if I delete private/var/folders/zz to free up space will it cause any problem?

I am very new to mac. I want to upgrade to the latest version of mac but there is not enough space in my mac. After some digging, I found there is a folder called private that is taking more than 38GB of storage. I have given the screenshot below. But some forums on the internet say, I should not delete the private/var/folders. I am not sure what to do. I have no important data to lose. Now should i delete this folder? If yes what is the correct way to delete these huge files?


In , Herbert uses a macro definition  \def\defpoint#1#{\expandafter\defpoint@i#1;;\@nil}   which Joseph Wright reports as having a "grab to #{" argument. How does this work? Where is it useful? Are there any restrictions? Does it extend in the same way nested macro definitions would? As in, using ##{ if redefining a macro within another one.


Is Ubuntu Server only available with the command line?

One day my company is going to need a server, and I like Ubuntu since it has the least amount of viruses out of all the OSes (I think), but when I look at the Ubuntu Server it only has black background and white text, which is command line. Is that all to Ubuntu Server? Or is it like Ubuntu Desktop, and a modules for command line? I don't really want it to just be the command line.  I'm new to the Ubuntu OS stuff. Even now I still use windows.


Per line text gradient (ala beeline reader)

I've looked at the demo of Beeline reader and would like to test it out on a physical version of my books, which are done in LaTeX. I'm wondering if it would even be possible.   Beeline reader takes online test a puts a slight gradient on the letters for a single line of text. On the next line it reverses the direction of the gradient. The idea being that it helps tracking text and improves speed of reading.  Any hints or suggestions as to how to do this in LaTeX?  What follows is an example taken from


$f:(0,\infty)\rightarrow \Bbb R$, $x\mapsto 1/x$ show that f is continuous

$f:(0,\infty)\rightarrow \Bbb R$, $x\mapsto 1/x$  show that $f$ is continuous.  To prove the continuity on the given domain, for each $x_0\in(0,\infty)$ and $\epsilon>0$ we need to determine a $\delta(x_0,\epsilon)$ which satisfies $|x-x_0|<\delta(x_0,\epsilon)\Rightarrow|f(x)-f(x_0)|\lt \epsilon$.  In which way one could easily find $\delta(x_0,\epsilon)$?


Temp tables not being created in SQL Server Azure

I have created a stored procedure that creates multiple temp tables for use in the sproc and then drops them at the end of the sproc. The problem I am encountering is I can execute the stored procedure just fine in management studio, but when I attempt to create an SSIS data flow that retrieves the rows returned by the sproc, it give me the following error:     Invalid object name '#tempRuns'   Is there something special I need to do in order for temp tables to work with SSIS in Azure?


I am currently on 91 points, and I have got the Edit Community Wiki privilege! Why?


list-item automatically span to text width

I would like to span the list-item to textwidth automatically. If it's possible to align in 4 list to text-width (based on the long-length text) otherwise if it's to align in 3 list to text-width.  My MWE is:  \documentclass{book} \usepackage{amsmath} \usepackage{enumitem} \setcounter{secnumdepth}{0}  \begin{document}  \section{Digital Resources for this chapter}  In the Interactive Textbook: \begin{itemize} \item Videos \item Literacy worksheet \item Quick Quiz \item Solutions (enabled by teacher) \item Widgets \item Study guide \end{itemize}  In the Online Teaching Suite: \begin{itemize} \item Teaching Program \item Tests \item Review Quiz \item Teaching Notes \end{itemize}  \end{document}   My Expected Final Output is :


How to manually change sort and name format of reference list in latex

In my bibliography, I have an author named 'R de Jong'.  Using the apacite package, in my reference list the author is sorted under 'd' and is displayed as  de Jong, R. (year). article name etc.   However, as it concerns only one author, I would like to manually change this into  Jong, R. de (year). article name etc.    and sort this author under 'j'. How should I do that?  I am currently using Jabref for managing my references.


Equivalent definitions of normal subgroups

Those 5 Statements are all equivalent to the Statement that $H$ is a normal subgroup of $G$:  $(1) \forall g \in G, h\in H$ we have $ghg^{-1} \in H$  $(2) \forall g \in G, gHg^{-1} \subseteq H$  $(3) \forall g \in G, gH = Hg$  $(4)$ Every right coset of $H$ is a left coset  $(5) H$ is the kernel of a homomorphism of $G$ to some other Group  In class we used the Definition 3 can someone explain me why 3 and 1 are equivalent?  Edit: It would be convenient to show the equivalence of all 5 statements


Could S[OUF] get a tag cloud similar to the one on The Climate Deal StackExchange?

So I really like the tag cloud on Climate Deal. Is there anyway we could get something similar to this on StackOverflow? I don't necessarily mean that we should replace the interesting/ignored tags with this but something like this on the front page would be nice.


I want a compensation equal to the value of my time.   I was told by a native speaker that this is the correct expression (instead of saying equal to my time value), but I don't know why.  Could someone explain and give other examples?


Stop Google automatically to copy favorites from one computer to another

I have some favorite sites added to favorites in google Chrome.  Now with my surprise I saw that these links  also show up in my work computer!!!  No clue how they came here!!!  I think Google somehow transferred them( I logged to my gmail in theoffice). This is not good as I do not want my office mates to see my personal links  Question: is this a known issue and if yes how to prevent it.


What is the current state of apple device (iPhone, iPod, etc.) support?

What ubuntu applications provide support? (guides, how to's, status) Also, specifically, details on support for syncing music to iPhone's and iPod's with the latest OS version:   Can you sync music to apple devices using >iOS4? (iPhone & iPod) What applications allow you to do this and how? (guides, how to's, status)    What has already been established is:   Apple does not support Linux and has no plans to.  provides some support, however it currently does not support music/video synchronization with devices >iOS4. Go to  and scroll to the section titled "" to see if your device version is supported.


I mean like :    They aren't linked to any account.


How to interpret the results from a binary model done in R?

This is a binary model that my colleagues and I developed that regards a connection between the distance (dependent variable) and overall satisfaction with public transport (covariate). I don't know how to interpret the results shown below.


Dilemma: Present Perfect Or Perfect Continuous?

I am very much confused with two aspects which are perfect aspect and present perfect continuous.  From the sentences below I am not sure what to use..  Perfect aspect:     I've lived here for ten years.   Perfect Continuous aspect:     I've been living here for ten years.


When to use "none" as singular or plural?

Can someone please tell me which is most appropriate?  (a) "At this time, none of the parties is planning to file a motion"; or   (b) "At this time, none of the parties are planning to file a motion."


Classification of groups with $2021$ elements

We are in the year $2021$, why not finding all groups of order $2021$? First, note that $2021=43 \cdot 47$, its decomposition in primes (useful to keep in mind). Then, applying the Euler's totient function: $\varphi(2021)=42 \cdot 46$, so $2021$ and $\varphi(2021)$ are coprime. Thus, $2021$ is a . We can conclude that there is only one group of order $2021$, up to isomorphism, $\mathbb{Z}_{2021}$. I want to find out other proofs that any group of order $2021$ is cyclic, besides this simple observation. Any ideas are welcome, but I'm more interested in proofs that do not use powerful theorems like Sylow, with internal direct product (as in ). I need something that can be understood by a high school student (he only knows the basics), if possible. I was thinking of another approach: it is enough to prove that any group of order $2021$ is abelian, then, using the formula for the number of abelian finite groups (), we get: $a(2021)=p(1)^2=1$, so this group must be cyclic. We reach the same result if we notice that $2021$ is , but again, we discuss only the abelian case. P.S. Do not understand me wrong, I know about Sylow theorems, but I just can't explain in this manner to a boy that has just learned about groups.


Variance is given as: $\operatorname{Var}(X) = \mathbb{E}[(X-\mathbb{E}(X))^2]$.  Is there an intuition behind this and can you find this formula starting from the second generating moment ?


Which Stack Exchange site to post an OS installation problem

I am curious as to what SE I should post this question on:  I am trying to reformat my Alienware M15x laptop which has a aftermarket graphics card installed (NVidea Geforce 675m). No matter what OS I try to install, as soon as I get past the first part of the installation and it tries to actually start up the OS, the screen is white and I cannot do anything. How can I fix this? I have an exam tomorrow and need this fixed before then!


Change in Kinetic Energy in two different reference frames (one of them non-inertial)

Let's say an object of mass 10 kg is fired from a cart of mass 90 kg. The object and the cart, of total mass 100 kg were initially moving together with a speed of 10 m/s. Then, the object is fired by some means from the cart such that it's velocity increases to 15 m/s (w.r.t ground), in the same direction. Finding the change in kinetic energy from ground and cart frame yields different values. Calculating the kinetic energy difference in ground and cart frame of reference, From Ground frame: $$m_1  = 10 kg, \ m_2 = 90 kg,\  u_1 = 10 m/s , \ u_2 = 10 m/s, v_1 = 15 m/s, v_2 = ?$$ Applying momentum conservation, $$ v_2 = 85/9 \ \ m/s$$ $$  \bigtriangleup KE = 1/2 ( \ 10 \times 15^2 + 90 \times (85/9)^2 - 100 \times 10^2 )$$ $$ = 1250/9 J \ = 138.888 J $$ From Cart frame (non-inertial): $$m_1  = 10 kg, \ m_2 = 90 kg,\  u_1 = 10 m/s , \ u_2 = 0 m/s, v_1 = (15 - 85/9) m/s = 50/9 m/s, v_2 = 0 m/s$$ $$ \bigtriangleup KE = 1/2 \times 10 \times (50/9)^2 $$ $$ = 154.321 J $$ There is a discrepancy of change in kinetic energy calculated from inertial and non-inertial frame. If one takes an inertial frame going with 10 m/s in the direction of the cart, the calculation from the frame will same change in kinetic energy as that given from the ground frame. What correction does the calculation from non-inertial frame need? (Note: This problem deals with actual calculation of kinetic energy changes in a non-inertial frame. Here the pseudo-force is not constant/tractable, only impulse is.) The question in  is about calculating KE in different inertial frames. That question was resolved by saying that kinetic energy may be different for different inertial frames, but work energy theorem (related to change in kinetic energy) still holds. In this question,  We have gone a step ahead and actually applied the work-energy theorem, rather than just calculate kinetic energy from different frames. The query here is about how to apply the work energy theorem for a non-inertial frame, to account for the change in kinetic energy.


Email as username during signup/login? Your experience?

I currently have a signup form that has a username and an optional email field.  I want to make this form appear simpler by getting rid of a field. What has been your users' experience with only using email for username? (Email would then become non-optional). Personally, I don't like this because my email is longer to type than my username. But, I am seeing this more and more. Is it the future?


Should I use plastic/insulating washers when attaching a motherboard to the case?

