Travelling through UK, what is considered a "common format residence permit"?

I will be travelling through UK (Manchester) from Africa to Paris.   I will pass through border controls since I have to pick up my luggage and check in again in a different terminal but still at Manchester Airport. It is a landside transit.  My flight to Paris is on the same day (7 hours later). I have a Lebanese passport and a 10-year French residence permit (titre de séjour).  It was issued in April 2010 (to April 2020).  It is plastified, pink/purple in color, and has a bull and 5 stars on it. It does not have a chip.  It is a little bit bigger than the "credit-card sized model" (mine is 10.5 cm by 7.5 cm).  Having a common format EEA residence permit allows me to transit via the UK.   Is the residence permit that I have considered a common format residence permit? Even without a chip and not the credit card size?


I have a Schengen visa and invitation letter came from France, but I want to stop  at Frankfurt instead. Frankfurt is only 1 hr from Fauburg where I want to go. Paris is 4 hr plus changing flight from Frankfurt and immigration and all at Paris will take around 7 hr plus for me. I have a ticket on Lufthansa to Paris with one stop at Frankfurt.   My question is whether can I stop at Frankfurt even though my final destination is Paris.


Notification when a trivial edit is made on my post

Currently, a user does not get any notification when a trivial edit (less than 6 characters, by a user who has the ) is made on one of his/her posts. As in .  Even though the user is trust-worthy (owing to the rep of the user), wouldn't it be nice for the OP to get a notification whenever an edit is made, even trivial?


Google search of links:mysite.com returns less links than imagined

I did a Google search links: example.com and it only returns 3 results.  I know there are a lot my more back links in existence than that. Why does Google not show the other links I have to my site?


Is there a word or a term used for someone who hops from idea to idea?  More specifically, for someone who jumps from idea to idea without ever really completing any of them.


Why is 'ping' unable to resolve a name when 'nslookup' works fine?

On my Windows XP workstation, I can find the machine I want to connect to in DNS with nslookup:  nslookup wolfman Server: dns.company.com Address: 192.168.1.38  Name: wolfman.company.com Address: 192.168.1.178   But, when I try to connect to that machine, I get an error telling me that the machine can't be found (i.e., can't be looked up in DNS):  C:\> ping wolfman Ping request could not find host wolfman. Please check the name and try again.   I am able to connect if I use the IP address directly:  C:\> ping 192.168.1.178  Pinging 192.168.1.178 with 32 bytes of data:  Reply from 192.168.1.178: bytes=32 time=41ms TTL=126 Reply from 192.168.1.178: bytes=32 time=41ms TTL=126 Reply from 192.168.1.178: bytes=32 time=44ms TTL=126 Reply from 192.168.1.178: bytes=32 time=38ms TTL=126   I could work around this by adding an entry to my hosts file, but I would rather find out why this is happening.  The problem is transient, most of the day I can connect to the machine just fine.  How is this possible?  ETA: I left this out for brevity, but it was asked for:  C:\> ping wolfman.company.com Ping request could not find host wolfman.company.com. Please check the name and try again.   ETA: Other applications get the same results.  I only tried ping to simplify.  telnet can't connect, Cygwin apps print a "unknown host wolfman" message.  Update: Using wireshark, I found that my workstation is not attempting a DNS lookup.  It's just reporting the "could not find host" error message.


Python printing statements for a biased coin flip?What does the last 2 lines mean?

So I got these codes that for printing the statements but I don't get the purpose of the last two lines of the if loop? from random import random  def flip(bias):     """     Flip a coin once.     `bias` is the likelihood of the result being heads, 0. <= bias <= 1.     Returns True for heads or False for tails     """     return random() < bias  def main():     bias = float(input("What bias do your coins have? "))     count = {False: 0, True: 0}     for i in range(1, 4):         toss = flip(bias)         count[toss] += 1         print("Coin flip {} has a value of heads: {}".format(i, toss))     print("Final result: {} heads, {} tails".format(count[True], count[False]))  if __name__ == "__main__":     main()   Thanks in advance.


Gravity: Why is the inverse square law exactly $1/r^2$ instead of just close to 2?

Is there something intrinsic about the structure of space that gravity is proportional to 1/r^2 instead of, for example,  1/r^2.143 ?  What makes the exponent turn out to be a nice even number?


I am working on industrial output data and running a lot of tests for it, before I proceed to make an ARIMA model for it.   Before I do that, I need to decide whether or not to "log" the data.   I am having trouble spotting whether the data is growing exponentially or not. And even if it's not - it's logical to assume that industrial growth has constant growth and its variance goes up with time.     Bottom line - would you advise to log the data in general (not just for ARIMA) when I do things like seasonally adjust it and smooth it, etc.


quadratic rate of convergence of modified NR method

Let $f\in C^3(\mathbb{R})$, suppose there exists $r\in\mathbb{R}$ such that  $$f(r)=f'(r)=0,f''(r)\neq0$$  The iterations are  $$x_{n+1}=x_n-\frac{\alpha f(x_n)}{f'(x_n)}$$  with a starting point $x_0$ that was chosen such that $x_n$ converges to $r$.  Find an $\alpha$ for which the rate of convergence is quadratic.  Prove for this $\alpha$ that  $$\lim\limits_{n\to\infty}\frac{|x_{n+1}-r|}{|x_n-r|^2} = \frac{f'''(r)}{6f''(r)}.$$


Can DNA produce ribozyme-like structures?

RNA is known to act as an enzyme via its ability to fold itself in specific ways.   Is DNA capable of such structures? Or is it some biochemical reason stopping the folding? Have they been observed in nature?


Fisher Information as measurement of curvature and hence information

(We may just assume single parameter model and single variable data for this discussion).  I understand that the "observed information" evaluated at the MLE measures the curvature and hence gives a gauge of how much information our data is giving us. "Observed information" here refers to having already obtained a sample and then computing $-d^2l/d\theta^2$ ($l$ here is log-likelihood).  I also understand the definition of Fisher Information, and I understand that $l$ is random before the data is drawn. However, in terms of an intuitive explanation, Wikipedia and various other sources say that Fisher Information gives a measure of curvature or still tells us information in the same way as I described for observed information. This, I disagree. When I evaluate $I(\theta)$ by average the curvature over all possible $l$, we must keep in mind that $\theta$ need not be the peak of $l$ - for some $l$, it is, but for other $l$, we may be way, way away from the peak, and the curvature that these scenerios contribute to the Fisher Information may lead to funny effects. Why would we care about the curvature at $\theta$ for these weird $l$ where $\theta$ is clearly not a good estimation?  Basically, I am not very convinced on the intuitive explanation given for Fisher Information. Is the intuitive explanation commonly given a correct one?


Is it possible to add new alphabets to unicode-math?

In ordinary LaTeX, one can easily add new math alphabets by using \DeclareMathAlphabet. One is then able to use, say, cmsy, eus, and rsfs letters side-by-side. Unfortunately, there does not seem to be a similar mechanism in unicode-math, or at the very least \DeclareMathAlphabet doesn't do what it's supposed to do.  Question. How can I set up my own math alphabets in unicode-math?   Attempted workarounds  Since unicode-math has lots of math alphabets, one workaround might be to replace an unused alphabet with the desired one using \setmathfont[range=...->...]. This doesn't quite work right in my example:  \documentclass[12pt]{article} \usepackage{fontspec,xltxtra,xunicode} \defaultfontfeatures{Mapping=tex-text}  \usepackage{unicode-math}  \scrollmode  \setmathfont{xits-math.otf} \setmathfont[range={\mathscr,\mathbfscr},StylisticSet=0]{xits-math.otf} \setmathfont[range={\mathcal,\mathbfcal},StylisticSet=1]{xits-math.otf} \setmathfont[range={\mathtt->\mathcal}]{latinmodern-math.otf}  \begin{document} \[ \begin{array}{c} \mathcal{A B C D E F G H I J K L M N O P Q R S T U V W X Y Z} \\ \mathscr{A B C D E F G H I J K L M N O P Q R S T U V W X Y Z} \\ \mathtt{A B C D E F G H I J K L M N O P Q R S T U V W X Y Z} \end{array} \]   I suspect the problem is that the codepoints of the calligraphic letters in Unicode are not contiguous.   Using \mathversion seems to work better:  \documentclass[12pt]{article} \usepackage{fontspec,xltxtra,xunicode} \defaultfontfeatures{Mapping=tex-text}  \usepackage{unicode-math}  \setmathfont{xits-math.otf}  \setmathfont[version=eucal]{latinmodern-math.otf} \newcommand{\eucal}[1]{\mathchoice %   {\mbox{\mathversion{eucal}$\displaystyle\mathscr{#1}$}} %   {\mbox{\mathversion{eucal}$\mathscr{#1}$}} %   {\mbox{\mathversion{eucal}$\scriptstyle\mathscr{#1}$}} %   {\mbox{\mathversion{eucal}$\scriptscriptstyle\mathscr{#1}$}}}  \setmathfont[range={\mathcal,\mathbfcal},StylisticSet=1]{xits-math.otf}  \begin{document} \[ \begin{array}{c} \mathcal{A B C D E F G H I J K L M N O P Q R S T U V W X Y Z} \\ \mathscr{A B C D E F G H I J K L M N O P Q R S T U V W X Y Z} \\ \eucal{A B C D E F G H I J K L M N O P Q R S T U V W X Y Z} \end{array} \] \end{document}   But this feels very inefficient.


How important is relevant research for an undergrad?

I'm a student in electrical engineering, and my interests lie primarily in areas with a large overlap between physics and electrical engineering. I'm currently doing research with a professor of computer engineering, doing computer engineering research, which doesn't exactly line up with my interests, but it is research experience.  Now, when I'm applying for graduate schools, I believe I'll have to write a statement of purpose. How does it affect my chances of getting into graduate schools if I write about how I want to do research in [certain area of EE], but the school sees that all of my actual research experience is in an entirely different branch of electrical engineering?  Or in other words--do graduate admissions committees care about what field I do my undergrad research in, or do they only care that I do research in general?


How Can i control the 'total' output in 'ls -l' command?

the question is, how can control the ls -l total output ? first impression with example that give us total = 0  els3@els3PC:~/test$ touch file els3@els3PC:~/test$ ls -l total 0 -rw-r--r-- 1 els3 els3 0 Jul 20 12:05 file   As i mention this example give us this result total = 0 by creating empty file.  in other way I will try to create a non empty file2 contain '3ls3' .  els3@els3PC:~/test$ cat > file2 3ls3 ^C els3@els3PC:~/test$ cat file2 3ls3 els3@els3PC:~/test$ ls -l total 4 -rw-r--r-- 1 els3 els3 5 Jul 20 12:11 file2   this second example give us total 4 by creating a non empty file. the hole Q is how can i get for e.g total 1 or total 2 etc.. by creating a new file.


Should you avoid cooling a frying pan with water?

Sometimes after I fry something, I wash it immediately in water because it's a bit easier to wash (before the remains stick to the pan).  Does this damage the pan in any way?


