Pendulum Poincare map
// PendulumPoincare.javaimport java.awt.*;
import java.awt.event.*;
import java.awt.Graphics;
public class PendulumPoincare extends Frame
{
public PendulumPoincare()
{
setSize(600,500);
addWindowListener(new WindowAdapter()
{ public void windowClosing(WindowEvent event)
{ System.exit(0); }}); }
public void fsystem(double h,double t,double u[],double hf[])
{
double a = 0.2, b = 1.0;
double k = 1.09; double Omega = 0.8;
hf = h*u;
hf = h*(-a*u-b*Math.sin(u)+k*Math.cos(Omega*t));
}
public void map(double u[],int steps,double h,double t,int N)
{
double uk[] = new double;
double tk;
double a[] = { 0.0, 1.0/4.0, 3.0/8.0, 12.0/13.0, 1.0, 1.0/2.0 };
double c[] = { 16.0/135.0, 0.0, 6656.0/12825.0, 28561.0/56430.0,
-9.0/50.0, 2.0/55.0 };
double b[][] = new double;
b = b= b = b = b = 0.0;
b = 1.0/4.0; b = 0.0; b = 0.0; b = 0.0;
b = 0.0;
b = 3.0/32.0; b = 9.0/32.0;
b = 0.0; b = 0.0; b = 0.0;
b = 1932.0/2197.0; b = -7200.0/2197.0;
b = 7296.0/2197.0; b = b = 0.0;
b = 439.0/216.0; b = -8.0;
b = 3680.0/513.0; b = -845.0/4104.0; b = 0.0;
b = -8.0/27.0; b = 2.0; b = -3544.0/2565.0;
b = 1859.0/4104.0; b = -11.0/40.0;
double f[][] = new double;
for(int i=0;i<steps;i++)
{
fsystem(h,t,u,f);
for(int k=1;k<=5;k++)
{ tk = t+a*h;
for(int l=0;l<N;l++)
{ uk = u;
for(int j=0;j<=k-1;j++) uk += b*f;
}
fsystem(h,tk,uk,f);
}
for(int l=0;l<N;l++)
for(int k=0;k<6;k++) u += c*f;
}
}
public void paint(Graphics g)
{
g.drawRect(40,40,500,450);
int steps = 1; int N = 2; int counter = 0;
double h = 0.005;double Omega = 0.8;double t = 0.0;
double u[] = { 0.8, 0.6 };// initial conditions
for(int i=0;i<800000;i++)
{
t += h; map(u,steps,h,t,N);
if((counter>10) && (Math.abs(t-2.0*Math.PI*counter/Omega)<0.02))
{
int m = ((int)(10.0*u)+350);int n = ((int)(40.0*u)+200);
g.drawLine(m,n,m,n);
}
if(t > 2.0*Math.PI*counter/Omega) { counter++; }
}
}
public static void main(String[] args)
{
Frame f = new PendulumPoincare(); f.setVisible(true);
}
}
钟摆系统的庞加莱截面程序，感谢liliangbiao分享，只是由于语言的差异看不太懂，希望有人出来解释一下，不知道与论坛上已有的matlab程序在原理上有什么不同？ liliangbiao先生用java写的，map函数不太明白，太多赋值语句了，如果做映射应该在paint函数里面吧，但是不太清楚，还是请别的高手路过吧！ 没有学过JAVA呢，看您的程序，只能了解您编程的思想，但是还是很受用的。试着用MATLAB实现您这一思想。 这就对了，只需要了解编程思想就可以了，试试用Matlab或者其他语言编写一下，应该不难理解的！编写对了，欢迎共享！ 调试的时候，我只有半个图，是不是我开的窗口太小了？
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