I'm screwing in a motherboard, around the screw holes in the motherboard there is a white painted circle and inside that circle are what look like eight pieces of solder.   Do I need to put plastic/paper washers between the screws and the motherboard? Each screw goes into a little metal stand which is clipped onto the metallic case. If I don't use plastic washers will there be an issue with static?


jQuery - binding to elements that are not yet created

[Not duplicate] - I checked the  question, and its answer is actually the start point of my question. I start off with $parent.on('click', '.specificChild' ... etc.). I already know that (see it for wrapper1). The first part of my question has nothing to do with the referenced SO question.    Within a parent element, I want to create a child element and then grand-child elements, and have a click event on a grand-child element.  Is it possible to pre-define child element and also pre-define the click event, even before the child/grand-child elements are created ?    // wrapper1 related -- it works var $wrapper1 = $('.wrapper1'); var $number1 = $wrapper1.find('.number'); $wrapper1.on('click', '.incrementButton', function () {     var currentVal = parseInt($number1.html(), 10);     $number1.html(currentVal + 1); });   // wrapper2 related - doesn't work // define the elements upfront var $wrapper2 = $('.wrapper2'); var $foundation = $wrapper2.find('.foundation'); var $number2 = $wrapper2.find('.number'); $wrapper2.on('click', '.incrementButton', function () {     var currentVal = parseInt($number2.html(), 10);     $number2.html(currentVal + 1); });   $wrapper2.html('

'); var htmlContent = '' +         '
' +         '
1
' +         '
+ 1
' +         '
'; $foundation.html(htmlContent); .wrapper1, .wrapper2 {     background-color: #E8EAF6;     padding: 1em;     width: 12em;;     margin: 1em; } .foundation {     background-color: #9FA8DA;     padding: 1em; } .arithmetic {     background-color: #5C6BC0;     padding: 1em;     overflow: hidden; } .number {     width: 1.5em;     height: 1.5em;     text-align: center;     line-height: 1.5;     background-color: white;     float: left;     color: #3949AB;     margin-right: 1em; } .incrementButton {     overflow: hidden;     height: 1.5em;     line-height: 1.5;     text-align: center;     background-color: #3949AB;     border: 1px solid white;     color: #E8EAF6; } .incrementButton:hover {     cursor: pointer;     background-color: #283593; }

1

+ 1

     More specifically, the question is:   How can I define $foundation before its creation ? i.e. before this line $wrapper2.html('

') ? How can I bind the click function to incrementButton within wrapper2, even before the creation of the incrementButton element ?


The Functional Equation $ ( x + y ) \big( f ( x ) - f ( y ) \big) = ( x - y ) f ( x + y ) $, need solution have answer

Find all functions $ f: \mathbb R \to \mathbb R $ such that for all reals $ x $ and $ y $, $$ ( x + y ) \big( f ( x ) - f ( y ) \big) = ( x - y ) f ( x + y ) \text . $$ I actually got the answer by guessing and checking, $ f ( x ) = a x ^ 2 + b x $, but I want to see the solution. My friend suggested surjectivity but I don't see how to continue. $ f ( x ) = f \left( \frac x { f ( x ) ^ 2 } \right) $; this is what I just got. The answer is correct, just need a solution. Thanks!


Is drawing multiple cards an atomic action?

Is drawing multiple cards an atomic action, or do effects triggered by drawing a card trigger for each card drawn instead?  Consider , which reads:     Whenever a player draws a card, Spiteful Visions deals 1 damage to that player.   If a player were to be compelled to draw more than one card, would that player be dealt the damage all at once, or one at a time? For example, how many times would  need to be activated to prevent all damage?  Furthermore, if there exist additional effects that are triggered by damage dealt in this way, are such effects resolved together atomically or is each resultant effect resolved individually?    How about tutors, or other cards not using the word 'draw', eg:      If you would draw a card, look at the top three cards of your library instead. Put one of those cards into your hand and the rest on the bottom of your library in any order.


How do I search the question text of my questions?

What is the syntax to use for searching the text of the questions that I've posted? i.e. Limit the search to just the questions that I've asked and just the Title/Subject/Question part of it....


Display filters in the "Hot questions" sidebar

I have a  that consist of the sites I'm interested in. It'd be cool if I didn't have to go to this page to see the filter, as most of the cool network questions I see are just because I glanced at the side. Any thoughts?


Proof by Induction for inequality, $\sum_{k=1}^nk^{-2}\lt2-(1/n)$

Let $n$ be a positive natural number, $n\ge 2$. Then $\displaystyle\sum_{k=1}^n \frac{1}{k^2} \lt 2 - \frac{1}{n}.$   The basis step was easy but could someone give me a hint in the right direction as to how to do the induction step?  I tried this:  $\displaystyle\sum_{k=1}^k \frac{1}{k^2} + \frac{1}{(k + 1)^2} \lt 2 - \frac{1}{k + 1}$  But it's getting me nowhere or I am doing something wrong. I am no expert so a clear explanation would be appreciated. Thanks.


Graph Theory: Tree has at least 2 vertices of degree 1

Prove that every nontrivial tree has at least 2 vertices of degree 1 by showing that the origin and terminus of a longest path in a nontrivial tree both have degree 1.  Ok, so this statement is pretty obviously true, but I am having trouble proving it using graph theory language. What I have is that the origin and terminus must have degree 1 because if they had degree >=2, then they would not be the said origin and terminus but the vertex they are connected to would then be the origin or terminus. If that point has degree greater than or equal to 2 then the vertex that is connected to would be the origin or terminus and so on. Can someone help me put this into graph theory language, please.  Thanks


Trying to upgrade from 12.10 to 14.04 and not having any luck...404 error occurs

This is a long winded question so bear with me!   I am trying to upgrade my 12.10 Quental Ubuntu to the 14.04 version. This has led to a problem within my system not being able to update. For information, this build of Ubuntu does a dual-boot with my Windows 7 package.  I initially tried to find the update manager on my system which has dissapeared. I then searched on Google and came to this page:    When typing in sudo apt-get update, it hits 18% and says, "Waiting for headers."  A couple of errors occur. The last two lines of the error log state:  "W: Failed to fetch   404  Not Found [IP: 91.189.91.13 80]  E: Some index files failed to download. They have been ignored, or old ones used instead."  I have checked online and found this page in answer to this problem:    During the main answer it suggests to type these three lines into the command line:  sudo add-apt-repository ppa:fossfreedom/packagefixes  sudo apt-get update  sudo apt-get install banish404  After I run sudo banish404, I still get the same error message.  My final aim is to just update Ubuntu to 14.04 in my Dual boot machine. My fear is if I download an ISO and try to run it from booting my machine, it will either wipe everything, (and there is a lot of stuff within my Windows account!) or provide a triple boot scenario whereby I choose between Windows, Ubuntu 12.10 and Ubuntu 14.04.  My experience is very limited with Linux and the command line, (did a short course a couple of years ago with my uni.) Although it has increased a lot in the last two days, (I have created to a Kali Linux virtual machine and a SIFT forensics virtual machine, both in virtual box on my windows account.)  Any help?


Travelling to the UK on an accompanied visa, unaccompanied

I am a Europen Union member and I applied for my brother to accompany me to the UK. He was granted an a visa to accompany to the UK and before the UK left the EU, I applied for settlement. I now live in the UK, can my brother come to the UK alone without me having to travelling from where he was to the UK? He is not a minor.


Why do some selected objects have a yellow outline and others have an orange outline?

Whenever I select an object in Blender it will be outlined in orange or yellow. How is it decided which colour will be used for the outline, and what does each one mean?


I've completed the Blood on Ice quest, I just don't know what else I have to do. I'm not too far into the main quest line so I'm worried about siding with the stormcloaks and how that might affect the main quest. Do I have to tell Ulfric that I came to Windhelm to fight the imperials to get on his side and to be able to buy the house?


The connection of Fibonacci sequence with matrices with Euclidean algorithm?

I prove that: $$ \begin{pmatrix} 1 & 1\\ 1 & 0 \end{pmatrix}^n =  \begin{pmatrix} F_{n+1} & F_n\\ F_{n} & F_{n-1} \end{pmatrix}$$ I succeeded to prove that by induction, now my question is how it's related with the Euclidean algorithm? Is there a connection?


Does Hisoka like Gon sexually or as a toy to play with?

Hisoka doesn't want Gon to die, but he still fights him like he wants to fight to the death. What's up with that? It's kinda like he's playing with him, but I'm not sure, because they do have a lot of sexual tension, even when they are fighting. Hisoka will laugh almost hysterically when he and Gon are in close proximity. He's always staring at Gon, like he's the most important thing. Does Hisoka like Gon sexually, or does he merely see him as a toy to play with?


"They're using a cell phone" vs. "They're using cell phones"

The usage of singular and plural has always been confusing for me.   I often see sentences like these         People are using cell phones.   People are using a cell phone.      Does the first sentence mean everyone has a phone and they are all using their own?  Does the second sentence mean they are sharing one cell phone?   If I see a group of people holding a cell phone in their hand(s), <- even this is confusing for me, should I use the first sentence then?   Another example: you see two men, and both of them are carrying a bag. Which sentence should I say/use?        They are carrying backpacks          They are carrying a backpack      Could you please make it clear for me?


Group-benefitting ammo overrides in Mass Effect 3

If a group member has, say, Armor-Piercing Ammo skill set to benefit the whole group at 50%, does this mean that it will override my own Armor-Piercing Ammo skill that is leveled to maximum and that I have to re-enable it, same as any other team member who wants to use Warp Ammo or Incendiary Ammo?  Or does the game know that my character's AP Ammo skill is superior to the group members and just enables that? The GUI isn't very helpful in that regard.


Creating layout with include toolbar layout and one fragment

Design is simple but dont know what causing the error.   <?xml version="1.0" encoding="utf-8"?>     <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"         xmlns:app="http://schemas.android.com/apk/res-auto"         xmlns:tools="http://schemas.android.com/tools"         android:orientation="vertical"         android:layout_width="match_parent"         android:layout_height="match_parent">              <LinearLayout                 android:layout_width="match_parent"                 android:layout_height="wrap_content"                 android:orientation="vertical"                 android:layout_gravity="top">                  <include                     android:id="@+id/toolbar"                     layout="@layout/toolbar" />             </LinearLayout>              <include layout="@layout/activity_main"/>            <fragment             android:id="@+id/fragmented1"             android:layout_width="match_parent"             android:layout_height="match_parent"             android:layout_gravity="top"             app:layout="@layout/search_box"             tools:layout="@layout/search_box" />      </LinearLayout>      public class MainActivity extends AppCompatActivity {          RelativeLayout search;         TextView textView;         ImageView close_btn,filter_cars;         Intent intent;          @Override         protected void onCreate(Bundle savedInstanceState) {             super.onCreate(savedInstanceState);             setContentView(R.layout.main);             search=(RelativeLayout) findViewById(R.id.searchingcars);             textView=(TextView) findViewById(R.id.searchcars1);             close_btn=(ImageView) findViewById(R.id.search_close_btn);     //        filter_cars=(ImageView) findViewById(R.id.filter);      /*       filter_cars.setOnClickListener(new View.OnClickListener() {                 @Override                 public void onClick(View view) {                     intent=new Intent(this,Filtercars.java);                     startActivity(intent);                 }             });*/             close_btn.setOnClickListener(new View.OnClickListener() {                 @Override                 public void onClick(View view) {                     search.setVisibility(View.GONE);                 }             });             textView.setOnClickListener(new View.OnClickListener() {                 @Override                 public void onClick(View view) {                      search.setVisibility(View.VISIBLE);                 }             });         }     }   Error : Unable to start activity ComponentInfo{in.mega.sliderdrawer/in.mega.sliderdrawer.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ImageView.setOnClickListener(android.view.View$OnClickListener)' on a null object reference


I have a Python program and I would like to generate an UML diagram from from. Which programs can do that?  edit: I would like to have an option of editing the generated diagram


I have been riding my hard tail on the road for the last 3 years on some knobbly 26 x 2.1 tyres. After just starting a new job and with the need to commute further I am considering purchasing some slicks, however I do not know how best to decide on which tyre to choose. What width should I be going down to and what kind of tread?  I like the look of these  but they also come in two widths, is it the thinner the better?


