What is it called when a word can serve more than one part of speech? 'Aggregate', for example, can be used as a Noun, an Adjective, or a Verb.


I want to compare following date in Javascript. Please help me.  $fromdate=2014-12-08 $todate=2014-12-12  I want to compare both the dates with current date. Please tell me how to code in if loop.


How can I permanently suppress sites from Google search results?

I stay logged into Google. I would very much like to permanently blacklist sites that I know to be spammy or low quality from showing up in some of the modules like news and search. Any suggestions on how? I know how to do it case by case in search (-site:lame.example.com) but that's not permanent.  EDIT: The solution presented below (Personal Blocklist) does in fact work for search (thanks!) but not for news - anyone?


I installed MariaDB on a computer with CentOS using the instructions given here:  The basic command I used was: sudo yum install MariaDB-server MariaDB-client    and I did not install Maxscale or percona. MariaDB installation has compleetd successfully, but now if I enter a yet uninstalled command in the bash shell, I am getting this error: Failed to search for file: Failed to download gpg key for repo 'mariadb-main': Curl error (37): Couldn't read a file:// file for file:///etc/pki/rpm-gpg/MariaDB-Server-GPG-KEY [Couldn't open file /etc/pki/rpm-gpg/MariaDB-Server-GPG-KEY]  For example, if I enter the command ftp, previously I would have got a message indicating that ftp was not installed, and I would have got some recommendations on which command I meant and would like to download. However, now I get this: [username@localhost ~]$ ftp bash: ftp: command not found... Failed to search for file: Failed to download gpg key for repo 'mariadb-main': Curl error (37):     Couldn't read a file:// file for file:///etc/pki/rpm-gpg/MariaDB-Server-GPG-KEY [Couldn't open file   /etc/pki/rpm-gpg/MariaDB-Server-GPG-KEY] [username@localhost ~]$  After some searching around I have found that it is because the file etc/yum.repos.d/mariadb.repo has an entry: gpgkey = file:///etc/pki/rpm-gpg/MariaDB-Server-GPG-KEY      and the MariaDB-Server-GPG-KEY file does not exist in etc/pki/rpm-gpg I suppose this should have been created automatically when I installed mariadb? How do I make this bash error go away? Is there any way I can download or create this file manually? --- EDIT --- This was resolved as follows: Downloaded RPM-GPG-KEY-MariaDB as explained in Philip's answer () Copied it to /etc/pki/rpm-gpg/ In /etc/yum.repos.d/mariadb.repo changed the line gpgkey = file:///etc/pki/rpm-gpg/MariaDB-Server-GPG-KEY to gpgkey = file:///etc/pki/rpm-gpg/RPM-GPG-KEY-MariaDB Set the gpgcheck for other entries in the  mariadb.repo file to 0 (I don't have maxscale and mariadb enterprise installed)


What is the easiest way to have a better quality image from a given image

I am a novice for graphic design.  I have a low quality image which is given by my friend, its size is really small, but we want to make it bigger and clearer so that we can use it as a banner or logo or etc.    So my question is what is the easiest way to get a better quality image from a given(smaller, low quality) image?   Should I manually draw it, and how, what tools to use? Or is there a way which I can easily convert it to a vector and then increase the size and then save it back as a png?


Import a library with DOM properties to LWC

I'm trying to use a library with DOM properties in an LWC but many things are not working because DOM properties as document.getElementById or document.defaultView.getComputedStyle are not allowed in LWC js. Is there a way to import another library with DOM properties so I allow the LWC to use them? How ? I'm open to other solutions too.


Any open subset of $\Bbb R$ is a countable union of disjoint open intervals

Let $U$ be an open set in $\mathbb R$. Then $U$ is a countable union of disjoint intervals.    This question has probably been asked. However, I am not interested in just getting the answer to it. Rather, I am interested in collecting as many different proofs of it which are as diverse as possible. A professor told me that there are many. So, I invite everyone who has seen proofs of this fact to share them with the community. I think it is a result worth knowing how to prove in many different ways and having a post that combines as many of them as possible will, no doubt, be quite useful. After two days, I will place a bounty on this question to attract as many people as possible. Of course, any comments, corrections, suggestions, links to papers/notes etc. are more than welcome.


Is it possible to adapt lens from one brand into another brand's body?

I'm thinking about buying my first DSLR (I have no experience) and was thinking about the lens brand issue. I'm thinking I should buy a Pentax Kx because of it's cost-effective value, but I'm wondering if some time from now I'll end up spending more because I decided to change platforms, know what I mean?   So the question is: is there any way I could adapt lenses from Nikon or Canon into a Pentax body and what are the implications of doing this?


How to delete all files and directory except one named directory from a specific folder in centos

I want to delete all files and directories from a specific directory except for one directory. For the same operation I had run this command   # rm -R -df !(dir_name_not_to_delete)  It works in Ubuntu but it gives an error in CentOS; i.e.,  -bash: !: event not found  " what is the reason for this error"   What do I have to use in CentOS to get this to work?   Is there any alternative of '!' this sign in Centos?


Why do I have to press the key 4 times to get a '`' symbol?

I'm using Windows 8.1 Pro, with a Microsoft Gaming keyboard. When I'm writing posts on StackOverflow I often need to enclose things in code marks (`). In order to get these, I have to press the ¬ | key on my keyboard 4 times, which produces two of these.     Why do I need to do this? Why doesn't this key work as others?


C# - Visual Studio - Export DLL's to EXE File

I am using Visual Studio Community to make a C# Console Application. After I installed a NugetPacket there are a lot of DLL files being exported to the Release folder, when building my application. Is it there a quick way to export all the dll files into my exe file, so they can be accessed from my application? I am talking about more than 40 DLL files.


What is a good user group size for going out into the field to test your interface with users, one to one?

If I want to take a paper or pdf version out to test with typical users, one to one, how many users should I find to test on to get the most helpful results?


I have this code below. As you can guess, when I press on "foobar", a new element is added. The problem: when I click on the the new element nothing happens, why? Im using jQuery 2.1.
   foobar


Displaying long division manually with some caveats

Due to odd circumstances, I need to present long division manually (in math mode). That is, without using a macro. Moreover, I cannot use \multicolumn or \cline. Normally, I would do:  \[ \begin{array}{cccc} & 0. & 7 & 5 \\ \cline{2-4} \multicolumn{1}{c|}{4} & 3. & 0 & 0 \\ & 2. & 8 & \\ \cline{2-3} & & 2 & 0 \\ & & 2 & 0 \\ \cline{3-4} & & & 0 \end{array} \]   but is there a way to obtain similar results without \multicolumn or \cline? I'm also open to options using asymptote.  I'm not looking for a generator as they don't insert a 0 when the divisor does not go into the dividend. I'd like a manual way of doing this that looks half-way decent.


Replace all `r, g, b` values with `hex` in JSON string

const jsonString = JSON.stringify(myJson, null, 2);   {       "object1": {         "subobject1": {           "r": 0,           "g": 0,           "b": 0         },         "someOtherProperty": 1       },       "allColors": {         "object2": [           {             "subobject2": {               "r": 4,               "g": 5,               "b": 6             },             "subobject3": {               "r": 7,               "g": 8,               "b": 9             },             "subobject4": {               "r": 9,               "g": 10,               "b": 11             }           }     ......     ......     }   What is the correct regex and way in JS to replace all r, g, b values with hex inside the same string object? For  example:     "subobject2": {       "r": 4,       "g": 5,       "b": 6     }   would turn into:  "subobject2": "#040506"


I got tired to put code in SO. The four indentations I made is not working. For example, I am posting below line with four spaces forth and the back.  print("Haihello");


I understood that quantum field theory is essentially based on a problematic mathematical basis. Can someone please explain what is the fundamental problem to formulate QFT as a rigorous mathematical theory? It's clear that it has to do with renormalization but similar techniques are already exist in analytically number theory (and are considered to be a mathematical theory).


How to typeset 'et al.' in italic with the agsm bibliography style?

I'm using the natbib package with the agsm bibliographic style to generate and use the bibliography in a report.   But whenever I cite an article having many authors, the layout in the document is 'Author et al.'   Which command can I use to have the following result: 'Author. F et al.', i.e. to italicize 'et al.'?


Best way to deal with questions answered by the OP in the question instead of in an answer

I saw this question:   I don't know what the best option is for dealing with such a question, because I've seen questions like this several times already.  So, what should we do with questions that are:   poorly asked finally answered by the OP as an update to the question itself, not as an answer.


Is the nature of the Vulcan/Romulan divide biological or political?

As the title suggests what is the nature of the Vulcan Romulan divide?  Is it biological, are the Romulans biologically distinct enough to be considered a different species ?  For example would a medic treating injuries in war time need to check if the patient was from Romulus or Vulcan in order to provide adequate care ?  Or is it political with the only thing separating them is their differing philosophies ?


Change the color of the specific portion of a string wrapped in a div

How to change the color of the specific portion of a string wrapped in a div:  We have a div like this:
Stack Overflow is the largest, most trusted online community for developers
   How we can change the color of the 'trusted online community' portion to red using the code template below?    let text = document.getElementById("text");  // We want to only change the color of this portion of the text changeColor('trusted online community');   function changeColor(portion){      // code to change the text color     ...          // function to animate the color from black to red     function changeToRed(el) {   el.classList.add("colorRed");     }      }; .colorRed {     animation: colorRedAnime 0.8s cubic-bezier(0.785, 0.135, 0.15, 0.86);       animation-fill-mode: forwards ; }  @-webkit-keyframes colorRedAnime {   from { color: #808080 }   to   { color: #e80000 } }

Stack Overflow is the largest, most trusted online community for developers


How to get the GNOME 3 login manager installed?

I was wondering if it is possible to get the GNOME 3.2 GDM login theme working on Ubuntu 11.10. I installed GDM alongside LightDM, but the GDM greeter is really ugly.


How does handling a lightsaber (weight and momentum) compare with an equal-sized sword?

Potentially the balance of a lightsaber is very different from that of a sword. With a sword, the weight and momentum of the blade significantly affect the depth of the cut.  When the lightsaber is active, does the weight increase?  Or is swinging it just like swinging the handle?  Perhaps like swinging a Wii controller.


Non-Linear Diophantine Equation in Two Variables

How many solutions are there in $\mathbb{N}\times \mathbb{N}$ to the equation $\dfrac{1}{x} + \dfrac{1}{y} = \dfrac{1}{1995}$ ? I could solve till I got to the point where $1995^2$ is equal to the product of two variables but I couldn't sort out the pairs of factors solving the equation. Help is greatly appreciated.


