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MathGroup Archive 1998

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DSolve&NDSOLve with 3.0.1, w95

  • To: mathgroup at smc.vnet.net
  • Subject: [mg12858] DSolve&NDSOLve with 3.0.1, w95
  • From: mhicks <marlyn.hicks at Cubic.COM>
  • Date: Wed, 17 Jun 1998 00:28:01 -0400
  • Organization: xcubic
  • Sender: owner-wri-mathgroup at wolfram.com

I need some advice! 
Both the instructions below return solutions with math 2.2.1. 3.0.1
returns excuses by the page full. Am I missing something, or has
mathematica lost something between 2.2.1 and 3.0.1?  I suspect the
fault is mine since I have not noted discussion of this problem here or
otherwise. 
I would appreciate any help anyone can offer. meanwhile, I will
carefully retain 2.2.1..... 

gv=1;gp=.02;gr=.0001;ar=1;ai=.99;
DSolve[{ac'''[t]+gv ac''[t]+gp ac'[t]+gr ac[t]== (ai-ar) gr, ac[0]==0,
 ac'[0]==(ai-ar) gv, ac''[0]==(ai-ar) gp-gv ac'[0]},  ac[t], t]


Clear[ai,ar,t,v];kv=1;ka=.2;kj=.0016; vt=NDSolve[{v''''[t]+kv v'''[t]+ka
v''[t]+kj v'[t]== ka ar'[t]+kj ar[t], p''''[t]+kv p'''[t]+ka p''[t]==
v'''[t]+kv ar'[t]+ka ar[t],  ar'[t]==.1, v[0]==0,  v'[0]==.9,
v''[0]==.09+kv-.9 kv, v'''[0]==ar'[0] kv +ka ar[0]-v''[0] kv-v'[0] ka, 
ar''[0]==0,  ar'[0]==.1, ar[0]==1, p'''[0]==.29, p''[0]==.9, p'[0] ==0,
p[0]==0}, 
{v[t], p[t], ar[t]}, {t, 0, 1000}]
-- 
ned!


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