From Bash Reference Manual     : (a colon)      : [arguments]      Do nothing beyond expanding arguments and performing redirections. The   return status is zero.   I wonder how to use this builtin command?   What is its used for? I am trying to improve my understandings about expansions and redirections, and hope it can be useful.  Does "expanding arguments" mean all kinds of word expansions?  How can I see the result from performing expansions and redirections? : [arguments] doesn't write anything to stdout.

I've hacked on a lot of shell scripts, and sometimes the simplest things baffle me. Today I ran across a script that made extensive use of the : (colon) bash builtin.  The  seems simple enough:   : (a colon)        : [arguments]         Do nothing beyond expanding arguments and performing redirections. The return status is zero.    However I have previously only seen this used in demonstrations of shell expansion. The use case in the script I ran across made extensive use of this structure:  if [ -f ${file} ]; then     grep some_string ${file} >> otherfile || :     grep other_string ${file} >> otherfile || : fi   There were actually hundreds of greps, but they are just more of the same. No input/output redirects are present other than  the simple structure above. No return values are checked later in the script.  I am reading this as a useless construct that says "or do nothing". What purpose could ending these greps with "or do nothing" serve? In what case would this construct cause a different outcome than simply leaving off the || : from all instances?


How could that be possible? The model is significant too.  The null model already predicted 70% correctly. After adding predictors, the model predicts 100%. But no single predictors are significant. I used SPSS. Here are the results captures

If you have a variable which perfectly separates zeroes and ones in target variable, R will yield the following "perfect or quasi perfect separation" warning message:  Warning message: glm.fit: fitted probabilities numerically 0 or 1 occurred    We still get the model but the coefficient estimates are inflated.   How do you deal with this in practice?


The method calls at the end of the main method are giving me an error saying "non-static method cannot be referenced from a static context" I'm not sure what I'm doing wrong in the method call.       public static void main(String[] args)   {     ArrayList<Candidate> voteCount = new ArrayList<Candidate>();    //add objects to voteCount     printListResults(voteCount);    totalListVotes(voteCount);    printListTable(voteCount); }  public void printListResults(ArrayList<Candidate> election)  {      //some code } public int totalListVotes(ArrayList<Candidate> election)  {      //some code } public void printListTable(ArrayList<Candidate> election)  {           //some code     }

The very common beginner mistake is when you try to use a class property "statically" without making an instance of that class. It leaves you with the mentioned error message:     You can either make the non static method static or make an instance of that class to use its properties.   Why? I am not asking for solutions. I would be grateful to know what is the reason behind it. The very core reason!  private java.util.List<String> someMethod(){     /* Some Code */     return someList;             }  public static void main(String[] strArgs){                // The following statement causes the error. You know why..     java.util.List<String> someList = someMethod();          }


It's not really noticeable if you have a high-speed low-latency connection, but after many tries, I snapped a screenshot that displays the problem

I've noticed that recently many websites are slow to display their text. Usually, the background, images and so on are going to be loaded, but no text. After some time the text starts appearing here and there (not always all of it at the same time).  It basically works the opposite as it used to, when the text was displayed first, then the images and the rest was loading afterwards. What new technology is creating this issue? Any idea?  Note that I'm on a slow connection, which probably accentuates the problem.  See below for an example - everything's loaded but it takes a few more seconds before the text is finally displayed:


I have applied for UK visitor Visa two weeks ago and I have received this email:     Your UK visa application has been processed. Please contact TLS at pos.tlscontact.com/kbp_en/index.php/contact if you have not been contacted within the next 2 days regarding return of your documents   Is there anyway to know the decision without having to wait until I receive my passport back?

I received the following email this morning. Does it mean that my visa has been granted?  UK Visas & Immigration has now assessed your UK visa application and made a decision. Your documents and the decision will be sent back to either the UK Visa Application Centre where you applied, where we will contact you by email over the next few days to collect them, or if you are using the courier return service, will be sent directly back to the address provided. Please note that TLScontact does not know the outcome of the assessment and has played no role in the decision-making process. Kind regards, TLScontact UK VIsas & Immigration


My Ethernet works fine but it is not even showing options of available networks in Wi-Fi (Initially it was working fine).  The output of lspci -knn | grep Net -A3; rfkill list, is as follows:  03:00.0 Network controller [0280]: Broadcom Corporation BCM43142 802.11b/g/n [14e4:4365] (rev 01)     Subsystem: Hewlett-Packard Company BCM43142 802.11b/g/n [103c:804a] 0: hci0: Bluetooth     Soft blocked: no     Hard blocked: no   Also o/p of sudo modprobe wl is:  modprobe: FATAL: Module wl not found in directory /lib/modules/4.15.0-29-generic   Also command sudo apt install --reinstall bcmwl-kernel-source shows error:  Can't create report and wl not found.

I have Ubuntu 16.04 installed on my laptop. It was working fine until one day an update was there. After the update, I am on kernel 4.15.0-13-generic and there it is. My Broadcom Wifi drivers were nowhere to be detected. On Notification panel, there is no option to switch ON/OFF wifi.  result of lspci -nnk | grep 0280 -A3:  02:00.0 Network controller [0280]: Broadcom Limited BCM43142 802.11b/g/n [14e4:4365] (rev 01)     Subsystem: Foxconn International, Inc. BCM43142 802.11b/g/n [105b:e071] 03:00.0 Ethernet controller [0200]: Realtek Semiconductor Co., Ltd. RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller [10ec:8168] (rev 0c)     Subsystem: Sony Corporation RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller [104d:90be]   I tried different kernels on the present in the grub and they are working fine. Currently, I have to switch to kernel 4.4.0-119.143 to use my wifi.  Here is the error output of command sudo apt-get install bcmwl-kernel-source:  Reading package lists... Done Building dependency tree        Reading state information... Done The following NEW packages will be installed:   bcmwl-kernel-source 0 upgraded, 1 newly installed, 0 to remove and 0 not upgraded. Need to get 1,544 kB of archives. After this operation, 8,064 kB of additional disk space will be used. Get:1 http://in.archive.ubuntu.com/ubuntu xenial-updates/restricted amd64 bcmwl-kernel-source amd64 6.30.223.271+bdcom-0ubuntu1~1.2 [1,544 kB] Fetched 1,544 kB in 5s (295 kB/s)                 Selecting previously unselected package bcmwl-kernel-source. (Reading database ... 290899 files and directories currently installed.) Preparing to unpack .../bcmwl-kernel-source_6.30.223.271+bdcom-0ubuntu1~1.2_amd64.deb ... Unpacking bcmwl-kernel-source (6.30.223.271+bdcom-0ubuntu1~1.2) ... Setting up bcmwl-kernel-source (6.30.223.271+bdcom-0ubuntu1~1.2) ... Loading new bcmwl-6.30.223.271+bdcom DKMS files... First Installation: checking all kernels... Building only for 4.15.0-20-generic Building for architecture x86_64 Building initial module for 4.15.0-20-generic ERROR: Cannot create report: [Errno 17] File exists: '/var/crash/bcmwl-kernel-source.0.crash' Error! Bad return status for module build on kernel: 4.15.0-20-generic (x86_64) Consult /var/lib/dkms/bcmwl/6.30.223.271+bdcom/build/make.log for more information. modprobe: FATAL: Module wl not found in directory /lib/modules/4.15.0-20-generic update-initramfs: deferring update (trigger activated) Processing triggers for initramfs-tools (0.122ubuntu8.11) ... update-initramfs: Generating /boot/initrd.img-4.15.0-20-generic   Also, tell me if I update my ubuntu 16.04 to ubuntu 18.04 will help to solve this problem.


Something weird is happening where the manipulator arrows moves where ever the 3D cursor is. I don't want this.

I think I accidentally pressed something to make it like this:    See how the XYZ arrows are at the 3D cursor instead of those vertexes I've selected?  How do I fix that? Whenever I select on a vertex or something, those blue, red, green arrows would always be where I selected, now it just keeps going to the 3D cursor.


I'm running MongoDB 4.0 with the WiredTiger storage engine under CentOS 7. The data files are held on a mounted XFS volume.  I can't use my hosting provider's backup service because it doesn't support XFS volumes. This means I need to take snapshots some other way and copy them over to a redundant file system that does have backups enabled.  I've read  which gives various options for taking the snapshots, but it doesn't go into detail about how to ensure a .  In addition to the LVM method described I've also looked at xfsdump and have even considered rsync (because the data comprises many small files). But regardless of the snapshot/copy method, how do I ensure that the backup is in a consistent state?

I'm running Mongodb on AWS EC2 instance. Data/log/and journal are stored in a separate volume, formatted as xfs. Currently we are stopping the mongodb instance to take a snapshot, but reading this:  apparently there is no need to stop the service during the snapshot since journal is enabled. Am I correct? Can I create consistent snapshot even if the service is running?


Hi guys! A newbie here. I don't know what's causing this (I was doing a lighthouse project before this). Then when I wanted to add a base color, this happened. I loaded my old project which was tables and chairs(it was finished with wood textures and stuff), same thing happened. Tried with a new default cube and still the same result. Answers are greatly appreciated! PS. Sorry for my bad grammar.

I don't know why but now, when i go in material preview or rendered (in solid mode it works fine), my object is entirely gray, or invisible idk, because it has the same color of the background. I've been working for days on this project without having this issue, it suddenly showed up. I tried opening other old projects and suddenly they all do the same so i guess it is some blender program setting that applies for all the projects, but idk how it happened cuz i didn't change anything :/, anyone got any tips?


