Question: Problem in Solving Non-linear PDE

I am not able to numerically solve a non-linear PDE using "pdsolve". The problem seem to be arising due to non-linearity in the PDE. Once I remove the non-linearity (by removing a partial derivative in X below), the error goes away. The code and the error are included below: X:= Q(t,r)/(Q(t,r)+(0.75*diff(Q(t,r),r))); PDE:=diff(Q(t,r),t)+X*(diff(Q(t,r),r)*1.5*(0.03-r))+Q(t,r)*r=0; IBC:={Q(1,r)=0.01*r,Q(t,1)=10*(exp(1-t)-0.999),Q(t,0)=(exp(1-t)-1)}; ANS:=pdsolve(PDE,IBC,numeric,time=t,range=0..1,method=Box); Error, (in pdsolve/numeric/process_PDEs) selecting function must return true or false The Maple documentation seems to suggest that non-linear PDEs can be solved using "pdsolve". I would appreciate any help in resolving this problem. Thanks, vt33
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