How Is This a Bijection from $P(X)$ to $2^X$?

Let $X$ be a set, $P(X)$ the power set of $X$, and $2^X$ the set of all function from $X$ to $\{0, 1\}$.  Now define $J: P(X) \rightarrow 2^X$ by $J(A) = \chi_A$, where $\chi_A$ is the characteristic function.  Show that $J$ is a bijection from $P(X)$ to $2^X$.  I can demonstrate that $J$ is a bijection from $P(X)$ to $\{\chi_A | A \subset X\}$.  But how do I know for sure that $\{\chi_A | A \subset X\} = 2^X$?  Or, is there a function in $2^X$ that does not take the form of $\chi_A$?  I am not seeing how the answer is no, but I can't think of any counter examples either.


How can I edit a picture into an existing PDF file?

I have a scanned PDF file which is , and a picture which is the scanned version of my signature (for example, ) and can be in any image format such as EPS or PNG. I would like to put the signature picture on the blank space right to "APPLICANT:" on the second page of the application form. I wonder how to do that?  I have tried the following methods, but none succeeded:   The first way is using gimp. I first import the application form into gimp, and then paste the signature picture on the space right to "APPLICANT:" on the second page of the application form.   The problems are that:   It seems that I can only import one page of the application form into gimp, not all of the two pages.  Also when I save the modification, the closest format to PDF I can save to is PS, and the resolution has been downgraded and the storage size of the saved file is 10 times bigger than the original application form and the signature picture.  The second way is using Libreoffice Draw. I have installed the libreoffice-pdfimport package. But after I import the application form into Libreoffice Draw,    all the scanned content is not imported, and  the layout is different from the layout of the original application form.    So what other ways can I try? I would prefer some way that can lay the signature picture directly on the application form PDF file,    without having to convert between formats,  without having to create much bigger files while keeping the original resolution, without having to split and combine pages of a multi-page pdf file, without having to rasterize other parts of the PDF file, i.e. without losing the text that I added later to the application form PDF file by having to convert the whole PDF into images.


What is the difference between `grep`, `egrep`, and `fgrep`?

Can anyone tell me the technical differences between grep, egrep, and fgrep and provide suitable examples?  When do I need to use grep over egrep and vice versa?


My understanding is that I should only use a comma before "but" if it precedes an independent clause.  What if I want a "pause comma" before "but" and it does not precede an independent clause?  Example:  One day, Ted thought he saw another boy dancing, but it was just the reflection of himself.


Providing root ssh access to virtual servers behind NAT?

We are a web hosting company. We have 4 Servers which are running OpenVZ on top of CentOS. Each of the server has around 50 containers running on top of it.   We are planning to provide ssh root access to some of the customers (around 50). All of these 50 users will be developing and hosting modules of a single website. For eg. there is a website xyz.com Now there will be a module xyz.com/module1 This module1 will be hosted by different developers and hosted on different containers. Similarly there will be other modules developed by different developers and hosted on other containers. The problem is that these containers are running behind a NAT firewall. There is a public I.P for xyz.com.  We do not want to do port forwarding as it will open unnecessary ports in the Firewall.  We were thinking of forwarding all the ssh requests to xyz.com to a single container (ssh-temp) and then allowing ssh to other containers from ssh-temp container only. But this approach is not feasible as the users will be having root access to their containers and can modify the firewall rules.  Is there any better approach to perform this task. I was thinking of having a scheme where a user could run a command such as:  ssh user@module1.xyz.com   The user would then be redirected to that particular module. How can I achieve such a scheme?  Thanks  Edit: I do realize that providing root access to containers within a network is a bad idea but for now this is a compulsion and not a choice.


Strange, similar services running on my PC: are they viruses?

there are a couple of services from UnistackSvcGroup, BcastDVRUserService and others running on my Windows 10 machine with a weird name. I did some research on the web about services from these groups and they seemed fine (simply part of the services that come with Windows), but what I found odd was that they were duplicated with a strange rename with them: _a1bddec, like:   BcastDVRUserService and the duplicate, BcastDVRUserService_a1bddec BluetoothUserService and the duplicate, BluetoothUserService_a1bddec etc.   I googled for this "name" and I couldn't find anything, nor could I find anything about duplicated services from such groups. More then that, I discovered this services when I was trying to understand why suddenly my computer started to suffer performance issues while I was watching a movie with nothing working behind that would justify gradual performance changes. After closing some apps plus stoping these services, my computer went back to normal, what leads me to think if it's not a virus of some sort.  So what do you know of these "double services" with different end names? Here are some prints with all of them:          EDIT  Following the comments below asking me to clarify my question, here is what I want to know: What are these duplicated services with different end names on my PC?. Knowing if they are viruses and why they are here would be part of the answer.  Since I'm already editing this post, it is worth to know that today, after restarting my PC, I found the previously shut down services had vanished from my PC and in their place I found a complete list of duplicated services with different end names, some of which were already stoped:    while some were running:


Why is this cumulative formula not working for my array?


Display difference between two dates using JavaScript

I need to display the difference between two dates in a text box using JavaScript. I tried the following code but it did not work:  function showdatediff(){     //get value of  the two dates     var date1 = document.getElementById('date1').value;     var date2 = document.getElementById('date2').value;     //cheack the diffrence     var timeDiff = Math.abs(date2.getTime() - date1.getTime());     var diffDays = Math.ceil(timeDiff / (1000 * 3600 * 24));     document.bookform.displaytextbox.value = (diffDays); }


As a stage 4 vampire, how can I feed without getting noticed?

I'm currently a stage 4 vampire in Skyrim. As soon as I try and sneak into a town to feed, I get spotted like a kilometer away, even with an invisibility potion. Nothing seems to work! I don't want to make a new character since I'm a pretty high level. Is there any way I can look for a place to feed without them noticing me!?


When developing a general purpose time-series software, is it a good idea to make it scale invariant? How would one do that?  I took a time series of around 40 points, and then multiplied by factors ranging from 10E-9 to 10E3 and then ran through the ARIMA functions of Forecast Pro and Minitab. In Forecast Pro, all resulted in the same answer (automatic modeling), whereas in Minitab, they were not. Not sure what Forecast Pro does, but they might just scale up or down all the numbers to a certain scale (let's say 100s) before running the model. Is this good idea in general?


What causes a black-body radiation curve to be continuous?

The  (unlike the quantized emission seen from atomic spectra), is continuous over all frequencies.  Many objects approximate ideal blackbodies and have radiation curves very similar in shape and continuity to that of an ideal black-body (often minus some emission and absorption lines from the atoms in an object, such as radiation curves seen from stars).  I am wondering what exactly gives rise to a basically continuous black-body radiation curve in real objects? Since atomic energy states are quantized, it seems real life black-body curves would have some degree of measurable quantization to them (or perhaps the degree of quantization is so small the radiation curves look continuous).


I have a script in my .bash_profile that prompts for X sessions to boot.  When I launch tmux, I get this prompt that I had only intended for the TTY login.  Is there something I can put in .bash_profile that will simply run bash if it is part of tmux?  That is, can I check with bash if .bash_profile is being read within tmux?


I have an AMD Radeon 8490 Graphics card running in an HP Prodesk desktop PC with an AMD A8-6410 CPU.  The system (and the garphics card) is 5 years old.  I am running Windows 7 professional (64-bit).  I will not upgrade to Windows 10.  There is a list from AMD of operating systems that my graphics card will run with. One is Ubuntu x86 64-Bit.  My questions is: does Ubuntu 18.04.4 LTS have the same foundation as Ubuntu x86 (to put another way) is 18.04.4 LTS the same basic operating system (ubuntu x86) that would be compatible with the AMD drivers for my graphics card that were released back in 2015?  Maybe I should also ask AMD the same question.  Thank you in advance for your help!


Scaling problem with fillbetween in pgfplots

I recently ran into scaling problems with the very nice pgfplots library fillbetween. See the following example, which is perfectly fine:  \documentclass{standalone} \usepackage{pgfplots} \usepgfplotslibrary{fillbetween} \pgfplotsset{compat=newest}  \begin{document}  \begin{tikzpicture}[scale=1.0]  \begin{semilogxaxis}[xmin=1,xmax=256,grid=both,legend pos=north west,             xlabel=Nb. of sub-domains,ylabel=Number of neighbors,legend cell align=left,             every axis y label/.style={at={(ticklabel cs:0.5)},rotate=90,anchor=near ticklabel},             xtick={1,2,4,8,16,32,64,128,256},xticklabels={1,2,4,8,16,32,64,128,256}] \legend{Min., Max., Average};  \addplot[color=blue,very thick,mark=*,name path=A] coordinates { (1,0) (2,1) (4,3) (8,4) (16,3) (32,3) (64,4) (128,4) (256,5) }; %Min \addplot[color=gray,very thick,mark=*,name path=B] coordinates { (1,0) (2,1) (4,3) (8,6) (16,9) (32,12) (64,15) (128,15) (256,16)}; %Max \addplot[color=black,very thick,mark=*] coordinates { (1,0) (2,1) (4,3) (8,5.5) (16,6.12) (32,7.88) (64,9.59) (128,10.50) (256,11.37)}; %Avg \addplot[orange,opacity=0.4] fill between[of=A and B];  \end{semilogxaxis}  \end{tikzpicture}   \end{document}     Now, I just change scale=1.0 to scale=0.8, and I obtain the following result:    Note that if I comment the "fillbetween" line in the code, everything works fine when scaling the picture. Does anyone has an idea about this ?  Cheers


Where is this traffic with doubleclick.net referrers coming from, and how can I block it in Google Analytics?

We're seeing Google Analytics report a huge amount of hits and large drop rate on some of our pages, but investigating this further reveals more questions than answers.  For instance, one page is reported to have over 1000 hits this month, but in our database (Magento) we only see 6 hits.  When I look into the Apache access log, I do see many GETs for this URL, but they all have a referrer like this:  http://dp.g.doubleclick.net/apps/domainpark/domainpark.cgi?client=dp-oversee17_3ph_xml&channel=001071&hl=en&adtest=off&max_radlink_len=20&r=m&fexp=21404&domain_name=hcartoon.com&optimize_terms=off&terms=Cartoon%2C%20Flash%20Animation%2C%20Caricature%2C%20Cartoon%20Picture%2C%20Free%20Animated%20Ecards%2C%20Cartoon%20Animation%2C%20Funny%20Posters%2C%20Cartoon%20Clip%20Art%2C%20Cartoonist%2C%20Toons%2C%20Cartoonist%2C%20Toons%2C%20Funny%20Picture%2C%20Cartoon%20Posters%2C%20Caricatures%2C%20Cartoonists%2C%20Toon%2C%20Business%20Cartoons&drid=as-drid-  And it goes on...  I'm assuming it is a feeble attempt to DDoS, but that's not the question, I'll save that for a different SE.  Could this be skewing our Google Analytics numbers?  If so, how can we sanitize Google Analytics so that these types of GETs aren't counted?  EDIT: We do not use AdWords.  We do have an AdWords account set up but have never utilized it.  I traced the logged IP addresses to various places outside the U.S. like  Sri Lanka, Taiwan, ...ad nauseam.  EDIT 2: All of the GET requests seem to have a ?gclid= in the URL.  I'm beginning to wonder if there's some black-hat SEO aimed at making us think our metrics are bad so we'll hire one of them.  We do get SEO spam all the time...  Regardless, still looking for a way to filter past Google Analytics data.


