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I am getting the two different path that are basically file path , injected through xml by spring ioc.. private String FilePath1; //it consists path c:\abc folder private String FilePath2; //it consists of c:\abc\def now I need to check that if they two are equal then they should go inside the condition otherwise not please advise how to achieve this.. what I have tried is .. if (FilePath1 =! FilePath2) { filemove(mcrpFilePath, zipfileName); //i want if two file paths are not wqula then it // should go inside filemove } | 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 have some issues with nvidia drivers on ubuntu 14.04, switchable graphics (intel HD + nvidia GT 740M). Currently installed (from xorg-edgers repository): nvidia-352 (was recommended by ubuntu-drivers devices) + nvidia-prime + nvidia-settings. Issues (appears only when nvidia is selected in prime, with intel no problems): Blackscreen on login screen (I can hear sound, if I run startx from ctrl-alt-f1 and then stop it, or suspend/standby my pc and turn it on again - display appears). when using touchpad it freezes every few minutes, and ctrl-alt-f1 then ctrl-alt-f7 unfreezes it. I saw bug report regarding this issue and it was marked as patched/fixed so not sure what the problem is. Nvidia settings can show temp etc and seems like the driver has good communication with nvidia card. I tried to purge nvidia*. I tried using different drivers (nvidia-331). Both cause the same issues. | Okay, I have an HP Envy 17 laptop that was preloaded with Windows 8.1. I ditched Windows in favour of Linux. My laptop comes with the NVIDIA Geforce 840m. I install Ubuntu 14.04, and go to the Additional Drivers tab, and my GPU is not detected. So I go to the Nvidia website, and was glad to see that they support the Geforce 840m. I followed a Youtube tutorial on how to install the Nvidia driver . All went well until the Nvidia installer said it did not detect a supported GPU. I then proceeded to install the PPA to see if that would activate my GPU. It does, and I am able to select different versions of the driver in the Additional Drivers tab. However, the moment I do anything that uses the GPU, the driver crashes. No matter what driver version I use, I get the same result. Please help, I do a lot of 3D modelling, and I don't want to go back to using Windows!!! |
Okay I have a VPS (DO 512 MB) and AWS RDS free tier . I wanna get the maximum performance , please help me cause I'm a little confused . I run a nginx server on the VPS and it can handle 1K traffic/Sec without much panic . My problem is do I host the MySQL on the VPS or on AWS ? You migh say benchmark it , right !? I did , and here's the results (i have a pretty small database 500 Row , 15 columns ) i tested query executing time from my local location connecting to both of the servers . i ran a big query to test them 4 times to be 100% sure of results ,both servers are optimized using the same parameters . AWS -RDS - MYSQL 1st time :2.97 2nd time :2.88 3rd time :1.61 4th 4rd time :3.19 VPS - MYSQL 1st time :1.88 2nd time :1.81 3rd time :2.14 4th time :1.88 i get even faster VPS results executing queries Locally( on the VPS). and i got php+mysql test with Loader.io and here's the results too . Even though the VPS mysql is faster in all ways but it uses a lot of system resources (5.7% MEM X 6 Process) . is the speed difference worth the resources eaten from the VPS? any recommendation . | This is a about Related: I have a question regarding capacity planning. Can the Server Fault community please help with the following: What kind of server do I need to handle some number of users? How many users can a server with some specifications handle? Will some server configuration be fast enough for my use case? I'm building a social networking site: what kind of hardware do I need? How much bandwidth do I need for some project? How much bandwidth will some number of users use in some application? |
I have been noticing some strange behaviour when I type characters like ' or the backtick. Whenever I type it, the > symbol shows up everytime I type something, and everything I type seemingly does not do anything. But when I type the character again, it returns to normal. user@debian:~$ ' > command > ' -bash: command : command not found user@debian:~$ What is this feature? As far as I know, the man page for bash did not say anything about this Debian Jessie | Alright, when I run certain commands the wrong way, (misspelled, etc.) The terminal outputs this: > instead of computername:workingfolder username$, and when I type enter it goes like this: > > > That would be if I pressed enter 3 times. |
If I am typing a user tag, e.g. @Noble, and the autocomplete box appears, I want to complete the name with a keypress, not a mouse click. I've tried tab, up arrow, and right arrow, none of which have worked. Is this possible? | I find I'm doing the Unix / name completion thing where I type a few letters of the username and hit tab when I'm entering comments. Please consider adding a bit of JavaScript code that: When focus is on a comment input box When tab is pressed If the preceeding 'word' is 'like' a username in the comment list or post then complete the name (else, tab to the next tab-able element as per normal) |
I am wanting to learn how to parry people/npcs/enemies. Is there a good location to practice? What are some good starting weapons or shields I should use for both Dark Souls 2 and Scholar of the First Sin? What are some good ways to parry, with controls? | I am well informed in how to parry, but I haven't mastered parrying with all weapons. I would like to find a area that spawns slow moving, slowly attacking monsters in low numbers (I would also appreciate you telling me the nearest bonfire). |
I want to cleanup my cmake project and run this command find -name CMakeFiles -o -name CMakeCache.txt -exec rm -rf "{}" + It deletes files CMakeCache.txt but refuses to remove directories. So I have to workaround it with this hack find -name CMakeFiles | while read line; do rm -rf $line; done Does anybody know what might be the reason why find/rm behaves this way and how to make it work properly? Update: I found out. The problem is in operator precedence. Operator -o makes -exec work only for the second operand CMakeCache.txt . So the correct syntax needs parens () find \( -name CMakeFiles -o -name CMakeCache.txt \) -exec rm -rf "{}" + Thanks for posting the related question. | I'm trying to understand why the find command is not deleting files in one particular case. I've got the following command: find C:\\path\\to\\Pictures\\pmcctv -name cap_*.jpg -o -name cap_*.ogg -o -name cap_*.flv -o -name cap_*.mp4 -o -name cap_*.webm -mtime +7 Which returns the files I would expect: C:\path\to/Pictures/pmcctv/cap_20160915T193251_620067800.jpg C:\path\to/Pictures/pmcctv/cap_20160915T193322_742708800.jpg C:\path\to/Pictures/pmcctv/cap_20160916T081046_394767500.jpg C:\path\to/Pictures/pmcctv/cap_20160916T081125_615129600.jpg C:\path\to/Pictures/pmcctv/cap_20160916T081129_503678200.jpg C:\path\to/Pictures/pmcctv/cap_20160916T081255_842394600.jpg C:\path\to/Pictures/pmcctv/cap_20160916T161008_693586800.jpg C:\path\to/Pictures/pmcctv/cap_20160916T161012_749396800.jpg C:\path\to/Pictures/pmcctv/cap_20160916T161043_774132200.jpg C:\path\to/Pictures/pmcctv/cap_20160916T161150_497251900.jpg C:\path\to/Pictures/pmcctv/cap_20160916T161154_437379600.jpg C:\path\to/Pictures/pmcctv/cap_20160916T161337_350955300.jpg C:\path\to/Pictures/pmcctv/cap_20160916T161341_452596000.jpg C:\path\to/Pictures/pmcctv/cap_20160916T161412_870774000.jpg C:\path\to/Pictures/pmcctv/cap_20160916T161443_969064400.jpg C:\path\to/Pictures/pmcctv/cap_20160916T161554_468109900.jpg C:\path\to/Pictures/pmcctv/cap_20160916T161558_378086000.jpg C:\path\to/Pictures/pmcctv/cap_20160916T161916_668433100.jpg Now if I try to run the same command with -delete, the files are not deleted: find C:\\path\\to\\Pictures\\pmcctv -name cap_*.jpg -o -name cap_*.ogg -o -name cap_*.flv -o -name cap_*.mp4 -o -name cap_*.webm -mtime +7 -delete I've also tried with -exec rm, but they are also not deleted: find C:\\path\\to\\Pictures\\pmcctv -name cap_*.jpg -o -name cap_*.ogg -o -name cap_*.flv -o -name cap_*.mp4 -o -name cap_*.webm -mtime +7 -exec rm {} \; find returns no error and the files are owned by me with permissions 644. Any idea what could be causing this? (note: I've cut the commands to make it more readable but normally there's no line break) |
The model was exported as a/an XML file. an XML file sounds better to me – is it exception like an hour? | 99% of the time, I'm clear on when I should use "a" versus "an." There's one case, though, where people & references I respect disagree. Which of the following would you precede with "a" or "an," and why? FAQ FUBAR SCUBA [Note: I've read the questions and , but the rules given there don't necessarily apply here.] [Edited to add] Here's a shorter (and hopefully clearer) version of the question… In written English, which is correct (and why): "a FAQ" or "an FAQ"? Some references with differing opinions: an: the and a: the Microsoft Manual of Style for Tech Publications, 3e either: the and |
child= [[]] * 10 child[0].append(3) I expected the output to be child [[3], [], [], [], [], [], [], [], [], []] where output came out to be child [[3], [3], [3], [3], [3], [3], [3], [3], [3], [3]] | I needed to create a list of lists in Python, so I typed the following: my_list = [[1] * 4] * 3 The list looked like this: [[1, 1, 1, 1], [1, 1, 1, 1], [1, 1, 1, 1]] Then I changed one of the innermost values: my_list[0][0] = 5 Now my list looks like this: [[5, 1, 1, 1], [5, 1, 1, 1], [5, 1, 1, 1]] which is not what I wanted or expected. Can someone please explain what's going on, and how to get around it? |
I'm working with multiple scripts at a time, all in diferent languages and I'm tired of typing python3 main.py for python scripts and sh main.sh for shell Not even mentioning c. Basically something like this. run main.py run main.sh run main.c | If I want to execute a bash script which doesn't have its execution permission set, I can do: bash script.sh What should I use instead of bash if the script isn't executable and I don't know the correct interpreter? Is there a command that looks up the interpreter from shebang line and executes the script with it? |
This is my line of code that shown products from database, but I want to show it randomly every time. Code: $products = DB::select("SELECT * FROM products ORDER BY category = 75 DESC LIMIT 4"); | How can I request a random row (or as close to truly random as is possible) in pure SQL? |
The statement of Schur's lema for Lie algebras says that. Let $(\rho,\mathcal{V})$ is a complex irreducible finite-dimensional representation of a Lie algebra $\mathfrak{g}$. If $T$ conmmutes with $\rho$, then exists $k\in\mathbb{C}$ such that $T = k\operatorname{Id}_{\mathcal{V}}$. Is the reciprocal satisfied? That is, if the only operators that commute with the representation $\rho$ are multiples of $\operatorname{Id}_{\mathcal{V}}$, then the representation is irreducible? | I am trying to prove (or disprove) the converse of Schur's Lemma in finite dimensional vector spaces. I am not sure if it holds in this case, but I have tried to apply the idea that proves it in representation theory (see for example Theorem 4.3 that uses Maschke's theorem or in questions and ). The converse of Schur's Lemma in finite dimensional vector spaces is: Let $V$ be a finite dimensional vector space over the complex numbers. Let $S$ be a set of endomorphisms of $V$ and assume that every endomorphism $A$ of $V$ such that $$AB=BA\text{ for all }B\in S$$ is of the form $\lambda I, \ \lambda\in\mathbb{C}$. Then $V$ is a simple $S$-space. (*an endomorphism of $V$ is a linear operator from $V$ to $V$ *$V$ is a simple $S$-space if the only $S$-invariant subspaces of $V$ are $V$ itself and the zero subspace) What I've tried so far: Assume to the contrary that $V$ is not a simple $S-$space. Then, there exists a subspace $W$ of $V$ such that $W\not =\{0\}$, $W\not= V$ and $W$ is $S$-invariant. Let $W'=V\setminus W$. Then, since $V$ is finite, we can easily prove that $V=W\oplus W'$ (this is my attempt to translate Maschke's theorem in vector spaces). Consequently, for every $v\in V$, there exists unique $w\in W$ and $w'\in W'$, such that $v=w+w'$. Define the projection $P:V\rightarrow V$ by $Pv=w$ for every $v\in V$. What is left to prove is that $PB=BP$ for all $B\in S$. Then $P$ is clearly not a scalar and thus we have the contradiction we are looking for. There is a difficulty in showing that $PB=BP$ for all $B\in S$, because $W'$ might be $S$-invariant or not. More precisely: Let $v\in V=W\oplus W'$ and $v\not =0_V$. If $v\in W$ then $Bv\in W$ because $W$ is $S$-invariant, therefore: $PBv=Bv$ and $BPv=Bv$. If $v\in W'$ then $Pv=0$, hence $BPv=B\cdot 0=0$, and (i) if $Bv\in W'$ then $PBv=0$. (ii) if $Bv\in W$ then $PBv=Bv$ and this is where the problem occurs. Any hints, ideas or counterexamples would be very helpful. |
