Proving consecutive quadratic residue modulo p

Let p be a prime with p > 7. Prove that there are at least two consecutive quadratic residues modulo p. [Hint: Think about what integers will always be quadratic residues modulo p when p ≥ 7.]


Will rehashing an SHA256 hash continually, eventually produce every possible value?

So let's say you had infinite time and energy. You have a hashed string of some sort. Because you have infinite time and energy, you can produce a collision(or the original value) easily enough. But, there is a problem. The hashed string was hashed an unknown amount of times. (ie, it may have been produced by sha256(sha256("foobar")) or by sha256(sha256(sha256(sha256("foobar"))))).   You were given a hint by your adversary though. They give you (say) 10 strings, of which one is the initial value that is hashed.   Is it possible to determine with absolute certainty that you chose the correct string? Is it possible that hashing "foobar" recursively an infinite amount of times will eventually yield any arbitrary hash value?  Although my question is about SHA256, I'd be equally curious of other hash algorithms as well


Transit visa Sydney international airport

I am landing in Sydney at T1 from Fiji. 3 hours later I need to have collected luggage and checked in for my Sydney to UK flight, still at T1, just a different carrier. Does this mean I will have to go through customs and immigration? I’ve no idea.  Basically, I need to know if I need a transit visa. The immigration website states that if I'm in transit and don’t leave the transit lounge then it’s fine but... what’s the transit lounge? The terminal?


In his  of the Solitaire keystream generator algorithm, Bruce Schneier warns not to use the same key for two different messages:     The first rule of an output-feedback mode stream cipher, any of them,   is that you should never use the same key to encrypt two different   messages. Repeat after me: NEVER USE THE SAME KEY TO ENCRYPT TWO   DIFFERENT MESSAGES. If you do, you completely break the security of   the system. Here's why: if you have two ciphertext streams, A+K and   B+K, and you subtract one from the other, you get (A+K)-(B+K) =   A+K-B-K = A-B. That's two plaintext streams combined with each other   with no key involved, and is very easy to break. Trust me on this one:   you might not be able to recover A and B from A-B, but a professional   cryptanalyst can. This is vitally important: never use the same key to   encrypt two different messages.   Intuitively, this makes sense, but as he said, I'm not able to recover A and B.  What sort of attack is he talking about?


Why has this question become hot twice within a few seconds of interval? Is that expected to see this in the question log?


I am wondering about the partition function of the classical microcanonical ensemble. It contains Planck's constant and also an indistinguishability argument about the particles I am looking at and I find this confusing for the following reasons:  If I describe for example an ideal gas using classical mechanics, there is no reason why I should assume that there is a problem to distinguish the gas molecules or why $\hbar$ should occur there.   I mean, how could people like Gibbs etc. derive this equation if they did not know about QM?   In some sense, there has to be a reason why we have these two QM properties in there and maybe it is just to get the limit to QM right, but is this really the only reason for this?  I would love to receive a few ideas about this strange definition by this community, in order to get impressions, why we model a (NVE) ensemble this way?


How does a recipient bank, in international wire transfers, gets back its money which it credits to the recipient since there won't be any physical movement of cash from the sender's bank to that of the receiver's?


I created the file ~/.bash_aliases within these lines:  # my alias here  eclipse="eclipse</dev/null &>/dev/null &" okular="okular</dev/null &>/dev/null &" libre="libreoffice</dev/null &>/dev/null &"   My ~/.bashrc is ready to find aliases:  if [ -f ~/.bash_aliases ]; then     . ~/.bash_aliases fi   I then executed . ~/.basharc and also source .bashrc but aliases I created still don't work.


I am struggling with the correct cast. May someone can show me the right direction? See my example below: public enum E_Enum1 { Value1, Value2, Value3 }  public enum E_Enum2 { Bla, blubb, whatever }  public void myMethod(Enum e) { //print e.value in int //print e.toString() }   myMethod(E_Enum2.whatever); myMethod(E_Enum1.Value2);  I want to get a result of: 2 whatever 1 Value2


Why is there this strange contradiction between the language of logic and that of set theory?

In standard probability theory events are represented by sets consisting of elementary events. Consider two events for which (as sets) $A \subset B$. If an elementary event $x \in A$ takes places then we say that $B$ takes place as well. Since $A \subset B$, $x \in A$ implies that $B$ takes place too.  It seems that when for sets (representing events) $$A \subset B$$ $$then \ A \ implies \ B .$$  On the other hand, if we use the language of logic for the events then $$A \supset B$$ $$ \ means\  that \ A\  implies\ B .$$  Why is this strange virtual contradiction between the language of sets and the language of logic?  (In order to avoid down votes and unplesant comments I reveal that I happen to know that the true translation of the sentence $A \supset B$ of logic to the language of sets (representing events) is $\overline{A \cap \overline B}$.)


Problem with system of nonlinear equations

I need help for one math project.  It's about a system of non-inear equations. The system go like this:  $$ f(x)=\left\{ \begin{array}{ll} x^5+y^3*z^4+1 \\  x^2*y*z \\  z^4-1 \end{array}  \right. $$  The right side of the equation is 0.  a) Calculate all the zeros in the system (manually) b) Find the Jacobian matrix, J(x). (Notice that J(x) is singular for z = 0) c) Consider independent two starting solutions:  1) x(0) = {-0.01, -0.01, -0.01}T  2) x(0) = {-0.1, -0.1, -0.1}T  I have tried something but I don't know whether I am right...  $$ f(x)=\left\{ \begin{array}{ll} x^5+y^3*\pm1=-1 \\  x^2*y*\pm1=0 \\  z=\pm1 \end{array}  \right. $$  So because in the middle line there is 0 in the right side some of X and Y must be 0. When i get for Y=0 the result is this: $$x= -1 ,   y= 0,   z= \pm1$$  And for X=0 the result is this: $$x= 0 ,   y= -1,   z= \pm1$$  I dont know where to go after this...  Please help me. Thank you!


How do you persuade an organization to value UX?

UX is such an underrated field in a lot of industries. I wonder how companies consider employing UX designers and even heavily valuing their suggestions. Some big companies happen to see the light and invest in UX, and that keeps them on top of others. However, UX people rarely make it to the top management. In Don Norman's talk (  ), out of so many UX people (I don't know exactly), only two were vice presidents. I assume that there are even less influential UX designers in developing countries, and that's what makes it even harder for people like me. In the same talk, Don Norman suggested that UX designers should approach their executives like marketing people, showing how investing in something will affect profit. Perhaps, it's the best thing to do but it has to be mastered for it to be executed successfully.   I'm a fresh grad and am looking for a job. I think, working for a company with a more conventional job description would be the way to go. When I'm already influential enough, I'll go up to the executives and show them how UX will improve sales (in whatever industry it is. I just want to do UX)  Do you do UX as consultants or are you employed? How do you persuade companies to invest in UX? Are you lucky enough to be employed by people who you didn't have to persuade to value UX?


What's the terminal command for finding out a process's id

I want to exit a process using the command line, but I can't recall the command to look up the process's ID.  Does anyone know it?


Creating new layers using ArcPy to define Definition Query for each field value?

I am trying to set multiple definition queries for one layer based on one field using python.  ie.  I have a City layer with a field that holds the city name.  I want a copy of the layer in an MXD with the Definition query set for each value in the City field.  So essentially, I have one source layer, with a copy of the layer as many times as there are values in the City field.  The query would look like this: CITY = 'Atlanta'


I have an older version of this bike:    They have made some changes to the components since I bought my bike but it is more or less the same.  Here are the .    I was hoping to put a solid fork on my bike for the winter.  I want to keep the mountain feel and have lots of clearance for wide tires, etc but I want to get rid of the weight and give my fork a rest.    When choosing a solid fork what do I need to know?     Will any solid fork fit onto my bike?  Do forks come in different sizes?  Different diameters?  Different lengths?  I heard something like you need a special fork if you are going to put it on a bike that was designed to be used with shocks.   I know that I want a fork with disk break mounts so this makes the search slightly more difficult.  Ideally I would also like rack/fender mounts.  (For future touring).   My wheel size is 26 inches, what would happen if I used a 700c fork on my bike?  This seller claims thats what he was using  for.    Edit:  Thanks for the great information.  After reading I have been looking around for a used local fork.  I think that I found one possibility.  But any feed back would be appreciated.     The fork was designed to be used with 700C or 29 inch wheels but it has an axel to crown length of roughly 17 inches (431 mm).  I currently have 100mm Travel in my suspension fork so  that I should get a fork with a length of 455 mm (17.9 inches).  Is this reasonable?  Does it matter if it was designed for a 700C tire if the fork length is correct? As you can see in the picture of the fork the fork has some rake.  Is this a problem?  Will that amount of rake make the bike ride strangely/differently? The steer tube/ headset size is 1 1/8th standard size which is the same as my bike so no concern there.     Here is a picture of the fork:


What's the point in adding a new line to the end of a file?

Some compilers (especially C or C++ ones) give you warnings about:  No new line at end of file   I thought this would be a C-programmers-only problem, but github displays a message in the commit view:  \ No newline at end of file   for a PHP file.  I understand the preprocessor thing explained in , but what has this to do with PHP? Is it the same include() thing or is it related to the \r\n vs \n topic?   What is the point in having a new line at the end of a file?


Conventions regarding the use of space in mathematical expressions

The Chicago Manual of Style (sec. 12.16) suggests medium space (a ¼ em) before and after   signs for binary operations (i.e., conjunctions); symbols of integration, summation, or union; and signs for binary relations (i.e., verbs)   except in exponents; also medium space after commas between "coordinate points" or between elements in a list; and "no space after a binary operation or relation sign when it is modifying a symbol (i.e., used as an adjective)".  I don't know whether LaTeX follows these guidelines, but anyway I would like to know the (generally accepted) "right" amount of space in the following situations (that is, do I need to add/remove space, and if so how much?)   after logarithm: \log x before factorial symbol: y! in an implicit multiplication: x y before and after "for all" symbol: x > 0 \forall x between equations separated by a comma: x = 1, y = 2 between equations separated by text: x = 1 \text{ and } y = 2 after a comma separating elements of a set: \{0, 1\} after a comma separating arguments of a function: f(x, y)


I want to study Riemannian geometry but I don't know a perfect book for beginners, can you give me  references in riemannian geometry for beginners?


I have winforms application which has a popup dialog. I need the dialog to popup but without showing itself. This is how I currently do it:  DialogForm myDialog = new DialogForm(); myDialog.Show(); myDialog.Visible = false;   The problem with this method is that for a split second the dialog shows up and then disappears. From a functional point of view it works fine, but it does annoy some users of my application and actually takes the "focus" away from the main form. I've also tried this but it doesn't work:  DialogForm myDialog = new DialogForm(); myDialog.Visible = false; myDialog.Show();   There has to be a way to create the dialog and run it in the background without having to call "Show()." Thanks for any possible help!


