my problem is that some script in php or some other script or program is sending spam.  I am not able to trace where this program runs.  do the following:  ps aux | grep sendmail nginx    28286  0.0  0.0  39316  3328 ?        Ss   07:27   0:00 sendmail -S -t -i -fsamantha_perkins@mydomain.org nginx    28287  0.0  0.0  39316  3352 ?        Ss   07:27   0:00 sendmail -S -t -i -fmuriel_maldonado@mydomain.org nginx    28288  0.0  0.0  39316  3248 ?        Ss   07:27   0:00 sendmail -S -t -i -fann_owens@mydomain.org   I use Debian 8 and OpenSMTPD

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


Is it true that: $$T\text{ isometric}\iff T^*\text{ left inverse}$$ Obviously: $$\text{"}\Rightarrow\text{": }\langle x,\tilde{x}\rangle=\langle Tx,T\tilde{x}\rangle=\langle x,T^*T\tilde{x}\rangle$$ $$\text{"}\Leftarrow\text{": }\langle Tx,T\tilde{x}\rangle=\langle x,T^*T\tilde{x}\rangle=\langle x,\tilde{x}\rangle$$ My problem is that I'm not sure about if the adjoint is left inverse then the operator necessarily is bounded so that domain issues might come into play...


Is possible to add collation search with IQueryable.  this is my code:  public IQueryable<Book> FilterQueryable(IQueryable<Book> queryabable) {     if (!string.IsNullOrEmpty(Term))         queryabable = queryabable.Where(c => (c.Name.ToLower().Contains(Keyword.ToLower()))); }   My problem is, when I search for eg. "crepe" its not returning records that contains "crépe"  é its ignored.  EDIT 1  Text in db is stored Easy crépe recipe, this is why I used contains (LIKE).  Thank you.

I need to compare 2 strings in C# and treat accented letters the same as non-accented letters. For example:  string s1 = "hello"; string s2 = "héllo";  s1.Equals(s2, StringComparison.InvariantCultureIgnoreCase); s1.Equals(s2, StringComparison.OrdinalIgnoreCase);   These 2 strings need to be the same (as far as my application is concerned), but both of these statements evaluate to false. Is there a way in C# to do this?


I've been wondering for a long time what (if any) the difference is between the following:  Dim myString() as String   and  Dim myString as String()

This may sound trivial, but what is the difference between  Dim v As String()   and  Dim v() As String   in VB.NET?


When reading the book of (Chapman & Hall_CRC Texts in Statistical Science) Joseph K. Blitzstein-Introduction to Probability Chapter 2. I have great puzzles about the second last paragraph. To build correct intuition, let’s consider an extreme case. Suppose that there are a million doors, 999,999 of which contain goats and 1 of which has a car. After the contestant’s initial pick, Monty opens 999,998 doors with goats behind them and o↵ers the choice to switch. In this extreme case, it becomes clear that the probabilities are not 50-50 for the two unopened doors; very few people would stubbornly stick with their original choice. The same is true for the three-door case. The author give a extreme case. After opening the $999,998$ doors. Why 'it becomes clear that the probabilities are not $50-50$ for the two unopened doors; very few people would stubbornly stick with their original choice'? I still can not abandon the idea that the probabilities are $50-50$. How to think about it? Thanks for any help!

I was watching the movie 21 yesterday, and in the first 15 minutes or so the main character is in a classroom, being asked a "trick" question (in the sense that the teacher believes that he'll get the wrong answer) which revolves around theoretical probability.  The question goes a little something like this (I'm paraphrasing, but the numbers are all exact):  You're on a game show, and you're given three doors. Behind one of the doors is a brand new car, behind the other two are donkeys. With each door you have a $1/3$ chance of winning. Which door would you pick?  The character picks A, as the odds are all equally in his favor.  The teacher then opens door C, revealing a donkey to be behind there, and asks him if he would like to change his choice. At this point he also explains that most people change their choices out of fear; paranoia; emotion and such.  The character does change his answer to B, but because (according to the movie), the odds are now in favor of door B with a $1/3$ chance of winning if door A is picked and $2/3$ if door B is picked.  What I don't understand is how removing the final door increases the odds of winning if door B is picked only. Surely the split should be 50/50 now, as removal of the final door tells you nothing about the first two?  I assume that I'm wrong; as I'd really like to think that they wouldn't make a movie that's so mathematically incorrect, but I just can't seem to understand why this is the case.  So, if anyone could tell me whether I'm right; or if not explain why, I would be extremely grateful.


Say a Human Warlock-6/Mindbender-1 was to gain another level in Warlock and decided to swap out his Charm invocation (required for Mindbender entry) for the Flee the Scene invocation.  Is this a legal move, or is it just not allowable?  And if it is a legal move, are there any negative ramifications (other than not being able to level up in Mindbender again)?...Such as would I love the Mindbender's telepathy class feature until I qualified for the PrC again, etc?  Similarly, what if you retrained a feat you used to enter a class?  Ie.  A Human Warlock-5/Chameleon-2 decided to retrain his Able Learner feat (required for Chameleon entry) for Improved Initiative.  Or...An Epic level character getting Epic Leadership, then swapping out Leadership.  Now I know in the case of feat retraining, the PHB2 goes over that not only do you have to meet the requirements when you retrain it, but also must have been able to have taken it at the time when the original feat was chosen...However, I have not come across any resource saying that you cannot retrain a feat if it was the requirement for another feat or a Prestige Class (I found one for PF saying you cannot, but I haven't seen one for 3.5)...Nor do I see anything referring to the similar situation about the invocations.  Now I am sure that RAI (and many DM's would rule), that you cannot give up a requirement, but is there any official ruling anywhere?  There has to be some sort of official ruling out there right?...I mean there has to have been plenty of ppl who took/tried to take advantage of feat/skill retraining to get rid of unwanted requirements for feat tree and or PrC's right?

Certain prestige classes detail a list of requirements that are possible for the player to lose (alignment, casting at a certain level), but not what happens if you no longer meet those requirements (acting in an opposed way to your alignment, suffereing from energy drain). Some classes and prestige classes do detail what happens if you no longer meet your requirements, but not all do so.  So I am asking: if you no longer meet the requirements of your prestige class by choice or external influences, will you lose the class features gained from it, despite this loss not being detailed in the class itself?


I'm a second-year undergrad, and I've always been on a first-name basis with anyone in academia or in a research setting. I first worked in a laboratory in high school, and since everyone was on a first-name basis with everyone else there, I sort of just applied that logic to other labs and to my college professors.   But when I was talking to a researcher (my "supervisor", if that's relevant) at the lab I'm currently interning at this summer, one of my fellow interns told me afterwards she thought it was "odd" and "unprofessional" to call him by his first name. I understand where she's coming from, but if this were any other type of environment (say a business office), I think it would be awkward to call my boss anything but his first name (Mr. X seems a bit too formal for the boss-employee relationship).   For what it's worth, my boss doesn't seem put off by the way I address him, and I don't think my professors are, either. Maybe my perspective's a bit skewed because of how I was introduced to the scientific/academic culture. Am I out of line here? What did you call your professors/advisors/bosses as an undergrad?

I've read at least one career advice essay that calls out asking your PhD students to call you by your first name as unprofessional.  My coworkers and I always called our PhD advisor by his first name, and a graduate student calling any professor by their last name, much less their own advisor, strikes my sensibilities as quaint and old-fashioned (undergraduates are a different story, of course).  What is the standard practice for this?


I am using the educational institute internet service using Wifi as well as wired LAN.   The basic setup what i understand is that whole institute is covered with wifi and there are multiple wifi access point with different names. There is a dedicated wired lan service in each of the dorms and departments(They are multiple). I donot know how the internal network is setup?  Every host is connected to outside internet access through proxy servers.   What i want is that how i can list each and every hosts connected(name, ipaddress) in all the dorm and departments to different wifi routers as well as the Wired LAN using any of wlan or wired lan?  The internal ip's in my network is 10.xxx.xxx.xxx. How nbtscan helps in this regard?  NOTE : I want to do this using linux. I am little bit new to these networking concepts. So apologies for any ambiguous question. Please do correct such text.

In my work there is a lot of computer and I want make a joke. I can close computer over the network but finding IP addresses is hard to me.  How can I easily find all online IP adresses from 192.168.1.aa to 192.168.1.zz?


I'm tired of lurking. Every question I can think of, I've been able to answer with diligent enough searching. I want to thank good answers, upvote good responses, and offer valuable feedback. Any questions I can think of, I've been able to answer with sufficient searching.  Ironically, except this one. :)

I'm not sure if this is a stupid question, but here goes anyway... I have only recently started learning PHP and Javascript and I'm reasonably proficient. One of the reasons I'm so proficient is because I LOVE Stack Overflow and find most of the solutions to my dilemmas here.   But I've found that I never get the chance to ask a question because it has normally been asked many times before and when I go through the unanswered questions to try and help someone else, they are generally WAY over my head.  So I'm not sure how to get more privileges. I can't even vote up answers that I like or that helped me. I can't comment to thank someone for their solution. It is most tragic and demoralising... How do I change the situation?


Playing with values of $\zeta(n)$ in excel I find those two interesting results $$\sum\limits_{n=2}^{\infty}\frac{\zeta(n)}{2^n}=\ln(2)$$ $$\sum\limits_{n=2}^{\infty}\frac{\zeta(n)}{(-2)^n}=1-\ln(2)$$ How is it obvious? How can I prove it?

If $f\left(z \right)=\sum_{n=2}^{\infty}a_{n}z^n$ and $\sum_{n=2}^{\infty}|a_n|$ converges then, $$\sum_{n=1}^{\infty}f\left(\frac{1}{n}\right)=\sum_{n=2}^{\infty}a_n\zeta\left(n\right).$$ Since if we set $C:=\sum_{m=2}^{\infty}|a_m|<\infty$, then $$\sum_{n=1}^{\infty}\sum_{m=2}^{\infty}|a_m\frac{1}{n^m}|\leq\sum_{n=1}^{\infty}\sum_{m=2}^{\infty}|a_m|\frac{1}{n^2}\leq C\sum_{n=1}^{\infty}\frac{1}{n^2}<\infty$$ and by Cauchy's double series theorem, we can switch the order of summation: $$\sum_{n=1}^{\infty}f\left(\frac{1}{n}\right)=\sum_{n=1}^{\infty}\sum_{m=2}^{\infty}a_m\frac{1}{n^m}=\sum_{m=2}^{\infty}a_m\sum_{n=1}^{\infty}\frac{1}{n^m}=\sum_{n=2}^{\infty}a_n\zeta\left(n\right).$$ This shows that $\sum_{n=2}^{\infty}\frac{\zeta(n)}{k^n}=\sum_{n=1}^{\infty}\frac{1}{kn(kn-1)}$.  My Questions:  1) It's obvious that $\sum_{n=1}^{\infty}\frac{1}{2n(2n-1)}=\log(2)$, but how can I evaluate $\sum_{n=1}^{\infty}\frac{1}{3n(3n-1)}$?  2) Is there another method to evaluate $\sum_{n=2}^{\infty}\frac{\zeta(n)}{k^n}$?


