What is exactly a ? I have my explanation of what it is but it's probably wrong and I would like that you correct me.  I see phonons like this:  We take a crystal. It allows some waves to propagate on.  In first approximation we can say that our crystal can be modelled as an ensemble of harmonic oscillators having the same frequency. The properties of the wave propagating on it will be defined by :  The frequency of the wave $w$  The wavevector $k$  The polarisation of the wave (is it longitudinal, transversal).  But all we said is purely classical and phonons are linked to Quantum Mechanics. So in fact to define a phonon we have to quantize our model of harmonic oscillators.  We assume that all oscillators have the same oscillation frequency $w(k)$. Then the hamiltonian can be written as a sum of harmonic oscillators (a first sum on the possible $k$ and a second for each node of the crystal). A phonon will be an eigenvector of this Hamiltonian. So it represents an excitation of the system (and if we want a link to the classical world, as it is an excitation of an ensemble of harmonic oscillators, it represents a wave travelling on the crystal).  And because we have a wave function we can say that the phonon is a particle : if we do a measure at a give $\overrightarrow{r}$ of our wave function we would have a probability $| \Psi(\overrightarrow{r}) |^2$ to find a phonon here.  Could you correct me if I am wrong, or give me more details?

I am trying to understand intuitively what a  is, but for the moment I find it quite difficult (having a limited background in quantum mechanics, an undergraduate course in non-relativistic QM). In fact, I find it hard to formulate good questions, so I hope my questions below make some sense.  I read that phonons are (the quantum mechanical analog of) normal modes of vibration in a crystalline system of atoms or molecules, so I guess a superposition, i.e. a general vibration should also be a phonon. Is that so? Why would they then be described as normal modes?  Could we say that a phonon is a particle whose position wave function extends over the whole crystal? Are the quantum mechanical frequency and wave vector the same as the frequency and wave vector of the corresponding classical oscillation (vibration in the crystal)?  In what sense is it (like) a particle? In that it is always observed or it always interacts at a specific location?


In Tim Burton's Planet of the Apes... what is up with the final scene?  It was my favorite scene in the movie but is there actually a plausible explanation for it?

In the last scene of the movie,       Leo gets into the pod and returns back to the electromagnetic field.  He is pushed back in time - the display of the pod starts somewhere  around 2700 and reaches somewhere around 2100. (The original time when  Leo left earth was 2029) The past earth seems to be now inhabited by  Apes and somehow Thade is considered a hero in this world.   How the heck did this happen? What is the meaning of this ending?


I need proof that: Let ${x}_n$ be a sequence of points in $\mathbb{R^d}$. Suppose that there exists an $\alpha \in (0,1)$ such that $$\Vert x_{m+1} - x_{m} \Vert \leq \alpha \Vert x_m - x_{m-1} \Vert$$ Prove that it is a Cauchy sequence. I tried to do the following: $$\Vert x_{m+1} -x_m \Vert \leq \alpha \Vert x_{m} -x_{m-1} \Vert \leq \alpha^2 \Vert x_{m-1}- x_{m-2} \Vert\leq ...\leq \alpha^m \Vert x_1 - x_0\Vert $$ Sea, $n>m$, then, $$\Vert x_n - x_m \Vert = \Vert x_n - x_{n-1} + x_{n-1}-x_{n-2}+x_{n-2}-...+x_m\Vert \leq \Vert x_n - x_{n-1}\Vert +\Vert x_{n-1}-x_{n-2}\Vert+...+\Vert x_{m+1}-x_m \Vert$$ But, $$\Vert x_{m+1} - x_m \Vert \leq \alpha^m \Vert x_1 - x_0 \Vert \hspace{20pt} \forall m \in \mathbb{N} $$ So, $$\Vert x_n-x_m \Vert \leq \alpha ^m \cdot (n-m-1)\Vert x_1-x_0\Vert$$ But i didn't know how continue, Any comments would be very helpful :)

$a_n$ is a sequence that satisfies the following contractive condition;  $|a_{n+2}-a_{n+1}| \le c|a_{n+1}-a_n|, n\ge 1 $ for some $ 0 \lt c \lt 1.$ Show the sequence $a_n$ is a Cauchy sequence and converges.  Consider the sequence $x_n$ given by $x_1=2$ and $x_{n+1} = 2+ \frac{1}{x_n}$   Show that $x_n$ is bounded below by 2 Show that $x_n$ satisfies the contractive condition in the first part and converges Find lim $x_n$   Not looking for the answers. Just strong hints to guide me to the answer. The first part of the problem itself, makes sense. I'm unsure on the steps needed to prove this though. The second part for (1), would I want to use induction to show that it keeps getting closer to 2 but never reaches it. For part (2), I may be way off, but as simple as plugging into the contractive condition above? I am confused on part 3.  A lot here, I appreciate any sort of help. Thanks


edit: I don't see how the other question answers mine. I already have an explicit cast (E[]) which the author of the other question doesn't have.  I also tried something like seq1 = (Integer[]) iw.result(); but that doesn't work either.   I have the following code:  public class Something<E extends Comparable<E>> { E[] seq; public Something() {     seq = (E[]) new Object[100]; }  public E[] result() {     return sequence; }  public static void main(String[] args) {     Something<Integer> iw = new Something<Integer>();     Integer[] seq1 = new Integer[100];     seq1 = iw.result(); }}   I get an errormessage in the way of: [Object can't be cast to [Comparable  So I change the Something-Constructor to:  seq = (E[]) new Comparable[100];   Now I get an errormessage in the way of: [Comparable can't be cast to [Integer  Is there any way to make the above code work? I know I would be better off working with Collections here, but I'm just curious what's wrong with my code.

Due to the implementation of Java generics, you can't have code like this:   public class GenSet<E> {     private E a[];      public GenSet() {         a = new E[INITIAL_ARRAY_LENGTH]; // error: generic array creation     } }   How can I implement this while maintaining type safety?  I saw a solution on the Java forums that goes like this:  import java.lang.reflect.Array;  class Stack<T> {     public Stack(Class<T> clazz, int capacity) {         array = (T[])Array.newInstance(clazz, capacity);     }      private final T[] array; }   But I really don't get what's going on.


I have found some mixed messages in terms of the effective sample size to shoot for (ranging from 2,000 to 10,000) .  I'm wondering if anyone could give me more information on choosing a guideline for effective sample size?  In particular, I am using a No-U-Turn Sampler.

When obtaining MCMC samples to make inference on a particular parameter, what are good guides for the minimum number of effective samples that one should aim for?  And, does this advice change as the model becomes more or less complex?


We consider he following proposition. Two $n\times n$ complex nilpotent matrices are similar if and only if they have same nilpotence index. How do I show that the statement is correct for  $n=3$ ? And why isn't it correct for $n=4$?

I have to show that all $n \times n$ nilpotent matrices of order n are similar. My initial approach was to show that for all nilpotent matrices their minimun characteristic polynomial is of the form: $$\lambda^n$$  Is this sufficient?  Can someone show me a formal approach to this problem?  Thanks!


At the end of The Return of the Jedi, the emperor tells Luke just after Luke defeated Vader in a duel,  "Now fulfill your destiny and take your father's place at my side."  If I was Vader, I would be thinking, "Palpatine is just going to throw my life away like he did Count Dooku. I'm a goner unless I take out the emperor soon!"  The Emperor then turns his back on Darth Vader while zapping Luke with bolts of electricity. Palpatine should know not to trust Vader. He seems so engrossed in torturing Luke that he doesn't notice Vader walking up behind him and grabbing him. He should know not to trust Vader for a second. He knows a Sith apprentice becomes a master by killing the previous master. He could have killed Luke quickly and then kill Vader, instead of spending almost two minutes torturing Luke. He also had a chance to zap Vader a couple of times when Vader was nearly helpless, lying there on the bridge before getting up to stand by his master's side. One zap to Vader's breather would probably have short-circuited it. Why did he make himself vulnerable to Darth Vader? Edit to address why this is not a duplicate of another question. The other question focuses on whether Palpatine erred in torturing Luke in front of his father. Palpatine already suspects Vader's feelings for Luke.  Palpatine: Strange that I have not felt him. Are your feelings clear on this? Vader: They are clear, my lord.  My question is about why Palpatine would trust Vader since he knows the Rule of Two. It is a Sith tradition for Sith Lords to kill their masters (or apprentices). He should know to never trust Vader for even half a second, yet he makes himself vulnerable for almost two minutes. That was all the time Vader needed to pick up the Emperor and throw him down the elevator shaft.

I know he's supposed to be an evil super-genius, but the Emperor seems to lack common sense here.  He sensed that Vader's feelings about Luke weren't clear pretty early on, and while he was using Force lightning on Luke, Vader was doing the exaggerated "Look at Luke, now look at the Emperor.  Look at Luke, now look at the Emperor" thing for a good 15 seconds or so.  Granted, the Emperor had little peripheral vision with his hood on, but Vader can't turn his head without also turning his torso to some extent, and someone with the Force should be able to tell when someone in the room is moving.    EDIT:  I just found out that the 2011 Blu-Ray edition has  while the Emperor is using his Force Lightning on Luke.  This makes the Emperor's obliviousness even harder to explain.  Why does it seem like it never occurred to him that Vader might react badly to seeing his son being brutally tortured to death in front of him?  Why have Vader stick around to see that?


In the program below, where is the value of return 0 stored and what does it actually mean?  #include <iostream.h>  int main() {   cout<<"Hello World";   return 0; }

What is the correct (most efficient) way to define the main() function in C and C++ — int main() or void main() — and why? And how about the arguments? If int main() then return 1 or return 0?  There are numerous duplicates of this question, including:       — For C++, with a very good answer indeed.     Related:


Using the following R code I obtain a decision tree using the agaricus dataset:  data(agaricus.train, package='xgboost')  bst <- xgboost(data = agaricus.train$data, label = agaricus.train$label, max_depth = 3,                eta = 1, nthread = 2, nrounds = 2,objective = "binary:logistic") # plot all the trees xgb.plot.tree(model = bst) # plot only the first tree and display the node ID: xgb.plot.tree(model = bst, trees = 0, show_node_id = TRUE)   I want to understand more clearly the "value" output of the tree (the 3rd line in the oval shaped object). Here we can see that tree 0 leaf 7 gives a value 1.90174532. (That is the first terminal node in the image). I want to know if this value is the same as the log-odds score. So, all observations which follow the upper path of the decision tree will obtain a log-odds score of 1.90174532. Then in a new decision tree the observations will fall into a different split depending on each observations characteristics and will obtain a "new" value Then we sum up all these values across all trees to obtain a final log-odds score which can then be converted to a predicted probability using the logistic function.  Is my intuition correct? Does value = log-odds.  (  )

I have been trying to understand gradient boosting reading various blogs, websites and trying to find my answer by looking through for example the XGBoost source code. However, I cannot seem to find an understandable explanation of how gradient boosting algorithms produce probability estimates. So, how do they calculate the probabilities?