Can't connect with repositories when trying to update

When trying to update, I received the following error message: sudo apt update Obj:1 http://archive.canonical.com/ubuntu focal InRelease . . . Err:7 http://ppa.launchpad.net/compiz/ppa/ubuntu focal Release   404  Not Found [IP: 91.189.95.85 80] Des:8 http://ky.archive.ubuntu.com/ubuntu focal-backports InRelease [101 kB] Reading package lists... Done E: El repositorio "http://ppa.launchpad.net/compiz/ppa/ubuntu focal Release" does not have a Release file. N: Updating from such a repository can't be done securely, and is therefore disabled by default. N: See apt-secure(8) manpage for repository creation and user configuration details.. E: Release file for http://security.ubuntu.com/ubuntu/dists/focal-security/InRelease is not valid yet (is not valid for another 4h 45min 31s). Release file for this repository. E: Release file for http://ky.archive.ubuntu.com/ubuntu/dists/focal-updates/InRelease is not valid yet (is not valid for another 4h 45min 44s). No Release file for this repository. E: Release file for http://ky.archive.ubuntu.com/ubuntu/dists/focal-backports/InRelease is not valid yet (is not valid for another 4h 46min 10s). No release file for this repository.  What's wrong with this, the same error I received when I install MySQL?


what factors affect your admission in PhD in Biological Sciences

I am a student with both Master's and Bachelor's degree in Biotechnology with a good aggregate. But, i have a low GRE score of 295. My TOEFL score is 107 along with a research project going on.   What do you think are my chances of getting in in a PhD program for Biological sciences?  I have had a good academic as well as extracurricular career.  Apart from GRE what factors should i be concerned about which might affect my admission?


General question about LateX and doctoral thesis

Hi guys I am new here.  I am PhD student at the pharmacognosy and started learning/writing in LaTeX two months ago, for practice. Even though I do not have many math formula I gave a latex a chance, because writing in Word is so annoying, it crashes every time after 30 pages. So my question is, from a LaTeX expert perspective, is it good to start slow in LaTeX and in the end write thesis in it, or are there easier ways/better programs to write with?


How do I recover the contents of a file?

I accidentally executed man ls > info.txt and now I don't know how to recover the contents of the file.


I was wondering if there was anyway to change the way the current powershell autocomplete works. I have been using bash and had changed them to offer a few features that I'd like in my powershell experience.   Currently powershell as I'm writing a command with a folder it will tab autocomplete and also cycle through my folders. This works how I like but one feature that I miss is using partial matching of a command and hitting the up key and it would find that command that matches the rest of what I do.   So Id write 'echo test'  Then id write other commands and try 'ec' and tap up and 'echo test' would complete and not the last command I typed  Just wondering if there is anyway anyway to get this back?


I have never understood a word Alice "has said" or "said"

I am not sure about the use of present perfect in the subordinate clause. I want to say I've never understood Alice for as long as I've known her, so should I use the present perfect aspect in the subordinate clause or the past tense?      I have never understood a word that Alice has said.    or      I have never understood a word that Alice said.    To me, the first sentence sounds like I haven't understood what Alice has just said.


I've always wanted to have a function that would allow the user to navigate to a random page on a certain site, that one might observe a question and see if one could furnish any degree of usefulness to that question. This seems possible (easy, at that). I'm not entirely sure how to suggest a feature request, but I might think this would be the way...


Why does JavaScript's document.cookie require a web server?

'document.cookie' in JavaScript does not work without a web server. Using the protocol for local file-access 'document.cookie' will always contain an empty string.  Please see the accepted answer in this !  As far as I know are cookies text-files stored in some sub-directory of the particular used browser. Containing key-value pairs.  So, after setting a cookie it should be there on the client-side.  Why has a web server to be involved?  I have made myself this demo:    writeMessage(); // Call the function when page is loaded. => No cookie there.  function writeMessage() {   var message;    document.cookie.indexOf('foo') === -1 ?     message = 'Cookie does not exist.' :     message = 'Cookie is there!';    document.querySelector('div').innerHTML = message }  document.querySelector('button').addEventListener('click', () => {   document.cookie = "foo=bar";   writeMessage(); // Call the function again when the cookie has been set. });

 <button>Set Cookie</button>     When the button is clicked then the cookie is set.  Then the function checks if a cookie exists. It finds that this is true and shows the according message.  !! There haven't been a second request to the web server !!  So why doesn't work cookies when using  for accessing the page?


The sizeof() function followed by square brackets

I've seen an example showing as int n = sizeof(0)["abcdefghij"]; cout<<n;  What does that thing in square brackets mean? I've read somewhere that (0)["abc"] is equivalent to ("abc")[0]. Meaning the above expression is simply n = sizeof("abcdefghij")[0];   i.e. the first element.


How can I make the `cmd.exe` window full-screen in Windows 7?

How can I make the cmd.exe window full-screen in Windows 7?


Use a set database schema or EAV design?

I have already created a database design with a set schema. The database schema is for a web quotation form. PS it is not a simple quotation form and hence need to customise the form, form builders like Gravity Form have been tried and suitable in this case.  I have about 15 tables (mostly in 2NF and 3NF) with set attributes and datatype.  But the question is should I stick with the traditional normalized schema design or use EAV design instead for some tables? It seems Gravity Form uses EAV DB design but that is due to the dynamic nature of a form builder.  This question has come up due to the fact that later on a attribute may need to be added, removed or updated from one or set of tables. The fields in the quotation form are reasonably standard with research done and I don't imagine modifying the fields and hence the attributes in the DB often.  I have read there are concerning pitfalls of EAV design. So if the fields are not going to changed often then is a set schema design with relationships useable?  Also in the event of modifying the schema is ALTER table going to cause any issues? If one adds a attribute to a table with ALTER table what would the previous data sets in the table have the value of the new attribute? What are the alternative of ALTER table?


How can I delete files to the Recycle Bin from a batch file?

I want to create a batch file for others to run, but don't want it to permanently delete files. Is there any way without third party software and without displaying any dialogs to delete files to the Recycle Bin from a batch file?  [Someone is saying this question is same as , but there a third party software is being requested which I don't want. So how is it a duplicate question?]


How susceptible are spinning disks to vibrations?

I have a man cave that has to hold all my toys, so my large collection of computers with spinning hard drives is about 10 feet from my drum set. The drum set is largely idle, but my kid is now old enough to start playing, and I fear for my spinners.  Are the tolerances of WD blue hard drives such that I shouldn't worry about it?


I need to combine two images in C# ( 4.7.2 ), and have the top image transformed putting each of the four corners at specific coordinates in the image. Is that possible? Preferably with a solution that doesn't require spending a ton of money. As far as I can tell i can't do it with the Bitmap/Graphics classes.


Evaluating $\int_0^1 \log \log \left(\frac{1}{x}\right) \frac{dx}{1+x^2}$

Show that $\displaystyle{\int_0^1 \log \log \left(\frac{1}{x}\right) \frac{dx}{1+x^2} = \frac{\pi}{2}\log \left(\sqrt{2\pi} \Gamma\left(\frac{3}{4}\right) / \Gamma\left(\frac{1}{4}\right)\right)}$  This question was posted as part of this question:     I cannot think of a change of variable nor other integrating methods. Maybe there is a known method that I am missing.


What would happen if two wizards made each other a Horcrux? Would they be invincible? How would you kill one of them?


How can the density of a region of space go from finite density to infinite when there are no numbers larger than any Aleph0 number but smaller than any Aleph1 number (no decimal point in front of it, of course)? Aren't Planck volumes and strings designed to sidestep infinities? My point there, stated differently, is how can the density go from finite to infinite when there is a 'no-number gap' between finite and infinite, with Cantor losing his mind contemplating that gap? And did he not prove that none was constructible/possible? The entropy of the visible universe is $\sim (10^{122})^2$, if I'm not too far off the mark. This is a stupendous number but no closer to infinity than any other integer or real. And there is no room in it to tuck a singularity away. In simpler terms. Our BH has a finite mass. If it has a region of infinite density, that region must be infinitesimal. But the Planck length is the lower limit on the size of regions of space. There are, therefore, no points in space, no infinitesimals, only punctoids, my term  of convenience, the utility of which may become obvious in future posts.And no infinities.


How much money is the minimum do i need for bank statement, visit the uk for 4 months

yoooo guys, im eric from taiwan, and i am planning to continue my nomad life in the uk after virus( hopefully), since i am a low budget traveler with no income right now, but i have 7000us dollars in my bank account right now, is that enough to be acceptable by officer?? Q2: ive done some research and some information point out that its better if i could have receive money from work or from people montly, meaning "  i have stable money resource" , i could transfer my other bank account to my main account every month 300us dollars, could this work??   thank you so much guys:))


Book (pre 1982) - recalled mercenary only survivor of radiation weapon

I read a book somewhere around 1981 or 82 at our local library. It was the first book in a series. I can almost remember the entire book just not the title nor the author.  I would love to find out if the author continued the series.   It starts out that there is a planet of mercenaries who hire out their services to other planets. There is a planetary distress call which recalls all the warriors back to the home planet. One warrior whose starship malfunctions, is left in orbit as the rest of the warriors enter the planets atmosphere and are immediately killed by a extremely lethal radiation weapon that has killed the entire planet.    He was close enough to the planet to become terminally ill, and ends up going out into the universe seeking who sent the bomb in the grain supply and killed his people and to try and find another warrior.  On the way, he meets up with a scientist who knows what is going on. They replace his bones through some process to keep him alive.   There is also a creature that reminded me of a ghost. That is all that I remember.


I'm using the following code to draw the electron wavefunction around an atom. I'd like to fade out the line towards it's end. I've read all the relevant questions I can find, but I fail to get what I want.  Do you have any ideas?  \documentclass[]{article} \usepackage{tikz} \begin{document} \begin{tikzpicture}[scale=3,very thick] \draw[color=red,domain=0:12.56,samples=200,smooth] plot (canvas polar cs:angle=\x r,radius={28-8*sin(2.25*\x r)});  \draw[dashed,domain=0:6.28,samples=200,smooth] plot (canvas polar cs:angle=\x r,radius={0.5 r}); \draw[fill=black](0,0)circle (.5mm); \end{tikzpicture} \end{document}


How can I delete everything from my MacBook Pro before selling it?

