that $\mathbb{Q}[t]_{deg \leq n}$ is countable $\forall$ n  As $\mathbb{Q}[t] = \bigcup_{i=0}^{\infty} \mathbb{Q}[t]_{deg \leq i}$ , $\mathbb{Q}[t]$ is countable by the lemma.  Show that $$E = \bigsqcup_{p_i \in \mathbb{Q}[t] \backslash \{0\}}^{\infty} A_i $$  . With $A_i , i \in \{0,...,n\}$ the set of roots of the polynomial $p$  is countable  (E is a disjoint union)  Conclude by saying that is the $A_i$ are disjoint, we are done and if they aren't, you can rewrite them as $A'_i$ that form a disjoint union equal to the union of $A_i$  Thank you!


Why does this code:  class A {     public:          explicit A(int x) {} };  class B: public A { };  int main(void) {     B *b = new B(5);     delete b; }   Result in these errors:   main.cpp: In function ‘int main()’: main.cpp:13: error: no matching function for call to ‘B::B(int)’ main.cpp:8: note: candidates are: B::B() main.cpp:8: note:                 B::B(const B&)   Shouldn't B inherit A's constructor?  (this is using gcc)


How to output a specific paragraph based on a pattern?

I have a sample file below:  # This is a test file. This is a test file. This is a test file   This is a test file. This is a test file. This is a test file.   This is a test file.  # Need to output just this paragraph.Need to output just this paragraph.   Need to output just this paragraph TOO. Need to output just this paragraph.   Need to output just this paragraph.   I need to output just the second paragraph starting from "#" till the last sentence in the paragraph.   How do I grep and output based on the pattern? Say if the file has more paragraphs, and I would like to output the paragraph which contains the word "TOO".


Understanding reference counting with Cocoa and Objective-C

I'm just beginning to have a look at Objective-C and Cocoa with a view to playing with the iPhone SDK. I'm reasonably comfortable with C's malloc and free concept, but Cocoa's references counting scheme has me rather confused. I'm told it's very elegant once you understand it, but I'm just not over the hump yet.  How do release, retain and autorelease work and what are the conventions about their use?  (Or failing that, what did you read which helped you get it?)


Keeping rotation values within a range of 0 to 360°

How can I keep the rotation values within a range of 0 to 360° no matter how many times I actually rotated an object? I need this as a value for a driver variable.  For example 945° => 225°.


At the end of Ex Machina Caleb is left imprisoned in Nathan's isolated villa and, without any possibility to call outside, he is doomed to death. Ava decides to do so, deliberatingly causing Caleb to die, despite he helped her to escape and he is in love with her. Why?


Flying to Germany from another country where the visa has been issued

I got my Schengen Visa for Germany in Australia, and I’m planing to visit in February. Is it going to be a problem if I fly to Germany from a country other than Australia?   I’m planing to visit my home country (Iran) and fly to Germany from there.


Comet comes into Earth's orbit and the inside gives access to multiple parallel Earths

I am looking for the title of a book telling the story: an object which at first seems to be a comet comes into orbit of Earth. It turns out to be a tube? that is a fixed size but inside it is endless. It gives access to multiple parallel Earths.     The title was one word (like "eos" => not). I read this book in the early 90s. I'm not sure if I read it in English or Dutch but I think the original language was English.


Is eliminating debt smart when considering a home purchase?

I'm entering into the latter half of my twenties, and I'm now faced with a question I've seen a few times before on this site: should I pay off my student loans or use the money as a down payment for a house?  The reason I'm asking instead of using the answers to those questions is that none of those questions have directly looked into the "opportunity cost" (caused by mortgage rate changes) of not purchasing a home. My student loans are on the order of 20K @ 5.5%. I already overpay them each month. I'm looking into purchasing a house around 200K - 300K. Paying my loans off early would save me a few thousand dollars over the loan's lifetime (8-10 years). However, even a minor fluctuation in interest rates would cause the "cost" of a home to go up tens of thousand of dollars or more over its lifetime. Assume I have enough cash currently to either make a 20% down payment on a home or pay off my student loans.  To me this seems like a simple decision (buy the house while interest rates are low, saving more money in the long run), but it seems to fly in the face of the nearly-ubiquitous advice of "get rid of debt first", so I'm wondering if I'm missing anything.  I've heard it said many times that you shouldn't view your home as a money-generating asset, but for the purposes of this question I am looking at purely the financial considerations.  Financial assumptions I have that may be wrong:   Freeing up the "cash flow" of not having a student loan payment each     month would make owning a home easier (there are a lot of "hidden     costs") When interest rates rise, so will the interest rate of other     investments (thus decreasing the "opportunity cost" of not buying a     house with low rates) Purchasing a home with less than a 20% down     payment (incurring PMI) is such a bad financial decision it is not     even on the table I understand that interest rates aren't guaranteed     to go up or down, but given the historical lows they are currently     experiencing, I personally expect them to rise over the next few     years.


$f:\mathbb{R}^n \to \mathbb{R}$ has expansion $\sum_i g_i(x)x^i$

Problem 2-35 on page 34 of Spivak's Calculus on Manifolds states      If $f: \mathbb{R}^n: \to \mathbb{R}$ is differentiable and $f(0) =0$,   prove that there exist $g_i: \mathbb{R}^n \to \mathbb{R}$ such that   $f(x) = \sum_{i=1}^n x^ig_i(x)$.       Hint: if $h_x(t) = f(tx)$, then $f(x)  = \int_0^1 h_x'(t)$.   I understand the answer he wants, but hasn't he left out a hypothesis that would ensure $h_x'(t)$ is integrable? (For instance the continuity of $df$.)   Secondly, I'm wondering if this theorem is used anywhere. Perhaps in differential geometry it might be useful to write locally $f \in C^\infty (M)$ as $\sum_i g_i(x) x_i$ for some coordinates $x_i$.