Removal of the Lock/Switch Account menu in gnome desktop Ubuntu 14.04 LTS

We are looking for a way to remove the list of previously logged on users from the shutdown menu in Ubuntu 14.04 LTS running Gnome Classic Desktop. We have lots of computers in a lab environment where we do not want other users to know login names of previous users that have used that particular machine.  Any help on removing this list would be appreciated.  Note, this is after a user logs into Ubuntu 14.04 LTS and when you click on the little gear icon in the upper right-hand corner to shutdown|Logout|Suspend|Restart it also displays Lock/Switch Account along with a list of user names.  Thank you!


How do target selectors like @a and @p work in multiplayer?

I'm building on a custom map that should work for both singleplayer and multiplayer.  I'm wondering how target selectors like @a and @p work in multiplayer. I know @a targets all players and @p targets the nearest player, but if i do:  /execute if entity @a[scores={kills=10..}] run say HI   ...does it mean all players must have at least 10 kills or does it mean it checks all players and if one of them have 10 kills it says HI?


Why does the trace show up in such expressions?

I've been studying different scattering processes (from Mandl & Shaw QFT's book, chapter 8) and there's always a purely-mathematical common step I do not understand: the showing-up of the trace. Let me give two specific examples.  $$A_{(l) \alpha \beta}=\sum_{s_1} \sum_{s_2} \Big[ \bar u_{s_2} (\vec p_2') \gamma_{\alpha} v_{s_1} (\vec p_1'))(\bar v_{s_1}(\vec p_1')\gamma_{\beta} u_{s_2} (\vec p_2'))\Big]_{(l)}=Tr\Big[\frac{\not{\!p_2'}+m_l}{2m_l} \gamma_{\alpha} \frac{\not{\!p_1'}-m_l}{2m_l}\gamma_{\beta}\Big] \ \ \ \ (1)$$  $$X= \frac 1 2 \Lambda_{\delta \alpha}^+ (\vec p') \Gamma _{\alpha \beta} \Lambda_{\beta \gamma}^+ (\vec p) \tilde \Gamma _{\gamma \delta}=\frac 1 2 Tr \Big[\Lambda^+ (\vec p') \Gamma \Lambda^+ (\vec p) \tilde \Gamma \Big] \ \ \ \ (2)$$  Where:   $\not{\!A} := \gamma^{\alpha} A_{\alpha}$ $\Gamma$ is a $4 \times 4$ matrix $\tilde \Gamma := \gamma^0 \Gamma^{\dagger} \gamma^0$ $u, v$ are the Dirac Spinors (which are $4 \times 1$ matrices) The Dirac-$\gamma$-matrices are $4 \times 4$ matrices and the adjoint is defined as $\bar w := w^{\dagger}\gamma^{0}$ $\Lambda^+$ is the positive energy projection operator defined as  $$\Lambda_{\alpha \beta}^+ (\vec p) := \Big( \frac{ \not{\!p}+m}{2m} \Big)_{\alpha \beta}$$ $\Lambda^+$ has the following property   $$\Lambda_{\alpha \beta}^+ (\vec p) = \sum_{r=1}^2 u_{r \alpha} (\vec p) \bar u_{r \beta} (\vec p)$$  But what I do not understand is why does the Trace show up in $(1)$, $(2)$   Any help is appreciated.  EDIT  Let's write out the spinor indices explicitly for $(1)$  $$A_l = \Big(\sum_{s_1} u_{s_1 \color{red}{\delta}}(\vec p_2') \bar u_{s_1 \color{blue}{\alpha}}(\vec p_2')\Big) \gamma_{\color{blue}{\alpha}\color{green}{\nu}}\Big(\sum_{s_2}v_{s_2 \color{green}{\nu}}(\vec p_1') \bar v_{s_2 \color{gray}{\beta}}(\vec p_1')\Big)\gamma_{\color{gray}{\beta}\color{red}{\delta}} \ \ \ \ (3)$$  We know the following properties  $$\Lambda^+_{\color{red}{\delta}\color{blue}{\alpha}}(\vec p_2')= \sum_{s_1} u_{s_1 \color{red}{\delta}}(\vec p_2') \bar u_{s_1 \color{blue}{\alpha}}(\vec p_2')=\Big(\frac{\not{\!p_2'}+m_l}{2m_l}\Big)_{\color{red}{\delta}\color{blue}{\alpha}} $$  $$\Lambda^-_{\color{green}{\nu}\color{gray}{\beta}}(\vec p_1')= -\sum_{s_2}v_{s_2 \color{green}{\nu}}(\vec p_1') \bar v_{s_2 \color{gray}{\beta}}(\vec p_1')=-\Big(\frac{\not{\!p_1'}-m_l}{2m_l}\Big)_{\color{green}{\nu}\color{gray}{\beta}}$$  Thus we get  $$A_l = \Lambda^+_{\color{red}{\delta}\color{blue}{\alpha}}(\vec p_2')\gamma_{\color{blue}{\alpha}\color{green}{\nu}}\Lambda^-_{\color{green}{\nu}\color{gray}{\beta}}(\vec p_1')\gamma_{\color{gray}{\beta}\color{red}{\delta}}=-\operatorname{Tr}\Big[\frac{\not{\!p_2'}+m_l}{2m_l}\gamma_{\alpha}\frac{\not{\!p_1'}-m_l}{2m_l}\gamma_{\beta}\Big]$$  Now I have two questions:  1) Why are we allowed to manipulate $\sum_{s_1} \sum_{s_2} \Big[ \bar u_{s_2} (\vec p_2') \gamma_{\alpha} v_{s_1} (\vec p_1'))(\bar v_{s_1}(\vec p_1')\gamma_{\beta} u_{s_2} (\vec p_2'))\Big]_{(l)}$ in such a way to get $(3)$? What I mean is that I do not see what mathematical properties allow us to do so.  2) I get a negative sign. I guess it gets cancelled out due to an antysymmetric swap of certein indices, but what pair specifically?  Thank you :)


How do I turn a full color design, into a 1-color design?

I was asked to design a piece of junk-mail advertising. It has to be one color. Here are links of how it should look:      What I want to know is, how do you get your design like that?   It's like everything was full color and changed to black and white.... well in this case to blue and white.  Is there a specific way to design like that. Or can you design in full color, and the printers will print it only in one color?


How to organize my papers and notes from the beginning of my PhD?

I'm a first year PhD student.   I'm in my first stage (doing a literature review) but I face problem in organizing the papers I read and the notes I take for all papers. Should I put all that in one MS Word file for example, or different MS word files, or maybe use a different software?  I don't want to come after month from now and get confused about the way I organize my papers and notes in.   So, any helpful ideas?


MySQL: Count all duplicates and update additional column with acs numbers relative to the duplicated values


Prove $\sin x$ is uniformly continuous on $\mathbb R$

How do I prove $\sin x$ is uniformly continuous on $\mathbb R$ with delta and epsilon?   I proved geometrically that $\sin x<x$ and thus, $$|f(x_1)-f(x_2)|=|\sin x_1 - \sin x_2|\le|\sin x_1|+|\sin x_2|<|x_1|+|x_2|$$   But this doesn't help me much finding a delta...   Thanks for any help!  P.S. I'm only at the beginning of calculus so I can't use many theorems and derivation  (because they haven't been regorously proven).


Does Electrostatic potential energy bend Space-time?

Okay, there are various questions.  First, "matter and energy bends space-time" does this mean any form of energy can bend space-time?  Does theory of relativity assume that there is no other form of energy other than mass energy (includes kinetic energy) and light energy?  And is it true? I mean, is every form of energy in basic form is mass energy (includes kinetic energy) or light energy? For example, I think that electrostatic potential energy is virtual potential energy caused due to exchange of bosons, which basically is mass energy.  So, Does electrostatic potential or magnetic potential energy bend space-time? Can field theory and relativity co-exist?


"cd" command in git bash script not working

I am relatively new to Git Bash.  Given below is the script that I am trying to execute. I saved the given below 3 lines in a file sshExec and tried running it in Git Bash. The first two line ran as expected but 3rd line didn't run. There is no error or warning as well. So there was no directory change as I wished my script to do.   Why is it that "cd anyPath" is not working in script?    eval "$(ssh-agent)" ssh-add C:\\Users\\xyz\\.ssh\\id_rsa cd D:/Repositories/RELEASE_2017_BugFixing/deltagen_teamlogic


Posts per Page on custom Taxonomy Template

I'd like to show 20 posts on my custom tax template, using this filter:  function customize_customtaxonomy_archive_display ( $query ) {     if ( ( $query->is_main_query()) && ( is_tax() ) ){         $query->set( 'posts_per_page', '20' );         $query->set( 'number_posts', '20' );         $query->set( 'orderby', 'rand' );         return;      } }  //Hook the function  add_action( 'pre_get_posts', 'customize_customtaxonomy_archive_display' );   If I set it to 2, two posts are shown. If I set it to 20, 12 posts are shown. There are never more than 12 posts displayed, although 34 are published.  What could be the issue?


Unable to start VMWare Workstation after upgrade to 13.04

After upgrading to 13.04 I am unable to start VMWorkstation. I get the following message:     Before you can run VMware, several modules must be compiled and loaded   into the running kernel.      Kernel Headers 3.8.0-19-generic      Kernel headers for version 3.8.0-19-generic were not found. If you   have installed them in a non-default path you can specify the path   below.   Does anyone have any idea what to do next?  Ubuntu 13.04 64bit  If I direct the path to:  /usr/src/linux-headers-3.8.0-19-generic   I get the following message:     C header files matching your running kernel were not found.   Thanks  Additional:  As suggested I run this in terminal:  cd /lib/modules/$(uname -r)/build/include/linux   sudo ln -s ../generated/utsrelease.h   sudo ln -s ../generated/autoconf.h   sudo ln -s ../generated/uapi/linux/version.h   However, now I get the following:      Before you can run VMware, several modules must be compiled and loaded into the kernel    CANCEL / INSTALL   I INSTALL, the window closes and nothing happens.... Any ideas?  ADDITIONAL:  I installed this:  sudo apt-get install open-vm-tools open-vm-tools-dev open-vm-dkms open-vm-toolbox open-vm-tools-dev   And it all launched...  Many thanks for the suggestions and help... This is what I love about Ubuntu... it has a great helpful community... !   Note: Also found this which may help others too:   ADDITIONAL ERROR:  Could not open /dev/vmmon: Is a directory. Please make sure that the kernel module `vmmon' is loaded.  Failed to initialize monitor device.  Monitor settings all greyed out  RESOLUTION:   Re-installation of Nvidia Drivers


Any way to install python 3.4 on Ubuntu 18.04?

I have some project that needs python 3.4 but since I am on Ubuntu 18.04 I have python 3.6 installed. If I try to setup the project on 3.6 I get compatibility issues. Please guide how do I install python 3.4 alongside 3.6. And is there a way to make virtualenv use python 3.4 to setup environments.


Is the correct phrase "Doing it healthy and safe" or Doing it healthy and safely?"

I'm working on a tshirt and want to use the phrase      "Doing it healthy and safe."    Or should it be      "Doing it healthy and safely."


