I have downloaded a set of linux operating systems that include Ubuntu 15.04, Linux Mint 17, Fedora 21, ArchLinux and Bodhi linux. In totla, all sum up to a size of 4.4 gigabytes. Now what I want to do is to create a bootable dvd that would contain all these OS on it. And when I boot to the DVD, it should show me a menu for choosing the OS to install.

What I want is to create a bootable pen drive that shows GRUB menu and I can select any of the several bootable systems from there to install/run. I have several ISO images that I want to install in the USB like Ubuntu, Fedora, System Rescue CD, Windows XP and Windows 7 (The windows versions are optional, mostly am looking for a multi installer for Linux distros, specially Ubuntu version)  The default Startup Disk Creator only works with Linux Images and only 1 at a time (At least for the mean time. If it allows more systems and multiple ISOs it would be awesome)  What method exists that I can use step by step to create a bootable USB Drive with multiple images than can be booted from the USB and selected from GRUB. It must support Windows Images and Linux Images.  Alternatively, is there also a way to have multiple versions of the Ubuntu installation ISO on same USB Drive, such as, when booting from it, I get to choose what Ubuntu version and architecture to install, for example:     BOOT MENU   Ubuntu 12.04 32 Bit   Ubuntu 12.04 64 Bit   Ubuntu 12.10 32 Bit   Ubuntu 12.10 64 Bit   UPDATE: Wanted to add that the English version for the post mentioned by daithib8 is here:


Hello this might be a weird question but I've been arguing about this with a native English speaker (I am Dutch) and I would like to know who is right.  I will give the example now:  Person 1: "You never do anything in the house." Person 2: "Actually, I do"  Person 1 (native) stated that when I say "actually" it's a comparison.  Person 2 (me, non native) I'm saying that when there's no "In contrary to what you said" or something similar in the sentence it is not a comparison.   Who is correct?

Sometimes I wonder if he is actually/really  as lavish as he   pretends to be.   I know that this sentence can work without either actually or really, but if we were to use one of them to make an impact on the listener, which one should it be?


Every time I log in to a remote server with SSH, OS X keychain prompts me to remember the SSH passphrase. I type in the passphrase and check the box to remember it. I then connect ok to the server but then the next time I get prompted again and so on...  I have a private key to ssh into my server and the connection works. In my hosts file I have:  Host myhost     HostName xxx.xxx.xxx.xx     GlobalKnownHostsFile ~/.ssh/known_hosts     port 22     User myuser     IdentityFile ~/.ssh/mykey_dsa     IdentitiesOnly yes   .. and then I type ssh myhost  This is only a recent problem so I suspect and issue with Keychain? To be clear, I can 're-add' to keychain every time and connect but this defats the purpose. The permissions on my dsa key are set at 600 or -rw-------@  I tried repairing disk permissions but that did no good. My Google-foo is also failing me, nothing of use came up. So I am not sure if this an OS X / keychain issue or an SSH issue.   update: When I try ssh -vvv myhost, I think it reveals the issue:  debug1: Trying private key: /Users/danny/.ssh/mykey_dsa debug1: PEM_read_PrivateKey failed debug1: read PEM private key done: type <unknown> debug3: Not a RSA1 key file /Users/danny/.ssh/mykey_dsa. debug1: read PEM private key done: type DSA Identity added: /Users/danny/.ssh/mykey_dsa (/Users/danny/.ssh/mykey_dsa) debug1: read PEM private key done: type DSA debug3: sign_and_send_pubkey debug2: we sent a publickey packet, wait for reply debug1: Authentication succeeded (publickey).   ... and after that I get connected. I think this crux of the matter is:  PEM_read_PrivateKey failed   Update 2: After trying the same key and settings on another Mac with 10.6.8 as well, everything worked fine so I think this is a Mac specific question, possibly a permissions keychain issue.   Update 3 I also tried a clean install of Mountain Lion (10.8.1) and alas the same issue which I totally don't get.   Possibly related:   Update 4

I installed my SSH private key in ~/.ssh/id_rsa and set its permissions to 0600.  When I connect to an SSH server which uses my private key in Terminal.app via ssh, a dialog pops up and asks me to enter my password to access the id_rsa file:    I see the same dialog when I connect to an FTP server with the Interarchy GUI client.  Update: I see this dialog every time I connect regardless of whether I check "Remember password in my keychain".  It appears two more times if the OK button is clicked regardless of what is entered in the password field.  When I relax these permissions to, say, 0640, I no longer see a dialog asking me for my password but ssh aborts with the following error:  @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ @         WARNING: UNPROTECTED PRIVATE KEY FILE!          @ @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ Permissions 0640 for '/Users/myusername/.ssh/id_rsa' are too open. It is recommended that your private key files are NOT accessible by others. This private key will be ignored. bad permissions: ignore key: /Users/myusername/.ssh/id_rsa  I find the password dialog extremely annoying and I am sure there must be some way to avoid having to dismiss this dialog SSH needs to access the id_rsa file.  Note: I am running Mac OS X 10.6.8.


This is not the same question as  although one of it's answers is a partial answer to this question.  This question does not relate to "what does sth mean?" but those that it has that meaning for.  In  user @jon-hanna explains that the abbreviation originated in dictionaries, guides, and reference books, misleading readers into thinking that such abbreviations are standard use.  This answers one meaning of the where part of the question, leaving open the when which @jon-hanna has not addressed, and where this has been observed.    I'm a native speaker, born and living in england, and widely read from modern books and many classics.  I've seen sth as an abbreviation of something, but only informally from those who have learned English as a second language.  I've seen this from Chinese and also those from eastern Europe.  I the late 1990's I asked one user where he learned the term and he reported that his language teacher taught that abbreviation as being current in the English speaking world.  When I first saw this on a computer forum I had to ask what it meant, as the obvious sexually transmitted herpes (derived from STD) did not fit the context.  So the questions are:   where and when did this abbreviation originate? have you seen this used by native English speakers anywhere in the world? (particularly pre-internet age, ~1990)

I came across this line in a site:      Can u make sth effective for a sports betting related product?   I can't understand what is meant by sth effective here. I tried to google it but was unable to understand. Can anybody explain to me what is meant by this word? Is it an English word or is it from another language?


Could any one tell me how to solve this two?  $1.$ As a ring $\mathbb{Z}[i]/(3-i)\cong\ ?$ $2.$ $L=\mathbb{R}[x]/(x^2-x+1),\ M=\mathbb{R}[x]/(x^2+x+1),\ N=\mathbb{R}[x]/(x^2+2x+1)$. Who is isomorphic to whom as a ring?  I know the definition of $\mathbb{Z}[i]/(3-i)= x(=a+ib)+(3-i)=c+id$ please help.

A very basic ring theory question, which I am not able to solve. How does one show that    $\mathbb{Z}[i]/(3-i) \cong \mathbb{Z}/10\mathbb{Z}$. Extending the result: $\mathbb{Z}[i]/(a-ib) \cong \mathbb{Z}/(a^{2}+b^{2})\mathbb{Z}$, if $a,b$ are relatively prime.   My attempt was to define a map, $\varphi:\mathbb{Z}[i] \to \mathbb{Z}/10\mathbb{Z}$ and show that the kernel is the ideal generated by $\langle{3-i\rangle}$. But I couldn't think of such a map. Anyhow, any ideas would be helpful.


I always missed a built-in exception type in c# which would indicate that an object is corrupted. What do you throw in such cases?  Usually I miss it when I realize that a method, that is supposed to work on an object, would fail if the object had a certain state. In such situations I often suspect that this state probably won't be ever reached. But being defensive about it, I'd like to throw an exception just in case it will (e.g. after a future code change).  For method arguments we have ArgumentException so we can deny invalid parameters. But for object state? In Java I'd use IllegalStateException.  Of course you could argue that the methods, that are actually changing the state, could check for state correctness. And they better should, but then if they don't (say in legacy god classes)?  Edit:  Although InvalidOperationException seems to be the best fit, as the accepted answer states (and also ), please note:  It is subtle, but semantically this has a different meaning than InvalidOperationException. InvalidOperationException indicates a problem in the "protocol" of the object, which the caller has to obey (e.g. not initialized, closed already, ...). In my case the caller did nothing wrong, it's the object that is broken. I would like to transport exactly that message.  Example:  switch(this._someType) {   case SomeType.A: doSomething(); break;   case SomeType.B: doSomethingElse(); break;   /*...*/   default:     // Unexpected type! Someone introduced a new type and didn't update this.     throw new IllegalStateException("Unknown type "+this._someType);  }

What exception should I throw if I encounter an illegal state - for instance, an initialization method that should only be called once being called a second time?  I don't really see any built-in exception that makes sense.  This seems like something that should be in the framework - am I not poking in the right spot?


I would appreciate any help with a problem that I have with reference to figures in my appendix. For example, instead of (Fig. A.1 ), I only get (Fig. A). I read all the previous posts but they did not help me. According to a previous post, I even added   \renewcommand\thesection{\Alph{section}} \renewcommand{\thefigure}{\thesection.\arabic{figure}}   after the \appendix command, but that did not help either. Here is the minimal code I use:  \documentclass[reprint, superscriptaddress,  amsmath,amssymb,  aps, ]{revtex4-1}   \section{AAA}\label{AAA} Blah blah Fig. \ref{xyz}  blah blah.  \appendix \section{ BBB}\label{BBB}  \begin{figure} \begin{center} \includegraphics[scale=0.5]{xyz.png} \caption{blah blah} \end{center}\label{xyz} \end{figure}

I was using the amspset document class for generating exam practice problems. I had wanted to add some referencing to the problems so I started a new counter like this (adapted from some Tex Exchange post)  \newcounter{P} \newcommand{\plb}[1]{\refstepcounter{P}\label{#1} \textbf{P-\ref{#1}.}}  \begin{problem} \plb{p1} A parallel-wire transmission line is constructed of \#6 AWG copper wire (diameter $d=0.162$ in., conductivity $\sigma_c=5.8\times 10^7$ S/m) with a 12-inch separation in air. Assuming no leakage between the two wires, find $R'$, $L'$, $G'$, and $C'$. Assume a working frequency of 1 MHz. \end{problem}  \begin{solution} Using Table.~\ref{tab:tlparam} and Fig.~\ref{fig:tlempl},  \[ Rs = \sqrt{\pi f \mu_c/\sigma_c} = 2.61\times10^{-4}~ \Omega\] \[ R' = \frac{2R_s}{\pi d} = 4.04\times10^{-2} ~\Omega\text{/m} \] \[ L' = \frac{\mu_0}{\pi} \ln{\frac{2D}{d}}=2.0~\mu \text{H/m} \] \[ C' = \frac{\pi \epsilon}{\displaystyle\ln{\frac{2D}{d}}}=5.56 ~\text{pF/m} \] $G'=0$ because the problem states that there is no leakage between the two wires. \end{solution}  \begin{figure}[ht] \begin{centering}     \includegraphics{fig24}     \caption{(Fig.2-4 from FAE) A few examples of transmission lines.} \end{centering} \label{fig:tlempl} \end{figure}  \begin{table}[ht] \caption{(Table 2-1 from FAE)Transmission-line parameters $R'$, $L'$, $G'$, and $C'$ for three types of lines.}     \begin{tabular}{c}         \hspace{3cm}\includegraphics{tb21}     \end{tabular} \label{tab:tlparam} \end{table} ... and more   Now all the figure references stop working, I get "Fig. " instead of "Fig. 1". The table references are alright though. Any idea what the problem could be?


