I don't know why, its been a while since I've been on blender but I've opened my project and everything in rendered is blue unless this object (that gray guy, he shouldnt be gray) is close I can not see it and it sinks behind the blue. I might just have a box checked somewhere or it might be something dumb. I am using version 2.7.7

I'm having an odd issue - When I try to zoom in on a detail using my MMB, the "camera" in the 3D view seems to be cutting off the exterior surface of my object and showing me the inside instead. I'd expect this behavior, but only when I was much more zoomed in.  If I zoom out a bit (one click on the scroll wheel) then I can see the exterior as I intend.  Is there any way to adjust this behavior?  Thanks!


I need to set the specific size and position for objects in Illustrator. For example, I need to set the size to 100 × 50 mm, but Illustrator automatically sets its size to 100.189 × 50.094 mm. Same thing happens with position.

I am using Adobe Illustrator CS6 to create small images (like icons) for my app so I need pixel precision.  How can I avoid X, Y, W and H properties to have decimals? Can I configure 0 decimals for this properties on my document?  If I use the textboxes with this properties it does right, it increases pixel by pixel, but when draggin with the mouse it uses up to 3 decimals.


I'm not really sure since I'm still new to Linux distros in general

I want to take a screenshot of a whole desktop with Applications Menu selection.How to do this?


I'm traveling to two different American airports before my airport. Because there is a 4-hour connecting time between flights, where would I pass through immigration? Or do I do that on all of them? Thanks.

I'm a British citizen travelling from London Heathrow (LHR) to the Hartford, Connecticut airport, and have a two hour stopover in Newark, New Jersey (EWR) on my itinerary. At what stage would I clear immigration and customs on arriving in the USA?


I'm  trying to retrieve data from my Database but the app kept crashing with an exception java.lang.String com.google.firebase.auth.FirebaseUser.getUid()' on a null object reference    public class SettingsActivity extends AppCompatActivity {     private DatabaseReference mDatabase;     private FirebaseUser mCurrentUser;     FirebaseDatabase database = FirebaseDatabase.getInstance();      @Override     protected void onCreate(Bundle savedInstanceState) {         super.onCreate(savedInstanceState);         setContentView(R.layout.activity_settings);          mCurrentUser = FirebaseAuth.getInstance().getCurrentUser();           mDatabase = FirebaseDatabase.getInstance().getReference().child("Users").child(mCurrentUser.getUid());          mDatabase.addValueEventListener(new ValueEventListener() {             @Override             public void onDataChange(@NonNull DataSnapshot dataSnapshot) {                 Toast.makeText(SettingsActivity.this, dataSnapshot.toString(), Toast.LENGTH_SHORT).show();              }              @Override             public void onCancelled(@NonNull DatabaseError databaseError) {              }         });      } }     This is my MainActivity, If the User is not Registered it will send him to StartActivity where he can either create an account or Login to an existing Account     @Override     public void onStart() {         super.onStart();         // Check if user is signed in (non-null) and update UI accordingly.         FirebaseUser currentUser;         currentUser = mAuth.getCurrentUser();         if (currentUser == null){         sendToStart();         } }      private void sendToStart() {         Intent startIntent = new Intent(MainActivity.this, StartActivity.class);         startActivity(startIntent);         finish();     }     And this is my LoginActivity where Users can login to there existing accounts and return to the MainAcivity   String email = mEmail.getText().toString();                     String password = mPassword.getText().toString();              if (!TextUtils.isEmpty(email) || !TextUtils.isEmpty(password)) {                 signIn(email, password);             }else{                 Toast.makeText(LoginActivity.this, "Please fill the form correctly", Toast.LENGTH_SHORT).show();             }         }     }); }  private void signIn(String email, String password) {     mAuth.signInWithEmailAndPassword(email, password)             .addOnCompleteListener(new OnCompleteListener<AuthResult>() {                 @Override                 public void onComplete(@NonNull Task<AuthResult> task) {                     if (task.isSuccessful()){                         FirebaseUser user = mAuth.getCurrentUser();                          Intent main_intent;                         main_intent = new Intent(LoginActivity.this, MainActivity.class);                         main_intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_CLEAR_TASK);                         startActivity(main_intent);                     }else {                         Toast.makeText(LoginActivity.this, "Login Failed Pls Check your Details and try again", Toast.LENGTH_SHORT).show();                     }                 }             });   Above is my code. Can someone help out, please?

What are Null Pointer Exceptions (java.lang.NullPointerException) and what causes them?  What methods/tools can be used to determine the cause so that you stop the exception from causing the program to terminate prematurely?


difficult question I need help with.  We are asked to show that $n! = \sum_{k=0}^n (-1)^k\binom{n}{k}(n-k)^n$  There is also a hint "try to think of the number of permutations of n elements using inclusion-exclusion"

The successive difference of powers of integers leads to factorial of that power. Here's the formula:     $$\sum_{r=0}^{n}\binom{n}{r}(-1)^r(n-r)^n=n!$$   Can anyone give a proof of this result?  Note: The original question was to prove the more general     $$\sum_{r=0}^{n}\binom{n}{r}(-1)^r(l-r)^n=n!$$   for an integer $l$, which some of the answers address.


How do I add a placeholder into the password field using the Logintoboggan module?

function customization_form_user_register_form_alter(&$form, &$form_state, $form_id) {  $form['account']['pass']['#attributes']['placeholder'] = t('Password'); }   I am trying to set placeholder on password field in registration form.  I seted placeholder on username and email, but on password field won't work...  Any help? Thank you!


I started studying "Measure Theory and Integration" and went through the first section which talks about Lebesgue Outer Measure of a set. All was well until I started with the second section which starts with the definition of Measurable sets :  ** The set $E$ is Lebesgue Measurable if for each set $A$ we have**  $m^*(A)=m^*(A\bigcap E)+m^*(A\bigcap E^c)$  I know the $\leq$ inequality comes from subadditivity.  So it all boils down to showing the $\geq$ inequality.  Though I read the definition and am able to solve questions on the topic. I don't quite understand it intuitively. Any help would be appreciated.  Also give me an example where $\geq$ inequality is not satisfied.   Thank you.

This week I saw the definition of a measurable set for an outer measure.     Let $\mu^*$ be an outer measure on a set $X$. We call $A \subseteq X$ measurable if $$\mu^*(E) = \mu^*(A\cap E) + \mu^*(A^c\cap E)$$ for every $E \subseteq X$.   This is not the first time I've seen this definition. Unlike most other things in mathematics, over time I have gained absolutely no intuition as to why this is the definition.   The only explanation I've ever seen is that a set is measurable if it 'breaks up' other sets in the way you'd want. I don't really see why this is the motivation though. One reason I am not comfortable with it is that you require a measurable set to break up sets which, according to this definition, are non-measurable; why would you require that? Of course, you can't say what a non-measurable set is without first defining what it means to be measurable so I suppose no matter what your condition is, it will have to apply to all subsets of $X$.     Is there an intuitive way to think about the definition of measurable sets? Is there a good reason why we should use this definition, aside from "it works"?


I’m playing unmodded Minecraft on the xbox 360, in survival mode. I have explored the entire map, and found 1 village. The last villager died. What can I do to get villagers back?

I am building an iron farm and have almost completed it, when it struck me! Where do I get the villagers from? The simple answer is, go off and find a village, but I don't really want to be wandering around for miles looking for a village, then have to take them back by some means.  What I was wandering was, is there an easier way?  Thanks


I have noticed people using "myriad" when they mean "uncountable" or simply many.   Is "Myriad" not prevalent in "day to day speech Can it be used for definite but large amount of anything.

The vast majority of the time when I see the word "myriad" it is in a sentence like "He had a myriad of things."  However I don't like the extraneous words so I normally use it like "He had myriad things." My boss corrected the latter usage while editing something I wrote.  I averted an argument by simply changing the sentence to "He had various things." but was I incorrect?


My goal is very simple to describe: I want all JS from wp-includes to be served via my CDN (cloudfront to be specific). This just means I need to change the domain from:  Should be served from:   I know this question resembles this:   But the answer to that Q suggested eventually to go over each and every JS in the folder and deregister/register them...This seems like a lot (!) of work to the point it's not really feasible to be done...  Is it really impossible to be achieved easily ? For comparison to do the same with wp-content, involves one line of configuration (wp-config.php): define( 'WP_CONTENT_URL', '');  Thanks.

The WordPress Codex points to an extremely simple way to change the URL of the wp-content directory, which is, adding this in wp-config.php:  define( 'WP_CONTENT_URL', 'http://example.com/wp-content');   And that does the job of serving most of the JavaScript and CSS files on my website from the different domain, except two.  http://mywebsite.com/wp-includes/js/comment-reply.js http://mywebsite.com/wp-includes/js/quicktags.js   The reason is very clear — these JavaScript files are served from within the wp-includes directory, which is not affected by the aforementioned rule.  So, is there a similar or simple method to have them served from example.com i.e. the domain of my choice? or is unregistering and enqueuing the scripts from a custom URL (done in functions.php) the only way?


I have an administrative accout with no password yet it still asks for authentication and  it won't except my old password or "user". What should I do?

I'm working on a Ubuntu system, and my client has completely forgotten his administrative password. He doesn't even remember entering one; however it is there.  I've tried the suggestions on the website, and I have been unsuccessful in deleting the password so that I can download applets required for running some files. Is there a solution?


I'm looking for an adapter for my Keyboard piano. I am not sure about the specifications of the original adapter, but I've looked up some online and I've found two adapters that supposedly should fit my keyboard. The problem is that one of them says for the output: 12V 1A while the other is 12V 600mA.   My broken adapter is not original but it says Output: 12V 600mA on it.   Is it very bad if I would use the 1 Ampere adapter?

Power supplies are available in a wide range of voltage and current ratings.  If I have a device that has specific voltage and current ratings, how do those relate to the power ratings I need to specify?  What if I don't know the device's specs, but am replacing a previous power supply with particular ratings?  Is it OK to go lower voltage, or should it always be higher?  What about current?  I don't want a 10 A supply to damage my 1 A device.


I am trying to add a new instance to the Class User to an ArrayList of User. Whenever I run my program however, I keep getting a Null Pointer Exception. I've looked up similar issues on this site but it seems like most problems arise when the ArrayList is never established. However, as you can see from the code below, I establish my list at the top. Are there any other reasons this exception could be thrown when adding to the list? import java.util.ArrayList;  public class Users {     private static Users users;     private ArrayList<User> userList = new ArrayList<User>();      private Users() {         userList = DataLoader.loadUsers();      }      public static Users getInstance() {         if (users == null) {             users = new Users();         }         return users;     }      public ArrayList<User> getUsers() {         return userList;     }      //add get user by ID     public boolean addUser(int userID, String password) {         if(haveUser(userID, password)) {             return false;         }         User user = new User(userID, password);         System.out.println(user.toString());  // I added this to make sure my parameters are being passed in correctly. They are.         userList.add(user);  // This is the line where the NullPointerException is being thrown.         return true;     }      public boolean haveUser(int userID, String password) {         if (userList == null) {             return false;         }         for (User user : userList) {             if (user.getUserID() == userID && user.getPassword().equals(password)) {                 return true;             }         }         return false;     }

What are Null Pointer Exceptions (java.lang.NullPointerException) and what causes them?  What methods/tools can be used to determine the cause so that you stop the exception from causing the program to terminate prematurely?