$P(X_1 < \min(X_i,\ldots, X_n))$ across different normal random variables

I have a set of mutually independent normal distributions $X_1$ to $X_5$ (with means and standard deviations) which represent finishing times for swimmers over a certain distance. The actual data is as follows:  $$X_1(60, 3.0)$$ $$X_2(61, 1.0)$$ $$X_3(58, 2.3)$$ $$X_4(63, 2.4)$$ $$X_5(61, 1.7)$$ So swimmer 1 ($X_1$) has a mean finishing time of 60 seconds with a standard deviation of 3.0 seconds.  Question 1: What is the probability of an event where $X_i$ finishes first. e.g.  $$P(X_1 \lt X_i, i=2,\ldots,n)$$  Question 2: If I calculate this for all swimmers, can I simply order the results to determine the most probable finishing order?  This is not homework.  Based on the answers to this , I have tried to solve this problem based on the first answer. i.e.  $$\Pr(X_1 \le X_i, i=2,\ldots,n) = \int_{-\infty}^{\infty} \phi_1(t) [1 - \Phi_2(t)]\cdots[1 - \Phi_n(t)]dt$$  Where  $\phi_i$ is the PDF of $X_i$ and $\Phi_i$ is its CDF.  Based on this formula, the results I obtained were:  $$\Pr(X_1 \le X_i, i=2\ldots5) = 0.259653$$ $$\Pr(X_2 \le X_i, i=1,3\ldots5) = 0.214375$$ $$\Pr(X_3 \le X_i, i=1\ldots2, 4\ldots5) = 0.611999$$ $$\Pr(X_4 \le X_i, i=1\ldots3, 5) = 0.0263479$$ $$\Pr(X_5 \le X_i, i=1\ldots4) = 0.0697597$$ However, the probabilities add to 1.182135 when they should add to 1.0. I’m not sure if the formula is incorrect or my implementation of the integral (I used Excel and the trapezoidal method).  I also attempted to solve the problem using Dillip’s method (from the above mentioned question) as follows:  \begin{align*} P(X_1 < \max X_i) &=  P\{(X_1 < X_2) \cup \cdots \cup (X_1 < X_n)\\ &\leq \sum_{i=2}^n P(X_1 < X_i)\\ &= \sum_{i=2}^n Q\left(\frac{\mu_1 - \mu_i}{\sqrt{\sigma_1^2 + \sigma_i^2}}\right) \end{align*}  However, the probability results were much greater than 1 in most cases so abandoned this approach. By the way, what exactly does $\max X_i$ mean?  Any assistance in calculating the probability would be appreciated.


Where can I travel using an Italian-issued refugee residence permit?

I am a Pakistani national and I have refugee status in Italy and an Italian-issued refugee residence permit which is valid for 5 years. I have also been issued a refugee passport.   Where am I able to travel using these documents, and without having to obtain a visa. Am I limited to Europe, or can I go to non-European countries?


Users are calling me a plagiarist. What do I do?

Other users have been leaving me angry and hostile comments accusing me of plagiarism and saying that I'm a liar and I should stop stealing answers. But I have only been copying content from other sites, not taking answers from other users.   I don't understand what is wrong here. Shouldn't we be focused on building all the content and knowledge in a single place, much like Wikipedia does?  What does it matter that I copy and paste content I've found elsewhere so long as the question gets an answer?


Ubuntu installation on i5-2430m possible?

I want to install Ubuntu 13.10 in my VirtualBox.  When I try it with the 64-bit version, I get this error:  This kernel requires an x86-64 CPU, but only detected an i686 CPU   Ii have an Intel core i5-2430m. as far as I know, it's an 64-bit CPU, and I tried it with the 32-bit version and got this error:  This kernel requires the following features not present on the CPU: PAE   So what should I do now to make it run?  Thank you


I have a point layer for the cold air flow in specific region. I would like to simplify all the single points to a polygon shape as to be able to join the data with other spatial data. My way is pretty complicated (buffer the points e.g.400m, dissolve, simplify) because I have to extract the single values (orange, blue, light blue) and then do it with all these single values separately. Afterwards there is the need to create differences in order to avoid doubles. I wonder if somebody knows a more convenient way.


how to design three button if in same page?

I have one page there displaying three different action buttons. As per UX guidelines how to display or style this button and more focus able.   If can be three action level :    Primary Secondary Third


How do I mount an LVM LUKS encrypted drive on Ubuntu 20.04 without making it unbootable?

I have just added a new NVME drive to my system, I want to use it as my primary boot drive and I wanted to take the opportunity to do a cleanup of my OS. To do that I installed a clean copy of Ubuntu 20.04 on the NVME drive with LVM and LUKS encryption. The new OS boots up fine, but now I want to copy my files over from my other drive; which was also an encrypted ssd with Ubuntu 20.04 installed. My problem is that both drives are picked up with the same LV Path; /dev/vgubuntu/root and the same VG Name vgubuntu. I know that I could use sudo vgrename aaaaaa-aaaa-aaaa-aaaa-aaaa-aaaa-aaaaaa old-ubuntu to change the VG name of the old volume and access it, but ideally I'd like to be able to boot to both until I'm happy with the setup on the new drive. Reading other related questions suggests that if I rename the old volume with vgrename then I won't be able to boot into it. Running sudo lvdisplay outputs this (trimmed) and you can see that the new system root and swap are available while the old system is unavailable:   --- Logical volume ---   LV Path                /dev/vgubuntu/root   LV Name                root   VG Name                vgubuntu   LV UUID                aaaaaa-aaaa-aaaa-aaaa-aaaa-aaaa-aaaaaa     LV Status              NOT available   ...       --- Logical volume ---   LV Path                /dev/vgubuntu/swap_1   LV Name                swap_1   VG Name                vgubuntu   LV UUID                bbbbbb-bbbb-bbbb-bbbb-bbbb-bbbb-bbbbbb   LV Status              NOT available   ...       --- Logical volume ---   LV Path                /dev/vgubuntu/root   LV Name                root   VG Name                vgubuntu   LV UUID                cccccc-cccc-cccc-cccc-cccc-cccc-cccccc   LV Status              available   ...       --- Logical volume ---   LV Path                /dev/vgubuntu/swap_1   LV Name                swap_1   VG Name                vgubuntu   LV UUID                dddddd-dddd-dddd-dddd-dddd-dddd-dddddd   LV Status              available   ...   On other distros this  might work. But unfortunately /dev/SysVolGroup doesn't exist on Ubuntu 20.04. How can I mount my old LUKS encrypted volume on Ubuntu without making it unbootable?


$T$ be minimal sufficient statistics. If $T = H(U)$ where $U$ has the same dimension as that of $T$, is $U$ minimal sufficient?

Suppose $T$ is minimal sufficient statistics for a family of distribution. If $T = H(U)$ where $U$ has the same dimension as that of $T$, then does it imply that $U$ is also minimal sufficient?  I think the answer to this question should be NO. I will give one example for this... Consider for a single observation $X$ for the family $\{f_0(x), f_0(x) \;| \;x\in \mathbb{R}\}$ where $f_0(x) = \frac{1}{\sqrt{2\pi}}\exp(-\frac{x^2}2)$ and $f_1(x) = \frac{1}{\pi(1+x^2)}$ Then, we know that $\frac{f_1(x)}{f_0(x)} = \frac{\pi(1+x^2)\exp(-x^2/2)}{\sqrt{2\pi}} = T(x)$ is minimal sufficient for this family. Let $U = x^2$, then clearly $T$ is a function of $U$, however, $U$ is not a function of $T$. Hence, $U$ has the same dimension as $T$, but not minimal sufficent


I have two arrays like this:  A=(vol-175a3b54 vol-382c477b vol-8c027acf vol-93d6fed0 vol-71600106 vol-79f7970e vol-e3d6a894 vol-d9d6a8ae vol-8dbbc2fa vol-98c2bbef vol-ae7ed9e3 vol-5540e618 vol-9e3bbed3 vol-993bbed4 vol-a83bbee5 vol-ff52deb2) B=(vol-175a3b54 vol-e38d0c94 vol-2a19386a vol-b846c5cf vol-98c2bbef vol-7320102b vol-8f6226cc vol-27991850 vol-71600106 vol-615e1222)   The arrays are not sorted and might possibly even contain duplicated elements.   I would like to make the intersection of these two arrays and store the elements in another array. How would I do that? Also, how would I get the list of elements that appear in B and are not available in A?


Evaluating the integral $\int_0^\infty \frac{\sin x} x \,\mathrm dx = \frac \pi 2$?

A famous exercise which one encounters while doing Complex Analysis (Residue theory) is to prove that the given integral: $$\int\limits_0^\infty \frac{\sin x} x \,\mathrm  dx = \frac \pi 2$$ Well, can anyone prove this without using Residue theory?  I actually thought of using the series representation of $\sin x$: $$\int\limits_0^\infty \frac{\sin x} x \, dx = \lim\limits_{n \to \infty} \int\limits_0^n \frac{1}{t} \left( t - \frac{t^3}{3!} + \frac{t^5}{5!} + \cdots \right) \,\mathrm  dt$$ but I don't see how $\pi$ comes here, since we need the answer to be equal to $\dfrac{\pi}{2}$.


I am relatively new to Java and I found user input to be more tricky than in C++. I wanted to make an AI Tic-Tac-Toe opponent as a fun mini project but I am having a couple problems. Here is my code:  enter code here import java.util.Scanner;  public class Game {     public static void main(String[] args) {         Scanner input = new Scanner(System.in);         System.out.println("Hello, want to play a game? (Yes/No)");         String answer = input.nextLine();         if (answer == "Yes"){             System.out.println("Welcome to Riverita's TicTacToe.");             else if (answer == "No"){                 System.out.println("Have a good day!");             }         }     } }   The first problem is that on my else if statement I get the error "Syntax error on token "else", delete this token" but I don't know what is wrong with it. Also, it seems as though you cannot check that a variable is equal to a string because if I change String answer to int answer and I type in an integer, then the code will execute and my message will pop up. Is this a correct assumption?


In Drupal 7 we could edit the system table to set a module a version back to let the hook_update_n run again.  In Drupal 8 there is no system table.  Where can I find what version of the module is installed so I can change this and make sure the update hook is run again?  This is useful while developing hook_update_N() of my module so I can test this.


not working as writing 3rd and 4th level characters

I originally asked a question here:  but was asked to submit a new question including more info  I want to be able to type special characters such as ellipsis, en dash and em dash using the same key combinations as in osx (that is, alt+period for ellipsis, alt+hyphen for en dash, alt+shift+hyphen for em dash, etc.) Apparently, Right Alt is supposed to function this way natively. Both of my Alt keys work as normal Alt keys in keyboard shortcuts, but I'm not able to use them to create special characters.  My keyboard looks like this:     (with eject instead of power button). Ubuntu's original Norwegian (macbook) layout has a lot of errors ( | instead of ' etc.), so I use a custom layout file that I found on github: github.com/gulrotkake/Ubuntu-MacBook-Norwegian-keyboard I checked the file, and the 3rd and 4th level characters are included:  key <AB09>  { [    period,      colon, ellipsis,   periodcentered ] }; key <AB10>  { [     minus, underscore,       endash,       emdash ] };   I tried changing back to the original layout file (which I had stored as a backup), but I am still not able to produce any of the special characters.  I followed the advice of this post:  by going into org.gnome.desktop.input-sources and adding 'lv3:ralt_switch', 'misc:typo'. gsettings get org.gnome.desktop.input-sources xkb-options now outputs ['ctrl:swap_lwin_lctl', 'compose:rwin', 'lv3:ralt_switch', 'misc:typo']  This lets me write 3rd and 4th level characters with my Right Alt key, but they aren't mapped correctly (and I'm also no longer able to use the Right Alt key in my keyboard shortcuts). When I type alt+period I get » instead of ellipsis, alt+hyphen gives ellipsis instead of en dash, and so on.  I'm using Ubuntu 20.04 LTS  Edit: cat /etc/default/keyboard outputs:  BACKSPACE=guess XKBLAYOUT=no XKBVARIANT=mac   gsettings get org.gnome.desktop.input-sources sources outputs:  [('xkb', 'no+mac'), ('ibus', 'mozc-jp')]   I|ve tried using the custom keyboard layout from github as well as the default one. The behavior of the two keyboard layouts is the same: i normally cant write any special characters using Right Alt. Adding 'lv3:ralt_switch', I can write the characters but they are mapped incorrectly. Pressing the period key gives me  . : · ÷  and pressing the hyphhen key gives me - _  ̣ ˙ Adding 'lv3:ralt_switch', 'misc:typo' the mapping is different but still incorrect. pressing the period key gives me . : » > and pressing the hyphen key gives me - _ … ˙   Also, this might or might not be relevant, but before I switched to the github layout I tried to fix the wrong bindings on the default layout using sudo dpkg-reconfigure keyboard-configuration - choosing MacBook Pro international and norwegian. This made æ å ø and several other keys disappear. And this persisted on reboot. I fixed it by switching to the github layout. I|m unsure whether the Right Alt key functioned properly before doing this.