Why is the output displaying “Base” given the fact that object “a” was assigned to object “b”? Why does it not output "Derived"? #include <iostream> class A { public: virtual void display() { std::cout << "Base"; } }; class B: public A { public: void display() { std::cout << "Derived"; } }; int main() { B b; A a = b; a.display(); return 0; } | Someone mentioned it in the IRC as the slicing problem. |
city.exr, courtyard.exr, forest.exr, interior.exr, night.exr, studio.exr, sunrise.exr, sunset.exr are shipped with Blender 2.92 and courtyard.exr wants to load by default into a simple refraction construct--it's visible here in the area below the UV skydome I set on top of the XY plane: Before I discovered these samples in the Shading top-screen tab, I think I encountered the list of same .exr names elsewhere in the side screen control panels (but I don't remember where). Therefore my question is where are these .exr files in Properties dropdowns and elsewhere in Blender? | Blender 2.8 contains a number of HDRi's in it by default for the LookDev. I'd like to know how to use them in final renders (EEVEE or Cycles), because quite frankly they appear fantastic. |
When making a table, should number values inside of table cells be entered in the math environment? Or is that unnecessary? | Should numbers inside the text be placed inside a math environment? For example, if I am writing ...indent code by 4 spaces..., should I write it this way or ...indent code by $4$ spaces...? Perhaps the output is the same but semantically they are not and maybe LaTeX can treat them differently in some cases. Which is the right one? For instance, how does LaTeX treat the numbers in the counters it uses for numbering the sections or pages, etc? Does it treat them as numbers in a Math environment or as numbers inside text? Of course, if the output can never be different in any situation, then well, it just doesn't matter. |
I tried to make copy of an object with list of other objects. I came up with solution which threw NullPointerException. After a lot of time spending on it I managed to make it work but I am very confused about the origin of exception. I seek for an logical explanation of described issue. After changing return type from long to Long everything works fine as described in comment line in code sample. import java.util.ArrayList; import java.util.List; public class JustDontGetItApp { public static void main(String[] args) { Dog dog1 = new Dog("Max"); Dog dog2 = new Dog("Buddy"); AnimalSchelter animalSchelter = new AnimalSchelter("Hope"); animalSchelter.getAnimals().add(dog1); animalSchelter.getAnimals().add(dog2); AnimalSchelter copy = animalSchelter.copy(); } } class AnimalSchelter { private String name; private final List<Animal> animals = new ArrayList<>(); public AnimalSchelter(String name) { this.name = name; } public AnimalSchelter(AnimalSchelter animalSchelter) { name = animalSchelter.getName(); animalSchelter.getAnimals().stream().map(Animal::copy).forEach(animals::add); } public AnimalSchelter copy() { return new AnimalSchelter(this); } public String getName() { return name; } public List<Animal> getAnimals() { return animals; } } abstract class Animal { private Long id; public Animal() {} public Animal(Animal animal) { id = animal.getId(); } protected abstract Animal copy(); //LINE long -> Long fixes everything public long getId() { return id; } } class Dog extends Animal { private String name; public Dog(String name) { super(); } public Dog(Dog dog) { super(dog); name = dog.getName(); } @Override protected Animal copy() { return new Dog(this); } public String getName() { return name; } } | 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 having trouble figuring out how to create a graph like this in LaTeX. Any help would be greatly appreciated! | can anybody help me to draw this minimal example of an xy axis? I couldn't find anything similar on the forum. The axis should be black but the grid behind it a shade o gray, dashed. It would be great if the axis were a little bit thicker than the grid also. |
A photon from the big bang has lost most of its momentum and energy. What does it push against? Does it break the 'laws' of conservation of energy and momentum? Is there any possibility that momentum is conserved or that in any other way these ancient photons are not precisely identical modern photons of the same wavelength? If the photon's momentum and energy is given up to expand the universe, but the flux of photons at a point of empty space is not perfectly even over a long time scale, what does this imply? | So I have learned in class that light can get red-shifted as it travels through space. As I understand it, space itself expands and stretches out the wavelength of the light. This results in the light having a lower frequency which equates to lowering its energy. My question is, where does the energy of the light go? Energy must go somewhere! Does the energy the light had before go into the mechanism that's expanding the space? I'm imagining that light is being stretched out when its being red-shifted. So would this mean that the energy is still there and that it is just spread out over more space? |
From Humphreys' Introduction to Lie Algebras and Representation Theory, written in parentheses: (It can be shown that even dimensionality is a necessary condition for existence of a non-degenerate bilinear form satisfying $f(v,w)=-f(w,v)$.) Why is this? Suppose we have odd dimensionality. So $n$ is odd. We have an $n\times n$ matrix $S$ with independent rows such that $v^TSw=-w^TSv$ for all vectors $v,w$. How does this provide a contradiction? | There is the standard proof using $$\det(A)=\det( A^{T} ) = \det(-A)=(-1)^n \det(A)$$ I would like a proof that avoids this. Specifically, there is the proof that for $A$ a $\bf{real} $ matrix, the transpose is the same as the adjoint, which gives (using the complex inner product) $\lambda \|x\|^2 =\langle Ax, x \rangle= \langle x, -Ax \rangle=-\overline{\lambda } \|x\|^{2}$, so any eigenvalue is purely imaginary. Then we conclude that, since any odd-dimensional real matrix has a real eigenvalue, that eigenvalue must be zero. This argument doesn't work for a general complex skew-symmetric matrix. Is there something I'm missing, is there a way to modify this argument to get that zero is an eigenvalue for the complex case? Also, can somebody please give a geometric reason why odd-dimensional skew-symmetric matrices have zero determinant (equiv., a zero eigenvalue)? Thanks! |
When we say that an electron is in a quantum state that is a linear combination of two eigenstates, one with the probability of 75% and the other 25%, what is actually happening? Is the electron "really" somehow magically in these two eigenstates at once? OR The electron is in only one of these eigenstates at a time point, we just can't tell which one it is without observing it. And when we observe the electron many times, we find it in one eigenstate in 75% of the time, and in the other eigenstate in 25% of the time, because the electron switches between these two states and just spends three times more time in one eigenstate than the other? Obviously, I think the second case is correct. But which case is correct? The 1st or the 2nd? My reactions to your possible answers: If the 1st case is correct: That's insane, thank you! If the 2nd case is correct: Then, isn't the principle of superposition just an "assumption" that should not be taken literally? That is, the electron is not at two eigenstates at once, but one of them at a certain time point, and we just have no way of finding out which state, before observing it? So we just say that it is in an eigenstate X with a probability P(X), such that the sum of probabilities for all eigenstates equal to 1? I could also, for example, say: I don't know where my friend Max currently is. He could be at school with a probability of 75% and at a bar with a probability of 25%. We all know that Max is not at school and the bar simultaneously, and we can just call him to find out where he is. But before calling him, for the sake of being able to conduct our calculations, we can "assume" that he is at school and the bar simultaneously, with the assigned probabilities, but we actually know that we just made this assumption to be able to carry on with our calculations about Max. Isn't it just a fancy way of saying that something is in state X with P(X) and state Y with P(Y), and it is in only but only one of these states at all times, however, we just can't find out which state before observing that something, but can merely say with which probability we're likely to find it at a certain state? Then why is everyone so surprised about the superposition principle? | What's an atomic superstate/, and how is it possible? I understand the basics - being something can be moving and staying still at the same time; the observer changes the behaviour - but I'd like to know a little more, as it interests me, and how is it possible without actually interfering with said thing? |
How can I insert the following scripts to run during bootup? These scripts are: apm=off no=hlt The function of these scripts is to prevent premature laptop shutdown when my laptop is a little bit hot but not hot enough to burn the CPU. | I need to add the boot parameter foo=bar to my kernel. How can I do this once for testing, and permanently if testing was a success? |
The following aligned equation gives an error 'Extra }, or forgotten \right.': \begin{equation} \begin{aligned} U&=\mathbb{R}^{M N}\\ V&=\mathbb{R}^{2 M N}\\ W&=\mathbb{R}^{4 M N}\\ \min_{v\in V} \left\{E_p(v)&=\|\nabla v\|_{W,1}+\lambda \|\rho(v)\|_{U,1} \right\} \end{aligned} \end{equation} Removing the \left and \right commands avoids the error: \begin{equation} \begin{aligned} U&=\mathbb{R}^{M N}\\ V&=\mathbb{R}^{2 M N}\\ W&=\mathbb{R}^{4 M N}\\ \min_{v\in V} \{E_p(v)&=\|\nabla v\|_{W,1}+\lambda \|\rho(v)\|_{U,1} \} \end{aligned} \end{equation} I don't understand why having the alignment marker inside a \left \right command is an error. How do I align an equation with the alignment inside a \left \right command? | I want to align equations (using the align environment from the amsmath package) inside matching \left( and \right) commands. For example: \documentclass[a4paper,12pt]{article} \usepackage{amsmath} \begin{document} \begin{align} a \left( b &= c \right)\\ d \left( e &= f \right) \end{align} \end{document} But that code gives this error: Extra }, or forgotten \right. The error disappears when I remove the delimiters. Is there a workaround for this? |
Hi to all first of all i am sorry because my first language is not english I want understand which one is faster C# data types or .net data types i try to understand by below code and i think .net data types is faster(is this correct?) i test this code both with x86 and x64 platform SW.Start(); for (Int32 i = 0; i < 99999; i++) { for (Int32 j = 0; j < 999; j++) { Int32 a = 37; Int32 b = 37; Double c = Math.Pow(a, b); String d = "abcde"; String e = "abcde"; String f = d + e; } } Console.WriteLine(SW.Elapsed.TotalMilliseconds); SW.Stop(); Console.ReadKey(); and my second code Stopwatch SW = new Stopwatch(); SW.Start(); for (int i = 0; i < 99999; i++) { for (int j = 0; j < 999; j++) { int a = 37; int b = 37; double c = Math.Pow(a, b); string d = "abcde"; string e = "abcde"; string f = d + e; } } Console.WriteLine(SW.Elapsed.TotalMilliseconds); SW.Stop(); Console.ReadKey(); thank a lot | Example (note the case): string s = "Hello world!"; String s = "Hello world!"; What are the guidelines for the use of each? And what are the differences? |
I'm trying to build my first "serious" webpage. I have just started and I stuck on applying old event listeners on new div section. I would like to apply all old listeners on $(".novo").append("new div ..") I have tried to use on() functions but it doesn't seem to work. And also I have issues when adding new list. It adds to every present div. I want to add it only on clicked div. <body> <button class="novo">Novo</button> <div class="container"> <div class="grupa"> <h1>To-Do List<span id="form"><i class="fas fa-edit"></i></span></h1> <input type="text" placeholder="Add New Todo"> <ul> <li><span><i class="fas fa-trash-alt"></i></span> Sabah</li> </ul> </div> <script type="text/javascript" src="Assets\JS\projekt.js"> </script> </body> jS: $("ul").on("click", "li", function(){ $(this).toggleClass("completed"); }); $("ul").on("click", "span", function(event){ $(this).parent().fadeOut(500, function(){ $(this).remove(); }); event.stopPropagation(); }); $("input[type='text']").keypress(function(key){ if(key.which === 13){ var todoText = $(this).val(); $("ul").append("<li><span><i class='fas fa-trash-alt'></i></span> " + todoText + "</li>"); } }); $("#form").click(function(){ $("input[type='text']").fadeToggle(150); }); $(".novo").on("click", function(){ $(".container").append("<div class='grupa'><h1>To-Do List<span id='form'><i class='fas fa-edit'></i></span></h1><input type='text' placeholder='Add New Todo'><ul><li><span><i class='fas fa-trash-alt'></i></span> Sabah</li></ul></div>"); }); Thank You!! | I have a bit of code where I am looping through all the select boxes on a page and binding a .hover event to them to do a bit of twiddling with their width on mouse on/off. This happens on page ready and works just fine. The problem I have is that any select boxes I add via Ajax or DOM after the initial loop won't have the event bound. I have found this plugin (), but before I add another 5k to my pages with a plugin, I want to see if anyone knows a way to do this, either with jQuery directly or by another option. |
