Paulo Baumbach

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14 years, 245 days

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@tomleslie 

Yes, you are right. Thanks for the good remarks about the problem.

@Carl Love 

I did not succeed . Maybe the Heaviside function can help.
Anyway, thank you very much for your help.

@Carl Love 

Well, after fixing some errors, I have one more problem. Now in relation to the amount of boundary conditions. I believe this is related to an earlier discussion (https://mapleprimes.com/questions/225219-Why-Does-Pdsolve-In-Numeric-Mode-Return).

Thank you for your help.

Test_1.mw

@Rouben Rostamian  

Yes, most expressions have an error. Thanks for your comments and for your help.

@Carl Love 

Yes, you're right. Thanks for your comments and for your help.

@acer 

It is true. You're absolutely right. I was careless in my placements.

Your routine works perfectly.

Thanks a lot for the help.

@acer 

Your response exceeded my expectations. Thank you.
However, in my version 18 the shadebetween function does not seem to exist. I checked the online help and saw that this function has been available since version 15. Can this be a bug in my program?

@Preben Alsholm 
Perfect ... Everything is working ... Thank you very much.

@Preben Alsholm 

I think the problem is still not resolved.

The boundary conditions of the ode system depend on H, which is updated within the loop (H [i + 1] = H [i] + dH).

So, with each loop we have the same ode system with different ics.

Thank you

@Preben Alsholm 

Yes, now it works very well... Perfect result, with a very short processing time...

Well, just to clarify a point... As you well observed, the loop closes at i = 742... This is natural, since the purpose of the routine is to find a value of t that fulfills the condition "if fvp> = 0 then "... After observation on i, the value of dt (specifically Ts) can be adjusted, causing the loop to be executed close to the value 20000, which improves the discretization of the problem ...

Thanks a lot for the help...

@Preben Alsholm 
As always, you are helping me a lot. Not only with the maple but also with the math. And for that, I thank you.

Well, I'm looking at your code suggestion, line by line. However, when executing it, the following error occurs in the command "resNew: = dsolve ({sys_ode} ...": "Error, (in dsolve / numeric / process_input) input system must be an ODE system, got independent variables { x, H-47.3135421221118} ".

Any tips on this?

@mmcdara 

The variable nn is equal to 20, which causes this loop to execute at this speed ... But I usually need nn = 10000 or nn = 20000 ... In these situations the time processing is much larger ...

Also, I still deal with 8 more loops of this type, with the same problem ... So processing time really is my primary issue ...

About the Bcs you mentioned, they are correct ...

Thank you

@acer  

Well, in this example (ODE.mw) I used the optimize = true option and this worked very well...

However, the compile option did not work... I saw a discussion on the topic (https://www.mapleprimes.com/questions/205037-Compiletrue-In-Dsolvenumeric) and I confess that I was a bit confused ...

Anyway, I thank you for your clarification.

@Carl Love Perfect! Thank you!

@tomleslie 

The answer is simple: I am a beginner.
Thanks for your help.
I hope your next answers are more friendly.

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