Let $F$ be a field and let $K$ be an extension of $F$. Show that if $\alpha\in K$ is algebraic over $F$, $F[\alpha]=\{p(\alpha)\mid p(x)\in F[x]\}$ is the smallest subfield of $K$ containing $F$ and $\alpha$.

Let $F$ be a subfield of a field $K$, $a$ an element of $K$.  Prove that $a$ is algebraic over $F$ iff $F[a]=F(a)$.  For the first direction I've tried this: $a$ is algebraic over $F$ $\Rightarrow$ there is a polynomail $f$ over $F$ such that $f(a)=0$ $\Rightarrow$ $1,a,a^2,...,a^m$ are linearly dependent $\Rightarrow$ $\deg(F[a])<m$.    but it contains $f(a)$ so they are equal..  is that correct? about the other direction.. i simply have no clue


I have ASP.NET Core MVC project (targeting .NET 4.62) and I'm trying to save files. Everything works while the length of the path is under 260 (or 248 I'm not sure), but when it's longer I get a System.IO.DirectoryNotFoundException. Previously when I was targeting .NET 4.61 I was getting Path too long exception, I've read that the problem is fixed in .NET 4.62 but not for me.  Here's exception that I'm getting while path is too long    File.Copy(file, Path.Combine(path, dbFile.Id.ToString()));   I'm pretty sure that directory exists.

I'm designing a database table which will hold filenames of uploaded files. What is the maximum length of a filename in NTFS as used by Windows XP or Vista?


I am writing a loop that increments with a float, but I have come across a floating-point arithmetic issue illustrated in the following example:  for(float value = -2.0; value <= 2.0; value += 0.2)     std::cout << value << std::endl;   Here is the output:  -2 -1.8 -1.6 -1.4 -1.2 -1 -0.8 -0.6 -0.4 -0.2 1.46031e-07 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8   Why exactly am I getting 1.46031e-07 instead of 0? I know this has something to do with floating-point errors, but I can't grasp why it is happening and what I should do to prevent this from happening (if there is a way). Can someone explain (or point me to a link) that will help me understand? Any input is appreciated. Thanks!

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


From what I understand, MLE for a model helps us find out what parameters in the model will suit the data most.  Thus, in linear regression, we try to find $L(\theta)$ as $\prod_{i=1}^{m}p(y|x;\theta)$ i.e., we try to find what $\theta$ will suit the data points most and we already have $x$ given to us. This is similar to logistic regression, where also we maximize $\prod_{i=1}^{m}p(y|x;\theta)$. However, for GDA and Naive Bayes, we define $L(\theta)$ as $\prod_{i=1}^{m}p(y,x;\theta)$ because these are generative models and we find both $x$ and $y$ ourselves.  Is my understanding correct? If not, then why is MLE calculated differently for GDA and linear regression?

Could anyone explain to me in detail about maximum likelihood estimation (MLE) in layman's terms? I would like to know the underlying concept before going into mathematical derivation or equation.


May I know when Edubuntu 18.04 LTS will be released? Edubuntu is Ubuntu for education. It skipped 16.04 LTS so the next upgrade is 18.04 LTS.

I want to know where I can find updated information about all the stable and in-development versions of Ubuntu, where I can find this information?     This question is meant to be a canonical question. It expects to answer the following questions:         Is X version stable yet?   Is X version in beta?   Is X version still supported?   What versions are still supported?   What are the versions in Beta/Alpha?   Until where X version will be supported?   Have X version ceased support?   When will be X version released?   Where I can download any release?   When will the next LTS version of Ubuntu be released?         The list is not exhaustive.


Find a function f(x) such that g(f(x)) = x for some g(x), but such that there is no function h(x) with f(h(x)) = x. I think I've got something backwards in my head because I can easily find the reverse case and this case seems provably impossible. I start with Spivak's definition of a function as a set of ordered pairs: Suppose f(x) = { (1,2) , (3,4) } I.e: f(1) = 2 and f(3) = 4 and undefined for everything else. Clearly you can find h(x) such that f(h(x)) = x, just take the set of the pairs switched around. h(x) = { (2,1) , (4,3) } I.e: h(2) = 1 and h(4) = 3 and undefined for everything else. The only way I can see to get around this problem is to choose order pairs that have the same last term: Suppose f(x) = { (1,3) , (2,3) } I.e: f(1) = 3 and f(2) = 3 and undefined for everything else. Now you can't find just flip the pairs because then h(x) wouldn't be a function: If h(x) = { (3,1) , (3,2) } Then does h(3) = 1 or 2? It's ambiguous! But you can still find h(x), just pick one of the pairs and exclude the other(s). h(x) = { (3,1) } f(h(x)) = x still holds? Furthermore, the same logic can seemingly be applied to g(x) to prove g(x) doesn't exist! Suppose f(x) = { (1,3) , (2,3) } We need to find g(x) such that g(f(x)) = x So g(f(1)) = 1 and g(f(2)) = 2 But f(1) = f(2) = 3 !!! So 1 = g(f(1)) = g(3) = g(f(2)) = 2 1 = 2 !!! What have I done?

Spivak's Calculus 4th edition, Chapter 3 Functions, Page 47:  DEFINITION: A function is a collection of pairs of numbers with the following property: if (a,b) and (a,c) are both in the collection, then b = c; in other words, the collection must not contain two different pairs with the same first element.  He continues:  This is our first full-fledged definition, and illustrates the format we shall always use to define significant new concepts. These definitions are so important (at least as important as theorems) that it is essential to know when one is actually at hand, and to distinguish them from comments, motivating remarks, and casual explanations. They will be preceded by the word DEFINITION, contain the term being defined in boldface letters, and constitute a paragraph unto themselves.  Ok got it. Fast forward to the problem set, I'm up to problem 25)  25) Find a function f(x) such that g(f(x)) = x for some g(x), but such that there is no function h(x) with f(h(x)) = x  I asked about this on MSE (see ), and after much discussion came to the resolution that the problem 25 is impossible given the above definition of a function. In summary, the problem is that in order to find f(x), you need to choose f(x) to be a non-surjective function, which requires the concept of codomain. However the above definition does not include the concept of codomain, only domain and image, hence it is impossible. My question is: What was Spivak thinking (and I mean literally)? How did Spivak intend for us to solve this problem? Is it an error on his part? Or is there a way to intuitively infer from the above definition that functions must be specified a codomain (codomain, not image) in order to be defined? If I had the solutions book to Calculus 4th Edition, this would greatly help answer my question, but I can't find it anywhere for free.


I'm currently creating a .vbs script which is used to change the default program for a specific file extension however I'm not fully certain as to what registry keys/values I need to change. Doing a google search, I came across many posts in which they all mentioned to change values in HKLM, HKCR and HKCU, it was a bit confusing because it's all pointing towards different places.  Let's say I want to change the .txt file extension so it opens using CustomProgram.exe, what are all the Keys/Values and their locations in which I need to change in order for it to work without any sort of error?

After installing Adobe PDF reader, it opens files with the .PDF file extension. Ones' default web browser opens .html files and notepad opens .txt files, etc.  Where exactly in the registry are these filetype - program associations stored in the registry?   In other words, how does Windows know with which software/program it must open a certain file(type)?


I am trying to use the navigation to custom sObject record edit page by passing recordid as mentioned in the document. However, it says "it is not a function".  Any thoughts?  import { NavigationMixin } from 'lightning/navigation';  navigateToCorpconEdit(row) {         let { linkName } = row;                     let recordid = linkName.substr(1);          this[NavigationMixin.Navigate]({             type: 'standard__recordPage',             attributes: {                 recordId: recordid,                 objectApiName: 'npe5__Affiliation__c',                 actionName: 'edit'             },         });     }   Error:     [this[h.NavigationMixin.Navigate] is not a function]

When attempting to use the Lightning navigation service in my component's base class (.js), I get the following error when functionally testing in the UI:  this[f.NavigationMixin.Navigate] is not a function  I am calling the NavigationMixin function provided by the lightning/navigation module. I have imported the module: import { NavigationMixin } from 'lightning/navigation';  And am calling the function as below: this[NavigationMixin.Navigate]({     type: 'standard__recordPage',     attributes: {         recordId: this.org.Id,         objectApiName: 'Account',         actionName: 'view'     } });


I switched to ubuntu from windows just today. and im currently using 16.04 and i want to update it to 18.04. whenever i open software updater and try to install, it says "requires installation of untrusted packages" and  i fail... then i tried to do it in terminal i used the code sudo apt update this kind of errors occured:  E: https://archive.ualinux.com/ubuntu/pool/all/ualinux/karbo/karbowanec_1.3.4up_amd64.deb  Failed to retrieve from network. 404  Not Found    what should i do? i tried these below :  sudo apt-key adv --recv-keys --keyserver keyserver.ubuntu.com XXXX sudo apt-get update

It didn't fixed the error. So, how do I fix my GUI update?  For every software I have to install it from command line because I got same error when install software from Ubuntu Software Center.


I am trying to use template but it does not work, the error is : " previously declared here"  this is my Matrix.h file:  #ifndef MATRIX_H #define MATRIX_H  template <class T> class Matrix { public:      Matrix(int); // default cunstractor  private:     int rows, columns; };  #include "Matrix.cpp" #endif   and this is my Matrix.cpp file  #include "Matrix.h" #include<iostream> using namespace std;  template <class T> Matrix<T>::Matrix(int a) // Default constructor {    columns = a;    rows = 0; }   and this is the main file:  #include<iostream> #include "Matrix.h" using namespace std;  int main() {  Matrix<int> m1(5); return 0; }   I know the code seems very stupid and simple but I wrote much more, I reduce it to very simple code like this and again it doesn't work. Even I removed  #include "Matrix.cpp"   inside the Matrix.h file but still have problem.

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.)


Why is the following statement valid, and how can I break it down so that it is easier to understand?     Buffalo buffalo Buffalo buffalo buffalo buffalo Buffalo buffalo.

Could anybody please  explain in detail  the sentence     "Buffalo buffalo Buffalo buffalo buffalo buffalo Buffalo buffalo."   I have seen the  but am unable to get it properly.


