I reset my windows 10 laptop . I am trying to log in now with my old username n password but it doesn’t work   I have try to reset it again but now it say “this laptop has no administration account , log in first n than try it again”  But how can I log in when my username n password is not working.  I am not able to log in by either local account nor Microsoft account.  I am certain that I remember my password and log in I’d.  I am not able to run any command like windows +R .  My laptop can’t detect USB too.   So how would I log my laptop now.   Please do suggest .


I just installed QGIS 3.6. How can I update OpenLayers plugin? I tried to georeferenced Google Earth but I was not able to source Google OpenLayers plugins. I wish I can get a link to download.


Write to file - Recieving Null Pointer Exception

I'm receiving a null point exception when attempting to write to a file. The error is coming from the line below.  outputWriter.write(animals[p].toString());   Im assuming its because im passing null with the array. The array is previously created and is filled with objects with different values.  Here is my write file:  public void writeAquatic() {     try     {          BufferedWriter outputWriter;         String fileName = "Output.txt";         outputWriter = new BufferedWriter(new FileWriter(fileName));         for(int p = 0; p < animals.length; p++)         {             outputWriter.write(animals[p].toString());             outputWriter.newLine();         }         outputWriter.flush();         outputWriter.close();     }     catch(IOException ex)     {         System.out.println(ex.getMessage());     }     catch(NullPointerException e)     {         System.out.println("Null Pointer Exception");     } }


More numbers between $2$ and $4$ than between $2$ and $3$? (I am not a mathematician.)

Between $2$ and $3$ there are infinite numbers and between $2$ and $4$ there are infinite numbers.  So which "infinity" is greater?


Which package can easily write a graph, as an arbitrary curve or area, just for indication? The circle and ellipse don't be considered for their particular shape. TIKZ's Bézier curve is too non-intuitive to use.


How many MB/sec can I expect copying to USB 3.0 enclosure with SATA drive?

I have a new laptop with USB 3.0 ports, and a new SATA 5200 rpm hard drive I just put into a new USB 3.0 enclosure.  I am copying my backups from the local hard drive to the new USB 3.0 hard drive/enclosure.  It has settled at 26.1 MB/sec.    Is that the speed I should expect, or might something be wrong?  Thanks.


Minecraft Agrarian skies server spawn to death

I've been trying to find a solution to the problem I'm having, which is that I spawn in the middle of nowhere and die right away in Agrarian skies. I can't find any sollution for multiplayer, only for singleplayer.   Is there anything I can change in my server to spawn on the actual island? Ive tried switching to creative mode and writing /jspawn, but that does nothing. I've also tried downloading the map and putting it in the saves folder, but that prob only works for singleplayer.   Anyone that has done this and knows what I need to do? please


Why are meta communities restricted by reputation per community?

I have enough reputation to open a meta question in one community, but I don't have enough reputation to open a meta question in a different community.   I thought the point of requiring some reputation was to filter out spammers, wouldn't some reputation in any community show that a user isn't a spammer?


Why is cancelling differentials not okay?

I know this has been covered before in , but I still don't fully understand why cancelling differentials —not just inside an integral, but in general— is not considered okay or valid among mathematicians.  I'm currently studying physics at college, and my teachers —those who are physicists and not mathematicians, at least— do it all the time without it causing any trouble. In fact, the first (and less rigorous) method we were taught for solving differential equations relies heavily on treating differentials like numbers and derivatives like fractions. I don't know if it has a proper name, but I mean something like:  $$ \frac{\text{d}I}{\text{d}t}\cos(\omega t) = I\omega \sin(\omega t)  \implies  \frac{\text{d}I}{I}=\omega \tan(\omega t)\space\text{d}t $$  Now, I know that differentials aren't 'really' numbers. I mean, they can be understood both as the "linear part" of a variation or as a linear form, and the former looks like it should be okay to treat them like numbers.  Even the chain rule and the derivative of inverse functions seem to tell us that treating them like so should be consistent, when you write them using Leibniz's notation.  Is there really a situation where treating differentials like numerators and denominators causes any trouble?


If: $X:(\Omega,A) \to (E,\xi)$ is a random variable $Y: (\Omega,\sigma(X)) \to (R,B_R)$ is measurable Then $\exists \rho: (E,\xi) \to (R,B_R)$ measurable so that $\forall w$ $Y(w) = \rho(X(w))$


Is it possible to double your proficiency bonus twice?

Let's say I'm a multiclass rogue/ranger and I have taken Expertise in survival checks. Now, if a ranger is in their favored terrain it says they double their proficiency bonus in intelligence and wisdom checks relating to you environment. If I am in my favored terrain and use my already doubled survival check, will it double again?


What's the deal with a leading underscore in PHP class methods?

While looking over various PHP libraries I've noticed that a lot of people choose to prefix some class methods with a single underscore, such as  public function _foo()   ...instead of...  public function foo()   I realize that ultimately this comes down to personal preference, but I was wondering if anyone had some insight into where this habit comes from.  My thought is that it's probably being carried over from PHP 4, before class methods could be marked as protected or private, as a way of implying "do not call this method from outside the class".  However, it also occurred to me that maybe it originates somewhere (a language) I'm not familiar with or that there may be good reasoning behind it that I would benefit from knowing.  Any thoughts, insights and/or opinions would be appreciated.


Determine the convergence of $ \sum_{n=1}^{\infty}\left[1-\cos\left(1 \over n\right)\right] $

I'm having trouble determining the convergence of the series:  $$ \sum_{n=1}^{\infty}\left[1-\cos\left(1 \over n\right)\right]. $$  I have tried the root test:  $$\lim_{n\rightarrow\infty}\sqrt[n]{1-\cos\frac{1}{n}}=\lim_{n\rightarrow\infty}\left(1-\cos\frac{1}{n}\right)^{1/n}=\lim_{n\rightarrow\infty}\mathrm{e}^{\frac{\log(1-\cos\frac{1}{n})}{n}}=\mathrm{e}^{\lim_{n\rightarrow\infty}\frac{\log(1-\cos\frac{1}{n})}{n}}$$  Now by applying the , that upper limit is equal to:  \begin{align} \lim_{n\rightarrow\infty}\frac{\log(1-\cos\frac{1}{n+1})-\log(1-\cos\frac{1}{n})}{(n+1)-n}&=\lim_{n\rightarrow\infty}\left(\log(1-\cos\frac{1}{n+1})-\log(1-\cos\frac{1}{n})\right) \\&=\lim_{n\rightarrow\infty}\log{\frac{1-\cos{\frac{1}{n+1}}}{1-\cos{\frac{1}{n}}}} \end{align}  Now I'm totally stuck, unless that quotient is actually 1, in which case the limit would be 0, the Root test result would be $\mathrm{e}^0=1$ and all this would have been to no avail.  I'm not sure this method was the best idea, the series sure seems way simpler than that, so probably another method is more appropriate?


Publishing with a master's degree and no academic affiliation?

Currently I am finishing a master's degree in linguistics. I was accepted for a Ph.D at my university, but I decided not to do it in the end. I love my research and my field, but I don't see myself as a professor and I'm not sure a purely academic career is for me. Furthermore, my husband and I would suffer from the 'two body problem' if I got my Ph.D since he already graduated from his Ph.D program, and that is a situation I want to avoid. I am considering doing a clinical master's in SLP to apply my background in linguistics and biology in a clinical rather than purely academic setting. For the time being I will be taking a year off, but I am wondering about the idea of 'independent researchers'. If I continued with my research (which I can do from my computer using open access corpora and other corpora I have access to) could I publish/present my findings? If I became an SLP could I continue to publish even though I wouldn't have a Ph.D? Thank you in advance.


I'm already half a year into planning a Turn Based Strategy (4X) game for mobile phones. Recently I tried to play Civilization 6 and while playing, totally horrified, I realized that my idea and Civ 6 are very, very similar. So what should I do? Do you recommend that I should change elements that are too similar, or create game I planned, not looking at similarities to Civ 6? Could there be any legal consequences due to similarity of those two games?


Where do I ask opinion based questions on Stack Exchange? Why can't we have a stack-exchange that works like Quora? There has been a lot of research based on people's opinion. I think it is really not bad to have a SE on Opinions.  If there is already one please let me know  P.S This question is different from  ,  and  please don't mark as duplicate by linking to those questions!!  P.S.S : My question is completely different that . The question sounds same but the description and the answers are totally different. I have anyway received a reasonbly good answer. So it doesn't matter


I am connected to a machine via SSH and I often need to listen to WAV files on that machine. I usually open another terminal window and do ssh host 'cat /path/to/sound.wav' | aplay, but that's tedious since I have to enter my password every time (I cannot use public-key authentication) and the file paths are long.  What I would like to do is start magic-command on my local computer, and then whenever I need to listen to a remote file, run play-locally sound.wav from the remote shell and hear the sound from my speakers. Is this possible?


On Linux, (which I am used to), /home is the place where home folders live.  On a Mac, home is some kind of crazy mutant:  $ mount /dev/disk1 on / (hfs, local, journaled) devfs on /dev (devfs, local, nobrowse) map -hosts on /net (autofs, nosuid, automounted, nobrowse) map auto_home on /home (autofs, automounted, nobrowse)   Other than to be non-conformist, is there some purpose to this auto_home mount point?  Considering how it mucks up things that come right out of the box, there must be some wonderful thing that it accomplishes, but I can't figure out what that would be.....


Is Pauli-repulsion a "force" that is completely separate from the 4 fundamental forces?

You can have two electrons that experience each other's force by the exchange of photons (i.e. the electromagnetic force). Yet if you compress them really strongly, the electromagnetic interaction will no longer be the main force pushing them apart to balance the force that pushes them towards each other. Instead, you get a a repulsive force as a consequence of the Pauli exclusion principle. As I have read so far, this seems like a "force" that is completely separate from the other well known forces like the strong, electroweak and gravitational interaction (even though the graviton hasn't been observed so far).   So my question is: is Pauli-repulsion a phenomenon that has also not yet been explained in terms of any of the three other forces that we know of?  Note: does this apply to degenerate pressure too (which was explained to me as $\Delta p$ increasing because $\Delta x$ became smaller because the particles are confined to a smaller space (Heisenberg u.p.), as is what happens when stars collapse)?


Unzipping geoprocessing package (GPK) file?

I was under the impression that all ArcGIS package files could have their contents examined and potentially used by renaming them to *.zip and unzipping them.  This impression is supported for map package (*.mpk) files by  to  and I thought I had used it succesfully on geoprocessing package (*.gpk) files in the past.  However, today I am unable to use a  which I think is because it was created using ArcGIS Desktop 10.5.x when I am using 10.2.1.01. When I rename this *.gpk as *.zip and try to examine it in Windows Explorer I get:     Compressed (zipped) Folders Error      Windows cannot open the folder      The Compressed (zipped) Folder ....zip is invalid.     Is it possible to unzip a geoprocessing package (*.gpk) file to see whether it may contain some useful ArcPy code when that *.gpk cannot be unpacked to provide a usable toolbox?