Im using virtual server on hosting. There is Ubuntu 12.04 LTS. Im building pool websites, and stratum mining. I can connect to stratum on port 3333 via minerd on server, but cant connect from outside cpu miner, like mine. Here is a list which i get when trying this command netstat -ntlp | grep LISTEN :  root@vm9807:~# netstat -ntlp | grep LISTEN tcp        0      0 0.0.0.0:3334            0.0.0.0:*               LISTEN      1757/python      tcp        0      0 127.0.0.1:10025         0.0.0.0:*               LISTEN      1219/master      tcp        0      0 127.0.0.1:3306          0.0.0.0:*               LISTEN      987/mysqld       tcp        0      0 0.0.0.0:587             0.0.0.0:*               LISTEN      1219/master      tcp        0      0 127.0.0.1:11211         0.0.0.0:*               LISTEN      1121/memcached   tcp        0      0 0.0.0.0:8332            0.0.0.0:*               LISTEN      1721/python      tcp        0      0 0.0.0.0:8333            0.0.0.0:*               LISTEN      1757/python      tcp        0      0 0.0.0.0:32333           0.0.0.0:*               LISTEN      1686/betacoind   tcp        0      0 0.0.0.0:110             0.0.0.0:*               LISTEN      969/dovecot      tcp        0      0 0.0.0.0:143             0.0.0.0:*               LISTEN      969/dovecot      tcp        0      0 0.0.0.0:9333            0.0.0.0:*               LISTEN      1678/litecoind   tcp        0      0 31.31.75.108:53         0.0.0.0:*               LISTEN      999/named        tcp        0      0 127.0.0.1:53            0.0.0.0:*               LISTEN      999/named        tcp        0      0 0.0.0.0:22              0.0.0.0:*               LISTEN      856/sshd         tcp        0      0 0.0.0.0:25              0.0.0.0:*               LISTEN      1219/master      tcp        0      0 127.0.0.1:953           0.0.0.0:*               LISTEN      999/named        tcp        0      0 0.0.0.0:4190            0.0.0.0:*               LISTEN      969/dovecot      tcp        0      0 127.0.0.1:7777          0.0.0.0:*               LISTEN      1117/python      tcp        0      0 0.0.0.0:993             0.0.0.0:*               LISTEN      969/dovecot      tcp        0      0 0.0.0.0:995             0.0.0.0:*               LISTEN      969/dovecot      tcp        0      0 0.0.0.0:3333            0.0.0.0:*               LISTEN      1721/python      tcp6       0      0 :::32332                :::*                    LISTEN      1686/betacoind   tcp6       0      0 :::32333                :::*                    LISTEN      1686/betacoind   tcp6       0      0 :::80                   :::*                    LISTEN      1319/apache2     tcp6       0      0 :::9333                 :::*                    LISTEN      1678/litecoind   tcp6       0      0 :::53                   :::*                    LISTEN      999/named        tcp6       0      0 :::9334                 :::*                    LISTEN      1678/litecoind   tcp6       0      0 :::22                   :::*                    LISTEN      856/sshd         tcp6       0      0 ::1:953                 :::*                    LISTEN      999/named        root@vm9807:~#    My vserver hosting is not blocking any ports, im not using any firewall. Help me please thankx

I would like to see what ports are open on my machine, e.g. what ports my machine is listening on. E.g. port 80 if I have installed a web server, and so on.  Is there any command for this?


"Notepad++ (Install) 7.3.3" looks to be the better one based on the number of downloads, but why is there also "Notepad++ 7.3.3" ?

example:   Does Chocolatey run the native program installer? If I prefer simplicity, should I avoid packages with (Install) in their name?


I am working on a simple side project and can't figure out how to put the "varColor" variable's value as the background color of a web page. (I omitted the lightswitch portion of the code because it is functional)  I tried many different ways to call the value but haven't gotten any results yet.   okay, so I tried lots of methods from the answers and can't seem to get it to react based off the light switch's value. some help on that too?       <meta name="viewport" content="width=device-width, initial-scale=1.0">

          <title>Link catalog</title>            lightSwitch
         <input type="checkbox" name="onoffswitch" class="onoffswitch-checkbox" id="lightSwitch">
     the new code is in the same location in comparison to the original file, on the bottom of the page.  yes I am aware the words aren't visible while the page is white, I'll fix that after I get the switch functional.

Anyone know a simple method to swap the background color of a webpage using JavaScript?


I have an area where players drop down from the lobby in the sky down to the ground on my server but I want the area where they drop down to have a thing set up so they become adventure mode, but when leave that radius go into survival mode, and when go back in the area the become adventure mode again. So like spawn protection but I want to use command blocks. I know how to use them I just need the command for it!

Is there a way to set an "Adventure Mode Boundary" in Minecraft?  I am trying to create this village where players can spawn in, and then set out to explore the world and build and do normal minecraft stuff. I don't want them to destroy this village, so I want them to be in adventure mode when they are in the village and then switch them to survival when they leave, and vice-versa. When they return to the village, they get switched back to adventure mode.  In other words, I want to set an "Adventure Mode Boundary" to protect buildings. I am working without mods. I am hoping there is an simple way using command blocks.


I've heard many theories that Lelouch is alive or dead, and many find this as a religious issue, but i want to find out the truth already. Is he alive or dead? Many say in the original Japanese version Lelouch was the cart driver at the end, but this scene was later cut out. Others say Lelouch gained his father's code before he died so then he was immortal?? People claim that Nunnally seeing his memories is proof of this,but really? Is it? Please any proof i want, whether he is alive or dead...

At the ending of Code Geass R2, the last scene showed someone whose face wasn't showed riding a horse-pulling-cart with CC. I believe that it is indeed Lelouch (who was previously stabbed by Suzaku wearing Zero's uniform as part of their Code Zero plan to free Elevens), and that he had gained immortality because of his frequent usage of his Geass.   Lelouch's Geass first leveled-up the episode when he accidentally ordered his sister Euphemia to kill all Elevens. Then, his father King Charles was beaten by him and I'm thinking that King Charles' immortality was transferred to him.   If that person was really Lelouch, then, has he already gained immortality by that time?


We have a mobile music application that has a header with a floating button underneath it, something along the lines of this crude image:    People understand to click the button to play a song, but it is not obvious to them that can swipe the button left or right to move to the previous or next track.  Is there a cue we can use? Or does anyone have any guidance on creating a tutorial we can fire up when the user first starts the app?

There are a lot of mobile UI design patterns that support swiping, and these are designed based on interaction and animation that indicate the behaviour. Examples include the 'swipe/pull down to refresh' and also the page flip when users swipe left or right.   I also know that there are some applications that show swiping interactions for only specific sections of a page, but I generally don't see any cues or hints to suggest that this behaviour is possible. An example of a discussion about this for Android applications . Are these supposed to be discoverable interactions or are there some standard notations for this type of behaviour?


After watching Life of Pi for the 16th time, I realized I had plenty of questions: the tiger in the movie could be a metaphor for God or Pi himself (according to the two stories provided), also the zebra could be a metaphor for the Buddhist, the orangutan for his mother, and the hyena for the cook.  He could have lied about the story in the ending, since the Japanese wanted a realistic story, but it could also have been the truth, as he couldn't face the real story.  I really don't know which story to believe. Is there any conclusion which one is real?

At the end of the movie  Pi tells us two stories. One with the tiger (unrealistic) and one without the tiger (realistic).  I believe that he was metaphorically referring himself as the tiger who enters the forest (world) after being rescued.  Is my thinking correct? can you explain me the ending?  At the end did Irfan Khan (older Pi/narrator) say that "even God chose the first story"? Does it mean that the first story was indeed real?


i am having trouble to get my biblatex to recognize any references. here is the output of a minimal examples i found on the web (others behave similar). can you help me? I am using full Miktex installation (all packages pre-installed), and the results below are same for both TexWorks and TexStudio.   Minimal example taken from    \begin{filecontents}{\jobname.bib} @book{Labov1972,     Address = {Philadelphia},     Author = {William Labov},     Publisher = {University of Pennsylvania Press},     Title = {Sociolinguistic Patterns},     Year = {1972}}  @book{Chomsky1957,     Address = {The Hague},     Author = {Noam Chomsky},     Publisher = {Mouton},     Title = {Syntactic Structures},     Year = {1957}} } \end{filecontents}  \documentclass{article} \usepackage[style=authoryear]{biblatex} \addbibresource{\jobname.bib} \begin{document} Some famous linguists wrote a couple of books \autocite{Labov1972,Chomsky1957}. \printbibliography \end{document}   gives me    instead of     the log says   Citation 'Labov1972' on page 1 undefined Citation 'Chomsky1957' on page 1 undefined Empty bibliography There were undefined references. Please (re)run Biber on the file:(biblatex) spielwiese3(biblatex) and rerun LaTeX afterwards.   The .bib file generated by the second minimal example reads (dunno if this is relevant)  %% LaTeX2e file `spielwiese3.bib' %% generated by the `filecontents' environment %% from source `spielwiese3' on 2018/07/31. %%  @book{Labov1972,   Address = {Philadelphia},   Author = {William Labov},   Publisher = {University of Pennsylvania Press},   Title = {Sociolinguistic Patterns},   Year = {1972}}   @book{Chomsky1957,   Address = {The Hague},   Author = {Noam Chomsky},   Publisher = {Mouton},   Title = {Syntactic Structures},   Year = {1957}} }   Running Bibtex results in  Prozess gestartet: bibtex.exe "spielwiese3"  This is BibTeX, Version 0.99d (MiKTeX 2.9.6500 64-bit) The top-level auxiliary file: spielwiese3.aux I found no \citation commands---while reading file spielwiese3.aux I found no \bibdata command---while reading file spielwiese3.aux I found no \bibstyle command---while reading file spielwiese3.aux (There were 3 error messages)  Prozess endete mit Fehler(n)   as of writing this cry for help i discover that manually running Biber (not Bibtex!) => PDFLatex returns the desired result:    could someone explain me what happens?

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


I am new to Ubuntu. I want to know if sh is a symbolic link to bash. Similarly, if "/usr/bin/awk" is a symbolic link to gawk and if "/usr/bin/yacc" is a symbolic link to bison or a small script that executes bison. How do I do it?

As far as I understand bash is the default shell in Ubuntu, so why does /bin/sh point to /bin/dash?


I know that 13.04 is affected (or at least my installation is) because of the OpenSSL version currently installed. However, after running  sudo apt-get update sudo apt-get upgrade   I checked my OpenSSL version and it was still an unpatched build.  I also checked  and 13.04 isn't listed. What can I do to patch OpenSSL on my machine?

This is a  about understanding and remediating the Heartbleed security issue.   What exactly is CVE-2014-0160 AKA "Heartbleed"? What is the cause, what OSs and versions of OpenSSL are vulnerable, what are the symptoms, are there any methods to detect a successful exploit?   How can I check to see if my system is affected? How can this vulnerability be mitigated? Should I be concerned that my keys or other private data have been compromised? What other side effects should I be concerned about?


Is it possible to hear / speak to lobby chat and my teammates mid-game via the Kinect? I'm not wearing headphones and I'm not in a party.

How do we use the Kinect to chat instead of a headset for game chat?  For example, using Kinect for chat while playing Call of Duty: Ghosts.


I created a model in SketchUp and exported it as a .dae file.    Then I imported the .dae file into Blender and created an animation with it.     However, when I render the video, the model looks like it is flickering (as can be seen in the top-left window below). Does anybody have any suggestions on how to fix this? Your help is greatly appreciated!

I was following  on creating a watch and noticed that when I rendered the watch, some pieces were messed up.  I'm new to 3D modeling and I've just learned Blender, I can't explain it well, so here's a picture:    Other examples:     I don't know if it's a problem with my World texture, the object, or the object's texture/material, so I can't even guess how to fix it. What causes this? Is it possible to fix it?