I am using Ubuntu 18.04. When I start error with Started User Manager for UID 1000, latest 10 minutes, restart it will show a black screen with this message: Started Wait until snapd is fully seeded.

I'be been running 18.04 since a clean SSD install on the day of it's official release, without issues. Power on to login was seconds (max 10)  Then, I did a regular upgrade this morning:  $ sudo apt update && sudo apt dist-upgrade   The packages installed/upgraded were:  Install: linux-headers-4.15.0-24:amd64 (4.15.0-24.26, automatic), linux-headers-4.15.0-24-generic:amd64 (4.15.0-24.26, automatic), linux-modules-extra-4.15.0-24-generic:amd64 (4.15.0-24.26, automatic), linux-modules-4.15.0-24-generic:amd64 (4.15.0-24.26, automatic), linux-image-4.15.0-24-generic:amd64 (4.15.0-24.26, automatic) Upgrade: gnome-control-center-data:amd64 (1:3.28.1-0ubuntu1.18.04.1, 1:3.28.1-0ubuntu1.18.04.2), linux-headers-generic:amd64 (4.15.0.23.25, 4.15.0.24.26), gnome-control-center:amd64 (1:3.28.1-0ubuntu1.18.04.1, 1:3.28.1-0ubuntu1.18.04.2), linux-image-generic:amd64 (4.15.0.23.25, 4.15.0.24.26), linux-signed-generic:amd64 (4.15.0.23.25, 4.15.0.24.26), gnome-control-center-faces:amd64 (1:3.28.1-0ubuntu1.18.04.1, 1:3.28.1-0ubuntu1.18.04.2), linux-generic:amd64 (4.15.0.23.25, 4.15.0.24.26)   I rebooted once the upgrade had completed, and noted a 2-3 minute delay on the Ubuntu loading/splash screen (prior to login) (without any progress/activity indicated on the dots).  I powered off and tried to boot again, but am getting this delay consistently now. Also close down is much slower too.  Update #1 (2018-07-03): Analysis on systemd:  $ sudo systemd-analyze blame 3min 53.073s plymouth-quit-wait.service     2min 20.699s snapd.seeded.service          49.949s snapd.service           6.186s NetworkManager-wait-online.service           1.148s dev-sda2.device           1.098s plymouth-start.service   Showing that plymouth-quit-wait.service (which I now believe is related to the Ubuntu loading/splash screen) and snapd.seeded.service were by far the longest running services to initiate. So I compared the times before the dist-upgrade and after:  $ journalctl -u plymouth-quit-wait.service --since today -- Logs begin at Fri 2018-04-27 13:01:30 BST, end at Tue 2018-07-03 12:38:05 BST. -- Jul 03 04:15:43 user-laptop systemd[1]: Starting Hold until boot process finishes up... Jul 03 04:15:46 user-laptop systemd[1]: Started Hold until boot process finishes up. -- Reboot -- Jul 03 04:21:17 user-laptop systemd[1]: Starting Hold until boot process finishes up... Jul 03 04:24:52 user-laptop systemd[1]: Started Hold until boot process finishes up.   Before the upgrade plymouth-quit-wait.service took 3 seconds. After the upgrade it took 3 minutes 35 seconds  $ journalctl -u snapd.seeded.service --since today -- Logs begin at Fri 2018-04-27 13:01:30 BST, end at Tue 2018-07-03 12:42:14 BST. -- Jul 03 04:15:43 user-laptop systemd[1]: Starting Wait until snapd is fully seeded... Jul 03 04:15:43 user-laptop systemd[1]: Started Wait until snapd is fully seeded. -- Reboot -- Jul 03 04:22:47 user-laptop systemd[1]: Starting Wait until snapd is fully seeded... Jul 03 04:24:49 user-laptop systemd[1]: Started Wait until snapd is fully seeded.   Before the upgrade snapd.seeded.service took 0 seconds. After the upgrade it took 2 minutes 2 seconds.  Update #2 (2018-07-06): This morning's boot saw the return of the delay. So I guess we're still waiting for the kernel/plymouth/snapd update.  Update #3 (2018-07-12): The problem seems to be resolved, but I didn't see any update to snap or plymouth, and I'm still running 4.15.0-24 kernel. So I'm not sure which package update fixed the problem, or if it just resolved itself somehow. Reading the bug updates on launchpad it's unclear to me what was done (or is being done) to what package/s. If anyone can clarify that would be very useful.


I have a late 2013 15" Macbook Pro Retina (the newest model as of the time of this question). I've seen numerous blog posts that show this computer powering 3 external displays, plus the built in retina display, but I can't make it work. I have a 22" ASUS connected by mini display to VGA adapter, a 30" Hannspree connected by mini display to HDMI adapter, and a 22" LG connected to the built-in HDMI. I can get every combination of 2 monitors working plus the built-in, but I can't get all 3 external on at the same time. I've tried with the built-in open and closed. I've also tried using 2 mini display to VGA adapters. According to a CNET article, this should work!

Several people have posted about how they use 3 external monitors with their MacBook Pro Retina. see:        However, when I attempt to do this on my 15" late 2013 MacBook Pro Retina, I can only run 2. Either, 2 thunderbolt, or 1 thunderbolt and 1 HDMI. When I plug in all 3, only 2 of them work.  Apple tech says     Yep. You can only have 2 external monitors (unless you want to add a usb monitor).   Is there some trick I am missing? Some setting to tweak? I have 3 monitors just waiting for the solution. One of my monitors feels quite left out...


I'm looking for a way to make the Unity Launcher always show while the desktop is visible, but hide when a program like Firefox or any other maximized program is open.  The only other "solutions" I've found for this seem to involve keyboard shortcuts, which I don't want. The previously available Dodge Windows feature sounds like what I need, but unfortunately is no longer supported.  Is this possible? If so, how?

I was trying to control Ubuntu 14.4.1 Launcher's behavior. I want it to auto-hide every time I have browser window like firefox maxmaized. I found this solution:  #!/bin/bash  ## Change value of "hide" to the command which worked for you to hide the panel hide='gsettings set com.canonical.Unity2d.Launcher hide-mode 1;'  ## Change value of "show" to the command which worked for you to show the panel when it was hidden show='gsettings set com.canonical.Unity2d.Launcher hide-mode 0;'  ## Look for the grep value, add a new browser or application name followed by "\|" eg: 'firefox\|google\|chromium' while [ 1 ]  do z=$(wmctrl -l -p | grep -i 'firefox\|google');     if [ -n "$z" ]; then          eval $hide     else         eval $show     fi;     sleep 2; done;   but is seems too old to work then I found   I tried to combine the two scripts together so here is what I did:  #!/bin/bash  AUTOHIDE=$(dconf read /org/compiz/profiles/unity/plugins/unityshell/launcher-hide-mode) if [[ $AUTOHIDE -eq 1 ]] then      dconf write /org/compiz/profiles/unity/plugins/unityshell/launcher-hide-mode 0 else      dconf write /org/compiz/profiles/unity/plugins/unityshell/launcher-hide-mode 1 fi  ## Look for the grep value, add a new browser or application name followed by "\|" eg: 'firefox\|google\|chromium' while [ 1 ]  do z=$(wmctrl -l -p | grep -i 'firefox\|google');     if [ -n "$z" ]; then          eval $hide     else         eval $show     fi;     sleep 2; done;   But script doesn't work. can anybody refine this script to me and get it to work?


Suppose the quotient group $G/C$ is cyclic and generated by element $Ca$ of $G/C$. Prove for any two elements $x,y \in G$ that $xy=yx$.  I am having trouble formulating a proof. In a preceding problem I was able to prove that for every $x \in G$ there is some integer $m$ such that $x=ca^m$ which I am guessing I can use to write $y=c'a^n$. Where would I go from here?

Continuing my work through Dummit & Foote's "Abstract Algebra", 3.1.36 asks the following (which is exactly the same as exercise 5 in ):     Prove that if $G/Z(G)$ is cyclic, then $G$ is abelian. [If $G/Z(G)$ is cyclic with generator $xZ(G)$, show that every element of $G$ can be written in the form $x^az$ for some $a \in \mathbb{Z}$ and some element $z \in Z(G)$]      The hint is actually the hardest part for me, as the quotient groups are somewhat abstract. But once I have the hint, I can write:  $g, h \in G$ implies that $g = x^{a_1}z_1$ and $h = x^{a_2}z_2$, so \begin{align*}gh &= (x^{a_1}z_1)(x^{a_2}z_2)\\\  &= x^{a_1}x^{a_2}z_1z_2\\\ & = x^{a_1 + a_2}z_2z_1\\\ &= \ldots = (x^{a_2}z_2)(x^{a_1}z_1) = hg. \end{align*} Therefore, $G$ is abelian.  1) Is this right so far?  2) How can I prove the "hint"?


Show  $$1+\cosθ+\cos(2θ)+\cdots+\cos(nθ)=\frac12+\frac{\sin\left(\left(n+\frac12\right)θ\right)}{2\sin\left(\frac\theta2\right)}$$ I want to use De Moivre's formula and $$1+z+z^2+\cdots+z^n=\frac{z^{n+1}-1}{z-1}.$$  I set $z=x+yi$, but couldn't get it.

I would to prove that  $$1+\cos \theta+\cos 2\theta+\ldots+\cos n\theta =\displaystyle\frac{1}{2}+  \frac{\sin\left[(2n+1)\frac{\theta}{2}\right]}{2\sin\left(\frac{\theta}{2}\right)}$$ given that  $$1+z+z^2+z^3+\ldots+z^n=\displaystyle\frac {1-z^{n+1}}{1-z}$$ where $z\neq 1$.  I put $z=e^{i\theta}$. I already got in left hand side cos exp in real part, but there is a problem in the right hand side, I can't split imaginary part and real part. Please help me. Thanks in advance.


This might be trivial, but here goes.  In terminal, I tend to find myself moving/renaming/copying files that are not in my current working directory instead of cd-ing to the directory of those files first. For example, I find myself doing:  mv long/path/to/a/folder long/path/to/a/folder.old   Sometimes, this can be a "long/path with spaces/to/a/folder".  My question is: is there a way/shortcut for the <target path> to be relative to the <source path>? For instance, does something like this exist:  mv long/path/to/a/folder ``/folder.old   Where `` means "the same path or the same parent path of the file/folder I'm trying to move", so in my example `` would stand for long/path/to/a/.  I know I could of course cd long/path/to/a/ and then mv folder folder.old, but that involves an extra command, and I'll end up in another working directory.