How to repeat a "block" in a django template

I want to use the same {% block %} twice in the same django template. I want this block to appear more than once in my base template:  # base.html <html>     <head>         <title>{% block title %}My Cool Website{% endblock %}</title>     </head>     <body>         <h1>{% block title %}My Cool Website{% endblock %}</h1>     </body> </html>   And then extend it:  # blog.html {% extends 'base.html' %} {% block title %}My Blog{% endblock %}  # pictures.html {% extends 'base.html' %} {% block title %}My Pictures{% endblock %}  # cats.html {% extends 'base.html' %} {% block title %}My Cats{% endblock %}   I will get an exception, as Django wants the block to appear only once:     TemplateSyntaxError at /      'block' tag with name 'title' appears   more than once   A quick and dirty solution would be duplicating the block title into title1 and title2:  # blog.html {% extends 'base.html' %} {% block title1 %}My Blog{% endblock %} {% block title2 %}My Blog{% endblock %}   But this is a violation of the  principle. It would be very difficult as I have a lot of inheriting templates, and also because I don't wanna go to hell ;-)  Is there any trick or work-around to this problem? How can I repeat the same block in my template, without duplicating all the code?


When a sentence includes a word like 'today' that indicates present time, can a past form of verb be used?

Today an excruciating accident has taken place in our vicinity. Today an excruciating accident took place in our vicinity.   Today indicates the present time. So I prefer has taken, which has been used in first sentence. But a native speaker of English said that he would prefer took place, though he didn't tell me why he would do this.  Now I ask to the members of this site what do they think about this?


Prove that for any $m > 0$, $\gcd(mb,mc) = m\gcd(b,c)$.

Property of GCD     For any $m > 0$ , $\gcd(mb,mc) = m\gcd(b,c)$.   Please prove this. I am learning the Theory Of Numbers in Detail but I am not able to find the proof for this. It is not available in the internet also. So please help me with this problem. Please prove this without using the Euclidean Algorithm as it is deriver from this.


Changing NVIDIA Drivers makes Ubuntu freeze on startup

I recently followed  by TensorFlow/Google on how to install all needed drivers/libraries in order to use Tensorflow with my GPU. That is a NVIDIA 1080Ti running on Ubuntu 18.04. In before, I was using the proprietary 430 (I think) driver, that gets automatically managed by Ubuntu.  After executing the following commands:  # Add NVIDIA package repositories wget     https://developer.download.nvidia.com/compute/cuda/repos/ubuntu1804/x86_64/cuda-repo-ubuntu1804_10.0.130-1_amd64.deb sudo dpkg -i cuda-repo-ubuntu1804_10.0.130-1_amd64.deb sudo apt-key adv --fetch-keys     https://developer.download.nvidia.com/compute/cuda/repos/ubuntu1804/x86_64/7fa2af80.pub sudo apt-get update wget http://developer.download.nvidia.com/compute/machine-learning/repos/ubuntu1804/x86_64/nvidia-machine-learning-repo-ubuntu1804_1.0.0-1_amd64.deb sudo apt install ./nvidia-machine-learning-repo-ubuntu1804_1.0.0-1_amd64.deb sudo apt-get update  # Install NVIDIA driver sudo apt-get install --no-install-recommends nvidia-driver-410 # Reboot. Check that GPUs are visible using the command: nvidia-smi   and rebooting, I am faced with the following situation: Ubuntu always freezes on Startup, with no mouse movement/keyboard presses being accepted. Although my auto-login works (and the time in the top bar gets synchronised correctly), I am not able to do anything thereafter.  What I tried:     I was able to get into recovery mode with networking. There, I installed the nvidia-driver-430 package and auto-removed all older NVIDIA drivers. However, I am still faced with the exact same problem. Adding nomodeset into the kernel options does not resolve the problem either (Ubuntu still freezes on startup).   My question: How can I stop Ubuntu from freezing?  Edit: This is not a duplicate of  or  because    nomodeset didn‘t work I thus had to operate in recovery mode Ctrl+Alt+F1 didn‘t work


When does order of partial derivatives matter?

I've taken multivariate calculus and am wondering if I can see a specific function where the order of taking the partial derivative matters. I've been told that there are some exceptions where $ \dfrac{\partial ^2 f}{\partial x \partial y} \ne \dfrac{\partial ^2 f}{\partial y \partial x} $, so I'm curious to see what this looks like.  EDIT: And why would this true?


Using wilcox.test() and t.test() in R yielding different p-values

This is a repost from the R forum, as I was told to post here instead.  I would like to test whether there's a significant difference in the mean between this two samples:  withincollaraccuracyknn<-c(0.960, 0.993,0.975,0.967,0.968,0.948) withincollaraccuracytree<-c(0.953,0.947,0.897,0.943,0.933,0.879)   The data is normally distributed as you can see after running a Shapiro-Wilk test:  > sh<-c(0.960,0.993,0.975,0.967,0.968,0.948,0.953,0.947,0.897,0.943,0.933,0.879) > shapiro.test(sh)      Shapiro-Wilk normality test  data:  sh W = 0.91711, p-value = 0.2628   However, using t.test() or wilcox.test() yield different p-values:  > t.test(withincollaraccuracyknn,withincollaraccuracytree)      Welch Two Sample t-test  data:  withincollaraccuracyknn and withincollaraccuracytree t = 3.1336, df = 7.3505, p-value = 0.01552 alternative hypothesis: true difference in means is not equal to 0 95 percent confidence interval:  0.01090532 0.07542802 sample estimates: mean of x mean of y  0.9685000 0.9253333   > wilcox.test(withincollaraccuracyknn,withincollaraccuracytree)      Wilcoxon rank sum test  data:  withincollaraccuracyknn and withincollaraccuracytree W = 35, p-value = 0.004329 alternative hypothesis: true location shift is not equal to 0   Could somebody please let me know why? On the Wikipedia page of Mann-Whitney U test, it is stated: "It is nearly as efficient as the t-test on normal distributions".  Note also a Warning when the data is not normally distributed:  > withincollarprecisionknn<-c(0.985,0.995,0.962,1,0.982,0.990) > withincollarprecisiontree<-c(1,0.889,0.96,0.953,0.926,0.833) >  > sh<-c(0.985,0.995,0.962,1,0.982,0.990,1,0.889,0.96,0.953,0.926,0.833) >  > shapiro.test(sh)      Shapiro-Wilk normality test  data:  sh W = 0.82062, p-value = 0.01623  >  >  > wilcox.test(withincollarprecisionknn,withincollarprecisiontree)      Wilcoxon rank sum test with continuity correction  data:  withincollarprecisionknn and withincollarprecisiontree W = 30.5, p-value = 0.05424 alternative hypothesis: true location shift is not equal to 0  Warning message: In wilcox.test.default(withincollarprecisionknn, withincollarprecisiontree) :   cannot compute exact p-value with ties   Any help is appreciated. Note that I need to run similar analyses for other datasets having not normally distributed data, so using wilcox.test() instead of t.test() would be an advantage!


80s sci fi film with quest to replace lost female droid companion

I vaguely remember watching a science fiction movie with my mother sometime in the 80s (I was born in 84, so I'd be quite young at the time)... The movie was from the 80s, and this is what I remember about it:  The main character has a female "companion" droid that looks just like a human female.  Something happens to her, and he wants to "fix" her, but there is only one place he might find an identical model, which is somewhere in a desert?  Her "mind" (hard-drive/emotions/memories) is stored on some kind of removable media, I want to say it was like a CD, but I'm not sure. It was located somewhere around the back of her head, maybe under the hair?  I seem to remember the droids being stored in clear-vinyl body-bags inside a pyramid-type structure in the desert?  I want to say the film had a lot of visuals and themes reminiscent of blade runner, flying cars and such.


I am studying masters in the UK and living with my 2 children and husband for only since this September, 2018. In my home country we lived with my mom as well and now she lives in our house with my brother and his family. As my mom has lived with us for the last 4 years i wanted to invite to visit us more often until our visas are expired, Jan, 2020.   She applied for 2 year visa, 3 months for the first visit, 1.5 months for the second during school break and 2 weeks for my graduation ceremony. But her visa has been rejected based on UK visa immigration rule of V 4.2 a, c and e. Pls see  the full refusal letter. Basically she was rejected because she doesn't have her own source of fund although we provided the evidence of her monthly pension which is very small (200$) and i will fund her. She lived in another city before moving to our house and she had a property which she has a copy of certificate but very old from 2013. She didn't include it as it is now on my cousin's name and she doesn't live at that address.   This large deposit made is because i sold my car to support her application which is additional fund to my family expense in the UK. I am a full Scholarship holder for myself only from the UK government and provided evidence of my fund as some portion of savings, the income from selling our garage, for my husband and children's visa.   My mom now lives in our house with my brother and his family during our absence. He supports her in addition to her monthly pension. He has has also 2 children and wife who is not working. So i didn't include anything about themselves. My mom will definitely go back to the country but i don't know how to demonstrate that strongly.  Should i now try again but for 6 month visa for 2 months as 3 months seems to be long for a visit. My mom looked after my children most of the time as me and my husband are busy with work so they are very close. I would like my mom to visit my family and spend time with my children as they miss her.   Please advise how i should demonstrate strong evidence against the refused grounds and any solicitor who is affordable please recommend.   Thanks


It is said that iron deficiency anemia is characterised by microcytic-hypochromic RBCs. I would like to ask how iron deficiency causes decrease in the volume of RBCs? If the volume is decreasing because of low hemoglobin, then why  does the concentration of hb too decreases causing hypochromic RBCs? Why don't they decrease in same pace?


why maximize likelihood, rather than maximizing the inverse of the likelihood?

Let $X$ be a vector of sample data, and $W$ is a vector of parameters of a model based on that data, and we want to estimate a vector $W^*$ that is, informally speaking, "as close to $W$ as possible".  Then shouldn't we maximize $P(W^*|X)$? that is, we should choose the parameter estimates W* such that the probability that they are the actual parameters, is maximized.  Why then, in maximum likelihood, do we want to maximize $P(X|W^*)$ instead? I don't see the (intuitive) justification behind it.  (On a more general note, I also don't see why $P(X|W^*)$ is called "likelihood of $W^*$, given $X$", since "likelihood" and "probability" seem to me to be synonymous in the original meanings of the words).


PDF-format causes figure to be moved to end of chapter

I have tried the following code with various alterations to the positioning index: \begin{figure}[!ht] \includegraphics[width=5cm,trim={0 0cm 0 0cm},clip]{Img/CustomerDevelopment.pdf} \centering \caption{The figure shows an example of how a customer changes the policies affiliated with the company and how that changes his segment over his first 3 years.} \label{fig:CustomerDevelopment} \end{figure}  However, whatever I do my figure will always go to the end of the chapter and I would like them to stay near the text. If I open the PDF-document in Adobe Reader and save it as a .png that I then import in LaTeX it works perfectly. I would like the PDF-format though seeing as I want to be able to zoom in on the figures. Does anyone know how to solve this so I can use .pdf? I've included an image below using the \fbox{ command to illustrate the issue.


Why the centre of Newton's rings is dark?

Why the centre of  is dark? At the point of contact there is absolutely no air film between lens and glass sheet. then how can light reflected from this point produce destructive interference?


I have these buttons like so:  <input type="button" id="deleteButton" name="deleteButton" class="btn btn-default deleteButton" value="Delete">   I say these because there are multiples (about 30 of them)  and I have this bind event:  $(".deleteButton").bind("click", function () {          var id = $(this).parent().parent().find('input[name=ID]').val();          $.ajax({             url: "/DepositLog/DeleteItem",             type: "POST",             data: { ID: id, Usr: $("#Usr").val() },             success: function (data) {                  MVCGrid.reloadGrid('DepositLogGrid');               }         });      });   And it only works the first time I use it, after that it does not work at all, I have tried using the id as the selector, I have also tried an on event and that also did not work $(".deleteButton").on("click", function () {  What am I doing wrong?