I currently run MacOS 10.12.4 Sierra on a mid-2011 iMac.  I want to upgrade to 10.13 High Sierra.  On the App Store, the only option (after Sept 24) is 10.14 Mojave.  Where should I go to get High Sierra?  If I go to ,  there are many different download options, but they all are updates, such as 10.13.6.

Sometimes it's hard to search for older versions of macOS & OS X  on the App Store.  This is an attempt to provide the canonical QA for this issue, as per the Meta QA -  I expect it to be modified over time to hopefully become a complete information resource.  How can I get any older version of a Mac OS to be able to run as a VM, or to reinstall on my Mac?


Usually a home router has only one uplink connection, enabling a single internet provider at a time. But suppose I hack my router (ie. installing linux), could I use 2 internet providers then?

We have a broadband line coming into our building which delivers around 8-10Mbps, which is okay but not great. Fiber is available in our area (30-100Mbps) but it's not available where we are just yet.   Is there some way we could connect two lines (which we would take from two different providers so we would have redundancy if one failed) and merge them into one signal which we could distribute?  Is there some sort of setup that can do this?  Of course we have the option of a leased line but for 12Mbps symmetrical upload/download we'd be looking at around £500 per month compared to £15 per month for normal or fiber broadband.  I made a small pseudo flow chat of the setup below:


There are so many questions which have no answers but are solved. What should happen with them?  Why nothing is not good answer:   These questions are displayed in unanswered list. These questions cannot be selected as duplicate. Reading such question is a time spending until you realise that question was resolved. It's annoying.

I'm trying to go through and provide answers to every unanswered question (search "closed:0 answers:0"), somewhat following the spirit that was blogged about at  .  However, I'm finding this much more difficult than it needs to be, as many of the questions have already been answered without the use of an "answer" - but instead, in the form of a comment by either the OP or another poster. I wouldn't mind reading through and skipping these, as long as there was some appropriate action I could take to at least assist with preventing these questions from being seen again from the same query - either by myself or another SO member.  Is there such an appropriate action?  Should we vote to close?  If so, using what reason? Even if I vote to close, what are the chances that 4 other users will also view the question and also vote to close?  (i.e., will my individual vote even do any good?  Is there any report to show recent close votes, so that others may also review and contribute supporting close votes?) Should we post some sort of an answer - even just something to the effect of "this was already answered by the OP's own comment to his answer (above)"? Would something like this be appropriate to flag for moderator attention, and let the moderators deal with it?  (Or would this be considered too trivial?) Should we rename the question title to something standard that can be used in a search exclusion?  (Maybe "SOLVED:"?)  Basically, how can I help to denote questions as "This question is no longer in active search of an answer - though better answers may still be appreciated."? I've already reviewed , which was closed as a duplicate of  - but this requires effort on part of a user who may very likely no longer be active. Otherwise, is there something I should be doing to improve my search to filter out these types of questions? I've run across this many times, so I don't consider it to be a rare issue.  However, the last question like this I just ran across, prompting this question, was .  In this case, the question was self-answered by the OP in the form of a comment, this question is the OP's only question, the OP has no other visible activity on SO, and the OP hasn't been seen on SO since he registered and posted the question 5 months ago. Another one I just ran across is .  However, here the "answer" comment was posted by a reputable and recently active SO member.  Should I leave a comment directed at him, asking him to re-post his comment as an answer, or should I post my own answer echoing his comment?  (Or something else?) Yet another is .  Interestingly, the OP actually self-edited the question to include the "SOLVED:" prefix on to the question, instead of posting his resolving comment as an answer (and ideally accepting it) as he was asked to do by another comment.  This brings up another good idea - is there a "standard" we should use to rename the titles on these "resolved but unanswered" posts that could be used as a search exclusion?  (Also added to the above list.)


I have a 20,000 Banca Central de Nicaragua Veinte Mil cordobas bill how much in U.S. dollars can I get for this?

I have heard that the exchange rate of Nicaragua's currency is "pegged" to the US dollar, and varies at a fixed, predicable rate rather than varying naturally with the markets. What is the rate currently, and how can I find what the rate will be for a given date in the future?


Can we create an array of chars in postgresql i.e (Column_name char[5]) and does it take only 5 bytes in disk ? since type char takes only one byte

When I use varchar(5) in a INSERT query it means that the attribute in the table will take exactly 5 bytes in memory? (Given that one printable character takes one byte)?


I have a text file containing a list of strings, for example a.txt one two three  I also have another text file containing a list of strings, for example b.txt threetwo onetwothree zero twozero  What I wish to do is compare the two and find whether any of the fields inside b.txt contain fields from a.txt Example of output in this case would be, threetwo > two, three onetwothree > one, two, three twozero > two  If my explanation wasn't explanatory enough then I have this written in C# which will produce my expectations. List<string> allElements = new List<string> { "one", "two", "three" }; string str = "onetwothree"; var containingElements = allElements.Where(element => str.Contains(element)); foreach(string element in containingElements) {     Console.WriteLine(element); }  you can run the above code on dotnetfiddle.net I would prefer this to be achieved using awk, any help would be appreciated :).

I have a couple of big text files and in the file UNIQS.txt I have a list of strings to grep from another file. The code I use is  grep -f UNIQS.txt EEP_VSL.uniqs.sam > UNIQ_templates.sam   which does nothing - the file generated is empty. But when I do  grep -F -f UNIQS.txt EEP_VSL.uniqs.sam > UNIQ_templates.sam   it works correctly. This confuses me because I didn't think grep would interpret the entries in UNIQS.txt as regexp patterns without quotes and slashes and so on being in the file (which there aren't). Is it the case in general that if you are getting the patterns from a file then it will automatically think that they are regexp patterns?  Edit: In the UNIQS.txt file, there are newline separated strings of the form  HWI-ST365:215:D0GH0ACXX:2:1101:10034:186783   (called template names) and the file EEP_VSL... tab separated columns, with about 14 columns and the first column is the template name, so basically I want to extract the line corresponding to each template in the file.


I created this script, which listens for characters received on a hardcoded pipe, and tries to eval those characters. I call my script loop_executor.sh This is all it contains:  !/bin/bash  while : do     x=`cat /tmp/console_test`;     echo "received $x"     eval $x done;   I execute my script with a double click.  I want to see what files this process has open:  > $ pgrep loop_executor.sh 1234  > $ ll /proc/1234/fd dr-x------ 2 userX domain^users  0 Oct 20 17:57 ./ dr-xr-xr-x 9 userX domain^users  0 Oct 20 17:57 ../ lr-x------ 1 userX domain^users 64 Oct 20 17:57 0 -> /dev/null l-wx------ 1 userX domain^users 64 Oct 20 17:57 1 -> /dev/null l-wx------ 1 userX domain^users 64 Oct 20 17:57 2 -> /home/local/groupX/userX/.xsession-errors lr-x------ 1 userX domain^users 64 Oct 20 17:58 255 -> /home/local/groupX/userX/Desktop/loop_executor.sh* lr-x------ 1 userX domain^users 64 Oct 20 17:57 3 -> pipe:[225812]   FD 3 points to a "pipe". Well i know what file it uses, because I'm the one that hardcoded the file in the script, but I'd like to get this information (if possible) from another source (since my script is just a POC, and it could be a process whose code is not open to me).  What I understood, is that pipe:[225812] doesn't point to the inode of my file.  ll -i /tmp/console_test  16519395 prw-r--r-- 1 userX domain^users 0 Oct 20 18:14 /tmp/console_test|   So my question is: If processess can open pipes, which are files on my system, can I determine which files those pipes "corresponded" to?  I'm using ubuntu 12.04 if that matters.  [EDIT] Found the cat process that was reading from my pipe. It has the same opened pipe as its parent process, so it doesn't make much of a difference here -> i still don't know just by looking at pipe:[225812] what file -if any - that is.

In Linux, in /proc/PID/fd/X, the links for file descriptors that are pipes or sockets have a number, like:  l-wx------ 1 user user 64 Mar 24 00:05 1 -> pipe:[6839] l-wx------ 1 user user 64 Mar 24 00:05 2 -> pipe:[6839] lrwx------ 1 user user 64 Mar 24 00:05 3 -> socket:[3142925] lrwx------ 1 user user 64 Mar 24 00:05 4 -> socket:[3142926] lr-x------ 1 user user 64 Mar 24 00:05 5 -> pipe:[3142927] l-wx------ 1 user user 64 Mar 24 00:05 6 -> pipe:[3142927] lrwx------ 1 user user 64 Mar 24 00:05 7 -> socket:[3142930] lrwx------ 1 user user 64 Mar 24 00:05 8 -> socket:[3142932] lr-x------ 1 user user 64 Mar 24 00:05 9 -> pipe:[9837788]   Like on the first line: 6839. What is that number representing?


How to iterate over SObject list returned from server side controller in Lightning Component using <aura:iteration> to show the field values in table using dot notation.I am asking for passing field names dynamically with dot notation.  Some are marking it as duplicate, which is not. It may be possible that these guys are not getting it correctly or don't have solution to it. So please read it again to understand the problem,  what I am asking. It is totally different.  Attributes I have used  <aura:attribute name="records" type="Object[]"/> **This contains sObject records** <aura:attribute name="fieldsAPI" type="String[]"/> **Selected fields API names** <aura:attribute name="fieldsName" type="String[]"/> **Selected fields label Names**   Here is what I have tried and done so far : My Record Area

                         <aura:iteration items="{!v.fieldsName}" var="fieldName">
{!fieldName}
                             	                         </aura:iteration>

                     <aura:iteration items="{!v.records}" var="record">
                             <aura:iteration items="{!v.fieldsAPI}" var="fieldAPI">
{!record.fieldAPI}
                                 	                             </aura:iteration>
                     </aura:iteration>

   If I replace {!record.fieldAPI} with literal like {!record.Name} it gives what I required, but I want it dynamically here, without javascript way to create it there and append where I want.

I am trying to dynamically create a data table with two arrays (SObject array and a String array which has field API name).  The two arrays are Contact[] and String[], where String[] consists of ["Id", "Name"].  What I've tried dot notation and square bracket notation but neither worked.  <!-- row --> <aura:iteration item="{!v.contacts} var="contact">     <!-- column -->     <aura:iteration item="{!v.fieldNames} var="fieldName">         {!contact.fieldName}          {!contact[fieldName]}     </aura:iteration> </aura:iteration>   Not quite sure what is the correct approach to do this.


