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rate constants determination: from ODEs solving v.s. numerical integration

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Again in the book "chemical kinetics with maple and mathcad", chapter 4 introduces different ways for rate constants determination.

 

Take figure 4.8 as an example (corresponding attached file is "Fig_4_08_PineneIsomerization_InvTask_MC14"  ), numerical integration method is used searching rate constants:

integ method 1.PNG

integ method 2.PNG

but i think that  solving ODEs is more direct and general than integration method, so I solve the problem with ODEsolve method:

diff method 1.PNG

diff method 2.PNG

Both methods looks good enough, but differential method results are closer to that of DYANFIT than for integral method.

 

But differential method seems much more initial-condition sensitive than integral method, e.g. if guess values of k1--k4 are all set to 1, the calculation will be very time-consuming. and I dont know how to improve this situation.

 

Does anybody give any suggestions on "lowering/ reducing" the initial - condition sensitivity of differential method?


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