I am learning Regular expression for bash scripting. However, when I was testing string match, the lines always can't pass. Here is what I am testing:  I have a txt file contains a list of "songs":  $ cat soundtrack.txt Ludwig Van Beethoven - 01 - Allero.oog Ludwig Van Beethoven - 02 - Adag.mp3 Ludwig Van Beethoven - 03 - Beach.oog Ludwig Van Beethoven - 04 - Caven Adven.wmv   I would like to use Regex to get the "track number" which are the numerical ones.  Here's the script:  $ cat soundtrack.sh #!/bin/bash IFS=$'\n' for CD in `cat soundtrack.txt` do     if [[ "$CD" =~ "([[:alpha:][:blank:]]*)- ([[:digit:]]*) - (.*)$" ]]     then         echo "Found ${BASH_REMATCH[2]}"     fi done    However, the bash debug shows the string was unable to match the regex:  $ bash -x soundtrack.sh + IFS=' ' ++ cat soundtrack.txt + for CD in '`cat soundtrack.txt`' + [[ Ludwig Van Beethoven - 01 - Allero.oog =~ \(\[\[:alpha:]\[:blank:]]\*\)- \(\[\[:digit:]]\*\) - \(\.\*\)\$ ]] + for CD in '`cat soundtrack.txt`' + [[ Ludwig Van Beethoven - 02 - Adag.mp3 =~ \(\[\[:alpha:]\[:blank:]]\*\)- \(\[\[:digit:]]\*\) - \(\.\*\)\$ ]] + for CD in '`cat soundtrack.txt`' + [[ Ludwig Van Beethoven - 03 - Beach.oog =~ \(\[\[:alpha:]\[:blank:]]\*\)- \(\[\[:digit:]]\*\) - \(\.\*\)\$ ]] + for CD in '`cat soundtrack.txt`' + [[ Ludwig Van Beethoven - 04 - Caven Adven.wmv =~ \(\[\[:alpha:]\[:blank:]]\*\)- \(\[\[:digit:]]\*\) - \(\.\*\)\$ ]]   But, if I test directly in the shell with the same expression, it works:  $ if [[ "Ludwig Van Beethoven - 01 - Allero.oog" =~ ([[:alpha:][:blank:]]*)-\ ([[:digit:]]*)\ -\ (.*)$ ]]; then echo yes; else echo no; fi yes   What's wrong with my script? Do I have to add extra quotas or backslashes? Just doesn't make sense to me.  P.S.  $ bash --version GNU bash, version 4.3.48(1)-release (x86_64-pc-linux-gnu)

The following code  number=1 if [[ $number =~ [0-9] ]] then   echo matched fi   works. If I try to use quotes in the regex, however, it stops:  number=1 if [[ $number =~ "[0-9]" ]] then   echo matched fi   I tried "\[0-9\]", too. What am I missing?  Funnily enough,  suggests this should work.  Bash version 3.2.39.


I have an iframe I am working with, when I place it on my wp site and try to apply the css it is not applying, the external css is still there. Please see this page:   If you inspect it and go the .cover class, I am trying to change the width and height to 65px. However it is not applying. I put this in my theme css:  .cover-overlay, .cover { width: 65px !important;   }   Help!  <link type="text/css" rel="Stylesheet" href="http://gandlp.com/radio?sccss=1&ver=4.3" />  <iframe name="frame" frameborder='no' scrolling='no' src='http://radio.securenetsystems.net/songdata/v5/index.cfm?stationCallSign=CIDC&width=573' allowtransparency='true' style='width:573px;height:250px;margin-top:10px;overflow-y:auto;overflow-x:hidden;border:1px solid #676767;'></iframe>  <script type="text/javascript">  var cssLink = document.createElement("link")  cssLink.href = "http://gandlp.com/radio?sccss=1&ver=4.3";  cssLink .rel = "stylesheet";  cssLink .type = "text/css";  frames['frame'].document.body.appendChild(cssLink); </script>

I have a simple page that has some iframe sections (to display RSS links). How can I apply the same CSS format from the main page to the page displayed in the iframe?


I am very new to physics and I want to pursue Unified Field theory now when I read about how to unify quantum mechanics with relativity as they are essentially the same thing and a relation must be found I read that this can be done by unifying to he forces now I have not studied the math so if someone could explain to me why is this necessary?

It is well known that quantum mechanics and (general) relativity do not fit well. I am wondering whether it is possible to make a list of contradictions or problems between them?  E.g. relativity theory uses a space-time continuum, while quantum theory uses discrete states.  I am not merely looking for a solution or rebuttal of such opposites, more for a survey of the field out of interest.


$\{a_n\}$ sequence $a_1=\sqrt{6}$ for $n \geq 1$ and $a_{n+1}=\sqrt{6+a_n}$ show that it convergence and as well find $\lim \limits_{n \to \infty} a_n$  In order to show that that sequence convergence I need to show that :  $$\lim_{n \to \infty} a_n= L$$  While $L$ is finite.  Using the calculator. I assume that L=3 because :  $$\sqrt{6+\sqrt{6+\sqrt{6+\sqrt{6........}}}}=2.999 \cong  3$$  I really don't think that this method is good enough to established that $\lim \limits_{n \to \infty} a_n= 3$ since it based on intuition.  I'll be glad to hear any ideas for an established method to show this.?  Any help will be appreciated.

(Fitzpatrick Advanced Calculus 2e, Sec. 2.4 #12)  For $c \gt 0$, consider the quadratic equation $x^2 - x - c = 0, x > 0$.  Define the sequence $\{x_n\}$ recursively by fixing $|x_1| \lt c$ and then, if $n$ is an index for which $x_n$ has been defined, defining  $$x_{n+1} = \sqrt{c+x_n}$$  Prove that the sequence $\{x_n\}$ converges monotonically to the solution of the above equation.  Note: The answers below might assume $x_1 \gt 0$, but they still work, as we have $x_3 \gt 0$.    This is being repurposed in an effort to cut down on duplicates, see here: .  and here: .


Either my fan or my battery on my refurbished laptop is malfunctioning and it frequently overheats and shuts itself down. I wasn't able to determine the culprit and thought it best to show my laptop to an expert.  I also have an active warranty that lets me replace any malfunctional parts for free, so that's another reason for not buying my own hardware and trying-and-erring my way through. However, I'm somewhat paranoid about the fact that I have all sorts of sensitive information lying about on my laptop.  Even if I could clear the cookies/passwords for my browser, some sensitive information (credit card details, a host of passwords, and whatnot) that I foolishly left off on some notes, will probably remain. What is more, clearing the said cookies is a troublesome process that I'd rather avoid, if I possibly can.  The guy who runs the local repair shop tends to ask for an admin password, which I'm loathe to give, but have to relent nonetheless. Presuming that I will take my laptop to the repair shop, what is the best possible way to protect all the sensitive information under such circumstances?

Recently bought a new laptop with an extended warranty. Wondering if when a laptop needs to be sent in to the manufacturer for a repair (specifically a hardware repair),  is it ok to remove the hard drive when sending it in?  I don't want to risk my data (security) while in transit and out of my hands.  Nor do I want to delete sensitive files and restore them when my laptop is restored.  I guess this would make it tougher to troubleshoot issues and repair the laptop. I don't know what else I could do.


Given the following dataset, I am trying to find a way to use Regex to pull out city names.  Boston (MA), New York City (NY, CT, NJ) New York City (NY, CT, NJ), Philadelphia (PA, NJ) Indianapolis (IN), St. Louis (MO, IL) St. Louis (MO, IL), Kansas City (MO, KS)  I want the output of the Regex to be:  Boston,New York City New York City,Philadelphia Indianapolis,St. Louis St. Louis,Kansas City  I attempted to pattern match based on two criteria: (\\w+\\w(?=.())) | (\\w+\\W\\h\\w+(?=.()))  Cities consisting of letters from [a-zA-Z]+ such as Boston or Philadelphia One-word consisting of additional characters such as periods/additional spaces.  The expression accurately matches the first case. However, for the second case, it only matches the first occurrence of St. Louis. I also tried the following: (\\w+ ?\\w(?=.())) | (\\w+\\h\\w+\\h\\w+(?=\\s.()))| (\\w+\\h\\w+(?=\\s.()))  The first covers the same case as listed above - consisting of one-word cities. The third one manages to cover the case of New York City, however, just as the first one, fails to recognize cases of the same pattern following that. And the same case as used in the last pattern, which matched St. Louis fails to match, and matched Kansas City instead.

I don't really understand regular expressions.  Can you explain them to me in an easy-to-follow manner?  If there are any online tools or books, could you also link to them?


The default sequence of symbol footnote is *,\dag,\ddag,... How can I make the footnote starting from \dag, i.e., the sequence \dag,\ddag,...? Thanks in advance. (I have the package \usepackage[perpage,symbol]{footmisc}). My question is answered in the link:

I'm using footmisc package for handling footnotes. I want to remove the star (*) from the symbol list?  I tried all the combination of  \DefineFNsymbols*{}{}   and  \setfnsymbol{}   except the correct one!:)  Could someone be so kind to point me to the correct command? Thanks!


I want to find a way to restore my phone in case the process of rooting my phone or dual booting a custom rom breaks it. However, most of the ones I've looked at require the phone to be rooted before installing. I know I can create a nandroid backup through system settings, but I don't know how to recover that without rooting my device, or if there are better options. I'm not terribly concerned for any personal data on my phone (I can backup my pictures pretty easily), but I mostly just want to be able reinstall Android OS or reset to factory default in case my device breaks. Thanks! Edit: I am going to ask a new question (one different enough to justify not simply modifying this one) with the new info I learned from the possible duplicate.

