In SQL Server, what is the probability of creating tow GUIDs with the same value with this code?  DECLARE @EmployeeID UNIQUEIDENTIFIER; SET @EmployeeID = NEWID();

I'm working on a database in SQL Server 2000 that uses a GUID for each user that uses the app it's tied to. Somehow, two users ended up with the same GUID. I know that microsoft uses an algorithm to generate a random GUID that has an extremely low chance of causing collisons, but is a collision still possible?


I'm looking for a build for a new Swordsage character and I bumped into the , but all of the links are broken. As I read, there was some changing in the site forum engine and the links were lost at that time. Does anyone have a backup or a currently working copy?

I was looking for the Wizard Handbook but all the links were broken.  Somewhere on the handbooks of other classes (on other forums) I saw a      This was archived by WotC, here's the link   But the link leads to the welcome page of WotC (since it's broken).  Is there a way to get all that info back? Do you know where to get it from? The Wayback Machine did not archive the forums.


I am learning about virtual functions in C# and I've come across this problem I can't wrap my head around. I have the following code in C#:  namespace ConsoleApp1 {     class A     {         public virtual void F()         {             Console.WriteLine("A.F");         }     }     class B : A     {         public override void F()         {             Console.WriteLine("B.F");         }     }     class C : B     {         public new virtual void F()         {             Console.WriteLine("C.F");         }     }     class D : C     {         public override void F()         {             Console.WriteLine("D.F");         }     }     class Program     {         static void Main(string[] args)         {             D d = new D();             A a = d;             B b = d;             C c = d;             a.F();             b.F();             c.F();             d.F();             c = new C();             c.F();             Console.ReadLine();         }     } }   Why the output is this? It doesn't make sense to me at all. Can someone explain? Output:  B.F  B.F  D.F  D.F  C.F

What are differences between declaring a method in a base type "virtual" and then overriding it in a child type using the "override" keyword as opposed to simply using the "new" keyword when declaring the matching method in the child type?


I'm trying to solve this. I'm unable to use the Euler-Fermat theorem and I don't know how to carry on. Any help?

How do I efficiently compute $a^b\bmod c$:  When $b$ is huge, for instance $5^{844325}\bmod 21$? When $b$ is less than $c$ but it would still be a lot of work to multiply $a$ by itself $b$ times, for instance $5^{69}\bmod 101$? When $(a,c)\ne1$, for instance $6^{103}\bmod 14$?  Are there any other tricks for evaluating exponents in modular arithmetic?  This is being asked in an effort to cut down on duplicates, see  and .


what actually amplifies the current in CE mode of a transistor(npn here)? When the input is applied betn emitter and base, the forward biasing causes the electrons to move from source to the emitter say 100 electons. The same 100 electrons move towards the base where very few no. of electrons combine with holes say 2. they move out of the base towards source. so remaining electrons are 98 which move to the collector and out to the output circuit. So where is the current amplification? i have considered the Veb as 0.7 and Vce to be 1.

I've tried really hard to understand the basic operational principle of a transistor. I've referred to many books and been to forums but have never got a convincing answer.  Here are the things I want to understand:   A transistor is similar to a reverse biased diode unless a voltage is applied to the Base.  Since the Emitter-Base junction is forward-biased, there will be conduction of - say - electrons (npn). What happens then? Is it true that these electrons from the Base break the barrier of the Collector-Base junction and then the combined current passes to the Emitter? (IB + IC = IE)  And why is that we are getting more current? Where is amplification? It can't be like creating something out of nothing. I know I'm missing some crucial point here. Can somebody explain me clearly in simple terms?  It has been a week I'm tryin to understand this. :(


I've been using Latexian for a while. Its LivePreview feature is very convenient, which is why I'm keeping using it.  Recently, I've heard about LuaTeX / LuaLaTeX. I tried a couple of examples but I couldn't make it work with Latexian.  Specifically, compiling the following code via terminal "lualatex test.tex" works ok.  \documentclass{article}  \begin{document} The standard approximation $\pi = \directlua{tex.sprint(math.pi)}$ \end{document}   As expected, this doesn't compile in Latexian since it uses "pdflatex".  I tried to delete "pdflatex" file in /usr/texbin and create a symbolic link named "pdflatex" pointing to "lualatex" to trick Latexian, but it didn't work. I get the following error:   This is LuaTeX, Version beta-0.76.0-2013061817 (rev 4627)   \write18 enabled.  ---! pdflatex.fmt was written by pdftex (Fatal format file error; I'm stymied)    Even in terminal, trying to compile with "pdflatex" (now pointing to "lualatex") doesn't work. Same error as above.  Any ideas?

The Mac editor Latexian has built in methods for compiling using latex+dvips, pdflatex and xelatex.  Furthermore, it assumes bibtex and makeindex to deal with bibliographies and indexes, respectively.  How do I customize Latexian to use, e.g. LuaTeX for compiling or Biber for bibliographies?


Assuming humans could use all of their muscle strength at once, with no need of cooling or energy, how fast could we theoretically run?

I'm a runner (cross country) and I'm always amazed at how fast Olympic sprinters are. There's a lot of hype about those in the 100-meter dash being the fastest in the world, and we're constantly seeing the 100-meter time dropping. But is there a limit? How fast can human being, propelled only by its own energy (i.e. without any external assistance) run?


I want to get rid of the noise but I can't for the sake of god find out what is causing it. I am using an HDRI. I am not using glass materials. I blocked all the HDRI light with objects apart from 2 windows (no glass, no geometry, just 2 big openings). Here is a picture (32 samples) : (I am new to blender but I am very familiar with 3d environments) (HDRI is hidden by ''world-> ray visibility-> camera (uncheck)'' but checking it doesnt make any difference anyways)  EDIT: My question here lies on, why does this happen? The problem is solved, I can just increase the samples and activate the denoiser. The problem I have with this is that previewing with 32 samples is different than previewing with 100 or 500 samples. At one point I added a glass material and it acted as a noise trap and after removing the material, the noise trap persisted. I want to know why that happened.

I know that this question is a bit old or maybe overdone, but I'm running the latest edition of Blender and when I use the Cycles engine I get really fuzzy results and I can't find a simple, non-compromising solution to the quality.  I don't know exactly what I'm doing wrong here, but I'm sure others share my frustration.  Leaving everything in default settings, I started a new project and switched to the Cycles render.  I duplicated the cube and set colors for two Diffuse BSDF shaders, then went ahead and made walls and a floor all sharing the same diffuse shader.  I made two windows to emit blue light.  The screenshot has gaps between the walls because of the setup:  I'm aware that it's considered very incomplete and many have come to terms with some amount of noise, but is this normal?  Furthermore, with default settings or not, I can't change the amount of noise produced.  Supposedly, using "progressively refine" in the rendering tab should make it refine itself indefinitely, however Cycles only counts to 10 refines and then stops, creating a render which is a pixel-perfect match of the ordinary rendering method when it's completed.  I understand that there are tricks that can be used to reduce noise, but at the cost of extra processing time and usually small quality conflicts, like blurring.  My question essentially boils down to is this Cycles' current limit?


After asking a question, it receives a couple of points but has no responses or answers. What is the best practice for proceeding? What is the preferred waiting period before proceeding?

I asked a question almost as soon as I got my account. I got a few decent answers, but none of them helped solve my problem. The question has long since become buried by newer questions, and there's still no accepted answer. Unfortunately, because there are quite a few answers with votes, to a casual observer it probably looks like the question was answered and I just neglected to mark an answer as accepted, and the system does not consider it "unanswered".  Or, I asked a question that was a bit more difficult to answer. After waiting for some time, I received no answers, little or no comments, and only a few views. The question does show up in the "unanswered" list, but no one has answered my question.  In either case, what's the protocol for me to try to get this question answered?  I see several options:   Post the question a second time, possibly linking to the original, to get attention for the original question. This is encouraged on sites like Reddit.  However, it's probably not appropriate here, since we're encouraged to check for duplicates and not submit a question that's already been asked by someone else, so this probably falls under that heading. Wait for some kind of wiki-like talk page to be implemented, then post a plea on the talk page for input and hope that activity on the talk page bumps up the question. Edit the question, but do nothing further on the Stack Exchange site. If I edit my post to say that I haven't accepted any of the current answers but am looking for more, then the question might get answered eventually by people browsing through old questions to find something they can answer. Post the question on other sites, but link to my original question on Stack Exchange. People will either answer here, or they'll answer on the other site and I can post the accepted answer here myself.  This might be considered spamming, so it might be better to do this without the link.      For more information, see the "" page in the .


I made excuses to not go to school.  I made excuses not to go to school.    Are both of them correct?

This is one thing that keeps bugging me, and maybe there's a direct answer. Grammatically, which one is more correct of these two?  Does it make a difference?  I tried not to do that. I tried to not do that.


According to Edwin Hubble our Universe is expanding because he noticed that other galaxies are moving away from us. But then how Andromeda galaxy will collide with Milky Way in ~4.5 billion years, as it should also move away from us?     I am some bit confused, please help me.

Hubble's law says that the universe is expanding. How come the Milky Way and the Andromeda galaxies are on a collision course? How will they end up colliding with each other?


I have a HP Pavilion g4-1363la Notebook PC with the i3 Core CPU and Intel HD3000 graphics.  I had Windows 8 on it, but i guess it got corrupted somehow or something, it wouldn't start up anymore.  My uncle, who somewhat knows a thing or 2 about computers, says that i need a new OS, because it was missing or something, so i checked out this Ubuntu & saw that u could install it to a laptop via USB flash drive, i have done everything i need (at least i think i have), every time i turn on my laptop, it shows me the Ubuntu install menu.   The options that i have are:   "Try Ubuntu without installing" "Install Ubuntu" "Check for disc for defects" "Test memory" "Boot from first hard disk"    The first 3 options takes me to a black screen, then the screen sorda turns off. "Test memory" takes me to a blue screen with a bunch of weird statistics that i have no idea what it is for, then i have options like "(ESC)Reboot" - "(c)configuration" - "(SP)scroll_lock" - "(CR)scroll_unlock". The "Boot from first hard disk" also takes me to the black screen till the screen turns off, unless i hit enter, it shows me the installing menu again.  I really need help installing Ubuntu, do i really need to repair my laptop?? am i missing something? or am i doing something wrong??

I am trying to boot Ubuntu on my computer.  When I boot Ubuntu, it boots to a black screen.  How can I fix this? Table of Contents:


I noticed a pretty unfixable error in one of my answers today and thus went to delete it. However, on the Android mobile app, the only options were to share, edit, or flag the post (no deletion). Would it be possible to add the delete option to posts as well on the mobile app?

If was pointed out to me that one of my questions was a duplicate, so I went to delete it. No such option available?


