How did Harry’s watch work at Hogwarts?
How do people at Hogwarts usually tell the time?
Proof about Graph with no triangle Sometime I see many application such as msn, windows media player etc that are single instance applications (when user executes while application is running a new application instance will not created).  In C#, I use Mutex class for this but I don't know how to do this in Java. Let $(X, Y)$ be distributed as a multivariate normal with parameters  $$ \mu = \begin{bmatrix} \mu_X \\ \mu_Y \end{bmatrix} \qquad \Sigma = \begin{bmatrix} \sigma_X^2 &amp; \sigma_{XY} \\ \sigma_{XY} &amp; \sigma_Y^2 \end{bmatrix}. $$   I would like to calculate $E(X | y_1 &lt; Y &lt; y_2)$, where $y_1$ and $y_2$ are constants.  From , I have managed to work out that $$ E(X | Y &gt; y_1) = \mu_X + \frac{\sigma_{XY}}{\sigma_Y} \left[\frac{\phi\left(\frac{y_1 - \mu_y}{\sigma_Y}\right)}{1 - \Phi\left(\frac{y_1 - \mu_y}{\sigma_Y}\right)}\right]\\ E(X | Y &lt; y_2) = \mu_X - \frac{\sigma_{XY}}{\sigma_Y} \left[\frac{\phi\left(\frac{y_2 - \mu_y}{\sigma_Y}\right)}{\Phi\left(\frac{y_2 - \mu_y}{\sigma_Y}\right)}\right] ,$$ where $\phi(\cdot)$ and $\Phi(\cdot)$ are, respectively, the p.d.f. and the c.d.f. of the Normal distribution. I could not figure out how to calculate $E(X | y_1 &lt; Y &lt; y_2)$, though.  I have searched for an answer in similar posts from the Stack Exchange network, but I couldn't get a clue from them that would solve this issue. For the record, here are some of them: $\int_0^{\pi/2}\ln(\sin(x))$? From this paper:     Shouldn't $du$ be $dt$? And also how do you get from that line to the final result if $du$ is not $dt$? Two footnotes in a heading, only one is displayed at the end of the page I'm adding two footnotes to a section heading:  \documentclass{article} \usepackage[english]{babel} \usepackage[utf8]{inputenc} \usepackage[T1]{fontenc} \usepackage{lipsum}  \usepackage[stable]{footmisc}  \usepackage{titlesec}  \begin{document} \section{test \footnote{This is footnote no1.} \footnote{This is footnote no2.} } \lipsum[4] \end{document}   The heading will have both of the footnotes, but at the end of the page only the second is displayed. The problem appears to be \usepackage{titlesec}, because it works fine without it.    Stuff I specified in \usepackage{titlesec}:  \renewcommand\thesection{\arabic{section}}  \renewcommand\thesubsection{\arabic{subsection}}  \renewcommand\thesubsubsection{\arabic{subsubsection}}  \titleformat{\section}[block]{\Large\scshape\centering}{\thesection}{1em}{}  \titleformat{\subsection}[block]{\large\scshape}{\thesection.\thesubsection}{1em}{}  \titleformat{\subsubsection}[block]{\large\scshape}{\thesection.\thesubsection.\thesubsubsection}{1em}{}   Thanks in advance! How to ask a smart question The title of  of  is, "Is it posible [sic]?"  This doesn't provide any information at all. It should be mandatory for everyone asking questions on the Internet to read , which says:     Help your community learn from the question. When you field a good question, ask yourself "How would the relevant documentation or FAQ have to change so that nobody has to answer this again?" Pros and Cons of a Decentralized Puppet Architecture We have around 300 RHEL servers that are currently connecting to a Puppetmaster server.  However, we have noticed some performance bottlenecks and it is the point of failure in our system.  I am fairly new to puppet in general and I am considering creating a decentralized puppet architecture instead of having Puppet clients connect to the Puppetmaster server.  Aside from what I would suspect to happen such as performance gain and lack of signing and exchanging SSL certs for new machines, what are other pros and cons to setting up a decentralized architecture? What's the typical microclimate in the aircraft passenger cabin? ceiling fan from a switch with only black and red wires? The current switch controls an outlet in the corner of the room for a lamp. I pulled it out and noticed three sets of individual wires: two set of wires coming up into the box from the bottom, and one set with a red wire coming down into box.  All the white and grounding wires are capped.  Also all the black wires are capped; one set I’m assuming is the hot since I see it contains a red wire. On the back of the switch, the top two ports have black wires and the bottom right has the one red wire.  