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dharr

Dr. David Harrington

8440 Reputation

22 Badges

21 years, 28 days
University of Victoria
Professor or university staff
Victoria, British Columbia, Canada

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Contact Dr. David Harrington
I am a retired professor of chemistry at the University of Victoria, BC, Canada. My research areas are electrochemistry and surface science. I have been a user of Maple since about 1990.

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These are answers submitted by dharr

try a substitution?...

dharr 8440
October 25 2005
0 0
you could try to change variables so that x=infinity is at a finite value. E.g. u=1-exp(-x) has u=0 at x=0 and u=1 at x=infinity. The d.e. then becomes I think f'(u)*(1-u)+f(u)*f''(u)=0 and you could then do the same for the boundary conditions.

non-linear eqns with more eqns than vari...

dharr 8440
October 16 2005
0 1
With more eqns than variables it is likely that there is no solution. But in any case, I find that once Maple starts to use virtual memory on disk (with the symptoms you mention) it's a waste of time proceeding.

F=ma solving...

dharr 8440
October 14 2005
0 0
Your r.r needs to be r(t).r(t) to get the expression you want. But there is still a problem since this is a scalar and you are adding it to a vector. You can't differentiate a vector like this; you need to code your problem as three separate differential equations.
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