The name is absent



Stata Technical Bulletin

31


Population density


O Prey population (n)           д Predator population (n)

900
800
700
600
500
400
900
800
700
600
500
400

Figure 3


Figure 4


Figure 3 shows the simulations of the Volterra model of prey-predator interactions. In the top panel, no delay between predation and predator birth is
assumed. In the bottom panel, a time lag of 0.3 years is assumed to exist between predation and the new births. Figure 4 shows the growth process
of an organism, without limitations (a) and with a maximum value obtainable (b).

Figure 5


O Warm water flux (l/s)

2

(a)

Topt

1.5

1

5

cold water flux

15

.5

0

•30

•20

10

50

30

20

10

0

2

4

6

8

10 12


S Shower water temperature

50

•40 1.5

1

.5

0

•50 2

40

30

20

10

0

2

4

6

8

10 12


2

40 1.5

1

.5

0

50

40

30

20

10

0

2

4

6

8

10 12

Figure 6


Time (s)


Figure 5 shows the growth process of an organism, switch-off (a) and switch-on (b) effects of the SWTC function. Figure 6 shows the shower water
temperature regulation: a) perfect (no delay); b) long pipe (constant information delay); c) long pipe (information delay, variable as a function of total
flux); d) lizard adjusting (material delay, variable as a function of the mixed water temperature).

References

ACSL. 1987. Advanced Continuous Simulation Language, User Guide/Reference manual, Edition 4.1. Concord, MA: Mitchell and Gauthier Assoc.

Brennan, R. D., C. T. De Wit, W. A. Williams, and E. V. Quattrin. 1970. The Utility of a Digital Simulation Language for Ecological Modeling.
Oecologia (Berlin) 4: 113-132.

Dent, J. B. and M. J. Blackie. 1979. System Simulation in Agriculture. London: Applied Science Publishers.

de Wit C. T. and J. Goudriaan. 1978. Simulation of ecological processes. Wageningen: PUDOC.

Ferrari, T. J. 1978. Elements of System-Dynamics Simulation—A textbook with exercises. Wageningen: PUDOC.

Forrester, J. W. 1968. Principles of Systems. Cambridge: MIT Press.



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