I have installed PostgreSQL on my Windows machine for development. Now I haven't used it for a while, and have forgotten the password for user postgres (default admin user in PostgreSQL). How can I reset the password for postgres in PostgreSQL on Windows?    I followed Milen's suggestion, but got this message when trying to reload the configuration file:  C:\Program Files\PostgreSQL\9.1\data>pg_ctl reload -D . pg_ctl: could not send reload signal (PID: 3396): Operation not permitted   In Windows there is a menu option "Reload Configuration" that worked better, as shown below:

This morning I’ve been trying to connect the PostgreSQL database on my Windows 7 Professional desktop.  The default value is ‘postgres’, but sure enough I forgot what password I used when I originally installed it.  I have googled and found a  related to resetting your password. I followed the steps, but the end result is a bit different then mentioned in the post. I used—  net user postgres postgres   to reset the password for my database but instead of a success message I am getting:     "System error 5 has occurred. Access is denied."   system error. How do I avoid this error and reset the password?


I have python code with the directory structure -     main.py basics.py component1   file1.py   file2.py component2   file1.py   file2.py   I want the code in the directories component1 and component2 to use code from basics.py. What is the most pythonic way of doing this?  Thanks!

How do I import a Python module given its relative path?  For example, if dirFoo contains Foo.py and dirBar, and dirBar contains Bar.py, how do I import Bar.py into Foo.py?  Here's a visual representation:  dirFoo\     Foo.py     dirBar\         Bar.py   Foo wishes to include Bar, but restructuring the folder hierarchy is not an option.


How do I index into an enum via "item index" instead of the "value indexing": "Value indexing" (not useful to me with what I am doing): eSerialBauds eBaud = static_cast<eSerialBauds>(1200); // yields eBaud1200  I want "item indexing": ( How to get the following? ) eSerialBauds eBaud = static_cast<eSerialBauds>(3); // to yield eBaud1200   // values (from WinBase.h) #define CBR_110             110 #define CBR_300             300 #define CBR_600             600 #define CBR_1200            1200 #define CBR_2400            2400    enum class eSerialBauds {   eBaud110 = CBR_110,   eBaud300 = CBR_300,   eBaud600 = CBR_600,   eBaud1200 = CBR_1200,   eBaud2400 = CBR_2400, }   Please note that I am given this enum class from another class.  There are many. So I have to work with what is given to me. I did write a work around method but it would be nice to have a more elegant way of getting the result.

I was wondering in C++ if I have an enum can I access the value at the second index?  For example I have  enum Test{hi, bye};   if I want 'hi', can I do something like Test[0], thanks.


What is the best way to inform users of an add-on's warnings, info, or things they must do for the function to work? As it seems to be hard to add info to the main header, is it better to use (Blender dreaded) pop-ups? So what are your preferred ways and how do you do it, code-wise?  (I don't mean info view or console, because users do not have these things open - so this is not a duplicate question)

I wonder if it is currently possible to print or send messages to the Report window in the Info view? this would be quite useful sometimes.


What is the geometrical interpretation of Riemann Stieltjes Integration ?   We know that for Riemaan integration $\int_{a}^b f(x)dx$ represents the area bounded by the curve $y=f(x)$& the straight lines $x=a$ & $x=b$.  But when we integrate $f(x)$ with respect to another function $g(x)$ then which area represents that integration geometrically ?

What is the intuition/idea behind integration of a function with respect to another function? Say $$\int f(x)d(g(x)) \;\;\;\;\;?$$ or may be a more particular example $$\int x^2d(x^3)$$  My concern is not at the level of problem solving. To solve we could simply substitute $u=x^3$ and then $x^2=u^{2/3}$. My concern is rather about what meaning physical/geometrical does this impart?  ADDED if you ask what kind of meaning I seek, integration of a function w.r.t a variable gives the area under the curve and above x-axis.


How to prove $\mathbb R\times \mathbb R \sim \mathbb R$?  I know you have to split the problem up into two claims, for each direction to prove that it is a bijection, but i don't know how to go much further than that...

Could any one give an example of a bijective map from $\mathbb{R}^3\rightarrow \mathbb{R}$?  Thank you.


I'm coding a tool in java that need some input passed by args[] I know how to use argument but i wish to handle better this input.  this is a part of my code:  if (args.length > 0 ) {          switch (args[0]) {          case "scan": blah blah         break;         case "some cases": some code         break;   but of course args are strictly bounded to their position, in fact in the command line i have to call:     java javaProgram arg1 arg2 arg3   i really don't like this...  What i want is to better manage this arguments with options like any other c programmed tool, indipendent from positions:  example:     java javaProgram -ip 127.0.0.1 -database data.txt -vv -out output.txt   any help will be appreciated!  Dave  (i'm thinking about an array list of arguments, can be a solution?)

What is a good way of parsing command line arguments in Java?


Can a malware occupy memory without getting noticed by or displayed in "Windows Task Manager"? How can we detect such malware, if any? Can you give examples of such malware?

If I would have a running virus on my system, would I be able to see the process in taskmanager? I mean, would it be possible for a running virus to circumvent the taskmanager so the process doesn't appear in the tasklist of windows7?  Or in other words. If I really now all the processes in taskmanager to be secure, I also know that my PC is clean?


First of all, sorry about my english. I installed ubuntu like, 5 months ago, but now my ubuntu gets freezed and stuck, it waits too way long to load an application,  I had to run another OS to do somenthing that I could perfectly do in Ubuntu. Do you guys know, how to "clean" my ubuntu? I mean, to make it faster? like it used to be at the beginning Thanks in advance.

What are your tips for improving overall system performance on ubuntu? Inspired by this  I realized that some default settings may be rather conservative on Ubuntu and that it's possible to tweak it with little or no risk if you wish to make it faster.  This is not meant to be application specific (e.g. make firefox load pages faster), but system wide.  Preferably 1 tip per answer, with enough detail for people to implement it.  A couple of mine would be:   Install  (via Software Center or sudo apt-get install preload); Change  value - "which controls the degree to which the kernel prefers to swap when it tries to free memory";   What are yours?  PS: Since this is not intended to have a unique answer but rather, several useful tips, I'm making this community wiki out-of-the-box.


I am very new to ubuntu. During ubuntu installtion, I choose an option that allow ubuntu (12.10) to replace my window 7 without knowing that it will formate and repartition my hard disk. Then, all my important files are gone.  Could you please tell me how can I get my files back? or if possible, Could i recover all partition back?  Your help will be appreciated.

I am on Ubuntu 12.04 64-bits  I accidentally deleted a NTFS 255 GB partition using Gparted, and yes it contains LOTS of important data.  Upon realizing the deletion I haven't yet created any file-system on it. So it still shows Unallocated.    I tried Testdisk , but it shows entire partitions created from the beginning.  This sdb is my secondary drive with Xubuntu and Kubuntu on it. And that 255 GB NTFS  partition was cross platform storage drive.  I am currently in sda with Ubuntu and Win7 in dual boot, which enables me to use it as Safe recovery option rather then Live USB drive.   First ,  should i allocate it to ? file-System for better recovery .  Second , i really need to recover data from this drive so please give me possible  suggestions and proven methods of data recovery.  Third ,does Testdisk requires deleted partition to be allocated for its recovery .  I am currently trying the answer seen here  with Testdisk scanning for partition second time, hoping to recover it.   It looks a duplicate but i can't confirm if the OP got it right. Since my first doubt is to allocate it or not.  If any clarification required please do comment ,i will add it.  Edit: TestDisk deeper search results.      The following partitions can't be recovered:          Partition               Start        End    Size in sectors     >  HPFS - NTFS          22241 107 11 55592   3 27  535777280        FAT32 LBA            274460 158 19 460576 228 16 2989957948  NTFS, 274 GB / 255 GiB & for FAT32 LBA 1530 GB / 1425 GiB


If the spacetime of the universe is infinite now, then it must have been infinite at every point in its history, right? How then can Big Bang be an expansion of space and time? Can somebody show the compatibility of the idea of a singularity and the possible infinity of spacetime extent.

TV documentaries invariably show the Big Bang as an exploding ball of fire expanding outwards. Did the Big Bang really explode outwards from a point like this? If not, what did happen?


I have my date and time settings set to use the "automatic time zone" and that is reflected in timedatectl:   amanda@rajje:~$ timedatectl status                       Local time: Fri 2019-11-15 14:01:29 EST                   Universal time: Fri 2019-11-15 19:01:29 UTC                         RTC time: Fri 2019-11-15 19:01:29                        Time zone: America/New_York (EST, -0500)        System clock synchronized: yes systemd-timesyncd.service active: yes                  RTC in local TZ: no   But it doesn't update itself. Today I turned on my laptop, connected to a brand new coffee shop internet wifi that is definitely in California, aka America/Los_Angeles (PST, -0800) but I'm still seeing EST on my system clock. I've traveled a bunch over the last few months and my laptop consistently does not updated the timezone.   I know that at least my browser knows where I am because Google Maps defaults to the neighborhood I'm in. So the problem isn't that I'm using an internet connection that's hiding my location.   I thought that sudo systemctl restart systemd-timedated would do it, but that has no effect.  I can quickly change the time zone with timedatectl set-timezone America/New_York or timedatectl set-timezone America/Los_Angeles but I'm wondering if there's a way to use timedatectl or another tool to just tell Ubuntu to figure out what time zone I'm in. A sort of "I'm pretty sure that's wrong, could you check again?" trigger or command?

[Running Ubuntu Gnome 15.10]  I recently brought my computer from PST to EST in North America.  Once in EST my laptop did not update the timezone.  I tried toggling the "Auto Time Zone" switch which had no effect.  Finally, I rebooted the machine which also didn't have an effect.  Running /usr/lib/geoclue-2.0/demos/where-am-i doesn't return any result.


Hi I have two Java Files as below:              case 6:                   System.out.println("List All Property Details For Rent >>>"); //              System.out.println(Arrays.toString(Property_list));                 int i=0;                 while(i<count){                     ppty.property_list[i].viewPropertyDetails("RENT");                     i++;                 }                 System.out.println("++++++++++++++++++++++++++++++++++++++++++++++++++++++++");                 break;           }      }         }  }   Guys, This is basically an array of properties, and a Menu to do some operation with the list. I was planning to improve my code with a java ArrayList, because its more dynamic in nature. Could anyone tell me how I can convert this array (property_list) into an ArrayList? What are the changes do I need to make? Thanks in advance.

I have an array that is initialized like:  Element[] array = {new Element(1), new Element(2), new Element(3)};   I would like to convert this array into an object of the  class.  ArrayList<Element> arraylist = ???;


I applied for a visa at the Belgian embassy for Luxembourg (Belgium handles consular affairs on Luxembourg's behalf in my country). I submitted a flight reservation with Frankfurt as my port of entry into the Schengen area. I also declared on the visa application form that Germany will be the Schengen country of first entry.   Now I'm thinking of flying into Paris or Brussels and taking the train to Luxembourg since it's much cheaper. If I do this, will there be a problem at immigration?