Python sort dictionary. I want to sort the below dictionary using name key.  I try this but not working.  {k: v for k, v in sorted(mydict.items(), key=lambda item: item[1])}   Sample dictionary  [         {             'id': 34,              'pid': 7,              'name': '1.1. Data Foo',              'open': 'open',             'children' : [                 {                     'id': 23,                     'pid': 89,                     'name': '1.1.1. Data 4',                     'open': 'open'                 },                 {                     'id': 23,                     'pid': 89,                     'name': '1.1.4. Data 6',                     'open': 'open'                 },                 {                     'id': 23,                     'pid': 89,                     'name': '1.1.2. Data 14',                     'open': 'open'                 },             ]         },          {             'id': 32,              'pid': 7,              'name': '1.3. Data Bar',             'open': 'open',             'children' : [                 {                     'id': 23,                     'pid': 89,                     'name': '1.2.1. Data 14',                     'open': 'open'                 },                 {                     'id': 23,                     'pid': 89,                     'name': '1.4.4. Data 86',                     'open': 'open'                 },                 {                     'id': 23,                     'pid': 89,                     'name': '1.0.2. Data 114',                     'open': 'open'                 },             ]         },          {             'id': 33,              'pid': 7,              'name': '1.2. Data Rex'              'open': 'open',             'children' : [                 {                     'id': 23,                     'pid': 89,                     'name': '2.1.1. Data 4o0',                     'open': 'open'                 },                 {                     'id': 23,                     'pid': 89,                     'name': '14.1.4. Data 676',                     'open': 'open'                 },                 {                     'id': 23,                     'pid': 89,                     'name': '1.11.2. Data 1423',                     'open': 'open'                 },             ]         },     ]

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


I would like to design a battery management system for low voltage systems. I am developing a BMS for a 48V, 20Ah battery pack system.  When it comes to battery balancing, I am confused in between resistor based passive and capacitor based active cell balancing method.  Which one is better for my low voltage system application?  Passive cell balancing: Shunt resistor method: It bleeds the charge through resistors and transistor switch, but the energy is wasted through a resistor as heat.  Even though it is a low voltage battery pack my confusion is will this heat increase the temperature and will this be a problem?  Active cell balancing: Switched capacitor cell balancing in this method the battery is getting balanced by transferring the charge from high voltage cell to low voltage cells by using capacitor and transistor switch. It is more efficient than passive cell balancing but it takes more time to get equalized and it depends on large voltage variation.  Other cell balancing methods like inductor or transformer based and converter based are more efficient but more complex and expensive for low voltage BMS and as a beginner.  So I am confused as to which cell balancing method is best for a low voltage (48V, 20Ah) system. Please suggest to me which method is best to use based on my requirements.

As a beginner, I am going to design and develop a BMS (Battery Management System) for low-voltage applications (electric bike). So I would like to know which cell balancing method is perfect for low-voltage BMS.  Is active cell balancing method (fixed resistor, shunt resistor) or passive cell balancing methods best for low-voltage battery pack?  How should I decide that?  Please explain in a way that will be helpful as a beginner.


We know that $$\sum_{r=0}^{k}{\binom{k}{r}}^2=\binom{2k}{k}$$ Can we prove such identity for the above case. I can check the identity for some numerical values. For example $k=4$ case satisfies it.

Problem was to find $$\sum_{r\ge 0} \binom{n}{r}\binom{n-r}{r} 2^{n-2r}.$$ My partial progress i tried to motivate such that upper term in binomial terms gets constant rather than variable , so i thought of changing it to form $\binom{n}{n-r}\binom{n-r}{n-2r}$. Now it's of the form $\binom{n}{m}\binom{m}{k}$. We know it is equivalent to $\binom{n}{k}\binom{n-k}{m-k}$. Doing this we get $\binom{n}{2r}\binom{2r}{r}2^{n-2r}$. Now what I need to do as next step as such still nothing the upper or lower terms r any constant values(sum to ) , all are variables still. Now by one answer by Robpratt i got by snake oil , is there any other way to solve this problem ?


I'm trying to use pgfplots to plot a graph but I run into the following error:  ! Undefined control sequence. \pgfplots@width ->0.95\textwidth -\heightof {ylabel}-\widthof {ymax}   Here is my document:  \documentclass[12pt]{article}  \usepackage{pgfplots} \usepackage{pgf}             \usepackage{tikz} \pgfplotsset{compat=newest} \usepgfplotslibrary{external}  \tikzexternalize  \begin{document} Hello world! \begin{figure}[htbp]     \centering     \begin{tikzpicture}         \begin{axis}[%         scale only axis,         separate axis lines,         ytick={-20,0,20,40,60,80,100,120,140},         xmin=1,         xmax=1.8,         xlabel={$\lambda (\epsilon + 1)$ },         ymin=-20,         ymax=140,         ylabel={$\sigma_{11} (kPa)$},         legend style={legend pos=north west, legend cell align=left,align=left,draw=none},         yticklabel style={align=right,inner sep=0pt,xshift=-0.1cm},          grid=none,         max space between ticks=40,         major tick length=0.15cm,         minor tick length=0.075cm,         tick style={semithick,color=black},          width=0.95\textwidth-\heightof{ylabel}-\widthof{ymax},         height=0.5\textwidth ] \addplot [color=black,mark size=2.5pt,only marks,mark=*,mark options={solid,fill=white!75!blue}]   table[row sep=crcr]{% 1.00781861  0.0102718\\ 1.0193275   -0.00690492\\ 1.0289739   0.0408018\\ 1.040467    0.0701334\\ 1.05104 0.0993509\\ }; \addlegendentry{Experimental data};  \addplot [color=blue,solid,line width=1.0pt]   table[row sep=crcr]{% 1.00781861  0.190117075896132\\ 1.0193275   0.474231238225642\\ 1.0289739   0.717201161857507\\ 1.040467    1.01366753959628\\ 1.05104 1.29424479212858\\ }; \addlegendentry{Ogden model};  \addplot [color=red,solid,line width=1.0pt]   table[row sep=crcr]{% 1.00781861  0.777179697089887\\ 1.0193275   1.92137205791344\\ 1.0289739   2.88076259714836\\ 1.040467    4.02448983176329\\ 1.05104 5.07751266247692\\ }; \addlegendentry{Neo-Hookean model};  \addplot [color=green,solid,line width=1.0pt]   table[row sep=crcr]{% 1.00781861  -3.7155599786856\\ 1.0193275   -7.79892723072965\\ 1.0289739   -10.2011747706551\\ 1.040467    -12.1140706845337\\ 1.05104 -13.154421182274\\ }; \addlegendentry{Mooney-Rivlin model};          \end{axis}      \end{tikzpicture}     \caption[]{Experimental data fitted to the hyperelastic models models}     \label{figure:curve_fitting_from_data} \end{figure} \end{document}

The following has worked for me for quite some time.  \documentclass[11pt]{book} \usepackage[margin=1in]{geometry}             \geometry{letterpaper}                  \usepackage[parfill]{parskip}     \usepackage{tikz, pgf, calc} \usetikzlibrary{matrix, shapes, positioning, calc, decorations.pathreplacing, shapes.geometric, arrows}  \newcounter{Day}  \newcounter{pt}[Day]    % CORRECTNESS POINTS FOR HW RUBRICS \newcommand{\pt}[2]     % NUMBER OF POINTS, ITEM IN STARBURST     {#2\begin{tikzpicture}[remember picture, overlay]         \node (A) [starburst,              draw = red, opacity = .8,              fill = red!20, fill opacity = .2,              xshift = -.5*\widthof{#2},             yshift = .5*\heightof{#2}             ]             {\phantom{#2}};         \node (B) at (current page.west) {};         \path let \p1 = (A), \p2 = (B) in node [draw = red,              color = red] at (\x2+.625in,\y1) {#1 pt(s)};     \end{tikzpicture}     \addtocounter{pt}{#1}     }  \begin{document}  \pt{1}{lorem}  \end{document}   Recently, I updated several packages with MikTeX 2.9.  Below is a screenshot of the packages that were updated.    Since the updates, the \widthof and \heightof commands are causing errors.  If I change the xshift and yshift to something else, everything compiles just fine (but isn't the way I want my command to work).  I have two questions:   Why did this work before and not now? How can I change my code to make it work correctly again?   Thanks in advance for any help!


If a directory is a special file in unix with filenames and corresponding inodes, is there any way to print the entire contents of this file?

In the past, I learned that in Linux/UNIX file systems, directories are just files, which contain the filenames and inode numbers of the files inside the directory.   Is there a simple way to see the content of a directory? I mean the way the files names and inodes are stored/organized.  I'm not looking for ls, find or something similiar. I also don't want to see the content of the files inside a directory. I want to see the implementation of the directories. If every directory is just a text file with some content, maybe a simple way exists to see the content of this text file.  In the bash in Linux it is not possible to do a cat folder. The output is just Is a directory.  Update The question  addresses the same issue but it has no helpful solution like the one from .


I am a Linux newbie trying to setup Lubuntu 16.10 on my Dell desktop. This forum has helped me learn a good bit about Linux and Ubuntu in the last few days.   I'm now having trouble getting app packages to install and was wondering what I'm doing or not doing wrong. I have a couple of applications I've downloaded, they are:   VirtualBox-5.1_5.1.12-112440-Ubuntu-yakkety_i386.deb. audacity_2.12-1build1_i386.deb   When I try to install them, it opens software manager app, I click on " install and it does nothing. Doesn't confirm install, nothing seems to be added to the system. Then I back out of the software app and on the top of the window where it has 3 tabs - •All, •Installed, and •Updates I see under •Installed tab there is a blue 2 highlighted. Also I am not connected to the internet and a message popped up saying a software update was needed to show all installed apps. Could this be why?

I have a friend who has got a computer that is not connected to the Internet. Is there any way to install software offline easily?


I thought about the parameterizing the 4D sphere using $$x_1= r\cos(\theta_1), x_2= r\sin(\theta_1)\cos(\theta_2), x_3= r\sin(\theta_1)\sin(\theta_2)\cos(\theta_3),\\ x_4= r\sin(\theta_1)\sin(\theta_2)\sin(\theta_3),$$ where $x_1,x_2,x_3,x_4$ are my 4D space coordinates. But what will be the range of values of $\theta_1, \theta_2, \theta_3$ to make the mapping from $(r,\theta_1, \theta_2, \theta_3)$ to $(x_1,x_2,x_3,x_4)$ bijective ?

What's the analogue to spherical coordinates in $n$-dimensions? For example, for $n=2$ the analogue are polar coordinates $r,\theta$, which are related to the Cartesian coordinates $x_1,x_2$ by  $$x_1=r \cos  \theta$$ $$x_2=r \sin  \theta$$  For $n=3$, the analogue would be the ordinary spherical coordinates $r,\theta ,\varphi$, related to the Cartesian coordinates $x_1,x_2,x_3$ by  $$x_1=r \sin  \theta  \cos  \varphi$$ $$x_2=r \sin  \theta  \sin  \varphi$$ $$x_3=r \cos  \theta$$  So these are my questions: Is there an analogue, or several, to spherical coordinates in $n$-dimensions for $n>3$? If there are such analogues, what are they and how are they related to the Cartesian coordinates? Thanks.


