I'm a maths undergrad taking a course on electromagnetism, I've drawn a diagram to represent this following question, but I'm having a bit of trouble approaching it:  "Two tiny balls of mass m = 0:1 g and charge q are suspended on silk threads of length l = 30 cm (see picture below). Their centers are separated by D = 6 cm. Find the charge q."

In a question:            Two small plastic balls hang from threads of negligible mass. Each   ball has a mass of 0.110g and a charge of magnitude q. The balls are   attracted to each other, and the threads attached to the balls make an   angle of 20.0 deg  with the vertical, as shown in the figure   How do I compute the magnitude of electric force acting on each ball?   I tried using coulomb's law: $F = k \frac{Q_1\cdot Q_2}{r^2} = 2.248 \times 10^{13} q^2$ but seems like the answer is wrong. The hint was that the answer did not depend on $q$ I guess I have to use other info? But how?


Let $0^0 = 1$.  It can be shown by the inequality introduced below that "my number" $\sum_{n=0}^∞ \frac{1}{n^n}$ is strictly between $2$ and $e$:  \begin{align} 2 & =\frac{1}{0^0}+\frac{1}{1^1} <\text{“my number''}=\frac{1}{0^0}+\frac{1}{1^1}+\frac{1}{2^2}+\frac{1}{3^3}+\cdots \\[10pt] & = \frac{1}{1}+\frac{1}{1}+\frac{1}{4}+\frac{1}{27}+\cdots<e=\frac{1}{0!}+\frac{1}{1!}+\frac{1}{2!}+\frac{1}{3!}=\frac{1}{1}+\frac{1}{1}+\frac{1}{2}+\frac{1}{6}+\cdots \end{align} Desmos.com () shows that this number is equal to approximately 2.291. My questions are:   Can this number be expressed by any other way(s) than this one? Is this number rational, algebraic irrational or transcendental?

Earlier today, I was talking with my friend about some "cool" infinite series and the value they converge to like the Basel problem, Madhava-Leibniz formula for $\pi/4, \log 2$ and similar alternating series etc.  One series that popped into our discussion was $\sum\limits_{n=1}^{\infty} \frac{1}{n^n}$.  Proving the convergence of this series is trivial but finding the value to which converges has defied me so far. Mathematica says this series converges to $\approx 1.29129$.  I tried Googling about this series and found very little information about this series (which is actually surprising since the series looks cool enough to arise in some context).  We were joking that it should have something to do with $\pi,e,\phi,\gamma$ or at the least it must be a transcendental number :-).  My questions are:   What does this series converge to? Does this series arise in any context and are there interesting trivia to be known about this series?   I am actually slightly puzzled that I have not been able to find much about this series on the Internet. (At least my Google search did not yield any interesting results).


I just installed Archlinux and want to install netstat. However using the command pacman -Ss netstat outputs irrelevant package names. A search on internet revealed that netstat is owned by net-tools. Installing net-tools gave me access to netstat.   How should one proceed to find the package name to install with pacman when only the final bash command is known ?

I'm looking for a package that provides a specific binary, so I can install it. how can I search to find out what packages provide this binary? (note: I know there's at least one tool that does this, but I have forgotten its name.)


Could someone suggest me a good book to start differential geometry which is not very hard to start with? I have learnt several variable calculus in the previous semester but haven't yet read any stuff about differential geometry.

I have a hazy notion of some stuff in differential geometry and a better, but still not quite rigorous understanding of basics of differential topology.  I have decided to fix this lacuna once for all. Unfortunately I cannot attend a course right now. I must teach myself all the stuff by reading books.  Towards this purpose I want to know what are the most important basic theorems in differential geometry and differential topology. For a start, for differential topology, I think I must read Stokes' theorem and de Rham theorem with complete proofs.   Differential geometry is a bit more difficult. What is a connection? Which notion should I use? I want to know about parallel transport and holonomy. What are the most important and basic theorems here? Are there concise books which can teach me the stuff faster than the voluminous Spivak books?  Also finally I want to read into some algebraic geometry and Hodge/Kähler stuff.  Suggestions about important theorems and concepts to learn, and book references, will be most helpful.


I am working on various plugins in QGIS which I have made, so I was wondering if it is possible to make one plugin which would call these plugins in a predetermined order, so that I would not have to call them individually.

Is there a way to access QGIS plugins in Python?   I'd like to write a script to do some geoprocessing, and I'd like to use the clip, regular points and convex hull tools in fTools, as well as the Road graph plugin. The latter is probably a different can of worms because it is a C++ rather than Python plugin.


Consider a list of dicts with a date property and an amount property:  transactions = [     {'date': '2013-05-12', 'amount': 1723},     {'date': '2013-07-23', 'amount': 4523},     {'date': '2013-02-01', 'amount': 2984}, ]   I would like to add a balance property, but to do so I must iterate over the list in date order:  balance = 0 for t in transactsions:    # Order by date     balance += t['amount']     t['balance'] = balance   How would one go about this? If I were to replace the dicts with Transaction objects having date and amount properties, would it then be possible?

I have a list of dictionaries and want each item to be sorted by a specific value. Take into consideration the list: [{'name':'Homer', 'age':39}, {'name':'Bart', 'age':10}]  When sorted by name, it should become: [{'name':'Bart', 'age':10}, {'name':'Homer', 'age':39}]


A friend of mine is going to fly from Beijing to Toronto, but he'll stop over in Chicago for 7 hours. Does he need the US visa?

In Europe usually you don't need to go through immigration to change planes (unless you are entering/exiting Schengen). Is it the case in the US as well? May I catch a connecting flight on one of the US airports if I don't have US visa?


I know that the limit doesn't exist, using Fixed Point Iteration Method and some appropriate inequalities. I can't think of any way to find the explicit form for $a_n$ from the following recurrence relation. $$a_{n+1}=a_n+\frac{1}{a_n}$$  (If this can be solved, then can $a_{n+1}=ka_n+\frac{l}{a_n}$ be solved?)

Today, we had a math class, where we had to show, that $a_{100} > 14$ for  $$a_0 = 1;\qquad a_{n+1} = a_n + a_n^{-1}$$  Apart from this task, I asked myself: Is there a closed form for this sequence? Since I didn't find an answer by myself, can somebody tell me, whether such a closed form exists, and if yes what it is?


I have been given a question:  Suppose that $F(x)=P(X\leq x)$. Show that if $F$ is continuous and $Y:=F(X)$, then $P(Y\leq y)=y$ for all $y\in [0,1]$.  I have been having difficult even starting to prove anything, since the definiton of $Y$ seems to me somewhat self refrencing. I will be thankful for any clues.

This question is related to  , with the difference being that $F_X$ (the probability distribution function of random variable $X$) is an arbitrary continuous distribution function, not necessarily strictly increasing.  I think the proof is similar, but we have to take care of the possibility that $F_X$ may not be $1$-to-$1$.  I list my attempt below, and would appreciate it if someone can confirm if it's correct, and, in particular, if it can be improved.  Thanks a lot!  The goal is to show $F_Y(y)=y$ for any $y \in [0,1]$.  To do so, note that $F_Y(y)\triangleq\mathbb P(\{Y\le y\})$, and  $\{Y\le y\}=\{F_X(X)\le y\}=\{X\in F_X^{-1}([0, y])\}.$  Since $F_X$ is continuous, $F_X^{-1}([0,y])$ must be closed.  So it follows that   $\sup F_X^{-1}([0, y])=\max F_X^{-1}([0, y])=\max F_X^{-1}(\{y\}),$ which let's denote by $a$.    Therefore, $F_Y(y)=\mathbb P(\{X\le a\})=F_X(a)=y.\quad$  (Q.E.D.)


Let $W=\{p(B):p \text{ is a polynomial with real coefficients}\},$ where $B=\begin{pmatrix}0&1&0\\0&0&1\\1&0&0\end{pmatrix}.$ Then find the dimension of $W.$  I have shown $B^4=B$ and $c_1B+c_2B^2+c_3B^3=0\implies c_1=c_2=c_3=0$ and hence $\{B,B^2,B^3\}$ is a basis of $W.$ So $\dim W=3.$  Am I right?

Let $W = \{ p(B) : p \text{ is a polynomial with real coefficients}\}$, where $$B= \begin{pmatrix} 0 & 1 & 0\\  0 & 0 & 1\\  1 & 0 & 0 \end{pmatrix}$$  Which of the following possibilities presents the tightest bounds on the dimension $d$ of the vector space $W$?     $4 ≤ d ≤ 6$    $6 ≤ d ≤ 9$    $3 ≤ d ≤ 8$    $3 ≤ d ≤ 4$


so I got a barely used phone from my buddy. He had thought it was stolen just after buying it, but has recently found it and given it to me because it has a little port for a SIM card. Since I have T-mobile I thought that I would simply have to root and unlock the phone via some online tutorial and pop the SIM in, but to no avail. I can't find much info on the phone and it seems to only run CDMA. Nothing happens when I insert my SIM card. It is the ZTE Engage V8000. It is a Muve Music phone from Cricket.  I was wondering if I could just put Ubuntu for Phones on it and it would detect my SIM. Would that work? I feel like Ubuntu for Phones might be thrown out there enough for it to work. If not, how can I get my SIM card to work on the Android OS? Do I need to install a whole new operating system? Is there any way that I can use this phone? My current phone doesn't seem to have a strong enough antenna for my area. It's a cheapy knock-off from Hong Kong so anything else would work. Any help is much appreciated

With the announcement of the Ubuntu Phone OS I'd like to know what phone (and tablet) models are supported at this time.  Note from foss & Oli: We are making this the master question for all future "Will this work on <insert random tablet/phone/device here>?!" questions


Is there any point to using a ring flash for styles other than macro (i.e. portrait, landscape, wide angle, street, etc.)?

I just saw Death in Paradise Season 5 Episode 3, which features a photographer using a DSLR to shoot a fashion runway performance.  He had a flash that was a ring around the lens.   I thought that was for macro shots only, where the extreme close-up has trouble with normal flash placement.  For normal photos you want the flash far from the lens, like on a boom on a separate handle framing the camera.  I've seen some recent trendiness in having ring-shaped catch lights, but I supposed those would be positioned in the normal manner: off-angle from the lens.  I suppose if an on-camera had any effect at all it would be for some subtle fill flash.  Is this a realistic thing to see from a pro? Or is it just a cool-looking prop that doesn't really fit the situation?


What is the best and the easiest way to install a working and stable Sopcast-Player in Ubuntu?

I have tried to find some PPA's for Ubuntu 14.04 but didn't find any. So I tried to install the package for previous releases, with no luck and a lot of dependencies issues.


When I try to restart apache2 by using the command:  sudo service apache2 restart   It gives me this error:  Failed to restart apache2.service: Unit apache2.service is masked.   Is this a hosting-related problem?

root@gcomputer:~# systemctl status x11-common ● x11-common.service    Loaded: masked (/dev/null; bad)    Active: inactive (dead)   I tried systemctl unmask x11-common and systemctl unmask x11-common.service but that did not change anything.  How do I unmask it?