404 Not found error when I type sudo apt-get update

In a terminal when I insert this command line  sudo apt-get update  W: Failed to fetch http://ppa.launchpad.net/gwibber-daily/ppa/ubuntu/dists/trusty/main/binary-amd64/Packages  404  Not Found E: Some index files failed to download. They have been ignored, or old ones used instead.


A prettier way of on how to prove the identities

I am just curious to know the direct and precise to prove the identities  (1) $$\cos(A+B)=\cos A \cos B-\sin A \sin B$$ and   (2)  $$\sin(A+B)=\sin A \cos B+ \cos A \sin B$$ I tried to come up with right-angled triangles but I failed to connect them and get some logic out. Thank's in advance.


Is there any way to decrypt the data which is affected and encrypted by locky ransomeware hackers. one of our companies system (windows 7) is affected. i have Ubuntu installed on my PC. please help anyone , if there is any war for the recovery.  Thanks.


I want to add event to public Calendars using Apex code in trigger. Currently I have hardcoded id of public  Calendar in my code. But I don't want to hardcode id of Calendars. I want to query it in my code. But I am not able to query it as it says sObject type 'Calendar' is not supported.  Any help is appreciated.  Thanks Ankush


How can I change a file type's default program while keeping its current default icon on Windows 7

Let's say I want to open XML files in Notepad, I can change the default program through Control Panel > Programs > Default Programs > Associate a file type or protocol with a program.   However, that will also change its default icon to that of a text file. If I repeat the process for other file types then I lose the ability to easily distinguish different files in a folder based on their icon.  So after I change the default program, I would like to 'roll back' the icon change.   HKEY_CLASSES_ROOT\xmlfile\DefaultIcon stays the same as before the default program changed: %SystemRoot%\System32\msxml3.dll,0  I tried adding HKEY_CURRENT_USER\Software\Classes\xmlfile\DefaultIcon, as well as HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts\.xml\DefaultIcon but neither seem to work.  What registry key(s) should I change to get back the old icon (%SystemRoot%\System32\msxml3.dll,0) but keep Notepad as the default program?  I downloaded  and it shows %SystemRoot%\System32\msxml3.dll,0 as the default icon for XML files, even though that is not the icon I see in Explorer, and even in FileTypesMan itself!


.toArray(new MyClass[0]) or .toArray(new MyClass[myList.size()])?

Assuming I have an ArrayList  ArrayList<MyClass> myList;   And I want to call toArray, is there a performance reason to use  MyClass[] arr = myList.toArray(new MyClass[myList.size()]);   over  MyClass[] arr = myList.toArray(new MyClass[0]);   ?  I prefer the second style, since it's less verbose, and I assumed that the compiler will make sure the empty array doesn't really get created, but I've been wondering if that's true.  Of course, in 99% of the cases it doesn't make a difference one way or the other, but I'd like to keep a consistent style between my normal code and my optimized inner loops...


Shutdown, Reboot and Logout buttons in the GNOME App Launcher

I somehow have added buttons for Shut Down, Reboot and Logout into the app launcher in Ubuntu. This is a pretty fresh install of Ubuntu and it wasn't there when I started. If I had to pinpoint one moment this started, I would say it MIGHT be when I accidentally tried to install Unity Tweak Tool not realising I am using a GNOME desktop (it was late, I was tired...). This did result in a bunch of things being installed like Rhythmbox which I have since removed, but these buttons can't be removed as far as I can tell. Has anyone seen this before? Can you suggest what might remove these useless buttons?


Ubuntu Server monitor goes to sleep in 10 minutes

Is there a possibility to disable the monitor sleep in Ubuntu server 14.04? After 10 minutes my monitor goes to sleep. I've already tried several options, from


Are Fuchsian groups without elliptic and parabolic elements at most countable?

Let $G \subset PSL(2, \Bbb R)$ be a discrete subgroup without elliptic or parabolic elements. Does it follow that it is at most countable?  Subgroups as above have the property that the quotients of the hyperbolic upper half-plane $H$ by them are compact smooth surfaces. The fact that $G$ acts properly discontinuously on $H$ makes me suspect that it cannot be uncountable (otherwise, "something" would have a limit point, and this would somehow contradict the proper discontinuous action), but since I cannot visualize these objects, I do not know how to encode my intuition into a formal reasoning.  (For me, $G$ acts properly discontinuously on $H$ if and only if for every $z \in H$ there exist an open subset $U_z \subset H$ such that $U_z \cap g U_z = \emptyset, \ \forall g \in G \setminus \{1\}$. This is equivalent to $G$ being a discrete subgroup with no elliptic elements.)    A posteriori, the fact that, for $f \in L^1 (H)$ and $D$ a fundamental domain for $G \backslash H$, one may write $\int _H f = \sum _{g \in G} \int _{gD} f$, is a further argument that $G$ must be at most countable, otherwise $\sum _{g \in G}$ wouldn't make sense. This, on the other hand, is not a proof.


Replace a line with the full text of a second file

I know how to replace a line with another line or several other lines with tools like sed. But is there an easy way, to replace a line in a file with the whole content of a second file?   So, let's have an example. I have a file  called file1.txt:  A 1 B 2 C 3   And I have a second file file2.txt:   line 1 line 2 line 3   Now, I want to replace line 2 with the whole content of file1.txt, so in the end, it should look like this  line 1 A 1 B 2 C 3 line 3   One way I could think about would be something like this:  sed -i "s/line 2/$(cat file1.txt)/g" file2.txt.    But then I also have to check some special characters like / and maybe more. I have to assume, that every possible readable character could be in file1.txt.  So, back to my question: Is there an easy way, to replace a line in a file with the whole content of a second file? It doesn't have to be sed. It could be also another tool, if it could do the job better...


contents in list of figures are crossing the border

Please look at the figure above. The contents in the List of Figures are crossing the border and they are not appearing fully.  This is the code that I found in the source latex file.   \newpage  \makeatletter  \let \asas \ps@plain  \let \ps@plain \ps@empty  \makeatother \large  \tableofcontents  %\makeatletter  %\let \ps@plain \asas  %\let\asas\relax  %\makeatother  %\thispagestyle{empty}  \listoffigures  %\thispagestyle{empty}  \listoftables   %\thispagestyle{empty}   What can be done ?


Do I use a comma when there are two items/people listed?

I am often confused when writing a sentence with an "and" or an "or." If I want to then follow the two items/people with what they are doing, do I have to use commas to break off the second item/person so that the reader doesn't think that the action only applies to the second item/person? Which example found below looks correct? It is tricky because the sentence is long.   "The school does not allow the president, or the vice president, to vote in the election." "The school does not allow the president or the vice president to vote in the election."


Why does Ubuntu have its own site, but other Linux distributions don't?

The title says it all. What makes Ubuntu so special that it deserves a particular treatment that is not received by any other distribution? Shouldn't it be merged with Unix & Linux SE? For users of other distributions it would be VERY beneficial to have their own sites in Stack Exchange. I know  is not a proof. But do we have a proof that Ubuntu is used WAY more than the other distros? Edit: So my question is challenged to ask practically the same as  one. That's false. My question is about what the merit for Ubuntu is to have it's own SE, not for knowing what the differences are. Of course there are differences, I have no doubt what there are. I understand what their differences are, perfectly, and this question didn't ask for them. As a metaphor, the fact that I understand the differences between a democracy and a dictatorship doesn't mean I have to agree with both existing in the world.


How can a moving frame transmit energy (a fighter plane shoots a bullet)?

shows that a bullet shot from a flying plane receives a large amount of energy from the plane, even much more than the energy from the propellant of the bullet.  But I wonder how can the plane transfer additional energy to the bullet? For example, the propellant gas expands and creates the pressure that pushes the bullet forward, this energy is limited by the propellant itself. While the plane only recoils backward, how can the plane transfer force, or energy to the bullet, in what method since it even does not touching the bullet? If the barrel is a part of the plane, the plane even pulls the bullet backward by friction.


What/Which towns do we go through on the way?

What is the difference between "what" and "which" here? Which one do we prefer? Do they mean the same?   What towns do we go through on the way? Which towns do we go through on the way?


Synonym privileges - make universal for top users

I know this has been touched on in other questions, but I'd like to bring up a possible solution for discussion.  I think this is different because it offers a possible new solution that I don't believe has been considered in the past. I would like to get some consensus from the group to see if it is something to be adopted.  There has been debate on who should have synonym privileges and to what degree. Who should have blanket privilege to act on tags, particularly for the SE groups that have smaller forums or limited numbers of active moderators. I agree that they should have a minimum score (maybe 2500, can be debated), but to help these forums, what about a criteria like "the top x number of users" or "the top 5% of users", combined with the minimum score criteria?  I put my own case out as a good example. in CS50-beta, we have only 2 or 3 very active moderators (who work really hard, the others are Harvard CS50 staff and can't put in that kind of time), followed by a handful of really high scoring members. I have the highest reputation score on the forum at almost 35k, double the next high score, yet I'm still bumping into an inability to deal with tags and synonyms easily. Somehow, I would think that the top handful of users on a forum would know what we're doing and should have more ability - at minimum to suggest ANY synonyms, if not to vote on them, without restriction.  Automatically authorizing the top users seems like a reasonable solution. The number of users or percentage and a minimum score can be debated, or what privilege should be permitted - suggesting, voting, automatic execution, etc. - or perhaps allowing the moderators to authorize a certain privilege to certain (super?)users would help.   So, what is the consensus?


I changed my password a while back, and now want to change it back to THE ORIGINAL PASSWORD. But it says it is not strong enough. What can I do?  (I am using Ubuntu 14.04 on a lenovo think pad.)


How can $\pi$ be irrational if it can be calculated using an infinite series of rational numbers?

Just a curiosity. I just saw a video where pi was being calculated by the series  $$1-(1/3)+(1/5)-(1/7)+...$$  My question is how can $\pi$ be irrational if we can calculate it using rational numbers?


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


A monoid with left identity and right inverses need not be a group

Let $G$ be a set with an operation $\ast:G\times G \rightarrow G$ such that:  (1) For all $a,b,c \in G$ we have $(a\ast b)\ast c=a\ast (b\ast c)$ (associativity),  (2) There is $e \in G$ such that $e\ast a=a$ for all $a\in G$ (left identity),  (3) For all $a \in G$ there is $a^{\prime}\in G$ such that $a\ast a^{\prime}=e$ (right inverse).  Show that $(G,\ast )$ need not be a group.  I can't think of a counter example that satisfies this not being a group.


I would like to sum the total area of my attribute table to reflect in the print setup

I have the following attribute table and I wish to show the total area in hectares seperate to my attribute table on the print setup. I currently have to add these values manually. Is there a way to get QGIS to calculate this automatically?


