Problem 7.33-b) (Daniel.V.Schroeder-An introduction to thermal physics):     When attractive forces of the ions in a crystal are taken into   account, then the allowed energies are grouped into bands, separated   by gaps where there are no allowed energies. In a conductor the Fermi   energy lies within one of the bands; in this section we have treated   the electrons in this band as "free" particles confined to a fixed   volume. In an insulator the Fermi energy lies within a gap, so that at   $T=0$ the band below the gap is completely occupied and the band above   the gap is unoccupied. A semiconductor is an insulator in which the   gap is narrow enough for a few electrons to jump across it at room   temperature. Figure below shows the density of states in the vicinity   of the Fermi energy for an idealized semiconductor, and defines some   terminology and notation to be used in this problem.      b) Normally the width of the gap is much greater than $kT$. Also, let $g(\epsilon)=g_0\sqrt{\epsilon-\epsilon_c},$ where $g_0$ is a constant independent of $\epsilon.$ Working in   this limit, derive an expression for the number of conduction   electrons per unit volume, in terms of temperature and the width of   the gap.     I found a solution online which calculates the number of conduction electrons using  $$N_c=\int_\limits{\epsilon_c}^{\infty}g(\epsilon)\bar{n}_{FD}(\epsilon) \ d\epsilon=g_0\int_\limits{\epsilon_c}^{\infty}\frac{\sqrt{\epsilon-\epsilon_c}}{\exp((\epsilon-\epsilon_F)/kT)+1} \ d\epsilon. \tag1$$  What I don't understand here is that in the same book they state that for $T=0$ we have $\mu=\epsilon_F$ and the formula for the number of electrons is given simply by  $$N=\int_\limits{0}^{\infty}g(\epsilon) \ d\epsilon.\tag2$$  So why doesn't $(2)$ apply to the problem at hand?  The correct answer seems to be  $$\frac{N_c}{V}=\left(\frac{2\pi m k T}{h^2}\right)^{3/2}2e^{-2(\epsilon-\epsilon_F)/kT}.$$  Using the theory about the limit of the Fermi-Dirac distribution in  thread then I should get   $$N_c=\lim_{T\rightarrow 0}g_0\int_\limits{\epsilon_c}^{\infty}\sqrt{\epsilon-\epsilon_c}\cdot\frac{1}{\exp((\epsilon-\epsilon_F)/kT)+1} \ d\epsilon = g_0\int_{\epsilon_c}^{\infty}\sqrt{\epsilon-\epsilon_c} \ d\epsilon = \infty.$$  Thus the theory in that thread does not help here at all?

In my book (Daniel V.Schroeder - An introduction to thermal physics) in page 267 they introduce the Fermi-Dirac distribution is given by  $$\bar{n}_{FD}=\frac{1}{e^{(\epsilon-\mu)/kT}+1}. \tag{1}$$  But a few pages later they claim that the Fermi-Dirac distribution becomes a step function and then proceed to define the Fermi energy as  $$\epsilon_F=\mu(T=0).$$  Questions:  1) How does $\bar{n}_{DF}$ become a stepfunction at $T=0$? It's not even possible to plug it in the distribution since then we have division by zero.  2) The expression for the chemical potential $\mu$ is given by  $$\mu=-kT\ln{\frac{Z_1}{N}},$$  where $N$ is the number of particles and $Z_1$ is the partition function for any single particle. So setting $T=0$ should just give $\epsilon_F=\mu=0$. But this is apparently not the case. Why?


In other words, is there an algebraic proof showing that $\sum_{k=0}^{N} {N\choose k} = 2^N$? I've been trying to do it some some time now, but I can't seem to figure it out.

I'm well aware of the combinatorial variant of the proof, i.e. noting that each formula is a different representation for the number of subsets of a set of $n$ elements. I'm curious if there's a series of algebraic manipulations that can lead from $\sum\limits_{i=0}^n \binom{n}{i}$ to $2^n$.


How can one get rid of the hyperref warning about the $ signs in the subsection title that are generated in the following minimal example?  \documentclass{book}  \usepackage{titlesec}             \usepackage{titletoc}                 %\newcommand{\subsecformat}[1]{\parbox[b]{\linewidth}{ %    \normalsize\selectfont %    \filright\textcolor{black}{\textsc{#1}}}}     \usepackage{hyperref}  \begin{document} \subsection{Can light move faster than $c$?} No. \end{document}   Probably the command \subsecformat needs to be improved. How should this be done?

Possible Duplicate:          The following code:  \subsection{The classes $\mathcal{L}(\gamma)$}   generates the errors:  Package hyperref Warning: Token not allowed in a PDF string (PDFDocEncoding): (hyperref)                removing `math shift' on input line 1938.   Package hyperref Warning: Token not allowed in a PDF string (PDFDocEncoding): (hyperref)                removing `\gamma' on input line 1938.   Package hyperref Warning: Token not allowed in a PDF string (PDFDocEncoding): (hyperref)                removing `math shift' on input line 1938.   What do I have to do to keep \gamma in the subsection, so that it is also listed in the table of contents?


I would like to add some "commands for editing" in TeXstudio. For instance in the menu "TI" on the left which stands for 'TikZ', there is some "commands for éditing" TikZ commands, you click on it and you have some squeleton of commands in your source file, and you just have to modify it to custom it.  I would like to add some personnal "commands for editing". Is it possible to do it in TeXstudio, and if yes, how do we do that ?

I'd like to know if in my TeX editor, TeXstudio, the buttons can be customized? i.e: The marked button produces $  $, and I'd like to have ${}$  This other button produces \\ and I'd like to have \par %   Is that possible?


I understand that there is a similar question about this, but I would like to phrase this in a different way.  In Harry Potter and the Sorcerer's Stone there is a series of tests that someone attempting to get to the stone must pass. There is the locked door, Fluffy, Devil's Snare, the key room, the chess room, and the potion room. However, most of these tests could have been much better implemented.  For example, why a giant game of chess? It is made clear that if they didn't play the game, the stone statues wouldn't let them cross, but this is not very efficient. Lord Voldemort is a very smart wizard and would be able to win a simple game of chess. Instead, it could have been just an army of stone statues that attacked whoever came close.   Since the enchantments were made by Hogwarts teachers, if someone needed access, they would never actually do the tests, rather the professors would simply undo the enchantment to let (let's say) Dumbledore through.    Therefore, it seems pretty crappy to have these obstacles have a way around them. Why not just put it in a room with no doors that only Fawkes can apparate into? Then only Dumbledore would be able to get in with side-along-apparition.   Is Dumbledore intending Harry to fight Voldemort? Is there some reason someone, who was not well liked by the staff might need it who wasn't evil? They seem to be taking unnecessary risk. So, is there an actual reason? Or was it just a plot device?  Edit: As I said, I am aware of the similar question. That question asked IF the Stone was well protected. I am asking, rather, WHY was it NOT well protected? Why was there ANY possibility to bypass the protection? Why were there tests that could be passed, instead of obstacles that could not be circumvented?

The Sorcerer's (Philosopher's) stone was moved from Gringotts to Hogwarts  Dumbledore wanted the stone to be better protected.  In Harry Potter and the Sorcerer's Stone however, Harry, Ron, and Hermione, three 11 year-olds, manage to get through seven magical obstacles designed to protect the Sorcerer's (Philosopher's) Stone.   If it was possible for three first year kids to get through the obstacles, then how was the Stone well protected at at all. Did Dumbledore really expect that the teachers' defenses would work against Voldemort?


I have a Dell Optiplex-980 with an Intel-i5 CPU and 16 gb ram, is there any chance that I could install Ubuntu Server 16, 18 or 20 on it? Will it Work?

This question is here just to avoid you choosing the wrong Ubuntu version number.  So, this is not about:     nor about   nor   nor   nor   nor .   So in the answer below a simple guide as to what Ubuntu version is good for you, independent of future releases!


Is there some free software that can show CPU temperature in real time for OS X El Capitan?   doesn't provide such an option.

I tried  and  but it does not update the temperature and I do not wish to change the fan speed.


Beta plus decay seems to be violating law of conservation of mass-energy-- when a proton changes to neutron a very small quantity of Mass is added to the right side of equation -- but where does this mass come from?

$\beta +$ decay is where a proton gets turned into a neutron and a positron and a neutrino.  However, a neutron is heavier than a proton, so obviously this reaction is endothermic. So then, why does it happen? I've seen an explanation here in the question    It describes that the final binding energy of the nucleus increases, thus making it possible by becoming more stable. But what actually causes the reaction to go in the first place? It's like saying this ball will go down the hill because it will lose energy - what gives it the nudge required? Is it something like energy from external gamma rays or something?


I do not get one major plot point in James Bond, Skyfall. Why did Bond take M to the home where he grew up? Why did they ("they" as in Bond, M and the gamekeeper) want to take on Silva and his 10+ thugs alone? Why didn't they call for backup when his helicopter arrived? They weren't operating outside of the law so why didn't they involve MI6?

I think I am missing a key plot point here.   Bond had to fake-kidnap M and bring her to Skyfall in order to lure Silva there for one last stand. Why did this have to be a secret from his colleagues at MI6? Why couldn't there have been other agents there to help defend the house and take down Silva?  Also, why did he have to have Q lay a fake trail to get Silva to follow him to Skyfall when he was actually going there, and he wanted Silva to follow him?


Prove: If $G = \{a_1, a_2, ..., a_n\}$ is a finite abelian group, then $(a_1 a_2...a_n)^2 = e$, where $e$ is neutral in $G$.  I don't even now how to begin this.

Let $G$ be a finite abelian group. Prove that $(a_1 a_2 \cdots a_n)^2=e$.   My proof: $$\forall a \in \{a_1,a_2,\cdots,a_n\} \exists ! a^{-1} \in \{a_1,a_2,\cdots,a_n\}:a^{-1}a=aa^{-1}=e$$ hence, $$(a_1a_2\cdots a_n)^2=(a_1a_2\cdots a_n)(a_1a_2\cdots a_n)=(a_1a_2\cdots a_n)(a^{-1}_1a^{-1}_2\cdots a^{-1}_n)=(a_1a^{-1}_1)(a_2a^{-1}_2)\cdots (a_na^{-1}_n)=ee\cdots e=e$$  I tried showing that all $n-1$ elements in $G\setminus \{e\}$ contain a unique ($\leftarrow$ is even this true?) inverse in $G$. Is this proof valid? Should I show/explain more between the steps $(a_1a_2\cdots a_n)(a_1a_2\cdots a_n)=(a_1a_2\cdots a_n)(a^{-1}_1a^{-1}_2\cdots a^{-1}_n)$?  Thank you.


