My nickname on Stack Overflow is , while doing an "ego search" on Google, I also found .  How is this possible? Shouldn't nicknames be unique?
What is the reasoning behind the design decision to allow users to create a display name which matches another existing users exactly?    This is opposed to the common practice of enforcing unique user names, and I'd really like to learn something.
What is the angle at which water is splashed when a vehicle tyre rides in water on the road? I would like to know the following:   What is the angle at which water gets splashed when I ride my vehicle through a water on the road? How does angle of water varies with speed? What is the relation between the distance the water goes with the speed of the vehicle?   Thanks! I hear a lot of talk about apparmor, I want to know the following:    What is apparmor? How does apparmor work? How to show that $|D_{2n}| = 2n$ via the presentation? Consider the dihedral group  $$D_{2n}= \langle a,b \mid a^n = 1 = b^2, b^{-1}ab = a^{-1}\rangle$$  How can I show that $|D_{2n}| = 2n$?   I'm trying to show that we can write every element in the form  $$x = a^i b^j$$ where $i= 0, 1, \dots, n-1$; $b = 0,1$.   I managed to show existence, and it is clear that there are $2n$ such elements, so if I can show that every choice of $i,j$ gives a distinct element, I'll be done.  Any ideas? Prove that $a^{2^n}=1 \mod 2^{n+2}$ I would like to prove that  $$a^{2^n}\equiv 1 \pmod {2^{n+2}}$$  I tried induction but could not get it.  Thank you very much! Is $R^2$ useful or dangerous? I was skimming through  by Cosma Shalizi (in particular, section 2.1.1 of the ), and was reminded that you can get very low $R^2$ even when you have a completely linear model.  To paraphrase Shalizi's example: suppose you have a model $Y = aX + \epsilon$, where $a$ is known. Then $\newcommand{\Var}{\mathrm{Var}}\Var[Y] = a^2 \Var[x] + \Var[\epsilon]$ and the amount of explained variance is $a^2 \Var[X]$, so $R^2 = \frac{a^2 \Var[x]}{a^2 \Var[X] + \Var[\epsilon]}$. This goes to 0 as $\Var[X] \rightarrow 0$ and to 1 as $\Var[X] \rightarrow \infty$.  Conversely, you can get high $R^2$ even when your model is noticeably non-linear. (Anyone have a good example offhand?)  So when is $R^2$ a useful statistic, and when should it be ignored? Can't specify the 'async' modifier on the 'Main' method of a console app Anyone knows what software tool is used to draw these circuit schematics I was reading online and found this site:   I was very curious how this professor drew all these circuit diagrams in his lecture notes (such as this one: ). They just look very very good.   And example is shown below:      To be more specific about what I mean, by "publication quality" I mean the following:   The software must output vector graphics, such as eps, or windows meta files. It would be good to have control over the style of the graphics, such the style of the components, line width, figure size, etc. It would be good to have a graphical user interface. I understand LaTeX is very powerful but it's just too painful to write a 100 line script to generate a circuit diagram.   So in short, I'm not really looking for a schematic capture program. I'm looking for a program that can generate pretty circuit schematic illustrations so that I can put them in papers and presentations.  (I am aware of other posts on this forum, such as this one: .  None of the software mentioned in that post seems to get you publication quality figures.) What happens to the second Marty at the end of Back to the Future? In  (the original movie), Marty comes back from 1955 10 mins early to prevent Doc from being shot (which he fails at). He then rolls up to the Lone Pine Mall and sees himself hit 88 mph and shoot back to 1955 (again). Marty then carries on with this life as usual. What happens to the Marty that goes back to 1955 at the end of the film?  This obviously is a recursive problem where it would create another timeline and Marty would keep coming back 10 mins early to view another Marty zip back to 1955? From the Cracks in time and space story arc it's known that if a TARDIS is blown up (possibly while in the Time Vortex) it rips creation itself apart. Also, from the Stolen Earth / Journey's End we learn the Daleks' masterplan which is subjugating creation itself via destroying it with the Reality Bomb (unfading Z-neutrino energy radiation).  In the Last Great Time War all sorts of temporal weapons were used and it's known that Daleks have the ability of time travel as well. Why didn't they use the Time Vortex back then to win the war once and for all via detonating a TARDIS while inside? Why CAN we see the new moon at night? I understand that the Moon's phases are determined by its position in orbit relative to the Sun. (See: ). The "shadow" is not cast by the Earth (a common misconception - this is actually a lunar eclipse), but by the moon's body itself.  It would appear that, in order for the moon to be a new moon, it would have to be somewhere between the Earth and the Sun. However, it would seem that, if we were looking at a new moon, we'd necessarily be looking at the Sun as well.  Why, then, can we sometimes see a new moon at night? Why doesn't it vanish at night for a half-month every month, between its last/first quarters? Internet through wireless hotspot, intranet through wired network - can I use both at the same time? We need to prove that $$\dfrac{\sin\theta - \cos\theta + 1}{\sin\theta + \cos\theta - 1} = \frac 1{\sec\theta - \tan\theta}$$  I have tried and it gets confusing. From Windows Vista to 7, can I get rid of folder Windows.old? I've just changed my laptop OS from Windows Vista to Windows 7.  I didn't choose to have both OS together, I just want to have Windows 7.   I was specting Windows 7 instalation program to format/clean my HD and leave me most of its capacity for a fresh start. But I've found, once the OS has been isntalled, that all files and programs from the Vista era are still in my HD, in a folder called Windows.old   I don't need these programs and files, I want to have as much HD space as possible and Windows 7 as clean as possible, what should I do?  Can I just delete Windows.old folder? Would that affect the how Windows 7 works?  Maybe is because I ended up angry with Vista, but I don't like the fact that there wasn't any cleaning/formatting ..   Thanks a lot How to store date/time and timestamps in UTC time zone with JPA and Hibernate How to remove \xa0 from string in Python? Can I live in the UK for a long time through repeat visits? I had recently entered the UK without a visa to be with my partner, from 21 July 2016 until 16 December 2016. I hope to return on the 9th of January. We don't meet the income requirement for a Spouse visa. I recently applied to university, and got in, and was intending to return to the UK on a student visa, but my university did not tell me about maintenance fees and my loan wasn't large enough to cover it all, so my visa would have been denied.  Now, I am hoping to attend university in the next semester, and therefore return to the US to apply for that visa. Do you think that if I try to return to the UK without a visa, I will be turned away?  I won't be working or studying during this time, however, I'm afraid that they'll consider it living in the UK illegally; I don't have a criminal record or anything like that. At what speed does our universe expand? I have both Windows 7 and Ubuntu installed on a shared machine. Because a lot of the non-developers use Windows, I'd like to change the boot order to make it easier for them.  Currently the boot order looks like the following:   Ubuntu 11.10 kernelgeneric *86 Ubuntu 11.10 kernelgeneric *86 (safe boot)  Memory test Memory test Windows 7 on /dev/sda6   How do I change the default order so that Windows 7 is at the top of the list?   Windows 7 on /dev/sda6 Ubuntu 11.10 kernelgeneric *86 Ubuntu 11.10 kernelgeneric *86 (safe boot)  Memory test Memory test Reference: Why are my "special" Unicode characters encoded weird using json_encode? I'm using BibLaTeX to handle my bibliography and I want a reference to be placed in a footnote on every page where I cite the same work and have the same number. Also I want to be able to cite the same work on one page several times. The latter could be done by using  from the Joseph Wright's blog. However, it puts a reference in a footnote only once.