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I know this: $\sqrt{x}^2 = |x|$, but $\sqrt{(-1)^2} = \sqrt{(-1)^2}$ $(-1)^\frac{2}{2} = \sqrt{-1 * -1}$ $(-1)^1 = \sqrt{1}$ $-1 = 1^2$, then $-1 = 1$ What step is wrong? | I know there must be something unmathematical in the following but I don't know where it is: \begin{align} \sqrt{-1} &= i \\\\\ \frac1{\sqrt{-1}} &= \frac1i \\\\ \frac{\sqrt1}{\sqrt{-1}} &= \frac1i \\\\ \sqrt{\frac1{-1}} &= \frac1i \\\\ \sqrt{\frac{-1}1} &= \frac1i \\\\ \sqrt{-1} &= \frac1i \\\\ i &= \frac1i \\\\ i^2 &= 1 \\\\ -1 &= 1 \quad !!? \end{align} |
I need to parse my HTML page to replace some links, this is the form of a link <a href="/{localLink:1144}" title="Bas-rhin">Mauris nec</a>. The problem is that my regex expression doesn't end properly, I think it's because of the ". This is my Regex expression : Regex r= new Regex("<a href=\"(/{localLink:)(.*)}\" title=\"(.*)\">(.*)</a>"); That regex doesn't end after each link, and the third group doesn't contain the title property but almost all the html until the last of my html. I tested it with this site : So, why doesn't the third group end directly after Bas-Rhin" ? | It seems like every question on stackoverflow where the asker is using regex to grab some information from HTML will inevitably have an "answer" that says not to use regex to parse HTML. Why not? I'm aware that there are quote-unquote "real" HTML parsers out there like , and I'm sure they're powerful and useful, but if you're just doing something simple, quick, or dirty, then why bother using something so complicated when a few regex statements will work just fine? Moreover, is there just something fundamental that I don't understand about regex that makes them a bad choice for parsing in general? |
i get following errors when trying to open programs over ssh. $ thunar Thunar: Cannot open display: $ libreoffice Failed to open display $ firefox Error: GDK_BACKEND does not match available displays $ keepassx keepassx: cannot connect to X server $ keepass2 Unhandled Exception: System.TypeInitializationException: The type initializer for 'System.Windows.Forms.XplatUI' threw an exception. ---> System.ArgumentNullException: Could not open display (X-Server required. Check your DISPLAY environment variable) Parameter name: Display at System.Windows.Forms.XplatUIX11.SetDisplay (IntPtr display_handle) <0x41b3c8a0 + 0x00b9b> in <filename unknown>:0 at System.Windows.Forms.XplatUIX11..ctor () <0x41b3ab20 + 0x001df> in <filename unknown>:0 at System.Windows.Forms.XplatUIX11.GetInstance () <0x41b3a8d0 + 0x0005b> in <filename unknown>:0 at System.Windows.Forms.XplatUI..cctor () <0x41b3a160 + 0x00137> in <filename unknown>:0 --- End of inner exception stack trace --- at System.Windows.Forms.Application.EnableVisualStyles () <0x41b38870 + 0x0001b> in <filename unknown>:0 at KeePass.Program.Main (System.String[] args) <0x41b376c0 + 0x0008b> in <filename unknown>:0 [ERROR] FATAL UNHANDLED EXCEPTION: System.TypeInitializationException: The type initializer for 'System.Windows.Forms.XplatUI' threw an exception. ---> System.ArgumentNullException: Could not open display (X-Server required. Check your DISPLAY environment variable) Parameter name: Display at System.Windows.Forms.XplatUIX11.SetDisplay (IntPtr display_handle) <0x41b3c8a0 + 0x00b9b> in <filename unknown>:0 at System.Windows.Forms.XplatUIX11..ctor () <0x41b3ab20 + 0x001df> in <filename unknown>:0 at System.Windows.Forms.XplatUIX11.GetInstance () <0x41b3a8d0 + 0x0005b> in <filename unknown>:0 at System.Windows.Forms.XplatUI..cctor () <0x41b3a160 + 0x00137> in <filename unknown>:0 --- End of inner exception stack trace --- at System.Windows.Forms.Application.EnableVisualStyles () <0x41b38870 + 0x0001b> in <filename unknown>:0 at KeePass.Program.Main (System.String[] args) <0x41b376c0 + 0x0008b> in <filename unknown>:0 :06:22 PM~/Documents$ gimp Cannot open display: $ wireshark QXcbConnection: Could not connect to display Aborted (core dumped) $ gedit Failed to connect to Mir: Failed to connect to server socket: No such file or directory Unable to init server: Could not connect: Connection refused (gedit:23724): Gtk-WARNING **: cannot open display: i've always been able to open aplications over ssh, this just started yesterday. using ubuntu 16.04 on both machines. please DO NOT flag this as a repeat question, the following solutions didn't help: if specific info is needed, please ask, i'll do my best to answer. | I am trying to run gedit from an SSH terminal on Windows, connected to an Amazon EC2 instance running Ubuntu 12.04 Server and I am getting this error: Cannot open display: How do I fix it? |
I want to convert the code from C++ to C#, there is one line code regarding with memcpy. Not sure how to convert it. memcpy(Bucket, nBucket, 4 * L); The original code is from I finished most of them except a few lines. | I have 2 objects from the same type and i would like to shallow copy one state to the other. In C++ i have memcpy which is great. How can i do it in C#? The MemberwiseClone() is not good enough because it creates & returns a new object and i like to copy to an existing object. I thought of using reflection but i'm afraid it will be too slow for production code. I also thought of using one of the .Net serializers but i think they also create object rather than setting an existing one. My Use Case: I have a template object (class not struct) which needs to be updated by one of its instances (objects made of this template) Any ideas? |
Can you hire a Rental car in Dublin, travel to Scotland, and return the car to Dublin (the trip would be about a week). | My wife, two kids and I will be traveling in Ireland and the UK Nov. 1st through 21st. We're flying into and out of Dublin. Our plan is to do a clockwise tour: Fly into Dublin -> Belfast -> Scotland -> England/London -> Back to Dublin to fly home. We've been planning to rent a car when we land in Dublin (doing just things outside Dublin at the start of the trip) and have a car all the way until London, then turn in the car and take a train/ferry to get back to Dublin before flying home. However, reading through the car rental section of Rick Steve's 2012 Ireland book is causing us to question if this is the right plan. He says (p. 480): If your trip covers both Ireland and Great Britain, you're better off with two separate car rentals, rather than paying for your car to ride the ferry between the two islands. On an all-Ireland trip, you can drive your rental car from the Republic of Ireland into Northern Ireland, but be aware of drop-off charges ($75-150) if you return it in the North. So it seems like he recommends against doing one car rental for both islands, but he also recommends against renting in the Republic of Ireland and returning it in Northern Ireland (our other option for our current itinerary). So we're not sure which is best here. A few questions about this: If we do one car rental all the way from Dublin to London, will there be a similar $75-$150 fee? Is there an easy place to return a car on the Northern Ireland side of one of the Northern Ireland -> Scotland ferries, and an easy place on the Scotland side to rent a car? We'd like to minimize the number of buses/whatever we need to take between car rentals since we'll be lugging around car seats for both of our children (on top of carrying them and our luggage). Will one way be significantly cheaper than the other? Besides the basic cost of taking the car on the ferry and the drop-off charges, our credit card will cover insurance in Scotland/England but not in Ireland, so we could potentially get a better rental rate by renting a second vehicle once we're on Great Britain. Although, I know you often get a better rate when keeping a car rental for longer, so that may negate any benefit from the credit card covering the insurance. |
Let us take this title for example, " The Cars should Be sold in Three Years". If lowercase or uppercase rules are from the Chicago Manual of Style, the word should is lowercase or uppercase? I have browsed this website and seen , but the answers there do not mention modal verbs. | Are there any concrete rules that say which words (parts of speech) in a title should start with a capital letter? What would be a correct capitalization for the title of this question? |
So I know this is a commonly asked question (I've been looking into this for a while now), however, I've been having some issues. I'm inserting a piece of data into my SQLite database, and then I want to retrieve the ID of that newly inserted row. I have a 'globalId' column which is an auto incrementing integer. I've tried many things such as using last_insert_rowid(), getting the max id in the database after inserting it, but neither seem to work. DBConnection.sql.modifyQuery("INSERT INTO pp_data (...) VALUES (...)"); is my modifyQuery, I've replaced all the actual data with ... because there's a lot of stuff. I then have a readQuery method which will return a ResultSet, and with that, I need to get the column Id. Thanks in advance! | What's the best way to get the last inserted id using sqlite from Java? Google is giving me different answers--some say select the last-insert-rowid; others say call statement.getGeneratedKeys(). What's the best route to take? (I just want to return the id, not use it for other inserts or anything.) |
We know that an additive identity in a ring is always a multiplicative annihilator. But this doesn't need always be true in case of a semiring. Consider that $e$ is the additive identity of a semiring $S$, then for any $a\in S$, we see that $a.e=a.(e+e)=a.e+a.e \implies a.e=e \iff -a.e \in S.$ Looking for a better suggestion. Thanks | What is an instructive example of a set $X$ equipped with two monoid structures $(X,+,0)$, $(X,\cdot,1)$, such that $+$ is commutative, the distributive laws hold, but $0 \cdot x = 0$ or $x \cdot 0 = 0$ do not hold? Notice that in case these two absorbing laws hold, one calls $(X,+,0,\cdot,1)$ a semiring. At first sight, it might be surprising that these laws have to be imposed, but this is quite natural from a more general point of view, namely the multiplication $\cdot : X \times X \to X$ should be an additive monoid homomorphism in each variable, and it is known that one has to demand that monoid homomorphisms preserve the neutral element. |
LastPass Sesame (Ubuntu/Debian) Sesame was working normally before the new Ubuntu update 15.10. However, now I get this error when I try to execute the command. John@John's-PC:/media/crypt1$ ./sesame_x64 ./sesame_x64: error while loading shared libraries: libssl.so.0.9.8: cannot open shared object file: No such file or directory So, I did a clean install following the instruction below. Right-click the download button and choose 'Save Link As' Extract the tar.bz2 file Run 'sudo apt-get install ca-certificates libssl0.9.8' to update necessary packages When I run the sudo apt-get install ca-certificates libssl0.9.8, I get this message:Reading package lists... Done Building dependency tree Reading state information... Done Package libssl0.9.8 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 N: Ignoring file 'getdeb.list.bck' in directory '/etc/apt/sources.list.d/' as it has an invalid filename extension N: Ignoring file 'getdeb.list.bck' in directory '/etc/apt/sources.list.d/' as it has an invalid filename extension E: Package 'libssl0.9.8' has no installation candidate Anyone know how to fix this problem? Thanks so much! | What does the above Error mean? What is an installation candidate? I was trying to do sudo apt-get install munin-memcached and I get this message: Reading package lists... Done Building dependency tree Reading state information... Done Package munin-memcached is not available, but is referred to by another package. This may mean that the package is missing, has been obsoleted, or is only available from another source E: Package munin-memcached has no installation candidate I googled for the problem and someone said to do a apt-get upgrade but it still did not solve my problem. |
So I am an active contributor of Stack Overflow in Russian and I joined the election this year. Because of my ban on MSE (damn it! ;)) my candidacy was removed from the election. But I found out that I can rejoin the election! I'm gonna add some images: I guess it is a bug, isn't it? Or is it the... the... SECOND CHANCE ? ?? ;) P.S I tried to add my candidacy just to test SE for a bug. Wha? Wha? NO! I'm not cheatin' ;) | We're having , and this week, nominations opened up. A user nominated themselves, but they've been suspended elsewhere on the network and are currently suspended on a different site; as per , a Community Manager went through the nomination removal process. For various reasons, the user is now suspended on Worldbuilding, too - the site having the election. As of yesterday, their nomination was gone, after it had been reposted, and they were (and still are) suspended. The thing is, their nomination is back . . . again (). The user normally has enough rep to run, but when they're suspended, their rep is reduced to 1 . . . which is obviously not enough meet the minimum requirements to run in an election. I would think the system would automatically see that they have only 1 reputation point if they tried to nominate - let alone re-nominate - and prevent them from nominating . . . which didn't happen. I'm reporting this as a bug; if it's not a bug, I'd like to make a feature request that users be automatically prevented from running for moderator if they're currently suspended on the site. I can't trust someone as a moderator if in the middle of the election, they're suspended. |
In many definitions of O(n log(n)), I typically see as a requirement that the subproblem must be a division of the original problem size by two. However, in particular, I have seen that O(log(n)) need only be a problem of reducing size. Do we necessarily need to divide the problem into halves to get a problem of nlog(n)? Or could it be merely a reductive problem? Like so: for (i = 0; i < A.length(); i++) { for (j = i; j < A.length(); j++) { //do something } } Would something like this also be categorized as n(log(n))? Or is it closer to O(n^2)? | I need to calculate the time complexity of the following code: for (i = 1; i <= n; i++) { for(j = 1; j <= i; j++) { // Some code } } Is it O(n^2)? |