Limit of $\lim\limits_{n\to\infty} (1 + \frac{x_n}{n})^n$

Many websites and calculus books give this well known result \begin{equation} \lim\limits_{n\to\infty} \left(1 + \frac{x}{n}\right)^n = e^x \end{equation} However, a textbook I was reading casually mentioned that if $x_n \rightarrow x$ then  \begin{equation} \lim\limits_{n\to\infty} \left(1 + \frac{x_n}{n}\right)^n = e^x \end{equation} Why is this true? It seems very intuitive but I feel some explanation is missing. Thank you!


Setting workspace as Python script tool variable/parameter in ArcPy?

I'm trying to write a script and as I want to automate it as much as possible.  Is it possible to set the workspace as a variable so that when it is run as a standalone script, or as a tool in ArcToolbox, that it will allow everything else to run?  Below, for example, I want the user to select a workspace and then for the script to pick up the shapefiles from this workspace and also create the new geodatabase there.   # Create file Geodatabase # Import ArcGIS modules import arcpy print arcpy.ProductInfo() # Check out the ArcGIS Spatial Analyst Extension arcpy.CheckOutExtension("spatial") # Need to be able to OverWrite Outputs arcpy.env.overwriteOutput = True # Set workspace arcpy.env.workspace = "C:/Prog_Data" # Set up variables out_folder_path = "C:/Prog_Data" out_name = "Prog.gdb" # Execute CreateFileGDB arcpy.CreateFileGDB_management(out_folder_path, out_name) # Set local variables before importing shapefiles to Geodatabase inFeatures =  ["Points.shp", "Extent.shp", "Rivers.shp", "Population.shp"] outLocation = "Prog.gdb" # Execute shapefile to Geodatabase arcpy.FeatureClassToGeodatabase_conversion(inFeatures, outLocation)


Book recommendations : Classical Mechanics

I know this question has been asked so many times on this website but neither do the questions nor the answers satisfy my requirements accordingly.  I'm yet to go to a university with a keen interest in Mathematics. So, no wonder I would like to see no-nonsene math (not heavy either) in a Physics textbook.  I started reading R. Shankar's Fundamentals of physics and I have started to understand the physical phenomenon. I love this book.  But I don't like the way he gets all the $\mathrm{d}t$'s cancelling $\mathrm{d}x$ from both sides.  So, here is my requirements:   An Introductory Physics Book having a good portion of Classical Mechanics The text should have fresh math. I would more than love to see a calculus-based approach.  Not more than 500 pages, please!


If r stands for counter-clockwise 90 degree rotation, s stands for horizontal flip. $D_4= \{1, r, r^2, r^3, s, rs, r^2s, r^3s\}$. What rule should I apply to find the subgroups of $D_4$? Should I just put elements with same order in the same subgroup?


What is that makes some objects transparent while some are opaque objects.?  While considering the atomic theory of matter every thing is made of atoms. Glass as well as wood.   I was recently studying the photon absorption and emission theory which somewhat explained different refractive indeces. At that time I thought about this.   For instance, take example of Carbon allotropes ; diamond and graphite - both made with carbon atoms  If bonding is considered : there are many solids analogous to diamond   Then what factors decide opaqueness, transparency and translucency of objects?


Faulty right alignment for comments in algorithmic package

I'm trying to right align comments in a pseudocode environment using the algorithmic package. So I renewed the algorithmiccomment command.   There's a different way to create comments for "normal" statements and for pre-defined statements such as "for", "if", etc.   The problem is, that the right alignment differs for the "normal" comments and the others. How can that be fixed, so that all comments nicely align?  Here's what I mean.    And this is the code to reproduce my example. Any help is greatly appreciated.  \documentclass[a4paper]{article} \usepackage{algorithmic} \renewcommand{\algorithmiccomment}[1]{\hfill \tiny//~#1\normalsize}  \begin{document} \begin{algorithmic} \FORALL[This comment is not quite right aligned]{ $a \in B$}     \STATE X  \COMMENT{This comment is further to the right} \ENDFOR \end{algorithmic} \end{document}


Find all element of order 5 in $Z^*_{36}$

I brute force the solution of order 5 in $Z^*_{36}$ by using the following $a^5 \equiv 1 \mod 36$ and I see that there is no solution for this. However, I don't quite know how to prove this. Can someone help me?


Editor invited after accept minor revisions required

I sent an article and it was accepted minor revision required. After resubmitting the paper the status appeared editor invited and has not changed in more than a week. The first time I submitted it, they just assigned an editor. What does this mean?


Linearly dependent sets of elements in finitely generated module over an integral domain

Let $R$ be an integral domain, $M$ an $R$-module and $\{m_1,\dots,m_n\}$ a set of generators for $M$. I want to show that any set of elements of $M$ with cardinality $n+1$ is linearly dependent.  My approach was as follows: After reordering we can always choose a non empty maximal linearly independent set $\{m_1,\dots,m_s\}$ for $1\leq s \leq n$ since otherwise $M$ would be torsion and the result holds trivially. Then we can consider the free module $F$ generated by this set and is easy to show that $M/F$ is torsion. Hence given any  $a_1,\dots,a_{n+1}$ in $M$ we can find non zero $x_1,\dots,x_{n+1}$ such that $x_1a_1,\dots,x_{n+1}a_{n+1}$ are in $F$. Then given that we know the result holds for free modules and given that $R$ is a domain we are done. Now to show this holds for free modules suppose for contradiction that there exists a linearly independent set of $n+1$ elements in $M=R^n$ then we get an injective map $R^{n+1}\rightarrow R^n$ which is impossible by the famous exercise 2.11 in AM. But exercise 2.11 does not assume the fact that $R$ is a domain so I was wondering whether there is a way around this that takes advantage of this further assumption.


Cycles and quick smoke: the fire doesn't show up rendered video

I'm trying to render an animation. It's a space launch vehicle that is moving up, and I've added a quick smoke effect with a square mesh attached to it at the bottom, but when I render it, the fire doesn't show up at all. I can only see the smoke. Are there any particular settings that I should change or add? I rendered it in blender cycles. I would really appreciate if someone out there knows why this is happening or if there are setting that need to be added, or modified.  Thank you, Mari


Draw a decorative line thin - thick - thin

Does anybody know how you can draw a line, that starts very thin and then gets thick to the middle and then thin again? I hope this is clear because I cannot produce a minimal example here.  I think this should be possible with tikz but any solution / suggestion would be welcome.  I would like to use it to separate the Author from the title on the titlepage.


How can I repair a buried 120v cable splice to make it meet code?

I have an electrical question. I have a cable feeding an outdoor yard light. It was cut, I spliced it, soldered it and wrapped it with tape. Is there a way to splice and bury it safely to code? If not, I'll need to dig a 30 foot trench to replace the whole length.  Was about 8 inches below ground, surfaced over the years and probably hit with the weed trimmer.   It is outdoor cable inside copper tubing. Years ago when I bought the wire I knew outdoor was gray. The box said outdoor but it is white like indoor wire.   It was spliced about 20 years ago but am fixing up house and like to hide the ugly splice.


Showing the minimal polynomial for an element in an extension field is the same as the minimal polynomial of a linear transformation.

This is problem 31b) from Dummit and Foote chapter 14.2. I am looking for a hint on how to attack the problem, since I have been thinking about it for a couple of hours but I don't even know where to start. The problem says:  Let $K$ be a finite extension of $F$ of degree $n$. Let $\alpha$ be an element of $K$. Prove that the minimal polynomial for $\alpha$ over $F$ is the same as the minimal polynomial for the linear transformation $T_{\alpha}$. In this problem, $T_{\alpha}$ is an $F$-linear transformation of $K$ that arises from $\alpha$ acting by left multiplication on $K$.  I appreciate any helpful suggestions on how to start attacking the problem or any possible hint. Thanks!


Restricting a user to a certain directory on SSH login

I am having trouble restricting a user to a fixed directory when they connect with SSH  I want the user restricted to /var/www/home  however I connected myself and they are free to move about the system  I set the home directory to /var/www/home so they go there upon login however this doesnt restrict them.  I have tried a few things from suggestions in Google but nothing so far seems to work / do what I want  For example I have changed the chmod of www to 755 and root owned but still no effect


Enable ReadyBoost on a second internal HDD?

I have two SATA HDDs in my desktop PC (one for daily activity, one for storage and backup). I can finely use ReadyBoost with pendrives, but I wonder, Is there a way I could use my underutilized second HDD to participate in the cacheing mechanism (same concept as having two CPU cores crunch things in parallel: have two HDDs fetch data in parallel)? Clearly speaking: I want to enable ReadyBoost on my separate D: drive.


I'm having a little trouble understanding how to orient a surface in $\mathbb{R}^3$ For example, how would I orient the ellipsoid given by:  $$x^2+y^2+z^2+xy+xz+yz=\frac12$$   for $(x,y,z) \in \mathbb{R}^3$ ?


Switching between multiple .tex files and single .tex file

I'm using LaTeX to draft a journal paper and I'm writing with TeXMaker. To make the navigation easier, I broke down the paper into several .tex files. The master .tex file looks like this:  \section{Introduction} \input{introduction.tex} \section{Method} \input{method.tex} ...   The journal to which I am submitting the draft (FYI I refer to Physical Review E) requires me to submit only one .tex file, meaning that I am not allowed to use \input. For the first submission I just manually copied and pasted all the contents of separate .tex files into the master .tex file. Since it's likely that there will be several revisions before the paper is accepted, I would like to keep the separate .tex files structure to make revision easier.   Therefore, my question is: Is there an automatic way (scripts, special program, etc.) to combine those separate .tex files into one single master .tex file? or better yet, a way to switch between having separate .tex files and having one single master .tex file?


After cutting down his limbs, should Obi-Wan have spared Vader of the horrible pain of a slow death in the lava as a tribute to an old friend?

This is not a duplicate of this: .  EDIT:   The question I mentioned answers why Obi-Wan didn't kill Vader to make sure he's no longer a threat?. The answer to that question is     Anakin was Obi-Wan's best friend, student and a war buddy who saved his life many times. NOT someone you would be terribly interested in offing.    After cutting down his limbs, clearly one of these two would eventually happen:  1) Vader somehow survives and continues to be a dangerous Sith Lord  2) Vader would die a slow, horribly painful death, basically getting burned alive.  In light of no. 2, wouldn't it make more sense for Obi-Wan to do a favour for his old friend and finish him off, thus sparing him of so much pain and horror that would have been his last moments if he had died on the lava?  Clearly one cannot say "it is not the Jedi way" as from that perspective it makes even more sense to kill him right away. And besides, it's not like Jedi should not kill the Sith they fight with.  How do we explain why Obi-Wan left his "best friend, student and war buddy" to die in great pain?