HTML5/JS How to create an autocompleted tag input like StackOverflow Tags field

I want to create an input for tags/labels/flags etc. similar to the one shown at: .  I found similar questions using jQuery UI Plugins, but I am searching for a very lightweight solution. (I want to use this with Phoenix and Bootstrap 3).  Related questions I've found (I find it hard to google for this since both tag and label already have a meaning in html):     (Essentially the tag-it plugin is what I am searching for, except that it requires jQuery UI)


Is there a way to disagree with the review systems "recommendation"

When approving a post that system thinks should not have you are presented with something along the lines of  This post has severe quality issues. It is abusive nonsense, noise, spam, blatantly off-topic or otherwise irredeemable - readers will find it offensive or repulsive rather than helpful. You should delete or recommend deletion when reviewing such posts. Don't worry, we've already handled this post appropriately - but please take a minute to look it over closely, keeping in mind the guidance shown above.  With a "I understand" button, what about if you disagree with that assertion? Is there a way to indicate that? If there isn't perhaps one should be added so that data can be collected to improve the system. For example: While reviewing the low quality posts queue I got the following answer from  to to the question   Try  (I'm a developer). It does exactly what you're looking for, free of charge.  Which I approved and the system responded that I should have recommended deletion. From what it looks like to me the OP is asking a question about adding basic username/password authentication for an Amazon s3 hosted website and the answer is mentioning a free product/service that does what the user wants. It is true that the user answering is affiliated (they posted a disclaimer) with the product but from what I understand that is .


Question about the existence of a specific function $f: \mathbb{R} \to \mathbb{R}$

Does there exist a function $f: \mathbb{R} \to \mathbb{R}$ such that for all non-empty, open, and uncountable subset $E \subseteq \mathbb{R}$, $f(E) = \mathbb{R}$?  I have been thinking about it for a bit, but really can't think of any way to prove or disprove it. I have a hunch that if a set $E \subseteq \mathbb{R}$ is open and uncountable, then there should be a bijection to $\mathbb{R}$. This may not be true, however. I'm not well versed in the more advanced concepts of cardinality, so I'm unsure if there is an uncountable set $E \subsetneq \mathbb{R}$ such that there is no bijection from $E$ to $\mathbb R$.  I'm having great difficulty imagining a function with this property. I understand that proving existence doesn't imply that construction of such a function is feasible, but I want to understand if such a function even exists.  Any help would be greatly appreciated.


I have played around with this question for a bit, but my answer doesn't feel right. I'm not happy with how I converted the binomial. it feels a bit hand-wavy. Is there any way I can make this proof better?  Let's say that we have two teams that are both size $n$. Let's call one team the Blue team and the other team Red. We are going to send a mixture of Blue and Red players to an event (they can also send no one). There are $\binom{2n}{a}$ ways we can select players, but if we want to only send an even sum of players then $a$ must be even. Lets rewrite it as $\binom{2n}{2k}$. Considering all possible $k$-values tells us that the total ways to send an even sum of randomly composed Blue and Red players is $$\sum_{k=0}^n \binom{2n}{2k}$$ Since both teams have $n$ players, we know that there are $2^{2n}$ subgroups that could be sent. But again we only want to consider even groups so we divide by 2 to get rid of all odd groups. Thus we have $$2^{2n}/2 = 2^{2n-1}$$ Both methods give the same result.


Where does the energy from tidal power plants come from?

Tidal power plants taps into the energy in the motion of the oceans due to the gravitational interaction between the earth and the moon, so much is clear to me. This question is about where would this energy be if it were not exploited by humans. Does it actually make a difference in the orbit of the moon, or would the same energy just become heat in the ocean though friction anyway? To rephrase, are we just redirecting the flow of energy going from the earth-moon orbit into the heating of the earth, or are we actually pulling on the moon to extract energy?


Are My Flags Marked Useful or Helpful Here?

I was scanning the new Profile page to see of I could catch any bugs but this one has been bothering me for rather long time. Looking at the tooltip when the cursor is hovering over the helpful flags, it says that...    ...     Total number of raised flags marked useful   Yet the flags are supposedly marked helpful. So to stop the confusion, can we change the original tooltip to this tooltip?:     Total number of raised flag marked helpful   Edit: This is not a duplicate to Oded's question on the new bugs and feedback question for the profile page. This is just one feature-request I want implemented, not a bug.


Novel about a girl who climbs around inside the walls of a spaceship

I remember reading a young adult novel in the '90s about a girl traveling on a spaceship. If I recall correctly, there's a dangerous race of aliens who can disguise themselves as humans, and she discovers that one of them is on the ship with her. She somehow ends up inside the walls of the spaceship, I believe in order to spy on the alien, and I think it ends up pursuing her through the walls toward the end of the book. Anybody know what it could be?


I am having problems at the moment of initialize the array and returning it. The method is suppose to return common items of a generic array, but i cant initialize array "a" or returning it. Any advice??   public static <T> T[] commonItems( T[] arr1, T[] arr2) {     T[] a;     int pos = 0;     for( int i = 0; i < arr1.length; i++)     {         for(int j = 0; j < arr2.length; j++)         {            if(arr1[i].equals(arr2[j]))            {                a[pos] = arr1[i];                pos++;            }         }     }     return a; }


Non-UFD integral domain such that prime is equivalent to irreducible?

In the integral domain every prime is irreducible. But the converse is not true, for example, $1+\sqrt{-3}$ is an irreducible but not a prime in ${\Bbb Z}[\sqrt{-3}]$. In a UFD, "prime" and "irreducible" are equivalent.   Here is my question:     Is there a non-UFD integral domain such that prime is equivalent to irreducible?


How to define a Bijection between $(A^B)^C$ and $A^{B \times C}$

Here are two sets which I need to define a bijection function in order to show they are equivalent: $$ (A^B)^C \triangleq \{f:C\rightarrow \{g:B\rightarrow A\} \} $$ $$ (A^{B \times C}) \triangleq \{ h:B \times C \rightarrow A\} $$ where $A, B, C$ are sets, and $f, g, h$ represent functions.  I am trying to define a function $F : C \rightarrow A$ , but still struggling with its formal description, and how to use functions like $g$ above.  What is the right way of showing that such bijection $F$ exists?


How can I reset all the bind keys in my Bash?

I bound some keys by mistake, and they don't work any more, such as HOME, END, UP, DOWN, LEFT, RIGHT.  Is there a way to reset all the bound keys to their original state?


I accidentally removed my windows when I install ubuntu. How to install windows after ubuntu? and how to make memory partition in ubuntu?


Why do some movies originally shot on film have notably vivid reds and skin tones?

Many older movies seem to have vivid reds and particularly realistic or noticeable skin tones (they certainly seem to stand out from typical skin tones on TV or the majority of movies). This applies even in DVD or online versions and is not, given the range of material I've noticed the effect in, an artifact of special post processing or deliberate colour manipulation.  All the movies I've noticed the effect in are from the film era, especially from when colour became common to the late 1960's. I used to think it was just Technicolor but I've seen things recently that don't claim to be Technicolor that also show the effect.   claims the effect was due to the final print being constructed late in the process for separate black and white film strips for each primary colour allowing the final dyes to be very vivid and clear:     The rich colors that the Technicolor process gave came in part from the fact that the color was not added to the process until the final stages. The color information was recorded and processed as separate black and white images which were relatively easy to control and preserve.   Is this a good explanation?


Will an undead companion naturally recover Hit Points?

Here is the background. So, I am playing in a campaign where I have a homebrew spell with allows me a Zombie-like companion (basically a Zombie with additional HPs).   If I cast the spell every 8 hours for 8 days, I get to keep it as a permanent companion. However, I'm trying to work out how I can restore or increase its HPs, so that it doesn't die (lol) on me.   Would a Zombie companion (un)naturally recover HPs each day?   This is not a question about "healing" an undead creature such as a zombie.


Proving that if a set is both open and closed then it is equal to the real numbers

Prove that if $A$ is both open and closed then $A = \mathbb{R}$ also as one suggested let $A \neq \emptyset$  You may use what ever definition of open and closed you would like, just avoid going into metric spaces, haven't covered that topic yet. My question is well essentially how to prove this statement but considering I like to do things myself, I was wondering if anyone had any particular suggestions to help me solve this.  attempted proof: Let $a\in A$ then since $A$ is open there exists an open interval $N(a,\epsilon)$ such that $$a\in N(a,\epsilon)\subset A$$ Then $a$ must be an interior point of $A$, but since $A$ is also closed then $a$ must also be an accumulation or limit point of $A$ as well.   I am going to stop here because I am not sure if this is the right approach here, any suggestions would be greatly appreciated.


How to install curl package .deb file in ubuntu 16.04?

I download curl deb file from curl official site : . I want to install curl deb file but meet this trouble:     Please tell e how to fix this trouble. I'm not edit anything on /etc/apt/sources.list. Why this trouble happend to me?


I'm making an earth in blender and the edge of the night is wavy and sharp. and here is the picture of the shader editor.


Two Email Accounts in Mail.app / Can I disable notifications for one of them?

Hopefully this is an easy one! :-) I am working in Mail.app these days in Mountain Lion and I have two mail accounts within. I'd like to disable all notifications for one of those accounts. This means no popups or items in Notification Center.   Is this possible?


Why are StackExchange "hot questions" now invisible?

I used to click on "Hot Questions" in the top bar as I am fond of them. But I cannot do that now ever since the top bar was redesigned. I now have to visit  for that. Why was it removed? And are there plans to bring it back?


Does 1,864 centimorgans indicate half-siblings?

My sister, daughter and I all took DNA tests for fun. My sister and I show up on Ancestry as "close family," and share 1864 Centimorgans, and we do not share any relatives that my daughter and I share on one my father's side of the family.   I wonder whether she may be only a half sibling?    I am hesitant to ask to see her matches, and my other siblings are dead.   Any ideas how to pursue?


How to calculate raster statistics for polygons?

how can I calculate sums, averages etc of raster-points (multi-band) per polygon of a vector-layer. I was told that this is called "zonal statistics". I tried that with QGIS first.   There is a way to do it but that is much too slow (convert raster to vector, intersect with second vector-layer, calculate geometry, export numbers, calculate statistics with spreadsheet or other program, re-import the results, takes forever for my 350.000 raster-points).  I was also given the hint to use saga-gis. That has "zonal statistics" but those are based on categories from a raster-band, not on polygons from a vector-layer. So to use this I would have to convert my vector-layer to raster and then calculate the statistics.  This seems to be the wrong way to solve this. There would be no way to account for raster-points that belong to 2 or more polygons because they are intersected by the polygon-boundary. I assume that polygon-based statistics should be able to handle this so I also assume that I haven't found the correct module yet.  Saga-gis has really many modules. Please let me know which one is the right one for this application.


Sometimes people are referring to mechanical objects as "she":     I love my car. She always gets the best service.   Are there any rules when it is appropriate to use "she" instead of it, and is "he" ever used in such context?


How can I make video calls on Ubuntu 16.04?

I would like to know the easiest method of video calling from my new laptop running Ubuntu 16.04.   I have tried Skype but it keeps crashing and also tried whatsApp, which does not provide a video call option for this version.


Prove that $\tan(x) \gt x$ for any $x$, $x\in(0,π/2)$

I'mm trying to prove that with Lagrange sentence,  $F(x)= \tan(x)$  $G(x)= x$  I was trying to show that for any $x\in(0,π/2)$, $F'(x)=G'(X)$.  Then according to Lagrange: $G(X) = C\cdot F(X)$ which means that $F(X)\lt G(X)$ for any $x\in(0,π/2)$.


