I need to understand why does the summary output of aov() in R vary when the order of independent variable changes. Like for example: summary(aov(y~A+B, data)) is different from summary(aov(y~B+A,data)).

My primary question is how to interpret the output (coefficients, F, P) when conducting a Type I (sequential) ANOVA?   My specific research problem is a bit more complex, so I will break my example into parts. First, if I am interested in the effect of spider density (X1) on say plant growth (Y1) and I planted seedlings in enclosures and manipulated spider density, then I can analyze the data with a simple ANOVA or linear regression. Then it wouldn't matter if I used Type I, II, or III Sum of Squares (SS) for my ANOVA. In my case, I have 4 replicates of 5 density levels, so I can use density as a factor or as a continuous variable. In this case, I prefer to interpret it as a continuous independent (predictor) variable. In R I might run the following:  lm1 <- lm(y1 ~ density, data = Ena) summary(lm1) anova(lm1)   Running the anova function will make sense for comparison later hopefully, so please ignore the oddness of it here. The output is:  Response: y1           Df  Sum Sq Mean Sq F value  Pr(>F)   density    1 0.48357 0.48357  3.4279 0.08058 . Residuals 18 2.53920 0.14107    Now, let's say I suspect that the starting level of inorganic nitrogen in the soil, which I couldn't control, may have also significantly affected the plant growth. I'm not particularly interested in this effect but would like to potentially account for the variation it causes. Really, my primary interest is in the effects of spider density (hypothesis: increased spider density causes increased plant growth - presumably through reduction of herbivorous insects but I'm only testing the effect not the mechanism). I could add the effect of inorganic N to my analysis.   For the sake of my question, let's pretend that I test the interaction density*inorganicN and it's non-significant so I remove it from the analysis and run the following main effects:  > lm2 <- lm(y1 ~ density + inorganicN, data = Ena) > anova(lm2) Analysis of Variance Table  Response: y1            Df  Sum Sq Mean Sq F value  Pr(>F)   density     1 0.48357 0.48357  3.4113 0.08223 . inorganicN  1 0.12936 0.12936  0.9126 0.35282   Residuals  17 2.40983 0.14175    Now, it makes a difference whether I use Type I or Type II SS (I know some people object to the terms Type I & II etc. but given the popularity of SAS it's easy short-hand). R anova{stats} uses Type I by default. I can calculate the type II SS, F, and P for density by reversing the order of my main effects or I can use Dr. John Fox's "car" package (companion to applied regression). I prefer the latter method since it is easier for more complex problems.  library(car) Anova(lm2)             Sum Sq Df F value  Pr(>F)   density    0.58425  1  4.1216 0.05829 . inorganicN 0.12936  1  0.9126 0.35282   Residuals  2.40983 17     My understanding is that type II hypotheses would be, "There is no linear effect of x1 on y1 given the effect of (holding constant?) x2" and the same for x2 given x1. I guess this is where I get confused. What is the hypothesis being tested by the ANOVA using the type I (sequential) method above compared to the hypothesis using the type II method?  In reality, my data is a bit more complex because I measured numerous metrics of plant growth as well as nutrient dynamics and litter decomposition. My actual analysis is something like:  Y <- cbind(y1 + y2 + y3 + y4 + y5) # Type II mlm1 <- lm(Y ~ density + nitrate + Npred, data = Ena) Manova(mlm1)  Type II MANOVA Tests: Pillai test statistic         Df test stat approx F num Df den Df  Pr(>F)     density  1   0.34397        1      5     12 0.34269     nitrate  1   0.99994    40337      5     12 < 2e-16 *** Npred    1   0.65582        5      5     12 0.01445 *    # Type I maov1 <- manova(Y ~ density + nitrate + Npred, data = Ena) summary(maov1)            Df  Pillai approx F num Df den Df  Pr(>F)     density    1 0.99950     4762      5     12 < 2e-16 *** nitrate    1 0.99995    46248      5     12 < 2e-16 *** Npred      1 0.65582        5      5     12 0.01445 *   Residuals 16


A set "a" has 6 elements.In how many ways can the elements be divided into 2 groups?  Options given: 1) $62$  2) $31$  3) $52$  4) $32$  My Approach:  I divided the items into 2 unequal groups of 4 and 2,5 and 1,6 and 0,3 and 3.  I get  $6!$/$2!$ . $4$!=$15$  $6!$/$3!$ . $3$!=$20$  $6!$/$1!$ . $5$!=$6$  $6!$/$0!$ . $6$!=$1$  total=$42$     Can anyone can give me hint how to solve this problem?

The order of the groups does not matter The size of group must be at least 1   For example, in a more specific question , we got the answer 15 from Jared, which is the sum of 5 ways to split in group size 1 and 4, and 10 ways to to split in group size 2 and 3.  For more general cases, what is the formula to calculate this?


How can i lock a file then clear its contents and write to it? Clearing a file can be as simple as:  FileOutputStream fos = new FileOutputStream(someFileObject);   And acquiring the lock would be by:  FileLock lock = fos.getChannel().lock();   But what i need is to lock the file before i clear it because i don't want any edits to happen before the program gets the lock for the file.  I tried using 2 FileOutputStream objects one that is set to append and is just used for locking and the other one with append set to false for clearing the file like so:      File log = new File("test.txt");     try (FileOutputStream forLocking = new FileOutputStream(log, true)) {         FileChannel fileChannel = forLocking.getChannel();         FileLock lock = fileChannel.lock();         try (FileOutputStream fos = new FileOutputStream(log); PrintWriter out = new PrintWriter(fos);) {             out.println("Test this stuff");         }     } catch (IOException e) {         e.printStackTrace();     }   but apparently only the Channel that has the lock can make any changes to it in the same jvm at least.  Is there anyway i can go about with this without having to delete the file and recreate it?  I appreciate the help.  @Roman Puchkovskiy I know how to lock. and i know how to clear a file. My question is how can i acquire a lock then clear the file in the respective order. The link you sent is not helpful at all thanks for trying though.

I have a Java process that opens a file using a FileReader. How can I prevent another (Java) process from opening this file, or at least notify that second process that the file is already opened? Does this automatically make the second process get an exception if the file is open (which solves my problem) or do I have to explicitly open it in the first process with some sort of flag or argument? To clarify: I have a Java app that lists a folder and opens each file in the listing for processing it. It processes each file after the other. The processing of each file consists of reading it and doing some calculations based on the contents and it takes about 2 minutes. I also have another Java app that does the same thing but instead writes on the file. What I want is to be able to run these apps at the same time so the scenario goes like this. ReadApp lists the folder and finds files A, B, C. It opens file A and starts the reading. WriteApp lists the folder and finds files A, B, C. It opens file A, sees that is is open (by an exception or whatever way) and goes to file B. ReadApp finishes file A and continues to B. It sees that it is open and continues to C. It is crucial that WriteApp doesn't write while ReadApp is reading the same file or vice versa. They are different processes.


If $a$ is not a multiple of a prime $p$, then prove that there is an integer $b$ such that $p^b-1$ is a multiple of $a$.

I tried many approaches but none of them really worked I treated $p^b-1$ as a Geometric progression but it didn't work and that is about as far as I have been able to go I have no clue how to move forward


I'm a newbie to electronics, so apart from the obvious physical size issues there may be a clear reason as to why this is a dumb question, but if the general rule of thumb is to use a bypass capacitor for all ICs on a board, why not just build capacitors right into the components? Is there a reason this never became a standard feature?  Sure, there's a size issue on smaller ICs (especially SMD chips and the like), but in a lot of applications vertical height doesn't seem to be an issue and it would simplify circuitry and BOMs etc.

The title is probably good enough, but I've always wondered why decoupling caps aren't built into the chip or at least the IC packaging?


If a,b,c are the sides of a triangle ABC then prove $$ a/(b+c) + b/(a+c) + c/(a+b) < 2 $$I tried to solve this by triangle inequality but i was not able to get to the solution.

How can one show that for triangles of sides $a,b,c$ that   $$\frac{a}{b+c}+\frac{b}{c+a}+\frac{c}{a+b} < 2$$  My proof is long winded, which is why I am posting the problem here.   Step 1: let $a=x+y$, $b=y+z$, $c=x+z$, and let $x+y+z=1$ to get   $\frac{1-x}{1+x}+\frac{1-y}{1+y}+\frac{1-z}{1+z}<2$  Step 2: consider the function $f(x)=\frac{1-x}{1+x}$, and note that it is convex on the interval (0,1), so the minimum of   $\frac{1-x}{1+x}+\frac{1-y}{1+y}+\frac{1-z}{1+z}$  is reached when the function takes the extreme points. i.e. $x=y=0, z=1$.    But going back to the fact that this is a triangle, we note that $x=y=0 \implies a=0$ which is not possible, so the inequality is strict.


Let we have $C$ the set of complex numbers and $z_1 , z_2 \in C $ we have $Z_1 , Z_2 \in S$ correspond on riemann sphere and we will define : $$ d(Z_1,Z_2)=\frac{2|z_1-z_2|}{\sqrt{1+|z_1|^2} \sqrt{1+|z_2|^2} } $$ How can I prove $d$ is a distance

For $x,y\in \mathbb R^n$ define  $$d(x,y)={\|x-y\| \over \sqrt{1+\|x\|^2} \sqrt{1+\|y\|^2}}$$ Here $\|x\|$ is the euclidean norm of a vector. How to prove that $d$ (the spherical metric) is indeed a metric?     Progress so far:    $d(x,y)\ge 0$ is obvious. $d(x,y) =0 \iff \|x-y\|=0 \iff x=y$, so the positivity holds. $d(x,y) = d(y,x)$ is clear from the formula, so symmetry holds.    But I am having difficulties with the triangle inequality. Writing it out in coordinates leads to a complicated inequality with square roots all over the place in denominators. Is there a better way?


About 1987, I read an adventure/fantasy novel series about a boy who learns magic and his adventures. He would learn new spells with each new book of the series. I'm looking for any additional info or suggestions.  The titles went along this line based on a new spell:   "I" is for Invisible or Illuminate   "T" is for Teleport(ation)   "L" is for Levitate or similar.   The story was consecutive in flow, book to book, and 150ish pages each and they were geared toward grade-school to middle-school kids.  Illustrations were included in the writing occasionally.  The writing and publishing was going on in the 1980's.  The locations and names were all fictitious.  The boys friends were not necessarily human as creatures were involved.

Can you help me identify a book I read?  It was intended for teenagers.  I believe I read it in the late 1980s or early 1990s.  The main character is a teenage human boy from earth, who is learning to use magic with the help of a humanoid lizard companion, who knows all about magic, but can't use magic himself.  They travel to numerous worlds.  I remember one of the lessons was to draw in magic from the ground with every step he takes.  And there are different lines or streams of magic flowing through the world.  Different areas have different concentrations of magic to draw from.  At one point they travel to another world where there is a bazaar or marketplace selling lots of different things.  I believe at one point they travel to yet another world where they are hanged.  The main character survives by lifting himself up by using magic, and the lizard companion uses his strong neck muscles to avoid being killed.  I believe there's also a house where the front door is in one world, but the rest of the house is in a different world.


