This is the error I get when I run google-chrome in the terminal:  [0505/065554:ERROR:nss_util.cc(94)] Failed to create /home/pipi/.pki/nssdb directory. [0505/065554:ERROR:nss_util.cc(94)] Failed to create /home/pipi/.pki/nssdb directory. [3545:3545:0505/065557:ERROR:nss_util.cc(94)] Failed to create /home/pipi/.pki/nssdb directory. [3545:3545:0505/065558:ERROR:process_singleton_posix.cc(417)] readlink failed: Permission denied [3545:3545:0505/065558:ERROR:process_singleton_posix.cc(253)] readlink(/home/pipi/.config/google-chrome/SingletonLock) failed: Permission denied [3545:3545:0505/065558:ERROR:process_singleton_posix.cc(253)] readlink(/home/pipi/.config/google-chrome/SingletonLock) failed: Permission denied [3545:3545:0505/065558:ERROR:process_singleton_posix.cc(277)] Failed to create /home/pipi/.config/google-chrome/SingletonLock: Permission denied [3545:3545:0505/065558:ERROR:process_singleton_posix.cc(417)] readlink failed: Permission denied [3545:3545:0505/065558:ERROR:process_singleton_posix.cc(253)] readlink(/home/pipi/.config/google-chrome/SingletonLock) failed: Permission denied [3545:3545:0505/065558:ERROR:chrome_browser_main.cc(1213)] Failed to create a ProcessSingleton for your profile directory. This means that running multiple instances would start multiple browser processes rather than opening a new window in the existing process. Aborting now to avoid profile corruption.

I have installed the 14.04 LTS in clean. then I use wget the chrome.deb for 64 bit from Google and dpkg -i *.deb to install the chrome in my Ubuntu 14.04,however I can't launch it and get errors as below, could you please help me to solve this problem?  $ google-chrome [2697:2697:0616/211443:ERROR:process_singleton_linux.cc(394)] readlink failed: no authority [2697:2697:0616/211443:ERROR:process_singleton_linux.cc(240)] readlink(/home/frank/.config/google-chrome/SingletonLock) failed: no authority [2697:2697:0616/211443:ERROR:process_singleton_linux.cc(240)] readlink(/home/frank/.config/google-chrome/SingletonLock) failed: no authority [2697:2697:0616/211443:ERROR:process_singleton_linux.cc(264)] Failed to create /home/frank/.config/google-chrome/SingletonLock: no authority [2697:2697:0616/211443:ERROR:process_singleton_linux.cc(394)] readlink failed: no authority [2697:2697:0616/211443:ERROR:process_singleton_linux.cc(240)] readlink(/home/frank/.config/google-chrome/SingletonLock) failed: no authority [2697:2697:0616/211443:ERROR:chrome_browser_main.cc(1209)] Failed to create a ProcessSingleton for your profile directory. This means that running multiple instances would start multiple browser processes rather than opening a new window in the existing process. Aborting now to avoid profile corruption.


Are there any larger implications of allowing a variant rule Ability Score Improvement/Feats in a multi-classing campaign?  In one campaign we have all multi-class players. There has been a frustration about having to take a 4th or 8th level in a class for the sole purpose of having access to an Ability Score Improvement (ASI) or a Feat.   I want to suggest we have a character level progression system instead of class, when it comes to ability score improvements and feats. This seems simple enough.  The majority of classes get an ASI or feat at levels 4, 8, 12, 16 and 19 - with the exception of a Fighter who also gets this at levels 6 and 15 and a Rogue who gets it at level 10.   The variant rule would be that a PC gets the option of an ASI/feat when it reaches character levels: 4, 8, 12, 16 and 19. If the player chooses to develop into the Fighter/Rogue class, then that PC would get an ASI/feat upon reaching Fighter level 6 and 14 or Rogue level 10.  There is a similar mechanic with cantrips for multi-classing players, where the upgrades depend on overall character level, rather than class level (PHB, p.164).      Variant Rule: Ability Score Improvement, or Feat      When you reach 4th level on your overall character level, and again at 8th, 12th, 16th, and 19th level, you can increase one ability score of your choice by 2, or you can increase two ability scores of your choice by 1. As normal, you can’t increase an ability score above 20 using this feature. The increase is based on your character level, not your level in a particular class. Using the optional feats rule, you can forgo taking the Ability Score Improvement feature and take a feat of your choice instead.      In addition: if you train as a Fighter, you get an Ability Score Improvement at upon reaching 6th and 14th level in that class; or at level 10 if you train as a Rogue.   Would this create any great unbalance? I can't see it, but I might be missing something.

I'm trying to figure out why Dungeons & Dragons 5th edition designers decided that ASI or feats would be given every 4 class levels and not every 4 character levels.  If I allowed my players to get an ASI or feat at character levels 4, 8, 12, 16 and 19, how would the game balance be concretely impacted? How could the players abuse this?  The peculiarities of some classes such as the fighter and the rogue would be kept: a rogue would still gain an ASI at rogue level 10 and a fighter at fighter levels 6 and 14.


Hi, I'm new to design.Can you tell me what is the problem that makes my printout color so much different from the file. Printer is RICOH aficio MP c4502

I’m trying to print from Illustrator (CMYK) and it comes out red: All the blue tones appear black and everything that was either beige or grey looks like it has a red layer over it. All the colours seem to be affected (except for white).   The printer is an HP Envy 4500. I’ve tried to save it as a PDF and print from that PDF instead but it didn’t work.


If a program is not allowed to handle or ignore SIGKILL and SIGSTOP, and must immediately terminate, why does the kernel even send the signal to the program? Can't the kernel simply evict the program from the CPU and memory? I assume the kernel would have the ability do directly do this.

When I used killall -9 name to kill a program, the state become zombie. Some minutes later, it stopped really. So, what's happening during those minutes?


I'm studying for an exam over series, and here is a question that I cannot complete.  Let $a_1,a_2,...>0$. Prove that if  $\lim_{n\to\infty} n(\frac{a_n}{a_{n+1}}-1)>1$ then the series $\sum_{n=1}^{\infty}a_n$ converges.  I've tried rewriting the given inequality in terms of the ratio $\frac{a_{n+1}}{a_n}$, but then the inequality becomes  $\frac{a_{n+1}}{a_n}<\frac{n}{n+1}\to 1$, so that the ratio test would be inconclusive. I'm not seeing the algebra required to ensure the series converges.  Any help is appreciated. Thanks.

Let $\sum a_n$ be a series of non-negative terms and let $$L = \lim_{n\to\infty}n\left(1-\frac{a_{n+1}}{a_n}\right)$$ Prove that the series converges (resp. diverges) if $L > 1$ (resp. $L<1$). I've tried, for example, that when $L<1$, $$n\left(1-\frac{a_{n+1}}{a_n}-L\right)= \frac{n(a_n-a_{n+1}-La_n)}{a_n}\ge\frac{n(a_n-a_{n+1}-a_n)}{a_n}=\frac{-na_{n+1}}{a_n}$$ and then using epsilons and the sort, but I can't get anywhere. Any tips?  P.S. using Kummer's test doesn't count


Following  answer.  I notice that the cpg (decoding declaration) file isn't delete using .deleteShapeFile pyQgis function.  Any suggestion on how to delete these files using automatic method?

In the Browser it's not possible to delete Shapefiles. In ArcMap you can delete Shapefiles easily within the Catalog.   How can I delete Shapefiles in QGIS without minimizing the QGIS-Window, navigating to the folder on my computer, select all the files that belong to a Shapefile (shp, dbf, shx, prj, etc.) and delete it?


I have an Orders table, with OrderId as PK. I also have an Order_Products table with OrderId as FK. Each Order_Product row has columns like Product_Name, Product_Status,Product_Delivery_Date, etc. The tables are joined in one-to-many relationship on OrderId.  I am trying to design a query which will consolidate the two tables such that I get a row for each OrderId, but the query must have a Description column which will have the Oder_Name values of all Order_Product rows concatenated; I also need to have the aggregate Product_Status calculate using some logic like (if one of the products is 'NotCompleted', then the aggregate Product_Status will be 'NotCompleted'. Finally I would like to have the OrderDeliveryDate calculate such that it will be the MIN value of all Order_Product Product_Delivery_Date values.  I am using MySql. Can you please give me some advice as to how to achieve these three tasks?   Example:  Orders Table:  OrderId  CustomerName  1001     CustomerX    OrderProducts Table:  Id  OrderId  ProductDescription  ProductDeliveryDate   ProductStatus 20  1001     ProductA                        2015-01-30            NotCompleted 21  1001     ProductB            2015-01-15            Completed 24  1001     ProductC            2015-02-13            NotCompleted  Desired Query Output:  OrderId    CustomerName   Description                  OrderDeliveryDate     OrderStatus '1001'    'CustomerX'     'ProductA,ProductB,ProductC' '2015-01-15'          'NotCompleted'

Using MySQL, I can do something like:  SELECT hobbies FROM peoples_hobbies WHERE person_id = 5;   My Output:  shopping fishing coding   but instead I just want 1 row, 1 col:  Expected Output:  shopping, fishing, coding   The reason is that I'm selecting multiple values from multiple tables, and after all the joins I've got a lot more rows than I'd like.  I've looked for a function on  and it doesn't look like the CONCAT or CONCAT_WS functions accept result sets.  So does anyone here know how to do this?


Let $b > 0$. Use the deﬁnition to prove $\lim_{n \rightarrow \infty} b^{\frac1n} = 1$.   please help me with that.

Hope this is a meaningful question, but I'm curious if is possible to show that   $$\lim_{n\to\infty} a^{\frac{1}{n}}=1, \text{where  }a>0$$  using $\delta-\epsilon$ directly or other methods. One method that I am aware of is to use the following:     If $\{s_n\}$ is a nonzero sequence, then $\liminf\bigl|\frac{s_{n+1}}{s_n}\bigr|\le \liminf |s_n|^{\frac{1}{n}}\le \limsup |s_n|^{\frac{1}{n}}\le\limsup\bigl|\frac{s_{n+1}}{s_n}\bigr|$


How to proceed after the below step. Also is there a simpler way to solve this integral?

how i evaluate this integral with integration by substitution $x=\frac{\pi}{2}-t$  $$\int _0^{\frac{\pi }{2}}\:\frac{\sqrt[3]{\sin^2\left(x\right)}}{\sqrt[3]{\sin^2\left(x\right)}+\sqrt[3]{\cos^2\left(x\right)}}dx$$


How would I go about increasing the strength/distance of an Emission texture without the texture getting brighter in Blender Cycles?  Lets say I take the following texture and make a light mask out of it. I then mix them equally with the Texture as a Diffuse BSDF and the Mask as an Emission.    With the Strength set as 1.000 the texture looks ok but I feel it just isn't bright enough. But if I set it to something higher (like 100.000) the texture gets oversaturated.    Is there some way I can have the light emit to infinity if I so pleased, yet have the texture remain the same brightness in Cycles?