How to differentiate many lines in a chart?

I create a chart with many (actually 10) lines in different colors (see example). I want to make it as easy as possible to differentiate the different lines.    Some possibilities I have in mind:   Take most different colors Avoid light colors (e.g. yellow - on prints the line are hard to see) Use patterns (dashed, dotted, different dash pattern)  Use different thickness (I don't believe this is a good idea)   Are there best practices, rules or guides for this task?  My example code:  \documentclass[border=5mm] {standalone} \usepackage{pgfplots, pgfplotstable} \begin{document} \pgfplotstableread[col sep=&, header=true]{ description&A&B&C&D&E&F&G&H&I&K 2009&46&0&33&3&0&74&3&7&2&7 2010&35&0&22&1&0&90&2&5&3&3 2011&38&0&33&3&1&77&1&9&2&8 2012&25&0&15&0&4&55&4&5&0&1 2013&18&0&8&0&0&46&5&4&0&3 2014&37&0&54&1&3&54&5&12&10&2 2015&29&0&63&8&1&77&0&8&7&5 }\datatableentry \begin{tikzpicture} \begin{axis}[   title={My Chart},   enlarge y limits ={value=0.2,upper},   xtick=data,   xticklabels ={2009,2010,2011,2012,2013,2014,2015},     x tick label style={rotate=-45,anchor=west,font=\tiny},   legend style={font=\tiny,legend pos=north west,legend cell align=left}, ] \addlegendentry{A}; \addplot [color=blue] table [y=A, x expr=\coordindex] {\datatableentry}; \addlegendentry{B}; \addplot [color=cyan] table [y=B, x expr=\coordindex] {\datatableentry}; \addlegendentry{C}; \addplot [color=gray] table [y=C, x expr=\coordindex] {\datatableentry}; \addlegendentry{D}; \addplot [color=yellow] table [y=D, x expr=\coordindex] {\datatableentry}; \addlegendentry{E}; \addplot [color=green] table [y=E, x expr=\coordindex] {\datatableentry}; \addlegendentry{F}; \addplot [color=lime] table [y=F, x expr=\coordindex] {\datatableentry}; \addlegendentry{G}; \addplot [color=black,loosely dashed] table [y=G, x expr=\coordindex] {\datatableentry}; \addlegendentry{H}; \addplot [color=red,densely dashed] table [y=H, x expr=\coordindex] {\datatableentry}; \addlegendentry{I}; \addplot [color=blue,dotted] table [y=I, x expr=\coordindex] {\datatableentry}; \addlegendentry{K}; \addplot [color=cyan,dashed] table [y=K, x expr=\coordindex] {\datatableentry}; \end{axis} \end{tikzpicture} \end{document}   Disclaimer: I'm not sure if this question belongs to . The main problem is a design question, but the solution is needed in Tikz.


Where is the focal point of a concave spherical mirror

As I read in a book  I am a little bit confused. I drawn a concave spherical mirror and here is what I have drawn by Geogebra  As you can see, the angle DAC = angle ADC ( both equal to the incident angle because the normal line AD go through A). Similarly, angle AEC = angle CAE. I induced that CA = CD = CE. However, this is impossible because C is not the center of the mirror ( A is ) If I move the focal to the center of the mirror, and the point we call " center of curvature" to the B point in the following picture, I got a reasonable picture:  Could someone please explain why did I wrong, thank you!


Can an MDM system (e.g. GOOD) report on iOS app usage?

If a company uses an MDM system (like GOOD or MobileIron) to deploy apps to their iPads and iPhones does iOS provide the MDM system data about when the app is used, so it will show up in their usage reports?


Failed to login:invalid session (try restarting your game) And logs me out

My Minecraft has been doing this for a good couple weeks now. I have been completely unable to join any servers and it's really frustrating. I log into my account through the launcher and run mc. I try to join a server and it says "Failed to login:invalid session (try restarting your game)" But when I close mc and open the launcher, it makes me log in again. When I try and log in, it says my password is incorrect. I have changed it an immeasurable amount of times, and I know what it is. Once I finally get logged in again, it just does the same exact thing. I haven't been able to play Minecraft for so long and it just sucks. I have tried using different versions, changing my security questions, logging out of other accounts in my launcher, updating Java, deleting and redownloading Minecraft completely, and restarting my computer many times. I've scoured the internet looking for any resolution, but have yet to find anything to fix the issue. I'd really appreciate any help you guys can offer.


[December 28, 2018]  I've been experiencing delays using the caps lock key. As you can see in the title, uppercase letters appear consecutively (CAps) even though I pressed the caps lock key (C - caps lock  - A) before I press another letter.  In order to achieve proper capitalization I need to stop typing for a second whenever I press the caps lock which messes with my typing rhythm. The slow keys is off in Universal Access. This problem doesn't exist in Windows. I'm new to Ubuntu and I'm trying to give it a chance but this problem is bugging me for a while now. Any help regarding this matter will be greatly appreciated. The version of my Ubuntu is Ubuntu 18.04.1 LTS.  To illustrate the problem (pressing caps lock alternately):  Windows - AaAaAaAa  Ubuntu - AAAAAAAA    [December 29, 2018]  Is there any other way to fix this problem rather than switching to Shift key. I'm used to caps lock key and I have a good reason why I can't just switch to Shift. I also tried using different keyboards, 2 local brand and 2 international brand (I have 3 spare keyboards = 4 keyboards in total) and the problem is still present. If there is no other fix to this problem then I have no choice but to replace Caps lock with Shift which is disappointing and will cause delay to my workflow.


Carry on cheese grater on domestic U.S. flight?

Will I be permitted to pack a cheese grater in my carry-on bag for a domestic U.S. flight, or will this be considered a "potential weapon" and prohibited?