It is really annoying that I cannot add comments or follow-on questions to topics without enough "reputation points". I recently upgraded to Ubuntu 20.04 and now my fslint won't work. I found a discussion about fslint here, but I cannot ask a simple followup question. How do I: #1 increase my reputation points, and #2 run fslint in Ubuntu 20.04 after installing it? (see thread below) | I tried to install fslint :~# apt install fslint and I received Package fslint is not available, but is referred to by another package. This may mean that the package is missing, has been obsoleted, or is only available from another source E: Package 'fslint' has no installation candidate Well, fslint was avaliable in Ubuntu 19.10. In the fslint website shows it is available for Ubuntu. What happened? Was it removed from the 20.04 repository? Or they substituted for another package or name? |
I need to travel from Spain to UK and return on my US passport. Is there a reason I cannot do this? Thanks. | I'm a British National (Overseas), which basically means that while I don't have the right of abode in the UK, I am permitted to visit the UK without a visa. However, my passport has expired, and while it's being renewed, the schedule is a bit tight. At the same time, I'm an US Citizen, and since I'm only planning to visit the UK, I don't need a visa if I enter on my US passport. I'm not familiar with UK immigration law, and given that this probably isn't too common a situation, the UK Border Agency website doesn't have an answer that I can can find, nor do they seem to have a contact form that fits my situation, so here's hoping someone knows—given that I'm a British National (Overseas), am I required to enter the UK on my UK passport, or can I just use my (valid) US passport? |
Here is my conversation with HP regarding scanners: 08/30/2013 07:34:15AM Agent (Janelle M.): "Hello, Ken." 08/30/2013 07:34:22AM ken schutter: "Hello" 08/30/2013 07:35:06AM Agent (Janelle M.): "Ken, I appreciate your interest in HP products." 08/30/2013 07:35:40AM ken schutter: "Hp is my preference for all printers because they work out of the box in linux." 08/30/2013 07:35:57AM Agent (Janelle M.): "I am very sorry to inform you though, however, our scanners and All-in-one printers with scanning capability do not support Linux anymore." 08/30/2013 07:36:32AM ken schutter: "Too bad. HPLIP is no longer valid driver?" 08/30/2013 07:36:57AM Agent (Janelle M.): "Yes, it is no longer a valid driver, Ken. I am sorry." 08/30/2013 07:37:14AM ken schutter: "I will try elsewhere. Thanks" 08/30/2013 07:37:27AM Session Ended | Let's assume that one has some modern HP printer and/or scanner which is not supported by HPLIP package from official repository. Currently Ubuntu versions have : trusty (14.04LTS): 3.14.3-0ubuntu3.4 xenial (16.04LTS): 3.16.3+repack0-1 bionic (18.04LTS): 3.17.10+repack0-5 focal (20.04LTS): 3.20.3+dfsg0-2 groovy (20.10): 3.20.5+dfsg0-3build1 hirsute (21.04): 3.21.2+dfsg1-2 What can one do if printer is supported in newer version of HPLIP (checked this in )? |
I would like to include this diagram into my work However, I don't know how to start, since I have never used tikz, but the more modest tikzcd for my commutative diagrams. I should point out three things I absolutely have no idea how to introduce them into any kind of diagram: In the diagram, there appears a circle with a 1 inside it. It should appear where it is, and as it is. The arrows If you notice, the elements of the face that meets both cubes have some inclination, so that they are parallel to the corresponding lines. It would be cool to emulate that effect. I know it is habitual to expose some code of what the one making the question has tried, but in my case, I have absolutely no experience with tikz... Sorry for the inconvenience, and thanks. | I want to draw this digram below in Latex and thank you . |
A general question of mine who working on API endpoints as backend system. I wonder what if all endpoint methods are , and when it is better to use ? | From what I can gather, there are three categories: Never use GET and use POST Never use POST and use GET It doesn't matter which one you use. Am I correct in assuming those three cases? If so, what are some examples from each case? |
The lipo has a high discharge of 4A 30C. i read that arduino can only handle 2A does this mean it uses 2A out of 4A or is there some kind of system to limit the amp draw? | Power supplies are available in a wide range of voltage and current ratings. If I have a device that has specific voltage and current ratings, how do those relate to the power ratings I need to specify? What if I don't know the device's specs, but am replacing a previous power supply with particular ratings? Is it OK to go lower voltage, or should it always be higher? What about current? I don't want a 10 A supply to damage my 1 A device. |
I am having some issues charset and special chars in this page : i have added in my header section charset code : <html lang="fr"> <meta charset="UTF-8"> i tried to add in the body section header('Content-Type: text/html; charset=utf-8'); nothing changed still the same problem , i went to htaccess file i added AddDefaultCharset UTF-8 but it didn't solved this issue can you help with a solution to that situation | I'm setting up a new server and want to support UTF-8 fully in my web application. I have tried this in the past on existing servers and always seem to end up having to fall back to ISO-8859-1. Where exactly do I need to set the encoding/charsets? I'm aware that I need to configure Apache, MySQL, and PHP to do this — is there some standard checklist I can follow, or perhaps troubleshoot where the mismatches occur? This is for a new Linux server, running MySQL 5, PHP, 5 and Apache 2. |
How does $U(1)$ gauge group at long distances, give rise to ? Also why is it said that Dirac monopole is a topological defect in a compact $U(1)$ gauge theory? | Does a magnetic monopole violate $U(1)$ gauge symmetry? In what sense and why? Insofar as I know, there are at least two types of magnetic monopoles. One is the Dirac monopole while the other is the monopole in Grand Unified Theories (GUT), e.g., 't Hooft-Polyakov monopole. In the latter case, some non-Abelian gauge theory breaks down to a (compact) $U(1)$ gauge theory wherein monopoles can be observed from a large distance. The monopole field is not from the $U(1)$ degrees of freedom and nothing is singular. On the contrary, Dirac monopole is singular (topological defect?) and we must introduce Dirac string or patches of vector potential $\vec{A}(x)$. Are these no more than artifacts arising when one tries to describe the monopole field within the $U(1)$ gauge theory by assuming $\vec{B}=\nabla\times\vec{A}$? It seems true since two Maxwell's equations that magnetic monopole might affect can be cast in the differential form $\mathrm{d}F=0$ and $F=\mathrm{d}A$ in Minkowski spacetime, from which $U(1)$ gauge invariance manifests for $\mathrm{d}(A+\mathrm{d}\chi)=\mathrm{d}A$. However, I later noticed two seminal papers on Dirac monopole & , in which the authors claimed the following electromagnetism without monopole $\rightarrow$ connection on a trivial $U(1)$ bundle electromagnetism with monopole $\rightarrow$ connection on a nontrivial $U(1)$ bundle And the wave function of an electron around a Dirac monopole should be regarded as a section which is free from discontinuities. I've no idea about fibre bundle. Anyway I guess $U(1)$ theory does not necessarily expel Dirac monopoles. It has something to do with the topology of some manifold in the theory? Which manifold? Can anyone shed light on this intriguing issue? Thanks in advance. |
if(preg_match("/" . $filter . "/i", $node)) { echo $node; } This code filters a variable to decide whether to display it or not. An example entry for $filter would be "office" or "164(.*)976". I would like to know whether there is a simple way to say: if $filter does not match in $node. In the form of a regular expression? So... not an "if(!preg_match" but more of a $filter = "!office" or "!164(.*)976" but one that works? | I know it's possible to match a word and then reverse the matches using other tools (e.g. grep -v). However, is it possible to match lines that do not contain a specific word, e.g. hede, using a regular expression? Input: hoho hihi haha hede Code: grep "<Regex for 'doesn't contain hede'>" input Desired output: hoho hihi haha |
I stumbled upon it in this . It is at 1 hour 21 minute and 42 second. If the Israelis would ever once just say we got screwed in 1948, and we are sorry it happened, we would be willing to make peace. I think it is quite clear that the sentence is conditional, thus it is not correct to use would in the if clause. Did the lecturer say that by mistake? Or is that some kind of grammar I am not aware of? And by the way, what does get screwed mean there? | I'm having a discussion with my wife on . She says we cannot have "would" in a hypothetical if statement: If I would want to change my address, should I let you know? She says that "would" can only occur in the second part (as in Type 2). If this is the case, is there then no way to describe "a hypothetical situation in which I would want to change my address" as conditional? I feel like this sentence is different from: If I want to change my address, should I let you know? Then again, maybe it is just that I'm confused with how we would say it in Dutch. And what about if it is the change, not the wanting to change, that is hypothetical? In other words: If I would change my address, should I let you know? |
I have a logo it's an image of earth and around it are arrows, I would like to trace a plane along those arrows please if there's any special instructions to extruding it please let me know | I am currently working on converting my logo vectored as a SVG to a 3D model using the 2.72 version. I ran into a problem with my logo because it contains a black stroke and an orange stroke (see both images below), but currently all I have is the interior color of each shape. I was wondering whether or not there was a simple way to add in these strokes, and how exactly to go about creating the strokes. Thank you in advance community! |
I had an HDD in my Laptop. I connected that HDD to some other laptop via USBtoSATA bridge and it dint show in My Computer. After trying for several times, I went to disk management, and as soon as it opened it said I need to initialize my disk. I selected intialize in MBR and then it showed unallocated space for my 1 TB HDD. I immediately disconnected my HDD. My laptop is in service center and will be available after one week. If I attach my HDD back into my laptop, will it work the way it used to ? Is my data lost ? | I was reformatting one of my extra hard drives with Windows DiskPart and accidentally selected the wrong hard drive. I used the clean command, but it wasn't long before I realized I cleaned the wrong one. I only cleaned the drive, I did not format it or tool with it in anyway. The drive I wiped had two partitions on it, one was unencrypted and the other was encrypted with TrueCrypt. Is it possible to recover my encrypted partition? I do not have a backup of the header, but I've heard it's possible. If anyone can shed some light on the situation, or point me in the right direction, it'd be greatly appreciated. Thank you! |
