// slowren.java
// slowly renewable source use
// adapted from a program in basic by H.T. Odum & E. Odum, 1994

import java.applet.Applet;
import java.awt.*;

public class slowren extends Applet
{
  Label pr1,pr2;
  TextField in1,in2;
  float q,e0,k0,k1,k3,k4,j,e,dq,de,t,ti,qi,ei;

  public void init()
  {
	pr1 = new Label("Initial amount in reserve tank: ");
	in1 = new TextField("159",4);
	add(pr1);add(in1);
	pr2 = new Label("Inflow of slow renewal source: ");
	in2 = new TextField("2",4);
	add(pr2);add(in2);
  }

  public boolean action(Event event, Object o)
  {
	e = (float)Integer.parseInt(in1.getText());
	j = (float)Integer.parseInt(in2.getText());
	repaint();
	return true;
  }

  public void paint(Graphics g)
  {
	q=3;e0=1.2f;k0=0.001f;k1=0.001f;k3=0.03f;k4=0.01f;
	t=0;ti=t;qi=q;ei=e;
	g.drawRect(50,80,320,180);
	while (t<320)
	{
	  dq=k1*e*q-k3*q;
	  de=j-k0*e*q-k4*e;
	  e+=de;
	  q+=dq;
	  t+=1;
	  g.setColor(Color.red);
	  g.drawLine((int)(50+ti),(int)(260-qi),(int)(50+t),(int)(260-q));
	  g.setColor(Color.blue);
	  g.drawLine((int)(50+ti),(int)(260-ei/e0),(int)(50+t),(int)(260-e/e0));
	  ei=e;qi=q;ti=t;
	}
  }
}
// S. Kontur & E. Ortega. September, 2000.