How can I stop Microsoft Excel from auto formatting data when imported from a text file?  Specifically, I want it to treat all of the values as text.  I am auditing insurance data in excel before it is uploaded to the new database.  The files come to me as tab delimited text files.  When loaded, Excel auto-formats the data causing leading 0's on Zip Codes, Routing Numbers and other codes, to be chopped off.    I don't have the patience to reformat all of the columns as text and guess how many zeros need to be replaced.  Nor do I want to click through the import wizard an specify that each column is text.  Ideally I just want to turn off Excel's Auto-Formatting completely, and just edit every cell as it were plain text.  I don't do any formula's or charts, just grid plain text editing.

Though I try to avoid it, I occasionally have to open a CSV file in Excel. When I do, it formats columns containing numbers, which makes them useless for my purposes. As far as I can tell, the only way to prevent this from happening on import is to rename the file so the extension isn't .csv and use the import wizard to specify the format of each column individually. For files with 50-60 columns, this is impractical.  Since every answer for this oft-asked question on the internet suggests either some means of converting the formatted numbers back once the file is open (which won't work for me - I want to solve the general problem, not a few specific cases) or manually selecting the format type of each column (which I don't want to do), I'm looking for a way to set a global preference or style such that all columns of all CSV files opened are always formatted as text.  I know about "armoring" the numbers with quotes, too, but the files I get don't come like that and I was hoping to avoid having to pre-process the files so Excel doesn't screw them up.  Is there a way to do specifically this: Always format all columns in opened CSV files as text, without manually selecting each column every time during import?  I'm using Excel 2003, but I'll take answers for 2007 if that's what you know.


A manager is interviewing 3 applicants for a job. The duration of each interview follows an exponential distribution  with parameter 1/2, time being measured in hours.  The interviews are scheduled to begin at 8:00, 8:15, and 8:30. Assume that the job candidates (interviewees) arrive exactly on time.  For each of the three candidates, what is the probability that he/she will have to wait before his/her interview begins? (Provide 3 answers.)  How do I work out the answer for the third candidate?

I have the following problem, for which I am having trouble finding a solution:  A manager is interviewing 3 applicants for a job. The duration of each interview follows an exponential distribution  with parameter 1/2, time being measured in hours. The interviews are scheduled to begin at 10:00, 10:15, and 10:30. Assume that the job candidates arrive exactly on time.  For each of the three candidates, what is the probability that he/she will have to wait before his/her interview begins?  I think that the first applicant won't have to wait, the probability that the second has to wait is P(First Interview > 15min) and I am having trouble with the third.   My best guess is that he will have to wait if the sum of the remaining time for the first interviewee and the time for the second interviewee is greater than 15 minutes. Suppose that $X$ is first interviewee's remaining time, $Y$ is the second interviewee's time and $Z = X + Y$.  $$P(Z \ge 15) = 1 - P(Z \le 15)$$  and   $$P(Z \le 15) = \int_{0}^{15}\int_0^zf_x(x)f_y(z-x)dxdy$$   I'm not sure about that last integral. My idea is to using convolution integration to integrate everything that adds up to a certain sum and integrate that sum between 0 and 15. I'm having trouble with integration limits though. I used o and z in the inside integral because $z-x \ge 0$ (support of the exponential distribution) and so $z \ge x$.


I need to design a standee 3x4 feet (36x48 inches at 300 DPI). The main element would be a 10-15 MB photo  (4000x5000 pixel dimensions approx.) inside it and a text heading and 1-2 design elements.  The problem: When I create a document in either Photoshop or Illustrator for print (36x48 inches, 300 DPI), it is extremely slow in Photoshop. Illustrator still manages it but I also need a little Photoshop work.   The main problem occurs in Photoshop while creating any shape or writing text. It's very slow.  The confusion: Is it a right way to design at actual dimensions (say 36x48 inches instead of 12x16 inches inches)? Or most designers design at small size and later scale it up? (Unsolved)  Confusion 2: If I design at small size in Illustrator, but use the actual image, would scaling it up (until the image is not scaled up more than its original dimensions) for print give the same image quality, OR has it lost its quality already when scaled down (since text would create no problem, easily scalable)? (Unsolved)  Confusion 3: I need to save the work in PDF file. Now, if you design at small scale (say 12x16 inches instead of 36x48 inches) in Illustrator, is it possible to scale it up while saving as PDF (I couldn't find such option)? (Unsolved)  Confusion 4: It's possible to scale up the design in Illustrator (not sure about PDF). But there's no such option in Photoshop. Does it mean you should always design at actual dimensions in Photoshop? (Unsolved)  Confusion 5: If i place the assets in my laptop's SSD (currently in Hard Disk), would it increase design speed? (Unsolved)  My laptop specs: i7 8th Gen processor, 8GB RAM, NVIDIA 940MX GPU.  PS: I know there are too much confusions and queries, but I honestly couldn't find answers to these specific things. I believe all of them are somehow related. It might be very useful for future.  EDIT: I read 3-4 top answers on the question that is referred here, it helped me, but it solved another problem that is not directly asked in this question. My confusions are different, and still are not answered. I've edited the question detail wherever it was necessary to explain the confusions better. Please remove duplicate tag.

For wall-sized graphics and large banners (e.g. 3m × 5m), what is an acceptable PPI for print? As I understand it 300 ppi is the typical for 'small' artworks (esp. for clean text resolution). However, for small artworks, the audience usually engages at a much closer distance. Therefore, in the interests of keeping a bitmap file down to a reasonable size, can you get away with a much-reduced PPI for a large format/banner print?


There is possible to install Ubuntu on a tablet Asus TF101 With Android 4.0.3? If is possible, which version would be appropriate in my case? Thanks Ioan

With the announcement of the Ubuntu Phone OS I'd like to know what phone (and tablet) models are supported at this time.  Note from foss & Oli: We are making this the master question for all future "Will this work on <insert random tablet/phone/device here>?!" questions


The last 2 days http://trafleyb-sw.ru/ry5/rtk/mgpg is the link which gets connected automatically in my browser. I use Bitdefender total security to counter internet problems. But after multiple scan the problem still persists. I don't know why the particular Russian domain keeps opening.   Moreover, I would like to mention that I am using Google Chrome as browser.   Is there a solution? In addition I would like to know why the problem exist and persist? How can this be counteracted, provided I have a registered internet security software.

What should I do if my Windows computer seems to be infected with a virus or malware?  What are the symptoms of an infection? What should I do after noticing an infection? What can I do to get rid of it? how to prevent from infection by malware?   This question comes up frequently, and the suggested solutions are usually the same. This community wiki is an attempt to serve as the definitive, most comprehensive answer possible. Feel free to add your contributions via edits.


I have searched by google but cannot find a right solution.The scenario is like this: in my mac, there are two users, lets say user1, user2. these two users are in the same group, which is staff actually.  Now in user2, there is a .bash_profile for user2's terminal, can i share this profile with the user1? I know i can copy one from user2 to user1. but if i copy one, when there is something changed in user2, i have to copy it again. I wonder whether there is a way to share it with user1?

I have set up two user logins on my computer, one for home and one for work. I would like to be able to share any of my bash and vim settings between the two users. Is there anyway to do this? Thus far, I've been copying them from one account to another, but I'd like to be able to just have one file between the two so I can make changes in only one place. Is this even possible? Thanks.


I created a directory somewhere with permissions rwxrwxr-x so that other users in my group can create files and directories in it.  I do need to be able to delete the contents in this "public" directory, but it seems that while I am able to remove any files in this directory I cannot remove and subdirectories under it.   Is there a way to remove such subdirectories owned by others under a directory owned by me?

I am a non-root user, and have made a directory into which other users in my group can write. The directory is setgid, so files and directories within it have the same group.  I can delete files placed into this directory, but if a user creates a subdirectory with files in it, I can't seem to delete those. Is there something special I can do (other than, say, bothering the user in question or the sysadmin about it) to get rid of this subdirectory?  EDIT: Inevitably, of course, someone asks "why?"  The shared folder in question is a mercurial repository. We can't use a shared-account ssh-key-based server for this like mercurial-server, and we can't just host it externally for various reasons. But that part works fine. We use Redmine for project management, but it does not yet read the repo index for file contents - it reads the working directory. So the working directory must be kept up-to-date. crontab has been disabled by the sysadmin, so that's out. So I naïvely put a changeset hook in the shared repo that performed an "hg update". This seemed to work fine initially, until, of course, someone pushed a commit with a new directory. While I had vague thoughts of trying to make a setuid script for the hook, I'll probably just consider safer avenues.


Prove by induction that:  $64 \mid 3^{2n + 2} - 8n - 9$, $n > 0$  I've tried to manipulate $P(k + 1)$ and haven't come up with anything like $P(k)$.  $P(k): 64 \mid 3^{2k + 2} - 8k - 9, k > 0 $ $P(k+1): 64 \mid 3^{2(k+1) + 2} - 8(k+1) - 9$

I cannot complete the third step of induction for this one. The assumption is $3^{2n+3}+40n-27=64k$, and when substituting for $n+1$ I obtain $3^{2n+5}+40n+13=64k$. I've tried factoring the expression, dividing, etc. but I cannot advance from here.


In comparing different SSL certificates I see "Server-Client Authentication" listed as a benefit of a paid certificate over a free one.    But what exactly is this added benefit that basic SSL does not already provide?  EDIT:   In other words, if you search that other question for the term, "Server-Client Authentication", it's not found.

I've been comparing prices of different SSL certificates and found a massive difference in prices between different providers.  If we take  as an example, what would be the advantage of going for the Geotrust certificate for $48.88/year over the RapidSSL $9.95/year option?


I suddenly got a problem with my bash history. When I type history, it only shows:  1  history  I tried following commands: set -o | grep history  echo $HISTFILE echo $HISTSIZE echo $HISTFILESIZE  and I got, respectively, the following results: history         on /home/mary/.bash_history 1000 2000  I added also to my bashrc, the following lines: # Avoid duplicates HISTCONTROL=ignoredups:erasedups # When the shell exits, append to the history file instead of overwriting it shopt -s histappend  # After each command, append to the history file and reread it PROMPT_COMMAND="${PROMPT_COMMAND:+$PROMPT_COMMAND$'\n'}history -a; history -c; history -r"  Everything seems OK but I can't scroll back to retrieve commands and the reason seems the fact that nothing has saved in history and that is why the command history does not contain anything. Could you please help me to solve this issue ?

