I need to draw a circle with n legs and one with n+2 legs. Usually I would connect to legs to the circle with the anchors. But north, north east, north west, etc... simple aren't enough. It looks oddish...  What can I do to make it look better?  \documentclass[utf8]{article}  \usepackage{tikz} %For Drawing with pdflatex \usetikzlibrary{decorations.markings} % For Arrow heads in the middle \usetikzlibrary{decorations.text} % For text along path  \usetikzlibrary{positioning} % For relative positioning \usetikzlibrary{backgrounds} % For background layer \usetikzlibrary{fit} % To make background fit \usetikzlibrary{calc} % To calculate e.g. the distance between nodes \usetikzlibrary{shapes} % more shapes    \begin{figure}[h] \centering \resizebox{0.8 \linewidth}{!}{ \begin{tikzpicture} \node[draw,circle, minimum size=1cm] (c1) {1L}; \node [above right=.5cm of c1.north east] (l1c1) {\tiny 1}  edge [thick] node [] {} (c1.north east) ; \node [above left=.5cm of c1.north west] (lnc1) {\tiny n}  edge [thick] node [] {} (c1.north west) ; \path [postaction={decorate,decoration={text along path, text=.....,text align/left indent={3cm}}}] (c1) circle (.7cm) ; % \node [right =.2cm of c1.east] (eq) {=} ; % \node[right=.2cm of eq.east,draw,circle, minimum size=1cm] (c2) {0L}; \node [above right=.5cm of c2.north east] (l1c2) {\tiny 1}  edge [thick] node [] {} (c2.north east) ; \node [above left=.5cm of c2.north west] (lnc2) {\tiny n}  edge [thick] node [] {} (c2.north west) ; \node [above left=.5cm of c2.north] (ll1c2) {\tiny $l_1$}  edge [thick] node [] {} (c2.north) ; \node [above right=.5cm of c2.north] (ll2c2) {\tiny $l_2$}  edge [thick] node [] {} (c2.north) ; \path [postaction={decorate,decoration={text along path, text=.....,text align/left indent={3cm}}}] (c2) circle (.7cm) ;  \end{tikzpicture} } \caption{The Ansatz for $A_n^+$} \label{fig:nap} \end{figure}   My attempt:

I frequently find myself needing more than the standard anchors TikZ nodes provide, i.e. north, north east, east and so forth. I usually use coordinate calculations for this, as in the example below, but it's a bit tedious for such a seemingly simple task.  Do you have a better idea for accessing points on the sides of nodes? Ideally, what I'd like are anchors like north north east for the standard shapes.  \documentclass{article} \usepackage{tikz} \usetikzlibrary{positioning,calc}  \begin{document} \begin{tikzpicture} \tikzstyle{every node}=[draw,fill=yellow,minimum width=2cm,thin] \tikzstyle{every path}=[-latex,ultra thick] \node (A) {A}; \node (B) [below=2mm of A] {B}; \node (C) [below=2mm of B] {C}; \node (D) [right=of B,fill=green] {D};  % Is there an easier way to get the lines from A and C to off-centre points on the left side of D? \draw (A.east) -- ($(D.south west)!0.75!(D.north west)$); \draw (B.east) -- (D.west); \draw (C.east) -- ($(D.south west)!0.25!(D.north west)$); \end{tikzpicture} \end{document}


Can someone please help me understand the concept of "finitely generated" vector space, I am having a hard time visualizing and understanding it..  Thanks :)

I've somehow managed to go through 3 years of my Maths degree without truly understanding what the term "finitely generated vector space" means.   Generated by what? Generating what? And for what? I have a very vague idea of what this term means and usually gloss over it when doing proofs but I think I just want a simple break-down of the meaning of this.


I'm using Blender 2.77 and i can't find the Alpha Over Node.  I'm getting crazy.  Thanks for any help

I am looking for the  but it is not available under the Vector nodes menu or any other menu. I have Blender 2.77 which cooresponds with the manual version in the above link.    I also cannot find the Texture Coordinate or Gradient Texture.  Likely I am doing something wrong.


I saw a question over here, says that Nvidia Graphics jumps to 90º and fan goes at maximum speed. So, I want to use the Intel graphics integrated, but in Nvidia Settings (I use Ubuntu 18.04, Nvidia driver 390) doesn't appear the option to use Intel graphics. In Ubuntu 16.04 I don't know if it's the driver or what, but doesn't work this option (but appears in Nvidia Settings) because then Ubuntu doesn't allow go to your session. You try to enter but it returns to the gdm. Maybe in this version doesn't have this fail.

I recently made the switch to Ubuntu. Everything on my laptop works fine except my hybrid graphics card. It is Intel graphics combined with Nvidia GeForce GT650M. I tried Bumblebee, but primusrun doesn't work (segmentation fault, core dumped) and optirun works with glxspheres64, but steam games look worse with optirun than with Intel graphics (e.g. Surgeon Simulator 2013 runs fine with Intel and hangs a lot with optirun)   I tried Nvidia Prime, but it gives me a black screen on startup after install, so I can't do anything and have to power off my PC with the power button. I also tried nvidia-prime 0.5 on Ubuntu 14.04, and then I get 'low-graphics mode' and I can't get to Unity.


Given a TASK_ID, what is the most efficient way to retrieve the latest version of each file?  Here is an example table I am working with.  ID    TASK_ID    FILENAME    VERSION_NUMBER    RANDOM_COLUMN 1     1          a.txt       1                 112 2     1          b.txt       1                 231231 3     1          c.txt       1                 234356 4     1          a.txt       2                 35 5     1          b.txt       2                 84 6     1          b.txt       3                 97604 7     2          aa.txt      1                 6956 8     2          bb.txt      1                 9760054   This is what I have so far.  SELECT FILENAME, TASK_ID, MAX(VERSION_NUMBER) FROM TABLE_NAME GROUP BY FILENAME, TASK_ID HAVING TASK_ID = '1';   Unfortunately, the above only gives me the 3 columns I have in the SELECT statement instead of the entire row and adding more columns will give me an error.  FILENAME    TASK_ID    MAX(VERSION_NUMBER) a.txt       1          2 b.txt       1          3 c.txt       1          1   How might I go about getting the entire row?  I plan on adding this SQL query to a Query annotation within a Spring Repository and run it as a native query. Is that the best way?  EDIT: I ended up with this SQL query, which gets what I want, but I am not sure whether this is correct or how efficient it is.  SELECT ta.* FROM TABLE_NAME ta INNER JOIN (SELECT FILENAME, TASK_ID, MAX(VERSION_NUMBER) vn   FROM TABLE_NAME   GROUP BY FILENAME, TASK_ID   HAVING TASK_ID = '1') sq ON ta.FILENAME = sq.FILENAME AND ta.TASK_ID = sq.TASK_ID AND ta.VERSION_NUMBER = sq.vn;   Result of above SQL query  ID    TASK_ID    FILENAME    VERSION_NUMBER    RANDOM_COLUMN 3     1          c.txt       1                 234356 4     1          a.txt       2                 35 6     1          b.txt       3                 97604

Table:   UserId, Value, Date.   I want to get the UserId, Value for the max(Date) for each UserId. That is, the Value for each UserId that has the latest date. Is there a way to do this simply in SQL? (Preferably Oracle)  Update: Apologies for any ambiguity: I need to get ALL the UserIds. But for each UserId, only that row where that user has the latest date.


This was a different question but it simplifies to this. I want to calculate this $n$ as efficiently as possible. The time complexity of naive approach will be $O(d)$ for some number $d$ such that $d - na \ge 0$. Can we calculate this value in any less time?

When I am faced with a simple linear congruence such as  $$9x \equiv 7 \pmod{13}$$ and I am working without any calculating aid handy, I tend to do something like the following:  "Notice" that adding $13$ on the right and subtracting $13x$ on the left gives: $$-4x \equiv 20 \pmod{13}$$  so that $$x \equiv -5 \equiv 8 \pmod{13}.$$  Clearly this process works and is easy to justify (apart from not having an algorithm for "noticing"), but my question is this: I have a vague recollection of reading somewhere this sort of process was the preferred method of C. F. Gauss, but I cannot find any evidence for this now, so does anyone know anything about this, or could provide a reference? (Or have I just imagined it all?)  I would also be interested to hear if anyone else does anything similar.


Firstly I would like to say that as a learner I am deeply indebted to Stack Overflow and it has saved me many sleepness nights but I have found that I am sometimes reluctant to post a question, no matter how desperate I am for the answer, for fear of being patronised by other members.  There maybe times when I don't phrase a question as well as perhaps I might, but that would be because I am learning about the language I'm asking the question about and I don't know the 'correct' way to phrase it.  And the same goes for searching for answers.  I always search for an answer first because I want to work it out for myself but sometimes I don't know how to phrase the question, draw a blank, post the question and get marked down for not looking or asking a duplicate.  Answers that consist of just links to the php manual with a comment telling me I should have read it doesn't help either, I would have looked there before posting and not been able to understand how to put the answer in context with my problem.  There are times when I ask a question and people are very quick to make sarcastic comments about how I edited it etc and mark it down whether it has any bearing on the actual question or answer.  Like I said, I am very grateful to this site and this is not meant in anyway to be a criticism but more a request for other users to be more tolerant of newbies like myself rather than making them feel intimidated and not wanting to post, which is sometimes how I and other Stack Overflow users that I know feel.  The idea is to encourage learners, not put them off.

Because comment flags were historically some of the worst / least appropriately used flag types, we made comment flags require a reason:    Requiring a reason definitely helped improve existing comment flags that we now see.  The current default comment flagging reasons are   rude or offensive not constructive / off-topic obsolete too chatty other (requires text)   Do these default reasons capture -- without getting into obsessive detail -- the most common, valid reasons to flag a comment?


I have duplicated this problem in both QGIS and mapnik. For this question, I will show the problem using QGIS.  I have imported heightmap images along a coastal area.    I then added an overlay layer with  from OSM. This renders perfectly fine at higher zoom levels:    Once I start to zoom out, lines appear between the water polygons. These lines make it into the final rendered image.    What can I do to remove these lines?