Non-trivial cyclic group with unique generator

Let $G$ be a non-trivial cyclic group with an unique generator. Show that $G$ has exactly two elements.   Let $g$ be a generator of $G$. My first idea to approach the problem was to show that if $|G|=n > 2$ then there is an integer $k$ between 1 and $n$ such that $\langle g^k \rangle = G$ or, equivalently, $g \in \langle g^k \rangle$. My second idea was to analyse the problem in 2 separate cases. For the first one, if $n$ is prime, let $k$ be a positive integer then, by Lagrange's Theorem, $|g^k| \mid n$ and, therefore, $\langle g^k \rangle = n$. Hence, we must conclude that, if $n > 2$ the generator cannot be unique. For the second case, where $n$ is composite, I was hoping to get to a contradiction, but could not advance any further. Is there a way to develop either of these ideas or is it necessary a new approach?


I would like to animate a jet of smoke as in  (from the movie Interstellar). Here's a short preview:    Note the important elements are:   The smoke is translucent The smoke is very fast at the exhaust The smoke is turbulent and its "radius" increases away from the source, becoming more turbulent The smoke has quite a well defined "contour" - it is not washed out, but ends abruptly in sort of sharp turbulent blades towards the end   I would also like to be able to toggle the jet on and off via a parameter that can be keyframed, simulating the jet firing/shutting off.  So far, I can get a washed out (4 not satisfied) and fairly uniform (3 not satisfied) jet of smoke using pretty much the default Quick Smoke properties together with a particle system flow source. However, I am unable to get the rich turbulent texture of the smoke in the above video. I also do not know how to turn the smoke on/off efficiently such that when it is "off", render time is fast (I don't want to just set the material to nothing, because the physics simulation will then still take up a lot of time).


In Windows XP, I see that there are many copies of a process called scvhost.exe, some running as local services, some other as network services and yet some other owned by the system. One of this copies is using up to 50% of the processor (I'm using Windows XP as a Guest OS in VirtualBox with two cores, Host OS is Debian 7), and every time it runs starts throwing high temp alerts. To stop the warnings, I frequently kill the process, and the problem goes away.  So, my questions are:   What is this svchost.exe process? Why are there so many copies running? Is it a good idea to kill the process? (Windows seems to work just normally with or without that "cpu-hungry" svchost.exe process running) Can I, somehow, tweak the configuration to stop this "rogue" copy of the process?   I will appreciate any help.


Speed of sound faster in less dense air?

First, it is observed that sound travels faster in denser mediums, therefore a sound wave will travel the fastest through solids. But again it is observed that because hot air is less dense sound passes through it faster than in cold air? It is totally opposite of the first case, how?


why the calss member n of B have different value , when destructor of class A is virtual or non virtual?

#include <iostream> using namesapce std; class A {   public:          virtual ~A(){cout<<"delete A"<<endl}; }; class B: public A {   public:          B(int n):n(n){}          void show(){cout<<n<<endl;}          ~B(){cout<<"delete B"<<endl;}   private:          int n;  } int main() {    A *pa;    B *pb = new B(1);    pa = pb;    delete pa;    pb->show();    return 0; }   when destructor of calss A is virtual ~A(){...},the output of program:     delete B   delete A   1  when destructor of class A is ~A(){...}, the output of progarm:     delete A    0  why the value of n is different, when destructor of class A is virtual or non virtual?  when call destructor of B to destroy object, why the calss member n is still existent?


How do I enqueue a js file in functions.php for a if lt IE 9 statement?

I'm coding a theme that uses the Twitter Bootstrap 3 files and in the header I want to include:  <!--[if lt IE 9]>  <script src="<?php echo get_stylesheet_directory_uri(); ?>/js/html5shiv.js"></script>   <script src="<?php echo get_stylesheet_directory_uri(); ?>/js/respond.min.js"></script> <![endif]-->   I've been told by a theme reviewer that I can't put it in the header file (only one js is allowed).     Required: Theme can include only one JS within header.php, please enqueue the additional > respond.min.js using the hook wp_enqueue_scripts in functions.php    as it is I have to enqueue it, but I don't know how to do this in a way that put's it in the "if it IE 9" statement.  Please could someone help me? Thanks


Can I install any iOS version I wish by picking and choosing which firmware to restore?

I'm trying to downgrade my iPhone from the current iOS to an older one, as per .  But every time I try, I always receive this error:     The iPhone could not be restored. This device isn't eligible for the requested build.     I have tried many times with and without DFU mode. Any ideas regarding this?


Calculating a matrix element, $\langle x|p\rangle$?

I've often just assumed   $$\langle x|p\rangle = \frac{1}{(2\pi\hbar)^{1/2}}e^{ipx/\hbar}$$  Is there a formal way to prove this?  My guess is that, since $\langle x|x'\rangle = \delta(x'-x)$, and a summation of wavepackets is essentially a delta function, we can prove the result starting from the definition of the delta function.


How to deal with very large transaction logs in SQL Server

Here is my situation: I have being asked to deal with a SQL Server 2008 R2 database that has a transaction log that is several times bigger than the database itself. The database is in full recovery mode and the transaction log has never been backed up.   I intend to run the transaction log backup every 15 minutes but I am afraid that the first backup may take a very very long time (hundreds of GBs of data).   What is the right course of action here?   I'm a developer by training and not a DBA so I would appreciate a more detailed answer. Thanks in advance.


How to use Python 3 to extract text between certain html tags?

I am trying to scrape a web page containing the names of companies. The names are between  tags. The format is:  <option value="15589" id="optExhibitor15589" title="N571  Company One, Inc">N571 Company One, Inc</option> <option value="16441" id="optExhibitor16441" title="N873  Company Two">Company Two</option> <option value="14863" id="optExhibitor14863" title="N219  Company Three">N219 Company Three</option>   I've tried breaking the file into a list of lines using .readline() but I cannot figure out how to extract the text between thetitle= and ">.  I have hundreds of these names I want to extract and I want to produce a list of the company names.


