System Dynamics Modeling Overview

1
System Dynamics ModelingOverview

• Dr. R. MacKay

2
What is a Model
3
(No Transcript)
4
(No Transcript)
5
Conceptual Models
Red Sunset

• http//serc.carleton.edu/introgeo/conceptmodels/in
  dex.html

6
Physical Analog Model

• Make a model analogous to a real system.

7
Statistical Model

• Data is gathered from a population and
  information about probable mean, variance, and
  correlations are calculated.

8
Visualization Models

• Especially useful for processing and
  understanding large data sets

9
Mathematical Models

• Two basic types
• 1) Analytical 2) numerical

10
(No Transcript)
11
(No Transcript)
12
(No Transcript)
13
Systems Thinking
14
Systems Thinking
15
Systems Thinking(system components)

• Stocks can be thought of as storage bins where
  something accumulates. (Energy (temperature),
  water level in a bucket, bank balance, child
  height)
• Flows provide inflow or outflow for a stock

16
Systems Thinking(key ideas)

• Equilibrium (a stock is at equilibrium when the
  inflow matches the outflow)
• Stability
• Instability
• Time delay (everything takes time)
• Feedback processes
• The whole system is greater than the sum of the
  individual parts of the system.

17
The Blind Men and the Elephant

• It was six men of Indostan
• To learning much inclined,
• Who went to see the Elephant
• (Though all of them were blind),
• That each by observation Might satisfy his
  mind4

18
The Blind Men and the Elephant

• It was six men of Indostan
• To learning much inclined,
• Who went to see the Elephant
• (Though all of them were blind),
• That each by observation
• Might satisfy his mind

Godfrey Saxe (1816-1887).
http//en.wikisource.org/wiki/The_Blindmen_and_the
_Elephant
19
Systems Thinking

• Systems of information-feedback control are
  fundamental to a life and human endeavor, from
  the slow pace of biological evolution to the
  launching of the latest space satellite
  Everything we do as individuals, as an industry,
  or as a society is done in the context of an
  information feedback system. -Jay W. Forrester

20
Systems Thinking(common behavior)

• No change
• Linear growth (loss)
• Quadradic growth
• Exponential growth

time
time
21
Systems Thinking(common behavior)

• Quadradic growth
• Exponential growth

time
22
Systems Thinking(common behavior)

• Exponential decay

23
Systems Thinking(common behavior)

• Goal seeking

24
Systems Thinking(common behavior)

• Overshoot and collapse

25
Systems Thinking(common behavior)

• Oscillatory behavior

26
Why are models useful?
27
Why are models useful?

• Creating a model forces one to better understand
  the real system. Models can help explain
  observations and help guide the development of
  future experiments.
• Models can be extremely useful in explaining how
  a system works to yourself and to others.
• Experiments can be performed to help understand
  the response of a system to changes without
  harming the real system.
• A model is the only method that one can use to
  estimate the future behavior of a system to past,
  present, and future processes that may influence
  a system.
• More ideas

28
Static vs Dynamic Models
http//www.youtube.com/watch?vP0Fi1VcbpAI
29
Model construction

• Identify a problem (global warming) and create a
  sketch of the expected behavior of the important
  variable over time. Try to identify policies
  that may improve the performance of the system
  (reduce global warming).
• Identify key variables (sun, temperature,
  atmosphere, CO2, Water Vapor,)
• Obtain data related to these key variables.
• Create a simple model to emulate the systems
  behavior at present. You may want to start with
  the system at equilibrium and then add
• Use the model to explore how the system responds
  to changes in key variables.
• Identify weaknesses in the model and refine as
  needed.

30
Several additional quotes relevant to using
models and developing theories include "All
models are wrong but some are useful" George E.P.
Box "Make your theory as simple as possible,
but no simpler." A. Einstein "For every complex
question there is a simple and wrong solution."
A. Einstein. Ockhams Razor "A rule in science
and philosophy stating that entities should not
be multiplied needlessly. This rule is
interpreted to mean that the simplest of two or
more competing theories is preferable and that an
explanation for unknown phenomena should first
be attempted in terms of what is already known."
The American Heritage Dictionary of the English
Language Fourth Edition. 2000.
31
Models and environmental systems
32
Units are very important See Appendix
A Basic Math review in Appendix B