I'm using Microsoft Visual Studio 2012 as my IDE environment. Obviously, my machine is running Windows 7 x64, and I am trying to develop a 64 bit program.  Note, however, that the compiler is Nvidia's nvcc (I've verified that I downloaded the 64 bit version).  For the sake of detail, this is the compile command that Visual Studio prints out:   D:..."C:\Program Files\NVIDIA GPU Computing Toolkit\CUDA\v5.5\bin\nvcc.exe" -ccbin "C:\Program Files (x86)\Microsoft Visual Studio 11.0\VC\bin\x86_amd64"  -I"C:\Program Files\NVIDIA GPU Computing Toolkit\CUDA\v5.5\include" -I"C:\Program Files\NVIDIA GPU Computing Toolkit\CUDA\v5.5\include"  -G   --keep-dir x64\Debug -maxrregcount=0  --machine 64 --compile   -g   -DWIN64 -D_DEBUG -D_CONSOLE -D_MBCS -Xcompiler "/EHsc /W3 /nologo /Od /Zi /RTC1 /MDd  " -o x64\Debug\kernel.cu.obj "...kernel.cu" -clean    It appears that it is compiling in 64 bit as it should.  If that is the case, this is what I have noticed:  When compiled to run on a Windows platform...  (1) sizeof(int) == 4 (2) sizeof(long) == 4 //Where 1 and 2 are true regardless of platform, x86 or x64 (3) sizeof(long long) == 8   Is this accurate? And if it is, does this mean that I have to declare a long long in order to work with an 8 byte "like" integer in Windows? (Meaning that I need to avoid doubles and floats).

Not to long ago, someone told me that long are not 64 bits on 64 bit machines and I should always use int. This did not make sense to me. I have seen docs (such as the one on Apple's official site) say that long are indeed 64 bits when compiling for a 64-bit CPU. I looked up what it was on 64-bit Windows and found         Windows: long and int remain 32-bit in length, and special new data types   are defined for 64-bit integers.      (from )  What should I use? Should I define something like uw, sw ((un)signed width) as a long if not on Windows, and otherwise do a check on the target CPU bitsize?


I'll get into the math straight away $C_1, C_2, C_3$ each are charged to $q$. The energy is $$\frac{q^2}{2\left(\frac{1}{\frac{1}{C_1}\frac{1}{C_2}\frac{1}{C_3}}\right)}$$ $$\frac{1}{2}\left(\frac{q^2}{C_1} + \frac{q^2}{C_2} + \frac{q^2}{C_3}\right)$$  If I then connect them in parallel, the energy now is $$\frac{1}{2}\left(\frac{9q^2}{C_1 + C_2 + C_3}\right)$$ They are obviuosly not equal. Can someone tell me where the difference in energy goes (and also how it gets dissipated.)

The question at hand is:  "Two capacitors of capacitances $C_1$ and $C_1$ have charge $Q_1$ and $Q_2$. How much energy, $\Delta w$, is dissipated when they are connected in parallel. Show explicitly that $\Delta w$ is non-negative."  I'm confused about what the physical situation is. I took the assumption that these capacitors were somehow pre-charged, and then connected to each other in parallel without a voltage source. However, I don't understand how this would work. If a circuit is composed of only 2 elements, I don't see how they could be in any arrangement but series. Nevertheless, I tried solving it that way:  Two capacitors in parallel have the same voltage drop. Charge will be redistributed to make it the same voltage for both. Let $Q_1'$ and $Q_2'$ be the charges on the capacitors after they are connected. Now, picture the equivalent capacitor  $C_{eq} = C_1 + C_2 =$ $\frac{Q_1' + Q_2'}{V_f}$   conservation of charge:  $Q_1' + Q_2'= Q_1 + Q_2$,        $C_{eq} =$ $\frac{Q_1 + Q_2}{V_f}$  $V_f = $$\frac{Q_1 + Q_2}{C_1 + C_2}$  The initial energy of the capactiors is:  $U_0 = $$\frac{Q_1^2}{2C_1}$$+\frac{Q_2^2}{2C_2}$  $U_f = $$\frac{1}{2}$$(C_1 + C_2)V_f^2 = $$\frac{(Q_1 + Q_2)^2}{2(C_1 + C_2)}$  $\Delta U$$ = $$\frac{(Q_1 + Q_2)^2}{2(C_1 + C_2)}$-$\frac{Q_1^2}{2C_1}$$-\frac{Q_2^2}{2C_2}$  However, I don't see how this is necessarily non-negative.


Hello I am really new to learning python, and I am getting confused working with lists.  I wrote the following and I get the following     TypeError: list indices must be integers, not str   My code is:  numlist = list() listy = ['341', '22', '1803'] for i in listy:     numlist = int(listy[i])   So in this program I am trying to write, part of it includes a list of numbers. I want to take those numbers and append them to another list (numlist) that converts each entry in the first list to an integer type.   So I thought I needed to step through each entry in listy.  Does the problem stem from 'i' referencing the entry (ex: '341' and not index 0)? If so...how do you refer to the index? I thought that's what I was doing, but clearly not :(.  Any help would be much appreciated. I looked through some other questions posted to Stack with the same Type Error but I'm so new to this that they all just confused me further.

What's the difference between the list methods append() and extend()?


This is a piece of my Database Class, what I want it to do is to get the String from the name Textfield in my Main Class and insert into the Database with the method insertIntoTable(). But all I get when I run the Application is Error in JavaFX Thread Null Pointer Exception.    Database Class:      Connection connect() {         Connection conn = null;          try {             Class.forName("org.postresql.Driver");             conn = DriverManager.getConnection(url, user, password);           //System.out.println("Connected to the PostgreSQL server successfully.");          } catch (Exception e) {              e.getMessage();          }          return conn;     }       public void insertIntoTable(String naam) {         try {             conn = this.connect();             Statement st;             st = conn.createStatement();             ResultSet rs = st.executeQuery("INSERT INTO eigenschappen (naam)  VALUES (" + naam + ")");             while (rs.next()) {                 System.out.println(rs.getString(1));             }         } catch (SQLException e) {              e.getMessage();          }     } }   The Textfield in Main Class(JavaFx)  Main Class      TextField contactNaamField = new TextField();     Button opslaan = new Button("Opslaan");     Database db = new Database();       public static void main(String[] args) {         launch(args);      }      public void start(Stage primaryStage) throws Exception {          opslaan.setOnMouseClicked(e -> {             String naam = contactNaamField.getText();              db.insertIntoTable(naam);         });     } }

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?


How can I safely remove an LVM physical volume (PV) without data loss?  There is enough space on the remaining PV to hold the data.

For testing purposes I've tried to extend my logical volume by attaching one more Physical Volume (USB drive). Making the USB drive part from the logical volume with the following steps:    Created partition from the device Created Physical Volume from the new partition Attached the Physical Volume to the already configured Volume Group And finally extending the Logical Volume   My question is how to unmount and remove the USB drive without losing any data on the already existing Logical Volume?


I know that these are some existing sums that are true: $$\sum_{r=1}^{n}r = \frac{n(n+1)}{2} = \mathcal{O}(n^2)$$ $$\sum_{r=1}^{n}r^2 = \frac{n(n+1)(2n+1)}{6} = \mathcal{O}(n^3)$$ $$\sum_{r=1}^{n}r^3 = \frac{n^2(n+1)^2}{4} = \mathcal{O}(n^4)$$  I may be butchering the definition of Big O' Notation, but I believe it describes the form of the function, i.e. the highest power of $n$ in these cases. Is there a proof for: $$\sum_{r=1}^{n}r^k = \mathcal{O}(n^{k+1})$$ since there seems to be this pattern?  Or even better, is there a general formulae that mirrors $$\sum_{r=1}^{n}r^k$$ in terms of only $n$ and $k$?  I didn't know how to phrase the question very well on Google, so I apologise if this question has been answered many times.

I have been wanting to understand how to find the sum of this series.   $$1^p + 2^p + 3^p +{\dots} + n^p$$  I am familiar with Gauss' diagonalised adding trick for the sum of the first $n$ natural numbers.  I can prove the formulas for  $$\begin{align}   \sum_{1}^{n} k^2 &= \frac{n(n+1)(2n+1)}{6}\\  \sum_{1}^{n} k^3 &= \frac{n^2(n+1)^2}{4}\\ \sum_{1}^{n} k^4 &= \frac{n(n+1)(2n+1)(3n^2+3n-1)}{30} \\ \end{align}$$  With mathematical induction. But, beyond that even proofs with mathematical induction are difficult.  I'm interested in learning the theory and the proof behind Faulhaber's formula. What is the knowledge required to understand this proof ?


I was wondering if anyone knew or could point to a tutorial of how to create this type of gradient.   How is it done with three colors and with such a smooth transition between the colors without banding?

I should create a vector rectangle filled with a gradient made of 4 colors, one for each corner. I could just find some very generic information about using live blends, but I am not sure that is the best tool and still I was not able to do this. How would you get that in Illustrator exactly? (And secondary in Photoshop?)


W:Failed to fetch   404  Not Found , E:Some index files failed to download. They have been ignored, or old ones used instead.

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


I currently use nautilus as my default file manager. When I search for some file or folder, I also need to switch to the directory that contains the particular file or folder. It feels tedious to go to the properties then copy the path and open the same path. How can I save time, could there be some shortcut to switch to the directory that contains the file (or folder) being looked upon.

After searching for a file in Nautilus, how can I open its parent folder?


How do I render a custom block type (block_content) programmatically with a specific display view?

I'm developing a site using Drupal 8 beta-14. I've created a view block of different terms and now I want to display it using code. How can I display it programatically?  I used to do it in Drupal 7 using this code but I'm confused about Drupal 8.  $block = module_invoke('block', 'block_view', '4'); $text_block = render($block['content']);


I am working on an imported model I found (it's Machamp from Pokémon Sun and Moon). Of course, I am working on it for personal uses, nothing commercial. It's a .dae file, and it contains armature and references to materials and textures. Everything  seems right, except for the bones. These appear to be disconnected, all of them. This makes it impossible to even apply IKs AFAIK (but I am still an amateur in terms of time spent on Blender). I'll provide an example.    As you can see, this does not resemble a skeleton at all. Now, on to the question. Am I doing something wrong? Am I importing it in an incorrect way? Or is it possible that the bones were placed like this from the very beginning? Other models, like Eevee, have some disconnected bones, but the most of them are connected. Thanks in advance, if any additional info is needed, ask right away!

I downloaded few 3d models from a recent pokemon game, then I found this. It doesn't look like a regular skeleton, and I don't think anybody has told me how to do this. Yes, I'm relatively new to this game, but I was just sort of curious. Can you make a bone look like this in blender?


