Does someone know how can I prevent my title text slightly overlapping like this?  (I have to say that it is something that happens only with my current thesis title: if I put different words it does not happen - this is why I kept some of the problematic words in the example)    This is my code  \documentclass[a4paper, 12pt, twoside]{book} \usepackage{graphicx}  \begin{document}  \begin{titlepage}     \begin{center}         \includegraphics[width=0.5\textwidth]{BlackBox}\\         \vspace{4em}         {\Large \textsc{University something\\ ``Some Name''}}\\         \vspace{1em}         {\Large \textsc{Faculty of Engineering, Information Technology and Statistics}}\\         \vspace{1em}         {\small \textsc{Master of Science in Engineering in Computer Science}}\\         \vspace{3em}         {\normalsize Master of Science presentation}\\         \vspace{2em}         {\LARGE \textbf{ This Is My Very Long Title Analysis from Advertisements for Characterizing Industry Differences.}}\\     \end{center}      \vskip 2 cm     \begin{center}         \begin{tabular}{l c c c c c c c c r}             \textbf{Candidate} & & & & & & & & & \textbf{Supervisor} \\[0.2cm]             \large{Name Surname} & & & & & & & & & \large{Name Surname}\\[0.3cm]             \textbf{} & & & & & & & & & \textbf{External Supervisor} \\[0.2cm]             \large{} & & & & & & & & & \large{Name Surname}\\[0.3cm]             \footnotesize{ID 1234567}  & & & & & & & & &  \\[0.3cm]         \end{tabular}          \normalsize A.y. 2016/2017     \end{center}   \end{titlepage} \maketitle \end{document}

If I type something like this:  {\itshape\LARGE   Dunt venim dolorerosto do odit   ametum vulla conum dolore   conulput in vero od el   Dunt venim dolorerosto do odit   ametum vulla conum dolore   conulput in vero od el }   it results in a block of 4 lines with narrow spacing between the 1st and 2nd line and between the 3rd and 4th line. Line spacing between the 2nd and 3rd line is normal.  I can't fully explaing it to myself so I am looking for a short description for this behaviour. I know for example that with a \par at the end of the text (inside the group), the calculation would correct. But I have no idea why...


I changed my phone number and can't verify my Gmail account.  How do I fix this? I know my password. I've tried accessing my alternative email. Nothing is working.  I can't regain access to my old number. How do I access my account?

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


I'm Yemeni, living in Saudi Arabia, where I have permanent residency.  I have passport from two countries, Yemen and Cyprus. The information used in the Saudi immigration system is from my Yemeni passport. The Yemeni passport, unlike the Cypriot one, does not allow me to travel to many countries without a visa.   If I want to use my Cypriot passport to travel, do I also have to show my Yemeni passport? What passport should I show at the airport in Saudi Arabia? When I'm able to enter a country visa-free with my Cypriot passport, do I also have to get a visa in my Yemeni passport?

I am a citizen of two different countries, and have two passports.  How should I use my passports when traveling?


I have submitted a paper in a reputed math journal. It is under review for 7 months. 2 month ago I inquired and I was told that one reviewer has sent review and they are waiting for the other review.  Is it time common in Math journal

I am asking this question because I've always had the impression that manuscripts submitted to a journal in my field (theoretical linguistics) take an insanely long time to get published, and sometimes I get the impression that this is because, most of the time, nobody other than the author cares about getting things done within a reasonable amount of time. Some examples from personal experience follow.   For the last paper I submitted before getting my PhD, I had to wait nine months from the submission date to get reviews back from the referees. Last week I got a review request from a journal I had never reviewed for previously. The review deadline is March 15 (almost four months). In early October, I submitted a manuscript to a journal that I know asks reviewers to return reviews within 6 weeks. I checked the status of the manuscript online and it still says "with editor". Earlier this year, I was about to start writing a review when my wife went into labor. By the time we came back from the hospital, I had forgotten about the review, so I missed the deadline. The editor didn't contact me to ask about the review until two months after the deadline. Late in 2013, I was asked to write a survey chapter for a handbook. The expected publication date of the handbook is summer 2016.   All of this is not me being unlucky with editors and referees. In private conversations through the years, many colleagues have confirmed that it is virtually unheard of to get reviews back within 3 months of submission; 5 or 6 months seems to be a good average, but in some cases it can take longer (see my first point above). In general, everybody seems to have accepted that the submission-to-printed-journal process is going to take a bare minimum of one year, and that's assuming that the manuscript is accepted without revisions. If revisions are required, two years is not out of the question. Also, it's not like our papers are ridiculously long. I've reviewed about 100 papers so far, and the longest one was about 50 single-space pages; 30-35 single-spaced pages is closer to average.  I remember that, when I was a postdoc, my astrophysics housemate mentioned that in his field the entire submission-to-printed-journal process took only three or four months. I really can't see a good reason why theoretical linguistics shouldn't operate on similar timeframes, other than the fact that everybody seems to have grown used to things taking way longer than they really need to. What are the wait times in other fields? How do you manage to get things done quickly?


Ramanujan stated this radical in his lost notebook:  $$\sqrt{5+\sqrt{5+\sqrt{5-\sqrt{5+\sqrt{5+\sqrt{5+\sqrt{5-\cdots}}}}}}} = \frac{2+\sqrt 5 +\sqrt{15-6\sqrt 5}}{2}$$  Where the pattern of the signs is $++-+++-++++-+++++-\cdots$  I do not have access to his lost notebook. I wonder how we can prove this.  For periodic sign changes this kind of question is easy but for nonperiodic Im clueless.

Ramanujan stated this radical in his lost notebook:  $$\sqrt{5+\sqrt{5+\sqrt{5-\sqrt{5+\sqrt{5+\sqrt{5+\sqrt{5-\cdots}}}}}}} = \frac{2+\sqrt 5 +\sqrt{15-6\sqrt 5}}{2}$$   I don't have any idea on how to prove this.  Any help appreciated.  Thanks.


Greedings,  I've been looking through everything with google, but i just cannot find an answer.  How can i convert a string "5" to an integer 5 in Universal Windows Platform (UWP) with C++ ?  I've already tried to just convert it by (String^) and so, i know it's pointless but you never know with UWP.  The msdn documentation does not describe anything about type conversions and i just can not find it anywhere. I do not want to do something like String ^ => wchar_t => char -> atoi. Is there a better method for this ? or do i have to do this long memorytaking process ?  EDIT: It's not the same as you marked... can you read my description before you mark it ? The link you've send is converting std::string to an integer, that's easy, but i need to know how to convert String^ To an int (int32)

What's the C++ way of parsing a string (given as char *) into an int? Robust and clear error handling is a plus (instead of ).


Let $n$ be an odd integer and  $A$  an $n \times n$  symmetric matrix with integer entries such that all diagonal entries are zero. Show that $detA$ is even. My Attempt Since all the entries of $A$ are integers its characteristic polynomial $p(x)\in Z[x]$ with the constant term of $p(x)$ being the determinant of $A$. If I can show that 2 is an eigenvalue of $A$ then we are done. But I can't exhibit such an eigenvector. Please Help.

If $A$ is a symmatric matrix of odd order with integer entries and the diagonal entries $0$ then $A$ has determinant value even.  I can prove the result if I can show that the eigenvalues of $A$ are integers,but I am unable to do that. Thanks for any help.


\footnotetext{TOV: Tolman, Oppenheimer, Volkoff (1939)} \footnotetext{Richard C. Tolman: Phys. Rev 55 (1939), 364-373. Static Solutions of Einstein's Firld Equations for mass of Fluid.} \footnotetext{ J.R Oppenheimer \& G. M Volkoff, phys Rev 55 (1939), 374-381. On Massive Stellar Core}   These footnote texts come up with superscripts and subscript numerical values. How do I get them cleaned?

I would like to have a footnote about the funding source of my work in the first page without marker.   I tried below approaches:   \footnotetext{text goes here} This creates a footnote but with '0' as marker. However, the marker reference does not  appear within the normal text where I placed this command. Used \def\blfootnote{\xdef\@thefnmark{}\@footnotetext} definition provided at . I placed this definition in the main tex file just after package declaration. But, this gives the below error.     ! Use of \@ doesn't match its definition.    \blfootnote ->\xdef \@thefnmark{}\@f                                        ootnotetext


I installed  on VirtualBox. I logged in, installed VirtualBox additions and restarted the system. The system did not load again, instead I see this:    The aspect ratio of the image is preserved in this screenshot and it doesn't make much sense to me - no screen has such dimensions. I did not do anything else special that I could mention. This is the only thing I see before the screenshot above:

Inside a VirtualBox VM, I have installed myself an Ubuntu 16.04.1 LTS Server installation. However, when I installed the ubuntu-desktop package and rebooted, this happened:    Exact command I used: sudo apt-get update; sudo apt-get install ubuntu-desktop ..and then a reboot command.  This just seems like a corrupted top-left portion of the screen, as my cursor can appear in view (but corrupted):    This is a purely graphical issue because I can use the keyboard to successfully progress to a desktop:    Note: On startup it shows correct graphics for a split-second then reverts to glitch.    Any help on this?


Is it possible to pin IE tiles that when you tap it, it open IE in desktop mode? I imagine it will be possible to make a shortcut with iexplorer.exe /somecommand or something like that and then pin it to Start, but I don't know the command, there must be some sort of flag command since IE pinned in taskbar is always open in desktop and IE pinned in Start Screen always open as Modern IE.  The end result I want is to have 2 tiles of IE on Start, one for desktop and the other for Modern version. Yes, IE is the default browser.  UPDATE: Found a workaround. Since the Modern IE pinned in Start is IE 64 bit, I can pin the IE 32 bit as desktop shortcut.  Since the question is marked as duplicate, I can't make an answer.

Possible Duplicate:          I'm not sure if I like the whole idea of Start screen yet, but I would find it more useful with certain web based sites as a tiles in the group.  This question is similar to my other one at:  but this is meant to cover only those using IE as their default!


