System Dynamics Introduction
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Transcript of System Dynamics Introduction
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8/14/2019 System Dynamics Introduction
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Dennis T. Beng Hui, De La SalleUniversity-Manila
System Dynamics
Understanding system
behavior by identifying
system structure
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Dennis T. Beng Hui, De La SalleUniversity-Manila
Some Phrases to Ponder..
Experience is an expensive school Benjamin Franklin
Experience is something you get afteryou need it anon
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Dennis T. Beng Hui, De La SalleUniversity-Manila
What is a System?
A collection of
parts organized for
a purpose.
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Dennis T. Beng Hui, De La SalleUniversity-Manila
Why does a System Fail?
It fails to achieve its purpose. The parts are poorly designed or poorly
connected.
It is knocked off course because of externalshock.
It is inherently incapable of meeting its purposeor it attempts to adjust to changes.
Its policies are badly designed.
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Dennis T. Beng Hui, De La SalleUniversity-Manila
Linear Thinking of Events
Information ActionConsequences
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Dennis T. Beng Hui, De La SalleUniversity-Manila
Dynamic Behavior of a
System
Consequences
Information
Action
Delay choice
Delay in State
Delay in Knowledge
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Dennis T. Beng Hui, De La SalleUniversity-Manila
Critical Elements in a Dynamic
Behavior
Delay - time lags or reaction timeof the decision with respect to its
effect on the systemAmplification - when an action
turned out to be more forceful thanwhat it was intended
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Dennis T. Beng Hui, De La SalleUniversity-Manila
History of SD System Dynamics was originally
developed in the 1950's and 1960'sat MIT by Jay Forrester
An Electrical Engineer who invented the
random-access magnetic core memory in digitalcomputers.
Applied his background in computer sciencesand engineering to the development of
computer modeling and analysis of socialsystems.
The SD methodology was based on ideas of
feedback, such as encountered in electrical andmechanical control systems.
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Dennis T. Beng Hui, De La SalleUniversity-Manila
History of SD
He was also the founder ofMIT System Dynamics group.He directed the System Dynamics
Program in the Sloan School until 1989 SD was developed to evaluate how
alternative policies affect growth,
stability, fluctuation, and changingbehavior in corporations, cities, andcountries.
http://www.sis.pitt.edu/~mbsclass/hall_of_fame/forres.htm
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Dennis T. Beng Hui, De La SalleUniversity-Manila
What is System Dynamics
It is the investigation of information-feedback characteristics of managed
systems. The use of models for the design of
improved organizational form and
guiding policy.
- Jay Forrester (Founder of SD)
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Dennis T. Beng Hui, De La SalleUniversity-Manila
What is System Dynamics (SD)?
Deals with the time-dependent behavior ofmanaged systems.
Aims to describe the system and understand it.
(Focuses on patterns of behavior not onevents).
Apply qualitative and quantitative models on
how information feedback govern its behavior. Designing robust information feedback
structures and control policies through
simulation and optimization.
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Dennis T. Beng Hui, De La SalleUniversity-Manila
SD Approach by R.G. Coyle
Problem recognition Problem understanding and system
description
Qualitative analysis
Simulation modeling and testing
Policy design and testing
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Dennis T. Beng Hui, De La SalleUniversity-Manila
SD Approach by Richardson
and Pugh
Problem identification and definition System conceptualization
Model formulationAnalysis of model behavior
Model evaluation Policy analysis
Model use or implementation
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Dennis T. Beng Hui, De La SalleUniversity-Manila
Characteristics of a Messy Problems(Or why are problems messy?)
Dynamic all is change Tightly coupled you cant do just one
thing
Governed by feedback our decisions alterthe state of the world
Nonlinear effects are rarely proportional
History-dependent you cannot unscramble
you eggs
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Dennis T. Beng Hui, De La SalleUniversity-Manila
Characteristics of a Messy Problems(Or why are problems messy)
Self organizing dynamics arise from internalstructure
Adaptive people change over time
Counterintuitive too focused on symptoms ofdifficulty rather than the underlying cause
Policy resistant many obvious solutions fail or
worsen the situation Characterized by trade-off high leverage policies
cause worst to better behavior, while low leverage
policies result to temporary improvement beforegetting worse
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Dennis T. Beng Hui, De La SalleUniversity-Manila
Elements of a Dynamic
Problem
Dynamic behavior of importantvariables identify and graph thosevariables in the system that are the
symptoms of the problems we wishto study.
Time horizon period of time overwhich the problem plays itself out.
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Dennis T. Beng Hui, De La SalleUniversity-Manila
Elements of a Dynamic
Problem
The reference behavior mode patterns over time that will bereferred to again and again.
Thinking in terms of graphs overtime looking for long-term dynamic
consequences. Use graphs todescribe, define, and analyze a
problem.
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Dennis T. Beng Hui, De La SalleUniversity-Manila
Example of a problem
statement
There is a an exponential growth ofpeople in Metro Manila from 1900 2000 which can lead to urban decay.
There is a recurring pattern on theoccurrence of Dengue Fever among
young children (1 to 10 years old) inTondo between 1990 to 2000 which led
to child deaths.
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Dennis T. Beng Hui, De La SalleUniversity-Manila
Barriers to Learning
Dynamic complexity
Limited information
Confounding variables and ambiguity
Bounded rationality and the misperceptions offeedback
Flawed cognitive map
Erroneous inferences about dynamics
Unjustified reasoning (judgmental errors and bias)
Defensive routines and interpersonal impediments toto learning
Implementation failure
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Dennis T. Beng Hui, De La SalleUniversity-Manila
Watson Card Puzzle
You are shown 4 cards. Each card has aletter on one side and a number on theother side. What is the smallest number
of cards you should turn over to test therule that cards with vowels on one side
have even numbers on the reverse?Which are they?
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Dennis T. Beng Hui, De La SalleUniversity-Manila
Watson Card Puzzle
E 4 7K
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Dennis T. Beng Hui, De La SalleUniversity-Manila
Questions
What are the important symptom variables? What is the time horizon of your problem?
What reference behavior mode you expect to
see? (What is, what should, what you think is,what could)
What are the long term dynamic consequencesof the problem?
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Dennis T. Beng Hui, De La SalleUniversity-Manila
Group work
Identify the problem by answering its 4elements.
Construction of government projects.
Population of the Philippines.
Traffic congestion in Edsa.
Garbage collection in Baclaran market.
Corruption in the government.
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Dennis T. Beng Hui, De La SalleUniversity-Manila
Group work
Identify the problem by answering its 4elements.
Dieting
Addiction
Population of the World
Use of Credit Card
Salary/Wage Increase
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Individual Work
Electricity Cum GPA
National Population Imported product