In the below program,  #include<stdio.h> #include<stdlib.h> int main(){   const char *str1 = "abc";   char *str2 = (char *)malloc(sizeof(char)*4);   str2= "def";   str2[1]='s';   printf("str2 is %s", str2);  }     Debugger :  (gdb) ptype str1                                                                                type = const char *                                                                                (gdb) ptype str2                                                                                type = char *                                                                                (gdb) n                                                                                7         str2[1]='s';                                                                                (gdb) n                 Program received signal SIGSEGV, Segmentation fault.                                                                                0x00000000004005ab in main () at main.c:7                                                                                7         str2[1]='s';                                                                                (gdb)     SIGSEGV on str2[1] = 's';   As per my understanding, one cannot modify abc pointed by st1, due to declaration const char *st1 = "abc", where string literal is constant.  Why char * type str2 does not allow modifying the elements? Is stringliteral def also a constant string literal.


Number with a user details while search user

What is mean why that number below a user ('565' in the attached image) while searching user in stackoverflow site?


what is the best strategy to deal with a situation where a student asks all of homework problems on an online forum

I teach a course, every week I assign homework. I put several hours to choose the right homework problems which cover the course material and permit them to be prepared for the exams.  I encourage students coming to my office hours and to ask all of their questions, I may also help them to solve the homework problems. During the class I normally give some hints about the homework's difficult problems (in any).   The homework load is (in my opinion) reasonable: 4-5 exercises, maybe 3-4 out of them are easy and maybe 1-2 is a little challenging. The homework has 10% point.  Today, to my surprise I saw a user who has asked all of my homework problems (including the easy ones) on math stackexchange. And all of them have been answered. Regarding the particularity of my homework problems and the time of posting the questions, I am sure that the user is one of my students, I am not sure which one.   To be precise I had not prohibited the students about posting the homework questions online as I was not expecting this situation.   My question is what is the best strategy to deal with this situation.


Is the least squares estimator of the intercept term in any linear regresssion model always the sample mean of the responses?

Given a linear model $y=\mathbf{w^T}\mathbf{\phi(x)}+ \epsilon$ Where $\phi_0(\mathbf{x})=1 $(as is common), is the least squares estimator of $w_0$ always the mean of the observed y-values(i.e. the sample mean of the response)?


Identifying $L^p$-space of a measure space with the $L^p$-space of a set.

Let $\Omega$ be a measure space. Then the set $L^2(\Omega)$ is a Hilbert space. Hence it has an orthonormal basis $B$, which yields an isometry of Banach spaces: \begin{align*} L^2(\Omega)\cong L^2(B)\end{align*} Now I was wondering: does there also exist an isomorphism $L^p(\Omega)\cong L^p(B)$, for $p\in [1,\infty]\setminus \{2\}$?


Where to Download Special Ubuntu Images Designed for Pre-installed Systems (OEM)?

Background  My Lenovo X250 is arriving in two weeks, which according to  will work well only with "a special image of Ubuntu pre-installed by the manufacturer."   points out that the X250 has "Excellent" compatibility to the Linux OSes they install. On the other hand, a quick search on  or  shows that a standard image of Ubuntu on the X250 is rife with hardware problems.  Ubuntu Certified Hardware acknowledges this for the X250: "Standard images of Ubuntu may not work at all on the system or may not work well." This  clearly shows the difference between an Ubuntu standard image installation and the one that comes pre-installed by the manufacturer. Hardware seems to work fully on the OEM version.  Question  Any idea where we may access or download these "special images of Ubuntu"?  (Hopefully not only for the X250, but also for the other systems out there.)


Change size of individual point symbols in QGIS

I have some point data (towns) with population levels. I'd like to show the smaller populations with small dot and increase the size of the dot symbol as the population increases.  I can do this in Mapinfo but I want to do it in QGIS.


Did spacetime start with the Big Bang?  I mean, was there any presence of this spacetime we are experiencing now before big bang? And could there be a presence/existence of any other space-time before the big bang?


If $a$ is an odd positive integer $>$ $2$ such that 3 $\not$ | $a$, then $12$ $|$ $(a^2 -$1 ))

So I have the following proposal:    $a$ $\in$ $\mathbb{Z}_{+}$ : $a$ = $2k +1$ $>$ $2$ : 3 $\not$ |  $a$ and $>2$ then $12$ $|$ $(a^2 -$1 ).  My initial idea was to show:  $a^2 -1\equiv 0 \mod 12$  Logically it follows:  $(2k+1)^2 -1\equiv 0 \mod 12$  $4k^2 + 4k\equiv 0 \mod 12$  However I do not know where to go from here. This proof also doesn't incorporate the condition 3 $\not  |$ a . Any tips? Sorry for formatting, this is my first time using MathJax.


Is it mandatory for some students to fail in an exam using relative grading?

I am seeing the relative grading structure of few of the institutions. The formula they follow for grading is as follows. For a large batch of students:  they take the final marks of students Calculate the mean marks Calculate the standard deviation of marks Then for those students whose marks are greater than mean + 1.5* standard deviation are assigned A+ ( the highest grades). those students whose marks are less than mean - 1.5* standard deviation are assigned F( failed).  My question is if the distribution turns out to be symmetric around mean (like Gaussian), will it not be true that there must be some students that will fail mandatorily. I may be wrong but I find this concept quite absurd and amusing. Can someone help me with this? I have many times seen in class having relative marking all the students to pass, how this is achieved or the distribution is not symmetric there?


How can I direct a pipe input to ls command?

When I type something like:  find . -name *foo* | ls -lah   it returns the same result as a plain ls command, as though it had no input.  However:  ls -lah $( find . -name *foo* )   works well, but only when the find command has results.  Is it possible to pipe to ls ?


Django Admin Interface - Custom App Name

Using the 'app_label' in the 'Class Meta' will solve this problem. But it won't create tables while issuing 'syncdb' command.  Because the app name won't match with INSTALLED_APPS entry. Is there any way to achieve both (custom app name and creating tables with syncdb)


We know that the first request to Asp.net MVC web aplication causes the aplication to start and Application_start event to run.  I want to know when the Application is closed.thus a new request will trigger Application_start event(something like AplicationTimeout not SessionTimeout).  If available ,is it Adjustable by developer or related to iis settings?


How can I find the closed form of   a) 1+3+5+...+(2n+1) b) 1^2 + 2^2 + ... + n^2   using induction?  I'm new to this site, and I've thought about using the series 1 + 2 + 3 +...+ n = n(n+1)/2 to help me out But isn't that technically using prior knowledge and hence invalid? Am I on the right track? Thanks.


Verifying representativeness of a sample, after simple random sampling

I just used the standard formula to determine the sample size of a sample to match the mean of a pupulation with an error margin  of 3 percentage points and with a 90% probability. I know would like to check that the mean of my sample is actually within the 3% margin of error of the mean in the population. To do so I am taking the population and appending the sample, identifying observations in the sample with a dummy called sample. Then I run the following regresion: reg var1 sample And I am testing wheter the coefficient for the dummy variable sample is less than 3 percentage points. To do so I am using a one sided t test.  But this is only ok when the coefficient of the dummy variable "sample" has the "right" sign. I would like to test the joing hypoithesis that the coefficient of the dummy variable sample is greater than -3 and lower than 3. Does anyone have any insight on how to do this test? Thanks in advance.


Do they have to take checked suitcase off the airplane, if passenger does not show up at the gate?

Is it correct, that if the passenger checks in a suitcase - but never shows up at the gate - they have to take the suitcase off the plane before take-off?   Is this a regulatory issue - or is it a company policy?  Edit: I was asking in general, but if an answer requires specifics... :) In this case it was RyanAir flying Malta to UK. They were delayed so much, that it was no longer possible to make the connecting flight (separate booking), but refused to remove the suitcase from the airplane, so my girlfriend could just leave and catch a better flight tomorrow. This surprised me, as I have always heard and believed they will take your suitcase off the plane if you don't show up at the gate.


How do I drag and drop a link to the desktop?

I was just trying Ubuntu 19.10 last week, and tried something that frustrated me on Linux Mint a few months ago: .  Using the default installed browser (Firefox), I tried dragging a link from the icon next to the address bar, first to the desktop and then to an arbitrary folder in the file manager application, as I'm accustomed to doing in Windows. The former did nothing, and the latter failed with an error:    This for me is a basic usability feature, so I'd like to ask:   Why is this so hard? Is there any way I can get this working without having to go through tedious menus and the like?


What happened to the tag badge progress counts?

So it looks like there was a recent change or regression that isn't showing the score/answer counts for the tag tracking.  What happened to the counts?  Please add it back, or at least explain why it needed to be removed.  The counts are shown for regular non-tag badges...    This makes the tag selection page mostly useless now, especially with the different scaling for the different badge levels.


Unable to use sudo apt-get update: "NO_PUBKEY 26EB39123AAAAA96"

Every time I try to run apt-get update, I get the message below: W: GPG error: http://as-repository.openvpn.net/as/debian focal InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 26EB39123AAAAA96  I'm quite new to Ubuntu, and Linux/Terminal in general, so despite as much as I've looked around and tried solutions, I can't seem to solve it. I've tried sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 26EB39123AAAAA96 which results in: Executing: /tmp/apt-key-gpghome.U6CXBaZaHQ/gpg.1.sh --keyserver keyserver.ubuntu.com --recv-keys 26EB39123AAAAA96 gpg: keyserver receive failed: No data  I also tried sudo apt-key update, which resulted in this: Warning: 'apt-key update' is deprecated and should not be used anymore! gpg: key 3B4FE6ACC0B21F32: 3 signatures not checked due to missing keys gpg: key 3B4FE6ACC0B21F32: "Ubuntu Archive Automatic Signing Key (2012) <ftpmaster@ubuntu.com>" not changed gpg: key D94AA3F0EFE21092: 3 signatures not checked due to missing keys gpg: key D94AA3F0EFE21092: "Ubuntu CD Image Automatic Signing Key (2012) <cdimage@ubuntu.com>" not changed gpg: key 871920D1991BC93C: 1 signature not checked due to a missing key gpg: key 871920D1991BC93C: "Ubuntu Archive Automatic Signing Key (2018) <ftpmaster@ubuntu.com>" not changed gpg: Total number processed: 3 gpg:              unchanged: 3  I'm at an absolute loss here. I use this machine regularly, and can't update some of my packages, which is causing a couple of programs to not work. Any help would be greatly appreciated. I can also provide any other necessary info.


How can I change permissions on external drives?