I have a Mac that runs Snow Leopard and I intend to upgrade it to Mountain Lion and sell it on ebay. However, I only have one hard-drive, and I'm sure I can't use something in my OS to delete my OS and all user data.  Is there something for this that's built into the firmware that I can do on boot, or otherwise?   I have source code on my Mac for multiple corporations' proprietary software and I can't risk somebody gaining access through the use of any sort of disk recovery tool. I plan to use a 7 pass erase rather than simply deleting the directory.


Getting error whenever installing virtualbox on ubuntu on windows 10

I have just downloaded the ubuntu on windows 10. I have been trying to run virtualbox and i have been getting the about   dpkg: error processing package virtualbox-dkms (--configure):    dependency problems - leaving unconfigured  Errors were encountered while processing:   libbinutils:amd64   binutils  binutils-x86-64-linux-gnu    gcc-7   g++-7    gcc    dpkg-dev    dkms   g++   build-essential  virtualbox-dkms   E: Sub-process /usr/bin/dpkg returned an error code (1)   How can I fix them and get docker and kubernetes running? Also I wish to get GUI options how can I use them?


What do the "+n" values mean at the end of a method name in a stack trace?

When reading a stack trace like:  [FormatException: Input string was not in a correct format.]    System.Number.StringToNumber(String str, NumberStyles options, NumberBuffer& number, NumberFormatInfo info, Boolean parseDecimal) +2755599    System.Number.ParseInt32(String s, NumberStyles style, NumberFormatInfo info) +112    System.Convert.ToInt32(String value) +68   What do the +68, +112, etc. numbers mean. I'm guessing that they're offsets to something. If so, what?


How do you partition when installing ubuntu 14.04 as sole OS?

I have a 2008 notebook, Acer Aspire 4930, with 250 GB HDD and 2 GB RAM.  I'm planning to use all the HDD for installing Ubuntu as a single OS in my notebook, but I don't understand how much should I allocate disk space on partition and where to allocate? For file system, swap, temp, etc  I want to make as maximum my notebook can do


JavaScript unchek checkbox with dynamic id

I have a problem with unchecking checkbox with dynamic id.  Both of them are checked but I need to set if one is clicked that other one is disabled then this is example:  <input id="value_Ture_do_30_15_0" class="rnr-checkbox" name="value_Ture_do_30_15[]" value="1" checked="checked" type="checkbox">  <input id="value_Ture_preko_30_15_0" class="rnr-checkbox" name="value_Ture_preko_30_15[]" value="1" checked="checked" type="checkbox">   I have tried this like:  $("[id^='value_Ture_do_30']").checked = false   Also this:  $(function () {     $("[id^='value_Ture_do_30']).click(function (event) {         if (event.target.checked) {             $("[id^='value_Ture_preko_30']").find('input').removeAttr('checked');         }     });     $("[id^='value_Ture_preko_30']").click(function (event) {         if (event.target.checked) {             $("[id^='value_Ture_do_30']").find('input').removeAttr('checked');         }     }); });   Also this solution did not work for me:  But it does not work. If you can help me Thanks  Solved it like this:  $("[id^='value_Ture']").click(function() {     var $this = $(this),          wasChecked = $this.attr("checked") === "checked";     $("[id^='value_Ture']:checked").removeAttr("checked");     if (wasChecked) {         $this.attr("checked", "checked");     } });


Logs show lots of user attempts from unknown IP

I lost access to my instance which I host on AWS. Keypairing stopped to work. I detached a volume and attached it to a new instance and what I found in logs was a long list of  Nov  6 20:15:32 domU-12-31-39-01-7E-8A sshd[4925]: Invalid user cyrus from 210.193.52.113 Nov  6 20:15:32 domU-12-31-39-01-7E-8A sshd[4925]: input_userauth_request: invalid user cyrus [preauth] Nov  6 20:15:33 domU-12-31-39-01-7E-8A sshd[4925]: Received disconnect from 210.193.52.113: 11: Bye Bye [preauth]   Where "cyrus" is changed by hundreds if not thousands of common names and items.  What could this be? Brute force attack or something else malicious? I traced IP to Singapore, and I have no connection to Singapore.  May thought is that this was a DoS attack since I lost access and server seemed to stop working. Im not to versed on this, but ideas and solutions for this issue are welcome.


Proving that a convex function is Lipschitz

I am trying to show that if $f$ is convex in $(a,b)$ it is  in $[c,d]$ where $a \lt c \lt d \lt b$.  Here's what I have so far:  Let $t_1,t_2 \in \mathbb{R}$ such that $a \lt t_2 \lt c \lt d \lt t_1 \lt b$  and let $x_1,x_2 \in [c,d]$.  Because $f$ is convex I know that $$\dfrac{f(c)-f(t_2)}{c-t_2} \lt \dfrac{f(x_2)-f(x_1)}{x_2-x_1} \lt \dfrac{f(t_1)-f(d)}{t_1-d}$$  I think I'm almost there, but what is the right $C$?


I currently have ubuntu 14.04 and mainly use windows 7. I don't know what partitioning is and I don't know how ubuntu was originally installed on my computer. All I know is that the 14.04 is very buggy and won't even boot properly.  So I just downloaded another ubuntu 14.04 iso file and burned it to a dvd. Now I want to uninstall my current ubuntu and install it again using the cd.  The problem is, I don't know how. I read a thread that said to download MiniTool Partition Wizard Home Edition to get rid of ubuntu but it didn't say anything else.  When I run the wizard I get this image and I'm too scared to change anything.    So here is my main problem in case I wasn't clear.  I want to install ubuntu 14.04 alongside my windows 7. To do this, I need to uninstall my current buggy ubuntu then install ubuntu again from a cd. How do I uninstall my current buggy ubuntu?


Making a sftp server with 2 different internet connection

I'm making an sftp server with OpenSSH, I have 2 lines of internet and connect to the server via 2 different route  Route 1 has gateway 192.168.2.1 and the LAN IP for the server is 192.168.2.11  Route 2 has gateway 192.168.5.1 and LAN IP 192.168.5.11  I test the connection to the server via 2 LAN IP and it working good. Next, I test the connection via 2 external IP and only 1 IP can connect.  So is there any way to build an sftp server can connect by both 2 different internet line? Please send me the link if you have a topic about this.


So I'm trying do detect a particular circle in an image, I'm using an openCV function, I tried tweaking the parameters but I'm not happy.  So I'm going to bruteforce the 4 parameters.  To do this I wrote this piece of code wich generates a list containing all the values to try on one parameter :  def paramlistgene(increment, fromvalue, tovalue):     paramlist = [fromvalue]     while paramlist[-1] < tovalue:         paramlist.append(paramlist[-1] + increment)     return paramlist   for example paramlistgene(0.1, 0.1, 20) should generate :  [0.1, 0.2, 0.3, 0.4, 0.5, ..., 20]   but it generates this :  [0.1, 0.2, 0.30000000000000004, 0.4, 0.5, 0.6, 0.7, 0.7999999999999999, 0.8999999999999999, 0.9999999999999999, 1.0999999999999999, 1.2, ...]   Why does this happens?  I tried print 0.1+0.1+0.1 and it does print 0.3.  Thanks


How to change filename and extension while downloading a text file from data uri

When i download a data uri(this works in chrome/FF),using  url1 = "data:attachment/plain;base64,encodeuri(<base64data-xyz>)"   Here using attachment mime type forces it to download, using any other mime type like(text/html) will open the content of file in new tab, since i wanted to download ,i used attachment/plain-xyz [MIME type].  I tried the download attribute, but everytime,the file name downloaded is "download", and there is no extension, so it gets appeneded in my downloads folder as ".FILE", whereas i need to store it using "variable.txt"  Please do guide me how you are able to change "download.FILE" to some "variable.txt", i have tried all attributes of data, download, data-downloadurl, contentdisposition,even tried setting pom attributes etc..  Please help in converting the downloaded file content to a file with some filename and .txt as extension


I have created List custom button for student__c object classic and lightning working fine but not working partner community

I have created custom button called "New Employee" on employee object and it is related with both account and contact objects via lookup relation. If i click on "New Employee" button on employee related list under Account detail page, working fine in both salesforce classic and lightning experience but not in partner portal.  /a03/e?CF00N342300009cAB8={!Account.Name}&CF00N342300009cAB8_lkid={!Account.Id}&CF00N90000009cUVB={!Contact.Name}&CF00N90000009cUVB_lkid={!Contact.Id}&retURL={!Account.Id}


Change the size of multiple selected polygons as a post-extrude operation

Is there a way to change the size of evenly extruded polygons AFTER performing Extrude/Inset?  It can be very helpful in modeling to be able to work with sets of geometry and yet retain control over the individual elements as if they were being worked on one at a time.  I have tried to use various Pivot settings in combination with Scale but do not have the control over sets of selected faces that will allow me to shape the model the way I'd like to do for mechanical/architectural models.  Step 1: Inset several faces.  This works fine.    Given that the four interior faces are selected;  How can I re-size them in relation to one another without them scaling towards each other with a bias they normally would not have if I were working on them individually?  Step 2: Batch Scale the selected Faces.  Now everything is disproportional.    I have tried changing the Pivot for the Scaling operation but could not get the symmetrical results I was hoping to acheive.


The Twin paradox concept in Asimov's universe

In the story Escape! the Brain sends Gregory Powell and Mike Donovan to space. When they get back, everything seems normal, like time has not passed since they went away.  According to the , Powell and Donovan should have returned later in the Earth point of view (e.g. people would be older and waiting for them for years).  Did Isaac Asimov ignore this concept, or maybe the Brain did not send the technicians far away enough to feel the concequences of the concept?


Subfield of $\mathbb{R}$ such that $\Bbb R/K$ is finite.

Is there a field $K \subset \mathbb{R}$ such that $1 < [\mathbb{R} : K] < \infty$? i.e a proper subfield of $\mathbb{R}$ such that the field extension $\mathbb{R}/K$ is finite.


Would Gringotts convert Wizard money to Muggle money?

