Consider the bibliography file biblio.bib  @article{Sutter-TheFreeLunchIsOver,   author={Herb Sutter},   title={The Free Lunch Is Over: A Fundamental Turn Toward Concurrency in Software},   journal={Dr.\ Dobb's Journal},   year={2005},   volume={30},   number={3},   month= mar }   and the latex file main.tex  \documentclass{article} %\documentclass{IEEEtran} \usepackage[backend=biber,bibstyle=ieee]{biblatex} \addbibresource{biblio.bib} \begin{document} \cite{Sutter-TheFreeLunchIsOver} \printbibliography \end{document}   No matter whether we are using the article class or the ieeetran class, a "no." without a number is printed to the PDF obtained from pdflatex main && biber main && pdflatex main:    I have no idea why the number entry (number={3}) in the .bib file is ignored and whether the printing of "no." without a number is a bug or a feature. Apparently, it is hard to turn off, since the biblatex-ieee documentation also has this bug/feature as of March 2, 2017.  In any case, I'd like to avoid "no., " altogether or to have "no. 3," instead. Any help?

When compiling a tex file including references (by Texstudio editor and Miktex distribution) using biblatex with bibtex backend and ieee style, the results of the displayed references in the output pdf is messed up at the "volume" and "issue number" entries as follows:   The volume label "vol." is missing (Ref. 1 & 2 in the given example below). The numeric issue number "3" is missing (Ref. 1 in the given example). The issue number label "no." is displayed although NO input entry was being given (Ref. 2 in the given example).   If it helps, this behavior was noticed after the recent update of Miktex on March 11, 2017, including  package (ver. 1.2a 2017-03-02). As before which, everything was going fine!  So is this issue noticed by someone else? Is there any idea about the reason of such strange act by biblatex?  \documentclass{article} \usepackage{filecontents} \begin{filecontents}{reference.bib}     @article{author1,         author  = "George Green",         title   = "Basic latex",         year    = "2000",         journal = "Sharelatex Journal",         volume  = "10",         number  = "3",         pages   = "100--101"     }     @article{author2,         author  = "Carol White",         title   = "Basic studio",         year    = "2010",         journal = "Club Journal",         volume  = "20",         pages   = "200--201"     } \end{filecontents} \usepackage[backend=bibtex, style=ieee]{biblatex}  \addbibresource{reference.bib} \begin{document}     Hi there! \\     Ref 1 Green \cite{author1}. \\     Ref 2 White \cite{author2}.     \printbibliography  \end{document}   The output is as follows:


$ABCD$ is a convex quadrilateral such that $ \angle ABC\ge120^{o} , \angle BCD\ge120^{o}$ , then is it true that  $AC+BD>AB+BC+CD$ ?

In a convex Quadrilateral ABCD, $\measuredangle ABC  = \measuredangle BCD = 120^{\circ}$.Prove that:    $$ AC + BD \ge AB + BC + CD$$  My attempt  Tried to use cosine formula twice' i.e ($\triangle ABC$ and $\triangle BCD$) and tried to make and inequality.But couldn't prove.


For shooting portraits, why is 50mm preferable? For example with an APS-C sensor, why is it not ok to take photos with 35mm equivalent and simply crop them (to 50mm equivalent)? or take photos closer to the subject?  What's the difference?

What focal length or range of focal lengths are usually used for portraits?   What is used by professionals? Why would one select a certain focal length? What are the advantages and disadvantages of different choices, and are there certain situations where an unusual choice might be better?


LatexDraw is a PSTricks code generator for Latex. LatexDraw generates PSTricks codes of any fugure are drawn.    Are there any such tools that will generate pgf-tikz code of any figure for latex? If yes please suggest me. Thank you in advance.

Are there any   editors for ? Perhaps something similar to    but for PGF/TikZ?   If there is no WYSIWYG editor for this tandem, is there one perhaps that allows the user to easily generate PGF/TikZ templates?  Alternatively, how can I most easily generate PFG/TikZ code from a visual conception? Do people mostly code their PGF/TikZ graphics from scratch?


Often when I am writing emails or any other documents, I would like to use the irregular forms of dream (dreamt) or learn (learnt). But the computer spellcheckers always underline these words as being “wrong”, including right now on this very question that I am writing !  However, I know I have seen the words before. Don't know where, but surely I don’t have a habit of making up words of my own. Also, I believe that checking  confirms that the words do exist and should be correct?  Can someone please clear up what this is all about, and why (some?) spellchecking software treats dreamt and learnt as incorrect?

While perusing ShreevatsaR's answer to , it occurred to me that my own verbal usage is out of step with what I see in current American literature. When speaking in the past tense, I prefer to use the following forms:   dreamt (past tense of to dream) leapt (past tense of to leap) swept (past tense of to sweep) lit (past tense of to light)   However, when reading recently written novels, I see the more regular conjugation of the past tenses, which instead yields dreamed, leaped, sweeped, and lighted. Is it a difference of dialect (US - New England), register (university education), or (possibly) my age (early forties)? I am especially irritated by "lighted" because it takes so much more effort to say than "lit".  CLARIFICATION: Given Jon Hanna's answer below, I would just like to clarify the question a bit more. What I was originally after was why these separate verb forms exist in the same past tense. In other words, variations such as "I dreamt" vs. "I dreamed", not the variation between different forms in different pasts. I am not a linguist, so I hope that clears things up a bit.


I can't seem to find a white laser pointer for sale anywhere. Is it just me or is it somehow not possible to make it? I see only color laser pointers like red, green, blue, etc.

Why is it that, while there are red, green, and blue laser out there, I can't seem to find lasers that shine light over the full spectrum of colors"white lasers"? How hard is to make one? Is it possible?


In the following method, how can I prevent the contents of my array from being modified accidentally or otherwise?  Can it be done without changing the array to another type, such as a list?      public static int LinearSearch(int[] myArray, int target)     {         int idx = -1;         for (int i = 0; i < myArray.Length; i++)         {             if (myArray[i] == target) { idx = i; break; }         }         return idx;     }

Is it possible to somehow mark a System.Array as immutable.  When put behind a public-get/private-set they can't be added to, since it requires re-allocation and re-assignment, but a consumer can still set any subscript they wish:  public class Immy {     public string[] { get; private set; } }   I thought the readonly keyword might do the trick, but no such luck.


I am looking to find the intersection number of the affine plane curves $F=Y^2-X^3+X$ and $G=(X^2+Y^2)^3-4X^2Y^2$, and I need to do it with the order function of the local ring of $F$ at the origin.   So my attempt goes as follows:  $$k[X,Y] \twoheadrightarrow \Gamma(F)=k[X,Y]/(F) \hookrightarrow \mathcal{O}_{(0,0)}(F)$$ $$ G \mapsto \bar{G} = G\mod (F) \mapsto \frac{\bar{G}}{1} $$  Then I get the intersection number as $I((0,0),F\cap G) = \text{Ord}_{(0,0)}^F(\bar{G})$.  For the map onto the coordinate ring of $F$, I wrote $X\mapsto x, Y\mapsto y : y^2=x^3-x$. From there I thought that $\bar{G} = (x^2+(x^3-x))^3 - 4x^2(x^3-x)$. The map into the local ring (which I know should be a DVR as the origin is a simple point of $F$) is a natural injection, so I thought I should be able to write $\bar{G} = u\cdot t^n$ as one can do in a DVR. I can't! I'm not sure what is going wrong.

Firstly, I apologise that this question is specific to two polynomials. I understand that this post will not help a lot of people, and for that I am sorry. I will make it up to you all by anwsering lots more questions in the future! However, as my lecturers enjoy time off on the weekend, I am unable to ask this to anyone else who would know what the heck I'm talking about. Sorry if my notation is not widely used, I can elaborate more if required. Please excuse my poor Latex too.  Let:  $B = Y^2 - X^3 + X$, and   $F = (X^2 + Y^2)^3 - 4X^2Y^2$.  I wish to find the intersection number of $B$ and $F$ at $P = (0,0)$  i.e $I(P,F \cap B). $  However, I want to use the following proposition to do this:  If $P$ is simple on $B$ then $I(P,F \cap B) = ord_P^B(F) $.  I will omit proving that $P$ is simple on $B$ as I hope it is clear to see it is.  I know that $I(P,F \cap B) > M_p(F) * M_p(B) = 1 * 4 $, where $M_P(G)$ is the multiplicity of $P$ on $G$.  Now, consider the Image of $X$ and $Y$:  $K[X,Y] \longrightarrow \frac{K[X,Y]}{Y^2 - X^3 + X} \longrightarrow O_P(Y^2 - X^3 + X)$  $X \longrightarrow x$  $Y \longrightarrow y$  Where lower case denotes the image.  Then $ord_P^{Y^2 - X^3 + X}((X^2 + Y^2)^3 - 4X^2Y^2)$  Can be found by substituting $y^2 = x^3 - x$ into $(x^2 + y^2)^3 - 4x^2y^2$  Which gives:  $ord_P^{Y^2 - X^3 + X}(x^9+3x^8 -5x^6 -4x^5 +3x^4 +3x^3)=3$  i.e $I(P,F \cap B) = 3$, a contradiction to  $I(P,F \cap B) > 4$ as above.  The correct answer I know is 6, so where have I gone wrong?


Is it a good idea to redirect http://www.example.com to http://example.com or keep both ?

After having read various articles on this site about WWW or Non-WWW website setup, ,  and , and after having setup a correct redirection rule in .Htaccess to at least eliminate duplicate contents (currently the non-www solution (e.g. http://example.com) I have a feeling that my site rank less since I changed this.   My confusion was strengthened by these two opponents:     &     Could the change of www.example.com >> http://example.com have a factual impact on ranking?  say either is better or worse. Are they holding information back?  I am confused fellow folks...  As much as I would like to separate facts from fiction, I am aware that not all the good valid information is written. Not on google webmaster site and perhaps not elsewhere. If so it seems out of date!  Does or does not a WWW domain impact SEO/rank better than its NON-WWW version? (Given that you have setup a proper redirect to avoid duplicates and go with one)


I have noticed that some companies, in the weeks prior to a first listing day or IPO, have share prices listed. This often seems to happen before a spinoff, such as in Xylem's (XYL) 2011 spinoff from the ITT Corp. According to , XYL began trading under its own ticker effective Nov. 1; however, Yahoo and Google have price information . Another case is YUM Brands (YUM). I'm not as certain of the official ticker launch date for YUM spinning off from Pepsi, but Crunchbase lists it as Sep. 26, 1997; Google and Yahoo have .  I'm wondering how to interpret these prices. Are they OTC or privately traded prices from early shares, that are incorporated into the public price once trading begins? Are they somehow derived from the share price of the parent corporation? Is the "official ticker start date" somewhat fungible, and is public trading of these entities already occurring? Or is it something else?  I have observed this mostly with spinoffs, I believe, but there may be other situations where this pattern occurs.

The IPO date I find for the MMM Corporation is 1/13/1978 ().   Google Finance has price data going back to that date ().   However, Yahoo Finance goes back to 1970 (), as well as other ticker sources.  The main concern, of course, being: How can there be published price information from before an IPO?