Sometimes, suspended users request deletion, which is usually provided to them.  However, if they log in again with the same OpenID, a new profile is created (attached to the same network account), with a new association bonus. No traces of their previous incarnation is left (not the deleted posts, nor the suspension record, etc).  In the case that sparked this request, a user was suspended and later self-deleted. He came back to that site much later, and started causing the same problems, asking the same types of bad questions. If the account hadn't been deleted, the first bad question would be a resuspension. Instead, the mods have to go through the intermediate steps of commenting and mod messaging because they don't know that the user has been warned before. In this case, fortunately the mods remembered and re-suspended.  If a user with some record of undesired activity requests deletion and re-logs in with the same network account, the account should be undeleted. Or moderators should at least get an indication somewhere that this is a reincarnation of a deleted account which has received this-and-this mod message before (and whatever other data is needed to ease the handling of the user).  Ideally,  would cover this, but that one is broader.

A common scenario we run into on Stack Overflow is that we have a troll, spammer, or obvious sock puppet of another user and moderators decide to delete this user. We go on about our business only to find out an hour or two later that the account we just deleted has been recreated, using the same credentials, and is now back to trolling, spamming, or committing voting fraud once again.  I've seen some people recreate an account like this using the same credentials four or five times (multiple times in the last week, in fact). The only thing that stops them is if we remember to suspend the account for right before we destroy it. Accounts recreated using the same credentials as an account that was suspended will be locked into the same suspension the old account was serving.  In particular, this becomes a real problem with sock puppet accounts that have a network association reputation bonus attached to them, because the recreated accounts keep getting that 100 point bonus and can immediately be used for voting fraud, to troll chat, or to spam comments. I've had to deal with quite a few puppet accounts like this by suspending them for a year before deletion.  I propose that all moderator-deleted accounts behave as if they were suspended for a year upon deletion, so that recreating these accounts using the same credentials will cause the new account to be locked in a one-year suspension. This would prevent the new accounts from being used to abuse the site in the same manner as their old account did.  This won't put an end to people creating new spam, troll, or puppet accounts after we delete them, but it will at least slow them down by forcing them to create new login credentials each time. It also would curb abuse of account association bonuses by puppets.


If I gave an answer with some upvotes and then I remove it, will my acquired reputation decrease proportionally to the upvote's score?

If you delete a question with a positive score will you get reputation back? Basically what I'm asking is, suppose you have a question with a score of 22, and I delete the question. Would I lose reputation? If so, how long does it take  for it to re-calculate the reputation?


I am using the 2.8 RC2  I want to create a Material that is seethrough and colored as there will be an object inside that must be visible. It will be a red Light Emitting Diode with innards.  Therefore Under "Material" > "Blend Mode" I chose Additive.  Just having a red "Principled BSDF" go into the Material Output's Surface is not enough as it is way too light on its own. Therefore i took a Principled Volume and put it into the Output's Volume slot. The color is about the same now as it would be with just an opaque surface.  But there is a problem:  The volume is also outside the containing object in what looks like a cubid around my object. I created a MRE with just a sphere with a nontransparent red surface and added volume the same way but in green for contrast.   I tried switching from EVEE to Cycles and even disabled GPU acceleration to exclude error sources.  I tried the same with Blender 2.79b (Cycles) and it works. No Volume outside of the object.  Is this a bug or did I forget something?

So I was in the middle of making a ball-shaped smoke, but the volumetric effect didn't work following the basic shape. It remains cube in Eevee Blender 2.8; while in Cycle it works, but in Cycle it takes thousands of years for Render.


I was painting the textures onto the model when I decided to do an incremental save as to not lose all my work, so I pressed Ctrl S and saved the blend file.  When I looked at Blender again (I did not close Blender at all) the object was black and I can't find the texture image I saved? Sorry, I'm really new to Blender. Here's a screen:

I was following a  on how to use the Texture Paint feature on blender so I could paint on a terrain I am modeling. I was successful to paint the whole terrain with beautiful, exuberant vegetation, and crystalline water running through the valley.  So I saved my file, and I went to sleep. But now I've reopened the file and everything seems like I left it yesterday, except that I can see no texture in the terrain... The weird thing is that the textures i used are still there... I don't understand, I barely understand the interface, please help. I'm not even sure if the texture is there or if it was never "saved" or something...     I am now going through the second part of the tutorial for possible answers but I (and hopefully many more) will be grateful for your help.


The definition of Differential Manifold or Smooth Manifold include $\text{Second countability}$ and $\text{Hausdorffness condition}$.  My question is why we include Second countability and Hausdorffness in the defintition of Differentiable manifold?  I got something from a online article that Second countability is used to exclude large space .  But I could not mean it.  Can someone explain why we take Second Countability and Hausdorffness condition ?

I've seen there are few questions similar, but I haven't seen anyone so precise or with a good answer.   I'd like to understand the reason why we ask in the definition of a manifold the existence of a countable basis. Does anybody has an example of what can go wrong with an uncountable basis? When does the problem arise? Does it arise when we want to differentiate something or does it arise before? Thank You


I am trying to build VLC player on Ubuntu 14.04.  It's been a tough road but I am learning along the way. However I am really stuck with this lib libavcodec that is required as prompted by this message.  configure: error: Requested 'libavcodec >= 57.16.0' but version of libavcodec is 54.35.0. Pass --disable-avcodec to ignore this error.   What I don't understand is why apt does not have libavcodec above 54. Is this a common issue where libs are updated, but not on apt? If so how do I got about getting the version I need?

Why are packages in the official Ubuntu repositories older than the latest (upstream) versions from Debian Sid, PPAs, the authors, etc.?


i need some help to write correct regex validation. I want password with no spaces, min. 6 symbols, doesn't matter numbers or letters or symbols. Alphabet a-zA-Z and а-яА-Я(RU). How i can do that?

I don't really understand regular expressions.  Can you explain them to me in an easy-to-follow manner?  If there are any online tools or books, could you also link to them?


Why is map imported as #include <map>, but stdio imported as #include <stdio.h>?

What is the difference between using #include<filename> and #include<filename.h> in ? Which of the two is used and why is it is used?


In metric space every convergent sequence is a Cauchy sequence, but what about the converse?

A Cauchy sequence doesn't necessarily converge, e.g. take the sequence $(1/n)$ in the space $(0,1)$.    Maybe my intuition is wrong but I tend to think of this as, "it does converge but what it converges to is not in the space".  Are there any examples of a Cauchy sequence that does not converge and avoids this type of saying?


I came across this answer which is specific to Keras. But my question is at concept level. I am getting confused, How can RNN handle variable size inputs?  The answer  says RNN can handle variable sequence inputs.  My question is, How exactly the weights matrix W (see my figure) work with different length inputs?  Let us suppose we want to do a  sentiment classification.  Training batches of different length : Which I think means all training examples in a batch must be of same length but different batches can have variable length training examples.  Now, suppose length of training examples in    batch-1 = 10,  batch-2 = 15. batch-3 = 18  ... so on   Now while training batch-1 , In the unrolled RNN there would be 10 columns in the below figure to handle input of sequence 10. By columns I mean different timestamps in RNN. The shared weights W, U,V dimensions must be in sync with sequence length. What I mean by this is,  the shared weights to handle sequence of length 10 would be something like w1,w2,..w10 (horizontal connection that connects columns.)  I understand till this part.  Now, while processing batch-2 which is of sequence length 15, The unrolled RNN must take sequence of length 15. That means there are 15 columns in the below figure  and corresponding weights will be like w1,w2,..w15.  The number of weights W changed from 10(w1,w2,...w10) to 15(w1,w2,..w15) as we go from batch-1 to batch-2.   The W dimension changes. Things don't add up here for me.   What happens to shared weights? How are they learnt?

* Note: The premise of my question was incorrect in the first place. My question assumes that an LSTM maintains a separate set of weights for each time step in the memory it is given as a design parameter. As , only a single set of weights is learned. So an LSTM cell does not care about how long a sequence is - it applies the same set of weights to each step in the sequence. Please don't let my question convolute your understanding of LSTMs.   Terminology:  Cell: the LSTM unit containing input, forget, output gates and the hidden hT and cell state cT. Hidden units/memory: How far back in time the LSTM is "unrolled". A hidden unit is an instance of the cell at a particular time. A hidden unit is parameterized by [wT, cT, hT-1]: The gate weights for the current hidden unit, the current cell state, and the last hidden unit's output. Where wT represents input, output, forget gate weights.   An LSTM maintains separate gate weights wT for each hidden unit. This way it can treat different points in time of a sequence differently. (see *Note above) Let's say an LSTM has 3 hidden units so has gate weights w1, 2, w3 for each of them. Then a sequence x1, x2,...xN comes through. I am illustrating the cell as it transitions over time: @ t=1 xN....x3    x2    x1                   [w1, c1, h0]                       (c2, h1)  @ t=2 xN....x4    x3    x2                   x1                   [w2, c2, h1]                       (c3, h2)  @ t=3 xN....x5    x4    x3                   x2    x1                   [w3, c3, h2]                       (c4, h3)  But what happens at t=4? The LSTM only has memory, therefore gate weights, for 3 steps: @ t=4 xN....x6    x5    x4                   x3    x2    x1                   [w?, c3, h2]                       (c4, h3)  What weights are used for x4 and all the following inputs? In essence, how are sequences that are longer than an LSTM cell's memory treated? Do the gate weights reset back to w1, or do they remain static at their latest value wT?  Edit: My question is not a duplicate of  question. It is asking about multi-step prediction from inputs. However, I am asking about what weights are used over time for sequences that are longer than the internal hidden cell states. The question of weights is not addressed in that answer.


I'm working on outputting multiple MySQL JSON rows to an HTML table via PHP (server side) and jQuery (front end) through a simple search box. I've successfully managed to parse one row of JSON to the table but now need to accommodate multiple rows of JSON data.  My HTML table on the search page looks something like this:  ARTIST | TITLE | LOCATION  U2     | One   | Ireland  Foals  | Miami | UK   and the JSON file passed to it utilises similar headings:  {"ARTIST":"Katy Perry","LOCATION":"United States", "TRACKTITLE":"Roar"}   I've been playing around with the code for a while, incorporating arrays to loop through the data. This works in as much as it loops through the MySQL rows correctly and successfully sends multiple rows of data back in JSON format (I've decoded my search page in Firebug). The problem is that my jQuery file can't place it into my HTML table, resulting in a blank page. I've tried various methods of arrays from previous Stackoverflow questions but can't quite get it to work, being returned the 'ARTIST', 'TRACKTITLE' and 'LOCATION' fields with every returned result  extract from PHP file:  $result = mysql_query($sql); $data = array(); while ($array = mysql_fetch_assoc($result)) { $data[] = $array; } echo json_encode($data);   Edited to include jQuery extract and more specific question:  function(data) { var sentData=JSON.parse(data) for (var i = 0; i < sentData.ARTIST.length; ++i) { tr = $('
'); tr.append("" + sentData.ARTIST + "	"); tr.append("" + sentData.TRACKTITLE + "	"); tr.append("" + sentData.LOCATION + "	"); $('#multiple').append(tr); } });   How can I parse only the corresponding values of each 'ARTIST', TRACKTITLE' and 'LOCATION' result using the JSON.parse method? This is the full returned JSON string:  [{"ARTIST":"Katy Perry","TRACKTITLE":"Roar","LOCATION":"United States"}, {"ARTIST":"U2","TRACKTITLE":"One","LOCATION":"Ireland"}]

How do I use the json_encode() function with MySQL query results? Do I need to iterate through the rows or can I just apply it to the entire results object?