There are two black pigtail wires coming off the black capped wires. I tried to connect a separate switch to control a ceiling fan with remote. I ran new wire making the old switch box into a two switch. I ran 14/2 gauge wire to ceiling for fan / light remote combo. Fan didn’t work after multiple re-wiring  combinations. The breaker did pop and half click when it popped. Then I thought to re-wire the ceiling fan wires as if I was going to make it into outlet only and use a tester to indicate an open ground, or a wiring error but the two light on tester are both orange indicating correct wiring. I heard that sometimes the ceiling fan remote transformer goes bad. Should I check batteries and/or unit placement? I’m really confused at this point why the light is not working at least with remote after follow wiring installation instructions that were included with the fan. I think it’s my wiring with the switch. The way I left the wiring is that it has constant power. As if we’re a outlet the current switch does not turn it off. Why do I see a double variable initialized to some value like 21.4 as 21.399999618530273? double r = 11.631; double theta = 21.4;   In the debugger, these are shown as 11.631000000000000 and 21.399999618530273.  How can I avoid this? How do you join or create a server in multiplayer? In this video, a college basketball player steals the ball, races down court, and avoids the defender by throwing a pass to himself off the backboard.    In all the (disorganized) basketball games I've played in, a shot had to hit the rim before the shooter was allowed to rebound. And that looks like a shot to me.  Obviously the officials allowed it, but I couldn't find an explicit mention in the . Is this ruled as a shot, and if so, why is it legal? I'd be interested in the answer for any level of basketball, though NCAA is the most relevant. Starting scheduled task by detecting connection of USB device I know it has been discussed that it is not possible to start an application from an usb drive upon connection due to limitations of autorun (or autoplay??) in Win 7. But it is possible to create a scheduled task having an event type trigger. Surely there must be an event occurring when the drive -- or any USB device, for that matter -- is connected.    Does anybody have the slightest idea which Event ID should I use? Or at least what type of event? Where can I find the event in event viewer? How to set up USB for Virtualbox? Flair: 500 Internal Server Error - http://stackexchange.com/error?aspxerrorpath=/users/flair/378431.png I have no idea how to do this. Any help would be appreciated. The chapter I'm on is about differentiation and the mean value theorem.  Prove $a^\alpha b^{1-\alpha} \le \alpha a + (1 - \alpha)b, \; a,b &gt; 0,\; 0 &lt; \alpha &lt; 1$ If a prime divides a product then it must divide a factor of the product [Euclid's Lemma] We have $q, p$ prime and $tq = (p-1)(p+1)$ for some positive integer $t$. The book I'm reading says that because $q$ is prime, it divides $p-1$ or $p+1$.   Question: Why exactly does it matter that $q$ is prime here? Further anonymize deleted accounts by changing the username in close/delete notices When an account is deleted, the username in the user's posts and comments is changed to a generic user&lt;userID&gt;. But the username stays the same on close and delete notifications on posts the user had voted to close / delete1. I think it shouldn't, especially for users who used their real name as their username, if they chose to distance themselves from the site and remove their accounts, it makes sense that they wouldn't really want their name plastered on close and delete notifications.   A perhaps easy way to avoid the actual username remaining visible would be to change it to the generic user&lt;userID&gt; (or anything generic enough, like "anonymous") prior to deletion, and wait a bit for the generic username to propagate all over the site. If I'm not horribly misreading , this was part of the process in the old days.   This could be automated or added as a suggestion to the .  Glaring example can be seen , where the deleted user also posted a comment where their name is properly anonymized:        1 I've seen it on close notifications and self deleted answers. I'm not sure it happens on deleted questions, or deleted answers that aren't self deletions, and I don't have a way to verify it - other than stumbling on them accidentally I was browsing through the apt folder to try my proxy settings and I was unable to find the apt.conf file in Ubuntu 11.04. Is there any alternative file for it?  Adding proxy settings to 99-synaptic in apt.conf.d does not help as it gets overwritten everytime I restart the system. What is the advantage of using wp_mail? What is the advantage of using wp_mail() over mail(). Codex says they're similar, but they seem to be very similar.