Harddrive used up in gparted, after fresh install of 13.10  I have just installed Ubuntu 13.10 on an old HP computer which ran on Xp. On installing Ubuntu first through memory pen and later reinstalled by disk, by computer is really slow. You can se the process of a window closing in 10 secounds before its finished.  I did top in terminal and saw that Compiz was taking all resources and I tried to mend that, but now think that the graphic card driver is a dead end.   I saw later that there is something wrong in the partition and disk use.  In Gparted the whole disk is used, but not in real life(se picture)  I am no able to resize the partitions and have no clue what to do.  Can anybody point me in the right direction.  the image below shows the disk situation

I want to shrink my second (LVM) partition, in order to create a new partition in the newly freed space. I am using the Live CD to do so, because I know I can't resize/move this partition while it is in use. When I opened GParted in the Live CD, I realized that I could not resize the partition, because when I right-click it, the option "resize/move" is disabled.  I tried to unmount it, to "lazy" unmount it (umount -l /dev/sda2) but it didn't work.  A screenshot from GParted:


Is there a convenient way of reading/sending text messages from my phone through Windows? I remember Nokia's Symbian phones had a piece of software to do just that, but I can't find any simple solutions for Android.  I'm using Android 5.1 on a Nexus 4.

I'm looking for an app that will let me type text messages on my PC and send the SMSs directly from the PC through my phone, or save the messages to the phone for later use.  I'm basically looking at something like Nokia PC Suite's equivalent.  EDIT:  Google Voice is only for US, doesn't work in India at least, and also defeats the purpose (it will go through the internet, why, when it's possible through the usb cable/modem/wifi). DesktopSMS is a good program, but kept crashing, for some reason. PDANet worked for me. But I liked the tiny . It's weird, and I had to change the bluecove library jar file for Windows 7 x64, but it's compact (a concern for me).


"What's the best program/service to do whatever?" "What are the most used whatever for this?"  A quite common type of question that's usually closed by mods. Any chance a stack is made specifically for that? Some place one can ask what's the best way to solve a problem but instead of repliers describing the solution, they suggest a program/service/whatever that can do it for him. It could be aimed at any kind of person who's looking for a new service provider to replace his current. If this grows big a developer can have an idea what are the most request features/services that don't exist yet. Example: I'm looking for something that can organize my tasks like a to-do list but online. It helps if it has some kind of feature that shows my progress graphically in the most complex tasks.

I have an idea or subject that should have a Q&A, and want to propose a new site. How can I do this?  Related:


For my new city bike I'm thinking of getting a U-lock. Price of the bike is around $900, so I probably don't way to spend more than 10% of its price on the lock.  So far, Kryptonite locks look pretty good, altough that may be due to hype. Their "yellow series" locks seem pretty safe, but I doubt I would lug around a 2 kilo beast for long. The mini series lock looks nice too (and cheaper!) with its 1 kilo of weight. But is it secure enough? Are there are (perhaps less hyped, but good) brands that I should consider?  Note that I won't be parking my bike on the street for too long. I just want to be able to pop into a store without being on a paranoid lookout for my bike every second of my grocery shopping. Is going for the more expensive lock overkill in such scenario?

I recently lost the keys to my lock and had to borrow a bolt cutter to free my bike. It was a bit of an eye opener to realise a) just how easy it was for the bolt cutters to cut through my D Lock (<10 seconds), and b) that nobody on a busy town shopping street batted an eyelid at me doing so.  When choosing a new lock, what should I look for in terms of build material or design that would make it harder to cut through (using relatively small/discrete bolt cutters)?


My harddrive is full, but according to the size of all my folders, I should have more than half of my drive left over.

My Vista 64 installation has drive C, a 150 GB hard drive.  I also has a 1.5 TB drive D.  My C drive has 12.3 GB free.  I don't know what's using up all the space.  There's almost 83 GB unaccounted for!!!  As per  question and  question, I downloaded  and .  WinDirStat, once I found the right options, tells me there's 82.9 GB of .  SpaceMonger, which has a particularly nice display of the data, tells me there's 82.3 GB "Unscanned", with 2 unscannable folders.  Where do I turn now?  Both tools roughly agree there's a large amount of data on my drive, but neither seem to be able to tell me what.  I've tried the standard approach; disk cleanup, remove hibernation file, set the virtual memory to the D drive instead of the C drive.


I'm almost positive I'm going to be marked for duplicate, but I really really just need this sorted out once and for all with a simple example.  I don't understand how a small p-value is evidence against the null hypothesis.  Take a simple example: testing if a coin is fair. This is modeled with a binomial distribution with $n$ fixed (the number of times we flip the coin) and parameter $p$. The null hypothesis $H_0$ is $p = 0.5$.  Now, let our test statistic be $D = |X - np|$, where $X$ is the number of heads in the sample (binomially distributed). The p-value is defined as $p = P(D \ge d\ |\ H_0)$, where $d$ is our observed value of the statistic.  Lets say we find, initially, for $100$ tosses that $60$ heads occurred. So $d = 10$. Then $p = P(D\ge 10\ |\ H_0)$.  Here begins my interpretation:  Then a small p-value means its unlikely for D to be greater than 10, assuming our hypothesis is true.  This means, its more likely for $D \le 10$, which is "near" $0$. That means that the sample $X$ is very likely close to a binomial distribution with p=.5.  That's my innterpretation of it, for which I can't find anything wrong. Why, then, does a small p-value indicate strong evidence against the hypothesis?  That makes zero sense to me. If $p$ is small, then our test statistic is close to zero, meaning our model is mostly likely correct! Why on Earth is that evidence against $H_0$, that's completely in support of it! Please, what is wrong with this? I can't for the life of me tell.

After taking a statistics course and then trying to help fellow students, I noticed one subject that inspires much head-desk banging is interpreting the results of statistical hypothesis tests.  It seems that students easily learn how to perform the calculations required by a given test but get hung up on interpreting the results.  Many computerized tools report test results in terms of "p values" or "t values".  How would you explain the following points to college students taking their first course in statistics:   What does a "p-value" mean in relation to the hypothesis being tested?  Are there cases when one should be looking for a high p-value or a low p-value? What is the relationship between a p-value and a t-value?


SELECT * FROM Users WHERE UserId = " + txtUserId   How do I prevent data injection?  The following code is appropriate?  $username = mysqli_real_escape_string( $GET['username'] ); mysql_query( "SELECT * FROM tbl_members WHERE username = '".$username."'");

If user input is inserted without modification into an SQL query, then the application becomes vulnerable to , like in the following example:  $unsafe_variable = $_POST['user_input'];   mysql_query("INSERT INTO `table` (`column`) VALUES ('$unsafe_variable')");   That's because the user can input something like value'); DROP TABLE table;--, and the query becomes:  INSERT INTO `table` (`column`) VALUES('value'); DROP TABLE table;--')   What can be done to prevent this from happening?


I wish to get the file extension of an image I am uploading, but I just get an array back.   $userfile_name = $_FILES['image']['name']; $userfile_extn = explode(".", strtolower($_FILES['image']['name']));   Is there a way to just get the extension itself?

This is a question you can read everywhere on the web with various answers:  $ext = end(explode('.', $filename)); $ext = substr(strrchr($filename, '.'), 1); $ext = substr($filename, strrpos($filename, '.') + 1); $ext = preg_replace('/^.*\.([^.]+)$/D', '$1', $filename);  $exts = split("[/\\.]", $filename); $n    = count($exts)-1; $ext  = $exts[$n];   etc.  However, there is always "the best way" and it should be on Stack Overflow.


I have a debian 8 box. It is a plesk server with 90+ websites.  It seems somebody access to my server and delete the user root. I go to /etc/passwd and the file is not owned by root:root is owned by hacker:root as hacker is an username of the person who probably do this.  I can´t write on /etc/passwd and there is no root:x:0:0:root:/root:/bin/bash line. I have this line:  hacker:fiMWeeeegx9rM:0:0:pwned:/root:/bin/bash  And now no root proccess are running, all proccess run under hacker name in the server.  Two questions:  1.- I think I can reboot the server to change the hacker user password but how I can undo the changes, restore root password and all proccess that run under hacek username run again under root name?  2.- The access to the server is only rsa key and IP. How it is possible this? If I fix it, how can I protect the box in the future?  Thanks

This is a  about Server Security - Responding to Breach Events (Hacking)   See Also:                  Canonical Version I suspect that one or more of my servers is compromised by a hacker, virus, or other mechanism:   What are my first steps? When I arrive on site should I disconnect the server, preserve "evidence", are there other initial considerations? How do I go about getting services back online? How do I prevent the same thing from happening immediately again? Are there best practices or methodologies for learning from this incident? If I wanted to put a Incident Response Plan together, where would I start? Should this be part of my Disaster Recovery or Business Continuity Planning?   Original Version       2011.01.02 - I'm on my way into work at 9.30 p.m. on a Sunday because our server has been compromised somehow and was resulting in a    attack on our provider. The servers access to the Internet   has been shut down which means over 5-600 of our clients sites are now   down. Now this could be an FTP hack, or some weakness in code   somewhere. I'm not sure till I get there.      How can I track this down quickly? We're in for a whole lot of   litigation if I don't get the server back up ASAP. Any help is   appreciated. We are running Open SUSE 11.0.            2011.01.03 - Thanks to everyone for your help. Luckily I WASN'T the only person responsible for this server, just the nearest. We managed   to resolve this problem, although it may not apply to many others in a   different situation. I'll detail what we did.      We unplugged the server from the net. It was performing (attempting to   perform) a Denial Of Service attack on another server in Indonesia,   and the guilty party was also based there.      We firstly tried to identify where on the server this was coming from,   considering we have over 500 sites on the server, we expected to be   moonlighting for some time. However, with SSH access still, we ran a   command to find all files edited or created in the time the attacks   started. Luckily, the offending file was created over the winter   holidays which meant that not many other files were created on the   server at that time.      We were then able to identify the offending file which was inside the   uploaded images folder within a  website.      After a short cigarette break we concluded that, due to the files   location, it must have been uploaded via a file upload facility that   was inadequetly secured. After some googling, we found that there was   a security vulnerability that allowed files to be uploaded, within the   ZenCart admin panel, for a picture for a record company. (The section   that it never really even used), posting this form just uploaded any   file, it did not check the extension of the file, and didn't even   check to see if the user was logged in.      This meant that any files could be uploaded, including a PHP file for   the attack. We secured the vulnerability with ZenCart on the infected   site, and removed the offending files.      The job was done, and I was home for 2 a.m.            The Moral   - Always apply security patches for ZenCart, or any other CMS system for that matter. As when security updates are released, the whole   world is made aware of the vulnerability.   - Always do backups, and backup your backups.   - Employ or arrange for someone that will be there in times like these. To prevent anyone from relying on a panicy post on Server   Fault.