I have two variables:  result = 121.0 #  initialized in code, assigned in loop dd = -121.0 #  value returned from result of function   So, when I do  result += dd    result becomes 2.84217094304e-14 (name of this representation of numbers and algorithm of reading is welcome)  But when I assign same values in python console - it returns proper result - 0.0  What is the problem?

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


Trying to write a paper and this larger vertical white space will not go away. How do I get rid of it or at least move the list up?  The code I'm using is:  \documentclass[12pt]{report}  % I cut all the packages out  \section*{Table of Contents}    \addcontentsline{toc}{section}{\protect\numberline{}Table of Contents}   \tableofcontents   I believe that is all the reliant code.   Please help, thanks in advance

I've been trying to figure out a way to easily reduce the space/gap from the top of the page to the table of contents title, as in to reduce the vertical space before the table of contents begins.  Below is my MWE:  \documentclass[final,a4paper,11pt]{report}  %%% Packages %%% \usepackage[hidelinks,breaklinks]{hyperref} % hyperref for linking references for pdf \usepackage{tocloft}    % tocloft for table of contents style \usepackage[compact]{titlesec}  % titlesec for title section layout  % Format the title for chapters \titleformat{\chapter}[hang]{\huge\bfseries}{\thechapter.}{1em}{} \titlespacing*{\chapter}{0pt}{-3em}{1.1\parskip} \titlelabel{\thetitle\quad}  % Begin document \begin{document}  \tableofcontents \addtocontents{toc}{\vskip-40pt} % this is to reduce the gap for the first table of contents entry  \clearpage  \chapter{Introduction} \section{Background} Need to reduce the space before the Contents title, was able to reduce the space before chapter fine. \end{document}   How does the report class handle the table of contents? It doesn't seem to be a chapter, else it would have moved up when I changed the chapter spacing?


I tried installing rails according  to , and when I do, I get this error:  $ sudo gem install rails   WARNING:  Error fetching data: Errno::ENOENT: No such file or directory - getaddrinfo (http://rubygems.org/specs.4.8.gz)   WARNING:  Error fetching data: Errno::ENOENT: No such file or directory - getaddrinfo (http://rubygems.org/latest_specs.4.8.gz)   Building native extensions.  This could take a while...   ERROR:  Error installing rails:       ERROR: Failed to build gem native extension.            /usr/bin/ruby1.9.1 extconf.rb   /usr/lib/ruby/1.9.1/rubygems/custom_require.rb:36:in `require': cannot load such file -- mkmf (LoadError)       from /usr/lib/ruby/1.9.1/rubygems/custom_require.rb:36:in `require'       from extconf.rb:1:in `<main>'     Gem files will remain installed in /var/lib/gems/1.9.1/gems/json-1.8.0 for inspection.   Results logged to /var/lib/gems/1.9.1/gems/json-  1.8.0/ext/json/ext/generator/gem_make.out   I've never seen anything like this before, so any feedback would be greatly appreciated.

I am using Ubuntu 14.04. I wanted to use the latest ruby (version 2.1.3), so I installed it with RVM.  rvm install ruby --latest rvm use ruby --latest --default   But when I try to install Rails, i get the following error:  vagrant@vagrant-ubuntu-trusty-64:~$ sudo gem install rails Building native extensions.  This could take a while... ERROR:  Error installing rails:     ERROR: Failed to build gem native extension.          /usr/bin/ruby1.9.1 extconf.rb /usr/lib/ruby/1.9.1/rubygems/custom_require.rb:36:in `require': cannot load such file -- mkmf (LoadError)     from /usr/lib/ruby/1.9.1/rubygems/custom_require.rb:36:in `require'     from extconf.rb:1:in `<main>'   Gem files will remain installed in /var/lib/gems/1.9.1/gems/json-1.8.1 for inspection. Results logged to /var/lib/gems/1.9.1/gems/json-1.8.1/ext/json/ext/generator/gem_make.out   What is wrong?


New here, so apologies if it has been asked before.  I was curious as to whether Its known when TRIM first started being implemented into SSD’s?

From the Wikipedia page of  I get the impression that TRIM was introduced to lower the writes to a SSD, but letter the file system taking case of which blocks are unused.  If that is correct, does that mean, that SSD's that don't use TRIM writes zeros to the blocks, when a file is deleted, to let the SSD know the blocks are free?  Reading      File systems within a guest tend to   not reuse blocks which means that even   if a file system remains small   relative to the virtual image size,   the actual image size tends to grow   until it reaches the maximum size.   leads me to think, SSD's don't overwrite with zeros? Or are file systems in guests, something completely different?


There is a word in Russian "отписка", which could mean "unsubscription" but also has in some context could mean "written reply in a very formal way with no intent to really help". Like a very polite "fuck off" reply. So I feel like there should be a similar idiom or a slang word for this in English. Are there any?

A financial planner treated us in a dismissive fashion and I want to say that he "gave us the back of his hand" but that phrase doesn't seem to have the meaning of dismissive. Does it or is there a similar idiom?


Let $a, b, c$ be positive real numbers such that $abc=1.$ Prove that:  $$\left(a-1+\dfrac1b\right)\left(b-1+\dfrac1c\right)\left(c-1+\dfrac1a\right)\le1$$  or equivalently:  $$(ab-b+1)(bc-c+1)(ca-a+1)\le1$$  What I have tried:  Computing $\left(a-1+\dfrac1b\right)$ using $abc=1$ and similarly computing others and then multiplying them. But it didn't help.  Any help will be appreciated.

Let $a,b,c\in\mathbb{R}^*_+$, $abc=1$.  How can i show that $\left(a-1+\frac{1}b\right)\left(b-1+\frac{1}c\right)\left(c-1+\frac{1}a\right)\leq1$ ?  I got $\left(ab-b+1\right)\left(bc-c+1\right)\left(ca-a+1\right)\leq abc=1$, but i can't go any further ...  If i expand it :   $2-ab-\frac{b}a-c-ac-\frac{a}c-b+2a+\frac{2}a-bc-\frac{c}b-a+2b+\frac{2}b+2c+\frac{2}c-4$  Which gives using $c=\frac{1}{ab}$ :   $5ab-\frac{b}a-\frac{1}{ab}-a^2b+\frac{1}a+b+\frac{1}b-2$


Suppose I have a string "IICCIICCIICBIICCIICDII". The string is of the pattern II[CBD][CBD]II[CBD][CBD]II... It is a repeated pattern. Now I am trying to find all overlapping substrings which satisfies following condition:   Substring does not start or end with letter I. Suggested solution: (?<=[CBD]), (?=[CBD]) Substring contains at least(but as less as possible) certain number of occurrences of letter C, B, and D. These letters can exist in any permutation and can have different number of occurrences. Suggested solution: something along the lines of [C]{m, n}?  These pre-defined numbers are variable so that I can dynamically generate regex with change in requirement for these variables. Order and number of occurrences of letter I doesn't matter Adding to condition 1: Start/end of a substring can't have two occurrences of [CBD] (e.g., CCIIB or BIICC is an invalid match) (sorry about that)   For example, for a pattern with at least 2 Cs: CIIC (three of them), 2 Cs and 1 B: CIICBIIC, BIICCIIC  I do not think my question is similar to the question quoted in one of the answers. I have looked at that question (titled "shortest repeated substring"). My question differs in the sense that repeated pattern needs to have a certain number of occurrences of certain characters. The question quoted is just finding shortest repeating pattern. That question IS helpful though.  Let me know if the question is clear and not a duplicate. Thanks.

I can't seem to find an answer to this problem, and I'm wondering if one exists. Simplified example:  Consider a string "nnnn", where I want to find all matches of "nn" - but also those that overlap with each other. So the regex would provide the following 3 matches:   nnnn nnnn nnnn   I realize this is not exactly what regexes are meant for, but walking the string and parsing this manually seems like an awful lot of code, considering that in reality the matches would have to be done using a pattern, not a literal string.


What are workspaces in Ubuntu? What do these workspaces do exactly? Is their any documentation I can refer to?

Is a viewport different from a workspace? What's the distinction? It seems like the terms get used interchangeably.   I'm trying to accomplish something that other people have been stabbing at for a while -- I have a script that launches a bunch of programs at once and I'd like to launch them in a specific workspace. The question's been asked:      But the answers hop between talking about "viewports" and "workspaces" -- how are they different?


Does 5e large scale battle exist in spreadsheet form, or is it more ethereal like making strategic and creative decisions and inspiring the DM in roleplay?

For instance, a party of four player characters raise a force of 30 militia men to go take a bandit camp. When they get there the bandit camp has 40 men, and none of them notable.  For the sake of simplicity, both the 30 men and the 40 bandits are armed with long swords, and wearing leather armor.   Is there a proper way to handle combat between the 30 man militia and the 40 bandits while also incorporating our four player characters? If no "proper" way exists, is there a generally accepted "best" way?


I've been  and am interested in gaoithe's answer for        Does the disk usage really go up when free space declines? If so, why?      I can see why this can happen with a HDD, but can this happen with an SSD?  I have a 128GB Corsair M4 SSD, with only 3GB space left; is this drive performing poorer than if it had 40GB space available?  If so, why?

I was wondering if having less than 5-10GB of free space on an SSD would affect performance. Is it specific to SSD or is it more of an operating system aspect?  For example, on an Intel X-25 G2 that has TRIM support (on Windows 7).


I am watching , and at 3:45 Justice Scalia says he gets upset when he hear "infer" used to mean "imply"  Is there any real world example of "infer" used to mean "imply"? Why "infer" cannot be used to mean "imply"? What's the correct usage of "infer"?