I'm learning C just started today and I'm coming from knowing a bit of Python and a little bit of Javascript and I want to know how I would get the int base of a string for example in Javascript you can do this:  parseInt("myString", 36);   That would return 1799765255212   In Python it would be this:  int("myString", 36)   Which would also return 1799765255212  Is there a C equivalent? If not, how would I make one?

How does one parse an integer to string(char* || char[]) in C? Is there an equivalent to the Integer.parseInt(String) method from Java in C?


I am travelling to Denmark today, and will be there tomorrow.  My visa period is for 10 days, from 4th June 2016 to 14th June. I miscalculated the days, and my return flight is on 14th June (so, in 11 days).  This would mean I would overstay my visa by 1 day.  What are my options?

My daughter applied at the Italian Consulate in Philadelphia, and they gave her two entries for 20 days (we thought it was for 20 days each entry). She was in Italy 12 days, then went to England for 1 week and flew to Venice to take a 10-day cruise. She couldn't make it because they said she has only 8 remaining days, but she still has a land tour already paid this week.  What can she do? Can she extend the Schengen visa for 12 more days? Right now, she is in Madrid, but next week she has to fly from Barcelona to Paris to start with the tour. What would happen if she decides to take the tour with the expired visa? She is a US permanent resident.


I would like to slim a cuboid with the base of the heart. I want to slim it down only in relation to the X and Y axes by exactly 0.4 mm. I would like the edges of the new and old hearts to be 0.4mm apart. The scaling operation does not do what I would like. Gaps of various widths are created. I wish the gaps were 0.4mm wide everywhere. I attached a picture from another program because it was easier for me to show my problem. The picture shows what I don't want to get. Does anyone have an idea how to efficiently modify an object the way I would like?

How can I inset/extrude a face, so that the outer faces have the same width?    Any kind of help is appreciated


Thansk I'm using ArcGIS 10.   My task is to map forest cover with the image classification tool. The problem is some of the patches of forest are dark and are been classified as cloud shadows in the image classification. I need to convert raster values that represent cloud shadows into the raster value for forests. But only only want to do this for an area that falls within in a polygon.   Is there way to reclassify a raster but only the cells that fall within a polygon?

I'm trying to reclassify only a certain part of a raster...not the entire raster.  Here's the problem.  I have a LULC raster of the entire US.  There are some issues with the raster that I want to fix, namely some cells that should be water are classified as wetlands.  These are mainly off the coast, not inland.  However, some cells that are classified as wetlands should really be wetlands (mainly inland) and I don't want these to change.  I plan on using a ZIP Code boundary file to determine which cells are considered "off the coast" and which ones are not.  I have access to ArcGIS 10.1 and R with the appropriate raster packages I need so a solution in either software would be fine.  Can anyone help me figure this out?


I recently purchased a domain and created the website. I found that this belongs to "None" category and so found blocked in cyberoam firewall.    I tried with all possible meta tags at index.html. But any content from this domain is blocked (otherwise can say categorized NONE). The image's url is also blocked    In Godaddy I can find only "Auto-Renew, Lock, Nameservers, Forwarding, Premium DNS, DS Records, Host Names, Authorization Code" features to customize.  And Some Upgrade features like "Privacy, Domain Ownership Protection, Certified Domain , Premium Listing, CashParking, GoDaddy Auctions, SSL Certificate, Business Registration, Domain Appraisal".  Please help me where / how to categorize my domain as "Personal"?  Is anything needs to be changed in robots.txt?

I run a large and high trafficked WordPress powered platform. One of my editors informed me that our site is blocked at his workspace as a "games site". They use WebCat to filter the traffic.  The issue here is that our platform is not a gaming site, although it does have a games category that covers news. And that is a very minor part of the site.  My question is, what can I do to unblock the site? How does WebCat work? Do they use a universal database to filter the traffic (meaning that the site is blocked on all workspace with WebCat) etc. Obviously they need to improve their filtering algorithm.


I have the following graphic:  Which is taken from the solution . I would like to add some additional text to the graphic, such that, it looks something like:  To show the high bias, low bias and combination of the two -  along with the "overfitting", "underfitting" and "Good balance" labels. How can I incorporate this text into the current tikzpicture Code: \documentclass[tikz,border=3.14mm]{standalone} \usetikzlibrary{calc} \begin{document} \begin{tikzpicture}[font=\sffamily, declare function={f(\x)=0.5*pow(abs(\x-2),2)-0.06*pow(\x-2,3);}]  \foreach \Z in {1,...,42}  {\pgfmathsetmacro{\X}{\Z/10}  \pgfmathsetmacro{\Y}{f(\X)+0.9*rnd}  \ifnum\Z=1   \xdef\LstOne{(\X,\Y)}   \xdef\LstTwo{"(\X,\Y)"}  \else   \xdef\LstOne{\LstOne (\X,\Y)}   \xdef\LstTwo{\LstTwo,"(\X,\Y)"}  \fi} %  \begin{scope}[local bounding box=over0] %  \foreach \Z in {1,...,42} %  {\pgfmathsetmacro{\Coor}{{\LstTwo}[\Z-1]} %  \fill \Coor circle[radius=1pt]; %  } %  \draw plot[smooth] coordinates \LstOne; %  \end{scope}  \begin{scope}[local bounding box=over,xshift=-5cm]  \foreach \Z in {1,...,40}  {\pgfmathsetmacro{\Last}{{\LstTwo}[\Z-1]}  \pgfmathsetmacro{\Current}{{\LstTwo}[\Z]}  \pgfmathsetmacro{\Next}{{\LstTwo}[\Z+1]}  %\typeout{\Last,\Current,\Next}   \edef\temp{\noexpand\path ($0.6*\Current+0.2*\Last+0.2*\Next$)   coordinate    (p\Z);}   \temp   \ifnum\Z=1   \xdef\LstThree{(p\Z)}   \else   \xdef\LstThree{\LstThree (p\Z)}   \fi   }  \foreach \Z in {1,...,42}  {\pgfmathsetmacro{\Coor}{{\LstTwo}[\Z-1]}  \fill \Coor circle[radius=1pt];  }  \draw[thick,blue] plot[smooth] coordinates \LstThree;  \end{scope}  %  \begin{scope}[local bounding box=good,xshift=-10cm]  \foreach \Z in {1,...,42}  {\pgfmathsetmacro{\Coor}{{\LstTwo}[\Z-1]}  \fill \Coor circle[radius=1pt];  }  \draw[thick,blue] plot[smooth,domain=0.1:4.2,variable=\x] (\x,{f(\x)+0.45});  \end{scope}  %  \begin{scope}[local bounding box=under,xshift=-15cm]  \foreach \Z in {1,...,42}  {\pgfmathsetmacro{\Coor}{{\LstTwo}[\Z-1]}  \fill \Coor circle[radius=1pt];  }  \draw[thick,blue] (0.1,0.4) -- (4.2,2);  \end{scope}  %  \foreach \X in {over,good,under}  {\draw[gray,thin] ([xshift=-3pt,yshift=3pt]\X.north west) rectangle   ([xshift=3pt,yshift=-3pt]\X.south east);  \draw[stealth-stealth,thick] ([xshift=-3pt,yshift=3pt]\X.north west) node[right=1.5pt,fill=white]{Values}   |- ([xshift=3pt,yshift=-3pt]\X.south east) node[below left]{Time};} \end{tikzpicture} \end{document}

I'm working with overleaf and trying to add texts in these red marked positions. For example, I want to add 4,5 and 6 respectively. I've tried with \put(0,0), but it always disables the \resizebox attribute and makes the image out of proportion, also the text doesn't get placed in the position at all. What changes can I make in the code mention below to add 4,5 and 6 in these three positions? Picture can be found in . \begin{figure}[!h]     \centering     \resizebox{1\linewidth}{!}{%     \includegraphics{picture.png}     }     \caption{Flowchart of Heuristic adjustment 1.}     \label{fig:heuristic_1_FC} \end{figure}


I want to print 6.5 to 6.05. And 6.12 to 6.12.  How it could be achieved using java utilities?  I tried DecimalFormat as below:  DecimalFormat df = new DecimalFormat("##.0#"); System.out.println("sam --------- " + df.format(6.5));   But not working. Any help on this?

What I would like is a method to convert a double to a string which rounds using the half-up method - i.e. if the decimal to be rounded is 5, it always rounds up to the next number. This is the standard method of rounding most people expect in most situations.  I also would like only significant digits to be displayed - i.e. there should not be any trailing zeroes.  I know one method of doing this is to use the String.format method:  String.format("%.5g%n", 0.912385);   returns:  0.91239   which is great, however it always displays numbers with 5 decimal places even if they are not significant:   String.format("%.5g%n", 0.912300);   returns:  0.91230   Another method is to use the DecimalFormatter:  DecimalFormat df = new DecimalFormat("#.#####"); df.format(0.912385);   returns:  0.91238   However as you can see this uses half-even rounding. That is it will round down if the previous digit is even. What I'd like is this:  0.912385 -> 0.91239 0.912300 -> 0.9123   What is the best way to achieve this in Java?


I'm currently running version 14.04. Is it safe to upgrade only kernel to the recently released 3.16?

I had several friends ask me to update their Ubuntu to a newer kernel without changing the version of Ubuntu. So for example, staying in 10.04 with the 3.3 Kernel version.  When having an older or present Ubuntu version, many users want to apply the newer stable/unstable kernel version to the Ubuntu version they are using thinking that it is similar to upgrading a program. So what I am looking for, are some simple answers to explain the dangers (that are pretty much bigger than the advantages) of forcing a newer kernel version in a Ubuntu release that was not meant for it.  What can I tell them or explain to them of why they should NOT update to a newer/older kernel when having an Ubuntu version that was not made for that kernel version.


In both the books and films, it's made clear that Harry saw his mother dying when he was a baby. He clearly remembers this, due to the flashbacks that are induced every time he gets near a Dementor.  However, he only sees the Thestrals (creatures that require you to have seen death for them to appear visible to you) after Cedric Diggory dies.  Why is this?