I want to install latest version of chromium in my Ubuntu desktop 12.04. Please guide me How to install latest version of chromium via ppa repository.


UK visa rejected. No salary deposited in bank account

I want to travel to UK. I have Thailand passport. Currently working in Malaysia as a domestic worker. My employer want to sponsor me to follow his wife to travel to UK and Paris. but my visa UK visa got rejected.   Based on the refusal, I need to provide a letter of leave from my employer. I can get that letter as he is the one who is sponsoring me  second reason is because I can't provide a bank statement that prove my salary. I did provide them with my bank statement. But I received my salary in cash every month. I am currently working with the same employer for more than 7 years.  Can I provide my payslip to support my income as I only received my monthly salary by CASH. I have no other bank account and all my money is saved somewhere but not under my name.  Can i reapply again and submit the necessary document(leave letter from employer and payslip) and deposit all my previous salary that i received in cash and provide the payslip to justify the large deposit amount ?  please help


What if Stack Exchange sites gave a provisional/initial reputation to new users?

What if new users were given an initial rating of say, 300? instead of just 1? Then, based on their good/bad contributions we could assess their "true" reputation. The benefit is that if there is an average new user(non spammer) it would take them a lot of energy and time to get to their "true" reputation i.e get the privileges they deserve, and many privileges (like commenting, voting, editing) are locked for new users as well; so a provisional reputation might solve this problem. A question mark like in 300? would tell that the reputation is provisional, so that others know that the user is new. The question mark would go away after user gets more than 10 up/down votes on their posts.     I got this idea while I was playing chess on , which initially gave me a provisional rating of 1500?. I thought wouldn't this be a good idea for Stack Exchange?  More about provisional rating on Lichess .


How to compute this limit: $\lim_\limits{n\to\infty} \sum_\limits{k=1}^n\frac{1}{1+3^k}$ or written as:  $\lim\limits_{n\to\infty}(\frac{1}{1+3^1}+\frac{1}{1+3^2}+\frac{1}{1+3^3}+...+\frac{1}{1+3^n})$  this limit includes computing a summation of series: $\sum_\limits{k=1}^n\frac{1}{1+3^k}$ so that also arouses a more general question: how to compute a summation like $\sum_\limits{k=1}^n\frac{1}{1+a^k}$, where $a=2,3,...,$?


Show that $\phi(n)=\frac{n}{2}$ if and only if $n=2^k$ for some positive integer k. I think I have it figured and would like to see if I am on the right track. Thank you.


Java: toString error "error: incompatible types: int cannot be converted to String"

I just need a quick help with my toString. This involves playing cards.  public class Card {   //Data   private int rank;   private char rank2;   private char suit;    //more codes (constructor etc.)    //toString     public String toString ( )     {     if (rank == 11)         rank2 = 'J';     else if (rank == 12)         rank2 = 'Q';     else if (rank == 13)         rank2 = 'K';     else if (rank == 14)         rank2 = 'A';     else         return rank2 + suit; // <----error here.     }   I am trying to figure out how to return a rank and a suit. For example, if someone were to input 11 for the rank and 'S' for the suit, then I should return a JS. However, I am running into an error:     "error: incompatible types: int cannot be converted to String"


Essentially, when is $\dfrac{x^2 +y^2+1}{xy}$ a positive integer?    I've tried many approaches such as considering the above equation as a quadratic in $x$ or $y$ but I haven't had much success. The only solutions I could find were $x=1$, $y=1$ and $z=3$.  A similar problem: I know that the only solutions to $\dfrac{x^2+y^2}{xy}$ to equal a positive integer is for $x$ and $y$ to both be one. This is pretty much considering when a number, not necessarily an integer, and it's inverse sum to make a positive whole number. However, the problem is a slight variation, it asks when a number $\frac{p}{q}$ summed with it's inverse $\frac{q}{p}$ plus $\frac{1}{pq}$ is a whole number.


How does a fan moves air towards you (I mean in 1 direction). Also propeller and fan have different shapes, does it mean they work different?


Show decimal on a division even if it results to a whole number

I would like a way to force at least 1 decimal to appear in the result of an integer division.  int a = 2, b = 1; std::cout << a/(double)b; >>>> 2   int a = 2, b = 1; std::cout << (1.0*a)/(1.0*b); >>>> 2   I would like to print 2.0 but only gets 2 trying above tricks.  Answer:  std::cout.precision(1); std::cout << std::fixed << a/(double)b;


Subgroups of given index of a finitely generated group

Let $G$ a finitely generated group. Prove that for a given natural $n$, there exists finitely many subgroups of index $n$ in $G$.  I tried to keep on this approach :   Here is my effort to edit or complete the above idea: My main emphesize is on this theorem:  If $H$ is a subgroup of finite index $n$ in a group $G$, Then there exists homomorphism $\phi:G\rightarrow S_n$ such that $Ker(\phi)=Core(H)=\displaystyle\bigcap_{x\in G}{xHx^{-1}}$.  As $G=\langle \{g_1,\cdots,g_m\}\rangle $, it's sufficient to find $\phi$'s effect over $g_i$s in order to determine whole $\phi$. Now $\phi(g_i)$ has $n!$ states to be chosen. Therefore, number of whole $\phi$s can be defined, are less than $(n!)^m$. But if we suppose number of such $H$s is infinite, we must have this fact that infinite number of $Core(H)$s are equal. Also if the left cosets of $H$ are $H,a_1H,\cdots,a_nH$, we can show $Core(H)=\displaystyle\bigcap_{i=1}^{n}{a_iHa^{-1}_i}$ Any idea is welcome for the rest. Thank You


How do I press Ctrl+Alt+Delete in VirtualBox?