In a hollow conductor and in a spherical shell the charges reside on its surface and there is no electric field inside it.Please tell me the reason behind it.

My textbook says that when a conductor is placed in an electric field, the electrons in it realign so that the net electric field inside the conductor is zero. There isn't a proof for this. It merely states that the electrons drift opposite to the applied electric field and create an opposite electric field inside the conductor canceling the external one.   I imagine Gauss's Law would provide a simple proof. If we try enclose a point inside the conductor in a gaussian surface, and note that the enclosed charge is zero, so the flux through the surface is zero and so is the electric field at the surface.   When I looked back at my reasoning, I realized that I had assumed that the charges induced on the conductor always stay at the surface, which I had no way of proving. How do I prove this formally?


I want to save HTML symbols in my database but they do get converted to random characters. I already have set every default character type to utf8_general_ci. When I do copy-paste the string in PHPmyAdmin into the table it is rendered as question marks.  what is happening copy "√∛∜(∑" into database colum gives output on website "???(?" send "√∛∜(∑∫π∠≤≥<>=≠≈≉≡≢⁰¹²³⁴⁵⁶⁷⁸⁹·⁺⁻⁼⁽⁾ⁿ" to databse is being saved as, and also being displayed on the website as:  "Ã¢ÂˆÂšÃ¢ÂˆÂ›Ã¢ÂˆÂœ(Ã¢ÂˆÂ‘Ã¢ÂˆÂ«ÃÂ€Ã¢ÂˆÂ Ã¢Â‰Â¤Ã¢Â‰Â¥<>=Ã¢Â‰Â Ã¢Â‰ÂˆÃ¢Â‰Â‰Ã¢Â‰Â¡Ã¢Â‰Â¢Ã¢ÂÂ°Ã‚Â¹Ã‚Â²Ã‚Â³Ã¢ÂÂ´Ã¢ÂÂµÃ¢ÂÂ¶Ã¢ÂÂ·Ã¢ÂÂ¸Ã¢ÂÂ¹Ã‚Â·Ã¢ÂÂºÃ¢ÂÂ»Ã¢ÂÂ¼Ã¢ÂÂ½Ã¢ÂÂ¾Ã¢ÂÂ¿"  Some additional information about the databse:  DEFAULT_CHARACTER_SET_NAME : utf8 DEFAULT_COLLATION_NAME : utf8_general_ci           Some additional information about the column:  Type : varchar(4096) Collation : utf8_general_ci  UPDATE:  By adding the following line to the submit file the symbols are put correctly into the database  $con -> set_charset('utf8mb4');

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.


Where can I find the default content of /etc/apt/sources.list  in Ubuntu 18.04 LTS (Bionic Beaver)  cat /etc/apt/sources.list shows    # deb cdrom:[Ubuntu 16.04.2 LTS _Xenial Xerus_ - Release amd64 (20170215.2)]/ xenial main restricted  # See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to # newer versions of the distribution. deb http://in.archive.ubuntu.com/ubuntu/ bionic main restricted universe deb-src http://in.archive.ubuntu.com/ubuntu/ bionic multiverse restricted universe main #Added by software-properties # deb-src http://in.archive.ubuntu.com/ubuntu/ xenial main restricted  ## Major bug fix updates produced after the final release of the ## distribution. deb http://in.archive.ubuntu.com/ubuntu/ bionic-updates main restricted universe deb-src http://in.archive.ubuntu.com/ubuntu/ bionic-updates multiverse restricted universe main #Added by software-properties # deb-src http://in.archive.ubuntu.com/ubuntu/ xenial-updates main restricted  ## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu ## team. Also, please note that software in universe WILL NOT receive any ## review or updates from the Ubuntu security team. # deb-src http://in.archive.ubuntu.com/ubuntu/ xenial universe # deb-src http://in.archive.ubuntu.com/ubuntu/ xenial-updates universe  ## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu  ## team, and may not be under a free licence. Please satisfy yourself as to  ## your rights to use the software. Also, please note that software in  ## multiverse WILL NOT receive any review or updates from the Ubuntu ## security team. deb http://in.archive.ubuntu.com/ubuntu/ bionic multiverse # deb-src http://in.archive.ubuntu.com/ubuntu/ xenial multiverse deb http://in.archive.ubuntu.com/ubuntu/ bionic-updates multiverse # deb-src http://in.archive.ubuntu.com/ubuntu/ xenial-updates multiverse  ## N.B. software from this repository may not have been tested as ## extensively as that contained in the main release, although it includes ## newer versions of some applications which may provide useful features. ## Also, please note that software in backports WILL NOT receive any review ## or updates from the Ubuntu security team. deb http://in.archive.ubuntu.com/ubuntu/ bionic-backports main restricted multiverse universe deb-src http://in.archive.ubuntu.com/ubuntu/ bionic-backports main restricted multiverse universe #Added by software-properties # deb-src http://in.archive.ubuntu.com/ubuntu/ xenial-backports main restricted universe multiverse  ## Uncomment the following two lines to add software from Canonical's ## 'partner' repository. ## This software is not part of Ubuntu, but is offered by Canonical and the ## respective vendors as a service to Ubuntu users. # deb http://archive.canonical.com/ubuntu xenial partner # deb-src http://archive.canonical.com/ubuntu xenial partner  deb http://security.ubuntu.com/ubuntu bionic-security main restricted universe deb-src http://security.ubuntu.com/ubuntu bionic-security multiverse restricted universe main #Added by software-properties # deb-src http://security.ubuntu.com/ubuntu xenial-security main restricted # deb-src http://security.ubuntu.com/ubuntu xenial-security universe deb http://security.ubuntu.com/ubuntu bionic-security multiverse # deb-src http://security.ubuntu.com/ubuntu xenial-security multiverse # deb https://pkg.jenkins.io/debian-stable binary/

I have Ubuntu 12.04 LTS. I need the correct output because I edited it because it wasn't working but it has only made it worse.


Hardware : Netgear ReadyNAS RN102 2-Bay running ReadyNAS OS 6.4 Hard Disks : 2x Seagate Barracuda 2TB ST2000DM001, mfg Thailand 04/2014, same model number, diff serial number issue : beeping and clicking sound, NAS would not boot. disk1 crashed on Jan 4th. Disk 2 crashed Jan 11. Luckily I bought another drive and resynced RAID1 between those days so I didnt lose data. The new disk seems to be working fine so far, but i do think I hear some clicking sometimes (though i cant be absolutely sure I'm not imagining it. Question: is this situation probable/possible in real life or is this an electrical fault that weakened/killed the disks? should I replace just the disks, the power brick, the entire NAS? what can I do to debug? moreinfo: The NAS was connected to power through a power strip and I have now replaced it with a belkin surge protector. I also stripped and inspected each board in the NAS for any burnt components or charring. it looks clean. the one thing I did find out is that jiggling the power plug where it goes into the NAS can cause the NAS to lose power. the power port on the board seems solid so it might be the brick.

Yesterday we received some new drives for our in-house fileserver. We ordered 6 12TB HC520 from a supplier and they sent us four which are labeled 4 MAR 2020 and two labeled 18 AUG 2018.  They are meant to be used in a single volume, operating underneath ZFS in a 4:2 configuration (two drives failure protection).  Will the different dates have an affect on the performance or aging of the disks, are the older disks more prone to failure?


I came across ${!i} in the body of a for-loop of the form  for ((i=$#; i>0; i--)); do     # ...     if <SOME_TEST>; then         # ...         accumulator="${!i}:${accumulator}"         # ...     fi     # ... done   Given this range of possible values, my guess is that ${!i} means something like "expand as the i-th positional argument".  Be that as it may, I'd like to know more about this notation.  (In particular, is ${!i} a special case for $@, or is it a particular instance of a syntax applicable to any array?  This is why I'm curious about how the expression gets parsed.)  I can't find documentation for this notation, though.  If I search the bash man page for the sequence ${!, I find only the following strings     ${!name[@]}    ${!name[*]}    ${!prefix*}    ${!prefix@}   ...and I can't fit the documentation surrounding these occurrences to the code I'm puzzling over.  (Actually, if possible, please quote any relevant documentation in your answer, so that I can sort out why I missed it.)    EDIT: For my original post I copied the wrong for-line from the original code.  I've fixed it now.  (The interpretation is the same, though.)

I have the following lines in my .cfg bash script file  DDF_SOURCE="siebel_DATA_DATE_FORMAT" DATA_DATE_FORMAT=${!DDF_SOURCE}   how is ${!DDF_SOURCE} evaluated? It would be !siebel_DATA_DATE_FORMAT, which doesn't make sense to me.


A rather old short story... maybe the 70's or 80's... possibly the 90's but I doubt it... that has two aliens sitting on a hill, watching some new aliens arrive (humans). They watch the aliens struggle for a while and cannot figure them out as their behavior seems very strange, and can't decide whether or not to help them. Eventually one of the aliens has an idea: he figures out that the new aliens reproduce sexually (male/female), that is why they have such bizarre behavior, and so he decides they should help them.

I once read a SF short story in the 80's, but I can't remember either the name nor the author. The protagonists are two alien anthropologists (one shaped like a tiger, the other like a dragon, I think) intent  on secretly studying two Terran explorers. The Terrans (dubbed "the big one" and "the small one") we soon learn are a couple and at one point they get in some kind of danger.  The two alien anthropologists decide to save them and manage to do so without revealing themselves, thus also "saving" their study.


I am not sure when this happened (or if its just my imagination), but lately I've been noticing that answers aren't sorted by their vote counts. I noticed this on couple of questions that I answered my question had the highest rating but wasn't on top. So was this feature never there and I was living in an illusion (in which case I apologize)? Or has something changed? I personally think sorting by upvotes count is a good idea.

For me at least,  has answers that are not sorted by score:    Is this normal?  I've tried refreshing the page a few times, but the order doesn't change...


I'm curious what will happen if we 'drive' a car with (almost) the speed of light, and all of sudden we switch the car headlights on? Will the car headlights ray have double speed (speed of 600.000km/h) or that ray will never be seen?

The title says it all.  If I was on a bus at 60 km/h, and I started walking on the bus at a steady pace of 5 km/h, then I'd technically be moving at 65 km/h, right?  So my son posed me an interesting question today: since light travels as fast as anything can go, what if I shined light when moving in a car?  How should I answer his question?


I have 2 computers, each with 2 ethernet ports connected to 2 unmanaged switches using linux Bonding Mode: load balancing (round-robin). Can the 2 switches connect to each other without causing a problem?   It seems to operate fine and things work better when I artificially create some failures, but I wonder if it will cause some problem I don't notice.

I've read up a little bit on bonding nics with ifenslave; what I'm having trouble understanding is whether there is special configuration needed in order to split the bonds across two switches. For example, if I have several servers that all have two nics each, and two separate switches, do I just configure the bonds and plug 1 nic from each into switch #1 and the other from each into switch #2? or is there more to it than that?  If the bonds are active-backup, will a nic failure on single machine mean that server may become disconnected since the rest of the machines are using the primary nic and it's using the secondary? Or do you link the switches with one cable as well?