I have a use-case like this: Based on the parameter passed - I have to create an object corresponding to it but the underlying functionality remains same. public void selectType () { String type = "ABC"; publishType(type); } public void publishType(String type) { if (type.equals("ABC")) ABCtype publishObject = new ABCtype(); if (type.equals("XYZ")) XYZtype publishObject = new XYZtype(); publishObject.setfunctionality(); } What is a better way to approach this? Which design pattern does it fall in? Another doubt I have is - how to initialize publishObject? It gives an error like this. | 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 am coming from Windows back-ground (never used Linux), and HTC Wildfire is my first Android phone. I can see that many app like Facebook for HTC Sense, Flickr, Footprints, Friend Stream, Gmail, Peep, Stocks and many more as start-up apps. How can I find which apps are start-up apps, and how to remove a particular app from starting up at boot (or say soft reset) | Possible Duplicate: I've installed some applications that I mostly like, except for the fact that they all decided they were too important not to auto-start. None of them give me any option within the application to disable the auto-start "feature." Can I stop these applications from auto-starting? And if so, how? Note: My phone is not rooted, so I'm especially interested in solutions that do not require a rooted device, but all answers are welcome, even if they require rooting the device, since I may do this eventually. Also note: I'd prefer not to fiddle around with clumsy auto-kill features in task-killer programs, as I've found them to be incredibly unreliable on my phone (Motorola Milestone/Droid). |
Prove that every integer greater than $17$ is a non-negative integer combination of $4$ and $7$. In other words, for all natural numbers $n$, $n$ greater or equal to $17$, there exists non-negative integers $i(n)$, $j(n)$ such that $$n = i(n)4 + j(n)7.$$ | I want to determine the set of natural numbers that can be expressed as the sum of some non-negative number of 3s and 5s. $$S=\{3k+5j∣k,j∈\mathbb{N}∪\{0\}\}$$ I want to check whether that would be: 0,3, 5, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, and so on. Meaning that it would include 0, 3, 5, 8. Then from 9 and on, every Natural Number. But how would I explain it as a set? or prove that these are the numbers in the set? |
I'm looking to optimize MySQL INNODB by tuning buffer pool individual instances. According to the MySQL documentation: "The total size you specify is divided among all the buffer pools. For best efficiency, specify a combination of innodb_buffer_pool_instances and innodb_buffer_pool_size so that each buffer pool instance is at least 1 gigabyte." However, this doesn't specify the optimum approach to defining innodb_buffer_pool_size. Which of these is considered a better approach: a) a larger number of smaller buffers (given that each buffer instance is >1GB) e.g. 45 buffers instances over 50GB buffer pool or b) a smaller number of larger buffers e.g 5 buffer instances over 50GB buffer pool ? | Server Characteristics Total system RAM: 8GB (running MySQL + other stuff than MySQL on it i.e. not dedicated to MySQL) Number of CPU Cores: 6 I have data in the db amounting to about 2GB I have InnoDB Buffer Pool Size set to 4GB Which is better: Innodb Buffer Pool Instances set to 1? Innodb Buffer Pool Instances set to 2 (2GB in each)? Innodb Buffer Pool Instances set to 4 (1GB in each)? Innodb Buffer Pool Instances set to 8 (the default setting) I'm thus not sure as to how to reason when it comes to Buffer Pool Instances and also the whole "use instances or suffer OS Swap when having such large InnoDB Buffer Pool Size". |
I'm testing Eevee and it seems quite nice ! This is a scene with just a sun. Here's how it looks in Eevee: And now, with Cycles: The mugs and the computers on the table almost don't have shadows with Eevee... I know it is NOT Cycles and that shadows won't render as good as it. But anyway, this look almost unrealistic. What should I do to get better shadows ? Thanks a lot ! | I get different lightning render with the same scene camera setup. Cycles render (both experimental and supported feature set) gets weaker lightning and needs more energy. How can I get the same lightning and reflection setup with EEVEE and Cycles? |
So i just finished a small Java program that I've been working on throughout the week and I want to generate an .exe file of it so I can share with my friends. I'm working on Apache Netbeans 11.3 and JDK 8. I can successfully generate the .jar file but that's pretty much useless. | If I have a Java source file (*.java) or a class file (*.class), how can I convert it to a .exe file? I also need an installer for my program. |
I am trying to solve following : $$a(n)=2\cdot a(n-1)+5\cdot a(n-2)+6\cdot a(n-3)$$ with the initial conditions given by $a(0)=3,a(1)=2,a(2)=14$. So first of all, I want to mark that there exists a theorem which states the following: Let $P(x)=u_n\cdot x^n+u_{n-1}\cdot x^{n-1}+....+u_1\cdot x+u_0$ be a polynomial with real coefficients, and $u_n\neq 0$. If $P(x)$ has rational roots, they are of the form $\pm p/q$ where $p|u_0$ and $q|u_n$. So first what I have tried is to construct characteristic equation or $$r^3-2\cdot r^2-5\cdot r-6=0$$ Now I have a problem to solve cubic equation also from the theorem I need a few help to understand it well. Please help me. Thanks a lot. | In my text book, to solve cubic equations, I need to find by trial & error what $f(a)$ will make the equation 0. The factor will be $(x-a)$ then the other factor will be $Ax^2+Bx+C$ then I can solve using compare coefficient But for te first part, is there any other way apart from trail & error? Or is there some technique to guess the factor of an equation? The question I am currently doing happens to be $2x^3+3x+4=9$ UPDATE: $2x^3+3x+4=9$ should be $2x^3+3x+4=9x^2$ UPDATE 2 So I am going to try substituting $x=\pm{1}, \pm\frac{1}{2}, \pm{2}, \pm{4}$ When $x=-\frac{1}{2}$, one of the provided answers, $2(−0.5)^3−9(−0.5)^2+3(−0.5)+4=-18.75\neq 0$ did I make a mistake? |
'on vs upon' and 'in vs into' They are very similiar and I think there could be an equation, literllay: upon= up+on and in+to. Is ther any big difference when learners of English should keep in mind? | While conversing with my friend I got confused between these two sentences: It depends upon the context. It depends on context. Which one is more apt in usage and why? |
Serial number EY121000136 it's a 20 inch bmx bicycle | We often get questions on bicycles.stackexchange about identifying a bicycles manufacturer, model, make, and year. Often these questions are downvoted or closed -- usually with a comment attached to them that it's not necessary to know the exact model/make/year of a bicycle if you want to fix, repair, or ride your bike. Why should owners not care about the model/make/year of their bicycle? Especially when it comes to less expensive bikes (aka BSOs) and BMX bicycles? This is intended as a canonical question that we can point closed questions to. Also see (generally not helpful for identifying a brand/model) |
Here's my situation: I'm trying to make a page with two DIVsfilling whole page (height 100%, width 50% each). Also, the content in the DIVs is to be vertically aligned to middle. Is there an easy way to achieve this without hacks or javascript? I've tried body,html{height:100%;} .mydiv {display:table-cell;height:100%;vertical-align-middle} but that doesn't work...and with that code, i have to specify width in pixels instead of percentage | I want to center a div vertically with CSS. I don't want tables or JavaScript, but only pure CSS. I found some solutions, but all of them are missing Internet Explorer 6 support. <body> <div>Div to be aligned vertically</div> </body> How can I center a div vertically in all major browsers, including Internet Explorer 6? |
A teacher has sent us an exercise in which we have to use the terminal to display an image as ASCII, if we can put color on it, it is a 10. Originally, the exercise is proposed for Linux, but I wonder if this can be done in the new Windows Terminal. I know for Linux or Osx there are tools like gif-for-cli and I would like to know if there is support for 256 colors in Windows. Thank you. P.D: The script has to be in python EDIT I found that prompts all 256 colors in the terminal. So I think the answer is yes | How can I output colored text to the terminal in Python? |
How can I save a uploaded file (a pdf for example) to a MemoryStream? Thanks!! | What is the best way to copy the contents of one stream to another? Is there a standard utility method for this? |
I am learning JavaScript and now I am trying to run the following codes in Node to display the values in an array: let array = [1, 2, 3]; for (let a in array) { console.log(a); } I expect the above codes will print 1, 2 and 3 However, it prints 0, 1, 2. Can anyone tell me what's going wrong in my code? | I've been told not to use for...in with arrays in JavaScript. Why not? |
I'm stucked at calculation this limit. Using $Z_n =\sum\limits_{n=1}^{\infty} \frac{1}{n}$ I could rewrite my series as $Z_{2n} - Z_n$ but I couldn't go any further since harmonic series diverges and I wasn't able to calculate the sum. | $$\lim_{n\rightarrow\infty}\sum_{k=1}^{n}\frac{1}{k+n}$$ Could you please give me a hint how to find this limit? |
I have the keyboard shortcuts screen open. I'd like to add a Custom Shortcut which maps copy and paste to Super + C or Super + V. However I don't know what to call this shortcuts name and command. Is there a list of these anywhere? | I switch back and forth between two computers constantly: OSX Snow Leopard Ubuntu 10.10 I'd like to be able to make Ubuntu use the same keyboard shortcuts as OSX System Wide, for the following keyboard sequences only (ie I don't want to make Ctrl act like Super) Super+C -> Copy Super+V -> Paste Super+T -> Open a new tab in whatever browser I'm in. Super+W -> Close a tab in whatever browser I'm in. So in short, is there anyway for me to map just these keyboard sequences to the following, system wide ? Super+C -> Ctrl+C Super+V -> Ctrl+V Super+T -> Ctrl+T Super+W -> Ctrl+W I know there are ways for me to do this for vim, and Firefox, and I'm sure specifically for most applications... but I would prefer to have to do this just once and have it work that way system wide! I'm using a standard PC keyboard, that is "Generic 105 key (intl) PC" on Ubuntu. I'm also using the same keyboard on my Mac mini. |
I have a simple CSV of {lat,lon,text} and I want to export it as a WGS84 Shapefile. How can I achieve this? | I am using QGIS 2.6.1 and have worked in an Excel file database (which was actually converted from a Shapefile). I have managed to convert it as CSV file and load it into QGIS (displays data fine) but I have trouble to convert it to a shapefile. I can view it but I can´t add or alter data in this file. I think I have to save it as a database. Any clues how to convert the xlsl-data to a database and finally to a shapefile? |
I have the following code to get the last day of the month but what is strange is that returns 31 for the last day. On that month of the year there should be only 30 days. Therefore, when I tried to parse the string data, I get Caused by: java.text.ParseException: Unparseable date: "2020/6/31 00:00:00" Some tips or example will be lovely. I would love to hear from you! val cal: Calendar = Calendar.getInstance().also { it.clear() it.set(Calendar.YEAR, 2020) it.set(Calendar.MONTH, 6) } val lastDaysOfMonth = cal.getActualMaximum(Calendar.DAY_OF_MONTH) | In java.util.Calendar, January is defined as month 0, not month 1. Is there any specific reason to that ? I have seen many people getting confused about that... |
I'm taking a course in algebraic number theory and we are starting to discuss lattices and Minkowski theory. We were given this introductory exercise: Let $K$ be a field of numbers of order $n$ and embbedings $\tau_1, ..., \tau_n:K\to\mathbb{C}$. Show that $\phi:K\otimes_{\mathbb{Q}}\mathbb{C}\to \prod_{\tau}\mathbb{C}$ defined by $\phi(a\otimes z)=(z\,\tau_1(a), ..., z\,\tau_n(a))$ is an isomorphism between $\mathbb{C}$-vector spaces. I've already seen a solution, which uses linear independence of characters (which I'm familiar with) to prove injectivity and then uses a dimension argument to conclude bijectiviy. I know I'm able to follow the outline of that proof, but actually my problem is more basic: I just don't know what the sets $K\otimes_{\mathbb{Q}}\mathbb{C}$ and $\prod_{\tau}\mathbb{C}$ actually mean. I'm familiar with the tensor product $U\otimes V$, when $U$ and $V$ are both $\mathbb{F}$-vector fields (i.e., both have the same base field), so when I see the notation $U\otimes_{\mathbb{Q}} V$, I assume implicitly that $U$ and $V$ are both $\mathbb{Q}$-vector spaces, but that is not the case with $K\otimes_{\mathbb{Q}}\mathbb{C}$. That is really confusing me: take for example $K=\mathbb{Q}(i)$. What is the canonical basis for $\mathbb{Q}(i)\otimes_{\mathbb{Q}} \mathbb{C}$? How am I supposed to write $1\otimes \sqrt{2}$ in the canonical basis? Like $\sqrt{2}(1\otimes 1)$? But am I allowed to "pull out" an irrational number from the second coordinate like that? Then what does $\mathbb{Q}$ in "$\otimes_{\mathbb{Q}}$" stand for? I can't make sense of it. Second, I thought $\prod_{\tau}\mathbb{C}$ should be the set of $n$-uples $(\tau_1(a), ..., \tau_n(a))$ where $a\in K$. But then how do I know that $\phi(a\otimes z)=(z\,\tau_1(a), ..., z\,\tau_n(a))$ is of the form $(\tau_1(b), ..., \tau_n(b))$ for some $b\in K$? If there is no such $b$, $\phi$ would not be well defined... Any help would be useful, thanks in advance! | In §5 of chapter 1 of Neukirch’s Algebraic Number Theory on Minkowski theory, it is claimed that $$ℂ \otimes_ℚ K → K_ℂ,~z \otimes a ↦ zj(a)$$ yields an isomorphism. Here, $K$ is an algebraic number field, $K_ℂ = \prod_τ ℂ$ (where $τ$ runs through all field embeddings $K → ℂ$) and the map $j$ is given by $$j \colon K → K_ℂ,~a ↦ (τa)_τ.$$ I’m having a hard time seeing this isomorphism. What’s the inverse map? |
