Issue after upgrading from Ubuntu 12.04LTS to 14.04LTS

I recently migrated from Ubuntu 12.04LTS to 14.04 LTS .I had issues with my 12.04 so I did a factory restore and then upgraded to 14.04.My system is upgraded to 14.04 with no issues but The first thing I see is after restarting a pop up comes system problem detected.If I cancel it I don't see any issues,however the real problem is when I try to install nodejs using the below link---  curl -sL https://deb.nodesource.com/setup_8.x | sudo -E bash -   then I see some weird erros---------  Fetched 23.7 MB in 23s (1,028 kB/s)                                             W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/trusty/main/source/Sources  Hash Sum mismatch W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/trusty/main/binary-amd64/Packages  Hash Sum mismatch W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/trusty/main/binary-i386/Packages  Hash Sum mismatch E: Some index files failed to download. They have been ignored, or old ones used instead.   I did try with below solution  sudo rm -vf /var/lib/apt/lists/* but it again gives this error rm: cannot remove ‘/var/lib/apt/lists/partial’: Is a directory  Please help me on this as I am struggling with this.


There has been an awakening...but of what exactly?

Snoke says to Kylo Ren:  There has been an awakening. Have you felt it? ... The dark side and the light...  It seems clear throughout Episode VII that Rey is waking up to her own potential, and that Kylo Ren takes definite steps to solidify his position with the Dark Side. Do these events represent the extent of Snoke's comments or is he hinting at broader events and possibilities? How should we understand this "awakening"? I'm hoping that the novelizations shed additional context.


In JQuery, why does $(this) == $(this) return false?

I have run the following lines in my console (once a jquery script has been loaded), and received the following results:  $(this) > [Window] $(this) != $(this) > true $(this) == $(this) > false $(this) === $(this) > false   And I don't know what steps to take to figure out what is going on. My guess is that there is some object that holds a time based value which is changing, but I wonder if it's something different. I will try to compare the values in the meantime, but I was hoping someone might understand what is going on here.  Edited to address the point that I was unaware of the underlying implementation of $(arg). I did not know that it returned a new reference object. Therefore, I don't believe this is a duplicate of "How to determine equality for two JavaScript objects?".


How much does Ubuntu 14.04 cost to purchase?   Also, are there different versions, such as Enterprise, Starter, etc?


How to dynamically provide lookup field name in Django query?

I want to look for a certain string in several fields of a Model in Django. Ideally, it would go something similar to:  keyword = 'keyword' fields = ['foo', 'bar', 'baz'] results = [] for field in fields:     lookup = "%s__contains"     results.append(Item.objects.filter(lookup=keyword))   Of course this won't work, as "lookup" can't be resolved into a field. Is there any other way to do this?


I have seen similar questions on s.e. but I really can't seem to understand the proofs given.  So the question is the following:  Let $V$ be a finite-dimensional vector space. show that there is an isomorphism between $V$ and $V^{**}$ where $V^{*}$ is the dual space of $V$.


What actually happens to someone whose account is hacked by a spammer or hostile?

In an answer on Meta Stack Overflow, Brad Larson ♦ ,  In the vast majority of cases where the 100-point penalty is applied and a moderator notices, the account is also destroyed.... The few outlier cases tend to be when you have an otherwise good account that all of a sudden posts something bizarre. Sometimes it's a compromised account, sometimes people leave themselves logged in at a shared computer, etc.  In the cases where a contributing user does get hacked, and the hacker starts making red-flaggable posts (e.g. Spam, nonsense, or personal attacks), is there a procedure for separating out the penalties due to the hacker and negligence penalties applicable to the original account owner once the owner regains control? That is, if someone hacks my account and spams with it, am I "stuck" with the applicable black marks against my account (-100 rep penalty for each post, suspensions, question bans, etc.), or is it normal or expected for such posts to be disassociated or at least have applicable penalties reversed? For example,  I have disassociated the three Spam posts that the hacker made with your account, which will refund the 300 rep you lost as a result and lift your question ban. Unfortunately, it seems that you are not entirely innocent because you left your account logged in at a public library where the spammer found and took advantage of it, so I am Suspending you for a week so you can spend some time thinking about best practices in information security. Come back in a week to continue contributing.  At first I thought that it would be normal, natural, and just for all penalties to be reversed against the hacking victim upon submission of proof of victimhood, but then I remembered that I have dealt with some organizations other than Stack Exchange that have had Terms of Service clauses that more or less said "You agree to keep your login credentials secure and will be held solely responsible for any actions taken using your account", but I haven't been able to find such as clause for .


Are there any Force users that are "lower life forms"?

Obviously there are non-human Force users (both Jedi and Sith), all of them that I can recall seeing though are still fairly humanoid and seem to be at a similar intelligence level to humans. However, I doubt that they are all equally intelligent and thus I would assume there is some minimum sentience or intelligence required to be a Force user.  Have there been any instances of what one might call "lower life forms" using the Force? By lower life form I mean something that we could not directly communicate with through speech. So for example a squirrel would probably be too "dumb" to be trained in the Force, but could a smarter animal like a dolphin be trained?


Is it posible that the JIT compiler will make a static method inlined?  For exmaple, we have some code:  class A {      public static int c(int v)      {           return v*2      } } .............. Console.WriteLine(A.c(2));   In wihich circumstances can method public static int c(int v) be inlined by the JIT compiler?


A student of mine has been self-studying some elementary number theory. She came by my office today and asked if I had any hints on how to prove the statement      If $m$ is odd then $\gcd(2^m-1,2^n+1)=1$.    It's been a while since I took number theory and I'm not sure what to do. She said she is learning about congruences, primitive roots, and power residues.  She has not taken any group theory.


Assigning Shaders Based off UV Map Colours

I am wondering if it is possible to assign different shader's based off the colours of a Texture Painted UV Map that is assigned to an object? I've seen a couple of tutorials that use the Separate RGB node to split the colours, and then assign the shaders based off the result, but i was unsure if there was a simpler setup that followed a rule of 'if UV mapped texture = certain colour, assign this shader', possibly involving a ColorRamp node, for example?  Here is my progress so far:  Essentially each colour on the sphere would have a different shader assigned to it.  Thanks!


What is the internal representation of inf and NaN?

A friend & I were debating how Inf's and NaN's are stored during lunch today.  Take Fortran 90 for example.  4-byte reals can obtain the value of Inf or NaN.  How is this stored internally?  Presumably, a 4-byte real is a number represented internally by a 32 digit binary number.  Are Inf's and NaN's stored as 33 bit binary numbers?


Program run from udev cannot open a window

I have a script, written in python:  #!/usr/bin/python3 from tkinter import messagebox variable = messagebox.showinfo('title', 'question')   This python script does nothing else than showing a message box on my screen. I want to start that script whenenver I connect an usb drive to my computer.  So I created a new file 10-myself.rules in the directory /etc/udev/rules.d/.  KERNEL="sdb",RUN+="/usr/bin/python3 /home/user/projects/path_to_python.py"   But I do not see any message box when put the usb drive into my computer. Where is the error? How can I debug that?  I also called the command  udevadm control --reload-rules   And I tried to change the rule to  KERNEL="sdb*",RUN+="/usr/bin/python3 /home/user/projects/path_to_python.py"   or to the rule  KERNEL="sdb1",RUN+="/usr/bin/python3 /home/user/projects/path_to_python.py"   If  I change the script to   file1 = open("/home/user/udev.txt", "w") file1.write("Hello") file1.close()   then this script works.


I've just installed xubuntu-desktop on my trusty Lenovo X61 on top of Lubuntu 13.10. However, when the machine boots up it always logs straight into a Lubuntu session without asking. To resolve this I tried uninstalling lubuntu with sudo apt-get remove lubuntu-desktop but this turned out to be a bad idea as it booted to a black screen.  In tty1 I re-installed lubuntu and now I'm back to square 1. But I want Xubuntu!  I've heard taskel can be used to manage startup but wondered what the community would recommend. Many thanks.  Robin


Functions satsify $f'=f^{-1}$ with $f^{-1}$ is compostional inverse of$ f$

let $f$ be a function such that :$f:\mathbb{C}\to \mathbb{C}$ and $f^{-1}$ is the compositional inverse of $f$, I seek for the analyticity of $f$ at $0$, then my question here is :          Question:     Are there functions satisfy:$f'=f^{-1}$ with  $f^{-1}$  is compostional inverse of  $f$ ?


SQL Server SELECT column not in Group By clause?

As you can see my query, this is the working one  SELECT m.MerchandiseId, m.MerchandiseName, createdAt =  MAX(i.CreatedAt) FROM Inbox i INNER JOIN [User] u ON i.FromUserId = u.UserId LEFT OUTER JOIN Merchandise m ON u.MerchandiseId = m.MerchandiseId  OR i.ToMerchantId = m.MerchandiseId WHERE i.ToCompanyId = 10 OR i.FromCompanyId = 10 GROUP BY m.MerchandiseId, m.MerchandiseName     What if i want to SELECT one more field as i.InboxMessage with the Last record of each group?  SELECT m.MerchandiseId, m.MerchandiseName, i.InboxMessage, createdAt =  MAX(i.CreatedAt) FROM Inbox i INNER JOIN [User] u ON i.FromUserId = u.UserId LEFT OUTER JOIN Merchandise m ON u.MerchandiseId = m.MerchandiseId  OR i.ToMerchantId = m.MerchandiseId WHERE i.ToCompanyId = 10 OR i.FromCompanyId = 10 GROUP BY m.MerchandiseId, m.MerchandiseName   I've tried some ways that I found in stackoverflow, but I still not manage to do it. Thousand of thanks if anyone would help on this.


But the boy was trying to fight off the dementors, even though Harry could see their cold, draining power starting to affect him. The crowd was jeering, some of them on their feet, as the woman swept out of the dungeon, and the boy continued to struggle.       “I'm your son!” he screamed up at Crouch. “I'm your son!”      “You are no son of mine!” bellowed Mr. Crouch, his eyes bulging   suddenly. “I have no son!”      The wispy witch beside him gave a great gasp and slumped in her seat.   She had fainted. Crouch appeared not to have noticed.      “Take them away!” Crouch roared at the dementors, spit flying from his   mouth. “Take them away, and may they rot there!”   What does "may they rot there" mean? Is it let them rot in the prison Azkaban?  -- From Harry Potter and the Goblet of Fire


May I have some help understanding the intricacies of the List. Sort Methods?

I'm trying to figure out how to sort a list of strings that I have. The default comparer is doing something fun with the file names, though it totally makes sense. My list is a list of file names that come out of a folder in this order: 8_1-MDX 501 9_1-MDX 501 10_1-MDX 501 11_-MDX 501 12_1-MDX 501  And it's outputting them in this order: 10_1-MDX 501 11_1-MDX 501 12_1-MDX 501 8_-MDX 501 9_1-MDX 501  I get why it wants to do that, but the List. Sort methods are a bit confusing and I'm brand new to this. Thanks for any help I can get, and if someone wants to knock me for not understanding delegates well enough, I completely understand. Thanks!


I'm looking for an Access 2007 equivalent to SQL Server's COALESCE function.  In SQL Server you could do something like:  Person  John Steve Richard   SQL  DECLARE @PersonList nvarchar(1024) SELECT @PersonList = COALESCE(@PersonList + ',','') + Person FROM PersonTable  PRINT @PersonList   Which produces: John, Steve, Richard  I want to do the same but in Access 2007.  Does anyone know how to combine rows like this in Access 2007?