The books make it clear that they offer the reverse service (see the following question: ). According to the canonical answer to that question,  Q: When people trade in Muggle money for Wizard money, what does Gringotts do with the Muggle money? JKR: Those goblins are sneaky people. They manage to put the Muggle money back into circulation. They are like "fences" --British slang, do you understand it? (src: America Online chat with JKR transcript, AOL.com, 19 October 2000)  The answer also makes reference to a comment by  Dharini Chandrasekaran:  Just speculation, but squibs who go out into the muggle world to work will need Muggle money and also wizards might need it while doing Muggle studies research or trying to remain under cover, so I guess they keep it for reverse exchange.  This seems entirely reasonable speculation. Nevertheless, I don't recall any example in the books of converting Galleons to British pounds or other forms of Muggle currency. Does anyone have a more canonical source than speculation that indicates that this happens? At one point in the books, Harry seems to overlook or ignore the possibility:  Stored in an underground vault at Gringotts in London was a small fortune that his parents had left him. Of course, it was only in the wizarding world that he had money; you couldn’t use Galleons, Sickles, and Knuts in Muggle shops. He had never mentioned his Gringotts bank account to the Dursleys; he didn’t think their horror of anything connected with magic would stretch to a large pile of gold. (CoS, Ch4, "At Flourish and Blotts"*)  (This passage was brought to my attention by DVK's answer here: ) But maybe he's just worried that if he converts some gold to Muggle money and tries to spend it, it will look suspicious if either Muggle authorities or the Dursleys find out. Economically, I can't see any reason why they wouldn't offer this service. Galleons clearly have value, so the goblins should have no problem accepting them. They get some Muggle money from exchanges, and they seem resourceful enough to be able to obtain it in other ways if need be. Converting wealth in the Wizarding world to wealth in the Muggle world is also the subject of the following question: . However, I don't see an answer to my question there. One issue brought up is inflation of Muggle currencies, but as long as the goblins aren't printing Muggle money, I don't see why this would be a problem. There is also speculation that the Ministry of Magic doesn't want wizards to become suspiciously wealthy in the Muggle world. Even if those answers are right, however, that doesn't answer my question. Gringotts could just restrict the amount of money that it will convert for a single person in a certain amount of time. (In case it wasn't clear enough in previous versions of this question: I think that they do, but I wanted an answer that relies on more than speculation. Evidence could come from the books, direct or indirect, or from outside sources like author interviews, stuff like that. Economics in Harry Potter doesn't always seem to work the way I'd expect it to based purely on logic.)


Speed of light and current dimensions of the universe

I've seen several documentaries explaining that the diameter of the universe is currently estimated at over 90 billion light-years. And which that - in the face of the age of the universe being about 13.7 billion years - that doesn't contradict the "speed of light" limit, because in the very beginning "space - not matter - could expand faster than light".  What does it mean? All I can see is that we can actually visualize galaxies 13.5 billion light-years away from us in every direction (Isn't it?). Therefore 13.5 billion years ago they were up to 27 billion light-years apart from one another, having had "only" 0.2 billion years from big bang to reach those positions ... This is not "space" expanding, this is matter composing galaxies having travelled much faster than light! Moreover, they all keep saying that - in peering at galaxies 13.5 billion light-years away from us - we are close to looking at the "beginnings of the universe".  But if the Big Bang was 13.7 billion years ago, we (the matter now building up our planet) were together with them (the matter composing those far away galaxies) just 0.2 billion years before ... How can we see light coming from so far away from us, emitted by objects which were together with us "just a little while" before?


Do non-invertible MA models imply that the effect of past observations increases with the distance?

Update (2019-06-25): changing title from "Do non-invertible MA models make sense?" to distinguish it from .  While reviewing MA($q$) models, I came across  (Alonso and Garcia-Martos, 2012). The authors state that, while all MA processes are stationary, if they are not invertible you have      "the paradoxical situation in which the effect of past observations   increases with the distance."   This can be seen in by the decomposition of the MA(1) process: $$ y_t = \epsilon_t - \theta \epsilon_{t-1} $$ into $$ y_t = \epsilon_t -\sum_{i=1}^{t-1} \theta ^i y_{t-i} - \theta^t \epsilon_0,$$ where clearly $|\theta|>1$ translates into history having more and more influence over the present. Two things about this bother me:   It's not hard to imagine a situation where there's a one-time period lag in the effects of something This  has an answer which claims:      "Invertibility is not really a big deal because almost any Gaussian, non-invertible MA(q) model can be changed to an invertible MA(q) model representing the same process"   Is it true that the effect of past observations increases with the distance? If so, does that make the models unfit for describing real world phenomena?  Update (2019-11-09) Found this in the text Time Series Analysis and Its Applications (Shumway and Stoffer, page 85) which also supports the case that it doesn't really matter if an MA model in non-invertible, but we may want to chose the non-invertible version of the model for convenience.


Are there uncountably many surjections from $\mathbb N$ to $\mathbb N$?

Statement: There are uncountably many surjections from $\mathbb N$ to $\mathbb N$.  Is the following proof valid:  The real numbers are uncountable.   There exists a bijection between the set of real numbers and the set of all functions from $\mathbb N$ to $\{0,1\}$.   Given a function, $f$, from $\mathbb N$ to $\{0,1\}$, construct a surjection from $\mathbb N$ to $\mathbb N$, denoted $g$, as follows:  We map the $n$th composite number to $n$, and the nth prime, to $f(n)$.   Clearly this is a surjection since the composite numbers are countable. Clearly different functions $f$ lead to different surjections $g$. Since there are uncountably many $f$s, there are uncountably many surjections $g$.


Federal taxes for nonresident alien whose only income in 2016 was a 2015 state tax return

I am from Europe, and I did an internship in the US (California) in 2015. When filing my 2015 taxes, I ended up having to pay some small difference for the federal taxes, but got a refund on my state taxes, of roughly $1.6k. That was all the income I had in the US in 2016.  I did not enter the US in 2016 at all.  I managed to figure out that I don't need to file any California tax forms for 2016 (source: ) but I am not sure about federal taxes.  I tried researching the problem, and got some information on it, but the situation is still a bit unclear. It seems that since I listed my state tax as an itemized deduction in my 2015 tax report, which I filed in 2016, the state refund I got in 2016 is, in fact, taxable.  In this situation, would I have to file my taxes (and possibly pay owed tax) for 2016, even though I never set foot in the US in that year, and my total income is just $1.6k?


For fighting COVID19, Why we give the body the RNA and not give the body the protien itself?

If I understand things correctly the popular COVID 19 vaccine gives the body RNA that teaches the body cells to create a protein that looks like the virus. And then the body learns to fight against it. Now my question is, why not to give the body directly the protein and skip the RNA stuff. If it's hard to create that protein, why not use animals for that. Many people are against the vaccine because of the RNA, so maybe it's a better approach?


How loud or flashy are verbal and somatic spells?

I was trying to cast prestidigitation on a guard behind his back and my DM said that he would definitely know I did it because the verbal part of the spell would be in a loud voice. He also said that the somatic part would be flashy and with grand movements of the hands. How loud does the verbal need to be and how flashy are the gestures?


My ma'am gave me one question to solve. To predict the output of the following code.  #include <stdio.h> int main() {     int i = 0, j = 0;     printf("Output is : ");     while (i < 5, j < 10)    // Doubt: how does while accept 2 arguments?? and how it works??     {         i++;         j++;     }     printf("%d, %d\n", i, j); }   I thought it was a syntax error. But when I tried to run, it gave me output.  Output is : 10, 10   But How? Can anyone explain?  But if I remove the first printf statement printf("Output is : "); and run it, my antivirus give me a alert that a Trojan is detected. But how it becomes a Trojan?


Getting null pointer exception for radio.setOnclicklistner

I am having listview with employeename and radiobutton. I am using setonclicklistner for radioButton but i am getting nullpointer exception and app got crashes. Can someone help me with this problem?  delivery.setOnClickListener(new View.OnClickListener() {         @Override         public void onClick(View v) {             LayoutInflater inflater1 = (LayoutInflater) ct.getSystemService(Context.LAYOUT_INFLATER_SERVICE);             View v1 = inflater1.inflate(R.layout.activity_employees_list_for_pop_up, null);             RadioButton employeechecked = (RadioButton) v1.findViewById(R.id.employeeChecked);             final Button ok = (Button) v1.findViewById(R.id.do_ok);             Button cancle = (Button) v1.findViewById(R.id.do_cancle);             ok.setEnabled(false);             listView = (ListView) v1.findViewById(R.id.employeePopUpList);             employeePopUpAdapter = new EmployeePopUpAdapter(ct, employeeIdNameBeans);              //enable ok button if listitem is checked             employeechecked.setOnClickListener(new View.OnClickListener() {                 @Override                 public void onClick(View v) {                     int pos=listView.getCheckedItemPosition();                     if (pos > -1)                     {                         ok.setEnabled(true);                     }                     else if (pos <= -1)                     {                         ok.setEnabled(false);                     }                  }             });   error I am getting nullpointer exception when i click on textview   java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.RadioButton.setOnClickListener(android.view.View$OnClickListener)' on a null object reference   at com.example.jithendra.businessstorestart.adapters.DeliveryOrdersListAdapter$3.onClick(DeliveryOrdersListAdapter.java:300)   at android.view.View.performClick(View.java:4756)   at android.view.View$PerformClick.run(View.java:19749)   at android.os.Handler.handleCallback(Handler.java:739)   at android.os.Handler.dispatchMessage(Handler.java:95)   at android.os.Looper.loop(Looper.java:135)   at android.app.ActivityThread.main(ActivityThread.java:5221)   at java.lang.reflect.Method.invoke(Native Method)   at java.lang.reflect.Method.invoke(Method.java:372)   at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)   Here is layout file  <LinearLayout     android:id="@+id/lv1"     android:layout_width="match_parent"     android:layout_height="wrap_content"     android:orientation="horizontal">      <TextView         android:id="@+id/employeeId"         android:layout_width="0dp"         android:layout_height="wrap_content"         android:layout_weight="1"         android:text="@string/loading"         android:textColor="@color/TextcolorforBlack"         android:textSize="20dp" />      <TextView         android:id="@+id/empFullName"         android:layout_width="0dp"         android:layout_height="wrap_content"         android:layout_weight="3"         android:text="@string/loading"         android:textColor="@color/TextcolorforBlack"         android:textSize="20dp" />      <RadioButton         android:id="@+id/employeeChecked"         android:layout_width="wrap_content"         android:layout_height="wrap_content"         android:background="@color/TextcolorforBlack"         />  </LinearLayout>  <LinearLayout     android:layout_width="match_parent"     android:layout_height="wrap_content"     android:orientation="horizontal">      <ImageView         android:layout_width="match_parent"         android:layout_height="1dp"         android:layout_weight="0"         android:background="@color/TextcolorforBlack" />  </LinearLayout>   This is list I am inflating it in listview. In this listview I am having radiobutton. If radiobutton check I need to enable button


Is there any difference between "talk to someone" and "talk with someone"?

Possible Duplicate:          Well, the question is in the title. I always had the impression that "talk to someone" refers to situations when some information must be conveyed to someone else, while "talk with someone" refers to cases that involve a more complex two-sided interaction. E.g., I "talk to my colleague" to tell him that I'm going for a lunch break (no response is required apart from maybe an acknowledgment), while I go and "talk with my colleague" if I have to discuss something with him in detail. Is this correct, or is there any difference between the two phrases, or is there no difference at all?