I received a shapefile about invasive species. I am using ArcGIS 10.2 for desktop. In Attribute Table, there is column called "Infested_Area" and its got number mix with text, for instance "9100 sq feet". Since I can not run statistic on string I was wondering if it's possible to create a new filed and somehow get rid of the text portion of it and only have number!

How can I change the data type in an attribute table in ArcGIS for multiple fields?    For example, if the fields have been exported as a string from Excel, and I would like to use them as numerical values?


I'd like to convert any cell that is type float to type int:  My thought was use lambda functions like this:  df["ev_id"].apply(lambda x: [int(x) if x is type(float)])   But this raises a syntax error which I'm not able to catch. Any help would be much appreciated.   Original data:  ev_id " " 343.0 234.0 " " 212.0 "Temp"   Transformed:  ev_id " " 343 234 " " 212 "Temp"

What is the best way to check whether a given object is of a given type? How about checking whether the object inherits from a given type?  Let's say I have an object o. How do I check whether it's a str?


NOTE: I saw a couple similar questions, but I didn't see the answer I was looking for.   I was uploading images to question I had in a Stack Exchange community, and one of them I uploaded without cropping out a part I didn't want. For Personal/Privacy reasons I want it removed. I fixed the image and the question I made now has the fixed image, however the one with privacy concern was still uploaded on the stack.imgur, and I'd like it removed.   I've sent a couple requests to imgur, and one support form to the Stack Exchange community in questions support.   Will the image be removed for good? I have not referenced the link on any webpage. What are the chances of it appearing in Google searches?

I want to remove some photos from , because they are breaking my privacy (they contain my personal information). How can I do that or who should I ask to do that?


Test 1  if((0.011-0.007) >= 0.004){     echo 'YES!'; }else{     echo 'NO!';  }   Output: NO! <--- INCORRECT  Test 2  if((0.004) >= 0.004){     echo 'YES!'; }else{     echo 'NO!';  }   Output: YES!  Test 3  if((0.012-0.008) >= 0.004){     echo 'YES!'; }else{     echo 'NO!';  }   Output: YES!  Test 4  if((0.011-0.008) >= 0.003){     echo 'YES!'; }else{     echo 'NO!';  }   Output: NO! <--- INCORRECT  Test 5  if((0.01-0.007) >= 0.003){     echo 'YES!'; }else{     echo 'NO!';  }   Output: YES!  Test 6  if((0.011-0.007) >= 0.003){     echo 'YES!'; }else{     echo 'NO!';  }   Output: YES!  Conclusion  Something very strange with the number '0.011'

Consider the following code:   0.1 + 0.2 == 0.3  ->  false   0.1 + 0.2         ->  0.30000000000000004   Why do these inaccuracies happen?


How can I include inline styling that functions like the <strong> or <u> tags? <strong> strong text </strong><div style="color:rgb(160, 160, 160)"> inline styled text </div>  I would like this to show "strong text inline styled text" all on one line, where 'inline styled text' is colored with a light grey.

I would like to ask for some simple examples showing the uses of <div> and <span>.   I've seen them both used to mark a section of a page with an id or class, but I'm interested in knowing if there are times when one is preferred over the other.


I have a dell mini that would not boot to Ubuntu. It sat in my closet for over a year and a half. My son wanted a laptop, so I decided to try and fix it. With the help of this website and adding rootedelay=130 it finally booted but now it's asking for the key ring password which I can't remember cause it's been so long since I've used it. I'd very much appreciate any help in resetting the password. Thank you in advance for any help.

I'm working on a Ubuntu system, and my client has completely forgotten his administrative password. He doesn't even remember entering one; however it is there.  I've tried the suggestions on the website, and I have been unsuccessful in deleting the password so that I can download applets required for running some files. Is there a solution?


So, I’m level 46 with 100 smithing and enchanting. I want to make the best armor I possibly can, so I was wondering how to break the smithing cap with potions the best way that was intended. What I mean by this is I don’t want to exploit the system for smithing to be boosted to some ridiculous number like 1440%, rather, what is the best boost I can do to my armor and weapons while not feeling like a cheating as*wipe. I also understand alchemy will most likely be needed, so I’ll be sure to 100 that as well.

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


I really need help. Even if you are not sure of the solution, please suggest something. I really need it.  I formatted a pendrive in macOS using disk utility (GUID, macOS extended journaled). Then I copied macOS setup for hackintosh. Then I used clover(software to make macOS pendrive bootable) to mount the efi partition. It created a 200MB efi partition. Later I needed to format the drive to use it. On windows, disk management doesn't show the option to delete the efi partition. It shows option to delete the larger partition but even after clicking delete nothing happens. I read many articles on internet. I used diskpart as administrator and selected my disk and used clean command. It showed disk cleaned successfully but it lied. The disk is the same. With efi partition and the data on the main partition also there. I first tried macOS disk utility to erase the disk but it says failed to erase the disk. Under details, it says partition not unmounted. I booted into my linux, used terminal df to list disks. Then unmounted the pendrive using umount. Then formatted using mkfs. All commands are sudo. Terminal showed cleaning disk, creating partition table etc. After it was over, I see again that the disk is unaffected. It's new pendrive. Worked fine. No problems with pendrive whatsoever.   I also tried third party softwares but they all do what diskpart in Windows and terminal in Linux did which is => showed formatting completed but actually nothing happened to the pendrive. Please help me format it.

When I plug in my USB flash drive, it shows up on my computer as write-protected or read-only. I am unable to transfer data to it, nor can I modify or delete any files already stored on it. I also cannot repartition or reformat the drive using Windows Disk Management, DiskPart, GParted, or other tools. The drive does not have a write-protect switch.  Why did this happen and what can I do about it? Is there a way to remove the write protection?  (Note that this can happen with some memory cards, too, as they often use controllers similar to those used in flash drives. In some cases, the system may report that the drive or card was formatted successfully even though it was never actually formatted; the original data reappears when the device is reinserted.)     This question comes up often and the answers are usually the same. This post is meant to provide a definitive, canonical answer for this problem. Feel free to edit the answer to add additional details.


As i discussed with travel agent, he was willing to block an international flight ticket with a low fare for 3-4 days.  Now in such cases where ticket is blocked and then released if person decides not to purchase then does it change air fares on various travel portals?  Take a scenario that a last ticket is remaining for cheapest airfare and somebody blocks it. This implies that the fare is not available anymore but if it is released back then same fare will be available again...right?  This can create a situation where one purchases an expensive ticket and next day, a cheap fare becomes available!!   Is this possible?

Based on the question , I got curious. Is there a guide or resource that describes how the price of a ticket is determined?  When you search you often see curious effects like cheaper tickets for a flight from A to B with a layover compared to a direct flight. This seems counter-intuitive from an outsider's perspective since you fly twice. Also one way tickets more expensive than 2 ways.  It can be a short set of rules. Something that helps someone to get started with finding good prices. I know these can be very complex and they probably change over time and over airline interests but there is probably a simplified set of rules that can be enunciated.


I have this java code and I tried to check by system output the variables if it's all good and I don't get out of while loop, why? I insert alex as username and mihai as password and I don't get out of while loop. And I think it is really strange cuz everything is ok right?  boolean isGoodUandP = false;  String username = ""; String password = "";  while (isGoodUandP == false) {     System.out.print("Please enter username: ");     Scanner sUsername = new Scanner(System.in);     username = sUsername.nextLine();     System.out.println("username este " + username);      System.out.print("Please enter password: ");     Scanner sPassword = new Scanner(System.in);     password = sPassword.nextLine();     System.out.println("parola este " + password);      if ((username == "alex") && (password == "mihai")) {         isGoodUandP = true;         System.out.println("Bine ati venit!");     } }

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


I noticed people using pronouns next to their names Jo (she/her). I understand the reason behind the first part (she), but I completely don't get the second part. Doesn't "she" imply "her"? Is it even possible to use something else, "She changed his mind" (same person) - it wouldn't make sense (from the grammar perspective), would it? So my question is: why the second part is there? I understand this may be a delicate matter, I don't mean to offend, just trying to understand a grammatical (and possibly cultural) phenomenon.

It is becoming more common for people to explicitly state the pronouns to be used in addressing themselves: he/him, she/her, or they/them. For example, a name tag for a conference might read:  Cory Lopez Some Company She/Her   Usage seems to have settled on the singular they and them as gender neutral pronouns. Alternatives that were once widespread in niche communities, such as sie/hir, seem to have died out.   Whether or not one agrees with this language  shift, the pairing between subject and object case is fixed.  It's difficult to imagine someone who uses "he" as his subject case using anything but "him" as object case, and it's even harder to imagine that such a person would succeed in getting people to use a non-obvious collection of personal pronouns. (And you may see what I did -- flat out assumed that "he" and "his" automatically go together.)  What are the roots of the practice of presenting subject and object case pronouns as opposed to just subject case, subject and possessive, or some other combination?   (Note: I am not interested in a discussion of the gender politics and cultural shifts involved, just the mechanics of how the current representation was chosen.)


I have below method that does work Okay but I believe we can make it better by some how getting rid of these if conditions, but not sure how?   protected void SaveSession<T>(T sessionProperty, Management management) where T : class         {             string propertyType = typeof(T).Name;              if (propertyType.Equals(typeof(A).Name))             {                 management.A = sessionProperty as A;             }             else if (propertyType.Equals(typeof(B).Name))             {                 management.B = sessionProperty as B;             }             else if (propertyType.Equals(typeof(C).Name))             {                 management.C = sessionProperty as C;             }              Session["mysession"] = management;         }   I am using latest C# version 7.0

Seeing as C# can't switch on a Type (which I gather wasn't added as a special case because is relationships mean that more than one distinct case might apply), is there a better way to simulate switching on type other than this?  void Foo(object o) {     if (o is A)     {         ((A)o).Hop();     }     else if (o is B)     {         ((B)o).Skip();     }     else     {         throw new ArgumentException("Unexpected type: " + o.GetType());     } }


Suppose we have a bivariate normal (X, Y), whose mean is zero, and variance 1, and correlation \rho.  Is there an easy formula for  P(X < x | Y < y ) ?

The application here is interpreting the correlation coefficient $r$ in terms of $X$'s ability to predict $Y$ for extreme values of $X$. For example, if $r = .8$, then what is $p(Y < 0 | X < -2)$?


I'm portuguese and the citation and the bibliografy have to be in portuguese. I want "Afonso, D. e Ribeiro, A. F. (2018)" instead of "Afonso, D. and Ribeiro, A. F.(2018)".

