Does racism against aliens exist in the Star Trek world, given that aliens are so different from humans?

Sad to say, it is human nature to be uncomfortable with other races or even dislike them, particularly if they are very different from us. The contrast between humans and aliens are even greater. Therefore, the likelihood of racism against aliens is even higher.   It is hard to believe advancement of technology can change human nature. It is quite unimaginable that humans can shed their basic selfish and greedy nature and expect most of them to become kind saints.  What are some incidents of alien racism, if any, in Star Trek?


Why are Perl 5's function prototypes bad?

In   asserted:     I would advice you not to use prototypes. They have their uses, but not for most cases and definitely not in this one.   Why might this be true (or otherwise)? I almost always supply prototypes for my Perl functions, and I've never before seen anyone else say anything bad about using them.


How do I search for double quotes in Stack Overflow?

Long story short, I'd like to search for question containing the text operator"".


I'm using \hl{} from soul  package to highlight some words in my document. However, I'd like a "realistic" highlighting, simulating the result of a "manual" note: a not-so-regular rectangle with "waves" here and there.  I think a long time ago I saw something like that here in StackExchange but I could't find it.  Edit  Yes, this is a duplicate of . I can't understand all the code but it is what I need. Just one more thing: is there a way to recreate the darker spot corresponding to the point where the highlighter is removed from the paper, like in the (exaggerated) image?    I don't really need it but it would make the document look more hand-drawn.


Windows 8.1 missing font files after restart

Some days ago I rebooted my windows 8.1 system. After the reboot all my system texts were very cryptic - showing only some strange symbols. After some investigation I discovered that my c:\windows\fonts folder was nearly empty. So I copied the font files from another windows 8.1 installation to the nearly empty folder. As soon as I had copied the files the system texts were readable again.  But after another reboot the problem occured again - the systems font folder was empty again. Does anyone know why windows deletes my font files during a restart?


WoeUSB Installation failed! Exit code: 256

I am new to using Ubuntu. I tried to create a Windows 10 USB boot medium with WoeUSB. I have configured a USB drive with an NTFS partition, but WoeUSB gives this error message:  Installation failed!   Exit code: 256    Log:   WoeUSB v@@WOEUSB_VERSION@@ ==============================  Mounting source filesystem...   Wiping all existing partition table and filesystem signatures in /dev/sdc... wipefs: error: /dev/sdc: probing initialization failed The command "wipefs --all  "${target_device}"" failed with exit status "1", program is prematurely aborted    Unmounting and removing "/medi/woeusb_source_1530017199_18199"...   You may now safely detach the target device   How can I proceed?


I'm trying to prevent SQL Injection using PHP with PDO. I've used this as a reference.  . My code doesn't give me any error but the values that are getting in are all null.  The vlaues I'm trying to insert are not null. I know this because I've echo'ed them out:  echo "\nDate: ".$date." Name: ".$name." mail: ".$mail."Comment: ".$comment." website: ".$website;  $sql = "INSERT post SET timeDate = :timeDate and name = :name and mail = :mail and comment = :comment and website = :website"; $stmt = $db->prepare($sql); $stmt->bindParam(":timeDate", $date); $stmt->bindParam(":name", $name); $stmt->bindParam(":mail", $mail); $stmt->bindParam(":comment", $comment); $stmt->bindParam(":website", $website); $stmt->execute();


What's best investment option? Mutual fund or Property

I had purchased a home year ago and given it on rent. The rent I'm getting is only 5% of total cost of home while stock fund industry (mutual fund) is paying 20% minumum (reports from my country here mufap.com.pk/nav_returns_performance.php?tab=01 ) i.e. I'm getting 15% loss every year and that is a big amount.  I'm not really assure if my home also increase it's value by 15% every year. But I don't think it will be.  Now I'm thinking to sell that home and invest all of my money in mutual growth fund. Can you please advise me in this regard  Note: Even one fund has given 55% in 365 last days ( See 'JS Islamic Fund' here )  Thanks


This specific add keeps popping up as overlay at random. It's always the same Facebook Maket thing. I'd appreciate any hint on how to get rid of it.


I have an old, slow netbook. I love Ubuntu and also Ubuntu has good repositories.  Is there any version of Ubuntu without a desktop environment?


Well-formed formulas: Difference between $\forall x(x \in A \implies x \in B)$ and $(\forall x \in A) x \in B$?

Let $A$ and $B$ be sets. There seem to be two ways of writing $A \subseteq B$: \begin{equation} \forall x(x \in A \implies x \in B) \end{equation} or \begin{equation} (\forall x \in A) x \in B \end{equation}  I usually see the first one written. I am curious to know if the second version is in proper form, logically. Is it a well-formed formula (wff)? Is there any way to prove these two formulas are logically equivalent?    By the way, I am quite interested in this area of question. For example, I commonly want to know when it is better to write \begin{equation} (\forall x \in A) x \in B \end{equation} or \begin{equation} \forall x \in A (x \in B) \end{equation} is there anything I could read that would teach me the difference, and which is more preferable?


Full screen mode in virtual box. Nothing helps

In previous versions of Ubuntu I followed this  and manually did the trick. In fact, I did this:  cd /media/VBOXADDITIONS_4.2.4_81684/ sudo sh VBoxLinuxAdditions.run   But in a newer version of Ubuntu, I see that /media folder is empty. I next followed this  and installed guest additions, but still I can't locate them and /media folder remains empty. Simply doing Devices -> Insert Guest Additions CD image... does not work, but results in a warning, saying that something is inaccessible. So, something wich should be just the most trivial thing in the world turns out to be a kind of sacred knowledge that only chosen ones know.


I am trying to install freetds-common, freetds-bin, unixodbc, and php5-sybase on Ubuntu 16.04.  When I run sudo apt-get install freetds-common freetds-bin unixodbc php5-sybase, I get the following errors:  Reading package lists... Done Building dependency tree        Reading state information... Done E: Unable to locate package php5-sybase   How can I install this package?


Does anybody know if there is a way to statistical calculate the similarity of two polygons using PostGIS?    I want to know how similar is the polygon (red outline) with the polygon (black outline).


How $$\int_{-\infty}^{\infty}\frac{dx}{1+x^2}$$ exists?   It is difficult question to me. i have tried to evaluate by using fact that $$\int_{-\infty}^{\infty} f(x) \ dx =\int_{-\infty}^{0} f(x)\, dx + \int_{0}^{\infty} f(x)\, dx$$ but i have failed in this one.   any hints on this one?


In our glorious chat system (may it live forever!), I have noticed a grain of sand in the pearly gear system.  This grain of sand is that when a message with a ping is sent, it pings (fine and well).  Then, when the sender edits the message, it pings again.  Then, when they edit it again, it pings again (unsurprising, at this point).  99.99% of the time, these edits are adjusting typos, obscuring profanity, or doing some other minor edit.  I am wondering if this only bothers me, or if other people have noticed it too?  It is definitely not a make-or-break problem, but it would be nice if it was changed so we only get pinged the first time, and if there are substantial changes, the user can just delete the message and send a new one.


How can I change leading zero in umask 0022? Can it be changed? I searched the usual methods for information and my local system was of little help. $ man umask   No manual entry for umask    $ umask --help bash: umask: --: invalid option umask: usage: umask [-p] [-S] [mode]  I found an  with the following:  umask [-p] [-S] [mode] mode ... File creation mask -S  ........  Print the mask in symbolic format -p  ........  Output in a form that can be reused as input  Based on this, I tried a few basic umask commands: $ umask 0022  $ umask -p umask 0022  $ umask -S u=rwx,g=rx,o=rx  I was surprised to find that I could not run umask with sudo $ sudo umask   [sudo] password :   sudo: umask: command not found    I changed the regular umask as follows: $ umask 021 $ umask 0021  $ umask 0022 $ umask 0022    Finally, I hit an error while trying to change the leading zero $ umask 1022 -sh: umask: 1022: octal number out of range    So, back to my original question, how does one change the leading zero (0)?  Is it for the super user (root)? Can it be updated, and if so, to what? I reviewed a similar question  and found:  I don't know that you would unmask the first bit with umask, but technically you could ...  and  I don't believe you can actually set the umask to allow you to enable any of these extra bits by default  So, these uncertain and contradictory statements do not answer this question.


Splitting raster into smaller chunks using GDAL?

I have a raster (USGS DEM actually) and I need to split it up into smaller chunks like the image below shows. That was accomplished in ArcGIS 10.0 using the Split Raster tool. I would like a FOSS method to do this. I've looked at GDAL, thinking surely it would do it (somehow with gdal_translate), but can't find anything. Ultimately, I'd like to be able to take the raster and say how large (4KM by 4KM chunks) I would like it split up into.


App will not allow me to edit other people's posts

On stackoverflow.com I can edit a post and it goes into a queue for approval. The Android app let's me do the edit and then says 'this account is not allowed to edit'. Either it should allow me to edit or it should not. I like the look and feel of the app.


Windows Server 2012 R2 Standard + Essentials Setup for Small Office

We want to setup a "small" server for on of our offices (8 Client Computers, local Domain not linked). We need to have an Exchange Server. Unfortunately we cannot use SBS since its support is running out.  We already do have a Windows Server 2012 R2 Essentials Licence and an Exchange Server 2013 Licence (+CALs).  As Exchange does not run on Essentials (thanks Microsoft for that!) we need to run a Standard Licence.  My Setup would be the following:   Host Machine Windows Server 2012 R2 Standard with Hyper-V on it 1 Virtual Machine Running Windows Server 2012 R2 Standard + Exchange Server 1 Virtual Machine Running Windows Server 2012 R2 Essentials (Domain Controller)   As Microsoft does not recommend running the domain controller on the same instance as the Exchange Server and we do have less than 25 Clients i would go for that setup. Seems a bit over complicated but as far as i understand it follows Microsoft's recommendations.  Do you have any recommendations concerning the hardware? Right now we have a Lenovo RD340 equipped with 8GB RAM, 1 SSD 128GB and 3*3TB HD in Raid 5. Maybe we should upgrade it to 16GB RAM, but as the Hyper-V can manage the required memory it could be enough right now. Where should we install the Guest VMs? On the SSD?