Is there any way of executing a mv command without typing the full path in the second argument?  Example:  mv my/file/that/has/a/really/long/path/foo.bar some_magic_operator_that_means_the_same_directory/foo.baz


I know you can do  this.GetType().FullName   To get  My.Current.Class   But what can I call to get  My.Current.Class.CurrentMethod

Like the title says: Can reflection give you the name of the currently executing method.  I'm inclined to guess not, because of the Heisenberg problem.  How do you call a method that will tell you the current method without changing what the current method is?  But I'm hoping someone can prove me wrong there.  Update:     Part 2:  Could this be used to look inside code for a property as well?   Part 3:  What would the performance be like?   Final Result I learned about MethodBase.GetCurrentMethod().  I also learned that not only can I create a stack trace, I can create only the exact frame I need if I want.    To use this inside a property, just take a .Substring(4) to remove the 'set_' or 'get_'.


Till now I rendered my images and took them to Photoshop and did some color corrections there. Made aware of Color Management options in Blender by Rick's answer on  I am now diving somewhat deeper in Color Management in Blender.   I don't want this post to be a dupe, I just want some basic understanding of color management in Blender. How monitor profiles, color spaces and Blender act together. Like I have some basic understanding how working spaces, monitor profiles act together in Photoshop.

If I need to use Blender within a colour-accurate workflow, what do I have to do to set that up (including hardware calibration, etc)?


My Thinkpad runs Windows 8.1 and Ubuntu 14.4 on dual boot. But since I tried Puppy Linux via a bootable USB stick my Ubuntu does not show up, Windows 8.1 just boots. Any solutions?  My BIOS is UEFI.

I installed Windows 7, which ate Ubuntu's boot file. When starting up the computer, it now goes straight to Windows, without giving me the option of booting Ubuntu.   How can I get Ubuntu back?


I am looking for the name of a kids animated space movie from the 70's or 80s.  I vaguely remember the people or one species thought the other creature/species was bad. The bad "creatures" looked like a beetle type thing that had many round glass spheres like eyes and tentacles.   By the end they realise the creatures are actually good and need help to survive and the tentacles can heal.

I can not remember much but I have had this film in my head for years I searched everything I can remember on every website I can think of.  I don't remember the exact story but I'll list everything about it can   Apocalyptic future possibly Two main characters: a boy and a girl riding ostrich-like creatures through a valley An old blind lady that senses things Crashed spaceship looking like a submarine Giant creatures looks like yaks with blue eyes, whose eyes turn red when something is about to happen The old lady says "Some say they went to the stars" while looking at the spaceship The two main characters do something and their eyes turn blue in the distance and the village cheers   This film is at least ten years old and I would appreciate it so much if you knew anything about it, or could help me find the title.


Consider a continuous standard brownian motion $(B_t)_{t\ge 0}$. I want to show, that $$\mathcal{L}(\{t\ge 0: B_t=0\})=0$$  I also have a hint that I need to show that $B:\mathbb{R}_+\times\Omega\longrightarrow\mathbb{R}$ is measurable. Then I shall find, that $E[\mathcal{L}(\{t\ge 0: B_t=0\})]=0$ and conclude the statemate above. I would appreciate any help! Thanks in advance!

Let $B_t(w)$ be a Brownian associated with a measure $P(dw)$. Suppose that $X$ is a random set of times $t$ where $0 \le t \le 1$ such that $B_t=0$. Show that $X$ has Lebesgue measure zero $P$ almost surely.


I got a Dell Latitude D620 from work on condition it had to be DBAN DOD wiped prior to removal. It is a DuoCore 1.6GHz 1GB RAM machine which sounded like LUBUNTU would be good fit... All of it worked including wireless on MS XP SP3.   So I installed LUBUNTU today and am working on on wired connection but wireless does not show up... Tried iwconfig in terminal, which I would copy and paste here but copy{CTRL+C} in Xterm just results in ^C, however it shows lo which looks like a loopback and eth0 which is my wired... No Wireless...  In System Information:  Operating System reports Kernel "Linux 3.13.0-37generic (i686)"  Operating System reports Distribution "Ubuntu 14.04.1 LTS"  In Kernel Modules I see a wl but its blank however several 802.11 modules show up...  In the PCI devices I see "Network Controller Broadcom Corporation BCM4311 802.11a/b/g (rev01)"... That all said the LED is off and the hardware switch is on. On WinXP the blue light was on when the switch was on... Here in PCI Devices it knows its Dell and seems to have Broadcom driver...  Is there something like Device manager in windows? Or is System Information as close to that as there is?  I see a couple other Questions requarding this specific model and none seem to have a solution... Concerns me starting into UBUNTU... Hopefully there is a solution. Thanks,

I'm having serious problems installing the Broadcom drivers for Ubuntu. It worked perfectly on my previous version, but now, it is impossible.   What are the steps to install Broadcom wireless drivers for a BCM43xx card?  I'm a user with no advance knowledge in Linux, so I would need clear explanations on how to make, compile, etc.    lspci -vnn | grep Network showed:   Broadcom Corporation BCM4322 802.11a/b/g/n Wireless LAN Controller [14e4:432b]      iwconfig showed:  lo        no wireless extensions. eth0      no wireless extensions.   NOTE: Answer below is updated every time new information is added and confirmed working.


How to clear browser cache (Active Logins).  In IE we can delete it with  document.execCommand('ClearAuthenticationCache', false);   but this doesn't work in firefox or chrome.  I need for changing client certificate without clearing Active Logins via browser interface.

I have a few internal .net web application here that require users to "log out" of them. I know this may seem moot on an Intranet application, but nonetheless it is there.  We are using Windows authentication for our Intranet apps, so we tie in to our Active Directory with Basic Authentication and the credentials get stored in the browser cache, as opposed to a cookie when using .net forms authentication.  In IE6+ you can leverage a special JavaScript function they created by doing the following:  document.execCommand("ClearAuthenticationCache", "false")   However, for the other browsers that are to be supported (namely Firefox at the moment, but I strive for multi-browser support), I simply display message to the user that they need to close their browser to log out of the application, which effectively flushes the application cache.  Does anybody know of some commands/hacks/etc. that I can use in other browsers to flush the authentication cache?


My dell Studio 1749 is over 6 years old and has never given any problems.I need to reinstall windows becasue a few weeks ago after doing updates from windows it started telling me my copy of windows build 7601 was not genuine.So I took the machine in to be cleaned etc and using my oem installation disks (64bit) reinstalling windows.  Unfortunately the oem disks have become corrupted but I have the product key etc. Dell do not seem to be interested.  I live in Turkey and a friend downloaded another windows 7 on my computer but 32bit.  The video drivers seem to need updating and everything is slower than before.   As you can see I am useless at this sort of thing and because of my location there is the added language problem.  Can anyone come up with any ideas of how I can get my lovely machine back?

I just bought a serial for Windows 7 on-line from the Microsoft store (the most painful shopping experience EVER!). I selected that I wanted to download my version of Windows 7 after purchase. After payment, I have listed a Product Key but no download link in sight.   Where do I download my Windows 7 ISO to burn to disk?  Note: I'm not a Technet or MSDN subscriber.


For example, I add a circle shape, and give it a material named Material. When I duplicate it, it has a new material named Material.001. That isn't helpful at all, and is something I've proven to be a cinch in cluttering my hard-earned material stash for, say, logo remakes.

how can I prevent Blender 2.8 from duplicating materials every time (?) I duplicate a mesh.


I have problems understanding a specific notation of the gradient, more specifically the following question  What is the meaning of the gradient notation grad_x H where H is a function?  My attempt at answering this question is:   Assume that H = H(x,y) then we know that grad_x ( H(x,y) ) = d/dx ( H(x,y) )  Is this correct?

What is the meaning of "gradient with respect to $\mathbf x$"?    I am talking about the symbol $$\nabla_\mathbf x$$  Does that simply mean derivative with respect to $\mathbf x$?


I want to rename an image with the text in that image. For that I use an OCR and I try to store the name in a variable and use that variable in the mv command but I get mv: target ‘file’ is not a directory. I also want to know how to avoid making the file $item.txt with a pipe.  item=1 convert $item -crop 100%x50% +repage $item tesseract $item-0 $item # Delete newlines tr -d '\n' < $item.txt > name; rm $item.txt # Delete leading white space sed -i 's/^ *//' name name=`cat name` mv $item $name

Or, an introductory guide to robust filename handling and other string passing in shell scripts.  I wrote a shell script which works well most of the time. But it chokes on some inputs (e.g. on some file names).  I encountered a problem such as the following:   I have a file name containing a space hello world, and it was treated as two separate files hello and world. I have an input line with two consecutive spaces and they shrank to one in the input. Leading and trailing whitespace disappears from input lines. Sometimes, when the input contains one of the characters \[*?, they are replaced by some text which is is actually the name of files. There is an apostrophe ' (or a double quote ") in the input and things got weird after that point. There is a backslash in the input (or: I am using Cygwin and some of my file names have Windows-style \ separators).   What is going on and how do I fix it?


I submitted paper to a journal of Elsevier. Now it has been 1 month from submission with status: "with editor". Is this normal? And should I contact the journal to ask about the long time of that status?

What steps does a manuscript typically go through from submission to publication (or rejection) in a typical journal? How are these steps referred to, in particular by editorial systems, and how long do they each typically take?  Note that this question is about the typical situation and hence not about:   Journals with an atypical workflow, e.g. those that allow for an instantaneous reviewer–author interaction. Exceptional steps or rare occurrences such as withdrawal or .   This is a canonical question on this topic as per . Due to its nature, it is rather broad and not exemplary for a regular question on this site. Please feel free to improve this question.


Hi i try to display dates between two dates(i don't have any table ) using mysql. simply i have two dates 2013-10-01 and 2013-10-05 but i did't success   ;WITH cte AS ( SELECT CASE WHEN DATEPART(Day,@StartDate) = 1 THEN @StartDate              ELSE DATEADD(Month,DATEDIFF(Month,0,@StartDate)+1,0) END AS myDate UNION ALL SELECT DATEADD(Month,1,myDate) FROM cte WHERE DATEADD(Month,1,myDate) <=  @EndDate ) SELECT myDate FROM cte OPTION (MAXRECURSION 0)     i think this works on only sqlserver not in mysql  i want output like  2013-10-01 2013-10-02 2013-10-03 2013-10-04 2013-10-05

Using standard mysql functions is there a way to write a query that will return a list of days between two dates.  eg given 2009-01-01 and 2009-01-13 it would return a one column table with the values:   2009-01-01   2009-01-02   2009-01-03  2009-01-04   2009-01-05  2009-01-06  2009-01-07  2009-01-08   2009-01-09  2009-01-10  2009-01-11  2009-01-12  2009-01-13   Edit: It appears I have not been clear. I want to GENERATE this list. I have values stored in the database (by datetime) but want them to be aggregated on a left outer join to a list of dates as above (I am expecting null from the right side of some of this join for some days and will handle this).


