% semi-infinite heat conduction
% with surface convection
clear
x=0.04;a=1.5e-6;h=12;k=0.5;
bi=h*x/k;tau=x*x/(4*a)
n=0;

for u=0.025:0.025:2
   
   n=n+1;t(n)=1/u;tn=t(n);
   y(n)=erfc(u)-exp(bi+(bi*bi/(4*u*u)))*erfc(u+bi/(2*u));
   
end

 figure(1); clf;
 plot(t,y,'linewidth', 1.0)
 xlabel('t^* = \tau/t = x^2/4\alphat')
 ylabel('\eta')
 grid on

% fig=figure(1);
% print(fig,fullfile(pwd, 'Figure6_2.tif'),'-dtiff','-r600')