I'm assuming this is using strong induction/ regular induction. However, besides the "base case" I'm really confused with the inductive steps in my notes.  The inductive steps in my notes use the alpha (golden ratio) but I'm confused on how that connects with the proof and how the it's used.

The definition of a Fibonacci number is as follows:  $$F_0=0\\F_1=1\\F_n=F_{n-1}+F_{n-2}\text{ for } n\geq 2$$   Prove the given property of the Fibonacci numbers for all n greater than or equal to 1. $$F_1^2+F_2^2+\dots+F_n^2=F_nF_{n+1}$$  I am pretty sure I should use weak induction to solve this. My professor got me used to solving it in the following format, which I would like to use because it help me map everything out...  This is what I have so far:  Base Case: Solve for $F_0$ and $F_1$ for the following function: $F_nF_{n+1}$.  Inductive Hypothesis:  What I need to show: I need to show $F_{n+1}F_{n+1+1}$ will satisfy the given property. Proof Proper:  (didn't get to it yet)  Any intro. tips and pointers?


(Please understand me about my broken English.)  I am a student in South Korea.  I am making a quite restricted Lenovo tablet, to make it a perfect education device. The goal is to "help" students to study hard.  To do that, I have to prevent the users from changing the system time in the "Settings", Because changing system time is a easy way to pass my time-dependent application block.  So I am trying to delete the date and time menu from the system settings, to keep only auto time:    By an experience of deleting a guest mode in the system, I think I should use the Buildprop app. But I don't know, what I should delete and change in the system.   Of course it's okay not using Buildprop.  I have a rooted device and my Android version is nougat, 7.1.1.  I'm sorry for using broken English and thanks for reading this.  Have a good day!

The Settings app is common to all Android devices, some have more features than others, but most of them are common, such as "Wireless and networks", "Sound", "Screen" and so on.  However, I am faced with the desire of disabling access to some of these components, while keeping access to some others. Using apps such as "SmartAppProtector", I am able to lock access to the entire Settings application, but can't configure access on a deeper level.  Is there a way to do so? How can I, for example, enable access to the "Wireless and networks" component and disable access to the "Screen" component?  Rooting is no problem, thank you.


I have a variable in bash script dirs= "4"; I want to get this number from another file so I am using a command dirs= sed -n '1p' < test.txt; It gets me the number, I see it in the terminal. But Later in the code, I want to use a loop for dir in dirs.. it does not work because in the script it does not understand that dir is number.  d= sed -n '1p' < test.txt for dirs in $d     do   echo "$dirs" done dirs= read $dirs  speeds= sed -n '2p' < test.txt   for speeds in $s     do   echo "$speeds" done for dir in $dirs do   for speed in $speeds   do     echo "speed=$speed   dir=$dir" done done

I want to assign the result of an expression (i.e., the output from a command) to a variable and then manipulate it – for example, concatenate it with a string, then echo it.  Here's what I've got: #!/bin/bash cd ~/Desktop; thefile= ls -t -U | grep -m 1 "Screen Shot"; echo "Most recent screenshot is: "$thefile;  But that outputs: Screen Shot 2011-07-03 at 1.55.43 PM.png Most recent screenshot is:   So, it looks like that isn't getting assigned to $thefile, and is being printed as it's executed. What am I missing?


Like a circular bead with a thread passing through it and the system being rotated . It can't be centrifugal force as it is pseudo only and has no existence when we are already in an inertial frame like an stationary person outside the assembly. Help in clearing the doubt taking all cases in account :- Uniform and Non Uniform motion, presence and absence of friction between the thread and bead.

I don't understand how the centripetal force, which always points to the center of our circular motion can cause this scenario:  We have a big stone which spins very fast, so fast that a part breaks down, because of the centrifugal force (this is at least how my text books describes it).   My problem: the centrifugal force does not really exist (we only use it in accelerated frames of reference, so the newton laws still work there), so if we're in a laboratory frame of reference, which force would "pull" that piece of the stone to the outside of the circle, when we only have the centripetal force (as mentioned pointing to the center of the circular motion...)?   (Please don't try to explain it in an accelerated frame of reference, because there I understand it, but I don't understand it in a laboratory frame of reference)


I am reading the yellow book Conformal Field Theory by Francesco et al, and am deeply confused by the authors' derivation of the current associated with symmetry transformations (pages 40-41). This is described in . Keeping $O(\omega)$ terms (without any integration by parts), we can show that $$ S' = S + \int d^dx \, \omega_a f_a      - \int d^dx \, (\partial_\mu \omega_a) j_a^\mu $$ where $j_a^\mu$ is the current, given by eq (2.141) (I have verified it), and $f_a$ is some weird quantity found to be (hope that there is no mistake) $$ \begin{aligned}     f_a &\equiv     \mathcal{L} \, \partial_\mu      \frac{\partial x'^\mu}{\partial \omega_a}     + \frac{\partial F}{\partial \omega_a}     \frac{\partial \mathcal{L}}{\partial \phi}     \\ &\quad     +      \frac{\partial \mathcal{L}}{\partial (\partial_\mu \phi)}      \left[         \partial_\mu \frac{\partial F}{\partial \omega_a}         - (\partial_\nu \phi) \,          \partial_\mu          \frac{\partial x'^{\nu}}{\partial \omega_a}     \right] \end{aligned} $$ In the   (and also in the book) where global uniform transformation is considered, I understand their argument that $f_a$ should vanish identically (in that answer, $f_a$ is denoted by $[...]_2$). But it seems that this statement is not trivial to understand: (Edit: According to @Qmechanic, the scaling symmetry holds in $d = 2$ only; but I think it does not prevent us to consider it as an example) For example consider the infinitesimal uniform scaling for scalar fields (here we have only one controlling parameter $\omega$, which is the same everywhere) $$ x' = (1 + \omega) x \qquad \phi'(x') = F(\phi(x),\omega) = \phi(x) $$ Then obviously $$ \frac{\partial x'^\nu}{\partial \omega} = x^\nu \qquad \frac{\partial F}{\partial \omega} = 0  $$ By direct calculation, we find $$     \begin{aligned}         f &=         \mathcal{L} \, \partial_\mu x^\mu         +          \frac{\partial \mathcal{L}}{\partial (\partial_\mu \phi)}          \left[             - (\partial_\nu \phi) \,              \partial_\mu x^\nu         \right]         \\         &= \mathcal{L} \times d         - \frac{\partial \mathcal{L}}{\partial (\partial_\mu \phi)} \partial_\mu \phi     \end{aligned} $$ where $d$ is the spacetime dimension. It does not look like zero at all. So my question is: Is there any concrete example supporting that $f_a$ vanishes identically? (instead of just give some vague "physical argument")

(Cf. Di Francesco et al, Conformal Field Theory, pp. 40-41) I am trying to derive eqn. (2.142) or   $$\delta S = \int d^d x ~\omega_a~\partial_{\mu}j^{\mu}_a  \tag{2.142}$$   in the book CFT by Di Francesco et al.  I have obtained the final expression   $$\delta S = \int d^d x\,\partial_{\mu} \omega_a \left[\frac{\delta F}{\delta \omega_a} \frac{\partial L}{\partial(\partial_{\mu}\Phi)} - \frac{\delta x^{\nu}}{\delta \omega_a}\partial_{\nu}\Phi \frac{\partial  L}{\partial(\partial_{\mu}\Phi)} + \frac{\delta x^{\mu}}{\delta \omega_a}L\right] +$$ $$ \omega_a\left[ \frac{\delta F}{\delta \omega_a}\frac{\partial L}{\partial \Phi} + (\partial_{\mu}\frac{\delta F}{\delta \omega_a})\frac{\partial L}{\partial(\partial_{\mu}\Phi)} - \partial_{\mu} (\frac{\delta x^{\nu}}{\delta \omega_a})\partial_{\nu}\Phi \frac{\partial L}{\partial(\partial_{\mu}\Phi)} + \partial_{\mu} (\frac{\delta x^{\mu}}{\delta \omega_a})L\right]\tag{A}$$   and indeed the terms multiplying $\partial_{\mu}\omega_a$ there are exactly $j^{\mu}$ as obtained in eqn. (2.141).  The problem I am having is that the terms multiplying $\omega_a$ don't appear to vanish. (The first two do as a consequence of the classical equations of motion but the last two do not)  The method Di Francesco employs is to assume a position dependent parameter $\omega = \omega(x)$, then make it constant at the very end.  So, if we make $\omega$ independent of position at the end (i.e impose the rigid transformation), then $$\partial_{\mu}\omega_a = 0\tag{B}$$ identically. In which case, we are left with $$\omega_a\int d^dx [..] = 0,\tag{C}$$ by further considering a symmetry transformation, where [..] are the terms multiplying $\omega$ in the expression above.  So I am not sure how Di Francesco is left with   $$ \delta S~=~-\int d^d x~ j^{\mu}_a ~\partial_{\mu} \omega_a  \tag{2.140}.$$    The paragraph preceding eqn. (2.140) seems to be contradictory to me (in particular the first and last sentence) and if indeed he is imposing a rigid transformation then shouldn't $\partial_{\mu}\omega_a = 0$ be zero in (2.140)?


I'm trying to figure out how to convert a message to a message representative (non-negative integer) in RSA. I think I understand how the OS2IP primitive (converting from message to integer). It involves finding the sum of all the integer representations of each byte multiplied by 256 to the power of the length of the message minus the index for the byte. However, I don't understand how the opposite process works. PKCS#1 says to write the message representative x in its    xLen-digit unique representation in base 256. I'm not very good with the actual mathematical processes here, so I'm not sure how the integer is supposed to be separated into the separate bytes multiplied by powers of 256.

I started working with RSA two weeks ago. But I couldn't really understand how exactly I2OSP & OS2IP are working. I am using some open source for signature verification through RSA PSS algorithm.  I am trying to generate "EM" from a signature of length 256 bytes, public modulus $n$ (256 bytes) and exponent $e$ (0x10001). But I am not getting the expected output ("EM"). So I started debugging code.  Can someone clearly explain what OS2IP & I2OSP do?


I want to have a command line at the top of terminal and history moving down. Is it possible? I am using Ubuntu 16.04, gnome-terminal+tmux.