My 18yo niece and I made a contest: who can find more differences between the books and Game of Thrones TV show?  My question is not answered by  - that questions was (and has been closed as being) too broad. My question is more specific and I am focusing only on specific characters and how they are presented/missing/ending. Of course in the broad view the books and TV are different, look at my examples: characters that are missing, characters faith is different and characters that affect the plot, e.g. Lady Stoneheart changes the 4th book which is considered to be the worst of them.   The question  - I am asking also about characters that appear in ASoIaF and does not appear in GoT.  The questions  is limited to S3-S5 while I am asking about ALL Seasons (S1-S7) and ALL the Books.  My question is: Did we miss other characters that appear in the book and not on TV or vice versa?  Here are the differences we found (in no specific order):   Ser Barristan Selmy does not die in the book. On TV Ser Barristan Selmy dies in S5. Tyrion's face is horribly disfigured in the book. On TV Tyrion never loses his nose.  Shae uses Tyrion in the book. On TV Shae loves Tyrion and is even jealous when he marries Sansa Stark. The end of their relationship is the same in the book and on TV. Robb Stark marries Jeyne, Jeyne lives because Robb leaves his wife behind when he goes to his uncle's wedding at the Twins, a move that saves her life. On TV Robb Stark marries Talisa, Talisa dies with him in the Red Wedding. Lady Stoneheart is a zombified Catelyn Stark who kills everyone connected/related to The Red Wedding in the 4th book. On TV Lady Stoneheart is nowhere to be found. Donal Noye serves the Night's Watch in the books. On TV Donal Noye does not exist. Olly is not in the books at all. On TV Olly is a young boy living south of the wall and his village is sacked by wildlings, he joins the Night's Watch and becomes Jon Snow's assistant. Ygritte is killed anonymously in the books and everybody stabs Jon Snow. On TV Olly kills Ygritte and stabs Jon Snow. 'Reek' is Ramsay's servant in the books. On TV 'Reek' is a nickname Ramsay gives Theon. The Hound is killed(?) by one of Gregor's men in the books. On TV The Hound is nearly killed by Brienne. Princess Myrcella is wounded but doesn't die in the books. On TV Princess Myrcella is poisoned and dies. Varys stays in King's Landing in the books. On TV Varys leaves King's Landing. Shireen lives in the books. On TV Shireen Dies (burned to death in S5). Jaime and Cersei (After Joffrey dies) make mutual love in the books. On TV Jaime rapes Cersei in the hall where Joffrey's body on display. Mance Rayder escapes execution in the books, later it is revealed that the burning turns out to be a trickery. On TV Mance Rayder Dies. The Sand Snakes plans are foiled in the book. On TV The Sand Snakes take over Dorne Ramsay Bolton marries and rapes Jeyne Poole in the books. On TV Ramsay Bolton marries and rapes Sansa Stark.   My question is: Does anyone know/noticed other characters that appear in the book and not on TV or vice versa?  My question refers only to specific characters that appear in one but not the other. I am NOT asking for adaptation comparison!

I started out watching the Game of Thrones series (just about to watch season 4), then became intrigued enough to also read the A Song of Ice and Fire series (soon to acquire book 5).  Obviously a TV series cannot cover the detail one might expect in the books, so some characters from the books would not be mentioned in the TV shows, but it intrigued me that  (the prostitute that travels from Winterfell to King's Landing to continue her career) is in the TV series but does not appear anywhere in the books!  I guess she was inserted to allow the film makers to show aspects of certain characters and drive other bits of the story that were simplified/shortened & otherwise would have needed expounding.  Are there any other characters that are portrayed in GoT that are not in ASoIaF?


Scenario: I have created a lookup column  with two columns.  A department column and Expiration Date column.  Each Department has a Expiration Date.  For example see the image.  When the Department Expiration date is met or passed, I want the department to drop off the lookup column list.      Possible Solution:   1. Create the look up column and enter in the department names and expiration dates  I created a calculated column that filters the lookup column and the dates.  (I think)   This is the formula I used:  =DATEIF([DepartmentExpDate]=>TODAY,"")   The formula is not working.  I am not sure if any of this is correct.    Question:  How would I filter the lookup column to have the department drop off the list once the Expiration date equals today's date or passes automatically?

I have a list of departments. This list will change over time adding new departments and "deactivating" others (because of structural changes).  I would like to use this list as a look-up for other lists, but I would only want to look-up the active departments (can be detected by a bit field "Deactivated") which should be false, when the department is active.  I'm sure this can be done, but how?


I have a Java application, to start it I use     java -jar myapp.jar   To stop it I use CTRL+C.  Now I need to convert that application to something that I can start with:     /etc/init.d/myapp start   And I can stop with:     /etc/init.d/myapp stop   The problem is all about saving the PID of the process, I think I saw somewhere a recipe for doing this, I don't remember where and I'm not able to find it.  I saw that there is a project called , but I look for something free that does not limit memory usage. And I think that this work could be done in a single bash script.

I have a Java program that I'd like to daemonize on a linux system. In other words, I want to start running it in a shell and have it continue running after I've logged out. I also want to be able to stop the program cleanly.  I found  which uses a combination of shell scripting and Java code to do the trick. It looks good, but I'd like something simpler, if possible.  What's your preferred method to daemonize a Java program on a Linux system?


i want to write small select something like this   select t.id,func(t.name) from table t where func(t.name)>0   but i want to call function func only once  Can anybody help me?

I have a query which is meant to show me any rows in table A which have not been updated recently enough. (Each row should be updated within 2 months after "month_no".):  SELECT A.identifier      , A.name      , TO_NUMBER(DECODE( A.month_no              , 1, 200803               , 2, 200804               , 3, 200805               , 4, 200806               , 5, 200807               , 6, 200808               , 7, 200809               , 8, 200810               , 9, 200811               , 10, 200812               , 11, 200701               , 12, 200702              , NULL)) as MONTH_NO      , TO_NUMBER(TO_CHAR(B.last_update_date, 'YYYYMM')) as UPD_DATE   FROM table_a A      , table_b B  WHERE A.identifier = B.identifier    AND MONTH_NO > UPD_DATE   The last line in the WHERE clause causes an "ORA-00904 Invalid Identifier" error. Needless to say, I don't want to repeat the entire DECODE function in my WHERE clause. Any thoughts? (Both fixes and workarounds accepted...)


which is correct:  Thank you for your and your team's time  or  Thank you for yours and your team's time  and should (or does it make a difference if) I place commas before and after "and your team's"  ... thanks!!

Which of the following should I use?     Today is me and Joey's anniversary   Today is mine and Joey's anniversary


I'm searching for a simple solution for a prioritized power path controller to maintain a system supply line through a rechargable battery when the main supply fails.  My goal is to make the cheapest solution. During a long searching on the internet I came accross Ti's design . It uses a voltage window comparator and two couples of back-to-back mosfet for the changeover.  I studied the circuit (Page 8, Figure 4). carefully and I can see a basic problem here. Considering the secondary rail a Li-ion battery 3.7V and the primary rail with a significant greater voltage, for example >5V or >12V. In that case, when the primary rail fails, after the switchover and exactly after the Q1 is fully on (lowest Rds) the battery will see a charged capacitor (C1) with a primary's rail voltage, because when the mosfet is on it does allow the flowing of reverse current. If the load's current is very low, the Capacitor on the load will not discharge enough during the switchover and that remaining amount of voltage may cause damage to the battery.  I found that the problem is solved by ideal diode controllers or ORing controller but I wasn't able to find anything reasonable cheap. In addition, my circuit (load) demands current above 2.5A. Unfortunately, some embedded and cheap TI's chip, are capable to handle maximum 2A.  The TI's schematic above, does not implement any solution for reverse current blocking while the mosfets are on.

I've search for a solution to my problem both on this site and on Google but I did not find a complete and adequate response.  I need a circuit that switches two 12v sources (one that comes from a lead-acid battery powered by a solar panel and the other source comes from the output of a 220-12v switching power supply) without the final power output being interrupted during switching (this is very important!).  Notes:  - The final power output will be used to power 12v devices (30 Ampere maximum).  - The sources voltage range is 11-14.7v  How can I switch between two 12V sources?


I've been using Boot Camp with Windows 7 from almost the day I bought my MacBook Air in 2012. Recently, I noticed that I had a lot more free space in Windows than I needed so I shrunk it using Windows' built-in tools, intending to allocate that extra space to Mavericks.  I've been trying to expand my primary OSX partition and disk utility allows me to increase the size, but then when I press 'apply', a few messages show up above the button as if it is performing the change successfully, but then the partition layout diagram 'jumps' back to the original position.  I verified and repaired the disk (in recovery mode) due to inconsistencies but that still hasn't changed the behavior of disk utility.  I've also looked at the list of partitions from the command line, it it appears that the recovery partition is at the start of the free space, which the GUI app doesn't show at all. I assume Boot Camp moved every OSX related partition to be before Windows'. Here's the output of diskutil list:  $ diskutil list /dev/disk0 #:                       TYPE NAME                    SIZE       IDENTIFIER 0:      GUID_partition_scheme                        *121.3 GB   disk0 1:                        EFI EFI                     209.7 MB   disk0s1 2:                  Apple_HFS Macintosh HD            70.0 GB    disk0s2 3:                 Apple_Boot Recovery HD             650.0 MB   disk0s3 4:                  Apple_HFS Macintosh HD 2          19.9 GB    disk0s6 5:       Microsoft Basic Data Windows                 30.5 GB    disk0s4   So now I'm under the assumption that the resize is failing because of the recovery partition. Is there a way to move or copy the partition, or is there another way to reclaim the space as part of the main startup partition?  I forgot to mention that Macintosh HD 2 (19.9GB) is the empty space that I want to merge with Macintosh HD. Diskutil won't show an entry for unformatted space as far as I could tell.

I can't make my main Macintosh HD partition bigger. It's limited by the partition in the middle, which seems to be frozen, I can't move it down to make space for my main partition. Also I can't seem to delete it. The format of disk0s4 is Mac OS Extended (Journaled).  Some background, I created a partition to experiment with bootcamp to use windows. Once done I deleted that new partition, it became a no-man's land that neither partition can claim.  As a seperate issue, boot camp assistant has been giving me this error:   Anyone has any ideas? Much appreciated!  The closest problem I've found is here, this is a FAT partition.


I need to create a report where the number of columns changes based on the data being passed to iReport just like with a subreport. Is there a way to do this?

I'd like to show/hide a column at runtime based on a particular condition. I'm using "Print when expression" to conditionally show/hide this column (and it's header) in my report. When the column is hidden, the space it would have occupied is left blank, which is not particularly attractive.  I would prefer if the extra space was used in a more effective manner, possibilities include:   the width of the report is reduced by the width of the hidden column the extra space is distributed among the remaining columns   In theory, I could achieve the first by setting the width of the column (and header) to 0, but also indicate that the column should resize to fit its contents. But JasperReports does not provide a "resize width to fit contents" option.  Another possibility is to generate reports using the Jasper API instead of defining the report template in XML. But that seems like a lot of effort for such a simple requirement.


How can i make a new SSH user for linux (Ubuntu) which will allow the user only to access that folder and not to go back to other folder, I have searched many tutorials/support for this but those all didn't help me as it was working on the first time of login in SSH and when i go back to other folder and disconnects the ftp and reconnects it doesn't take me to the setted file.

I installed SSH, but I found if I use my original account to login to Ubuntu, it has too many permissions.  I want to constrain the user to only have permissions for specific folders in Ubuntu. How can I configure such a user?


I have a Lenovo u430 laptop and would like to dual boot Ubuntu and Windows 8. If I disable ueif can I do that and install Ubuntu with the installer?