Goodness-of-fit tests for logistic regression

from my knowledge, there are two approaches to evaluating whether the model fits the data in logistic regression. First is the predictive power. Second is from using goodness-of-fit tests.  My question is that if the results from Pearson's chi-square and Hosmer-Lemeshow test are in conflict (one significant, the other insignificant), what should I do next? Try to fit in interactions & non-linearities?   I know these two tests have their limitations. Pearson requires sufficient expected number of events/non-events for each profile or covariate pattern. Conclusion from HL test depend on the number of groups chosen, and there is no established theory to guide the choice of that number. I think the other alternative tests are not implemented in Stata yet.   On a side note, I noticed that many papers actually do not report any tests to assess their models. Why is that so?


not able to understand how compiler(gcc) is interpreting the command(c) and giving output of the statement

Can anyone help me out, I am not getting how gcc is compiling the below statement and printing its output.:-  printf("%d",7["sunderban"]);


Redirect to login page if login block fails

If you fail to log in correctly from a login block, I would like the user to be directed to the login page to log in from there.  How can this be accomplished?


Prove that $\sup[f(x)+g(x)]\le \sup(f(x)) + \sup (g(x))$

How to prove that: $ \sup[f(x)+g(x)]\le \sup(f(x)) + \sup (g(x))$  For me, it sounds very logical and obvious but I did not find the way to prove this. I will be glad for any tips.


How to read a windows registry file using java?

Is there any Java library available to handle the windows registry file (.reg).Like read and write KEYS, SUBKEYS and DATA from an selected registry file.  NOTE: There is solutions available to handle the Windows registry by java. But the needed is to reading registry values, keys and data from (.reg) extension file not directly from registry.


Recurrence. Nonhomogeneous recurrence relation.

Given the following recurrence relation: $$ {a_{n+1}}={(a_{n})}^2-2 ,\\a_0=\frac{5}{2}$$   Prove that $\left \lfloor{a_{n}}\right \rfloor $ is a power of 2 for every natural number n, using recurrence equation transformations ( i.e. without induction).


I am having issues with a class project, one part of it specifically.   this is what the assignment says Write a program that manages a list of up to 10 players and their high scores in the computer's memory - do not write to the disk. Use one array of Player objects. The Player class should store the players name and score, with suitable constructors, accessors, and mutators. The Player class should also override the equals and toString methods appropriately. Your high score program should support the following features: - add a new player and score - print all of the players' names and their scores to the screen - allow the user to enter a player's name and output that player's score or a message if that player's name has not been entered - allow the user to enter a player's name and remove the player from the list  Create a menu system that allows the user to select which option to invoke.  So far I have been able to create a menu, add a player and a score, and print all of the players added. The issue I am having is searching the array for a specific name and then being able to remove that player.  below is a snippet from my handler class that handles the information.      public void removePlayer(String playerName)     {         //remove player from player array         //it doesn't work and I do not know how to get it to work         //the issue I have is I dont know how to compare a string to         //an array of players it doesnt compile correctly         //with the error "Incompatible Operand types players and String".          for (int i = 0; i< players.length; i++)         {             if(this.players[i] == playerName)             {                 for (int x = i; x<players.length; x++)                 {                     this.players[x] = this.players[x+1];                 }             }         }     }   I understand this is wrong but I do not know what to do to make it correct. here is the players class that takes in the info.  public class players {     private String playerName;     private int playerScore;      public players(){      }     public players(String newName, int newScore){         playerName = newName;         playerScore = newScore;      }        @Override     public boolean equals(Object otherPlayer){         return false;     }     @Override     public String toString(){         return playerName + " " + playerScore;     }  }   and lastly the handler code for the array. and how it adds players.  public class highScoreHandler {     private final static int PLAYER_LIMIT=10;     private players[] players;     private int pointer;       public highScoreHandler(){      this.players = new players[PLAYER_LIMIT];      for (int i = 0; i< players.length; i++)     {         this.players[i] = new players();     }      this.pointer = 0;  }      public boolean addPlayer(players newPlayer)     {         //add new player to player array         if(this.pointer > this.players.length-1)         {             System.out.println("please remove a player.");             return false;         }            else         {             this.players[this.pointer] = newPlayer;             this.pointer +=1;             System.out.println("Player has been added!");             return true;             }      }   any help would be greatly appreciated, thank you.


Is  there a way to show \sum limits partially in inline mode and partially in display mode? I want to write:  \begin{equation} \sum_{n=-\infty}^{+\infty} [...] \end{equation}   but this way the lower limit is too wide, and I don't like it. So I was hoping to write something like this:  \begin{equation} \sum_{-\infty}^{+\infty}\nolimits_{n} [...] \end{equation}   to write the index n on the right side of the sum symbol, while the limits of the summation remain above and below.  Of course it doesn't work, LaTeX is pissed because there is a double subscript. Anyone knows if it's possible to do what I want to?


Spiderman: Far From Home - Disney or Sony Rights?

I have just watched the Spider-Man: Far From Home trailer, and I'm confused. If this is an MCU-connected film, does Disney/Marvel own the rights? Or does Sony Pictures?   I thought Disney/Marvel owned the MCU films/stories, but the trailer is put out by Sony Pictures, which I didn't think Disney owned. Am I mistaken?   Who actually owns this film?


How to reinstall Ubuntu 13.04 Raring Ringtail safely?

How can I reinstall Ubuntu 13.04 safely, without losing anything except settings? Is it possible? Or at least keep only programs and the home directory?  I want to reinstall as I have recently experienced various issues like the scrolling being very jumpy and lightdm rendering weirdly. Can someone more experienced explain how to reinstall Ubuntu as I have been searching in vain for days. Thanks in advance.


Documents to carry for Europe vacation travel

I'll be traveling to Europe from India for 7-8 days… I am planning to visit France/Switzerland/Italy/Austria/Liechtenstein  Paris is the first stop in Europe.  This being my first international visit, I just wanted to understand if just carrying the passport (with Schengen visa) was enough OR should I carry any additional documents as well. For things like SIM card, are there any other docs required ?


SVN discover when a code was inserted at a given file

Using SVN for version control, is it possible to discover when a specific code was inserted at a given file?   Can i give to SVN, or using tortoiseSVN, a piece of code and a file and SVN discover when that code was first inserted ?


Is it possible to have two gerunds consequently?

Is it correct to say "more and more people are quitting buying CD's and DVD's because of the ..........."   ?  Please help me, I'm writing an essay and this doubt is making me go crazy.


Convert 'intercept/drift' term to 'constant' term in arima/auto.arima functions, in case of higher orders - R

suppose for a time series, the auto.arima output is:  ARIMA(1,0,1) with non-zero mean   Coefficients:          ar1     ma1  intercept       0.7456  0.2775   767.7463 s.e.  0.0804  0.1197     0.1072   It is specified in help file of arima function that definition used for this function is  X[t] = a[1]X[t-1] + … + a[p]X[t-p] + e[t] + b[1]e[t-1] + … + b[q]e[t-q]   and if we include mean(m),  this formula applies to X - m rather than X.  My questions are:  (1)  For the model considered above, what will be the arima equation?    (a) X[t] =  767.7463 + 0.7456*X[t-1] + 0.2775*e[t-1]    or    (b) X[t] =  195.3258 + 0.7456*X[t-1] + 0.2775*e[t-1],   where constant term is achieved by 195.3258 = 767.7463*(1-0.7456).  (2) How to interpret this constant term if we have more than one AR coefficient?  e.g. ARIMA(2,0,2) with non-zero mean   Coefficients:           ar1      ar2     ma1     ma2  intercept       -0.0124  -0.6945  0.3629  0.9414    -0.1288 s.e.   0.1172   0.1132  0.0598  0.1270     0.0636   (3) What should be the ARIMA equation in presence of drift term?  e.g. ARIMA(1,1,0) with drift           Coefficients:          ar1   drift       0.3307  0.3981 s.e.  0.0946  0.1463


Why does autoboxing make some calls ambiguous in Java?

I noticed today that auto-boxing can sometimes cause ambiguity in method overload resolution. The simplest example appears to be this:  public class Test {     static void f(Object a, boolean b) {}     static void f(Object a, Object b) {}      static void m(int a, boolean b) { f(a,b); } }   When compiled, it causes the following error:  Test.java:5: reference to f is ambiguous, both method     f(java.lang.Object,boolean) in Test and method     f(java.lang.Object,java.lang.Object) in Test match  static void m(int a, boolean b) { f(a, b); }                                   ^   The fix to this error is trivial: just use explicit auto-boxing:  static void m(int a, boolean b) { f((Object)a, b); }   Which correctly calls the first overload as expected.  So why did the overload resolution fail? Why didn't the compiler auto-box the first argument, and accept the second argument normally? Why did I have to request auto-boxing explicitly?


understanding resolv.conf nameserver through system calls

I am trying to understand how /etc/resolv.conf /etc/nsswitch.conf exactly works and what is significance of nameserver entry 127.0.1.1  I did strace ping google.com to get to know about the system calls involved , one part is :  stat64("/etc/resolv.conf", {st_mode=S_IFREG|0644, st_size=172, ...}) = 0 socket(PF_INET, SOCK_DGRAM|SOCK_NONBLOCK, IPPROTO_IP) = 4 connect(4, {sa_family=AF_INET, sin_port=htons(53), sin_addr=inet_addr("127.0.1.1")}, 16) = 0 gettimeofday({1413780874, 913366}, NULL) = 0 poll([{fd=4, events=POLLOUT}], 1, 0)    = 1 ([{fd=4, revents=POLLOUT}]) send(4, "\0040\1\0\0\1\0\0\0\0\0\0\6google\3com\0\0\1\0\1", 28, MSG_NOSIGNAL) = 28 poll([{fd=4, events=POLLIN}], 1, 5000)  = 1 ([{fd=4, revents=POLLIN}]) ioctl(4, FIONREAD, [204])               = 0 recvfrom(4, "\0040\201\200\0\1\0\v\0\0\0\0\6google\3com\0\0\1\0\1\300\f\0\1"..., 1024, 0, {sa_family=AF_INET, sin_port=htons(53), sin_addr=inet_addr("127.0.1.1")}, [16]) = 204 close(4)                                = 0 socket(PF_INET, SOCK_DGRAM, IPPROTO_IP) = 4 connect(4, {sa_family=AF_INET, sin_port=htons(1025), sin_addr=inet_addr("173.194.123.36")}, 16) = 0 getsockname(4, {sa_family=AF_INET, sin_port=htons(58830), sin_addr=inet_addr("192.168.1.13")}, [16]) = 0 close(4)   can any one please explain what is going on here ? specially connect on 127.0.1.1 as it is namsserver entry in my resolv.conf Why we need to make socket connection to 127.0.1.1 ? and how do we get response from it ?


How to create a horizontal tree using braces

I want to create a horizontal tree-like structure using braces, as in:    Please forgive my lack of creativity.  I tried using an equation, for example  \begin{equation*} \text{Animals} \left\{ \begin{aligned} & \text{Cats} & \\ & \text{Dogs} \end{aligned} \right. \end{equation*}   except this is difficult to read and I cannot get the third layer.  I suspect the forest package would work.