Let $(a_n)$ be a sequence of positive terms and suppose that $\sum_\limits{n=0}^{\infty} a_n$ converges. Show that $\sum_\limits{n=0}^{\infty} a_n^2$ converges.   This is in the section on the Comparison Test so that must be what I'm supposed to use.  But I don't see how.  $(a_n)^2$ might be smaller or larger than $a_n$ depending on $a_n$.  And I can't use the Comparison Test with some other series because there's no info here about how fast $\sum a_n$ converges.  Hmm.  Any hints?

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


For A/B testing purposes i'd like to change the class name of an  element. I can add Javascript to the A/B testing tool to achieve this. As i'm quite new to javascript, i could use some help.  The current  element:
   Must be changed to:
   How can i perform this by using Javascript?

How can I change the class of an HTML element in response to an onclick or any other events using JavaScript?


I am trying to login with phone number and password but to get the phone number from firebase database through model class is giving a null pointer exception. Please Help  I have already tried to get all the other String variables which works properly except the phone number.  Model Class  public class Users {      private String Name;     private String Address;     private String Phone;     private String Email;     private String Password;      public Users() {     }      public Users(String name, String address, String phone, String email, String password) {         this.Name = name;         this.Address = address;         this.Phone = phone;         this.Email = email;         this.Password = password;     }      public String getName() {         return Name;     }      public void setName(String name) {         this.Name = name;     }      public String getAddress() { return Address;  }      public void setAddress(String address) {         this.Address = address;     }      public String getPhone() {         return Phone;     }      public void setPhone(String phone) {         this.Phone = phone;     }      public String getEmail() {         return Email;     }      public void setEmail(String email) {         this.Email = email;     }      public String getPassword() {         return Password;     }      public void setPassword(String password) {         this.Password = password;     }  }   Login_Actvity  private void allowAccesstoAccount ( final String phonestring, final String passwordstring){      final DatabaseReference database = FirebaseDatabase.getInstance().getReference();     database.addListenerForSingleValueEvent(new ValueEventListener() {         @Override         public void onDataChange(@NonNull DataSnapshot dataSnapshot) {             if ((dataSnapshot.child(parentName).child(phonestring).exists())) {                      Users usersData = dataSnapshot.child(parentName).child(phonestring).getValue(Users.class);                      //`userData.getPhone()` gives warning                     //while  `userData.getPassword()` works properly                       if(usersData.getPhone().equals(phonestring)){                     if(usersData.getPassword().equals(passwordstring)){                         Toast.makeText(Login_Activity.this, "Login Successful ", Toast.LENGTH_SHORT).show();                         loadingBar.dismiss();                          Intent intent = new Intent(getApplicationContext(),Home_Activity.class);                         startActivity(intent);                     }                 }                 else {                     Toast.makeText(Login_Activity.this, "Login Failed ", Toast.LENGTH_SHORT).show();                     loadingBar.dismiss();                 }             }             else {                 Toast.makeText(Login_Activity.this, "Account with this " + phonestring + " phone number does not exist", Toast.LENGTH_SHORT).show();                 loadingBar.dismiss();                 Toast.makeText(Login_Activity.this, "Try the correct one", Toast.LENGTH_SHORT).show();             }         }         @Override         public void onCancelled(@NonNull DatabaseError databaseError) {         }     });   java.lang. NullPointerException is the exception

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?


Does the partial derivative of $\langle x'|\alpha\rangle$ with respect to $x'$ equal $|\alpha\rangle$? Why?   Note: $|\alpha\rangle$ is an arbitrary ket, $x'$ is an eigenvalue, and $\langle x'|$ is an eigenket corresponding to $x'$.  In particular, I do not understand how these two expressions are equivalent:  $$\langle x' - \Delta x' | \alpha \rangle = \langle x' |\alpha\rangle - \Delta x' \frac {\partial} {\partial x'} \langle x' | \alpha \rangle $$

How is the momentum operator derived in Dirac formalism? I am reading Quantum Mechanics by Sakurai and he gives the following derivation. But I don't understand how he goes from the third equation to the last equation in (1.7.15). What I don't understand is where the partial derivative with respect to $x^{\prime}$ comes from. Here is the derivation from the book.     Momentum Operator in the Position Basis      We now examine how the momentum operator may look in the $x$-basis - that is, in the representation where the position eigenkets are used as base kets. Our starting point is the definition of momentum as the generator of infinitesimal translations:      $$\begin{align} \biggl(1 - \frac{ip\Delta x'}{\hbar}\biggr)\lvert\alpha\rangle &= \int dx' \mathcal{J}(\Delta x')\lvert x'\rangle\langle x'\lvert\alpha\rangle \\ &= \int dx' \lvert x' + \Delta x'\rangle\langle x'\lvert\alpha\rangle \\ &= \int dx' \lvert x'\rangle\langle x' - \Delta x'\lvert\alpha\rangle \\ &= \int dx' \lvert x'\rangle\biggl(\langle x'\lvert\alpha\rangle - \Delta x'\frac{\partial}{\partial x'}\langle x'\lvert\alpha\rangle\biggr).\tag{1.7.15} \end{align}$$      Comparison of both sides yields      $$p\lvert\alpha\rangle = \int dx'\lvert x'\rangle\biggl(-i\hbar\frac{\partial}{\partial x'}\langle x'\lvert\alpha\rangle\biggr)\tag{1.7.16}$$      or      $$\langle x'\rvert p\lvert\alpha\rangle = -i\hbar\frac{\partial}{\partial x'}\langle x'\lvert\alpha\rangle,\tag{1.7.17}$$


I installed Oracle JDK on Ubuntu 16.04 LTS using the following commands:  sudo add-apt-repository ppa:webupd8team/java sudo apt-get update sudo apt-get install oracle-java8-installer   But I tried various suggestions from the forums and that didn't solve the issue. I purged the ppa and did an update also but it wouldn't remove.

I didn't find any related articles about . There are some related articles but they didn't solve the problem.  I installed Oracle JDK tarball file from Oracle site by following this article . It was very helpful. But still I don't know what I should do in order to uninstall Oracle JDK.


Why are all meta.sitenamehere.stackexchange.com sites HTTP-only?  For example,  supports HTTPS, but its meta site  does not support HTTPS. Placing HTTPS into the URL just redirects you to the HTTP version.  This does not affect StackExchange sites with their own domains, however.  supports HTTPS, and its meta site  also supports HTTPS, unlike the meta site on a stackexchange.com subdomain like Unix SE.

Steps to reproduce:   In Firefox (with ), visit a non-trilogy Stack Exchange site (for example, ) Get redirected to the HTTPS version Click on meta link (for example, )   What should happen:   Meta site opens   What happens instead:   "This Connection is Untrusted" message appears:      meta.movies.stackexchange.com uses an invalid security certificate. The certificate is only valid for the following names: *.stackexchange.com, stackexchange.com, meta.stackexchange.com, *.meta.stackexchange.com, *.stackoverflow.com, stackoverflow.com, serverfault.com, stackauth.com, sstatic.net, meta.serverfault.com, superuser.com, meta.superuser.com, stackapps.com, openid.stackauth.com (Error code: ssl_error_bad_cert_domain)   Notes:   It also happens if you visit  instead (you get redirected to HTTPS and the error occurs) Another random example,  Trilogy metas work,  works (but  doesn't - I am not sure what gave me that link) Replacing URL with https://*.meta.stackexchange doesn't work   Here is the screenshot:


When is "z" pronounced "zee" and when "zed"?  From what I found out "zee" is AmE and "zed" is BrE. And in abbreviations the letter is always pronounced "zee" like in LZ (landing zone).

When we learned the ABC song and English alphabet, we pronounced Z as [zed]. But in the practical usage, I never heard people say [zed], but they always say [zi:]  So when shall we say [zed]?  Or such pronunciation is totally archaic and not used in the modern English.


I tried to open window from thread, but open window was frozen. Code in the first window(inside a thread):  MyProject.MainModuleWindow mmw = new MyProject.MainModuleWindow(); mmw.Show();   How to do it correctly?

I'm trying to make a crossplatform C# application using C#, mono/GTK# on Linux and .NET/GTK# on Windows, however the startup sequence seems to need to be slightly different under the two platforms:  Under Linux:  public static void Main (string[] args) {     Gdk.Threads.Init ();     // etc...   Under Windows:  public static void Main (string[] args) {     Glib.Thread.Init ();     Gdk.Threads.Init ();     // etc...   Both require it to be done that way: Windows complains about g_thread_init() not being called with the linux code, and linux complains about it already being called with the Windows code. Other than this, it all works wonderfully.  My first attempt at a "solution" looked like:  public static void Main (string[] args) {     try {         Gdk.Threads.Init ();     } catch (Exception) {         GLib.Thread.Init ();         Gdk.Threads.Init ();     }     // etc...   But even this messy solution doesn't work; the error is coming from GTK+, unmanaged code, so it can't be caught. Does anyone have any bright ideas about the cause of the problem, and how to fix it? Or, failing that, have bright ideas on how to detect which one should be called at runtime?


My company just implemented whole disk encryption on all laptops () and the concept seems flawed.  Please correct me if I'm wrong, but if I have known file in plain text and that same file in encrypted text, it possible to use that information to find the key for decryption.    If there is a better stack to ask this question on, please let me know and I'll repost.

I have a file, which was encrypted with AES-128 in ECB mode. I know the format of the original file and know that all files in this format have the same headers. So, I have an encrypted block and the original block.  Can I get the encryption key, using this information?


I'm using the hanging package to create paragraphs with hanging indents. From what I understand, the basic way to do this with this package is to do  \hangpara{15pt}{1} Your paragraph. The second sentence.   Where "15pt" is the size of the indent, and "1" is how many lines will not be indented. However, when using this with my other normal paragraphs, the first line of my hanging paragraphs is not lining up with all the other normal paragraphs. Right now my hack of a fix is just  \hspace{-3pt}   and it looks really close, but I know its not the same and its bugging me lol. How can I use the hanging package and \hangpara to get the output I desire, with all "non-indented" lines lining up? Here is an image of my current output ("non" and "Morbi" should be lining up):    And here is my code:  \documentclass[letterpaper]{article}  % For hanging indents \usepackage{hanging}  % Even though 15pt is default but just to be precise \setlength\parindent{15pt}  \begin{document}  Lorem ipsum dolor sit amet, consectetur adipiscing elit. Integer velit nibh, viverra vitae placerat eget, porta a ipsum. Integer ullamcorper, odio vulputate molestie  condimentum, massa tellus consectetur quam, viverra condimentum ligula nibh ut risus.  Vivamus sit amet eros eu ligula efficitur finibus vel a mauris. Ut ut est facilisis, mollis purus in, maximus est. Praesent ut libero nec enim vulputate scelerisque. Fusce  congue dui dolor, at dictum ante pulvinar non. Quisque ultrices sagittis venenatis.   \hangpara{15pt}{1} Morbi vitae lacus quis elit tincidunt commodo. Fusce magna massa, aliquam vitae  facilisis sit amet, feugiat non lectus. Nulla rutrum ac justo a suscipit. Duis dictum turpis euismod velit ultricies rhoncus. Proin pellentesque id justo eu fermentum. Duis  nmi leo, scelerisque quis augue sed, ultrices fermentum elit. Maecenas in nunc  feugiat, euismod eros id, placerat lacus. Donec eu nunc augue. Proin volutpat quam a  orci aliquet porta. Cras pellentesque nibh ac diam faucibus, eu suscipit augue  aliquam. Vestibulum convallis semper fermentum.   \end{document}   If there is an alternate, simple solution that does not use the hanging package I'm all for that as well. Thanks!