I'm absolutely new to Linux. I would like to know how to install Ubuntu alongside the pre-installed Windows 8+ OS.  Should I do it with Wubi, or through the Live USB/DVD?  What steps do I need to take to correctly install Ubuntu?


Let $x=(n+1)!+2$. I get how to prove that $x$ or $x+1$ is prime, but there is a step in my book that proves that $x+i$ is prime like this:  $x+i=(1)(2)(3)(4)....(n+1)+(i+2)$.   But then it factors out to this:                $x+i=(1)(2)(3)(i+1)(i+3)...(n+1)+1$.  How does $i+2$ factor out to this?

I need help proving that for every positive integer $n$, there exist $n$ consecutive positive integers, each of which is composite. The hint that came with the problem is: Consider the numbers $2+(n+1)!,3+(n+1)!,...,n+(n+1)!,n+1+(n+1)!$.  I honestly have no idea how to begin here. I am specifically confused about what it means when it says "there exist $n$ consecutive positive integers". Does this mean that if $n = 5$, for example, then somewhere in the positive integers there are 5 consecutive composite integers, and that we want to prove that? I get that composite means that they are not prime, so they have more factors than 1 and themselves.  Any help would be greatly appreciated.  Thank you!


On my MacBook Air, I upgraded from Ubuntu 16.04 to Ubuntu 18.04. Everything is fine, but booting with Ubuntu takes approx. 6 minutes!  Running $ systemd-analyze time outputs:  Startup finished in 4.480s (kernel) + 6min 545ms (userspace) = 6min 5.026s graphical.target reached after 6min 535ms in userspace   The final part of $ systemd-analyze time:  ... [    7.005447] Bluetooth: BNEP socket layer initialized [    7.354030] IPv6: ADDRCONF(NETDEV_UP): enx00e04c6800c5: link is not ready [    7.359359] IPv6: ADDRCONF(NETDEV_UP): enx00e04c6800c5: link is not ready [    7.363620] IPv6: ADDRCONF(NETDEV_UP): wlp3s0: link is not ready [    8.977999] r8152 2-1.4:1.0 enx00e04c6800c5: carrier on [    8.978018] IPv6: ADDRCONF(NETDEV_CHANGE): enx00e04c6800c5: link becomes ready [  359.996525] random: crng init done [  693.520385] thunderbolt 0000:07:00.0: resetting error on 0:b. [  693.520465] thunderbolt 0000:07:00.0: 0:b: hotplug: scanning [  693.520471] thunderbolt 0000:07:00.0: 0:b: hotplug: no switch found [  693.820626] thunderbolt 0000:07:00.0: resetting error on 0:b. [  693.820711] thunderbolt 0000:07:00.0: 0:b: got unplug event for disconnected port, ignoring [ 1338.638266] thunderbolt 0000:07:00.0: resetting error on 0:b. [ 1338.638283] thunderbolt 0000:07:00.0: 0:b: hotplug: scanning [ 1338.638288] thunderbolt 0000:07:00.0: 0:b: hotplug: no switch found [ 1338.938543] thunderbolt 0000:07:00.0: resetting error on 0:b. [ 1338.938568] thunderbolt 0000:07:00.0: 0:b: got unplug event for disconnected port, ignoring [ 1357.411889] Bluetooth: RFCOMM TTY layer initialized [ 1357.411894] Bluetooth: RFCOMM socket layer initialized [ 1357.411900] Bluetooth: RFCOMM ver 1.11 [ 1358.945100] rfkill: input handler disabled   The etc/fstab file:  ... # <file system> <mount point>   <type>  <options>       <dump>  <pass> # / was on /dev/sda4 during installation UUID=2ef34bb8-5360-460a-8a8a-646d3a102a3a /               ext4    errors=remount-ro 0       1 # /boot/efi was on /dev/sda1 during installation UUID=67E3-17ED  /boot/efi       vfat    umask=0077      0       1 # swap was on /dev/sda5 during installation UUID=7c820859-65c5-44ac-9704-b3e0bb8c8020 none            swap    sw              0       0   How can I further troubleshoot and possibly solve this problem? Thank you in advance.  Mario

I'be been running 18.04 since a clean SSD install on the day of it's official release, without issues. Power on to login was seconds (max 10)  Then, I did a regular upgrade this morning:  $ sudo apt update && sudo apt dist-upgrade   The packages installed/upgraded were:  Install: linux-headers-4.15.0-24:amd64 (4.15.0-24.26, automatic), linux-headers-4.15.0-24-generic:amd64 (4.15.0-24.26, automatic), linux-modules-extra-4.15.0-24-generic:amd64 (4.15.0-24.26, automatic), linux-modules-4.15.0-24-generic:amd64 (4.15.0-24.26, automatic), linux-image-4.15.0-24-generic:amd64 (4.15.0-24.26, automatic) Upgrade: gnome-control-center-data:amd64 (1:3.28.1-0ubuntu1.18.04.1, 1:3.28.1-0ubuntu1.18.04.2), linux-headers-generic:amd64 (4.15.0.23.25, 4.15.0.24.26), gnome-control-center:amd64 (1:3.28.1-0ubuntu1.18.04.1, 1:3.28.1-0ubuntu1.18.04.2), linux-image-generic:amd64 (4.15.0.23.25, 4.15.0.24.26), linux-signed-generic:amd64 (4.15.0.23.25, 4.15.0.24.26), gnome-control-center-faces:amd64 (1:3.28.1-0ubuntu1.18.04.1, 1:3.28.1-0ubuntu1.18.04.2), linux-generic:amd64 (4.15.0.23.25, 4.15.0.24.26)   I rebooted once the upgrade had completed, and noted a 2-3 minute delay on the Ubuntu loading/splash screen (prior to login) (without any progress/activity indicated on the dots).  I powered off and tried to boot again, but am getting this delay consistently now. Also close down is much slower too.  Update #1 (2018-07-03): Analysis on systemd:  $ sudo systemd-analyze blame 3min 53.073s plymouth-quit-wait.service     2min 20.699s snapd.seeded.service          49.949s snapd.service           6.186s NetworkManager-wait-online.service           1.148s dev-sda2.device           1.098s plymouth-start.service   Showing that plymouth-quit-wait.service (which I now believe is related to the Ubuntu loading/splash screen) and snapd.seeded.service were by far the longest running services to initiate. So I compared the times before the dist-upgrade and after:  $ journalctl -u plymouth-quit-wait.service --since today -- Logs begin at Fri 2018-04-27 13:01:30 BST, end at Tue 2018-07-03 12:38:05 BST. -- Jul 03 04:15:43 user-laptop systemd[1]: Starting Hold until boot process finishes up... Jul 03 04:15:46 user-laptop systemd[1]: Started Hold until boot process finishes up. -- Reboot -- Jul 03 04:21:17 user-laptop systemd[1]: Starting Hold until boot process finishes up... Jul 03 04:24:52 user-laptop systemd[1]: Started Hold until boot process finishes up.   Before the upgrade plymouth-quit-wait.service took 3 seconds. After the upgrade it took 3 minutes 35 seconds  $ journalctl -u snapd.seeded.service --since today -- Logs begin at Fri 2018-04-27 13:01:30 BST, end at Tue 2018-07-03 12:42:14 BST. -- Jul 03 04:15:43 user-laptop systemd[1]: Starting Wait until snapd is fully seeded... Jul 03 04:15:43 user-laptop systemd[1]: Started Wait until snapd is fully seeded. -- Reboot -- Jul 03 04:22:47 user-laptop systemd[1]: Starting Wait until snapd is fully seeded... Jul 03 04:24:49 user-laptop systemd[1]: Started Wait until snapd is fully seeded.   Before the upgrade snapd.seeded.service took 0 seconds. After the upgrade it took 2 minutes 2 seconds.  Update #2 (2018-07-06): This morning's boot saw the return of the delay. So I guess we're still waiting for the kernel/plymouth/snapd update.  Update #3 (2018-07-12): The problem seems to be resolved, but I didn't see any update to snap or plymouth, and I'm still running 4.15.0-24 kernel. So I'm not sure which package update fixed the problem, or if it just resolved itself somehow. Reading the bug updates on launchpad it's unclear to me what was done (or is being done) to what package/s. If anyone can clarify that would be very useful.


Let (X, d) be a metric space. Show that the metric d is continuous. A metric space is a pair (X, d), formed by a nonempty set X and a function d: X × X → R≥0, called the distance or metric function of X, such that  d (x, y) = 0 if and only if x = y, d (x, y) = d (y, x) for all x, y ∈ X d (x, y) ≤ d (x, z) + d (z, y) for all x, y, z ∈ X please help

Given a metric space $(X,d)$, how to prove that the function $d \colon X \times X \to \mathbf{R}$ is continuous?   If we take any two arbitrary real numbers $a$ and $b$ such that $a < b$, then we need to show that the set $d^{-1} (a,b)$ given by   $$ d^{-1} (a,b) :=  \{ (x, y) \in X \times X | a < d(x,y) < b \} $$  is open in the product topology on $X \times X$.   A basis for this product topology is the collection of all cartesian products of open balls in $(X,d)$.


I'm trying to write a function that returns:  ['cat', 'cot', 'cut']   When passed this list:  ['c', 'aou', 't']   But would also return:  ['cats', 'catz', 'cots', 'cotz', 'cuts', 'cutz']   When passed:  ['c', 'aou', 't', 'sz']

How can I get the Cartesian product (every possible combination of values) from a group of lists?  Input:   somelists = [    [1, 2, 3],    ['a', 'b'],    [4, 5] ]   Desired output:  [(1, 'a', 4), (1, 'a', 5), (1, 'b', 4), (1, 'b', 5), (2, 'a', 4), (2, 'a', 5) ...]


So I’ve become fairly used to Ubuntu and plan to make it my main OS. In fact it’s already my main OS I never use windows anymore and I have nothing important saved on my windows OS so how would I go about uninstalling it after I’ve already dual booted it with windows?

I downloaded Ubuntu 12.04 LTS to my Dell Dimension 4600 with Windows XP installed.  I now have a neat dual-boot system, but I want to get rid of the XP OS and keep Ubuntu as my only OS.  How do I do this?


Sometimes we add a file readme.txt in our folder for notes or things to know about.  Using Markdown, it is pretty easy to make it into a nicely formatted document. Can we write a README.md and can use any free and reliable app and use the Mac to read it?  (So far I know  which can be activated by using the keyboard shortcut Control + Shift + M, but if there is a one click preview app, it'd be the best. There is , but I am wondering if I should alter my OS? If there is a trustworthy app that can do it, it'd be best).

Is there an application to preview markdown files (.md files) on OSX (for instance on Maverick)?


I've got very basic HTML/CSS code. I am trying to center everything inside the center class using flex box but it is not working. I've managed to center the content horizontally but not vertically. Any idea hat am I missing?   .content {   display: flex;   flex-direction: column;    align-items: center;   justify-content: flex-start; }  .searchContainer {   display: flex;   flex-direction: row; } <!DOCTYPE html>         <meta charset="UTF-8" />     <meta name="viewport" content="width=device-width, initial-scale=1.0" />     <title>Document</title>     <link rel="stylesheet"/>           Header

Find Your Next Thing

SearchBar

SearchButton

I want to center a div vertically with CSS. I don't want tables or JavaScript, but only pure CSS. I found some solutions, but all of them are missing Internet Explorer 6 support.
Div to be aligned vertically
   How can I center a div vertically in all major browsers, including Internet Explorer 6?