I have currently decided to test my double monitors in the vertical configuration, and I came across a problem that I had never had before:  the input line on my terminal is too far down the screen!  I was wondering if there is a way to make the output scroll downwards, so that the input line stays at the top.  e.g., a normal terminal view looks like this:  PING 8.8.8.8 (8.8.8.8) 56(84) bytes of data. 64 bytes from 8.8.8.8: icmp_req=1 ttl=46 time=28.3 ms 64 bytes from 8.8.8.8: icmp_req=2 ttl=46 time=13.7 ms 64 bytes from 8.8.8.8: icmp_req=3 ttl=46 time=19.1 ms 64 bytes from 8.8.8.8: icmp_req=4 ttl=45 time=20.8 ms 64 bytes from 8.8.8.8: icmp_req=5 ttl=45 time=15.6 ms 64 bytes from 8.8.8.8: icmp_req=6 ttl=46 time=15.3 ms 64 bytes from 8.8.8.8: icmp_req=7 ttl=46 time=15.3 ms 64 bytes from 8.8.8.8: icmp_req=8 ttl=45 time=14.3 ms 64 bytes from 8.8.8.8: icmp_req=9 ttl=45 time=14.3 ms 64 bytes from 8.8.8.8: icmp_req=10 ttl=45 time=15.5 ms 64 bytes from 8.8.8.8: icmp_req=11 ttl=45 time=16.9 ms 64 bytes from 8.8.8.8: icmp_req=12 ttl=45 time=16.3 ms 64 bytes from 8.8.8.8: icmp_req=13 ttl=45 time=20.0 ms ^C --- 8.8.8.8 ping statistics --- 13 packets transmitted, 13 received, 0% packet loss, time 12017ms rtt min/avg/max/mdev = 13.773/17.391/28.343/3.812 ms me@my_computer:~$    and instead I would like to have something like this:  me@my_computer:~$  rtt min/avg/max/mdev = 13.773/17.391/28.343/3.812 ms 13 packets transmitted, 13 received, 0% packet loss, time 12017ms --- 8.8.8.8 ping statistics --- ^C 64 bytes from 8.8.8.8: icmp_req=13 ttl=45 time=20.0 ms 64 bytes from 8.8.8.8: icmp_req=12 ttl=45 time=16.3 ms 64 bytes from 8.8.8.8: icmp_req=11 ttl=45 time=16.9 ms 64 bytes from 8.8.8.8: icmp_req=10 ttl=45 time=15.5 ms 64 bytes from 8.8.8.8: icmp_req=9 ttl=45 time=14.3 ms 64 bytes from 8.8.8.8: icmp_req=8 ttl=45 time=14.3 ms 64 bytes from 8.8.8.8: icmp_req=7 ttl=46 time=15.3 ms 64 bytes from 8.8.8.8: icmp_req=6 ttl=46 time=15.3 ms 64 bytes from 8.8.8.8: icmp_req=5 ttl=45 time=15.6 ms 64 bytes from 8.8.8.8: icmp_req=4 ttl=45 time=20.8 ms 64 bytes from 8.8.8.8: icmp_req=3 ttl=46 time=19.1 ms 64 bytes from 8.8.8.8: icmp_req=2 ttl=46 time=13.7 ms 64 bytes from 8.8.8.8: icmp_req=1 ttl=46 time=28.3 ms PING 8.8.8.8 (8.8.8.8) 56(84) bytes of data.   I could not find any such documentation or question on the forums. If anyone has an idea, please let me know! (also if you think it's not possible)  Thanks!  PS: I'm using Ubuntu 12.04


Everywhere within my code when I interact with a float value in my database, I always round(); it to 2 decimals in PHP, how come I get values like this: 0.00000305176 within my database sometimes?

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


One of the popular Kronecker delta and Levi-Civita identities reads $$\epsilon_{ijk}\epsilon_{ilm}=\delta_{jl}\delta_{km}-\delta_{kl}\delta_{jm}.$$ Now, is there an intuition or mnemonic that you use, that can help one learn these or similar mathematical identities more easily? Also, what is the motivation for expressing Levi-Civita symbol in terms of Kronecker Delta in the first place?

In order to prove the following identity: $$\sum_{k}\epsilon_{ijk}\epsilon_{lmk}=\delta_{il}\delta_{jm}-\delta_{im}\delta_{jl}$$ Instead of checking this by brute force, Landau writes thr product of Levi-Civita symbols as: $$\epsilon_{ijk}\epsilon_{lmn}=\det\left|    \begin{array}{cccc}       \delta_{il}   & \delta_{im}  & \delta_{in}   \\       \delta_{jl}   & \delta_{jm}  & \delta_{jn}   \\       \delta_{kl}   & \delta_{km}  & \delta_{kn}       \end{array} \right| $$  The proof that the equalty holds is quite straightforward if you consider what values the indices can take. But I've been told that there's a much more profound and elegant demonstration based on the representation of the symmetric group.  Does anybody know this approach based on group theory?


Where can I ask a question that looks like this?     What are some popular general-purpose note-taking software apps that support Markdown formatting?

I have a list of requirements for a program, but I don't know what program meets these criteria. That's about general-purpose software, for example, not a programming IDE or statistical workbench, questions about which would certainly go to respective sites.  Is this question appropriate on Stack Overflow? Where should I ask about it? On Super User or elsewhere?


I am studying a two-body central force system in which the two particles, one of mass $m$ and one of mass $M$, experience a force directed along the line connecting the two particles.   We can reduce this to a system of just one fictitious particle with reduced mass and a central force. Why is linear momentum not conserved in the CM frame when it was conserved before shifting to the CM frame?

I am trying to understand conservation linear momentum with in angular momentum  Herewith i just explain what i am  looking for.    Imagine an object of mass(M), velocity(V), is undergoing circular motion    with radius(R)     Angular momentum L = RMV  (R-radius M-mass- V- tangential velocity)  Mass is constant here  Since L is conserved   so when R is decreased tangential velocity(V)     has to be increased to keep angular momentum constant.  Does this mean linear momentum not conserved when radius of rotation changes?  When linear momentum is not conserved then what is the force that increases the velocity of object when R decreases.  Could anyone clarify this. or could any one say is my basic understanding about momentum is wrong. for easy understanding i am only considered magnitude of momentum's not cross product of vectors


I am applying for my son and my mother to bring him on a visit to the UK. Do I make separate applications or a joint application, please?

I am a permanent resident of USA. I am making a trip to India but planning a stop-over in London,UK for a week. For this stop-over , I am applying for a standard visitor visa. My biometric appointment has already been completed. Now I have to send applications for the visa for both me and my wife.  1.) Should I send both applications in same envelope? Maybe, put each application in small envelope and then put both applications in a bigger envelope?  2.) Should I put my financial documents (Bank statements , Pay Slips) in both applications(i.e. mine and my wife's)?  3.) I have an old passport which is expired. Is there any need to send this passport as well with my application?  Thanks!


Having just read  article about why there is a time limit on editing questions, I thought about questioning why comments do not have an edit history.  I think (I couldn't find any statistics, so if anyone does, please tell me) that there must only be about 1 edit made to each answer/comment on average and the amount of space that would take is minimal.  Is there another reason not to have edit history on comments?

Possible Duplicate:          Is there any way to view edits made to comments to a reply ? For example if someone modify one of their comments, can the original be seen ?


Let $u,v,w \in S^2$ and let $[u,v,w]$ be a spherical triangle. I want to find its inscribed circle. However, I don't know how to approach this problem. Would someone please explain?  In my understanding, one needs to somehow find the altitudes of the spherical triangle and then the point of its intersection (circumcentre)? Then what about the radius?

Given three vectors $u,v,w \in S^2$ and the triangle $[u,v,w]$ I want to find its circumscribed circle. However, I don't know how to approach this problem. Would some one please explain?  In my understanding, one needs to somehow find the altitudes of the spherical triangle and then the point of its intersection (circumcentre)? Then what about the radius?


I need to back up a directory with  zip -r /savehere/backup_`date +%y%m%d%H%M%S` /save/this -q   It works fine. But not from crontab:  * * * * zip -r /savehere/backup_`date +%y%m%d%H%M%S` /save/this -q   neither   * * * * cd /savehere/; /usr/bin/zip -r /savehere/backup_`date +%y%m%d%H%M%S` /save/this -q    Оther commands in this crontab are working.  What is wrong with this command?

This is a  about using cron & crontab.   You have been directed here because the community is fairly sure that the answer to your question can be found below. If your question is not answered below then the answers will help you gather information that will help the community help you. This information should be edited into your original question.  The answer for 'Why is my crontab not working, and how can I troubleshoot it?' can be seen below.  This addresses the cron system with the crontab highlighted.


How can I view the password for a email account in Microsoft Outlook? I lost my password because of a virus attack.

How can I recover a password for an Outlook 2007 account?


Whenever I am talking on my phone and walk into the elevator the call drops as soon as the doors close, and also the WiFi signal completely stops.  Why does this happen?  Note: I am asking this question because me and my friends are brainstorming for a project proposal to work on.

Why can I listen to my mobile phone's radio clearly inside the bus, inside the train, but not inside the elevator? Also, there is an interference of radio signal when the train is accelerating or decelerating. What is the reason behind this?


For example: "Request you to respond as soon as possible." I've encountered this sentence in a few e-mails (without subject words like "I" or "we").

"Thought you'd never ask" is "I thought you'd never ask" with "I" omitted. "Hope this helps" is "I hope this helps" with "I" omitted.   In English grammar, normally every sentence should have a subject, right?   My first thought is that these two examples are so often used that they are like set phrases. But these are not really set phrases. You can alter the words after "thought" and "hope".  Another possible explanation is the tendency to drop the subject if it is the first person pronoun. It seems that in many languages, such as Spanish, Italian and Japanese, the first person subject is usually omitted. Maybe English is going the same way? (Not exactly the same, since in Italian, verb forms change according to the person, so the subject is not necessary to understand who one's referring to.)  And, apparently, such omission is more common in spoken English than in written English.  Are there more examples of such first person subject omission? How frequent is it?


I just came across  question on English.SE. The banner says it was closed by a moderator as "general reference", which is not one of the 5 standard close reasons (duplicate, off-topic, too broad, unclear what you're asking, and primarily opinion based). It is similar to a current ELU off-topic close reason, just displayed in a different way.    Of course, the question was closed before the beginning of , so the rules were probably different back then.  Were closed questions previously displayed with the off-topic close reason shown at the top of the banner (rather than just "off-topic")? If so, why? If not, why was the close reason shown as "general reference" in this case?

There is a certain amount of questions that are absolutely trivial in nature: How to format a date, how to concatenate a string, et cetera. Questions that could be solved by taking a look into the manual.  Random examples from the tags I frequent:                What those OPs need is a link to the right manual, which we should give them. But the question serves no purpose. They don't even have a use by being searchable,  because any sane search query would lead to the actual manual as the first hit.  Jeff discusses the possibility of introducing a new close reason for this over at  According to Robert's suggestion there, it could go like this:     general reference: this question is too basic; the answer is indexed in any number of general internet reference sources designed specifically to find that type of information.   Please please implement this.  Add a field (like the "enter duplicate ID here" popup) for users to suggest the correct manual link:    The suggested links would then be shown in a block in the top section of the question, like duplicate links.   Also, the amount of reputation earnable from these trivial questions is appalling. I'm sure a great portion of most high-rep users' points (including mine) is from answering "what was that function for replacing a string again?" type questions. This dilutes the value of reputation as a measure of true expertise a great deal.  I would suggest that answers to questions that get closed as "general reference" are made community wiki retroactively, taking away any reputation earned.


