Sample sentence:  There's not a dad in the world who compares to you, and there's not a daughter in the universe who's more grateful than (me or I).

Consider the sentence "I can run faster than 15 miles per hour." Its meaning is clear and to my eyes obviously grammatically correct. Now let me present some variations that have given me trouble for a long time.  I am faster than 15 miles per hour. – To me this is clearly incorrect. Directly comparing me to a speed doesn't seem right. We need to compare my speed to a speed, or me to another person.  I can run faster than him. – Compared to the base sentence, there is a distinct shift in meaning of the comparison. While before I named a speed faster than which I can run, now I am naming a person. It doesn't seem quite right. I realize the parts of speech can change, but my initial objection is that "him" is not a speed.  I can run faster than he. – This seems most correct to me, but still somehow feels objectionable. Is this in fact the correct way to say it? And if so, is it proper as is or need I say "... faster than he can" or even "... faster than he can run?"  I am faster than him. – With "am" instead of "can run" it now seems slightly more correct. But is it?  I am faster than he. – I'm in doubt here. It doesn't seem wrong to me to say, "I am faster than he is" or even "I am faster than he is fast." (Though I suppose that is a given since I could hardly properly compare to some other category as in "I am faster than he is smart.")  My speed is faster than his. – Hmm. This seems more proper as "my speed is greater than his."   So which of these constructions is correct and which is incorrect? Is there a general rule that I can follow? UPDATE The scholarly article  may be of great interest to some readers!  Once we accept that the elided constituent and its antecedent can differ in form, it becomes reasonable to ask how large this difference can be. The answer in Rooth (1992), Fiengo and May (1994), Chung et al. (1995) and subsequent work is that the wiggle room is actually quite small: the elided constituent and its antecedent are allowed to differ only in the realization of inﬂectional morphology. Other than that, both constituents have to be syntactically and lexically isomorphic.


I use a browser launched from the command line (Qutebrowser) and I'd like to make an automator application that takes a URL as input and launches it via a shell script, qutebrowser "$@" &> /dev/null &" so I can set it as a default browser, open links from other applications, etc. The problem is, it seems like Automator apps can only accept local files and folders as input. Is there any way around this? I emphatically do not want to make a service which cannot be used as a default application as far as I know.

I'm currently trying to modify the default URL handling behavior in OS X. I would like, when clicking on any link outside of a web browser, to copy this URL to the pasteboard instead of opening it in the default web browser – for instance, clicking a link in a Skype conversation should copy this URL to the OS X pasteboard instead of opening it in Firefox (which is currently my default web browser).  I have thought about solutions, but I’m currently unable to implement one. If I can create an application that puts URLs into the pasteboard that are sent to it, and can set this application as the default web browser, I would be able to achieve my goal.  I created an application with Automator that executes the shell command pbcopy and have set this application as my default web browser, but I didn’t get the expected result. I did some testing and I can confirm that the application runs on clicking on a link, however, I cannot get the URL passed to the application / shell script. I tried both stdin or a passed argument, but without success.  Is there a way for an application created with Automator to retrieve a clicked URL and send it to pbcopy, when that application is set as a (default) handler for URLs?  Alternatively, is there a better way to create a fake web browser that takes the input and puts it in the pasteboard than Automator? Or is there any other way that I can achieve my goal without a custom application / script?


I raised a flag on a question which was very poorly formatted. But soon after the flag was raised it was edit and nicely formatted. I feel bad about it. What can I do?

I'm wondering (since it just happened to me), is it possible to "cancel" ("undo", "delete", "retract", whatever) a flag I just raised if I misclicked it, so the mods won't waste time?  I looked everywhere, but I can't find such a feature.


If you want to perform a PCA, I guess that using SVD will always work. Eigendecomposition on the covariance matrix only works when your data is not high dimensional(so n > p). But I'm wonder if there are circumstances in practice where you would prefer eigendecompostion over SVD?

This question is about an efficient way to compute principal components.   Many texts on linear PCA advocate using singular-value decomposition of the casewise data. That is, if we have data $\bf X$ and want to replace the variables (its columns) by principal components, we do SVD: $\bf X=USV'$, singular values (sq. roots of the eigenvalues) occupying the main diagonal of $\bf S$, right eigenvectors $\bf V$ are the orthogonal rotation matrix of axes-variables into axes-components, left eigenvectors $\bf U$ are like $\bf V$, only for cases. We can then compute component values as $ \bf C=XV=US$. Another way to do PCA of variables is via decomposition of $\bf R=X'X$ square matrix (i.e. $\bf R$  correlations or covariances etc., between the variables ). The decomposition may be eigen-decomposition or singular-value decomposition: with square symmetric positive semidefinite matrix, they will give the same result $\bf R=VLV'$ with eigenvalues as the diagonal of $\bf L$, and $\bf V$ as described earlier. Component values will be $\bf C=XV$.   Now, my question: if data $\bf X$ is a big matrix, and number of cases is (which is often a case) much greater than the number of variables, then way (1) is expected to be much slower than way (2), because way (1) applies a quite expensive algorithm (such as SVD) to a big matrix; it computes and stores huge matrix $\bf U$ which we really doesn't need in our case (the PCA of variables). If so, then why so many texbooks seem to advocate or just mention only way (1)? Maybe it is efficient and I'm missing something?


If I had a library with 3 classes that I included in my java build path as an external lib and it was composed of:  ClassA:  public class ClassA {     public String getData() {         return ClassB.useThis();     } }   Class B:  public class ClassB {     public static String useThis() {         return "I'm class B.";     } }   Class C:  public class ClassC {     public int someMethod() {         // Some irrelevant stuff     } }   And then in my project I did:  System.out.println(new ClassA().getData());   And then exported this as a runnable jar, would Class C be included in this jar regardless of the fact that it's not referenced in any of the other classes or even used?  This has pondered my mind as you see libraries in C++ that are more than 10mb yet the exported executable that uses that library is substantially smaller. So, is this the same case for java?

Is it possible to specify a Java classpath that includes a JAR file contained within another JAR file?


I want to prove:      $B$ is similar to $A \Leftrightarrow m_A(x) = m_B(x)$ and $P_A(x) = P_B(x)$, where $m,P$ are the minimal and characteristic polynomial, respectively.   "$\Rightarrow$" Let $A$ to be similar to $B$, then they have the same rational canonical form. On the other hand, the characteristic polynomial is the product of the invariant factors, but the invariant factors of an $n \times n$ matrix over a field $F$ are the invariant factors of its canonical form. Since $A,B$ have the same rational canonical form, then the characteristic polynomials are the same, hence: $P_A(x) = P_B(x)$, but the minimal polynomial is the largest invariant factor, so the minimal polynomials are the same and every other invariant factor divides the minimal polynomial, hence: $m_A(x) = m_B(x)$. (This comes from the fact that similar matrices have the same determinant)  "$\Leftarrow$" Let $A, B \in M_3(F)$ with the property that they have the same characteristic and minimal polynomial, that is: $P_A(x) = P_B(x) = f(x),$ $m_A(x) = m_B(x) = g(x).$ we want to prove that $A$ and $B$ are similar. First, recall that since we have a $3 \times 3$ matrix, this implies that the characteristic polynomial will have degree $3$, $g | f$ and every irreducible factor of $f(x)$ appears in $g(x)$. Moreover the degree of $g(x)$ is at most $3$. To prove similarity, it is enough to prove that they have the same set of invariant factors, which implies that the companion matrices will be the same.   $\deg(g(x)) = 3$ If the degree of $g(x)$ is $3$, basically we cannot do a lot, so, we have that: $f(x) = g(x)$, so in this case the minimal polynomial is just $f(x)$ which implies that they are similar. $\deg(g(x)) = 2$ Notice that $f(x) = (x-a)g(x)$ for some $a \in F$ and $(x-a)$ is irreducible. On the other hand, every irreducible factor of the characteristic polynomial must appear in $g(x)$, which implies that: $g(x) = (x-a)(x-b)$ for some $b \in F$ and $f(x) = (x-a)^2 (x-b)$. Again, in this case the set of invariant factors is given by $\{(x-a),(x-a)(x-b)\}$ Then, they share the same invariant factors, so the companion matrices are the same, hence there are similar. $\deg(g(x)) = 1$ clearly, we have that: $g(x) = (x-a)$ for some $a \in F$. Then, the only possibility is that the invariant factors have the following form: $$\{(x-a),(x-a),(x-a)\}$$ Then, the matrices, $A,B$ have the same set of invariant factors and the same companion matrix, which implies that they are similar

Why and how is the  of a matrix in $M_3(\mathbb C)$ fully determined by its characteristic and minimal polynomials? And why does it fail for $n >3$?   Thanks.


As seen from the image below, when using higher strength value for Emission, it seems some aliasing effect appears. Why? And how to fix it?

Often when a mesh light is visible in the camera, the edges are not anti-aliased.  No matter how many samples I do, the lamp border always looks jagged and pixelated.  Is this a rendering error? How can I get around this issue?    And zoomed in 4x:


I have the following code in python:  #-*-coding:cp1252-*- from random import randint  matriz = [[0] * 5] * 5 print matriz for i in range(5):     for j in range(5):         numero = randint(0,10)         matriz[i][j] = numero  for  i in matriz:      print i   Why the all rows are the same???  by example, a random double list generated:  [0, 5, 1, 0, 10] [0, 5, 1, 0, 10] [0, 5, 1, 0, 10] [0, 5, 1, 0, 10] [0, 5, 1, 0, 10]   Thanks.

I needed to create a list of lists in Python, so I typed the following: my_list = [[1] * 4] * 3  The list looked like this: [[1, 1, 1, 1], [1, 1, 1, 1], [1, 1, 1, 1]]    Then I changed one of the innermost values: my_list[0][0] = 5  Now my list looks like this: [[5, 1, 1, 1], [5, 1, 1, 1], [5, 1, 1, 1]]    which is not what I wanted or expected. Can someone please explain what's going on, and how to get around it?


As you can see, there's these weird planes stretching down :(. Does anyone know what causes this, & how I can fix it?

So I am having a problem where the subdivision modifier will constantly distort my models in a very odd way. The subdivision modifier causes the model to warp inside itself at the middle of my model. I will include a before and after picture of the application of the subdivision modifier. I am getting fairly annoyed with this problem so I would very much appreciate if some one could clarify why this is happening.  Thanks, Nova


I want to check my disk partition in Ubuntu as i want to install windows OS and create partition

I've got Ubuntu 10.10 installed to use my whole hard-disk, but would like to use the 130GB of free space I've got to create a new partition and do some development on Unity and Natty.  Can I use gparted to do this?  If so how?


Hello Folks I'm new to Linux and was wondering about the RAM and which version to install 32 or 64 bit? The following is the RAM on my system - 2,048 (1,024 + 1,024) MB, DDR2 RAM (800 MHz).  Cheers and thanks for any reply it's appreciated.

What is the difference between 32-bit and 64-bit Ubuntu? I've heard the 64-bit platform performs better and can detect more than 4GB of RAM. Also, while some apps haven't ported to 64-bit yet, ia32-libs lets a 64-bit machine run them.  If so, why not promote 64-bit over 32-bit?


Is there any open source software that can rival Windows Live Writer

I want a software for blogging like Live Writer in Linux and GNOME.  Do you have any idea?