I downloaded Ubuntu 18.04.3 but cannot install until I go through the "verification" process.  As a new user, I do not understand or really have time for learning the nuances of Linux, that can come later; I just want to donwnload, install and use the program.  Sick of Windows 10, want to get away from it.  Thanks in advance.

I would like to see a full how-to guide on how to install Ubuntu.


In the below code I got a NullPointerException:  Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException  timer.setInitialDelay((int) delay);   I tried to add     //timer = new Timer(0, null); long delay = dates.getTime() - System.currentTimeMillis();   timer = new Timer(0, null);   new TimerStart();   if (delay >= 0) {    timer.setInitialDelay((int) delay);    timer.restart();   }   to avoid the Exception, it works but doesn't trigger the timer ?  With this Example it works with timer trigger too, but how could it be corrected in the code above :  import java.awt.BorderLayout; import java.awt.event.ActionEvent; import javax.swing.JFrame; import javax.swing.JLabel; import javax.swing.JPanel; import javax.swing.JSpinner; import javax.swing.SpinnerDateModel; import javax.swing.SpinnerModel; import java.util.Date; import javax.swing.Timer; import javax.swing.event.ChangeEvent; import javax.swing.event.ChangeListener;  public class SpinnerTest {   Timer timer;  Date date;  public static void main(String args[]) {    new SpinnerTest().startApp();  }   private void startApp() {  JFrame frame = new JFrame("JSpinner Sample");  frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);   date = new Date();  SpinnerModel model1 = new SpinnerDateModel(date,null,null,0);  JSpinner spinner1 = new JSpinner(model1);   spinner1.addChangeListener(new CalendarListener());  spinner1.setEditor(new JSpinner.DateEditor(spinner1, "HH:mm dd-MM-yyyy"));   JLabel label1 = new JLabel("Times/Dates");  JPanel panel1 = new JPanel(new BorderLayout());  JPanel panel2 = new JPanel(new BorderLayout());   panel2.add(label1, BorderLayout.WEST);  panel1.add(spinner1, BorderLayout.CENTER);   frame.add(panel1, BorderLayout.CENTER);  frame.add(panel2, BorderLayout.WEST);   frame.setSize(200, 90);  frame.setVisible(true); }   private class CalendarListener implements ChangeListener {    @Override    public void stateChanged(ChangeEvent e)  {     JSpinner jSpinner = (JSpinner) e.getSource();     date = (Date) jSpinner.getValue() ;     long delay = date.getTime() - System.currentTimeMillis();     //System.out.println(delay);     timerStart();     if (delay > 0) {     timer.setInitialDelay((int) delay);     timer.restart();    }   }     }  private void timerStart() {      this.timer = new Timer(Integer.MAX_VALUE, (ActionEvent evt) -> {      System.out.println("okey");     });}    }

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 getting an error about an operation involving a QPyNullVariant:  TypeError: unsupported operand type(s) for *: 'QPyNullVariant' and 'float'   I wanted to put a check into my code to skip these values. However, my IDE (Eclipse) [and more over the terminal Python interface] doesn't recognize this as part of the PyQt4.QtCore module whereas it seems fine within QGIS. I have updated all my packages and restarted my computer.  import PyQt4.QtCore as pyqt import sys print(sys.version)    #1 print(pyqt.__file__)  #2 pyqt.QPyNullVariant   #3   in all cases this produces the following out put for 1 and 2:  2.7.6 (default, Jun 22 2015, 17:58:13)  [GCC 4.8.2]  /usr/lib/python2.7/dist-packages/PyQt4/QtCore.so   However in Eclipse (with PyDev) and in the terminal interpreter the call to PyQt module for a QPyNullVariant attribute fails:  AttributeError: 'module' object has no attribute 'QPyNullVariant'   whereas in the QGIS python interpreter you get:  <class 'PyQt4.QtCore.QPyNullVariant'>   Thoughts?

I have read post on that problem (). The problem is even with a sys.path.append it couldn't import processing. It's very frustrated. Here the code I used:  #!/usr/bin/python  def main():     layer = QgsVectorLayer('/path/to/file.shp', "BAT","ogr")     QgsMapLayerRegistry.instance().addMapLayers([layer])      # Testing processing     try :         Processing.runalg("qgis:creategrid")     except:         print "Processing module has not been loaded"      #Check the QgsMapLayerRegistry for the layers     print QgsMapLayerRegistry.instance().mapLayers()     # Check if they are valid     print layer.isValid()  if __name__=="__main__":     import sys     from PyQt4.QtGui import *     from qgis.core import *     app = QApplication([])     QgsApplication.setPrefixPath("/usr", True)     QgsApplication.initQgis()      sys.path.append('home/qsuser/.qgis2/python/plugins')      # try to load processing     try:         from processing.core.Processing import Processing         Processing.initialize()      except:         print "unable to load processing"      main()      QgsApplication.exitQgis()   I could load QGIS and layer is valid that's ok, but processing resist to me. I am on Ubuntu 14.04 I use Pycharm to do it.  I tried on terminal with the python console, it raised this error:  Traceback (most recent call last):   File "<stdin>", line 1, in <module>   File "/usr/lib/python2.7/dist-packages/qgis/utils.py", line 572, in _import     mod = _builtin_import(name, globals, locals, fromlist, level)   File "/home/qsuser/.qgis2/python/plugins/processing/__init__.py", line 28, in <module>     from processing.tools.dataobjects import *   File "/usr/lib/python2.7/dist-packages/qgis/utils.py", line 572, in _import     mod = _builtin_import(name, globals, locals, fromlist, level)   File "/home/qsuser/.qgis2/python/plugins/processing/tools/dataobjects.py", line 35, in <module>     from processing.core.ProcessingConfig import ProcessingConfig   File "/usr/lib/python2.7/dist-packages/qgis/utils.py", line 572, in _import     mod = _builtin_import(name, globals, locals, fromlist, level)   File "/home/qsuser/.qgis2/python/plugins/processing/core/ProcessingConfig.py", line 30, in <module>     from PyQt4.QtCore import QPyNullVariant, QCoreApplication, QSettings ImportError: cannot import name QPyNullVariant   I don't know what I am missing.   Settings :  Qgis 2.12.1-Lyon Ubuntu 14.04 Trusty IDE : Pycharm 5 community Processing : 2.12.2   -- Edit -- And with the changes suggest by mathias kuhn  #!/usr/bin/python  def main():     layer = QgsVectorLayer('/path/to/file.shp', "BAT","ogr")     QgsMapLayerRegistry.instance().addMapLayers([layer])      # Testing processing     try :         Processing.runalg("qgis:creategrid")     except:         print "Processing module has not been loaded"      #Check the QgsMapLayerRegistry for the layers     print QgsMapLayerRegistry.instance().mapLayers()     # Check if they are valid     print layer.isValid()  if __name__=="__main__":     import sys     from qgis.core import *             from PyQt4.QtGui import *     app = QApplication([])     QgsApplication.setPrefixPath("/usr", True)     QgsApplication.initQgis()      sys.path.append('home/user/.qgis2/python/plugins')      # try to load processing     try:         from processing.core.Processing import Processing         Processing.initialize()      except:         print "unable to load processing"      main()      QgsApplication.exitQgis()


I have a data set with 40 participants that underwent 20 different tests. For most of these tests all the data is there. For 2 of the 20 tests, 2 out of the 40 values are missing. However, for 5 of the tests (due to financial limitations and this test being expensive) we only about 25 participants have data. Is it possible to fill in those remaining 15 values for those 5 tests using data imputation or is that too many values missing?

Currently I am working on a large data set with well over 200 variables (238 to be exact) and 290 observations for each variable (in theory). This data set is missing quite a lot of values, with variables ranging from 0-100% 'missingness'. I will eventually be performing logistical regression on this data, so of my 238 columns I will at most only be using ten or so.  However as almost all of my columns are missing some data, I am turning to multiple imputation to fill in the blanks (using the MICE package).  My question is; given that I have a large amount of variation in the missing data, at what percentage missing should I start to exclude variables from the mice() function?   Can mice function well with variables that are missing 50% of their values? What about 60%, 70%, 80%, 90%?


Is there a rule regarding the use of there is vs there are at the start of a list containing both singular and plural nouns? For example; There is an apple, an orange, a carrot and some bananas in the bag. Sounds incorrect to me even though the 1st noun is singular, however there are does not sound much better... There are an apple, an orange, a carrot and some bananas in the bag. There are some bananas, an apple, an orange and a carrot in the bag, sounds OK as the 1st noun is plural. Is there a better way of writing this? The text is being automatically generated by a computer programme.

It seems I put a   Bounty assigned by outside party, two lengthy, reference-citing answers, one "-1" (awarded the bounty), one "-2", two others scored "0" and "-2" respectively, the answers suggesting one or the other is correct, 73 comments and no consensus so far - and me, as the asker, lost without a clue what to think of the answers anymore -  this is no longer "Learners' Level" question, so I thought I'd bring it here and hear what the experts have to say.    Original question:  Plurality of verb depending on plurality of list elements  An edit was suggested to my sentence.     There was were an orange, some grapes, two apples and a small pile of cherries on the plate.   In my native language plurality of the verb always follows plurality of the first element on the list. There were an orange,... sounds awkward to me, no matter what follows up. My simple solution was reordering:     There were some grapes, an orange, two apples and a small pile of cherries on the plate.   But that's not the first time I faced this situation and I'd like to know what the rules of grammar say about that - was my editor overzealous or am I trying to copy rules of my language that don't apply in English?    Someone linked a  for negatives, where the situation is more clear-cut ("There is no..."). Same applies to connection with "or" apparently, per accepted answer there. Still, nothing for "and".  It seems there is a consensus that in that if the verb goes after the list, it will be plural.     an orange, some grapes, two apples and a small pile of cherries were on the plate.   There doesn't seem to be clear consensus for:     On the plate { was | were } an orange, some grapes, two apples and a small pile of cherries   Adding more to the confusion is the abbreviated form: "There's"     One last note. In North America, at least, there is a widespread use of using a singular form like "there is" and "there was", without regard for the subject item or items, and this "there is" is often shortened to "there's":           There's three apples on the table!      Could you please clarify this mess?


To my understanding (which is pretty basic), energy is the ability to do work. But if for example, I push a wall, I do exhaust my energy, but no work is done since the wall is not moving. So what is happening to the energy? Thanks.

I read the definition of  as  $$W ~=~ \vec{F} \cdot \vec{d}$$  $$\text{ Work  =  (Force) $\cdot$ (Distance)}.$$ If a book is there on the table, no work is done as no distance is covered. If I hold up a book in my hand and my arm is stretched, if no work is being done, where is my energy going?


Windows 10 Professional (10.0.17134.228) and iPhone 6 (iOS 11.4.1). iTunes is not installed, can't have it, and don't want it. (Work computer) Under:      C:\Program Files\Common Files\Apple , there is no    \Mobile Device Support\Drivers   When I connect iPhone to USB for charging, there's no pop-up message in Windows, but a popup to allow this device on iPhone, every time!  How do I get rid of it?  The most commonly cited fix, updating driver manually pointing it to the folder mentioned above is not (!) an option, since the path is incomplete, meaning folder/s mentioned are missing.

I have an iPhone at work, and I charge it by connecting it to my work laptop (Windows 7) via USB. Every damn time I do this, the phone asks me to Allow this device to access photos and videos? with the choices Allow and Don't allow.   I want to say never allow because I don't want any data connection at all but Apple has not provided this useful choice. What workaround can I use?  Note: I would just use a wall charger instead but there are no power sockets in my workspace.    added: The phone is listed as an Unspecified device under Devices and printers. When I open the properties, it just says This device is working properly. and I am not allowed to update the drivers. See screenshot:


I'm making a windows 10 bootable usb device to boot from because I forgot the admin password for my main computer via a fedora virtual machine on virtualbox(was installed before I forgot)  do I need mkfs.ntfs? seems to me that parted or fdisk already does the job with regards to formatting the file system as ntfs. Is this the case or did i misread something? What exactly is mkfs.ntfs meant to do?

I'd like to create a Windows bootable USB stick, but I don't have a Windows machine with me at the moment to do so. How could I achieve the same using Ubuntu?


About $\frac{\partial^n f}{\partial x^n}$ ,for $f(x)$,What should I think, when $n[\in (\mathbb R\backslash \mathbb Q)^+]$ ,pozitive irrational? or  $(\in \mathbb C)$  For example;  $f(x)=x^2+3x\quad$  and $\quad n=\sqrt2\quad\to\quad \dfrac{\partial^{(\sqrt 2)} f}{\partial x^{(\sqrt2)}}=?$  and,  $f(x)=x^2+3x\quad$ and $\quad n=\sqrt i\quad\to\quad\dfrac{\partial^{(\sqrt i)} f}{\partial x^{(\sqrt i)}}=?$  And I think,I did grammar mistakes in the tittle, sorry about this.

I need to find the $k$'th derivative of $1/p(x)$, where $p(x)$ is a polynomial and $k\in\mathbb{R}$  It dosen't have to be an explicit formula, an algorithm which finds a formula for some $k$ is fine.


Has anybody found any loop holes to FRP BYpass for this ZTE model Android?  Plz do share!

I won a Samsung Galaxy S6 Edge, signed into it with my Google account, played around with it, wiped it, and sold it.  Now the person can't get past setup because it's saying he must login with an account previously synced to the phone.   Is there anything I can do from my side to remove this lock?


I'm initializing using public static ThreadLocal<AtomicLong> count = new ThreadLocal<>();  How do I use AtomicLong method for count? The below throws a NPE:  count.get().addAndGet(records.size());

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 found the following code. But I can't undestand what it is. Looks like inner class. But seems very strange. What is is? How can we define class and create it? As I know here must be inheritance from  DefaultHandler, but where is it?  DefaultHandler handler = new DefaultHandler() { boolean bfname = false; ...  public void startElement(String uri, String localName,String qName,      Attributes attributes) throws SAXException { ... }  public void endElement(String uri, String localName,    String qName) throws SAXException { ...  }  ...  };

What is the use of anonymous classes in Java? Can we say that usage of anonymous class is one of the advantages of Java?


I need a list of all sobject records that got modified today. this is not just for one object but for all objects in the system. Is there a simpler way to do this?  Please reply.


Completely newby question please. I always had shared hosting. Now I am about to get a dedicated Centos server. I now need to know whether I should get a managed one or not. 2 questions please:   Whats the learning curve (approx. days/months) assuming I am a fast learner? If I managed it myself, how much of my time (approx. each day) do I need to commit in managing the server? (Assuming normal circumstances).    thank you for any help!

This is a  about System Administration Careers   When I start my job as System Administrator, what basics skills should I know/learn?  Are there any key differences for Network, Storage, Database, and other Administrators?


I have libertine as my base font. While using pgfplots to plot a graph, the axis labels do appear in the base font, but the tick label numbers revert to default computer modern. I have tried using tick label style={font=\normalfont} but no avail. How can I get the base font of the document on the tick label numbers? MWE \documentclass{article}  \usepackage{libertine}  \usepackage{pgfplots}  \begin{document}  \begin{tikzpicture} \begin{axis} [xlabel={Time 123(s)} ,ylabel={Distance (in)}, tick label style={font=\normalfont}] \addplot [red,mark=*,line width=1.pt] coordinates { (1,0.25) (2,1) (3,2.25) (4,4) (5,6.25) (6,9) }; \end{axis} \end{tikzpicture}   \end{document}

I am using a sans font for my figures. Hence I also want the tick labels of the pgfplots to be in sans. The tick labels, however, are set in a math enviroment. So changing the text font does not change anythings here. I have seen a  here on tex.SE. The problem is that get many error messages like that:  ! LaTeX Error: Symbol font `um_fam1' not defined.  See the LaTeX manual or LaTeX Companion for explanation. Type  H <return>  for immediate help.  ...                                                l.23        \end{axis}   I think the problem is that a non-math font is used with unicode-math, which is not the intended use case for unicode-math. I really tried many ways to change the math font to sans, see for example , but the essence is that a sans math font is not possible.  Since it is not possible to use a sans math font, maybe it is possible to change the pgfplots to use not an mathematical enviroment. I'm asking here, if it is possible to patch pgfplots to use an non mathematical enviroment for the tick labels? I understand this enviromnent is needed for fractions or some log scales. But I actually don't use those. So I'm fine with a solution ignoring those cases. The only important characters are digits and commas.  % !TeX program = lualatex \documentclass{article}  \usepackage{siunitx} \sisetup{locale = DE}  \usepackage{unicode-math} \setmainfont[Ligatures=TeX, Numbers=OldStyle]{TeX Gyre Pagella} \setmathfont{TeX Gyre Pagella Math} % In reality I do not use Adventor but another sans font \setsansfont{TeX Gyre Adventor}  \usepackage{pgfplots} \pgfplotsset{compat=1.10} \SendSettingsToPgf  \begin{document}     \begin{tikzpicture}[font=\sffamily]         \begin{axis}[xlabel=x direction, ylabel=y direction, xmin=-1, xmax=1,domain=-1:1]             \addplot {x^2};         \end{axis}     \end{tikzpicture}      \textsf{1,2,3,4,5,6,7,8,9,0} \end{document}


Next year we plan on flying to Florida, spend a few days there and then fly to South America and spend five nights there, then fly back to Florida and spend a week there and fly back home (We are British citizens). We were planning on using an ESTA to enter but we have a question:  Will we need to apply for two ESTA, for both entries to the US or can we use the same one and leave and comeback?

I am visiting the US in August 2014 for a week, returning home to the UK & will then be visiting for another 2 weeks in October 2014.  My question is, can I use the same ESTA or would I need to reapply for the second visit? I think the ESTA lasts 90 days but I am unsure if you can leave & re-enter?


I'm taking an intro to android programming course running into some issues adding to the sqlite database  Any suggestions what might be causing this error. I think it is related to not having the proper assignment to the mDatabase field variable.   It seems like the issue is that mDatabase variable in the addCustomer function needs different context.    private static ContentValues getContentValues(Customer customer) {       ContentValues values = new ContentValues();       values.put(UUID, customer.getId().toString());       values.put(FULL_NAME, customer.getName());       values.put(ADDRESS, customer.getAddress());       values.put(CREDIT_CARD_NUMBER, customer.getCreditCardNumber());       values.put(EMAIL, customer.getEmail());       values.put(SESSIONS_REMAINING, customer.getSessionsRemaining());       values.put(PRINT_RECEIPT, customer.getPrintReceipt() ? 1 : 0);       values.put(EMAIL_RECEIPT, customer.getEmailReceipt() ? 1 : 0);       return values;   }    public void addCustomer(Customer c) {      ContentValues values = getContentValues(c);      mDatabase.insert(CustomerDbSchema.CustomerTable.NAME, null, values);      Log.d("DATABASE", "Customer Added");   }    File Links on Github below:


I have a copy of an existing database with existing records. when i was playing around with the table designer and noticed some of the column names have [] around them. they all seem to be arbitrary typed (float, datetime, netext, nvarchar etc) and there is nothing in column properties that gets rid of the []. I tried to rename delete the [] but it reappaears as soon as I exit edit.   according to  post, it is a keyword column for xml columns? but none of those columns are xml columns. Would someone kindly explain the purpose of this to a ms-sql newbie? thanks

I've noticed that Visual Studio 2008 is placing square brackets around column names in sql. Do the brackets offer any advantage? When I hand code T-SQL I've never bothered with them.  Example:  Visual Studio:  SELECT [column1], [column2] etc...   My own way:  SELECT column1, column2 etc...


I have an SVG graphic represented in a string svg_string='<svg height="100" width="500"><ellipse cx="240" cy="50" rx="220" ry="30" style="fill:yellow" /><ellipse cx="220" cy="50" rx="190" ry="20" style="fill:white" /></svg>'  I want to display the graphics represented by svg_string, which is 2 ellipses, on a window initiated from Python. The pseudo code of which should be something like import pygame   def display_svg_figure(screen, svg_string):     #   Code that draws the rendered SVG string on     #   the screen     pass  background_colour = (255, 255, 255) (width, height) = (900, 900)  screen = pygame.display.set_mode((width, height)) pygame.display.set_caption('Display SVG') screen.fill(background_colour)  pygame.display.flip()  svg_string='<svg height="100" width="500"><ellipse cx="240" cy="50" rx="220" ry="30" style="fill:yellow" /><ellipse cx="220" cy="50" rx="190" ry="20" style="fill:white" /></svg>' display_svg_figure(screen, svg_string)   running = True while running:     for event in pygame.event.get():         if event.type == pygame.QUIT:             running = False  I am basically looking at an implementation of the method display_svg_figure(screen,svg_string) I am open to a using non pygame libraries too as long as it follows the simple interfaces of the following and is possible to include it in pygame from SOME_LIBRARY import SOME_COMPONENT  svg_string="......" SOME_COMPONENT.display(svg_string)  I have already looked at pynanosvg but that's no longer supported and is failing so does not suffice my need. The solution given in  does not seem to fit the bill as it is not working in PyGame. If someone can make it work kindly let me know.

In a  application, I would like to render resolution-free GUI widgets described in SVG.  What tool and/or library can I use to reach this goal ?  (I like the  toolkit but it seems to be bitmap dependent for its rendering)


I'm new to Ubuntu and I'm not sure which version to install.  Which offers better performance? Which would you recomend? Thanks in advance.

What are the differences between an Ubuntu Long Term Support release (LTS) and a normal release?


If Liouville’s theorem states that an area in phase space doesn't change, then can the area go scattered, but with total area conserved? If not, wouldn't it be contradicted to the entropy law?

The second law says that entropy can only increase, and entropy is proportional to phase space volume. But Liouville's theorem says that phase space volume is constant.  Taken naively, this seems to imply that the entropy can never change. What's wrong with the reasoning here?


I live in Serbia and have 2 passports, a Serbian and a Croatian. My Croatian passport allows me to travel freely in Europe (for the time being! ;-) )  I'm flying to the US and have got a VISA under my Serbian passport. I'm flying back from the US via London. If I use my Serbian passport at passport control in London, I won't be let in as I need a VISA to the UK which I don't have! uh oh!   However, if I show my Croatian passport at passport control (where I don't need a VISA to the UK as it's my Croatian passport, you get where I'm going with this? ;-) ) will that be ok?  I'm worried that when they scan my Croatian passport, it won't sync with a ticket or a departure terminal), can anyone offer advice on this?  Any advice would be greatly appreciated.  Thanks,  Vlada

I am a citizen of two different countries, and have two passports.  How should I use my passports when traveling?


If I understand it a bit the standard answer for this is: the pushing/holding apart of fermions and the pulling/holding together of bosons is just a result of symmetrization requirement (Griffths' term). But if it does force particles to move or be in a certain place, how come it is not a force? Is this just a way to say it is not the result of any of the four fundamental interactions?

It is commonly known that it is the electron degeneracy pressure that prevents the collapse of a white dwarf into a neutron star, and it is not the electromagnetic force. However, it is also widely accepted that all the forces in the universe are just manifestations of the four elementary forces in the universe. So can the degeneracy pressure, caused due to Pauli's Exclusion principle, be shown to be due to one of these forces? I have read some other questions in SE , , and they do not answer my question fully.  In one of the links, the degeneracy pressure is described as an 'entropic force', but as far as I understand, all entropic forces can be explained by the underlying fundamental forces. If the degeneracy pressure is something that is fundamentally different from the other forces, why isn't it classified as a separate force?


in QGIS 2.18.3, Windows 10, I've got a raster file in which each color defines a type of crop. See image:    Each cell value represents a type of crop. What I need to do is to extract to a new file, only the cells containing a certain value (e.g., the value 24 which corresponds to the brown cells) Ultimately, the objective is to calculate the surface of each crop within a given area.  Is there any process that can help me with this analysis?

I want to extract certain values of a raster image in order to create a new raster which then should only contain the extracted/chosen values.  How to do this in QGIS?


When doing a project in QGIS it is very hard to find a satellite images suiting to be used as the BASE MAP of my project. Therefore, I would like to have a Google or Bing or Esri like BASE MAP as the Base Map of my project Therefor please explain, How to add a Satellite or Terrain or Satellite/Terrain Street Hybrid Base Map to my QGIS project which will be Automatically Updating.

ArcGIS Desktop has the option of using basemaps from ArcGIS Online. Does QGIS have any such options?


Inside my string there a one or more occurrences of a tag starting with [foo] and ending with [/foo]. So imagine a string like this:  string = "[foo] Text inside tags [/foo] Text between tags [foo] Text inside tags [/foo]"   I want to capture the text inside each occurrence. If there were just one occurrence my regex could simply be:  regex = /\[foo\](.*)\[\/foo\]/   As anything could be inside the tags I have to capture it with .*. However by doing that I end up capturing everything between the first [foo] and the last [/foo]:  < string.scan(regex) => [[" Text inside tags [/foo] Text between tags [foo] Text inside tags "]]     How do I avoid this?

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


I am frequently using ssh terminal. If I enter a command that spans multiple lines, the characters which do not fit onto the first line are going to the beginning... not of the next but of the current line! As if no \n, but just \r was inserted. This get even more messed up when I am scrolling up the history, as the terminal starts to delete previously output lines, and if I delete some characters in a previously used multiline command, not only that character but a whole previous line gets deleted.  The bash version on the server I am connecting to is 2.05b.0(1) (yep, that old - ask our server administrator). SSH version is OpenSSH 7.4.

I have an issue with my terminal prompt line. When the line is too long it wraps on the same line and then Up arrow makes it look even worse.   I have already checked , but it looks like I am apparently closing all the squared brackets for non printable characters.  This is my PS1:   \[\e]0;\u@\h: \w\a\]${debian_chroot:+($debian_chroot) }\[\033[01;36m\]\u@\h\[\033[00m\]\033[01;34m\]\w\033[00m\][$(type __git_ps1 >/dev/null 2>&1 && __git_ps1 "(%s)")]   Consider this as my standard prompt line   MELISC@work~/dev/bin_tools[((main))]   I was able to get  assdasdasdasdasdadasdsadadasdaddasdadadasdadsadasdsa((main))] asdsadsadsadsadasdasdassdasdasdassdasdassdasdasdasdasdasdasdsadsad   I have already checked my .bashrc  I have and shopt -s checkwinsize should autocheck the columns


I'll be getting a laptop soon. It only has 500 gigs. Windows is for gaming and Ubuntu for fun stuff.    Should I go 150:350gigs, or 200:300? Do I make 4 partitions (os+data) for each os, or do I just flop windows on one partition?   2.a Is it customary on Linux to have two partitions?   Should I make the Ubuntu partitions when creating Windows, or should I make 1 or 2 partitions for Windows, and let the rest be unallocated space, and then the Ubuntu installer will recognize that and let me format it? How can I prevent windows from accessing my Ubuntu drives, while ubuntu being able to access windows? The goal is that windows doesn't steal my data. Do I need to worry about the UEFI thingie?

I'm absolutely new to Linux. I would like to know how to install Ubuntu alongside the pre-installed Windows 8+ OS.  Should I do it with Wubi, or through the Live USB/DVD?  What steps do I need to take to correctly install Ubuntu?


Let $\square ABCD$ be a square with sides $r$. Draw a quarter circle starting in each corner, as pictured below. The question is wheter there exists some elementary method to figuring out the value of the padded square in the middle ($z$).    Using integration we can see that   $$ z = 4\int_{r/2}^{\sqrt{3}r/2} \biggl( \sqrt{a^2-x^2} - \frac{a}{2} \biggr) \mathrm{d}r = \frac{r^2}{4}(3 + \pi - 3\sqrt{3}) $$  However, this is far from something a high-school student could come up with. I tried to create a system of equations   $$ \begin{align*}     4x + 4y + z & = r^2 \tag{1} \\      2x + 3y + z & = \frac{\pi r^2}{4} \tag{2}  \end{align*} $$  Alas, I was unable to find a third linear independent equation describing the system.

Let the centers of four circles with the radius  $R=a$ be on 4 vertexs a square with edge size $a$. How calculate the shaded area in this picture?


public class StringEqual   {  public static void main(String[] args)    {   String str1 = "abcd";   String str2 = "abcdefg";   String str3 = str1 + "efg";   System.out.println("str2 = " + str2);   System.out.println("str3 = " + str3);   if (str2 == str3)   {      System.out.println("The strings are equal");   }   else   {      System.out.println("The strings are not equal");   }    }   }   so far i've created this code. Now i am trying to figure out how do i make it so that str2 and str3 are equal when they are compared?

I've been using the == operator in my program to compare all my strings so far. However, I ran into a bug, changed one of them into .equals() instead, and it fixed the bug.  Is == bad? When should it and should it not be used? What's the difference?


Let me know how to align text in the center of 'p' element.  I think Aligning text in p element is not same as aligning text in div element.   <!DOCTYPE html>
This is some text in a paragraph.
                     Thanks in advance     I am expecting like this:

How can I horizontally center a
 within another
 using CSS?

Foo foo


Interesting thing I tried on a test site: I switched permalink structure from date/postname to postID/postname. From WordPress Permalinks panel - no plugins, no .htaccess entries, nothing, just switched permalink structure.  Then tried old post links, using the date/postname link. They were automatically redirected to the new address (postID/postname). I see no changes to .htaccess (made by WordPress).  Any idea how WordPress implements this? Does it affect performance?

I'm currently using permalink structure: /%year%/%monthnum%/%day%/%postname%/  I want to change that to: /%post_id%/%postname%/  I expect it to be:   faster (database is sorted by post_id?) shorter URLs (and clearly visible short verstions, just leaving the %postname%/ out) more SEO friendly - since my content is "evergreen" so publishing date is irrelevant (and written at each post, along with last update date) - so this would give shorter URLs, with no downsides compared to using year/month/day structure.   THE QUESTION: Does WordPress handle all the 301 redirects automatically? I can fix internal links to the new structure (though I'd expect that to be automatic as well), but worry about outsite links, pointing to my posts/articles.  If not, what's the best way to implement this change? Any links or full answers here are welcome.  I have about 120+ posts already, will this change affect the speed since it's not been done from the start?


My question was marked as a duplicate so I've made a couple edits. As I said, I was able to find many similar questions when I searched but none were quite what I needed.  I am not validating a string where the only thing present will be the phone number (this seems to be what most of the other questions are addressing).  Rather, I am attempting to pull out all phone numbers (which will then be manually checked by the user) from a larger block of text.  The problem I am having is that my regular expression is matching zip codes with extensions (ex: 45202-4787), and I am not sure how to alter my regex to avoid that.  If this truly is a duplicate question then I apologize for not being able to find the existing one that deals with my issue.    My specifications for phone number format are:  1) -, ., and space as delimiters (and in any combination)  2) area code may appear with or without parentheses  A few examples:  (xxx) xxx-xxxx (xxx) xxx.xxxx xxx-xxx-xxxx xxx xxx-xxxx xxxxxxxxxxx   I am using Anirudh's regex from the comments:  (\(?\d{3}\)?)?[. -]?\d{3}[. -]?\d{4}   Again, my problem is that this regex matches zip codes with extensions (ex: 45202-4787).  I would be grateful for any help, as I'm very new to using regular expressions. Thanks!

I'm trying to put together a comprehensive regex to validate phone numbers. Ideally it would handle international formats, but it must handle US formats, including the following:   1-234-567-8901 1-234-567-8901 x1234 1-234-567-8901 ext1234 1 (234) 567-8901 1.234.567.8901 1/234/567/8901 12345678901   I'll answer with my current attempt, but I'm hoping somebody has something better and/or more elegant.


Take a surface S. Suppose there is a sphere with a finite radius such that every point on S falls within the sphere. Then given two points P1 and P2 such that a geodesic on S exists betwwen them, is there an upper bound on the length of the shortest geodesic between these points? Does this upper bound apply to all points on the surface?  I'm dealing with an algorithm for finding geodesics on certain surfaces and it falls apart if there are two points such that only one geodesic exists and the length is infinite. I know with toroidal shapes that one can produce an infinite geodesic thar never repeats itself. However this path is not the only way to reach certain points and there is an upper bound on length of all shortest distance geodesics on that shape. My concern is where such "infinite" geodesics are the only option.  For context I'm working with surfaces made up of triangles only. However my curiosity demands the more general not strictly polygonal case.

This has been asked about here: , and  said      Personally I'd say $M$ wasn't a valid manifold with boundary because the $\{2\}$ doesn't have a neighborhood with any structure like an open ball/half-ball.    This is actually an exercise from An Introduction to Manifolds by Loring W. Tu and is not mentioned in an .        I have spent almost 2 hours thinking about an exercise that looked like it would take only 15 minutes and even tried pasting lemma (it's a good thing Professor Tu has solutions unlike ): The result of all that thinking is that I don't think $[0,1) \cup \{2\}$, $(\varepsilon,1) \cup \{2\}$ or $\{2\}$ is homeomorphic to any open subset of $\mathscr H^1$ or $\mathscr L^1$. I was able to show $\{0\} \subseteq \partial M$ and $(0,1)\subseteq M^0$, but I don't quite know where $2$ belongs. I believe $M$ is not locally $\mathscr H^1$. Also, I have double checked: I believe "manifold boundary" was defined for manifolds with boundary, so this isn't some trick where "manifold boundary" is actually defined for a Hausdorff and second countable space that need not be locally $\mathscr H^n$.     To generalize,     Is a half-open interval and a point not in the interval's closure a manifold with boundary?


One thing struck in my head about mysql/sqlserver i.e delete/ truncate  Which one is better and faster ?  where to use delete?  where to use truncate?

What's the difference between TRUNCATE and DELETE in SQL?  If your answer is platform specific, please indicate that.


OS X Mavericks 10.9.2 / Chrome 33.0... / Safari 7.0.2  I am unable to log in to StackOverflow using Chrome or Safari. Clicking the "log in" link displays a login page UN-styled by CSS and where the "Login" button does not respond to mouse clicks. I am, however able to log in using FireFox, which I am using to post this question.  In Chrome I tried disabling all Extensions, but the faulty page display persisted.  Any thoughts?  Edit with Additional Information:  Opening the Developer Consoles while on the Login page [ in both Chrome and Safari, I am seeing certificate issues for cdn.sstatic.net resources:   Failed to load resource: net::ERR_INSECURE_RESPONSE (in Chrome) Failed to load resource: The certificate for this server is invalid. You might be... (in Safari)   While I am able to reach cdn.sstatic.net in all browsers via http, I am blocked in Safari/Chrome when I try to access it via https:   The site's security certificate is not trusted! and Safari can't verify the identify of the website "cdn.sstatic.net"   Safari show me that the certificate ("ssl4121.cloudflare.com") is for cloudflare.com whereas the link is for sstatic.net, thus throwing the error.  My Interim Solution   Visit  in Safari/Chrome Click "Proceed anyway" in Chrome Click "Show Certificate" in Safari, then select "Always Trust" in the "Trust: When using this certificate" dropdown.   Now, visiting the login page correctly displays the correct CSS and allows me to Log In (finally).  Feels like a bit of a hack, but it worked.  Certificate: Unknown Authority  I removed the certificate ("ssl4121.cloudflare.com") from my Keychain in Keychain Access in order to re-test this issue. The results were the same, with an unstyled and unusable Login page.  After I re-imported the certificate into Keychain Access, the message "This certificate was signed by an unknown authority" is displayed in red near the top. When I mark it again as "Trusted", that message disappears.

Stack Overflow seems to be having some CSS issues right now. At first, it presented as CSS disappearing when refreshing in Firefox (though hitting Enter from the address bar seemed to restore it - I'm thinking that's a cache issue though). I loaded my blank Firefox profile and discovered CSS wasn't rendering on Stack Overflow at all (Meta seems fine; haven't checked other SE sites).  I've since checked the site in Chrome and Opera, and can repro in both.


Let $(X,S,\mu)$ be a $\sigma$-finite measure space, and $g \in M(X,S)$ such that $gs \in L_1(\mu)$ for any simple function $s \in L_p(\mu)$, with $p \in (1, \infty)$. Suppose $A \geq 0$ exists such that $|\int gs \mu| \leq A \|s\|_p$ for any function $s$. Prove:  $g \in L_q$ with $\dfrac{1}{p} + \dfrac{1}{q}=1$ and $\|g\|_q\leq A$

Does anyone know how to do this exercise? I couldn't do it.  Let $(X,S,\mu)$ be a $\sigma$ -finite measure space and $g\in M(X,S)$ such that $gs\in\mathcal{L}_1$ for any simple function $s\in\mathcal{L}_p$, $p\in(1,\infty)$. Suppose there is $A\geq0$ such that $\left|\int gs\,d\mu\right|\leq A||s||_p$ for all $s$. Show that $g\in\mathcal{L}_p$ with $\frac1p+\frac1q=1$ and $||g||_q\leq A$.


I've been working on some problems in my introductory discrete mathematics course, and I am trying to figure out a proof that $R(3,3,3) \leq 17.$ I initially consider an instance where we have a $K_{17}$ colored in the arbitrary colors $c_1,c_2,c_3$. Consider a vertex $v \in K_{17}.$ It should have 16 edges coming out of it, so by the pigeonhole principle, it should have 6 edges coming out of it that are colored in one color. Without loss of generality, we can say that these are colored $c_1$. Consider these $c_1$ adjacent vertices $v_1,...,v_6$. If there is a $c_1$ colored edge between any one of them, we are done. Otherwise, I am not entirely sure what I can do with 6 vertices whose colors are arbitrary colored $c_2$ or $c_3$. Any recommendations for this problem?

If the edges of the complete graph $K_{17}$ (on 17 vertices with no three collinear) are each colored one of three colours can it be proven to have two or more monochromatic triangles?


I am study exceptions in Java and came across this snippet:  public class Test {     public int b()     {         try         {             System.out.println("try block");             return 0;         }         finally         {             System.out.println("Finally block!");         }      }       public static void main (String[] args)      {           Test t= new Test();           t.b();      } }   Since the finally block is always executed and in this case you have a return 0 before it, will it still be executed? (What exactly would the output be).

Considering this code, can I be absolutely sure that the finally block always executes, no matter what something() is?  try {       something();       return success;   }   catch (Exception e) {        return failure;   }   finally {       System.out.println("I don't know if this will get printed out"); }


My question is not about the random perks that soldiers get when they are promoted while you have an AWC built (like ).  My question is about the button appearing at the top of the AWC to change the soldier abilities. What does the feature at the top do?

One of the first buildings available to you is the Advanced Warfare Center (AWC).   Once you have this building, your soldiers can randomly be granted bonus perks when they level up. Obviously, perks are pretty powerful, so I'd like to acquire as many as possible.  How many bonus perks can you receive? What determines what bonus perk you get? And are there any limitations on which perks you can actually receive?


I'm rendering a cartoon figure, it's working fine in Render preview, but missing the feet in final render. This always happen when the cartoon is far from the camera. I have set the camera Clip End to 2000 but still the same. Could anyone help to identify the problem? Thanks a lot!  The Render preview:    The final render:

This is meant to solve this problem once and for all. What is every reason an object isn't showing up in a render or viewport in when using the cycles render engine?


I am looking at the following  from Math Exchange.  In the post guest196883 writes      The rule stated only applies for definite integrals. That is:   $$\int_a^b\alpha f\,dx = \alpha \int_a^bf \,dx$$   Does this mean it is NOT true in general for indefinite integrals? That is:  $$\int\alpha f\,dx = \alpha \int f \,dx$$  There was a short discussion in the comments of the post on this but I don't believe it was ever fully addressed. Thank you in advance!

Let us consider this small problem: $$ \int0\;dx = 0\cdot\int1\;dx = 0\cdot(x+c) = 0 \tag1 $$ $$ \frac{dc}{dx} = 0 \qquad\iff\qquad \int 0\;dx = c, \qquad\forall c\in\mathbb{R} \tag2 $$  These are two conflicting results. Based on  question, Sam Dehority's answer seems to indicate: $$ \int\alpha f(x)\;dx\neq\alpha\int f(x)\;dx,\qquad\forall\alpha\in\mathbb{R} \tag3 $$  However, this clearly implies that indefinite integration is nonlinear, since a linear operator $P$ must satisfy $P(\alpha f) = \alpha Pf, \forall\alpha\in\mathbb{R}$, including $\alpha=0$. After all, a linear combination of elements of a vector space $V$ may have zero valued scalars: $f = \alpha g + \beta h, \forall\alpha,\beta\in\mathbb{R}$ and $g, h\in V$. This all seems to corroborate that zero is not excluded when it comes to possible scalars of linear operators.  To take two examples, both matrix operators in linear algebra and derivative operators are linear, even when the scalar is zero. In a matrix case for instance, let the operator $A$ operate a vector: $A\vec{x} = \vec{y}$. Now: $A(\alpha\vec{x}) = \alpha A\vec{x} = \alpha\vec{y}$. This works even for $\alpha = 0$.  Why is $(3)$ true? Can someone prove it formally? If $(3)$ is false, how do we fix $(1)$ and $(2)$? When exactly does the following equality hold (formal proof)? $$ \int\alpha f(x)\;dx  = \alpha\int f(x)\;dx,\qquad\forall\alpha\in\mathbb{R} $$  I would appreciate formal answers and proofs.


I recently installed Ubuntu 20.04 on a new dell laptop. For some reason, ads/notifications keep popping up at the top of my screen saying things like "you need to renew norton" or "click here for toe fungus cream." I have no idea what is causing this, I ran clamAV to see if there was something installed on my computer doing this, to no avail. These popups are not part of any application I know of since they appear even when I have nothing open but my terminal. Does anyone know what could be the cause of this? thank you.

Recently whenever I open Firefox I get a message in notification center. It's not always the same and it keeps changing. here is an example:     It's not always this. It gives other messages too and when I click it it sends me to phishing sites. I don't know how I got it.   Could someone please help me get rid of it? I tried Clam antivirus but it found nothing.


As we know that the range of unsigned long long int is 0 to 18,446,744,073,709,551,615   Means , unsigned long long int is capable for handling 19-20 digits easily.  So, I want to know why my this program is returning different value.  Program :  #include<bits/stdc++.h> using namespace std; typedef unsigned long long int ulli; int main() {     double a,b;     cin>>a>>b;     ulli result = (ulli)pow(a,b);     cout<<"result = "<<result<<"\n"; }   After giving this input :  a=15 , b=15  Expected output is :  437893890380859375  ( 18 digits number )  But , it is giving this : result = 437893890380859392  ( last 2 digits are different ).  Can anyone help me out why I am getting different result ?

Consider the following code:   0.1 + 0.2 == 0.3  ->  false   0.1 + 0.2         ->  0.30000000000000004   Why do these inaccuracies happen?


I'm interested in  likelihood $L(\theta | x) = P( x | \theta)$ seen as the function of $\theta$ for a given $x$.  I have been reading in books and other posts that $L$ is generally not a probability function (with respect to $\theta$) because it may not integrate to 1 and, moreover, there my be even no $\sigma$-field defined over the $\theta$ space.  In the Bayesian approach, we define a prior probability $P(\theta)$ and so the $\sigma$-field had to be defined.  What other properties we need to be able to interpret $L(\theta|x)$ as the conditional probability $P(\theta|x)$? Perhaps normalization to integrate to 1? What else? (whuber mentions some regularity conditions in this post . What would these be?)  EDIT  After some searching, I believe the answer is in Fisher's fiducial distribution. See Casella&Berger(2002, sec. 6.3.1), the original Fisher's papers (1933,1935) or this question:   EDIT2  Now that I know the key-word is fiducial, there is a fairly good explanation in the answer to this question:

The  claims that likelihood and probability are distinct concepts.     In non-technical parlance, "likelihood" is usually a synonym for "probability," but in statistical usage there is a clear distinction in perspective: the number that is the probability of some observed outcomes given a set of parameter values is regarded as the likelihood of the set of parameter values given the observed outcomes.    Can someone give a more down-to-earth description of what this means?  In addition, some examples of how "probability" and "likelihood" disagree would be nice.


The shortest distance between two points $P_{1}(x_1,y_1,z_1)$ and $P_{2}(x_2,y_2,z_2)$ is given by  $d=\sqrt{(x_1-x_2)^2+(y_1-y_2)^2+(z_1-z_2)^2}$.       If both $P_1$ and $P_2$ lie on the sphere   $(x-x_0)^2+(y-x_0)^2+(z-z_0)^2=r^2$, then what is the length of the   shortest path between the two points such that the path lies on the   surface of the sphere?     The formula for distance written above will not work to solve this problem.    How to express the length of the shortest path that lies on the sphere in terms of $x_0,y_0,z_0,x_1,y_1,z_1,x_2,y_2,z_2,$ and $r$?    I think the arc length using integration is the right way, but I am struggling with it. Any help will be appreciated.