Note:  I do not agree this is a duplicate of the linked issue.  While that is an issue, that is not the question.  Please see below.  When I assign a new class instance to an array, the base class' virtual function  is used instead of the overridden derived class virtual function.  I was told the problem with the code below is .  However, according to , this should work.  I am a beginner at C++, so I'm not sure who is right.  Can someone point me in the right direction or tell me what's wrong?  Is this because I'm copying the object to the array instead of "pointing" to it?  However, I can't figure out how to do this correctly.  See code below for what I've tried.  Addendum:  There is in fact an object slicing problem here.  However, the purpose of my question and what I did not understand is that overriding only works if you use pointers or an array of pointers and not if you declare an array of instances.  #include <iostream>  // I know these should be structs since they're all public! class Animal {   public:     Animal() { std::cout << "Animal constructor\n"; }     virtual void speak() { std::cout << "Animal/Hello!\n"; } };  class Dog: public Animal {   public:     Dog() { std::cout << "Dog constructor\n"; }     void speak() override { std::cout << "Dog/Bark!\n"; } };  int main() {   const int Size = 4;    Animal* Kingdom = new Animal[Size];   Dog* rover = new Dog;    // Legal because of polymorphism:   Animal* spot = new Dog;    // Legal because of polymorphism;   // Believe this is wrong - I think I'm copying the value rather than   // pointing to it, but not sure what the right way is...   Kingdom[0] = *(new Dog);   // &Kingdom[0] = new Dog;  // Error - left operand must be l-value   // Kingdom = new Dog;  // Wrong - changing array base, leaking memory    Kingdom[1] = *rover;   Kingdom[2] = *spot;    // Virtual method followed here:   std::cout << "\nIndividual invocations:\n";   rover->speak();   spot->speak();    std::cout << "\nInvocation from array:\n";   for (int i = 0; i < Size; ++i)     // Doesn't work - virtual method not followed, not sure why...     // Kingdom[i].speak();     // No difference between these two forms:     (Kingdom + i)->speak();    // PS - I know I should put deletes in here not to leak memory! }

Someone mentioned it in the IRC as the slicing problem.


How can I pass data from operator to another operator in one panel? Specifically I have a dialog box, I want to get back the path of the selected box to a label and activate another operator(button) Thanks

I was watching this  on making a custom UI tab using Python, and in the line from bpy.types import Menu, Panel, UIList, I see the names of objects that look like they can all be used to make different UI elements. Does bpy.types contain all the objects that people use when they want to make custom UI elements?


I am wondering how to judge what kind of encounter will be right for my group. I would like to design challenging encounters, but not ones which will be impossible or far too easy.  How will I know if I can present them with a demon, for example, without killing them outright or whether a horde of chaos heretics is far too easy for them?  I've read  to a similar question, which says:     EG: PC's average Toughness is 40... so T=4. Average torso armor was 4.   Weapon damage was averaging 8 (1d10+2), with Pen 4.      NPC side had T6 and AV8, average damage 7 (1d10+3), pen 0...      PC Side was 8+4 vs 6+8, for -2 NPC side was 7+0 vs 8, for -1.   Now, it has to be shifted to positives; move both up the same amount   so the lower is +1. In this case, PCs 1, NPC's 2. Now multiply by the   numbers. I had 7 PC's, and used 4 NPC's... for 7 and 8. Then multiply   by average skill as a percentage... PC average was 45, NPC was 33, for   7*0.45=3.15 and 8*0.33= 2.64. It's clear the PC's have an advantage,   but a very weak one... and since in the initial stage, both were   negatives, it's going to involve a lot of armor staging.   But I don't understand why he's multiplied the PCs' WS with the NPC damage (or at least that is what it looks like for me). Can anyone explain this more clearly?

I've been reading through Deathwatch and I've finally gotten a grip on the fact that space marines are seriously tough characters compared to the other games in the Warhammer 40k RPG line.  The monsters listed in the back of the book are particularly nasty and vile, fitting opponents.  I'm a little concerned on how to guage the balance on them.  Would a dozen Tau fire warriors make an appropriate encounter for a group of rank 1 Deathwatch marines?


Let A=B=$\mathbb{N}$  R is: (a,b)$\in$R iff for some q$\in$Integers a=5q+b WHERE 0$\leq$b<5  Given a relation, show that it's a function.  To Show:  1) $\forall$a$\in$A$\exists$b$\in$B((a,b)$\in$R)   2) $\forall$a$\in$A, there is a unique b$\in$B((a,b)$\in$R)  Proof: Let a$\in$A. Assume (a,b)$\in$R and (a,c)$\in$R where b,c$\in$B.  Do MATH  $\therefore$ b=c. QED  What math should I do to get the full proof. Thanks!

Let $A=B=\mathbb N$. Relation $R$ is: $(a,b)\in R$ iff for some $q \in \mathbb Z$ we have $a=5q+b$  Given a relation, show that it's a function.  To Show:   $\forall a \in A \ \exists b \in B$ such that $(a,b)\in R$  $\forall a \in A $ there is a unique $b\in B$ such that $(a,b) \in R$.   Proof Outline: Let $a \in A$. Assume $(a,b)\in R$ and $(a,c) \in R$ where $b,c \in B$.  then some steps leading to.... $\therefore$ b=c. QED     What math should I do to complete  the   proof?


I've seen two different spellings of this word - which is correct: hurray, or hooray? As in:     You haven't got any outstanding alerts to action — hurray!   I'm interested specifically in British English, although I'm also curious as to American English.

Is this word onomatopoeic, just an interjection, both, something else?


I am building an Eldritch Knight fighter/War wizard multiclass character for D&D 5e. The eldritch knight has a limited pool of spells known, but does not have to prepare them; the wizard, on the other hand, needs to prepare his spells each day.  Are the spells known from the Eldritch Knight part of my character and can be cast without preparing them? Or am I now stuck preparing spells like a normal wizard?  For example, as a level 3 Eldritch Knight I know 3 spells, and I do not have to prepare them to cast them. Then I take a level of wizard; as a 1st-level wizard, you get a spellbook containing 6 spells, and can only prepare a number of spells to be cast from this book equal to Int modifier + wizard level.  For example, if my character has an Intelligence score of 14, he could prepare 3 spells as a wizard, but he already knows 3 other spells from being an Eldritch Knight that don't need to be prepared to be cast, at least as far as I understand the rules.  Is my character now limited to preparing spells only, or does he keep his Eldritch Knight spells as always being able to be cast?

If I multiclass into 2 or more classes/subclasses that can cast spells, how do I determine what spells I know or can prepare?  For instance, if I am playing a multiclassed character with 1 level in warlock, 2 levels in bard, and 3 levels in paladin, how do I determine which spells I know/have prepared?    Related:


Is there a two-dimensional random variable $(X,Y)$, whose CDF is continuous, but whose marginal CDFs are discontinuous?  My question differs from  in that a random variable that has a continuous CDF, which is the condition stipulated in my question, is not necessarily a continuous random variable, which is the condition stipulated in the other question. Thus, my question is more general than the other one.

Just need help understanding this question, as I don't really understand what a continuous random vector is. My limited understanding is that a continuous random vector must be completely continuous (so for continuous X and Y this is satisfied) and that to get the probability of the random vector occurring, we double integrate over the supports (of X and Y obviously). My guess is then, that the c.r.v (X,Y) IS a continuous random vector.  Also, what of the converse? If (X,Y) is a continuous random vector, then are X and Y continuous random variables? I also think this is correct, as the continuity of the vector MUST imply the continuity of X and Y, although I'm honestly not sure.  Thanks


I am looking for a way to make my Chat GUI in front of all the applications not only in windows. AlwaysOnTop does not solve this problem. As I mentioned mainly during playing games on full screen. I couldn't find anything on the internet so here I am :P  EDIT: I found out that if you change display settings in the game to "Borderless" or "Windowed full screen" your GUI window will stay on top with "AlwaysOnTop". Thanks for help anyways.

In Java, is there a way to have a window that is "Always on top" regardless if the user switches focus to another application?  I've searched the web, and all of the solutions lean to some sort of JNI interface with native bindings.  Truly this can't be the only way to do it?.. or is it?


I am building a hobby EEG and I am interested in quantifying how effective are the various noise reduction techniques.  The basic circuit would be two electrodes going to an instrumentation amplifier. Then the signal goes to various filtering stages and then to a final "mundane" amplifier. I am interested in noise reduction before the filtering. Here are the steps that I am considering (hopefully this can evolve into a community wiki).   Adding a right leg electrode directly linked to the ground of the circuit. (against 60Hz hum) Adding a driven right leg electrode for common mode rejection. (against 60Hz hum) Adding passive low pass filters in front of the inputs of the instrumentation amplifier (). (against DC difference between the electrodes and bias current from the inputs) Faraday cage (against 60Hz hum) Shielded cables for the electrodes (against 60Hz hum)   Are there any technical manuals discussing these approaches? Could you share your knowledge about the effectiveness of each approach? Could you suggest other approaches?

When recording electrical signals from cells (in a dish or inside a living human or animal body), one major problem is to increase the signal to noise ratio. These signals are usually in the 10uV to 100mV range and are generated by very low power sources that can yield currents in the order of nanoAmps. Often signals of interest fall within 1Hz-10KHz range (most often 10Hz-10KHz). To make the matters worse usually there are lots of noise generating tools that are necessary to be around (in the clinic these are other monitoring, diagnostic and therapeutic devices in the lab these are other monitoring, scientific devices). To reduce the impact of noise and increase the signal to noise ratio, there are a few generally applied rules like:  If possible use a current amplifier (often called head-stage), an amplifier with very high input impedance and rather low voltage amplification or even no voltage amplification. very near to the signal source (body). To connect the source (recording electrodes) to the first stage amplifier (head-stage) use wires that don't have shields (to avoid capacitative distortions of the signal). Avoid ground loops When possible use differential amplifiers (to cancel the induction noise from the electromagnetic sources around). Always use Faraday cages and grounded shields (usually Aluminium foils) to cover the signal source and anything connected to it (body, equipment ...). You can't do this without proper filters (usually a 10KHz high cut and a low cut that depending on the signal may be anywhere from 1Hz to 300Hz ) If you can't get ride of the mains noise (50Hz or 60Hz in different countries) and only if your signal covers that range you can use active filters like Humbug   My question is: Are there any other suggestions that I missed? Is any of these suggestions flowed or wrong? Usually people in this fields (like me) do not have formal education in electrical engineering  and sometimes there are myths passing from a teacher to student generation after generation without proper evidence. This is an attempt to correct this. EDIT:  if possible use batteries or very well regulated power supplies in all your devices, including any pumps, microdrives, monitoring devices, even you can put filters on the mains of your computers (although this usually is not a serious issue).


I currently have Ubuntu 14.04 but whenever I try to access "System Settings" -> "User Accounts" the OS just stalls there. I can still access other things. Is there a fix for this?