In the past I have just manually matched the color of the border to the color of the fill, but this can be time consuming.   I am wondering, is there any way to have the program automatically match the border color to that of the fill?   The fill color is being assigned through the styling tab in layer properties.  Using QGIS 2.8.6


The below code executes karaf commands in the console,    public class DummyCallable {     @Inject     protected SessionFactory sessionFactory;     private Session session;     private ExecutorService executor;      private ByteArrayOutputStream byteArrayOutputStream;     private PrintStream printStream;     private PrintStream errStream;      public DummyCallable() {         byteArrayOutputStream = new ByteArrayOutputStream();         printStream = new PrintStream(byteArrayOutputStream);         errStream = new PrintStream(byteArrayOutputStream);          executor = Executors.newCachedThreadPool();         session = sessionFactory.create(System.in, printStream, errStream);     }      public String executeCommand(final String command) throws IOException {         byteArrayOutputStream.flush();         byteArrayOutputStream.reset();          String response;         FutureTask<String> commandFuture = new FutureTask<String> (new Callable<String>() {             public String call() {                 try {                     System.err.println(command);                     session.execute(command);                 }                 catch (Exception e) {                     e.printStackTrace(System.err);                 }                  printStream.flush();                 errStream.flush();                 return byteArrayOutputStream.toString();             }         });          try {             executor.submit(commandFuture);             response = commandFuture.get(10000L, TimeUnit.MILLISECONDS);         }         catch (Exception e) {             e.printStackTrace(System.err);             response = "SHELL COMMAND TIMED OUT: ";         }          System.err.println(response);          return response;     } }   I am getting "java.lang.NullPointerException" at the line     "session = sessionFactory.create(System.in, printStream, errStream);"   It's the detail info:  java.lang.NullPointerException     at java.util.concurrent.FutureTask.run(FutureTask.java:262)     at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471)     at java.util.concurrent.FutureTask.run(FutureTask.java:262)     at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)     at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)     at java.lang.Thread.run(Thread.java:745)   Can anybody help me ?

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


I have read a lot of threads concerning this question but I still seem not to understand the reason we normalize data for PCA. If we normalize the data, every feature is on the same scale. To make use of this normalized data for, say, making similarity prediction, we have to normalize new data and project the new data to the obtained PC's. However, if we don't normalize the training data and simply perform PCA, although the PC will change direction to favor features with large variations, we don't need to normalize input data to make similarity prediction anymore. And the new data's features will be on different scales which nicely fit into the PCA model without normalization. Wouldn't it achieve the same thing as normalizing everything and making predictions on normalized data?

What are the main differences between performing principal component analysis (PCA) on the correlation matrix and on the covariance matrix? Do they give the same results?


So I have a question of utilizing quadratic (second order) predictors with GLMs in R. Basically I have three predictor variables $(x, y, z)$ and a response variable (let's call it ozone). $x$, $y$, and $z$ are not inherently quadratic predictors yet so I square them (X2 <- x^2, and likewise for y and z).    Now I understand that if I wanted to model ozone based on these predictor variables I would use the poly() or polym() function (to create orthogonal polynomials).  However, when it comes to using interaction terms between these three variables, that's where I get lost. For example, if I wanted to model the interaction between the quadratic predictors of $x$ and $y$ I believe I would be typing in something like this  ozone <- x + y+ x^2 + y^2+ xy + x^2y + xy^2 + x^2y^2  # (I hope this is right)   My questions are:     Is there an easier way of inputting this (with three terms that's a lot of typing).  Why does the quadratic predictor flip signs of the coefficients? When I just run the predictor variable $x$ the coefficient is positive but when I use a quadratic predictor the coefficient almost always ends up being negative.      If you follow , it'll show you my initial question on Stack Overflow. In terms of the context of this question (which was non existent in the initial post), it's based on a dataframe consisting of predictor variables of radiation, temperature, and wind and the response variable of ozone levels in the atmosphere. Therefore, x, y, and z in the initial post were those three predictors.   Ultimately, are the statistical solutions given by others in that post valid?

In my logistic regression the sign of coefficients of a variable (location distance of an amenity) changes based on other variables (with time -ve, with travel distance +ve) in the model. When the location distance is the only variable in the model, it has +ve sign.    Should the variable need to maintain the +ve sign no matter what other variables are added in the model? Does changing sign signify a multicollinearity issue? Some IVs are gaining significance while in a bivariate model, they didn't show significance and vice versa. Is it okay to add variables that don't have much significance (ex: travel distance has a significance of 0.33 individually, but 0.05 when added with other variables) but becomes significant in the model? thanks.


For $f:[a,b]\rightarrow [a,b]$ is a continuous . Prove that $f$ has a fixed point . Is that true if we change $[a,b]$ by $[a,b)$ or $(a,b)$.

Question: Let $a, b \in \mathbb{R}$ with $a < b$ and let $f: [a,b] \rightarrow [a,b]$ continuous. Show: $f$ has a fixed point, that is, there is an $x \in [a,b]$ with $f(x)=x$.  I suppose this has to do with the basic definition of continuity. The definition I am using is that $f$ is continuous at $a$ if $\displaystyle \lim_{x \to a} f(x)$ exists and if $\displaystyle \lim_{x \to a} f(x) = f(a)$. I must not be understanding it, since I am not sure how to begin showing this... Should I be trying to show that $x$ is both greater than or equal to and less than or equal to $\displaystyle \lim_{x \to a} f(x)$ ?


For a System to be stable the poles have to be on the Left half of the s plane. But what is the significance of zeroes? Does it control the system in anyway? Thanks.

Suppose we have two third order systems (a and b), with three poles and two zeroes,poles for both the systems are at the same positions in frequency domain but these systems differ in the placement of their zeroes as shown in the figure below:  The abovve figure is a plot of the loop gain of the systems. Here za1 and za2 are the zeroes for system a and zb1 and zb2 for system b. The exact shape of the magnitude plot of loop gain would differ for the two plots, I only intend to highlight the position of zeroes for the two systems. In system a the zeroes lie before the unity loop gain frequency whereas in system b they lie after the unity loop gain frequency. Suppose unity gain frequency lies away from the zeroes of both the systems. Clearly the phase margin in case a is close to 90deg while that in case b is close to 270deg. Thus we would conclude that system b is unstable. My question is, since the stability depends only on the system poles which are same in both the cases, how do these systems differ in their stability?


In an article document, I have sections 1 and 2. the subsections of section 1 go from 1.1 to 1.4, and I want the subsections of section 2 to go from 2.5 onwards (rather than starting at the usual 2.1). Is there a command to do this automatically, rather than forcing it manually? Moreover, I am not planning on putting a table of contents, so I would be happy with tricking LaTeX into hiding the first four subsections. [P.S. Please tell me if the question can be rephrased better, I couldn't find a similar question online]

I am writing a constitution for a society.  I would like to have the subsections numbered independently of the way that the sections are numbered, i.e:  Section 1     Subsection 1     Subsection 2 Section 2     Subsection 3   How can this be done?


Solve the system of congruence relations: $$5x+17y\equiv 1 \pmod{24}$$ $$6x+10y\equiv 2\pmod{24}$$ Can someone help me? I usually use Chinese theorem, but here that is not possible.

Solve the system of congruence relations:  $2x+3y\equiv 1\pmod {11}$  $x+4y\equiv 4\pmod {11}$  Could someone give a hint how to solve this system.  I know that Chinese remainder theorem can't be used because modulo numbers ($11$) are not relatively prime.


I would like to calculate partial sum of divergent series: $$f(k) = \sum_{n=1}^{m}{(-1)^{n+1}n^k}$$ From wolframalpha.com I know that: $$f(0) = \frac{1}{2}((-1)^{m+1} + 1)$$ $$f(1) = \frac{1}{4}(-2(-1)^{m} m + (-1)^{m+1} + 1)$$ $$f(2) = - \frac{1}{2} (-1)^m m (m+1)$$ $$(...)$$ How can I calculate partial sum of this divergent series without any software?

The series $$F(n,m) := 1^n + 2^n + \ldots + m^n = \sum_{k=1}^m k^n$$  Is known as the .  I've tried to find a formula for this similar series but I've failed so far.  $$\mathcal{F}(n,m) := m^n - (m-1)^n + (m-2)^n -\ldots\pm 1^n= \sum_{k=1}^m (-1)^{m-k}k^n$$    EDIT:  Thanks to André Nicolas' answer I arrived to the following formula:  $$\mathcal{F}(n,m) = (-1)^m\left(F(n,m) - 2^{n+1}F\left(n,\lfloor m/2\rfloor\right)\right)$$


I've currently moved an active user site over to Pantheon. It's structured and themed extensively using Panels Everywhere, Panels, Views, and Display Suite.  What I would love to do now, is on the Dev/Test version is to revamp the site structure and display. But while that work is being done, every day new users are interacting with site changing its content, uploading files, etc...  From this previous post...        I understand that the following is a best practice...   code should go from dev -> test -> live  database should go from live -> test -> dev   My question is in this scenario, how can I work on my site (ala Panels, Views, Display Suite) in a Development environment and then push those changes to the Live environment?  There seems to be no way to do this purely in Pantheon since a large majority of the site changes will be on the DB, and if I push that to the Live environment, it will override all the new and changed user content.  Can someone point me in the right direction on this? I seem to be chasing my own tail about how I should be going about this in a sustainable fashion.

What is the best procedure for merging work done on a development copy of a site to the live production copy? Often times there has been a lot of new content added to the site since development started on the newest features. And most additions to a site will involve database changes. So copying any new files is easy, but what about the database? How do you merge your changes with the existing production database without losing new content that was added since the last time you updated the production site? Are there any modules that help with this?


UPD: I'm sorry, apparently i added 2 id's to my checkbox cause i forgot to delete the default one  I am using a check box and I get this error when running apk:  Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.CheckBox.setOnClickListener(android.view.View$OnClickListener)' on a null object reference   on the line I want to use checkbox.setOnClickListener  this is the code  final CheckBox settings_1 = (CheckBox) findViewById(R.id.settings_1); settings_1.setOnClickListener(new View.OnClickListener() {         @Override         public void onClick(View v) {             if( go_to_menu == 1)             {                 settings_1.setChecked(false);                 go_to_menu = 0;                 SharedPreferences sharedpref = getPreferences(Context.MODE_PRIVATE);                 SharedPreferences.Editor editor = sharedpref.edit();                 String key = getString(R.string.check1);                 editor.putInt(key, go_to_menu);                 editor.commit();             }             else             {                 settings_1.setChecked(true);                 go_to_menu = 1;                 SharedPreferences sharedpref = getPreferences(Context.MODE_PRIVATE);                 SharedPreferences.Editor editor = sharedpref.edit();                 String key = getString(R.string.check1);                 editor.putInt(key, go_to_menu);                 editor.commit();             }         }     });

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


The Dirac equation is given by:  $[iγ^μ ∂_μ − m] ψ(x) = 0$ .   We can prove that it's Lorentz invariant when:   $ψ(x) \to S^{-1} \psi'(x')$ and $\partial_\mu \to \Lambda^\nu_\mu \partial'_\nu$, where   $S(\Lambda) = 1 -\frac{i}{4} \sigma_{\mu\nu}\epsilon^{\mu\nu}$  which applying that for Dirac equation covariance that $\Lambda^\nu_\mu S \gamma^\mu S^{-1}=\gamma^\nu$   Now the Weyl spinors equations are given by:  $i \bar{\sigma}.\partial\psi_L=0,~~~~~~~(1)$  $i \sigma.\partial\psi_R=0, ~~~~~~~~~~(2)$  where $\sigma^\mu\equiv (1,\underline{\sigma})$ and $\bar{\sigma}^\mu\equiv (1,-\underline{\sigma})$  Look for instance Peskin's book "An Introduction To Quantum Field Theory"  where the Lorentz transformation of $\psi_L$ and $\psi_R$ are given by:  $\psi_L \to (1-i\theta.\frac{\sigma}{2}- \beta.\frac{\sigma}{2}) \psi_L$,  $\psi_R \to (1-i\theta.\frac{\sigma}{2}+ \beta.\frac{\sigma}{2}) \psi_R$,  How one can show that (1) and (2) are Lorentz invariant ?