What does it mean by the Integration notation?

$\int_a^b f(x)  dx = 1 -------------------(*)$  I know that this means:  (1) Integral of $f(x)$ within $a$ and $b$ is $1$.  or,   (2) The area under the curve represented by the function $f(x)$  between the interval $a$ and $b$ is $1$.   But, my question is, what is $dx$ doing in the equation $(*)$?  And, how is it effecting the result of the equation?  What is the value of $\int_a^b f(x)$ in this context (i.e. without $dx$)?


I am running Ubuntu 15.10 in VMware Workstation.  HOST OS -WINDOWS 10  Now my hard disk  is full and i attached a new vmdk hard disk and rebooted the system but while trying to mount it using  sudo /dev/sdb1 /data it's giving following error   mount: wrong fs type, bad option, bad superblock on /dev/sdb    How to properly mount hard vmdk disk?


Proving that $a^2+b^2\neq 3c^2$ for any positive nonzero integers $a$, $b$, and $c$

I'm meant to prove the statement above and I chose to do so by thinking about the equation modulo $4$ and residue classes. My simplified process is below:  $c^2$ is either the residue class $1$ (if odd) or $0$ (if even). After being multiplied by $3$, it is either the residue class $3$ or $0$. Similarly, $a^2$ and $b^2$ are either the residue classes $1$ (if odd) or $0$ (if even). Because of this, $a^2+b^2$ can never equal $3$ (which is $3c^2$'s residue class if it's odd), meaning that $a^2$ and $b^2$ must both be even so that $0 + 0 = 0$.  Where I'm lost is where to go from here. My instinct is to say that, since we ignoring the cases where $a$, $b$ and $c$ are zero, then the case above is invalid because $0$ is part of the residue class $0$, but that doesn't seem correct to me. Does anyone have any advice on where to go from here (or if I missed something in my proof?)


Reprojecting MODIS-Sphere ESRI GRID file to WGS84 using QGIS/GDAL

I have an ESRI GRID file projected in MODIS-Sphere (here's the dataset ) that I need to convert to a WGS84 GeoTIFF.  I tried Raster > Projections > Warp (Reproject) and got this nonsense:   I then thought I'd use the MODIS reprojection tool or HEG to convert it, but they only accept HDF files and using QGIS' warp or translate functions to convert this file to HDF throwns an error. This guy was trying to do the same thing in Arc, no joy:   I looked for clues in the metadata, and the file seems a little goofy; gdalinfo yields:  Driver: AIG/Arc/Info Binary Grid Files: seto_uf        seto_uf.aux        seto_uf/.aux.xml        seto_uf/.DS_Store        seto_uf/dblbnd.adf        seto_uf/hdr.adf        seto_uf/log        seto_uf/metadata.xml        seto_uf/sta.adf        seto_uf/vat.adf        seto_uf/w001001.adf        seto_uf/w001001.tif        seto_uf/w001001.tif.aux.xml        seto_uf/w001001x.adf Size is 7468, 2911 Coordinate System is `' Origin = (-17345341.010356999933720,8423784.764957003295422) Pixel Size = (5000.000000000000000,-5000.000000000000000) Corner Coordinates: Upper Left  (-17345341.010, 8423784.765)  Lower Left  (-17345341.010,-6131215.235)  Upper Right (19994658.990, 8423784.765)  Lower Right (19994658.990,-6131215.235)  Center      ( 1324658.990, 1146284.765)  Band 1 Block=256x4 Type=Byte, ColorInterp=Undefined   Description = Seto_UF   Min=0.000 Max=101.000    NoData Value=255   So it can't determine the coordinate system.  There's a .tif included in the directory, but gdalinfo on that shows:  Driver: GTiff/GeoTIFF Files: w001001.tif        w001001.tif.aux.xml Size is 7468, 2911 Coordinate System is: GEOGCS["Unspecified datum based upon the GRS 1980 Authalic Sphere",     DATUM["unknown",         SPHEROID["unnamed",6371007,1]],     PRIMEM["Greenwich",0],     UNIT["degree",0.0174532925199433],     AUTHORITY["EPSG","4047"]] Origin = (-17345341.010356999933720,8423784.764957003295422) Pixel Size = (5000.000000000000000,-5000.000000000000000) Metadata:   AREA_OR_POINT=Area Image Structure Metadata:   INTERLEAVE=BAND Corner Coordinates: Upper Left  (-17345341.010, 8423784.765)  Lower Left  (-17345341.010,-6131215.235)  Upper Right (19994658.990, 8423784.765)  Lower Right (19994658.990,-6131215.235)  Center      ( 1324658.990, 1146284.765)    So it says the units are degrees but those huge corner coordinates and origin values don't agree.  Any ideas?  My setup: OSX 10.9.4 QGIS 2.6.1 Brighton GDAL 1.11.2 (apparently there are newer versions but this is the latest you can get on OSX without having to compile it yourself)


Why don't I need to install any Drivers for Ubuntu

So when I install the Windows, I need to install all the drivers that are respective to my laptop.   Why don't I do the same with Ubuntu installation?   Does the installation somehow detects my hardware and install proper drivers on its own?  Thanks


There's a simple property of the Fourier transform on $\mathbb{R}^n$ that I'm having trouble establishing.  Let $\lambda > 0$. I would like to show that $(D_\lambda f)^\hat{}(\xi) = \lambda^{-n}(D_{\lambda^{-1}}\hat{f})(\xi)$, where $D_{\lambda}f(x) := f(\lambda x)$.  The substitution $u = \lambda^{-1}x$ gives me the following:  $\lambda^{-n}(D_{\lambda^{-1}}\hat{f})(\xi)$ = $\lambda^{-n} \int_{\mathbb{R}^n} f(x)e^{-2\pi i x \cdot \lambda^{-1}\xi}dx$ = $\lambda^{1-n}\int_{\mathbb{R}^n} f(\lambda u)e^{-2\pi i u \cdot \xi}du$ = $\lambda^{1-n} (D_\lambda f)^\hat{}(\xi)$, which isn't quite what I want. What am I doing wrong here?


Looking for 70's movie title -- Secret agent with camera in glass eye

I'm trying to find a movie from the mid to late 1970's.  The scene that is stuck in my brain goes something like this:  A man walks into a very high security vault.  One of the security systems was a full body 'x-ray' (very much like the body-scanners today).  The man was not allowed to carry his watch, wallet or even a fountain pen that the xray showed on a blue screen.  His head didn't get xrayed because the machine only went up to his neck (this is an important plot point).  Once in the vault, he finds a file in a drawer and reads the papers in the file.  While he is doing this he taps his temple seeming to be concentrating.  He finishes, put the folder back in it's filing cabinet, and walks out.  On the way he retrieves his personal items, and thanks the guard.  Once he gets home (i think), he goes to a closet, and opens up a secret room.  The room is clearly a small photographic darkroom.  He pops out his eye on the side where he was tapping his temple.  He pulls it apart and reveals that it is a tiny-film camera.  He attaches it to some kind of spinning wand, and proceeds to dip in it several liquid filled trays.    Then he attaches the eye-camera to a projector, and we see the papers he was reading earlier.  I think they were in negative.  The papers had diagrams and stuff on them.  I think they were related to some kind of space program.  Does this sound familiar to anyone?


Find the sum $ \displaystyle\sum_{n=1}^{\infty} \frac{1}{n^{2}(2n-1)}$  $= 1 + \dfrac{1}{3\cdot 2^{2}} + \dfrac{1}{5\cdot 3^{2}} + \dfrac{1}{7\cdot 4^{2}} \ldots$  Then, I'm stuck. I didn't find any pattern to solve.  I just need a hint.


If $G$ is a finite group s.t. $|G|=4$, is it abelian ? To me it's isomorphic to $\mathbb Z/2\mathbb Z\times \mathbb Z/2\mathbb Z$ or $\mathbb Z/4\mathbb Z$, but a friend of me said that they are not the only group of order 4, and there exist some non-abelian. Do you have such example ?


'ask question' anonymously on security.stackexchange?

I was thinking, perhaps after 100 reputation or something, that you should be able to post questions anonymously on  kind of like the way people can on   Then you would be able to delete or edit the question for say, 24/48 hours, but then after that, there would be no server-side trace of the question to that user's account, whether the user is logged in or logged out. And perhaps reputation is rewarded within the 24/48 hours, but not afterwards, due to it not being possible.  The reason for this is that, with the way things currently are, people could easily leave a Hansel & Gretel 'breadcrumb trail' of their security habits, actually making it easier for them to be attacked - the opposite of the intention of security.stackexchange!  On the other hand, I suppose people could simply use 'burner' accounts instead? Though I'd suppose those burner accounts would still have server side records of IP addresses, e-mails, etc. which introduces a point of failure?  I suppose I'm trying to find a solution to the issue of anonymity that a rewards based system such as Stack Exchange can facilitate.


Number of different bijections between a set $S$ with $n$ elements and itself

I am trying to solve exercise 2.1 in Aluffi's textbook "Chapter 0":  How many different bijections are there between a set $S$ with $n$ elements and itself?  Here is my attempt. My "non-rigorous" answer is that I can make the function injective by choosing $n$ elements for where to make the first element of $S$, $n-1$ possibilities for the second, and so forth, giving $n!$ functions. Then this is a function injective function from $S$ to $S$ which is finite, so it is immediately surjective. (I don't think surjectivity just "follows" without invoking this kind of obvious, though it sounds obvious that it's surjective, though it's somewhat tough to prove.) Here is my attempt at making the argument rigorous, but I'd appreciate feedback on this above sketch as well.  Since there are $|n|$ choices for where to send each $s_i \in S$, there are exactly $n^n$ functions $f: S \to S$. If $f(s_1) = f(s_2)$ for $s_1 \neq s_2$, then $\mathrm{Im}(f) \not \subset S$, i.e., its cardinality is $< n$, so it is not surjective; furthermore, it is not injective. There are $n!$ mappings $S \to S$ with no repeated inputs or repeated outputs, which are the only bijections $S \to S$.  How does this look? Are there ways to make it more rigorous?


Is it possible to browse folders in a jar and if no, why?