I tried to use the command gnome-control center -l and it gave me an errors saying some shared objects are missing . This is the result :   gnome-control-center -l  libwayland-egl.so.1: cannot open shared object file: No such file or directory Failed to load module: /usr/lib/i386-linux-gnu/unity-control-center-1/panels/libuser-accounts.so Unknown option -l   Run /usr/bin/unity-control-center --help to see a full list of available command line options.  So I tried this and it also gave the same result :  unity-control-center -l  libwayland-egl.so.1: cannot open shared object file: No such file or directory Failed to load module: /usr/lib/i386-linux-gnu/unity-control-center-1/panels/libuser-accounts.so Unknown option -l   Run unity-control-center --help to see a full list of available command line options.  Following  thread I tried the following commands and those gave me the following results :  sudo apt-file update  sudo apt-file find libwayland-egl.so.1  libhybris: /usr/lib/i386-linux-gnu/libhybris-egl/libwayland-egl.so.1 libhybris: /usr/lib/i386-linux-gnu/libhybris-egl/libwayland-egl.so.1.0.0 libwayland-egl1-mesa: /usr/lib/i386-linux-gnu/libwayland-egl.so.1 libwayland-egl1-mesa: /usr/lib/i386-linux-gnu/libwayland-egl.so.1.0.0 libwayland-egl1-mesa-dbg: /usr/lib/debug/usr/lib/i386-linux-gnu/libwayland-egl.so.1.0.0 libwayland-egl1-mesa-lts-utopic: /usr/lib/i386-linux-gnu/libwayland-egl.so.1 libwayland-egl1-mesa-lts-utopic: /usr/lib/i386-linux-gnu/libwayland-egl.so.1.0.0 libwayland-egl1-mesa-lts-vivid: /usr/lib/i386-linux-gnu/libwayland-egl.so.1 libwayland-egl1-mesa-lts-vivid: /usr/lib/i386-linux-gnu/libwayland-egl.so.1.0.0   It said about missing dependency account plugin ubuntuone . So I tried installing it but it installed some packages meant for ubuntu mobile . I removed those wrong packages and reinstalled the previous ones following  thread and after that everything is good like before but the error I mentioned before about libwayland-egl.so didn't get solved . And still user-accounts.so shows failed to load .   How do I solve this ? I am trying to solve it because I can't access user-accounts from system settings . Whenever I try to access user accounts it always keep showing system settings over and over again . I can't even close it in anyway possible . It just keeps showing up .


Though it is a bit inactive as of yet, it might be nice to have a tag to group all () questions about .  I don't have the points needed to do this myself.  Overview:   Specific examples:

Can someone please create the tag  on our site? We need to have it because        Foo is a recent/upcoming release / edition / model / episode of a popular, established OS / board game / bike brand / TV show   Foo is a hot new language / ingredient / game   we're currently using some other tag for questions about Foo, but it's causing ambiguity with a separate thing that's also named Foo      This is not a joke post. We get a lot of feature requests that ask for this or that tag to be created, and every time, a discussion ensues wherein people explain that there is no "tag creation department" and that community members create tags just by using them. I'm posting this "question" so that future requests of that type can be closed as a duplicate of this, saving time and eliminating redundant conversations for everyone involved.     See also:


Consider the graph of $y=|x|$ from $-1<x<1$. Equip it with a single chart, the projection onto the $x$-axis. Is it now a smooth manifold? It seems like it shouldn't be smooth, but perhaps with only one chart, any manifold is smooth (because it trivially satisfies the compatibility condition)?  What chart could we put on there that would not be smoothly compatible with this first one?

Let $M=\{(x,|x|): x \in (-1, 1)\}$. Then there is an atlas with only one coordinate chart $(M, (x, |x|) \mapsto x)$ for $M$. We don't need any coordinate transformation maps to worry about differentiablity. So I thought $M$ is a differentiable manifold. However my teacher says it is not. He says the sharp corner at $x = 0$ is a problem. I can't understand why it is a problem.


Why $\lim_{x \to ∞} 1^x=1$ even though $1^∞$ in indeterminate? I'm genuinely not getting it. Any help is appreciated!

From : In calculus and other branches of mathematical analysis, an indeterminate form is an algebraic expression obtained in the context of limits. Limits involving algebraic operations are often performed by replacing subexpressions by their limits; if the expression obtained after this substitution does not give enough information to determine the original limit, it is known as an indeterminate form.    The indeterminate forms include $0^{0},\frac{0}{0},(\infty - \infty),1^{\infty}, \ \text{etc}\cdots$   My question is can anyone give me a nice explanation of why $1^{\infty}$ is considered to be an indeterminate form? Because, i don't see any justification of this fact. I am still perplexed.


I have been logging into Ubuntu VM for about a month or more with no problem. Now the Ubuntu logo appears and it does not finish starting. After some time the rotating ring of Ubuntu disappears and after some time Ubuntu written at the time of starting as well. After some time my screen completely goes blank and only a blinking cursor appears on my screen. I have virtualization already enabled for my system.

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


Im trying to rewrite a file while its being used. I'm changing a line in a file which im reading ('students.txt') to a line which is similar the change would look like  Raymond_Red 0000000000000 0   to  Raymond_Red 0000000000000 1   The issue is is that i'm getting this error beacuse im opening a file which is already open using 'fileinput'      PermissionError: [WinError 32] The process cannot access the file because it is being used by another process: 'students.txt' -> 'students.txt.bak'   I have no idea how to get around this issue. Thanks in advance for your help!   #Code by Byron Dalberg     import time     import fileinput     lunch = str('inout {0}.txt'.format(time.strftime("%Y-%m-%d")))     while True:         variable = input()         with open ('students.txt') as f:             for eachline in f:                 name,inout,rfid = eachline.rsplit(None,2)                 if variable == rfid:                     print("yay")                     if(inout == 0):                         f.close()                         linein = str('{0} {1} {2}'.format(name,inout,rfid))                         lineout = str('{0} 1 {1}'.format(name, rfid))                         for line in fileinput.input('students.txt', inplace=1):                             line.replace(linein, lineout),                         with open('inout.txt','a+') as fp:                             log = str('{0} loggged out at {1}(ID: {2})\n'.format(name,time.strftime("%H:%M"),rfid))                             fp.write(log)                     else:                         linein = str('{0} {1} {2}'.format(name,inout,rfid))                         lineout = str('{0} 0 {1}'.format(name, rfid))                         for line in fileinput.input('students.txt', inplace=1):                             line.replace(linein, lineout),                         with open('inout.txt','a+') as fp:                             log = str('{0} loggged in at {1}(ID: {2})\n'.format(name,time.strftime("%H:%M"),rfid))                             fp.write(log)                 else:                     print("nope")   Thanks in advance!

I want to loop over the contents of a text file and do a search and replace on some lines and write the result back to the file. I could first load the whole file in memory and then write it back, but that probably is not the best way to do it.  What is the best way to do this, within the following code?  f = open(file) for line in f:     if line.contains('foo'):         newline = line.replace('foo', 'bar')         # how to write this newline back to the file


Where my mouse icon is, the number 53, what does it mean?

What is the emblem in the top right corner of the screen next to the rupees when you're looking at the map? I've looked all over and can't find it but I have noticed that it changes frequently.


Just now, when reviewing close votes I voted to close a question and saw that there were four other votes cast for off-topic     but clicked off-topic I could only see one other vote, the other 3 was missing.    I have been seeing this issue many times today.

I've found strange behavior when closing this  - I definitely see that there are 3 closing votes and 2 of them are at "Off-topic" section:   -but there are no explanations on section itself:   -while, normally, it's expected that it will appear. In custom comments section there are also no closing-votes displayed.   Perhaps it's just my browser (which is FF 26 x64 under Win) - so marking this as a "possible bug". Thank you for your attention.


If $G$ is a torsion-free group, such that there exists a subgroup $H \cong \mathbb Z$ of finite index, then $G \cong$?   I guess $G\cong \mathbb Z$. It clearly satisfies the requirements, but I'm afraid that there are multiple possibilities. Is this a characterization of $\mathbb Z$? Thanks in advance.

It is well known that a torsion-free group which is virtually free must be free, by works of Serre, Stallings, Swan...     Is there a simple cohomological proof of the fact that a torsion-free group which is virtually-$\mathbb{Z}$ must be isomorphic to $\mathbb{Z}$?   Thanks.


I intend to initialize a list of list with length of n. x = [[]] * n  However, this somehow links the lists together. >>> x = [[]] * 3 >>> x[1].append(0) >>> x [[0], [0], [0]]  I expect to have something like: [[], [0], []]  Any ideas?

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?


In an article I am reading from Bloomberg Businessweek, there is a use of "staffs". I thought staff is a collective noun and has no plural. The full sentence reads  Companies such as Uber Technologies Inc. and DoorDash Inc. have established or expanded programs allowing employers to distribute meal credits to their staffs."  Shall I interpret "staffs" as different groups of staffers, just like "foods" mean different types of food, and in this context meaning one staff (group of employees) for each of the aforementioned employers (Uber, DoorDash)?

This is a sentence in a book by Rudy Giuliani.     I could ensure my deputies and commissioners were working off the same   page and could carry a coherent message back to their staffs.   Isn't staff a mass noun with no plural when referring to people?


First of all I'm new to Linux and don't quite understand the platform yet, I'm trying to execute a python script to run a bioinformatics program that cannot be run on windows.  When I unpack the file, change directories and then try to execute the script:  $ tar -zxvf IEDB_MHC_II-2.22.3.tar.gz $ cd mhc_ii $ ./configure.py     the following message appears:   bash: ./configure2.py: /usr/bin/python: bad interpreter: No such file or directory   I have Anaconda 3 installed and when I type python in the terminal it responds by saying that python 3.7 is installed under anaconda3.  How can i solve this and manage to execute the file?

I have installed ubuntu 18.04 in virtual box and when trying python -v, it says you have python3 installed, I want to remove python 3 or disable so that can use python2.7 and run some scripts i have.


I do not know exactly what I did, but I am a beginner/noob with Blender. When I select one shape all of the shapes have an orange outline. I don't really know but they are all somehow on the same line/tab. I wanna put them each back to their own tab. Look at the picture to see what I mean. 3 of the shapes have an orange outline when I click "cube" even though it should only be one cube. I wanna make each one its own line again. See how the cones are not selected, each cone has its own separate line/tab. I feel like it is really simple to fix, but it is probably a rare problem so I do not know how to fix it since I am new. Any help would greatly be appreciated.

I've just made a set of armor by using a male body mesh model I downloaded and selecting certain faces from the model and duplicating them to create viable armor pieces.   Since the pieces are just duplicated from the same mesh male model, then it's still part of the same object.   How do I separate the armor piece from the model to make the pieces separate?