I am trying to prove the Lorentz invariance of the (left-handed) Weyl Lagrangian: $$\mathcal L=i\psi^\dagger\bar\sigma^\mu\partial_\mu\psi$$  A Lorentz transformation is realized as $\psi\to M\psi$, where $M=\exp[-\frac{i}{2}\omega_{\mu\nu}S^{\mu\nu}]$, and $S$ are the generators of the representation, i.e., $S^{0i}=-\frac{i}{2}\sigma^i$ and $S^{ij}=\frac{1}{2}\epsilon^{ijk}\sigma^k$. Therefore, the Lagrangian transforms as $$\mathcal L=i\psi^\dagger\bar\sigma^\mu\partial_\mu\psi\to i\psi^\dagger M^\dagger\bar\sigma^\mu M\partial_\mu \psi$$ so that if it actually is invariant, we must have $M^\dagger\bar\sigma^\mu M=\bar\sigma^\mu$ (and, in particular, $M^\dagger M=\mathbb I$). I think this is a nice relation, which expresses the invariance of the symbol $\bar\sigma^\mu$.  Now the thing is, I think this relation is not true. Take, for example, a boost in the $z$-direction with rapidity $\omega$. This means $$M=\exp[-i\omega S^{03}]=\exp\left[\frac{\omega}{2}\begin{pmatrix}-1& 0\\0&1\end{pmatrix}\right]=\begin{pmatrix}e^{-\omega/2}&0\\0&e^{\omega/2}\end{pmatrix}$$  In this case, it is easly seen that $M^\dagger M\neq\mathbb I$. My question is: what went wrong in my argument?


My transaction log is larger than I'd like it to be, and I want to know how I can fix that.

This one seems to be a common question in most forums and all over the web, it is asked here in many formats that typically sound like this:  In SQL Server -  What are some reasons the transaction log grows so large? Why is my log file so big? What are some ways to prevent this problem from occurring? What do I do when I get myself on track with the underlying cause and want to put my transaction log file to a healthy size?


I am using Ubuntu 16.04. Following error is coming while updating through Software Updater.  The repository 'http://download.opensuse.org/repositories/home:/sarimkhan/xUbuntu_14.04 ./ Release' does not have a Release file. N: Data from such a repository can't be authenticated and is therefore potentially dangerous to use. N: See apt-secure(8) manpage for repository creation and user configuration details. E: Failed to fetch http://download.opensuse.org/repositories/home:/sarimkhan/xUbuntu_14.04/./Packages  404  Not Found [IP: 195.135.221.134 80] E: Some index files failed to download. They have been ignored, or old ones used instead.   How to solve this?

When updating, I get the following error message:   W: The repository 'http://ppa.launchpad.net/mc3man/trusty-media/ubuntu xenial Release' does not have a Release file.   Here, I find another statement on this error:   This recommends removing certain PPAs; and, I'm not sure if I should do that since it might mean not getting the updates that I need.    Is this what I should do?


I was recording with a hypercam, then my computer closed (empty battery), the file is over 2 GB. Is there no way to get back anything of this file? I know there is no media player to play UNDF, but is there really nothing left of the whole file? Its very important so i really hope someone can help me out here!

By accident, I recently removed some videos from my phone. I tried to restoring them with Recuva and TuneUp Utilities and the results were "undf" files.  I tried to open with VLC, Media Player Classic and other video players to no avail. Where/how do I find out the codec for these files?   I would really love to be able to watch these videos again.


Define $R(m,n,k)$ and show that $R(3; 3; 3) = 17$  How would I solve this? I am slowly starting to wrap my head around 2 variable ramsey numbers but not quite on 3. Here I know that R(m,n,k) are vertexes which mean there are 17 vertices and that there are 3 different colored edges. And each of these colors create a monochromatic triangle of the m,n,k colors on a graph. How would I go about showing R(3,3,3) = 17.   Thank you for any guidance.

If the edges of the complete graph $K_{17}$ (on 17 vertices with no three collinear) are each colored one of three colours can it be proven to have two or more monochromatic triangles?


I was recently editing  when I needed to include the picture and found I had to do it from the app since the mobile site had no button for it. Is this intended or is it a bug in the mobile site?

With the release of iOS 6, the most commonly used mobile browser now supports standard generic image upload buttons. This is actually really handy.  I can take screenshots on my phone or iPad, and use them to answer questions about apps made to run on those devices (or ) to answer questions. Until the release of iOS 6 however, the only way to use these images in my answer was to either sync them over to my computer, and then answer from a desktop, or use a specialized app to upload the images, such as PicUp or DropBox, and then manually write out the markdown code.  After iOS 6, the Image Upload button works just fine, if I switch to viewing the full site from my iDevice, rather than the mobile view. I can upload images directly, and the markdown is handled for me. It's awesome, except for the fact that the non-mobile site is decidedly non-awesome on the small screen of my phone.  Which brings me to my feature request: Add the Image Upload button (and other markdown shortcuts, as deemed worthwhile) to the ask/answer editors on the mobile version of SE sites.


At the moment I'm using;       <form name="frmSearch" method="get" action="<?=$_SERVER['SCRIPT_NAME'];?>">

       Keyword         <input name="txtKeyword" type="text" id="txtKeyword" value="<?=$_GET["txtKeyword"];?>">         <input type="submit" value="Search">

 </form> <? if($_GET["txtKeyword"] != "")     {       $objConnect = mysql_connect("XXXXX","XXXX","XXXX") or die(mysql_error());     $objDB = mysql_select_db("XXXX");     // Search By Name or Email     $strSQL = "SELECT * FROM blogs WHERE (title LIKE '%".$_GET["txtKeyword"]."%' or metadescription LIKE '%".$_GET["txtKeyword"]."%')";     $objQuery = mysql_query($strSQL) or die ("Error Query [".$strSQL."]");     $Num_Rows = mysql_num_rows($objQuery);       $Per_Page = 2;   // Per Page      $Page = $_GET["Page"];     if(!$_GET["Page"])     {         $Page=1;     }      $Prev_Page = $Page-1;     $Next_Page = $Page+1;      $Page_Start = (($Per_Page*$Page)-$Per_Page);     if($Num_Rows<=$Per_Page)     {         $Num_Pages =1;     }     else if(($Num_Rows % $Per_Page)==0)     {         $Num_Pages =($Num_Rows/$Per_Page) ;     }     else     {         $Num_Pages =($Num_Rows/$Per_Page)+1;         $Num_Pages = (int)$Num_Pages;     }       $strSQL .=" order  by id ASC LIMIT $Page_Start , $Per_Page";     $objQuery  = mysql_query($strSQL);      ?>

CustomerID

Name

Email

   <?     while($objResult = mysql_fetch_array($objQuery))     {     ?>

         <?=$objResult["id"];?>
	     <?=$objResult["title"];?>	     <?=$objResult["metadescription"];?>
   <?     }     ?>

 Total <?= $Num_Rows;?> Record : <?=$Num_Pages;?> Page : <?     if($Prev_Page)     {         echo " << Back ";     }      for($i=1; $i<=$Num_Pages; $i++){         if($i != $Page)         {             echo "[ $i ]";         }         else         {             echo " $i ";         }     }     if($Page!=$Num_Pages)     {         echo " Next>> ";     }      mysql_close($objConnect);      }    ?>     This works fine but I'd like to make it more secure so it can withstand injection and xss attacks etc. Basically I need to make it 100% secure.  I'm trying to change it to PDO and I have got the following so far;  $stmt = $pdo->prepare('SELECT * FROM blogs WHERE title LIKE = ?'); $stmt->execute($_POST['txtKeyword']);   Which I think is correct and as its two separate interactions with the DB it should be secure from injections (i think?)  problem is; 1) I'm not sure how to implement this and 2) what else is needed to make sure the search is secure   I'd really appreciate any help

If user input is inserted without modification into an SQL query, then the application becomes vulnerable to , like in the following example:  $unsafe_variable = $_POST['user_input'];   mysql_query("INSERT INTO `table` (`column`) VALUES ('$unsafe_variable')");   That's because the user can input something like value'); DROP TABLE table;--, and the query becomes:  INSERT INTO `table` (`column`) VALUES('value'); DROP TABLE table;--')   What can be done to prevent this from happening?


We have the following approach to merge two singly-linked list in java  /**  * Definition for singly-linked list.  * public class ListNode {  *     int val;  *     ListNode next;  *     ListNode(int x) { val = x; }  * }  */ public class Solution {     public ListNode mergeTwoLists(ListNode l1, ListNode l2) {         //the next node of dummy will be pointing at the final result so it is easier to return         ListNode dummy = new ListNode(0);         ListNode result = dummy;         while (l1 != null && l2 != null) {             if (l1.val < l2.val) {                 result.next = l1;                 l1 = l1.next;             } else {                 result.next = l2;                 l2 = l2.next;             }             result = result.next;         }          if (l1 != null) {             result.next = l1;         } else {             result.next = l2;         }          return dummy.next;     } }   My question is after assigning dummy to result, dummy changes as result changes. This is intuitively correct because when I access the next of result, I am accessing the next of dummy.   However, for when I have an assignment like int a = 5; and change reassign a = 6, we would not get 5 == 6 apparently.   Or if I do result = ListNode(1), my guess is dummy would not be changed to ListNode(1).   What is the logic behind their distinctions?

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?


A scene in this video for school necessitates a shot of someone driving towards the camera under varying light conditions. How can I reduce the glare on the windshield? It's very hard to get a clear shot, especially if the headlights are on.

When I take a picture through a window, I often see a reflection on the glass. I have noticed that this occurs mostly when it is dark or overcast outside or it is especially bright on my side of the glass. How can I stop this?


In a group $G$:     If $x^2 a x=a^{-1}$, then $a$ has a cube root. (Hint: Show that $xax$ is a cube root of $a^{-1}$.)   So essentially $\exists y\in G:a=y^3$. The hint probably confused me more than anything. How should I approach this? I am looking for hints, not complete solutions. Thanks.