Most alien/extra-terrestrial tropes based movies often depict them as losing despite being far more advanced physically and/or technologically. This is seen in cases like Aliens, Predators, Independence Day (computer virus, seriously?!), Species, Pacific Rim, Edge of tomorrow, you name it.  In some movies we see aliens losing interest or probably over protective of humans. Arrival, Day the earth stood still, etc. And in some very few movies it's depicted as though we lost war, like Andromeda Strain (2008 miniseries, not the 1971 movie where we succeed), Invasion of body snatchers, Cloverfield, etc.  I've excluded space opera from this because it deals with way too many species (mostly anthropomorphic) and often end up with a democratic union of sorts. That's out of scope of this question anyway.  The very idea that these aliens have travelled across space is evidence enough of their superiority anyway. Why are film makers hell-bent on showing humans as stalwart heroes who can overcome any sort of adversary who are intellectually, physically and technologically far superior to humans?  Note: This is not a duplicate of  as the idea clearly portrays that there are bad guys. Where as aliens in Aliens or Predator are not bad nor are shown as bad. Aliens are merely surviving, while Predators are just hunting. This is clearly different from a dedicated 'bad guy' trope whose intentions are evil.


WPF/C# Bind Content from two Textboxes to a single label

I've been trying to bind two textboxes to a single label so the label always update depending on the content of two textboxes. However without luck. I managed to solve how to bind a single one.  by using  Content="{Binding Text,ElementName=PersonName,UpdateSourceTrigger=PropertyChanged}"   So it looks like this  <UserControl x:Class="FitTracker.CreateTrackItem"              xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"              xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"              xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"               xmlns:d="http://schemas.microsoft.com/expression/blend/2008"               xmlns:local="clr-namespace:FitTracker"              mc:Ignorable="d"               d:DesignHeight="300" d:DesignWidth="300">   <Grid>         <TextBox Name="PersonName" HorizontalAlignment="Left" Height="23" Margin="10,77,0,0" TextWrapping="Wrap" Text="Name" VerticalAlignment="Top" Width="280" />     <TextBox Name="PersonLevel" HorizontalAlignment="Left" Height="23" Margin="10,105,0,0" TextWrapping="Wrap" Text="Level" VerticalAlignment="Top" Width="280"/>     <Label Name="TrackDetails" Content="{Binding Text,ElementName=PersonName,UpdateSourceTrigger=PropertyChanged}" HorizontalAlignment="Left" Margin="10,133,0,0" VerticalAlignment="Top" Width="280" FontWeight="Bold" Background="#00000000" Foreground="White" />   </Grid> </UserControl>   However I cannot do it with two text boxes. any ideas or guides that could help me on the right path.  I've been searching around for some hours now.


Lets say, someone walking through a road saw an accident happened beside his walkway. Now if the person who was walking didn’t go and save the injured, can we say he did an immoral act? Can an inaction be labelled as moral or immoral?


How to disable billing address in Drupal Commerce while using Paypal WPS

I'm setting up a very simple online shop for a charity. They'll use Paypal WPS and don't want to collect customer's billing address as those will be entered in Paypal anyway. Is there a way to remove the billing address from Drupal Commerce.  I'm only using PayPal, so the aforementioned answer doesn't apply.


Refresh lightning component Opportunity page on Stage progress bar

I have a lightning component on the opportunity layout. I want it to refresh on stage change. Currently, it works when you change the stage using the edit button using the following code.  <aura:dependency resource="markup://force:recordSaveSuccess" type="EVENT" /> <aura:handler event="force:refreshView" action="{!c.doInit}" />     When changing stage using the Sales Path component (pic below for reference), this event does not seem to be fired. Has anyone been able to subscribe to this component's events? Am I missing something?


What is the math font being used in these notes?

This set of  seems to employ the standard LaTeX math font. However, in Eq. (2.29) the calligraphic D looks like the one from the eulervm package instead of the standard one:  What math font is this? If it is the standard math font how does one get this calligraphic D instead of the standard one?


I am watching a tutorial on how to UV map a model and I have this horse I created.  There should be a section named 'Surface' beneath the section named 'Preview' which is required to select the image. I have tried restarting blender and it just isn't there. I really hope that I don't have to re install blender.


after running Galera Replication for MariaDB , performance (TPS) does huge diffrence

I have two VM machines (with exact hardware-software configuration on two ESXI Servers in same rack and same subnet too) that is running with nginx + PHP-FPM + and MariaDB 10.4. in each ESXI server I have just 1 VM with 24G RAM, 24 Core CPU On standalone nodes the TPS is 8000 avg. But when I switched to galera Master-Master replication mode with below conf, The TPS is decrease into 1100 avg! each server's app using It's local DB. here is my.cnf  [mysqld] skip-name-resolve binlog_format=ROW wsrep_on=ON wsrep_replicate_myisam=ON wsrep_provider=/usr/lib64/galera-4/libgalera_smm.so wsrep_cluster_address="gcomm://192.168.7.11,192.168.7.12" wsrep_cluster_name="my_cluster" wsrep_node_address="192.168.7.11" wsrep_node_name="node1" wsrep_sst_method=rsync wsrep_slave_threads=16 innodb_flush_log_at_trx_commit=2 innodb_flush_method = O_DIRECT   What am I missing?


According to Wikipedia, $^44$ has $8.1 \cdot 10^{153}$ digits. How can I calculate the number of digits for an arbitrarily large tetration, such as $^{11}11$?  Thank you!


Adjusting the response variable to incorporate scaling effects

I am using a random forest regression to model a count of species from a number of different survey areas. Each survey area has a different size. My question is how to model the response variable, to account for these scaling effects? Should I scale the Count prior to fitting the model? Count <- Count / Survey_area_km2 model < fit(Count ~ pred1 + pred2 + ...)  And then when predicting over a set of survey areas, adjust the response variable prediction by the size of the survey areas I am trying to predict. This will give a count that is in proportion to each survey area? Count_predictions <- predict(model, prediction_areas) Rescaled_Counts <- Count_predictions * prediction_areas


I want to solve the following problem in T.Tao's random matrix theory book. Let $X$ be a random variable with finite second momment. A median $M(X)$ of $X$ saisfies $\mathbb{P}(X>M(X)),\mathbb{P}(X<M(X))\leq 1/2$. Now I wan to prove that for any median: $$M(X)=\mathbb{E}(X)+O((\mathbb{Var}(X))^{1/2})$$  I think we have to use Chebyshev's inequality for this, which I have done to obtain: $$\mathbb{P}(X>\lambda \sigma)\leq \mathbb{P}(|X|>\lambda \sigma)\leq \frac{1}{\lambda ^2}$$ where $\sigma=(\mathbb{Var}(X))^{1/2}$. But I fail to interprete this...


What is the meaning of double pound symbol (number sign, hash character) ##1 in an argument?

I've seen sometimes that people use a double pound sign (##) when defining/using arguments.  What is the difference between the normal argument, #1, and the double sign one, ##1? Are there any restrictions for its use? Can you list the good practices, if any, for this type of arguments.


One watch, two watches, three watches.. If I get three will someone get none?

"Two time's a charm"... but "two watches's an error".  Apparently DHL has just started getting ready for shipment of the watches from the . Some users already got a mail from them...  ... but some got TWO.   It doesn't appear to be just a dupe message - the two mails do indeed have different item numbers and waybill codes. This seems to indicate that there was an error at some point and some users are being sent two watches instead of one.  I will be honest: I don't really dislike the idea of a second watch. There are so many uses for it: give it to a friend, keep it under a glass dome as a collector item, wear a watch on both hooves arms... But a part of me is fearing that due to the same error someone may receive zero watches instead.  I also realize that probably by now it could be anti-economical to try to fix the error, but I think something will have to be done in the case some users are left without their prize.  I am therefore posting this message to warn the staff. I have considered using the contact mail too, but I am somehow assuming this may be the fastest option right now.    Recap:   some users are apparently being sent two watches if this doesn't create any problem, I doubt any of them will take the second free watch as a personal offense  you may have to do something if some winners are left without a watch.     EDIT - Just received a third mail, different waybill code as usual.


Can a Banderhobb make 2 attacks and teleport?

The VGM's Banderhobb can grapple and restrain enemies with his attacks. The Tongue attack allows him to do a Bite attack as a bonus action.     Bite. Melee Weapon Attack: +8 to hit, reach 5 ft., one target.   Hit: 22 (5d6 + 5) piercing damage.      Tongue. Melee Weapon Attack: +8 to hit, reach 15 ft., one creature. Hit: 10 (3d6) necrotic damage, and the target must make   a DC 15 Strength saving throw. On a failed save, the target is   pulled to a space within 5 feet of the banderhobb, which can   use a bonus action to make a bite attack against the target.   He can also use his Shadow Step to teleport, and make an attack as part of the teleport, before or after teleporting.     Shadow Step. The banderhobb magically teleports up to 30   feet to an unoccupied space of dim light or darkness that   it can see. Before or after teleporting, it can make a bite or   tongue attack   Can the Banderhobb use Shadow Step to: Tongue an enemy, Bite him as a bonus action, and then teleport?


How to use Computer as a HeadSet using a bluetooth dongle paired with Android phone

My goal is simple. Whenever someone makes a called on my phone I want to be able to use my computer as a headset. This way I could use my Mic to talk back at the person on the other end, and my headphones to listen.   I'm running Ubuntu Linux 15.10, and using a bluetooth dongle 4.0   Progress.. I have no problems pairing my phone with my computer, nor any issue with sending files over the bluetooth connection. The phone, however, doesn't see the computer during calls.   Anyone out there knows what to do?


Using mysql_real_escape_string() instead prepared statement in IN operator

I'm in a situation where I can't mix named and positional parameters in my PDO prepared statement. It's a long story but to simplify I decided to just ditch prepared statements when using IN operator.  E.g., use plain WHERE column IN (1, 2, 3) instead of WHERE column IN (?, ?, ?).  To ensure data is still safe, can I just use mysqli_escape_string() instead?   E.g.,WHERE column IN ('.mysqli_escape_string($a).', '.mysqli_escape_string($b).', '.mysqli_escape_string($c).') ?  In a nutshell, I want to know if mysqli_escape_string() is a good replacement for prepared statement in my use case?  Edit: replaced mysql_* with mysqli_*


Modular Arithmetic ( using Euler's Totient Theorem )

Please help me find the last two digits of $312^{84}$ ; I am stuck right here: $312^\phi \equiv 1 \pmod{100}$.


We just built a new SP 2013 farm. For some reason when I access the sites, I see I am sometimes logged in as one of our service accounts (sp_crawl). If I refresh the browser, it switches to my normal AD account. I haven't determined a pattern, it seems rather random. Sometimes it opens as me, other times the crawl account. Sometimes it takes multiple refreshes before it switches. My coworker also saw the crawl account, but even more concerning was she saw my name too.  Any ideas?  We are using standard http and Kerberos and have UPS set up and synced.  Edit: I looked in the web app user policy and none of the entries have "Account operates as System" checked.   Pertaining to the duplicate question, I did reset my browser and checked windows credential manager (it has nothing in it). However, my coworker was having the same issue.