I'm running VirtualBox with Windows Vista as host OS and Windows Server 2008 as guest OS. To login to Windows Server I have to press Ctrl+Alt+Delete, but my host OS reacts on that so I can not send it to VirtualBox. How can I do it?


I'm not sure what I pushed, but all of the sudden, all of my materials look like blobs and don't match the edges.     Sorry, I'm brand new to Blender and I did try googling this, but my 3d modeling vocab is bad enough that I wasn't sure what question to ask.


Downgrade iOS 12.4.8 to iOS 11.3.1 - iPhone 6 (Without SHSH blobs)

Is there any way to downgrade iOS 12.4.8 to iOS 11.3.1 on iPhone 6 (Without SHSH blobs). The firmware is not signed by the apple anymore. I'm stuck at iOS 12.4.8 on iPhone 6 and cannot use Wi-fi Calling, was able to use the feature back in 11.3.1.So need to go back. Please help.


I'm about to start my journey into the world of Malazan and to my despair I've found that the series consists of the following series:    The Malazan Book of the Fallen (10 books) The Tales of Bauchelain and Korbal Broach (5 books) Novels of the Malazan Empire (6 books) The Kharkanas Trilogy (2 -so far- books)   I want to read them all but I've heard that the Malazan books are quite complicated. So, what's the best order to read them all without having spoilers and keep track of things?


Ppening an HTML file on localhost in XAMMP/apache 2.2 using subdirectories under htdocs

I have a site directory for html (dreamweaver CSS3) with lots of subdirectories that contain HTML files for a number of drop down menus. They work fine where they are, but they all have menus that are JavaScript and could be kept in a separate file. So, I want to use Include. I don't want to have to FTP my files to HostGator every time I want to test the includes. I want to have this on my local machine. So, I am attempting for the first time to setup XAMMP and then run my html files (site) on localhost, so I can see what they look like before ftping everything to HostGator and putting it live.  I tried copying the main site folder to htdocs, and then copying the path to the file I want to run in front of the localhost in Firefox, but it gave me file not found:   Do I have too many subdirectories? Why isn't the file being found? It is there.  Tried this too:   No go.


Database of names similar to bibliography in arabic

The example is with the particular case of Arabic, but could be extended to a more general case.  When writing academic papers containing Arabic names, each journal has a particular transliteration system. I would like to know if I could build my database of names with different romanizations for each name (some of them require diacritics, others don't) and then use the one I need for each journal. It would work similar to a bibliographic database :  @name{tusi, arabicname = {{محمد بن محمد بن الحسن ,{طوسی}, latinname = {Nasir al-Din Tusi} translit1 = {{Ṭūsī}, Naṣīr al-Dīn Muḥammad ibn Muḥammad}, translit2 = {Ṭusi}, Nasir al-Din Muhammad ibn Muhammad}, translit3 = {another one}, ....}   Then, I would "cite" them and choose the transliteration I want for each document. I could choose also the format: transliteration (Arabic name), or transliteration (Arabic name as footnote).


Nullpointer exception when retrieving Data from firebase

I am using firebase database for my app and I saved my users in it. This is my UserInformation class:  public class UserInformation {   private String email1; private String Password1; public HashMap<String, Boolean> SayingsLevels=new HashMap<>(); public HashMap<String, Boolean> songs=new HashMap<>();  public UserInformation (String email, String Password){     this.email1=email;     this.Password1=Password;     SayingsLevels.put("1", false);     SayingsLevels.put("2", false);     SayingsLevels.put("3", false);     songs.put("1", false);     songs.put("2", false);     songs.put("3", false);  }   And I saved it with this code on my main activity:  firebaseUser=FirebaseAuth.getInstance().getCurrentUser();                 UserInformation user=new UserInformation(email1,password1);                 String id=firebaseUser.getUid();                 mDatabaseReference.child("user").child(id).setValue(user);   Now, I want the get the hashmap data that was stored in my database. I used the following code:  mDatabase.addValueEventListener(new ValueEventListener() {          @Override         public void onDataChange(DataSnapshot dataSnapshot) {              mDatabase = FirebaseDatabase.getInstance().getReference();             firebaseuser=FirebaseAuth.getInstance().getCurrentUser();             id=firebaseuser.getUid();             for(DataSnapshot dataSnapshot1: dataSnapshot.getChildren() ){                UserInformation user= dataSnapshot1.child("user").child(id).getValue(UserInformation.class);              }   but on variable user I'm getting all the time null, what I did wrong? Thanks for help!


Can I use 2 exact same switching power supplies in parallel?

I would like to achieve 6 amps with those, is it possible?


Variations: Propagate Lists Programmatically

I have defined variations with two Labels (source and target)  I have selected "Publishing Sites and List with variations and all pages" in one of the settings. The pages are created in the target site but the Lists doesn't seem to propagate. Until and unless I go to List and define it under variations from UI.  Found the option to make it under Variations (screenshot below)    How can I do this programmatically when a new List is created, it should by default be under Variations..?   Is there a configuration way?


MySQLi and PHP allow special characters in form submission, but not SQL insert?