The command history between sessions is not getting saved. I'm using guake and the history for the session is working fine. I noticed that .bash_history had some commands I executed in sudo -s mode and tried the same again and all the commands while in the session got saved so I tried: chmod 777 .bash_history  Now the old commands appear at the start of a session but no new commands are getting saved.


I bought this bike 2 days ago. I searched for some info, but couldn't find it. The only information I found was to be around 1972

This is a canonical question that will hopefully encompass all of the questions we get asking us to determine what year a bicycle was manufactured (how old is my bike, how old is my frame, etc.). Each "answer" should address a different way to determine the manufacturing year of a bicycle. To some extent, these will also help you narrow down the model as well as it will tell you what distinguishing features to look at.  The span of answers would include things such as:      Skiptooth cranks Cartridge bottom brackets (BB30/90 etc) Elliptical chainring Quick releases versus contemporary through-axles How the steerer attaches to the fork (quill vs. threadless)  Braking system (especially with mountain bikes: v-brake, direct pull, etc.)   Shifting ramps and pins on cassettes/sprockets and chainrings (versus flat sprockets) Frame material (e.g., shift from tubular steel to use of CF and hydroformed aluminium)  Frame tubing type (e.g. Reynolds 531 tubing introduced around 1934, still used today; Reynolds 501 tubing introduced around 1983). So a frame with an original 501 decal can't be from the 70', 531 decal doesn't help as much because of the range of years produced. Also, see Decals.   *Decals: style/design, amount, placement, color, etc. can help not only determine models, but also year of manufacture. Many changed decal design for the same model bike often yearly, with special/limited editions even more specific. This applies only if decals are original or have been replaced with the identical design. Tubing decals (Reynolds, Columbus, etc.) also changed designs for same tubing made in different years, although the changes aren't made as often, and manufacturers didn't always put tubing Brand decals on every model. Earlier bikes tended to have less fancy, less colorful, less quantity of decals.   Headbadges: most early bikes had actual "badges", often quite detailed and fancy, made of metal, then plastic, and finally just using decals on the headtube. Most bikes lost their metal badges in the 60's and early 70's, although some brands still have actual badges to this day, but in general a real badge indicates an earlier model bike. Dropout style (including the later inclusion of lawyers lips) Presence or absence of CPSC reflectors (USA only) Manufacturing method (shift from lugs to TIG welding, for example)  Number of gears (shift from 2x5 ten-speed to 3x8, 2x9, 1x11, etc.)  Inspection of lug design: pantographs, cut-out, stampings, custom brazing/filing, chrome, fork crow n sweep, etc. Frame/Fork Braze-ons. Race bikes tended have less braze-ons the earlier the year of manufacture. Most 60's racers and earlier had few or none with cable guides/stops, shifters, bidons, etc. being clamp-on. By the 80's if it was clamp-on, it was a sign of very cheap models and most frames had braze-ons for all cables, with multiple bottle and accessory bosses depending on style and use.   and so forth. Please edit this question if you have an answer that isn't in the index above.   A couple of caveats:   A previous owner could have replaced or upgraded components on a bicycle, so this guide only applies to original equipment There is a delay between the introduction of a technology (such as indexed shifting) and when manufacturers start selling products that use it. Low-end manufacturers may continue using technology that is severely outdated (such as one-piece cranks, freewheels, or quill stems) because it is cheaper to do so. A number of bikes are built in a Retro style, but with modern components.  Dutch bikes, trendy coffee cruisers, and beach cruisers may be modern but appear to be 1950s styling.  These tend to have modern rims and brakes as a giveaway.     Note that bicycles.stackexchange does not do valuations of bicycles. How much your bicycle is worth depends on the location of the buyer and seller, how much the buyer wants the bike, etc. etc. etc.


I've tried searching for this both with "infinite factorial series" and on approach0.xyz to no avail.  Wolfram|Alpha gives: $$\sum_{i=0}^{\infty}\frac{i!}{(i+4)!}=\frac{1}{18}$$ I was wondering where this came from. It's the infinite limit of the partial sum formula given by Wolfram|Alpha, as expected, but that also raises the question of where the partial sum formula comes from.  Any help would be appreciated.

I have a series question which I can not solve for two days.  $$\sum_{n=1}^∞\frac{1}{(n+1)(n+2)(n+3)....(n+p)} = \frac{1}{p.p!}$$  How can I prove and solve this equation?


I am putting together a flyer for our company. We have three different logos. The logos are actually trademarked or registered names such as ReMan, LiftTrax, LiftSafe and all are in the same font. When I import them, they are all different sizes. I need all the three of these logos to be the same size for placement purposes. How do I get all three of these logos to be the same size? Thank you.

A regular challenge that I face is balancing two (or more) logos. Whether they need to be equal or one needs to be given priority. Some logos however might be squares, others rectangles, circles, etc...   As a quick sample I snagged a nice high resolution photo from  and pretend its going to be an advertisement that needs to show some footwear brand logos on it. In this case I used Adidas and Saucony.  This is certainly not balanced even though they're height is the same:    Likewise this is not balanced even though they're width is the same:    So then the question becomes when are they in balance, is this balance:    Maybe a little more adjustment, is this balance:    And in these examples I'm only working with two Black Logos. Factor in color and it can get even more difficult to balance. Another issue being when there's tiny text as part of the logo.  So the question is, other than estimating / eye-balling it, what tips, methods or even tools are there to balance different sized logos?


Dear Blender community,  I am new in Blender, and I build the landscapes for some specific application. After creating Landscape (Shift+A, Mesh -> Landscape), I lose the panel "Landscape." Do you know how to access this panel again?

When you first add a cylinder, you have the option to change the number of vertices, etc, but once you do anything else in blender, it seems you no longer can edit those parameters.   Is there a setting anywhere or an add-on that allows these parameters to be edited later on? If not, how easy would such an addon/feature be to create for anyone reading this?


I am looking to create a file printing 0 to 10000 with padded zeros  For example: 00001 00002 00003 00004 ... 09999 10000  How could I achieve this? Thank you!  Edit, I see that this was marked as duplicate for the leading zeros, my issue is more the printing all numbers out to file. Thanks!!

Given: a = 1 b = 10 c = 100  How do I display a leading zero for all numbers with less than two digits? This is the output I'm expecting: 01 10 100


I forgot a grocery bag in my trunk, and didn't realize it until 24 hours later.  I had bean sprouts in the bag, and it says to keep refrigerated.  Are they safe to eat? I am not sure what happens to bean sprouts if left unrefrigerated.

If I left food out of the refrigerator for some period of time, is it still safe? If I left it out too long, can I salvage it by cooking it more?


Given: sed -e '/pattern1/,/pattern2/!d' file.org  How can I match the first occurrence of the lines between pattern1 and pattern2, but not the rest?  For example:  pattern1 aaaa pattern2 pattern1 bbb pattern   should output: aaa  Alternatives solutions (using grep, awk or whatever) are welcomed.

How can I select first occurrence between two patterns including them. Preferably using sed or awk.  I have:  text something P1 something content1 content2 something P2 something text something P1 something content3 content4 something P2 something text   I want the first occurrence of the lines between P1 and P2 (including P1 line and P2 line):  something P1 something content1 content2 something P2 something


I'm trying to create a new UI for database project. However, I keep getting a nullpointerexception at creating a new GUI object, and when adding content. Here is my code:  class DatabaseGUI extends JFrame implements ActionListener {  JTextField input; JTextArea restult; JButton loadButton; JButton saveButton;    public static void main(String[] args){      DatabaseGUI databaseGUI = new DatabaseGUI();     databaseGUI.setVisible(true);  }  DatabaseGUI(){      this.setTitle("Emplyoee Database");     this.setDefaultCloseOperation(EXIT_ON_CLOSE);     Container content = getContentPane();     content.setLayout(new FlowLayout());      content.add(saveButton);   }

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


I recall that before the 2 days that need to elapse before a bounty can be assigned, there was a button for it, anyway. Can't see it now in . Am I going madly blind (or maybe blindly mad)?!

It's possible to offer and award bounties of reputation on questions.   What is a bounty? How can I find questions that have a bounty attached? How do I start a bounty? When can I start a bounty? Why is the system requiring me to choose a bounty amount that's higher than the minimum? Can I use Markdown formatting in the bounty remarks? Can I edit the remark? How long is the bounty period? How do I award a bounty? Can I award a bounty to my own answer? Can I award a bounty to an old answer? If I offer a bounty on someone else's question, can I award the bounty to their answer? After awarding the bounty, can I remove it or move it to another answer at a later time? What happens if there's no answer after the bounty period? What happens if I feel my question is still unanswered? What is automatic awarding? Are bounty awards exempt from the 200 points/day reputation limit? How does Community Wiki mode affect bounties? How does user deletion or post dissociation affect bounties? Can I award a bounty to an answer from a deleted user or one where the author was dissociated? Can I offer a second bounty after the first one has expired? Can I raise my bounty? What happens if a bounty question is closed or deleted? Why can't I vote to close or migrate a bounty question? What happens if I delete my account while I have an active bounty? Do I keep an awarded bounty when I delete my answer? What happens if a question where I awarded a bounty later gets deleted or migrated? Can I cancel my bounty? Can I affect / divide / share part of my bounty to two (or more) users? How many outstanding bounties can a single user have?      See also:  in the Help Center


I am working on a Project in which the I am using vectors since the size of array is unknown initially. Does using arrays instead of vectors reduce the run time of code?If Yes, Then How can i initialize/declare the array of unknown size i.e. Size of array is variable(based on input)? "OR" Is it better to use vectors only?  Note :- I want to know Which better reduces the Execution time of Program.

In our C++ course they suggest not to use C++ arrays on new projects anymore. As far as I know Stroustroup himself suggests not to use arrays. But are there significant performance differences?


I throw 2 coins at once, and my friend tells me that one of them landed heads. Find the probability of the other one being tails. I have 2 approaches in mind: The first one is to consider that there are 4 different events {HH,TT,HT,TH}, then the options of one being heads are {HT,TH,HH}. And those that have a tail are {TH,HT}. Then the probability of the other coin being tails is $\frac{card\{TH,HT\}}{card\{HT,TH,HH\}}=\frac{2}{3}$ However I also find intuitive that both are independent so the probability of having tails should be $\frac{1}{2}$

In a family with two children, what are the chances, if one of the children is a girl, that both children are girls?  I just dipped into a book, The Drunkard's Walk - How Randomness Rules Our Lives, by Leonard Mlodinow, Vintage Books, 2008. On p.107 Mlodinow says the chances are 1 in 3.   It seems obvious to me that the chances are 1 in 2. Am I correct? Is this not exactly analogous to having a bowl with an infinite number of marbles, half black and half red? Without looking I draw out a black marble. The probability of the second marble I draw being black is 1/2.


Do closed questions ever get deleted and, if so, is reputation recalculated (subtracted) for that question and all its answers?  What happens here in meta, given that feature request "questions" are closed when they are completed?