I think one of the best capabilities of ArcGIS desktop 10.1 and 10.2 is Database Connection. Users can connect to every Database servers without using Middleware(ArcSDE) . You can Distribute, manage users  and other capabilities.But why ESRI release ArcSDE 10.1 or 10.2 while we can use Database connecion? What are capabilities of ArcSDE VS Database Connection?   Thanks For advance

Through my frustration of not finding the post-installation wizard with ArcSDE 10.1 and being unsuccessful with the command line tool to start an SDE service on our SDE databases, I found I was able to access the databases and copy/past/add features/delete features/etc. all through direct connections to our SQL Server 2012 machine. This was WITHOUT ArcSDE running.   So... The question is, why do I need to go through the trouble of trying to get the SDE services to run if I can manage our databases through the Desktop tools? I was even able to create an enterprise geodatabase and verified that all of the necessary business tables were created. I have even recreated all our map services in ArcGIS Server 10.1 with direct connect and the web editing is perfectly working.   Perhaps I'm missing something...  UPDATE:  As indicated in the  topic:     "The recommended method to access enterprise geodatabases is to   connect directly from ArcGIS clients. If you only use direct   connections to your geodatabase, you do not have to install the ArcSDE   application server."   If you need to edit settings in the ArcSDE system tables, though, you should still install the command line tools included with the application server. I don't think editing system tables directly through SQL is supported technically.


I tried to uninstall atom from ubuntu 16.04 using    sudo apt remove atom || sudo apt remove --purge atom   command and following are the errors, please help me in resolving the issue.  E: Malformed entry 1 in list file /etc/apt/sources.list.d/sublime-text.list (Suite)     E: The list of sources could not be read.     E: Malformed entry 1 in list file /etc/apt/sources.list.d/sublime-text.list (Suite)     E: The list of sources could not be read.   While running the following command   cat /etc/apt/sources.list.d/sublime-text.list   this was the output: deb

I have unistalled and reinstalled the Ubuntu Software Center as per info I found in a similar thread and I got the same response about line 91 or something like that.  I just tried to upload a screen shot but since I'm new it won't allow me to.  I also can not figure out how to cut and paste anything so I have to hand type what the error screen says, both when I attempt to open the software center and nothing happens, when I try to enter commands into the terminal to uninstall, reinstall, whatever I get the same following:  COULD NOT INTITIALIZE THE PACKAGE INFORMATION An unresolvable problem occured while initializing the package information Please report t:his bug against the 'update-manager' package and include the following error message: 'E: Malformed line 91 in source list/etc/apt/sources.list (dist parse)  E: The list of sources could not be read.,  E: The package list of status file could not be parsed or opened.   How do I report bugs?  What can be done about this.  I have searched and everything everyone says to do leads me back to the same line error message.  So, I don't know how to get to line 91 in the source list; to tell you what it says. Sorry, I'm really new to this. That is what I need is to find out how to get there and fix what it says. I would really like to NOT have to re partition my hard drive and start from scratch, so I'm really looking forward to getting this problem solved. I need to be able to install new software.


I want to know what mathematical theories I should be aware of for a deep understanding of the standard particles model.

What are some good sources to learn the mathematical background of Quantum Mechanics?  I am talking functional analysis, operator theory etc etc...


I am confused with Logical 'And' and 'or' combination in python  I got some idea from  but I couldn't understand combination of 'AND' and 'OR'     a=3    print(a%2 and 'odd' or 'even')   I understood how even was printed if a is 2 ie., a= 2, 2%2 = 0 => False. Then Note String object is considered as True so 'odd' and 'even' are True. So False and True(odd) or True(even) will give be False(even) object.  But when I didn't understand how even works. If 1st object is True then the output should be immediate True without checking other condition(or operations), how is it going further and printing 'even'

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


I am having similar problem. The aim is booting from a clean Ubuntu flash memory stick, then cloning and test-building a large repository onto a hard drive partition.  Unfortunately, my situation is under the restrictions that I can't copy the script, nor does the partition seem to be readonly of noexec.  Here is how the partition is mounted:  ubuntu@ubuntu:/media/ubuntu/data/test/0ad$ grep '/media/ubuntu/data' /etc/mtab | grep noexec ubuntu@ubuntu:/media/ubuntu/data/test/0ad$ grep '/media/ubuntu/data' /etc/mtab /dev/sda4 /media/ubuntu/data fuseblk rw,nosuid,nodev,allow_other,default_permissions,blksize=4096 0 0   Here is a demonstration of the problem:  ubuntu@ubuntu:/media/ubuntu/data/test/0ad/build/workspaces$ ll update-workspaces.sh  -rw------- 1 ubuntu ubuntu 4608 Apr 16 06:41 update-workspaces.sh ubuntu@ubuntu:/media/ubuntu/data/test/0ad/build/workspaces$ chmod +x update-workspaces.sh  ubuntu@ubuntu:/media/ubuntu/data/test/0ad/build/workspaces$ ll update-workspaces.sh -rw------- 1 ubuntu ubuntu 4608 Apr 16 06:41 update-workspaces.sh   I researched the mentioned mount options, but forund nothing suspecious.    Clarifications:  1. I can't move the script, because it is special in that it is a part of a larger build system, that I do not understand. I am following the  for the application.   2. The problem is not with what the script contains, because I tried creating a simple script in the same folder, and that too can't be executed:  #!/bin/bash  echo "Hello World!"`   3. sudo doesn't help.  4. Here is the full /etc/mtab, as requested. The partition I am trying to use is the last one data.  /cow on / type overlayfs (rw) proc on /proc type proc (rw,noexec,nosuid,nodev) sysfs on /sys type sysfs (rw,noexec,nosuid,nodev) udev on /dev type devtmpfs (rw,mode=0755) devpts on /dev/pts type devpts (rw,noexec,nosuid,gid=5,mode=0620) tmpfs on /run type tmpfs (rw,noexec,nosuid,size=10%,mode=0755) /dev/sdb1 on /cdrom type vfat (ro,noatime,fmask=0022,dmask=0022,codepage=437,iocharset=iso8859-1,shortname=mixed,errors=remount-ro) /dev/loop0 on /rofs type squashfs (ro,noatime) none on /sys/fs/cgroup type tmpfs (rw) none on /sys/fs/fuse/connections type fusectl (rw) none on /sys/kernel/debug type debugfs (rw) none on /sys/kernel/security type securityfs (rw) tmpfs on /tmp type tmpfs (rw,nosuid,nodev) none on /run/lock type tmpfs (rw,noexec,nosuid,nodev,size=5242880) none on /run/shm type tmpfs (rw,nosuid,nodev) none on /run/user type tmpfs (rw,noexec,nosuid,nodev,size=104857600,mode=0755) none on /sys/fs/pstore type pstore (rw) systemd on /sys/fs/cgroup/systemd type cgroup (rw,noexec,nosuid,nodev,none,name=systemd) gvfsd-fuse on /run/user/999/gvfs type fuse.gvfsd-fuse (rw,nosuid,nodev,user=ubuntu) /dev/sda6 on /media/ubuntu/2f54e44f-46ee-4e9d-a9b7-05963a5a6b61 type ext4 (rw,nosuid,nodev,uhelper=udisks2) /dev/sda1 on /media/ubuntu/571CDF3F0AB7ABFD type fuseblk (rw,nosuid,nodev,allow_other,default_permissions,blksize=4096) /dev/sda2 on /media/ubuntu/0b4a4dc5-cf55-429d-85a5-ccb40c3796fc type ext4 (rw,nosuid,nodev,uhelper=udisks2) /dev/sda4 on /media/ubuntu/data type fuseblk (rw,nosuid,nodev,allow_other,default_permissions,blksize=4096)   5. Underlying file system:  ubuntu@ubuntu:/media/ubuntu/data/test/0ad/build/workspaces$ sudo file -sL /dev/sda4 /dev/sda4: x86 boot sector   According to GParted, this is a primary ntfs partition. I have a Windown 7 on another partition and an Ubuntu on another set of partitions:

I have a script that I need to execute on an NTFS partition. The script's permission is set to 600.  I attempted to modify the permissions by running chmod 755 script.sh, which doesn't report a failure or anything - but it also doesn't change the permissions on the file:  $ stat script.sh    File: `script.sh'   Size: 297070      Blocks: 584        IO Block: 4096   regular file Device: 811h/2065d  Inode: 35515       Links: 1 Access: (0600/-rw-------)  Uid: ( 1000/  xxxxxx)   Gid: ( 1000/  xxxxxx) Access: 2010-09-30 14:05:16.041621000 -0700 Modify: 2010-09-30 14:05:05.070157000 -0700 Change: 2010-09-30 14:05:05.070475000 -0700  $ chmod 755 script.sh $ stat script.sh    File: `script.sh'   Size: 297070      Blocks: 584        IO Block: 4096   regular file Device: 811h/2065d  Inode: 35515       Links: 1 Access: (0600/-rw-------)  Uid: ( 1000/  xxxxxx)   Gid: ( 1000/  xxxxxx) Access: 2010-09-30 14:05:16.041621000 -0700 Modify: 2010-09-30 14:05:05.070157000 -0700 Change: 2010-09-30 14:05:05.070475000 -0700   As you can see, it remains unchanged.


This is my third question in the series of transforming some (~167) documents from HTML to LaTeX.  The other questions were related to  and .  The original document have several graphics (~168) from different sources and different naming conventions.  I am using the graphicx package with the \includegraphics command. I don't have any problems with PNG and JPEG files with only letters, numbers and hyphens in their names.  I have a couple of GIF files (non-animated) which I attempted to solve using the receipt here:  . Unsuccessfully.  (Also command \epstopdfDeclareGraphicsRule fails in XeLaTeX, and as there are only two files I might rather convert them manually or with my conversion script.)  However I have a problem with PNG and JPEG files with special charactes, mainly those including a period . (includegraphics things that something.svg.png is an unrecognized .svg.png), an underscore _ (if I don't mask that character it attempts to shift to mathmode; if I mask it it does not find the file), and a percent sign % (as most of these files were downloaded from internet URL, special chars are masked using the percent sign and I preserved that convention in the filenames.  Again, with the masked percent '\%' '\includegraphics' does not find the file and without it the TeX engine assumes it is an end-of-line and the code breaks).  While I can still rename the files to something LaTeX and graphicx will handle, I still would like to now what are the correct way to mask special characters, and particularly ., _, and %.

\includegraphics cannot handle filenames that contain more than the one dot, separating the filename from the extension. Apparently it uses everything after the first dot as extension and then, of course, complains about an unknown graphics extension.  This is annoying as I very often have filenames that contain parameter values, e.g. plot_a0.4_b0.6.pdf.  Is there a way to teach LaTeX to interpret only the string behind the last dot as extension?