I was checking my old set of homework problems that I found this one:     If $G$ is a group, show that $x^2ax=a^{-1}$ has a solution if and only   if $a$ is a cube in $G$.   One direction is easy. If $a$ is a cube in $G$ then there exists $y \in G$ such that $a=y^3$. Now with direct manipulations it is shown that $x=y^{-2}$ is a solution to $x^2ax=a^{-1}$.  The other direction is harder though. I first attempted to isolate $x$ and then somehow show that it's necessary for $a$ to be a cube. But since I had no idea how to isolate $x$ I gave up. Then I decided to prove the existence of $y \in G: a=y^3$ by showing that a particular map is bijective so I can come up with a nice variable change to conclude that $a$ must be a cube, but this attempt failed as well. I'm tired now, so I think I'm giving up. I'm looking for a hint or a complete solution if a hint is not possible at this stage.


I was going to upgrade to 20.04 from my recently install 19.10, but when I run sudo do-release-upgrade it tells me there is no LTS version to install. Is 20.04 not ready for server installation? I am running a cloud server with Ubuntu.

Update  appear to have been updated recently (as of writing this the last update appears to have taken place on 3rd of June) to include the following statement:  The -d switch is necessary to upgrade from Ubuntu 18.04 LTS as upgrades have not yet been enabled and will only be enabled after the first point release of 20.04 LTS.  Also note that .  TLDR (as of 15 Aug 2020):   is the canonical tracking document for the first Focal Fossa point-release (20.04.1). It’s a live document. The Ubuntu release team will be updating it as we work on releasing 20.04.1. […] Upgrades from 18.04 to 20.04.1 are still disabled as we are working through a few upgrade blockers   Edit The answers (so far) do not answer the question. The question is pretty simple. Ubuntu.com points to a "FinalRelease", which turns out to be a "Development Release", see evidence below. I'm not asking how and when to upgrade. I'm pointing out what seems to me to be an apparent inconcistency (in semantics, linguistics, logic) in the way Ubuntu names or labels its releases. From an answer to the question I'd except someone to pick up and acknowledge this inconsistency. An answer could start with a "Yes, ..." or a "No, ...", for starters. (Moreover, a good answer could distinguish between the release being in dev stage and/or the upgrade process (e.g. from LTS to LTS) being in dev stage, if appropriate.) This question, as I see it, is not a duplicate. Futher, I think it is a question which deserves a non-patronizing answer. Thanks.   indicates that today (23rd April 2020) the new Ubuntu 20.04 LTS is to be released.  See "condensed screenshot" here:  Indeed, it seems that that's what happened, see  and :  However, when following the instructions to upgrade (from 18.04 LTS to 20.04 LTS) found  and elsewhere (edit: actually , too!), even prior to the July point release, I'm a bit confused to see that the instruction is to use update-manager -d which also points to the "Development Release" (see screenshot below) rather than the "FinalRelease" (see screenshot and link above). Is the "Final Release" (which I'm after) the/a "Development Release"? Why isn't it called something like "Production Release" or "Final Release"? When will it no longer be referred to as "Development Release"? In July? I'm confused :(


when I am using this document on web server it is running ok but when this file is running to use the plugin in WordPress then I have to put the shortcode of the file on the page on which I want to apply effect of that plugin.... but when I am putting the shortcode then it only shows the string of that shortcode, not the effect. plz find the below coded file and provide a solution.  <?php function sac_form() { echo ""; echo ""; echo ""; echo "<form>"; echo "
"; echo '
Name	<input type="text" name="Name">
'; echo '
Email	<input type="text" name="Email">
'; echo '
Subject	<input type="text" name="subject">
'; echo '
Message	<textarea rows="4" cols="50"></textarea>
'; echo '
<input type="submit" name="submit" value="Submit">
'; echo "
 </form>  "; } add_shortcode( 'short_code', 'sac_form' ); ?>

The shortcode produced by this function - a list of all sites in a multisite - outputs above the content in the loop, no matter where it is placed in the editor.  I've looked at the other related questions and answers on WPSE and realize that it has to do with the function using echo instead of return, but it's not as easy as replacing the instances of echo with return in the function below. Or adding echo=0 with a WP function like wp_list_pages()  Any ideas? Where is the function that needs to be returned instead of echoed?  // Output a single menu item function projects_menu_entry($id, $title, $link_self) {     global $blog_id;     if ($link_self || $id != $blog_id) {         echo '
';         if ($id == $blog_id) {             echo '';         }         $url = get_home_url($id);         if (substr($url, -1) != '/') {             // Note: I added a "/" to the end of the URL because WordPress             // wasn't doing that automatically in v3.0.4             $url .= '/';         }         echo '' . $title . '';         if ($id == $blog_id) {             echo '';         }         echo '
';     } }  // Output the whole menu // If $link_self is false, skip the current site - used to display the menu on the homepage function projects_menu($link_self = true) {     global $wpdb;      echo '
';      projects_menu_entry(1, 'Home', $link_self);      $blogs = $wpdb->get_results("         SELECT blog_id         FROM {$wpdb->blogs}         WHERE site_id = '{$wpdb->siteid}'         AND spam = '0'         AND deleted = '0'         AND archived = '0'         AND blog_id != 1     ");      $sites = array();     foreach ($blogs as $blog) {         $sites[$blog->blog_id] = get_blog_option($blog->blog_id, 'blogname');     }      natsort($sites);     foreach ($sites as $blog_id => $blog_title) {         projects_menu_entry($blog_id, $blog_title, $link_self);     }     echo '
'; }  // Adds a [bloglist] shortcode  function bloglist_shortcode($atts) {     projects_menu(false); }  add_shortcode('bloglist', 'bloglist_shortcode');


I would like to get an idea of what "quantum probability" means and how it differs from classical frequentist or Bayesian probability. Can anyone enlighten me in non-too-technical terms?

Why is the application of probability in  (QM) fundamentally different from its application in other areas? QM applies probability according to the same  as in other areas of physics, engineering, etc.  Why is there a difference?  Naively one would assume one of these possibilities:   It is not the same probability (theory?) It is a matter of interpretation (of the formalism?) Something else?   Many answers (which I am still studying) focus on the fact that the combined probability of two mutually-exclusive events in QM is not equal to the sum of the probabilities of each event (which holds classically by definition). This fact (appears to) makes the formulation of another probability (a quantum one) a necessity.   Yet this again breaks down to assumed independent, if this is not so, the "classic probability" is applicable (as indeed in other areas). This is one of the main points of the question.


Refer to the first answer here  , i want to do a block with items inside that keep position after overlay ?  ** Edited   I managed to do what I wanted naively because i don't know how it works with [<+->] \documentclass{beamer} \usetheme{Berlin} \begin{document}  \begin{frame}     \frametitle{Présentation de MedsoftWorks Consulting}     \begin{itemize}         \item<1->Ingénierie applicative          \item<5-> Développement web         \item<9> Digital et application mobile     \end{itemize}         \only<2-4> {\begin{block}{Les offres}            \begin{itemize}             \item<2-4> La formalisation des besoins.             \item<3-4> La conception de cahier de charge.             \item<4>  La réalisation du progiciel adapté à la            \end{itemize}                 \end{block}                }          \only<6-8> {\begin{block}{Les offres}           \begin{itemize}             \item<6-8> La gestion des moyens de paiement.             \item<7-8> La gestion de paiement sécurisé.             \item<8> Le Webmastering et maintenance.         \end{itemize}             \end{block}               }     \end{frame}  \end{document}

I have  this slide for a presentation:  \begin{frame} {Bonjour}  Hi  \begin{itemize}  \item blabla  \begin{itemize}  \item A  \item B \end{itemize} \end{itemize}  \begin{overlayarea}{1\textwidth}{0.6\textheight} \only<1>{ \begin{block} {La solution1}  blablablablablablablablablabla \end{block}  } \only<2>{  \begin{block}  {La solution2}    blablablablablablablablablabla   \end{block}        }   \end{overlayarea}    \end{frame}   I want the subitem A and B to disappear when La solution1 and La solution2  appear and at the same time they should take the places of A and B. The Hi should stay though.


Forgive me if this question has been answered elsewhere, but my googling was unable to find the solution.  Below is a MWE. The issue is that the link which I am trying to include on the copyright page is not being colored. I would like it to be colored. I think the issue might be due to the fact the I am using \input to include the content of the copyright page. I prefer to do this because I need to make several PDFs of this content but in different formats and keeping the content separate from the formatting is just easier for me. When I compile this with pdflatex the link for the url is black. The workaround  is an option, however I would prefer to set this through the hypersetup environment.  document.tex:  \documentclass[12pt, letterpaper, draft]{memoir} %% Packages \usepackage{graphicx} \usepackage{xcolor} \usepackage{hyperref} \usepackage{hyperxmp} \usepackage{lipsum}  %% Package Configuration \graphicspath{{../}} \makeatletter   \AtEndDocument{\hyxmp@find@metadata\hyxmp@embed@packet} \makeatother \hypersetup{     colorlinks=true,     linktoc=all,     urlcolor=blue,     pdfauthor={An Author},     pdftitle={A Title},     pdfcopyright={Copyright © 2017 by An Author. Rights reservation statement.} } %%%% The documet \begin{document} \title{A Title} \author{An Author}  \frontmatter %% Copyright \input{copyright.tex}   %% Table of Contents, Introduction \tableofcontents*  \mainmatter \part{A Part} \lipsum \backmatter \end{document}   copyright.tex:  \begin{titlingpage} \centering Copyright \copyright ~ 2017 An Author.  Rights reservation statement. \url{https://tex.stackexchange.com/questions/} \end{titlingpage}

I'm trying to get hyperref to work with pdflatex, but I'm getting the error hyperref Warning: Draft mode on and since all hyperrefs are disabled in draft mode, there are no links being created.  I tried doing the following: \usepackage[final]{hyperref} but still no success.  I'm using document class book: \documentclass{book} so nowhere do I say that I want draft enabled.  Tried compiling on two different machines with TexnicCenter using pdflatex(LaTeX=>PDF).  Any suggestions?


If I see a lightning I must wait many seconds to hear the thunder because of the different velocity of light and sound in the air. This is true, I think. But why thunders lasts 1-2 second and the lightning only milliseconds? I've thought that this thing is given by the length of it: Maybe the noise of the thunder arrive from all the point of the lightning and so the noise that arrive from the top arrive later then the bottom one. But really I don't know. Thank you for your answers

Why does the sound of thunder last several seconds even when lightning lasts for only fraction of a second?