What circumstances can cause a question or answer to be deleted, and what does that actually mean?    How can a post be deleted? When can't I delete my own post? Can I still see my post even after it's deleted? Can I see a list of my deleted posts? How can I undelete one of my posts? What does deletion mean for a post? How do votes to delete work? What are the criteria for deletion? What else should I know about deleted posts? If I flag my question with a request to delete it, what will happen?       For more information, see the articles about  and  in the .


It's always been in the back of my head that the Universe is 13.8~ billion years old and that the Observable Universe is 46~ billion light years in radius. How is this so? It would logically be only 13.8~ billion light years in diameter as that is the length of time it would take for things 13.8~ billion years to get to us?

The observable universe is approximately 13.7 billion years old. But yet it is 80 billion light years across. Isn't this a contradiction?


Is there a non-vulgar version of “pulled it out of their ass” ? It's a useful phrase, but not one to be used in professional environments.   For example:     There is no way John’s projections for next year’s sales are accurate. He ____.

Are "barking up the wrong bush" or "sailing on the wings of imagination" close?


When profiling execution time of java code, the common approach is to utilise the following approach:  long start = System.nanoTime(); expensiveMeothd(array); long runtime = System.nanoTime() - start;   Unfortunately this approach is not applicable in the confines of Java8 stream syntax.  What is the best practice for measuring a stream method execution time? For example if I wanted to calculate how long:   .map(x -> someexpensiveMeothod(x)) takes to execute.  One approach I have considered is wrapping the stream return in an object that stores the nanotime. However this approach seems less than ideal. Here is my concept:   public class Profiler {     public List list;     public long startTime;     public long endTime;      public Profiler(List list, long s, long e) {         this.list = list;         this.startTime = s;         this.endTime = e;     } }  List<Profiler> results = myList.stream()                .map(x -> new Profiler(x, System.nanoTime(), null))                .map(x -> {                     expensiveMethod(x.list);                     x.endTime = System.nanoTime();                      return x;                  })                .collect(Collectors.toList());   Additionally, is it actually appropriate to measure the execution time of individual stream method calls on principle?

How do you write (and run) a correct micro-benchmark in Java?  I'm looking for some code samples and comments illustrating various things to think about.  Example: Should the benchmark measure time/iteration or iterations/time, and why?  Related:


I have a method in an object that is called from a number of places within the object. Is there a quick and easy way to get the name of the method that called this popular method. Pseudo Code EXAMPLE: public Main() {      PopularMethod(); }  public ButtonClick(object sender, EventArgs e) {      PopularMethod(); }  public Button2Click(object sender, EventArgs e) {      PopularMethod(); }  public void PopularMethod() {      //Get calling method name }  Within PopularMethod() I would like to see the value of Main if it was called from Main ... I'd like to see "ButtonClick" if PopularMethod() was called from ButtonClick I was looking at the System.Reflection.MethodBase.GetCurrentMethod() but that won't get me the calling method. I've looked at the StackTrace class but I really didn't relish running an entire stack trace every time that method is called.

When logging in C#, how can I learn the name of the method that called the current method? I know all about System.Reflection.MethodBase.GetCurrentMethod(), but I want to go one step beneath this in the stack trace. I've considered parsing the stack trace, but I am hoping to find a cleaner more explicit way, something like Assembly.GetCallingAssembly() but for methods.


There is the numerical series of $\sqrt{n^{2} +1} -n$. I tried to use D'Alembert criterion to conclude if it converges but the limit is equal to 1. Even the Cauchy criterion does not work. Thank you for your guidance.

Test the series whose general term is: $$\sqrt{n^2 + 1} - n$$   This is from Higher Algebra by Henry Sinclair. I'm struggling to understand how this series is divergent. If you do the following expansion: $$\sqrt{n^2 + 1} - n$$ $$= n\biggl(1 + \frac{1}{n^2}\biggr)^\frac{1}{2} - n$$ $$= n + \frac{1}{2n} - \frac{1}{8n^3} + ... - n$$ $$= \frac{1}{2n} - \frac{1}{8n^3} + ... $$  The remaining series appears to converge to zero as $n$ approaches infinity.  Their explanation is similar to mine, but at the end they say that the above series approaches $\frac{1}{2n}$. From there they directly say that the series is divergent. Earlier in the chapter, it's proved that the expansion of $(1 + x)^n$ is convergent for $x < 1$. In this case, $\frac{1}{n^2} < 1$ as $n$ approaches infinity, so I would assume that the series converges.  The solution to the problem is given  (number 17)  Any help is appreciated. Thanks.


I've been trying to find what causes the periodic appearance of major and minor grooves in DNA but have not yet been successful. Geometrical explanations would also be appreciated as I cannot understand any of the geometrical explanations I have come across so far. As far as my knowledge of DNA is concerned I know of all the high school basics (e.g complimentarity, bonding between the individual components of a nucleotide etc.)

I understand that they arise due to the pairing of bases of two opposite stands and are sites through which important proteins needed for replication and transcription of DNA interact. But I don't get how the arrangement of bases really generate the grooves.


One reason why One Time Pads are impractical is that sender and receiver need copies of the same random numbers. This can quickly exhaust the set of numbers if communication is frequent. Proposal: The set of random numbers kept by pairs of senders and receivers is only the seed values for a shared PRNG. If the seeds are known to sender and receiver thru a shared list then the numbers produced by the PRNG should be identical. If the seeds are ransom then would not the output be random and usable for encoding and decoding? Process: In effect, pairs of communicators would share the same list of random seeds. As a message is created, the next random seed is pushed into the PRNG and the numbers produced are used to encode the cipher stream. The sender's list of shared random numbers is decremented by one. The receiver looks up the current random number seed and pushes it into the same PRNG. This delivers identical numbers which are used to decrypt. They receiver decrements their random number list by one. Clearly, the messages will always be shorter than the list of numbers generated by the PRNG. I don't know if keeping lists of true random numbers is a storage issue and whether this scheme saves much storage. However, it would only require 1 random number per message instead of potentially hundreds for any given message. The PRNG could be on a local PC, smart phone or on the net. The scheme would get complex with multiple communicators since each would need a list of seeds for their communication only and each would be decremented with each message. I believe it would extend the time before periodicity appears. In this sense it would be a more efficient use of random numbers. Whether security is compromised or is worse than a true OTP is beyond me.

I've stumbled (jobwise) over a system where small messages (512 Bytes or less) are encrypted and decrypted using a simple XOR using a OTP. That OTP is created using a seed based on the individual user passwords and a simple PRNG.  I'm currently seeing the following problem: Alice always keeps her password absolutely secret and it is never shared or transmitted. But the crypto-message may be intercepted by Eve, who may be smart enough to detect the pattern used to XOR the message (as the PRNG functionality is widely used as simple C-lib rand() functionality and therefore publicly available).   The reason why "they" used the OPT approach is to ensure "speedy encryption" (before transmission via SSL, secured storage, etc.).   My counter-argument is that it may be speedy, but because the seed is generated using a simple byte-addition (which results in a seed between 0 and 255), Eve has pretty good chances to quickly find the used seed and thereby the PRNG offset... which will allow her to decrypt the complete crypto-message(s) within 256 trail-and-error approaches.  Personally, I am about to advise them to use an acknowledged crypto-scheme (like AES) and make them drop their weak and insecure OTP-based crypto thing.   For as long as I can remember, I have been reading and have been told that an OTP may be regarded to be theoretically secure — but for that, the OTPs must be absolutely and truly random. From my point of view, a PRNG (cryptographically secure or not) does not seem to be a secure way to generate an OTP for crypto-purposes (using simple XOR).  But this got me thinking — maybe I am missing something in the big sea of crypto-schemes, functions, and implementations.   To avoid I'm missing something, I would embrace any feedback on the question:  Do any (non-hardware) RNGs exist which could be used (or securely abused) to create an OTP for crypto purposes?


Let $A \subset B$ be commutative integral domains with $\operatorname{Quot}(A) =  \operatorname{Quot}(B).$  Now consider the multiplicatively closed subset $S = \{x\in A\setminus\{0\}: x^{-1}\in B\}$.   I want to show that $S^{-1}A = B$. I would appreciate any help.

Let $R$ be an integral domain and let $S$ be a ring with $R \le S \le \text{Frac}(R)$ (fraction field).   Question: Is there a multiplicatively closed subset $U \subseteq R\setminus \{0\}$ such that $S=R[U^{-1}]$ ?


I'm a student of physics. Please could someone give me the explanations of the observed physical phenomena of time and energy. Especially, the differences between the two and how they relate to oneanother. Many thanks.

This is an attempt to gather together the various questions about time that have been asked on this site and provide a single set of hopefully authoritative answers. Specifically we attempt to address issues such as:   What do physicists mean by time? How does time flow? Why is there an arrow of time?


package com.example.android.appname; import android.app.Activity; import android.content.Intent; import android.media.MediaPlayer; import android.os.Bundle; import android.view.MotionEvent; import android.view.View; import android.widget.Button;  public class SampleActivity extends Activity {  Button b1;  MediaPlayer player=MediaPlayer.create(Activity.this,R.raw.sound);   @Override protected void onCreate(Bundle savedInstanceState) {     super.onCreate(savedInstanceState);      setContentView(R.layout.activity_screen);     b1 = (Button)findViewById(R.id.button1);     b1.setOnTouchListener(new View.OnTouchListener() {          @Override         public boolean onTouch(View v, MotionEvent event) {            if (event.getAction() == MotionEvent.ACTION_DOWN);             player=MediaPlayer.create(DisplayActivity.this,R.raw.sound);             player.start();             else if (event.getAction() == MotionEvent.ACTION_UP)                 player=MediaPlayer.create(DisplayActivity.this,R.raw.sound);                 player.stop();                 return true;         }     });}  public void onClick(View view) {     Intent intent = new Intent(this, Activity.class);     startActivity(intent); }   }   When I try to open a screen with the button playing sound, app crashes and in logcat appears something like this:  java.lang.RuntimeException: Unable to instantiate activity    ComponentInfo{com.example.android.appname/com.example.android.appname.'NAME'Activity}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.res.Resources android.content.Context.getResources()' on a null object reference   Also 'else' in 'else if' goes redlined and says: 'else' without 'if'  Please tell me what should I do to make this work :)

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


Is there any electromagnetic radiation associated with the electrons moving in the conductor (eg copper wire) if the current is constant (DC)?  From what I know, electrons don't move with steady speed but they "leap" from one position to the next and since the "leaping" involves acceleration and deceleration some kind of electromagnetic radiation should arise - true?