Inside a class BaseClass I have a public function:  virtual void Call(){};   Inside of a derived class Archer I have the function:  void Call(){ cout << "whatever" << endl; };   I also have a vector set up:  vector<BaseClass> classes;   wherein I push 3 classes derived from BaseClass. The problem seems (to me, I'm probably wrong) to be that I am calling Call() from a reference to BaseClass even though I push them into the vector through a method like:  BaseClass Player::CharChoice(string character) {     if(character == "Archer") return *new Archer();     else if(character == "Knight") return *new Knight();     else if(character == "Sorcerer") return *new Sorcerer();     else cerr << "CHARACTER NOT DEFINED" << endl; };  for(int c = 0; c < chars.size(); c++) {     classes.push_back(CharChoice(chars[c])); }   If I instead set up a variable such as:  Archer *archer = new Archer();   and call Call(), it works how I would intend. I'm fairly new to C++ and cannot think up a solution to this.

As a general rule, I prefer using value rather than pointer semantics in C++ (ie using vector<Class> instead of vector<Class*>). Usually the slight loss in performance is more than made up for by not having to remember to delete dynamically allocated objects.  Unfortunately, value collections don't work when you want to store a variety of object types that all derive from a common base. See the example below.  #include <iostream>  using namespace std;  class Parent {     public:         Parent() : parent_mem(1) {}         virtual void write() { cout << "Parent: " << parent_mem << endl; }         int parent_mem; };  class Child : public Parent {     public:         Child() : child_mem(2) { parent_mem = 2; }         void write() { cout << "Child: " << parent_mem << ", " << child_mem << endl; }          int child_mem; };  int main(int, char**) {     // I can have a polymorphic container with pointer semantics     vector<Parent*> pointerVec;      pointerVec.push_back(new Parent());     pointerVec.push_back(new Child());      pointerVec[0]->write();      pointerVec[1]->write();       // Output:     //     // Parent: 1     // Child: 2, 2      // But I can't do it with value semantics      vector<Parent> valueVec;      valueVec.push_back(Parent());     valueVec.push_back(Child());    // gets turned into a Parent object :(      valueVec[0].write();         valueVec[1].write();          // Output:     //      // Parent: 1     // Parent: 2  }   My question is: Can I have have my cake (value semantics) and eat it too (polymorphic containers)? Or do I have to use pointers?


As logged on in Stack Overflow and clicking the Stack Exchange dropdown (top of window client area, far left) my expectation was to be automatically logged in to Server Fault...  That did not happen ... WHY?

While on other Stack Exchange sites like Game Development and Code Review they recognize if I am logged in to Stack Overflow or Stack Exchange and after refresh request from page I am logged in there too. This autologin feature does not happen on Super User.  Even if I go to the login page, it does not offer me automaticaly to login with my connected SE account.  I know I am registered on Super User as I even asked a question there.


I watch VLC for a while, then about 15 min. later, it sleeps.  Where can i find the how to disable the screen-saver or how to disable sleep?

I am using Ubuntu 11.10 and my screensaver keeps coming on while I'm watching a movie.  I don't remember this happening in 11.04 and can't remember how to stop it?


What is the relationship between Kendall tau and the area under the receiver operating characteristic curve (AUC ROC)?

I am trying to understand the relative behavior of the following rank correlation statistics:   Spearman coefficient Kendall Tau / Concordance percentage Normalized Gini coefficient (area under curve of percentage captured versus percentage observations) Normalized Area under ROC curve (for binary classifiers)   I don't believe any of these are functionally related to the others.  The accepted answer  references  and Spearman and Kendall are highly correlated (as one would expect).  Are there good intuitions behind/discussions of relative (across datasets) or absolute (for a given dataset) differences for (any pair of) these measures?


I am trying to write a small C++ library to do simple matrix calculations. It consists of a Matrix class with static member functions altering given matrices.  I have one function which adds a scalar to each element, however the loop isn't working:  // Member function to add a scalar to the matrix void Matrix::add_scal(double** arr, double s) {     for (size_t x = 0; x < sizeof(arr) / sizeof(*arr); ++x) {         Serial.println("test");         for (size_t y = 0; y < sizeof(*arr) / sizeof(**arr); ++y) {             arr[x][y] += s;         }    } }   "Test" is only printed once and the inner loop isn't run at all. Here is the function I use to create a matrix:  double** Matrix::init(int rows, int cols) {     double** temp = new double*[rows];     for (int i = 0; i < rows; i++) {         temp[i] = new double[cols];         for (int j = 0; j < cols; j++) {             temp[i][j] = 0.0;         }     }     return temp; }   The following two lines create a matrix and are supposed to add a scalar to it:  double** test = Matrix::init(3, 3); Matrix::add_scal(test, 2.5);

First off, here is some code:  int main()  {     int days[] = {1,2,3,4,5};     int *ptr = days;     printf("%u\n", sizeof(days));     printf("%u\n", sizeof(ptr));      return 0; }   Is there a way to find out the size of the array that ptr is pointing to (instead of just giving its size, which is four bytes on a 32-bit system)?


I trained an image auto-encoder on a large dataset, and now have for every image, an n-dimensional feature vector. This vector is not spatially correlated to the image. I now used this embedding space directly for classification, using fully connected dense layers. I have 55 classes, and the vector dimensionality is 1024. Even a single classification layer on top of the embedding, means 1024*55 parameters and it very easily overfits.  Since my embedding is not spatial in any sense, does it make sense to use Trees for classifying over the embedding space? I.e, feed the feature vectors to a tree based classification method, instead of a fully connected network. Are there cases, depending on the data, where trees outperform neural networks. If yes, what are such cases?

I was experimenting with different modelling methods including KNN, Decision Trees, Neural Networks and SVN and trying to fit my data to see which works the best. To my surprise, the decision tree works the best with training accuracy of 1.0 and test accuracy of 0.5. The neural networks, which I believed would always perform the best no matter what has a training accuracy of 0.92 and test accuracy of 0.42 which is 8% less than the decision tree classifier.   Could someone please explain the circumstances/cases where neural networks could have low accuracy when compared to a modelling technique like the decision tree. I had tried my neural network with different configurations like:  1 hidden layer and 1 neuron : Train Accuracy 34% Test Accuracy 42% 7 hidden layers and 5 neurons in each layer: Train Accuracy 79% Test Accuracy 42% 1 hidden layer and 100 neurons: Train Accuracy 34% and Test Accuracy 35%   but not in a single case, I found the neural network to beat the decision tree test accuracy of 50%.


We are adding a bathroom fan to our bathroom that never had one.  We found power from the attic that we may be able to use.  This power joins the hallway ceiling light to the hallway switch.  We would be using a 2 pole switch (top switch for vanity light and bottom switch for exhaust fan). Is it possible to take power from that attic power? If so how and would we need 12/3 wire.

In our attic we have a junction box that has the power wire connected to a hallway ceiling light. Can we tap into that to get power to install a bathroom exhaust fan? We would be putting in a double rocker light switch in the bathroom (top switch would be for the vanity light and the bottom switch would be for the exhaust fan switch). How would we wire this?


So yesterday I changed password on ubuntu, but today I wanted to revert it so I entered user accounts and tried to change it, but sadly I could not. It told me password is not secure enough or something then i disabled log in options, but i want it back as it was     I cannot use sudo as I don't know what password to enter.  Now I can not change password at all  any way to make it as it was?

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


I posted , for which I received two answers.  is particularly long (and very well explained). I would like to post another answer with further info, an elaboration of the two answers, etc.  To improve readability of my answer, I would like to be able to hyperlink to a point in the middle of answer #2, not to its beginning (it would be almost useless in this case). In other cases, it might be convenient to link to points in the middle of other questions, or in answers to different questions.  Then, I propose that hyperlinking to points in the middle of questions/answers is allowed.

I admit this feature request is probably somewhat limited in useful scope, but I'm throwing it out there anyway. Inspired by , and because I want to use it on , I'm requesting that name be supported on a tags in posts.  On very long answers, such as the closing/migration guidance answer, this would allow direct linking to the specific closure reason. This would then allow us, when someone , to link directly to the appropriate reason and description thereof.  I recognize the limited scope of this, however, I have seen other long answers that could stand to have that kind of "deep" linking ability as well.  (The original incarnation of this post had either name or id, but preferenced name. Per Koper's answer, which I agree with, I took out the idea of supporting id, because Koper's right -- too dangerous.)


I'm new to ubuntu . I have to setup ftp server on ubuntu , vsftpd service always failing after basic installation and changes in /etc/vsftpd.conf file.  I've done below changes after install vsftpd software .  write_enable=YES local_umask=022 chroot_local_user=YES allow_writeable_chroot=YES pasv_min_port=40000 pasv_max_port=40100  I'm getting below error while checking the status of the service. Please help  root@helmor:~# sudo systemctl status vsftpd ● vsftpd.service - vsftpd FTP server    Loaded: loaded (/lib/systemd/system/vsftpd.service; enabled; vendor preset: enabled)    Active: failed (Result: exit-code) since Sun 2017-06-04 19:13:59 IST; 22s ago   Process: 1801 ExecStart=/usr/sbin/vsftpd /etc/vsftpd.conf (code=exited, status=2)   Process: 1798 ExecStartPre=/bin/mkdir -p /var/run/vsftpd/empty (code=exited, status=0/SUCCESS)  Main PID: 1801 (code=exited, status=2) Jun 04 19:13:59 helmor systemd[1]: Starting vsftpd FTP server... Jun 04 19:13:59 helmor systemd[1]: Started vsftpd FTP server. Jun 04 19:13:59 helmor systemd[1]: vsftpd.service: Main process exited, code=exited, status=2/INVALIDARGUMENT Jun 04 19:13:59 helmor systemd[1]: vsftpd.service: Unit entered failed state. Jun 04 19:13:59 helmor systemd[1]: vsftpd.service: Failed with result 'exit-code'.  I'm using this guide

I'm on Ubuntu 15.04 and I just installed vsftpd.  When I run the command service vsftpd status, I get the following output:  vsftpd.service - vsftpd FTP server   Loaded: loaded (/lib/systemd/system/vsftpd.service; enabled; vendor   preset: enabled) Active: failed (Result: exit-code) since Fri 2015-10-09 19:18:50 IST;  3min 11s ago Process: 2981 ExecStart=/usr/sbin/vsftpd /etc/vsftpd.conf (code=exited, status=2) Process: 2979 ExecStartPre=/bin/mkdir -p /var/run/vsftpd/empty (code=exited, status=0/SUCCESS) Main PID: 2981 (code=exited, status=2)  Oct 09 19:18:50 harshal-Lenovo-B40-70 systemd[1]: Starting vsftpd FTP  server... Oct 09 19:18:50 harshal-Lenovo-B40-70 systemd[1]: Started vsftpd FTP server. Oct 09 19:18:50 harshal-Lenovo-B40-70 systemd[1]: vsftpd.service: main process exited, code=exited, status=2/INVALIDARGUMENT Oct 09 19:18:50 harshal-Lenovo-B40-70 systemd[1]: Unit vsftpd.service entered failed state. Oct 09 19:18:50 harshal-Lenovo-B40-70 systemd[1]: vsftpd.service failed.   I checked /etc/vsftpd.conf, it exists and I did not find anything wrong in it. How can I solve this?