Opening Lightning Application with not enough security access level raises internal error with Gack Id -227057212

Opening Lightning Application which refers to SObject for which current running user doesn't have permission raises internal server error with Gack Id -227057212  Steps to reproduce:   Create custom object Custom_Object__c Create Apex Class   public class PILexCont { @AuraEnabled public static Custom_Object__c performBusinessLogic( ){     Custom_Object__c record = new Custom_Object__c();     insert record;     return record; } }  Create an App  <aura:application controller="PILexCont"> <aura:attribute name="record" type="Custom_Object__c"/> <button onclick="{!c.performLogic}">Perform business logic</button> </aura:application>  With Javascript Controller   ({ performLogic : function(component, event, helper) { var action = component.get( "c.performBusinessLogic" );  action.setCallback(this, function(response  ) {     var state = response.getState();     if (component.isValid() && state === "SUCCESS") { /* component.isValid() simply, checks if the component has been destroyed or not. (http://salesforce.stackexchange.com/questions/81998/what-does-the-lightning-component-method-component-isvalid-do) */         alert('component valid, state success');          var record = response.getReturnValue();         component.set("v.record", record );      } else {         alert('error?'  );     }   }); $A.enqueueAction(action); } })  Open an app by a user who doesn't have permission to Custom_Object__c      Obtain the error         An internal server error has occurred     Error ID: 1557802061-15979 (-227057212)


How to tell LaTeX what I write should stay as it is, and not as a mathematical expression

I'm trying to write my thesis on LaTeX and I don't have much experience with it. I try to put an information about some arrays I used as a table one like looks like this: column names:  FileName, Strain, Replicate   for this I use this code:  \begin{tabular}  US45102998_251897210500_S01_GE1_107_Sep09_1_3.txt & RAL765 & 1 \  \end{tabular}   what latex thinks it is: US45102998251897210573S01GE1107Sep0911.txt It creates this line where the numbers after underscore are subscripts of the former text. I used \textdollar{} and it didn't work for me . I used \verb{}, and it worked (it didn't turn the text into a mathematical expression), but now I see } sign right after the text and it doesn't break the line.  the full code is:  \begin{center}  \tablehead{Array Information}  \toprule  \tableheadline {File Name} & \tableheadline{Strain} & \tableheadline{Replicate} \ \midrule  \hline}  \tabletail{\multicolumn{4}{r} {Continued on next page...} \}  \tablecaption{Array information}  \xentrystretch{0}  \begin{tabular}{llll{5 cm}}  \label{xtab: arrayinformation}  And at the end it is:  \hline  \end{xtabular}  \end{center}   Any suggestions? Note: I'm not so familiar with LaTeX lingo.


Estout and dcolumn: Overriding decimal alignment

I'm using estout (esttab actually) to produce a table in Latex from Stata. I'm using the dcolumn package to align the decimal places in my table.   I want to override the alignment for a single row; to be specific the number of observations row. Is there a way of doing this? Or, equivalents, if there a way to prefix each element in a row with "\multicolumn{1}{c}{" and suffix with "}", which would override the dcolumn alignment?  Example:  \begin{table}[htbp]\centering \caption{My Table} \begin{tabular}{l*{3}{D{.}{.}{-1}}} \toprule                             &\multicolumn{1}{c}{Mean/s.d.}&\multicolumn{1}{c}{Mean/s.d.}&\multicolumn{1}{c}{Mean/s.d.}\\ \midrule Var A               &        8.68&        8.51&        8.92\\                     &        2.42&        2.51&        2.26\\ Var B               &        2.14&        1.98&        2.37\\                     &        1.33&        1.29&        1.35\\ \midrule Observations        &       38040&       22054&       15986\\ \bottomrule \end{tabular} \end{table}   Thanks!


How to get  element to align with element next to it?

I'm relatively new to CSS and I'm having a weird issue:    Why is my "Forgot Password" span floating higher than "Remember Me"?  Here's the React component DOM:

Welcome

Login

         <form onSubmit={login}>              Username:                 <input id="username" type="text" className="loginBox" ref = {node => user = node}/>                           Password:                 <input id="password" type="password" className="loginBox" ref = {node => pass = node}/>

                                      <input type="checkbox" id="rememberMe"/>                     Remember Me                                  Forgot Password?
             <input id="loginSubmit" type="submit" value="Sign In" />           </form>

   And my CSS:  body {   padding: 0;   font-family: sans-serif; }     #loginTitle {   margin: auto;   text-align: center; }     #loginTitle h1 {   color: #4971b2; }     #loginForm {   margin: auto;   width: 200px;   font-size: 10px; }     #loginSubmit {   width: 100%;   display: block;   background-color: #4971b2;   color: white; }     .loginBox {   width: 100%;   display: block; }     #forgotPass {   float: right; } #loginCheck {   float: left; }   How can I make the Forgot Password span align with the span next to it?


NullPointerException on returning NumberFormatException

This code snippet:  public class NumberFormatException extends IllegalArgumentException {  public NumberFormatException (String test) { super (test); }  static NumberFormatException forInputString(String test) {     return new NumberFormatException("Caused By: \"" + test + "\""); } }   throws NullPointerException:  java.lang.NullPointerException  at java.lang.NumberFormatException.forInputString(NumberFormatException.java)   I'm unable to ascertain what value of 'test' can be the root cause of a NullPointerException since in the concatenation, null is printed on the screen if the value of a String is null.


At the moment, when I open a terminal on my Mac, it automatically calls:  source ~/.bash_profile.  What bemuses me, however, is that my shell does not seem to inherit any of the content from ~/.bashrc or ~/.profile. But that might be typical.  I have a number of scripts to inherit using source or .; if I put those calls in ~/.bash_profile, it can take some time to load a new shell window, sometimes 3 or 4 seconds, and that gets old. I imagine that there is some way to source those scripts just once and have my ~/.bash_profile file inherit it somehow.  Note that calling source ~/.bashrc or source ~/.profile from my ~/.bash_profile is not what I want to do, and is also probably a bad idea. It's not what I want to do because it doesn't solve the problem of a slow load for each new shell.  I added some echo statements; every time I open a new bash terminal window, this is logged:  starting to load /etc/profile finished loading /etc/profile starting to load bash_profile finished loading bash_profile   that makes sense, but what is disheartening - do I really need to load these every time a new shell is opened? Why can't it do some fancy inheritance so that we don't have to reload everything every time?  I created a video demo'ing the problem.  I have 4 terminal applications I use regularly:  terminal.app                  # misbehaves iterm2                        # misbehaves webstorm terminal emulator    # misbehaves vscode terminal emulator      # behaves!   VSCode actually behaves in the way I would desire. I am guessing that it does this by loading ~/.bash_profile in a parent shell, and only doing that once, when vscode boots up. All of the terminal windows in the app, are then subshells of that one parent shell.  Hopefully this video makes the issue clear:   This is a legit issue - most terminal applications do this whole thing wrong, however, quite miraculously, it appears that VSCode from Microsoft actually does this whole thing the right way, see this issue:


I just harvested some scallions from the garden, where it's getting bit chilly (late November in Seattle).  After chopping them, I realized that their insides were covered in a gelatinous, slippery, viscous goo!  What is it? Is it safe to eat?


Considering shopping for PC parts for my personal rig in Hong Kong. I would like to know about Indian import taxes

I found out there is 36.05% (Basic Customs duty @ 35% + Education Cess @3%) on the value of dutiable goods that is in excess of the Duty Free Allowance of 50000 rupee, according to 2016 Indian baggage rules.  Are there any other applicable taxes on top of this?


SQL Server 2008 R2 backup fails to restore on SQL Server 2008 R2 SP2

My DR SQL Server got automatically updated by Windows update from 2008 R2 to 2008 R2 SP2 and since then I can't restore backups from my production machine which is still on 2008 R2.  10 percent processed. 20 percent processed. Msg 3183, Level 16, State 2, Line 1 RESTORE detected an error on page (0:0) in database "si7500_1" as read from the backup set. Msg 3013, Level 16, State 1, Line 1 RESTORE DATABASE is terminating abnormally.  I can restore backups that were made prior to the DR update but not ones made since even though the production machine that made the backup hasn't changed. This makes me think that this is something other than the actual DB engine version that is wrong as I'd have expected all old backups to fail in that case. I've tried removing the SP2 update but this makes no difference? Anyone has any ideas on what to do as I'm reluctant to update my live server without a working DR backup.


Find the general solution of $4u_{xx}+5u_{xy}+u_{yy}+u_x+u_y=2$

How do I solve the following second order partial differential equation?  $4u_{xx}+5u_{xy}+u_{yy}+u_x+u_y=2$  I have classified the equation to be hyperbolic and changed variables to obtain the canonical form as $u_{\epsilon\nu}={1\over{3u_\nu}}-{8\over9}$ which I believe is correct but I am struggling to find the general solution? A step by step solution would be appreciated.


How to statistically prove if a column has categorical data or not using Python

I have a data frame in python where I need to find all categorical variables. Checking the type of the column doesn't always work because int type can also be categorical.   So I seek help in finding the right hypothesis test method to identify if a column is categorical or not.   I was trying below chi-square test but I am not sure if this is good enough  import numpy as np data = np.random.randint(0,5,100) import scipy.stats as ss ss.chisquare(data)   Please advise.


'find exec' once with all found names as arguments

Short question is: how to call some command or a script once with all found names as arguments plus some extra arguments?  Long question is:  Why does this work (prints all file names 1 name per line):  find . -type f -exec sh -c "echo {}" \;   but this doesn't (prints nothing):  find . -type f -exec sh -c "echo {}" +   However, this works (prints all file names in a line):  find . -type f -exec echo {} +   but this fails with message find: missing argument to '-exec' :  find . -type f -exec echo {} more args +   However, this prints file names but not more args:  find . -type f -exec echo '{} more args' +   (prints ./file1.txt ./file2.txt while I expected ./file1.txt ./file2.txt more args)  I know there is a limit on how long the argument list can be, but I tested it with just a few file names so it shouldn't matter.


How is the spread devided between buyer, seller and market maker?

For a given stock, if:   a seller places a sell limit order at 100 dollars; a buyer places a buy limit order at 200 dollars;   At what price will the transaction be executed and who will pay/get how much?


How to implement Copy to ClipBoard (Trigger Windows Ctrl+C Event) functionality?

I need to implement a Copy to ClipBoard functionality in my screen   <!DOCTYPE html> <html> <head> <script src="http://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script> <script>  $(document).on("click", "#inputbtn", function () {  var text = $("#comment").val();          });  </script> </head> <body>  Enter Comment: <input type="text" id="comment"><br> </br>   <input type="button" id = "inputbtn" value="Copy It ClipBoard">  </body> </html>   Not having any idea how to continue further on this   I have seen this link     which isn't working in Chrome  Is this can be done without using any plugins   Thanks in advance .


When to properly use Present Progressive statements?

Can present progressive statements be use at present or for the future? or both?


Show if $R$ is Noetherian, then $R_S$ is Noetherian.  here is what I have read from somewhere else. Suppose $R$ is Noetherian and $J$ is an ideal $R_S$. Then $J=IR_S$ for some ideal $I$ of $R$. Since $R$ is Noetherian, $I$ is finitely generated, say $I=(r_1,r_2,…r_n)$  Thus $J=(r_1/1,r_2/1,…r_n/1)$. Hence every ideal in $R_S$ is finitely generated and so $R_S$ is Noetherian.  My confusion is how to get $J=(r_1/1,r_2/1,…r_n/1)$ from $I=(r_1,r_2,…r_n)$. And I also confuse about the notation of $r_1/1$, what are they, are they suppose just be like $r_1/1=r_1$ ? Thank you.


