Ok, so I am in the 10th grade, and Physics is my life, and so I always try to enquire things. We were studying the chapter of Work and Energy during our Physics lecture, and when our lecturer described the derivation of formula to calculate the Potential Energy (U) = mgh, something struck me.                                        The derivation goes in this way :- Gravitational Potential Energy, is measured in terms of work done in bringing a body from the ground level to a certain height against the forces of gravity, the work done then gets stored in the form of Potential Energy in the body. Therefore, in our textbook it was given,                             Work = Force x Displacement                                     The least force required to lift the body from the ground will be mg i.e. its mass x acceleration due to gravity(this part is bothering me). Therfore the Force will be mg, while the displacement done by the force will be  the height at which it was raised against the forces of gravity that is h. Therefore :-  Total Work Done in lifting the body = mgh (force x displacement)    Therefore, Potential Energy = mgh.  But isnt it true that the least force required to lift the body should be greater than mg. Since the force of gravity acting on that body too will be mg but in opposite directions and these two forces should cancel each other and the net force will be zero, therefore displacement will be zero and the body will remain in equilibrium. I dont know if this is stupid but can anyone pls answer.

My calculus text (Swokowski, Olnikc, Pence, 6th edition) gives the  formula for work as $W = Fd$ and then goes on to explain that if the force varies over the distance the formula becomes an integral.    As part of an example, it then shows that the work to lift a 500 lb beam 30 feet would be 500 * 30 = 15,000 ft-lb.  But don't we have to exert an upward force greater than the weight of the beam somewhere in our model in order to get the beam to move up?  Then the work would be greater than 15,000 ft-lbs according to the definition of work.  It seems that in setting up integrals or just using the formula  W = Fd examples always use the weight of the increment or object to be  lifted without taking into account the fact that more than that force  must be exerted at some point in order for the thing to move upwards. By the formula W = Fd, if we greatly accelerate an object upwards, the  work done lifting the object will be greater than if a lesser  acceleration is applied across the same distance, but examples in my  book don't seem to take this into account.  (I am assuming that  F = ma, and of course the mass stays constant.)


Show that the vectors $v_1=(1, 1+i, i)$, $v_2=(i, -i, 1-i)$, $v_3=(0, 1-2i,2-i)$ in $\mathbb C^3$ are linearly independent in the field of real numbers but dependent over the field of complex numbers.

I have some basic thing I don't understand.     How can two vectors be dependent in one field and independent in another one?   For example, assume I have the following two vectors: $u = (1-2i, 3+i)$, $v = (2-5i, 7-i)$. Is it possible that they are dependent above $\mathbb{C}$ and independent over $\mathbb{R}$?  What I had in mind is that if two vectors are dependent, that means that there exists a scalar $\alpha$, such that $u = \alpha v$ and if $\alpha \in \mathbb{C}$ then they are dependent only in $\mathbb{C}$. Is that correct?


I initial object db and called its method from my current class:          db = new DBHelper(context);         db.addCallerInfo(FragmentCaller.iName.getText().toString(),                 FragmentCaller.sex.getSelectedItemPosition(),                 FragmentCaller.iAddress.getText().toString(),                 FragmentCaller.iTel.getText().toString(),                 FragmentCaller.callerType.getSelectedItemPosition(),                 FragmentCaller.iSpecify.getText().toString());   In DBhelper class:  public void addCallerInfo(String name,int   sex ,String address,String  tel,int  callerType_id,String  specify) {         ContentValues values = new ContentValues();         values.put("name", name);         values.put("sex", sex);         values.put("address", address);         values.put("tel", tel);         values.put("specify", specify);         values.put("callerType_id", callerType_id);         db.insert(TableHelper.TABLE_callerInfo, null, values);     }   Then it has problem java.lang.NullPointerException:   Attempt to invoke virtual method long android.database.sqlite.SQLiteDatabase.insert(java.lang.String, java.lang.String, android.content.ContentValues) on a null object reference  Help please! Thanks.

What are Null Pointer Exceptions (java.lang.NullPointerException) and what causes them?  What methods/tools can be used to determine the cause so that you stop the exception from causing the program to terminate prematurely?


This question is directed mostly at people who are expert in (beyond) standard model(s) of elementary particles, but input by other physicists or students is very much appreciated. A friend asked me about a  that I wasn't aware of it until now. Let me explain  first. Quarks can decay into leptons and the standard model predicts that bottom (beauty) quarks would decay into muons at the same rate as they do into electrons. But, the experimental results of CERN reveal that the quarks appeared to decay into muon less often than they decayed into electrons (around 85 muon decays for every 100 electron decays). This evidence signals that some before unseen particle or a new force are involved in the decay process! As they claimed, this means the need for a better theory beyond the standard theory will become clearer. If the experimental data are correct (according to , results are really strong since the uncertainty of the result is over three sigma, but not enough yet), what will be the properties of the new particle or (perhaps) the new force? This observation cannot be explained within the current state of physics?

I have came across this recent development in the LHC: Breakthrough at the Large Hadron Collider:  Leptoquarks and leptons - quarks unification:   Leptoquarks (LQs) are hypothetical particles that would interact with quarks and leptons. Leptoquarks are color-triplet bosons that carry both lepton and baryon numbers. Their other quantum numbers, like spin, (fractional) electric charge and weak isospin vary among theories.  Does this mean that we are heading for a strong-EM forces unification? Is the Electron after all coupled to the individual quarks in the nucleus via these new boson? And therefore new unifying force discovered?


let $V$ be the vector space of all sequences of real numbers which are eventually $0$, that is $ V=\{s=(a_1,a_2, . . .) | \exists N$  such that $a_N = a_{N+1} = · · · = 0\}$.  We know the natural linear map $V → V''$ is not an isomorphism, where $V''$ is the double dual of $V$, but I am not sure why. Could someone explain this to me, thanks a lot!

As in the title, my question is: What is the algebraic dual space of $\mathbb{R}^{\mathbb{N}}$ - the space of all $\mathbb{R}$-valued sequences. I think that it should be the direct sum $\bigoplus_{\mathbb{N}} \mathbb{R}$, via the natural duality, but I cannot proof it.


When I track a file in realtime using descriptor i.e tail --follow=descriptor file_name, it doesn't show the changes made in the file, whereas if i track the file in realtime using name i.e tail --follow=name file_name, it shows the changes made to the file. Also everytime i write to the file while tracking the file with tail using --follow=name, tail output shows that the file is removed and then reappears, here's the output tail: file_name: No such file or directory tail: 'file_name' has appeared;  following new file, What is happening? Is the file being rewritten from beginning? Also is the descriptor of the file changing each time the file is written?

I'm using tail -f a.txt to watch updates on a file called a.txt.  If I update the file using something like ls -a >> a.txt in a second virtual console, the changes will display in real-time in the first one.  If I update the file using Vim in a second virtual console, the changes will not display in the first one.  I don't necessarily expect it to trigger an update in that window - but why exactly doesn't this update the terminal running the tail -f command?


I was following along making the Blender Guru Donut® when I found that when I switch to sculpting mode a pattern of holes appear on my icing. I thought it couldnt hurt, maybe it was just for reference or something. But when I was done pulling arround the mesh (and thus some holes) and switched back to layout you could indeed see some artifacts of the holes in the form of spikes, and now my delicious donut is totally ruined. Im guessing this could have to do with some setting being turned on/off? Can anyone give any help?  Edit: Yes thank you Rjg, that does indeed solve it

I tried to follow the new Blender 2.8 tutorial from Blender Guru.   When entering "Sculpting" with the icing there were suddenly alot of holes in it. Why is this?


My old passport in which an ECR was stamped,with passport expiry date in 2017.I got a Dubai visit visa on its passport number but later on as I was told that it'l be a problem for me to travel to Dubai so I got a new passport re-issued with ECNR with a new passport number.  So will it be a problem for me to travel or do I have to get my UAE visit visa details of my old passport number change to my new passport number?

I have a Kuwait visa, obtained from a hotel in Kuwait, with my old passport number. But as the validity of the present passport is expiring within 6 months, I got a new passport with a new passport number. Can I travel with the same visa or do I have to obtain a new visa with my new passport number?


I'm trying to make a really simple game using python.   The game is snake ladder where the player goes from start to finish (0 - 100)  from random import randint from time import sleep  board = ["1" ,"2", "3", "4", "5", "6", "7", "8", "9", "10", "11" ,"12", "13", "14", "15",      "16", "17", "18", "19", "20", "21" ,"22", "23", "24", "25", "26", "27", "28", "29",      "30", "31" ,"32", "33", "34", "35", "36", "37", "38", "39", "40", "41" ,"42", "43",      "44", "45", "46", "47", "48", "49", "50", "51" ,"52", "53", "54", "55", "56", "57",      "58", "59", "60", "61" ,"62", "63", "64", "65", "66", "67", "68", "69", "70", "71",      "72", "73", "74", "75", "76", "77", "78", "79", "80", "81" ,"82", "83", "84", "85",      "86", "87", "88", "89", "90", "91" ,"92", "93", "94", "95", "96", "97", "98", "99",      "100"]  def print_board(board):     print ("   ".join(board[0:10]))    #first row     print ("   ".join(board[10:20]))    #second row     print ("   ".join(board[20:30]))    #third row     print ("   ".join(board[30:40]))    #fourth row     print ("   ".join(board[40:50]))    #fifth row     print ("   ".join(board[50:60]))    #six row     print ("   ".join(board[60:70]))    #seventh row     print ("   ".join(board[70:80]))    #eight row     print ("   ".join(board[80:90]))    #ninth row     print ("   ".join(board[90:100]))    #tenth row   dice = randint(1, 6)   #random number 1 - 6 def roll_dice(dice):       #function to roll the dice     print ("Rolling the dice...")     sleep(1.5)     print ("..."), dice     return   player_score = 0    #starting point / score  def player(player_score):    #for Information     print ("You are now at %d") % player_score  def main():                          #game starts     print ("Let's play a game")     while player_score < 100:        #This is the problem, the while doesn't recognize player_score         print_board(board)         player_choice = input("put R for Rolling or I for Information: ")         player_choice = player_choice.upper()          if player_choice == "R":             roll_dice(dice)             if dice == 1:                 player_score = player_score + 1                 print ("Player moves.. ")                 player(player_score)                  elif dice == 2:                 player_score = player_score + 2                 print ("Player moves.. ")                 player(player_score)             elif dice == 3:                 player_score = player_score + 3                 print ("Player moves.. ")                 player(player_score)             elif dice == 4:                 player_score = player_score + 4                 print ("Player moves.. ")                 player(player_score)             elif dice == 5:                 player_score = player_score + 5                 print ("Player moves.. ")                 player(player_score)             elif dice == 6:                 player_score = player_score + 6                 print ("Player moves.. ")                 player(player_score)         elif player_choice == "I":             player(player_score)     else:         print ("Congratulations, you won the game!")   But the problem is, the loop doesn't even start. it says:     "local variable 'player_score' referenced before assignment".   Also: How can i continue the game to the player_choice again with the player_score already added?