I received an email from the university saying that the similarity report for my work identified that one of my answers shows a similarity to the answer within the script of a fellow student. They are asking to write a statement and explain what happened. Basically myself and my partner...we are studying the same thing and he copied one of my answers as he came from a night shift and he was very tired and he couldn’t think. Could you please advise what to answer. He received the same email and he has to write a statement as well. What should he write? Thank you for your answers and advice.

I got caught cheating in a two-hour engineering exam consisting of 100 multiple choice questions which was done online through the  e-learning software. I feel like my life is almost over.  Having not studied well and having no time to study, I decided to cheat. I know there are no excuses for cheating. Before the exam I dug up research about moodle exams, and it turned out you can take the exam anywhere you want to as long as you have the quiz password. Taking advantage of this, I went up to my engineering library and asked a close friend who was taking the exam to send me the quiz password before he starts.  What I had prepared:   Calculator (was not allowed during the quiz). Printed material (consisted of more than 200 pages). Google search engine (on a laptop ready to help). Whatsapp (to ask questions for a friend who took the quiz last year).   As I sat down, I did the first 50 questions, suddenly the quiz froze and moodle told me:      you are not allowed to take the exam from this location.   While I was leaving, one instructor responsible for the course (there are 5) came and found me. She accused me of cheating, took my mobile and made come with her to a huge office where two instructors searched all my mobile (took the name of my friend who gave me the password), and started talking to me, asking for all details of this crime. They took and confiscated my phone and looked at everything: Whatsapp conversations, all my emails, and images. The instructor took the mobile from my hand without asking me and kept it with her. It seems that the instructors are going to report me as well as my friend who sent me the password for the exam.  The university's Student Code Conduct said that cheating will result in one of the following: a Dean's Warning, Suspension, or Expulsion. If any of that happens, my future is over. A dean's warning will cancel my financial aid. A suspension would be for at least two years, and coming back would require a lot of work. An expulsion will be definite.  I've learned the lesson about cheating, now how can I fix this? How can I prevent the five instructors from reporting me? It's obvious that I should speak to them, but what should I say? What can I do? My future is almost over, but many of you are teachers and instructors here, what can I do to fix this?    EDIT: Wow, it has been almost 3 years. I would like to update on how I dealt with the situation.   Lesson: It was obvious to never ever cheat under any circumstances, and it was not whether you'd get caught or not.    Consequences: I received a Dean's warning but the financial aid wasn't revoked. However, I couldn't stay in the department as engineering was not for me and I was even ashamed to stay in the university.  What happened next: I transferred to an ABET-accredited Computer Science institution and I graduated with distinction in 2.5 years. It was extremely stressful as I had taken 6 major courses (18 credits) in one semester, but I had to do it.  Future plans: I'm going for an MSc in Computer Science in St Andrews next year.


I want to activate my users in my django server when they follow a link from their email with a token, like this:  http://127.0.0.1:8000/user-activation/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJ1c2VybmFtZSI6ImdhYm8iLCJ1c2VyX2lkIjoxOSwiZW1haWwiOiJsYXRvcnJlZ2FiQGdtYWlsLmNvbSIsImV4cCI6MTQ2NDE3ODk1N30.5FDKdxKxWuOkqe3rMNE-eHwmtrlWpD7EZ-EXw0yQM3U/   I have this pattern   url(r'^user-activation/(?P<id>\w+)/', views.UserActivation.as_view()),   But it's returning 404. I searched a lot and nothing seems to work. What am I doing wrong?  I couldn't find any answer that works reading    nor    Edit:   I've read the post    But there was no example about receiving hyphens and dots at the same time, which was what caused my confusion.  The marked answer solved my problem. Thanks

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


Please find below a snapshot of my Table Of Content page. When I click on links to pages ii, v, vi, and vii, the first page (title page) shows up. But the links for chapter pages work correctly. How can I solve this issue?

Inspired by question :  When do I need to invoke \phantomsection?  In what condition is invoking \phantomsection necessary?


I've seen this in several designs. What purpose do these serve?

When you look at the board, there is a weird part of the PCB right of the top left mounting hole. There is also another one above the top right mounting hole.    ****                            ↓ Here's one                                            **   This image is directly copied from .    What are these? Is this just created when this is manufactured (to grip to to move the board or to grip during solder mask creation), or does it serve a purpose (something to hook a multimeter to)?


I have a figure to be used in an IEEE conference paper. I have written the tikz code in separate file (fig.tex) as illustrated below  \documentclass[tikz]{standalone} \begin{document} \begin{tikzpicture}[>=Stealth]  \begin{axis}[ylabel={Label y},xlabel={Label x}] ... \end{axis} \end{document}   I compile this file and include the pdf in main.tex . However, the fonts in the figure are not the same as the one in main.tex which has IEEEtran as the documentclass.  How do I get the font settings of IEEEtran in fig.tex ?

I'd like to define the font size in a standalone document so that it is identical to the one in my "real" big document.    I have several standalone-documents. In those, I'd like to implement an option which makes the standalone-documents simply adhere to what is written in font-config.tex (see MWE)--which is currently empty.  (In my main document, I of course define the size as an option for the documentclass (scrreprt), but I am a bit clueless what to do here since standalone does not take \KOMAoptions obviously.)  What should I write into font-config.tex so that it basically mimics whatever I define for my real document?  MWE  \documentclass[ 12pt ]{standalone}  \usepackage[T1]{fontenc} \usepackage[utf8]{inputenc} \usepackage{lmodern}  \input{font-config} %\KOMAoptions{fontsize=11pt}  \usepackage{ tikz, }  \begin{document} \begin{tikzpicture}[font=\small] \draw (0,0) coordinate (A) (1,1) coordinate (B) ; \draw[thick] (A) rectangle (B) node[anchor=south west, align=left] {Words abc.\\Test.}; \end{tikzpicture} \end{document}


public class SearchCity {      public void tc() throws InterruptedException, IOException {         System.setProperty("webdriver.chrome.driver", "C:\\Selenium\\chromedriver.exe");         WebDriver driver = new ChromeDriver();         driver.navigate().to("http://localhost/allmapview/");         Thread.sleep(3000);          ArrayList<String> data0 = readExcelData(0);         ArrayList<String> data1 = readExcelData(1);          for(int i=0; i<data0.size(); i++) {             driver.findElement(By.xpath(".//*[@id='from']")).sendKeys(data0.get(i));             Thread.sleep(3000);              driver.findElement(By.xpath(".//*[@id='to']")).sendKeys(data1.get(i));             Thread.sleep(3000);              driver.findElement(By.xpath(".//*[@id='calculate-route']/div[3]/div/div[2]/button")).click();             Thread.sleep(8000);              String strText = driver.findElement(By.id("google_dt")).getText();             String strText1 = driver.findElement(By.id("mmi_dt_2")).getText();              FileInputStream fis = new FileInputStream(new File("D:\\Screenshots\\Book1.xlsx"));             XSSFWorkbook workbook = new XSSFWorkbook (fis);             XSSFSheet sheet = workbook.getSheetAt(0);             XSSFRow row = sheet.getRow(1);             XSSFCell cell = row.getCell(2);             cell.setCellValue(strText);             XSSFRow row2 = sheet.getRow(1);             XSSFCell cell2 = row2.getCell(3);             cell2.setCellValue(strText1);             fis.close();             FileOutputStream fos =new FileOutputStream(new File("D:\\\\Screenshots\\\\Book1.xlsx"));                 workbook.write(fos);                 fos.close();               File screenshot = ((TakesScreenshot)driver).getScreenshotAs(OutputType.FILE);             FileUtils.copyFile(screenshot, new                     File("D:\\Screenshots\\Screen" +i));             Thread.sleep(2000);              driver.findElement(By.xpath(".//*[@id='calculate-route']/div[3]/div/div[3]/input")).click();             Thread.sleep(3000);            }     }      public ArrayList<String> readExcelData(int colNo) throws IOException {         File src = new File("D:\\Screenshots\\Book1.xlsx");         FileInputStream fis = new FileInputStream(src);          XSSFWorkbook wb = new XSSFWorkbook(fis);         XSSFSheet sheet1 = wb.getSheetAt(0);         Iterator<Row> rowIterator = sheet1.iterator();         rowIterator.next();          ArrayList<String> list = new ArrayList<String>();         while(rowIterator.hasNext()) {             list.add(rowIterator.next().getCell(colNo).getStringCellValue());         }           System.out.println("List :::"+list);         return list;      }        public static void main(String[] args) throws IOException, InterruptedException {         // TODO Auto-generated method stub         SearchCity city = new SearchCity();         city.tc();   I have written a code to read an excel file to fill some entries in a webpage and I want to fetch some data from that webpage and write it into my excel sheet, but I got NullPointerException in my code at different lines, and it is not a duplicate question I think, so please suggest some answers.     Exception in thread "main" java lang NullPointerException         at SearchCity SearchCity tc(SearchCity java:56)         at SearchCity SearchCity main(SearchCity java:104)

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


I have a Google sheet that has multiple spreadsheets, let's say Sheet1, Sheet2 and Sheet3. In all of those spreadsheets, column H is a particular field of which I want all the values with blanks filtered out.  I'm not sure where to begin with this, I've tried unioning all the columns into one in another sheet and then filtering all of them but can't get the union to work.   End result would ideally be a single list of all the values from  Sheet1.colH, Sheet2.colH, and Sheet3.colH.

I have the following QUERY  =query(XX!A2:A;" select A where A>'50' ")   and  =query(YY!A2:A;" select A where A>'50' ")   how do I combine these two data sources so I don't have to have two separate columns they process data to?   best would be if the 1st row from XX is followed by the 1st row of YY, 2nd row followed by 2nd row... and so on If the above option is not easily possible, it is OK for one query to be followed by the second one (if I expect correctly that the start of the second will be moved with newly added data into the first one)


I am having problems with the following series:  $$ \sum_{n=1}^{\infty} q^n \sin(n\alpha), \quad|q| < 1. $$  No restrictions on $\alpha$. I need to find out whether it converges and if yes, evaluate its sum.  I can see that it's convergent using the comparison test. But I fail to find its sum. So far I tried grouping subsequent terms and using trigonometric formulas, but it didn't help me much.   Where should I start when I see trigonometric functions in a series? In general, I have no idea where to take off in such situations.  Thanks in advance.

I need to prove that $\dfrac{a \sin(bx)}{1 - 2a \cos(bx) + a^2} = \sum_{n=1}^\infty a^n \sin(nbx)$ where $|a| < 1$.  It seems that this can be proved by using Euler's formula identities for $\cos(bx)$ and $\sin(bx)$ and substituting $z = e^{ibx}$. From that, I get $$ \dfrac{a \sin(bx)}{1 - 2a \cos(bx) + a^2} = \dfrac{a (z - 1/z)}{2i(1 - a(z + 1/z) + a^2)}$$ $$= \dfrac{a (z^2 -1)}{2i(z - a(z^2 +1) + za^2)}$$ $$= \dfrac{a (z^2 -1)}{-2ai(z^2 - z(1-a^2)/a + 1)}$$  I don't understand what I am supposed to do next.