Assume I have the following function: def func(a, b=0, c=1, d=2,...): # Code goes here  I want to use it inside another function like this: def do_sth(...):    func(...)  do_sth(...)  The number of parameters of func is big. What should I do to pass (optional) params to func when calling do_sth, because the following method is usable but not pythonic: def do_sth(a, b, c...):    func(a=a, b=b,c=c...)  do_sth(a, b, c...)

In the following method definitions, what does the * and ** do for param2?  def foo(param1, *param2): def bar(param1, **param2):


I created a plot in matplotlib and saved it as a PGF file.  I insert the figure into Latex with the following:  \begin{figure}     \centering     \input{test_fig.pgf} \end{figure}   With \usepackage{pgf} in the preamble.  The figure is then inserted but its to big, i.e. stretching far off the page.  I should mention that this is in a beamer document class.  Is there a method to scale the figure so that its as wide as the \textwidth?  I have tried inserting the figure with \includegraphics[width=\textwidth]{test_fig.pgf}, but I get the error Unknown graphics extension: .pgf.  Here is a MWE, with the PGF figure attached :  \documentclass{beamer} \usepackage{beamerthemeshadow} \usepackage{pgf}  \begin{document} \title{Slide Title}   \author{Author} \date{\today} \frame{\titlepage}  \section{Section 1}  \frame{\frametitle{Title} \begin{figure}     \centering     \resizebox{0.8\textwidth}{!}{\input{test_fig.pgf}} \end{figure} } \end{document}

I have a pgf picture which I insert with:  \input{m1.pgf}   But the image is too big. Instead of regenerating a smaller image, I'd rather take advantage of vector graphics, and have XeLaTeX scale it. How do I set the width of pgf picture (keeping its aspect ratio)?  MWE  tex:  \documentclass{article}  \usepackage{fontspec} % enagles loading of OpenType fonts \usepackage{polyglossia} % support for languages  % fonts: \defaultfontfeatures{Scale=MatchLowercase,Mapping=tex-text} % without this XeLaTeX won't turn "--" into dashes \setmainfont{DejaVu Sans} \setsansfont{DejaVu Sans} \setmonofont{DejaVu Sans Mono}  % pgf: \usepackage{pgf}  \begin{document}  \input{m1.pgf}  \end{document}   Sample pgf:  (it's too big to cite it here, and I can't make much smaller).


I'm trying to build Emacs from sources. When configure options were listed without an array Emacs configured properly. When I added a Bash array to add optional options it broke configure. Here is the broken array:  BUILD_OPTS=('--with-xml2' '--without-x' '--without-sound' '--without-xpm'     '--without-jpeg' '--without-tiff' '--without-gif' '--without-png'     '--without-rsvg' '--without-imagemagick' '--without-xft' '--without-libotf'     '--without-m17n-flt' '--without-xaw3d' '--without-toolkit-scroll-bars'      '--without-gpm' '--without-dbus' '--without-gconf' '--without-gsettings'     '--without-makeinfo' '--without-compress-install')  if [[ ! -e "/usr/include/selinux/context.h" ]] &&    [[ ! -e "/usr/local/include/selinux/context.h" ]]; then     BUILD_OPTS+=('--without-selinux') fi      PKG_CONFIG_PATH="${BUILD_PKGCONFIG[*]}" \     CPPFLAGS="${BUILD_CPPFLAGS[*]}" \     CFLAGS="${BUILD_CFLAGS[*]}" CXXFLAGS="${BUILD_CXXFLAGS[*]}" \     LDFLAGS="${BUILD_LDFLAGS[*]}" LIBS="${BUILD_LIBS[*]}" \ ./configure --prefix="$INSTALL_PREFIX" --libdir="$INSTALL_LIBDIR" \     "${BUILD_OPTS[*]}"   When configuring with the array it results in:  configure: error: invlaid package name: xml2 --without-x --without-sound --without-xpm --without-jpeg --without-tiff --without-gif ...   I've been through  but I don't see what I am doing wrong. Changing to double quote and no quote did not help.  What is the problem and how do I fix it?

says:  If the index number is @ or *, all members of an array are referenced.  When I do this: LIST=(1 2 3) for i in "${LIST[@]}"; do   echo "example.$i" done  it gives the desired result: example.1 example.2 example.3  But when I use ${LIST[*]}, I get example.1 2 3  instead. Why? Edit: when using printf, @ and * actually do give the same results.


I am trying to run a program as it is saying to do on the website but it doesn't work. I am really new on Ubuntu and I would appreciate any help please. On the website is saying :    To run it: unzip the file, CD to the sedlog-3.1 directory and type java -jar SedLog.jar.  sedlog-3.1 is the name of the program I am trying to run. When I type java -jar SedLog.jar on the sedlog-3.1 directory, I get this message back :  kate@Riley:~/sedlog-3.1$ java -jar SedLog.jar The program 'java' can be found in the following packages:  * default-jre  * gcj-5-jre-headless  * openjdk-8-jre-headless  * gcj-4.8-jre-headless  * gcj-4.9-jre-headless  * openjdk-9-jre-headless Try: sudo apt install <selected package>   I really don't know what stupid mistake I do and I can't short that out.

How do I install Java, including in my browser, so websites with Java work?


I just installed 14.04 today, found seems the system still have Shellshock issue:  dli@srv:~$ lsb_release -a No LSB modules are available. Distributor ID: Ubuntu Description:    Ubuntu 14.04.1 LTS Release:    14.04 Codename:   trusty dli@srv:~$ env x='() { :;}; echo vulnerable' bash -c "echo this is a test" vulnerable this is a test   I think might be better to get it fixed from the installation image?

Recently, there have been news going around regarding "CVE-2014-6271" (See ), which is a vulnerability in Bash. How do I know if I am affected by this, how can I fix it, and why should I care?  This is designed as a canonical answer for this vulnerability, due to its scope and severity.


In a PID $R$ with $ a\in R $ irreducible and $\langle a \rangle$ the ideal generated by $a$, and $b \in R\setminus \langle a \rangle$,   is $1\in \gcd(a,b)$. Why is it sufficient to show that $g \in \gcd(a,b)$ is a unit in R to show the above?

Let $R$ be a PID (Principal Ideal Domain) and $x$ is an element R. Prove that the ideal $\langle x\rangle$ is maximal if and only if $x$ is irreducible.   Ok, so I know what an irreducible is. I'm thinking that this problem is asking us to set up a proof by contradiction but I can't see how. No one in my study group has any clue.


I need to emulate the 3-button mouse and number pad, which requires accessing 'User Preferences.' But clicking on 'User Preferences' closes Blender immediately! Any answers?

The machine that I'm currently using is an extremely slow netbook. Whenever I go to change user preferences in Blender, it stalls out. What I need to do is activate the "emulate 3 button mouse" checkbox. Is there a way to do this via console/script?


My editor is giving me the option to choose between:    The Creative Commons Attribution 4.0 International License (CC BY 4.0) The Creative Commons Attribution-Noncommercial-NoDerivative Works 4.0 International License (CC-BY-NC-ND 4.0).    to publish my article in their journal.  If I understand it, the basic difference between the two is that the first one allows for commercial use of the content of my paper from third parties.  Would the first one be less restrictive in terms of citations to my article? What is the most common option for research articles?

Why would a scientist or mathematician want to publish a paper under the Creative Commons CC BY licence?  This licence allows the work to be modified.  Why would you want to allow a scientific paper to be altered?  Yet Arxiv at  seems to offer only licences that allow changes.  Similary Nature Communications at :  "Nature Communications articles are published open access under a CC BY license".  The CC licences that do not allow change are the ones with ND (no derive). So the natural choice would seem to be either BY-ND or BY-NC-ND. Can anyone shed light?


I'm looking for a geometric way to identify functions that are continuous but not uniformly continuous without using the definition. I can't really put my hands on a concrete difference between the two.

Can we explain  between ordinary continuity and Uniform Continuity difference geometrically?  What is the best way to describe the difference between these two concepts? Where the motivation of Uniform Continuity came from?    Thank You.


Is there any method to convert an infinite sum (of any type) into an infinite product? That is, a method such that  the equality   $  \sum_{n = 0}^{\infty}a_n = \prod_{n = 0}^{\infty} f(a_n)$   holds.

I am working on studying infinite products. I know that it is possible to convert an infinite product to an infinite sum using logarithms, where  $$\log \prod s_n = \sum \log s_n$$  My question is, it always possible go from sum to product with $e$, where  $$\exp \sum s_n = \prod e^{s_n}$$  Also, are there any other methods to convert sums into products?  Thanks in advance.


I just ran the Software Updater (on Ubuntu 16.04). While installing the new packages (including a new kernel version) I got a Grub Secure Boot alert. After that the Software Updater crashed.  It stuck at post-installation-triggers on shim-signed.  After having killed all processes related to dpkg I tried to configure it again  sudo dpkg --configure -a   which returned the following:  Setting up shim-signed (1.32~16.04.1+0.9+1474479173.6c180c6-1ubuntu1) ... debconf: DbDriver "config": /var/cache/debconf/config.dat is locked by another process: Resource temporarily unavailable dpkg: error processing package shim-signed (--configure): subprocess installed post-installation script returned error exit status 1 Errors were encountered while processing: shim-signed   I fear that if I restart I'll have problems with booting. Can I reconfigure shim-signed, or can I revert the update somehow?

I'm trying to install the flashybrid but when I enter the apt-get install flashybrid command, I get this error:  root@user-desktop:/home/user# apt-get install flashybrid Reading package lists... Done Building dependency tree Reading state information... Done flashybrid is already the newest version. 0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded. 1 not fully installed or removed. After this operation, 0B of additional disk space will be used. debconf: DbDriver "config": /var/cache/debconf/config.dat is locked by another process: Resource temporarily unavailable Setting up flashybrid (0.15+nmu2) ... debconf: DbDriver "config": /var/cache/debconf/config.dat is locked by another process: Resource temporarily unavailable dpkg: error processing flashybrid (--configure): subprocess post-installation script returned error exit status 1 Errors were encountered while processing: flashybrid E: Sub-process /usr/bin/dpkg returned an error code (1)   I also tried this one to find what is already using that file:  root@user-desktop:/home/user# lsof | grep /var/cache/debconf/config.dat lsof: WARNING: can't stat() fuse.gvfs-fuse-daemon file system /home/user/.gvfs Output information may be incomplete. dpkg-prec 4672 root 4rW REG 8,6 39658 1697827 /var/cache/debconf/config.dat   But I don't know how to fix this.


I want to test if an exception was raised how can I do that? In my file.py I have this function: //file.py  def unlink(self):         for rec in self:             if rec.state in ('progress', 'done'):                 raise ValidationError(_('Error!!))          return super(MyClass, self).unlink()  //test_file.py  my_obj.button_validate()  my_obj.unlink()  When adding : my_obj.unlink() in the function , I got the output in log like  this:   raise ValidationError(_('Error!!')) odoo.exceptions.ValidationError: Error!!  How can I add test if the validation error is shown or not ?