Pass id from account button to visualforce page

The new button in Contact related list on the Account page points to a VF page which serves as an extra step to create a new Contact (to require them to enter certain info).  Normally, when the new button is standard, AccountId is valued on the new Contact record.   How can I get that AccountId to my controller so I can set it on the new Contact record?


I'll try to be clear. I'd like to ask you if you know some books or chapters in textbooks which explaining the "meaning" of some physical phenomena or entities.   I may try to be more specific using an example to explain what i'm looking for. Let's take electrodynamics: we use both fields and potentials to describe the whole spectrum of electromagnetic phenomena. I have this doubt:    which concept is "more real" and fundamental: the field or the potential?  Are the potentials just a useful mathematical escamotage?    It may be banal but i don't know the answer. I read that in modern times the vector potential plays a central role in the theory and it is good to build the theory around it, why? "Just" less mathematical complication or a more physical insight? Maybe I never even thought about some interesting question about the fundamental quantities and therefore I'll never look for those answer.  As other example of what I mean I may say I'd like something in the style of the first chapter $1$ of the Feynman vol. $II$, the chapter 19 on the Principle of Least Action, or the chapter on electromagnetic mass in the same book.  Edit: it's not a duplicate. I didn't ask for an undergraduate electrodynamics course. I asked for a book different in the way it explains stuff and not just about EM, but about physics in general. I made the electrodynamical example to explain what I needed. That question thred that has been put here it's of no help


Can we decrypt in this order when the message is encrypted twice?

If we encrypt a message twice with symmetric key $k_1$ first and then $k_2$ like $E_{k2}\{E_{k1}\{m\}\}$ , ideally we should decrypt with $k_2$ first and then $k_1$ but is it possible to decrypt with $k_1$ and then with $k_2$ ?  Using any of the AES Modes preferably ?


How can i create this crease detail on glass?

I've been using blender for over 6 months now. I'm doing this rum bottle and I don't know how to make the detail in the glass.     When i try, i get this result:


Prime dividing the binomial coefficients

It is quite easy to show that for every prime $p$ and $0<i<p$ we have that $p$ divides the binomial coefficient $\large p\choose i$; one simply notes that in $\large \frac{p!}{i!(p-i)!}$ the numerator is divisible by $p$ whereas the denominator is not (since it is a product of numbers smaller than $p$ and $p$ is prime).  My problem is with generalizing this argument for $q=p^n$. I'm looking for the most elegant and simple way to prove that $p$ still divides $\large q\choose i$.


How can I emulate 1.7.10's adventure mode in 1.8?

Up until Minecraft 1.7.10 I enjoyed playing in adventure mode, which restricts one to use the right tools to destroy or harvest blocks (to have a more realistic experience).  In this version (and before that), it was still possible to place blocks without much restrictions. But now in 1.8, sadly, I discovered that this behaviour was changed, and my favourite gamemode was "gone": I'm unable to place any blocks and cannot break any blocks even when using the proper tool (axe for trees etc.).  How can I emulate 1.7.10's adventure mode while playing the new version (1.8)? Can I define rules for every tool with the command block somehow?  (PS: i would prefer a solution without modding the game, staying with pure vanilla MC if possible)


Hey there I was wondering why the "return ask" here does not change the value of 'ask' when I print it out on my main method (it prints out 0 in the main but works in the Log method) and how I can fix it. Thanks in advance!  public static int Log(int ask){      int b=0;     int c =0;     c = scannerobj.nextInt();     b = scannerobj.nextInt();     ask = b*c;     System.out.println(ask);     return ask; }  public static void main(String [] args){     int ask=0;      Log(ask);      System.out.println(ask);  }


What Linux version of Flash do I download?

I don't know what Linux version of Adobe Flash to install for Ubuntu 13.04; Also: once I get it, how do I install it?


Generally how much time is spent in reviewing an undergraduate/graduate applications to universities

Generally, how much time does a professor grant to review a single application? With thousands of applications, how is it ensured that each application is given proper weightage and importance because applying filters might not always work. Some person who is good at one thing, might not be for the other. So predefined filters would act against him.


Undefined control sequence error for equation

I am trying to reproduce the following equation in LaTeX:     nopt(d, B) = argminn {Pt - LMI (d, n, ω + 0.5B) >= Pth }   and the syntax I have used is the following:  $n_{opt}\left(d, B\right) = argmin_n\lbraceP_t - L_{Mi}\left(d, n, \omega + 0.5B\right) \geq P_{th}\rbrace$   This does not compile and I get the     !Undefined Control Sequence Error.   Any suggestions on what I am missing here?


What's the difference between "established" and "founded"

In this sentence: "CARE was ...... in 1945 to help people after World War II."    A. founded  B. built C. established D. constructed    The answer is C. But why don't we use "founded" in this case, I think they have the same meaning. Can you help me to give a reason for that?


Removing Clouds From (Landsat8) NDVI Imagery with ArcMap?

I recently was able to generate NDVI images from Landsat 8 using Arcmap. My end goal is to run some zonal statistics over specific neighborhood polygons, however with the cloud values (ranges of 0.002< X <0.025) still in my images, this will skew my results. I've thus far tried to figure out how to remove this using raster calculator but I'm not certain I'm actually doing what I think I am.   Using ArcGIS Desktop 10.5.1, how could I remove the above data range without altering the rest of my image?


I've tried to set Opera as my default browser in Ubuntu 16.04 LTS. I've tried in Opera's settings, and in the Ubuntu System Settings. I hit all the right buttons in both paces, but it just doesn't work.  Any suggestions? Is there a Terminal command that'll make it work?


Angles of intersection between two semi-circles

I am trying to recreate the following images but so far I have only been able to replicate the two semi-circles intersecting.              \documentclass[a4paper,12pt]{article}      \usepackage{tikz}     \usetikzlibrary{angles, calc, intersections, positioning, quotes, backgrounds}     \usepackage{pgfplots,caption}     \pgfplotsset{compat=1.9}     \begin{document}      \begin{center}             \begin{tikzpicture}                 \begin{scope}                      \clip (-3.5,0) rectangle (3.5,2);                      \draw (0,0) circle(1.1);                      \draw(1.8,0) circle(1.6);                  \end{scope}                         \draw (-2,0) -- (4,0);           \node at (-1.1, 0)[below] (1){ -6};          \node at (1.1, 0)[below] (2){  6};          \node at (0.2, 0)[below] (3){  $4\sqrt{2}$};          \node at (3.4, 0)[below] (4){  $6\sqrt{2}$};             \end{tikzpicture}         \end{center} \end{document}   So far I only have this


Why am I getting 'Data tag parsing failed: Unbalanced quotation' for this command?

I'm trying to make a command that creates a book that has many items with enchantments at level 1,000. However, I don't know why it keeps saying:     Data tag parsing failed: Unbalanced quotation:   {ench:[{id:0,lvl:1000}],Unbreakable:1,display:{Name:"Prot   It's supposed to say "Protection Armor", but it only shows "Prot" for some reason. This is the same with all of my other items. Here is the one part of the command that I've showed you:  {ench:[{id:0,lvl:1000}],Unbreakable:1,display:{Name:"Protection Armor"}}


Why is "origin/HEAD" shown when running "git branch -r"?

When you run git branch -r why the blazes does it list origin/HEAD? For example, there's a remote repo on GitHub, say, with two branches: master and awesome-feature. If I do git clone to grab it and then go into my new directory and list the branches, I see this:  $ git branch -r origin/HEAD origin/master origin/awesome-feature   Or whatever order it would be in (alpha? I'm faking this example to keep the identity of an innocent repo secret). So what's the HEAD business? Is it what the last person to push had their HEAD pointed at when they pushed? Won't that always be whatever it was they pushed? HEADs move around... why do I care what someone's HEAD pointed at on another machine?  I'm just getting a handle on remote tracking and such, so this is one lingering confusion. Thanks!  EDIT: I was under the impression that dedicated remote repos (like GitHub where no one will ssh in and work on that code, but only pull or push, etc) didn't and shouldn't have a HEAD because there was, basically, no working copy. Not so?


I just wondered if somebody could tell me what this means:  E: dpkg was interrupted, you must manually run 'sudo dpkg --configure -a' to correct the problem. reidsr@ubuntu:~$ sudo dpkg --configure -a dpkg: error: dpkg status database is locked by another process reidsr@ubuntu:~$    How do I run sudo dpkg --configure -a  manually?


Can I include a more permissive license for my code contributions in my profile?

..and will that have any effect?  Currently, I want all of my contributions on StackExchange to be available not just under SE's licensing terms (that goes without saying), but also under a version of "Unless you're preventing other people from using it, fair game" kind of license.  Is that legally somehow possible without rehosting all of my content on say github?  To elaborate: I want people to be able to do anything they want with my code, without attribution, and the only thing they shouldn't be able to do is prevent other people from using my code. That means that I don't need or want credit and that the code can be used as much as anyone desires in any application.


Notepad++ auto complete HTML end tags after </ (like Dreamweaver does)

In Dreamweaver typing </ will automatically close the last open tag, so you don't have to type it all out, and it helps if you aren't sure if you closed one or not. Is there a plugin that dose this for Notepad++?  This is not like text FX where typing the opening tag/bracket adds the close on the other side of the cursor. This behavior is an auto completion that happens when </ is typed, DW finds whatever the innermost open tag is, and closes it. I find that, when I have the option of using DW, I will use this feature far more often than anything else that DW provides. Thus I would love to know if there was a way to do it in NPP.  Here is DW preference in question:  Notice how there is a different option that does what text FX does, but I don't want that.  I am not opposed to unorthodox suggestions, some kind of macro, or hack of a plugging. Anything to emulate the functionality. If need be, I could write a plugin, I just have no idea how to go about it.


