system dynamics introduction

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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Some Phrases to Ponder..

Experience is an expensive school Benjamin Franklin

Experience is something you get afteryou need it anon


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What is a System?

A collection of

parts organized for

a purpose.


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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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Linear Thinking of Events

Information ActionConsequences


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Dynamic Behavior of a

System

Consequences

Information

Action

Delay choice

Delay in State

Delay in Knowledge


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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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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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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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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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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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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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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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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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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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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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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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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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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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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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Watson Card Puzzle

E 4 7K


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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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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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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

system dynamics introduction

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