Due to a series of unfortunate incidents, I lost all my data during a botched system update (noob here). I managed to use photorec to recover files to a specific folder "temp" on my desktop. I want to recover all my baby pics, so most likely JPEG that are more than 1MB in size. Since the number of files in the "temp" folder are in the thousands and have files of extension "txt", "png", "jpg", and others, my computer freezes if I try to use the GUI to find and move files.  Is there a way for me to move all JPGs that are more than 1MB in size to a different folder "temp2" via terminal? Current OS is a fresh, minimal installation of 18.04.

I have a bunch of video files which I would like to segregate based on file size I have decided.  Example:  Folder BB has 15 files of various file size.  I have sub folder set as:   less than 100 MB     -- folder A 100 MB to 500 MB     -- folder B more than 500 MB     -- folder C   So instead of manually doing it can it be done via Bash or a script.  I have a general idea that find command and a proper if else would work, but have no idea how to script it.  Anyway, a general programming frame would be:  float _size=[file_size]; // Reads the file size  if(_size<100)    // File size is less than 100 MB   {  exec mv [file] /A/* ; // Move to folder A } else if(_size>500) // File size is greater than 500 MB   {  exec mv [file] /C/* ; // Move to folder C } else if((_size<=500)||(_size>=100)) //file size is between 100 to 500   {  exec mv [file] /B/* ; // Move to folder C} else   {print("file error");}   So I hope it is easy to do. The above was just a general idea I would have done.


Let $\Omega, F, P)$ be the classic setting. I saw that if $f$ is a function which satisfies some assumptions then the integral with respect to the brownian motion is Gaussian. Ie $\int_{0}^{t} f_u dB_u \sim normal$  1)How we can see this gaussianity?  Ok generally, the integral of a progressively measurable process $f$ is a limit of the integrals $I(f^{n}) = \int_{0}^{t} f^{n}_u dB_u$ where $f^{n}$ are simple processes and these integrals are gaussian by definition. In fact we have also $L^{2}\Omega)$ convergence which implies weak one. So the distribution functions of $I(f^{n})$ random variables  converge uniformly( for all $x \in R$) to the distribution function of $I(f)$. But why this implies gaussianity of $I(f)$. Ok I get that the distribution function of $I(f)$ should be continuous but why gaussian? Actually this is a simple question in probability theory but I'm just thinking about it )))  Thanks

I'm trying to prove this conclusion but have some problems with one of the steps.  Assume $X_1,\ldots,X_n,\ldots$ is a sequence of Gaussian random variables, converging almost surely to $X$, prove that $X$ is Gaussian.  We use characteristics function here. Since $|\phi_{X_n}(t)|\leq 1$, by dominated convergent theorem, we have for any $t$  $$ \lim_{n\rightarrow\infty}e^{it\mu_n-t^2\sigma_n^2/2}=\lim_{n\rightarrow \infty}\phi_{X_n}(t) = \lim_{n\rightarrow \infty}\mathbb{E}\left[e^{itX_n}\right] = \mathbb{E}\left[e^{itX}\right] = \phi_X(t) $$  this is the step that I cannot figure out: $e^{it\mu_n-t^2\sigma_n^2/2}$ converges for any $t$ if and only if $\mu_n$ and $\sigma_n$ converges.   Let $\mu=\lim_n \mu_n$, and $\sigma=\lim_n\sigma_n$, then $\phi_X(t)=e^{it\mu-t^2\sigma^2/2}$, which proves that $X$ is a Gaussian random variable.  Why can we get that $\mu_n$ and $\sigma_n$ converge? This looks intuitive for me, but I cannot make a rigorous prove.


Why we can ask the question  "Who baked the cake?" when we should use did link verb?

What did you say?  What you said?   What did you wear? What you wore?    Where did you go? Where you go?    I know that sometimes in English, people do not use “do” in “wh-” questions. I have heard somewhere that people do not use “do” when the answer is a proper noun or a unique thing. Am I right?


Whenever I see my currently active bounties from a mobile site, I feel as if they've already been awarded. This is how it looks from my chrome browser in Android:    The blue colour of the +100 box is too dark: on the Desktop site this colour is used when the bounty is already awarded. A lighter tone should be used in mobile sites too, to denote active bounties.

Let's play a small game first:  Illustration: Has the bounty been awarded?  Here are two images cut from two screenshots. One of them has an active bounty, while the other has an awarded bounty. Make your guess base on the images!     Haha I bet you can't, so here's the answer:       and the original (uncut) screenshot:      and the original (uncut) screenshot:     Actually they look identical! Shouldn't that be changed and make unawarded bounty (the "award" button) look lighter like the grey tick for "accept this answer" button do?


When I move a window close to the top, it snaps to maximum size. I am using Ubuntu 18.04, GNOME 3.28.2.    How do I disable that? I searched about six months ago, no way to disable back then.  1/5/19 Yes, solved!  Thank you!   These two worked on my Ubuntu 18.04     gsettings set org.gnome.mutter edge-tiling false   dconf-editor   These did not work     GNOME Tweaks  (disable "Edge Tiling" not available)   gsettings set org.gnome.shell.overrides edge-tiling false    Thank you Kulfy, Hamza Saeed, vanadium, PRATAP.

In Ubuntu 18.04, when moving the windows there is a resize effect that occurs when accidentally touching one of the screen edges.  This control was available in CCSM and Ubuntu Tweak in previous versions with Unity.  I'm not finding it in GNOME Tweaks.  I also searched the repository with:  apt search ubuntu.*tweak


, "[...] any body completely or partially submerged in a fluid (gas or liquid) at rest is acted upon by an upward, or buoyant, force the magnitude of which is equal to the weight of the fluid displaced by the body. The volume of displaced fluid is equivalent to the volume of an object fully immersed in a fluid or to that fraction of the volume below the surface for an object partially submerged in a liquid."   The emphasis is mine, and it is that last part that got me thinking about something: What if a body stays afloat on a liquid whose volume is less than that of the object? That seemingly contradicts Archimedes' Principle because the fluid that the body displaces obviously cannot be equivalent to its actual volume; there's not enough liquid.   Take a look at the image* below:    The can has a volume of 350 mL, so it would theoretically displace roughly that much liquid if it were immersed, but this cannot happen because there is only 230 mL of (artificially colored) water. So, how does Archimedes' Principle account for this apparent paradox? Furthermore, why isn't this discussed more often?  (*The source for the picture is an article written in a foreign language, so I won't bother posting it. Interestingly, I could not find a similar setup on websites in English.)

I am confused.  Some sources say it is possible at least theoretically (  ) and some say it is not true (  )  Is it necessary or not that there exists an amount of water around the ship that weights at least the same as the weight of the ship?


In my case, the creature is a player who is doing death saving throws and the intention is to teleport both, the carrier and the carried.  Note: The creature is being carried, so the answer in "" doesn't apply as it does only to grappling (which was also in the question next to "carried" but removed then when seen the existance of an answer to that case).

I am an Eladrin elf and have the ability to use the misty step spell to teleport with my clothing and items. However, can I grapple a party member (or NPC or other creature) and use the misty step spell to bring them with me when I teleport? Would they have to be willing?


After i dual booted Ubuntu on my laptop i noticed things haven't been right on my windows 7 OS and some programs that i'm trying to download on my ubuntu os is not working because of the other OS files interfering after the hard drive.besides the fact i want to know if there is a way to instead of dual booting linux to somehow bring back up the installation and do a full install of ubuntu instead of just dual booting.

My laptop is filled with viruses and Windows XP is just becoming impossible to work with.   I've been interested in Ubuntu for a while, so, would I be able to use something like Debian to clear my HDD and OS and then install Ubuntu and start fresh?


I have a manuscript which looks like:  \documentclass{article}                \usepackage{amsmath, amsthm, amssymb}  \begin{document}  [...]   \cite{ref}   [...]   \cite{anotherref}   [...]   \bibliography{references}   \bibliographystle{plain} \end{document}   My .bib file, references.bib, looks like this:  @book{ref,     title = {String theory and M-theory},     isbn = {978-0521860697},     publisher = {Cambridge University Press},     author = {Schwarz, John and Becker, Katrin and Becker, Melanie},     date = {2007-01-15} }  @article{anotherref,     title = {Locality problem for the Liouville field},     volume = {274},     issn = {0370-2693},     url = {http://www.sciencedirect.com/science/article/pii/037026939291992I},     doi = {10.1016/0370-2693(92)91992-I},     pages = {323-330},     number = {3},     journaltitle = {Physics Letters B},     author = {Balog, J. and Palla, L.},     date = {1992-01-16}, }   For some reason, my manuscript does not compile properly. Instead of the inline references coming up as numbers, I get [?]'s. The bibliography does not appear at all.   What's very surprising is that even the  in BibTeX's official website results in the same bug.   Another manuscript that had previously compiled properly for me, now produces the same error.   I am very puzzled by this. The bug is observed both in TeXmaker's Quick Build, and ShareLaTeX.   Anybody knows the cause of this bug?  Thanks!  P.S. Please feel free to vote to close this if it is off-topic.

I've browsed the forums and found a number of posts that have addressed this issue, but none of the solutions seem to work for me. I have the following script that I just copied from the bibtex home page to get familiar with it. Instead of the citation number I get a question mark. I compile using Latex+Bibtex+Latex+Latex+PDFLatex+ViewPDF just as has been previously suggested and the problem persists.   \documentclass[11pt]{article} \usepackage{cite}  \begin{document}  \title{My Article} \author{Nobody Jr.} \date{Today} \maketitle  Blablabla said Nobody ~\cite{Nobody06}.  \bibliography{mybib} \bibliographystyle{plain} \end{document}   My bibliography (Bib.bbl)  @misc{ Nobody06, author = "Nobody Jr", title = "My Article", year = "2006" }    Looking at previous posts one thing that is concerning is that my .bbl looks empty as shown below. Further, I don't have a .blg  \begin{thebibliography}{}  \end{thebibliography}


I have a 240fps video and I want to merge/average every 4 frames into 1, resulting in a 60fps video with a motion blur type effect. Any ideas how I can do this with ffmpeg?

To average two frames in FFmpeg, one can use something like "tblend=all_mode=average,framestep=2". However, this only supports blending two frames at a time. Daisy chaining them only allows you to blend 2^N frames. What if I want to blend 3 frames, 5 frames, 6, 7, 9, and so on?  For my project in particular, I need to average 5 video frames into one. The source footage is 120fps, so this conversion would effectively reduce the framerate to 24. With tblend, this just won't be possible. How else can I go about this?