The following code works as expected in both Python 2.5 and 3.0:  a, b, c = (1, 2, 3)  print(a, b, c)  def test():     print(a)     print(b)     print(c)    # (A)     #c+=1       # (B) test()   However, when I uncomment line (B), I get an UnboundLocalError: 'c' not assigned at line (A). The values of a and b are printed correctly. This has me completely baffled for two reasons:   Why is there a runtime error thrown at line (A) because of a later statement on line (B)? Why are variables a and b printed as expected, while c raises an error?   The only explanation I can come up with is that a local variable c is created by the assignment c+=1, which takes precedent over the "global" variable c even before the local variable is created. Of course, it doesn't make sense for a variable to "steal" scope before it exists.  Could someone please explain this behavior?


Let $A$ and $B$ be two observers and suppose they meet when both their clock are  zero.  Suppose that  $B$ moves with constant  velocity $v$ in relation to $A$  then we have  $$t=\frac{1}{\sqrt{1-\frac{v^2}{c^2}}}  t'$$  where $t$ is the time for observer $A$ and $t'$ the time for observer $B$.For simplicity  suppose that $\gamma=\frac{1}{\sqrt{1-\frac{v^2}{c^2}}}=0.5$ then when the clock of $B$ is $t'=1$ the clock of $A$ is $t=2$.   From the point of view the observer is moving with velocity $-v$ and so by symmetry  $$ t'=\frac{1}{\sqrt{1-\frac{v^2}{c^2}}} t$$  So when the clock of observer $A$ is $t=2$ the clock of $B$ is $t'=4$   That is if the clock of $A$ run faster than $B$, the clock of $B$ run faster than the clock of $B$ by symmetry.  Isn't this a contradiction ?

Suppose we have two twins travelling away from each other, each twin moving at some speed $v$:    Twin $A$ observes twin $B$’s time to be dilated so his clock runs faster than twin $B$’s clock. But twin $B$ observes twin $A$’s time to be dilated so his clock runs faster than twin $A$’s clock. Each twin thinks their clock is running faster. How can this be? Isn’t this a paradox?


How to show that $\gcd(a + b, a^2 + b^2) = 1\mbox{ or } 2$ for coprime $a$ and $b$?  I know the fact that $\gcd(a,b)=1$ implies $\gcd(a,b^2)=1$ and $\gcd(a^2,b)=1$, but how do I apply this to that?

If $\gcd(a,b)=1$, how can I find the values that $\gcd(a+b,a^2+b^2)$ can possibly take? I can't find a way to use any of the elemental divisibility and gcd theorems to find them.


I was examining my battery usage and noticed this:  I don't know what this "-5" app is supposed to be. Could it be malicious or is it just a bug? I own an OnePlus 6 with Android 10 (OxygenOS 10.3.5).

There is a mysterious app, 99070 that is consuming power on my Nexus 5X. Any idea how I determine what it is?  There is no option to stop or uninstall it. My phone is a Nexus 5X running stock Android 6.0.


I have two questions regarding hosting livecam broadcasting websites:   What is your advice for where to host sites like this? What are the hosting requirements?   I need to build a "clone" of chaturbate or cam4 for a client. I know these are not 100% legal websites. Therefore, I need an advice to warn them about hosting issues.  1. WHERE ?  What are the most secure and popular hosting providers, which TOS will allow hosting websites on their servers.  2. HOW ?  What are the requirements. I have never built a site like this. And as this is broadcasting live cam website - I suppose it has some requirements as RAM, Banwidth or maybe VPS... Can you tell me which one? Or maybe to give me some hosting package that will be enough for running this.

This is a "catch-all" question designed to serve as an answer for all questions about choosing web hosting.  Pro Webmasters no longer accepts new questions about how to choose hosting.  All future questions pertaining to finding web hosting should be closed as a duplicate of this question. For more information about this policy please see .    How to find web hosting that meets my requirements?  What we're looking for in answers to this question are the basics about web hosting:   What is web hosting? What is the difference between shared, VPS, and dedicated hosting? How does a content delivery network relate to web hosting? Anything else you feel is helpful in finding a web host.   What we do not want is:   Endorsements or recommendations for specific web hosts We do not want your experience or other subjective information (just the facts please)


$G$ is a group with $e$ as it's identity element. The commutator group $[G,G] = <[x,y]|x,y \in G>$ such that $[x,y]=x^{-1}y^{-1}xy \: \: \: \forall x,y \in G$  Show that $[G,G]\triangleleft G$  Solution: If $[G,G]\triangleleft G$, then $g^{-1}[x,y]g$ must belong to [G,G].  $$g^{-1}[x,y]g$$ $$g^{-1}x^{-1}y^{-1}xyg$$  I am stuck here. I am not sure how to proceed since we have three elements...  Thanks for the help!

It is suggested as an exercise in Serge Lang's book "Algebra" to show that the commutator subgroup $G^c$ of a group $G$ is a normal subgroup.   I'd like to do that but I am afraid I need help,   I think the first thing I need to figure out is how a general element in the commutator subgroup looks like, so that I can check that the defining condition for normality is satisfied.  That is, supposing for a moment that a general element in $G^c$ is denoted by $g$, I need to show that $aga^{-1} \in G^c,$ for all $a \in G$.  But here I get stuck, first because I am unsure how to write a general element in $G^c$ - a simple product in $G^c$ is of the form $xyx^{-1}y^{-1}aba^{-1}b^{-1}$ where $a,b \in G$. I cannot see a way to simplify this - I am sure there is one, but somehow I am blind today.  The second thing then is, even if one tries out the conjugation of a simple element like $xyx^{-1}y^{-1}$ in $G^c$, again not simplification offers itself easily I think .. what am I missing ?  An alternative would be to find a homomorphism of $G$ whose kernel is precisely $G^c$ - here I tried to think of this as a map $G \times G \to G$ but whatever I cook up is not a homomorphism.  Thanks for your hints !!


I'm using Overleaf with the tufte-book class to create lecture notes for an aviation course.  When departing from Dallas-Fort Worth International Airport, one of the possible departure procedures is the HRPER3 procedure, properly displayed just as you see it here.  In the body text of the book, however, the numerals become subscripted.  Also notice that this happens whether or not I use \textsc{} but it does not happen in the sidenotes. This seems to be because I have sfsidenotes activated in the preamble.  However, I don't really want my body text in sans serif.  Is there a way to prevent this automatic subscripting in the body text of a tufte-book?    Minimal working example:  \documentclass[sfsidenotes,oneside,justified,marginals=raggedright]{tufte-book}  \begin{document} \mainmatter \chapter{Enroute} \section{Preferred and Coded Departure Routes} \subsection{Coded Departure Routes}  CDRs are relatively new\sidenote{They've only been around since 2007} and they're not perfect yet.  Here's an example.  Suppose you plan to depart from KDFW on your way to KMKE, and suppose that the preferred routing uses the \textsc{HRPER3} departure,\sidenote{I have no idea if HRPER3 really is the preferred route} but there's storms directly along your route.  As you're doing your preflight planning, you realize those storms might interfere with your proposed departure, so you review the coded departure routes as well.  You discover that the DFWMKE1E CDR would provide adequate separation from all severe weather and file that CDR as an alternate in your flight plan.  \end{document}

I am using tufte-latex package, which uses mathpazo with old style numerals. To make figures (plots) I would like to use lining numbers.  The problem is that the figures are converted from svg to pdf using inkscape and the numbers are not in mathmode (In math mode the numbers are lining numerals by default).  I think of two possible solutions:  a) Is there any command similar to \oldstylenums that does the opposite work?  b) inkscape put the text of the figure in \smash{-22.22} commands. Is any way,  using sed, awk, perl,... to change that to \smash{$-22.22}?


How do I book flights Boston area to St. Thomas to Seattle to Boston area?  Which site allows me to put in this A to B to C to A itinerary for cost and convenience comparisons?

Several airline and trip planning sites will allow you to check "I am flexible with my dates" or a similar option.  Is there any way to also search more broadly for location?  For example, if you wanted to leave from YYZ or YKF and arrive at any airport in California, can a search for such flights be done somehow?  I ask because when I plan plane trips, I want the lowest price.  I'm OK with leaving a day or two later if I save $200 (same with the return trip).  There are 3 airports within 80 km of me, I'll leave from the one with the cheapest flight. And I'm also OK with changing the trip to spend time exploring San Francisco instead of lying on the beach near San Diego, and that sort of thing.  Normally this would take dozens of searches, but I'd like to see it all at once.


I am running Debian 9 but this is a more universal Linux question.  I have an Intel NUC (i5-4250U) with integrated graphics. When I run memory-intensive tasks in the background my system lags graphically. I am using the built-in i915 driver. I have 16GiB of memory and at no time am I swapping to disk.  I would like to have this process pause when I am using my computer. The best way I can think of determining if my computer is in use is to query the status of the screen blanking mechanism.  The tasks I am running in the background deal with being paused (manually) with no ill effects. They take days to run so when I forget to unpause them I lose a lot of potential work.  Ideas?  Thanks!  Edit #1: I was running Wayland, but I switched back to X so I can use the "" command, which returns the number of milliseconds since the user last did something.  , I modified the bash script to pause/unpause a particular PID. It would be neat to specify part of a process name but I can work with the PID okay.  There is most certainly a better way to do it, but this works for now.  #!/bin/bash pid=11677 idle=false idleAfter=10000 while true; do   idleTimeMillis=$(xprintidle)   if [[ $idleTimeMillis -gt $idleAfter && $idle = false  ]] ; then     kill -CONT $pid     idle=true   fi   if [[ $idleTimeMillis -lt $idleAfter && $idle = true ]] ; then     kill -TSTP $pid     idle=false   fi   sleep 1 done

I want to run a command when the user becomes inactive (the system is idle). For example:  echo "You started to be inactive."   Also, when the user becomes active again (the system is not idle anymore):  echo "You started to be active, again."   I need a shell script that will do this. Is this possible without a timer/interval? Maybe some system events?


I have a couple of games that need AIR and I thought I might take a look to see if there was a Linux version out there. There is, so I grabbed that off Adobe and tried to install it.   The first problem was that it wanted libgnome-keyring. I installed that from a old rpm and symlinked it with the specific library that it wanted. The next problem is that even though ar and dpkg-deb are installed and can be used, it still failed with the installation.  I have no clue whatsoever to do from here so I'm wondering, is it possible to install Adobe Air 2.6 on a modern Linux system?

I am a heavy user of certain applications that are built on AIR.   It appears that AIR has discontinued support for Linux. Even the older versions in the Adobe AIR Archives seem to support only 32 bit Linux distributions and I am on 64 bit currently.  Is there even a slight possibility that I could run AIR in these conditions? If so, can you please tell me where can I get a detailed step by step installation for this?