Question:  We need to prove the following inequality :-     $$\displaystyle \sum_{cyclic} \frac{x^4}{8x^3 + 5y^3} \geq \frac{x+y+z}{13} \ \ \ \ \ \ \ \ \ \ \ x,y,z \in \mathbb{R}^+ $$   As we know by AM-GM that,   $$\displaystyle  \frac{x+y+z}{13} \geq \frac{3(xyz)^\frac{1}{3} }{13} $$  Can we say it is similar to prove  this  $$\displaystyle    \sum_{cyclic} \frac{x^4}{8x^3 + 5y^3} \geq \frac{3(xyz)^\frac{1}{3} }{13}$$  instead of the original equation.  Because then,  SOLUTION  $\displaystyle \sum_{cyclic} \frac{x^4}{8x^3 + 5y^3} \geq \frac{x+y+z}{13}  \geq \frac{3(xyz)^\frac{1}{3} }{13}$  So We can say  $$\displaystyle \   \     \   \sum_{cyclic} \frac{x^4}{8x^3 + 5y^3} \times 13(x^3 + y^3 +z^3)   \geq  (x^2 + y^2 + z^2)^2  \  \   \       \  $$    By Cauchy-Schwarz Inequality  more precisely Titu's Lemma  Also we can see that $\displaystyle  \          \  (x^2 + y^2 + z^2)^2  \geq 9(xyz)^\frac{4}{3} $  This will result in      $$\displaystyle \sum_{cyclic} (\frac{x^4}{8x^3 + 5y^3}) \times (x^3 + y^3 + z^3) \geq 3(xyz) \frac{3(xyz)^\frac{1}{3} }{13}$$   Now we can tell $\displaystyle  {(x^3 + y^3 + z^3)} \geq {3(xyz)} \ \ \ $ (always true) i.e it is equivalent to say that $\displaystyle \sum_{cyclic} (\frac{x^4}{8x^3 + 5y^3}) \geq \frac{3(xyz)^\frac{1}{3} }{13} .$  Am I correct ?


I'm Yemeni, living in Saudi Arabia, where I have permanent residency.  I have passport from two countries, Yemen and Cyprus. The information used in the Saudi immigration system is from my Yemeni passport. The Yemeni passport, unlike the Cypriot one, does not allow me to travel to many countries without a visa.   If I want to use my Cypriot passport to travel, do I also have to show my Yemeni passport? What passport should I show at the airport in Saudi Arabia? When I'm able to enter a country visa-free with my Cypriot passport, do I also have to get a visa in my Yemeni passport?


Remove empty rows in ganttchart title (gantttitlecalendar)

When using \ganttitlecalendar from the , it automatically inserts empty rows between the title rows. Is there a smooth way to prohibit this without having to create my own title?  MWE:  \documentclass[tikz]{standalone} \usepackage{pgfgantt}  \begin{document} \begin{ganttchart}[ x unit=0.7cm, hgrid, vgrid, time slot format=isodate-yearmonth, title/.append style={shape=rectangle, fill=black!10}, bar/.append style={shape=rectangle, fill=black!20}, compress calendar ]{2016-06}{2018-09} \gantttitlecalendar{year, month} \\   \ganttbar{Task1}{2016-06}{2018-07} \\ \end{ganttchart} \end{document}


It is discouraged to simply catch System.Exception. Instead, only the "known" exceptions should be caught. Now, this sometimes leads to unnecessary repetitive code, for example: try {     WebId = new Guid(queryString["web"]); } catch (FormatException) {     WebId = Guid.Empty; } catch (OverflowException) {     WebId = Guid.Empty; }  I wonder: Is there a way to catch both exceptions and only call the WebId = Guid.Empty call once? The given example is rather simple, as it's only a . But imagine code where you modify an object multiple times, and if one of the manipulations fails expectedly, you want to "reset" the object. However, if there is an unexpected exception, I still want to throw that higher.


Compare models from different data subsets

I'm looking to compare linear regression models from different data subsets in r. The models are not nested. I have a model from the complete dataset with sex as a factor and then 2 separate models from 2 subsets of this data (subset1 = all male data, subset2 = all female data). I am trying to see if it is better to have one model with sex as a factor or if there is benefit having a separate model for each gender. I am looking at the MAE (mean absolute error) and RSME (root mean square error) specifically. Can I compare the raw values or the MAE and RSME (e.g. MAE from the complete model on the complete set vs female on the female set and male on the male set)?


Why I got NameError when I am using pygame?

Why do I get a NameError exception in this program? I am programming a Python plane fight game using pygame. I have just finished added the plane PNG to the background. However, when I want to test the movement of the plane, the error is raised and I couldn't find why it occurred. Error traceback: Traceback (most recent call last):   File "C:\Users\Desktop\Plane Fight\Plane Fight.py", line 34, in <module>     main()   File "C:\Users\Desktop\Plane Fight\Plane Fight.py", line 29, in main     draw_window()   File "C:\Users\Desktop\Plane Fight\Plane Fight.py", line 12, in draw_window     win.blit(leftjet, (left.x, left.y)) NameError: name 'left' is not defined  Code: import pygame import os  win = pygame.display.set_mode((900, 500)) #生成一个900*500分辨率的游戏界面 pygame.display.set_caption("Plane Fight Game")  leftjet = pygame.transform.rotate(pygame.transform.scale(pygame.image.load(os.path.join('fighterjet.jpg')), (55 ,40)), 270) rightjet = pygame.transform.rotate(pygame.transform.scale(pygame.image.load(os.path.join('fighterjet.jpg')), (55 ,40)), 90)  def draw_window():     win.fill((0, 0, 0)) #设置背景为黑色     win.blit(leftjet, (left.x, left.y))     win.blit(rightjet, (right.x, right.y))     pygame.display.update()  def main():     left = pygame.Rect(100, 100, 55, 40)     right = pygame.Rect(800, 100, 55, 40)          run = True     while run:         pygame.time.Clock().tick(60) #设置游戏帧率为60帧          for event in pygame.event.get():             if event.type == pygame.QUIT:                 run = False          right.x += 1         draw_window()              pygame.quit()  if __name__ == "__main__":     main()


How permanent magnets work?Are they working with motion of electrons?


writing simple fractions (1/2, 1/4) in social science text

As part of a social science text, in one place I need to write fractions like 1/2, 1/4, 1/3. How can I write these fractions in an elegant way without using mathematical packages?


Enter value to produce keys in dictionary [Python]

I have made my own Morse Code translator where you can enter the code and the corresponding letter prints out. However, what I want to do is that whenever I enter a letter, the code prints out. Here's my code:  MorseCode = {'.-':'A',             '-...':'B',             '-.-.':'C',             '-..':'D',             '.':'E',             '..-.':'F',             '--.':'G',             '....':'H',             '..':'I',             '.---':'J',             '-.-':'K',             '.-..':'L',             '--':'M',             '-.':'N',             '---':'O',             '.--.':'P',             '--.-':'Q',             '.-.':'R',             '...':'S',             '-':'T',             '..-':'U',             '...-':'V',             '.--':'W',             '-..-':'X',             '-.--':'Y',             '--..':'Z',             '.----':1,             '..---':2,             '...--':3,             '....-':4,             '.....':5,             '-....':6,             '--...':7,             '---..':8,             '----.':9,             '-----':0 }  print "Type 'help' for the morse code." print "Type 'end' to exit the program.\n" while True:     code = raw_input("Enter code:")     if code in MorseCode:         print MorseCode[code]   So the question is: Is there a way to somehow invert this dictionary so whenever I enter 'A', '.-' will print out? I'm only studying python for two weeks now so I'm still mastering the basics before I move on to the more advanced levels. Thank you!


I want to draw arrows on a pgfplots plot. For the blue colored arrow everything is fine, but the red and green arrow are not drawn as I'd like. The red arrow tip is cut, the green one is just draw half. I think the problem is, that they are partial outside of the plot. What to do?  \documentclass[tikz]{standalone} \usepackage{pgfplots} \pgfplotsset{compat=newest}   \begin{document} \begin{tikzpicture}   \begin{axis}[     grid=major,     axis lines=middle,     axis line style={->},     x label style={at={(axis description cs:0.5,+1.1)},anchor=north},     xticklabel style = {yshift=0.65cm},     y label style={at={(axis description cs:-0.1,.5)},rotate=90,anchor=south},     y dir=reverse,     xlabel={x in m},     ylabel={y in $m$},     % scale     x=10cm, y=10cm,z=0cm,     ymax=1.29, ymin=0,     xmax=1.59, xmin=0,     ]    \addplot[only marks] coordinates {     (0,0) (0.1,0.00556) (0.2,0.02224) (0.3,0.05004) (0.4,0.08896) (0.5,0.13900) (0.6,0.20016) (0.7,0.27244) (0.8,0.35584) (0.9,0.45036) (1.0,0.55600) (1.1,0.67276)%     (1.2,0.80064) (1.3,0.9364) (1.4,1.08976) (1.47,1.20146)  };  % Boden  \draw[very thick] (axis cs:0, 1.2) -- (axis cs:1.59, 1.2);  \draw[->,red,very thick] (0,0) -- (0.3,0);  \draw[->,blue,very thick] (0.8,0.35584) -- (1.1,0.35584);  \draw[->,green,very thick] (1.47,1.2) -- (1.77,1.2); \end{axis}   \end{tikzpicture}  \end{document}


Can someone provide a derivation of the  for electromagnetic induction? To be clear,  $$ d\vec{B}~=~\frac{\mu_0}{4\pi}\frac{I d\vec{\ell}\times \vec{r}}{r^3}. $$  Is there a simple way to compute the magnetic field at a point between two Helmholtz coils, if the radii of the coils are the same and the current through each coil is the same?


Every time I export a new print composer (either image, svg, or PDF) in QGIS 2.18.1, I lose my composer

As the title suggests, whenever I attempt to make a new print composer (in either windows or Linux, I have tried both) with my map, it goes blank and the file is not exported.  When I attempt to export as a PDF, I get the message "Advanced composition effects such as blend modes or vector layer transparency are enabled in this project, which cannot be printed as vectors. Printing as a raster is recommended." Would this prevent my ability to make a PDF from the print composer?   If so, how can I rectify this?  Since I have a low reputation, if you need pictures I can provide them in the comments.


How to run psmouse with "proto=imps" on startup?

I have ubuntu 16.04. I want to add  sudo modprobe -r psmouse && sudo modprobe psmouse proto=imps   to my startup applications.  I added it succesfully but it isn't running with the startup.  I think because of the password requirement.  Please help me as I want it to run along with start of my laptop.  Is there any other way or is there a way to fulfill my above requirements? Please let me know....


Determine if generic type (where T: struct) has the ability to have maths performed on it?