How many devices does one purchase of Android app support?

I have purchased an app from the Play Store. How many times I can install the same app on different Android devices?  Is there a limit?


I am getting the duplicate array like this:-   Array ( [0] => Afghanistan [1] => Albania ) Array ( [0] => Afghanistan [1] => Albania )    How I remove the this duplicate array... I want output like this..  Array ( [0] => Afghanistan [1] => Albania )   Please help me out. Thanks in advance.


Problem: I use a index.php wich includes other php files.  index.php declares:   <meta http-equiv="Content-Type" content="text/html; charset=utf-8"/>   All ok until here with portuguese characters "é,ç,ã".  When I include php files, chars are wrong encoded. With the use of utf8_encode() in the php file being included, things work fine. But, this is to much work encode every sing piece of text in several php files. So, I'm looking for a global solution.  I already tried: 1- use (as the first thing in the index.php file), nothing changes.  header('Content-Type: text/html; charset=utf-8',true);   2- use (as the first thing in the index.php file), in this case the include files work fine but index.php are wrong enconded now.  header('Content-Type: text/html; charset=iso8859-1',true);   3- insert the lines of code above everywhere in index.php and in beinginclued.php files, nothing changes.  Any help will be wellcome.


"I certainly could" or "I could certainly"

Which is better or correct?     That’s good advice that I certainly could do with heeding.      That’s good advice that I could certainly do with heeding.


How can I get started in pen-and-paper RPG as quickly as possible without any experienced players (including me)?

My friend and I would like to try RPGs out, but we would rather "jump to the fun" as quickly as possible and not engage any other people in the play at first. Which RPG system would be minimalistic enough to learn it within hours (the less the better) and what resources would I need to get started? I would prefer to avoid spending hours reading books just to start.  Per comments:     What genre are you most interested in?   To be honest, I don't know what genres exist. Middle-age fantasy, magical world sounds good though.     Do you have ready access to dice?   I've got 4-, 6-, 8- and 20-eye dice. I guess we could play online though and then I would have access to any dice using some website.     Do you care if physical books exist for the system?    Not really, as long as it's not too much reading to play.     What was is it about RPGs that you are most interested in?   I would say that I prefer rules rather than roleplaying — basically I enjoyed playing computer RPG games so far — creating and developing a character, staying in the same world and exploring it, making decisions.


I am rewritting a custom QGIS application as a plugin for QGIS. I am testing it by writing some new code, then deactivate/activate the plugin in the plugin manager, which seems to me a bit cumbersome. Is there a way to reload the plugin faster?


The model I make is all messed up and probably has too many vertices. I tried subdividing too many times.


Why does the reputation dropdown not show this upvote?

Over at Science Fiction & Fantasy, I answered this question:  (spoilers for Harry Potter 6/7!). This brought my reputation up to 10,565. However... this upvote didn't show up in the dropdown. Some screenshots:  The dropdown, showing +120 today:    My ?tab=reputation page, showing +130:    My /reputation page, showing the upvote:    So...  Why is it not showing in the dropdown?    This also happened with  - the dropdown is exactly the same as before, and yet I gained another 10 rep, and it's showing in all the other places. And on this question - there's no change in the dropdown. And again on SO - I had a  approved, which gave me +2, and... nothing in the dropdown.


Modeling a dependent variable as a ratio in regression with an interaction

I've read  regarding using ratios in regression, specifically using the ratio as an IV. The case he makes is that the ratio is an interaction term and thus should include it's components, and further suggest including the components, and the ratio itself as an interaction.I want to make sure I understand correctly.  As an illustrative example, suppose I think bmi is predictive of head circumference in children.  library(mice) # for the data data(boys) boys$hgt <- boys$hgt/100 # convert to cm mo <- lm(hc~bmi,data=boys) # (1) mo <- lm(hc~ I(1/(hgt^2)) + wgt + bmi, data=boys) # (2) bmi without considering it's an interaction mo <- lm(hc~ I(1/(hgt^2)) + wgt + wgt*I(1/(hgt^2)), data=boys) # (3) bmi set as an interaction term, very similar to above mo <- lm(hc~ hgt + wgt + bmi, data=boys) # (4) simpler and performs marginally less   From the data it seems all models are superior to (1) (better $R^2$, lower residuals etc), and while bmi as ratio is significant, it actually provides very little as a measure over using height (which is the main influence factor) and weight.  To sum: 1) which is the best modelling form? should I always make these examination and infer based on data, or is form (3) always preferred? 2) Am I correct in the last paragraph?  Thanks


A movie where thorns sting a woman's feet while she's trying to infiltrate some base

This was a scene in a movie that I watched in the 2000's or early 2010's (possibly earlier). Regardless, it wasn't recent, and I don't remember much of it, only images. I know the leading role is a woman (I think she had black hair). This woman has some robot-like behaviors (I don't think she is a robot but she is acts as though controlled and fights really well). The woman and some other people are trying to infiltrate a base. They are trying to prevent something, kill the people in charge, or something. I remember when they are trying to get in, there's the main woman and her friend in a field full of grass. They're fighting with the enemy but thorns erupt from the ground, and the thorns sting one of the woman's feet.


I generate some images using a PHP lib.  Sometimes the browser does not load the new generated file.   How can I disable cache just for images created dynamically by me?  Note: I have to use same name for the created images over time.


My laptop's screen is far too bright at night, even if I set it to minimum brightness. I know that it is capable of being dimmer, because Windows will dim it further if I leave it idle. However, I can't figure out how to dim it lower to minimum on Ubuntu. Is there a way?  I've looked at  question, but it's talking about Windows.


If I tap a creature to use its activated ability before combat, can I use the same creature to block or attack on the same turn?  My guess: you cannot block and/or attack with a tapped creature on the same turn.


Changing my Apple ID's email: address is not available

When I try to change my Apple ID's email address (a Hotmail address), I get the message This email address is not available. Choose a different address.   The email address I intended to change (a Gmail address) is mine and I had another Apple ID opened with that earlier. I was not able to delete that account, as Apple doesn't allow that. Hence, I put a Yahoo email in the account so I could remove the Gmail from the account. So, currently, there is no Apple ID registered with the Gmail address.    Why can't I switch my current Apple ID to the Gmail address?  Should I transfer all my info to the Gmail as a newly Apple ID and use that if the change is not possible?


How do I keep track of failed SSH log-in attempts?

I'd like to see if somebody has been trying to log-in by brute-force into my Ubuntu 12.04 server over SSH. How can I see if such activities have been taking place?


Can I re-enter the US from Mexico with just a learner driving permit?

I recently crossed into Mexico from the US, forgot to bring my passport. Could I go back using my learner driving permit? I am 17 years old.   OP comment: US citizen, born and raised in Arizona.


Is there a single word to describe the canary in the phrase "Canary in a coalmine"?  The best I can come up with is sentinel, but I'm nearly positive there's a more precise option.  Edit: To clarify I'm not looking for words that describe the canary but rather for a word the encapsulates the entire phrase.  That is, I don't want to finish the phrase "the canary is a ...".  I do want to finish the phrase "$PERSON was a ..." where the blank implies as many of the attributes of the proverbial canary as possible (e.g. going down the dangerous road first, warning those that follow, connotations of captivity, &c).  I'm reluctant to use the phrase, or "canary" as it strikes me too colloquial/lighthearted for the work at hand.    @senex suggestion of bellwether and @bib suggestion of tocsin are closest to what I'm looking for thusfar.


How do I check if a number is a palindrome?  Any language. Any algorithm. (except the algorithm of making the number a string and then reversing the string).


I have a whitespace that's taking up about half a page between an image and my text in one of my columns of a two-column paper. It looks like this (contents blurred). How do I get rid of this space? Thanks!


All of the force-particles in the standard model are bosons, now my question is pretty short, namely:     Why are all force particles bosons?   This can't be a coincidence.


strings are missing after concatenating two or more variable string in bash

When I am running two while loop and trying to concatenating two variable strings (from two loops), the final output (string) is weird. I have tried different way to concatenating but did not get the answer: Below is the code: [I need vfile="var1_Amon_My_model1*.nc"]  #!/bin/bash jcount=1 extn="*.nc" while read line do mname=$line echo " Working on model - " $mname echo " and model number = "$jcount while read line do vname=$line vfile="${vname}""_Anom_""${mname}""${extn}" echo $vfile done<varlists.txt echo "******************************************" jcount=$((jcount+1)) done<model_test1.txt   In varlists.txt  var1 var2   In model_test1.txt  My_model1 My_model2   After executing the script, it is showing   Working on model -  My_model1  and model number = 1 *.ncm_My_model1 *.ncm_My_model1 ******************************************


How to disable the guest account via the GUI?

Possible Duplicate:          I know you can  to disable the guest account, but is there any option to do that via the Ubuntu 12.10's GUI?  It's hard for me to believe that a simple on/off option wasn't implemented since the guest account was added to Ubuntu, and I'd be glad to find that option added as a feature to the 12.10 release.


Add a privilege to grant another user the ability to comment on a question

TL;DR: A privilege should be added to be able to "vouch for" another user's usefulness to a particular question, giving them the ability to comment on that question.  Sometimes, especially in programming teams, someone who is very familiar with a piece of software may discover or be directed to a question that they are very qualified to solve. Of course, this could also apply to a game developer finding a question about their game on Arqade or a researcher finding a question about their area of expertise on Computer Science.SE. In some cases, this person may have trouble answering the question because they have insufficient reputation to ask for clarification.  I propose that we provide a mechanism for another user to vouch for this expert's expertise or ability, which would allow that user to post comments on the question. This should require significantly higher reputation than what is required to comment (I think the "Established user" privilege, at 1000, would be a good spot). Doing this would also not notify the user, to avoid the primary problem with "private message" and "ping" suggestions. Instead, the "vouching" user would have to notify the "expert" user out of band.


Probability Density Function of the sum of N random variables

I have N random variables: $X_{1}, X_{2}, ... X_{n}$ which are all independent.  The probability density function for the ith random variable is $f_{i}(x)$.  What is the pdf $f_{X}(x)$ where $f_{X}(x)$ is the sum of all the random variables?  This is similar to calculating the sum of n dice, but a little more complicated.  Does anyone have any suggestions, tips, or places for me to look to help guide me to the solution?  Thanks in advance!