I am trying to make a computer monitor. This means I have to have an image texture for the screen. My image texture is currently connected to an Emission BSDF shader. Unfortunately, when the emission is bright enough to emit light, the image is white-washed. I tried adding a Brightness/contrast node to the image before pushing it into the Emission BSDF, but it seems to directly counter the Emission's strength.  The desired light level   The desired image brightness


i'm using a java application on my terminal wich listen to a specific port for specific connections .  i'm using it in terminal like :   java -jar Server.jar   everything works perfectly except that when i disconnect from the ssh session ( using putty ) , the connection get lost and the server stops .  i want to let the connection or the server open even after ending the ssh session .

Let's say I launch a bunch of processes from a ssh session. Is it possible to terminate the ssh session while keeping those processes running on the remote machine?


I would like to be able to defer the construction of the elements of a list until they are accessed for the first time. The obvious solution (using a generator as below does not work since it is iterable more than once, etc).   For example, the following prints 0 -> 9. I would like to print 0-> 9 twice.  def costly_build_function(i):     return i def my_function():     return (costly_build_function(i) for i in range(0,10)) tmp = my_function() # print 0 to 0 for i in tmp:     print i # print nothing for i in tmp:     print i

I would like create my own collection that has all the attributes of python list and also knows how to save/load itself into/from a database.  Also I want to make the load implicit and lazy, as in it doesn't happen at the point of creation of the list, but waits until its first used.  Is there a single__xxx__method I can override to load the list on first usage of any list property  (such aslen,getitem,iter...etc) without having to override them all?


Let $σ=(1234)∈S_6$. List all elements in $N(σ)={α∈S_6∣σα=ασ}$.   I know that this is related to cycles and orders, but I am having trouble finding the order of $N(σ)$ initially.   I also know that $σ$ has 8 different permutations.   And I also know that $e(1234)e^{-1}=(1234)$  And I do know that one is $α=(13)(24)$  I would just like some help getting to the rest of the elements in  $N(σ)={α∈S_6∣σα=ασ}$.   Thank you!

Let $\sigma = (1234) \in S_6$. List all elements in $N(\sigma) = \{\alpha\in S_6 \mid \sigma\alpha=\alpha\sigma\}$.   I know this relates to cycles and orders, but I am having trouble finding the order of $N(\sigma)$ and then the list of elements.


So this is one of the questions on my physics assessment and I would like to know how to calculate how much work is done when pushing against a brick wall.  My teacher has told me the calculation is: weight(kg)x10 (this gives me the force)x distance.   But what is the weight of and the distance of? As when you push against a brick wall the wall doesn't move and you can stop yourself from moving.  Please answer as soon as possible, also I'm kind of younger so could you explain clearly(sorry)   Emsee

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?


For the third time now, I've received a consecutive days badge when I know for a fact that I haven't earned it. The first time was reported  and the second time .   I just looked at my achievements menu, and saw this:    While I love PPGC, I know I haven't visited it for a month straight, let alone 100 days. I've been busy with work and a Neural Net project, so I haven't been checking it frequently. I think I checked it last a few days ago, and before that a week or two prior.   Things to note:   I don't have any scripts, browser or otherwise that check or even have access to SE.  My SE account is tied to Google, which has two-step verification in place, and monthly activity reports. My account is spotless. This isn't a case of someone logging in to my account (and checking PPCG!?). Again, I know for a fact that I haven't even visited the site daily for at least a month, if not more.  I predominantly use the Android app. PPCG is listed as one of my favorite sites in the left menu.   While I'd like to keep the badge(s), I thought I'd post another report since the first 2 didn't have any kind of resolution.

I just received an "Enthusiast" badge on Code Review.   As much as I'd like to keep the badge, I'm certain that I did not visit Code Review every day, for 30 days straight.   Is this a bug?   I don't have the "consecutive days" stat:        But I still got the badge:        And it happened again. Reported .     Update: I just received a third badge in error; this time a fanatic badge for Software Engineering. This is even stranger, since I use that site less than I do CR, and I don't recall getting the 30 days badge.


I am a new user and I am having trouble working around this issue. When I sudo-apt update, I get the error:
Hit:1 http://us.archive.ubuntu.com/ubuntu groovy InRelease                      Ign:2 http://ddebs.ubuntu.com groovy-updates InRelease                          Hit:3 http://ppa.launchpad.net/system76/pop/ubuntu groovy InRelease             Hit:4 http://us.archive.ubuntu.com/ubuntu groovy-security InRelease             Ign:5 http://ddebs.ubuntu.com groovy-security InRelease                         Hit:6 http://apt.pop-os.org/proprietary groovy InRelease             Hit:7 http://us.archive.ubuntu.com/ubuntu groovy-updates InRelease   Ign:8 http://ddebs.ubuntu.com groovy-proposed InRelease              Hit:9 https://repo.nordvpn.com//deb/nordvpn/debian stable InRelease  Hit:10 http://ddebs.ubuntu.com groovy-updates Release                Hit:11 http://us.archive.ubuntu.com/ubuntu groovy-backports InRelease Err:12 http://ddebs.ubuntu.com groovy-security Release   404  Not Found [IP: 91.189.94.8 80] Hit:13 http://ddebs.ubuntu.com groovy-proposed Release Err:14 http://ddebs.ubuntu.com groovy-updates Release.gpg   The following signatures couldn&apos;t be verified because the public key is not available: NO_PUBKEY C8CAB6595FDFF622 Err:15 http://ddebs.ubuntu.com groovy-proposed Release.gpg   The following signatures couldn&apos;t be verified because the public key is not available: NO_PUBKEY C8CAB6595FDFF622 Reading package lists... Done E: The repository &apos;http://ddebs.ubuntu.com groovy-security Release&apos; does not have a Release file. N: Updating from such a repository can&apos;t be done securely, and is therefore disabled by default. N: See apt-secure(8) manpage for repository creation and user configuration details. W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: http://ddebs.ubuntu.com groovy-updates Release: The following signatures couldn&apos;t be verified because the public key is not available: NO_PUBKEY C8CAB6595FDFF622 W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: http://ddebs.ubuntu.com groovy-proposed Release: The following signatures couldn&apos;t be verified because the public key is not available: NO_PUBKEY C8CAB6595FDFF622
  What can I do to fix this? Thank you.

Did something expire that should not have? I am using debug symbols on my Ubuntu 20.10 install, and now I get this when I run the apt-get update command. W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: http://ddebs.ubuntu.com groovy Release: The following signatures were invalid: EXPKEYSIG C8CAB6595FDFF622 Ubuntu Debug Symbol Archive Automatic Signing Key (2016) <ubuntu-archive@lists.ubuntu.com>


BA 1536 24APR DFW(Dallas)->CDG(Paris) HK1  1505  #0735   BA 307 09MAY CDG(Paris)->LHR(London) HK1  1030   1050   BA 119 09MAY LHR(London)->BLR(Bangalore) HK1  1420  #0445  I have a flight which originates from Dallas, goes to Paris, and from Paris gets to Bangalore via London. The transit time is less than 3 hours and I will not have any check-in luggage (so no border control?). As per my understanding I should be exempt since I have a valid US visa.   But my travel agent says I need a transit visa for London. Does anybody know the updated rules for transit?

Is there a website or some other way to find out if I need a transit visa for a short stop in the UK on my way somewhere else? Ideally this should give me the answer for all nationalities, and take into account any other visas I may have.


Sometimes comments are helpful enough to be considered answer.  What do you think about a button or something that allows to convert a comment into an answer?

Allow converting comments to answers, so they can become accepted answers.  I asked a question. Someone commented on it, and it was an awesome comment that fully answered the question. As the original questioner, I would like to convert that comment to an answer in order to accept it.  Or, if you prefer, I would be okay with being able to simply mark the comment as accepted.


Let's say $X=(X_1,X_2)'$, where $X\in \mathbb{R}^2$. What is the expectation of the copula function $C(F_{X_1}(x_1),F_{X_2}(x_2))$ - i.e. $\mathbb{E}_X\left[C(F_{X_1}(x_1),F_{X_2}(x_2))\right]$?

Yesterday, I asked the following question regarding copulas:     "Let's say $X=(X_1,X_2)′$, where $X\in \mathbb R^2$. What is the expectation of the copula function $C(F_{X_1}(x_1),F_{X_2}(x_2))$ - i.e. $\mathbb E_X[C(F_{X_1}(x_1),F_{X_2}(x_2))]$?"   Here, I rephrase this question in a form familiar to most:     Let's say $X=(X_1,X_2)′$, where $X\in \mathbb R^2$. What is the expectation of the joint CDF $F(F_{X_1}(x_1),F_{X_2}(x_2))$ - i.e. $\mathbb E_X[F(F_{X_1}(x_1),F_{X_2}(x_2))]$?


Stackoverflow have come to the point (and way beyond) where all geeks and programmers out there would suffer a great deal if it went black tomorrow.  I don't doubt that Stackoverflow have a good backup regime, but a lot of things could happen.  It be great if Stackoverflow had some sort of db-dump feature to mitigate this. It doesn't haveto be a full dump. But a dump with the questions and accepted answers would be almost just as good. It would also be a great offline-search tool for places without internet..  Is this up for consideration?

According to this blog article dated Sept 2011:    While we will always continue to produce Stack Exchange creative commons data dumps, we are moving to a quarterly schedule for all future dumps.  Clearbits, the recommended site to get the data dump torrents at , lists the most recent dump as December 2011. Is the plan still to provide quarterly data dumps? If so, when will they resume?


I would like to kindly request please provide the Ubuntu OS to us. if you send it I can install it in 85 schools and in our office. Installation of this software will benefit over 3000 persons.  I hope your will send positive replay   Best Regard,

I need to upgrade my existing Ubuntu system, and I also want to install Ubuntu on a new laptop.  I would like to have an installation CD or DVD to do both of these.  Where exactly I can order or request an Ubuntu installation CD/DVD/USB?


What I understand:  In addition to valid references to the referenced table, a column with a foreign key is also allowed to hold a NULL value. The SQL standard defines several match modes for foreign keys, like MATCH SIMPLE and MATCH FULL. For multi-column foreign keys, MATCH SIMPLE allows a wrong (= not referencing) value in any of the columns as long as at least one column of the foreign key holds a NULL value.  Multi-column foreign keys are rare (because multi-column primary keys are), but I can imagine valid use cases. For example a translation of a blog post might have a primary key (post_id, language_id). Now something that references such a translation (for example which translation a user is currently editing) would have a multi-column foreign key.  What I don't understand:  Why would I ever use MATCH SIMPLE for my foreign key?  In above example it doesn't make sense to have a "currently editing" entry that only references by post_id and not by language_id.  What would be an example where it does make sense?

I've noticed a MATCH SIMPLE and MATCH FULL, but I don't understand what they do. I see default is MATCH SIMPLE; but, how do the other MATCH clauses to the FOREIGN KEY constraint function?


