I've wondered what is the logic behind choosing these designs and descriptions for the hats of Winter Bash 2017?
Inspired by a , here's a list of the 'etymology' for the  hats. For pictures and a list of criteria, see  instead.  The list is a community wiki; feel free to edit it if you have more information about a hat. If you like to do some research, most hats have been featured in earlier editions, so you might be able to find more information in old Meta Stack Exchange questions.
What is the dimension of $R[[X]]$ where $R$ is a Noetherian ring? If $R$ is a Noetherian ring then we know that the Krull dimension of the polynomial ring $R[X]$ is $\rm dim(R)+1.$ Is there any formula for the Krull dimension of the power series ring $R[[X]] $ When $R$ is a Noetherian ring ? How does the drift velocity of electrons in a conductor depend on the temperature? How does the drift velocity of electrons in a conductor depend on the temperature?  I have two contradicting views for this.    First, we can say that increasing the temperature of the conductor will increase the kinetic energy of the electrons. Hence, their drift velocity should increase with increase in temperature.  Or, from the relation $v_d = \frac{eE}{m}T$ ($T$ is the relaxation time) we can say that the drift velocity is directly proportional to the relaxation time. Increasing the temperature will obviously decrease the relaxation time - as collisions will become more frequent - and thus decrease the drift velocity. Hence, an increase in the temperature will cause a decrease in the drift velocity.   So which view is correct? Evaluating $\int_0^\infty \frac{dx}{1+x^4}$. Can anyone give me a hint to evaluate this integral?  $$\int_0^\infty \frac{dx}{1+x^4}$$  I know it will involve the gamma function, but how? How to replace all occurrences of a string in JavaScript? See code:   var file1 = "50.xsl"; var file2 = "30.doc"; getFileExtension(file1); //returns xsl getFileExtension(file2); //returns doc  function getFileExtension(filename) {     /*TODO*/ } I know that the product of two Gaussians is a Gaussian, and I know that the convolution of two Gaussians is also a Gaussian. I guess I was just wondering if there's a proof out there to show that the convolution of two Gaussians is a Gaussian. Why are the laws of thermodynamics "supreme among the laws of Nature"? Eddington wrote     The law that entropy always increases holds, I think, the supreme position among the laws of Nature. If someone points out to you that your pet theory of the universe is in disagreement with Maxwell's equations — then so much the worse for Maxwell's equations. If it is found to be contradicted by observation — well, these experimentalists do bungle things sometimes. But if your theory is found to be against the second law of thermodynamics I can give you no hope; there is nothing for it but to collapse in deepest humiliation.   and Einstein wrote     [classical thermodynamics] is the only physical theory of universal content which I am convinced will never be overthrown, within the framework of applicability of its basic concepts.   Why did they say that? Is it a very deep insight they had, or is it something one can be convinced of quite easily? Or even, is it trivial? A Linear Diophantine Equation is of the following form:                                                                                        $Ax+By+C=0$, where $x_1 \leq x \leq x_2$ and $y_1 \leq y \leq y_2$.  If the value of $A,B,C,x_1,x_2,y_1,y_2$ are given and $x_1 \leq x_2$ and $y_1 \leq y_2$, then how many solutions can be found? How can I find out the total number of solutions according to the above condition. Did this character even qualify for being Azor Ahai or The One Who Was Promised? In the books and to some degree in the show as well there is a prophesy about the legendary figure Azor Ahai. But in the latest Game of Thrones episode (S08E03) we see Arya      killing the Night King.   However in a  we discussed​ all possible candidates but nobody thought about Arya. Does she even fulfill the prophecy? If she does, how? How do I install HP P1102W printer driver Are configurations written and read directly to/from .yaml files or still to the database? Background  Drupal 7 and previous versions have attracted criticism for Drupal web site admin configuration being stored in the MySQL database, the criticism being that being in a database means that it cannot be directly managed in git together with the PHP code based development for a Drupal site (custom modules, themes etc.).   Secondly with configuration being in the database along with content, transporting configuration between development, test, staging and live servers as part of development activity is complicated, though Features module (and related) can help.  Reading through:   ...I'm getting the impression that, in Drupal 8, the database is still used to store the config, when for example a site builder creates a new content type, rather than this being written to a .yaml file which is used directly.  