‘I too once passed the Dimril Gate.’ said Aragorn quietly; ‘but though I also came out again, the memory is very evil. I do not wish to enter Moria a second time.’   (The Lord of the Rings, A Journey in the Dark)   Is there any other reference and/or literature to support this story or even tell this story?

When the Company is forced to abandon their attempt to cross the Misty Mountains via the Redhorn Gate (the pass of Caradhras), Gandalf proposes they go "neither over the mountains, nor round them, but under them," via Moria. During the debate Aragorn remarks:     "I too once passed the Dirmrill Gate but though I also came out again, the memory is very evil. I do not wish to enter Moria a second time."    I haven't read much beyond the LOTR trilogy other than The Silmarillion. Does Tolkien ever describe Aragorn's first visit to Moria anywhere?


[UGC-CSIR-NET 2014 December]     Let $\{a_n:n\ge 1\}$ be sequence of real numbers such that the series   $\sum a_n$ converges and the series $\sum |a_n|$ diverges. Let $R$ be   the radius of convergence of the power series $\sum a_n x^n$; then   which of the following is true.         $0\lt R \lt 1$   $1\lt R \lt \infty$   $R=1$   $R=\infty$      In this question, I am a little confused regarding the role of the series $\sum a_n$ in its power series $\sum a_n x^n$ in earlier questions that I have faced, I find the radius of convergence of absolute version of coefficient of power series, where absolute version converges for those 'x' values origional power series also converges. Is that right?  But as we see here absolute version diverges, so what does it imply we can't use ratio, root test etc to find radius of convergence here?

Let $\{a_n:n \geq 1\}$ be a sequence of real numbers such that $\sum_{n=1}^{\infty} a_n$ is convergent and $\sum_{n=1}^{\infty} |a_n|$ is divergent. Let $R$ be the radius of convergence of the power series $\sum_{n=1}^{\infty} a_n x^n$. Then what is $R$ ?  I dont know how to start, if the series is given we could use Radius of convergence formula, but how to solve this question?Pls help


I'm using Lyx 2.3.2 and biblatex for my PhD thesis and I keep coming up against a strange issue with some in text citations. I am using author year format, which for references with more than two authors should give the citation (author1 et al., year). However, for two of my references I am getting (author1, author2 et al., year). The only thing I have been able to find out is that lyx would normally do this if just having the author and year could cause confusion due tohaving two citations that are the same, but refer to different references (i.e [Author1, AuthorX et al., 1999], [Author1, AuthorY et al,. 1999]). However, in my instance this is not the case. I have looked through the associated Bib file and found nothing out of the ordinary, I have tried various different author, year reference styles, and I have deleted the two references from my computer and added them back into my reference manager. Nothing seems to work. Does anyone know what might be causing this? The only other thing I can think of is if the papers had dual first authorship, but as far as I am aware this isn't the case either. Any advice would be greatly appreciated. Below is the bib for the two references: @article{Hodgson2012, author = {Hodgson, Jenny A. and Thomas, Chris D. and Dytham, Calvin and Travis, Justin M.J. and Cornell, Stephen J.}, doi = {10.1371/journal.pone.0047141}, editor = {Getz, Wayne M.} issn = {19326203}, journal = {PLoS ONE}, keywords = {Climate change,Conservation science,Electric conductivity,Extinction risk,Fractals,Habitats,Species colonization,Species extinction}, month = {oct}, number = {10}, pages = {e47141}, pmid = {23082145}, publisher = {Public Library of Science}, title = {{The Speed of Range Shifts in Fragmented Landscapes}}, volume = {7}, year = {2012} } @article{Hodgson2016, author = {Hodgson, Jenny A. and Wallis, David W. and Krishna, Ritesh and Cornell, Stephen J.}, doi = {10.1111/2041-210X.12614}, isbn = {2041-210X}, issn = {2041210X}, journal = {Methods in Ecology and Evolution}, keywords = {circuit theory,climate change,dispersal,ecological restoration,indicators,invasion,networks,optimisation,reserve design,systematic conservation planning}, number = {12}, pages = {1558--1566}, title = {{How to manipulate landscapes to improve the potential for range expansion}}, volume = {7}, year = {2016} }

In the header of my document I set the maximal author names to 2:  \usepackage[style=authoryear-icomp, maxbibnames=9, maxcitenames=2, backend=biber]{biblatex}   Now, when I cite texts with two authors, LaTeX gives me the following:     (Author_A/ Author_B 2012: 232)   When I have three authors or more, LaTeX makes it:     (Author_A/ Author_B et al. 2012: 232)   But I want LaTeX to just name the first author if there are more than two authors ... like this:     (Author_A et al. 2012: 232)   Any tips on how to achieve this ?


What is aether (ether) actually? Is it space-time fabric curve or is it anti-matter? If not this what is it then, does it exist? Why is the concept disregarded after Einstein's theory of Relativity? But Ether experimentally satisfies maxwell's equation and is it due to ether we define relative permitivity?

As I understand it, electromagnetic waves have two components which are the result of each other, i.e., when a moving electric charge creates a changing magnetic field at point X then a changing electric field is created at point Y and this repeating process is what creates EM waves, so therefore, it requires no medium. Is my understanding correct?  One thing that I'm surprised to know is that light is also called an electromagnetic wave.  Does this include light of any kind, for example: light from a bulb, a tube, and also from the Sun? How do they contain electric and magnetic fields?


I am trying to apply a mirror onto my Cheetah model, in edit mode the resting position is how I want the mirror to be applied, however, when it is in object mode, the resting position is that of the animation and the mirror is applied to that position. How can I apply the mirror to the position of edit mode?   How do I fix this?

I am using a mirror modifier for modelling. When viewing the mesh in edit mode, the vertices in the center are firmly stuck together and cannot be separated.     When in pose mode, I manipulate a wrist bone on my model and the mesh splits in two along the mirror axis center.    I have tried removing the subsurface modifier to see if this was the problem leaving only the armature at the top of the modifier list,i.e. as first modifier (which I am told is the bottom of the stack) and the mirror as the second.  It doesn't separate in edit mode and I've also tried increasing the merge limit to 0.1 and there's no change. Manipulating bones separates the mesh.


I've been watching nature shows on Netflix (Wildest series) and different animals of the same "family" are actually different species.   e.g. Asian elephants vs African elephants. Asian elephants are much smaller than their African counterparts.  Also with monkeys, different locations have their own species. Take langurs for example (see link below)      Just in the Indian subcontinent, there are many species of the same "gray langur".  In saying all that, how many species are there of modern day humans? It can't be just 1 homo sapiens it's quite obvious there are differences based on location. (Africans have darker skin. East asians have distinctly-shaped eyes and etc). Monkeys have lots of species even of the same "family" (see example above) and we're also primates.  thoughts? thanks

Like other animals, why don't humans have species & breeds ?  Even my pet dog is one type of breed, but we (humans) lack breeds & species?  What is the main reason?


It's my first question there so please don't be so cruel .   I've got problem with my program , it means i don't know why i have got NullpointerException , anybody knows why ?   My code : `package ex2;  public class Screen extends JPanel {      private BufferedImage image ;      private Timer tm ;      private Graphics g ;     private static int index = 0 ;      private ArrayList<String> paths = new Test().getArrayList();     public Screen(){         System.out.println(paths);         String interval  ;          interval = JOptionPane.showInputDialog("Please write time interval "                 + "between images in miliseconds");         tm = new Timer(Integer.parseInt(interval), new ActionListener() {              @Override             public void actionPerformed(ActionEvent e) {                 try {                     paint(index);                     index += 1 ;                     if (index >= paths.size())                         System.exit(index);                      } catch (IOException e1) {                                       e1.printStackTrace();                 }                                                            }         });         tm.start();     }     public void paint(int i) throws IOException{         image = ImageIO.read(new File(paths.get(i)));         g.drawImage(image, 40, 30, image.getWidth() , image.getHeight() , null);     } }

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


I'm trying to insert a .eps figure into my document. I'm using LuaLaTeX. I have already tried to remove the ".eps" extension from the \includegraphics{} command, but it didn't work. Makes no difference (do not compile) It always says the error:     Unknown graphics extension: .eps   I also tried the package epstopdf, but that didn't work either. It shows the error:     Package pdftex.def error: File 'fig/VocSOCGeneric-eps-converted-to-.pdf not f [I think it is "not found"].   In the path "fig/" no pdf is created (and no pdf is created in the project directory also). I also tried to insert the -shell-escape and --enable-write18 commands, but unsuccessfully.  It seems that all alternatives from converting eps to pdf are only suitable for pdfLaTeX, and not for LuaLaTex. Also, there is almost no documentation about eps figures AND LuaLaTeX, leading me to think that LuaLaTeX should deal naturally with eps graphics. But I don't know how!  Code example below.  \documentclass[addressstd,a4paper,10pt]{report}  \NeedsTeXFormat{LaTeX2e} \RequirePackage[2015/01/01]{latexrelease}  \RequirePackage{fix-cm}  \RequirePackage{tabularx} \RequirePackage{url}  \RequirePackage{amsmath} \RequirePackage{unicode-math}  \RequirePackage{luatextra} \RequirePackage{fontspec} \RequirePackage{lmodern}  \RequirePackage{graphicx} \RequirePackage{caption} \RequirePackage{chngcntr}  %\RequirePackage{epstopdf}  \counterwithout{figure}{chapter} \renewcommand{\thefigure}{\arabic{figure}} \renewcommand{\figurename}{Figura}  \captionsetup[figure]{labelsep=endash,         justification=justified,singlelinecheck=false,format=hang}  \begin{document}      Text before      \begin{figure}[h!]     \centering     \caption{Curva Característica Voc SOC de uma bateria Li-ion NCA.}     \includegraphics[scale=1]{fig/VocSOCGeneric.eps}     \label{fig:cap1VocSOC}     \end{figure}      Text after  \end{document}

There several types of graphics files. In no particular order .jpeg .eps .pdf .png .tif .jif (and no doubt others). Some work with latex, dvips and some work with pdflatex. How am I supposed to know which?  Just to confuse matters, metapost produces .eps but I can use these with pdflatex as long as I put in a four line incantation.  Can anyone explain this?


A team I work with has a habit of escaping IDs and integers in SQL like this:   $var = $var + 0; $sql = "SELECT * FROM whatever WHERE id = $var";   Is this an acceptable way to prevent SQL injection in PHP, or is it vulnerable?