To redirect from   - http://www.domain.com  - http://domain.com  - https://www.domain.com   to   im using the following (apache)htaccess:  <IfModule mod_rewrite.c>    RewriteEngine On    RewriteCond %{HTTPS} !=on    RewriteRule ^(.*)$ https://%{HTTP_HOST}/$1 [R=301,L] </IfModule>  <IfModule mod_rewrite.c>     RewriteEngine On     RewriteCond %{HTTPS} !=on     RewriteCond %{HTTP_HOST} ^www\.(.+)$ [NC]     RewriteRule ^ https://%1%{REQUEST_URI} [R=301,L] </IfModule>  # BEGIN WordPress  <IfModule mod_rewrite.c> RewriteEngine On RewriteBase / RewriteRule ^index\.php$ - [L] RewriteCond %{REQUEST_FILENAME} !-f RewriteCond %{REQUEST_FILENAME} !-d RewriteRule . /index.php [L] </IfModule>  # END WordPress   This works, but I think it's not the best way. The first two sections would still be to combine, but I don't know how.

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 have intention to rent a Mustang in LA , but the thing is, insurances are so expensive and I do not want to be robbed by the renters.  Which insurances should I choose absolutely?

We just arrived in Hawaii this afternoon, and when I went to pick up the rental car, I discovered I hadn't done my homework with regard to the insurance options.  I recall that my credit card will provide some level of insurance when I use it to rent a car, but when I mentioned it to the Customer Services Representative, he informed me that my credit card only covers collision, and he suggested I purchase liability insurance from the rental agency.  For the future, what information do I need to collect in order to make an informed decision about what insurance policies I should (or should not) purchase when I rent a car?


There are some excellent posts on various sites - both questions and answers; Of course, for the more technical it's harder to appreciate them but I would love to have a newsletter of "the best of SE".  Couple of posts I would like to see there:       Because someone personally checked the place for an answer and that's just the last two days.

Although I'm mostly interested in programming I like to read very good questions and answers from other areas as well.  A network-wide newsletter could contain:   top questions from the stackexchange.com "hot questions" feed (I'm currently following that one in Google Reader, but it's hard work) announcement of new sites from Area 51 (at the moment, I have to remember checking regularly) network-wide announcements (basically blog.stackoverflow.com) content from the new site blogs more interesting things I didn't think of   What I would like best is to be able to customize my newsletter (e.g. "I want to read all hot questions from Unix, but only the very hot questions from Cooking"), but I realize that would probably be too much work and possibly cause confusion.


I hold both US and UK passports but will reside in the UK for the duration.  I just wanted to know if it is OK to enter the US on my US passport but leave only showing my UK passport when i return to the UK?  i.e. only show my US passport at Heathrow and only show my UK passport at JFK.  Thank you.

I am a citizen of two different countries, and have two passports.  How should I use my passports when traveling?


In this sentence, which verb is correct?  (Is/Are) staff given discounts on supplies?

Which one of these two statements is correct?     Our staff do ...      Our staff does ...   And is staffs ever correct?


I'm using the following commands to produce a header and footer on all of the pages of my homework assignment:  \usepackage{fancyhdr} \pagestyle{fancy} \lhead{Math 185 Spring 2014} \chead{Problem Set 3} \rhead{Jacob Kent} \renewcommand{\headrulewidth}{0.25pt} \renewcommand{\footrulewidth}{0.25pt}   How would I remove the header/footer from just the first page of my document? I want it to be on all of the other pages, just not the first one.

How to suppress the fancy header and footer on the first page? On other pages, they should be visible.


I have a string with a return value, i want to compare return value with an edittext's text. but i cant do this. my code is like this :      public static String  login (String a)       {             String Pass = null;             InputStream is = null;             String result = "";             ArrayList<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>();             nameValuePairs.add(new BasicNameValuePair("UName", a));              try{                     HttpClient httpclient = new DefaultHttpClient();                     HttpPost httppost = new HttpPost(LoginAddress);                     httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));                     HttpResponse response = httpclient.execute(httppost);                     HttpEntity entity = response.getEntity();                     is = entity.getContent();              }catch(Exception e){                  Log.e("log_tag", "Error in http connection "+e.toString());                 Pass = "Error Connection";             }              //convert response to string             try{                     BufferedReader reader = new BufferedReader(new InputStreamReader(is,"iso-8859-1"),8);                     StringBuilder sb = new StringBuilder();                     String line = null;                     while ((line = reader.readLine()) != null) {                             sb.append(line + "\n");                     }                     is.close();                     result=sb.toString();             }catch(Exception e){                     Log.e("log_tag", "Error converting result "+e.toString());                     Pass = "Convert Error";             }             //parse json data             try{                     JSONArray jArray = new JSONArray(result);                     for(int i=0;i<jArray.length();i++){                          JSONObject json_data = jArray.getJSONObject(i);                             Log.i("log_tag", "UPWord: "+json_data.getString("UPWord"));                             Pass = json_data.getString("UPWord");                      }             }catch(JSONException e){                     Log.e("log_tag", "Error parsing data "+e.toString());                     Pass = "Wrong Username or Password";             }              return Pass;         }      and i call it like this :          public void onClick(View v)         {             StrictMode.setThreadPolicy(policy);               EditText Username = (EditText) findViewById(R.id.Usernme1);             EditText Password = (EditText) findViewById(R.id.Passwordd1);               String Result = DownLeftFragment.login(Username.getText().toString());              if (Result == Password.getText().toString())             {                 Intent intent = new Intent(MainActivity.this,HomePage.class);                 startActivity(intent);             }             else if (Result == "Wrong Username or Password")             {                 Toast.makeText(MainActivity.this, "Wrong Username or Password", Toast.LENGTH_SHORT).show();                  }             else if (Result == "Error Connection")             {                 Toast.makeText(MainActivity.this, "Error in network connection", Toast.LENGTH_SHORT).show();                     }             else if (Result == "Convert Error")             {                 Toast.makeText(MainActivity.this, "Error in app", Toast.LENGTH_SHORT).show();                    }             else              {                 Toast.makeText(MainActivity.this, Result, Toast.LENGTH_SHORT).show();                      }          }   i defined 2 edittexts, Username1 and passwordd1, it works fine with Username1.getText().toString(), but not with passwordd1.  (if) works fine with all of (else if)s . but not with main if (if (Result == Password.getText().toString()))

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


I am calculating some simple multiplication with double data type.But I don't know why I am getting some unexpected and slightly wrong output.  I am using IntelliJ IDE  public class Main {      public static void main(String[] args) {     // write your code here          double a = 1;         double b = 2;         double c = 3;         double d = 4;         double e = 5;         double f = 6;         double g = 7;         double h = 8;         double i = 9;         double num = 33;           System.out.println(a * 1.1);         System.out.println(b * 1.1);         System.out.println(c * 1.1);         System.out.println(d * 1.1);         System.out.println(e * 1.1);         System.out.println(f * 1.1);         System.out.println(g * 1.1);         System.out.println(h * 1.1);         System.out.println(i * 1.1);         System.out.println(num * 1.1);       } }   Expected Output:   1.1 2.2 3.3 4.4 5.5 6.6 7.7 8.8 9.9 36.3   Output I am getting:   1.1  2.2  3.3000000000000003  4.4  5.5  6.6000000000000005  7.700000000000001  8.8  9.9  36.300000000000004

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


As I understand this, some numbers can't be represented with exactitude in binary, and that's why floating-point arithmetic sometimes gives us unexpected results; like 4.35 * 100 = 434.99999999999994. Something similar to what happens with 1/3 in decimal.   That makes sense, but this induces another question. Seems that in binary both 4.35 and 435 can be represented with exactitude. That's when it stops making sense to me. Why does 4.35 * 100 evaluates to 434.99999999999994? 435 and 4.35 have an exact representation in the double type dynamics:   double number1 = 4.35; double number2 = 435; double number3 = 100; System.out.println(number1); // 4.35 System.out.println(number2); // 435.0 System.out.println(number3); // 100.0 // So far so good. Everything ok.   System.out.println(number1 * number3); // 434.99999999999994 !!! // But 4.35 * 100 evaluates to 434.99999999999994   Why?  Edit: this question was marked as duplicate, and it is not. As you can see in the accepted answer, my confusion was regarding the discrepancy between the actual value and the printed value.


At the end of an upgrade from 12.10 to 13.04, I received an error message something to this effect:  some programs could not be installed. You will have to reinstall them after reboot.   My question: Is there a log produced during the upgrade that I could see to tell me what these programs that failed installation were?  UPDATE:  $ ls -al /var/log/dist-upgrade total 8 drwxr-xr-x  2 root root 4096 Apr 19  2013 . drwxr-xr-x 15 root root 4096 Oct 23 08:12 .. $   sigh

I've upgraded to Ubuntu 12.04 and did it . I didn't look at the "packages to remove" section before clicking next - I've done Ubuntu upgrades many times and assumed it was just the normal set of obsolete library packages etc. But I do tend to watch the terminal text go by and see what it's doing, and I saw it removing a number of packages I wanted. I guess these are packages that aren't on the CD that can't co-exist with the new Ubuntu.  Anyway, I want to find which packages have been removed. So does the update log get saved somewhere?  Then I can start doing some grepping on it and then reinstall the packages I did want.


I wrote a code for changing values of list by function:  package test3; import unit4.collectionsLib.*; public class main {      public static void change (Node<Integer>first) {         first = new Node<Integer>(12,first);     }     public static void main(String[] args) {         Node<Integer> first = new Node<Integer>(1);         first = new Node<Integer>(2,first);         first = new Node<Integer>(3,first);         Node<Integer> pos = first;         while (pos!=null) {             System.out.print(pos.getInfo()+"->");             pos = pos.getNext();         }         System.out.println();         change(first);         pos = first;         while (pos!=null) {             System.out.print(pos.getInfo()+"->");             pos = pos.getNext();         }                    }         }   the output is :    3->2->1-> 3->2->1->   How do I pass an object in the function for changing the list?

I always thought Java uses pass-by-reference. However, I've seen a couple of blog posts (for example, ) that claim that it isn't (the blog post says that Java uses pass-by-value). I don't think I understand the distinction they're making. What is the explanation?


So I'm a newbie in Blender, and when I rendered the model, there were some annoying black pixels. Can you help me?

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


I am trying to solve for the equations of motion to simulate a . I decided to use the spherical coordinates. The Lagrange equation is, $$ L=T-V=\frac{1}{2}m\left(l\dot\theta\right)^2+\frac{1}{2}m\left(l\sin\theta\dot\phi\right)^2-\left(-mgl\cos\theta\right), $$  where $l$ is the length of the rope, $ϕ$ is the angle of the projection of the rope on $x$-$y$ plane with $x$-axis and $θ$ is the angle with the $-z$-axis.   Now, From Noether's theorem, we know that the quantity  $$ J=\dfrac{\partial L}{\partial \dot{\phi}}=ml^2\dot{\phi}sin^2\theta $$ is constant. The equation of motion for $\theta$ follows from the Lagrange's equations and is   $$ ml^2\ddot{\theta}=ml^2\dot{\phi}sin\theta cos\theta-mglsin\theta $$ We can substitute $\dot{\phi}$ for the constant J in the expression to get an equation entirely in terms of $\theta$ which we choose to write as   $$ \ddot{\theta} = -\frac{\partial V_{eff}}{\partial \theta} $$   where the effective potential is defined to be  $$ V_{eff}(\theta) = -\frac{g}{l}cos\theta  + \frac{J^2}{2m^2l^4}\frac{1}{sin^2\theta} $$  Now, if I had substituted J for $\dot{\phi}$ directly into the Lagrangian and solved, I would've derived a similar equation as above, but I would've got a minus sign wrong. And apparently the reason is that Lagrange's equations are derived under an assumption that $\theta$ and $\phi$ are independent. I do get that. But since we get $J$ from the Lagrangian, shouldn't substituting $J$ back and solving still work?   I am looking at this as just a mathematical operation and cannot seem to wrap my head around it. Could somebody give me a stronger reason as to why this doesn't work or maybe explain the above reason more explicitly?