I know I'm asking for the close-to-impossible -- as a real full-backup certainly requires root permissions. But still there are many folks around not wanting to root their devices -- afraid of voiding their warranties or bricking their devices, or just not having their devices supported by any rooting method.  I also know there were a lot of questions asked already on this topic, and I checked all of them having the backup tag -- none covers the entire topic, all just have pieces, and especially people new to Android (but other non-power-users as well) would have a hard time figuring out the best way.  So I want a detailed canonical answer to the question:  Not involving root-solutions, how to achieve a backup as close as possible to a full backup?  Please do not give simple one-liner answers like "Use app xyz [full-stop]." If mentioning an app (and I doubt a single app would be the answer here), include what parts are covered by it -- as well as ideas on how to fill the gaps it leaves. (And to make it absolutely clear: I know the first thing coming to mind is Titanium Backup -- I use it myself, but this does not apply here: This question is strictly about methods for non-rooted devices!) Moreover, the answer should be as generic as possible in terms of applying to a wide range of devices (i.e. it should not be restricted to one device or manufacturer).  I already mentioned having investigated all questions here tagged backup. These will certainly be helpful providing details for answers here, so I will list up the topmost ones concerning my question:            All these provide some details for my question (so feel free to get inspired by them) -- but I feel there are still details missing. Also it would be helpful to have a summary -- say, an answer including the full description of "the maximum possible".  A last criterium: While I'd consider cloud-based solutions legit, I'd favour local solutions. If you can provide both: all the better. But some people value privacy quite high (I'm one of them), and thus would not trust their data to some cloud service.    Thanks to Ryan, we now have a solution for a really complete backup of all apps and their data -- which I didn't dare to hope for! The only disadvantage: His solution only works for less than 10% of all Android users; namely those whose devices are running at least with Android 4.x.  So again, I ask the close-to-impossible: Any solutions applicable at least on Gingerbread (2.3.x) or, better, even Froyo (2.2.x) -- so they cover the majority of current devices? These solutions may involve multiple tools (try to keep it as simple as possible though; think of your mother to follow your instructions ;)  And keep in mind: NO ROOT!    To further motivate high-quality answers (and hopefully avoid low-quality ones), I will be a harsh one here: As I rarely do, I will down-vote answers not fitting the mentioned criteria on one end -- but on the other end, I will setup a bounty for the best answer (which cannot be done immediately, but earliest after 2 days).


When I enter different numbers in "studentNumber" and "testNumber" variables, the code closes at a specific place. No matter what value I give to the variables, the code stands in the second exam part of the 1st student. Code terminates with this error "Process returned -1073741819 (0xC0000005) execution time: 11.105 s" #include <iostream>  using namespace std;  int studentNumber=0; int testNumber=0; struct Student { string name,grade; int studentNo,*testResults; double average; };  void getValue() {     cout << "Enter the number of students: ";     cin >> studentNumber;     Student Students[studentNumber];     cout << "Enter the number of tests: ";     cin >> testNumber;     int Arr[testNumber];     Students[0].testResults = Arr;      for(int i=1; i<=studentNumber; i++)     {         cout<< "\n" << "Enter the name of the " << i << ". student: ";         cin >> Students[i].name;         cout<< "\n" << "Enter the number of the " <<  i << ". student: ";         cin >> Students[i].studentNo;          for(int z=0; z<testNumber; z++)         {             cout<< "\n" << "Enter the " << z+1 << ". exam grade of the " << i << ". student: " ;             cin >> Students[i].testResults[z];         }     } }  int main() {     getValue(); }  result:

I know that the compiler will sometimes initialize memory with certain patterns such as 0xCD and 0xDD.  What I want to know is when and why this happens.  When  Is this specific to the compiler used?  Do malloc/new and free/delete work in the same way with regard to this?  Is it platform specific?  Will it occur on other operating systems, such as Linux or VxWorks?  Why  My understanding is this only occurs in Win32 debug configuration, and it is used to detect memory overruns and to help the compiler catch exceptions.  Can you give any practical examples as to how this initialization is useful?  I remember reading something (maybe in Code Complete 2) saying that it is good to initialize memory to a known pattern when allocating it, and certain patterns will trigger interrupts in Win32 which will result in exceptions showing in the debugger.  How portable is this?


This is a minor grammar quibble with respect to the UI.   Is it possible to add some logic to the Network Profile page, on the accounts tab, that changes the label "answers" to the singular "answer", in the case of there only being one question or answer?        Admittedly this is a duplicate of the question . The answer to that question was that it will not be fixed. However, the logic already exists elsewhere on the site. The logic required is . Here, you can find words "1 Question" & "1 Answer".        In addition, Oded's  on his  to the question  suggests that it could quite easily be fixed now.

Under accounts tab of a user's profile, words questions and answers are used even when count is 1. For live example, you can go to my profile & click accounts tab. Scroll down to Drupal Answers row where you can find "1 answers" which should be "1 answer". Or, scroll down to Server Fault row to see both "1 questions" and "1 answers".


At first glance, it seems /usr/share/X11/xkb/keycodes/ contains the mapping of raw keycodes reported by the device, and 'showkey --scancodes` command can return the scancode. It's easy to think that they are the same thing.  But they are evidently different.showkeys -scancodes reliably returns the Linux Keycode, as in  converted to hex; while 'raw keycode' in xkb refer to are always different than the table.  Take the key 1 for example:   showkey --scancodes returns 0x02 as the keycode of 1 in xorg, the symblic name is <AE01>, which has 10 as its raw keycode, certainly not 0x02.  $ grep AE01 /usr/share/X11/xkb/keycodes/evdev  &ltAE01> = 10;   So, for the purpose of configuring xkb, how to find the raw keycode for any key, given that showkey --scancodes is not suitable?

I'm trying to use xmodmap to remap Alt / Super keys on Dell L100 keyboard, and have trouble getting the keycodes.  For instance, using xev doesn't give me keycode for Alt   FocusOut event, serial 36, synthetic NO, window 0x4a00001,     mode NotifyGrab, detail NotifyAncestor  FocusIn event, serial 36, synthetic NO, window 0x4a00001,     mode NotifyUngrab, detail NotifyAncestor  KeymapNotify event, serial 36, synthetic NO, window 0x0,     keys:  122 0   0   0   0   0   0   0   0   0   0   0   0   0   0   0               0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0      For Right Super key, xev and showkey give different keycodes -- 134 and 126 respectively.  What's going on with these keycodes?  I tried getting keycodes from showkey -k, and using xmodmap file below, but that gave a weird map which remapped b key:  clear Mod1 clear Control keycode 125 = Meta_L keycode 126 = Meta_R keycode 58 = Control_L keycode 56 = Control_L keycode 100 = Control_R add Control = Control_L Control_R add Mod1 = Meta_L Meta_R


Consider the problem of the choice of estimator of $\sigma^2$ based on a random sample of size $n$  from a $N(\mu,\sigma^2)$ distribution.   In undergraduate, we were always taught to use the sample variance  $$\hat{s}^2 = \dfrac{1}{n-1}\sum_{i=1}^{n}\left(X_{i}-\bar{X}\right)^{2}$$   instead of the maximum likelihood estimator  $$\hat{\sigma}^2 = \dfrac{1}{n}\sum_{i=1}^{n}\left(X_{i}-\bar{X}\right)^{2}.$$  This is because we learned that $\hat{s}^2$ is an unbiased estimator and that $\hat{\sigma}^2$ is biased.  However now I'm studying for a PhD and I've read that we choose estimators based on minimizing mean square error (=bias$^2$ + var).   that $$mse(\hat{\sigma}^2) < mse(\hat{s}^2 ).$$  So, why do most people use $\hat{s}^2$?

I am totally confused: On the one hand you can read all kinds of explanations why you have to divide by n-1 to get an unbiased estimator for the (unknown) population variance (degrees of freedom, not defined for sample size 1 etc.) - see e.g.  or .  On the other hand when it comes to variance estimation of a supposed normal distribution all of this doesn't seem to be true anymore. There it is said that the maximum likelihood estimator for variance includes only a division by n - see e.g. .  Now, can anyone please enlighten me why it is true here but not there? I mean normality is what most models boil down to (not least due to the ). So is the choice "division by n" yet the best choice for finding the best estimation for the true population variance after all?!?


Imagine a string "Hello World".  The regular expression for that is "Hello World".  In my regular expression class, I was told that a complement of a regular expression is a regular expression.  Say I want to check that a string doesn't contain Hello World. How do I do so?  I can do that for one character  [^a] for example will match anything that's not the letter a  How to do so for longer strings?  What's the equivalent of ^ for a string with length more than 1  Note: the other questions is not really a match.  In fact, one of the answer says that regular expression cannot really do this. Academically speaking academic regular expression CAN do this. It's complement.  I don't look for a look around. I look for complement.  For example. Say I am parsing html. Say I want to match the content of table. I want to match something between contentsome other table  Basically a pattern would be (not )  Now how would I do (not )?

I know it's possible to match a word and then reverse the matches using other tools (e.g. grep -v). However, is it possible to match lines that do not contain a specific word, e.g. hede, using a regular expression?   Input:  hoho hihi haha hede   Code:  grep "<Regex for 'doesn't contain hede'>" input   Desired output:  hoho hihi haha


I have to switch to Windows for the duration of a project.   I have only just started, and I already dislike using cmd.  Is there a shortcut for C:\Users\<current user>\Documents\ ?

I am used to using   cd ~   to get right into my home directory. In Windows command prompt I have to do  cd Users\username   to get there. Is there a shortcut like the Linux one? It would be nice if I could get there by doing  cd username   Is something like this possible in Windows Vista?


I've a
, in which I'm adding <input> and an  dynanically using jQuery.  Like this:
 is getting filled when addServicePanel() is called:  function addServicePanel() {     var wrapper = $(".main_wrapper"); //Fields wrapper     var add_button = $(".add_ele_button"); //Add button ID     var x = 1; //initlal text box count     $(add_button).click(function (e) { //on add input button click         e.preventDefault();         if (x < max_fields) { //max input box allowed             $(wrapper).append('

                                 Pipeline
                                     <input id="pipeline" name="pipeline" type="text"/>
                                     Add Board (+)

             '); //add input box         }     }); }   Function I've already written to work with .add_field_button:  function addSubPanel() {     var max_fields = 40; //maximum input boxes allowed     var wrapper = $(".input_fields_wrap"); //Fields wrapper     var add_button = $(".add_field_button"); //Add button ID      var x = 1; //initlal text box count     $(add_button).on("click", this, function (e) { //on add input button click         alert(" cliked"); // THIS IS NOT GETTING CALLED         e.preventDefault();     });  }   When I click on the  tag, I want a function to be called, which I've already written in my js file.  Issue I'm facing is that fucntion is not getting called when I click .  I think it is because on page load, the element is not rendered yet, so nothing is binded with that function.  How can I fix it?  Thanks

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


I am  making a class for graph, maybe i am not doing it the best way but the idea was to start for somewhere.  I have this class graph.h  template <class T> struct node {     int index;     T name;     vector<int> neighbours; };  struct lengths{     int node_1;     int node_2;     int length; };  template <class T> class graph : public vector<node<T>> {      public:         graph();       ... }   and graph.cpp  template <class T> graph<T>::graph(){     directed = false;     //flag for dir graph, default false     nodes = 0;               //number of nodes in the graph  }   and in main i have   graph<int> g;   but when i try to build it i get error  main.cpp undefined reference to `graph<char>::graph()'   I use GNU GCC Compiler [-std=c++14]

Quote from :     The only portable way of using templates at the moment is to implement them in header files by using inline functions.   Why is this?  (Clarification: header files are not the only portable solution. But they are the most convenient portable solution.)