I am not convinced that it gives me all possibilities for my problem 1) xso said it was not a good answer 2) I would like to find an easiest solution 3) I doesn't address my question why browse the files in a jar has to be different as browse the files in the file system 4) it is an old thread, maybe it changed in Java 8 or Java 9 or in another library ? even the new link doesn't convince me. Where is addressed the problem to find directories in directories ? Here it is only files in the jar. In my case, I don't know (and I don't want to know) the list of animals, the list of colors,...  I am developing games for eye-trackers (). These games are done in particular for disabled children and their parents are often not accustomed to use computers. Hence, I try to release a software as easy as possible to run. I have made it with java/javafx. My soft has to be downloaded as a jar and double clicked. In a new game,  the idea is to show some pictures to the child, a voice gives the order and (s)he stare at the correct one. For instance, « Where is the elephant ? » and the child has to select the elephant. It can be the same with colors, cartoon characters,… I  tried to do something as generic as possible hence for animals, all are ordered in an « animals » directory where there is a directory for each animal (one for horses, one for eagles,…) and in each directory several images. It is hence easy to add a new animal (just need to add a directory) and easy to add a new picture (add it to the directory). It is easy to make a new game, build a new hierarchy of directories (one for colors, one for cartoon characters,…). Here is an excerpt  of my actual directory structure.   It works pretty well in my IDE but unfortunately it doesn’t work in my jar. It seems easy to show an image if you know its complete path but impossible to use functions as File listFiles(). I try to find solutions but they don’t seem to work. Some people seem to say that is it is possible with nio but I was not able to make it works. I have two questions : is it possible and if no, why is it impossible ? Folders exist in my jar, they don’t disappear, why is there no way to list their content ? If no, how can I implement a solution as easy as possible ? Thank you !


Wrong multimeter readings measuring 12V lead acid battery

I just got my first multimeter and when I measured a 12V 1.2ah lead-acid battery I get AC 28.8V and DC 13.4V. Is this normal?  In addition I tested an AA 1.5V battery and I got 2.9V (AC setting 200) and 1.58V (DC setting 20).  Is my multimeter broken?   The meter is a  and the lowest AC range is 200V.  LATE UPDATE I went to the store and tested another UT33C and it also displayed an AC voltage. I asked to try a different model (UT39A) and it correctly displayed 0VAC when I tested an AA battery, so I exchanged my multimeter for the other model. Thanks.


How to Compare two strings in android with optimization?

I already tried with string.equal function which will compare two strings, but what will be optimize way of doing same. Suggestions are welcome.  Hi all got it may help others   Thanks Saurabh for sharing link.


The development cycle of the company I work include building alfa prototypes, sometimes in breadboards, and beta prototypes in printed circuit board assembly.  A considerable slice of the development time is wasted waiting for PCBs prototypes to be builted by PCB manufacturer here in Brazil. Since the time spent is a lot, I'm thinking in ways to somehow speed up the production of these prototypes in my company.  Do you have any suggestions or experience that you'd like to share on this particular subject? Maybe some cost affordable machine DIY to build PCBs at home?


What's the best way to loop through a set of elements in JavaScript?

In the past and with most my current projects I tend to use a for loop like this:  var elements = document.getElementsByTagName('div'); for (var i=0; i<elements.length; i++) {     doSomething(elements[i]); }   I've heard that using a "reverse while" loop is quicker but I have no real way to confirm this:  var elements = document.getElementsByTagName('div'),      length = elements.length;  while(length--) {     doSomething(elements[length]); }   What is considered as best practice when it comes to looping though elements in JavaScript, or any array for that matter?


On mu Ubuntu 12.04 setups my tmux clipboard copy and paste commands are setup as follows:  set -g prefix M-a unbind C-b bind C-c run "tmux save-buffer - | xclip -i -sel clipboard" bind C-v run "tmux set-buffer \"$(xclip -o -sel clipboard)\"; tmux paste-buffer"   This worked great for the longest time up until a month or so ago, when I suspect some configuration change or package change was made that broke the above. In GNOME terminal, pasting still works fine with both prefix+ctrl-v and ctrl-shift-v.   However the xclip copy command no longer works no matter what I do, and I have tried removing the custom prefix binding above, using -select instead of -sel, not using clipboard etc. This is pretty much a show stopper for a GVim user like me, since I don't even have the GNOME terminal workaround of ctrl-shift-c with tmux taking over the shell. I go into copy mode, select text with space+movement, and when I execute prefix+ctrl-c absolutely nothing happens. Before this broke, tmux would display a confirmation message in the notification section at the bottom.  Does anybody have suggestions as far as how one might debug this? This is a pretty big productivity hit. I can probably use the , but it'd be great to know just what happened to xclip.


For a long time I've felt that the search for foundations in mathematics doesn't have an answer, that it is almost like physics where you can keep asking where things come from.  However, is this not the case? People say that set theory is the/one foundation for mathematics, but set theory uses logic. Moreover, in logic, and here is my largest concern, we define things like strings of characters and statements with truth value.  These things don't appear to require any other mathematical objects, however it seems somewhat non-rigorous to introduce strings and truth values and characters. Is there a chicken-and-egg issue somewhere here, are these ideas well-formulated, should I be confused? In what sense is set theory the foundation of mathematics?


Can no Longer Find Convert to PDF Option

There used to be an option to convert my stackoverflow careers profile to a PDF file, which is a great feature.  However, I can no longer find an option to do this. Was it removed?


I have content type recipes and a view page that list all of my recipe nodes, that view has an exposed filter block that i placed in header. So in header i have views exposed filter ( search terms ) that works as recipe finder.   Now on that view page with results i want to add more exposed filters (3 select drop down) that will filter my selected taxonomies.  Problem is  if i just add those filters in my view, they will all show up in same block in header, but there i need just search.   Is there a way to have just 1 exposed filter in block and others on a view page.


So I enter at night, I sneak to where Grelod the Kind is sleeping, kill her by one shot -- and somehow Constance Michel notices this in her room with locked doors, and afterwards runs across the orphanage scared, telling me she yields and cannot be calmed.  This is not the way of a good assassination.  How can I kill Grelod the Kind without anybody noticing?


I need to check whether my window service is running or not every 15 minutes or so.   If it is not running, then how can I restart the windows service again?


I know this rather goes against the idea of enums, but is it possible to extend enums in C#/Java?  I mean "extend" in both the sense of adding new values to an enum, but also in the OO sense of inheriting from an existing enum.    I assume it's not possible in Java, as it only got them fairly recently (Java 5?).  C# seems more forgiving of people that want to do crazy things, though, so I thought it might be possible some way.  Presumably it could be hacked up via reflection (not that you'd every actually use that method)?  I'm not necessarily interested in implementing any given method, it just provoked my curiosity when it occurred to me :-)


How to effectively balance research, teaching and project work?

Starting from the upcoming semester besides my research for the PhD, I will also have to work on a loosely related project (w.r.t. my research), and do teaching as well.  I am overwhelmed from this. It seems that I will never have enough time for the actual research while the project work (50%) and teaching will eat up all my time.  Besides these duties there are also students to supervise, lab to maintain etc.  How do the more experienced ones in AcademiaSE deal / have dealt with such situations?


Creating a Network Dataset in ModelBuilder?

I am working on modeling a project that requires me to create a network dataset in ArcCatalog. To do this, you simply right click on the roads shapefile and choose, "Create Network Dataset". You then just follow the wizard. I was wondering how that can be modeled in ModelBuilder.   There is a "Build Network Dataset" tool, but that doesn't seem to be what I'm looking for.


looking for a tv episode where tiny men go around recreating the world in between seconds

Looking for a TV episode where tiny men go around recreating the world in between seconds, behind the main characters backs/just out of sight. I think it was older. My memories say it was in Black and White. Similar concept to Twilight Zone's "Matter of Minutes," different execution.


limit of the sequence $a_n=1+\frac{1}{a_{n-1}}$ and $a_1=1$

Problem: Find with proof limit of the sequence $a_n=1+\frac{1}{a_{n-1}}$ with  $a_1=1$  or show that the limit does not exist.  My attempt:  I have failed to determine the existence. However if the limit exists then it is easy to find it.  The sequence is not  monotonic and I have failed to find any monotonic subsequence subsequence. The sequence is clearly bounded below by $1$. I have observed that the sequence is a  continued fraction so it alternatively increases and decreases.   So, please help me.


How do we get the last day of the month from a given date

Is there a function or method to give the last day of a month? For example if the date is 27 feb 2013, the last date should be 28 feb 2013 , it become 29 if its a leap year. if the date was 2 jan then it should return 31 Jan.  If there is no function then any ideas on how we can get this?  Thanks


How can I show that this sequence of integrals goes to zero?

$$\int_0^{2\pi} f(x)\cos(nx)dx$$  for $f(x)$ real valued and continuous on $[0,2\pi]$.  How can I show that the limit of the integrals, as n goes to infinity, is zero?  I have thought of and tried integration by parts, with not much insight gained.  I also thought that perhaps the Fourier transform is lurking in the background of this problem, but I'm not sure how to utilize it.


Another meta question identified a bug that was marked as designed. To summarize the bug, the little number that appears next the Review link in the header shows an incorrect value most of the time.         I would like to propose that the feature be dropped. Honestly, I would prefer it be fixed, but the response to the question above gives me little faith that it will be. Half of the time, I click that little brown box and find out that I was lied to. There's nothing to review.  The little number no longer does the job it was created to do.        Oh sweet! Three things I can review!        Just kidding...


UK visa refused due to length of previous stay (paragraph 4.2) - what to do?

That was thw refusal letter i got .. been traveling to the uk since 2011 and all through my travel history have never stayed this long.. i own my company an i stayed dis long cause of marital issues.. came bach home as soon as everything was ok. pls house kindly advice on what to do. thanks in anticipation


Does Linux Mint have /etc/debian_version?

I am trying to write a script which works based on the knowledge that each Linux Mint release was based on a particular Ubuntu release.  However, I do not want to install Linux Mint to verify that, but instead let the users of the script test it, if they need it.  Can I rely on the presence of /etc/debian_version, though? I am doing this in order to detect Debian and its derivatives. It works reliably on Debian and Ubuntu, but does Linux Mint have this file?  Note: I am aware of lsb_release and I am using that in order to figure out more details later on. But the existence of /etc/debian_version is a way to make assumptions about certain things before even checking for and invoking lsb_release.


In the famous equation , the variables stand for:     $E$ is energy, $m$ is mass, and $c$ is the speed of light (in vacuum).   And I understand the equation fairly but limited in knowing in its effects/outputs in reality, honestly.   Some example? Could anybody please give me some sort of examples in real world which are done by this equation?


I have some questions concerning sentences.   ... majoring in Biological Systems Engineering chosen by [full name] conclude with preparation of a thesis and the engineering exam. The title of the thesis prepared by ... ... majoring in Biological Systems Engineering chosen by [full name] conclude with preparation of the thesis and the engineering exam. The title of the thesis prepared by ... ... majoring in Biological Systems Engineering chosen by [full name] conclude with preparation of thesis and the engineering exam. The title of the thesis prepared by ...   Which sentences is correct? Which sentence is better?  Thank you for your help in advance.