I see that the code in many packages and examples contains percent signs % at the end of (many) lines. What are they used for? Do they affect the parsing of those lines?


I'm brand new to GIS (and this site) so bear with me if there is an obvious answer for this but I've done a lot of looking and haven't found anything that worked.  I have two polygon layers that show the same waterway buffer for a large area but one is more extensive than the other. I want to subtract the smaller layer from the larger one so that I am left with the areas that are only covered by the larger. This seems like the type of problem that could be easily solved with the "erase tool" but I don't have access to that. The "select by location" seems to be a popular suggestion but I've played around with it and haven't gotten it to work. Also the two layers are not quite identical.  What should I do?

I have two polygon layers, one is green that represents all non-public right-of-way land. I have another polygon that is just a circle with a specified radius.  I would like my output to be a polygon layer that represents all the white space (the gaps) in the private land polygon layer that is also within the black circle.    How does one do this (In ArcGIS 10.2)?


Determine all the connected subsets of $\mathbb{Z}.$?  I thinks $\mathbb{N} $ will  be the all connected subset of $\mathbb{Z}.$  I'm right or wrong

The answer are the singletons of $\mathbb{Q}$. I can show that the open intervals of $\mathbb{Q}$ are disconnected by choosing some irrational in the open set and using it to form a separation. But strangely enough, I am having a hard time seeing why the subset $\{p,q \}$ of $\mathbb{Q}$ is disconnected. If say $p < q$ and we choose some irrational $p < x <q$, the separation of $\{p,q \}$ would, I think, be given by $ \{p\}$ and $\{q\}$. But these aren't open in $\mathbb{Q}$ ...?


I have certain doubts, shall we say, about which of the following is correct:   I don't know where precisely you live; I don't know where precisely do you live.   For some reason I feel that the first one is correct, but I'm not sure about any actual rules governing the decision in this specific instance.  Would you please be so kind as to educate me what is the general guiding principle for such cases?  Sincerely Yours, Adrianna W. McCrory

I know that to indirectly ask:     What is your name?   I should say something like:     I don't know what your name is.   But what if the subject of question is longer than "your name"? Something like:     What is the benefit of closing school when there's a flu outbreak   It just doesn't sound so good to me to indirectly ask the above question when the distance between what and is gets too long:     I don't know what the benefit of closing schools when there's a flu outbreak is.   So, I am wondering if it is Ok to ask the indirect question like this:     I don't know what is the benefit of closing schools when there's a flu outbreak.


I am sending an email address value to a third party service. I have following regex to validate email addresses:   `^\w+([\.-]?\w+)*@\w+([\.-]?\w+)*(\.\w{2,})$`   but suppose someone tries to send as email address:  'WQWQQWWQQWQWWQWQQWW@WEOIWEOIEWOIEWIOWEIOEWIOEWPIOWEPOIWEPEWIOPIOWEOIWEOIEWIOWIOEWIOPEWIOPWIOEPIOWPEIOEWOIEWOIPIOEW.COM'    this address is valid and then I get error in response object from the service.  My question is, what can be the possible maximum character limit for the domain part?

What is the maximum length of a valid email address? Is it defined by any standard?


public class Login extends JFrame {     private JPanel panel1;     private JButton btnLogin;     private JTextField txtEmail;     private JPasswordField txtPassword;     public static Users users;      public Login(){          initComponent();     } private void initComponent(){         setContentPane(panel1); //here is the problema, Why?         setSize(600,400);         setDefaultCloseOperation(3);         setLocationRelativeTo(null);     }  ![The image is on the link :(][1] [1]: https://i.stack.imgur.com/ar5u8.jpg

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?


A well-known result, Cayley's theorem, says that any group is isomorphic to $S_n$ for some $n$. Given a (finite) group $G$, is there a standard name for the smallest such $n$?  This seems like a very basic concept which has surely been studied and named, but my searches have found nothing so far.  Is it easy to calculate $n$? An obvious lower bound is the Kempner number $(|G|)$.    Note: there is a  but it doesn't address my issue.

I'm considering finite groups only. Cayley's theorem says the a group $G$ is isomorphic to a subgroup of $S_{|G|}$. I think it's interesting to ask for smaller values of $n$ for which $G$ is a subgroup of $S_n$. Obviously, it's not always possible to do better than Cayley's theorem. But sometimes it is possible (for example, $\mathbb{Z}_6$ as a subgroup of $S_5$).  So I'm asking:        Given a finite group $G$, is there an algorithmic way to find or approximate the minimal $n$ for which $G$ is isomorphic to a subgroup of $S_n$?   If the answer to $(1)$ is not known, is it known for specific classes of groups?   In particular, for finite abelian groups, is it true that for a prime $p$, the minimal $n$ for $\mathbb{Z}_{p^{t_1}} \times \mathbb{Z}_{p^{t_2}}$ is $p^{t_1}+p^{t_2}$ (I can prove that is is true for different primes $p_1$ and $p_2$, but have problems when it's the same prime in both factors).      Thanks!


I am a tuna fan. I usually pour it from a tin onto a sandwich without cooking it. Yet there is one kind of tuna that is a problem for me: tinned "lemon pepper" tuna. I don't mind a bit of pepper kick. But a certain well known brand makes lemon pepper tuna that to me is uneatable; the pepper is so strong and abrasive that my mouth is on fire but in a really nasty way.   In my kitchen cupboard I must have about 20 tins of this stuff. I have a tin in my hand now. Ingredients: skipjack tuna, 59%, water. lemon juice, 10%, sunflower oil, black pepper, salt, traces of wheat, milk, egg, crustacea, soy and sesame. [yes, I know I also wonder what formed the 31%]   Is there any way of making this stuff less of a nuclear bomb taste? I have to have any one tin at the time for food safety; I don't keep anything from a tin stored in a fridge. So any idea of having a little bit with something else doesn't work. Is there any strategy? Reducing the taste somehow? Masking it with something else? Reducing acidity if that helps?   I can't throw it to the birds or cats. I have found that animals don't touch tinned fish of any type. Don't know why.

Sometimes when I'm making a sauce or soup that needs to be a bit spicy, I have no troubles spicing how I want to.  But if the dinner party is a bit late, or I made the sauce in advance to really draw out all the flavors of the spices, vegetables and meat, sometimes I end up with a way too spicy/hot dish.  You can always pour a bit water and try to dilute it a bit, but that also takes away all of the good flavor. So is there some trick that I'm missing I can use, when this happens to me (other than being more careful or using the spices later)?


Let $a$ and $b$ belong to a group.  If $|a|$ and $|b|$ are relatively prime, show that $\langle a \rangle \cap \langle b \rangle = \{e \}$.  The most I can figure to do is to let $a^k = b^j$ for some $a^k$ and $b^j$ in $\langle a \rangle$ and $\langle b \rangle$, respectively.  I'd assume that I'd need to show that the only possible element either could be would be $e$ (the identity element) but I'm not seeing a way.  Would it make sense to say that $aa^k \neq bb^j$ because then otherwise $\langle a \rangle = \langle b \rangle$, therefore the only option is to have $a^k = e$ and $b^j = e?$

Let $H$ and $K$ be subgroups of $G$. Let $H$ have order $m$ and $K$ have order $n$, where $m$ and $n$ are   relatively prime. Then  $H \cap K=\{e\}$   My proof:  Let $H$ and $K$ be subgroups where the $ord(H)=m$ and $ord(K)=n$ and $m,n$ are relatively prime. We know that $H \cap K$ is a subgroup of $H$ and $K$ since it contains the elements of both in $H$ and $K$. We shall let the ord($H \cap K$)=d.   Then, by Lagrange's theorem, the order of $H$ is a multiple of the order of $H \cap K$. In other words, $m$ is a multiple of $d$ or $d|m$. Similarly,  by Lagrange's theorem, the order of $K$ is a multiple of the order of $H \cap K$. In other words, $n$ is a multiple of $d$ or $d|n$. Since $d$ divides both $m$ and $n$ and we know $m$ and $n$ are relatively prime then, the order of $H \cap K$ must be $1$.   Since $H \cap K$ is a subgroup, then by properties of subgroup, it contains an inverse which means it must also contain an identity and since $H \cap K$ contains one element, it must contain the identity. As a result, $H \cap K=\{e\}$  Hopefully, someone can confirm or correct any mistakes I made. Thanks!


I use stackoverflow often. As a web developer, I notice nowadays many sites use bootstrap to be responsive web site. When you reduce the size of browser, you will see a little bit different layout and it fits to browser. Especially it's useful if you are in tablet or smartphone. I saw  changes it's header content when you reduce browser size, but not full content. Footer exceeds from browser screen. Is there any reason why stackexchange.com sites are not responsive/mobile friendly?  PS: I'm not complaining. All stackexchange sites are cool. Just want to know reason. Maybe they are planning to do it.  EDIT  I don't use mobile version of stackexchange sites. So I didn't know that  there were different mobile version (and app) of the site for mobile devices. My question is only for desktop version. It's not fully responsive. I mean There shouldn't be scrollbar horizontally (Bottom of the screen). Of there could be scrollbar within question/answer body.

I'm sorry if this is a duplicate before I begin.  As everybody knows, there has been major growth on tablets and mobiles within the last few years. I am aware of Stack Overflow's mobile site but wouldn't it be more useful for the site to have a responsive design layout so that users of every screen size would be able to see all the content without having to sniff the user agent to show the mobile site?  I have worked with responsive design in my current project and it works very well for all devices that I have tested it on.  What do you think? Should Stack Overflow be remodeled with a responsive design?


