In "Introduction to Mathematical logic" by Elliot Mendelson , page $50$ and $56$ . I couldn't understand why they sometimes use double subscripts . For example , in page $50$ :  "We shall often indicate that some of the variables $x_{i_1},..., x_{i_k}$  are free variables in a wf $\mathscr B$ by writing $\mathscr B$ as $\mathscr B(x_{i_1},..., x_{i_k} )$ This does not mean that $\mathscr B$ contains these variables as free variables, nor does it mean that $\mathscr B$ does not contain other free variables. This notation is convenient because we can then agree to write as $\mathscr B(t_1,..., t_k)$ the result of substituting in $\mathscr B$ the terms $t_1,..., t_k$ for all free occurrences (if any) of $x_{i_1} , ... , x_{i_k}$ respectively."  Here , I didn't understand why they used double subscript notation in $x_{i_1},..., x_{i_k}$ instead of single subscript notation like in $\mathscr B(t_1,..., t_k)$ . In page $56$ :  "Moreover, instead of talking about the $n$-tuples of objects that satisfy a wf that has $n$ free variables, it is much more convenient from a technical standpoint to deal uniformly with denumerable sequences. What we have in mind is that a denumerable sequence $s = (s_1, s_2 , s_3 , ... )$ is to be thought of as satisfying a wf $\mathscr B$  that has ${x_j}_1 , {x_j}_2 ,  ... , {x_j}_n$ as free variables (where $j_1 < j_2 < ... < j_n$ ) if the $n$-tuple $\langle {s_j}_1 , {s_j}_2 ,  ... , {s_j}_n \rangle$ satisfies $\mathscr B$ in the usual sense."  Again , they used Double subscript notation in ${x_j}_1 , {x_j}_2 ,  ... , {x_j}_n$ but also there is this condition $j_1 < j_2 < ... < j_n$ . This just adds to the confusion to me because I don't understand at all why do they use Double subscript in the first place (To the point that it seems completely unnecessary. Now , I am completely new to subjects like first order logic and model theory , so I might struggle sometimes with the significance of some notation which actually has a good technical reason for using.This might be the case for this one as well.Can someone tell me the deep technical reason why we use double subscript sometimes below variables? (It could be possible that there are multiple reasons)

In "Introduction to Mathematical logic" by Elliot Mendelson , page $59$ . I couldn't understand the basic preliminary notations for the rigorous definition of Satisfiability. For example , at a line they said, "Moreover, instead of talking about the $n$-tuples of objects that satisfy a wf that has $n$ free variables, it is much more convenient from a technical standpoint to deal uniformly with denumerable sequences. What we have in mind is that a denumerable sequence $s = (s_1, s_2 , s_3 , ... )$ is to be thought of as satisfying a wf $\beta$ that has ${x_j}_1 , {x_j}_2 ,  ... , {x_j}_n$ as free variables (where $j_1 < j_2 < ... < j_n$ ) if the $n$-tuple $\langle {s_j}_1 , {s_j}_2 ,  ... , {s_j}_n \rangle$ satisfies $\mathscr B$ in the usual sense." I didn't quite understand why they used ${s_j}_1$ and ${x_j}_1$ instead of $s_1$ and $x_1$ . Maybe there is a critical detail I am missing out? Also , Another passage for the rigorous definition: "Let $M$ be an interpretation of a language $\mathscr L$ and let $D$ be the domain of $M$. Let $\sum$ be the set of all denumerable sequences of elements of $D$. For a wf $\mathscr B$ of $\mathscr L$ , we shall define what it means for a sequences $s= (s_1, s_2, ... )$ in $\mathscr L$ to satisfy $\mathscr B$ in $M$. As a preliminary step, for a given s in $\sum$ we shall define a functions $s^*$ that assigns to each term $t$ of $\mathscr L$ an element $s^{*}(t)$ in $D$." They did say that for each $s = (s_1, s_2, ... )$ , there is a defined function $s^*$ , but even after further reading the text afterwards , I still did not understand how exactly $s^*$ is defined from $s$ . Can someone tell me where the gap in my understanding here is?


By creating a Console application (Console Application) with .Net; Netstat -a -n command via Windows cmd will read the output and write a "json" file type application in the following format, where the port and its Associated Address (Foreign Address) are only foreign ip,

How do I invoke a console application from my .NET application and capture all the output generated in the console?   (Remember, I don't want to save the information first in a file and then relist as I would love to receive it as live.)


Let $a\in G$, where $G$ is a group. Prove that $a$ commutes with each of its conjugates in $G$ if and only if $a$ belongs to an abelian normal subgroup of $G$.   This is what I did:  $"⟹"$   First, I thought  of $<a>$ to be that normal subgroup containing a. But if it is true, I am not sure how to prove it. Then I thought of another subgroup, namely $C_G(a)$.   I conclude from the hypothesis given that $Cl_G(a) ⊂ C_G(a)$  And I know that  $|Cl_G(a)| = |G :  C_G(a)|$ by G acting transitively on $Cl(a)$ by conjugation. But I don't know how to get that $ C_G(a)$ is normal in $G$.  I am thinking also of  a normal subgroup of $G$ , say $K$ containing $a$, so  $<a>$ $\cap$ $K$ and  $ C_G(a)$ $\cap$ $K$ are subgroups of G inheriting abelianity from   $<a>$  and $ C_G(a)$ respectively, and normality from $K$.  $"\Leftarrow"$   Let $a ∈ H$ s.t. $H$ is an abelian normal subgroup of G. So $ah=ha$, ∀ $h∈H$.  Since $H$ is normal in $G$, hence $g^{-1}hg ∈ H$, ∀ $g∈G$   So $g^{-1}ag ∈ H$, ∀ $g∈G$   Which means     $Cl_G(a)$ $\subseteq$ $ H$  Therefore, a commutes with each of its conjugates in G.  Could someone correct me?

Let $a$ be an element of a group G. Prove that $a$ commutes with each of its conjugates in $G$ iff $a$ belongs to an abelian normal subgroup of $G$.   My Try:  I proved the backward direction. For forward one, given $g\in G, a(gag^{-1})=(gag^{-1})a$. I was trying to prove that $a\in Z(G)$. In order to prove that, I must show that $ag=ga$. But failed. Am I on the right track? Can anybody please give me a hint? I want to try it myself.


In photoelectric experiment, we always keep the work function constant. It seems to me that as the metal plate loses its negative charge, it may take more energy to pick up an electron off the surface of the conductor.  Is my intuition correct? And if so, does the maximum kinetic energy of photoelectrons decrease with time?

In a photoelectric effect we remove electrons from a metal using high energy photons, the work function is the minimal energy required for this effect.  My question is why doesnt the work fucntion depended on time? The more electrons we take out from the metal, the more ionized it becomes (if we remove a lot of negative charge, it will turn positive), and as a result we would expect to need more energy for this effect (the possitive charge of the metal would make it harder to remove the remaining electrons).  Why does the work function remains constant no matter how much electrons we take out?


The problem is,  Find all continuous functions $f: \mathbb{R} \to \mathbb{R}$ such that if $x-y$ is rational, $f(x)-f(y)$ is rational.  I was thinking that only constant functions would work. How would I prove this??

Find all the continuous functions $f:\mathbb{R}\rightarrow \mathbb{R}$ such that if $x-y\in \mathbb{Q}$ then $f(x)-f(y)\in \mathbb{Q}$.   Can somebody give me some hint to solve this problem. I think that the functions are $f(x)=mx+b$ where $m\in\mathbb{Q}$.  Thanks!


I am using Quick OSM in QGIS 3.12.3-București. When I 'Run query' for a specific geocodeArea, eg London, and I specify the 'Key', eg Highway, but I leave the 'Value' blank; (img 1). The result is one layer in QGIS with all of the Values of highway on it; (img 2) (well its 3 layers - Nodes, lines and hatches. but for the sake of this question, let's just say it's one layer). What I would like to achieve is to have all of the Values for the Key (eg highway) to be on individual layers in QGIS. So I can avoid having to 'run query' for each and every value of 'highway'. As this is a laborious process and there must be a faster way. I have looked into the 'Overpass query' method, but iv'e only found it gives me the same result of everything in one layer. Is there a piece of code I can add into the Overpass query to tell it to load the values on to separate layers? Or is there a way to split the layer after it has been loaded, into separate layers of the Values of the Key?

I have a polyline shapefile with about 20 kinds of roads. I would like to know how can I create automatically a vector file for each one. I am aware of how to do it using ArcGIS Desktop - see  How do I do it using QGIS or SAGA?


I want to show some nicely formatted source code, e.g.:  er ist ein bisschen ein ötto geworden   My document:  \documentclass[a4paper,10pt,ngerman]{scrartcl} \usepackage{babel} \usepackage[T1]{fontenc} \usepackage[utf8x]{inputenc} \usepackage[a4paper,margin=2.5cm]{geometry} \usepackage{listings}  \begin{document} Ünnormal diggi hä \lstinputlisting[language = python]{testinclude.txt} \end{document}   The text outside the listing works, but the txt file produces the error Package utf8x Error: Character182appearedalone.  How do I show code that contains special characters?  Like  suggested, I tried escaping the ö or setting a literate to \''o, but both times I only got this in utf8 and utf8x:

I'm having some problems with listings and UTF-8 in my document. Maybe someone can help me? Some characters work, like é and ó, but á and others appear at the beginning of words...  \documentclass[12pt,a4paper]{scrbook} \KOMAoptions{twoside=false,open=any,chapterprefix=on,parskip=full,fontsize=14pt}  \usepackage[portuguese]{babel} \usepackage[utf8]{inputenc} \usepackage[T1]{fontenc} \usepackage{listingsutf8}  \usepackage{inconsolata} \lstset{     language=bash, %% Troque para PHP, C, Java, etc... bash é o padrão     basicstyle=\ttfamily\small,     numberstyle=\footnotesize,     numbers=left,     backgroundcolor=\color{gray!10},     frame=single,     tabsize=2,     rulecolor=\color{black!30},     title=\lstname,     escapeinside={\%*}{*)},     breaklines=true,     breakatwhitespace=true,     framextopmargin=2pt,     framexbottommargin=2pt,     extendedchars=false,     inputencoding=utf8 }  \begin{document} \begin{lstlisting} <?php  echo 'Olá mundo!'; print 'Olá mundo!'; \end{lstlisting}  \end{document} \end{lstlisting}


I am a 2nd year math PhD student. If one specializes in pure math (say dynamical systems with no particular real-world application in mind), how difficult can it be to transition into industry after the PhD? What are measures one can take to make this a smooth transition? I am not particularly interested in applied math at the moment, but I'm not too optimistic about the future of the pure mathematician (unless he/she solves some Millennium Prize Problem!!). I would like to think that I have the option of switching from academia to industry if I had to. I am haunted by words of one of my undergrad math professors: "No one should major in pure math. You major in applied math and you continue to study pure math if you're interested in it."  I have a M.A. in math, and my thesis was concerned with estimating the fractal dimension of sets arising in dynamical systems. My ideal profession with a PhD in math would be to teach and to do research. My research need not be limited to pure math.