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


I'm trying to enlarge the home partition on Ubuntu. When I click on resize in GParted, it can't be done even though I have 100 GB of unallocated space:

My dual-boot machine has partitions as follows:   sda1 50 GB NTFS sda2 15 GB unallocated sda3 20 GB ext3 sda4 20 GB ext4   I would like to allocate the unused space on sda2 to my Ubuntu partition on sda4, hopefully leaving the other two partitions untouched, leaving this configuration:    sda1 50 GB NTFS sda3 20 GB ext3 sda4 35 GB ext4   Is this possible? If so, how can it be done, preferably using GParted?


Some of methods that I see in C++ code are of this structure:  void Class::method1(int &a);   and are called like this:  int a; class->method1(a);   But sometimes I see structures like:  void Class2::method2(int* a);   And these methods are called like this:  int a; class2->method2(&a);   I understand that in the first case the method accepts an address of a variable, and in the second - pointer to a variable, right?  Could someone explain to me what is the difference between these two approaches, and when to use which?  Also, in the first example, it seems that a method can be taking "int& a" or "int a", and in both cases we would call it the same way: int a; class->method1(a); ? This seems confusing.  Thanks.

I know references are syntactic sugar, so code is easier to read and write. But what is the difference between a pointer variable and a reference variable?


Would like to ask if someone could help me draw this tree diagram using Latex. Any assistance will be much appreciated. Thanks

I am trying to make in LaTeX this probability tree:    I tried using the tikz package but I keep having some issues. This is the best I got so far (link: ):      \documentclass{article}      \usepackage{tikz}     \usetikzlibrary{trees}      \begin{document}     \pagestyle{empty}      \tikzstyle{level 1}=[level distance=3cm, sibling distance=3cm]     \tikzstyle{level 2}=[level distance=3.5cm, sibling distance=2cm]      \tikzstyle{bag} = [circle, minimum width=10pt, inner sep=2pt]     \tikzstyle{end} = [circle, minimum width=3pt, fill, inner sep=0pt]      \begin{tikzpicture}[grow=right, sloped]      \node[bag]{}     child {             node[bag] {O}                         child {                     node[end, label=right:{O}] {}                     edge from parent                     node[above] {}                     node[below]  {$1-\lambda$}                     child {                     node[end, label=right: {O ...}] {}                     edge from parent                     node[above] {}                     node[below]  {$1-\lambda$}                 }                 child {                     node[end, label=right: {S ...}] {}                     edge from parent                     node[above] {$\lambda$}                     node[below]  {}                 }                 }                 child {                     node[end, label=right: {S}] {}                     edge from parent                     node[above] {$\lambda$}                     node[below]  {}                 }                 edge from parent                  node[above] {}                 node[below]  {$1-\lambda$}         }         child {             node[bag] {S}                     child {                  edge from parent                     node[above] {1}                     node[below]  {}                     node[bag] {O'}                                child {                                     edge from parent                                     node[above] {$1$}                                     node[below] {$$}                                     edge from parent                     }                     }             edge from parent                          node[above] {$\lambda$}                 node[below]  {}         };       \end{tikzpicture}     \end{document}   As you can see, they are quite different, but I can't seem to be able to progress any further, would you be able to help me? I can't seem to realize what are the errors.  Best.


I'm trying to edit the values of attributes in QGIS, but it does not work. I tried to google an answer, but couldn't find anything so far. This is what I'm doing:   Open QGIS. Drag in a GeoJSON file. It becomes a vector layer. Menu bar > Layer > Toggle Editing.   I cannot toggle editing. It is greyed out. Am I missing something (I'm relatively new to QGIS)?  QGGIS Version  QGIS version 2.10.1-Pisa QGIS code revision  Compiled against Qt 4.8.6 Running against Qt 4.8.6 Compiled against GDAL/OGR 1.11.2 Running against GDAL/OGR 1.11.2 Compiled against GEOS 3.4.2-CAPI-1.8.2 Running against GEOS 3.4.2-CAPI-1.8.2 r3921 PostgreSQL Client Version 9.4.4 SpatiaLite Version 4.2.0 QWT Version 6.0.2 PROJ.4 Version 491 QScintilla2 Version 2.9

We have vector files in the format of geoJson files. We need to keep it in geoJson format as it is picked up by mobile devices via Restful services.  The problem is we want to change the attributes of the features in QGIS but it seems like this is not possible. We don't have to add or remove columns. We simply need to edit the existing data.  Is there a work around for this?  Are there any plugins that I can download that will allow me to do this in QGIS?


Running netsh interface ipv4 show interfaces in cmd shows some network interface information, including the state (connected or disconnected). Is this information stored in the registry and, if so, where can I find it? I know IP addresses are found in subkeys of HKLM\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\Interfaces (as answered ), but I'm not seeing state information there. I found the StaleAdapter value in subkeys of HKLM\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\DNSRegisteredAdapters, which updates on connection/disconnection. However, I doubt that this is really what I'm looking for, as there are less subkeys than there are network interfaces in the netsh output.

In a LAN, I configure my IP address as needed, but once in a while I move to a different subnet and need to update my IP address quickly so I am thinking of making a simple application to help me with this. Thus I would like to know where is the IP address settings stored in Registry?  In the old days of Win95 I could just search for the string, but now in Win10, the registry has become so huge it would probably take 8 days to end the search. Halp.


I'm applying to a PhD program in computer science. My friends and advisors all recommend that I cold-email the professors I'm most interested in working with and have a conversation with them about their research. However, I feel like just asking something like "What type of research do you do?" would just come off as lazy since most professors already have information on their website.  So that leads me to wonder, what are some productive questions that I could actually ask professors in the context of a cold-email or scheduled phone call?

I'm applying for graduate school (PhD in computer science), and I'm considering writing to faculty whose research areas match with what I intend to pursue, to understand:   Whether they'd be looking for new students at all in the coming year? If they did, would they be potentially interested in my profile (I know no-one would guarantee an acceptance without me going through the process of application), but it would help to know if they would not be interested at all in me - which would leave me  free apply to other schools in which I get a neutral/positive response.   Keeping the above in mind, what would be the best way to introduce myself in the first mail?   What should be the salutation - I know "Respected Sir" sounds archaic, but was wondering if "Dear Professor X" sounded too informal or not! Do I state my credentials (details of where I did my undergrads/masters) first, or do I state my purpose in writing to him/her? How to mention my background concisely, without giving too much details, while at the same time not "underselling" myself as a potential grad student? I want to give a link to my resume/profile hosted on my website - should I embed the hyperlink, or is it better to write the link in plain text? How do I end such a letter - the obvious ones (such as "see you soon" or "till we meet again") being not quite suitable in this case)?   I'm basically afraid of saying too much (causing vexation) or too little (resulting in no response to my missive). I understand that the faculty are accustomed to seeing their inbox flooded with such mails each year, few of which ever get a positive response - which may not always be due to lack of an interesting profile, but the manner in which the mail is worded (Many professors have explicitly mentioned on their websites that they would not respond to generic "Do you have funding" type of queries no matter what the credentials of the student are!).   Though my interest is specific to CS, I believe it would apply to other fields as well. Also, I would be interested in the opinions of both present faculty members (who have to sort through such mails), and past applicants to grad-school (who have the experience of successfully writing to their advisers before applying)...


I have read that when matter and antimatter collide they just cancel out each other with the emmision of bright light. But doesn't it violate law of conservation of mass? If the the atoms dissapear into nowhere?

I don't understand why it is said that the (rest) mass of a system is not conserved in relativity. I mean, the momentum of a system is conserved (i.e.: it remains constant in a frame of reference without any external influence). Also the energy of a system is conserved in relativity: it doesn't change without any external agency  and the (rest) mass of a system is just  $$m^2=E^2-p^2$$  $E$ is constant, $p$ is constant, how can $m$ change?  For example, entropy is not conserved in a system, that means that the entropy of the system will increase spontaneously with time, which is really the case. But, is this true for mass?   here is the problem from Griffiths and exact solution as given in the Griffiths,  Two lumps of clay, each of rest mass $m$, collide head-on at $3c/5$ and they stick together. Question: what is the rest mass $M$ of the composite lump?  Solution: In this case conservation of momentum is trivial it is zero before and zero after. The energy of each lump prior to the collision is $$mc^2/\sqrt{1-v^2/c^2} =5mc^2/4.$$ The energy of the composite lump after the collision is $Mc^2$ (since its at rest). so the conservation of energy says: $5mc^2/4 + 5mc^2/4 =Mc^2$ and hence $M=5m/2$.  Notice that this is greater than the sum of the initial masses! Mass was not conserved in this collision; kinetic energy was converted into rest energy, so the rest mass increased.


So the question that comes to my mind is  does differentiability require continuity? I have read it many a times but what I think of it like this, lets say a piecewise function as below is defined $$f(x) =\begin{cases} x^2 & x \leq 0 \\[2ex]\ x^2-1 & x \gt \mathbb 0 \end{cases}$$ Now as $x\rightarrow0$ the right hand derivative approaches zero and so does the left hand derivative. So apparently the derivative should exit at all points, even though it isn't continuous. Am I somehow wrong here? I recently completed my school so an answer at that level would be really helpful.

Consider the function $$f(x)=\left\{\begin{array}{cc} x^2-4 & \text{ if }x\leq 2\\4x+3&\text{ if } x\gt 2\end{array}\right.$$ This function is differentiable at $x=2$ since $\lim_{h\to 0^{\pm}}\frac{f(2+h)-f(2)}{h}=4$ (EDIT: this actually isn't true but it is true that $\lim_{x\to 2^-}f^\prime (x)=4=\lim_{x\to 2^+}f^\prime(x)$); however, it's not continuous at $x=2$. How is that possible, doesn't differentiability at $x=a$ imply continuity at $x=a$? This question came up when I tried to answer the question of finding $a$ and $b$ such that the function $$f(x)=\left\{\begin{array}{cc} ax^2-b & \text{ if }x\leq 2\\bx+3&\text{ if } x\gt 2\end{array}\right.$$ The solution is achieved by finding conditions on $a$ and $b$ such that it's continuous, and also such that the left/right derivates exist. The left/right derivative question gives $4a=b$. With the condition of continuity you get the additional condition that $4a-b=2b+3$, giving a unique solution. But doesn't differentiability imply continuity? What's wrong with just solving $4a=b$ like in the first example above?


I can't eat onions of any kind, from shallots, green onions, red, white, yellow, or purple. What might I use as a subtitute for flavor?

I love the taste of onions and garlic and it seems lots of other people do too.  But they upset my stomach so much that I can't really cook with them.  What can I use in their place to give my food a similar flavour?