Okay that's a crazy title, but bear with me.  Got into a good natured discussion with someone on another stack exchange site, and I was "correcting" him on the use of infer vs. imply.    (The discussion can be found here: )  He pointed me to a dictionary entry for "infer" that seems to use the definition for imply.    The 4th definition that is given there reads:     suggest, hint  -  "are you inferring I'm incompetent?"    That, to me, is a classic example of where someone should not use "infer", but should use "imply".  But maybe I'm wrong?  Granted, it's the 4th of four definitions, and so presumably less common, but I thought the two, "imply" and "infer" had totally distinct meanings.  According to definition #4 on that link "infer" can imply "imply".    Am I nuts?  Am I the only one surprised by this?  (very possible...I'm often surprised by English).  Or is it possible that the dictionary is...something less than accurate?  It's not a mom-and-pop shop, so that seems unlikely...but I throw it out there as a possibility...but if the dictionary is wrong, where do you go to to find evidence of it?  (Who watches the watchmen?)


Can someone please explain the use of const when its being used in function declarations and classes? I understand that if a function returns a const variable/object, then that thing can not be used on the left side of an assignment operator? Is this correct? Also, i noticed that if you were to do:  int x = 1; int &i = x;    The above code would not compile unless i were a "constant reference" to the int. For functions, do the arguments passed into the function parameters have to be constant if the parameters are declared constant?   One example of my book has the following code:  const Array &Array::operator=(const Array &right) { if (&right != this) //avoid self assignment   //blah blah return *this; //enables x = y = z for example }   Why does this function permit the object Array assignments such as x = y  = z but prevents ones like (x = y) = z?? The book's reasoning is "because z cannot be assigned to the const Array reference that's returned by (x = y). But in the first case, doesn't x = y also return a constant Array reference???  Also, when you do assign 1 object of a class to another, the compiler uses member wise assignment unless the the user provides a default copy constructor, in which case THAT is invoked right?  Thankyou so much! Sorry I have a lot of specific questions. I greatly appreciate it.

As a novice C++ programmer there are some constructs that look still very obscure to me, one of these is const. You can use it in so many places and with so many different effects that is nearly impossible for a beginner to come out alive. Will some C++ guru explain once forever the various uses and whether and/or why not to use them?


As we all know, Superman is invulnerable, nothing can harm him except kryptonite. We always see Superman in clean shave. So how is it possible, and with what blade does he shave?

I've seen several times when Superman is sporting a beard. How does he shave his indestructable hair?  I remember once in Superman the Animated Series that he used his heat vision, but that doesn't make sense to me seeing as he can fly through a star and not get burned.  Also related, how does he go from Super Mullet to short hair? IE, how does he cut his hair?


Today I received a spam message with the topic of n question at Stackoverflow:     Topic: Re: chrome.identity.getAuthToken cannot get Token in Chrome   Extension      Hi Ole,      Just wondering if you ever got this question answered.  If not, maybe   a brief chat with a Javascript wizpert could help: link (Link removed)      [...]   As this seems quite focussed on my SO-Post and my Mail is private: How did they do that? What can I do to stop that in the future?

Well today as I was going home I got a strange email, in my private inbox (email associated with S.O.) asking me if I had solved a question on S.O. that I didn't ask. To be more precise I had given an answer.   After reading:       and several other email related issues on S.O. I decided to let you all know about this because probably I am not the only one.   So the mail subject was:     Re: Deleted facebook account - Cannot access my apps?   which refers to   And the body (masked last name of sender):      Hi Jimmy,      Just wondering if you ever got this question answered.  If not, maybe   a brief chat with a html wizpert could help: link   .      Good luck getting this resolved!      Cheers,      Michael      ------------------------- Michael W%^%^GF Founder, CEO @ Wizpert   Now I know that my email address is not visible and I read about the MD5 regarding gravatar but I don't think this is the case. I thought about some methods and sure it's possible via metadata, github, etc for someone to get my mail, but I do not dare to think that this has reached an automated level, so that some service could easily get the email of S.O. members.   I didn't get annoyed by the message, since the CEO took the time to contact me :-p but someone else could get annoyed by these kinds of messages, since they come in the important inbox of gmail.   What is more strange is that Wizpert seems to be a nice site and also is active in the Careers 2.0 if I am not mistaken.   Another thing that crossed my mind is that since Wizpert needs unanswered questions to promote their services, possibly this is an action of Wizpert trying to attract people into their services.   Well that's it, I hope I did good to let you know (maybe I did't include the correct tags).


There's a list of people whose info should be fetched. I have made a simple pagination for that list. However, List looks fine, but the buttons does not work after the first page. Here is the HTML Code:
  <input type="text" class="search" style="width: 50%" placeholder="Search..." />

<button id="people_1" class="btn btnlink name">People 1</button>

<button id="people_1" class="btn btnlink name">People 1</button>

<button id="people_2" class="btn btnlink name">People 2</button>

<button id="people_3" class="btn btnlink name">People 3</button>

<button id="people_4" class="btn btnlink name">People 4</button>

<button id="people_5" class="btn btnlink name">People 5</button>

<button id="people_6" class="btn btnlink name">People 6</button>

<button id="people_7" class="btn btnlink name">People 7</button>

<button id="people_8" class="btn btnlink name">People 8</button>

<button id="people_9" class="btn btnlink name">People 9</button>

<button id="people_10" class="btn btnlink name">People 10</button>

  Library:      Here is The jQuery code: var monkeyList = new List('test-list', {   valueNames: ['name'],   page: 5,   pagination: true, });  for button click: $(document).ready(function() {                         $(".btnlink").on("click", function(){                                                   var id = $(this).attr('id');          alert(id); }); });  After first page, button click doesnt give alert, not working; i also tried event binding functions, but doesnt work also.

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


I'm a French citizen with a US J1 visa that will expire in 2 days. In 2 days I will visit Canada, and I would like to re-enter USA 10 days later just to take my flight back to France. I thought it was possible for up to 1 month after visa expiration, but I just heard that I was wrong. Can I make an ESTA to re-enter US, stay 1 day waiting my flight, and leave? And if it is theoretically possible, is it still possible knowing that I do not have much time left?

I'm from Italy and I had a J1 visa for the US for a year and a half. Now it's expired (I'm in the grace period) but I want to stay longer in California to travel a little bit, because this year I did this trainee-ship and I didn't have the possibility to visit all places that I wanted to.  The question is: Can I go to Canada and come back to the US with an ESTA? I'm not subject to the two years rule to go back to Italy? Is it risky after a J1? Do they believe me? How can convince them that I want to travel a little?   Is it easier to do this via Canada than Mexico? My lawyer said yes but I want to be sure.


public class MainActivity extends FragmentActivity {     TextView textView = (TextView) findViewById(R.id.textbox);      //rest of code.........   Above code generates the following exception,      Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.view.Window.findViewById(int)' on a null object reference     at android.app.Activity.findViewById(Activity.java:2090)     at com.example.kuldeep.myapplication.MainActivity.<init> (MainActivity.java:24)   When I debugged this, I come to know that this code is executed even before the onCreate() method.  How is this possible? and How to catch this type of exceptions?

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


$a$ and $m$ are natural numbers and $a>1$. Prove that $m | \phi(a^m -  1)$.   Any hints how can I prove this statement?

I need to show that $n$ divides $\phi(a^n -1)$ where $a, n$ are positive integer without using concepts of abstract algebra  I know that $$a^n\equiv 1\pmod {a^n-1}$$  How do I proceed from there?


When Dobby speaks to Harry Potter:  Dobby has heard of your greatness, sir...but never has he been asked to sit down by a wizard, like an equal.  Why does Dobby hesitate to say "I"?

In the Potterverse we see house elves speak broken English. Winky is the best example     House elves does what they is told. I is not liking heights at all, Harry Potter...but my master sends me to the top and I comes, sir.   But in fact they all speak oddly. Given the fact that most of them seem to live in British families for their whole lives it is strange they can't speak properly.  I can see two reasons why a person would speak broken language:   They are not native speakers Their IQ does not allow them to grab the complicated grammar   In case of house elves we can consider both reasoning. Or can we?..


Prove that for positive real numbers $a,b,c$ we have $$\dfrac{a}{b+c}+ \dfrac{b}{a+c}+\dfrac{c}{a+b} \geq \dfrac{3}{2}.$$   Attempt  I tried using AM-GM and got $ \dfrac{a}{2\sqrt{bc}}+\dfrac{b}{2\sqrt{ac}}+\dfrac{c}{2\sqrt{ab}} \geq \dfrac{a}{b+c}+ \dfrac{b}{a+c}+\dfrac{c}{a+b}$ but that doesn't seem to help since that gives an upper not lower bound.

I am currently attempting to prove the following inequality   $\dfrac{a}{b+c}+\dfrac{b}{a+c}+\dfrac{c}{a+b} \geq \dfrac{3}{2}$ for all $ a,b,c>0$   My instinctive plan of attack is to use the AM/GM inequality with $x_1=\dfrac{a}{b+c}$ etc.  Using that I get this  $\dfrac{a}{b+c}+\dfrac{b}{a+c}+\dfrac{c}{a+b} \geq 3\times \sqrt[3]{\dfrac{abc}{(a+b)(b+c)(a+c)}}$   From here, I used the fact that $(a+b)(b+c)(a+c)\geq 8abc$, which can be easily proven by considering that $a+b\geq 2\sqrt{ab}$   But by using this, I get the following...  $\dfrac{a}{b+c}+\dfrac{b}{a+c}+\dfrac{c}{a+b} \geq 3\times \sqrt[3]{\dfrac{abc}{(a+b)(b+c)(a+c)}} \leq 3 \times \sqrt[3]{\dfrac{abc}{8abc}} = \dfrac{3}{2}$   Everything seems so perfect because I get the value $\dfrac{3}{2}$ as required, but this method isn't valid due to the change in direction! What is going on?  Is there a way of proving this inequality otherwise then?


I would like know if it is allowed creating a package with a KVM virtual machine + Ubuntu as OS and sell this package. Is there any restriction due to copyright or fees to pay?  I would not modify anything on the KVM or Ubuntu (just add java & firefox), just add my scripts on Ubuntu for the customers. I saw that KVM's parts are licensed under various GNU licenses:   KVM kernel module: GPL v2 KVM user module: LGPL v2 QEMU virtual CPU core library (libqemu.a) and QEMU PC system emulator: LGPL Linux user mode QEMU emulator: GPL BIOS files (bios.bin, vgabios.bin and vgabios-cirrus.bin): LGPL v2 or later   And ubuntu with GNU GPL. Any idea?  Thanks for your feedback!