Why couldn't Harry see Thestrals at the end of Goblet of Fire after the senseless and shocking death of Cedric Diggory?   At the end of Goblet of Fire, the carriages still appeared horseless to Harry:     Hermione turned away, smiling at the horseless carriages which were now trundling towards them up the drive, as Krum, looking surprised, but gratified, signed a fragment of   parchment for Ron.   Goblet of Fire - Page 629 - British Hardcover - Adult Edition   At the beginning of Order of the Phoenix, Harry sees the Thestrals for the first time:     Here stood the hundred or so horseless stagecoaches that always took the students above first year up to the castle. Harry glanced quickly at them, turned away to keep a lookout for Ron and Hermione, then did a double-take.   The coaches were no longer horseless. There were creatures standing between the carriage shafts.   Order of the Phoenix - Page 178 - British Hardcover - Adult Edition   We know that only those who have seen death can see Thestrals:     ‘Don’ worry, it won’ hurt yeh,’ said Hagrid patiently. ‘Righ’, now, who can tell me why some o’ yeh can see ’em an’ some can’t?’   Hermione raised her hand.   ‘Go on then,’ said Hagrid, beaming at her.   ‘The only people who can see Thestrals,’ she said, ‘are people who have seen death.’   ‘Tha’s exactly right,’ said Hagrid solemnly [...]   Order of the Phoenix - Page 394 - British Hardcover - Adult Edition   A month went by between Cedric's death and the end of the spring term -- is this enough time for Harry to have truly internalized Cedric's death? Goblet of Fire indicates that Harry was in shock following Cedric's murder, but was able to relate the story of Cedric's death to Mr. and Mrs. Diggory.     When he looked back, even a month later, Harry found he had few memories of the following days. It was as though he had been through too much to take in any more. The recollections he did have were very painful. The worst, perhaps, was the meeting with the Diggorys that took place the following morning.   [...]   ‘He suffered very little, then,’ she said, when Harry had told her how Cedric had died.'   Goblet of Fire - Page 621 - British Hardcover - Adult Edition   So, then, why couldn't Harry see Thestrals at the end of Goblet of Fire?


Stanford University (and others) usually publish slides/lecture notes on the corresponding websites. For instance, this one:  If I teach a course in the same topic, can I just use the slides/lecture notes? Do I need to acquire permission? I will keep the name of Stanford on the slides and clearly stated that the slides are made by Stanford professors. Thanks

To prepare the lecture material. I use the book, my own slides, but I also take a few slides from MIT or other top universities open courses.  What is the best way to give credit?  I must provide source information on each slide?  Or Is it better to enlist all the resources/citations in the first/final slide?


NOTE: I see it suggested that this is a duplicate question. Certainly there is substantial overlap between the two questions. This one explicitly mentions the Beta function and explicitly invites arguments for doing it the other way. One of the more able regular posters here stated today in a comment that it ought to be done the other way; I would be curious to see that case made. end of NOTE  One sometimes sees it opined that instead of $$ \Gamma(\alpha) = \int_0^\infty x^{\alpha-1} e^{-x} \,dx $$ one should follow a convention that puts simply $\alpha$ where $\alpha-1$ appears. Similarly with both $\alpha$ and $\beta$ in $$ \operatorname{B}(\alpha,\beta) = \int_0^1 x^{\alpha-1} (1-x)^{\beta-1} \, dx. $$  What facts can be adduced on which to base arguments for one or the other convention?  (I will post a brief answer of my own, but possibly some very different answers can be readily written.)

As a physics student, I have occasionally run across the gamma function  $$\Gamma(n) \equiv \int_0^{\infty}t^{n-1}e^{-t} \textrm{d}t = (n-1)!$$  when we want to generalize the concept of a factorial.  Why not define the gamma function so that   $$\Gamma(n) = n!$$  instead?  I realize either definition is equally good, but if someone were going to ask me to choose one, I would choose the second option.  Are there some areas of mathematics where the accepted definition looks more natural?  Are there some formulas that work out more cleanly with the accepted definition?


I noticed that I cannot edit . The tooltip explains  that      Suggested edits are not allowed on non-tag-wiki posts on meta sites   After searching I found  and  that says that this is by design. I do get the reason why I can't edit (not enough rep), my problem is that the tooltip explanation is not very clear to me. What exactly is meant by 'non-tag-wiki posts'?. Does it mean that if someone with enough rep adds a 'wiki' tag to the question then I will be able to edit the post?

I was browsing around the new  and when I browsed to the  I was greeted with an "edit tag wiki" link. So I edited it and created some text. Very cool.  So I have a few questions.   What is the requirement to be able to edit this tag wiki? I clearly can't do it on all tags, so I'm guessing there is some activity requirement within the tag space before you get the ability to edit the wiki. What should the content be? I browsed around a little, but I couldn't find any other examples with any content. I just included some basic text for the  one. "Questions relating to the Microsoft .NET framework" with a link to http://www.microsoft.com/net/.


I am working on a project that requires me to have control of shadows in the compositor (specifically, to darken or lighten them.) In BI, I would simply take the shadow pass and ramp it, them multiply it back in. But my scene involves mesh lights, and the Shadow pass only has Lamps and Environment lighting.  It seems that it should be possible to get the info I need for mesh lights from Direct Passes, and for indirect light from Indirect passes. But I am stuck on how to do this without also getting too much other info from those passes. From googling around, I've seen that others have run into this problem, but I couldn't find anybody that had actually tried to solve it.  Does anyone know a way to do this? Or can it be confirmed that it cannot be done for some reason?  EDIT: It is not enough to get shadows cast on other objects, which is covered by some other answers. I need the shading on each model itself as well. This is not for a shadow catcher, it is for isolating both cast shadows and shading so they can be worked with.

I am superimposing CGI over video footage, and have run into a problem in making materials for objects that act as 'shadow catchers'.  Essentially I want a shader that is shadeless—like an emitter—but catches shadows and light from other objects. This is so I can reconstruct objects in footage so other objects in the scene interact convincingly with them.  Here's an overcomplicated diagram to illustrate my point:   (In this particular scenario, the problem could be glossed over by using RGB curves, but that is definitely not the case with more complicated scenes)  Isn't this a common situation? How to the real guys do it? Thank you.  (I am welcome suggestions of other ways of doing this.)


Is it possible to mapping a image around a ring shaped mesh? I would imagine there should be a way to curve/distort the image around the mesh. If not, how can I straighten out the mesh easily instead to fit the image?

For my banked road I sort of managed to make it look like it is a racing track.  I am really stuck with the pink part that is completely flat. I have a road texture and want to apply it to that, so that it follows the road   I think it should be easy but I don't know how to do it. I have searched but can't seem to find the right tutorial for this.


When I'm trying to run the cd command on my virtual pc is shows error as shown in pic above. How can I change the directory?

How do I change directories to downloads, from the home folder, in the latest version Ubuntu 12.10? I tried cd /downloads, but it gave an error saying that there is no such directory.


I have a D-Link DWA-182C1 wireless dongle which did work in 19.04, the latest update to 19.10 doesn't work. Ubuntu recognizes it, finds the driver and installs it but nothing happens. I am not experienced with Ubuntu and need step by step instructions on how to fix this.

On Ubuntu 19.04 I had current rtl8812au (AC1200) and rtl8814au (AC1750) dkms drivers for my USB wireless dongles installed and running fine. They both broke after I upgraded to Ubuntu 19.10. I've been able to find a replacement/newer rtl8812au driver that works with kernel 5.3 on Ubuntu 19.10. I haven't been able to find a replacement/newer rtl8814au driver that works with kernel 5.3 on Ubuntu 19.10. Github.com has a number of rtl8814au drivers available, even some that proport to compile with kernel 5.2. I believe that I've tried about 6 different rtl8814au drivers from github, but none of them work, even though some of them do compile with kernel 5.3. Does anybody know of a working rtl8814au driver that works with kernel 5.3 on Ubuntu 19.10?


After I installed Plank and I clicked it, the plank show up. but if I restart or turn on the laptop. The Plank not automatically opened (show). How can I show automatically show Plank after reboot or turn on the laptop?

How can I make an application automatically start when I have logged in?


I am trying to have virtual box guest in Ubuntu 18.04 but now able to succeed. peter@LAPTOP-UMBBINAR:~$: sudo apt-get install virtualbox-guest-additions-iso peter@LAPTOP-UMBBINAR:~$ Reading package lists... Done Reading: command not found peter@LAPTOP-UMBBINAR:~$ Building dependency tree Building: command not found peter@LAPTOP-UMBBINAR:~$ E: Unable to locate package virtualbox-guest-additions-iso  Any idea how to run the command  ?

I've recently installed Ubuntu on Oracle's Virtualbox.  Now I want to install the guest additions.  I started up my Ubuntu guest OS, clicked "Devices" and chose "Install Guest Additions". Nothing happened, and I don't see the CD icon on my desktop.  How can I make this work?


I'm wondering how you can receive a categories parent name and link for a breadcrumb I've written.  I basically want to have the following structure  if child category blog > parent_category  else if grandchild category blog > grand_parent_category > parent_category

I'm currently trying to figure out how to display a categories parent / grand parents name and url for a custom breadcrumb I'm working on.   I simply need to know how to show the parent categories information on a child category page.   For example  if parent blog  else if child  blog > parent_category  else if grandchild blog > grand_parent_category > parent_category


I recently had a meeting with a prospective advisor. It mostly went well, though I'm worried I "overshared" a bit and introduced awkwardness. Nonetheless, after the meeting, she sent me a kind e-mail. I should have thanked her right away (at least within a day), but I hesitated. I spent two weeks contemplating how and whether I should reply and finally did yesterday. I just thanked her for the info., apologized for the awkwardness, and ended by saying that I look forward to applying to the program. I'm now worried that my reply was too late, and she now thinks I'm rude and won't want to work with me. I guess the situation isn't very egregious, but I'm nonetheless worried because this is the only school I want to attend, and we have similar research interests/seem like a good fit. I'm also worried that she sees me as red flag now. Even though she was empathetic, she might have reservations about me now (due to the oversharing)? First: how offensive was my late email reply?  Next: Is it likely that she'll have concerns about me from the beginning or choose not to work with me at all? (I didn't get that impression from the email, but she also didn't explicitly agree to advise me.)

A couple of weeks ago, I emailed a professor (at a different university) about becoming my graduate advisor. While they didn't explicitly agree to do so (the program isn't accepting new students until next year), they expressed interest in my proposed thesis topic and asked the program director about a specific disability accommodation I mentioned. They also gave me his email in case I had further questions about the logistical issues etc. My question is: Would it be impolite not to email him or would that seem like I wasn't seriously interested in the program. (The professor answered my questions pretty thoroughly.) I've thought about asking him if they have "rolling admissions" or if it would be too early to apply within the next couple of months (currently studying for the GRE, so I can't apply before I take it), but then I thought that asking such a trivial question might be worse than not contacting him at all. Also, should I have thanked the professor for their reply? Would replying to such a thorough email with one line such as "Thank you for the information" seem curt, and is it too late since almost two weeks have passed since then? Update: I emailed the director, and he sent me a friendly reply answering my questions about the deadlines etc. I genuinely was curious about the deadlines, it wasn't that I was making up an excuse to email him, but I thought it might have been a "trivial" question. I don't know how he actually perceived it, but his email was polite and welcoming. I then thanked him for the information.