In the  (semi-classical, but should still apply here I think), the conducting electrons are in a constant electric field, and, in between collisions with the lattice ions (that happen, on average, in a time $\tau$ since their last collision) in which their velocities are reset to an average of 0, they are accelerated and gain a momentum  $$p = qE\tau (=mv)$$, where $q$ is its charge and $E$ is the electric field from the applied voltage. This obviously means in between the collisions, the electron accelerates $a$, from $v_f = v_i + a\tau$.  Accelerating charges give off . So does a DC carrying wire give off radiation one can measure?  I suspect it does, but it's of an insanely small magnitude. A quick order of magnitude calculation with the following values gives me:  $$q \sim 10^{-19} \,{\rm C}, \\ E\sim 1\,{\rm V}/1\,{\rm cm}=100\,{\rm V/meter},\\ m\sim10^{-30}\,{\rm kg} \\ \Rightarrow a = qE/m \sim 10^{13}{\rm m/s}^2 \\ \Rightarrow P \sim q^2a^2/\epsilon_0c^3 \sim 10^{-28}\,{\rm W}$$  Which is obviously pretty small. I'm not sure what's the smallest power that can be measured, but I'm guessing by increasing the applied voltage one could increase the radiated power. But is the idea even fundamentally sound?


Can I forward a variable from script tag to a current script? Something like this:  <script type="text/template" id="myscript" myvar="123123">      var filename = document.getElementById("myscript").myvar;  </script>

How can I reference the script element that loaded the javascript that is currently running?  Here's the situation. I have a "master" script being loaded high in the page, first thing under the HEAD tag.  <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"  "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> <head> <script type="text/javascript" src="scripts.js"></script>   There is a script in "scripts.js" which needs to be able to do on-demand loading of other scripts. The normal method doesn't quite work for me because I need to add new scripts without referencing the HEAD tag, because the HEAD element hasn't finished rendering:  document.getElementsByTagName('head')[0].appendChild(v);   What I want to do is reference the script element that loaded the current script so that I can then append my new dynamically loaded script tags into the DOM after it.  <script type="text/javascript" src="scripts.js"></script> loaded by scripts.js--><script type="text/javascript" src="new_script1.js"></script> loaded by scripts.js --><script type="text/javascript" src="new_script2.js"></script>


If you have an asteroid for example and a planet, isolated from all other gravitational influence and initially at rest with respect to each other, how would you find a position vs time function for the asteroid and the planet falling toward each other?

Suppose an object of mass $m$ starts at rest at a radial distance $ r_0$ from a perfectly spherical mass $M$ (where $m << M$), $r_0 > R =$ radius of $M$.    Can we analytically determine when $m$ will hit the surface of the $M$?  In other words, can we analytically solve this initial value problem:  $$ \frac{d^2r}{dt^2} ~=~ - \frac{GM}{r^2} ,$$ $$ \dot{r}(0) ~=~ 0 ,$$ $$ r(0) ~=~ r_0? $$


As a system administrator I want to give permission for user let's say "teacher" to run commands as root without knowing password of root, what to do?

After I add a user using adduser, I can't see it via System > Administration > Users and Groups unless I log out and then log in again. Is that normal?  Also, can I set a newly added user as a sudoer or do I have to change that only after adding it? How can I do that via the shell?  Finally, can I delete the original user that was created upon initial installation of Ubuntu, or is this user somehow 'special'?


Can someone please explain why the calculated value 180 * 2.2 will be different when stored in a decimal vs. a double; and perhaps also explain why .NET is calculating 180 * 2.2 with a decimal point in the first place?   Standard Calculator: 396 Expression (Double): 396.00000000000006 Expression converted to decimal: 396

What is the difference between decimal, float and double in .NET?  When would someone use one of these?


When I try jQuery selector after append html element, event is not working but when all page loaded and I try again selector like drag-drop or click event anything else it's working. I used  setTimeout function trying this event after 3 seconds its okay but I don't want to do this. Do we have another way? I'm working with Google Chrome.   $('#conf'+objId).on('toolbarItemClick',  function(event,buttonClicked){      var itemId=buttonClicked.id;      var clickedItemId=event.target.id.slice(4);       var _obj=getObjectById(clickedItemId);      switch (itemId) {     case 'objeEdit':         editBoxNameDialog(clickedItemId,"obj",_obj);     break;     case 'objeCircle':         clearObjectBackground(_obj);     break;     } });

I have a bit of code where I am looping through all the select boxes on a page and binding a .hover event to them to do a bit of twiddling with their width on mouse on/off.  This happens on page ready and works just fine.  The problem I have is that any select boxes I add via Ajax or DOM after the initial loop won't have the event bound.  I have found this plugin (), but before I add another 5k to my pages with a plugin, I want to see if anyone knows a way to do this, either with jQuery directly or by another option.


As a group, most of the players at our table are fans of rolling for stats. This leads and has led to multiple amazing characters and some .. a bit less amazing.  Something that is rather consistent is that players are often good at emphasizing what their characters are specialized in based on their stats (for example: the charismatic bard, the nimble rogue, the strong barbarian). The thing that lags behind in this concept are often the characters flaws that come from their lower skills.  The roll of the dice gives us a basic way of handling this, because the character will simply fail a lot of the checks related to this skill, but this only goes so far.  An example was our recent very charismatic (17) warlock who wasn't that blessed when it came to Intelligence (7). The problem here is that the player behind the character is far from dimwitted and has an in-depth knowledge of the lore of the world that's being played in.  The question is two-fold:   Should a DM enforce a base-level of adherence to a characters stats when they're RPing? If yes, what would be a good way of enforcing this?    Shouting "Your character doesn't know that, they are not intelligent enough!" whenever the player makes a profound observation about History or the use of Arcana will most likely turn stale very quickly.

When creating a character we obviously place our stats where they are needed. What I am wondering is how do those stats effect the character itself from a role playing perspective.  I went back and read through the PHB pages 173-178. There was a bit about how the stats effect some parts of the character, but not what I was looking for. What I was thinking of was something along the lines of a range of a stat determines a bit of how the character is role played.  For instance does low intelligence (e.g. < 6) always mean that the character cannot read?  Or a low charisma mean the character is a jerk?  Are there rules governing this? Or would this be purely governed by the DM and rules agreed on by the group?


I have a Samsung Galaxy S3 and I do not mind when the location consent screen pops up when I turn on GPS, in fact I prefer it As I always choose disagree  The one that says "allow google's location service to collect anonymous data... etc "  Yesterday I hit agree and now the prompt does not come on when I turn on GPS. In the past, if I went to location services and turned off high accuracy mode (GPS Only) it would bring back the prompt so I could disagree again.  Does anyone know how to get this prompt back (Get the dialog box back). I have tried resetting app preferences to default, disabling google app services, google play services, clearing the cache, opening location services and selecting GPS ONLY then re-enabling the google app and google apps, but nothing has worked..  I do NOT want to share anonymous information with google so I need this prompt back. Also - Is there a way to get Location Services to default to GPS only instead of High Accuracy?  This is the opposite of THIS problem

Like many, I found the Location Consent prompts to be annoying. I was excited when Google finally extended the option to 'remember this setting' in the latest update, but dismayed when I could only have the phone remember a 'yes' answer.  Unfortunately, when I handed the phone to a friend to coordinate GPS while driving she checked 'Remember this setting' and consented into the program. I would like to undo this, but cannot for the life of me find where this setting is stored on my phone. It does not appear to be listed in the 'Location' or by clearing the cache of the LocationServices app (which doesn't appear to actually work)  How can this be undone? Phone is a Motorola Razr HD running 4.4.2


I reviewed  some days ago. After I rejected it, something similar to  (documented in ) happened:     Approved Jun 17 at 11:07:      michaelb958 reviewed this Jun 17 at 11:06: Reject   This edit is incorrect or an attempt to reply to or comment on the existing post.   And that's all there was.  Viewing  indicates the edit was actually approved. The Meta question I linked to dates from 2012, and indicates that whatever bug was responsible was fixed. (Also, that was a question, whereas this is an answer.) What's going on here?    Edit:  provides a possible explanation - at time of writing, if the OP approves an edit after running out of suggested edit reviews, it doesn't show up on the edit's summary.

I've completed 20 suggested edits reviews today. Then, I came across a  and I approved it.   Then, I had a doubt that whether the review count has incremented or not, oh! it's not incrementing. System works fine.  But, take a look at review page,     The edit was already reviewed by one reviewer and then I reviewed it. As I'm the Owner of the post it's enough to approve the edit. But, the review history doesn't show the detail that I had approved it. It's misleading that only one vote of a reviewer who is neither the community user nor the OP nor the moderator, is enough.  So, what should we do in this type of situation?  Is it correct to make OP to review the suggested edit after completing daily limit?  Should we need to display/hide the OP has approved the edit in the review history?


I just ran inxi -m (version 2.2.16-0ubuntu1 on Ubuntu 15.10 64-bit), which should...  -M   Show machine data. Motherboard, Bios, and if present, System Builder (Like Lenovo).  Older systems/kernels without      the  required /sys data can use dmidecode instead, run as root. If using dmidecode, may also show bios revision as      well as version. -! 33 can force use of dmidecode data instead of /sys.   (excerpt from man inxi)   ...but in my case, it filled the result mask with file names from my home directory!  $ inxi -M Machine:   System: MAXDATA product: Desktop v: Documents serial: Downloads            Mobo: Pictures model: Public v: PythonProjects serial: Templates            Bios: Videos v: bin rv ASUSTeK date: iconlist.txt   Can I apply any patch or workaround myself to fix it?

I found a problem with an application on Ubuntu.   Questions :   How do I best report the issue?  What sort of information should I provide?


I need to make some directory of Author name. It's easy when doing them alone. I can simply  mkdir "Mario Luis Garcia"   This will create one directory named "Mario Luis Garcia"  But when trying do it massively with shell script, I failed.  for i in "Mario Luis Garcia" "etc.";     do          mkdir $i     done;   This will create 4 separate directories instead of 2. I tried to use {}, ()to enclose the quoted text in. Doesn't work.  How to do that?

Or, an introductory guide to robust filename handling and other string passing in shell scripts.  I wrote a shell script which works well most of the time. But it chokes on some inputs (e.g. on some file names).  I encountered a problem such as the following:   I have a file name containing a space hello world, and it was treated as two separate files hello and world. I have an input line with two consecutive spaces and they shrank to one in the input. Leading and trailing whitespace disappears from input lines. Sometimes, when the input contains one of the characters \[*?, they are replaced by some text which is is actually the name of files. There is an apostrophe ' (or a double quote ") in the input and things got weird after that point. There is a backslash in the input (or: I am using Cygwin and some of my file names have Windows-style \ separators).   What is going on and how do I fix it?