I wanted to change permissions on my external drives that are automounted however I have tried by sudo nautilus and then going to gui and permissions and changing it however it does not let me.  I ran the ls -l and get  drwx------ 1 xbmc xbmc   the gui shows below.  owner xbmc folder access create and delete files file access ---  Group xbmc folder access none file access ---  others folder access none file access ---   how can I change it so that everyone has permission to access the drive and ALL folders/files inside of it. I am trying to get plexmedia server running and I cant see my drives via the webpage manage to add it to my source to be able to stream my content.  I want to change the "others" access so that I can access all my drives on the /media path to get read and write for all my folders from anywhere.  you can see my drives that are mounted here (external drives are #18,19,20)


Denest $\sqrt {\sqrt[3]{5}-\sqrt[3]{4}}$.   I have tried completing square by several method but all failed. Can anyone help me please? Thank you.  p.s. I'm a poor question-tagger.


Java object doesn't changes outside the method

I'm working on my Spring MVC project. So, here is my controller's login method:  @PostMapping("/login")     public String login(         Model model,         @ModelAttribute("user") @Valid User user, BindingResult result) {         if (result.hasErrors() )             return "login-form";          try {             userService.login(user);         } catch (UserNotFoundException | IncorrectPasswordException e) {             model.addAttribute("message", "Incorrect email or password");             model.addAttribute("tryAgainLocalHref", "/showLoginForm");             return "authorization-failure-page";         }          //debug:         System.out.println(user.getFirstName() + " " + user.getLastName());          return "authorization-success-page";     }    UserService's login method:  @Override     @Transactional     public void login(User user) throws UserNotFoundException, IncorrectPasswordException {         User currentUser = userDAO.getUser(user.getEmail());         if (currentUser == null)             throw new UserNotFoundException();         UserSecurity currentUserSecurity = getUserSecurityByUserId(currentUser.getId());         String inputPasswordHash =              SecurityManager.hashPassword(user.getPassword(), currentUserSecurity.getSalt());          if (!inputPasswordHash.equals(currentUserSecurity.getPasswordHash()))             throw new IncorrectPasswordException();          user = currentUser;                 //debug:                 System.out.println(user.getFirstName() + " " + user.getLastName());      }    Here you can see that in UserService 'user' object is replaced on 'currentUser'. In my business logic, 'user' has only two not-null fields: email and password, and 'currentUser' has four not-null fields: email, password, firstName, lastName. As you can see, in controller's login method I print user's firstName and lastName. And it writes: null null. But why??? It is replaced by 'currentUser' in UserService! When I print user's firstName and lastName fields in UserService, it writes current firstName and lastName from database! So why does 'user' object changes have no impact outside the method? 'User' is non-primitive type...


Are these responses from top journals just boiler plate? or anything atleast miniscule to salvage from them?

thanks for submitting your paper to XXXXX Journal. It is an explicit and interesting analysis of a natural problem. However, in my opinion, it does not reach the level of XXXXX Journal. I therefore have decided not to pursue the evaluation process in order not to delay the publication of your paper elsewhere. Please don’t take it too bad, XXXXX Journal receive a lot of very very strong submissions in every aspect of mathematics and we publish only 700 pages per year, so we have to make some hard choices. Best regards, XXXXX (Editor-in-chief)   Dear Professor XXXXX, The XXXXX Journal of XXXXX recently received a very large number of submissions.  We are also attempting to reduce our publication backlog. Consequently, the editors are unable to consider every manuscript for further review.  So we regret to inform you that we will not be able to publish your manuscript. We hope that you will submit your paper to a more specialized journal where your work may be more fully appreciated. Sincerely, The Editors XXXXX Journal of XXXXX  Are both of these are just boiler plate or anything to salvage from them. I must say both are really top journals in mathematics.


Python urlopen function raises an error when an https site is given as input

Please don't mark the question as a duplicate. I have gone through every possibility, but I didn't find an answer. I use Ubuntu 12.04(LTS)  Python urlopen function raises this error message when an https site is given as input:  Traceback (most recent call last):   File "fb.py", line 13, in <module>     htmlfile = urllib.urlopen(url)   File "/usr/lib/python2.7/urllib.py", line 86, in urlopen     return opener.open(url)   File "/usr/lib/python2.7/urllib.py", line 207, in open     return getattr(self, name)(url)   File "/usr/lib/python2.7/urllib.py", line 436, in open_https     h.endheaders(data)   File "/usr/lib/python2.7/httplib.py", line 954, in endheaders     self._send_output(message_body)   File "/usr/lib/python2.7/httplib.py", line 814, in _send_output     self.send(msg)   File "/usr/lib/python2.7/httplib.py", line 776, in send     self.connect()   File "/usr/lib/python2.7/httplib.py", line 1161, in connect     self.sock = ssl.wrap_socket(sock, self.key_file, self.cert_file)   File "/usr/lib/python2.7/ssl.py", line 381, in wrap_socket     ciphers=ciphers)   File "/usr/lib/python2.7/ssl.py", line 143, in __init__     self.do_handshake()   File "/usr/lib/python2.7/ssl.py", line 305, in do_handshake     self._sslobj.do_handshake() IOError: [Errno socket error] [Errno 8] _ssl.c:504: EOF occurred in violation of protocol   How do I fix this?


Why do capacitors in a dielectric have the same charge as without the dielectric

If you imagine a dielectric of height $d$ and dielectric constant $\kappa$  placed evenly in a capacitor of height $D$. We define $\Delta x = \frac{D-d}{2}$.   The equivalent capacitance is now  $$\begin{align} \frac{1}{C_{eq}} &= 2 \frac{\Delta x }{\epsilon_0 A} + \frac{d}{\kappa \epsilon_0 A} \\ &= \frac{D-d}{\epsilon_0 A} + \frac{d}{\kappa \epsilon_0 A} \\ &= \frac{\kappa(D-d)+d}{\kappa\epsilon_0 A} \end{align} $$  At this point   $$C_{eq} = \frac{\kappa\epsilon_0 A}{\kappa(D-d)+d}$$  Based on prior knowledge, it should be that the charge on the equivalent capacitor is the same as the charge on the original, non dielectric capacitor  In other words:  $q = CV = C_{eq}V$ and voltage hasn't changed.   But $CV \ne C_{eq}V$!  What am I missing?


My attached image isn't shown. Old other images from another peoples also

My attached image isn't shown. Neither are older images from another people.  Example where I don't see the image:


Vanishing \footcite if the titlesec package is loaded

I'm trying to use multiple \footcite citations at the end of a \section. This works as expected as long as I don't have the titlesec package loaded, but as soon as I do, all but the last \footcite in the \section vanish: In the printed heading, there appears a footnote marker, but there is no corresponding footnote at the end of the page.  Here's an example, hopefully making clear what I mean:  \documentclass{book} \usepackage[a4paper, total={6in, 4in}]{geometry}  \usepackage{filecontents} \begin{filecontents*}{bibliography.bib} @article{A, author = {Alpha, Amber}, title = {Title}} @article{B, author = {Beta, Bryan}, title = {Title2}} \end{filecontents*}  \usepackage[english]{babel} \usepackage[backend=biber,citestyle=authortitle]{biblatex} \addbibresource{bibliography.bib} \usepackage[bottom,multiple]{footmisc}  \usepackage{titlesec}  \begin{document}  \chapter{Chapter Heading% \footcite{A}\footcite{B} }  \section{Section Heading% \footcite{A}\footcite{B} }  Text% \footcite{A}\footcite{B}  \end{document}   This produces the following PDF; notice how footnote 3 is missing at the bottom:   However, if I comment out the line \usepackage{titlesec}, I get the desired result:   The \footcites in the \chapter and in the text are only included to show that for some reason, the effect does not appear there.  How can I solve this problem (except for avoiding titlesec)?  I'd also be curious to learn why this happens in the first place, but please consider this only a "bonus question" of sorts; my primary concern is a practical solution of the prblem.  This happens both with pdfLaTeX and LuaLaTex with TeX Live 2013, in the way it comes with Ubuntu 14.04, except that I manually updated the titlesec package to the newest version in CTAN.  Any help would be greatly appreciated! Thank you very much in advance!


Dual 4k monitor setup at 60hz with 2015 15" MacBook Pro with Intel Iris Pro over display port

Is it possible?   Apple site says it can run two 4k displays. But can it drive them both at 60Hz?  Upd. Question was marked as duplicate, but this is not fully correct - 2015 MBP 13 and 15 have different integrated video cards from Intel. And surprisingly 13's card is better than 15's ( 13 - Intel Iris Pro 6100, 15 - Intel Iris Pro 5200).


I had read wiki and some sources.  ,     the background is that:  You have Xi ∼ N(θi, 1), and we want to estimate the each θi. Where Xi are independent。  For MSE risk of vector (X1,...,Xn), when n>=3.   the MLE estimator $\hat θ_i = x_i$ is inadmissable .  While James-Stein estimator is better than MLE in such case.     Looking from Shrinkage  quote from Larry Wasserman:     Note that the James-Stein estimator shrinks {X} towards the origin. (In fact, you can shrink towards any point; there is nothing special about the origin.)    I know the James-Stein estimator is special to MLE for its shrinkage behavior. I still dont get it, the variables are independent.    Why James-Stein estimator shrinkage to arbitrary point can improve the MSE risk versus where MLE do not shrinkage at all ??    and seeing this from Larry Wasserman:     This can be viewed as an empirical Bayes estimator ....   If view it from Empirical Bayes case, it is shrinkage to a overall mean, but that is nonsense if you have independent variable to estimate.    Is there better example or intuitive explanation for it?? THANKS.


What to do when ubuntu freezes completely?

I had Ubuntu 14.04 and have done a clean install of 16.04. I had problems on 14.04 and on upgrade all problems were solved except ubuntu freezing.  Now it is freezing occasionally and only a force shutdown works. I have tried magic sysreq method, ctrl+alt+del, alt+f2, nothing can solve it. What should I do?


I seem to have turned some weird setting on in Salesforce that "highlights" the line of code that the cursor is currently at. Whatever it is, it doesn't work very well and covers up text that I need to see. What is this and how do I turn it off?   I've googled the problem and come up with nothing. Here's some pictures of what I'm talking about.


Discrete Probability: Four dice are thrown, what's the probability that...