I was using blender and might've accidently pressed some keys and so when I go to my section to add color it is not at the original perspective that I want it to be. I need this back because it gives me like 3 options for color and none of them add nodes to my node editor. please help.   How do I change it from this perspective    Back to this?

Complete beginner here.  I'm trying to follow  tutorial on Anisotropic shaders, but my property panel looks nothing like the property panel in the tutorial.  For example, when creating a material, this is what his property panel looks like:    But this is what mine looks like, if I follow the same path:    I'm sure I'm missing something obvious.  How can I see the property panel shown in the tutorial?


How can I mathematically check if $n\times m$ area can be filled with pieces with $a \times b$ area and find the remainder?  For example, can $6\times 6$ area be filled with $1 \times4$ tiles? My made up notation and answer is as follows:    6*6 = 6*(1*4) + 6*2   6*2 = 2*(4*1) + 2*2   6*6 mod 1*4 = 2*2 hence it can't be filled with 1*4 tiles.   This one is just written to fit the answer I've found mechanically and not valid notation. Is there a valid rigorous way to do this for any $n\times m$ sized area and $1 \times4$ sized tiles?   How to find the area of the reminder?

Why can't I tile a $100 \times 100$ table with $1$ by $8$ pieces?  If we look at the number of tiles, $100^2$ is divisible by $8$. So this does not contradict existence of such tiling.  The  of coloring the squares by black and white color does not help here either, since the $1\times8$ domino has the same number of white and black squares and so does the whole board.


After testing the Pop theme via their PPA, I made a distribution upgrade from Focal Fossa to Pop!_OS by mistake. I did not realize that installing the System76 PPA meant that the system would try to "upgrade" from Ubuntu to Pop!_OS... Is there a way to get back to Ubuntu Focal Fossa without re-installing the OS? The file /etc/apt/sources.list looks "normal": deb http://archive.ubuntu.com/ubuntu focal universe restricted multiverse main deb http://security.ubuntu.com/ubuntu/ focal-security restricted universe multiverse main deb http://archive.ubuntu.com/ubuntu focal-updates restricted universe multiverse main deb http://archive.ubuntu.com/ubuntu focal-backports restricted universe multiverse main  But there is another file in /etc/apt/preferences.d called pop-default-settings which explicitly references pop: Package: * Pin: release o=LP-PPA-system76-pop Pin-Priority: 1001  Package: * Pin: release o=LP-PPA-system76-proposed Pin-Priority: 1001

I'm running Ubuntu 20.04.1 LTS. I was recently prompted to install an update from Ubuntu's GUI software updater, but I'm not sure which update. Now, I seem to have... a strange amalgamation of Ubuntu and PopOS all of a sudden? After booting up today, my desktop looks quite different:  It appears to be using Pop Shell, the tiling window manager that PopOS uses. The left-hand dock is gone. Looking at 'Appearance -> Background' in Settings, the PopOS wallpapers are present. If I go to 'Appearance -> Appearance', the light/dark theme chooser shows a visual with "Pop!_OS User" in it. The scrolling direction has been reversed. The icons are different. The Ubuntu Software Center is missing, but there's no "Pop Shop" in its place. The list goes on...  At the same time, a lot of my system is still very much how it was a few days ago when it was "pure Ubuntu" so to speak. My browser, IDE, files/folders, etc. are all the same... For context, I used to dual boot Windows and PopOS on a single SSD, but I've since wiped the drives I use (including resetting partitions). Now I use Windows on the SSD and Ubuntu on a new second drive... I can't imagine how anything from my old PopOS installation would carry over, let alone suddenly reappear inside Ubuntu after an update. EDIT: When running Software Updater again, it shows a full list of what it's trying to install: . When I try to install these packages, it fails midway through. That partially explains things... but why is this even happening? EDIT2: It is trying to install pop-gnome-initial-setup.deb which seems to conflict with gnome-initial-setup. Weird.


While i'm playing around with the python interpreter, i noticed that it outputs the value 0.7999999999999998, as the answer of 4-3.2 (4 subtract by 3.2) which is not correct. What is the reason for this? Isn't this going to be effected to those who use python programs in their businesses? How can i solve this in python?

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


Let G be an abelian group and let H and K be finite cyclic subgroups with |H| = r and |K| = s. Show that G contains a cyclic group of order lcm(r, s).  I already try many times.  I don't know how to complete proof.  When I prove this problem, i find error.....  help me.

Let $G$ be abelian, $H$ and $K$ subgroups of orders $n$, $m$. Then G   has subgroup of order $\operatorname{lcm}(n,m)$.   This is a statement that my lecturer mentioned in my (beginners') Abstract Algebra class. I'm not sure I understand why it's true.  What I have so far: Use the abelian group structure theorem on $\langle H, K\rangle$ (finite group generated by $H$ and $K$). Then $\langle H,K\rangle=C_{a_1}C_{a_2}\dotsm$ and $n, m |\langle H,K\rangle$. Which means it's also true that $\operatorname{lcm}(n,m)|\langle H,K\rangle$. Can I leverage this to say there's a subgroup of order $\operatorname{lcm}(n,m)$?


So I have the following integral:  $$\int_0^2 \frac{dt}{4+t^2}$$  In order to solve it am I able to say it is equivalent to the following integral?  $$\int_0^2 \frac{1}{4+t^2} dt$$  If not how can I go about solving it. Thanks!

How do I solve an integral with a differential on top? E.g.: given this integral to evaluate: $$\;\int \frac{dt}{(\cos(t))^2}\;\;?$$  What does it even mean when there's a differential?


In this question, I would like to ask two things:    outlier detection normality test   Details are as follows:  I need to detect and remove outliers in my data. Before doing that, I want to test if my data is normally distributed or not. I have two variables X(independent) and Y(dependent) and have 951 records for both of them.   I want to know that while testing the normality, do I need consider both the variables simultaneously or both the variables but one at a time? (Somewhere, I have read that only dependent variable is considered to test the normality).  The attached figures show the results of normality test (Analyse>>Descriptive >>Explore) of dependent variable. If normality test is done only on dependent variable, then it shows that the data is highly skewed. In such a case, how can I remove the outliers?  The significance level of Shapiro-Wilk test and Kolmogorov-Smirnov test is 0.00. Skewness has statistic of 22.909 with SE of 0.079.

A former colleague once argued to me as follows:      We usually apply normality tests to the results of processes that,   under the null, generate random variables that are only   asymptotically or nearly normal (with the 'asymptotically' part dependent on some quantity which we cannot make large); In the era of   cheap memory, big data, and fast processors, normality tests should   always reject the null of normal distribution for large (though not insanely large) samples. And so, perversely, normality tests should   only be used for small samples, when they presumably have lower power   and less control over type I rate.   Is this a valid argument? Is this a well-known argument? Are there well known tests for a 'fuzzier' null hypothesis than normality?


I want to display the number in fax format. If the user enter the number as 12345678910 it need to be formated as (1234)(567)(8910) can it be possible through formula field without writing trigger. If possible please help me how can we achieve it through formula field or please suggest me any other best way to achieve it.

I have an import of phone numbers and fax numbers that get updated every night into the standard phone and fax fields.  The problem is they get save without formatting (ex. 1234567899)  I need to have these updated with the correct phone number format with the dashes (ex 555-555-5555).  Does anyone know a formula I can use? to create a workflow rule to have these updated or a validation rule? Thanks.


I'm looking for code which gives me permutations of the numbers in the range 0-9.  The permutations should be of length x and the numbers can repeat.  I want to get these permutations one by one. When I find the permutations I need, I don't need the remaining ones.  All possibilities I have found so far give me all permutations simultaneously and it takes too much time to generate all of them.

How do you generate all the permutations of a list in Python, independently of the type of elements in that list?  For example:  permutations([]) []  permutations([1]) [1]  permutations([1, 2]) [1, 2] [2, 1]  permutations([1, 2, 3]) [1, 2, 3] [1, 3, 2] [2, 1, 3] [2, 3, 1] [3, 1, 2] [3, 2, 1]


I am using Smote to treat Class Imbalance and I apply Smote only on the train data. I fit a model using balanced data("Smoted" data). Now I need to check recall and precision for train and test data(to see if the model is stable or not). For checking recall and precision in train data, should I use the balanced train data(on which Smote was applied) or the imbalanced train (original train) data ?

I am building a binary classification model for imbalanced data (e.g., 90% Pos class vs 10% Neg Class).  I already balanced my training dataset to reflect a a 50/50 class split, while my holdout (training dataset) was kept similar to the original data distribution (i.e., 90% vs 10%).  My question is regarding the validation data used during the CV hyperparameter process. During each iteration fold should:  1) Both the training and test folds be balanced  or  2) The training fold should be kept balanced while the validation fold should be made imbalanced to reflect the original data distribution and holdout dataset.  I am currently using the 1st option to tune my model; however, is this approach valid given that the holdout and validation datasets have different distributions?


I can't understand the output of this program .  What I get of it is , that , first of all , the pointers p, q ,r ,s  were pointing towards null .   Then , there has been a typecasting . But how the heck , did the output come as 1 4 4 8 . I might be very wrong in my thoughts . So , please correct me if I am wrong .   int main() {      int a, b, c, d;      char* p = (char*)0;      int *q = (int *)0;      float* r = (float*)0;      double* s = (double*)0;       a = (int)(p + 1);      b = (int)(q + 1);     c = (int)(r + 1);     d = (int)(s + 1);      printf("%d %d %d %d\n", a, b, c, d);       _getch();     return 0;  }

What are all the common undefined behaviours that a C++ programmer should know about?  Say, like:  a[i] = i++;


I'm using a laptop with Ubuntu 14.04, using a external monitor I can adjust the color temp of the external monitor using its physical buttons in the monitor.  The question is, is there a way to adjust Brightness, Contrast. R,G,B slider with Ubuntu using a Graphical User interface, is there such a GUI for adjusting color temperature?

How do I go about changing my laptop's display's color temperature? And I don't mean through something like the Red, Green, Blue sliders in the NVIDIA config menu. I'm talking about like adjusting in degrees, like editing a photo's white balance.  So now I've found Redshift and it's doing me pretty good. I thought it might be helpful if I out here the command I'm using.  redshift -t 5000:5000 -g .5   By adding this to my start up commands I should be good.  I'm still open to other suggestions, because I'd like something that actually edited my xorg.conf or something like that.


Is there a notation for addition form of factorial?  $$5! = 5\times4\times3\times2\times1$$  That's pretty obvious. But I'm wondering what I'd need to use to describe  $$5+4+3+2+1$$  like the factorial $5!$ way.  EDIT: I know about the formula. I want to know if there's a short notation.

(Pardon if this seems a bit beginner, this is my first post in math - trying to improve my knowledge while tackling Project Euler problems)  I'm aware of Sigma notation, but is there a function/name for e.g.  $$ 4 + 3 + 2 + 1 \longrightarrow 10 ,$$  similar to $$4! = 4 \cdot 3 \cdot 2 \cdot 1 ,$$ which uses multiplication?   Edit: I found what I was looking for, but is there a name for this type of summation?


There is a new machine that need to install a Windows OS. However, you are given an ISO file (that contains the Windows OS) and an external hard disk only.   How do I go about to install it?  Please note that you are not provide any blank CD or DVD to burn the ISO file.

Is it possible to install Windows from an external hard drive?  I have Windows XP installed on my laptop, and I want to remove it and install Windows 7.  My Windows 7 installation is in an .iso format on an external USB hard drive.  Is it possible to install it or will I need to put in a DVD before I start installing?


The quadrilateral $ABCD$ is cyclic $(O)$; $AB=a, BC=b, CD=c, AD=d, AC=x, BD=y$.     Prove : $\frac{x}{y}=\frac{ad+bc}{ab+cd}$   Thanks :)  P/s : I have no ideas about this problem ! :(

If $ABCD$ is a cyclic quadrilateral, then  $$ AC\cdot(AB\cdot BC+CD\cdot DA)=BD\cdot (DA\cdot AB+BC\cdot CD) $$ I tried using many approaches, but I could not find a proper solution. Can anyone please help me with this problem?


$X \geq 0$ be a random variable defined on $(\Omega,\mathcal{F},P)$. Show that $\mathbb{E}[X]<\infty \iff \Sigma_{n=1}^\infty P(X>n) < \infty $.  I got the reverse direction but I am struggling with the $"\implies"$ direction. So far, I have the following worked out:  $\mathbb{E}[X]<\infty$  $\implies \int_0^\infty (1-F(x)) dx < \infty$ (where $F$ is the distribution function of the random variable X)  $\implies \int_0^\infty (1-P(X\leq x)) dx < \infty$  $\implies \int_0^\infty P(X>x) dx < \infty$  Consider $\int_0^\infty P(X>x) dx$  $= \Sigma_{n=1}^\infty \int_{n-1}^n P(X>x) dx$  This is the point I am stuck at. Any help will be deeply appreciated!

Let $X$ be a non-negative random variable and $F_{X}$ the corresponding CDF. Show,   $$E(X) = \int_0^\infty (1-F_X (t)) \, dt$$   when $X$ has : a) a discrete distribution, b) a continuous distribution.   I assumed that for the case of a continuous distribution, since $F_X (t) = \mathbb{P}(X\leq t)$, then $1-F_X (t) = 1- \mathbb{P}(X\leq t) = \mathbb{P}(X>  t)$. Although how useful integrating that is, I really have no idea.


I know implicit conversion from char ** to const char ** cannot be done and why, and that the conversion to char *const * works.  See bottom for links to explanation on that.  It all makes sense apart from one particular thing.  So I have the following code:  #include <stdio.h>  void print(const char *const*param) {     printf("%s\n", param[0]); }  int main(int argc, char **argv) {     print(argv);     return 0; }   If I compile this as a C++ code, it compiles quite fine.  However, if the same code is compiled as a C code only, I get an error (well, a warning, but let's suppose -Werror, i.e. treat warnings as errors).  gcc:  test.c: In function ‘main’: test.c:12:11: warning: passing argument 1 of ‘print’ from incompatible pointer type [-Wincompatible-pointer-types]      print(argv);            ^ test.c:4:1: note: expected ‘const char * const*’ but argument is of type ‘char **’  print(const char *const*param)  ^   clang:  test.c:12:11: warning: passing 'char **' to parameter of type 'const char *const *' discards qualifiers in nested pointer types [-Wincompatible-pointer-types-discards-qualifiers]     print(argv);           ^~~~ test.c:4:25: note: passing argument to parameter 'param' here print(const char *const*param)                         ^   Both behaviours are standard-independent and also compiler-independent.  I tried various standards with both gcc and clang.  There are two reasons for this inquiry.  Firstly, I want to understand whether there is a difference and, secondly, I have a function that does nothing with any layer of the pointers and I need it to be able to work with const char ** as well as char *const * and char **.  Explicitly casting each call is not maintainable.  And I have no idea how should the function prototype look like.    This is the question that started my curiosity:   And here is another nice explanation for the char ** => const char** problem:   If the links are confusing related to this question, feel free to edit them out.

The following code snippet (correctly) gives a warning in C and an error in C++ (using gcc & g++ respectively, tested with versions 3.4.5 and 4.2.1; MSVC does not seem to care):  char **a; const char** b = a;   I can understand and accept this. The C++ solution to this problem is to change b to be a const char * const *, which disallows reassignment of the pointers and prevents you from circumventing const-correctness ().  char **a; const char* const* b = a;   However, in pure C, the corrected version (using const char * const *) still gives a warning, and I don't understand why. Is there a way to get around this without using a cast?  To clarify: 1) Why does this generate a warning in C?  It should be entirely const-safe, and the C++ compiler seems to recognize it as such. 2) What is the correct way to go about accepting this char** as a parameter while saying (and having the compiler enforce) that I will not be modifying the characters it points to? For example, if I wanted to write a function:  void f(const char* const* in) {   // Only reads the data from in, does not write to it }   And I wanted to invoke it on a char**, what would be the correct type for the parameter?


Show that if $f$ is continuous on $[0,1]$ and $0\leq f(x) \leq 1$ for all $ x \in [0,1]$, then there exists one point  $c \in [0,1]$ at which $f(c)=c$.      (Hint: Apply the Intermediate Value Theorem to the function $g(x)=x−f(x)$.)   I have some idea how to do this, but the area where I am getting stumped is...the value of $f(x)$?  How can I find the value of $f(x)$?  Do I even need to find $f(x)$?  Edit:  okay I got something...  I only need f(0)>0 and f(1)<1 to show  g(0)<0  So then what happens for f(0)=0 or f(1)=1 ?

Question: Let $a, b \in \mathbb{R}$ with $a < b$ and let $f: [a,b] \rightarrow [a,b]$ continuous. Show: $f$ has a fixed point, that is, there is an $x \in [a,b]$ with $f(x)=x$.  I suppose this has to do with the basic definition of continuity. The definition I am using is that $f$ is continuous at $a$ if $\displaystyle \lim_{x \to a} f(x)$ exists and if $\displaystyle \lim_{x \to a} f(x) = f(a)$. I must not be understanding it, since I am not sure how to begin showing this... Should I be trying to show that $x$ is both greater than or equal to and less than or equal to $\displaystyle \lim_{x \to a} f(x)$ ?


What kind of logical fallacy is this, if any?  A person (Mr. A) complains about climate change. A critic (Mr. B) replies, "You own a car, so you can't complain."  Mr. B's argument is that anyone who owns a car uses fossil fuels. Therefore that person contributes to climate change, which makes him or her a hypocrite for complaining about climate change.  Of course, MILLIONS of people are virtually forced to either own cars or ride the bus. They aren't advocating for a return to horse and buggy days. What they want is a sensible approach to mitigating climate change, like encouraging mass transit and regulating industry.

I've heard many people say if you X, then you're part of the problem. I'm not a logic or philosophy expert so I was wondering if this is a logical fallacy (or something along those lines)? If so, what is the name of the fallacy?  A personal example (I'm Man B):   Man A: You going to vote? Man B: No, I' don't vote. Man A: Why not? Man B: Personal reasons. Man A: You're part of the problem.   That's the entire conversation. Man B has personal reasons why Man B doesn't do something, then Man A (although asked as if he wanted to understand) concludes that Man B is part of a problem only Man A is aware of. Man A may care about low voter turnout, who the winner is, the future of voting, principle of honoring your nation's history, etc.   For the sake of argument, say Man A cared about the future of voting (and it's effect on future communities). And also say Man B doesn't want to vote because he doesn't have time to be properly educated on each candidate (2 jobs, grad school, kids, sick parents, etc.), and therefore does not want to vote blindly. However, Man A does not think this is a good enough reason and concludes Man B is just "part of the problem". Note, for Americans, don't think of this in context of Donald Trump as a candidate. It's obvious why Trump is a bad choice (for most people I know at least). Think of all candidates being fair choices.


Here's the scenario. I got the Hylian shield (I'm sure I saved), I then got out of castle and travelled to buy ancient armor. Then bowling. Then re-up my arrows. I then saved again and ended my game. Today I started the game (after software update) and have the arrows, money, and armor, but the Hylian shield is nowhere to be seen.  I'm pretty sure I didn't drop it or anything else like that, but I guess it's possible. So my question is, if I go to my oldest autosave and it's still missing, am I able to go back to a more recent save? I don't want to lose more stuff.  If anyone else can suggest what my options are, I'd appreciate it.

I would like to revisit and re-do certain one-off events in this game such as Eventide Island. There's probably a save file where I haven't done Eventide yet - what will happen if I load that? Will the game keep my newest save files intact, so that I can resume normal play after a short time travel?  I assume it does, would be pretty awful if it somehow automatically overwrote manual saves - but I wanna check to be sure.


Let $(X, \Sigma, \mu)$ be a measure space and $f$ be a measurable function.  For each $1\le p<+\infty$, setting $$\|f\|_{p}:=\left(\int\limits_{X}|f|^{p}\, \mathrm{d}\mu\right)^{\frac{1}{p}} \text{(not necessary finite)}.$$  The question is that $$\|f\|_{p}\to \|f\|_{p_{0}}\, \text{ as }\, p\to p_{0}?$$

I ran into the following problem when I was doing my homework, and I have no thoughts on where I should start with:  (1) If $f\in L^{2}$, show that $\displaystyle \lim_{p \rightarrow 1^{+}}\int_{[0,1]}|f|^{p}=\int_{[0,1]}|f|$  (2) If $0<p$, show that $\displaystyle \lim_{q\rightarrow p^{-}}||f||_{q}=||f||_{p}$  My first thought was Generalized LDCT, but it didn't seem to work. I also made some other attempts but none of them were successful... Can anybody give me some hints on how I should look at this question?  Also, I know if $p\rightarrow\infty$ then $||f||_{p}\rightarrow||f||_{\infty}$ on $[0,1]$, but does similar continuity in p holds for other $L^{p}[0,1]$ norms in general?  Thank you!  Edit:   Sorry if I did not make it clear enough in the question. All $L^{p}$ refers to $L^p[0,1]$.  The first question is found  (thanks to t.b.), but the second question remains, mainly because $f$ is not guaranteed to be in any $L^{p}$.


I recently asked a question which I still haven't gotten the answer to, yet some people decided to downvote my question. I agree that downvoting is useful for discerning which solution is the right one, but why do people downvote questions?   I am a beginner iOS developer, so maybe a lot of the questions I ask are not useful for intermediate or advanced developers, but I am using this site just like anyone else: to learn. It saddens me that there are some people out there who choose to use their privilege of downvoting so that my question is shown fewer to the users on this site. If the question is not useful to you advanced developers, it is useful to someone, especially to the person asking the question.   So to those who downvote questions, why do you do it?