I know Serre gave a way to convert a nice enough scheme over $\mathbb C$ to a complex manifold in his famous GAGA article but is there a way to go back? Here are a few thoughts.   Let $M$ be a noncompact complex manifold, then we can define a locally (maybe not locally, I don't know?) ringed space X to be the set of points on $M$ with the topology defined by letting the sets $f^{-1}(0)$ be closed for all holomorphic functions $ f: M \rightarrow   \mathbb C$ and structure sheaf given by $$\mathscr O_X(U) =  \mathscr O_M(U)$$  Letting $\mathscr O_M$ be the sheaf $\mathbb C$-valued holomorphic function on M.  Is X a scheme? If so, M obviously cant be compact since then any holomorphic function to $\mathbb C$ is constant but are there other constraints or does all such M define a scheme?  Or would it perhaps be wiser to follow the construction made on p.78 in Hartshorne. Consider t(M) to be the set of all nonempty closed complex submanifolds of M (M is now possiby compact).  The resulting locally (again not sure if its local) ringed space has topology given by defining closed sets to be of the form $t(N')$ for all closed submanifolds N' of M.  Then there is a continuous function $$\alpha : M \rightarrow X, p \mapsto cl\{P\}$$and we let the structure sheaf on t(M) be the sheaf $\alpha_* \mathscr O_M$.  Is t(M) a scheme?  Edit: I just realized that Chows theorem is important for the case where M is a closed submanifold of some $\mathbb{CP}^n$. I think it shows that for such M, t(M) is indeed a scheme.  Second edit: Someone has identified a possible duplicate of my question but this similar question does not answer my very specific question of is X or t(M) schemes for complex manifolds M?

The question in the title doesn't quite make sense. I was always wondering if the scheme is the generalization of manifold. The precise statement should be like following:  If $X$ is a complex (smooth)manifold, is there a scheme $Y$ over $\mathbb{C}$ such that the corresponding analytic space $Y^{an}$ isomorphic to $X$?  I guess if $X$ is projective, then this is Chow's theorem. And I doubt the question has an affirmative answer if $X$ is non-compact (I guess that $X: y-e^x=0$ in $\mathbb{C}^2$ might be an example, but I do not know how to show this).  Edit 1:  There are also example (as @hunter pointed out) of a complex torus but not an abelian variety shows that a compact manifold might not be a variety, however, is it possible to be a scheme ?(according to Hartshorne, the category of varieties is a subcategory of quasi-projective, integral, separated scheme. But could there be some non-quasiprojective scheme($Y$ has to be integral, separated in our case according to GAGA, I guess) )?  Edit 2: Another question I think of is: is (Artin) Stack a generalization of manifold? I really want to know if manifold could be think of some subcategory of some category of with "algebraic objects".


I'm using the package "chngcntr" to restart the chapter count in each part of my work. It's working just fine. However, in the table of contents, the chapters and all other sections numbers overlap the text. It's look awful. Does anyone knows how to solve this problem?  Thank you,  Pedro

I am using \tableofcontents to create TOC in my document. however it is appearing as shown in the image. As the numbers increase the gap between the number and text is reducing.   Thanks for your help Aku


Can i change a 26×1.95 tire to 26×1.75 tire on the same wheel? If possible,am i need to change the innertube also?

We often get questions on bicycles.stackexchange about fitting wider or narrower tires to bicycles. We have a large number of these with answers suiting the specific bike or style of bicycle in question, but I have been unable to find one that provides a generic answer covering off all things that need to be considered. For most bicycles, the answer is the same regardless of the specific style and sizes of tires in question.   This is intended as a canonical question that we can point closed questions to.


The other day i was trying to create an object by calling the default constructor of another class, and it ended up making a function declaration, Here is an example:  struct integer {     integer(){} //Default constructor. };  struct rational {     rational(integer n, integer d){} //Default constructor. };  void multiply(rational(), rational()) { //Valid syntax? Takes two function pointers.  }  rational one_half() {     return rational(integer(), integer()); //Here doesnt make a function declaration. }  int main() {       rational num(integer(), integer()); //Here makes a function declaration,                                         //instead of constructing a rational object.     multiply(one_half, one_half); //function taking two function pointers. }   Why does this happen? I know and can call the constructor like this integer::integer() but i would like to understand what's happening here and why integer() is behaving like integer(*)() in this example.

Is there any good reason that an empty set of round brackets (parentheses) isn't valid for calling the default constructor in C++?  MyObject  object;  // ok - default ctor MyObject  object(blah); // ok  MyObject  object();  // error   I seem to type "()" automatically everytime. Is there a good reason this isn't allowed?


Hi I have a strange problem with my code and I cant figure out whats wrong.  I have:  ArrayList called players  Class: Player  Class: Name  Player class contains Name class which contains 3 Strings FirstName MiddleName LastName  The problem is when im trying to do   For( int i = 0; i < players.size(); i++) {     if( players.get(i).getName().getFirst() == "First1")     {          // Some Code      }      System.out.printf(players.get(i).getName().getFirst()); }   If statement is never true, weird thing is when im using system.out to check as below  System.out.printf(players.get(i).getName().getFirst());   it returns:  First1 First2 First3  getName() method returns object name and getFirst() returns String FirstName  Any ideas where the problem is?

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 think I misunderstand Horcruxes here - are they used up? Or do they just exist to stop the person dying but are not actually 'used up' in the process? By this logic someone could be killed infinite times and still not die?

A few questions regarding the Horcruxes.   Had Voldemort actually succeeded in using a Horcrux, would he come back the same age (biologically and/or aesthetically) he was when he made the Horcrux, or the age he would biologically be if he had never died (half died)? If Harry was a Horcrux, then in the graveyard, when Wormtail added Harry's blood to the potion to bring Voldemort back, didn't that technically use up the Horcrux inside of Harry? So in Deathly Hallows when Voldemort kills Harry, shouldn't Harry have actually died rather than just have the Horcrux inside him destroyed, seeing as it was technically used in the Goblet of Fire?


I have this, and I am not allowed to touch the HTML.
     <input type="checkbox" class="checkbox" name="dynamic002" id="dynamic003">
  Sample Text

     Is there any way to force Sample Text to be inline with the checkbox, using only CSS?

Given this HTML:
foo

bar

baz
   How do you make them display inline like this:     foo bar baz   not like this:     foo   bar   baz


I tried to show that if \X_n is a sequence such that \X_1 < \X_2 < \X_N < ..... and \X_n converges to C that it is an increasing sequence by definition bounded by A and B such that B < \X_n < A for all positive n. Then I supposed \X_n increases without bound. Then I got to \X_n > A but then it was increasing without bound and so B < \X_n and A < \X_n so \X_n is not in (a,b) and thus does not converge.   However my professor says I only considered an increasing sequence and need to resubmit my proof.   Do I need to show that the same would happen for a decreasing sequence?  I don’t know how to directly show that it it is bounded then it has to converge... I can show that it it’s increasing, it’s not bounded, it doesn’t converge and that if it is decreasing, it is not bounded and does not converge.

(Taken from an old exam - no homework:)      Prove that every convergent sequence of real numbers is bounded.   It would be cruel if our professor would take a task like that in the exam because I rather prefer calculating than doing theory (in an exam where you haven't got much time to describe things..). But I'll be honest and say I dislike theory in general! :-)  Anyway, for the task, I really got no idea how to proof that but I'll give it a try...    We know that if a sequence is convergent it has exactly ONE limit where the sequences (sry my English here) accumulate. So the sequence will have an upper bound or lower bound, based on the limit, thus it will be surely bounded if it's convergent sequence.    Even if my proof is wrong (most likely..) I'd like to see a proof like mine, where you avoid using (complicated) maths symbols. Just using words any human can understand would be awesome! :-)  Of course a more formal proof is welcome too but not necessarily preferred ^.^


I am trying to understand how one would use differential forms to calculate the components of the connection and the curvature tensor given a metric. Can anyone point me to relevant resources for the same? I have a basic understanding of differential geometry.

Can someone suggest a textbook that treats general relativity from a rigorous mathematical perspective? Ideally, such a book would   Prove all theorems used. Use modern "mathematical notation" as opposed to "physics notation", especially with respect to linear algebra and differential geometry. Have examples that illustrate both computational and theoretical aspects. Have a range of exercises with varying degrees of difficulty, with answers.   An ideal text would read a lot more like a math book than a physics book and would demand few prerequisites in physics. Bottom line is that I would like a book that provides an axiomatic development of general relativity clearly and with mathematical precision works out the details of the theory.  Addendum (1): I did not intend to start a war over notation. As I said in one of the comments below, I think indicial notation together with the summation convention is very useful. The coordinate-free approach has its uses as well and I see no reason why the two can't peacefully coexist. What I meant by "mathematics notation" vs. "physics notation" is the following: Consider, as an example, one of the leading texts on smooth manifolds, John Lee's Introduction to Smooth Manifolds. I am very accustomed to this notation and it very similar to the notation used by Tu's Introduction to Manifolds, for instance, and other popular texts on differential geometry. On the other hand, take Frankel's Geometry of Physics. Now, this is a nice book but it is very difficult for me to follow it because 1) Lack of proofs and 2)the notation does not agree with other math texts that I'm accustomed to. Of course, there are commonalities but enough is different that I find it really annoying to try to translate between the two...  Addendum (2):  For the benefit of future readers, In addition to suggestions below, I have found another text that also closely-aligns with the criteria I stated above. It is, Spacetime: Foundations of General Relativity and Differential Geometry by Marcus Kriele. The author begins by discussing affine geometry, analysis on manifolds, multilinear algebra and other underpinnings and leads into general relativity at roughly the midpoint of the text. The notation is also fairly consistent with the books on differential geometry I mentioned above.


Broken Link on the Review page on Stack Overflow  Steps to reproduce:   go to Stack Overflow click the review link on the top find the yellow banner on the right      click the link 'you' (pointing to ) receive a message that the link is no longer found and that you can report a broken link on the feedback site (meta)

The page  has a link like this:  which doesn't seem to exist anymore. This is the same on  And also on


I have been trying to figure out a practical way to select events of specific period of a machine. I have a historical data of product arrival/process_start/process_finish times (DateTime) to a machine and events (breakdown,repair,maintenance etc.) of the machine with event_start/event_type/event_finish times (DateTime).  I want to identify those events happened at the machine for a product from time it arrives to it finishes the process.       foreach(var product in productList)      var resultEvents = from events in eventList                          where (data.Machine == product.Machine) && (events.Start<product.Arrival && event.Finish < product.Finish)   This is not giving me proper states, and it gets confusing and ambigious as I outline options when a machine may go down... Is it that I should also use process start or am I looking at more && statements?  A quick feedback is greatly appreciated :) Thanks!