How does one write a unittest that fails only if a function doesn't throw an expected exception?


is there a simple way to find out if my website is being integrated e.g. via iFrame/ JS on another page? I am planning on writing a C# tool to detect these external uses of my page for statistics.      I am currently trying to read the request header from the client so that I can access the "referrer". This should indicate if a user is coming from an external site or just clicked a link on mine.        Is it possible to convert the request.header into a JSON so that I can access the referrer like this: .referrer?  string headers = String.Empty;             List<string> headerlist = new List<string>();             foreach (var key in Request.Headers.Keys)             {                 headers += key + "=" + Request.Headers[key];                 headerlist.Add(headers);             }

I am writing an iframe based facebook app. Now I want to use the same html page to render the normal website as well as the canvas page within facebook. I want to know if I can determine whether the page has been loaded inside the iframe or directly in the browser?


Given $(G,*)$ a group. Show the function $f: G \to   G$ defined as $f(a)=a^{2}$ is an homomorphism if and only if G is abelian.  My attemp was:  $\to$ suposse $f$ and homomorphism, to show $a*b=b*a$ \begin{align}  f(a*b)=f(a)*f(b) \\  & = a^2*b^2 \\   & = (a*a)*(b*b) \\  & = (b*b)*(a*a) \\   & =f(b)*f(a) \\  \end{align}  I think it is wrong because I used commutative property.  For the last part:  $\leftarrow$ suposse G is abelian, to show $f$ is homomorphism  \begin{align}  f(a)=a^2 \\  & = a*a \\  \end{align}  Can you help me to clarify the proof?

I'm working on the following problem:     Let $G$ be a group. Prove that $G$ is abelian if and only if   $\varphi(g) = g^2$ is a homomorphism.   My solution: First assume that $G$ is an abelian group and let $g, h \in G$. Observe that $\varphi(gh) = (gh)^2 = (gh)(gh) = g^2h^2 = \varphi(g)\varphi(h)$. Thus, $\varphi$ is a homomorphism.  I'm having trouble completing the proof in the reverse direction. Assume that $\varphi$ is a homomorphism. We then know that $\varphi(gh) = \varphi(g)\varphi(h)$ and $\varphi(hg) = \varphi(h)\varphi(g)$. However, I don't see a way to use this to show that $gh = hg$.  Could anyone lend a helping hand?


The  KOMA-Script package scrletter by default typesets the word "Page" (or language-dependent equivalent) preceding the actual page number in the footer. How may this behavior be disabled, in favor of typesetting simply an unlabelled number?  See  for solution to this question for class scrlttr2.


I have created FiltersQueryAdapter as mainAdapter which has been passed to setupPhotoFilters Method where mainadapter is assisgned to setAdapter. Is possible that as parseGeoPointfromLocation not being within the scope of FiltersQueryApdapter its returning null what i cloud do in this case?    /*   * Helper method to get the Parse GEO point representation of a location   */     public ParseGeoPoint geoPointFromLocation(Location loc) {         return new ParseGeoPoint(loc.getLatitude(), loc.getLongitude());     }       FiltersQueryAdapter mainAdapter = new FiltersQueryAdapter(this, PhotoFiltersAdapter.class             , new ParseRecyclerQueryAdapter.QueryFactory() {         public ParseQuery create() {             Location myLoc = (currentLocation == null) ? lastLocation : currentLocation;             ParseQuery query = ParseQuery.getQuery("PlaceFilters");             //query.include("user");             query.orderByAscending("GeoArea");             query.whereWithinKilometers("GeoArea", geoPointFromLocation(myLoc), radius);             query.setLimit(6);             return query;         }     });       private void setupPhotoFilters() {         rvFilters.setHasFixedSize(true);         rvFilters.setAdapter(mainAdapter);         rvFilters.setLayoutManager(new LinearLayoutManager(this, LinearLayoutManager.HORIZONTAL, false));     }

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


So, I have a script that needs to install a software but the script needs to be run as root.   I have created a desktop icon on the GUI (using Ubuntu desktop) where ideally, the user will click this icon, it will prompt for password and then run the script as root.  So far the script does what is intended if ran as root, but not as the user. Script looks like this:   #!/bin/bash -l  zenity --question --text "This script will reboot after installation is complete" --title="Warning\!" 2> /dev/null if [ $? = 0 ]; then   install dependencies    dpkg -i package.deb   etc fi  reboot   However, if I click on the icon to run the script, it loads and it doesn't do anything, then I check the logs and realize that it fails: sudo: no tty present and no askpass program specified I know I can modified the sudoers files but I do not want to do this as I need to keep this user independent.  Is there a way to force when running the script to ask the user to become root? or to force the GUI to ask for a password? what is the best way to get this done? I need users to run this program but I need to run the program as root and sudo is not doing it for whatever reason.

I want to give non-sudo access to a non-root user on my machine, there is a user dns-manager, his only role is to run all the BIND commands(rndc, dnssec-keygen) etc.   Now everytime he has to run a command, he types,  sudo rndc reload   Is there a way I can get rid of this sudo, but only on a particular set of commands(and only for dns-manager)?


In terraria I have 2 above ground mushroom bio,e 2 block thick and suitable homes. It says he would like to settle but he won't come. Plz help. Ps I have defeated plantera

I currently find myself in a pickle because even after I've built the mushroom biome and met all other requirements, the Truffle NPC won't move in.   I've defeated not only the Wall of Flesh but Ocram already. Created a surface mushroom biome. Built a house made out of mushrooms with mushroom furniture.   I have no idea how long it takes for the NPC to move in or if I'm wrong in any of the steps.


It's really frustrating when you post a new question, and a person down votes it and then they close the tab. The OP can add a comment such as "Why down vote?", the post would still be down voted even though the OP fixed the issue making the down vote invalid. Then it would still be -1, unless someone up votes the post (but then this gets tricky: the up voter just wanted to fix the -1, not necessarily up vote it and give rep). So a solution: subscribe the down voter to the question, no?  That'd mean he would get notifications when OP's post is edited or new comments on the question or comment.

To me, a downvote usually indicates a problem with an answer. When I downvote it's to mark the answer as having a problem, not the person. If the answer is fixed, I want to remove that downvote - but it's tricky to keep track of all the questions I've looked at over the last few hours.  I don't actually downvote very much, but it's very easy to forget what's going on.  It would be nice to have some way of indicating in an edit that you (the editor/answerer) believe the reason for the downvote has now been resolved, so that the downvoters could come and undo their downvotes or explain why it's still not fixed.  (Note: this isn't about rep-recovery, but quality control. I would feel a lot better about downvoting on "iffy" answers if I felt it was likely that the answer would be fixed and I could undo the vote. Whether or not I'd get back the cost of the downvote is somewhat immaterial.)


public class MyClass:MyClassBaseClass, IInterface  {    public static method A()    {    }     public static method B()     {     } }   Consider the snippet above.  I want to implement an interface in my class. I want to make all the implemented methods from interface IInterface as static in my class so that I do not have to create an instance before calling the method. Why I am not allowed to do it and what are the possible solutions and workaround to do the same thing which I wish to do.

Why was C# designed this way?  As I understand it, an interface only describes behaviour, and serves the purpose of describing a contractual obligation for classes implementing the interface that certain behaviour is implemented.  If classes wish to implement that behavour in a shared method, why shouldn't they?  Here is an example of what I have in mind:  // These items will be displayed in a list on the screen. public interface IListItem {   string ScreenName();   ... }  public class Animal: IListItem {     // All animals will be called "Animal".     public static string ScreenName() {         return "Animal";     } .... }  public class Person: IListItem {      private string name;      // All persons will be called by their individual names.     public string ScreenName() {         return name;     }      ....   }


Throughout Star Wars various Sith have referred to themselves as 'Darth', Darth Vader, Darth Maul, Darth Revan, etc. I learned from  that a Darth was seen as greater than a Sith Lord in legends, which made me wonder, what exactly does the title mean? What is the difference between 'Bob who is a Sith' and 'Darth Bob'?

I watched Star Wars, Episode IV: A New Hope for the first time in a while a few days ago (the first step in taking my Daughter through the Machete Order). One thing that stood out was the pre-duel smack talk between Vader and Obi-Wan:     Vader: When I left you, I was but the learner; now, I am the master.   Obi-Wan: Only a master of evil, Darth.   From memory, this is the only example I can think of where 'Darth' is used as if is was Vader's first name, as opposed to the title that we (eventually) learn that it is, once we meet other Darths.   I wonder when Lucas decided that Darth would be a title for dark side Jedi (not called 'Sith' until the prequel trilogy)? In Empire and Jedi, Darth Sidious is referred to only as 'The Emperor', but 'Darth Vader' ceases to be called Darth if only one word is used; e.g. Yoda's "Vader, you must face Vader".  Is this just an example of Lucas making stuff up as he went along, rather than having it all planned out from the start (not actually all that unreasonable)? Or is there some reason that Obi-Wan used 'Darth' instead of 'Vader'? On previous viewings (i.e. before the prequels existed) I'd interpreted this as Obi-Wan being informal with his old student by using his first name, rather than his last. However, the reverse interpretation could be true once you know that Darth is a title, i.e. that Obi-Wan is using his title rather than his name in order to be as cold and impersonal as possible (i.e. replace 'Darth' with 'Sir' and put Bastard swords in their hands instead of light sabers).


Somebody on the site said it was possible to transfer a GTA Online account to a different account if you call Rockstar support. Is this true?

I had a high rank on my girlfriend's account, but now have my own place and want to take my progress from her account to mine. Is this possible?  Starting back from 0 doesn’t seem right, I had houses, cars and was a CEO. I can log in as her and play on her account, but she doesn’t have PSN anymore and I don’t want to buy it just to play GTA 5, as I already have PSN for myself and all the games I got to play are there.   Is there any way I can transfer her account's progress (my old profile) to my new one, which is rank 9?


On Stack Overflow there a many questions pertaining to statistical software such as .  Most of these questions are programming questions and undoubtedly belong on SO.  However, some questions are really about the underlying statistical ideas, and not about how to use R per se.  They belong on stats.SE (i.e., ).  However, when I flag such questions, CV is not listed with the other SE sites as an option.  Can we add CV to that list?

Earlier, I voted to close  as off-topic.  The question has since been closed.  There is an , but it didn't show up in the list when I selected "off-topic".  The options were:   Meta Stack Overflow Server Fault Super User Webmasters Programmers   Questions:   Should Wordpress appear in this list? Are there any other sites that should appear in the list?   Should all non-beta sites appear in that list by default?