One can understand the concept of natural power, as $x^n$, being a product of a number by itself $n$ times: $$x^n=\underbrace{x\cdot x\cdot\dotsb\cdot x}_n$$  We can also get the idea of a rational power, $x^{\frac{p}{q}}=\sqrt[q]{x^p}$ , looking for the $q$-th root of a number, where $q$ is a integer, so it is the same idea as a power of a natural number.  But how can we understand a power of a irrational number $x^r$? Of course we can define it as the limit of the power of the rational number who is tending to the number $r$, but is there a better more intuitive way of explaining this, staying with the number $r$, instead of its approximation?


Understanding the output of SVD when used for PCA

I'm doing principal components analysis (PCA) on quite a bit of data (3000 variables, 100079 data points). I'm doing this mostly for fun; data analysis is not my day job.  Normally, to do a PCA I would calculate the covariance matrix and then find its eigenvectors and corresponding eigenvalues. I understand very well how to interpret both of these, and find it a useful way to get to grips with a data set initially.  However, I've read that with such a large data set it's better (faster and more accurate) to do the principal components analysis by doing singular value decomposition (SVD) on the data matrix instead.   I have done this using . I don't really understand SVD, so I might not have done it right (see below), but assuming I have, what I end up with is (1) a matrix U, which is of size $3000\times 3000$; a vector s of length $3000$, and a matrix V of size $3000\times 100079$. (I used the full_matrices=False option, otherwise it would have been $100079\times 100079$, which is just silly.)  My questions are as follows:   It seems plausible that the singular values in the s vector might be the same as the eigenvalues of the correlation matrix. Is this correct? If so, how do I find the eigenvectors of the correlation matrix? Are they the rows of U, or its columns, or something else? It seems plausible that the columns of V might be the data transformed into the basis defined by the principal components. Is this correct? If not, how can I get that?   To do the analysis, I simply took my data in a big $3000 \times 100079$ numpy array and passed it to the svd function. (I'm aware that one should normally center the data first, but my intuition says I probably don't want to do this for my data, at least initially.) Is this the right way to do it? Or should I do something special to my data before passing it to this function?


Python3 - Use x elements of a list until list is empty

I am working with Selenium to input URLs from a list into a form. The form can only accept 10 URLs at a time and my list may contain over 300 URLs. I want to take x items from the list, input into form, and once completed do that again until all elements of the list have been used.  Should I be placing the items into another list, popping them off the old list, input this new list, and then repeat? Suggestions appreciated!


Renaming set of files in multiple folders in Windows command line

I have a 320 folders each having a set of two files:    FilenameA.wav  FilenameB.txt.    In each folder, I want to rename the .wav file based on the name of the .txt file in the same folder:  FilenameA.wav renamed to FilenameB.wav    Can I do this with a single command line to handle the renaming in all of the folders?


Incorrect user is shown at closed question

There was a  asked earlier today, so I thought of closing the question, but in the close popup already two other users voted to close as unclear.  Still I went ahead and closed it as duplicate question. Now it is showing:     marked as duplicate by davidism, Shadow, VR46   But I am the only one who closed it as duplicate. Is this the way it works or is something wrong here?


can i use fonts of google fonts for commercial use?

can i use fonts from google fonts for commercial use? like logo design or flyer or brochure,etc  i have already entered the page named "Open Font License web version" but i still can't understand if i can use these fonts for other commercial designs like logos and flyer and social media designs.  i have seen some questions here but it's old and the license might be change, so i put another question.


What is meant by "Constant Amortized Time" when talking about time complexity of an algorithm?


Inclusion of $L^p$ spaces for functions has been discussed .  Does this apply to $l^p$ space of sequences similarly?   I tried to show the following: For $1\leq p<q<\infty$, $l^q\subset l^p$ By using Hölder inequality but it doesn't seem to work.  My question is that is this true? If yes, what's the right way to prove it and what's a good counter example for showing $l^p\subset l^q$ is not true? Thanks.


How do Expertise and the Acrobat feat proficiency effects combine?

Scenario : I make a character (rogue) and put proficiency in acrobatics, at level 1 I get expertise and double my acrobatics proficiency buff. (text from roll20):     Your proficiency bonus is doubled for any ability check you make that uses either of the chosen proficiencies.   At level 4, I then decide to take the Acrobat feat:      You gain proficiency in the Acrobatics skill. If you are already proficient in the skill, you add double your proficiency bonus to checks you make with it.   They are worded differently, the expertise class skill says to double my existing proficiency bonus before adding it while the acrobat feat says I get to double what I add to my skill check proficiency bonus.  Does this mean I can get +8 to my proficiency modifier or no? I looked at past related topics and all of them seemed to be asking about doing this through 2 class abilities by dual classing, save for one. That one was labeled a duplicate and unanswered and then linked to an old question about using 2 different class abilities to meet a similar result. This is through 1 class ability and then a feat. Does that not make a difference?  The equation is the same regardless of how it'd be ordered correct?   1d20 + (3 ability score + ((2 prof + 2 feat) × 2 expertise) or  1d20 + (3 ability score + ((2 prof × 2 expertise) + 4 feat)    The common answer is "you still only add it once and multiply it once" If this is correct then how is it not doable? Expertise doubles you bonus while the feat adds it twice. Is that not different to doubling it twice?   The end result is Expertise makes your proficiency bonus double where applied for that skill by default, the feat specifically states to add that proficiency bonus to the skill twice. Is that not how it is worded?  I do not think Jeremy Crawford's answer that is being quoted is correct in this scenario; you are not multiplying the proficiency twice, you are multiplying it once(which doubles the prof bonus) and then add that result twice as the feat says you do.   If you can not do this, then that would mean the feat is not able to apply regardless of having expertise because the feat specifically states for you to add your proficiency modifier twice to your roll.


How do I access a flash drive that has been ejected without physically plugging it out and back in?

When I plug in my flash drive, it gets auto-mounted.  If I right click on the drive and select 'eject', then it's unmounted.    Now, I want to remount the drive in Terminal.  How do I do this?  I've been Googling this for 30 minutes and I haven't found anything that works.    I've read to run 'sudo fdisk -l' but the USB drive isn't there.  lsusb gives me nothing either.    I want to make this clear: I know that if I plug the flash drive in again, that I can run mount to find where it is.  However, what I really want to know is, if the drive is still plugged in and was just 'ejected', how do I then remount it from Terminal without physically touching the flash drive?


Some Data Failed to Reconstruct, Motion Tracking

I added tracks and stuff, but then when I tried to solve motion track, there was a error that said:     Some Data Failed to Reconstruct   and it also said to look into the console for details, which I did. This is what the console said:    By my understanding, my video is 372 frames long, and Blender is cutting the footage at 318 for some reason. Here is the image of the scene:    Why? Here are links to  and also . Also the next morning I did a camera solve, but then most of the frames went red.


(OS X) How do I bind "enter" to a combination of keys at the left side of my keyboard?

I would like to bind "enter" to a combination of keys at the left side of my keyboard. How do I go about doing this? (I would like the combination of keys to be Ctrl+Shift+Q, or maybe there is a better one out there?). It's sort of becoming tedious to reach around or let go of the mouse from my right hand whenever I enter something.


What is a "loopback", can it cause "damage"?

The high school I attend won't allow students to have the WiFi password. Our entire education system is evolving and becoming more and more dependent on the internet. Therefore, I brought my own laptop with an Ethernet cable and adapter so that I could directly access the school's internet and work on assignments. The 'computer lab lady' saw me doing this one day and had a FIT about it. She started screaming at me to "remove that cable! It will cause a 'loop back'. " So naturally I asked what that is and she couldn't even answer it herself. So I've been doing research and decided explaining the situation is my best bet. To anyone who cares enough to read this paragraph, please explain to me why that lady got so upset about me plugging an ethernet cable into another computer. Will this harm the "system"? My Father is a computer engineer and gave me a completely different description of loop back than she did.


Keeping a process running on server even SSH is closed

I am running long program on server, which is basically Jar file of java program. I want to keep this program running even if SSH terminal is closed, how I can keep this program running on server?


How to use Parseval' identity( Plancherel)?

(May be this is very basic question for MO)  Let $f\in L^{2} (\mathbb R)$ with $\lim_{t\to \pm \infty} f(t)=0.$ Put  $$F_{n} (x)= \frac{1}{2\pi} \int_{-n}^{n}e^{itx} f(t) dt \ (n=1,2,...)$$  Fix $\alpha \in (0, \infty)$ and we define $H_{n}(x)$ as follows: $$\frac{1}{2\pi}\int_{-n}^{n} e^{itx} (f(t+\alpha) -f(t-\alpha))dt = (e^{-i\alpha x}- e^{i\alpha x})F_{n}(x) + H_{n}(x)$$     My Question: Can we expect to prove: $H_{n}(x) \to 0$ as $n\to \infty$ in $L^{2}(\mathbb R)$ ?   I guess some where we need to use ; but I am bit confused, how to use it.  Thanks


Is there a reason behind the ordering of letters in the English alphabet? i.e. why are we taught “A,B,C,D,E,F,...,Z”? Why not “L,A,S,U,I,Z,...,C”?  I am asking this because, in some of the languages I know, I am told that the ordering of the letters in the alphabet is based on the ease with which they can be pronounced or the frequency with which they are used or depending on the part of the vocal cord that needs to be stressed to pronounce the letter.  Is there a similar rationale?  EDIT  You can see a couple of references for arrangement of letters in Sanskrit  and .


Compute infinite sum of a arithmetico-geometric series $\sum_{i=0}^{\infty} \frac{i}{2^i}$

I am trying to compute the sum  $\sum_{i=0}^{\infty} \frac{i}{2^i}$  which I know should be equal to $2$, but I cannot prove it.  If I am not mistaken, it should be a arithmetico-geometric series (), hence the title.  Any help greatly appreciated!


Where is my program located that I run from command prompt

I run command svn in command prompt and it works fine. Now I need to know where this executable located on my file system. How to know it?


Enter password only once for script making many sudo calls

I am writing a script to download build and install a bunch of packages. Building sometimes takes a while, and installing requires root priviledges:  make; sudo make install  What happens alot is that when a build takes a while I need to keep entering my password. I want to be able to only enter it once. I could call the script with root access, but then (as I understand it) every call it makes will be with root priviledges. I don't want this because then, eg., many files and folders get created that can't be deleted without root access.   so what is the best way to do this?


How to use border-radius in IE.(All Browsers)  because firefox,chrome support border-radius but how to use for IE?