Four dice are thrown, what's the probability that:  a) None of them fall higher than three?  b) None of them fall higher than four?  c) That four is the highest number thrown?  So for a, I wanna think about the denominator first. There are 6 possible outcomes for each dice, and we have four dice. So we're technically picking r out of n objects, aka picking 4 possible values out of 6. So the denominator/sample space should be $6^4$ right?  Now this is where I'm getting tripped up. Order technically shouldn't count, because we only care about the quadruplets that don't have a value higher than 3. I might be wrong, maybe I am, but could someone explain a bit more? My professor stated that typically in the sample space/denominator, we want order to count.   So I'm trying to think of the numerator now, so we want to find the probability that no values appear higher than 3, so some events that can occur are: $(1, 1, 2, 3), (1, 2, 2, 3), (1, 1, 1, 1)$ etc. Again, I can't see why order should count here, because if we only are concerned about what appears rather than how they appear, then we can say $(1, 1, 2, 3)$ is equal to $(1, 2, 1, 3)$? So if order does not count, and we have replacement, then does this lead the case where we use $$\binom{n-1+r}{r}$$to find out the probability?   I'm pretty sure if I can do a), I could prob do b), but if someone could maybe lead me in the right direction for c) I would appreciate that too!


Is there a shell for quickly experimenting in C?

I'm not looking for csh, I'm looking for a shell for C similar to the Python or the Scala shells.   I understand that C is a compiled language, but is there anything out there that would let me quickly play around with things so I can e.g. better learn how pointers work? It should at least be theoretically possible to do this, wondering if anyone has taken the time to implement it.


Let's remove the "Get updates..." notification

Recently this notification has started showing up quite repeatedly on Stack Exchange sites:    The problem is that it's not necessary, and even if it is, it should not be showing up repeatedly.  In just the last few months, these sorts of notifications have really risen on the Internet (think of YouTube's new notifications in the lower-left hand corner), and they are very stressful to deal with for three reasons:   They add clutter to the site's UI. They are typically not necessary or relevant for the user. Users should not have to dismiss the same notification over and over again.   All of these issues apply here.  Can we please get rid of this notification, and can we please keep the site's UI clean?  A clean, non-spammy UI is one of the reasons Stack Exchange got to be as popular as it is.    EDIT:  As Mark Kirby pointed out in the comments, there was a very similar  to .  That answer and my own post are suggesting two fairly similar things, with one difference:  The one answer suggests making the dismissal of this notification sitewide, and I suggest getting rid of it altogether.  In fact, I suggest never having notifications for things like this in general.  Clean notifications for community activity and such are great, but messy notifications for UI features, news updates, and so on are basically just clutter and an irritant.  So there is some similarity between the two suggestions, but there's a little bit of difference as well.


Macro for textinput without any formatting

Is there a LaTeX macro that just compiles whatever I type into it? Something like \text or \textnormal. I want to display a LaTeX code inline without any formatting, but don't want to escape everything. Especially I want to display the text in caption as well.  This is the LaTeX code I want to have as regular text.  x = \frac{-b\pm\sqrt{b^2-4ac}}{2a}


Running interactive commands in Paramiko

I'm trying to run an interactive command through paramiko.  The cmd execution tries to prompt for a password but I do not know how to supply the password through paramiko's exec_command and the execution hangs.  Is there a way to send values to the terminal if a cmd execution expects input interactively?  ssh = paramiko.SSHClient() ssh.connect(server, username=username, password=password) ssh_stdin, ssh_stdout, ssh_stderr = ssh.exec_command("psql -U factory -d factory -f /tmp/data.sql")   Does anyone know how this can addressed? Thank you.


Why the result of the function invoked twice is different?

function makeCounter() {     var i = 0;     return function() {         console.log( ++i );     }; }  var counter = makeCounter(); counter(); // logs: 1 counter(); // logs: 2   why the result of counter() invoked the second time is '2' but not '1'?  I try to find out its executing processes, so I rewrite makeCounter():  function makeCounter() {     var i = 0;     console.log('outer');     return function() {         console.log('inner');         console.log( ++i );     }; }  var counter = makeCounter(); counter(); counter();   and result is:  outer inner 1 inner 2   Can I think that: i is the argument of function counter(), the first counter() executed, i changes to '1'. So the second counter() executed, i is '2'.


Let $G$ be a finite group, $A\subseteq G$ and put $A^{-1}=\{ a^{-1}:a\in A\}$.  Is it true that if $|A|>\frac{|G|}{2}$ then $A^{-1}A=AA^{-1}=G$?


Is there a method to find which numbers to use when simplifying quadratics?   For example $x^2 + 5x + 6$ is easy enough to find, but what if I have bigger numbers, or I have this quadratic expression: $x^2 + 7x – 6$, then it gets very hard to think of a valid simplification.  EDIT: Here's an example: $(x^2 + 5x + 6)/(x + 2)$. When simplifying the first half we get $(x + 2)(x + 3)/(x + 2)$, then we can cancel out $(x + 2)$ and the answer would be $(x + 3)$. The question is: How to always find the right numbers which to put in? (in this example they where 2 and 3)


How to find all polynomials P(x) such that $P(x^2-2)=P(x)^2 -2$?

I am trying the fallowing exercise : Solve $P(X^2 -2)=P(X)^2 -2$ with P a monic polynomial (non-constant)  My attempt :  Let P satisfying $P(X^2-2) = (P(X))^2-2$  Then $Q(X)=P(X^2-2) = (P(X))^2-2$   Therefore,  $$Q(X^2-2) = (P(X^2-2))^2-2 = (P(X)^2-2)^2-2 = Q^2-2$$  As X is a solution, by defining the sequence:  $(P_n)_{n \geq 1}$ with $P_1 = X$ and for all $n \geq 1, P_{n+1} = P_n^2-2$  We obtain a sequence of polynomials which are solutions.   But I don't know how to prove it's the only one. If someone have an idea to prove it or an another method to solve the problem ?   Thank you in advance for your time.


Is it possible to render 360° panoramic images in Blender, usable to make a 360° pano presentation?


How to do one-class text classification?

I have to deal with a text classification problem. A web crawler crawls webpages of a certain domain and for each webpage I want to find out whether it belongs to only one specific class or not. That is, if I call this class Positive, each crawled webpage belongs either to class Positive or to class Non-Positive.  I already have a large training set of webpages for class Positive. But how to create a training set for class Non-Positive which is as representative as possible? I mean, I could basically use each and everything for that class. Can I just collect some arbitrary pages that definitely do not belong to class Positive? I'm sure the performance of a text classification algorithm (I prefer to make use of a Naive Bayes algorithm) highly depends on which webpages I choose for class Non-Positive.  So what shall I do? Can somebody please give me an advice? Thank you very much!


Let the function $f(x)$ be differentiable  and $f'(x)$ be continuous in $\left(-\infty,\infty \right)$ with $f'(2)=14$ then evaluate the limit  $\lim_{x\to 0}\frac{f(2+\sin x)-f(2+x\cos x)}{x-\sin x}$  My attempt:  $\lim_{x\to 0}\frac{f(2+\sin x)-f(2+x\cos x)}{x-\sin x}$  $\lim_{x\to 0}\left(\frac{f(2+\sin x)-f(2+x\cos x)}{\sin x-x\cos x}\right)$ $\frac{\sin x-x\cos x}{x-\sin x}$$=\left(f'(2)\right)(2)=28$  Is the method used here correct


Are spells in Harry Potter invented or discovered?

Are the spells in the magical world of Harry Potter invented or discovered?  Maybe someone just said “Avada Kedavra” and the rest is history.


I use the following code to draw a cylinder. How can I fill it with gradient colour to look like the attached image.  \documentclass{beamer} \setbeamertemplate{navigation symbols}{} \usepackage{tikz}  \usetikzlibrary{shapes.geometric} \begin{document} \begin{frame}[t] \frametitle{} \begin{tikzpicture}[scale=1., transform shape] \node [cylinder,draw=blue,thick,aspect=2.,minimum height=5cm,minimum width=4cm,shape border rotate=0,cylinder uses custom fill, cylinder body fill=blue!30!white,cylinder end fill=blue!20!white] at (0,0){}; \end{tikzpicture} \end{frame} \end{document}


I am new to Linux. I have read the basic docs.   I have just installed Filezilla. I first tried apt-get but the repository does not appear to be up to date. I then downloaded it from the Filezilla web site, unzipped, and I am now able to use the program from unity.  I am trying to understand the command line though... if I type:  Desktop/Filezilla/bin/filezilla   The program opens but throws a bunch of errors in the console:  (filezilla:2767): Gtk-Critical **: IA__gtk_widget_set_size_request: assertation 'width >= -1' failed   I would like to know how to "map" the location of the executable to a simple command like:   $filezilla   And also if there is a reason for the errors when I type in the path directly. Sorry if I am missing something easy but thanks for helping a newbie :)


Pure Python script: create a particle system from Python script in 2.9

My application should run on a headless server, thus I cannot rely on Blender GUI, and I need a stand-alone python script.. I have been looking all over the place for an example of the creation on a particle system in pure Python API, but all the examples either assume the GUI usage or are not up to date with the API. Can someone provide a minimal snippet for the creation of a particle system in Python? Thanks, Simon


I just bought a house built in 1984 it has PEX plumbing. I need to remove a toilet to install a new floor and I noticed the water supply line to the toilet connects to a water shut off valve that I’ve never seen before. It looks like a PVC bonnet or nut cap thing With a half crescent ring that you turn left or right to turn the water on or off. Are these reliable or should I replace with a quarter turn ball valve. I really don’t want to do anything unnecessary but a PVC shut off valve gives me anxiety as an inexperienced DIY homeowner


make a bootable usb for windows 8.1 recovery in Ubuntu

how do i make a windows 8.1 recovery bootable flash drive in Ubuntu?


I have friction shifters and for some reason the front one gives me a bit of trouble. It tends to return to its most untensioned state. So say I want to shift to a higher gear, it will try to drop me back down to my lower gear. My guess is I might need to lube up the cable and shifter. Any other known solutions?


What is a complete book for introductory quantum field theory?

There's a fairly standard two or three-semester curriculum for introductory quantum field theory, which covers topics such as:   classical field theory background canonical quantization, path integrals the Dirac field quantum electrodynamics computing $S$-matrix elements in perturbation theory, decay rates, cross sections renormalization at one loop Yang-Mills theory spontaneous symmetry breaking the Standard Model   What is a good, complete and comprehensive book that covers topics such as these?


Debian: Why my debian_version is "buster/sid" after upgrading from stretch to testing

I installed a Debian stable from ISO.  /etc/debian_version was "9.5".  Then I changed apt from "stretch" to "testing" and upgraded.  Now debian_version is "buster/sid"!?  I thought sid is always "unstable" so why is there sid in the version-string?


My question is out of curiosity and got me thinking. How did viruses with the head, tail and tail fibres actually evolve? These viruses look more like machines than biological entities. Are there any theories to how these viruses evolved?


Thousands of 404 errors in Google Webmaster Tools

Because of a former error in our ASP.Net application, created by my predecessor and undiscovered for a long time, thousands of wrong URLs where created dynamically. The normal user did not notice it, but Google followed these links and crawled itself through these incorrect URLs, creating more and more wrong links.  To make it clearer, consider the url     example.com/folder   should create the link     example.com/folder/subfolder   but was creating     example.com/subfolder   instead. Because of bad url rewriting, this was accepted and by default showed the index page for any unknown url, creating more and more links like this.     example.com/subfolder/subfolder/....   The problem is resolved by now, but now I have thousands of 404 errors listed in the Google Webmaster Tools, which got discovered 1 or 2 years ago, and more keep coming up.  Unfortunately the links do not follow a common pattern that I could deny for crawling in the robots.txt.  Is there anything I can do to stop google from trying out those very old links and remove the already listed 404s from Webmaster Tools?


Under the circumstances (holiday, overworked SE employees), when can I expect my profile to be deleted for SE Meta?

I requested deletion of my profile on SE Meta on 12/23/19.  My profile states     This account is scheduled to be deleted Dec 24 at 14:38.   That is 96 hours ago.  I realize that this is a holiday week and many employees are probably taking days off, but I am asking when can I expect my profile to be deleted? I am concerned that my request fell through a crack.


Counterexample to divisibility of subgroup indices?

Let $G$ be a group, with $H,K\subset G$ subgroups of finite index. Show by counterexample that the index $[H:H\cap K]$ need not divide $[G:K]$.  It's pretty easy to prove that $[H:H\cap K]\le [G:K]$ using group actions. I've considered all the cyclic and product groups I can think of to no avail.


Creating a new DOM element from an HTML string using built-in DOM methods or Prototype

I have an HTML string representing an element: '
text
'. I'd like to append it to an element in the DOM (a ul in my case). How can I do this with Prototype or with DOM methods?  (I know i could do this easily in jQuery, but unfortunately we're not using jQuery.)


How to mark a question as a “maybe-duplicate”, when you don't want to use the dupe hammer?

I have a gold badge on some tag, which apparently lets me decide all by myself that a question is a .   However - I don't always want to do that. In fact, I usually want to, at first, mark it as “maybe-a-dupe” and see what others think. Can I do this?


Problem changing from PHP 5.6 to PHP 7.2

I have a problem with an old theme that can't be updated. My hosts (1&1) are now charging to continue using PHP 5.6 but I get the following errors when switching to PHP 7.2 and I don't know what to do. If anyone can help, it would be much appreciated. Thanks in advance.  Warning: Declaration of mysiteDescriptionWalker::start_el(&$output, $item, $depth, $args) should be compatible with Walker_Nav_Menu::start_el(&$output, $item, $depth = 0, $args = Array, $id = 0) in /homepages/36/d129703868/htdocs/mightyoak/bhd-wp/wp-content/themes/construct/lib/classes/menu-walker.php on line 45   Warning: Declaration of mysiteResponsiveMenuWalker::start_lvl(&$output, $depth) should be compatible with Walker_Nav_Menu::start_lvl(&$output, $depth = 0, $args = Array) in /homepages/36/d129703868/htdocs/mightyoak/bhd-wp/wp-content/themes/construct/lib/classes/menu-walker.php on line 87  Warning: Declaration of mysiteResponsiveMenuWalker::end_lvl(&$output, $depth) should be compatible with Walker_Nav_Menu::end_lvl(&$output, $depth = 0, $args = Array) in /homepages/36/d129703868/htdocs/mightyoak/bhd-wp/wp-content/themes/construct/lib/classes/menu-walker.php on line 87  Warning: Declaration of mysiteResponsiveMenuWalker::start_el(&$output, $item, $depth, $args) should be compatible with Walker_Nav_Menu::start_el(&$output, $item, $depth = 0, $args = Array, $id = 0) in /homepages/36/d129703868/htdocs/mightyoak/bhd-wp/wp-content/themes/construct/lib/classes/menu-walker.php on line 87  Warning: Declaration of mysiteResponsiveMenuWalker::end_el(&$output, $item, $depth) should be compatible with Walker_Nav_Menu::end_el(&$output, $item, $depth = 0, $args = Array) in /homepages/36/d129703868/htdocs/mightyoak/bhd-wp/wp-content/themes/construct/lib/classes/menu-walker.php on line 87


What the best way to design an increase/decrease field?

I'm working on a simple settings panel for an ecommerce site for adjusting a product's inventory quantity in a trackable manner. My team is in disagreement in regards to the most efficient way to design a form to adjust the quantity. We're currently in two camps.  First Option (Manual)    A user chooses "Increase" or "Decrease", then enters a value that will be used absolutely  Second Option (Automatic)    A user enters a positive or negative number (using a minus sign), then receives confirmation via a small badge  We want our users to easily understand what kinds of values the Amount field accepts, but we also want it to be as efficient as possible.   The Manual option is clearer, since the user knows whether addition or subtraction will be performed.   On the other hand, the Automatic is slightly less clearer on what sort of values are acceptable, but becomes faster to use once the user understands how the form works.  What's the best way to design this?


How can I duplicate a mesh along a curve?

I want to outline a curve in the form of text with a mesh (UV-sphere, cube etc.). How can I do that while saving mesh geometry without using the Curve modifier?


How to prove the value o $\zeta(2)$ by Functional Analysis?

I have a question about $\sum_{n=1}^{\infty} 1/n^2$ = $\pi^2/6$ I know it can be proven with standard 1 variable analysis (working on Taylor series of $\arcsin$ or something like that) or basic complex analysis. But someone told me it has also great prove using Functional Analysis. He suggested it is proved on standard first course of FA, but it was not in my case. Can You write here the proof using FA or leave a link in comment? Thanks in advance.


I read in several sources that the Quasi Poisson model and the Negative Binomial, should produce (on average) the same results. I tried a simple example and, although very close to each other, the numbers are not quite the same.  Does this depends on the numerical algorithm or is there something else I am not considering? Thank you phi = 3 a = 1/50 b = 3 x = 1:100  mu = exp(a*x+b)  y = rnbinom(n = length(mu), mu = mu, size = mu/(phi-1)) #random negbin generator  glmQP = glm(y~x, family=quasipoisson) glmNB = glm.nb(y~x)  glmQP glmNB  glmQP$fitted.values glmNB$fitted.values  plot(x, y) lines(x, glmQP$fitted.values, col = "red") lines(x, glmNB$fitted.values, col = "blue")


Showing an entire function is a polynomial

If $f(z) = \sum_{n=1}^\infty a_nz^n$ is an entire function which does not have an essential singularity at $\infty$, then $f$ is a polynomial. I'm trying to apply Liouville's Theorem, but I am not guaranteed that $f(z)$ is bounded.


USER_DEBUG [223]|DEBUG|Lista de mapas:: ({0={ApexNombrePromo=HBO por 2 Meses}, 1={ApexNombrePromo=Prueba - Promo 13})  I get this code in debugging is the printing of a two-element matrix. How can I get the value "ApexPromoName" of each element


What is the approximation of pi in a fraction form. I am very curious to know what it is. I have been seeing pi almost everywhere.


Nothing to do in this review but "No action needed"

In this locked question it is not possible to do anything. Only "No action needed" and "Skip" are enabled, and clicking that will throw "STOP! Look and Listen." box


$ABAB=0_{n\times n}$, then must $BABA$ be $0_{n\times n}$?

Let $A$ and $B$ be $n\times n$ matrices such that $ABAB=0_{n\times n}$.  Can we conclude that  $BABA$ must be  $0_{n\times n}$?   I fail to give a counterexample when $n=2$， so I guess the answer is "yes"


If $V_1, V_2$ are $\mathbb{Q}$-vector spaces and $f \colon V_1 \to V_2$ is additive, then $f$ is $\mathbb{Q}$-linear

If $V_1$ and $V_2$ are vector spaces over the field of rational numbers and $f \colon V_1 \to V_2$ is a map such that $f(x+y)=f(x)+f(y)$ for all $x, y \in V_1$, show that $f$ is a linear transformation.   It is easy to show that $f(0)=0$ and $f(-x)=-x$. Here scalars are from rationals. If scalar is an integer then clearly $f(\alpha x)=\alpha f(x)$. Hence $f$ is a linear transformation.  Now I have to show that when $\alpha$ is not an integer then $f(\alpha x)=\alpha f(x).$


Excel isn't calculating the SUM of cells

I am trying to use a very simple formula which is =SUM(B9:B11). However the cell doesn't compute for some reason.  I've used Excel for years and have never had this problem. Any idea why it may be failing to update the SUM?  I'm using Excel 2007 on Windows 7 Pro. I've opened the spreadsheet on multiple different machines with the same results so it appears to be an issue with the spreadsheet itself and not Excel or the computer.  Additional Note: If I recreate the =SUM formula it will recompute the total. However, if I change one of the number it still doesn't auto-recalculate.  Also, if I press F9 the SUM will recalculate being manually forced to.


How to split a string in every three words (JAVA)

I need to split a string in every three words (using JAVA). For example:  "This is an example of what I need."   The output would be:  This is an is an example an example of example of what of what I what I need I need   Thanks for the help!  I've tried like this. I don´t know how to get the last two words or what to do when the phrase has less than 3 words.  String phrase = "This is an example of what I need." String[] splited = phrase.split(" ");  for (int i = 0; i < phraseSplited.length - 2; i++) {       threeWords = splited[i] + " " + splited[i+1] + " " + splited[i+2];       System.out.println(threeWords);     }


The smallest prime factor of a factorial plus one

What is the smallest prime factor of 712! + 1? What equations do I need to use? Is there a good resource to practice finding the prime factors of a factorial? Thanks


how to raise superscript inside overline?

I want to N squared inside overline. The superscript in $\overline{N^2}$ is too low. How to raise superscript higher? Thanks


Should the Help Center sidebar also match the theme color of the website?

While checking out the Help Center, I noticed something that I think in my opinion should be slightly changed.   Should the sidebar of the Help Center (The box which holds all of the questions and topics in the Help Center) be changed to the website's theme color?     Right now, the sidebar looks like we're in Stack Overflow.  The reason why I think this should be changed is because I think this would make the site look better for some users.     But of course, I think this is mostly on people's opinions, and that's the reason we should discuss about this minor change.  How do you people think of it?


How normal should variables be to run PCA?