In case, if I get a multiple-entry Schengen visa in one of the embassies in Ukraine, Kyiv - should my first trip be to the country which issued the visa?  Any there any requirements of this sort? Does this condition vary depending on embassy which issued the visa?  What are the possible consequences on not visiting that country first? Does it somehow depend on country where the embassy is (i.e. non-Schengen and not EU members)?


The program below outputs This No. is not same. Why does it do this when both numbers are the same?  void main() {     float f = 2.7;      if(f == 2.7) {         printf("This No. is same");     } else {         printf("This No. is not same");     } }

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


I have the following table and I don't know how to determine if an operation is associative based on the table. Is there an easy way to do it? Or it's just brute force  \begin{array}{|c|c|c|c|c|c|} \hline *& a & b & c &d &e \\ \hline  a& a&b &c&b&d\\ \hline  b&  b&c &a&e&c\\ \hline  c& c &a &b&b&a\\ \hline  d&b&e&b&e&d\\ \hline  e&d&b&a&d&c\\ \hline \end{array}  We can see that it's not commutative because $b*e \neq e*b$, but how do we check if it's associative?

Most properties of a single binary operation can be easily read of from the operation's table. For example, given $$\begin{array}{c|ccccc} \cdot & a & b & c & d & e\\\hline a     & e & d & b & a & c\\ b     & d & c & e & b & a\\ c     & b & e & a & c & d\\ d     & a & b & c & d & e\\ e     & c & a & d & e & b \end{array}$$ it is easy to check that it is closed (no elements occur in the table which don't occur as row or column index), commutative (the table is symmetric), has a neutral element (the row and column of $d$ are copies of the index row/column), and has an inverse element for each element (there's a $d$ in each row and column). In other words, almost all important properties can immediately be seen. The only part missing is associativity.  Therefore my question: Is there a simple way to see directly from the operation's table (i.e. without doing explicitly all the calculations) if an operation is associative?


I need a formal expression to designate the police siren and lights together. In Hungarian they are both called with the same name: distinctive signals which is different from what we call them when using one of them alone. Is there a word or expression that I can use in an essay? Thanks in advance for your answers.

Police cars or ambulances have lights on their roof, which are on when the sirens are on. What are these lights called? Is it something like signal lights or alarm lights?   I am looking for an official term/word.  Example sentence:     ……………… create an interesting atmosphere at night.


$$\sum_{k = 0}^n \binom nk^2 = \binom {2n}n$$  I know how to "prove" it by interpretation (using the definition of binomial coefficients), but how do I actually prove it?

I was hoping to find a more "mathematical" proof, instead of proving logically $\displaystyle \sum_{k = 0}^n {n \choose k}^2= {2n \choose n}$.  I already know the logical Proof:  $${n \choose k}^2 = {n \choose k}{ n \choose n-k}$$  Hence summation can be expressed as:  $$\binom{n}{0}\binom{n}{n} + \binom{n}{1}\binom{n}{n-1} + \cdots + \binom{n}{n}\binom{n}{0}$$  One can think of it as choosing $n$ people from a group of $2n$  (imagine dividing a group of $2n$ into $2$ groups of $n$ people each. I can get $k$ people from group $1$ and another $n-k$ people from group $2$. We do this from $k = 0$ to $n$.


All my server mails going to spam in hotmail and yahoo. Here is my full mail source. Can any one please help me to sort out this issue ?  x-store-info:4r51+eLowCe79NzwdU2kRyU+pBy2R9QCDI9u8Kc1Jen/cHV1gUaS24G4DKF5OyCzEFltdVYxf/U4tC+z+83a3F/1TyfPewdH0QdEYMQ951mB/P/Dw5iT8myYw8K7+zHdz+DroxAfdvg= Authentication-Results: hotmail.com; spf=pass (sender IP is 162.144.82.142) smtp.mailfrom=admin@mycompany.com; dkim=pass header.d=mycompany.com; x-hmca=pass header.id=admin@mycompany.com X-SID-PRA: admin@mycompany.com X-AUTH-Result: PASS X-SID-Result: PASS X-Message-Status: n:n X-Message-Delivery: Vj0xLjE7dXM9MDtsPTA7YT0wO0Q9MjtHRD0yO1NDTD00 X-Message-Info: 11chDOWqoTl6HjGE9/H8+/QjhgnGC21ffJDOn7finCyTTlyUaI24NGi3HjF9PjrBnpP3zY0bOifg5AWLM70RH0F+LNUcDBsxVH0/nssTRy8HGIzJUOKwUY4nCWJs/1Oa2Ywkqv/1NjHwNJs+hRHIr0rPcSiWEjCzvtYidS+dRA9tMkNlFUot7ktYDutSn6TzfS/Xlde5FOYPJyqgafnLKWnwHbAQ50cU Received: from tic.mycompany.com ([162.144.82.142]) by COL004-MC1F19.hotmail.com over TLS secured channel with Microsoft SMTPSVC(7.5.7601.23008);      Mon, 20 Apr 2015 23:10:09 -0700 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=mycompany.com; s=default;     h=Content-Transfer-Encoding:Content-Type:MIME-Version:Message-ID:Subject:Reply-To:From:To:Date; bh=vyg7nyFcpbqkWqkPyefi/tzDbA0NJc81DZjIqWk7A5c=;     b=OTeHkTJ0sZZG5Lgx/PUHM/ylmUdwWp8Lp0TiCSEdZoAhbuntVIVxW9tfkznTKQtfdnsH26AouGvk8M3CIweXByvPtqlXADddNrXjR34xObOD+AJI0M/1X6sj2SDaN/06yqtlctDUp3NXrGFCM3uEDp96NpzxCr0EtV9p/p9Dw5s=; Received: from mycompany.com ([162.144.137.136]:46281 helo=www.mycompany.com)     by tic.mycompany.com with esmtpa (Exim 4.85)     (envelope-from <admin@mycompany.com>)     id 1YkRNo-0007KS-8h     for mymail@hotmail.com; Tue, 21 Apr 2015 01:10:08 -0500 Date: Tue, 21 Apr 2015 06:10:07 +0000 To: mymail@hotmail.com From: admin <admin@mycompany.com> Reply-To: admin <admin@mycompany.com> Subject: Test mail from code Message-ID: <961ddc2e972e3ba3c12e509a43179d23@www.mycompany.com> X-Priority: 3 X-Mailer: PHPMailer 5.2.9 (https://github.com/PHPMailer/PHPMailer/) MIME-Version: 1.0 Content-Type: text/html; charset=iso-8859-1 Content-Transfer-Encoding: 8bit X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - tic.mycompany.com X-AntiAbuse: Original Domain - hotmail.com X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - mycompany.com X-Get-Message-Sender-Via: tic.mycompany.com: authenticated_id: admin@mycompany.com X-Source:  X-Source-Args:  X-Source-Dir:  Return-Path: admin@mycompany.com X-OriginalArrivalTime: 21 Apr 2015 06:10:09.0403 (UTC) FILETIME=[D1FFF4B0:01D07BF9]  Test mail from code.   Thanks in advance

This is a  about avoiding outgoing mail being classified as spam.   Also related:                    I'm wondering how to prevent my emails from my site being marked as spam? I'm using sendmail.  I'm trying to send emails through my ruby-on-rails application. The mails are all written in swedish (if that does make a difference?). I don't know why they keep getting marked as spam.  Are there any things that I can do to minimize the risk?


I'm using Ubuntu Server 20.04 for Raspberry Pi 4, I'm trying to get a .sh file to run at boot, so I can just plug the Pi in and it runs the script, but how do I do that.

I'd like to startup an Apache Spark cluster after boot using the following command:  sudo ./path/to/spark/sbin/start-all.sh   Then run this command when the system prepares to reboot/shutdown:  sudo ./path/to/spark/sbin/stop-all.sh   How can I get started? Is there a basic template I can build on?  I've tried to use an extremely simple (file: /lib/systemd/system/spark.service):  [Unit] Description=Spark service  [Service] ExecStart=sudo ./path/to/spark/sbin/start-all.sh   Which doesn't work.


I have a class ClassA in package packageA and ClassA import ClassB in packageB.(in fact ClassA import a lot of java file)  Then the directory is ：  root     pom.xml     src           packageA                   classA                   pom.xml          packageB                   classB   My goal is to generate a jar include classA and classB by only telling maven that I input classA.  the pom.xml in the packageA directory is like  <dependencies>     <dependency>         <scope>system</scope>         <systemPath>D:\path\to\my\local.jar</systemPath>         <groupId>com.abc</groupId>         <artifactId>abc</artifactId>         <version>0.0.1-SNAPSHOT</version>     </dependency>     <dependency>         <!--other dependency in maven repo-->     </dependency> </dependencies> <build>     <plugins>         <plugin>             <artifactId>maven-assembly-plugin</artifactId>             <configuration>                 <archive>                     <manifest>                         <mainClass>fully.qualified.MainClass</mainClass>                     </manifest>                 </archive>                 <descriptorRefs>                     <descriptorRef>jar-with-dependencies</descriptorRef>                 </descriptorRefs>             </configuration>             <executions>                 <execution>                     <id>make-assembly</id>                      <phase>package</phase>                      <goals>                         <goal>single</goal>                     </goals>                 </execution>             </executions>         </plugin>     </plugins>     <sourceDirectory>.</sourceDirectory> <!--if I don't add this line ,the output jar will not include anything of my own project--> </build>   You know, if I don't add <sourceDirectory>.</sourceDirectory> it will not build any thing.But if I add<sourceDirectory>.</sourceDirectory>,the output jar only contains the <sourceDirectory>'s path's classes and the dependencies of maven repo , without my jar of local system path  (In fact the local jar of my own is to support the <sourceDirectory>'s path's classes' build .Also in fact the local jar contains the classB)  Why my own jar's related classes have not been added in the output jar?

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


I've searched the internet for similar problems, but I couldn't find an answer. Thus, my question is:  After upgrading my windows 8 to 8.1, I am no longer able to boot windows from the GRUB menu. Ubuntu still functions fine. Whenever I select the option to boot windows, the screen goes to black.

I just got my new working notebook with Windows 8 pre-installed. After installing Ubuntu 12.10 the grub menu says that there is an "invalid EFI file path" and it won't boot Windows. Ubuntu works fine...  Is there anything I can do about this?