My Initial implementation approach in .cpp is like the following:  using namespace std; ... template <typename T> void print2dvector(vector<vector<T> > v) {     for(int i = 0; i < v.size(); i++) {         for(int j = 0; j < v[i].size(); j++) {             cout << v[i][j] << " ";         }         cout << endl;     } }   The declaration in .h file is the following  template <typename T> void print2dvector(std::vector<std::vector<T> > v);   Here is how I use it,  print2dvector<int>(vec_of_vec);   The compile stage passes, but failed in linking stage. The error is the following:  Undefined symbols for architecture x86_64:   "void print2dvector<int>(std::__1::vector<std::__1::vector<int, std::__1::allocator<int> >, std::__1::allocator<std::__1::vector<int, std::__1::allocator<int> > > >)", referenced from:    spiral_matrix_ii_Challenge::Execute() in spiral_matrix_ii.o ld: symbol(s) not found for architecture x86_64 clang: error: linker command failed with exit code 1 (use -v to see invocation)   Please let me know if I miss anything conceptually in implementing this.

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


Let $A$ be a closed subset of $\mathbb R^n$ :   1) Is it true that for some smooth function $f: \mathbb R^n \to \mathbb R$ , $A=f^{-1}(\{0\})$  2)Is it true that for some smooth function $f: \mathbb R^n \to \mathbb R$ , $A$ is the set of all critical points of $f$ ?

For each closed set $A\subseteq\mathbb{R}$, is it possible to construct a real continuous function $f$ such that the zero set, $f^{-1}(0)$, of $f$ is precisely $A$, and $f$ is infinitely differentiable on all of $\mathbb{R}$?  Thanks!


Due to  I will have to revert back to Ubuntu 12.04 LTS when . I see that , LibreOffice 3.5, and other outdated (functionality-wise) software.  Though I have no problem compiling Firefox, LibreOffice, and other apps, I would like to know how could I find out what the currently available software versions are. How could I check this before installing Ubuntu 12.04? I suppose that at least Firefox would have been updated (due to Mozilla update policy), but I would like to check first before I install.  Is there some way to query the Canonical repos for the latest software versions available for 12.04 from my current 12.10 system? Would it be easier to check from some web interface on Launchpad? I'm looking for something similar to aptitude show foobar, but for which I could specify the distro version that the results would be returned for.  I could install a virtual machine to check, but I find that cumbersome and not really practical as a day-to-day solution should I ever need to do a similar check in the future.

How can I check the version of the available package in the Ubuntu repositories without installing it?


I am unsure how to return all possible sequences within a list of lists. It is important that the index in the main list corresponds to the position in the sequence. Input: list = [["Lys", "Arg"],['Gly'],["Phe", "Tyr"]]  Output: ["Lys", "Gly", "Phe"] ["Arg", "Gly", "Phe"] ["Lys", "Gly", "Tyr"] ["Arg", "Gly", "Tyr"]  Thanks in advance.

How can I get the Cartesian product (every possible combination of values) from a group of lists?  Input:   somelists = [    [1, 2, 3],    ['a', 'b'],    [4, 5] ]   Desired output:  [(1, 'a', 4), (1, 'a', 5), (1, 'b', 4), (1, 'b', 5), (2, 'a', 4), (2, 'a', 5) ...]


I am trying to make a data pack in Minecraft 1.16 where you can equip gear without taking up space in the player's inventory.  I have it set up that when a player holds a specific item, a donkey is teleported in front of them.  So then the player can access its inventory, but I don't want the players riding the donkey.  How do I make the donkey unrideable, but players can still access its inventory.  I tried putting an armor stand on the donkey that works to prevent me from riding the donkey, but I can't access the donkey's inventory.  I can't use a chest in a minecart because I can't make that invisible without removing the minecart texture (which I don't want to do).  If mules work but donkeys don't that's fine. Any Ideas?

I'm working on a custom crafting system and I'm trying to use donkeys/mules as a way for players to put in crafting items. The mule's chest is used for inserting items and having an item output. This is how I spawn one such mule:  /summon minecraft:mule ~ ~ ~ {Tame:1b,Silent:1b,NoAI:1b,ChestedHorse:1b,ActiveEffects:[{Id:14b,Amplifier:1b,Duration:1000000,ShowParticles:0b}]}   Using this, and invisible mule, and players can access the chest, where the custom crafting would take place. The only problem with this is that the player is able to ride the mule, so I add a passenger to prevent this.  /summon minecraft:mule ~ ~ ~ {Tame:1b,Silent:1b,NoAI:1b,ChestedHorse:1b,Passengers:[{id:"minecraft:armor_stand",Marker:1b,Invisible:1b}],ActiveEffects:[{Id:14b,Amplifier:1b,Duration:1000000,ShowParticles:0b}]}   However, doing so makes the player unable to access the chest. Is there any way to make a mule unrideable, but also making that mule's chest accessable to players?


I'm practicing testing multiple models on the iris dataset with python and I have the following code: for name, model in models:     # kfold     kfold = KFold(n_splits=10, random_state=7, shuffle=True)     # score     score = cross_val_score(model, X_test, y_test, cv=kfold, scoring='accuracy')     # Add results     results.append(score)     names.append(name)     msg = "%s: %f" % (name,score.mean())     print(msg)  Every time I run this I get slightly different results for the score.mean() can anyone explain to me why this happens and how to reduce the variability of the results. I'm new to machine learning so any help would be great. Thanks.

So I am using LASSO in order to reduce the amount of independent variables (~150) I have for my logistic model (n=1200). However, when doing so, the end result (i.e. number of predictors) it chooses varies depending on the seed I provide. 2-3 predictors are consistent, but then sometimes others are added. I guess this is due to the cross-validation for the best lambda parameter often used for LASSO. However, it just seem so inconsistent.  I mean I am using bootstrap in order to validate my results. So in the end I end up with meaningful standard errors, frequency of predictors, corrected statistics etc., but that doesn't change the fact, that the main model, defined on the original data, is kind of random depending on the seed.  How does one "solve" this ? Run the "main model" (i.e. original data) with 100-1000 different seeds to see which predictors are most frequently chosen, and then chose the model that actually has these predictors, or is there anything else that could be recommended ?


Let's assume we have following query (greatly simplified, of course):  SELECT * FROM MyTable Where A or B   The query takes about 30 seconds to run  When I rewrite the query as  SELECT DISTINCT * FROM  (     SELECT * FROM MyTable Where A     UNION ALL      SELECT * FROM MyTable Where B ) q   then I get results in about 4 seconds. I have seen the same pattern multiple times in the past - replacing OR with UNION improves performance a lot  Question: is there a way to make SQL Server to convert all those OR conditions to UNION internally, while preparing execution plan?  I was trying to find a query hint but no luck so far. We are using SQL Server 2016 SP2

Why is the following query slow?  select count(*)   from [dbo].[mt_dispatch_link]     , [dbo].[_mt_dispatch] [_mt_dispatch]  where   (mt_dispatch_link.contract_id_1 = _mt_dispatch.contract_id       and mt_dispatch_link.dispatch_id_1 = _mt_dispatch.dispatch_id)     or   (mt_dispatch_link.contract_id_2 = _mt_dispatch.contract_id       and mt_dispatch_link.dispatch_id_2 = _mt_dispatch.dispatch_id)     It takes over 10 minutes, and then I tend to stop it at that point. My question is more about how to make sense of the query plan.  Looking at the query plan I can see that the bottom clustered index scan is returning about 250000 records, but the cost is 0% and it is being put into a temporary table.  The top index scan is about 25000 records.  But the cost of 95% comes from the nested join. What conclusions should I draw from this?  The above query plan shows two index scans, does that mean it is doing 25000 + 250000 index scans, or does it mean that it is doing 25000 * 250000 index scans?  If I change the query to this (adding FORCESEEK):  select count(*)   from [dbo].[mt_dispatch_link]     , [dbo].[_mt_dispatch] [_mt_dispatch]       WITH (FORCESEEK)  where   (mt_dispatch_link.contract_id_1 = _mt_dispatch.contract_id       and mt_dispatch_link.dispatch_id_1 = _mt_dispatch.dispatch_id)     or   (mt_dispatch_link.contract_id_2 = _mt_dispatch.contract_id       and mt_dispatch_link.dispatch_id_2 = _mt_dispatch.dispatch_id)   I end up with a much better plan and the query runs instantly:    I ran update statistics on both tables. Didn't fix it unfortunately. The table design is not very good, so I think SQL Server doesn't really understand and is thus coming up with a poor query plan. Some more info about the table design at .  Why is the query optimiser not coming up with the optimum plan?


When I run applications like Synaptic or Gparted, I'm prompted by the lovely screen on the left, to enter my admin password. I think this has something to do with pkexec.  But when I run applications using gksu I am prompted by the ugly window on the right.   I'd like to run Nautilus or Gedit sometimes as root and be prompted by the nicer window on the left.     Update 2015/4/09 6:00pm     $ pkexec gedit gdk_mir_display_open Failed to connect to Mir: Failed to connect to server socket: No such file or directory Unable to init server: Could not connect: Connection refused  (gedit:9664): Gtk-WARNING **: cannot open display:

Reading these questions and answers:        brought me another one that will create problems for new users of that command:   How to configure pkexec for easy usage?   For example when doing the following:  (Opening a file in terminal)     pkexec nano /etc/mysql/my.cnf     (Opening a file in GUI)     pkexec gedit /etc/mysql/my.cnf     The last one gets the following error:   pkexec must be setuid root   Now this brought me the following questions:   How to configure pkexec to avoid getting this? Similar to how sudo/gksu behave when doing the same thing (they only ask for the password). If applicable, how to tell it to not ask for a password after the first time applying it to a command (or including the first command if configurable)? Where to save the configuration file if not yet existing? Is there a GUI app to configure pkexec usage (Policy Kit)?


I am looking to learn quantum physics and I know a few things I need to learn but do I  need to learn algebraic trig to learn quantum mechanics?

Could someone experienced in the field tell me what the minimal math knowledge one must obtain in order to grasp the introductory Quantum Mechanics book/course?  I do have math knowledge but I must say, currently, kind of a poor one. I did a basic introductory course in Calculus, Linear algebra and Probability Theory. Perhaps you could suggest some books I have to go through before I can start with QM?


I am a Canadian PR holder with an Indian passport. I am planning to visit London for 3 days on my way to India. What kind of visa will I need? I will be going out in London and rent a car to see the whole city.

Is there a website or some other way to find out if I need a transit visa for a short stop in the UK on my way somewhere else? Ideally this should give me the answer for all nationalities, and take into account any other visas I may have.


I would like to know if it is safe to connect in parallel the outputs of a power supply like , and in case it is feasable, how to proceed.

I have recently been working on a custom sound system in my living room. For the subwoofer, I am using a 1000W amplifier. This is currently running off of a 12V computer power supply that outputs around 650W (The power supply shuts off at a certain volume because of lack of power). I have another power supply (not a computer power supply) that is 500W but has a voltage of 13.5V, not 12. I've read that this voltage is actually better for running car audio equipment and I am using another 13.5V power supply for the head unit to power the highs and mids.  I am wondering if it would be possible for me to connect these two power supplies in parallel to increase the power to this amplifier since they are both safe voltages. Would this be possible? Would I need to use a resistor to match voltages? Or is this just not a good idea altogether?  Update: This is car audio equipment so high power ratings should not be a shock.


I am running Ubuntu within Ubuntu using VirtualBox. I want to switch to virtual terminal on guest system. When I press Ctrl+Alt+F4 within guest system, host system switches to virtual terminal instead of guest system. Although, lock screen (Ctrl+Alt+L) working as expected within guest system.  My question is, is there a way to make my guest system to switch virtual terminal.  VirtualBox version is 5.2 and both guest and host machines are running Ubuntu 16.04.