A mass of point performs an effectively 1-dimensional motion in the radial coordinate. If we use the conservation of angular momentum, the centrifugal potential should be added to the original one.     The equation of motion can be obtained also from the Lagrangian. if we substitute, however, the conserved angular momentum herein then the centrifugal potential arises with the opposite sign. So if we naively apply the Euler-Lagrange equation then the centrifugal force appears with the wrong sign in the equations of motion.   I don't know how to resolve this "paradox".


I just upgraded to ubuntu 20.04 and I can't hide my desktop icons, I've tried dconf-editor and tweaks but none of them worked.     In deconf-editor I've disabled the show-desktop-icons option in org/gnome/desktop/background but it has no effect on the desktop.

After upgrading from Ubuntu 18.10 to 19.04, Gnome has upgraded from 3.30.2 to 3.32.0. My handy desktop icons, links, and mounted volume icons are gone, the Desktop tweaks are gone to bring them back, and the Desktop shortcut is gone in the sidebar of Nautilus (Files). The actual files and Desktop are still there when you navigate under Home obviously, but this makes them so inconvenient to get to or use.  I found and installed the Gnome extension called Desktop Icons and that works...but not well. They're difficult to size, sort, and arrange. And they used to be clickable on top of or through my Conky stuff. Now they are below Conky and I cannot click on them. So it really renders Conky unusable for me. I have to turn off Conky to use my desktop icons. I really want the old Gnome desktop back.   I realize it's too late or extremely difficult to go back to Ubuntu 18.10 at this point. Can I stay on 19.04 and revert back to Gnome 3.30.2? If so, how?


This is probably an easy one, but I can't think of the right combination of keywords. I read it as a hardback around the late 1980s to the early 1990s. It involved a brother and sister who somehow wound up back in early ages of Celtic Ireland. They meet a young man who turns out to be , although I want to say that he used a different name, so it took the children a while to catch on. It was definitely a fantastic take on it, as I remember Cuchulain using Gáe Bulg, his magic spear. Specifically, there was something involving chasms belching poisonous gasses, but he could breath with his mouth by the spear (which does not seem to be among the legendary qualities of that weapon).  I vaguely remember that the children first encounter Cuchulain by a body of water, I think as he was bathing. When the children are returned home, they return with a carved comb of bone or ivory. I remember they also came home with a case of lice, which required boiling the comb. Things that stick with you... There might have been a sequel, but I don't remember any details if so.  I think (and this is very tenuous) that the cover had the brother and sister stepping out of a forest, hand in hand, with Cuchulain down by the water's edge, as per that first meeting.

So, I read this book in the mid-nineties (no idea if it was new or not).  I can't recall the title (obviously), but relevant plot points:  It starts off like the Narnia series, where a young (tween) sister and brother are sent to live with relatives in a country estate.    If I recall correctly, the girl was older, and the boy was more of a child, she was closer to being a teen (or actually being a teen). I remember specifically that he was referred to as having baby fat still, and being more childish than her.  They discover salmon swimming in the pool, and there was an old woman. Turns out she was a druid who had turned a man into a salmon for (reasons). Both he and her are from the ancient past (you know, when druids were more common), and the guy starts to resemble the famous Irish hero Finn MacCool.  I am pretty sure he was called Finn also, but I don't think they ever gave him a last name in the book, so I'm pretty sure it's not the eponymous book "Finn MacCool" which I saw later on.    The druid takes the kids and young man back in time with her, and they live in the woods for a while having adventures.  I don't recall all of them, but I do recall that Finn had to catch and eat the "salmon of wisdom" or similar, and burned his thumb in doing so, which made him think he had to stick his thumb in his mouth to think.    Eventually the kids were returned to their own time, leaner and harder and more tan, and the boy faced up to some bullies and didn't let himself get pushed around (evidence of his character development, I suppose).    I thought it'd be a fun book for my daughter, but can't for the life of me remember the name to find it.


Is there an idiom like ‘the quæstion raises itself, whether …’?

I'd like to say something like "Then, we have the question: why did this happen?" What is a proper way to say this using the phrase "The question then arises..."? Is it "The question then arises as to why this happened."? If this is correct usage, are there other continuations of this phrase (i.e. "The question then arises") that I could use?


Can anybody help me, what i am doing wrong here.   I want to add an class, and when I click on the class, it should remove the class.     $(".processing-signs-direction-cover-sign-direction-selection-process").click(function() {   $(this).addClass("selected-sign"); });  $(".selected-sign").click(function() {   $(this).RemoveClass("selected-sign");   alert(23); }); <script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>     Thank you

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


I am in the process of trying to run a script which usually sits on an AIX machine on its new host Linux node.  The code I am running looks like this:      (uuencode $path/info.dat info.csv; uuencode $RESULTS results.log) | mail -s "Info" $MAIL_RECIPIENTS   So normally what this does is take the .dat file and standard outs it in a csv format - and sends the mail with no body but just the info.csv and results.log attached.  What is actually happening is the encoded output that uuencode produces (if you were to just run it independently) is being sent in the message body and there are no attachments.  The email body looks like this:   begin 775 info.csv  M+3`U+C`S+C4S+C(Q-#`W."(L(D%55$]314Y$("`B+")!551/4T5.1"`@(BPB etc.. etc... end  begin 775 results.log M+3`U+C`S+C4S+C(Q-#`W."(L(D%55$]314Y$("`B+")!551/4T5.1"`@(BPB etc... etc... end   The version of uuencode on the new machine:   uuencode (GNU sharutils) 4.7 Copyright (C) 1994, 1995, 1996, 2002, 2005, 2007 Free Software Foundation, Inc. This is free software; see the source for copying conditions.  There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

e.g., I've got files I want to send by sendmail but the receiving mailbox (for posting pictures to my blog) will not accept uuencode files a la   $uuencode file | sendmail user@domain  I'm guessing it'll accept MIME though. So what command can I use instead?


Here is the situation, I foolishly decided to install several apps to a D: drive rather than the C: drive in my Windows 10 install. I thought this would help me get up and running faster in the event of having to reinstall. Very few apps actually worked this way, so I decided to cut my losses and go back to the way it was. Silly me, I didn't uninstall the app from the D: drive first. I just deleted the partition. This has caused a problem, mostly with my Anti-Virus software Malwarebytes. The program is still listed under programs via control panel and the settings menu. Uninstalling it from the settings menu tells me the path does not exist, and the control panel tells me I do not have permission. When running the Windows uninstall troubleshooter from Microsoft I have to manually key in the product ID for the Malwarebytes. It runs and says the program is gone. It did not work though, even after a restart the program remains. I attempted to install the program again, but it simply tries to force me to install to a D: drive that no longer exists. I cannot change the file path. Having encountered this before, I tried to clean the Registry. This did not work. It seems this is not a common enough issue to yield good results on my Google searches, as running the troubleshooter seems to fix it for most people. I am on Windows 10 Pro Version 20H2 OS build    19042.985 Experience  Windows Feature Experience Pack 120.2212.2020.0

So I'm cleaning out an old computer, and several of the programs it thinks it has were actually installed on an old drive, that's now gone. For some of them, it prompts to get rid of them because it can't find the drive, so that's all well and good.  But, for LibreOffice and a couple of others, it tries to run the LibreOffice Uninstaller, and only quits with a fatal error when the LibreOffice uninstaller can't find the drive.   The difference here is that in the first case, Windows can't even find the drive with the uninstallers on them, so it prompts to remove them; but in the second, its found the uninstallers on the local disk somewhere and is trying to run them, prompting a fatal error when the uninstaller can't find them.  What should I do here? How can I remove what's left of these programs/erase their names from the family tree?  Thanks!  evamvid


With reference to the question , when reviewing in SO, we have to refresh the page every now and then to view the newly added entries to the review queue.  However, votes and reputation are updated on the display as soon as a vote is cast, and as soon as reputation changes. Is it possible to integrate this kind of feature to see the number of pending entries in the review queues page.  This request is probably not a duplicate of , where the feature is requested for a counter in front of the title of the page. But, my question adresses the .

I would like to see the review page refresh automatically if I have done some reviews and get the message that there are currently no more reviews to perform.  Refreshing the whole page is, in my opinion, a little too much overhead. The review itself seems to work with AJAX. So, a small refresh button to trigger would be nice too, if the real-time updates are too complex.


Wondering why you would choose to use smaller capacitors in parallel vs one bigger one.  Here's an example:      Is this a component size and track width choice?  Thanks!

I've seen some circuits where a decoupling capacitor is used as well as a reservoir capacitor, like this (C4 and C5):    I've read about  and for me it looks as if they are meant to remove small fluctuations in the supply voltage. Then I thought - wasn't that the purpose of a  as well? Why wouldn't the reservoir capacitor be able to filter out the small fluctuations, if it is able to filter out the large fluctuations?  So I feel like I have a basic misunderstanding here. What is the purpose of a decoupling capacitor next to a reservoir capacitor, when we assume we place both equally near to the power consuming part? Or is the only advantage of the decoupling capacitor that it is smaller and can therefore be easily placed more near to the power consuming part?


I create data in Excel 2013 and save it as .csv. We have an application that imports files of type .address so after saving the file as customer.csv, I change the extension to customer.address. This is a custom file format specific to us, but essentially this is just CSV.   When I want to edit this customer.address file, I open this in Excel by selecting the    Delimited option Select Comma in Delimiters Finish   I edit my changes and when I press Save, this is the default dialog box that pops-up.     When I click Yes, it saves my file as Tab delimited not Comma delimited.  What I'm actually expecting is this, to preserve the commas.    How do I make this work such that when I save, the default option should be CSV (Comma delimited)?

I'm trying to save an Excel 2007 file as a pipe-delimited text file but in the Save As list, I see only tab-delimited and csv options.  How do I go about specifying the delimiter, which as I recall was possible in earlier Excel versions via a wizard?


Let's say that I want to ask a simple question like "How are planes able to fly?" or "Where on the internet can I find the list of all presidents of USA?". Asking these questions I'd have to add a description because otherwise I get the error:     Body is missing.   What if I have nothing to add? Should I repeat the question? In my opinion adding why I need the answer to these questions is useless and clutters the thread.  Edit: This is not the same question as mentioned "How to leave body of question empty?". I'm asking why can't it be empty. Ramhound's comment on that question does not satisfy me at all. Not exery question needs more details. Examples what I should add as a description to mentioned above questions are welcome so I can feel what to add to my future simple questions.  The Tin Man's comment also doesn't satisfy me. In my opinion, SE is also for simple questions and they are not always simple.

