Diapositiva PPT

In a plantation the quantity of wood growths according to a

logistic curve whose differential equation is:

w' = k * (1 - w / wm) * w

When the quantity is greater than wm, a cutting process starts

which decides the proportion of wood to be extracted according

to a function of the actual price, p(TIME) and the mean price pm.

The time for the cut process is negligible compared with the

rates of growth.

NETWORK

Growth (C) :: w' := k * (1 - w / wmax) * w;

if w >= wm then ACT(Cut, 0);

GRAPH(0, 50, BLACK; TIME: 7: 0, WHITE; W: 6: 0,Wood, 0, 10000, GREEN;

price(TIME): 6: 0, Price, 0, 100, YELLOW);

Cut (A) :: w := w - MIN(0.3 * wm, MinCut + MAX(0, cc*(price(TIME) - pm)));

INIT TSIM := 50; ACT(Growth, 0);

k := 0.21; wm := 6000; MinCut := 500; cc := 40.2; pm := 24;

w := 100; wmax := 9500;

DT_Growth := 0.125;

price := 0, 30 / 10, 20 / 20, 15 / 30, 25 / 40, 30 / 50, 42 /

55, 45;

DECL VAR k, wm, wmax, MinCut, cc, pm: real; w: CONT;

GFUNCTIONS price SPLINE (real): real: 8;

END.