I want to upgrade RAM in my HP LAPTOP model number - AU111TX. Current Specification of RAM installed on my laptop is  Can I add RAM in empty slot of different speed i.e. 2666MHz? How do I know that this RAM speed is compatible with my laptop? This is the RAM that I am planning to buy.

I don't have any knowledge in hardware and would like to know which RAM should I buy for my laptop.  How do I discover what RAM I need & how much my machine can take?  I have a Razer Blade 15 (RZ09-02705F76) 2018 but don't know if there is a specific type or format of RAM that suits it and don't know where to find this information.


Is there any way I can get current html element dimensions (width/height) if they are not explicitly defined in CSS? Using just JavaScript? For example if I have image  var image = document.getElementsByClassName("top-image")[0];   And let's say I have click event. How can I get dimensions in the moment when event happened?

Are there any JavaScript or jQuery APIs or methods to get the dimensions of an image on the page?


Can someone help me giving a qualitative answer to this problem in General Relativity:  Imagine you are on earth with two perfectly synchronized clock's. If you hold on in your hand but you throw the other one in the air and catch it after a certain time interval, would they still give the same time?  I think that the one in the air would run faster but I cannot explain why.  Thank you!

Suppose I'm on a non rotating planet. I have two identical, perfect watches. I synchronize them. Then I throw one of them into the air and catch it. Does the one I throw into the air gain or lose time with respect to the one I was holding?


the new Blender 2.81 synchronize outliner object to viewport and vice versa feature is fantastic.  It matches up with behaviors in other 3D software like 3DS and Maya.  One question on its behavior to see if it can do this as well:  When the collections are collapsed or the object selected in the viewport is not in the outliner view, the object gets selected in the outliner but it's not brought into view in the outliner.   Is there a way to get the outliner to "jump" to the selected object - expanding and/or scrolling the outliner as needed?  Many thanks!

How can I jump to the selected object in the out-liner, I've got over 200 objects in my scene, all named cube.___ ... and I can't seem to find my selected object. How can I jump to it?


The code  \subsection{\textsc{Should be in small caps} $\cdot$ Normal tekst} \textsc{This text is in small caps}   gives the output    The \textsc command works fine in normal text but not in a subsection title. As shown, I do not want to change the entire title format, only a small portion within. Thus I cannot find out to make a general renewcommand feature.  Is there a method to accomlish this?  My document head is the article type \documentclass[11pt,a4paper]{article}

When I try to do something like \section{Heading with \textsc{small caps}}, the compiler complains with "LaTeX Font Warning: Some font shapes were not available, defaults substituted." and replaces the small-caps with normal test.  Any suggestions on how to fix this?


I have a meat piece which I want to weigh. Now there can be anything like fish, cheese, or other items that we can cut and measure. I want the weight to be determined by myself instead of determining from getting the surface of the item as it varies with different tris count. Currently, I am calculating the weight from the following code. public static float CalculateSurfaceArea(Mesh mesh) {     var triangles = mesh.triangles;     var vertices = mesh.vertices;      double sum = 0.0;      for (int i = 0; i < triangles.Length; i += 3)     {         Vector3 corner = vertices[triangles[i]];         Vector3 a = vertices[triangles[i + 1]] - corner;         Vector3 b = vertices[triangles[i + 2]] - corner;          sum += Vector3.Cross(a, b).magnitude;     }     // weightMultiplier is a constant value for getting a reasonable weight value.     return (float)(sum / 2.0) * weightMultiplier; }  So if there's a meat piece like bellow and I want it to be a weight of let's say 3kg(6.6lb)  then when I cut it into half it should give me values respectively (1.5kg).  So I want the weighing factor to be in my control so that if in the future we have really detailed high poly items the weight shouldn't get affected by that.

Let's say I have a cube, and that cube breaks apart into 100 different unevenly sized pieces.   How can I get the volume of each of those pieces compared to the cube's volume?  Using this in order to get the mass of each piece; for example, if the large cube is 100 mass, then the largest piece might be 30 and there might be some that are 0.2, etc...  Using C# and Unity with Rigidbodies


Show that for $\frak{g} = \frak{sl}_{n}(\Bbb{C})$, the Killing form is given by $K(x,y) = 2n tr(xy)$.    This is problem 5.2 in Kirillov's book on Lie Algebras. Recall that $K(x,y) = tr (\text{ad } x \text{ ad } y)$, where $\text{ad } x \text{ ad } y$ is a composition of two operators acting on $\frak{sl}_{n}(\Bbb{C})$. From my understanding, in order to compute the trace, we need to compute a matrix representation of $\text{ad } x \text{ ad } y$ with respect to some basis of $\frak{sl}_{n}(\Bbb{C})$, and then look at the diagonal entries.   However, this seems like an awful task. I am told that it suffices to compute $K(E_{ij},E_{ji})$. But it still is proving to be an awful task. Am I missing something, or is this just a very calculation heavy problem?

Consider the Killing form of the Lie algebra $\mathfrak{gl}_{m}$. Then $\{e_{ij}\}$ is a basis for this Lie algebra where $e_{ij}$ is a matrix with 1 in the $i$th row, $j$th column and 0 everywhere else. Then every $A = (a_{ij}) \in \mathfrak{gl}_{m}$ can be written as $A = \sum_{i, j = 1}^{m}a_{ij}e_{ij}$. Since $[e_{ij}, e_{kl}] = \delta_{jk}e_{il}-\delta_{li}e_{kj}$, we have $ad(a)e_{ij} = \sum_{kl}(a_{ki}\delta_{lj} -a_{jl}\delta_{ki})e_{kl}$. From this we have $$ad(a)ad(b)e_{ij} = \sum_{k, r, s}(a_{rk}b_{ki}\delta_{sj} + a_{ks}b_{jk}\delta_{ri} - a_{ri}b_{jk}\delta_{sk} - a_{js}b_{ki}\delta_{rk})e_{rs}.$$ From this how can I see that the Killing form is $2m tr(ab) - 2tr(a)tr(b)$. I know that the Killing form is just the trace of the above centered equation, but I seem to be getting confused with all the indices.


The following MWE works fine when plotting a square using pstricks with xelatex.   \documentclass{article}  \usepackage{pstricks}  \begin{document}    \def\x{0 } % Notice that there MUST be a white space after 0    \psframe(\x, 1)(!1 \x add 1 1 add)  \end{document}   The problems is, when I try to make the \psframe in a whiledo loop with a counter, the space after a command is swallowed. Look at the following MWE:   \documentclass{article}  \usepackage{pstricks}  \newcounter{Y}  \setcounter{Y}{1}  \begin{document}    \def\x{0 }    \def\Y{\theY  }    \psframe(\x, \Y)(!1 \x add 1 \Y add)  \end{document}   When compile with the command xelatex test where test.tex is the name of the source file, it throws the following error:   Using PSTricks configuration for XeTeX+xdvipdfmx  ))) (/usr/share/texlive/texmf-dist/tex/generic/pstricks/pst-fp.tex))  (./test.aux) [1] (./test.aux)Error: /undefined in 1add  Operand stack:     --nostringval--   0.0   true   0.0   28.4527   1   1   Looks like after expanding \Y in \psframe, the second coordinate becomes (!1 0 add 1 1add) where the white space between the last 1 and add is swallowed.  How can the value of a counter be used in the coordinate calculations in pstricks? Thanks.

\psElectricfield only accepts a coordinate in space-separated values as follows. For example, a charge of -0.1 unit at (-1,0) is written as [-0.1 -1 0]. I have attempted to write in PS notation but it still does not work.  \documentclass{article} \pagestyle{empty}  \usepackage{pst-electricfield,multido} \def\M{2}  \begin{document} \multido{\i=0+30}{12}{% \begin{pspicture*}(-\M,-\M)(\M,\M)     \psElectricfield     [         Q={[-0.1 -1 0][-0.1 1 0][0.1 !\i sin 2 mul \i cos 2 mul]}     ] \end{pspicture*}\newpage} \end{document}   How to express  a polar coordinate for a macro that only accepts space-separated values?


So i am fairly new to SharePoint and i have stumbled upon a problem wherein i want to copy an item in column A to Column B in the same list through a workflow  but there is only an option for copying from one list to another.  Could you please help me out in solving this issue.  Thanks in advance.

how can i copy values from one column to another? I'm using a workflow but i cant see the option "Copy List Item"   ps: I'm using Sharepoin On-line


I have a linear system $$A x = b $$ with $A$ being an $m \times n$ matrix ($m < n $) and $b $ being an $n $ vector, both over $\mathbb R_{\geq 0} $ (non-negative real numbers).  The system is guaranteed to have at least one non-negative solution (not known to us). I want to find the set of all non-negative solutions of the system.

Here's the environment of my problem: I have a linear system of 4 equations in 8 unknowns (i.e. $Ax = b$, where $A$ is $4 \times 8$, $x$ is $8 \times 1$, and $b$ is $4 \times 1$, with $A$ given and $b$ varying with some exogenous parameters, i.e. essentially given). So, after reducing the system, the solution space can be described by a linear function $f \, : \, \mathbb{R}^4 \rightarrow \mathbb{R}^4$, which I can find explicitly.  Because of the nature of the problem, I am interested only in nonnegative values for each of the 8 unknowns. So, I can restrict the function $f$ to the domain $\mathbb{R}^4_{\geq 0}$ (i.e. examine only nonnegative values for each of the 4 free variables). What I'm interested in knowing (and classifying for different parameter values, which will change $b$) is whether solutions exist for which all 8 unknowns are nonnegative--or equivalently, whether the function $f$ takes nonnegative values in the nonnegative domain $\mathbb{R}^4_{\geq 0}$.   If there's a way to figure this out analytically, that would be great; alternatively, if there's a good way to do this numerically (I use MATLAB), that would be only slightly less great. Thanks in advance!    Thank you all so much for your answers--this has been a huge help. Working out the solution by hand using the LL Dines paper may prove to be too cumbersome, as it requires knowing the sign of the coefficients, and we examine thousands of different sets of coefficients (as we vary several parameters); however, if nothing else, it's really nice to know that there is an algorithm for (analytically) determining the existence of nonnegative solutions. Moreover, all of the software advice given has been extremely helpful. I've looked into all of your suggestions, and for now I think we'll try using lsqnonneg. Thanks again for your help!


As a teenager I read a story about a great tree that sat upon the eroding cliff of an alien world. A party of human explorers arrived upon this world, and one of their number, a man of intellect, but physically weak, is endowed with special powers by the tree shortly before it dies. At the moment the conscience of the man and the tree combine, the tree urgently told the man, "Alien, I die soon." I've never forgotten that line, and would like to read this story again. What is the story's name and by which author ? Thank you.