I am new to statistics and it this the first time I am trying to normalise variables. Thus, sorry for my incompetence.  My goal is to classify the landscape by cluster analysis (using kmeans in R) and see if there is a relationship between species distribution and type of the landscape.  However, some of the variables (totally there are 10 variables) I am using are strongly correlated. Thus, I decided to do PCA and run cluster analysis with principal components. I tried to do it without normalising variables before PCA (however, I standardised them with data.frame(scale(data,center=T,scale=T)) function), but the results I got didn't impressed me, since, I observed stronger and more interpretable relationship, when I tried to run cluster analysis with 4 uncorrelated and hypothetically the most important variables (also standardised). So now I want to normalise the variables and try to rerun PCA and cluster analysis. But to make matters worse, some of the variables I am using are far from normal, the sample sizes are large (n=40038) and I've got no experience in transforming the data.  I have read that tests of normality are useless in cases of large samples and, generally, for deciding if one is able to use parametric methods for his data. So I am inspecting normality visually and by values of kurtosis and skewness. So for example, I have one, very problematic variable with many zero values which looks like to follow gamma distribution:    I transformed the variable to the power of 0.3 (x^0.3) and got the following results:  Skewness= 0.5006657 Kurtosis= 3.255236    I also tried other transformations and yeo.johnson() function, but none of them produced me a better result. However, I see that the result I have is far from normal. Nonetheless, maybe it is still fair enough approximation of normal distribution for PCA, as this method doesn't have a strict requirement for it? And to rephrase this question - what will happen if I run PCA with that kind of variable, while other variables follow more or less normal distribution, and later use k means to classify principal components' values? Finally, maybe there is a better way to transform this variable?


I need to recursively append a Node to a linked list, not sure why my code doesn't work public void RecursiveAppend(Node example, Node add){    if(example == null){        example = add;     } else {        RecursiveAppend(example.next, add);    } }  Method to print list public void IterativeTraversal(){        Node example = m_head;        while(example != null){            System.out.print(example.data + " ");            example = example.next;        }    } public class LinkedListDemo {     public static void main (String [] args){         LinkedList example = new LinkedList();         Node A = new Node(10);         Node B = new Node(30);         Node C = new Node(50);         Node D = new Node(70);         example.append(A);         example.append(B);         example.append(C);         example.RecursiveAppend(D);         example.IterativeTraversal();     } }  Result: 10 30 50


I have seen this construction quite often:      Online ads have been around since the dawn of the Web, but only in   recent years have they become the rapturous life dream of Silicon   Valley.   What is the rule there?. When your sentence doesn't start with pronoun + verb, invert them as verb + pronoun?. I know it sounds awkward but is it possible (grammatically correct) to use something similar to:      Online ads have been around since the dawn of the Web, but only in   recent years they have become...   And in any case, does this only work with have (or has)? Maybe it works fine with 'had' but I can't think of an example right now.


I want to make a new paragraph, but when I try to put some text, and then a blank line in my code, it gives me a BadBox error. How can I make paragraphs with the following format, without receiving BB errors?  "Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum." "Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum."  The following is only a snippet from my code, as each of the sections are identical, and all produce the same BB error: \begin{document}     \section{Fermat's Last Theorem} The question of Fermat's Last Theorem has puzzled mathematicians for centuries. The problem, although simple to state, was a beast the likes of which people had never seen. For many years, this problem remained unsolved. \newline \newline \noindent The hypothesis was as follows: For $n,x,y,z \in \mathbb{N}$, the equation $x^n+y^n=z^n$ has no solutions. Equivalently, using the theorem's connection to elliptic curves, the theorem can be stated as: If $a,b,c$ is a non-trivial solution to $x^p+y^p=z^p$ where $p$ is an odd prime number, then $y^2 = x(x-a^p)(x+b^p)$ will be an elliptic curve. \end{document}


Similar to '', is it also ok to add an example?   I was going to  but I noticed that one answer had most of the things I needed to say, except perhaps that the questioner didn't perhaps understand the answer and  I feel that an example may help.


Why does the existence of independent statements not prove consistency?

I've read before that, by the Principle of Explosion, if a theory is inconsistent, then absolutely any statement can be proven within it.  Obviously, there are statements which are independent of ZFC (Continuum Hypothesis, etc). It seems to me that this proves that ZFC is incomplete. Why does it not then follow that ZFC is consistent? It seems to me that we could say "Assume ZFC is inconsistent. Then the the Continuum Hypothesis is provable in ZFC. But the Continuum Hypothesis is neither provable nor disprovable in ZFC. Therefore ZFC is consistent."  What am I missing here?


How to boot to the recovery mode if it is not listed in Grub?

I want to boot Ubuntu into recovery mode but there is no grub menu entry allowing me to do so. I pressed e and now I am able to edit boot options. It looks like that:  setparams 'Ubuntu , with Linux 3.6.0-26-generic'  recordfail gfxmode $linux_gfx_mode insmod gzio insmod part_msdos insmod ext2 set root='(hd0,msdos5)' search --no-floppy --fs-uuid --set=root <uuid> linux /boot/vmlinuz-3.5.0-26-generic root=<uuid> ro ipv6.disable=1 quirt splash $vt_handoff initrd /boot/initrd.img-3.5.0-26-generic   The  documentation says:     Boot to the recovery mode even if it is not listed on the menu:         Remove existing kernel options from the linux line and add single      But this sentence doesn't make any sense, maybe the wiki page is broken somehow. How to modify the boot menu to boot directly into recovery mode?  Note: I don't have access to grub config or anything else, only the boot menu edit page is available.


Comparison of Linear dependency between $2$ families of vectors in $\Bbb R^n$.

Let $T:\Bbb R^n\longrightarrow\Bbb R^n$ be a linear transformation, where $n\geq 2$. For $k\leq n$,  let $E=\{v_1,v_2,\dots,v_k\}$ contained in, equal to $R^n$ and $F=\{Tv_1,Tv_2,\dots,Tv_k\}$. Then  a). If $E$ is linearly independent, then $F$ is linearly independent.  b). If $F$ is linearly independent, then $E$ is linearly independent.  c). If $E$ is linearly independent, then $F$ is linearly dependent.  d). If $F$ is linearly independent, then $E$ is linearly dependent.  a) part can be correct if $T$ is one-one. And since our transformation is finite dimensional $n$-to-$n$. Therefore, it is one-one, which implies that $F$ is linearly independent if $E$ is linearly independent.  I thought of part c) as follows: supposingly I take $E=\{(1,0,0),(0,1,0)\}$ contained in $\Bbb R^3$ and $F=\{T(1,0,0),T(0,1,0)\}$. Now $E$ is linearly independent, if I define $T(x_1,x_2,x_3)=((x_1+x_2),0,x_3)$ then $T(1,0,0)=(1,0,0)$ and $T(0,1,0)=(1,0,0)$ , this shows that $T(v_1)$ and $T(v_2)$ are linearly dependent.   This implies that both part a) and c) are correct? can someone please give the explaination for part b) and d)?


I'm not sure if it's actually grammatically correct at all. However, if it is, would it mean 'when help is needed' or 'when help is necessary' (the usual meaning of 'if need be'). In particular, I've had in mind a dedication "To someone, for support when it was needed", but phrased in a slightly more poetic way. However, I've been second guessing myself.   Thank you.


So, I've been struggling to solve the following exercise:  $$ \int_0^1 \sqrt{4-x^2}\,dx $$  Most of the solutions I've seen online use substitution using $x = \cos(t)$ or $x = \sin(t)$, however I'm wondering how the substitution without $\cos$ or $\sin$ would work? Any help is appreciated!


For weather forecasts on TV, many claims are made about the probability of single events like there is a “40% chance of thunderstorms tomorrow.” Can claims like this make sense given the definition of probability as a ratio of favorable outcomes to possible outcomes? Is there another way of thinking about probability that help these claims make more sense?


Faithful representations and character tables

Suppose an n-dimensional irreducible complex representation is not faithful.  Then a non-identity element gets mapped to the identity matrix in $GL_n(\mathbb{C})$ so that the value of its associated character on the conjugacy class of this element is $n$.  Thus, $n$ appears at least twice in the corresponding row of the group's character table.    I suspect the converse is true: if the row corresponding to an irreducible $n$-dimensional complex representation contains the dimension of the representation in more than one column, then the representation is not faithful.  I have looked in a few of the standard algebra references and have been unable to find a proof.  Can anyone point me in the right direction?  We proved this for $n=2$, but it seems that it would be difficult and messy to generalize.  I wonder if there is a simpler proof.


1) The number of books in economics that we need to buy (is/are) three.   or       2) A number of books in economics that we can buy for the course (is/are) available in the college book store.   Possible answers:  a)is  b)are  My approach:  I am confused here why is and are are used in the 1 and 2 sentence.  What they exactly mean according to subject verb agreement rules.


Cannot print outside the first elif block

I'm scanning log files (in a directory) for specific lines, need to output all in a text file.  For some reason, I do not understand, I have an error:  NameError: name 's' is not defined   I tried to assign Var s to a different Var but still cannot get around the problem.  In my code, I going to have one "if" and 5 "elif" like this:  If    var1 elif    var2 elif    var3 elif    var4 elif    var5 elif    var6 write.output_file(var1+var2+var3+var4+var5+var6+'\n')   Here is the code:  import os import re  start_tm  = ',"  Start Time' test_ID   = ' Host Name: '  cell_f = open('C:\\03\\OUTCOME.txt','w') given_path = 'C:\\02\\en15\\TST2'   for filename in os.listdir(given_path):     filepath = os.path.join(given_path, filename)     if os.path.isfile(filepath):         #print("File Name:   ", filename)          print("File Name\\Path:", filepath+'\n')          with open(filepath) as mfile:                     for rn_l in mfile:                 rn_l= rn_l.rstrip()                  if start_tm  in rn_l:                     *extraWords,st_t1 = rn_l.split('Time') # Grtting Start Time #                     s=str(st_t1)                     s=s.replace('"','')                      print ("Start String \"s\"is a TYPE  ", type(s))                     print ("START TIME STRING "+s)                  elif test_ID  in rn_l:                                           *extraWords,t_id1,t_id2, = rn_l.split( )                                                      print ("TESTER ID --->>> "+t_id1)                                                            t_id11,t_id12, = rn_l.split('Host')                       *w,e,c,d = re.split(" +", t_id11)                     cell = str(e+'_'+c)                     cell = cell.replace('[','').replace(']','')                     print ("Cell Line " + cell+'\n')


Meaning of centrifugal term in the mechanical energy of a orbiting planet

For a planet under the effect of gravitational force the mechanical energy can be written as  $$E=\frac{1}{2}\mu {\dot{r}}^2+\frac{L^2}{2\mu r^2}-\gamma \frac{m M}{r^2} \tag{1}$$  Where $\mu$ is the reduced mass of the system planet-star.  Consider now the term $$U_{centrifugal}=\frac{L^2}{2\mu r^2}$$  This is  a kinetic term in the mechanical energy expression (actually the one regarding $v_{\theta}$), but, since $L$ is constant, it has been rewritten as a function of the $r$ coordinate only. I read that this "makes" it a sort of potential term. That's clear, since it does not involve the velocity, but what is its real meaning?  The name "centrifugal" is because it sort of makes a "centrifugal barrier" which is the reason why the planets with non zero angular momentum stay in orbit instead of "fall" on the star.  I can see this from this graph if I think about the fact that kinetic energy cannot be negative.   But I still do not get the physical meaning of $U_{centrifugal}$. To what extent is $U_{centrifugal}$ to be considered a potential term and how does it prevent the orbiting planet to meet the star, mathematically, from $(1)$?