In a solution for a problem from W. Sierpinski's book "250 problems in elementary Number theory", it says:  ...  Since $9k+4 = 4(2k-1)+(k+8)$, while $2k-1 = 2(k+8)-17$, we have $(9k+4, 2k-l) = (2k-l, k+8) = (k+8, 17)$.  What does he mean by $(9k+4, 2k-l) = (2k-l, k+8) = (k+8, 17)$? I've never seen anything like this before and I have no idea what it could possibly mean. If it's needed, here is a screenshot of the problem, followed by the solution: ,

In my textbook on elementary number theory from a class last year, as well as elsewhere through my academic experience and even posts here, I often see the greatest common divisor notated as $(a,b)$ (where this represents the greatest common divisor of $a,b$).  My question is, why is such an unusual notation used? I say it's unusual (if not a bit absurd), for a couple of reasons:   It is unintuitive. It does not grant the reader an immediate knowledge of what it means. In particular, I can easily see it being misinterpreted as an ordered pair of points, and not as a function (which it basically is and I touch on in a second) or representing a single value. Good notation would be immediately understood, no? One should not struggle with parsing through the context or meaning. A clearer notation is often used, and just three letters away. You could certainly think of $(a,b)$ as an ordered pair, if we consider it a function. I often see the alternate $gcd(a,b)$: a function, which takes in two inputs ($a$ and $b$), and outputs their greatest common divisor (or factor, if you prefer). Merely adding the three letters makes the notation clearer by clarifying it is  a function, and using a relatively well-accepted acronym. (Or, at least, I often hear it abbreviated "g.c.d." in school.)   I've mulled this over for a while and I can't think of much without borrowing inspiration from other "unusual" notations. For example:   Common understanding in context: consider the $\log(x)$ function. Depending on context, without a base stated as seen here, it can be presumed to mean whatever is most "appropriate." It could be base $e$ (common in mathematics), base $10$ (common in engineering), or base $2$ (common in computer science). The ambiguity is essentially resolved by context in other words - personally, not a fan of that (I like the explicit stating of bases for full clarity), but if such a motivation holds elsewhere, it might stand to reason that $(a,b)$ could just be taken as a shorthand and "understood" in the context of number theory to simply be the greatest common divisor. That it is in fact used despite $gcd(a,b)$ being clearer and somewhat common also does seem to suggest this playing a role. Perhaps it just started that way and it kept being used. For example,  (based on a ) regarding how logarithms, roots, and exponentiation can be unintuitive from a notation perspective, and proposes an alternative, easier to understand notation. I haven't been in middle school in nearly a decade, but guessing from discussions online, that obviously hasn't really picked up too much. In that sense, perhaps it's like that for $(a,b)$: like we still notate exponentiation, etc., the same way today despite how counterintuitive it is (at least for students), perhaps it just "stuck" and proliferated?   I wasn't able to easily find any reason why online, and it bugs me a bit, so I ask:     Why do we so unintuitively notate the greatest common divisor of two numbers $a,b$ as $(a,b)$?   I of course recognize that this is somewhat moot in light of how easily it's made clear - as established above, all I have to do is append the front of the parenthetical by $gcd$ or $gcf$ to make it way better. And of course, people do that. But I'm more curious in where this ambiguous former notation arose and, in light of a better notation, why it is still used today.


Fellow Physics community, I am an undergraduate about to graduate with an Econ major & Math minor. I have never taken a physics class at the university & it bugs me how ignorant I am about the physical word. I am planning on picking up some Physics textbooks once I graduate to educate myself out of this state.  My question: Given that I have already taken the Calculus Series + Linear Algebra/Diff Eq’s classes & read their textbooks, what are some good entry level Physics Texts that don’t dumb the math down to purely algebra?

Every once in a while, we get a question asking for a book or other educational reference on a particular topic at a particular level. This is a meta-question that collects all those links together. If you're looking for book recommendations, this is probably the place to start.  All the questions linked below, as well as others which deal with more specialized books, can be found under the tag  (formerly ).  If you have a question to add, please edit it in. However, make sure of a few things first:   The question should be tagged  It should be of the form "What are good books to learn/study [subject] at [level]?" It shouldn't duplicate a topic and level that's already on the list   Related Meta:


I'd please like to know what software (or see the list) is in that repository. I enabled it and of course let the system update the package list.. but I can't seem to find both Chrome nor Skype after it (using Ubuntu Software).  Any idea??? Shouldn't it be in a wiki or the official documentation? Thanks :)

In Software Sources under the Other Software tab, there is an option of enabling "Canonical Partners" repository: software packaged by Canonical for their partners.  Do I understand correctly that this repo includes third-party created applications that by arrangement are packaged and maintained by Canonical?  Does this mean Canonical can look at the source code of these third-party applications and hence ensure the security and stability of these apps in Ubuntu, making them as secure & stable as the software in the Main repo?


I have renewed my passport and want to transfer my Canadian Visa to the  new passport. Can I do it? If yes, then what will be the  validity of the visa, same or it can be extended by the Canadian Consulate with its discretion upto the validity of the new Passport?

I recently renewed my passport. I also have an expired passport which has my Canada visa (visitor's) valid for another three years. I have already used my Canadian visa which is multiple entry. I am planning to visit Canada this summer.  Since my valid Canadian visa is in my old/expired passport, do I need to renew/transfer my Canada visa or can I simply travel with valid visa in old passport?


I have thousands of files named 1.txt 2.txt and so on. Some of those files are missing. Which would be the easiest way to find out which files are missing?


I was playing around with geometric series and I wondered if it was possible to find a formula for the sum of an altered geometric series (which actually stops being geometric) of the form: $S_N = \sum_{n=0}^{N}na^n$ Under the condition $1>a>0$ Is there a way to compute this sum other than summing term by term? Can we find a formula that depends on $N$ and $a$ for this sum? Thank you in advance!

I want to know the general formula for $\sum_{n=0}^{m}nr^n$ for some constant r and how it is derived.  For example, when r = 2, the formula is given by: $\sum_{n=0}^{m}n2^n = 2(m2^m - 2^m +1)$ according to   Thanks!


I've been experimenting with some photography for a few months now and I noticed that this happens on pictures with lower shutter speeds:     What is this, why does it happen and what can I do to prevent it/fix it? It has affected some pictures I think are pretty good otherwise. Pictures were taken with a Nikon D3300 and a Tamron 18-200mm f/3.5-6.3 Di II VC on a tripod. Shutter speeds of about 30 seconds.

Shutter speed - 32 sec.  Aperture - f/9 ISO - 100 Lens - EF-S18-55mm f/3.5-5.6 IS II Focal Length - 39 mm   I have took the photo through the window, with the lights off


I have a textbox. If selected and hit the tab key, a new line will open. This works fine so far. However, the same action doesn't work in that dynamically created textbox. Even if it has the same class which the original textbox was called on. I tried to find the explanation on the internet, but I couldn't get/understand a right answer. Could someone please help me?    $('.list').keydown(function(key){     if(key.which === 9) {         $('.ingredients_list').append('
<input class="list" type="text"/>
');      } });

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


I am trying to do a practice problem where I have to write a method that takes a string of curly brackets and returns true if the brackets match up and false if they don’t. If I'm passed the empty string, it needs to return true. We can also assume that the given string can have { and } in it or be empty.  Matching has to be in the correct order of pairs like "{}" not "}{" These are examples of brackets matching: {} {}{} {{}} {{{}{{}}}}  These are examples of the brackets not matching: { }{ {{} {{}}}{}  This is what I currently have (Keep in mind I'm relatively new to coding):  public boolean bracketsMatch(String brackets) {     int count = 0;     if (brackets.length() % 2 == 1){         return false;     }     for(int i = 0; i < brackets.length(); i++){         if ((brackets.charAt(i)+"") == "{"){             count++;         } else if ((brackets.charAt(i)+"") == "}"){             count--;         }         if (count == -1){             return false;         }     } return count == 0; }   Inputs like this }{ and {}}{}{ this still dont return the right output.

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?


Let's say there are   List<string> a1 = new List<string>();  List<string> a2 = new List<string>();   Is there way to do like this?  if (a1 == a2)  {  }

I would like to compare the contents of a couple of collections in my Equals method.  I have a Dictionary and an IList.  Is there a built-in method to do this?  Edited: I want to compare two Dictionaries and two ILists, so I think what equality means is clear - if the two dictionaries contain the same keys mapped to the same values, then they're equal.


Why use #import in objective c? if we use #include what happens?

What are the differences between #import and #include in Objective-C and are there times where you should use one over the other? Is one deprecated?  I was reading the following tutorial:  and its paragraph about #import and #include seems to contradict itself or at least is unclear.


How do I delete frames that have been place by the auto key frame insertion tool thingy?

I have a rig, and I want to change all the key frames for my right arm. When I delete one, all of them delete across the entire rig. How do I delete for one part of the rig, i.e. my right arm.


Hi All, During the installation, I am not able to select the available disks which are already stamped using ASM. Any idea what could be the reason? I have tried to select using keyboard space as well but doesn't work out. Appreciate your help. Thanks.

Hi All, During the 11g installation on Win 2012, I am not able to select the available disks which are already stamped using ASM. Any idea what could be the reason? I have tried to select using keyboard space as well but doesn't work out. Appreciate your help. Thanks.


I would like to know if I can edit with reduced files from 4k footage and when I'm done with my editing in low res, change folder so that Blender does the exact same editing but with the 4k footage in another folder. Is that possible?  Thanks

Is it possible to render in Blender with reduced low res files and then ask Blender to render the final render with 4k high res files? Low and high res files would be numbered identically but would be located in different folders.  Many thanks


I have a Column of ip addresses which look like xxx.xxx.xxx.xxx:PORT_NUM. I want to get that ip which is xxx.xxx.xxx.xxx using regex or equivalent. This is a column of type string. If it was Pandas, then one option was to do column_name.iloc[0:12].   Is there anything similar for Spark Data Frame? I am using Scala.  I tried like, rlike but realized that they are only for Characters. I am unable to Index string on Scala DataFrame. I tried regex for ip address in Scala and it didnt work too.  Any other ideas?

Does anyone have a regular expression handy that will match any legal DNS hostname or IP address?  It's easy to write one that works 95% of the time, but I'm hoping to get something that's well tested to exactly match the latest RFC specs for DNS hostnames.


The common way of finding the work done on some object is by applying the equation: force*displacement.  However, suppose we apply a force of F newtons on an object of mass M for a duration of T seconds. We can then express the work done in terms of T and F, by expressing the change in velocity in terms F and T and then by applying the work-energy theorem.   If we do some further substitutions (Express displacement in terms of F, initial velocity and T), we can show that the above 2 methods produce the same result for a given force (according to what I calculated, do correct me if I am wrong).  Why is the equation force*displacement used instead of the latter case? To me, calculating the work done with respect to time is more intuitive because the increase in momentum of an object (under a constant force) is the same per unit of time. On the other hand, the increase in momentum per unit of displacement of an object gets progressively smaller due to the acceleration of the object.

The change in energy of an object can be determined by the work equation, where work is the change in energy:  $$ W = F \cdot d $$  I conceptualize the transfer of energy as simply a series of small "packets" of energy being transferred at every Planck length. These small "packets" of energy add up to the total energy transferred (i.e. work). I'm not sure if this conceptualization is correct, so correct me if I am wrong.  However, it makes me wonder why the amount of energy transferred is dependent on distance and not time.  $$ m_1 = 10~kg \\ m_2 = 20~kg \\ W_1 = (10~N)\cdot(5~m) = 50~J \\ W_2 = (10~N)\cdot(5~m) = 50~J \\ W_1 = W_2 \\ t_1 \neq t_2 $$  If I apply a constant force on an object, why isn't the energy transferred at a constant rate with respect to time? The energy transfer rate varies dependent on how long it takes to cover the set distance.  In other words: why is the energy transferred consistent per unit of distance, and not per unit of time?