I had a reikling as a follower and I told it to wait (in whiterun I think, I checked and it's not there.) now I cannot accept another follower and I'm one of those people who like to collect cool weapons and it's really putting a damper on my collecting. Help?

I had parked my follower at an inn with a bunch of valuable items that I didn't want to carry. I guess I have been out a bit too long as this message appears:      Your follower tires of waiting and leaves.    There have been other situations where my follower has mysteriously disappeared as well.  How can I find my follower when they get up and leave or disappear into thin air?


My scanner (Brother MFC-J825dw) will only scan one side at a time in the sheet feeder. I have a document that is double sided. How can I make a PDF out of it so the pages are in order, automatically? If I scan both sides, I end up with 2 PDFs, one with even pages, and one with odd pages (that might be backwards). I have a PDF editor (PDF Viewer Plus) that can insert/delete/move pages, but that gets ridiculous for so many pages.

I have two searchable PDF  documents, say even.pdf and odd.pdf which contain even and odd pages of a book, respectively.   I can decompile each PDF to separate files 001.pdf 002.pdf 003.pdf, et cetera. The question is how to merge them?  They are both even and odd sequences numbered 1, 2, 3. If the numbering in the decompile process with pdftk were different, e.g. 1, 3, 5 for even and 2, 4, 6 for odd instead of 1, 2, 3, 4, I could simply merge them.  Can I do this any other way?


I have a header file:  #ifndef DATA_HPP #define DATA_HPP  #include <cstdint>  namespace f { namespace t { namespace e {  uint32_t a = 99;  class Test { public:     Test();     ~Test(); };  } } } #endif   With CPP file try.cpp:  #include "try.hpp"  namespace f { namespace t { namespace e {  Test::Test() { } Test::~Test() { }  } } }   And the main file - main.cpp:  #include "try.hpp"  int main() { f::t::e::Test a; }   But when I compile my code:  c++ --std=c++11 try.cpp main.cpp   I get below error:  (.data+0x0): multiple definition of `f::t::e::a' try.cpp:(.data+0x0): first defined here   I already have the header file guard - so why the error is being reported and how can I fix it?

I have a header file  x.h which is included by more than one *.c source files. This header file has some structure variables defined.  I have put multiple inclusion prevention guard at the beginning of the header file as:  #ifndef X_H #define X_H ... .. //header file declarations and definitons.   #endif//X_H   On building I get linker errors related to multiple definitions. I understand the problem.   Won't a multiple inclusion prevention guard at the top of header file as I have, prevent multiple inclusions of the header file x.h and thereby avoid multiple definitions of the variables that are there in x.h? #pragma once does not work on this particular compiler, so what is the solution?  Someone had posted  answer to a similar question. It doesn't seem to work for me. How does this solution work?


In my script I use  winccoaID=$(ps -aux | grep -v 'color=auto' | grep -i 'WCCOAui -console' | tr -s ' ' | cut -d ' ' -f 2) winccLogID=$(ps -aux | grep -v 'color=auto' | grep -i 'WCCOAtoolLogView'  | tr -s ' ' | cut -d ' ' -f 2)   each line looks for a certain process and assigns the pid to the value.  On cli the command works as expected. BUT in the script the commands grab another random value and adds it with a space between the 2 values. I have checked the numbers against the process list. The numbers do not relate to other process. So there is no bogus grep spoiling my fun.  Can someone tell me what is going on?

ps aux  | grep firefox   Lists all processes having the string "firefox"  ps aux  | grep -v firefox   Lists all the processes without the string "firefox"  ps aux  | grep -v grep | grep firefox ?  What does this second grep does ? grep itself is a command then why we are grepping another grep ?


When I studied Linear Algebra over 55 years ago, we used a book by Hoffman and Kunze. I still cannot solve the last problem of Chapter $1$. I don't have the book any more but I remember the problem. It is: Show that for all $n$ the following matrix has an inverse with integer entries. \begin{bmatrix} \frac {1}{2} & \frac {1}{3} ...\frac {1}{n+1}\\ \frac {1}{3} & \frac {1}{4} ...\frac {1}{n+2}\\ ...\\ \frac {1}{n+1} & \frac {1}{n+2} ...\frac {1}{2n}\\ \end{bmatrix} The proof should only use the material that would be reasonably covered in Chapter $1$ of a reasonable Linear Algebra text. That means without determinants. I was able to confirm it for some small $n$; I think up to $6$.    After posing this question, it was alleged that it was a  and it certainly looks that way, superficially. However,     This question asks for an elementary solution. The solution(s) proposed to the alleged duplicate are not elementary. This is the primary difference. (To be elementary the solution should not involve determinants. For example, it could show that the linear transformation represented by the matrix is $1-1$ or onto and that the inverse is an integer matrix, or that the form of the inverses  as $n$ grows follows a well-defined pattern, or that there is a well defined sequence of elementary row operations which row-reduces the matrix to the identity matrix and the product of which is a n integer matrix.) The entries in this matrix are $\frac {1}{i+j}$ but in the alleged duplicate they are $\frac {1}{i+j-1}$. Since I am working with an old memory, I am probably mistaken about the exact statement as originally posed in Hoffman and Kunze. But, in any case, the problems are different. It is not clear if this difference is significant or just a quibble.  The title of this question is different than the alleged duplicate. People looking for the solution to this problem may not be aware that the matrix in question is called a Hilbert matrix.

Let $A$ be the $n\times n$ matrix given by $$A_{ij}=\frac{1}{i + j - 1}$$ Show that $A$ is invertible and that the inverse has integer entries.  I was able to show that $A$ is invertible. How do I show that $A^{-1}$ has integer entries? This matrix is called the Hilbert matrix. The problem appears as exercise 12 in section 1.6 of Hoffman and Kunze's Linear Algebra (2nd edition).


def square(x):   return x * x  def twoPower(x, n):   while n > 1:   x = square(x)   n = n/2 return x   twoPower(2, 8) gives 256 when we bind x = 5, n = 1. Why?

What exactly are the Python scoping rules?  If I have some code:  code1 class Foo:    code2    def spam.....       code3       for code4..:        code5        x()   Where is x found?  Some possible choices include the list below:   In the enclosing source file In the class namespace In the function definition In the for loop index variable Inside the for loop   Also there is the context during execution, when the function spam is passed somewhere else. And maybe  pass a bit differently?  There must be a simple reference or algorithm somewhere.  It's a confusing world for intermediate Python programmers.


i have a couple of columns in my data which are postively skewed. they are non-normal from the hist plots. plotting a qq plot further cinfirms this. i should remove outliers from my data for xgboost. however what method should i use to remove outliers from postively skewed dataset.    i have considered log transform and cube root to transform but this still leaves it skewed (note i do have some negative values which are expected)

I found many articles that state that boosting methods are sensitive to outliers, but no article explaining why.   In my experience outliers are bad for any machine learning algorithm, but why are boosting methods singled out as particularly sensitive?  How would the following algorithms to rank in terms of sensitivity to outliers: boost-tree, random forest, neural network, SVM, and simple regression methods such as logistic regression?


Can we explicitly solve $n$ in terms of $a$? Can we rewrite this inequality in the form of $n>f(a)$ without using $n!$ the factorial?

Is there any way I can 'undo' the factorial operation? JUst like you can do squares and square roots, can you do factorials and factorial roots (for lack of a better term)?   Here is an example: 5! = 120.  Is there a way I can work out the number that must be factorialed (??) to give the answer 120?


I'm using Ubuntu 14.04 LTS, 32 bits and I want to install Genymotion.  But when I go to the official Genymotion's website to download its packages, I see that there is only Genymotion 2.7.2 with support for Ubuntu 15.10 (Wily Werewolf) or above (64bit).   So do you know if there is any other Genymotion version that I can install?

I just installed Virtualbox, downloaded genymotion-2.7.2-linux_x64.bin and tried chmod +x and chmod 777 on it before trying ./genymotion-2.7.2-linux_x64.bin within the folder. I get permission denied error as given below  bash: ./genymotion-2.7.2-linux_x64.bin: Permission denied   I even tried sudo before ./genymotion-2.7.2-linux_x64  To test my luck, used sudo bash and ran ./genymotion-2.7.2-linux_x64 as root. Still, no luck.  The Genymotion website says Ubuntu 15.10 (Wily Werewolf) or above (64bit) . I however have 14.04.  I did try other guides. But nothing was referring to 2.7.2 of Genymotion with 64 bit 14.04  I have VirtualBox installed already.


I was struck by PM Johnson's 'neither he nor I are' a few days ago, which seemed to me obviously ungrammatic, and searched this site, where I found this:    where the answer claims that 'neither you nor I is' is 'of course .. totally wrong,' and that it would have to be 'neither you nor I am,' since the verb is closer to 'I' than to 'you.'  I am unconvinced.  What are some authoritative sources on this issue? And is there really no authority, grammatic or literary, in support of 'neither you nor I is'?  My sense is that it must be 'neither you nor I is' and 'neither he nor I is.'  It seems to me that, regardless of what the pronoun closest to the verb is, the third person ''wins'' when there is conflict, even when the contestants are the 2nd & 1st persons.  (As regards the number of the verb, it seems to me that it must be singular, seeing as what is being denied is a statement about a singular thing, namely that (at least) one of two is something.)  NOTE that my bold-faced question has been implied but neither focused nor answered in the other post.

I was watching the film A Game of Shadows starring Robert Downey Junior and Jude Law when this line came up, "...neither you nor I is in control..." (I can’t remember the exact words that ended the phrase; if anyone can supply them, it would be much appreciated.)   It immediately struck me as being odd. When I mentioned this to my boyfriend; an English native speaker, with a PhD in something sciency, he told me it was correct. When I asked why, he couldn't explain but put forward the following sentence as an example. "Neither of us is in control..." However, I disagreed with the wording and said the sentence should have been: "Neither one of us is in control..." The genderless third person, one, is singular, and hence, so too the verb that follows. And we say, "one is" NOT "one are".      "Neither you nor I are in control over ..."    I believe the above sounds better, but it is more logical to say:     "Neither you nor I am in control..."    because the verb agrees with the subject closest to it; however, I'm not sure if I have ever read or heard this solution. So, I tried inverting the subject and auxiliary verb order and the resulting phrase was:    "Neither you nor am I in control..."    which sounds very formal, pompous, and ... odd. Am I imagining things?  The two subjects you and I are two separate individuals who are not joined together, I agree the verb should be in the singular; but why should we use "is"? We don't say, "you is" or "I is". Before anyone rushes off to claim my question is a duplicate of a previous Stackexchange one:  I want to explain why the answer to that question fails to explain why my boyfriend and the film makers consider the  sentence below correct:     Neither you nor I is in control...   As I see it, Michael and Albert are two separate individuals, it therefore stands to reason that the verb should be singular, and "is" agrees with the subject. If I rephrase the neither and nor construction, I would get:          Michael is not correct but neither is Albert   OR          Michael is not correct and Albert isn't either.      Which have the same meaning, (either being the negative equivalent of neither) the sentences are grammatical which leads me to conclude that the verb must be singular and hence         Neither Michael nor Albert is correct      However, when I rephrase the "neither you nor I" sentence following the same procedure I have to say this:        You are not in control but neither am I (‘I am’ is ungrammatical)   OR              You are not in control and I’m not either.      which leads me to surmise that the sentence below must be grammatically correct        Neither you nor I am in control"      So, why does my boyfriend insist that the sentence ought to be:     Neither you nor I is in control   Which one of us is right and why?


