一个最简单的球体模型，表面１００度，球心的温度大致可以近似为

T=100+sita*(T0-100)

sita=-.992013*exp(-32.1468*t).*cos(11.6869*t) ...
-.731745*exp(-32.1468*t).*sin(11.6869*t) ...
-.434135e-2*exp(-17.9198*t).*cos(56.0056*t) ...
-.663919e-1*exp(-17.9198*t).*sin(56.0056*t) ...
+1.99635*exp(-9.86681*t);

t=time*k/R^2;

k=thermal diffuvisity