In the course slides for the Stanford Convex Optimization course by Boyd it states that if   $$K=\{(x, t) \,|\, ||x||_1 \le t\}$$  then its dual cone is  $$K^* =\{(x, t) \,|\, ||x||_\infty \le t\}$$  Why is that?   If $x = (-t, 0)$ and $y = (t, 0)$ then $x \in K$ and $y \in K^*$ but $x^ty = -t^2$, which is negative, contrary to the definition of a dual cone.

I am listening to convex optimization lectures and I hear that dual cone of a $L^1$ norm cone is a $L^{\infty}$ norm cone. Can anybody please explain how? I understand that every point in the dual cone must have an non-negative inner product with any point in its corresponding cone.  How does that bring a diamond shaped $L^1$ norm to a square shaped $L^{\infty}$ norm?


I have installed cocoa versions of both Emacs and MacVim using homebrew. After the installation, the actual applications are installed in /usr/local/opt/emacs/Emacs.app and /usr/local/opt/macvim/MacVim.app  They are then symlinked to /Applications  They now appear in my Applications folder, but if I want to start them using Spotlight, they do not turn up in the search results when I start typing (like other applications do)  Is there anything I can do to remedy this?

I used brew to install MacVim and it put it in /usr/local/Cellar/macvim/7.3-61/MacVim.app  I would like to be able to go to spotlight and type MacVim to launch the app. I tried creating a symlink in the Applications directory to /usr/local/Cellar/macvim/7.3-61/MacVim.app. But that doesn't seem to show up in Spotlight. I set the executable bits on the symlink. open MacVim.app from the command line works. How can I get MacVim to show up in Spotlight search?


This question is similar to:    and    but need to do this programmatically with JTS.  This question is not for overlapping polygons or touching polygons but for adjacent polygons that is the difference when they don't touch but next to each other. the answer to this question  , worked for intersecting..but not for adjacent.  I am trying to  implement this using JTS/GeoTools.. i found the .dissolve(..) thinking that would do the trick but it is not working.  The original GeoJson( //loadAdjacentGeoJson() )     Updated Solution:   for (GeoJsonPolygon geoJsonPolygon : geoJsonPolygonList) {                 Coordinate[] coordinates = toCoordinateArray(geoJsonPolygon);                 SimpleFeatureBuilder simpleFeatureBuilder = new SimpleFeatureBuilder(simpleFeatureType);                 simpleFeatureBuilder.add(inflate(geometryFactory.createPolygon(coordinates)));  //add inflated polygons                  SimpleFeature simpleFeature = simpleFeatureBuilder.buildFeature(Integer.toString(index));                 simpleFeature.getUserData().put("zipcode", postal.getZipCode());                 index = index + 1;                 geometryList.add((Geometry)simpleFeature.getDefaultGeometry());             }          Object obj = geometryFactory.buildGeometry(geometryList);          GeometryCollection geometryCollection = (GeometryCollection) obj;          Geometry union = geometryCollection.union();  //perform union          LOGGER.info(new GeoJsonWriter().write(geometryCollection)); //shows inflated polygons with overlap          LOGGER.info(new GeoJsonWriter().write( deflate( union ))); //deflate back.   inflated polygons so union will work.:    inlate/deflate methods:  private Geometry deflate(Geometry geom) {         BufferParameters bufferParameters = new BufferParameters();         bufferParameters.setEndCapStyle(BufferParameters.CAP_ROUND);         bufferParameters.setJoinStyle(BufferParameters.JOIN_MITRE);         Geometry buffered = BufferOp.bufferOp(geom,-.0001, bufferParameters);         buffered.setUserData(geom.getUserData());         return buffered;     }      private Geometry inflate(Geometry geom) {         BufferParameters bufferParameters = new BufferParameters();         bufferParameters.setEndCapStyle(BufferParameters.CAP_ROUND);         bufferParameters.setJoinStyle(BufferParameters.JOIN_MITRE);         Geometry buffered = BufferOp.bufferOp(geom,.0001, bufferParameters);         buffered.setUserData(geom.getUserData());         return buffered;     }   results:

Is there a way to remove an overlap from multiple polygons to make one final polygon?..programmatically, I am using the GeoTools or/and OpenGIS/JTS.. any ideas to put me on the right path...  example initial:  final:


Let $\sum_{n=1}^{\infty}{a_n}$ be a sequence such that $a_n > 0$ for all $n$ and   $\sum_{n=1}^{\infty} a_{n}$ converges. Decide if  $\sum_{n=1}^{\infty} a^2_n$ converges of diverges.  I simply put $\sum_{n=1}^{\infty} a^2 = \frac{1}{6}(n+1)(2n+1)$ and when n approaches infinity, so does the sum, so my conclusion is that the series diverges.   I'm not sure if this is the right way to approach the problem though, as I'm not using the information given at the beginning: Where does the convergence of $\sum_{n=1}^{\infty} a_n$ come into play? By comparison $a_n < a^2_n$ , but that doesn't lead me anywhere, as it would have to be opposite for the test to work, right?

I'm trying to re-learn my undergrad math, and I'm using Stephen Abbot's Understanding Analysis. In section 2.7, he has the following exercise:  Exercise 2.7.5 (a) Show that if $\sum{a_n}$ converges absolutely, then $\sum{a_n^2}$ also converges absolutely. Does this proposition hold without absolute convergence?  I'm posting about this here because my answer to that last question about whether the proposition holds without absolute convergence is "Yes", but my suspicions are raised by him merely asking the question. Usually questions like this are asked to point out that certain conditions are necessary in the statement of propositions, theorems, etc. I just want to see if I'm missing something here.  Anyway, here's how I prove the absolute convergence of $\sum{a_n^2}$, and note that I never use the fact that $\sum{a_n}$ is absolutely convergent:  Proof: Let $s_n = \sum_{i=1}^n{a_n^2}$. I want to show that $(s_n)$ is a Cauchy sequence. So, let $\epsilon > 0$ and $n > m$, and consider, \begin{equation}   \begin{aligned}     |s_n - s_m| &= |(a_1^2 + a_2^2 + \cdots a_n^2) - (a_1^2 + a_2^2 + \cdots a_m^2)|\\                 &= |(a_{m+1})^2 + (a_{m+2})^2 + \cdots + a_n^2|\\                 &= |a_{m+1}|^2 + |a_{m+2}|^2 + \cdots + |a_n|^2\\   \end{aligned} \end{equation} Now, since $\sum{a_m}$ converges, the sequence $(a_m)$ has limit 0. Therefore I can choose an $N$ such that $|a_m| < \sqrt{\epsilon/n}$ for all $m > N$. So for all $n > m> N$,  we have, \begin{equation}   \begin{aligned}     |s_n - s_m| &= |a_{m+1}|^2 + |a_{m+2}|^2 + \cdots + |a_n|^2\\                 &< \left(\sqrt{\frac{\epsilon}{n}}\right)^2 + \left(\sqrt{\frac{\epsilon}{n}}\right)^2 + \cdots + \left(\sqrt{\frac{\epsilon}{n}}\right)^2\\                 &< \left(\sqrt{\frac{\epsilon}{n-m}}\right)^2 + \left(\sqrt{\frac{\epsilon}{n-m}}\right)^2 + \cdots + \left(\sqrt{\frac{\epsilon}{n-m}}\right)^2\\                 &= \epsilon   \end{aligned} \end{equation} Therefore $(s_n)$ is Cauchy and $\sum{a_n^2}$ converges. And since $\sum{a_n^2} = \sum{|a_n^2|}$, the series $\sum{a_n^2}$ is absolutely convergent. ∎  Am I doing something wrong here? Am I right in thinking that $\sum{a_n}$ need not be absolutely convergent for $\sum{a_n^2}$ to be absolutely convergent?


I want to composite a cube over a background while still keeping the alpha channel for the cube. I want the composited image to be a cube over an image. The alpha channel should be only the cube. I would like to use the alpha channel as a mask for further compositing. The problem is that with my current node setup there is a border around the cube.

If I press the "include alpha-button" in the Mix-Color-Node, I get white borders. Otherwise i've got a perfect alpha but no blue background.


Can anyone help with this Abstract Algebra problem? Thank you so much! Show that if p is prime then p not=(a/b)^2 for a and b integers.

It is well known that $\sqrt{2}$ is irrational, and by modifying the proof (replacing 'even' with 'divisible by $3$'), one can prove that $\sqrt{3}$ is irrational, as well.  On the other hand, clearly $\sqrt{n^2} = n$ for any positive integer $n$.  It seems that any positive integer has a square root that is either an integer or irrational number.        How do we prove that if $a \in  \mathbb N$, then $\sqrt a$ is an integer or an irrational number?      I also notice that I can modify the proof that $\sqrt{2}$ is irrational to prove that $\sqrt[3]{2}, \sqrt[4]{2}, \cdots$ are all irrational.  This suggests we can extend the previous result to other radicals.        Can we extend 1? That is, can we show that for any $a, b \in \mathbb{N}$, $a^{1/b}$ is either an integer or irrational?


I have a 2012 retina MacBook Pro that lags in a very specific way: I have normal ping times for about 5 seconds and then they spike to 100-300ms more than normal for about 5 seconds, and back and forth. Example:  64 bytes from 216.58.192.46: icmp_seq=844 ttl=58 time=5.694 ms 64 bytes from 216.58.192.46: icmp_seq=845 ttl=58 time=5.508 ms 64 bytes from 216.58.192.46: icmp_seq=846 ttl=58 time=6.203 ms 64 bytes from 216.58.192.46: icmp_seq=847 ttl=58 time=6.665 ms 64 bytes from 216.58.192.46: icmp_seq=848 ttl=58 time=6.074 ms 64 bytes from 216.58.192.46: icmp_seq=849 ttl=58 time=7.480 ms 64 bytes from 216.58.192.46: icmp_seq=850 ttl=58 time=54.219 ms 64 bytes from 216.58.192.46: icmp_seq=851 ttl=58 time=101.125 ms 64 bytes from 216.58.192.46: icmp_seq=852 ttl=58 time=144.924 ms 64 bytes from 216.58.192.46: icmp_seq=853 ttl=58 time=188.527 ms 64 bytes from 216.58.192.46: icmp_seq=854 ttl=58 time=5.604 ms 64 bytes from 216.58.192.46: icmp_seq=855 ttl=58 time=5.553 ms 64 bytes from 216.58.192.46: icmp_seq=856 ttl=58 time=9.515 ms 64 bytes from 216.58.192.46: icmp_seq=857 ttl=58 time=5.364 ms 64 bytes from 216.58.192.46: icmp_seq=858 ttl=58 time=16.086 ms 64 bytes from 216.58.192.46: icmp_seq=859 ttl=58 time=8.182 ms 64 bytes from 216.58.192.46: icmp_seq=860 ttl=58 time=28.378 ms 64 bytes from 216.58.192.46: icmp_seq=861 ttl=58 time=27.358 ms 64 bytes from 216.58.192.46: icmp_seq=862 ttl=58 time=73.504 ms 64 bytes from 216.58.192.46: icmp_seq=863 ttl=58 time=119.722 ms 64 bytes from 216.58.192.46: icmp_seq=864 ttl=58 time=174.853 ms 64 bytes from 216.58.192.46: icmp_seq=865 ttl=58 time=210.945 ms   And so on. It does this at home and at work, and plugging into ethernet via thunderbolt does not exhibit these behaviors. I don't have corresponding spikes in CPU usage so I'm unsure of how to track this issue down.  Please help!  EDIT:  After doing a binary search of killing apps, I have discovered that killing the  app causes the spikes to go away, which is strange because I wouldn't figure that an audio enhancement app would have anything to do with the network. It's not sending or receiving bytes according to Activity Monitor, but merely being active somehow causes ping times to fluctuate in this manner only on wifi. Anybody have an inkling of why this might be the case?