My givens are  int random = 3; string xml = "<Numbers> <Num>1</Num> <Num>2</Num> <Num>3</Num> <Num>4</Num><Num>5</Num> </Numbers>";   I want to iterate through this string and find if random is a number between <Num></Num>. Is there a way of doing this in C# Visual Studio?

Is there a simple method of parsing XML files in C#? If so, what?


I have a brand new Nikon D5500.  The 55-200mm macro lens is not working properly as far as I can tell.  It was acting funny the other day when I was trying to take pictures. The pictures were coming out a little blurry. I tried to use it today and it is not capturing whatsoever. There is no image and everything is extremely blurry.  I tried putting on the 18-55mm lens and it took pictures just fine. I changed the battery just to make sure, but when I put the macro lens back on my camera I get nothing. I put it on auto, like I always use mostly. It makes a bunch of noise like it's trying to focus when I partially push down the button to take the picture. Could there be something wrong with the lens already?  I've only had this camera for less than two weeks. It was taking great pictures with both lenses previous to today. Am I missing something like a setting or whatever?

Probably a novice question, but how do I correctly diagnose from a photo for what reason that camera wasn't able to focus properly?  It can be any 1 of the following   Unsteady hand Lens issue Metering Re-Calibration required in camera or ...   Is there a set of unsaid protocols that needs to be followed by a photographer?  Goal is to get a sharp and crisp image prior to editing.  [PS: I own a Nikon D5200.]


I am working on a poster in Latex. I found that the integral sign (and also the summation sign) appears to be small. What could make this happen? I never see this in a regular article. I guess it must have something to do with the poster template. I'm using this template:

I am using the tikzposter package and am fairly happy with it except for one small thing: When I have an equation with a sum the sum becomes ridiculously small.    I have read the questions about  and am using amsmath. Putting \displaystyle in front of \sum doesn't change anything.   Does anyone have any idea how to get a "normal" sum symbol?  MWE:  \documentclass[25pt, a0paper, portrait]{tikzposter} \usepackage[utf8]{inputenc} \usepackage{graphicx} \usepackage[T1]{fontenc}  \usepackage{lmodern}  \usepackage{amsmath} \usepackage{amssymb}  \title{lalala}  \begin{document} \maketitle  \block{test}{   \begin{equation*}     \Psi = \displaystyle\sum^{n_{max}}_{n=1}C_n   \end{equation*} }   \end{document}


I have maven project with module A and module B which depends on module A. For example I have abstract unit test in module A and I want to use this unit test in unit tests for module B. Is there any way to achieve that?

How can you depend on test code from another module in Maven?    Example, I have 2 modules:   Base Main   I would like a test case in Main to extend a base test class in Base.  Is this possible?  Update: Found an , which involves creating a test jar.


Hello There I am playing  pokemon go But suddenly i can't Catch any pokemon   i am trying form 2 hrs   Even 10 cp pokemon run away   please help me

I can't do anything now. Can't catch Pokemon, can't get items. Does anyone have the same problem?


JRN Financial Solutions, i have been applying for Jobs online and got a random mail offering me a personal assistant role! Is it safe to go ahead with this?

Seems shady. Here is what has happened so far:  Job offer in newspaper: personal assistant, 10-15 hours per week, $500 per week.  I took the job. Didn't have to fill out any W-2 forms or anything.  Gave them my name, email, and mailing address.  Received a check for ~$1900. Had a note to keep $250 of it, and send the rest to another person via Walmart. I did that.   Now I'm thinking this seems very weird and I'll probably let him know I don't feel comfortable with this and just bail out. What does this look like to you guys?


This is my first time using Linux so I'm still new to all this. I have forgotten my admin password, and I've tried opening the grub menu after a reboot, but it doesn't open even after holding down the left shift key. So I think I have the grub bug, but I can't install the fix b/c of not remembering my admin password...so I find myself stuck.... if anyone has any information about this it would be greatly appreciated.

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


Hi I would like to teach my students about false conjectures and computer approaches to them. I need references and/or direct examples of statements of the form $(\forall n \geq n_0)P (n)$ where $P$ is a relatively simple property (e.g. of elementary number theory) such that the smallest number $m$ for which $P (m) $ is false is ridiculously bigger than $n_0$.

I just came back from my Number Theory course, and during the lecture there was mention of the Collatz Conjecture.  I'm sure that everyone here is familiar with it; it describes an operation on a natural number – $n/2$ if it is even, $3n+1$ if it is odd.  The conjecture states that if this operation is repeated, all numbers will eventually wind up at $1$ (or rather, in an infinite loop of $1-4-2-1-4-2-1$).  I fired up Python and ran a quick test on this for all numbers up to $5.76 \times 10^{18}$ (using the powers of cloud computing and dynamic programming magic).  Which is millions of millions of millions. And all of them eventually ended up at $1$.  Surely I am close to testing every natural number? How many natural numbers could there be?  Surely not much more than millions of millions of millions. (I kid.)  I explained this to my friend, who told me, "Why would numbers suddenly get different at a certain point?  Wouldn't they all be expected to behave the same?"  To which I said, "No, you are wrong!  In fact, I am sure there are many conjectures which have been disproved by counterexamples that are extremely large!"  And he said, "It is my conjecture that there are none! (and if any, they are rare)".  Please help me, smart math people.  Can you provide a counterexample to his conjecture?  Perhaps, more convincingly, several?  I've only managed to find one! (Polya's conjecture). One, out of the many thousands (I presume) of conjectures. It's also one that is hard to explain the finer points to the layman. Are there any more famous or accessible examples?


I'm new to blender 2.8. I have used Blender 2.78 in the past and had some good tutorials bookmarked but I'm having no luck finding good tutorials for 2.8. Danged near ever tutorial I find is made by someone who rattles on too fast, uses too many key board short cuts and fails to cover key steps. I've made some objects, I need to UV unwrap them, texture them (like glass), then set up a light scene and view them. I am making items for Skyrim SSE. I remember a tutorial series by a woman for 2.78, and she was very thorough, and actually showed HOW to do these things. Does anyone know of a good channel?

Since asking for tutorials, videos, resources, links to other content or downloads is considered off topic here, this is a specifically created Community Wiki which gathers resources for Blender and it has been approved by the .  Just write in the appropriate answer/section. If you have concerns, questions, post a  question, so we don't clutter the comments, but you can link your meta question from the comments.  Questions regarding such resources are not allowed anymore, except for very specific and on topic requests (ask on  if you're unsure about your question). Follow the instructions made in the question about how to post, what can be posted, etc.  Learning             Assets    (also see: )   Reference Images/Blueprints (also see: )    Tools    (also see: )      Other   Special Interest ()     Also see the .


Here's something I realized recently. If your post has a certain error (eg: duplicate title) and you click the post button, Stack Overflow detects it as a submission.   This means scrolling back up and fixing the title and then pressing the submit again will display the error you can only submit once every 90 minutes.  I have not tried this out in other sites on the SE.  Update: After trying several times repeatedly, I was able to post it after 10 mins from the original time.

I noticed that I can only perform certain actions such as commenting a finite number of times in a given period of time. Obviously, rate limiting is in place to prevent accidental misuse or intentional abuse of certain features.  Where else is rate limiting applied on Stack Exchange sites, and what are the limits?


I'm using the Minim 2.2.0 library with JAVA.  The library requires us to define a helper class defining two methods and pass an object of this class to the Minim constructor. I wrote the MinimHelper class as follows.  public class MinimHelper {     String sketchPath( String fileName ) {         return "C:\\Users\\Martin\\Downloads\\"+fileName;     }      InputStream createInput(String fileName) {         InputStream is = null;         try{             is = new FileInputStream(sketchPath(fileName));         }         catch(Exception e){             System.out.println(e.toString());         }         return is;     } }   And I wrote my main as follows  public class Main {     public static void main(String[] args) {         // TODO Auto-generated method stub         AudioPlayer player;         Minim minim = new Minim (new MinimHelper());         player = minim.loadFile("Butterfly.mp3");         player.play();     } }   However, I'm getting the following error in the console.  ==== JavaSound Minim Error ==== ==== Couldn't find a sketchPath method on the file loading object provided! ==== File recording will be disabled.  ==== JavaSound Minim Error ==== ==== Couldn't find a createInput method in the file loading object provided! ==== File loading will be disabled.  ==== JavaSound Minim Error ==== ==== Error invoking createInput on the file loader object: null  Exception in thread "main" java.lang.NullPointerException     at ddf.minim.javasound.JSMinim.getAudioRecordingStream(Unknown Source)     at ddf.minim.Minim.loadFile(Unknown Source)     at ddf.minim.Minim.loadFile(Unknown Source)     at Main.main(Main.java:9)   Please tell me where I'm doing wrong.

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?


When i am rendering my scene in 1920×1080 at 100℅, and with a sample value of 500, I am getting a low qulality image which got rendered in just 8 seconds. How can I fix this!

Can someone help me determine why my render is coming out in such low quality? I have Cycles up to 500 Render Samples, but I have no idea why it looks like it's only using one.


I meet this situation sporadically (example , ). Although I'm sure that they do receive notifications of my reply, I think they just decide to ignore it. Or simply they are overwhelming with the notification or don't know how to answer my comment.   What are my options in this case?   Open a new related question?  Ping them in the comment to get their attention back? It works sometimes (like , I deleted the ping comment when they get back), but I feel it's like an help vampire. Make a slight edit or bounty? Sometimes it seems that the answerer is the only one who can answer or interest the topic. If they don't get back, no one will get back.