I'm at the beggining of a Group Theory course, and I'm trying to solve this problem: Let $G = 1$ (being $1=\{e\}$, $e$ the neutral element in $G$) be a group containing no subgroup different from $1$ and $G$. Prove that $G$ is cyclic of prime order. I've consider using that, given $g\in G$, $n\in\mathbb{N}$, $r=|g|$, I can conclude that $$g^n=e \Leftrightarrow r|n \text{ ($r$ divides $n$)},$$ but I'm not sure if it's useful without proving first that $G$ is cyclic, and I'm not sure how to do it. Any help will be appreciated. | This is something I'm supposed to be able to prove for an upcoming test, but I can't find anything to help me prove this in my notes or the chapter, which is on cosets and Lagrange's theorem. If all I start with is the group having no proper subsets, then that means any subset is the whole group. By Lagrange's theorem, that means the index is $1$, but that doesn't get me anywhere. Where do I start? |
The question I have is: Why is space (almost perfectly) flat in our neighbourhood? (I am disregarding the deviations due to the sun and the planets.) Is it correct to say that space is (almost) flat because throughout the universe, masses are distributed (almost) homogeneously? (Greetings to Sciama.) Or is it more correct to say that space is (almost) flat because that is what occurs without any mass at all? In this case, the answer might be: space is almost flat because there is so little mass in the universe. Is this closer to the truth? Or is there a third answer? | I know that in our particular case the inflaton field expanded the volume of the universe while simultaneously maintaining a mass-energy density close to the critical density all the while, thus the flatness. But why that number? Why didn't the inflaton field maintain a density which would have caused some other kind of curvature instead? I thought inflation was supposed to solve the fine tuning problem but I still run into the problem. Basically, what makes inflation "choose" which energy density to maintain? And if it always picks the critical density (for flat curvature), why is that? |
I'm trying to do the Boethiah's Calling quest and I need a follower for it of course to sacrifice. But whenever I ask someone to be my follower they say I already have one. This is a problem because I don't have a follower. I had a dark brotherhood follower a month or two ago but I lost her and haven't been able to find her since. I've fast traveled and slept and tried multiple things to find her but to no avail. Now I can't get a new follower for the quest or get rid of my old one. | Whenever I try to get somebody to follow me in Skyrim they something in the lives with "You already have a follower.". The problem is, I don't. I have not, to my recollection, had a follower at any given point in the game. The only thing I can think of is that I have (spoiler) finished Anriel's Endeavors and gotten him as a summon creature. Or do I have a hidden follower that I can't remember. A dog or a horse perhaps? Note that I do not have a dog or horse following me now. I talked to dog once, and had a horse that died. Is this a common/known issue? Is there a work around? Any tips? |
I need to download database structure with data. Total size of the DB is more than 3GB. If i use phpmyadmin it is not working. I have also tried by increasing the execution time in php.ini. I need some tool to import and Export the data base. My database server is Mysql server. My requirement is any tool that will help to download Large database and Upload to another server. It should hold the download when internet fails. IF internet is ready it should continue the download process. The answer already existing haven't worked for me. My issue is I need to export and import data from one server to other. if Internet Connection fails. It should not start a fresh export. It should continue the incomplete process. | I need to move 20 Gb MySQL database from on Debian server to another. The problem is that there is no way to create its backup since there are almost no free HDD space on the source server. What would you suggest? |
I am a Filipino and have just been refused a UK Standard Visitor visa. My husband is British and currently working as a groundworker. It is so frustrating because the officer stated that my husband doesn't have the funds to support me. They even said that they're not convinced that my husband and I have a genuine relationship! That is totally absurd. What should we do next? We are planning to go to the embassy next month to complain about the result. Appended is a scan of the refusal letter. | Many of the UK visa refusals we see here share a common pattern and the prevailing reasons refer to V 4.2 (a) and (c). I do understand that, while the applicants may describe very different individual circumstances, there's a consistent pattern and, broadly, fall into specific categories: Credibility (lifestyle, lack of ties, visit history, lies & omissions) Funding (insufficient funds, provenance of funds, funds parking) Sponsorship (family, friends, employer) Question: What most commonly triggers a UK visa refusal where V 4.2 (a) and (c) are given as the grounds? Secondarily: Given that there is a clear pattern, to what extent are these refusals predictable? Does sponsorship make a difference? Is there a set of personal circumstances, however abstract, where a refusal is all but guaranteed? For example, why do those we see here on TSE who sought entry for the PLAB or British Army appear to be refused with a common theme? Is there a uniform shortcoming or is it just discrimination? PLAB: What is about applications for a visa, for the purpose of sitting the Professional and Linguistic Assessments Board (PLAB) exam, that seem to invite refusals. After all, the test is given so that international medical graduates can show that they qualify to practise medicine in the UK. The first part, PLAB 1, can be taken in centres outside of the UK. However, PLAB 2 can be taken only in the UK. Why can't you can't get a visa just to sit the exam, promising that you'll leave immediately after? British Army: Since Commonwealth citizens are eligible to apply online to join, even those who don't reside in the UK, why is it so difficult to get a visa just to attend an interview to see whether you are suitable? Even with an invitation from the Army, such visa applications seem to be unsuccessful. Isn't a career in the British Army a valid reason? Lastly: After such a refusal, what approaches would increase the chance of a successful application? |
What is the correct punctuation when repeating a question as a statement? See the following example, and my best guess: John: Sorry I missed your phone call. What's happening? Bob: I was wondering if you wanted to get some lunch. My discomfort with Bob's response is the following: Bob's response very strongly alludes to an underlying question, but because it is technically a statement, it doesn't get punctuated with a question mark. Question: If I wanted to communicate this response but include a question mark (to more obviously visually communicate that there is a question that needs answering), how could this be done? My best idea is to simply restate the question in its entirety and join with a colon. For example (please correct me if any part of is incorrect): I was wondering: "Do you want to get some lunch?" | This may be related to a general grammar rule, but which of these is correct? I wonder if Steve Jobs will be giving the keynote speech at WWDC this year? or I wonder if Steve Jobs will be giving the keynote speech at WWDC this year. My hunch tells me the question mark is incorrect, but I find myself instinctively wanting to add it. Is there a rule about this type of situation? |
I was looking around a bit and stumbled on something I found really strange... First thing that prompted my curiosity was seeing a certain user who obtained the badge "Enlightened" several times in a row within a short time span of 1 minute: Looking around some other badges ("Nice Answer", "Good Answer", "Great Answer"), there seemed to be some more of the same thing. Well, no more about badges (you can see a bit of them on the activity page under badges), let's move on. Onto the user's page, all the rep are in multiple of 3: I mean, don't you just find it strange? Even the downvotes are in multiple of 3 and at exactly the same time. Could it be a bug or is it really that easy to stack up so many badges in a row. If so, I'd like to know the secret ;) NOTE: I hope it's okay if I don't blur the username. I don't want to bring the user negative attention, but it just jumped out to me. I'm not sure what to tag, so I'm using the discussion tag for now, since I'm not even sure what's happening here. | I just took a look at the Recent Badges column and the high frequency of occurrence of a username caught my attention: I then visit the links of these badges to see how this user (jrharshath) earn all these badges at once. It turns out that these questions are quite old and he should have earned them a long time ago. Famous Question: Notable Question: Good Question: Why did he earn all these badges at the same time? |
How do I, and is it even possible, get actual maximum size of character array passed to a function as a pointer? int size=0; while (char_array[size++]) this won't work, as it will return number of characters in the array, and I need its actual size. Also I cannot use any libraries (specifically string) or my own classes or basically anything useful. EDIT as it turns out, I will have to explain the assignment quickly. And I am told not to do it in the comments. So here it is: I have to implement a function that has three character arrays passed as pointers. Cannot change that in any way. First one is a string with commands included in that string (important). The commands are simple: delete x letters, and so on, but some are tricky, like add x letters from second/third character array to the right. Why tricky? Because those arrays may contain more commands, which will then be added to the string I'm working on. So one way to do it is to work on the string passed to a function, but that would be very slow, and I would have to add/delete characters in the middle, which basically means moving the rest of the letters many times. So I would have to have m*n opertions, where n is size of string and m is ammount of commands. But only n operations if I could write to another string. However I don't know how much space would I need, because the commands could add more commands, which would add more letters to initial ammount of characters. Checking the ammount and type of commands beforehand would be slow and make the whole thing rather pointless. However I know that the string passed to the function will have enough space (it's in the assignment specifications). So if I just could access it's size, I could declare another string with same size, knowing it would fit the resulf for sure. So what will I do? I will declare this local string that I'm writing into with initial size and then if the result is greater I will rewrite it to a bigger string. Which will give me n times z operations, where z is a number of rewrites, which is still better than n times m, but worse than just n. | First off, here is some code: int main() { int days[] = {1,2,3,4,5}; int *ptr = days; printf("%u\n", sizeof(days)); printf("%u\n", sizeof(ptr)); return 0; } Is there a way to find out the size of the array that ptr is pointing to (instead of just giving its size, which is four bytes on a 32-bit system)? |