It was an old book... I'm pretty sure it was a book, and pre-1990's I think. The basic plot was this man somehow interacted with this tree, and as a result he became a carrier of the tree's 'seed'. They were in a symbiotic relationship: the man got a much longer life, more strength, etc.; but when he did die the tree would grow up from his body.


While completing a C programming test, I was given a question regarding  the expected output from a function which seem to return two values. It was structured as follows:  int multi_return_args(void) {  return (44,66); }   The question caught me by surprise and inherently thought that if possible the first argument would be passed to the caller.   But after compiling it, the result is 66 instead. After a quick search I couldn't find anything about structuring a return statement like this so was wondering if some could help me.  Why does it behave like this and why?


When I press the "Play game" button I get referred to the Monster game. While playing the game I just earn more card drops instead of the cards.  By playing the Monster game for a while I have earned 8 card drops, but where are the actual cards?

The cards that it says I've unlocked aren't in my inventory. Do you just get them after the whole event? I have two from just buying games actually in my inventory, but the cards I've 'unlocked' aren't around. I'm Steam Level 7, so I know they should be dropping...


A  is able to grapple up to 10 creatures with its tentacles, the reach for this attack is 30 ft.     Tentacle. Melee Weapon Attack: +17 to hit, reach 30 ft., one target. Hit: 20 (3d6 + 10) bludgeoning damage, and the target is grappled (escape DC 18). Until this grapple ends, the target is restrained. The kraken has ten tentacles, each of which can grapple one target.   Can a creature with a reach of 5 ft. which is grappled 30 ft. away from the Krakens position attack it with a melee weapon attack? It would make sense, that one could aim for the grappling tentacle, but is it RAW/RAI?

The froghemoth from Volo's Guide to Monsters has a tentacle attack that can grapple a target from 20ft away. Grappling means that a targets speed is reduced to 0. Does that mean that characters cannot attack the froghemoth with melee attacks if they are 20ft away and grappled?


On Ubuntu 18.04.1 LTS I tried installing LTSP in "chroot" mode, following this .   The initial command   apt install --yes --install-recommends ltsp-server-standalone epoptes   Returned:   Reading package lists... Done Building dependency tree        Reading state information... Done Some packages could not be installed. This may mean that you have requested an impossible situation or if you are using the unstable distribution that some required packages have not yet been created or been moved out of Incoming. The following information may help to resolve the situation:  The following packages have unmet dependencies:  epoptes : Depends: faketime but it is not installable            Depends: iperf but it is not installable            Depends: x11vnc but it is not going to be installed            Depends: xterm but it is not installable            Depends: xvnc4viewer but it is not installable or                     tigervnc-viewer but it is not installable or                     ssvnc but it is not installable or                     vnc-viewer but it is not installable            Recommends: epoptes-client but it is not going to be installed  ltsp-server-standalone : Depends: ldm-server but it is not going to be installed                           Depends: ltsp-server (>= 5.18.04+t201809080524~ubuntu18.04.1) but it is not going to be installed                           Depends: openbsd-inetd but it is not installable or                                    inet-superserver but it is not installable                           Recommends: ltsp-docs but it is not installable E: Unable to correct problems, you have held broken packages.   My question is: how do I correct these broken packages, and also if I succeed in installing this system will I be able to emulate VMs using the CT-3000 Huawei thin client, which does not have ubuntu mate installed on it. I am also looking for info on how to install mate.

How do you use terminal to enable Universe source? Or any those 4 from Software Sources: Main, Universe, Restricted, Multiverse Main is on by default and Restricted is on if durring Ubuntu installation i tick Enable Restricted Formats. Answer with line where version checked so it auto detects it. Like command I know for partner but that goes to Other Software tab sudo add-apt-repository "deb http://archive.canonical.com/ $(lsb_release -sc) partner"


I have two empty div elements inside a div. The two elements are class labeled as "img" and "overlay". On the "img" I attached a background url and the "overlay" I only want to add a background color on top of the background url adding an overlay effect. I tried playing with positions, height and padding but it only misalign the items. The divs are inside another div which has a grid display property. Html Part:

  Css Part: .img{   height: 100%;   width: 100%;   background: url("../img/star.jpg");   background-size: cover;  }  .overlay{   background-color: green;  }

I want to overlay one image with another using CSS. An example of this is the first image (the background if you like) will be a thumbnail link of a product, with the link opening a lightbox / popup showing a larger version of the image.   On top of this linked image I would like an image of a magnifying glass, to show people that the image can be clicked to enlarge it (apparently this isn't obvious without the magnifying glass).


Question is : In how many ways can the letters be put into the envelopes, so that at least one letter goes to the correct address ?  Answer is 15.  All i could think of is : 4 envelop choices for each letter, so 4*4 = 16.  A little fertilizer for my withered grey-matter ?

There are n letters addressed to n eople at different addresses. The n addresses are typed on n envelopes.  A disgruntled secretary shuffles the letters and puts them in the envelopes in random order, one letter per envelope.  Find the probability that at least one letter is put in a correctly addressed envelope. [Hint: use the inclusion-exclusion formula.] What is the probability approximately, for large n ?    My attempt at a solution:  P(all correct) = $\frac{1}{n!}$  P(n-1 correct) = ${n \choose n-1} \frac{1}{n!} = \frac{1}{1!(n-1)!}$  ${n \choose n-1}$ ways of selecting n-1 correct letters.  P(n-2 correct) = ${n \choose n-2} \frac{1}{n!} = \frac{1}{2!(n-2)!}$  ...  P(n-n correct) = ${n \choose n-n} \frac{1}{n!} = \frac{1}{n!(n-n)!} = \frac{1}{n!}$  This all looks ok to me, but I tested this for a case of 4 people, (I think the theoretical value should be $\frac{9}{24}$ but obviously that is not what I got. Can someone correct my logic please? Also, with regards to the hint about inclusion/exclusion - where would that come in?  I read about derangements on Wikipedia but it did not make total sense to me (the derivation).  I would appreciate any advice whatsoever including references to other material.


I have an overmolded PCBA on a cable with passive components only. Some of the components are hard to identify, but I'm still concerned about the possibility of competitors trying to reverse engineer it. What are the best materials I can put on the components to make it extremely hard (expensive, time-consuming, etc.) for anyone to get to those components in-tact? I'm concerned that standard potting materials, conformal coating materials, and epoxies would be too easy to remove with heat, chemicals, sanding, or milling. Essentially I'd like to have something that bonds so strongly to the components that trying to remove the material also destroys the components. Of course if the material is too hard on the hardness scale, or has a high thermal expansion co-efficient, then the board components might get damaged during manufacturing or during use in the field.

Im trying to find a coating for my PCB in order to protect it from reverse engineering. I want it opaque, non-conductive and with a low thermal resistance.  Basically I do not want that someone replicates my circuit easily. I´ve beens searching a lot on coatings but did't find anything that suits to all my requirement. Anyone with an idea?


How exactly is foreach implemented in C#?  I imagine a part of it looking like:  var enumerator = TInput.GetEnumerator(); while(enumerator.MoveNext()) {   // do some stuff here }   However I'm unsure what's really going on. What methodology is used for returning enumerator.Current for each cycle? Does it return [for each cycle] or does it take an anonymous function or something to execute the body of foreach?

Which types of classes can use foreach loops?


Let say $A \in \mathbb{F}^{n\times m}$ and $B \in \mathbb{F}^{m\times n}$. I am wondering weather there is any standard result stating the relationship between eigen values of $AB$ and $BA$ matrices.  I know that eigen values are same for $AB$ and $BA$ when both $A$ and $B$ are square matrices. But in a general setup, we can not use the result that- $\det(AB) = \det(BA)$.

If $X \in \mathbb{C}^{m \times n}$ and $Y \in \mathbb{C}^{n \times m}$ ($m \geq n$), how to prove the following?  $$\sigma (XY) = \sigma(YX) \cup \underbrace{\left \{ 0, ..., 0 \right \}}_{m-n}$$  Here, $\sigma$ denotes the set of eigenvalues/spectrum.


I want to redirect a main domain to a subdomain for example www.abc.com to xyz.test.com. Whenever i type www.abc.com it should be redirect to xyz.test.com. Both domain are hosted on same server.  Subdomain xyz.test.com is not a virtual host of web server (i.e. apache & nginx) it is code generated website and you can directly access it via . I'm using apache and nginx both so whatever best fit i will use. Any help would be appreciated.  Thank You :)

This is a  about Apache's mod_rewrite.   Changing a request URL or redirecting users to a different URL than the one they originally requested is done using mod_rewrite. This includes such things as:   Changing HTTP to HTTPS (or the other way around) Changing a request to a page which no longer exist to a new replacement. Modifying a URL format (such as ?id=3433 to /id/3433 ) Presenting a different page based on the browser, based on the referrer, based on anything possible under the moon and sun. Anything you want to mess around with URL   Everything You Ever Wanted to Know about Mod_Rewrite Rules but Were Afraid to Ask!  How can I become an expert at writing mod_rewrite rules?   What is the fundamental format and structure of mod_rewrite rules? What form/flavor of regular expressions do I need to have a solid grasp of? What are the most common mistakes/pitfalls when writing rewrite rules? What is a good method for testing and verifying mod_rewrite rules? Are there SEO or performance implications of mod_rewrite rules I should be aware of? Are there common situations where mod_rewrite might seem like the right tool for the job but isn't? What are some common examples?   A place to test your rules  The  web site is a great place to play around with your rules and test them. It even shows the debug output so you can see what matched and what did not.


I'm getting a syslinux screen upon boot from USB, is there any way to avoid this? It's happening for any OS that I'm trying to install.  The exact message is: SYSLINUX 4.03 2010-10-22 EDD Copyright (C) 1994-2010 H. Peter Anvin et al  I've researched this and every response I've found has been tried with no success.  I'd love if someone could help me out, thanks.

I am trying to install linux on my laptop, a Toshiba Satellite C6550-S5200. I did it once but something happened so I removed it then I had to destroy all data on hard drive so now I have nothing on it. Well I got a iso file burned to a CD and to a flash drive. With the flash drive I get.   SYSLINUX 4.06 EDD 4.06-pre7 Copyright (C) 1994-2012 H. Peter Anvin et al  With the CD it will start booting it but somewhere loading it up, the dots turn all orange and stay that way and my CD drive turns quiet.  Oh and some more info the images work because I tried loading them up on another pc and it worked just fine.  I manage to get the CD to boot I just had to let me pc boot up first then insert the CD and have it boot the CD then. Once I get done installing ubuntu it works fine but I have to leave the PC on 24/7 for if I turn it off the PC will freeze 5-10 seconds after booting back up no matter how I install it.