S型增长实例

S型增长实例

clip_image002

该实例具体演示了S型增长曲线,该曲线前半部分为指数增长,后半部分为负反馈起作用。

具体方程如下:

(1) FINAL TIME = 250

Units: Month

The final time for the simulation.

(2) INITIAL TIME = 0

Units: Month

The initial time for the simulation.

(3) LEV状态1= INTEG (

RT速率2,

1)

Units: **undefined**

(4) myRTV(

[(0,-10)-(1200,100)],(0,0),(100,5),(200,10),(300,15),(400,20),(500,25),(600

,20),(700,15),(800,10),(900,5),(1000,0),(1100,-5),(1200,-10))

Units: **undefined**

(5) RTV3=

myRTV(LEV状态1)

Units: **undefined**

(6) RT速率2=

RTV3

Units: **undefined**

(7) SAVEPER =

TIME STEP

Units: Month [0,?]

The frequency with which output is stored.

(8) TIME STEP = 1

Units: Month [0,?]

The time step for the simulation.

clip_image004

可以看出,LEV状态呈现的是S型曲线。最后稳定在一定的值。

clip_image006

从图可以看出,RT速率开始时是正增长,后来转变为负增长。

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