This is the content of a text file, and I want to only keep BMP. 这是无效的字符 𡛂 这是正常的字符 哈 In the , I find there is a solution, but it doesn't work here. iconv -f utf-8 -t utf-8 -c test.txt The utf-8 of 𡛂 is F0A19B82 (located in CJK Unified Ideographs Extension B), utf-8 of 哈 is E59388（located in CJK Unified Ideographs). If I want to delete all characters(the size greater than 3 Bytes) like 𡛂 in text file , how to do it? | Is there a way to match some Unicode range exactly. Let's use the as an example: U+400 to U+52f The whole range of chars could be printed (from bash or zsh) with: $ echo -e $(printf '\\U%x' $(seq 0x400 0x52f)) ЀЁЂЃЄЅІЇЈЉЊЋЌЍЎЏАБВГДЕЖЗИЙКЛМНОПРСТУФХЦЧШЩЪЫЬЭЮЯабвгдежзийклмнопрстуфхцчшщъыьэюяѐёђѓєѕіїјљњћќѝўџѠѡѢѣѤѥѦѧѨѩѪѫѬѭѮѯѰѱѲѳѴѵѶѷѸѹѺѻѼѽѾѿҀҁ҂҃҄҇ҊҋҌҍҎҏҐґҒғҔҕҖҗҘҙҚқҜҝҞҟҠҡҢңҤҥҦҧҨҩҪҫҬҭҮүҰұҲҳҴҵҶҷҸҹҺһҼҽҾҿӀӁӂӃӄӅӆӇӈӉӊӋӌӍӎӏӐӑӒӓӔӕӖӗӘәӚӛӜӝӞӟӠӡӢӣӤӥӦӧӨөӪӫӬӭӮӯӰӱӲӳӴӵӶӷӸӹӺӻӼӽӾӿԀԁԂԃԄԅԆԇԈԉԊԋԌԍԎԏԐԑԒԓԔԕԖԗԘԙԚԛԜԝԞԟԠԡԢԣԤԥԦԧԨԩԪԫԬԭԮԯ $ a=$(zsh -c 'echo -e $(printf '\''\\U%x'\'' $(seq 0x400 0x52f))') To filter some range of it, lets use 0x452 to 0x490, this is the expected output: $ b=$(bash -c 'echo -e $(printf '\''\\U%x'\'' $(seq 0x452 0x490))') $ echo "$b" ђѓєѕіїјљњћќѝўџѠѡѢѣѤѥѦѧѨѩѪѫѬѭѮѯѰѱѲѳѴѵѶѷѸѹѺѻѼѽѾѿҀҁ҂҃҄҇ҊҋҌҍҎҏҐ $ echo "$b" | xxd 00000000: d192 d193 d194 d195 d196 d197 d198 d199 ................ 00000010: d19a d19b d19c d19d d19e d19f d1a0 d1a1 ................ 00000020: d1a2 d1a3 d1a4 d1a5 d1a6 d1a7 d1a8 d1a9 ................ 00000030: d1aa d1ab d1ac d1ad d1ae d1af d1b0 d1b1 ................ 00000040: d1b2 d1b3 d1b4 d1b5 d1b6 d1b7 d1b8 d1b9 ................ 00000050: d1ba d1bb d1bc d1bd d1be d1bf d280 d281 ................ 00000060: d282 d283 d284 d285 d286 d287 d288 d289 ................ 00000070: d28a d28b d28c d28d d28e d28f d290 0a ............... But it seems impossible to filter with sed. This doesn't work: $ echo "$a" | sed 's/[^\x452-\x490]//g' Nor this (the result match other characters (probably a collating issue)): $ echo "$a" | sed $'s/[^\u452-\u490]//g' АБВГжзийклмнопрстуфхцчшщъыьэюяёђєѕіїјљњћќѝўџҋҍҏҐҗҙқҝҟҡңҥҧҩҫҭүұҳҵҷҹһҽҿӂӄӆӈӊӌӎӐӒӔӝӟӡӣӥӧөӫӭӯӱӳӵӹԅԇԉԋԍԏ Not even this (same collating issue): $ echo "$a" | sed 's/[^ђ-Ґ]//g' This work with awk: $ echo "$a" | awk '{gsub(/[^ђ-Ґ]/,"")}1' But the only way to use an hex range is to use shell to convert hex to an unicode character $ echo "$a" | awk $'{gsub(/[^\u452-\u490]/,"")}1' or (two solutions): $ c=$(bash -c 'printf "\u452-\u490"') $ echo "$a" | awk '{gsub(/[^'"$c"']/,"")}1' $ echo $a | awk -v ra="[^$c]" '{gsub(ra,"")}1' Questions: Is there a way to do this with sed? Could awk do it in hex numbers without a higher shell. If possible, what is exactly the range matched by the collating sequence that sed use with sed 's/[^ђ-Ґ]//g'. P.S.: I know that could be done in perl, thanks. |
I'm trying to learn how RSA works. From what I found online, I'm supposed to generate private key using Extended Euclidean algorithm. I've managed to generate the public key, but don't know how to use EEA to generate the private key. How should I exactly input into EEA, and how to process the output? | When given $p = 5, q = 11, N = 55$ and $e = 17$, I'm trying to compute the RSA private key $d$. I can calculate $\varphi(N) = 40$, but my lecturer then says to use the extended Euclidean algorithm to compute $d$. That's where I get stuck. Here's my work so far: First I use the Euclid algorithm to calculate: 40 = 2(17) + 6 17 = 2(6) + 5 6 = 1(5) + 1 = gcd So I know the GCD is 1. Applying the 'extended' section of the algorithm: 6 = 40-2(17) 5 = 17-2(6) 1 = 6-1(5) 1 = 6-1(17-2(6)) 3(6) = 1 (17) 3(40 - 2(17)) - 1(17) 3(40) - 3(17) I know the answer is $33$, but I have no idea how to get there using the extended Euclidean algorithm. I can't figure out why I'm getting $3(40) - 3(17)$ when I know the answer should contain $33$. |
I have time value from server returned as 13:00:45:888 which is returned as TIME value from SAP backend . How can I convert it to 01:00 PM | How to format correctly according to the device configuration date and time when having a year, month, day, hour and minute? |
I need to prove $$\lim\limits_{n\to\infty} \left( 1-\frac{1}{n} \right)^n = \frac{1}{e}$$ For now, I only know the e definition: $\lim\limits_{n\to\infty} \left ( 1+\frac{1}{n} \right)^n = e $, and I need to proof all the partial results in between to reach the wanted result. | Q1: Could someone provide a proof for this equation (please focus on this question): $$e^z = \lim \limits_{x \rightarrow \infty} \left( 1 + \frac{z}{x} \right)^x$$ Q2: Is there any corelationn between above equation and the equation below (this would benefit me a lot because i at least know how to proove this one): $$e = \lim \limits_{x \rightarrow \infty} \left( 1 + \frac{1}{x} \right)^x$$ |
\documentclass{article} \usepackage{amsmath} \usepackage[noend]{algpseudocode} \usepackage{algorithm} \makeatletter \def\BState{\State\hskip-\ALG@thistlm} `\makeatother \begin{document} \begin{algorithm} \caption{AIP}\label{euclid} \begin{algorithmic}[1] \State \textit{$\sum^{N_agent}_{i=1}$$L_A$} $\gets$ position of \textit{$agent_i$} \BState \emph{loop}: \State \textit{$i$}$\gets one \State \textit{$i$ plus one} \If {\textit{distance(eNB,$L_i$)} $< \delta$} \textit{close $agent_i$} \IF {\textit{distance(eNB,$L_i$)}$>\Delta$} \textit{$agent_i$ power equals P$} \State \textbf{goto} loop \end{algorithmic} \end{algorithm} \end{document} Can someone help me compile this successfully? | I have to use algpseudocode package to improve my paper look like more professional But I can't compile successfully. \usepackage{amsmath} \usepackage{algorithm} \usepackage[noend]{algpseudocode} \makeatletter \def\BState{\State\hskip-\ALG@thistlm} \makeatother \begin{document} \begin{algorithm} \caption{AIP}\label{euclid} \begin{algorithmic}[1] \Procedure{MyProcedure}{} \State $\textit{locationAgent} \gets \text{position of }\textit{{agent}}$ \State $\textit{locationMD} \gets \text{position of }\textit{{MD}}$ \If {\textit{distance(eNB,$agent_i$)}}>$\delta$ \BState \emph{loop}: \State $j \gets \textit{patlen}$ \If {$\textit{string}(i) = \textit{path}(j)$}\Return TURE \State $j \gets j-1$. \State $i \gets i-1$. \State \textbf{goto} \emph{loop}. \State \textbf{close}; \EndIf \State $i \gets i+\max(\textit{delta}_1(\textit{string}(i)),\textit{delta}_2(j))$. \State \textbf{goto} loop \EndProcedure |
In Game of Thrones s05e10 Sansa Stark and Theon Greyjoy (Reek) jump off the wall of Winterfell to escape Ramsay Bolton. In the scene the wall looked rather high and even though the ground was covered by snow, I just can not believe they would have survived that jump. Even if survival is possible, they should have had a couple broken bones, especially their legs. So how did they make that jump and were able to keep traveling after it? | We could see that Theon Greyjoy helped Sansa Stark escape from Winterfell which was under Ramsay's control by jumping off the wall. The outer wall is said to be about 80 feet high. How did both of them survive jumping from that height? It is highly unlikely to survive that jump even if there was snow. |
I have 2 monitors, when I open the start screen it does only open on 1 monitor. Is there a way to have the start screen displayed on both monitors at the same time (like an extended start screen)? | Is the Windows8 start screen capable of spanning 2 monitors? This is not a question of multiple monitor support; this is a question of whether the Windows-8 start screen is able to display across 2 monitors, not as a mirrored display but as a additive display to the width of the single screen start screen. Or, does a app exist that I can purchase for it to do this? |
I've been trying to solve this for hours, but I just can't seem to do it. And yes, I know I have to show that $(k+2)^{\frac{1}{k+2}} < ... < (k + 1)^{\frac{1}{k+1}}$ from the starting assumption that $(k+1)^{\frac{1}{k+1}} < k^{\frac{1}{k}}$. Any hints would be highly welcome. | I am currently helping a friend of mine with his preperations for his next exam. A big topic of the exam will be induction, thus I told him he should practice this a lot. As at the beginning he had no idea how induction worked, I showed him some typical examples. Now he showed me an exercise he was having trouble with, which states that one should prove $$n^{n+1} > (n+1)^n$$ for all $n \geq 3$. I have to admit that I too have trouble showing this inequality, as in all of my attempts, my lower bound is too low. Also, I have not yet figured out, how one gets the $(n+2)^{n+1}$, primarely the number $2$ is a problem. I think this might be solved using the binomial theorem, however, I don't think they have already seen the binomial theorem in school. Is there an easy method to show this inequality by induction not using the binomial theorem? If no: How can one show it using the binomial theorem? Thanks for answers in advance. |
Does anyone know why bringing the limit inside the sum doesn't work sometimes, other than the fact that sometimes the resulting answer contradicts the answer when the limit is not inside the sum? | I have seen that the method of "dominated convergence" implies that sometimes a limit cannot be brought inside of a sum, but is there a more basic way to understand this, preferably without using integrals? A conceptual or simple answer would be helpful. Thank you! |
I installed Universal Media Server 3.6 on ubuntu 14.04 desktop. What I want to do is, to launch it during startup. How to add this into startup? Any suggestions? Thanks in advance. | How can I make an application automatically start when I have logged in? |
I have been studying the Riemann zeta function and I came across such a representation of zeta function $\zeta(s)=(1-2^{1-s})^{-1} \sum_{n=1}^{\infty} (-1)^{n-1} n^{-s}$. Then it says in the book that this alternating series converges for $Re(s) > 0$. And there is my question. How can we show that this series converges in that region? We can't use the alternating series test because we deal with complex numbers, but please correct me if I'm wrong, so how can we do it? Also, could anyone explain to me or recommend any book to read why the imaginary part does not have any impact on convergence of a series? Thanks! | If $$\sum_{n=1}^{\infty} \frac{a_{n}}{n^{s}}$$ Converges( s is real) and $\operatorname{Re}(z)>s$. Then $$\sum_{n=1}^{\infty} \frac{a_{n}}{n^{z}}$$ also converges. $a_n$ is complex sequence. |
I am trying outsmart these tragic systems designed in hell knows when. I managed to nail this last year, but this year Lufthansa seems to killed it. Allow me to explain. I have to get pretty much all across the world from Lithuania to New Zealand. Last year I managed to book this in one lump via Lufthansa with 1 week layover in Singapore and months later with a week long layover in Tokyo (both legs stopping in Frankfurt). This year I am trying to replicate something similar but stop in Malaysia, Bangkok or Singapore, but looks like Lufthansa site claims The selected route cannot be booked online or is not served by Lufthansa. Although booking flight straight from Vilnius to Auckland works (but obviously I do not want 33hr long journey with no break). Booking thru Thai Airways site could almost work, but then they do not even recognise Vilnius as a city. Booking from Air New Zealand does not allow to start your multi-part journey from Europe. Epic fail. I have tried using these awful, awful world-the-globe pages from both alliances which seem to be broken (would never complete the journey). Sites like Skyscanner or Kayak suggest flying via Russia (lol). Is there a site that I am missing, perhaps some more advanced alliance search tool? Please help me tackle this problem. I do not want to pay thousands of dollars for what is worth around €1.5k. Edit: David asked for more information why I think that sites are awful. Well, first of all, none of them allow to search actual multipart flights. One World round the world tool only lets you fly one direction (literally round the world! haha, you get it guys!). Star Alliance doesn't even work without Flash player. In year 2015, trillion dollar business is using web technology that is decade old (the rest looks like its build on IBM's WebSphere, so theres another few hundred million of expenditures). | Is there a search engine that considers "mix&match" flight combinations? My current problem: I need to go from FRA to YLW (Frankfurt/Germany to Kelowna/Canada) on July 29th, and arrive no later than 5pm. The search engines I checked only offer €3000+ flights. I found a 2-stop combo through LHR and YVR for half that price. I'll probably have to check my baggage out and back in twice, but if the layover times are long enough, who cares? A real search engine could find that for me (or something that's even better). Or, hell, give me a place to bulk-download the flight schedules from and I'll program it myself (of course I'd also need a way to check seat availability …). Update: Please read before answering. A search engine which does this should, at minimum, show the flight combination through LHR which I found manually. Note that I need to arrive before 5pm, on the same day. Also note that this is a generic question; I'm not looking for a specific good flight here -- but the details are useful to illustrate whether an answer is actually valid. :-/ NB: Typo, should have been July 29th. |
I get this after rsync the .sh file to the server: sudo: unable to execute ./run_vps_post_config.sh: No such file or directory To fix, I open the file with winscp and save it. Then it runs again. (this is nothing to do with permissions. It runs ok.) Same thing happens when I zip->rsync->unzip. However if I unzip with -aa option (treat ALL files as text), then it is OK. I looked in rsync for a similar option to treat files as text, but none was found. | When I copy my bash script across from Notepad++ into a new file with nano editor inside SSH and save. It runs fine. (sh ./install). But if I save the file (Exact same contents), upload to my web server, download it using Wget on the same machine. I get syntax errors. I've checked the encoding and they seem to be the same. I have since used a plethora of character encoding to see if it will resolve the issue. I am also setting the file to executable once I download it using wget! The file runs fine and I have zero errors when copy and pasting using nano. Any idea what this may be? |