I am trying to add a click event to an element that I appended through jQuery. If I have the item in my HTML code the click event works fine. I hope the code explains it better  HTML
Add new Item

   JS  var data; $('#addNew').click(function () {     $('#priceWrapper').append('
(I dont work i was not here on load)I AM AN ITEM WICH COSTS 2.5€
'); }); $('#Item').click(function () {     data = $(this).attr("data-js");     alert(data); });   Example in   Thanks for your help

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'm using a wordpress plugin to add classes to comments as 'editors' picks'.  On the page I have two buttons, one to show the comments and one to show the editors picks. All is working just fine.  Code:-   $(document).ready(function () {       $("#editors-picks").on("click", function(e){          $("ol.commentlist li").not(".featured").fadeOut(); // fade out any comments that aren't 'featured'      });      $("#comments").on("click", function(e){          $("ol.commentlist li").not(".featured").fadeIn(); // fade all comments back in      }); });   The problem is comments dynamically added to the DOM tree(via ajax). After a new comment is added the function doesn't work. I thought using .on would fix this, but it does not.


I have made a building and texture for it. I want to make this building for a night scene, which means that I want it to glow or emit light from the window to look realistic. Is it possible to make it glow or emit light from the texture?  Texture Building  Night Render view  Nodes  What extra nodes should I add to give a light or emission glow from the window?

So I have a giant object that is completely uv unwrapped. I would like to make areas of the object with a specific area of texture emit light.   The problem is that this object (and it is only one object) only has one material. I would like the lava to emit light, but I cannot move it to a separate material without breaking something.  I'd like to find a method where I can select a part of the texture and tell blender that whatever has that part of the texture emits light.  Is this possible?  Thanks.


i have a follow up question to a previously answered one regarding commas in citations and references:      it works for me in the reference section, but as a text-citation, there is still a comma missing. according to APA 6th, there should be also a comma in front of the "&" when 3 or more authors are used.   like this:     (Tom, Jerry, & Donald, 2012).   right now it looks like this:     (Tom, Jerry & Donald, 2012).   How can i fix it?

I have been trying to solve this problems for hours, but there is no solution in sight.  Until a few weeks ago, my biblatex-apa style was working like a charm. Although, after installing the updates and Biber, the reference section became a problem. It should display a journal article by two authors with a comma after the first author, but it doesn't:     Weber, M. & Ruch, W. (2012). The role of character strengths in adolescent romantic relationships: An initial study on partner selection and mates’ life satisfaction. Journal of adolescence, 35(6), 1537–1546. doi:10.1016/j.adolescence.2012.06.002   it should look like this:     Weber, M., & Ruch, W. (2012). The role of character strengths in adolescent romantic relationships: An initial study on partner selection and mates’ life satisfaction. Journal of adolescence, 35(6), 1537–1546. doi:10.1016/j.adolescence.2012.06.002   This is how my document looks like:   \documentclass[12pt, onecolumn]{apa6}   \usepackage[utf8]{inputenc} \usepackage[american]{babel} \usepackage{csquotes} \usepackage[style= apa, backend=biber]{biblatex} \bibliography{testbib} \DeclareLanguageMapping{american}{american-apa}   \begin{document}  Some text \parencite{Weber2012}.  \printbibliography \end{document}   And the BibTeX file:  @article{Weber2012, abstract = {}, author = {Weber, M. and Ruch, W.}, doi = {10.1016/j.adolescence.2012.06.002}, file = {}, issn = {1095-9254}, journal = {Journal of adolescence}, number = {6}, pages = {1537--1546}, pmid = {22749517}, publisher = {Elsevier Ltd}, title = {{The role of character strengths in adolescent romantic relationships: An initial        study on partner selection and mates' life satisfaction.}}, url = {http://www.ncbi.nlm.nih.gov/pubmed/22749517}, volume = {35}, year = {2012} }    I have tried various things so far, but none of it helped: e.g,   \renewcommand*{\finalnamedelim}{ \finalandcomma}   or  \renewcommand\finalandcomma{\addcomma}   Even in the biblatex manual, the reference examples of two authors is without the comma (it works for three or more authors). There should be a comma, according to . Why is that comma not there? And how could I insert that into my references?


How can I make a redirect page in jQuery/JavaScript?  I mean how can one program in client side script to  redirect browser from page1 to  page n?

How can I redirect the user from one page to another using jQuery or pure JavaScript?


I don't know how to prove that $p\Rightarrow q$ is equivalent to $\neg p\lor q$ ,here is the link  . And I don't know how wolframalpha generate "Minimal forms" .   Can you prove $p\Rightarrow q \equiv \neg p\lor q$,  and explain how to get "Minimal forms" ?  Thanks!

Is there a proof for the logical equivalence of $a \rightarrow b$ and $\lnot a \vee b$?


Let $A=\emptyset$ and $B=[a,b]$ where $R⊃A,B$  What is $A \times B $ where $\times$ denotes the cartesian product?  How can we explain this $A\times B$ in $R^2$, what does it look like?

Given two sets $A$ and $\varnothing$, where $\varnothing$ is the empty set. The Cartesian product is defined by  $$A \times \varnothing = \{ (x,y) \mid x \in A, y \in \varnothing \}$$  Why is $ A \times \varnothing = \varnothing$?


I have laptop (HP Notebook - 15-ac132ne),I have a problem that if I move the laptop from a Wi-Fi device more than a meter, it don't connect to the Wi-Fi network , and if I move  the laptop from a Wi-Fi device more than two meters, the Wi-Fi network disappear and This problem didn't encounter me when I was using Windows  mohamed@mohamed-HP-Notebook:~$ lspci -knn | grep Net -A3; rfkill list 0d:00.0 Network controller [0280]: Realtek Semiconductor Co., Ltd. RTL8723BE PCI e Wireless Network Adapter [10ec:b723]     Subsystem: Hewlett-Packard Company Device [103c:804c]     Kernel driver in use: rtl8723be 1: phy0: Wireless LAN     Soft blocked: yes     Hard blocked: no 3: hci0: Bluetooth     Soft blocked: no     Hard blocked: no mohamed@mohamed-HP-Notebook:~$

I have a HP 14-AN001NA laptop. It came with Windows 10 installed on which the Wi-Fi worked fine anywhere in the house.   However I removed Windows 10 and installed Ubuntu 16.04 instead and since I have had terrible Wi-Fi anywhere aside from about three foot away from the router. I don't know if it's relevant but my Wi-Fi is not called wlan0 but wlo1 for some reason (I didn't change it).  When running lspci -knn | grep Net -A3     I get the following output:  05:00.0 Network controller [0280]: Realtek Semiconductor Co., Ltd. RTL8723BE PCIe Wireless Network Adapter [10ec:b723] DeviceName:   Subsystem: Hewlett-Packard Company RTL8723BE PCIe Wireless Network Adapter [103c:81c1] Kernel driver in use: rtl8723be Kernel modules: wl, rtl8723be


I'm a new reviewer and I would like to get some feedback.  I've flagged  as not an answer.  My flag was declined, with the reasoning - "a moderator reviewed your flag, but found no evidence to support it", while:   This post asks multiple "sub questions", that wasn't even addressed. In the only thing it did try to answer  - he only provided a link.   Would appreciate your opinion.

What is the "Not an Answer" flag and what is its purpose? When should I use this flag? When should I not use this flag? But I'm still not sure if I'm using the flag correctly... An answer is "Not an Answer", but the flag was declined or disputed!   See also:


Consider the square $[0,1]^2$ with the dictionary order (the restriction of the dictionary order on $\mathbb R^2$ to the subset $[0,1]^2$. I'm trying to understand why the set $A=\{1/2\}\times (1/2,1]$ is not open in the order topology on $[0,1]^2$.   Munkres give this picture that should clarify things:    The order topology on the square is given by the basis that consists of all elements of the form $[a_0,b)$ where $a_0=(-1,1)$, $(a,b_0]$ where $b_0=[1,1]$, and $(a,b)$ (w.r.t. the dictionary order). The definition of $A$ being open is this: for every every $t\in A$ there is a basis element $U$ s.t. $t\in U\subset A$. Its negation is: there is $t\in A$ such that for all basis elements $U$ it is not true that $t\in U\subset A$. But I couldn't find such $t$ and unravel "it is not true that $t\in U\subset A$".

Yesterday I asked a very similar  but now I am confused again...  Let $I=[0,1]$. The dictionary order on $I\times I$ is just the restriction to $I\times I$ of the dictionary order on the plane $\mathbb{R}\times\mathbb{R}$. now, how can I show that the set $\{1/2\}\times (1/2,1]$ is not open in the order topology? The maximum element of $I$ is 1. So the order topology on $I\times I$ has intervals of the form $(a,1]\times (b,1]$ as basis elements. Isn't $\{1/2\}\times (1/2,1]$ itself a basis element of the order topology?


In the algebra lecture i need to solve the following exercise     Use the universal property of the tensor product to show that    $$(\Bbb{Z}/4\Bbb{Z}) \otimes (\Bbb{Z}/6\Bbb{Z})\cong \Bbb{Z}/2\Bbb{Z}$$   Here is my job:  I tried to follow the example seen in the lecture where we showed that $(\Bbb{Z}/2\Bbb{Z}) \otimes (\Bbb{Z}/3\Bbb{Z})=0$. In that example the professor listed all the generators of $(\Bbb{Z}/2\Bbb{Z}) \otimes (\Bbb{Z}/3\Bbb{Z})$ and then showed that every generator is actually zero just by using the properties of the tensors. Namely  $$\begin{array}{|cc|}\hline 0\otimes n = 0\otimes n + 0\otimes n &\implies 0\otimes n =0 \\\hline 1\otimes0=1\otimes 0 + 1 \otimes 0 &\implies 1\otimes 0 =0 \\\hline 1\otimes 2 =2(1\otimes 1) = 0\otimes1&\implies1\otimes 2=0 \\\hline 1\otimes1 =1\otimes 4 = 1\otimes2 + 1\otimes 2 & \implies 1\otimes 1 =0\\\hline \end{array}$$  for $n= 0,1,2$.  Now to show that $(\Bbb{Z}/4\Bbb{Z}) \otimes (\Bbb{Z}/6\Bbb{Z})\cong \Bbb{Z}/2\Bbb{Z}$ I tried to list all the generator and try to show that they are equal to $0$ or $1$. We have $4\cdot 6=24$ generators and i noticed that if a generator has a even integer than it is equal $0$. The problem is that i can not show that some generators are equal $1$. Indeed the generators equal $0$ are  $$\begin{array}{|cc|}\hline 0\otimes n=0\otimes n + 0\otimes n& \implies 0\otimes n =0 \,\,\,n\in \{0,1,2,3,4,5\} \\\hline n\otimes 0 = n\otimes 0 + n \otimes 0&\implies n \otimes 0 =0 \,\,\, n \in \{0,1,2,3\}\\\hline  \end{array}$$  and  \begin{align*} 1\otimes 2=0 && 1\otimes 4=0 && 1\otimes 6=0 \\ 2\otimes n=0 && 3\otimes 2=0 && 3\otimes 4=0 \\ 3\otimes 6=0 \end{align*} for $n \in \{0,1,2,3,4,5\}$  The other generator can be brought back at the case $1\otimes 1$ and therefore i wish i could show $1\otimes 1$ can be considered as $1$, but i'm not able to. I know that i should use the universal property of the tensor product but i don't really know how to use it, therefore i think that there must be another procedure to solve the exercise. Is what i've done so far correct?

