I'm absolutely new to ubuntu. I'm going to program java using eclipse, so I extracted file "eclipse-standard-kepler-SR1-linux-gtk-x86_64.tar.gz" in some folder, and tried to run "eclipse" in the extracted folder.  But it showed the following message:  "Could not display eclipse.    There is no application installed for 'executable' files. Do you want to search for an application to open this file?"   I clicked "yes" and installed "pypar2" as its recommendation. But still I cannot execute this file.  What should I do to start using eclipse?  Can anyone please help me?
I installed Ubuntu 15.04 on the VM and I have downloaded Eclipse Luna. When I try to install it, this error occurs:      An error has occurred.   See the log file   /home/master/.eclipse/1473617060_linux_gtk_x86_64/configuration/1442224462970.log   Can you help me to fix  it? Thanks
A field extension of prime degree Suppose that $E$ is an extension of $F$ of prime degree. Show that $~~\forall~ a \in E : ~ F(a)=F$ or $F(a)=E$   Attempt: Suppose that $E$ is an extension of a field $F$ of prime degree, $p$. Therefore $p = [E :F] = [E : F(a)][F(a) : F]$. Since $p$ is a prime number, we see that either $[E : F(a)] = 1$ or $[F(a) : F] = 1$.   Now, $[E : F(a)] = 1 \implies $ there is only one element $x \in E$ which forms a basis and every element in $E$ is generated by $x$ i.e. $E = \{x~c~|~ c \in F(a)\}$  $[F(a) : F] = 1 \implies $ there is only one element $y \in F(a)$ which forms a basis and every element in $F(a)$ is generated by $y$ i.e. $F(a) = \{y~d~|~ d \in F\}$  Have I inferred it correctly? How do I move ahead?  Thank you for your help. Where can I find good literature for beginners? I am trying to find some database tutorials,books and similar, since I have started this course in college, and received some material, but it is really hard to manage through all the info on the net. I searched through the questions on the site but didn't find any. Thankfull for all your input. Sphere rolling up a ramp In this question, I did energy conservation, with the states being the initial one and the one where it is at the top , and I got $$ .5 I w^2 + .5 mv^2 = mgh$$ However, in  the answer key they have done, $$ .5 mv^2 + .5 Iw^2 = .5 Iw^2 + mgh$$ Now why would the k.e be turned to p.e but not the rolling energy?? Is there an official list of Disney Princesses? Sum of points and rank according to points Test -n gives unexpected result I understand test -n &lt;expression&gt; to return false if the expression evaluates to a string length of greater than 0.  Why then does the following happen?  Macbook:~ echo ${#undeclared_variable} 0 Macbook:~ test -n $undeclared_variable &amp;&amp; echo Foo Foo   Bash 4.x  My expectation is that since test -n $undeclared_variable should evaluate false, that Foo should not be echoed.  If I use [[  ]] instead of test, it works as expected. Why gravity is an attractive force? Why gravity is an attractive force?     One may say that it is because of space time curvature but General Relativity is built on this law: $\displaystyle G \frac{m_1 \times m_2}{r^2}$ (To be more precise, it is  from it's potentiel form known as  that can be written like this: $\nabla \cdot g = - 4\pi Gp  $). So GR can't explain why gravity is attractive. General Relativity only explains how gravity occurs in terms of space time.    Another may stick with the Quantum theory stating that gravitons are responsible for the force of gravity, but why a massless particle with spin 2 will exchange positive momentum? In other words, can I do something like  for() {     for {        for {        }     } }   Except N times? In other words, when the method creating the loops is called, it is given some parameter N, and the method would then create N of these loops nested one in another?  Of course, the idea is that there should be an "easy" or "the usual" way of doing it. I already have an idea for a very complicated one. We have a SQL Server 2012 instance that contains a database with data for many product lines.   We are looking for a way to take subsets of this data into another database on the same instance.  This doesn't have to be continuous as we are looking for ways to make it easy to export backups of the subsets that we can send out to vendors (we have a company that loads this data into their own sql server to produce a product we sell, naturally its huge and we want to trim it down to just the product lines they work with on a regular enough basis) or use to load SQLite DB's for use with offline applications.  ProductDB - the superset of all product line data.  ProductLine1DB - A subset identical in structure to ProductDB, but with data only relevant to product line 1.  ProductLine2DB - A subset identical in structure to ProductDB, but with data only relevant to product line 2.  This can be done nightly, weekly, as often as we need to but not a continuous replication.  We don't want to add in distributor servers or even extra subscriber servers. We would like the replication to happen on the same server with the subscriber databases being on the same server.  Is this a good candidate for transactional replication?  Why or why not?  We obviously have other options to load this data, but it seems like this might be a good case to use something like transactional replication. I've heard its powerful but prone to issues when not setup optimally.  Note: I am not a DBA, simply a developer, but we are currently looking for a new DBA and some of us are taking over duties like this temporarily. What is the best method of re-rendering a web page on orientation change? Where's my 5 minute grace period gone? I just posted an answer. (Revision history .)  I edited it a few seconds later (within my 5 minute grace period), and it comes up as a new revision!? Why?    ^^You can see 'answered 1 min ago', and then 'edited 1 min ago' - how is that possible?  Additionally, !?    I don't think this is a dupe of . See my comments on AI.E's answer. If you're a mod, it will really help. Inspired by a , here's a list of the 'etymology' for the  hats. For pictures and a list of criteria, see  instead.  The list is a community wiki; feel free to edit it if you have more information about a hat. If you like to do some research, most hats have been featured in earlier editions, so you might be able to find more information in old Meta Stack Exchange questions. Can you provide me historical examples of pure mathematics becoming "useful"? I am trying to think/know about something, but I don't know if my base premise is plausible. Here we go.  Sometimes when I'm talking with people about pure mathematics, they usually dismiss it because it has no practical utility, but I guess that according to the history of mathematics, the math that is useful today was once pure mathematics (I'm not so sure but I guess that when the calculus was invented, it hadn't a practical application).  Also, I guess that the development of pure mathematics is important because it allows us to think about non-intuitive objects before encountering some phenomena that is similar to these mathematical non-intuitive objects, with this in mind can you provide me historical examples of pure mathematics becoming "useful"? Local colormaps in global coordinate system I am trying to get a surface graph with two colormaps.  Instead of using the full Z range i want to give the first surface its own colormap  and the second surface should receive its own colormap too (it may be even the same)... however the current version takes the full range of Z-Data and calculates the colormap. Is there any way?  \begin{tikzpicture}     \begin{axis}[grid = major, colormap={bw}{gray(0cm)=(0); gray(1cm)=(1)}, view={-30}{15}]   \addplot3[surf]    table     {DATA1.dat};   \addplot3[surf]    table     {DATA2.dat};  \end{axis} \end{tikzpicture}   Right now it looks like that:   I want each of the surface to be scaled individually... just to see more clearly how the amplitude changes :)  Any ideas?  Thanks, Alex Transforming Differential Equation to a Kummer's Equation I'm trying to transform an equation of the form $$ yw^{\prime\prime}(y) - [b - ay] w^\prime(y) - [d + ey]w(y) = 0 $$ into the form of a Kummer's or confluent hypergeometric differential equation: $$ y w^{\prime\prime}(y) + [f - y] w^\prime(y) + g w(y)  = 0 $$ I know it may have something to do with merging two of the singularities of the original equation, and maybe doing something with $y$, making it $\frac{y}{b}$ and taking b to infinity, but I don't know and can't find the details for this process, and for my equation specifically. There's not too much difference between the two but just enough so that I can't get it. Thanks in advance for any help! Network-wide HTTPS: It's time Can I use a one time pad key twice with random plaintext? I understand the basics of OTP: $|\text{key space}| = |\text{plaintext space}|$ implies perfect security, key reuse destroys this.  Cryptanalysis on the $N$-Time Pad for $N &gt; 1$ involves finding patterns in the ciphertext; this, however, all seems based on the premise that patterns exist in the plaintext (e.g. English language).  My question is: if $m_1$ and $m_2$ are two truly random strings, and they are both encrypted with the same OTP key to yield $c_1$ and $c_2$, is it possible to recover $m_1$ and $m_2$ from $c_1$ and $c_2$?  In other words: while "perfect security" (aka perfect indistinguishability) is obviously lost (constructing a distinguisher for two messages is trivial), is the plaintext still safe? I get these weird characters when I try to print out a vector element! I recently updated my profile bio (from Arqade) and clicked 'Save and copy changes to all public communities'. This appears to have broken/reset my profile picture on all but Arqade. Note that I did not update my profile picture as part of my changes. Arqade:  Meta SE for comparison:  I haven't touched my profile picture in years. Is this a bug?  Update: It appears my profile pic across all communities has been set back to 'Identicon'. I went on to Stack Overflow and changed my profile picture back to 'Gravitar' and clicked 'Save and copy to all communities' again, but this did not update my profile picture anywhere but SO. (I did the same on Sustainability to be doubly sure). Update 2: This is a persistent bug - I had changed most of my SE communities back to my 'Robotnik' display pic over the past little while. Today I edited my profile again on Arqade, Clicked 'Save and copy' - and the display pic reverted back to identicon again across all sites. Update 3: I have re-uploaded my profile picture and the 'Save and copy' function worked. It appears that this is actually a bug to do with the old images from Gravatar. Facebook: Ways to preserve image quality of uploaded images?