Why do not I have 64 bit options on General -> Basic -> Version and also UEFI in bios?(trying to install ubuntu on vm and getting kernel error)
Cannot install Ubuntu in VirtualBox due to "this kernel requires an x86-64 CPU, but only detects an i686 CPU, unable to boot" error
Why is the field inside a conducting shell zero when only external charges are present? Product norm on infinite product space How to raise a complex number to the power of another complex number? How do I calculate the outcome of taking one complex number to the power of another, ie  $\displaystyle {(a + bi)}^{(c + di)}$? Do we have different set of badges in different SE sites. eg. I don't see any 'Pundit' badge in badges popup in Hinduism SE.  Also, if the above is true, then can we include the left badges in a SE site at a later stage. How to prove $ \prod_{d|n} d= n^{\frac{\tau (n)}{2}}$ Should actors in a game be responsible for drawing themselves? I am very new to game development, but not to programming.  I am (again) playing around with a Pong type game using JavaScript's canvas element.  I have created a Paddle object which has the following properties...   width height x y colour   I also have a Pong object which has properties such as...   width height backgroundColour draw().   The draw() method currently is resetting the canvas and that is where a question came up.  Should the Paddle object have a draw() method responsible for its drawing, or should the draw() of the Pong object be responsible for drawing its actors (I assume that is the correct term, please correct me if I'm incorrect).  I figured that it would be advantagous for the Paddle to draw itself, as I instantiate two objects, Player and Enemy. If it were not in the Pong's draw(), I'd need to write similar code twice.  What is the best practice here?  Thanks. Exposing database IDs - security risk? I received a mail today from Academia.edu (a site I wasn't previously aware of), asking me to confirm that I co-authored a paper with a colleague.  Having looked into it a little it sounds like it might be a useful site - the idea of a "social network for scientists" is one I've seen the need for in the past. However, partly due to bad experiences with the seemingly similar ResearchGate, I'm also skeptical.* Without signing up for an academia.edu account the site doesn't offer much information, so I would like the following information:   What specific features does academia.edu offer to its users? Is it genuinely useful for any of the following purposes (each of which seems genuinely needed)   as a platform for networking with academics for discovering relevant research as an effective system for post-publication peer review for organising references among a small team of people working on a project  Will it send out mails to my colleagues without my express and explicit permission? (I.e. are the mails I received today the result of a deliberate action by my colleague, who is aware that I will be emailed and wishes me to join the site; or are they essentially spam from a social networking site aggressively trying to expand its user base?) It's clear from its  that it's a private, venture-capital funded company. What is its business model?   In short, is this a site that has some genuine utility for academics, or should I just ignore it?  *I've never signed up for ResearchGate but I regularly receive spam from it purporting to be from my colleagues, who aren't aware that it's being sent on their behalf. I would be mortified if my senior colleagues received such mails claiming to be from me, so I won't touch it with a barge pole. I have fish density data that I am trying to compare between several different collection techniques, the data has lots of zeros, and the histogram looks vaugley appropriate for a poisson distribution except that, as densities, it is not integer data. I am relatively new to GLMs and have spent the last several days looking online for how to tell which distribution to use but have failed utterly in finding any resources that help make this decision. A sample histogram of the data looks like the following:   I have no idea how to go about deciding on the appropriate family to use for the GLM. If anyone has any advice or could give me a resource I should check out, that would be fantastic. How fast a (relatively) small black hole will consume the Earth? This question appeared quite a time ago and was inspired, of course, by all the fuss around "LHC will destroy the Earth".   Consider a small black hole, that is somehow got inside the Earth. Under "small" I mean small enough to not to destroy Earth instantaneously, but large enough to not to evaporate due to the . I need this because I want the black hole to "consume" the Earth. I think reasonable values for the mass would be $10^{15} - 10^{20}$ kilograms.   