Trying to reuse an existing "SysV" init script with new Linux version that uses "systemd" (RHEL 7). Just copying it into "/etc/init.d/" fails to work as expected. Can only manually Start/Stop service using the commandline as if the script was a user file. The systemd enable and start/stop fail. Where should "SysV" init scripts be copied to on a system that is using systemd ? Where should any custom systemd scripts for system/user service daemons be created ? What are common problems found or required actions before I can use the old init scripts with the new systemd ? | I have 2 graphics cards on my laptop. One is IGP and another discrete. I've written a shell script to to turn off the discrete graphics card. How can I convert it to systemd script to run it at start-up? |
Let $f(z)$ be a positive harmonic function on the unit disk such that $\frac{1}{f(z)}$ is also harmonic. Show $f(z)$ must be constant. | Is it true that a positive harmonic function on $\mathbb{R}^n$ must be a constant? How might we show this? The mean value property seems not to be the way...for that we would need boundedness. |
I have a char[] that I am attempting to append values to. However, at the line newStringAr[count] = ar[j][i], I am receiving an error: java.lang.NullPointerException: Attempt to invoke virtual method 'char java.lang.Character.charValue()' on a null object reference. When I changed my array to a Character[], this error was resolved, but then I was not able to convert my array to a string as shown in the last line of the code sample below. How can I resolve this issue? Note that ar is a previously-defined array of Characters (Character[] not char[]). int count = 0; char[] newStringAr = new char[ch.length]; for (int i = 0; i < ar.length; i++) { for (int j = 0; j < ar.length; j++) { if (count<ch.length) { newStringAr[count] = ar[j][i]; count++; } } } String out = new String(newStringAr); | What are Null Pointer Exceptions (java.lang.NullPointerException) and what causes them? What methods/tools can be used to determine the cause so that you stop the exception from causing the program to terminate prematurely? |
So simple: Will this sail-based moving system work? Why? | How it this possible? Even if the gif is fake, the Mythbusters did it and with a large sail it really moves forward. What is the explanation? |
For a UART that takes baud as generic, I want to prevent design compilation in modelsim and quartus ii if the baud rate is not in specific range. The baud rate is passed as a generic. One option is to enum for baud rate so this problem does not arise. But provided that I use the natural type, how do I prevent design compilation using assert if the baud rate is wrong? I could write a function that will determine if baud rate is correct. | I have a parameterised module in verilog, where the parameters are a clock rate and refresh rate, which is used to calculate how many cycles of inactivity are inserted between instances of a repeating operation. However, it is very easy to set parameters that cannot be attained (because the operation takes a non-trivial length of time, so the repeat would have to occur before it had completed), and at the moment the design does not give any feedback on this. I was wondering if there was some way I could trigger an error during synthesis (or compilation prior to simulation) if the conditions cannot be met (i.e. if one localparam is less than another)? Some equivalent of the popular C/C++ compile-time-assert hack, perhaps. |
I am beginner i want to get text in EditText and compare it with another string . I want to check if text writed in EditText is equals a 'String' then show a Toast but it is not working I debug and check the value of both are exactly admin but if block is not working and shows else block. if (editText.getText().toString() == "admin") { //Never enter this block when i type "admin" in the EditText. Toast.makeText(MainActivity.this,"ok",Toast.LENGTH_LONG).show(); } else { Toast.makeText(MainActivity.this,"Wrong User Or Pass", } | I've been using the == operator in my program to compare all my strings so far. However, I ran into a bug, changed one of them into .equals() instead, and it fixed the bug. Is == bad? When should it and should it not be used? What's the difference? |
I am working on AIX unix and trying to remove non-printable characters from file the data looks like Caucasian male lives in Arizona w/ fiancÃÂÃÂÃÂÃÂÃÂ in file when I view in Notepad++ using UTF-8 encoding. When I try to view file in unix I get ^▒▒^▒▒^▒▒^▒▒^▒▒^▒▒ instead of the special characters. I want to replace all those special characters with space. I tried sed 's/[^[:print:]]/ /g' file but it does not remove those characters.My locale are listed below when I run locale -a C POSIX en_US.8859-15 en_US.ISO8859-1 en_US I even tried sed -e 's/[^ -~]/ /g' file and it did not remove the characters. I see that others stackflow answers used UTF-8 locale with GNU sed and this worked but I do not have that locale. Also I am using ksh. | Is there a way to match some Unicode range exactly. Let's use the as an example: U+400 to U+52f The whole range of chars could be printed (from bash or zsh) with: $ echo -e $(printf '\\U%x' $(seq 0x400 0x52f)) ЀЁЂЃЄЅІЇЈЉЊЋЌЍЎЏАБВГДЕЖЗИЙКЛМНОПРСТУФХЦЧШЩЪЫЬЭЮЯабвгдежзийклмнопрстуфхцчшщъыьэюяѐёђѓєѕіїјљњћќѝўџѠѡѢѣѤѥѦѧѨѩѪѫѬѭѮѯѰѱѲѳѴѵѶѷѸѹѺѻѼѽѾѿҀҁ҂҃҄҇ҊҋҌҍҎҏҐґҒғҔҕҖҗҘҙҚқҜҝҞҟҠҡҢңҤҥҦҧҨҩҪҫҬҭҮүҰұҲҳҴҵҶҷҸҹҺһҼҽҾҿӀӁӂӃӄӅӆӇӈӉӊӋӌӍӎӏӐӑӒӓӔӕӖӗӘәӚӛӜӝӞӟӠӡӢӣӤӥӦӧӨөӪӫӬӭӮӯӰӱӲӳӴӵӶӷӸӹӺӻӼӽӾӿԀԁԂԃԄԅԆԇԈԉԊԋԌԍԎԏԐԑԒԓԔԕԖԗԘԙԚԛԜԝԞԟԠԡԢԣԤԥԦԧԨԩԪԫԬԭԮԯ $ a=$(zsh -c 'echo -e $(printf '\''\\U%x'\'' $(seq 0x400 0x52f))') To filter some range of it, lets use 0x452 to 0x490, this is the expected output: $ b=$(bash -c 'echo -e $(printf '\''\\U%x'\'' $(seq 0x452 0x490))') $ echo "$b" ђѓєѕіїјљњћќѝўџѠѡѢѣѤѥѦѧѨѩѪѫѬѭѮѯѰѱѲѳѴѵѶѷѸѹѺѻѼѽѾѿҀҁ҂҃҄҇ҊҋҌҍҎҏҐ $ echo "$b" | xxd 00000000: d192 d193 d194 d195 d196 d197 d198 d199 ................ 00000010: d19a d19b d19c d19d d19e d19f d1a0 d1a1 ................ 00000020: d1a2 d1a3 d1a4 d1a5 d1a6 d1a7 d1a8 d1a9 ................ 00000030: d1aa d1ab d1ac d1ad d1ae d1af d1b0 d1b1 ................ 00000040: d1b2 d1b3 d1b4 d1b5 d1b6 d1b7 d1b8 d1b9 ................ 00000050: d1ba d1bb d1bc d1bd d1be d1bf d280 d281 ................ 00000060: d282 d283 d284 d285 d286 d287 d288 d289 ................ 00000070: d28a d28b d28c d28d d28e d28f d290 0a ............... But it seems impossible to filter with sed. This doesn't work: $ echo "$a" | sed 's/[^\x452-\x490]//g' Nor this (the result match other characters (probably a collating issue)): $ echo "$a" | sed $'s/[^\u452-\u490]//g' АБВГжзийклмнопрстуфхцчшщъыьэюяёђєѕіїјљњћќѝўџҋҍҏҐҗҙқҝҟҡңҥҧҩҫҭүұҳҵҷҹһҽҿӂӄӆӈӊӌӎӐӒӔӝӟӡӣӥӧөӫӭӯӱӳӵӹԅԇԉԋԍԏ Not even this (same collating issue): $ echo "$a" | sed 's/[^ђ-Ґ]//g' This work with awk: $ echo "$a" | awk '{gsub(/[^ђ-Ґ]/,"")}1' But the only way to use an hex range is to use shell to convert hex to an unicode character $ echo "$a" | awk $'{gsub(/[^\u452-\u490]/,"")}1' or (two solutions): $ c=$(bash -c 'printf "\u452-\u490"') $ echo "$a" | awk '{gsub(/[^'"$c"']/,"")}1' $ echo $a | awk -v ra="[^$c]" '{gsub(ra,"")}1' Questions: Is there a way to do this with sed? Could awk do it in hex numbers without a higher shell. If possible, what is exactly the range matched by the collating sequence that sed use with sed 's/[^ђ-Ґ]//g'. P.S.: I know that could be done in perl, thanks. |
I try to run git pull command with loging output message to file every 5 minutes. But i got error like this, (root) CMD (cd /var/www/sites/ && git pull origin master | sed -e "s/^/$(date +\") (CRON) error (grandchild #1111 failed with exit status 2) My cronjob command as follows. */5 * * * * cd /var/www/site/ && git pull origin master | sed -e "s/^/$(date +\"%d-%m-%y\ %T\"), /" >> /var/log/crond/site.log How can fix it? | I want to create a log file for a cron script that has the current hour in the log file name. This is the command I tried to use: 0 * * * * echo hello >> ~/cron-logs/hourly/test`date "+%d"`.log Unfortunately I get this message when that runs: /bin/sh: -c: line 0: unexpected EOF while looking for matching ``' /bin/sh: -c: line 1: syntax error: unexpected end of file I have tried escaping the date part in various ways, but without much luck. Is it possible to make this happen in-line in a crontab file or do I need to create a shell script to do this? |
To save myself some keystrokes, I tried to define an abbreviation for \begin{align} and \end{align} \documentclass[reqno, 11pt]{article} \usepackage{amsmath, amsfonts, mathtools, amsthm} \usepackage{fullpage} \newcommand{\ba}{\begin{align*}} \newcommand{\ea}{\end{align*}} \title{Article Template} \author{You} \begin{document} \maketitle \section*{3} \ba e=mc^2 \ea \end{document} For some reason, the abbreviation for \begin{align} seems to work, but the abbreviation for \end{align} does not. I thought perhaps that \ea was already in use, but tweaking the name didn't change anything. Any ideas? | I have created some new short command using \newcommand in the following example: \documentclass[12pt,twoside,a4paper]{book} \usepackage{enumerate,amsmath} \newcommand{\ba}{\begin{array}} \newcommand{\ea}{\end{array}} \newcommand{\ben}{\begin{enumerate}} \newcommand{\een}{\end{enumerate}} \newcommand{\bal}{\begin{align}} \newcommand{\eal}{\end{align}} \newcommand{\bc}{\begin{center}} \newcommand{\ec}{\end{center}} \newcommand{\de}{^\circ} \begin{document} \bc $5\de$ \ec \ben \item Text \item Text \een $\ba{cc} a & b\\ c & d \ea$ \bal & r\\ & f \eal But \begin{align} & r\\ & f \end{align} is working. \end{document} All \newcommands are working well except \bal and \eal. I don't know why it is not working. |
There has been a trend now two persons downvote it then it goes on like that. So let there be down voting but do not display the downvotes till the user votes on it. Else the user reads it with an impression that the question is not good. Am I missing something? | I don't like seeing negative score as the value of a question. I don't know, maybe it's just me, but it just does not look good when a question has a -1 or -5 score. This is especially annoying when someone adds a negative vote to your question. I even feel offended when my own question suddenly becomes a -1 or lower. I have a feature request: Allow negative votes as before but when displaying a score, show the 0 score instead. This may be implemented easily like score=max(0, score) or something like that. The negative votes will still be allowed but will only affect questions that already have some positive score, will have no affect on 0 scored questions. What do you think? |
I followed the Pierre Hermé éclairs recipe: 60mL water 75mL whole milk 3g salt 3g caster sugar 56g butter 75g flour A little over 2 eggs I did the recipe and it called for 45 minutes of baking at 185°C. I baked them for 40 minutes and left them in the oven for an extra 10 minutes before removing them. The result was that the exterior was terrific, but the inside was too doughy and I couldn't fill it with crème pâtissière (custard). Is skipping the 5 last minutes of baking the reason it failed? | Last time I tried to make Chocolate eclairs (similar to cream puffs), the choux pastry just sat in the oven and basically fried. It didn't rise/grow and so I couldn't hollow out the shells. Any suggestions? Recipe was from The Australian Women's Weekly Original Cookbook (Golden Press Pty Ltd, 1977) p. 204 It is almost identical to the one published on their website , with the exception that the cookbook recipe used 1C water and 1C plain flour. |
I'm new on Ubuntu 14.04 LTS (64bit) and I'm just getting a hold of this new way of doing things. I am using a program built for UNIX and I managed to install it and get it all work perfectly, but I am a little bit lazy so I'm trying to figure out a way to make an application shortcut just by double clicking on it (without using Teminal to go to the path and then typing the command for the program). The command after I get into the right path: java -cp jts.jar:total.2013.jar -Xmx512M -XX:MaxPermSize=128M jclient.LoginFrame . Please try to make it as detailed as poosible because, as I said, I'm very new at this. | In older versions it was easy to create a launcher on my desktop. All I had to do is right click on my desktop and select the "create launcher" option. How can I create such launchers now? |
The power category in GNOME Tweaks only show a "suspend when laptop lid is closed". However, there is no distinction between whether the laptop is plugged (for instance to a docking station or a charger) or operating on battery power. In my case, I would like my laptop to suspend when closing the lid on battery power, but leave it when plugged to its charger. Is there a way to achieve that? | In Ubuntu versions before Gnome Shell, I could set what I wanted to happen when I close the laptop lid depending on whether the laptop is connected to power or not. Now the default is standby which I can disable in Gnome Tweak Tool. My preferred setting is to only go to standby when on battery and stay on when connected to AC. Using systemd I only know of options to completely enable or disable lid-actions alltogether. How did Unity solve this in Ubuntu 17.04? |
I'm asking more about what this means to my code. I understand the concepts mathematically, I just have a hard time wrapping my head around what they mean conceptually. For example, if one were to perform an O(1) operation on a data structure, I understand that the number of operations it has to perform won't grow because there are more items. And an O(n) operation would mean that you would perform a set of operations on each element. Could somebody fill in the blanks here? Like what exactly would an O(n^2) operation do? And what the heck does it mean if an operation is O(n log(n))? And does somebody have to smoke crack to write an O(x!)? | I'd prefer as little formal definition as possible and simple mathematics. |