I've just started to learn about the tensor product and I want to show: $$(\mathbb{Z}/m\mathbb{Z}) \otimes_\mathbb{Z} (\mathbb{Z} / n \mathbb{Z}) \cong \mathbb{Z}/ \gcd(m,n)\mathbb{Z}.$$  Can you tell me if my proof is right:  $\mathbb{Z}/m\mathbb{Z}$ and $\mathbb{Z} / n \mathbb{Z}$ are both finite free $\mathbb{Z}$-modules with the basis consisting of one single element $\{ 1 \}$. So $(\mathbb{Z}/m\mathbb{Z}) \otimes_\mathbb{Z} (\mathbb{Z} / n \mathbb{Z})$ has the basis $\{ 1 \otimes 1 \}$.  Therefore, any element in $(\mathbb{Z}/m\mathbb{Z}) \otimes_\mathbb{Z} (\mathbb{Z} / n \mathbb{Z})$  is of the form $(ab) 1 \otimes 1$ and any element in $\mathbb{Z}/ \gcd(m,n)\mathbb{Z}$ is of the form $k 1 = k$ where $k \in \{ 0, \dots , \gcd(n,m) \}$.  I would like to construct an isomorphism that maps $ab$ to some $k$. Let this map be $ab (1 \otimes 1) \mapsto ab \bmod \gcd(n,m)$.  This is a homomorphism between modules: it maps $0$ to $0$ because it maps the empty sum to the empty sum. It also fulfills $f(a + b) = f(a) + f(b)$ because there is only one element, $a = 1$.   It is surjective. So all I need to show is that it is injective. But that is clear too because if $ab \equiv 0 \bmod \gcd(m,n)$  then both $a \equiv 0 \bmod n$ and $b \equiv 0 \bmod m$ so the kernel is trivial.  Many thanks for your help!!


Ming the Minotaur Gladiator took it really bad during the "undead night fight" event at the Westgate arena.  He got some negative levels while fighting some vampires. Eeek.  Now 24h later, he made all his saves, except one. He is ....  Can he lose one of his monster HD (instead of a level of fighter, for example)?

What happens when one is affected by something such as energy drain, and permanently loses levels when one only has racial HD? Does the victim of the spell die? Or do they permanently lose racial HD?


so let's suppose there is a wheel, which rotates thus moving on a flat plane, without any slopes, and the gravitational pull throughout the plane is the same as well. The height of the center of  mass of the wheel does not change as well. So my question is does the wheel do work against gravity?  Personally, I believe it does because when you take the contact point of the wheel to the plane, its height changes as the wheel rotates, thus changing the potential energy of the point while rotating. However, I couldn't be sure if my hypothesis was correct by researching in various websites and couldn't conduct any simulations or experiments. So I would love to hear your opinions on the topic.

Perhaps this is trivial: how does one prove that the work done by a homogeneous gravitational field on a system of particles is equal to the work done on a point mass with the total mass of the system, located at the center of mass of the system.


You are in hell for all eternity and the devil gives you two dollar bills every day with increasing serial numbers. He then takes the dollar bill you have with the smallest serial number. At the end of your infinite stay in hell, do you have infinite money or no money?  The intuitive answer for me was that if you look at the partial sums, on the Nth day you'll have $N$ dollars. So clearly after infinity days you should have infinity dollars.  On the other hand, you can also prove that for every dollar you ever received, there's a corresponding day that the devil takes it back, leaving you with nothing in the end.  Which one is the right answer?

A friend of mine asked me the following question:      Suppose you have a basket in which there is a coin. The coin is marked   with the number one. At noon less one minute, someone takes the coin   number one and put into the basket two coins: the number two and the   number three. At noon less $\frac{1}{2}$ minute, he takes the coin   number two and put into the basket the coins number $4$ and the number   $5$ and so on. At noon less $\frac{1}{k}$ he takes the coin number $k$   and put two other coins.       The question is: How many coins I can find in the basket at noon?   Intuitively the answer is $\infty$ because I added one coin for infinite times. But the correct answer seems to be $0$ because every coin numbered $k$ has been removed at noon less $\frac{1}{k}$ of minute. What is the correct answer? Thanks.


Hi I get this error when connecting to SQL Server remotely from a website. I checked the SQL Server logs and get the error:  Login failed for user 'NT AUTHORITY\ANONYMOUS LOGON'. Reason: Token-based server access validation failed   The SQL Service account is running as LocalSystem. From what I have read, SQL Server service automatically adds this account to SPN on startup.  TCP/IP is also enabled on the SQL Server.  Any ideas on what I need to do? Thanks!

As the title states, I'm getting the following error when attempting to use a ASP.NET webapp:  Login failed for user 'NT AUTHORITY\ANONYMOUS LOGON'. Reason: Token-based server access validation failed with an infrastructure error. Check for previous errors. [CLIENT: 192.168.x.x]  This is from the "Application" log on the SQL server. I currently have a clustered setup (using Microsoft Failover Cluster) although the second node has not been configured yet. I've tried configuring SPNs:  setspn -L myserviceaccount  Registered ServicePrincipalNames for <DN>:         MSSQLSvc/*SQL.corp.*.local:1433         MSSQLSvc/*SQL.corp.*.local   And indeed, SQL Server does register it correctly as per its logs:  Message The SQL Server Network Interface library successfully registered the Service Principal Name (SPN) [ MSSQLSvc/my.sql.fqdn ] for the SQL Server service.   However, the query SELECT auth_scheme FROM sys.dm_exec_connections WHERE session_id = @@spid ; returns NTLM and not Kerberos. I've restarted the server a few times to no avail. SQL Server runs under a domain user account with the appropriate delegation privileges.  Am I missing something?  UPDATE:  I was successfully able to get the SQL Server to use "Kerberos" as per the above query, but I'm still having no luck getting the IIS level to work.


I am using 3 different USB HDDs of the same model for regular backups with Acronis. This software wants me to set up a target path for the backup files, so I depend on my external HDDs to always have the same drive letter (E:), otherwise it will fail.  Now, I usually only have one HDD at a time plugged in and I set up the drive letters for each device to E: in the Device Manager. Every HDD gets automatically assigned the letter E: when I plug it in.  This works, but only if I strictly take care that never more than one of those three devices is connected at the same time. If I e.g. connect all three devices to check and compare the backups and delete old ones, the first device I plug in gets assigned to E:, the second to F: and the third to G:. This would be ok and can't be different, of course, but afterwards, when I disconnect all of them and plug in a single device to run my backup, it keeps its reassigned letter (E: F: or G:) instead of switching back to E:.  My question is: How can I tell Windows to assign a device a specific letter whenever possible (if the letter is currently not occupied by another device, but again if the letter is free the next time I connect it)?  Note that for the backup, I need exactly the same drive letter and directory structure (--> same backup target directory address) on all three devices!  From OPs comment:  This is not a duplicate of the question as it has been closed. It's just the opposite. The other questions asks is like "How can I make my red USB key always be drive D: and my blue USB key always be drive E:?" This question is like "How can I make sure that no matter which of red, blue, or green external USB backup drives I connect that it will always be drive D: when possible?"

Depending on what's currently connected to a PC, a USB key does not always get the same drive letter.  This is an issue for me because I want to use this key as a backup destination, and I thus have to change the path that's used from time to time.  Is it possible to make sure that a specific key always ends up with the same letter?


A while ago I flagged  as "not an answer". However, my flag got the status:  declined - a moderator reviewed your flag, but found no evidence to support it  Which I find a bit interesting. I think that the answer should be a comment to Deep's answer considering he is the only one who mentions a getV method.  Why was this flag declined? Is it just me who thinks it should be a comment to Deep's answer? Am I missing something here?

One of my flags for "non-answer" was declined and I was wondering if I misunderstood what "non-answer" means. I saw someone post an answer that was just a block of code, with nothing in it that was even the slightest related to the question, it was just a random block of code with no explanation. Should I have not used the "not an answer" tag even though the description explicitly says that it should be used when answers "do not attempt to answer the question"?


I have manually copied the skyrim directory of steamapps from my old computer to a new one.  After installing Steam again, I tried to copy all files back again to start the game, but, when I start steam, it doesn't recognize Skyrim as installed, and need to download again 10Gb of game. :-/  I didn't know about the Steam Backup feature, so, someone can help me, I think it is a Windows Registry Keys that are missing, but I can't find anything on web related to that!  Any suggests?

I have just bought a new computer and I have everything migrated over except for my Steam games.  I looked in Program Files/Steam/ and I found a folder full of the games I have downloaded, but I do not know if it is safe to just copy these folders from one computer to another (seeing as a lot of other applications will not work if you do this), or is there another recommended way?  I don't really feel like re-downloading all my games. I don't have the time nor bandwidth to download 20GB over a 1.5mbps connection.  Is it possible to contact Valve and get a disk with the games on it?


How many different ways you can arrange zeros and ones such that the total number of ones before any point in the sequence is greater than or equal to the number of zeros before that point. This can also be interpreted like this, how many different ways you can arrange zeros and ones in a sequence such that the sum till whatever point you take in the sequence is non negative. There are 2n ones and zeros. For example consider this sequence of 6 ones and zeros,  111000, 110100, 101010, 111111, 111110 are all permutations that we are looking for. But 011100, 100110, 000000 are permutations that we are not interested in as there is at least one point in the sequence before which the sum is non positive.  Thanks in advance;)

In the book I'm using on Catalan numbers, the author gives a scenario in order to develop the formula for Catalan numbers.   The scenario is that a boy has an empty jar. Every day he either puts in a dollar coin or takes on out for $2n$ days. At the end of the $2n$ days, the jar is empty. In how many ways can this happen?  I understand how he gets to the Catalan numbers. But there is one part where he says this:     note that if $n\gt 0$ then there had to be a first day other than the starting day when the jar was empty.   I'm having trouble understanding why this is the case. When I think of taking or putting a coin in a jar as the equality $y=x$, you could just add a coin in for the first $n$ days, then take one out for the remaining $2n - n = n$ days.   Why does there have to be a day other than the starting day in which the jar was $0$?


Are they here?  1) Yes. They arrived.  2) Yes. They have arrived.    I cannot understand what the difference is.  Of course I know 1) is 'past' and 2) is 'present perfect'  But in my country, 'Present perfect tense' is not exist.  So I cannot understand detail meaning between them.  My teacher told me that 'Present perfect tense' occurred in the past, but still related to present.  But I cannot figure out.  Here is another dialogue that I cannot understand.    Are you hungry?  1) I had lunch.  2) I have had lunch.    Please tell me the difference between them.   Thank you.