Given two date ranges, what is the simplest or most efficient way to determine whether the two date ranges overlap?  As an example, suppose we have ranges denoted by DateTime variables StartDate1 to EndDate1 and StartDate2 to EndDate2.


This happened to me after installing java. I believe I messed with the ./bashrc file if I'm correct.  I've checked my files and sudo is still there, but ubuntu seems to not be able to find it.  Before installing java I could use sudo.   Any help is greatly appriciated.

This seems to be a chicken-egg problem. The most common task using sudo is installing and removing software.  sudo apt-get purge <appname>   But sudo itself can be removed.  sudo apt-get purge sudo # Do not run this command on production computers!   This is where the fun comes  ubuntu@ubuntu:~$ sudo bash: /usr/bin/sudo: No such file or directory   Although it's obvious that no person in his right mind will purge sudo (other than me), someone can be fooled to run this command (not directly, in its hex mode, or whatever it's called) or a person could SSH in disguised as tech guru and do the mess.  So is there a way of reinstalling sudo?


I have to limit to 2 rows.  But can't do it for a SQL-Fetch.  select * from employee;

Is there a way to make an Oracle query behave like it contains a MySQL limit clause? In MySQL, I can do this: select *  from sometable order by name limit 20,10  to get the 21st to the 30th rows (skip the first 20, give the next 10). The rows are selected after the order by, so it really starts on the 20th name alphabetically. In Oracle, the only thing people mention is the rownum pseudo-column, but it is evaluated before order by, which means this: select *  from sometable where rownum <= 10 order by name  will return a random set of ten rows ordered by name, which is not usually what I want. It also doesn't allow for specifying an offset.


Hello guys I'm actually new to Terminal and Python. Just started following a Python tuturial on my Ubuntu and I've reached a part where it asks me to save a .py file and open it in Terminal.  Only when I try to type on Terminal $ python egotrip.py I get $: command not found Then I try to type it in python and I get   File "", line 1     python egotrip.py                  ^ SyntaxError: invalid syntax  But I mean all names are correct :(  Then I gave also tried /home/anacah/Desktop/python/egotrip.py And I get   Traceback (most recent call last):   File "", line 1, in  NameError: name 'home' is not defined  What am I doing wrong? :(  can someone please help?

Trying to learn how to run my scripts through Ubuntu's terminal regularly.  That being said I am familiar with bash, wget, and awk being called but how do I call python files to run in the terminal?  I would like to learn this but I am unsure on where to research it.  I have a .pyw file that references several .py files in a folder.


I went to animate a project, Blender was returning a blank screen.  I have attempted to restart both Blender and my laptop, as well as re-downloading the program.  With each attempt, Blender exported a black movie, which I attempted to watch multiple times.  I even attempted to reanimate one of my older Blender files, and even that reexported as a black movie.  I have attached a picture of what I see when I render. Please Help! Thank you!😀

I've rendered about 300 frames for a short clip. The frames look fine, but when I compile into a movie all I get is a black screen. I haven't been able to find anything to solve this problem. The individual frames are well lit, capture what I want them to, look great. Just creating the AVI or MPEG results in a clip that has nothing but black.


Let's say we have a commutative ring $R$ with a unit and elements $a,b \in R$ which divide each other, e.g. $a | b$ and $b|a$. The question is now:     Does there exist an invertible element $\epsilon \in R^\times$ with $a \epsilon = b$ or are there counterexamples e.g. rings and elements as above, for which you can't find such an $\epsilon$?   This question arose from an exercise I gave to my students for commutative rings without unit (where there are plenty counterexamples, e.g. $R=\mathbb Z \times 2\mathbb Z$). Since we couldn't find counterexamples or a proof for unital rings I am asking here the question.  Stuff we already tried/figured out:   It is quite clear, that in a counterexample $a$ and $b$ are zerodivisors. It is useless to consider cross-products of rings, since you can solve the problem pointwise. $\mathbb Z / n \mathbb Z$ are no counterexamples.

Recall the following relevant definitions. We say that   $b$ is divisible by $a$ in $R$, or $a\mid b$ in $R$, if $b = r a$ for some $r\in R$. $a$ and $b$ are associates  in $R$ if $a\mid b$ and $b\mid a$, (or, equivalently, if $aR = bR$). $u\in R$ is a unit if it has a multiplicative inverse (a $v\in R$ such that $uv=vu=1$). $a$ and $b$ are unit multiples in $R$  if $a = ub$ for some unit $u\in R$.   Given these definitions, my question is,     If $R$ is a commutative ring with unity and $a,b\in R$ are associates in $R$, are $a$ and $b$ unit multiples in $R$?   I was told that this not always true. But I encountered some difficulties in finding a counterexample.


Everything was fine as long as I used CyanogenMod 11 (Android 4.4) on my HTC One S. I recently switched to LineageOS 14.1 (Android 7.1.2) and since then couldn't use its non-removable 16-GB sdcard as an internal storage.  Now there is /storage/emulated/0 instead of it. I logged in via ADB and mounted the card inside this directory (mount -t vfat -o rw,uid=0,gid=1015 /dev/block/mmcblk0p36 /storage/emulated/0/sdcard) and could browse it there, but still not on my phone. Permissions are similar for the mounted directory and the rest of the storage.  Any sugestions?

I installed a nightly build, but now some important features of my phone don't work: it boot-loops, or can't make calls, or can't use mobile data, or something like that. What can I do about it?     N.B. This is a "canonical question" for all similar questions, because questions about specific bugs in one particular nightly build of a ROM are way too specific to have any long-term value. See  to learn why this question was created, and why your particular question about nightly builds might have been closed as a duplicate of this one.


Suppose that $X_k$ are iid $\mathrm{Bernoulli}(1/2)$for $k=1, \ldots, n$ and  $$Y_n = \sum_{k=1}^n \frac{X_k}{2^k} $$ Given $U\sim \mathrm{Unif}(0,1)$ then the mgf of $U$ is $$m_U(-s) = \mathbb{E}(\exp(-sU)) = \frac{1-\exp(s)}{s} $$ (they gave it like this).    Show that $Y_n$ converges in distribution to $U$ by showing $$\lim_{n\to\infty}\mathbb{E}(-sY_n) = \frac{1-\exp(s)}{s}.$$    I computed the left hand side to be $$\mathbb{E}(-sY_n) = \frac{1}{2^n}\prod_{k=1}^n (1+\exp(-\frac{s}{2^k}))   $$ and am now stuck on how to take the limit. Also, how does showing the limit converging of the MGF imply they converge in distribution?    (I'd like to do it by finding the limit of the MGF).

I know that the finite sum of Bernoulli i.i.d. random variables is a binomial distribution, but what is the distribution of $$\lim_{n \to \infty}\sum_{k=1}^{n} \frac{x_k}{2^k}$$ where $x_k$ is a Bernoulli random variable with parameter $\frac12$?


The British discontinued the usage of "gotten"  while the Americans retained its use. "Have gotten" in AmE is therefore preferably to "have got". What is then the difference between have gotten/have got and have got?      In American English, the past participle of “get” in its literal sense   of “receive” or “become” is usually “gotten”. In the sense of “must”   or “have”, the past participle is always “got”.         But I don't understand the distinction between gotten / got (especially since  Americans use have gotten for how the British say "have got"--where in British English the past participle of "get" is only "got".)  Take these for example:        I have never gotten a gift. (= I have never received a gift.)   I’ve gotten interested in chess. (= I’ve become interested in chess.)              She’s got five children. (= She has five children)    I’ve got to go now. (= I must go now.)        If we take the definition of "got" as in to mean "must" or "have", then I would disagree with number 3 as surely you can have five children as you would in number 1? As in to possess or not to possess "a gift". Although, I admit it would be weird to say that you own a child "I have gotten 5 children" (as in to be in possession or ownership of them), but would surely be accepted, although controversial, if the person had just "adopted" five children? There is no distinction in BrE as there would be in AmE, take these for example:        I have got five children   I have got five presents      Would British people consider number 6's use of "got" in the sense of to have or possess as colloquial or incorrect, as would Americans?    My question is not the difference between the usage in American English but highlights that there is no difference in British English. I'm looking for guidance particularly which version would be "correct"--the American or British version, namely example 6) I have got five presents or I have gotten five presents. And again, would British people consider example 6, colloquial or incorrect?     In UK English, "have got" is the only grammatical possibility. In US   English, there is no situation where you could grammatically   substitute one for the other without changing the meaning. So there is   a difference, although it blurs when you combine US and UK English.       – Peter Shor       Oct 28 '11 at 13:31      @  (SE)

I see these two expressions are used almost identically in different contexts. Is there a difference between I have got and I have gotten?


If 5 squares are chosen at random from a chess board, what is the probability that they lie on a diagonal line?  this is the  indeed. Answer is given by Mr.Brian M. Scott. But I got a doubt in that.  Why the answer is limited to 64 squares. Don't we need to consider the possibilities of bigger squares also (total 204 squares)?  for example, five 2*2 squares can also be on same diagonal right?

This is a modified version of the question  and asked based on the clarifications obtained .   If 5 squares are chosen at random from a chess board, what is the probability that they lie on a diagonal line (squares can overlap and all 204 possible squares shall be considered)  Note: Assume squares lie on a single diagonal line if their diagonals are parallel and overlapping. for example, squares such as the ones given in the image are in the same diagonal .


How do I post images on Stack Exchange using Imgur? Do I have to make an account on Imgur?

Sometimes I need to upload, embed, or display inline an image in a question or answer. How can I do that?


It is  as this:  $$(a,b)(c,d)=(ac-bd,ad+bc).\,$$  I don't see anywhere where the decision to have - these components $ac-bd$ and + these components $ad+bc$ was made. Or why it is like this. Wondering if one could explain why it's like this, without using or referencing $i$ or $\sqrt{-1}$, just using the idea of complex numbers as an ordered pair of reals.

I understand that the complex numbers have a geometric representation as ordered pairs of real numbers. From what I understand complex numbers are very useful for working in two dimensions mathematically. The fact that $i^2 = -1$ follows from the definition of multiplication of complex numbers:  $(a,b)(c,d) = ac-bd+(bc+ad)i$  My question is this: If one was simply working with ordered pairs of real numbers with no knowledge of $i=\sqrt{-1}$, would this definition of multiplication ever follow logically from a practically arising situation?