Uncommitted work pending in unit test with trigger and queueable callout

I have an after insert trigger that invokes queueable Apex which makes a callout.  The trigger and callout work fine in the UI and I don't get any errors in normal operation.  However, my unit test keeps failing with the "uncommitted work pending" error despite all my attempts to separate the callout.  I've used a testVisible variable to disable the callout from the trigger so that I can invoke the queueable job explicitly in a startTest/stopTest block after the DML that fires the trigger.  I've pored over the callout class to make sure it's not doing any DML beforehand.  Anyway, if it was doing DML, I should get the uncommitted work pending errors in the UI, right?  I've tried API version 37 and version 41 but the unit test still fails.   I've had a case open with Salesforce premier support for 6 weeks now but haven't made any progress.  Any suggestions?  The unit test:  @isTest static void testCallout() {     // Disable the callout while setting up data.     CCx_EHR_CMCT_Services.isQueueSendEnabled = false;      // Set up the data and execute the DML.     / ...     insert act;      // Set up the http mock     // ...      // Now enable and execute the callout     Test.startTest();     CCx_EHR_CMCT_Services.isQueueSendEnabled = true;     Test.setMock(HttpCalloutMock.class, mock);     System.enqueueJob(new QueueSendToRedox(new List<ActivityHL__c>{act}, desk)));     Test.stopTest();  }   Trigger:  trigger HL_ActivityHL_c on ActivityHL__c (before insert, before update, after insert) {     if (Trigger.isAfter) {         if (Trigger.isInsert) {             CCx_ClientDataDomain.sendEHRClinicalComm(Trigger.new);         }     } }   Trigger handler class:  public without sharing class CCx_ClientDataDomain {     public static void sendEHRClinicalComm(List<ActivityHL__c> triggerNew) {     // do some processing here.     // ...     // then queue the callout job.     System.enqueueJob(new CCx_EHR_CMCT_Services.QueueSendToRedox(             deskActivities.get((Id) desk.getDeskId()), desk));     } }   Queueable job class with callout method:  public with sharing class CCx_EHR_CMCT_Services {     // isQueueSendEnabled is an attempted workaround for unit tests     @testVisible     private static Boolean isQueueSendEnabled = true;      public class QueueSendToRedox implements Queueable, Database.AllowsCallouts {         private List<ActivityHL__c> activities;         private CCx_DeskHierarchySelector.Desk desk;         private Boolean isEnabled;          public QueueSendToRedox(List<ActivityHL__c> activities, CCx_DeskHierarchySelector.Desk desk) {             this.activities = activities;             this.desk = desk;             this.isEnabled = isQueueSendEnabled;         }          public void execute (QueueableContext context) {             if(this.isEnabled) sendClinicalCommToRedox(activities, desk);         }     }      public static void sendClinicalCommToRedox(List<ActivityHL__c> activities, CCx_DeskHierarchySelector.Desk desk) {         // Set up data for the callout.  No DML actions are executed before the callout.         HttpRequest req = buildRequest();         // ...          // Callout         Http http = new Http();         HttpResponse resp = http.send(req);     } }


Lifespan of an SSD (NAND Flash) for minimal write use archive purposes: Write once, toss in (proverbial or literal) storage closet

Okay,  which was closed as being too localized and I understand the idea of that closure: Systems, environments and usage are all different. But my question is about using SSD for minimal write use, archival purposes. Meaning, instead of storing tapes, optical media (BluRay, DVD-R, DVD-RAM, etc…) or even a hard drive somewhere safe, what about SSD which uses NAND flash memory for storage? I assume the act of simply plugging in an SSD, copying data and then tossing the drive in safe/secure archival space disconnected from a system is a solid (no pun intended) way of storing long term data? I have worked with institutions that routinely archive things on hard disk drives in such a way. But as we all know a hard disk drive is one drop away from being wiped out. SSDs seem inherently much more resilient.  seems to state that modern SSDs — even those used on a daily basis — will outlast their own self-professed max lifetime. The reason I am asking this now is SSDs on a very basic consumer level are very cheap nowadays with — for example — 120GB SSDs going for as low as $40, I believe these things would be a good long term storage for things such as archived photos, videos and such… And will only get cheaper as time goes on.


If $a_{ij}=\max(i,j)$, calculate the determinant of $A$

If $A$ is an $n \times n$ real matrix and       $$a_{ij}=\max(i,j)$$       for $i,j = 1,2,\dots,n$, calculate the determinant of $A$.   So, we know that   $$A=\begin{pmatrix} 1 & 2 & 3 & \dots & n\\  2 & 2 & 3 & \dots & n\\  3 & 3 & 3 & \dots & n\\  \vdots & \vdots & \vdots & \ddots  & \vdots\\   n& n & n & \dots & n \end{pmatrix}$$  but what do I do after?


Preimage of maximal ideal is maximal (why is this answer wrong?)

Let $\phi:R\to S$ Be a surjective ring homomorphism and $M \subset S$ is maximal, then $\phi^{-1}(M)$ is maximal in $R$. Here is what I wrote (it is known the preimage is an ideal, so prove only maximality)  Assume $\phi^{-1}(M) \subset W \subset R$. Then first $\phi(\phi^{-1}M) = S$ because $\phi$ is surjective. Hence $\phi(\phi^{-1}M) \subset \phi(W) \subset \phi(R) \implies S \subset \phi(W) \subset S \implies \phi(W) = S$. Now let $w \in W$ and $\phi(w) \in \phi(W) = S = \phi(\phi^{-1}M)$, so $w \in \phi^{-1}M$? Or this only shows $x \in \phi^{-1}(M)$ such that $\phi(x) = \phi(w)$?  Is there a way to complete the proof with what I wrote? (I already have witness the solution, basically $\phi^{-1}M \subset R$ is an ideal. Then by isomorphism theorems $S/M \approx R/\ker(\pi \circ \phi)$ where $\pi$ is the quotient map and usually field argument implies $\ker (\pi \circ \phi) = \phi^{-1}M$ because fields contain only two ideals)


Show that the sequence $\{x_n\}$ defined by $x_n = ( 1 + 1/n)^n$ is a convergent sequence

Show that the sequence ${x_n}$ defined by $x_n = ( 1 + 1/n)^n$ is a convergent sequence I've just answer : the proof will begin by demonstrating that the sequence is :  $1$. Monotonic increasing  that is $x_n < x_{n+1}$ $2$.bounded above


Standard Visitor visa staying the full 6 months

My mother-in-law is currently taking care of my borther's new born baby. We applied for a 2 year Standard Visitor visa, assuming she would be stay for 6 months at a time, with a month or two break in-between coming back to South Africa.   Upon entry in the UK, border control informed her the limitation is not per visit, but she would be able to return again within the same 12 month cycle. In other words, she would have to return back to South Africa for at least 6 months before she would be able to return again to the UK.   The page explaining the visa and it's purposes, is not very clear and open to interpretation, which is why we chose the 2 year Standard Visitor visa in the first place. All information and documentation supplied supports out initial intent as well.     Question: would she be allowed back in, considering the situation, without a 6 month break?


According to canon, what is the primary style of hand to hand combat utilized by Kirk in Star Trek TOS?

The hand to hand combat prowess of STNG Starfleet's security personnel is lauded by Tasha Yar in the accepted answer to .      Tasha: I think you should know that there is no physical training   anywhere that matches Starfleet, especially its security people.   It is likely combat training evolved during the time elapsed between TOS and STNG, but Kirk definitely had specific moves which he seemed to be trained in and repeatedly used during his 5 year mission.     While some of the moves are identifiable, I find it difficult to pin a label on the double handed, flying hip check, style William Shatner utilized in his portrayal of James Kirk. According to canon, is Kirk practicing , and if so, what is it?


What's meaning of the `d` and `t.` of the `drwxrwxrwt.` in linux?

In the / directory, I use:   ls -alFd /tmp     to check the /tmp directory permissions and I get drwxrwxrwt.  I know rwxrwxrw means user, group, other permissions are read, write and execute.  But I don't know the meaning of the d and t. of the drwxrwxrwt, can someone explain it?


Without brute force, how can we show that 1729 is the smallest number that can be expressesed as the sum of two cubes in two different ways?

It's very known that 1729 is the smallest number that can be expressed as the sum of two cubes in two different ways, but is there a proof that not uses brute force?  If we let $n$ be the smallest number such that $n=a^3+b^3=c^3+d^3$ with $a\neq c$, $b \neq d$ and $a,b,c,d > 0$, then:  $n = (a+b)(a^2-ab+b^2)$   $n=(c+d)(c^2-cd+d^2)$  But I don't have any idea how to follow from here. If we take a look at 1729:  1729=13·19·7  It seems obvious that if a number is the product of only 2 primes then it can't be expressed as the sum of two cubes in two different ways, but I don't know how to prove either that the least number which such property must be product of 3 primes or more.  Does anyone has any idea of how to approach this?


So I'm doing some random practice for an upcoming exam, and I don't know if it's the fact that I've been reviewing for hours and my brain isn't functioning, or something in this code is wrong.  I'm attempting to make a very simple java program that asks the user for the amount of numbers they wish to enter (totalNum), create an array that long, and then ask the user for each individual value.  After it asks the user for each value in the array, it prints the array.  Here is my code:  import java.util.Scanner; public class Practice1 {   public static void main(String[] args) {     Scanner s = new Scanner(System.in);     System.out.println("How many numbers would you like to store?");     int totalNum = s.nextInt();      int[] numbers= new int[totalNum];       for (int i = 0; i>totalNum; i++) {         System.out.println("Number" + i + " :");         numbers[i] = s.nextInt();         i++;     }     numbers.toString();     System.out.println(numbers);   } }   When I run it it asks the user for the numbers I want to store, then prints [I@33909752 and stops.  I've done dozens of programs like this and for the life of me I can't figure out where I went wrong.    Any help would be appreciated, thanks!


I cannot find a way how to change a color to another, say "yellow" of a quadrangle on the torus surface. I'm also interested in the possibility of changing an entire concentric circle of quadrangles around the torus to some other specific color.


Integral of $\tan^{-1}(\sin(x))$ from $0$ to $\frac{\pi}{2}$ without dilogarithms

Integral of $$\int_{0}^{\frac{\pi}{2}}\tan^{-1}(\sin(x))$$ can be given in the following form (obtained from CAS):   $$ I =  \text{Li}_2\left(-\frac{1}{\sqrt{2    }}\right)-\text{Li}_2\left(-1- \sqrt{2}\right)+\frac{\pi    ^2}{12}+\frac{\log    ^2(2)}{8} \\ -\log \left(1+\sqrt{2}\right) \log    \left(2+\sqrt{2}\right) $$  It can be derived using integration under the differential sign (found here):    the approximate numerical result is: $$ I \approx 0.845291$$  I have also found that expression $$ \frac{\pi ^2}{8}-\frac{1}{2} \log    ^2\left(1+\sqrt{2}\right) $$ yields the same numerical results to within thousands of digits.  Is it possible to find this closed-form solution without dilogarithm from this integral?


Basis for adjoint representation of $sl(2,F)$

Consider the lie algebra $sl(2,F)$ with standard basis $x=\begin{bmatrix} 0 & 0 \\ 1 & 0 \end{bmatrix}$, $j=\begin{bmatrix} 0 & 1 \\ 0 & 0 \end{bmatrix}$, $h=\begin{bmatrix} 1 & 0 \\ 0 & -1 \end{bmatrix}$.      I want to find the casimir element of the adjoint representation of $sl(2,F)$. How can I go about this? Thanks.


Should bug-report/feature-request *questions* that duplicate Grab-bag *answers* be closed as duplicates?

Meta Stack Exchange is seeing a fair few of these "Grab bag" questions that announce a biggish change to the sites and then encourage bug-reports and feature-requests to be posted as answers to that question.  For example:   Recently,  as a  question.   BUT, it turns out that  as an answer to one of those "Grab bag" questions.  So my question:  Should the new bug report be closed as a duplicate of the "Grab bag" question?  Or should the original answer be edited to point to the new bug report?  Something else?


If a person holds prejudice against people because of their nationality, would that be considered racist?

Would it be considered racist if a store owner believes all Canadians are thieves and does not let any Canadians into his store? Racism pertains to discriminating based on race, and (correct me if I'm wrong) Canadians are not a race. What would be an appropriate word to describe an individual such as the  store owner?  The discrimination is specific to Canadians, not foreigners in general. I'm looking for a word that could be applied to someone who lives in the country they discriminate against. For example if a Canadian announces "all Canadian culture is stupid!" what would that be called?


