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Topic: Problem with discontinuity in NDSolve[]
Replies: 1   Last Post: Jul 11, 1996 12:49 AM

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Axel Kowald

Posts: 4
Registered: 12/7/04
Problem with discontinuity in NDSolve[]
Posted: Jun 26, 1996 3:09 AM
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Hi everybody,

I have a problem with NDSolve if my equation contains a discontinuity.
If I try

NDSolve[{y'[t] == 10 - y[t] * If[y[t]-15 <= 0, 0, 1],
y[0] == 0}, y, {t,0,20}]

I always get the error: Maximum number of steps reached.
The solution should be a linear increase until y = 15 followed by an
exponential decay until a steady state is reached by y = 10


Funny enough if I try

NDSolve[{y'[t] == 10 - y[t] * If[t-15 <= 0, 0, 1],
y[0] == 0}, y, {t,0,20}]


causing the discontinuity to be at t = 15 instead of y = 15 NDSolve has no
problems at all. (But of course this is not what I want.)


ANY SOLUTIONS ??? ANY IDEAS ???



Many thanks


Axel Kowald


P.S. I'm using Mma 2.2 on a Mac with 7.5.3 and 24 MB RAM








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