How can I change the citation conjunction from english "and" to catalan "i"?  Otherwise  Author = {Kirk, D. and MacPhail, A.},   would get cited as (Kirk and MacPhail, 2002) when it should be (Kirk i MacPhail, 2002).  When there are more than 2 authors I get et al. which is fine.  I've seen  and  which do not work with apalike style.  Also, I'd rather not use biblatex if possible.


I am trying to make a custom dialog but am experiencing a problem. My app crashes when I push the button which shows the dialog.  Here is my code:   public class Cartas extends AppCompatActivity {      Dialog myDialog;     Button senmacho;     Button cerrar;      @Override     protected void onCreate(Bundle savedInstanceState) {         super.onCreate(savedInstanceState);         setContentView(R.layout.activity_cartas);          senmacho = (Button) findViewById(R.id.senmacho);         senmacho.setOnClickListener(new View.OnClickListener() {             @Override             public void onClick(View view) {                 senamacho();             }         });     }      public void senamacho(){         myDialog = new Dialog(Cartas.this);         myDialog.setContentView(R.layout.macho);         myDialog.requestWindowFeature(Window.FEATURE_NO_TITLE);         cerrar = (Button) findViewById(R.id.cerrar);         cerrar.setOnClickListener(new View.OnClickListener() {             @Override             public void onClick(View view) {                 myDialog.cancel();             }         });         myDialog.show();     } }

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


Given a family of complex numbers $(z_n)_n$ prove that there exists a subsequence $(z_{n_k})_k$ such that   $$\sum_{n} |z_{n}|\le \pi \left|\sum_{k} z_{n_k}\right|$$  I ailled to find a counter example of this inequality. what tricky me here is the constant $\pi$. How does that constant appears here? How can I prove this inequality?   Any hint or idea?

Consider the following problem.  Fix $n \in \mathbb N$. Prove that for every set of complex numbers $\{z_i\}_{1\le i \le n}$, there is a subset $J\subset \{1,\dots , n\}$ such that   $$\left|\sum_{j\in J} z_j\right|\ge \frac{1}{4\sqrt 2} \sum_{k=1}^n |z_k|.$$  I believe I proven have a stronger statement. Is this proof correct, and if so, what is the optimal constant?  My proof. Consider all the $z_i$ with positive real part. Call the real part of the sum of these numbers $X^+$. In a similar way, form $X^-$, $Y^+$, and $Y^-$. Without loss of generality, let $X^+$ have the greatest magnitude of these.  Note that because $|\operatorname{Re}(z)|+|\operatorname{Im}(z)|\ge |z|$, we have  $$ \left(\sum_{k=1}^n  |\operatorname{Re}(z_k)|+|\operatorname{Im}(z_k)| \right) \ge \sum_{k=1}^n |z_k|.$$  But note that $\sum \limits_{k=1}^n  |\operatorname{Re}(z_k)|+|\operatorname{Im}(z_k)| = X^+ + |X^-|+ Y^+ +|Y^-|$, so we have  $$ 4X^+ \ge \sum_{k=1}^n |z_k|.$$ By choosing $J$ to be the set of complex number with positive real part, this proves a stronger statement, because the factor of $1/\sqrt 2$ isn't needed.


I am a fan of Stack Overflow, and I see that SO has many sister sites, like Server Fault, etc. I really appreciate them, but their names need to give hints about what each site is all about.

There seems to be more than a few computer science/programming Stack Exchange networks (is that the correct term?). Stack Overflow, being the first, has by far the most users, questions, and answers.  What is the reasoning for creating the others, and are there clear guidelines for which kinds of questions should be posted? I can see a large amount of potential overflow, many cases of people not getting a good answer to their question, because the person who has the answer isn't browsing that particular network at the moment.  I understand that they were probably created for organizational purposes, but wouldn't it almost make more sense to just have them as categories under Stack Overflow, keep them separated but still connected, instead of making people have to create multiple 'account's, one for each network?  I am sure there was a very good reason to break them up, but as someone that is new to SE, it can be somewhat intimidating to decide which one to post in to ensure you get a good answer. For example, if I am a computer science student, my first instinct might to be to post in the computer science network, until I see that it literally has 1% of the users as the Stack Overflow network, which still seems to be for programming/computer science related questions.  So my second instinct would then to be to post it into the Stack Overflow site on the basis that I have a significantly higher chance of my question being seen and getting a good answer. Then I notice that there is also a 'programmers' network, and I don't even begin to know where that fits in. I, and I am assuming most people, will probably just post on Stack Overflow to be safe.  My question is, other than the short little description blurb of each one, is there a clear cut set of guidelines which what each network is intended for, what kinds of questions should go to each one, and is anything being done to encourage people to post in these newer, smaller (more specialized?) networks as opposed to just posting in big daddy Stack Overflow?  Now again, this is for computer science/programming/"why isn't this code doing what I want?" related questions, I am not saying that if I had a question about Linux or WordPress or something I would have the same confusion.


Today I noticed the support for my current Ubuntu version has expired (17.04). To upgrade, I tried apt-get update && apt-get dist-upgrade, but most of the  Zesty repositories don't work anymore. (does no longer have a Release file) My update manager and software manager don't give an indication for upgrading at all, refreshing does not work anymore.  Am I stuck with this version or could I still upgrade some way?

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


Lets suppose there is an event that gives a random outcome each time it happens. The set of possible events is finite, but their probabilities differ, sometimes by orders of magnitude. (imagine a heavily weighted dice)  How does one establish an upper bound for the probability of an event that is not in the set of possible outcomes? (eg. prove that with 99% probability a six sided dice will not give you a 7)  Usually when you sample a random event like this you can estimate the probability of a given outcome by $P_i = \frac{n_i}{N}$, where $P_i$ is the estimated probability of the $i$-th event, $n_i$ is the number of samples where the $i$-th event happened and $N$ is the total number of samples taken.  Obviously if the event is impossible, the estimated probability will always be zero. But as long as we have a finite number of samples, we cannot know for sure that the event is indeed impossible, or just have a really low non-zero probability. So the best we can do is to establish an upper bound, with a given confidence.  My question is: how to actually calculate that upper bound, based on the number of samples taken and the desired confidence? The solution is probably really simple, but so far the solution has eluded my attempts to find it via search. (but probably I was using the wrong search terms)

I have a large population of data instances (say, 1000 instances) that are either of class1 or of class2. I would like to obtain a confidence interval for how many instances are of class1 without exhaustively checking all instances. I have randomly sampled 50 instances, and all 50 were of class1. I used the  to determine that a 95% confidence interval for the percentage that an instance is of class1 is  [0.94, 1].  From my sampling, I know that at least 50 instances are of class1. For the remaining 1000 – 50 = 950 instances whose classes are unknown, I assume I can apply the [0.94, 1] confidence interval found above. Therefore, can I conclude that, with a 95% confidence, there are at least 50 + (1000 – 50)(0.94) = 943 instances from the population of 1000 that are of class1?  If this conclusion isn’t statistically sound, how can I obtain a confidence interval for class1?


I'm 42, got my master degree in Feb 2017. I´ve 17 years of work experience in the industrial field and I'm still doing academic research with my former supervisor and publishing papers.   I am going to pursue my higher education in Australia or New Zealand.  I also need to apply for a student visa once I get my admission.   Can my age play as an obstacle in my Ph.D. application?  Would my age cause trouble when I issue a student visa too?

Are there any age limits (formal, informal, or guidelines) that schools use when deciding to accept someone into a PhD program? I'm most curious about the upper age limits. For example, will most schools accept someone in their 40's? How about their 50's?


After downloading the SLDS I have copied a detail form from the lightning design system to the salesforce console. But when I save there is a popup saying  "No COMPONENT named markup://svg found".  I have found in some other topics that I have to replace < svg>  < svg class="slds-button__icon" aria-hidden="true">    < use xlink:href="/assets/icons/utility-sprite/svg/symbols.svg#down">< /use> < /svg    by  lightning:icon iconName=...."  BUT I don't understand how it can replace it exactly.. Both are very different and I can't figure out how it can replace it. That's why I am making a new topic. How exactly do we replace it?  Thank you !

Followed the Trailhead tutorial and I still get the same error about svg.  The code I am using is taken from the Lightning Design System. I created the supporting files as specified in the tutorial. Here is a snippet of the Component code (just note not all the code is included since it came directly from the LDS. The error is (Failed to save undefined: No COMPONENT named markup://svg found : [markup://michelleemanuel:forecastPlanComponent]: Source). Some of the other responses I saw said to read the tutorial - I have gone down that path and it did not work. I am not invoking this from a Visualforce page but from a Component.            <table class="slds-table slds-table--bordered slds-max-medium-table--stacked-horizontal">                                                         select all                                Opportunity Name                                                       Sort          ....


When I use ! as a field separator e.g. awk -F! it is giving error message bash: !: event not found. Why? It is accepting awk -F"\!". Bash version 3.2.25

I tried to create a script by echo'ing the contents into a file, instead of opening it with a editor  echo -e "#!/bin/bash \n /usr/bin/command args"  > .scripts/command   The output:     bash: !/bin/bash: event not found   I've isolated this strange behavior to the .  $ echo ! !    $ echo "!" bash: !: event not found  $ echo \#! #!  $ echo \#!/bin/bash bash: !/bin/bash: event not found    Why is bang causing this?   What are these "events" that bash refers to?     How do I get past this problem and print "#!/bin/bash" to the screen or my file?


What happened:   A little before 19:09 yesterday I found the . I clicked Trigger Reputation Recalc to see what happened. Within the next minute, I gained 92 reputation points. (See screenshot below) This morning, I see -105 reputation for Serial upvoting reversed     My question:   Was the increase a coincidence, or was it triggered by the recalc? If it was triggered by the recalc, should it have been removed?   Thanks

I just noticed that I lost a bunch of points from my reputation score, and I used the "reputation" tab on my user profile page to try and track down the cause.  During my investigation, I noticed there was an unusual event of type "reversal". In the normal place of a question title, it says "voting corrected".     What does this mean, and what caused it?  Did I do something wrong? Why did I lose all of that reputation? Is the system punishing me for leaving too many good answers?  Is there any way to earn it back?