I have a Virtual Box machine with Ubuntu.  I need to send Ctrl+Alt+F1 to guest machine, but when I press them it is captured by host.  How can I fix it ?


If I have two connected nodes of different widths, which are aligned on the left (west) side, the connector between them is diagonal (or -| which I don't want for this application).  Here's what it looks like:  \begin{tikzpicture}[>=latex, thick]     \tikzstyle{all nodes}=[shape=rectangle]     \tikzstyle{box}=[draw]     % % Nodes     \node[box, label=above:{Short box}](init)     {This box is short};     \node[box, below=of init.west,            align=left, anchor=west, label=below:Long box]     (country)     {         this box is really really really long. Much longer.     };      % % Connectors     \draw [->] (init) -- (country); \end{tikzpicture}     I'd really like that diagonal arrow to lead from the bottom centre of Short box to wherever is required on the top of Long box to make the arrow vertical.  Is that possible?

When drawing a line between two nodes in TikZ, you can specify the anchors on the beginning and end nodes in order to control how the line is drawn.  I would like to specify the anchor on the beginning node, and the angle at which the line is drawn, and let TikZ figure out where it will intercept the end node.  The usual use case is when I'm connecting to a "big node" and I would like the lines to be vertical.  I can cheat by placing a coordinate behind the big node, drawing a line to the coordinate instead, and then drawing the big node so that it covers things up.  However this won't work if I need to put an arrow on the end.  I could try to calculate the intercept coordinate on the edge of the big node manually, but that seems against the TikZ spirit.  |- doesn't work in this case.  \documentclass[10pt]{minimal} \usepackage[active,tightpage,pdftex]{preview} \usepackage{tikz}  \begin{document} \begin{preview}  \tikzstyle{RectObject}=[rectangle,fill=white,draw,line width=0.5mm] \tikzstyle{line}=[draw] \tikzstyle{arrow}=[draw, -latex]   \begin{tikzpicture}   %%%%%%%%%%%%%%%%%%%%%%%%   %%  LEFT SIDE   %%%%%%%%%%%%%%%%%%%%%%%%   \draw (1,0) node[RectObject] (Small1A) {A};   \draw (3,0) node[RectObject] (Small1B) {B};   \coordinate (Cheat1A) at (1,2);   \coordinate (Cheat1B) at (3,2);   \path [line] (Small1A.north) -- (Cheat1A);   \path [line] (Small1B.north) -- (Cheat1B);    % need to draw Big Node last to cover up our cheating   \draw (2,2) node[RectObject, inner xsep=1cm] (Big1) {Big Node};    \draw (2,4) node[text width=4cm] (text1) {L: Cheating to control line orientation. Arrows would be hard.};    %%%%%%%%%%%%%%%%%%%%%%%%   %%  RIGHT SIDE   %%%%%%%%%%%%%%%%%%%%%%%%   \draw (7,2) node[RectObject, inner xsep=1cm] (Big2) {Big Node};   \draw (6,0) node[RectObject] (Small2A) {A};   \draw (8,0) node[RectObject] (Small2B) {B};   \path [arrow] (Small2A) -- (Big2);   \path [arrow] (Small2B) -- (Big2);    \draw (7,4) node[text width=4cm] (text2) {R: No cheating. Arrows easy. Can't control line orientation.}; \end{tikzpicture} \end{preview} \end{document}   Here's a side-by-side example of "cheating", which shows what I want to be able to do, and "not cheating", which does not do what I want.    The left side of this example shows what I want to be able to do, except I want to do it without cheating, and I'd like to put arrows on the end of the lines.


I am stuck on a problem in having my counter increment.  I'm not sure what I am doing wrong though. Sorry if this is a beginner mistake, but I have not found a solution where I understand or helps yet.    public static int duplicates(String[] text, int numWords){             int currentCount = 1;             for (int i=0; i<numWords-1; i++){                 for (int j=i+1; j<numWords; j++){                     if (text[i] == text[j]){                         currentCount++;                      }                 }                }              return currentCount;         }

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


I don't have any experience in Lightning so far, currently we have a Challenge to Develop a new VF page to replace a page in Console. It seems to be Lightning type of page. Please find the image below.    How can I get start with the development?

Where should I start learning? There are various topics to learn like Objects, Classes, Apex, Visualforce, SOSL, SOQL, Triggers, etc. There are so many options out there to start learning. I couldn't decide what topic to learn first, and then step by step get proficiency in all aspects of Saleforce.


There are some people, who always need to do something. They can't just sit and relax. If they are on the job, they constantly try to change something (e. g. propose new approaches to existing tasks). If they go on vacation, they visit all possible places.  These people are mentally healthy, even though sometimes you may suspect them having ADHD or being in a maniac phase of manic-depressive disorder.  Note that most of the time their active nature is beneficial (stuff is get done, innovation happens), but can also have negative consequences (e. g. they may bully everyone to start a project at work, which doesn't make sense economically).  Also, they are very active not because they have to, but because it seems to be part of their nature.  What do you call such people?  In Russian there is an idiom of people having an awl in the anus (шило в попе), which makes it hard for those guys and gals to sit still. I'm looking for something similar in English.

Moving here does not mean moving to a new city or something like that. I am talking about the people that just can't stay at one place. It is impossible for them to sit put at one place and relax.


I am looking at a flight from Ecuador to Singapore which stops in JFK.    Do I need a transit visa if I am not leaving the airport?    The layover is four hours, the same on my return. Also stops in Toyota. I have an Ecuador passport.

In Europe usually you don't need to go through immigration to change planes (unless you are entering/exiting Schengen). Is it the case in the US as well? May I catch a connecting flight on one of the US airports if I don't have US visa?


I'm in my first coding class and still getting the hang of it.  I need to write a code that will print a line of '+' a certain amount of times in the same line but also new lines at the same time depending on the number entered.  So far I only have the code to print '+' once each time in a new line:  def draw_a_line_of_plus(length):   for i in range (length):     print ('+', end='')

I'd like to do it in Python. What I'd like to do in this example in C: #include <stdio.h>  int main() {     int i;     for (i=0; i<10; i++) printf(".");     return 0; }  Output: ..........  In Python: >>> for i in range(10): print('.') . . . . . . . . . . >>> print('.', '.', '.', '.', '.', '.', '.', '.', '.', '.') . . . . . . . . . .  In Python print will add a \n or space, how can I avoid that? Now, it's just an example, don't tell me I can first build a string then print it. I'd like to know how to "append" strings to stdout.


For the first part,      I am trying to show that any subring of $E/F$ is a subfield where $E$ is an extension of field $F$ and all elements of $E$ are algebraic over $F$.    My solution is to just show an element of a subring has an inverse and we will be done. Let $R$ be the subring and $r\in R$. Since $r$ is algebraic over $F$ we can find a polynomial $p(x)=a_0+a_1x+a_2x+\cdots + a_nx^n$ such that $p(r)=0$ where $a_i \in F$. Using this expression I explicitly computed what an inverse of $r$ must look like.      However, the second part of the question asks to prove that any subring of a finite dimensional extension field $E/F$ is a subfield.   Is the second part of the question redundant? I didn't use whether the extension was finite or infinite for my solution in the first part. Will both the parts have the same solution that I wrote above?

Let $E|F$ be an algebraic field extension and a ring $K$ such that $F\subseteq K\subseteq E$. It is true that $K$ is a field?


Ubuntu, sed remove ze if ze is alone on the line  The closest I got is sed "s/\bze\b//g" and sed "s/^\bze\b//g" which does not produce the desired result.  Before sed:  ze.com example.ze zero.com ze   After sed:  ze.com example.ze zero.com

I have a txt file  123 456 789 456 123456   I want to delete specific characters from the file i.e (123).  I tried with  $ sed -i '/123/d' dummy.sh $ vi dumm.txt 456 789 456   In the below command when I run both the words (123 and 123456) are getting deleted but I need to delete only 123 from the file   $ sed -i 's/123//g' dummy.sh $ vi dumm.txt 456 789 456 456   when I run the below command the 123 is getting replaced with null.  Can anyone say how to delete a whole line if it contains only specific number?


I know about some idiotic EU "law" that made every damn website add the most obnoxious garbage ever: a huge "warning" about how they are "using cookies", which doesn't let you do anything until you "accept" it. I've been forced to use a special browser extension to get rid of that cancer; it was pure torture, as bad as blinking, screaming advertisements.  When I was running websites, I never once implemented this. Anyone who did/does has something wrong in their head as far as I'm concerned. It's a typical example of blindly following any madness just because "it's a law", regardless of whether it makes any sense or not.  I'm now wondering if not having that crap (which pisses off every single visitor) actually has ever resulted in any kind of "legal action", and if so, but who? I would argue that even if this did happen, the savings in goodwill from not subjecting every visitor to that crap would make up for it no matter how big the monetary penalty is.

EUROPA websites must follow the Commission's guidelines on privacy and data protection and inform users that cookies are not being used to gather information unnecessarily.    Many people find this EU cookie directive, when implemented, a broken toy law and a waste of time for all parties involved and because of that don't implement it.  4+ years further, have any of the bodies in the EU sued or attempted to sue any site(s) for not displaying a notice that cookies were in use?  It seems the EU got really quiet about it after the firestorm meteor shower of OP resentment hailed down uponith them and I would love to know how far they actually took it.


On my website, I will have an error message that says:  * Please Choose an Option   Should an be upper or lower case?

We have created a  where children can learn Vegetables and Fruits. When the child answers a question they receive a notification to tell them whether they got it wrong or right.  My opinion is that the capitalization of the letters should not be in sentence case, so for example,       Wrong Answer - Try Again    is incorrect in my opinion. I think it should be       Wrong answer - try again    i.e. written as a normal sentence.  Is there a particular way it should be?  For reference purposes, here is the game just in case my question does not make sense. Click on a vegetable to see the message.


I know that my direction for this proof is correct, but it feels like my reasoning for few things are off because I am still trying to grasp the Schroder-Bernstein so I would appreciate the guidance! Please note that I am novice on a good day..   Let A be an infinite set and B a countable set.  Prove $|A|=|A\cup B|$  Suppose $B\subset A$, meaning union of A and B are disjoint, this results in $|A\backslash B|=|A|=|A\cup B|$ according to our claim.  This also means that $A\backslash B$ is also infinite, since A is infinite. Let C be a denumerable subset of $A\backslash B$, and since B is countable and C is denumerable their union must also be denumerable. This means that  $|B\cup C|=|C|$ such that there is a bijection $f:B\cup C\rightarrow C$. Now suppose we split A into two pieces, i.e. $A\backslash (B\cup C)$ which is the same as $(A\backslash B)\backslash C$. We already have a bijection $f:B\cup C\rightarrow C$, and we can form another bijection $g:(A\backslash B)\backslash C\rightarrow (A\backslash B)\backslash C$ meaning to itself. Let h be the function that is $f\circ g$, which by definition of composite functions, another bijection such that $h:A\rightarrow A\backslash B.$

I am going over my professors answer to the following problem and to be honest I am quite confused :/ Help would be greatly appreciated!     Let $A$ be any uncountable set, and let $B$ be a countable subset of $A$. Prove that $|A| = |A - B|$    The answer key that I am reading right now follows this idea:  It says that $A-B$ is infinite and proceeds to define a new denumerable subset $A-B$ as $C$. Of course since $C$ is countably infinite then we can write $C$ as ${c1,c2,c3...}$   Once we have a set $C$, we know that the union of $C$ and $B$ must be denumerable (from another proof) since $B$ is countable and $C$ is denumerable.  This is where I start to have trouble. The rest of the solution goes like this...  Since the union of $C$ and $B$ is denumerable, there is a bijective function $f$ that maps the union of $C$ and $B$ to $C$ again. The solution then proceeds to define another function $h$ that maps $A$ to $A-B$.   I am just so lost. The thing is I don't even understand the point of constructing a new subset $C$ or defining functions like $f$ or $h$.  So I suppose my question is in general, how would one approach this problem? I am not mathematically inclined unfortunately, and a lot of the steps in almost all of these problems seems arbitrary and random. Help would be really appreciated on this problem and some general ideas on how to solve problems like these!!!  Thank you so very much!


