I was browsing the HNQs (Hot network questions) when I saw that some of the gravatars had different usernames, but the same gravatar. When investigating further, I found that in fact, they all belong to different users, and those users have profile pictures that are not the same as those displayed on the HNQ page. Here is an example from page 1 (around UTC 1900)  And another example from page 3 (around 19:05)  However, when I click on the profiles of the generic green Gravatar icon for any of the below users, such as  on Worldbuilding SE, it takes me to their profile page on that site... with a completely different profile picture. As this is a recurring bug (the same happened for all the other ones I clicked on) is this a problem with my device/browser/operating system (I'm using Windows 10 on a PC on Chrome) or is this a larger, site-wide bug? Edit: Just checked for the other Gravatars; they seem to work fine as the bug only occurs with the teal/white generic one.
Same gravatar is displayed for different users in the stackexchange.com , under the Top Network Askers in the right side bar.   The red circled image's source (&lt;img src=) are from   https://www.gravatar.com/avatar/?s=18&amp;d=identicon&amp;r=PG&amp;s=30                                ^   Seems the gravatar id is missing here in the image source.  For an example from the list, the user  gravatar id should be    https://www.gravatar.com/avatar/66c66c4d97a7bc3859a85253f003e1fb?s=18&amp;d=identicon&amp;r=PG&amp;s=30   but it is mapped with   https://www.gravatar.com/avatar/?s=18&amp;d=identicon&amp;r=PG&amp;s=30   which caused the display issue.
Laptop (Asus x555u) screen turns off as soon as you remove the power cord Strange distance measurements in distance matrix I'm trying to create a distance matrix between two point shapefiles in QGIS 2.6. Both are in WGS84 UTM Zone 30N co-ordinates (and so is the project file), but the distance matrix returns values such as 5673346.938, instead of expected numbers of between 1 and 5km.  I saw a similar thread mentioning disabling 'on the fly projection changes' - I've done this, and no change. Threads already checked:     Here are samples of the two shapefiles I'm using, stripped down to just ID and location. Analytic solution for $x=\ln(x+1)$ How to show that $\int_{0}^{\pi}{\sin^5 x\over 1+\cos^3 x}\mathrm dx=\ln 3?$ Given the integral $(1)$     $$\int_{0}^{\pi}{\sin^5 x\over 1+\cos^3 x}\mathrm dx=\ln 3\tag1$$   This integral seems to be quite tough, I can't even know where to start. I have try substitution $u=1+\cos^3 x$ and $u=\cos^3 x$, can seem to remove the x variables.  We have the following identities   $$\sin^5a={5\over 8}\sin a-{5\over 16}\sin 3a+{1\over 16}\sin 5a\tag2$$  $$\cos^3 a={3\over 4}\cos a+{1\over 4}\cos 3a\tag3$$  We may write $(1)$ as  $$\int_{0}^{\pi}{\sin x(1-\cos^2 x)^2\over 1+\cos x(1-\sin ^2 x)}\mathrm dx\tag4$$  $u=1-\sin^2 x\implies \mathrm du=-2\sin x\cos x\mathrm dx$ then $(4)$ becomes  $${1\over 2}\int_{0}^{1}{(1-u)^2\over \sqrt{u}+u^2}\mathrm du\tag5$$  $u=v^2\implies du=2vdv$ then $(5)$ becomes  $$\int_{0}^{1}{(1-v^2)^2\over v+v^4}\cdot{v\mathrm dv}\tag6$$ Simplify to  $$\int_{0}^{1}{(1-v)(1-v^2)\over 1-v+v^2}\mathrm dv\tag7$$  I guess using partial decomposition of fraction and integrate term by term, seem lengthy process  How else can we prove $(1)$? What are good books/other readings for elementary set theory? I am looking to expand my knowledge on set theory (which is pretty poor right now -- basic understanding of sets, power sets, and different (infinite) cardinalities). Are there any books that come to your mind that would be useful for an undergrad math student who hasn't taken a set theory course yet?   Thanks a lot for your suggestions! Use grep --exclude/--include syntax to not grep through certain files I'm looking for the string foo= in text files in a directory tree. It's on a common Linux machine, I have bash shell: grep -ircl &quot;foo=&quot; *  In the directories are also many binary files which match &quot;foo=&quot;. As these results are not relevant and slow down the search, I want grep to skip searching these files (mostly JPEG and PNG images). How would I do that? I know there are the --exclude=PATTERN and --include=PATTERN options, but what is the pattern format? The man page of grep says: --include=PATTERN     Recurse in directories only searching file matching PATTERN. --exclude=PATTERN     Recurse in directories skip file matching PATTERN.  