Pair bluetooth keyboard when not logged in

I have a brand new Bluetooth keyboard (replacing an old one I spilt coffee on) and I would like to pair it with my iMac.   Trouble is, I can't log in to the iMac because the keyboard is not paired.  How do I resolve this chicken-and-egg situation? (I don't have any other keyboards to hand.)


What are people using currently for virus and malware checks? I realize there is far less need for this with Linux than with Windows, but I still prefer wearing a seat belt just moving my car out of the driveway. I installed rkhunter and chkrootkit from Aptitude. Is there anything else in general favor? Most posts I read on this topic are five to ten years old, so I thought I'd ask again. Thank you.


Combinatorial proof of $\sum\limits_{k=0}^n \binom{2k}{k} \binom{2n-2k}{n-k} =4^n$

$$\sum_{k=0}^n \binom{2k}{k} \binom{2n-2k}{n-k} = 4^n$$  Is there a combinatorial proof of above identity, without any arithmetic transformation?  Thanks...


How can I capture stdout/stderr in a file but still see it in my console?

I'm using bash script on AMazon Linux.  When I want to redirect stderr and stdout to a file, I can run  ./my_process.pl &>/tmp/out.txt   Is there a way I can redirect this output to a file and continue to see it on the console (in my shell)?  How is this done?


NullPointerException when calling method on a null Map

Why the below code throws null pointer excetion in test.put(1,"sd")  public class HashMap {   @SuppressWarnings("null")   public static void main(String a[]){     Map test = null;     test.put(1, "sd");       System.out.println(test);   } }


Did Odo create his communicator or hide it?

Odo has a working communicator:    Is that a part of himself (like his clothes)? Or is it real but he conceals it?  I imagine it is the latter (would be hard for him to create) but I don't know if it is ever addressed.


I have the following code: (just a test file for encryption/hashing)  <!doctype html>       <?php      error_reporting('off');      if (isset($_POST['submit'])) {         $salt = "2bZ@<^$";         $hash = hash("sha512", $_POST['hash']);         $hash = $salt . $hash;         $hash  = md5($hash);         echo $hash;         $hashLen = strlen($hash);         echo "
The length of the hashed word is " . $hashLen . " characters long!";     }      ?>      <form action="hashed.php" method="post">       <input type="text" name="hash">       <input type="submit" value="Hash" name="submit">     </form>      How safe is this? I know this most probably can be hacked, but how long would it take? I am currently making a php/mysqli registration form and want to make the user's passwords as secure as I can, so that it would take a hacker a very long time to crack one of the user's passwords. To encrypt it even more I can use this for example:   Hashing it with sha512, md5(md5), adding a different salt, two more sha512, another md5 and another different salt!  How secure does that sound? How long would it take a hacker to crack that password? Please could you advise me with using a very, very secure encryption method. Also, I want to keep a user logged in with a cookie: need a secure way to store their information in a cookie!  Thanks in advance :)


So I attempted to prove that between every rational numbers is an irrational as an exercise, and wanted to see if there are problems in my solution.  Proof: Suppose $n \in \mathbb{N}$ and $x$ is a positive  irrational real number and $y \in \mathbb{Q}$ By the archimedian property there is a $n>0$ such that nx>y Let $x$ and $y$ be such that $y<nx<x+y$ As $nx>y$, $(n+1)x>y$ , and similarly,$nx<x+y$, so $(n-1)x<y$ so $$(n-1)x<y<(n+1)x$$ Diving throughout by $2m$ and $x$, where $m \in \mathbb{N}$ we get $$\frac{n-1}{2m} < \frac{y}{2mx} < \frac{n+1}{2m} $$ in the case that $n$ is odd, then $n = 2k+1$ where $k \in \mathbb{N}$ which simplifies the inequality to $$\frac{k}{m} < \frac{y}{2mx} < \frac{k+1}{m}$$ AS $\frac{y}{2mx}$ is irrational (can be proven by contradiction), this completes the proof  A similar argument can be constructed if $n$  is even, and if $x$ is negative.  Is this proof valid? can i just say this "Let $x$ and $y$ be such that $y<nx<x+y$"?     Proof that between a pair of rationals $\frac{a}{b}$ and $\frac{c}{d}$ there exists a pair of rationals $\frac{k}{m}$ and $\frac{k+1}{m}$ such that $\frac{a}{b} \leq \frac{k}{m} \lt \frac{k+1}{m} \leq\frac{c}{d}$ where $a,b,c,d,k,m \in \mathbb{Z}$    First consider the case where $b=d$. Then $\frac{a}{b} <\frac{c}{b}$.  So $(c-a)\geq 1$ so for any $n>1 \in \mathbb{N}$, $n(c-a) \gt 1$, and $nc>na+1$ Thus we can say $\frac{na}{nb} \lt \frac{na+1}{nb} \lt\frac{nc}{nb} $ and the pair of rationals are $\frac{k}{m} =\frac{a}{b}$ and $\frac{k+1}{m} = \frac{na+1}{nb}$    For the case where $b \neq d$ , we simply multiply the RHS by d/d and the LHS by b/b and the proof follows from the one above.


I know very little of Probability and Statistics, and am wishing to learn.  I see the word "distribution" used all over the place in different contexts.  For example, a discrete random variable has a "probability distribution."  I know what this is. A continuous random variable has a probability density function, then for $x\in\mathbb{R}$, the integral from $-\infty$ to $x$ of the probability density function is the cumulative distribution function evaluated at $x$.   And apparently just "distribution function" is synonymous with "cumulative distribution function," at least when talking about continuous random variables (question: are they always synonyms?).  Then there are many famous distributions.  $\Gamma$ distribution $\chi^2$ distribution, etc.  But what exactly is a $\Gamma$ distribution?  Is it the cumulative distribution function of a $\Gamma$ random variable?  Or the probability density function of a $\Gamma$ random variable?  But then a frequency distribution of a finite data set appears to be a histogram.  Long story short: in Probability and Statistics, what is the definition of the word "distribution"?    I know the definition of distribution in Mathematics (an element of the dual space of the collection of test functions equipped with the inductive limit topology), but not Probability and Statistics.


How to copy and paste files with CLI and have a status

I am trying to copy large amounts of data using SSH so all I have is the CLI.  I am using the cp -a /source/* /dest/ method but I can't tell how fast it is copying or what the progress is.  Is there anything I can add to this command to see this info?


Can I use an HDRI for reflections only, and not have its light affect the scene?

I have my scene perfectly lit without the use of a HDRI, however I would now like to add one just so I can have some world reflections in my glossy objects. I can't seem to get the HDRI reflecting in my objects without it also adding light to the scene, though. Is there any way to use an HDRI solely for reflections, and not have its light also affect the scene? I am using Cycles.  Thanks


What can ghosts make physical contact with?

Moaning Myrtle could go through anything you can name, but makes physical contact with water in her toilet, and can turn on taps. Why's that? What can ghosts touch and what can't they touch?


I'm using Ubuntu 12.04 LTS amd64 and I really need to install libgl1-mesa-glx. First I install with this command  sudo apt-get install libgl1-mesa-glx:i386   Then I got this errors  aungthiha@aungthiha:~$ sudo apt-get install libgl1-mesa-glx:i386 Reading package lists... Done Building dependency tree  Reading state information... Done Some packages could not be installed. This may mean that you have requested an impossible situation or if you are using the unstable distribution that some required packages have not yet been created or been moved out of Incoming. The following information may help to resolve the situation:  The following packages have unmet dependencies:  libgl1-mesa-glx:i386 : Depends: libglapi-mesa:i386 (= 8.0.4-0ubuntu0.7)                         Recommends: libgl1-mesa-dri:i386 (>= 7.2) E: Unable to correct problems, you have held broken packages.   So I tried this.  sudo apt-get install libgl1-mesa-glx-lts-quantal:i386   Similar error Occur  aungthiha@aungthiha:~$ sudo apt-get install libgl1-mesa-glx-lts-quantal:i386 [sudo] password for aungthiha:  Reading package lists... Done Building dependency tree        Reading state information... Done Some packages could not be installed. This may mean that you have requested an impossible situation or if you are using the unstable distribution that some required packages have not yet been created or been moved out of Incoming. The following information may help to resolve the situation:  The following packages have unmet dependencies: libgl1-mesa-glx-lts-quantal:i386 : Depends: libglapi-mesa-lts-quantal:i386 (=   9.0.3-0ubuntu0.4~precise1) but it is not going to be installed                                 Recommends: libgl1-mesa-dri-lts-quantal:i386 (>=  7.2) but it is not going to be installed E: Unable to correct problems, you have held broken packages. aungthiha@aungthiha:~$   how do I solve this. Please, help!


Virtualbox not able to run VMs. Kernel driver not installed

VirtualBox does not want to run VMs. It says the kernel driver is not installed. I reinstalled the virtualbox-dkms package and ran 'modprobe vboxdrv' as root but it still doesn't work.


What can I do to get out of a command block teleporting loop?

I accidentally forgot that I was using a repeating command block, and teleported myself to the front of my house. Now I can't move because my clock is fast and on the lower level. There is another repeating command block spamming gold blocks and I can’t turn it off. I’m surprised my game isn’t lagging, because it’s been going on for 20 minutes while the text to speech for chat is saying over and over “you have been teleported to ...” How can I stop this loop?


I'm trying to include a function in my terminal program (in python) that does the following:  Takes a command - checks if it actually is a command - if it is, run it - if it's not, treat it as function.    Like so;  else:     try:         print("Navigating...")         (input)()   as in, it would then try to go to def (input):  How can I get this to work?


Is there a method to concatenate multiple ArrayLists?  ex:  ArrayList<Integer> a ArrayList<Integer> b ArrayList<Integer> c  ArrayList<Integer> d = a + b + c   where d is a single ArrayList<Integer> that contains all of the values of a,b,c in their preserved orders


Lattice of congruences of a lattice is distributive

Let $\mathcal{L}=(L;\land,\lor)$ be a lattice. Show that the lattice $(\operatorname{Con}\mathcal{L},\subseteq)$ is distributive.  I understand that I only need to show that for any $a,b \in L$ and congruences $A,B,C$ that $$(a,b ) \in(A\land(B\ \lor C)) \Rightarrow (a,b) \in ((A\land B) \lor (A\land C)).$$  If we take $(a,b) \in (A\land(B\ \lor C))$ then $(a,b) \in A$ and $(a,b) \in (B \lor C)$ and we only need to show that $(a,b) \in   B$ or $(a,b) \in C.$  It should be easy, but for some reason I can't prove this.  Any help would be greatly appreciated.