User pushes the button on site and by this ajax request starts than Server returns True or False. If the result is True than another ajax request is to be processed, but I am getting nothing (I guess inside of ajax).  Here is my js code:  document.getElementById('next_in').onclick = function (){      $.ajax({         data: {             login: document.getElementById('log').value,             password: document.getElementById('pass').value         },         type: 'POST',         url: '/user_login',         success: function (localRes) {             if(localRes.result==true){                 $.ajax({                     data: {                         login: document.getElementById('log').value                     },                     type: 'POST',                     url: '/private',                     success: function () {                         alert('Connected')                     },                     error: function () {                         alert('There is a mistake!')                     }                  });             }             else{                 alert('Incorrect login or password!');             }         }     }); }   and python code:  @app.route('/private', methods=['POST']) def private():    return render_template("rates.html")   Then after pushing the button on site I recieved "Connected", but then (I supposed this event calls my python function) there is no redirect to rates.html...   I do not understand what is wrong here..   Please. I hope at leaste to understand problem of which side it is and how to fix it?   Thank you!  EDIT ONE  I did shorten my python function just to show the issue. In actual case before return render_template("rates.html") there is huge proccessing (request to database, some calculation and so on), so python function is:  @app.route('/private', methods=['POST'])     def private():        # ******************** HUGE processing        return render_template("rates.html")   Sorry, if I confused you, but simple redirect to .html is not what I want. I want calling python function in nested ajax requests.

I'm using $.post() to call a servlet using Ajax and then using the resulting HTML fragment to replace a div element in the user's current page. However, if the session times out, the server sends a redirect directive to send the user to the login page. In this case, jQuery is replacing the div element with the contents of the login page, forcing the user's eyes to witness a rare scene indeed.   How can I manage a redirect directive from an Ajax call with jQuery 1.2.6?


In my car there is a  charger it is producing 5v/2amps,but there is a clock in my car, this clock is connected to this car charger it need only 5v/500ma,how can i reduce the current to this clock?

Power supplies are available in a wide range of voltage and current ratings.  If I have a device that has specific voltage and current ratings, how do those relate to the power ratings I need to specify?  What if I don't know the device's specs, but am replacing a previous power supply with particular ratings?  Is it OK to go lower voltage, or should it always be higher?  What about current?  I don't want a 10 A supply to damage my 1 A device.


Trying to log in with JavaScript disabled does not work.  Using a Stack Exchange email and password, the "Log in" button does nothing.  This is likely because the <input type="button"> instead of standard HTML type="submit", which doesn't trigger a POST.  However, pressing Enter does submit the form and let me login.

I'm using stackoverflow.com with JavaScript off. I accept this comes with somewhat less functionality, however for the most part SO works fine.  If I look at the home page (), every single button on there except for two types works with JS off.  The first second is that the "x Votes; y answers;z views" mouse-over indicates they're links but clicking them does nothing. This one is less of an issue because the user can still click the question title, and they're only implied buttons anyway.  The second (and bigger) issue is the "Add" buttons next to "Favorite Tags" and "Ignored Tags". These are explicit buttons that don't do anything with JS off. There is no working JS substitute for them (the "tag subscriptions" link itself works, but the page it goes to doesn't work with JS off, but that's another bug report).


I want to find all Sylow 2-subgroups of $D_6 = \{ e, r, r^2, r^3, r^4, r^5, s, sr, sr^2, sr^3, sr^4, sr^5\}$.  $r$ is the rotation element, and $s$ is the reflection element.  $|D_6| = 12$, and the order of a Sylow 2-subgroup of $D_6$ must be the highest order of $2$ that divides $12$ which is $4$.  Also, the order of each element of the Sylow 2-subgroup must be a power of $2$.  Using this information I was able to come up with only this Sylow 2-subgroup $\{ e, s, r^3, sr^3 \}$.  However, I do not know if there are more Sylow 2-subgroups of $D_6$.  Lastly, I figured out, by Sylow's Third Theorem, that the number of Sylow 2-subgroups of $D_6$ must divide the order of $D_6$, and also be congruent to 1 mod 2.  The first part of this statement suggests that there can only be either $1,2,3,4,6$, or $12$ Sylow 2-subgorups of $D_6$, but I am unsure of what congruent to 1 mod 2 means.  I know that 1 mod 2 $= 1$, but what does congruent mean?

I am trying to describe the Sylow $2$-subgroups of an arbitrary dihedral group $D_n$ of order $2n$.   In the case that $n$ is odd, $2$ is the highest power dividing $2n$, so that all Sylow $2$-subgroups have order $2$, and it is fairly easy to describe them.  However, if $n$ isn't odd, we may factor a power of $2$ out and write $|D_n|=2^{k}m$ for some odd integer $m$.   There is  that there exist precisely $m$ Sylow $2$-subgroups, but it does not provide an explicit description of such subgroups in the case $n$ is odd.   Additionally, someone has asked a similar question in the past, and they claim to give a description of the Sylow $2$-subroups in the case $n$ is odd, but I can not find a source or an explanation. The question is .     Can anyone provide a description of how one may determine precisely the Sylow $2$-subgroups for the case $n$ is odd?    Thank you.


If I run this query on our system:  SELECT STATS_DATE(t.object_id, s.stats_id) AS stdate, *  from    sys.stats s WITH (NOLOCK) INNER JOIN sys.tables t WITH (NOLOCK) ON t.object_id = s.object_id WHERE t.name LIKE 'mytable%'   I sometimes see that the stats_date function returns NULL.  This should not be possible according to BOL, except if there is an error. It does not state which error.  The table is quite big, 11 billion rows. If I run:  UPDATE STATISTICS fct.mytable ( pk_mytable)   the stats_date comes back again as not null.  Why is the date null, and how can I prevent that?  It is only the stats for the primary key that is NULL.  If I run:  DBCC SHOW_STATISTICS ('fct.MyTable', 'IX_MyTableID')    it comes back with the 3 result sets that I expect. If I run:  DBCC SHOW_STATISTICS ('fct.MyTable', 'PK_MyTable')    It returns:

We have a large partitioned SQL Server database utilizing incremental statistics. All of the indexes are partitioned aligned. When we try to rebuild a partition online by partition all of the statistics disappear after the index is rebuilt.   Below is a script to replicate the issue in SQL Server 2014 with the AdventureWorks2014 database.  --Example against AdventureWorks2014 Database  CREATE PARTITION FUNCTION TransactionRangePF1 (DATETIME) AS RANGE RIGHT FOR VALUES  (    '20130501', '20130601', '20130701', '20130801',     '20130901', '20131001', '20131101', '20131201',     '20140101', '20140201', '20140301' ); GO  CREATE PARTITION SCHEME TransactionsPS1 AS PARTITION TransactionRangePF1 TO  (   [PRIMARY], [PRIMARY], [PRIMARY], [PRIMARY], [PRIMARY],    [PRIMARY], [PRIMARY], [PRIMARY], [PRIMARY], [PRIMARY],    [PRIMARY], [PRIMARY], [PRIMARY] ); GO  CREATE TABLE dbo.TransactionHistory  (   TransactionID        INT      NOT NULL, -- not bothering with IDENTITY here   ProductID            INT      NOT NULL,   ReferenceOrderID     INT      NOT NULL,   ReferenceOrderLineID INT      NOT NULL DEFAULT (0),   TransactionDate      DATETIME NOT NULL DEFAULT (GETDATE()),   TransactionType      NCHAR(1) NOT NULL,   Quantity             INT      NOT NULL,   ActualCost           MONEY    NOT NULL,   ModifiedDate         DATETIME NOT NULL DEFAULT (GETDATE()),   CONSTRAINT CK_TransactionType      CHECK (UPPER(TransactionType) IN (N'W', N'S', N'P')) )  ON TransactionsPS1 (TransactionDate);   INSERT INTO dbo.TransactionHistory SELECT * FROM Production.TransactionHistory --  SELECT * FROM sys.partitions --  WHERE object_id = OBJECT_ID('dbo.TransactionHistory');  CREATE NONCLUSTERED INDEX IDX_ProductId ON dbo.TransactionHistory (ProductId)    WITH (DATA_COMPRESSION = ROW, STATISTICS_INCREMENTAL=ON)     ON TransactionsPS1 (TransactionDate)  DBCC SHOW_STATISTICS('dbo.TransactionHistory', IDX_ProductId); PRINT 'Stats are avialable'    ALTER INDEX [IDX_ProductId] ON [dbo].[TransactionHistory] REBUILD    PARTITION = 9 WITH (ONLINE = ON , DATA_COMPRESSION = ROW)  PRINT 'After online index rebuild by partition stats are now gone' DBCC SHOW_STATISTICS('dbo.TransactionHistory', IDX_ProductId);  PRINT 'Rebuild the stats with a rebuild for all paritions (this works)'  ALTER INDEX [IDX_ProductId] ON [dbo].[TransactionHistory] REBUILD    PARTITION = ALL WITH (ONLINE = ON , DATA_COMPRESSION = ROW,    STATISTICS_INCREMENTAL = ON)  PRINT 'Stats are back' DBCC SHOW_STATISTICS('dbo.TransactionHistory', IDX_ProductId);  PRINT 'Works correctly for an offline rebuild by partition' ALTER INDEX [IDX_ProductId] ON [dbo].[TransactionHistory] REBUILD    PARTITION = 9 WITH (ONLINE = OFF , DATA_COMPRESSION = ROW)      --stats still there   DBCC SHOW_STATISTICS('dbo.TransactionHistory', IDX_ProductId);  ALTER INDEX [IDX_ProductId] ON [dbo].[TransactionHistory] REBUILD    PARTITION = 9 WITH (ONLINE = ON , DATA_COMPRESSION = ROW)  DBCC SHOW_STATISTICS('dbo.TransactionHistory', IDX_ProductId); PRINT' stats are gone!!!!!!'   As shown, we cannot rebuild indexes by partition online without losing all statistics for index. This is a major maintenance issue for us. It almost appears that stats incremental option needs to be a part of the single index rebuild syntax or the online option needs to properly handle it like the offline option does.   Please let me know if I am missing something?  Updates:  As far as our need for incremental stats: We are partitioning on an internal customer id and not a date. So when a new client is brought in (large back-load of data) we can simply update the stats for the partition and quickly avoid any ugly plans being created for this new customer. I think I will file it with Microsoft as a bug and see what they have to say and go with the solution of just re-sampling the stats for that partition.  Connect bug report:    Update: Microsoft has confirmed that it is a bug.