Does an object traveling near the speed of light create a gravitaional field?

Does a particle traveling near the speed of light create an observable/measureable gravitational field around it?  I know most elementary particles travel near the speed of light and have no gravitational effect, but I'm talking about a more massive particle, say, iron for instance.  As a more specific example of what I'm trying to say; if you had a particle accelerator, could you create a decent, measurable gravitational effect in the epicenter of the circle outlined by the accelerator by accelerating a very heavy element close to the speed of light?


Validate if an input only contains numeric values - Javascript

I am currently using the script below to take my inputs and convert them to what I want with some validation included. I have got my server side validation set up and would like to have some client side also, I have validated the lengths of the inputs but now need to ensure that they only contain numbers. This is for the Variables day, month and year. I have tried using IsNumeric() but to no avail  <script type="text/javascript"> function timeMachine() {      var day     = $("#date_day").val();     var month = $("#date_month").val();     var year    = $("#date_year").val();      if (day == "" && month == "" && year != ""){         if (year.length != 4){             alert("Please enter a valid year!");         } else{             window.location = "/date/" + year ;         }        } else if (day == "" || month == "" || year == ""){         alert("Please enter a full date!");     } else{         var myDate = new Date(year, month-1, day);          var monthNames = [ "january", "february", "march", "april", "may", "june","july", "august", "september", "october", "november", "december" ];             window.location = "/date/" + year + "/" + monthNames[myDate.getMonth()] + "/" + day;     }     return false; } </script>   Thoughts?


How to Convert these ASCII values into Binary in C

I'm trying to convert the ASCII values of each letter, into Binary but I'm not sure how to grab the decimal values and convert them. Here's the code that prints out a word with their ASCII values to the right  #include <stdio.h> #include <string.h>   int main (void) {     char c[20];    printf("Enter a word: ");    scanf("%s",&c);     int i;    char *str = c;    int length = strlen(str);     for (i = 0; i < length; i++) {       printf("%c = %d \n", str[i] , str[i]);    }    return 0; }   Example output:  Enter a word: Program P = 80 r = 114 o = 111 g = 103 r = 114 a = 97 m = 109


installing packages from usb to ubuntu server 14.04

I want to install these packages to my Ubuntu server from USB as i have tried many thing by editing mirrors in /etc/apt/sources.list to install some packages for Ubuntu server 14.04 know I want to try installing them from USB so would any one guide me how should I?  sudo apt-get install git build-essential libacl1-dev libattr1-dev libblkid-dev libgnutls-dev libreadline-dev python-dev python-dnspython gdb pkg-config libpopt-dev libldap2-dev dnsutils libbsd-dev attr krb5-user docbook-xsl libcups2-dev libpam0g-dev ntp -y


In which book did alien protagonists absorb and mutate humans, turning their flesh into biological weapons that they then used against other humans? I believe the book starts with a human encountering a lone member of the alien species, who promptly subsumes him and uses his flesh to make weapons that it can use. It then goes in search of more raw material.. I think the human discovered one of the aliens when he was atempting to salvage a small object adrift in space.  If I recall correctly, the human then crashed his ship on earth. I think the aliens were more insectile (lots of legs) and could control a human by inserting a proboscis into their spine. Once they didn't need the intact human, they injected them with something (nanotech?) that let them repurpose the flesh and bones into new forms. This could be done to dead humans too, as long as the body hadn't significantly decayed. The aliens had previously lost an interstellar war and were believed to be extinct. The species had different casts, with the one at the start of the story being an infiltrator/scout. I probably read the book between 1983 and 1999.


How to transform RegExp code to solve Invalid regular expression: invalid group specifier name on Safari?

I have this JavaScript RegExp code: str.replace(new RegExp('(?<!\..*)(\d)(?=(?:\d{3})+(?:\.|$))', 'g'), '$1 ');  It works on Chrome well, but in Safari I get Invalid regular expression: invalid group specifier name error. Anybody has idea how can I transform this RegExp to solve this error message?


On , there is the votes count on the "Summary" page, which shows my correct number of votes.    However, if I go to my  and select "Downvotes," it says I have casted 0 downvotes.    Am I doing something wrong?


I have a database, that due to some silly code issues has grown hugely. It is now sitting at 24GB, most of it is very unnecessary logging information (system generated debug information).  My server lives on a cloud hosted server. I am now sitting with 2 issues because of the file size:   I pay for storage. I am happy to pay for my core business, but paying for silly data seems....silly My backups are now huge also. I do nightly full backups, and then ship them off to an FTP server. This process is taking longer and longer.   Given my issues, is shrinking so bad? I will rebuild all my indexes. I did a dry run, and brought my database down to 6GB.  This guy (who I have always trusted as my SQL guru), says it's bad....mkay


Dropbox works but no icon shows in the panel

I installed Dropbox on Xubuntu 14.04 using the package provided by Dropbox on its download web page.  Now, Dropbox works, but its icon does not show in the panel at startup, and I have to run dropbox stop && dropbox start in a terminal in order to get it.  I read that a simple workaround is to install package nautilus-dropbox via apt-get.  There are 2 issues:   I don't know how to uninstall Dropbox safely, without messing anything up. My Dropbox folder is already synced on my PC. Once I install nautilus-dropbox, I'd like to make it read this folder without resyncing all that stuff. Is that feasible?


I am trying to solve a central force problem and came to an equation like this:  $$\frac{d^2 y}{dx^2} + y = \frac{1}{y^3}$$  I can't find a decent method to solve it.


How to find dead-ends in road network using ArcGIS for Desktop or GRASS?

I'm trying to remove all the dead-end roads in a road dataset (lines) that are less than 100m long.   How do I identify roads that are dead-ends (no exit)?   The 100m part is easy.   I know how to use ArcGIS for Desktop proficiently and can use GRASS.


Does Samuel L. Jackson exist in the MCU?

In Spider-Man: Homecoming, Ned has a LEGO Death Star. Additionally, in Captain America: Civil War, Peter references The Empire Strikes Back. This means that Star Wars exists in the MCU.  One example of a Star Wars actor? Samuel L. Jackson, who plays Mace Windu. S.L.J also plays Nick Fury in the MCU. So who plays Mace Windu in the MCU? Does Nick Fury play them? Does Samuel L. Jackson exist in the MCU, and play Mace Windu? If so, do people mention how Nick Fury and Samuel L. Jackson look identical?


I'm writing a little programme to remove a word from a string. C segfaults in the for-loop inside the removeWord function (the third printf is never executed). What can the reason be? I'm an absolute newbee in C. When I try to print str[j] as %s inside the for loop, the compiler complains about str being an integer, not a string. Why is that?  #include <stdio.h> #include <stdlib.h> #include <string.h>  void removeWord(char * str, char * toRemove) {     int i, j, k, stringLen, toRemoveLen;     stringLen   = strlen(str);      // Length of string     toRemoveLen = strlen(toRemove); // Length of word to remove // ...(code for finding the word)...         printf ("str='%s' StrLen=%d ToRem=%d i=%d j=%d\n",str, stringLen, toRemoveLen, i, j);         for(j=i; j<=stringLen - toRemoveLen; j++)         {             printf ("j=%d\n", j);             str[j] = str[j + toRemoveLen];         }         printf ("i=%d j=%d\n", i, j); }  int main(void) {     char * term = "from the ";     removeWord(term, "from");     return 0; }


Nullable type issue with ?: Conditional Operator

Could someone explain why this works in C#.NET 2.0:      Nullable<DateTime> foo;     if (true)         foo = null;     else         foo = new DateTime(0);   ...but this doesn't:      Nullable<DateTime> foo;     foo = true ? null : new DateTime(0);   The latter form gives me an compile error "Type of conditional expression cannot be determined because there is no implicit conversion between '<null>' and 'System.DateTime'."  Not that I can't use the former, but the second style is more consistent with the rest of my code.


Will my skills improve when I make them Legendary?

Will my skills become stronger when I make them Legendary?


Can you restart a quest from the beginning?

I'm currently doing the quest "Diplomatic Immunity" and I'm stuck. I wish to begin the quest over again so I can continue on with the game.


HTTPS activated, how to refuse HTTP connections

I recently installed an SSL certificate on my server and now HTTPS seems to work for all the pages.   However, the server is still accepting connections from HTTP. How do I enforce HTTPS?   I use a CentOS Linux distribution on my server.


Ubuntu 18.04: "sudo -H nautilus" causing system problem detected

I am using Ubuntu 18.04 and I wanted to access a directory which only root could read or write to. I read somewhere I could launch nautilus as root with this command: sudo -H nautilus which opened a file explorer which still didn't have root permissions. This is the error that came up in the console:  $ sudo -H nautilus Gtk-Message: 11:26:52.751: GtkDialog mapped without a transient parent. This is discouraged.  (nautilus:3453): Gtk-CRITICAL **: 11:26:52.752: gtk_widget_show: assertion 'GTK_IS_WIDGET (widget)' failed  ** (nautilus:3453): CRITICAL **: 11:26:52.752: setup_side_pane_width: assertion 'priv->sidebar != NULL' failed  ** (nautilus:3453): WARNING **: 11:26:52.925: Unable to get contents of the bookmarks file: Error opening file /root/.gtk-bookmarks: No such file or directory  ** (nautilus:3453): WARNING **: 11:26:52.925: Unable to get contents of the bookmarks file: Error opening file /root/.gtk-bookmarks: No such file or directory   I then found out I could reach the directory just by directing a normal file explorer to admin://<absolute path of directory>. That did it, but now every time I log into my account there's a popup showing up after a couple of minutes saying System problem detected. I am guessing it has something to do with that sudo -H nautilus I ran. I didn't reboot in between the two solutions so I can't really say.  PS: That directory I wanted to access was one created by an unfinished photorec I did to recover a file. For some reason I wasn't able to delete that directory, named recup_dir.1, because I didn't have permission.


What is wrong with this proof that the power set of the natural numbers is countable?

Here I offer a "proof" of why the power set of the natural numbers is countable by creating a supposed bijection. I know that my proof is wrong, but where? If anyone could point it out, that'd be awesome.  Consider the power set of the natural numbers. We can form a bijection $f:\mathbb{N}\to\mathcal{P}(\mathbb{N})$ as follows.  For any $f(x)$ convert $x$ to its binary representation, which is a string of $0$s and $1$s. If the $i$-th digit is $1$, then include $i$ in the output set $S=f(x)$. Otherwise do not include $i$. Note that $i$ is $0$-indexed and starts from the right-most digit.  So in this case $f(5)=\{1,3\}$. Supposedly we can construct any set in $\mathcal{P}(\mathbb{N})$ with an appropriate choice of $x$.  Where does this proof blow up?


Find the value of $~\int_0^{2\pi}\frac{d\theta}{1-2a\cos\theta + a^2}~~~$ for $~|a|<1~.$

Using residue theorem, find the value of $$~\int_0^{2\pi}\dfrac{d\theta}{1-2a\cos\theta + a^2}$$ for $~|a|<1~.$  I know that the value of the integral is $~\frac{2\pi}{1-a^2}~$(I found it by using the rule of normal definite integral), but don't know how to find the same by using residue theorem. Any one please provide me a complete solution by using residue theorem.