This  states that:  When you use the present perfect tense you have to be talking about a period of time that you still consider to be going on. For example, if it’s still morning, you can say, "I’ve shaved this morning." If it is afternoon or evening, all of a sudden "I’ve shaved this morning" sounds really weird.  "I've shaved this morning" sounds more like past perfect, and indication of specific time (in the morning) makes this sentence incorrect.  Am  I spot on? Then what is the difference between the construct of past perfect, present perfect and future perfect?


I have a Dell Inspiron 1525 laptop and I am planning on purchasing a mac mini, new version , I am tight on money for a while and want to use my current laptop screen as monitor for mac mini, I just want to know if it is at all possible to do, I have windows 7 and ubuntu 11.04 installed in my laptop, and I don't really care if need to wipe them out, or purchasing a monitos is the only option left, also I am planning to use it for coding and stuff, so VNC is probably not a good choice.

I want to buy a Mac Mini and I want to use it with my laptop monitor. My laptop is Lenovo Y510P. I searched some documents for using Mac Mini with laptop monitor and I only found a solution to using with an Apple laptop unfortunately.  My laptop doesn't have a video input but can I use the Mac Mini via an external video capture devices etc? Or is there a way to use Mac Mini with laptop monitor?


When writing a noun that shows a parenthetical plural suffix option, which is acceptable, "policy(ies)" or policy(s)"?

Sentences constructed with a word written in the singular and parenthetically in the plural are straightforward when that word does not end in -y, e.g.:     List all applicable employee(s).   How does one handle words ending in -y? Is this correct:     I will attend the party(ies).


For example, say I already got some Dratinis, and one Dragonair, and now, if I catch a Dratini versus if I catch a Dragonair, does it matter if I am going to transfer it to the Professor to get an extra candy to evolve my Dragonair to Dragonite?  That is, if I catch a Dratini and transfer, I get one Dratini candy, versus if I catch a Dragonair and transfer, I get one Dratini candy also?  So there is no extra benefits of catching a Dragonair vs a Dratini?  P.S. if so, a strategy can be, find out how many candies you need to evolve to a Dragonite first, and once you know it is 100, then when you have 25 candies, don't evolve to a Dragonair first, because if you catch one along the way, then the 25 candies you spent can be considered a waste.

I was just wondering if the number of candies we get while transferring the pokemon to professor is same for any stage of evolution ?   For example, you would get a pidgey candy for transferring a pidgey. Is it same number of candies for transferring pidgey, pidgeotto or pidgeot ?


$c_n>0$ in $\mathbb{R}$, prove$$\limsup \frac{c_{n+1}}{c_n} \geqslant \limsup \sqrt[n]{c_n}$$ Tried to present $\sqrt[n]{c_n}=c_1 \frac{c_2}{c_1}...\frac{c_{n+1}}{c_n}$. Seemingly $\sqrt[n]{c_n}$ is some kind of mean of $c_1$ to  $c_{n+1}/c_{n}$. However nothing can be done...any hint?

This may have been asked before, however I was unable to find any duplicate. This comes from  of "Mathematical Analysis: An Introduction" by Browder. Problem 14:     If $(a_n)$ is a sequence in $\mathbb R$ and $a_n > 0$ for every $n$. Then show:   $$ \liminf(a_{n+1}/a_n) \le \liminf((a_n)^{(1/n)}) \le \limsup((a_n)^{(1/n)}) \le \limsup(a_{n+1}/a_n)$$   The middle inequality is clear. However I am having a hard time showing the ones on the left and right. (It seems like the approach should be similar for each). This is homework, so it'd be great if someone could give me a hint to get started on at least one of the inequalities.  Thanks.


I noticed this doing review just now. A user with 11 rep is showing as having participated in reviewing suggested edits. Obiviously this is not high enough rep to do so, but also this user shouldn't be able to have an expandable badge on hover like this, if I understand that feature correctly.  Am I not understanding the recent reviewers list?

When clicking "edit" I see:  Your edit will be placed in a queue until it is peer reviewed. We welcome edits that make the post easier to understand and more valuable for readers. Because community members review edits, please try to make the post substantially better than how you found it, for example, by fixing grammar or adding additional resources and hyperlinks.  Like:     Likewise, when I am not logged in, clicking "improve this question" or "improve this answer" shows:  You are not . Your edit will be placed in a queue until it is .  And when I click 'Save', I get:  Thanks for submitting an edit. It is only visible to you until it's been approved by trusted community members  Like:     Who can suggest an edit? Where do suggested edits go? Who can vote on a suggested edit? How do suggested edits get reviewed? Can I earn reputation? What about abuse or bad edits? Sometimes the Community user approves or rejects my edit. Why is that? When can I not suggest an edit? Is there a minimum change requirement for a suggested edit? How do I check my suggested edit history? I disagree with the reasons why my suggested edit was rejected. What can I do? How do I know whether there are edits waiting for review? Someone suggested an edit to my own post, and the reviewers took the wrong action. What can I do? Are tag wikis included in this scheme? What do the "Improve Edit" and "Reject and Edit" buttons do? Why are apparently valid links to rejected edits resulting in 404 errors?   For more information about editing, see "" in the .


In my Apex controller, I have a Constructor method which initializes two variables by querying custom objects using id from URL:  ApexPages.currentPage().getParameters().get('Id');   Am I able to write a test method to the Controller's constructor?

How can I test the below controller and get greater than 0% coverage?  My controller class looks like this:  public with sharing class EmployeeController  {     public EmployeeController(ApexPages.StandardController controller)     {      }      public PageReference pdf1()     {          return Page.Employee_PDF;     }         public list<Certification__c> certification      {         get         {                 certification = [SELECT Date_Certified__c, Name, Principle__c, Year_Certified__c FROM Certification__c WHERE Employee__c =:ApexPages.CurrentPage().getparameters().get('id')];                 return certification;         }         set;      }      public list<Project_Experience__c> proj         {                 get                 {                         proj = [SELECT Client__c, Duration__c, Location__c, Position__c, Project_Description__c, Project_Name__c, Responsibilities__c FROM Project_Experience__c WHERE Employee__c =:ApexPages.CurrentPage().getparameters().get('id')order by Project_End_Date__c desc];                         return proj;                 }                 set;         }      public list<Training__c> training     {         get         {                 training =[SELECT Location__c, Name, Principle__c, Trainer__c, Year__c FROM Training__c WHERE Employee__c =:ApexPages.CurrentPage().getparameters().get('id')];                 return training;         }         set;     }          public list<Employee__c> emp         {                 get                 {                         emp = [SELECT Name, Sex__c, Foreign_Language_Proficiency__c, Nationality__c, Qualifications__c, Tools__c FROM Employee__c where Id = :ApexPages.CurrentPage().getparameters().get('id') ];                         return emp;                 }                 set;         }    }   Here is my current test class:  @isTest private class EmployeeControllerTestClass2 {     static testMethod void myUnitTest()      {        Employee__c emp = new Employee__c(Name = 'empTest',Employee_Status__c='Active' );         insert emp;          Project_Experience__c project = new Project_Experience__c (Employee__c = emp.id, Project_Name__c='Indosat');         insert project;         Training__c training = new Training__c (Employee__c = emp.id, Name='Salesforce Adm 201');        insert training;           PageReference pageRef = Page.Employee_Pages;         Test.setCurrentPage(pageRef);         ApexPages.Standardcontroller sc = new ApexPages.Standardcontroller(emp);         ApexPages.currentPage().getParameters().put('Id',emp.id);          Test.StartTest();     } }


I have accrossed in my text book this integral :$ \int_{0}^{1}\frac{\log^2 (x+1)}{x}$  and i used integration by part but i can't get any result compatible with  , i'm really confused how this integral had a relationship with polylogarithm function and why it's closed form result depend to the Riemann zeta function  , function which i didn't know before, then my question is : how do i evaluate this integral : $$ \int_{0}^{1}\frac{\log^2 (x+1)}{x}$$  ?

The definite integral  $$\int_0^1\frac{\log^2(1+x)}x\mathrm dx=\frac{\zeta(3)}4$$  arose in my answer to . I couldn't find it treated anywhere online. I eventually found two ways to evaluate the integral, and I'm posting them as answers, but they both seem like a complicated detour for a simple result, so I'm posting this question not only to record my answers but also to ask whether there's a more elegant derivation of the result.  Note that either using the method described in  or substituting the power series for $\log(1+x)$ and using  $$\frac1k\frac1{s-k}=\frac1s\left(\frac1k+\frac1{s-k}\right)\;$$  yields  $$ \int_0^1\frac{\log^2(1+x)}x\mathrm dx=2\sum_{n=1}^\infty\frac{(-1)^{n+1}H_n}{(n+1)^2}\;. $$  However, since the corresponding identity without the alternating sign is used to obtain the sum by evaluating the integral and not vice versa, I'm not sure that this constitutes progress.


I'm using developer preview of Yosemite for a while, now that Yosemite is released I want to have it installed on top of my Yosemite partition.  Clicking on "Download" in App Store Yosemite page, I see that I am prompted with an error note, saying :     Os X v10.10 is already installed on this computer. Use the Updates page to install the 10.10 update or if you would like to download the full OS X installer click Continue.   There's only two buttons; "Learn More" and "OK". OK does nothing, and there's no relevant update note regarding switching to full version of Yosemite so it's not rleevant neither.  How can I download full, final OS X Yosemite 10.10 release and install it on top of preview partition?

I did sign up for Apple's Public Beta program but was too late and missed out on the Developer Preview as they were offered to only the first one million sign-ups. Anyway, today I just managed to grab a copy off a torrent site and it's now lying on my computer.  Now before I proceed to install it, I would like to know what happens to me when Apple releases future beta updates. Will I be able to just update my OS as a regular copy or will I again need to search for and download an updated copy off the torrent? What happens when Apple finally releases the official copy come fall? Will I be able to just hit the Software Update option in the Apple menu and get it done or will I have to download the whole shebang all over again?  P.S. I understand there are risks involved with installing Dev Previews and am not worried about them. Thanks.