I have a Figure with 3 images inside (a) (b) and (c) when I want to write the description of each image in the figure this description is not so well aligned I mean I would like to see something like this:   Figure 2  (a) Image corresponding to...            (b) Image corresponding to...            (c) Image corresponding to...    Everything aligned in the center just like in the other figures.  But instead of that I am having.     Figure 2 (a) Image corresponding to... (b) Image corresponding   to...(c) Image corresponding to...   I do not know if I was clear enough but I would appreciate any answer  Thanks a lot.

I'm trying to align a legend inside a table caption, so that the colons are vertically aligned. I can do it with the align ambient outside of the caption, but if I use the same code inside the caption the pdf won't compile (I use LuaTeX to compile). I'm using the package caption.  EDIT: i want something like this:    for which i've written this code:  \begin{align} \begin{split} a : {} & the~first~letter~of~the~alphabet \\ b : {} & the~second~one \\ and : {} & so~on \end{split} \end{align}   There might be a more elegant way... but i don't know it.  Anyway, I can't do it inside the caption, that's why i'm stuck.


“We make an identity for ourselves”   or   “We make identities for ourselves?”  Which one is better? Why?

When speaking of a group of people and referring to a body part of which there is only one (e.g. head, nose, mouth, etc.), do we use the singular or plural form? Which of the following is correct, or are both possible?  Our stomach is full.  Our stomachs are full.


My attempt: $$ \lim_{x \rightarrow 0} \frac{\sin(\tan(x)) - \tan(\sin(x))}{ \sin^{-1}(\tan^{-1}(x)) - \tan^{-1}(\sin^{-1}(x)) }  = \lim_{x \rightarrow 0} \frac{f(x)}{g(x)}$$ then we try to work $$ \lim_{x \rightarrow 0} \frac{ \cos(\tan(x)) \sec^{2}(x) - \sec^{2}(\sin(x)) \cos(x)   }{ \frac{1}{\sqrt{1- (\tan^{-1}(x))^{2}} (1+x^{2})} - \frac{1}{\sqrt{1 - x^{2}} \left[ 1+(\sin^{-1}(x))^{2} \right]}  } $$ and since $\lim_{x \rightarrow 0} \sin(x) = \lim_{x \rightarrow 0} x$, then it becomes $$ \lim_{x \rightarrow 0} \sec^{2}(x) \lim_{x \rightarrow 0} \frac{ \cos(\tan(x)) -  \cos(x)   }{ \frac{1}{\sqrt{1- (\tan^{-1}(x))^{2}} (1+x^{2})} - \frac{1}{\sqrt{1 - x^{2}} \left[ 1+(\sin^{-1}(x))^{2} \right]}  } $$ $$ = \lim_{x \rightarrow 0} \frac{ \cos(\tan(x)) -  \cos(x)   }{ \frac{1}{\sqrt{1- (\tan^{-1}(x))^{2}} (1+x^{2})} - \frac{1}{\sqrt{1 - x^{2}} \left[ 1+(\sin^{-1}(x))^{2} \right]}  } $$ then also $\sqrt{1- (\tan^{-1}(x))^{2}}$ and $1+(\sin^{-1}(x))^{2}$ converge to $1$, so the above is just $$ = \lim_{x \rightarrow 0} \frac{ \cos(\tan(x)) -  \cos(x)   }{ \frac{1}{(1+x^{2})} - \frac{1}{\sqrt{1 - x^{2}} }  } $$ $$ = \lim_{x \rightarrow 0 } (\sqrt{1-x^{2}} (1 + x^{2} ) \lim_{x \rightarrow 0} \frac{ \cos(\tan(x)) -  \cos(x)   }{ \sqrt{1-x^{2}} - 1 - x^{2}  } $$ $$ =  \lim_{x \rightarrow 0} \frac{ \cos(\tan(x)) -  \cos(x)   }{ \sqrt{1-x^{2}} - 1 - x^{2}  } $$ Using L'hopital approach for the above, we work on: $$ \lim_{x \rightarrow 0} \frac{ \sin(x) - \sin(\tan(x)) \sec^{2}(x)   }{ -\frac{x}{\sqrt{1-x^{2}}} - 2x  } $$ but also $\tan(x) \rightarrow x$ as $x \rightarrow 0$, so we will end up $$ \lim_{x \rightarrow} \frac{\sin(x)}{x} \lim_{x \rightarrow 0}  \frac{ 1 -  \sec^{2}(x)   }{ -\frac{1}{\sqrt{1-x^{2}}} - 2  } = 0$$ But the answer should be $1$, what rules do I violate and why?

While reading this  I do not understand that how can we claim that there exist a polynomial with the properties, even if it exist then how is it same for the function and the inverse.


When looking at the Accounts tab, the icons shown for achivements all belong to the specific website you are looking at, not the Stack Exchange website shown to the left. For example, here is what I see looking at the "Accounts" tab from Android Enthusiasts Stack Exchange:    To visualize the suggested change: all the websites shown in the list (besides Android Enthusiasts) would show a circle, not the Android robot's head.  I feel that this should be changed because it would provide a better representation of the sub-website in the "Accounts" list.

Badges look differently on each SE site, as per the unique themes of each site.  However, when looking at the Summary of Accounts in a user's profile, the badges for all sites use the icon for the site that the viewer is viewing the page from at that time.    I think it would be an aesthetic improvement to keep the badge icons consistent with their site of origin, and not where they are being viewed from.    The effect of this change would be subtle, but I think it would help reinforce the appealing idea that the badges from the different sites are unique, different types of rewards, and make it more engaging to collect from all over SE as opposed to focusing on single sites.


I was browsing Aviation.SE site when I noticed "+10" on the reputation dialog.  I clicked on the achievements icon in the top nav bar to see what I got that rep for.  It was for a answer on Stack Overflow, but that's irrelevant.  Also in the drop-down achievements panel were listed a couple of my recent badges from SO - but with an icon for the Aviation.SE - see the screenshot below.    Of course, there's a site icon indicating which site the badges were for, yet I was confused for a second when I saw a little plane badge.  So, is this a slight oversight/bug or an intended behavior?

It's so cool that the notification reminds you of the colour of badge you've earned. But I am a little puzzled by the symbols:      Is it feasible to use the symbol from the earned site? At the moment it uses the symbol from the site I happen to be on (as you can see by looking to the left of the dropdown in each case.)


evaluate $\lim_{n\rightarrow\infty}\frac{1}{n}\sum^n_{k=1} k^{\frac{1}{k}}$  I could guess that it converges to 1 but I'm having trouble showing how

I have a problem with the calculation of the following limit. \begin{equation} \lim_{n\rightarrow \infty} \frac{1+\sqrt{2}+\sqrt[3]{3}+\cdots+\sqrt[n]{n}}{n} \end{equation} I do not know where to start! Thank you very much


I wish to draw the following diagram, but I do not know how to draw it correctly, may you please help me

I wish I knew how to draw the this commutative diagram with the TikZ package.    I would also like to know how to put subtitles in the diagram.


What is the difference between grey and gray? I've seen both used and I'm wondering which I should use when talking about the color. Why are there two spelling's for the same word and is there a difference in the meaning between the two?

Yesterday I wrote "gray" in the meaning of the color, but my friend corrected me and told me to write "grey". Today I checked in the  and I found that they are both correct for the same meaning. So, now I just have doubt which one of them is more common in use.


In pgfplots, pos=a , with a between 0 and 1, refers to the relative x coordinate on a plot. I was wondering if there is an equivalent construct that accept the absolute x coordinate rather than the relative value?

I'm trying to put some arrows on the left and right side of the maximum of a curve. The arrows should point along the curve. My problem is that if I use the [pos=X] notation I don't know where I am in relation to the maximum. And if I use absolute coordinates the node is not sloped.   \documentclass{article} \usepackage{pgfplots} \usetikzlibrary{shapes.geometric} \pgfplotsset{compat=1.7}  \begin{document} \begin{tikzpicture} \tikzset{myarrow/.style=          {sloped,isosceles triangle,anchor=apex,fill=black,inner sep=2pt}} \begin{axis} \addplot [smooth] {-x^2}  node[pos=0.4,myarrow,rotate=180]{} %ok  node[pos=0.6,myarrow]{}; %ok  \addplot[smooth,green] {-x^2+2*x-4}  node[pos=0.4,myarrow,rotate=180]{}  node[pos=0.6,myarrow]{} %wrong side  node[myarrow,fill=red] at (axis cs:4,-12){}; %wrong rotation! \end{axis}  \end{tikzpicture}  \end{document}     Edit: Some remark about Jake's answer  Jake's code (naturally) works but    for my case it is a bit too complicated. Jake gets the correct rotation for the arrow by drawing a short path from x-1pt to x (cool idea). He gets the coordinates for this small path with intersections. But as my plot is based on a function I can simply calculate the values (e.g. with \pgfmathparse) and then draw the small path after the plot:  \path  (axis cs:3.99,-11.94012) -- (axis cs:4,-12) node[pos=1,myarrow]{};   The same can also be achieved by redrawing the plot but with a restricted domain:  \addplot[draw=none,domain=3.99:4] {\MyFunction{x}}  node[pos=1,myarrow,fill=yellow]{};  I also looked if there is a way to decide where I am relative to the maximum (so that I can change the rotation) and in theory it is possible: If I use the code found here  \pgfplots@metamax is known after the plot and can be used in calculations.


I have a copy of my RPi's SD card made with dd if=/dev/mmblk0 of=backup.img. This creates a 32GB file. Only about 6GB of it is actually used, the rest is just data from deleted files. How would I remove the old, useless data? It doesn't have to shrink the image file, just zero out whatever isn't needed

I've copied the USB drive to an .img file using dd:  dd if=/dev/sdc of=myimage.img   I want to reduce the size of the partition in the image. I've tried several methods and always end up with a loopback-mounted image whose partition is still the full size of the USB.    How do I modify myimage.img to have a smaller partition once loopback-mounted? Do I need to copy zeros into the empty part of the partition before doing so? Do I need to defragment so that when I reduce the image size, I'm deleting empty bytes? (From what I've read, Linux spreads out into the whole partition so I have no expectation that all of the data at the end of the image are zero bytes. Even writing all zeros will just consume the empty bytes wherever they lie.)   NOTE: I'm not trying to save disk space, so zipping doesn't help me.  BACKGROUND  I have Linux installed on a USB drive using ext4. I intend to duplicate the install for multiple devices. I've done so successfully but would like to create on the same USB drive a read-only partition with the system and a small partition that allows persistent storage. Rather than break my USB, I'm trying to modify a copy of the USB. I hope we don't get distracted by this background.  In short, I've done the following:  # Create mount point in current directory sudo mkdir mnt # Loopback mount the image fdisk -l myimage.img sudo mount -o offset=<partion_block_start * block_size> myimage.img mnt # Copy all zeros to remaining space of the image cd mnt sudo dd if=/dev/zero of=filler conv=fsync bs=1M rm filler cd ..   First, I tried to use parted as described in  and qemu-img as described in .  sudo umount mnt parted myimage.img # At parted command prompt (parted) resizepart 1 # Entered my end <target size>. Note that parted uses zero-based  # indexing. This could be your final image size. In my case, the way the # Linux installer worked, the partition started at 1M. (parted) print # I see that the partition is now sized as I expect (parted) exit # Just another sanity check sudo parted -m esp3_007.img unit B print # I see that the partition is now sized as I expect   When I try to mount the image again, it works fine but df still shows the partition as the same size. So then I tried  qemu-img resize myimage.img <target_size>   And now, when I try to mount the image, I get the "mount: wrong fs type, bad option, bad superblock..." error message.  Then I tried using gparted as described in . The GUI showed a full partition unless I ran parted in the first place. Even then, the GUI wouldn't let me resize the partition.  For trying to force the partition size to be smaller, and starting with a fresh copy of myimage.img I tried fdisk described in   sudo fdisk myimage.img Command (m for help): d Command (m for help): n Command action    e   extended    p   primary partition (1-4) p Partition number (1-4, default 1): 1 # defaults on the rest seemed to be correct in my case.   When I mounted the partition, it still showed as the same size.