I have been writing a PHP script for a "Contact Us" form that I am using on a website to allow users to comment about the site. It has several fields, including a name field and a textarea for comments. After the user submits the form, the comment is entered into database, which is then queried for the five most recent comments and displays them on the site. However, users cannot currently enter apostrophes (') in either the name field or the comments area and have them display properly.   This is the sequence of events:  "User Submit -> Prepare SQL -> Insert Record -> Query Database -> Return recent Comments"   Currently, this is what I have for PHP:  //Function that will trim the input, and run it through a small security check function test_input($input) {     $input = trim($input);     $input = stripslashes($input);     $input = htmlspecialchars($input);     return $input; }  $name = test_input($_POST["txtName"]); $comments = test_input($_POST["txtComments"]);  //Prepared statement to insert a new Contact record $stmt = $conn -> prepare("INSERT INTO tableName (name, comments) VALUES (?, ?)");  //Create the parameters of the prepared statement $stmt -> bind_param("ss", $param_name, $param_comments);  //Set the parameters of the statement, running them through a security check $param_name = mysqli_real_escape_string($conn, $name); $param_comments = mysqli_real_escape_string($conn, $comments);  //Execute the prepared statement $stmt -> execute()   As you can see, I am running the variables through both the htmlspecialchars() function and the mysqli_real_escape_string() function. However, I still get a strange output when I run the function.    Input  Name with Apostro'phe I'm happy with the "/" and "\" of the present.   How It Looks In...  ...database  Name with Apostro\'phe I\'m happy with the &quot;/&quot; and the &quot;&quot; of the present.    I understand that the &quot; is from the htmlspecialchars function, and think that the \' is from the mysqli_real_escape_string() function.   ..website comment section (populated from database)  Name with Apostro\'phe I\'m happy with the "/" and the "" of the present.    Same here with the \'. How do I get it so that when it redisplays in the HTML after being queried from the database that the apostrophes display normally?   However, this is not what I want. When it displays in the comments section (after being queried from the database), I want it to display as it was input by the user. I don't really care how it looks in the database, as long as it displays properly when it is returned to HTML by the query to populate the list.    What should I do so that users can input apostrophes in their name/comments, and have it display as such after being returned from the database; but at the same time, not run the risk of SQL injection? I have looked at several related questions, but have not found anything that answers my question.     I have already tried the methods in this post without success      I don't need anything like this, only apostrophes   Let me know if I need to clarify anything!


QGIS attribute table shows attributes of only one polygon at time

I have multiple shapefiles each with many polygons. I am used to the attribute table listing them all in rows and columns. In this case, all attribute tables show me the attributes of a single polygon which I can select from a list on the left (see screenshot). How do I change my attribute table to the standard view? My QGIS version is 3.14


Can a user split their Stack Exchange network account into two independent ones?

This is basically a reverse of .  Let's say a user has a single account on several SE sites that are linked (for example, Stack Overflow, Programmers, Gaming and RPG).  They want to expose their SO and Programmers professional accounts to a professional audience, but don't want anyone to link that to their more "frivolous" Gaming/RPG accounts.  Is it possible - as a one-time event - split that one SE account into two separate accounts? The assumption is that they would be 100% independent of each other, with different logins, and no further association between them? If so, what would be the procedure?


I couldn't find something that resembles this but one day I used my stainless steel pan and I think I didn't clean it properly so I woke up to discover these "stains" on it (BKF didn't help scrub them off):    Anyone know what these could be and how to treat it? Not sure if it's even safe to cook in it anymore.


How to write to common chat in Heroes of the storm?

Is it possible to write to the common chat during Heroes of the storm game?  'Enter' gives me allies chat only, 'Cmd+Enter', 'Alt+Enter' (on Mac) don't help either.


Given something like this - where the string contains line breaks and carriage returns; I added the character in to the example for brevity:  AB01 88 99 10 \nHH01 123 123 \nHH02 123 123 \nHH03 123 123 \nXX10 88 99 10 \nHH01 456 789 \nHH02 456 789 \nHH03 456 789 \nXX10 99 10 11   I am trying to extract groups of HH01 to HH03  I'm expecting a result like this.  groups = [         "HH01 123 123\nHH02 123 123\nHH03 123 123",         "HH01 456 789\nHH02 456 789\nHH03 456 789"          ]   I'm trying to extract it with regular expressions, though am not fully understanding what I'm doing.   My expression looks like this: /HH01(.*)HH03/  I can't figure out how to handle the line breaks. I've tried /HH01(.*)HH03/m too.  Can anybody help point me in the right direction?


"all boot options are tried" after installation on Samsung Ativ Book 9 Lite

Hi i have the samsung ativ book 9 lite I just installed ubuntu 13.10 after removing windows 8.1 and have gotten the error all boot options are tried, after the installation After having a look around the forum ihave made sure that I have disabled secure boot and fast boot However I think the problem may be that i have been unable to disable the framebuffer. I am getting no F6 option when I am trying to install ubuntu that will allow me to select nomodeset.  I am a bit of a noob and do not understand what the grub prompt way is? Is there any way I can fix the error : "all boot options are tried press  key to recover ...  " I would be extremely appreciative if you could give me a detailed answer. Thanks and looking forward.


I just installed Ubuntu 16.04.3 LTS alongside Windows 10, but now I can't find it or boot to it

I finished installing Ubuntu 16.04.3 alongside Windows 10. I made sure to turn off Hibernate and Fast Shutdown on Windows, made my BIOS UEFI and unsecured. When I boot I still can't find Ubuntu. I also tried going to the live version on my USB and running the boot repair with no help. Ubuntu made a new partition in my hard drive the size it said it was going to, but I have no idea how to access this. I can get into Windows and only Windows. I keep seeing that Grub Loader or something should let me choose which OS to load, but I haven't seen anything even close to that. I can't even choose Ubuntu from the BIOS menu when I hit F12. I have no idea what to do and all of the articles I have read haven't helped me at all. A little more information is that I am running on an Acer Aspire Laptop. I look forward to any help anyone can provide.


Do subclasses have all the properties and methods of the parent class?

Do subclasses have all the variables and methods of the parent class? Including the Private properties and methods of the parent class?  Or does the subclass have only accessible variables and methods of the parent class? Like public, default, protect?


Why does nature have higher atomic nuclei if Iron(Fe) has higher binding energy per nucleon?

From the binding energy per nucleon (B.E./A) vs atomic number (Z) we know that Iron (Fe) is most stable nuclei in the nature. Here comes the question that if nature has found the stable nuclei then why does it has nuclei in higher mass region?