Is there a theoretical argument which shows that among all the possible shapes, the best choice for a wheel is to be circular?   Intuitively, it makes quite a lot of sense to me, but I'd be interested to see a kind of characterization of the circle as the most efficient wheel possible. Where, of course, "most efficient" should be defined in a suitable manner (and I guess this the hear of my question).  There is this  which states that "the wheel has a unique property: at every moment of motion, the touching point between the wheel and the ground is not in movement and therefore no work is done by the friction force." However, I'm having a hard time to understand why there should be more friction if a car has squared wheels. Indeed, I can fairly imagine that squared wheel are quite inefficient, but this is because you have to lift the car up to pass the corners, and not because of the friction (I might be wrong though).

I recently wondered whether there is a simple proof that circular wheels maximise mechanical efficiency. By this I mean:     Show that for a wheel with a given width and cross-sectional area, the   circular wheel reaches the bottom of an incline faster than a wheel   with any other shape.   This sounds like a rather elementary problem in classical mechanics but I haven't found a proof of this fact in any of the classical mechanics texts that I have read.   Note 1: I assume that the distribution of mass is uniform across the wheel so comparable wheels will have equal mass.   Note 2: Dry friction is assumed to be present.


I had installed MS Word through Wine on my Ubuntu Desktop. It work perfectly.  But everytime when I run MS Word 07 I have error message. If close this a error window. Word still runs and works fine.    How to fix this pesky message ?

Can .exe and .msi files (Windows software) be installed in Ubuntu?


What do I need to do to install Ubuntu on my Samsung Laptop from 2013? I heard that I can brick it. If I need to do an update then please give me instructions. Sorry for asking such an easy question. I'm a linux noob.

I have been reading about the issue of Samsung laptops bricking when attempted booting from live USB. I have Samsung Series 7 NP700Z5C (-S02UB to be specific) laptop. It came with Windows 8 preloaded. Some posts claim that they disabled secure boot and installed Ubuntu in EFI mode.  On the otherhand comments on this  report state the issue to be with UEFI implementation and not with Secure Boot.  I really want to dual Ubuntu with Windows 8. Can someone help with UEFI mode installation process ?


I found the most beautiful font . I want to use it. I tried following:  @font-face {     font-family: myFirstFont;     src: url(http://fontsforweb.com/font/show/?id=78041); }  div {     font-family: myFirstFont; }   (Source: )

Is there a way to add some custom font on a website without using images,  or some other graphics?  For example, I was working on a wedding website, and I found a lot of nice fonts for that subject. But I can't find the right way to add that font on the server. And how do I include that font with CSS into the HTML? Is this possible to do without graphics?


I have a main file where I include several chapters including a couple of appendices, like this:  \usepackage{appendix} \begin{document} ...  \include{chapter1} \include{chapter2} ... \include{chapter7}  \backmatter  \include{appendixA} \include{appendixB}   Inside the appendixA.tex, I have:  \appendix \chapter{Appendix A: my Title} \label{app:A}   When I reference \ref{app:A} I get the label   7.3.3   which is the label of the last subsection of the chapter before the Appendix A also, tables in the main sections appear as  Table 1   instead of:  Table A.1   It looks like the top level (chapter) numbering doesn't start at all, since the label refers to the last subsection. How do I make the appendix have a lable of its own?  Thanks in advance

I'm using the standard book class. If I write  \documentclass{book}  \begin{document}  \frontmatter \tableofcontents  \mainmatter \chapter{foo} \section{Donald}  \backmatter \chapter{bar} \section{Mickey}  \end{document}   I expect to have chapter bar numbered as appendix A and section Mickey as A.1. Instead chapter bar is not numbered and section Mickey is 1.2, following section Donald. If I insert the appendix command to obtain  \documentclass{book}  \begin{document}  \frontmatter \tableofcontents  \mainmatter \chapter{foo} \section{Donald}  \backmatter \appendix \chapter{bar} \section{Mickey}  \end{document}   then chapter bar is unnumbered and section Mickey is numbered as .1.  What am I doing wrong?


When should we use local classes? The Best practice approach?  Is it possible to make them abstract or static?  Any other solution to avoid them?

What is the advantage of local classes in Java or in any other language that makes use of this feature?


I have a multiple entry Greece visa valid for 90 days. After going to Greece and returning home to India, can I go to Paris a month later using the same visa issued by Greece? The Paris trip would be for a week or so. Will it be possible or will there be any problems?

My wife was just issued a multiple entry visa by France, which is good for one year.  Our first trip will be to France, the issuing country.  My question is: after we leave the EU and return, must future trips also start in France? Or may we go directly to (say) Greece from the US on a later visit?


As thisuser, I go to shell and run $ su anotheruser. It asks for password and then switches the user. Then I run $ gedit anyfile. But now instead of opening gedit, it gives error:  No protocol specified (gedit:388): Gtk-WARNING **: cannot open display: :20.0   How do I get this running?  EDIT:  Output of ls -l "$XAUTHORITY" when run as anotheruser  -rw------- 1 thisuser thisuser 260 Mar 31 22:35 /home/thisuser/.Xauthority

I've read  and am interested in this line:     You should never use normal sudo to start graphical applications as Root.   Why? What is the difference? Please provide a simple explanation, as I'm just a normal desktop user.


Can someone help me learning Salesforce development with good recommendation of blogs or books.  Thanks

Where should I start learning? There are various topics to learn like Objects, Classes, Apex, Visualforce, SOSL, SOQL, Triggers, etc. There are so many options out there to start learning. I couldn't decide what topic to learn first, and then step by step get proficiency in all aspects of Saleforce.


The test I know are Cauchy's root test, Cauchy's integral, Raabe's test, logarithmic test and D' Alembert's Ratio Test. I dont know which test I can use to prove that this series converges? $$\sum \left( (n^3+1)^{\frac{1}{3}} -n \right) $$

I want to expand and test this $\{(n^3+1)^{1/3} - n\}$ for convergence/divergence.  The edited version is: Test for convergence $\sum_{n=1}^{\infty}\{(n^3+1)^{1/3} - n\}$


In Classical Mechanics one usually considers the Lagrangian as $L = K - U$ where $K$ is the kinetic energy of the system and $U$ is the potential energy. One then gets the Euler-Lagrange equations and everything is fine: if we have a system we can plug in the kinetic energy and potential and find the Lagrangian for it.  The point is that I've already seen a different object: the Lagrangian density $\mathcal{L}$ which is on the other hand a $4$-form on space-time. The main difference being that the action is the integral of $L$ over time and the integral of $\mathcal{L}$ over all space-time.  The problem is that apart from that, no relation between $\mathcal{L}$ and other quantities is given at first. So for instance, in electrodynamics we have  $$\mathcal{L} = -\dfrac{1}{4\mu_0}F^{\alpha \beta}F_{\alpha\beta}-A_\alpha J^\alpha$$  Where $A$ is the $4$-potential and $F=dA$ is the electromagnetic tensor. It is not clear at first, why this is the right Lagrangian density in the sense that it becomes a little hard to see where it comes from.  So, the Lagrangian itself is just $K-U$, but what about the Lagrangian density? How does one find it?

So I know that for an electromagnetic field in a vacuum the Lagrangian is $$\mathcal L=-\frac 1 4 F^{\mu\nu} F_{\mu\nu},$$ the standard model tells me this. What I want to know is if there is an elementary argument (based on symmetry perhaps) as to why it has this form. I have done some searching/reading on this, but have only ever found authors jumping straight to the expression and sometimes saying something to the effect that it is the "simplest possible".


Let $X$ and $Y$ be two random variables that are uniformly distributed in the square of vertices $(1,0), (0,1), (-1,0)$ and $(0,-1).$   Are they independent?   My thinking: To answer the question I must see whether or not the joint density function is the product of the marginal distributions which can be found once I have written the joint pdf.  I check for the area of the square in which they are uniformly distributed (so I can do simple substitution and find my joint pdf), I find this area is $2$. Now my joint pdf is:  \begin{align} &\begin{aligned} f_{X,Y}(x,y) =  \begin{cases}       1/2, & \text{if } (x,y)\in D \\       0, & \text{otherwise}     \end{cases} \end{aligned} \end{align} where $D$ is my square.  Off to find $f_Y(y)$ and $f_X(x)$. By definition, $f_Y(y)=\int_{-\infty}^{\infty} f_{X,Y}(x,y)\text{d}x$. So I see that $-1<x<1$ and therefore $f_Y(y)=\int_{-1}^{1} (1/2) \text{d}x = (1/2)[x]_{-1}^{1}=(1/2)\cdot 2 = 1$. And due to similar arguments I'd get $f_X(x)=1$. So $f_X(x)\cdot f_Y(y)\neq f_{X,Y}(x,y)$, which goes against what those well versed in probability and statistics know, and it's that they indeed are independent.  Page four of ('') says: "Suppose that $X$ and $Y$ have a joint density function that is uniform on the square $[a,b]\times[c,d]$, then they are independent."  So naturally the question arises, what am I doing wrong?

Let $X,Y$ absolutely continuous random variables with density finctions $f_X,f_Y$. Assume that the mutual density $f_{X,Y}$ equals to a constant $c$ in $\{(t,s)\in\mathbb{R}^2:|t|+|s|<1\}$. Are $X,Y$ independent?    I guess I need to use $\int_{-1}^0 \int _{1+s}^{−1−s}f_{X,Y}(x,y)dxdy+\int_0^1\int_{1−s}^{s−1}f_{X,Y}(x,y)dxdy=c$, But I'm not sure how can it help me.  The defenition of independent random variables is random variables $X,Y$ such that $\forall(t,s)\in \mathbb{R}^2, F_{X,Y}(t,s)=F_X(t)F_Y(s)$.


I am using the 64-bit version of Ubuntu, but I need to install a 32-bit version of a package to use with a proprietary extension for it, which is only available in 32-bit. How can I install the 32-bit version of the package, while I am running a 64-bit system?

I have a 64-bit version of Ubuntu 13.10.  I want to run a 32-bit version of a program.  However I see ia32-libs is not included in 13.10.  Is there a replacement package for this or what?


I have some Queues which needs to move to other sandbox. Please suggest the package.xml structure

I know I can move Queues from instance to instance using Change Sets, but is there any way to do it with the Force.com Migration Tool (Ant)?


How to curl and unzip to a certain directory?  you curl a file to stdout then unzip to some dir.

I have to download a file from this . The file download is a zip file which I will have to unzip in the current folder.  Normally, I would download it first, then run the unzip command.  $ wget http://www.vim.org/scripts/download_script.php?src_id=11834 -O temp.zip $ unzip temp.zip   But in this way, I need to execute two commands, wait for the completion of first one to execute the next one, also, I must know the name of the file temp.zip to give it to unzip.  Is it possible to redirect output of wget to unzip? Something like  $ unzip < `wget http://www.vim.org/scripts/download_script.php?src_id=11834`   But it didn't work.      bash: wget   http://www.vim.org/scripts/download_script.php?src_id=11834   -O temp.zip: ambiguous redirect   Also, wget got executed twice, and downloaded the file twice.