Error loading jquery.min.js from googleapis.com in Iran

I hope this won't be off-topic. I know this is not a technical bug, but I am living in Iran and as you might know we are in sanction and google is blocked our request to CDN libraries. I recently get the 'Stackoverflow requires external java script from another domain which is blocked' error.     Since your site is international I was wondering if is it possible to load jquery from your site or another source which is not blocked in our country?  p.s: When I use antifilter or vpn programs (which change my ip to another country) everything is OK.


What is the difference between on and about?

For example,        We have a conversation on food.   We have a conversation about food.


Why normalize when all features are on the same scale?

So I'm doing the tensorflow tutorial found here:    Basically, my input is a [28x28] matrix (image) that I flatten to a [1x784] vector.  The tutorial then says:     We scale these values to a range of 0 to 1 before feeding to the neural network model. For this, cast the datatype of the image components from an integer to a float, and divide by 255.   My question is why do we need to normalize in this case? My understanding is that when we have features that are on different scales, we need normalization if not the output of the model is distorted. But in this case all pixel ranges go from 0 to 255 (all features are the same scale)  I went ahead and ran it with normalization, and get an accuracy of over 85%, whereas no normalization, my accuracy falls to 10%.  Any ideas?


I have a Rapid Pulser connected to a Command Block, coordinates to the middle of nowhere, and when I get even 300 blocks close to it, it warps me to the coordinates. How can I destroy these blocks without getting close?


Why doesn't Stack Exchange develop an IM-like rich client to get answers real-time?

Why doesn't Stack Exchange develop an IM-like rich client for us to more conveniently ask questions and get answers in real-time?  I want to join this open source project if somebody is interested.


How to create a .desktop entry for .run file

I tried to add a new Desktop Entry but it failed... I think the reason is the run file type.    Is it possible to make a .desktop entry for a run file?  [Desktop Entry] Version=1.1 Type=Application Name=XAMPP Comment=XAMPP Control Panel Icon=/opt/lampp/htdocs/dashboard/images/xampp-logo.svg Exec=/opt/lampp/manager-linux-x64.run Path=/opt/lampp Actions= Categories=Development;


I have a render scene in blender that is meant to look like this:  however the render looks like this (its abit hard to see but the only thing in that image is the stickman drawring and the background is transparent?:  However its not transparent in the world film options so I have no idea what has happened. I had a similar issue like this in my younger blender days of 2.79 however you cant do "W" "clear all restrict render" anymore... Please help. Also the visibility in the layer settings is all set so it should be seen in render... Also if you still cant see the stickman this may help you (youll need to enlargen the image potentially to see it and the background has that transparent checker texture as well. Also the compositing has nothing to do with it.:


How to show an indicator when an item has been added to a folder in a document library (SharePoint 2010)

I have a requirement to show some sort of indicator when an item has been added to a folder in a document library. At the item level, SharePoint has the "New" indicator. This does not seem available at the folder level. Is this true?  I tried to use the column "Modified", but this seems to be specific to the folder as well, rather than the items in the folder.  Can someone help me through this, or provide some alternatives? If my assumptions above are incorrect, please let me know.  Thanks in advance.


Can't run Java applications (like logisim) due to "Assistive Technology not found" error

I tried it and the errors are:  Exception in thread "main" java.awt.AWTError: Assistive Technology not found: org.GNOME.Accessibility.AtkWrapper at java.desktop/java.awt.Toolkit.newAWTError(Toolkit.java:472) at java.desktop/java.awt.Toolkit.fallbackToLoadClassForAT(Toolkit.java:488) at java.base/java.util.stream.ForEachOps$ForEachOp$OfRef.accept(ForEachOps.java:183) at java.base/java.util.stream.ReferencePipeline$2$1.accept(ReferencePipeline.java:177) at java.base/java.util.HashMap$KeySpliterator.forEachRemaining(HashMap.java:1608) at java.base/java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:484) at java.base/java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:474) at java.base/java.util.stream.ForEachOps$ForEachOp.evaluateSequential(ForEachOps.java:150) at java.base/java.util.stream.ForEachOps$ForEachOp$OfRef.evaluateSequential(ForEachOps.java:173) at java.base/java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234) at java.base/java.util.stream.ReferencePipeline.forEach(ReferencePipeline.java:497) at java.desktop/java.awt.Toolkit.loadAssistiveTechnologies(Toolkit.java:532) at java.desktop/java.awt.Toolkit.getDefaultToolkit(Toolkit.java:613) at java.desktop/javax.swing.UIManager.getSystemLookAndFeelClassName(UIManager.java:660) at com.cburch.logisim.gui.start.Startup.parseArgs(Startup.java:250) at com.cburch.logisim.Main.main(Main.java:32)   The error seems to be...     Caused by: java.lang.ClassNotFoundException: org.GNOME.Accessibility.AtkWrapper       at  java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:582)       at   java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:190)       at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:499)       at java.base/java.lang.Class.forName0(Native Method)       at java.base/java.lang.Class.forName(Class.java:374)       at java.desktop/java.awt.Toolkit.fallbackToLoadClassForAT(Toolkit.java:485)       ... 14 more     OUTPUT for  apt-cache policy logicsim logisim  logisim:   Installed: 2.7.1~dfsg-1   Candidate: 2.7.1~dfsg-1   Version table:  *** 2.7.1~dfsg-1 500         500 http://in.archive.ubuntu.com/ubuntu bionic/universe amd64 Packages         500 http://in.archive.ubuntu.com/ubuntu bionic/universe i386 Packages         100 /var/lib/dpkg/status N: Unable to locate package logicsim   OUTPUT for update-java-alternatives -l  java-1.11.0-openjdk-amd64      1101       /usr/lib/jvm/java-1.11.0-openjdk-amd64 java-1.8.0-openjdk-amd64       1081       /usr/lib/jvm/java-1.8.0-openjdk-amd64


Do I need exterior grade cables or conduit to run wire in an enclosed soffit?

I'm looking to add some lights on motion detectors (un-switched) and security cameras under the eaves of our house.  I know standard romex is often used in attics, but the soffits seem like they might be more exposed to weather.  Our soffits are enclosed, like so: (picture from )   So, do I need to protect any wires which reach into the soffit, such as would power the pictured light?  Or should I use wire rated for exterior use?  I'm also plotting some Cat 5e runs of a similar nature, should those be protected/exterior as well?


$ z = 1 + 2i $ - Prove that $ z^n \notin \mathbb{R} $

$$ z = 1 + 2i \ (complex \ number) \\ z^n = a_n + b_ni \ (a_n, b_n \in \mathbb{Z}, n \in \mathbb{N}^*) \\ We \ know \ that: \ b_{n+2} - 2b_{n+1} + 5b_n = 0 \\ a_{n+1}=a_n-2b_n \\ b_{n+1}=b_n+2a_n $$  Prove that $ z^n \notin \mathbb{R} $  What I tried:  We know that $ b_{n+2} - 2b_{n+1} + 5b_n = 0$  If $ z^n \in \mathbb{R} $ it means that $ b_n = 0 $  So,  $ b_{n+2} - 2b_{n+1} = 0 $ and I tried to get a contradiction but I can't because I get $ -3b_n = 0 $.  How can I solve this problem? Thank you!


I've come across this a few times, the most recent being this chain:      404   If it was just closed, okay, that would make some sense.  But deleted?  It makes the marked-as-duplicate closing of no use to anyone.  Why is this allowed by SE/is this a bug?


I want to show that, if $k$ is an algebraically closed field,   $k[x,y,z]/<y-x^2,z-x^3> \simeq k[x]$ and I wanted to use that, as $x^3,x^2 \in k[x]$, then $$k[x,y,z]/<y-x^2,z-x^3>\simeq K[x][y,z]/<y-x^2,z-x^3>\simeq k[x],$$ by using (1) in the last isomorphism, where   (1): Let $R$ be an integer domain and $r_1,\ldots,r_n \in R$.   Then  $R[x_1,\ldots,r_n]/<x_1-r_1,\ldots,x_n-r_n> \simeq R$  But I don't know if (1) is true.


Computer won't boot up without a password and I never assigned one

I have this problem but I cannot sign on to my computer, because I have no idea what password windows 10 is looking for, and it will not boot up without one. K Barbero


How to List Unmounted partition of a harddisk and Mount them?

How to list the disk partition when they are unmounted?  And how to mount them through terminal?


redirect awk exec results to another folder

Trying to capitalize the content of the files that match the filename pattern "_base.txt"; then output the results to another folder with the original filename plus the "_cap.txt" in the end.  I plan to do this through 3,000 files. So I am testing it on a few files at the moment.  First I was able to get the content capitalized. But all output results were not redirected.   BASE="/home/dir/input/" find "$BASE" -type f -iname "*.txt" -exec awk '{print toupper($0)}' {} +    Then I added the following, which allowed me to output to a new filename ended with "_cap.txt"  BASE="/home/dir/input/" find "$BASE" -type f -iname "*_pv_bind_basefile.txt" -exec awk '{print toupper($0) >> (FILENAME "_cap.txt")}' {} +     The problem showed up when I try to output to a specific folder  BASE="/home/dir/input/" OUT_FOLDER="/home/dir/output/" find "$BASE" -type f -iname "*_pv_bind_basefile.txt" -exec awk '{print toupper($0) >> ($OUT_FOLDER FILENAME "_cap.txt")}' {} +   I got the following error message     awk: illegal field $(), name "OUT_FOLDER"  input record number 1, file   /home/dir/input/TAB1.a1.001.txt  source line number 1   I tried several iterations to output the files and failed miserably after a few hours...It must be some simple thing that I overlooked or not knowing how to do it. Any suggestions would be highly appreciated. Thank you.


When I calculate an area with area measure in QGis, it gives as a result values of area 44% more area than in reality, any idea why?


How to vertically align both text and image middle of div?

It's part of my blog's logo. I have logo image and text inside the div. Now, the image is aligned middle but the text is not in the middle of the div. How can I do this without using margins? Here's my code:
            PORTFOLIO


How can I mimick the listing caption style for my custom "Listing (cont.)" caption?

I have the following LaTeX code which works fine:  \documentclass[12pt,a4paper]{article} \usepackage[a5paper]{geometry}% just for the example \usepackage[utf8x]{inputenc} \usepackage{listings} \usepackage[labelfont=bf, font=small]{caption} \usepackage[framemethod=tikz]{mdframed}   \lstset{ breaklines=true, breakatwhitespace=false, xleftmargin=1em, frame=single, numbers=left, numbersep=5pt, }  \newcommand\mylstcaption{}  \surroundwithmdframed[ hidealllines=true, middleextra={   \node[anchor=west] at (O|-P)     {\lstlistingname~\thelstlisting\  (Cont.):~\mylstcaption};}, secondextra={   \node[anchor=west] at (O|-P)     {\lstlistingname~\thelstlisting\  (Cont.):~\mylstcaption};}, splittopskip=2\baselineskip ]{lstlisting}  \begin{document}  \renewcommand\mylstcaption{Example listing of code} \begin{lstlisting}[language=C, caption=\mylstcaption, label=lst:c1]  struct safe_buffer { struct list_head node;  /* original request */ void    *ptr; size_t  size; int direction;  /* safe buffer info */ struct dmabounce_pool *pool; void    *safe; dma_addr_t  safe_dma_addr; };  struct dmabounce_pool { unsigned long   size; struct dma_pool *pool; #ifdef STATS unsigned long   allocs; #endif };  struct dmabounce_device_info { struct device *dev; struct list_head safe_buffers; #ifdef STATS unsigned long total_allocs; unsigned long map_op_count; unsigned long bounce_count; int attr_res; #endif struct dmabounce_pool   small; struct dmabounce_pool   large;  rwlock_t lock;  int (*needs_bounce)(struct device *, dma_addr_t, size_t); };  #ifdef STATS static ssize_t dmabounce_show(struct device *dev, struct device_attribute *attr, char *buf) { struct dmabounce_device_info *device_info = dev->archdata.dmabounce; return sprintf(buf, "%lu %lu %lu %lu %lu %lu\n", device_info->small.allocs, device_info->large.allocs, device_info->total_allocs - device_info->small.allocs - device_info->large.allocs, device_info->total_allocs, device_info->map_op_count, device_info->bounce_count); }  static DEVICE_ATTR(dmabounce_stats, 0400, dmabounce_show, NULL); #endif  \end{lstlisting}  \end{document}   Part of the result looks like:  page 1    page 2    Now I would like to have similar looking captions (same font size etc.) which is currently not the case.


Why doesn't the momentum of the system change after an inelastic collision?

What I know:  Wen an inelastic collision takes place the momentum of the two objects before the collision: m1 * v1 + m2 * v2 is equal to the momentum of the objects after the collision: (m1 + m2) * u  But the energy in the system gets a bit lower because some energy gets lost in warmth.  Here comes the question:  If something is warmed up, the particles in it are just getting faster, right? Faster particle means higher momentum, so where does the increase in momentum for the particles in the object warmed up in this case come from? If the momentum came from the colliding objects, the momentum in the system would not stay the same, pretty much like the energy. But it does. This really blows my mind.  Maybe I'm just being dumb but this vector vs scalar think and other mathematical approaches are totally logical to me. The thing I described in the question still blows my mind anyway.  (Sorry for my bad English, I'm a foreign speaker)


I know $\int_0^{+\infty}\sin(x^2)\ \mathrm dx$ converges, but $\sum\limits_{i=1}^{\infty}\sin(i^2)$ diverges. How to prove it?


How to make custom shortcuts to open or create any app

I want to know the technique of making custom keyboard-shortcuts to open or create any app.


Removing the TK icon on a Tkinter window

How to remove tkinter icon from title bar in it's window


How do I use reflection to configure all implementations of interface for DI as IOptions?

Introduction  I'm using IOptions<> in ASP to provide configuration to services. Currently I have to setup each POCO individually. I would like to do this in a generic way.  I would like to use some sort of reflection to automaticly configure all POCO's that are used for configuration injection with IOptions. Thus avoiding calling the services.Configure<Poco>() for each class.  The working setup  My appsettings.json file.  {   "DemoOption": {     "OptionOne": "hello",     "OptionTwo": "world"   } }   POCO for configuration section:  public class DemoOption {     public string OptionOne { get; set; }     public string OptionTwo { get; set; } }   Enables me to do this:  public void ConfigureServices(IServiceCollection services) {     services.Configure<DemoOption>(configuration.GetSection(nameof(DemoOption))); }   And use it like this:  public class MyService {     public IOptions<DemoOptions> _options { get; set; }      public MyService(IOptions<DemoOptions> options)     {         _options = options;     } }   What I've got this far  To use reflection I create and add an IOption interface to my POCO class:  public class DemoOption : IOption // Added empty IOption interface {     public string OptionOne { get; set; }     public string OptionTwo { get; set; } }   This is where I'm stuck. I've gotten all the implementations of the IOptions interface, but I can't figure out how to call the services.Configure() method.  public void ConfigureServices(IServiceCollection services) {     // This actually works and finds all implementations.     var options = AppDomain.CurrentDomain.GetAssemblies()         .SelectMany(x => x.GetTypes())         .Where(x => typeof(IOption).IsAssignableFrom(x) && !x.IsInterface && !x.IsAbstract)         .Select(x => x).ToList();      // This does not work     foreach (var o in options)     {         // What should I write here?         services.Configure<o>(configuration.GetSection(nameof(o)));     } }   All help appriciated.


Tag synonym suggestion textbox is overlapped by "Suggest" button

Tag synonyms suggestion textbox is overlapped by Suggest button    Example  (requires 2500+ reputation), also reproduced the same on Stack Overflow in Russian. I don't have other site accounts where I have 2500+ reputation to be sure that it affects other communities than Stack Overflow plus localized versions.  All major browsers on Windows have this issue: Chrome, Firefox, Edge, IE.


Article 'the' use in front of television

Use of  ' the' before television???????~ above 1st photo from use of 'the' is different from 2nd photo please solve my question


Negative Lookahead in RegExp constructor

I am new to javascript and regular expressions.So sorry if this question looks silly.  I want to use negative lookahead to find last matched word in a string. Pattern is dynamic i.e. it may change.  Ex Find "foo" in "this foo is not same foo" here regex should return index of last "foo". To find it I used foo(?!.*foo) negative lookahead. But I need to keep "foo" in variable so that i can find other pattern also.   I am trying to use RegExp() constructor to use variables but unable to find ways in which i can use negative lookahead syntax.So is there any way to use negative lookahead in RegExp constructor ? If yes, what is it ?


Choice of tense and meaning in "My friend considered going to an event where X came (had come?)"

My friend considered going to an event to see X. Now if I wanted to convey a similar meaning, which of the sentences below would you suggest I use? And what's the difference between the two?  My friend considered going to an event where X had come.  My friend considered going to an event where X came.


I use the following mystic TeX so as to display the Landau's notations for big and small O.  There is one partial solution to improve the scriptscriptstyle so as to not use a small o : see the secund answer below. The problemen with \smallOBis is the wrong spacing, contrary to \smallO. How can I do this ?  % Sources : %     1) http://forum.mathematex.net/latex-f6/bonnes-commandes-de-base-t12278.html %     2) http://tex.stackexchange.com/questions/30944/mathcalo-and-font-size  \documentclass{article}     \usepackage{amsmath}     \usepackage{amsfonts}     \usepackage{amssymb}      \usepackage{graphicx}      \newcommand{\bigO}[1]{\ensuremath{\mathop{}\mathopen{}\mathcal{O}\mathopen{}\left(#1\right)}}      \newcommand\smallO[1]{         \mathchoice             {% \displaystyle                 \ensuremath{\mathop{}\mathopen{}{\scriptstyle\mathcal{O}}\mathopen{}\left(#1\right)}             }             {% \textstyle                 \ensuremath{\mathop{}\mathopen{}{\scriptstyle\mathcal{O}}\mathopen{}\left(#1\right)}             }             {% \scriptstyle                 \ensuremath{\mathop{}\mathopen{}{\scriptscriptstyle\mathcal{O}}\mathopen{}\left(#1\right)}             }             {% \scriptscriptstyle                   \ensuremath{\mathop{}\mathopen{}{o}\mathopen{}\left(#1\right)}             }     }      \newcommand\smallOBis[1]{         \mathchoice         {% \displaystyle             \scriptstyle\mathcal{O}\left(#1\right)         }         {% \textstyle         \scriptstyle\mathcal{O}\left(#1\right)         }         {% \scriptstyle         \scriptscriptstyle\mathcal{O}\left(#1\right)         }         {% \scriptscriptstyle         \scalebox{0.8}{$\scriptscriptstyle\mathcal{O}$}\left(#1\right)         }     }   \begin{document}  \[     \renewcommand{\arraystretch}{1.2}%     \begin{array}{llll}          \textbf{Style}            & \verb!\bigO!         & \verb!\smallO!                          & \verb!\smallOBis!         \\ \hline         \verb!\displaystyle!      & \displaystyle      \bigO{\frac{1}{n}}         & \displaystyle      1 + \smallO{\frac{1}{n}} - 2 & \displaystyle      1 + \smallOBis{\frac{1}{n}} - 2         \\         \verb!\textstyle!         & \textstyle         \bigO{\frac{1}{n}}         & \textstyle         1 + \smallO{\frac{1}{n}} - 2 & \textstyle         1 + \smallOBis{\frac{1}{n}} - 2         \\         \verb!\scriptstyle!       & \scriptstyle       \bigO{\frac{1}{n}}         & \scriptstyle       1 + \smallO{\frac{1}{n}} - 2 & \scriptstyle       1 + \smallOBis{\frac{1}{n}} - 2         \\         \verb!\scriptscriptstyle! & \scriptscriptstyle \bigO{\frac{1}{n}}         & \scriptscriptstyle 1 + \smallO{\frac{1}{n}} - 2 & \scriptscriptstyle 1 + \smallOBis{\frac{1}{n}} - 2     \end{array} \]  \end{document}


setup apache www directory for multiple users over sftp

I have standard Ubuntu 16.04 droplet over digitalocean with LAMP stack. By default I have one user with root privileges (for admin use). I access any directory from root through ssh like with filezilla or netbeans. It all works fine as it should upto this.   I need more users created so that I can configure them to be able to access a particular vhost directory say like /var/www/html/domain2.com  or probably only /var/www/html/*  Also I need to be sure that doing so will not affect any Apache related permissions on folders and files. Say if I create a folder say uploads from user1 and www-data user cant read or write into that folder uploads.  How can I do this ?


Does anyone know the book where it has slaves and people with powers, a slave girl gets to know the prince but he doesn't know who she is, they have an arena where the people with power (special abilities) fight and she gets chosen to serve at the match and tries to avoid the prince but then she falls in the pit and her powers manifest and the prince is in Awe etc? I've been looking forever!


Visiting Canada and back on WT/WB admission

Is it possible to go for a quick visit to Canada while the US before going back to one's home country flying from the US ? Would one be denied re-entry even if the stamp on the passport is still valid ? Cheers, E


error: linker command failed with exit code 1 (use -v to see invocation) c++ clion

Im using c++. Does anyone know how i can fix this? Undefined symbols for architecture x86_64: "Template::Template(std::__1::basic_string<char, std::__1::char_traits, std::__1::allocator >, int)", referenced from: _main in main.cpp.o ld: symbol(s) not found for architecture x86_64 clang: error: linker command failed with exit code 1 (use -v to see invocation) basically writing a merge sort algorithm main: int main() {   int SORT_MAX_SIZE = 16;   int userNumInput;   std::string userDataType;   std::cout << "What type of data would you like to enter options: int, string "                "or Dollar objects" << std::endl;   std::cin >> userDataType;   std::cout << "Please enter the number of elements you would like to enter"             << std::endl;   std::cin >> userNumInput;   if (userNumInput > SORT_MAX_SIZE) {     std::cout << "Please enter the number of elements less then 16"<< std::endl;     std::cin >> userNumInput;   }   Template createTemp = Template(userDataType, userNumInput);   int userData; //todo:how to change this to a different data type   for(int i = 0; i < userNumInput; i++) {     std::cout << "Please enter an element for the spot " + std::to_string(i) <<               std::endl;     std::cin >> userData;     createTemp.userArray[i] = userData;   }   RecurMergeSort(createTemp.userArray, userNumInput);   std::cout << "Sorted Array:" << std::endl;   print(createTemp.userArray, userNumInput);   return 0; }  template class: #include "Template.h" #include "Dollar.h"  Template::Template(const std::string d, int a) {   dataType = d;   numInput = a; }  void Template::createTemplate() {   //create an array based on the information provided above   if (dataType == "int") {     int userArray[numInput];   } else if (dataType == "Dollar objects") {     Dollar userArray[numInput];   } else if (dataType == "string") {     std::string userArray[numInput];   } }


How could McGonagall afford a Nimbus 2000 on a teacher's salary?