My question is next: "Can I modify some version of Ubuntu Linux, add some software related to electrical engineering, modify look and some functions of Ubuntu, basically customize the entire system so it suits the needs of electrical engineers working on the field or in the office, and then that customized system sell in order to make profit?"   I'm not sure am I allowed to do that (is it legal?), so I would appreciate answer.


I have a large file, but I need a part of it, the lines between line m (1000) and line n (2000).  How can I get it? (and put it into a new smaller file, or print on screen)

I have a ~23000 line SQL dump containing several databases worth of data. I need to extract a certain section of this file (i.e. the data for a single database) and place it in a new file. I know both the start and end line numbers of the data that I want.  Does anyone know a Unix command (or series of commands) to extract all lines from a file between say line 16224 and 16482 and then redirect them into a new file?


This is in my preambule: \usepackage[ backend=biber, style=numeric, sorting=ynt ]{biblatex} \addbibresource{literatura.bib}  I have a literatura.bib file containing this: @book{latexcompanion,     author    = "Michel Goossens and Frank Mittelbach and Alexander Samarin",     title     = "The \LaTeX\ Companion",     year      = "1993",     publisher = "Addison-Wesley",     address   = "Reading, Massachusetts" }  In main file I have this: \printbibliography  And this is how I cite it: \cite{latexcompanion}  This produces no bibliography and no results, other than [latexcompanion]  where the citation is placed, which is not clickable. What am I doing wrong? EDIT: .blg output: This is BibTeX, Version 0.99d (TeX Live 2019/Debian) Capacity: max_strings=200000, hash_size=200000, hash_prime=170003 The top-level auxiliary file: literatura.aux I found no \citation commands---while reading file literatura.aux I found no \bibdata command---while reading file literatura.aux I found no \bibstyle command---while reading file literatura.aux You've used 0 entries,             0 wiz_defined-function locations,             83 strings with 494 characters, and the built_in function-call counts, 0 in all, are: = -- 0 > -- 0 < -- 0 + -- 0 - -- 0 * -- 0 := -- 0 add.period$ -- 0 call.type$ -- 0 change.case$ -- 0 chr.to.int$ -- 0 cite$ -- 0 duplicate$ -- 0 empty$ -- 0 format.name$ -- 0 if$ -- 0 int.to.chr$ -- 0 int.to.str$ -- 0 missing$ -- 0 newline$ -- 0 num.names$ -- 0 pop$ -- 0 preamble$ -- 0 purify$ -- 0 quote$ -- 0 skip$ -- 0 stack$ -- 0 substring$ -- 0 swap$ -- 0 text.length$ -- 0 text.prefix$ -- 0 top$ -- 0 type$ -- 0 warning$ -- 0 while$ -- 0 width$ -- 0 write$ -- 0 (There were 3 error messages)

Running the minimal example  \documentclass{article} \usepackage{filecontents} \begin{filecontents*}{\jobname.bib} @ARTICLE{example,   author  = {Other, Anthony Norman},   title   = {Some things I did},   year    = {2014},   journal = {J.~Irrep. Res.},   volume  = {1},   number  = {1},   pages   = {1-10} } \end{filecontents*} \usepackage[backend=biber]{biblatex} \addbibresource{\jobname.bib} \begin{document} Hello\cite{example}. \printbibliography \end{document}   I get the warning There were undefined references.  I have read  and know that I need to run:   LaTeX Biber LaTeX   However, my editor is only set up to run BibTeX. How do I go about setting up my editor/IDE to be able to run Biber, and how do I run the LaTeX/Biber/LaTeX cycle?  Answers (sorted alphabetically by editor name)                    Answer guidelines   Each answer should be for one editor. If the editor is cross-platform, if possible give a single answer with notes covering the minor platform variations. Please edit the question to include new answers in the 'link list' Each answer should be 'stand alone', i.e. don't say 'It's almost the same as editor Y but ...' for the editor part Instructions for 'build tools' such as arara or latexmk are welcome but should explain how to set up the editor in question as not all editors allow simple addition of arbitrary tools


I'm asked if $\mathrm Z_9$or $\mathrm Z_{17}$ under multiplication is cyclic or not, proof needed. I understand the rules with addition, but under multiplication i can't make sens of the rules. I tried to manually calculate it with but did not find a generator thus i assumed that it is not cyclic but with $\mathrm Z_{17}$ it's a little bit more excruciating, what is the best way to prove if a group like this is cyclic or not? thanks in advance.

How to find generators of $(\mathbb Z_{17}-\{0\},\times)$?  Is there a faster way to find generators than trying every element in the group?  I know that for additive group, if a number say m is relatively prime to n (in this case 17), then it's a generator of that group. Do we have something like this for multiplicative group?


X works but Y does not. Whats the difference between X and Y? And passing them as base reference to foo? class Base { }; class Derived : Base{};  void foo(Base& p) {}  int main() {     Derived x = Derived();     Derived y();      foo((Base&)x);     foo((Base&)y); }

Is there any good reason that an empty set of round brackets (parentheses) isn't valid for calling the default constructor in C++?  MyObject  object;  // ok - default ctor MyObject  object(blah); // ok  MyObject  object();  // error   I seem to type "()" automatically everytime. Is there a good reason this isn't allowed?


This is purely out of curiosity. But if I were to type in the IP of a website, would the request still go through the forward lookup process? If not, at what point and by which step is it realized that this is the location by IP and not a hostname as a string?   Also, how would this be recorded in my hostfile? If it goes through the entire lookup process, will the hostfile contain the string hostname as well as the IP and populate locally?

If I use a name like "www.example.com" to go to a web page, the browser will start from right to left, looking at the TLD to find the domain and then proceed further. If I enter the IP address of that host, how will the browser parse it?


I have a map with location of schools within districts. I was wondering if I can extract all fields of each data point within a polygon and how to go about doing it in ArcMap 10.5?  I produced this map by overlaying a district boundary map (shapefile) and a csv file of school attributes including XY coordinates of the schools. The file includes more than 60 fields for each school, including the XY coordinates.  What I want is a list of schools per district, including the 60 fields. For instance - schools_within_district_A.csv and schools_within_districtB.csv, and so on. If there are 20 schools within one district (one polygon), I would like to obtain the fields for the district. So basically this is equivalent to subsetting the overlayed data by one district.  I tried looking into spatial join, but this seems to find the sum of attributes per polygon. What I want is not the sum but all of the individual fields for each school for a selected district.    For each data point, I have more than 60 fields, including categorical and dummy variables:   My boundary shapefile looks like this, where name is district name:   And my desired excel output would look like this, for a selected district, assuming that the district has 7 schools within:

I need to develop a process for merging the attributes of each point in a SDE feature class with a polygon in a SDE feature class that contains the point to create a third feature class. The third feature class should contain the attributes of the point with the geometry of the polygon. This seems to be a spatial join. Is that assumption correct?  The points represent incident locations. The polygons represent counties. The team is requesting I intersect the incident with the county to create the third feature class. There will be multiple incidents per county so they expect to see a row for each incident and the county geometry will be repeated.  I've been using ArcToolbox > Analysis Tools > Overlay > Spatial Join. Setting the Target Feature to the incidents layer and the Join Features to the counties layer yields the correct number of rows but the geometry is a point. I need a polygon. Switching the Target Feature and Join Features yields the correct geometry but not the correct number of rows.  How should I be approaching this?


Suppose we have a dependent variable $Y$ that has normal distribution with a mean of $0$. If I run a regression model using the absolute value of $Y$, $|Y|$, i.e. $|Y| = b_1 + b_2 X + u$, my dependent variable is actually truncated at $0$. My guess is that then OLS is not efficient anymore. What would be the usual model to use in this case? Tobit? And what would happen with the OLS estimates – are the coefficients still unbiased and only the standard errors are wrong (or OLS is inefficient) or are the coefficients biased?

I have the following model: $$ |X| = B_0 +B_1 \cdot y + B_2 \cdot z , $$ where $z$ and $y$ are normally distributed random variables, and $B_1$ and $B_2$ denote the coefficients.   My dependent variable contains either the positive or negative values of $X$. The positive and negative values of $X$ together are normally distributed, with a mean and median of around zero. For statistical reasons I would like to separately test the positive and negative values. This splits the left and right side of the otherwise normally distributed variable $X$. This clearly violates the normality assumption used for linear regression models. If I want to compare groups I would use a nonparametric type of test, but in this case I want to run the equivalent of a linear regression.  Is this possible?


I would like embed my module JS / CSS files only in specified cases. Like on a /url/ or if a custom content type is rendered?

I am trying to set particular javascript files for a specific node page by getting the path alias. like this:  $path=drupal_get_path_alias();   if($path == 'about-us')   drupal_add_js(drupal_get_path('theme', 'mytheme') . "/page-download.js");   which it doesnt work.  But when i add the particular javascript file to my .info file it works.  Also in other pages i will have to unset some of the javascript files if the above does not work but still unsetting javascripts does not work.   unset($vars['js']['all']['page-download.js']);


I searched for the phrase "Cross Post" here in meta stack overflow. Still unclear on how it applies to my current circumstances.   I have a problem. I went to some length to document the entire procedure (with screen caps at every step) and posted a question about it  three days ago. Still no answer. Will my reputation be hurt if I post it in the regular stack overflow ?   Perhaps a better question is: Where are the experts who know what to do in this case ?   For the moment, I want to know if it's okay to post a shorter version of the question to other Stack Exchange sites, and link to the SuperUser question to provide the details.

It is possible to migrate a question from one Stack Exchange site to another by closing, but if I have a question that I think is on-topic for multiple Stack Exchange sites, is it OK to post it on both (multipost)?   For example, I have a question that's earned me the tumbleweed badge on SO and I'm not sure what the best thing to do with it is. It's about a web server so it might be answerable on Server Fault but it's really more of a programming thing, hence the posting the question on Stack Overflow.    Is there any way to make the question visible on multiple sites (crosspost) and then accept the answer wherever it came from?


I don't understand how there is an uncountable infinite amount of real numbers. Why can't we do the same thing with fractions (there is a countable amount of fractions). We do this by creating a table where the horizontal axis lists all the numbers from 0 too infinity. The vertical axes lists all the powers of ten from 0 too -infinity. If we would fill the table we would have all real numbers. We can make a list of this by drawing a line criss-cross through the table. This table can be viewed by clicking the link.    Could somebody please explain what is wrong with my thinking. Thank you.

