function [ res ] = mu_rel_2(r,z)
persistent r0 z0 res0
if( isequal(r,r0) && isequal(z,z0) )
  res = res0;
end
global fea0
p = [r(:), z(:)]';
A = evalexpr('A', p, fea0);
Ar = evalexpr('Ar', p, fea0);
Az = evalexpr('Az', p, fea0);
res = 2890*exp(-((sqrt((A./(r+sqrt(eps))+Ar).^2+Az.^2)-0.7)./0.66).^2)+1;
res = reshape(res,size(r));
r0 = r; z0 = z; res0 = res;
