Model class properties should private or public?
Why Not Use Public Member Functions
require_once () or die() not working How do I delete my commands quickly? I use terminal for almost all tasks. Let's say I have entered a huge command like this:  sudo a-huge-command   What is the easiest way to delete the whole command with a single shortcut, rather than keep on hitting backspace key?  I'm a Ubuntu newbie looking to use Ubuntu in a professional way. Does Python support short-circuiting? I have come across both the phrases - 'on the internet' and 'over the internet.'   I'm pretty sure that both are correct but then which to use when?  Please note, I'm well aware of all over the Internet which I'm not concerned about. TP-Link Archer T3U Plus USB adapter Cannot make this wireless adapter work on Ubuntu 20.04... please help. I've tried this:  and now lsusb sees the device, but still doesn't work. lsusb: Bus 002 Device 006: ID 2357:0138 TP-Link 802.11ac NIC uname -r: 5.4.0-39-generic Edit: It works on my other computer with Ubuntu 18.04 using T2U Plus driver from here:  But it does not work with Ubuntu 20.04... sudo modprobe 88x2bu: Gives nothing. modinfo 88x2bu | grep -e version -e 0138 : version:        v5.6.1_30362.20181109_COEX20180928-6a6a srcversion:     9C5282368F93050B7206C8D parm:           rtw_chip_version:int  dmesg | grep 88x2 : [ 8087.334869] 88x2bu: loading out-of-tree module taints kernel. [ 8087.336610] 88x2bu: module verification failed: signature and/or required key missing - tainting kernel [ 8087.341389] usbcore: registered new interface driver rtl88x2bu I am reading separable extension. I don't quite understand why $\text{char} 0$ fields must be perfect. If $F$ is a $\text{char} 0$ field, $f(x)$ is an irreducible polynomial in $F[x]$. Then why $f$ must be separable? Assume $f$ has multiple roots, say $r$ is a multiple root of $f(x)$. Then $r$ is also a root of $f'(x)$. $r$ is in the splitting field of $f(x)$ over $F$, denote it as $E$. Then why $f$ must divide $f'$? I know $f$ is irreducible but I don't know how the argument goes on. Thanks for any help! If neutrinos are disfavoured as DM candidates why aren't axions? Numerical simulations of observed large-scale structure formation work best with Cold Dark Matter (CDM; see the answer ). Neutrinos are candidates for Hot Dark Matter (HDM), and hence they cannot account for the total dark matter abundance of the Universe. By the same token, axions are also relativistic because they have very tiny masses. Aren't they also candidates of HDM like neutrinos? Shouldn't they also be disfavoured for the same reason? Root Android virtual device with Android 7.1.1 Calculate the uncertainty in velocity of electron I got this question in one of my periodic test in coaching, I (seemingly) solved the question but later recognised what mess I did.  So, the question is :      Calculate the uncertainty in velocity of an electron. If the uncertainty in its position is ${10^ {-15}} \; \mathrm m$.   By simple calculations one can see that the answer would be ${5.79\times{10^{10}}} \; \mathrm{m/s}$. However, as one can see, the uncertainty in velocity is greater than the velocity of light then how is that possible or there is some other way to handle such problems.  P.S. I know the concept of dynamic mass but I am not very familiar with it. (I think that would work here, but don't know how?) How to enable hibernation? How do I change JPanel inside a JFrame on the fly? To put it simple, there's a simple java swing app that consists of JFrame with some components in it. One of the components is a JPanel that is meant to be replaced by another JPanel on user action.  So, what's the correct way of doing such a thing? I've tried  panel = new CustomJPanelWithComponentsOnIt(); parentFrameJPanelBelongsTo.pack();   but this won't work. What would you suggest? How can one motivate the relativistic momentum? Motivating the non-relativistic momentum $$\mathbf{p} = m\mathbf{v}$$ is quite easy: it is meant to represent the quantity of motion of the particle, and since the mass is one measure of quantity of matter it should be proportional to mass (how much thing is moving) and should be proportional to velocity (how fast and to where it is moving). Now, in Special Relativity the momentum changes. The new quantity of motion becomes $$\mathbf{p} = \dfrac{m\mathbf{v}}{\sqrt{1-\dfrac{v^2}{c^2}}}$$ Or, using $\gamma$ the Lorentz factor $$\mathbf{p} = \gamma(v) m\mathbf{v}$$ where I write $\gamma(v)$ to indicate that the velocity is that of the particle relative to the frame in which the movement is being observed. The need for this new momentum is because the old one fails to be conserved and because using the old one in Newton's second law leads to a law which is not invariant under Lorentz transformations. So the need for a new momentum is perfectly well motivated. What I would like to know is how can one motivate that the correct choice for $\mathbf{p}$ is the $\gamma(v)m\mathbf{v}$. There are some arguments using the mass: considering a colision, requiring momentum to be conserved, transform the velocity and then find how mass should transform. Although this work, it doesn't seem natural, and it is derived in one particular example. On my book there's even something that Einstein wote saying that he didn't think it was a good idea to try transforming the mass from $m$ to $M = \gamma(v)m$, that it was better to simply keep $\gamma$ on the new momentum without trying to combine it with the mass. So I would like to know: without resorting to arguments based on transformation of the mass, how can one motivate the new form of momentum that works for special relativity? LEFT JOIN vs. LEFT OUTER JOIN in SQL Server What is the difference between LEFT JOIN and LEFT OUTER JOIN? Why doesn't my ~/.bash_profile work? I'm using Linux Mint. My login shell (cat /etc/passwd | grep myUserName) is bash.  After I start my graphical desktop environment and run a terminal emulator from it, I can see that .bash_profile is not sourced (environment vars that are exported in it are unset). But if I log in from a text console (ctrl+alt+F1) or manually run bash -l from the terminal emulator, .bash_profile works fine.  Am I wrong when I think that .bash_profile should be sourced when X starts and all export'ed vars should be available in the terminal, running from X?  P.S. Placing everything in .bashrc and sourcing it from .bash_profile is not good idea (): environment stuff should be sourced only once. Inhumans vs. Mutants in the Marvel Universe What's the difference between those two? Aren't Inhumans supposed to be an evolution of the human race "forced" by the Kree? Which is almost the same as Mutants, the natural evolution of the human race...  What exactly am I missing? Dubai (UAE) visa requirements when staying in the airport for a French citizen? What do the E and R prefixes stand for in the names of Intel 32-bit and 64-bit registers? Is there any built-in software or terminal method allowing me to view the hardware profiles on my system? Windows equivalent of such a feature would be Device Manager. Why do Borg move so poorly (like 50s movie robots)? Find all integral solutions of $y^2=x^3+7$ Find all integral solutions of $y^2 = x^3+7$.  I tried to use many different moduli, but it never works. With modulo $9$, you can get $x$ is divisible by $3$.