Possible Duplicates:                This question might not be allowed but I am going to try...   I have noticed that asking a question during certain times of the day will elicit much fewer responses then questions asked at peak hours of the day. If I have a question that didn't get much traffic, I didn't get an answer I was looking for, and now is getting towards the bottom of the "Stack" so few people are looking at it, how can I get more traffic to my question? Is there a good way other than offering a bounty? I shouldn't have to sacrifice my points should I?


Out of curiosity, I'm just asking if a moderator is global or site-based. In other words, will a moderator only moderate a specific site or moderate all SE sites? And is there any privileges for moderators (e.g. Gain lots of reputation instantly)?

Some people have a diamond after their username (e.g. )    What special privileges do diamond moderators have? How can I become a diamond moderator? Who are the diamond moderators?  How many are there?      For more information, see  in the .     Note: not to confuse with certain Stack Exchange employees, for example  members or "community managers", who often have diamonds as well, but are not ordinary moderators.


I tried removing the '.' directory. I thought I could just delete my working directory without having to go into a parent directory.  The point of my question is to look for some insight into how the linux system works to delete files.

I've seen many explanations for why the link count for an empty directory in Unix based OSes is 2 instead of 1. They all say that it's because of the '.' directory, which every directory has pointing back to itself. I understand why having some concept of '.' is useful for specifying relative paths, but what is gained by implementing it at the filesystem level? Why not just have shells or the system calls that take paths know how to interpret it?  That '..' is a real link makes much more sense to me -- the filesystem needs to store a pointer back to the parent directory in order to navigate to it. But I don't see why '.' being a real link is necessary. It also seems like it leads to an ugly special case in the implementation -- you would think you could only free the space used by inodes that have a link count less than 1, but if they're directories, you actually need to check for a link count less than 2. Why the inconsistency?


There are some business category e.g. Travel Agency, Hotel, Car Rental etc. Roles:   Management rolesSuper Admin, Staff Customer side roles are Owner, admin and sales counter May be etc. customer side roles will be added   Status i.e. On-Hold, Active, In-Active, Blocked, Deleted etc. Scenario:   Each user in the database has its role and status with other credentials Super Admin or Staff creates a customer (USER) with category e.g. "Travel Agency" and provide owner details Now this Travel Agency (USER) has its own SUB_USERS that may be one or many  Now I am confused between user and sub users.  The work that I done so far is as following in shape of ERD:  Please put me on the right path as to how can I create a USER with its SUB USERS? Thanks in anticipation

B2B Scenario I am trying is that:  The following Roles exists in the system:  Super Admin Super Admin Staff Owner (client) Admin (owner i.e. client and creates admin to define sales counters) Sales Counters  That means there are users who'll create their own sub users e.g.  [FLAG-A] ROLE "SUPER ADMIN" creates a ROLE "Owner" and "OWNER" creates its own sub users ROLES i.e. "ADMN" & "SALES COUNTER". Each role obviously has its info to login to the system I tried to design database as following:  In this diagram I am assuming that main user creates sub user that in my view many to many relationship so I have to add table between them as "USER_PERSON". Problem is to set "WHO CREATED USER" in the system. I mean which user has created sub user as described in [FLAG-A]  Please check this diagram


I know this is easy to lots of you but I am just struggling to find the solution.  How can I prove the sum of the highlighted angles in the following 3 times 3 square grid is equal to $\pi$?

Playing around on wolframalpha shows $\tan^{-1}(1)+\tan^{-1}(2)+\tan^{-1}(3)=\pi$. I know $\tan^{-1}(1)=\pi/4$, but how could you compute that $\tan^{-1}(2)+\tan^{-1}(3)=\frac{3}{4}\pi$ to get this result?


public function  booking() {                         $this->load->helper(array('form'));                         $this->load->library(array('session','email'));                         $this->load->helper('string');                         //$nwdb['wen_memid']        = $wen_memid                ='W'.random_string('alnum',3).'E'.random_string('alnum',3).'N';                      $name      = $this->input->post('name');                      $phone     = $this->input->post('phone');                      $email         = $this->input->post('email');                      $date  = $this->input->post('date');                      $message   = $this->input->post('message');                                               $config['protocol'] = 'sendmail';                         $config['mailpath'] = '/usr/sbin/sendmail';                         $config['charset'] = 'iso-8859-1';                         $config['wordwrap'] = TRUE;                         $config['mailtype'] = 'html';                          $this->email->initialize($config);                         $this->email->from('mail@gmail.com');                         $this->email->to('mail@gmail.com');                                              $this->email->subject('Appoinment Booking');                         $this->email->message('
Contact Us

                                      Name: 	 '.$name.'

                                       Phone: 	 '.$phone.'
                                       Email: 	 '.$email.'

Date :	    '.$date.'

Message:    	'.$message.'

                                                           ');                                                                                if ($this->email->send())                         {                             redirect('/welcome/bookonline');                         }                         else                         {                             //error                             $this->session->set_flashdata('msg','
There is error in sending mail! Please try again later
');                             redirect('/');                         }                                                  }  The above is my controller welcome code. welcome/booking is controller name. The form contain "name, email, date, contact number and message" section on it. i want to get the mail to the inbox section.i dont use smtp for this. But here, Every mail is sending to the spam mail. please help me as soon as possible.

This is a tricky one and I've always relied on techniques, such as permission-based emails (i.e. only sending to people you have permission to send to) and not using blatantly spamish terminology.  Of late, some of the emails I send out programmatically have started being shuffled into people's spam folder automatically and I'm wondering what I can do about it.  This is despite the fact that these particular emails are not ones that humans would mark as spam, specifically, they are emails that contain license keys that people have paid good money for, so I don't think they're going to consider them spam  I figure this is a big topic in which I am essentially an ignorant simpleton.


I am writing to search function. My Db field as string (Nvarchar(MAX)) and this field have string and number   DB DATAS    EF ORDER          I want to a 1          a 1                a 1 a 20         a 12               a 2 a 2          a 2                a 12 a 12         a 20               a 20 a 25         a 25               a 25 b 1          b 1                b 1 b 5          b 5                b 5 ....         ...                ....

Anyone have a good resource or provide a sample of a natural order sort in C# for an FileInfo array?  I am implementing the IComparer interface in my sorts.


I am using panasonic 25mm 1.7 lens in olympus omd-em10 ii body. Neither of them have a uv coating. Will it hurt lens/processor health if I use it without filter?

Is it still required/highly recommended that I buy a UV or similar filter to 'protect' the front element of my lens?  I ask because this advice has  been around for 30 years and you would think that the lens maker would have solved this problem with a built-in protection or something like that. It's good to check these old assumptions from time to time.


What is the difference between generating functions and exponential generating functions?   I mean, we can solve a combinatorics sum by using just simple generating functions.   Or simply, for which parts in combinatorics do we use simple generating functions and in which parts we use exponential generating functions?

I've been introduced in my last lectures. And for the following problem:     Having 3 different types of books $a,b,c$ in how many ways can we take four different books putting them in a shelf such that the book $a$ can only be taken at most $1$ time, $b$ can be taken at most $3$ times and $c$ can only be taken at most $2$ times?   The ordinary generating function for this problem is:  $\quad \quad \quad \quad \quad \quad \quad $  Looking at the exponential generating function of the same problem, the only part of interest is the coefficient of $x^4$, which is:  $$\left(\frac{ab^3}{1!3!}+\frac{b^3c}{3!1!}+\frac{ab^2c}{1!2!1!}+\frac{b^2c^2}{2!2!}+\frac{abc^2}{1!1!2!}\right)$$ And then multiply it by $4!/4!$. But why do I need an exponential generating function? Isn't only needed to take the coefficient of $x^4$, divide each term of it by $a_1!a_2!\dots a_n!$ with $a_n=\text{power of a,b,c,}\dots$ and then multiply it by $4!4!$? It's not clear why such complication is needed.  By complication I mean to expand that generating function with the factorials, I could expand the ordinary generating function and then artificially add the factorials.


I am looking for a biblioraphy style that adds to the type webpage from BibDesk the attribute Last accessed.  Is there an out of the box citation style doing this? If not, how can I add it to a citation style? Currently I am using \bibliographystyle{agsm} which only includes the URL, but no Last accessed attribute. I get      Warning--entry type for ... isn't style-file defined of file ref.bib

I would like to change the URL output from:  URL: the html link  into:  [Online]URL: [Accessed on]  I am using:  \usepackage[comma]{natbib} \bibliographystyle{agsm}


I have a Lenovo ThinkPad E460 and one HDMI out. How can I extend desktop to two external monitors? Extend desktop meaning different content. I'm not really sure how to do it.  Since there are lot of old answers available, maybe considering using displayport and linking multiple Dell monitors could be an option, and if I am able to get HDMI > DP running (without expensive docking stations).

Equaling 3 Displays Total (or 2, if the laptop display cannot be used).  I work at home on two large monitors, but at the office on a laptop with a single large monitor. Is it possible to attach two (or more?) external monitors to a laptop without having them clone each-others display?


What are the integers (or at least natural numbers)$x_1$ and $x_2$ which satisfy this equation: $3x_1 + 7x_2 = 1000$. And is there a name for such a problem?

I want to find a set of integer solutions of Diophantine equation: $ax + by = c$, and apparently $\gcd(a,b)|c$. Then by what formula can I use to find $x$ and $y$ ?   I tried to play around with it: $x = (c - by)/a$, hence $a|(c - by)$.     $a$, $c$ and $b$ are known. So to obtain integer solution for $a$, then $c - by = ak$, and I lost from here, because $y = (c - ak)/b$. I kept repeating this routine and could not find a way to get rid of it? Any hint?  Thanks, Chan


I am attempting to make a template for holographic effects in blender for a project I'm working on, however I'm not sure how to create a lighting effect for the projection of the hologram (The god rays and volumetric effect around the globe). Below I have included the blender file along with an example of the type of effect I'm looking to reproduce. Any help would be appreciated.      Edit  With some minor tweaks and modifications I was able to make an effect that looked pretty much exactly as I wanted. Thanks to PGmath, Shady Puck and everyone else for the helpful suggestions and tips.  Final Result:

Is it possible to create a holographic lighting in cycles? This is possible In the Blender Internal render engine, but I'm not going for linking lamps. Here is what I mean (the light that is holding the sphere inside it) -


I asked  how to make cd protect spaces. Tab completion is great, but sometimes you paste the path from the clipboard so this is useful.  The solution breaks with parentheses however. No matter how you try to escape and protect the input it always returns:  bash: syntax error near unexpected token `('   Is there some way to have it also deal with parentheses? What I want is that when I enter this, it works:  cd My path with spaces (and parentheses)

I want to enter the following folder in the terminal:  Milano, Torino (Jan)-Compressed   How should I write the command cd to enter this directory?  Spaces and several other special characters like \, *, ), ( and ? cause problems when I try to use them in the command line or scripts, e.g.:    $ cd space dir bash: cd: space: No such file or directory  $ cat space file cat: space: No such file or directory cat: file: No such file or directory  $ cat ( bash: syntax error near unexpected token `newline'  $ echo content >\ > ^C  $ ls ? (  )  *  ?  \   How do I enter file or directory names that contain special characters in the terminal in general?