Let $M$ be a square $N\times N$ matrix with linearly independent columns.   I was wondering why the $QR$ decomposition is unique in this case and how to show it? The linked question below does not explain why $Q$ is also unique and I didn't quite understand its explanation of why $R$ is unique also.


$$\lim_{x\to 0}\frac{10^x - 2^x - 5 ^ x + 1 } {x\tan x} $$ This is an indeterminate limit.  I want help in solving this problem. Thanks in advance


Prove that A is isomorphic to the subring of K[T] generated by $T^2$ and $T^3$

Let $A = K[x,y]/\langle y^2-x^3\rangle$. Show that $A$ is isomorphic to the subring of $K[T]$ generated by $T^2$, $T^3$.   I tried to show a map from $\phi : A \to K[T]$ which sends $x \to T^2$ and $y \to T^3$ is an isomorphism. But couldn't prove it.  Can anyone help me out?    Also,     Show that fraction field of $A \cong K(T)=$ (field of rational functions in $T$) .


confusion with instanceof Array and String

i read ,but i have a question When i code  ["a","b"] instanceof Array   why it reutrns true as the same as   new Array("a","b") instanceof Array   while   "a" instanceof String   returns false not as the same as   new String("ab") instanceof String    ?  very appreciate for your answers and help!


Where can I find a list of computers guaranteed to work with Ubuntu?

Before I buy my next laptop, I'd like to make sure that it will work perfectly with Ubuntu. Is there a list of completely supported computers anywhere?


Notifications with a HTML encoded entity render improperly if a truncation occurs in the middle of the entity

I received the below notification yesterday:    The chat message itself can be found at :     iunno I'm just saying that it's not out of the question for it to just be a "hey I took care of a thing" situation   What seems to happen here is that the truncation point falls right in the middle of a HTML-encoded entity, which then doesn't render properly.  While creating this bug report, I have found a number of earlier bug reports dealing with the same issue: ,  which leads me to believe there is some sort of regression during the implementation of the new header.


Squares of positive semidefinite matrices

Suppose $L_1  \succeq L_2$, where $L_1,L_2$ are positive semidefinite matrices (actually combinatorial Laplacians). Is the following inequality true, and if no, under which conditions?  $$L_1^2  \succeq L_2^2$$


Why is force invariant under a Galilean transformation?

I've had a look around online, but I haven't been able to find something which answers this in a way I understand. Essentially, I'm trying to figure out why force is invariant under a Galilean transformation.  The answer to this  question wasn't really what I'm looking for. I think the framework of the answer is too advanced, as I am looking for something in a more simple framework than metrics on a four dimensional space. It's also not clear to me why the fact that force is coordinate free means it is invariant under a Galilean transformation. Could one not argue that since it is coordinate free, it's invariant under any coordinate transformation? But I know this is wrong, since force isn't invariant under a transformation to a non-inertial frame of reference?   is another similar question which has been pointed out to me, which I also saw when I was looking around. The actual question is written in a way which I do not understand - I think the question is posed at a more advanced level than I am considering, judging by the notation. The answer agrees that the topic is complicated, and suggests reading about affine tensors in shell theory. Since this question is relevant to some sub-honours undergraduate university material, I shouldn't think it is so advanced to require reading that.  I've seen an argument in Resnick's Introduction to Special Relativity, but it seems to assume that the force is conservative, then differentiating the resulting potential, whereas I am looking for something more general. I'm also convinced that there must be a simpler way to see this.  I've also seen something along the lines of "force is a vector, and so transforms nicely in this way" - however, I didn't really understand why this argument should hold.  The kind of level of reasoning I'm looking for is touched on in the . I'm looking for a more intuitive argument, rather than a more rigorous mathematical proof. The author writes     It seems reasonable to assume that a given force acting on a body shouldn't change depending on the frame of reference, i.e. that F' = F, since physical laws should be observer independent and hence the equations describing them should also be observer independent.   However, I don't want to just assume that a force shouldn't change depending of the frame of reference of the observer. Again, if we changed to an accelerating reference frame, this wouldn't be true, and so I'm convinced there must be a way to see this more clearly from the fact Galilean transformations relate coordinates in frames of reference moving at constant velocity relative to each other.  Can anyone shed any light on this?


LINQ Select Distinct with Anonymous Types

So I have a collection of objects.  The exact type isn't important.  From it I want to extract all the unique pairs of a pair of particular properties, thusly:  myObjectCollection.Select(item=>new                                 {                                      Alpha = item.propOne,                                      Bravo = item.propTwo                                 }                  ).Distinct();   So my question is:  Will Distinct in this case use the default object equals (which will be useless to me, since each object is new) or can it be told to do a different equals (in this case, equal values of Alpha and Bravo => equal instances)?  Is there any way to achieve that result, if this doesn't do it?


I'd like to match if x > 64 then return 0, 0 end inside this string.   function if x > 64 then return 0, 0 end return 1, 0 end   I'm using if(.*)then(.*)end. However, this matches: if x > 64 then return 0, 0 end return 1, 0 end, which is one end too many.


In order to  address traffic jam and reduce carbon footprint In order to  address traffic jam and to reduce carbon footprint  Which one is correct?


Ubuntu guest in VMWare stucks before login

I have Ubuntu 18.04 installed on my VMWare Fusion for months without any issues. After recent update through Software Updater, it required a restart.  Currently when I'm trying to load my Ubuntu it is stuck on the purple screen just before the login prompt.  I tried to use nomodeset in GRUB and I'm getting to the login screen but black screen after.  How can I make my virtual machine boot up successfully to the desktop?


I've been starting to shoot some live music recently and have been doing an okay job and see an improvement with each time I shoot. However recently I was shooting and all of my photos have come out very dark, too dark to use really. I was shooting in manual with 1/100 shutter speed aperture as wide as possible and a 6400 iso. Any advice is welcome. Thanks in advance.


Transit visa for Finland while final destination is Italy

I have issued an Italian short-term visa to attend a course. My connecting flight is from Finland. Do I have to get a transit visa for the layover in Finland?


How exactly does applying the Equipartition Theorem to radiation leads to UV catastrophe?

I'm reading a book by George Gamow, "Thirty years that shook Physics" and have trouble understanding his way of describing the UV catastrophe. In a first part he points out that applying the Equipartition Theorem (or principle) to radiation would lead to a situation in which every wave of each frequency should have $0$ energy (or, better, $E/\infty$, if $E$ is the original amount of energy of the system). Next he states that if we introduce for instance red light in a Jeans cube and we apply the principle to this situation, we could have the absurd consequence that the cube could be a source of high fequency radiation ($\gamma$, $X$, etc).  Now, how can the second situation even exist if (equvalently absurd) each frequency had zero energy to begin with? I cannot see a "UV" catastrophe, rather a "disappearing energy" catastrophe. What am I missing?


How/when to become independent in research as a graduate student?

I am in the last months of my MSc and I have done my thesis. I have published some conference papers but most of them were literature reviews.  My MSc thesis is about solving wave equations by means of method of potentials and boundary elements. I am interested in pursuing research in another field (differential equations) but I have no idea how to start any topic that may lead to a journal publication.    By asking this question, I want to understand how a research student, whether a recently graduated MSc student or a PhD student, can start searching for a new research topic and develop some researches based on his own interests. Specially, I would like to know:   To what extent should a graduate student be dependent on faculty members? How can he be more independent and start his own research activities? Is it a good idea that the graduate work on another topic with the faculty member or work independently on a more recent research topic? If the person is in a research group or at the university, is it a good idea or is it ethical that he develop his own research interests, besides to the topics which are being developed in that institute? How should a graduate student manage this and make some progress in the research fields of his own interest? (In particular, sometimes the faculty members are not interested in the topics you are interested in and the person has to start his own research activity.)      And also, if this research is part of his independent research, at the time of publishing what affiliation should be used in the publications. Should it be "Independent Scholar" as mentioned in  or something else? This is important in academic publications, because sometimes, the person is in a research group, but he is publishing a paper as part of his own researches not the things he is doing in that institute; in this case, has he mention that institute's affiliation or use his own one? So please make it clear that how the affiliation would be when the person does research independently in the cases like when he is not working in a research group or he is working with a professor or research group but his publication is output of his own research activities? It is a little unclear.


I was wondering if there is any classification for normal subgroups of $SU(n)$?  In particular, I think that the answer is no for $n = 2$ by looking at the covering map onto $SO(3)$, but I was curious if there were any results for arbitrary $n$?  I'm actually looking for finite normal subgroups of the unitary group (a lot to ask for, I know).


Find $\lim_{n \to \infty} \frac{s_1+s_2+s_3\cdots+s_n}{n}$

If a sequence is defined as $a_k=(-1)^{k-1}$ and $s_n=\sum_{k=1}^{n} a_k$ Then Find $$\lim_{n \to \infty} \frac{s_1+s_2+s_3\cdots+s_n}{n}$$  My try: we have $$s_n=\frac{n+1}{2} $$ when $n$ is Odd and $$s_n=0$$ when $n$ is Even  So if we define new sequence $b_n$ as: $$b_n=\frac{1}{n}\sum_{r=1}^{n}s_r$$  We have:  If $n=2p-1$ Then:  $$b_{2p-1}=\frac{1}{2p-1}\left(1+2+3+\cdots+p\right)=\frac{p(p+1)}{2(2p-1)}=\frac{(n+1)(n+3)}{8n}$$  Now If $n=2p$  We have: $$b_{2p}=\frac{p(p+1)}{4p}=\frac{n(n+2)}{8n}$$  Now how to find $\lim_{n \to \infty}b_n$


How to prove that there aren't square matrices $A$ and $B$, such as $AB - BA = I_n$

I don't know if the matrices $AB$ and $BA$ are invertible, nor do I know if $A$ or $B$ are invertible. I also don't have the matrices to check.  The only thing I know is that they're square $_n._n$.  With this information, how can I prove that there aren't matrices $A$,$B$, such as $AB - BA = I_n$?


I have created a many to many relationship between two objects, A and B, using a junction object. That works fine, and the related lists show up on A and B with standard layout pages. Is it possible to display fields from object A on object B using this relationship, i.e. using the junction object? How would I reference the fields from A in B on a Visualforce page? Where can I find the name of the relationship?


This  popped up, and got for sure quickly downvoted and delete-voted in 7 minutes. Anyway: it reads:     I am undertaking a research study on the use of communication API tools and am looking for help. It will take no more than 2 minutes of your time. We are offering a prize for respondents. ... link ... some more details   As the author is disclosing his identity - am I correct in not flagging this as SPAM?  Edit: the core of my question is if flagging as spam is appropriate - as  for example clearly states that spam is about commercial advertisement. The only reference to "survey == spam?" is an answer that says "flagged it as spam" - without giving any further arguments why that is appropriate.   Given the severe consequences of flagging as spam - I think a more canonical (argument based) answer is needed.