Add inline JavaScript to end of page dynamically

Use case:  I have a custom block:  /**  * Provides a 'Hello' Block  *  * @Block(  *   id = "my",  *   admin_label = @Translation("My Block"),  * )  */ class MyBlock extends BlockBase {    /**    * {@inheritdoc}    */   public function build() {      $build = array(       '#markup' => 'SOME WEIRD ADS HTML HERE'     );      SOME_COOL_STUFF_TO_ADD_INLINE_JAVASCRIPT_TO_THE_CLOSING_BODY_TAG      return $build;   } }   Is there a way to add inline javascript to the end of the page just when this block is rendered anywhere (in theme or panel page)?


What is the difference between "to meet you" and "to meeting you"?

Why the below one is correct?      I look forward to meeting you.   And why this one is wrong?     I look forward to meet you.   I generally do these mistakes in letter writing.


Why do we need vectors and who invented it?

It is natural to understand the need for scalars (numbers), but why did we invent vectors? Who invented it and for what?  EDIT: As George Lowther pointed out, the problem is too broad; I added the following questions as concrete supplements.   It's easy for humans to understand the law of addition of scalar numbers, but why does the vector addition follow the parallelogram rule, and not some other law? (link to physics: How do we know that the addition of forces follows the parallelogram law?) The length of a 2-dimensional vector is the hypotenuse of the triangle constructed from the two components of the vector and the length of 3-dimensional vector also follows this way. But what about 4-dimensional vectors? Why do we define dot products of vectors like it is now? Is it because of its physical essence or its equivalence to the law of cosines?


How is direct sum of two vector subspaces different from the sum of two vector subspaces i.e. how is $X\oplus Y$ different from $X + Y$, where $X, Y$ are subspaces.


Cannot run apt update in a Debian docker container

I've got the error in the docker container  E: Release file for http://deb.debian.org/debian/dists/buster-updates/InRelease is not valid yet (invalid for another 9h 1min 57s). Updates for this repository will not be applied.  after running: apt-get -o Acquire::Check-Valid-Until=false update   Here is a full log: Step 2/15 : FROM php:7.2.20-cli  ---> 5656cb179dc0 Step 3/15 : MAINTAINER Nick Jones <nick@nicksays.co.uk>  ---> Using cache  ---> 5c856c7b88d5 Step 4/15 : RUN apt-get -o Acquire::Check-Valid-Until=false update  ---> Running in 145c283ee52d Get:1 http://deb.debian.org/debian buster InRelease [122 kB] Get:3 http://deb.debian.org/debian buster-updates InRelease [49.3 kB] Get:2 http://security-cdn.debian.org/debian-security buster/updates InRelease [65.4 kB] Get:4 http://deb.debian.org/debian buster/main amd64 Packages [7907 kB] Get:5 http://security-cdn.debian.org/debian-security buster/updates/main amd64 Packages [176 kB] Reading package lists... E: Release file for http://deb.debian.org/debian/dists/buster-updates/InRelease is not valid yet (invalid for another 9h 1min 57s). Updates for this repository will not be applied.   I assume that's not about a certain container but about Debian and repositories. As you see I used some workaround:  ...but it doesn't work. So, what's wrong?


One of my friends ask me about this code and I and he are unable to find out, what is happening in the if condition. Can you guys explain how this condition works?  int main() {    int i;     if (i = (1, 2, 0))        printf("Mehrose");    else        printf("Hello ");     printf("%d\n", i);     return 0; }   The output for this code is Hello 0


Say you have a number $x^{\sqrt 2}$.  Is there any way to represent this number so that there's no root (or irrational) as the exponent (so that it's easier to understand for me)? I just can't wrap my head around this.  I was thinking something like $$x^{2^{1/2}}$$ and extending on that idea, but I don't know how.  Also, what about for $x^{\sqrt 3}$? Or $x^{\sqrt n}$?


Does an Artificer (Artillerists) Eldritch Cannon provoke opportunity attacks?

The rules for the eldritch cannon state:     The cannon is a magical object. Regardless of size, the cannon has an AC of 18 and a number of hit points equal to five times your artificer level.   The rules for an opportunity attack state:     You can make an opportunity attack when a hostile creature that you can see moves out of your reach.   Does this mean that an eldritch cannon cannot provoke opportunity attacks?


How many antisymmetrical relations are there on a set $B =\{ 1,2,3\}$?

How many antisymmetrical relations are there on Set $B$ if Set $B = \{1,2,3\}$?  I believe its three?


I was trying to solve some change of basis exercises, so I've done them and I want you to tell me if I've done it correctly.     1) Given the coordinates system $(O'; X'' Y'')$ asociated to the    basis $B=[{b_1=\frac{1}{\sqrt{2}}; \frac{1}{\sqrt{2}};  > b_2=\frac{-1}{\sqrt{2}}; \frac{1}{\sqrt{2}}}]$ with origin in    $O'=(2;5)$, find the intersection between $Q: y''^2=-4 \sqrt{2} x''$    and the straight line in $(O,XY)$ $V=(0;5)+t(-1;1) t\epsilon R$    Well, first I tried to write $Q$ in terms of $X$ and $Y$, and not in terms of $X''$ and $Y''$. I used the formula:  $(\begin{matrix}  X''\\  Y'' \\  \end{matrix})$ =$(C)_B$ × $(\begin{matrix}  X-2\\  Y-5 \\  \end{matrix})$   Then I replaced those values in the equation of $Q$ and I got $Q: \frac{(-x+y-3)^2}{2}=-4 \sqrt{2} \frac{(x+y-7)}{\sqrt{2}}$   After that, I found the intersection between $Q$ and $V$ using equations and I got that the intersection points in $(O;XY)$ are $P_1(3;2)$ and $P_2(-1;6)$      2)Given the coordinates system $(O,X'Y')$ asociated to the basis    $B=[{b_1=\frac{1}{\sqrt{2}}; \frac{1}{\sqrt{2}};  > b_2=\frac{-1}{\sqrt{2}}; \frac{1}{\sqrt{2}}}]$ with origin in    $O=(0;0)$ and the ellipse $9X'^2+5Y'^2-3X'+2Y'-10=0$ find the    coordinates of the centre of the ellipse in $(O,XY)$    So, here I found the centre of the ellipse in $(O,X'Y')$ and it was $(\frac{1}{6}; - \frac{1}{5})$, then, doing something similar to what I've done before I found out that the centre in $(O,XY)$ was $( \frac{11}{30 \sqrt{2}};$ $\frac{-1}{30 \sqrt{2}}$)