For a random number experiment, I want to simulate from a trivariate Normal distribution with correlation matrix.   $\left(\begin{matrix}1&a&b\\a&1&c\\b&c&1\end{matrix}\right)\quad (a,b,c > 0)$  The correlations $a$ and $b$ are parameters in my experimental setup, and the third value, $c$, I can choose somewhat freely. Obviously, for any given values of $a$ and $b$, there are values of $c$ for which the matrix is not positive definite. I am wondering if I can somehow work out the "allowed" values of $c$, if $a$ and $b$ are given.  I tried to find conditions that make all eigenvalues positive. The characteristic polynomial of the eigenvalue problem is  $x^3 - 3x^2 + x(3-a^2-b^2-c^2) + (a^2+b^2+c^2-2abc-1)$  That only told me that the problem is symmetric in $a,b,c$. But for my actual question, it didn't really get me anywhere. Any help how to approach this is much appreciated.    Answer: Thanks for the links to duplicated questions. In particular  has the bounds on correlation I was looking for:  $ab - \sqrt{(1-a^2)(1-b^2)} \le c \le ab + \sqrt{(1-a^2)(1-b^2)}$

I know empirically that is the case.  I have just developed models that run into this conundrum.  I also suspect it is not necessarily a yes/no answer. I mean by that if both A and B are correlated with C, this may have some implication regarding the correlation between A and B.  But, this implication may be weak.  It may be just a sign direction and nothing else.    Here is what I mean...  Let's say A and B both have a 0.5 correlation with C.  Given that, the correlation between A and B could well be 1.0.  I think it also could be 0.5 or even lower.  But, I think it is unlikely that it would be negative.  Do you agree with that?    Also, is there an implication if you are considering the standard Pearson Correlation Coefficient or instead the Spearman (rank) Correlation Coefficient?  My recent empirical observations were associated with the Spearman Correlation Coefficient.


Use the fact that 11322, 13209, 29189, 56661, and 15096 are all divisible by 17 to show that   $$\begin{vmatrix}  1&1&2&5&1\\ 1&3&9&6&5\\ 3&2&1&6&0\\ 2&0&8&6&9\\ 2&9&9&1&6 \end{vmatrix}$$   is divisible by 17 without directly evaluating the determinant.

Consider the fact that $25875, 46552, 41354, 48691, 95818$ are all divisible by $23$. Use this fact to determine if \begin{vmatrix} 2 &5 &8 &7 &5 \\ 4 &6 &5 &5 &2 \\ 4 &1 &3 &5 &4 \\ 4 &8 &6 &9 &1 \\ 9 &5 &8 &1 &8 \end{vmatrix} is divisible by 23 or not, without directly evaluating the determinant.


I've seen this phrase repeated multiple times regarding what a 95% confidence interval actually means. However, I am confused, because if you're given a set of samples, can't you only compute a single 95% confidence interval from this set of samples? If that's the case, then it doesn't make sense to me why you can say "95% of the confidence intervals calculated from these random samples" when there's only a single 95% CI that can be computed. I could maybe be misunderstanding. Is the statement actually that if you random multiple times and obtain different sets of samples, and then you compute a 95% CI for each set, then 95% of these CIs will contain the true value?

It seems that through various related questions here, there is consensus that the "95%" part of what we call a "95% confidence interval" refers to the fact that if we were to exactly replicate our sampling and CI-computation procedures  many times, 95% of thusly computed CIs would contain the population mean. It also seems to be the consensus that this definition does not permit one to conclude from a single 95%CI that there is a 95% chance that the mean falls somewhere within the CI. However, I don't understand how the former doesn't imply the latter insofar as, having imagined many CIs 95% of which contain the population mean, shouldn't our uncertainty (with regards to whether our actually-computed CI contains the population mean or not) force us to use the base-rate of the imagined cases (95%) as our estimate of the probability that our actual case contains the CI?   I've seen posts argue along the lines of "the actually-computed CI either contains the population mean or it doesn't, so its probability is either 1 or 0", but this seems to imply a strange definition of probability that is dependent on unknown states (i.e. a friend flips fair coin, hides the result, and I am disallowed from saying there is a 50% chance that it's heads).  Surely I'm wrong, but I don't see where my logic has gone awry...


Prove that the equation $x^3+y^3+z^3 -3xyz -1=0$ defines a surface by revolution and determine the equation for the axis of revolution.   I know I have to end up with something that looks like this: $(x-a)^2+(y-b)^2+(z-c)^2=r^2$  $dx+ex+fx = g$ but I don't know where to start...  (I am aware that there is a similar question on this site but I  need a simpler answer than the one given there.)

Prove that the equation $x^3+y^3+z^3-3xyz=1$ defines a surface of   revolution and find the analytical equation of its axis of revolution.   I think that I need to apply Euler's formula, so that I get rid of the third-grade polynomial there: $x^3+y^3+z^3-3xyz=1 \Leftrightarrow (x+y+z)(x^2+y^2+z^2-xy-xz-yz)=1$ but then I stuck on how to prove it defines a surface of revolution.  The textbook notes that: $f(x,y,z)=0$ defines a surface of revolution around the axis with equation $\frac{x-x_0}{a}=\frac{y-y_0}{b}=\frac{z-z_0}{c}$ if and only if it can be written as a polynomial of $(x-x_0)^2+(y-y_0)^2+(z-z_0)^2$ and $ax+by+cz$. Any hint for that one?


I am trying to find the Laplace Transform of $$\frac{1-\cos(ax)}{x}.$$ I have tried to directly compute the integral and also tried to see if I could use the convolution theorem in some way but both lead nowhere. Any help would be appreciated!

How do I calculate   $$u(w)=\int_0^\infty \frac{1-\cos(wt)}{t}\,e^{-t}\,dt$$  I tried to do it, I use partial integration but I get lost. Is there any nice simple way to calculate it?


I am getting an error in a test class      System.LimitException: Too many query rows: 50001   Here is the line in the code. There are not 50,000 ProductCategoryMappings, only ~4,400. Seems I am misunderstanding the nature of the limit. Can someone assist and explain why I am hitting the limit? Thanks.   List<Product_Category_Mapping__c> listOfProductCategoryMappings = new List<Product_Category_Mapping__c>(             [SELECT Id, Segment__c, Site__c, Product_Name__c, Product_Category__c,                 Product_SubCategory__c, Product_Cat_SubCat__c, Product_Type__c              FROM Product_Category_Mapping__c]);

I realize that this is a very basic exception but I don't understand why it is being thrown although I am limiting the number of results to 10,000. My question is  but nothing there helps. I also looked at . Here is my query/code:  Map<Id, LoginGeo> location_dump = new Map<Id, LoginGeo>();                 for(LoginGeo lg : [SELECT Id, City, Country, CountryIso, latitude, longitude, PostalCode, LoginTime, Subdivision                                      FROM LoginGeo                                      WHERE Id IN :geo_ids                                      ORDER BY LoginTime DESC LIMIT 10000])                     location_dump.put(lg.Id, lg);   where geo_ids is a Set<Id> containing ids of type LoginGeo.   Why is it pulling 50,000+ records?  I get System.LimitException: Too many query rows: 50001 exception for that query.   Might be helpful:   This will work only on API version 35.0 and above.   The query alone returns exactly 10000 records, like it should, in Developer Console. The exception is thrown in a test method while deploying it to Production org. This works super fine in my sandbox, because the data there is limited. Fortunately for me these are standard objects, so you can try it in your orgs if at all.


I have created below batch apex class. I have also created test class for this. But this test class is only covering 27% of batch apex class. Also, it is not calling execute method of batch apex class.  Batch Apex class:    global class LeadDuplicateRemove implements Database.Batchable < sObject > {       global Database.QueryLocator start(Database.BatchableContext bc) {         return Database.getQueryLocator('select Id, CreatedDate, Phone, Status, Email from Lead Where convertedbusiness__c != null and LeadAudit__c = null  and isDeleted = false order by CreatedDate ASC Limit 1');     }      global void execute(Database.BatchableContext bc, List < Lead > scope) {         for (Lead lead: scope) {             Database.QueryLocator leadQueryLocator = Database.getQueryLocator([Select Id, CreatedDate, Phone, Status, Email from Lead where convertedbusiness__c != null and LeadAudit__c = '1' and isDeleted = false order by CreatedDate ASC Limit 1]);              Database.QueryLocatorIterator iterator = leadQueryLocator.iterator();             while (iterator.hasNext()) {                 Lead leadObj = (Lead) iterator.next();                  if(lead.ConvertedBusiness__c == leadObj.ConvertedBusiness__c){                     lead.ConvertedBusiness__c = null;                 }             }         }      }     global void finish(Database.BatchableContext bc) {     } }   Test class:  @isTest global class LeadDuplicateRemoveTest {     @testSetup      global static void setup() {          Lead lead1 = new Lead(LastName='testlead1 ', RAF_Nurture_Campaign__c = 'None',                               company='test', Email='testemai@email.com.invalid',Phone = '1111111111',Status ='Completed');          insert lead1;         insert new Lead(LastName='testlead1', RAF_Nurture_Campaign__c = 'None',                                company='Vtest', Email='testemai@email.com.invalid',Phone = '222222',Status ='Open');      }     @isTest global static void TestRun() {                  Test.startTest();         Database.executeBatch(new LeadDuplicateRemove());         Test.stopTest();      }  }

This is a canonical question and answer developed by the community to help address common questions. If you've been directed here, or your question has been closed as a duplicate, please look through the resources here and use them to shape more specific questions. To browse all canonical questions and answers, including more unit test resources, navigate to the  tag.  This canonical question is intended to address several classes of common questions by providing a quick summary and links to comprehensive resources:   How is code coverage obtained and calculated? How do I increase my coverage?  Why can't I cover these lines? Why isn't the body of my loop or conditional statement covered?


I know that  It is time (understood: for the speaker or for a group of people including the speaker) to do something.  and  It is time I or we did something.  do not mean the same thing: the first is a simple statement of fact, whereas the second means there is some kind of emergency.  How about these same structures when the action is to be performed by a second or third person?  Does the nuance stated above cease to exist between  It is time for you/him/her/them to do something.  and  It is time you/he/she/they did something.  ?

I'm watching Suits TV Series, and there was something that caught my attention. 2 guys meet, have a drink, chat, and then one guy says:     I mean it's time I told you. I made a deal with Darby to take over the   firm from Jessica.   Why is "told you" in paste tense? What exactly does it mean? He is saying that news right now. If I were to say that, I would say "it's time to tell you" or "it's time I'm gonna tell you".  Thanks!


I'm quite a newbie, but I know every time you start Terminal, some files are taken into account; and among those there is ~/.profile, which contains the following lines: if [ -d "$HOME/bin" ] ; then   PATH="$HOME/bin:$PATH" fi  I created the directory ~/bin because I want to put there some personal stuff. I closed Terminal and re-opened it, but PATH doesn't include ~/bin. So, as an experiment, I added a stupid echo "hello world!"  at the bottom of ~/.profile, saved changes and re-logged in with terminal, but nothing. It seems that file is totally ignored. Am I wrong? Or something changed?