One of the characters of the Dota2 that Is called  has an interesting material effect If you look In below gif at the body and feet you can see this effect.It looks like .I like to know how can I make something like this In blender:    I downloaded the  and tried to Implement it but I couldn't do it.    After reviewing the textures , I found a texture as specular wrap It seems that this texture has been used for this effect.I used this texture as specular but not work , I think special shader used to make this effect.

Is it possible to create an  shader in Cycles? Specifically for something like , , , etc..


How would I change the ownership of a recently made file to root user ownership from its original owner? Every time I type in the following (below), I get a message saying that  it can't change the ownership.   For Example:  touch myfile chown root myfile

I would like the user to have full rights on this folder (as well as all sub-directories and files in it):  ~/.blabla   currently owned by root.  I have found numerous posts (in this forum and elsewhere) on how to do this for files but I can't find a way to do it for whole folders.


I'm a beginner photographer and I want to try take a picture of my friend dancing in the rain. I own a canon sx60 but unsure of what settings and accessories I need to pull it off.

What are recommended settings for my Nikon Coolpix P1 to best portray rain?  Here's what I got. No retouching was applied.   The picture I took when the rain was heavy with the automatic settings:  The picture I took with the "Sports" program; by then, however, the rain was not as hard. Ugh, ugly gray strip at the bottom, that was the flat surface I put my camera on to get a stable picture.   My main problem is that the actual rain and hailstorm is very hard to see in the picture. The overall effect is, instead, of fog.    Follow-up from the thread, courtesy of more rain, now with less hailstorm and more thunder.  The feedback amounted to flash and faster shutter. I took a few photos and I'm having some trouble to reconstruct what I did to get each result. Two representative results:   Fast shutter, with some guest starring:I'm talking about that horrible building obviously. Faster shutter and flash:Kinda difficult to say those pictures were taken sixty seconds of each other. :)   I'm not sure, however, that either of this is really an improvement of the original results.


I'm currently ubuntu 20.04 and I want to delete it completely and install Windows 7. How do i do that?

I have absolutely no experience with Linux, and I desperately need to get my computer back up and running again with Windows.  How do I remove Ubuntu and reinstall Windows?    Editor's note: many of the answers are about removing Ubuntu from dual-boot but keeping Windows (which is a bit complicated), while other answers are about removing Ubuntu from single-boot (which is easy: basically just format the disk while installing Windows). The question as written is ambiguous between dual-boot or single-boot.


i'm using ubuntu 14.10 utopic beta 2 (waiting for the officiel release) i've two partitions (FAT32) where i save my documents.. i would like to make those two partitions starts with boot.more clearly, to mount them when the system start... i hope my question was clear. Thanks !

I 've unmounted a disk /dev/vdc1 on my machine, after I format it into xfs file system, I didn't mount it again, either didn't add the adequate line to fstab file.  Now when i want to mount this partition, but I can't access to it: mount: can't find dev/vdc1 in /etc/fstab or /etc/mtab.  So how should I put in fstab file so the system recognizes it again ? the partition was mounted on /Data


I have the following code:  DECLARE @Latest TABLE (     DomainId bigint,      [date] datetime2 )  DECLARE @Rows int DECLARE @History int  INSERT INTO @Latest (DomainId, date) SELECT DomainId, MAX(Date) FROm DomainDetailDataHistory GROUP BY DomainId  SELECT @Rows = COUNT(DomainId) FROM @Latest  SET @History = @Rows * 5  SELECT DISTINCT TOP(@History)    c.DomainId   , c.[Date]   , Passed  FROM DomainDetailDataHistory c JOIN  @Latest h ON h.DomainId = c.DomainId WHERE c.[Date] != h.[Date] ORDER BY c.Date DESC   This code gets me the latest inserted row given by Id and the last 5 insertions.   Problem:   This works all good when I have 5 insertions of every unique DomainId.  I tried adding a new one and since the new one did not have any prior insertions the code gave me the top 7 insertions to compensate for the extra domain.   Clarity:  @History gives me how many different domains I have. I multiply this by 5 to get 5 of each.   Problem is when one of the domains do not have 5 insertions, lets say it only has one then I get more than the top 5 of the other domains.  How do I make sure that I always only get 5 of each and NOT MORE?

I often need to select a number of rows from each group in a result set.  For example, I might want to list the 'n' highest or lowest recent order values per customer.  In more complex cases, the number of rows to list might vary per group (defined by an attribute of the grouping/parent record). This part is definitely optional/for extra credit and not intended to dissuade people from answering.  What are the main options for solving these types of problems in SQL Server 2005 and later? What are the main advantages and disadvantages of each method?  AdventureWorks examples (for clarity, optional)   List the five most recent recent transaction dates and IDs from the TransactionHistory table, for each product that starts with a letter from M to R inclusive. Same again, but with n history lines per product, where n is five times the DaysToManufacture Product attribute. Same, for the special case where exactly one history line per product is required (the single most recent entry by TransactionDate, tie-break on TransactionID.


What package should I use to draw these circuits?   Is it circuitikz?

What are some ways to draw electric circuits in TeX systems?  I'm making this community wiki since I haven't found a question related to this.  I was thinking along the lines of . What do you think of that? Other examples are more than welcome, of course.


I was solving the problem from linear algebra and was able to complete it almost but I have the last step which I cannot solve by myself but I have spent like 3-4 hours trying to crack it.   Suppose $V$ is a finite dimensional vector space and $T:V\to V$ is a linear operator such that it has the following matrix in some basis: $$\begin{bmatrix} 0 & 1 & 0 &\cdots & 0 \\ 0 & 0 & 1 & \cdots & 0 \\ \vdots & \ddots & \vdots \\ 0 & 0 & 0 & \cdots & 1 \\ a_0 & a_1 & a_2 & \cdots & a_{n-1}  \end{bmatrix}$$  Show that characteristic polynomial  of this operator is the same as the minimal polynomial. Find the characteristic polynomial.  My approach: I was able to find the characteristic polynomial which is $$P(t)=(-1)^n(t^n-a_{n-1}t^{n-1}-\dots-a_2t^2-a_1t-a_0).$$  But I don't know how to show that minimal polynomial coincides with characteristic polynomial. Moreover, I think that the converse of this problem is also true.  Would be very thankful if you can show the solution. Please avoid using Jordan canonical form and Rational canonical form and other difficult topics since this problem is before those topics and the solution should be not so difficult.

of a monic polynomial $f \in \mathbb F\left[x\right]$ in $1$ variable $x$ over a field $\mathbb F$ plays an important role in understanding the structure of finite dimensional $\mathbb F[x]$-modules.  It is an important fact that the characteristic polynomial and the minimal polynomial of $C(f)$ are both equal to $f$. This can be seen quite easily by induction on the degree of $f$.  Does anyone know a different proof of this fact? I would love to see a graph theoretic proof or a non inductive algebraic proof, but I would be happy with anything that makes it seem like more than a coincidence!


[...] tonnes of rubbish are being accumulated and the lack of space for (IT/THEM) is becoming a complex problem.    Should it be IT or THEM? And why?

I've always said "$100 were taken" not "$100 was taken" because I thought $100 is plural. Could you explain why "was" not "were"? Any other helpful notes about the issue would be appreciated.     Nearly £20 was taken from my bank account


Not a duplicate since the linked question does not answer this question: A measure of similarity should be maximal for instances which are the same (e.g. similarity between (1,1) and (1,1) should be higher than the similarity between (1, 1) and (1, 2) ). This is not the case. Therefore the dot product is not a measure of similarity. Where am I wrong?  All explanations of the kernel trick I read take for granted that the dot product is a good measure of similarity for instances. I know that the dot product is zero if the vectors are orthogonal.  However, in this image, from my intuitive understanding $x_1$ and $x_3$ are quite similar, while $x_1$ and $x_2$ are very different. Yet, the dot product between $x_1$ and $x_2$ is large, and between $x_1$ and $x_3$ is smaller.  Take for example $x_1 = (1, 1)^T$, $x_2 = (20, 20)^T$, $x_3 = (1, 0.9)^T$. In what sense are $x_1$ and $x_2$ more similiar than $x_1$ and $x_3$? Why does the angle matter so much in practise?

I know how to CALCULATE dot product, but still don't understand MEANING of it.  I mean, If I have to explain vector addition I would say that "Sum of two vectors give you the third vector that has the same effect as other two combined"  But I don't know how to explain dot product. For example we have two vectors: v=(3,1) and w=(2,4). Dot product of these two is 3*2 + 1*4 = 10. What does this result (10) tell us?


I am fairly new to electronics, and whilst messing around with a simple LED circuit on my breadboard I noticed that when connect my resistor and LED on two separate rows, the LED lights up as it expected. However when I connect them on the same row, the LED doesn't light up. I tired this other rows and checked all the connections to see if there was a problem. Can someone please explain to me why the LED doesn't light up when I try to connect everything up on the same row?

As an absolute layperson in electronics I just found out that an LED only lights up when connected like in figure 1 but not when connected like in figure 2. And I just don't get why?  I know an LED is a diode and current can only move through it in one direction, but that's the case in both constructions. I don't see a difference in both constructions.  So why does it obviously make a difference?  figure 1 (battery not depicted):  figure 2 (battery not depicted):


I downloaded Catalina but it broke critical applications on my computer, I need to restore it to El Capitan as it was before, can I do it safely with a bootable USB?  Thank you

I have downloaded the El Capitan dmg file (InstallMacOSX.dmg) provided by Apple. The expanded dmg image contains the package "InstallMacOSX.pkg" which should be run to create the El Capitan installer but fails with the following message "This version of OS X 10.11 cannot be installed on this computer." presumably because quite reasonably it would not make sense to install on top of a later version of the OS. However in this case I want to create a boot USB drive for an installation on another Mac.  I am stuck in a chicken and egg situation where I need another machine running El Capitan or earlier to create and El Capitan boot installer.