I am trying to implement a delete and deleteAll method to remove one occurrence or all occurrences of a string from my linked list using recursion, then returns an LLNode object. In my code I am, conceptually, trying to identify if a node (ie node1) is pointing to a node with an occurrence of the specified element (node2), and if so, have node1 instead point to the node that node2 is pointing to.  My code works for the most part, but the problem I am running into is that it seems to skip over the first node in the list.   public class LinkedTest {  public static void main(String[] args) {     // TODO Auto-generated method stub      LLNode<String>list = new LLNode<>("susan");     list = addNode(list, "matt");     list = addNode(list, "susan");     list = addNode(list, "bob");     list = addNode(list, "matt");      printNodes(list);      list = deleteAll(list, "susan");     System.out.println("\nPrint nodes forward after delete of susan");     printNodes(list);      list = deleteAll(list, "matt");     System.out.println("\nPrint nodes forward after delete of matt");     printNodes(list); }  public static LLNode<String> addNode(LLNode<String> list, String info) {     LLNode<String> newNode = new LLNode<>(info);     newNode.setLink(list);     list = newNode;     return list; }  public static void printNodes(LLNode<String> node) {     System.out.println("Print list forward");     while (node != null) {         System.out.println(node.getInfo());         node = node.getLink();     } }  public static LLNode<String> delete(LLNode<String> node, String name){     if(node.getLink().getInfo() != name){         delete(node.getLink(), name);     }     node.setLink(node.getLink().getLink());     return node; }  public static LLNode<String> deleteAll(LLNode<String> node, String name){     if(node.getLink() != null){         deleteAll(node.getLink(), name);          if(node.getLink().getInfo() == name){             node.setLink(node.getLink().getLink());         }     }     return node; }  }   When this is run, this is the outcome:  Print list forward matt bob susan matt susan  Print nodes forward after delete of susan Print list forward matt bob matt  Print nodes forward after delete of matt Print list forward matt bob   In the output you can see that the first instance of "matt" has not been deleted. The same problem happens when implementing the delete method.  Any help is greatly appreciated!

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


According to , unlike the other three interactions, weak interaction does not produce bound states. However, according to  and , the weak force should be attractive between particles with opposite "weak charges." Neutrino and electron have opposite weak isospins, so why can't weak interaction bind them together through neutral current?

My understanding is that the exchange of Z bosons could yield an attractive or repulsive "force" between two fermions. For most combinations the electromagnetic or strong interactions will take place.  However, if we have two neutrinos, or a neutrino and a charged lepton, only the weak interaction comes into play. Are these possible bound states?


I need to check input value before save in db table.  I have a domains, and I want to check inserted link in url field. If url use one of domains from list validation true else false.  Ex.  $urls = array('domain.com','domain2.com','domain3.com');   In url field will put link e.x (domain2.com/priflie/1234 OR domain.com/profile/4321)  I try with this, but no work  if (in_array($url, $urls))  { // error code here  }

I need to build a function which parses the domain from a URL.  So, with   http://google.com/dhasjkdas/sadsdds/sdda/sdads.html   or  http://www.google.com/dhasjkdas/sadsdds/sdda/sdads.html  it should return google.com  with   http://google.co.uk/dhasjkdas/sadsdds/sdda/sdads.html  it should return google.co.uk.


template<class mapT, class K, class V> void f(mapT& m, const K& k, const V& v) {     pair<mapT::iterator, bool> p = m.insert(make_pair(k, v)); }   MSVC accepts this code with no errors or warnings. What does the standard have to say about this? Are we allowed to (optional), not allowed to (forbidden), or required to (mandatory) qualify T::iterator with typename in the example above? I am particularly interested in C++03 rules although if anything has changed for 11 it would be nice to know. Thank you.

In templates, where and why do I have to put typename and template on dependent names? What exactly are dependent names anyway?    I have the following code:  template <typename T, typename Tail> // Tail will be a UnionNode too. struct UnionNode : public Tail {     // ...     template<typename U> struct inUnion {         // Q: where to add typename/template here?         typedef Tail::inUnion<U> dummy;      };     template< > struct inUnion<T> {     }; }; template <typename T> // For the last node Tn. struct UnionNode<T, void> {     // ...     template<typename U> struct inUnion {         char fail[ -2 + (sizeof(U)%2) ]; // Cannot be instantiated for any U     };     template< > struct inUnion<T> {     }; };   The problem I have is in the typedef Tail::inUnion<U> dummy line. I'm fairly certain that inUnion is a dependent name, and VC++ is quite right in choking on it. I also know that I should be able to add template somewhere to tell the compiler that inUnion is a template-id. But where exactly? And should it then assume that inUnion is a class template, i.e. inUnion<U> names a type and not a function?


I tried going on the Stack Overflow chat and got the following notice:    The console shows:     Failed to load resource: the server responded with a status of 500 (Internal Server Error)   Update #1  It seems like this issue intermittently occurs.  Update #2  Browser: Chrome (60.0.3112.113)  Access Type: HTTPS  VPN: N/A  Country: UK

When two accounts are merged, all the posts/votes are moved over to the "master" account, and the other account ("slave"?) is deleted. The merge is propagated network-wide, so a similar thing happens on each site.  But, this does not happen to the chat user. The "slave" chat user is kept, with a 404 parent profile link. I feel that the chat user should be merged as well, re attributing all the chat messages.  Thoughts?


I'm breaking my head over this. If (a,b,c) are positive real, show that \begin{align} \sqrt{\frac{2a}{a+b}}+\sqrt{\frac{2b}{b+c}}+\sqrt{\frac{2c}{c+a}}\le3 \end{align}  (There is equality only when $a=b=c$)

Let $a,b,c \gt 0$. Prove that (Using Cauchy-Schwarz) :   $$\sqrt{\frac{2a}{b+c}}+\sqrt{\frac{2b}{c+a}}+\sqrt{\frac{2c}{a+b}} \leq 3$$   I tried to use Cauchy-Schwarz in the following form $$\sqrt{Ax}+\sqrt{By}+\sqrt{Cz}\leq \sqrt{(A+B+C)(x+y+z)}\tag{1}.$$   I wrote $$\sqrt{\frac{2a}{b+c}}+\sqrt{\frac{2b}{c+a}}+\sqrt{\frac{2c}{a+b}}=\frac{\sqrt{2a(c+a)(a+b)}+\sqrt{2b(b+c)(a+b)}+\sqrt{2c(b+c)(c+a)}}{\sqrt{(a+b)(b+c)(c+a)}}.$$  and then I applied on $(1)$:  \begin{eqnarray} A &=& 2a(c+a)   &\mbox{and}&  x=a+b;\\  B &=& 2b(a+b)   &\mbox{and}&  y=b+c;\\ C &=& 2c(b+c)   &\mbox{and}&  z=c+a , \end{eqnarray}  but I did not obtain anything. Thanks for your help. :)


I've read  that in order to create a file inside a directory in Linux, one should have write permission to that directory. However when examining this (in Ubuntu Server 14) it did not worked.  osboxes@osboxes:~$ mkdir mydir  osboxes@osboxes:~$ chmod 200 mydir  osboxes@osboxes:~$ ls -l d-w------- 2 osboxes osboxes 4096 May 25 09:52 mydir  osboxes@osboxes:~$ touch mydir/myfile touch: cannot touch 'mydir/myfile': Permission denied   only after adding execute permissionto mydir I could touch that file. So execute permissions are also needed in order to touch a file?  EDIT: from @Pablo Bianchi  I learn that      Write (w)      The ability to rename files in the directory, create new files, or   delete existing files, if you also have Execute permissions. If you   don't have execute perms, then write perms are meaningless."   So I guess that execute perms are ndeed required in order to use write perms to create new files.

I am having a bit of trouble understanding what the execute permission means for directories. Do I understand it correctly that anything in a directory for which a user does not have x-rights is inaccessible even if the things inside the directory gives specific rights to the user?  Or will the user still have direct access to the things in the directory, but simply cannot list what is in the directory?  (What I am really trying to understand is how safe a directory is from access from other users if they do not have x-permission for it.)


The display of usernames in the list of responses on user profiles is broken, at least on some sites (the screenshot is from meta.cstheory, and for me it’s also broken on stackoverflow, but not on main cstheory):    Tested in Firefox 72.

and        ()   I just noticed that change. I didn't find new reports under .  Note the names and badge count in the first screenshot, and the badge count in the second one.  PS I can't link to the responses tab as it shows only to the profile owner.


I want to know wether if |f| is continuous at every point of R, then f is continuous also or not?  and what about its converse? if f is continuous in every point of R, does that means |f| also continuous?  Thank you

If $|f(x)|$ is continuous at $a$, is $f(x)$ continuous at $a$?  I tried doing it using composite functions. If $g(x)= |x|$, then $g\circ f(x)= |f(x)|$. Since $g(x)$ and $g\circ f(x)$ are continuous, $f(x)$ is continuous.  I don't know if this is correct. Please help.


I have updated the game but I couldn't find the fruit jetpack anywhere. I thought that I could get it by completing a specific mission but I couldn't get it, the party, nor the water jetpack. How do I get the missing jetpacks?

There is no fruit jet pack. I can't get it. How do I get it? I looked at the jetpacks many times. There are none.


If we have an infinite slab that is not uniformly charged and is not a conductor, how can we find an expression for the electric field everywhere? Here's a picture  Things we know about the slab:   The width is $2b$ It is lying on the $yz$ plane (centered at the origin) the charge density varies as $\rho = \rho_0(x/b)^2$   where $\rho_{0}$ is constant.  I know that I have to use Gauss's law with a right Gaussian cylinder. This is what I have so far:  The closed integral  $$\int EdA = \frac{q_\text{enclosed}} {\epsilon_{0}} \, .$$  To solve for $q_\text{enclosed}$, I believe it would be $\int ρdV$.  From here, I can plug in $ρ_0(x/b)^2$ for $ρ$ and $dV$ is just the area of the circle (I'll call that $A$) multiplied by $dx$.  So the integral becomes (by pulling out all the constants) $ρ_0(1/b^2)A\int x^2dx$ and I am integrating from $-b$ to $b$. Evaluating these bounds in this integral gives me a final answer of $q$ enclosed of $\frac{2ρ_0Ab}{3}$.

So if we have a large sheet that is not uniformly charged and is NOT a conductor, how can I find an expression for the electric field everywhere?  Things we know about the sheet:   the width is 2b it is lying on the yz plane (centered at the origin) the charge density varies as ρ = ρ(0)(x/b)^2 ρ(0) is constant   I'm not sure if I can actually use Gauss' law because there's not the same symmetry as if it was uniformly charged. Is there some other law of electricity or formula that exists? How do I go about tackling this problem?


In my toolbox doesn't exist any grass function, what act I should do?

I am trying to learn GRASS and QGIS using the instructions here: . I am running on Windows and open the version of QGIS with GRASS. When I enable the GRASS plugin, however, I see only two buttons on the toolbar. The panel is telling me to open a GRASS mapset but the button to create a new mapset is not visible in the toolbar. What am I missing here?  I'm using QGIS 2.14.3 with GRASS 7.0.4


If $\sum a_n$ with $a_n>0$ is convergent, then is $\sum {a_n}^2$ always convergent? Either prove it or give a counter example.  Im trying in this way, Suppose $a_n \in [0,1] \ \forall\  n.\ $ Then ${a_n}^2\leq a_n\ \forall\  n.$ Therefore by comparison test $\sum {a_n}^2$ converges.  So If $a_n$ has certain restrictions then the result is true.  what about the general case?  How to proceed further? Hints will be greatly appreciated.