Suppose $f(n)$ is $O(g(n))$ and $d(n)$ is $O(e(n))$. How do i use Big O to show that $f (n)$ + $d(n)$ is $O(g(n) + e(n))$?

Suppose $f(n)$ is $O(g(n))$ and $d(n)$ is $O(e(n))$. How do I use Big O to show that  $f(n) + d(n)$ is $O(g(n) + e(n))$?


I'm attempting to tie classwork theory with an actual work example just now. Yesterday I attended a lecture on hypothesis testing and my notes and lecture slides cover hypothesis testing with one sample of data.  I want to tie what I'm learning to a real world work question. We are an email marketing vendor and have been asked to split test an email message which is being deployed to the clients database. The goal of the email deployment will be opens. So if we change the subject line can we get more people to open the email?  The results of this experiment might look like this:                  Sent  | Opened | Open Rate Original Email  9,000 | 900    | 10.0% New Variant     1,000 | 125    | 12.5%   If my hypothesis is that there is no difference between the emails then what method should I use to get a p-value in order to determine if the difference seen was reasonably likely to happen anyway (>5%)?   Chi-Square?  Another method?    How should I decide with method to use for the test?  Notes:   I'm a learner of stats and at a pretty foundational level right now so please bear that in mind in any responses I'm assuming that the mean I want to compare to is the open rate of those who received the original? I did Google this question before posting. But the search results were crowded out with "Hypothesis test with 1 sample" not "Hypothesis test with 1 observation"


I have the following question:    Show that if $z=x+ct$ and $y=x-ct$ then:  $$\frac{\partial^2 u}{\partial t^2}-c^2\frac{\partial^2u}{\partial x^2}=0\text{ implies } \frac{\partial^2 u}{\partial z \partial y}=0$$    If I had $u$ it would follow trivially I imagine, but I don't have $u$. It would seem that $u$ is linear in $t,x$ and since $t,x$ are linear in $y,z$ it seems logically consistent, but I am not sure what to do. Perhaps this is related to harmonic functions.  What should I first do to get this started?    Perhaps I notice that $c=\frac{z-x}{t} \text{ and } c=\frac{x-y}{t}$  and thus $\frac{z-x}{t} =\frac{x-y}{t}\implies x-y=z-x\implies 2x=y+z$


If/Testing the existence of certain numerous files

In bash, I have a directory that holds some file names that start with underscore _ and others that don't.   I want my script to check if a folder has any files that don't start with _. I write  if [[ -f $dir/[!_]* ]]   then echo "There are unmarked files."   else echo "All files marked." fi    But when I run using a folder with files that do and do not start with _, the if statement has the opposite effect of what I intended. I list the entries in the folder that clearly display files without _, but the output keeps saying, All files marked.  What am I missing?


why should you tell on a cheater on a test?


Is the gravitational field an illusion, a by-product of geometry?

The principle of general covariance from the Equivalence Principle (EEP) tells us that there is no way in principle  to locally distinguish between an inertial acceleration and the effects of a gravitational field.  When general covariance is expressed in tensorial form we find that if the equation holds true in an inertial frame that it must hold true in a non-inertial frame of reference.  My question is, if the above is true, is a gravitation field just an illusion?  Why do we have to consider a gravitational field at all.  Why not think of gravity as the effect of the bending of space and time, with gravitation revealed as an illusion, a by-product of geometry.  I feel it is the presence of matter that warps space around it, giving us the illusion that there is a gravitation force pulling on neighboring objects.


Let $n$ be positive and $a > 1$. Show that $\gcd(\frac{a^n - 1}{a-1}, a-1) = \gcd(a-1, n)$

I know that $\frac{a^n - 1}{a-1}$ is a geometric series, but I don't know how that can help me solve it.  This is not a duplicate question...


Java Diamond operator in method parameter doesn't validate the type of objects in the collection received as argument from calling method

Scenario: A method addList in class expects a List of Integer objects.  main method sends an ArrayList argument containing objects of multiple types, not just Integer.   Result: Call to method addList is successful and it is also possible to retrieve the objects stored in the ArrayList and print them.   Question: Should not we expect that on run-time when the list is received in the called method, its content will be validated and it will result in some exception?  However, in addList method, if I am trying to insert a non-Integer object in the ArrayList, it fails at compile time only.   Does this conclude that Diamond operator constraint is only while inserting the objects in a Collection?  Please note,  is different question and doesn't provide answer to this question.   package com.rnd.nirav;  import java.util.ArrayList; import java.util.List;  public class OverRidingTest {  public static void main(String[] args) {      List list = new ArrayList<>();     list.add(Integer.valueOf(1));     list.add("Nirav");     list.add(Float.valueOf(1.1f));      addList(list);  }  public static void addList(List<Integer> list) {     list.add("Khandhedia"); // This fails as expected.     System.out.println("List size = " + list.size());     Iterator itr = list.iterator();     while(itr.hasNext())     {         System.out.println("Element is " + itr.next());     } }  }


"user is not in the sudoers file. this incident will be reported" when trying to run as an admin

Just recently installed Ubuntu 20.04.1 LTS replacing entirely Windows 10. I set up everything the way I wanted and I also installed Timeshift and made a backup successfully. I tried to go into Timeshift today and it requested my password to login, so I put the one and only password I have, which is the same password I log into Ubuntu with. The password is not accepted. I assumed it was because I wasn't a root user so I tried to become one using sudo -i and sudo -s (I read that ) and I got a Password prompt and here, again, I inputted the one and only password I have which is the same one I use to log into Ubuntu. That's when I got the message "user is not in the sudoers file. this incident will be reported". So I investigated the problem and tried this link . All seemed to have gone well with no problems or errors and I've also found the same information in multiple websites but the problem still persists. Does anybody have any ideas as to what else I can try? I don't care about being root in general, I just want to be able to open my apps like Timeshift and my Firewall app. Any help much appreciated. Note: I am entirely new to Ubuntu so forgive me if I haven't performed some basic actions. Also, the website brings  question as suggested but does not help my situation. Most questions I came across containing the specific error message are solved by running some simple commands such as sudo -i and sudo -s but in my case that approach is not sufficient.


Keyboard shortcut to paste selected text to SECONDARY clipboard

I am aware that mouse selection and CTRL+C adds content to the PRIMARY and CLIPBOARD X Selections but I need a keyboard shortcut(or mouse) to have the selected text in SECONDARY Selection.  Any leads would be very helpful.


How to show that $(\operatorname{Im}{A})^⊥ = \ker(A^⊤)$, $\operatorname{Im}{(A^⊤)}= (\ker A)^⊥$?

Let now $A ∈ L(V)$, where $V$ be an Euclidean vector space.  I need to show that:  $$(\operatorname{Im}{A})^⊥ = \ker(A^⊤)$$ $$\operatorname{Im}{(A^⊤)}= (\ker A)^⊥$$


My progam crashes when using custom dialog

I am trying to make a custom dialog but am experiencing a problem. My app crashes when I push the button which shows the dialog.  Here is my code:   public class Cartas extends AppCompatActivity {      Dialog myDialog;     Button senmacho;     Button cerrar;      @Override     protected void onCreate(Bundle savedInstanceState) {         super.onCreate(savedInstanceState);         setContentView(R.layout.activity_cartas);          senmacho = (Button) findViewById(R.id.senmacho);         senmacho.setOnClickListener(new View.OnClickListener() {             @Override             public void onClick(View view) {                 senamacho();             }         });     }      public void senamacho(){         myDialog = new Dialog(Cartas.this);         myDialog.setContentView(R.layout.macho);         myDialog.requestWindowFeature(Window.FEATURE_NO_TITLE);         cerrar = (Button) findViewById(R.id.cerrar);         cerrar.setOnClickListener(new View.OnClickListener() {             @Override             public void onClick(View view) {                 myDialog.cancel();             }         });         myDialog.show();     } }


NullPointerException when pressing JOptionPane Cancel button

I am writing a program to choose between different shape and then input the values (e.g. radius) to calculate the volume of the shape using JOptionPane, I did some input validation, but the problem is whenever I press the cancel button of the JOptionPane.showInputDialog, the program crash with the following error,  where is the problem comes from? And how can I solve it? Thanks!  while(choice.equalsIgnoreCase("y")) {      .......      if (n== JOptionPane.YES_OPTION)     {          while (notDone) {               try {                radiusStr = JOptionPane.showInputDialog("Please enter the radius of the sphere");               radius = Double.parseDouble(radiusStr);               notDone = false;               }               catch (NumberFormatException e ){                     JOptionPane.showMessageDialog(null, "Input error!  Please enter a number.");                     continue;                   }               volume = new CircularVolume(radius);


Identify story/book where paralegals are also a paramilitary group

I remember reading this story/book about 5-7 years ago. It was in English. The main thing I remember is that the paralegals, probably for a corporation or some other entity, were also militarized. The one scene I remember is the paralegals dropping in from a helicopter and breaking into a building in order to steal information, or something like that. I think it may have taken place in an alternate reality, but I can't be sure of that. Any help would be appreciated!


Are black holes in a sense transparent? Meaning, they don't 'hide' any stars that happen to be 'behind' them?  A regular object obviously blocks a point source of light emanating from 'behind' it. Meaning it creates an area of space photons cannot get to us from. But a massive object curves space, and so via gravitational lensing we can sometimes see distant stars that are 'behind' other stars (by behind I mean that if the star in the middle would suddenly vanish, the trajectory of photons traveling from the distant star to Earth would have passed through the volume now occupied by the middle star).  My thinking, is that black holes curve space so much, that from ANY source of light outside it, light has a trajectory to reach us on Earth (assuming of course no other object blocks it on its way).  The reasoning for this is: Suppose we draw the straight line between us and the light source (as if the black hole wasn't there at all). Photons from our light source crossing the event horizon would obviously 'fall' inside. A photon in theory traveling exactly tangent to the event horizon would in a sense go 'into orbit' around the black hole (obviously there is no such thing, because the black hole isn't perfectly spherical, and there are quantum effects and so forth. But I'm focusing on the geometry), crossing our straight line exactly at the intersection of our line and the event horizon. Any photon passing near the event horizon, but a bit farther, would follow a curve that intersects our line a little farther from the event horizon. Continuing this, there would be at last be a photon that would exactly curve our way.


Is it possible to make writing to .bash_history immediate?