I need to know what model and year my Rocky mountain bike is

RM01XXG02FT0151 this is the serial number


USB configuration within Developer Options doesn't save

Just bought a Samsung Galaxy s7 Edge with Marshmallow pre-installed. I'm trying to get my phone to work with Android Auto.  The only way I could make my phone connect to my car is to enable Developer Options in the settings menu and change the USB configuration to "MTP Media Transfer Protocol".  My problem is that whenever I disconnect my phone, the change I made goes away and reverts back to "charging". So, now, every time I want to connect my phone to use Android Auto, I need to enter the settings and change the USB configuration back to MTP for it to work... really a pain in the butt.  Does anyone know if this is an Android issue or a Samsung issue? Also, is there a way to correct this?


Has Stack Overflow reached a saturation?

I am relatively new in computer science, but I am finding that that is very difficult for new programmers to survive on this website. This is because if a question is very basic, or if it appears too easy, the experienced programmers simply downvote it.  This was not the case when the website was started. For example, the people who asked questions like "Why main method should be static?" have 100k of reputation or even more. Why is this happening? Or do I have the wrong perception?


Can I use a strong alcoholic drink (40 % of ethanol) to disinfect frequently touched surfaces against COVID-19?

Can I use a strong alcoholic drink (containing mostly water and 40 % of ethyl alcohol) to disinfect the frequently touched surfaces indoors or even packed food items I buy in the supermarket)?   Vodka is still available at the shop, and the proper disinfecting fluid is not. I talked about external usage, I do not even think to drink it. Would it work at least in some degree?


I am an undergraduate taking a second semester course in Abstract Algebra. We just got started on Field and Galois theory, and my professor told us that he will teach us Grothendieck's formulation of Galois theory. He started talking about (basic) category theory, étale algebra, separable extensions, category of finite G-sets.  Can someone point me in the direction of one or several self-contained expositions of this approach to Galois theory that is suitable for a relatively inexperienced undergraduate? I have taken all the basic courses (calculus, linear algebra etc) plus a semester in topology and algebra, and I would like to see clear exposition with lots of examples if possible. Thank you.


Is there a software to automatically crop a scan of multiple images?

I want to digitize my old family albums using a scanner and there are lots of photos in them. Thus far, my method has been to scan 4 images at a time and then manually cropping them in a simple editor like Picasa or Windows Live Photo Gallery. This has been pretty time consuming as each scan is followed by 4 crop operations. Scanning each image individually would possibly be even more time consuming.  Is there any software or simple plugin (preferably free) that does this job? The best solution I have found is in , but that's an overkill. Is there a similar feature for one of the free photo editors like Paint.NET or GIMP?


Are there exceptions in the International Statute of Secrecy?

I was wondering what a wizard should do when a Muggle is about to be killed (let's say in a car accident) and a present wizard notices this in time to prevent this (for example by levitating the victim out of the way). Would the wizard be prosecuted because he violated the Statute or is there some kind of exception? From there, the next question is of course: (TLDR;) are there any exceptions in the Statute? Which?


"Let $R$ be an integral domain. Assuming that the Division Algorithm holds in $R[x]$, prove that $R$ is a field."

Let $R$ be an integral domain. Assuming that the Division Algorithm holds in $R[x]$, prove that $R$ is a field.   Can someone tell me if I am going about proving this correctly? My tactic was going to be to prove that every integral domain that works with the Division Algorithm (so I guess a Euclidean Domain) is finite, and thus would be a finite ring, which would make it a field based on the theorem that states just that. I don't know if this is valid logic, so could someone tell me if I'm at least on the right path?


Non-constant entire function-bounded or not?

Show that if $f$ is a non-constant entire function,it cannot satisfy the condition: $$f(z)=f(z+1)=f(z+i)$$  My line of argument so far is based on Liouville's theorem that states that every bounded entire function must be a constant.  So I try-to no avail-to show that if $f$ satisfies the given condition, it must be bounded. I haven't made much progress with this, so any hints or solutions are welcome.


Evaluating the integral $\int_{-1}^{1} \frac{\sqrt{1-x^{2}}}{1+x^{2}} \, dx$ using a dumbbell-shaped contour

I'm trying to evaluate the integral $$ I =\int_{-1}^{1}\frac{\sqrt{1-x^{2}}}{1+x^{2}} \, dx $$ by using a dumbbell/dogbone contour, but I'm having difficulty determining the residue at infinity.  I started by defining  $\sqrt{1-z^{2}}=\sqrt{(1-z)(1+z)} $ so that it is a well-defined function if the line segment $[-1,1]$ is omitted.  Similar to an , I choose the branches where $0 < \arg(1-z) \le 2 \pi$ and $-\pi < \arg(1+z) \le \pi$.  Then I integrated $ f(z) = \frac{\sqrt{1-z^{2}}}{1+z^{2}}$ clockwise around a dumbbell contour.  Just above the branch cut, $\arg(1-z) = 2 \pi$ and $\arg(1+z) = 0$.  And just below the branch cut, $\arg(1-z) = 0$ and $\arg(1+z) = 0$.  So the integral evaluates to $-I$ both above the cut and below the cut.  Since the integrand is meromorphic outside the contour, I get  $$ - 2I =  2\pi i \left( \operatorname{Res}[f,i]+ \operatorname{Res}[f,-i]  + \operatorname{Res}[f,\infty] \right),$$ where  $$\begin{align}  \operatorname{Res}[f,i] &=\lim_{z\to i }\frac{\sqrt{|1-z|e^{i\arg(1-z)}\ |1+z|e^{i\arg(1+z)}}}{z+i} =\frac{\sqrt{\sqrt{2}e^{\frac{7\pi i}{4}}\sqrt{2}e^{\frac{\pi i}{4}}}}{2i} \\ &=\frac{\sqrt{2}e^{\pi i}}{2i}=-\frac{\sqrt{2}}{2i}, \end{align}$$  $$ \begin{align}\operatorname{Res}[f,-i] &=\lim_{z\to-i }\frac{\sqrt{|1-z|e^{i\arg(1-z)}\ |1+z|e^{i\arg(1+z)}}}{z-i}=\frac{\sqrt{\sqrt{2}e^{\frac{\pi i}{4}}\sqrt{2}e^{\frac{-\pi i}{4}}}}{-2i} \\ &=\frac{\sqrt{2}e^{ 0\pi i}}{-2i}=-\frac{\sqrt{2}}{2i}, \end{align}$$ and  $$ \begin{align}\operatorname{Res}[f,\infty] &=\operatorname{Res}\left[-\frac{1}{z^{2}}f\left(\frac{1}{z}\right), 0 \right]= \operatorname{Res}\left[-\frac{\sqrt{z^2-1}}{z(1+z^{2})},0\right]\\ &=-\lim_{z\to 0}\frac{\sqrt{z^2-1}}{1+z^{2}} = -(-1)^{\frac{1}{2}}. \end{align}$$  But what is $(-1)^{\frac{1}{2}}$?   I assume it must be $i$, but I don't know how to argue that it can't be $-i$.  EDIT:  There is also the issue that Ted Shifrin mentioned of assuming that $\sqrt{z^{2}}=z$.


Unable to dismiss the suggested duplicate

Today someone suggested that my post was a duplicate of another post. I disagreed and dismissed the message by selecting the [No] button below, and clicking the [Submit] button.  This however doesn't dismiss this question. It comes back time and time again when reloading the post.


I have simulated the circuit with the following values. VDD = 1.8V, Vin is a sine wave with fin = 450MHz, pin = -5dBm, L1 = 12.5nH, C1 = 10pF, RL=50 ohm. I also gave a biasing dc voltage at the gate of MOSFET as 1V. I got the following graph after simulation.    The red graph is the input sine wave. The yellow graph is the current at the drain of MOSFET and the green one is the voltage at the drain of MOSFET. But I am not exactly getting what the graph means or how to interpret it? If I am using it as a power amplifier how can I improve the output values of voltage and currents?


Show that $x^{p^n}-x$ is the product of all monic irreducible polynomials in $\mathbb{Z}/p\mathbb{Z}[x]$ of a degree $d$ dividing $n$.

I know that if $F$ is a field of $p^n$ elements contained in an algebraic closure $\overline{\mathbb{Z}/p\mathbb{Z}}$ of $\mathbb{Z}/\mathbb{Z}p$, then the elements of $F$ are the zeros $x^{p^n}-x$, and also that the degree of $F$ over $\mathbb{Z}/p\mathbb{Z}$ is $n$, but I don't know where to go from here. Since the elements of $F$ are the zeros of $x^{p^n}-x$ in $\mathbb{Z}/p\mathbb{Z}[x]$, that means $x^{p^n}-x$ is the product of polynomials whose zeros are the elements of $F$, but how do I know that the degree divides $n$?


Caret gives non-zero test R-squared with linear model without predictors: why?

NOT A DUPLICATE For the persons who marked this question as a duplicate of : this is not a duplicate, as the correlation obtained with an intercept-only linear model would be NaN or 0, not 0.1 as mentioned in my post. Further I am asking how to use the most common R squared formulation and no answer is provided to that post.  Original post   I used caret with glmnet and selected repeatedcv (10-fold, 5 repeats) to choose the best glmnet parameters (alpha and lambda) in terms of Rsquared (i.e. better = larger Rsquared).  library(glmnet) library(caret) alpha.grid <- (1:20) * 0.05 lambda.grid <- 10^seq(4,-4,length=200) EN.param.grid <- expand.grid(.alpha=alpha.grid, .lambda=lambda.grid) train.params <- trainControl(method="repeatedcv", number=10, repeats=5) EN.fit <- train(x=X, y=Y, method="glmnet", tuneGrid=EN.param.grid,                  trControl=train.params, standardize=TRUE, metric="Rsquared")   Despite the best model having no remaining predictors (i.e. only an intercept), the associated Rsquared as provided by caret (as seen in EN.fit$results$Rsquared dataframe) should be 0 but it is not (in my case 0.1). Then, questions coming to mind are:   Is the test Rsquared calculated in caret in terms of correlation instead of the more traditional sum-of-squares method (as suggested by )? How to correct this behavior to obtain a test Rsquared of 0 for an intercept-only model (as many would expect), and still be able to correctly optimize a glmnet parameter search on Rsquared?


For any n>2 and any n by n matrix A over an arbitrary field, the adjugate of the adjugate of A equals the determinant of A to power n-2 times A. Is there a unified way, without dividing into two cases - A invertible and A non-invertible, to prove this result ?