Seems like the best piece of equipment for a sport that is played professionally and has such a big public following probably costs quite a bit. Did McGonagall buy it in a private capacity or perhaps with funds available to her as head of house?


Why is ROC AUC equivalent to the probability that two randomly-selected samples are correctly ranked?

I found there are two ways to understand what AUC stands for but I couldn't get why these two interpretations are equivalent mathematically.   In the first interpretation, AUC is the area under the ROC curve. Picking points from 0 to 1 as threshold and calculate sensitivity and specificity accordingly. When we plot them against each other, we get ROC curve.  The second one is that the AUC of a classifier is equal to the probability that the classifier will rank a randomly chosen positive example higher than a randomly chosen negative example, i.e. P(score(x+)>score(x−)).  (from )


please I tried to find counterexamples to see that $l^p$ is not norm with $p<1$ in the triangle inequality but I have problems with convergence when I choose some successions. Thanks.


how to recover 10 days back data in ubuntu 16.04

how to recover data of deleted files in Ubuntu, i have tried test-disk to recover my file but the file is empty so it will be good to recover 10 days back data to restore it


An align environment for too many lines of equations

It seems that if I write too many lines of equation within an align environment after some text, that environment will not span more than one pages, and leave blank at the bottom half of the previous page. How can I make it span more than one pages? Thanks.


C# - Calculating time difference in minutes

I have got the following code:  DateTime start = DateTime.Now; Thread.Sleep(60000); DateTime end = DateTime.Now;   and I would like to calculate the difference in minutes between start and end. How am I supposed to do it? For the example above, the result should be '1'.  Thanks in advance!


How can I  de-spawn mobs in Minecraft multiplayer?

I ask the owners of all the servers I go to, and none of them tell me how to de-spawn mobs. I'm the only admin in my server, and there are a lot of magma cubes. I want to know how to get rid of them.


what are the project related scenarios in which we have to make a class Final in java?

What will be the scenario in a real project to specially use the Final Class?  P.S: Final Class is for preventing the class from sub-classing that class.


How to SSH into my Android Phone's command prompt

I have a non-rooted Android phone with the  app installed. I can run ifconfig on the phone's terminal and see the IP address of wlan0, and I can ping the phone's IP from the terminal on my computer. Is it possible to SSH into it from a computer on the same network? If so, what would the username and password be?  I know the openssh package is installed on the phone: apt list | grep openssh returns openssh/stable,now 8.1p1-4 arm [installed].  I can also run the ssh command in the phone's terminal (Termux).  Are there any extra packages I would have to install via pkg or apt? Please let me know, anything helps.


Why the subsurf and smooth are not working in my model?

I try to smooth my model. I have tried with Surb surf and Smooth in Modifier but nothing.    Thank you so much  The ears are completed circle in Edit mode.   When I redered the ears are....  Why?  Many thanks


I have free space on the disk but I can't add that space to the ubuntu partition, gparted doesn't let me resize the ubuntu partition at all.  I'm running the livecd 14.04 LTS, my ubuntu version is 15.04  gparted screen shot   Edit:  sda1 and sda2 are the windows partition sda3 is my data partition  I want to shrink my data partition (sda3) by around 50gb and add that 50gb to my ubuntu partition (runnning low on space frequently)  I can't add that free space to the sda4  Current state:   Solved:  The free spaces must be next to the partition you want to resize, and all the partitions must not be mounted, even the swap partition (select swapoff)


I have a requirement to send a specific report as an attachment on schedule basis.  So, i have created a schedule class with future annotation to send.But now when i'm trying to setup apex class I'm getting below error.     Error Message Methods defined as TestMethod do not support getContent   call   Apex class:  global class CallSubscriptionReportScheduler { @future(callout=true)     public static void SentSubscriptionData()     {         Id userdetail=[Select id from user where email='xyz@gmail.com'].id;         OrgWideEmailAddress[] owea = [select Id from OrgWideEmailAddress where Address = 'info@xyz.com' Limit 1];         ApexPages.PageReference report = new ApexPages.PageReference('/00O6F00000CGpHH?csv=1');         Messaging.EmailFileAttachment attachment = new Messaging.EmailFileAttachment();         attachment.setFileName('Data_Report.csv');         attachment.setBody(report.getContent());         attachment.setContentType('text/csv');         Messaging.SingleEmailMessage message = new Messaging.SingleEmailMessage();         message.setFileAttachments(new Messaging.EmailFileAttachment[] { attachment } );         message.setSubject('Data');         message.setPlainTextBody('The report is attached.');         message.setOrgWideEmailAddressId(owea.get(0).Id);         message.setReplyTo('sfdcadmin@xyz.com');         message.setTargetObjectId(userdetail);         message.setSaveAsActivity(false);         Messaging.sendEmail( new Messaging.SingleEmailMessage[] { message } );      } }   Test class:  @isTest public class TestWeeklySubscriptionData {     public static String CRON_EXP = '0 0 1 ? * MON';     static testmethod void testsubscription() {                     Test.startTest();             WeeklySubscriptionData uca = new WeeklySubscriptionData();             String jobId = System.schedule('ScheduledApexTest',CRON_EXP,new WeeklySubscriptionData());             Test.stopTest();             // after the testing stops, assert records were updated properly             //System.assertEquals(6, [select count() from Lead where Lead_Type__c='Insurance' AND RecordTypeId ='0126F0000016MZP']);     } }   Could someone help me.


How do you craft command blocks because they are out in MCPE now

Please tell me I really want to know help me here


Mobile web view displays active tab as white rectangle

The mobile web view of several Stack Exchange sites displays the  "active tab" as a white rectangle:    Observed with Safari on OS X and Mobile Safari on iOS,   on , , , not on .


pdf of a product of two independent Uniform random variables

Let $X$ ~ $U(0,2)$ and $Y$ ~ $U(-10,10)$ be two independent random variables with the given distributions. What is the distribution of $V=XY$?   I have tried convolution, knowing that   $$h(v) = \int_{y=-\infty}^{y=+\infty}\frac{1}{y}f_Y(y) f_X\left (\frac{v}{y} \right ) dy$$  We also know that $f_Y(y) = \frac{1}{20}$,    $$h(v)= \frac{1}{20} \int_{y=-10}^{y=10} \frac{1}{y}\cdot \frac{1}{2}dy$$ $$h(v)=\frac{1}{40}\int_{y=-10}^{y=10} \frac{1}{y}dy$$  Something tells me, there is something weird here since it is discontinuous at 0. Please help.


Justifying an Assumption Made While Deriving the Method of Variation of Parameters

I never fully understood the derivation of the method of variation of parameters. Consider the simple case $$y'' + p(x)y' + q(x)y = f(x)\,.$$  The homogeneous solution is $y_h=c_1y_1+c_2y_2$ and the particular solution that we guess is $y_p =u_1y_1+u_2y_2$ for some function $u_1(t)$ and $u_2(t)$. Next we take derivatives of the particular solution and substitute those back into the original ODE.   The part done next is the part I don't quite see the justification for. We assume that our functions $u_1$ and $u_2$ will satisfy the constraint $$u_1'y_1 + u_2'y_2=0\,,$$  and this particular constraint will yield a cleaner result when looking at $y'_p$: $$u_1'y_1'+u_2'y_2'=f(x)\,.$$  At least in the textbook I'm looking at, the justification for assuming that $u_1$ and $u_2$ satisfy $u_1'y_1 + u_2'y_2=0$ is simply omitted. How do we know that the solutions we're after satisfy that constraint? All other sources I look at just say something like, "okay we are going to impose this constraint. Now moving on ..."  Could someone give me a proper explanation as to why we can make this assumption?


Is it possible to put the output of one command into the middle of another

I am asking if there is a way to automatically put the output of a command into the middle of another.  multimon-ng outputs: ZCZC-WXR-TOR-029037+0030-1051700-KEAX/NWS and i want that output to get sent to where i put three question marks : python2.7 easencode.py -z ??? output.wav  can i do this with pipe and if so, how?


Is there an analogue of Lebesgue’s Dominated Convergence Theorem for a net $ (f_{\alpha})_{\alpha \in A} $ of measurable functions?

Is there an analogue of Lebesgue’s Dominated Convergence Theorem for a net $ (f_{\alpha})_{\alpha \in A} $ of measurable functions defined on a measure space $ (\Omega,\Sigma,\mu) $, where the index set $ A $ (assumed to be directed) is not necessarily $ \mathbb{N} $? That is, if   $ (f_{\alpha})_{\alpha \in A} $ converges pointwise almost everywhere to a measurable $ f $, there exists a measurable $ g $ such that $ |f_{\alpha}| \leq |g| $ almost everywhere for each $ \alpha \in A $, and $ \displaystyle \int_{\Omega} |g| ~ \mathrm{d}{\mu} \leq \infty $,   then does $ \displaystyle \lim_{\alpha \in A} \int_{\Omega} f_{\alpha} ~ \mathrm{d}{\mu} = \int_{\Omega} f ~ \mathrm{d}{\mu} $?


Holomorphic function with constant absolute value

Show that if a holomorphic function has a constant absolute value, it must be a constant.   Suppose $f(z)=u(z)+iv(z)$ is holomorphic (where $z=x+iy$ is complex), and that $(u(z))^2+(v(z))^2=C$ for some constant $C$.   We have $\dfrac{\partial((u(z))^2+(v(z))^2)}{\partial x}= 0$. Applying the chain rule, we find that $$u(z)\cdot\dfrac{\partial u(z)}{\partial x} + v(z)\cdot\dfrac{\partial v(z)}{\partial x} = 0$$  Similarly, $$u(z)\cdot\dfrac{\partial u(z)}{\partial y} + v(z)\cdot\dfrac{\partial v(z)}{\partial y} = 0$$  Using the Cauchy-Riemann differential equations satisfied by any holomorphic function: $$u(z)\cdot\left(-\dfrac{\partial v(z)}{\partial x}\right) + v(z)\cdot\dfrac{\partial u(z)}{\partial x} = 0$$  We can write as a matrix form:  $$\begin{pmatrix} u(z) & v(z) \\ v(z) & -u(z)\end{pmatrix}\begin{pmatrix}\frac{\partial{u(z)}}{\partial{x}}\\\frac{\partial{v(z)}}{\partial{x}}\end{pmatrix} = 0$$  For values of $z$ such that the matrix $A=\begin{pmatrix} u(z) & v(z) \\ v(z) & -u(z)\end{pmatrix}$ is invertible, we get $\dfrac{\partial{u(z)}}{\partial{x}}=\dfrac{\partial{v(z)}}{\partial{x}}=0$. But what can we do for values of $z$ such that the matrix $A$ is not invertible?


Move files from multiple folders all into parent directory with command prompt

I have multiple .rar files in multiple folders like this:    C:\Docs\Folder1\rarfile1-1.rar C:\Docs\Folder1\rarfile1-2.rar C:\Docs\Folder1\rarfile1-3.rar    C:\Docs\Folder2\rarfile2-1.rar C:\Docs\Folder2\rarfile2-2.rar C:\Docs\Folder2\rarfile2-3.rar    C:\Docs\Folder3\rarfile3-1.rar C:\Docs\Folder3\rarfile3-2.rar C:\Docs\Folder3\rarfile3-3.rar     I want to move all of the .rar files to the parent directory 'C:\Docs'. I have a lot more than 3 folders, so I was thinking of making a batch file or something. What would be the commands to do this? Thanks


Why are thermodynamic potentials minimised?

Why is it that, at equilibrium, certain potentials are minimised? That is, for a system at constant temperature and pressure, the Gibbs free energy is minimised, and for fixed volume and temperature, the Helmholtz free energy is minimised. I haven't been able to find a reason for this.


How can I set it so that the selected bone in the photo will move the entire rig with it?  Essentially, the selected bone acts like a parent for all the bones in the rig.


I am trying to figure out if it is possible to do a 301 redirect for a particular IP address (in this case brute force password bot).  I want to send this guy to a project honeypot link rather than just banning the IP.  Something like the following?  RewriteEngine On RewriteCond %{REMOTE_ADDR} !^xxx\.xxx\.xxx\.xxx Redirect 301 ^/adminlogin/$ http://www.example.com/honeypotlink.php


Border of control flickers in windows forms in C#

In my custom control file:  namespace myApp {     public partial class MyStatusBar : Label {        public MyStatusBar () {           InitializeComponent ();           this.BorderStyle = System.Windows.Forms.BorderStyle.FixedSingle;           this.Dock = DockStyle.Bottom;       }        protected override void OnPaint (PaintEventArgs pe) {           base.OnPaint (pe);           pe.Graphics.DrawRectangle (new Pen (Color.Azure), ClientRectangle);                }     } }   In my form:  MyStatusBar mStatusBarLabel = new MyStatusBar ();  public MCADDrg() {      InitializeComponent ();       this.SetStyle (ControlStyles.OptimizedDoubleBuffer, true);      this.SetStyle (ControlStyles.AllPaintingInWmPaint, true);      this.SetStyle (ControlStyles.UserPaint, true);      this.SetStyle (ControlStyles.SupportsTransparentBackColor, false);      this.SetStyle (ControlStyles.Opaque, false);      this.SetStyle (ControlStyles.OptimizedDoubleBuffer, true);      this.SetStyle (ControlStyles.ResizeRedraw, true);       splitContainer1.Panel2.Controls.Add (mStatusBarLabel);         splitContainer1.Panel2.MouseMove += Panel2_MouseMove; }  void Panel2_MouseMove (object sender, MouseEventArgs e) {     if( splitContainer1.Panel2.ClientRectangle.Contains(e.Location))         mStatusBarLabel.Text = "X = " + e.X + " Y = " + e.Y;     } }     How can I get rid of this? I tried some other posts answer. But didn't work for me. Assume that (in fact) I'm a newbie.


I recently installed Ubuntu 19.10. on my digital slave.   From official repositories, there is no chance of an installation of Arduino IDE. Please confirm.


Which Geometry Workflow should i follow Tris,quads or Ngons

I am pretty confuse that how i go with the gemoetry flow for my model, I personaly follow quads but the problem is that going with quads geometry adds a  extra triangle and verts which is not optimal for game in term of optimizng  game assets. So which geometry workflow to be followed for certain scenario or ones have to stick with quads for better geometry


How do I get the path to a resource in the model? I need to store it in the database and would like the same url as you get from resourcename_path(resource)


$$1+ \frac12 + \frac14+\dots+\frac1{2^n}$$  To find the sum of the equation you have to find $n$, the number of terms in the geometric sequence and I don't know how...  The answer in the text book is $2-\frac1{2^n}$.


Regardless of what viewport mode I'm in, everything is completely invisible. For the record I am using Blender 2.80 and this started after a graphics driver update. I've tried reinstalling blender 2.8 and it didn't help. However, 2.9 does not have this problem. But, there is an addon that has not been updated to 2.9 that I am in need of for my current project. Edit: 2.9 no longer works either


Is it possible to downgrade my Ubuntu 16.04 installation to 14.04?   I have recently upgraded my Ubuntu 14.04 to Ubuntu 16.04, but it is not compatible with my laptop. Most often I have to face lagging. Is there any official way to get back my Ubuntu 14.04?


What will happen if the output from a NOT-gate injected- BACK to its OWN input?

Not-gate, if get a 0(Off) input, it gives an 1 (On) output. And if get a 1 (On) input, gives-back a 0(Off) output.  Now, if-I could bring the output back to the input of the not-gate, then what will happen? If the gate is getting a 1 input, it is giving a 0- output, and then if it is getting a 0 input, it is giving an 1 output.  The situation sounds-like a physical-model of a "self-contradiction" (self- false)  (like when fever-attacked kid-Bertrand Russel waiting to be april-fooled by his brother, taking preparation against all possible tricks,  Bertrand Russel's brother made Bertrand an april-fool by doing "no-april-fool" at all; and if Bertrand's brother uses any april-fool trick, Bertrand will Not be april-fooled, and if Bertrand's brother use no april fool that means Bertrand hasbeen april-fooled by-his brother).  Now, what will-be happen in case of the real hardware called a NOT gate?  I ASSUME the possibilities;   the gate will always remain as 0 (off)-output . the gate will always remain as 1(on)-output . The gate will be "PULSATING"; once it will 1 output; at the next-moment, after receiving that 1(on)-signal it will give-out a Zero (off) signal, and the cycle will run on and on. The frequency of this oscillation will depend on physical-characteristics of circuit component. the circuit will be get-damaged ( due to some anomalous current, overheating, etc) and soon permanently stop working.   Will something happen within-these assumptions?   PS. I'm thinking about this-problem from my schooldays, but since yet I do-not know, how to assemble a not-gate in a circuit, from-where they could be bought, etc; I yet could-not test it experimentally.


Professor not replying to my email. Why?

I wrote an email to my professor yesterday to ask makeup exam. But he doesn't reply until now.  Test was taken a week ago. But, I can't take it because of family emergency(my grandfather passed away) and sudden move into new room (my hostfamily kicked me out without prior notice.I think the reason is outbreak of covid-19, and I'm Asian). Those are my nightmare!   In your opinion, can he admit my makeup test? and why doesn't he reply my email...?


How can I find the expected value and variance of the Wilcoxon Sum of Ranks test?

Given two samples $X$ and $Y$ where $X$ has $X_1,...,X_n$ independent r.v's with unknown distribution $F$ and $Y$ has $Y_1,...,Y_m$ independent r.v's with unknown distribution $G$, find the expected value and variance of  $$R=\sum_{i=1}^{n+m}iA_i$$ (where $A_i$ is $1$ iff the $i$th smallest value of $X$ and $Y$ belongs to $X$ and is zero otherwise) assuming that $F=G$  If $F=G$ then I believe that implies that we have $n+m$ independent and identically distributed random variables, and therefore $\mathbb{P}(A_i=1)=\frac {n}{n+m}$ making $\mathbb{E}[R]=\frac {n(n+m+1)}{2}$. The variance causes me more trouble because $R$ is a sum of random variables and I am therefore not sure if using $\mathbb{E}\left[\binom{R}{2}\right]$ to calculate $\mathbb{E}[R^2]$ would be a good idea or if I need to expand $R^2$ and then use linearity of expectation.   I am not so certain about either of these results and even if they were correct, I am not satisfied with the way I obtained them. Is there a more rigorous and systematic way of getting to these answers? What if I had had to compute the expected value and variance of $R$ when $F\ne G$?  I would like to know how to obtain the $\mathbb{P}(A_i=1)$ so that I can calculate $\mathbb{E}[A_i]$ and consequently the expectation of $R$. I would like to do this formally, not just by saying that "because all the random variables in $X$ and $Y$ are equally likely to be the $i$th smallest, then $\mathbb{P}(A_i=1)=\frac {n}{n+m}$". I feel like this argument is a little hand wavy and dismissive, at least I would like to know if it could be derived from identities or other formulas.


Nautilus context menu option to create new file

I use  3.10.1 on  7.0 GNU/Linux. In context menu, there is no such option like create new file/document. So, I want to add such an option (which may work like that of existing option: New folder).   Is there any nautilus plug-in available? or I have  installed. So, what command/script I can use for this purpose?   Further I am also interested in featuring options like: New  Document, New  Document, etc.


2.8 remove doubles has changed to Merge by Distance

I'm using 2.8  Is there no default short key combo to remove duplicates now?  I see that I can quickly add a shortcut for it - but it seems to me that it's something that should be in the mesh (w) menu. I use it all the time.  Thanks!


How to understand intrinsic property of surfaces?

This semester began to study classical differential geometry, some conceptual things keep confusing me. When I saw Gauss's Egregium theorem, I didn't feel any special place in this theorem. I thought that intrinsic geometry studys invariant properties of a surface completely out of Euclidean space. I've heard that the quantity that is completely determined by the first fundamental form is the intrinsic quantity, but the first fundamental form seems to me to just relate every point on the surface to the surrounding Euclidean space(keep inner product unchanged). That seems not the property of the surface out of Euclidean space, right? In addition, how do we know the first fundamental form of a surface if we don't leave the surface, ultimately all of the studies of surfaces still has to embed surfaces in surrounding space? I know there must be many fallacies in my understanding, please help me correct... thanks!


Can a group be non-empty by definition of 'group'?

By the definition of a group, "A group is a set combined with a binary operation".  By this definition, would a non-empty set constitute as being a group? By virtue of the definition of what a group is, a non-empty should constitute as being a group.  Can someone confirm?


Are there any other tools wizards can use as they would a wand?

Is wands the only tool used for spellwork? Are there any wizards that use staffs, like Gandalf, in Harry Potter? Is there any mention of other tools you can use to perform spells?


Euro symbol does not show up when defined as a unit for `siunitx`

I am trying to use \officialeuro symbol redefined as a unit for siunitx package. LaTeX seems to interpret the unit as letter instead of a symbol \documentclass{book}  \usepackage{eurosym}  \usepackage{siunitx} \DeclareSIUnit{\euro}{\officialeuro}  \begin{document}          $\SI{110}{\kilo\euro}$      \end{document}


Is ed25519 quantum resistant? I am using ed25519 as a cryptographic primitive for decentralized identity platform, thus this very crucial question.


I forgot my sudo password and I need to change it with the terminal

I have got a computer running Windows 8.1 and Ubuntu and I can't change it via grub.


iPhone 4 locked by it's previous owner iCloud account

I've bought a iPhone 4 of an auction site. When this iPhone got delivered and I turned it on, it asked me for the PIN code of the previous owner and noticed that the iPhone 's language was completly in French.  When trying the most common PIN codes (0000, 1234, 4321, etc...), and all attempts failed (from all the tries, I had to wait an hour to try again....), I decided restoring it in iTunes.  After restoring it in iTunes to the latest supported IOS; 7.1.2, and putting an SIM card into the phone, I had to configure the language and such. After that screen, it asked me to login on the previous owner's iCloud account.  The problem is, I dont know the previous owner of the iPhone.  Can I remove the previous owner's iCloud settings from the phone?


While studying Newtonian mechanics, we are concerned with only three laws of motion that describes force and it's relations. But when we switch to rotational dynamics, we are presented with torque and moment of inertia as being the rotational analogue of force and mass. With no laws other than Newton's laws describing motion of this type. How, did we actually arrived at the idea of torque and moment of inertia from force and other related concepts?


Group Theory. I worked on it . but ı couldn't reach any clear proof

If G is a group of order p^n and N is a normal subgroup of order p where p is prime and n is natural number, then prove that N is contained in the center of G.