I often open lots and lots of Terminals [Right now I have 7 open on this workspace] and I often search history with grep to find a command I've just written recently, but I don't want to hunt down the terminal and then scroll up and hunt for it more, etc.. Sometimes my terminals close without 'exit,' and everything I've written is lost [Sometimes I've needed something I'd written in a terminal that was killed].  So is there a way to make it so each terminal writes to .bash_history immediately? or at least once a minute, or something like that?


How do I find out if the infinite sum of $ \ \frac{1}{(\ln k)^{\ln k}} \ $ is convergent or divergent? I'm given a hint: $ \ \ln k \ = \ e^{\ln(\ln k)}$ but I can't figure out how to apply that.


How do I complete this figure using tikz

Ok so I have been trying to draw this figure:     I have made it till the above diagram. The three captions that I made in the topmost picture is what that is remaining. 1. The outer boundary of the rectangle should also be colored blue or some color.  2. The small circles should be labeled with a matrix.  3. The rectangle should be filled with horizontal lines  Here is the code for what I have done:      \documentclass{article} % say \usepackage{tikz} \begin{document} \begin{tikzpicture} \draw  (0,5) node (yaxis) [above] {$y$} |- (5,0) node (xaxis) [right] {$x$}; \draw (-0.5,0) -- (4,0); \draw (0,-0.5) -- (0,4); \definecolor{mycolor}{RGB}{178,181,255} \filldraw[fill=mycolor] (0,0) rectangle (2,2); \filldraw [cyan] (0,2) circle [radius=2pt]; \filldraw [cyan] (2,0) circle [radius=2pt];  \end{tikzpicture} \end{document}   Any help would be appreciated.


Error: "an object reference is required for the non-static field, method or property..."

I'm creating an application in C#. Its function is to evaluate if a given  is prime and if the same swapped number is prime as well.  When I build my solution in Visual Studio, it says that "an object reference is required for the non-static field, method or property...". I'm having this problem with the "volteado" and "siprimo" methods.  Where is the problem and how can I fix it?  namespace ConsoleApplication1 {     class Program     {         static void Main(string[] args)         {             Console.Write("Write a number: ");             long a= Convert.ToInt64(Console.ReadLine()); // a is the number given by the user               long av = volteado(a); // av is "a" but swapped              if (siprimo(a) == false && siprimo(av) == false)                 Console.WriteLine("Both original and swapped numbers are prime.");             else                 Console.WriteLine("One of the numbers isnt prime.");             Console.ReadLine();         }          private bool siprimo(long a)         {             // Evaluate if the received number is prime             bool sp = true;             for (long k = 2; k <= a / 2; k++)                 if (a % k == 0) sp = false;             return sp;         }          private long volteado(long a)         {             // Swap the received number             long v = 0;             while (a > 0)             {                 v = 10 * v + a % 10;                 a /= 10;             }             return v;         }     } }


What do you do when you have a database that is marked as Suspect?  Restore from the last backup?  Please advise.


Composition of covering maps is a covering map if the inverse image is finite.

Let $q: X \to Y$ and $r: Y \to Z$ be covering maps. Let $p=r \circ q$. Show that if $r^{-1}(z)$ is finite $\forall z$, then $p$ is a covering map.  $\textbf{My Attempt:}$  Let $U$ be an arbitrary open set in $Z$. Then $p^{-1}(U)=q^{-1}(r^{-1}(U))$. Since $r$ is a covering map, we know that $r^{-1}(U)=\bigcup_{i=1}^{N} V_i$ where $V_i$ is open $\bigcap_{i=1}^{N} V_i = \emptyset$.   Is the following true,  $q^{-1}(\bigcup_{i=1}^{N} V_i)=\bigcup_{i=1}^{N} q^{-1}(V_i)$ ?  Now since $q$ is covering for each $V_i$ we have that $q^{-1}(V_i)=\bigcup_{\alpha} K_{\alpha}^i$ where the $K_{\alpha}^{i}$ are all disjoint and open.   Then, $q^{-1}(\bigcup_{i=1}^{N} V_i)=\bigcup_{i=1}^{N}(\bigcup_{\alpha} K_{\alpha}^i)$.  So we just need to show that $\bigcap_{i=1}^{N}(\bigcup_{\alpha} K_{\alpha}^i)=\emptyset$ which is fairly straightforward.   I am not sure if this is the right way to go about this proof as I have not utilized the fact that the number of $V_i$ will be finite.   How do I use the fact that $r^{-1}(z)$ is finite?


Create a "continuous" minitoc at the beginning of each chapter

I am required to have, at the beginning of each chapter of my thesis and just after chapter number/name, something like this (e.g. for Chapter 1):     Table of contents: 1.1 chapter1section1name 1.2 chapter1section2name 1.3 chapter1section3name 1.4 chapter1section4name 1.5 chapter1section5name 1.6 chapter1section6name    That is, a minitoc but without going to a new line for each entry. What's the best way to achieve this result? I really have no clue...


i'm not an native english speaker. I came across the "Dying ! Dying in the night " poem by E. Dickinson. A verse is bothering me: "Where is Jesus gone ?" Is it grammaticaly correct ? Would "Where has Jesus gone ?" be better ? Or by her initial sentence, it means: where is he now that he is dead ? I'm not implying that such an acclaimed poet could do grammar errors but i've never seen anything like this. Thanks for your help.


My Friend recently gave me her old iPhone 6 and she said that it was currently iCloud locked to AT&T. I have no clue what an iCloud locked AT&T iPhone means. Can I still use the iCloud Locked AT&T iPhone 6 as an iPod to store some music on?


Composition of analytic functions is analytic

I want to find a proof that shows the composition of two analytic functions is analytic. I know I should prove this using Cauchy-Riemann equations, but I wasn't able to use them in the proper way in order to solve the problem.


How come $x \notin N \cup P$ becomes $(x \notin N \text{ and }x \notin P)$ and $x \notin N \cap P$ becomes $(x \notin N \text{ or }x \notin P)$?

The expressions are part of the proofs of the expressions $M\setminus (N \cup P) = (M \setminus N) \cap  ( (M\setminus P) \text{ and } M\setminus (N ∩ P) = (M \setminus N) \cup  ( (M\setminus P)$. So when I was trying to prove the first one I thought $\{x \mid x \in M  \text{ and } x \notin N \cup P\}$ would be expressed as  $\{x \mid x ∈ M \text{ and } x \notin N  \text{ or } x ∈ M  \text{ and } x \notin P\}$ as the "and" from the intersection would distribute over the "or" from the union. Yet to prove the equality, it should be $\{x \mid x \in M  \text{ and } x \notin N  \text{ and } x \in M  \text{ and } x \notin P\}$ so that the equality holds until last step. For the second example just change the middle "and" with "or". Again I thought it should have been "and" as "and"s have associativity. I can simply memorize it and use it this way whenever a similar proof comes. Yet, I would be more than happy if someone tells me the reason behind this expressions, so that I see what's going on.   Edit: My question has been identified as a possible duplicate of Proving DeMorgan's Theorem. First of all, my problem is not about proving the entire theorem. I actually have the proof in front of me. It is about a proof step I couldn't internalize. In the linked question there is limited mention of that specific step except for the fact that it is taken for granted as in the proof in front of me now (so again after reading the question and answers, I am at where I was before). I want an explanation of that step specifically and my question is about that step not a whole proof. Moreover, although I have to admit that my question depicts a step on proving DeMorgan's theorem, in this case M is not fixed as a universe and difference relation is not absolute but relative. As such the equalities can be thought of displaying properties of set difference as well. After I understand these relative difference properties (including a third one) and the specific steps I mentioned in my question, I want to continue with DeMorgan. As such I would appreciate help on a topic that is a step in moving to a more advanced topic and a question on a minor detail rather than the proof of a whole theorem.


Statistical method for finding minimum numbers of selections for popularity of an item

Suppose that we have a population of N= 1000 people and they want to select 5 items (for simplicity) {A, B, C, D, E} (but actually the number of items is in the order of thousands). Number of selections for items is {3, 142, 52, 633, 800}. Each person (selector) is free to select as many items as they want. Selecting one item may affect the selection of another item by one person. For example, if items are goods in a supermarket, the first person may select items A and C. The second person may select all items. Each person can select each item just once. We want to find “the minimum number of selections”, named T, so that if the number of selections for an item is larger than T, we can say that item is interesting or popular for the population since at least T people have selected that item. We want to find this number (T) by “a statistical method”. Thanks.


Upgrading current installation of python packages for all users

I have installed several python (Python 3.6, Ubuntu Server 18.04.5 LTS) packages with pip, but this installation was made with pip3 install package, and so it is valid only for the users who installed them. How can I upgrade this installation to all users, without doing a double installation? I think that sudo pip3 install package installs a package for all users. Is it safe? What do you recommend?


Is there random variation in post-evolution CP?

Say my friend and I are both level 20, with identical XP, and we simultaneously catch an identical 500CP Pokemon. If we then both evolve this Pokemon, will it always have the same post-evolution XP?  Additionally, what other factors would influence variation in post evolution CP?   Would a size/height disparity result in different post evolution HP? (I've seen some discussion on this but no definitive answer).  How about if my friend evolved immediately, but I waited until I was level 21?  Do all Pokemon of the same species increase in post-evolution CP at a similar rate? If so, how does this rate vary across different species?


How much voltage/current is "dangerous"?

Related:        From what I've heard:   110 V (or 220 V; household voltage pretty much) is dangerous (i.e. can kill you) I think there's consensus on this, no need to try :) 60 V (old telephone lines) is supposedly dangerous (never tried, only heard it once... probably won't try)   From what I know first-hand:   9 V is not dangerous (I've put a 9-V battery on my tongue, nbd... actually it kinda hurt!) 1.5 V can indeed be quite shocking with enough current (fell for one of those "Do you want some gum?" tricks back in high school...), but they sometimes do not use 1.5 V with the low amperage levels, some use a DC motor to vibrate and complete the trick.   So I guess there's two parameters here, voltage and current... but are there rough numbers on how much of each (or in combination, which I guess would be power) would be considered hazardous?  No old telephone lines have always been 48vDC well at least since from 1950s, if your skin is wet you can feel it slightly, like on your forearm.  Now the ring voltage is 90-110vAC with a 2 on 4 sec off cycle (USA).  It will ring your bell but good, should you be touching the wires when someone calls. The ring voltage rides on top of the 48vDC, so its present on the same two conductors that the voice voltage(DC) is on. Luckily it's 4 seconds off will give you a chance to get off the conductors with a scream (of pain).