I understand the purpose of up/downvoting answers -- some answers are better than others, some answers may be wrong, .etc.  With regard to questions, though, there are other mechanisms to deal with "bad" questions:  comments, close, flag.  A poorly written question should be improved.  A bad question should be closed/deleted.  Often, though I see poorly written questions downvoted. I'm not sure what this accomplishes.  I get loss of rep for offensive or spam questions, but for an off-topic question?  or one that is just poorly written?   Why?  It seems to me that rep ought to be based more on answers on a site of this type.   Fundamentally, it seems that rep ought to be based on what you add to the site, not what you ask of it.  A particularly good question does add to the site, but a poor question doesn't really detract from it in the same way that a bad (wrong) answer does. Sure, go ahead and give people more rep for asking a particularly good question, but why punish people for asking bad questions when there are other ways of handling that.  Why not handle questions more like comments and allow upvotes, but not downvotes?  It seems to me that many, if not most, of the downvoted questions are first timers.  It's more likely that your first introduction to the site will be in asking a question, rather than answering. There is a significant risk to alienating new users when their questions are downvoted -- there's a visceral response to seeing that negative number next to your question.  Why not let the close/flag system weed out questions that don't belong and the comment system work to improve poorly worded questions.


I'm setting my report's parameters with default values and I don't want the report run until the user click in View Report button...  Can someone tell me how can I do it please?  thankssss

We have some SQL server reporting services reports. I didn't write then but I have to take care of them.  These reports fire when opened in the browser, and with the default parameters (search terms and restrictions are blank) they retrieve a lot of data, which is slow. The client would prefer that the report is not generated until the user enters parameters and presses "view report"  Unfortunately I don't know SSRS at all well - how do I stop the report from firing when it is opened?   The details of how to do it on a deployed report (as per Rihan Meij's answer) is as follows:   Click on a report, click on "properties" at the top. You may have to wait a bit, because the slow report may be running now. Then click on "parameters" on the left.   For each parameter, make sure that "Prompt User" is checked, and for at least one parameter, "Has Default" is not checked. Click on "View" again at the top left (or go back to the folder and click on the report name) to view the report, and note that the report does not fire right away.  In the report builder, you can do this via the "Filter" menu. De-select values from at least one filter, and save the report.  Is it also possible to stop reports from firing on loading when the report has no parameters?


I have installed the trial Ubuntu on my Mac Air. When I click in applications explore it can't find any. How can I work this please?

I did an upgrade today to the latest version of ubuntu. Everything looked good and fine only for me to discover that I cannot find my applications after clicking the 'Show Applications' icon. The same applies when I search for an application in the search bar, I do not see it. It shows me an endless search.  These are the screenshot images of the problem:      In the meantime, I access my applications from the menu at the top bar and also use the terminal to run applications with CLI.


What is the difference?  I can see that the 'Additional drivers' section installed drivers that are older than the latest ones available on the website.  Are there any drawback to installing Nvidia drivers straight from the website with the .run file?

I just ordered the Nvidia GTX card. I have a dilemma, though. Should I keep using the driver which is available in "additional drivers" in Ubuntu, or should I install the driver from the Nvidia site?  So which driver is the best for me?


When I add phablet-team's PPA using  sudo add-apt-repository ppa:phablet-team/tools   I get:  Err:17 http://ppa.launchpad.net/webupd8team/atom/ubuntu disco Release 404  Not Found [IP: 91.189.95.83 80] Reading package lists... Done                        W: GPG error: https://packages.microsoft.com/repos/vscode stable InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY EB3E94ADBE1229CF E: The repository 'https://packages.microsoft.com/repos/vscode stable InRelease' is not signed. N: Updating from such a repository can't be done securely, and is therefore disabled by default. N: See apt-secure(8) manpage for repository creation and user configuration details. E: The repository 'http://ppa.launchpad.net/mystic-mirage/pycharm/ubuntu disco Release' does not have a Release file. N: Updating from such a repository can't be done securely, and is therefore disabled by default. N: See apt-secure(8) manpage for repository creation and user configuration details. E: The repository 'http://ppa.launchpad.net/noobslab/apps/ubuntu disco Release' does not have a Release file. N: Updating from such a repository can't be done securely, and is therefore disabled by default. N: See apt-secure(8) manpage for repository creation and user configuration details. E: Failed to fetch http://repo.mysql.com/apt/ubuntu/dists/disco/InRelease  Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?) E: The repository 'http://repo.mysql.com/apt/ubuntu disco InRelease' is not signed. N: Updating from such a repository can't be done securely, and is therefore disabled by default. N: See apt-secure(8) manpage for repository creation and user configuration details.   what can I do??

When updating, I get the following error message:   W: The repository 'http://ppa.launchpad.net/mc3man/trusty-media/ubuntu xenial Release' does not have a Release file.   Here, I find another statement on this error:   This recommends removing certain PPAs; and, I'm not sure if I should do that since it might mean not getting the updates that I need.    Is this what I should do?


What is the minimum value of  $|x-1| + |x-2| + |x-3| .... + |x - k + 1| + |x-k|$ equal to?  I suppose it depends on whether or not $k$ is even or odd.   I was able to solve for $k = 3$ (three terms) using the triangle inequality - but couldn't generalize it to the above. Please help.

Prove:$|x-1|+|x-2|+|x-3|+\cdots+|x-n|\geq n-1$   example1: $|x-1|+|x-2|\geq 1$  my solution：(substitution)  $x-1=t,x-2=t-1,|t|+|t-1|\geq 1,|t-1|\geq 1-|t|,$  square,  $t^2-2t+1\geq 1-2|t|+t^2,\text{Since} -t\leq -|t|,$  so proved.  question1 : Is my proof right? Alternatives?  one reference answer:   $1-|x-1|\leq |1-(x-1)|=|1-x+1|=|x-2|$  question2 : prove:  $|x-1|+|x-2|+|x-3|\geq 2$  So I guess:( I think there is a name about this, what's that? wiki item?)  $|x-1|+|x-2|+|x-3|+\cdots+|x-n|\geq n-1$  How to prove this? This is  question3. I doubt whether the two methods I used above may suit for this general case.  Of course, welcome any interesting answers and good comments.


I have ubuntu server 12.10 and installed ubuntu-desktop to access it via GUI and changed the default runlevel to 5. Now I get the GUI login screen with my username (display name) but when i enter my password the screen just flicks and comes back to login screen ( doesnt give me any error). the same user works fine with same credentials in CLI.  strange thing is when i click on guest, it logs me in straight away and works fine.  Any solution please.   PS: I am new to Ubuntu/linux, Keeping in mind, please be basic and simple.

My Ubuntu is stuck in a login loop when trying to enter my desktop. When I login, the screen gets black and soon after that the login screen comes back.   I've read that the problem might be caused by an error depending on the graphics, here's my graphics card: ATI Radeon 7670M


Getting Below error in the installation Extracting VMware Installer...done. /tmp/vmis.HSyzgr/install/vmware-installer/vmware-installer: line 420: /tmp/vmis.HSyzgr/install/vmware-installer/vmis-launcher: cannot execute binary file: Exec format error

We are trying to install jevois-inventor onto the ubuntu18.04 but we flashed the ubuntu18.04 onto a raspberry pi 4 which is an arm64 architecture(we think). We tried to install amd64 packages individually on ubuntu terminal, but we can not install build-essential, gcc, etc packages for amd64.(We are new to Ubuntu and raspberry pi)


So couple of my classmates are chatting in a group & ...   A: Turn off your GPS, now everyone knows where you are!  B: Ok then tell me where I am/where am I?  Which one is correct in this situation?  My thought was because she already knows where she is, tell me where I am is the correct response here.

The grammars I've seen state that dependent clauses never undergo inversion. This agrees with sentences like     Tell me where he is.   But how sentences like     Tell me, where is he?   should be analyzed? Isn't where is he a dependent clause in this case?


I'm a beginner in machine learning. I'm working on the . One of the features in this problem is the passenger class. The passenger class can be either 1st, 2nd, or 3rd class. I was thinking of using logistic regression to solve this problem, and the passenger class would be one of the features, where 1st passenger class is assigned value 1, 2nd assigned value 2, and so on.  I have few questions:   Is it valid to use the approach of assigning numerical values for non-numerical features, i.e. the classes? If so, does it matter what value you assign to each type for a feature? That is, would it make a difference in the outcome if I assign say 3 for class 1, 1 for class 2, and 2 for class 3?   For the second question, I'm pretty sure it'd have an effect on the parameters that are learnt, but I'm wondering whether it'd have any effect on the accuracy of the hypothesis function.

I am using a logit model. My dependent variable is binary. However I have an independent variable which is categorical and contains the responses: 1.very good, 2.good, 3.average, 4.poor and 5.very poor. So, it is ordinal ("quantitative categorical"). I am not sure how to handle this in the model. I am using gretl.  [Note from @ttnphns: Although the question says the model is logit (because the dependent is categorical), the crucial issue - ordinal independent variables - is basically alike, be the dependent categorical or quantitative. Therefore the question is equally relevant to, say, linear regression too - as it is to logistic regression or other logit model.]


I found this model over here  But the model is imported without its materials. How can I import it into Blender with its proper materials so it looks as it does in UE4?

I used node textures in a mesh I exported to .FBX.  I then imported it into Unreal Engine 4 and it didn't import any textures; I clicked the Upload Textures option in Unreal Engine.  Is there something I'm doing wrong or is it Blender?


Given two paths, how can I compute the relative path from one to another?  I thought about using split in fancy ways, but it seems kind of hacky, especially in cases like: "http://foo.com/bar/baz#header" or "http://foo.com/bar/baz"?param=value.   An example would be:  String url1 = "http://foo.com/bar/baz"; String url2 = "http://foo.com/bar/qux/quux/corge";  System.out.println(relative(url1, url2)); // -> "../qux/quux/corge"

Given two absolute paths, e.g.  /var/data/stuff/xyz.dat /var/data   How can one create a relative path that uses the second path as its base? In the example above, the result should be: ./stuff/xyz.dat


Trying to backup my System using Deja Dup I receive errors about files my normal user can not access. To backup my System I need to configure and later run DejaDup as root.  I know a similar question exists here  but the solutions do not work in Ubuntu 17.10. for me.  When trying to gksu deja-dup-preferences as suggested by @Jakob or following the detailed explanation of Fran, I get the Errormessage:  "Unable to copy the user's Xauthorization file."  Further reading about  teaches me, that this is Ubuntu 17.10. new feature not to allow GUIs as root. I wonder what would be the best practice to get to run DejaDup as root in such a way that I can configure the backup settings and then start the backup-process. Any suggestions or ideas would be kindly appreciated. Thx.

