Why $ \lim_{t\to\infty} \frac{W_t}{t} = 0 $  I tried to write it as Wiener process is defined which is:  $ \lim_{t\to\infty} \frac{W_t}{t} = \lim_{t\to\infty}\lim_{N\to\infty} \frac{\sum_{k=1}^{\lfloor Nt \rfloor} \varepsilon_{k}}{\sqrt{N}*t}*\frac{\lfloor Nt \rfloor}{\lfloor Nt \rfloor} $  and then use a Law of large numbers but I got expression $ 0*\infty $   any hints or solution would be appreciated.

In “Brownian Motion” by Schilling and Partzsc, they give a HINT to prove the Law of Large Numbers for Brownian Motion (not in their solutions, fyi) by  (1) Noting that $\left|\frac{B_{t}}{t}\right|\leq\left|\frac{B_{t}-B_{\left\lfloor t\right\rfloor +1}}{\left\lfloor t\right\rfloor }\right|+\frac{\left\lfloor t\right\rfloor +1}{\left\lfloor t\right\rfloor }\left|\frac{B_{\left\lfloor t\right\rfloor +1}}{\left\lfloor t\right\rfloor +1}\right|\leq\max_{\left\lfloor t\right\rfloor \leq s\leq\left\lfloor t\right\rfloor +1}\left|\frac{B_{s}-B_{\left\lfloor t\right\rfloor +1}}{\left\lfloor t\right\rfloor }\right|+\frac{\left\lfloor t\right\rfloor +1}{\left\lfloor t\right\rfloor }\left|\frac{B_{\left\lfloor t\right\rfloor +1}}{\left\lfloor t\right\rfloor +1}\right|$  and (2) showing that the first term on RHS converges to 0   in $L^{2}$   using the Reflection Principle and then making a subsequence argument.  I've made the following observations, but other than that, I'm stuck. First, the usual (strong) law of large numbers gives us $\frac{\left\lfloor t\right\rfloor +1}{\left\lfloor t\right\rfloor }\left|\frac{B_{\left\lfloor t\right\rfloor +1}}{\left\lfloor t\right\rfloor +1}\right|\rightarrow0\;\mbox{a.s.}\; t\rightarrow\infty.$  Hence it suffices to show that $\max_{\left\lfloor t\right\rfloor \leq s\leq\left\lfloor t\right\rfloor +1}\left|\frac{B_{s}-B_{\left\lfloor t\right\rfloor +1}}{\left\lfloor t\right\rfloor }\right|$   converges a.s. to 0   (or maybe something weaker is enough??).  If we can show $L^{2}$   convergence to 0  , then we have a.s. convergence for a subsequence. I've been able to show the $L^{2}$   convergence (see below), but I cannot get my head around the subsequence argument. Diverging from the Hint, I've proved the a.s. convergence directly by Borel-Cantelli and Doob's Inequality. But I'd really like to understand the $L^{2}$   approach as well.  $L^{2}$ convergence to 0: By $\left(B_{s+n}\right)_{s\geq0}\overset{D}{=}\left(B_{s}+B_{n}\right)_{s\geq0}$   and Doob's Inequality we get $\mathbb{E}\left(\left(\max_{\left\lfloor t\right\rfloor \leq s\leq\left\lfloor t\right\rfloor +1}\left|\frac{B_{s}-B_{\left\lfloor t\right\rfloor +1}}{\left\lfloor t\right\rfloor }\right|\right)^{2}\right) = \frac{1}{\left\lfloor t\right\rfloor ^{2}}\mathbb{E}\left(\left(\max_{\left\lfloor t\right\rfloor \leq s\leq\left\lfloor t\right\rfloor +1}\left|B_{s}-B_{\left\lfloor t\right\rfloor +1}\right|\right)^{2}\right)  = \frac{1}{\left\lfloor t\right\rfloor ^{2}}\mathbb{E}\left(\left(\max_{s\leq1}\left|B_{s+\left\lfloor t\right\rfloor }-B_{1+\left\lfloor t\right\rfloor }\right|\right)^{2}\right)  = \frac{1}{\left\lfloor t\right\rfloor ^{2}}\mathbb{E}\left(\left(\max_{s\leq1}\left|B_{s}-B_{1}\right|\right)^{2}\right)  \leq \frac{1}{\left\lfloor t\right\rfloor ^{2}}(2^{2}\mathbb{E}\left(\left|B_{1}\right|^{2}\right)+constants)$ On a sidenote, I didn't seem to use the Reflection Principle?


A sequence is defined to be bounded provided there is a positive real number M such that |an|< M for every natural number n. I need to prove that {an} is bounded if and only if there are real numbers a and b with a < b such that {an} is a sequence in [a, b]. So far I have been unable to produce a formal proof. Please help.

Why is it that a sequence in a closed, bounded interval [a, b] is a bounded sequence? What is the formal proof of this proposition from the definition of a bounded sequence?


I read a lot of books in the 1980's and some I borrowed from friends. I would like to find this series if anyone can figure out what it was.  The story started out with a person or several persons escaping in a large ship from certain doom.  They traveled across the galaxy searching for something that was spread out across 5 planets.  They could transform their body mass to become any other being or creature as long as it had the same or less mass.   They were chased across the galaxy by robots called "Val's" or something like that. Eventually they found the last clue on Earth. It was a secret kept by native Indians or air base or something like that.  Again my memory is fuzzy on the details.  If I recall this was either a 3 book series or 5 book series.

I'm looking for a series of books that deals with humans escaping Earth and having a mother ship full of humans who are being sent throughout the universe to different planets. The ship can transform the humans into whatever type of alien the planet holds. One set of sisters is transformed to cow-like aliens and sent to spy on that planet. All the while the group that's taken the mother ship full of human colonizers is trying to evade/escape the government people from Earth.    The 9 or 10 humans who steal the colonizing ship drop a couple of humans (transformed to whatever the indigenous species is) to the planet to spy...the end result is to try and overthrow the Earth government.  The humans that the colonizing ship transform to aliens cannot be turned back into humans ever again so when they take on the assignment to spy they do so knowing that they won't ever be able to be humans again.


This might be a repeated question, but I couldn't relate to any previous answer. I basically want to run my shell-script from anywhere in ubuntu 16.04 (whether I'm inside the directory where the shell-script is placed or not).  I know the first method which is to place the shell-script inside the /home/user/bin directory (that is already set in the $PATH), change the shell-script permission mode and, finally, reset the bash by re-starting the terminal. This way everything worked fine.   But, since I want to learn how to set the environment myself, instead of using /home/user/bin I would like to use my own created directory.  So, I placed my shell-script inside a newly created /home/workspace/myproject/bin directory and, of course, I changed its mode. Then run the following command:  echo $PATH   Then, amended the $PATH variable as follow:  PATH="/echo/command/result:/home/workspace/myproject/bin"   Then, set the environment:  source /etc/environment && export PATH   But it doesn't work !  UPDATE   I know I could also do it through editing the ~/.profile file. But my aim is to do it directly from the terminal without having to open and edit a file. And you can see why, using only two commands in a row, immediately after finishing writing the shell-script, is much faster, right ?   To be clear: I want to know why resetting of the /etc/environment didn't work?

How do I add a directory to the $PATH in Ubuntu and make the changes permanent?


Example of a function that its derivative is the same as its inverse. That is  $$f'(x)=f^{-1}(x)$$  In  Michael Penn, shows a technique and presents a function with that property. The example is  $$f(x)=\sqrt[\varphi]{\dfrac{1}{\varphi}} \cdot x^{\varphi}$$ where $\varphi=\dfrac{1+\sqrt{5}}{2}$  But his technique is based on an intelligent guess, is it possible to solve this problem in another way and find another function with this property?

What are some good examples of a function  $f : \mathbb{R} \to \mathbb{R}$ where its derivative is equal to its inverse? I attempted to find a monomial that satisfied it by starting with $f(x) = ax^b$ and showing that $f^{-1}(x) = f'(x) \implies b-1=\frac{1}{b} \implies b=\phi$ and got $$f(x) = \frac{x^\phi}{\sqrt[\phi]{\phi}}$$ Which seems to work according to WolframAlpha, but I'm having trouble double-checking it. Any other ideas?


I've looked on some of the same questions around here but couldn't find what i need. I think i messed up my IIS 7.5 ( and i don't even know how - only thing that comes to my mind is that maybe i uninstalled something but i don't remember ). A while back all was working perfectly and now not even an empty site doesn't work anymore. I just get the 500.19 internal error for every one.  Example:     Error Summary HTTP Error 500.19 - Internal Server Error      The requested page cannot be accessed because the related   configuration data for the page is invalid.      Detailed Error Information      Module    IIS Web Core      Notification BeginRequest      Handler   Not yet determined      Error Code    0x80070005      Config Error  Cannot read configuration file due to insufficient   permissions      Config File   \?\C:\Users\stalker\Desktop\BDI\Proiect\web.config      Requested URL       Physical Path C:\Users\stalker\Desktop\BDI\Proiect\Default.aspx      Logon Method  Not yet determined      Logon User    Not yet determined      Config Source -1: 0:   web.config file for the site  <configuration>     <system.web>         <compilation debug="true" targetFramework="4.0"/>     </system.web> </configuration>   This site was tested on another computer and worked. As all my other site applications. I'm thinking of reinstalling it >.< but maybe you can offer another solution.

I created an ASP.net MVC developed web application and I am trying to set up IIS.   The Error: Http error 500.19, error code 0x80070005, Cannot read configuration file due to insufficient permissions,  config file:  C:\inetpub\wwwroot\BudgetManagerMain\BudgetManager\web.config  If I set the AppPool to use 'administrator' i have no problems and can access the site just fine. If i set to NETWORK SERVICE (or anything else including self-created admin or non-admin user accounts), i get the above error.  Things I have tried:   identity for Application pool named 'test' is 'NetworkService' Set full access privs for wwwroot and all children files/folders verified effective permissions and NETWORK SERVICE has full access. Authentication on my site is set for anonymous and running under Application Pool Identity I do not have any physical path credentials set on the website confirmed website is set to run under the application pool named 'test'   using Process Monitor, here is a summary of what i found on the ACCESS DENIED event  EVENT TAB:   Class: File System Operation: CreateFile Result: Access Denied Path: ..\web.config      Desired Access: Generic Read Disposition: Open Options: Sybnchronous IO Non-Alert, Non-Directory file Attributes: N ShareMode: Read AllocaitonSize: n/a   PROCESS TAB  ...lots of stuff that seems irrelevant  User: NT AUTHORITY\NETWORK SERVICE


I need to reorganise my blender folder and move it to another PC and I am afraid that i might lose some linked texture/image sequences/etc that are used in the .blend files. What should i do to avoid that?  Pack all data into the blend files Make all paths relative  ? thank you for your help.

I'm moving all files to a new computer, via an external hard drive. I am certain that broken links will be a concern. What can I do to fix this? Is there a 'Best Practices' kind of way to prevent this problem beforehand? I have many hundreds of .blend files, and of course, I fear losing them.


I know this is a newbie  question, and most likely a duplicate, but for some reason can find it. Were do I find the explanations about flags, what they are in one compact place. I resonantly flagged a comment as offensive, but it was declined. Latter I discovered that the definition of offensive is something other than I thought. Although the comment was clearly offensive towards me it was not offensive in the definition of the flag so I was incorrect to flag it as such. So yes, to avoid it in the future:  Where can I find the definition and usage of all the flags?

When flagging, there are two special case options: spam and rude or abusive.   What is spam, and when should I flag content as such? What is considered offensive, rude or abusive content? How does the spam flag differ from the rude or abusive flag? What is the effect of these special flags? When are these flags removed?


When trying to turn on Bitlocker on an external 4 TB USB HDD using Windows 7, there's error A device attached to the system is not functioning. in a rather unhelpful dialog, as shown below:    Now according to , there are a few solutions, but the answers aren't very detailed. First of all, the solution in  (uninstall ) is unlikely to work I suppose, because this is external drive and uninstalling that would disable using Bitlocker on it completely. And then answers lack an exact way to format the drive to the maximum capacity, if that's the only way on external drive. So I'm looking for a succinct answer to these:   Does uninstalling  and then reinstalling it later work or not, with external drives? What's the exact command/method to format the drive to maximum working capacity? Other known-to-work ways to enable Bitlocker on the drive, like acquiring a Win8 PC to do it?

I'm trying to enable BitLocker on a 4TB drive with 4K physical sectors (Advanced Format) on a 64-bit Windows 7 box with SP1.    The drive is partitioned GPT (1 partition using all of the available space) and formatted with NTFS.    When I right click on the drive and select 'Turn on BitLocker...', a dialog appears that says 'Staring BitLocker' and 'Please wait while BitLocker initializes the drive'.  There is also a warning (same dialog) that says 'A device attached to the system is not functioning.'  The progress bar never moves and there is no disk or CPU activity.  I'm not seeing anything in the event viewer, either.  How do I get BitLocker turned on for this drive?  The drive is is a 4TB Hitachi DeskStar 7K4000 in an internal bay connected via SATA-II (host has no SATA-III ports).  It's not a boot drive.  I'm creating a single GPT partition (using the whole drive).  The motherboard has an Intel P55 chipset with no TPM.  No yellow exclamation marks in Device Manager.  I've waited over an an hour, nothing happens with the dialog box.  The drive has 4K physical sectors, 512 byte logical sectors (it's Advanced Format 512e/512 emulation, not 4Kn/4K Native).  When I formatted the volume, I left the allocation unit size at 'Default', which ended up being 4k.  Is there some requirement for a different allocation unit size for volumes over a certain threshold size?  It seems that I can create a smaller partition (2TB) and there is no problem. It seems that the magic limit is 3815174 MB, which is a 144 MB less than the available capacity of 3815318 (according to the New Simple Volume Wizard).  Can anybody explain that?  I updated the motherboard BIOS to the latest version, that seems to have had no effect on this issue.  I want to know why I Bitlocker fails to encrypt a single partition using all of the available space (according to the 'New Simple Volume Wizard), but will encrypt a partition 144 MB smaller?  I have 2TB Hitachi drives with a single partition, no unallocated space and they encrypted just fine.  According to the Disk Management snap-in in the Microsoft Management Console, I have 145 MB of unallocated space on the 4TB Hitachi.  A way to avoid wasting the 145 MB would be nice.  It's not a lot of space, but I don't want to screw around with finding the magic number again on a different 4TB drive.     I just tried to encrypt a 3815318 MB single volume on the drive with the manage-bde command line tool:  manage-bde -on X: -RecoveryPassword   I get this:  Volume X: [New Volume] [Data Volume] Key Protectors Added:  ERROR: An error occurred (code 0X8007001f): A device attached to the system is not functioning.


If $X$ is a random variable with a continuous uniform distribution on (0,10), and $Y$ is also from a continuous uniform distribution on (0,10) how do I calculate the CDF of $X+Y$?

Let $X,Y$ be two independent (and identically distributed) random variables. Let $Z:=X+Y$.  It's easy to check that the moment generating function $\phi_Z(t):=\mathbb{E}[\,e^{itZ}\,]$ can be expressed as $\phi_Z=\phi_X\cdot\phi_Y$.  Is there a way to express the cumulative distribution function $F_Z(z):=\mathbb{P}(Z\leq z)$ using the cumulative distribution functions of $X$ and $Y$ ?  Edit: note I don't assume that $X$ and $Y$ have a density.


In the PHB p.20      Speed. Your base walking speed is 25 feel. Your   speed is not reduced by wearing heavy armor.   The thing is I cant seem to find anywhere that heavy armor reduces speed. So to what is this referring to?

I noticed in the PHB, page 20, under Speed for Dwarves:     Speed. Your base walking speed is 25 feet. Your speed is not reduced by wearing heavy armor.   However, I cannot find anywhere in PHB that mentions that wearing Heavy Armor imposes any speed reduction.  Does anyone know if I've missed something, or if this is actually some inconsistency in the book and Heavy Armor in fact doesn't impose any speed reduction?


I am writing my B.Sc. report. Here I have write a part  of introduction. but the problem is I want begin the sentences with a gap like...  **

I am just curious that the following format looks good to you or not? The preamble I used is just   \documentclass[12pt,a4paper]{article}  \usepackage{amsmath} \usepackage{amsthm} \usepackage{amssymb}   I don't feel it's so good because the first paragraph has no indent but the second does. If the first paragraph is much longer, than it's fine. But if not, it looks strange. Should I leave it, or you have suggestions for this?


This  motivated think again my following tables but I am still uncertain how to store variables/results from data analysis for quick selection in post-processing.  If stored, I think it is well done with partial indexes (B-tree) because only a subset of data is required in my application described . Assume you have three orthonormal tables: measurements, events and headers where all have some static (size of events in bytes, etc) columns but wonder if the storage of some numbers from data analysis is beneficial or not.   Example of my table schema measurements without names:  SERIAL                     | NOT NULL INTEGER                    | NOT NULL INTEGER                    | NOT NULL TIMESTAMP WITH TIME ZONE   | DEFAULT CURRENT_TIMESTAMP   where I am worried about increasing the schema size by INTEGER fields because of my need in statistics.  I do not want to store in the main tables variables which are used rarely.  I do not want cause my indexes not being used as described in the book PostgreSQL Up & Running and this article   Possible sources    and his blog      When should the static/dynamic statistics stored in tables?  How can static/dynamic statistics be stored efficiently in partial indexes of PostgreSQL?

I have a PostgreSQL table. select * is very slow whereas select id is nice and quick. I think it may be that the size of the row is very large and it's taking a while to transport, or it may be some other factor. I need all of the fields (or nearly all of them), so selecting just a subset isn't a quick fix. Selecting the fields that I want is still slow. Here's my table schema minus the names: integer                  | not null default nextval('core_page_id_seq'::regclass) character varying(255)   | not null character varying(64)    | not null text                     | default '{}'::text character varying(255)   |  integer                  | not null default 0 text                     | default '{}'::text text                     |  timestamp with time zone |  integer                  |  timestamp with time zone |  integer                  |   The size of the text field may be any size. But still, no more than a few kilobytes in the worst case. Questions  Is there anything about this that screams 'crazy inefficient'? Is there a way to measure page size at the Postgres command-line to help me debug this?


Lets say I have the following text and I want to extract the text between "Start of numbers" and "End of numbers" there are dynamic amount of lines and the only thing which changes in the numbers in them eg: first, second, etc. Each file I'll be extracting data from has different amount of lines between between "Start of numbers" and "End of numbers". How can I write a regex to match the content between "Start of numbers" and "End of numbers" without knowing how many lines will be in the file between Start of numbers" and "End of numbers"?  Regards!  This is the first line This is the second line  Start of numbers  This is the first line This is the second line This is the third line This is the ...... line This is the ninth line  End of numbers

For example, this regex  (.*)<FooBar>   will match:  abcde<FooBar>   But how do I get it to match across multiple lines?  abcde fghij<FooBar>


I was looking around and I found a few answers that use ClassLoader.findLoadedClass(String className) but they all require overriding the permissions with setAccessible(boolean flag), and that just seems like you shouldn't be doing that.  (What's the point of permissions anyway if you can just change them in runtime).  is there any other way to see whether or not a classes is loaded?  This seems like it would be a pretty basic thing to check.

Is it possible to know whether a Java class has been loaded, without attempting to load it? Class.forName attempts to load the class, but I don't want this side effect. Is there another way?  (I don't want to override the class loader. I'm looking for a relatively simple method.)


I have to find out number of integers that have every digit $(0-9)$ in it where integer starting with zero doesn't count i.e leading zero shouldn't be there.  So this makes the length of an integer $ \ge 10$.  For eg - for $10$ length $1234567890,9876543201,4567891023$ and so on   For 11 length = $12345678900, 12345678009$ and so on..  For $19$ length =$1122334556677889900,99887766554433220011$ and  so on..  Now given a range $L,R$ I need to find out how many such integers falls in between them.  Now I was trying out all combinations and checking if it lies within range. Is there a way to apply permutation and combination to do so efficiently and smartly ?

Count how many number are there from $1$ to $N$ who have all $10$ digits in it at least once.       Can we have a generalized method to solve this problem?


I have been quite interested in biology lately,and I would like to know whether it is a good choice to look up taxonomic information there.

I found phylogenetic tree in wikipedia is lacks of accuracy. It actually confusing with versions. Some terms was not scientifically accurate with dna analysis anymore  So are there anyone know where is the most updated datasource on the internet?


So I understand that similar questions has been asked before. There is a specific aspect I don't understand which I don't think has been explained. If I shine a light on a surface and then I add a barrier, isn't there still a some photons remaining on the other side of the barrier which will still be travelling toward the same surface. Therefore, wouldn't the shadow moving across the surface be travelling at a slower speed than that of light. I've made a rough illustration of what I mean. (Sorry it's an MSPaint job).

I'm just a layman with no real science background  (a) I'm not really sure what a shadow is. Some people are saying that it's the absence of something (a photon?) and therefore it is not subject to laws of physics. But I know when I'm in a shadow and when in sunlight... that's "information", and I thought that information flow can't break the speed of light limit.  (b) Some others use the laser pointer/flicking wrist example to talk about laser dots moving faster than light speed. But that can't be right, can it? The photons from the laser point have to travel from A to B and (after wrist flick) from A to C ... but the photons are all moving at the speed of light - there's no law-breaking in moving the laser dot from point B to point C because the photons are moving either from A to B or A to C ... the distance from B to C is not material (is it?).  (c) Also, can a shadow be thought of as a gap in a photon flow? E.g. if I interrupt a beam of single photons then can I think of it as e.g. PPPSSSPPPSSSPPPSSSPPP, etc where P = photons and S(shadow) = no photon &, if so, the "SSS" is effectively travelling at the speed of light ... no faster.


I'm looking for a bijective mapping which maps an n-tuple onto/into a subset {1, 2, 3, ..., nCr) of Z where the n-tuples are (non-repeating) combinations of the integers {0, 1, 2, ..., r - 1}.  For example,     (1, 5, 10) maps to x where (1, 5, 10) is an ordered triple representation of a combination of {0, 1, 2, ..., 14} and thus 1 <= x <= 15C3.  For our purposes, assume the elements of the tuple are zero based but the result is 1 based.  Also, assume the elements of the tuple are in ascending order.  I need the solution to either be a formula or an algorithm and not just "calculate all possible combinations in an orderly way and number them".   This is somewhat like Lehmer encoding but I need it for combinations rather than permutations.  Does anyone know a solution to this?  Edit: Though none of the solutions in the linked question are marked as the solution, I was able to use (with a slight tweak) joriki's solution for my purposes. Thanks guys!

This question has an inverse:     What would be the most efficient way to translate a combination of $k$-tuple into its positions within the $\left(\!\!\binom{n}{k}\!\!\right)$ combinations? I need this to be fast for combinations of $\left(\!\!\binom{70}{7}\!\!\right)$ order of magnitude - very large, but not exceeding 2 billion (fits into int32 maximum value).  Below is an example of $\left(\!\!\binom{6}{3}\!\!\right)$, where the aim is to quickly translate (a, d, f) tuple to value 9, while in the real problem $k$ ranges between 5 and 8.  $$\begin{array} {cccccc|c} a&b&c&d&e&f&^{combination}/_{sort\_order}& \\\hline x&x&x& & & &1\\ x&x& &x& & &2\\ x&x& & &x& &3\\ x&x& & & &x&4\\ x& &x&x& & &5\\ x& &x& &x& &6\\ x& &x& & &x&7\\ x& & &x&x& &8\\ x& & &x& &x&9\\ x& & & &x&x&10\\ .&.&.&.&.&.&.\\  & & &x&x&x&20\\ \end{array}$$  I know that I could pre-calculate all the combinations and reverse the lookup dictionary. However, such dictionary would not be efficient in terms of memory usage. Therefore I am looking for either calculation-based approach, or a more efficient data structure to perform this mapping.


Consider the following stochastic differential equation: $$\ddot{X_t}+\omega_0^2X_t=dW_t.$$ I thought the way to do this would be to let: $$dX_t=\dot{X}_tdt,$$ $$d\dot{X}_t=-\omega_0^2X_tdt+dW_t,$$ however, this  says that the system of equations should be this: $$dX_t=\dot{X}_tdt+dW_t,$$ $$d\dot{X}_t=-\omega_0^2X_tdt.$$ The way it is done in that post seems to be correct as they are able to reproduce theoretical results numerically. Edit: The code in the linked post does not work if I switch the force vector around? Do you know why it doesn't work?

I have written some python code which was designed to try to solve the following differential equation: $$\ddot{x}+\omega_0^2x=\eta(t),$$ where $\eta(t)$ is the gaussian white noise, with mean 0 and variance 1. The initial conditions are: $$x(0)=\dot{x}(0)=0.$$ The code is given here:  import numpy as np import matplotlib.pyplot as plt from scipy.stats import norm  class HarmonicOdeSolver:     def __init__(self, dt, x0, xd0, omega_squared):         "Inits the solver."         self.dt = dt         self.dt_squared = dt ** 2         self.t = dt         self.omega_squared = omega_squared         self.x0 = x0         self.xd0 = xd0         self.x = [xd0 * dt + x0, x0]      def step(self):         "Steps the solver."         xt, xtm1 = self.x         xtp1 = (2 - self.omega_squared * self.dt_squared) * xt - xtm1 \              + self.dt_squared * norm.rvs()         self.x = (xtp1, xt)         self.t += self.dt      def step_until(self, tmax, snapshot_dt):         "Steps the solver until a given time, returns snapshots."         ts = [self.t]         vals = [self.x[0]]         niter = max(1, int(snapshot_dt // self.dt))         while self.t < tmax:             for _ in range(niter):                 self.step()             vals.append(self.x[0])             ts.append(self.t)         return np.array(ts), np.array(vals)  solver = HarmonicOdeSolver(1e-2, 0, 0, 1) snapshot_dt = 1.0 ts, vals = solver.step_until(1000, snapshot_dt) plt.plot(ts, np.sqrt(vals ** 2)) plt.plot(ts, np.sqrt(ts / 2))   The code was taken from and explained . I naively hoped that I could simply add the following line of code:  self.dt_squared * norm.rvs()   to simulate Gaussian white noise. One problem I have noticed is that the results appear to be highly dependent on the time step used. In a similar  we found that the variance of the oscillator should grow as: $$\sqrt{\langle x(t)^2\rangle}\sim\sqrt{\frac{t}{2}}.$$ I would like to reproduce this result, does anyone know of a simple way to simulate a harmonic oscillator driven by white noise?  EDIT: Thanks for the help WoofDoggy, however, I am still confused. When you turned the ODE into a system of stochasic differential equations should you have not done this: $$dX_t=\dot{X}_tdt,$$ $$d\dot{X}_t=-\omega_0^2X_tdt+dW_t,$$ but instead you have done this: $$dX_t=\dot{X}_tdt+dW_t,$$ $$d\dot{X}_t=-\omega_0^2X_tdt?$$


I have a datetime I want to convert to a formatted date and time. The format is 109(9). I have always used:  CONVERT(char(26), c1.DateTime, 109)   Which works successfully, but at least on SQL Server 2014 the Cardinality Estimator is throwing a warning:     Type conversion in expression (CONVERT(char(26),c1.DateTime,109)) may affect "CardinalityEstimate" in query plan choice.   I would like to correct this if possible at all, but maybe this is the improved cardinality estimator I am not sure.  The full query in this contrived example is from a temp table populated from an real table which is what I am trying to correct.   CREATE TABLE #Vic (     DateStamp   datetime    not null,     TIN int not null ); GO INSERT INTO #Vic VALUES ( N'1985-09-06T00:00:00', 123456789 ),  ( N'2003-01-14T20:55:00.983', 123456789 ),  ( N'1997-08-07T00:00:00', 123456789 ),  ( N'2016-11-15T09:31:28.15', 123456789 ),  ( N'2003-01-14T20:45:29.247', 123456789 ); GO  SELECT TOP (10) CONVERT(char(26), v.DateStamp, 109) ,     CONVERT(varchar(26), v.DateStamp, 9) ,     CONVERT(nvarchar(26), v.DateStamp, 9),     CONVERT(nvarchar(30), v.DateStamp, 9),     CONVERT(varchar(9), v.TIN) FROM    #Vic AS v;   This gives a warning on every column listed.   This may be related to , but I am not sure the context is the same based on the query this Connect item provides.

create table T(ID int identity primary key) insert into T default values insert into T default values  go  select cast(ID as varchar(10)) as ID from T where ID = 1   The query above has a warning in the query plan.  <Warnings>   <PlanAffectingConvert ConvertIssue="Cardinality Estimate" Expression="CONVERT(varchar(10),[xx].[dbo].[T].[ID],0)" /> </Warnings>   Why does it have the warning?  How could a cast in the field list affect the cardinality estimate?


Next year the Keukenhof will be open from 21 March until 19 May 2019. We will be in Amsterdam 27-29 March 2019. How different will the early bloom be from the peak bloom in April? Their website says that the large tulips will not be in bloom:     Flowering at Keukenhof parallels that in nature. The crocuses, daffodils,    hyacinths and early tulips flower at the start of the season. Other flowers   bloom later in the season such as the (larger) tulips. Our pavilions feature   entrancing flower shows from the first to the last day of the season.   Is a 28 March visit still worthwhile or will it not look like the pictures on the website?

I would like to see the tulip fields in the Netherlands.  Where and when is the best time to do it? (after the flower blooms and before the crop) Is it possible to go by public transportation or is it better to do it by car?     Is there a train that crosses those fields?


I have been browsing the Stackoverflow site on my Firefox browser of my desktop system, and when i resized my browser, the site is not getting adjusted automatically (non-responsive).    While i browsed the site on my Android, the site looks perfectly responsive, with good UI.  Just curious to know why Stackoverflow was not made responsive for the desktops, by default. Because there are many responsive HTML frameworks available today like , ,  and .  Is there a plan for implementing this feature in the future?

When will SO stop wasting real estate of my screen by having static width layout?  EDIT  It would be very interesting to hear how does Joel, being UI specialist, feel about this. JoelOnSoftware site has fluid layout...


So one thing which is still giving me a real hard time is incoming traffic from outside the city limits. I just can't seem to figure out a good way to deal with it and I always end up with a ton of gridlock. Here I've got a 6 lane one way road going around, and I'd think that would alleviate congestion some but it sure doesn't, besides which everyone seems to use only one lane anyways.  I've tried actual roundabouts but seem to have trouble getting them to work right.

I noticed that I got some initial traffic problems at the point where the initial highway is connected to my city. At the beginning I simply elongated both roads that came from that highway, but this doesn't seem to scale.  What I wanted to do now is to create a single six-lane highway from these two four-lane roads. I'd be open to continue to use two roads in parallel here, but I didn't manage to add any way of crossing between the lanes when I tried that idea.  So, how do I merge two one-way roads into a single two-way road? Or, if my idea is really bad, what is a good way to connect the initial highway access to my fledgling city?  Here's a screenshot of the roads I want to connect, if my description wasn't entirely clear:


$$\int_{0}^{\infty} \frac{x}{1+e^x}dx=\int_{0}^{\infty} \frac{x(e^x+1-e^x)}{1+e^x}dx=\int_{0}^{\infty} x\cdot dx - \int_{0}^{\infty} \frac{x\cdot e^x}{1+e^x}$$  I can't think of a way to proceed further

Let's set: $$ \int_0^\infty\mathrm{d}x\frac{x}{e^x+1}=I. $$ I would like to compute it using, presumably, the methods of complex analysis and contour integration.


Question:  I'm implementing a recursive add() method on a tree type datastructure, implemented with a generic class representing tree nodes.  How can I create a sub-tree in that recursion, if the sub-tree is a generic type - thus has no constructor I can call?  Details of Situation:   I have a generic class set (which underneath is a map) that is designed to implement maps of maps of maps of ... of objects (basically, N level tree).  public interface NodeInterface<KeyType, ValueType> {     public void add(List<KeyType>, ValueType);     public ValueType getSubTree(KeyType); // Get subtree map }  // Generic map class.  // Leaf level nodes are maps too, just not maps containing other maps public abstract class NodeMap <KeyType, ValueType> implements NodeInterface<> {     protected Map<KeyType, ValueType> map; // actual map     ...  }  // Leaf level objects - map NOT containing other maps public class LeafNode extends NodeMap <String, MyDataType> {     public void add(List<KeyType>, ValueType) {} // implementation for leaf add     ... }  // Tree nodes (non-leaf) public class ParentNodeMap <ValueType extends NodeMap <?,?>>     extends NodeMap <String, ValueType> {      // This class is needed because there are methods that must be       // implemented on a map that can't be implemented on leaf level nodes.      ... }  // Actual tree node classes (needed as syntactic sugar, to avoid end users  // having to deal with HashMap<String, Hashmap<String, HashMap<String, ...MyDataType>>>>> public class Level2Node extends ParentNodeMap <LeafNode> { } public class Level1Node extends ParentNodeMap <Level2Node > { }   What needs to be done:  I'm trying to implement a method which will recursively insert the leaf level object into this map of map of maps (described in the interface).  E.g., the desired behavior is:  tree = new Level1Node(); List<String> keys = Arrays.asList("key1", "key2"); // I think I need 3 here? irrelevant. MyDataType data = new MyDataType(); tree.add(keys, data);   Problem:  I can't seem to implement creation and insertion of the subtree map in the add() method for ParentNode  This is what I tried in ParentNodeMap class:  public void add(List<KeyType> keys, ValueType value);     KeyType key = getFirstKey(keys);     createMapIfNull(); // creates "map" as new HashMap<KeyType, ValueType>()     ValueType subTree = getSubTree(key); // Gets me child subtree from map     // PROBLEM! that subtree is now "null" since we just created an new Map      // which has no key "hey"      // Now here's where we should create a new subtree and add it:     if (subTree == null) {         subTree = new ValueType<>(); // THIS IS WHAT FAILS!!!!         map.put(key, subTree);         subTree.add(keys.removeFirstKey(), value); // recursively add to subtree     }   Now, what I'm specifically stuck on is: How can I create an subTree object (of NodeMap type); where its type is generic ValueType extends NodeMap <?,?> and that's all I know of it?   Calling new ValueType() gives "Cannot instantiate the type ValueType" error.

Is it possible to create an instance of a generic type in Java? I'm thinking based on what I've seen that the answer is no (due to type erasure), but I'd be interested if anyone can see something I'm missing:  class SomeContainer<E> {     E createContents()     {         return what???     } }   EDIT: It turns out that  could be used to resolve my issue, but it requires a lot of reflection-based code, as some of the answers below have indicated.  I'll leave this open for a little while to see if anyone comes up with anything dramatically different than Ian Robertson's .


So if I have a string like:   plz_work = "text I want to get rid of HELLO want to keep this text HELLO want to keep this text"   I want to remove all the text before the first instance of HELLO, like the following:   "HELLO want to keep this text HELLO want to keep this text"   In this case, I used regex, and tried the following off of  and :    re.sub(r'.*HELLO','HELLO',plz_work,1)   But I get this:   'HELLO want to keep this text'   Why does this happen? I thought the last parameter signified  and means that it would only perform 1 substitution... why is it going wrong here? Any help would be greatly appreciated, thanks!!

I have this gigantic ugly string: J0000000: Transaction A0001401 started on 8/22/2008 9:49:29 AM J0000010: Project name: E:\foo.pf J0000011: Job name: MBiek Direct Mail Test J0000020: Document 1 - Completed successfully  I'm trying to extract pieces from it using regex. In this case, I want to grab everything after Project Name up to the part where it says J0000011: (the 11 is going to be a different number every time). Here's the regex I've been playing with: Project name:\s+(.*)\s+J[0-9]{7}:  The problem is that it doesn't stop until it hits the J0000020: at the end. How do I make the regex stop at the first occurrence of J[0-9]{7}?


I did a question in which, the intensity of the incident radiation on a metal surface was kept constant but the wavelength of the photons has been reduced. The question inquired what will be the effect on the maximum photoelectric current? The initial wavelength was smaller than threshold wavelength of the metal surface.  My thinking was since the intensity remains constant, thus the number of photons emitted from the source remains constant and thus the number of electrons emitted from the metal surface. And since number of electrons per unit time isn't changed, the current will remain the same.  However, the answer key stated "Fewer photons (per unit time) so (maximum) current is smaller"   How does decreasing wavelength (equivalent to increasing the energy of photons) result in a fewer photon emission?

We all know that the amount of current flowing b/w the plates is independent of the frequency. If I were to ask why doesn't it depend then you'd probably say that it depends on the number of electrons rather than the frequency or you might show me a current vs frequency graph.  But here is my theoretical argument. Electric current is defined as the amount of charge flowing through a point/space/wire per unit time. Let I be current due to photo electrons ejected by photons of some frequency. Now if I would increase the frequency, the kinetic energy of the ejected electron would increases, therefore it will move faster and therefore contribute more current (charge will through the same point many times per unit time) . Thereby, giving a net current greater than I.  What is wrong with my argument?  After thinking a lot, I came up with a possible reason. However fast the electrons may move, but when they hit the metal plate, they would lose their velocity and start moving in drift velocity. Now there is a problem with this argument. If this were to be true then I should expect to see a big chunk of extra electrons getting stuck at the anode.  If my reasoning was correct, then why can't I see a big charge buildup at the anode.


The famous double slit experiment shows how light behave like a wave when sensors near one slit are on and recording vs not recording. I didn't find a lot of details, but especially given the case that something similar could happen for light traveling around the universe... it raises for me the question:  What if someone/something recorded the particle at the slit or not with a 50% chance of recording. Supposing we wouldn't/couldn't know which it is, it should behave like a wave (my expectation). Couldn't we possibly later open that box and ask/check if it was actually recording or not?  More accurately, would the results change if we could and could not later know if the sensor was actually recording or not?  I know of the delayed double slit (especially the ) but here I'm not asking regarding time travel but more regarding possible knowledge or lack of it. Because if anything that could observe light would force it to collapse, it seems that it could tell us if something observed that particle, ever (ok no need to put aliens here but it could).

I'm still struggling a bit with some ideas around double slit experiments. One that keeps cropping up for me is the role of observers.   Imagine a classic double slit experiment with a hidden observer who has arranged an apparatus to detect which slit the electrons are passing through. This person and their measurements are hidden to you and you have no interaction with them.  So the question is, do you see an interference pattern or not?  Additionally: And if the answer is Not, then is the reason because they "disturbed" the electron (by say firing photons at them) or is it for another reason? And if it is because they "disturbed" the electron, then how is it that unobserved electron's are not disturbed since they certainly interact with other objects, for example other atoms in the matter around the slit(s) will feel a slight gravitational tug as it passes through.


Let $G$ be a cyclic group of finite order $n$. Then, the order of the cyclic subgroup $\langle g^k\rangle$ is $\frac {n}{\operatorname{gcd}(n,k)}$  Proof:  $G$ cyclic $\Rightarrow \exists g \in G: G = \langle g\rangle$ $\Rightarrow \operatorname{ord}(g) = \lvert G\rvert = n $  We know, because every subgroup of a cyclic group is cyclic, that $\lvert\langle g^k\rangle\rvert =  \operatorname{ord}(g^k)$. Therefore, we only need to find the order of $g^k$.  Let $l$ be the order of $g^k$. Then:  $(g^k)^l = e \iff g^{kl} = e \iff n|(kl)$  I'm now trying to show that $l = n/{\operatorname{gcd}(n,k)}$, but this seems difficult for me. I tried to assume that there was an element $l' < n/{\operatorname{gcd}(n,k)}$ that satisfied the conditions, in the hope of reaching a contradiction, but this did not work out. Can anyone help?

This is an exercise from "Contemporary Abstract Algebra" I'm not sure how to solve.     Exercise: Let $\langle a\rangle $ be a (cyclic) group of order $n$. Prove that the order of $a^k=\frac{n}{\gcd(n,k)}$.   Direction: (1) Let $d=\gcd(n,k)$, thus by the Euclidian algorithm we can find $X,Y\in\mathbb{Z}$ s.t. $d=Xn+Yk$, thus, $a^d=a^{Xn+Yk}=a^{Xn}a^{Yk}=(a^n)^X(a^k)^Y=(a^k)^Y$. What to do from here?  (2) We know that $d|n$, thus $\langle a^{n/d} \rangle$ is of order $d$ and $\langle a^d \rangle$ is of order $\frac{n}{d}=\frac{n}{\gcd(n,k)}$. Is it mean that $d=k$? Where is my mistake?


I've noticed from the event log, that something is backing up SQL Server databases, separately to our maintenance plan backups. We can see something running SQL backups at 03:00. Our intended backups only kick off at 04:05.  The backup logs look like this:      Database backed up. Database: master, creation date(time):   2015/11/15(09:39:37), pages dumped: 490, first LSN: 743:441:73, last   LSN: 743:472:1, number of dump devices: 1, device information:   (FILE=1, TYPE=VIRTUAL_DEVICE:   {'{9BCE7BA5-E8AB-4459-8655-365988420F35}12'}).   There seems to be no other backup of the database files themselves which might trigger a volume shadow copy (VSS writer) that we can see, so it's a mystery what's causing these.   The worry is of course, that these backups will interfere with the restore process for point-in-time restore as we have no access to these full backups, yet they are presumably resetting the transaction log.   The server is a Virtual Machine and I originally theorised that perhaps something was backing up the entire VM at this time, and perhaps that was causing VSS to create the backups, but apparently there is no machine imaging backup set up on this server - only file based backups of certain folders and the main SQL data folder is not backed up.   Is there anything I can set up which could provide any clues as to what's running these backups?

We have an instance of SQL Server 2008 installed on a customer server. The customer's IT department is in charge of the various backups of the machine.  The SQL Server log shows there is a full backup every day at 7 PM but we can't find evidence of any plan scheduled in SQL Server.  The technicians we contacted couldn't tell us if there was some sort of automatic backup, all they told is that the entire machine is being backup up.  Using a script I found in  I found out that the physical device name is a GUID and that this means that this is an external backup process:  USE [msdb] GO  SELECT      [bs].[database_name],      [bs].[backup_start_date],      [bs].[backup_finish_date],      [bs].Server_name,     [bs].user_name AS [BackupCreator] ,     [bmf].physical_device_name FROM msdb..backupset bs   INNER JOIN msdb..backupmediafamily bmf ON [bs].[media_set_id] = [bmf].[media_set_id]  ORDER BY [bs].[backup_start_date] DESC   This is a row from the above query:     db_name 2015-09-16 19:01:23.000   2015-09-16 19:01:28.000SERVER_NAME  NT AUTHORITY\SYSTEM{424F084A-F35D-4A66-8FC7-072268A89A77} 5   Moreover the backup start and finish date spans only for 5 seconds, so I guess it's clear it's not a job of sql server.  This is a line from the log:     2015-09-03 19:02:30.71 Backup   Database backed up.   Database: db_name, creation date(time): 2012/10/12(20:52:11), pages dumped: 3290021,   first LSN: 276028:152755:172, last LSN: 276028:152827:1, number of dump devices: 1,   device information:   (FILE=1, TYPE=VIRTUAL_DEVICE: {'{95380B0A-D50B-408F-B95F-1AB8975BA7F8}5'}).   This is an informational message only. No user action is required.   So, since they can't help us what can I do to track down the process responsible of the backups? We need this because we want to coordinate the backup in an ordered manner, and do the transaction log backups too in order to keep the log at a reasonable size (now we do shrink the log every week, and this is not the good way to go).


At the beginning of season 5 in Agents of SHIELD, Coulson's team is (mostly) abducted from Rae's Diner by Enoch and a crew of men. These men all seem to be human. One of them even says:     My wife thinks that I'm at a friend's house for our fantasy draft. Doesn't even occur to her that we're in the middle of the season. Doesn't even occur to her.   They are also wearing standard-looking military gear for humans. Together these hint to me that they are human.  What is really strange is that Enoch claims frequently that he isn't supposed to interfere unless there are dire situations (extinction-level events). So how does he have a team or humans already picked out that has done this before (the man asks another man if he has done one of these recently and mentions that he hasn't) and has all of their gear? They are also the ones that hand him the device to freeze Coulson's team.

We know that Enoch is a Chronicom, which is to say a sort of alien temporal observer.   When Enoch and his agents came and kidnapped       Coulson’s team,   for the purpose of sending them where they wanted; were these other agents also Chronicoms? I’m inclined to think they must have been (would Enoch have shared their advanced technology and goals, etc. with mere mortals), but on the other hand only one pod was mentioned.


When my HP laptop wakes up from suspend I can't connect to the wi-fi. The adapter is lost.  ifconfig -a doesn't show it  lshw -C network returns an empty list  Only reboot helps.  Ubuntu 16.04, 4.18.5-041805-generic (I've tried on different kernels and the problem is the same).  None of the answers to  help me.  wireless info before suspend (wifi work)   wireless info after suspend

This particular version of the "doesn't work after suspend" came after upgrading to 16.04. It seems that the upgrade includes a Wicd applet (added to Metacity Classic Gnome task bar alongside regular network icon), but doesn't seem to work after a suspend. A sudo service network-manager restart duplicates this problem. It takes a complete reboot to get Wifi going again. Any ideas why?


I am able to set the value to a certain amount of days past the current day, like so:  $(function () {     $("#PriorityLevelID").on("change", function() {         $("#DueDate").datepicker("setDate", 2);     }); });   But is there a way to exclude weekends? For example, 2 days past Friday would not be Sunday, it would be Tuesday in business days.

I use a datepicker for choosing an appointment day.  I already set the date range to be only for the next month.  That works fine.  I want to exclude Saturdays and Sundays from the available choices.  Can this be done?  If so, how?


The reputation graph seems broken when using latest Chrome:    The overview at the bottom does not display correctly when opening any user rep graph. It works with Firefox though.

As you can see, if you go to the reputation graph on your profile on Stack Overflow, the bars in the bottom overview will be white. This makes them invisible unless they are selected.  Eeek!  This does not happen on meta or any other site. Also, I cannot seem to reproduce it on others' profile. Possibly a bug only on your own profile? EDIT: I think I've existed for too long. If I change the CSS on one of the bars to stroke: none, then it becomes green. I think the outline is covering the fill because the bars are too skinny. EDIT2: Confirmed hypothesis by reproducing on Jon Skeet's graph. Proposed solution: enforce minimum bar width and add horizontal scrollbar. EDIT3: Can only repro on Chrome 29.0.1547.57 (Official Build 217859) m (the latest version). Norepro on older versions of Chrome, IE9 (winces), all versions of FF, and all versions of Safari. EDIT4: Can be fixed simply by running the JavaScript $('rect').css('stroke-width', '0') or a userstyle rect { stroke: none }. I may make a user[style|script] to fix this.


Is it safe to use variable as column name like I use in this code?  public function SelectForum($column, $value) {     global $database;     $database->query('SELECT * FROM forums WHERE '.$column.' = :value');     $database->Bind(":value", $value);     $database->execute();     $ForumsData = $database->resultset();     $ForumsCount = $database->RowCount();     if($ForumsCount == 0) {         return null;     } else {         return $ForumsData;     } }

If user input is inserted without modification into an SQL query, then the application becomes vulnerable to , like in the following example:  $unsafe_variable = $_POST['user_input'];   mysql_query("INSERT INTO `table` (`column`) VALUES ('$unsafe_variable')");   That's because the user can input something like value'); DROP TABLE table;--, and the query becomes:  INSERT INTO `table` (`column`) VALUES('value'); DROP TABLE table;--')   What can be done to prevent this from happening?


I couldn't find the solve of my problem. So, problem is: in LibreOffice there are cut-off hints. I show it in the screenshot below.    Ubuntu version is 16.04.  P.S. Sorry for my English. There is Russian on the screen.

I have LibreOffice 5, and since I installed Ubuntu 16.04 LTS, LibreOffice's icons tips show it's text/info incomplete.  I can't find a way to fix it.  I've tried: Tools > Options > Libre Office > View  There I turn on/off the "Screen font anti-aliasing", fixing it temporarily, but after closing LibreOffice the problem returns.  Any idea of how to fix it definitely?  Image of the problem:


I have a function call that will occasionally get stuck. I would like to wrap this function with a decorator that throws an exception if the function call takes more than (say) 60s to complete. How would I do this? I thought about using a separate thread with a counter that would automatically manage a timer. The thread timer should automatically reset after the function completes, as I don't want to keep spawning new threads. How would I do this? Does this already exist in a library? Thanks!

There is a socket related function call in my code, that function is from another module thus out of my control, the problem is that it blocks for hours occasionally, which is totally unacceptable, How can I limit the function execution time from my code? I guess the solution must utilize another thread.


I graduated with 2.7 undergrad, and currently pursuing a masters degree and will graduate with 3.3. I plan to apply for PhD programs in engineering for 2017 Fall.   Here is my question: Many schools state that they require 3.0 GPA or so, but how do I know that whether they intend undergrad GPA?  Do you think should I apply to such school that states that     Minimum GPA: The MS and PhD program has a minimum GPA requirement of   3.0 on a 4.0 scale.    ?  Is it waste of my time if I have stellar letters of references and cool research experiences?

I am a senior year undergrad student from a prestigious institute in India. I intend to pursue a PhD after graduating. While researching universities, I stumbled upon the fact that many of the top schools have a minimum GPA requirement. For example UCSD has 3.4/4 as its minimum requirement.   My GPA is 7.2 on a scale of 10. It is quite above average in my school, but it translates to a 2.9 on a scale of 4 which looks pretty bad. DOes this mean that my application is likely to be rejected outright?   Also, I heard that most universities don't consider converted scores (by WES, for example) in a good light. I have research experience in my undergraduate years to offset the GPA. I really hope that the universities have a look at that.   Should I not apply to schools with such a requirement?


Is there any data explorer query that allows to find the users who bookmarked a specific question? EDIT: I tried searching for a direct hit on  but didn't find any post having a descriptive title for this functionality. As linked in the comments, two versions of the query can be found here , and here . Additional information on SEDE is available in the linked duplicate targets.

Over at , in  query, it shows the vote type (or what should be the vote type) "bookmark" as "favorite":  Can we update that to say "bookmark", since ?


I'm using AIX 6.1 which isn't supporting in -B and -A flags:  grep: Not a recognized flag: B   Lets say I want to run:  cat file | grep -E -B4 'Directory entry type.*Indirect' | grep "Database name" | awk  '{print $4}'   How can I do this kind of logic in AIX?  EDIT  My real code is as follow:  NAME_EXISTS=`db2 LIST DB DIRECTORY | grep -E -B5 'Directory entry type.*Remote' | grep "Database alias" | awk '{print $4}' | grep -i ${NAME} | wc -l` if [ ${NAME_EXISTS} -gt 0 ]; then     db2 LIST DB DIRECTORY | grep -E -A5 "Database alias.*${NAME}" fi   The idea is to find if there is a remote DB named $NAME, if it finds it - show the 5 lines beginning Database alias.*${NAME}. $NAME is unique in Database alias .  And the db2 LIST DB DIRECTORY output something like this:   System Database Directory   Number of entries in the directory = 3  Database 1 entry:   Database alias                       = OLTPA  Database name                        = OLTPA  Local database directory             = /db2/data  Database release level               = 10.00  Comment                              =  Directory entry type                 = Indirect  Catalog database partition number    = 0  Alternate server hostname            =  Alternate server port number         =  Database 2 entry:   Database alias                       = OLTPF  Database name                        = OLTP  Node name                            = OLTPN  Database release level               = 10.00  Comment                              =  Directory entry type                 = Remote  Catalog database partition number    = -1  Alternate server hostname            =  Alternate server port number         =  Database 3 entry:   Database alias                       = ADMIN  Database name                        = ADMIN  Local database directory             = /db2/data  Database release level               = 10.00  Comment                              =  Directory entry type                 = Indirect  Catalog database partition number    = 0  Alternate server hostname            =  Alternate server port number         =   For NAME=OLTPF output will be:   Database alias                       = OLTPF  Database name                        = OLTP  Node name                            = OLTPN  Database release level               = 10.00  Comment                              =  Directory entry type                 = Remote   For NAME=OLTPE there will be no output.

grep -A 2 -B 3    prints 2 lines after the grep string and prints 3 lines before.   grep -C 3   prints 3 Lines before and 3 lines after  Unfortunately, the grep I'm using does not support these options. Are there any alternative commands or script available to simulate this? Using sed/awk/perl/shell scripts?


I have a laptop (T14) with Win10 installed. Recently, it crashed and on startup it automatically goes to repair mode. Drive is locked with Bitlocker (I have the key available). So when I log in I try chkdsk which doesn't work as it says the drive is in readonly. When I try to clean attribute it tells me disk has errors and I need to repair them first for attributes to be cleared. I tried with USB with win installation on them. I cannot do format because the drive is locked with Bitlocker. I tried to suspend it but was unable, it returns error. So I am open to any solutions, repair the existing windows, formatting the drive... anything I don't mind just to get it up and running. Thx!

I have a HD protected by Bitlocker. Login, password and restorekey are unknown and all I want to do is wipe the whole drive. When I try to boot from a windows installation cd I have no access to the drive since it asks for the restore key I don't have.  Is there a way to format the whole drive to make it usable again?


Firstly, would a 26 x 2.0 tyre fit, and would there be a noticeable difference compared to my original tyre? (I am going from 2.10 to 2.0)

We often get questions on bicycles.stackexchange about fitting wider or narrower tires to bicycles. We have a large number of these with answers suiting the specific bike or style of bicycle in question, but I have been unable to find one that provides a generic answer covering off all things that need to be considered. For most bicycles, the answer is the same regardless of the specific style and sizes of tires in question.   This is intended as a canonical question that we can point closed questions to.


For some reason i can't boot Ubuntu live cd on my desktop pc while installation media works perfectly on laptop. I'm getting this error :  Any suggestions?

I am trying to boot Ubuntu on my computer.  When I boot Ubuntu, it boots to a black screen.  How can I fix this? Table of Contents:


I did a fresh install of Ubuntu 20.04, however after the install, I couldn't see any network options. I checked to see if my network hardware was detected, it was, but I still can't connect to the internet. I am using a MacBook Air, and my wireless adapter model is bcm4360 802.11ac wireless network adapter by Broadcom.

I'm having serious problems installing the Broadcom drivers for Ubuntu. It worked perfectly on my previous version, but now, it is impossible.   What are the steps to install Broadcom wireless drivers for a BCM43xx card?  I'm a user with no advance knowledge in Linux, so I would need clear explanations on how to make, compile, etc.    lspci -vnn | grep Network showed:   Broadcom Corporation BCM4322 802.11a/b/g/n Wireless LAN Controller [14e4:432b]      iwconfig showed:  lo        no wireless extensions. eth0      no wireless extensions.   NOTE: Answer below is updated every time new information is added and confirmed working.


According to the book "An introduction to the analysis of algorithms (written by Michael Soltys)", the author says in chapter 1 as follows.     Let $\mathbb N = \{0, 1, 2,...\}$ be the set of natural numbers. Suppose that $S$ is a subset of $N $ with the following the two properties: first $0 \in S$, and second, whenever $n\in S$, then $n+1\in S$ as well. Then, invoking the Induction Principle(IP) we can conclude that $S=\mathbb N$.   I am wondering if it is fine to define the set of natural numbers like the author. Why the author put the number $0$ into the set of natural number $\mathbb N$?

Is there a consensus in the mathematical community, or some accepted authority, to determine whether zero should be classified as a natural number?  It seems as though formerly $0$ was considered in the set of natural numbers, but now it seems more common to see definitions saying that the natural numbers are precisely the positive integers.


Also, what makes lightGBM run faster than XGBoost?

I've seen that in Kaggle competitions people are using lightgbms where they used to use xgboost. My question is: when would you rather use xgboost instead of lightgbm? What about catboost?


I want to convert a mathematics document to pdf, but I am getting missing $ errors.  Here is my code:   \documentclass{article} \begin{document} 1. All prime numbers are odd  Universal Statement: For all x \in \mathbb{N} such that for any a,b \in \mathbb{N} x = ab where a or b must be equal to 1 and for any k \in \mathbb{N}, x = 2k + 1  Counterexample will comprise of: A counterexample will be an x \in \mathbb{N} such that there exists a k \in \mathbb{N} such that x = 2k  Counterexample: 2   6. For all real numbers x, we have x^2-2x+2 > 1  Universal Statement: For all x \in \mathbb{R}, we have x^2-2x+2 > 1  Counterexample will comprise of: A counterexample will be an x such that x^2-2x+2 < 1  Counterexample: 1   14. For all functions f : \mathbb{R} \rightarrow \mathbb{R}, if f is not increasing, then it must be decreasing.  Universal Statement: For all functions f : \mathbb{R} \rightarrow \mathbb{R} for all x_1, x_2 if x_1 < x_2 and f(x_1) \ngeq f(x_2) then f(x_1) \leq f(x_2)  Counterexample will comprise of: A counterexample will be a function f such that for all x_1, x_2 if x_1 < x_2 and f(x_1) \ngeq f(x_2) then f(x_1) \nleq f(x_2)  Counterexample: None, the statement is true  \end{document}

Beginner here with an issue on a simple presentation using beamer  \documentclass{beamer}  \begin{document} \begin{frame}   \tau \epsilon \chi \end{frame} \end{document}   The above fails with the message "! Missing $ inserted." and waits for me to do something when converting to pdf. I have tried adding the instruction \usepackage[utf8]{inputenc} and also \usepackage[greek]{babel}. I have not seen references either to needing to use any other package. What is exactly I am missing?


I just read that finder has purposely restricted access when it comes to connecting to FTP sites. Not sure how any apple exec could possibly think this is acceptable. Simply put, I need to find a way to force finder to allow write access for a FTP server. Transmit no longer provides this functionality. Im not looking for any third party software. There should be a terminal command that forces finder to allow access?

I have just found out that I can enter a built-in FTP client on my Mac by simply pressing ^ Ctrl + K. Great thing!   But after I have successfully connected to my server and a 'folder' with files located there appeared, it occurred that I can't upload files by simply drag & drop'ing them. When I checked the 'Get info' I saw that it is marked as 'You can only read', yet the ftp account itself is okay, because I could upload files there from dreamweaver (unfortunately I have only Windows licence for this app).  Why is it marked as 'You can only read' and how do I fix that?  Please help!  P.S. Could you explain it in an easy way? Because I'm new to Mac (just bought one few days ago).


I am not native English speaker. I get frustrated when it come to articles. Can you please tell me whether the sentence below is grammatically correct.  She spent all the night in rereading a letter from her sister

I can’t for the life of me figure out where to use a and where to use the — and where there is no article at all. Is there a simple rule of thumb to memorize?   The standard rule you always hear:     “If a person knows which item you are talking about then use "the"   . . . doesn’t clear things up for me, as I have no idea whether or not they know.


I am currently running Ubuntu 16.04 LTS and downloaded Folder Color as described in .    But though I restarted my pc again the option is not available when I right click on any folder.    What can I do now?    Note: The answer I accepted is because it worked, I had already installed the Folder Color software and was using it for a long time but it stopped working one day so this question is regarding what to do if the Folder Color is not working if Installed already.Still, if you consider it duplicate of any XYZ question please think again.

How do i change the folders colors? i am using this icon theme   and there are several folders. like black, gray, purple, orange(which is the default), yellow, green, red, blue, brown and lightblue  How can i use any of them? for example have a blue folder called "family" in images and another right beside that have a purple folder called "others".  Basically why have he created all those folders with different colors?


I'm in trouble at the following exercise:     (Ex. 6, page 143 - Um Curso de Álgebra Linear; Coelho, Flávio Ulhoa)   Show that if $A\in M_2(\mathbb{C})$, then $A$ is similar (or conjugated) to a matrix of one of the following forms   $$\left(\begin{array}{cc}a&0\\0&b\end{array}\right) \text{ or } \left(\begin{array}{cc}a&0\\1&a\end{array}\right), \text{ with } a,b\in\mathbb{C}.$$   What I've tried: Be $A\in M_2(\mathbb{C})$. Consider $T:\mathbb{C}^2\to\mathbb{C}^2$ the linear operator whose matrix at the standard basis $\mathscr{C}=\{(1,0),(0,1)\}$ of $\mathbb{C}^2$ is $A$, i.e., $[T]_\mathscr{C}=A$. Since $\mathbb{C}$ is algebraically closed and we know that the characteristic polynomial of $T$ is monic and has degree 2, we have that it is of the form $p_T(x)=(x-a)(x-b)$, for some $a,b\in \mathbb{C}$. Of course $a$ and $b$ are eigenvalues of $T$.    Case 1: $a\neq b$; Considering the dimensions of the eigenspaces of $T$, we conclude that $T$ is diagonalizable and, therefore, exists a basis $\mathscr{B}$ of $\mathbb{C}^2$ such that $$[T]_{\mathscr{B}}=\left(\begin{array}{cc}a&0\\0&b\end{array}\right),$$ and, through basis exchange, $A$ is similar to a matrix of the first kind.  Case 2: $a=b$ and $p_T(x)=(x-a)^2$ In this case, if the geometric multiplicity $m_g(a)=2$ then, again, there is a basis $\mathscr{B}$ of $\mathbb{C}^2$ of eigenvectors of $T$ and  $$[T]_{\mathscr{B}}=\left(\begin{array}{cc}a&0\\0&a\end{array}\right).$$ Now, if $m_g(a)=1$, then the eigenspace $Eig_T(a)$ spanned by the eigenvectors associated to the eigenvalue $a$ has dimension one, say, $Eig_T(a)=[v]$. And then, completing a basis $\mathscr{B}=\{u,v\}$ of $\mathbb{C}^2$, I only know that $$[T]_{\mathscr{B}}=\left(\begin{array}{cc}a_1&0\\a_2&a\end{array}\right).$$ From here, I've tried to find some suitable $u$ such that $T(u)=au+v$ in a way that $a_1=a$ and $a_2=1$, but solving this system seems impossible (in general) to me! Is this right?  Suggestions? Ideias? Thank you once more, guys...

We have a general linear group $GL_{2}(\mathbb{C})$ that acts on the set of $M_2(\mathbb{C})$ set of $2\times 2$ matrices by conjugation.   I want to classify the orbits of its action.  What I know:  $$ Orb_{G}(A) = \left\{ BAB^{-1} : \text{where } B \in GL_2(\mathbb{C})\right\}.$$


The following cron job fails to execute. What's wrong with it? It works fine when I run it directly from the shell prompt.      www-data@etl:~$ crontab -l SHELL=/bin/bash MAITO=""  0 5 * * *   export YESTERDAY=$(date --date "yesterday" "+%Y-%m-%d"); cd /var/www/project && source .env/bin/activate && ./manage.py get_orders --date="$YESTERDAY" && sleep 5m && time ./manage.py merch --date="$YESTERDAY" && time ./manage.py order_flat_report --date="$YESTERDAY" && time ./manage.py update_hourly_report --date="$YESTERDAY"   I'm getting this error message:  Return-Path: <www-data@etl> X-Original-To: www-data Delivered-To: www-data@etl Received: by localhost (Postfix, from userid 33)     id E170C43EC7; Fri, 18 Apr 2014 05:00:01 -0400 (EDT) From: root@etl (Cron Daemon) To: www-data@etl Subject: Cron <www-data@etl> export YESTERDAY=$(date --date "yesterday" "+ Content-Type: text/plain; charset=ANSI_X3.4-1968 X-Cron-Env: <SHELL=/bin/bash> X-Cron-Env: <MAITO=> X-Cron-Env: <HOME=/var/www> X-Cron-Env: <PATH=/usr/bin:/bin> X-Cron-Env: <LOGNAME=www-data> Message-Id: <20140418090001.E170C43EC7@localhost> Date: Fri, 18 Apr 2014 05:00:01 -0400 (EDT)  /bin/bash: -c: line 0: unexpected EOF while looking for matching `"' /bin/bash: -c: line 1: syntax error: unexpected end of file    Ubuntu 13.10 (GNU/Linux 3.11.0-14-generic x86_64) GNU bash, version 4.2.45(1)-release (x86_64-pc-linux-gnu)

This is a  about using cron & crontab.   You have been directed here because the community is fairly sure that the answer to your question can be found below. If your question is not answered below then the answers will help you gather information that will help the community help you. This information should be edited into your original question.  The answer for 'Why is my crontab not working, and how can I troubleshoot it?' can be seen below.  This addresses the cron system with the crontab highlighted.


I'm a simple man living my life and enjoying mathematics now and then. Today during lunch my friend asked me about complex numbers and $i$. I told him what I knew and we went back to work.  After work I decided to read up on complex numbers and I somehow ended up with this equation:  $$ 1 = \sqrt 1 = \sqrt{(-1)(-1)} = \sqrt{(-1)} \  \sqrt{(-1)} = i \cdot i = i² = -1 $$  Somehow I got that $1 = -1.$  I can't see a contradiction. Did I just break math? What happened? Where is my mistake?

I know there must be something unmathematical in the following but I don't know where it is: \begin{align} \sqrt{-1} &= i \\\\\ \frac1{\sqrt{-1}} &= \frac1i \\\\  \frac{\sqrt1}{\sqrt{-1}} &= \frac1i \\\\  \sqrt{\frac1{-1}} &= \frac1i \\\\  \sqrt{\frac{-1}1} &= \frac1i \\\\  \sqrt{-1} &= \frac1i \\\\  i &= \frac1i \\\\  i^2 &= 1 \\\\  -1 &= 1 \quad !!? \end{align}


Given an arbitrary set $X$, can one always find an element outside $X$? I think this question boils down to whether there exists a universal set that contains everything, including itself. But wiki says that assuming the existence of a universal set leads to . So given a set $X$, can one explicitly construct an element that does not belong to $X$? For example, is $\{X\}$ such an element?