I was just thinking about this recently, and I thought of a possible bijection between the natural numbers and the real numbers.  First, take the numbers between zero and one, exclusive.  The following sequence of real numbers is suggested so that we have bijection.    0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 0.01, 0.02, ... , 0.09, 0.10, 0.11, ... , 0.99, 0.001, 0.002, ... , 0.999, 0.0001, etc.  Obviously, this includes repeats, but this set is countable.  Therefore, the set of all numbers between zero and one is a subset of the above countable set, and is thus countable.  Then we simply extend this to all real numbers and all the whole numbers themselves, and since the real numbers, as demonstrated above, between any two whole numbers is countable, the real numbers are the union of countably many countable sets, and thus the real numbers are countable.    Please help me with this.  I understand the diagonalization argument by Cantor, but I am curious specifically about this proof which I thought of and its strengths and flaws.  Thanks.


$$A = \lim_{n\to\infty} \left(\binom{n}{0}\binom{n}{1}\binom{n}{2}\dots\binom{n}{n}\right)^{1/n(n+1)}$$ We need to find the value of $A$.  My attempt: I tried taking log both the sides and went from there. $$ \ln A = \lim_{n\to\infty} \bigg(\frac1{n(n+1)} \bigg[(n+1) \ln n! - 2 \sum_{k=0}^n(n-k+1) \ln k )\bigg]\bigg)$$ I don't know how to proceed from here. Also, can we some how utilize gamma function in this question since we will be dealing with factorials?

I am facing difficulty with the following limit. $$ \lim_{n\to\infty}\left(\binom{n}{0}\binom{n}{1}\dots\binom{n}{n}\right)^{\frac{1}{n(n+1)}} $$ I tried to take log both sides but I could not simplify the resulting expression. Please help in this regard. Thanks.


I get warnings from biber:  Biber warning: [1960] Utils.pm:193> WARN - BibTeX subsystem: warning: comma(s) at end of name (removing) Biber warning: [1960] Utils.pm:193> WARN - BibTeX subsystem: author, warning: comma(s) at end of name (removing)   but the bib file I'm using has more than 10,000 entries so manually finding these is not possible. How can I find the entry or entries that cause biber to emit these warnings?

When I run bibtex on document with a citation such as \cite{European00Presidency} and the .bib entry looks like this:  @MISC{European00Presidency,       author = {European Council,},   title = {Presidency conclusions},   year = {2000},   keywords = {Lisbon Strategy},   publisher = {European Council,},   type = {Government Document},   url = {http://www.consilium.europa.eu/uedocs/cms_data/docs/pressdata/en/ec/00100-r1.en0.htm} }   I get the very unhelpful warning message that " "European Council," has a comma at the end for entry European00Presidency" Which i really don't care about. But it hides other warnings such as entry not found or what ever. I would like to turn that warning off in Bibtex. Does anyone know how to do that.   I'm using MikTex 2.9, Jabref 2.9.2 and texmaker 4.1.1  As this is a problem for anyone dealing with large numbers of corporate authors I think there should be an option of changing this


Setup  Introducing this spinorbital notation:  \begin{align} \Psi_1=\chi_{(r1)}\alpha_{(\omega1)}  &= 1 \\ \Psi_1=\chi_{(r1)}\beta_{(\omega1)}  &= \bar{1} \end{align}  and the Slater's determinant, for a system of two electrons, is:  \begin{align} |\Psi\rangle = \frac{1}{\sqrt{2}}\cdot \left|  \begin{array}{cc} 1 & \bar{1}  \\ 2 & \bar{2}  \\ \end{array}  \right| = |1\bar{2}-\bar{1}2\rangle \end{align}  Question  Based on the example, what would be the Slater's determinant representation for an excited state like $\Psi_a^r$ (i.e. with parallel spins like: $|\bar{1}\bar{1}\rangle$ or $|\bar{1}\bar{2}\rangle$) and $\Psi_{ab}^{rs}$ (feel free to use any number) ?

Setup  Introducing this spinorbital notation:  \begin{align} \Psi_1=\chi_{(r1)}\alpha_{(\omega1)}  = 1 \\ \Psi_1=\chi_{(r1)}\beta_{(\omega1)}  = \bar{1} \end{align}  and the Slater's determinant, for a system of two electrons, is:  \begin{align} |\Psi\rangle = \frac{1}{\sqrt{2}} \Big|  \begin{array}{cc} 1 & \bar{1}  \\ 2 & \bar{2}  \\ \end{array}  \Big| = \frac{|1\bar{2}\rangle-|\bar{1}2\rangle}{\sqrt2} \end{align}  Question  Based on the example, what would be the Slater's determinant representation for an excited state like $\Psi_a^r$ (i.e. with parallel spins like: $|\bar{1}\bar{2}\rangle$) and $\Psi_{ab}^{rs}$ (feel free to use any number) ?


I searched a lot to find information about why I can't open .desktop files from nautilus but in  vain. Well I could open .desktop in Ubuntu 20.04 but in Groovy Gorilla, No I can't. I tried changing preferences but none came to any help either. And When I choose to be asked whether to open or edit in preferences then a dialog box does crop up and I click Run it just vanishes and nothing happens. But I can run these files from desktop well because this isn't part of nautilus I guess. I know it's not that important but though when I remember I could do that in previous version I can't help but try this to make possible. So any help here? And as a side note, I saw lots of videos which they even have icons in .desktop files(might be 19.10 or so).

After installing the latest Ubuntu I find that the icons in the applications folder (viz. /usr/share/applications), when opened in the Files application (Nautilus), come up as a blank page with a gear in the middle. If I try to open them I get a read only text box.


I have confusion about said and told.   It may seem like very small thing, because said and told are synonyms, but I wonder if there are times when one is more appropriate or correct than the other.

a.1) He said he was moving to New York.    a.2) *He said me he was moving   to New York.      b.1) *He told he was moving to New York.    b.2) He told me he was moving   to New York.   Why is a.2) wrong, but b.2) is right?   Can anybody explain what the difference between these verbs (say, tell) is, obviously with regard to the rule, if any, for which "me" has to be omitted in a.1) but not in b.2).


I just read about inductively defining a set as follows :         Take a set of objects U.   Take a set of starting objects B ⊆ U.   Let C be the smallest subset of U that contains B and is closed under all operations on some class F.           Any set S that contains B and is closed under all operations in F is called inductive.           For example , consider the set of natural numbers as :          U = R , B = {0} and F = {S} where S(x) = x+1        My Question is can we define positive Real Numbers as follows :      U = R , B = [0 , 1) and F = {S} where S(x) = x+1    If so , can we prove property P(x) of positive real numbers inductively as follows :        P is true in interval [0,1).   If P(x) is true ,P(x+1) is also true.

One of my Fellows asked me whether total induction is applicable to real numbers, too ( or at least all real numbers ≥ 0) . We only used that for natural numbers so far.  Of course you have to change some things in the inductive step, when you want to use it on real numbers.  I guess that using induction on real numbers isn't really possible, since $[r,r+\epsilon]$ with $\epsilon > 0$, $r \in \mathbb R$ is never empty.  Can you either give a good reason, why it isn't possible or provide an example where it is used?


I would like to use git to track changes in crontab.  I have initialized a new git repository in /var/spool/cron/crontabs/  Now the problem is, when crontab is saved, the second line of the header changes because it contains timestamp.  # DO NOT EDIT THIS FILE - edit the master and reinstall. # (/tmp/crontab.ubNueW/crontab installed on Thu Aug  1 06:29:24 2019)   What would be the easiest way to ignore these irrelevant changes ?  The  does not address the main point of my question: How to ignore the first 2 irrelevant lines from crontab. Instead, it addresses some other questions which I have not asked, such as some hooks.

On OpenBSD and with OpenBSD's  and , is it possible to store the  of a user in a  repository of the same user?  What would be the proper way to accomplish something like this?  (To steer the answer into the correct direction, I would not be opposed to changing some permissions in the system, although I'd rather not have to recompile the binaries, nor violate any good security paradigms.)


I am trying to prove the above proposition. I tried to prove it by way of contradiction letting $S$ be such nonempty proper subset of $R$. Then $T=R-S$ would also be a nonempty proper subset of $R$ which is both open and closed. The method I thought of to lead contradiction is to create a sequence like this.   Take $s_0$ from $S$ and $t_0$ from $T$. Then consider the point $\frac {s_0+t_0}{2}$ and if this point belongs to $S$ call it $s_1$ otherwise $t_1$. Repeat this process then eventually there is a sequence $s_m$ and $t_m$ which both converge to the same limit. But then since both sets are closed the limit point belongs to both sets, which is a contradiction.   It's clear that such a sequence exists intuitively but I'm having trouble rigorously constructing such a sequence. Since I have no idea which set each of the newly constructed point belongs to, I don't know how to prove by $\epsilon-N$ definition of a sequence that both sequences converge to the same number. Can anybody help me?   Moreover, how may I be able to generalize this proposition to the $R^n$ setting?  Thanks.

In other words, are $\emptyset$ and $\mathbb{R}$ the only open and closed sets in $\mathbb{R}$? Why/Why not?  I tried by assuming a set is equal to its interior points and contains its limit points.  A bounded set will not do since stuff like $[1,4]$ and $\{5\}$ will not work, though that is not really proof. Help please?  Anyway, it must then be unbounded.  If $a$ is a real number then $(a,\infty)$, $(-\infty,a)$, $[a,\infty)$ and $(-\infty,a]$ don't seem to cut it so it must be $\mathbb{R}$.


When reviewing a manuscript as a peer reviewer and providing written feedback on a manuscript that is clearly a Reject, how does one decide how much feedback to provide? By "clear Reject," I mean poorly written, lack of novelty, experiments not satisfactory, issues with references, etc. Should the time be taken to provide comprehensive feedback for all aspects of the paper (i.e., what I'd typically do for a major revision) or do I just note the major components that led to the rejection recommendation? In other words, how much time should I spend providing feedback for a paper that is not reasonably salvageable?

I've just been invited, for the first time, to review an article. The request was somewhat of a surprise to me, as I'm still a PhD student and I'd always thought that reviewers were generally PhD graduates. Judging by the article's abstract, I am moderately familiar with the subject area, as my master's thesis was on a similar topic. The article would appear in an online journal and would be relatively short (6-8 pages). I assume that my review would be anonymous.  I'm unsure whether to accept the invitation as I'm quite busy with my research.   If I agree to review the paper, what will be expected of me? How much time can I expect this to take?


I've started to learn python and have less than 1 hr with it. i've searched on how to use the :: with a list but cannot find an answer. my_list = [10, 'x', 20.02, 'y', '30j', 'z', '10L', False]  what is the use of the : operator and :: in splicing? how do use the :: operator? What comes before and after the :: I do not understand why my_list[::3]=[10, 'y', '10L']  Why is my_list[::1] = [10, 'x', 20.02, 'y', '30j', 'z', '10L', False, 'new element']  and my_list[::2] = [10, 20.02, '30j', '10L', 'new element']

I need a good explanation (references are a plus) on Python's slice notation.   To me, this notation needs a bit of picking up.   It looks extremely powerful, but I haven't quite got my head around it.