I was just wondering, if I write float main(), why do I need to write a return statement?  I know about the C99 standard, which states     If the return type of the main function is a type compatible with int, a return from the initial call to the main function is equivalent to calling the exit function with the value returned by the main function as its argument;10) reaching the } that terminates the main function returns a value of 0. If the return type is not compatible with int, the termination status returned to the host environment is unspecified.   Since float is compatible with int, return statement should not be necessary?

What is the correct (most efficient) way to define the main() function in C and C++ — int main() or void main() — and why? And how about the arguments? If int main() then return 1 or return 0?  There are numerous duplicates of this question, including:       — For C++, with a very good answer indeed.     Related:


Here is a problem from Herstein's "Topics in Algebra":  If $G$ is abelian and if $N$ is any subgroup of $G$, prove that $G/N$ is abelian  I have already proved this; it's quite simple. There's a very natural question that arises: is the converse true? I say it's not. The reason is because the quotient group $G/N$ always require $N$ to be normal in $G$, and although every subgroup of an abelian group is normal the converse is not true. So $G$ is not abelian. Is my intuition faulty?

I try to prove the following:     Let $G$ be a group and $N$ be a normal subgroup. Suppose $N$ is abelian and $G/N$ is abelian. Then $G = N \cdot (G/N)$ is abelian.   Proof:   For the first assertion that $G = N \cdot (G/N)$ let $g \in G$, then $g = g n n^{-1} \in gN \cdot N$ and then $gN \in G/N$ and $n^{-1} \in N$.  For the second assertion, let $g_1,g_2 \in G$. Then $$ g_1 g_2 = g_1 n_1^{-1} n_1 g_2 n_2^{-1} n_2 = g'_1 n_1 g'_2 n_2 $$  where $g'_i = g_i N$. Then $$g'_1 n_1 g'_2 n_2 = g'_1 g'_2 n'_2 n_2$$ since $N$ is normal, and $$  g'_1 g'_2 n'_2 n_2 = g'_2 g'_1 n'_2 n_2$$ since $G/N$ is abelian, and $$ g'_2 g'_1 n'_2 n_2 = g_2 n_2^{-1} g_1 n^{-1}_1 n'_2 n_2$$ and here I am stuck.


I am trying to create a classifier using SVM on a dataset that is composed of 6 sets of data for each of my observations. When I train the SVM (rbf kernel), I get a better performance of the classifier when I use only 2 out of 6 sets of features (reducing the number of features to about half): when I add features, my accuracy degrades by over 5%. I understand that "junk in, junk out", but we were surprised by the magnitude of this effect. Note that I scale the features to all have the same range and variance before training the SVM (using sklearn's MinMaxScaler()).  Our interpretation of this result is that we are not representing the feature space correctly - by calculating a single kernel on all 6 sets of features at the same time, I lose information from each single set of features. To make up for this, I want to calculate a kernel on each feature set independently (and so also find the optimal gamma separately) and then concatenate the results to train the classifier (a bit like what described ). Basically, I would like to do:   $$ k_{final} = k_1(X_1) + k_2(X_2) + k_3(X_3) + k_4(X_4) + k_5(X_5) + k_6(X_6) $$   Is this something that can be done and a sensible thing to do? And would it help with my problem? If so, can I implement this in sklearn? If so, how?   I have found a way to calculate kernels in sklearn (), and so I could calculate the kernel on each set separately. However, once I output the distance matrix, I am not sure how I would use it to train the SVM.  My understanding of kernels is only very intuitive, so I would appreciate an answer with limited maths!

I am reading the Pattern Recognition and Machine Learning book by Bishops. I have some difficulties proving the (6.21) equation. Can someone help me?   N.B: If someone has a better title for this question, i'm opened to it as i couldn't find the good words.


I bought a chain riveting tool. Here is how it looks like:    It works fine, I was able to push the rivet out of a test chain. But faced an unexpected difficulty: after I restore the rivet to it's proper position the chain link becomes very hard to move.  I think, the cause of this  is that my tool is not as precise as those, used in the factory, when manufacturing the chain. And when I restore the rivet, I shift it a little bit from it's ideal position. It creates extra friction, not allowing the plates to move freely as they should.    Is it normal? Am I doing something wrong? Maybe, there are better tools?

I disassembled my bike's drivetrain to degrease and regrease all the components. I used a chain-breaker for the first time (previous bikes had a master link) to open a chain link and remove the chain. Afterwards, I reassembled the chain but found the link I'd opened is very stiff to the point where, as the link emerges from the chainring, it stays bent until it moves through the derailer and which point it snaps straight again.  I tried making small adjustments to the rivet holding the link together and adding additional lubricant with no success. I even removed that link from the chain completely (assuming I'd bent something slightly), only to have the next link I opened/closed become the stiff one.  Is this normal after using a chain-breaker to open a link? Should I expect the stiffness in the link to work itself out, or have I done something wrong? Is there anything else I can try to loosen up the stiff link?


I've been searching this site and googling everywhere and can't find an answer so chances are that I'm out of luck and not possible to do...  Anyway, I'm working on a old site that adds elements with IDs. Those elements can be present more than one on the same page... and yes, I know that is bad practice, but that is the way I got it and can't change it so I have to work with I have.  So my question is if it's possible to add a number to the ID in the html page, that I can access, to make it so that those IDs be something like name_123, being that the number would change for every new element added into the page?  I suposse I can change the IDs to class but I would still need a way to have an unique identifier...  Any help pointing me in the right direction? Or any other sugestion?  Thank you.

When creating the id attributes for HTML elements, what rules are there for the value?


In Simple Terms  Annie and Ben are both doing the question...  A 100m cliff erodes by 2/7 of its height each year. (a) What will the height of the cliff be after 10 years?  Annie believes the answer is 100*(5/7)^9 because using the geometric progression formula exactly is common sense. Ben believes the answer is 100*(5/7)^10 because it's 10 years later. In your answer, determine whether Annie is right or wrong, giving reasons. Also determine whether Ben is right or wrong, also giving reasons. The Actual Question  An extension to . Can the question...  A 100m cliff erodes by 2/7 of its height each year. (a) What will the height of the cliff be after 10 years?  ...Be interpreted in different ways so that you could answer like this:  100*(5/7)^10 =976562500/282475249 =3.46m to 2d.p.  Or this:  100*(5/7)^9 =195312500/40353607 =4.84m to 2d.p.  I tried to convince my teacher that his answer wasn't correct but he said that his answer was an interpretation. The answer made in  supported my answer, but my teacher still thinks he is right. Can you really interpret this question in the 2 ways above or is there only just one right and the rest wrong? (Excluding the simplification of answers. Also some other questions are designed to have more than one answer.)

Here is the math question.  A 100m cliff erodes by 2/7 of its height each year. (a) What will the height of the cliff be after 10 years?  This is how I worked out the question. 100*(5/7)^10  Which is 3.46m to 2d.p. However my teacher said that it is wrong (to the whole class and also insulted me a bit >_>) and that I didn't follow this formula. Tn = ar^(n-1)  And that I should have done 100(5/7)^9  Which is instead 4.84m to 2d.p.  This doesn't make sense because if you used the formula and the question was  What will the height of the cliff be after 1 year?   100(5/7)^(1-1) =100(5/7)^0 =100  That doesn't make sense at all! Am I right or is the teacher right? ADDITIONALLY my teacher said his answer is an interpretation of the question. Is his answer a valid interpretation of this question? Or is it just incorrect mathematics?  BTW Also my teacher said my answer has no common sense and that I won't be able to do the HSC well if I keep reading questions wrong.


Let $L= \mathfrak{sl}(3, F)$, with $charF= 3$. I want to prove that $L/Z(L)$ is semisimple. I already know that $Z(L)$ is the set of scalar matrices in $L$. I think it is sufficient to show that every solvable ideal, or equivalently, the radical lies in $Z(L)$, but I don’t know how to move on from here. Any hints?

I have problem to solve Exercise 5.6 in a book named "Introduction to Lie algebra and Representation Theory" from Humphreys. I want to show that special linear algebra $ \mathfrak sl (3, F)$ modulo its center is semisimple, but its killing form is nondegenerate, where field $F$ has characteristic 3. My attempt is to consider basis of $ \mathfrak sl (3, F)$ and calculate arbitrary solvable ideal of given lie algebra. However, this does not go well. May I ask for a help?


I have a PM2 process for my NodeJS server and it crash after few minutes. I read somewhere I need to run PM2 as root to not crash. So I do : debian@vps:~$ pm2 start server [PM2] Applying action restartProcessId on app [server](ids: [ 1 ]) [PM2] [server](1) ✓ [PM2] Process successfully started ┌────┬────────────────────┬──────────┬──────┬───────────┬──────────┬──────────┐ │ id │ name               │ mode     │ ↺    │ status    │ cpu      │ memory   │ ├────┼────────────────────┼──────────┼──────┼───────────┼──────────┼──────────┤ │ 1  │ server             │ fork     │ 991  │ online    │ 0%       │ 13.8mb   │ └────┴────────────────────┴──────────┴──────┴───────────┴──────────┴──────────┘ Current process list running is not in sync with saved list. App app differs. Type 'pm2 save' to synchronize. debian@vps:~$ pm2 stop server [PM2] Applying action stopProcessId on app [server](ids: [ 1 ]) [PM2] [server](1) ✓ ┌────┬────────────────────┬──────────┬──────┬───────────┬──────────┬──────────┐ │ id │ name               │ mode     │ ↺    │ status    │ cpu      │ memory   │ ├────┼────────────────────┼──────────┼──────┼───────────┼──────────┼──────────┤ │ 1  │ server             │ fork     │ 991  │ stopped   │ 0%       │ 0b       │ └────┴────────────────────┴──────────┴──────┴───────────┴──────────┴──────────┘ Current process list running is not in sync with saved list. App app differs. Type 'pm2 save' to synchronize.  debian@vps:~$ sudo pm2 start server sudo: pm2: command not found  So I can't run it as root?

If I issue sudo my-command  how does Linux look for that my-command? The my-command is in my PATH. I can invoke it without any problem. However, when I invoke it with sudo, I'll get command not found. How to overcome it? EDIT: That "Possible duplicate"'s selected answer is wrong, well, at least not to the point. This answer, from terdon, is the correct one.


I'm looking to purchase my first cyclocross bike and just found a good deal from someone. It's a Cannondale CAADX tiagra 2015 with a frame size of 56 cm (top tube 56cm basically). I'm a little bit afraid it might be too big for me. My height is 180 cm (5'11) with an inseam of 82 cm. Do you think it would be too big for me, especially on long rides?   From what I've read, it seems that a 54cm frame would be much better for me, but this is a real good deal.  I can't test the bike, because the guy lives in another city.  Thanks!

