3.2 Risky Population Model Equations
POPULATION(t) ¼ POPULATION(t À dt) + (BIRTHS À DEATHS) * dt
INIT POPULATION ¼ 2
INFLOWS:
BIRTHS ¼ .07 * POPULATION
OUTFLOWS:
DEATHS ¼ DEATH_RATE * POPULATION
SUM_POP(t) ¼ SUM_POP(t À dt) + (CURRENT_POP) * dt
INIT SUM_POP ¼ 0
INFLOWS:
CURRENT_POP ¼ IF TIME > 100 THEN POPULATION ELSE 0
AVG_POP ¼ IF TIME 6 ¼ 100 then SUM_POP/(timeÀ100) else 0
DEATH_RATE ¼ (IF DR_DIST_CONTROL > NOMINAL_DR THEN
DR_DIST_CONTROL ELSE NOMINAL_DR) * 1 +0 * DR_DIST_CONTROL
+0 * NOMINAL_DR
DR_DISTRIBUTION ¼ NORMAL(NOMINAL_DR,0.005 * POPULATION)
DR_DIST_CONTROL ¼ IF (DR_DISTRIBUTION ! 0.01) AND
(DR_DISTRIBUTION 1) THEN DR_DISTRIBUTION ELSE 0.01
NOMINAL_DR ¼ (EXP(À.01 * TIME) * .03 + .01) * 1 + .04 * 0
46
3 Risky Population