Given that the universe is expanding in the three spatial dimensions, is it possible that the time dimension is also changing over time?  If the rate of the passage of time is changing over time, would this effect match or partially match the observed and theorised effects of dark energy, inflation or both?


How can I backup old hard drives intact without Finder changing the "Date Modified" attribute inside each of the folders within the drive?

I currently have a lot of old hard drives I am trying to backup. I am backing them up onto a large external hard drive formatted to be HFS+. Each time I do the click and drag method of transferring the folders from the old hard drive onto a new folder I create in the large external, the "Date Modified" attribute inevitably changes each time I click into folders. How can I keep everything intact? Would I rely on dd, changing the permissions of the drives, etc? thanks


I would like to run Ubuntu on my new Thinkpad E470. Is Nvidia Optimus supported? It used to be that you would have to run the proprietary drivers with the dGPU enabled always instead of using the iGPU. Has the situation improved, especially regarding battery life? If possible I would just run with the iGPU as I don't plan to do any gaming. Would I just refrain from installing the proprietary driver to achieve this?


I have dict like this: d = {'A1': 200,  'A2': 150,  'A3': 100}  I want to multiply each element by 2 but the newvalue can't be more than 300. for above example my output will be.. d_final = {'A1': 300,  'A2': 300,  'A3': 200}  Can this be done using lambda or map??


Cannot get noise free realistic render in blender cycles

I am a beginner modeler, trying to get realistic result. I have tried my best but i cannot remove the white spots from my scene in cycles. Lighting is not looking realistic. Please help me how can i do that i have also attached link below.


How to ask an editor to exclude a reviewer when the reasons are personal

I am submitting a manuscript to a journal. I wish to exclude a colleague from being the reviewer of the manuscript. The journal has a single blind review: authors are known, reviewers are anonymous.  Question in short: The reason for this exclusion request are personal (see below), and I'm not sure I want to expose those reasons. What is the most effective ways to exclude a reviewer whom you don't trust to make a fair judgement?  Personal reasons for exclusion request::   We had a couple of harsh interactions. She had criticized me personally, and  had short arguments about our different attitudes towards publishing, writing and research.    I believe she has already wrote a "reject" review on my manuscript (for a different venue). To my judgment, she has standards that are uncommon in my research community, and so would judge my work on unconventional higher standards. Her personality, in my view, is harsh and critical (and unpleasant) and so each of her judgments are prone to be more negative than others, on average. She is related to the area of my manuscript (I have cited her manuscript and given her full credit for the work she did), and from her point of view me publishing the manuscript would, psychologically, be a personal disappointment, because her related work has not been published.    Questions: 1. Can I ask the editor not to send it to her review?    Should I ask the editor for this? Would it benefit me? How can I explain my request, and should I explain it?   Notes:  i) I don't want to write any of the reasons I listed above! Because they are mostly personal! And would put me in a very unpleasant situation psychologically at least.  ii) I believe that the review process in general is very subjective, and so there is always a way to consider the same work in two opposite perspectives: positive and negative. I believe the reviewer I want to exclude would highlight the negatives, and diminish the positives. And recommend a rejection.    This question is different from:  ,  because the current question asks how to exclude a reviewer  irrespective of the justifications of this exclusion. In other words, I'm not asking what are "sound reasons to exclude a reviewer",  but rather HOW to exclude her, independent from the existence of sound reasons.  More details of the difference:  In  the term "sound" is probably meant to be an objective term. However I claim that the reviewing process is not an objective process at all. Thus, there are at least three different interpretations of :   What kind of reason would be regarded as sound by the editor of the journal?   Or   Is there a set of objective reasons that the scientific community views as legitimate to exclude a reviewer?   Or   What can I, as an author do, to exclude a reviewer, if I think he/she has a grudge against me, irrespective of the objective reality, or the justifications of this act of excluding the reviewer?   The OP has not clarified whether he/she means 1, 2, 3 or another question. These are all different questions. I'm asking 3.  =====  I cannot merge my account with I am a guest (which is also me) because I don't remember the email I used for "I am a guest".


Are the new generic top level domains confusing to users? Should they be used or avoided?

If you are not aware, ICANN has approved quite a few generic top level domains and they intend to approve more. By generic, they mean regular old words will replace the common .com or .net, so we will have the option for domains names that end in words like:   .photography .media .education .finance .vision     I personally like the idea and I think it's been too long, but I'm not convinced I should switch my site over to an optimized version using one of these new tld's just yet. I think the average user, especially in America, sees something wrong with non .com's. Whenever I see a .net I always wonder why they don't have the .com. Also, I can just see myself getting "Is this a website" questions for a while if I start printing this on my business card and things.  What are the general advantages and disadvantages of using these generic tld's? If they are currently not a good idea, when will they be, if ever? What will it take to convince the populace that .com is not the gold standard in domain names anymore?  In my specific scenario, my company name is DigiVision Media. Our current website is . Recently, I've purchased  and . My current thoughts are that the main site can be moved to digivision.media and I can use digi.vision as a link shortener. What are the advantages and disadvantages of using these specific tld's for my circumstances?


How to convert a 2-dimensions char array into an array of strings

So I created a method that takes in a 2D char array that was originally from a text file and would end up outputting a string array. The only problem is the string.split() method doesn't take into account new lines or empty lines and I need the string.length() to be accurate to obtain a word count. Is there code that I am missing? This is the code I have so far.      public static String[] textString(char[][] text) {     String string = "";     for (int i = 0; i < text.length; i++) {         for (int k = 0; k < text[i].length; k++) {             string += text[i][k];         }         string += "\n";     }     String[] stringA = string.split(" ");     return stringA; }


Do small title edits constitute trivial edits?

Being a fairly new user something I don't seem to be able to locate is information on whether small edits to the title are considered as trivial edits. I see the usual recommendation when suggesting an edit is:     Avoid trivial, tiny one-letter edits unless absolutely necessary.   I can see the logic in that for most cases, but for example I just read a question with a title containing "Andriod" which would be trivial in one way but also affect the ability of users to locate the question using both the site and external search engines. Would it be frowned upon to suggest an edit for those cases?


Why do cylinders roll easily and not square or rectangular slabs?? Let us say both have same materiel and vertical dimensions? What is the reason for the slab always tends to slide?


what is this grammar? A plural noun with a singular object

Happy New Year all!  I was travelling in a public transport and saw the passenger notice. One of the statements on the notice has this information:     Passengers are advised to wear a surgical mask when having symptoms of   fever.   I am wondering why a singular object, i.e. a surgical mask is used. It sounds like to me that all passengers are advised to share the same surgical mask when aboard.  Could you explain it please?


Taylor Expansion of $\log(\frac{1+z}{1-z})$ around $z=0$  But $\log(1+z)=\sum_{n=1}^{\infty}(-1)^{n+1}\frac{z^n}{n}$  How can I continue from here?


Prove that $\exp(x)>0$ using only formal definition of exp

This problem would be easy if I could use the fact that $\exp(x)=e^x$, but I have to use the following definition: $$\exp(x)=\sum_{n=0}^{\infty}\frac{x^n}{n!}$$ I can also use the fact that $$\exp(x+y)=\exp(x)\exp(y)$$ So how do I prove, using those two equations, that $$\forall x\in \mathbb{R}:\exp(x)>0 $$ I mean, I can't just use the definition, because if $x<0$ then it isn't so obvious that $\exp(x)=\sum_{n=0}^{\infty}\frac{x^n}{n!}>0$. Can someone give me a hint or two?  Thanks!


As far as I've seen, there are only two types of vector multiplication defined, dot product/inner product which is defined in a vector space of any dimension, even infinite, and cross product, which is only defined in three dimensions. Are there more definitions of vector products?


Get BSSID (MAC address) of wireless access point from C#

How can I get the BSSID / MAC (Media Access Control) address of the wireless access point my system is connected to using C#?  Note that I'm interested in the BSSID of the WAP. This is different from the MAC address of the networking portion of the WAP.


I am a student from China. I'm going to attend Carnegie Mellon University in Pittsburgh, PA. I have planned my itinerary, where I will first take a flight from Shanghai to Los Angeles, then I will take another flight from LA to Pittsburgh (layover in Boston). Is there any issue at port of entry with this schedule?


Integral of an integral with variable limits

I'd like to prove the following but not sure where to start:  $$\int_{-\infty}^\infty\int_{-\infty}^a\frac{1}{\sqrt{2\pi}}\exp\left(-\frac{x^2}{2}\right)dx\frac{1}{\sqrt{2\pi\sigma^2}}\exp\left(-\frac{(a-\mu)^2}{2\sigma^2}\right)da\\ =\int_{-\infty}^{\frac{\mu}{\sqrt{1+\sigma^2}}}\frac{1}{\sqrt{2\pi}}\exp\left(-\frac{x^2}{2}\right)dx$$  Note that the hard part is due to the fact that the $a$ is a variable limit,   If it helps, the first term inside the integral is $\mathcal{N}(x;0,1)$ the second term is, $\mathcal{N}(a;\mu,\sigma^2)$


Map scale will only double and halve in QGIS

When I zoom in or out in QGIS, my scale will only halve or double respectively. This is the case whether I manually type the scale into the window at the bottom of the screen or select one of the set scale options. The scale automatically jumps to the nearest scale that is an exponent of base 2,256 (the smallest scale allowable for some reason), where the exponent is a multiple of 2. For example, if my scale is 144,447 and I type in or select 250,000, it automatically jumps to 288,895. This is occurring prior to adding any layers. I probably just have to uninstall/reinstall but though I would check here first.