Background Many events are included in the revisions list, primarily: edits deletions closures However, the only thing that creates the link to the revisions list is edits. This link is in the form of "edited x minutes ago". This means an assortments of events can occur to a question that has never been edited without any evidence of that fact. I tested this on a question of my own which I had never edited, but probably needed a minor edit. You can see the . I deleted it then undeleted it, all without any revision list link appearing, I finally edited it and the full revisions list was available How this affected me This affected me when I asked a question regarding an on going event. I was criticised for posting a duplicate of a question that was "still on the front page!". However what had actually happened (I eventually found out) was that the original was posted, self deleted and then undeleted a few minutes later (for whatever reason). I posted my duplicate while the original was deleted but there was no (available) record of that until the question was later edited. Request Have any event that are included in the revisions history also generate an appropriate link to the revisions list on the question | In the latest I saw this: 2013-02-18: The revision history of a question that was closed as a duplicate is now showing the chosen originals as part of the "Closed as duplicate" notice. That sounds cool, so I went to go see what it looks like and realized that questions with , but no edits, don't have an "edited <date>" link to click. This applies to questions which had a bounty posted, or have been closed, reopened, locked, deleted, etc. Examples: , revisions: , revisions: I realize I can manually type the URL: https://meta.stackoverflow.com/posts/168761/revisions But it would be nice to simply click. It could say "revised" instead of "edited" if there were no edits: |
trigger Splittrigger_newclass on Indexing__c (before delete,after insert) { list<C_Voyage__c> lstvoyage=new list<C_Voyage__c>(); list<string> q = new list<string>(); list<string> p = new list<string>(); //To store parent ids list<id> IndIds=new list<id>(); for(Indexing__c Ind:trigger.old) { IndIds.add(Ind.id); system.debug('inids>>>'+IndIds); } //Collecting all child records related to Parent records list<C_Voyage__c> listVoyage=[select id,main_case_id__c from C_Voyage__c where Indexing__c in :IndIds]; system.debug('listVoyage'+listVoyage.size()); //deleting child records delete listVoyage; for(Indexing__c y:trigger.new) { system.debug('INdex>>>>>'+y); if(y.Voyage_Created_Ref__c !=null) { p=y.Voyage_Created_Ref__c.split(','); for (Integer i = 0; i < p.size();i++) { C_Voyage__c tst = new C_Voyage__c(); tst.Voyage_Ref__c = p[i]; tst.Voyage_Type__c = 'Created'; tst.Indexing__c= y.Id; tst.main_case_id__c= y.Case_Indexing_Ref__c; lstvoyage.add(tst); system.debug('listofvoyage>>>>>'+lstvoyage); } upsert lstvoyage; if(y.Voyage_Amended_Ref__c !=null) { q=y.Voyage_Amended_Ref__c.split(','); for (Integer j = 0; j < q.size();j++) { C_Voyage__c atst = new C_Voyage__c(); atst.Voyage_Ref__c = q[j]; atst.Voyage_Type__c = 'Amended'; atst.Indexing__c= y.Id; atst.main_case_id__c= y.Case_Indexing_Ref__c; lstvoyage.add(atst); } upsert lstvoyage; } } } } | This is a canonical question and answer developed by the community to help address common questions. If you've been directed here, or your question has been closed as a duplicate, please look through the resources here and use them to shape more specific questions. To browse all canonical questions and answers, including more unit test resources, navigate to the tag. This canonical question is intended to address several classes of common questions by providing a quick summary and links to comprehensive resources: How is code coverage obtained and calculated? How do I increase my coverage? Why can't I cover these lines? Why isn't the body of my loop or conditional statement covered? |
When you accept an answer, it seems you should also (by etiquette?) upvote the answer. Why doesn't the checkmark count as an automatic upvote? | Is there ever a case where you would want to accept an answer, but not upvote it? I can't think of a single situation where this would be the case.. So would it not make sense to have the "Accept" button upvote the answer too? |
Often we see in news they say AstraZeneca is 95% effective, while Chinese vaccine is 50%. I have question how to interpret these numbers. Does this mean that if you get vaccinated with AstraZeneca for example, then assuming above numbers, there is 5% chance you will get the virus? Also my question is do these percentages say anything about whether you will develop severe symptoms or not? For example does it mean that when we say Chinese vaccine is 50% effective does it mean it will reduce the severity of symptoms on half (due to 50%)? | Pfizer's paper () published recently states the following in the Efficacy subsection of the Results section: Between the first dose and the second dose, 39 cases in the BNT162b2 group and 82 cases in the placebo group were observed, resulting in a vaccine efficacy of 52% (95% CI, 29.5 to 68.4) during this interval and indicating early protection by the vaccine, starting as soon as 12 days after the first dose. Can anyone explain in simple terms the calculation of 52%? I am guessing that this number was obtained from: But why is that the calculation? Does it depend on the fact that the vaccine and placebo groups were in equal numbers, such that by observing 82 COVID-19 cases in the placebo group, we match 82 subjects in the vaccine group, and since only 39 confirmed cases were observed in the vaccine group, the authors conclude that the "complementary (to 82)" 43 subjects did not become sick, and thus the vaccine is efficient in 52% of the subjects? |
I heard several strategy about macbook power supply connection: keeping alway at least 50% of battery level let unplugged until reaching the 10% warning perform once a month a full discharge What is the best strategy to keep the battery performant on the long run? I suppose it involve some physical battery notion but also how OSX handle the battery management at the software level. | How do you maximize the cycle count of your battery? There seems to be a debate between: Leave plugged in 24/7 but do a full cycle once a month Charge to ~100%, drain to ~10%, repeat. NOTE: Taking your Which method is better and why? How much of a difference does it really make? Here are some of the better sources I've found about battery behavior so far. Even still I feel they don't conclusively answer the question above. See my elaborations below: Elaborating on Option 1 Now IF Apple engineers were smart and optimized for AC draw when plugged in to not use up your charge cycles, then it seem logical to assume that you are using effectively none of your 1000 charge cycles while plugged in. If that's the case, it would seem that the LiPo drop from holding at 100% would be vastly outweighed by the fact you're not using any charge cycles. However, this is a purely speculative assumption and I could find no evidence to either confirm or deny. If this is NOT true, and the AC adapter only goes to charging the battery, then there would be no difference. Your battery would drain to 99%, then back up to 100%, then back down to 99%, etc. Those micro-charge cycles would add up at the same rate as 100% -> 0% -> 100%, and you would get no gain. In this case the negative effect of holding LiPo batteries at 100% would outweigh everything else. Elaborating on Option 2 There are lots of good reasons why Option 2 is the way it is: Because of known LiPo chemistry issues, holding a 100% charge for a long time causes the battery to degrade Apple specifically recommends not to leave it plugged in all the time Draining a battery all the way to zero all the time is bad for the cell (Which is why ~10% is used) Heat is a killer, and when plugged in AND charging, you get extra heat that causes damage. There are a couple reasons why I'm challenging Option 2: It seems silly that the most intuitive use case for thousands of people that use their macs as primary computers is wrong. If the hypothesis in option 1 is true, you're just burning unnecessarily through your finite charge cycles. It's a pain to have to remember to keep plugging in and plugging out and be worried about whether or not your device is plugged in. |
The question is about ship stability calculations. We need to solve moment = force × distance, but in stability they put mass × distance. How, and why? Deadweight is the total weight of cargo, stores, etc. which a ship carries or can carry. -"this will produce a maximum dead weight of 72,350 tons". If it is in tonnes how can it be weight? It should be mass. If the cargo of 200 kg is loaded 2 meters from center line it will create momentum of ? Moment = 200 × 2 = 400 kg m, or 0,4 tm. How can we put mass in equation for moment, is should be force, and force is in Newtons. Weight is force, mass is not. In water ship has weight or mass? Why do they use word weight in stability when the measure is in kg or tonnes. It should be mass?! I know that in physics mass and weight are two different things. Mass is not a force, weight is force, but ship in water has force, but we express it in tonnes, not newtons. Is it because mass × gravity = volume × density × gravity so if we remove gravity we get mass = volume × density, so if the ship, water it floats in and cargo that is going to be loaded are in the same gravity force field we can use amount of mass as weight? | Yeah, those circular metal disks. Weights or masses? I call them weights because when I attach them to a spring I'm interested in their weight, but it feels odd saying a "Pick up the 100g weight". "Pick up the weight with a mass of 100g sounds better" but it still feels wrong. I don't like to call them masses, because I've never heard anyone else call them masses, unless it's someone trying to correct me for making the 'mistake'. |
How to search a string in c# using Regex, ignoring accents; For example in Notepad++, for ancient Greek, searching with regex : [[=α=]] will return: α, ἀ ἁ, ᾶ, ὰ, ά, ᾳ, .... I know Notepad++ is using PCRE standard. How to do this in c# ? Is there an equivalence syntax ? Edit: I've already tried string normalization. Is not working for Greek. for example : "ᾶ".Normalize(NormalizationForm.FormC) will return ᾶ. It looks like normalization removes accents only in case of "Combining characters". The ᾶ character is a separate character in Unicode! | I'm trying to convert some strings that are in French Canadian and basically, I'd like to be able to take out the French accent marks in the letters while keeping the letter. (E.g. convert é to e, so crème brûlée would become creme brulee) What is the best method for achieving this? |
I encountered idea of considering Sample space $\Omega$ as collection of function so far as I saw. Can you show the proof of thesis $x \neq \{x\}$? In a book I saw this thesis is included in context of Russell's paradox. Best regards, | In Russell's famous paradox ("Does the set of all sets which do not contain themselves contain itself?") he obviously makes the assumption that a set can contain itself. I do not understand how this should be possible and therefore my answer to Russell's question would simply be "No, because a set cannot contain itself in the first place." How can a set be exactly the same set as the one that contains it? To me it seems unavoidable that the containing set will always have one more additional level of depth compared to all the sets which it contains, just like those russian matryoshka-dolls where every doll contains at least one more doll than all the dolls inside it. Of course one can define something like "the set of all sets with at least one element" which of course would include a lot of sets and therefore by definition should also include itself, but does it necessarily need to include itself just because its definition demands so? To me this only seems to prove that it's possible to define something that cannot exist beyond its pure definition. |
According to the "list verse" time gets to a pause when someone or something travels at the speed of light. But a question still lies in my mind, if time always travels forward and does not stop at any point then how come it gets to a pause with respect to a body travelling at speed of light? | I read with interest about Einstein's Theory of Relativity and his proposition about the speed of light being the universal speed limit. So, if I were to travel in a spacecraft at (practically) the speed of light, would I freeze and stop moving? Would the universe around me freeze and stop moving? Who would the time stop for? |
It's always bugged me. My research behind this question was rather shallow, so I apologize if it's a duplicates. Thanks! Edit, example: Say you don't know who you are talking to on Reddit, you simply know -their- username. Is it just the way in English to call people when you don't know who -they- are? Thanks again! | Is there a pronoun I can use as a gender-neutral pronoun when referring back to a singular noun phrase? Each student should save his questions until the end. Each student should save her questions until the end. |
So I have a String of text lets say "hello world () (foo bar) (foo bar 2 (this looks cozy)) (foo bar 3..." Is there a regex pattern I could use that will get the parentheses and include any parentheses inside them to nth depth. So the matches would be "()", "(foo bar)", "(foo bar 2 (this looks cozy))", ...? | I need a regular expression to select all the text between two outer brackets. Example: some text(text here(possible text)text(possible text(more text)))end text Result: (text here(possible text)text(possible text(more text))) |