I have trouble understanding what \[\e]0;$PWD\007\] and \[\e(0\]b\[\e(B\] mean. I am setting up my prompt on MobaXterm on Windows and those two sequences were in the default one. They were at the very beginning and very end respectively.  Here is a screenshot of the resulting prompt:   I think the second one is used to show the small arrow replacing the traditional $ but I have no idea how it achieves this result. It almost looks like garbage. I suppose it's some kind of unicode trick?  Regarding the first one, I have absolutely no idea what its purpose is. I'm even more troubled by the $PWD part.  About the linked question:     Well, as I mentionned, I know that the second sequence displays the arrow but why does it use two escape sequences separated by a plain b? That's very strange.   And, regarding the first one, it doesn't show the PWD. In my screenshot, this sequence is displayed at the very beginning, even before the date is printed. The purple path uses a classic \w. I don't understand why it uses $PWD inside an escape sequence, that's why I asked the question.

I just ran across a screenshot of someone's terminal:    Is there a list of all of the characters which can be used in a Bash prompt, or can someone get me the character for the star and the right arrow?


So it's my understanding that the current models predict that a super massive object will collapse beyond the event horizon into a singularity of infinite density.  My question is the following: isn't such a prediction contradicted by the observable universe, since we observe expansion from the Big Bang? How could a singularity form if at some point in time there was a much more massive and dense object (the Universe) that did not remain or achieved singularity but inflated ?  edit 1: Or in other words, as Tom B. suggested [but see edit 2]:      IF the universe was inside of its own event horizon, which seems   reasonable given its huge mass and tiny size just after the big bang,   how did it escape?   edit 2 [edited a bit the initial question, comments below]: I believe this question is different from  question, because I'm not suggesting that the forces leading to black hole formation would counteract the Big Bang.   I'm indicating that there are two potential instances  of singularity in the Universe, the Big Bang t0, and black-hole singularities. The Big Bang singularity (if it ever existed) is not stable and can be observed to have degraded into inflation.  Similarly, shouldn't this observation lead one to think that a black-hole singularity, if formed, would lead to a similar inflation? I understand that the black-hole environment is not homogenous whereas the big-bang conditions were mostly homogenous, but from both singularities' referentials would that matter?

Wasn't the density of the universe at the moment after the Big Bang so great as to create a black hole? If the answer is that the universe/space-time can expand anyway what does it imply about what our universe looks like from the outside?


In the derivation of F=ma, when we reach the point F=kma, we take k=1. Why can't we take 'k' as some other value?

It seems intuitive that $a\; \propto \frac{F}{m}$, as the greater the force that is applied on an object, the greater its acceleration will be. Inversely, the greater the mass of the object, the slower the acceleration will be.  However, when rewriting proportions as equations, you must introduce a constant of proportionality, and in this case of a direct proportion, if $a \propto \frac{F}{m}$ then when rewriting as an equation you will have $$a = k\cdot\frac{F}{m}$$  In order to get the standard formula $F = ma$ this constant must be $1$. However, how do we know that this is the case? How do we know that the constant isn't $2$ and the formula $F = \frac{1}{2}ma$, for instance?


If I have a connecting flight through a country I am unable to enter. Can I retrieve my bags to recheck for my connect?

I received an undesirable status for overstaying a SA visa while hospitalized for injuries sustained in Lesotho. I had to cross into SA from Lesotho. Now I am banned entry into SA until Feb 2016 and though I have submitted a waiver request to remove the undesirable status, I hear from some the waiver request may take 4-5 months or even take longer than the time of banishment.  I have a pre-paid safari planned in October in which I need to fly through Johannesburg to get to Botswana. The Jburg border control requires tourists to pass through SA immigration even when simply changing planes.  1) Will SA grant me "transit" access if I don't leave the airport?  2) Will SA allow me to spend a night in the airport as the layover is 12 hours>  Thanks for passing on any info.


If you take two sheets of finished metal for example and put oil between them they are almost impossible to separate perpendicular to the contact plane. Sheets of glass and water have the same property.   What is the reason for this attraction? Van der Waal, surface tension, suction, or some sort of adhesion of thin films? I have tried researching this based upon those topics, but can't seem to find any information that shows a definite relationship.  Thanks!

When there is a film of water in between an object and the tabletop it rests on, it is difficult to pull the object directly upward. However, when you slide the object, it comes off easily. What is the physics behind this?


I have had a long history of not being able to run .sh files. I don't understand what the underlying problem is,(I'm a little bit new to Ubuntu/UNIX based systems). When I try to run certain .sh scripts I get the following error, accompanied by the Ubuntu Software Center starting up:  "The file "/home/user/Downloads/netbeans-8.1-cpp-linux-x86.sh" could not be opened."  As a clarification, I have been double clicking directly on the .sh file in the file system.

Whenever I open a .sh file, it opens it in gedit instead of the terminal. I can't find any option similar to Right Click → Open With → Other Application... → Terminal.  How do I open this file in the terminal?


I'm wondering if it is possible to disable or uninstall this bar that I show on this image. I'm sorry i don't know what it is named that is why I included the image (click to enlarge). I'm using Android version 4.1.

A couple of weeks ago a sliding app section appeared on my home-screen. I have no idea how it got there, and no clue on how to disable/remove it. I tried all I could on the homescreen, to no luck.  Using Galaxy S3, Android 4.1.2, everything standard (so no custom launcher).    Any ideas on how to remove it?


I know I can use Math.java functions to get the floor, ceil or round value for a double or float, but my question is -- Is it possible to always get the higher integer value if a decimal point comes in my value   For example   int chunkSize  = 91 / 8 ;    which will be equal to 11.375  If I apply floor, ceil or round to this number it will return 11 I want 12.  Simply If I have 11.xxx I need to get 12 , if I have 50.xxx I want 51  Sorry The chunkSize should be int  How can I achieve this?

I'm thinking in particular of how to display pagination controls, when using a language such as C# or Java.  If I have x items which I want to display in chunks of y per page, how many pages will be needed?


Let $a_1$ $a_2$,..., $a_n$ be positive numbers. Prove that  $\frac{a_{1} + a_{2} + a_{3} +...+ a_{n}}{n} \geq \sqrt[n]{a_1 \cdot a_2 \cdot a_3 \cdot ....a_n}$. Mine is about trying to understand how can i use induction to make some justifications so this has nothing to do with solving inequalities

The arithmetic - geometric mean inequality states that $$\frac{x_1+ \ldots + x_n}{n} \geq \sqrt[n]{x_1 \cdots x_n}$$ I'm looking for some original proofs of this inequality. I can find the usual proofs on the internet but I was wondering if someone knew a proof that is unexpected in some way. e.g. can you link the theorem to some famous theorem, can you find a non-trivial geometric proof (I can find some of those), proofs that use theory that doesn't link to this inequality at first sight (e.g. differential equations …)?  Induction, backward induction, use of Jensen inequality, swapping terms, use of Lagrange multiplier, proof using thermodynamics (yeah, I know, it's rather some physical argument that this theorem might be true, not really a proof), convexity, … are some of the proofs I know.


While I had been typing out a message, I had accidentally pressed Esc instead of `, which resulted in chat clearing the whole message I have written, together with the edit history, so pressing Ctrl+Z didn't help.  It would be nice if this pitfall was removed, or at least, if it didn't clear the edit history.

In the chat, we often use backticks highlight code inside of sentences, exactly like how we do it here.  Unfortunately, it's located peculiarly close to the esc key, which has a nasty effect of clearing the chat input.  Outside of making a userscript, would it be alright to disable that effect so that I (and probably a bunch of others) don't throw my computer out the window when I lose a larger post to a misplaced keystroke?  Note: command+z (OSX) does not undo the delete.


So for example lets say I used the console line java AddPerson -c <sin>  -g <gender>  -age <age> -y <year>  [-w <when>] The inputs can be in any order and the -w input is optional. My goal is to take these variables and add them to a database but I cant figure out how to find and store the inputted variables. This is the 'pseudo-code' for what I have. public AddPerson (String[] args) {  //connection to db  public boolean newPerson(){ }         }

What is a good way of parsing command line arguments in Java?


i want to know why Web Application Projects have designer.cs files  and web site not in asp.net   like this  //------------------------------------------------------------------------------ // <auto-generated> //     This code was generated by a tool. // //     Changes to this file may cause incorrect behavior and will be lost if //     the code is regenerated. // </auto-generated> //------------------------------------------------------------------------------  namespace JavaScript {       public partial class WebForm1     {          /// <summary>         /// form1 control.         /// </summary>         /// <remarks>         /// Auto-generated field.         /// To modify move field declaration from designer file to code-behind file.         /// </remarks>         protected global::System.Web.UI.HtmlControls.HtmlForm form1;     } }

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


Lets see this example:  char var1[100] = "test    "; char* var2;   If I do this:  var2 = &var1;   I'll get it with spaces.  I want var2 to be the trim of var1.

Is there a clean, preferably standard method of trimming leading and trailing whitespace from a string in C? I'd roll my own, but I would think this is a common problem with an equally common solution.


May I just say, I was born and raised in the United States and I use the term "spelt" but others say it should be "spelled" but... why is spelt apparently a grammatical error?

In the following sentence, should I say spelled or spelt:     You spelt/spelled "Pneumonoultramicroscopicsilicovolcanoconiosis" wrong.


What if a user is banned from asking questions and there is no choice for him/her to improve his/her questions, will that user be banned permanently from asking questions on SO?

If you are reading this, you may have been affected by one of our post quality bans. If so, it is important that you  to understand what has happened and how to regain the permissions that you lost. While trying to ask a question, one could see:  We are no longer accepting questions from this account. See  to learn more.  Likewise, for answers:  We are no longer accepting answers from this account. See  to learn more.   Why am I getting this message? Are deleted posts taken into account too? Is a question/answer ban the same as a suspension? How do I avoid getting a question ban? How long do I have to wait before I can post again? What can I do to release the ban? How can I reactivate my account? Can I simply create a new account? I'll just ask somewhere else on the SE network, and they'll migrate my question to the correct site! Will a ban on one Stack Exchange site affect my standing on other sites in the network? Does this apply to meta sites too? My account is in good standing. Why am I still blocked?


What am I looking for exactly?  The hint I was given: show that we can find such a fraction between any two given real numbers.

How can I show that the set of rational numbers with denominator a power of two form a dense subset of the reals?