I have written a letter and I want to cite the references of my paper. However, I don't want the reference section to appear at the end of my letter. How can I hide this section? I have used the \begin{thebibliography} and \bibitem for the references and I am citing them by \cite{marcam2(alfa)}. \begin{thebibliography}{1} \bibitem{marcam2(alfa)} M. Abramowitz and I. A. Stegun, {\it Handbook of mathematical functions with formulas, graphs, and mathematical tables}. U. S. Department of Commerce, 1972. \bibitem{choi(2u)} H. Bolcskei, R. U. Nabar, O. Oyman and A. J. Paulraj, `` Capacity scaling laws in MIMO relay networks, " {\it IEEE Trans. Wireless Commun}., vol. 5, no. 6, pp. 1433-1444, June 2006. \end{thebibliography} | How do you produce a document with citations (\citep, \citet) working properly in the paper but without a bibliography at the end? I've come up with one solution that is bad because it breaks my makefile. latex file.tex bibtex file # comment out \bibliography{} command latex file.tex Similarly, is there a way to produce the bibliography with no accompanying text? Again, I've come up with a solution: fill an otherwise blank .tex file with \nocite{} commands. However, this is a pain because I have to keep two files synced by hand (and regular expressions to search for \citep{author1, author2} can be a huge pain when there are pagebreaks...). |
I'm curious about whether to use comma before "and". Some people told me that using comma to connect two different sentences and two different subjects. Please provide some examples to explain the usage of this. Thanks a lot! | Should I put a comma before the last item in a list? I would like crackers, cheese and some soda. I would like crackers, cheese, and some soda. |
Can I use software designed for power saving on laptops on Home PC. (not a laptop) Or maybe someone could suggest alternative tools designed for saving power on PC desktop? What are the other steps required to reduce energy consuming under Ubuntu? | I'm trying to install the Jupiter power settings app but, I read it is no longer compatible with the new kernel. Is there a similar program or a way to manage the power settings on 13.04? |
I have a circuit which has uC, Bluetooth module and some other ICs. Current consumption of it varies between 100uA and 20mA. I want to see current waveform using oscilloscope. I worked before high current measurement(above 1Ampere) using low-side sensing technique but not so small this. How to setup a small circuit to see current values of each phase(sleep, active, transmission) separately? Note: The circuit is powered by battery | This might be old news in a half a decade or two but by today's means, I am referring to electronic prototypes and designs which would draw in a μA (uA) and even nA range of current. Some recent MCUs, such as SAMD21 that I am using atm are armed with internal clocks such as ,always on, Ultra Low Power Internal 32kHz RC Oscillators which would draw only 125nA, and the whole microcontroller is capable of consuming only 6.2μA on STANDBY mode with a live RTC. In these type of quiescent current and power consumption levels the smallest limitations in the internal machinery of bench measurement devices such as multimeters and oscilloscopes could add a fair bit of error to the overall measurement or even measure a flat out wrong value in situations like a different relay kicking in when changing the resolution from 6 to 8 decimal places accuracy on your multimeter. What is the most precise method of measuring the overall quiescent current/power consumption for such applications? Update: As I mentioned in one of the replies, measuring low currents is hard but very possible, however, making conclusions on the integrated amount of current consumption to come up with numbers for the realistic over all power consumption is more what I had in mind. I have bumped into some solutions such as , however the wide range in this application note is only limited to the max of 200uA and in my case, my max current can rise to milliamps when my radio is transmitting and could drop to as low as 3uA when the whole system goes to sleep. |
I'm no php programmer, only site admin, I've recently adopted a site with web panel that causes sql injection when trying to post html code in TinyMCE, containing apostrophe. Problematic html code; img onmouseover="this.src='layout/gfx/wiecej1.png' php code; $edytuj = $_POST['edytuj']; sql query; if($edytuj) { $podstrony_id = $_POST['id']; $podstrony_id_kategorie = $_POST['id_kategorie']; $podstrony_id_moduly = $_POST['id_moduly']; $podstrony_tytul = $_POST['tytul']; $podstrony_szablon = $_POST['szablon']; $podstrony_tresc = $_POST['tresc']; $podstrony_aktywnosc = $_POST['aktywnosc']; $zapytanie = "UPDATE $tab_podstrony SET id_kategorie='$podstrony_id_kategorie', id_moduly='$podstrony_id_moduly', tytul='$podstrony_tytul', szablon='$podstrony_szablon', tresc='$podstron$ $wynik = mysql_query($zapytanie); Site uses php-cgi-5.4.39 and mysql-5.5 I don't have access to previous environment (where this panel worked fine), so I can't find out if it's configuration or code problem. | If user input is inserted without modification into an SQL query, then the application becomes vulnerable to , like in the following example: $unsafe_variable = $_POST['user_input']; mysql_query("INSERT INTO `table` (`column`) VALUES ('$unsafe_variable')"); That's because the user can input something like value'); DROP TABLE table;--, and the query becomes: INSERT INTO `table` (`column`) VALUES('value'); DROP TABLE table;--') What can be done to prevent this from happening? |
Im Iraqi citizen holding a green card ,living in USA now. I want to visit my relatives in Iraq and stay there for a month. Do I need a visa to re-enter the USA when coming back from Iraq please?! | I am a US citizen but my wife is an Iranian citizen with US permanent resident status, which she obtained through our marriage. We were planning to travel to Iran to visit my in-laws. However, we are worried, , that there will be problems for us and that she will not be able to re-enter the US without a visa. Will she be able to re-enter the US without having to apply for a visa? Update: Just wanted to update this question with our experience. We were able to go to Iran and come back without any problems. As the answers to this question pointed out, the green card lets you return and the changes to the Visa Waiver Program has no impact if you are a permanent resident. |
The other day I was browsing a German-localized website but needed to order something from their UK site. There was a country selection dropdown so I tried to use that one. I'm not fluent in German so It was hard to figure out that what I was looking for was "Großbritannien". I did look at all countries starting with "U" for UK, "E" for England, "B" for Britain and finally even starting with G but did not easily read Großbritannien as Große Britannien. My question is, wouldn't it make more sense for this kind of dropdown to show the - or one of the local country names in one of the local languages? Edit: After posting, I remembered the particular offending website: | Imagine a site that's available in multiple languages. The language is detected automatically by looking at the IP or the browser header. But that's not bulletproof, so a few users might end up on a page in language they don't understand. I am wondering what the best way is to present the language selection? – Wireframes created with Q: Should the languages in the language selection be listed translated into current language, used to display the site in (good if the detected language was correct)? native name of the language, so everybody looking for their language could see it in the very same language (good if the detected language was not correct and users don't know the current language)? always in English assuming most users would understand this? Feel free to add if I missed something! |
I'm asking if the SE sites or new proposals could have code analysis in its scope similar to , or it's against Stack Exchange rules? One example of question is , which was closed as off-topic (code analysis), therefore I've created the new (similar to ) where (malicious) code analysis is on-topic and defining exactly what kind of code it's expected to be analysed. Is that perfectly fine, fine, worth to try or code analysis is not suitable on SE sites at all? | Is it OK to ask on SO for help in explaining someone else's working piece of code, from Open Source projects or library examples etc.? Or does this belong somewhere else? |
I knew that floats float around and sometimes are placed far away from where one wants them to be. With the times I learned to work with it, and there are already many posts about it. I have a kind of different problem. I'm writing my bachelor thesis and defined some environments for definitions and such. And of course I'm using floats as well. But now I have the problem that one of my floats are placed in one of my definitions. This is of course something I really don't want to have. If some of the floats are one page after or before they are referenced, that is ok, but having them in my definitions is no option. I don't know how to create a MWE for this without posting my whole thesis, but this is as close as I can get: \documentclass{article} \usepackage[utf8]{inputenc} \usepackage[english]{babel} \usepackage{blindtext} \usepackage{graphicx} \newenvironment{myblock}{% \vspace{.5\baselineskip} \hrule\nopagebreak\vspace{.35\baselineskip}\nopagebreak} {\nopagebreak\vspace{.5\baselineskip}\nopagebreak\hrule\vspace{.5 \baselineskip}\noindent} \newcounter{definition}[section] \renewcommand*\thedefinition{\thesection.\arabic{definition}} \newenvironment{definition}{% \refstepcounter{definition} \begin{myblock} \noindent\textbf{Definition \thedefinition} } {\end{myblock}} \begin{document} \Blindtext \section{MWE} \begin{definition} \blindtext \end{definition} \begin{figure} \includegraphics[scale=.5]{lorem} \end{figure} \Blindtext \end{document} This is the picture I used for this example. Well in this example the picture isn't placed that bad, but in my thesis it is placed inside the definition environment. So my real question is, how can I keep the figure out of that environemnt? PS: If you see any problems with my definition environment that is not related to this question, please let me know. I'm always happy to learn something new. | Given following situation: \begin{figure}[ht!] ... \end{figure} \begin{equation} ... \end{equation} Some one-line text. \begin{eqnarray} ... ... \end{eqnarray} how can I make sure that the float doesn't get placed between the equation and the equation array? Also the part to protect goes over two pages, if that's of any importance. |
I succeed in finding the following limit applying binomials and squeeze theorem: $$\lim(\sqrt{n+1} - \sqrt{n}) = \lim\frac{1}{\sqrt{n+1} + \sqrt{n}} = 0$$ because $0 \leq \frac{1}{\sqrt{n+1} + \sqrt{n}} \leq \frac{1}{\sqrt{n}}$ But I need help because I'm not finding any way to simplify and solve the following limit: $$\lim(\sqrt[3]{1-n^3} + n)$$ | I need to find simple limit: $$\lim_{n\to\infty}{\sqrt{n+1}-\sqrt{n}}$$ I can't use L'Hôpital's rule, which I think is natural for such problems. How to calculate such limit using only basic methods (definition and simple transformations etc.)? It's one problem (from 50 problems) I don't know how to solve from my homework. Thanks for help. |
I a few months ago. And I can't restore deleted email. How can I restore or merge my old SO account with the new one? | A while ago I tried to login to stack overflow, but I couldn't remember what email address I used when I registered. Now I've figured it out but the email address is dead, the domain no longer exists. Would it be possible to merge the accounts and ? |
The Dirichlet distribution is the conjugate prior to the multinomial sampling distribution. What is the conjugate prior (if any) if the sampling distribution is itself Dirichlet? That is, our samples are nonnegative vectors $\mathbf{p} \in \mathbb{R}^k$ which sum to 1, and we are trying to estimate a distribution over the parameters $\mathbf{\alpha}$ to the Dirichlet distribution that produces $\mathbf{p}$. | I want to estimate parameters of Dirichlet mixture models using Gibbs sampling and I have some questions about that: Is a mixture of Dirichlet distributions equivalent to a Dirichlet process? What is their main differences if is not? Also, if I want to estimate a single Dirichlet distribution's parameters, which distribution for parameters should be selected as priors in Bayesian framework? In all of the papers I found an estimation of a multinomial distribution using Dirichlet priors. I need estimation of a Dirichlet distribution using multinomial priors, perhaps. Is the posterior function also in the form of DIRICHLET(α+N) similar to the case “estimation of multinomial distribution using Dirichlet priors”? as the multiplication of probability density function for iid samples are not considered in the definition of the likelihood function. I again cannot understand why. e.g. as expressed in this paper: or so thanks for your attention my data is Hyperion (a kind of hyperspectral remote sensing imagery) and i want to perform hyperspectral unmixing using mixture of Dirichlet sources and i will apply Gibbs sampling method for parameter estimation. my data is in dimension (614*512*224) which is commonly available AVIRIS sensor data for Cuprite Nevada district and is almost 200MB. also this data is available via (). unfortunately i don't know how can i sent my data. i just ask you to help me in statistical modelling tasks for my PHD thesis. i will be so grateful if you help me to solve my confusions in modelling. all the best solmaz |
Could we get the help text for comments tweaked a tiny bit? I always find [link](http://www.example.com) confusing, because is a link. Just now, I actually went to one of my answers and posted a comment so I could experiment with it and not disturb anyone. If you could just change it to [link text](http://www.example.com), I'd never be confused again. I'll be the first to admit, this is a very similar question to , but that one didn't seem to generate much impact, so I'm hoping this one will. This is what I currently see on SO: Comments use mini-Markdown formatting: [link](http://example.com) _italic_ **bold** `code`. The post author will always be notified of your comment. To also notify a previous commenter, mention their user name: @peter or @PeterSmith will both work. Learn more… | This is the help for comments: Comments use mini-Markdown formatting: [link]() _italic_ **bold** `code`. The post author will always be notified of your comment. To also notify a previous commenter, mention their user name: @peter or @PeterSmith will both work. Learn more… I've stumbled often over [link](http://example.com) because the link is not the "link", but the text that is linked. I often find myself putting the URL in the link part because it is confusing. Proposed changes Here are two alternatives to make the help text for that tag a bit clearer; maybe the community can identify better ones. option 1 [text](http://example.com) option 2 [text](url) What do you think? |