What if the whole question is contained in the title? What should I place in the body?


Suppose I have the following finite sum;  $$S_n=\sum_{k=1}^n{\left\lfloor{\frac{n}{k}}\right\rfloor}$$ I've never dealt with something like this before and was curious of a way to express it with a closed form.  I can see the first few sums are  $$S_1=1$$ $$S_2=2+1=3$$ $$S_3=3+1+1=5$$ $$S_4=4+2+1+1=8$$ $$S_5=5+2+1+1+1=10$$

$$ \sum_{i=1}^N\left\lfloor\frac{N}{i}\right\rfloor $$ Is there a closed form expression to the above sum? (Mathematica doesn't give me anything)


Would it violate any special laws, if someone were to change the axiom of SR that      "Speed of light in vacuum is the same with respect to all reference frames"   To      "Speed of light in vacuum is the same with respect to all reference frames, but it's own reference frame, where it is the minimum".   I can then assign the photon a rest mass. Of course, it will get a reference frame as well. With no direction, time or speed.  I mean if I got in the concept of 0 here, then it would be possible to assign the photon a rest mass, and say that the photon exhibits both these traits. Mass and EM wave both.  The mass trait not part of an EM field.  Could factor in the extra mass in the universe, and can be checked using calculations as well I guess?

Why can't photons have a mass? Could you explain this to me in a short and mathematical way?


I'm having a little trouble understanding the recommendation to setup a separate user for the file permissions of www/html folder in apache. See point 5 from   The recommendation is out of the box Apache sets your html folder to nobody or daemon. But this isn't a good idea!  I have a VM on  and when uploading files it only lets you do this to your home folder. Then from their with ssh I can move them over to my html folder.  When I do a ls -a on my html folder after the move, it has kept the username for my local machine that I uploaded the files and folders from.  Long story short have I, albeit without knowing, basically adhered to this above recommendation? Or do I need to create a completely new user on the box and assign the html folder to that user?

I want to stop having to use sudo everytime I work in /var/www. How can I do that? I simply want to put all of my sites into this directory and work with them without too much pain.


I wanted to know how to write in LaTeX an integral but not in italic. Please!

Having searched around I couldn't find a package that could produce the following integral sign.    How do I produce this bold looking vertical symbol? Xe-/LuaTeX are totally fine with me.  \documentclass{article} \begin{document} $\int_a^b$  \end{document}


So, let $A,E\in M_{nxn}(\mathbb{R})$ and $(A+E)^3=O$. Show that $A$ is a regular matrix and find $A^{-1}$.  What I tried to do is represent $A$ as a $_{3x3}$ matrix and try to prove that it's regular using $(A+E)^3=O$, but I after calculating $A^2$ I realized it's not the right way to do it. Any ideas?

If $A\in M_{n\times n}\left(\mathbb{R}\right)$ is such that $ (A+I)^3=0$, show that $A$ is an invertible matrix and find the inverse of $A$.  My idea was: \begin{eqnarray*} 0&=&\left(A+I\right)^3\\ &=&A^3+3A^2I+3AI^2+I^3\\ &=&A^3+3A^2+3A+I, \end{eqnarray*} then $$I=-A^3-3A^2-3A,$$ so $$I=A\left(-A^2-3A-3I\right).$$ It follows that $$A^{-1}=-A^2-3A-3I.$$ Now I found the inverse matrix, but how does this show that an inverse actually exists?


My code needs to get user input, and print the letter that occurred the most in that input. I know I need to do something along the lines of switching the String input into char[], but what to do after words? how to check for each character's apperance? any ideas how?  I need to do it using only loops & Wrapper classes, it's a part of an assignment so I have to be specific.    public static void main(String[] args){     int frequencyCount = 0; //count each letters frequency     char popularChar = ' '; //letter with the most frequency     for (int i = 0; i < array.length; i++){       for(int c = 0; c < array.length; c++){         frequencyCount++;       } }

I have the string   a.b.c.d   I want to count the occurrences of '.' in an idiomatic way, preferably a one-liner.  (Previously I had expressed this constraint as "without a loop", in case you're wondering why everyone's trying to answer without using a loop).


Here is the problem statement:  Let $a$, $b$ $\in$ $\Bbb{R}$. A sequence $(a_{n})_{n \in \Bbb{N}}$ is defined recursively by $$a_{0}:=a, \qquad a_{1}:=b, \qquad a_{n} = \frac{1}{2}(a_{n-1}+a_{n-2}) \quad \text{for} \quad n \geq 2.$$ Prove that $\lim_{n\to\infty}a_{n}$ exists and compute its value.  Now I have proved that the limit exists. My idea was to use the Monotone Convergence Theorem as follows: Proof: Without loss of generality, assume $a<b$. By inspection of the first two terms of $a_{n}$, we see that $$a_{3} = \frac{1}{2}(a_{2}+a_{1})=\frac{1}{2}\left[\frac{1}{2}(a_{1}+a_{0}) + a_{1}\right] = \frac{1}{2}(a_{1}+a_{0})+\frac{1}{4}(a_{1}-a_{0})=a_{2}+\frac{1}{4}(a_{1}-a_{0})>a_{2} \quad (\because a_{1}>a_{0}).$$ Therefore we need to show that the sequence is increasing, so our inductive hypothesis is $a_{n}<a_{n+1}$. $$a_{n}<a_{n+1}\implies a_{n+1}=\frac{1}{2}(a_{n}+a_{n-1})<\frac{1}{2}(a_{n+1}+a_{n})=a_{n+2}.$$ Thus $a_{n}$ is increasing for $n\geq 2$. Now we need to show that it is bounded. By inspection, $a_{3}=\frac{1}{2}(a_{2}+a_{1})<\frac{1}{2}(a_{1}+a_{1}) = a_{1}$, and $a_{4}<a_{1}$ and so on. So again assume by induction $a_{n}<a_{1}$ and we have $$a_{n+1}=\frac{1}{2}(a_{n}+a_{n-1})<\frac{1}{2}(a_{1}+a_{1}) = a_{1}.$$ Thus $a_{n}$ is bounded above. Hence by the Monotone Convergence Theorem, sequence is convergent and $\lim a_{n}$ exists.$\quad\square$ However, I'm stuck in finding the limit. Any hints would be appreciated.

How can I find the limit of the following recursive formula?  $a, b \in \mathbb{R}$ $a_0=a; a_1=b; a_n= \frac{1}{2}(a_{n-1}+a_{n-2})$ $\lim\limits_{n \rightarrow \infty}{a_n} = ?$  Many thanks in advance.


What is the generating function of partitions of $n$ into $a_1, \ldots, a_r$ where $a_1 \le  \ldots \le a_r$, $a_1 = 1$ and $a_i - a_{i-1} \le 1$ for $2 \le i \le r$?  Hint: find a bijection between set of these partitions and some set of partitions with a well-known generating function.  I've tried to find a bijection using Ferrers diagrams but with no result.

Division of number $n$ on parts $a_1,...,a_r$ where $a_1 \le ... \le a_r$ we call a plain if $a_1 = 1$ and $a_i - a_{i-1} \le 1$ for $2 \le i \le r$. Find enumerator (generating function) for plain divisions.  my try  The hint was to use bijection between plain divisions and some commonly know enumerator. I tried to use enumerator of divisions on different parts: $$ (1+x)(1+x^2)...(1+x^r)$$ where number of plain divisions is  $$[x^n](1+x)(1+x^2)...(1+x^r) $$ let function  $$f(n,r) = [x^n](1+x)(1+x^2)...(1+x^r) $$  For some first divisions it works. For example: $$f(4,3) = 1 $$ $$f(6,3) = 1 $$ $$f(11,5) = 2$$ But when I tried to find bijection, I failed. I found that this function isn't correct because $f(15,6) = 4$ but should be equal to $3$ because: $$15 = 1,1, 2, 3, 4, 4 \\ 15 = 1, 2, 2, 3, 3, 4\\ 15 = 1, 2, 3, 3, 3, 3 $$. There I stucked.


I  where user only get articles to edit.  How can I set up the page that it opened when a user logged in?

I have a view in Drupal 7 that lists PDF files. I want to keep track of the users that open that file; so I want that, if they are not logged in when they click, they are sent to the login/sign up page. I have already accomplished this using two views with different permissions, but the problem is that, after they sign up, they are redirected to the user profile page, as opposed to the PDF file.   How can I accomplish this?


I have two folders in Windows 8.1. The first folder, a, has 50 .jpg files numbered 01.jpg through to 50.jpg. My second folder, b, has the same amount of .jpg files named in the exact same manner.   My goal is to merge these two folders, but rename the files in b 51.jpg through to 100.jpg so that they stay in the same order.

I've got a bunch of files named with a the pattern 99 - DescriptiveName.txt and I'd like to remove the number from the front so I just have DescriptiveName.txt.  How can I do this? Can I do it from the command line or is there a utility that can do this?


If the quadratic equations $x^2-mx+n=0$ and $x^2+mx-n=0$ both have integral roots, prove that $6|n$.   I've proved that $3|n$, and that $2|n$ for odd $m$, but I can't seem to prove it for even $m$.   Please help.

Problem:  Let $x^2+mx+n$ and $x^2+mx-n$ give integer roots where $(m,n)$ are integers. Show that $n$ is divisible by $6$  My attempt:  Since the roots are integers then the discriminants of both the equations should be perfect squares.   Let $a=\sqrt{m^2-4n}$ and $b=\sqrt{m^2+4n}$, then $(ab)^2=m^4-16n^2$ where $(a,b,m,n)$ are all integers. I am stuck here...


I'm attempting to setup a network with hundreds of fanless (ARM)PCs. Each will have its filesystem on a 32G sd card. The image I'm working with uses Debian 6.x and the card is formatted with EXT2 as one large partition.  Last night one of the test machines started throwing errors as follows:  sd 0:0:0:0: [sda] Device not ready sd 0:0:0:0: [sda]  Result: hostbyte=0x00 driverbyte=0x08 sd 0:0:0:0: [sda]  Sense Key : 0x2 [current] sd 0:0:0:0: [sda]  ASC=0x3a ASCQ=0x0 sd 0:0:0:0: [sda] CDB: cdb[0]=0x28: 28 00 00 2d 78 86 00 00 08 00 end_request: I/O error, dev sda, sector 2979974 EXT2-fs (sda2): previous I/O error to superblock detected  sd 0:0:0:0: [sda] Device not ready sd 0:0:0:0: [sda]  Result: hostbyte=0x00 driverbyte=0x08 sd 0:0:0:0: [sda]  Sense Key : 0x2 [current] sd 0:0:0:0: [sda]  ASC=0x3a ASCQ=0x0 sd 0:0:0:0: [sda] CDB: cdb[0]=0x2a: 2a 00 00 01 78 86 00 00 08 00 end_request: I/O error, dev sda, sector 96390 EXT2-fs (sda2): error: read_block_bitmap: Cannot read block bitmap - block_group = 11, block_bitmap = 360448   Does this mean the media is bad? Or decaying somehow? I'm going to try reformatting it and see if it happens again.   Is there a better way to setup this card? Different file system?  EDIT: Possible related post

I just plugged my SD Card to my PC after a long videography day, and I suddenly got this problem:    It is also not showing all the videos I took on my camera so what is the solution?