First of all I explain my situation: On my University most of the careers are doing videos to explain what we do and try to atract more people to our careers.  I'm in a really bad position, because the people who are in charge of the video want me to explain what a pure mathematician do and how it help society (with practical examples and maybe naming some companies that work with pure mathematician and what they do in that companies) in only 5 or 10 mintues, so I think that the best that I can do is make a example.  Other reason that have me in a bad position: In my University we have the career "Mathematical engineering" and they do most applications and some research in numerical analysis, optimization. (*)  I know that pure mathematics are increasing its importance in society every year.  Many people in my country think that mathematics has stagnated over time and now only engineers develop science.  I think that the most practical thing I can do is give some examples of what we are doing with mathematics today (since 2000).  If some of you can help me I need the following:    A topic in mathematic that not appear in (*). Preferably dinamical systems, logic, algebraic geometry, functional analysis, $p$-adic analysis or partial differential equations. A research in that topic. Practical applications of that research and the institution that make the application.   Extra 1. If you know a institution (not a University) that contract pure mathematicians and you know what they do there you can tell me too.  Extra 2. If you have a very good short phrase explaining "what a mathematician do" or "how mathematics help society" i will regard it too.  Thanks in advance.

I hesitate to ask this question, but I read a lot of the career advice from MathOverflow and math.stackexchange, and I couldn't find anything similar.   Four years after the PhD, I am pretty sure that I am going to leave academia soon. I do enjoy teaching and research, but the alpha-maleness, massive egos and pressure to publish are really unappealing to me, and I have never felt that I had the mathematical power to prove interesting results. However, I am really having trouble thinking of anything else to do. Most people seem to think that the main careers open to mathematicians are in banking and finance. I really want to work in some field where I can use mathematics, but it is also important to me to feel like I am contributing something positive or at least not actively doing harm. For this reason, financial speculation is very unappealing to me, although I do find the underlying mathematics quite fascinating.  Here is my question: what careers which make a positive contribution to society might be open to academic mathematicians who want to change careers?


this is my code and I don't know why    "one == null" and "two == null"    are always False and I can't send any Null argument to my method! please help me public class RepeatInString {     public int StringInString(String one, String two) {         if (one.equals("") || two.equals("") || one == null || two == null){             return 0;         }         else{             char[] oneChar = one.toCharArray();             char[] twoChar = two.toCharArray();             int repeatCounter = 0;             int matchChars = 0;             for (int i=0 ; i < (one.length()-two.length()+1) ;i++ ){                 matchChars = 0;                 for (int j=0; j<two.length() ;j++) {                     if (oneChar[i + j] == twoChar[j])                         matchChars += 1;                     else                         break;                 }                 if (matchChars == two.length())                     repeatCounter += 1;             }             return repeatCounter;         }     }

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


So I got this assignment. And I was wondering how is it possible to get a limit from a constantly changing formula.  $$\lim_{x\to+\infty}\frac{\sin(x)}{x}$$ Can I only look in the domain $]0,2\pi[$?

I've just started learning about limits. Why can we say $$ \lim_{x\rightarrow \infty} \frac{\sin x}{x} = 0 $$ even though $\lim_{x\rightarrow \infty} \sin x$ does not exist?   It seems like the fact that sin is bounded could cause this, but I'd like to see it algebraically.   $$ \lim_{x\rightarrow \infty} \frac{\sin x}{x} =  \frac{\lim_{x\rightarrow \infty} \sin x} {\lim_{x\rightarrow \infty} x}   = ? $$  L'Hopital's rule gives a fraction whose numerator doesn't converge. What is a simple way to proceed here?


I want to send a cross domain ajax request but I am getting below error for this I have also tried the below code which I have got from the one stack article is it possible to send a cross domain request or not.  Code which I have tried for sending cross domain request.  $(document).ready(function () {     $.ajax({         type: 'POST',         url: "http://testdomain.com/config.php",         crossDomain: true,         data: 'rejected_by_loid=' + 1,         success: function (msg) {             $('#survey').html(msg);         }     }); });   Error on console log:  Cross-Origin Request Blocked: The Same Origin Policy disallows reading the remote resource at . (Reason: CORS header ‘Access-Control-Allow-Origin’ missing).  Please help me to solve this problem.

How do I send a cross-domain POST request via JavaScript?  Notes - it shouldn't refresh the page, and I need to grab and parse the response afterwards.


I want to grep variable pattern which is in first column.   $ cat test.txt     abc.xyz    abc.def pqr.tap pqr.abc abc.mnp mnp.abc abc.pqr abc.mob   If variable pattern is abc then output should be  abc.xyz abc.def abc.mnp abc.pqr abc.mob   If variable pattern is mnp then output should be  mnp.abc   If pattern is not variable then I can do by command (For pattern mnp)  awk -F"." '{ if($1 == "mnp") print $0;}' test.txt

Possible Duplicate:          I have a script, in which a script snippet is  x=3 awk '$2=$x{print $1}' infile   the external variable is x,  but it prompts an error in awk  so in this situation,how to make awk run successfully?  thanks!


Our school is wanting to switch from a mix of Windows 8 laptops and Chrome OS laptops to all running Ubuntu 20.04, we got a few working and running as a test and there running amazing, what we were wondering was if we needed any special licensing as we did with the others or if we were good to go with just installing Ubuntu on the rest of them?

What license does Ubuntu fall into (GPL, MIT, a mix)? Would it be legal to modify it and redistribute my modified version?


Is there any way to toggle it with i.e. osascript? I'm on Yosemite.

I would like to toggle the Do Not Disturb in the notification center with a keyboard shortcut.  I am using BetterTouchTool for some extra keyboard shortcuts but it does not support enabling/disabling the notifications in the default options.  It has an option for executing a terminal command so I'm asking here how to enable/disable Do Not Disturb from the terminal?  I found  and I tried to run the commands but it didn't seem to work.


My bash does not know the letter p. zsh does though.   When I type a p in bash, it simply ignores it, and even pasting in text that contains a p will result in no p in the pasted text.  This behavior is the same across terminals (I tried, urxvt, st and tty)  I tried commenting out everything in my ~/.profile, ~/.bash_profile and ~/.bashrc, the problem still persists. Using root though, everything is fine. My /root/.profile, /root/.bash_profile and /root/.bashrc are symlinked to the files in my home directory. So the problem can't originate there, but it's got to be something that is different for root and my user.  I use a custom keyboard layout, but when I switch to standard US keyboard layout, the problem still persists as well.   Just to rule  out as well: I do not use gnome.  Where else can I look?

I was swapping some readline settings in my .bashrc earlier today and mistyped the following (bind since it's not in .inputrc):  bind "mark-symlinked-directories on"  I forgot to put a set in there before mark-symlinked-directories, the end result of which was that my "d" key stopped working in the terminal.  Lame.  Some messing around with other bindings indicated that whatever the first letter of the last "word" was would be unusable, i.e.,  bind "page-completions off" messed up c  bind "visible-stats on" messed up s  bind "completion-query-items 42" messed up i  My question is why?  What is bind doing that renders those keys useless, and why that specific key?


Pick up the paperwork between 8:00 am to 8:30 am.  Is the word "to" incorrect?  I was informed by a coworker that it should read "between 8:0 am and 8:30 am." If a correction is needed, can you tell me why. Thank you for your input.

I looked at , but it didn't mention a third variation I've been hearing more often, recently.  Even on the Australian national broadcaster, the ABC, I've heard statements by reporters like      The cost was estimated to be between A to B dollars.   Have the rules of grammar changed, or is this as ungrammatical as I think it is?


Consider two fields:  $K: $ $F_2[X]/(X^3+X+1)$. Let $a$ be the class of $X$ (so $a=X+(X^3+X+1))$  $L: $ $F_2[X]/(X^3+X^2+1)$. Let $b$ be the class of $X$ (so $b=X+(X^3+X^2+1))$  $F_2$ denotes the field with $2$ elements. Field $L$ is ismorphic with $K$.   If $\phi$ : $F_2[X]/(X^3+X+1)$ $\rightarrow$ $F_2[X]/(X^3+X^2+1)$ is an isomorphism, then prove that $\phi(a)=b+1$.  They give as a hint: $b+1$ is a root of $Y^3+Y+1$.  I came up with the following:  Fill in $a$ in $K$, so you get $a^3+a+1$.  Fill in $b+1$ in $L$, so you get $(b+1)^3+(b+1)^2+1 = b^3+b^2+b+1+b^2+1= b^3+b+1$, which is equal to the $a$ part above.  But I don't know if this is a way to actually prove that $\phi(a)=b+1$. How can I do this?

Suppose $K$ is a finite field, $K = \mathbb F_{p^s}$. If we take an irreducible polynomial $f$ of degree $d$ over $K$, then the splitting field $L$ of $f$ is $K(\alpha)$ where $f$ is the minimal polynomial of $\alpha$. But then $L = \mathbb F_{p^{sd}} $. Since $\mathbb F_{p^{sd}}$ is unique, we see that this is the splitting field of every irreducible polynomial of degree $d$ over $K$.   Take $K = \mathbb F_2$ and let $P(X) = X^3 + X + 1$, $Q(X) = X^3 + X^2 + 1$. Let $L$ be the splitting field of $P$ and $L'$ be the splitting field of $Q$. The above tells us that $L$ and $L'$ are isomorphic. I would like to construct an explicit isomorphism between $L$ and $L'$.   I know that $L \cong \mathbb F_2[X] /(X^3 +X + 1)$ and $L' \cong \mathbb F_2[X] / (X^3 + X^2 + 1)$. Intuitively, I want to find an isomorphism $\phi : \mathbb F_2[X] \to \mathbb F_2[X]$ such that $\phi((X^3 + X + 1)) = (X^3 + X^2 + 1)$. A little playing around gives me $\phi(X) = X+1$. It now feels like I'm falling at the last hurdle: how do I finish the construction of an isomorphism between $L$ and $L'$? I don't think $\phi$ makes sense as a map from $L$ to $L'$, yet it seems the map I want.


I want to replicate some graphs that I drew by hand on millimeter paper. Here is a picture:    My current code is as follows (I didn't worry about the data yet):  \documentclass{report}  \usepackage{pgfplots} \usepackage{siunitx}  \begin{document}  \begin{tikzpicture}[scale = 2]             \begin{axis}[                 axis lines = middle,                 xlabel = t\lbrack\si{\second}\rbrack,                  ylabel = x\lbrack\si{\metre}\rbrack,                  x label style = {anchor = north west, font = \scriptsize},                 y label style = {anchor = north east, font = \scriptsize, shift={(0,0.5cm)}},                 xtick = {0,10,...,20},                 minor xtick = {1,2,3,4,5,6,7,8,9,11,12,13,14,15,16,17,18,19},                 ytick = {0,10,...,20},                 minor ytick = {1,2,3,4,5,6,7,8,9,11,12,13,14,15,16,17,18,19},                 tick style = {line width = 0.3pt},                 ticklabel style = {font = \tiny, fill = white},                 axis line style = {-latex},                 grid = both,                 ymin = 0,                  ymax = 21,                  xmin = 0,                  xmax = 21,                 ]                 \addplot[                 only marks,                 mark size = 2,                 black,                  error bars/.cd,                  y dir = both,                  x dir = both,                  y explicit,                  x explicit                 ]                 %table[x= temp, y = temp, x error = temp, y error = temo]                 %{\datafile};                 coordinates {(6.4,7.2) +-(1,0.5)};             \end{axis}         \end{tikzpicture} \end{document}   (Note that I used dummy values, coordinates, sc and variables; they aren't important right now).  By setting the major and minor grid style I was able to get thick lines on my labeled coordinates and thin lines in between:  \pgfplotsset{minor grid style = {line width = 0.1pt}} \pgfplotsset{major grid style = {line width = 0.4pt}}   But this is where I get stuck. There are several things that I'm not able to do by going this route:   I need major grid lines every centimeter, independent of the label. On millimeter paper there are 3 grids; besides the major one with 1cm spacing and the minor one with 1mm spacing, there is a third one every 5mm (with a thickness somewhere between the 2 grids). Using pgfplots I am only able to edit the major and minor grid styles, but I can't seem to find a way to add further grids to a certain graph. Display the plot in "landscape mode" so that it takes up the whole page, as shown in the picture.   I'd appreciate it if somebody could help me out with those issues.  Thanks!