I'm trying to re-learn my undergrad math, and I'm using Stephen Abbot's Understanding Analysis. In section 2.7, he has the following exercise:  Exercise 2.7.5 (a) Show that if $\sum{a_n}$ converges absolutely, then $\sum{a_n^2}$ also converges absolutely. Does this proposition hold without absolute convergence?  I'm posting about this here because my answer to that last question about whether the proposition holds without absolute convergence is "Yes", but my suspicions are raised by him merely asking the question. Usually questions like this are asked to point out that certain conditions are necessary in the statement of propositions, theorems, etc. I just want to see if I'm missing something here.  Anyway, here's how I prove the absolute convergence of $\sum{a_n^2}$, and note that I never use the fact that $\sum{a_n}$ is absolutely convergent:  Proof: Let $s_n = \sum_{i=1}^n{a_n^2}$. I want to show that $(s_n)$ is a Cauchy sequence. So, let $\epsilon > 0$ and $n > m$, and consider, \begin{equation}   \begin{aligned}     |s_n - s_m| &= |(a_1^2 + a_2^2 + \cdots a_n^2) - (a_1^2 + a_2^2 + \cdots a_m^2)|\\                 &= |(a_{m+1})^2 + (a_{m+2})^2 + \cdots + a_n^2|\\                 &= |a_{m+1}|^2 + |a_{m+2}|^2 + \cdots + |a_n|^2\\   \end{aligned} \end{equation} Now, since $\sum{a_m}$ converges, the sequence $(a_m)$ has limit 0. Therefore I can choose an $N$ such that $|a_m| < \sqrt{\epsilon/n}$ for all $m > N$. So for all $n > m> N$,  we have, \begin{equation}   \begin{aligned}     |s_n - s_m| &= |a_{m+1}|^2 + |a_{m+2}|^2 + \cdots + |a_n|^2\\                 &< \left(\sqrt{\frac{\epsilon}{n}}\right)^2 + \left(\sqrt{\frac{\epsilon}{n}}\right)^2 + \cdots + \left(\sqrt{\frac{\epsilon}{n}}\right)^2\\                 &< \left(\sqrt{\frac{\epsilon}{n-m}}\right)^2 + \left(\sqrt{\frac{\epsilon}{n-m}}\right)^2 + \cdots + \left(\sqrt{\frac{\epsilon}{n-m}}\right)^2\\                 &= \epsilon   \end{aligned} \end{equation} Therefore $(s_n)$ is Cauchy and $\sum{a_n^2}$ converges. And since $\sum{a_n^2} = \sum{|a_n^2|}$, the series $\sum{a_n^2}$ is absolutely convergent. ∎  Am I doing something wrong here? Am I right in thinking that $\sum{a_n}$ need not be absolutely convergent for $\sum{a_n^2}$ to be absolutely convergent?


I'm currently experimenting with different regression techniques on this data set that I have, and I some sources state a method called "polynomial regression". I looked it up and I can't really find any clear explanation of what it is exactly. It sounds quite similar to linear regression - can anyone tell me the difference (if any)?  Thanks!

If polynomial regression models nonlinear relationships, how can it be considered a special case of multiple linear regression?  Wikipedia notes that "Although polynomial regression fits a nonlinear model to the data, as a statistical estimation problem it is linear, in the sense that the regression function $\mathbb{E}(y | x)$ is linear in the unknown parameters that are estimated from the data."  How is polynomial regression linear in the unknown parameters if the parameters are coefficients for terms with order $\ge$ 2?


I am going to check if a JLabel is the same as a name of a tv show.  I have the code   public int lastEp() {     if(name.getText() == "Dexter") {         switch (season) {         case 1:             return 12;         case 2:             return 12;         // etc.         }     }     return -1; }   I have checked in console what i get from name.getText() and the console prints "Dexter". Still my if statement wont return true. System.out.println(name.getText() == "Dexter") gives false, while System.out.println(name.getText() + " " + "Dexter") gives "Dexter Dexter". What is happening?  Also bonus question, if anyone know what i should return instead of -1 if no other option fits, if there is a good standard to follow.

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


I have two datasets that I'm trying to compare.  In one dataset, the points appear to be pretty uniformly distributed.      In the second dataset, they appear to somewhat more clustered - i.e. there appears to be some cluster centers where nearly all values are the same (although other points in the set are not at all clustered).    Are there any measures I could use to describe the tendency of the set towards clustering or overlap or something like that (without actually using any clustering methods)?  The mean, standard deviation, and coefficient of variation are very similar between the two sets.   I should add that I'd like some kind of measure because although one set does appear more uniform than the other, since the first set is about 4 times the size of the second set, it is hard to confirm that it truly is more uniform...

I'm trying to come up with a metric for measuring non-uniformity of a distribution for an experiment I'm running.  I have a random variable that should be uniformly distributed in most cases, and I'd like to be able to identify (and possibly measure the degree of) examples of data sets where the variable is not uniformly distributed within some margin.    An example of three data series each with 10 measurements representing frequency of the occurrence of something I'm measuring might be something like this:  a: [10% 11% 10%  9%  9% 11% 10% 10% 12%  8%] b: [10% 10% 10%  8% 10% 10%  9%  9% 12%  8%] c: [ 3%  2% 60%  2%  3%  7%  6%  5%  5%  7%]   <-- non-uniform d: [98% 97% 99% 98% 98% 96% 99% 96% 99% 98%]   I'd like to be able to distinguish distributions like c from those like a and b, and measure c's deviation from a uniform distribution.  Equivalently, if there's a metric for how uniform a distribution is (std. deviation close to zero?), I can perhaps use that to distinguish ones with high variance.  However, my data may just have one or two outliers, like the c example above, and am not sure if that will be easily detectable that way.   I can hack something to do this in software, but am looking for statistical methods/approaches to justify this formally.  I took a class years ago, but stats is not my area.  This seems like something that should have a well-known approach.  Sorry if any of this is completely bone-headed.  Thanks in advance!


Hello I am learning PYTHON and was learning about string splitting .so I have a hex string named  A="aca80202"   I want to convert it into a list of 2 characters   B=["ac","a8","02",02"]   is there any way to do it?

I have a list of arbitrary length, and I need to split it up into equal size chunks and operate on it. There are some obvious ways to do this, like keeping a counter and two lists, and when the second list fills up, add it to the first list and empty the second list for the next round of data, but this is potentially extremely expensive.  I was wondering if anyone had a good solution to this for lists of any length, e.g. using generators.  I was looking for something useful in itertools but I couldn't find anything obviously useful. Might've missed it, though.  Related question:


I want to install Miniconda but I don't want to do so as root. Is there a directory (except ~/) where I can install external software as a non-root user?  I don't want to install it in the default directory ~/miniconda3

Occasionally I install applications manually, rather than using apt or another package manager.   What location (/usr/, /usr/local/, /opt/, /home/, etc.) is suggested by "best practices" for the installation of user applications?


So, in order to multiply 2 matrices, there must be the same number of columns in the left matrix as there are rows in the right matrix. So if $A$ is an $m \times n$ matrix and $B$ is a $p \times q$ matrix, must not $n = p$ in order for $AB$ to exist and mustn't $q = m$ in order for $BA$ to exist. By this logic, we should only be allowed to multiply a $1 \times 1$ matrix by either a $1 \times n$ matrix on the right or a $n \times 1$ matrix on the left. However, if $C$ is a $1 \times 1$ matrix and $D$ is a $m \times n$ matrix, where neither $m$ nor $n = 1$, we're allowed to multiply the 2 matrices simply by multiplying each entry in $D$ by the entry in $C$. Why? Shouldn't the rules for a $1 \times 1$ matrix be the same as for all the other matrices?

For matrix multiplication to work, you have to multiply an $m \times n$ matrix by an $n \times p$ matrix, so we have $$\bigg(m \times n\bigg)\bigg(   n\times p \bigg).$$  But what about a $1 \times 1$ matrix? Is this just a scalar? But every matrix can be mulitplied by a scalar; so do $1 \times 1$ matrices break the rule?


A basis for $sl(2,\mathbb{C})$ is given as $\{e = \left(\begin{matrix}0 & 1 \\ 0 & 0\end{matrix}\right), \; f = \left(\begin{matrix}0 & 0 \\ 1 & 0\end{matrix}\right), \; h = \left(\begin{matrix}1 & 0 \\ 0 & -1\end{matrix}\right)\}$ with relations $[e,f]=h$, $[f,h]=2f$ and $[h,e]=2e$.  A basis for $so(3,\mathbb{C})$ is given as $\{x = \begin{pmatrix}0&0&0 \\ 0&0&-1 \\ 0&1&0 \end{pmatrix}, \; y = \begin{pmatrix}0&0&1 \\ 0&0&0 \\ -1&0&0 \end{pmatrix}, \; z = \begin{pmatrix}0&-1&0 \\ 1&0&0 \\ 0&0&0 \end{pmatrix} \}$ with relations $[x,y]=z$, $[y,z]=x$ and $[z,x]=y$.  My thought are, that I somehow need to map these basis elements in the right way st. two basis have the same relations, and then construct a map from the mapping of the basis elements.  My first idea was $e\mapsto 2x$, $f\mapsto y$ and $h\mapsto 2z$, but it doesn't seem to work out, when expecting the map together with the lie bracket. I've tried some different maps, but without any succes.

I know from various sources ( and   are two) that the complex orthogonal Lie algebra of dimension 3, $\mathfrak{o}_3(\mathbb C)$, (by which I mean the space of skew-symmetric matrices of size 3) is isomporphic to $\mathfrak{sl}_2(\mathbb C)$, but I cannot come up with an explicit isomorphism. Can someone give me one?


I'm new in JS and quite confused about the following code:  HTML  <button id="btn0">Click Me</button> <button id="btn1">Click Me</button> <button id="btn2">Click Me</button>   JS version 1  var test = {     clk: function () {         for (var i = 0; i < 3; i++) {             this.setup(i);         }     },     setup: function (data) {         var btn = document.getElementById("btn" + data);         btn.onclick = function () {             test.show(data);         }     },     show: function (data) {         alert(data);     } } test.clk();   If I run the program and click the 3 buttons, then they show each value of data they kept which are in turn 0, 1, 2  However, if I change the JS code to:  var test = {     clk: function () {         for (var i = 0; i < 3; i++) {             var btn = document.getElementById("btn" + i);             btn.onclick = function () {                 test.show(i);             }         }     },     show: function (data) {         alert(data);     } } test.clk();   Run and click the 3 buttons, then all give the same result of 3? how come the result of 3? How come each does not give 0, 1, 2? How is the JS version 1 different from the version 2?  I come from Java background, and all I thought was when the 3 buttons are clicked, all would give the result of 2?

How would you explain JavaScript closures to someone with a knowledge of the concepts they consist of (for example functions, variables and the like), but does not understand closures themselves?  I have seen  given on Wikipedia, but unfortunately it did not help.