Background  I have a 5th generation AirPort Time Capsule, bought refurbished from Apple about 6 months ago. It is on software version 7.7.3 and has worked without issue until recently.  Problem  Two days ago the performance of my AirPort Time Capsule's wifi dropped dramatically.  Whereas before I had no problem with AirPlay, or streaming videos stored on the Capsule over wifi, now videos buffer every few seconds, and AirPlay is chopped up to smithereens.  Web browsing is also noticeably slower, and file transfer speeds to and from the device have fallen through the floor.  Diagnosis  The problem seemed to start a day or so after I added an HP Envy 5530 printer to my network, though this could just be a coincidence.  To get an idea of exactly how slow the wifi had become, I put my Mac directly next to the Capsule and timed copying a 2GB (16000Mb) file to and from the device:   To: 390s ≈ 41Mbps From: 527s ≈ 30Mbps   Both are less than a tenth of the theoretical maximum of 450Mbps reported when I alt-click the wifi icon in the top bar, so something is clearly amiss.  To isolate the wifi as the culprit, I connected my Mac to the Capsule over an Ethernet cable.  I then saw that videos streamed without issue, files transferred at reasonable speed, and web browsing returned to normal.  To isolate environmental interference and/or my Mac's wifi client as the problem, I took the Capsule into the office and repeated the transfer using a  360MB file on a Windows laptop.  The results were even worse than above:   To: 88s ≈ 31Mbps From: 136s ≈ 20Mbps   Here is a screenshot from  taken at home while a slow file transfer was in progress.  The top two networks are mine (5GHz and 2.4GHz) and it shows there is no channel contention.  The transfer occurred around the middle 50% of the graph.    Remedy  I tried a few things to fix the problem, but with no luck:   Ran Wireless Diagnostics but no problems were found. Assigned the wifi channels manually to a few different random combinations. Specified a different SSID for the 5GHz wifi and tried connecting through that. Removed the HP software and deleted the printer from my Mac, and unplugged the printer from the wall. Performed a factory reset of the Capsule.   Next steps  Short of returning the unit to Apple, is there anything else I should try?


Let $A$ be an arbitrary $n\times n$ matrix over $\mathbb{C}$ and define the linear transformation $T:F^{n\times n}\rightarrow F^{n\times n}\text{,}\quad T(B)=AB-BA$.  I want to prove that $\dim \operatorname{Im}(T)\leq n^{2}-n$  The rank nullity theorem gives $\dim\operatorname{Im}(T)=n^{2}-\dim \operatorname{Ker}(T)$, so this is equivalent to proving that $\dim \operatorname{Ker}(T)\geq n$, i.e. the subspace of matrices commuting with $A$ is at least $n$ dimensional.  In the case that $A$ is diagonalizable, it isn't too hard to show that $n\leq \dim\operatorname{Ker}(T)\leq n^{2}$, the minimal case occuring for $A$ having $n$ distinct eigenvalues (in this caase the kernel is the subspace of diagonal matrices), and the maximal case provided by $A=I$.  It is the general/non diagonalisable case I'm not sure on, and any hints or pointers would be appreciated.  I'm not sure how relevant it is, but by noting that $T(A)=T(0)=0$, while $A\neq 0$ in general we see that $T$ is not injective, so $\det T(B)=0$.

Let $A$ be an $n \times n$ complex matrix and $V = \{B\mid AB=BA\}$.  I've proved that $V$ is a vector space. How can I prove that $\dim V \ge n$ for any $A$?


I'm using FFmpeg and I'm aware that it is the fastest offline video and audio converter. Suddenly I've tried to convert portrait videos into landscape but upon checking its Outcome, it changes its aspect ratio and the video become chubby and that is what I don't like at all. I want to convert portrait videos into landscape video that maintains the aspect ratio and its orientation as portrait.

I have a html 5 video player which is 700px wide, 400px high. I'm trying to use avconv to use ffmpeg to resize (while retaining the aspect ratio) and making sure it fits into my player.  Input can be a file of any size, so I need to resize the larger ones but center the smaller ones with black bars. So far I've tried: -s and -aspect, I've seen pad being used with the -vf switch but don't understand how it works enough to get what I need.    This is a rough idea of what I need. I'm not sure if it's even possible. It's almost like CSS's max-width/max-height. I realise this may just be a jumble of words but if anyone happens to understand what I'm talking about, I'd appreciate help, Thanks.  avconv command:  avconv -y -i control.avi -vcodec libx264 -b 2000k -bufsize 20M -acodec aac -strict experimental -ar 44100 -ab 256k bigbuck_out.mp4


I have Dell Inspiron mini 10v with Intel Atom processor that was given to me. IT believe this has 1GB RAM.  Unsure if it is HDD or SSD but how do I find out?   It does not have CD.  However, I have usb 2.0 thumbdrive though.  For the performance to work, I d like to be able to use text editor, browse the surf and watch videos such as Netflix and Youtube.  Does anybody have instructions or recommendations?

I am using Dell Ubuntu Mini 10 version of Ubuntu.  The problem is: I tried both 12.04 and 13.04, but both are extremely slow on this laptop.So I am now running 11.04 which is near it's End Of Life and will give no further support.  So what should I do now? Is there any better option than using 11.04?


Today I came across this, during a web search:    Is this some kind of clone?

of Stack Overflow, all content posted on Stack Exchange sites by their users (i.e. you wonderful people) has been provided to the whole universe under . For my fellow non-lawyers, that license basically means:   Anyone can use any Stack Exchange posts at any time without having to ask for permission Making money off of the copied content is permitted You don't even have to copy stuff from here verbatim; you can just use it as a starting point and make whatever edits you want There are just two rules you have to follow:   You have to provide . Simple links to the original post and author info are just fine. You have to  and allow other people to use your content, as long as they follow these very same rules. How meta!    (If you ever forget any of that, and want to refresh your memory, the license info is linked to in the footer of every page.)  There are, in fact, a lot of people who republish varying amounts of our content for assorted reasons. Unfortunately, there are some Stack Content Republishers Attributing Poorly and/or Excelling at Ranking (SCRAPERs, for short).  In this context, "attributing poorly" means any use that doesn't follow our attribution rules or make any other reasonable attempt at give credit. This can get pretty egregious; I've seen SCRAPERs that not only don't link back to SE originals, but also use fake author info and post dates to make it harder to find originals. By "excelling at ranking," I'm referring to copycat sites that end up higher in Google results than the original SE sites do for the same content. That's not necessarily wrong, but in some cases, it indicates inappropriate SEO hackery.  So, the question is: what can you do if you spot a SCRAPER?


Consider space $\mathcal{S}=\mathbb{R}^{n\times n}$. Let $\mathbf{X},\mathbf{Y}\in\mathcal{S}$. The inner product between $\mathbf{X},\mathbf{Y}$ is defined as ()  \begin{equation} <\mathbf{X},\mathbf{Y}> = trace(\mathbf{Y}^{T}\mathbf{X}^{})=\sum_{i=1}^{n}\sum_{j=1}^{n} \mathbf{X}_{i,j}\mathbf{Y}_{i,j}  \end{equation}  In $\mathbb{R}^2,\mathbb{R}^3$, "Inner Products" give us a notion of "angle" between the two vectors i-e  \begin{equation} <\mathbf{x},\mathbf{y}> = \|\mathbf{x}\|\|\mathbf{y}\| cos(\theta)  \end{equation}  I am wondering how to extend this geometric interpretation to matrices? What does it mean for two matrices to be "aligned". Does it mean their singular vectors are aligned?

$\langle A,B \rangle := Trace (AB^t)$ is an inner product over the vector space $M_n(\mathbb R)$ of all real matrices of size $n$ , I would like to know whether this inner-product has any Geometrical or Physical significance (interpretation) or not ? Please shed some light . Thanks in advance


Why does the Community user sometimes approve or reject edits? How does a machine know if my edit is valid? What does it mean if my edit was rejected by Community?     See also:

When clicking "edit" I see:  Your edit will be placed in a queue until it is peer reviewed. We welcome edits that make the post easier to understand and more valuable for readers. Because community members review edits, please try to make the post substantially better than how you found it, for example, by fixing grammar or adding additional resources and hyperlinks.  Like:     Likewise, when I am not logged in, clicking "improve this question" or "improve this answer" shows:  You are not . Your edit will be placed in a queue until it is .  And when I click 'Save', I get:  Thanks for submitting an edit. It is only visible to you until it's been approved by trusted community members  Like:     Who can suggest an edit? Where do suggested edits go? Who can vote on a suggested edit? How do suggested edits get reviewed? Can I earn reputation? What about abuse or bad edits? Sometimes the Community user approves or rejects my edit. Why is that? When can I not suggest an edit? Is there a minimum change requirement for a suggested edit? How do I check my suggested edit history? I disagree with the reasons why my suggested edit was rejected. What can I do? How do I know whether there are edits waiting for review? Someone suggested an edit to my own post, and the reviewers took the wrong action. What can I do? Are tag wikis included in this scheme? What do the "Improve Edit" and "Reject and Edit" buttons do? Why are apparently valid links to rejected edits resulting in 404 errors?   For more information about editing, see "" in the .


I have newest Latitude 5490 with 8th gen i7 and 16gb of RAM.  The screen of my laptop is little bit yellowish in comparison to my previous laptop (Latitude 5480). I have updated all the drivers and tried all the conventional methods available on YouTube like :  -- setting different RGB in color management I have tried selecting sRGB2.1 profile. -- changing color setting in Intel Graphic control like contrast , hue options. -- turning on off , night mode.   but none worked , can anyone help me please its urgent.

I have newest Latitude 5490 with 8th gen i7 and 16gb of RAM.  The screen of my laptop is little bit yellowish in comparison to my previous laptop (Latitude 5480).  I have updated all the drivers and tried all the conventional methods available on YouTube like :   setting different RGB in color management I have tried selecting sRGB2.1 profile. changing color setting in Intel Graphic control like contrast , hue options.   but none worked.  can anyone help me please.