Find all integer   for  triplets$(a,b,c)$  that  $a+b+c =3$    $a+b^2+c^2=17$  and $a^2 +b^3+c^3 =21$  I have try to start with   $17-a =   ( 3-a   )^{2} - 2bc  \ \ $ and  $21-a^2 =   (3-a)\left ((17-a) -  bc  \right ) +3abc$  but It seems to not be working for me. Could you please guide me any brilliant solution for this problem? Thank you very much.


A finite group $G$ is abelian iff all its irreducible representation $\rho$ have dimension 1.   I'm looking for a counter-example when $G$ is an infinite group. Are there any?  EDIT  We're dealing with finite representations over $\mathbb C$.

All irreducible representations of an abelian group are one-dimensional. For a finite group, the coverse is also true - if all irreducible representations are one-dimensional then the group is abelian.     Is there a nonabelian group $G$ such that all of its finite-dimensional complex irreducible representations are one-dimensional (such group $G$ is necessarily infinite of course)?


In the inline math mode ($...$), if the formula is too long, LaTeX will try to break it on operators, e.g.  very long text followed by a very long equation like $a+b+c+d+e+f+g+h+i+j+k+l$ etc   may be rendered as  very long text followed by a very long equation like a+b+c+d+e+f+g+h+i+ j+k+l etc   However, the break won't happen if they are separated by commas, e.g.  very long text followed by a very long equation like $a,b,c,d,e,f,g,h,i,j,k,l$ etc   will overflow the page like  very long text followed by a very long equation like a,b,c,d,e,f,g,h,i,j,k,l etc   How to make LaTeX able to insert line breaks after a comma too?


Don't worry, my ceiling fan do not have any mechanical problem(if i will not mention it most of you will say repair your fan) it's just a part of home experiment.  Once looking at the blades of my fan I supposed can I increase the speed of blades (and hence amount of air coming from it) just by applying some physics??  The  interesting point came  when one of my friend said yes you can just bend the blades of your fan. I tried it but it didn't worked so for the final suggestion, I supposed to come here.  Someone of you may say that this question is not clear so forget all,the question you have to answer is Can I increase speed of blades of my fan just by applying some physics.  I m not asking about any formula or procedure to measuring the speed of blades, i m just asking how can i increase the speed of blades

Is there any formula for computing fan speed by using air mass,air flux, air density or specific heat? I have computed air mass and air flux, and found the values for air density and specific heat, but now I am stuck at finding a correlation between these and fan speed.


Prove:   $A \subseteq B$ iff $A \cap B=A$   Can someone give me a hint on how to start this? I know in order to prove two sets are equal you have to take an arbitrary item from one set and show it is in the other and then vice versa but how do I apply it to this case?

Showing   $A \subset B \iff A\cap B=A$  How would I show this?  My proof  Assume  i. $A \cap B \subset A$  ii.$A \subset A \cap B$  Let $x$ be any element.  Assume $x \in A \cap B$. Then $x \in A$ and $ x \in B$. By hypthesis $x \in A \rightarrow x \in B$ Thus $x \in A$  ii.  Let $ x \in A$ By hypthesis $x \in A \rightarrow x \in B$   thus $x \in A \cap B$.  Part 2  $ A\cap B=A \rightarrow A \subset B$  But I find myself stuck here.


I think my observation linux to navigate to the previous directory (or back) command is cd- but it is not working code cd-

First i did pwd, it says:  /home/user   I changed my directory using :  cd /Italic/Food/Places   Now, I want to go back to original directory: /home/user. How can I do this?


This question is a little bit stupid and silly.   As I am chemist, I don't remember electricity physics very good. As I remember it shouldn't harm anything, but I need to be sure.  LEDs will be blinking sometimes together. But not longer than 50ms.  They will be parallel for only short time. Because they supposed to blink reporting 2 modes 1st - normal, 2nd - error. And switching between them can be no longer than 50ms.         – Schematic created using   I use resistor for both LEDs, but it just curiosity question.

Why can't you use a single resistor for a number of LEDs in parallel instead of one each?


I have a page with a url of:     domain.com/page.jsp?pID=01   And I have code:  <% String pID; %> <% if (request.getParameter("pID") == "01") { %>      <%@include file="page01.jsp" %>              <% } else if (request.getParameter("pID") == "02"){ %>      <%@include file="page02.jsp" %>              <% } %>   All I get is a blank page.  Why is this?

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


Running Lubuntu on HP G61. No wifi.   Search in "Additional Drivers" shows nothing.  I have searched for a solution but googling does not help in this set of circumstances.  What to do?    As requested:  john@john-HP-G61-Notebook-PC:~$ lspci 00:00.0 Host bridge: Advanced Micro Devices, Inc. [AMD] RS880 Host Bridge 00:01.0 PCI bridge: Hewlett-Packard Company Device 9602 00:05.0 PCI bridge: Advanced Micro Devices, Inc. [AMD] RS780/RS880 PCI to PCI bridge (PCIE port 1) 00:06.0 PCI bridge: Advanced Micro Devices, Inc. [AMD] RS780 PCI to PCI bridge (PCIE port 2) 00:11.0 SATA controller: Advanced Micro Devices, Inc. [AMD/ATI] SB7x0/SB8x0/SB9x0 SATA Controller [AHCI mode] 00:12.0 USB controller: Advanced Micro Devices, Inc. [AMD/ATI] SB7x0/SB8x0/SB9x0 USB OHCI0 Controller 00:12.1 USB controller: Advanced Micro Devices, Inc. [AMD/ATI] SB7x0 USB OHCI1 Controller 00:12.2 USB controller: Advanced Micro Devices, Inc. [AMD/ATI] SB7x0/SB8x0/SB9x0 USB EHCI Controller 00:13.0 USB controller: Advanced Micro Devices, Inc. [AMD/ATI] SB7x0/SB8x0/SB9x0 USB OHCI0 Controller 00:13.1 USB controller: Advanced Micro Devices, Inc. [AMD/ATI] SB7x0 USB OHCI1 Controller 00:13.2 USB controller: Advanced Micro Devices, Inc. [AMD/ATI] SB7x0/SB8x0/SB9x0 USB EHCI Controller 00:14.0 SMBus: Advanced Micro Devices, Inc. [AMD/ATI] SBx00 SMBus Controller (rev 3c) 00:14.2 Audio device: Advanced Micro Devices, Inc. [AMD/ATI] SBx00 Azalia (Intel HDA) 00:14.3 ISA bridge: Advanced Micro Devices, Inc. [AMD/ATI] SB7x0/SB8x0/SB9x0 LPC host controller 00:14.4 PCI bridge: Advanced Micro Devices, Inc. [AMD/ATI] SBx00 PCI to PCI Bridge 00:18.0 Host bridge: Advanced Micro Devices, Inc. [AMD] Family 10h Processor HyperTransport Configuration 00:18.1 Host bridge: Advanced Micro Devices, Inc. [AMD] Family 10h Processor Address Map 00:18.2 Host bridge: Advanced Micro Devices, Inc. [AMD] Family 10h Processor DRAM Controller 00:18.3 Host bridge: Advanced Micro Devices, Inc. [AMD] Family 10h Processor Miscellaneous Control 00:18.4 Host bridge: Advanced Micro Devices, Inc. [AMD] Family 10h Processor Link Control 01:05.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] RS880M [Mobility Radeon HD 4225/4250] 01:05.1 Audio device: Advanced Micro Devices, Inc. [AMD/ATI] RS880 HDMI Audio [Radeon HD 4200 Series] 02:00.0 Network controller: Qualcomm Atheros AR9285 Wireless Network Adapter (PCI-Express) (rev 01) 03:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8101E/RTL8102E PCI Express Fast Ethernet controller (rev 02) john@john-HP-G61-Notebook-PC:~$

How to install the driver for Atheros AR9285 in Ubuntu 11.10.  Still no package for 11.10 according to this      Here is the output of the commands  marc@fer-VPCYA1V9E:~$ sudo lshw -class network   *-network DISABLED              description: Wireless interface        product: AR9285 Wireless Network Adapter (PCI-Express)        vendor: Atheros Communications Inc.        physical id: 0        bus info: pci@0000:02:00.0        logical name: wlan0        version: 01        serial: 4c:0f:6e:d6:65:cc        width: 64 bits        clock: 33MHz        capabilities: pm msi pciexpress bus_master cap_list ethernet physical wireless        configuration: broadcast=yes driver=ath9k driverversion=3.0.0-12-generic firmware=N/A latency=0 link=no multicast=yes wireless=IEEE 802.11bgn        resources: irq:16 memory:d3400000-d340ffff   *-network        description: Ethernet interface        product: AR8131 Gigabit Ethernet        vendor: Atheros Communications        physical id: 0        bus info: pci@0000:03:00.0        logical name: eth0        version: c0        serial: 54:42:49:a2:1f:bc        capacity: 1Gbit/s        width: 64 bits        clock: 33MHz        capabilities: pm msi pciexpress vpd bus_master cap_list ethernet physical tp 10bt 10bt-fd 100bt 100bt-fd 1000bt-fd autonegotiation        configuration: autonegotiation=on broadcast=yes driver=atl1c driverversion=1.0.1.0-NAPI firmware=N/A latency=0 link=no multicast=yes port=twisted pair        resources: irq:43 memory:d2400000-d243ffff ioport:1000(size=128)   And the second command  marc@fer-VPCYA1V9E:~$ rfkill list 0: sony-wifi: Wireless LAN     Soft blocked: no     Hard blocked: no 1: sony-bluetooth: Bluetooth     Soft blocked: no     Hard blocked: no 2: phy0: Wireless LAN     Soft blocked: no     Hard blocked: no 3: hci0: Bluetooth     Soft blocked: no     Hard blocked: no 4: acer-wireless: Wireless LAN     Soft blocked: yes     Hard blocked: no   Is there a way to make it work?


I know about quantum mechanical model of an atom and how electrons behave like a standing waves and there isn't any lower level energy available for electrons below ground state energy and energy comes in discrete packets and so on...  I am just having a hard time to imagine and understand that why electrons, which are negatively charged and nucleus of an atom which is positively charged, because of protons remains separated from each other .  I mean opposite charges attract each other; so why electrons just stay in there orbitals and not collapse in the nucleus which is positively charged ?  What is that force which keeps electrons in their orbitals and thus overcome the attractive force which is being applied by the protons ?

We all learn in grade school that electrons are negatively-charged particles that inhabit the space around the nucleus of an atom, that protons are positively-charged and are embedded within the nucleus along with neutrons, which have no charge. I have read a little about electron orbitals and some of the quantum mechanics behind why electrons only occupy certain energy levels. However...  How does the electromagnetic force work in maintaining the positions of the electrons? Since positive and negative charges attract each other, why is it that the electrons don't collide with the protons in the nucleus? Are there ever instances where electrons and protons do collide, and, if so, what occurs?