Just installed Ubuntu 14.04.1 LTS.  According to .profile,  # ~/.profile: executed by the command interpreter for login shells.  # This file is not read by bash, if ~/.bash_profile or ~/.bash_login exists.   There is no ~/.bash_profile or ~/.bash_login.  It does not seem to source .profile when opening a terminal.   Why doesn't it source .profile when opening a terminal? Why is .profile there if it is not sourced? How do I know/control what is sourced when a new terminal is opened? When a new terminal is opened, does it do a "login"? Where is a good place to add $HOME/bin to my path? .bashrc? Will that cause a problem because .profile has the same code?


I am asked to solve the following problem $$\sum_{n=0}^\infty{\frac{\sin^3{(3^n)}}{3^n}}$$ My work: Using the identity $\sin{(3x)}=3\sin x-4\sin^3x$ $$\sum_{n=0}^\infty{\frac{\sin^3{(3^n)}}{3^n}}=\frac{1}{4}\sum_{n=0}^{\infty}{\frac{3\sin 3^n-\sin{3^{n+1}}}{3^n}}$$ From here I do not know how to procede, even tough it looks like it is a telescoping series, I cannot find a way to arrive at it. I also tried: $$n\rightarrow3^n\\ \sum_{n=1}^{\infty}{\frac{\sin^3{n}}{n}}\\ \text{Applying the identity}\\ \frac{1}{4}\sum_{n=1}^{\infty}{\frac{3\sin n-\sin{n}}{n}}$$ Which again looks like it might telescope, but I do not see how to arrive at the result. Any help, hint or solution is welcome!

How do I find the sum of this series?   $$\sum_{n=0}^{\infty}{\sin^{3}\left(3^{n}\right) \over 3^{n}}$$   Hints in the right direction would be appreciated.


I developed a Complete SPA application with jquery with ajax like asana. In this app, including some features like, Listing Users,  When clicking a user loading his tasks, When clicking a specific task loading the task details . etc...  I completed all the development parts with jquery, But When a user clicking a task from my app, I collecting the task id from an html element attribute and sent to ajax php page.   We can change the attribute value with firebug easily. After that clicking the task name its collecting a wrong value.  How can I solve this type of Security issues with jquery.

Which is better to do client side or server side validation?  In our situation we are using    jQuery and MVC.   JSON data to pass between our View and Controller.     A lot of the validation I do is validating data as users enter it. For example I use the the keypress event to prevent letters in a text box, set a max number of characters and that a number is with in a range.   I guess the better question would be, Are there any benefits to doing server side validation over client side?    Awesome answers everyone. The website that we have is password protected and for a small user base(<50). If they are not running JavaScript we will send ninjas. But if we were designing a site for everyone one I'd agree to do validation on both sides.


I just overheard a conversation between two foreign students and one of them was complaining abot something like this: "I attend every single class while my classmates skip whole days and dare I not share my notes with them , I suddenely become the meanest person in the world."  I'm not sure if I caught it properly, but this dare I not thing got me thinking. Is this correct grammatically? Or how else would you put it? Thanks in advance! :)

To my surprise, there's a missing question about this particularly interesting verb, dare. All I know about it is the fact it can be in two forms, as an auxiliary (without to: "I dare not mention their names") and main (with to: "Did anyone dare to admit it?") verb and the difference has something to do with agreeing with subject. Can somebody explain in a greater detail?


Use strong Principle of induction to prove that the amount of postage greater than or equal to 8cents cents can be made using a combination of 3 cent and 5 cent postage  this is what i have so far: Proof: let r(n):n=3p+5q,p,q∈N,n>0 Base case n=8,9,10 n=8,3(1)+5(1)..p(8) is true  n=9,3(3)+5(0)..p(9) is true  n=10,3(0)+10(1)..p is true  Assume p(k) is true for up to k≥10 k≥32  ⇒k+1≥10 ⇒(k+1)−3≥11  ⇒k−2=8  k-2=3p+5q  add 3 on both sides to get k+1  k+1=3p+5q+3  k+1= 3(p+1) +5q

Use strong Principle of induction to prove that the amount of postage greater than or equal to $30$ cents can be made  using a combination of $10$ cent and $3$ cent postage  this is what i have so far: Proof: let $r(n) : n=3p +10q, p,q \in \mathbb{N},n>0$  Base case $n=30,31,32$  $n=30, 3(10) + 10(0)..p(30)$ is true  $n=31, 3(7) + 10(1)..p(31)$ is true  $n=32, 3(4) + 10(1)..p$ is true  Assume $p(k)$ is true for up to $k\geq 32$  $k\geq 32$   $\Rightarrow k+1\geq 33$  $\Rightarrow(k+1)-3\geq 30$   $\Rightarrow k-2=30$


Please add possibility to check any set of offtopic reason. They are very different to group.  For example I'd review general offtopic/custom offtopic/belongs to other site but I don't like  reviewing "please post SSCCE" and "minimal understanding reasons.

Given the ever growing close vote review queue, I think it would help things along if we could streamline the filtering a little more.  At the moment we can filter by tag and by close reason, but off-topic has 7 sub-close-reasons. It may improve the workflow a bit to be able to narrow it down to one or two sub-close-reasons.       There are . About half of all the CV review queue. Supporting data :


At first, I thought that the timezone the servers were located in may be UTC, but from other MetaSO questions I see that .   that the clock on the servers is set to UTC.  Is this the reason why reputation seems to have a display error?  See the image below.  "Today" I received some +2 reps, for mods done "13 hours ago"...... but 13hr ago was 9/10/2013 for me, not 9/11/2013.    note; all these little reps are tag-cleanup that I'm doing.

When does a day start on the Stack Exchange network? Some badges (Enthusiast, , ) and voting limits are bound by and relate heavily to the concept of a day. Do days correspond to calendar days? What time zone is used?  Related


So I have ubuntu 12.04 on my usb, it loads perfectly and works. When I boot up my laptop (Windows 7) a menu box appears to ask how I want to run ubuntu, the first selection is Default which I use, the next being somewhere along the lines of "Install ubuntu", then a load of other selections  What I ask is, is there a way for Ubuntu to boot up without bringing up the box? Like when I boot up with my normal operating system...  Sorry if I'm confusing ;_;

I'm a teacher and will ask my students to either bring their laptops with Ubuntu installed with an specific list of packages preinstalled or bring a USB Drive or External Hard Drive with Ubuntu and the packages preinstalled.  For those who are going to bring the USB are two posibilities:   Install with the Ubuntu's "Startup disk creator" program, and telling it to reserve some space for persistence. Boot with a LiveCD and Install Ubuntu in the USB drive.   Then, in either case, boot with that media and install the packages.  So, for my purpose or any other purpose:   What is the best choice and why? Do we have another option? full explanation please.


I am trying to change the icon of my Java application. Here is the structure of my project:  src    gui       FileCopyManager.java images     folder.png   Now I have the following code:  public class FileCopyManager extends JFrame{     public void changeIcon() {         this.setIconImage(new ImageIcon(Toolkit.getDefaultToolkit()                 .getClass().getResource("../../images/folder.png")).getImage());     }     public FileCopyManager() {         changeIcon();         this.setSize(800,600);         this.setVisible(true);     }     public static void main() {         new SwingUtilities.invokeLater(()->{             new FileCopyManager();         });     } }   However when I try to run this code I get a NullPointerException on the this.setIcon line.  Any ideas?

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


whenever i try to log into any server with my premium account on the official launcher this error always pops up. i've tried restarting the game, deleting the game and even gone as far as resetting my laptop but nothing works. i'm currently using windows 10 and this has only recently been occurring and i'm wondering why this is happening since the cracked version works perfectly fine on my brothers laptop. any suggestions??  UPDATE: i have found a work around solution that works and enables me to log in fine without this error message. using a VPN (cyberghost 6) i connect to another IP and log into my mojang account from the launcher startup.

When I try to connect to servers or join up on lan worlds in Minecraft it says "Failed to Login : Invalid session (Try restarting your game)". Multiplayer used to work fine but now keeps coming up with this error. Can anybody help?


What are the uses for **kwargs in Python?  I know you can do an objects.filter on a table and pass in a **kwargs argument.    Can I also do this for specifying time deltas i.e. timedelta(hours = time1)?   How exactly does it work? Is it classes as 'unpacking'? Like a,b=1,2?

In the following method definitions, what does the * and ** do for param2?  def foo(param1, *param2): def bar(param1, **param2):


The invention is a sheet metal (top) place high above the ground. The sheet of metal is connected to a capacitor (the ⊔⊓ shapes) connected to the Earth. (The other stuff on the right of the image is a load intermittently driven when the charge on the capacitor rises high enough.) When I asked my question, I was confronted with the following statement. Your question has been identified as a possible duplicate of another question. If the answers there do not address your problem, please edit to explain in detail the parts of your question that are unique. The other question is titled. Does Tesla's photoelectric “solar cell” really work?  The first line is Tesla patented a device for gathering energy from light, using the photoelectric effect. It should be noted that I looked at this question and studies the answers before I asked my question.  In fact, I asked my question because I believe that "Does Tesla's photoelectric “solar cell” really work?"  was not answered, and most of the answers are looking in the wrong direction.  The device proposed in the patent works. Numerous experiments show that an electrode (metal plate)  above the ground will generate electricity when grounded through a load. It also gathers energy at a high voltage if placed high enough. There is a Scientific American Amateur Scientist article on this topic and does this experiment.  However, it is my opinion, and I believe most scientists' opinion, that the device does not gather its energy from the photoelectric effect.  This was put forth by an answer by  Carl Brannen for the question.  He stated, “Finally, it seems to me that you're restricted to the voltage of the electrons, i.e. about 12.4 - 4 = max photon - aluminum = 8 volts. I don't see how he got extremely high voltages. Maybe I misread it and he only got high charges (by waiting a long time). “ I agree with Carl Brannen.  I believe that the energy that Tesla sees is from atmospheric electricity. Thus. I asked the question, “does Tesla’s invention collect energy from the sun through the photoelectric effect, or does it collect energy from atmospheric electricity the way any electrode place above the ground does, or does it collect energy both from the photoelectric effect and atmospheric electricity? I then go on and ask the more pertinent question.  Does the field around the plate affect the positive charge left behind on the plate by the emitted electron?  Does the positive charge raise to the voltage that the atmosphere has induced on the plate? This is pertinent because it will further the understanding of electrostatics and would, if the field does affect the positive charge on the plate, make Tesla’s device more commercially viable. The patent says the invention collects energy from the sun.  My question is, does it collect energy from the sun through the photoelectric effect, or does it collect energy from atmospheric electricity the way any electrode place above the ground does, or does it collect energy both from the photoelectric effect and atmospheric electricity? Tesla states that the capacitor is charged to a high voltage.  In the photoelectric effect, the electron emitted would be at most 12 electron volts.  The electron would flow away from the plate due to the field around the plate.  However, does this affect the positive charge left behind on the plate by the emitted electron?  Does the positive charge raise to the voltage that the atmosphere has induced on the plate?