I need some help to modify the \gear macro of  in order to be able to fill the drawn gear with a solid color.  I've tried to move the \draw command outside the loop, but it does not work as expected (missing semicolon???):  \newcommand{\gear}[3]{%     \def\modu{#1}     \def\Zb{#2}     \def\AngleA{#3}      \pgfmathsetmacro{\Rpr}{\Zb*\modu/2}     \pgfmathsetmacro{\Rb}{\Rpr*cos(\AngleA)}     \pgfmathsetmacro{\Rt}{\Rpr+\modu}     \pgfmathsetmacro{\Rp}{\Rpr-1.25*\modu}     \pgfmathsetmacro{\AngleT}{pi/180*acos(\Rb/\Rt)}     \pgfmathsetmacro{\AnglePr}{pi/180*acos(\Rb/\Rpr)}     \pgfmathsetmacro{\demiAngle}{180/\Zb}     \pgfmathsetmacro{\Angledecal}{(\demiAngle-2*\AnglePr)/2}      \draw[fill=black!20] \foreach \zz in{1,2,...,\Zb}{          ({(\zz))/\Zb*360-\Angledecal}:\Rb)             -- (\zz/\Zb*360-\Angledecal:\Rp)             to[bend right=\demiAngle] (\zz/\Zb*360+\Angledecal:\Rp)             -- plot[domain=-0:\AngleT,smooth,variable=\t]                 ({{180/pi*(-\t+tan(180/pi*\t))+\zz/\Zb*360+\Angledecal}:\Rb/cos(180/pi*\t)})             %              to[bend right=\demiAngle]                  ({{180/pi*(\AngleT+tan(180/pi*-\AngleT)) +(\zz+1)/\Zb*360-\Angledecal}:                     \Rb/cos(180/pi*-\AngleT)})         %              plot[domain=-\AngleT:-0,smooth,variable=\t]                 ({{180/pi*(-\t+tan(180/pi*\t)) +(\zz+1)/\Zb*360-\Angledecal}:                     \Rb/cos(180/pi*\t)})     } -- cycle; }   Edit: add missing fill color

To answer , I would use plot in a foreach loop used into a single path. But it seems that it is impossible...  Here, an example to show my problem:  \documentclass{standalone} \usepackage{tikz} \begin{document} \begin{tikzpicture}   \draw   (0,0)   \foreach \myvar in {1,2,3}{     --     plot[domain=0:1] (\myvar-\x,\myvar)   }; \end{tikzpicture} \end{document}   This document should produce this result:    In fact, it produces following error:  ! Package tikz Error: Giving up on this path. Did you forget a semicolon?.   Edit: I add a more complex example to show the problem.  Here, a code without \foreach:  \documentclass{standalone} \usepackage{tikz} \begin{document} \begin{tikzpicture}   \draw   (0,0)   --   plot[domain=0:120] ({1-cos(3*\x)},{1-sin(\x)})   --   plot[domain=0:120] ({2-cos(3*\x)},{2-sin(2*\x)})   --   plot[domain=0:120] ({3-cos(3*\x)},{3-sin(3*\x)})   ; \end{tikzpicture} \end{document}   And the result:    And the factorized code with \foreach (but this code produces the error):  \documentclass{standalone} \usepackage{tikz} \begin{document} \begin{tikzpicture}   \draw[dahsed]   (0,0)   \foreach \myvar in {1,2,3}{     --     plot[domain=0:120] ({\myvar-cos(3*\x)},{\myvar-sin(\myvar*\x)})   }; \end{tikzpicture} \end{document}


Thanks to Galois we know that the solutions of a general fifth order equations cannot be expressed by means of radicals.   Can we exclude that a formula exists if we are allowed to also use (any composition of) trascendental functions like: $\exp$, $\log$, $\tan$, $\arctan$?

By  an arbitrary polynomial equation of degree $\ge 5$ is not solvable  using , unlike the polynomial equation of second degree which is solvable by radicals (because of the  of order 5, the symmetry group is not ).  Is this the only way an arbitrary polynomial equation can be (exactly) solved?  Does Galois Theory provide universal concept of general solvability?  Are there other methods except using radicals (for exact, not approximate or numerical solution)?  PS. A related


I am trying to display both the datetime and the IP address of my log file:  Apr 20 07:03:53 123.345.45.123 ^             ^ ^            ^ |---datetime--| |-----IP-----|      my code:  datetimeRegex = re.compile(r'^\w{3}\s\d\d\s\d\d:\d\d:\d\d')  IPRegex = re.compile(r'\d+.\d+.\d+.\d{1,3}')  f = open("logfile.log","r")  count = 0  for line in f.readlines():     datetime = re.match(datetimeRegex, line)     IPaddr = re.match(IPRegex, line)     if datetime and IPaddr:         count += 1         print str(count) + ":" + str(datetime.group()) + "IP: " + str(IPaddr.group())   I tried to see what is not matching and I think it is IPaddr that isn't matching because I removed IPaddr from my if statment and my output would print the dates. It is when I added IPaddr that nothing would print. So I think I am not matching my IP address correctly. However I tried a sample IP and my regex on an online regex tester and it seemed to work. Is there something missing in my REGEX? Or perhaps there is something wrong with my logic? If there is a faster or more efficient way to parse through the log file, I am open to suggestions.

Does anyone have a regular expression handy that will match any legal DNS hostname or IP address?  It's easy to write one that works 95% of the time, but I'm hoping to get something that's well tested to exactly match the latest RFC specs for DNS hostnames.


If we have that $\tau, \nu$ are stopping times and that $\tau \leq \nu$, if $X_n$ is a submartingale, how can I show that $E(X_{\tau \wedge n}) \leq E(X_{\nu \wedge n})$? Is there a way to characterize it by a Martingale transform or is there a simpler idea? thanks


I am a PhD student in a quantitative social science field. For the first study of my dissertation, I was given the opportunity to ask some questions that could be applied to an ongoing survey. Affiliated researchers have already used some of this data for a short commentary/descriptive article, and there is interest to apply the data in a slightly different 'modelling' study.  However, the underlying study design leaves much to be desired. Although the sample is relatively large, it is a convenience sample from only a fraction of all possible survey sites in the population. There is no opportunity to expand the data collection process. The data itself is unlikely to have measurement error, but almost any estimate produced from the dataset is highly likely to suffer from sampling bias.  Nevertheless, I realize this is a somewhat 'common' situation graduate student find themselves in. There is active interest from the affiliated partners to carry out the study, the design isn't 'ideal', and there are logistical considerations of invested time (or as I see it, sunk cost fallacy).  While I have many questions, I think the most straightforward is: should I attempt to make 'lemonade out of lemons' or 'stand my ground' that such a modelling study would be inappropriate?   Other potential information:   Supervisor is 'ardent' that such a study should be carried out I have sought out external input as to what methods would be 'most' appropriate, there are some that might be 'less' worrisome than others

I am a PhD student in mechE. After paying the first year tuition out of pocket, I accepted a PhD project due to desperation for funding. However, after an year I realized that I hate the project. Here I made a mistake of not leaving/changing the project, I just waited out hoping I would like the project. I also asked my advisor a couple for a different project and he did not want to change my project due to sponsor obligations. For some reason I couldn’t assert myself and stayed on. However my hate for the project only grew with time and now I am in my fifth year. I have reached a stage where I absolutely hate the project and don’t know what to do. I can hardly do any work. I feel like quitting everyday and still feel it is wrong to quit this late. I have a very substandard thesis. I am lost and feel stuck, please advise on what to do. Thanks


I am performing an interrupted time series analysis. I plotted the data and then checked for autocorrelation using ACF and PACF.    par(mfrow=c(1,2))  acf(residuals(model_ols), main="ACF")  acf(residuals(model_ols), type = "partial", main="PACF")   How do make sense of this plot now? Can someone tell me what should be the next step?

Following are acf and pacf plots of a monthly data series. The second plot is acf with ci.type='ma':    The persistence of high values in acf plot probably represent a long term positive trend. The question is if this represent seasonal variation?  I tried to see different sites on this topic but I am not sure if these plots show seasonality.           Edit: following is the graph for lag upto 60:     Following are plots of diff(my_series):     And upto lag 60:     Edit: This data is from:  Here the contributors did not consider acf and pacf plot of original or differenced series worth mentioning (so it must not be important). Only acf/pacf plots of residuals was referred to in a couple of places.


I have a 16GB SanDisk SD memory card that suddenly started showing this message to me on my phone:  “UNSUPPORTED SANDISK SD CARD”  And says:  “This device doesn't support this SanDisk”  It then takes me to the formatting and erase option. I tried connecting the card to my computer with card reader but it is not showing up in “My Computer.” However the sound does come when I connect but the card is not shown. I did a virus scan just to be sure of my computer while it is fixed, its clean. I need the files in the card.

I am trying to help a friend who is very concerned that she has just lost all of the data on her 32GB SanDisk microSD card.  I told her I would post this and see if anyone could offer help.  Here are the details:   The SanDisk microSD card is less than two years old.  Probably only about a year old.  The store will take it back, but that doesn't really help.  She wants her data. She used the card in her Samsung Galaxy S4 smartphone for over a month.  The phone was never exposed to water or temperature extremes. Today, her phone suddenly said something like "Your SD card is blank or an unsupported format". Her phone was then unable to read the SanDisk microSD card at all.   Here's what she has tried:   Rebooting her phone.  Had no effect. Taking out the SanDisk microSD card and putting it inside a full-size SD card adapter, and inserting it into a Windows 7 SP1 computer.  The computer did not recognize its presence at all. Putting the SanDisk microSD card into a USB 2.0 external card reader and inserting the card reader into a USB port on a Windows 7 SP1 computer.  The computer recognized the card reader and installed drivers for it.  The card reader shows up as 'Removable Disk' in Windows Explorer.  Clicking on 'Removable Disk' in Windows Explorer results in the error "Insert disk: Please insert a disk into the Removable Disk". After trying #3, tried opening the 'Removable Disk' in FreeCommander.  Doing so results in the error "The device is not ready".   She does not have access to a linux box, but does have access to her Android phone.  What can she do to recover the data on her 32GB SanDisk microSD card?


Dispel Magic says (emphasis mine):  Choose one creature, object, or magical effect within range. Any spell of 3rd level or lower on the target ends. For each spell of 4th level or higher on the target, make an ability check using your spellcasting ability. The DC equals 10 + the spell's level. On a successful check, the spell ends.  At high level play, I've found that players often have long-term buff spells in effect (i.e. Heroes Feast, Mindblank, etc.), which are a major factor in them being able to survive. If one of these characters is affected by a save or suck kind of spell (i.e. Mental Prison, Irresistable Dance, etc.), the need to remove that spell becomes imperative. With this in mind, can a caster of Dispel Magic target only a negative spell under the assumption that it is a discrete 'magical effect' subject to removal? Or must they target the 'creature' and risk removing all spells, both positive and negative? For reference, we see a potentially unique 'magical effect' in  about Yeenoghu's flail. This effect is similar to a spell in its function (target is affected by the Confusion spell if they fail the save), but has clear differences from a spell because the spell would require Yeenoghu's concentration and have a different duration. Conversely,  suggests that a 'magical effect' only applies to things that wholly separated from the creature.

Suppose an enemy have blur and slow cast on them.  Can I use dispel magic to end the magical effect blur, without dispelling slow?    The above spells are just examples. This question mainly ask about how dispel magic can be used to end one spell affecting a creature without dispelling other spells.  What are the conditions must be satisfied to do this? Does the will-be-dispelled spell must have a perceivable effect to be able to be targetted? Does the spell must be lower than dispel magic? Must I name the spell I wish to end? Must I name the effect ("whatever making him looks blurry")?


How will a bullet having very high velocity and having little mass  behave when fired from the Earth perpendicular to the surface? It will be a great help if somwone explained it? Will it come back? Or will it escape into the outer space?