Removing all elements from map that does not match leads to java.util.ConcurrentModificationException

I wrote the following code: for (Character currentChar : userDocuments.keySet()) {     List<QueryDocumentSnapshot> currentList = userDocuments.get(currentChar);     if (currentList == null) {         userDocuments.remove(currentChar);         continue;     }     for (int index = 0; index < currentList.size(); ++index) {         final String currentFullName = currentList.get(index).getString("full_name");         if (currentFullName == null || !(searchText.contains(currentFullName))) {             currentList.remove(index);         }     }     if (currentList.size() == 0) {         userDocuments.remove(currentChar);     } }  I want to iterate over a map Map<Character,List<QueryDocumentSnapshot>> check if the full_name (field of each QueryDocumentSnapshot) contains searchText and if it's not, remove this element from the list. In case list is empty, remove the entire list. But for some reason I get java.util.ConcurrentModificationException on the first line. Also, how can I use contains without case sensitive?


Limit of sum of $\sum_{n=1}^{\infty}\frac{\sin(nx)}{n^2}$

find the lim $$\lim_{x\to 0}\; \sum_{n=1}^{\infty}\frac{\sin(nx)}{n^2}$$    Is it correct to do this: $$\lim_{x\to 0} x\frac{\sin x}{x}+x\frac{\sin2x}{4x}+x\frac{\sin3x}{9x} + \cdots$$ this becomes $$\lim_{x\to 0} x+\frac{x}{2}+\frac{x}{3}+\cdots $$  or $$\lim_{x\to 0} x\left(1+\frac{1}{2}+\frac{1}{3} + \cdots \right) $$  now what does this result to?  if this way is wrong, then can we first find sum of $\displaystyle\sum_{n=1}^{\infty}\frac{\sin(nx)}{n^2}$  , how to proceed to find this sum?


American Living Abroad not working for a US company, what kind of taxes do I pay?

I am an US citizen living abroad, I understand that I need to pay taxes even abroad, but how do I pay taxes if I'm not working for a US company?


TikZ: Having circle borders only grown to the outside

How do I let circle borders only grow to the outside? If I write  \node[circle, draw, minimum size=2cm, line width=4mm] {};   Then the inside of the circle has a diameter of 16mm, since 2mm of the 4mm grow inside the 2cm and 2mm of the 4mm grow outside of the 2cm. How do I get the circle to only grow to the outside? The trivial answer would be  \node[circle, draw, minimum size=2cm+4mm, line width=4mm] {};   Is there a better way of doing it? (Meaning a command that is intended for this?)


Prove that $n^{1/k}$ is irrational unless $n$ is itself an integer $k$th power

Hello I have a maths book and this is one of the questions. It unfortunately doesn't provide the answers for this and I don't know how to go about it. So far I have proof by contradiction suppose that  $n^{1/k} = a/b$ where $a,b$ are in the lowest form let $n = l^{p+k}$, so  $$n^{1/k} = a/b \Longrightarrow (l^p . l^k)^{1/k} = a/b$$ right away if we let $p=0$ we get $n=l=a/b$ therefore is rational how we prove the irrational part I am stuck on and would very much appreciate some assistance thank you all!


Error message when running Eclipse in Terminal

Seems like the Java IDE Eclipse has issues running on my system. When I try to start the program I receive the message:  OpenJDK 64-Bit Server VM warning: Ignoring option MaxPermSize; support was removed in 8.0   This is the logfile:  !SESSION Wed Feb 13 20:52:53 CET 2019 ------------------------------------------ !ENTRY org.eclipse.equinox.launcher 4 0 2019-02-13 20:52:53.576 !MESSAGE Exception launching the Eclipse Platform: !STACK java.lang.ClassNotFoundException: org.eclipse.core.runtime.adaptor.EclipseStarter     at java.base/java.net.URLClassLoader.findClass(URLClassLoader.java:466)     at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:566)     at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:499)     at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:626)     at org.eclipse.equinox.launcher.Main.basicRun(Main.java:584)     at org.eclipse.equinox.launcher.Main.run(Main.java:1438)     at org.eclipse.equinox.launcher.Main.main(Main.java:1414)   How can I solve these errors?


My computer reboots, seemingly completely at random, about once every week to two weeks but has occasionally gone months. It just goes from running fine to the POST with no error messages or anything and doesn't seem to be due to heat or usage as it's happened a couple of times when the computer has booted just a few moments ago and is idling. It's been happening for as long as I've had this computer, almost two years. It's happened in both Vista and Windows7.  I strongly suspect it's a hardware problem. But due to the rareish and random nature of the crashes my normal strategy of just removing hardware until the problem stops isn't really practical. My guess would be Power Supply, Ram, or Motherboard. But I just don't know how to test an issue this random and want to figure out how to confirm which it is before I go replacing things. So is there some software or hardware that can be used to test these sorts of errors? I did run memtest86 for about 8 hours without finding any issues. And the power supply is more than capable of running my system.


Should I include a paper with a low impact factor in my CV

I'm a Masters Student who has an old paper. I wrote a paper years ago with a research group in my old school. However, it's a really simple idea and was published in a not very reputed journal (Impact Factor 0.3). It was a long time ago, and honestly I would rather not be affiliated with it.  International Journal of Advanced Trends in Computer Science and Engineering  Should this be included in my CV?    It's relevant to what I'm doing now but just not very important and I consider it a not very good use of my time


I am not getting the posts under custom taxonomy(fabric_building_types). I am getting cat_id and cat->name also but not able to get the posts.  $args = array(     'type'                     => 'post',     'child_of'                 => 0,     'parent'                   => '',     'orderby'                  => 'name',     'order'                    => 'ASC',     'hide_empty'               => 1,     'hierarchical'             => 1,     'exclude'                  => '',     'include'                  => '',     'number'                   => '',     'taxonomy'                 => 'fabric_building_types',     'pad_counts'               => false  );   $categories = get_categories( $args );  foreach ( $categories as $cat ) {      // here's my code for getting the posts for custom post type      $posts_array = get_posts(         array(             'showposts' => -1,             'post_type' => 'fabric_building',             'tax_query' => array(                 array(                     'taxonomy' => 'fabric_building_types',                     'field' => $cat->cat_ID,                     'terms' => $cat->name,                 )             )         )     );     print_r( $posts_array );  }   Can anyone please help me out...Thanks in advance


How to find out if the Windows are still bootable?

Back in the days I installed both Ubuntu & Windows on two separate partitions of my SSD. Then I stopped using computers for a few years. I forgot a lot. After I pulled my PC back out of storage I turned it on and my Ubuntu 16.04 started. I didn't get an option of choosing OS while booting. I didn't even remember there is Windows installed alongside Ubuntu. I updated Ubuntu to 20.04 and then I found there is still a partition on my SSD containing Windows. Can I still possibly boot up into this Windows anyhow?


When renaming a file in Windows, CTRL + Backspace does not delete whole words

The Ctrl+Backspace shortcut for deleting whole words is a feature in most text editors and text inputs. Due to their usefulness, they have become a part of my everyday typing habits. However, in Windows Explorer, when renaming files, Ctrl+Backspace enters a  character instead of deleting the previous word. Oddly enough, it's lesser used sibling for deleting the next word Ctrl+Delete works as intended when renaming files.  This is a problem on my work PC, which uses Windows 7. But I recall this being a problem in my home PC,  which is running Windows 10.  Why does this seemingly universal shortcut not work in this scenario? Are there workarounds (be it first party or third party) to implement this functionality?


Find the value of $$\sum_{i=0}^{100}\dbinom{k}{i}\dbinom{M-k}{100-i}\frac{k-i}{M-100},$$ where $M-k>100,k>100$.   My approach: The Vandermonde's identity states that $$\sum_{i=0}^r\dbinom{m}{i}\dbinom{n}{r-i}=\dbinom{m+n}{r}$$ for any non-negative integer $m,n,r$.   Therefore setting $m=k$, $n=M-k$ and $r=100$, in the Vandermonde's identity we have, $$\sum_{i=0}^{100}\dbinom{k}{i}\dbinom{M-k}{100-i}=\dbinom{M}{100}.$$  This implies that $$\sum_{i=0}^{100}\dbinom{k}{i}\dbinom{M-k}{100-i}\frac{k-i}{M-100}$$ $$=\frac{k}{M-100}\sum_{i=0}^{100}\dbinom{k}{i}\dbinom{M-k}{100-i}-\frac{1}{M-100}\sum_{i=0}^{100}\dbinom{k}{i}\dbinom{M-k}{100-i}i$$$$=\frac{k}{M-100}\dbinom{M}{100}-\frac{1}{M-100}\sum_{i=0}^{100}\dbinom{k}{i}\dbinom{M-k}{100-i}i.$$  I need help in evaluating the expression $$\sum_{i=0}^{100}\dbinom{k}{i}\dbinom{M-k}{100-i}i.$$


For the consistency check of a backup program, I want to define a function which counts all files in a directory including all files in subdirs, subsubdirs and so on.  The solution I am trying so far is as follows:  countfiles() {   local cdir=$1   local files=$(ls -la $cdir | grep -cv '^[dl]')    local dirstring=$(ls -la $cdir | grep '^d' | egrep -o ' \.?[^[:space:].][^[:space:]]+$')   local directories=(${dirstring//"\n"/})    echo ${directories[@]}     for dir in ${directories[@]}; do     echo -n "$dir "     echo -n 'filecount >> '     local dirfiles=$(countfiles "$cdir/$dir")     echo -n $dirfiles     echo ' <<'     #files=$(($files+$dirfiles))   done    echo $files  }   Which gives me the following output:  .config .i3 .scripts .config filecount >> gtk-3.0 termite gtk-3.0 filecount >> 2 << termite filecount >> 2 << 1 << .i3 filecount >> 5 << .scripts filecount >> 2 << 5   While the actualization of my $files counter is commented atm and I may need to unlocalize it, right now I set all variables as local to avoid any interference.  The directory tree is as follows:  /.scripts/backup_dotfiles.sh /.config/termite/config /.config/gtk-3.0/settings.ini /.i3/config /.i3/i3blocks.conf /.i3/lockicon.png /.i3/lockscreen.sh /.gtkrc-2.0 /.bashrc /.zshrc /.i3 /.Xresources   My questions:   Why does it always count the files +1 except for the master directory? Why does it count anything in the '.config' directory, as there are no files in there? How can I fix this?


$\int_{-\infty}^{+\infty} e^{-x^2} dx$ with complex analysis

Inspired by  recently closed question, I'm curious whether there's a way to do the Gaussian integral using techniques in complex analysis such as contour integrals.  I am aware of the calculation using polar coordinates and have seen other derivations. But I don't think I've ever seen it done with methods from complex analysis. I am ignorant enough about complex analysis to believe it can somehow be done without knowing how it would be done.


Hard Drive Utilization over time on Windows 10?

I've noticed the hard drive use light flashing like crazy and I'm not using this PC (hardly ever do). How can I log what's going on for a time period?   For example: what files are being created/accessed/deleted/moved/copied etc, what folders or programs are being used/accessed. If an external device/site is doing the access (I do have a Cloud/NAS), note that, perhaps a MAC ID, IP address, etc. I've seen a number of software apps to take a snapshot of disk usage, but I want to see what's going on without my (seeming) intervention.


How can the median number of sexual partners be 6.1 and 3.6?

Median number of female sexual partners in lifetime, for men 25-44 years of age, 2006-2008: 6.1  Wouldn't it only be able to be x.5 or x.0?