I installed Ubuntu 17.10. Now I am having trouble with gksu:  $ gksu -dg synaptic No ask_pass set, using default! xauth: /tmp/libgksu-HgUjgQ/.Xauthority STARTUP_ID: gksu/synaptic/8760-0-alex-XPS-15-9530_TIME4974977 cmd[0]: /usr/bin/sudo cmd[1]: -H cmd[2]: -S cmd[3]: -p cmd[4]: GNOME_SUDO_PASS cmd[5]: -u cmd[6]: root cmd[7]: -- cmd[8]: synaptic buffer: -GNOME_SUDO_PASS- brute force GNOME_SUDO_PASS ended... Yeah, we're in... Unable to init server: Could not connect: Connection refused (synaptic:8767): Gtk-WARNING **: cannot open display: :1 xauth: /tmp/libgksu-HgUjgQ/.Xauthority xauth_env: (null) dir: /tmp/libgksu-HgUjgQ   If I don't use -g, the password dialog is disabled. So looks like a problem with creating a tty for root.  Any advice?


Can an astronaut in free space turn his head without moving (turning) the rest of his body (and also not moving hands or legs) in opposite direction?

We know that if an imaginary astronaut is in the intergalactic (no external forces) and has an initial velocity zero, then he has is no way to change the position of his center of mass. The law of momentum conservation says: $$ 0=\overrightarrow{F}_{ext}=\frac{d\overrightarrow{p}}{dt}=m\frac{d\overrightarrow{v}_{c.m.}}{dt}$$  But I don't see an immediate proof, that the astronaut can't change his orientation in the space. The proof is immediate for a rigid body (from the law of conservation of angular momentum). But the astronaut is not a rigid body.   The question is: can the astronaut after a certain sequence of motions come back to the initial position but be oriented differently (change "his angle")? If yes, then how?


I understand what a Java WeakReference is. What I want to know is on which kind of concrete problems it's used normally as a solution. Are there any patterns that include them?

The use of weak references is something that I've never seen an implementation of so I'm trying to figure out what the use case for them is and how the implementation would work. When have you needed to use a WeakHashMap or WeakReference and how was it used?


Is there a name for the operator that reflects a matrix over the diagonal running from the top-right to the bottom-left? For the moment, define this reflection of a matrix $A$ as $A^*$. Is there a name for the family of matrices such that $A = A^*$? For example, let $$ A = \begin{bmatrix} 1 & -1 & -1 & 1\\ 0 & 1 & 0 & -1\\ 0 & 0 & 1 & -1\\ 0 & 0 & 0 & 1 \end{bmatrix}. $$

I have a matrix which is kind of symmetrical with the other diagonal, i.e., something like  $$A = \left[ \begin{array}{c c c c}    a & b & c & d \\    e & f & g & c \\    h & i & f & b \\    j & h & e & a  \end{array} \right]$$  Does this matrix have a special name in literature? What are it's properties?  And a matrix that is symmetrical by both diagonals   $$A = \left[ \begin{array}{c c c c}    a & b & c & d \\    b & e & f & c \\    c & f & e & b \\    d & c & b & a  \end{array} \right]$$  What's the name of it? Any interesting properties?


I want to create in blender a realistic physic simulation with bottles that have balls inside, first example is created Blender and the second in another 3D software. How to create this simulation in blender? I have to checked the normals, applied all transforms for scale, position and rotation, set Origin > origin to geometry, increasing the Steps per second and Solver Iterations in the Rigid Body World settings (I tried with the maxima 1000 and 100), set collision shape to Mesh and tried 0.4 or 0 as margins and source to final, but doesn't work..., the simulation is a mess...   I have attached here the blend file, Who can help me how to configure the rigid body settings to achieve a realistic result similar with the second example ?  Kind Regards!

I want to create in blender a realistic physic simulation with bottles that have balls inside, first example is created Blender and the second in another 3D software. How to create this simulation in blender? I have to checked the normals, applied all transforms for scale, position and rotation, set Origin > origin to geometry, increasing the Steps per second and Solver Iterations in the Rigid Body World settings (I tried with the maxima 1000 and 100), set collision shape to Mesh and tried 0.4 or 0 as margins and source to final, but doesn't work..., the simulation is a mess...  I have attached here the blend file, Who can help me how to configure the rigid body settings to achieve a realistic result similar with the second example ?  Here it is my blend file:     Who can help me... ?


Let $V=\mathbb{R}^n$ with an inner product. I need to show that $\operatorname{ker}(A^T) = (\operatorname{Im} A)^\perp$. I showed that $\operatorname{Im} A^T \subset \operatorname{ker}(A^T)$ but somehow I'm not able to show the other way $\operatorname{ker}(A^T) \subset \operatorname{Im} A^T$. Can someone give me just the idea how to show the other way (no full proof!) Thank you very much! ;)

How can I prove that, if $V$ is a finite-dimensional vector space with inner product and $T$ a linear operator in $V$, then the range of $T^*$ is the orthogonal complement of the null space of $T$?  I know what I must do (for a $v$ in the range of $T^*$, I have to show that $v\perp w$ for every $w$ in $\ker(T)$ and then do the opposite), but I don't know how to show that this inner product is zero.


A part of my document looks like this:  \paragraph{blah}   \begin{figure}[ht!]  \centering  \includegraphics[width=4.5in]{3a.jpg}  \caption{(a)}     \end{figure}  \begin{figure}[ht!]  \centering  \includegraphics[width=4.5in]{3b.jpg}  \caption{(b)}  \end{figure}  \begin{figure}[ht!]  \centering  \includegraphics[width=4.5in]{3c.jpg}  \caption{(c)}  \end{figure}   and image 3a shows before the 'blah' paragraph heading. Why is it doing that and how do I fix it?

I would appreciate if someone could tell me difference between [t] and [ht] in the following example? I don't see a difference in the output pdf file.  \begin{figure}[ht] ... \end{figure}   and  \begin{figure}[t] ... \end{figure}


, I'm curious to know how it was possible for him to become more powerful.  In reference to this quote:     You can't win, Darth. If you strike me down, I shall become more powerful than you could possibly imagine.   Just after this Darth Vader swings at Obi-wan and just prior to being sliced cleanly in half Obi-wan dissipates, and as such he remains unstruck.  Would Obi-wan have been more powerful if he got Darth Mauled in twain?

In Star wars: IV A New Hope, Obi-Wan says to Darth Vader:     You can't win, Darth. If you strike me down, I shall become more powerful than you could possibly imagine.    What did he mean by this? Was he bluffing? Was he alluding to him being able to help Luke as a Force Ghost? Or was he talking on behalf of The Force?


Problem Show that $\text{trace}(A^TA) \ge 0$ and $\text{trace}(A^TA)=0$ if and only if $A = O$ when $A \in \mathbb{R}^{n \times n}, n \in \mathbb{N}$. Symbol $O$ denotes zero matrix. Attempt to show I think I know intuitively this is right but how to prove this? I could show some example but unfortunately, this won't exactly prove anything. The problem is how to approach this proof?

Given that $A_{m \times n}$ has real entries, I want to prove that $\operatorname{trace}(A^TA) = 0$ if and only if $A = 0$. In other words, I want to show that the only way for the trace of $(A^TA)$ to be zero is if $A$ is a zero matrix, and that if $A$ is a zero matrix then $A^TA$ has a trace of zero. Intuitively this makes sense to me. My idea is that in order to get zeros on the main diagonal of any product of matrices I'd need at least one of the matrices to have zeros on its main diagonal. In this case, because the product is between $A$ and its transpose, I figure it $A$ does indeed need to be a zero matrix. However, I'm having difficulty turning my intuition into an actual proof.


I have the following code  public static void main(String[] args) {  String word = "Super";  reverseString(word);  System.out.println(word);  }  public static String reverseString(String word) {  String helper = "";  int i = word.length() - 1;  while (i >= 0) {     helper += word.charAt(i);     i--;  }  return helper;   I do not understand why when I'm printing the "word" variable it still prints "Super" even though I changed it in the reverseString method. I understand that strings are passed by reference and not a copy like primitive values.  If I do word = reverseString(word) it prints the reverse what I expect, "repuS"  Thanks

I always thought Java uses pass-by-reference. However, I've seen a couple of blog posts (for example, ) that claim that it isn't (the blog post says that Java uses pass-by-value). I don't think I understand the distinction they're making. What is the explanation?


which is better to use Mysql or Mysqli and in what conditions? I want to start a project that requires a database just wanted to know which of the two is better

Which is better, MySQL or MySQLi? And why? Which should I use?  I mean better not just in terms of performance, but any other relevant feature.


I'm trying to add share feature to my app I tried this code and it's work fine on Android 5.0 and Android 7.0 but when I run my app on Android 6.0.1 I get this error     Process: maa.myapp, PID: 20195                                                                            java.lang.NullPointerException: uriString                                                                                at android.net.Uri$StringUri.(Uri.java:476)                                                                                at android.net.Uri$StringUri.(Uri.java:466)                                                                                at android.net.Uri.parse(Uri.java:438)                                                                                at maa.myapp.full$2$2.onResourceReady(full.java:122)                                                                                at maa.myapp.full$2$2.onResourceReady(full.java:118)   Here is my code:  Glide.with(getApplicationContext())                     .load(url)                     .asBitmap()                     .diskCacheStrategy(DiskCacheStrategy.ALL)                     .into(new SimpleTarget<Bitmap>() {                         @Override                         public void onResourceReady(Bitmap resource, GlideAnimation<?super Bitmap> glideAnimation) {                             String bitmapPath = MediaStore.Images.Media.insertImage(getContentResolver(), resource,"title", null);                             Uri bitmapUri = Uri.parse(bitmapPath);                             Intent intent = new Intent(Intent.ACTION_SEND);                             intent.setType("image/png");                             intent.putExtra(Intent.EXTRA_STREAM, bitmapUri);                             startActivity(Intent.createChooser(intent, "Share"));                             lt.success();                         }                     });

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 have a staging server that accidentally got indexed by google. I want to remove ALL pages from google for that site: i.e. stagingserver.mycompany.com. I added a robots.txt to the root of the site with following content:  User-agent: * Disallow: /   After several weeks, none of the pages have been removed. When I google:  site:stagingserver.mycompany.com   I get pages and pages of results. I went into Webmaster tools. I created many removal requests, and they only work for those specific pages. When I add a directory removal:  http://stagingserver.mycompany.com/*   it takes a few hours for the status to turn from pending to removed, but all the unwanted pages are still not removed. It seems that there's no way to remove ALL pages from google. Is this right?  NOTE:  I can't send a 404 for every page because this is a development site, that is being worked on and reviewed by clients.