Consider a gun or rifle fired directly upwards. My original question was what speed would be required to escape the Earth.  The escape velocity from the surface of the Earth is the classic $$v_e = \sqrt{ 2GM \over r } \approx 11,000 \text{ m/s}$$ and bullets typically (see ) leave the muzzle with a maximum speed one order of magnitude lower, ~$1,000$ m/s. Terminal velocity of bullets in STP is another magnitude lower, ~$100$ m/s.  Even if a bullet were fired with speed $v_e$ that of course would not be sufficient due to drag which would slow the bullet down. So a theoretical required speed  $v_T > v_e$.   If the bullet were fired with anything close to $v_e$ or $v_T$, would it would burn up very rapidly in STP? I understand that rockets typically don't achieve anything like $v_e$ until they are high in the atmosphere at least in part for this reason And hence is there no speed possible in realistic conditions with which a bullet could be fire and escape the Earth? If it is possible, what model of drag should one use to calculate $v_T$ and concretely,  does anyone have an estimate of its value?


I'm on Ubuntu 19.04 and I would like to make sure that if I try to install some software with a hard Python 2 dependency that it would just fail instead of installing 2 on my system.

Can I configure Ubuntu to never install a specific package even if it is required by another package I install?


I'm trying to create a float that spans two columns that has multiple side-by-side subfigures.  I've included the subcaption environment, and here's what I've got so far:  \begin{figure*}[h] \begin{center}     \begin{subfigure}[h]{0.3\textwidth}     \begin{tikzpicture}     \begin{axis}     \addplot[color=black!100,mark=x] coordinates {         (1, 4.89)         (2, 6.74)     };     \end{axis}     \end{tikzpicture}     \end{subfigure}      \begin{subfigure}[h]{0.3\textwidth}     \begin{tikzpicture}     \begin{axis}     \addplot[color=black!100,mark=x] coordinates {         (1, 21.9)         (2, 15.6)     };     \end{axis}     \end{tikzpicture}     \end{subfigure} \label{Results2} \end{center} \end{figure*}   However, this ends up giving me two subfigures one over the other.  What am I doing wrong?  Thanks in advance for the help

I want to put four figures in a single row. The code I am trying to use is taken from .  This puts three figures in a row. When I add a fourth one, I get three images in row and the last one appears in the second row. But I want all of them in one row. Here is my code.  \documentclass[12pt,twoside]{report}% Use this line for the print version of the thesis   \usepackage{graphicx} \usepackage{caption} \usepackage{subcaption} \begin{document}  \begin{figure}         \centering         \begin{subfigure}[b]{0.3\textwidth}                 \centering                 \includegraphics[width=\textwidth]{gull}                 \caption{A gull}                 \label{fig:gull}         \end{subfigure}%           \begin{subfigure}[b]{0.3\textwidth}                 \centering                 \includegraphics[width=\textwidth]{gull}                 \caption{A gull2}                 \label{fig:gull2}         \end{subfigure}%          ~ %add desired spacing between images, e. g. ~, \quad, \qquad etc.           %(or a blank line to force the subfigure onto a new line)         \begin{subfigure}[b]{0.3\textwidth}                 \centering                 \includegraphics[width=\textwidth]{tiger}                 \caption{A tiger}                 \label{fig:tiger}         \end{subfigure}         ~ %add desired spacing between images, e. g. ~, \quad, \qquad etc.           %(or a blank line to force the subfigure onto a new line)         \begin{subfigure}[b]{0.3\textwidth}                 \centering                 \includegraphics[width=\textwidth]{mouse}                 \caption{A mouse}                 \label{fig:mouse}         \end{subfigure}         \caption{Pictures of animals}\label{fig:animals} \end{figure} \end{document}   As I have mentioned above, it works for three figures.  But I can not use it for four figures. What should I change?   What does  width=\textwidth mean?   I changed    \begin{subfigure}[b]{0.3\textwidth}   to  \begin{subfigure}[b]{0.2\textwidth}   but it didn't help.  Then, I changed     \includegraphics[width=\textwidth]{mouse}   to  \includegraphics[width=0.5\textwidth]{mouse}   Still no solution.


Sometime ago I messed with opening chm files. I set a pdf viewer as the default app for viewing chm files and now I want the Microsoft HTML help Viewer to be set as default chm viewer. The problem is Im not able to find the app either in the System32 folder or in the Windows folder. If somebody can tell me where exactly the Microsoft HTML Help Viewer is stored it would be of great help. Thank you.

I know that that WinHelp is discontinued. No more included since Windows Vista. However, while Vista was still supported by Microsoft, I still could install it. Now, no more. Every time I got error in my Windows Vista related to run old software using winhlp32.exe, I am always directed to this Microsoft . From there I can download a package file, name Windows6.0-KB917607-x86.exe. Unfortunately, it is not allowed to download the required file to run *.hlp file.  Now, I need that Windows Vista/Windows 7's WinHlp32.exe that I can copy and put manually to my C:\Windows. Where can I get it? Can someone help or share?


f1 score is defined as F1 = 2 * (precision * recall) / (precision + recall) However if true positives are zero, this gives 0/0. How to deal with this scenario?

Recently, I built a classification model based on the imbalanced data set(positive sample is minority and negative sample is majority), and the model gave the following result for the test set:  True Positives = 0 True Negatives = 139 False Positives = 0 False Negatives = 10.  My question is: for the result, can Matthews correlation coefficient ( ) and  be used for estimating the classifier? Since the denominators for MCC and F-measure are zero, it seems meaningless. If so, MCC and F-measure is not always works for estimating the classifier, and sensitivity and specificity as well as g-mean should be better. Is that right? Any help is appreciated.


I have uninstalled and reinstalled the app, but every time I want to upload any photo, the app replies something went wrong.   App Version: 1.0.95 Device Manufacturer: PANASONIC Device Model: ELUGA_I2   OS Version: 5.1 (1440411390)

When trying to upload a picture from my phone, the Android app crashes a few different ways, depending on whether I select the Gallery or Photos image source. (Uploading by manually entering a URL works perfectly.) The problem occurred using beta versions 1.0.63, 1.0.71, 1.0.72, and now 1.0.73, on a Samsung Galaxy S4 running Android 4.1.2.  These are the steps which I've used:   Open an Ask/Answer a Question window, enter a sentence. Click on the picture icon, which opens a "Choose Image Source" window. Select "From Device," which opens a window offering a choice of "Gallery" or "Photos."   If I select Gallery, when the pictures open, choosing one causes the app to immediately crash. The circle goes around for about 15 seconds (see picture on left below), then re-opens to the Ask a Question window, where the original text is still visible. The camera icon isn't live (it's grayed-out), so trying to post again in that window is not an option.   If I select Photos, when the pictures open, I can choose one. It pauses, which I interpret as an effort to post. After about 10 seconds, however, the app crashes to the feed screen, and an error message in a black box appears which says "Unfortunately, the process com.stackexchange.marvin has stopped." (See picture on right below.) There are Report and OK options under the error message. Initially I was able to get a screenshot, however the message disappeared before I could select Report, then the app crashed. However, on 8/11/15, and a few times since, I've been able to submit a report before the crash.  Update 9/2/15: With version 1.0.72, the error message varied, and many tries produced a picture a few times. There was no indication as to when or why it would happen, and each of those times, the picture posted sideways. With version 1.0.73, the error message has returned to the original, and fifty tries have not produced a posted picture from either Gallery or Photos. I'm updating this report in the hope that others are experiencing the same problem, or to be notified if the developers are aware of it. Thanks!


I've been trying to identify this movie that I saw as a child for years, with no luck. I remember that a non-military ship visits a shipwreck and the crew downloads the logs from the main computer that's still operational. The logs shows that the wreck has been visited by a number of tubular, hexagon (octagon?) base vessels. Soon after these tubular ships show up and it turns out they are parts of a modular battleship as they lock to each other. They are asked to surrender, and they pretend to do so while they construct a "lightning cannon" that they use when the battleship attempts to dock. A person whom they probably picked up along the way built the weapon and dies when he holds a broken panel together by his hands when they fire it. Anybody could help me figure out which movie is this? Thanks!

When I was a kid we had a VHS tape of some Disney live action (not animated) sci-fi movie. It may have been a mini-series or a made-for-tv movie, but I'm not sure. I'm also not sure about the year but it would probably have been late 80s or early 90s based on when I would have seen it. I know it was Disney because they had some live action Goofy and Mickey running around the movie's set as an introduction discussing the plot with a host before the movie.  The plot is basically as follows:   A starship is loaded with mostly children and teenagers as a cross-galaxy human settling effort. Accidents (which are not really accidents and later revealed) cause adult crew members to be killed.  They travel to another planet and face all sorts of troubles. It arrives at the new planet after overcoming obstacles.   Other memorable scenes that may help:   Navigating out of earth's asteroid belt made out of space junk. One of the adults was killed via an airlock malfunction. The ship was supposed to be peaceful with no weapons. At one point they bring on board some crazy guy who puts together a rail gun. There's a memorable line like "Do you want no weapons at all or a well aimed rock?"  There's a planet or space station (I can't remember which) that has a fight scene with the evil bad guy. This scene takes place on what looks to be a carnival or fairground. The bad guys are trying to steal the ship the kids are on because it has some kind of really good futuristic space drive.   Hopefully you remember it better than I do! I've tried looking online for it before with no luck.


I understand the principle behind choosing either 'that' or 'which' but I still find myself struggling to know in certain situations whether to use it or not. For example, "Here is a link to the article, which can be found on the Environment section of the website". Would it be that or which? I would use assume 'which'.  Do any of you have tips/strategies for knowing when to use 'that' or 'which' when writing a sentence?  Thanks

When is it appropriate to use that as opposed to which with relative clauses?


The pattern [aeiou][^vr]e(?=[^r]) works fine when testing at RegexPlanet.com, but when I use the same pattern with re.match in Python I get no matches.  import re pattern = r'[aeiou][^vr]e(?=[^r])' list = ['pale.', 'taste', 'kite'] for word in list:     if re.match(pattern, word):         print(word)   Expected Result:  pale. kite.

What is the difference between the search() and match() functions in the ?  I've read the  (), but I never seem to remember it.  I keep having to look it up and re-learn it.  I'm hoping that someone will answer it clearly with examples so that (perhaps) it will stick in my head.  Or at least I'll have a better place to return with my question and it will take less time to re-learn it.


How to return double datatype with 4 decimals in a function in java ?     public static double fun(){     double d=2.5d;     String s=String.format("%.4f",d);     double ans=Double.parseDouble(s);     return(ans); }  actual output=2.5 expected output=2.5000

What I would like is a method to convert a double to a string which rounds using the half-up method - i.e. if the decimal to be rounded is 5, it always rounds up to the next number. This is the standard method of rounding most people expect in most situations.  I also would like only significant digits to be displayed - i.e. there should not be any trailing zeroes.  I know one method of doing this is to use the String.format method:  String.format("%.5g%n", 0.912385);   returns:  0.91239   which is great, however it always displays numbers with 5 decimal places even if they are not significant:   String.format("%.5g%n", 0.912300);   returns:  0.91230   Another method is to use the DecimalFormatter:  DecimalFormat df = new DecimalFormat("#.#####"); df.format(0.912385);   returns:  0.91238   However as you can see this uses half-even rounding. That is it will round down if the previous digit is even. What I'd like is this:  0.912385 -> 0.91239 0.912300 -> 0.9123   What is the best way to achieve this in Java?


