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MathGroup Archive 2000

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Apparently easy ODE

  • To: mathgroup at smc.vnet.net
  • Subject: [mg22922] Apparently easy ODE
  • From: Kurt Taretto <Kurt.Taretto at ipe.uni-stuttgart.de>
  • Date: Thu, 6 Apr 2000 02:04:38 -0400 (EDT)
  • Organization: Comp.Center (RUS), U of Stuttgart, FRG
  • Sender: owner-wri-mathgroup at wolfram.com

Hi, I'm having some problems solving PDE's, for example the folowing
notebook


Clear["Global`*"];

(* constants definitions *)

Es =11.8*8.85418`50*10^-14;
q = 1.60218`50*10^-19;

Nd = 1.0`50*^16; g = 1.0`50*^-4; G = 1.0`50*^20; u= 500.0`50; DD =
25.0`50;
k1 = q/Es;

solution = NDSolve[{e'[x] == k1 p[x],

        G - u e'[x] p[x] - u e[x] p'[x] + DD p''[x] == 0,

        e'[0] == 0, p[g] == 1.0`50*^10, p'[0] == 0},

      {e, p}, {x, 0, g}, WorkingPrecision -> 20];

Plot[p[x] /. solution, {x, g/100, g}, PlotRange -> All];

causes an error message, "Cannot find starting value for the variable
x.", and obviously no solution is given.  Apparently this error message
is about the internals of the algorithm, but I can't figure out what I'm
doing wrong.  Any help on this would be appreciated.

Thanks!

Kurt Taretto



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