I just read the formula to determining the no. of paths of length $m$. It was $\frac{n(n-1)\cdots(n-m)}{2}$ Do we have something for cycles too?I think it should be $\frac{n(n-1)\cdots (n-m+1)}{2}$. Does this make any sense? It is just a basic question so if you think it is not something to response then I humbly request you to not answer but please don't downvote this. As I this is my first course in graph theory! (In complete graphs) * Thanks

Hello everyone interested. Here's a seemingly simple problem.  Suppose $G$ is a complete, simple graph with vertices $\{1,2,..,n\}$, $n\geq k\geq 3$.  How many cycles of length $k$ can we have on $G$?  The statement seems simple but I have trouble putting everything together.  So I say fix a vertex and start forming cycles with length k. But I get nowhere... What is the proper approach to this problem since counting is not easy? Is there a relevant theorem that I am unaware of?  Thanks for any help...


How do you find the distance from a point to the plane when the point and the basis for the plane are given?

I am having trouble with this:      Find the distance from the point $(1,1,1)$ to the plane $2x+2y+z=0$.   Any ideas? Thanks.


On some pictures from the Internet there are colors in terminal. Even Cygwin under Windows has colors in its terminal. Here a pic from the Internet, for example:    I have installed Xubuntu and my terminal is like Windows cmd - has only two colors: background and text color. Name of user is not green. Only folders are shown in blue on ls command. No more any colors.  How to enable colorful terminal in Xubuntu 13.04?

I am accessing an Ubuntu 10.04.2 LTS server via SSH from OSX. Recently the colors stopped working. I think it happened while I was installing/troubleshooting RVM, but I am not positive.  In .bashrc I uncommeneted force_color_prompt=yes, and when I run env | grep TERM I get TERM=xterm-color. But still no colors.   Any ideas? Thanks!  Here is the output of cat .bashrc  # ~/.bashrc: executed by bash(1) for non-login shells. # see /usr/share/doc/bash/examples/startup-files (in the package bash-doc) # for examples  # If not running interactively, don't do anything [ -z "$PS1" ] && return  # don't put duplicate lines in the history. See bash(1) for more options # ... or force ignoredups and ignorespace HISTCONTROL=ignoredups:ignorespace  # append to the history file, don't overwrite it shopt -s histappend  # for setting history length see HISTSIZE and HISTFILESIZE in bash(1) HISTSIZE=1000 HISTFILESIZE=2000  # check the window size after each command and, if necessary, # update the values of LINES and COLUMNS. shopt -s checkwinsize  # make less more friendly for non-text input files, see lesspipe(1) [ -x /usr/bin/lesspipe ] && eval "$(SHELL=/bin/sh lesspipe)"  # set variable identifying the chroot you work in (used in the prompt below) if [ -z "$debian_chroot" ] && [ -r /etc/debian_chroot ]; then     debian_chroot=$(cat /etc/debian_chroot) fi   # set a fancy prompt (non-color, unless we know we "want" color) case "$TERM" in     xterm-color) color_prompt=yes;; esac   # uncomment for a colored prompt, if the terminal has the capability; turned # off by default to not distract the user: the focus in a terminal window # should be on the output of commands, not on the prompt force_color_prompt=yes  if [ -n "$force_color_prompt" ]; then     if [ -x /usr/bin/tput ] && tput setaf 1 >&/dev/null; then     # We have color support; assume it's compliant with Ecma-48     # (ISO/IEC-6429). (Lack of such support is extremely rare, and such     # a case would tend to support setf rather than setaf.)     color_prompt=yes     else     color_prompt=     fi fi  if [ "$color_prompt" = yes ]; then     PS1='${debian_chroot:+($debian_chroot)}\[\033[01;32m\]\u@\h\[\033[00m\]:\[\033[01;34m\]\w\[\033[00m\]\$ ' else     PS1='${debian_chroot:+($debian_chroot)}\u@\h:\w\$ ' fi unset color_prompt force_color_prompt  # If this is an xterm set the title to user@host:dir case "$TERM" in xterm*|rxvt*)     PS1="\[\e]0;${debian_chroot:+($debian_chroot)}\u@\h: \w\a\]$PS1"     ;; *)     ;; esac  # enable color support of ls and also add handy aliases if [ -x /usr/bin/dircolors ]; then     test -r ~/.dircolors && eval "$(dircolors -b ~/.dircolors)" || eval "$(dircolors -b)"     alias ls='ls --color=auto'    alias dir='dir --color=auto'    alias vdir='vdir --color=auto'      alias grep='grep --color=auto'     alias fgrep='fgrep --color=auto'     alias egrep='egrep --color=auto' fi  # some more ls aliases alias ll='ls -alF' alias la='ls -A' alias l='ls -CF'  # Alias definitions. # You may want to put all your additions into a separate file like # ~/.bash_aliases, instead of adding them here directly. # See /usr/share/doc/bash-doc/examples in the bash-doc package.  if [ -f ~/.bash_aliases ]; then     . ~/.bash_aliases fi  # enable programmable completion features (you don't need to enable # this, if it's already enabled in /etc/bash.bashrc and /etc/profile # sources /etc/bash.bashrc). if [ -f /etc/bash_completion ] && ! shopt -oq posix; then     . /etc/bash_completion fi  [[ -s "/usr/local/rvm/scripts/rvm" ]] && . "/usr/local/rvm/scripts/rvm"


I've created my crawler using file_get_contents function but when I crawl some sites I'm getting this character: � when I should get this: é. Some ideas of what is happening?  This is for a windows vps server running php.   I've already tried:          But all these things didn't work.   PD: My file where I'm running this code is on UTF8.      $url = "https://play.google.com/books/reader?id=4rqYDwAAQBAJ&hl=en_US";     $options = array('http'=>array('method'=>"GET", 'header'=>"Accept-language: en-US,en;q=0.8\r\n" ."Accept-Charset: UTF-8, *;q=0"));             $context = stream_context_create($options)             $profile = file_get_contents($url,false,$context); echo $profile   I'm expecting to get accented characters and not this diamond character �.

I'm setting up a new server and want to support UTF-8 fully in my web application. I have tried this in the past on existing servers and always seem to end up having to fall back to ISO-8859-1.  Where exactly do I need to set the encoding/charsets? I'm aware that I need to configure Apache, MySQL, and PHP to do this — is there some standard checklist I can follow, or perhaps troubleshoot where the mismatches occur?  This is for a new Linux server, running MySQL 5, PHP, 5 and Apache 2.


For example orange - orange describes exactly what it is.  I thought that the word was onomatopoeia but when I looked it up — it's described as sounds; e.g. bleat for lamb or miaow for cat.  I was watching a TV cop programme, and one of the female officers was being unkind/rude about a fellow male officer who was called Dick, saying he was an onomatopoeia. I am sure I did look this up at some point and was given the nicer description of orange as an example of an onomatopoeia. So can someone clarify for me?

I'm having fun with paradoxes, and I'm trying to come up with a catchy word for non-self-descriptive.  Maybe "autosemantic" fits the bill for self-descriptive (definitely open to other suggestions!), but I'm having a hard time negating it in a natural way.  For an example of the sentence I'm trying to construct:     Is "inautosemantic" inautosemantic?   It just isn't flowing.


How performant is a shared mounted EFS if there are multiple ec2 instances with multiple containers all writing to separate files in separate directories? Can write performance on one container be detrimentally affected by another container writing (on the same or different node).   Writes are normally extremely small (~kbs) and can burst to ms frequency.

This is a  about  Related:      I have a question regarding capacity planning. Can the Server Fault community please help with the following:   What kind of server do I need to handle some number of users? How many users can a server with some specifications handle? Will some server configuration be fast enough for my use case? I'm building a social networking site: what kind of hardware do I need? How much bandwidth do I need for some project? How much bandwidth will some number of users use in some application?


How can I list all sections under a chapter in TOC, in one (wrapped) line (without pagenumber is fine)? Thanks.  Expected,:  Chapter 1 .................................................... 10  section 1 -- section 2 -- section3 -- section 4 - secti-  on5 -- section6 -- section 7  Chapter 2 .....................................................15  section 1 -- section 2 -- section3 -- section 4 - secti-  on5 -- section6

I need that, in the ToC, all the \paragraph references appear in the same line, like.   1 First Chapter................................................1  1.1 First Section.............................................1    One paragraph 1, Another § 3, One more § 4  1.2 Second Section.......................................7    § in sec. two 7, Another § in sec. two 11   And so on… I'm using the memoir class, which, in its manual, actually uses this for its subsections, but don't explain how to do it.


In Fantastic Beasts and Where to Find Them we see the following dialogue:         Newt: [hands Jacob a helmet] Put this on.   Jacob: But why would I have to wear something like this?   Newt: Because your skull is susceptible to breakage under immense force   Is Newt implying that his skull isn't (and wizard bones in general aren't) susceptible to breakage under immense force?  Or is it to be taken literally, and he is giving Jacob the protection he would normally use (and possibly is implying "Oh I'll be fine, but you need this").

In "Fantastic Beasts and Where to Find Them", the main character () meets a muggle () who is bitten by a .      Thats definitely the Murtlap. You must be particularly susceptible.   Then Newt says:      See, you're a Muggle. So our physiologies are subtly different.   How do muggles and wizards differ? If the only difference is exposition to magical creatures then muggle borns should also have different physiologies. What about Squibs, do they share the same physiology as wizards or muggles?


In case there are two or more admins in ubuntu, can one admin prevent another admin from accessing his/her data ?  Regards.

I am sharing my personal Ubuntu PC with one of my colleagues.   I created another user with a different password (he knows of course) and added it to the sudoer list.   Given that there are two sudo users in a single Ubuntu system:   Are the private files (specified by owners and permissions) of any of these users still private?  Can I modify my colleague's files via sudo command, even sudo su, or vice versa?


I am working on to shrink my C drive. To do so, I need to remove my System Volume Information and defragment my drive. I have tried various versions of tutorial online yet the same happens : the system cannot find the file specified.  The command typed on prompt :  c: rmdir "system volume information" /s /q The system cannot find the file specified   The command prompt is already run as administrator and I have unhidden the directory. Is there anything else I miss? I am sorry if this question has been asked before.  Thanks everyone.  Edited : Here is another method I tried yet unsuccessful. This is copied from  regarding similar question.     Start Button -> System Preferences -> System Left Pane - System   Protection Mark the Volume you are working on, then hit Configure In   the Dialog popping up hit the delete button and confirm, it basically   deletes all Windows Restore Points, nothing else.   Yet the system volume information folder is still not empty, though system protection consumes 0 byte according to the system setting in System. I don't have enough reputation to post a screencap. Sorry for the inconvenience.  Edited : As requested, a few pictures are attached.  Screen cap of setting. All the restore points are deleted. The restoring function contains 0 bytes. Sorry it is in traditional Chinese.    The "system volume information" directory after setting "no restore and delete all restore points". Obviously it is not empty. It contains only ~400Mb according to "properties".    Edited :  Initially I wanted to do this for better defragmentation, yet still unsuccessful after several attempts. After following more suggestions, I ultimately remove the whole windows for ubuntu-windows dual boot.