Does there exist an example of a topological space $X$ which can be drawn, whose fundamental group is $S_3$? I know that every group is the fundamental group of a topological space, but I need a concrete example.

There exists an example of a topological space $X$ who can be $drawn$, whose fundamental group is $S_3$? I know that every group is the fundamental group of a topological space, but I need a concrete example.


This question is ported directly from Physics SE, because the guys there believe this is the right place for it.  In digital photography, there's the principle of lens equivalency, according to which, when you shoot with a camera which has a smaller sensor than a full frame sensor (which is the same dimension as classic photography film), you effectively reduce your field of view (relative to shooting with the same optics and a full frame sensor). The resulting crop of the optical image is associated with saying that you are shooting a full frame sensor, but a lens with a greater focal length.  So in terms of the resulting image, one should think of the lens as having a focal length of ff (the real focal length) times the crop factor CC associated with the sensor being used (C≥1). this is all well and good intuitively but then comes the 'weird' part.  It is said that if you're to think of your lens to have a focal length fC, then you must also think of the camera's f-number as being multiplied by C as well. This means that if you increase your f-number (which is proportional to the numerical aperture), then you also increase the depth of field of the camera - and surely enough, for a smaller sensor, you yield a greater depth of field (for the same field of view) - even when your actual physical f-number is the same in both cases.  How can two optical systems with the same f-number\NA, have different depths of field?  I realize that some of you might say it's related to the pixel size of the cameras, but it goes the other way around: the system with smaller pixels (which means less tolerance for the spread of the PSF) has the greater depth of field. This is best demonstrated in modern days smartphones, where for the same f-number as full frame cameras, the depths of field are worlds apart.  What is the physical explanation for this phenomenon? My best guess is that for systems with smaller sensors, one must position the camera further away from the object to capture the same field of view, such that the light rays travel a greater distance and thus become more parallel before being collected by the optics, but I'd like to know for sure.

If APS-C and similar crop-sensor digital cameras have a focal length multiplying effect such that a 50mm lens has an apparent focal length closer to the field of view of an 80mm on a full frame camera, and yet at the same time the depth of field for the smaller sensor camera is more like the depth of field a 50mm lens would produce on a full frame camera (using the same aperture), then this would seem to suggest the concept of an "aperture dividing effect."  In other words, a 50mm f/1.8 lens on an APS-C camera would act more like a 80mm f/2.8 (approx. 1.8 * 1.6x) lens in 35mm equivalent — for depth of field, not considering exposure.  Can someone with a better understanding of the physics involved clarify this for me.  I've never seen this concept explicitly mentioned anywhere, so I am a bit suspect of it.


I am trying to join 2 tables and select the latest timestamp only and the field values associated with that latest timestamp  Data tables:  device_count  id  device_name     platform    version     timestamp 1   abc             123         x           2013-12-30 2   abc             123         y           2014-01-01 3   def             345         x           2013-12-30   device_list  id      device_name     Network     Division    Market 2657    def             a           f           d 2656    abc             a           b           c   The desired result should be   device_name     platform    version     network     division    market  timestamp abc             123         y           a           b           c       2014-01-01 def             345         x           a           f           d       2013-12-30   I have used the following query but I'm not getting the correct results  SELECT device_count.device_name, device_count.platform, device_count.version, Max(device_count.`timestamp`), device_list.Network, device_list.Division, device_list.Market FROM device_count INNER JOIN device_list ON device_count.device_name = device_list.Device_Name GROUP BY device_count.device_name, device_count.platform, device_count.version, device_list.Network, device_list.Division, device_list.Market   It results in   device_name     platform    version     network     division    market  timestamp abc             123         x           a           b           c       2013-12-30 abc             123         y           a           b           c       2014-01-01 def             345         x           a           f           d       2013-12-30   The first record should not be included. I only want the version and platform values from the latest timestamp (record id 2)

Table:   UserId, Value, Date.   I want to get the UserId, Value for the max(Date) for each UserId. That is, the Value for each UserId that has the latest date. Is there a way to do this simply in SQL? (Preferably Oracle)  Update: Apologies for any ambiguity: I need to get ALL the UserIds. But for each UserId, only that row where that user has the latest date.


I understand that:  $True \implies True$, is true.  $True \implies False$, is False.  But why is it that  $False \implies True$, is True.  and  $False \implies False$, is True.  If $a$ is false I don't understand how we can say $a \implies b$ is true.

I am studying entailment in classical first-order logic.  The Truth Table we have been presented with for the statement $(p \Rightarrow q)\;$ (a.k.a. '$p$ implies $q$') is: $$\begin{array}{|c|c|c|} \hline p&q&p\Rightarrow q\\ \hline T&T&T\\ T&F&F\\ F&T&T\\ F&F&T\\\hline \end{array}$$  I 'get' lines 1, 2, and 3, but I do not understand line 4.      Why is the statement $(p \Rightarrow q)$ True if both p and q are False?  We have also been told that $(p \Rightarrow q)$ is logically equivalent to $(~p || q)$ (that is $\lnot p \lor q$).  Stemming from my lack of understanding of line 4 of the Truth Table, I do not understand why this equivalence is accurate.       Administrative note. You may experience being directed here even though your question was actually about line 3 of the truth table instead. In that case, see the companion question  And even if your original worry was about line 4, it might be useful to skim the other question anyway; many of the answers to either question attempt to explain both lines.


Question:     If $x = \sin 1^\circ$, find the value of the expression:    $$\frac{1}{\cos0^\circ \cos1^\circ} + \frac{1}{\cos1^\circ\cos2^\circ} + ... + \frac{1}{\cos44^\circ\cos45^\circ}$$   in terms of $x$   I really can't see how I would simplify this expression in terms of $x$. Any hint would be appreciated.

Find the sum of the following :   (i) $$\frac{1}{\cos0^\circ \cos1^\circ}+\frac{1}{\cos1^\circ\cos2^\circ} +\frac{1}{\cos2^\circ \cos3^\circ}+......+\frac{1}{\cos88^\circ \cos89^\circ}$$  I tried :  $$\frac{1}{\cos1^\circ}\left[\frac{\cos(1^\circ-0^\circ)}{\cos0^\circ\cos1^\circ} + \frac{\cos(2^\circ-1^\circ)}{\cos1^\circ\cos2^\circ}+...\right]$$  = $$\frac{1}{\cos1^\circ}\left[\frac{\cos1^\circ\cos0^\circ}{\cos0^\circ\cos1^\circ} - \frac{\sin1^\circ \sin0^\circ}{\sin0^\circ\cos1^\circ} + \frac{\cos2^\circ \cos1^\circ}{\cos1^\circ\cos2^\circ} -\frac{\sin2^\circ \sin1^\circ}{\cos1^\circ\cos2^\circ}...\right]$$  For this, as well, I am not getting any pattern to solve further. Please suggest, thanks.


The recent epidemic has made people change a few habits. We no longer shake hands and a few of us touch each other  elbows as an alternative practice.   Has this kind of salutation a proper name?

This is probably answerable with a general reference (or a pair of such references), but I have not been able to find one.   Etymology Online does not cover the origin of "rubbing-elbows" as meaning to socialize or mingle in a crowd in either the section covering  or . Other top search hits just cover the meaning of the phrase in discussions of synonyms for socializing (hob-nob etc.), without going into the history and origins.  There is also the "elbow-handshake" (or less formally the "elbow-bump"), where literally rubbing elbows or forearms substitutes for a handshake greeting.  traces this to a leprosy outbreak circa 1970 (in Hawaii, among peoples whose primary language may or may not have been English), but is very light on references. I first recall hearing of this handshake from watching a documentary about one of the , where it was presented as a de-facto greeting replacement that crossed cultures, creeds and nations.  My questions are what is the origin and time period of the phrase "rubbing elbows"? And does the practice of greeting with elbows or arms instead of hand have a more definite origin? And if so, is there any evidence that it was adopted with any conscious awareness of a literal acting out of a the common idiom "rubbing elbows"?


I'm not an ubuntu expert but when trying to install skype though terminal I receive this error message:  stardust@stardust:~$ sudo apt-get install skype [sudo] password for stardust:  Reading package lists... Done Building dependency tree        Reading state information... Done E: Unable to locate package skype   How can I fix this problem and finally install skype on my laptop?  Thank you for your help!

I want to install Skype, but I can't locate it in Software Center or by using Synaptic Package Manager. Can anyone help me?


I'm trying to confirm the method by which the body physically loses weight during "long-term" weight loss.  I'm specifying "long-term" here because obviously there are lots of ways to temporarily lose weight.  Loss of water (jogging in the sun while wearing garbage bags to promote sweating?) can potentially lead to quick weight loss, but presumably the body just reclaims that water later.  I'm referring to scenarios where a person, for instance, loses 100 pounds over a course of months via lifestyle changes like exercise and dieting.  When this happens, how does the human body physically remove the weight?  It's long been my understanding that the answer is, effectively, "by breathing it out" (you breath in O2 and breath out CO2, with CO2 weighing more).  This fact has always amused me (it's hard to imagine someone losing 100 pounds one breath at a time).  I mentioned this "fact" to my wife recently and she looked at me very incredulously.  I then realized two things: I had come to this conclusion myself but never actually verified it, and I wasn't sure how to explain the details enough to convince my very dubious wife.  I'm especially curious how much weight is actually lost (on average) per breath, and if there might be other physical processes which contribute to long-term weight loss.  Obviously I'd be especially interested to find out that my expectation is completely wrong!

When your body burns calories and you lose weight, obviously mass is leaving your body.  In what form does it leave?  In other words, what is the physical process by which the body loses weight when it burns its fuel?    Somebody said it leaves the body in the form of heat but I knew this is wrong, since heat is simply the internal kinetic energy of a lump of matter and doesn't have anything do with mass.  Obviously the chemical reactions going on in the body cause it to produce heat, but this alone won't reduce its mass.


please dont send link please give me programming example where Inner class going to use and why we should use inner class

What is the main difference between an inner class and a static nested class in Java? Does design / implementation play a role in choosing one of these?


Assuming you're not doing some early cheese build, I'd think this would be something you could just do some math on to figure out which is better. Has this problem been solved? Which is better, and what is the math behind it?

What is the advantage on saving the money for the overlord when you have 9 drones, and not filling your supply first and then getting the overlord?  In my theory, in the first case you get to wait the saving time with 9 drones, and get to wait almost the same time with 10 drones in the second case. Second case should be better, since 10 drones mine faster than 9? So why does everybody go with the first case?  All this is assuming you go 12 pool or something like that, where you will get more drones after the overlord. 6- and 8-pools are obviously different.