How much memory is free? From my understanding i have 1GB of memory, and it says free is 71MB?   But why does it say that i have 536 free in buffers? So am I really using all my ram or not?               total       used       free     shared    buffers     cached Mem:           994        923         71          0        111        352 -/+ buffers/cache:        458        536 Swap:            0          0          0


Passport stamp when visiting multiple Schengen countries

I have a multiple entry Schengen visa for 1 year. When I enter France from outside Schengen, I get a French entry stamp, right? But if in France, after 10 days, I take a flight to Italy and I arrive there, will I get an Italian entrance stamp in my passport too? And when I take a plane from Italy to Denmark, will I get a Danish stamp too? Once I leave Europe I will get the exit stamp in my passport from the country where I leave to my outside EU home country, right?


Why did Death Star need to orbit around Yavin for so long?

We are talking about battle station with a hyperdrive. And there we have to wait till it orbits around Yavin to get a shot at the moon.   .  But why didn't they navigate DS1 so that it had a clear shot at the rebel moon in the first place?  And why couldn't it orbit faster?    (Source: )


How should I transform "Jane has just broken her leg" into a question starting with "Who" and whose answer is "Jane"?

How should I transform this sentence into a question?  Jane has just broken her leg.  How do I form a question from that sentence so that it starts with who and whose answer is Jane?  Q: Who__________? A: Jane.  Is it all right to ask it this way:  Who has just broken his or her leg?


Prove that, if a, b are prime numbers $a > b$, each containing at least two digits, then $a^4 - b^4$ is divisible by $240$. Also prove that, $240$ is the gcd of all the numbers which arise in this way.  Looking at the prime factorisation $240=(2^4)*3*5$, i know i need to prove that the given difference is divisible by each of these.  How do i proceed from here? i have no idea. Thanks.


Is there a way for me to create a RSS feed of all my posts across all Stack Exchange sites?

What about an RSS feed for activity like the one shown ?


Is it true $\mathbb Q(\sqrt{2},\sqrt[3]{2})=\mathbb Q(\sqrt{2}+\sqrt[3]{2})$? If yes prove it if not explain why I can show that  $\mathbb Q(\sqrt{2}+\sqrt[3]{2})$ ⊂  $\mathbb Q(\sqrt{2},\sqrt[3]{2})$ but im not sure that $\mathbb Q(\sqrt{2},\sqrt[3]{2})$ ⊂ $\mathbb Q(\sqrt{2}+\sqrt[3]{2})$.


For my thesis, I want to mention that Apple Pay is often stylized as  Pay, but the compiler warns me that this is an unknown character. It outputs Ô£ø. I have found that this symbol is encoded as \uF8FF.  How can I put this so that it outputs the apple symbol?


I made a suggested edit here:   removing the iPhone tag as the question didn't relate to iPhone. The edit was rejected by "Community", but the same edit was made later () by   Just wondering why my edit to remove the tag wasn't good enough, while Geoffroy's was?


Null pointer Exception in java while finding no of values in given range in val tree

I am trying to print no of  node values in a given range in an avl tree .But when I try to run the program I get NullPointerException.  I couldn't get much help from previous questions of same topic.How can i correct it here.Here's my code of that portion:  public void range(int low, int up){     if(low >up){         System.out.println("Illegal input");     }      if(this.root != null){         System.out.println(rangeS(this.root,low,up) +"");     }  }  public static int rangeS(AvlNode root,int k1 ,int k2){     int c = 0;     if(root.key >= k1 && root.key <= k2){         c = c+1;     }     if(root.key > k1 ){         rangeS(root.left,k1,k2);     }      if(root.key <k2){         rangeS(root.right,k1,k2);     }     return c; }


What is the best place for storing uploaded images, SQL database or disk file system?

I'm writing an application that allows users to upload images onto the server. I expect about 20 images per day all jpeg and probably not edited/resized. (This is another question, how to resize the images on the server side before storing. Maybe someone can please drop a .NET resource for that in the comment or so).  I wonder now what the best place for storing uploaded images is.   Store the images as a file in the file system and create a record in a table with the exact path to that image. Or, store the image itself in a table using an "image" or "binary data" data type of the database server.   I see advantages and disadvantages in both.  I like a) because I can easily relocate the files and just have to change the table entry. On the other hand I don't like storing business data on the web server and I don't really want to connect the web server to any other datasource that holds business data (for security reasons)  I like b) because all the information is in one place and easily accessible by a query. On the other hand the database will get very big very soon. Outsourcing that data could be more difficult.


What does this warning message mean?  Underfull \hbox (badness 10000) in paragraph at lines 49--50   This is my code, I can't see what happens, it is a simple itemize. As you see, there is an admiration symbol, I don't know what is going on.    I have also this warning, another admiration symbol:  Underfull \hbox (badness 6893) in paragraph at lines 77--78     I am working in article as class document. That is just text, no reference mode.


How to combine several C/C++ libraries into one?

I'm tired of adding ten link libraries into my project, or requiring eight of them to use my own. I'd like to take existing libraries like libpng.a, libz.a, libjpeg.a, and combine them into one single .a library. Is that possible? How about combining .lib libraries?


Server error when client accesses concurrently

Good afternoon .. can anybody help me? The following error below is occurring on the server, when many clients connect at the same time. "java.net.SocketException: connection reset." Does anyone know what this error is?


I want to model the earth 1:1 in unity, but I can only zoom to a certain value in the scne window of unity


Is there a more efficient way to turn mobile hotspot on / off?

I'd like to reduce the number of steps needed to turn mobile hotspot on or off. Currently it's unlock, then five taps.  Galaxy Note 4, Android 5.0.1 Lollipop.  I did find , but it's from 2012 and a lot has changed since then probably.


File manager's column "Date Modified" doesn't show time?

I am using Xubuntu 14.04. In the File Manager, the Date Modified column doesn't show the modification time. How can I make it display the time, along with the date?


If $x^2+y^2 \equiv 0\pmod{p}$, then $p \equiv 1 \pmod{4}$

Prove that if $x^2+y^2 \equiv 0\pmod{p}$ where $p$ is a prime and $x,y$ are not both divisible by $p$, then $p \equiv 1 \pmod{4}$.   I tried using that $x^2 \equiv -y^2 \pmod{p}$ and conjectured that $-1$ must a quadratic residue modulo $p$, but I am not sure how that would help.


What would be the difference in output between "man ifconfig" and "man ifconfig | less"?

I am stuck currently on this question while learning Linux. Can anyone help me?


What happens to the air in the area, when things are transported or replicated?

A fundamental law of physics is, in short, that two things cannot exist in the same space at the same time.  This is easily demonstrated by dropping a relatively large mass, such as pasta noodles, into a container of water, such as a pot.  The water level will rise as it "makes room" for the pasta, and will overflow if you've put in too much of either.  Conversely, if you were to scoop all of the noodles out (presuming you had a way to scoop just the noodles, without taking along any water at all) you would see the water sink down to its original level (or lower, if it had overflown earlier).  Taking this into consideration, I see a problem with transporter technology which I'm not sure I've ever seen addressed:  What happens to the air surrounding a transport subject's origin point, or occupying the destination?  The transporter must have some means of compensating for the displacement, otherwise each transport should in theory be accompanied by a loud pop at each end - at the origin when the air collapses to fill a vacuum left behind, and at the destination when a relatively large volume of air is forced away to make room for the subject.  This effect should be even more pronounced, and perhaps even hazardous, in closed environments such as spacecraft where the air has really no place to go.  One option would be to have the transporter exchange the air (or other matter, such as dust or raindrops) at the destination for the matter of the subject, as it is being transported.  However, this is not seen as we would often notice small portions of dust storms or downpours getting dropped onto the transporter pad when people are transported into adverse weather conditions.  Imagine having that cleanup as part of the Transporter Chief's job duties.  Another option would be to process the matter from the destination through the replicator, so that it is congruous with the same volume of air at the origin.  This would be a fairly complex operation though, and could result in a lag too long to be acceptable by the laws of physics.  Come to think of it, this same (or a similar) issue should affect replicator and holodeck technology as well.  Has any of this ever been addressed canonically, either in a Star Trek episode or in technical manuals?


Is it appropriate to access a class' private members by casting it to a void pointer and then to a struct?    I don't think I have permissions to modify the class that contains the data members that I need to access.  I don't want to take a risk accessing the data members in an indirect way if it is not ethical.  EDIT: Had to edit this further... I am pretty sure the class wouldn't be modified, so it's ok to that extent... my only concern is, if the person who coded that class gets to know of this, it might not go down well with him :(.


Mbp 15 retina early 2013-waiting for disks to reappear

I have a mbp 15 early 2013 model. It was running smoothly until yesterday suddenly it passed out with a folder question mark screen. so I went to recovery because I can't boot up. In the startup disk I can't find my ssd and in disk utility can't first aid my ssd and even can't erase my ssd to perform a fresh install.. when tried erasing in terminal it shows up the error waiting for disks to reappear.. so I think that ssd is working fine because it shows up on the disk utility, so this might be a controller problem in which in my case I don't have a hard drive cable, instead I think it's part of the logic board where ssd has to be plugged.. suggest me a solution.. Sorry for my explanation if it's bad.. I'm very much worried 😯 as of now..  My question is different.. the apple genius couldn't figure out whether it's logic board or ssd.. because both are functioning properly in diagnosis.  how it is different.. I cant able to format using gparted.. so by using terminal I tried pdisk commands and was able to create and write partitions.. so does it conclude that ssd is still working.. if so what could have been the error


Do I need a transit visa at Amsterdam to stay in airport?

I have an Indian passport and would be travelling from Japan to St. Petersberg (Russia) via Amsterdam. I have 20 hours stopover for KLM flight at Amsterdam. Though I have hotel bookings outside, but it seems I do not have time to get a Schengen visa to go out of Airport. So in this case can I stay inside the terminal for 20 hours without any need of VISA? I can manage only with cabin bag and all the flights are with KLM. I have exactly same situation during return trip.


Why is a forward declaration not enough even if the data type is never used

I know that similar questions have already been asked and there are answers describing that in the situations describe below forward declaration is not enough. However, these answers do NOT tell WHY it is not enough. Therefore, I don't think that this is a duplicated question.  I have some difficulties to understand why the compiler has to see the definition of a data type (a foward declaration is not sufficient) in the following situation:  Let's consider we have a simple "main.cpp" as shown below, which does absolutely nothing except including the header file "MyClass.hpp"  #include <MyClass.hpp>  int main(int argc, char **argv) {     return 0; }   Now, let's consider that the content of "MyClass.hpp" looks as follows:   #include <vector>  class Data1;  class MyClass { public:     MyClass();                                      // default constructor     MyClass(MyClass const & p_other);               // copy constructor     MyClass(MyClass && p_other);                    // move constructor     ~MyClass();                                     // destructor     MyClass & operator=(MyClass const & p_rhs);     // copy assignment     MyClass & operator=(MyClass && p_rhs);          // move assignment private:     Data1 *            m_a; // forward decl. always OK     Data1              m_b; // forward decl. always not OK     std::vector<Data1> m_c; // forward decl. OK if MyClass is not instantiated };   MyClass contains several member variables:    "m_a" is a pointer to "Data1",  "m_b" is an instance of "Data1", "m_c" is a vector with elements of type "Data1".    The definition of "Data1" is neither included in "MyClass.hpp" nor in "main.cpp". It is just forward declared.  The compiler never has a problem with member variable "m_a", it doesn't require its definition for compiling "main.cpp" -- even if we would intantiate "MyClass".  Because we are not instantiating "MyClass", the compiler also doesn't have a problem with member variable "m_c". It also does not require the definition of "Data1" in this case.  However, the compiler has a problem with member variable "m_b":     Impl1.hpp:16:24: error: field 'm_b' has incomplete type 'Data1'   My simple question is: why?  Please consider that we have user-defined default constructor, copy constructor, move constructor, a user-defined destructor, and user-defined copy assigment operator and move assignment operator, i.e., the compiler doesn't have to generate code for any of these constructors/methods. So for what purpose does the compiler need to see the definition of "Data1" when compiling only "main.cpp"?  Does anybody know the answer?