Tesla patented a device for gathering energy from light, using the photoelectric effect. ():    Basically just a sheet of "highly polished or amalgamated" metal (top) connected to a capacitor (the ⊔⊓ shapes) connected to the Earth.  (The other stuff on the right of the image is a load intermittently driven when the charge on the capacitor rises high enough.)  The patent says it would be able to collect energy from the sun.  Would this actually work?  Why or why not?  Does it need to be in a vacuum?  The patent seems to say that it works better in a vacuum but that it is not required.  Would the plate stay charged after electrons are thrown off, or would they be attracted and drift back to it and neutralize it?  How does the capacitor to earth make this better than a plate hanging in space?  It allows more charge to be stored for the same work function voltage of the metal?  The patent demonstrates that he doesn't understand the cause of the photoelectric effect ("sources of such radiant energy throw off with great velocity minute particles of matter which are strongly electrified, and therefore capable of charging an electrical conductor"), but he understands the results.  (Incidentally, I have tried building this with a piece of aluminum foil, electrolytic cap, and wire strong enough to stick a few inches into the ground.  I didn't see any voltage with a multimeter in bright sunlight.)


It seems that algebraists are particularly interested in sets equipped with binary operations that are well-behaved. I'm curious as to whether mathematicians have studied analogous structures equipped with non-binary operations. For example, why not have a set $G$ with some operation $\phi: G \times G \times G \to G$ such that $G$ is closed with respect to $\phi$? Granted, I'm not sure if the concept of an inverse can be maintained with a non-binary operation, (maybe associativity becomes non-sensical as well...?). Regardless, are there any interesting articles that address these kinds of questions?

Undergraduates learn about algebraic objects with one operation, namely groups, and we learn about algebraic objects with two "compatible" operations, namely rings and fields. It seems natural to then look at algebraic objects with three or more operations that are compatible, but we don't learn about them. I asked one of my professors why this is so and she posed this question in response: we have left-modules and right-modules, but there are no top-modules or bottom-modules, or any other ways of combining two elements to produce a third. I can't think of any satisfactory answer to either of these questions. Can anyone shed any light on them?  Edit: Now that I know these objects are studied, what I meant by "we" is essentially "Why are these objects not introduced to undergraduates (at least in a standard curriculum) given how natural they seem?"


Let $k$ be an arbitrary field and consider the corresponding one point field scheme $Spec(K)$.  Set $G:=\text{Gal}(K_s/K)$ the corresponding Galois group of separable closure.  Denote by $\mathbf{Sh}\big(\text{Spec }k)_{\text{et}}$ the category of etale sheaves over $Spec(k)$.   I often heard that known theorem that the exist a category equivalence between  $$ A: \mathbf{Sh}\big(\text{Spec }K)_{\text{et}} \cong\{\text{category of discrete G-modules}\} $$  given explicitely by   $$\mathcal F \mapsto \varinjlim_{K'/K\text{ finite separable extension}} \mathcal F(\text{Spec }K') $$  with inverse  $$\big(\text{Spec }k'\mapsto M^{\text{Gal}(\overline K/K')}\big) \leftarrow M $$  My question question is why this category equivalence also induces the identification of Etale cohomology with Galois cohomology?  In other words why  $H^i_{et}(X,\mathcal F)\cong H^i(G,A(\mathcal F))$ resp $H^i_{et}(X,A^{-1}(M))\cong H^i(G,M)$ always holds for etale sheaf $\mathcal F$ and $G$-module $M$?

Why is étale cohomology a natural generalization of Galois cohomology ?    I would like to inform you that I have a few quite sufficient prerequisites Galois cohomology and its application to solve the $90$ - th problem of Hilbert . So I can understand what you're going to tell me eventually.  However , in theory , I take a little well how to define étale cohomology which is based on the sheaves theory and sheaf cohomology , but so far, I have not had the opportunity to apply the etale cohomology theory to a calculation that proves practical . So it can pose obstacles thereafter, but I count on you anyway. If I do not well captured something that repulses me the way, I point you.  Thank you in advance for your help.


I get this error when running sudo apt-get update. What's it mean?  Err:10 http://ppa.launchpad.net/tualatrix/ppa/ubuntu xenial/main amd64 Packages   404  Not Found Ign:11 http://ppa.launchpad.net/tualatrix/ppa/ubuntu xenial/main i386 Packages Ign:13 http://ppa.launchpad.net/tualatrix/ppa/ubuntu xenial/main all Packages Ign:14 http://ppa.launchpad.net/tualatrix/ppa/ubuntu xenial/main Translation-en_IN Ign:15 http://ppa.launchpad.net/tualatrix/ppa/ubuntu xenial/main Translation-en Ign:16 http://ppa.launchpad.net/tualatrix/ppa/ubuntu xenial/main amd64 DEP-11 Metadata Ign:17 http://ppa.launchpad.net/tualatrix/ppa/ubuntu xenial/main DEP-11 64x64 Icons Fetched 94.5 kB in 8s (11.0kB/s) Reading package lists... Done W: The repository 'http://ppa.launchpad.net/tualatrix/ppa/ubuntu xenial Release' does not have a Release file. W: Data from such a repository can't be authenticated and is therefore potentially dangerous to use. W: See apt-secure(8) manpage for repository creation and user configuration details. E: Failed to fetch http://ppa.launchpad.net/tualatrix/ppa/ubuntu/dists/xenial/main/binary-amd64/Packages  404  Not Found E: Some index files failed to download. They have been ignored, or old ones used instead. suresh@suresh-Lenovo-G50-70:~$

PPA seems to be constantly offline. Whenever I use sudo apt-get update, this error is shown:  W: Failed to fetch http://ppa.launchpad.net/ 404  Not Found   How do I fix these errors?


My question is about flags... Many times the users asks question with no code, without effort and their work behind his question. We have to ask/comment him "Show your effort" , "What are doing so far " and so on.. So Is there any kind of flag for this ? or If it is not It should be added.

Questions can be closed or marked as duplicates.  What does it mean for a question to be "closed"? What does it mean for a question to be marked as a "duplicate"? Who can close a question? What are the reasons for closing a question ? Is closure the end of the road for a question? When are closed questions eligible for deletion?   Related        For more information, see "" in the .


Maybe it is something else other than video card which makes some games run on my system when others don't.  I can play , released November 11th, 2005. However, I can't run ,  or , which actually are older and have lower requirements!  My system specs:   Processor: P4 2.80 Ghz Ram: 512 mb   chipset: intel 845g   graphic controller: built-in intel 82845G   OS : Win XP     How can i verify which game will be playable and which game will not be playable on my system?

Is there a service that I can use to check if my machine will be able to run a certain game?


The entertaining but often deliberately inaccurate CinemaSins channel put out this video some time ago:                                  At 5:24, they have this dialogue:     RON: Don't remember this [the tunnel from the Hog's Head Inn to the Room of Requirement] on the Marauder's Map.   NEVILLE: That's because it never existed til now.   JEREMY (V.O.): So... a magical painting of Dumbledore's sister just dug a secret tunnel to Hogwarts.  THAT I am totally down with and have no questions about. [Goes on to ask why they didn't do this in the previous seven movies.]    Do the books clarify this? Did CinemaSins accidentally on purpose leave out the part where the movie clarifies this? Or did Neville actually mean the tunnel was brand new?   Charitably, I'd like to interpret Neville's "now" as "this year or thereabouts" rather than "literally right now".  That would certainly be consistent with Ron never having seen the tunnel on the Marauder's Map.  But I would be interested in hearing if Dumbledore's Army or anyone else had been using the tunnel before this point in the story. It does seem very convenient to the plot that they can just smuggle Harry and company into Hogwarts as soon as they arrive in Hogsmeade.

Did someone create the tunnel a very long time ago, or did the Room of Requirement create it as soon as Neville and co got hungry?  And how did he get into a tunnel while being in a room starting on the 5th floor or is it just rearranging all the time?


Hey so I am working on a system login window for my computer science course. The professor wants a system login window with a checkbox to mark if username is case sensitive and another check box to show the password. So far my code compiles but it will not run and I cant figure out why, my code isn't finished but Im unsure where to go from here. When I compile I get the following   ----jGRASP exec: java Win_SystemLogin  Exception in thread "main" java.lang.NullPointerException     at java.awt.Container.addImpl(Container.java:1097)     at java.awt.Container.add(Container.java:417)     at Win_SystemLogin.CreateComponents(Win_SystemLogin.java:71)     at Win_SystemLogin.<init>(Win_SystemLogin.java:37)     at Win_SystemLogin.main(Win_SystemLogin.java:100)    ----jGRASP wedge2: exit code for process is 1.   Here is my code  import java.awt.*; import javax.swing.*; import java.awt.event.*;  public class Win_SystemLogin extends JFrame {    final String SYS_USERNAME = "Fernando";    final String SYS_PASSWORD = "Zavala";     int WIN_WIDTH = 400;     int WIN_HEIGHT = 400;     private JPanel panelN;    private JPanel panelS;    private JPanel panelE;    private JPanel panelW;    private JPanel panelC;     private JLabel       attemptsLabel;    private JTextField   attemptsTextField;    private JLabel       userNameLabel;    private JTextField   userNameJTextField;    private JLabel       passwordLabel;    private JTextField   passwordJTextField;    private JButton      loginButton;    private JButton      exitButton;    private JCheckBox    caseSensitiveCheckBox;  public Win_SystemLogin() {    setTitle("System Login");    setSize(WIN_WIDTH, WIN_HEIGHT);    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);    setLayout(new BorderLayout() );      CreateComponents();    add (panelN,BorderLayout.NORTH);    add (panelS,BorderLayout.SOUTH);    add (panelE,BorderLayout.EAST);    add (panelW,BorderLayout.WEST);    add (panelC,BorderLayout.CENTER);    setVisible(true);     loginButton.addActionListener(new ButtonListener());    exitButton.addActionListener(new ButtonListener()); } private void CreateComponents() { userNameLabel = new JLabel("Username"); passwordLabel = new JLabel("Password"); userNameJTextField = new JTextField(); passwordJTextField = new JTextField(); attemptsLabel = new JLabel("Attempts"); attemptsTextField = new JTextField(10); loginButton = new JButton("Login"); exitButton = new JButton("Exit");  JPanel panelN = new JPanel(); JPanel panelE = new JPanel(); JPanel panelS = new JPanel(); JPanel panelW = new JPanel(); JPanel panelC = new JPanel();  panelC.add(userNameLabel); panelC.add(userNameJTextField); panelC.add(passwordLabel); panelC.add(passwordJTextField); panelE.add(attemptsLabel); panelE.add(attemptsTextField); panelE.add(caseSensitiveCheckBox); panelS.add(loginButton); panelS.add(exitButton);  pack(); setVisible(true);   } private class ButtonListener implements ActionListener {    public void actionPerformed(ActionEvent e)    {    String actionCmd = e.getActionCommand();     if (actionCmd.equals("Login"))    {     JOptionPane.showMessageDialog(null,"Welcome" );    }    else if(actionCmd.equals("Exit"))    {    System.exit(0);    }     } } public static void main(String args[]) {    new Win_SystemLogin(); } }

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


I want to install Ubuntu 16.04 on my new PC and to keep Windows 10. I have a 128GB SSD and a 1TB HDD. I have read that I should install Ubuntu on the SSD. I am now at the partitioning step and I have to choose where to install Ubuntu. If I choose "Install ubuntu alongside Windows 10" I am under the impression that it will be installed on the HDD. Therefore I chose the advanced partitioning option. The installer shows me my partitions (I did not create anything):   /dev/sda   /dev/sda1 (efi, Windows Boot Manager, 272MB) /dev/sda2 (16MB) /dev/sda3 (126712MB (53182MB used) ntfs) /dev/sda4 (1027MB, ntfs) two free space partitions of 1MB and 5MB  /dev/sdb with two ntfs partitions (one of 986GB and one of 13 GB)   What do I have to choose as device for boot loader installation? Do I have to create new partitions? I am a bit lost and I don't want to lose Windows.  Moreover where should I put my personal files? On HDD or SSD?

