Hi, 

does anyone remember of a recent question (maybe a post) about a bouncing ball over a hilly ground?
I can't put the finger on it.

TIA

One decade on MaplePrimes

Always I Wish A Wonderful Year In Mathematics As Annus mirabilis

Fereydoon Shekofte

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Since we have such a great community here at MaplePrimes, we wanted to reach out and ask if there are any articles or questions that you'd like to see added to our FAQ.

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I want to solve the following system using PDE Solve command but finding an error. Please help me in this regard. Thanks!
 

restart; d1 := 1; d2 := 1; AA := 0.2e-2; BB := 0.79e-1; L := 1;
with(PDEtools, casesplit, declare);
PDE1 := diff(u(x, t), t) = d1*(diff(u(x, t), x, x))-u(x, t)*v(x, t)^2+AA*(1-u(x, t)); PDE2 := diff(v(x, t), t) = d1*(diff(v(x, t), x, x))+u(x, t)*v(x, t)^2-BB*v(x, t);
                      /  2         \                           
         d            | d          |                  2        
PDE1 := --- u(x, t) = |---- u(x, t)| - u(x, t) v(x, t)  + 0.002
         dt           |   2        |                           
                      \ dx         /                           

   - 0.002 u(x, t)
                          /  2         \                   
             d            | d          |                  2
    PDE2 := --- v(x, t) = |---- v(x, t)| + u(x, t) v(x, t) 
             dt           |   2        |                   
                          \ dx         /                   

       - 0.079 v(x, t)
IBC1 := {u(0, t) = 1, u(1, t) = 1, u(x, 0) = 1-(1/2)*sin(Pi*(x-L)/(2*L))^100}; IBC2 := {v(0, t) = 0, v(1, t) = 0, v(x, 0) = (1/4)*sin(Pi*(x-L)/(2*L))^100}; dys1 := {IBC1, IBC2, PDE1, PDE2};
         /              /  2         \                           
         | d            | d          |                  2        
dys1 := < --- u(x, t) = |---- u(x, t)| - u(x, t) v(x, t)  + 0.002
         | dt           |   2        |                           
         \              \ dx         /                           

   - 0.002 u(x, t), 

                /  2         \                                     
   d            | d          |                  2                  
  --- v(x, t) = |---- v(x, t)| + u(x, t) v(x, t)  - 0.079 v(x, t), 
   dt           |   2        |                                     
                \ dx         /                                     

   /                                                           100
   |                                        1    /1           \   
  < u(0, t) = 1, u(1, t) = 1, u(x, 0) = 1 - - sin|- Pi (x - 1)|   
   |                                        2    \2           /   
   \                                                              

  \   
  |   
   >, 
  |   
  /   

   /                                                       100\ 
   |                                    1    /1           \   | 
  < v(0, t) = 0, v(1, t) = 0, v(x, 0) = - sin|- Pi (x - 1)|    >
   |                                    4    \2           /   | 
   \                                                          / 

  \ 
  | 
   >
  | 
  / 
pds := pdsolve(dys1, numeric, time = t, range = 0 .. 1);
Error, (in pdsolve) invalid input: `pdsolve/numeric` expects its 2nd argument, IBCs, to be of type {list, set}, but received time = t
p1 := pds:-plot(t = 0, numpoints = 50);

p2 := pds:-plot(t = 1/8, numpoints = 50, color = blue);

p3 := pds:-plot(t = 1/4, numpoints = 50, color = green);

plots[display]({p1, p2, p3});
Error, `pds` does not evaluate to a module
Error, `pds` does not evaluate to a module
Error, `pds` does not evaluate to a module
Error, (in plots:-display) expecting plot structures but received: {p1, p2, p3}

When writing a post on MaplePrimes it is possible to access the source code, which allows to introduce/edit many attributes. Is it possible to observe the source of another post?

Generally when I respond to questions on this site, I make sure that I tick the checkbox requesting that I get an email when updates are made to the thread.

I've just realised that I have been receiving no such updates for a week or so. Two possibilities

1. Problem with Mapleprimes website, meaning that email updates aren't being generated/sent
2. Problem with my ISP

Before I try investigating (2) above, I'd just like to know if anyone else has seen any issue which might be explained by (1) above

Surely there is some button I can click that simply shows all my posts/questions without having to search?

It has become more and more common to meet questions as labelled as "Spam". What does this classification mean?
Strangely if you click on the little red flag "Spam" it even seems that you can delete the corresponding question.
Does it mean that some people here have the power to decide if a question deserves to be answered or merits to be put on the trash?
Given that these questions are answered the same way than any other non spam labelled question, why are they labelled as spam?

 

Markiyan has contributed valueable mapleprimes posts and comments.  His account is unaccessible to view listed posts.  Is his information deleted?

If I create  and save a worksheet in Maple 2019, then try to up load it here, it uploads but contents won't display

No issue if I have an "identical" worksheet in Maple 2018.

See the attachment attempts below

#### Result of trying to upload Maple 2019 file here

Maple Worksheet - Error

Failed to load the worksheet /maplenet/convert/fibon2019.mw .
 

Download fibon2019.mw

But "same" file from Maple 2018 "works"

Download fibon2018.mw

Earlier today (30/12/2018), I answered a fairly routine question  relating to solving the PDE for a vibrating string problem where the initial string profile was given by a piecewise function. No big deal - a fairly simple answer. Only thing that struck me at the time as odd/unusual, was that 2-3 days ago there was a very (very!) similar problem which I had also answered.

These two problems were posted from different usernames, but I did reference the earlier problem in my solution to the later one, just because they were so similar.

Both of these questions (and obviously my answers) have now "disappeared" -how/why?

1. I can (just about?) understand that an OP might be allowed to delete his/her question, but I am surprised that (s)he can delete a complete thread - ie after response(s) have been provided
2. I suspect that both questions came from the same individual employing different user names (why?). I guess this is pretty much impossible for MapleSoft to verify, particularly if the OP has multiple email addresses??
3. Would I be correct in assuming that this is a method for students to get their homework" done whilst leaving little/no trace for their academic supervisors to find?
4. Since all trace of both questions have disappeared and I can't actually remember the usernames (or emails with which they are associated), presumably the OP could repeat this behaviour indefinitely?

It seems that the forum activity of the user  Markiyan Hirnyk   is no longer accessible.
Is it a site problem?

I have multiple accounts. I would like to delete them. Please tell me how to delete it. Thank you.

I hate it when a user bumps every Question that they've ever asked over the past five years to the top of Recent (aka Active Conversations) stack! This is not the first time that this has happened. I rely heavily on that stack being truly the threads with the most-recent material. Can't something be done about this short of deleting the threads? That seems too drastic: While this user has occasionally been a pest in the past, they've also posted some decent material. There should be some way for a moderator to just reset the stack positions to what they were previously.

Does Maple have a way to upload a screenshot of a worksheet or a savefile of a worksheet to MaplePrimes?