I stay logged in on https://*.stackexchange.com for weeks except on , where I have to log in again every few days. Why?
I know that we don't have automatic login for the Data Explorer, but what's with the automatic timeout/logout?  There have been times that I am logged into the site, maybe I walk away for a little bit, and I come back to being logged out.    Is there a reason for logging us out of Data Explorer?  If so, is it possible to either remove the timeout or extend the period of time before timeout?
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. Often, TeX outputs underfull hbox and vbox warnings when running and in the generated log file. What are these and how can I get rid of them? Proving inequality $(a+\frac{1}{a})^2 + (b+\frac{1}{b})^2 \geq \frac{25}{2}$ for $a+b=1$ I'm currently building a sitemap for my web app.  Note: my app is a single page app built with React and Firebase.  Basically I wan to index blogPost and product pages. So I intend to generate my sitemap dynamically (on server). It's a small website (around 500 pages).  I want to build something like this:  &lt;urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9"&gt;   &lt;url&gt;     &lt;loc&gt;       https://www.myproject.org/blog/some-blog-post-slug     &lt;/loc&gt;     &lt;lastmod&gt;2019-11-14T20:22:43.502+00:00&lt;/lastmod&gt;     &lt;changefreq&gt;weekly&lt;/changefreq&gt;     &lt;priority&gt;0.8&lt;/priority&gt;   &lt;/url&gt;   &lt;url&gt;     &lt;loc&gt;       https://www.myproject.org/dp/some-product-slug     &lt;/loc&gt;     &lt;lastmod&gt;2019-11-15T13:08:52.127+00:00&lt;/lastmod&gt;     &lt;changefreq&gt;weekly&lt;/changefreq&gt;     &lt;priority&gt;0.8&lt;/priority&gt;   &lt;/url&gt; &lt;/urlset&gt;   And I keep the following properties in my database, both for blogPosts and products:  createdAt: &lt;Timestamp&gt; lastModifiedAt: &lt;Timestamp&gt;  // UPDATED EVERYTIME I UPDATE THE RECORD   And I'm thinking about using my lastModifiedAt value as the &lt;lastmod&gt; tag for the sitemap.  So far, so good! Everytime I update my blogPost or product objects in my database. The next time the sitemap is requested, the new modifiedDate will show on those that have been changed.  QUESTION  But what if I make a change not in the database itself, but in the way I render all the product pages, for example.  Imagine that I've added some structured data tags to display rich results on google, with price, reviews etc. So my product info is the same, but from that point on, all of my product pages will render those extra tags that I need to be re-indexed.  Example (add a structured data tag with the product price):   &lt;div property="schema:price" content="119.99"&gt;&lt;/div&gt;   In that situation, will I have to update all &lt;lastmod&gt; for all the products? How Google will know that it needs to re-crawl those pages and be able to see the structured data tags?  What if I change only the styles for the productPages? Do I have to update the &lt;lastmod&gt; for every product in this case? How to read off coefficients of tensor-like expression in a speedy way? How can I increment a date by one day in Java? I'm working with a date in this format: yyyy-mm-dd.  How can I increment this date by one day? In recent versions of PostgreSQL (as of Dec 2013), can we share a query between two or more cores to get a performance boost? Or should we get faster cores? $\mathbb{R}$ \ $\mathbb{Q}$ and $\mathbb{R}^2\setminus\mathbb{Q}^2$ disconnected? If I want to prove that $\mathbb{R} \setminus \mathbb{Q}$ is disconnected, does it suffice to say that there are two open disjoint sets that cover $\mathbb{R}\setminus\mathbb{Q}$, namely:  $$(- \infty, 0), (0, \infty)\text{ ?}$$  Along the same lines, I want to prove or disprove that $S = \mathbb{R}^2 \setminus \mathbb{Q}^2$ (points $(x, y) \in S$ that have at least one irrationais connected. I feel that it is also disconnected; does it suffice to say that there are two open disjoint sets that cover $S = \mathbb{R}^2 \setminus \mathbb{Q}^2$, namely $((- \infty, - \infty), (0, 0))$ and $((0, 0), (\infty, \infty))$? (Very iffy on my assertion and my notation, sorry.)  Thanks! Homology Groups of $S^n$ $(p\!-\!1\!-\!h)!\,h! \equiv (-1)^{h+1}\!\!