So actually it seems that the role of the yaml file(s) is a much more purer (than Features) vehicle for the configuration. Whereas with Features it was PHP code which was harder to read what the configuration was, including if doing diffs between commits where config had been updated resulting in a new version of the Features-based config export. By that I mean not that PHP itself is hard to read, as I'm familiar enough with it, having written custom modules, hooks, themes. What I mean is that to express a configuration in PHP is perhaps not the most legible way to do it. So I can see the rationale of using yaml. The difference is that yaml will be read by a parser to apply a config. The complexity of applying the config is in the parser, which most folks need not concern themselves with most of the time, so the yaml can more cleanly describe the config. whereas in Features, there is no parser / yaml (or other script) separation. The descripton of the config and the means to apply it are necessarily in the same place as PHP code which is executed directly, so it's bound to be a bit harder to read the config, particularly if doing git commit diffs.  So there's the rationale for yaml, a Declarative Programming approach to storing configuration management in Git, contrasted with Features which is an Imperative Programming approach. And next what I need to know is this the case that Drupal 8 does still store config in the database does still and yaml files are the means for transporting config (replacing what Features did in D7 and before)?  (By the way I am a big fan of Drupal and spend most of my time at work, working with it for the sites that my organisation produces and maintained and am also involved in the community. So this question is not a stealth campaign against Drupal in favour of other platforms. It is a genuine question to try to dispel the apparent mystique around Drupal 8 and the new config management system)  Update @Berdir's answer (accepted) is a great definitive summary as to the state of Drupal 8 regarding configuration management.  I recently discovered that using yaml for config in Drupal 8 is a concept that has been developed for Drupal 7 with the  module, also read a  on it which includes comparing features.   Update   Is a definitive answer about making config active from DB storage, which corroborates with @Berdir's answer. Is there any way to kill a Thread? Is it possible to terminate a running thread without setting/checking any flags/semaphores/etc.? How to make a figure span on two columns in a scientific paper? If I just try to set the figure's size to 0.9\textwidth my figure will just end up on the right column, sized to be two-columns wide.  Has anyone done this before? Disable Narrator shortcut key in Windows I've install Windows 8 on a BootCamp macbook air The problem is that the command key located differently from the winkey in a normal keyboard, therefor, I keep clicking Winkey+Enter which starts the narrator (which is really annoying!)  Is there a way to disable this shortcut? How to use a C++ string in a structure when malloc()-ing the same structure? For example, here are top five accounts in each site (this picture was taken when I was in Biology SE).    As you can see, all the badges are DNA, while Academia's badges should be hats, so on.  What do you think? What do you call snow that has collected between a car body and the tire? Is there an operation similar to inset that creates faces in the opposite direction? That is, instead of creating faces inwards, they create faces outwards? A normal inset operation:  What I would like: How to get more complete references Sometimes when I work I write something like  \begin{proposition} \label{my new result} ... \end{proposition} ... blah blah in Proposition \ref{my new result} blah...   but then I realize that the Proposition should actually become a Lemma. So I change it to  \begin{lemma} \label{my new result} ... \end{lemma}   The problem is that I then have to hunt down all the places where I wrote Proposition and change it to Lemma, which is tedious and error-prone. Well, we have search facilities in editors, so it is not really that complicated, but still it feels the wrong way to do this. I would be happier to write  \begin{proposition} \label{my new result} ... \end{proposition} ... blah blah in \labelNameFor{my new result} \ref{my new result} blah...   where labelNameFor is a hypothetical magic command which outputs "Proposition". Then I could forget about all the places where I reference the result and just make any changes I wish.  Is there a way to do something like this? As far as I understand the label/ref mechanism is simply based on counters, so I do not see a straightforward way, but maybe someone more clever and industrious then I am has given the problem some thought. Can anyone explain to me why I would want to use IList over List in C#?  Related question: