Looking for people to hire, I was wondering if is there any way to search for person of one particular country and maybe contact them.  Is there a place for that ?  Thanks, and sorry if this question is out of topic, I wasn't sure after reading the FAQ.
This was talked about a few podcasts ago. And they referenced some other site that does this.  Currently location is a string but adding a country dropdown (and for the usa a state drop down) could be a great addition to the site.  Then allow for user filtering by country / state.
Is there any tool available for extracting the X, Y and Z coordinates from a .las file and exporting them to a .csv or similar file? How does one prove the following limit? $$   \lim_{n \to \infty}   \sqrt{1 + 2 \sqrt{1 + 3 \sqrt{1 + \cdots \sqrt{1 + (n - 1) \sqrt{1 + n}}}}} = 3. $$ the (surely simplistic) model of a bipolar junction transistor one is taught in foundational physics course appears to be symmetric. - So, what is the difference between the collector and the emitter of a real BJT? If the transistor were symmetric one would not make this distinction...  Also:   Do BJTs have a 0.6V voltage drop like diodes? Are BJTs conductive in both directions, i.e. E-C and C-E?   Many thanks. Infinity, is clearly not . But there is some dissent on whether or not zero is finite. I have seen authors use "finite" to indicate the value of $0$ is excluded as well as infinity.  Is there any rule about this? SQL Server - how to determine if indexes aren't being used? Renaming files in lexicographical order with a numerical pattern that increases sequentially with fixed padding I have files such as  a bb ccc abc emrls   I would like to rename them so that, after sorting them (for example, lexicographically), each file gets the following name:  00001 00002 00003 etc   where the # of digits for the 0 padding is specified a priori, e.g. 6 in the case above (assuming that we know how many digits are needed).  Since the shell I am most comfortable with is zsh, I'm interested in solutions that benefit from features on zsh (maybe using zsh's zmv?). I would also be interested in solutions that are compatible with Bash. How to determine which Python install is being used by the interpreter? Total number of solutions of an equation What is the total number of solutions of an equation of the form $x_1 + x_2 + \cdots + x_r = m$ such that $1 \le x_1 &lt; x_2 &lt; \cdots &lt; x_r &lt; N$ where $N$ is some natural number and $x_1, x_2, \cdots, x_r, m$ are integers?  Also, what would be the solution in the relaxed case where $x_1, x_2, x_3, \dots, x_r$ could be equal? Show that $\sqrt{n^2+1}-n$ converges to 0 I want to use the definition of the limit to show that $\sqrt{n^2+1}-n$ converges to 0.  The definition is as follows: if $\sqrt{n^2+1}-n$ converges to 0, then $\forall \epsilon&gt;0$, there exists an $N&gt;0$ such that $n\ge N \implies \mid\sqrt{n^2+1}-n\mid&lt;\epsilon$.  Now I want to start backwords in order to figure out how to pick N. I know:   $\mid\sqrt{n^2+1}-n\mid=\sqrt{n^2+1}-n$   since $n$ is a natural number and $\sqrt{n^2+1}&gt;n$. So I need to pick an N such that $\sqrt{n^2+1}-n&lt;\epsilon$. I tried multiplying $\sqrt{n^2+1}-n$ by $\frac{\sqrt{n^2+1}+n}{\sqrt{n^2+1}+n}$ but that didn't really seem to help.   Do you have any ideas on how to find this N?  Thanks Prove that $∂A$ is closed given $∂A = \text{Cl}(A) − \text{Int}(A)$ Similar questions have been asked, but none with the given information. My textbook doesn't give me the fact that  $∂A = \text{Cl}(A) − \text{Int}(A)$. If that were the case, I could just state that definition and note that it's the intersection of closed sets.   I have very little knowledge of set theory and proofs, so I'm not sure how else to prove this. As always, I appreciate any help.  The question comes from “Introduction to Topology: Pure and Applied” by Colin Adams and Robert Franzosa.   "Let $A$ be a subset of a topological space $X$. Prove that $∂A$ is closed given  $∂A = \text{Cl}(A) − \text{Int}(A)$" How to mix three different shaders on the same material? Reusable functions in jQuery callback Please tutor the usage of patchcmd and xpatch I understand that the  package provides a command \patchcommand that can be used to add material at the beginning and/or end of the replacement text of an existing macro. It works for macros with any number of normal arguments but has limitations for macros with optional arguments.   was introduced to take care of the above limitations as well as provide some additional functionality.   Now, when I try to comprehend the usage of the above packages by reading the user documentations (, ), I get the feeling that they move to implementation details a little too quickly compared to other package documentations. There are not enough explanations or examples.  I also tried to grasp the concepts by reading the  and more or less understood whatever is presented there. However, that is not enough.  So, do you think we can ask for a complete tutorial on the usage of patchcmd and xpatch? Explaining the usage of the relevant commands like \patchcmd, \pretocmd and \apptocmd as well as, \xpatchcmd, \xpretocmd and \xapptocmd with sufficient examples should suffice. How to curve my mesh I'd like to curve my object, but I'm considering two options.  