I am buying a new road bike. I have looked online for calculators but I am getting different answers on which frame size I should get. I've got 53 cm on a calculator that only considers inseam height and 56 cm on another one that also considers riders height so I don't know which one is correct because I don't want to end up with a bike that is either too big or too small for me.


So according to google:      a photon is a particle that transmits light.    Ok, but light is considered a wave, not a stream of particles(I'm pretty sure that this is what Young's double slit experiment proved?)  So what is it exactly? I assume something like wave-particle duality comes into play here, but i don't know much about it, other than the name, and what I can infer from the name.   Thanks for reading and hopefully answering. I'm really new to physics, but trying my best to learn it!!

Consider the question, .  The answers say, "an elementary particle" and not much else. They don't actually answer the question. Moreover, the question is flagged as a duplicate of,  – the answers there don't tell me what a photon is either. Nor do any of the answers to  mentioned in the comments. When I search on , I can't find anything useful. Questions such as,  look promising, but bear no fruit.  say things like, "the photon is an excitation of the photon field." That tells me  nothing. Nor does the , which says:     The photon is the quantum of the electromagnetic four-potential, and therefore the massless bosonic particle associated with the electromagnetic force, commonly also called the 'particle of light'...   I'd say that's less than helpful because it gives the impression that photons are forever popping into existence and flying back and forth exerting force. This same concept is in the  too - but it isn't true. As , "Virtual particles only exist in the mathematics of the model." So, who can tell me what a real photon is, or refer me to some kind of authoritative informative definition that is accepted and trusted by particle physicists? I say all this because I think it's of paramount importance. If we have no clear idea of what a photon actually is, we lack foundation. It's like what :     Photons seem to be one of the foundation ideas of quantum mechanics, so I am concerned that without a clear definition or set of concrete examples, the basis for understanding quantum experiments is a little fuzzy.   I second that, only more so. How can we understand pair production if we don't understand what the photon is? Or the electron? Or the electromagnetic field? Or everything else? It all starts with the photon.   I will give a 400-point bounty to the least-worst answer to the question. One answer will get the bounty, even if I don't like it. And the question is this:    What exactly is a photon?


I recently found an annual "America the beautiful" pass with no signatures in the back.  I seems to be new, as it is still valid for a eleven months.   I was wondering if there is any way to return it... is it registered to someone? If not, does anything speak against using it? Will I get in trouble if I just put my signature on it?   Would appreciate your feedback!

can be owned/signed by "two pass owners that do not have to be related or married".  That is why there are a lot of valid passes with only one signature on eBay.  Selling it is another issue, probably more problematic but let's assume I've obtained such pass for free. So please don't focus on eBay part, unless it makes a practical difference.  The question is: Are there any obstacles in just signing it and going for a trip? (what non-transferable really means?)


I want to create a link and download an excel file that is stored in static resource.How do i do that?

I have uploaded an excel sheet into static resource of my environment. I have it as a demo for my product how to create a excel sheet for import records into sf. Can any body guide me how can i provide link on the VF page so that user can download the record at single click.I want to into a managed package and want users to be able to click the link on the Vf page to download. Right now i have my demo excel sheet in static resource. I am open if you have any other ideas to get the process done.


I was reviewing some suggested edits and some other posts on SO today.  Aftera short while I have exhausted by contigent of reviews for the suggested edits queue. As I still wanted to do some other reviews, I stumbled upon a minor bug.  Despite not being allowed to do any reviews, I got the topbar indicating that there is pending reviews. I took a screenshot (and edited it to decrease the size by removing all the other review queues from the image).    This did not happen all the time, but could be reproduced by using the review link in the topbar now and then.

Once a user has exhausted their (currently) 30 edit suggestion approval/rejections, the pending edit box in the top bar can still show up:    You click through and see some edits suggested to vote yay or nay on.   But when trying to approve/reject you get the warning:      Out of votes - you may only vote 30 times a day.   Don't tease me, bro!


I have three controls on my form - a texbox, button and a picturebox. After clicking a button, both textbox and button itself become inactive. Also I have and Form1_KeyDown(object sender, KeyEventArgs e) to send pressed buttons that will be displayed on picturebox, but for some reason everytime I press any key it beeps. I've noticed that it happens only with button and TextBox deactivated. Why is that happening and how do I press keys without that annoying beeps?   e.SuppressKeyPress = true is preventing the input of keys to control, I don't need that, I just need to rid of that sound (why is it there anyway, when I'm disabling two controls?)  UPD: I think the problem is that PictureBox doesn't have a focus and also a KeyDown event.

I'm looking for a best way to implement common Windows keyboard shortcuts (for example Ctrl+F, Ctrl+N) in my  application in C#.  The application has a main form which hosts many child forms (one at a time). When a user hits Ctrl+F, I'd like to show a custom search form. The search form would depend on the current open child form in the application.  I was thinking of using something like this in the ChildForm_KeyDown event:     if (e.KeyCode == Keys.F && Control.ModifierKeys == Keys.Control)         // Show search form   But this doesn't work. The event doesn't even fire when you press a key. What is the solution?


I would like to know how to install Aircrack on Ubuntu 16.04. Please provide detailed guidance on all the steps needed. Also, could you provide the link where I can download the latest version of Aircrack?

Whenever I attempt to install aircrack-ng in terminal I get the following error:  Package aircrack-ng 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 However the following packages replace it:   iw  E: Package 'aircrack-ng' has no installation candidate"   I'm new to Ubuntu and so have no idea what to do.


My husband writes for an outdoor magazine and we go backpacking/canoeing/kayaking/etc a lot for his stories. I would love to learn real photography (and maybe one day take pictures to go along with his articles). I had a few photography classes in college so I have a rough grasp of the basics. I would love a recommendation of what type of camera would help me to really learn about all the art that goes into photography, take good pictures and is semi-professional (but I imagine I will upgrade when I get better) and will not cost my entire life savings. The pictures I would take are of wildlife at a distance and landscapes.

I am thinking of buying a camera to learn photography. Most of the time I'll be shooting portraits and landscapes. But I am not sure where I should start. Most of my friends tell me that I should get an entry level DSLR, but I am not sure if I have the persistence and enthusiasm to carry it all day in a backpack. But the camera on my cellphone doesn't seem to be enough to begin with.  So what I want is some expert advice (preferably with professional experience). Can most compact fixed-lens or mirrorless cameras fit the situations I mentioned? Or do I really need to go to a DSLR to get a tool to learn photography?


I'm trying to round up numbers using C# in a way that it always rounds to the next number. For instance:  0.409 -> 0.41 0.401 -> 0.41 0.414 -> 0.42 0.499 -> 0.50 0.433 -> 0.44   Is there a way to do this using .NET built-in functions?

I want to do this using the Math.Round function


Prove that characteristic polynomial of a complex matrix $A$ divides its minimal polynomial if and only if all eigenspaces of $A$ are one-dimensional.   As far as I can see I the only possible case is when minimal polynomial equals characteristic one.   All distinct eigenvalues with multiplicity 1 grant us that the eigenspaces would be one-dimensional, I thought that this is the key to the solution, however we have the theorem stating that on the other side, eigenspace dimension could be less then or equal to its eigenvalue algebraic multiplicity. Everything now mixed up, will be thankful for any help.

Assume that we are working over a complex space $W$ of dimension $n$. When would an operator on this space have the same characteristic and minimal polynomial?    I think the easy case is when the operator has $n$ distinct eigenvalues, but what about if it is diagonalizable? Is that sufficient, or can there be cases (with repeated eigvals) when char poly doesn't equal min poly? What are the general conditions when the equality holds? Is it possible to define them without use of determinant? (I am working by Axler and he doesn't like it.)  Thanks.


In one of my wordpress theme function, this code is being used to calculate total billable amount: ceil(($cost * (1 + ($charges / 100))) * 100);  There is a little miscalculation happening for below scenario.  Scenario:  $charges = 9; $cost = 100;  echo ceil(($cost * (1 + ($charges / 100))) * 100);   The above code outputs 10901 whereas it should be 10900.  It works fine for other scenarios like:  $charges = 4; $cost = 90.7;  echo ceil(($cost * (1 + ($charges / 100))) * 100);  //outputs 9433, which is fine because manual calculation results 9432.8   Question:   Why is that happening? How can I prevent that? Any alternate function to round to next nearest integer? (only if amount is floating value)

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


I am going through the steps of installing Linphone, following this.   When I typed the command flatpak --user install --from   Terminal said The application com.belledonnecommunications.linphone depends on runtimes from  configure this as a new remote 'gnome'? (y/n)  I wasn't sure but I said yes to that.  Then Terminal said: Required runtime for com.belledonnecommunications.linphone/x86_64/4.4.1 (runtime /org.freedesktop.Platform/x86_64/1.6) found in remote gnome. Do you want to install it? (y/n)  Just wasn't sure what this all means and the implications.

When trying to install flapaks in a script,  $ flatpak install program_I_am_installing  I get prompted with  Found similar ref(s) for 'program_I_am_installing' in remote 'flathub' (subsystem).  Use this remote [Y/n]:  The default goes to "n" when running the script since I have no way of entering Y withing the script.  I tried giving flatpak the full Application ID, but that didn't stop the question from being asked.  I'd either like to find how to answer the question Y in the script or know how to more specificaly state the program name so this question isn't asked.


Say a specific user is my friend. Naturally, I follow the user's activity and each time he/she posts an answer, I upvote it. Of course I do that only after a careful read and if I find it useful, at least for the OP.  Is it considered inappropriate? Would some automatic algorithm track my upvoting activity and cancel it?  And what if that friend also gives me the same attention?  Again, I don't mean . The relation just attracts attention to the user's activity which is followed by probable upvote (as that friend is by all means no less than the ultimate professional).

Almost every time a colleague of mine asks a question, we have discussed this problem beforehand. Also, we sometimes meta-discuss the question for stackoverflow (why did I get the "this might be subjective" warning, is this understandable enough, etc). This is less so with answers, but I could believe for some groups this works the same. For now I'll stick to questions, but you could s/question/answer if you like. The resulting question is almost always  Interesting for me, and a problem I don't know the answer to. I probably would favorite it According to me a valid and good question (as we talked about it beforehand) I would probably want to upvote it.  Now I believe to read that "ring voting" is a thing, and I tried to find some questions about this, but didn't find many. I did find and read this blogpost from 2008:  . It reads to me that upvoting 'fraud' is more commonplace then downvoting and it might seem anomalous that I would upvote almost all questions from one user. If all colleagues would do this to their team, you'd get some mediocre questions getting a lot of votes, and some users getting a lot of attention, points etc from that. If you would -as seems to be done -, sort the amount of upvotes for my colleague, you'd get me being 'anomalous' in front of the crowd. On the other hand, as explained above, I do want to upvote almost all stuff some of my colleagues put on here for (I believe) the right reasons: they are questions I consider good and interesting. It's just that I know of all their questions (as they tell me about them), which obviously isn't the case for a random user. So what is the deal?  When is upvoting content from one user frowned upon? Would my usecase be in danger of being a (what I consider 'false') positive for the fraud-detection? (and would you agree with that or not) How to prevent this false positive (if you agree with me it is one, otherwise this is a moot question) -> As noted in the comments: I'm not looking for tricks, so an answer could be "don't vote for your colleagues". I agree that there should be no to 'tricks' around that could be used for real fraud of course


I have a function that calls another function.  For some reason, the variable in the first function is updated by the second function.  Is python passing a variable by ref as a default?  Basically why is 'AA' updated in the second run? And how can I make it the same, just like the first run.  For simplicity, I created a short sample code that has the same issue.  I have a function (test) that calls (test2).  The variable 'AA' in 'test' is updated by 'test2' when I perform BB.append(list_position[0]).  The two function is below:  def test(A, childs):      for x in range(0,childs):         list_pos = [x]          AA = A          print("")         print("AA: ", AA)         print("list_position: ", list_pos)         test2(origin,list_pos)  def test2(B,list_position):       BB = B     list_len = len(BB)      print(list_position[0])     #BB.append(list_position[0])   Output of the first run (with last code commented out):  AA:  []     list_position:  [0]     0  AA:  []     list_position:  [1]     1  AA:  []     list_position:  [2]     2  AA:  []     list_position:  [3]     3   Output of the Second run (with last code uncommented):  AA:  []     list_position:  [0]     0  AA:  [0]     list_position:  [1]     1  AA:  [0, 1]     list_position:  [2]     2  AA:  [0, 1, 2]     list_position:  [3]     3

I'm trying to understand Python's approach to variable scope. In this example, why is f() able to alter the value of x, as perceived within main(), but not the value of n?  def f(n, x):     n = 2     x.append(4)     print('In f():', n, x)  def main():     n = 1     x = [0,1,2,3]     print('Before:', n, x)     f(n, x)     print('After: ', n, x)  main()   Output:  Before: 1 [0, 1, 2, 3] In f(): 2 [0, 1, 2, 3, 4] After:  1 [0, 1, 2, 3, 4]


I've used Windows for many years, using Dreamweaver as my editor as it had a file tree which is based on a project (via Local, FTP or SFTP).  I need a web development IDE with the following functionality:   syntax highlighting for PHP, HTML, CSS, JavaScript  file tree - Local, FTP, SFTP, Project-Based (e.g. via the methods of Local/FTP/SFTP) in other words, like Dreamweaver can open multiple files (tabbed)   Additionally, I wouldn't mind features like debugging, class listings, etc, as long as I can hide them away.

This question exists because it has historical significance, but it is not considered a good, on-topic question for this site, so please do not use it as evidence that you can ask similar questions here. See  for more information.   This is a community wiki for IDEs available on Ubuntu. Please post one IDE per answer (including more than just a screenshot or a link, please at least put a short description).  In your answer, tell us what the IDE is for (which language(s) or if it is RAD capable).


I've deleted the wrong partition of my disk where is my ubuntu, and I have important files there, is there any way to recovery them?

I normally dual-boot with 12.04 and Win XP pro sp3 on a Thinkpad R60.  I needed to reinstall windows because of problems piling up, so I ran the computer's built-in hard-disk recovery software.  I told it not to mess with the other partitions, but somehow it deleted the Linux partition.  That's what I was using to backup all of my windows files, so now everything I have is gone.  I just ran the USB setup with linux, and the partition is deleted - it just shows it as empty space.    Is there ANY way to get all of my files back?


I need to prove that $\mu_{f}(A)=\sup \left\{\sum_{x \in F} f(x): F \subseteq A \text { is finite }\right\}$ is a measure on $(\mathbb{R},S)$ where $f:\mathbb{R} \rightarrow [0,\infty)$ and $\mathcal{S}=\{A \subseteq \mathbb{R}: \text { either } A \text { is countable or } \mathbb{R} \backslash A \text { is countable }\}$. I have done everything apart from proving that for disjoint sets $\mu\left(\bigcup_{i \in \mathbb{N}} E_{i}\right)=\sum_{i \in \mathbb{N}} \mu\left(E_{i}\right)$. I think it would be easier to prove the measure is an outer measure and then prove that for every set in the $\sigma$-algebra, $\mu$ is $\mu$-measurable. But apart from this i am very stuck. Thanks in advance.

Let $X=\mathbb{R}$ and let $\mathcal{S}=\{A\subseteq \mathbb{R}:$ either $A$ is countable or $\mathbb{R}\setminus A$ is countable }. Let $f:\mathbb{R}\rightarrow [0,\infty)$ be any function, and define $\mu_{F}:\mathcal{S}\rightarrow[0,\infty)$ by $\mu_{f}(A)=$sup $\{\Sigma_{x\in F}f(x):F\subseteq A$ is finite$\}$ Show that $\mu_{f}$ is a measure on $(\mathbb{R},\mathcal{S})$. Now I know that a measure on $(X,\mathcal{S})$ is a function $\mu:\mathcal{S}\rightarrow[0,\infty]$ such that $\mu(\bigcup_{k=1}^{\infty}E_{k})=\Sigma_{k=1}^{\infty}\mu(E_{k})$, but I am unsure of how to incorporate the disjoint sets into the definition for $\mu_{f}(A)$. I know that if $E_{1}\cup E_{2}\cup...=A$ where each $E_{i}$ is disjoint then we have \begin{equation*} \begin{split} \mu_{f}(E_{1}\cup E_{2}\cup...)=\mu_{f}(A)&=\text{sup}\{\Sigma_{x\in F}f(x):F\subseteq A \space  \text{is finite}\}\\ &=\text{sup}\{f(x_{1})+...f(x_{n}):\{x_{1},...,x_{n}\}\in F\} \end{split} \end{equation*} and somehow the last line should equal $\mu_{f}(E_{1})+\mu_{f}(E_{2})+...$ . Any help would be appreciated. Thank you


I am looking for ways to validate mileage charged by our contractors.  They are paid from a central location to a customer, and then from the customer to a drop off location.    I use QGIS for a bunch of stuff and also have access to MapInfo Pro.     I need to do the following:        route individual trips to get total distance in each direction   also need to know if parts of one trip overlap the other, and by how much (i.e. km)    and if the second trip ends anywhere along the route of the first trip (i.e. they came back the same way they went out)       I have been messing around with PostgreSQL and pgRouting for a couple days and it's pretty confusing to me.

I was wondering if there are any alternatives to  tools.  Thinking about it for a bit, I think the only alternative is to use R or RPY to do the analysis.   Basically I'm trying to solve routing problems based on nonPostGIS databases. As most of my data is actually stored in a different format; however, it's not to hard to convert. I'm finding that pgRouting to my dumb silly brain is difficult to implement. So perhaps a non-database solution that I can easily tweak would be ideal for me


Good day;  I'm making a Monthly budget to keep track of where I spend my paychecks. I stumbled upon the rent part; would that be considered a debt? Since it's basically something that I "accept" I'll be paying for the next 12 months, each month, in accordance to the lease?

I am taking a financial assessment. It asks me:     What is your total monthly debt payment (e.g. student loans, vehicles, credit cards, personal loans, etc.)?   Then the next questions are about household essentials and non-household essentials.  But should I include rent in any of this?


We see the Sun about eight minutes after light left it. Presumably this means we are also experiencing the Sun's gravity 8 minutes after it 'left' the Sun.  So are we orbiting around the Sun we can see or around the Sun's actual position?

Gravitational change occurs at the speed of light. As a consequence, we experience on Earth the gravitational attraction of the Sun based on its position relative to us ~8 minutes ago. How does this delay affect the geometry of Earth's orbit compared with the classical Newtonian model?  Nordvedt postulated that a gravito-magnetic component makes it appear as if the interaction is instantaneous  (i.e.) classical Newton with infinite speed of interaction. Was Nordvedt correct?


UTF-8 is present in the header, but still most 'less common' symbols are not converted correctly.  Example: the game The Interactive Adventures of Dog Mendon�a & Pizzaboy --> that should be 'ç'  This is the part of the code where the problem occurs:
            ".$date." 	           {$row['game_name']}	           {$row['game_platformlist']}	           ";                 $query="SELECT * FROM genre WHERE genre_id=".$row['game_genre'];                  $genreresult=mysqli_query($link,$query);                                    $genrerow=mysqli_fetch_assoc($genreresult);                     echo $genrerow['genre_name'];                     echo "	           {$row['game_dev']}	           {$row['game_type']}	                                        	           {$row['game_note']}
";   Is there a way to solve this problem? I tried iconv ISO-8859-1 but that didn't work.

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.


If $\lvert\,G\,\rvert=p^{2}\cdot\,q$ where $q,p$ are primes, How can i show $G$ has a normal p-sylow subgroup ? I tried working with the sylow theorem but i cant reach any contradiction when $Np = q$ and $Nq = p,p^2$ Also tried searching the same question but couldn't find in Stack Exchange

Suppose that I have a group $G$ of order $p^{2}q$ for two distinct primes $p$ and $q$.  I need to first show that one of its Sylow subgroups is normal.  I start by letting $H$ be a Sylow $p$-subgroup and $K$ be a Sylow $q$-subgroup.  If $K$ is not normal, then letting $r$ denote the number of Sylow $q$-subgroups, I have that $r|p^{2}$ and $r\equiv 1$(mod $q$).  I also have by the second Sylow theorem that $r\neq 1$.  So $r = p$ or $p^{2}$.  If $r = p^{2}$, I can write out the Sylow $q$-subgroups, and count their combined elements to show that $H$ is uniquely determined and then again imply Sylow number $2$ to obtain that $H$ is normal.  But if $r = p$, then I cannot see how to proceed.  Can anyone give any advice?  Thank you.  ( I am happy to provide more detail for the $r = p^{2}$ case if it is desired or appropriate. )


Given $f:X\rightarrow Y$ as a function, the image of $x$ if $f(x)$. The preimage of $y$ is $f^{-1}(y)=\{x\ |\ f(x)=y\}$, with the symbol PreIm$(Y)$  Given the definition, could you prove the following statement? Thank you.  Given that $f:X\rightarrow Y$ is a function, and that $A, B \subseteq Z$.  PreIm$(A\cup B)$ = PreIm$(A) \cup$ PreIm$(B)$

I just wonder if my following solution is true. Let $X,Y$ be sets, let $f:X\to Y$ be a function, let $\{Y_i\}_{i\in I}$ be a family of subsets of $Y$. (Note: I use equalities instead of mutual containment) $$\begin{align}f^{-1}\left[\bigcup_{i\in I} Y_i\right]  &= \{x \in X: \mbox{there exists an}\quad i \in I\mbox{ such that } y \in Y_i,f(x)=y\}  \\&=\bigcup_{i \in  I} f^{-1}\left[Y_i\right] \end{align}$$ I initially do not know how to get from the left to right, but when I put both sets in set notation, they turn out to be the same, hence the one line proof. Something go ultimately wrong?