I'm interested in mathematical research, but want to know if there are good jobs besides being a professor.  Are there any lucrative research-centric careers out there for someone with a PhD in pure mathematics?


So I bought my iPod from someone, and their iCloud account is still on here, which means the pictures I take and everything, they can see. I just noticed this and I tried to delete it, but it asks me to put in a password to turn off "find my iphone" and I do not have that password because it is someone else's iCloud account.

I bought a used iPhone 5 today. When I insert a Nano SIM and try to activate it, it says the previous user has locked the phone and that I need to insert a number to get it unlocked.  I bought the phone through an online site olx.com so I am not able to get in touch with the person to get it unlocked.  I hope that the phone was not stolen and sold to me. I have the bill of the phone, the charger, and knowledge that the device is still under warranty.  Any idea on how I can gain access to the device?


Say we have the following problem ():      Bobo the amoeba has a 25%, 25%, and 50% chance of producing 0, 1, or 2   offspring, respectively. Each of Bobo’s descendants also have the same   probabilities. What is the probability that Bobo’s lineage dies out?   You can probably the probability of extinction $p$ as  $$p = \frac{1}{2}p^2 + \frac{1}{4}p + \frac{1}{4}$$   Which if you solve leads to solutions 1 and .5. That said, why is the "correct" answer 1/2?  There is a discussion of a similar problem on some of the comments on this thread (), but I don't really understand the reasoning, especially since in this problem we don't have a root above the value of 1.   Thoughts?

I was asked this question during an interview for a trading position with a proprietary trading firm. I would very much like to know the answer to this question and the intuition behind it.  Amoeba Question:  A population of amoebas starts with 1. After 1 period that amoeba can divide into 1, 2, 3, or 0 (it can die) with equal probability. What is the probability that the entire population dies out eventually?


I'm trying to make some LED lamp but the EMISSIVE feature doesn't react as I expect. I read on the Blender manual that the emission power is defined in Watts per Square Meter. It doesn't really seem to work the right way. From 0 to 1 it works well, but then, raising it to 10, it's not decuplicating the light, and even shooting it to 100000 won't really change much. You can see in the images how the change from 1000 to 10 millions doesn't change anything in the final image. For a test, I added an area light on top of the emissive model, and a 1 W light assigned to it makes faaaar more light than the emissive material. You can see the difference in the final image. What may be happening here? Now, I may trick and just use the area lamp, but I want to know what is happening so to know how to work in the future.        Real world sizes. Emissive surfaces are exposed, nothing in between. Actually, Eevee is not really lighting anything with the model, it just adds glow, a lot of it XD Tried in a brand new scene, same problem: emissive power doesn't do anything past a certain threshold. It looks like the power is logarithmic. You can download it here:  Also added the original file:

Since two or three month I'm building a Titanic Model in Blender 2.74. I'm using Cycles Renderer and a GTX750TI for rendering.  On A-Promenade I built the Windows with a Diffuse-Material for Frame, a Glas-Material for (guess what!) the Glas and an Emission-Material on the Backside of the Window. This works pretty well and makes a nice light on this Deck.     But I also need some white light from Lamps so I built these Lamps in a Diffuse- (For Frame) and an Emission-Shader (For "illuminated" Glass) but I get no light from the Emission of the Lamp-Material.     When I turn off the Emission from Windows the whole Deck is black (except the Faces themselve). Even if I set the Strength from Lamp Emission to 100000 or more there would be no light.   I don't want to add a Point-Lamp for every Lamp I built so what else can I do?   Here's the simplified .blend File:


I am visiting Iceland in July and am interested in knowing how difficult it will be for an English and Spanish speaker to navigate the country?

We're going to Iceland for the first time in September. Will we be able to get around ok just speaking English, or should we try to learn some rudimentary Icelandic? And is that even what their language is called?


I am applying for jobs and certain job postings specifically "welcome applications from" certain groups that "contribute to diversification."   I am in one of these groups that they state, but you have to get to page 4 of my CV or page 2 of my teaching statement to find out.  Why are they especially welcoming these groups? Is there part of their evaluation criteria that considers this diversification? Should I make the committee more aware of my belonging to such a group? If so, how?  [Nota bene: This is a North American job.]

I was browsing PhD position offers in Europe on different websites and I was quite surprised to find that several offers contained sentences such as     University of X value equality and diversity. We strongly encourage women and BAME applicants for this position.    where BAME stands for Black, Asian and Minority Ethnicities; or     The research group aims to increase the number of women in scientific positions. Female candidates are therefore encouraged to apply.   Is it considered normal in the academic environment to discriminate between  candidates according to their race and/or gender for "egalitarian" reasons?   How is the choice of a candidate based on their gender and/or race considered "egalitarian"?


Why does smaller f-number imply greater aperture diameter and consequently, greater amount of light entering the lens of a camera?  As evidenced from my study across a number of resources, an absolute statement is:  A smaller f-number means greater amount of light being allowed in, and vice-versa.  The f-number is, after all, the ratio of a lens's focal length to the diameter of the aperture. Now, if the aperture diameter is kept constant and the focal length is just decreased, that would, in turn, reduce the f-number too.  Yet, in this case, the lens's f-number is reduced, which as per theory, should allow greater amount of light into the system (as evidenced by all theory I've read stating that smaller f-numbers mean greater light being allowed in).  But, ultimately, I believe the amount of light being let in is controlled by the diameter of the lens aperture that does remain constant.  Can someone explain this concept to me?

I'm trying to wrap my head around the math/physics of how illuminance on the film/sensor plane remains equal for a given f-number regardless of the focal length of the lens.  Since a longer lens will have a larger entrance pupil at a given f-stop than a shorter lens at the same f-stop, how can the light falling on the film/sensor be equivalent?  Empirically, I know this to be true.  Say I take an incident meter reading (not reflected/TTL) off my subject, and get f/5.6 at 1/100s, I'll get proper exposure at the point at which i took the meter reading with that setting whether I use a 50mm lens or a 200mm lens (obviously composition will be different).    Wikipedia's  reads:     A 100 mm focal length f/4 lens has an entrance pupil diameter of 25   mm. A 200 mm focal length f/4 lens has an entrance pupil diameter of   50 mm. The 200 mm lens's entrance pupil has four times the area of the   100 mm lens's entrance pupil, and thus collects four times as much   light from each object in the lens's field of view. But compared to   the 100 mm lens, the 200 mm lens projects an image of each object   twice as high and twice as wide, covering four times the area, and so   both lenses produce the same illuminance at the focal plane when   imaging a scene of a given luminance.   I'm not sure I agree with the explanation on wikipedia.  The film/sensor doesn't care how big the image is that falls outside the bounds of the sensor; the film/sensor "sees" what it sees, and that's it.


I have a solution for a problem in my country. I decided to make a small project about it, not a startup. I need some advice about my project (which kind of server should I rent, for example). Should I ask it on Stack Overflow? My question has no code.

Stuff like polls, recommendations based on subjective constraints, puzzles, webcomics etc. do not belong on the serious main SE sites, where professionals should be considered at work and having just a few spare minutes ("code's compiling") to answer questions, so they should not be distracted by such things. However, I'd also like to have a home for these things still using the SE engine. For the reason I mentioned before, this needs to be a separate place though. Let's call it four.[sitename-here].com.


for (int i = 0; i < arrayP.size(); i++) {          if (arrayP.get(i) == What to put here?) {               arrayP.remove(i)         } }   If I put i+1 it just compares side by side. How can I get it to run through each element?   Element 1 then run through the whole ArrayList. Then element 2 run through ArrayList.

How could I go about detecting (returning true/false) whether an ArrayList contains more than one of the same element in Java?  Many thanks, Terry  Edit Forgot to mention that I am not looking to compare "Blocks" with each other but their integer values. Each "block" has an int and this is what makes them different. I find the int of a particular Block by calling a method named "getNum" (e.g. table1[0][2].getNum();


I wanted to do a little cleanup in Gaming, and set off to search old closed questions other than exact duplicates, which would be candidates for deletion.  I was unable to find a way to specifically search for that, as searching for closed:1 doesn't let me exclude the duplicates which I don't want to delete.  The only option I had was to click on every result to see in the question what the close reason was.  Could we have an advanced search option, or a section in the mod tools, that would allow me to search all closed questions that are not duplicates?

I often search for closed questions and sift through the ones that are not duplicates to see if any of them need to be killed. Technically, closure is the first step towards deletion and the only closed posts that are actually useful are duplicates (unless it's a crappy one).  For the rest, if the community hasn't bothered to reopen it after a while or if the OP has made no effort to edit their question, I delete it if it has no redeeming content. For example, the only closed posts seen on  are exact dupes.  But this does become tedious when there are several results for various close reasons with duplicates interspersed between them. I'd like to be able to search as:  closed:1 duplicate:0   so that it gives a list of questions closed as OT/NaRQ/NC/TL. This will be similar in behaviour to migrated:0|1.   This will also be useful for 10k+ users on all sites (2k+ in beta) in the network, especially SO, so that they can search for questions to spend their delete votes on— especially closed, non-dupe questions in the tag they specialize in. More often than not, I hesitate to vote on questions that are outside my area of interest (unless it is crappy).


I'm currently trying to write a function in my bash script that does the following: Take in a file as an argument and calculate the sum of the numbers within that file. I must make use of a for loop and the bc command.   Example of values in the file (each value on their own line):  12 4 53 19 6   So here's what I have so far:  function sum_values() {   for line in $1; do   #not sure how to sum the values using bc   done }   Am I on the right track? I'm not sure how to implement the bc command  in this situation.

I am looking for a command that will accept (as input) multiple lines of text, each line containing a single integer, and output the sum of these integers.  As a bit of background, I have a log file which includes timing measurements. Through grepping for the relevant lines and a bit of sed reformatting I can list all of the timings in that file.  I would like to work out the total. I can pipe this intermediate output to any command in order to do the final sum.  I have always used expr in the past, but unless it runs in RPN mode I do not think it is going to cope with this (and even then it would be tricky).  How can I get the summation of integers?