I'm dealing with failing WD 750 GB laptop hdd. Scan perfmormed with MHDD booted from flash disk indicated few (about 6) bad sectors.  Data on the hdd is not important, however I would like to still use this disk.  S.M.A.R.T data of the disk :   I've found a tutorial that suggested 'zeroing' the drive with use of MHDD "ERASE" command and then remapping the drive; it was supposed to allow disk to work again by skipping bad sectors logically.  After about hour or two (of estimated 150), ERASE process resulted in "Catastrophical Error", with adnotation of "Broken drive".   Not being sure if there's anything more to be done, I've launched another scan with "remapping" the drive; when process encountered the first bad sector, the following happened: .   "Blue" blocks are supposed indicate a remap attempt. Looks like it's the first bad sector that MHDD tried to remap.  Given above data, I would like to ask:   Do this data (especially SMART results) indicate that disk is already critically damaged and unusable at all? Is there a way to get this hdd working again for short period of time (propably by skipping damaged sectors)?   I'll take any questions about facts relevant, yet not inclued here.  EDIT: Thread that I'm suposedly duplicating suggests using HDD Regenerator (I did it - failed to make difference here) and Spinrite (which I've failed to run due to other issues). This question is bit broader in scope.


80s-90s anime (movie or series) in which an armored girl exchanges age with a dying man on a beach

What is the name of an anime from 80s-90s movie/series in which there is a scene, maybe the end, where a girl (who has an armor) exchanges age with a dying man in a beach, so the man transforms into a baby and the girl grows to a woman?


Ubuntu 13.10 boots into blank screen after grub

Recently after force shutting down during a long Shutdown then when it started up it would go to grub and then it would flash a login screen before going black with a not moving terminal cursor. After searching for a result I saw a solution to a similar problem which was to change the boot code in grub from quiet splash to Nomodset and when I tried that it worked for a while but now I have to constantly change the boot code and its a random chance if it works, no pattern showing. Can anyone help me?


I have an issue which I've been struggling with today. The JSON is returned back to me with a project Id as the key, this Project Id is dynamically generated and due to this I have not been able to come up with a way to deserialize this response. Any suggestions?   {      "success":true,    "numRows":5,    "data":{         "23000079":{            "projectId":"23000079",          "name":"Mcdonalds",          "departmentId":"9383",          "responsibleUserId":"7444434"       }    } }


I installed Ubuntu 16.04 alongside Windows, giving it 50 Gb of space. Now, I need more space. I'm using gParted and I managed to unallocate a piece of partition. How can I extend Ubuntu with the space I reserved? Many thanks


I have bit of a problem. I have no idea how to install the Ubuntu 13.04. The only thing I have is USB. My machine is Intel i3 with Windows 8 already installed but I am kind of tired of Windows so I decided to make my 8 gb ram 1 tb HD. a dual boot. Any Help Is appreciated ! :)


How get the number of rows count by ResultSet in Java

I want to get the row count of a ResultSet.  ResultSet rs; Statement s; rs=s.executeQuery("SELECT * FROM mytable");  //rs.getRowCount; ???


C++ guarantees that variables in a compilation unit (.cpp file) are initialised in order of declaration. For number of compilation units this rule works for each one separately (I mean static variables outside of classes).  But, the order of initialization of variables, is undefined across different compilation units.  Where can I see some explanations about this order for gcc and MSVC (I know that relying on that is a very bad idea - it is just to understand the problems that we may have with legacy code when moving to new GCC major and different OS)?


Let's say I have 3 users on my server:   /home/bob /home/joe /home/fred   I want to create a folder at /share in which bob and joe can both add and delete files. I want all of files added to that directory to have permissions such that both users can modify or delete them.  The issue is that when directories are created within /share/, they are created with permissions for the owner. If a folder is created in /shared then it belongs to the creator, and nobody else can modify/delete its contents.  I need to have this folder behave such that everything created in it has full rwx permissions for everyone.


Search Launchpad for PPAs matching software or package name?

Is there a way to search though LaunchPad's PPAs for a certain package name? For instance if I was looking for PPAs with Firefox packages I could search for "firefox" and retrieve a list of all the PPAs which contain a firefox package.


Disable drag and drop option for multiple file uploader

These are the screenshots of multiple file uploader from the same SharePoint 2010 site. Some users are seeing the first and some are seeing the second one. Is it possible to disable the second view(drag and drop) by editing upload.aspx in the layouts folder?      Thank you


Travelling when my Schengen visa expires: Can I renew it in a country where I am not a resident?

I have a multiple-entry Schengen visa that is valid until December 2016. I will arrive in  The Netherlands on September and will leave on November BUT I need to go back to The Netherlands on February 2017. By that time the validity of my visa is expired. And the thing is, I will not be in my home country on the month which it will expire... lets say for example I will be in Thailand. Can I apply for a Schengen visa in Thailand - NOT my country of residence? Or Can I extend my visa there?   Or while I am in The Netherlands, can I extend the validity of my visa?


I have a collection of objects in my scene that I want to randomly duplicate in a similar fashion to the Array modifier. How would I go about doing this, would I need to program this function myself? Picture if I didn't explain this clearly:


PHP XPath - Select one specific node and his parent node with one rule

I'm working on parsing some XML files using Xpath. I want to select one specific Category node and his parent node (Sport) with one expression?!  XML document: livescore_full.xml  <? xml version = "1.0" encoding = "UTF-8" ?> <LivescoreData generatedAt="2013-08-18T09:41:19 CEST" type="full">     <Sport SportId="1">         <Name language="en">Soccer</Name>         <Category CategoryId="48">             <Name language="en">Argentina</Name>             <Tournament TournamentId="68" UniqueTournamentId="155">                 <Name language="en">Primera Division, Torneo Inicial</Name>             </Tournament>         </Category>         <Category CategoryId="49">             <Name language="en">Brazil</Name>             <Tournament TournamentId="69" UniqueTournamentId="156">                 <Name language="en">Brazil Primera Division</Name>             </Tournament>         </Category>     </Sport>     <Sport SportId="2">         <Name language="en">Basketball</Name>         <Category CategoryId="55">             <Name language="en">Spain</Name>             <Tournament TournamentId="545" UniqueTournamentId="453">                 <Name language="en">Primera Division, Torneo Inicial</Name>             </Tournament>         </Category>         <Category CategoryId="56">             <Name language="en">England</Name>             <Tournament TournamentId="654" UniqueTournamentId="5656">                 <Name language="en">England</Name>             </Tournament>         </Category>     </Sport> </LivescoreData>    $xml = simplexml_load_file("livescore_full.xml");  $data = $xml->xpath('//Category[@CategoryId="48"]');   print_r($data); // only return data for specific Category node   $data contains data about Category node id=48, but there is no information about the sport id and sport name.   How to write Xpath rule to select Sport and Category data using CategoryId attribute? I tried some variations with the ancestor-or-self, but without success.


How to reduce circuit elements of a decomposed $C^2(U)$ operation?

This question refers to Nielsen and Chuang's Exercise 4.22:   Prove that a $C^2(U)$ gate (for any single-qubit unitary U) can be constructed using at most eight one-qubit gates, and six controlled-not gates.    To prove this, I decomposed all $C(V)$ operations into $AXBXC$ form and ended up with 9 single-qubit gates and 8 C-NOT gates. So I need to now get rid of one single-qubit gate and 2 C-NOT gates. To do the former, I changed the order of $V's$ and got rid of 2 single-qubit gates with combining 2 pairs of single-qubit gates.  For example: as $C=R_z((\delta - \beta)/2)$ and $A=R_z(\beta)R_y(\gamma/2)$  became                 $CA=R_z((\delta - \beta)/2)R_z(\beta)R_y(\gamma/2)$   For the CNOT gates, I can't touch the 2 C-NOT operations on qubits 0 and qubit 1 because they are important for the functioning of $V^\dagger$. The only way then is to reduce the 4 CNOT gates that compose the 2 $C(V)$ gates. I am encountering some difficulty here. Any help/hint will be appreciated.   *This is not a homework question. I am self-studying from Nielsen and Chuang for an independent project.


I have a problem where the crucial variable is the integral of the squared PDF of a random variable, i.e.  $\int f(x)^2dx$  How should I interpret this property of a distribution?  If $f(x)$ is gaussian, then this is inversely proportional to the variance, $\sigma^2$, but I don't think this is generally true.  (Note that this is also equal to $\int F(x)f'(x)dx$ ).


Orphaned tag wiki edits have broken activity entries

If a user makes an edit to a tag wiki that subsequently becomes orphaned, the activity entries on their profile are left looking a bit broken. For example,  shows the following:    I believe that it used to say something like "orphaned wiki" in the marked sections, which would be preferable to nothingness.


I like the chat feature and I am one of the regular users for it. The thing is, sometimes I love to read what guys talk about in a chat room, but without being visible to them usually to avoid pings  (we have a very good chat community in Travel.SE). Currently I open another browser where I am not logged in and open the chat there to see it without appearing. I also can load the transcript but that requires me to refresh.  Is there a way to be a spectator in a chat room (your name not in the users list) and without being logged out? If not can that be done?  Note: There is a  which suggested the transcript, which is not a practical solution IMO. So I am reviving that request again hoping it will get attention.


Are they the same function? $y = x^2/x$ and $y = x$

Are they the same function?  $$y=\frac{x^2}{x}$$ and $$y=x$$  For the first function, if we don't divide both the numerator and the denominator by x, then the domain of it is the real line except the point x = 0, which is different from the domain of the second function.


Can Network Adapter RTL8821E be made to work on Ubuntu 18.04?  If so, what driver is needed?


Please add a reply button to messages in the pinned/starred section

I've run into this a few times; I'll rejoin chat after being away for a while and notice something interesting in the starred section.  I'd like to reply directly to the message but there's no reply button.  Currently, the only ways to explicitly reply to one of those messages are either:-   find the message by scrolling up and looking for it, then click the reply button or; copy and paste the permalink, deleting all the way up to the fragment identifier and adding the colon at the start.   Please add a reply link, even if it just goes in the popup menu it's an improvement.