How to plan for buying drive capacity for a NAS?

I am, planning a NAS upgrade. We are currently running dozens of low capacity, cheap drives. We are upgrading to a Synology NAS with far fewer, higher capacity drives. As such, these drives will have a higher cost per TB that our lower capacity drives if bought today.  Based on the  that just came out, prices per TB have leveled out, so assuming that trend remains the same for the next few years to come, there little risk of buying drives a t price per TB far greater than what it will be in a few years.  So, assuming drive price per TB remains relatively constant, is there a standard rule/guidance/practice for planning capacity for a NAS? In other words, how should I determine if I should buy capacity for 1, 2, 3, 4, or 5 years from now for storage requirement that is growing year over year?  I realize this question could be seen as subjective, however, I am asking for an objective standard rule/guidance, or commonly accepted IT best practice for planning NAS capacity, which hopefully, makes it more of an objective ask.  It has been pointed out that this question may be a duplicate of an  on Server Fault, but the only answer that comes close to addressing my question references an "Axiom" that summarizes one should just buy large drives instead of small ones. My concern is around for how many years in the future should one buy drive capacity. Based the the responses so far, it may be that there isn't an IT standard rule/guidance/practice for planning such a thing. If that is the case, then that is my answer.   Thank you.


Does Marvel/Disney have film rights to the Human Torch android?

In Captain America: The First Avenger, we see in the Stark Expo a reference to 'Phineas T. Horton's Synthetic Man'.  In Marvel comics, this was the original Human Torch.    Does Marvel actually have the rights to this character, or was this kind of a cheeky nod to Chris Evans playing a Human Torch?


What is the LINQ way to implode/join a string array?

I have the following string array:  var sa = new string[] {"yabba","dabba","doo"};   I can convert it to "yabba, dabba, doo" it using string.Join() but what is the super-cool LINQ way of doing it?  The Join extension method seems promising but for a novice like me very confusing.


Simplifying the infinite series $\sum_{n = 1}^{\infty} \left(\frac{1}{2}\right)^{3n}$

Does anyone know of a way to simplify   $$ \sum_{n = 1}^{\infty} \left(\frac{1}{2}\right)^{3n} $$  to a number?


Java Maven project cannot find dependency

Whenever I try to run my project as maven install, it creates a completely normal jar file. It is a swing gui application. However, when I click a button in the GUI that uses this , it ouputs the error below. Exception in thread "Thread-2" java.lang.NoClassDefFoundError: com/neovisionaries/ws/client/WebSocketException     at bot.BotFunc.run(BotFunc.java:30)     at java.lang.Thread.run(Thread.java:748) Caused by: java.lang.ClassNotFoundException: com.neovisionaries.ws.client.WebSocketException     at java.net.URLClassLoader.findClass(URLClassLoader.java:382)     at java.lang.ClassLoader.loadClass(ClassLoader.java:418)     at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:352)     at java.lang.ClassLoader.loadClass(ClassLoader.java:351)     ... 2 more  my pom.xml looks like this: <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">   <modelVersion>4.0.0</modelVersion>   <groupId>HelixBot</groupId>   <artifactId>HelixBot</artifactId>   <version>1.1</version>   <build>     <sourceDirectory>src</sourceDirectory>     <plugins>       <plugin>         <artifactId>maven-compiler-plugin</artifactId>         <version>3.8.1</version>         <configuration>           <source>1.8</source>           <target>1.8</target>         </configuration>       </plugin>       <plugin>         <groupId>org.apache.maven.plugins</groupId>         <artifactId>maven-jar-plugin</artifactId>         <version>3.2.0</version>         <configuration>           <archive>             <manifest>               <mainClass>gui.GUIMain</mainClass>             </manifest>           </archive>         </configuration>       </plugin>     </plugins>   </build>   <dependencies>   <dependency>     <groupId>com.neovisionaries</groupId>     <artifactId>nv-websocket-client</artifactId>     <version>2.14</version>   </dependency>   </dependencies>   <packaging>jar</packaging> </project>  As you can see, the correct dependency is added, so I am not sure why this error is appearing. I have tried clean building it and checked the .project and .classpath files. It may be due to the fact that I converted it to maven from a regular java project, but I have not found anything. Please let me know if there is a possible solution.


Prove that there are two numbers among them such that one divides the other

We have n+1 numbers from the set {1...2n} and prove that there are 2 such that one divides the other... I just could not understand the solutions that already exist some


The following code  \documentclass{amsart} \usepackage{fontspec} \usepackage{unicode-math} \setmainfont{Minion Pro} \begin{document}   \title{A motif approach to the Mordell conjecture}   \author{Shurik G.}   \maketitle \end{document}   compiles differently with XeTeX:  and LuaLaTeX:  Why does LuaLaTeX produce the title in italic? How can one solve the problem keeping the LuaLaTeX engine? I checked that LuaLaTeX works correctly with other fonts, including Cambria. TeXlive 2016 with updates, Linux x86_64.


I am trying to count all cells that contain this exact string somewhere in the cell   "(w)" The formula below shows 1 when there are none found How can I make it show 0 if none are found?      COUNTA(FILTER(D2:D55, REGEXMATCH(D2:D55, "(w)")))


I have a partially downloaded video file (the download was paused). It is a large file and a significant portion has already been downloaded. I accidentally renamed it to .mp4 and its format got changed to .mp4. But I need to convert it back to .part to resume the download. I tried renaming it to .part but that didn't change its format, just the name got changed.  How do I convert the file to .part format?


I would like to do something like this:  \immediate\write18{git log -1 --pretty=format:"%h-%ad" --date=short > /tmp/temp.dat }   however, xelatex cannot proceed because the % means comment out if I do this:  \immediate\write18{git log -1 --pretty=format:"\%h-\%ad" --date=short > /tmp/temp.dat }   The call is actually:   git log -1 --pretty=format:"\%h-\%ad" --date=short > /tmp/temp.dat   which will have extra \ in it.  How can I let the shell command use % instead of \% ?


disable launcher icons in another workspace

I use one workspace for watching movies and another workspace for my work. I don't want that folder icon opened in one workspace to be displayed in other workspace  i.e. and  . How can I remove the highlighted firefox in 2nd workspace? I am using ubuntu 14.04


Anybody can participate in chat by just joining 20 sites?

I just noticed  who is able to participate in chat despite not having any more than 1 reputation point on any site. Unless there's a hidden profile involved here, it looks like just joining 20 sites is enough to get chat privileges. This specific user isn't causing any trouble, he/she is perfectly fine, I'm concerned that this rep totaling behavior can be used to get around the necessity of amassing some reputation before joining chat. Is this intended? If rep summation should be usable to gain entry to chat but this strategy shouldn't, the algorithm could subtract one from every profile before considering it; that way, only earned points would count. There would probably have to be the extra complication of checking if any profile owned by the user has 20 points, otherwise one would need to get 21 points.


As part of am exam question (Q21F ), I'm trying to prove that if $X$ and $Y$ are path-connected, locally path-connected spaces with universal covers $\widetilde{X}$ and $\widetilde{Y}$, respectively, then if $X \simeq Y$ then $\widetilde{X} \simeq \widetilde{Y}$.  My attempt might be correct, but it seems too complicated and amongst the jumble I may have made some incorrect assumptions. So what I'm looking for is (a) verification or correction; and (b) ideas as to how I could simplify my argument.    My argument:  Let $p:\widetilde{X} \to X$ and $q:\widetilde{Y} \to Y$ be the covering maps, and let $X \overset{f}{\underset{g}{\leftrightarrows}} Y$ be a homotopy equivalence.  Fix a point $\widetilde{x} \in \widetilde{X}$, let $x=p(x) \in X$ and $y=f(x) \in Y$, and fix $\widetilde{y} \in q^{-1}(\{y\}) \subseteq \widetilde{Y}$. Also let $x' = g(y) \in X$ and fix $\widetilde{x'} \in p^{-1}(\{x'\}) \subseteq \widetilde{X}$.  Define a map $\widetilde{f} : \widetilde{X} \to \widetilde{Y}$ as follows. For $\widetilde{z} \in \widetilde{X}$ let $\widetilde{u}:[0,1] \to \widetilde{X}$ be a path from $\widetilde{x}$ to $\widetilde{z}$. Let $z=p(z)$ so that $u=p\widetilde{u}$ is a path in $X$ from $x$ to $z$. Let $v=fu$, so that $v$ is a path in $Y$ from $y$ to $f(z)$. Lift $v$ to a path $\widetilde{v}$ in $\widetilde{Y}$ with $\widetilde{v}(0) = \widetilde{y}$. Define $\widetilde{f}(\widetilde{z}) = \widetilde{v}(1)$.  Notice that $q\widetilde{v}=v$ so that $q\widetilde{f} = fp$.  Define $\widetilde{g}:Y \to X$ analogously: For $\widetilde{z} \in \widetilde{Y}$ let $\widetilde{a}:[0,1] \to \widetilde{Y}$ be a path from $\widetilde{y}$ to $\widetilde{z}$. Let $z=q(z)$ so that $a=q\widetilde{a}$ is a path in $Y$ from $y$ to $z$. Let $b=fa$, so that $b$ is a path in $X$ from $x'$ to $g(z)$. Lift $b$ to a path $\widetilde{b}$ in $\widetilde{X}$ with $\widetilde{b}(0) = \widetilde{x'}$. Define $\widetilde{g}(\widetilde{z}) = \widetilde{b}(1)$.  Likewise, notice that $p\widetilde{g}=gq$.  Claim: $\widetilde{X} \overset{\widetilde{f}}{\underset{\widetilde{g}}{\leftrightarrows}} \widetilde{Y}$ is a homotopy equivalence.  We have $p\widetilde{g}\widetilde{f} = gq\widetilde{f}=gfp \simeq p$ and $q\widetilde{f}\widetilde{g} = fp\widetilde{g} = fgq \simeq q$.  This shows that $\widetilde{g}\widetilde{f}$ and $\widetilde{f}\widetilde{g}$ are covering translations (deck transformations) and are therefore homotopic to the respective identity maps. So we have a homotopy equivalence.    Any comments would be appreciated.


I used to use Windows and Ubuntu on my pc. But I'm no longer a Windows user, now only Ubuntu. I tried to instal Ubuntu over the Windows, but grub still installed and asks every boot which system should it start. Theres a way to remove completly and start straight on Ubuntu?