I have a $3$-D sphere of radius $R$, centered at the origin.   $(x_1,y_1,z_1)$ and $(x_2,y_2,z_2)$ are two points on the sphere.   The Euclidean distance is easy to calculate, but what if I were to restrict myself to traveling on the surface of the sphere?    Two approaches come to mind: use  in some way, or simply use trigonometry: calculate the angle between the two points and get a distance from that.    Will both/either of these methods work? Which would be easier?  Somewhat related to . Maybe it will inspire someone to go answer it!


I remember reading something like "out from something's mouth/jaws (like a dragon) and into another..."

Are there idioms or expressions in English that describe going from one bad situation to one that's even worse?  I heard "between a rock and hard place" but this describes a dilemma not really a transition. I am looking for an expression that describes someone trying to get out of a bad situation but after much effort, the situation only got worse.


To reproduce:   upvote an answer with 0 current votes edit the question   Expected behavior: answer shows 1 vote Actual behavior: answer shows 0 votes  You will know that the server already received your upvote because if you  upvote again it will say that your vote is locked in.   App Version: 1.0.85 Device Manufacturer: LGE Device Model: Nexus 4   OS Version: 5.1.1 (2237560)

Related:   I am using 1.0.71 on KitKat.  Immediately after voting, the arrow is displayed in red and the vote count is correct. However, when I scroll to read answers and then back to the top, the arrow is grey again and the vote count is reset to the previous value.  A reload of the question (pulling the finger down) is needed to show the correct situation, which is kept from then on.  This case was on security.stackexchange.com but I observed the same behavior on other sites too.  Screenshots   original state:  upvoted:  scrolled down and back up  after a reload


I have this composition of twice differentiable functions : $$ \Bbb R ^m \overset{f}{\longrightarrow} \Bbb R^n \overset{g}{\longrightarrow} \Bbb R^k$$ And I'm trying to get this result from a book : $$ (g \circ f)''(x) (h,k) = (g''\circ f')(x)\big(f'(x)h,f'(x)k\big) + (g'\circ f)(x)\big(f''(x)(h,k)\big) $$ A poor attempt : $$  \begin{align} (g \circ f)^{\prime\prime}(x) (h,k)   & = \bigg(\big((g' \circ f)(x) f'(x)\big)(h)\bigg)'(k) \\   & = \big((g' \circ f)(x)\big)'(k) f'(x)(h) + (g' \circ f)(x)\big(f''(x)(h,k)\big) \\   & = (g'' \circ f)(x)f'(x)(k) f'(x)(h) + (g' \circ f)(x)\big(f''(x)(h,k)\big) \\ & = (g''\circ f \space)(x)\big(f'(x)k,f'(x)h\big) + (g' \circ f)(x)\big(f''(x)(h,k)\big) \\  (?) & = (g''\circ f')(x)\big(f'(x)h,f'(x)k\big) + (g'\circ f)(x)\big(f''(x)(h,k)\big) \end{align}$$ So It feels like it follows the rules of bilinear differentiation but then $h$ and $k$ should swap places and there's that extra $f'$. What am I doing wrong.

Say, we have three Banach spaces $X, Y, Z$ and $g:X \to Y, \ \ f:Y \to Z$ are twice (Fréchet) differenciable. The question is: what is $(f \circ g)''$?  Since $(f \circ g)'':X \to   \mathcal{L}^2(X,Z)$, I am interested in the most explicit form: $(f \circ g)''(a)[k, h]$ which would describe the entire action taking place.  Let's pick some $a \in X$ and get started:  \begin{align}  \\ (f \circ g)''(a)[k, h] &= D_{k}D_{h}(f \circ g)(a) \\  &= D_{k} \bigg( D_{h}(f \circ g)(a) \bigg) \\  &= D_{k} \bigg( (f \circ g)'(a)[h] \bigg)  \\  &= \bigg( D_{k} (f \circ g)'(a)\bigg) [h] \ \ \ \ \ \text{(by linearity)} \\  &= \bigg( D_{k} f'(g(a)) \circ g'(a)\bigg) [h] \ \ \ \ \ \text{(chain rule)} \\  &= \bigg( \frac{d}{dt} f'(g(a+tk)) \circ g'(a+tk)|_{t=0}\bigg) [h] \end{align}  I’m really confused what to do next. It looks like we’d need to apply some sort of the product rule (but there is no product here: only compositions). And whatever I do next, I immediately lose track of how it all fits with $k$ and $h$.  Any explanations (the more detailed the better) are hugely appreciated.


I just saw this syntax in PHP:  // Fetches the value of $_GET['user'] and returns 'nobody' // if it does not exist. $username = $_GET['user'] ?? 'nobody';   Why don't we have the same in JavaScript?  I am tired of doing:    var name = obj['name'] ? obj['name'] : 'GOD';

Is there a null coalescing operator in Javascript?  For example, in C#, I can do this:  String someString = null; var whatIWant = someString ?? "Cookies!";   The best approximation I can figure out for Javascript is using the conditional operator:  var someString = null; var whatIWant = someString ? someString : 'Cookies!';   Which is sorta icky IMHO. Can I do better?


I'm currently trying to install Ubuntu 14.04.2 alongside Windows 7 (64 bit) but when I followed through the wizard it didn't give me the option to install alongside windows.   I then went back into windows and created a new partition. The install alongside windows option still didn't appear so I selected the 'something else' option and tried to select the new partition but it says that it's unusable. Any help would be appreciated.  I have tried to follow instructions but they don't seem to work for me.

I would like to see a full how-to guide on how to install Ubuntu.


The space-time invariance principle states that:  $(c^2)(\Delta t^2) - l^2 = \rm invariant$ for any inertial frame.  Consider two events that occur at the same time in inertial frame $S$, and frame $S_1$ moves with translational speed $v$ relative to $S$. It seems that by the length contraction, the distance between these events should be shorter in $S_1$ because the events are moving, yet since these events do not happen simultaneously in frame $S_1$, then $(c^2)(\Delta t^2) - l^2$ for frame $S_1$ is larger than for $S$, which is a contradiction. Can someone please explain the issue in this contradiction (without using Minkowski diagrams)?

I am having a serious trouble finding an agreement between the two facts in Special Relativity:  (1) given two events $A$ and $B$ in spacetime separeted by a spacelike interval $s$, the distance in space between the two events will be the shortest in the reference frame which the two events occur simultaneously:   The invariance of the interval says $s^2=(\Delta x)^2-(c\Delta t)^2$ and $\Delta x$ is minimum when $\Delta t=0$  (2) the length contraction says $L=\dfrac{L_0}{\gamma}$ where $\gamma=(1-(v/c)^2)^{-1/2}$ , $L_0$ is the proper length of an object in a reference frame which the object is at rest and $L$ is the length of the object in a reference frame which the object moves with speed $v$ in the $x$ direction.  This says that the lenght of the object in the $x$ direction is the largest in the comoving reference frame of this object.  The question is: According to (1), the reference frame in which two events $A$ and $B$ occur simultaneously is the reference frame that gives the shortest distance in space between the two events. Let $A$ and $B$ be the two end points of a meter stick in a reference frame in which the stick is at rest and at time $t=0$. This two events occur simultaneously, so the distance in space between the two is the shortest acording to (1). But according to (2) shouldn't this distance be the largest?  What is wrong?


I have a road bike that has a flat tire, the rim is marked with the text     700Cx28/38c  ETRTO 622x20   I am specifically looking at . Under the sizing options there is an option      700 x 25-32cc   Which I think is the one that I want. The picture of the box (not necessarily correlated to my choice in sizing) has the text     20-622 > 25-630   Which again seems to confirm that this inner tube will be correct.  Will the tube size mentioned above fit the rim I describe? Or, should I select the size 32-42cc because the range on the rim (28/38c) has more #'s in the range 32-42 (6) than it does in the range 25-32 (5)?    I have been reading for a bit now and from what I understand the text on the rim (28/38cc) means that the tire (not tube) size that the rim will fit is between 28mm and 38mm. But what is confusing me here is the sizing of the tubes listed as that are listed as, for instance, 25-32cc. Does this mean the tube itself will fit on rims that can fit tires (not tubes) in the range of 25mm to 32mm?  In the end what exactly should I be looking for; what sizes of tubes will fit this rim properly?    I hate to "beg" for the answer seeing how much it is looked down upon on the stackexchange sites but I seem to actually be at a loss in understanding this correctly...    EDIT: Ok so I think I understand this much better now. My tire itself has the text 700x40c. Which means that the tire itself "prefers" a tube with a cross section of 40mm; moreover the tires cross sectional area is 40 mm!? So I can then buy any tube that says it will fit/(inflate to) a tire with a cross sectional area of 40c.

My bike's manufacturer page specifies that it has a rim size of 700CX14GX36H.  It provides a tire size of 7X28C.  It also mentions that it uses high performance 700C tires, which I think is also referenced in the rim size.  I just replaced my tube by myself for the first time, and it was easy enough to determine that I needed a 700x28c size tube, but I would really like to know what all these specifications I'm seeing mean.    Can someone provide an explanation of what general rim, tire and tube size specifications mean?


I have a simple landing page with a fullscreen background image and no other content. However, when I load this, the footer comes all the way up to the Navbar and stops the image from being fullscreen (image is fullscreen on pages with content). This is how it looks:   My CSS for the background image is the following:  .index {   background: url('/Content/images/home2.jpg') no-repeat center center;   background-size: cover;   min-height: 100%;   padding-top: 20px;   padding-bottom: 20px; }   Also, my Navbar is getting in the way of this image which I also need to rectify.

I have a simple 2-column layout with a footer that clears both the right and left div in my markup.  My problem is that I can't get the footer to stay at the bottom of the page in all browsers.  It works if the content pushes the footer down, but that's not always the case.


Using Vieta's Trignometric Solutions, I am getting $$\dfrac{2\sqrt{19}}{3}\cos{\left(\dfrac{1}{3}\arccos{\dfrac{7}{\sqrt{76}}}\right)}-\dfrac{1}{3}\tag{1}$$ And it is also equal to $$2\left(\cos\left(\frac {4\pi}{19}\right)+\cos\left(\frac {6\pi}{19}\right)+\cos\left(\frac {10\pi}{19}\right)\right)\tag{2}$$  My Question: How would you get from $(1)$ to $(2)$, and is there a way to generalize it? Anything helps!

I'm wondering if there is a mathematical way of finding the roots of $y=x^3+x^2-6x-7$?  Supposedly, the roots are $2\cos\left(\frac {4\pi}{19}\right)+2\cos\left(\frac {6\pi}{19}\right)+2\cos\left(\frac {10\pi}{19}\right)$, $2\cos\left(\frac {2\pi}{19}\right)+2\cos\left(\frac {14\pi}{19}\right)+2\cos\left(\frac {16\pi}{19}\right)$ and $2\cos\left(\frac {8\pi}{19}\right)+2\cos\left(\frac {12\pi}{19}\right)+2\cos\left(\frac {18\pi}{19}\right)$.  Anything helps. I don't think substituting $x$ with something like $t+t^{-1}$ will work.


I'm not a biology person at all so please forgive me if my question is silly. I was just wondering that why didn't evolution cause us to digest, without issues  decomposed food?

If a trait would be advantageous to an organism then why hasn't it evolved yet?  Conversely, if a trait is not advantageous or mildly disadvantageous, why does it exist?  In other words why does evolution not make the organism more "perfect"?    This is a general question that would be applicable for any kind of trait. Please keep the answers precise and scientific.   Read this meta post for more information: