function y= fun2(x0,tt);
% 反相特性環節的估計函數

% Copyright 2001-2002 ECUST. 
%   $Revision: 1.2 $  $Date: 2001/05/11 22:18:41 $

dd=(tt-x0(3)).*(tt>x0(3));
y=x0(1)*(1-exp(-dd/x0(2)))-x0(4)*(1-exp(-dd/x0(5)));