Here's the fragment class code which has a logout button.  import android.app.Fragment; import android.content.Intent; import android.os.Bundle; import android.view.LayoutInflater; import android.view.View; import android.view.ViewGroup; import android.widget.Button;  import com.marshall.gruppo.R; import com.marshall.gruppo.helper.SQLiteHandler; import com.marshall.gruppo.helper.SessionManager;  public class MyPageFragment extends Fragment implements View.OnClickListener {      Button logout;     View view;     SessionManager session;     SQLiteHandler db;      public MyPageFragment(){}      @Override     public View onCreateView(LayoutInflater inflater, ViewGroup container,                              Bundle savedInstanceState) {         View rootView = inflater.inflate(R.layout.fragment_mypage, container, false);         logout = (Button) view.findViewById(R.id.logout);         logout.setOnClickListener(this);         return rootView;     }      @Override     public void onClick(View v) {         switch(v.getId()) {             case R.id.logout:                 logoutUser();                 break;         }     }     private void logoutUser() {         session.setLogin(false);         db.deleteUsers();         Intent intent = new Intent(getActivity().getApplicationContext(), LoginActivity.class);         startActivity(intent);         getActivity().finish();     } }   But when I run the code, it throws a NullPointerException with the following log.  07-10 13:03:25.521  13363-13363/com.marshall.gruppo E/AndroidRuntime﹕ FATAL EXCEPTION: main     Process: com.marshall.gruppo, PID: 13363     java.lang.NullPointerException             at com.marshall.gruppo.ui.MyPageFragment.onCreateView(MyPageFragment.java:28)             at android.app.Fragment.performCreateView(Fragment.java:1700)             at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:890)             at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1062)             at android.app.BackStackRecord.run(BackStackRecord.java:684)             at android.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1453)             at android.app.FragmentManagerImpl$1.run(FragmentManager.java:443)             at android.os.Handler.handleCallback(Handler.java:733)             at android.os.Handler.dispatchMessage(Handler.java:95)             at android.os.Looper.loop(Looper.java:146)             at android.app.ActivityThread.main(ActivityThread.java:5602)             at java.lang.reflect.Method.invokeNative(Native Method)             at java.lang.reflect.Method.invoke(Method.java:515)             at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1283)             at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1099)             at dalvik.system.NativeStart.main(Native Method)   When writing the code it did not show any errors, so I really wonder where it has a fault.. According to the log, it is this part that throws the exception.  logout = (Button) view.findViewById(R.id.logout);   Any advice on this issue?

What are Null Pointer Exceptions (java.lang.NullPointerException) and what causes them?  What methods/tools can be used to determine the cause so that you stop the exception from causing the program to terminate prematurely?


I'm living in the UK and I'm about to move flat. In the five years in my current flat I've accumulated around 20kg of mixed coins - from £0.05 to €2 at a glance. Are there any easy ways to exchange this with a bank or other institution/individual for some reasonable approximation of its worth?

So I have about $50 in pennies, dimes and nickels.  What would you do with it?  I'm asking because I don't think spending hours rolling up the change and taking it to the bank is the best/most creative thing.  More info:  I took the change to the bank (not rolled up).  The banker asked me if I knew the exact amount... when all I had was a huge bag of change weighing like 30-40 pounds :-p  I said I didn't know the exact amount.  So the banker put all the change into a different bag, gave me a little receipt and said look for a deposit to your account in about a week.  Next time I'll just find a coinstar machine. I don't like waiting a week to have my change counted.  Also I'm sure the banker could fish out the quarters and no one would be the wiser :-)


I am new to ubuntu server. I want some GUI features in ubuntu server.Is it possible to  install GUI on ubuntu server.If yes then please help me.

Trying to run a Ubuntu server for the first time... But everything is in a terminal. Is there a way to switch to a GUI?


when recovery email address is not provided in g mail account then how can I answer to Google for my disabled account?

I have forgotten the password or username for my Google account, or I'm unable to access my account for other reasons.  How can I recover my account?  (This Q&A is meant as a general description for all Google and Gmail username/password questions. See: )


I was cleaning up my computer to essentially start fresh, and at one point I was on OneDrive to clean that up as well. But when I went to load up a certain image to admire, that's when I realized it - I've just accidentally removed all my files on OneDrive, and Emptied the Recycle Bin after that! And I can't even recover them no matter what I've tried.  I've tried file recovery programs, only to be hit by surprise price tags, and I even tried restoring my OneDrive to yesterday's state, but it literally did nothing at all.  I've could've easily lost all my hard work, all because I didn't realize that OneDrive files on my PC would go with those on the actual OneDrive on the website itself.  I need to know how to restore these files again, in any way possible.  By the way, I've tried both sources, in File Explorer, and OneDrive on a browser itself. I have not used the OD app yet.

What steps can I take to try to recover lost or inaccessible data from any storage device?  Answers:   This applies to any computer storage device, e.g. internal/external hard drives, USB sticks, flash memory. The most important thing is to STOP using it, any type of I/O can ruin your chances of a recovery.     We have separate questions covering common problems with USB flash drives in greater detail:


I have a web page that displays content after fetching it from database. The table has values as expected, but when it fetches and displays it is showing something like below:  advertiser���ˌ_s  The correct value in the table is:  advertiser's    I have done the following settings in my php file:  <meta http-equiv="Content-type" value="text/html; charset=UTF-8" />   The database file looks like:  $mysqli->set_charset('utf8mb4');   Can someone please tell what is going wrong.

I'm setting up a new server and want to support UTF-8 fully in my web application. I have tried this in the past on existing servers and always seem to end up having to fall back to ISO-8859-1.  Where exactly do I need to set the encoding/charsets? I'm aware that I need to configure Apache, MySQL, and PHP to do this — is there some standard checklist I can follow, or perhaps troubleshoot where the mismatches occur?  This is for a new Linux server, running MySQL 5, PHP, 5 and Apache 2.


Ok so I was playing with GeoGebra by plotting various functions, then I come up with the following kind of graph when I plot $\log(x)$ to various positive powers and $f(x)=x$.   The green one is the function $f(x)=x$ and the blue one is $g(x)=(\log(x))^4$.  So it seems for sufficiently large $x$, any positive power of $\log(x)$ is less than $x$. But I am unable to prove this fact. Can anyone give me a hint as how to approach to this problem?

How can I prove that $\log^k(n) = O(n^\epsilon)$? (for any $\epsilon > 0 $ and for any integer and positive $k$).  I tried to do it by - definition , and to prove that exists $c,n_0 > 0$ so that for any $n > n_0 $ exists: $c \cdot n^\epsilon > \log^k(n) $, but I don't have idea how to continue for this point.    I will be happy to listen ideas :).


In his algebraic geometry notes, Vakil suggests the exercise (remark 3.6.3) of showing that a ring $A$ is a product $A = A_1 \times A_2$ iff $\operatorname{Spec} A$ is disconnected.  His hint is to show that both conditions are equivalent to the existence of two elements $a_1, a_2 \in A$ s.t. $a_1^2 = a_1$, $a_2^2 = a_2$ and $(a_1 + a_2) = 1$, and hence $a_1a_2 = 1$.  2 questions: 1) Does it really follow that $a_1a_2 = 0$ from the other assumptions on $a_1$ and $a_2$ I tried deducing it but the most that I succeeded in showing was:  $$1=(a_1+a_2)^2 = a_1^2 + a_2^2 + 2a_1a_2 = a_1 + a_2 +2a_1a_2$$ $$0=2(a_1a_2)$$  However, I fail to see why this implies that $a_1a_2 = 0$, since he didn't mention any assumption of $2$ being regular.  2) How does one get that $\operatorname{Spec} A$ disconnected implies the existence of such $a_1,a_2$?  I reasoned the following:  taking $U = V(a_1), W = V(a_2)$ to be clopen sets such that $U\cap W = \varnothing$ and $U\cup W = \operatorname{Spec} A$ we get: $$\cup_{i\in I} D(f_i) = V(a_2)$$ $$\cup_{j\in J} D(f_j) = V(a_1)$$  where the left hand side is the expression of an open set as a union of basis elements and the right hand side is the definition of a closed set. From the fact that $V(a_1) \cup V(a_2) = V(a_1a_2) = \operatorname{Spec} A$ we get that $a_1a_2$ is nilpotent, but I can't seem to get anything else.

I'm solving a problem from Atiyah-Macdonald.      I have to show that if $X=\mathop{\mathrm{Spec}}A$ is not connected then $A$ contains idempotents $e \neq 0,1$.    The converse is easy. If $e \in A$ is an idempotent then $(e)+(1-e)=(1)$ and $(e)\cdot(1-e)=0$ so that $$   V(e) \cup V(1-e) = V(  (e) \cdot(1-e))=V(0) = X, \\   V(e) \cap V(1-e) = V( (e)+(1-e))=V(1)=\varnothing $$ then $V(e)$ and $V(1-e)$ are both closed and open and $X$ is not connected.   Now let $\mathfrak{a}$ and $\mathfrak{b}$ be ideals in $A$ such that $V(\mathfrak{a}) \cup V(\mathfrak{b})=X$, $V(\mathfrak{a}) \cap V(\mathfrak{b}) = \varnothing$. Then $$    V(\mathfrak{a}) \cup V(\mathfrak{b}) = V( \mathfrak{a} \cap \mathfrak{b} ) = X, $$ i.e. $\left\{ \mathfrak{p} - \text{prime} \mid \mathfrak{a} \cap \mathfrak{b} \subseteq \mathfrak{p}  \right\} = X$, i.e. $\mathfrak{a} \cap \mathfrak{b} \subseteq \cap \mathfrak{p} = \mathfrak{n}$ (nilradical). On the other hand since $$   V(\mathfrak{a}) \cap V(\mathfrak{b}) = V(\mathfrak{a}+\mathfrak{b})=\varnothing $$ we have $\left\{ \mathfrak{p} - \text{prime} \mid \mathfrak{a}+\mathfrak{b} \subseteq \mathfrak{p} \right\} = \varnothing$. Then $\mathfrak{a}+\mathfrak{b}=(1)$ because any ideal that is not equal to $(1)$ is contained in some maximal ideal. Then $\mathfrak{a}$ and $\mathfrak{b}$ are comprime and $\mathfrak{a} \cdot \mathfrak{b} = \mathfrak{a} \cap \mathfrak{b}$. So I have two ideals $\mathfrak{a}$ and $\mathfrak{b}$ with properties $$    \mathfrak{a} + \mathfrak{b} = (1), \\    \mathfrak{a} \cdot \mathfrak{b} = \mathfrak{a} \cap \mathfrak{b} = \mathfrak{n}. $$ I don't see any way to obtain a nontrivial idempotent $e \in A$ here. Please help me.


for(creature a : horde.creatures){   always throws a nullpointer, even though I defined it before:  private swarm horde;   This is the swarm class:  public class swarm { public creature creatures[] = new creature[100]; }   which is just an array of creatures:  public class creature { Random r = new Random(); public boolean hostile = r.nextBoolean(); public double[] velocity = new double[2]; public double[] position = new double[2];   The whole window class:  package de.towdo.intellia;  import java.awt.*; import javax.swing.*;  final public class window {  JFrame frame; DrawPanel drawPanel;  private swarm horde;  public static void main(String[] args){     new window().go(); }  private void go(){     frame = new JFrame("Window");     frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);      drawPanel = new DrawPanel();      frame.getContentPane().add(BorderLayout.CENTER, drawPanel);      frame.setVisible(true);     frame.setResizable(false);     frame.setSize(500, 500);     frame.setLocation(340, 55);     moveIt();  }  class DrawPanel extends JPanel{      public void paintComponent(Graphics g){         for(creature a : horde.creatures){             if(a.hostile){                 g.setColor(Color.RED);             }             else{                 g.setColor(Color.GREEN);             }             g.fillRect((int)a.position[0], (int)a.position[1], 1, 1);         }     } }  private void moveIt(){     while(true){         try {             Thread.sleep(10);         }         catch(Exception exc){             exc.printStackTrace();         }         frame.repaint();     } } }


I'm running Ubuntu 17.10 in VirtualBox and the keyboard shortcut for switching to a new workspace doesn't work. Please show me a screenshot that shows how to switch workspaces from the desktop environment in Ubuntu 17.10 without pressing the keyboard shortcut.

A system like the workspaces in Unity7 had an icon on the dock or something similar that give you the possibility of cycle through virtual desktops with mouse buttons or wheel.     For who is not familiar with Unity7 workspaces and virtual desktops,  to understand.  How can I do the same on GNOME Shell (17.10+)?


I am currently using ubuntu on my laptop......Now I  want to dual boot windows alongside ubuntu....I want to ask will I be loosing data that is currently present in ubuntu if I dual boot windows

I am already using Windows 7. I want to install Ubuntu 13.04 along side Windows 7 in a partition that I already made in one of my hard drive but I am worried about losing the data on my drive. Is there any possibility of data loss?


I have h1 tag in a page. I do not want to display it to user but want to make sure that its content will be used for SEO. What is recommended way of achieving it these days. I can think of:   in css: position absolute; left: -99999em; display: none; visibility: hidden; (even though it still exists in flow of document) remove h1 with javascript when page loads   As far as I know 1,2,3 will be easily detected by Google and penalised accordingly, is that right? Would 4 be the only option not resulting in being penalised? What other options are available and safe to use?  BTW I'm not trying to trick user or search engines in any way, it just happens that h1 is in a way and need to get rid of it.

So apparently hiding content using "display: none" is bad for SEO and seen by googlebot as being deceptive. This according to a lot of the posts I read online and questions even on this site.  But what if I hide keyword rich text using javascript? A jquery example:  $(function() {    $('#keywordRichTextContainer').hide(); });   or using visibility hidden:  $(function() {    $('#keywordRichTextContainer').css({       visibility: 'hidden',       position: 'absolute'    }); });   Would any of these techniques cause my site to be penalized? If googlebot can't read javascript then if I'm hiding through js it shouldn't know right?  What about using "text-indent: -9999px"?


It has always been a personal pet peeve of mine when Native Americans are referred to as "Indians." It has nothing to do with respect for Native Americans or political correctness; it is entirely about actual correctness. Calling them Indians means having to actually differentiate between Indians, from the subcontinent of India, and Indians, from the Americas. It seems like laziness is the biggest factor. It is far easier to say and write/type "Indian" than "Native American." But, my History teacher and even my textbook both use the word "Indian." Is this really acceptable practice in higher education (it's my freshman year)? Is it accepted in academia in general?

No more than four syllables, more PC than Indians.  EDIT: I arbitrarily chose four syllables because any more seemed like a mouthful. I like to be PC and not have to stumble over 6+ syllables.


I am trying to find the distribution of the maximum of a set of four continuous independent random variables that have a general distribution.  I have found resources that discuss how to find such a distribution when the probability density function is known, but I am curious to know the generalized solution.

If an item follows normal distribution, average also follows normal distribution. What about minimum and maximum?


It also is built by myself. It is blank. I have tried from a usb and cd, nothing seems to work.  I have downloaded ubuntu live for my computer onto a blank cd.

I want to burn Ubuntu Minimal CD ISO to an old, 1 GB USB thumbdrive. Regular ISO doesn't fit. I already tried Startup Disk Creator and Unetbootin but both failed. I tried installing GRUB and pointing it to boot like this:  insmod part_msdos linux /linux initrd /initrd.gz   but it doesn't work. I also tried dd but I ended up with not bootable drive.  Rufus worked on Windows with the same thumbdrive but I no longer use Windows.  What else can I do?


An example of it in use would be...  if (temp < 30 || temp > 90) { MessageBox.Show("Error"); }   What do two pipes (||) together mean?

I have always used || (two pipes) in OR expressions, both in C# and PHP. Occasionally I see a single pipe used: |. What is the difference between those two usages? Are there any caveats when using one over the other or are they interchangeable?


I am trying to get to grips with es6 classes and I seem to be unable to pass a boolean value to a constructor.  In the following code  export default class site_alert {   constructor(options) {     this.message = options.message || 'default cookie message';     this.autoDisplay = options.autoDisplay || true;     console.log(this.autoDisplay);   } }  var sitemessage = new site_alert({   message:"Some string",   autoDisplay: false });   autoDisplay is always true, it takes the default value regardless of whats being passed to it when I create an instance of the class.  If I change autoDisplay to be a string it works fine.  Are you unable to pass booleans to the constructor like this?

I have now seen 2 methods for determining if an argument has been passed to a JavaScript function. I'm wondering if one method is better than the other or if one is just bad to use?   function Test(argument1, argument2) {       if (Test.arguments.length == 1) argument2 = 'blah';        alert(argument2);  }   Test('test');   Or   function Test(argument1, argument2) {       argument2 = argument2 || 'blah';        alert(argument2);  }   Test('test');   As far as I can tell, they both result in the same thing, but I've only used the first one before in production.  Another Option as mentioned by :  function Test(argument1, argument2) {     if(argument2 === null) {         argument2 = 'blah';     }      alert(argument2); }   As per Juan's comment, it would be better to change Tom's suggestion to:  function Test(argument1, argument2) {     if(argument2 === undefined) {         argument2 = 'blah';     }      alert(argument2); }


I am a participant on , which . As of writing, I have ~1800 rep on Lifehacks.SE. However, on , Lifehacks.SE is not seen in the graph. On , which , I have a mere ~350 rep, but that is shown in the reputation graph. Since Q&A from private beta sites show on my network profile, why doesn't reputation?

I noticed that private beta accounts are shown on FlairTM but not on the accounts tab or reputation graph of your SE user page.   explains why private beta accounts are shown on FlairTM but not on the accounts tab of your SE user page. The reason given for this is a good one:     However when it comes to flair, we show it off, as much reputation as you have everywhere all added up, because showing it causes no harm or navigational confusion.   But I think this argument isn't sound when it comes to the reputation graph: the reputation graph is showing off as much as is FlairTM.      In the private beta case, anyone not in the private beta couldn't use the link to go to your profile there...so showing it on the Accounts tab doesn't really make sense.   Also this isn't a sound argument when it comes to the reputation graph, since that doesn't include links to the accounts.  So, how about showing private beta accounts in the reputation graph?


Let $(X_1,d_1)$ and $(X_2,d_2)$ be metric spaces. Take $$\mathcal{B}(X_1)\times \mathcal{B}(X_2)=\sigma(\{A_1\times A_2 | A_1\in \mathcal{B}(X_1), A_2\in \mathcal{B}(X_2) \})$$ Where $\sigma(A)$ denotes the smallest $\sigma$-algebra generated by $A$, and $\mathcal{B}$ denotes Borel $\sigma$-algebra.  Define the following metric on the product space: $$d((x_1,x_2),(y_1,y_2))=\sqrt{d_1(x_1,y_1)^2+d_2(x_2,y_2)^2}$$  Let $X=X_1\times X_2$, and $$\mathcal{B}(X)=\sigma(\{ \textrm{All open sets in } (X,d)\})$$     If $(X_1,d_1)$ and $(X_2,d_2)$ are separable metric spaces then $\mathcal{B}(X)=\mathcal{B}(X_1)\times \mathcal{B}(X_2)$.   Is it possible to show by counter-example that separability is necessary in that assertion?

The following is a proposition in Folland's Real Analysis about product sigma algebra:    Here $\mathcal{B}_X$ denotes the Borel $\sigma$-algebra on $X$.      Could anyone come up with an example that    $$ \mathcal{B}_X\setminus\otimes_{1}^n\mathcal{B}_{X_j} $$   is nonempty?


I need to solve $\displaystyle \sum_{j=0}^\infty \sqrt{\frac{j!}{j^j}}$  Does this converge or diverge?

I need to solve    $$\sum_{j = 1}^{\infty} \sqrt{\frac{j!}{j^j}}$$  Does this converge or diverge and why?


Newbie to Mac. I am trying to open a file under /usr folder using Atom editor.  File path : /usr/local/Cellar/maven/3/libexec/conf  I am not able to find an option like windows browse where I can type/paste the file or directory name.   Another option that I am missing is the ability to open files from the network directly from the internet using Text editors within Mac.

It seems that by default there is no way to enter a whole path in the Finder, so instead one should traverse through all the tree to get somewhere deep in the filesystem. Is there anyway to overcome this problem? If there is no GUI for it in the Finder maybe launching it from the command line with the path? Something like:     $ finder /Library/Frameworks/Python.framework/Versions/


From the point of view of the reader, we’re made aware (via The Silmarillion mostly) about the different powers in Middle-earth and the creation of Arda. For the reader there’s Eru, the Valar and the Maiar.  The Quenya names seem to imply that Elves are aware of their existence and their role to some extend but my question is:  To what extend is each of the races aware of the existence and meaning of the different deities and specially Ilúvatar. Do the Elves recognise and know him as all powerful, omniscient creator of the world? Are Men or Hobbits even aware of his existence? What about Valar? Is there any worshipping going on?

One thing that is notably absent in Middle-earth is any mention of temples, churches, priests or religious rites.  There are passing mentions of Men who would "worship" Sauron, but generally the world of Middle-earth seems much less religious than medieval Europe, or even classical antiquity.  One never hears about "the cult of Aule" or "the cult of Yavanna," although historically there were many "cults of Athena" or "cults of Poseidon."  Aragorn doesn't (to my memory) make an offering to Tulkas before battle, nor does he pray to Eru Ilúvatar for victory, and all the holidays and solemnities seem to commemorate historical figures, not religious ones.  This is especially strange in a world where there are still living witnesses, like Galadriel, to the actions of the Valar and other "divine" beings, and where there are still Maiar wandering around talking to people and putting on flashy firework shows.  Now, a lot of people talk about how Tolkien didn't want the Valar to be considered "gods," but at the same time he did use phrases like "the gods of old" numerous times.  Clearly, these beings would have qualified for worship in most cultures.  And even without the Valar being considered a true pantheon, there is still Eru, a closer analogue to the Christian God of Tolkien's beliefs, and we know the denizens of Middle-earth knew of him (Him?) because of the line "Eru, who in Arda is called Ilúvatar."  And yet, Ilúvatar seems not to be terribly important to anyone on a daily basis.  So my question is this: how familiar with the "theology" of Middle-earth were the citizens of Middle-earth?  Would the average merchant in Rohan know about the Valar and the Maiar and Iluvatar and the Music of the Ainur?  The average noble in Minas Tirith?  The younger Elves, like Legolas?  The Dwarf Lords?  Were the theological truths about the formation of the world, the Valar and the Maiar just so well known that they weren't worth commenting on, or had they been forgotten by most?  And if they had been forgotten, why wasn't the knowledge (whether through deliberate teachings or casual conversation) re-invigorated by witnesses like Gandalf or Galadriel?


Though vibration is a common concept in sound and “high temperature”, the essential difference between the two is mentioned to be the way the vibration takes place. The former has vibrations that follow certain characteristics (has got an amplitude, frequency, wavelength, speed, etc.) while the latter is random.   The definition is crystal clear in differentiating sound and “high temperature”.  But what is the physical reason of our ears not perceiving random vibration as “sound” when the ears are not aware of the difference in the definitions?

In other words, given a magical room with walls that produce no vibration and transmit zero vibration from the outside, and nothing on the inside except room temperature air, what would be the noise level in dB SPL () from the  of the air itself?  (Similar to the  of electronics being determined by  in the conductors.)  What is the quietest possible anechoic chamber?  What is the noise floor of air?  For reference: Sound pressure is defined as the root-mean-square value of the instantaneous pressure, measured in pascal = N/m².  SPL is the same number, but expressed in decibels relative to 20 µPa.  (I assume that it has a white spectrum, but I could be wrong.  Thermal noise in electronics is white, but other types of electronic noise are pink, and blackbody thermal radiation has a bandpass spectrum.)   in the context of underwater acoustics.  Not sure how this applies to air:     Mellen (1952) developed a theoretical model for thermal noise based on classical statistical mechanics, reasoning that the average energy per degree of freedom is kT (where k is Boltzmann’s constant and T is absolute temperature). The number of degrees of freedom is equal to the number of compressional modes, yielding an expression for the plane-wave pressure owing to thermal noise in water. For non-directional hydrophones and typical ocean temperatures, the background level due to thermal noise is given by:      NL = −15 + 20 log f (in dB re 1 µPa)      where f is given in kHz with f >> 1, and NL is the noise level in a 1 Hz band. Note that thermal noise . There are few measurements in the high-frequency band to suggest deviations from the predicted levels.    Citation is R. H. Mellen, The Thermal-Noise Limit in the Detection of Underwater Acoustic Signals, J. Acoust. Soc. Am. 24, 478-480 (1952).


This is a pretty straightforward question, but to stand up from being prone takes half your movement speed. When entangled, your speed is 0, so are you able to stand up without becoming un-entangled?

In a one-shot I recently played the players were fighting a homebrewed . It has a walking speed of 0 ft. and can teleport 80 ft. on its turn under some conditions. One of the players knocked the monster, over by using the shove action. On its turn, the monster was prone with a speed of 0 ft. It then used an ability to teleport away and appear upright again (Impossible Movement). Now there are three options on how to rule this situation:  The monster uses half of 0 ft., so still 0 ft., to get up from being prone and proceeds as normal The monster lifts the prone condition simply by teleporting The monster is prone, and can't get up anymore  I am asking about a general creature that has a walking speed of 0 ft., not explicitly about the Weeping Angel. According to the rules, which of this rulings (if any) would be correct?


Plot Summary/Details  The story is told from the viewpoint of a male swashbuckling type.  I would guess the time frame to be late middle ages or thereabouts.  The protagonist is recounting his adventures with his best friend, a fellow rake.  There is reminiscing about drunken scraps, dashing sword fights, encounters with lusty women, and the like.  I seem to remember the story to have a poetry like quality to it.  I can't remember if it was actually in poem form, or if it was merely the writing style.  The twist (and scifi connection) to the story comes when the protagonist's friend slips during a sword fight with a couple of rogues, and falls.  The friend is mortally wounded in the belly, and the protagonist makes some statement to the effect of "it was then I learned that you were not of this world."  The meaning being, the internal organs of the friend were not those of a human.    The protagonist goes on to say he slew the two men they were fighting, so they could not speak of this to anyone.  And I believe the protagonist buries his friend in secret, so none would ever learn of the truth.  I believe that is the ending of the story.  Publication Details  I am almost 100% sure I read this in an issue of Omni magazine.  It would have been very early 1980s when I read the story.  I've tried searching a few databases, but my Google-Fu has yet to turn anything up that looks like the story I'm trying to remember.

Read this in the 80's in a compilation of military Science Fiction short stories.  The author/speaker is a human time traveller who has gone back in time and become a mercenary at a time when swords and pikes are the weapons.  The time traveller's unit gets wiped out and while looking at the body of his buddy realizes the buddy was an alien (because of the green blood). there is a line about where he says you never told me you were (type of alien) and I never told you I was from the future.


The matrix is  $$ \begin{bmatrix} 1 & 1 & -3 \\ 2 & 0 & 6 \\ 1 & -1 & 5 \end{bmatrix} $$  I understand where the eigenvector $[-3, 0, 1]$ comes from because the eigenvalue is $\lambda = 2$ and when you substitute it into the matrix and then row reduce you get $$ \begin{bmatrix} 1 & 0 & 3 \\ 0 & 1 & 0 \\ 0 & 0 & 0 \end{bmatrix} $$ But the answer also puts $[1, 1, 0]$ as an eigenvector. Any idea where this comes from?

If I have a $2\times 2$ or $3\times 3$ matrix, how should I go about computing the eigenvalues and eigenvectors of the matrix?  NB: I am making this question to provide a unified answer to questions about eigenvalues of small matrices so that all of the specific examples that come up can be marked as duplicates of this post. See .


When using sudo, su, or simply the login screen from Linux Mint Cinnamon or Debian with Cinnamon, they all hang for a second when you enter an incorrect password.  For me, the fact that it hangs tells me "it's incorrect" already, making me Ctrl+C a sudo command and then retry with uparrow -> Enter, or close a login dialog with Escape and start typing to try again. This works just fine.  It appears to be an attempt at rate limiting, but it does not work because an attacker can just setup parallel guesses. If it actually wanted to rate limit, it should limit how many queries can be inputted per time period, not how long it takes before the output is returned (and it's only delayed in the failure case, another dead giveaway).  What is the reasoning behind doing it this way?

I notice a weird (well, according to me) thing about passwords. For example, if I type an incorrect password during login, there will be a few seconds' delay before the system tells me so. When I try to sudo with a wrong password I would also have to wait before the shell says "Sorry, try again".  I wonder why it takes so long to "recognize" an incorrect password? This has been seen on several distributions I use (and even OSX), so I think it's not a distribution specific thing.


I've searched pretty hard - but cannot find out how to make Nautilus in Ubuntu 17.10 show 'Make Link'on right clicking a directory, either directly or via Properties. I'd like to set symlinks for use by Insync but since updating Ubuntu to 17.10 this option has disappeared. Possibly it doesn't help that I'm now using Budgie-Ubuntu but even adding alternative desktop environments doesn't do the trick. (Not using Wayland, by the way...) I just cannot understand why the devs would remove this option! David

I just upgraded to Ubuntu 17.10 but all my desktop shortcuts are gone.  There is no longer a Create Shortcut option when I right-click either.   How do I add these now?


I want to put the first word(title:) in bold in a text only with css, no html tags title: description

This one has me kind of stumped. I want to make the first word of all the paragraphs in my #content div at 14pt instead of the default for the paragraphs (12pt). Is there a way to do this in straight CSS or am I left wrapping the first word in a span to accomplish this?


I'm searching for a word with a meaning similar to Racism or Sexism but within the context of religion. Is there a word for this meaning?

I've heard "racist" being used in a few cases to describe bigotry towards people of a certain religion. It's a bit annoying because it implies that all people of a religion are the same race, which is hardly the correct case. However I'm also bewildered that there doesn't seem to be an appropriate one-word substitute coined to describe prejudice/discrimination/sense of superiority in terms of religion. What (if any) word exists for it?


Does any one know if I can do this figure in Latex?  I know I can make the cube by the following code but how I can put that plan in the middle and write those numbers below it? \begin{figure} \begin{center} \caption{A labeled cube} \begin{tikzpicture}\label{f1} \foreach \n/\x/\l/\p in{ 1/{( 0  , 0)}/{$3$}/below, 2/{( 4, 0)}/{$4$}/below, 3/{( .8, 1)}/{$7$}/south east, 4/{( 4.8, 1)}/{$8$}/right, 5/{( 0, 4)}/{$1$}/left, 6/{( 4, 4)}/{$2$}/south west, 7/{( 0.8, 4.8)}/{$5$}/above, 8/{( 4.8, 4.8)}/{$6$}/above } {         \node[inner sep=2pt,circle,draw,fill,label={\p:\l}] (\n) at \x {};     } \draw (1) -- (2) -- (6) -- (5) -- (1); \draw (5) -- (6) -- (8) -- (7) -- (5); \draw (2) -- (4) -- (8) -- (6) -- (2); \draw[dashed] (1) -- (3) -- (4); \draw[dashed] (3) -- (7); \end{tikzpicture} \end{center} \end{figure}


Is transferring Gen 6 and under Pokemon from Sun/Moon to ORAS a feature in Pokebank?   I'd like to breed on sun and moon, transfer to ORAS to get move tutors, then back to sun and moon.

Title says it all, I don't see confirmation in  and a cursory google search seemed to say assume no and speculate about the pokemon bank.


Which spelling is recognized more as the proper spelling globally?

There are many places suggest not to mix British and American spelling in IELTS test, such as the articles on  and nativespeakeronline (No link here. I don't have enough reputation to post more than 2 links). When I search on forums, the most common idea is people in North America prefer -ize and people in other places prefer -ise. However, an article on  says:     the Oxford University Press insists that words such as computerize, capitalize, capsize, organize, organization, privatize, publicize, realize should take the -ize ending     And for some words in this list like "organization", people on forums say most British still prefer "organisation". In this case, if I stick to using British spelling on IELTS test, should I use -ise or -ize for the words in this list?