So there are a few posts about this already, but they skip over the problem I have.  The proof of Cantor's theorem elegantly shows that if we consider $f:A\rightarrow \mathcal{P}(A)$, the set $B=\{x\in A : x\not\in f(x) \}$ by its definition cannot lie in the image of $f$, precluding it from being a bijection - hence power sets have strictly greater cardinality.  But now, I thought one (obvious) way to characterise the "set of all sets" would be $S=\mathcal{P}(S)$, as indeed, it contains all possible sets (perhaps here is the problem, but I don't immediately see how using this as a definition for the set of all sets is bad). Now consider simply taking the identity function $i:S\rightarrow S$. Then $B=\{x\in S : x\not\in x \}$ - the set of all sets which do not contain themselves. But this doesn't exist. It's exactly the set of Russell's paradox. If this isn't a set, and so is not in $S$, then the proof no longer offers an obstruction to $i$ being surjective.    Each other post I've seen on the matter uses Cantor's theorem to show such a set doesn't exist. My query is to find that something else that must be happening, since I think the proof has issues for this particular set. I'm expecting other issues to arise with the definition $S=\mathcal{P}(S)$...


I have a list of elements I'd like click to copy the values inside. the elements all have the class datavalue. I'm thinking a Jquery selector with some javascript copy would help.

IDM

             FirstName

       John

             SecondName

       Baxter

             DBrith

       12/25/1982

What is the best way to copy text to the clipboard (multi-browser)? I have tried: function copyToClipboard(text) {     if (window.clipboardData) { // Internet Explorer         window.clipboardData.setData("Text", text);     } else {         unsafeWindow.netscape.security.PrivilegeManager.enablePrivilege("UniversalXPConnect");         const clipboardHelper = Components.classes["@mozilla.org/widget/clipboardhelper;1"].getService(Components.interfaces.nsIClipboardHelper);         clipboardHelper.copyString(text);     } }  But in Internet Explorer it gives a syntax error. In Firefox, it says unsafeWindow is not defined. A nice trick without using :


I came across a problem that required finding the first 10 numbers (n > 2) with the following property:  all positive numbers x less than n that have GCD(x, n) = 1 should be prime  example:  12 is such a number because all x that have GCD(x, 12) = 1 are prime (those being 5, 7 and 11)  15 isn't such a number because GCD(4, 15) = 1 for instance, but 4 isn't a prime number  I wrote a simple program that tries to look after such numbers, the first eight being:  3, 4, 6, 8, 12, 18, 24 and 30 being the last found (either because the next one is a really big number or because there isn't another one).  So my guess right now is that there aren't more than 8, which brings me to my question. Is there a way you can prove there aren't more than 8 using math? (or work some sort of logic that tries to find out how big would the next one be if there is)

Show that only finitely many positive integers $n$ have the property that for all $m$ for which $1<m<n$ and $\text{gcd}(m,n) = 1$, $m$ is prime.    I am able to show that a positive integer with the specified property is prime, but I do not know how to prove that there are "finitely many" of them.  EDIT: Adding a proof of the mentioned claim that "a positive integer with the specified property is prime."  If $m$ is prime $m$ has no factors but $1$ and $m$. So gcd$(m,n)$ can only equal 1 or $m$.  If gcd$(m,n) = m$ then $m|n$.  So $n \ge m$. If $n < m$ then gcd$(m,n)=1$. Conversely, if gcd$(m,n)=1$ for all $n < m$, then no number less than $m$ divides $m$ (other than $1$).  Since no number larger than $m$ divides $m$, $m$ has no divisors except itself and $1$. So $m$ is prime.


I know that the industrial standard is normally sending data in the following format:  Send Encr(msg, Sign(msg))   Is the following way a secure as well?  Send Enc(msg) and Sig(msg)   By secure, I mean no one will be able to read my message, and no one will be able to tamper my message.

Frequently, we want to send messages that are (a) encrypted, so passive attackers can't discover the plaintext of the message, and (b) signed with a private-key digital signature, so active attackers can't make Alice think that a message came from Bob when it didn't. Is it better to (a) generate the digital signature from the (hashed) plaintext, and then encrypt a file containing both the plaintext message and the digital signature? Or is it better to (b) encrypt the message first, and then generate a digital signature from the (hashed) encrypted file? Or (c) combine encryption and public-key digital signatures in some other way? A closely related earlier question (  ) seems to focus on symmetric-key MAC authentication. As , Do the same issues with (symmetric-key) MAC-then-encrypt apply to (public-key) sign-then-encrypt?


I need help regarding the following two exercises:     a) Show that $(\mathbb R^2, d_2)$ and $(\mathbb R,d_1)$ $d_2,d_1$ being the respective euclidean metrics, are not isometric isomorphic, i.e. there is no bijective isometric map between those metric spaces.   b) Let d be the restriction of the euclidean metric of $\mathbb R$ on $(-1,1) \times (-1,1)$. Find a metric $d':\mathbb R \times \mathbb R\to \mathbb R$ such that the spaces $((-1,1),d)$ and $(\mathbb R,d')$ are isometric isomorphic.   For a) I think I have solution but I am not really sure: Does it suffice to say that for every possible candidate $f$ for an isomorphism it can't be injective since it must be norm preserving, i.e. $$||f(x)||_2 = ||x||_2, \quad ||f(-x)||_2 = ||-x||_2 = ||x||_2$$ with $||\cdot||_2$ being the respetive euclidean norm?   For b) I don't really know how to start.

Can someone help me solving the following problems?        $(\mathbb R^2,d_2)$ and $(\mathbb R, d_1)$, $d_2, d_1$ being the respective euclidean norms, are not isometric isomorphic, i.e. there is no distance preserving isomorphism between them.     Let $d$ be the restriction of the euclidean metric on $(-1,1) \times(-1,1).$ Find a metric $d':\mathbb R \times \mathbb R \to \mathbb R$ such that the spaces $((-1,1),d)$ and $(\mathbb R,d')$ are isometric isomorphic.      For 1.)  I thought it suffices to prove that if there was a isomorphism between those two, it wouldn't be distance preserving since it then also must be norm preserving which can't be injective since $||f(x)||_2 = ||x||_2 = ||f(-x)||_2$.    I don't know if that suffices or if it is even true. I would be glad if someone could prove me why they can't be isomorphic in the first place.    For 2.) I don't know what to do.


Suppose:   The "counter field" is about: NONCE || CTR-VALUE. I have multiples messages $M_a, M_b, M_c, \dots$ Each message can be divided into x-bits blocks ($M_{a1}, M_{a2}, M_{a3}, \dots$).   Each message $M$ (for instance $M_a$) is encrypted following a randomly and uniquely generated key. In this case, does I really need the NONCE part of the "counter field" ? If I really need a nonce, and knowing that each key is again unique-per-message, is there a secure way to derivate the nonce from the key ?

I took a look at  but my question is not the same.  I have unique keys encrypting each plaintext (in CBC mode, AES-256) and I do not use a key to encrypt more than one plaintext. Is it insecure to use null IVs in this case? If it is insecure, why?


Given:   We are getting lots of problems with the quality of questions from new users. The unwillingness to register shows a lack of commitment to the site and hence is a good indication that the person will not spend the time learning how to post good questions. We are getting a lot more questions than we need, it could be claimed that Stack Overflow is becoming less useful due to the volume of questions.   Should unregistered users only be allowed to answer questions and not post questions?  In the old days Stack Overflow benefited from lots of questions being asked, so it made sense to make it easy for anyone to ask questions,  I no longer see the bandit from increasing the already great volume of questions.  (The site I use other the Stack Overflow, don’t seem to be getter the same problems with the volume of poor questions.)    The way I think of it is when a nation is first formed, anyone including convicts are let in, but once something worthwhile has been built, a system is put in place to only allow in people that are a net benefit to the current residence.   I am now thinking that a lot of the new unregister users that are asking questions will never become a net benefit to the current committed users.

I know SO's policy is "you don't have to register to ask questions," but there are so many new members and so many hit-and-runs... The majority of the questions I see now are coming from new users (i.e., it's their first question). Although unregistered users should still be able to ask questions, I think we should encourage users to create an account. Here is a couple of ways we could do that:  Explicitly encourage people to get an account: there's currently nothing telling people to do that. Maybe tell people something like "Get an account, it's easy!" and maybe show some of the perks of having an account (and having rep).  Maybe give a few bonus points for registering; and have that enable a basic privilege. It could be taken from one of the , for example.   Of course getting people to register is just half of the battle. I don't know what the stats are on this, but I think there's a number of users who create multiple accounts anyways. We could curb that by:  Having smart(er)? duplicate account detection systems, alerting someone who is about to create a new account and possibly has an account already. Give them a message like "Hey, it looks like you already have  account, are you sure you want to create a new one?"  Create a new privilege (10k? 20k?) that gives users tools to detect possible duplicate accounts, eg: "List users with the same e-mail," "List users with the same IP addresses,"  etc. (without revealing said emails and IPs). Then the 10k/20k can look at other stuff (e.g.: posts) and refer the new user to a moderator for a possible merge.


I am having a little trouble understanding this state:  $$ \,^3D\left[3/2\right]_{1/2} $$  What does the $[3/2]$ indicate here?

Atomic  are used to notate the angular momentum content of the electronic states of an atom, and are normally written down as $$^{2S+1}L_J$$ where the state has total spin $S$, spin multiplicity $2S+1$, total angular momentum $J$, and total orbital angular momentum $L$.  Occasionally, though, one comes across term symbols which cannot fit in this scheme, because they have a half-integral "$L$", such as $$^3[3/2]_{1/2}.$$ (For an example, see  () or the ).   In addition, one can sometimes see even weirder beasts with both an $L$ letter and a half-integer in square brackets, such as () $$^1D[3/2]_{1/2}.$$  Neither of these types of term symbols are covered in normal quantum mechanics textbooks even in passing, even though the states do make an appearance now and then. What do these term symbols mean, and how does one interpret them?


Since 6 years, I am the happy user of a bicycle with a  internal hub gear.  German quality squeezing 14 gears and a 526% gear range into the rear hub.  Less known is the newer and equally German  gear, which reportedly has 18 maintenance-free gears and a 636% gear range — all squeezed into the bottom bracket.  Wow.  The Pinion website features the logos of many high-end touring brands like Santos, Idworx, and Koga.  What are the advantages and disadvantages of squeezing the gears into the bottom bracket, as opposed to into the rear hub?