Get recursive file count (like `du`, but number of files instead of size)

Since I'm having performance problems with rsnapshot, I'd like to identify directories with great number of files recursively. I think the problem is not the size of the files, but the file count in particular subdirectories, because the generations (daily.0, daily.1, ...) are not volatile and only have few changes compared to the total number of files.  Unix command du would be exactly what I want, if it returned only the file count and not the sum of file sizes.  I already have a  of all direct subdirectories (recursing into subdirectories), but it's cumbersome to use, because I have to dig deeper and deeper and always have to wait.  Found also a , but not summing up file count of subdirectories. It shows only the number of files in this directory, not from its children.  Doesn't have to be a shell script - I'm open to other scripting languages like Ruby, Python, Perl, JavaScript, ...  Example:  dir1/    file1    subdir1/        file2, file3, file4, file5    subdir2/        file6, file7, file8        subdir3/            file9 dir2/     fileA, fileB   Desired output (listing subdirectories and sum up to top):  4   dir1/subdir1 1   dir1/subdir2/subdir3 4   dir1/subdir2 9   dir1/ 2   dir2/   What I don't want (only listing totals):  9   dir1/ 2   dir2/   and not (only listing file count of . directory):  4   dir1/subdir1 1   dir1/subdir2/subdir3 3   dir1/subdir2 1   dir1/ 2   dir2/


Is $(\Bbb{Q},+)$ isomorphic to $(\Bbb{Q}_{>0},\cdot)$?

I want to know if $(\Bbb{Q},+)\cong (\Bbb{Q}_{>0},\cdot)$, but have no idea where to begin my proof. Can anyone offer a hint?  Thanks!


Given $n$, how to construct $n$ points on a plane s.t. any 3 points are not on a line, and the distance between any 2 points is an integer?  Below is how to do it for $n=6$ here ABC is the 3,4,5 triangle.


When to use "among" instead of "between"

In the following sentence, shouldn't "among" be used instead of "between?"  It has been determined between all three departments that the science department is the most appropriate department to be in charge of this assignment.


Meet-in-the-middle attack (on custom encryption scheme)

This is a question I had from an exercise session.  Exercise: First we do DES in CBC encryption mode using a key $K_1$ and $IV_1 = O^n$. Then we do DES in ECB decryption mode using $K_1$. And then DES in CBC decryption mode with a secret $IV_2$ and key $K_2$.  My solution:  $IV_1$ = $C''_0$ = $O^n$  and $C'_0$ = $IV_2$  I think encryption would be something like this $C_i$ = $D_{K2}$($D_{K1}$($E_{K1}$($P_i$ $\oplus$ $C''_{i-1}$))) $\oplus$ $C'_{i-1}$ with $C'$ and $C''$ be the intermediate solutions (and $C''$ the first) of each encryption/decryption method.  For decryption I have this P = $D_{K1}$($E_{K1}$($E_{K2}$($C_i$ $\oplus$ $C'_{i-1}$)) $\oplus$ $P_{i-1}$)  The question: Is this construction safe against meet-in-the-middle attack?  Wouldn't the first two operations negate themselves because $C_1$ would decrypt into $P_1$?


Do not enumerate a section, but add it into table of contents

How do I rid of number of a section in the way that it still would be in the table of contents.  If I use   ... \section{SN1} ...   then I see this section name in table of contents as   1 SN1  2 SN2  3 SN3  ...   If I use   \section*{SN}   I don't see it in the content:   1 SN2  2 SN3   How to get in content just   SN1  1 SN2  2 SN3   ?


Prove that the point of intersection of the diagonals of the trapezium lies on the line passing through the mid-points of the parallel sides

Prove,by vector method,that the point of intersection of the diagonals of the trapezium lies on the line passing through the mid-points of the parallel sides.    My Attempt: Let the trapezium be $OABC$ and that the O is a origin and the position vectors of $A,B,C$ be $\vec{a},\vec{b},\vec{c}$.Then the equation of $OB$ diagonal is $\vec{r}=\vec{0}+\lambda \vec{b}................(1)$ And equation of $AC$ diagonal is $\vec{r}=\vec{a}+\mu(\vec{c}-\vec{a}).......(2)$ And the equation of the line joining the mid points of $OA$ i.e.$\frac{\vec{a}}{2}$ and $BC$ i.e. $\frac{\vec{b}+\vec{c}}{2}$ is $\vec{r}=\frac{\vec{a}}{2}+t(\frac{\vec{b}+\vec{c}}{2}-\frac{\vec{a}}{2}).........(3)$. Here $\lambda,\mu,t$ are scalars. I do not know how to solve $(1)$ and $(2)$ and put into $(3)$ to prove the desired result. Please help me.Thanks.


My UK visit visa application got refused due to low income. Can I reapply?

Reason for the refusal is inconsistent bank statement and they are not statisfied by my income, I had applied for 40 days visit visa.


Unique factorization domain and principal ideals

If R was a unique factorization domain, can we deduce that for a nonzero element d in R, d has a finite number of divisors?   I need this in solving this question  "If R is a unique factorization domain then there are only finite number of distinct principal ideals that contain the ideal (d)."  My idea to solve it: if a divides d then (d) is contained in (a), so if we have finite divisors then we have finite principal ideals. Am I wrong?


Trace and determinant of composition of a left-multiplication and a right-multiplication on a space of matrices

Determine the trace and determinant of the linear operator (on the space $\mathbb{F^{n\times n}}$) that sends the matrix $M\to AMB$ where $A$ and $B$ are $n\times n$ matricies


How do I convert from a possibly Windows 1252 'ANSI' encoded uploaded file to UTF8 in .NET?

I've got a FileUpload control in an ASP.NET web page which is used to upload a file, the contents of which (in a stream) are processed in the C# code behind and output on the page later, using HtmlEncode.   But, some of this output is becoming mangled, specifically the symbol '£' is output as the Unicode FFFD REPLACEMENT CHARACTER. I've tracked this down to the input file, which is Windows 1252 ('ANSI') encoded.   The question is,   How do I determine whether the file is encoded as 1252 or UTF8? It could be either, and How do I convert it to UTF8 if it is in Windows 1252, preserving the symbol £ etc?   I've looked online but cannot find a satisfactory answer.


So I am trying to load an ecommerce checkout but based on the number a user enters:  var finalAmount = convert_amount( $('#input').val() );   The convert amount is to return the amount * 100 like this:      function convert_amount( amount ) {         return ( amount * 100 );     }   Ok so here's the problem. For most numbers it works ok, but for some that I have tried it doesn't work correctly. If I enter something like 8.32 then it returns 832 which is perfect. I found that if I enter 8.72 then it returns 872.0000000000001. I don't get why it is adding the .0000000000001 onto the number.   Another interesting case is if I put in 8.70 it spits back 869.9999999999999.   It was recommended to me to try doing return ( new Number( amount ) * 100 ); but that still did not do the trick.   The reason this is a major problem is because it makes the ecommerce platform reject the amount, saying it is invalid.  Any idea or experiences with this are greatly appreciated.  Thanks!


Can anyone suggest me any algebraic topology books which are written in a lucid language than Allen Hatcher but in that same pattern?

Can anyone suggest me any algebraic topology books which are written in a lucid language than Allen Hatcher but in that same pattern. If someone of Mathstack member has written or they know some easy pdf notes on this topics please let me know. It will be of a great help.


Define $S\equiv\{ x\in \mathbb{Q}\mid x^2<2\}$. Show that $\sup S=\sqrt{2} $.     For this question, I think that I would use the completeness axiom. As $3$ is greater than $2$, so $S$ has a upper bound. To yield a contradiction, I think I need to find there exists an constant $c$ which is a least upper bound such that $b^2>2$, then there exists a number $r$ such that $b-r$ also in upper bound of $S$ which gives a contradiction since $b$ is the least upper bound of $S$. Then we can end the proof.    Does the idea right? If not, can anyone give a suggestion or a hit to write a better proof? Thanks.


Using Python, how to check if an object is linked from external blend file?

bpy.data.objects['my linked object'].library I found this code through a search and tried to check the linked object, but in 2.91, this code doesn't seem to print anything. Is there a new way to check if an object is linked from external blend file?


From a technical perspective, what exactly is RAW and how does it differ from JPG or bitmap images? I'm not asking about the pros/cons versus another format, but rather what constitutes RAW format, how is the data stored, how does it differ from JPG (other than lack of compression), and how is it different than bitmap?


Expandably change letter case and use inside \csname, without a package

I want to change the letter-case of a single character argument, and use that changed letter inside a \csname.  And I want to do it without an additional package.  For example, I want to pass a macro the letter {S}, and have it execute the macro \csname macros\endcsname, or pass it the letter {T}, and have it execute the macro \csname macrot\endcsname.    In my MWE, I show three approaches:   I didn't expect \lowercase to work, since I recall reading that it is not truly expanded until the last possible moment.  Surprisingly, it goes into an \edef okay, but it must not be truly expanded, because it breaks the \csname. I also formulated an approach where I used \numexpr to add 32 to the ASCII code of the argument and perform a \char upon that result.  Like \lowercase, it gives the appearance of being expandable, but it also fails inside the \csname. I finally achieve success with the stringstrings package.  Having written the package, I know the conversion was not pretty... essentially, it is an exhaustive 26-fold check of the form \if #1Aa\else\if #1Bb\else\if #1Cc\else...\fi\fi\fi, which has the virtue that it can be expandably placed into an \edef, and so it works.   There has to be a better way.  The MWE works only because I use the inefficiently calculated \tmp from METHOD 3 inside the \csname.  If I use \tmp from either of the two earlier methods, it breaks.  \documentclass{article} \usepackage{stringstrings} \def\macros{Expandably converted an S to a s} \def\macrot{Expandably converted a T to a t} \newcommand\convert[1]{%   %MAKE THE ARGUMENT LOWER CASE   1) LOWERCASE\\   \edef\tmp{\lowercase{#1}}% PRETENDS TO EXPAND, BUT FAILS IN \csname   Here is the ``expanded'' conversion: \tmp\\   % OR   2) ASCII CONVERSION\\   \edef\tmp{\expandafter\char\numexpr`#1+32\relax}% PRETENDS TO EXPAND, BUT FAILS IN \csname   Here is the ``expanded'' conversion: \tmp\\   % OR   3) STRINGSTRINGS PACKAGE\\   \caselower[q]{#1}\def\tmp{\thestring}% WORKS BUT USES A PACKAGE   Here is the ``expanded'' conversion: \tmp\\   %   Now use it in a csname: \csname macro\tmp\endcsname% } \begin{document} \convert{S}\par \convert{T} \end{document}       SUMMARY OF ANSWERS:  I have added egreg's code snippets into this MWE to produce a document (and not just terminal output), showing the methods put forth to this point:  \documentclass{article}  %%%%%%%%%%%%%%%%%%%%%%%%%%%% L3 APPROACH  \usepackage{expl3}  \ExplSyntaxOn \cs_set_eq:NN \Xexplower \tl_expandable_lowercase:n \ExplSyntaxOff  %%%%%%%%%%%%%%%%%%%%%%%%%%%% EGREG'S LESS HACKY SOLUTION  \def\explowerchar#1{%   \ifcase\numexpr`#1-`A\relax    a\or b\or c\or d\or e\or f\or g\or h\or i\or j\or k\or l\or m\or    n\or o\or p\or q\or r\or s\or t\or u\or v\or w\or x\or y\or z\else    #1\fi }  \def\explower#1{%   \doexplowerchar#1\relax }  \def\doexplowerchar#1{%   \ifx#1\relax   \else     \explowerchar{#1}\expandafter\doexplowerchar   \fi }  %%%%%%%%%%%%%%%%%%%%%%%%%%%% STEVE'S HACKY PACKAGE APPROACH  \usepackage{stringstrings}  %%%%%%%%%%%%%%%%%%%%%%%%%%%%  \def\macros{Expandably converted an S to a s} \def\macrot{Expandably converted a T to a t}  \begin{document}  \textbf{Steve's hacky approach}  \caselower[q]{S}\csname macro\thestring\endcsname\par \caselower[q]{T}\csname macro\thestring\endcsname  \textbf{egreg's less hacky approach}  \edef\lcstring{\explowerchar{S}}\csname macro\lcstring\endcsname\par \edef\lcstring{\explower{T}}\csname macro\lcstring\endcsname  \textbf{L3 approach}  \edef\lcstring{\Xexplower{S}}\csname macro\lcstring\endcsname\par \edef\lcstring{\Xexplower{T}}\csname macro\lcstring\endcsname  \end{document}