If a,b,c are positive prove that $(1+a)^7.(1+b)^7.(1+c)^7>7^7.a^4 b^4 c^4$  My approach I tried (1+a)(1+b)(1+c) =1+[a+b+c+ab+bc+ac+abc] Find the AM of Square Bracket, them AM $\ge$ GM But if I add 1 then AM>GM. Please help me with my approach

Problem. Prove that if $ a,b,c > 0 $, then $ [(1 + a) (1 + b) (1 + c)]^{7} > 7^{7} (a^{4} b^{4} c^{4}) $.   I don’t know how to solve this problem... What I can think of is to just simplify this inequality: $$ \left[ \frac{(1 + a) (1 + b) (1 + c)}{7} \right]^{7} > a^{4} b^{4} c^{4}. $$ How can I proceed with solving this problem?    Note: This is a question of sequence and series, specifically AM-GM-HM inequality...


I am running queue for my laravel app using systemd. Here's my service file [Unit] Description=Mosharaf isdp queue  [Service] User=nginx Group=nginx Type=simple Restart=always Nice=10 WorkingDirectory=/var/www/html/mosharaf_isdp/ ExecStart=/usr/bin/php artisan queue:work  --sleep=10 --timeout=1800 --tries=1 TimeoutStartSec=30 [Install] RequiredBy=multi-user.target  Using this service file all of my jobs are being processed one by one. I have followed steps given in  and . Both of them says To run multiple workers you have to list them in "queue" parameter  by this i am guessing they mean to add it in below line like that. ExecStart=/usr/bin/php artisan queue:work --queue=default --sleep=10 --timeout=1800 --tries=1  But my question is isn't it specifying which queue to run ? All of my jobs are stored as default and i want multiple workers to process them. How can i do that ? N.b., While i was using supervisor there was a key in it's config file as numprocs which specified number of workers. Is there something like this here or i have to put my jobs in different queue say q1,q2,q3 and add them like below to activate 3 workers ? ExecStart=/usr/bin/php artisan queue:work --queue=q1,q2,q3 --sleep=10 --timeout=1800 --tries=1

I found this systemd service file to start autossh to keep up a ssh tunnel:   [Unit] Description=Keeps a tunnel to 'remote.example.com' open After=network.target  [Service] User=autossh # -p [PORT] # -l [user] # -M 0 --> no monitoring # -N Just open the connection and do nothing (not interactive) # LOCALPORT:IP_ON_EXAMPLE_COM:PORT_ON_EXAMPLE_COM ExecStart=/usr/bin/autossh -M 0 -N -q -o "ServerAliveInterval 60" -o "ServerAliveCountMax 3" -p 22 -l autossh remote.example.com -L 7474:127.0.0.1:7474 -i /home/autossh/.ssh/id_rsa  [Install] WantedBy=multi-user.target   Is there a way to configure systemd to start several tunnels in one service.  I don't want to create N system service files, since I want to avoid copy+paste.   All service files would be identical except "remote.example.com" would be replace with other host names.  1.5 year later ...  I asked this question roughly 1.5 year ago.  My mind has changed. Yes, it's nice, that you can do this with systemd, but I will use configuration-management in the future.  Why should systemd implement a template language and substitute %h? .. I think it makes no sense.  Several months later I think this looping and templating should be solved on a different level. I would use Ansible or TerraForm for this now.


I'm looking to build a simple vase for 3d printing and I'm keen to understand how I can do this.    I've tried the screw modifier, however it appears to be lacking the right level of detail to work properly (I've create a simple shape and then applied several subdivides to it in order to increase the mesh density)  There's bound to be a smart way to achieve this, appreciate any pointers/tips!

I am trying to create a vase that looks similar to this:    If there is another post out there I will happily remove this one or redirect it there.  Specifically, I am trying to create the creased effect in the geometry that looks like it is twisting around the vase.  I have tried using Checker Deselect and extrude->scaling the verts but that really screws up my mesh.  Link to my model if it helps:


I am searching kill command's full manual, but in man kill or even with Google, I cannot find this command's meaning below:  kill -n 9 0   I am sure it has a very easy answer.

I just wonder why kill -9 0 ends my tty console session?   What exactly is PID 0, it is not listed on a ps aux?


First, I consider the LC circuit with an ion in the capacitor, which is like this:  The current $I$ can be derived easily using Shockly-Ramo theorem \begin{equation}  I = -\frac{qp}{dM} + C\dot{U} \ \ \ (1)  \end{equation} where $q$ is the charge and $M$ is the mass of the particle, $p = M\dot{z}$ is the momentum of the particle, $d$ is the separation of the two plates, $C$ is the capacitance and $U$ is the voltage across the capacitor. By taking the circuit-charge $Q$ on the capacitor as the generalized coordinate and the magnetic flux through the inductor $\Phi = L\dot{Q}$($L$ is the inductance of the inductor) as the momentum, it is easy to derive the canonical equations of the circuit with Kirchhoff's law $U = -\dot{\Phi}$. \begin{equation}  \dot{Q} = \frac{\Phi}{L}\ \ \ (2)  \end{equation} \begin{equation}  \dot{\Phi} = -\frac{Q}{C} - \frac{qz}{Cd}\ \ \ (3)  \end{equation} Now we consider the series RLC circuit case. My question is that how to find the canonical equations of the series RLC circuit with the same canonical coordinates(which is $Q$ and $\Phi$)? it says that there will be two more terms added in equation(3), $-\Gamma\Phi$ and $\sqrt{2\Gamma L k_BT}\xi(t)$, where $\Gamma = \frac{R}{L}$. So the first term is the damping term and the other term, according to that paper, should be the thermal noise of the resister. I just can not find the correct canonical equations that satisfies the result in the paper.

First, I consider the LC circuit with an ion in the capacitor, which is like this:  The current $I$ can be derived easily by using Shockly-Ramo theorem \begin{equation}  I = -\frac{qp}{dM} + C\dot{U} \ \ \ (1)  \end{equation} where $q$ is the charge and $M$ is the mass of the particle, $p = M\dot{z}$ is the momentum of the particle, $d$ is the separation of the two plates, $C$ is the capacitance and $U$ is the voltage across the capacitor. By taking the circuit-charge $Q$ on the capacitor as the generalized coordinate and the magnetic flux through the inductor $\Phi = L\dot{Q}$($L$ is the inductance of the inductor) as the momentum, it is easy to derive the canonical equations of the circuit with Kirchhoff's law $U = -\dot{\Phi}$. \begin{equation}  \dot{Q} = \frac{\Phi}{L}\ \ \ (2)  \end{equation} \begin{equation}  \dot{\Phi} = -\frac{Q}{C} - \frac{qz}{Cd}\ \ \ (3)  \end{equation} Now we consider the series RLC circuit case. My question is that how to find the canonical equations of the series RLC circuit with the same canonical coordinates(which is $Q$ and $\Phi$)? , it says that there will be two more terms added in equation(3), $-\Gamma\Phi$ and $\sqrt{2\Gamma L k_BT}\xi(t)$, where $\Gamma = \frac{R}{L}$. So the first term is the damping term and the other term, according to that paper, should be the thermal noise of the resister. I just can not find the correct canonical equations that satisfies the result in the paper.


In the Big Bang Theory, one of the main characters is "Penny". In the 12 seasons, does it get mentioned what's Penny's full name before she married to Leonard Hofstadter?

The characters of Big Bang Theory are:   Sheldon Lee Cooper    Leonard Leakey Hofstadter  Howard Joel Wolowitz    Rajesh Ramayan Koothrappali    Bernadette Maryanne Rostenkowski-Wolowitz    Amy Farrah Fowler   AND....  Penny!? That's it? No last name, or even a middle name?


I work on a Windows 8.1 Enterprise PC. I Would like to upgrade my Command Line terminal (cmd.exe) to the one offered in the latest version of Windows 10, which has many handy features that the old one lacks. EDIT: I mean UI features like the automatic word wrap and the ability to maximize in the whole window. Is it possible?  I would prefer the traditional cmd.exe and not PowerShell.

I'm running a Windows 7 Machine and wish to use it with my Windows 10 Batch file, however the colored text it uses does not support the Windows 7 Console (see  ). Is there any way I can run the Windows 10 CMD on Windows 7?


I am trying to fit a 3 way ANOVA using R. Then i realized the sums of squares of the output has changed when the order of the variables in the model are changed.Can anyone figure out the reason for that ?  There seems to be something wrong because in normal situation the sums of squares in R not affected by the order of variables in the model

Am I correct to understand that the order in which variables are specified in a multifactorial ANOVA makes a difference but that the order does not matter when doing a multiple linear regression?  So assuming an outcome such as measured blood loss y and two categorical variables   adenoidectomy method a, tonsillectomy method b.   The model y~a+b is different to the model y~b+a (or so my implementation in R seems to indicate).  Am I correct to understand that the term here is that ANOVA is a hierarchical model since it first attributes as much variance as it can to the first factor before trying to attribute residual variance to the second factor?  In the example above the hierarchy makes sense because I always do the adenoidectomy first before doing the tonsillectomy but what would happen if one had two variables with no inherent order?


I am getting this error when trying to upgrade:  E: Failed to fetch http://archive.ubuntu.com/ubuntu/pool/main/l/linux-firmware/linux-firmware_1.157.15_all.deb  Hash Sum mismatch   To check what is wrong I downloaded the package from  and checked the md5 which is showing something different in my machine from the one given on the website.

When I check for updates, I get a "Failed To Download Repository Information" error.   This is what comes up under details:   W: Failed to fetch gzip:/var/lib/apt/lists/partial/us.archive.ubuntu.com_ubuntu_dists_natty_main_source_Sources  Hash Sum mismatch,  E: Some index files failed to download. They have been ignored, or old ones used instead.


Sorry for this naive question, but I try in this moment to revise my classis. Could you help me please to demonstrate : $$\frac{\partial T^{\prime\mu}}{\partial x^{\prime \alpha}}=\frac{\partial}{\partial x^{\prime \alpha}}\left(\frac{\partial x^{\prime \mu}}{\partial x^{v}} T^{v}\right)$$ i.e by using a changing of coordinates between $x^{\mu}$ and $x^{\prime\mu}$. $T^{\mu}$ represents the contravariant components of a "vector" (I mean a tensor of rank 1). That demostration would be done by  proving that : $$T'^{\mu}\text{d}x^{\nu}=T^{\nu}\text{d}x^{\prime\mu}$$ How to justify this equality if I apply a 1-form $\text{d}x^{\mu}$ or another 1-form $\text{d}x^{\prime\mu}$ on a vector $T$ ?