Searching on grep include, grep include exclude, grep exclude and variants did not find anything relevant If there's a better way of grepping only in certain files, I'm all for it; moving the offending files is not an option. I can't search only certain directories (the directory structure is a big mess, with everything everywhere). Also, I can't install anything, so I have to do with common tools (like grep or the suggested find). Is two-thirds plural? Is 2/3 always, sometimes or never plural?  E.g.     1a) 2/3 of the pizza were eaten.     1b) 2/3 of the pizza was eaten.      2a) 2/3 of the visitors were men.     2b) 2/3 of the visitors was men.   I feel that example 1 could go either way but example 2b sounds very wrong.  Is there a rule for this? By the time, many files are still on my system and I don't need them anymore, so how to delete all files that are one year old at least? Is there a way to do an "upside down" \widehat? I've come across this in a book I'm looking through, but I can't find the code for it. I want it to look exactly like the \widehat and go above text like \widehat does...I just want it to be (vertically) flipped! Plot a piecewise function with black and white disks marking discontinuities Excel automatic hyperlinks Why couldn't the Jedi detect Senator Palpatine as having powers? In Return of the Jedi, when trying to sneak into the base on a shuttle, Luke said he senses Darth Vader's presence and said he shouldn't have come lest he jeopardize the mission. Darth Vader also sensed Luke, but let him in anyways. Also, Yoda and Obi-Wan could detect the Force in young Anakin.  So if Jedi and Sith can detect each other, why couldn't they detect Senator Palpatine to begin with? It seems like a giant plot hole. CUDA Driver API vs. CUDA runtime When writing CUDA applications, you can either work at the driver level or at the runtime level as illustrated on this image (The libraries are CUFFT and CUBLAS for advanced math):   (source: )    I assume the tradeoff between the two are increased performance for the low-evel API but at the cost of increased complexity of code. What are the concrete differences and are there any significant things which you cannot do with the high-level API?  I am using CUDA.net for interop with C# and it is built as a copy of the driver API. This encourages writing a lot of rather complex code in C# while the C++ equivalent would be more simple using the runtime API. Is there anything to win by doing it this way? The one benefit I can see is that it is easier to integrate intelligent error handling with the rest of the C# code. Optimal drive configuration for SQL Server 2008R2 I have a fairly busy database server running SQL Server 2008 R2 that has the following setup:   SATA RAID 1 (2 Drives)  - OS / Programs SAS  RAID 10 (4 Drives) - Sql Database Files (data and logs) SAS  RAID 1 (2 Drives)  - TempDB (data and logs)   Assuming I can't add additional drives into this server, have I made the best use of the configuration I have available? Or should I consider another scheme here where logs are isolated from the data files, for example?  Update:  For those that requested further hardware details:   The SATA drives (used for the OS / Program partition) are: WD 7200 RPM 3 Gb/s 3.5 Inch SATA The SAS drives used in the other arrays are: Seagate 15K RPM 6 Gb/s 3.5 inch SAS The RAID controller used is an: LSI 9260-8i SAS/SATA 6 Gb 8 port   Update 2:  Based upon the feedback I've received, it looks like I have the following viable options to choose from - I will award the bounty to someone that can tell me which is likely to be the best in the environment that I've outlined:   Leave everything as is - I probably won't do much better  Move my 2 SAS RAID 1 drives into my existing RAID 10 array to have it composed of 6 disks in total  Move my log files onto the SAS RAID 1 and/or relocate TempDB (data or logs) back to the RAID 10 I have noticed a couple of kinds of behavior that seem to crop up in the SO community, and it really seems to artificially boost reputation. There may not be a solution (or it may not be a problem!) but here are some thoughts.  