I am working on the following problems and I have a couple of questions.     Suppose $a_n>0, s_n = \sum_{i = 1}^{n}$ and $\Sigma a_n$ diverges.      RTP      (a)  $\Sigma \frac{a_n}{1+a_n}$ diverges.      (b) By showing $$\sum_{i=1}^{k} \left[ \frac{a_{N+i}}{s_{N+i}} \right] \ge 1 - \frac{s_N}{s_{N+k}}$$      prove that $\sum \frac{a_n}{s_n}$ diverges.      (c) By showing  $$\frac{a_n}{s_n^2} \le \frac{1}{s_{n-1}}-\frac{1}{s_n}$$      and deduce that $\sum \frac{a_n}{s_n^2}$ converges.      (d) What can be said about       $$\Sigma \frac{a_n}{n a_n +1} \text{ and } \Sigma \frac{a_n}{a+n^2a_n}$$   I understand (a).  But I am generally very iffy with proving these kind of problems because I usually get stuck with showing some inequalities being true.  1), How are the rest of the problem solved ?  2), Is there a general way to solve most of these inequalities ? Especially with those that have summations ?  3), Are these problem considered easy ? I am teaching myself analysis and it's such a struggle for me.


What is the best approach to capitalize words in a string?


It seems that a well-designed SMPS has a capacitor connecting the ground planes of the primary and secondary sides of the transformer, such as the C13 capacitor . What is the purpose of this capacitor?  I've let myself understand that it's for EMI suppression, but what kind of EMI does it suppress, and how? It seems to me to be the only leg of an open circuit and thus completely inert, but obviously I'm wrong about that.


How can I move a file from a linux computer to my mac laptop?

I have a file in my Linux work computer that I need on my personal Mac laptop and I wanted to know how I could get that to my mac computer. I can't email it to myself because it's a dmg file and it's too large via email. How can I send this file to myself using terminal commands? Also I have no administrative capabilities so I can't use sudo


Islands and similar where visitors cannot take a car

I love car-free islands and other locations where visitors cannot take a car, but that are still reachable by public transportation, inhabited or not.  Some examples, in no particular order:   Channel Islands National Park, California, USA Zermatt, Switzerland (not an island) Toronto Islands, Toronto, Canada Isles of Scilly, England Small Isles, Inner Hebrides, Scotland Vlieland, Netherlands Harstad peninsula near Harstad, Nordland, Norway Apparently, some island/s near Toulon, France   Is there any resource listing such car-free and nearly-car-free islands (and non-islands)?


How do I get rid of these edges? I've tried the Join Tool. I've tried to highlight them with the white and the black arrow and then Object>Path>Join.  At this point I don't know what to google for, since everytime I search for a solution only the same suggestions come up, which I've tried.  Thanks


Bash method for viewing beginning and end of file

On queue-based clusters the Queue of pending jobs is shown from a command, say showqueue.   The command returns, in columns, a list of reasonable data like names, etc, but the columns/data don't really matter for the question.  I like using the utility watch like watch showqueue at times (with an alias of alias watch="watch " to force alias expansion of my command to watch). There is valuable data (Running jobs), in the first few lines, then pending jobs, etc, and some valuable summaries at the end.   However, at times the output of showqueue goes off the screen (Unbelievable, I know)! Ideally, I'd like some way to be able to see the beginning and end of the file at the same time.   The best I have so far is: showqueue > file; head -n 20 file > file2; echo "..." >> file2 ; tail -n 20 file >> file2; cat file2, and using watch on an alias of that.   Does anyone know of anything a little more flexible or single-utility? My solution gets a little nastier with bash loops to make the "..." break multilined, it's not adaptive to resizing the terminal window at all, and I'm sure there's more that I missed.   Any suggestions?


Internal energy for a diatomic gas that undergoes an adiabatic process?

Why do we use $\Delta E_{int}=nC_{V}\Delta T$ when finding internal energy for a diatomic gas that undergoes an adiabatic process? Isn't this supposed to be used only when the volume is constant? And why is it do we choose to use this instead of $\Delta E_{int}=nC_{P}\Delta T$, even though neither is the volume nor the pressure is constant? I just don't fully understand why, and the textbook I am using doesn't really explain why.


Why can't I install apps when I have enough storage?

In "Settings" > "SD card & phone storage settings" under "Internal Phone Storage" it lists "Available Space" as 13.78MB.  I'm trying to install an app that is 2.38MB.  Why do I get the "Insufficient storage available" error message?  I clearly have enough space.  If it's relevant, my phone is an LG Optimus V.


How to adapt a Linux like fedora, ubuntu etc. to make my own linux distro?

I want to make my own Linux distro. Now what I want to change is, "its logo", "wallpapers", "Browser", and add some Backtrack tools to it, etc.   How can I do this?


Is there an IDE which can run on Ubuntu that supports C, C++ and Java? I installed , but it only supported Java. I installed the C/C++ package manually, but that package gives an error if I include iostream.   Is there any other IDE which can satisfy my needs? Or can I get NetBeans with all packages pre-installed in it?


Always on(SQL server 2016) is configured between four standalone servers Server1,Server2,Server3,Server4. These servers contains one availability Group(AG01) which contains 3 databases. How to apply SQL server patch for these servers? Do we need to apply patch for all servers at same day? These servers are production servers.


redirecting openshift rhcloud domain to custom domain for SEO purposes

Openshift application url: example.rhcloud.com  Custom domain: example.com  I came across this  and added the redirection rule. However, I can not access example.rhcloud.com now. My custom domain is www.example.com.  To avoid duplicate content problems, I tried this redirection.   Here is my .htaccess file:  RewriteEngine on   # Uncomment the following lines to force HTTPS #RewriteCond %{HTTP:X-Forwarded-Proto} !https  #RewriteRule .* https://%{HTTP_HOST}%{REQUEST_URI} [R,L]   # WordPress Defaults RewriteBase / RewriteRule ^index\.php$ - [L] RewriteCond %{REQUEST_FILENAME} !-f RewriteCond %{REQUEST_FILENAME} !-d RewriteRule . /index.php [L]  # Redirect Https traffic to Http RewriteEngine on  RewriteCond %{SERVER_PORT} ^443$ [OR] RewriteCond %{HTTPS} on RewriteRule  ^(.*)$ http://%{HTTP_HOST}%{REQUEST_URI} [R=301,L]   # Redirect non-www to www RewriteEngine on  RewriteCond %{HTTP_HOST} !^www\. [NC] RewriteRule ^(.*)$ http://www.%{HTTP_HOST}/$1 [R=301,L]    # Redirect openshift rhcloud domain to custom domain RewriteEngine on  RewriteCond %{HTTP_HOST} ^example.rhcloud.com$ RewriteRule (.*)$ http://www.example.com/$1 [R=301,L]   Why is example.com not redirecting to ww.example.com? How do I fix this?  Also, I see that since I have https to http redirection and non www to www redirection, my blog has been loading slow. How can I reduce it to lesser number of rules?  Edit:  In chrome:   In Firefox:     The page isn't redirecting properly, Firefox has detected that the server is redirecting the request for this address in a way that will never complete.     This problem can sometimes be caused by disabling or refusing to accept cookies.


Prove that there is no integer a for which $a^2 - 3a - 19$ is divisible by 289. Not got any clue. Please help.


Best way to center a  on a page vertically and horizontally?

Best way to center a <div> element on a page both vertically and horizontally?  I know that margin-left: auto; margin-right: auto; will center on the horizontal, but what is the best way to do it vertically, too?


Ok, I have a bunch of files starting with a dash, -. Which is not so good... and I want to rename them. In my particular case I would just like to put a character in front of them.  I found the following line that should work, but because of it dash it doesn't:  for file in -N*.ext; do mv $file x$file; done   If I put an echo in front of the mv I get a bunch of  mv -N1.ext x-f1.ext mv -N2.ext x-f2.ext   Which is correct, except of course it will think the first filename is options. So when I remove the echo and run it I just get a bunch of  mv: illegal option -- N   I have tried to change it to  for file in -N*.ext; do mv "$file" "x$file"; done   but the quotes are just ignored it seems. Tried to use single quotes, but then the variable wasn't expanded... What do I do here?  Update: I have now also tried to quote the quotes. Like this:  for file in -N*.ext; do mv '"'$file'"' '"'x$file'"'; done   And when I echo that, it looks correct, but when I actually run it I just get  mv: rename "-N1.ext" to "x-n1.ext":: No such file or directory   I have just no clue how to do this now... sigh


Add ;; to the top and bottom of each file in a list

I have a list of the locations of each text file that need this done inside add.txt  For example inside add.txt I have the following  /root/QuestDiary/MapQuest_Def/Mon_Umyounkijang.txt /root/Market_Def/06Inn_SamakwAr-5.txt   I need a script to open every text file in that list and add ;; to the top and bottom of each of them. It also must also open files/folders that have capitals, it's listed as /root/Market_Def/06Inn_SamakwAr-5.txt in the file but the actual file name is /root/Market_DEF/06Inn_SamakWar-5.txt  06Inn_SamakWar-5.txt currently looks like  %100 +40 +1  [@main] #IF checkpkpoint 2  #SAY #INCLUDE [..\Convert_Def\Market_Def\01Meet_BichonSung-10.txt] @Convert_01Meet_BichonSung-10_0   #ELSESAY #INCLUDE [..\Convert_Def\Market_Def\01Meet_BichonSung-10.txt] @Convert_01Meet_BichonSung-10_1  [@buy]  #SAY #INCLUDE [..\Convert_Def\Market_Def\01Meet_BichonSung-10.txt] @Convert_01Meet_BichonSung-10_2  [@sell]  #SAY #INCLUDE [..\Convert_Def\Market_Def\01Meet_BichonSung-10.txt] @Convert_01Meet_BichonSung-10_3  [Goods]  Jerk 1000 1  [@TalkToQuest] #CALL [NPCQuest_Def\02Weapon_BichonSung-10.txt] @NPCQuest_Check  [@everythingreward] #CALL [System\TotalRewardSystem.txt] @TotalRewardSystem   It should change to  ;; %100 +40 +1  [@main] #IF checkpkpoint 2  #SAY #INCLUDE [..\Convert_Def\Market_Def\01Meet_BichonSung-10.txt] @Convert_01Meet_BichonSung-10_0   #ELSESAY #INCLUDE [..\Convert_Def\Market_Def\01Meet_BichonSung-10.txt] @Convert_01Meet_BichonSung-10_1  [@buy]  #SAY #INCLUDE [..\Convert_Def\Market_Def\01Meet_BichonSung-10.txt] @Convert_01Meet_BichonSung-10_2  [@sell]  #SAY #INCLUDE [..\Convert_Def\Market_Def\01Meet_BichonSung-10.txt] @Convert_01Meet_BichonSung-10_3  [Goods]  Jerk 1000 1  [@TalkToQuest] #CALL [NPCQuest_Def\02Weapon_BichonSung-10.txt] @NPCQuest_Check  [@everythingreward] #CALL [System\TotalRewardSystem.txt] @TotalRewardSystem  ;;


How to create a foreign key to multiple tables?