I tried making a ticket using:      Ticket ticket = ForgeChunkManager.requestTicket(this, this.minecraftServer.entityWorld, ForgeChunkManager.Type.NORMAL);   The above code is in my main mod class. I get a NullPointerException when I try to run my mod.

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'm having a hard time rendering a fire and smoke simulation. I wanted to  record a animation and get the .pngs wiht alpha channel, but in the final render the objects in my case a meteor is transparent.  My goal is to achieve a animation file that works like an rgba.  How do achieve the correct results ?  I tried rendering .png looks transparent I tried composition nodes and with a blue and black background and it looks awful. Ill tried rendering .png and converting into .MOV with png rgba format and it looks like the final render , transparent thing and also I went to Adobe after effects and followed this steps ---> ` and is gets some of the solution but is still 70% transparent.   I am ussing Blender 2.79 for windows 10 and using cycles.  Here is my example.

When rendering volumes with Film > Transparent enabled, the alpha appears to be the wrong type (premultiplied/straight). In the 3D view it works as expected:    This is a known .  Is there any way to work around this?


I have a list of email subjects like  <XYZ> commented on <ABC> Weekly review for <Company> Your account is ready    And I want to find patterns in them so I can group them.  Is there a well known algorithm I can use?

I have a list of email subjects like:  <XYZ> commented on <ABC> Weekly review for <Company> Your account is ready    And I want to find patterns in them so I can group them.  Is there a well known algorithm I can use?    Preferably with wide language implementations or easy re-implementation. The algorithm should be unsupervised. The number of different emails is not known.   Update:  I think I can break this down into two problems:   Group subjects by the similar words they use, resulting in the following. Each group should be very distinct from the rest (they should be almost perfectly exclusive) and the algorithm should give relatively small number of groups with good length of the common words.  [commented, on] [weekly, review] [your, account, is, ready]  Once grouped, it should be easy to find a state automaton that accepts only the group's subject and thus eliminates variable Then I can go back and check if there are any intersections and tweak the variables.   Having said that, is it better to use a completley different approach like neural nets maybe? I have zero experience with those, but if it makes more sense, I am open to learning.


I am trying to use latex to write the below. The code I have makes the underbrace contained in the square root so the square root symbol is larger, but I want it like it is in the bottom picture. This is what I have:    This is what I want:    Here is my code:  $ \sqrt{\underbrace{\overline{xx\cdots x}}_{2n}-         \underbrace{\overline{yy\cdots y}}_{n}}=   \underbrace{\overline{zz\cdots z}}_{n}$

Inspired by  on the math StackExchange, suppose you want to typeset the square root of the number 144...4, that is, 1 followed by n 4's. If you write $\sqrt{1\underbrace{44\ldots4}_{n\ \text{times}}}$, as in the current version of the question, you get a huge radical sign that reaches down to match the "n times" text below the number. Is there an elegant way to typeset this so that the radical sign looks like it would with $\sqrt{144\ldots4}$, but also keeping the underset text in the right place?


Here is the Issue... I have Ubuntu 12.04LTS my room mates all have windows 7 computers, I am tired of Burning CD's for them... How do I share my second HDD (Media Drive), that has all the files that always want copies of with them... In a way that they can access them from their Win7 computers?

I have a desktop (Ubuntu 13.04 & Win 7 Home Premium) and a Laptop (Ubuntu 12.04), both having WiFi adapters. I also have a WiFi router connected to internet which both my computers can access.  I want to share files between my desktop and my laptop using WiFi (similar to Homegroup on Windows 7 but without using Ethernet cables).  How do I set-up that?  I want to share files using both OSs, if anyone have have information about sharing files with any of the OS please answer!


A growing interest in Quantum Computing -particularly in its eventual applications on Machine Learning- has taken over me and I would like to follow that path. I have strong Maths (Calculus, Multivariate Calculus, Linear Algebra, Math. Analysis, etc) and Probability foundations but my knowledge in Physics is rather poor. I also have some knowledge in common Machine Learning. What subjects should I study and -if possible- what books per subject could I try? I will probably do this on my own but I don't mind taking rigourous books if it's needed. Thanks a lot, I know the answer to my question is a large one and I appreciate the effort it will take to approach it.

I am a computer science student and am currently searching for resources from where I can learn about quantum computers, quantum computing models, their working principles, their gates and some simple quantum algorithms.


This is Venkat  I was created a file. Name is '-file1'. So how can we open or find these type of files  Thanks, Venkat.K

How do you remove a file whose filename begins with a dash (hyphen or minus) -?  I'm ssh'd into a remote OSX server and I have this file in my directory:  tohru:~ $ ls -l total 8 -rw-r--r--    1 me  staff  1352 Aug 18 14:33 --help ...   How in the world can I delete --help from a CLI?  This issue is something that I come across in different forms on occasion, these files are easy to create, but hard to get rid of.  I have tried using backslash  rm \-\-help   I have tried quotes  rm "--help"   How do I prevent the minus (dash or hyphen) character to be interpreted as an option?


I am well aware of the advantage in using static_cast rather than C-style casting for pointer types.  If the pointer types are incompatible, then:   static_cast will yield a compile-time error at a specific line within the source code C-style casting might lead to a runtime error at a "random" point in the execution of the program   But I am unable to find any similar example for non-pointer types.  In other words, both casting methods yield the same result for non-pointer types.  Is that correct, or have I missed anything?  If yes, is static_cast used for non-pointer types only in order to maintain coding consistency?

I've been writing C and C++ code for almost twenty years, but there's one aspect of these languages that I've never really understood. I've obviously used regular casts i.e.  MyClass *m = (MyClass *)ptr;   all over the place, but there seem to be two other types of casts, and I don't know the difference. What's the difference between the following lines of code?  MyClass *m = (MyClass *)ptr; MyClass *m = static_cast<MyClass *>(ptr); MyClass *m = dynamic_cast<MyClass *>(ptr);


I want to upgrade from Lubuntu 19.04 to 20.04 and I am curious if there is some way of doing this from the terminal while erasing all my old files at the same time. I think there's a term for upgrading an OS while wiping the hard drive but I can't remember it, so I haven't been able to find anything searching for pre-existing answers. I am not sure if this matters, but I originally downloaded Lubuntu 19.04 from lubuntu.net, not lubuntu.me. It's running on a chromebook with the original OS mostly removed. I have it set up so if anything goes wrong I can just reinstall chrome OS before overwriting it again. I don't have a cd/dvd drive, and I only have one usb stick, so I'd rather not go through the hassle of installing from usb.

I want to install Ubuntu on my laptop that doesn't have a CD-ROM drive and I have no spare USB disk. I've tried Wubi, but that doesn't seem to work (since it prompts me to have the CD in the drive, which I don't have).  How can I install Ubuntu, easily and in a fast way?  P.s: I want to dual boot it with Windows 7 (which was preinstalled).  Edit:   When extracting the ISO to a folder and running Wubi it does install, but when I reboot the computer, it doesn't show GRUB, nor can I choose if I want to boot Ubuntu or Windows 7. After trying for the third time today, wubi gives me an error: Permission denied   I'm the administrator on the PC.


I was surprised to find that there's a growing convention of capitalizing the word "black" when referring to the race, i.e.:  A Black person.  I thought this was wrong, because I thought it was only proper nouns, like cultures, nationalities and ethnicities, that were to be capitalized. Black denotes a race, and nothing more, as there are many nationalities, cultures and ethnicities that fall within the black race. Calling black a culture or ethnicity would be reductive. However, this capitalization rule apparently applies to race as well; see the 10th item . If this rule is in fact true, then that means black is to be capitalized when denoting a person of the black race. It also means that white is to be capitalized when denoting a person of the white race. Caucasian, which is a word denoting a race, is capitalized. It is a synonym to white. So, if Caucasian is capitalized, and if people want black to be capitalized when referring to race, why isn't white supposed to be capitalized? Is white not a race? I'm no biologist, nor anthropologist, but if white is too genetically broad to be considered a race, then I'm pretty sure black would be too. EDIT: As user Cascabel pointed out in the comments, Caucasian is derived from the Caucasus Mountains, which is a place, and therefore a proper noun. Therefore, regardless of what capitalization rules one employs, Caucasian has to be capitalized, and is therefore not necessarily an example of people capitalizing racial classification. EDIT 2: CMS have changed their preferred capitalization rules as of the 17th edition, which means that the answers to the linked  that this post was designated a duplicate of, are no longer valid.

What is the accepted custom regarding capitalization when it comes to "White" and "Black" when referring to race, whether they are being used as nouns or adjectives?


Let x be a real number with $|x|<1$, and q be a real number. Show that the series $\sum_{n=1}^{\infty} n^{q}x^{n}$ is absolutely convergent, and that $\lim_{n\to\infty} n^qx^n=0$.  My attempt:   Let $c = n^q$   Then since, $$\sum_{i=m}^{n} (ca_i) = c(\sum_{i=m}^{n} a_i),$$ we can write  $$c\sum_{n=1}^{\infty} x^{n}$$ and by a Lemma concerning geometric series, if $|x|<1$ then $$\sum_{n=1}^{\infty} x^{n}$$ is  absolutely convergent. If it is absolutely convergent it is also conditionally convergent. Now I can use the zero test and we see that the limit of $x^n$ as n->infinity = 0.

I'm having trouble with proving the following for my math study:  Let $x$ be a real number with $|x| < 1$, and $q$ be a real number. Show that the series $\sum_{n = 1}^\infty n^qx^n$ is absolutely convergent, and that $\lim_{n \rightarrow \infty}$ $n^qx^n = 0$  I tried this:  $\sum_{n = 1}^\infty n^qx^n$ = $x + 2^q + 3^qx^3 + ...$ $= x(1 + 2^qx + 3^qx^2 + ...)$  So far, I don't know how I have to do this, I tried to apply the root test on this, but for that I would need to compute the lim sup of the series, so I thought that was not correct. Could you explain me how to prove this?  Thanks in advance!