What is the difference between   public static void Main (String[] args)   and   public static void Main (string[] args)   in C#? I am using SharpDevelop 4.3.1 as the development environment.   If I am using string it is highlighted in red but when I am using String it is highlighted in black. Checking online I found out that both String and string are the same, if so why are they highlighted differently?

Example (note the case):  string s = "Hello world!"; String s = "Hello world!";   What are the guidelines for the use of each? And what are the differences?


I have a large Acrobat file (currently 92 pages, 25MB) which is constructed from lots of different sources (1 InDesign and 80 Illustrator files). Since I first brought these sources together, each page of it has been replaced a good dozen times, and the file is starting to creak under the weight. Acroat is giving me warnings about possible corruption, and crashes occasionally when saving.  No data has been lost yet, but it's enough to give me pause. I could reconstruct the file from sources if I had to, but it would take forever to get all the bookmarks and links set up just the way they used to be.  Is there any way of getting Acrobat to rebuild the file from the ingredients and make it easier to work with?

Does anyone have any recommendation or procedures for repairing a corrupt PDF?  When I open the file I get "There was an error opening this document.  the file is damaged and cannot be repaired."  There seems to be a myriad of tools out there but none that I could describe as reputable.  Are there any opensource linux based solutions for this possibly?


I have the code to graph a rational function f(x)=(3x^{2}+5x)/(2x-3) with a vertical asymptote and a slant asymptote. The equation for the vertical asymptote is x=3/2. I decided to have two parts to the domain: one on the interval [-15, 1.4] and one on the interval [1.6, 22]. f(1.4)=-64.4 and f(1.6)=78.4.  Near the vertical asymptote, the smallest and biggest the function gets is about -17 and 34.5, respectively.  I use the commands ymin=-23,ymax=40 and restrict y to domain=-23:40 though. Why isn't the graph drawn down to -23 and up to 40?  (I understand that part of the graph near 3/2 would be missing.)  Points on the graph are plotted with coordinates less than -17 or more than 35; these points are far from the vertical asymptote.  By the way, the command ymin=-23,ymax=40 instructs TikZ to only plot those points (on the graph of the rational function and the two lines) with coordinates between -23 and 40. Doesn't the command restrict y to domain=-23:40 do the same thing?  \documentclass{amsart} \usepackage{tikz} \usepackage{pgfplots} \pgfplotsset{compat=1.11}  \pgfkeys{/pgfplots/Axis Labels At Tip/.style={         xlabel style={at={(current axis.right of origin)},xshift=1.5ex,yshift=-1.5ex, anchor=center},         ylabel style={at={(current axis.above origin)},xshift=1.5ex,yshift=1.5ex, anchor=center}         }         }   \begin{document}   \begin{tikzpicture} \begin{axis}[width=7in,axis equal image,clip=false,     axis lines=middle,     xmin=-20,xmax=25,     domain=-20:25, samples=101,     xlabel=$x$,ylabel=$y$,     ymin=-23,ymax=40,     restrict y to domain=-23:40,     enlargelimits={abs=1cm},     axis line style={latex-latex},     ticklabel style={font=\tiny,fill=white}, %    xtick={\empty},ytick={\empty}     Axis Labels At Tip ] \addplot[samples=251,domain=-15:1.4] {(3*x^2+5*x)/(2*x-3)} node[left,pos=0.15]{$\scriptstyle{y}=\frac{3x^{2}+5x}{2x-3}$}; \addplot[samples=251,domain=1.6:22] {(3*x^2+5*x)/(2*x-3)}; \addplot [dashed, latex-latex,domain=-17:25] {(3/2)*x+5/2} node [pos=0.95, anchor=north, font=\footnotesize, sloped] {$y=\frac{3}{2}x+\frac{5}{2}$}; \addplot [dashed, latex-latex,domain=-23:40] (1.5,x) node [pos=0.05, anchor=north, font=\footnotesize, sloped] {$x=\frac{3}{2}$}; \end{axis} \end{tikzpicture}  \end{document}

The following code is compiled by pgfplots to graph an exponential function and its inverse. I have some questions about the code, and I would like to modify some of the features of the graphs.  How is pgfplots instructed to draw grid lines 5 units apart? Why is the graph of the exponential function between the vertical lines x=-5 and x=3.8, I guess?  Why is the graph of the line y=x between the vertical lines x=-5 and x=5?  Why does the label for the logarithmic function interfere with the graph of the logarithmic function?  I would like the numbers on the axes to be in white nodes - so that the grid lines are not drawn over them.  The grid lines are drawn too high and too far to the right. I would like either the grid lines to be drawn a bit shorter or the axes to be drawn a bit longer.  The domain of the exponential function (that is graphed) should be from -6 to 4, and the domain of the linear function should be from -6 to 16.  \documentclass[10pt]{amsart} \usepackage{tikz} \usetikzlibrary{calc,angles,positioning,intersections,quotes,decorations.markings} \usepackage{tkz-euclide} \usetkzobj{all} \usepackage{pgfplots} \pgfplotsset{compat=1.11}    \begin{document} \begin{tikzpicture} \begin{axis}[grid=both,           xmax=18,ymax=17,           axis lines=middle,           restrict y to domain=-7:17,           enlargelimits] \addplot[dashed]{x} node[fill=white, above, right]{$y=x$}; \addplot[green]  {pow(2,x)} node[fill=white, above, right]{$y=2^x$}; \addplot[blue,domain=1/2^6:16,samples=100]  {log2(x)} node[fill=white, below] {$y=\log_2(x)$}; \end{axis} \end{tikzpicture}  \end{document}


import android.content.Context;  import android.content.SharedPreferences;  import android.os.Bundle;  import android.util.Log;  public class MainActivity extends AppCompatActivity {      @Override     protected void onCreate(Bundle savedInstanceState) {         super.onCreate(savedInstanceState);         setContentView(R.layout.activity_main);          SharedPreferences           sharedPreferences=this.getSharedPreferences("com.example.sharedpre",Context.MODE_PRIVATE);         SharedPreferences.Editor editor = sharedPreferences.edit();         editor.putString("username", "VJ").apply();         String user=savedInstanceState.getString("username","");          Log.i("username",user);     } }

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


I was hoping if someone could show me the proof of exactly why this converges to the Euler–Mascheroni constant.

I'm searching for a really simple and beautiful proof that the sequence $(u_n)_{n \in \mathbb{N}} = \sum\nolimits_{k=1}^n \frac{1}{k} - \log(n)$ converges. At first I want to know if my answer is OK.  My try: $\lim\limits_{n\to\infty} \sum\limits_{k=1}^n \frac{1}{k} - \log (n) = \lim\limits_{n\to\infty} \sum\limits_{k=1}^n \frac{1}{k} + \sum\limits_{k=1}^{n-1} \log(k)-\log(k+1) = \lim\limits_{n\to\infty} \frac{1}{n} + \sum\limits_{k=1}^{n-1} \log(\frac{k}{k+1})+\frac{1}{k}$     $ = \sum\limits_{k=1}^{\infty} \frac{1}{k}-\log(\frac{k+1}{k})$ Now we prove that the last sum converges by the comparison test: $\frac{1}{k}-\log(\frac{k+1}{k}) < \frac{1}{k^2} \Leftrightarrow k<k^2\log(\frac{k+1}{k})+1$ which surely holds for $k\geqslant 1$      As $ \sum\limits_{k=1}^{\infty} \frac{1}{k^2}$ converges $ \Rightarrow \sum\limits_{k=1}^{\infty} \frac{1}{k}-\log(\frac{k+1}{k})$ converges and we name this limit $\gamma$ q.e.d


def h(y):     x = x + 1  x  = 5 h(x) print(x)   So this is from the MIT 6.00.1 course.  This bit of code throws an UnboundedLocalError: local variable 'x' referenced before assignment.  I even tried doing this like this:  x = 5 def h(y):     x = x + 1  h(x) print(x)   But that also gives the UnboundLocalError.  My thought process was that declaring x = 5 before the function is created and placed into the global stack (sorry if the lingo is wrong) would ensure that when we call h(x) the globally scoped variable x would have a value to pass to the function.  I'm also curious that this somewhat similar snippet of code does NOT produce the UnboundLocalError:  x = 12 def g(x):     x = x + 1     return x  g(x)   And I am running these code snippets through Python Tutor, I (am fairly sure) that I generally understand the order in which things are occurring as the code executes.    Sorry, and thanks in advance - I am looking to understand what's really going on here instead of glossing over it.  I realize that usually locally scoped variables are less confusing and less likely to cause weird bugs.

How can I create or use a global variable in a function?  If I create a global variable in one function, how can I use that global variable in another function? Do I need to store the global variable in a local variable of the function which needs its access?


I did one of the following and can't play PewDiePie's Tuber simulator with the progress linked to my account:   I logged out and can't login I logged out and tried to login in another device I tried to login on a second device without logging out My device broke and I can't login from another one I restarted my device / reinstalled the game and my progress didn't save   And possibly even:   I don't know how to login I forgot my login name and password   How can I fix each of these problems, and can I prevent them somehow?

How do I login to the Gamecenter on PewDiePie's Tuber Simulator, if you have not done it when they asked?


Earlier I had asked a question about the series: $$ \sum_{n=1}^{\infty} \sum_{m=1}^\infty \frac{1}{{n^2 +m^2}}. $$ Which looks like some kind of double series version of the Basel problem.  Much to my disappointment this series was shown to diverge here ().  There could still be a series worthy of being called the Double Basel Problem. $$ \sum_{n=1}^{\infty} \sum_{m=1}^\infty \frac{1}{{(n^2 +m^2)^2}}. $$ This double series is certainly convergent; however evaluating the sum involves tackling some series I have never seen before.   Using the same kind of trick from the other problem and differentiating, this double series can be reduced into: $$ \sum_{n=1}^{\infty} \frac{\pi^2}{4n^2} {csch}^2\pi n + \frac{\pi}{4n^3} \coth \pi n - \frac{1}{2n^4} $$ Has anyone seen series like the first two? How do we even begin to make progress on this kind of thing? Thanks for all of your help!