The following is a proof that higher (angular) frequencies have a greater deflection than lower frequencies through a glass prism:      It was omitted in the image above, but $n_{\text{air}}$ is taken to be unity, which is the reason for the $1$ in Snell's law.  My problem is as follows; in a general dielectric (such as a glass prism) we have the following dispersion relation:  $$v_{\text{phase}}=\frac{\omega}{k}=\frac{1}{\sqrt{\mu_0\,\epsilon}}=\frac{c}{{\epsilon_r}^{1/2}}=\frac{c}{n}\tag{1}$$  so in short $$\frac{\omega}{k}=\frac{c}{n}$$  or $$n=\frac{k\,c}{\omega}$$   therefore $$n\propto \frac{1}{\omega}\tag{2}$$  Now looking at the writing in the image it says:      $v_{\text{phase}}$ decreases with $\omega$   According to $(1)$ $v_{\text{phase}}$ increases with $\omega$; since $v_{\text{phase}}\propto\omega$.  But that's not the only problem the text also says:     $n_{\text{glass}}$ increases with $\omega$   According to $(2)$ $n$ decreases with $\omega$. Another contradiction.    Is there anyone that can explain why $v_{\text{phase}}$ decreases with $\omega$ and why $n_{\text{glass}}$ increases with $\omega$?    EDIT:  I'm voting to close this question now since I no longer care whether or not it it is a duplicate of  as I already have accepted an answer to my question.

It is well known that a  can "split light" by separating different frequencies of light:    Many sources state that the reason this happens is that the  is different for different frequencies.  This is known as .  My question is about why dispersion exists.  Is frequency dependence for refraction a property fundamental to all waves?  Is the effect the result of some sort of non-linearity in response by the refracting material to electromagnetic fields?  Are there (theoretically) any materials that have an essentially constant, non-unity index of refraction (at least for the visible spectrum)?


I have a page which contains a script tag which pulls in a survey form from JotForm. Basically placing a  tag in the HTML pulls in content from the 3rd party, which is a form. The code pulled in is a full page ie: contains html element which contains an iframe.  The problem is that there is a class called form-all which has a width set at 690 which does not fit in our site, it's too wide so cuts off.  I need to know how I can remove this width on the form-all class from my html code?  The structure would be something like:  <html> <!-- My html element //-->  ...  ...     <html> <!-- html element pulled in from 3rd party code, everything within is 3rd party //-->      <iframe>         <div class='form-all'>          </div>      </iframe>    </html>  </html>   How do I remove the width on form-all by placing code in my code which I control?  Thanks.

I would like to manipulate the HTML inside an iframe using jQuery.  I thought I'd be able to do this by setting the context of the jQuery function to be the document of the iframe, something like:  $(function(){ //document ready     $('some selector', frames['nameOfMyIframe'].document).doStuff() });   However this doesn't seem to work. A bit of inspection shows me that the variables in frames['nameOfMyIframe'] are undefined unless I wait a while for the iframe to load. However, when the iframe loads the variables are not accessible (I get permission denied-type errors).  Does anyone know of a work-around to this?


I download ubuntu-13.04-desktop-amd64.iso and write on a DVD then check it with a MD5 checker and it's OK. I decide to Install Ubuntu on my PC that have Windows 7 sp1 64-bit simultaneously. I follow  from Ubuntu website.  In step 4 when I choose "Install Ubuntu alongside Windows 7" and click continue my screen turn black and DVD would be ejected and When I press Enter the system would be restarted.   Also in windows I can't use wubi, When I Run wubi with administrator permission it show nothing, I try wubi.exe --force-wubi and did nothing.  I have this problem with Ubuntu 12.04.2.  :  ASUS N53SV  CPU: Intel Corei7 2630QM  RAM: 4.00 GB  Graphic Card: Nvidia Geforce GT 540M & Intel HD Graphic Family

Any of the partitions makes in Windows was not recognised by Ubuntu, or Zorin OS, or LinuxMint. It's like a blank hard disc, 250 gb free. I'm a new Linux user, but what confuses me is that I was able to install Ubuntu alongside Windows on my laptop with no problems, but on PC... no way!


I'm an Indian citizen, holding a valid Canadian visitor's visa. I'm traveling from Canada through Dublin to another destination. Does Dublin require a transit visa?

My parents are Indian Citizens. They hold a valid B2 Tourist Visa to USA. I'm planning to book a flight with Hyderabad (India) - Abu Dhabi (UAE) - Dublin (Ireland) - USA. The leg from Hyderabad to Dublin is operated by Etihad and I know there is no problem hopping at Abu Dhabi. The leg from Dublin to US is operated by Aer Lingus. I called Aer Lingus customer care agent told me a transit visa is required to land in Dublin. She did not care to ask for the citizenship of traveller or about the USA visa. I went through Irish immigration website - (), India is not in list of countries that require transit visa. I'm now confused. Can some one confirm if they traveled with the same itinerary recently  Update: I called Aer Lingus again. Another agent told as long as I don't exit the airport, a transit visa is not required. I think these people don't really understand trouble we go through when boarding is denied. I put this question because I read a person was denied boarding earlier - . His case mentions about denied because of different day. But I see his transit time is 12 hours only.


I am trying to understand what additional security the the consumer secret(client_secret) for OAuth 2.0 provides. If one want to avoid using the consumer secret when authenticating you can use the User Agent flow rather than Web Server flow.  As far as I can see there is no way to restrict which flow that you allow to be used for your connected app. So what is the purpose of the consumer secret when anyone can easily avoid using consumer secret for authentication by selecting a different response_type(=token) in order to retrieve an access token?  Is this not just like having two doors into the same house. One with two locks, and the other with just one?

After looking into the different OAuth types and reading , I'm still confused on the specific pros and cons of user-agent vs web server flows.  The best explanation I can find says that user-agent tends to be used for mobile but it seems that they can both be used for desktop.   What makes it more appropriate to use one over the other in certain scenarios?


My task is to be able to generate a unique number for every input a user gives my program and save this number along with their input in a file I called customer_references. I want the file to present something like this :  Case number: 1 Issue: My issue is....  Case number: 2 Issue: My phone is...   Case number: 3 Issue: ...... (etc.)  And also need to be able to print the case number for the user to know on python. I tried using randint but this wasn't efficient enough as the case number has a chance of being repeated for a different user  This is my unfinished code :  def issue_details():      #prints aplogy message for not being able to find a solution     print("Sorry we were unable to provide a suitable solution")      #Takes further information on details of issue from the user     issue = input("Please explain your issue in as much detail so we can direct you to a technician: ")       #opens the file I created to store the customers details to append the issue into it.     customer_file = open("Customer_references.txt","a")      #inputs the issue into the text file     customer_file.write(issue)      #Here I need to generate the case number and add it to my file beside the users issue     #The case number must always be unique      print("Thank you for your cooperation. Contact us on 0844558888 and give the technician your reference number so we can try help you\n", "Your reference is: ",#case_number )     customer_file.close()

How do I create a GUID in Python that is platform independent? I hear there is a method using ActivePython on Windows but it's Windows only because it uses COM. Is there a method using plain Python?


public class Node<T> {     T data;     Node<T> next;     Node(T data){         this.data = data;     } }   public  class LinkedListUse{      public static void print(Node<Integer> head){         Node<Integer> temp = head;              while(temp != null){             System.out.print(temp.data +" ");             temp = temp.next;         }         System.out.println();     }          public static void increment(Node<Integer> head){         Node<Integer> temp = head;         while(temp != null){             temp.data++;             temp = temp.next;         }     }          public static void main(String args[]){              Node<Integer> node1 = new Node<Integer>(10);         Node<Integer> node2 = new Node<Integer>(20);         node1.next = node2;         increment(node1);         print(node1);     } }  Since node1 has been passed by value (and not pass by reference) in the function increment, hence the output should be 10 20 according to me, but the solution is 11 21. Can you please help me out with the explanation behind this

I always thought Java uses pass-by-reference. However, I've seen a couple of blog posts (for example, ) that claim that it isn't (the blog post says that Java uses pass-by-value). I don't think I understand the distinction they're making. What is the explanation?


Recently my house has been invaded by acrobat ants. They are everywhere. On our tables, in our plates, in our glasses. They tend to be menace and have caused us a lot of trouble.

Is it enough to pour boiling water in their mount?


I want to remove some objects (if they meet a condition) of an ArrayList while looping through it. But that will obviously throw a 'ConcurrentModificationException'.  So, what's the best way of doing this?  edit: My condition is a number comparision, so if an objects' variable is greater than a value, the object must be removed from the list..

We all know you can't do the following because of ConcurrentModificationException:  for (Object i : l) {     if (condition(i)) {         l.remove(i);     } }   But this apparently works sometimes, but not always. Here's some specific code:  public static void main(String[] args) {     Collection<Integer> l = new ArrayList<>();      for (int i = 0; i < 10; ++i) {         l.add(4);         l.add(5);         l.add(6);     }      for (int i : l) {         if (i == 5) {             l.remove(i);         }     }      System.out.println(l); }   This, of course, results in:  Exception in thread "main" java.util.ConcurrentModificationException   Even though multiple threads aren't doing it. Anyway.  What's the best solution to this problem? How can I remove an item from the collection in a loop without throwing this exception?  I'm also using an arbitrary Collection here, not necessarily an ArrayList, so you can't rely on get.


I am making carrot cake "cupcakes" from a recipe meant for round 9" cake pans (3 layers, if that matters).  The cake pans are supposed to cook 25-30 min at 350.  How should I cook the cupcakes?  Thanks!

I'm looking at the side of my "breakfast - O - meal" box at a recipe for 12 muffins. The kind you would use with a standard muffin tin. What kind of variation should can I use to make the recipe work in a larger 6 large muffin tin?  I tried this once before with corn bread muffins and they never seemed to be able to bake all the way though. Ideally I would like to try this with some other cupcake / muffin recipes I have too.  So what's the secret? Less liquid? More Egg? My underused large muffin tin needs to know.