Apologies up front if this has been addressed somewhere but I feel like a clarification about the domains of each Stack Exchange site should be posted . I am always confused by the . What algorithm do you guys use to decide where to ask your question? Some recent examples of my conundrums:  I am looking for an app/shell script that would let me control individual volume of my apps on my Mac/Linux on an app-by-app basis with location/time & WiFi-name based profiles. Should I ask this question in , ,  (since a script would do too),  or ? I ended up asking the question  but I feel it could have been equally valid/cross-posted to either of these places?  I also have some questions regarding some game that I am developing in HTML5 but I also want it to embed it in a mobile app (specifically Android). I am really confused - should I ask the question in ,  or .  The above game itself is a simple puzzle game - you are given a NxM matrix where some cells are "good" and some cells are "bad" and you are tasked to draw the minimum number of vertical or horizontal lines that cover all "bad" cells in the matrix. If I want to inquire about an efficient algorithm to solve such a puzzle. Should I post my question on  or  or  sites? I know that what I am asking for is essentially , so I can conceivably also ask my question in  or  sites too. Since these sites are relative desert town compared to , I will probably end up asking my question in Stack Overflow itself but I feel guilty of ignoring all these places...   I am not looking for specific answers to my above problems but I am looking for some general guidance to follow so I do not have to spend time thinking or looking through the list of sites to decide which is the correct place to post my question. It should be trivially obvious to me where I should post my questions or at least let me cross post?

If I have a specific question I want to ask about, but I don't know which Stack Exchange site would be on topic for asking that question, where can I ask where to ask that question?  Is there any generic place where we can ask for advice? Is it here?  This is not about a specific question but in general.  For example: "Where should I ask for advice about fishing?", or if I need to know where I should ask "What would be the best fishing rod to fish for salmon?" (regardless of how good/bad these examples are)


I have been using Stack Overflow for many years now, and recently I started contributing. My filtered questions have: C, Objective-C, and Unix in them. I want to help some guys, so I click questions which are "unanswered"  The fact it: most of these questions were in fact already answered, but people posted a reply in comments, instead of "Answer" field.  Is there a solution for this? Is there a way to promote a reply to an answer?

I have a question and have seen others to which the best and most relevant answer (at least the one that solved my particular problem) is placed in the comments to the question as opposed to the answers:   I would like to recognize the commenter as the person who correctly answered the question, but there doesn't seem to be any way to do that. The only thing I could think of was to ask the commenter to repost his comment as an answer, but I cannot figure out a way to contact him. In the meantime the question is sitting unanswered and I am getting other "answers" (leading me to believe that people are not reading the comments and answers already posted before trying to answer it themselves).  How are we supposed to do this?  Note: I don't want to accept the comment as an answer (I agree completely with the answers to this question that comments are comments and answers are answers and they should stay that way). I do wonder if there should be some way to contact people in a reasonable manner (comments on their profile that they must opt in to receiving in email?).


I created the following model by following an online tutorial in order to add it in a game:  Here is the shader graph that I used to create the same:  But when I tried to export in .glb format and view it in a glb viewer, I found out that it was just showing a sphere which was emitting white light, and no other colors/textures were visible.  But I want to export (into .glb) the exact figure that is visible in blender. I am new to blender, and might be making some silly mistake. I searched about this issue online, but I am unable to find the solution to it. I might be using the wrong terminology for the same.

I used node textures in a mesh I exported to .FBX.  I then imported it into Unreal Engine 4 and it didn't import any textures; I clicked the Upload Textures option in Unreal Engine.  Is there something I'm doing wrong or is it Blender?


If $n>1$ is a natural number, how to prove that  $$(n+1)^n > 2^n n!$$

Show that $$n! \leqslant \left(\frac{n+1}{2}\right)^n \quad \hbox{for all } n \in \mathbb{N}$$  I know that it can be done by induction but I always find line where I do not know what to do next.


I recently changed from Windows 10 to Ubuntu, but when I try to boot after installing Ubuntu I only see a white flash and then a black screen. I'm not running Dual Boot, I did a clean install.   My specs are the following: Intel Core I5 4670k Motherboard Gigabyte Z87X-UD3H MSI GTX 750TI 8GB RAM Kingston Hyperx Fury  Before putting the encryption password this appears:  Ivmetad is not active yet,  using direct activation during sysinit Volume group "ubuntu-vg" not found Cannot process volume group ubuntu-vg  I re-installed 3 times to check if it was an error but I keep getting this black screen  If you could help me I would really appreciate it.

I am trying to boot Ubuntu on my computer.  When I boot Ubuntu, it boots to a black screen.  How can I fix this? Table of Contents:


Let $\phi:G\to H$ be a homomorphism of groups.  Under what conditions does  $\frac{G}{ker (\phi)} \simeq im(\phi)$ imply there exists an isomorphism $G\simeq im(\phi) \oplus ker(\phi)$, and why?  The answers in the possible duplicate question are not sufficient for me, as I do not have an understanding of category theory or exact sequences. I'm looking for a detailed answer that makes use of basic group theory alone.  In particular I am interested in knowing if $G$ or $H$ being abelian makes any difference.

Suppose you have a group isomorphism given by the first isomorphism theorem: $$G/\ker(\phi) \simeq \operatorname{im}(\phi)$$ What can we say about the group $\ker(\phi)\times \operatorname{im}(\phi)$? In particular, when does the following hold: $$G\simeq \ker(\phi)\times \operatorname{im}(\phi)?$$ I ask this question because i want to prove that $GL_n^+(\mathbb{R}) \simeq SL_n(\mathbb{R}) \times \mathbb{R}^*_{>0}$, with $GL_n^+(\mathbb{R})$ the group of matrices with positive determinant. I proved that $SL_n(\mathbb{R})$ is a normal subgroup and that $GL_n^+(\mathbb{R})/  SL_n(\mathbb{R}) \simeq \mathbb{R}^*_{>0}$, using the surjective homomorphism $\det(M)$. I tried something with semidirect products but I got stuck.


This question was asked in my real analysis quiz and I couldn't solve it.  For a>0 , the series$\sum_{n=1}^{\infty} a^{\ln n}$ is convergent in which largest interval?  The problem is that I am unable to manipulate the $\ln n$ in exponent of a to use ratio test ? Can you please help me with that ? OR any alternative way to solve it.

If $x>0$, find the set of all values of $x$ such that series is convergent$$\sum_{n=1}^{\infty} x^{\ln{n}}$$   My attempt:- I used Ratio test for finding the set of all values of $x$ such that series is convergent.   $$\lim_{x\to\infty}\frac{x^{\ln{n+1}}}{x^{\ln{n}}}$$  $$=\lim_{x\to\infty}x^{\ln\frac{n+1}{n}}$$ This quantity must be less than one for getting a convergent series, I am not able to judge. Can you please help me to find the interval of convergence?


How do I show that $$\lim_{n\to\infty} \sqrt[n]{a^n+b^n}=\operatorname{max}(a,b)$$ with $a,b\ge0$.  I tried to do this by dividing it in two cases, when $a=b$ and $a\gt b$.  In the case $a\gt b$ I factored $a^n$ like this: $$\lim_{n\to\infty} \sqrt[n]{a^n \left(1+{b^n\over a^n} \right)} = \lim_{n\to\infty} a\sqrt[n]{1+{b^n\over a^n}} = a\lim_{n\to\infty} \sqrt[n]{1+{b^n\over a^n}}$$  Then I expressed it in exponential way. $$a\lim_{n\to\infty} \left({1+{b^n\over a^n}}\right)^{1/n}$$  Now I need to prove that $\lim_{n\to\infty} \left({1+{b^n\over a^n}}\right)^{1/n}=1$ so the whole limit is equal to a. The problem is that I don't know how to take the limit of $\lim_{n\to\infty} \left({1+{b^n\over a^n}}\right)^{1/n}$ I tried to use the natural logarithm, but it ended up like this: $$\lim_{n\to\infty} \log\left({1+{b^n\over a^n}}\right)^{1/n}=\lim_{n\to\infty} {1\over n} \log\left({1+{b^n\over a^n}}\right)=\lim_{n\to\infty} {1\over n} \lim_{n\to\infty}\log\left({1+{b^n\over a^n}}\right)=0$$ What did I do wrong and how can I do it right?

How can I prove the convergence of the sequence $b_n=\sqrt[n]{x^n+y^n}$ where $x, y > 0$?  Can I divide it in two cases?  Case 1: $x > y$.  $$ b_n=\sqrt[n]{x^n+y^n} < \sqrt[n]{x^n+x^n} = \sqrt[n]{2 \cdot x^n}=x \cdot \sqrt[n]{2} $$  Case 2: $x < y$.  $$ b_n=\sqrt[n]{x^n+y^n} < \sqrt[n]{y^n+y^n} = \sqrt[n]{2 \cdot y^n}=y \cdot \sqrt[n]{2}$$  Result: Does the sequence converges to $\max(x,y)$?


I was going through the JPA 2 specification and found two statements that sounds contradictory to me.   "If X is a preexisting managed entity, it is ignored by the persist operation." - Pg 76  "The EntityExistsException may thrown by the persistence provider when the persist operation is invoked and the entity already exists." - Pg 129    The statement 1 says something that sounds different from statement 2. So, my question is what is the difference between "preexisting managed entity" and "entity already exists"?

Hibernate has a handful of methods that, one way or another, takes your object and puts it into the database. What are the differences between them, when to use which, and why isn't there just one intelligent method that knows when to use what?  The methods that I have identified thus far are:   save() update() saveOrUpdate() saveOrUpdateCopy() merge() persist()


I'm interested in showing that $CX=\frac{I\times X}{\{1\}\times X}$ is contractible.  I defined the d.r $F(s,[t,x])=[(1-s)t+s,x]$ and the only missing part for me is to show that it is continuous. How do I do that?  I did see some related questions (example:  ), but couldn't understand completly why $F$ is continuous iff $F\circ(q×1)$ is continuous.  Also, is there a more traditional way to show the continuity?  Thanks

Let $X$ be a topological space. I want to show that the cone $CX$ is contractible. Here we construct a deformation retraction from $CX$ to  the tip point of the cone  $$H_t: CX\to CX;\; (x,t')\mapsto (x,t'(1-t))$$ is this correct?