I installed Java using the terminal and I also installed Java using Wine to try and run a windows App and well didn't work so now I want to remove all Java 100%. How do I go about doing so?  java version "1.7.0_25"

How can I completely remove all traces of Java on my system?   I already know  in case I need it again.


Can this be done using 1 SOQL Query?  I came up with the following:  SELECT Id, Name FROM Profile WHERE Id in     (SELECT Parent.ProfileId     FROM ObjectPermissions     WHERE SObjectType = 'Account'       AND (PermissionsCreate = true OR PermissionsEdit = true))   But this gives me an error:     The inner select field 'Parent.ProfileId' cannot have more than one level of relationships   This could probably be done in 2 queries, but it would be ideal for me to retrieve in a single result set otherwise I would have to write a script to combine results.

Since I couldn't think of how to write this query off the top of my head, I thought it might be worth sharing. How can I query which Profiles have Read permission on a specific object? I knew it would have something to do with ObjectPermissions and PermissionSet, but had to look up the documentation for both to piece it together.


Suppose the $R^2$ value of $x_1$ with $y$ is equal to $0.15$. The $R^2$ value of $x_2$ with $y$ is equal to $0.35$. Can there exist constants $a,b$ such that the variable $X=ax_1+bx_2$ has an $R^2>0.5$ with $y$? I'm thinking no, but I can't find anything on the subject online to verify this. I know in some cases this obviously wouldn't be possible (such as if the sum of the r-squared values of the input variables exceed 1). But can it ever be true? Is there a rule related to this subject?

A very basic question concerning the $R^2$ of OLS regressions   run OLS regression y ~ x1, we have an $R^2$, say 0.3 run OLS regression y ~ x2, we have another $R^2$, say 0.4 now we run a regression y ~ x1 + x2, what value can this regression's R squared be?   I think it's clear the $R^2$ for the multiple regression should be no less than 0.4, but is it possible for it to be more than 0.7?


Given $X_1, X_2,\ldots, X_n$ are i.i.d with $f(x) = \frac{1}{\pi}\frac{1}{1+x^2}$. Find the minimal sufficient statistic for $\frac{1}{\pi^{n}(\prod_{i=1}^{n} 1+(x_i-\theta)^2)}$.  My question: Using Bahadur's Factorization and Lehman-Scheffe's theorems, I obtain the sufficient statistic as $T(X) = (x_1, \ldots, x_n)$. However, the correct answer turned out to be $T(X) = (x_{(1)}, x_{(2)},\ldots, x_{(n)})$. But I cannot see why the first answer is incorrect, because if we are given the entire sample set, we could easily obtain the order statistic of that sample, so how could $T(X) = (x_1, \ldots, x_n)$ is wrong?

I'm trying to find the minimal sufficient statistics for a Cauchy distributed random sample $X_1,...,X_n$, here \begin{equation} f(x|\theta) = \frac{1}{\pi[1+(x-\theta)^2]} \end{equation} I begin by guessing that the order statistics are the minimal sufficient statistics (first of all, they are sufficient). Then I try to prove that \begin{equation} \frac{f(X|\theta)}{f(Y|\theta)} = \prod_{i=1}^n\frac{1+(y_i-\theta)^2}{1+(x_i-\theta)^2}=C \end{equation} Where $C$ is a constant of $\theta$, I want to prove that the above equation holds iff $T(X)=T(Y)$, where $T(X)$ is the order statistics of $X$.  I am really stuck and don't know how to show why that if it holds then $T(X)=T(Y)$, can anyone help me on this proof? Thanks in advance!  p.s., a similar thread  discusses the problem but offers no proof for the minimal sufficiency.


I am writing a program that does server management on remote systems. While I can run almost all commands using the:  $ chroot <directory> /bin/bash -c <command>   format and get the results back, starting and stopping the services or getting their status aren't possible because of the systemctl restrictions.   I have tried the options offered in these:    .    They're either long winding or not a simple solution like the one chroot /bin/bash -c offers.  I'm on a CentOS machine with systemctl 2.19 and there is no --shell option via machinectl. Is there a simple chroot <> /bin/bash like shortcut to run start/stop/restart the services running inside the chroot environment?  For e.g., OpenLDAP's solserver service runs inside the chroot. How do I get the output of systemctl status solserver from the host without logging into the container?

I have a systemd container running, and I can login into it with machinectl login <container>. How can I execute a command inside the container directly, i.e. without first logging in, executing the command, and then logging out?  Another way to put it is that I'm looking for the systemd equivalent of:   $ docker exec <container> <command>    or   $ ssh <host> <command>


Currently there is 1 known type of electric field, it has positive(positrons and protons) and negative(electrons) charges. I would expect the charges of alternate electric fields to act the same regarding attraction and repulsion. They could hypothetically have different electric permittivities and magnetic permeabilities though.  I'm wondering if it's possible that there are other kinds of electric fields with their very own charges in existence. If they did exist, they would be very hard to detect.  Because these charges would be electrically neutral from our electric field's perspective they would essentially act like neutrinos and pass through everything. They may be able to interact with our matter gravitationally. This might be the cause of unusual phenomena like dark matter and energy.  Is it possible, given our current understanding of physics, that these alter-charges could exist?

Upon reading my book on physics, it mentions that there are only two discovered types of electric charges. I wonder if there could be a third type of elusive charge, and what type of effects could it have upon matter or similarly?


I noticed that a folder with the name of a website I removed keeps appearing under /var/www. I checked and it is created by www-data. I suspect that it's something malicious.  How can I find out what causes this?

This is a  about Server Security - Responding to Breach Events (Hacking)   See Also:                  Canonical Version I suspect that one or more of my servers is compromised by a hacker, virus, or other mechanism:   What are my first steps? When I arrive on site should I disconnect the server, preserve "evidence", are there other initial considerations? How do I go about getting services back online? How do I prevent the same thing from happening immediately again? Are there best practices or methodologies for learning from this incident? If I wanted to put a Incident Response Plan together, where would I start? Should this be part of my Disaster Recovery or Business Continuity Planning?   Original Version       2011.01.02 - I'm on my way into work at 9.30 p.m. on a Sunday because our server has been compromised somehow and was resulting in a    attack on our provider. The servers access to the Internet   has been shut down which means over 5-600 of our clients sites are now   down. Now this could be an FTP hack, or some weakness in code   somewhere. I'm not sure till I get there.      How can I track this down quickly? We're in for a whole lot of   litigation if I don't get the server back up ASAP. Any help is   appreciated. We are running Open SUSE 11.0.            2011.01.03 - Thanks to everyone for your help. Luckily I WASN'T the only person responsible for this server, just the nearest. We managed   to resolve this problem, although it may not apply to many others in a   different situation. I'll detail what we did.      We unplugged the server from the net. It was performing (attempting to   perform) a Denial Of Service attack on another server in Indonesia,   and the guilty party was also based there.      We firstly tried to identify where on the server this was coming from,   considering we have over 500 sites on the server, we expected to be   moonlighting for some time. However, with SSH access still, we ran a   command to find all files edited or created in the time the attacks   started. Luckily, the offending file was created over the winter   holidays which meant that not many other files were created on the   server at that time.      We were then able to identify the offending file which was inside the   uploaded images folder within a  website.      After a short cigarette break we concluded that, due to the files   location, it must have been uploaded via a file upload facility that   was inadequetly secured. After some googling, we found that there was   a security vulnerability that allowed files to be uploaded, within the   ZenCart admin panel, for a picture for a record company. (The section   that it never really even used), posting this form just uploaded any   file, it did not check the extension of the file, and didn't even   check to see if the user was logged in.      This meant that any files could be uploaded, including a PHP file for   the attack. We secured the vulnerability with ZenCart on the infected   site, and removed the offending files.      The job was done, and I was home for 2 a.m.            The Moral   - Always apply security patches for ZenCart, or any other CMS system for that matter. As when security updates are released, the whole   world is made aware of the vulnerability.   - Always do backups, and backup your backups.   - Employ or arrange for someone that will be there in times like these. To prevent anyone from relying on a panicy post on Server   Fault.


How can I set the default terminal emulator? Preferably from the command line.  I am running Ubuntu 14.04.03, and Unity and Lubuntu desktops

How can I set the default terminal used in Unity?  I would like to use the Ctrl+Alt+T hotkey to start a non-default terminal. The default terminal is gnome-terminal.   Where can I change the default terminal value?


i have an array of card types that looks something like this  var cards = new Array();  cards [0] = {name: "VISA", length: "13,16", prefixes: "4", checkdigit: true}; cards [1] = {name: "VISA_DELTA/ELECTRON", length: "16", prefixes: "417500,4917,4913",     checkdigit: true};   however id like to be able to find the card type depending on the card number entered. e.g if they select their card type from a drop down list i.e visa, then the credit card number should start with 4 otherwise when they submit the form a message of some sort should be display saying this is (whatever card it is, please change card type). Any help would be appreciated.  the id for the card number text field is CardNumber. Im not sure what other info may be needed, i have a function called Validate which validates the rest of the form and a function call Calculate which does the luhn check.

I'm trying to figure out how to detect the type of credit card based purely on its number. Does anyone know of a definitive, reliable way to find this?


In reference to , I made a  on an answer. I then realized I was saying the same thing, so commented again. It's late, so I forgot to tag the other user. I went to edit my comment to add the @ tag, and it wouldn't take/save/show up. Whats the deal? Note the other user in question has a username of only three characters, and the comment tag system only looks at the first three characters. Could this be the reason?  Looking again, I notice that I had tried to tag the user in my first comment, which it appears to not be there. What gives?  Asking on meta, since I don't think this would be a site specific issue.

How do the comment replies (aka "pinging users") work?  Who can I send an @reply to? How do I respond to a specific user when entering my comment? Will they be notified? What do people mean when they talk about "pinging" another user?  Related:


I am being offered an iPad at a really good price but the seller says he can't remember his iCloud information so the tablet is locked. Is there a way to get this corrected?