I am creating a static class that is used to asynchronously wait for some T targetValue to be "approximately" some T currentValue. I have already implemented a function to check for exact equality as shown below, but I am having a difficult time with an "approximate value"  public delegate T GetValueMethod<T>() where T: struct;  public static Task<Boolean> WaitForExactValueAsync<T>(GetValueMethod<T> getValue, T targetValue, CancellationToken cancelWaitToken, int msTimeout = 10000) where T: struct {     return Task.Run<Boolean>(async () =>     {         // Create a CancellationToken that times out, then link it with the argument token that requests a the wait to be cancelled         var timeoutTokenSource = new CancellationTokenSource(TimeSpan.FromMilliseconds(msTimeout));         var timeoutAndCancelTokenSource = CancellationTokenSource.CreateLinkedTokenSource(timeoutTokenSource.Token, cancelWaitToken);          // Continually check to see if we reached the target value or have timed out         T currentValue = getValue();         while (!targetValue.Equals(currentValue) && !timeoutAndCancelTokenSource.IsCancellationRequested)         {             try { await Task.Delay(500, timeoutAndCancelTokenSource.Token); }catch (Exception ex) { }             currentValue = getValue();         }          // If we got here and the token is not cancelled that means we have reached the target value         return !timeoutAndCancelTokenSource.IsCancellationRequested;     }); }   The methods I am creating are meant to only work with primitive types such as int, double, Boolean, etc. I do this by implementing  which describes a way to limit generic types to primitives by forcing the T to be a struct.   The function above seems to work nicely for my situation because (I think) we can always equate struct with Equals to determine equality. My issue when creating the approximately equal version is when the type of T is something like Boolean.   I plan to allow the user to pass in a "closeness" percentage to the function to specify when the two values are "approximately equal" (If the current is within x percentage of the target return true). If T is a numeric value I can do this with maths easily, but when its non-numeric it makes no sense to use this method but to simply use Equals.  Is there a way to tell from T (where T : struct) if I can perform the maths I need to on it (To implement the IsValueClose method below)?  private static Boolean ValueIsClose<T>(T target, T value, double percentAsDecimal)    where T: struct {     // if(value.CanDoTheMaths)     {         return Math.Abs((value / target) - target) <= percentAsDecimal;     }     // else     {         return target.Equals(value);     } }   Furthermore once this happens how can I refer to target and value as a type that can perform these maths?  From asking somewhat relate questions before I do not think this is quite possible or good practice for generic methods. So from what I can currently tell, my only good solution is to make an "approximate" method for each type I plan to use (the best practice), or to check the Type of T in IsValueClose to see if it is something that I know I can do maths on and go from there (Bad practice for generics).   Though possibly there is a simpler more elegant solution that someone could suggest?


Existence of a Fibonacci number divisible by $10^n$

Prove that for any given positive integer $n$,there exists a Fibonacci  number divisible by $10^n$.   Another application of pigeon hole principle,and the main problem is finding the holes and pigeons.If we consider $10^n+1$ consecutive Fibonacci numbers,we can NOT  claim that one of them is certainly divisible by $10^n$,but of course two of them have equal remainders mod $10^n$. I DO KNOW this question has an elementary solution using pigeon hole principle,although  the older question asked for $n=2014$ has received many advanced solutions.


Diplay time in win 7 reversed in 2 hours back , after operation ubuntu

I am working in dual opretion systems on one pc ,win 7 and ubuntu 16.04 . After  disconnecting from ubuntu and boot to  win 7,  the display time show 2 hours delay .  please advise how to solve this problem .


I am in the middle of a problem and having trouble integrating the following integral:  $$\int_{-1}^1\frac1{(1+x^2)^2}\mathrm dx$$  I tried doing partial fractions and got:  $$1=A(1+x^2)+B(1+x^2)$$  I have no clue how to solve this since it is obvious there is no way to cancel out either $A$ or $B$ to get the other variable. Please guide me.  Thank you.


How to install an unsafe APK after allowing Play Protect to block it?

I was just wondering, when installing an APK from an unknown source and you click OK to allow Play Protect to block it, is there a way of installing that app without fully disabling Play Protect?  When trying to install the same app after allowing the block, it shows App not installed.


Will my checked luggage freeze in the airplane?

I'm taking some freeze-sensitive items in a checked luggage for a short flight. It's cheese, chocolate, toothpaste and wine. I would like to know whether the luggage can get "frozen" in the aircraft. Sometimes it happened to me that my stuff actually was quite cold after the flight, so I'd like to be quite sure. Especially the cheese was really expensive and freezing it would very likely demage it.  Usually I pack everything well in clothes, but this time the things are just too many so it's tough to do more than just protect the wine from breaking.  Some details: It's an A320 flight taking 1.5 hours, with Czech Airlines, from Paris CDG to Prague PRG.


Examples proving that the tensor product does not commute with direct products

Examples proving why the tensor product does not distribute over direct products? In fact the canonical map is not surjective; can you give me a simple example?


I am using the following expression for URL validation.   ^(https?:\/\/)?([\da-z\.-]+)\.([a-z\.]{2,6})([\/\w \.-]*)*\/?$   However, when I have   "httpcolonforwardslashessite" (colon = : and foward slashes = //)   it still passes it as a url. how can I modify the above expression to make sure that there is ".com/net" at the end?  Thank you  tldr: I want to check for .com or .net at the end of url. What changes can I make to above exp to achieve this?


Consider a sentence of the following form:     X, and the Y which comes with it, is good.   Assume X and Y are nouns, and X is singular. Should "is" be replaced with "are"? Is there some other grammatical error I am missing?


Hi I want to program a card game, in my game each card can do multiple actions, depend on the situation in which the player is facing. For example There is an "Attack" card which can attack another player, the attacked player can defend itself in multiple ways - it can use "Run Away" card, it also may use another card to rule a cube to avoid the attack etc, The "Attack" may also be used to shot an attacker to avoid dying. In short each card can be used in all sort of ways and I'm having trouble to code these rules, How can I create the session between 2 players? (attacker and defender)  thanks


How to find the unitary operation of a depolarizing channel?

Suppose we have a depolarizing channel operation $$E(\rho)=\frac{p}{2}\textbf{1}+(1-p)\rho$$ acting on a Spin$\frac{1}{2}$ density matrix of the form $\rho=\frac{1}{2}(\textbf{1}+\textbf{s}\cdot\textbf{$\sigma$})$. I have found the Kraus operators to be: $$E_1=\sqrt{\left(1-\frac{3}{4}p\right)}\textbf{1}, E_2=\frac{\sqrt{p}}{2}\sigma_x,E_3=\frac{\sqrt{p}}{2}\sigma_y \text{  and  } E_4=\frac{\sqrt{p}}{2}\sigma_z$$ I am now supposed to find the unitary matrix U such that the Operation can be expressed in a bigger system i.e. after adding a System S. As far as I understand it, the new operation can be written as: $$E(\rho)=\sum_kE_k\rho E_k^\dagger=\text{Tr}_S(U\rho\otimes\rho_EU^\dagger)$$ Supposing the new system S is prepared on a state $|e_0\rangle$, How do I find the correct unitary matrix? I appreciate your cooperation.  Crossposted to qc:


When sending letters home our school uses 'Dear Parent' as the salutation.  The person in charge of proof-reading our outgoing correspondence insists that the sign-off should be 'Yours sincerely'.  I was always taught that 'Yours faithfully' should be used when the addressee is not mentioned by name. Does any of this matter, and if so, who is correct? Thanks English experts,  Yours faithfully? Brotherwarren


Can I run Baldur's Gate on my Windows 7 computer?

I have heard that there are some technical problems with running Baldur's Gate on a computer with Windows 7, but the Virtual Machine I have sucks, because the mouse pointer is always flickering. What I want to know is, if I install Baldur's Gate, will my computer have any problems?


Using an "is" check when with an explicit cast

How does the "is" operator work in C#?  I have been told that this :  if (x is string) {      string y = x as string;      //Do something }   is not as good as this:  string y = x as string; if (y != null) {      //Do something }   Which is better and why?


Ubuntu Server - How to connect to wireless WPA2 personal network?

Connecting to the wireless is relatively simple.  After some struggle, you have wifi in your installer. You can install Ubuntu Server and everything is alright. You are ready to boot your new system.    After setup finished, wifi settings disappeared.  tl;dr: How do I connect to a wireless (WPA2 Personal) network from Ubuntu Server 12.10?    What I have tried so far:  Connected with iw* commands. Obtained IP address with dhclient. Put these commands to etc/rc.local.  On boot, the server waits 120 seconds with message "Waiting for network to come up"  To fix this, I removed everything /etc/network/interfaces (wpa-psk and wpa-ssid). This did not work. It was still waiting. I found an answer, which said I could just remove the /etc/... (the file that was in charge of the 120 second wait time.)    I did that, and kept a backup of it. Now the server waits ~3 seconds (modified sleep within the file) and boots up. However, there's no network connection available. It's some dhcp error.  As I was out of options, I tried using the one in comment. The one that used "tee". Turns out it does not work either.    How can this whole thing be so inconsistent? How can they not install the firmwares on the ISO while it would perfectly fit (673+~10MB = 683). How can the installer NOT copy the necessary files and set up the connection to be used later? (Or ask if the user wants to use it.)


Python list : python 3d list assign and index different result

When I assign to an element in 3d python list, it will change 3 element. Do anyone know what happened?


Can I leave the UK and come back in, on a Tourist visa?

I am a United States citizen with a 6-month Tourist visa to the UK (a stamp in my passport). Additionally, in 2013 I spent about two months in the UK on tourist visas, split between two separate occasions (one month in April-May, and one in August-September). My passport was stamped in December of 2013, and I have two other stamps from those previous visits (so three total, now)  My original intended departure date from the UK was March 1, but that is no longer the case, as I plan to stay out the duration of my visa.  My question is, can I leave the UK (to travel in Europe for a week, for example) and come back in with this visa? Will they re-stamp me, or see that my existing stamp is still valid? Will it be a problem that I've been coming-and-going in the UK relatively frequently? Are there any other concerns I should be aware of?


In which topologies do open sets maintain open under countable or arbitrary intersection?

We know that in the usual topology, countable or arbitrary intersection of open sets can zoom into a singleton, hence is not in the topology.   I am curious if there is well known classes of topologies, whose open sets maintains their openness after countable or arbitrary intersection.   I know two examples:      1) In the discrete topology, $\mathcal{T} = \mathcal{P}(X)$. The power   set is a $\sigma$-algebra, hence "closed" under countable   intersections, so a countable intersection of open sets in the   discrete topology is open.      2) In the particular point topology, given $x_o \in \mathbb{R}$,   $\mathcal{T}_{x_o} = \{U \subseteq \mathbb{R}| x_o \in  U\}\cup\{\varnothing\}$, an arbitrary intersection of open sets will   always contain $x_o$, in particular $x_o$ is open. Hence a countable   intersection of open sets in the particular point topology topology is   open.   Are there a lot more well known classes of topology whose condition on intersections of open set can be extended?


Possible incompatibility between babel, listings and arsclassica

\documentclass{scrbook}  \usepackage[english]{babel}  \usepackage[listings]{classicthesis} % or \usepackage{listings} - also causes the error \usepackage{arsclassica}  \begin{document}  \paragraph{a~b}  \end{document}   The above code causes an error:     ! Undefined control sequence.   <<inserted text>> az;                      b   l.10     \paragraph{ab~cd}   After removing any one of three lines with packages: babel, listings or arsclassica, document compiles successfully.  What is important, changing ~ to  makes the code working again. Similarly, putting ~ outside disposition commands (\paragraph{}, \section{} etc.) to the text body also works.  I cannot trace the source of the error further.  Is it possible to use these three packages together in some way?