Looking into an IGH it seems the biggest disadvantage is having a huge amount of rotating mass. I've seen one handmade bike where the IGH sits above the bracket, inside a carbon fibre shroud around the place some bikes have rear suspension. There are two chains, one driving the IGH and another to drive the rear wheel.   Why not have an internally geared bottom bracket where the cranks drive the input shaft and the crank ring rotates at a ratio selectable by the gear lever?   Then the rear wheel could have a single drive wheel driven by a chain or belt and a lightweight hub just solid enough to mount the spokes and disc. Then you could have mud-free gearing while reducing rotating mass even below what you have with a conventional cassette... and given that you have thrown out the bottom bracket the overall weight gain would be less.  Quite a job for the home builder to adapt an existing hub I guess but it should be possible.


with a query, I get a value of "date" from the SQLite database, in the format "YYYY-MM-DD". Now I want to convert this format to display the date in the format getInstance (). How can I do?   DateFormat fmtDateAndTime=DateFormat.getDateInstance();    GregorianCalendar dateAndTime = (GregorianCalendar) GregorianCalendar.getInstance();   I get the date:  private void Mto() {     String id_ricevuto = (i.getStringExtra("id_p"));          SQLiteDatabase db = mHelper.getReadableDatabase();     String tabella = "SELECT _id, date FROM Table1 WHERE _id = '"+id_ricevuto+"'";     Cursor c = db.rawQuery(tabella, null);     while (c.moveToNext()){         String id = c.getString(0);         String date = c.getString(1);         //here I want to convert the data before displaying it in the TextView                   idw.setText(id);          mBtnPickDate.setText(date);       }      c.close();     db.close(); }

How to format correctly according to the device configuration date and time when having a year, month, day, hour and minute?


i am getting this error when i try to run the update list command in order to correct the red minus sign on the top bar:   $ sudo apt-get update  E: Type' !DOCTYPE' is not known on line 1 in source list /etc/apt/sources.list.d/playonlinux.list E: The list of sources could not be read.   Solution please??

Every once in a while I see users having issues to update due to errors like this:  E:Type 'ain' is not known on line 1 in source list /etc/apt/sources.list.d/some-ppa.list'   with varying types/line numbers/source list files (often after removing a PPA).  How can such an error be fixed?


I'm going to start a degree course in physics next year. So far in high school I covered some physics without calculus.  I know that I will start everything from the beginning at university, but I would like to prepare in some ways. Then the question is: what should I do? Should I revise what I studied? Should I go head?   Can you suggest (from your experience) what should I do before starting a physics degree course?  PS In case you recommend to study some material, can you suggest a book?

Every once in a while, we get a question asking for a book or other educational reference on a particular topic at a particular level. This is a meta-question that collects all those links together. If you're looking for book recommendations, this is probably the place to start.  All the questions linked below, as well as others which deal with more specialized books, can be found under the tag  (formerly ).  If you have a question to add, please edit it in. However, make sure of a few things first:   The question should be tagged  It should be of the form "What are good books to learn/study [subject] at [level]?" It shouldn't duplicate a topic and level that's already on the list   Related Meta:


I am using this query to select rows in MySQL  SELECT * FROM `table` WHERE `id` IN (5,2,3,1,4);   Now by default the rows will be ordered by their id: 1, 2, 3, 4, 5  Is there any way that I can order rows as they are in the query, so the order should be: 5, 2, 3, 1, 4 ?

I am wondering if there is away (possibly a better way) to order by the order of the values in an IN() clause.  The problem is that I have 2 queries, one that gets all of the IDs and the second that retrieves all the information. The first creates the order of the IDs which I want the second to order by. The IDs are put in an IN() clause in the correct order.  So it'd be something like (extremely simplified):  SELECT id FROM table1 WHERE ... ORDER BY display_order, name  SELECT name, description, ... WHERE id IN ([id's from first])   The issue is that the second query does not return the results in the same order that the IDs are put into the IN() clause.  One solution I have found is to put all of the IDs into a temp table with an auto incrementing field which is then joined into the second query.  Is there a better option?  Note: As the first query is run "by the user" and the second is run in a background process, there is no way to combine the 2 into 1 query using sub queries.  I am using MySQL, but I'm thinking it might be useful to have it noted what options there are for other DBs as well.


Is it possible to replace a particular icon with one of our choice in 16.04 Ubuntu ? If yes, kindly share.

I want to change icon of a binary file which is placed on my desktop. The binary file is related to unetbootin. I want to execute unetbootin from the desktop so I want to change the icon. How can I achieve this?


Further to my problem :   I ran wireless-info, as instructed, found on this recommended page:  and pasted the results here: No network devices available on 19.04 if I use kernel 5.0.0-23 Wireless works fine on 19.04 if I use kernel 5.0.0-21 Wireless works fine on Windows 10 (dual boot) Realtek RTL8188CE 802.11b/g/n WiFi Adapter [10ec:8176] (rev 01)   Thank you Pilot6 very much, but my adapter is RTL8188CE, and the download referred to in your link is another model, not supported on >18.10.  I can't understand why I get wifi using kernel 5.0.0-21 yet not on 5.0.0-23?  Thank you to everyone.  In case it helps, I have pasted the result of wireless-info script from 19.04 when I am using kernel 5.0.0-21 (on which I do have wifi):   I don't know whether the comparison with the script result on kernel 5.0.0-23 (without wifi) would help?  My problems did actually start with the update I ran a week after I had upgraded from 18.10 (wifi worked fine until then), so is it possible it could be broken packages?  Once again apologies, I am away from my own computer until weekend. Thanks again!

I just recently bought an arduino and requires gcc-avr/avrdude to compile the software. I installed avr for another microprocessor component a while ago but is obviously an outdated version (gcc version 3.3 20030512 (prerelease)) so I went ahead to update these but it didn't work.   (Please note that before hand I also broke my aptdaemon through an incomplete wine installation (couldn't get passed font installation agreement) but I fixed that via a re-installation then accepting the agreement.)   I am trying to update these by running  but the dependencies it requires cannot be installed due to avr... terminal reports   Reading package lists... Done Building dependency tree        Reading state information... Done build-essential is already the newest version. libncurses5-dev is already the newest version. libncurses5-dev set to manually installed. libusb-0.1-4 is already the newest version. libx11-dev is already the newest version. You might want to run 'apt-get -f install' to correct these: The following packages have unmet dependencies: arduino-core : Depends: gcc-avr but it is not going to be installed avr-libc : Depends: gcc-avr (>= 1:4.3.4) but it is not going to be installed Depends: binutils-avr (>= 2.20) but it is not going to be installed binutils-dev : Depends: binutils (= 2.21.0.20110327-2ubuntu3) but 2.21.0.20110327-2ubuntu2 is to be installed libcwidget-dev : Depends: libcwidget3 (= 0.5.16-3ubuntu2) but it is not going to be installed Depends: libsigc++-2.0-dev but it is not going to be installed Depends: libncursesw5-dev but it is not going to be installed libmpfr-dev : Depends: libgmp3-dev (>= 4.2.dfsg-1) but it is not going to be installed python-dev : Depends: python (= 2.7.1-0ubuntu5.1) but 2.7.1-0ubuntu5 is to be installed Depends: python2.7-dev (>= 2.7.1-1~) but it is not going to be installed tk8.4-dev : Depends: tk8.4 (= 8.4.19-4) but it is not going to be installed E: Unmet dependencies. Try 'apt-get -f install' with no packages (or specify a solution).   But running   apt-get -f install   results in   (Reading database ... 163021 files and directories currently installed.) Unpacking binutils-avr (from .../binutils-avr_2.20.1-1ubuntu2_i386.deb) ... dpkg: error processing /var/cache/apt/archives/binutils-avr_2.20.1-1ubuntu2_i386.deb (--unpack): trying to overwrite '/usr/bin/avr-size', which is also in package avr-binutils 2.13.90.030512-2 dpkg-deb: error: subprocess paste was killed by signal (Broken pipe) Unpacking gcc-avr (from .../gcc-avr_1%3a4.3.5-1_i386.deb) ... dpkg: error processing /var/cache/apt/archives/gcc-avr_1%3a4.3.5-1_i386.deb (--unpack): trying to overwrite '/usr/bin/avr-g++', which is also in package avr-gcc-c++ 3.2.90.20030512-2 dpkg-deb: error: subprocess paste was killed by signal (Broken pipe) Errors were encountered while processing: /var/cache/apt/archives/binutils-avr_2.20.1-1ubuntu2_i386.deb /var/cache/apt/archives/gcc-avr_1%3a4.3.5-1_i386.deb E: Sub-process /usr/bin/dpkg returned an error code (1)   I have tried running update manager and updating my system via it but all I get is an error message  The following packages have unmet dependencies: arduino-core: Depends: gcc-avr but it is not installed avr-libc: Depends: gcc-avr (>= 1:4.3.4) but it is not installed Depends: binutils-avr (>= 2.20) but it is not installed   which then tells me to try running apt-get -f install which just results the same as last time.  So how can I fix my system, I really need the new avr, please :) BTW, my system is Ubuntu 11.04


Give an example to show that integrability is not preserved by composition; that is, give an example   of two bounded real-valued functions f on an interval [a, b] ⊂ R and g on an interval [c, d] ⊂ R   containing f([a, b]) such that $\int_a^bf$ and $\int_c^dg$ exists   $\int _a^bg ◦ f$ does not.   I thought about Riemann function, Dirichlet function and topologist's sine function but none of these works..   Could you please think of any?

Suppose $f,g$ are two Riemann  Integrable functions .Is it true that $f\circ g$ is also Riemann  Integrable?  Trying this for a long time but not getting the answer


What is a good way to respond to a boomerang answer, an answer that basically responds with "You don't want to do that, do this other thing"? Maybe I do want to use my cat as a mop for my kitchen floor (Stack Overflow Podcast). I asked a question, a person answered a bit of it, and then they  summarized it with "You only need to trust the service doing the access". The user put a bit of good work into the answer that I think is useful. But I would like to point out to them that it is not an answer to my question, without losing their work.

A number of times I have asked a certain kind of ‘attractive nuisance’ question – that is, one in which I anticipate a certain kind of answer would be given that I already know I am going to find insufficient or entirely inadequate. Some examples:      A more abstract example would be asking ‘is it possible to do this 100% correctly’, where people itch to come up with hacks, workarounds and half-baked solutions of various degrees of robustness – while the point of the question is obtaining a fully correct and reliable solution.0 I try to be very explicit in the question body about what kinds of answers I am not interested in. And yet, every time I ask such a question, someone gives such an answer anyway, or an outright XY-type, i.e. frame-challenge answer – where in fact the framing of the question is exactly how I want it, and I don’t want it challenged. Since I have already said in the question body that such an answer would be inaqeduate, when I get one, I downvote it. I believe it’s only appropriate, but it tends not to be received very well – I get insulting comments and downvotes in retaliation. I realise that a proper answer would be much harder to come up with than an ‘obvious’ inadequate answer. I suspect that often a real answer should be negative: ‘there is no way to do that’ or ‘there is no way to answer that for sure’. Nevertheless, if that is the right answer, this is the one I want posted – I don’t want the Internet polluted with more tumbleweed of what is already well-known (and may even be subtly wrong), and I don’t want to give ‘A for effort’ upvotes. What is the most appropriate way to act in such a situation?  0 I am also reminded of when Gary Bernhardt  while trying to avoid reflexive ‘don’t use eval’ replies. Of course, expecting nuance from Twitter of all places is silly, but that’s beside the point.