I bought a used iPhone 4.  The previous owner re-set the phone, but did not remove the device from their iCloud.  It is asking me for their iCloud information when I try to set-up the phone.  I don't have contact with the previous owner anymore.  Is there a way to remove the device from their iCloud so I can use a new one?


So I have a 'for' statement that appends items onto the end of one list, but I only want a set amount of these items to be added to the list, before starting a new one. I thought the easiest way to do this would be to take the end list, and for every 7 items (the amount I need), create a new list (doesn't have to be in a variable) EG:  list1 = [1,2,3,4,5,6,7,1,2,3,4,5,6,7,1,2,3,4,5,6,7]   I want:  [1,2,3,4,5,6,7]     [1,2,3,4,5,6,7]     [1,2,3,4,5,6,7]       to be derived from this, anyone got any ideas?

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:


In a particular Bayesian problem, I have encountered a choice of parameters that leads to a uniform posterior distribution. Given prior \begin{equation}     p(\boldsymbol{\pi}) =Dirichlet(\boldsymbol{\alpha}), \quad \text{with}\ \boldsymbol{\alpha} = [0,\dots,0]. \end{equation} we consider a multinomial distribution whose support is $\{x_1, x_2, \dots, x_n\}$ and $\text{Pr}(X=x_i)=\pi_i(\sum_i\pi_i=1)$ \begin{equation}     \label{eq:likelihood}     p(X|\boldsymbol{\pi}) = \mathcal{M}ulti_{k}(n,\boldsymbol{\pi}), \end{equation} we find the posterior \begin{align*}     p(\boldsymbol{\pi}|X) &\propto p(X|\boldsymbol{\pi})p(\boldsymbol{\pi})\\     & \propto \prod_{i}\pi_i\prod_{i}\pi_{i}^{\alpha_i-1}\\     & \propto \prod_i\pi_i^{\alpha_i}. \end{align*} to be a uniform distribution \begin{equation}     p(\boldsymbol{\pi}|X) =Dirichlet(\boldsymbol{\alpha}), \quad \text{with}\ \boldsymbol{\alpha} = [1,\dots,1]. \end{equation} I was wondering if it is uniform, why is this called a posterior then? How can we have a posterior distribution that is a uniform distribution?

The Bayesian bootstrap was introduced by  as a Bayesian analog of the original bootstrap. Given dataset $X=\{x_1, \dots, x_N\}$, instead of drawing weights $\pi_{n}$ from the discrete set $\left\{0, \frac{1}{N}, \ldots, \frac{N}{N}\right\},$ the Bayesian approach treats the vector of weights $\pi$ as unknown parameters and derives a posterior distribution for $\pi$. Rubin (1981) used an improper, non-informative prior, $\prod_{i=1}^{n} \pi_{i}^{-1},$ which when combined with the multinomial likelihood, leads to a Dirichlet(1,...,1) distribution for the posterior distribution of $\pi$. In other words, our prior is \begin{equation}     p(\boldsymbol{\pi}) =Dirichlet(\boldsymbol{\alpha}), \quad \text{with}\ \boldsymbol{\alpha} = [0,\dots,0]. \end{equation} and posterior is \begin{equation}     p(\boldsymbol{\pi}|\boldsymbol{x}) =Dirichlet(\boldsymbol{\alpha}), \quad \text{with}\ \boldsymbol{\alpha} = [1,\dots,1]. \end{equation} Now my questions are:  I was asked the following questions which I was not able to answer: How can you have a posterior distribution that a/ does not depend on data and b/ is a uniform distribution?  Are both the prior and the posterior non-informative? I understand that the posterior is a uniform distribution, which is non-informative. Also, I see that the prior is referred to as non-informative prior. Does that mean it's flat?   I believe that section 5 in  addresses these questions, but I do not comprehend that discussion. Any clarification or pointing out what I may be misunderstanding would be appreciated.  EDIT: I just noticed one more issue when computing the posterior. Let $d=\left(d_{1}, \ldots, d_{K}\right)$ be the vector of all possible distinct values of $X$, and let $\pi=\left(\pi_{1}, \cdots, \pi_{K}\right)$ be the associated vector of probabilities $$ P\left(X=d_{i} \mid \pi\right)=\pi_{i}, \quad \sum \pi_{i}=1 $$ Let $x_{1}, \ldots, x_{n}$ be an i.i.d. sample from the equation above and let $n_{i}$ be the number of $x_{j}$ equal to $d_{i}$. If we use improper prior above over the sampling weights $\pi$, we can compute the posterior over $\pi$ \begin{align*}     p(\boldsymbol{\pi}|X) &\propto p(X|\boldsymbol{\pi})p(\boldsymbol{\pi})\\     & \propto \prod_{i}\pi_i^{n_i}\prod_{i}\pi_{i}^{\alpha_i-1}\\     & \propto \prod_{i}\pi_i^{n_i}\prod_{i}\pi_{i}^{-1}\\     & \propto \prod_i\pi_i^{n_i-1}. \end{align*} How does this yield a flat Dirichlet posterior? Are we assuming $n_i=1$ for $i=1,\dots,K$? In that case, is the vector of all possible observations $d=\left(d_{1}, \ldots, d_{K}\right)$ (the original sample that we resample from) our observation?


I was recently accepted by a university as a PhD student. During the whole process, my potential supervisor agreed to supervise me along with some of his colleagues as my co-supervisor. Although, I have been accepted as a PhD student by the university, but I didn't get the scholarship. I a mentally as well as financially prepared for the expenses. But now my supervisor is saying that I should decline the offer. I told him that I can manage my expenses, but in every mail he is giving me some other excuse for not accepting this offer. I am confused now as to what I should do. Since the graduate school has accepted me, now it's up to me whether I should accept or not. But I am not able to understand why my supervisor is not willing to take me. Any suggestions for what should I do now are highly appreciated. Thank You.

What should I opt for?   Option A) very well paid PhD, around €3000 per month at a respectable university or;  Option B) a non-paid PhD, where I have to pay €2000 per year at one of the top 10 universities of the world?  EDIT: Actually they are both UK universities, Option B  is ranked between the top 10 in the world in engineering and tech, and I do get a scholarship that pays 18000 pounds which covers the difference between international student tuition and EU tuition. In Option A, I will be doing research in a good university and will be working alongside giants in the industry.


I'm confused about the behaviour of dictionaries with global function. In the following examples, why does the first case print {'abc':123} but the second {'abc': 456}? I am using python 2.7.   first example:  def foo():   test_dict = {}   bar()  def bar():     test_dict['abc'] = 123   test_dict = {'abc':456} foo() print test_dict   second example:  test_dict = {'abc':456}  def foo():   test_dict = {}   test_dict['abc'] = 123 foo() print test_dict

What exactly are the Python scoping rules?  If I have some code:  code1 class Foo:    code2    def spam.....       code3       for code4..:        code5        x()   Where is x found?  Some possible choices include the list below:   In the enclosing source file In the class namespace In the function definition In the for loop index variable Inside the for loop   Also there is the context during execution, when the function spam is passed somewhere else. And maybe  pass a bit differently?  There must be a simple reference or algorithm somewhere.  It's a confusing world for intermediate Python programmers.


I'm kinda new to blender so don't know a lot, but I apply a material to my object I can't see it in material preview mode. It seems to just show a grey highlight. I've done some searching and my driver is up to date and I have the latest version of blender. I have a Radeon RX 560 graphics card. I just have no idea why I can't see my materials. Any help is appreciated thanks. This is what it looks like in material preview mode.

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?


I am from Denmark and my English teacher insists on 'they' being grammatically incorrect when it is used in a singular sense (their hand reached...) No matter what I tell her she is convinced it's incorrect. Are there any "official" rules regarding this matter?

Is it good English to say "They have just left", when talking about a single person (perhaps someone you don't know the gender of)?  (I am a native English speaker, I'm looking for the view held by lexicographers).


sudo dpkg -i code_1.20.0-1518023506_amd64.deb [sudo] password for wolfubuntu:  (Reading database ... 189470 files and directories currently installed.) Preparing to unpack code_1.20.0-1518023506_amd64.deb ... Unpacking code (1.20.0-1518023506) over (1.20.0-1518023506) ... dpkg: dependency problems prevent configuration of code:  code depends on libgconf-2-4; however:   Package libgconf-2-4 is not installed.  dpkg: error processing package code (--install):  dependency problems - leaving unconfigured Processing triggers for gnome-menus (3.13.3-6ubuntu5) ... Processing triggers for desktop-file-utils (0.23-1ubuntu3) ... Processing triggers for mime-support (3.60ubuntu1) ... Errors were encountered while processing:  code

The media is gushing about the snap package for Visual Studio Code, and how wonderful it is (apparently has a plug in that cures gout ;-). So I thought I'd give it a whirl. I dutifully typed:  $ sudo snap install --classic vscode error: cannot install "vscode": snap not found   Where the articles all too early? Has vscode not yet landed in snap?