Why do some trailers contain scenes that aren't in the movie?

I'm an avid watcher of trailers. I watch trailers over and over again. I even watch trailers of movies that I don't plan on watching.  But sometimes, I notice that some trailers contain some additional scenes that aren't in the movie.  I noticed this in a few trailers/movies before. A notable example is the  of  where the following [amazing] scenes aren't in the movie:        Cyborg .   Aquaman .   Cyborg .   The Flash .   Wonder Woman, Aquaman and Cyborg .      So, Why do trailers have those additional scenes? Are those scenes filmed just for the trailers? Isn't that needlessly expensive?


Bibliography style elsarticle-num-names with DOI and hyperlinks but no explicit url

I prepared my article with elsarticle, using \citep & \citet throughout. I originally used apalike bibliographystyle but now need to change it to elsarticle-num-names for citation formatting requirements (see point #2 below).  Now, I am attempting to make 2 changes:     add DOIs to the bibliography change reference style to [1] for \citep and Author et al. [1] for \citet.   I want to keep hyperref and do not want explicit URLs (only DOIs) but cannot make this work!  Thank you for any help you might have!  MWE:  \documentclass[preprint,12pt]{elsarticle} %\usepackage{hyperref}  \journal{Test Journal} \begin{document} \begin{frontmatter} \title{The Title} \author{Prof. Big Ol' Wanker} \address{123 Happy Lane} \begin{abstract} TEXT \end{abstract} \begin{keyword} keyword 1 \sep keyword 2 \sep keyword 3 \end{keyword} \end{frontmatter}  \section{SECTION1TEST} \noindent cite: \cite{Richards1931} \\ citep: \citep{Richards1931} \\ citet: \citet{Richards1931} \\  \bibliography{library} \bibliographystyle{elsarticle-num-names}  \end{document}   Here is the reference for Richards1931 from my library.bib file:    @article{Richards1931, author = {Richards, LA}, doi = {10.1063/1.1745010}, file = {:D$\backslash$:/Papers/Richards - 1931 - Capillary Conduction of Liquids Through Porous Mediums - Journal of Applied Physics.pdf:pdf}, issn = {01486349}, journal = {Journal of Applied Physics}, pages = {318}, title = {{Capillary Conduction of Liquids Through Porous Mediums}}, url = {http://scitation.aip.org/content/aip/journal/jap/1/5/10.1063/1.1745010}, volume = {1}, year = {1931} }   without hyperref (wanted hyperlinks present, DOI displays correctly, but unwanted URL is present):    with hyperref (hyperlinks not present, DOI displays incorrectly, and unwanted URL is present):


Why does $A$ times its inverse equal to the identity matrix?

I was trying to come up with a proof of why: $AA^{-1} = I$.  If we know that: $A^{-1}A = I$, then $A(A^{-1}A) = A \implies (AA^{-1})A = A$.  However I don't like setting $AA^{-1} = I$ for fear that it might be something else at this point, even though we know that $IA=A$. For example, could $A$ times its inverse equal something other than the identity leading back to the original matrix $A$.  Does anyone have a another proof for why $A$ times its inverse would give you the identity or could explain something I'm missing?


I have a dataset for which I have multiple sets of binary labels. For each set of labels, I train a classifier, evaluating it by cross-validation. I want to reduce dimensionality using principal component analysis (PCA). My question is:  Is it possible to do the PCA once for the whole dataset and then use the new dataset of lower dimensionality for cross-validation as described above? Or do I need to do a separate PCA for every training set (which would mean doing a separate PCA for every classifier and for every cross-validation fold)?  On one hand, the PCA does not make any use of the labels. On the other hand, it does use the test data to do the transformation, so I am afraid it could bias the results.  I should mention that in addition to saving me some work, doing the PCA once on the whole dataset would allow me to visualize the dataset for all label sets at once. If I have a different PCA for each label set, I would need to visualize each label set separately.


I'm a teacher and I teach at/in school OR at/in a school

There are a lot of posts on this topic, but I can't find any answers to my question.  I came across the following two definitions of 'school':        [uncountable] (used without the or a) the process of learning in a   school; the time during your life when you go to a school (British   English)   [uncountable] (used without the or a) the time during the day when   children are working in a school      Source:   I know there are better ways to convey the message, but which sentence would a teacher utter if he was a school teacher teaching students, adults, etc.? What about a janitor, director, and secretary?     I teach at/in school OR I teach at/in a school   The above definitions concern students, and not working individuals like teachers or janitors.  I would appreciate if you also stated whether you're American, Canadian, British, etc.


I recently encountered the above notation for sets, and I've never encountered it before. What does it refer to?


Installing Debian I have to choose between the kernels   linux-image-3.2.0.4-amd64 linux-image-amd64   What's the difference?


What do Android application permissions mean?

When installing an application, the application lists permissions that it needs to perform its  functions.    I am creating this list of the the system defined permissions and a description of what they mean. It is a community wiki so if new permissions are added in the future they can be added to this list.