I'm reading a file line-by-line with Java and parsing the data in each line for a report. Periodically, there will be a URL that's been written to a line, and I want to bypass that line. I need to set up an if...then that tests for the presence of a URL -- in this specific case, I define that as the first four bytes of the line reading http. If the condition is true, read the next line in the file, but if the condition is false, send the current line to the parser for report output. Simple, no? I'm running into issues where I cannot get my if..then statement to accurately recognize a true condition. My only clue is that when my inputString is equal to the test value, it passes as true. Beyond that...I can't spot anything out of the ordinary. public class testClass { public static void main(String args[]) { String inputString1 = "http://www.google.com/r"; String inputString2 = "google"; String inputString3 = "google search"; String inputString4 = "http"; parseInput(inputString1); parseInput(inputString2); parseInput(inputString3); parseInput(inputString4); } // private static void parseInput(String inputString8) { int httpFlag; if (inputString8.substring(0,4) == "http") { httpFlag = 1467; } else { httpFlag = 10644; } System.out.println(inputString8+" "+inputString8.toLowerCase().substring(0,4)+" "+httpFlag); } } Here's my output: http://www.google.com/r http 10644 google goog 10644 google search goog 10644 http http 1467 I am expecting 1467 for both inputString1 and inputString4. The console appears to display my input and substring properly, and nothing in the Java Documentation suggests that my substring would be a char array or anything apart from a string, so I can't figure out why http as the first four bytes of a 4-byte string is "different" from the first four bytes of a (4+x)-byte string. What am I missing? | 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 am looking to take a portable AC unit and hopefully run a tube through a wall in another room while still cooling the room the unit is located. I have searched to attachments that could help but have come up empty. Any help would be appreciated. DR | I have a Kenmore portable air conditioner model - 408.72012. this particular model can be housed on the outside of the building and the A/C air is vented into the inside space (normally through a window). Almost the opposite of what you normally do with a portable A/C unit. I have an office right next to my LR and want to pump the A/C into my LR sometimes and other times into my office. Because I did not have a window to have my A/C Air come into my office through a hole we cut and placed and fit a flexible dryer vent pipe (the white floppy accordion style)through the wall and on the inside of my office I have the dryer vent cover with flaps (like you would normally see on the outside. This prevents and critters from getting in. I am trying to figure out how to split the out flowing A/C air though a "dual Y pipe of some type to flow into my office when I want it in there and my LR when I want it in there. IS there any such thing as a U pipe that is not rigid that I could use for this and also some how block them when I want it to flow in only one side or the other? |
Does anyone know any simple way to retrieve the country from a given IP Address, preferably in ISO_3166-1 format? | I want to retrieve information like the city, state, and country of a visitor from their IP address, so that I can customize my web page according to their location. Is there a good and reliable way to do this in PHP? I am using JavaScript for client-side scripting, PHP for server-side scripting, and MySQL for the database. |
Today i installed ISO on my USB through Rufus. At the end of unpacking progress it gave me a crash and now my USB is in read-only mode. I tried all ways on Windows and even something on live Ubuntu. Nothing helps. | When I plug in my USB flash drive, it shows up on my computer as write-protected or read-only. I am unable to transfer data to it, nor can I modify or delete any files already stored on it. I also cannot repartition or reformat the drive using Windows Disk Management, DiskPart, GParted, or other tools. The drive does not have a write-protect switch. Why did this happen and what can I do about it? Is there a way to remove the write protection? (Note that this can happen with some memory cards, too, as they often use controllers similar to those used in flash drives. In some cases, the system may report that the drive or card was formatted successfully even though it was never actually formatted; the original data reappears when the device is reinserted.) This question comes up often and the answers are usually the same. This post is meant to provide a definitive, canonical answer for this problem. Feel free to edit the answer to add additional details. |
What is the difference between following two implementaion,if no difference why we need Extension methods ? (public static List<TSource> ToList<TSource>(this IEnumerable<TSource> source);) 1.IEnumerable<Student> myExtension = mtyStudent; // "mtyStudent is colletion" myExtension.ToList(); 2.List<Student> myStudent= Enumerable.ToList(myExtension); | A "non-believer" of C# was asking me what the purpose to extension methods was. I explained that you could then add new methods to objects that were already defined, especially when you don't own/control the source to the original object. He brought up "Why not just add a method to your own class?" We've been going round and round (in a good way). My general response is that it is another tool in the toolbelt, and his response is it is a useless waste of a tool... but I thought I'd get a more "enlightened" answer. What are some scenarios that you've used extension methods that you couldn't have (or shouldn't have) used a method added on to your own class? |
We know that dna is an acid which is elaborated by deoxyribo nucleic acid.It has 4 nucleo bases.Now,the question arises, why dna has no uracil base? | What is the advantage gained by the substitution of thymine for uracil in DNA? I have read previously that it is due to thymine being "better protected" and therefore more suited to the storage role of DNA, which seems fine in theory, but why does the addition of a simple methyl group make the base more well protected? |
I want to publish the title of last uploaded videos of my favorite channels on my blog. Is there any feature on YouTube for that? | The default "Subscriptions" feed on the YouTube homepage shows all of the activity of the people that I am subscribed to on YouTube or have in circles on Google+. However, I'm most interested in new videos that the people I subscribe to (either on YouTube or by circling on Google+) create and post (neglecting comments or sharing other people's videos - what you see when you check the "show uploads only" checkbox on the YouTube homepage). However, being able to bring anything off of the YouTube homepage and into Google Reader as an RSS feed would be good. Is there a way to do this? |
I'm reading the following book: . In page 26, they attempt to prove the following theorem using Induction: For all $n \in \mathbb{N}$: $$1 + 2 + \cdots + n = \frac{n(n+1)}{2}$$ In order to prove the theorem we need to prove the following statements: $P(0)$ is true. For all $n \in \mathbb{N}$, $P(n)$ implies $P(n + 1)$. Proving the first one is easy: $$P(0) = 0 = 0 * (0 + 1) / 2$$ $$= 0 = 0 * 1 / 2$$ $$= 0 = 0 / 2$$ $$= 0 = 0$$ In order to prove the second, they state the following: $$1+2+\cdots + n + (n+1) = \frac{n(n+1)}{2} + (n+1) \tag{1}$$ $$ = \frac{(n+1)(n+2)}{2} \tag{2}$$ I don't understand how they get from (1) to (2) and how that proves that proves that for all $n \in \mathbb{N}$, $P(n)$ implies $P(n + 1)$ is true. I'm clearly missing something in the process. Can someone clear the fog for me? | I am currently studying proving by induction but I am faced with a problem. I need to solve by induction the following question. $$1+2+3+\ldots+n=\frac{1}{2}n(n+1)$$ for all $n > 1$. Any help on how to solve this would be appreciated. This is what I have done so far. Show truth for $N = 1$ Left Hand Side = 1 Right Hand Side = $\frac{1}{2} (1) (1+1) = 1$ Suppose truth for $N = k$ $$1 + 2 + 3 + ... + k = \frac{1}{2} k(k+1)$$ Proof that the equation is true for $N = k + 1$ $$1 + 2 + 3 + ... + k + (k + 1)$$ Which is Equal To $$\frac{1}{2} k (k + 1) + (k + 1)$$ This is where I'm stuck, I don't know what else to do. The answer should be: $$\frac{1}{2} (k+1) (k+1+1)$$ Which is equal to: $$\frac{1}{2} (k+1) (k+2)$$ Right? By the way sorry about the formatting, I'm still new. |
I left my bone broth out after pressure cooking for 3 hours. It was warm when I got home and consisted of a chicken carcass, lamb bones with a bit of meat and the second boiling of marrow beef bones with some vinegar. It gelled so perfectly in the fridge but should we eat it? Would boiling it again for a while make it safe? | If I left food out of the refrigerator for some period of time, is it still safe? If I left it out too long, can I salvage it by cooking it more? |
I'm wondering if there is a historical explanation as to why the New in "New York" is pronounced /nu/ (as in "Noodles") rather than /nju/ (as in RP "New Year"). Has this always been the case? Or did the pronunciation change over time? | My coworker and I have been having this discussion for a day or two... What is the most correct way to pronounce 'new' or 'news' ? Does it rhyme with 'few' ? or 'snooze' ? Does 'new crew' rhyme? I know both 'noo' and 'nyoo' are correct, but what are the origins of the two different pronunciations? Asking around the office, it seems that 'nyoo' might have a British English origin, but I would like to know if anyone is more knowledgeable on this topic. |
I'm running MacOS Mojave. For months, I have the following file in my bin which I'm unable to remove: ~/.Trash/Recovered files #1/(A Document Being Saved By Quick Look Helper)/thumbnails.fraghandler Stuff I've tried: sudo rm -rf ~/.Trash/Recovered\ files\ \#1/(operation not permitted) chflags uchg thumbnails.fraghandler(operation not permitted) chmod the directory (operation not permitted) I can move the file to another folder (e.g. Desktop), but unable to remove it from there as well. | I have this file (see attached); And I cannot delete it. it doesn't exist... I have tried typing rm in the prompt then dragging the file on to it, I have gone to the actual location of the file and it's not there, I have deleted .Trash folders left right and center and I still can't find it... I have just run First Aid on ALL the volumes I have and the file still mocks me. Does anyone else have any suggestions? |
How do you get these arrows in math mode? Is there a standard command or package? | I know what my symbol or character looks like, but I don't know what the command is or which math alphabet it came from. How do I go about finding this out? |
It isn't too hard to show that there are infinitely many non-invertible matrices, and finitely many invertible ones. But how do we find all the possible matrices? Edit : The other question has not given all the matrices. | The question is: If A is a square matrix such that $A^2=A$ then $A^n =A$ for all natural numbers $n$ greater than one. What is $A$ if $A \ne 0$ and $A \ne I$. I figured out an answer but I can't tell if that's the only answer. Let's say that $a_{kk}$ is a value in $A$. Every value in $A$ is $0$ except for $a_{kk}$ and $a_{00}$, they're $1$. I haven't gotten this answer mathematically. I've tried a few approaches but ended up with the identity matrix. |
There were a group of kids (3 or 4) and they were joined by a Chinese girl from a well off family. I remember they visited a plant and something about flies buzzing in their brains at the end where she betrayed her shipmates or something. There was something about having 'encoded cards' that they got on the black market. | I'm looking for a sf story that was broadcast on BBC children's TV in the early 1980's, probably as part of the long running Jackanory series. Based on what i recall of other events at the time of watching I think this was 1982. The story is of a group of children who are either orphans or in a boarding school and who build a spaceship from the scrap of other ships and (I think) an asteroid. They launch it into space and have subsequent adventures. One scene that particularly sticks in my mind was the oxygen failing on the ship and the children all falling asleep except for a girl who is bullied by a robot into fixing the problem. I'm reasonably sure that the author of the stories would be British as it was an adaptation for the BBC. I also have a feeling that this was adapted from a series of children's books with each volume being compressed into one episode. It ran Monday to Friday for one week. I vaguely recall a female narrator. The story was interspersed with still drawings and acted scenes with children. I'm looking for the title of the story (stories) in either TV or book form and the author. Note, the description of acted scenes and drawn illustrations makes this sound like Captain Zep: Space Detective, another BBC show. It was not this one although they would have been made at similar times. Hope there is enough detail here for a answer. Thank you! |