I met the same problem of not being able to shrink the Windows OS partition C: as much as I plan to due to unmovable files.  Having learned from , I would like to "turn System Restore off and remove System Volume Information folders". So I was wondering where and how I can "turn System Restore off and remov System Volume Information folders"?  This is the only way I can find out to solve my problem. If you have other way please let me know.


I am doing a ordinary least squares fit. I have data which was recorded at different times. The fit could depend on time so I want to trust my older data less. The obvious way to do this is to weight the data based on how old each data point is and use a weighted least squares fit.   For example, suppose I am trying to fit a linear relationship to estimate the number of people inside McDonald's based on the number of cars in the parking lot. I have [people,cars] data points from many location for the last year recorded a sporadic times. The most recent data should be more useful to predict this relationship as it may change over time but I do not want to throw out older at some arbitrary age.   Is there a standard for this sort of issue or do I need to make some assumption about how the quality of my data ages? Is there a better way to conceptualize this problem?  EDIT: It is quite possible that there is a trend in the dependant variable as the age changes. In fact the error of each measurement should not change. It might be a better idea to fit that dimension as well and take it out after. In the above example this would be to fit the number of customers inside as a function of cars outside and how long ago the measurement was taken. Then use the current time for predictions.

In a regression fit of vectors varying with time $t$ $\qquad y \sim [x_t\ x_{t-1}\ x_{t-2}\ ...] \cdot [c_t\ c_{t-1}\ c_{t-2} \ ...] $ , how can one down-weight the older $x_t$ to model "older is less relevant" (than the regression gives) ? Say that rows in data matrix $X$ are observables (stocks, market segments ...) and columns are times. Correct me,   weights rows; how does one weight columns, times ?  Added: Down-weighting older data in time series looks complex, much more so than linear least squares with i.i.d. errors in rows (observations) -- just divide through by $\sigma_i$; or classification  with i.i.d. errors in columns (e.g. features) -- just centre each column. Can anyone say either   yes, I downweight time series; here are some examples on the web no: down-weighting time series is complex, not for novices.   (  discussed this question 10 years ago, mentioning Kalman filters and hierarchical Bayes, but with no examples.)


I have this regulular expression to validate email id but I can't allow two consecutive hyphen on domain, However it doesn't works for me whatever the fix I made. Could anyone please help?  /^[a-zA-Z\-0-9](([^<>()[\]\\.,;:\s@\"]+(\.[^<>()[\-\].,;:\s@\"]+)*)|(\".+\"))@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\])|(([a-zA-Z\-0-9]+\.)+[a-zA-Z]{2,}))$/   Test Id to fail case: sant@y--t.com   Please help, Thanks for your assisstance!

Over the years I have slowly developed a  that validates MOST email addresses correctly, assuming they don't use an IP address as the server part.  I use it in several PHP programs, and it works most of the time.  However, from time to time I get contacted by someone that is having trouble with a site that uses it, and I end up having to make some adjustment (most recently I realized that I wasn't allowing 4-character TLDs).  What is the best regular expression you have or have seen for validating emails?  I've seen several solutions that use functions that use several shorter expressions, but I'd rather have one long complex expression in a simple function instead of several short expression in a more complex function.


I am considering keeping my emergency fund in a Roth IRA (as described in ) in order to maximize the amount of capital I can potentially invest tax free in the future. However, this would involve a significant chance of having to make early withdrawals of my Roth IRA contributions.  This could lead to a few confusing situations:   (A) I could contribute money, earn some interest, and then have withdraw some or all of the contributions made so far in the year. (B) I could end up withdrawing contributions from a previous year, and then pay it back. (C) I could contribute some, have to withdraw it all & more, and then want to return some (or all) before the end of the year.   In case (A):   What happens  to the interest my contributions earned in the Roth IRA (and which remain behind in the account) between the time of my contribution & my withdrawal Does the money I contributed at the beginning of the year still count against my contribution limit after it is withdrawn (Say I deposited $5,500 in January and withdrew $5,500 in June. Can I put the money back in by December)?   In case (B): Does the money I return to the Roth IRA count against my contribution limit?  What about case (C)?  Forgive me if this question is a little long, the whole thing just seems so confusing.

I have been thinking about putting my emergency fund into a Roth IRA (in an FDIC insured High Yield Savings Account, so liquidity isn't an issue). My reasoning is as follows:   I can always withdraw my contributions without a penalty. The interest payments (which I can't withdraw) are not a major contribution to my emergency savings I cannot fully fund a retirement account and build up a large enough emergency fund at the same time right now, so by putting the money in a taxable account, I will lose the opportunity for the tax savings forever. On the other hand, if, in the future, I can afford to save above the Roth contribution limits, I can use the extra money to start a new emergency fund, and invest some of the old one.   Are there any reasons why I shouldn't go ahead with this?


Swift 4 can't decode properly if json data contain new line ("\n"). What i can do for this case. Please take a look of my sample code :  var userData = """ [  {   "userId": 1,  "id": 1,  "title": "Title \n with newline",  "completed": false  } ] """.data(using: .utf8)  struct User: Codable{ var userId: Int var id: Int var title: String var completed: Bool  }  do { //here dataResponse received from a network request let decoder = JSONDecoder() let model = try decoder.decode([User].self, from:userData!) //Decode JSON Response Data     print(model) } catch let parsingError {     print("Error", parsingError) }   If i change the userData value as like below that time it can decode properly.  var userData = """ [      {       "userId": 1,      "id": 1,      "title": "Title \\n with newline",      "completed": false      } ] """.data(using: .utf8)

I've generated some JSON and I'm trying to pull it into an object in JavaScript. I keep getting errors. Here's what I have:  var data = '{"count" : 1, "stack" : "sometext\n\n"}'; var dataObj = eval('('+data+')');   This gives me an error:   unterminated string literal   With JSON.parse(data), I see similar error messages: "Unexpected token ↵" in Chrome, and "unterminated string literal" in Firefox and IE.  When I take out the \n after sometext the error goes away in both cases. I can't seem to figure out why the \n makes eval and JSON.parse fail.


I have completed my Bachelor of Computer Applications (BCA) from India. The minimum requirement for admission into the MS in Computer Science program requires a 4 year college degree. My BCA degree was a 3 year degree and I am planning on pursuing a 1 year Post Graduate Diploma in Computer Applications (PGDCA) from Indira Gandhi National Open University (IGNOU) and would like to find out if these total 4 years satisfy as minimum requirements for admission consideration.

Is a three years bachelors degree in Commerce and three years bachelors degree in Law from India termed to be equivalent to have a four years graduate degree from the US?


I bought some chicken and I accidentally forgot to put it away and I put it in the fridge in the morning and I want chicken can I like boil it and the bacteria will boil away or what?

If cooking meat kills bacteria, and bacteria are responsible for problems with eating meat which has been left out, then why is it dangerous to eat meat which has been left out at room temperature and then thoroughly cooked?   mentions that "Even if the bacteria is dead, toxins can remain if the food was out too long, causing problems".  However, there's no further detail given.  Are these toxins as dangerous as the bacteria themselves?  How long does meat have to be left out to accumulate a dangerous level of toxins and thus be dangerous even if thoroughly cooked?  Are these toxins the reason for the usual guideline of keeping meat unrefrigerated for a maximum of 2 hours?  update  The revelation, courtesy of Aaronut, that e. coli is actually dangerous because of its toxins — which cannot be denatured at temperatures which will leave meat in an edible state — has pretty much answered this question.  And also given me further incentive to stop eating meat altogether :)  Our discussion (see the comments on hobodave's answer) has progressed into the realm of microbiology.  Some highlights from my ongoing research:  .  These seem to be the reason for the importance of keeping meat at a high temperature for a period of time.  .  This also provides fascinating insight into how bacteria evolved immunity to antibiotics.  Fungi.


Right, in this program I am supposed to be able to search for a person in the list. If I search for someone who is not in the list then the Found variable should be kept at false. If I search for someone who is in the list eg: "Ben" then Found should be set to true.   However for some reason, searching for someone who is in the list does not set found to true. It seems like the if statement which checks the player's input to the array is not working properly. I have no idea why this is. There are no errors. Can anyone help? Thanks  code:      package com.test.main;  import java.util.Scanner;      public class Main {     public static void main(String[] args){     String[] Names = new String[4];     Names[0] = "Ben";     Names[1] = "Thor";     Names[2] = "Zoe";     Names[3] = "Kate";      int Max = 4;     int Current = 1;     boolean Found = false;      System.out.println("What player are you looking for?");     Scanner scanner = new Scanner(System.in);     String PlayerName = scanner.nextLine();      while(!Found && Current <= Max){         //System.out.println(Names[Current-1]);         //System.out.println("PLAYERNAME: " + PlayerName.length() + ", ARRAY: " + Names[Current-1].length());         if(Names[Current-1] == PlayerName){             //System.out.println("found");             Found = true;         }         else{             Current++;         }     }     //System.out.println(Found);     if(Found){         System.out.println("Yes, they have a top score");     }     else{         System.out.println("No, they do not have a top score");     } } }

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


I know this question has been asked so many times (since 2011 from what I found out), but none of the responses seem to resolve the issue in my laptop, so apologies for the repetition.  I tried appending "nomodeset" to the grub boot and it no only doesn't work, but also it disables hardware acceleration, rendering X11 unusable.  I also tried some other configurations ("vga=773", like the different "video:"), but nothing seems to work.  $ lspci | grep -i vga 00:02.0 VGA compatible controller: Intel Corporation Broadwell-U Integrated Graphics (rev 09)   I installed packages grub2-splashimages and grub2-themes-ubuntu-mate, assuming it could be that just there was nothing configured, but nothing makes any difference.  Booting on text by adding "set gfxpayload=text" works, and it shows the textual booting process. But I didn't get anything useful from that ... (but that it takes a minute to start the cryptswap thing, the longest part of the boot process apparently)  I didn't see anything in dmesg that stand out, but then I wouldn't know what to look for.  Also I get random blanking of the screen during normal work: the computer is still working (even sound works), but some times the screen suddenly goes black while I'm typing. I recover from that by pressing the power button (going to suspend mode) and then coming back. I've seen reports of this also elsewhere, but it is a different graphics card.  Any ideas ? Many many thanks in advance for any help!  ps: let me know if any other information I can post here would help  Some references I looked and tried already:      After trying the answer to the apparently duplicated question:    It seemed to have worked for a week, but I think it was only a coincidence, it's now randomly happening again. I've tried repeating the same commands and it doesn't have an effect.  It even happened once in the session manager, while i was typing my password to log in.  Any ideas ? Thanks in advance!