Limit of a sequence $\frac1{n + 1} + \frac1{n + 2} + \cdots + \frac1{n + n}$

Do you know how to calculate $$\lim_{n\to\infty}\left(\dfrac1{n + 1} + \dfrac1{n + 2} + \cdots + \dfrac1{n + n}\right)\,?$$  Would be it correct to present this as $$\lim_{n\to\infty}\left(\sum_{k = 1}^n\dfrac1{n + k}\right)\,?$$


biblatex not recognizing references (but does in Overleaf)

A document in Overleaf compiles fine with references. However, using the same compiler locally yields "Citation x on page n undefined (...)", and the references are not showing, only the bracket with the labels: [label]  Using biblatex as so:  \documentclass{report} \usepackage[utf8]{inputenc} \usepackage{biblatex}  \addbibresource{references.bib}  \begin{document} \paragraph{} yoyo \cite{kniberg2015}  \printbibliography  \end{document}   with references.bib:  @book{kniberg2015,     title     = {Scrum and XP from the trenches - How we do Scrum},     author    = {H. Kniberg},     year      = {2015},     publisher = {C4Media} }   As mentioned, this works fine in Overleaf. I do have biblatex installed locally.


For any subset $S\subseteq\{1,2,\ldots,15\}$, call a number $n$ an anchor for $S$ if $n$ and $n+\#(S)$ are both elements of $S$. For example, $4$ is an anchor of the set $S=\{4,7,14\}$, since $4\in S$ and $4+\#(S) = 4+3 = 7\in S$.   Given that $S$ is randomly chosen from all $2^{15}$ subsets of $\{1,2,\ldots,15\}$ (with each subset being equally likely), what is the expected value of the number of anchors of $S$?     Mila has four ropes. She chooses two of the eight loose ends at random (possibly from the same rope) and ties them together, leaving six loose ends. She again chooses two of these six ends at random and joins them, and so on, until there are no loose ends. At this point she has somewhere between one and four loops of rope (inclusive). Find the expected value of the number of loops Mila ends up with.   I don't really know how to start, but thanks for helping.


Why do we use word prime with base pairing in DNA such as 5-3 prime.. prime stand for?

I was reading base pairing sequence in DNA and found 5-3 direction but my question is why we are using word prime with 5 or 3 such as 5 prime 3prime. Prime stand for?


how would i get the current size of the variable in java

Yes , this question is little bit vague and any serious programmer would laugh about it ! Although java does not tell about the sizes it assigns to the varibles ,i mean it can give more memory or less memory depending on the situation( that way it is abstracted !)i know that stuff! but what i am asking is ,is there any technique that i can know about the runtime variable size ? i want to find the addresses of the variables too ! This question does not want any answers like ,see java docs it does not provide those functionality you have asked , i want some kind of hack to do this kind of stuff!


Is she not a girl? Isn't she a girl? Am I not here? Am not I here?   Are tey all correct or right structured?


"assume to the contrary" vs "assume on the contrary"

I find that when proving a theorem by the method of contradiction, some authors start by saying "assume to the contrary" while some use "assume on the contrary". According to this , it seems that "to the contrary" and "on the contrary" have subtle differences. So my question is which one should I use, "assume to the contrary" or "assume on the contrary"? Below is an example.  Theorem. A is equal to B. Proof: Assume on/to the contrary that A does not equal B. ...


Algebraic closure not even finitely generated over base field

Show the algebraic closure $\bar{\mathbb{Q}}$  is not even finitely generated over the field $\mathbb{Q}$   I'm not sure how to go about this..


I have a sharepoint list with managed metadata column and I have to find items matching values from columns. If I filter the list for a column, let's say COLUMN1  <In>         <FieldRef LookupId='TRUE' ID='919cad04-5872-42a5-8c79-93e38e5e5b96' />         <Values>           <Value Type='Integer'>65</Value>         </Values>       </In>   It returns the record RECORD1.  Now i filter the list for a second column, let's say COLUMNB,   <In>         <FieldRef LookupId='TRUE' ID='5a6a5ee4-d125-4c99-9109-f943d8da7af0' />         <Values>           <Value Type='Integer'>68</Value>         </Values>       </In>   It returns record RECORD2. The issue is that if I run the query  <Or>         <In>           <FieldRef LookupId='TRUE' ID='5a6a5ee4-d125-4c99-9109-f943d8da7af0' />           <Values>             <Value Type='Integer'>68</Value>           </Values>         </In>         <In>           <FieldRef LookupId='TRUE' ID='919cad04-5872-42a5-8c79-93e38e5e5b96' />           <Values>             <Value Type='Integer'>65</Value>           </Values>         </In>       </Or>   No record is returned. I was expecting both record RECORD1 and RECORD2. BTW SharePoint version is 2010.  Any help is appreciated


.bashrc and .bash_profile not created with adduser but created with useradd

I am adding a user named 'test' in my Ubuntu 18.04 server. When I add the user using adduser, like this:  sudo adduser --system --group test --shell /bin/bash   all goes well, I can login fine, but .bashrc, .bash_logout and .bash_profile are not made by default in the home dir. Whereas when I added the user using useradd like this:  sudo useradd -m test -s /bin/bash   the user is added in the same way as adduser and I have a preconfigured .bash_profile, .bashrc and .bash_logout in the home dir.  Can someone explain why is there a difference ? Am I missing any flag in adduser usage ?


Sometimes, a volume refuses to eject because some program is using them.  Sadly, Finder doesn't give the identity nor gives a way to solve the problem.  So, how do you solve this problem in a clean way, without using a terminal ?  Using the terminal, I may find a way to eject it, but it's not reliable.  sudo lsof | grep volumeName certainly gives some information, but I don't feel like killing random processes in order to unmount a volume. Also, not everybody is willing to run command in a terminal.  I also don't want to force eject the volume. I think we shouldn't have to force the ejection when we didn't initially run the program that locks the volume.  Processes that are frequently involved are: mds and notifyd.  Killing mds does not guarantee that the ejection of the volume will be possible. mds process is respawned after getting killed, and continues preventing the ejection of the drive.  I also noticed that mds can be running and using files, and still not preventing the ejection of the volume, so I'm not even sure that it's mds fault.


What is the number of odd coefficients in the expansion of $(1+x)^n$  if $n = 3$  The coefficients for binomial expansion of $(1+x)^3$ are 1 3 3 1, out of which all are odd ,so answer is 4.  So what will be the answer in terms of $n$?


I had a theory that casting from long to int with a value greater than int.MaxValue or less than int.MinValue would result in an exception. The issue I had at the time was identifying which type of exception was going to be thrown. I naturally assumed it would be an OverflowException or an InvalidCastException, but imagine my surprise when the following snippet didn't explode at all! int x = 0; long y = int.MaxValue; y += 3;  try {     x = (int)y; } catch (Exception e) {     Console.WriteLine(e.GetType()); }  This instead resulted in a value equal to int.MinValue + 2: x:            -2147483646 int.MinValue: -2147483648  So my curiosity has the best of me at this point, and I've done a fair amount of digging to learn that I can cause an exception to be thrown (thanks to ) by utilizing the checked keyword (emphasis mine):  Overflow checking can be enabled by compiler options, environment configuration, or use of the checked keyword. The following examples ... Both examples raise an overflow exception.  Meaning, if I simply utilize the checked keyword, an OverflowException will be thrown (and it is): try {     x = checked((int)y); } catch (Exception e) {     Console.WriteLine(e.GetType()); }  After reading , I've learned that the default behavior is to allow the overflow to occur:  By default, these non-constant expressions are not checked for overflow at run time either, and they do not raise overflow exceptions. The previous example displays -2,147,483,639 as the sum of two positive integers.   TL/DR: Why is the default behavior in C# to allow overflow to occur? Doesn't this lead to unexpected behaviors? Note: I understand that the bit flips and that's what causes it to go negative; I'm just curious as to why it's allowed to flip instead of throwing an exception by default. In a nutshell, why do we have to explicitly state we want things to explode?


Input type=password, don't let browser remember the password

I remember seeing a way to have an <input type="password" /> such that the browser will not prompt the user to save the password. But I'm drawing a blank. Is there an HTML attribute or some JavaScript trick that will do this?


Why did the Time Turner change the events in Prisoner of Azkaban?

When Harry, Ron and Hermione were first trying to complete their task "strange" things kept happening, such as being hit with rocks, saving Buckbeak (whether he was actually killed the first time, or it was just implied, however the wincing look on the trios face upon witnessing the execution would suggest that he was) howling to distract the transformed Prof. Lupin and casting a physical stag Patronus.      It was later revealed that these were in fact caused by their future selves via use of the Time Turner to try and change how events went down.   After using the time turner, the "present" Harry and Hermione (as opposed to their future selves) were now the ones committing these acts. The same disruptions seemingly took place, yet the timeline somehow changed.  How is this possible?


Make back/forward work on paginated lists

When viewing a list of my own questions, if I switch to page 2 of the list I can't go back to page 1 by clicking the "Back" button in the browser.  I understand this is by design, but can the back button be made to work in this case please?


What is the most effective way for float and double comparison?

What would be the most efficient way to compare two double or two float values?  Simply doing this is not correct:  bool CompareDoubles1 (double A, double B) {    return A == B; }   But something like:  bool CompareDoubles2 (double A, double B)  {    diff = A - B;    return (diff < EPSILON) && (-diff < EPSILON); }   Seems to waste processing.  Does anyone know a smarter float comparer?


I write a vector with an arrow above the letter using \vec{p} and sometimes the vector needs to be primed using ' (or ^{\prime}, equivalently).  However, neither  \vec{p}'     nor  \vec{p'}     looks satisfactory (first option: prime dash overlaps with vector arrow, second option: arrow looks misplaced).  How would one write a primed vector?


Is there a way to transfer Jetpack joyride profiles from iphone to android?

I had a pretty solid profile with a few purchases on my ipod. have since upgraded to android. anyway to transfer my profile?


I tried to install git in my machine but i got a error message like below?

I tried all the possibility kindly let me know how resolve this error message and how to install git in my machine,  (personal)root@ubuntu:/home/shan/workspace/projects# apt-get -f install git-core Reading package lists... Done Building dependency tree        Reading state information... Done You might want to run 'apt-get -f install' to correct these: The following packages have unmet dependencies:  git-core : Depends: git (> 1:1.7.0.2) but it is not going to be installed  mysql-server-5.5 : Depends: mysql-server-core-5.5 (= 5.5.35-0ubuntu0.12.04.1) but 5.5.35-0ubuntu0.12.04.2 is to be installed E: Unmet dependencies. Try 'apt-get -f install' with no packages (or specify a solution).


Command Line Rendering - "cannot render, no camera"

I'm rendering a few scenes with command line and it works fine with most of them. But there is one scene where I get the following error: "cannot render, no camera". I can manually render it because there is indeed a camera in the scene.  I erased everything that could cause trouble ending up with only a cube and a camera. And all properties match with the working scenes but it's still not working with this file.