I want to find the limit of $\left(1+\frac{1}{n^{2}} \right)\left(1+\frac{2}{n^{2}} \right)...\left(1+\frac{n}{n^{2}} \right)$ as $n \rightarrow \infty$, any hint?

How can we compute the following limit:     $$\lim_{n\to\infty}(1+1/n^2)(1+2/n^2)\cdots(1+n/n^2)$$   Mathematica gives the answer $\sqrt{e}$. However, I do not know to do it.


I tried to post a  in the  and it didn't work:  However, I then tried to recreate the URL markdown problem using the exact same link, and also one with the same bold text, but they worked just fine.

We've come to rename Markdown to Letdown in the  because it lets you down so often. I've now just found a pattern. It seems markdown . That is, this  Letdown can't cope with multi-line comments. Let's see code?  fails to display code marked as code, while this works  But code works.  Now, I think it would be Ok if you said chat messages shouldn't be multi-line. (Although I'd be a bit annoyed, because I like them.) But if so, please don't render them as multi-line (as is the case with comments), so we aren't tempted to use them.


I have updated my system and I want to do some tests needed to remove the cache. I know the command download the packages list from the repositories,but where is the local database to store this infomation.

I have 20 to 3o computers on my network and I have a copy of the debian packages on /var/cache/apt/archives but when I take this downloaded copy to any other machine I need to hit an "apt-get update" , How do I avoid this ? Where is the list of packages which is updated by that command stored. I need to copy them as well, and use it on a computer which is completely offline.


Is there a way for a human character to increase their life span by any significant amount?  I want to expand his lifespan because I want him to eventually raise a dragon, but I know that's way outside of a human's or even elf's lifetime. Fluff-wise, the human is also draconic, as in he has dragon blood, though I'm not planning yet on taking any bloodline stuff for this.  We're playing Pathfinder, though D&D 3.5e material is allowed. Preferably he should remain himself and human. (This includes not becoming an evil lich.)  Also, since this will change answers by A LOT. I am going to be the host of the group. Which means I have GM duty since I'm the only one of us who's read dnd/pathfinder books.  Sources allowed as I know currently for sure  Pathfinder: Core rulebook, ultimate combat, ultimate magic, ultimate equipment, advanced class guide.  3.5: complete arcane. Races of Eberron*. complete warrior. Complete Arcane. Complete mage. PHB 2. Draconomicon. Races of the dragon.  Also pertaining to him he's most likely going to be a magus

I was thinking of a way for a humanoid (PC or NPC) to live forever in a D&D setting, but through rather "common" and reproducible means, such that they will be available to many. By this logic I exclude cases such as a god giving immortality (or some other intervention) or a unique item granting an endless lifespan etc.  To cover all bases I will note that miracle and wish cannot do this directly, nor can true resurrection (and its lesser brethren) "restore to life a creature who has died of old age".  I had came up with the following ruse:   Reach your deathbed with at least 2 HD (or levels). Have someone kill you so that the cause of death will not be "old age". Have a druid cast reincarnate on you into a young body. You "recall the majority of your former life". I assume your memories, personality/identity and experiences are preserved.   Rinse and repeat. It's not that difficult to recover the 1 HD lost through the course of almost a lifetime. The material components are worth 1,000 gp - might not be easy to get, but surely possible.  Furthermore, it is stated that "A wish or a miracle spell can restore a reincarnated character to his or her original form.". I assume the "original form" is the aged humanoid at his or her deathbed - not the direction we are looking for, unless it means that the humanoid restores his race only.  Is there a flaw in this plan? Is there another way of doing it?


I have just launched an EC2 machine, in the frankfurt region. The locale is corrupted:  ubuntu@myhost:~$ locale locale: Cannot set LC_ALL to default locale: No such file or directory LANG=en_US.UTF-8 LANGUAGE= LC_CTYPE="en_US.UTF-8" LC_NUMERIC=de_DE.UTF-8 LC_TIME=en_US.UTF-8 LC_COLLATE="en_US.UTF-8" LC_MONETARY=de_DE.UTF-8 LC_MESSAGES="en_US.UTF-8" LC_PAPER=de_DE.UTF-8 LC_NAME=de_DE.UTF-8 LC_ADDRESS=de_DE.UTF-8 LC_TELEPHONE=de_DE.UTF-8 LC_MEASUREMENT=de_DE.UTF-8 LC_IDENTIFICATION=de_DE.UTF-8 LC_ALL=   How can I correct the issue?

I'm having massive problems with Debian's locale Settings.   I want my server to talk to me in standard English (en_US.UTF-8?) and additionally have de_DE.UTF-8 available for a few Python scripts that require it. I fudged around with pretty much all combinations of locale-gen, dpkg-reconfigure locales and editing of config files.  Now, when logging into my server, I'm greeted with this:  Last login: Fri Mar 13 22:23:14 2015 from 1.2.3.4 -bash: warning: setlocale: LC_ALL: cannot change locale (de_DE.UTF-8) -bash: warning: setlocale: LC_ALL: cannot change locale (de_DE.UTF-8)   What does this even mean?  On my other server, I somehow managed to configure everything correctly, and locale -a correctly outputs the following there:  C C.UTF-8 de_DE.utf8 en_US.utf8 POSIX   On this server, however, I only get this at the moment:  C C.UTF-8 POSIX en_US.utf8   How do I fix this?


Is it possible to perform a database list refresh in T-SQL in the same way as in the SSMS right context menu Refresh option? I've a 2014 Express instance with 197 databases inside. In my C# app I have a method used to get all databases names. Some times it only returns 34 results and in the next call 197. I'm using the following script to get the database names : SELECT name, create_date FROM sys.databases  WHERE name NOT IN ('master','model','msdb','tempdb') AND name NOT LIKE 'ReportServer$%' AND HAS_DBACCESS(name) = 1  OPEN db_cursor   FETCH NEXT FROM db_cursor INTO @db_name, @create_date  WHILE @@FETCH_STATUS = 0   BEGIN        EXEC(' USE [' + @db_name + '];             INSERT INTO #temp_App                 SELECT ''' +  @db_name + ''',                 ''' + @create_date + '''                 FROM sys.extended_properties                 WHERE name = ''Application''                 AND value = ''app01''             ')      FETCH NEXT FROM db_cursor INTO @db_name, @create_date      END   CLOSE db_cursor DEALLOCATE db_cursor  SELECT * FROM #temp_App DROP TABLE #temp_App  And the c# code to execute the script List<DatabaseInfo> list = new List<DatabaseInfo>();                          using (SqlConnection connection = new SqlConnection(connectionString))             {                 try                 {                     connection.Open();                     using (SqlCommand command = connection.CreateCommand())                     {                                                  command.CommandText = query;                                               using (SqlDataReader resultReader = command.ExecuteReader())                         {                             while (resultReader.Read())                             {                                 string name = resultReader[0].ToString();                                 DateTime createDateTime = DateTime.Parse(resultReader[1].ToString());                                  list.Add(new DatabaseInfo(name, createDateTime));                             }                         }                     }                     connection.Close();                 }                 catch (Exception myException)                 {                     log.Error("Error occured  " + myException.Message);                 }                 finally                 {                     connection.Close();                 }             }             return list;         }

I know this question has been asked several times and I know the solution, but I am trying to understand the underlying cause of the problem:  I have the following code to perform database backups.   DECLARE @Filename   VARCHAR(256) DECLARE @FileDate   VARCHAR(15)  DECLARE @Path       VARCHAR(50)  DECLARE @Name       VARCHAR(50)   -- specify database backup directory SET @Path = '\MyPath'  -- specify filename date SELECT @FileDate = CONVERT(VARCHAR(20), GETDATE(), 112) + '_' + REPLACE(CONVERT(VARCHAR(20), GETDATE(), 108),':','')  DECLARE db_cursor CURSOR FOR     SELECT [name]         FROM master.sys.databases         WHERE [name] NOT IN ('master', 'msdb', 'model', 'tempdb')             AND [state_desc] = 'ONLINE'  OPEN db_cursor FETCH NEXT FROM db_cursor INTO @Name  WHILE @@FETCH_STATUS = 0 BEGIN      SET @Filename = @Path + @Name + '_Full_Backup_' + @FileDate + '.bak'     BACKUP DATABASE @Name     TO DISK = @Filename     WITH CHECKSUM,         COMPRESSION      FETCH NEXT FROM db_cursor INTO @Name END  CLOSE db_cursor DEALLOCATE db_cursor   Sometimes, only some databases are backed up, suggesting that the cursor is not iterating over all of the rows returned or that the query itself is not returning the names of all the databases it should be.  I am trying to understand why this happens. I know that the fix is to use a STATIC cursor, suggesting the issue is with the results in the underlying query   SELECT [name]     FROM master.sys.databases     WHERE [name] NOT IN ('master', 'msdb', 'model', 'tempdb')         AND [state_desc] = 'ONLINE'   are changing, but I can't see what would be changing (no database names would change and the Error log doesn't suggest that the database state has changed)


Let vectors P1, P2, and P3 be defined as follows:  P1 = [1 2 3 4] $^{T}$, P2 = [4 -2 -6 -7]$^{T}$, and P3 = [3 4 -2 1]$^{T}$  Let $x = [1 \, 2\, 3\, 7]^{T}$  This question is compromised into two parts:  a. Determine the closest vector $\hat{x}$ in span [P1, P2, P3].   b. Determine the orthogonal complement of x in span[P1, P2, P3].  Part a. is simply the projection x onto the subspace spanned by those vectors: $A(A^{T}A)^{-1}A^{T}x$. However, I am unsure about part b. I know that $x - \dot{x}$ is the orthogonal complement to the subspace spanned by [P1, P2, P3], but how do I find the orthogonal complement of x $\textbf{in}$ span [P1, P2, P3]?