I have two tables in my database namely tutors and students with the following structure:  tutors table +------------+--------------------+---------------------+ |tutor_id    |tutor_avail_credits |entry_time           | +------------+--------------------+---------------------+ |    20      |      300           | 2017-01-22 11:53:10 | +------------+--------------------+---------------------+ |    13      |      200           | 2017-01-24 13:58:45 | +------------+--------------------+---------------------+   students table +------------+--------------------+---------------------+ |student_id    |student_credits   |entry_time           | +------------+--------------------+---------------------+ |    20      |      50            | 2017-01-24 12:23:10 | +------------+--------------------+---------------------+ |    13      |      100           | 2017-01-24 15:58:45 | +------------+--------------------+---------------------+   I have a PHP script that allow students to reserve a tutor for a tutoring session that will run for minutes equivalent to student's credits. The way I had intended it to work was that, I run a query to fetch rows for the top most tutor(earliest since the list is sorted according to time)    $query = "SELECT * FROM tutors               WHERE (tutor_avail_credits > 0 )             ORDER BY entry_time ASC LIMIT 1 ";   If a student submits a form to reserve the top most tutor, his/her credits should be subtracted from the tutors credits until the tutor is fully reserved. Each time a reservation occurs tutor_avail_credits field should be updated until it's 0. So I have this code.         <?php           //Check if reserve button press         if(isset($_POST['reserve'])){             //Some code here.........          if($student_credits < $tutor_avail_credits){             $tutor_avail_credits = $tutor_avail_credits - $student_credits;             //Update table field.              $update = "UPDATE tutors                         SET  tutors_avail_credits = '$tutors_avail_credits'                        WHERE tutor_id = '$tutor_id'"             }            //Code continues.....            ?>   Now the problem is that the field tutor_avail_credits will be accessed by multiple users at the same time, won't this cause some problems? if so, is it possible for me to have additional column in tutors table where I can set a flag after running a SELECT query so that it will be used as a condition allowing other users to select tutors which are currently not selected.Here is the query.   $query = "SELECT * FROM tutors               WHERE (tutor_avail_credits > 0 AND status ='available')             ORDER BY entry_time ASC ";   Please I am a beginner point me in the right direction.

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?


I've been studying encryption on a hobby basis, and wanted to know if I got this basic cypher construction right (this is another experiment, see the AES ECB experiment thread earlier).  Encryption:   XOR plain text block, initialization vector and counter together. AES resulting block. Increment counter. Goto 1 until all plain text blocks are done.   Authentication tag:   Sha256 cipher text. AES resulting hash using authentication key.

As I understand it, CTR mode essentially turns a block cipher into a stream cipher like so:          _______________        |       |       |        | nonce |   i   |        |_______|_______|                |         _______V_______        |               |        |  block cipher | key -->|  (encryption) |        |_______________|                |                V plaintext --->(+)---> ciphertext   But by turning it to a stream cipher, one must be very careful not to reuse a nonce.  It seems like it would be safer to do it like this:          _______________        |       |       |        | nonce |   i   |        |_______|_______|                | plaintext --->(+)                |         _______V_______        |               |        |  block cipher | key -->|  (encryption) |        |_______________|                |                \---> ciphertext   While it still would be unwise to reuse a nonce, it seems like the effects would be less devastating if it were misused in this way.  I see one main disadvantage, and that's that with the first formulation, only the encryption part of the block cipher need to be implemented, whereas with this second formulation, both encryption and decryption need to be implemented.  My questions are:   Does this latter mode of operation have a name? Are there any obvious weaknesses in this latter mode? Are there any other reasons why CTR is defined the first way?


I have a question about structures. I'm trying to have the user input a letter and have the the computer return two values. Here's what I have till now:  #include <iostream> struct coords{ int coordsx1; int coordsy1; } a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p; int main() { char first; int coordsx1; int coordsy1;     a.coordsx=0;    e.coordsx=0;    i.coordsx=0;    m.coordsx=0;     b.coordsx=1;    f.coordsx=1;    j.coordsx=1;    n.coordsx=1;     c.coordsx=2;    g.coordsx=2;    k.coordsx=2;    o.coordsx=2;     d.coordsx=3;    h.coordsx=3;    l.coordsx=3;    p.coordsx=3;     cin >> first;     coordsx1= first.coordsx; // this is the part that doesn't work }   For example if the user inputs 'd' for the variable first, I want the computer to set the value of coordsx1 to be equal to 3 and coordsy1 to be equal to 0 (I haven't done the coordsy1 part yet). Also, is this a good way to return more than one value for a user input?

This is a somewhat bizarre question. My objectives are to understand the language design decision and to identify the possibilities of reflection in C++.   Why C++ language committee did not go towards implementing reflection in the language? Is reflection too difficult in a language that does not run on a virtual machine (like java)? If one were to implement reflection for C++, what will be the challenges?   I guess the uses of reflection are well-known: editors can be more easily written, program code will be smaller, mocks can be generated for unit tests and so on. But it would be great if you could comment on uses of reflection too.


I recently attempted to install a required update which was needed by software I installed on PlayOnLinux, however the update never installed.  The system would infinitely hang up on the install and I would be forced to kill the install process (not ideal I know). Now the system continues to show the software (ttf-mscorefonts-installer) as an update in the Discover Center on Kubuntu. I am not having success removing the update via Discover or at the command line. Also notice - it shows the page is 0 B in size. I included a screenshot of the update in Discover.  Here is my attempt to remove the update from the terminqal: scott@scott-ZenBook:~$ sudo apt remove ttf-mscorefonts-installer [sudo] password for scott:  Reading package lists... Done Building dependency tree        Reading state information... Done The following packages were automatically installed and are no longer required:   libllvm10 python3-debconf update-notifier-common Use 'sudo apt autoremove' to remove them. The following packages will be REMOVED:   ttf-mscorefonts-installer 0 upgraded, 0 newly installed, 1 to remove and 0 not upgraded. 1 not fully installed or removed. After this operation, 0 B of additional disk space will be used. Do you want to continue? [Y/n] y dpkg: error processing package ttf-mscorefonts-installer (--remove):  package is in a very bad inconsistent state; you should  reinstall it before attempting a removal dpkg: too many errors, stopping Errors were encountered while processing:  ttf-mscorefonts-installer Processing was halted because there were too many errors. E: Sub-process /usr/bin/dpkg returned an error code (1)  It says I should try to reinstall it before uninstalling.  Well, I can't.  The software consistently locks up the install process.  Is there a way to remove this once and for all?

After a recent update, ttf-mscorefonts-installer prompted me to accept its license agreement.     ┌─────────────────┤ Configuring ttf-mscorefonts-installer ├─────────────────┐  │                                                                           │   │ TrueType core fonts for the Web EULA                                          │                                                                               │ END-USER LICENSE AGREEMENT FOR MICROSOFT SOFTWARE                             │                                                                               │ IMPORTANT-READ CAREFULLY: This Microsoft End-User License Agreement           │ ("EULA") is a legal agreement between you (either an individual or a          │ single entity) and Microsoft Corporation for the Microsoft software           │ accompanying this EULA, which includes computer software and may include      │ associated media, printed materials, and "on-line" or electronic              │ documentation ("SOFTWARE PRODUCT" or "SOFTWARE"). By exercising your          │ rights to make and use copies of the SOFTWARE PRODUCT, you agree to be        │ bound by the terms of this EULA. If you do not agree to the terms of          │ this EULA, you may not use the SOFTWARE PRODUCT.                              │                                                                               │                                  <Ok>                                         │                                                                           │   └───────────────────────────────────────────────────────────────────────────┘    Screenshot:   For some reason my terminal will not allow me to accept, or for some reason I am pressing the wrong hotkey...  I've tried every letter on the keyboard and Enter among others...  I'm sure there is a very simple and obvious solution to this.  I've also just tried to remove the package completely however the terminal states that due to the package not being correctly installed, I should reinstall the package before removing it.  Very frustrating!  Essentially, because I cannot successfully install this package, I can't really ever upgrade my system because I always have to end up terminating the terminal with the license agreement (thus the upgrade fails).


I just want to know what is the difference between the add_action and add_filter. I just could not get it enough in the documentation of wordpress. Can anyone explain it more broader and simpler. Thank you in advance.

I have been looking at the plugin API a bit more in depth recently and I was wondering what real differences there were between action and filter hooks. They both are events that receive data as a parameter and they seem to both be able to do the same things.  Obviously I see that actions are called when actions take place and filters are called when data is manipulated, but it seems to just be a semantic naming difference.  Besides semantics and what they are used for, what real differences are there between them?


I have a non-rooted Android phone with the  app installed. I can run ifconfig on the phone's terminal and see the IP address of wlan0, and I can ping the phone's IP from the terminal on my computer. Is it possible to SSH into it from a computer on the same network? If so, what would the username and password be?  I know the openssh package is installed on the phone: apt list | grep openssh returns openssh/stable,now 8.1p1-4 arm [installed].  I can also run the ssh command in the phone's terminal (Termux).  Are there any extra packages I would have to install via pkg or apt? Please let me know, anything helps.

I am using Wi-Fi hotspot on Android. Can I SSH into it from my laptop which is connected to hotspot? How would I do this?


This has been bothering me for some time...the zombies seem to have heads without skulls, like over-ripe melons. I realize that their flesh is slowly rotting but bone does not rot! How are the survivors able to crush the zombie’s skulls to destroy the brain so effortlessly?

In The Walking Dead, the more we go through the seasons, the easier it seems to be to crush the zombies' head. The head literally explodes now with a hard hit.  This seems logical as after all this time, the zombies should be completely decomposed already.  So how are they even walking etc? The decomposition of their body should be in such an advanced state that any movement should make them break apart.  If the virus slows down the decomposition, how is it even possible? No blood is circulating, or anything, so I don't see how.


In the series, we see magic starts to come back with the birth of the dragons. We also see a resurgence of the Others as the series moves on.   Is there any correlation between these two events? Are the Others mystical creatures that exist only when magic does or have they just been amassing their strength until now?

Just watched the 4-th episode of season 4. In the end we see the scene where      the baby is turned into one of the white walkers by a magic ritual.   That means that      The white walkers actually aren't immortal, they grow older over the time, and they perhaps even can die from old age.   But if that's how the process of reproduction is organized for the White Walkers, that brings the question:  Who was the first white walker ever and how did he come to such a state?