I want to store a file structure similar to Google Drive. I can create files of several types (doc, spreadsheet, ..). Details of each file are stored in their table.  For example:  File [id, name, file_id] Doc [file_id, title, a, b, c] Spreadsheet [file_id, title, d, e]   How to do it right?


I am trying to define a custom CRS in QGIS 3.4 to work on some data in Central Asia. I want to use the Albers Equal Area Conic but change the parameters so that the transformation works best for my study area.   I first tried to go via "Settings" --> "Custom CRS". I defined the name and the +projstring as +proj=aea +lat_1=21 +lat_2=49 +lat_0=37 +lon_0=87 +x_0=0 +y_0=0 +datum=WGS84 +units=m +no_defs. But when I click "Ok", nothing happens.  I don't get an error message or any feedback, there's just no response. (I tried QGIS 3.10 as well, but the same problem occurred.) This looks like a bug to me or is there something I missed?  If this cannot be reproduced, I could also go the Python way, but I'm not so familiar with that. I've read through some documentation and found the following pieces of code but I'm not sure if they are in the right order or if something is missing:  my_crs = QgsCoordinateReferenceSystem() my_crs.createFromProj4("+proj=aea +lat_1=21 +lat_2=49 +lat_0=37 +lon_0=87 +x_0=0 +y_0=0 +datum=WGS84 +units=m +no_defs") my_crs.saveAsUserCrs("Albers_Central_Asia")


How to draw a line that tracks the path of an object on video

I am trying to find a solution to creating a follow flight path of a frisbee (but could be any object), similar to what is shown in this video ().  This video also shows how to do it in After Effects, but I want to do it on Blender. I've seen this done with lines () and I've seen it done with a particle emitter (). Does anyone know of instructions to do this in Blender 2.83?


I have working NFS (Networking File Sharing). It's server path will be mounted, but attempts to use umount are not working. It is getting some error.  $ sudo umount /nfs_server/     /nfs_server was not found in /proc/mounts     /nfs_server was not found in /proc/mounts   How can I solve this?


I am using mysql - 10.1.39-MariaDB - mariadb.org binary distribution - and phpmyadmin for managing my db:  I have the following table:  | ID  | NAME       | AMOUNT | CREATED_AT          | UPDATED_AT          | |-----|------------|--------|---------------------|---------------------| | 1   | Product 1  | 4      | 2019-08-30 19:03:16 | 2019-08-30 19:03:16 | | 5   | Product 1  | 3      | 2019-08-29 20:03:16 | 2019-08-29 20:03:16 | | 2   | Product 2  | 4      | 2019-08-30 19:03:16 | 2019-08-30 19:03:16 | | 3   | Product 33 | 3      | 2019-08-30 19:03:16 | 2019-08-30 19:03:16 | | 4   | Product 4  | 2      | 2019-08-30 19:03:16 | 2019-08-30 19:03:16 | | ... | ...        | ...    | ...                 | ...                 |   I would like to have all rows that have been updated last.  I tried the following:  SELECT     `name`, `updatedAt` FROM     issuers ORDER BY     updatedAt   However, I still get all rows in my result data.  Any suggestions what I am doing wrong?  I appreciate your replies!


Alignment issue in users page while searching user

There is an alignment issue occurred while searching the users in the .   The grid cells' height is increased while fetching the result. Once the result fetched, the grid's height become normal, so the issue is due to the searching indicator, when it is visible.  Screenshot for reference:        GIF for the same:


WIll a HTTPS page with video player & a video served off HTTP become insecure?

A page is on HTTPS and all content on it is served from HTTPS, however, this page contains a video player, and once user hits a PLAY button in it, it starts playing a video, that is served from HTTP.  2 questions:   Will this page show a broken padlock and get insecure? Will this page get SEO boost from Google (HTTPS factor)?


RecycleView click, showing message: Attempt to invoke virtual method 'Context.getPackageName()' on a null object reference

the wrong messsage is " Attempt to invoke virtual method 'java.lang.String android.content.Context.getPackageName()' on a null object reference". what I am trying to do is clicking one item on recycleView and jump to another page. the code is below:  public contactHolder(View itemView, Activity context) {     super(itemView);     this.context = context;      Fname = itemView.findViewById(R.id.getFname);     Lname = itemView.findViewById(R.id.getLname);     itemView.setOnClickListener(new View.OnClickListener() {         @Override         public void onClick(View v) {             startAnew(contactID);         }     });  } private void startAnew(String currentcontactID) {      Intent intent = new Intent(context, personActivity.class);     intent.putExtra(CONTACT_ID,currentcontactID);     context.startActivity(intent); }


What missions must be completed in the main game, to avoid having them spoiled in Dragon's Keep?

There's only a handful of big events or facts to be spoiled that I can think of in the main Borderlands 2 game. In no particular order:      - Angel is not an AI - she is a siren.  - Angel has been manipulating the Vault Hunters on Jack's behalf since the first game.  - Angel is Jack's daughter.  - You kill Angel.  - Jack kills Roland.  - Jack kills Bloodwing.   I'm aware there are some spoilers (particularly the last two items on the above list) in Tiny Tina's Assault on Dragon's Keep, but I haven't played all the way through to know what others there might be.  If the above list is all there is, then I believe a player only needs to complete up to the following point in the main game in order to be "spoiler safe" going into Dragon's Keep:      Where Angels Fear to Tread (Part 1)   Is this correct, or does Dragon's Keep have other significant spoilers from later on in the Story missions (or in some sidequests) that I haven't thought of? What are all the main game spoilers in Dragon's Keep, and what missions does a player need to complete in the main game to avoid them?  (Of course, please use spoiler notation where appropriate, by putting >! at the start of lines containing spoilers.)  Note: This question is not about preparation for DLCs in terms of game mechanics such as player leveling. I only want to know what part of the main story should be completed to avoid discontinuity and spoilers in this particular DLC.


Accessing variable assigned in a function

Here is a bare-bones example of my code: def function():   var_a = 1   var_b = 2   var_c = 3   return var_a, var_b, var_c  function()  (Apologies for wonky formatting). Basically, the function takes in no arguments and its single job is variable assignment. I need to be able to call on the function for quick assignment and then be able to use those variables in the rest of my code. The problem is that I can't get those variables out of the function. So if I use the above code and put a print(var_a) line after, then it will tell me that var_a is not defined. If I say values = function() , print (values) then I will get only the values printed in a list, but I won't be able to access them in the way I want.  Is there an easy way to fix this?


For every infinite cardinal $\kappa$, $\kappa^2 =\kappa$.

I can't seem to find a full proof that for every infinite cardinal $κ$, $k^2 = k$. Does anyone have one they could share?


The click-to-favorite button has unexpected behavior when using multiple tabs or the back button

Try the following steps:   Open this question in two different tabs. Favorite it in the first tab. Look at the icon in the second tab. It appears not to be favorited. Click the favorite icon in the second tab, causing the question to appear to be favorited.   The question now appears to be favorited in both tabs, but in fact is not. Your second click on the button unfavorited it.  Alternatively, another way to fall into the same trap:   Favorite this question. Follow any link on the page. Click the 'back' button in your browser. Look at the favorite icon. The question appears not to be favorited. Click the favorite icon again.   The question now appears to be favorited once more. However, it isn't. Again, your second click unfavorited it.  When hastily researching some issue, I frequently follow links and then click 'back', or follow loads of links and end up with multiple instances of the same question open in different tabs. As such, I've fallen into both of these traps a few times in reality.  The better behavior would be if clicking an unhighlighted favorites icon always caused the question to become favorited, regardless of whether it currently is or not, and clicking a highlighted one always caused it to become unfavorited. The icon's state becoming out of date doesn't bother me, but the fact that I can accidentally end up unfavoriting something I want favorited bothers me a little.  Any chance of a fix?


Find the cardinality of the set $A_p$ defined as the following :

For any prime number $p$, $A_p$=the set of integers $d\in \{1,2,3,\dots, n\}$ such that the power of $p$ in the prime factorization of $d$ is odd. Then  \begin{align*} A_p= & \lfloor\dfrac{n}{p}\rfloor-\lfloor\dfrac{n}{p^2}\rfloor+\lfloor\dfrac{n}{p^3}\rfloor-\lfloor\dfrac{n}{p^4}\rfloor+\dots \end{align*}      Any one can give me any idea how can I show this ?      Update:   I have gone through $1p,2p,3p,\dots, kp\leq n<(k+1)p\implies \lfloor \dfrac{n}{p}\rfloor=k$, but I can not understand after this step.


Change misleading tooltip for feature request questions

A downvote on a question generally means that the quality is low and should/can be improved.  However questions tagged  have a different meaning as per the      On posts tagged feature-request, voting indicates agreement or disagreement with the proposed change   That being said, when a question is downvoted the following tooltip is displayed (I guess only for low-rep users like myself)    I think the tooltip should be changed to something different that states clearly the difference between a feature request downvote and a "normal" one.  Also I believe the tooltips displayed when hovering the up/down arrows should be changed accordingly to something like I don't agree with this proposal / I support this proposal      There's was a similar proposal a couple of years ago () but it was about changing the tooltips on every question on meta and it has been rejected.  I instead propose to change the behavior only in questions tagged as , as this difference is clearly formalized in the site description.  The motivation behind this proposal is that being an experienced StackOverflow user but sort of a new user on Meta, not later than today I was very confused by the meaning of a downvote, until someone pointed me to the help center.


Slow Response from Journal: Should I withdraw a paper?

I submitted a paper to an Elsevier journal in August and the status has been "with editor" ever since. I was concerned that it had not been sent for review for 4 months and I sent inquiries twice without getting any response. I am wondering if I should just withdraw my paper?


My son is new to comuting by bicycle. He brought a brand new bike and after just one week was having problems with the brakes. He only rides approximately 6–8 miles a day. Halfords advised that his brakes need replacing. Is this right?


I have the B1B2 visa but can only stay for 90 days

I just got to the US, normally I use my ESTA but this time I asked and was granted the B1B2 visa. When I got to the airport in customs the officer was chatting with me, didn't stamp my passport. So I got home went to see my I 94 and says I can only stay the 90. What can I do to stay the 6 months? I do have the B1 B2 visa but it's like the officer didn't count it or saw it. What can I do


I'm looking at purchasing an ASUS Q504 laptop. I want to dual boot either W10 or Ubuntu Mate. The question is will new generation machines allow this? I recall installing mint on my wifes W8 laptop and needed to change to legacy boot. Is there any good way to tell which laptops will install, or is this just like a regular Dual boot install?   Mike -


Does $\sum_{j=1}^{\infty} {\frac{1}{j^k}}$ have a limit?

I was playing with the calculator recently and I noticed that we seem to have, as $k\to\infty,$ the limiting value of $$\sum_{j=1}^{\infty} {\frac{1}{j^k}}$$ to be $1.$  Is this in fact true? If so how can one see it? In particular, is there a proof for this somewhere?  Thanks.


Why does my object offset when setting its parent with Python?