I've been using Ubuntu(12.10) for a long time, and recently, my Ubuntu went through yet another update.  The whole update prompt showed up, following by a password prompt, and finally the good ol' progress bar...  Everything went well, and later on, I shut down my computer.  The next day, I turned my PC on, went to the login screen. I went ahead, and logged in, but after that, all I could see was a black screen, and my cursor!  I checked the forums, and got various tips, none of which worked...  Now I'm stuck with an Ubuntu installation that's completely useless.  One more thing:  I even tried logging in through Guest, but same problem! :\  My Computer Specs: Motherboard: Intel DG41WV Processor: Intel Core 2 Quad Q6600 @ 2.40GHz Graphics: Intel G41 Express Chipset RAM: Dual Channel, DDR3 2*2GB (4096 MBytes) HDD: Seagate 500GB SATA   ---- DETAILED INFO ----  To be a little more precise about my problem, after I log in, I can see a black screen and my cursor. Plus, importantly, I was able to see a login screen, hence I'm sure Ubuntu is rendering properly, and also pretty sure that there's no problem with the drivers (Otherwise I shouldn't even get a login screen, right?).  Anywho, another (probably) important thing is that, after logging in, I can hit Ctrl+Alt+1 and get up a recovery console.  The only thing that doesn't load is my actual GUI desktop  Then, I ran unity from the recovery console, it went through a few commands, got stuck at OpenGL for a few seconds, then zoomed throught many more lines of code, and ended up with this:  ERROR 2012-01-03 20.51.23 unity.launcher.Icon TrashLauncherIcon.cpp:62 Could not create file monitor for trash url: Operation not supported  *** glibc detected *** compiz: malloc(): memory corruption: 0x09c861d6 ***   After that. back at Ctrl+Alt+F7: Desktop Background + Cursor  So back to the terminal again, I had to hit Ctrl+C to get back again.  now, I typed unity again, and this was the output:  WARNING: no DISPLAY variable set, setting it to :D compiz (core) - Info: Loading plugin: core compiz (core) - Info: Starting plugin: core unity-panel-service: no process found   so now I did a sudo service lightdm restart :  X10: fatal IO error 4 (Interrupted system call) on X server ":0" after 131 requests (130 known processed) with 0 events remaining. lightdm stop/waiting lightdm start/running, process 2852   Im back at the login screen, and I login again, now Im back to black screen (Yes, I lost the Desktop Background as well)  So, once again, I try unity (same response as last time):  WARNING: no DISPLAY variable set, setting it to :D compiz (core) - Info: Loading plugin: core compiz (core) - Info: Starting plugin: core unity-panel-service: no process found   And still a black screen! :\


could you suggest me an easy book on abstract algebra with solved problems and theory. (or a pdf on the internet) thank you.

I am currently self-studying abstract algebra from . In that background, I am looking for a problem book in a spirit somewhat similar to  so that I have a lot of problems to solve.


For the second part of my project I'm trying to clear the screen after each operation using system("clear");.  This works fine but my teacher/lecturer works with windows and they get the following message in the console when they reach the cls:     'clear' is not recognized as an internal or external command,   operable program or batch file.   In that case I would have to change the system("clear") to system("cls");.   Is there anyway that I can check the OS and get the program to switch between "cls" and '"clear"`?  Here is my code:  printf("Please provide name: \n"); scanf("%[^\n]s", contact_name); getchar(); system("clear"); printf("Please provide contact number: \n"); scanf("%[^\n]s", tel_num); getchar(); system("clear"); // items printf("\t\t\t\t  Our Apparels: \n"); printf("\t\t\tApparels\t\tItem code\n"); printf("\t\t\ta)T-Shirts\t\t'T'\n"); printf("\t\t\tb)Bags\t\t\t'B'\n"); printf("\t\t\tc)Caps\t\t\t'C'\n\n"); printf("Enter corresponding item code: \n"); scanf(" %c", & code); // reading item code while (code != 'T' && code != 'B' && code != 'C') {   printf("Enter corresponding item code: \n");   scanf(" %c", & code);   getchar();   system("clear"); }

I need a cross platform solution for clearing the console in both Linux and Windows written in C++. Are there any functions in doing this? Also make note that I don't want the end-user programmer to have to change any code in my program to get it to clear for Windows vs Linux (for example if it has to pick between two functions then the decision has to be made at run-time or at compile-time autonomously).


I've looked a lot to find out where a user's account picture is stored in macOS. So exactly the path to be able to access it with the Finder. I haven't found a way to get the path anywhere. The only thing I've found is how to extract it as an address. But that is exactly the problem where is this address? dscl . -read /Users/$(stat -f %Su) JPEGPhoto  You can extract it like this: dscl . -read /Users/$(stat -f %Su) JPEGPhoto |xxd -r -p > ~/Kontobild.jpg  Any ideas where it could be stored? Thank you in advance

I took a picture to add to my account on Mac.   Now I want to use it on messenger, but I can't find it. On the account config, it's too small. I need to find the original.   Where are the accout pictures stored on a Mac?


Is it possible to install Ubuntu to usb drive and boot from it without installing it to the inbuilt hard drive? I have installed it on the hard drive before but now I want to install it to usb...please tell me the procedure if its possible..

If you are hurrying to reply, System → Administration → StartUp Disk Creator -- no, that's not what I'm talking about.   I want to try Ubuntu 11.04's Unity without touching my existing Ubuntu install.  To do this, I need to install the nVidia drivers first (sigh).  To do this, I need changes to persist a reboot.  To do this, I need to really install Ubuntu on a USB key.  How do you do that?    What I tried   I tried to make a USB key from , then boot from it, then choose "Install Ubuntu." The installer refused to install to the installation media itself. I tried, from my installed copy of Ubuntu:  sudo kvm /dev/sdb --cdrom .cache/testdrive/iso/ubuntu_natty-desktop-i386.iso   ...but the installer didn't detect the disk properly.


I know my question maybe too broad, but as someone who's planning to stay in academia, I want to ask anyone who is supervising PhD students about how you contribute to their papers in order to be included as authors.  Do you just need to discuss the problem (e.g what is it? Is it feasible or worth to be solved), point them to potential directions and review the drafts? You can also help writing other sections which don't directly involve in solving the problem such as: introduction, motivation or conclusion. This is the approach that my supervisor and most lecturers in my department are taking.  Or, do you have to directly take part in solving the problem such as analysing it, designing system, performing experiments and evaluating results?

I understand that in a lot of big-lab fields it is common for the principal investigator to append their name to a paper even if they did not write the paper, design the experiment, or collect data since they spend energy securing funding, and managing the whole lab. What about for small labs?  What are the requirements for a supervisor to be included as an author on a paper, as opposed to just appearing in the acknowledgements? If you are working on your own projects independently of your supervisor, but using funding provided by your supervisor (how does this change when the funding provides resources versus just your salary), are you suppose to add them as authors or just acknowledge the source of funding?


I've been trying to make use of the Shapechange spell as a 9th-level spell with a Druid class, but concentration seems to be a major issue. Say I transform into a Phoenix, can I use its 3 Legendary Resistances to automatically succeed in a damaging saving throw three times to prolong the form? This would make Shapechange viable for melee characters for at least a slightly longer period than a single turn.

As I was looking through some legendary creatures, I had a thought. Most legendary creatures get three Legendary Resistances per day, which they can use to automatically succeed on a saving throw.  A Concentration check is technically a Constitution saving throw, so does that mean that a creature can use a Legendary Resistance to automatically pass a Concentration check, or is it not considered a saving throw?


The question is like if the spring of unstretched length $L$ has mass $M$ with one end fixed to the rigid support and it is made up of uniform wire then what kinetic energy is possessed if the free end is pulled with constant velocity?   I tried this question.  If the free end is pulled with uniform velocity then that means there is no acceleration and initially the block of mass M was at rest position so it does not contain any kinetic energy initially due to pulling of the free it has virtue of kinetic energy so it might be $\frac12 mv^2$.  But the answer given is $\frac 16 mv^2$. Where am I going wrong?

Suppose we had a spring-mass system where the spring isn't assumed to be massless (has mass $M$) and is of length $L$. One end of the spring is held fixed and the other end I guess is left to freely oscillate. Here, I am told that the spring is assumed to uniform and stretches uniformly.  If I want to find the kinetic energy of the spring, we have to set up an expression for it  $$dT_{\text{spring}} = \frac{1}{2}u^{2} dm$$  where $dT_{\text{spring}}$ is the kinetic energy of an infinitesimal part $dm$ somewhere along the spring and $u$ is its corresponding velocity. Since the spring is uniform, I can find its mass density  $$ \lambda = \frac{dm}{dx} \longrightarrow dm = \lambda dx = \frac{M}{L}dx$$  so that $$dT_{\text{spring}} = \frac{1}{2}u^{2}\frac{M}{L}dx $$  The one step I am not understanding is how $u= \frac{x}{L}v$, where $v$ is, I think, the velocity of some point that has been displaced by the stretching of the spring (please correct me here if I'm wrong). Why is the velocity of a piece $dm$ linearly proportional to $v$ and how can I derive that expression mathematically, i.e. if $u = \alpha v$, how do I find $\alpha$ and why? Something is not registering in my head and I feel like it has to do with the fact that the spring is assumed to be uniform. That then begs the question: what if it wasn't? What would I do in that case?


Near the end of Captain America, Tony Stark discovers      the video where Bucky kills his parents.   Then he asks Cap' if he knew. He says yes.  How does he know?      I can't remember Bucky telling him. Is there any official answer?

Near the end of Captain America: Civil War we learn that      Howard and Maria Stark were assassinated by the Winter Soldier   and Captain America admits that he already knew.  But how did he find out? I don't recall this being revealed in any of the previous movies, and I can't think of a reason why the characters who already knew would have gone out of their way to tell Steve about it.


When setting the collision to the bowl I initially was seeing some of the pieces of rice sliding to the bottom and falling out. Now that I've updated the scene with a different bowl I'm unable to get the rice to collide with the bowl and it goes straight through. The end result that I'm going for is simply to fill the bowl with rice.

I am trying to create a natural arrangement of rubber thimbles in a jar.  What is the easiest method of doing this?   I've tried various settings with the jar being passive and using the various collision types like box, cylinder and mesh but none seem to work.   I tried dropping the thimbles into the jar but they either stop early and spill over or go through the jar! Is it better to use some sort of particle distribution? Thanks.


I use vim on windows (GVim portable off a USB stick) and Linux (standard command-line vim) and would like to synchronise my settings (_vimrc or .vimrc  respectively). As far as I can see (I haven't delved too deeply into it) the only difference should be the shell used for external commands. TLDR:   Is there a way in a vim script to test which OS it is running on? Are there any other incompatibilities between GVim and Linux vim as far as the vimrc is concerned?   Thanks in advance

I share my VIM configuration file between several computers. However, I want some settings to be specific for certain computers.   For example, font sizes on the high-res laptop should be different to the low-res desktop. And more importantly, I want gVIM on Windows to behave more windowsy and MacVim on OSX to behave more maccy and gVIM on Linux to just behave like it always does. (That might be a strange sentiment, but I am very used to switch mental modes when switching OSes)  Is there a way to make a few settings in the .vimrc machine- or OS-dependent?