I'm really confused by FQDN. So there is this file on my debian machine /etc/hosts. What exactly goes in there?  Say my VPS is located at ipadress: 39.22.11.99 And i have a couple of domains all pointing to this ip adress. Let's say: domainA.com, domainB.com, domainC.com  Those 3 domains do each server another purpose and are correctly configured with Nginx to point to the correct data say: websiteA, websiteB, websiteC  I have one mail server running on my VPS working and all. Yet somehow i think my /etc/hosts file is not configured correctly as all the mail goes into my spam folder even while i have an SSL certificate for all 3 domains and subdomains.  How would one configure his /etc/hosts file? And should virtual hosts/users help me sending mails from different domains?  For now my /etc/hosts file looks like this:  127.0.0.1    localhost           SomeAlias 39.22.11.99  domainA.com         SomeAlias 39.22.11.99  mail.domainA.com    SomeAlias 39.22.11.99  domainB.com         SomeAlias 39.22.11.99  domainC.com         SomeAlias

I just bought a  VPS hosting plan and was following this  to set up. In the "Setting the Hostname" section and "Update /etc/hosts " section, it says the FQDN/hostname to be set here does not need to be related with the websites I am about to host, which makes me confused.  I did my own research by reading lots of articles but am still not very sure what role the hostname/FQDN is playing in my web hosting business. Here are some basic facts I've managed to find out, feel free to correct me if anything wrong:   FQDN must be something like xxx.somedomain.com, if "xxx." is omitted then it is not a FQDN. the xxx, which I think could be loosely called a subdomain, can also be referred to as "hostname", according to . In my local machine, by adding the following line to the hosts file  63.117.14.58 www.yahoo.com whatever   every network requests for "www.yahoo.com" or "whatever" will be redirected to IP address 63.117.14.58(which is google.com's IP). It is a way to block unwanted sites in local machine.  Now the tutorial suggests adding this line to the "hosts" file in my server  12.34.56.78(//my server's IP) myhostname.anything.com myhostname   It mentions that in the above line, domain name may or may not be the domain I am about to host, but the hostname should be the one I have already set during previous steps. My questions are:  1)Based on Facts#3, I think this line redirects any requests on the server for myhostname.anything.com or myhostname to my IP address, but what does this mean? Shouldn't any request for myhostname.anything.com from a user's computer already be translated to a certain IP address(Be it or not my IP address)? Why do I have to redirect it on my server?  My understanding about how a HTTP request works is when user type in the domain name into the browser, the browser will contact the domain server, and the domain server will direct it to a DNS server based on the domain's DNS record, and then the DNS server will resolve the IP address, and then browser fetch data from that IP address. This procedure of my understanding seems having nothing to do with the "hosts" file on my server.  2) A.In regards of the FQDN, why the hostname has to be same with the hostname I set on my server and the domain name doesn't?   B.What will happen if I do set a different hostname here?   C.And what is the purpose to set or not set my domain name as the FQDN here?   D.And what will happen if I only set a FQDN but not the hostname? like this  12.34.56.78(//my server's IP) myhostname.anything.com   Lots of questions but I believe the answers to some of them are overlapped, and overall I think the big question is "What part does setting hostname/editting hosts file play in my webhosting business?"   Thank you for your time in advance.


A rifle is fired, and the bullet moves much faster than the rifle, and momentum is conserved. My question is whether the kinetic energy of the bullet is greater than the kinetic energy of the rifle because the mass of it is smaller, therefore the force acting on it (for the same time it acts on the rifle) results in greater acceleration, and thus greater final velocity (basically, the change in momentum needs to be equal and in opposite direction to the rifle, which has greater mass). On the other hand, kinetic energy depends on work done, which is force times displacement. Therefore, we can say that the force acted on the bullet for a greater distance traveled. Are these explanations stating the same thing, or are they causally different? (From the expression of the momentum formula as m. dx)

Momentum is defined by the product of mass and velocity. Now a projectile out of a gun has to have high velocity to penetrate a human body, as its mass isn't significant. But to reach this velocity, due to inertia/the law of energy conservation, momentum on both sides is to be equal. As there is strong negative acceleration in the opposite direction of the bullet, it should result in a strong force in the opposite direction of the bullet ($F = m*a $).  Therefore I wonder why shooting a bullet with a handgun is not ripping your hand apart.


Is the speed of a satellite self maintained ? Or it needs anything to be done externally ?  Condition : The satellite is in the orbit where it is held in equilibrium by the force of gravity and its centrifugal force.

The orbit of satellites around Earth eventually decays, or so I read. This is typically caused either by atmospheric drag, or by tides. I would assume most satellites have a limited service life in orbit. Hence the question - What is the typical orbital life of a satellite? How long before it's successor must be launched into orbit ?  EDIT: For instance, a weather satellite


I've been pondering where voting behavior on Meta came from in the sense that it's not the same as ordinary sites. In the meta FAQ it says something along the lines of people voting based on how much they like or agree with a question or answer.  In response to some negative feedback, I am not against the notion. In fact, I would like to know what drives it and what makes it so useful.       , most of them admittedly negative in opinion, I have found a number of troubling points that I now find myself considering:   If the current voting behavior was community-adopted as one post suggested, especially as a result of site-specific metas where reputation isn't tied to privileges, then it may not be as appropriate on MSE as on other meta sites. Since voting is , downvoting freely can discourage new questions and thoughts. It may punish individuality by scaring users into not asking questions, for fear of reputation loss. This might cause questions to lean towards topics known to be popular with the populace. There are a few cases of uncertainty regarding when or how to vote because a question on meta is researched and useful (or otherwise).   I know that it is ludicrous to ask the developers to change the tie to privileges and I respect their choices. I will not ask that. It just seems that voting might not be working out on MSE in the same way as it does on other meta sites as a result of this.  My question is on how the voting culture of MSE came about. I hope to understand why it is more effective, thanks.

A guest at my house over the weekend stood puzzled next to my driveway. "What is that for?" she asked, pointing to a framework of 2x4s and hardware cloth perched on an old tire amid piles of sand. "Sifter." I said. "For what?" "For sifting gravel." "Why?" "To line walking paths, such as the one you're standing on..." Spend enough time working with something, and it's easy to forget how strange and unnatural your makeshift tooling can appear to those unfamiliar with it.  Such is the nature of these meta sites. For 5 years, we've been directing folks to them for discussion and feedback, to commune with their community, hash out misunderstandings, propose changes and document the current state of things. And... We haven't always been good about helping them get past the initial shock and confusion of dealing with this system. This has manifested in several unfortunate behaviors:  Downvoting of legitimate support questions - those that are not duplicates and reflect an actual bug or honest misunderstanding of how the system operates. Folks who are acting in good faith should be treated as such - , not shutting them down.  Closing questions that seek input and discussion from the community - in hindsight, adding "primarily opinion based" as a close reason on meta sites was... a terrible idea. The old "not constructive" close reason made some sense for rants and so on, but for a discussion site closing down questions that solicit opinions is just silly. Here on MSE, we prefer the following off-topic reason instead:  This question does not appear to seek input and discussion from the community. If you have encountered a problem on one of our sites, please describe it in detail. See also:    The perception that Stack Exchange is disrupting the normal operation of the site by talking about future plans - even when those plans involve the community. I talked about this a bit more on , but seeing this kind of backlash toward folks at the company who were trying to be open and receptive to discussion about what they were doing was kinda disheartening - we need to be doing more of that, not less.  A reluctance to ask questions about asking questions - which is about as meta as you can get, and yet we probably get more of these via email than we see on meta, while being the least-qualified to answer them well.   After an increasing number of complaints from both core users and moderators on a number of sites, we're taking a hard look at how we can improve this situation... Starting with a change to :  Meta is for...  ...$SiteName users to communicate with each other about $SiteName (asking questions about how the websites work, or about policies and community decisions) ...$SiteName  users to communicate with Stack Exchange the company (posting bugs, suggesting improvements, or proposing new features), and ...Stack Exchange to communicate with the community (soliciting feedback on new ideas or features, or discussing policies that affect the whole network)  Lots of topics are fair game, as long as they are about the Stack Exchange family of Q&A sites in some way. Any issue that concerns the core Stack Exchange engine that runs all Stack Exchange websites is welcome here.  This replaces the previous bullet list of specific topics, and aims to outline broad purposes with examples for clarification rather than constraining the scope to those examples. So... that's a start. But a documentation change isn't going to change misconceptions that've already built up among newer users. So I'm asking y'all for help: What do you think meta should be used for, and how can we better communicate this intent to new users?


I am bit confused with the concept of empty set here.  Since {} is a subset of every set, it is a subset of itself? and hence {} = {{}}?  Also, say A = {a}, but since {} is a subset of A, is it true that A = {a, {}}, if so, what is its cardinality?

Sorry but I don't think I can know, since it's a definition. Please tell me. I don't think that $0=\emptyset\,$ since I distinguish between empty set and the value $0$. Do all sets, even the empty set, have infitinite emptiness e.g. do all sets including the empty set contain infinitely many empty sets?


Basically what I wanted was to create a session with an expire time of 24 hours. And I wrote this:  session_start(); if (!isset($_SESSION['TIME_START']) || $_SESSION['TIME_START'] < time()) {         $_SESSION['TIME_START'] = time(); } else if ($_SESSION['TIME_START'] > 60 * 60 * 24) {     session_destroy(); }   I would like to know if this is a valid, viable or good practice to do it. Thanks!

I need to keep a session alive for 30 minutes and then destroy it.


I'm trying to change my Minecraft username. I've logged onto my Mojang account, but can't find where to change my username.  When I log in, it should show me the games by Mojang that I own, as well as my username for them. However, it only shows me "My Gift Codes", and won't let me scroll up or down. I've tried videos, I went to the Mojang help site, and even my best friend isn't having this problem. Any ideas?

I want to change my Minecraft username, but I cannot find a way to do this anywhere. Is this possible? If so, how can I do so?


I would like to move to 18.04 LTS, can someone clarify me how to please? 16.04 installed Thanx

What are the different ways I can use to upgrade Ubuntu from one release to another?


I have not much do add to the title, for some reason works with Firefox but not with Chromium and I would like to fix it. I searched on the web and seems I'm not the only one but found not good answer, not one at least that fixed my problem. I red that could be something related to DRM content reproduction on the browse. I red  question but no solution for me.

After reading an article about Ubuntu's netflix support I decided to try running netflix through chromium but I got this error code: M7063-1913 I assumed that it was a problem with html5 but in the playback preferences it doesn't give me the option to use it.


I have a server based in the USA, where I am not a domain admin, and my permissions are limited to sql server only - where I am sysadmin.  after a migration of a few databases to a new server, I noticed that I needed to go back to the old server to get one of my logins and permissions related.  when I run the following command:  EXEC xp_logininfo 'gplondon';     I get:     Msg 15404, Level 16, State 10, Procedure xp_logininfo, Line 62 [Batch   Start Line 6] Could not obtain information about Windows NT group/user   'gplondon', error code 0xffff0002.   I understand I have all the    But what other permissions are missing that have disabled me (or the sql server service on that server) to interrogate the active directory?  in other words, everything was working fine before, what permissions are missing now?

I have a SQL Server 2008 R2 cluster on Win2008 R2.   I am unable to add a login for the service account.   Any other login I add to this instance works fine and I have been able to add the same service account login to numerous other SQL instances.   Moving the instance to other node does not resolve the issue.   when I run   CREATE LOGIN [DOMAIN\ServiceAccount] FROM windows;    I get the error  Msg 15401, Level 16, State 1, Line 1 Windows NT user or group 'DOMAIN\ServiceAccount' not found.      Check the name again.    When I run   exec xp_logininfo 'DOMAIN\ServiceAccount', 'all';    I get the error  Msg 15404, Level 16, State 11, Procedure xp_logininfo, Line 62 Could not obtain information about Windows NT group/user      'DOMAIN\ServiceAccount', error code 0xffff0002.    Any suggestions would be appreciated.


Why the  of $ \mathbb Q(\sqrt{-19}) $ is $ \mathbb Z\left[\frac{1+\sqrt{-19}}{2}\right] $?  I came up with this question when I was trying to understand this: . And this result seemed to be mentioned in an algebraic number theory book when I was looking for references.