Android: "java.lang.NullPointerException: Attempt to invoke virtual method ... on a null object reference" when creating socket

I'm attempting to send a message to a server using sockets. I'm using a Runnable and getting the following error:  W/System.err: java.lang.NullPointerException: Attempt to invoke virtual method 'java.io.OutputStream java.net.Socket.getOutputStream()' on a null object reference W/System.err:     at XXX.FullscreenActivity.attemptConnect(FullscreenActivity.java:387) W/System.err:     at java.lang.reflect.Method.invoke(Native Method) W/System.err:     at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:270) W/System.err:     at android.view.View.performClick(View.java:5198) W/System.err:     at android.view.View$PerformClick.run(View.java:21147) W/System.err:     at android.os.Handler.handleCallback(Handler.java:739) W/System.err:     at android.os.Handler.dispatchMessage(Handler.java:95) W/System.err:     at android.os.Looper.loop(Looper.java:148) W/System.err:     at android.app.ActivityThread.main(ActivityThread.java:5417) W/System.err:     at java.lang.reflect.Method.invoke(Native Method) W/System.err:     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) W/System.err:     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616) W/System.err: ERROR: Attempt to invoke virtual method 'java.io.OutputStream java.net.Socket.getOutputStream()' on a null object reference   This is the line I'm getting the error on:  PrintWriter out = new PrintWriter(new BufferedWriter(                         new OutputStreamWriter(clientsocket.getOutputStream())),                         true);   The full code of the connection code is:  EditText editTextAddress = (EditText) findViewById(R.id.address); EditText editTextPort = (EditText) findViewById(R.id.port); SERVER_IP_loc = editTextAddress.getText().toString(); SERVERPORT_loc = Integer.parseInt(editTextPort.getText().toString()); System.out.println("AttemptConnect: IP " + SERVER_IP_loc +     " Port: " + SERVERPORT_loc); Thread myTask = new Thread(new ClientThread(SERVER_IP_loc, SERVERPORT_loc)); myTask.start(); final String message = "CONNECT"; try{ PrintWriter out = new PrintWriter(new BufferedWriter(                         new OutputStreamWriter(clientsocket.getOutputStream())),                         true); } catch (Exception e) {     e.printStackTrace();     System.err.println("ERROR: " + e.getMessage()); }   The socket is apparently null, but I can't figure out why. I'm starting the socket before attempting to send the message. The ClientThread code is a runnable:  class ClientThread implements Runnable {     ClientThread(String addr, int port) {         System.out.println("IN CLIENT THREAD");         SERVER_IP = addr;         SERVERPORT = port;         testMainThread(8);     }     @Override     public void run() {         testMainThread(9);         try {             InetAddress serverAddr = InetAddress.getByName(SERVER_IP);             System.out.println("RUN2");             if(Looper.getMainLooper().getThread()==Thread.currentThread()) {                 System.out.println("in main thread, don't make socket.");             }             else {                 System.out.println("not in main thread, make socket.");                 try {                     clientsocket = new Socket(serverAddr, SERVERPORT);                  }catch (Exception e3) {                     e3.printStackTrace();                 }             }         } catch (Exception e1) {             e1.printStackTrace();         }     } }


In which Comic Book series is Batman actually Thomas Wayne?

I've heard people say that there is a series of comics where Batman is actually Thomas Wayne instead of his son, Bruce.   Where can I find this? What is the series called?


Reference in IEEE style: BibTeX-key appears instead of numbers

I have saved some references in a library.bib file, using JabRef. One of these entries is the following:   @Article{Feng2014,      author = {Bo Feng, Mengyin Fu, Hongbin Ma, Yuanqing Xia, Bo Wang},     title = {Kalman filter with recursive covariance estimatio - sequentially estimating process noise covariance},      journal = {IEEE Transactions on Industrial Electronics},     year = {2014},      volume = {61},     number = {11},     pages = {6253-6263} }   Now I want to include citations in my TeX-document:   \documentclass{article}   \usepackage[backend=biber,citestyle=ieee,sorting=none,dateabbrev=false,urldate=comp]{biblatex} \addbibresource{./library.bib} \begin{document} \section{First Section} Equations given in this section have been taken from \cite{Feng2014} and \printbibliography[heading=bibintoc] \end{document}   I am running PDFLaTeX, Biber, PDFLaTex, PDFLaTeX. The references should be included as numbers, such as [1], wherever the citation is used. Instead of the number, however, the name of the BibTeX-key is given. And the reference is not included in the bibliography.   I have tried to make this a MWE. When I run this code now, the bibliography is not printed at all and the reference within the text is given as the BibTeX-key.


If induced voltage (back-emf) is equal and opposite to applied voltage, what drives the current?

Suppose we have a circuit with a voltage source, a switch open and an inductor all in series. If we close the switch, the potential difference of the voltage source is instantaneously applied to the inductor. As the current starts to build up, induced voltage from the inductance opposes it. If the induced voltage (back-emf) is equal and opposite to the applied voltage, and the net voltage is zero, what drives the current then? All I could find  was this:     "...it is difficult to realise that there can be a current without a 'resultant' emf. Faraday's law states $e = LdI/dt$ and if there is no resistance $e = E$. It is the electrical analogy of constant velocity with no need for a resultant force. If there is resistance then $e = LdI/dt = E - Ir$ ... 'resultant' $\text{emf} = e$"   Could you expand a little bit more on this idea?


Scaling Tikz picture without overlapping text

I have a simular issue to the question asked in :  I have tried the solution provided by Jake. This makes that my picture fails to resize (scale) as i intend.  Whether i give Set scale=0.4 or Set scale=0.8 The size of the  picture remains the same  This is the code i use:  \begin{figure}[ht!] \centering \begin{tikzpicture}[Set scale=0.4, every node/.append style={transform shape},] % STYLES \tikzstyle{every node}=[rectangle,rounded corners, minimum width=100pt,     align=center,node distance=3cm,fill=black!10,inner sep=5pt,text width=3cm,minimum height=1.75cm,>=stealth,text badly centered] % Draw forces \node [force, above of=rivalry] (top) {Firm strategy, structure and rivalry}; \node [force, left=1cm of rivalry] (left) {Factor conditions}; \node [force, right=1cm of rivalry] (right) {Demand Conditions}; \node [force, below of=rivalry] (bottom) {Related and Supporting industries}; %%%%%%%%%%%%%%%% % Draw the links between forces \path[<->,thick]  (left) edge (right) (left) edge (top) (left) edge (bottom) (top) edge (right) (bottom) edge (right); \path[<->,thick]  (bottom) edge (top); \end{tikzpicture} \caption{Porter's Diamond source:~\cite{Porter:1980}}% \label{fig:diamond}  \end{figure}


Disproving that $\mathbb R[x]$ is a field

The task is to determine if $\mathbb R[x]$, which represents the set of all polynomials with real coefficients, is a field. My response is that it is not, since I feel that not all of these polynomials have a multiplicative inverse.  If I am correct, how would I show this in detail?


Are ArcMap Addins compatible with ArcGIS Pro?

In other words, can ArcGIS Pro load an ArcMap AddIn?


problems dual booting windows 10 & ubuntu MATE 16.04.3

I'm on win10 64bit on an ACER laptop and I'm trying to dual boot ubuntu MATE 16.04.3 alongside it. However on startup it still always boots into windows. System info says I'm booting windows in UEFI.   This is what I've done so far:   I have an SSD and HDD, and I started by shrinking around 400GB from my HDD. Then I used rufus with the ubuntu-mate-16.04.3-desktop-amd64.iso to make my USB flash drive a bootable one. I disabled fast boot from my power settings in windows, and I didn't seem to be able to find it in BIOS. In BIOS I have a supervisor password, my settings were set to UEFI on secure boot. I booted from my usb and accidentally chose the install ubuntu option at first and got a file not found error and exited to try again, this time from the try ubuntu option to install ubuntu from there. I connected to my wifi within the live version and ran the install process there. I ticked both boxes for installing updates and third party software. As secure boot was enabled, I entered a password in. I simply chose the install ubuntu alongside windows boot loader option. Then I restarted the laptop from ubuntu once it was done. It didn't boot into ubuntu or give me a choice, going straight to windows. I've tried turning off secure boot and running boot-repair within the live ubuntu running from my usb, as well as moving up my HDD to the top of the boot load order and running the bcedit cmd as suggested by boot-repair. None of these worked! In disk management in windows I now have 3 partitions alongside my windows partition in my HDD replacing the 400GB shrinked unallocated space from the start, however they all say they have 100% free space. Are they supposed to be like that? Maybe I should clear the partitions and reinstall or something?   This is my first go at natively installing anything linux after I've been using them in vms with no problems, except that it ran too slowly.  Edit: I don't believe this is a duplicate as I've got a specific situation that I'm having problems with, and it seems like I've gone through the steps given in that post already.


Delphi: initialization of boolean differs in 32 Bit and 64 Bit applications

I use Delphi 10.4 and build 32 and 64 Bit applications. I noticed that the initialization of boolean variables depends on the type of application (32 bit and 64 bit). I build a simple app. Here is my code: procedure TForm1.Button1Click(Sender: TObject); var   value: boolean; begin   ShowMessage(value.ToString); end;  In 32 bit value is true and in 64 bit value is false. Is this a normal behaviour? And how can I change it?


I have a column in an Excel spreadsheet with several hundred entries, and some of these entries are duplicated.  I would like to remove all duplicate entries from the column so that each entry remaining is unique.   Is there a way to accomplish this automatically?


How do you search through flags in the manpages?

Whenever I search the manpages, I'm almost always trying to find out what's going on with a specific flag. For example, when searching the man pages for  I was searching the for -f flag. I'm not sure how to say, quickly get to the flag which is here:  OPTIONS    General options        -f FORMAT, -r FORMAT, --from=FORMAT, --read=FORMAT   and filter out stuff like:  iconv -t utf-8 input.txt | pandoc | iconv -f utf-8              or  pandoc -f markdown -t latex hello.txt   I've tried searching for /-f, and I've looked at  and tried (^|\s)-f($|\s\) but it was invalid. So I'm wondering how do you quickly search less for "only the flag -f"?  Would love your thoughts or some other tool that you use to quickly go through documentation


Optocoupler with phototransistor base lead

I'm thinking about using  optocoupler - it has a separate lead for base of phototransistor. How do I use it? I suppose I can't leave it floating?


How does one add boarding passes to Apple Wallet?

I have been trying to add some boarding passes to wallet. I have downloaded the airline app and logged in. I have tried to "scan the code" as suggested in wallet, but the only code is a QR code and nothing happens when I try to scan. This should be that difficult but I cannot figure it out. Is there an easy way to get this done? Please explain to me how to do it. Thanks.


Higher energy of outer orbitals around nucleus

I remember reading that the outer orbitals of atom have higher energy. If an electron is given enough energy it goes to higher energy orbitals from $n=1$ to $n=2,3,4...$   My question is that why do the outer orbitals have higher energy? Is is because of charges?


Why java use quick sort algorithm instead of merge sort in small array?