Context: P.A.M. Dirac, Principles of Quantum Mechanics, 3rd Ed., Clarendon Press, 1947, p. 30-31. $\xi$ is a “real linear operator” (Dirac's terminology for what's known today a self-adjoint operator) and $|P\rangle$ is an eigenket of $\xi$. Problem: I don't understand why “the number $\left\langle P\left|\xi\right|P\right\rangle $ must be real.”

If the expectation value of operator $A$ in any state is real, then $A$ is Hermitian.   there is an uncompleted proof:  $$ \int(c_1\psi_1+c_2\psi_2)^* A (c_1\psi_1+c_2\psi_2)dx$$ $$=|c_1|^2\int\psi_1^* A \psi_1dx + |c_2|^2\int\psi_2^* A \psi_2dx +c_1^*c_2\int\psi_1^* A \psi_2dx +c_2^*c_1\int\psi_2^* A \psi_1dx $$  My teacher said that because  $$c_1^*c_2\int\psi_1^* A \psi_2dx +c_2^*c_1\int\psi_2^* A \psi_1dx$$  is real, then we can conclude that $$\int\psi_1^* A \psi_2dx = (\int\psi_2^* A \psi_1dx)^*$$  but I don't understand this last step, can someone explain it, or give another proof?


Im a programmer and I was writing a comment today that read:  Finds a XPath relative to the Node  From what I understand you should always use 'a' over 'an' when it proceeds a word starting with a vowel. such as  I ate an apple I ate a orange  It sounds weird to me the way "Finds a XPath" reads. It feels more comfortable reading "Finds an XPath". I know English is full of weird rules and I am wondering if this is one of them. What is the correct usage here? In case it is relevant heres a link to .

I was asking this question on Area 51: "How do I tell if an airport scanner is a X-ray scanner?", but I keep wanting to put an 'an' in front of X-ray because it starts with the 'eh' sound.  So is it 'a' or 'an'?


I'm trying to prove that when $f(x) =x^TBx$, then $f'(x) = (B + B^T)x$. I haven't found this formula online but going through the calculations using index notation this is what I came up with. This would simplify to $2Bx$ when $B$ is symmetric. The accepted response to  says that the solution is actually $f'(x) = x^T(B + B^T)$, going through the proof there, I see how he got there but I can't see where the mistake is in mine then.  The setup   $x \in \mathbb{R^n}$, it is always a column vector $B \in \mathbb{R^{n \times n}}$, $B$ may not be symmetric   My approach  Let $g(x)=x^TB$ and $h(x)=x$, then I can write $f(x)=g(x)h(x)$. Then   $f(x) \in \mathbb{R}$ $g(x) \in \mathbb{R^{1 \times n}}$ $h(x) \in \mathbb{R^n}$ $f'(x) \in \mathbb{R^n}$ $g'(x) \in \mathbb{R^{n \times n}}$ $h'(x) \in \mathbb{R^{n \times n}}$   I've gone through myself why $g'(x) = B$ and $h'(x) = I_n$, so I won't go through those here.  Then, using the product rule I get:  $$f'(x) = g'(x)h(x) + g(x)h'(x)$$  The problem is that the dimensions don't add up. I get $g'(x)h(x) = Bx \in \mathbb{R^{n}}$, which is good. However, I also have $g(x)h'(x) = x^TBI_n = x^TB \in \mathbb{R^{1 \times n}}$ and as far as I know I can't add up two vectors of different sizes.  I know that the solution is going to be the transpose of second term, I just can't seem to find where that transpose would come from.   Why do I need to take the transpose of the second term?  [Edit]: Please don't reply with a different proof. What I'm looking for is to understand where I made the mistake in my calculation because obviously I made a step which was incorrect and without understanding where that is I'm likely to make that mistake again.

It's stated that the gradient of:  $$\frac{1}{2}x^TAx - b^Tx +c$$  is   $$\frac{1}{2}A^Tx + \frac{1}{2}Ax - b$$  How do you grind out this equation? Or specifically, how do you get from $x^TAx$ to $A^Tx + Ax$?


I came across a capacitors problem that seemed to be very simple, but I can't figure reasoning as to why two approaches to the problem yield two different answers. One of them is wrong, but I can't tell why.  So in the figure above, consider the two faces of the cube connected by the wires as parallel plates of a capacitor, each with area $A$. It is filled completely with two materials of dielectric constants $\epsilon_1=2$ and $\epsilon_2=4$. The side length of the cube is $d$. Now, I thought of two ways to 'break' the system, as below:  The first figure is the correct way of doing the problem, and after calculating the capacitances of each individual block, and finding the net capacitance, the answer comes out to be $\frac{7A\epsilon_0}{3d}$. The second figure is what I thought could be another way of solving the question, but it yields a very different answer of about $\frac{12A\epsilon_0}{5d}$. And I cannot tell why. The reason could be that the potential of the face where I am making the partition in the second figure is not the same for both blocks (the ones to the right), so assigning them a parallel combination is an error. But I can't tell why the potential should be different. The charge is flowing to those blocks in a very uniform way from the left, they can't be at a different potential. Original question from JEE Advanced 2015 paper 2Apologies if the figure is a bit sketchy, I tried my best to recreate it as I could not find a clear image of the problem on the internet. Edit: In the first figure, the two blocks at the top are in series and the bottom block is in parallel combination with them. In the second figure, the two blocks at the right are in a parallel combination, and the block at the left is in a series combination with them.

In few questions, I am having some confusion on how to take the resultant capacitance of a parallel plate capacitor with a combination of dielectric in between parallel plates. Here is a an example  (From JEE Advanced 2000) $k_1, k_2, k_3$ represent the dielectric constants of the dielectric slabs. A is the plate area, d is the distance between the plates. I know that we could split it into equivalent capacitors and from there it is easy to find the resultant capacitance. But I am confused on how to split them. I have 2 possible approaches (i) (ii) ($k_1, k_2, k_3$ represent the dielectric constants of the dielectric slabs. A is the plate area, d the distance between the plates) The 2nd part makes more sense to me and it also turn out to be the right method. However I cannot understand why the 1st part shouldn't work out. Here is another example:  (From JEE Advanced 2015) Even here I could split it in 2 ways- (i) (ii) Here (i) is the correct way but (ii) isn't. I do not understand how either could be wrong or right. It Would really help if someone could point out what I am missing out. (Please Note: The spaces I have left between the dielectrics in my solution are just to illustrate how I split the system. They do not indicate real spaces.)


I was wondering what sort of tool works best for removing traces on a stripboard like the following:   .  Product page on .   Image from

Since I've started electronics I'm using this kind of board for permanent projects:     But sometimes it's a bit annoying, especially when I need a line going from the top to bottom of the board.  I've seen this kind of board:     My question is, how can I cut the strips?  By cutting the strip I don't mean cutting the board itself, just the copper strip. I've tried with a precision knife but I'm not sure about the method, the blade gets damaged really quickly and it's really hard to cut the copper.


I read in a paper on set theory that the supremum and the infimum of the empty set are defined as $\sup(\{\})=-\infty$ and $\inf(\{\})=\infty$. But intuitively I can't figure out why that is the case. Is there a reason why the supremum and infimum of the empty set are defined this way?

Let $E$ be an empty set. Then, $\sup(E) = -\infty$ and $\inf(E)=+\infty$. I thought it is only meaningful to talk about $\inf(E)$ and $\sup(E)$ if $E$ is non-empty and bounded?   Thank you.


I tried to install Arduino IDE software through 'Software'-named software in ubuntu. It failed with message 'authentication was required'. I think Linux is free software. Why I need to register? Who collect that information and what purpose? Then I tried to register and it was successfull but this stupidly named 'Software'-software does not accept my password. Why? Why I need to register for free software? I have been used Ubuntu for years and not never before needed to register anywhere. How I can break that software registration so that I can again freely use Ubuntu?  And, why this forum forces to use tags on this post? And then it does not allow tags like 'install', 'software' or 'ubuntu-should-be-free'... First I tried to post question to ubuntu forum, but it was read only! What sense is that?

I have an Arduino UNO, which I need to get working with Ubuntu.  Can somebody explain to me the steps required to install the IDE on Ubuntu?


I have an array of objects. Then I want to add another object and stick it to the one that already existed in my array. Which means the index of the new object should be larger by one in relation to my already existed object and rest of the element's indexes should be incremented by one.   For example:    I have array of 6 elements My new object is stick to existed object with index = 2 New Object enters into an array with index = 3 and all objects with indexes previously greater then 2 now get one place higher   I tried to split my array into two starting from index = 2, push my new element, and then join and again but my code do not work well.  for (var i in myArray) {   if (myArray[i].name === inheritedRate.inherit) {     var tempArr = [];     for (var n = i; n < myArray.length; n++) {       tempArr.push($scope.myArray[n]);       myArray.splice(n, 1);     }     myArray.push(inheritedRate);     myArray.concat(tempArr);   } }     in other words I have an array which looks like this:   myArray = [   {name: "not selected"},   {name: "not selected"},   {name: "selected"},   {name: "not selected"},   {name: "not selected"},   {name: "not selected"}, ]   And I want to put there an external element to make it look this:   myArray = [   {name: "not selected"},   {name: "not selected"},   {name: "selected"},   {name: "new element"}, // inserted   {name: "not selected"},             {name: "not selected"},   {name: "not selected"}, ]

I am looking for a JavaScript array insert method, in the style of:  arr.insert(index, item)   Preferably in jQuery, but any JavaScript implementation will do at this point.


Can anyone assist me in getting a part of a mirrored object to move without overlapping into itself?  In 3DSMax it consisted of changing the view from global to local and then the whole thing moved instead of overlapping. In Blender I've tried all the local views and they aren't working.  Below is what is happening -

When I add a mirror modifier it sometimes doesn't mirror correctly, giving me an overlapping mesh. How can I fix this?


I'm looking for some special parameter (like ?redirect=no, or something), which will prevent the redirection for the question from non-authenticated users.  Currently the questions are opened correctly when I'm authenticated (or for high-rep users), but when I'm sending this question somewhere else (like opening them in Privacy mode), it got redirected.  Is it possible to prevent that from happening by adding some special parameter? Or is there any workaround (like Wikipedia does that)?

Duplicate questions that use different words to describe the same problem are important for people to find the content via search engines. But the user experience when an anonymous user arrives at a duplicate is less than ideal.  They have to notice the duplicate link and understand that the answer they are looking for is likely behind that link. I don't think this is all that obvious to someone without experience with an SE site.  I propose to just redirect users to the duplicate automatically if the closed duplicate has zero answers. In that case they need to follow the link to the duplicate in any case, so we might as well redirect them to it in the first place.  I could imagine this being problematic with search engines, as we would be displaying different content than what the search engines see. If that is too problematic I would suggest to show a very obvious link to the duplicate in the answers section for anonymous users.