Ok, so I wanted to write a delete method that works for any "delete-case" for Binary Search Trees and this is my attempt:   public void delete(int key) {  if (root.value == key) {    root = root.right;    root.left = root.right.left;    return;  }  else {    deleteRecursive(key, root);  ***LINE 58***  }   }   public void  deleteRecursive(int key, BinaryNode node) {  if (node == null) {    System.out.println("ERROR");    return;  }  else {    if (key < node.value) {      // continue search on left      if (node.left.value == key) {        if (node.left.left == null && node.left.right == null) {          node.left = null;             }        else if (node.left.left == null){          node.left = node.left.right;        }        else if (node.left.right == null){          node.left = node.left.left;        }        else{          node.left = node.left.right;          node.left.left = node.left.right.left;  ***LINE 83***        }      }      else {        deleteRecursive (key, node.left);      }    }    else if (key > node.value){      // continue search on right      if (node.right.value == key) {        if (node.right.left == null && node.right.right == null) {          node.right = null;        }        else if (node.right.left == null){          node.right = node.right.right;        }        else if (node.right.right == null){        }        else if (node.left.left != null && node.left.right != null){          node.right = node.right.right;          node.right.left = node.right.right.left;        }      }      else {        deleteRecursive (key, node.right);      }    }  } }   But when I actually use the delete method in Main its gives out a NullPointerException.  The error-message reads :   Exception in thread "main" java.lang.NullPointerException         at BinaryTree.deleteRecursive(BinaryTree.java:83)         at BinaryTree.delete(BinaryTree.java:58)         at Main.main(Main.java:14)   So I assume that it is in line 83 and 58 (marked in code).  I've been sitting here for the last hour trying to figure it out and can't seem to get it.  I'm not the best in Java so I thought i could look for some help here! :)  Here are all the files to run the program (everything except for the delete method was already given) :

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?


My plan is to replace my laptop's current 256GB SSD with a 1 or 2 TB SSD. This means that the new SSD will be completely empty without any OS, or my data... I am using Windows 10 on the subject computer.  I have the ability to create a "Windows backup Image" (I do this weekly anyway) of my old SSD and put it on one of my external drives and I was hoping to "restore" this backup image onto the new SSD after it is installed into the laptop, so I can resume exactly how I'd left off but with more space. However, does Windows need to already be on that new SSD in order to do this? If so, are there any other solutions which solve the problem of needing to transfer data/OS image from current SSD to new SSD?  Please Note: This is not a request for a software recommendation. I am wondering about the method for which to go about this. For example, is it possible to restore an image to the SSD after the drive has been installed when the computer now has no current OS installed on it? Without an OS, how is this achieved?

I've recently bought a Dell Inspiron 3650, and would like to clone the disk onto a samsung SSD I have bought for it, in order to speed up boot times etc.  Samsung provide a clone tool called "Samsung data migration", which I've had success with in the past for cloning a system from a HDD to SSD.  Having tried it on the dell, the disk is not bootable, Leaving me with an error that no bootable media can be found. I've tried using a recovery usb to fix any boot system errors, but this fails with an error.  Booting into windows on the old HDD, the system recognises the disks have the same ID and disables the SSD, so it looks like the clone was successful.  I've tried disabling secure boot in the bios and then doing the clone, but this doesn't make a difference.  What else should I try? The system has Windows 10 home installed and is brand new, straight out of the box.


how to get from this:   id   foo_name 1        A 2        A 3        A 4        A 5        B 6        B 7        B 8        A 9        B 10       A   to this: 1 row only   foo_names A,B   I tried using GROUP_CONCAT but it give me this:  A,A,A,A,A,A,A,  B,B,B,B

Using MySQL, I can do something like:  SELECT hobbies FROM peoples_hobbies WHERE person_id = 5;   My Output:  shopping fishing coding   but instead I just want 1 row, 1 col:  Expected Output:  shopping, fishing, coding   The reason is that I'm selecting multiple values from multiple tables, and after all the joins I've got a lot more rows than I'd like.  I've looked for a function on  and it doesn't look like the CONCAT or CONCAT_WS functions accept result sets.  So does anyone here know how to do this?


I asked , and it was marked as . Although it's clear to me, and those who read both, that the questions are different.  My question----raised to issue the meaning of the phrase joga bonito, while its purported original pointed out the incorrect spelling of the word bounito.  So my question is about language usage (joga, a verb, versus jogo, a noun), while the original is about a spelling mistake (bounito should be spelt bonito).  Is there something I am missing about the definition of a duplicate question? The help center states the following:     The fundamental goal of closing duplicate questions is to help people   find the right answer by getting all of those answers in one place. ...   There are many ways to ask the same question, and a   user might not be able to find the answer if they're asking it a   different way.   It's obvious that the two questions are different. And why would mine warrant several down votes, while the purported original garnered 17 up votes? Is it so different to point out that usage might be incorrect?

I asked a question regarding a very specific feature of a program and whether or not it works with a larger program.  Within hours someone had marked it with "This question may already have an answer here of a similar question, but not related to my question.  The question I asked IS NOT ADDRESSED in the referred-to question. It's frustrating to spend half an hour putting together an intelligent and specific question, and then have someone mark it as a duplicate (or possible duplicate), which apparently causes people to skip over my question. I haven't received any more responses since the question was flagged.   Two questions:  (1) How do I get this flagging removed and (2) what's the best way to prevent these "helpful" flaggings in the future?


I am creating art prints using spatial data.  I use ESRI software every day for my regular job, therefore I am proficient in GIS. However, I can't afford ESRI software for my art projects at home.  Currently I am using QGIS. What are some recommended products for producing print-quality maps?

I work with people who use ArcGIS Desktop and they have found the best resolution output images are made by creating PDFs. They tell me that *.png and the rest out of ArcGIS Desktop are not satisfactory and that they do not bother with them. Typically we are making the output appear in a report and so the PDFs of the maps and words are assembled in a PDF editor package to make the final document.   As a result I have been toying around with QGIS on my Windows 7 machine and notice that the best output comes by printing directly out of the map composer.  This output on my Docuprint C2120 printer is as good as any of the ArcGIS Desktop PDFs and is truly impressive. QGIS makes very attractive maps in this configuration.   However, I do not seem to be able to create PDFs or .pngs and then print them which are anywhere near as good. I find the .svg output to Inkscape unrealiable where, for instance, the grid/graticule may come out oversized.   By way of example, the good quality output is where a sub-6 pt font can be read easily off the printed page.   Any thoughts?  I am using QGIS trunk.


I want to reference 2 pictures, but one is always shown as ?? in the pdf. I do not know what I am doin wrong. Below you find an example that reproduces this problem. Could you please help me? Thanks in advance.                \makeatletter     \makeatother     \usepackage[a4paper,left=3cm,right=3cm,top=3cm,bottom=3cm]{geometry}           \usepackage{booktabs}     \usepackage{caption}       \usepackage{etoolbox}     \usepackage{fancyhdr}     \usepackage[T1]{fontenc}     \usepackage{graphicx}     \usepackage[utf8]{inputenc}     \usepackage{latexsym}     \usepackage{lmodern}    % The Font Type     \usepackage{mdframed}     \usepackage{pgf}     \usepackage{tcolorbox}     \usepackage[flushleft]{threeparttable}     \usepackage{tikz}     \usepackage[absolute,overlay]{textpos}     \usepackage{xcolor}     \usepackage{xspace}                \makeatletter     \makeatother     \usepackage[a4paper,left=3cm,right=3cm,top=3cm,bottom=3cm]{geometry}           \usepackage{booktabs}     \usepackage{caption}       \usepackage{etoolbox}     \usepackage{fancyhdr}     \usepackage[T1]{fontenc}     \usepackage{graphicx}     \usepackage[utf8]{inputenc}     \usepackage{latexsym}     \usepackage{lmodern}    % The Font Type     \usepackage{mathtools}     \usepackage{mdframed}     \usepackage{pgf}     \usepackage{tcolorbox}     \usepackage[flushleft]{threeparttable}     \usepackage{tikz}     \usepackage[absolute,overlay]{textpos}     \usepackage{xcolor}     \usepackage{xspace}           \usepackage{hyperref}     \hypersetup{         colorlinks,         citecolor=black,         filecolor=black,         linkcolor=black,         urlcolor=black     }                      \begin{document}          \begin{figure}[h]          \begin{minipage}{\textwidth}             \begin{minipage}[t]{0.5\linewidth}                 \centering                                      \begin{tikzpicture}                     \draw (0,0)--(11,0)--(11,7)--(0,7)--cycle;                      \end{tikzpicture}                  \label{fig:A}                 \caption{Some text.}             \end{minipage}             \hskip60pt             \begin{minipage}[t]{0.5\linewidth}                 \centering                      \begin{tikzpicture} %, fill=ashgrey!25                     \path[draw, line width=0.5mm] (0,0) -- (13,0) -- (13,11) -- (0,11) -- (0,0)--cycle;                     \end{tikzpicture}                  \caption{Some text.}                 \label{fig:B}             \end{minipage}         \end{minipage}     \end{figure}        Some text \ref{fig:A} \ref{fig:B}     \end{document}

\documentclass{article} \usepackage{algorithm}  \begin{document} \setcounter{section}{54} \section{A section with no label} \begin{algorithm} \label{myalg} \caption{An algorithm with the label `myalg'.} \end{algorithm} Reference to myalg: \ref{myalg}. \end{document}   With this code, the reference givens 55 (the section number); if I move the label after the caption command, I get the correct reference (1).  Why should this be the case? I find it confusing: when thinking about an algorithm as an environment, you expect to be able to label it right after you began it. At the very least I would expect some kind of error or "??" to appear, rather than the previous environment or reference-able entity being used.


I am learning C# throught the C# via CLR book. And I come across the following piece of code (simplified to create minimal example):  using System;  public class Program  {     public static void Main(String[] args)     {      string text = "Test";      string reversed = new String(text.Reverse().ToArray());       Console.WriteLine(reversed);    } }   Before trying to run the code above a compiler tells the following:     'string' does not contain a definition for 'Reverse' and no accessible extension method 'Reverse' accepting a first argument of type 'string' could be found (are you missing a using directive or an assembly reference?) [Console.NET]csharp(CS1061)   I can not wrap my head where the Reverse method come from. Was the Reverse method present in an older version of C#?  Original code is the last page of the Delegates topic (417-418 page).

I've just had to write a string reverse function in C# 2.0 (i.e. LINQ not available) and came up with this:  public string Reverse(string text) {     char[] cArray = text.ToCharArray();     string reverse = String.Empty;     for (int i = cArray.Length - 1; i > -1; i--)     {         reverse += cArray[i];     }     return reverse; }   Personally I'm not crazy about the function and am convinced that there's a better way to do it. Is there?


I know lyrics sometimes do not respect grammar, but is it possible to use to know in the progressive form? For example -      I'm not even knowing if I'm coming or going, if to end or begin.    This is from a song of the Buzzcocks written by Peter Shelley  "I believe"

If "I'm thinking" is correct, why isn't "I'm knowing" correct in formal English?  think+ing = thinking is correct know+ing  = knowing isn't correct   Why?


now this is embarrassing. I'm writing quick script and I can't figure out why this statement don't work.   if [ $(pidof -x test.sh | wc -w) -eq 1 ]; then echo Passed; fi   I also tried using back-ticks instead of $() but it still wouldn't work.  Can you see what is wrong with it? pidof -x test.sh | wc -w returns 1 if I run it inside of script, so I don't see any reason why basically if [ 1 -eq 1 ] wouldn't pass.  Thanks a lot!