I read sort algorithms that Java used in Arrays, so I opened jar files and read what java used when we call  Array.sort();, so I found Java to check if the array's length is less then 286 and use quick sort otherwise use merge sort?     static void sort(int[] a, int left, int right,                      int[] work, int workBase, int workLen) {         // Use Quicksort on small arrays         if (right - left < QUICKSORT_THRESHOLD) {             sort(a, left, right, true);             return;         } .....


Where and who can I trade in my Korok Seeds to?

In Zelda: Breath of the Wild, where in Hyrule can I hand in my Korok Seeds to gain rewards?


Proving $\sum\limits_{k=1}^{n}{\frac{1}{\sqrt{k}}\ge\sqrt{n}}$ with induction

I am just starting out learning mathematical induction and I got this homework question to prove with induction but I am not managing.  $$\sum\limits_{k=1}^{n}{\frac{1}{\sqrt{k}}\ge\sqrt{n}}$$  Perhaps someone can help me out I don't understand how to move forward from here: $$\sum\limits_{k=1}^{n+1}{\frac{1}{\sqrt{k}}+\frac{1}{\sqrt{n+1}}\ge \sqrt{n+1}}$$ proof and explanation would greatly be appreciated :) Thanks :)  EDIT sorry meant GE not = fixed :)


As heard in "Another One Bites the Dust", by Queen and "Elastic Heart"  by Sia.


I've been wanting this forever, but today is the first time I've ever noticed apt downloading more than one update at a time:   Is this now a thing? Where can I read more about the extent of this new feature? I can't seem to find out anything about this so far in my internet searches.  FYI, I'm running Kubuntu 19.10.


Every planar graph has a vertex of degree at most 5.

I am trying to prove the following statement, any help!?     Prove that every planar graph has a vertex of degree at most 5.


I am aiming to make a simulated plot that looks SOMETHING like  however I have not been able to get the lines to match up. Please assist if you could!


Assume that $A$ is an $n\times n$ matrix. Assume that $u$ and $v$ are eigenvectors corresponding to eigenvalues $5$ and $9$. Determine all pairs of real numbers $α$ and $β$ such that $αu+βv$ is also an eigenvector of $A$.  Could someone please advise if this works! Since u and v are eigenvectors corresponding to eigenvalues 5 and 9,   We have Au = 5u …(1)       Av = 9v  …(2) Now we want to find all pairs of α and β  lets call them  α_i  and β_i  such that (α_i u+β_i v)  is eigen vector of A i.e.           $$      A(α_i u+β_i v)=e_i (α_i u+β_i v)    < => Aα_{i} u+Aβ_{i} v=e_{i} (α_{i} u+β_{i} v)    < => α_{i} Au+β_{i} Av=e_{i} (α_{i} u+β_{i} v)     < => α_{i} 5u+β_{i} 9v=e_{i} (α_{i} u+β_{i} v)     < => e_{i}=((α_{i} 5u+β_{i} 9v))/((α_{i} u+β_{i} v) )   …(3)   e_{i} $$ will be=k when         $$ α_{i}$$  happens to be the multiple of 9 i.e.$$α_{i}=9*k,        β_{i} $$ happens to be multiple of 5 i.e.5*k   except when k = 0   Thus for$$ (α_{i} u+β_{i} v) $$ to be eigenvector of A $$ (α_{i},β_{i} )=[(9*k,5*k)]  ∀ k = ±1,±2,±3$$…and k!=0    So my question is different from the possible duplicate highlighted below - as it has a specific linear combination to deal with


Ensure a burned DVD will work any dvd player?

My bro used to burn DVD's with some special format to ensure that they would even work on crummy, cheap, old DVD players.  Well, I'm using one of 'those' dvd players.  So, I want to be sure that I format my burned dvd's properly.  What can I do to be sure that my dvd's play properly?  As I recall, we could even use CD disks to on old DVD players, and the CD's would be loaded with .avi files.  I believe the format started with an s and had an h in it.


I am using macOS Mojave and would like to have a keyboard shortcut to open a new Finder window, similarly to how Win + E opens the File Explorer in Windows.  I am aware that it is always open, but I'd like to get a key combination to open its window, or a new window, rather than clicking on the icon using mouse/trackpad.  Is there a handy way to do it?


A power series with decreasing positive coefficients has no zeroes in the disk

Let $\sum_{n=0}^\infty a_n z^n$ be a formal complex power series, with $a_n$ strictly decreasing to 1 as $n\to \infty$. It is easy to see that the radius of convergence is 1, so that this power series represents a function $f$ holomorphic on the disk. The question is to  Show that f has no zeroes on the disk.  I've been looking at this a while and feel and tried a few different things.   $\cdot$ One easy observation is the similarity of this series with $\frac{1}{1-z}$, whose coefficients do not strictly decrease but which otherwise is an example of the thing to be proven.   $\cdot$ Rouché's theorem doesn't seem to have an immediate application—I've tried comparing $f$ to $\frac{1}{1-z}$ or to its partial sums by Rouché.   $\cdot$ If the partial sums had no zeroes, then neither would $f$ by Hurwitz's theorem  $\cdot$ If we could show the function had positive real part we'd obviously be done, which seems highly plausible—the condition gives that $f(-1) = \sum a_n \cos\pi n > 0$, but I don't know how to extend this argument to arguments other than $\pi$. Besides, if this technique were to work, it seems it would rely most on algebraic manipulations of power series, and I would vastly prefer a classical complex analytic approach (argument principle, Rouché's theorem, etc)  Please advise!


Analytic function on unit disk, Schwartz lemma type inequality

Let $f:\Bbb{D}\to\Bbb{C}$ be an analytic function that satisfies the inequality $|f(z)|\le\dfrac{1}{1-|z|}.$ How can I show that $|f'(0)|\le 4.$        Also, I am looking for the equality case. Is this a sharp upper bound?


This is from Axler's 1996 "Down with Determinants," I do not see why this basis would give the desired matrix representation. I would appreciate any help in seeing this.


Installation of Skype 4.3.with Synaptic to Ununtu 14.10

My question is:    Installation of Skype 4.3.0.37... with Synaptic to Ubuntu 14.10 - does Skype work OK with this installation ? In my Synaptic screenshot I see now following packets of Skype programs.   Packet:                               Last version: skype                                 4.3.0.37-OubuntuO.. pidgin-skype-dbg                      20130613+svn660+... emphaty-skype                         the same pidgin skype                          the same pidgin-skype-common                   the same    And my question is:   should I mark them ALL for installation or only the first one (skype 4.3.0.37 ..) and other packets LATER, when Skype is already working OK? When I look these 4 small packets, Skynaptic indicates, that     This plugin communicates with the Skype application in the background to perform its work, so it's necessary to have Skype installed and running   But, can Skype work even without these without these 4 small packets, if they are not installed simultaneously with skype packet installation?


Why does my X11 forwarding attempt fail with "connect /tmp/.X11-unix/X0: No such file or directory"?

On my local machine, I run:  ssh -X me@remotemachine.com   (For completeness, I have also tested all of the following using -Y with identical results).  As expected, this accesses remotemachine.com fine, and all appears well. If I then attempt to run xcalc however, I get:   connect /tmp/.X11-unix/X0: No such file or directory  Error: Can't open display: localhost:10.0   But,   $ ls -la /tmp/.X11-unix/ total 36 drwxrwxrwt 2 root root  4096 2012-11-23 09:29 . drwxrwxrwt 8 root root 32768 2012-11-29 08:22 .. srwxrwxrwx 1 root root     0 2012-11-23 09:29 X0   So not only does /tmp/.X11-unix/X0 exist, it has universal r/w/x permissions!  I've previously used x-forwarding without issue, though not in some time...  uname -a on the server for reference:  Linux machinename 2.6.32-25-generic #45-Ubuntu SMP Sat Oct 16 19:52:42 UTC 2010 x86_64 GNU/Linux   Been searching around on the web for a couple hours now without success. Other mentions of the same problem, but no solutions.


Sequences or 'chains' of adjoint functors

Suppose we have (some categories and some functors such that) $F_1$ is left adjoint to $G_1$, $G_1$ left adjoint to $F_2$, $F_2$ left adjoint to $G_2$. Will $F_1$ then be equal to $F_2$ (and $G_1$ to $G_2$)?  Or can there exist arbitrarily long 'chains' of adjoint functors that do not trivialize?


Are CFDs without leverage suitable for long-term investment?

According to , CFDs are inappropriate for long-term investments because of financing fees and margin calls. This conclusion appears to be true only if the CFD positions use borrowed money (leverage). Suppose I do not use leverage to buy CFDs; I always use 100% margin. Does this make long-term investing viable using CFDs? What are the pitfalls when making long-term investments using unleveraged CFD positions? (By "long-term", I mean an investment horizon of 1 to 10 years.)


$\{\ln(p)\}$ where $p$ is prime is linear independent.

I’m struggling to prove that the set $\{\ln(p): \text{$p$ is prime}\}$ is a linearly independent system in the Rational vector space of the real numbers.   Any help is greatly appreciated.


Why shouldn't root be allowed to login via ssh?

why should root access be disabled for ssh? I always hear that's for security reasons. But I don't get it. What's different to login as non-root and then sudo su -? What's the preferred way to handle tasks that need privileged permissions?  Thanks  Thomas


I always wanted to play D&D but i was always "friendless" amd live in a very urban area where no one plays i learn better if others teach me are there any videos that anyone could suggest that is helpful or any groups that are willing to take beginners?


I've seen  which say that the only upgrade path from 9.04 is to 9.10. And the same notes say that the only upgrade path from 9.10 is 10.04, and so on.  that I would need to perform at least 5 upgrades in order to turn a 9.04 installation into a 13.04 -- I hope I misunderstood something!  Given that I have a 9.04 installation that I want to move to the newest version, what's my best course of action? There isn't a lot of stuff on the machine right now, and data is backed up.   What happens to the current installation if I simply pop in a 13.04 CD and just install that?  Finally, if it really is better to wipe the machine and start from scratch, how can I best keep track of (or even preserve!) the installed apps, settings, and so on? Everything except user data itself which is backed up.


Adding new user/admin record in more secure way

I'm a learner and creating my first website. after adding a login and add new user forms to my website, i came to know that I must not save my passwords in DB as plaintext. I did some search and find out about md5(), salt, encryption etc etc. Most of my finding were from this same site but there were more long long codes, which I couldn't understand clearly. In short I want to know what modifications i must do to my code (given below)?  Adding new user/Admin form:  <form action="add_user.php" method="post"> New User Name : <input type="text" name="username" placeholder = "New User Name">
 New Password :<input type="password" name="password" placeholder = "New Password">
  Confirm Password :<input type="password" name="againpassword" placeholder = "Enter Password Again">

 <input type="submit" value="Save" name="Submit-Event" style="font-size:16px"><input type="reset" value="Reset" style="font-size:16px">
 </form>   php file: add_user.php  <?php $server="localhost"; $user="root"; $password=""; $database="camouflage_studio";  $con = mysqli_connect($server,$user,$password,$database); if (mysqli_connect_errno())   {   echo "Connection Error: " . mysqli_connect_error();   }  //check if password matches $firstpassword = $_POST['password']; $secondpassword = $_POST['againpassword']; $username = $_POST['username'];  if(($firstpassword == $secondpassword) and $firstpassword !== '' and $username !== '') {     // prepare and bind     $stmt = $con->prepare("insert into users (username, password) VALUES (?, ?)");     $stmt->bind_param("ss", $_POST['username'], $_POST['password']);     if(mysqli_stmt_execute($stmt))     {     echo '';     }     else     echo "Prepare Error: ",$con->error;     //remove $con->error before making ONLINE THE CODE. }  else     {       echo '';      } $stmt->close(); $con->close();  ?>


How does Biff come back to the original time line?