Which basic physics principle could I use to formulate a simple explanation of the homogeneous distribution of electric charge on the surface of a hollow metallic sphere? P.S.: targeted audience with no background in physics. | If the charge $q_1$ has to repel the charge $q_2$, the electric field has to go inside the conductor which contradicts the fact that electric field inside conductors is zero. Then why do the charges distribute themselves in a particular manner? Why can't they be distributed over a small place on the conductor? |
Is there a singleton design which can completely prevent the creation of more than one object? Asking this question keeping in mind that, in Java, we can recreate 'singleton objects' using serialization-deserialization and reflection. | What is an efficient way to implement a singleton pattern in Java? |
This is a minor bug which I noticed while reviewing.. I accidentally pressed backspace when the review question poped up. I then pressed forward to go back to review question, and I found that NEXT button now no longer functions.. See image below Notice there are duplicate question message appearing on screen which is uncommon. Then, I just did refresh and ISSUE seems to be resolved.. see image below.. I did term this as minor bug because it in no way affected the site functionality or did stop me from reviewing(after refresh of-course..) Steps to reproduce bug Go one screen back by clicking back or backspace button. then again go forward to the review question screen. Buttons dont work then. Can we look to solve this... | These are the steps to reproduce what I noticed. I clicked on the link to review the suggested edits, and I was given as post to review I clicked on "Skip" to pass to the next I was taken to I clicked on "improve" by mistake When I noticed that, I clicked on the back button to go out of the edit page After I did that, I was shown the previous post to review, but in that page the review buttons didn't work. What I described happens even in the case the suggested edit is already approved/rejected; in that case the "next" button doesn't work. Is this a bug, or is it expected to happen? It happens in Firefox 17, and Safari 6.0.1, and Google Chrome 22.0.1229.94. Stack Exchange revision is 2012.10.20.4492. |
You will see here: What is the trick with modulus for proving irrationality? What about $\sqrt{2}$ Can you prove this is irrational by that trick? | I was reading Ian Stewart's Concepts of Modern Mathematics. Using congruences, It's possible to explain why all perfect squares end in $0,1,4,5,6,9$ but not in $2,3,7,8$. With this I had the idea of exploring the congruences for both sides of $n^2=2m^2$ in Mathematica: Table[Mod[n^2, 9], {n, 0, 20}] Table[Mod[2 m^2, 9], {n, 0, 20}] And had the results: {0, 1, 4, 0, 7, 7, 0, 4, 1, 0, 1, 4, 0, 7, 7, 0, 4, 1, 0, 1, 4} {0, 2, 8, 0, 5, 5, 0, 8, 2, 0, 2, 8, 0, 5, 5, 0, 8, 2, 0, 2, 8} But I'm still not sure if the outputs really show what I'm looking for, I have also tried $mod \;10$. The idea is still pretty loose in my mind, I'm stuck on deciding if this proves something or what directions I could take in this enterprise. |
I made the mistake of installing Windows 10 after installing Linux (Kubuntu 18.04). How can I make Grub the controlling boot loader at this point without disturbing either of the existing installations? Most of the discussion of this subject seems to assume that one or the other of the systems has been installed, but not both. If the existing setup boots into Windows, how do I get Grub installed? (I also have a live Kubuntu on a memory stick.) Update: I've been able to get into my Kubuntu system by pressing Esc on power-up, which on this particular machine (HP Pavilion) gives me a choice of where to boot from. Kubuntu and Windows are the two important choices. But I still can't get the machine to boot directly into grub. I've installed and run Boot-Repair. It completed successfully but didn't solve the problem. Further Update: I've finally gotten the dual boot to work, but I did it the scorched-earth way: I completely cleared the disk by installing a new partition table with gparted, reinstalled Windows 10 and then reinstalled Kubuntu 18.04. My conclusion is that if you're in a bad initial state, fixing the problem is almost impossible unless you have specialized knowledge. Most of the fixes proposed in this forum are dependent on a favorable initial state. | I have Ubuntu on my laptop. Now I want install Windows 7 in a dual-boot. How can I do this? I can't lose my Ubuntu files, and I'm afraid that I might break . Go for UEFI only! |
A function $f : I\to \mathbb{R}$ is convex on an interval $I \subseteq \mathbb{R}$ when $\lambda f(x) + (1 − \lambda)f (y) \ge f (\lambda x+(1 − \lambda)y )$ holds for all $x,y \in I$. Prove $$ \sum_{i=0}^n \lambda_i f(x_i) \ge f\left(\sum_{i=0}^n \lambda_i x_i\right) $$ holds for all $n\ge 2, x_1, \ldots, x_n \in I$ and $\lambda_1, \ldots, \lambda_n \ge 0$ satisfying $1 = \sum_{i=0}^n \lambda_i$. My Attempt: If $\lambda_1>0$ then I take $\lambda_0 = \lambda_1 + \lambda_2$ and $\Lambda_1 = \lambda_1/\lambda_0, \Lambda_2 = \lambda_2/\lambda_0, x_0 = \Lambda_1 x_1 + \Lambda_2 x_2$ and $$ \lambda_0(\Lambda_1 f(x_1) + \Lambda_2 f(x_2)) + \sum_{j=1}^n \lambda_i f(x_i). $$ Pls help me on what to do next and how to complete the proof | I want to prove that Suppose there is a function $f:[a,b] \to \mathbb R$, and there are $x_i \in [a,b], w_i \gt 0 $ for $i=1,\dots,n$ such that $\sum_{i=1}^nw_i=1$, then if the function is convex, the following inequality holds $$\sum_{i=1}^nw_if(x_i) \ge f(\sum_{i=1}^n w_ix_i)$$ and if the function is concave, flip the sign of inequality. Please include (very) detailed explanation, because I do not have much mathematical maturity, and perhaps may not be able to understand what the equation defining convex means if the explanation is too concise. |
I have a list of objectsList<Batch> batchesList new List<Batch>();with fields string orderNo and int lineNo I print "orderNo-lineNo" I want to sort it by orderNo then lineNo. The problem I have is that using linq's sort(), this will sort as a string, thus 11AG131-13 would actually come before 11AG131-2 batchesList.Sort((x, y) => (x.orderNo + x.lineNo).CompareTo(y.orderNo + y.lineNo)); Thanks for help | I have two tables, movies and categories, and I get an ordered list by categoryID first and then by Name. The movie table has three columns ID, Name and CategoryID. The category table has two columns ID and Name. I tried something like the following, but it didn't work. var movies = _db.Movies.OrderBy( m => { m.CategoryID, m.Name }) |
Or should it be without the second "to" like this: "A manual written to help students understand the module"? I'm guessing that either is generally acceptable but is there a traditional grammar rule about this? Thanks | What is the correct way to use infinitive after the verb "help": with or without "to"? For example: Please, help me to understand this. or: Please, help me understand this. |
I've been experimenting with lights in Blender 2.8, and I came across a curious situation. When working and rendering with Eevee, adding or subtracting lights responds accordingly (i.e. no lights, dark render. add lights, lit objects render appropriately depending upon placement and number of lights). If however, I switch over to cycles for a comparison render, every object seems to be lit up whether there are lights in the scene or not. Renders the same way. Adding or subtracting lights makes no difference. It's almost as if the objects were 'emissing' their own light, but this makes no sense as plain objects I add to the scene without texturing or materials do the same thing. Is there a setting I am missing when I switch between the two? I've been through most of the settings, but it just doesn't seem to make sense. Has anyone else experienced this? Thanks... | I am making a house in Blender Cycles. In rendered mode, all shaders are somehow visible, even though I don't use any lamps. I do have an environment texture, however it shouldn't light up the inside of the house. Especially when there are no windows. Even if I set the background strength to 0, it still lights up the inside and outside of the house. So now, if I add any lamps, I has nearly no impact on shadows, shaders, reflections etc. What could be wrong with my scene? Let me know if you have any questions on my settings that might help you find the problem. File: These are the world settings: For the Ambient occlusion I always use this node: It usually works fine. |
I know it is probably silly question but I did not found the answer. I use ubuntu 16.04 and the terminal colors are just black and white even if using ls ll etc. The .bashrc file doesn't contain any content about the terminal colors for some reason. How can I set the terminal colors to match those in 18.04 version? (green usr name blue current path colored folders files etc.) I tried to change some things on the preferences menu but it didn't help to solve the issue. | Is it possible to change the colors in the command prompt for the user@computer, as well as the the current directory and command parts of the prompt display? I've already seen something like this done by OSX users, but I don't know how to do the same thing in gnome terminal (I can only change foreground and background colors). It'd be very useful when, for example, trying to compile programs that have errors, since long, unformatted messages make it hard to distinguish which lines are commands and which are output. |
If we send a photon away from earth, it would eventually reach a comoving distance of about 16.5 billion light years (the universe's event horizon). I'm interested in how far (in comoving distance) particles moving below $c$ can eventually travel and at what velocity they would arrive if they were to reach a distant comoving galaxy near the end of this journey. A simple answer to both would be that a particle moving at $kc$ (where $0<k<1$) could eventually travel $k$ times as far as light could. This is what I get if I assume $v_{peculiar}$ is always equal to $kc$ and $v_{recessional} = H(t) \cdot distance(t)$ (both in proper coordinates) and take the integral of velocity over time to get the distance. However, I've also heard that the momentum of a particle reduces as it travels, resulting in redshift for photons (since they can't lose velocity) and in velocity loss for other particles. It seems that this could affect the above calculations. For example, says $\frac{\dot{p}}{p}=-H$. Does this mean that a particle launched at $kc$ would instead travel less than $k$ times 16.5 billion light years and arrive at a galaxy near that limit with a relative (proper) velocity near zero? (Bonus points if you could derive an equation for the the maximum distance as a function of $k$.) | Suppose you have an object some distance from you and moving at a velocity different to the Hubble velocity you'd expect at that point. How does the motion of this object change with time? Does it travel in a straight line (i.e. geodesic), and if you wait long enough how far will it get? |
I'm writing a Windows/Mac app, it is the same as a mobile app I have. I have no experience releasing PC apps, only mobile apps. On mobile I know how to monetize with ads and sales, but on PC I have no idea what the preferred methods are. So, which Stack Exchange site would be the right one to ask that type of question? | So much I don't know. Would love to be able to ask, learn, and discuss as I do in your other forums. |
It just came to my attention that when flagging (not VTC) a Question as duplicate one is presented with the following options: As we can see, among those is the "a duplicate..." option. However, if we select the "should be closed..." option instead, we are presented again with an option to flag as duplicate: I wonder what is the reason for the redundancy in that specific option? Are users more prone to select "should be closed..." instead and thus justify including the option there as well? | We've changed the flagging format from today(AFAIK) as below, looks good. But, when I select it should be closed for another reason... I can see the same reason duplicate on the top. What is the need of placing that reason over there? It should not be there. Please remove the dupe. |
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