At the moment, if I want to look at the activity of a thread I've already read (new Answers, new Comments, new Answer/Question edits), I have to go through a tedious process. Luckily, we got a lastactivity button, but that only shows the latest activity:    By sequential activity, I mean a list of links sorted by latest activity first.  The reason I want this feature is because I often want to know what activity I missed. In my case, this is on threads I've Starred, in which I don't wanna miss a thing. It's easy to miss stuff when relying on lastactivity, especially on busy and/or large threads.    UPDATE: Good to know , but  it would nice if it was easily accessible. An example would be the following, where history links to that activity:  active: 8 months ago (history)

There is an experimental timeline view for questions now available on meta ONLY! (Now working on SO, SF, and SU as well)  This is partially motivated by comments about how difficult it is to follow very active questions which have a lot of activity, and also the feedback on the API which was heavily dominated by "we need to know what happened in this time range" type responses.  It can only be accessed through URL hackery at the moment. To get to it, enter question URLs like so:  https://meta.stackexchange.com/posts/{id}/timeline  This is a chronological timeline of everything that happened on a question, including   initial question ask answers  revisions comments closure, deletion, reopen, undelete, etc votes   all based on when they happened in chronological order.  We are thinking about making this a fourth tab on the question, like so:  Timeline | Oldest | Newest | Votes  Please try it out and provide feedback. It is still a little rough, so we are not looking for highly detailed bug reports, just more general feedback.  Timeline view for this question:


How do I list what dns servers are being searched for things that need to do dns searches?  It doesn't seem like what I have in resolv.conf is being used, So i want to troubleshoot and step one of that would be to have the system print out what servers it is using.  Everything I found so far assumes I have network manager installed, but I do not, and so nmcli or other such commands would not work.  Linux linuxtest 3.16.0-4-amd64 #1 SMP Debian 3.16.43-2+deb8u2 (2017-06-26) x86_64 GNU/Linux

How can I check which DNS server am I using (in Linux)? I am using network manager and a wired connection to my university's LAN. (I am trying to find out why my domain doesn't get resolved)


In Kung fu Panda 3, the panda village was a secret place. But when Kai attacked and destroyed Jade Palace, Tigress reached the panda village and informed Po about what happaned to everyone. But if the panda village is a secret place, then how could Tigress reach it?

In , How did Tigress And Kai find the location of panda village?


I have a null app which is quite annoying, I’ve searched up how to delete it but they all say go to storage and delete it from their but the app isn’t in storage and I haven’t found a way to delete it  iPhone SE iOS 12.0.1

In my usage list(settings>general>storage & iCloud usage>manage storage), there is an app that registers as (null) with no icon, a version number that doesn't match anything I've previously downloaded, and it's taking up storage space. I first noticed it about a week or two ago. And no, I can't download recent apps to find the one that it is, because I downloaded multiple apps recently, and didn't notice the (null) app until my storage was critically low and I was looking to delete something. I am running iOS 9.2.1 on an iPhone 5C.


I want instal Ubuntu on my notebook, Will Ubuntu Desktop 16.04.3 LTS work perfectly on;  AMD C-60 1GHz processor 1 GB RAM 30 GB HDD  I know the recommendation system requirements  I just want to know Ubuntu will work properly or not with this spech?? Please Answer :)

For a given hardware configuration, how do I find out if Ubuntu will run on it? What considerations should I take into account when choosing an Ubuntu version and  such as:    with a lighter desktop than the usual Gnome and Unity  with the even lighter LXDE desktop   Obviously Ubuntu does not run on some processor architectures. So how do I go about choosing the right version and derivate. How can I find out the minmal system requirements?


I was watching this video that talks about Reference Vs Value In JavaScript.    I was really stuck on his last example here.  let c = [1,2] //0x01 console.log('c = ${c}') add(c,3) console.log('c = ${c}') function add(array,element){     array = [element] }   The output is   c = 1,2 c = 1,2   I am trying to understand why that is. Based on my understanding, the add function should allocate [element] to a second address (let's say 0x02), then reassign c to 0x02. Which means that the value of c is now the memory address 0x02, hence c = [3]. What is it that I am not understanding correctly?

The primitive types (number, string, etc.) are passed by value, but objects are unknown, because they can be both passed-by-value (in case we consider that a variable holding an object is in fact a reference to the object) and passed-by-reference (when we consider that the variable to the object holds the object itself).  Although it doesn't really matter at the end, I want to know what is the correct way to present the arguments passing conventions. Is there an excerpt from JavaScript specification, which defines what should be the semantics regarding this?


I am currently making a cipher program in python but I can't seem to solve this one problem:  word = ['a', 'b', 'c'] -----enciphering process------- message = ['d', 'e', 'f']  print message[x],   What I want to happen:  'def'   What actually happens:  'd e f'   I know why the spaces are there, but I can't seem to get rid of them, I've tried using strip, replace, re.sub, message(map whatever I don't remember), and "".join. Those all work with a pre-determined list but not when I don't know what the list is going to be.  Help please.  *EDIT  What I meant was something like this:   Word = raw_input("Enter a word  ") Message = list(word)  w = raw_input("Enter a number  ") w = int(w) n = len(message)  Letters = ['a', 'b', 'c', 'd' and so on until z]  For y in range(0,n):     For index in range(0,26):        X = index + w        If x > 25:          x = x - 26        If message[y] == letters[index]:          print letters[x],   Not sure how to get rid of the spaces because I don't know what the message is gonna be

I'd like to do it in Python. What I'd like to do in this example in C: #include <stdio.h>  int main() {     int i;     for (i=0; i<10; i++) printf(".");     return 0; }  Output: ..........  In Python: >>> for i in range(10): print('.') . . . . . . . . . . >>> print('.', '.', '.', '.', '.', '.', '.', '.', '.', '.') . . . . . . . . . .  In Python print will add a \n or space, how can I avoid that? Now, it's just an example, don't tell me I can first build a string then print it. I'd like to know how to "append" strings to stdout.


I just got a new computer with Windows 7 on it and want to install  instead. I think I previously need to erase completely Windows from it and then replace it by Xubuntu, but I don't know how to proceed.   Has anybody some procedure to give me?  Thanks a lot!

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


We're doing a great deal of floating-point to integer number conversions in our project. Basically, something like this  for(int i = 0; i < HUGE_NUMBER; i++)      int_array[i] = float_array[i];   The default C function which performs the conversion turns out to be quite time consuming.  Is there any work around (maybe a hand tuned function) which can speed up the process a little bit? We don't care much about a precision.

What is the fastest way you know to convert a floating-point number to an int on an x86 CPU.  Preferrably in C or assembly (that can be in-lined in C) for any combination of the following:   32/64/80-bit float -> 32/64-bit integer   I'm looking for some technique that is faster than to just let the compiler do it.


My husband applied for visa and they refused it again. However they refused him on the things he’s included as evidenced when they stated that he hasn’t included them. I don’t understand how they can do that.

Many of the UK visa refusals we see here share a common pattern and the prevailing reasons refer to V 4.2 (a) and (c).    I do understand that, while the applicants may describe very different individual circumstances, there's a consistent pattern and, broadly, fall into specific categories:    Credibility (lifestyle, lack of ties, visit history, lies & omissions) Funding (insufficient funds, provenance of funds, funds parking) Sponsorship (family, friends, employer)   Question: What most commonly triggers a UK visa refusal where V 4.2 (a) and (c) are given as the grounds?  Secondarily: Given that there is a clear pattern, to what extent are these refusals predictable? Does sponsorship make a difference? Is there a set of personal circumstances, however abstract, where a refusal is all but guaranteed? For example, why do those we see here on TSE who sought entry for the PLAB or British Army appear to be refused with a common theme? Is there a uniform shortcoming or is it just discrimination?   PLAB: What is about applications for a visa, for the purpose of sitting the Professional and Linguistic Assessments Board (PLAB) exam, that seem to invite refusals. After all, the test is given so that international medical graduates can show that they qualify to practise medicine in the UK. The first part, PLAB 1, can be taken in centres outside of the UK. However, PLAB 2 can be taken only in the UK. Why can't you can't get a visa just to sit the exam, promising that you'll leave immediately after?    British Army: Since Commonwealth citizens are eligible to apply online to join, even those who don't reside in the UK, why is it so difficult to get a visa just to attend an interview to see whether you are suitable? Even with an invitation from the Army, such visa applications seem to be unsuccessful. Isn't a career in the British Army a valid reason?     Lastly:  After such a refusal, what approaches would increase the chance of a successful application?


When I use 's tab complete with :E (or any other method) it autocompletes a lot more forcefully that I'd like. For example if I want to go to the admin/products controller and I type :Econtroller ad and press tab, it might complete to :Econtroller addresses or I guess the first possible match. I wish it stopped and let me type more.  Is this an issue in rails.vim? Vim itself? Or a failure of my configuration?  I'm using MacVim v7.4. And the latest release of rails.vim installed via Vundle.  Any advice is appreciated.

When I'm opening a new file in Vim and I use tab completion, it completes the whole file name instead of doing the partial match like Bash does. Is there an option to make this file name tab completion work more like Bash?


For you, this might be very simple but I have no idea what the difference is.I just want to know the difference between these two codes. Suppose I have some codes as described below.   The first class is Animal which will be the Superclass   public class Animal {      private String name;     private int weight;     private String sound;      public void setName(String name){         this.name = name;     }      public String getName(){         return name;     }      public void setWeight(int weight){         if(weight > 0){             this.weight = weight;         } else {             System.out.println("Weight must be bigger than 0");         }     }      public int getWeight(){         return weight;     }      public void setSound(String sound){         this.sound = sound;     }      public String getSound(){         return sound;     } }   The second class is Dog which extends the class Animal   public class Dog extends Animal {      public void digHole(){         System.out.println("Dig a hole");     }      public Dog(){         super();          setSound("bark");     } }   The last class is the WorkWithAnimals which will print the output   public class WorkWithAnimals {      public static void main(String args[]){          Dog fido = new Dog();          fido.setName("Dadu");         System.out.println(fido.getName());          fido.digHole();         fido.setWeight(-1);     } }   My question is, what is the difference between Animal fido = new Dog() and Dog fido = new Dog() ?  Since Dog already extends Animal, why do we have to write the code like Animal fido = new Dog() ?  Both of them print the same result, don't they?

I have seen this mentioned a few times and I am not clear on what it means. When and why would you do this?   I know what interfaces do, but the fact I am not clear on this makes me think I am missing out on using them correctly.   Is it just so if you were to do:  IInterface classRef = new ObjectWhatever()   You could use any class that implements IInterface? When would you need to do that? The only thing I can think of is if you have a method and you are unsure of what object will be passed except for it implementing IInterface. I cannot think how often you would need to do that.   Also, how could you write a method that takes in an object that implements an interface? Is that possible?