Also let us suppose that the black hole is at rest relative to the Earth.  The question is: How can one estimate the speed at which the matter would be consumed by the black hole in this circumstances? It's a standard result that given $X_1,\cdots ,X_n $ random sample from $N(\mu,\sigma^2)$, the random variable $$\frac{(n-1)S^2}{\sigma^2}$$ has a chi-square distribution with $(n-1)$ degrees of freedom, where $$S^2=\frac{1}{n-1}\sum^{n}_{i=1}(X_i-\bar{X})^2.$$ I would like help in proving the above result. Thanks. Upvoting a downvoted answer will do +2 upvote? I have first downvoted an answer. Then, I decided to leave it the way it was before, meaning to undo my downvote just like it never existed, so I upvote to remove my downvote. Suprise! SO seems to consider it as two upvotes!  Let's say I have an answer with -3, then I decide to downvote it making it -4. After deeper thoughts, I prefer to remove my downvote to let it the way it was before I downvoted, meaning -3, but SO makes it -2 automatically!     Wouldn't it be supposed -3, and not -2? If someone else would have upvoted, it would have made it an upvote +1, not a +2!   Am I missing something here?  In fact, is there a way to tell SO that I only wish to undo my downvote, and not upvote the answer? I may understand why it does behave this way. I only wish to undo my downvote, though. Don't count non-printing characters, HTML comments or other content not displayed toward minimum character requirements Equivalence Relation problem Let $S$ be the relation on $\mathbb{N} \times \mathbb{N}$ defined by $(a,b)S(c,d)$ if and only if $ad=bc$. Prove this is an equivalence relation on $\mathbb{N} \times \mathbb{N}$.  I think I've found this to be reflexive and symmetric, but I'm stuck on transitivity. Can someone check my work so far and assist with testing transitivity?  Reflexive: Let $(x,y)S(x,y)$. Then $xy = yx$. So $S$ is reflexive. Symmetric: Suppose $(a,b)S(c,d)$. Then, $ad = bc$. Therefore, $da = cb$ and $cb = da$. Therefore, $(c,d)S(a,b)$. Thus, $S$ is symmetric.  Transitive: Suppose $(a,b)S(b,c)$. Then $ac = bb$.   This is where I'm stuck. Any ideas? Prevent malicious bots from posting spam Understanding the Basic Context of Trusted Hosts I got the trusted host settings error.      The trusted_host_patterns setting is not configured in settings.php. This can lead to security vulnerabilities. It is highly recommended that you configure this. See Protecting against HTTP HOST Header attacks for more information.    I read the  but I'm not understanding some of the basic context.   Are the "trusted hosts" me and other administrators who want to be able to administer the site remotely?  If so, would I add my PC's domain to the trusted host list? How can I stop the Devel module from generating blog/forum entries for Anonymous user? I'm using Devel's generate content feature to generate Blog/Forum entries for a site I'm working on and funny enough, I get to have a blog post by an anonymous user or forum topic by an anonymous user.  How can I stop Devel from doing this? I've only given Authenticated Users/ Administrators the permission to create a blog post or forum topic but still it generate for anonymous user. How can correct this? How many non-negative integer solutions does the equation $3x + y + z = 24$ have? mbstring is missing for phpmyadmin in ubuntu 16.04 When I installed phpmyadmin in Ubuntu 16.04 LTS, it gives me an error mentioned below.     The mbstring extension is missing. Please check your PHP configuration   then I tried to install php-mbstring, it says mbstring is up to date, Can anyone help me to solve this? $\dim(U_1+U_2) = \dim U_1 +\dim U_2 - \dim(U_1\cap U_2).$  I want to make sure that my intuition is correct. Suppose we have two planes $U_1,U_2$ though the origin in $\mathbb{R^3}$. Since the planes meet at the origin, they also intersect, which in this case is a one-dimensional line in $\mathbb{R^3}$. To obtain the dimension of $U_1$ and $U_2$, we add the dimensions of the planes (4), and the subtract the dimensions of the line (1), which results in (3).   *additional question(s):   Can we generalize this notion to $\mathbb{F^{n}}$?  Suppose we have an additional case where $U_1$ and $U_2$ are planes in $\mathbb{R^3}$, but $U_1 \subseteq U_2$. In this instance, $dim(U_1 + U_2) &lt; 3$, because the first two-dimensional plane is contained in the second and as a result, the dimensions of the subspaces when summed cannot exceed two. Since both subspaces $U_1,U_2$ are two dimensional and $U_1 \subseteq U_2$, then their intersection is also two-dimensional, concluding $dim(U_1+U_2)=2+2-2 = 2$.  Is this proper intuition?