I have an unordered map like this:  std::unordered_map<std::string, std::string> wordsMap;   I also have string like this  std::string text = "This is really long text. Sup?";   I'm looking for the fastest solution to split the text string by space and add each word to the unordered map without using third-party libraries. I'll only split it by space, so I'm not looking for solution with changeable delimiter.  I figured out this solution:  void generateMap(std::string const& input_str, std::string const& language) {     std::string buf; // Have a buffer string     std::stringstream ss(input_str); // Insert the string into a stream      while (ss >> buf)         wordsMap.insert({ buf, language }); }   Are there any faster solutions?

I'm trying to iterate over the words of a string.  The string can be assumed to be composed of words separated by whitespace.  Note that I'm not interested in C string functions or that kind of character manipulation/access. Also, please give precedence to elegance over efficiency in your answer.  The best solution I have right now is:  #include <iostream> #include <sstream> #include <string>  using namespace std;  int main() {     string s = "Somewhere down the road";     istringstream iss(s);      do     {         string subs;         iss >> subs;         cout << "Substring: " << subs << endl;     } while (iss); }   Is there a more elegant way to do this?


I am beginner in combinatorics and have been following this book PRINCIPLE AND TECHNIQUES IN COMBINATORICS by CHEN CHUAN-CHONG. In this book the authors improves the relation $R(s,t)≤R(s,t−1)+R(s−1,t)$ for $s,t>2$ to above relation by making a constraint that $R(s,t-1)$ and $R(s-1,t)$ are both even.  I am unable to follow through the author's reasoning for this proof.  Please help.

A cool lemma in Ramsey theory is the following:  $$R(m, n) ≤ R(m-1, n) + R(m, n-1).$$  It is not hard to prove it. However, a friend of mine said that, if $R(m-1, n)$ and $R(m, n-1)$ are both even, then  $$R(m, n) ≤ R(m-1, n) + R(m, n-1)-1.$$  How can I prove it?


i am a beginner in category theory. I like the CoLimit/Limit definition through universal arrows but i am still confused how to relate that thought with the tensor-product definition.  In CWM i found a example of the tensor-product for rings defined through the use of the colimit definition through  universal arrows and i wanted to ask if you could give me the example of the tensor-product R-module definition through universal arrows or the reason why this is not working...

The title says it all: what is the diagram that defines a tensor product?  (I'm using the term diagram here in the  it has in category theory.)  Edit: This question was motivated by the following statement:  "...all limits and colimits are initial objects somewhere, and we can even sort of take the view that all universal properties are initial objects somewhere", from  (@~9:15)  Thanks!


I am currently practicing series and I have come across this problem many times. I know how to prove that $$\large n^{\frac{1}{n}}$$ is bounded by $1$ and by $2$. What I don't know is how to prove its monotonicity for natural numbers without using derivatives and expansions. Can anyone help?

I've been dealing with this problem for almost 2 hours now, with hardly any progress. I'm to prove the following inequality using induction   $$\sqrt[n+1]{n+1}<\sqrt[n]{n}$$ where $n≥3$, $n∈\mathbb{N}$. How can this be done?


consider following,  <body>     <form id="form1" runat="server">         <div>             <input type="text" id="txt1" />             <input type="button" id="btn1" value="Submit"/>                     </div>     </form>     <script>                  $("#txt1").live("blur", function () {             console.log('blur');                         return false;         });          $("#btn1").live("click", function () {             console.log('click');             return false;         });     </script> </body>   Above code will log blur event and click event on trigger of respective events. If click or change something in text box and then click on button btn1 blur and click event will happen respectively.What i want is if blur event is happening because of btn1 then click event should not happen,it should log only blur event,I want to stop click event from happening. How to do this? Can anyone help?

Consider the following:
   something inside the header
   How can I make it so that when the user clicks the span, it does not fire the div's click event?


Why POCO objects are created using classes instead of structs in C#, while POCO is intended to carry only public attributes and not any behaviors?  Do we really need to create a class with get and set accessors? I think structs would be much cleaner and simple to carry object's state.

When should you use struct and not class in C#? My conceptual model is that structs are used in times when the item is merely a collection of value types.  A way to logically hold them all together into a cohesive whole.  I came across these rules :   A struct should represent a single value. A struct should have a memory footprint less than 16 bytes. A struct should not be changed after creation.   Do these rules work? What does a struct mean semantically?


I'm having problems upgrading packages in my Ubuntu 14.04. I retried several time but the problem persists and the message says I should report to developers  The following is my error  Reading package lists... Error! W: GPG error: http://archive.ubuntu.com trusty Release: The following signatures were invalid: BADSIG 40976EAF437D05B5 Ubuntu Archive Automatic Signing Key <ftpmaster@ubuntu.com> E: Encountered a section with no Package: header E: Problem with MergeList /var/lib/apt/lists/archive.ubuntu.com_ubuntu_dists_trusty_main_i18n_Translation-en E: The package lists or status file could not be parsed or opened.   How could I fix this?

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?


Given $f:A\to B$, and $g:f(A)\to A$, show that if $g \circ f = I_A$ and $f \circ g = I_{f(A)}$, then $f$ is one-to-one and $g=f^{-1}$  $I_A$ denotes the identity element in $A$ and $I_{f(A)}$ denotes the identity element of $f(A)$  I want to somehow get from $g \circ f = I_A$ to $\forall a_1, a_2 \in A, f(a_1)=f(a_2)\implies a_1=a_2$  I'm pretty lost...

For nonempty sets $A$ and $B$ and functions $ f: A \to B$ and $g: B \to A$, suppose that $ g \circ f = i_A$. Prove that if $f$ is onto, then $g$ is $1-1$.   Here is what I started, I don't think it's correct.   Suppose $f$ is onto  i.e for each element $b \in B$ there is an element of $a\in A$, $f(a)=b$. (definition of onto).   Let $y,\ z$ be any two elements of $B$.Then $y=f(a)$ and $z=f(b)$ for some $a,b \in A$.   If $g(y)=g(z)$, then $g(f(a)) = g(f(b))$,which implies that $a=b$, so $f(a)=f(b)$, so $y=z$.   Thus, whenever $g$ maps $y$ and $z$ to the same element in $A$, $y=z$, so $g$ is one-to-one.   PS: New to proof writing, any constructive criticism is much appreciated.


I'm looking for a story which has these elements: There is an alien species whose biology compels it to reproduce every couple of years, and they don't have a choice about it.  As they develop technologically, the population rises faster and faster until civilization falls again and a period of darkness comes to the world.  They try various ways to prevent it - drugs, infanticide etc, but they've never been adopted by the whole world, so civilization keeps rising and falling.  There is also some mention of different varieties of the aliens - soldiers, medics, etc. and perhaps trying to eliminate certain versions to reduce the population pressure.  The story takes place during a period of high technology.  The main characters stumble on an ancient subway line which has somehow survived.  I read it in the 90s, but it could have been written quite a while earlier.

I read this book when I was a teenager, or in my early twenties, so that puts it no later than 1979. My favorite authors at the time were (of course) Asimov, Bradbury, Clarke, Heinlein, and a few others. I've looked up the bibliographies of most of these, to no avail.  The story in general: Earth people spot a small alien craft near the sun.  Investigating, they find a lone passenger, a female pilot from an alien race, whose distinguishing characteristic is that her hands are claws of two different sizes: one large, one small.  She is suspiciously quiet about how she got there (I think).  Examining the video footage, they find that, as the Earth ship approached, she jettisoned four other passengers into the sun.  There is much talk about sexual practices (which makes me think Heinlein).  Earth society is going through another "sex is sinful" stage, but the alien female has a biological imperative to breed; if she doesn't have sex, she'll die.  Since her shipmates are gone, she keeps getting sicker.  They return her to her own world, and find that there are five different races, all of which build a fully-integrated society.  The creatures are of different size, shapes and colors, but all have the same mismatched claws.  One breed of alien is like a technician, and, for example, while waiting outside by the car (which are a story in themselves), he or she uses the larger claw as a tool to repair, upgrade, or modify the vehicle.  All of the aliens are capable of things like this, so there are no businesses to take care of it.  Basically, everyone does everything, if I recall correctly.  I don't remember the resolution of the story, and probably for that reason it's been bothering me for several months. If this sounds familiar to anyone, please let me know the title and author, and if I can download a digital copy somewhere.


In order to set the level until which (sub)sections are numbered, a user can set up the counter secnumdepth. \setcounter{secnumdepth}{whatever}  The trick works completely fine. However, if you try to increase the depth of the enumeration (for example up to 4), the change is not reflected in the Table of Contents at the beginning of the document. Specifically, it continues to show just the old depth of Chapter-Section-Subsection. No subsubsections appear How to add the numeration automatically in the Table of Contents?

So we have something like:  \documentclass{article} \setcounter{secnumdepth}{2} \setcounter{tocdepth}{2} \usepackage{amsmath}  \begin{document}  \tableofcontents  \section{Brushless Motor Fundamentals} \subsection{Brushless Motor Operation} \subsubsection{DC Motor Operation} Torque is generated in DC motors from the magnetic force, also known as the Lorentz force, which is produced when an electric current is passed through a coil in a magnetic field. This force is given by $F=q[E+(v\times B)]$, where $F$ is the force perpendicular to the coil, $E$ is the electric field in the coil, $B$ is the magnetic field, and $v$ is the velocity of the charged particles in the coil. From mechanics, torque is $\tau=F\times r$.  \section{Brushless Motor Fundamentals 2} \subsection{Brushless Motor Operation} \subsubsection{DC Motor Operation 2} If the electrical force is ignored and the remaining magnetic force is used, with the assumption that $v$ is perpendicular to $B$, we find that $\tau=qvBrsin\theta$.  \end{document}   How to show subsubsections and paragraphs in TOC?