:  Why and how are some questions deleted?  Analysing user biorhythm.. Merging with Russian botnet..   :  How do I ask a good question? I have two XmlDocuments and I would like to move an XmlNode selected from one of the documents and append it at a particular location in the other document. The naively intuitive approach of simply calling AppendNode(xmlNodeFromDocument1) at the appropriate place of document 2, of course doesn't work because the method does not take care of manipulating the owning document. I finally found the answer literally as I was writing up this question, but since it took so long for us to find it in the System.Xml classes, I figured I'd post it here to assist anyone else stuck searching for it.  Is it a bug? Joke? Break-in?


Why do two bodies of different masses fall at the same rate (in the absence of air resistance)?

I'm far from being a physics expert and figured this would be a good place to ask a beginner question that has been confusing me for some time.  According to Galileo, two bodies of different masses, dropped from the same height, will touch the floor at the same time in the absence of air resistance.  BUT Newton's second law states that $a = F/m$, with $a$ the acceleration of a particle, $m$ its mass and $F$ the sum of forces applied to it.  I understand that acceleration represents a variation of velocity and velocity represents a variation of position. I don't comprehend why the mass, which is seemingly affecting the acceleration, does not affect the "time of impact".  Can someone explain this to me? I feel pretty dumb right now :)


Is it possible to set the default web site to redirect to a virtual directory in IIS

Can you set up a website to make a default redirect to a virtual directory?  I tried to do this but it overrode every single website in my setup to that redirect.   I want to be able to open  and have that redirect somewhere.


Exception in thread "main" java.lang.NullPointerException in array

Is there a way to avoid this error java.lang.NullPointerException in array?  I create an array with allocated size. But sometimes it doesn't fill up. And I get the error. How to avoid it?  The code:  public static produktas[] surasti (produktas G[], int n){     try{     int x = 0;     BufferedReader in = new BufferedReader (new InputStreamReader (System.in));     produktas A[] = new produktas[5]; // size of array, but sometimes it may be 1 element, or two, or etc.     for (int j=0; j<5; j++){     System.out.println("Kokio produkto ieskosime?");     String found = in.readLine();     for (int i=0; i<n; i++){         if (found.equals(G[i].gautiPav())){              A[x] = G[i];             x = x + 1;         }     } }  return A;  } catch(IOException ie){         ie.printStackTrace();     }     return null; }   And I'm asking about how to make dynamical array or smth, so it's not related to that topic.


Cannot reset MySQL default root password after initial installation

I have installed mysql 5.7 on a Red Hat Enterprise Linux 5.5 server and when I tried to run following command after installation it is asking for a password for root@localhost.  /usr/bin/mysql_secure_installation   I have never set a root password and I'm logged in to Linux as root user.  Then I have found following documentation for resetting root password and followed that one too.    But even after starting the server with following command it is asking for a password  /etc/init.d/mysqld start --skip-grant-tables &   I have tried starting the server with init-file option, but no success.  Does anyone know how to reset the password correctly or default MySQL password?


How to properly do top-down aRPG melee attacks?

I'm reposting this from my own thread in reddit's gamedev community, since there were too few responses:  I've been looking for some info on that, but I mostly find articles on the , which are very useful, but not helpful from the coder's point of view. My main idea is similar to what the 2D Zelda games used to do, but with more directional freedom. In Zelda, you can only face one of the cardinal directions and attack the enemy there. My idea is to have the same but with any direction, since we now have analog sticks, or even mice. I'm pretty sure this has been done before, and a few Flash games come to mind, such as the Zombie Apocalypse game  (which is now done on Unity3D, but was Flash back when I played it)  I'm working with Unity3D (although I'm making a 2D game), and I'm not completely happy with where I'm going.    This:  is my current hacky solution for a Melee hit check. The green triangle is the player, the faint green circle is a trigger that checks if there are enemies in this trigger, and the red boxy thing is an enemy. When the player presses the "melee attack" button, it picks one of the enemies in the trigger (by order of the first one to enter the trigger) and causes damage.   Among a few things I've added to that are: Slow down the player movement during an attack, so that they can't "run n' slash" through an entire level, and also limit how many attacks the player can do per second. An attack cannot start if the previous one hasn't finished yet.  This is looking a bit crude, though. I just kind of hacked it together and it doesn't feel as natural as in other games I've played.  Here's my hacky Melee Attack script in my prototype (it uses a few magic numbers, such as the attack duration):  void Update() {  //other logic     if (Input.GetMouseButtonDown (0) && sec <= 0)      {         attackDuration = 0.5f; //setting how long the attack takes from start to finish     }     if (attackDuration > 0)     {         attackDuration -= Time.deltaTime;         if (attackDuration <= 0.25f && !done) //cause the damage when the attack is halfway done         {             if(EnemiesInRange.Count > 0)             {                 Enemy target = ((GameObject)EnemiesInRange[0]).GetComponent<Enemy>();                 target.health -= 10;                 if (target.health <= 0)                 {                     EnemiesInRange.Remove(target.gameObject); //if the enemy dies, it's no longer a valid target.                  }              }             done = true;         }     }     else     {         done = false;         sec = 0; //attack over, reset it to zero (to avoid stuff like -0,001)     } //other logic }   Meanwhile, in the CharacterMovement.cs script:  void Update() { //other logic     if(gameObject.GetComponent<MeleeAttack>().sec <= 0)     {                lookAtMouse();         transform.Translate(new Vector3(Input.GetAxis("Horizontal"), Input.GetAxis("Vertical"), 0) * baseSpeed, Space.World);     }     else     {         transform.Translate(new Vector3(Input.GetAxis("Horizontal"), Input.GetAxis("Vertical"), 0) * (baseSpeed*0.25f), Space.World);     } //other logic }   What I'm doing here is stopping the player to change their facing during the attack as well as slowing the movement down to 1/4 the base speed.  Anyway, any advice? How could I make attacking and moving feel more natural? What about the hit mechanics themselves?   My biggest gripe right now is: I don't think "Pick an enemy in a small circular area ahead of the player" is really good.  What should I do?


Books say that special relativity is indistinguishable from Newtonian mechanics when the speed of the primed frame ($v$) is small compared to the speed of light ($c$). This is what I mean by the "Newtonian limit" property of special relativity. (I don't know the correct name for it). But the transformation of the time coordinate  $$t' = \gamma \left(t + \frac{vx}{c^2}\right)$$  involves the spatial quantity $x$ which, if large enough, could balance out the smallness of $v/c^2$. So why doesn't this observation mess up the "Newtonian limit" property?


to know more about (already output) in logs

While using system.debug for a list  I get an already output statement added in the logs as     USER_DEBUG|[]|DEBUG|lstApprovalDetails   (ApprovalDetails:[startDate=2002-01-03, status=Rejected], (already   output))   CAppresponse.ApprovalDetails AppDet = new CAppresponse.ApprovalDetails();  for(Approval_RD__c appDetail:lstRD) {     AppDet.startDate=string.valueof(appDetail.Start_Date__c);     AppDet.status=appDetail.Status__c;      lstApprovalDetails.add(AppDet);      system.debug('lstApprovalDetails '+ lstApprovalDetails);     }    Wanted to know the meaning of this already output here .Thanks in advance


Determining the limit of $\lim_{h \to 0} \frac{cos(x+h) - cos(x)}{\sqrt{x+h}-\sqrt{x}}$ when x > 0

I'm pretty sure that this uses L'Hopital's rule but when I try to apply this I end up going in circles and am unable to ever find a limit.   Taking derivatives of numerator and denominator:  $\lim_{h \to 0} \frac{-sin(x+h) +sin(x)}{\frac{1}{2}({x+h})^{-1/2}-\frac{1}{2}{x}^{-1/2}}$  This still results in $\frac{0}{0}$ though.


I was trying to solve one exam question, where question was asked that what is the sizeof class A and class B?  class A {     char c;     short s;     char c2;     int i; }; class B {     int i;     short s;     char c, c2; };   As per me   sizeof class A : 8  (char:1, short:2, char:1, int:4  -- No Padding)  sizeof class B : 8  (int:4, short:2, char:1+1  -- No Padding)  When I tried in my system then I got different output than what I was expecting  sizeof class A : 12   sizeof class B : 8   When I made some changes in the class  class A {     char c,c2;     short s;     //char c2;     int i; }; class B {     int i;     short s;     char c, c2; };   Then Output was sizeof(A): 8 and sizeof(B): 8  Can someone please explain me that how output is 12 & 8? Thanks in advance


How to correctly choose the preposition in "fire (at, on, in, to) target"?


Notification for specific user's answers

I know that if I follow a question, I am notified if the question receives an answer. I am also notified for every single comment, edit, close, etc. I see some users who are actually good contributors. Most of the time, they provide answers to valuable questions. Also, they generally do not ask questions. Feature Request: For example, as I think user (M.x) is a good contributor on Stack Overflow, I want to be notified of all his answers, give us the ability to follow specific users' answers. I don't know about the possibility to implement that feature or about the complexity. For study purpose, would it be helpful? Personal Opinion: I  think it will be helpful for me. Note: I know there is a way for everyone to see all questions/answers and also without logging in. Also, I know If I go to one user's profile and vote on his questions/answers, that's serial voting and will be reversed and both accounts can be banned. Also, anyone can say that you can bookmark the user's profile and check their answers every day. Why? But notification is different. It will remind the user that you have something new you can read/learn now. If anyone thinks this way, it will be helpful.


Any group of order $p^2q^2$ is not simple for $p,q$ prime

I want to know if the following is correct:  If $G$ is abelian, then is trivial since any subgroup is normal and because of Lagrange, it has an element of order $p$.   If $G$ is not abelian, then, I can supose $q > p$, so, Sylow says that $n_p | q^2$, $n_p \equiv 1(p)$, $n_1 | p^2$, $n_q \equiv 1(q)$, so $n_q =1$ or $n_q = p^2$, since if $n_q=p$, it can't happen that $n_q \equiv 1(q)$.   If $n_q = 1$ then $G$ is not simple. Otherwise, $n_q = p^2$, so $p^2 \equiv 1(q)$, so $q | p^2-1 = (p-1)(p+1)$. Since $q$ is prime, this means that $q|p-1$ or $q|p+1$. But it can't be that $q|p-1$ for the same reason as before. So $q|p+1$. But the only primes that can accomplish this are $p=2$ and $q=3$. So I'm left with the case that $|G|=36$, but this is a case I already know from before that is not simple.  Is this correct?  Thanks


What is the difference between sudo -i and su?

It seems as if there is no difference whatsoever. When the whoami or id commands are run, they all yield root credentials. Is this an illusion? If the root account is disabled by default in Ubuntu, and therefore su gives and authentication error, then why allow sudo -I  Edit: Excuse me, the ONLY difference I have learned of is that sudo -I asks for the password of the user who invoked the command, and su asks for root, or some other target user's password.  Is there any OTHER difference?