Payload error while deploy Address settings (State & Country picklists)

Using Workbench i have retrieved the Address setting using package.xml  XML :  <?xml version="1.0" encoding="UTF-8"?> <Package xmlns="http://soap.sforce.com/2006/04/metadata">     <types>         <members>Address</members>         <name>Settings</name>     </types>     <version>42.0</version> </Package>   I have downloaded the Zip file and have added some countries in the Address.settings file. When I deployed the file my changes haven't reflected in the org.    Please help me out.   Also I have referred the below link also   This is the result i got in workbench .  Also when check in the deployment status i got Payload error says " No package.xml found"


C++ How to create two classes where one is a member of the other and viceversa

How can I make this work?  I know that MyOtherClass m_myOtherClass; is not known at this point and so I get errors, but what is the solution when you have to do stuff like that? Forward declarations and includes dose not work because the compiler does not know all it is needed, for example object size.  I know I can solve this problem with pointers, but this means that there is NO SOLUTION for a problem like this? when someone want the classes to be exactly like these?  #ifndef MYCLASS_H #define MYCLASS_H  class MyClass{  private:     MyOtherClass m_myOtherClass; //Error unknown type name };  #endif // MYCLASS_H   second header file:  #ifndef MYOTHERCLASS_H #define MYOTHERCLASS_H #include "myclass.h"  class MyOtherClass{ public:     MyClass m_myClass; };  #endif // MYOTHERCLASS_H


Han Solo was able to "make the Kessel Run in less than 12 parsecs" but how is it measured? Is it the distance spent out of hyperspace?


I want to prove it using Jensen inequality, so I need to prove that $g(x)=x\ln x$ is a convex function, which means  $$g\left(\frac{a+b}{2}\right)\le \frac{1}{2}\left(g(a)+g(b)\right).$$ How can I prove it?


How to remove a pip package installed with sudo -h

My question is quite simple: I've installed virtualenv with the following command: sudo  -H pip3 install virtualenv  It seems to be wrong, because in the tutorial that I watch pip downloads other stuff than on my pc. How can I undo it? Thx for your help and stay healthy!


If an element is not in the set difference $A\setminus B \: \:?$

Given two sets$$A=\{1,3,5\}\quad,\quad B=\{1,3,8\}.$$ Then I compute the $A\setminus B=\{5\}.$   But my book$^\dagger$said: ... . Also, observe that $x\notin A\setminus B$ does not mean that $x\notin A\lor x\in B$. Why?  I don't know how to explain the Why, please give me some example.    $^\dagger$, second edition, page $4$.  EDIT: My intuition tells me that it does mean that. I guess there is some special case about null-set or about the restriction of the universal set.


With $x_{n+1}=\sqrt{x_ny_n}$, and $y_{n+1}={x_n+y_n \over 2}$, $n\geq 2$. Show that $\lim _{n\rightarrow \infty}x_n=\lim_{n\rightarrow\infty} y_n$.

Let $0<a<b$, $x_1=a>0$, $y_1=b>0$, $x_{n+1}=\sqrt{x_ny_n}$, and $y_{n+1}={x_n+y_n \over 2}$, $n\geq 2$. Show that $\lim _{n\rightarrow \infty}x_n=\lim_{n\rightarrow\infty} y_n$.  I have considered the fact that $(y_n-x_n)^2>0$ implies that ${x_n+y_n \over 2}>\sqrt{x_ny_n}$. I'm not entirely sure how to prove this result. Any solutions/hints are greatly appreciated.


I  have 3 feeder wires coming up underground from the meter and main disconnect. They tie in to a 50amp receptacle box and a 6 AWG cord With 8Awg ground all in one. That cord goes into my electrical panel where the grounds and neutrals are mixed and bonded. As far as I know the green ground connects to the RV type receptacle box and goes nowhere except that it came with the cord. There is no ground at the meter or disconnect. The house has no grounding system, as I can not locate as much as a grounded water pipe. I can install 2 ground rods or maybe the ground wire to the water pipes was disconnected or cut. The 3 wire feeders leave the disconnect in conduit and I see no conduit coming out, just three wires. Perhaps the conduit is below the ground somewhere. It is a 30 foot run with 6AWG wire. What I need to know is: what Would be the best way to waterproof the connections and get them into my panel, not just replacing the RV type of box and 50 amp cord that lays on the ground with just loose wires running into it? That is why it was damaged in the first place  when the sewer backed up and corroded the receptacle and cord. It was fine for years, but what are my options? The disconnect is 100 Amp, as is my service panel. The home was installed in 1978. Can I just put conduit over the wires that come out of the ground and use a weather tight box. Should I replace the whole cord or just cut it and replace the plug end. Where should I install the grounds at. The meter disconnect or at my home. I think someone changed out the main panel as it is tag as being a sub panel with a main disconnect outside  not a service  entrance. I just checked the furnace it is 55amp minimum the water heater is 30Amp with a electric range and dryer and lights and receptacles also A 220a/c and 2 120A/C s in the summer time. I would not want to use a 50Amp power cord would i Would I be able to use the 100Amp service disconnect and 100amp panel  I believe the  service entry cables are6/2 4/0 with no ground in sight  no grounding rods nothing.  I rent the lot but own the home Would I or the landlord be responsible for the upgrade in lima,ohio. Should I upgrade to a 150amp panel with a 200amp disconnect outside how do I calculate the loads in the home to figure out what I need The flood and the over current has burned one side of the 50 Amp cord completely out I don't know what year the home was installed on this lot or if it was inspected as it is not even properly set up on it's foundation piers  it's just one mess after another. Thanks guys for your patience


Why do PHP regexes have the surrounding delimiters? It seems like it would be more clear if any pattern modifiers were passed in as a parameter to whatever function was being used.


Do sentences need to remain grammaticaly correct if text in parentheses is ignored?

This question is best explained by an example. Ignore the mathematical context, it doesn't really matter.     ... as x tends to 0, the point P slides towards P', so cos x (and hence 1/cos x) both have a limit equal to 1. ...   Given that parentheses are usually meant as an aside, if I read the text ignoring the parentheses:     ... so cos x both have a limit equal to 1 ...   the "both" here is grammatically incorrect (as, of course, cos(x) is a single "thing").  So here comes the question in the title: Do sentences need to remain grammatically correct if text in parentheses are ignored? And as a side question, what would be a better thing to use in the example?


Why isn't Cricket an Olympics sport event?

Olympics is the biggest sporting event on earth, but there are still some spots that are not included in the Olympics like Cricket. It is now a much more popular sport over the world but there are still no sign of it becoming an Olympics sport.


Deleting variables that are no longer in use, through the function

I know that C++ holds memory management internally with a lot of given points, and I know of the delete command to remove dynamically allocated data, and this question, could seem pointless within the fact that it may not ever come to be an issue due to the destruction of variables outside of the scope of the function that is using them, but is it possible to use a function such like delete to remove a variable that the user is no longer putting to use. Like say that you are on a heavily memory depleted piece of hardware, and need to make sure that even something as small as the 4 bytes that an integer normally takes up are given straight back. Is it possible to do this without wrapping the variable inside some function to make the assembler know to remove it immediately? This is in a sense of a point that I don't believe could ever happen, due to the expansion of memory, and the ways that it could be manipulated these days, but it seems as if it may have been an issue before, if I'm not mistaken.  Summary: Is there a way to manage non dynamic data directly, allocate it to the stack, and remove it from the stack through a function call, or is this completely run by the programs internal instructions?  Example:  void foo(){    short int operator;   /*Did what needed to be done with the operator variable***********/   //Pseudo-code     delete operator;    /*Even though it was not allocated dynamically,     and with the use of another function call*/ }


The general solution of $x^a = a^x$ for real $a >0$

What are the roots of $$f(x) = x^a - a^x$$ for real $a > 0$?   Case 1: For $0 < a < 1$ there is 1 solution, $x=a$. Case 2: For $1\le a < e$ there are 2 solutions: $x=a$ and $[x>a]$. Case 3: For $a > e$ there are 2 solutions: $x=a$ and $[x < a]$.     if we let b = a^(1/a). x = b^^ [use mathematica for tetration] or using the basic operators,  x = b^(b^(b^...))...) for a > e, this solves for the non-simple root < a  but for a < e it solves for  x = a i am looking for a similar solution for a < e


Retaining permissions when copying a folder

I am having an issue where I have Parent folder that has full permissions.. I can create a new folder and that folder also has full permissions. However when I copy a folder over to this parent Directory and try to create a new directory to this copied directory. it loses all permissions.. is there a way to retain permissions to the copied folders..


How can I create directory tree in C++/Linux?

I want an easy way to create multiple directories in C++/Linux.   For example I want to save a file lola.file in the directory:   /tmp/a/b/c   but if the directories are not there I want them to be created automagically. A working example would be perfect.


Are all galaxies we see really our Milky Way? Any possibility?

There is a possibility for our universe to be the surface volume of a (higher-dimensional) hyperspace. So if this possibility is true,then is there also a possibility that the other galaxies we see are our own galaxy after light has completed revolution around the three dimensional boundary (surface volume).  Know that we see different shapes for different galaxies.This can be perhaps due to other reasons like-   distance light travelled, the angle through which we look to see the other galaxy (possibly Milky Way) after     it made any number of revolutions, the part of the other galaxy (possibly Milky Way) which we see,and some other properties of light and space.   Only our Milky Way galaxy is just one possibility  Another possibilities are the number of galaxies are far less than we see because we see the same galaxy several times due to curved space.  Any possibilities for the above statements to be true?


In Unity for Android, how do I create touchable buttons?

I'm making a test game for Android in Unity 5, and I want to add left-right control buttons like the circles below, to move an object left or right.   (source: )    How can I do this?  Sorry if this question is basic. I'm new to Unity and I don't understand the methods of existing tutorials.


Ubuntu 16.04 unmet dependencies won't install

I am trying to install nodejs but it keeps having unmet dependencies and it continues to do so.  sudo apt-get install nodejs Reading package lists... Done Building dependency tree        Reading state information... Done Some packages could not be installed. This may mean that you have requested an impossible situation or if you are using the unstable distribution that some required packages have not yet been created or been moved out of Incoming. The following information may help to resolve the situation:  The following packages have unmet dependencies:  nodejs : Depends: python-minimal but it is not going to be installed E: Unable to correct problems, you have held broken packages.   and then ...  sudo apt-get install python-minimal Reading package lists... Done Building dependency tree        Reading state information... Done Some packages could not be installed. This may mean that you have requested an impossible situation or if you are using the unstable distribution that some required packages have not yet been created or been moved out of Incoming. The following information may help to resolve the situation:  The following packages have unmet dependencies:  python-minimal : Depends: python2.7-minimal (>= 2.7.11-1~) but it is not going to be installed                   Recommends: python but it is not going to be installed E: Unable to correct problems, you have held broken packages.   this continues indefinetly and loops back at some point. I also tried:  sudo apt-get install -f sudo apt-get update sudo apt-get upgrade   This worked for me:


Calling a derived function from an array of the base class

How do you call a derived function from an array of the base class?  Ex:  #include <iostream> #include <string>  class a{  public:     virtual void prnt(){         std::cout<<"a"<<std::endl;     } };  class b: public a{  public:     virtual void prnt(){         std::cout<<"B"<<std::endl;     } };  int main() {     a array[3];     array[0] = a();     array[1] = b();     array[2] = a();      array[1].prnt(); }   The output for this example is a.  is there anyway to fix this?


With tools like Process Hacker it's easy to find which Windows Services are being executed by an instance of svchost.exe, but this doesn't provide many informations.   Is there any way to find the CPU usage for each service?


Can someone help me out. I'm attempting to createChrome extension that changes the div class on page load. Based on what I'm reading I would need to create a Javascript loop that changes the following div class:  Current: div class="article-holder article-holder--less"  Change: div class="article-holder article-holder--more"  If anyone can provide how to successfully accomplish this task, it would be much appreciated.