I'm absolutely new to Linux. I would like to know how to install Ubuntu alongside the pre-installed Windows 8+ OS.  Should I do it with Wubi, or through the Live USB/DVD?  What steps do I need to take to correctly install Ubuntu?


Lets say someone is blocking an Eldrazi with annihilator. Can they sacrifice a creature they blocked with to count as one of the things sacrifice with annihilator?

Suppose Player 1 has a Dragon on the table and  in hand, while Player 2 has two Spiders on the table.  Player 1 chooses to attack with the Dragon and Player 2 chooses to block with one of the Spiders.  Before combat damage is to be dealt, Player 1 uses Unsummon on the blocking Spider.    Does Player 2 take any life damage from the attacking Dragon?


I tought one of my pokemon Strength to test if I could erase it with another TM. Turns out that no, you still have to do something special to forget HM moves just like prior generations.   How can I forget HM moves in Pokemon X/Y?

Where can I find these two NPC's in Pokemon X & Y?  I accidentally gave my main starter a stupid useless HM move, and now I'm very unwilling to sacrifice the other 3 to make room for another one.  If I'd like to delete a move, where can I find him? If I need to re-learn a deleted move, where can I find a move trainer?


Why did Americans come up with new words for the British English words like "sidewalk" instead of "pavement"?  I only see a reason they omitted certain letters in some words, like "colour" - "color", but I don't see any reason why they would make their own words.  Why didn't they stick with the British words?

Why do people in different areas speak differently? Where do accents come from, how do they change and/or survive over time and why do we have them?   Reading recommendations on this topic would be welcome.


Using terminal, I want to disable the feature of iTunes that causes it to run whenever a device is plugged in, but I want to do this entirely from the terminal, so that it can be part of an OSX setup script.

i know we already have topics about it, but i did not found my solution.  So i don't want to start iTunes, when i plug in iDevices. We have like 300 iPads, and i am using the configurator. iTunes still starting automatically, even when the Configurator is running.  I really don't want to turn off this settings under the iPad summary screen one by one. I have already turned off the autosync.


I'm starving trying to make the following thing work:  #!/bin/bash MARCOMIN=1 MARCOMAX=3 ENZOMIN=1 ENZOMAX=3 GIOVANNIMIN=1 GIOVANNIMAX=3 VALUEMARCO=12 VALUEGIOVANNI=4 VALUEENZO=12  for i in MARCO ENZO GIOVANNI; do         echo $$iMIN is $i\'s MIN         echo $$iMAX is $i\'s MAX         echo $VALUE$i is $i\'s VALUE done  exit 0   It doesn't writes macro as I'd like, though.  me@myhost:~$ bash test.sh 20341iMIN is MARCO's MIN 20341iMAX is MARCO's MAX MARCO is MARCO's VALUE 20341iMIN is ENZO's MIN 20341iMAX is ENZO's MAX ENZO is ENZO's VALUE 20341iMIN is GIOVANNI's MIN 20341iMAX is GIOVANNI's MAX GIOVANNI is GIOVANNI's VALUE   Obviously this is only one of my test. I tried many different ways of writing macros this way but I can't fix it. Found many similar questions here and on SO, but none matched my case.  bash -x test.sh follows:  + MARCOMIN=1 + MARCOMAX=3 + ENZOMIN=1 + ENZOMAX=3 + GIOVANNIMIN=1 + GIOVANNIMAX=3 + VALUEMARCO=12 + VALUEGIOVANNI=4 + VALUEENZO=12 + for i in MARCO ENZO GIOVANNI + echo 21466iMIN is 'MARCO'\''s' MIN 21466iMIN is MARCO's MIN + echo 21466iMAX is 'MARCO'\''s' MAX 21466iMAX is MARCO's MAX + echo MARCO is 'MARCO'\''s' VALUE MARCO is MARCO's VALUE + for i in MARCO ENZO GIOVANNI + echo 21466iMIN is 'ENZO'\''s' MIN 21466iMIN is ENZO's MIN + echo 21466iMAX is 'ENZO'\''s' MAX 21466iMAX is ENZO's MAX + echo ENZO is 'ENZO'\''s' VALUE ENZO is ENZO's VALUE + for i in MARCO ENZO GIOVANNI + echo 21466iMIN is 'GIOVANNI'\''s' MIN 21466iMIN is GIOVANNI's MIN + echo 21466iMAX is 'GIOVANNI'\''s' MAX 21466iMAX is GIOVANNI's MAX + echo GIOVANNI is 'GIOVANNI'\''s' VALUE GIOVANNI is GIOVANNI's VALUE + exit 0

I think an example is in order. Consider I have these two environment variables setup (by a Continuous Delivery tool): PACKAGE_VER=1.2.3 and USE_VERSION_FROM=PACKAGE_VER.  What I want now is a script that can't predict the name of the variable pointing out 1.2.3, only USE_VERSION_FROM. And so, I'm looking for a way to get my script to know the version to use (1.2.3) without knowing anything other than that USE_VERSION_FROM points out the name of the variable that holds the version number.  My naïve non-working first attempt:  #!/bin/bash VERSION_TO_USE="${${USE_VERSION_FROM}}"


Recently, I decided to get back into Blender, just as a fun hobby. After modeling some things, I tried to use an HDR image to light my scene. When I rendered the scene, the HDRi was not working properly.    As you can see, all the materials render fine, but the HDRi is not working properly. Below is the HDR image I used.

I'm having a problem rendering the environment map. I downloaded a sample project that has the same settings as my project but it renders without a problem. I tried using both a .hdr and .png image. Attached are screenshots with node settings. First is the incorrect render and 2nd image is the project the renders correctly. How do I go about fixing this?


Can anyone please explain Why we are using where 1=1 in SQL select query?  Select * from <TableName> Where 1=1 <cfif isdefined('Something)> AND  columnName = value </cfif>

Why would someone use WHERE 1=1 AND <conditions> in a SQL clause (Either SQL obtained through concatenated strings, either view definition)  I've seen somewhere that this would be used to protect against SQL Injection, but it seems very weird.  If there is injection WHERE 1 = 1 AND injected OR 1=1 would have the same result as injected OR 1=1.  Later edit: What about the usage in a view definition?    Thank you for your answers.  Still, I don't understand why would someone use this construction for defining a view, or use it inside a stored procedure.  Take this for example:  CREATE VIEW vTest AS SELECT FROM Table WHERE 1=1 AND table.Field=Value


I am attempting to install MATLAB on Ubuntu 14.04 LTS. I am following .   I downloaded the MATLAB 2015a ISO file. I then typed these commands into the terminal:    $ sudo mkdir /usr/local/iso $ cd ~/Downloads $ sudo mount -o loop R2015a-glnxa64.iso /usr/local/iso mount: block device /home/matta/Downloads/R2015a-glnxa64.iso is write-protected, mounting read-only $ cd /usr/local/iso $ ./install ./install: 1: eval: /usr/local/iso/bin/glnx86/install_unix: not found    The glnx86 folder does not exist but there is a glnxa64 folder in that location with an 'install unix' file inside. I tried modifying the install file but everything is read-only so I can't.  I have been using linux for 2 days now so sorry for any glaring errors.

I am trying to install Matlab on Ubuntu 12.04, I have a 32bits machine. I downloaded the files and set the file install to exectable, then run :  $ ./install -v   but then I got the error :  Error : Cannot locate Java Runtime Environment (JRE). The directory /Unix_MAC/sys/java/jre/glnx86/jre does not exist.   So I decided to add the path of matlab's jre to the command ( But before I went to sys/java/jre/glnxa64/jre/glnxa64 and changed the file java to executable), then tried :  $ ./install -v -javadir /home/mbenseddik/Unix_MAC/sys/java/jre/glnxa64/jre/   But then I got the following error :  Preparing installation files ... cp: impossible d'évaluer «/home/mbenseddik/Unix_MAC/bin/glnx86/*»: No such file or directory ->  DVD                 = /home/mbenseddik/Unix_MAC ->  ARCH                = glnx86 ->  DISPLAY             = :0.0 ->  TESTONLY            = 0 ->  JRE_LOC             = /tmp/mathworks_11294/sys/java/jre/glnx86/jre ->  LD_LIBRARY_PATH     = /tmp/mathworks_11294/bin/glnx86       Command to run:  /tmp/mathworks_11294/sys/java/jre/glnx86/jre/bin/java -Xmx512m  -splash:"/home/mbenseddik/Unix_MAC/java/splash.png" -Djava.ext.dirs=/tmp/mathworks_11294/sys/java/jre/glnx86/jre/lib/ext:/tmp/mathworks_11294/java/jar:/tmp/mathworks_11294/java/jar/ja_JP/:/tmp/mathworks_11294/java/jar/zh_CN/:/tmp/mathworks_11294/java/jarext:/tmp/mathworks_11294/java/jarext/axis2/:/tmp/mathworks_11294/java/jarext/guice/:/tmp/mathworks_11294/java/jarext/webservices/ com/mathworks/professionalinstaller/Launcher -root "/home/mbenseddik/Unix_MAC" -tmpdir "/tmp/mathworks_11294"   Installing ... /tmp/mathworks_11294/sys/java/jre/glnx86/jre/bin/java: 1: /tmp/mathworks_11294/sys/java/jre/glnx86/jre/bin/java: Syntax error: "(" unexpected Finished   It seems like it is looking for glnx86 whereas the only directory inside the sys/java/jre directory is glnx64...  Any idea on the matter ?