How can we calculate the Integral $\displaystyle \int \ln\left(1+2a\cos x+a^2\right)dx\;,$ where $a\in \mathbb{R}.$  $\bf{My\; Try::}$ Using $\displaystyle \cos (x) = \frac{e^{ix}+e^{-ix}}{2},$ we get ...  \begin{align}\displaystyle \int \ln(1+2a\cos x+a^2)dx &= \int \ln\left(1+2a\cdot \left(\frac{e^{ix}+e^{-ix}}{2}\right)+a^2\right)dx\\ &= \int \ln(1+a\cdot (e^{ix}+e^{-ix})+a^2)dx\\&=\int \ln \left((1+ae^{ix})\cdot (1+ae^{-ix})\right)dx\\  &= \int \ln(1+ae^{ix})dx+\int \ln(1+ae^{-ix})dx\end{align}  Now How can I solve after that  Help me  Thanks

For $a\ge 0$ let's define $$I(a)=\int_{0}^{\pi}\ln\left(1-2a\cos x+a^2\right)dx.$$ Find explicit formula for $I(a)$.   My attempt: Let  $$\begin{align*} f_n(x) &= \frac{\ln\left(1-2 \left(a+\frac{1}{n}\right)\cos x+\left(a+\frac{1}{n}\right)^2\right)-\ln\left(1-2a\cos x+a^2\right)}{\frac{1}{n}}\\ &=\frac{\ln\left(\displaystyle\frac{1-2 \left(a+\frac{1}{n}\right)\cos x+\left(a+\frac{1}{n}\right)^2}{1-2a\cos x+a^2}\right)}{\frac{1}{n}}\\ &=\frac{\ln\left(1+\dfrac{1}{n}\left(\displaystyle\frac{2a-2\cos x+\frac{1}{n}}{1-2a\cos x+a^2}\right)\right)}{\frac{1}{n}}. \end{align*}$$ Now it is easy to see that $f_n(x) \to \frac{2a-2\cos x}{1-2a\cos x+a^2}$ as $n \to \infty$. $|f_n(x)|\le \frac{2a+2}{(1-a)^2}$ RHS is integrable so $\lim_{n\to\infty}\int_0^\pi f_n(x)dx = \int_0^\pi \frac{2a-2\cos x}{1-2a\cos x+a^2} dx=I'(a)$. But  $$\int_0^\pi \frac{2a-2\cos x}{1-2a\cos x+a^2}=\int_0^\pi\left(1-\frac{(1-a)^2}{1-2a\cos x+a^2}\right)dx.$$ Consider $$\int_0^\pi\frac{dx}{1-2a\cos x+a^2}=\int_0^\infty\frac{\frac{dy}{1+t^2}}{1-2a\frac{1-t^2}{1+t^2}+a^2}=\int_0^\infty\frac{dt}{1+t^2-2a(1-t^2)+a^2(1+t^2)}=\int_0^\infty\frac{dt}{(1-a)^2+\left((1+a)t\right)^2}\stackrel{(*)}{=}\frac{1}{(1-a)^2}\int_0^\infty\frac{dt}{1+\left(\frac{1+a}{1-a}t\right)^2}=\frac{1}{(1-a)(1+a)}\int_0^\infty\frac{du}{1+u^2}=\frac{1}{(1-a)(1+a)}\frac{\pi}{2}.$$ So $$I'(a)=\frac{\pi}{2}\left(2-\frac{1-a}{1+a}\right)\Rightarrow I(a)=\frac{\pi}{2}\left(3a-2\ln\left(a+1\right)\right).$$  It looks too easy, is there any crucial lack?  $(*)$ — we have to check $a=1$ here by hand and actually consider $[0,1), (1,\infty)$ but result on these two intervals may differ only by constant - it may be important but in my opinion not crucial for this proof.


How can I rewrite the expression $\int \frac{-3}{2x^2-x-1} dx$ using log properties before solving for the integral?  I tried ln(-3)-ln(2x^2-x-1) but this doesn't seem to help. What do I do from here?

How to compute $\int \frac{-3}{2x^2-x-1}\ dx$?  I tried completing the square   and ended with :  $\frac{-3}{(2(x-1/4)^2-9/8)}$  Then I did U-sub for $u = x-1/4$  and got  $-3 \cdot 8 \cdot \int  1/(16u^2)-9 du$  What do I do from here?


I'm using Miktex 2.9 and TexnicCenter 2.02 and I would like to have a gray column in my table. I found some examples on the internet. They work, but if I use them, some of the cell borders (only in the gray column) disappear in my PDF (Adobe Reader XI). On zoom level 100%, only the middle hline is gone, on zoom level 125% also the top line and on 150% (or 75%) also the left line of the gray column. On 90% the middle line is even there but top and left are missing. So it seemes to be random.  This is my latex table:   \usepackage{colortbl} \definecolor{Gray}{gray}{0.85} \newcolumntype{a}{>{\columncolor{Gray}}c}  \begin{document} \begin{table} \begin{tabular}{| a | l |}      \hline     Spalte 1 & Spalte 2 \\     \hline     1 & 2 \\     \hline \end{tabular} \end{table} \end{document}   I also tried this alternative:  \begin{tabular}{|>{\columncolor[gray]{0.8}} l | r |}   Same problem here. I also found a similar question but with no answer and the comment, that a different viewer shoud be used. I tried it with PDF-XChange Viewer and actually the problem does not occur. But I know that my professor uses Adobe, so it has to work with this viewer. Does anyone got an idea? Thanks.  Edit: This \setlength\arrayrulewidth{0.6pt} or this \setlength\arrayrulewidth{1pt} does not solve the problem for me.

I'm using the xcolor package to colour the top row in a table. This is displayed properly using PDF viewers such as Preview or Skim (Mac). But using Adobe Reader 10.1.3 (either Windows or Mac) doesn't display the table line properly.   But removing the colouring for the table fixes it. Here is the example that works as expected:  \begin{table} \caption{Table showing Feature 5's Functional Tests} \hspace*{-0.5in} \begin{tabular}[h!]{|p{0.6cm}|p{4cm}|p{5cm}|p{4cm}|p{1.5cm}|} \hline {\bf Test ID } & {\bf Task } & {\bf Expected} & {\bf Actual} & {\bf Outcome} \\ \hline    5.1 & Something &  Something & Something &  Success \\ \hline    5.2 & Something &  Something & Something &  Success \\ \hline    5.3 & Something &  Something & Something &  Success \\ \hline    5.4 & Something &  Something & Something &  Success \\ \hline \end{tabular}  \end{table}   And here is the example with a coloured row:  \begin{table} \caption{Table showing Feature 5's Functional Tests} \hspace*{-0.5in} \begin{tabular}[h!]{|p{0.6cm}|p{4cm}|p{5cm}|p{4cm}|p{1.5cm}|} \hline \rowcolor{gray!25} {\bf Test ID } & {\bf Task } & {\bf Expected} & {\bf Actual} & {\bf Outcome} \\ \hline    5.1 & Something &  Something & Something &  Success \\ \hline    5.2 & Something &  Something & Something &  Success \\ \hline    5.3 & Something &  Something & Something &  Success \\ \hline    5.4 & Something &  Something & Something &  Success \\ \hline \end{tabular}  \end{table}   Removing the \rowcolor{} command replacing it with \cellcolor{} creates the same view. Any idea how to fix this?  I've tried printing it out of Adobe and the lines print fine, but as this will be read on as a soft copy it's pretty important. .  Any idea how to fix this?


While trying to check Palindrome String getting this error"String Index out of bound -1"  public static void main(String[]args) {      String s= "Madam";     String Temp=s;     String k=new String();     //System.out.println(s.length());     int m=s.length();      for (int i=5;i>=m;m--) {         System.out.println(m);         String t=String.valueOf(s.charAt(m-1) ) ;         k=k+t;         System.out.println(k);     }      System.out.println(k);      if (k==Temp) {         System.out.println("String is Palindrome"+" "+k);        } else {         System.out.println("String is not Palindrome");      } }

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


I'm very new to ssh and working with servers. I know how to make a connection to a server, and how to run a local script in a host server.  However I always have to have my terminal open while the script is running. The thing is that I'm about to run a script which is expected to finish in a couple of weeks. I cannot have my computer on for two weeks. How can I "send" the instruction to run my script and be able to shut down my computer while the server is running?  If this is not possible, can I copy the script to the server's hard drive and "send" the instruction to run that script, and be able to shut down my computer?  Thanks for your comments.

Which methods exist to keep a command that was started from shell on running after logging out from from shell?


If there is a charge in space, it is possible to calculate the magnitude of electric field generated by the charge at a point in space by using the formula $E = {{kQ}\over{r^2}}$ However,  If there is a permanent magnet in space, how is the magnitude of magnetic field (B) calculated at a certain distance away from the magnet?  For example, if there was a neodymium magnet graded at N42, how do we calculate the value of magnetic field $0.1 $m away from the center of the magnet?

We are always introduced to magnets by pictures illustrating a parallepiped magnet, a horseshoe magnet, etc... Anyway the first time we actually calculate a magnetic field is for eelectromagnets. Indeed I've rarely seen explaining or calculating the magnetic field of a permanent magnet. I know formulas for the magnetic field of a moving charge, around a conductive wire, inside a solenoid, but I don't have idea on how to go about calcualting the filed of a simple permanent magnet. It's like that without the help of electricity I'm stuck. I'd guess it would be heavily dependent on the magnetic material, its shape and the medium in which is placed. I hope that someone would provide me some insights on why such formulas are  never introduced in most physics courses and lay down some examples of a permanent magnet field caluclation.


I am using TexStudio and I am having trouble understanding the difference between Build & View and Compile  In the photo above, the 2 buttons are annotated.  These are my settings for each button.

In TeXstudio, what exactly is the difference between Build and view (F5) and Compile (F6)?


i have installed Ubuntu 14.04 in dual boot with windows 8.1 and want to know as to if ever in future if i need to remove Ubuntu . how will i do that? please help.

I have absolutely no experience with Linux, and I desperately need to get my computer back up and running again with Windows.  How do I remove Ubuntu and reinstall Windows?    Editor's note: many of the answers are about removing Ubuntu from dual-boot but keeping Windows (which is a bit complicated), while other answers are about removing Ubuntu from single-boot (which is easy: basically just format the disk while installing Windows). The question as written is ambiguous between dual-boot or single-boot.


i have XOLO Q1000 device which is rooted. I installed custom ROM of cyanogenmod on my device currently , i don't have previous backup of the stock ROM (jelly bean 4.2.1). Now i want the stock rom for my device from where i get that back

There are several reasons to be looking for a ROM:   Upgrading or downgrading your stock ROM Looking for firmware from a different region/language Flashing a custom ROM for different features, removing bloat, etc.   But where can one find ROMs in the first place?  What sites are likely to have the ROM I need?  ; please add to the wiki answer instead of posting separate answers.  See also:


Should insect in the following sentence be in a plural form?     It is a dragonfly. It is a kind of insect (or insects?).   Shouldn't we always use plural noun after a type/kind of ?

Which one is the most suitable option for the following sentence and why?  I do not like these kind of novels.  This kind Those kind This kinds None of the above   Please let me know the grammatical rule for this type of sentence.


Is there an online calculator to find the acceleration of gravity a massive object exerts from a specific distance? I know the effects of gravity kind of just fade out with distance but I'm asking for mass-specifics.  For example, you plug in the mass of the object and the distance from the object to get the m/s^2 (and maybe even the escape velocity)???  (I'm also thinking this would be some sort of exponential graph, like "acceleration" on the y axis and "distance" on the x axis)

The gravitational force on your body, called your weight, pushes you down onto the floor. $$W=mg$$ So, what is the weight equation through general relativity?