In a unitary space $\Bbb R^4$, subspace $M=\operatorname{span}\left\{b=\begin{bmatrix}1\\1\\1\\1\end{bmatrix}\right\}\leqslant\Bbb R^4$ is given. Find the best approximation of the vector $x=\begin{bmatrix}2\\2\\0\\0\end{bmatrix}\in\Bbb R^4$ by the vectors from the subspace $M^\perp$.     My attempt:  Let's extend $\{b\}$ to the basis $\{b,c_1,c_2,c_3\}$ for the whole $\Bbb R^4$ and let's apply Gram-Schmidt to it. I thought the following choice of linearly independent vectors $c_1, c_2,c_3$ would be the most convenient one.  $$b=\begin{bmatrix}1\\1\\1\\1\end{bmatrix},c_1=\begin{bmatrix}1\\0\\0\\0\end{bmatrix},c_2=\begin{bmatrix}0\\1\\0\\0\end{bmatrix},c_3=\begin{bmatrix}0\\0\\1\\0\end{bmatrix}$$  $\begin{aligned}e_1&=\frac1{\|b\|}\cdot b=\frac12\begin{bmatrix}1\\1\\1\\1\end{bmatrix}\\f_2&=c_1-\langle c_1, e_1\rangle e_1=\begin{bmatrix}1\\0\\0\\0\end{bmatrix}-\frac12\left\langle\begin{bmatrix}1\\0\\0\\0\end{bmatrix},\begin{bmatrix}1\\1\\1\\1\end{bmatrix}\right\rangle\frac12\begin{bmatrix}1\\1\\1\\1\end{bmatrix}=\frac14\begin{bmatrix}3\\-1\\-1\\-1\end{bmatrix}\\e_2&=\frac1{\|f_2\|}\cdot f_2=\frac1{2\sqrt{3}}\begin{bmatrix}3\\-1\\-1\\-1\end{bmatrix}\\f_3&=c_2-\langle c_2, e_1\rangle e_1-\langle c_2, e_2\rangle e_2=\begin{bmatrix}0\\1\\0\\0\end{bmatrix}-\frac12\left\langle\begin{bmatrix}0\\1\\0\\0\end{bmatrix},\begin{bmatrix}1\\1\\1\\1\end{bmatrix}\right\rangle\frac12\begin{bmatrix}1\\1\\1\\1\end{bmatrix}-\frac1{2\sqrt{3}}\left\langle\begin{bmatrix}0\\1\\0\\0\end{bmatrix}\begin{bmatrix}3\\-1\\-1\\-1\end{bmatrix}\right\rangle\frac1{2\sqrt{3}}\begin{bmatrix}3\\-1\\-1\\-1\end{bmatrix}\\&=\begin{bmatrix}-\frac14+\frac14\\\frac34-\frac1{12}\\-\frac14-\frac1{12}\\-\frac14-\frac1{12}\end{bmatrix}=\begin{bmatrix}0\\\frac23\\-\frac13\\-\frac13\end{bmatrix}\\\\e_3&=\frac1{\|f_3\|}\cdot f_3=\frac1{\sqrt{6}}\begin{bmatrix}0\\2\\-1\\-1\end{bmatrix}\\\\f_4&=c_3-\langle c_3,e_1\rangle e_1-\langle c_3,e_2\rangle e_2-\langle c_3, e_3\rangle e_3\\&=\begin{bmatrix}0\\0\\1\\0\end{bmatrix}-\frac12\left\langle\begin{bmatrix}0\\0\\1\\0\end{bmatrix},\begin{bmatrix}1\\1\\1\\1\end{bmatrix}\right\rangle\frac12\begin{bmatrix}1\\1\\1\\1\end{bmatrix}-\frac1{2\sqrt{3}}\left\langle\begin{bmatrix}0\\0\\1\\0\end{bmatrix},\begin{bmatrix}3\\-1\\-1\\-1\end{bmatrix}\right\rangle\frac1{2\sqrt{3}}\begin{bmatrix}3\\-1\\-1\\-1\end{bmatrix}-\frac1{\sqrt{6}}\left\langle\begin{bmatrix}0\\0\\1\\0\end{bmatrix},\begin{bmatrix}0\\2\\-1\\-1\end{bmatrix}\right\rangle\frac1{\sqrt{6}}\begin{bmatrix}0\\2\\-1\\-1\end{bmatrix}\\&=\begin{bmatrix}-\frac14+\frac14\\-\frac14-\frac1{12}+\frac13\\\frac34-\frac1{12}-\frac16\\-\frac14-\frac1{12}-\frac16\end{bmatrix}=\begin{bmatrix}0\\0\\\frac12\\-\frac12\end{bmatrix}\\\\e_4&=\frac1{\|f_4\|}\cdot f_4=2\begin{bmatrix}0\\0\\1\\-1\end{bmatrix}\end{aligned}$  We obtain an orthonormal basis $$\left\{\frac1{2\sqrt{3}}\begin{bmatrix}3\\-1\\-1\\-1\end{bmatrix},\frac1{\sqrt{6}}\begin{bmatrix}0\\2\\-1\\-1\end{bmatrix},2\begin{bmatrix}0\\0\\1\\-1\end{bmatrix}\right\}\ \text{for}\ M^\perp$$  $$x=\underset{\in\ M}{m}+\underset{ \in\ M^\perp}{n}$$  $\begin{aligned}n&=\sum_{i=2}^4\langle x, e_i\rangle e_i\\&=\frac1{2\sqrt{3}}\left\langle\begin{bmatrix}2\\2\\0\\0\end{bmatrix},\begin{bmatrix}3\\-1\\-1\\-1\end{bmatrix}\right\rangle\frac1{2\sqrt{3}}\begin{bmatrix}3\\-1\\-1\\-1\end{bmatrix}+\frac1{\sqrt{6}}\left\langle\begin{bmatrix}2\\2\\0\\0\end{bmatrix},\begin{bmatrix}0\\2\\-1\\-1\end{bmatrix}\right\rangle\frac1{\sqrt{6}}\begin{bmatrix}0\\2\\-1\\-1\end{bmatrix}+2\left\langle\begin{bmatrix}2\\2\\0\\0\end{bmatrix},\begin{bmatrix}0\\0\\1\\-1\end{bmatrix}\right\rangle2\begin{bmatrix}0\\0\\1\\-1\end{bmatrix}\\&=\begin{bmatrix}1\\-\frac13+\frac43\\-\frac13-\frac23\\-\frac13-\frac23\end{bmatrix}=\begin{bmatrix}1\\1\\-1\\-1\end{bmatrix}\end{aligned}$  So, $$\boxed{n=\begin{bmatrix}1\\1\\-1\\-1\end{bmatrix}}$$    Update note:  arithmetic mistake corrected.  Is this correct? If so, how could I improve it using, maybe, more efficient methods? Thank you in advance!


I pinned the SO meta to the SE site switcher. I looked at my reputation and it is 1. When I go to SO meta I am not suspended or my reputation is one. Is this intended? The SO meta reputation in the site switcher should match the SO reputation.

While using the top bar to navigate across communities, I noticed that the reputation displayed on meta sites on that list does not match the one of their corresponding main sites:    I have noticed on past situations that reputation gained takes a bit to "update" on the display on Meta sites (that is, if you gain rep on SO, for example, it will take some time for you to see your updated rep on MSO).  However, I have never noticed this behavior here, on the Sites List of the top bar. Furthermore, the "delay" here seems to be more severe, as the "outdated" rep showed is of several days ago (for example, I turned 3k on SO almost exactly a week ago, but the rep shown on MSO is still <3k).  Any idea what could be causing this behavior?    Update: 2 months later this persists: my main site rep updates correctly but their corresponding meta rep remains the same as in the image above.     Update: As per Catija's  I removed the site (MSO) and put it back in, but it didn't update the rep.   However, after removing one site (TWP Meta), waiting at least a day, and then adding it back I see that although the reputations still don't match, the number displayed did changed a bit (previously 29,924 but now 33,112):


My Gmail account keeps not taking my email password that I had written down they are having to be reset about everyday down email the next day it says invalid password. What is going on? It's happening to most of my accounts. I don't have time for this and besides this is so so a mess.  Please let me know what to do?

I have forgotten the password or username for my Google account, or I'm unable to access my account for other reasons.  How can I recover my account?  (This Q&A is meant as a general description for all Google and Gmail username/password questions. See: )


Related to  and .  This :    looks like this in the 'Hot Network Questions' section of e.g. :    I think Latex formatting of question titles should be disabled if the question comes from a site that don't use Latex formatting.

Recently, the TeX.SE question  got onto the Hot Network Questions list.  Like many questions on TeX.SE, it contains some TeX markup in its title.  Unfortunately, on , this markup gets parsed and rendered as math:    I propose that either:   the entire Hot Network Questions sidebar should be excluded from MathJax parsing by styling it with the tex2jax_ignore class, or at least, any hot questions from TeX.SE should be so excluded from MathJax parsing.   Or I suppose we could always implement , which asks for all questions with TeX in the title to be excluded from Hot Network Questions entirely.  That might be throwing out the baby with the bathwater, though.    Ps. This issue is partially masked by , which causes MathJax not to be rendered in many elements that are hidden by default and revealed using jQuery .show(), such as all but the first five questions in the Hot Network Questions sidebar.  The  user script contains a generic fix for that bug, so users who have it installed will see this issue more frequently, but it occurs even without SOUP whenever a question with TeX markup in the title happens to show up among the top five hot questions that are always visible by default.


In Blender 2.8 it's impossible to select edge loops with Shift + Alt and left (or right) click. Why?

I used to be able to select and edge loop with AltRMB and then just continue with ShiftAltRMB. But this no longer works in Blender 2.80 and nightly builds of 2.79.  Is there another way to achieve the same?  UPDATE  It's not related to the nightly builds since I am also experiencing the same with the latest official release. Deleting Blender's user preferences doesn't change anything, nor does resetting the keymaps.  So it might be related to the Linux distro I am using (elementary OS), I'll have to look into that and follow up here as soon as I found something.  UPDATE 2  In the meantime, I switched back form elementary OS to Pop!_OS, which resolved the issue. It seems that somehow, elementary OS was blocking the ShiftAltRMB combination. The issue persisted with all versions of Blender, be it 2.79 official, 2.79 nightly or 2.80. Now, all is fine. Even 2.80 works as expected.  UPDATE 3  As of now, Blender 2.80 is using left-click by default for selecting. Selecting edge loops is done by double clicking, which is so much more convenient.


In D&D 3.5 a wizard can leave open spell slots and then prepare spells into those slots later in the day. Can a wizard in 5e do something similar?

My wizard has just woken from a long rest and is thinking about what spells to prepare for a new day of adventuring. The PHB says on p.114:     You prepare the list of wizard spells that are available for you to cast. To do so. choose a number of wizard spells from your spellbook equal to your Intelligence modifier + your wizard level (minimum of one spell). The spells must be of a level for which you have spell slots.   And:     Preparing a new list of wizard spells requires time spent studying your spellbook and memorizing the incantations and gestures you must make to cast the spell: at least 1 minute per spell level for each spell on your list.   As a 1st level wizard with 16 intelligence I have 4 1st level spells I can prepare.   So my question is, can I prepare 3 spells in the morning and then wait until I see a situation that calls for a particular spell and spend 1 minute studying my spellbook to learn that spell, provided that I still have a 1st level spell slot left?


I can connect to and use wireless access points.  After several minutes, however, I can no longer use them.  The task bar applet shows a connection, but I can't send or receive data.  Using service network-manager restart fixes the problem, but only temporarily, and I'm getting very tired of having to do it constantly.  I've read page after page on this site and elsewhere of lists of commands to run.  Here's a summary of the information I've found as a result:  logical name: wlp4s0 driver=iwlwifi 04:00.0 Network controller: Intel Corporation Wireless 8260 (rev 3a)   I'm on a Lenovo ThinkPad T560.  iwconfig indicates Power Management is on.  rfkill indicates nothing is blocked, hard or soft  I've blocked IPv6 by adding  net.ipv6.conf.all.disable_ipv6 = 1 net.ipv6.conf.default.disable_ipv6 = 1 net.ipv6.conf.lo.disable_ipv6 = 1   to the /etc/sysctl.conf config file and rebooting, but that did nothing.  For the present, I'm more interested in learning how to figure out what the problem is than in fixing it.  How do I find out what's going wrong?  Info Edit 1: When this happens, I suddenly cannot load web pages.  I cannot ping my default gateway (100% packet loss), and I cannot ping sites by name ("unknown host").  Info Edit 2: I tried turning Power Management off using $ sudo iwconfig <wlan0> power off.  The problem recurred, even as I confirmed using iwconfig that Power Management remained off.  The problem also happens regardless of whether I'm on battery or cable power.  When the disconnection happens, there is little change in the output of iwconfig.  In particular, these parameters stay nearly constant:  Bit-rate=866.7 Mb/s Tx-Power=22 dBm Link Quality=70/70 Signal level=-40 dBm Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0 Tx excessive retries:0   Access Point remains a constant, valid MAC address throughout.  The only output that changes is Invalid misc, which increases in count noticeably and continuously after the disconnection.  Meta Edit: Someone has linked to a similar question at .  That user seems to have a more severe problem than I do.  I don't lose sight of networks or have the applet icon change, I just stop being able to send and receive internet data, as if the connection is being throttled down to nothing.  In any event, I emphasize that there is no resolution or accepted answer on that question, and no activity in nearly a year.  The existence of this similar question does not help me solve my problem.