I had a major issue in the last week where a site was found to be showing huge numbers of pages that it shouldn't have been. Naturally Google indexed all of these pages!   Rather than manually remove 5000+ links, I thought the nuclear option of removing the whole site would be the best option (using the Remove URL tool with no URL provided), since the site was poorly ranking anyway.   I had read that this was a good way to reset your site if you wanted to start over.  I removed the site, then after confirming that Google had removed it, I resubmitted the site for indexing and submitted a new sitemap and a new robots.txt to prevent indexing of the restricted pages.  The sitemap shows that it is indexed (or at least, a large portion of it is indexed) and I can see the Googlebot activity on the site.  However, on my dashboard I see severe health problems listed, with the main one being important page removed and a link to the removal request for the main site.  Furthermore, there are no links to the site in the Google index (when tested against site:example.com in a search).  Do I need to reinclude the site using the removal tool? If I do this, will it re-add all the bad URLs that I was trying to get rid of?


I'm looking for the last crystal piece and it's supposed to be in Volkrund Keep, but I can't get in (even if my follower opens uses the lever there's another closed door). Who gives the quest connected to that place or is there a way to complete Dreams In Oblivion without it?

For the Falskaar quest Dreams in Oblivion, where are the four crystal pieces located?


Apologies if this has been asked before - I could not find a question with this exact inequality.  Basically the inequality is  $$(a+b+c)^2 \leq 3 a^2 + 3 b^2 + 3 c^2$$  Expanding it out we see that  $$(a+b+c)^2 = a^2 +b^2 + c^2 + 2ab + 2bc + 2ac$$  so I guess it is equivalent to showing that  $$ab + bc + ac \leq a^2 + b^2 + c^2$$  Which makes sense to me. But how exactly do I prove it?  We can assume WLOG that each $a,b,c > 0$ since $ab \leq |a||b|$. From here, I guess we need to show that  $$ab \leq \frac{1}{2} \left(\max(a,b)^2 + \min(a,b)^2 \right)$$  And the result follows by adding up each term. But I'm not really sure why this must hold.

How can the following inequation be proven?  $$a^2 + b^2 + c^2 \ge ab + bc + ca$$


Is there any way to open a graphical program (for instance, gedit) while using X11 forwarding over SSH and transfer the X server connection back to the X server on the SSH host?

I have 2 computers (both running linux) and I'm currently using synergy to use them. This is great, but now I'm wondering, is there any way (is it possible? being worked on? tried and failed? definitely not possible?) to not only share a mouse/keyboard/clipboard between the computers, but to share an X session? What I'm thinking is being able to drag X windows between monitors.   I realize that this is extremely non-trivial to do and I know enough about linux (though not about xserver) that I'd like to pursue this idea even if there's nothing that does this for you.  Also, I don't need to be able to just "install this and it works". I'm completely willing (and would be surprised if it didn't require) to install custom kernals, or mount partitions between machines, or whatever it takes. Since I assume it would require the same instance of xorg server running on both machines.


I upgraded to 16.04 last week. After a daily update I rebooted my laptop and I found that my desktop icons look larger, my desktop wallpaper is changed to black and my menu looks classic.  I thought the problem was with Nvidia driver, so I removed it and reinstalled it, but the issue persists. Please, any idea can be helpful.

I've been messing around with Unity and broke something, how do I "start over"?


how do you restart game in java?  this is what i tried but did not work:  String playagain;     String y="y";     String n="n";   //there is a huge chunk of code that goes in here for the game  System.out.println("play another game?(y/n)");     playagain=input.next();     if(playagain==y){         Game.end();         Game.start();     }else if(playagain==n){         System.out.println("Goodbye");     }   game is the name of the class, but it insists i create a method for that to work. would anyone know an easier way to restart the game when player clicks y? Any help is appreciated

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?


When developing in APEX I'm frequently creating utility class where I put my static final strings (like picklist values etc.)  public static final String ATR_TYPE_PICKLIST = 'Picklist';   And then use them in the code like below:  if (type == ATR_TYPE_PICKLIST) {    ...  }   What would be the best approach to use corresponding pattern in Lightning Components? I would want to avoid using hardcoded values in the code like below:  if (attributeParam.name == 'ATR_BLOCATIONDETAILS_') {     ... }

With events being fired and also handled in a helper, I have multiple copies of simple constants and so there is some risk of silent failure due to typos.  Given the helper functions are defined as properties of an object, it appears possible to define constants in the same way and reference them via the helper instance:  ({     ADD_ACTION : 'ADD',     EDIT_ACTION : 'EDIT',      onRowAction : function(component, event, helper) {         var action = event.getParam('action');         switch(action.name) {             case this.ADD_ACTION:                 ...             case this.EDIT_ACTION:                 ...         }     }, })   But is there a better way to share constants between helper methods in a single Lightning Component?  PS  itzmukeshy7's use of objects to group the constants is a nice refinement:  ({     actions: {         ADD: 'ADD',         EDIT: 'EDIT'     },      onRowAction : function(component, event, helper) {         var action = event.getParam('action');         switch(action.name) {             case this.actions.ADD:                 ...             case this.actions.EDIT:                 ...         }     }, })


When using Gaussian processes, the covariance matrix $\mathbf{\Sigma}$ is often defined via a covariance function $K$ as follows $$ \mathbf{\Sigma}_{ij} = K(\underline{x}_i, \underline{x}_j) $$ where $\underline{x}_i, \underline{x}_j$ are coordinates of two points in some space of interest, and belong to some finite set of $n$ such points, resulting in a $n \times n$ covariance matrix.  Is it known whether the Gaussian (or 'squared exponential') covariance function $$ K(\underline{x}_i, \underline{x}_j) = a^2 \exp{\left(-\frac{(\underline{x}_i - \underline{x}_j)^{\top}(\underline{x}_i - \underline{x}_j)}{2l^2}\right)} $$ will always produce a positive-definite $\mathbf{\Sigma}$ for any chosen set of points and values of $a, l$?  Thanks!

How to prove that the radial basis function $k(x, y) = \exp(-\frac{||x-y||^2)}{2\sigma^2})$ is a kernel? As far as I understand, in order to prove this we have to prove either of the following:   For any set of vectors $x_1, x_2, ..., x_n$ matrix $K(x_1, x_2, ..., x_n)$ = $(k(x_i, x_j))_{n \times n}$ is positive semidefinite. A mapping $\Phi$ can be presented such as $k(x, y)$ = $\langle\Phi(x), \Phi(y)\rangle$.   Any help?


I'm currently writing a paper for my study on the applicability of Spring Batch (a java framework) for the use cases of the department I'm currently in.  For this, I'm citing parts of the Spring documentation, and I wanted to use a . in the bibliography entry identifier. While this at first had me worried that dots might not be permitted in identifiers, it turns out they are.  However, I can't help but wonder which characters are permitted - is it ASCII characters? A subset of ASCII characters (i.e. alphanumeric, ., - and _)? All unicode characters? Some unicode characters? Also, even if they are valid, are there characters that could create strange errors depending on which context the bibliography entry is referenced in?  No worries, I don't intend to use emojis in my identifiers, I'm just curious as to which characters are valid. Thanks in advance! :)

What characters are valid in a biblatex entry key?  I'm asking because  will export entry keys with <i>foo</i> in them, and  doesn't like that. But I don't know whether Zotero is too permissive, or pandoc-citeproc is too strict.  This is the error that pandoc-citeproc generates with an entry key like that:  pandoc-citeproc: "stdin" (line 10918, column 2): unexpected "A" expecting "c", "C", "p", "P", "s" or "S" CallStack (from HasCallStack):   error, called at src/Text/CSL/Input/Bibtex.hs:113:32 in pandoc-citeproc-0.10.4-BdOyQb33rzG2TMOLj4Fbp9:Text.CSL.Input.Bibtex pandoc: Error running filter pandoc-citeproc Filter returned error status 1


When I click on links in mails or Twitter, my default browser, which is Google Chrome, opens, but it always only displays the Google Chrome welcome page, not the link. I found that this is set in my default applications somehow:    You can see that the "getting started" page is set there. I don't know how this happened, how do I fix this?

When I open Google Chrome on Ubuntu 14.04, it opens a new window on a different launcher icon (I have Chrome in my Launcher pinned) and the title of the window is a tab that I don't have open any more. I have uninstalled and reinstalled Google Chrome.


I understand that when there is an impedance mismatch between an output stage, for example from an amplifier, and an input stage, for example, a transducer; power is reflected. I would like to know why this occurs, and what happens to that reflected power?

I am a licensed radio amateur, and find bewildering the many different explanations, which range from folksy urban myth to Maxwell-Heaviside Equations, of what happens at the termination of a transmission line or feeder. I realise that they all come to the same thing in the end (or should do, pun perfect), but none of them give me a gut feeling for what is going on.  I like diagrams, so an answer in terms of (graphical) phasors for the currents and voltages at the load would suit me best. How, for instance, does a step pulse down the line cause twice the voltage at an open circuit termination? Similarly for current at a short circuit. And how is the reflected step generated by the inductance and capacitance of the line?  Can anyone help, without getting all mathematical, and not telling any "lies to children"?


Why the nature has chosen the inverse square law. For instance, the gravitational force as well as the Coulomb force is inversely proportional to the square of distances. Why not these forces are inversely related with power 1 or 3 or may be some higher power of distance?

It seems paradoxical that the strength of so many phenomena (, ) are calculable by the inverse square of distance.   However, since volume is determined by three dimensions and presumably these phenomena have to travel through all three, how is it possible that their strengths are governed by the inverse of the distance squared?  The gravitational force and intensity of light is merely 4 times weaker at 2 times the distance, but the volume of a sphere between the two is 8 times larger.   Since presumably these phenomena would affect all objects in a spherical shell surrounding the source with equal intensity, they travel in all three dimensions. How come these laws do not obey an inverse-cube relationship while traveling through space?


I'm using the regex (?<=\()(.*)(?=\)) to match all content that's between a { & } whether on a single line or multi line. This works on single line, but not multi line. How can multi line be done? I've tried (?<=\()(.\r\n)(?=\)) (?<=\()(\s\S)(?=\)) // Works on this .a .ikd .Pf { -webkit-background-size: 307px 472px; background-size: 307px 472px; width: 100px; height: 125px;}  // Does not work on this     .a. ikd .rbSa {     -webkit-background-size: 307px 472px;     background-size: 307px 472px;     width: 58px;     height: 75px; }

What's the best/most efficient way to extract text set between parenthesis? Say I wanted to get the string "text" from the string "ignore everything except this (text)" in the most efficient manner possible.  So far, the best I've come up with is this:  $fullString = "ignore everything except this (text)"; $start = strpos('(', $fullString); $end = strlen($fullString) - strpos(')', $fullString);  $shortString = substr($fullString, $start, $end);   Is there a better way to do this? I know in general using regex tends to be less efficient, but unless I can reduce the number of function calls, perhaps this would be the best approach? Thoughts?


