Books to go Along with Dummit & Foote
Category Theory textbook (learning through guided discovery Dummit and Foote)
Double dual mappings Protected Question does not show Add an Answer button This question is protected. To answer it, I must have at least 10 reputation.        Ignoring the association bonus of 100, I should .  Yet, the Android app does not show the blue "Add an Answer" button at the bottom. The app also does not show the protection status.  If I view the question in the desktop or mobile browser (and I'm signed in), I can add an answer there. My months and days in my File Manager are in German, how do I change that? On the photo you see 'Dez' : It means Dezember (German for December). I also saw one day Mittwoch (German for Wednesday). How do I change that German issue? This is only my File Manager and not completly but partially. Weird. How to Identify Overfitting in Convolutional Neural network? I understand that dropout is used to reduce over fitting in the network. This is a generalization technique. In convolutional neural network how can I identify overfitting? One situation that I can think of is when I get training accuracy too high compared to testing or validation accuracy. In that case the model tries to overfit to the training samples and performs poorly to the testing samples. Is this the only way that indicates whether to apply dropout or should dropout be blindly added to the model hoping that it increases testing or validation accuracy Prove $ \sum \frac{\cos n} { \sqrt n}$ converges Don't invite people when moving their messages Assume a table structure of MyTable(KEY, datafield1, datafield2...).  Often I want to either update an existing record, or insert a new record if it doesn't exist.  Essentially:  IF (key exists)   run update command ELSE   run insert command   What's the best performing way to write this? Crafty solutions to the following limit The following problem came up at dinner, I know some ways to solve it but they are quite ugly and as some wise man said: There is no place in the world for ugly mathematics.  These methods are using l'Hôpital, but that becomes quite hideous very quickly or by using series expansions.  So I'm looking for slick solutions to the following problem:     Compute $\displaystyle \lim_{x \to 0} \frac{\sin(\tan x) - \tan(\sin x)}{\arcsin(\arctan x) - \arctan(\arcsin x)}$.   I'm curious what you guys will make of this. What is the proof that the total number of subsets of a set is $2^n$? How do I pass parameter TO a Visualforce page from a link in an email? Here's what I am trying to do:  1) User creates record A.  2) Time-based workflow sends an email to the Record A creator based on a date field in the record.  3) The email template has a URL link.  4) The URL links to a Visualforce page that is basically a form with fields to be filled out (this Visualforce page is in a managed package) and a save button that creates a new User record.  5) When the User clicks the URL link in the email, the Visualforce page opens in a new window.  6) I would like to pass the values of the fields in record A to pre-fill the Visualforce page fields.   Here's my link:  &lt;a href="https://cs19.visual.force.com/apex/CloneThisUser?Desktop=true&amp;Id={!Pending_User__c.User_to_CloneId__c}&amp;formGroupInputSmall={!Pending_User__c.First_Name__c}   And here's the code from the relevant section of the Visualforce page:  &lt;div class="form-group form-group-sm"&gt;       &lt;!-- &lt;apex:outputLabel styleClass="col-sm-2 control-label" for="formGroupInputSmall"&gt;First Name&lt;/apex:outputLabel&gt; --&gt;       &lt;div class="col-xm-11 col-sm-12"&gt;           &lt;apex:inputField html-placeholder="First Name" styleClass="form-control FirstNameInput"  value="{!u.FirstName}" id="formGroupInputSmall"/&gt;       &lt;/div&gt;     &lt;/div&gt;   I have only included the first field I would like to pass the parameter to, in order to keep this post simple.   The link passes the User_to_Clone_Id__c just fine but does not fill in the "First Name" field with the value of the First_Name__c .  What am I doing incorrectly? Thanks. UV Unwrapping a Modified Model I modified an existing model by removing unwanted vertices, then selecting surrounding vertices and creating faces one triangle at a time (By pressing 'F').  On UV unwrapping the mesh, the faces which were added by me seem to stretch from the very bottom left of the map, shown below.    How do I create a face so it appears on the UV map as expected? InDesign: How do I automatically align the bottoms of different columns of text boxes to the same height as the one with the most text? In InDesign, I have some filled text boxes, sized by columns, with the one on the left being three columns wide.   The wide text box is most likely to contain the most text (it's an invoice template).  I will use the 'Fit frame to content' button on the Selection Tool toolbar for automatically vertically resize it to fit the containing text.  How do I make the other three smaller text frames automatically adjust to the same height as the big (and longer) text box? Why is this true?  $(\exists x)(P(x) \Rightarrow (\forall y) P(y))$ I want to mount the device /dev/sda3 to the directory /foo/bar/baz. After mounting the directory should have the uid of user johndoe. So I did:  sudo -u johndoe mkdir /foo/bar/baz stat -c %U /foo/bar/baz johndoe   and added the following line to my /etc/fstab:  /dev/sda3 /foo/bar/baz ext4 noexec,noatime,auto,owner,nodev,nosuid,user 0 1   When I do now sudo -u johndoe mount /dev/sda3 the command stat -c %U /foo/bar/baz results in root rather than johndoe. What is the best way to mount this ext4-filesystem with uid johndoe set? I have a SNP table looks like this  A N N N N N N N N N N N N C N N N C N N N N N N N N N N N N N N N N N N N C N N N C N N N N N N N N N N N N N N N N N N C C N N N N N N N N N N C C N N N C C N N N N N N N N N N N N N N N N N   I want to count total number of N in each row? any idea how to do that After T-2, why not send back another T-800? I want to start using the terminal more often, but I don't know what are the different commands available to me. Is there a way to list all the different commands that I can make use of? Where can I find Vagrant packages? is a tool to build and manage virtual machines for developers.  It has a  guide that contains iffy-looking suggestions like  $ sudo ln -s /usr/bin/ruby1.8 /usr/bin/ruby  # wtf???   or installing RubyGems from source rather than from Ubuntu packages, and then using gem install to install vagrant itself.  I'm not feeling comfortable just following those instructions.  Is there perhaps a PPA?  Are there, perhaps, alternative tools that are packaged for Ubuntu? Don't replicators make the Ferengi rather pointless? Ferengis are all about acquisition and making a profit. But, in the age of replicators, where everything you want can be produced instantly, what would be the point of their lifestyle? Differences between hash- and encryption algorithms? There is a lot of confusion between hash- and encryption algorithms; I would like to understand:   When do we use a hash algorithm and when do we use an encryption algorithm (a cipher)? How difficult it is to reverse hash- and encryption algorithms? From the theoretical/mathematical perspective, what differentiates a hash- and encryption algorithm?