If Biff takes the time machine and goes back in time to deliver the Almanac to young Biff, how does old Biff return to his original time line if in the future he altered he became rich? Wouldn't he end up in the rich Biff future? Chronologically... he comes back from the past to his original time after altering the future.


What happens to waves when they hit smaller apertures than their wavelenghts?

I was wondering this for quite a long time now. Let's say you have a water wave (like ripples, not the ones you see during tsunamis) with wavelength 10 m. Imagine you put a boundary with an opening of 1 m. Will diffraction be observed? According to my research, no. But, then, what would be seen?


C# Cast List of base type to list of derived type

I'm casting list of base type to list of derived type  List<TicketDetail> ticketDetails = listResult.Cast<TicketDetail>().ToList(); List<TicketDetail> ticketDetails = listResult.ConvertAll(x => (TicketDetail) x).ToList();   I tried both of them and each one of them throws:     System.InvalidCastException: Unable to cast object of type   'WorkOrder.Service.Ticket' to type 'WorkOrder.Service.TicketDetail'.   here is my classes   namespace WorkOrder.Service {     using System;     [DataContract]     [KnownType(typeof(TicketDetail))]     public partial class Ticket     {         public int RecordId { get; set; }         public long TicketId { get; set; }         public string Summary { get; set; }         public string Details { get; set; }         public int CategoryId { get; set; }         public System.DateTime CreatedOn { get; set; }         public string CreatedBy { get; set; }         public string Status { get; set; }         public string TicketSource { get; set; }         public string TicketType { get; set; }         public string ManagedByGroup { get; set; }         public string ManagedByUser { get; set; }         public Nullable<long> SubscriptionId { get; set; }         public string PriorityLevel { get; set; }         public string Impact { get; set; }         public string ImpactOnBusiness { get; set; }         public string Risk { get; set; }         public string Comment { get; set; }         public Nullable<System.DateTime> PlannedStartDatetime { get; set; }         public Nullable<System.DateTime> ActualStartDatetime { get; set; }         public Nullable<System.DateTime> PlannedDeadlineDatetime { get; set; }         public Nullable<System.DateTime> ActualDeadlineDatetime { get; set; }         public System.DateTime TransactionDatetime { get; set; }         public string AssignedToGroup { get; set; }         public string AssignedToUser { get; set; }         public string CategoryName { get; set; }         public int CreatedById { get; set; }         public int StatusId { get; set; }         public int SourceId { get; set; }         public int TypeId { get; set; }         public int ManagedByGroupId { get; set; }         public Nullable<int> ManagedByUserId { get; set; }         public int AssignedToGroupId { get; set; }         public Nullable<int> AssignedToUserId { get; set; }         public int PriorityLevelId { get; set; }         public int ImpactLevelId { get; set; }         public int ImpactOnBusinessLevelId { get; set; }         public int RiskLevelId { get; set; }     } }   derived class:  namespace WorkOrder.Service {     [DataContract]     public class TicketDetail : WorkOrder.Service.Ticket     {         [DataMember]         public List<WorkLogView> WorkLogs { get; set; }     } }


How can I copy coverart from flac to opus with ffmpeg

I am trying to convert some flac files which all have coverart embedded to opus with ffmpeg. All but the coverart gets copied over just fine, but I find myself unable to move the cover over as well. Tried all sorts of -mapmetadata stuff I could find so far, but no luck, the result is always missing the coverart.  While the original .flac reports to have a video stream with the coverart  Duration: 00:02:53.51, start: 0.000000, bitrate: 910 kb/s    Stream #0:0: Audio: flac, 44100 Hz, stereo, s16    Stream #0:1: Video: mjpeg, yuvj420p(pc, bt470bg/unknown/unknown), 500x500 [SAR 1:1 DAR 1:1], 90k tbr, 90k tbn, 90k tbc   the created opus files does not have any graphics:  size=    2815kB time=00:02:53.51 bitrate= 132.9kbits/s speed= 104x video:0kB audio:2793kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.811556%   I tried -vcodec copy, -mapmetadata 0, -mapmetadata 0:s:0 so far, with no luck. Doesnt seem to have anything todo with opus, as I have the same problem converting to aac.  So is there a way to get the cover out of the flac file and move it over to the new file in on go using ffmpeg, or do I have to extract it first and then glue it back again later to the new file with extra commands?


Today I have looked over the port diagram presented in the datasheet for the Atmel 7810 controller (Chapter 13.2), in the logic diagram of the I/O ports, I noticed a strange logic gate, which I have not encountered until now and I have not found any information regarding this one.  Logic gate picture:   What kind of logic gate is this? Is it a composite of two logic gates like "inverted buffered gates in mirror"?  I have no explanation in this regard.


I want to prove that every field has exactly 2 ideals.   I know that the two ideals are $0$ and the whole set itself. That is clear to me. I am a little unsure how to prove it though.


How to aggregate points to polygons using ArcGIS Desktop?

I am trying to aggregate my data points to the polygons so that I could find out how many points I actually have in each polygon, and then export the data contained within each polygon to further look at the data properties as they pertain to each polygon.


How to tell if your USB ports support USB 3.0?

I'm a Ubuntu 10.04 user. What's the fastest way to tell if the two USB ports on my computer support USB 3.0? I'm not sure if they're 2.0 or 3.0, and I need to know. Thanks!


Struggling to create an efficient index for this query

I am struggling to create an index for a query and unfortunately I cannot change the query at all as it part of an ERP system. The problem is this query has over 1m reads and sometimes a duration of 10s  I Have tried using just the predicate, the seek predicate and a combination of both in different orders to no success.  Here is the query that cannot be changed:  SELECT  TOP (@0) "timestamp","Link ID","Record ID","URL1","URL2","URL3","URL4","Description","Type","Created","User ID","Company","Notify","To User ID"  FROM "Database".dbo."Record Link" WITH(READUNCOMMITTED)   WHERE ("Link ID">@1 AND (("Company"=@2 OR "Company"=@3) AND "Notify"=@4 AND ("To User ID" COLLATE Latin1_General_100_CI_AI LIKE @5 OR "To User ID" COLLATE Latin1_General_100_CI_AI LIKE @6)))  ORDER BY "Link ID" ASC OPTION(OPTIMIZE for UNKNOWN, FAST 50)   Here is the script for the table if it helps:  SET ANSI_NULLS ON GO  SET QUOTED_IDENTIFIER ON GO  CREATE TABLE [dbo].[Record Link](     [timestamp] [timestamp] NOT NULL,     [Link ID] [int] IDENTITY(1,1) NOT FOR REPLICATION NOT NULL,     [Record ID] [varbinary](448) NOT NULL,     [URL1] [nvarchar](250) NOT NULL,     [URL2] [nvarchar](250) NOT NULL,     [URL3] [nvarchar](250) NOT NULL,     [URL4] [nvarchar](250) NOT NULL,     [Description] [nvarchar](250) NOT NULL,     [Type] [int] NOT NULL,     [Note] [image] NULL,     [Created] [datetime] NOT NULL,     [User ID] [nvarchar](132) NOT NULL,     [Company] [nvarchar](30) NOT NULL,     [Notify] [tinyint] NOT NULL,     [To User ID] [nvarchar](132) NOT NULL,  CONSTRAINT [Record Link$0] PRIMARY KEY CLUSTERED  (     [Link ID] ASC )WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON, FILLFACTOR = 80) ON [PRIMARY] ) ON [PRIMARY] TEXTIMAGE_ON [PRIMARY] GO   Here is the stats for the time and IO    SQL Server Execution Times:    CPU time = 0 ms,  elapsed time = 0 ms. SQL Server parse and compile time:     CPU time = 0 ms, elapsed time = 4 ms.  (0 rows affected) Table 'Record Link'. Scan count 1, logical reads 1018402, physical reads 3, read-ahead reads 1018391, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.  (1 row affected)   SQL Server Execution Times:    CPU time = 8234 ms,  elapsed time = 12641 ms.   Here is the execution plan:   I would greatly appreciate it if someone could help me create an efficient index for this.  Here is a link to the execution plan:


I bought the Overseer's Guardian in Fallout 4 then gave it to Curie. After that I sent her to sanctuary, but now she's gone.   How can I find Curie? I know there are console commands but I cannot use them because I'm playing on the PS4.


Why do we need backing fields in C# properties?

NOTE: This is not a question about auto-implemented properties. Auto-implemented properties are about properties without logic in the getters and setters while I stated in my code very clearly that there is some logic. This is not a duplicate of  nither, since the question is really different, and so is the answer.  I see a lot of this: private int _age; public int Age {     get     {         if(user.IsAuthorized)         {             return _age;         }     }     set     {         if(value >= 0 && value <= 120)         {             _age = value;         }         else         {             throw new ArgumentOutOfRangeException("Age","We do not accept immortals, nor unborn humans...");         }     } }  But why do we need the backing field? Why no returning the Property itself? public object Age {     get     {         if(user.IsAuthorized)         {             return Age;         }     }     set     {         if(value >= 0 && value <= 120)         {             Age = value;         }         else         {             throw new ArgumentOutOfRangeException("Age","We do not accept immortals, nor unborn humans...");         }     } }


"undo your comment upvote" is missing in app?

There is an option to undo the comment upvote in stack exchange sites like an alert    Whereas using Stack exchange app, I'm able to upvote a comment but unable to undo it.   I think instead of showing Vote up again, it should show message like "undo upvote".  Something similar in stack exchange sites.


Negotiating cultures: tips on bargaining

In Argentina I was once charged the "gringo" rate for a bus and was later told I could have negotiated the price because locals pay less.   From an ex-colleague who spent 6 months in China I heard you need to negotiate everything, especially at markets, for cab rides and accommodation. I also heard the same about Mexican and Peruvian markets.   This  strongly recommends price negotiation because it's a cultural norm "in the East".  also seems to have a culture that expects prices to be negotiated.  What are some tips to negotiating prices (for things or services) across cultural boundaries ? If it's for sale, is it safe to assume it's negotiable ? How do I know what the local value of something is, that is, am I being ripped off ?


GPG error when installing Epson Scanner driver

I am trying to install Image Scan! bundle from Epson for my GT-1500 scanner. When I run ./install.sh I get the error: W: GPG error: https://downloads.plex.tv/repo/deb public InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 97203C7B3ADCA79D E: The repository 'https://downloads.plex.tv/repo/deb public InRelease' is not signed.  I looked into --allow-unauthenticated but doesn't seem to work for my case.


How to copy software DVD on another blank DVD

How can I copy a Windows7 DVD to another DVD using a single DVD drive?