
Re: Laplace and ODE  what is wrong?
WalterSchrabmair Feb 1, 2012 12:12 PM (in response to WalterSchrabmair)I have found my misunderstanding of Laplace transform. Only f(t) must be tranformed, see MC15 sheet.

LapODE.xmcdz.zip 296.6 K

Re: Laplace and ODE  what is wrong?
ValeryOchkov Feb 1, 2012 9:30 PM (in response to WalterSchrabmair)
Re: Laplace and ODE  what is wrong?
WalterSchrabmair Feb 2, 2012 4:09 AM (in response to ValeryOchkov)Dear Valery,
I want to solve a ODE by LaplaceTransformation. I have f(t) and in MMA the results is as follows. (see pic)
ANd in MC 15 I do get a other form. Is that the same? Thanks for help
Walter

MMA_HS.png 8.3 K

MathCAD_HS.png 12.3 K

Re: Laplace and ODE  what is wrong?
WalterSchrabmair Feb 2, 2012 4:45 AM (in response to WalterSchrabmair)Here I could solve the ODE with laplace in MMA successfully. BUT in MC it does n ot work .
WHY? Any advices are welcome.
Thanks
Walter

Re: Laplace and ODE  what is wrong?
FredKohlhepp Feb 2, 2012 5:23 AM (in response to WalterSchrabmair)
Re: Laplace and ODE  what is wrong?
WalterSchrabmair Feb 2, 2012 5:35 AM (in response to FredKohlhepp)Dear Fred,
thanks a lot for your fast response.
When I transform the f(t) with MMA I got this result. Are you sure that you did not miss the Theta(tau)?
Thanks for your reply.

MMA_HS_2.png 4.7 K

MMA_HS_2a.png 5.3 K

Re: Laplace and ODE  what is wrong?
ValeryOchkov Feb 2, 2012 5:43 AM (in response to WalterSchrabmair)There is (was) a lot of errors at Laplace Trans in Mathcad 14/15 (with MuPad not Maple Symbolic Engine).

Re: Laplace and ODE  what is wrong?
WalterSchrabmair Feb 2, 2012 5:46 AM (in response to ValeryOchkov)Yes I think that is still a bug. See inv transform of f(t) in pic.

MMA_HS_3.png 21.4 K

Re: Laplace and ODE  what is wrong?
ValeryOchkov Feb 2, 2012 5:59 AM (in response to WalterSchrabmair)Walter Schrabmair wrote:
Yes I think that is still a bug. See inv transform of f(t) in pic.
This is one reason why our (with V.Korobov) book has a titel "Chemical Kinetics with Mathcad and... Maple"

Re: Laplace and ODE  what is wrong?
WalterSchrabmair Feb 2, 2012 6:23 AM (in response to ValeryOchkov)thanks Valery, I tried it with Maple v15 but have problems in translate the MMA 8.0 sheet into Maple.
I have asked a help question in http://www.mapleprimes.com/questions/130265WhoCanHelpMeInTransformASimple?sq=130265
Maybe there is a helping hand for that problem on the Maple forum.
thansk
walter




Re: Laplace and ODE  what is wrong?
FredKohlhepp Feb 2, 2012 7:19 AM (in response to WalterSchrabmair)I'm flailing a bit, and my version 14.0 is having serious problems with the symbolic solver.
See if this makes sense:

pharmacy.xmcd.zip 57.9 K

Re: Laplace and ODE  what is wrong?
WalterSchrabmair Feb 2, 2012 8:10 AM (in response to FredKohlhepp)Looks good but got still an error that the X1 or X2 fn is not defined  even that in MC 15 the red invlap lines signals that is just to big to display but should be able to store in fn.
Please take a look.
Thanks a lot

Re: Laplace and ODE  what is wrong?
WalterSchrabmair Dec 4, 2012 8:42 AM (in response to WalterSchrabmair)THis Problem with Laplace substitution can also not be solve in MathCAD 15 M 020. WHat a shame!


Re: Laplace and ODE  what is wrong?
WalterSchrabmair Nov 27, 2013 2:45 AM (in response to WE)Thanks Werner, yes I agree to you. Let`s wait until PRIME 6.0, maybe they will correct this bug.

Re: Laplace and ODE  what is wrong?
WE Nov 27, 2013 11:44 AM (in response to WalterSchrabmair)Prime 6 already!? Thats what I call optimism and positive thinking ;)
But then, I won't bet on it.