I try currently to revise my classic. Could you help me please to demonstrate : $$\frac{\partial T^{\prime\mu}}{\partial x^{\prime \alpha}}=\frac{\partial}{\partial x^{\prime \alpha}}\left(\frac{\partial x^{\prime \mu}}{\partial x^{v}} T^{v}\right)$$ i.e by using a changing of coordinates between $x^{\mu}$ and $x^{\prime\mu}$. $T^{\mu}$ represents the contravariant components of a "vector" (I mean a tensor of rank 1). This demostration would be the same than proving : $$T'^{\mu}\text{d}x^{\nu}=T^{\nu}\text{d}x^{\prime\mu}$$ How to justify this equality if I apply a 1-form $\text{d}x^{\mu}$ or another 1-form $\text{d}x^{\prime\mu}$ on a vector $T$ ?


I have an old laptop prone to overheating and a good solution I found was limiting it's CPU usage to below 50%.  On Windows, I can do this by changing the power plan I am currently using, and altering the Minimum CPU Usage and and Maximum CPU Usage properties.  Where can I do something similar on Ubuntu 12.04 LTS?

I run distributed computing projects, which typically want to use 100% of the CPU.  How do I limit the CPU usage in terms of temperature instead of percent usage?  Also, what is the maximum safe temperature to keep an Intel i5 running 24/7?  (With no CPU limit FahCore_a4 causes this machine to run at 82 degrees Celsius.)


How can I prove that the number of surjective mapping from the set $A$ to a set $B$ is $\sum\limits_{r=1}^n(-1)^{n-r} \binom{ n}{ r}r^m $, where $|A|=m$ and $|B|=n$. I can't get any idea how to prove it. Is it possible to prove it?

It is quite easy to calculate the total number of functions from a set $X$ with $m$ elements to a set $Y$ with $n$ elements ($n^{m}$), and also the total number of injective functions ($n^{\underline{m}}$, denoting the falling factorial). But I am thinking about how to calculate the total number of surjective functions $f\colon X \twoheadrightarrow Y $.  The way I thought of doing this is as follows: firstly, since all $n$ elements of the codomain $Y$ need to be mapped to, you choose any $n$ elements from the $m$ elements of the set $X$ to be mapped one-to-one with the $n$ elements of $Y$. This results in $n!$ possible pairings. But the number of ways of choosing $n$ elements from $m$ elements is $\frac{m!}{(m-n)!\,n!}$, so the total number of ways of matching $n$ elements in $X$ to be one-to-one with the $n$ elements of $Y$ is $\frac{m!}{(m-n)!\,n!} \times n! = \frac{m!}{(m-n)!}$.  Now we have 'covered' the codomain $Y$ with $n$ elements from $X$, the remaining unpaired $m-n$ elements from $X$ can be mapped to any of the elements of $Y$, so there are $n^{m-n}$ ways of doing this. Therefore I think that the total number of surjective functions should be $\frac{m!}{(m-n)!} \, n^{m-n}$.  Is this anything like correct or have I made a major mistake here?


I've read in books that one can't put one's hand through a table because the table offers a "Normal Reaction" to the hand. And it is also stated that this force is electromagnetic in nature. But what is this force? Can it be explained using classical electromagnetism "in terms of something I'm more familiar with"?   Moreover, if it is this force that stops my hand from going through the table, why is it that certain other solid substances, like sand, don't produce the same result?   Also, is there any limit to this Normal reaction? I mean on pushing too hard my hand might go through the table. Is there any upper limit to this force?

If you've ever been annoyingly poked by a geek, you might be familiar with the semi-nerdy obnoxious response of      "I'm not actually touching you! The electrons in the atoms of my   skin are just getting really close to yours!"   Expanding on this a little bit, it seems the obnoxious geek is right. After all, consider Zeno's paradox. Every time you try to touch two objects together, you have to get them halfway there, then quarter-way, etc. In other words, there's always a infinitesimal distance in between the two objects.   Atoms don't "touch" each other; even the protons and neutrons in the nucleus of an atom aren't "touching" each other.  So what does it mean for two objects to touch each other?   Are atoms that join to form a molecule "touching"? I suppose the atoms are touching, because their is some overlap, but the subatomic particles are just whizzing around avoiding each other. If this is the case, should "touching" just be defined relative to some context? I.e, if I touch your hand, our hands are touching, but unless you pick up some of my DNA, the molecules in our hands aren't touching? And since the molecules aren't changing, the atoms aren't touching either?  Is there really no such thing as "touching"?


In my C# assembly "Abc", I have the following class and static method:  internal class Xyz {     protected internal static void MakeAwesome()     {         ...            } }   I noticed I can access this static method from anywhere in my assembly code. However, removing the "protected" from it seems to yield the same results:  internal class Xyz {     internal static void MakeAwesome()     {         ...            } }   Is the "protected" here making no difference because it's a static method? Or is it restricting something I overlooked?

Can someone please explain the difference between the protected and protected internal modifiers in C#? It looks like their behavior is identical.


I was trying different types of materials with Blender, and I tried to play with the glass with Cycles, but in the render, it makes weird blue pixels on my blue table.  Even in the preview tab it makes those :     And in the render, it is horrible :     This is a simple form ! How could this already fail ?  Thanks in advance for your time !    EDIT 15/11/2018 : A similar question has already been asked at this address, here is the link if you wanted some more intel : . I would not mark this question as a duplicate because of the "pixels artifacts" keyword, that would guide people like me which search on Google : "dead pixels artifacts". Thanks for sharing this question. Didn't knew these were "fireflies"

I often use Cycles' built in Glass BSDF shader to achieve realistic refraction effects, but in many cases, it seems that Cycles' glass caustics creates an unfortunately large number of fireflies (pixels that are abnormally bright relative to their surroundings). In some models of mine, even when I render for 3000 or more samples/pixel, my final image is still covered in fireflies. While I can improve this in many cases by increasing the total amount of light available in the scene, this loses a lot of the potency of the refractive effects I'm looking for, especially in scenes with low light levels.  So my question is, how can I reduce the amount of fireflies while using Cycles' caustics without sacrificing the quality of the refractive effects?  Note: I am aware that Cycles' caustics will perform much better once Cycles has full support for bidirectional path-tracing, but it looks unlikely that that will become , unfortunately.


I'm trying to dual-boot-install Lubuntu 20.04.1 through an USB drive created with Rufus on a PC which already has Windows 10 64bit installed on. My SSD is GPT formatted, I have UEFI, but when I decide to manually install Ubuntu after creating an ext4 partition, I get this error box: But it's strange, because I already do have an EFI partition installed by Windows as you can see:   So what should I do according to you? Thanks in advance!

I was replacing my Ubuntu 18.04 with Lubuntu 20.04. I wanted to keep my /home partition same. After creating /root , swap and changing mount point for /home partition the installer gave a warning that /boot/efi partition is not created Lubuntu 20.04 needs /boot/efi partition to boot. Please create a FAT32 partition and mount it as /boot/efi and enable flag esp. Then I created the /boot/efi  partition but there was no esp flag(s). I had installed Ubuntu 18.04 alongside windows10. What should I do now?


Let $C[0,1]$ be the set of all continuous function from $[0,1]$ to $\mathbb R$.  Is the cardinality of $C[0,1]$ larger than or equal to that of $\mathbb R$?

I believe that the set of all $\mathbb{R\to R}$ continuous functions is $\mathfrak c$, the . However, I read in the book "Metric spaces" by Ó Searcóid that set of all $[0, 1]\to\mathbb{R}$ continuous functions is greater than $\mathfrak c$:  "It is demonstrated in many textbooks that $\mathbb{Q}$ is countable, that $\mathbb{R}$ is uncountable, that every non-degenerate interval is uncountable, that the collection of continuous functions deﬁned on  $[0,1]$ is of a greater cardinality than $\mathbb{R}$, and that there are sets of greater and greater cardinality."  I understand that (via composition with the continuous function $\tan$ or $\arctan$) these sets of continuous functions have the same cardinality. Therefore, which claim is correct, and how do I prove this?


Can we label the phrase "a lot of water" as the pluralized form of "water"?  "a lot of" = expresses that something has a large amount  plural = more than one in number  But since we still cannot count "a lot of water," is it appropriate to label this phrase as plural?

I'd like to understand the logic behind uncountable nouns, such as "water", "meat" and others, specially "bread", for example.  I don't understand why can't we count them, since there are different kinds of water (e.g.: still, tap, sparkling, etc.), meat (e.g: beef, pork, etc.) and bread (baguette, bun, etc.).  Sorry if my question seems silly, but I'm not a native speaker.


I'm using Ubuntu 13.10 Saucy Salamander 64bit and Eclipse Kepler 64bit terminates after some random time without response. The windows simply disappears.  There's also no entry about the crash in .metadata/.log

All operating systems freeze sometimes, and Ubuntu is no exception. What should I do to regain control when...   just one program stops responding? nothing at all responds to mouse clicks or key presses? the mouse stops moving entirely? I have an    In what order should I try various solutions before deciding to pull the power plug?  What should I do when starting up Ubuntu fails?  Is there a diagnostic procedure I can follow?


problem with my network controller so i opened up cmd and started to check for interfaces. my Wifi network controller had 3 different Device ID (Transport id's) When i tried to disable the wifi card the different id's went away. i tested the same thing and it only shows 1 id? Device\NPF_{4A45A363-6346-48DA-8D28-13DD9C9C1E6A} Device\NPF_{E6994972-C66C-4ABF-BE27-17BAC7C1C971} Device\NPF_{B6394772-H66C-4ABF-HRE27-17JLC0H9C971} I am using snort to check for available interfaces. Can anybody explain why i am seeing this? WLC model: intel dual band wireless-ac 8265 running default settings on the adapter however i have hyper-v open

There was a problem with my network controller so i opened up cmd and started to check for interfaces. I noticed a strange thing that my Wifi network controller had 3 different Device ID (Transport id's) When i tried to disable the wifi card the different id's went away. On my other computer i tested the same thing and it only shows 1 id? Device\NPF_{4A45A363-6346-48DA-8D28-13DD9C9C1E6A} Device\NPF_{E6994972-C66C-4ABF-BE27-17BAC7C1C971} Device\NPF_{B6394772-H66C-4ABF-HRE27-17JLC0H9C971} I am using snort to check for available interfaces. Can anybody explain why i am seeing this? WLC model: intel dual band wireless-ac 8265 running default settings on the adapter however i have hyper-v open


I'm making vinegar by adding all natural apple juice to all natural apple cider vinegar with mother.  A scoby formed on top.  Mold is now growing on top of the scoby.  It's stuck on top of the scoby, not floating on top.  I can't easily scrape it off without scraping the scoby.  Should I leave this mold on top, will it affect the vinegar?