Cause of Alpha or Black Artefacts in Render

This is my Minecraft Animation. It is made in Blender Internal and is intended to be rendered in Blender Internal. The animation consists of me running infront of Minecraft trees. These trees are mapped with UV textures of Minecraft Leaves with alpha turned on so that the leaves are transparent in places. The Animation starts at frame 8 and ends at 40. This is not a case Z fighting.  However when I render the animation I get square alpha (sometimes black pixel) artefacts in the render. Every frame has diffrent result but still has the artefacts. This is what it looks like. The white is the alpha. Open in a new tab for closer inspection.    As I said some frames have this problem and some don't    This one has AA disabled. This makes the alpha only one pixel each. (Open in new tab to see individual pixels)   This problem does not occur in the rendered mode viewport.   Leaves' Material Settings     Leaves' Texture Settings     Edit: I decided to restrict the leaves from render and this is the result I have. Pretty ugly. Also added, glare and vector nodes just fyi.    I then decided to remove the wood as well and now this happened.    And now there's black and alpha.    Here is a link to a  showing the problem.  What is going on here! Is this blend file corrupted? Please if you know the answer or what causes this please mention this down below.  And because you asked here a stripped down version of the file:


Java Question on how to cancel system input

I want to print last message when user inputs q but it gives an error.  Language Translator Program Please enter the input sentence (press q to exit): Robin came to Montreal, Canada in 2009. Robin stays in Montreal for 11 years. Montreal is in Canada. Please enter the input sentence (press q to exit): Lucy came to Berlin, Germany in 2000. Lucy stay in Berlin for 20 years. Berlin is in Germany. Please enter the numbers along operation (press q to exit): q Thanks for using translator program. import java.util.Scanner;  public class MiniTranslator {     public static void main(String[] args) {         String message ="";         do {             //Declaring scanner             Scanner keyboard = new Scanner(System.in);              //Printing greeting message              System.out.println("---------------------------------------------------------\n"                                   +"\tLanguage Translator Program\n"                                 +"---------------------------------------------------------");              System.out.println("Please enter the input sentence (press q to exit): \n");             message = keyboard.nextLine();             String[] arr = message.split("[ ,.]+",8);             String name = arr[0];             String city = arr[3];             String country = arr[4];             String year = arr[6];              int noOfYears =2020 - (Integer.parseInt(year));              System.out.println("\n" + name +" stay in " + city +" for " + noOfYears +" years. "                                  + city +" is in " + country +".");             System.exit('q');             keyboard.close();         }         while(message!="q");         if(message =="q") {             System.out.println("Thanks for using translator program");         }     } }


Clarification on the Math of Logistic Regression

I am trying to get a better understanding of the math behind logistic regression.  Logistic regression is looking to give a prediction based on data likelihood.  From my understanding it is making a posterior prediction.  Suppose we have a two-class model. So this becomes the equation  \begin{align} p(C_1|x) &= \frac{p(x|C_1)p(C_1)}{p(x|C_1)p(C_1)+p(x|C_2)p(C_2)}\\ &=\frac{1}{1+\exp(-a)} = \sigma(a) \end{align}  where $a= \ln \frac{p(x|C_1)p(C_1)}{p(x|C_2)p(C_2)}$  My questions are what does $a= \ln \frac{p(x|C_1)p(C_1)}{p(x|C_2)p(C_2)}$ intuitively mean? Does it imply that the $\theta x$ of our model, is trying to estimate the ratio in $a$? And why in the first step is the equation equivalent to the same as the naive bayes classifier; how does logistic regressor distinguish itself from the naive bayes if the background math is the same


Why should two sub-atomic (or elementary particle) - say electrons need to have identical static properties - identical mass, identical charge? Why can't they differ between each other by a very slight degree? Is there a theory which proves that?  Imagine an alien of size of order of Milky-way galaxy examining our solar system with a probe of size of 10's of solar system dimension and concludes that all planets are identical.


Is it possible to hack the "Correct spelling automatically" setting in OS X to emit a sound when correcting?

There are many times when I curse the autocorrection mechanism for changing what I typed, but overall, much of the corrections are welcome so I don't really want to disable it. I do want to have it do it's work but alert me when it makes each change so I don't have to proofread everything or focus with perfect attention to the screen to see the momentary red and/or blue underlining that alerts me to the machine override.  I would love a way to turn on an audible beep (customizable of course) so that I also get a warning each time my typing gets corrected (and only when autocorrection occurs).


What is the title of sci-fi novel where lizards became more advanced than humans?

I've read some sci-fi novel long ago where lizards during natural selection became more advanced than humans. Also, as some clue, in that book's world transport was mostly biological - I remember giant fishes used as transport. Can't remember its title.


BibTeX handling of the Dutch "van" name prefix with natbib

I want to produce the following with LaTeX/BibTeX:  In the running text:     ... we refer the reader to the work of Van Noort (2010).   In the bibliography:     Thomas van Noort. An important paper. 2010.   I have tried many tricks, but I don't seem to able to fulfill all the requirements:   "Thomas van Noort" has to appear sorted in the bibliography by the name "Noort". In the running text, the "Van" needs to have an uppercase 'V' In the bibliography, the "van" needs to have a lowercase 'v' I am using hyperref, and I want the whole "Van Noort (2010)" text to link to the reference.   Using plain \citet will generate:     ... we refer the reader to the work of van Noort (2010).   Note the lowercase 'v'; this is not acceptable, as per standard treatment of Dutch names. Setting the BibTeX name to Van Noort, Thomas makes the running text citation look ok, but then in the bibliography I get     Thomas Van Noort. An important paper. 2010.   Note the uppercase 'V'; this is also not acceptable, as it should only be uppercase if it is not preceded by the first name.  (1) is easy: I set the BibTeX author field to {\noopsort{Noort}}{van Noort}, Thomas. (2) and (3) I can fake by saying something like we refer the reader to the work of Van Noort \citeyear{...}, but this is not nice, and does not fulfill (4).  Anyone has any suggestions? I was under the impression that LaTeX and BibTeX were designed with these kind of things in mind, so maybe I'm missing something...


My question is a duplicate of this; . The accepted answer from the link above says that at sunset the scattering occurs farther away and does not reach the observer, which is unsatisfactory and vague to me. (not even sure if it's the right and correct answer)  It doesn't quite make sense to me that at noon, we see scattered blue light whereas, at sunset, we see the sunlight itself minus the scattered blue light. At noon or at sunset, we are not seeing the sun, but the scattered sunlight indirectly. The logic should apply both cases equally and should imply that at sunset we see bluer sky than at noon because of more scattering.  Please let me know if this duplicate question was unnecessary because the accepted answer from the link above was enough to answer the question.


I hope this is the right place to ask this question.   and it was almost immediately closed by a moderator with the reason     Closed this as the only two possible answers are "yes it is" or "no it isn't".   I'm a long time SO user and I didn't remember this rule, so I searched here:       But in none of these threads was I able to find a rule that explains the reason why the question was closed.  Can you help me to understand?  What I can't understand, is that if I had opened the question with no context, then people would probably have asked me "what have you tried"? I added my context, and the question was closed because it's only a yes/no.  Moreover, this statement is not correct. In fact, an answer to a yes/no question can contain several additional details, as you can see from the comments. People are suggesting improvements and alternatives.


What is the fastest way to fill up disk space

I've got a big disk worth few TBs ( 5 TBs ) and i need fill up this disk space to about 95%, this is a linux centos box.  I've tried dd as in  dd if=/dev/zero of=o_File1.img bs=209715200 count=1000   even tried running in a loop like   #!/bin/bash  count_=0 parallel_=10  BS=2097152000 COUNT=100 while [ $count_ -lt $parallel_ ] do         file="Dummy_DD_BS_"$BS"_$(date +%Y%M%d%H%m%s)_$count_.img"         echo $file         `dd if=/dev/zero of=$file bs=$BS count=$COUNT > /dev/null 2>&1 &`         count_=$((count_+1)) done   but 5 TB seems like a hell lot.   is there a faster method, I'm Okay with any scripts python/perl/bash or anything, I'm looking for a fast optimized solution  Edit:  Okay so following the  did not really solve much anything     case 1 : dd    time dd if=/dev/zero of=filename10 bs=1G count=10     10+0 records in     10+0 records out     10737418240 bytes (11 GB) copied, 34.0468 s, 315 MB/s      real    0m34.108s     user    0m0.000s     sys     0m13.498s   so an estimated around 3 - 4  hours to fill this 5 TB      Case 2 : fallocate    fallocate failed: Operation not supported     its a custom file system not the popular ext*       Case 3 : truncate      this is the weirdest ones    it doesn't really fill the disk this seems to be just reserving the space for the file so definitely not suiting my requirements   so is there a better solution or I have to live with dd or create smaller partition to test this


Does any standard "comes with batteries" method exist to clear the terminal screen from a Python script, or do I have to go curses (the libraries, not the words)?


I have a file named aux in a directory  ...> ls aux  ...> dir  Wolumin w stacji C nie ma etykiety.  Numer seryjny woluminu: ...   Katalog: C:\Users\...\config  2015-07-15  23:14    <DIR>          . 2015-07-15  23:14    <DIR>          .. 2007-12-01  04:49               511 aux                1 plik(ów)                511 bajtów                2 katalog(ów)  76 382 707 712 bajtów wolnych   and when I'm trying to remove it (rm), I get the following error:  rm: aux: No such file or directory   del also doesn't work:  Nazwa pliku, nazwa katalogu lub składnia etykiety woluminu jest niepoprawna.   (File name, directory name or volume label syntax is invalid.)  How do I remove this file?


I'm completely unable to delete a file, which doesn't even show up in Windows, but does in OSX (Mountain Lion) this file was created after uninstalling AppServ (local webserver) Now I need to reinstall AppServ in the same location C:\AppServ, but I can't due to that location being used by that file.  As said, in Windows the file isn't even there (show hidden files checked of course)  In OS X, I've tried rm, rm -f and some file removal script called Trash It! all to no avail.  File in question:    Error - when I try to do anything with the File, deleting, renaming or anything else.    What other options do I have to remove this bugger ?


I've been trying to understand the complex function derivatives, but there are some issues that I'm encountering. I'm following the Ahlfors Complex Analysis. When he is demonstrating the derivative via the limit, he does it both with a pure infinitesimal Real and a pure Imaginary value, but I don't get why should it be concluded that they must have the same value since you are going in different directions of the complex plane (with the real value you are going in the real axis and with the imaginary value you are going with the imaginary axis). Also, I see some similarities with the multivariate calculus, without being the same, and that might be something that is causing me to some misconception.


Can I bring a beach sand to the US as a souvenir?

When entering the US, there is a question (11d) on Customs Declaration about bringing soil with me. Does a beach sand count as a soil? Can I still bring it? Do I have to declare it?  This is a different question from this one because I don't need to have it in a carry-on and I want to bring it from outside the US. The other question is about bringing a sand with you on board the plane within the US and addressing concerns regarding TSA. My question is about importing the sand to the US


How did Harry breach the Statute of Secrecy?