\pmod{\! p}\,$ [Wilson Reflection Formula] su command + authentication failure I am having problems with the su command. I know my password and I am typing it correctly but su indicates authentication failure.  So I checked on the internet and then went into recovery mode and changed my username's password to what I was entering before.  Even now entering the same password on su gives me authentication failure.  Please suggest what am I doing wrong?? To be honest I'm not sure how to run LAStools from within QGIS 2.8. I'm trying to learn by experimentation.  QGIS shows all the LAStools in the toolbox  If I double click on a LAStool in the toolbox I get the following message:     Missing dependency. This algorithm cannot run :-(   LAStools folder is not configured. Please configure it before running LAStools algorithms.   I can't find any LAStools *.exe files anywhere within my QGIS Wien file structure.  That makes me wonder how I could have LAStools show in the toolbox.  Could it be a *.dll somewhere?  What am I doing wrong? I am comfortable with the different sizes of infinities and Cantor's "diagonal argument" to prove that the set of all subsets of an infinite set has cardinality strictly greater than the set itself. So if we have a set $\Omega$ and $|\Omega| = \aleph_i$, then (assuming continuum hypothesis) the cardinality of $2^{\Omega}$ is $|2^{\Omega}| = \aleph_{i+1} &gt; \aleph_i$ and we have $\aleph_{i+1} = 2^{\aleph_i}$.  I am fine with these argument.  What I don't understand is why should there be a smallest $\infty$? Is there a proof (or) an axiom that there exists a smallest $\infty$ and that this is what we address as "countably infinite"? or to rephrase the question "why can't I find a set whose power set gives us $\mathbb{N}$"?  The reason why I am asking this question is in "some sense" $\aleph_i = \log_2(\aleph_{i+1})$. I do not completely understand why this process should stop when $\aleph_i = \aleph_0$.  (Though coming to think about it I can feel that if I take an infinite set with $\log_2 \aleph_0$ elements I can still put it in one-to-one correspondence with the Natural number set. So Is $\log_2 \aleph_0 = \aleph_0$ (or) am I just confused? If $n \rightarrow \infty$, then $2^n \rightarrow \infty$ faster while $\log (n) \rightarrow \infty$ slower and $\log (\log (n)) \rightarrow \infty$ even slower and $\log(\log(\log (n))) \rightarrow \infty$ even "more" slower and so on).  Is there a clean (and relatively elementary) way to explain this to me?  (I am totally fine if you direct me to some paper (or) webpage. I tried googling but could not find an answer to my question) Question about mosfet gate resistor I have n mosfet gate connected to  logic and Id is about 100mA. Both 4043 and mosfet has +5v. I have plan to use  mosfet  Questions are: How large gate resistor i need between 4043 and mosfet? Logic output is sometimes put on rapidly. How fast? Motherboard hdd led controls that. Do i need to place pull down resistor from logic to -0v, between 4043 and mosfet? Find Oracle JDBC driver in Maven repository Is there a way to summon Dogmeat to you? I've recently started playing Fallout 4, and I've acquired Dogmeat. Long story short, I told him to stay in a small building so I could down a few raiders quietly but I forgot about him and I can't find him. Is there a way to call Dogmeat back or do I have to retrace my steps until I'm reunited with him? When I'm about to install a program in the terminal it wants the password:  [sudo] password for xxx:   But when I start to type my password nothing happens. What should I do? hyperref: how to format text in a forms text-field I would like to pre-format the text in a form text-field, e.g. make it bold, italic or use a specific font. The following code generates a simple text-field:  \documentclass{scrreprt} \usepackage{hyperref} \begin{document} \textbf{The Text Field} \begin{Form} \TextField[]{\ } \end{Form} \end{document}   Is it possible to pre-format the text in the text-field? The hyperref package manual (10/2011) speaks of an optional parameter format and the use of JavaScript to format the field. Can this be used to format the text in the field? And if yes, how is it done? (I am not proficient in JavaScript) LuaLaTeX, TeXLive 2016, standalone: undefined control sequence How do you kill a java.lang.Thread in Java?