About 2-3 months ago I decided to start my own batch of vinegar.  I started with some Braggs apple cider vinegar which contains the mother, and I added some old wine and some fruit juice to the mix.  I kept it in a dark and warm place, as per instructions online.  A few layers of cheesecloth were placed on top to allow it to air, without letting anything else get into it.  When I recently opened it, I found a layer of what appears to be a yellow-orange mold on top.  There are also some small worms or maggots living on the top, but that doesn't seem as problematic to me.    As you can (sort of) see in this picture above, there is definitely a mother at the bottom.  The mother has grown since I last saw it.  I am not sure what to think about that top layer though.  Is the vinegar batch completely spoiled?  Picture #2 (a closer look at the top)


where I connect to internet, I have an always changing ip address and when I try to get ip address, it does not give my ipv4 address which I am using in my web services to call web service. can you suggest me anything? Thanks.

I need to somehow retrieve the client's IP address using JavaScript; no server side code, not even SSI.  However, I'm not against using a free 3rd party script/service.


I'm trying to simulate survival times from Weibull(or lognormal) distribution with parameters (shape,scale) including (?%) of right-censored observations.I need to obtain observations of a variable, which include some percentage of right-censored data.

I'm wondering how can I simulate a sample of n Weibull distribution lifetimes that include Type I right-censored observations. For instance lets have the n = 3, shape = 3, scale = 1 and the censoring rate = .15, and the censoring time = .88.  I know how to generate a Weibull sample but I do not know how to generate a censored data that have type I right-censored in R.  T = rweibull(3, shape=.5, scale=1)


It's well known that the / directory has inode number 2 (see also ). And we also know that hard links share the same inode number. So far so good.  Here's the confusing bit (notice the Inode: part):  $ stat /run   File: /run   Size: 940         Blocks: 0          IO Block: 4096   directory Device: 16h/22d Inode: 2           Links: 32 Access: (0755/drwxr-xr-x)  Uid: (    0/    root)   Gid: (    0/    root) Access: 2018-09-10 10:22:18.198727482 +0800 Modify: 2018-09-10 02:47:58.655999930 +0800 Change: 2018-09-10 02:47:58.655999930 +0800  Birth: -   The simple question is "Why do they have the same inode?" The /run directory is different from / and /run is not hardlink to /.

I find that under my root directory, there are some directories that have the same inode number:  $ ls -aid */ .*/  2 home/ 2 tmp/ 2 usr/ 2 var/ 2 ./ 2 ../ 1 sys/ 1 proc/   I only know that the directories' names are kept in the parent directory, and their data is kept in the inode of the directories themselves.  I'm confused here.  This is what I think when I trace the pathname /home/user1.   First I get into the inode 2 which is the root directory which contains the directory lists. Then I find the name home paired with inode 2. So I go back to the disk to find inode 2? And I get the name user1 here?


I am doing a proof for my logic class.   The goal is to prove:$$\exists x(P(x)\implies\forall yP(y))$$ from no premises.   I have come to:$$\forall y(P(x)\implies P(x))$$ in my main proof, but I don't know if i have gotten my goal formula in disguise....  What are the rules for moving quantifiers and is my goal sentence implicit in my proven sentence?

Why is this true?  $(\exists x)(P(x) \Rightarrow (\forall y) P(y))$


I am working through Kevin Houston's book . The question I am currently stuck on is to show that  $$x^2 + y^2 = z^n$$  has positive integer solutions for $n = 1,2,3,\dots$  My work thus far:  $f: \mathbb{N}^2 \rightarrow \mathbb{N}$ defined by $f(x,y) = x^2 + y^2$ with image $A = \{2,5,8,10,13,17,\dots\}$  $g: \mathbb{N} \rightarrow \mathbb{N}$ defined by $g(z) = z^n$ with image $B = \{1,2^n,3^n,\dots\}$  If I can show that $A \cap B \neq \varnothing$ for $n \in \mathbb{N}$ then this shows that there are integer solutions for all $n$. How can this be shown?

I was presented with the following problem:      Prove that there exist solutions to $x^2+y^2=z^n$ for all $n$, with $x,y,z, n \in \mathbb{N}$   I showed that by taking any Pythagorean triple $x^2+y^2=z^2$ and multiplying by $z^{2(n-1)}$ we get $(z^{n-1}x)^2+(z^{n-1}y)^2=(z^2)^n$, which allows me to generate solutions easily for any value of $n$. I managed to find several similar questions on this site, such as  concerning the specific case $n=3$. I notice that all of these questions take a similar approach and start with a Pythagorean triple and use it to generate general solutions.  Is there a way to prove the statement (or better yet provide solutions to the equation) without first relying on Pythagoras?


On an 8x8 chess board we place rooks so that the number of them is odd on each line  or collumn. Show that the number of black squares that have rooks is even.  What I found: Obviously, since the sum of all rooks is even, the numbers of black and white squares with rooks have the same parity. Also since every line or column have even number of squares, the number of them with/ without rooks have the same parity so every arrangement generates another one. This is basically the only relevant thing I have got. I still dont know how to get the parity

I'm having trouble fully understanding this introductory combinatorics problem; this is all that's provided, so it's most likely me not fully comprehending the question.  Any help is appreciated.  The problem is this:     Each square of a 1998 by 2002 chess board contains either 0 or 1 such that the total number of squares containing 1 is odd in each row and each column. Prove that the number of white unit squares containing 1 is even.   I have discovered that this is a legitimate question and has been copied out of a book entitled 102 Combinatorial Problems where the problem and solution are clearly stated . Thank you and apologies for the ambiguity.


I was reading up this  where I found these lines.      FOR SOLID BLACK BACKGROUND: When you want an area of solid black within your document, use Rich Black, as represented by C:50% / M:50% / Y:10% / K:100%, because using 100% black (K) only and not a solid saturated black will result in a dull black.      FOR SOLID BLACK TEXT: When you want your text to be solid black, use these percentages: C:0% / M:0% / Y:0% / K:100%, because using the the percentages for the Solid Black Background, immediately above, on text, will result in offsetting.   Q1. Why does a 100%K lead to a dull black?  Q2. Why would a solid black lead to offsetting?

explains what rich black is, but when should it be used?  If it gives a "blacker black", why not use it for all black elements in a CMYK job (body text/line art/tints)? Would there be any downsides?


I've downloaded a copy of the OS X - El Capitan Installer, which I want to make a bootable USB of.  However, it requires you to run the installer on whatever machine you are running, and installs it as an app.   But I cannot run the installer (to create the app) because I am using the computer running macOS Sierra.  It just gives an error "this installer is too old to run on this computer."

Does anyone have a Terminal command-line recipe for making a new bootable USB flash drive for one of the new MacBook Air's?  Is there a way to dd copy the USB boot device that comes in the box and make the new copy bootable?  I'd like to make a new backup copy of the USB rescue device for my MBA, preferably on a much larger flash drive with room for a backup of some of my working directories.  Added:  And is it possible to make, not just a rescue drive, but a bootable USB drive that will boot a fully updated version of the OS (say 10.6.8 or later)?  If so how on a MacBook Air 11, and how big a USB stick will this require?


So I am creating an application that plays audio-files in the background using clips() and I added a JSlider that allows the user to alter the volume of the audio-file. However, whenever I click the JSlider it gives me the following errors:   Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException at GoRacer.stateChanged(GoRacer.java:764) at javax.swing.JSlider.fireStateChanged(Unknown Source) at javax.swing.JSlider$ModelListener.stateChanged(Unknown Source) at javax.swing.DefaultBoundedRangeModel.fireStateChanged(Unknown Source) at javax.swing.DefaultBoundedRangeModel.setRangeProperties(Unknown Source) at javax.swing.DefaultBoundedRangeModel.setValueIsAdjusting(Unknown Source) at javax.swing.JSlider.setValueIsAdjusting(Unknown Source) at javax.swing.plaf.basic.BasicSliderUI$TrackListener.mousePressed(Unknown Source) at java.awt.Component.processMouseEvent(Unknown Source) at javax.swing.JComponent.processMouseEvent(Unknown Source) at java.awt.Component.processEvent(Unknown Source) at java.awt.Container.processEvent(Unknown Source) at java.awt.Component.dispatchEventImpl(Unknown Source) at java.awt.Container.dispatchEventImpl(Unknown Source) at java.awt.Component.dispatchEvent(Unknown Source) at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source) at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source) at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source) at java.awt.Container.dispatchEventImpl(Unknown Source) at java.awt.Window.dispatchEventImpl(Unknown Source) at java.awt.Component.dispatchEvent(Unknown Source) at java.awt.EventQueue.dispatchEventImpl(Unknown Source) at java.awt.EventQueue.access$500(Unknown Source) at java.awt.EventQueue$3.run(Unknown Source) at java.awt.EventQueue$3.run(Unknown Source) at java.security.AccessController.doPrivileged(Native Method) at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source) at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source) at java.awt.EventQueue$4.run(Unknown Source) at java.awt.EventQueue$4.run(Unknown Source) at java.security.AccessController.doPrivileged(Native Method) at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source) at java.awt.EventQueue.dispatchEvent(Unknown Source) at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source) at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source) at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source) at java.awt.EventDispatchThread.pumpEvents(Unknown Source) at java.awt.EventDispatchThread.pumpEvents(Unknown Source) at java.awt.EventDispatchThread.run(Unknown Source)   My code for my audio-player method is:    public void musicPlayer (String filePath, String loopYesNo, float userInput, long position, Clip a){   try{   File fileSong = new File (filePath);    AudioInputStream input = AudioSystem.getAudioInputStream(fileSong);    a = AudioSystem.getClip();   a.open(input);    a.setMicrosecondPosition(position);     FloatControl gainControl = (FloatControl) a.getControl(FloatControl.Type.MASTER_GAIN);    float range = (float) (Math.log(userInput) / Math.log(10) * 20);    gainControl.setValue(range);    a.start();      if (loopYesNo.equals("Yes")) {     a.loop(Clip.LOOP_CONTINUOUSLY);   }  } catch (Exception error) {   errorEnd();  }   }  And the code for the JSlider is:     public void stateChanged (ChangeEvent e) {   if (e.getSource() == volume) {    long clipTimePosition = clipMusic.getMicrosecondPosition();    clipMusic.stop();      programVolume =  (float)volume.getValue() / 100;       musicPlayer(mainFrameMusic, "Yes", programVolume, clipTimePosition, clipMusic); }   }  If I get rid of Clip in input parameters it seems to work fine;however, seeing that I will be needing to listen to multiple audio-files in this program it would be nice to use one method for all of them.

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 tried $u$-substiution with $u = x^2$ but that leaves me with $x$ values and not a simpler function to integrate.Is there a better way to integrate?

Can we express $ \displaystyle \int e^{x^{2}} \, \mathrm{d}{x} $ in terms of elementary functions? (Note: Infinite series are not allowed.) If not, then is there a proof that $ \displaystyle \int e^{x^{2}} \, \mathrm{d}{x} $ cannot be written in such a manner?


Attempt: Prove that if $A|B$ and $B|A$, then $A=B$? Both $A$ AND $B$ are positive integers. I tried to substitute with the fact that $A|B$ means $\exists c$ s.t $Ac_2=B$ and same $Bc_1=A$ when $B|A$, but I did not get anywhere.