On my brand new Lenovo P50 the wifi is unstable. sometimes it connects, sometimes it does not, or just stops working. Sometimes wifi networks are shown in the network manager, sometimes not. Sometimes even the wifi symbol disappears and changes to the symbol with the two arrows, even when no ethernet cable is connected.  sudo service network-manager restart   solves the problem for a while, but it comes back.  Hardware is Lenovo P50,    wifi adapter intel 8260 rev 3a  Ubuntu 16.04 with all updates installed as of today  Kernel 4.4.0-28-generic  driver is iwlwifi driverversion=4.4.0-28-generic firmware=16.242414.0  sudo lshw -C network   gives  *-network                   Beschreibung: Kabellose Verbindung    Produkt: Wireless 8260    Hersteller: Intel Corporation    Physische ID: 0    Bus-Informationen: pci@0000:04:00.0    Logischer Name: wlp4s0    Version: 3a    Seriennummer: 44:85:00:df:1f:b5    Breite: 64 bits    Takt: 33MHz    Fähigkeiten: pm msi pciexpress bus_master cap_list ethernet physical wireless    Konfiguration: broadcast=yes driver=iwlwifi driverversion=4.4.0-28-generic firmware=16.242414.0 ip=192.168.1.39 latency=0 link=yes multicast=yes wireless=IEEE 802.11abgn    Ressourcen: irq:133 memory:c4c00000-c4c01fff *-network    Beschreibung: Ethernet interface    Produkt: Ethernet Connection (2) I219-V    Hersteller: Intel Corporation    Physische ID: 1f.6    Bus-Informationen: pci@0000:00:1f.6    Logischer Name: enp0s31f6    Version: 31    Seriennummer: 50:7b:9d:fe:e7:83    Kapazität: 1Gbit/s    Breite: 32 bits    Takt: 33MHz    Fähigkeiten: pm msi bus_master cap_list ethernet physical tp 10bt 10bt-fd 100bt 100bt-fd 1000bt-fd autonegotiation    Konfiguration: autonegotiation=on broadcast=yes driver=e1000e driverversion=3.2.6-k firmware=0.8-3 latency=0 link=no multicast=yes port=twisted pair    Ressourcen: irq:130 memory:c5700000-c571ffff


I am not completely proficient when it comes to Ubuntu...yet.  When installing Ubuntu 12, when it comes to drive partition it offers to run it alongside Windows, in 13.0.4, it offers to delete all other OS's, or Encrypt the new Ubuntu installation for security, or Use LVM with the new Ubuntu installation, and lastly, Something Else.  Something else  just confuses me.  Any tutorials or ideas?  thanks.

Whenever I startup from the LinuxLive USB, and try to install Ubuntu 12.04, it only gives me two options instead of the usual 3 or 4. My options are "Replace Windows 7 with Ubuntu" and "Something Else". Whenever I go into "Something else", it looks extremely confusing. How do I install it side-by-side while using the "Something else" section? These are my partitions.   /dev/sda /dev/sda1 ntfs (104Mb, System Required Partition) /dev/sda2 ntfs (1000097Mb, Windows 7 Partition)   Or should I try reinstalling my installer on a CD rather than USB and maybe then it will have the "Install alongside" function?


is a similar question and I was interested in rolling out my own question on this subject.  My family in Spain provided this photo of my Great Great Grandmother's tombstone:    As you can see it clearly states that she died on 27-4-1943. Now, today I received her death certificate directly from the Spain Registry Office and the date that her death was reported was:    This says in part:     ... del dia veintiocho de abril de mil novocientos cuarenta y cuatro, ...   In English that means 28 April 1944. Further down the certificate  it states that she died ayer which means yesterday. This would make her date of death 27 April 1944.  Thus the date of her death is exactly a year out.   How can this kind of major difference come about?

I have an ancestor for whom I have very little information for.  I am trying to identify the exact birth date for this person.  I have a death certificate which lists the birth date as "May 1st", however the gravestone for this person lists "May 4".  I am certain that the numbers were readable, so there is definitely a discrepancy in the dates.  Which record should be trusted more?  I know that the family supplies the date for both the death certificate and the gravestone, however I would suggest the family would be more concerned that it be correct on the gravestone, as the death certificate might be created in haste.  Is there general guidance for this?  For those who may be curious, attached below are the records.  I missed it before, but the year of the birthdate is actually different by 1 as well. (1962 on the gravestone and 1961 on the death certificate)  I am actually more concerned about the year than the actual date, of course.


Assume that $A\in\mathbb{R}^{n\times k}, \ B\in\mathbb{R}^{k\times m}$   and that $\text{Rank}(A)=r, \ \text{Rank}(B)=s.$ What can be said   about $\text{rank}(C),$ where $C=AB?$   The only thing I can quickly see here is that $C\in\mathbb{R}^{n\times m}.$ I also know that $\text{Rank}(C)=\text{Dim}(V(C)).$ But what is the dimension of $C$ then?  The exam has a really messy solution where the answers are that the rank of $C$ is sometimes $=s$ and sometimes $=r$. I don't understand any of it.

How to prove $\text{Rank}(AB)\leq \min(\text{Rank}(A), \text{Rank}(B))$?


What is the cause of quantum entanglement?  When two particles become entangled what property of them basically changes as to establish a link between them and how the information is exchanged between them?  And can multiple particles be entangled with each other, if yes then suppose 10 particles are entangled to each other and some force is applied to one of the particle then all of the particles will reflect the same changes. But in another case if we apply different force on two of the particles then what would happen?  a) entanglement will be broken for all particles  b) only those 2 particles become untangled and others remain entangled  if case a) happens then doesn’t it pose a risk on quantum computers as a fault in a particle could bring down the whole system?

What is ?  Please be pedagogical.  Edit: I have updated my background under my profile.


(√7) is (IR) irrational Number. How to prove it√7 .   Firstly I tried a/b =√7 and  a^2 /b^2 =7  7b^2=a^2  And then I couldn't continue . How I can Prove it ?

I have seen the proof that  $\sqrt2$ is irrational However I'm a bit confused. The proof goes something like this. first assume $m$ and $n$ are integers such that $$ \frac{m}{n}  = \sqrt{2} $$ $$ \frac{m^{2}}{n^{2}}  = 2 $$ $$m^{2}  = 2 n^{2}$$  $\implies m^{2} $ is divisible by $2 \implies m$ is divisible by 2. Let $2q = m$. Then $$m^{2}  = 4 q^{2} = 2n^{2}$$ $$ n^{2}  = 2 q^{2}$$ This means that $n^{2}$ is divisible by $2 \implies n$ is divisible by $2$...... Hence $\sqrt{2}$ is irrational. $$$$If $ m^{2} $ is divisible by $2$ how do we know that $m$ is also divisible by $2$? If you say it's a prime number then I can argue that I didn't need to do all these steps. I could have just said that its factors don't multiply to $2$ hence $\sqrt{2}$ is irrational


I use MS SQL Server 2017 Express Database in Windows 2016 server, I find the ERRORLOG file of MS SQL Server increase 600M per day.  The following content is from ERRORLOG file.  Does it mean that MS SQL Server 2017 Express Database meet attack ?  How can I fix the problems?  2019-12-22 03:36:09.34 Logon       Error: 18456, Severity: 14, State: 8. 2019-12-22 03:36:09.34 Logon       Login failed for user 'sa'. Reason: Password did not match that for the login provided. [CLIENT: 14.253.239.25] 2019-12-22 03:36:09.34 Logon       Error: 18456, Severity: 14, State: 8. 2019-12-22 03:36:09.34 Logon       Login failed for user 'sa'. Reason: Password did not match that for the login provided. [CLIENT: 59.127.222.102] 2019-12-22 03:36:09.42 Logon       Error: 18456, Severity: 14, State: 8. 2019-12-22 03:36:09.42 Logon       Login failed for user 'sa'. Reason: Password did not match that for the login provided. [CLIENT: 104.238.63.33] 2019-12-22 03:36:09.70 Logon       Error: 18456, Severity: 14, State: 8. 2019-12-22 03:36:09.70 Logon       Login failed for user 'sa'. Reason: Password did not match that for the login provided. [CLIENT: 14.253.239.25] 2019-12-22 03:36:09.70 Logon       Error: 18456, Severity: 14, State: 8. 2019-12-22 03:36:09.70 Logon       Login failed for user 'sa'. Reason: Password did not match that for the login provided. [CLIENT: 59.127.222.102] 2019-12-22 03:36:09.74 Logon       Error: 18456, Severity: 14, State: 8. 2019-12-22 03:36:09.74 Logon       Login failed for user 'sa'. Reason: Password did not match that for the login provided. [CLIENT: 104.238.63.33] 2019-12-22 03:36:10.06 Logon       Error: 18456, Severity: 14, State: 8. 2019-12-22 03:36:10.06 Logon       Login failed for user 'sa'. Reason: Password did not match that for the login provided. [CLIENT: 59.127.222.102] 2019-12-22 03:36:10.06 Logon       Error: 18456, Severity: 14, State: 8. 2019-12-22 03:36:10.06 Logon       Login failed for user 'sa'. Reason: Password did not match that for the login provided. [CLIENT: 104.238.63.33] 2019-12-22 03:36:10.06 Logon       Error: 18456, Severity: 14, State: 8. 2019-12-22 03:36:10.06 Logon       Login failed for user 'sa'. Reason: Password did not match that for the login provided. [CLIENT: 14.253.239.25] 2019-12-22 03:36:10.39 Logon       Error: 18456, Severity: 14, State: 8. 2019-12-22 03:36:10.39 Logon       Login failed for user 'sa'. Reason: Password did not match that for the login provided. [CLIENT: 104.238.63.33] 2019-12-22 03:36:10.41 Logon       Error: 18456, Severity: 14, State: 8. 2019-12-22 03:36:10.41 Logon       Login failed for user 'sa'. Reason: Password did not match that for the login provided. [CLIENT: 14.253.239.25] 2019-12-22 03:36:10.42 Logon       Error: 18456, Severity: 14, State: 8.

I have Windows Server 2016, with SQL Server 2017, and found Windows Log Application is full of Login failed messages (as follows) :     Login failed for user 'sa'. Reason: Password did not match that for the login provided. [CLIENT: ****]    Client's IP addresses are various. I don't have any maintenance plan in SQL Server     What's the problem?


