Chapter 7
Causal Loop Diagrams
System dynamics helps us to analyze complex systems with special emphasis on the role of
information feedback. This chapter describes causal loop diagrams, a technique to portray the
information feedback at work in a syste
Chapter 14
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The Tucannon Salmon
System dynamics can be used to help policy makers and environmental managers improve
their instinctive understanding of dynamic behavior. This chapter illustrates how this may be
done with a simulation model of the salmon
Chapter 19
Volatility in Aluminum Production
Aluminum smelting is a commodity industry with highly volatile prices. This chapter uses
system dynamics to look inside the industry to help us understand the volatility. Aluminum
smelting is ofspeeial intere
Chapter 18
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Predator-Prey Oscillations on the
Kaibab Plateau
The relationship between predators and their prey has always occupied a special place in the
minds of ecologists. There has probably been more written on the subject of predatorprey
interaction
PART 111
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THE MODELING PROCESS Chapter 15
The Steps of Modeling
Building a model is an iterative, trial-and-error process. A model is usually built up in steps
of increasing complexity until it is capable of replicating the observed behavior of the sy
Chapter I 1
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The Numerical Step Size
Chapter 3 explained the numerical approach used to generate the simulation results in system
dynamics models. You learned that the calculations are repeated over and over as time is
advanced in small increments to co
Chapter 8
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Causal Loops and Homeostasis
Homeostasis refers to our remarkable capability to maintain a relatively stable physiological
state even when the outside environment is varying dramatically. This chapter explains home
ostasis with examples from
Chapter 9
Bull -Eye Diagrams
The structure of system dynamics models may be explained with stockandflow diagrams,
equilibrium diagrams, or causal loop diagrams. The best way to describe a model is with a
combination of all of these diagrams coupled with
PART I
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INTRODUCTION Chapter I
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Overview
A model is a substitute for a real system. Models are used when it is easier to work with a sub-
stitute than with the actual system. An architects blueprint, an engineers wind tunnel, and
an economists graphs ar
1 Chapter 6
S-Shaped Growth
Sshaped growth refers to a general pattern of growth that has been observed in a wide vari
ety of systems. Examples include the growth in certain animal populations (Ricklefs 1990),
the spread ofepidemics (Hastings 1997), and
Chapter 5
Equilibrium Diagrams
System dynamics is the study of how systems change over time. Our focus is on dynamics,
but dynamics are often difcult to understand. In watching students and professionals work
with dynamic models, I have noticed that the
Chapter 2
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Stocks and Flows
Stocks and flows are the building blocks of system dynamics models. A simple, everyday illus
tration of stocks and ows is the accumulation of interest in a bank account. Figure 2.1 shows
a simple model to keep track of the gro