Let $V,W$ be fixed $k$-vector spaces. Let $C$ be the category whose objects are linear map $f:V\to W$ and morphisms from $f$ to $g$ are pair of linear maps $(\alpha,\beta)$ where $\alpha:V\to V,\beta :W\to W$ such that $g \circ\alpha = \beta \circ f$. I want to find the product in this category. Note that $C$ is the full subcategory of $D$, whose objects are linear maps between any $k$-vector spaces, with morphisms $(\alpha,\beta)$ such that $g \circ\alpha = \beta \circ f$. I proved that in $D$, the product of linear maps $f_i:V_i \to W_i$, $ i \in I$ is given by $f: \prod_{i\in I} V_i \to \prod_{i\in I} W_i$ where $f((v_i))=(f_i(v_i))$. So given $f_i:V \to W$ in $C$, if there exists isomorphisms $\prod V\simeq V$ and $\prod W\simeq W$, we can also find the product in $C$. But is it the necessary condition? In other words, if there exists product of $f_i:V\to W$ in $C$, then is it true that $\prod V\simeq V$ and $\prod W\simeq W$? | Let $V,W$ be vector spaces. Let's define a category whose objects are linear map $f:V\to W$ and morphisms from $f$ to $g$ are pair of linear maps $(\alpha,\beta)$ where $\alpha:V\to V,\beta :W\to W$ such that $g \circ\alpha = \beta \circ f$. Does this category have some special name? If $f_i$ are indexed family of objects, is there product of them in this category? |
I have many questions I'd like to ask today. I'm currently studying for my A-levels which is a qualification mainly based in England. I'm taking A-level Further Maths, which involves the study of First and Second Order Differential Equations. It seems we are just being taught to apply recipes to these types of equations and are given no intuition as to why these things even work? This isn't just for teaching in England, I've watched many American lectures and lecture notes and the same thing is done. Let's take a look at Non-Linear Separable First Order Differential Equations. We have defined these equations to take the form $$ N(y)\frac{dy}{dx} = M(x)$$ We are taught to solve these equations by multiplying $\ dx $ to both sides and then integrate by their respective variables. Like so: $$ \int N(y)\ dy = \int M(x) \ dx $$ I have just accepted this for some time, but I'd like to get to the bottom of wtf is going on. We are taught from Year 12/Calculus 1 days that $\frac{dy}{dx} $ is not a ratio but can be treated like one in many cases. Ok... then could you explain really what we just did when solving the above differential equation? I can accept the fact that we can treat $\frac{dy}{dx}$ as a ratio but it's not really a ratio. So, can we be told what we are really doing? Is it some kind of hidden secret? I just want to know why we multiplied both sides by $\ dx$, what are we actually doing? I can assume that the reason we are not told is because it involves higher level math, that someone taking Calculus would not understand. But will actual reasoning behind why these recipes work be exposed to us during University math courses? | I see an equation like this: $$y\frac{\textrm{d}y}{\textrm{d}x} = e^x$$ and solve it by "separating variables" like this: $$y\textrm{d}y = e^x\textrm{d}x$$ $$\int y\textrm{d}y = \int e^x\textrm{d}x$$ $$y^2/2 = e^x + c$$ What am I doing when I solve an equation this way? Because $\textrm{d}y/\textrm{d}x$ actually means $$\lim_{\Delta x \to 0} \frac{\Delta y}{\Delta x}$$ they are not really separate entities I can multiply around algebraically. I can check the solution when I'm done this procedure, and I've never run into problems with it. Nonetheless, what is the justification behind it? What I thought of to do in this particular case is write $$\int y \frac{\textrm{d}y}{\textrm{d}x}\textrm{d}x = \int e^x\textrm{d}x$$ $$\int \frac{\textrm{d}}{\textrm{d}x}(y^2/2)\textrm{d}x = e^x + c$$ then by the fundamental theorem of calculus $$y^2/2 = e^x + c$$ Is this correct? Will such a procedure work every time I can find a way to separate variables? |
I was at work and I was curious if there was a limit for the formula $$f(x)=\left(\frac{x}{x-1}\right)^2$$ And I became curious on Desmos to see if there would a different limit for $$f(x)=\left(\frac{x}{x-1}\right)^x$$ It looked like it approached a constant value and, upon plugging it into a limit calculator, it returned $$\lim_{x\to\infty}\left(\frac{x}{x-1}\right)^x=e$$ What is the proof of this? I managed to work it down to $x^x(x-1)^{-x}$, but my calculus isn't good enough for me to work it past there... | How does one show that $\lim_{x\rightarrow\infty}\left(1+\frac{1}{x}\right)^x$ converges? I have a book that uses this to define $e$ but they don't show that it converges. I suppose we could give it an upper and lower bound but I don't know how to do this. I've seen this question before on here but I haven't seen an answer I like yet. |
When running multiple monitors on Windows and macOS there is a feature that allows you to set a sort of pressure or dead area on screen boundaries between monitors. You have to push through this area with your mouse cursor to get to leave the current screen/monitor and get to the next one. This makes it easier to stay within the bounds of whatever monitor your mouse cursor is on. I know KDE/Kubuntu has a Screen Edges setting, but setting/changing the "Toggle Window Switching" or Switch desktop on Edge" options didn't seem to have any effect. Edit: I am running Ubuntu 18.04 with KDE Plasma 5.12.6 Output of inxi -Sxxx: System: Host: ubuntu-portable Kernel: 4.15.0-23-generic x86_64 bits: 64 gcc: 7.3.0 Desktop: KDE Plasma 5.12.6 (Qt 5.9.5) dm: sddm,sddm Distro: Ubuntu 18.04 LTS Regarding being marked as duplicate: This is not a duplicate of the question provided in the link. I understand that there is confusion over the term "sticky edge". The linked question does not address how to enable the feature whereby the mouse cursor clings to the edge in a multi-monitor setup (whatever it is called). I can find no option in KDE for sticky edges. As posted in my photo, the Active Screen Corners and Edges setting panel seems like the logical place to put this, but I don't see it. Perhaps that is my answer, and that this feature isn't available in KDE. | I have installed Ubuntu 12.04 (Precise Pangolin). If I open System Settings >> Displays there is a new (?) on/off button for a setting named Sticky edges. Can someone tell me what this setting is supposed to control? |
I recently purchased a desktop just for office use. It did not come with an OS. I had someone install Ubuntu to prepare it for ViciDial because I work at home and some clients ask for me to provide for my own dialer. The guy said that I need Ubuntu for the ViciDial to work but he did not finish what he started and I can no longer find him. I don't know how to use Ubuntu. I searched online on what to do. I followed instructions on what keys to press and my partner and I even went as far as pressing keys from ESC to F12, to Shift (press and hold) and Del but we were still not able to access the boot menu so we can install the Win7 from a CD. Every time we turn the PC on, it just shows a black background with a gray text field in the middle asking for a password. We don't know what the password is. I'm sorry if I cannot provide other details. I don't have any other information on what he did with the computer. I'm lost and I just want to use my PC again. In addition, can I still use Win7 if I setup ViciDial? | I have Ubuntu on my laptop. Now I want install Windows 7 in a dual-boot. How can I do this? I can't lose my Ubuntu files, and I'm afraid that I might break . Go for UEFI only! |
I get this error when I try to run my file. I try to put in a reference, but I only got [?]. This is the main document: \documentclass[10pt,a4paper]{article} \usepackage{standalone} \usepackage[english]{babel} \begin{document} \tableofcontents \newpage % Hieronder voeg je de hoofdstukken in \input{../tex/hoofdstuk1} \input{../tex/hoofdstuk2} \newpage \section*{References} \bibliography{bibliography.bib} \end{document} And this is the .bib file. In the file hoofdstuk2 I refer to a source like this: \cite{Tsao2013558} I don't understand why my reference is displayed as [?]. Can someone help me? | I've browsed the forums and found a number of posts that have addressed this issue, but none of the solutions seem to work for me. I have the following script that I just copied from the bibtex home page to get familiar with it. Instead of the citation number I get a question mark. I compile using Latex+Bibtex+Latex+Latex+PDFLatex+ViewPDF just as has been previously suggested and the problem persists. \documentclass[11pt]{article} \usepackage{cite} \begin{document} \title{My Article} \author{Nobody Jr.} \date{Today} \maketitle Blablabla said Nobody ~\cite{Nobody06}. \bibliography{mybib} \bibliographystyle{plain} \end{document} My bibliography (Bib.bbl) @misc{ Nobody06, author = "Nobody Jr", title = "My Article", year = "2006" } Looking at previous posts one thing that is concerning is that my .bbl looks empty as shown below. Further, I don't have a .blg \begin{thebibliography}{} \end{thebibliography} |
Let $R$ be a commutative ring with unit. Is it true that given an ideal $I$ and $r \geq 2$ principal ideals $P_1, ..., P_r$, then if $I \subseteq \bigcup_{i = 1}^r P_i$, $I \subseteq P_i$ for some $i$? This would be the analogous of the Prime Avoidance Lemma for principal ideals. | Let $A$ be a commutative ring with $1$. Let $I$ and $J_k$, $k=1,\dots,n$ be ideals of $A$ with $I\subseteq \cup _{k=1}^n J_k$. Then I have obtained the following: (1) If $J_k$, $k=1,\dots,n$, are prime ideals, then there exists some $j$ such that $I\subseteq J_j$. (2) If $A$ is a principal ideal ring, then there exists some $j$ such that $I\subseteq J_j$. I want some counterexamples that for all $k=1,\dots,n$, $I$ is not contained in $J_k$. How to get the counterexamples? |
getting error that null pointer exception has occurred and trying to invoke virtual method public class after10th extends AppCompatActivity { ArrayAdapter<String> adapter; @Override protected void onCreate(@Nullable Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.after10th); ListView lv = (ListView) findViewById(R.id.searchten); ArrayList<String> after_ten = new ArrayList<>(); after_ten.addAll(Arrays.asList(getResources().getStringArray(R.array.after_ten))); adapter = new ArrayAdapter<>(after10th.this, android.R.layout.simple_list_item_1, after_ten); lv.setAdapter(adapter); } @Override public boolean onCreateOptionsMenu(Menu menu) { MenuInflater inflater = getMenuInflater(); inflater.inflate(R.menu.menu_search, menu); MenuItem item = menu.findItem(R.id.menusearchten); SearchView searchView = (SearchView) item.getActionView(); searchView.setOnQueryTextListener(new SearchView.OnQueryTextListener() { @Override public boolean onQueryTextSubmit(String query) { return false; } @Override public boolean onQueryTextChange(String newText) { adapter.getFilter().filter(newText); return false; } }); return super.onCreateOptionsMenu(menu);`enter code here` } } This is the error: 09-23 19:09:17.242 9000-9000/com.example.supriya.career_guidance E/AndroidRuntime: FATAL EXCEPTION: main Process: com.example.supriya.career_guidance, PID: 9000 java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.SearchView.setOnQueryTextListener(android.widget.SearchView$OnQueryTextListener)' on a null object reference | What are Null Pointer Exceptions (java.lang.NullPointerException) and what causes them? What methods/tools can be used to determine the cause so that you stop the exception from causing the program to terminate prematurely? |
I am new to python and one of the things every newbie do come across is the slice operator. I have a list: li=[1,2,3,4,5,6,7] As per my understanding calling li[:-1] is same as calling li[0:-1] and it is but when using it with a negative steps things do not work exactly as I thought they would. So getting to my question why the result of print(li[:-3:-2]) # is 7 but the result of print(li[0:-3:-2]) # is [] Looking forward to some explanation of how the negative step is being treated in this scenario. | I need a good explanation (references are a plus) on Python's slice notation. To me, this notation needs a bit of picking up. It looks extremely powerful, but I haven't quite got my head around it. |
Every single one of my apps, whenever I try to update them, or redownload offloaded apps (which I do very frequently) has this error: Unable to install APP_NAME, please try again later I’ve tried everything from turning my Wi-Fi on and off to signing out of my apple ID on the app store, doing a hard restart, and signing back in. Does anyone have any solutions they don’t think will have been in other answers? PS: This is not a duplicate of : About a different error. Mine only happens when redownloading any offloaded apps and updating nearly any app, the other users’ error only applied to default apps he’d deleted. On a different operating system. iOS of unknown version, I’m on iPadOS 13.3. With solutions I specifically mentioned I have already tried in my question, or was unable to try. I don’t have cell data, the solutions required cell data or were just restarting the device. | I’ve been trying to reinstall some default apps I had previously deleted such as “Watch” and “Files” through the App Store however with all of them I get the message: Unable to install ‘app name’ Please try again later. All other apps download fine, it’s just the default Apple apps that won’t install. |