Is it possible to have graph paper as an underlay and then run the usual latex commands?  For instance, instead of having a latex document written on a blank page, is it possible for the page to be graph paper instead?  I'm a tikz novice, but I'm proficient enough to do what I need to do, but grids and tikz and enumerated lists, don't play nicely together. If the paper was graph paper to begin with at least one of my problems would be solved.  I've found partial workarounds, although nothing definitive: one that allows me to have graph paper but only on the first page, and it overlays my title anyway - I use maketitle for that.  Any suggestions?


This is causing problems:  node "$SUMAN_PROJECT_ROOT/server.js" | bunyan -o short &> ${LOG_FILE}  &   this works:  node "$SUMAN_PROJECT_ROOT/server.js"  &> ${LOG_FILE}  &    the problem is that with the first command, the output is not being sent to the file. In the second command, it does get sent to the file. Why might it be the case the first command does not work - I would expect it would send the output to the file just like the second command. The bunyan command should act like grep, just filter and mapping the output from the node command.  My editor does not like a proposed solution:

I often see tutorials online that connect various commands with different symbols. For example:  command1 |  command2 command1 &  command2 command1 || command2     command1 && command2   Others seem to be connecting commands to files:  command1  > file1 command1  >> file1   What are these things? What are they called? What do they do? Are there more of them?    .


While booting Ubuntu 16.04 I got the following message for the first time. That message was displayed 2 times and the booting was a lot slower than usual. What is the problem and why did that happen?  /dev/sda1: recovering journal /dev/sda1: Clearing orphaned inode 49910977 (uid=1000, gid=1000, mode=0100664, size=16773) /dev/sda1: Clearing orphaned inode 49909604 (uid=1000, gid=1000, mode=0100664, size=32768) /dev/sda1: Clearing orphaned inode 49909603 (uid=1000, gid=1000, mode=0100600, size=31780) /dev/sda1: Clearing orphaned inode 49909500 (uid=1000, gid=1000, mode=0100640, size=85) /dev/sda1: Clearing orphaned inode 49918132 (uid=1000, gid=1000, mode=0100664, size=16773) /dev/sda1: Clearing orphaned inode 49917725 (uid=1000, gid=1000, mode=0100664, size=16773) /dev/sda1: Clearing orphaned inode 49917436 (uid=1000, gid=1000, mode=0100664, size=16773) /dev/sda1: Clearing orphaned inode 49909685 (uid=1000, gid=1000, mode=0100600, size=262144) /dev/sda1: Clearing orphaned inode 3939849 (uid=1000, gid=1000, mode=0100664, size=8192) /dev/sda1: Clearing orphaned inode 49909471 (uid=1000, gid=1000, mode=0100664, size=16773) /dev/sda1: Clearing orphaned inode 49909480 (uid=1000, gid=1000, mode=0100664, size=16773) /dev/sda1: Clearing orphaned inode 49905527 (uid=1000, gid=1000, mode=0100664, size=16773) /dev/sda1: clean, 333655/60911568 files, 7757819/243171328 blocks

After starting Ubuntu, I see the following lines. Should I be worried?  /dev/sda6: recovering journal /dev/sda6: clean, 355773/1835008 files, 470404803/7335680 blocks


A finite ring with more than one element and no zero divisors is a division ring. (Hungerford, Algebra, Exercise 6, Chapter 3, Section 1.)   This a problem taken from Hungerford's graduate algebra text. Hungerford defines left and right zero divisors and then says that an element is a zero divisor if it is both a left and right zero divisor. I took a peek at a solution to the exercise and the author of the solution says that for $r \in R-\{0\}=R^*$, $rR^*=R^*=R^*r$. I might be missing something.   Say I want to show $rR^*=R^*$. Pick $ry \in rR^*$. If $ry=0$ then this implies that $r$ is a left zero divisor and $y$ is a right zero divisor.      $R$ has no zero divisors, but I am assuming this doesn't exclude the possibility of elements being a right zero divisor or a left zero divisor. I am thinking correctly here?    Just answering this step is fine, I think I can try to continue working on the problem from this point. Thanks.

How can I prove this:       Finite rings without zero divisors are division rings.   I know how to prove it when the ring has $1$, but I have no idea if my ring needs to have an unity.


As we look into the Deep Field, we see the Hubble photos of early galaxies up to only $400$ millions years old:    Because there is no center of the universe expansion, we can look for early galaxies anywhere in the sky. The earliest galaxies appear to us as the most distant in every direction. Therefore the early universe appears from our viewpoint as the most distant and thus the largest sphere with the radius, as we see it, of $13.4$ billion light-years (based on the most distant object in the above Wikipedia link).  Oversimplifying the spacetime geometry for a moment, the circumference of the early universe appears to us as $84$ billion light years ($2\pi\cdot 13.4 $) at the age of only $400$ million years. Clearly this calculation is incorrect. Obviously the universe was much smaller. However, we can see numerous galaxies along this circumference of our viewpoint. So either the distances we see between the early galaxies are much smaller than they appear to us in the sky or else the early universe looks way too big for its age.  What is the logical explanation of this illusion?    EDIT  Since this question is misinterpreted and misguidedly closed, I have reposted it here:

TV documentaries invariably show the Big Bang as an exploding ball of fire expanding outwards. Did the Big Bang really explode outwards from a point like this? If not, what did happen?


How can I easily check if the square root of a number is a whole number and not a decimal without computing the square rood of said number. I could square root the number ((n^2)^1/2 or sqrt(n^2)) but I do not want to.

Given the radix-$r$ representation of a integer $n$, and a small integer constant $k$, there is an $O(\log n)$ algorithm for detecting whether $n$ is a multiple of $k$, namely, division, which produces as a byproduct the quotient $\lfloor n/k\rfloor$.  In general this is the best one can do. But for certain choices of $r$ and $k$, for example $r=10$ and $k=2$, there is an algorithm which answers the question much faster (constant time) without producing the quotient.  Given the radix-$r$ representation of a integer $n$, we can extract the integer square root $\lfloor\sqrt n\rfloor$ in something like $O(\log^3 n)$ time by doing binary search, which Joriki notes below can be improved to $O(\log^2 n)$ with a sufficiently clever implementation. This gives an $O(\log^2 n)$ algorithm for determining whether $n$ is a perfect square.  Is there a significantly faster algorithm which correctly decides whether $n$ is  perfect square, without also producing the square root? I suspect not, but I would be interested to see a proof.


Hello I am trying to access an array from another class I have the code written but there seems to be a error and I can't figure out what is wrong with it (This is in Java)  Here is the first class  import java.util.ArrayList;  import java.util.Collections;  import java.util.List;  public class Main {     private static List<String> Deck;      public static void ArrayList() {// Method to create the deck         Deck = new ArrayList<String>();         int i = 1;// counter variable for loops          ArrayList <String> Clubs = new ArrayList <String>();// ArrayList for all clubs cards         while (i < 11) {// while loop to put each number in up to 10             String c = String.valueOf(i);             c = c + "C";             Clubs.add(c);// adds the card             i++;             // each increases so each card is different so ace first time through then 2 then 3....         }         ArrayList <String> Spades = new ArrayList <String>();// same same for spades         while (i > 1) {             String s = String.valueOf(i);             s = s + "S";             Spades.add(s);             i--;          }         ArrayList <String> Hearts = new ArrayList <String>();// same same for hearts         while (i < 11) {             String h = String.valueOf(i);             h = h + "H";             Hearts.add(h);             i++;         }         ArrayList <String> Diamonds = new ArrayList <String>();// same same for diamonds         while (i > 1) {             String d = String.valueOf(i);             d = d + "D";             Diamonds.add(d);             i--;         }          // Adds all Cards to 1 Deck Array         for (int j = 0; j < 10; j++) {             Deck.add(Clubs.get(j));         }         for (int j = 0; j < 10; j++) {             Deck.add(Spades.get(j));         }         for (int j = 0; j < 10; j++) {             Deck.add(Hearts.get(j));         }         for (int j = 0; j < 10; j++) {             Deck.add(Diamonds.get(j));         }         Collections.shuffle(Deck);// shuffles deck         while (i < 10) {// while loop to put nine 0 in array so the program can end             Deck.add("0");// adds 0             i++;// counter variable     }          public List<String> getDeck() {// Method used to Store the ArrayList to be accessed Through other classes            return Deck;        } }   Here is the Next Class  import javax.swing.JButton;  import java.util.List;  import javax.swing.JFrame;  import java.util.ArrayList;  public class Window {          Main m = new Main();          public static void main(String[] args) {             Main m = new Main();//allows us to access other class             List <String> Deck1 = m.getDeck();// makes the new ArrayList equal the old Deck ArrayList              System.out.println (Deck1.get(1));// Testing this is where java says the error is }   Please let me know what is wrong and where I need to fix it

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


Take this scenario for example:  I am on a rocket ship that will take a trip into space and back at 90% the speed of light. And my friend "Bob" stays on Earth. As soon as I leave Bob and I both start our clocks and stop them when I return. The Theory of Relativity would obviously state that my clock should be behind when I return to Earth because the faster you accelerate towards the speed of light, the slower time passes for you. But how can this be because according to my view inside the speeding rocket, Bob's time is passing exceptionally quickly compared to mine. So relative to me I am passing time normally while Bob is the one whose time is incorrect.  But at the same time, according to Bob's view, my time is passing very slowly while HIS time is the correct time. So relative to him he has the correct time while mine was wrong.   So my question is who's perspective do we know is correct? Now I know most will say both of ours are correct but if that is so wouldn't my slowed perspective and his "quickened" perspective just cancel each other out and NEITHER are correct because the rocket could have only taken one certain amount of time to leave and return?  Maybe I just can't get my mind to wrap around the concept of time dilation but to me it seems like it can't work. So could someone please explain why it can?

