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11-24-2019
03:06 PM

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1 ACCEPTED SOLUTION

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11-25-2019
03:49 PM

11-25-2019
03:49 PM

"but it is solved by Mathcad":

Then show the Mathcad file that does it....

When I read the article, the authors state that Mathcad was used to calculate a couple of parameters; and it - could - be used to solve the set of ODE's.

Further, in both expressions of k.1 appears a value named C.Bs

This value is not explained in the document, it does not even appear in the list of symbols at the end.

Bottom line: The article is unclear (at least for a casual reader and not knowledgable on the subject) from a mathematical point of view.

What is clear, is that with a set of three differential equations it is not possible to solve 4 independent functions. (Note: the crux is in 'independent' here!) There may be a relation between the 4 functions that the article is solving, but they are not clearly explaining it.

The very same argument holds for your set of 5 differential equations and trying to find 6 functions....

Luc

7 REPLIES 7

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11-24-2019
03:07 PM

11-24-2019
03:07 PM

Re: too many initial conditions?

this is the problem

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11-24-2019
04:44 PM

11-24-2019
04:44 PM

Re: too many initial conditions?

Mathcad is right. You have too many initial conditions, as also you have too many functions to solve for.

The set of differential equation does not provide enough equations to solve for 6 functions, only 5.

So you can solve for 5 functions, e.g. by assuming that C.Ab(t):=0.1 (all the time) which is what I did in the attached sheet. I did not find a clue in the article regarding how C.Ab(t) was handled.

I hope you can find it.

Success!

Luc

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11-24-2019
10:50 PM

11-24-2019
10:50 PM

Re: too many initial conditions?

thank you but what you sent file is not showing graph ...

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11-24-2019
10:53 PM

11-24-2019
10:53 PM

Re: too many initial conditions?

hbu this one?

this is same style of problem.

Alos, it cannot solve?? but it is solved by mathcad

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11-25-2019
02:00 AM

11-25-2019
02:00 AM

Re: too many initial conditions?

Automatic calculation is switched OFF in the sheet.

To show the graphs: Press F9 .

Success!

Luc

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11-25-2019
03:09 PM

11-25-2019
03:09 PM

Re: too many initial conditions?

Hi,

If I knew, for example the diff. eq, f' (t)=f(t), there would be no problems, see image:

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11-25-2019
03:49 PM

11-25-2019
03:49 PM

"but it is solved by Mathcad":

Then show the Mathcad file that does it....

When I read the article, the authors state that Mathcad was used to calculate a couple of parameters; and it - could - be used to solve the set of ODE's.

Further, in both expressions of k.1 appears a value named C.Bs

This value is not explained in the document, it does not even appear in the list of symbols at the end.

Bottom line: The article is unclear (at least for a casual reader and not knowledgable on the subject) from a mathematical point of view.

What is clear, is that with a set of three differential equations it is not possible to solve 4 independent functions. (Note: the crux is in 'independent' here!) There may be a relation between the 4 functions that the article is solving, but they are not clearly explaining it.

The very same argument holds for your set of 5 differential equations and trying to find 6 functions....

Luc