Show that $\operatorname{Hom}_{R} (R,M) \cong M$

Let $R$ be a commutative ring with unit and $M$ a right $R$-module. Consider the assignment $\varphi: \operatorname{Hom}_{R} (R,M) \rightarrow M$, $f \mapsto \varphi(f) = f(1)$. Show that $\varphi$ is an isomorphism.  My approach: We have to prove $\varphi$ is a morphism, then $\varphi$ is a injection, surjection, hence $\varphi$ is an isomorphism. $\forall f,g \in \operatorname{Hom}_{R} (R,M)$ $\varphi(fg) = (fg)(1) = f(1)g(1) = \varphi(f) \varphi(g)$ $\Rightarrow \varphi$ is a morphism $\forall f,g \in \operatorname{Hom}_{R} (R,M)$ $\varphi(f) = \varphi(g) \Rightarrow f(1) = g(1) \Rightarrow f = g$ $\Rightarrow \varphi$ is injective $\Rightarrow \varphi$ is a homomorphism  How can I prove $\varphi$ is surjective to conclude $\varphi$ is an isomorphism? Sorry for my poor English.


So I have an Ubuntu 11.10 Live USB disk. I've noticed that my settings never get saved. Every time I reboot while in my Live USB and then boot back into it, all my settings and [un]installed programs revert back to default after the reboot. How can I set some sort of persistence on settings on a Live USB?


Can late recommendation letters have a negative impact on grad school application?

I am currently applying to some graduate programs. The schools I am applying to have all required recommendation letters from 3 people, and for many of the schools, the application deadline was today. Two of my professors have submitted their recommendation letters on time, but the last one - not being the epitome of a very organized person, sadly - has failed to meet the deadline. (Changing this recommender does not come into question, because she is my advisor, and she happens to be more familiar with me and my work than any other professor. Also, I cannot really ask anyone else to write a recommendation letter for me within such a narrow timeframe.)   This raises two questions for me: First, is the electronic system for submitting recommendation letters kept open beyond the deadline so that late recommendation letters can be received? (I understand that different schools may have different policies, but it would be relieving for me to know that my professor still has a chance to submit her recommendation. So I'd appreciate it if someone could inform me what the norm is in such cases. Before you ask, yes, I will e-mail the graduate admissions offices of the schools in question, too. But I do not think I can get a quick reply, as they are usually inundated with e-mails during the application season.)   Secondly, and more importantly, would the lateness of this recommendation leave a bad impression on the admissions committee?


Chrome on Windows: is there a keyboard shortcut to that brings up the contextual menu?

When typing in a text area in Chrome (e.g. in Gmail), I constantly have to reach the mouse to get spelling suggestions for a word that underlined in red, or to add a word to the dictionary.  Is there a keyboard shortcut that would show the contextual menu in that case, so you don't have to use the mouse to pick a suggestion or add a word to the dictionary?


Generating functions and central binomial coefficient

How would you prove that the generating function of $\binom{2n}{n}$ is $\frac{1}{\sqrt{1-4x}}$?  More precisely, prove that( for $|x|<\frac{1}{4}$ ):  $$\sum^{\infty}_{n=0}x^n\binom{2n}{n}=\frac{1}{\sqrt{1-4x}}$$  Background: I was trying to solve $$S=\sum^{\infty}_{n=0}\frac{(2n+1)!}{8^n(n!)^2}=\sum^{\infty}_{n=0}\frac{(2n+1)}{8^n}\binom{2n}{n}$$ Which if we let $f(x)$ be the generating function in question, would be simply $$f(x)+2xf'(x)$$ With $x=\frac{1}{8}$. Is there a simple proof of the first identity?  states it without a proper reference ( states it without proof). Is there an easier way of calculating $S$? (which is $\sqrt{8}$, by the way)


I have multiple *.jpeg pictures I like to merge into a single *.pdf file like so:  convert Blatt1.jpg Blatt2.jpg Blatt3.jpg Blatt4.jpg out.pdf   I am prompted with the following exception:  convert: attempt to perform an operation not allowed by the security policy `PDF' @ error/constitute.c/IsCoderAuthorized/408   What causes this problem and how can I fix it? I did some research but couldn't find anything about this particular problem.


In this sentence, "I still wished I could have done more", why isn't it saying, "I still wished I could do more"? Beauty and the Beast season 2 episode 16:   You okay? Yeah. [sic] I don't know, it's a little bittersweet, though. Yes, we finally stopped Sam, but, I don't know, it feels a little hollow, don't you think? We broke up their secret society. Just take a little bit of digging. We can put them away for a long time. Yeah, I still wished I could have done more, though. That's the old you talking. The one that used to take the law into his own hands. I like the new you better. Oh, you do, do you? Six years is a long time to hold onto all that pain and anger. Can't even imagine. I can.  I know the difference in meaning between 'could' and 'could have', but here, I can't seem to get the grammar.


Showing a particular part of toy contour tends to 0?

I am trying to solve:  $$\int_{-\infty}^{\infty}\frac{x\sin{x}}{x^2 + a^2}dx$$  I translate it to its complex equivalent:  $$\lim_{R \rightarrow \infty} \int_{-R}^{R}\frac{z\sin{z}}{z^2 + a^2}dz = \int_{C}\frac{z\sin{z}}{z^2 + a^2}dz - \int_{\gamma}\frac{z\sin{z}}{z^2 + a^2}dz$$  where $C$ is a half circle with radius $R$, above the real axis, and $\gamma$ is only the curved (top part) of the half circle.  I am trying to show that $$\int_{\gamma}\frac{z\sin{z}}{z^2 + a^2}dz$$ tends to 0 as $R \rightarrow \infty$.  I have that:  $$\left| \int_{\gamma}\frac{z\sin{z}}{z^2 + a^2}dz \right|\leq \pi R \cdot \sup_{\xi \in \gamma} \mid \frac{z\sin{z}}{z^2 + a^2} \mid$$  That is, the integral is upper bounded by the length of the contour multiplied by the supremium of the contour.   This leads me to:  $$\pi R \cdot \sup_{\xi \in \gamma} \left| \frac{z\sin{z}}{z^2 + a^2} \right| \leq \pi R \cdot \mid \frac{R}{R^2 + a^2} \mid$$  as $\sin{z}$ has a maximum of 1. But what other inequalities can I produce to show that this tends to 0 as $R \rightarrow \infty$?  Thanks.


How do I set $PATH to factory setting in Ubuntu 12.04 LTS

I executed this command from terminal:  export PATH=/home/ravinder/Java_Folder/Important_Programs/Servers/apache-maven-3.2.2/bin   So this is the only directory in my $PATH, I want to restore my path to default.


Set of probabilities distributions inside a infinite square well

Its been some years since I did the infinite square well. I am doing an econimics problems with probability distributions and I vaguly remember there being a name for either the wave functions in the inifinte square well, or the probability distributions. What is the equation if the well is between [0,1]? The equation of all possible probablity distributions, including the harmonics.


I want To do something like this: have a string "5+5" and when I convert it to integer, expected output want to be 10, but I get runtime error. Would appreciate your opinion.


Is it possible to make the object change color when touching another object?

I use Eevee and I decided to do synthesizer animation. Faced a problem that I do not know how to properly make the material. The essence of the material is the color change when animating the keys. Material in action:  Material nodes:  The problem is that the color change is associated with specific coordinates, and I cannot move the synthesizer. How to associate a color change, for example, with the touch of one object to another? Or change the color relative to the main part of the synthesizer? Maybe there is a better way?


Ubuntu says no LTS release available, trying to go 18.04 to 20.04.1

I am trying to upgrade to the newest LTS. What am I missing here? chris@chris-x1 ~> lsb_release -a  No LSB modules are available. Distributor ID: Ubuntu Description:    Ubuntu 18.04.5 LTS Release:    18.04 Codename:   bionic  chris@chris-x1 ~> sudo do-release-upgrade  Checking for a new Ubuntu release There is no development version of an LTS available. To upgrade to the latest non-LTS develoment release  set Prompt=normal in /etc/update-manager/release-upgrades.  Update with resolution  Run software-properties-gtk In the Ubuntu Software tab I selected the first 4 checkboxes (probably too many). This updates a bunch of caches Ran sudo do-release-upgrade  At this point the installation was kinda wonky. I had missing icons and my theme customizations were MIA. Couldn't run upgrades due to broken packages so I ran sudo apt dist-upgrade and this seemed to resolve everything. I can sort out the rest later.


Want to know what variable(query) is being passed around in the following lines of code

I understand that an array is being declared in line 3.  Line 6 queries the array. But how? I don't see any variable being passed around.  $(function(){      var currencies = ["stack", "over", "flow"];      // setup autocomplete function pulling from currencies[] array     $('#autocomplete').autocomplete({         lookup: currencies,         onSelect: function (suggestion) {         $('#outputcontent').html(thehtml);         }     });  });   Autocomplete Search:


Does PCIe 3×2 m.2 slot compatible with PCIe 3×4 nvme ssd?

My laptop has an m.2 slot which is PCIe gen 3×2 nvme SSD compatible. Now, Can I add a PCIe gen 3×4 nvme SSD On it? If yes then how much performance I will have to sacrifice? Both slot and SSD are 2280 in length.


It is known that in QFT the Euler-Lagrange equations are used to obtain the equations of the quantum fields. Nevertheless, from the path integral's point of view (where you integrate over all $\it{paths}$/possible field configurations, even if they don't satisfy Euler-Lagrange) the use of this equations makes only sense if you are looking for the classical field, since this one satisfies the least action principle.  So, why do we use these equations to obtain the ones for the quantum field?


I suppose getting the first revision of a particular post and get the date, right ?  How to do that?


Sharing a terminal with multiple users (with screen or otherwise)

I am setting up a server where there are multiple developers working on multiple applications.  I have figured out how to give certain developers shared access to the necessary application directories using the setgid bit and default ACLs to give anyone in a group access.  Many of these applications run under a terminal while in development for easy access. When I work alone, I set up a user for an application and run screen as that user. This has the downside that every developer to use the screen session needs to know the password and it is harder to keep user and application accounts separate.  One way that could work is using screen multiuser features. They do not work out-of-the-box however, screen complains about needing suid root. Does giving that have any downsides? I am pretty careful about using suid root anything. Maybe there is a reason why it isn't the default?  Should I do it with screen or is there some other intelligent way of doing what I want?


Why do files sometimes change but not the inode or vice versa?

When a file is updated then the corresponding inode gets updated. But sometimes the following condition occurs    file is same and inode is new  file gets changed but corresponding inode is older   Why ?


External force dependent on velocity on a Lagrangian

The question I have is, what conditions must satisfy an external force dependent on velocity so it can be a part of the lagrangian and Euler-Lagrange equations are still true.