I own a website .  We did not have proper content before so to prevent search engine from crawling our site  we added a robots.txt with code to prevent crawling.  Now we had updated our sites content and want to get it crawled, but Google is not crawling it yet. We removed the code from robots.txt to prevent Googlebot to crawl, but still it is not getting crawled.   We almost did this change before 20-21 days but still Google is not crawling our site and if search I search on Google it displays:     A description for this result is not available because of this site's   robots.txt – learn more.   Kindly guide me, what I need to do for this?


Suppose that $a$ and $b$ belong to a commutative ring $R$. If $a$ is a unit of $R$  and $b^{2}=0$ . Show that $a+b$ is a unit of $R$  I try it..  consider $(a+b)(b)=ab+b^{2}=ab=1$ Since a is unit


How to activate my iPhone with a broken home button

My iPhone says "press home to restart" but my home button is broken so there is no way to press home.  I can't use the answers in  as my iPhone isn't linked to my computer, and I can't activate Assistive Touch.  How can I activate my iPhone nevertheless?


function to print occurences of substring

I'm trying to print how many time a substring occurs. When I try to print this I get the error- Counter is undefined.     s = str("eewd")     substring = "e"     def count_substring(s,substring):         len1 = len(s)         len2 = len(substring)         i =0         counter = 0         while(i < len1):             if(s[i] == substring[0]):                 if(s[i:i+len2] == substring):                     counter += 1             i += 1              return counter  if __name__ == "__main__":        print(counter)  Also is     if __name__ == "__main__": needed in python 3?


Find the limit of sequence without using derivatives

$$\lim_{n\to\infty}\large n(a^\frac{1}{n}-1) 0$$ $$a>0$$ is the problem. So far what I tried was transforming $$(a^\frac{1}{n}-1)$$ by using the formula $x^n-1 = (x-1)(x^{n-1} + x^{n-2} +...+1)$ but I fail to see how this would help me in this instance, or I just may be doing it wrong because it's the nth root that is giving me problems. Any help would be appreciated


Sorry for the vague title, hopefully I can make my question clearer here.  I have some two-dimensional List<List<Double>> myList that contains two items each sublist: one explicit double, such as 2.0, and one double variable. Essentially what I want to do is instead of storing some constant value in the list, I want it to store a reference to the variable, because the variable will be changing in other parts of the program and the list should reflect that. Here is a very simplified version of what I want to do:  import java.util.Arrays; import java.util.List;  public class Example {      static double apples = 10.0;      static double oranges = 5.0;      static List<List<Double>> myList = Arrays.asList((Arrays.asList(2.0, apples)), (Arrays.asList(2.0, oranges)));      public static void main(String[] args) {          apples += 3;          oranges += 3;          for (List<Double> list : myList) {              // list.get(1) -= list.get(0);              System.out.println(list.get(1) - list.get(0));          }      }  }   The program output is the following:  8.0 3.0   However, it should be:  11.0 6.0   Because apples and oranges were both increased by 3. Furthermore, notice the commented out line list.get(1) -= list.get(0);. What I ultimately want to do is reduce the variable specified by list.get(1) by the amount specified by list.get(0). However, when I uncomment this line I get:  Error:(20, 25) java: unexpected type   required: variable   found:    value   I am thinking that both of these issues are due to the value of apples and oranges being stored in the list as constant values, and not a reference to the actual variables themselves. Is this because of me using Arrays.asList() to create myList? Or is it a problem in the way I define List<List<Double>>? Or is it some other problem altogether?   Thank you for any help.


Bootstrap 4 tooltip with dynamic title (ajax request)

I assigned several bootstrap tooltips to some span elements.  I use this javascript / jquery code:  function tooltip() {  $('.tooltipelement').tooltip({  trigger: 'click',  title:loadtranslation  }); }  function loadtranslation() {  var id = $(this).attr("data-id");  $.post("ajax.php",{"mode" : "w1", "id" : id},function(data){     return "x";  });             }   It doesn't work: The tooltip is not shown. If I skip the ajax request like this:  function loadtranslation() {     return "x";         }   The tooltip is shown and "x" is displayed. It is not a failure on the ajax request, because I even don't evaluate the result but just return "x" as well. I guess there is a kind of time-out issue (ajax request takes several milliseconds - mayto too long for the tooltip function?)


Just asked myself: Why isn't "Questions" the homepage? And why is the homepage only accessible with a click on the logo?  As far as I can see there is only one significant difference between the homepage and the Questions page: The sorting of the questions. And there is a sorting functionality on both pages - with different options though.  This doesn't make much sense to me. Is there a good reason for it?


What are some good books for learning/mastering duration analysis at an intermediate/advanced level? Would be interested in both modern suggestions as well as classics.


Proving “The sum of $n$ consecutive cubes is equal to the square of the sum of the first $n$ numbers.”

This   states:      Example $\boldsymbol 3$. The sum of consecutive cubes. Prove this remarkable fact of arithmetic: $$1^3 +2^3 +3^3 +\ldots +n^3 =(1 +2 +3 +\ldots +n)^2.$$   “The sum of $n$ consecutive cubes is equal to the square of the sum of the first $n$ numbers.”      In other words, according to Example $1$: $$1^3 +2^3 +3^3 +\ldots +n^3 = \frac{n^2 (n+1)^2}{4}.$$   Should: $$1^3 +2^3 +3^3 +\ldots +n^3 = \frac{n^2 (n+1)^2}{4}$$ not be: $$1^3 +2^3 +3^3 +\ldots +n^3 = \frac{n^3 +(n + 1)^3}{2^3}$$ as everything in the left-hand side is cubed?


Can't link Google Console with Google Analytics

I'm trying to link my google console with google analytics after I have verified my website as a domain. But according to GA there are no sites verified and there is a site but this is not linked to any web property in google analytics account. See attachment.  Now I have read that I should verify the property as a prefix instead. I'm not sure whether this is the solution. The problem is that I don't how to test it since the property is already been verified as a domain I don't know how to verify it again as a URL prefix.


Formatting numbers with regex JavaScript

I'm trying to format a number as brazilian currency, but I'm not sure what's going wrong.  function format2(n, currency) {     return currency + " " + n.toFixed(2).replace(^\s*(?:[1-9]\d{0,2}(?:\.\d{3})*|0)(?:,\d{1,2})?$/g, "$1,"); }


Recovery of files from dead windows using Ubuntu

Something happened with my windows 10 computer and it wont start up as it should. To solve this I have gotten myself a Ubuntu Live USB stick and plugged it and managed to start the Ubuntu OS up. So, now when I tried to access the harddrive from the “Files“ dropdown menu it gives the following error message...  “Unable to access “1000 GB Volume”  Error mounting /dev/sda4 at /media/ubuntu/0C1281071280F6CC: Command-line `mount -t "ntfs" -o "uhelper=udisks2,nodev,nosuid,uid=999,gid=999" "/dev/sda4" "/media/ubuntu/0C1281071280F6CC"' exited with non-zero exit status 14: The disk contains an unclean file system (0, 0). Metadata kept in Windows cache, refused to mount. Failed to mount '/dev/sda4': Operation not permitted The NTFS partition is in an unsafe state. Please resume and shutdown Windows fully (no hibernation or fast restarting), or mount the volume read-only with the 'ro' mount option.“   I have at least found out that I might be able to “force“ ubuntu to open the disk, but I do not know how. (Some comands to enter into terminal perhaps?)  My question, how do I get access to my harddrive through Ubuntu so I can save some files from the not functioning computer?


Expansion of universe faster then speed of light?

Watching one of the shows on discovery channel, I got to know that during the starting phase of universe its speed should have been faster then speed of light. But then didnt einstein say that nothing can go faster then the speed of light. IF it is true then the universe should have not expanded at that rate? note that I searched for this post but couldnt find any that solves my questions, except for one which is closely related to my question "Why is the age of universe 13.7 billion years?" Thank You


In windows I right click and then there is an option to create a text file.  How to do so in mac?


I really want a wildcard NS record in BIND. Is there a workaround?

We have a public DNS provider, a private DNS master, and a private DNS slave. The public DNS provides the "example.com" zone, and all of it's subdomains. Our private DNS also provides the "example.com" zone, but some A records point to internal IPs on our LAN instead of public IPs. The annoying thing about this configuration is that we need to duplicate all of our CNAME and MX records on both DNS masters.  On the private DNS master, it would be really cool if I could configure a few known subdomains on our private network, and then fall back to the public master for any undefined records. AFAIK, this could be done with a wildcard NS record, but those aren't allowed.  Examples:   example.com   Web server is publicly accessible Some pages on the web server are only available to requests from the private LAN  cdn.example.com   Is a CNAME pointing to amazon cloudfront    I don't want to define the cdn.example.com zone on our private DNS server. (And we have many other records that are duplicated.) It would be great if the private DNS server could be a master/slave hybrid for a particular zone, so that it can override certain records, but fetch the rest from the public DNS server.  If bind9 can't do this, is there something else that can?  Or maybe I should do this with a shell script that pulls down the master DNS records, before appending or overriding with our custom records?


Is there a reason why the number of non-isomorphic graphs with $v=4$ is odd?

I am working through Trudeau's Introduction to Graph Theory, which contains the following problem:     In the following table, the numbers in the second column are mostly even. If we ignore the first row on the ground that $v=1$ is such a trivial situation that its uniqueness is unremarkable, that leaves $v=4$ as the only number of vertices listed for which there are an odd number of graphs. Do you think this is due to chance, or can you think of some reason why $v=4$ should be unique?     v    number of non-isomorphic graphs  1            1  2            2  3            4  4           11  5           34  6          156  7        1,044  8       12,346  9      308,708   Note, this problem concerns the number of non-isomorphic graphs.  Here's what I have so far:  The maximum number of edges in a graph with $v=4$ is $\max(e)=\frac{1}{2}(v)(v-1)=\frac{1}{2}(4)(3)=6$. The graphs with $e=0,1,2,4,5,6$ come in pairs because each graph has a complement. So, there are an odd number of graphs with $v=4$ iff there are an odd number of graphs with $v=4$ and $e= \frac{\max(e)}{2}$.  There are 3 graphs with $v=4$ and $e= \frac{\max(e)}{2}=3$, so therefore there is an odd number of graphs with $v=4$.  However, I don't understand why $v=4$ should be special in this regard, even though it feels special.


ALL "forces" as manifestations of properties of space-time

I apologize if this seems like a quack question, but I need some insights by those who know much more than me in Physics.  Anyway, the gravitational "force" (not really a force) is a manifestation of the curvature of space-time, caused due to presence of mass. Suppose I conjecture that ANY force (electroweak, strong...) is also a manifestation of some property of space-time effected by "something" (as in mass in the case of gravity, and different for different types of forces).  So is there any blatant fault with this line of thought? (I'm asking for blatant faults, since it's a wild supposition anyway)