I’m trying to use the following definition to show the result listed below.  Definition of Convex Function: Let $f$ be a real-valued function on an open interval. Let $a,b$ be points in the domain with $a<b$. Function $f$ is convex if $$f(a)+\frac{f(b)-f(a)}{b-a}(x-a)\ge f(x)$$ for each $x\in(a,b)$.  Goal: The function $f$ (defined as in the above definition) is convex if and only if $f(x)$ does not have any points below any tangent line for each $x$ in the domain.   Attempted Proof: Suppose $f$ is convex. Let $x_1,x_2$ be points in the domain with $x_1<x_2$. From the definition of convexity given above, for each $x\in(x_1,x_2)$, $$f(x_1)+\frac{f(x_2)-f(x_1)}{x_2-x_1}(x-x_1)\ge f(x)$$  Let $x_*$ be a point between $x_1$ and $x_2$. For now, let $x\in(x_*,x_2)$. The tangent line to this point is given by $$t(x)=f(x_*)+f’(x_*)(x-x_*)$$  The Mean Value Theorem guarantees the existence of $c\in(x_*,x_2)$ such that $$f’(c)(x-x_*)=f(x)-f(x_*)$$  Next, consider the difference between the function and tangent line; our goal is to show this is nonnegative: $$f(x)-t(x)=f(x)-(f(x_*)+f’(x_*)(x-x_*))=f(x)-f(x_*)-f’(x_*)(x-x_*)=f’(c)(x-x_*)-f’(x_*)(x-x_*)$$  So, we have $$f(x)-t(x)=(x-x_*)(f’(c)-f’(x_*))$$  This is where I’m having difficulties performing any meaningful manipulation. If this can be shown true, the result for the left portion of the function can be shown analogously.

Consider a real-valued convex function $f$ defined on an open interval $(a,b) \subset \mathbb{R}$. Let $x,y \in (a,b)$.  I want to prove that \begin{equation} f((1-\lambda)x + \lambda y) \leq (1-\lambda)f(x) + \lambda f(y) , \lambda \in [0,1]\implies f(y) + f'(y)(x-y) \leq f(x) \end{equation} No other assumptions (regarding the second derivatives) is allowed.  While both facts are really obvious and clear, I am unable to prove this without making additional assumptions.


The markdown used on Stack Exchange and the one used on GitHub are fairly similar, but have some subtle differences. For example, on GitHub, you can add ``` before and after a set of lines to format them as code, but that doesn't work on Stack Exchange.  As someone who writes markdown on both sites, I find these subtle differences inhibit the development of muscle memory (e.g. I often type ``` on Stack Exchange, only to realize (again) that it doesn't work and erase and correct it).  Is there any plan /  path forward to converge these two flavours of Markdown?  Note: I gave ``` as an example, but I'm asking about general convergence between the two flavours, rather than one particular extension.

An official spec for  with reference implementation was released recently.   Will these specs (with optional additions like MathJax for those sites that already have it) be adopted? There are some places where the implementation deviates,  [link](foo(and(bar))) amongst others.   Or will it break too many posts?


I need to buy a prepaid SIM card with internet connection in London just for 6 days.  Any suggestion and prices?

Next month I am traveling to country X, where I would need Y minutes of calls, Z text messages and most importantly Q megabytes of data. How can I find the cheapest/most reliable SIM card for my needs?


Which of the following two sentences is correct?  He must decide who to be. He must decide whom to be.  I can think of arguments for both sides, but I'm not sure. To elaborate, is who(m) the object of decide, the subject of be, or the object of be? Does the infinitive form of be have any bearing on the answer? And is there anything else to consider about the position or role of who(m) in this particular sentence that would inform the answer? The answers to the linked question  say to "substitute he and him for who and whom." However, that doesn't give a clear answer in this context, because neither of those pronouns sounds right: "He must decide to be he"? "He must decide to be him"? Normally we'd use a reflexive pronoun here ("He must decide to be himself") and it's not clear what case that corresponds to.

I can never figure out whether I should use who and whom. Most people use who for both colloquially, but some people say this is not correct.  What’s the rule for using who and whom correctly?


Reading  I see the following phrase:     Parallel Computing uses more than one core. A core (also called   processor) is capable of executing one thread of computation.   From that description I take away that core and processor are synonyms - they mean the same thing.   But when I look at the MacBook Hardware description I can see the following:    From that description the MacBook has 1 processor but 2 cores. This cannot be right.   Where is the mistake? Is the definition incorrect I have found? Or is the MacBook display showing incorrect content?

After reading alot of links, it bothers me that there is so much overlap between simple definitions such as CPU, processor, core, etc.       Let's clarify first what is a CPU and what is a core, a central processing unit CPU, can have multiple core units, those cores are a processor by itself, capable of execute a program but it is self contained on the same chip.        A CPU, or Central Processing Unit, is what is typically referred to as a processor.   So which one is it?  A CPU (central processing unit) contains (1-many) cores. Each core can execute (1-many) threads depending on hyper-threading technology - it does the actual computation sort to speak.  So what is a processor? Does it refer to the CPU, the entire chip as  a whole? Does it refer to one core on a CPU? And what exactly does multiprocessor/multicore mean? Are they synonymous?


I don’t know how to formally prove that if $$\lim_{x \to \infty} \left(f(x+1)-f(x)\right) = L,$$ then $$\lim _{x \to \infty} \frac{f(x)}{x} = L$$  where L is a constant and the function is limited whit in a limited domain. I tryed to expand the definition of infinit limit but have no idea where to go on from there or even if that is the best aproach.

Let $f:(a,\infty)\to\mathbb{R}$ be a function. Suppose for each $b>a$, $f$ is bounded on $(a,b)$ and $\lim_{x\to\infty}f(x+1)-f(x)=A$. Prove  $$\lim_{x\to\infty}\frac{f(x)}{x}=A.$$  Here we assume $f$ to be arbitrary and no further conditions. $f$ could be continuous,discontinuous,as long as it fits all assumptions. I have some trouble with the intermediate steps.


No StackExchange site was accessible a short while ago. Even  said it was unreachable. See there ping results (16.Feb.2014 10:51   0 ms.)  What had gone wrong?

Stack Overflow was down for a long time here, probably about an hour.  What was the cause?


How to prove that prove that $S$ is weak$^*$-continuous from $Y^*$ to $X^*$ if  an only if $S=T^*$ for some $T\in B(X,Y)$  Thanks for any hints.  To show that  $T$ is continuous is straight forward but inverse is hard.

Let $X, Y$ be Banach spaces, $S \in B(Y^{*}, X^{*})$. Does such operator $T \in B(X, Y)$ exist so that $T^{*}=S$?  I suppose that the answer should be - no. Are there any hints that might help in constructing a counterexample?  Any help would be much appreciated.


I'm writing my masters thesis in computer science and I haven't found a good source for evaluation criteria of the protocols I'm looking at in my thesis.   What are the requirements before I can say "There is nothing on evaluation criteria in the literature."   Is the fact that I couldn't find any enough? When do I know that I put enough effort into searching?

I am writing a master's thesis (in Number Theory) and there are multiple places where I need to claim that something is not yet known. Since I am not an expert (and even if I were) I would like to reference some more authoritative source than myself or, say, Wikipedia.  For example, consider the following statement:     In 1980 Schmidt proved that [some property holds]. No other necessary or sufficient conditions are currently known, though.   For the first sentence I can cite Schmidt's original paper, but how can I substantiate the second claim?


I've taken about an hundered of pictures of a large painting with an iPhone at a distance of about 40cm. For each picture I moved the camera along the painting.   I was thinking to use  to build the final assembly. Unfortunately all the possible projections seems to apply only on a sphere not on a rectangle.   How can I automate the assembly of the painting I captured?

Here in Argentina, we have . All the houses and walls on that street have some kind of mosaic stuck to it, and it's very cool. It was made by a local artist .  Because to this piece of urban art is two blocks long, I've decided to make a panorama of it, by moving myself on an horizontal axis while taking photos. I mean, I took one photo, walked one step deeper along the street, took another photo, and so on.  When I tried to stitch it in AutoPano, the following deformed thing came out:   ()  And the other side of the block:   ()  After this, I've learned about parallax error and why you have to avoid moving when making panoramas. I mean, there are a lot of connection errors on both images. Especially in the second one, the part with the corner is quite problematic to stitch because to as I moved, the perspective of the view changed a lot.  So, is there any way to stitch this kind of panorama correctly? Would this only work on plain walls?


I use Transmission BitTorrent Client v. 2.84 (14307). Could you please help me to find it's proxy settings? That's what I see on it's preferences/network tab:

I have heard that Proxy Support in Trasmission has been removed as of version 2.12. Is it possible to use proxy by any other method?


I have read a lot of code examples in this subject but it doesnt work. It should be no problem but it failed in my project where in other people project it work. I have text box in C# that should be contains only numbers. In my project if i have a text box with text :   ----------------------- |         32          | |                     | ----------------------|   and i add a char " T" my resualt is :  ----------------------- |         T3          | |                     | ----------------------|   It remove the first char instead the last char My code :  private void txt_NumOfIkun_KeyPress(object sender, KeyPressEventArgs e)     {         char charAdded = e.KeyChar;          if (txt_NumOfIkun.TextLength > 1)                 txt_NumOfIkun.Text = txt_NumOfIkun.Text.Substring(0, txt_NumOfIkun.TextLength - 1);             else                 txt_NumOfIkun.Text= "";     }

I have a windows forms app with a textbox control that I want to only accept integer values. In the past I've done this kind of validation by overloading the KeyPress event and just removing characters which didn't fit the specification. I've looked at the MaskedTextBox control but I'd like a more general solution that could work with perhaps a regular expression, or depend on the values of other controls.  Ideally this would behave such that pressing a non numeric character would either produce no result or immediately provide the user with feedback about the invalid character.


In a Group $G$, $a^2b^2=b^2a^2$ and $a^3b^3=b^3a^3$ holds, $\forall a,b\in G$. Prove that the group $G$ is abelian.    My approach was the following:  Let $a,b\in G$  Then, $a^2b^2=b^2a^2$ and $a^3b^3=b^3a^3$ holds.  Now, $$\begin{align} a^3b^3=b^3a^3 \\ \implies aaabbb=&bbbaaa\\ \implies a\cdot a^2\cdot b^2&\cdot b=b\cdot b^2\cdot a^2\cdot a\\ \implies a\cdot b^2\cdot a^2&\cdot b =b\cdot a^2\cdot b^2\cdot a\\ \implies ab \cdot ba \cdot a&b=ba\cdot ab\cdot ba \end{align}$$  I am unable to proceed further.  What I need is a simple proof using simple theorems on groups, better if could be done using elementary properties.

Let $G$ be a group. Assume that $a^2b^2=b^2a^2$ and $a^3b^3=b^3a^3$ for all $a, b \in G$. Prove that the group $G$ is abelian.   Also please tell me whether there is any standard approach in proving commutativity of groups like this problem.