I'm facing a nested problem using PyQGIS (for QGIS master, but it can be replicated in any version of QGIS 2). I have a vector layer with some selected features and with a QgsFeatureRequest I can easily loop only on the selected features: vl = iface.activeLayer() # get the list of selected ids  ids = vl.selectedFeatureIds()  # create the request with the selected ids request = QgsFeatureRequest() request.setFilterFids(ids)  # use only the selected features in getFeatures for i in vl.getFeatures(request):     print(i.attributes())  Then I build an expression based on a field of the attribute table and I can use QgsFeatureRequest() to filter only the features that match that expression: exp = ''' "Piper" = 1 ''' request = QgsFeatureRequest() request.setFilterExpression(exp)  for i in vl.getFeatures(request):     print(i.attributes())  but what if I want to filter with the same expression only the already selected features? So actually use both requests in the same getFeatures loop?

The expression box has a handy "select from selection" button. Is there a way to emulate this with Python? I have the basic expressions down, but can't find a way to do this.


Is there any benefit of your comments being upvoted because I have a few and nothing is happening?

Comments can now be upvoted and flagged. How do those features work? Do users get rep for their upvoted comments? Do upvoted comments have any effect on comment sorting? And can users see their own comment upvote number somewhere?  Related:  The  about comments


After distro update to debian 9 my nginx reverse proxy stop working on all apps mostly dotnet one. It shows 502 bad gateway when app is trying to send post request Do you got any clue how to resolve it ? nginx version: nginx/1.14.2 built with OpenSSL 1.0.1t  3 May 2016 TLS SNI support enabled Here is my config  server {         listen 80;         server_name domain.com         return 301 https://urltodomain$request_uri;          access_log /var/log/nginx/domain_com-access.log;         error_log /var/log/nginx/domain_com-error.log error; }  server {     listen 443 ssl http2;    server_name    domain.com;    ssl on;    ssl_certificate /etc/ssl/domain/symlink_cert_ca.crt;    ssl_certificate_key /etc/ssl/domain/symlink_key.key;    ssl_session_timeout 5m;    ssl_session_cache shared:SSL:10m;     access_log /var/log/nginx/domain_com-access.log    error_log /var/log/nginx/domain_com-error.log debug;        location / {        client_max_body_size 20M;        proxy_set_header Connection "";        proxy_set_header Host $http_host;        proxy_set_header X-Real-IP $remote_addr;        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;        proxy_set_header X-Forwarded-Proto $scheme;        proxy_buffers 512 32k;        proxy_buffer_size 32k;        proxy_read_timeout 120s;        #proxy_pass http://127.0.0.1:5002;        proxy_pass http://dotnetto;    } }     upstream dotnetto {     zone dotnet 64k;     server 127.0.0.1:5002; }

This is a  about Connection Refused    We see a lot of questions to the effect      When I try to connect to a system I get a message      Connection refused      Why is this ?


Stuck in an infinite loop when trying to log in to my wordpress site. I type in the URL/wp-admin and then it loops me back to the regular website, not the admin login page.   I have tried with http and https to no luck...

There was a similar post to this, however the solution did not work for me.  I am having some difficulty logging into my WordPress site. When I attempt to visit example.com/wp-admin, I see the login page as per usual, however, once I enter my login details, the page essentially reloads and the url changes to:    This is a loop which I cant pass beyond. The front end of the website seems to be working as per usual. Visiting example.com/wp-login.php and entering my login details has the same behaviour as listed above.  I have confirmed this is not a problem with anything on my local machine as the behaviour persists across multiple browsers, devices and networks.  As suggested by others, I went into PhpMyAdmin > wp_usermeta > and deleted the meta_value for session_token. This did not fix the issue.  I turned on DEBUG and was provided with the following items when loading example.com/wp-login.php:  Warning: Cannot modify header information - headers already sent by (output started at /home//public_html/wp-includes/wp-db.php:1308) in /home//public_html/wp-login.php on line 425  Warning: Cannot modify header information - headers already sent by (output started at /home//public_html/wp-includes/wp-db.php:1308) in /home//public_html/wp-login.php on line 438  I have found numerous forum posts about the issue but none offer a satisfactory solution.  Please help as I urgently need to update content on the site.


Reading the book "YDKJS" about 'mixins' (manually copying one object into another) I ran into that statement: There are still some subtle ways the two objects can affect each other even after copying, such as if they both share a reference to a common object (such as an array or function). So I need an example of this statement. When I tried to change the common object(reference to it) It didn't work, they don't affect each other.    function foo() {   let array = [2, 2, 1];   return array; }  function mixin(sourceObj, targetObj) {   for (let key in sourceObj) {     if (!(key in targetObj)) {       targetObj[key] = sourceObj[key];     }   }   return targetObj; }  const Vehicle = {   engines: 1,   fooo: foo,   ignition: function () {     console.log('Turning on my engine');   },    drive: function () {     this.ignition();     console.log('Steering and moving forward');   } };  const Car = mixin(Vehicle, {   wheels: 4,    drive: function () {     console.log('Rolling on all ' + this.wheels + ' whells!');   } });    console.log(Vehicle.fooo()); console.log(Car.fooo()); Car.fooo = function () {   let array = [34, 65, 1];   return array; };  console.log(Car.fooo()); console.log(Vehicle.fooo());

So I was playing around the other day just to see exactly how mass assignment works in JavaScript.  First I tried this example in the console:  a = b = {}; a.foo = 'bar'; console.log(b.foo);   The result was "bar" being displayed in an alert. That is fair enough, a and b are really just aliases to the same object. Then I thought, how could I make this example simpler.  a = b = 'foo'; a = 'bar'; console.log(b);   That is pretty much the same thing, isn't it? Well this time, it returns foo not bar as I would expect from the behaviour of the first example.  Why does this happen?  N.B. This example could be simplified even more with the following code:    a = {}; b = a; a.foo = 'bar'; console.log(b.foo);  a = 'foo'; b = a; a = 'bar'; console.log(b);     (I suspect that JavaScript treats primitives such as strings and integers differently to hashes. Hashes return a pointer while "core" primitives return a copy of themselves)


Let X be a set and let $P(X)$ denote the set of all subsets of X, that is $P(X)=   \{A|A\subseteq X\}$. given $A,B\in P(X),$ define $A \triangle B:=(A\setminus B)\cup(B\setminus A)$.      Prove that $(P(X), \triangle)$ is a group.    Using the definition of a group I assume I have to show that there exist an associativity, identity, and inverse.

$G$ is the set of all subsets of a set $A$, under the operation of $\triangle\;$: Symmetric Difference of sets.  $A$ has at least two different elements.  I need to check if this is a group, and if it does to show if the group is abelian and/or finite.  Associativity - easy from Symmetric Difference. Identity element - empty group. Inverse element - each element is inverse to itself. Am I right?  abelian? finite?


Some sources introduce the inflaton field as the cause of the inflation period in the big bang theory, and some others relate it to the decay of electronuclear bosons. Which one of these is responsible for the expansion of the universe during inflation period?

I have two particular questions regarding the inflationary scenario. They are:  What is the physical origin of the inflaton field?  Why has the potential of the inflation field its particular form?


I'm the resident IT guy in an office with about 20 workers, amongst 3 separate companies who sublet an office.  We are wired with 24 ethernet ports dotted around the offices that all lead to a patch panel in my office. They are connected to 4 unmanaged switches into our ISP-supplied, cheap, router. (Internet is provided by a regular ADSL2+ provided by BT in the UK).  The problem is we are all one network, despite being separate companies, which is a security concern so we want to separate the logical/virtual networks (presumably, VLANs), but our current basic router doesn't support port-based VLANs.  I'm consider two options to isolate the networks, and I'd like advice which will do the trick:   A enterprise 4-port router (perhaps a  or ) that supports port-based VLANs, and plug our existing unmanaged switches into that:   (obviously, I would restricted to 3-4 VLANs, but that's fine Or, a large 24-port managed switch (like a Cisco), that supports allows me to define which of it's many ports belong to which VLANs.   I understand that this can just work in a "router-on-a-stick" configuration. Crucially, my network cupboard is too small to fit a typical 24 port switch, It's only got about 22cm depth.

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


I'm a developer of Android applications and a java programmer. I'm learning IOS programming but I don't have mac OS; I use Ubuntu.  I want way to program IOS apps in Ubuntu without using a virtual machine (in vmware or VirtualBox) And without MacOS.  Can I do that in Ubuntu?

I noticed Xcode has released a (non-snapshot) .   I looked for an article on how to install it and I couldnt find anything.  Can anyone advise how to do this?


Let $S$ be a set, $F$ a field, and $V(S;F)$ the space of all functions from $S$ into $F$, with the usual function addition and scalar multiplication. Let $W$ be any $n$-dimensional subspace of $V(S;F)$. Show that there exist points $x_1,...,x_n$ in $S$ and functions $f_1,...,f_n$ in $W$ such that $f_i(x_j)=\delta_{ij}$, where $\delta_{ij} = 1$ if $i=j$, and $\delta_{ij} = 0$ otherwise (i.e. the delta function is the Kronecker delta function).  If $S$ were an $n$-dimensional subspace, then the result is true. But I am not sure how to proceed. I was considering the set $(S^0)^0$, which is spanned by $S$, but I am sure where this leads me.  Edit: I found that, since $(S^0)^0$ is a subspace, we can find some $n$ points of a basis $a_1,...,a_n$ of that subspace such that its dual is $f_1,...,f_n$, and each $a$ of which is a linear combination of some elements in $S$. If those $a_i$ elements are in $S$, we are done. But I am having trouble proving the result if at least one $a_i$ is not in $S$.

I am self-studying Hoffman and Kunze's book Linear Algebra. This is Exercise 3.6.3(Linear Transformation-The Double Dual) from page 111.     Let $S$ be a set, $\mathbb{F}$ a field, and $V(S,\mathbb{F})$ the   space of all functions from $S$ into $\mathbb{F}:$   $$(f+g)(x)=f(x)+g(x)\hspace{0.5cm}(\alpha f)(x)=\alpha f(x).$$ Let $W$ be any $n$-dimensional subspace of $V(S,\mathbb F)$. Show   that there exist points $x_{1},\ldots,x_{n}\in S$ and functions   $f_{1},\ldots, f_{n}\in W$ such that $f_{i}(x_{j})=\delta_{ij}$.   Since $W$ is an $n$-dimensional subspace of $V(S,\mathbb{F})$ we can say find a basis $\mathcal{B}=\{f_{1},\ldots, f_{n}\}$. But I got stuck here. I don't know what to do from now on. I mean, what should I do in order to find those points $x_{1},\ldots,x_{n}\in S$ such that $f_{i}(x_{j})=\delta_{ij}$.


Why the definition of a topological space defined under finite intersection and arbitrary union What if we change the conditions by arbitrary intersection and finite union?

I was wondering if there is a reason why in the definition of a topologic space, the reunion of any collection of open sets is also an open set but the intersection has to be finite to be a set.  Is there because of the definition of an open set itself ? I have always seen it as a definition, but now I want to know why.  Thanks for your help.