I read a lot about the classical twin paradox recently. What confuses me is that some authors claim that it can be resolved within , others say that you need . Now, what is true (and why)?


I want to uninstall ubuntu 15.04 . I dual booted it with windows 8.1. Please help me step by step, how to safely uninstall it...  I dont want to loose any data. I used 2gb as swap area and 13 gb for ubuntu home partition .  and will it remove grub also? And yes, I don't have windows 8.1 recovery disk/installation disk. What is 'System Reserved' Drive??? Will it also delete after deleting ubuntu partition?

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


I have a complex function to which I applied Newton's method using a range of different initial (complex) values. I plotted a heatmap of how many iterations it took for the method to converge for each initial guess with reals on the x axis and imaginaries on the y axis. I found that there were some regions where the method did not converge at all. So I picked a point in one of these regions and re-used it as an initial value for Newtons method. However, this time i printed out the first 50 iterations of the method. The result was that after a while, the iterations were stuck between 2 guesses - by this I mean that at some point, the iterations printed ... a, b, a, b, a, b, a, b... After a point, these were the only 2 results from the Newton Method. My question is what is the mathematical explanation for Newtons method being stuck/trapped between 2 guesses when the method has an initial value that does not lead to convergence? I hope that's clear enough. THanks

$f(x)=2x^2-x^3-2$. This is a cubic type graph as shown.  The real root of this graph is $(-0.839,0)$.  So, the question is to use Newton's approximation method twice to approximate a solution to this $f(x)$.  I use an initial starting value of $x_0=1$. My first approximation is $x_1=2$, and my second one is $x_2=1.5$. I seem to not move any closer to the real solution as I keep iterating through the method.  Am I misunderstanding how to use this approximation?  Is the issue that my first guess was too far from the actual solution?


The value of $\int\limits_0^1 {\frac{{{x^4}{{\left( {1 - x} \right)}^4}}}{{1 + {x^2}}}dx}  = \_\_\_\_\_\_$ The official answer is $\frac{22}{7}-\pi$ My approach is as follow ${\tan ^{ - 1}}x = \theta $ $\frac{1}{{1 + {x^2}}}dx = d\theta $ $ \Rightarrow \int\limits_0^{\frac{\pi }{4}} {{{\tan }^4}\theta {{\left( {1 - \tan \theta } \right)}^4}d\theta } $ $ \Rightarrow \int\limits_0^{\frac{\pi }{4}} {{{\tan }^2}\theta \left( {{{\sec }^2}\theta  - 1} \right){{\left( {1 - \tan \theta } \right)}^4}d\theta }  \Rightarrow \int\limits_0^{\frac{\pi }{4}} {{{\tan }^2}\theta {{\left( {1 - \tan \theta } \right)}^4}{{\sec }^2}\theta d\theta }  - \int\limits_0^{\frac{\pi }{4}} {{{\tan }^2}\theta {{\left( {1 - \tan \theta } \right)}^4}d\theta } $ $ \Rightarrow \int\limits_0^{\frac{\pi }{4}} {{{\tan }^2}\theta {{\left( {1 - \tan \theta } \right)}^4}{{\sec }^2}\theta d\theta }  - \int\limits_0^{\frac{\pi }{4}} {{{\sec }^2}\theta {{\left( {1 - \tan \theta } \right)}^4}d\theta }  + \int\limits_0^{\frac{\pi }{4}} {{{\left( {1 - \tan \theta } \right)}^4}d\theta } $ I dont want to use $t=tan\theta$ How will I proceed

I have no idea how to find this integral:  $$\int_0^1\frac{(x-x^2)^4}{1+x^2}\ dx\ ?$$  Any help would be appreciated. Thanks in advance.


I know that a polycyclic group is a finitely generated solvable group. Also I know that, in the case of finite groups, the two notions: polycyclic group and solvable group are equivalent. But I can not  find an example of a finitely generated solvable group which is not polycyclic.

I am looking for examples of finitely generated solvable groups that are not polycyclic. In  Baumslag-Solitar group $BS(1,2)$ is an example. But how to prove this fact?


I am planning to install ubuntu landscape server for my local network, can any one share me installation document of it and also please tell me what are the basic setup requirement (software & hardware)  I have a trial account on , and I want to register my system on it, how I can do this?

I'd like to manage my home machines and laptops with Landscape, how can I do this?


When a conductor is placed in an external electric field, I know that the free electrons arrange themselves in such a way that the field inside the conductor due to these charges cancel the external field.   If the external field was uniform, then the field due to these induced charges would have to be uniform too.   How is an arrangement of electrons ( and positive charges)  possible so that it produces an uniform field at all points inside the conductor?

I would like to clear things up: How exactly the electric field inside a conductor is zero? Let  a really "powerful" electric field be outside of it, how can the "few" charges in a conductor balance the field? From my point of view, it's the conductor surface which stops their movement. I'm obviously missing something fundamental here. Thanks in advance.


Hi I have this laptop which is perfect and has 16 gb of ram, but some programs go crazy and I run outta ram. So not that perfect! I have another laptop which has 8gb of ram. What I'm trying to achieve could not work,and could be also stupid.That's why I'm asking here by the way. Now I want to use that 8gb ram as much as possible somehow. So my way would be,turn the ram into a ram disk on the second laptop,share it through network with the first laptop. Is it practical? A Lan cable could be the best option here? What's better than this if it's practical?And what to do instead if it isn't practical. Please don't suggest using ssd, I have an ssd on my first laptop already.I will never use it as a ram backup. Ssd's are not still ready for that,they're too fragile.

My colleague is using an application that consumes a lot of memory which makes the system too slow. Is it possible to share memory with other PCs over the Internet?   The system has 8 GB of RAM, and the application consumes more than 6 GB.


Overlap Congratulations block by profile tabs

When I visit  I see this:     The "Congratulations! You've earned (badge)" section has dropped down completely beneath the tabs under it. The "You've earned a new privilege!" section has a gap at the bottom:     Shog9 says in comments how to reproduce this:     Gotta have earned a badge, not dismissed the notification, and be looking at your own profile.


I wrote an email to my professor yesterday to ask makeup exam. But he doesn't reply until now.  Test was taken a week ago. But, I can't take it because of family emergency(my grandfather passed away) and sudden move into new room (my hostfamily kicked me out without prior notice.I think the reason is outbreak of covid-19, and I'm Asian). Those are my nightmare!   In your opinion, can he admit my makeup test? and why doesn't he reply my email...?

As a grad student, I just find it tremendously frustrating when emails are ignored by faculty (both at my institution and at other places). Is this acceptable? I'd be content with a simple response with one line along the lines of "I have read this email and am busy right now, will respond in X days when I can write a more detailed email." I understand that, as a first year student in my field, I'm not really in a position to request anything of anyone, but it just seems like common decency.  Instead, I never hear back, as if my email has been jettisoned off into oblivion.


I built a VF page that is used in a community and I am trying to grab the current page id using ApexPages.currentPage().getParameters().get('id'). For some reason, this always returns null. If I use a standard controller with extension, then I can see the value just fine on a page layout outside of the community, only issue is with user in the community pages. Could this be some type of profile setting that is off or is there a different way to grab this value in community? This is a custom object, the record id is shown in the url. I have tried using both a custom controller and an extension with the standard controller from the custom app object. Additional Details: The community walks the user through a series of screens which create the Application record. I am using a workaround right now where I query the last modified Application by the use since this will be the record that is created as the user is walked though the screens. This just seems like a less than optimal workaround.     public class OnlineAppController2{              public String getName(){         App__c app2 = [SELECT ID, Name FROM App__c WHERE ID=: ApexPages.currentPage().getParameters().get('id')];         return app2.Name;     }   }

Can any one explain the usage of controller and extensions in Visualforce? In which scenario we have to use controller and extensions?


I am beginning to work with micro controllers and programming them using C language.   All my programming experience is with Python language.   I know that if I want to test a script I have written in python, I can simply launch terminal and type in “python” with the path of the file I want to run.  I tried a web search, but most didn’t seem to understand what I was asking.  How do I run c from terminal?

I'm trying to run my first "process" program, but I get the following error :  ./fork.c: line 4: syntax error near unexpected token `(' ./fork.c: line 4: `int main()'   I'm pretty sure that the code is correct:   #include <sys/types.h>  #include <stdio.h>  int main() {      pid_t pid;      printf("Hello fork()\n");      switch(pid=fork())  {          case -1: printf("Error by fork().....\n"); exit(0);          case 0: printf("I'm the child process \n"); break;          default: printf("I'm the dad \n"); break;      }   exit(0); }   What is wrong?


I made a rather simple animation using video sequence editor (mostly blinking between two images), but for some reason I cannot render it. When I clicked render animation, all I see in the render result window is the blank "image" and nothing happens. I made the animation in blender 2.8 and I though maybe there is a problem in blender 2.8, but it didn't work (the same file) in blender 2.79 either. This was the second try of the same animation, first rendered fine, but crashed so I had to start over. This is what I get:  I can render image and get the first image of the video.

A scene I made is not rendering, at all. This grey screen stays the same and nothing changes.  Here are my settings:  [


Shouldn't there be an  badge for questions marked favorite by 10 users?  By analogy with question score:    Question score of 10 or more  Question score of 25 or more  Question  Question score of 100 or more   Question marked favorite:    Question favorited by 10 users or more  Question favorited by 25 users or more  Question  Question favorited by 100 users or more

There are currently two badges for questions favorited by a certain number of users:     Favorite Question Question favorited by 25 users   Stellar Question Question favorited by 100 users   Why isn't there a bronze badge for a question favorited by 10 users? This would fit with the pattern of Nice/Good/Great badges for questions/answers, which require 10/25/100 votes. Thanks!


I am a high schooler who's really interested in quantum mechanics. I just need a few suggestions as to the books I can refer to to give me an idea about the equations and theories about quantum mechanics.   I understand that this is a stupid question to ask on aplatform where everyone who has something to say generally literally has a phd in that subject but any guidance as to how to go about it would really help.

I'm really interested in quantum theory and would like to learn all that I can about it. I've followed a few tutorials and read a few books but none satisfied me completely. I'm looking for introductions for beginners which do not depend heavily on linear algebra or calculus, or which provide a soft introduction for the requisite mathematics as they go along.  What are good introductory guides to QM along these lines?