$R$ - commutative Ring, and $a$  non-zero-divisor  $R^x$ - multiplicative Monoid? (it's called Einheitsgruppe in German, maybe unitary group?)   I started by stating, that if $a\mid b$ and $b\mid a \rightarrow a=b$.  So for $a\mid b$, $\exists x\in R$ with $xa=b$ and for $b\mid a,\exists y\in R$ with $yb=a$  Now: $b=xa=xyb=wb$, with $w=xy$.  $\stackrel{a=b}{\rightarrow} b=wa$  Now the problem that I think I have with my proof, is that R is not a given Ring. For example $a=b$ wouldn't work in $\mathbb{Z}$. Is there any other way to do the proof?


I get this error:  Error: unknown filesystem. grub rescue>   I'm not exactly sure what I did. I believe I installed Ubuntu over Windows on my Acer netbook. I then tried to install , but it wouldn't start installing.  I turned the netbook off and back on. Now I get the error.  I have read a lot of other questions like this, but in my case I cannot boot a CD. If I put a Ubuntu CD or a Linux Mint CD into my external CD/DVD drive and change my BIOS to boot the CD-ROM first, it just gives me the same error screen.  Update copied from comment dated 2012-05-26 02:54:29Z  Here are some results from my commands:   grub rescue>ls (hd0) (hd0,msdos5) (hd0,msdos1)  grub rescue>ls (hd0,msdos5) unknown filesystem  grub rescue>ls (hd0,msdos1) unknown filesystem  grub rescue>ls (hd0) unknown filesystem

I have a multiboot system set up. The system has three drives. Multiboot is configured with Windows XP, Windows 7, and Ubuntu - all on the first drive. I had a lot of unpartitioned space left on the drive and was reserving it for adding other OSes and for storing files there in the future.  One day I went ahead and downloaded Partition Wizard and created a logical NTFS partition from within Windows 7, still some unpartitioned space left over. Everything worked fine, until I rebooted the computer a few days later.  Now I'm getting:    error: unknown filesystem.   grub rescue>   First of all I was surprised not to find any kind of help command, by trying:    help, ?, man, --help, -h, bash, cmd, etc.  Now I'm stuck with non-bootable system. I have started researching the issue and finding that people usually recommend to boot to a Live CD and fix the issue from there. Is there a way to fix this issue from within grub rescue without the need for Live CD?  UPDATE  By following the steps from , I was able to boot to initramfs prompt. But not anywhere further than that.  So far from reading the manual on , I was able to see my drives and partitions using ls command. For the first hard drive I see the following: (hd0) (hd0,msdos6) (hd0,msdos5) (hd0,msdos2) (hd0,msdos1)  I now know that (hd0,msdos6) contains Linux on it, since ls (hd0,msdos6)/ lists directories. Others will give "error: unknown filesystem."  UPDATE 2  After the following commands I am now getting to the boot menu and can boot into Windows 7 and Ubuntu, but upon reboot I have to repeat these steps.    ls ls (hd0,msdos6)/ set root=(hd0,msdos6) ls / set prefix=(hd0,msdos6)/boot/grub insmod /boot/grub/linux.mod normal   UPDATE 3  Thanks Shashank Singh, with your instructions I have simplified my steps to the following. I have learned from you that I can replace msdos6 with just a 6 and that I can just do insmod normal instead of insmod /boot/grub/linux.mod. Now I just need to figure out how to save this settings from within grub itself, without booting into any OS.  set root=(hd0,6) set prefix=(hd0,6)/boot/grub insmod normal normal   UPDATE 4  Well, it seems like it is a requirement to boot into Linux. After booting into Ubuntu I have performed the following steps described in the :  sudo update-grub sudo grub-install /dev/sda   This did not resolve the issue. I still get the grub rescue prompt. What do I need to do to permanently fix it?  I have also learned that drive numbers as in hd0 need to be translated to drive letters as in /dev/sda for some commands. hd1 would be sdb, hd2 would be sdc, and so on. Partitions listed in grub as (hd0,msdos6) would be translated to /dev/sda6.  UPDATE 5  I could not figure out why the following did not fix grub:  sudo update-grub sudo grub-install /dev/sda   So I downloaded  based on an answer from  post. That seemed to do the trick after I picked the "Recommended Repair (repairs most frequent problems)" option.


I was playing an online game and I noticed a player on my team with username "4PP13". I asked him what should I call him. He said "apple".  I didn't have second thoughts until I Googled it. It turned out "4PP13" does means apple according to .  So what's the deal? Is this a special case? If not, what is this called?

Sometimes, more in some languages than in others, a word is spelled using one or more numbers instead of letters. Is there a term for this?  The only example I can think of in English is se7en (seven).   Therefore,     The number se7en was not spelled entirely with letters; it was written in   ______.


I want to recursively grep on all files in subdirectories with extension csv but select only those files that are less than 4M in size. Is this correct way to do? find . -type f -size -4M | grep --include \*.csv 'pattern'  This command selects all the files with .csv, basically doesn't limit to less than 4M in size, although find alone correctly finds all files less than 4M.

So I'm relatively new to command line. I was able to use find to get an output of multiple files from multiple directories since there was no specific place these would be (I'm sure this can be shortened):  find ./ -name filename1.ext && find ./ -name filename2.ext && find ./ -name filename3.ext   Now that gave me the list of what I was wanting but now that I've found the files in question, I want to grep them for information.


When I use a graduated style and I set the outline of the polygons to transparent I can still see the border. If I set the width to "Hairline" and/or the style to "No pen" I can still see them.   I have found multiple similar questions with very manual intensive solutions that are simply not practical in my case:         This seems to be an old feature request, am I missing something?   I'm using QGIS 2.18.

In the past I have just manually matched the color of the border to the color of the fill, but this can be time consuming.   I am wondering, is there any way to have the program automatically match the border color to that of the fill?   The fill color is being assigned through the styling tab in layer properties.  Using QGIS 2.8.6


Given a complete graph of n vertices $K_n$ (has all possible edges – one edge between pair of vertices). Use counting to find a formula in $n$ for the number of edges in the graph.  I know that the formula is $\frac{n(n-1)}{2}$ (or at least that's what I think it is from what  said.  Though I am not sure how to actually start deriving the formula to come to that conclusion. Any guidance would be great.

I'm studying graphs in algorithm and complexity, (but I'm not very good at math) as in title:     Why a complete graph has $\frac{n(n-1)}{2}$ edges?   And how this is related with combinatorics?


I have a laptop with 4 GB RAM and CPU Intel i5 520-M it's a x64 bits processor in the specification. Is Ubuntu 15.10 amd64 ISO image compatible for this CPU, or only i386? Because the system starts quite slow. Help me until I install all software I need.

I'm downloading both versions of Ubuntu 12.04 at this moment. I'd like to install AMD64 on my portable, even though it's an Intel machine. Is there a website (or another way) where I can check compatibility?  Acer Aspire 5745G-724G50Mnks, Intel i7 with 4Gb RAM


Please consider the following LaTex document:  \documentclass[a4paper,11pt]{article} \usepackage{amsthm} \usepackage{amsmath} \usepackage{float} \usepackage{array}% in the preamble % define the title \title{Problems from Chapter 8} \author{Robert~J.~Sherry} \begin{document} \maketitle \noindent 8.64 Fit a least-squares line to the data in Table 8-31 using (a) $x$ as the indepenent variable, (b) x as the dependent variable. \begin{table} \caption{Table 8-31} \begin{tabular}{|c|c c c c c c|} \hline x & 3 & 5 & 6 & 8 & 9 & 11 \\ y & 2 & 3 & 4 & 6 & 5 & 8 \\ \hline \end{tabular} \end{table} \end{document}   LaTex is putting the table at the bottom of the page. I do not want it there. What should I do?  Thanks Bob

How to influence the position of float environments like figure and table in LaTeX?   This is a general question and should collect useful answers for all users. I hope we can use this as a reference


I found it very frustrating that CMD+TAB switches only between applications and not between windows of the same application. If I have several windows of Safari open, CMD+TAB will show only ONE instance of Safari. I know that SOME applications support CMD+` or something like this, but not all of them, some applications have also different keys shortcuts. I usually set up my key shortcut in preferences as "Move focus to next windows" and sometimes work, but for example, Terminal doesn't accept it. It's very frustrating, is there a way do move fast between windows? I also thought that swiping to another desktop was cool, but again, one application with all its windows can stay in only one desktop...

I opened two Google Chrome windows (because I am using multiple Gmails) and when I do the Cmd ⌘ Tab ⇥ shortcut it just shows me other applications that I opened but does not show me the other Chrome windows that are already opened.  How to switch to the other Google Chrome window that I opened using keyboard shortcut?


I posted this question a while ago () but got no answer I guess because the post was long so I'll try to keep it short this time.  After installing and booting with nouveau.modeset=0 I try to install the nvidia drivers usig additional drivers and only get black screen if I try to boot regardless if I use nouveau.modeset=0 or not.  during the black-screen mentioned above, when I try to access the command line all I get is      A start job is running for Hold until boot process finishes up (Xmin   Xs/no limit)   This post:   When I try to boot after using the solution in the post above with lightdm - I get a unity-like login screen, when I log in my screen shows a vert bugged version of itself for a few seconds, and which it starts correctly but then keeps spitting out      system problem detected   I wouldn't mind working with nouveau.modeset=0 but from what I understand this doesn't utilize my graphics card at all?  Any help at all would be greatly appreciated. Thanks!

I was installing ubuntu-Gnome 16.04 on my Asus ROG GL522VW laptop with an nvidia GTX 960m graphics card, and stumbled upon a problem.  After installation, I don't even get to the login screen. Instead my screen just freezes. I had this problem before, and got my answer in this post:   So I booted with nouveau.modeset=0, and everything boots just fine. But after I use additional drivers to install the NVIDIA binary driver - version 361.42 from nvidia-361 (proprietary, tested), I only get a black screen when I try to boot regardless of whether nouveau.modeset=0 is set or not.  While the screen is black, when I try to access the command line with ctrl + alt + f1 all I get is this: A start job is running for Hold until boot process finishes up (Xmin Xs/no limit) and no matter how much I will wait, it doesn't end and I have to reboot.  I followed the instructions in this post:   When I boot after reinstalling everything and choosing lightdm - it basically works but my login screen looks like a unity login screen, and when I insert my credentials it shows me a very bugged screen with all kinds of broken images with some of the things I had on my last boot, and after a few seconds my screen flashes on and off and it boots into my normal desktop, but still keeps spitting out system problem detected with only the option to close or report.  Also tried to install nvidia-355 and all kinds of versions, with no luck.  I wouldn't mind working with nouveau.modeset=0, but as far as I understand this disables my graphics card and doesn't utilize all of it's potential?  Any help or insight will be greatly appreciated. Sorry for the long post and if I should include more information please tell me what else I should include.  A huge thanks up front!  Edit: Reposted this question again and didn't know I can just edit the question to get it back up.  Edit2: Bumping again in a last effort to solve this issue  Please let me know if it is lacking information.