The first is the fact that "celebrity" users, or users with lots of reputation, are treated significantly better than others. Take Joel Spolsky's most recent question:    It was closed, opened, closed, and re-opened. And the question has earned Joel - what - 1030 reputation 103 votes, and lots of reputation! Wow! I'm not saying that Joel's question is a bad one. But lets compare to other questions that one might consider to be in the same equivalence class - easily answerable, specific questions, short questions:   (5 votes)   (5 votes)  If you look at the , I can hardly find any which are specific technical questions. So that Joel's question was so upvoted could only mean that:   It was upvoted based on his celebrity People have been interpreting the questions as a sort of zen-like wakeup call, designed to get people talking and thinking about they way they vote.   I do not mean any disrespect toward Joel, and again, I think his question was a good one. This post isn't about Joel! But the boost in reputation did not (imho) mean "Joel is really good at programming, and he has earned my trust as someone knowledgeable about computers." It may be true that Joel is a proficient computer expert, but not based on the merit of that one question.  Which leads me to an example about myself. I recently gave  (130 reputation) to a question about PHP's image-creating libraries. I am very appreciative of the community's support for my answer - an answer which I believe was well-thought and that I put effort into.  At the same time I can't look someone and tell them, with a straight face, that my reputation is a great reflection of my computer-related knowledge. Billions of people on the net have created tutorials for PHP's GD image library - I just happened to be the person to post a few of them. Heck if I know why it got 13 votes! (oh, but please don't downvote it!!)  SO is built by the community - so the community absolutely gets to decide what questions are important, and how they choose to dispense reputation. But in practice, I feel like peoples' reputation would be much lower if the community were more discriminating about the way they voted.  So: am I totally off base here? Is this even something that can be corrected with a different reputation algorithm? Or am I the only one who sees this as a detriment to the SO community?  (And, to be completely clear, I do not intend for this to be an ad hominem, and I am not jealous about not having a higher reputation. But I do take reputation with a grain of salt, in part for these reasons, and I thought I'd bring it up! It is meta, after all!) Prove that $\sqrt{n} \le \sum_{k=1}^n \frac{1}{\sqrt{k}} \le 2 \sqrt{n} - 1$ is true for $n \in \mathbb{N}^{\ge 1}$ I'm trying to prove commutativity of addition for vector spaces, using the axioms for vector spaces. Apparently commutativity can be proven! Im having trouble getting a good feel for what is allowed and what is not. Here's my work so far:  $u+v+u+v = 2(u+v) = 2u + 2v = u+u+v+v = u+(u+v)+v$  Here I just wanna claim that $u+(v+u)+v = u+(u+v)+v$   $\Rightarrow -u+u+(v+u)+v+(-v) = -u+u+(u+v)+v+(-v)$ : here im just adding -u to the right, and -v to the left. Question: is this "adding to both sides" really legit in this context? Why?   Quick help proof: $-v+v = (-1)v+(1)v = (-1+1)v = 0v = 0 = v-v$  And another: $ 0+v = v+(-v) + v = (1)v + (-1)v + v = (1-1)v + v = v = v+0$  We have $0 + (u+v) + 0 = 0+(v+u)+0 \Rightarrow u+v = v+u$  This feels ugly and not at all elegant, especially the great leap "add -u to both sides" feels completely out of place. Do I need more lemmas? Is there a more elegant way?   //not homework or anything, just for my own pleasure, feel free to provide theory, as it is more insightful than solutions. :) Thanks!   EDIT: corrected notation a little. Why do we use "./" (dot slash) to execute a file in Linux/UNIX? Why do we use ./filename to execute a file in linux?  Why not just enter it like other commands gcc, ls etc... I'm a teacher and will ask my students to either bring their laptops with Ubuntu installed with an specific list of packages preinstalled or bring a USB Drive or External Hard Drive with Ubuntu and the packages preinstalled.  For those who are going to bring the USB are two posibilities:   Install with the Ubuntu's "Startup disk creator" program, and telling it to reserve some space for persistence. Boot with a LiveCD and Install Ubuntu in the USB drive.   Then, in either case, boot with that media and install the packages.  So, for my purpose or any other purpose:   What is the best choice and why? Do we have another option? full explanation please. Linux - Help, I'm running out of inodes!