function dx=cdp4fpd2fun(w,x)
cao=0.037; 
v0=50.0;
al=0.005;
t1=((1.0-x(1))^0.5)*(2.5-2.0*x(1));
t2=(1.0-0.2*x(1))^(1.5);
t3=2.5*(cao^0.5)/v0;
r1=t3*t1*(x(2)^1.5)/t2;
r2=-al*(1-0.2*x(1))/(2.0*x(2));
dx = [r1;r2];