In the Twilight Princess, Ganondorf's [extended] monologue about the Triforce states that the "Chosen" (i.e. the ones bound to the Triforce) are destined to repeat this conlfict again [emphasis mine]:  When the Chosen Ones appear... They are always born into this world in perfect balance. That is the destiny of the Chosen. That is the fate decreed by your Gods, the only path for those who bear their crests. When this world brings forth another marked as you are... Know too, that it shall also be visited by one of my blood. Do not think this ends here... The history of Light and Shadow will be written in blood!   This comes across as a kind of "prophecy", that this conflict will simply keep happening over and over again. This explains the "rebirth" of Link through Hylia's history (Hero of Time; Hero of the Minish; Hero Chosen by the Gods; Hero of Light; etc), and Zelda's reincarnations as well, though Ganondorf seems to survive through history as the same person (likely due to his ties to the Triforce of Power). I was under the impression that when the Goddesses created Hylia, the Triforce was a symbol of unity, and there was no mention of any evil intent in that event? So my question is whay casued this in the first place, and why does this conflict keep arising?

In my last  it was mentioned that it is the same Gannondorf returning, and a different hero of ages is chosen.  Why does this 'triforce' cycle keep repeating itself? Is there an in-universe explanation?


How to show file size of featured image in post on single.php?  For example: File size of featured image is: xx kb/Mb  I need size of featured "full" rezolution, also file size of "medium" resolution would be great?  Best regards.

What I need is some function to echo file name of image used in post like "image-file-name.jpg", or just "image-file-name".  Also it would be great to be able to have even more information about image like:   image width,  image height,  image mime type / format,  image file size,  image extension.   Also this may be helpful, I have custom field named 'image_full_url' which contains full url address of image used in post. For example content of custom field named 'image_full_url' is:  http://www.example.com/wp-content/uploads/2012/12/image-file-name.jpg   I am using that custom field to echo that URL when I need it, and it would be nice to have something similar to echo other data about image.


After deciding elementary OS is too temperamental for my laptop, I decided to replace it with Ubuntu 17.04. I have Windows 10 installed in a separate partition and have successfully dual booted Linux in the past. This time, however, towards the very end of the installation process, I get a warning telling me that the installer was unable to install the Grub2 bootloader.  I am using a USB installation media created using Rufus 2.15. Following the advice of answers to various similar questions, I have so far ensured that the installation media is created on a freshly FAT32-formatted USB stick, and have attempted installation both directly from the boot menu and from a Live session. I also ran the boot-info utility that generated a .

I am attempting to install Ubuntu on a box which was previously running Windows 7.  I have also experienced the dreaded "Unable to install GRUB" error.  I am not attempting to dual boot. I have previously run a Windows boot disk and removed all existing partitions.  If I run the Ubuntu 12.04 install CD and click install after the config screens, I get the error   Executing 'grub-install /dev/sda' failed. This is a fatal error. (It is the same error as this question: )  All the questions I've read while looking for a solution are related to dual boot.  I'm not interested in dual boot, I'm after a clean out the box Ubuntu install. How can I achieve this?  (For my sanity, please use very simple instructions when responding. I don't claim to have any talent either for linux or as a sysadmin)    Additional details copied from comments dated: 2012-05-29 ~15:19Z  After booting from the CD, clicking Try Ubuntu, and then sudo fdisk /dev/sda I get fdisk: unable to seek on /dev/sda: Invalid argument  sudo fdisk /dev/sdb gives   Device contains neither a valid DOS partiion table, nor Sun, SGI or OSF disklabel.  Building a new DOS disklabel with disk identifier 0x15228d1d.  Changes will remain in memory only until you decide to write them.  After that of course, the previous content won't be recoverable.  Warning: invalid flag 0x0000 of partition table 4 will be corrected by w(rite).  Command (m for help):   I should add the Live CD desktop is graphically bad. I've got missing parts of programs and the terminal occasionally reflects to the bottom of the screen. But I can't imagine this is related.


Given U,V independent exponential R.Vs. Find the law of min(U,V).   I understand some of the basics, but I need exact formal proof at the beginning since I've seen very few of these questions. I will write the beginning which I hesitate of. Could you correct my mistakes? Or approve my 100% correctness.  My solution:   U and V are Random Variables. Thus we are looking for  $P\{\{t<U\} \bigcap \{t<V\}\}$  U, V are independent. Hence  $=P\{t<U\}\bigcap P\{t<V\}$  Which is in turn:  $=F_U(t)F_V(t)$  And then we calculate and differentiate.  Did I write it wrong somewhere? Is everything correct?

How can I prove that the minimum of two exponential random variables is another exponential random variable, i.e. Z = min(X,Y)


How to show that $$\lim_{\varepsilon\to0}\int_{\varepsilon a}^{\varepsilon b}\frac{f(x)}{x}dx=f(0)\ln(b/a)$$ where $a>0$ and $f:[0,1]\rightarrow\mathbb{R}$ a continuous function.  I tried integration by parts, but it doesn't work. Thanks!

I'm trying to integrate by parts but it has not been very effective.


I am a software engineer and not an astrophysicist but I want to know if anyone is working on sorting out what exists outside the universe?  So what about outside spacetime? what is there? or shall I assume there are infinite galaxies? and even that is not a satisfying answer.  I know this question might get closed soon ... but guys please tell me what is there outside the space as we know it? since childhood I have wondered about this.   Its really a simple question. If we say that we live "inside" a Universe ... then we are objectively saying that there IS something "outside" the universe as well? Am I crazy? What exists there? Is it just empty space? Or what?

If the universe is expanding, what is it expanding into? When the big bang happened where did it occur?  When the big bang happened how did it occur?  Where did the energy come from? Energy can not be created or destroyed does that mean, energy has existed before the universe was here?


Is there a way to evaluate  $$\lim \limits_{x \to 0} \frac {e^{-1/x^2}}{x}$$  without applying L' Hôpital's rule? I've tried subbing $y = \frac {1}{x}$ and it did not work, and I also tried evaluating the expression by the exponent's Taylor's series expansion and still got no idea finding an upper limit to it.  Thank you!

Small question, I'm trying to solve this limit but I just can't wrap my head around this problem.  $$\lim_{x\to 0} \frac {e^{-1/x^2}}{x} $$  L'Hopital just seems to make it messier.   It's probably pretty simple - I'd like to hear what I'm missing.


I would like to have an arrow with "1-1" above it and/or "onto" below it, with the arrow being normal size.  I get what I want with "1-1" using \stackrel:  \documentclass[12pt]{article}  \begin{document} \(  \stackrel{1-1}{\longrightarrow}\\  \stackrel{\stackrel{1-1}{\longrightarrow}}{onto} \)  \end{document}   I would like to position "onto" similarly below the arrow.  But using a nested stackrel makes the arrow to small and too high.  What should I do?

I want to write this:    I tried with $x_n \to_{n \to 0} 0$ but the $n \to 0$ doesn't go under the right arrow, it goes under but on the right, and I want it under but in the center, as in the picture above.


I see the term i386 instead of x86 in many places related to Linux. As of my knowledge, they are not interchangeable. x86 is a family of instruction set architectures where i386 is a specific one of the x86 processors. But why do Linux world uses the term i386 instead of x86 ?    References:

So when I run Raspbian (basically a ARM Debian derivative with LXDE), I can install any normal package using aptitude. But if, for example, I wanted to download a .deb file, I would have to choose 32-bit or 64-bit and download that, and try to run it on Raspbian (it wouldn't work).   Why does installing packages from the official repositories work on ARM systems? Why is it not incompatible?  I'm also a little confused about the difference between hardware and software bits. ARM is hardware, right?


I'm building git and get the following error:       DB2TEXI user-manual.texi /bin/sh: 2: docbook2x-texi: not found    How do I install docbook2x-texi?

Simple enough question: is there some shell command (or GUI method) I can use that, given the path to a file on my system, tells me what package put it there? Assuming the file did in fact come from a package, that is.  Bonus question: what if it's a file that isn't installed on my system? Is there, say, a website that will let me look up a file and see what packages, if any, provide it?


Is there a way to tell whether a host is a physical one or a VM and which virtual container it is running out of (e.g. VirtualBox or VMWare)?  I was wondering if that info may be in /etc some place.

I have command line access to a Linux machine which may or may not be virtualized. I want to determine what kind of virtualization technology it runs on, if any (VMWare, VirtualBox, KVM, OpenVZ, Xen, ). This isn't a hostile environment: I'm not trying to work against a VM that is trying to disguise itself, I'm diagnosing a flaky server that I know little about.  More precisely, I'm helping someone diagnose the issue, I'm not sitting at the helm. So I have to convey instructions like “copy-paste this command” and not “poke around /proc somewhere”. Ideally, it would be something like lshw: an easily-installable (if not preinstalled) command that does the poking around and prints out relevant information.  What's the easiest way of determining what virtualization technology this system may be a guest of? I'd appreciate if proposals mentioned which technologies (including bare hardware) can be conclusively detected and which can be conclusively eliminated. I'm mostly interested in Linux, but if it also works for other unices that's nice.


I am trying to parse json in JavaScript  var str = '{"id-1": "www.er.co.uk","id-2": "www.wer.co.uk","id-3": "wer.wer.com","id-4": "www.wwaer.co.uk"}';  var divWebsite = JSON.parse(str);   i am getting error ()     Uncaught SyntaxError: Unexpected token o   While at the same time my json is valid as you can see here  (sorry you will need to copy and past json)

Given a string of JSON data, how can I safely turn that string into a JavaScript object?  Obviously I can do this unsafely with something like:  var obj = eval("(" + json + ')');   but that leaves me vulnerable to the JSON string containing other code, which it seems very dangerous to simply eval.


I don't know how to prove the following result.  Let $p$ be a prime number and let $a,b \in \mathbb Z$ such that $\gcd(a,b)=1$  Then  $\gcd (a-b,\frac{a^p-b^p}{a-b}) = 1 $ or $ p $  (gcd should be $1$)  I know that $\dfrac{a^p-b^p}{a-b} = a^{p-1}+a^{p-2}b+\cdots $  I don't know what to do next...  Thanks for your help.

Let $p$ be prime number ($p\gt2$) and $a,b\in\mathbb Z$ ,$a+b\neq0$ ,$\gcd(a,b)=1$ how to  prove that $$\gcd\left(a+b,\frac{a^p+b^p}{a+b}\right)=1~~\text{or}~~ p$$  Thanks in advance .


I have a question that where can I see the md5sum to check my file? Yes, I know there is one in the iso file, but it cannot do any thing! If the file has been change by a attacker, he  will change the file either! Another problem is, the page show md5sum is on a http connect, not https, so I still cannot make sure it work.

I've just downloaded a CD image of Ubuntu. I know the installer has a check CD option, but how can I check that the image is good before burning it to CD?


I'm taking Pre-Calc, and if anyone could go through step-by-step on this problem I’d appreciate it greatly. ;)  Use mathematical induction to prove the formula for every positive integer n. $$1 + 2 + 2^2+2^3 + 2^4 + \dots+ 2^{n-1}= 2^n -1$$

$\displaystyle\sum_{i=0}^n2^i=2^{n+1}-1$.  I don't understand induction so I could use some help.