A new art form has captured the world's attention: the reconstruction of past personalities based on their works and historical records. When the Richard Strauss, composer of such works as Also Sprach Zarathustra [the theme music at the beginning of "2001: A Space Odyssey"!] is resurrected, he undergoes a difficult period of adjustment. Who is he, after all, and what use should he make of this new life? Eventually he gets down to work, and feverishly composes a new symphony that he is sure will be his best. The world is fascinated and it's a full house at the premiere. But as Strauss conducts his symphony, he is struck by its banality. He realizes that he has composed nothing truly new, but has combined themes and ideas from his older works. The applause, however, is deafening. As Strauss turns to face the audience, he realizes that the applause is not for him, but for the artist who reconstructed him.  I am not at all sure of the date of this short story, which I read in English in an anthology. It could date from the 70s or as late as the 00s.

I read this story a long time ago and cannot remember either the title or the author. It was written in the 60s or 70s. The setting is sometime in the 21 century.  Here is a summary of the plot.  One of the great classical composers (maybe it was Schubert, I'm not sure) is revived with some future technology. All the guys in the lab are very happy about it, the world cheers the achievement. The composer is also quite excited to be alive. Naturally, he is asked to perform a concert. He asks for ink and music paper. Nobody knows what that is: in those days everybody writes music directly in "frequency spectrum" and similar stuff.  The composer, excited to create music again, tries to come up with something but he doesn't like anything he writes. The music is well written, but lacks something essential, it doesn't sound like his real music. Finally, the composer realizes that the lab guys recreated his mind from reviews by music critics, and his music just sounds like that. He performs the concert. The audience enjoys it, applauds and bravos. Not only to composer, but also to the lab guys.   At the end, if I remember it right, the composer gloats over the  primitive taste of the audience. The audience who writes music in frequency spectrum and applauds to lab guys at the music concert did not see the failure in the concert and ate it as it is.  Does someone recognize the story?  PS all the recent talk of advent of AI machines with Machine Learning algorithms reminded me of this story.


Listen, Walter, because you shot Jesse James don't make you Jesse James. — Breaking Bad   Why is it don't and not doesn't?

I'd like to know how the sentence "That don't impress me much" sounds to a native English speaker.  The phrase is the title of a song by Shania Twain, and to my eyes it contains a clear error. It is obviously intended, and I want to know what was the effect that the author wanted to obtain.  Other examples that come to mind:   “She's got a ticket to ride, but she don't care” — The Beatles “My love don't cost a thing” — Jennifer Lopez “It don't matter” — Akon “She don't care about me” — heard in the Lost series “It Don't Mean a Thing” — a jazz album title “The Sun Don't Lie” — another album title


A group is said to be finitely generated if it can be generated by a finite set of generators.   Question : Is there difference between finitely presented groups and finitely generated groups?

Is there any easy group theoretical way of showing that the wreath product $G$ of two infinite cyclic groups is not finitely presented?  I was looking for a finitely presented group with a central subgroup isomorphic to the free group of countable rank and whose factor group is isomorphic to $G$; in this way assuming that $G$ is finitely presented we get a contradiction.   Any ideas?


I am trying to find a way where I can read a local text file using java script. am aware of file reader API however I want to do this in IE7 and the filereader is for IE10 above. Been searching the web and not many good solutions come up? any ideas?   thanks

Is there local file manipulation that's been done with JavaScript? I'm looking for a solution that can be accomplished with no install footprint like requiring .  Specifically, I'd like to read the contents from a file and write those contents to another file. At this point I'm not worried about gaining permissions and am just assuming I already have full permissions to these files.


It appears that site meta data isn't updated in SEDE. As an example, Moderators.SE was  to  in December 2014. It is still listed in SEDE as Moderators.SE, as of July 2015.  To search for Community Building data, we need to search the "Moderators" community:    It is not listed as Community Building:

I've removed the poll style answers in favour of open discussion.  I realise now this isn't the best way to have a proper discussion about this issue - sorry to anyone who commented/voted.    This is mostly a followup on this question:    As I've answered, the reason this is happening is that the root database (in the production Stack Exchange database server) is still called StackExchange.Programmers - a database name that propagates to SEDE and through it to the data dump.  The question here is what to do about it - the current situation is somewhat broken for users of the data dump.  These are the options we have:   Do nothing Update the root database name (requires downtime - so very undesirable) Update the update scripts so the SEDE database name is the new name, change will flow to the data dump export (breaks any queries using the old name) Update the export to the data dump so only it gets the new name Something else we haven't thought about   I have added all of these options as answers below - please vote on the one you most prefer, we will try to accommodate the top voted answer.


I need to count the number of lines in x files and compare which has more.  The one I've done only takes two files and compares them. Any idea how to make it x amount of files?  echo Enter the filename read fn  echo Enter another file read fn1  for WORD in $(cat $fn) do         echo "$WORD" done | wc -l  for WORD in $(cat $fn1) do         echo "$WORD" done | wc -l  if (cat $fn | wc -l > cat $fn1 | wc -l) then         echo First file has more lines than second file else if (cat $fn1 | wc -l > cat $fn | wc -l) then         echo Second file has more lines than first file.  fi

How can I list the number of lines in the files in /group/book/four/word, sorted by the number of lines they contain?   ls -l command lists them down but does not sort them


I tried to change my prompt to my own preferences, but when I'm switching through the commands I recently entered (with key-arrows), sometimes the whole line with the prompt is deleted only some chars of the prompt with the chars of the command I recently entered remain:  Expected Output:  bucky in [~]: cd ..   Output:  buccd ..   'buc' is part of the prompt, 'cd ..' is a command I recently typed.  My prompt:  PS1="\[\033[0;34m\u\] \[\033[0;37min\] \[\033[1;32m[\]\[\033[0;31m\w\]\[\033[1;32m]\]\[\033[0;37m:\] "   To give you a visualization here is an image:     If needed, I'm using Ubuntu 16.04

Often when I start looking at history of commands some of the characters from a command displayed aren't erased, for example:  What's happening:  prompt$ some_command prompt$ some_commanother_command   What should have happened:  prompt$ some_command prompt$ another_command   I can't erase those characters and bash ignores them when executing the command. They also disappear when a new prompt is being displayed (after pressing Enter for example).  I asked other people who work on Linux at my workplace and they said that they have that problem sometimes too, but they didn't have an idea on how solve that issue.  I have Ubuntu 11.10 and I'm using guake. Here is my PS1:  \e[0;31m\u \A ${PWD##*/}\e[0;32m$(parse_git_branch)\e[0;31m$\e[m   where parse_git_branch is  parse_git_branch () {     git name-rev HEAD 2> /dev/null | sed 's#HEAD\ \(.*\)# (\1)#' }   As far as I know my colleagues have that problem even with less "fancy" PS1.


I want to draw a schematic drawing from a network.There is an  in ArcMap that can do this. Is there an extension or a way to do this in QGIS?

I have a Telecom cable network in Geopackage format. How do I create a Network flow diagram from which to represent the relationship between Fiber distribution hub to Network access point?


Here is where i got a problem: When i want ot fire button Marchewkaim getting error null pointer exception:  public class MainFrame extends JFrame { public static  void Draw() {     mp.repaint(); } private static final long serialVersionUID = 1L; private JPanel jContentPane = null; static private MyPanel mp = null;  /**  * This method initializes mp     *    * @return MyPanel    */ private MyPanel getMp() {     if (mp == null) {         mp = new MyPanel();         mp.setLayout(null);     }     return mp; }  /**  * @param args  */ public static void main(String[] args) {      // TODO Auto-generated method stub     SwingUtilities.invokeLater(new Runnable() {         public void run() {             MainFrame thisClass = new MainFrame();             thisClass.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);             thisClass.setVisible(true);          }     });    }  /**  * This is the default constructor  */ public MainFrame() {     super();     initialize(); }  /**  * This method initializes this  *   * @return void  */ private JPanel getJContentPane() {     if (jContentPane == null) {         jContentPane = new JPanel();         jContentPane.setLayout(new CardLayout(0, 0));      }     return jContentPane; } private void initialize() {      this.setSize(668, 402);     this.setContentPane(getJContentPane());     this.setTitle("JFrame");     JPanel panel = new JPanel();     panel.setLayout(null);     this.getContentPane().add(panel, "Main");     panel.setVisible(true);     JButton btnMarchewka = new JButton("Marchewka");     btnMarchewka.setBounds(12, 25, 113, 49);     panel.add(btnMarchewka);      JButton btnArbuz = new JButton("Arbuz");     btnArbuz.setBounds(12, 87, 113, 49);     panel.add(btnArbuz);      JButton btnUsun = new JButton("Usun ostatni");     btnUsun.setBounds(12, 149, 113, 49);     panel.add(btnUsun);     btnMarchewka.addActionListener(new ActionListener() {         public void actionPerformed(ActionEvent e)          {             Draw();         }     });  }  /**  * This method initializes jContentPane  *   * @return javax.swing.JPanel  */   }  //  @jve:decl-index=0:visual-constraint="10,10"   Another class  public class MyPanel extends JPanel {  public GObject c;  public GObject w; //  @jve:decl-index=0: private static final long serialVersionUID = 1L; public List<GObject> list= new ArrayList<GObject>(); /**  * This is the default constructor  */ public MyPanel() {     super();     initialize(); } public void addCarrot() {     GObject[] c=new GObject[list.size()+1];     c[list.size()]=new Carrot();     list.add(c[list.size()]);     MainFrame.Draw();     } public void addWatermelon() {     GObject[] w=new Watermelon[list.size()+1];     w[list.size()]=new Watermelon();     list.add(w[list.size()]);      MainFrame.Draw();     }    public void remove()    {    list.remove(list.size()-1);      MainFrame.Draw();   }   /**  * This method initializes this  *   * @return void  */ private void initialize() {     this.setSize(400, 400);     this.setLayout(null); } @Override protected void paintComponent(Graphics arg0) {     // TODO Auto-generated method stub     super.paintComponent(arg0);     if             (list!=null){     for(int i=0;i<list.size();i++)     {         list.get(i).drawMe(arg0);     }     } }   }   I tried to resolve this error on my own but i cant find where im pointing at nothing. Doing this for 6 hrs and im sick and tired.Im looking for some tips .

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


Let F be a field, Show that: $$(A \setminus C) \setminus (B \setminus C) = (A \setminus B) \setminus C,$$         $\forall A, B, C \in F$  where \ indicates set minus.   I've started with left hand side and reached this point:  $$(A \cap C^c) \cap (B \cap C^c)^c$$  where ^c is the complement. I don't know where to go from here.