By using  bpy.data.objects['object1'].parent = bpy.data.objects['object2']    to parent one object to another the parented object gets a weird offset. Why does this happen and how can i fix this?


"Do you know what IS IT?" vs "Do you know what IT IS?"

What is the right way to embed one question inside another?  For example:        "Do you know what is it?"    "Do you know what it is?"      Are they both grammatical? If one of them isn't, then why is it ungrammatical?  I can say the question "What is it?", so I assume I can also say the question "Do you know what is it?" Can't I?


Is there a difference between $y(x)$ and $f(x)$

Oftentimes functions described by $f(x) = 2x+4$, and when this is mapped to the Cartesian plane, $f(x) = y$. This surely implies that $y = 2x+4$. Is there a difference between this and $y(x) = 2x+4$?


Every irreducible Polynomial is primitive or irreducible constant

Let $R$ be an . Is it true that an irreducible polynomial $f \in R[T]$ is either:   primitive $f \in R$ and irreducible in $R$ ?


Does pgRouting support turn-by-turn routing?

I have route list as result of pgRouting with street names. How to get messages "Turn left", "Go along" etc ... Can pgRouting do this or I need some other source and which?


Vertically align text within a table of absolutely positioned divs

I've created a table, within which I've used some absolute positioning to ensure that the cells are always square.  I'm running into an issue when I try to vertically center the text within these divs.  I can't find a good method to accomplish this, within the structure I'm working.  CODE    table.module-table {  width: 100%;  border-collapse: collapse;  border: none;  text-align: center; } table.module-table tr { vertical-align: middle; } td.module {  border: 1px solid rgba(255,255,255,0);  padding: 0;  width: 33.33%;  position: relative;  vertical-align: middle; } td.module:after {  content: '';  display: block;  margin-top: 100%; } td.module .module-number {  position: absolute;  top: 0;  bottom: 0;  left: 0;  right: 0;  background: #ccc;  transition: .5s all; } td.module a {  display: block;  color: #fff;  line-height: 1;  font-size: 55px;  font-weight: bold;  text-decoration: none;  white-space: nowrap; } td.module .module-number.one-one:hover { background: #e11b22; } td.module .module-number.one-two:hover { background: #c81b74; } td.module .module-number.one-three:hover { background: #800052; } td.module .module-number.one-four:hover { background: #46026b; } td.module .module-number.one-five:hover { background: #7f4e99; } td.module .module-number.one-six:hover { background: #2a2a86; } td.module .module-number.one-seven:hover { background: #105bac; } td.module .module-number.one-eight:hover { background: #00605d; } td.module .module-number.one-nine:hover { background: #809027; }

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Why is the reconstruction error for my training set larger than my test error using PCA on the MNIST data set?

I have a very strange behavior where I am trying to run PCA on the MNIST data set and then I check the test and train error. However, it seems that I get that the test error is lower than my train error, which seems totally bizarre for me. Is this normal? Has people ever experienced this type of behavior on the MNIST data set?  To make my bug totally reproducible I will give a link to  (i.e. the exact data set I used is there, and its small). Also, the code I ran is super simple:  clear;clc; load('data_MNIST_original_minist_60k_10k_split_train_test'); [N_train, D] = size(X_train) % (N_train x D) [N_test, D] = size(X_test) % (N_test x D) %% preparing model K = 10; [coeff, ~, ~, ~, ~, mu] = pca(X_train); % (D x R) = Rows of X_train correspond to observations and columns to variables.  %% Learn PCA X_train = X_train'; % (D x N) = (N_train x D)' X_test = X_test'; % (D x N) = (N_test x D)' U = coeff(:,1:K); % (D x K) = K pca's of dimension D X_tilde_train = (U * U' * X_train); % (D x N_train)= (D x N)' = ( (D x K) x (K x D) x (D x N) )' X_tilde_test = (U * U' * X_test); % (D x N_test)= (D x N)' = ( (D x K) x (K x D) x (D x N) )' train_error_PCA = (1/N_train)*norm( X_tilde_train - X_train ,'fro')^2 test_error_PCA = (1/N_test)*norm( X_tilde_test - X_test ,'fro')^2   then I got:  train_error_PCA =     29.0759   test_error_PCA =     28.8981   is this normal?  is this why people add background noise to the MNIST data set?  I am just using standard PCA library so I can't possibly see what might have gone wrong    I have also tested this with different non-linear auto-encoders, for example, I tried a 1 layer Radial Basis Function (RBF) and it produces the same strange result:    if you get close enough, the little circle (train) is above each start (test). Which is not expected.    I have now made the same test but with a more complicated MNIST data set that can be found () and I also included it with the git large file tracking () on the repo (it will eventually reach github). Now with this it seems the train error is lower than test, as I assume it should be:    and ran the code:  clear;clc; %load('data_MNIST_original_minist_60k_10k_split_train_test'); load('mnist_background_random_test'); load('mnist_background_random_train'); X_train = mnist_background_random_train(:,1:784); X_test = mnist_background_random_test(:,1:784); [N_train, D] = size(X_train) % (N_train x D) [N_test, D] = size(X_test) % (N_test x D) %% [coeff, ~, ~, ~, ~, mu] = pca(X_train); % (D x R) = Rows of X_train correspond to observations and columns to variables.   num_centers = 5; % <-- change start_centers = 10; end_centers = 500; centers = floor(linspace(start_centers, end_centers, num_centers));  train_errors = zeros(1,num_centers); test_errors = zeros(1,num_centers); for i=1:num_centers     K = centers(i);     %% preparing model     U = coeff(:,1:K); % (D x K) = K pca's of dimension D     X_train_T = X_train'; % (D x N) = (N_train x D)'     X_test_T = X_test'; % (D x N) = (N_test x D)'     X_tilde_train = (U * U' * X_train_T); % (D x N_train)= (D x N)' = ( (D x K) x (K x D) x (D x N) )'     X_tilde_test = (U * U' * X_test_T); % (D x N_test)= (D x N)' = ( (D x K) x (K x D) x (D x N) )'     train_error_PCA = (1/N_train)*norm( X_tilde_train - X_train_T ,'fro')^2;     test_error_PCA = (1/N_test)*norm( X_tilde_test - X_test_T ,'fro')^2;     train_errors(i) = train_error_PCA;     test_errors(i) = test_error_PCA; end fig = figure; plot(centers, train_errors, '-ro', centers, test_errors, '-b*'); legend('train errors', 'test errors');   I will leave the question because I am not sure if I truly fixed the error or not.


How do I get ruby to print a full backtrace instead of a truncated one?

When I get exceptions, it is often from deep within the call stack.  When this happens, more often than not, the actual offending line of code is hidden from me:  tmp.rb:7:in `t': undefined method `bar' for nil:NilClass (NoMethodError)         from tmp.rb:10:in `s'         from tmp.rb:13:in `r'         from tmp.rb:16:in `q'         from tmp.rb:19:in `p'         from tmp.rb:22:in `o'         from tmp.rb:25:in `n'         from tmp.rb:28:in `m'         from tmp.rb:31:in `l'          ... 8 levels...         from tmp.rb:58:in `c'         from tmp.rb:61:in `b'         from tmp.rb:64:in `a'         from tmp.rb:67   That "... 8 levels..." truncation is causing me a great deal of trouble.  I'm not having much success googling for this one:  How do I tell ruby that I want dumps to include the full stack?


Tipping customs in the United States can be surprising for people who travel there for the first time. It happened to me when I used a shuttle van service out of LAX a few years ago. To sum up the bias: I am French; a country where service charges are included and optional tips to waiters in restaurants are only a few euros.  Although I paid by credit card, the driver gave me a pen and a form on which I could write the tip amount. At that moment, I was really missing simple rules that could help me define how much a suitable tip could be.  Afterwards, I heard about different calculation tricks. Some people say it's 20%, others 18%; some suggest to double the sales tax.   Is the rule the same for all occasions to tip, or are there different amounts depending for a table service restaurant, the tip jar of a fast-food restaurant, a bar waiter, a taxi driver? When someone gives outstanding service although not used to get tips, how much is appropriate? For instance, we had an airport car rental shuttle bus driver calling a competitor rental company for us to see if they had cars available, since the rental company of that bus was sold out. Restaurants often add a gratuity for large parties. Are patrons expected to tip beyond this amount and how much?


If I am raging, can I enter the rage again, without dropping out of the rage, to reset the minute duration?  RAW preferred. RAI accepted.


I tried to start Tor Browser using the icon from the unzipped folder, but nothing happened.  Same with the line command :  ./start-tor-browser.desktop bash: start-tor-browser.desktop: command not found   How can I run the Tor Browser?


Wilcox.test for testing count based data in R studio large W

I'm doing a textmining project about a videogame review dataset. I divided de reviews into a positive (reviewgrade > 8) and negative (reviewgrade < 3) and want to draw conclusions based on the frequency of different grading factors mentioned in the text. I now have a dataframe with counts of certain categories mentioned per review.  0    13249 1     1565 2      292 3       65 4       19 5        6 6        4 7        3 8        2 9        1 Name: positive: gameplay, dtype: int64   0    5043 1     348 2      66 3      18 4       8 5       3 Name: negative: gameplay, dtype: int64   For example this are the distributions of the amount of reviews which have a certain amount of mentions of gameplay related words. There are for example 1565 reviews with precisely 1 mention of a word related to the category gameplay.  Now I want to use this data to determine if on average gameplay gets mentioned more in negative context than in positive or vice versa. Because the data is not normal distributed, I assumed a t-test is not appropriate, and found online that a Mann–Whitney U test might be suitable.  > wilcox.test(positive$gameplay, negative$gameplay, alternative = "two.sided", conf.int = TRUE)      Wilcoxon rank sum test with continuity correction  data:  positive$gameplay and negative$gameplay W = 43702925, p-value < 2.2e-16 alternative hypothesis: true location shift is not equal to 0 95 percent confidence interval:  2.963844e-05 4.797412e-05 sample estimates: difference in location            4.995671e-05    I do however get a very high W value, which doesn't seem to be correct. Is this not the appropriate test, or am I interpreting this wrong?


How do I show that $\frac{n}{\varphi(n)}=\sum\limits_{d \mid n} \frac{\mu^2(d)}{\varphi(d)}$?

As the title says. How do I get from  $\frac{n}{\varphi(n)}$ to $\sum\limits_{d \mid n} \frac{\mu^2(d)}{\varphi(d)}$?  I know that $$\frac{n}{\varphi(n)}=\frac{\sum\limits_{d \mid n} \varphi(d)}{\sum\limits_{d \mid n} \mu(d)\frac{n}{d}},$$ and I suspect it is down this road I should go. But I get totally confused by the sums and I have no clue on how to divide them and "combine" them into one again. Any hints or advice would be much appreciated.


RC Circuit, finding time it takes for Voltage across capacitor to rise from 0 to 5V

For the circuit shown below what is the time it takes for Vc to rise from 0 V to 5 V in (second). Assume Vc(0+) = 0 V    The answer is \$ t = 2\ln{2}\$, but I am unsure why. What I have so far:  $$ V(t) = [V(\infty) + V(0)]e^{-t/T} \qquad \text{where $\;T = RC$}$$ R = 2e3 and C = 1e-3 , so T = 2  $$ V(t) = [V(\infty) + V(0)]e^{-t/2}$$  at t= infinite, the capacitor acts like a broken circuit so V(inf) = 0 but the problem also states that V(0) = 0 so that would set whole thing to 0   Am I doing something wrong, or am I even on the right track here?