What's a quick-and-dirty way to make sure that only one instance of a shell script is running at a given time?


I'm new to installing Linux, but I do know that my chromebook has an Armv8 processor. I was following this  and everything was fine  but when I run  sudo startxfce4   I get an error   euid != 0 directory /tmp/.x11   and more stuff and then it tells me   server terminated with error (1). closing log file unable to connect to x server: connection refused.   What should I do?

I have installed Ubuntu 13.04 on my desktop (runs like a charm). Then I used Crouton to install Ubuntu 12. 04 on my chromebook samsung (ARM). It also works quite well.  Here comes my question. Can we have a true Ubuntu (preferably 13.04) on my ARM chromebook?  It seems that the Crouton/Ubuntu is not 100% the real thing.  The best option would be to have the full Ubuntu 13.04 and remove the Chrome OS.


Edit: .  I run a small hosting provider with more or less 1535 customers and I use Ansible to automate some operations to be run on all servers. Last night I accidentally ran, on all servers, a Bash script with a rm -rf {foo}/{bar} with those variables undefined due to a bug in the code above this line.  All servers got deleted and the offsite backups too because the remote storage was mounted just before by the same script (that is a backup maintenance script).  How I can recover from a rm -rf / now in a timely manner?

Please note: The answers and comments to this  question contains content from another, similar question that has received a lot of attention from outside media but turned out to be hoax question in some kind of viral marketing scheme. As we don't allow ServerFault to be abused in such a way, the original question has been deleted and the answers merged with this question.      Here's a an entertaining tragedy. This morning I was doing a bit of maintenance on my production server, when I mistakenly executed the following command:  sudo rm -rf --no-preserve-root /mnt/hetznerbackup /  I didn't spot the last space before / and a few seconds later, when warnings was flooding my command line, I realised that I had just hit the self-destruct button. Here's a bit of what burned into my eyes:  rm: cannot remove `/mnt/hetznerbackup': Is a directory rm: cannot remove `/sys/fs/ecryptfs/version': Operation not permitted rm: cannot remove `/sys/fs/ext4/md2/inode_readahead_blks': Operation not permitted rm: cannot remove `/sys/fs/ext4/md2/mb_max_to_scan': Operation not permitted rm: cannot remove `/sys/fs/ext4/md2/delayed_allocation_blocks': Operation not permitted rm: cannot remove `/sys/fs/ext4/md2/max_writeback_mb_bump': Operation not permitted rm: cannot remove `/sys/fs/ext4/md2/mb_stream_req': Operation not permitted rm: cannot remove `/sys/fs/ext4/md2/mb_min_to_scan': Operation not permitted rm: cannot remove `/sys/fs/ext4/md2/mb_stats': Operation not permitted rm: cannot remove `/sys/fs/ext4/md2/trigger_fs_error': Operation not permitted rm: cannot remove `/sys/fs/ext4/md2/session_write_kbytes': Operation not permitted rm: cannot remove `/sys/fs/ext4/md2/lifetime_write_kbytes': Operation not permitted # and so on..   I stopped the task and was relieved when I discovered that the production service was still running. Sadly, the server no longer accept my public key or password for any user via SSH.  How would you move forward from here? I'll swim an ocean of barbed wire to get that SSH-access back.  The server is running Ubuntu-12.04 and hosted at Hetzner.


Use the following algorithm to devise an algorithm for computing $a^n$,  Hint: use binary expansion of $n$ to evaluate $a^n$. The following algorithm is based on the above algorithm to evaluate $a^n$, but I don't see that it does anything extra and I don't see it using the hint too,  Question: We can use both algorithms above to evaluate $a^n$. I don't see how algorithm presented above based on the first algorithm above does answer the question?

I came upon an interesting way to relatively quickly compute modular exponentiation with large numbers. However, I do not fully understand it and was hoping for a better explanation.  The method basically states if you have $x^y \bmod N$, it can be computed by repeatedly multiplying by $x$ modulo $N$:  $$x \bmod N \rightarrow x^2 \bmod N \rightarrow x^4 \bmod N \rightarrow x^8 \bmod N \rightarrow \ldots \rightarrow x^{2[\log y]} \bmod N$$  This is supposed to calculate in $\mathcal{O}(\log_2 N)$ time.  An example is given:  $$x^{25} = x^{11001_2} = x^{10000_2} * x^{1000_2} * x^{1_2} = x^{16} * x^8 * x^1$$  I don't really understand how this is faster. Aren't you just doing the same thing? You're just breaking down the exponents into representations of base $2$. Also where does $x^{2[\log y]}$ come from? If you're breaking it down into exponents of two where does a logarithm come from? (Aren't logs representations of numbers in exponents of $10$?)  I'm sorry if this appears to be a really stupid question - I have minimal knowledge in math.  Also, I wasn't sure if this belongs here or on stack exchange, so give me the word and I'll move it.


What's $-\frac{1}{27}$ in $\Bbb Z_2$?  I was naively thinking take the repeating string of the standard binary representation of $3^{-n}$, put it to the left of the point and you get $-3^{-n}$ in $\Bbb Z_2$.  Hey presto, it works for $-\frac13$ and $-\frac19$ so why not?  But if I take $x=\overline{000010010111101101}_2$ I can see that $x+512x=-1$, so I get $-\frac1{513}$ in $\Bbb Z_2$.  It is at least a multiple of $\frac13$, but not the one I was expecting.  In general it would seem we get $\dfrac{-1}{2^{3^{n-1}}+1}$ by my naive method, which coincides for the two first cases - because $3$ and $9$ are one away from $2$ and $8$.  I should mention $3^{-n}$ have the peculiar property that one half of the repeating binary string is the inverse of the other.  This problem arose while I was trying to prove that fact - feel free to prove that if you're minded to do so!  How do I correctly calculate an arbitrary rational number such as $-3^{-n}$?

Suppose you have a rational number $0 < r < 1$, and you want to express it in some prime base $p$. Then assuming the denominator r has a periodic expansion in the base, we might ask how the base-p real expansion and the p-adic expansion are related. Messing around with a few examples here has led me to the following conjecture: Conjecture: given some rational $0 < r < 1$ that has a periodic expansion in some base $p$, the period is identical to that of the $p$-adic expansion of $-r$. Examples:  12/13, base 2 real expansion: $0.\overline{111011000100}...$ -12/13, 2-adic expansion: $...\overline{111011000100}$ 12/17, base 3 real expansion: $0.\overline{2010011202122110}...$ -12/17, 3-adic expansion: $...\overline{2010011202122110}$  and so on. This all seems intuitive enough from experimenting around with p-adic solenoids back in the day, which can be thought of as having infinite expansions to the left and right of the radix point, but where all periodic sequences infinite in both directions are equal to zero (for example, in the 2-adic solenoid, $...11111.11111... = 0$. However, I'm not quite sure how to prove this rigorously. Under what conditions does this hold, and how does one prove this formally? Can this be extended to rationals outside of the range mentioned?


I have a WMV file which I converted from streaming from a camcorder via a firewire port.  This worked perfectly before and I could watch it from start to finish in the past, as well as seek to any location in any video player.  What I've noticed today is, when I play it, I can only watch the first 3 hours, it won't let me watch the last hour in Windows Media Player.  Even worse in Media Player Classic, it will only let me watch the WMV if I watch it from the start, so I can't seek to 2 hours into the video and watch from there.  Anyone know if this is a common issue on WMV's or my file has just become corrupted?

Whenever I try to play .wmv in an media player, it won't start playing by itself. When I slide the bar a little further only then it does. Could be the .wmv file corrupted from the beginning? How can I check this to make sure if it is?


While watching videos online I've heard multiple brits pronounce "drawing" as "drawring". What dialect does that? Please contribute more examples of this as well, as that is the only one I can currently think of.

If I say two words consecutively, with the first ending in a vowel sound and the second starting with one, when is it correct to include a non-existent r between those two words?  Examples from phrases I've heard:        I saw (r)a movie   They saw (r)us   Law (r)and order   That's the idea, (r)anyway.      I heard the last one in the movie Edge of Tomorrow yesterday.  Is this grammatically correct? If so, is the omission of the r grammatically incorrect? Are there any rules regarding this?


I need to use something that looks like a 2 by n matrix as inline math.  How can I achieve this without it pushing the lines apart?  Example:  \left(\begin{array}{cccc} 1 & 2 & \dots & N \\ i_1 & i_2 & \dots & i_N \end{array}\right)     The problem with this code is that it takes as much space as display math would even when used as inline math.  I would like it to take no more space than a \frac{...}{...} or \binom{...}{...}.

This is my minimal example, the problem is the different size of the two x. I would expect the matrix to be shrunken too, but it isn't. Why is this and how is it corrected?  \documentclass[a4paper,12pt]{article} \begin{document} $\frac{\begin{pmatrix}x\end{pmatrix}x}{2}$ \end{document}   edit: I just realized: this is not matrix specific. \underbrace does it too. seems like the information to be smaller doesn't get through these "frames":  \documentclass[a4paper,12pt]{article} \begin{document} $\frac{\begin{pmatrix}x\end{pmatrix}x}{2}e^{\begin{pmatrix}x\end{pmatrix}x}\int_{\begin{pmatrix}x\end{pmatrix}x}$ $\frac{\underbrace{x}x}{2}e^{\underbrace{x}x}\int_{\underbrace{x}x}$ \end{document}


I did the following:  >>> a=10 >>> id(a) 31817408L >>> >>> id(10) 31817408L   So, we can see that id(a) equals id(10)  Now,i do  >>>a='what is this' >>> id(a)    35412416L >>> >>> >>> >>> id('what is this')    31951968L   why in this case id(a) not equal to id('what is this')? What is actually happening behind the scenes?

Why does the following behave unexpectedly in Python?  >>> a = 256 >>> b = 256 >>> a is b True           # This is an expected result >>> a = 257 >>> b = 257 >>> a is b False          # What happened here? Why is this False? >>> 257 is 257 True           # Yet the literal numbers compare properly   I am using Python 2.5.2. Trying some different versions of Python, it appears that Python 2.3.3 shows the above behaviour between 99 and 100.  Based on the above, I can hypothesize that Python is internally implemented such that "small" integers are stored in a different way than larger integers and the is operator can tell the difference. Why the leaky abstraction? What is a better way of comparing two arbitrary objects to see whether they are the same when I don't know in advance whether they are numbers or not?


I was just thinking about this when I typed out "processes" and realized that I've heard it pronounced both "process-izz" and "process-eez".  Is one incorrect, or is it considered an accent thing, or are they both completely acceptable?  I also thought of words like "parentheses" and "menses" as being strictly -eez but can see how those may be special exceptions.  Are there any other questionable words like this?

What is the correct pronunciation of the word processes? I am confused because my mother tongue is not English, and in my company some say it as "process-eez" and some say it "process-ess".


Is it possible to create two commands \disableOverfullWarnings and \enableOverfullWarnings that respectively disable and enable the printing of messages such as      Overfull \hbox (12.92616pt too wide) in paragraph at lines 157--158 ...   in the console (in the output of pdftex)?  Thanks  PS: If not possible, is it possible to disable all warnings for some part of the document?    EDIT: This is not a duplicate of  .

I want LaTeX not to give warnings for overfull hboxes up to some maximum of say 2 pts. How to achieve this?