Showing two ring homomorphisms that agree on the integers must agree on the rationals

I have two ring homomorphisms $f,g\colon \mathbb{Q}\to X$. I know that $f=g$ on the integers. How can I show that $f$ and $g$ agree on the rationals?   My attempt:  let $x,y \in \mathbb{Z}$, $y\neq 0$.  $$\begin{align*} f(x/y)&=f(x)f(1/y) &&\text{because }f\text{ is a ring homomorphism}\\  &=g(x)f(1/y) &&\text{because }f\text{ and }g\text{ agree on the integers} \end{align*}$$  I do not know how to rewrite $f(1/y)$ so that I can replace it with $g(1/y)$. Any hints will be much appreciated. Thanks.


Gaussian integral with imaginary coefficients and Wick rotation

Although this question is going to seem completely trivial to anyone with any exposure to path integrals, I'm looking to answer this precisely and haven't been able to find any materials after looking for about 40 minutes, which leads me to believe that it makes sense to ask the question here. In particular I'm looking for an answer wherin any mathematical claims are phrased as precisely as possible, with detailed proofs either provided or referenced. Also my search for a solution has led me to think I'm actually looking for a good explenation of Wick rotation, which I can't really claim to understand in detail. Any good references about this would be very welcome as well.  I'm looking to make sense of the following integral identity:  $$\int_{-\infty}^{\infty} dx \ \exp\left(i\frac{a}{2}x^2+iJx\right)=\left(\frac{2\pi i}{a}\right)^{1/2}\exp\left(\frac{-iJ^2}{2a}\right), \qquad a,J\in\mathbb{R}$$   (and various other sources) say that "This result is valid as an integration in the complex plane as long as a has a positive imaginary part." Clearly the left hand side does not exist in Lebesgue sense for real $a, J$. An answer to the question "" claims:      "it is convergent as a Riemann integral, thanks to some rather delicate cancellations. To make the integral well defined -- equivalently to see how these cancellations occur -- we need to supply some additional information.   Wick rotation provides a way of doing this. You observe that the left hand side is analytic in t   , and that the right hand side is well-defined if Im(t)<0. Then you can define the integral for real t by saying that it's analytic continued from complex t with negative imaginary part."   I want to see the gory details and all known motivation for the validity of this procedure for the kinds of applications where such integrals occur. Suggestions such as "include an $i\epsilon$ in order to make it finite" seem arbitrary. In that case one would have to motivate that prescription from the very start, that is within the modeling procedure that ends up giving that integral expression (which is likely the correct way to approach this). I'm also not sure how to interpret the right hand side, since it involves the square root of an imaginary number, which should involve some choice of branch cut, which I have never seen specified in connection to this formula.


Is there a function thats not in Big O and not in Big Omega?

I've been thinking about this problem for a while now but I can't fully come up with an example. It would make sense that this would exist and the only way I think it would work is if the functions were oscillating up and down and you could never find a point where f(n) is always bigger than c * g(n) and you could never find a point where f(n) is always less than c * g(n)


What does lens resolution expressed in megapixels mean?

In this , Tony Northrup says that because the kit lens of Nikon D3300 is 9 mega pixel, you won't use all 24 mega pixel provided by the sensor.  What is the lens resolution? I know that the sensor is made of small dots or pixels which define the sensor's resolution. How do we define lens resolution?


Example of auto-regressive integrated moving average (ARIMA) model

I need simple example of ARIMA model, that performs forecasting on a small time series set e.g., (x1,y1), (x2,y2), (x3,y3), (x4,y4), (x5,y5), (x6,y6)  I found many definitions from various places… but I couldn't find a solved example.


Have you been cooking something? or Have you been cooking anything?

"There is a strange smell here. Have you been cooking something?" Is something correct here? As far as I know we must use any in negative and interrogative sentences...


Convergence of Infinite Series - Complex numbers

Having trouble with this infinite series and deciding whether it converges or diverges.  The series:  $$\sum_{n=1}^\infty \frac{1}{2+i^n}$$  I tried using the ratio test but get stuck in the computation. Ended up with something like $$\lim_{n\to \infty}\frac{2+i^n}{2+i^n*i}$$  Do I have to take the modulus of the rational first? what's the modulus of $i^n$?


How can I add an integrated Google search to my website?

Basically I have a website.  I have a properly setup sitemap so I assume Google knows about all of my pages.  And I've seen on some sites, the search form leads to a page with the shell of the original site but the results are clearly provided by Google.  Similar to codinghorror.com's search, however his results aren't shown within his website's layout.  Any idea what I'm talking about or how to achieve this?


What are the most commonly used data backup methods for Mac OS X Yosemite version?

Please tell me in detail about that. I need some reliable solution for my Mac OS X.


How to prove that $|a-b|<\epsilon$ implies $|b|-\epsilon<|a|<|b|+\epsilon$?

Given  $ a, b, \varepsilon  \in  \mathbb{R} $ prove that   $$|a-b|<\varepsilon \implies |b| - \varepsilon < |a| < |b|+\varepsilon. $$  Hi,  I need help for proof this expression, which could be used arguments or results. I would appreciate any suggestions.


I would like to get some help with finding the derivative of the next function: $F: GL(n,\mathbb{R}) \mapsto GL(n,R) $ , defined by $F(A)=A^{-1} $. One can try find the derivative of the known formula for finding inverse of a metrix by $A^{-1}=\frac{1}{det(A)} adj(A) $ I tried to be sophisticated , using the inverse function formula, but the inverse of the given function, as I see it, is just the same function. Is that right?


SharePoint Images tag which has no alt attribute

On my SharePoint site, I have multiple pages which contains Image tag.  Currently I'm working on to find those image tag which contains no alt attribute.  Is it possible using   C# custom code Using javascript  PowerShell script.   Please Share some approach with useful articles.  Any kind of help would be appropriated.


How to determine if a noun is a place or a thing

I'm having difficulty determining if certain nouns are considered places or things. For example, I'm unsure if 'a park' is a place or a thing. More generally, with the standard definition of a noun as a person, place, thing, or idea, how does one determine the difference between a place, thing, idea, etc. Another example could be 'heaven', is this a place or an idea? I'd greatly appreciate any help. Thank you.


Is it possible to input a file from the web

I am using PHP on my server to create a latex table from a database, which is working fine.  The problem I have now is getting that into my latex document.  I thought that giving it the path would allow it to get the file from the web and input it like normal but that doesn't work and I've been unable to find anything online about doing this sort of thing.  Here is an example of what I'm trying to accomplish:  \documentclass{article} \begin{document} \input{http://example.com/generated-latex.php} \end{document}


Do anyone dissapoiint the achievement rules of Stack network?

I am curious why Stack Network can't count all websites' achievements together. If someone has many stack websites, it will not show all points of a contributor. It sounds that it's a waste of time to level up for other insignificant websites. The question differs from . In my opinion, it's strange to bound the site together on the menu but counts achievement separately.


c++ (double)0.700 * int(1000) => 699 (Not the double precision issue)

using g++ (Ubuntu/Linaro 4.6.3-1ubuntu5) 4.6.3  I have tried different typecasting of scaledvalue2 but not until I stored the multiplication in a double variable and then to an int could I get desired result.. but I can't explain why ???  I know double precission(0.6999999999999999555910790149937383830547332763671875) is an issue but I don't understand why one way is OK and the other is not ??  I would expect both to fail if precision is a problem.  I DON'T NEED solution to fix it.. but just a WHY ?? (the problem IS fixed)  void main() {     double value = 0.7;     int scaleFactor = 1000;      double doubleScaled = (double)scaleFactor * value;      int scaledvalue1 = doubleScaled; // = 700      int scaledvalue2 = (double)((double)(scaleFactor) * value);  // = 699 ??      int scaledvalue3 = (double)(1000.0 * 0.7);  // = 700       std::ostringstream oss;     oss << scaledvalue2;     printf("convert FloatValue[%f] multi with %i to get %f = %i or %i or %i[%s]\r\n",       value,scaleFactor,doubleScaled,scaledvalue1,scaledvalue2,scaledvalue3,oss.str().c_str());  }   or in short:  value = 0.6999999999999999555910790149937383830547332763671875; int scaledvalue_a = (double)(1000 * value);  // =  699?? int scaledvalue_b = (double)(1000 * 0.6999999999999999555910790149937383830547332763671875);  // =  700 // scaledvalue_a = 699 // scaledvalue_b = 700   I can't figure out what is going wrong here.  Output :  convert FloatValue[0.700000] multi with 1000 to get 700.000000 = 700 or 699 or 700[699]      vendor_id       : GenuineIntel      cpu family      : 6      model           : 54      model name      : Intel(R) Atom(TM) CPU N2600   @ 1.60GHz


Is there a reason why the spin of particles is integer or half integer instead of, say, even and odd?

It seems to me that we could change all the current spin values of particles by multiplying them by two. Then we could describe Bosons as even spin particles and Fermions as odd spin particles. Is there some consequence or reason why we can't simply change 1/2 as the smallest unit of spin into 1?  It just seems prettier this way. In fact, there's almost an interesting relation to even and odd functions in that if you switch any two bosons around the wave function stays the same while if you switch any two fermions around the wave function becomes negative.


how to make image frames that give animation effect of a ball or circular object separating from a thick substance

I am trying to draw individual image frames that when pieced together will to give the animation effect of a ball or circular object coming out of a thick (not necessarily sticky) substance or liquid. The idea is for a protruding object to form a circular object as it separates. How can I create these image frames using  illustrator?


AJAX js from the loaded part of the page doesn't work

I'm using vanilla Ajax. I've just loaded the second html page via the first one. In the second one, there are two rows of "script src". No one of it has been loaded. Is there any reason for that?  function loadPage(url)  {     let Request = new XMLHttpRequest();     let content = document.getElementsByTagName('main')[0];      Request.onreadystatechange = () => {         if (Request.readyState == 4 && Request.status == 200) {             content.innerHTML = Request.responseText;         }         else if (!Request) {             alert('Lalala');         }     }      Request.open('GET', url);     Request.send(); }   P.S. Please, advise me resolve without JQuery. THANKS!


How can I get the list packages I installed on my system?

I'm looking for a way to determine which packages I have installed on my system after having installed the OS.  Say for example I install Xubuntu 16.04, which already comes with a certain number of packages. Then I setup all my work stuff and install a whole bunch of other packages.  Is there a way to list only the packages that I personally installed after my distribution was installed ?


Add lines and line number to the pseudocode

I am trying to write some pseudocode. How can I add two line to the algorithm at the top and the bottom as well as adding line number.  Code:  \documentclass{article} %\usepackage{algorithmic}% http://ctan.org/pkg/algorithms \usepackage[]{algorithm2e} \begin{document} \begin{algorithm}[H] \SetAlgoLined \KwData{latitude, longitude, mac, route, direction} %\KwResult{how to write algorithm with \LaTeX2e }  initialize $list$ as an empty  list of integers. \\ %\While{not at end of this document}{ %read current\; $list$ = Get stop Order from behaviour; \\ \eIf{list size > 0}{   find the last stop name in the behaviour table of this mac; }{   find the closet stop of the producer current location; \\   insert it into next table; \\   find initializer; \\   \eIf{initializer is available}{      get the initializer stop name;  \\      restore all stop name for this mac to the behaviour table;    }  } \caption{Detection algorithm.} \end{algorithm}  \end{document}