Quadratic integer ring $\mathcal{O}$ is defined by \begin{equation}    \mathcal{O}=\begin{cases}       \mathbb{Z}[\sqrt{D}] & \text{if}\ D=2,3\ \pmod 4\\       \mathbb{Z}\left[\frac{1+\sqrt{D}}{2}\right]\  & \text{if}\ D=1\pmod 4    \end{cases} \end{equation} where $D$ is square-free.   I understand $\mathbb{Z}\left[\frac{1+\sqrt{D}}{2}\right]$ is not closed under multiplication if $D=2,3\pmod 4$. But still, isn't it more natural to define $\mathcal{O}=\mathbb{Z}[\sqrt{D}]$ for all square-free $D$? (in that case, it really seems like 'quadratic integer') I wonder what is the motivation of this definition.


I ma making a grenade like this one in the image:   And I have the main bumpy part here:   so I want to spin them to make that shape, but nothing seems to work. Any ideas? Thanks.

We know that the there is an Object Offset option for Array modifier, but when trying to make a circular array with that offset object as the center of the array circle, it always doesn't behave quite like what's expected. So how to make a nice and controllable circular array?  P.S.: There is an old  about moving the object's origin. I wonder if there is any way to do this without changing the location of the origin. :)


Are people allowed to post their email address in an answer, asking for code or possible solutions on any of the Stack Exchange sites?  I  the following:

Should I edit out the (thankfully obsfucated) e-mail address from this ?  Is this something we should allow on the site going forward?  I don't care about the "thank you" or "hello", but this might lead to an answer being sent by e-mail, which would mean it wouldn't be peer reviewed (for what that's worth), and the answer would be lost to the community.


Will CDC work with SQL Server Always on Availability groups? Do you need to set up CDC on both/multiples nodes if using Availability Clusters?

Does  work in a  setup?  There would be two nodes in the AlwaysOn Failover Cluster Instances setup and two Domain Controllers.  We are not using AlwaysOn Availability Groups.  Will CDC work? and will it failover?


My project looks something like this   maven-simple      src/main/java              src/main/resources     src/test/java         -com.org.central           -CommonMethods.java     src/test/resources      pom.xml   I am trying to create a jar file through this method in eclipse for the above project   Right Click -> Export -> Java -> Jar File  click Next -> Next -> Finish    exported jar file has been created in the path .  Then i am importing this jar file in some other project(for ex:- project b) to use the CommonMethods.java   But i am getting this error    ←[31mjava.lang.NoClassDefFoundError: com/org/central/CommonMethods  at stepDefinitions.Check.iSeeElement(Check.java:14)      Caused by: java.lang.ClassNotFoundException:  com.org.central.CommonMethods  at java.net.URLClassLoader.findClass(URLClassLoader.java:381)  at java.lang.ClassLoader.loadClass(ClassLoader.java:424)  at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:331)  at java.lang.ClassLoader.loadClass(ClassLoader.java:357)  at stepDefinitions.Check.iSeeElement(Check.java:14)   what have i done wrong ?

I want to package my project in a single executable JAR for distribution.  How can I make a Maven project package all dependency JARs into my output JAR?


I am using MikTex, and reduced the problem to the following document:  \documentclass[12pt, a4paper]{article} \usepackage[T1]{fontenc} % this causes the problem  \begin{document} Lorem ipsum dolor ..... \end{document}   If I compile this document using pdflatex test.tex and then open the resulting PDF in Google Chrome it looks like this:    Here's without \usepackage[T1]{fontenc}:    Needless to say, the latter looks a lot better. What could be causing this?

I have the following LaTeX-document:  \documentclass[a4paper,11pt]{article} \usepackage[utf8x]{inputenc} \usepackage[ngerman]{babel}  \usepackage[T1]{fontenc}  \title{Sample} \author{Litb}  \begin{document}  \maketitle  \begin{abstract}  This is a report about my praxis phase at the company foo bar which I enjoyed. \end{abstract}  \end{document}   Much to my frustration, compiling with pdflatex creates a document with Bitmap-fonts. The reader's font-list shows that it uses Type3 fonts.  If I remove the fontenc loading, then I get a PDF using vector-fonts, but I heard that I should keep it, for having native German Umlauts working.  Does anyone know how I can get vector fonts with T1, and why it keeps using bitmap fonts if I have that package-load line in it?


It is true that every group that has a finite number of subgroups is finite?   I think not, but I can not find counterexamples.

I'm trying to prove that any group $G$ of infinite order has an infinite number of subgroups.  I think that if the group has an element of infinite order, then it's easy because I can take the groups generated by the powers of this element.  What if it doesn't? Every element generates a cyclic subgroup. Every element belongs to at least one cyclic subgroup (that generated by itself). So the group is the union of its cyclic subgroups. If all these are finite, we would have to have an infinite collection of subgroups anyway.  Is that correct?


Prove by infinite descent that there do not exist integers $a,b,c$ pairwise coprime such that $a^4-b^4=c^2$.

While I was surfing the web, searching things about math, I read something about a particular theorem of Fermat. It said: let $a$ and $b$ be rational. Then $a^4-b^4$ cannot equal the square of a rational number, so $a^4-b^4\neq c^2$ with $c$ rational. My question is: did I understand the theorem? if not, what is the actual theorem? if yes, how can I proof this or is that too difficult?


What I'm asking is do subatomic particles like a proton have a volume or any 3 dimensional size? Or are they just points?

I am wondering if the mass density profile $\rho(\vec{r})$ has been characterized for atomic particles such as quarks and electrons. I am currently taking an intro class in quantum mechanics, and I have run this question by several professors. It is my understanding from the viewpoint of quantum physics a particle's position is given by a probability density function $\Psi(\vec{r},t)$. I also understand that when books quote the "radius" of an electron they are typically referring to some approximate range into which an electron is "likely" to fall, say, one standard deviation from the expectation value of its position or maybe $10^{-15}$ meters.  However it is my impression that, in this viewpoint, wherever the particle "is" or even whether or not the particle "had" any position to begin with (via the Bell Inequalities), it is assumed that if it were (somehow) found, it would be a point mass. This has been verified by my professors and GSIs. I am wondering if its really true.  If the particle was truly a point mass then wherever it is, it would presumably have an infinite mass density. Wouldn't that make electrons and quarks indistinguishable from very tiny black holes? Is there any practical difference between saying that subatomic particles are black holes and that they are point masses? I am aware of such problems as Hawking Radiation although at the scales of the Schwarchild radius of an electron (back of the envelope calculation yields $\tilde{}10^{-57}$ meters), would it really make any more sense to use quantum mechanics as opposed to general relativity?  If anyone knows of an upper bound on the volume over which an electron/quark/gluon/anything else is distributed I would be interested to know. A quick Google Search has yielded nothing but the "classical" electron radius, which is not what I am referring to.  Thanks in advance; look forward to the responses.


The first pin material I created is able to get assigned to the whole pin. The second stripe material I can't get assigned to anything.   Blend file:

How do you add more than one material to a mesh?   I have tried adding two materials to the object, and then assigning one of the materials to a vertex-group, but I could not find a place to assign it.  I am making a striped bouncy ball that I want to deform, so adding a different material by separating the mesh into different objects would not be ideal.


(I could not find any answer to the following question in other related questions posted on SE, so asking it here.)  In the derivation of D'Alembert's principle in his , Goldstein uses the relation,     Where the set {ri} is the set of cartesian coordinates used to describe the configuration of a given system and {qi} is the set of independent coordinates such that each ri can be expressed in terms of qi's. i.e. ri=ri(q1,q2,.......,t) where 't' is time. vi is given by the equation,      Now, my question is how is the expression (1.51)(given in the first image) obtained? I tried to directly differentiate the expression of vi, but it will give another term on the RHS of (1.51).  I tried to find out on google, and I got  pdf which also agrees with my doubt.

Why is the following equation true? $$\frac{\partial \mathbf{v}_i}{\partial \dot{q}_j} = \frac{\partial \mathbf{r}_i}{\partial q_j}$$ where $\mathbf{v}_i$ is velocity, $\mathbf{r}_i$ is the displacement, and $q_j$ is the generalized coordinate into which $\mathbf{r}_i$ is transformed. In reading further, I find that it's related to $$ \mathbf{v}_i \equiv \frac{\mathrm{d}\mathbf{r}_i}{\mathrm{d}t} = \sum_k \frac{\partial \mathbf{r}_i}{\partial q_k}\dot{q}_k + \frac{\partial \mathbf{r}_i}{\partial t} $$ I know that in transforming the virtual displacement $\delta\mathbf{r}_i$ into generalized coordinates, I can use $$ \delta\mathbf{r}_i = \sum_k \frac{\partial\mathbf{r}_i}{\partial q_k}\dot{q}_k $$ The first equation above is of course equivalent to $$\frac{\partial \dot{\mathbf{r}}_i}{\partial \dot{q}_j} = \frac{\partial \mathbf{r}_i}{\partial q_j}$$ I'm not sure why the dots vanish just like that. How do these all connect? In a non-mathematical explanation, I can understand that as $q_j$ changes, $\mathbf{r}_i$ changes as well. In the same way, as $\dot{q}_j$ changes, $\mathbf{v}_i$ changes, too. I'd like to know, mathematically, how these changes (for $\mathbf{r}_i$ and $\mathbf{v}_i$) turn out to be equal.


Let $Z_1,Z_2,\ldots,Z_{14} $ be 14 independent N(0,1) variables, and let $Y=Z_1^2+Z_2^2+\cdots+Z_{14}^2$. Provide answers to the following to two decimal places.   Evaluate the moment generating function $M_{Z^2_1}(t)$ of $Z_1^2$ at the point $t=0.14$  First I tried to find the new MGF for $Z^2_n$  $$M_{Z^2_1}(t)=E(e^{X^2t})$$  $$=\left(\frac1{\sqrt{2\pi}}\right)\int_{-\infty}^{\infty}e^{\left(\frac12\right)x^2(1-2t)} \, dx$$  then I have no idea how to integrate it....I know the solved integral and answer but don't know how to solve it

If $X\sim N(0,1)$, integrate to find the moment generating function of a random variable $X^2$ and identify the distribution of $X^2$ using the moment generating function. $$E\left[e^{tX^2}\right]=\int_{-\infty}^{\infty}{e^{tx^2}e^{-x^2}\over{\sqrt{2\pi}}}dx$$ which reduces to $$=\frac1{\sqrt{2\pi}} \int_{-\infty}^{\infty}{e^{tx^2}e^{-x^2}}dx =\frac1{\sqrt{2\pi}} \int_{-\infty}^{\infty}{e^{x^2(t-\frac12)}}dx$$ and thus I am stuck. I'm sure there must be some trick to this (like completely the square for the mgf of a standard normal variable X) but I can't figure out what it might be. Any hints?