This is a personal research that came to an end , since the results were not those which were being anticipated. I was unable to come up with a solution therefore I post the topic here:  Prove (it certainly holds because it was checked on a computer) that the following identity holds:  $$\sum_{n=1}^{\infty}\sum_{k=1}^{\infty}\frac{1}{\left ( n^2+k^2 \right )^2}=\zeta(2)\sum_{n=1}^{\infty}(-1)^{n-1}\frac{1}{\left ( 2n-1 \right )^2}-\zeta(4)$$  wheras $\zeta$ represents the zeta function defined as $\displaystyle \zeta(s)=\sum_{n=1}^{\infty}\frac{1}{n^s}, \;\; \mathfrak{Re}(s)>1 $. Of course both values of $\zeta$ appearing here are known. For complete of sakeness i quote them :  $$\zeta(2)=\frac{\pi^2}{6}, \;\; \zeta(4)=\frac{\pi^4}{90}$$  Now, one can also see (not trivial ) that:  $$\sum_{n=1}^{\infty}\frac{1}{n^2 \sinh^2 \pi n}=\frac{4}{\pi^2}\sum_{n=1}^{\infty}\sum_{k=1}^{\infty}\frac{1}{\left ( n^2+k^2 \right )^2} -\frac{\pi^2}{60}$$  This equation also holds (checked by computer). The following result was extracted by using the known formulae $\displaystyle \sum_{n=-\infty}^{\infty}\frac{1}{z+n}=\frac{\pi}{\tan \pi z}$ and the known (?)  Fourier series: $$\displaystyle \frac{1}{\sinh^2 \pi z}=\frac{1}{\pi^2 z}+\frac{4z^2}{\pi^2}\sum_{k=1}^{\infty}\frac{1}{\left ( z^2+k^2 \right )^2}-\frac{2}{\pi^2}\sum_{k=1}^{\infty}\frac{1}{z^2+k^2} $$  Of course the last sum at the last equation can easily be computed via residues. What remains now is the proof for the first equation in the post. No-one can guarantee that is going to be an easy task.    Some comments:  1. I came across the identity on a book. I checked the validity with a computer and yes it does hold.  2. I have ckecked enough books to see if there is in there somewhere , but unfortunately it was not. So, I speculate that it is not that famous.   3. It can also be linked with other sums (single or double). Unfortunately I don't have my papers in front of me in order to write them down. So, i think it is an interseting identity.  I would appreciate your help.


In eevee I put a texture into a displacement node, then that displacement into the material output displacement, which is what this site says is supposed to work, but unsurprisingly that doesn't. The shading/texture/display/view port/... w/e only acts as though it's the primitive Blender Render normal setting, not like an actual displacement modifier, which Blender Render does process correctly. How is this supposed to work for eevee?

I have a Blender 2.8 scene with animated true displacement. It is created using material nodes and works fine in Cycles. However, EEVEE doesn't displace my meshes truly, only normals are changed. Is it possible and how to solve the problem now or in the future?


So I just installed Ubuntu 19.04 on a Satellite L55-C5340 computer and it just says there is no wi-fi adapter found. All that comes up is the wired, VPN or proxy. I already checked and there is a Broadcom 802.11 LINUX STA wireless driver from bcwl-kernel-source under additional drivers.  The network controller that comes up after running lspxi -nn on the terminal is: Network controller [0280] : Broadcom Inc ... BCM43142 802.11B... (REV 01)  Does anyone know how to fix this?

I'm having serious problems installing the Broadcom drivers for Ubuntu. It worked perfectly on my previous version, but now, it is impossible.   What are the steps to install Broadcom wireless drivers for a BCM43xx card?  I'm a user with no advance knowledge in Linux, so I would need clear explanations on how to make, compile, etc.    lspci -vnn | grep Network showed:   Broadcom Corporation BCM4322 802.11a/b/g/n Wireless LAN Controller [14e4:432b]      iwconfig showed:  lo        no wireless extensions. eth0      no wireless extensions.   NOTE: Answer below is updated every time new information is added and confirmed working.


#include<iostream> using namespace std;  class A {     public:         A():m(1){};         int m; };  class B : public A {     public:         B (): A(),m(2),n(3){};         void print(){cout<<'?';};         int m,n; };  int main (int, char *[]) {     B b;     A a1 = b;     cout<<a1.m<<endl;       // This prints out 1 instead of 2.       return 0; };  Brief code explanation: I declared and defined two class A and B, where B inherits from A. Class A and B both contains member variable m. When I say A a1 = b;, I understand that member variable n of instance b won't get copied to a1, because of class slicing. My question is why member variable m is not copied as well? (My thought is like: Both instance a1 and b contain member variable m, so when initializing a1 with b, the copy constructor of a1 will be called, and member variable within class A will get copied from b.)   Is that correct? More generally, during class slicing, what exactly is copied to the recipient?

Someone mentioned it in the IRC as the slicing problem.


Basically, I've taken the current badges on StackOverflow, and broke them into actions you can perform on the site. (Posting, Editing, etc).   Once I decided on the actions, I gave each action a gold, silver, and bronze badge, and saw which badges actually fit into those categories.  This left me with a list that shows which site actions don't have certain levels of badges in them. I'm not saying that we should put these badges in place, I'm just giving an overview of where the disconnects are.  Enjoy!  Posting   Question   Views    [b] Popular Question - Asked a question with 1,000 views    [s] Notable Question - Asked a question with 2,500 views    [g] Famous Question - Asked a question with 10,000 views    Votes    [b] Student - Asked first question with at least one up vote    [b] Nice Question - Question with score of 10 or more    [s] Good Question - Question with score of 25 or more    [g] Great Question - Question with score of 100 or more    Favorite    [b]    [s] Favorite Question - Question favorited by 25 users    [g] Stellar Question - Question favorited by 100 users    Tagging    [b]    [s] Taxonomist - Created a tag used by 50 questions    [g]   Answers    Votes    [b] Nice Answer - Answer with score of 10 or more    [s] Good Answer - Answer with score of 25 or more    [g] Great Answer - Answer with score of 100 or more     [b] Teacher - Answered first question with at least one up vote    [s] Enlightened - First answer was accepted with at least 10 up votes    [s] Guru - Accepted answer and voted up 40 times    [g]    Commenting    [b] Commentator - Left 10 comments    [s] Pundit - Left 10 comments with a score of 5 or more    [g]     Bounty    [b] Altruist - First bounty you manually awarded on another person's question     [b] Benefactor - First bounty you manually awarded on your own question     [b] Investor - First bounty you offered on another person's question     [b] Promoter - First bounty you offered on your own question     [s]    [g]    Low-vote accepted answers    [b]    [s] Tenacious - Zero score accepted answers: more than 5 and 20% of total     [g] Unsung Hero - Zero score accepted answers: more than 10 and 25% of total   Reviewing   Voting   [b] Supporter - First upvote   [b] Critic - First downvote   [s] Civic Duty - Voted 300 times   [g] Electorate - Voted on 600 questions and 25% or more of total votes are on questions   Editing   [b] Editor - First edit   [s] Strunk & White - Edited 80 posts   [g] Copy Editor - Edited 500 posts   Retagging   [b] Organizer - First retag   [s]   [g]   Rollback   [b] Cleanup - First rollback   [s]   [g]   Flagging   [b] Citizen Patrol - First flagged post   [s] Deputy - Raised 80 helpful flags    [g] Marshal - Raised 500 helpful flags   Deleting   [b] Disciplined - Deleted own post with score of 3 or higher   [b] Peer Pressure - Deleted own post with score of -3 or lower   [s]    [g]  Site   Viewing   [b]   [s] Enthusiast - Visited the site for 30 consecutive days   [g] Fanatic - Visited the site each day for 100 consecutive days   Reputation   [b] Mortarboard - Hit the daily reputation cap for the first time   [s] Epic - Hit the reputation cap of 50 days   [g] Legendary - Hit the daily reputation cap on 150 days   Membership   [b] Autobiographer - Completed "About Me" section of user profile.   [s] Beta - Actively participated in the Stack Overflow private beta   [s] Yearling - Active member for a year, earning at least 200 reputation   [g]   Misc  [b] Scholar - First accepted answer on your own question  [b] Self-Learner - Answered your own question with at least 3 up votes  [b] Tumbleweed - Asked a question with no answers, no comments, and low views for a week  [s] Generalist - Provided non-wiki answers of 15 total score in 20 of top 40 tags  [s] Necromancer - Answered a question more than 60 days later with a score of at least 5  [g] Populist - Provided an answer that outscored an accepted answer with 10 votes by 2x  [g] Reversal - Provided answer of +20 score to a question of -5 score   Hopefully this may be of use to someone.

Formerly List of all badges with full descriptions.  What are badge name's requirements? Why didn't I get badge name ? Which badges can I earn multiple times?    Jump to:                    Note: Some badges are awarded based on score. The term score means the total number of upvotes minus the total number of downvotes.  Any badge with a *** next to it is one of 20 badges that count towards the  displayed on a moderator candidate in an election. The candidate score is a total of 40 points: the first 20 are awarded based on the user's rep divided by 1000 and rounded down; the second 20 represents the total number of unique badges earned of the 20 that count. Note that if the same badge is earned multiple times, it will only count once towards the candidate score.  Any badge with a "(retired)" next to it is no longer awarded, but is retained by users who previously earned them. See  for more info on what it means for a badge to be retired.       Visit the  of the  on any site to see a complete list of badges that you can filter by earned, unearned, or type.


On Windows, the key combination Alt + 2+ 5+ 5 creates a blank space. How can I achieve this on Ubuntu?

The title pretty much says it all: how can I type Unicode characters - specifically the em-dash —?


I believe the image says everything. I've noticed this on several pages thus far.

Currently I am posting this on a page without any CSS style. Anyone else experiencing this?  I am using Firefox 3.5.2 and have tried refreshing (CTRL + F5) multiple times, even closing the browser. I do have Stylish installed and was using it to create a Hot Dog Stand theme, but it was inactive when this happened.  Screenshot:


For example, I have the following situation:  An/The example of a password is shown in Figure 1.  a picture goes here  Figure 1 - An/The example of a password  What article should I use? Should I say "The example" or "An example"? The question is not about articles, it's more about figure captions and what I should use.  From  article I see that it may be omitted.

I can’t for the life of me figure out where to use a and where to use the — and where there is no article at all. Is there a simple rule of thumb to memorize?   The standard rule you always hear:     “If a person knows which item you are talking about then use "the"   . . . doesn’t clear things up for me, as I have no idea whether or not they know.


So I am iterating through a "list of lists" of integers in python 3.9.0 as follows: n = 3 adjList = dict.fromkeys([i for i in range(n)], []) p = [[1, 0], [2, 0]] for s, e in p:    if e not in adjList[s]:      adjList[s].append(e)  I would expect adjList to result in: {0: [], 1: [0], 2: [0]}  Instead I get: >>> adjList {0: [0], 1: [0], 2: [0]}  Why isn't append modifying the list specified in adjList[i] only where i is the integer key? I can get it to work by changing adjList[s].append(e) to adjList[s] = adjList[s] + [e].

I needed to create a list of lists in Python, so I typed the following: my_list = [[1] * 4] * 3  The list looked like this: [[1, 1, 1, 1], [1, 1, 1, 1], [1, 1, 1, 1]]    Then I changed one of the innermost values: my_list[0][0] = 5  Now my list looks like this: [[5, 1, 1, 1], [5, 1, 1, 1], [5, 1, 1, 1]]    which is not what I wanted or expected. Can someone please explain what's going on, and how to get around it?