clear;
Lx=1;Ly=2/3*Lx;
x1=[-Lx,3Lx,3Lx,-Lx,-Lx];
y1=[-3Ly,-3Ly,Ly,Ly,-3*Ly];
fill(x1,y1,[0.9,0,0]);hold on;
x2=[-Lx,Lx,Lx,-Lx,-Lx];
y2=[-Ly,-Ly,Ly,Ly,-Ly];
fill(x2,y2,[0,0,0.6]);hold on;
r=0.28*Lx;
N=100;
theta=linspace(0,2*pi,N+1); x3=r*cos(theta); y3=r*sin(theta); fill(x3,y3,[1,1,1]);hold on; Nt=12;