I would like to construct a formal proof of the following:  $$(A\setminus C)\setminus(B\setminus C) = (A\setminus B)\setminus C$$  Let $a∈A$ be an arbitrary element, we will show that $a\in A \cap \overline B \cap \overline C$.  For LHS, since $a\in A$, we have that $a\in (A \cap  \overline C) \cap  (\overline B \cap \overline C)$. This is equivalent to $a\in (A \cap  \overline B) \cap \overline C$.    For RHS, since $a\in A$, we have that $a\in (A \cap  \overline B) \cap \overline C$  $\therefore lhs \equiv rhs$ and this concludes the proof  I would be grateful for any feed back on this element chasing proof. Is it flawed or where should improvements be made?  Thanks


I'm reading a csv file like this:  import pandas as pd  arq_pedido = pd.read_csv('Pedido.csv',delimiter=";", encoding = "ISO-8859-1")   I have a ID column (this column is supposed to be an INT column, but in Brazil (Portuguese), thousand's numbers is represented like this: 1.000 instead of 1000. So, my ID column is dfloat64 at the moment.  I have one ID who is 1.908 (1908), and this number shows 1.9080000000000001. How can I transform dfloat64 to int? Or, how can I replace dots (.) for comma (,), to turned that numbers in thousands ones?

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


Each interior angle of a regular polygon with $n$ sides is $\frac{3}{4}$   of each interior angle of a second regular polygon with $m$ sides.      How many pairs of positive integers $n$ and $m$ are there for which this   statement is true?   $\frac{(n-2)*180}{n}$ is the value of one interior angle for a polygon with $n$ sides.  Therefore $\frac{(n-2)*180}{n} =\frac{3(m-2)*180}{4m}$ and $mn - 8m + 6n =0$  For how many pairs of positive integers $n$ and $m$ is the statement $mn - 8m + 6n =0$ true?

Original problem  Show that there are exactly 16 pairs of integers $(x,y)$ such that $11x+8y+17=xy$.  My work  From case by case analysis I come to know that the equation will hold if and only if $x$ is odd and $y$ is even.  Also I found that $(8-x)|(11x+17)$ and $(11-y)|(8y+17)$  This is all what I have found.  Please see that my work are right or not.  This is a new kind of question which I have encountered so please help me is solving this problem.


Supposedly there is some built in hard drive magic called "Secure Erase" which is wildly faster and more secure than "dd if=/dev/zero..."  I am most excited about the speed increase.  There seems to be a GUI for it as part of Parted Magic:   Is there something like this for Ubuntu?  Better yet, is there a way to actually issue this command "manually" like with smartctl or something?

I've just received my new SSD since the old one died. This Intel 320 SSD supports TRIM. For testing purposes, my dealer put Windows on it, but I want to get rid of this and install Kubuntu on it.  It does not have to be a "secure wipe", I just need the empty the disk in the most healthy way. I believe that dd if=/dev/zero of=/dev/sda just fills the blocks with zeroes and thereby taking another write (correct me if I'm wrong).  I've seen the answer , but it looks like it's suited for clearing empty blocks, not wiping the disk.  hdparm seems to be the program to do it, but I'm not sure if it clears the disk OR cleans empty blocks. From its manual page:     --trim-sector-ranges           For  Solid State Drives (SSDs).  EXCEPTIONALLY DANGEROUS. DO NOT           USE THIS OPTION!!  Tells the drive firmware to discard  unneeded           data  sectors,  destroying  any  data that may have been present           within them.  This makes those sectors available  for  immediate           use  by  the firmware's garbage collection mechanism, to improve           scheduling for wear-leveling of the flash  media.   This  option           expects  one  or  more  sector range pairs immediately after the           option: an LBA starting address, a colon, and  a  sector  count,           with no intervening spaces.  EXCEPTIONALLY DANGEROUS. DO NOT USE           THIS OPTION!!              E.g.  hdparm --trim-sector-ranges 1000:4 7894:16 /dev/sdz   How can I make all blocks appear as empty using TRIM?


Is it possible to create static class with [] Operator?  On non static classes the syntax is pretty simple:     public V this[K key]         {             get             {                //get stuff...             }             set             {                //set stuff....             }         }   However, I can't find a way to this on static objects.

Why are static indexers disallowed in C#? I see no reason why they should not be allowed and furthermore they could be very useful.  For example:  public static class ConfigurationManager  {         public object this[string name]         {             get => ConfigurationManager.getProperty(name);             set => ConfigurationManager.editProperty(name, value);         }          /// <summary>         /// This will write the value to the property. Will overwrite if the property is already there         /// </summary>         /// <param name="name">Name of the property</param>         /// <param name="value">Value to be wrote (calls ToString)</param>         public static void editProperty(string name, object value)          {             var ds = new DataSet();             var configFile = new FileStream("./config.xml", FileMode.OpenOrCreate);             ds.ReadXml(configFile);              if (ds.Tables["config"] == null)                 ds.Tables.Add("config");              var config = ds.Tables["config"];              if (config.Rows[0] == null)                  config.Rows.Add(config.NewRow());              if (config.Columns[name] == null)                  config.Columns.Add(name);              config.Rows[0][name] = value.ToString();              ds.WriteXml(configFile);             configFile.Close();         }          public static void addProperty(string name, object value) =>             ConfigurationManager.editProperty(name, value);          public static object getProperty(string name)          {             var ds = new DataSet();             var configFile = new FileStream("./config.xml", FileMode.OpenOrCreate);             ds.ReadXml(configFile);             configFile.Close();              if (ds.Tables["config"] == null) return null;              var config = ds.Tables["config"];              if (config.Rows[0] == null) return null;             if (config.Columns[name] == null) return null;              return config.Rows[0][name];         }     }   The above code would benefit greatly from a static indexer. However it won't compile because static indexers are not allowed. Why is this so?


Prove that $${\frac{xy}{x^5 + xy + y^5}} + {\frac{yz}{y^5 + yz + z^5}} + {\frac{zx}{z^5 + zx + z^5}}\le 1$$ for positive reals $x, y, z$ whose product is $1$.   I have tried proving the above inequality.  Since, $x^5 + y^5 \ge x^4y + xy^4$ by Muirhead's Inequality.  So, now we have to prove that $$\sum_{cyc}{\frac{1}{x^3 + y^3 + 1}} \le 1$$  I think it can be done with AM-GM inequality but am not sure.  Thanks.

Let $a, b$ and $c$ be posetive real numbers such that $abc=1$. I want to prove this inquality $$\sum_{cyc}\frac{ab}{a^5+b^5+ab}\le 1$$ I used AGM inequality but I didn't prove it.   Which should I use inequality? So thanks


I have a Nikon D-5300 with 18-140mm zoom lens, Recently I visited a place, where I wanted to capture the mountain and lakes with the subject. As a beginner I used to click in Auto mode. I was able to focus the subject and making the background in blur and vice versa with auto mode. Is there any way, so I can get a  clear back ground as well. Thanks

I am quite new to DSLRs and one of the first things I noticed was the incredible focus points and appearance of depth that you can achieve. That is great in a lot of scenarios, but not in all. When filming a landscape as a whole, I do not want to have the focus on that single tree, but on the whole skyline.  Is there a way by which you can sort-of "disable" the focus, so that the raw image is recorded without any added blur? I suppose something as simple as this is only a small function you can turn off, but I can't seem to find it in the manual of my camera.


I am a beginner in Blender and have some questions now after some experimentation. I'm making the face of a character (pictured below) and have no idea if I'm doing it right. Read a bit about edge flow, but also read something about avoiding triangles. As you can see in the picture, I have some triangles. When does this become a problem? (I intend to animate the model when it is finished)

I've read many times that triangles should be avoided in meshes, too give one reference: "Introducing Character Animation with Blender by Tony Mullen" says that equilateral triangles work fine as long you don't deform them.  It seems to be common in game development that the models are triangulated.   What issues are introduced by using triangles? Does the same apply for n-gons?


I know it is used to summon things. But can the summoner only summon things that he own or is there a range within which it can summon anything or visualizing something that he doesn't own summons the thing.  Could Harry have 'Accio'ed the horcruxes had he tried?

We know that Accio spell (aka ) has some limits:   It can be blocked (e.g. Harry couldn't Accio the Diadem in RoR in Deathly Hallows). Many more failures are listed on Wikia.   But what are the exact full rules and limitations governing the spell in Harry Potter world?   Distance?  Line-of-sight?  Knowing exact or approximate location?  Specificity of item (e.g. "Accio Broom" seemed to work for Weasleys in OotP to bring their locked-up brooms - why not just a random broom?) Types of Accio-able stuff? Can you Accio water? Lump of earth? Gases/liquids/etc...? Can you Accio based on jQuery selector (or an SQL where clause), for lack of a better description? E.g. "Accio the book that has the word 'Flammel'"? "Accio biggest green ball from this room"? Can you Accio ALL items of a kind? (the reason I thought of this whole question was seeing "Accio all guns" comment in ). Can you Accio vague stuff? ("Accio meal"). Other rules that can be inferred.   NOTE: While Wikia article has some of the info, it is clearly very lacking in details on specific rules based on specific instances in canon. I'm looking for a fully comprehensive, organized ruleset for the charm, not merely 1-2 tidbits in Wikia article.


I'm looking for a way to automatically adjust the reported precision of the label field for a float raster rendered in ArcGIS according to a classified symbology. Currently, the a classified raster symbology label is reported at the class break precision (8 decimal places).  I don't want to modify the class breaks itself, just round the reported break (e.g. to 2 decimal places) for producing a map layout.  I know I can modify the label manually but I don't want to have to do this for every class break and for multiple rasters.  Is there a setting automatically adjust the label?

I'm using ArcMap 10.3. In symbology, there are 6 decimal digits for the different classes of the variable I'm presenting. I'd like to show only 3 decimal digits. I can edit the label and change the decimals manually for each class. Is there any faster way to do this for all classes in ArcMap 10.3?


I need to generate a string for another application to locate my file. I need to know how to access this file dynamically.  customfile=/dev/sda1:/images/myfs.squashfs   Let's say I can stat some/file/here.txt. What command do I use to determine it's block device, and it's absolute path from that device?  Also, how do I then determine the absolute path to here.txt from the device?

I want to find out what device my file is on so that I can use it in a script. I can get this far:  $ df  . Filesystem   512-blocks      Used Available Capacity  Mounted on /dev/disk0s2  498438976 294369520 203557456    60%    /   but this output feels too clumsy; is there a better way than parsing this to get the first 'word' of the second line?  What I really need is something like this so I can pipe it to the next command:  $ somecommand . /dev/disk0s2   How can I achieve this, preferably without resorting to string hacking the 'df' output?