I used projected (Hungarian EOV) orthophoto for segmentation and classification in eCognition (I defined EOV in ecognition as well), the result was exported into shapefile. I opened orthophoto and shapefile in QGIS and ArcGIS, but exported shapefile doesn't overlap with orthophoto even they have the same coordinate system. Can anyone help me to deal with this issue.

I have two raster datasets, they have different projected coordinate systems; one in WGS_84_UTM_Zone_N34, another in Hungarian_1972_EOV,  they overlap each other perfectly if I open them in QGIS.   I would like to transform the coordinate system of the first raster into the second.  I tried Project Raster tool in Data Management toolbox (ArcGIS), it converted the first raster into Hungarian_1972_EOV, but it doesn't overlap with the second raster perfectly (There is a shift between two raster datasets fo about 10-15 meters).   Can anybody help me to find out what is the problem?


Simply, I want to create a field for all of my content types programmatically within my install file of a custom module.   ***WHAT would I need to ALSO put for the uninstall function to delete them.CODE example would be very helpful

How can I approach implementing the following in Drupal 7?  What I need to do is create a module which defines a new fieldable entity, called 'Company'. I have a list of, let's say, 20 fields that need to be filled out by each Company instance. These questions are predefined and some may contain custom validation.  At the moment, I'm at the point when I can add new fields to the Company entity. This works fine at the moment. My issue is that I need all these fields to be there as soon the module is installed, so adding them via the interface isn't an option.  I was wondering how can I approach this? I'd assume it comes down being able to do what can be done using the 'Manage Fields' UI programmatically.


What is the difference between this two declaration in java?  public int hashes[];  public int[] hashes;

I have recently been thinking about the difference between the two ways of defining an array:   int[] array int array[]   Is there a difference?


How to type un-perpendicular ? I found \nparallel for unparallel from amssymb package, however I only found \nvdash which is rotated. Are there another alternatives?

I found , which explains orthogonal and not orthogonal symbols.  I was able quickly to find the orthogonal symbols as \perp, \upvdash etc., but not able to find a top line which strikes the sign from the top left to bottom right. One idea is to combine to symbols e.g., use one of the aboves and add the line in top of it. However I don't know how to do it.


I am creating feature classes from  in ArcCatalog (10.2). When I do this with the file for Bolivia (bl.txt), the feature class is created correctly. When I try to do this with the file for Argentina, the columns LONG and LAT are recognized as Text instead of Double, so I cannot assign them as X and Y fields.  The formats for both files are identical. Both ar.txt and bl.txt contain only numeric values in the columns LONG and LAT, with . as decimal separator. I cannot identify any differences between the two files to explain the different behavior. Is there a way to force ArcGIS to recognize these columns as double precision fields?  As a workaround I can import the txt  files in an Excel spreadsheet and create the feature class correctly from that, but I believe I shouldn't have to.

Related to  I have a CSV file which contains a mixture of numeric and text fields: ID,Txt,Int,Dbl 12345,abc,45,56.78 12346,9,65,23.12 12347,10,66,23.13  According to this  if the top 8 rows contain a text value, the field will be classified as text, yet I am finding that the second field is classified as Long. This means that the value "abc" is omitted:  How can I force ArcMap to recognise this as a text field, while maintaining the data in CSV format? A workaround will be to create a geodatabase table, define the field as text, and Load the data, but I'm hoping to keep the table in CSV (it's the output of another process).


I have a long GPS track that I've converted to a shape file. I need to divide it into segments. The first time I use the "split features" tool, it makes a cut where I draw my line, but also splits the line into separate features at every intersection.  So suddenly I go from having 1 feature, to having 1000... I don't want this, I want to split my one line feature into two at the point I chose. NOT a every intersection.  Is there a setting somewhere I'm missing, or should I file a bug report?

I have a self-intersecting line that I tried to split using the Split Features tool in the Advanced Digitizing Toolbar. The problem is that when I try to split the line at one point, the line splits at every point where it crosses over itself.  This line was originally a tracklog generated in WGS 84 using a Garmin GPS. I imported it into QGIS in GPX format, and saved as a shapefile.  The line is styled with a red marker at the first node.  Before splitting at the blue circle:   After splitting:    What's going wrong here?


If $f:G\to H$ is a surjective homomorphism of finite groups, then $f$ sends Sylow $p$-subgroups to Sylow $p$-subgroups.   Here's what I have. Suppose $\vert G \vert=p^km$ with $(p,m)=1$. Let $P\in \text{Syl}_p(G)$. Then $\vert P \vert =p^k$. By the 1st Isomorphism Theorem, $\vert H\vert =p^km/ \vert \ker (f)\vert=p^ln$ for some $l\le m$ and $n\bigg\vert m$, with $(p,n)=1$. How can I show $f(P)$ has order $p^l$? Is there a better approach to this?

Let $G$ be finite group and $\phi$ : $G \to H$ be a group epimorphism. If $P$ is a Sylow p-subgroup of $G$ then $\phi(P)$ is a Sylow p-subgroup of $H$.   It looks very simple but I'm stuck here.  Let $\lvert P\rvert=p^{k}$. Clearly $\lvert \phi(P)\rvert=p^{n}$ where $n\leq k$. Suppose $\phi(P)$ is not a maximal p-subgroup in $H$ and let $Q$ be a maximal p-subgroup of $H$ containing $\phi(P)$. Then $\lvert Q\rvert=p^{m}$ where $n<m$ and $\phi^{-1}(Q)$ is strictly larger than $P$.   For the rest of the proof, what can I do? Thanks.


I am parsing an XML in Java to check for a certain attribute. The attribute I am searching for is ERG. My code is not working.  import java.io.File; import javax.xml.parsers.DocumentBuilderFactory; import javax.xml.parsers.DocumentBuilder; import org.w3c.dom.Document; import org.w3c.dom.NodeList; import org.w3c.dom.Node; import org.w3c.dom.Element;  public class Parser {  public static void main(String[] args){    try {       File inputFile = new File("parser.txt");      DocumentBuilderFactory dbFactory          = DocumentBuilderFactory.newInstance();      DocumentBuilder dBuilder = dbFactory.newDocumentBuilder();      Document doc = dBuilder.parse(inputFile);      doc.getDocumentElement().normalize();      System.out.println("Root element :"          + doc.getDocumentElement().getNodeName());      NodeList nList = doc.getElementsByTagName("database");      for (int temp = 0; temp < nList.getLength(); temp++) {         Node nNode = nList.item(temp);         if (nNode.getNodeType() == Node.ELEMENT_NODE) {            Element eElement = (Element) nNode;            String nodeAttribute = eElement.getAttribute("key");            if(nodeAttribute == "ERG"){                System.out.println("YES");            }         }      }   } catch (Exception e) {      e.printStackTrace();      }    } }   Here is my parser.txt  <?xml version="1.0"?> <databases> <database key='BC'    driver='com.micro'    url.local='456@we'    login='ses2adm'    password='12dr'     /> <database key='SGB'    driver='com.micro'    url.local='477@jj'    login='ses2adm'    password='12yh'   />   <database key='ERG'    driver='com.micro13'    url.local='2726@kk'    login='sdm123'    password='ghjhj'   />   <database key='MESH'    driver='com.micro'    url.local='hgh'    login='adgvnh33'    password='hghsj'   />   <database key='MESJ_EOM'    driver='com.micro'    url.local='jujj'    login='124hh'    password='sunn'   />   <database key='BSUJ'    driver='com.micro'    url.local='dkl12'    login='eh23'    password='fukll'   />   <database key='BSYH_EOM'    driver='com.micro'    url.local='skk'    login='3556'    password='eyii'   /> </databases>

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


I would like to take the output of a bash command (in this case grep) and insert a blank line every other line:  not like this ...  but  like  this!   Smart way to do it in bash?

When I have an output stream:  a b c d e   How can I double the newlines:   a  b  c  d  e


So I animated bones on an armature, things were normal for a long time. Today I decided to mess with the animation and to my surprise the keys are gone! The animation still plays normally, and the keys appear on the timeline, but channels and keys are nowhere to be found on the Graph Editor when selecting a bone.  I tried:  *Copying and pasting the same keys on the same channels on the same place or different places on the timeline to see if they would magically appear but it didn't work (by the way it works when copy-pasting keys from a bone to another, just create a key first then paste on the same channel)  *Messing with some controls on the Graph Editor that makes curves visible or hidden, and they didn't work  *Creating keys for the armature works but the keys are hidden too  *Creating keys for different objects, and it works. So the problem is not general, it's specific for the armature's bones  Can't provide the file right now but I guess that's enough info. By the way I am using version 2.79b. Researched a little bit to see if someone also had the problem. It seems to be a new thing.

I already made and rigged a character. When I make keyframes in the dopesheet to time my animation, the graph editor does not show any of my keyframes, for any of my animated parts. Even when I go to check the drivers, the driver pane is completely blank, just an empty graph as well.   The weird part is, a couple of sessions ago, it was working completely fine, because I know I was able to edit drivers then. So what could possibly be happening here? I unfortunately cant share the blend file due to the fact that it belongs to the project group I work with, but I was hoping for some general pointers on how I can figure this out. Keep in mind my dope sheet and NLA editor works completely fine, it's just the graph editor.  Here is an image of what it currently looks like:    and here is the corresponding dope sheet for the same animation:


I bought a new bike, online. It's a cube travel SLT, with belt drive, hydraulic brakes, alfine 11 hub.  In the box there were 2 of those plastic clips thingies, taken in the picture next to a set of hex keys for scale:   I have absolutely no clue what they could be used for, and google is not my friend here. What can/should I do with them?

I have recently purchased a hybrid bike with suspension (not sure if that is relevant to this question). It came with two pieces of plastic. Any ideas what they may be for?


I saw this phrase "In chapter 1 section 1". But I thought, "why do we not put a pronoun in front of chapter 1?" because, in the sentence, it's a specific chapter 1. Can anyone explain why? Thank you.

Is using the definite article here in this sentence incorrect? If yes, what's its reason? The word 'chapter' is a count noun.   Have you finished the chapter eight of your novel book?


How significant is the fact 1 isn't a prime number? What will happen if it is? What areas of Mathematics are affected by changing the fact? I know why and how 1 isn't a prime. My question is how significant is the fact.

Why is $1$ not considered a prime number?  Or, why is the definition of prime numbers given for integers greater than $1$?