Essentially comparing:  glm1 = glmer(Mortality ~ CCI + PatientRace + PatientSex + age_cat + (CCI | FacilityIdentifier),               data = tmp, family = binomial,               control = glmerControl(optimizer = "bobyqa"), nAGQ = 1)   to   m1 = glm(Mortality ~ CCI + PatientRace + PatientSex + age_cat,           family=binomial, data = tmp)   To determine if the random effect is a significant contributor, hopefully to show that each facility doesn't have varying practices in measuring CCI that may affect interpretation of mortality. Would appreciate any advice.

Given three variables, y and x, which are positive continuous, and z, which is categorical, I have two candidate models given by:  fit.me <- lmer( y ~ 1 + x + ( 1 + x | factor(z) ) )   and  fit.fe <- lm( y ~ 1 + x )   I hope to compare these models to determine which model is more appropriate. It seems to me that in some sense fit.fe is nested within fit.me. Typically, when this general scenario holds, a chi-squared test can be performed. In R, we can perform this test with the following command,  anova(fit.fe,fit.me)   When both models contain random-effects (generated by lmer from the lme4 package), the anova() command works fine. Owing to boundary parameters, it is normally advisable to test the resulting Chi-Square statistic via simulation, nonetheless, we can still use the statistic in the simulation procedure.  When both models contain only fixed-effects, this approach---and, the associated anova() command---work fine.  However, when one model contains random effects and the reduced model contains only fixed-effects, as in the above scenario, the anova() command doesn't work.  More specifically, I get the following error:   > anova(fit.fe, fit.me)  Error: $ operator not defined for this S4 class   Is there anything wrong with using the Chi-Square approach from above (with simulation)? Or is this simply a problem of anova() not knowing how to deal with linear models generated by different functions?  In other words, would it be appropriate to manually generate the Chi-Square statistic derived from the models? If so, what are the appropriate degrees of freedom for comparing these models? By my reckoning:  $$ F = \frac{\left((SSE_{reduced}-SSE_{full})/(p-k)\right)}{\left((SSE_{full})/(n-p-1)\right)} \sim F_{p-k,n-p-1} $$  We are estimating two parameters in the fixed effects model (slope and intercept) and two more parameters (variance parameters for the random slope and random intercept) in the mixed-effects model. Typically, the intercept parameter isn't counted in the degrees of freedom computation, so that implies that $k=1$ and $p=k+2=3$; having said that I'm not sure if the variance parameters for the random-effects parameters should be included in the degrees of freedom computation; the variance estimates for fixed-effect parameters are not considered, but I believe that to be because the parameter estimates for fixed effects are assumed to be unknown constants whilst they are considered to be unknowable random variables for mixed effects. I would appreciate some assistance on this issue.  Finally, does anybody have a more appropriate (R-based) solution to comparing these models?


I am trying to prove relation between G.C.D and L.C.M for three integers. Is the following relation even true. If yes, then I need hints please. let a, b and c be any integers then, $$lcm(a,gcd(b,c))=gcd(lcm(a,b),lcm(a,c))$$ Or in notations, $$[a,(b,c)]=([a,b],[a,c])$$

is $\operatorname{lcm}(a,\gcd(b,c))=\gcd(\operatorname{lcm}(a,b),\operatorname{lcm}(a,c))$? it should be true for positive integers because the commutative algebra by Atiyah says addition, intersection on the ideals of $\mathbb{Z}$ is distributive. how should i solve it?


What should I write in Terminal to see all main commands?

I want to start using the terminal more often, but I don't know what are the different commands available to me. Is there a way to list all the different commands that I can make use of?


I cannot correlate with closure, negative votes, no answers, or any common thread between questions that are grayed out, and those that are not.  One can still open them, and answer or comment at will.    Why do some questions have a different appearance?

I just refreshed the [iphone]-tag-site, and I'm seeing all kinds of questions with what appears to be a grey overlay (see image). What is this for/why am I seeing this? I have never seen anything like this before..


I've self studying Nathan Jacobson's Basic Algebra and I came across this question:  Let $G$ be a finite group with $\alpha$ a automorphism of the group. Denote, $$I =\{g \in G : \alpha(g) = g^{-1}\}$$ show that if  $|I| > \frac{3}{4}|G|$ then $G$ is abelian. Show that if $|I| = \frac{3}{4}|G|$ show that $G$ has an abelian subgroup of order 2.  So far what I've done is tried a proof by contradiction, saying suppose that $G$ is not abelian. Well then I computed for $g,h \in I$, $$\alpha(gh) = \alpha(g) \alpha(h) = g^{-1}h^{-1} \neq (gh)^{-1}$$ since $G$ is assumed not to be abelian.  I need to find a contradiction from this, i'm just not sure how to do that. Any help is appreciated, thanks.

Assume that $\pi$ is an automorphism of a finite group $G$. Let $S$ denote the set $\lbrace g \in G: \pi (g)=g^{-1} \rbrace$. Show that if $|S|>\frac{3|G|}{4}$, then $G$ is an abelian group.    Anyone has any idea on how to solve this ? I have no idea how to start.


After updating to latest iOS13.4 my iPhone XR gets shutdown even when the batter shows 20%. Tried to browse more on this, it was explained that it is a firmware issue. Can anyone suggest how to recover from this, as its quite annoying to have such behaviour.

My iPhone SE on iOS 12 has been acting strange recently.   Yesterday, it turned off at around 10% and when I tried to turn it on it said that it has no power. Two minutes later, it turned on and said it had 14% capacity remaining.  Today, when it was at around 10%, it turned off. Then I turned it on  and it said 12%. Two minutes later, it turned off. It says "connect to power."  After a few minutes I tried again and it turned on. Then it gives an error saying  that it "can’t connect to my mobile data network" and then the  phone crashes.   I turned it on again, and it worked normally.   What is causing this?  EDIT: After digging around my batter settings I found this:


$f$ is a real function on $[a,b]$ having $f^{(n-1)}$ continuous derivative on $[a,b]$, and $f^{(n)}(t)$ exists for every $t\in (a,b)$ , then $\exists x$ between $\alpha$ and $\beta$ such that $f(\beta)=P(\beta)+\frac{f^{(n)}(x)}{n!}(\beta-\alpha)^n$  How to use the Taylor theorem to get: $$ \left| f(b) - \sum_{j=0}^{n-1} \frac{f^{(j)}(a)}{j!} (b-a)^j \right| \leq \frac{\left| f^{(n)}(x) \right| }{n!} (b-a)^n. \tag{1}$$ Does it merely choose $\sup_{a<x<b} |f^{(n)}(x)|$?, but I wondering that $(a,b)$ is not compact and $x$ may not in $(a,b)$.

I'm trying to understand the remainder in Taylor's theorem from this source:     I don't understand the very last parts of the proof (the parts where the remainder $R_n$ is solved). Can someone explain why does it follow from:   $$\frac{f^{(n+1)}(a)}{(n+1)!}(x-a)^{n+1}+\int_a^x \frac{f^{(n+2)}(t)}{(n+1)!}(x-t)^{n+1} \;dt$$  that $$R_N = \frac{f^{(n+1)}(\xi)}{(n+1)!}(x-a)^{n+1}?$$  I think the changing between letters $a$ and $\xi$ confuses me...?


I tried my project on localhost and it works well, there are no errors.  But when I upload my project to a real server (bought server)  and when inserting a value to database (phpMyAdmin) it shows me an unknown language.  For example:  In page "signup" when user writes name and password using Arabic language it inserts in database like "Ø§ØÙ…Ø¯"   This images show unknown language   But in same page if user write name and password "using English language" its insert in database correctly  So how can I fix this? If user write in <input> using other language like Arabic language, insert it in database correctly  Note: when user write name and password using Arabic language and in database show like "Ø§ØÙ…Ø¯", and when I display it from database to my website it shows me he value correctly and there no errors.  My question: how can I fix encoding/charsets in database.  This is my code:  $insert_c = "INSERT INTO customers(username,password) VALUES('$username','$password')";  $run_c = mysqli_query($connect, $insert_c);   And sorry about my English language, I'm use Google translate  This image show utf8

I'm setting up a new server and want to support UTF-8 fully in my web application. I have tried this in the past on existing servers and always seem to end up having to fall back to ISO-8859-1.  Where exactly do I need to set the encoding/charsets? I'm aware that I need to configure Apache, MySQL, and PHP to do this — is there some standard checklist I can follow, or perhaps troubleshoot where the mismatches occur?  This is for a new Linux server, running MySQL 5, PHP, 5 and Apache 2.


Calculate big o of function. How do I calculate the big O notation in this function?  Example:    function fun1(int n) {   int s = 0;   for(int i = 0; s < n; i++)   {     s += i;     for(var j = s; j < n; j++)       {         console.log(j);       }   }   return s; }

I'd prefer as little formal definition as possible and simple mathematics.


What command can I write in main.tex as shorthand for "include all .tex files from a given folder". So I don't have to write a lot of \include{} commands for each file like \include{sections/introduction.tex} \include{sections/section2.tex} // And so on...  EDIT: MY SOLUTION \begin{document}  \foreach \folder in {sections, images} {%         \foreach \i in {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, ..., 19} {%         \edef\FileName{\folder/\i}%     The % here are necessary to eliminate any         \IfFileExists{\FileName}{%      spurious spaces that may get inserted            \input{\FileName}%           at these points         }     } }  \end{document}  Reference:

Possible Duplicate:          Using \input{filename}, I can input a file canned "filename.tex". I have a directory containing all of the files I want to include. How can I create a for loop, which inputs all of those files?   The contents of the directory sometimes changes (so I do not want to manually specify all of the files). The files are numbered (e.g. file01.tex, file02.tex), so the loop should have no difficulty inputing them in the correct order. Other code will be placed within the for loop (before and after the input command), so I do not want to simply list all of the files at once (e.g. \input{file01,file02}).


Our site has 3,000+ concurrent users when we open our registration on our website. The site was too slow and get the server down sometime, even sub accounts websites are down. Free memory was 400MB.  We upgraded our server to 8Gb for us to have a larger allocated memory. After upgrading our site still encountering server down/ slow site. What should be the best setting for our my.cnf so that our MySql Server would not give up?  This is currently our setting:  [mysqld] default-storage-engine=MyISAM performance-schema=0 max_allowed_packet=512M thread_cache_size=256K tmp_table_size=1G max_heap_table_size=1G open_files_limit=1000 max_connections=3000 interactive_timeout=180 wait_timeout=180 key_buffer_size=400M slow_query_log = ON   And now, this is the top result:    Thank you for any suggestion.

This is a  about  Related:      I have a question regarding capacity planning. Can the Server Fault community please help with the following:   What kind of server do I need to handle some number of users? How many users can a server with some specifications handle? Will some server configuration be fast enough for my use case? I'm building a social networking site: what kind of hardware do I need? How much bandwidth do I need for some project? How much bandwidth will some number of users use in some application?