When I render in User Ortho mode, I do not see the starfield background i have set up for the World Settings.  Only when I am in User Persp mode, and render, do I see my star background.    In other words, in order to view the starfield background, I must render the image using the User Perspective view.  But this distorts the look of my object (b/c of the perspective angles). I want to view/render my object in it's orthographic profiles, and view it from different angles, WITH the starfield background.

I'm trying to import a background image, and it shows the file name, but it does not show up. I put it in Ortho view but it still wouldn't show. I tried with lots of images just to make sure the image was corrupted or something.  Any ideas?


I upgraded my hp laptop from 19.10 to 20.04. (new installation).   Now I cannot activate the rtl8821ce WiFi module.   For 19.10. there was a hint in ask ubuntu   sudo dpkg -i rtl8821ce-dkms_5.2.5.2.1.30816.20190425-0ubuntu1_all.deb   which worked well, but it doesn't work with 20.04.

When I installed ubuntu 18.04 on my HP Pavilion 15z 6 months ago, I had trouble getting the wifi driver to work. Installing the  solved my problem. 6 months later, I'm having trouble again with the "No wifi adapter found". I booted into my Windows 10 and the wifi works, so my wifi card is fine.   I uninstalled and reinstalled the rt18821ce from the kernel with no problems.  cd rtl8821ce/ sudo ./dkms-remove.sh sudo /dkms-install.sh   Then rebooted, but still no connection to wifi card.  Following the instructions on , I removed the rt18821ce and then installed official ubuntu package.  sudo dpkg -i rtl8821ce-dkms_5.2.5.2.1.30816.20190425-0ubuntu1_all.deb   Rebooted, still have the issue.  Here's information on the details of my network card.  sudo lshw -C network    *-network UNCLAIMED               description: Network controller        product: RTL8821CE 802.11ac PCIe Wireless Network Adapter        vendor: Realtek Semiconductor Co., Ltd.        physical id: 0        bus info: pci@0000:02:00.0        version: 00        width: 64 bits        clock: 33MHz        capabilities: pm msi pciexpress cap_list        configuration: latency=0        resources: ioport:f000(size=256) memory:fe900000-fe90ffff   *-network        description: Ethernet interface        product: RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller        vendor: Realtek Semiconductor Co., Ltd.        physical id: 0        bus info: pci@0000:03:00.0        logical name: eno1        version: 15        serial: f8:b4:6a:a7:75:ff        size: 10Mbit/s        capacity: 1Gbit/s        width: 64 bits        clock: 33MHz        capabilities: pm msi pciexpress msix bus_master cap_list ethernet physical tp mii 10bt 10bt-fd 100bt 100bt-fd 1000bt-fd autonegotiation        configuration: autonegotiation=on broadcast=yes driver=r8169 duplex=half firmware=rtl8168h-2_0.0.2 02/26/15 latency=0 link=no multicast=yes port=MII speed=10Mbit/s        resources: irq:47 ioport:e000(size=256) memory:fe804000-fe804fff memory:fe800000-fe803fff   lspci -nnk | grep -A2 0280  02:00.0 Network controller [0280]: Realtek Semiconductor Co., Ltd. RTL8821CE 802.11ac PCIe Wireless Network Adapter [10ec:c821]     Subsystem: Hewlett-Packard Company RTL8821CE 802.11ac PCIe Wireless Network Adapter [103c:831a]     Kernel modules: rtl8821ce   dmesg | grep -i firmware  [    0.474628] ACPI: [Firmware Bug]: BIOS _OSI(Linux) query ignored [    1.328217] acpi PNP0A08:00: [Firmware Info]: MMCONFIG for domain 0000 [bus 00-3f] only partially covers this bridge [    2.721778] psmouse serio1: elantech: assuming hardware version 4 (with firmware version 0x4d5f02) [    4.700397] Bluetooth: hci0: RTL: rtl: assuming no firmware upload needed [    4.842078] [drm] Found VCN firmware Version: 1.73 Family ID: 18 [    4.842083] [drm] PSP loading VCN firmware [  120.770143] usb 1-2.3: r8712u: Loading firmware from "rtlwifi/rtl8712u.bin"   kernel version 5.0.0-37-generic  I have a  if that helps.


How can I do a combinatoric proof that for Stirling number of second type the equality if true: $${n\brace k} = \frac{1}{k!}\sum_{i=0}^{k}{k \choose i}i^n(-1)^{k-i}$$

This is a Homework Question.  I am required to give a Combinatorial proof for the following.  $$S(m,n)=\frac 1{n!}  \sum_{k=0}^{n} (-1)^k\binom nk (n-k)^m$$  Hint given is : Show that $n!S(m,n)$ equals the number of onto functions $f\colon A  \rightarrow  B$ when $ |A|=m$ and $|B|=n. $  There were some other combinatorial proof questions on the assignment which I found easier to do but this one not so much. Could use help.


I need to re-start some postgres sequences to start at number greater than the current value in that field. I'm trying to do something like this.... psql -U <myowner> -d <mydatabase> -c "ALTER SEQUENCE <mysequence> RESTART WITH (SELECT max(field1) FROM table1); "  The RESTART WITH clause seems to prefer something hardcoded so it seems I have to run the SELECT max() bit and then edit my original attempt with the number returned. like this. psql -U <myowner> -d <mydatabase>-c "ALTER SEQUENCE <mysequence> RESTART WITH 123456789 ; "  I need to do this quite a lot, is it possible to get the first method to work?

I ran into the problem that my primary key sequence is not in sync with my table rows.   That is, when I insert a new row I get a duplicate key error because the sequence implied in the serial datatype returns a number that already exists.  It seems to be caused by import/restores not maintaining the sequence properly.


Im trying to loop through a list in python and split words based on characters. I want to return a 1 dimension list as the result.  Example  wordlist = ['border\collie', 'dog\cat', 'horse\hound'] # slash fix   Expected outcome  new_list = ['border', 'collie', 'dog', 'cat', 'horse', 'hound']  Everything that Ive tried results in a 2d list.   def split_slash_words(text):     new_list = []     new_list.append([i.split("\\") for i in text])     return new_list    returned a two dimensional array, and I cannot also resplit the new_list (as it is in a list type)

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


I am a little bit confused what $$|-\sin t + \cos t|$$ is.   I heard that is $1$ but I thought $\sin t + \cos t$ was $1$.   Is it just that the progression of $t$ is reversed and the size stays the same?   What if the absolute sign is removed? Does it still stay $1$?  ----edit---- Well, they are vectors and the question is asking about the length of the vector. So the length is 1 no matter what the signs are.

$$|a\sin x+b \cos x|\leq \sqrt{a^2+b^2}$$   I have tried: $$|a\sin x+b \cos x|\leq |a+b|\leq \sqrt{a^2+b^2}$$  enough to prove: $$|a+b|\leq \sqrt{a^2+b^2}$$  But I can find how to continue from here


def fib(N):     if N <= 1:         return N     return fib(N-1)+fib(N-2)   I cannot calculate the Big-O for this function, anyone can help me using math method. Thanks！

I understand Big-O notation, but I don't know how to calculate it for many functions. In particular, I've been trying to figure out the computational complexity of the naive version of the Fibonacci sequence:  int Fibonacci(int n) {     if (n <= 1)         return n;     else         return Fibonacci(n - 1) + Fibonacci(n - 2); }   What is the computational complexity of the Fibonacci sequence and how is it calculated?


I have a doubt on how to interpret a result of a hypothesis test. For example, a scenario where I have an existing configuration and also a new configuration. I am trying to check if with the new configuration the program is faster.  The execution of the program in the existing configuration is 70.20 and in the new configuration is 65.10.  My hypothesis is  $H_0:$ The old configuration is better or same as the new configuration ($u>=0$)  $H_1:$ The new configuration is faster ($u<0$)  And I get a p-value of 3%.  Does this mean that getting 65.10 when the null hypothesis is true is unlikely, so we reject the null hypothesis? So because we get 65.10 the null hypothesis is true? I'm not understanding very well this part of the assuming that null hypothesis is true.

What conclusions can we draw if $p>\alpha$? Does not rejecting the $H_0$ mean anything?


I was evaluating a research paper in which the authors have 23 male participants and 117 female participants. They have applied t-test to calculate Gender differences and have even concluded on significance of the difference. I am not sure when the groups are so markedly difference in terms of their size, we can use it for drawing such conclusions. Please help me!!!

Take the case of book ratings on a website. Book A is rated by 10,000 people with an average rating of 4.25 and the variance $\sigma = 0.5$. Similarly Book B is rated by 100 people and has a rating of 4.5 with $\sigma = 0.25$.   Now because of the large sample size of Book A the 'mean stabilized' to 4.25. Now for 100 people, it may be that if more people read Book B the mean rating may fall to 4 or 4.25.   how should one interpret the comparison of means from different samples and what are the best conclusions one can/should draw?    For example - can we really say Book B is better than Book A.


I am pretty new to linux. I had to install the program as it wasn’t loading any apps or refreshing the first page, although search worked just fine. I tried replacing it with Snap Store and so so but those didn’t quite feel the same and snappy. So, is there any way to get that Ubuntu Software center/store back again? I am on 20.04 .

I updated Ubuntu last night (sudo apt get update && sudo apt get upgrade) and to  my surprise this morning I didn't find the 'Ubuntu Software' app and there's a new entry called 'Snap Store' which when opened looks just like the old 'Ubuntu Software' app. So has 'Ubunu Software' been renamed to 'Snap Store'? And if yes, why?


I'm trying to prove that $X\subset \mathbb N$ is countable, in another words, if there is a injection $i:X\to \mathbb N$ then $X$ is countable. I know this is true intuitively but I couldn't find any easy proof of this fact. My attempt is to find another injection $g:\mathbb N\to X$ and use Cantor-Bernstein theorem.   I need help to find a simple proof of $X\subset \mathbb N$ is countable.  Thanks

In my book, it proves that an infinite subset of a coutnable set is countable. But not all the details are filled in, and I've tried to fill in all the details below. Could someone tell me if what I wrote below is valid?  Let $S$ be an infinite subset of a countable set $T$. Since $T$ is countable, there exists a bijection $f: \mathbb{N} \rightarrow T$. And $S \subseteq T = \{ f(n) \ | \ n \in \mathbb{N} \}$. Let $n_{1}$ be the smallest positive integer such that $f(n_{1}) \in S$. And continue where $n_{k}$ is the smallest positive integer greater than $n_{k-1}$ such that $f(n_{k}) \in S$. And because $S$ is infinite, we continue forever. Now consider the function $\beta : \mathbb{N} \rightarrow S$ which sends $k \rightarrow f(n_{k})$.   So in order for $S$ to be countable, $\beta$ would have to be a bijection. $\beta$ is injective since if $f(n_{k}) = f(n_{j})$, then $n_{k} = n_{j}$ because $f$ is injective. We also can conclude $k = j$ because the various $n_{i}$ chosen were strictly increasing.   Edit: $\beta$ also needs to be surjective. So for every $r \in S$ there exists a $q \in \mathbb{N}$ such that $\beta(q) = f(n_{q}) = r$. We know that $f^{-1}(r) \in \{n_{1}, n_{2}, ..., n_{k} ... \}$, so we can let $f^{-1}(r) = n_{d}$. Thus $\beta(d) = f(n_{d}) = r$.