I recently watched Tenet. And I have lots of questions and one of them is that. If we see from the Protagonist's perspective, he was going to disarm/collect the bomb at staircase in the opera house, and is stopped by some armed man. Then we see a hole in the wall/seat getting filled up by concrete remains, and then we see Neil firing a shot. I understand that it was inverted Neil who actually fired a shot (if seen from his perspective) but when we see it from the viewer/Protagonist's perspective, we see bullet going in the gun that Neil is holding. So strictly from the viewer's/Protagonist's perspective, who put the bullet in the wall/hole at the first place. Imagine if I was one of the persons sitting there at the opera, I must have not seen any hole at the wall because it was not there before shooting started, then at the time Neil fired that shot, that bullet hole must be there for it to work. So how did it work from the viewer/Protagonist's perspective? Sorry if I sound confusing and for my bad English as it's not my first language.

In the first half of Tenet, there is a scene where The Protagonist and Neil break into Freeport and find a glass wall with bullet holes (could only find a good photo with Christopher Nolan in it):  In the next scene, we find out that these bullet holes were caused by an inverted armed man entering the room (exiting the room from their perspective) and reverse-shooting the glass, which removes the bullet holes from the future-facing perspective. This all makes sense, but raises a question: how long were the bullet holes there in the first place? Were they in place as soon as the glass was installed, possibly years ago? Or even back when the glass was manufactured?


I searched a prime of the form $4^n+n^4$ with $n\ge 2$ and did not find one with  $n\le 12\ 000$.    If $n$ is even, then $4^n+n^4$ is even, so it cannot be prime. If $n$ is odd and not divisible by $5$ , then $4^n+n^4\equiv (-1)+1\equiv 0 \pmod 5$.  So, $n$ must have the form $10k+5$.  For $n=35$ and $n=55$, the number $4^n+n^4$ splits into two primes with almost the same size.  So, is there an obvious reason (like algebraic factors) that there is no prime I am looking for ?

I have been stuck on this one for months, really simple to state, really giving me trouble.     Show that if $m^4 + 4^n$ is prime, $m>0$, $n>0$, then $m$ is odd and $n$ is even, except when $m=n=1$.   The case $m=n=1$ gives $5$, so that is why it is excluded. Clearly $m$ is odd, for if it was even, the number would be divisible by at least $4$, but I can't seem to get rid of the case where $n$ must be odd.   The only thing I've managed to try is to write $m$ as an odd number, say $m = 2k+1$, and $n = 2\ell + 1$, then get $$ m^4 + 4^n = (2k+1)^4 + 4^{2\ell+1} = 16k^4 + 32k^3 + 24k^2 + 8k + 1 + 4^{2 \ell + 1} $$ and this is congruent to $0 \mod 5$ unless $k \equiv 2 \mod 5$, and now it gives you an even more ugly polynomial if I write $k = 5j+2$, and it's not working. I've tried other inconclusive approaches, like trying to see if two numbers of some form generate numbers of the same form.. (for instance primes of the form 8k+1 and 8k+7 always generate primes of the same form when multiplied together, stuff like that).  Any ideas? Even just ideas you haven't gave a thought... they're welcome!


When we displace a body from ground to a height we do positive work against gravity and gravity too does work but negative. Do they cancel each other? Or does the external force do extra work?

Consider a particle on the ground. This particle is raised by a force of magnitude $mg$ to a height $h$ above the ground. At this point, the work done on the particle by the force is $mgh$, which is equal to the potential energy of the particle. But, during this period, the force of gravity also acts on the particle and is displaced by $h$, and so does a work of $-mgh$ on the particle. Shouldn't  the two cancel and no net work should be done on the particle?   If they don't cancel, then where did the energy that came from the work done by the force of gravity go?


I have a 3D matrix filled with "empty space" where I put some objects (objects are represented as bunch of occupied space).  The bullet is fired from coordinates (x1,y1,z1) at angles (verticalAngle,horizontalAngle).  How do I find the first coordinates in the bullet's trajectory line which is not market as "empty space"?  I suppose I'd have to loop through all the coordinates in that line till I find the not empty one (or the end of the matrix). But how do I calculate what are those coordinates that I have to go through?    When firing a bullet in 2D space I suppose this would be calculated as y = cos(angle) * x + startPosition where I'd increment x (in a for loop) to get y and check (x,y) cell for objects or "empty". Actually I'd have to increment y in the for loop to get x instead in case the trajectory line is closer to y-axis than x-axis.  But can someone help me with doing this in 3D space?  EDIT: Well I found this formula: (x,y,z)=(x0,y0,z0)+t(a,b,c) where (x0,y0,z0) are starting points and (a,b,c) direction factors, so I think I could increment t in a loop to get the coordinates.

I am developing a game with a Minecraft-like terrain made out of blocks. Since basic rendering and chunk loading is done now, I want to implement block selecting.  Therefore I need to find out what block the first person camera is facing. I already heard of unprojecting the whole scene but I decided against that because it sounds hacky and isn't accurate. Maybe I could somehow cast a ray in view direction but I do not know how to check the collision with a block in my voxel data. Of course this calculations must be done on the CPU since I need the results to perform game logic operations.  So how could I find out which block is in front of the camera? If it is preferable, how could I cast a ray and check collisions?


I'm trying to run this command in the terminal:  sudo apt install software-properties-common   This is the error message I get:  E: Could not get lock /var/lib/dpkg/lock-frontend - open (11: Resource temporarily unavailable)   E: Unable to acquire the dpkg frontend lock (/var/lib/dpkg/lock-frontend),     is another process using it?

I get this error when trying to use apt-get:  E: Could not get lock /var/lib/dpkg/lock - open (11 Resource temporarily unavailable) E: Unable to lock the administration directory (/var/lib/dpkg/) is another process using it?     How can I fix this?


See this minimum working example:  % compile with LuaLaTex and Biber  % !TeX encoding = UTF-8 % !TeX spellcheck = de_DE \documentclass[12pt,a4paper,titlepage,numbers=noenddot]{scrartcl} \KOMAoption{listof}{totocnumbered,leveldown} % unicode \usepackage[utf8]{inputenc} \usepackage[T1]{fontenc} \usepackage[utf8]{luainputenc}  \usepackage{amsmath} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{graphicx} \usepackage{booktabs}  % acronyms \usepackage{acro}  % https://tex.stackexchange.com/questions/192930/acro-package-handling-possessive-case-apostrophe-s#268225 \ExplSyntaxOn \ProvideAcroEnding{genetiv}{s}{s} \NewAcroCommand \acg {     \acro_genetiv:     \acro_use:n {#1} } \ExplSyntaxOff  \acsetup{     hyperref = true,     page-style = comma,     pages = all, %/first     % list-style = tabular     tooltip=true,     activate-trailing-tokens = {dash,babel-hyphen}, % German quotation for hyphen, see official doc     cite-connect = {} % no space before citation }  \DeclareAcronym{qrCode}{     short = {QR-\-Code},     long = \enquote{\foreignlanguage{english}{Quick Response}}-\-Code,     % short-genetiv = , }  % deutsch \usepackage[ngerman]{babel} \usepackage[ngerman]{isodate} \usepackage{lmodern} % font \usepackage[german=quotes]{csquotes}  \begin{document}      custom: \acg{qrCode}        plural: \acfp{qrCode}        for comparison, singular: \acf{qrCode}  \end{document}   The problem is the QR code acronym, defined via the package acro.  It looks like this:   Now in both the plural and the custom ("genetiv") defined word ending, the short version gets an s before the word (sQR-Codes) in addition to after the word ending.  This issue does not happen:   when you only request the single version standalone (without first appearance) via \acsp e.g. or, as demonstrated, when you request the singular version.

I have an acro first use that must be plural, but I am getting an erroneous "s" when I shouldn't be. I'm getting (sIMFs) when it should be (IMFs). See picture and code below. The problem only occurs on the first call and it does so for all my acronyms. Thanks in advance.   \documentclass[12pt,twoside]{report} \usepackage{acro} \DeclareAcronym{IMF}{     short = IMF,     long  = Intrinsic Mode Function,     class = abbrev}  \begin{document} \acp{IMF} \acresetall \ac{IMF} \acp{IMF} \acfp{IMF} \end{document}


Is there a way to exclude all files, in all subfolders, and keep the folder structure?

Let's say I have a directory tree like this:  FOLDER:     file1     file2     file3     Subfolder1:         file1         file2     Subfolder2:         file1         file2   If I used rm -r FOLDER/*, everything in FOLDER would be deleted including sub-directories. How can I delete all files in FOLDER and in its sub-directories without deleting actual directories?


I need to find $r'(t)$ and $||r'(t)||$ of $r(t)=<t,t,t^2>$, and tell where the curve hits the $xy$ plane (if it does). Also, I need to say something about how the curve looks like (do I just plot some points and figure out how it looks like?). I understand how to find $r'(t)$ and $||r'(t)||$, but how do I tell where the curve hits the $xy$ plane, and how do I describe the curve?  Here are my solutions for $r'(t)$ and $||r'(t)||$:    $r(t)=<t,t,t^2>$  $r'(t) = <1,1,2t>$     $||r'(t)||=\sqrt{2+4t^2}$

I have to find $r'(t)$ and $||r'(t)||$ for $r(t)=<t,t,t^2>$, which I know how to do.  $r'(t)=<1,1,2t>$ $||r'(t)||=\sqrt{2+4t^2}$  The problem is that my professor didn't explain how to find where each curve hits the $x-y$ plane (if it hits).  I'm guessing that I have to make $z=0$, but where?


I am translating a story from Turkish to English for my friends. In Turkish we don't have "he/she/it". We only have "O" and it includes all.  the story is about someone in depression. And his or her gender is intentionally unspecified, even avoided, since depression can happen to anybody. The writer just wanted the reader to put himself/herself in character's shoes. unspecified gender is kind of the whole point of story. I can't write "that night, he or she couldn't sleep again." What should I do?

Is there a pronoun I can use as a gender-neutral pronoun when referring back to a singular noun phrase?  Each student should save his questions until the end. Each student should save her questions until the end.


Can't remember much about the books. Read them probably 20+ years ago. There were vampires, only I think they might have been called "wampires." They rode around on big black beasts. The protagonist could travel using a portal/doors. I vaguely recall there being a war amongst the wampires and the hero had to team up with one of them. I think the wampires killed their human victims during sex, or at least they could, and that was what my 20 something year old mind fixated on.

I have been trying to identify a book that I read maybe 25-30 years ago (1987-1992), in which there are vampire or vampire-like creatures, but instead of being created in the traditional way (e.g. bite on the neck), something drops a drop of a fluid on the back of their neck, which is then absorbed into the body and transforms them. I have a vague notion that some sort of tree is what creates these drops. The drops may have had a shiny metallic appearance.  I've tried to find this book before and always came up short. I'm starting to think the whole thing was a dream and I never read it at all. But I really feel like it was a book or at least a short story.