I was implementing some templates for a memory allocator and came across some code that's compiling that I expected to not compile.  After writing and testing a template function to call a destructor, I found that it still worked after passing in an int*.  Test code:  #include <iostream>  template<typename Class> void CallDestructor(Class* InObj) {     InObj->~Class(); }  int main() {     int* test = new int;     *test = 5;     std::cout << *test << std::endl;     CallDestructor(test); // Why does this compile?     //test->~int();       // This does not compile which is what I expected for template function     std::cout << *test << std::endl;     delete test; }   The code compiles and runs on www.cpp.sh and also in Visual Studio 2013 for me.  Thank you for any insight!

In C++ the following code gives a compiler error:  void destruct1 (int * item) {   item->~int(); }   This code is nearly the same, I just typedef the int to another type and something magic happens:  typedef int myint;  void destruct2 (myint * item) {   item->~myint(); }   Why does the second code work? Does an int get a destructor just because it has been typedefed?  In case you wonder why one ever would like to do this: This comes from refactoring C++ code. We're removing the standard heap and replacing it with selfmade pools. This requires us to call placement-new and the destructors. I know that calling destructors for primitive types is useless, but we want them in the code nevertheless in case we later replace PODs with real classes.  Finding out that naked int's don't work but typedefed ones do was quite a surprise.  Btw - I have a solution that involves template-functions. We just typedef inside the template and everything is fine.


I'm new to Latex and was wondering if it'd be possible to change the text width for a paragraph without changing it for the whole document. Thank you.

Sometimes the margins need to be changed for a particular page, paragraph, or other section of text.  For example, if I'm writing a letter and want the left margin to be almost at the right side of the page for the four lines of my address, or if I am combining prose with poetry and want the poems to be indented relative to the rest of the work.  What is the best way to change both left and right margins on the fly?


I'm running hostapd on my raspberry PI to let it function as an accesspoint. It's working fine with the following command:  sudo hostapd /etc/hostapd/hostapd.conf  This will start hostapd and log all output to the console. Now I want to log this output using TEE or pipe. However, one the following commands will cause the program not to start.    sudo hostapd /etc/hostapd/hostapd.conf >> /home/pi/Desktop/loggin.txt sudo hostapd /etc/hostapd/hostapd.conf > /home/pi/Desktop/loggin.txt sudo hostapd /etc/hostapd/hostapd.conf | tee log.txt   The terminal will just hang and I have to use ctrl-x to terminate. Why isn't this working? And how can I possibly fix this?

I have a script which calls two commands:  long_running_command | print_progress   The long_running_command prints progress but I'm unhappy with it. I'm using print_progress to make it nicer (namely, I print the progress in a single line).  The problem: Connection a pipe to stdout also activates a 4K buffer, so the nice print program gets nothing ... nothing ... nothing ... a whole lot ... :)  How can I disable the 4K buffer for the long_running_command (no, I do not have the source)?


I am on a debian 9 system with unknown desktop environment (ssh access). How can I find out which program is used by default to view a file with a given extension (e.g. pdf)?  Edit: Since extension is not important to the decision, the mime type of the given file can be found by using file  file -i file.ext

Given xdg-open and an extension, is there a way to get the application which xdg-open is set to for that particular extension?  For example given xdg-open and .jpg the result is eog.


i have come accross an article on this site  about assigning a different keyboard layout automatically when a usb keyboard is plugged in. its the second option in the solution by Sadi. Im pretty much a noob when it comes to software and making changes to a computer. i can muddle my way through visual basic when im using excel and stuff but i've pretty much drawn a blank on this. im just wondering if anybody could  give me a basic tutorial for installing it? Thanks in advance!! Dan

I often plugin a USB keyboard to my laptop (in addition to external monitor and mouse, which all virtually convert my laptop to a desktop computer) and I prefer using a different keyboard layout then.  I have to manually change the current keyboard layout each time I plugin this USB keyboard.  And I'd like to use an automated way for this, if possible.  's answer to the question  gives some clues, but it seems I'll need a startup script for this task as the device ID for my USB keyboard changes every time the computer starts.  This startup script will probably first include the command xinput -list | grep "USB Keyboard", and another command to grab the first USB Keyboard ID number displayed and then use it in the final command to set my chosen layout for that USB keyboard as below:  setxkbmap -device <NUMBER> -layout <LAYOUT>


Someone else took this picture of me and didn't focus. :(   How can I fix this? Is there an app for that? I don't have Photoshop.

How can I fix this picture?  Somebody else took this picture and well he wasn't able to do it very well, and it's blurred.    I have photoshop


I want to know which HTTP method i use for developing a login API, GET or POST ?. I have developed my login API in PHP using post method, but my BOSS say that, why you use POST method instead of GET method.

When comparing an HTTP GET to an HTTP POST, what are the differences from a security perspective? Is one of the choices inherently more secure than the other? If so, why?  I realize that POST doesn't expose information on the URL, but is there any real value in that or is it just security through obscurity? Is there ever a reason that I should prefer POST when security is a concern?  Edit: Over HTTPS, POST data is encoded, but could URLs be sniffed by a 3rd party? Additionally, I am dealing with JSP; when using JSP or a similar framework, would it be fair to say the best practice is to avoid placing sensitive data in the POST or GET altogether and using server side code to handle sensitive information instead?


OK, here's my scenario: I'm dual-booting Ubuntu 17.10 and Windows 10, and I want to shrink my windows 10 partition, and allocate the free space to my Ubuntu partition. I have shrunk my Windows partition using GParted, now I need to extend my Ubuntu partition. Now, to do this, I figured I'd just go onto Windows 10 and extend my Ubuntu partition. Unfortunately, Windows 10 disk partitioning is super confusing and fiddly, so I'm trying to use Gparted instead. To extend my Ubuntu partition, I've been told I first need to unmount it, but I'm unsure whether to do this or not, as I don't want to unmount a partition that I'm in the middle of using.  tl;dr: Will unmounting the partition I'm currently using break my computer?  Sorry for the wall of text, and thanks for reading.  EDIT: I have tried using GParted live CD however I get tmp (7) errors, buffer I/O error and a few more. It will not boot in failsafe mode or safe mode.

Previously, I have installed Windows 7 on my 320 GB laptop with three partitions 173, 84 and 63 GB each. The 63 GB partition was where the Windows was installed. The rest were for file containers.  Now I changed my OS to Ubuntu 12.04 LTS. I installed Ubuntu by replacing the entire Windows 7 on the 63 GB partition. The rest of the partitions remain as an NTFS Windows partition and I can still access them both (the 173 and 84 GB partitions).  Now I want to change the two partitions of Windows into an Ubuntu format partitions plus most importantly, I want to extend the 63 GB partition to more than a 100 GB because at the moment I am running out of disk space. Whenever I try to install any application, especially using wine, it always complains for a shortage of disk space.  How do I do the extending activity before I entirely format my laptop again and lose all the important files on my partitions?


Is there a way to draw the axis arrows of a graph made via pgfplots longer than the graph itself? For reference, here is what my graph currently looks like:    And here is how I want it to look like:    (Sorry for paint)  I currently use axis line style = {-latex}.  Thanks!  Edit:  Minimal working example (by request):  \documentclass{article}  \usepackage{pgfplots}  \begin{document}     \begin{tikzpicture}         \begin{axis}[axis lines = middle, axis line style = {-latex}, grid = both]           \end{axis}     \end{tikzpicture} \end{document}

I need to plot a pgfplot where the axis arrows “overshoot” the grid by 10pt. Using enlarge x limits I can enlarge the arrows, but then the grid gets enlarged too.   \documentclass[]{standalone} \usepackage{tikz} \usepackage{pgfplots}  \begin{document} \begin{tikzpicture} \begin{axis}[     xmin=0, xmax=1, ymin=0, ymax=1,     axis x line=middle, axis y line=middle,     enlarge x limits={abs=10pt}, enlarge y limits={abs=10pt},     minor tick num=1,     grid=both     ] \addplot+[smooth] coordinates{ (0,0) (0.65,.8) (1,1)};   \end{axis}   \end{tikzpicture}    \end{document}   produces     where the grid lines “overshoot” the intended area [0,1]x[0,1].   How can I tell pgfplots to apply enlarge * limits to axis but not to grids?


Can a MAC address be altered, or is it like a computer's fingerprint and remains unique to that computer only? If a person has the computer's MAC address, can it be used to identify that computer proving ownership? I'm asking this because I had two laptops stolen and I'm going to go with the police to retrieve them. However, I'm sure the person who stole them will try to say they belong to him. I still have access to the antivirus programs, which also shows the Mac address for all devices registered. That's why it's important that I'm able to somehow prove ownership.

Again and again I read that devices are uniquely identified by their MAC addresses. But how are MAC addresses determined? (And do they tell us anything about the device which they represent?)


I have a system running on a remote VPS whose main feature is a long running script (it could run for about 10 hours, depending on the user input). The following are some of its features:  Database insertion and selection (MySQL) HTTP Post (cURL)  The following are some of the VPS/system features:  Intel(R) Xeon(R) CPU E5-2430 0 @ 2.20GHz, 11 cores Real memory of 1024 MB total OpenVZ Network Interface CentOS Linux 6.4 Apache version 2.2.15 PHP Version 5.3.3 MySQL version 5.1.69  Basically, the long running script should execute a lot of HTTP Post and Database selects and deletes (for a queue) per second. Each HTTP Post will send 50 kb out from my server to another uknown server, and each local Database operation will involve few bytes. What do I need? I need a server that perform per SECOND, AT LEAST:  10 HTTP Post involving 50 kb (total: about 500 kbps) 10 selects and 10 deletes in the Database (total: about 20 simple and light operation per second [for a queue])  Now, my server is performing 20% of what I need, but I feel that I can get much more from it (since the script itself is already optimized). So I want some tips and good pratices about server configurations in order to optimize its performance, cause I am very noob on it. For example:  OS, Apache, PHP and MySQL configuration (cache, enable or disable certain features, CPU and memory limit, etc); Disabling fool processes runing on CentOS by default; Configuring properly the server network interface; Increasing Server CPU cores or Memory or even changing the whole server features; Updating MySQL to 5.6 version  I (and, of course, another noobs) would apreciate a lot if anyone could help. Edit: Just got it! (can't answer my onw question... check my comment bellow) :D

This is a  about  Related:      I have a question regarding capacity planning. Can the Server Fault community please help with the following:   What kind of server do I need to handle some number of users? How many users can a server with some specifications handle? Will some server configuration be fast enough for my use case? I'm building a social networking site: what kind of hardware do I need? How much bandwidth do I need for some project? How much bandwidth will some number of users use in some application?


I have found a minor bug on the Stack Overflow Website. The notifications are not getting refreshed automatically when we click on some particular notification and click the back button, The notification is still there and it does not get auto refresh. Here are some screenshots.      When we click on the notification and view it. When I click the back button on the browser, The notification is still there. In this way if the user wants to go back to the previous page then the user will always be confused if the notification is new or old. My browser is Mozilla Firefox 70.0.1.

This may seem really trivial, but somehow it really annoys me.  I'm somewhat OCD, so I can't bear to have any unread notifications. Sometimes, when I'm reading a post, and I see a notification, I'll click it, see what it is, then quickly return. However, the notification icon is still there, and I have to refresh to get rid of it.  Also, if I write a comment, then click a link on the page, then click the back button, I have to refresh to see the comment I made.  Yup. I know, first world problem... but it really bothers me. Besides, it's all in the details.  Is this due to the way that the browser caches pages, or a bug in stackexchange?