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MathGroup Archive 2004

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Re: newbie question DSolve

  • To: mathgroup at smc.vnet.net
  • Subject: [mg52161] Re: newbie question DSolve
  • From: p-valko at tamu.edu (Peter Valko)
  • Date: Sat, 13 Nov 2004 04:40:10 -0500 (EST)
  • References: <cmppui$mll$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Let us use the values:

d=1/2;
L=1;
yL=1;

and denote the unknown y[d] by yd. Then

Solve[ yd == (y[x]/. DSolve[{-y[x] + Derivative[2][y][x] ==DiracDelta[d-x]*yd,
              y[0] == 0, y[L]== yL}, y[x], x][[1]])/.x->d];

%//InputForm

{{yd -> (2*Sqrt[E])/(1 + 3*E)}}

Regards
Peter




"Pratik Desai" <pdesai1 at umbc.edu> wrote in message news:<cmppui$mll$1 at smc.vnet.net>...
> Hello all
> 
> I am trying to use DSolve to solve a ode with discontinuity in it (wave 
> equation with a viscous damper injected at a location d)
> 
> This is what i am using
> 
> DSolve[{y''[x]-lamda^2*y[x]==DiracDelta[x-d]*y[x],y[0]==0,y[L]==
> =0},y[x],x]
> 
> the problem I am facing is that
> 
> y[x] on the right hand side (next the delta function) varies w.r.t to 
> the location
> 
> y[x]==y[x]&& 0<=x<=d
> y[x]==y[L-x]&&d<=x<=L
> 
> I can solve the above equation without the y[x] coupled to the delta 
> function
> 
> Please advise and thanks in advance,
> 
> 
> Pratik Desai
> 
> 
> ps: This is my third attempt at posting my query, I hope this time it 
> makes it to the list :)


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