After I edited the /etc/sudoers.d/my_sudoers file with nano I was unable to use sudo.  The following errors are giving when trying to use sudo:  sudo: parse error in /etc/sudoers.d/my_sudoers near line 4 sudo: no valid sudoers sources found, quitting sudo: unable to initialize policy plugin   I know exactly what is wrong but I have no way to edit the file since it is owned by root.  I can't use chown to change the ownership because that would involve using sudo.  pkexec has not been installed or configured on the server so I'm not sure if that is an option.  I have tried using the copy command to make a back up but I get the same errors.  Can someone please tell me how to solve this?  Please don't recommend reboot the server because that is not an option.

I messed around with the sudoers file without really knowing what I was doing using   Assume I did everything that was in the top answer along with editing it with vim and not visudo. How do I fix this?  I'm running Xubuntu 12.04, and I didn't set a root password.


Why is the limit of a function $f(x)$ defined as $$f(x)-L<\varepsilon$$$$x-a<\delta$$but not like $$f(x)-L \leq \varepsilon$$ $$x-a \leq \delta$$What problems would arise if it was defined like this as compared to the standard definition? P.S.- Some may point out these as silly questions, but I want to understand every bit that I read, not just know. Thanks.

Definition (As written in Michael Spivak's Calculus)     The function $f$ approaches a limit $l$ near $a$ means: for every $\epsilon >0$ there is some $\delta > 0$ such that, for all $x$, if $0<|x-a|<\delta$, then $|f(x)-l|<\epsilon$.   my question is: why can't it be: $$0<|x-a|\leq \delta,|f(x)-l|\leq \epsilon$$ After looking at limits of functions for a long time just to grasp it's meaning and using the definition quite a lot solving homework I realized I keep writing the same inequality without really understanding why.  The only explanation given in Spivak's book for this part of the definition goes over it without explaining the inequality. I tried looking for an explanation myself but wasn't really able to find anything wrong with it. Is it also possible to write the definition like that or is there a problem with that?   (first non-homework related question :p)


What is the best solution for me to reformat a Acer Aspire E14 with Windows 8.1 operating system that only have C Drive and every time I inserted USB flash drive file has been compressed and put into a shortcuts. And when I put and use my external hard-drive nothing happen. I never used my DVD/CD ROM because it not working or it's lens has been damage. I try to make a full scan on my laptop using 360 Total Security also nothing happen.   In addition, I try to put my USB flash drive every time my laptop still on its start up and even restarting fast and open configure bot menu but still it open on Windows 8.1 start screen and nothing happen or still the same.

What should I do if my Windows computer seems to be infected with a virus or malware?  What are the symptoms of an infection? What should I do after noticing an infection? What can I do to get rid of it? how to prevent from infection by malware?   This question comes up frequently, and the suggested solutions are usually the same. This community wiki is an attempt to serve as the definitive, most comprehensive answer possible. Feel free to add your contributions via edits.


There are two strings which have the same meaning in the Russian Language:  "СРЕДСТВО ДЛЯ МЫТЫЯ СТЁКОЛ" "СРЕДСТВО ДЛЯ МЫТЫЯ СТЕКОЛ"  MS SQL The first string is stored in the database. I can make where condition either with first string or second string but I am getting the record which is stored in the database. .Net I want the same result in .Net too but not succeed yet.  I have taken two string variables and directly compare with "==" with each other which gave me "false" result Checked with String.Equal with StringComparison parameter and result is "false" only  Any help is appreciated. Thanks!!

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


You have two dogs which are black and white, two white dogs, and two black dogs. Have the following sentences correctly distinghsed them?   There are white and black dogs (two white and two black only) There are white and black dogs (two white and black dogs only)

A black and a white dog means "two dogs". A black and white dog means "one dog".  Then what about black and white dogs?  Does this mean two things?  "Dogs, each of black and white color" and "dogs of black and dogs of white"?


I want to create a map object in javascript. I came to the following idea:   var a = new Array();  a["key1"] = "value1";  a["key2"] = "value2";   but then how I can find if a particular key exists or not?

As made clear in update 3 on , this notation: var hash = {}; hash[X]  does not actually hash the object X; it actually just converts X to a string (via .toString() if it's an object, or some other built-in conversions for various primitive types) and then looks that string up, without hashing it, in "hash". Object equality is also not checked - if two different objects have the same string conversion, they will just overwrite each other. Given this - are there any efficient implementations of hashmaps in JavaScript? (For example, the second Google result of  yields an implementation which is O(n) for any operation. Various other results ignore the fact that different objects with equivalent string representations overwrite each other.


The card  reads:  Target creature gets -2/-2 until end of turn.  If I used that on , a 2/1 creature, would Highland Game still die?

There are some spells and abilities that subtract from a creature's power/toughness: for example, part of  says "Target creature gets -3/-3 until end of turn."  If the target creature is only a 2/2, is that target destroyed (goes to graveyard) from the -3 toughness given to it? If not what happens, does it stick around with negative toughness?


I am using TeX (not LaTeX). I want to print our company logo in TeX Generated Invoice. Kindly help.

I used the OzTeX implementation of TeX, also I used to typeset my docs in plain TeX, not LaTeX for me, so I had no problem to insert an image using the OzTeX, now I'm back to TeX docs, am using the TeXWorks frontend, but I can't insert an .eps image file, it seems the \includegraphics macro its only for LaTeX, so I can't use it, any idea on how to insert an image when using plain TeX?


When I want to start a new ASP.Net project in Visual Studio 2012 but I'm given the option to create an ASP.NET Web Application or an ASP.NET Web Site.  What's the difference between the two ASP.NET Web Application and ASP.NET Web Sites? I've developed Web Sites before but never tried a Web Application and would like to know more.

When I start a new ASP.NET project in Visual Studio, I can create an ASP.NET Web Application or I can create an ASP.NET Web Site.  What is the difference between ASP.NET Web Application and ASP.NET Web Site? Why would I choose one over other?  Is the answer different based on which version of Visual Studio I am using?


Does anyone have recommendations on books/workbooks that I can read that goes beyond a beginner's level for Arcpy/Python with GIS?  I've written several scripts, some simple, some complex, but I want to learn how to be more efficient, and how to look at my code and improve upon it. I learn best interactive workbooks, so I'm looking for a learning medium like that.


I have an arithmetic sequence, $a+dn$, where $a$ and $d$ are constants and $n$ is the term number. How would I efficiently calculate solutions to the following equation, $$ (a+dn)\%b=0 $$ where $b$ is also a constant. (and $\%$ means modulo) I attempted the question myself and found out that I really just need to find the smallest $n$ that satisfies the equation and find the rest by adding ${kb\over GCD(d,b)}$ to $n$, where $k$ is any integer. I also noticed that the smallest solution will always be less than $b$ and if no solution exist within this range, then there is no solution. So I tried to find the solution by brute forcing from 0 to $b$, until I got a solution. But this method is not nearly as efficient as I need it to be.

Problem :   Solve in $\mathbb N$ :   $8n+9\equiv 0\pmod{1163}$  The mathematics give me : $n=435+1163k$ , $k\in\mathbb N$   $1163$ is a prime number   $8n\equiv -9\pmod{1163}$   $8n\equiv 1154\pmod{1163}$   I don't know any ideas to complete my work ?   I have to see your hints


Bases loaded with 2 outs. Ball is hit to shortstop. SS tags runner attempting to advance to 3rd. Does the run count from 3rd base

There is a runner on third with two out. Batter hits a slow roller to first base. First baseman charges and picks up the ball. Runner from third crosses home. First baseman tags the runner running from home to first, does the run count ?


I'm stuck on the equation $$\frac{\sin\theta}{1+\cos\theta}=\frac{1-\cos\theta}{\sin\theta}$$   I just can't figure how to start. I need to flip the equation and change the signs but I'm not sure where to start.

I'm doing some math exercises but I got stuck on this problem.  In the book of Bogoslavov Vene it says to prove that:  $$\frac{\sin x}{1-\cos x} = \frac{1+\cos x}{\sin x}.$$  It is easy if we do it like this: $\sin^2 x = (1-\cos x)(1+\cos x)=1-\cos^2 x$. But how to prove it just by going from the left part or from the right  Can anybody help me?  Thank you!


"Runs in the family" by Amanda Palmer contains the following lyrics:     Strips in the city and shares all her best tricks with      Me?      Well, I'm well   The first word of the bridge, "Me?", is also the last word in the preceding verse. However, unlike with anadiplosis where the word used in both sentences is repeated, here the word is only used once.  This may be a form of enjambment, but it seems slightly different to the examples I've come across. In particular, the three lines are not strictly well formed in conjunction, as the "me" is used both as the start and end of a sentence depending on which pair of sentences it is considered to belong. This is contrary to many examples of enjambment in which each line follows the previous semantically.  Is this difference a meaningful distinction, and if so, does the technique have a name?

Is there a name for when one phrase ends with a word that starts the next phrase. For instance:     life is a peach and cream   Or     sunscreen in the eye for detail   Or (from Dave Eggers' Heartbreaking Work of Staggering Genius)     JFKFC


I'm a beginner trying to use LaTeX. I tried to write a sentence which includes the %-symbol using \text{}, but the function that the %-symbol has in LaTeX seems to block me from using it in a normal text sentence.  \documentclass{article} \usepackage[utf8]{inputenc} \begin{document} \maketitle  \text{I can't use the %-symbol} \end{document}

I need to output the below text but since \ is a special character, I cannot:  [RegularExpression(@"\d+")]   Also sometimes I need use dollar sign $ as well but it seems to be a special char, too.  What is the way to escape those in LaTeX?  UPDATE:  I used \verb as suggested but I am unable to run commands inside it. Also, in the output the font and the opacity of the text is different than the default one:  \verb|[RegularExpression(\newline @"\d+")]|


I have a Toshiba Satellite laptop. My charger has stopped working.  I have access to a Lenovo charger. Can I use this charger on my laptop?

I've lost my original power adapter, and I can't find the proper one in any of the stores currently available.  I've HP Compaq 6730b, and as per  it outputs 18.5V 3.5A. However, I've found an older power adapter I have which outputs 19.5V 4.62 A.  So, my question is: how much of a difference between those two it really is, and more importantly, how much of a risk would it be if I tried the power adapter I already have.  P.S. I know pretty much nothing about electricity/electronics.


I run Ubuntu 12.10 when I attempt to install updates I get the following message:   ERROR: BrokenCount >0'.    How can I fix this?

I have the message:   Error Broken count >0 Check if you are using third party repositories. If so disable them, since they are a common source of problems. Furthermore run the following command in a Terminal: apt-get install -f Details: The following packages have unmet dependencies: firefox-globalmenu: Depends: firefox (= 19.0+build1-0ubuntu0.12.04.2) but 19.0+build1-0ubuntu0.12.04.1 is installed   Any suggestions?