The first one is to make the object up with lots of vertices, like a sphere can be. The second is to apply some kind of modifier curve to a straight mesh, as I've understood there is such a possibility.  Here's an awesome pen drawing of what I'd like to achieve:    and here's my current even more awesome result:    Rather non-awesomely, they don't quite match. So if someone would kindly point me to the correct method to achieving a nice-looking solution with relatively low polygons, I'd be much enlightened Define $\mathcal N$  $\mathcal N (A):=\mathcal P(A)\setminus\{\varnothing\}$  Does $\mathcal N$ has a special name and standard notation? Which Stack Exchange sites use MathJax? As the title says, I could use an exhaustive list of all Stack Exchange sites that use MathJax.  If the list included any site-specific customizations made to the MathJax configuration on each site, that would be even better. Error installing virtualbox-dkms on Ubuntu 20 Ubuntu 20.04. I installed virtualbox using package; it worked, I created and ran a RM. But then stopped to work after software update. I cannot run the VMs, message says : Kernel driver not installed (rc=-1908)  The VirtualBox Linux kernel driver is either not loaded or not set up correctly.  Please reinstall virtualbox-dkms package and load the kernel module by executing  'modprobe vboxdrv'  as root.  I managed to disable secure boot, so this is not related to this. Now I try to reinstall virtualbox-dkms package as requested : sudo apt remove virtualbox-dkms sudo apt install virtualbox-dkms  But then I get the following error : Préparation du dépaquetage de .../virtualbox-dkms_6.1.10-dfsg-1~ubuntu1.20.04.1_amd64.deb ... Dépaquetage de virtualbox-dkms (6.1.10-dfsg-1~ubuntu1.20.04.1) ... Paramétrage de virtualbox-dkms (6.1.10-dfsg-1~ubuntu1.20.04.1) ... Loading new virtualbox-6.1.10 DKMS files... Building for 5.8.0-34-generic Building initial module for 5.8.0-34-generic Error! Bad return status for module build on kernel: 5.8.0-34-generic (x86_64) Consult /var/lib/dkms/virtualbox/6.1.10/build/make.log for more information. dpkg: erreur de traitement du paquet virtualbox-dkms (--configure) :  installed virtualbox-dkms package post-installation script subprocess returned error exit status 10 Des erreurs ont été rencontrées pendant l'exécution :  virtualbox-dkms E: Sub-process /usr/bin/dpkg returned an error code (1)  If I look at /var/lib/dkms/virtualbox/6.1.10/build/make.log I see : /var/lib/dkms/virtualbox/6.1.10/build/vboxdrv/linux/SUPDrv-linux.c:760:38: error: ‘cpu_tlbstate’ undeclared (first use in this function); did you mean ‘cpuhp_state’?   760 |     RTCCUINTREG uOld = this_cpu_read(cpu_tlbstate.cr4);       |                                      ^~~~~~~~~~~~ ./include/linux/percpu-defs.h:318:9: note: in definition of macro ‘__pcpu_size_call_return’   318 |  typeof(variable) pscr_ret__;     \       |         ^~~~~~~~ /var/lib/dkms/virtualbox/6.1.10/build/vboxdrv/linux/SUPDrv-linux.c:760:24: note: in expansion of macro ‘this_cpu_read’   760 |     RTCCUINTREG uOld = this_cpu_read(cpu_tlbstate.cr4);       |                        ^~~~~~~~~~~~~ /var/lib/dkms/virtualbox/6.1.10/build/vboxdrv/linux/SUPDrv-linux.c:760:38: note: each undeclared identifier is reported only once for each function it appears in   760 |     RTCCUINTREG uOld = this_cpu_read(cpu_tlbstate.cr4);       |                                      ^~~~~~~~~~~~ ./include/linux/percpu-defs.h:318:9: note: in definition of macro ‘__pcpu_size_call_return’   318 |  typeof(variable) pscr_ret__;     \       |         ^~~~~~~~ /var/lib/dkms/virtualbox/6.1.10/build/vboxdrv/linux/SUPDrv-linux.c:760:24: note: in expansion of macro ‘this_cpu_read’   760 |     RTCCUINTREG uOld = this_cpu_read(cpu_tlbstate.cr4);       |                        ^~~~~~~~~~~~~ make[2]: *** [scripts/Makefile.build:290 : /var/lib/dkms/virtualbox/6.1.10/build/vboxdrv/linux/SUPDrv-linux.o] Erreur 1 make[2]: *** Attente des tâches non terminées.... make[1]: *** [scripts/Makefile.build:519 : /var/lib/dkms/virtualbox/6.1.10/build/vboxdrv] Erreur 2  What I am missing ? Post Link for Tag Info Wiki's display text should be better than "unknown" The displayed text for a [Post Link] where the underlying Id corresponds to a Tag/Info Wiki (where the link redirects successfully) is just &quot;unknown&quot;. For example, if you've ever edited a tag wiki: . It would be nice if this could be better identified. meaning of powers on trig functions I always forget this, when a trig function has an exponent does that mean multiply itself or apply itself to the result recursivly?  e.g. does $\sin(x)^2=\sin(x)\sin(x)$ or $=\sin(\sin(x))$? What about $\sin^2x$? I'm here with weird stuff again.  How can i continue numbering while changing numbering style to Arabic from Roman? For example let's assume I have total of 7 pages and I want to number the first 3 of them as : i,ii,iii; then I change back to Arabic again and continue counting as 4,5,6,7.