I'm using Microsoft's Visual Studio unit testing framework (the project does therefore I have to).  I'm sorely missing some of the more advanced assertions such as AreElementsEqual you find in MBUnit.  I'd like to make them.  As the class is static I can't inherit from it (to create a SuperAssert) and I can't add an extension method (as they're static methods).  I don't want to simply create another class and expect consumers to use the two different ones.  How can I expand the class?

I'm a fan of extension methods in C#, but haven't had any success adding an extension method to a static class, such as Console.  For example, if I want to add an extension to Console, called 'WriteBlueLine', so that I can go:  Console.WriteBlueLine("This text is blue");   I tried this by adding a local, public static method, with Console as a 'this' parameter... but no dice!      public static class Helpers {     public static void WriteBlueLine(this Console c, string text)     {         Console.ForegroundColor = ConsoleColor.Blue;         Console.WriteLine(text);         Console.ResetColor();     } }   This didn't add a 'WriteBlueLine' method to Console... am I doing it wrong? Or asking for the impossible?


Let $f $ be continuous on $\mathbb{R}$ satisfying $f(f(f(x)))=x$ for all $x\in \mathbb{R}$.  Prove/disprove that $f$ is an identity function. So far I have figured out that any  point $x$ such that $f(x)\neq x $ is not isolated(if it exists). i.e every neighbourhood of such a point contains other points where function is not identity. Cant proceed any further!

If $ f: \mathbb{R} \to \mathbb{R} $ is continuous, and $\forall x \in \mathbb{R} :\;(f \circ f \circ f)(x) = x  $, show that $ f(x) = x $.  The condition that $f$ is continuous on $\mathbb{R}$ is crucial for the proof. I can find functions such as $\displaystyle\frac{x-3}{x+1}$ that satisfies  $ (f \circ f \circ f)(x) = x $. I have tried to negate the conclusion to see if there's a contradiction, but got stuck.


I have downloaded the Ubuntu ISO file and I am new to the Linux and in learning phase.  How can I setup Ubuntu in my laptop?

I would like to see a full how-to guide on how to install Ubuntu.


I am new to java. Can anyone please tell me best way to access private method variables in another class. Thank u

In Java, are there clear rules on when to use each of access modifiers, namely the default (package private), public, protected and private, while making class and interface and dealing with inheritance?


In this short story a man tries to find the end of his city by sitting on a train (possibly a sleeper train) until it reaches the country. The train is underground and he checks property values every so often by leaving the train. The values reduce as he gets further from the city centre but eventually start increasing and he realises that the whole planet is one urban sprawl. He admits to having been on the train for a long time to some authority figure and is viewed as a disruptive person as a result. Can anyone tell me the title and/or author?

A man living in an underground city gets on his local subway train and keeps traveling, station after station, just to see where it goes.    Nobody has ever done this before. The staff on the train (who only each work a small section of train line) are interested in his journey, and allow him to continue.  The train passes through thousands of miles of continuous underground city, past contaminated and bricked-up areas, past thousands of stations, and finally after many months or perhaps years, comes back to where he started.  He realizes the world or universe is all city, entirely urbanized and occupied by people, all the way to the core, and can estimate its diameter. He also becomes concerned that the city-world may be slowly choking on its own toxic wastes... more and more areas are being walled-up and sealed off, and the whole civilization may eventually die.  As far as I can remember there is no mention of "sky" or even of a "surface" to a planet. Even the idea of "outside" is absent, if I remember correctly.  It's not clear if it is set in a large converted planet, or if the entire universe is city.   It was written in English. I read it in the 1980s, and it felt like it could have been written any time from the 1930s to about 1970s. It was almost certainly part of an anthology.


What differences between  and ? I cannot tell the differences between them.  In history, which concept was put forward firstly?  Are there some experiments to prove they are identical?

On this site, the Phys.SE question  has been asked. See also  Phys.SE question. The 'answer' provided on this forum has been that the curvature of spacetime explains both. The answer is still cryptic for me as I am more a concrete thinker.  Newton said $F=ma$. I can use this formula to measure inertial mass. Experimentally I can measure the motion of an object while applying a constant force to it. Newton also said $F=\frac{GMm}{r^2}$. In this case, what simple experiment will allow the measurement of gravitational mass?


It is well know that $SO(n)$ is connected and $O(n)$ has two connected components: $O^+(n)=\{A\in O(n):\det A=+1\}$ and $O^-(n)=\{A\in O(n):\det A=-1\}$.   In what book can I find this property?

I've noticed that $\mathrm{GL}_n(\mathbb R)$ is not a connected space, because if it were $\det(\mathrm{GL}_n(\mathbb R))$ (where $\det$ is the function ascribing to each $n\times n$ matrix its determinant) would be a connected space too, since $\det$ is a continuous function. But $\det(\mathrm{GL}_n(\mathbb R))=\mathbb R\setminus\{0\},$ so not connected.  I started thinking if I could prove that $\det^{-1}((-\infty,0))$ and $\det^{-1}((0,\infty))$ are connected. But I don't know how to prove that. I'm reading my notes from the topology course I took last year and I see nothing about proving connectedness...


I have a page with several articles/blogs. I would like to read all the Titles into a list using divs in another page like "check my latest blogs".  I want to read all the div's with a specific class from a specific page and show those title in another page. Initially, I thought to load those tags with PHP, Ajax into a JSON and echo the result. But so far I have no idea how I would do it.  Sounds complicated but I am trying to avoid code maintenance and make the page read and load the Title of the Article from another page automatic.   Yes, WordPress will do the work just fine but I am not a WordPress user.

I'm doing a bookmarking system and looking for the fastest (easiest) way to retrieve a page's title with PHP.   It would be nice to have something like $title = page_title($url)


I plan on making a druid character who later accepts the curse of lycanthropy  into his body in order to control it, something like a shapeshifter from Baldur's Gate. Am I able to use the multi-attack action and the bonus action I have to make a third attack (claw attack) as defined under the two weapon fighting style rules? I have yet to find anything saying whether or not natural weapons are light, as it seems common sense that a hand (claw) is considered light, as it is your hand.

Do natural weapons such as those granted by being a Tabaxi or an Aarakocra count for the purposes of two weapon fighting? Would they have the light property to allow it and if not what about if you take the dual wielder feat that removes the restriction on them being light?  From a logical perspective I would think claws or talons would be light enough to count and with them being "natural weapons" this means they are definitely weapons so it would make sense for them to be considered light and one handed.


Files in folder:  a.j ab.jp abc.jpg abcd.jpeg   dir command results:  Command       Result (Files shown) ----------    -------------------- dir ?.*       a.j dir ??.*      a.j, ab.jp dir ???.*     a.j, ab.jp, abc.jpg dir ????.*    a.j, ab.jp, abc.jpg, abcd.jpeg   So we can see single ? it means "0 or 1 letter".  Now more dir command results:  Command       Result (Files shown) ----------    -------------------- dir *.?       a.j dir *.??      a.j, ab.jp dir *.???     a.j, ab.jp, abc.jpg, abcd.jpeg --> What is this?! dir *.????    a.j, ab.jp, abc.jpg, abcd.jpeg   In 3rd command why ??? is showing jpeg? Can you explain? Is this bug in cmd?

I'm trying to recursively search a directory tree to find all of the .asp files using the following command:  dir *.asp /s   For some reason, this returns not only the asp files, but also the aspx files.  How can I force it to ignore the aspx files?


I have changed my Gmail password, and I can not recover it. I have the Old password, which was working fine. I have lost my account data. I have changed my phone number. The alternative email have been closed by server provider(I do not sign in for long time). So, I tried several things, all failed, but I have found a software called "Gmail Account Password Hacker", Can I trust and install it?

I have forgotten the password or username for my Google account, or I'm unable to access my account for other reasons.  How can I recover my account?  (This Q&A is meant as a general description for all Google and Gmail username/password questions. See: )


how   to open Mozilla browser home page in 2 mins of current time using the at command on command line?

Am trying to create a cron job to open a web page at a scheduled time.   I have edited my cron using crontab -e and append my job.  I wrote my job in a script like this: xdg-open (URL)  I saved this script in my /home/flicker directory.   However, when I edit my cron (crontab -e), it saves the file as /tmp/crontab.tIzXBv/crontab.   After saving it successfully says installing new crontab.   I made my file script executable, but still failing to handle the job.  I wanted the script to run at 14:30PM, so I added this line to my crontab:   30 14 * * * /home/flicker/open-web.sh   This is still failing to work please help. Here is my script below:  #!/bin/bash xdg-open https://www.google.com


I know that this is a 'bi'cycle forum, but I'm going to chance it and ask for unicycle buying advice.  What should I look for when buying a unicycle? I probably will do some leisure riding with it, maybe ride it around NYC instead of walking.

Motivation: I'm a casual cyclist (I ride around 4 miles per day, to school and work and back) but I wanted to get into unicycling to casually cycle through parks and the like; nothing too extreme, but just to be able to take it on a bus and cycle around the town.  I was unsure of what to look for in a beginner's unicycle, though.  Main Question: What types of things should a beginner unicyclist look for in their first unicycle?  Is it worthless to buy a unicycle labeled as a "beginner's unicycle"?  I browsed the other unicycle thread, but it didn't explicitly apply to people just starting to unicycle.


I beg your pardon but I have a doubt about this sentence:     "They failed to believe their eyes as they realized their world is   just an experiment"   So, if we are following a correct sequence of tense, we should use the past tense in both verbs. However, in the second clause we express certainty so the present simple ("is") appears appropriate. Is that correct? Thanks!

I'm describing a situation that happened in the past. To explain it, I want to use a description that is both true now and true when the situation happened.  Specifically, I want something like:     She touched me where my neck met my collarbone.   Since my neck is still attached to my collarbone (thankfully), I'm wondering if I shouldn't use the present tense here instead:     She touched me where my neck meets my collarbone.   Which is preferable, and why?


I am trying to minimise below 10 switch case but after trying few times I am not able to. Can somebody suggest what should I do?  Thanks in advance.   private int getCode(String digit) {      int keycode = 0;      switch (digit) {         case "0":             keycode = AndroidKeyCode.KEYCODE_0;         break;          case "1":             keycode = AndroidKeyCode.KEYCODE_1;         break;          case "2":             keycode = AndroidKeyCode.KEYCODE_2;         break;          case "3":             keycode = AndroidKeyCode.KEYCODE_3;         break;     }      return keycode; }   Thanks

What are the ways to eliminate the use of switch in code?


This shows up on my screen when I boot my laptop on Ubuntu.