I'm trying to make my .py files executable so I can run them using ./filename.py, but its not working for me.  What I did was adding the shebang #!/usr/bin python3 and used the command chmod +x filename.py. When I run ./filename.py then as normal user, I get the error message below   bash: ./filename.py: /usr/bin: bad interpreter: Permission denied   As superuser, it tells me this instead:  sudo: unable to execute ./filename.py: Permission denied   Opening the file the usual method (python3 filename.py) it works fine.  When I changed the shebang to #!/usr/bin/env python3 it tells me this:  /usr/bin/env: ‘python3\r’: No such file or directory

Trying to get casperjs running on Ubuntu 12.04. After installing it when I run I get:   09:20 $ ll /usr/local/bin/casperjs lrwxrwxrwx 1 root root 26 Nov  6 16:49 /usr/local/bin/casperjs -> /opt/casperjs/bin/casperjs  09:20 $ /usr/bin/env python --version Python 2.7.3  09:20 $ cat /opt/casperjs/bin/casperjs | head -4  #!/usr/bin/env python  import os import sys  09:20 $ casperjs : No such file or directory  09: 22 $ python Python 2.7.3 (default, Sep 26 2013, 20:03:06)  [GCC 4.6.3] on linux2   So Python is present and runnable, casperjs is pointing to the right place and it is a python script. But when I run it I get "No such file".   I can fix it by changing the first line of the casperjs python file from:    #!/usr/bin/env python   to:   #!/usr/bin/python   Result:   $ casperjs --version 1.1.0-DEV   I managed to fix it, but I'm wondering why it didn't work with #!/usr/bin/env python, since that seems to be a normal interpreter line. Do I have something configured wrong?   Here are the steps to get casperjs:   $ git clone git://github.com/n1k0/casperjs.git $ cd casperjs $ ln -sf `pwd`/bin/casperjs /usr/local/bin/casperjs $ casperjs : No such file or directory


I wanted to know can I install Java and other software on persistence Ubuntu (USB drive). How can we do that because when I tried sudo apt install default-jdk I got a msg related to dpkg and something that the drive is only read only,? Help plz

How do I install Java, including in my browser, so websites with Java work?


could someone explain why I get this weird result by executing following code?  '1.0.0.0'.split('.').map(parseInt);   Output:  [1, NaN, 0, 0]

From the :  [1,4,9].map(Math.sqrt)   will yield:  [1,2,3]   Why then does this:  ['1','2','3'].map(parseInt)   yield this:  [1, NaN, NaN]   I have tested in Firefox 3.0.1 and Chrome 0.3 and just as a disclaimer, I know this is not cross-browser functionality (no IE).  I found out that the following will accomplish the desired effect. However, it still doesn’t explain the errant behavior of parseInt.  ['1','2','3'].map(function(i){return +i;}) // returns [1,2,3]


I am running an Ubuntu virtual machine that has few sites installed on it. I think due to my error and wrong permissions a malicious code was uploaded on the server and the "worm" had root access for a while before I delete it. Now all looks fine apart of one thing, there is a process that gets started automatically called named and that process uses 100% of my CPU. I checked it in TOP and the path of the process is ./named -c named.conf which is relative to something not sure what. Second thing I tried was to get the PID and I checked /proc/[PID]/exe and it point to non-existent file in root: /root/named/named I presume because there is no file at this path it gives constant error and gets in some kind of loop.   Now I can stop the process which is fine but I can't find who or where is the process started. I am afraid there are still some files left behind that I didn't clear.   Can anyone help investigating this issue or give some tips on where to look for the malicious code or is there a way to block the process from starting completely on the server?

This is a  about Server Security - Responding to Breach Events (Hacking)   See Also:                  Canonical Version I suspect that one or more of my servers is compromised by a hacker, virus, or other mechanism:   What are my first steps? When I arrive on site should I disconnect the server, preserve "evidence", are there other initial considerations? How do I go about getting services back online? How do I prevent the same thing from happening immediately again? Are there best practices or methodologies for learning from this incident? If I wanted to put a Incident Response Plan together, where would I start? Should this be part of my Disaster Recovery or Business Continuity Planning?   Original Version       2011.01.02 - I'm on my way into work at 9.30 p.m. on a Sunday because our server has been compromised somehow and was resulting in a    attack on our provider. The servers access to the Internet   has been shut down which means over 5-600 of our clients sites are now   down. Now this could be an FTP hack, or some weakness in code   somewhere. I'm not sure till I get there.      How can I track this down quickly? We're in for a whole lot of   litigation if I don't get the server back up ASAP. Any help is   appreciated. We are running Open SUSE 11.0.            2011.01.03 - Thanks to everyone for your help. Luckily I WASN'T the only person responsible for this server, just the nearest. We managed   to resolve this problem, although it may not apply to many others in a   different situation. I'll detail what we did.      We unplugged the server from the net. It was performing (attempting to   perform) a Denial Of Service attack on another server in Indonesia,   and the guilty party was also based there.      We firstly tried to identify where on the server this was coming from,   considering we have over 500 sites on the server, we expected to be   moonlighting for some time. However, with SSH access still, we ran a   command to find all files edited or created in the time the attacks   started. Luckily, the offending file was created over the winter   holidays which meant that not many other files were created on the   server at that time.      We were then able to identify the offending file which was inside the   uploaded images folder within a  website.      After a short cigarette break we concluded that, due to the files   location, it must have been uploaded via a file upload facility that   was inadequetly secured. After some googling, we found that there was   a security vulnerability that allowed files to be uploaded, within the   ZenCart admin panel, for a picture for a record company. (The section   that it never really even used), posting this form just uploaded any   file, it did not check the extension of the file, and didn't even   check to see if the user was logged in.      This meant that any files could be uploaded, including a PHP file for   the attack. We secured the vulnerability with ZenCart on the infected   site, and removed the offending files.      The job was done, and I was home for 2 a.m.            The Moral   - Always apply security patches for ZenCart, or any other CMS system for that matter. As when security updates are released, the whole   world is made aware of the vulnerability.   - Always do backups, and backup your backups.   - Employ or arrange for someone that will be there in times like these. To prevent anyone from relying on a panicy post on Server   Fault.


This is a ridge regression problem. The following two problems are equivalent:  $(w_t, b_\lambda ) = argmin_{w,b}\{\sum_{i=1}^m (y_i-b-w^Tx_i)^2+\lambda w^Tw\} $  $(w_t, b_\lambda )= argmin_{w,b}\{\sum_{i=1}^m (y_i-b-w^T(x_i-\bar x))^2+\lambda w^Tw\} $  where:   $\bar x$ is the average of the input data.  $\lambda$ defines a trade-off between the error on the data and the norm of the vector $w$ (degree of regularization) I'm assuming $b$ is a bias term   I can't work out why, mathematically, centering the data, has no effect.   Not looking for the answer, just a push in the right direction. Intuitively, I understand that offsetting each data point will have no effect on the final $w$ vector, because the relationships between the data points remains unchanged. Showing this mathematically, however, I'm unsure.

Why is using centered or uncentered data equivalent in ridge regression? In other words, given two ridge regression problems: \begin{equation} (b',c')=\operatorname*{argmin}_{b,c}\Big[ { \sum_i^{m} (y_i - c - b^Tx_i)^2 + \lambda b^Tb}\Big] \end{equation}  $$(b'',c'')=\operatorname*{argmin}_{b,c} \Big[{ \sum_i^{m} (y_i - c - b^T(x_i - \bar{x}))^2 + \lambda b^Tb} \Big]$$ where $\bar{x}$ is the mean of the input data, why does $(b',c')$ correspond to $(b'',c'')$?  I'm writing a piece of code where this thing holds numerically, I was wondering what is the mathematical explanation.


I have what is essentially a glass dome modeled with internal and external faces, but Diffuse materials under it always turn nearly black no matter how smooth or what color the glass is.  To demonstrate, I put a white Diffuse cube under the dome, and you can see how it looks almost completely black. The materials are all really simple with no extra nodes.

My model has a clear plastic (or glass) dome with objects inside.  The objects appear dark.  I've tried the glass shader with color 100% RGB, with very small IOR, and using just a refraction shader.    I know Cycles has problems with caustics, but I just want broad illumination to fall clean through the glass.  The light-to-column path can ignore refraction, but is blocked or tremendously attenuated. The camera-column path needs refraction, and seems to work fine anyway.  This demo image offers all optical paths of interest:   light upon object, seen directly light upon object, seen through glass (looks okay) light through glass onto object, seen directly. This is the shadow on the lit side of the column just below the glass tubing.  I expect full illumination, but there is shadow.  There is some light, but it's diffuse light from the floor. light through glass onto object, seen through glass. This     I did at one point try non-progressive rendering, and find extremely coarse light where there shouldn't be shadow, but this is not a practical way to make nice images. I've even tried cranking up certain sampling settings to many thousands, but still get bad noise though less, at the cost of long render times. I  would like to finish my creations sometime before "Star Trek, the Generation After the Next" becomes real life, if you know what I mean.  The next image is an example. I think Transmission in Sampling was 5000, but not sure.    I'm using Cycles in Blender 2.67 on a quad core Linux machine, 16GB RAM. Machine limits have never been a problem for 3D rendering.  Possibly, I screwed up some setting when I made my startup file, and just need to fix it. OTOH maybe this is just a limitation of path tracing, or of the way Cycles does it. If that's the case, what to real-world Blender artists do when they need to produce images on a budget and schedule?  What is the practical real-world fix?


I want to open a form inside a panel by clicking btnPlaceOrder which is on the same panel  private void btnPlaceOrder_Click(object sender, EventArgs e)     {         frmDashboard.PanelDesktop.Controls.Clear();         frmPlaceOrder formPlaceOrder = new frmPlaceOrder();         formPlaceOrder.TopLevel = false;         frmDashboard.PanelDesktop.Controls.Add(formPlaceOrder);         formPlaceOrder.FormBorderStyle = System.Windows.Forms.FormBorderStyle.None;         formPlaceOrder.Dock = DockStyle.Fill;         formPlaceOrder.Show();     }  error im getting:  Error CS0120  An object reference is required for the non-static field, method, or property 'frmDashboard.PanelDesktop'   projectRMS  E:\projectRMS\projectRMS\frmOrders.cs   28  Active

Consider:  namespace WindowsApplication1 {     public partial class Form1 : Form     {         public Form1()         {             InitializeComponent();         }          private void button1_Click(object sender, EventArgs e)         {             //int[] val = { 0, 0};             int val;             if (textBox1.Text == "")             {                 MessageBox.Show("Input any no");             }             else             {                 val = Convert.ToInt32(textBox1.Text);                 Thread ot1 = new Thread(new ParameterizedThreadStart(SumData));                 ot1.Start(val);             }         }          private static void ReadData(object state)         {             System.Windows.Forms.Application.Run();         }          void setTextboxText(int result)         {             if (this.InvokeRequired)             {                 this.Invoke(new IntDelegate(SetTextboxTextSafe), new object[] { result });             }             else             {                 SetTextboxTextSafe(result);             }         }          void SetTextboxTextSafe(int result)         {             label1.Text = result.ToString();         }          private static void SumData(object state)         {             int result;             //int[] icount = (int[])state;             int icount = (int)state;              for (int i = icount; i > 0; i--)             {                 result += i;                 System.Threading.Thread.Sleep(1000);             }             setTextboxText(result);         }          delegate void IntDelegate(int result);          private void button2_Click(object sender, EventArgs e)         {             Application.Exit();         }     } }   Why is this error occurring?     An object reference is required for the nonstatic field, method, or property 'WindowsApplication1.Form1.setTextboxText(int)