A differential equation is if a numerical scheme requires a very small time-step in order to be stable for that equation. However I don't understand why it is called stiff (sometimes rigid). Even the wikipedia page says it's more of a phenomenon than a mathematically definable property. One characterization is the stiffness ratio, defined on the wikipedia page as $$ \frac{|Re\bar{\lambda}|}{|Re\underline{\lambda}|}$$ where I think $\bar{\lambda}$ and $\underline{\lambda}$ refer to the eigenvalues with maximum and minimum real parts. So why is it called this way? I don't know how to interpret this stiffness ratio. I was thinking of stiff as similar to "stringent" or "demanding" as a stiff person would be, which makes sense for the "requiring a small time step" definition. How is the requirement of a small time-step related to the stiffness ratio? | One of the mysteries that my numerics class left me with are "stiff systems". Our prof didn't really manage to explain what they are. Now that the class (and the test) are over, I'm still curious. The most concise definition about "stiff systems" I've found so far is: "There is no universally accepted definition of stiffness". So, if there is none, I don't expect one. I'd be thankful about information on both of the following points: From what kind of (real-world) problems do stiff systems arise? What's so "stiff" about them? What's the good thing - or the bad thing - that I'd worry about when I have to numerically solve such a real-world problem? |
I'm trying to install the mathabx package and am having some troubles. I am using MixTek 2.9 and running TexWorks. I have tried typing \usepackage{mathabx} into the console as usual before I \maketitle and start the paper etc. However, it keeps saying: Unfortunately, the package mathabx could not be installed.Please check the log file: C:/Users/mouse_000/AppData/Local/MiKTeX/2.9/miktex/log/miktex-pdftex.log ====================================================================== ! LaTeX Error: File `mathabx.sty' not found. Type X to quit or <RETURN> to proceed, or enter new name. (Default extension: sty) When I type \usepackage{mathabx} it prompts me to install the package and then gives me a list of sites (with countries listed in a separate column) that I can install it however trying a few of them it doesn't seem to work. it. Any help is appreciated on this. | I installed a new hard drive on my computer this summer and I'm trying to install MiKTeX on it now. There were no problems when I was using my old hard drive. My OS is Windows 8.1. I'm trying to compile the following very basic file with pdfLaTeX: \documentclass{article} \begin{document} hi \end{document} Here's the first error I get: Sorry, but "MiKTeX Configuration Utility" did not succeed. The log file hopefully contains the information to get MiKTeX going again: C:/Users/Tyler/AppData/Local/MiKTeX/2.9/miktex/log/initexmf.log You may want to visit the MiKTeX project page (http://miktex.org), if you need help. With the following errors in the log: 2015-09-03 22:23:51,625-0400 INFO initexmf - starting: MiKTeX Configuration Utility 2.9.5700 (MiKTeX 2.9 64-bit) 2015-09-03 22:23:51,631-0400 FATAL initexmf - Windows API error 32: The process cannot access the file because it is being used by another process. 2015-09-03 22:23:51,631-0400 FATAL initexmf - Info: C:\Users\Tyler\AppData\Local\MiKTeX\2.9\miktex/data/le\1e0c0e04cb3be262fbb8e6e7ace14b67.fndb 2015-09-03 22:23:51,631-0400 FATAL initexmf - Source: Libraries\MiKTeX\Core\win\winFile.cpp 2015-09-03 22:23:51,631-0400 FATAL initexmf - Line: 520 The second error: Sorry, but C:\Program Files\MiKTeX 2.9\miktex\bin\x64\miktex-pdftex.exe did not succeed. The log file hopefully contains the information to get MiKTeX going again: C:/Users/Tyler/AppData/Local/MiKTeX/2.9/miktex/log/miktex-pdftex.log You may want to visit the MiKTeX project page (http://miktex.org), if you need help. with the following errors in the log: 2015-09-03 22:16:18,715-0400 INFO miktex-pdftex - running 'initexmf --quiet --update-fndb' to refresh the file name database 2015-09-03 22:16:18,746-0400 FATAL miktex-pdftex - The operation failed for some reason. 2015-09-03 22:16:18,746-0400 FATAL miktex-pdftex - Info: C:\Program Files\MiKTeX 2.9\miktex\bin\x64\initexmf.exe 2015-09-03 22:16:18,746-0400 FATAL miktex-pdftex - Source: Libraries\MiKTeX\Core\Process.cpp 2015-09-03 22:16:18,746-0400 FATAL miktex-pdftex - Line: 290 Things I've tried: Uninstalling and reinstalling MiKTeX Downloading all packages whose name starts with miktex (which is a solution that worked for someone else in a different thread) Having nothing open but TeXworks when trying to compile Looking for processes that may be related to MiKTeX in the task manager (I didn't find any) How can I stop these errors? I apologize if my formatting is bad; this is my first stackexchange question. Thank you for your help. |
I am always confused where to use a "possessive apostrophe". From what I found on the internet it seems to me that children's literature is correct. What about garden chair? In my eyes it's the same. Garden is describing what kind of chair it is. Children is also describing what kind of literature I have in my mind. Could someone please explain? | In the following is it better to use a possessive noun with an apostrophe or an attributive noun without an apostrophe? The following list details the assumptions that have been made in conjunction with the Dell Company’s staff. Or The following list details the assumptions that have been made in conjunction with the Dell Company staff. Assume Company is the name of a company, such as Dell. |
Based on below, How can I calculate the distance of a point from Earth now vs 13 billion years ago? The excerpt below claims it is 8 times further now. Can someone provide relevant equations ? I have a question on an excerpt from the book “our mathematical universe”. It has the passage “If our universe is 14 billion years old, how can we see galaxies 30 billion light years away? How did their light have time to reach us? Answer is we are not seeing where the galaxies are now but where they were when the light was emitted” The next part: “Just as we see the sun as it was 8 minutes ago, We might see a distant galaxy the way it looked 13 billion years ago which was about eight times closer to the earth than now?” | How can I calculate the distance of a point from Earth now vs 13 billion years ago? The excerpt below claims it is 8 times further now. Can someone provide relevant equations ? |
What is the difference between attribute and parameter and argument? And how does this works? ex:- int a = 10;//attribute method(int a);//argument or parameter And if i pass a argument dynamically then whether it will be called parameter or argument. thanks. | When verbally talking about methods, I'm never sure whether to use the word argument or parameter or something else. Either way the other people know what I mean, but what's correct, and what's the history of the terms? I'm a C# programmer, but I also wonder whether people use different terms in different languages. For the record I'm self-taught without a background in Computer Science. (Please don't tell me to read because I'm asking this for the benefit of other people who don't already have a copy of 's marvellous book.) Summary The general consensus seems to be that it's OK to use these terms interchangeably in a team environment. Except perhaps when you're defining the precise terminology; then you can also use "formal argument/parameter" and "actual argument/parameter" to disambiguate. |
Deriving de Broglie's equation (as per my text and teacher) involves equating $E = mc^2$ with $E = h\nu$, where $\nu$ is the frequency. It goes like : $$mc^2 = h\nu$$ $$mc^2 = \frac{hc}{\lambda}$$ $$mc = \frac{h}{\lambda}.$$ Then we replace $c$ with the velocity of the particle to apply it generally i.e. $$mv = \frac{h}{\lambda}.$$ My doubt is exactly about this step. As far as I have read before and after learning this equation, I understood that $c$ in $E = mc^2$ was mainly used as a constant which can equate energy and mass rather than something relating energy, mass and velocity of the particle. Thus replacing $c$ with $v$ makes no sense as it would have contradicted the equivalence of $E=mc^2$ in the first place. Can someone explain how $c$ can be replaced with $v$ without contradicting $E = mc^2$, or just simply point out what is wrong with my thought process? | According to de Broglie's wave-particle duality, the relation between electron's wavelength and momentum is $\lambda =h/mv$. The proof of this is given in my textbook as follows: De Broglie first used Einstein's famous equation relating matter and energy, $$E=mc^2,$$ where $E=$ energy, $m =$ mass, $c =$ speed of light. Using Planck's theory which states every quantum of a wave has a discrete amount of energy given by Planck's equation, $$E=h\nu,$$ where $E =$ energy, $h =$ Plank's constant ($6.62607 \times 10^{-34}\:\mathrm{ J\:s}$), $\nu =$ frequency. Since de Broglie believes particles and wave have the same traits, the two energies would be the same: $$mc^2=h\nu.$$ Because real particles do not travel at the speed of light, de Broglie substituted $v$, velocity, for $c$, the speed of light: $$mv^2=h\nu.$$ I want a direct proof without substituting $v$ for $c$. Is it possible to prove directly $\lambda=h/mv$ without substituting $v$ for $c$ in the equation $\lambda =h/mc$? |
When converting strings to long double I lose precision in QNX. Do you know how to fix this problem? I am using c++. I have tried double and float and there were no problems. #include <iostream> #include <string> #include <limits> #include <sstream> int main(){ long double originalNumber = std::numeric_limits<long double>::max() / 2; long double convertedNumber; // From long double to string std::ostringstream ostr; ostr << originalNumber; std::string tmp_str = ostr.str(); //From string to long double std::istringstream istr(tmp_str); istr >> convertedNumber; // Check if they are similar if (originalNumber == convertedNumber) std::cout<< "The same\n"; else std::cout<< "Not the same\n"; return 0; } The result is always Not the same | Consider the following code: 0.1 + 0.2 == 0.3 -> false 0.1 + 0.2 -> 0.30000000000000004 Why do these inaccuracies happen? |
As title, I've done every single step to sync user's picture, but it's still doesn't work. I don't know what to do now to make it work. Any idea? I've selected "Use SharePoint Active Directory Import" in "Configure Synchronization Setting". In "Manage User Properties" I've set up the mapping with "thumbnailPhoto" attibute for Picture. I can see . "Picture---URL---thumbnailPhoto". I've run full sync and get 241 users from AD Then I open PowerShell Command and run "Update-SPProfilePhotoStore -CreateThumbnailsForImportedPhotos 1 -MySiteHostLocation mysitehostURL" . And there is no error. Finally I checked it again but still didn't work.? | I've followed this tutorial to try to sync user's picture from AD to SP 2013 but I've got issue in the first step: In dropdownlist for attribute I can't find 'thumbnailPhoto' to selected. It was disable. And there is some picture of my configuration and here is the problem After create connection, When I click Start Profile Synchronize, nothing happen. The status still idle. I'v sure that in my AD there are over hundreds UserProfile. The number 17 mean, there are 17 User have accessed to My Site. I don't know why? . Could it be the cause of my problem? There is one thing that I'm wonder. I can't start Profile Synchronization Service running because of I'm using "Sharepoint Active Directory Import". |
I have a 50mm prime lens and a 18-55mm standard lens at my disposal. How do I measure the magnification of a reversed lens when used with a reverse mount. What are the factors that come into play to calculate the magnification? | I am looking for a way to mathematically determine the maximum magnification ratio that is possible/practical to achieve by reverse mounting a non-macro lens, prior to purchasing the lens. See related questions: |
Stack Overflow Careers should sort experience by the date(s) of the experience and not by when it was entered. I am going to have to delete several old options from my profile because they are old and not the most relevant. | Just joined Stack Overflow careers and figured I'd chime in and ask for a feature. It appears that the order you insert the "Experience" items in is how they stay. I seem to have put mine in ascending order instead of the more traditional descending. It would be helpful if SO Careers had a sort feature for that section. I certainly want potential employers to see my latest experience first. |
I need to copy a file from one server to another. Here is my exact requirement. I am log in from server a and I have to copy a file from server b to server c . So what is the command for it ? | What is the best way to copy a directory (with sub-dirs and files) from one remote Linux server to another remote Linux server? I have connected to both using SSH client (like Putty). I have root access to both. |
I'm performing a regression where the dependent variable is a ratio, and the explanatory variable is the denominator of that ratio. In other words, I'm normalizing the dependent variable by $X$ and including $X$ as an explanatory variable: Dependent variable: $Y/X$ Explanatory variable: $X$ For example, I might be interested in whether countries with more people tend to have a higher proportion of women, in which case $X$ is total population and $Y$ is the number of women. Or I might be interested in how the number of dogs per cat varies with the size of the cat population in a country, and so on. $X$ appears in both the left hand side and right hand side of the regression equation, and I want to avoid any issues that could arise from this (e.g. mechanical correlations). Should I be worried about mechanical correlations (either generally or in certain situations)? If so, what kinds of situations, and how can I remedy them? And what other issues might arise? | Recently, randomly browsing questions triggered a memory of on off-hand comment from one of my professors a few years back warning about the usage of ratios in regression models. So I started reading up on this, leading eventually to Kronmal 1993. I want to make sure that I'm correctly interpreting his suggestions on how to model these. For a model with a ratio with the same denominator on both the dependent and independent side: $ Z^{-1}Y = Z^{-1}1_n\beta_0 + Z^{-1}X\beta_X + \beta_Z + Z^{-1}\epsilon $ Regress dependent ratio on the (inverse) denominator variable in addition to the other ratios Weight by the (inverse) denominator variable For a model with dependent variable as a ratio: $ Y = \beta_0 + \beta_XX + Z1_n\alpha_0 + ZX\alpha_X + Z^{-1}\epsilon $ Regress numerator by original variables, denominator, and denominator times original variables [what about categorical variables?] Weight by (inverse) denominator For model with only independent variable ratios: $ Y = \beta_0 + X\beta_X + Z^{-1}1_n\beta_{Z^{-1}} + W\beta_W + Z^{-1}W\beta_{Z^{-1}W} + \epsilon $ Include numerator and (inverse) denominator as main effects, ratio as interaction term. Are my interpretations here correct? |
Why the conversions between compatible reference types will compile (Excel 2010, .Net 4.5) in this case using Excel = Microsoft.Office.Interop.Excel; Excel.Application excelApplication = null; excelApplication = new Excel.Application(); Excel.Worksheet worksheet = workbook.Worksheets[1] as Excel.Worksheet; and in the case below it will not, although I saw exampales shown like that: Excel.Worksheet worksheet = (Excel.Worksheet)workbook.Worksheets[1]; In this case I get the following compiling error : > CSC : error CS0518: Predefined type 'Microsoft.CSharp.RuntimeBinder.Binder' is not defined or imported > error CS1969: One or more types required to compile a dynamic expression cannot be found. Are you missing a reference? Best, EDIT : Thanks to the both answerer below the following explanation sounds reasonable: without including Microsoft.CSharp in the Project References for projects with .Net Version >= 4.0, support for inter operation between the Dynamic Language Runtime (DLR) and C# is not possible, i.e. no dynamic cast is possible. | When programming interfaces, I've found I'm doing a lot of casting or object type conversion. Is there a difference between these two methods of conversion? If so, is there a cost difference or how does this affect my program? public interface IMyInterface { void AMethod(); } public class MyClass : IMyInterface { public void AMethod() { //Do work } // Other helper methods.... } public class Implementation { IMyInterface _MyObj; MyClass _myCls1; MyClass _myCls2; public Implementation() { _MyObj = new MyClass(); // What is the difference here: _myCls1 = (MyClass)_MyObj; _myCls2 = (_MyObj as MyClass); } } Also, what is "in general" the preferred method? |
Let $\mathbb F$ be a field and $\mathbb K $ be an extension field of $\mathbb F$ such that $\mathbb K$ is algebraically closed. Let $\mathbb L$ be the field of all elements of $\mathbb K$ which are algebraic over $\mathbb F$. Then $\mathbb L_{|\mathbb F}$ is an algebraic extension. My question is : Is $\mathbb L$ algebraically closed ? I am trying to prove the existence of algebraic closure, so please don't assume that every field has an algebraic closure. | If I have a field $K$ and an extension $L$ of $K$ such that all (non-constant) polynomials in $K[X]$ have a root in $L$, is the set of algebraic elements of $L$ over $K$ (the sub-field of all the elements of $L$ which are roots of a polynomial in $K[X]$) algebraically closed ? Do you have a counterexample ? |
I just want to know if you can, and what kind of applications can be downloaded. | Is it possible to run Android apps on Ubuntu? And I don't mean inside an emulator, but natively, as you would with any other application installed using the Ubuntu Software Center. |
I want to create top down game where you are Russian soldier in libGDX. The player controls the soldier with W/A/S/D and aims with the mouse. That way the soldier can run sideways and shoot towards enemy. What is best way to make his legs walk into the right direction but aim the weapon towards the mouse pointer? My idea is to make two sprites, for both torso/weapon and legs and let them lay over each other but I don't know if that is best way to do it. | is a perfect example of the shooting mechanic I'd like. The character aims perpetually toward the mouse. What's going on here? From what I've read so far, you could separate the arm and rotate that. I've also noticed some people use a different sprite for each weapon. How can I achieve this? |
What is reflection, is it the bouncing back of photon or re-emission of photon by first jumping to a higher energy state and then coming down due to interaction with incident photon? | The "equal angles" law of refection on a flat mirror is a macroscopic phenomenon. To put it in anthropomorphic terms, how do individual photons know the orientation of the mirror so as to bounce off in the correct direction? |
Can you guys give me some advice on how to make animation like that? I want to create an animation very similar to this in the video. Thanks for any advice | I'm trying to simulate a rope (that later might get pulled on the ends*) that interacts with some obstacles. So far I created a plane as the floor and a cube as an obstacle, and activated "collision" in the physics menu for both of them. *(In the end the goal is simulating a .) For modelling the rope, I tried using a long cylinder with enough subdivisions, and activate "cloth" in the physics menu. This resulted in the cylinder collapsing like a sleeve of a sweater, but I would like the cross section to remain roughly circular. Is there a way to directly avoid this? Another approach I tried now was just using a a line made up of vertices and edges (with the idea of later adding modifiers to give it a thickness), but this just fell through all the collision objects as it has no faces. Is there good way to do this? |
Here: #include <iostream> #include <cstdlib> #include <boost/lexical_cast.hpp> int main(void) { const char * str = "277499.84"; std::cout << boost::lexical_cast<double>(str) << std::endl; std::cout << strtof(str, NULL) << std::endl; std::cout << strtold(str, NULL) << std::endl; std::cout << atof(str) << std::endl; return 0; } output: 277500 277500 277500 277500 Why the output are not 277499.84? | In my I was printing a double using cout that got rounded when I wasn't expecting it. How can I make cout print a double using full precision? |
There are a number of monsters that make ranged weapon attacks with unusual qualities. For example the has a ranged attack that does 1d4 piercing and 1d6 fire damage, the 's longbow does an extra 1d8 poison damage, and the 's shortbow has no damage die but can poison an enemy or knock them unconscious. When using the monk's Deflect Missiles feature to make a ranged attack using a caught projectile are additional damage types and effects included with the attack? You can use your reaction to deflect or catch the missile when you are hit by a ranged weapon attack. When you do so, the damage you take from the attack is reduced by 1d10 + your Dexterity modifier + your monk level. If you reduce the damage to 0, you can catch the missile if it is small enough for you to hold in one hand and you have at least one hand free. If you catch a missile in this way, you can spend 1 ki point to make a ranged attack with the weapon or piece of ammunition you just caught, as part of the same reaction. You make this attack with proficiency, regardless of your weapon proficiencies, and the missile counts as a monk weapon for the attack, which has a normal range of 20 feet and a long range of 60 feet. on catching poisoned arrows is related but does not answer my question. The linked question asks about which damage needs to be reduced in order to catch the arrow. My question is about the damage that the arrow would do if the monk spends 1 ki point to make an attack with it. For a specific example: A Drider hits a monk with an arrow and deals 4 piercing damage (1d8+3) and 1 poison damage (1d8). The monk uses Deflect Missiles and reduces the damage by 35 (1d10 + 5 + 20) lowering the damage to 0. The monk then spends 1 ki point to make a ranged weapon attack with the caught arrow as per the Deflect Missiles. The monk hits with the attack. How do I calculate damage? | When catching an arrow tipped with poison (like the ones used by yuan-ti) with an ability like the one the monk has or the one given by arrow catching gloves: does the ability reduce the poison damage? If so, is the total damage or the piercing one caused by the arrow only the damage that must be downed to 0 to catch the missile? |
My students write sentences like this: She hasn't gone out with him since two months ago. so I want to know if this sentence is right or wrong in English grammar. | First, I check that my native language is not English, and the problem described below met on one of the exams. With this sentence: "The most important news is that my parents [...] a new restaurant a few weeks ago." Is the correct tense to use the Present Perfect (have opened) or Past Simple (opened)? I know that the word "ago" but rather that time Past Simple, but is it also possible to use the present perfect in some cases? I would be grateful for clarification. |
I have two arrays that list people, and I'm trying to figure out which people are in both arrays. $employees = Array("bob", "john", "jerry", "mike"); $homies = Array("bob", "john", "arnold"); I basically need to know which dudes are both employees and homies (in this case, bob and john) so that I have a new array: $employees_and_homies = Array("bob", "john"); I looked at like a dozen other questions on here, but I'm lost and nothings working for this particular case. | I have two arrays in PHP as follows: People: Array ( [0] => 3 [1] => 20 ) Wanted Criminals: Array ( [0] => 2 [1] => 4 [2] => 8 [3] => 11 [4] => 12 [5] => 13 [6] => 14 [7] => 15 [8] => 16 [9] => 17 [10] => 18 [11] => 19 [12] => 20 ) How do I check if any of the People elements are in the Wanted Criminals array? In this example, it should return true because 20 is in Wanted Criminals. |
$$\int\dfrac{x^2}{1+x^4}dx$$ I tried many standard approaches, but I didn't get too far! Here's the most promising of them: $$\int\dfrac{dx}{\frac{1}{x^2}+x^2}$$ knowing that $\left(1/x+x\right)^2=\frac{1}{x^2}+x^2+2$ we can change variables $1/x+x=t$. Unluckily this doesn't work either. | Integrate $$\int\frac{x^2dx}{1+x^4}$$ I've factored the denominator to $(x^2-\sqrt{2}x+1)(x^2+\sqrt{2}x+1)$ and got stuck. |
I've learned that in combustion chamber fuel and air are mixed and burned but I dont understand the outcome. Ive heard that after combustion it is still very hot and I also seen that you loss heat as a result. So can someone clear this up for me so its not so confusing, also if you need to burn the air and fuel mixture why can you just use the hot air from the compressors? | I'm trying to understand at a high level how a works. I want to know if the following summary I wrote is more or less accurate: The jet compresses regular air into a combustion chamber. Fuel is sprayed into the combustion chamber. The pressurized fuel/air mixture is ignited and this increases the pressure inside the combustion chamber even more. The hot highly presurized gas blasts out of the combustion chamber. The energy of this blast is captured by turbines. The turbines power the compressor and provide useable power to a shaft. Is my understanding correct? |
I am running Windows XP and have a phone mounted through USB by MTP. In Explorer, its address is: My Computer\SAMSUNG-SGH-I547\Phone\DCIM I would like to execute a command line command such as explorer "My Computer\SAMSUNG-SGH-I547\Phone\DCIM\Camera" so as to quickly go to the Camera folder. (Right-clicking the device or anything in it does NOT provide a "Create Shortcut" dialog.) But "My Computer" is not a valid PATH in Windows. Unlike USB flash drives, it seems the phone mounted by MTP does not get a letter drive name. So, what is the path of an MTP device in Windows? If the answer is there is no command line path, is there workaround? | Most MTP () devices show up in Windows File Explorer under their device name or a GUID, but they don't have a drive letter assigned. How can I access the files on such devices from the command line? Using either cmd.exe or PowerShell. |
Without touching the FlexBuilder app (I'm still going through the tutorials for Flex) is there a way to customize the pop-up that appears for the Locate Widget? I am assuming that I could go into the pop-ups folder and create a popup_Locate config file of some sort? Is this correct? Or is there a better way to customize the popups that appear when selecting from the list that populates from a Locate Widget search? | I want to add text where it says "score" to make it more clear that this is an address matching score. I am using the LocateWidget_US.xml and do not think I can do it here. I think the place to do it may be in the LocateWidget.mxml in this line???? locateResult.content = getDefaultString("resultScoreText") + " " + (addrCandidate.score % 1 == 0 ? addrCandidate.score : addrCandidate.score.toFixed(1)); |
I would like to ask you if anyone of you knows how can I save changes in the progrem so when It will be restarted, the changes would remain? for example, I have a boolean variable which his defualt value is "false". I want after the inital start, change the value to "true" so when I'll close and start the program, the boolean variable value would be true. | What I want to achieve is very simple: I have a Windows Forms (.NET 3.5) application that uses a path for reading information. This path can be modified by the user, by using the options form I provide. Now, I want to save the path value to a file for later use. This would be one of the many settings saved to this file. This file would sit directly in the application folder. I understand three options are available: ConfigurationSettings file (appname.exe.config) Registry Custom XML file I read that the .NET configuration file is not foreseen for saving values back to it. As for the registry, I would like to get as far away from it as possible. Does this mean that I should use a custom XML file to save configuration settings? If so, I would like to see code example of that (C#). I have seen other discussions on this subject, but it is still not clear to me. |
I'm looking to buy a Sony mirrorless camera. The draw back is the expense of extra lenses as Sony really is proud of their products. Has anyone here tried using a Canon EF lens on a Sony mirrorless camera? I'm looking at getting the a3000. I see that they make adapters but I have no idea if it's worth the effort. My budget has no room for a $1000 lens at the moment. I can however afford an adapter to make the canon lenses work on the Sony frame. I've found many used Canon lenses at pawn shops that are well within my budget.Thank you | I currently live in the Canon ecosystem, but really like the look of the Sony a7S. But before I switch I want to know just how well I'll be able use use my old EF-mount lenses on my new a7S. How well do the mount adapters perform? Are there any converters that would allow me to use my old EF lenses with 100% of the original functionality (auto-focus, IS, EXIF data, etc)? I would not normally ask, but this isn't the sort of thing I can try out in the store. |