Given $f = x ,  x \in \mathbb{Q}$ and $f =1 -  x ,  x \notin \mathbb{Q}$  I am trying to see this using sequence approach but couldnot get to it

How can I resolve the task below:  Given $f(x)= \begin{cases}   x, &x\in \mathbb{Q}\text{  }\\   1-x, &x\notin \mathbb{Q}\text{ (irrational)}  \end{cases}$, $0 \leq x \leq 1$.  Show $f(x)$ is continuous only in $x=\dfrac{1}{2}$.


I've been studying DC circuits recently, but I've run into some confusion concerning how batteries deliver energy to circuit elements.   From what I've read online, it seems that energy in circuits comes from waves that propagate through charges rather than the charges themselves. However, my book seems to convey that charges "pick up" potential energy at a battery and lose it in circuit elements.   These models of how energy is transferred seem to contradict each other. Which is right? And if the wave theory is right, then what does current or voltage have to do with it? Rather, how do current, voltage, and resistance explain the strength and properties of this wave?  If this matters, I'm using Halliday-Resnick-Krane 5th Edition Physics textbook.

I will give this question a little context. Firstly, as I understand it, as soon as I "close the switch" on a circuit, electric current pretty quickly establishes a steady state where, at any given cross section along a wire, the average kinetic energy of that slice is both constant and equal anywhere along the wire. (Please correct me if I am misunderstanding).   If the average kinetic energy is constant anywhere throughout the wire in the circuit (which confuses me, as I would think that the electrons should all accelerate after exiting the resistor since they are no longer being impeded as much), that means that the average velocity is constant. So, in the example of a simple circuit with a battery of v Volts and a resistor of o Ohms, my question is the following:  Because a 'voltage drop' is known to occur across the resistor, what type energy is being "traded" to generate the heat that radiates from the resistor? I would think that the reflexive answer is "electrical energy"...hence the VOLTAGE drop (the sacrificed energy is clearly not kinetic, as the velocity is constant everywhere). However, I find this confusing. Does this mean that if I had a positive test charge, it would be easier for me to bring it to the beginning of the resistor as compared to bringing it to the end of the resister?     Further, if the correct answer IS "electrical energy", why exactly DOES electrical energy get "dissipated" as the electrons pass through the resistor? I always here the comment Oh! It's because all the electrons are running into densely packed crap which impedes their flow but that to me sounds like a reason for their KINETIC energy to be reduced. However, clearly that's not the case. So, ultimately, I guess the real question is:  **What goes on in the resistor that is literally removing electrical energy **. I am sure that this is a quantum mechanics question, but my quantum mechanics knowledge is not terribly strong. If I could get an answer that is devoid of crazy wave function equations, I would greatly appreciate it. Thanks!


Let me go. / Let me do it. / Let me see, try, etc.   Q1. Which meaning are these more close to? "Allow me to go, do, see?" or "I'll go, do, see, etc?" There are two reasons I doubt this:    As far as I've seen, most of these LET-ME imperatives didn't seem to ask for some permission. As for Let's, it is actually Let us, but it's not necessarily asking for someone to allow.   Q2. To see LET-imperatives of other perspectives, third and second-person ones, like   Let the sun rise. Let's do this.   These let don't necessarily mean "allow someone to do" but actually work as kind of "auxiliary verbs." Why and from when did this happen?

The verb let means  “allow”, “permit”, “not prevent or forbid”, “pass, go or come”  and it's used with an object and the bare infinitive.         Are you going to let me drive or not?     Don't let him off the hook.     Before we let our children surf the Internet, they have to do their homework.     She lets the cats out before leaving.   He let us into the house.      The full form let us can be used similarly        Let us know as soon as possible.      Please, let us help you.   They will never let us forget.      None of the above can be contracted; however, when let us is used for making a suggestion; giving self-encouragement; expressing a consequence or plea,  it is often contracted to let's      Let's go out   Let's have a party   Let's see what happens   Let's stand together in this emergency   Let's not forget those who sacrificed their lives     Questions   I believe that let + us is the only instance where this type of contraction occurs. Is there an explanation as to why verbs such as (i) give + us, (ii) get + us or (iii) take + us were not similarly contracted? When was the apostrophe used to replace the omitted letter "u" in let us?  What is the origin of let's?


I am looking for a faster and more accurate way to check a Sequence:  List<int> sequence = new List<int> { 0, 1, 2, 3, 4, 5, 6, 7 … 41}    private bool IsSequential(List<int> sequence) {      int S = sequence[0];     int T = sequence[sequence.Count- 1];      List<int> Possible = Enumerable.Range(S, T).ToList();     List<int> Except = sequence.Except(Possible).ToList();      if (Except.Count == 0)         return true;     else         return false; }   My code returns 1 if the list is the same, I have some sort of count issue?  I wonder if there is a better way to check an integer sequence: 200, 201, 202... and so on.  Some Sequences may be out of sequence: 200, 210, 203, 204... I need to identify this issue.  Thanks

I would like to compare the contents of a couple of collections in my Equals method.  I have a Dictionary and an IList.  Is there a built-in method to do this?  Edited: I want to compare two Dictionaries and two ILists, so I think what equality means is clear - if the two dictionaries contain the same keys mapped to the same values, then they're equal.


I am writing a tool that connects to a server using a login and password. The tool's user has to provide at runtime the login and password for the tool to be able to connect to a server to fetch some information.  However, I am putting in place some integration tests for my tool, hence the tests should be able to connect to the server. I can use a generic server's account to do so. But I would like to automate those integration tests, so I would need to have the generic credentials stored encrypted somewhere and the integration tests to decrypt them when they get executed (even though they are generic, they are still credentials so I'm not comfortable in storing them un-encrypted).  What would be the way to work this out? If the tool is able to decrypt the password, then it means that it would hold some master key, and I do suppose this is wrong. Should I expose some external service to which I am sending the encrypted value to get it decrypted so the encryption/decryption would be processed outside the tool?  Thanks

We are busy developing a Java web service for a client. There are two possible choices:   Store the encrypted user name / password on the web service client. Read from a config. file on the client side, decrypt and send. Store the encrypted user name / password on the web server. Read from a config. file on the web server, decrypt and use in the web service.   The user name / password is used by the web service to access a third-party application.  The client already has classes that provide this functionality but this approach involves sending the user name / password in the clear (albeit within the intranet). They would prefer storing the info. within the web service but don't really want to pay for something they already have. (Security is not a big consideration because it's only within their intranet).  So we need something quick and easy in Java.  Any recommendations?  The server is Tomkat 5.5. The web service is Axis2.   What encrypt / decrypt package should we use? What about a key store? What configuration mechanism should we use? Will this be easy to deploy?


to start of with I want to explain my situation. I'm a young student in my early twenties in my last year to finish my bachelor in engineering. I have literally searched for months now on Google and on forums (especially this forum) on the best ways to get introduced to the financial world. I have learned a lot and got a whole good advice (and bad advice) in this subject, still it's kinda hard to know what is good and what is bad since I don't have any experience in the field.  My question is as many others on this forum, how can I get started and not end up in the wrong/slow direction?   specifies it good, but still the book that has the top comments is in the end about investing and putting money into Roth IRA's and long investing plans. I have no problem with these, it's just that I live in Sweden (and that's the reason for my English) and I don't know if these investing and saving methods work the same here. I can't find the correspondent to a Roth IRA here, we have something else I think.  What tax-advantaged retirement savings options might be available for me in Sweden?  Is there any book, website, blog that would be the best start for me to get knowledge and then later on develop investing strategies?   Some feedback that I have received for going through all websites/comments is that a lot of people suggest the book "" by Benjamin Graham. I bought this book and got through 50 pages till I got enough because I didn't know the terms, and they said this was the best first book to start with!   Some more about my background is that I have probably 1000$ to invest at the moment (It's not much, I know) and I will surely do an internship this summer before my master studies begin. I have a lot of free time to learn, that's why I need and want this.   All comments and feedback on good literature and websites will be much appreciated! Again, I know there are a lot threads about this matter, but can't get a specific answer from it regarding my case.  Thanks in advance

I am young, just started my career, and looking to begin investing so I can make my money work for me. I'm still living like I did in college (occasional purchase on myself, but most of it goes into savings) and I would like to take the extra money and invest it.   What would you suggest are the best options for me to begin? I was considering getting a personal investor [a financial advisor] for perhaps a year or so, but I've heard that they really are not worth the money. I wanted to get the input of the great minds here.


Me and my friend have this metal texture created in blender with nodes for a robot model. How would we take this shader and turn it into basic uv image texture with colors for the model in unity? Thanks in advance!

I have a sphere having a planet material MADE WITH NODES, and I want to convert this material into an image texture; because this material is made with nodes and only works in Blender, but I want to use in another software. This is my sphere material :   For Example : This is Jupiter :  And this is the texture :  In this case I used a downloaded image for Jupiter to be the material but I want the opposite, I want to change the material to image texture Like The shape of Jupiter texture. Is there anyway in Blender that can achieve my goal ? This is the file with my sphere material .  Textures Needed :  Albedo / Color / Diffuse Normal Map Roughness Glossines  I am using normal nodes and I am not useing the new Principled-shader


I can't decide whether to use the in these sentences.      [The] white chalk rock underground  has formed  beautiful hills and  valleys.   [The] grassland has a lot of flowering plants.   [The] coastline has a lot of wondeful beaches and cliffs.

Should we use the summer training or just summer training in the paragraph. As per me training is a noun and before singular noun we have to use an article and I am using the because I am talking about a specific training for engineers, I also know that before very common nouns we avoid articles, like bed, school, bus, university, so if you say we should use summer training then please give me a valid reason.     Company(name) has been providing the summer training for engineers   since 2010. We have been giving completely professional atmosphere for   engineers to complete the summer training with practical knowledge.   Our each faculty has a great experience in the education field. We   make sure you get all the important resources to make your summer   training a learning and an enjoyable summer training. You may call or   email us to get your confirmation about the training.   Thanks in advance.


I would like to further alias my login to include the -X flag I find myself typing over and over again.  Current usage:  ssh -X myserver   Desired usage:  ssh myserver   Current ~/.ssh/config entry:  Host myserver   Hostname     172.18.0.17   User         root   Port         1234   IdentityFile ~/.ssh/id_rsa   ProxyCommand???   I'm reading the manpage again but there isn't a clear mapping between flags and keywords in my opinion:

How do I add "-X" into my ssh default option? i.e., when I type ssh A.B.C.D, it should really do ssh -X A.B.C.D  I can alias it, but is there a more "elegant" solution to do that in .ssh/config file?