I made the changes in /etc/security/limits.conf   test        hard    maxlogins       2 sftptest    hard    maxlogins       2    After above entries I have tested below scenarios    Open 2 putty sessions when I tried to open 3rd sessions it disconnect automatically (Working fine with ssh user not for sftp user ) Open 2 putty sessions when I am trying to open 3rd session from the filezilla / winscp connection disconnected automatically (Working fine with ssh user ) 3.When I am trying to open 3 sessions in filezilla/winscp I am able to open 3 sessions ( Not working) when I am trying to open 3 sessions in filezilla/winscp with sftp users I am able to open all three sessions  -Is there any difference in putty client and winscp/filezilla ? -SSH users having shell login but sftp users don't have shell login  Is there any chance to  limit the connections 2 for sftp users?   I am pretty new to Linux.

How can I limit the number of active logins per user?  I've seen this on various servers before, and I was wondering how I could set this up myself.  Perhaps in those cases, this was accomplished by limiting the number of active SSH logins per user?  And I guess that would be the way to go.  How would I set this up?


Why should an equation () in which first time derivative is related to second space derivative have a solution that contains $i$?The wave function is supposed to be complex, but I am unable to understand why it can also be assumed to be complex directly from my previous statement as stated in Quantum Physics by . Can anyone help me develop an intuition?

1.  Why is the wave function complex? I've collected some layman explanations but they are incomplete and unsatisfactory. However in the book by Merzbacher in the initial few pages he provides an explanation that I need some help with: that the de Broglie wavelength and the wavelength of an elastic wave do not show similar properties under a Galilean transformation. He basically says that both are equivalent under a gauge transform and also, separately by Lorentz transforms. This, accompanied with the observation that $\psi$ is not observable, so there is no "reason for it being real". Can someone give me an intuitive prelude by what is a gauge transform and why does it give the same result as a Lorentz tranformation in a non-relativistic setting? And eventually how in this "grand scheme" the complex nature of the wave function becomes evident.. in a way that a dummy like me can understand.  2.   A wavefunction can be thought of as a scalar field (has a scalar value in every point ($r,t$) given by $\psi:\mathbb{R^3}\times \mathbb{R}\rightarrow \mathbb{C}$ and also as a ray in Hilbert space (a vector). How are these two perspectives the same (this is possibly something elementary that I am missing out, or getting confused by definitions and terminology, if that is the case I am desperate for help ;)   3.   One way I have thought about the above question is that the wave function can be equivalently written in $\psi:\mathbb{R^3}\times \mathbb{R}\rightarrow \mathbb{R}^2 $ i.e, Since a wave function is complex, the Schroedinger equation could in principle be written equivalently as coupled differential equations in two real functions which staisfy the Cauchy-Riemann conditions. ie, if $$\psi(x,t) = u(x,t) + i v(x,t)$$ and $u_x=v_t$ ; $u_t = -v_x$ and we get $$\hbar \partial_t u  = -\frac{\hbar^2}{2m} \partial_x^2v + V v$$ $$\hbar \partial_t v  = \frac{\hbar^2}{2m} \partial_x^2u - V u$$ (..in 1-D) If this is correct what are the interpretations of the $u,v$.. and why isn't it useful. (I am assuming that physical problems always have an analytic $\psi(r,t)$).


I am using MySQL 5.5 version  when i try to insert the ‘ special character in database it is automatically converted into â€™ .   i changed the database character set to utf8 & character_set_connection to utf8 but i unable to get the expected result.  how to solve this issue ?  kindly help on this

I'm setting up a new server and want to support UTF-8 fully in my web application. I have tried this in the past on existing servers and always seem to end up having to fall back to ISO-8859-1.  Where exactly do I need to set the encoding/charsets? I'm aware that I need to configure Apache, MySQL, and PHP to do this — is there some standard checklist I can follow, or perhaps troubleshoot where the mismatches occur?  This is for a new Linux server, running MySQL 5, PHP, 5 and Apache 2.


I'm so confused of the definition of the terminology, "normality". I mean, normality of what?   According to central limit theorem, regardless of the distribution of population,the computed values of the average will be distributed according to the normal distribution, which allows us to do statistical analysis.  However, lots of sources of information say that in order to do the parametric method which includes most of the statistical analysis we conduct, the data should follow normal distribution.   In my view at this point, tho arguments don't agree, and they contradicts to each other.  I want to specify the term, 'normality' of data.

In many different statistical methods there is an "assumption of normality".  What is "normality" and how do I know if there is normality?


I have a tex file with appendices. The publisher wants separate source files for the body of the document and the appendices. However, I have used many cross-referencing in the appendices that refer to equations and theorems in the document body.  Is there any way that I can provide a separate tex file for the appendices without replacing all cross-references by hard typed numbers?

I want to cross-reference between different .tex files, just because I want to put every chapters separately.  Let's say in file chapterI.tex I have \label{a} and I want to access this in file chapterII.tex using something like \ref{a}. How to do this exactly in LaTeX, moreover if LEd have an easy feature to cover this, it will be better (I have put those both files in the same project).  I found another question with similar title, but I just didn't really understand. It's here: .


FavPic is an array with a picture element stored in it, im trying to set the variable, pRef, equal to that array element. Instead, I keep getting Null Pointer Exception crashes. What exactly is a Null Pointer exception, and how would these few lines of code cause such a thing? Thanks!      public void setFavouritePicture (Picture pRef)   {     pRef = favPic[0];    }

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


I have a table where the third value is the sum of the first two: \documentclass{article} \usepackage{siunitx}  \begin{document} \centering \begin{tabular}{SSS}         \hline         $\alpha$ & $\beta$ & $\gamma$ \\         \hline         -12.34   &   -5.67  & -18.01   \\         -89.1    &   +2.3   & -86.8    \\          +4.56   &  -78.9   & -74.34   \\         \hline     \end{tabular} \end{document}  When I compile it, I get whis table:  It is what I need, except that the + symbol disappears. I suppose this is some LaTeX magic about typographical rules, but I have been asked to keep it to make it clear that the number is an addendum. So, how can I preserve the +?

I'm using siunitx's S columntype to align numbers in a table. The numbers are percentage values which should all have a preceding sign (some - and some +).  The numbers with a "-" are shown with a sign, the "+" sign vanishes as siunitx processes the numbers.   How can I keep the sign of the numbers including the "+" sign?


Let $n\geq1$ and a sequence of upper semi-continuous functions $f_n:E \to \mathbb{R}$ where $E$ is some space (we can suppose it compact).  Let $f:E \to \mathbb{R}$ be an upper semi-continuous function and assume that $f_n \xrightarrow[n\to\infty]{}  f$. Are there conditions I can add in order to say $$\sup_{E} f_n \xrightarrow[n\to\infty]{} \sup_{E} f \quad ?$$  Is an uniform convergence on $E$ helpful ?

Let $f: X \times Y \rightarrow \mathbb{R}$ be a continuous map. Show that if $Y$ is compact then the function $g: X \rightarrow \mathbb{R}$ defined by $g(x) = \inf \{f(x,y): y \in Y\}$ is also continuous.  No clue here. Can you please help?


In C++, I have often made a unit test class a friend of the class I am testing. I do this because I sometimes feel the need to write a unit test for a private method, or maybe I want access to some private member so I can more easily setup the state of the object so I can test it. To me this helps preserve encapsulation and abstraction because I am not modifying the public or protected interface of the class.  If I buy a third party library, I wouldn't want its public interface to be polluted with a bunch of public methods I don't need to know about simply because the vendor wanted to unit test!  Nor do I want have to worry about a bunch of protected members that I don't need to know about if I am inheriting from a class.   That is why I say it preserves abstraction and encapsulation.  At my new job they frown against using friend classes even for unit tests. They say because the class should not "know" anything about the tests and that you do not want tight coupling of the class and its test.   Can someone please explain these reasons to me more so that I may understand better? I just do not see why using a friend for unit tests is bad.

How do I unit test (using xUnit) a class that has internal private methods, fields or nested classes? Or a function that is made private by having  (static in C/C++) or is in a private () namespace?  It seems bad to change the access modifier for a method or function just to be able to run a test.


Suppose I have an ArrayList, which has paths to the specific file to be processed. But this file can only be proccessed, if there's only one in a folder. Here's what I mean:  My ArrayList  List<String> pathsToTheFile = new ArrayList<>();   has  C:\123\456\NameOfUniqueFolder0 C:\123\456\NameOfUniqueFolder1 C:\123\456\NameOfUniqueFolder2 C:\123\456\NameOfUniqueFolder3 C:\123\456\NameOfUniqueFolder4   Suppose my 5th element is   C:\123\456\NameOfUniqueFolder0  Obviosuly, it's a duplicate of my 0 element, since the file inside this folder  SHOULD NOT be proccessed at all. C:\123\456\NameOfUniqueFolder0 should be removed form the list.  I can not use a SET here, because it will "remove" the duplicate, but one path to the folder will be still there, and the file inside get proccessed.

I have an ArrayList<String>, and I want to remove repeated strings from it. How can I do this?


I am working on a licensing technique. I need it to expire after 30 days. In the mean time if user changes his/her time to the past time the licensing period is extending. I am new at this. so i thought of generating the license according to the VM's UUID. But i dont know how to retrive the UUID from server as all the info is stored in server. My Guest OS is always windows 7. It wont change. Now I need to find the UUID of the machine in which the Windows 7 is installed.  Help me out please.

I need to write a function that generates an id that is unique for a given machine running a Windows OS.  Currently, I'm using WMI to query various hardware parameters and concatenate them together and hash them to derive the unique id. My question is, what are the suggested parameters I should use?  Currently, I'm using a combination of bios\cpu\disk data to generate the unique id. And am using the first result if multiple results are there for each metric.  However, I ran into an issue where a machine that dual boots into 2 different Windows OS generates different site codes on each OS, which should ideally not happen.  For reference, these are the metrics I'm currently using:  Win32_Processor:UniqueID,ProcessorID,Name,Manufacturer,MaxClockSpeed Win32_BIOS:Manufacturer Win32_BIOS:SMBIOSBIOSVersion,IdentificationCode,SerialNumber,ReleaseDate,Version Win32_DiskDrive:Model, Manufacturer, Signature, TotalHeads Win32_BaseBoard:Model, Manufacturer, Name, SerialNumber Win32_VideoController:DriverVersion, Name