I am trying to prove this: Prove that a positive integer $n$ is a prime number, if no prime $p$ less than or equal to $\sqrt n$ divides $n$. This is how I thought of starting: Let us assume the smallest prime factor of $n$ to be $P$. So, $n = (m)(P)$ From this it follows that $(n) \geq (P)^2$ or $\sqrt n \geq (P)$ i.e $n$ has at least one prime divisor smaller than $\sqrt n$ whenever it is composite. So if it has no prime divisor, then it must be prime. However, I'm not quite satisfied with the proof. Can someone please provide me an easier approach to the proof? | I have the following theorem: If no prime less than or equal to $\sqrt{n}$ divides $n$, then $n$ is a prime. And the following proof (proof by contradiction) for said theorem: Suppose that no prime less than or equal to $\sqrt{n}$ divides $n$ but $n = ab$, with neither $a$ nor $b$ equal to $1$. Now $a$ and $b$ cannot both be strictly larger than $\sqrt{n}$ or their product would be larger than $n$. So one of $a$ or $b$ is not larger than $\sqrt{n}$: assume (without loss of generality) that $a \le \sqrt{n}$. Now $a$ cannot be prime (as we have assumed $n$ has no prime factor this small), and so is composite. Therefore $a$ has a prime factor $p$, which must be less than $a$. But then $p < a \le \sqrt{n}$ is a prime factor of $n$, and this contradicts our hypothesis. Hence $n$ is prime. We deduce that $a$ is composite. But why does this then mean that $a$ has a prime factor $p$? So this is saying that all composite numbers have a prime factor? Why? I would greatly appreciate it if people could please take the time to clarify this. PostScript: I am assuming that is the definition of composite number being used here. |
Suppose $f$ is differentiable at $0$ and $f(0)=0$. Prove that there exist some function $g(x)$ such that $f(x)=xg(x)$ and $g$ is continuous at $0$. I think I am on the right track, here: If I write $g(x)=\frac{f(x)}{x}$ then $g$ will be discontinuous at $0$ because $f(0)=0$. Now, as an example, let $f(x)=x^2$ and $g(x)=x$. How can I proceed? | (a) Let a function $g:I\to\mathbb{R}$ be continuous at $x_0\in I$. Prove that the function $f$ given by $f(x)=(x-x_0)g(x)$ is differentiable at $x_0$. (b) Let a function $f:I\to\mathbb{R}$ be differentiable at $x_0\in I$ and $f(x_0)=0$. Prove that there exists a function $g:I\to \mathbb{R}$ that is continuous at $x_0 \in I$ such that $f(x)=(x-x_0)g(x)$. Thought: (a) By $Fermat's$, since $g$ is continous, if $g'(x_0)=0$ then $g(x)$ is differentiable? but how does it connect back with $f(x)$? (b) use the definition of every differentiable function is continuous? Thus $f(x)$ is continuous and also $(x-x_0)$ so $g(x)$ too? Thank you!! |
The LIGO Scientific Collaboration and Virgo Collaboration that on the 14th of September 2015, at 09:50:45 UTC, they detected a transient Einstein gravitational wave, designated GW150914, produced by two merging black holes forming a single black hole. They stated that the speed of propagation of the gravitational wave is the speed of light. Is the speed of propagation of Einstein's gravitational waves unique or arbitrary? | Do gravitational waves have a certain speed? Is it the speed of light or infinite, or am I misunderstanding what a gravitational wave is? I think it is a ripple in spacetime caused by interactions between objects, but i could be wrong. |
Let $(a_n)_{n \in \mathbb{N}}$ be an infinite positive sequence of integers. Assume that $f(\lambda) = \sum\limits_{n=0}^{\infty} a_n \lambda^n$ is finite for any $\lambda \in [0, \lambda_0)$. Does this necessarily imply that $f(\lambda)$ is also continuous in $(0, \lambda_0)$, or might something strange happen? | I want to prove that every power series is continuous but I am stuck at one point. Let $\sum\limits_{n=0}^\infty a_n(x-x_0)^n$ a power series with a radius of convergence $r>0$ and let $D:=\{x\in\mathbb R:|x-x_0|<r\}$. Then $S(x)=\sum\limits_{n=0}^\infty a_n(x-x_0)^n$ is continuous on $D$. Proof: Let $x\in D$ and $r_0\in\mathbb R^+$ such that $|x-y_0|<r_0<r$ and for any positive integer $N$ let $S_N(y)=\sum\limits_{n=0}^{N-1} a_n(y-x_0)^n$ and $\phi_N(y)=\sum\limits_{n=N}^\infty a_n(y-x_0)^n$. Since the power series converges uniformly on the closed disk $|y-x_0|\leq r_0$, we may choose a positive integer $N_\varepsilon$ such that $|\phi_{N_\varepsilon}|<\frac\varepsilon3$ for all $|y-x_0|\leq r_0$. Since $S_{N_\varepsilon}$ is polynomial we can choose a $\bar\delta>0$ such that $|S_{N_\varepsilon}(y)-S_{N_\varepsilon}(x)|<\frac\varepsilon3$. So we get $|S(y)-S(x)|<\frac\varepsilon3+\frac\varepsilon3+\frac\varepsilon3=\varepsilon$ for $|y-x|<\delta$ Why is in the violet term $|\phi_{N_\varepsilon}|<\frac\varepsilon3$ correct? Don't I have two terms in the absolute value? Thanks for helping! |
Refer the title. Why was this required? How is this related to ultraviolet catastrophe? | I was reading some popular science book and there was this sentence. It says that energy has to be emitted in discrete portions called quanta. Otherwise the whole energy in the universe would be converted into high frequency waves. I'm not a physicist, so this conclusion seems to me like a huge leap. First, we assume that energy is emitted in a continuous way (not in quanta). And how do we get to the statement "the whole energy in the universe would be converted into high frequency waves"? |
, which prevents up/down votes, comments, answers and close votes. It would be nice to have a less draconian lock, that only locked the question text (and tags) but permitted up/down votes, comments, answers answers and close votes. It would assist against: Edit wars on the question. This would normally be handled by putting the question on hold until it is resolved. With this new lock, at some point the mod could make a final decision, and lock the question down, letting people actually start answering it. Frequent, deliberate bumping. If an OP keeps making trivial changes to the question for the sake of getting it back to the front page - but you aren't ready to suspend them for it - the question text could be locked. (Bounties would still be possible.) If people have an answer to provide, it should be open to that. Once answers are provided, people should be allowed to vote on them - it isn't the answerer's fault. | Locking a post has very severe consequences for a post, you cannot Upvote or downvote on it Edit it Vote to close or reopen it Comment on it Add new answers to it Because of these severe consequences I usually avoid locking altogether and try to deal with the problem in other ways. Locking just has far too severe side-effects for my taste, I don't want to prevent anyone from voting or answering just because there is an edit-war on the post. We now also have some locking reasons, ignoring the historical significance reason as it isn't relevant here, they are the following: Content dispute This post has been locked while disputes about its content are being resolved. For more info visit meta. Off-topic comments This post has been locked due to the high amount of off-topic comments generated. For extended discussions, please use chat. Both are common reasons for locking a post, and in both cases the locking is there to prevent only a small subset of what locking actually stops. Those locking reasons shouldn't only be a text attached to the lock, but they should also change the behaviour of the locks: A lock for off-topic comments should only prevent new comments A lock due to an edit war should only prevent edits to the post This would make using those locks less disruptive, and more useful to moderators. |
Observe the following (bad) question on Japanese.SE: The question reports the following in the close banner: closed as not constructive by sawa, , , , Nov 2 '11 at 6:45 Now, I happen to know that "user458" (the same user who made the last edit to the question on Nov 1 '11 at 23:35) was known as "sawa" before having their account removed. Shouldn't references to the user in the close banner also be anonymized to "user458"? Obviously, we're never going to succeed at perfectly anonymizing the user because of stuff like @mentions in the comments, but it seems like "system text" like the close banners at least ought to anonymize correctly. (I suspect that protection and deletion banners may have the same issue, though I haven't encountered any posts that were protected or deleted by a now-deleted user yet.) (Is this a duplicate of ? animuson marked it , so I'm not sure what's up.) | We recently had which showed that "Mik" had cast a close-vote on one of the questions however his profile wasn't linked. It became clear later on in the answers and comments that Mik's profile is now deleted and hence his name is not linked to his profile. Another example for same user: But then, why isn't the name of the user obfuscated like it gets done for posts/comments once the user gets deleted? |
Which one of these two statements is correct? 60% of staff work or 60% of staff works | Which one of these two statements is correct? Our staff do ... Our staff does ... And is staffs ever correct? |
I'm trying to solve problem 1.18 in Fulton's 'Algebraic Curves', which is illustrated in the attached image, but I'm having some difficulties understanding the first part. The ring R is assumed to be commutative and unital, so the first thing that came to mind was to consider the binomial expansion of $(a+b)^{n+m}$, but I don't see why powers of $a$ which are less than n, or powers of $b$ which are less than m should be contained in the ideal. An explanation as to how I can show that $Rad(I) $ contains $a+b$ would be appreciated, particularly I'd like to know if one can indeed be guaranteed the containment (in I) of the aforementioned terms from the binomial expansion. I suspect that I may be missing or forgetting some ring theoretic fact. | Possible Duplicate: Given a commutative ring $R$ and two nilpotent elements $r$, $s$ there exists an $n \in \mathbb{N}$ such that $$ (r+s)^n = 0.$$ I want to prove that in order to show that the nilpotent elements of a commutative ring are closed under addition (to show that the nilpotent elements form an ideal within a commutative ring). Is that a good way to do it? I'm a little stuck. |
I need help.. Question An examination of the function $f:\mathbb{R}^2 \to \mathbb{R}$, $f(x,y) = (y-3 x^2)(y-x^2)$ will give an idea of the difficulty of finding conditions that guarantee that a critical point is a relative extremum Show that (a) the origin is a critical point of $f$ : I solved easily (b) f has a relative minimum at $(0,0)$ on every straight line through $(0,0)$; that is, if $g(t)=(at, bt)$, then $f o g : \mathbb{R} \to \mathbb{R}$ has a relative minimum at $0$, for every choice of a and b; (c) the origin is not a relative minimum of $f$. It is hard to me (b) and (c).. | There is an exercise in my lists about those functions: $$f(x, y) = (y-3x^2)(y-x^2) = 3 x^4-4 x^2 y+y^2$$ $$g(t) = f(vt) = f(at, bt); a, b \in \mathbf{R}$$ It asks me to prove that $t = 0$ is a local minimum of $g$ for all $a, b \in \mathbf{R}$ I did it easily: $$g(t) = 3 a^4 t^4-4 a^2 t^2 b t+b^2 t^2$$ $$g'(t) = 2 b^2 t-12 a^2 b t^2+12 a^4 t^3$$ $$g''(t) = 2 b^2-24 a^2 b t+36 a^4 t^2$$ It is a critical point: $$g'(0) = 0; \forall a, b$$ Its increasing for all a, b: $$g''(0) = 2b^2 > 0; \forall b \ne 0$$ and $$b = 0 \implies g(t) = 3 a^4 t^4$$ which has only one minimum, at $0$, and no maximum However, it also asks me to prove that $(0, 0)$ is not a local minimum of $f$. How can this be possible? I mean, if $(0, 0)$ is a minimum over every straight line that passes through it, then, in this point, $f$ should be increasing in all directions, no? |
I was curious how often I'd used a couple of idiosyncratic terms in my answers, so I googled them together and was surprised to see them on an external site, having survived a translation into Spanish. The site appears to have translated portions of arqade.se and rpg.se. As someone who only speaks one language; that is, an American, I have no idea if their attribution or operation is in keeping with Stack Exchange fair-use guidelines. I was hoping someone more conversant could take a look around. | of Stack Overflow, all content posted on Stack Exchange sites by their users (i.e. you wonderful people) has been provided to the whole universe under . For my fellow non-lawyers, that license basically means: Anyone can use any Stack Exchange posts at any time without having to ask for permission Making money off of the copied content is permitted You don't even have to copy stuff from here verbatim; you can just use it as a starting point and make whatever edits you want There are just two rules you have to follow: You have to provide . Simple links to the original post and author info are just fine. You have to and allow other people to use your content, as long as they follow these very same rules. How meta! (If you ever forget any of that, and want to refresh your memory, the license info is linked to in the footer of every page.) There are, in fact, a lot of people who republish varying amounts of our content for assorted reasons. Unfortunately, there are some Stack Content Republishers Attributing Poorly and/or Excelling at Ranking (SCRAPERs, for short). In this context, "attributing poorly" means any use that doesn't follow our attribution rules or make any other reasonable attempt at give credit. This can get pretty egregious; I've seen SCRAPERs that not only don't link back to SE originals, but also use fake author info and post dates to make it harder to find originals. By "excelling at ranking," I'm referring to copycat sites that end up higher in Google results than the original SE sites do for the same content. That's not necessarily wrong, but in some cases, it indicates inappropriate SEO hackery. So, the question is: what can you do if you spot a SCRAPER? |
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