Something always bothered me with Fudge's accusations:     “Disciplinary hearing of the twelfth of August,” said Fudge in a   ringing voice, and Percy began taking notes at once, “into offences   committed under the Decree for the Reasonable Restriction of Underage   Sorcery and the International Statute of Secrecy by Harry James   Potter, resident at number four, Privet Drive, Little Whinging,   Surrey." - OotP Ch. 8 "The Hearing"   Harry cast the Patronus Charm, so he violated the Decree for Reasonable Restriction of Underage Sorcery alright - extinuating circumstances aside - but how did he breach the Statute of Secrecy?  The only witnesses were Dudley and Mrs. Figg, both of whom already knew that Harry is a wizard. Earlier, even Hermione gets it wrong (don't tell her!):     They haven’t even reported that you broke the International Statute of   Secrecy. We thought they would,... - OotP Ch. 4 "#12"   Yes, Harry does use magic in front of a Muggle, Dudley, but even Dudley is not so thick that the fact that Harry's a wizard would come as a revelation to him. Harry cannot breach the Statute of Secrecy to someone already in the know.  Shouldn't Dumbledore point out that glaring error in the indictment sooner rather than later? Or at least mention it, at all?  Is there maybe a source that mentions the Statute of Secrecy containing a clause, that even the mere possibility of magic being witnessed by an uninitiated muggle is sufficient for its breach?? Cause if so, wouldn't even adult wizards have a really tough time doing anything, ever.  Possibly related:


Please evaluate the limit $\lim\limits_{n\rightarrow\infty} \prod\limits_{k=1}^{n}\left(1+\dfrac{k}{n^2}\right)^2$ if it exists.   I have a heuristic argument to solve this limit but cannot prove it rigorously. The idea is that for large $n$, $\left(1+\dfrac{k}{n^2}\right)$ can be approximated by $\left(1+\dfrac{1}{n^2}\right)^k$. So, essentially the limiting value is equal to $\lim\limits_{n\rightarrow \infty} \left(1+\dfrac{1}{n^2}\right)^{2\sum\limits_{k=1}^{n} k}$. This quantity can be easily computed to be $e$. Please help me out to make this argument rigorous.


Background image resize in Ubuntu 18.04.1 LTS

Recently updated to 18.04.1 and now I cannot resize my background image from fill screen to center image.  How can I resize the image now that 18 doesnt have the quick resize feature?


consider a square of side length $x$, find the area of the region which contains the points which are closer to its centre than the sides.

Any ideas how to start.   I am having trouble figuring out the region itself   All ideas are appreciated  thanks


Logging every action with custom "debug" method. Good idea?

I'm creating my first full framework using Selenium and TestNG and recently implemented the ability to have logging enabled which will track every action (before and after).  public class CustomLogs {     //Set Logging_Level to "Debug" to enable logging     public String Logging_Level = "OFF";      public void Log(String message) {         if (Logging_Level == "Debug")         {System.out.println(message);         } else {         }     } }   Then, in my page objects, EVERY action method has a log statement before and after EVERY action.  public class LoginPage extends BrowserConfig {      final WebDriver driver;     private static CustomLogs customlogs = new CustomLogs();      //Elements on Page     @FindBy(id = "userId")     private WebElement userNameField;      //Constructor     public LoginPage(WebDriver driver) {         this.driver = driver;     }      //Fill Username     public void FillUsername(String userNameEntry) {         userNameField.clear();         customlogs.Log("Entering Username: "+userNameEntry+"...");         userNameField.sendKeys(userNameEntry);         customlogs.Log("Username entered.");   It seems like this is very beneficial, not only for debugging, but also because you can now print out every single action step, so keeping records or showing others what steps were completed is very straightforward.  But I can also see how this is cluttering the page object code.  Is this a good idea?  And/or is there a better way to do this?


Passing Parameter To a Batch file Which executes the DB2 commands

I have created a batch file and in inside the file i'm executing the below 2 commands in db2 command line. db2cmd -i -w db2clpsetcp db2 -tvmf D:\Db2_old.sql > D:\Vikas.log  I need to Pass a parameter to the batch file which will be used in the sql file for the extraction. Is there any way that we can achieve this?


Statistical interpretation of Maximum Entropy Distribution

I have used the principle of maximum entropy to justify the use of several distributions in various settings; however, I have yet to be able to formulate a statistical, as opposed to information-theoretic, interpretation of maximum entropy. In other words, what does maximizing the entropy imply about the statistical properties of the distribution?   Has anyone run across or perhaps discovered yourself a statistical interpretation of max. entropy distributions that does not appeal to information, but only to probabilistic concepts?  As an example of such an interpretation (not necessarily true): "For an interval of arbitrary length L on the domain of the RV (assuming its 1-d continuous for simplicity), the maximum probability that can be contained in this interval is minimized by the maximum entropy distribution."  So, you see there is no talk about "informativeness" or other more philosophical ideas, just probabilistic implications.


Deleted users still leave some trace behind

I am not sure whether this is a bug, but shouldn't the system message generated when a user deletes his/her post also be normalised if the user requests deletion?  Case in point (viewable for 10K and diamonds on Math.SE):   The user/OP's account was deleted, as one can see from the greyed-out normalised username attached to the post. But the system message indicating deletion still shows the user's original username.   Edit: Screenshot:    Ignore the "edited by" line, some other user edited the post before it was deleted. But look at the bottom left where it says "deleted by C" (I left the first letter to show that it is not "user9413"; it is also not one of the diamond mods); the displayed name there is/was the username of the now deleted user9413.


Show that the quotient ring R/N has no non-zero nilpotent elements.

An element $x$ in a ring $R$ is called nilpotent if $x^n=0$ for some $n\in \mathbb N$. Let $R$ be a commutative ring and $N=\{x\in R\mid \text{x is nilpotent}\}$.  (a) Show that $N$ is an ideal in $R$.   (b) Show that the quotient ring $R/N$ has no non-zero nilptoent elements.  What's the steps to prove (a) and (b)?


How to get notifications for Stack Exchange in the browser

Is there a way to get notifications from Stack Exchange in my browser? I know you can get notifications in the app, but is there a similar feature on the Chrome browser?


Show that every prime $p>3$ is either of the form $6n+1$ or of the form $6n+5$, where $n=0,1,2, \dots$


Irreducible topological spaces and irreducible Hausdorff space

A topological space $X$ is said to be irreducible if it cannot be written as a union $X = A∪B$, where $A$ and $B$ are proper closed subspaces of $X$  I want to try the following:  Show:  $(i)$ That every set with the indiscrete topology is irreducible, and every infinite set with the finite complement topology is irreducible.  $(ii)$ That an irreducible Hausdorff space contains at most one point.  Can you give me any suggestions on how to try this?


Is there any simple (IE: right click in Nautilus) way to password protect a particular folder/file in Ubuntu? I've got a few files containing sensitive info and I'd much prefer that if/when I leave my computer alone, they aren't accidentally accessed by someone else.  The secruty does not have to be extremely tight. My only concern is that when family/friends come over, I don't really like the idea of them looking at my bank details, accounts or, you guessed it, porn collection.  A simple, effective way to let me put my machine in the hands of someone else knowing that said machine can not cause me embarresment is the sole reason why I'd like to see this in Ubuntu.


How can I get a list of the biggest packages currently installed in order?

I am running out of disk space on my root partition, and I'm attempting to remove some packages and not others.


I read in a book that the following expression O(2^n + n^100) will be reduced to: O(2^n) when we drop the insignificant parts. I am confused because as per my understanding if the value of n is 3 then the part n^100 seems to have a higher count of executions. What am I missing?


Are there any data repositories commonly used in conjunction with arXiv?

I will soon be posting an article to arXiv, and I have supplementary data that is approximately 800MB in size, which I would like to make available somewhere. Are there any data repositories that are commonly used in conjunction with arXiv?


\index inside footnote: How to propagate the footnote number correctly with index package?

We're using the index package in order to get several indexes (name index, subject index, language index), and we're basically happy with it. There's only one obstinate problem: index does not propagate footnote numbers as desired, unlike makeidx (which doesn't support multiple indexes though):  \documentclass{scrbook}  \usepackage{index} \usepackage{hyperref}  \def\fn#1#2{% \hyperpage{#2}n#1% }%  \newcommand{\is}[1]{\if@noftnote% \index{#1}% \else% \index{#1|fn{\thefootnote}}% \fi% }  \makeindex  \begin{document}  \footnote{First footnote.} \footnote{Second footnote.\is{inside second footnote}} \footnote{Third footnote.}  \printindex  \end{document}   This outputs inside second footnote, 1n3 instead of inside second footnote, 1n2. Hence, \thefootnote seems to be expanded at the very end, and not immediately in the footnote.  Any suggestions how to do it right with index?


What settings should I be using to shoot "Supermoon"?

This weekend is a "Supermoon" (the largest full moon of the year, in perigee, the closest to Earth). Would someone please advise how I could make the most out of my Canon PowerShot to photograph this phenomenon?    What settings should I use?    What times are the best with respect to the exact times of moonrise and moonset provided by the U.S. Naval Observatory? In other words, is it better 30 min before it crosses the horizon? Or just at the crossing? Are there any tips and tricks for a beginner to benefit from?  Are moonrises or moonsets generally better/easier to capture? Are there different techniques for different phases of the moon?   I read that full moon tends to come out flat, but I also want to benefit from the perigee.


Does Tesla's photoelectric "solar cell" really work?

Tesla patented a device for gathering energy from light, using the photoelectric effect. ():    Basically just a sheet of "highly polished or amalgamated" metal (top) connected to a capacitor (the ⊔⊓ shapes) connected to the Earth.  (The other stuff on the right of the image is a load intermittently driven when the charge on the capacitor rises high enough.)  The patent says it would be able to collect energy from the sun.  Would this actually work?  Why or why not?  Does it need to be in a vacuum?  The patent seems to say that it works better in a vacuum but that it is not required.  Would the plate stay charged after electrons are thrown off, or would they be attracted and drift back to it and neutralize it?  How does the capacitor to earth make this better than a plate hanging in space?  It allows more charge to be stored for the same work function voltage of the metal?  The patent demonstrates that he doesn't understand the cause of the photoelectric effect ("sources of such radiant energy throw off with great velocity minute particles of matter which are strongly electrified, and therefore capable of charging an electrical conductor"), but he understands the results.  (Incidentally, I have tried building this with a piece of aluminum foil, electrolytic cap, and wire strong enough to stick a few inches into the ground.  I didn't see any voltage with a multimeter in bright sunlight.)


How to get div height to auto-adjust to background size?

How do I get a div to automatically adjust to the size of the background I set for it without setting a specific height (or min-height) for it?


After I installed Ubuntu 12.04, there are no sound at all on my headphone (rear jack panel).  On Sound settings > playback, it seemed that the sounds were detected after I choose 'play sound'.  Anybody can fix this issue??  Thanks.