I dual boot Ubuntu and Windows 7. I was browsing on FireFox in Ubuntu and all of a sudden I get some error message, so I rebooted.  Now when I try to boot into Ubuntu I get this message:  fsck from util-linux 2.26.2 /dev/sda6 contains a file system with errors, check forced. /dev/sda6: Inodes that were part of a corrupted orphan linked list found.  /dev/sda6: UNEXPECTED INCONSISTENCY; RUN fsck MANUALLY.         (i.e., without -a or -p options) fsck exited with status code 4 The root filesystem on /dev/sda6 requires a manual fsck  Busybox v1.22.1 (Ubuntu 1:1.22.0-15ubuntu1) built in shell (ash) Enter 'help' for a list of built-in commands.  (initramfs) _   How can I fix this?


How do i arrange my classes in CSS? How can I add a combination of letters and numbers?  Or what's the best way to have them arranged?

What characters/symbols are allowed within the CSS class selectors? I know that the following characters are invalid, but what characters are valid?  ~ ! @ $ % ^ & * ( ) + = , . / ' ; : " ? > < [ ] \ { } | ` #


I have malicious code in every php file. This malicius code is auto paste at the beginning of file. I want to remove this with UNIX command from console.   This is malicious code:  <?php $guobywgpku = '..... u=$bhpegpvvmc-1; ?>   I write this RegExp,   "/<\?php \$guobywgpku.*\?>/m"    and this RegExp work. I tested it .   The problem is, write command which remove this malicious code from every php file on the sever. Please Help me.   Now i have something like this.   sed "/<\?php \$guobywgpku.*\?>/m" index.php

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


I would like the option to organize sites in "Your Communities" by reputation.  As users like myself become active on different sites, changes in reputation can lead to the list displaying in a .   List of 9 favorite communities (unsorted)  Currently, I'm only able to sort the community list by reputation either by manually rearranging sites or resetting back to the default list of 5 communities.   Default list of top 5 communities (sorted by reputation)  Is it possible to display more than the top 5 communities in order of reputation?

I would have thought that someone must have asked this already but .  The ordering of the Stack Exchange drop-down menu is at times [in parts] logical, and then there are random positionings. Take a look at this:         to the question , does not explain the ordering that I see:     Sites where you have > 200 reputation will be sorted by reputation,   highest reputation accounts at the top.      Sites where you have < 200 reputation will then be listed in random   order. e at the top.   It is not because I need to wait 24 hours either, as it has been like this for nearly a week. In fact, it has always been badly ordered - only now am I analysing the order, or trying to.  3D Printing messes up the ordering at the top of the list - is this because I have always been on that site, in the past few weeks, and so it has been positioned as a favourite?  Surely Ask Ubuntu should be just below Stack Overflow, and Arqade at the bottom?   If I scroll down that menu, it gets even more random, and not all of them are < 200, so the explanation in the answer above, doesn't appear to apply:


I am trying to down load to a memory stick ubuntu 12.04 32 bit version but only seem to be able to get the 13.10 version. I think I am following the make a bootable stick instructions correctly but the page that comes up is not like the screen shots in the instructions.

I am looking at this:    I need to create a boot disk to test Ubuntu to make sure it will run on a PC (Compaq Mini CQ10-120LA) I was given. I can create the boot disk off of a Mac (in English) or Windows (but Windows is in Spanish and foreign to me).   Questions:     What format do I choose for the USB stick? (I wish the instructions stated this). What is Dash? (Will I know when I run the installer?) Can I do this from a Mac or Windows computer? Or only from Ubuntu?


I would really appreciate some help choosing a size of bike frame. I am stuck between choosing the large or the extra large.   I may go down the route of getting professionally checked on the bike, but there is every chance that since this is a frame company a long way from my house I won't be able to get it properly checked before I try and place an order, only testing on equivalent bikes. I have not decided if I am going for flat bars or drop bars, but more likely drop bars.  These are the bike sizes:    These are my measurements:    A: 186cm (6ft 1inch) B: C: 88cm D: E: 62cm (armpit to bottom of thumb as per picture) F:    Any help would be really appreciated. My feeling is that the large is the right size, but from my preliminary reading it looks like the extra large may be closer?   Thank you

I would like to get a Surly Cross-Check but the local bike shop doesn't stock them. They have suggested a 56cm, but I am concerned about the top tube length (I am more legs than torso). Are there proven ways to figure out whether a bike fits other than riding it?


I often get the warning Please avoid extended discussions in comments. Would you like to automatically move this discussion to chat? but a lot of the time, I am helping new users. What should I do to avoid discussion - should I suggest an external chat site, or continue using the comments?

Possible Duplicate:          I just tried the new feature to move a conversation to chat, and got the message indicated in the title.  The whole reason the comment chain got so chatty is because this is an inexperienced person who doesn't quite "get it" and isn't likely to get a lot of reputation any time soon. Isn't this exactly the sort of conversation that should be taken off-line?  I think if someone is invited to a chat by someone with enough reputation, it shouldn't matter what their own reputation is - they should be allowed into the chat.


Fetched 6.135 kB in 19s (321 kB/s)                                                  Reading package lists... Done     E: Failed to fetch http://ar.archive.ubuntu.com/ubuntu/dists/xenial-updates/main/dep11/Components-amd64.yml.xz  Hash Sum mismatch     E: Failed to fetch http://ar.archive.ubuntu.com/ubuntu/dists/xenial-updates/main/dep11/icons-64x64.tar.gz       E: Failed to fetch http://ar.archive.ubuntu.com/ubuntu/dists/xenial-updates/universe/dep11/Components-amd64.yml.xz       E: Failed to fetch http://ar.archive.ubuntu.com/ubuntu/dists/xenial-updates/universe/dep11/icons-64x64.tar.gz       E: Failed to fetch http://ar.archive.ubuntu.com/ubuntu/dists/xenial-updates/multiverse/dep11/Components-amd64.yml.xz       E: Failed to fetch http://ar.archive.ubuntu.com/ubuntu/dists/xenial-backports/main/dep11/Components-amd64.yml.xz  Hash Sum mismatch     E: Failed to fetch http://ar.archive.ubuntu.com/ubuntu/dists/xenial-backports/universe/dep11/Components-amd64.yml.xz       E: Some index files failed to download. They have been ignored, or old ones used instead.

When I check for updates, I get a "Failed To Download Repository Information" error.   This is what comes up under details:   W: Failed to fetch gzip:/var/lib/apt/lists/partial/us.archive.ubuntu.com_ubuntu_dists_natty_main_source_Sources  Hash Sum mismatch,  E: Some index files failed to download. They have been ignored, or old ones used instead.


I try with dd command and Disks & USB Image Writer, when the process is finished, still USB is empty.  :~$ sudo dd if=/home/user/Downloads/linux.iso of=/dev/sdb bs=4M conv=sync status=progress

This is the third time I've tried to install Ubuntu Server 14.04.03 64-bit on the same laptop, and each time it caused different problems.  Each time I wrote the same iso image to a USB flash drive by using a different application and OS.   Universal USB Installer (pendrivelinux.com) from Windows WinImage writer from Windows built-in image writer from Linux Mint 17.2    The iso image is the same in all three cases, the USB flash drive is the same, and the laptop is the same. However each time the installation of Ubuntu gave me different installation options. For example, the last time I installed Ubuntu, it didn't show all the packages to choose while installing (Basic Ubuntu server, etc.).


Ok, i've been seeing this the last week, tought it could be gone in a few days by itself, since i wasn't blacklisted and my DNS entries are all ok, but when i try to send e-mails to some user at Outlook, Live or Hotmail, i get this:  2015-02-11 14:54:58 1YLaYz-0000IT-I1 H=localhost.localdomain (higipel.com.br) [127.0.0.1]:41242 Warning: "SpamAssassin as cpaneleximscanner detected OUTGOING smtp message as NOT spam (-1.0)" 2015-02-11 14:54:59 1YLaYz-0000IT-I1 <= teste@higipel.com.br H=localhost.localdomain (higipel.com.br) [127.0.0.1]:41242 P=esmtpa A=dovecot_login:teste@higipel.com.br S=3532 id=5f640648ff1df4f59148f5c9cbbbd67b@higipel.com.br T="Lorem Ipsum" for [privarypreserved]@outlook.com 2015-02-11 14:54:59 cwd=/var/spool/exim 3 args: /usr/sbin/exim -Mc 1YLaYz-0000IT-I1 2015-02-11 14:54:59 1YLaYz-0000IT-I1 SMTP connection outbound 1423673699 1YLaYz-0000IT-I1 higipel.com.br [privarypreserved]@outlook.com 2015-02-11 14:54:59 SMTP connection from localhost.localdomain (higipel.com.br) [127.0.0.1]:41242 closed by QUIT 2015-02-11 14:55:01 1YLaYz-0000IT-I1 => [privarypreserved]@outlook.com R=dkim_lookuphost T=dkim_remote_smtp H=mx1.hotmail.com [65.55.37.72] X=TLSv1:AES256-SHA:256 C="250  <5f640648ff1df4f59148f5c9cbbbd67b@higipel.com.br> Queued mail for delivery" 2015-02-11 14:55:01 1YLaYz-0000IT-I1 Completed   And the weird thing is, i have a few hundred domains under 3-4 IP's at most, but just 4-5 domains are presenting this 'problem'  Anyone found a solution for this yet?

This is a  about how to handle email sent from your server being misclassified as spam.  For additional information you may find these similar questions helpful:                    Sometimes I want to send newsletters to my customers. The problem is, that some of the emails get caught as spam messages. Mostly by Outlook at the client (even in my own Outlook 2007).  Now I want to know what should be done to create "good" emails. I know about reverse lookup etc., but (for example), what about a unsubscribe link with an unique ID?  Does that increase a spam rating?


Today as I was performing my morning biological ritual, "dropping the kids off at the pool" and what not, the cold kiss of Poseidon on my behind inspired an idea for an experiment. What is the ideal height to poop in a toilet bowl to prevent splashing? There and then, I set up a scientific experiment. Trial # 1: I lowered the "factory's" height-above-water by a few inches. I thought "surely the lowered height will cause the falling logs to gain less total kinetic energy during their shorter journey to the bottom, thereby reducing the splash height". Unfortunately, while the splash height may have been lower, the factory was also lower, so Poseidon got me. Trial # 2: Then I raised the factory height, thinking "if I raise the height, the bog water won't reach!". Unfortunately, my hypothesis was wrong again. Poseidon got me once more. I quickly deduced that a higher drop height meant more kinetic energy, which led to a taller splash. But this trail might have been flawed; I think the log had slightly more mass that time. Therefore, I realized that this is more complex than I originally imagined, and it probably requires multivariable calculus to solve - something I was never good at. So instead, I wanted to continue through the trial-and-error route. I sat on the can for another 10 minutes, but alas, I'd run out of artillery, so the experiment will continue tomorrow. However, I figured that by asking here, I can increase the sample size by encouraging more trials among all of you. Or perhaps there is a physicist who can help deduce the ideal height (AKA, at what drop height above the water will there be the largest gap between the drop height and the splash?).

Suppose from a height $H$, I throw a ball of mass $M$ and radius $R$ with initial velocity $u$ into a pool of depth $x$ having a liquid with density $\rho$ and coefficient of viscosity $\eta$.  Upto what height will the Water Splash?   This may be a silly question! (Source : my brain) Assume every condition to be identical with no air resistance. Feel free to assume any other parameters if needed.  P.S. $\rightarrow$ I've see similar questions but some of them want an exact answer and some are not so direct while some are incomplete questions...  Small Note : We do not have to consider the highest 'single' drop... Just assuming almost every water droplet jumped upto a height $h$. Ideal conditions...  Feel free to assume the liquid as WATER if required!


Forced Vibrations are the vibrations under the influence of an external periodic force.  Their amplitude depends on the frequency of the external force. If it is equal to the natural frequency of the vibrating body then the amplitude is very large but when it is not equal then the amplitude is very small.  I am unable to understand this established relation between frequency and amplitude and why does this thing(which I stated above) happens.  P.S. : I am a tenth grader so please avoid the use of complicated terminologies.

While studying about the Resonance and Forced Oscillations, I came across a graph in my textbook that is given below:-  Now, the author writes      As the amount of damping increases, the peak shifts to lower frequencies.   Why does this happen? And does this imply that at higher damping levels one cannot achieve a higher amplitude by setting the period of the forced oscillation to be equal to the natural frequency? This seems strange because, the highest amplitude is achieved when the natural frequency is equal to the driving frequency. But, I guess that the rules are somehow different for the damping case.


I'm trying to pass a method to class Fighter. The method requires me to pass the instance of a the fighter class where I would normally just be able to use self. Is there any way to use self in a function that I'm passing to a class.  The constructor looks like this def melee_attack(fighter, target) and I would rather it look like this def melee_attack(self, target): so that when I call it I can just call fighter.attack(target) instead of fighter.attack(fighter, target)

I've read that it is possible to add a method to an existing object (i.e., not in the class definition) in Python.   I understand that it's not always good to do so. But how might one do this?


I never had this problem before. I know my internet is good. I usually have 60 fps and 25 ms when I play and even when the internet is bed, it's only the ms that gets lowered nmbut never the fps.  However, when I opened my League today to play, I only got FPS as low as 08 and as high as 19 FPS which is really annoying to play with. My ms is stable though.  I did my research and maybe it's bc of my running background programs. I usually play league with windows media player active on the background so I can listen to my music and the only other program I have on is my Garena client for my LoL.   When it comes to my computer storage I only have 176gb free out of my 420gb storage. Physical memory has a total of 3943, cached: 1305, available: 2698 and my free memory is 1452. My CPU usage is only (at average) 15-18% and ny Physical Memory is at 31%.  My system processor is: Intel(R) Core(TM) i3-3110M CPU @ 2.40 GHz  My installed RAM is 4.00gb with only 3.85 usable.  Note: I've had this issue before but it got back to normal after a few days. I didn't do even anything.

Is there a service that I can use to check if my machine will be able to run a certain game?


I'm trying to understand model in a propositional logic. Assume I have a set of formulas $F$, and a formula $\psi$. What exactly does $F \models \psi$ mean here? Does it only require that I have a single formula in $F$, such that it is model of $\psi$? Then, if I have $\psi \in F$, it must hold that $F \models \psi$, right?  Also, assume I have a formula $\phi = q_1 \wedge \cdots \wedge q_n \rightarrow p$. Can I say $\phi \models p$, if we have that $q_1,\ldots,q_n = TRUE$, as $p$ is implied by $q_1,\ldots,q_n$?

What does the notation $\Gamma \vDash \phi$ mean (in Mathematical Logic)?  I understand that $\Gamma$ represents a system of formulas, and that $\phi$ represents an individual formula.  I also know that $\Gamma \vDash \phi$ means " $\phi$ is a semantic consequence of $\Gamma$" - but I do not understand what this actually means. Can someone explain this idea to me in layman's terms?  Furthermore, suppose I had the following question:     Let $\Gamma \cup \{ \phi \}$. Does $\Gamma \vDash \phi$ hold for the set of formulae   $$ \Gamma = \{ p \rightarrow q, q \rightarrow r, r \rightarrow s \} \hspace{10 mm} \text{ where } \phi \text{ is } p \rightarrow s $$   Would I attempt this question by trying to prove that, for every formula $\psi \in \Gamma$, the valuation $v(\psi) = T$, based on the assumption that $v(\phi) = T$?


I am going to apply math grad schools this year. But, the problem is now I'm 30 years old.  Do you know anyone who is 30 or over 30, but got admission from top math grad school?

I am 33. I live in the US. I am a neither a US citizen, nor a green card holder. I have worked in various jobs as a research assistant (physics, biology, economics) usually involving programming, mathematics or statistics.  As a newly minted undergraduate, I didn't really have much confidence in myself and I completely ruled out graduate school as pointless.  I didn't think of myself as smart enough.  I drifted into working in labs, because those are some of the easiest ones for which one can get a work permit in the US as a non-American.  Having worked in academia for a while now, I've had a chance to leap into various fields and help build solutions to complex problems.  I think I have literally gone as far as I can go researching in academia with no higher degree.  I work at one of the top universities in the world.  (If you looked at US News rankings or the Academic Ranking of World Universities, it's in the top 5.)  Lately, I've been thinking about applying for graduate school.  I do have a few papers in various fields.  I'm thinking of a PhD in either pure mathematics, applied mathematics, statistics or computer science.   I see two big minuses to applying to graduate school:   Most people applying are more than a decade younger than I am.  (Alas, more than a few gray hairs have made an appearance in recent years.) Perhaps my achievements would look good for someone younger, but partially my achievements are the result of a long career rather than any special brilliance. So, I wonder how my record will be perceived.  I did take GRE and I scored 800 quantitative, 800 verbal and a 5 on the essay.  (I would most likely have to do a GRE subject test depending on what field I ultimately decided.)   Please advise on how accomplished, but older candidates, are viewed in the graduate school application process.


Let $M$ be a countable transitive model of $ZFC$, $\mathbb{P}\in M$ a forcing notion and $G$ a $\mathbb{P}$-generic filter over $M$.  Assume $( \mathbb{P}$ is c.c.c and $|\mathbb{P}|\leq \omega_{1})^{M}$  and $\Diamond$ holds in $M$. I want to show  $\Diamond$ is holds in $M[G]$.   How to use $ \Diamond $  in $ M $?

Assume $(\mathbb{P}$ is c.c.c.$)^M$ and $\Diamond$ holds in $M[G]$. Show that $\Diamond$ holds in $M$. Hint: It is sufficient to verify $\Diamond^-$ in $M$.  Should I try to create a $\Diamond$ sequence or $\Diamond^{-}$ sequence? Should I work with nice names?


I've often heard people saying this. And even I say it when someone accuses me of doing something that I didn't do.  I'd say:  Why would I do that?  But what's the grammar behind it?  Is it future from the past tense or something or what? It's obviously not a conditional construction 😒  Context from SE01 EP02 Austin & Ally  Austin: what does the jacket have to do with the music video?  Trish: It's a line in Ally's song, "my jacket's in the lost and found."  Ally: "my jacket"? It says "I like it." The line is "I like it when you hang around."  Dez: "hang around"? I thought it said "kangaroo." ♪ I like it when you kangaroo. ♪.  Ally: Why would I write "I like it when you kangaroo"?


I currently have a iMac (27-inch, Late 2009, Intel Core 2 Duo) which I would like to use as display for a new Mac Pro. How do I do that?

I currently have a iMac (27-inch, Late 2009, 3.06 GHz Intel Core 2 Duo) which I would like to use as display for a new Mac Pro.  How do I do that?


Considering the sum as a Riemann sum, evaluate $$\lim_{n\to\infty}\sum_{k=1}^{n}\frac{k}{n^2+k^2} .$$

How to find the value of $\lim_{n\to\infty}S(n)$, where $S(n)$ is given by $$S(n)=\displaystyle\sum_{k=1}^{n} \dfrac{k}{n^2+k^2}$$   is unable to calculate it.  This is a question from a questions booklet, and the options for the answer are--  $\begin{align} &A) \dfrac{\pi}{2} \\ &B) \log 2 \\ &C) \dfrac{\pi}{4} \\ &D) \dfrac{1}{2} \log 2 \end{align}$


I read that is possible to install Lubuntu on a 4 GB pendrive, so I would like to do the same on a 4GB virtual machine (on VirtualBox 5.2). The problem is that when I execute it, it says that there is no enough space and that 8GB are required. How can I install it?  EDIT: I'm asking a different question. How can I simulate the installation of Lubuntu on a 4GB pendrive on a virtual machine?

I want to install Ubuntu on a mini PC which has only 3.5GB disk space. Do you have any recommendations?


With the following query I can use the LAG() function to repeat the last non null value of c column:  SELECT coalesce(open_time, extract(EPOCH from date_trunc('minute', datetime)) * 1000)               open_time,    coalesce(o, LAG(c) over w)                                                                          o,    coalesce(h, LAG(c) over w)                                                                          h,    coalesce(l, LAG(c) over w)                                                                          l,    coalesce(c, LAG(c) over w)                                                                          c,    coalesce(v, 0)                                                                                v,    coalesce(close_time, extract(EPOCH from date_trunc('minute', datetime)) * 1000 + ((60000 * 1) - 1)) close_time from temporary_timeframe  window w as (order by datetime);   Getting the following result:    But I need to repeat the value of the c column while the current column value is null. I see that if PostgreSQL supports IGNORE NULLS attribute on window functions this would be solved. How to solve this without IGNORE NULLS?

I have a table like this:  create table foo (foo_label text, foo_price int, foo_date date);  insert into foo (           values           ('aaa', 100,  '2017-01-01'),           ('aaa', NULL, '2017-02-01'),           ('aaa', NULL, '2017-03-01'),           ('aaa', NULL, '2017-04-01'),           ('aaa', 140,  '2017-05-01'),           ('aaa', NULL, '2017-06-01'),           ('aaa', 180,  '2017-07-01')         );   As you can see a few values on the foo_price column are missing.  What I need is that missing values get filled up with the "previous" available value in this way:   foo_label | fixed_foo_price | foo_date -----------+-----------------+------------  aaa       | 100             | 2017-01-01  aaa       | 100             | 2017-02-01  aaa       | 100             | 2017-03-01  aaa       | 100             | 2017-04-01  aaa       | 140             | 2017-05-01  aaa       | 140             | 2017-06-01  aaa       | 180             | 2017-07-01   My attempt:  select      foo_label,      (case when foo_price is null then previous_foo_price else foo_price end) as fixed_foo_price,     foo_date from (   select        foo_label,        lag(foo_price) OVER (PARTITION BY foo_label order by foo_date::date) as previous_foo_price,        foo_price,       foo_date       from foo ) T;   As you can see from here:    It doesn't fill completely the '100' series.  Any idea how can I get the wanted result?


I am new to python2.7, i wanted to copy file placed in different directory and write to a file placed in current directory, but i don't know how to switch between different drectories.

How do I copy a file in Python?  I couldn't find anything under .


I am still new to ArcPy.   I'm running a really simple script, it selects a feature from a dataset (one town out of many), saves the data, and adds it to the (empty) dataframe.      map = mapping.MapDocument("CURRENT")     df = map.activeDataFrame        where_clause = "TOWN = " + "'"+GetParameterAsText(0)+"'"      arcpy.MakeFeatureLayer_management(statewide_towns, "TOWNS")     arcpy.SelectLayerByAttribute_management("TOWNS","NEW_SELECTION", where_clause)     arcpy.CopyFeatures_management("TOWNS", "OUTPUT_Single_TOWN")     arcpy.MakeFeatureLayer_management("OUTPUT_Single_TOWN", "TOWN_BND")     mapping.AddLayer(df,"TOWN_BND","AUTO_ARRANGE")   Throws me this error:   Traceback (most recent call last):   File "C:\path\to\myTool.py", line 58, in <module>     mapping.AddLayer(df,"TOWN_BND","AUTO_ARRANGE")   File "c:\program files (x86)\arcgis\desktop10.5\arcpy\arcpy\utils.py", line 182, in fn_     return fn(*args, **kw)   File "c:\program files (x86)\arcgis\desktop10.5\arcpy\arcpy\mapping.py", line 49, in AddLayer     assert isinstance(add_layer, Layer) AssertionError  Failed to execute (myTool).

I am trying to automate various tasks in ArcGIS Desktop (using ArcMap generally) with Python, and I keep needing a way to add a shapefile to the current map. (And then do stuff to it, but that's another story).  The best I can do so far is to add a layer file to the current map, using the following ("addLayer" is a layer file object):  def AddLayerFromLayerFile(addLayer):  import arcpy  mxd = arcpy.mapping.MapDocument("CURRENT")  df = arcpy.mapping.ListDataFrames(mxd, "Layers")[0]  arcpy.mapping.AddLayer(df, addLayer, "AUTO_ARRANGE")  arcpy.RefreshActiveView()  arcpy.RefreshTOC()  del mxd, df, addLayer   However, my raw data is always going be shapefiles, so I need to be able to open them. (Equivalently: convert a shapefile to a layer file without opening it, but I'd prefer not to do that).


In this MIDI-audio Patch circuit the capacitor has several lines though it - the lines look like ground lines - what do they represent ?  Does one connect the up and down triangles to each other, or are they separate (i.e. keep up triangles separate from down triangles ). I am assuming they are signal ground Thank you

I am looking at  (dual low-voltage power amplifier). On the fourth page, there is a sample circuit; right at the V+ input there is a symbol that looks like a capacitor. However, it looks like it is shaded in. What is that?


I'm trying to make a function that can generate a random number and specify how many bits the random number can be. More specifically, I am trying to generate a number that could either be 8, 10, or 12 bits long. This bit amount is specified by another variable. I then want to represent this number as a hex in string or as an signed and unsigned integer in decimal. I think i can just use the various Integer.toString methods for that part. How would I go about generating specific bit-length random numbers in Java? So far, I have this function skeleton in place: public static String generateQuestion(int numBits, int taskType){     String questionStr = "";     String questionVal = ""; // This is the string hexadecimal version of the randomly generated number     // TODO: Code to generate random value based on numBits           switch(taskType){         case 0: // Hex to Decimal             questionStr = "What are the signed and unsigned values for the " + numBits + "-bit value " + questionVal + "?";             return questionStr; // Return the constructed string         case 1: // Signed Decimal to Hex         case 2: // Unsigned Decimal to Hex         default:             throw new IllegalStateException("Unexpected Question Type: " + taskType); // In case the task type is something other than the 3 possible question types     } }

How do I generate a random int value in a specific range? I have tried the following, but those do not work: Attempt 1: randomNum = minimum + (int)(Math.random() * maximum);  Bug: randomNum can be bigger than maximum. Attempt 2: Random rn = new Random(); int n = maximum - minimum + 1; int i = rn.nextInt() % n; randomNum =  minimum + i;  Bug: randomNum can be smaller than minimum.


So, why isn’t hear an action verb, like its sensory siblings? I can write, “That feels disgusting” and substitute feels with looks, smells, and tastes, but “That hears disgusting” doesn’t make sense; we replace hears with sounds in such constructions.” Why is this so?

For the senses, we have:    flavor for taste aroma/odor/scent for smell sound for hearing ____? for touch/feel ____? for sight/see   So one tastes a flavor, smells an aroma, hears a sound, feels a(n) _____, and sees a(n) _____. For the former, part of me wants to say texture, but I feel that is too specific; for the latter, I want to use visual or sight, but but does that make sense, seeing a visual or a sight?


A function is defined as follows: $$  f(x) = \begin{cases}        x^2 & x \in \mathbb{R} - \mathbb{Q} \\       -x^2 & x \in \mathbb{Q}    \end{cases} $$ Show that $\lim_{x \to a} f(x)$ does not exist for $a \ne 0$. I'm really stuck on this problem. Is there a way to show this using epsilon-delta definitions or work with series? Thanks in advance!

I have a problem/proof that I can't quite solve.  Let $$f(x)=\begin{cases}x^2\quad &x \in \mathbb{R} \setminus  \mathbb{Q}\\-x^2 \quad &x \in \mathbb{Q}.\\ \end{cases}$$ Prove that $$\lim_{x\to n} f(x)$$ doesn't exist for $n$ other than $0$.  Maybe I can use the regular epsilon-delta proof? I tried that but wasn't sure of what assumptions I could make with the absolute values. I would appreciate any help.


i am currently working with a school task by making a webpage, but i can't seem to figure out how to align an image/icon with the other buttons in the navbar. I have tried to finsd the answer, but i can't seem to find the answer after several google search. Also, i am limited to html and css only and not allowed to use tools like bootstrap. my code for this page is below:  HTML code: <!DOCTYPE html>         <meta charset="utf-8">     <title>Zero hunger</title>     <link rel="stylesheet" href="css/master.css">

Home

Contact

Game

Hello World

      CSS code: body{   margin: 0;   font-family: sans-serif;  }  /*Navbar*/ nav ul{   margin: 0;   padding: 0;   text-align: center;   background-color: #D09E37; } nav ul li{   list-style: none;   display:inline-block;  } nav ul li.nav-button{   padding: 0 15px; } nav ul li.nav-button:hover{   background-color: #bf8000; } nav ul li a{   text-decoration: none;   font-size: 1.5em;   color: white;   line-height: 54px; } .nav-img{   height: 58px;   display: inline-block; }

I have a div with two images and an h1. All of them need to be vertically aligned within the div, next to each other. One of the images needs to be absolute positioned within the div. What is the CSS needed for this to work on all common browsers?

testing...


On the  there is a column with review resolution:    When you click on a link with "Close" resolution there is no post content on the result page, :    Any other resolution, i.e. Looks OK, Recommend Deletion, Delete refers to the page where post content is present, :

On Ask Ubuntu, when I try to view my Low Quality Posts review history and click on the action taken on questions, I can only see the actions taken and no preview of the question.   :    The question still exists on the site:   It seems question review history page is missing this HTML class:  <div class="reviewable-post reviewable-post-post_id">   On the other hand, everything is working fine for answers.


I know that the general method is to attempt getting the constant out of the summation, then use the summation formula on that and multiply the two. Is there any way to get K outside of the summation without knowing what k actually is?

Is there explicit formula for the expression $1^n + 2^n + \dotsc + k^n\,$?  I know that for $n=1$ the explicit formula becomes $S=k(k+1)/2$ and for $n=3$ the formula becomes $S^2$. But what about general $n$?  I know there is a way using the Taylor expansion of $f(x)=1/(1-x)=1+x+x^2+\dotsc\;$, by differentiating it and then multiplying by $x$ and then differentiating again. Repeating this $n$ times, we get  $$\frac{d}{dx}(x\frac{d}{dx}(\dots x\frac{d}{dx}f(x))\dots )=1+2^nx^n+3^nx^n\dots.$$  Now do the same process but with the function $g(x)=x^{k+1}f(x)$. Then subtract them and we get $1+2^nx^n+\dots k^nx^n$. Because we have the explicit formulas $f(x)$ and $g(x)$ we can find the explicit formula by this process for arbitrary $n$. A big problem is that as $n$ grows, it is going take a lot of time finding the explicit formula. My question is therefore: are there other ways?


I play Terraria on mobile and I'm getting bored. I would like to get to hard mode. I have tried 4 times without succes. The final is getting super close, but I keep getting killed by a hell bat. Is there a way to get rid of other mobs or any other overall advice?

I've been having trouble defeating this monster. Even with lots of buff potions, health potions, high tier armor (Molten), and ranged weapons with plenty of ammo (Minishark), I can't seem to kill this boss.  Worse, when I get it down to about 2000 hp, even if I'm fairly far away, it'll suck me in and continually rise towards the skybox, which doesn't allow me to do anything for some reason.  How do I defeat the Wall of Flesh? What gear should I be using and what kind of potions do I need?


The search results for my site have an added 0 in front of the title. Whereas in my title on my page it does not have any such thing in the title. Can somebody point me in the right direction of how to look into this issue.

I'm just wondering how it is possible that IGN.com has this in its title tag:      Video Games, Cheats, Walkthroughs, Game Trailers, Reviews, News, Previews & Videos at IGN   while on Google its title is simply "IGN".   How can one achieve such a thing? Does it use some special meta tag I can't see?


The latest macOS version at the moment is High Sierra (10.13), and I can't find the installer for macOS Sierra (10.12) at the App Store. How/where can I download the installer for macOS Sierra?

Sometimes it's hard to search for older versions of macOS & OS X  on the App Store.  This is an attempt to provide the canonical QA for this issue, as per the Meta QA -  I expect it to be modified over time to hopefully become a complete information resource.  How can I get any older version of a Mac OS to be able to run as a VM, or to reinstall on my Mac?