Models in IE Lecture 13

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Models in IE Lecture 13

• System Dynamics
• 2nd Lecture
• Systems Archetypes

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Lecture 13 Outline

• More examples of causal-loop diagrams
• Glucose and Insulin
• What is wrong?
• How could such a bad system evolve?
• Natural systems, man-made systems
• What to look for when systems behave poorly
• Common Patterns System Archetypes
• Success to the successful
• Escalation

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Analysis of an argumentorHow to make a
mountain out of a molehill
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As anger
As harshness


Bs harshness
Bs anger

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Mountains out of Molehills

• Whose fault is it?
• You started it
• Cause, effect, and blame are not clear in complex
  systems

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Eat Candy
Blood Glucose Level

-
Hunger Level
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Eat Candy
Blood Glucose Level
-


Delay
Hunger Level
-
Insulin Production
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Oscillations that increase in amplitude over time
area danger signal
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Glucose and Insulin

• How could nature be so stupid?
• How could such an unfit system survive?

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Nature isnt stupid -- We are!

• 1st appearance of insulin regulation
• 10,000,000-70,000,000 years ago
• 1st appearance of refined sugar
• 1500 to 2400 years ago

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Eat Complex Carbohydrates
Delay
Blood Glucose Level
-


Delay
Hunger Level
-
Insulin Production
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Eat Complex Carbohydrates

Delay
Blood Glucose Level


-
Eat Candy


Delay

Insulin Production
Hunger Level
-
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Natural Man-Made Systems

• Natural systems have usually evolved so that
  timings work well
• Introduce a new element into a smoothly running
  system and you are lucky if timings remain good
• As change rate of technology ? this problem
  occurs more frequently

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The road to hell is paved with good intentions

• The hurrieder I go,
• the behinder I get

The harder we run, the more we seem to stay in
the same place
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When your best isnt good enough

• I keep banging my head
• against the same wall

Time for a systems perspective
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Understanding System Performance
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System Archetypes

• Recurring, classic patterns
• Identified in Peter Senges book, The Fifth
  Discipline (Chapters 6-16, Appendix 2)
• Should become part of your permanent vocabulary

• Escalation
• Balancing loop with delay
• Success to the successful
• Tragedy of the commons
• Limits to growth
• Shifting the burden

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For Next Class

• Read about the different system archetypes
• Bring your book to class
• open book Quiz forecast w.p. .8

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Feedback class performance on homework

• Good but not excellent overall
• Dont complain about 6 hours/week!
• 2nd half of term much harder
• Many of the harder problems are difficult
  conceptually, not technically
• try harder
• try more than once (many already do).
• Most work on Littles Law problem, (6a.m, 6pm)
  was unsatisfactory.

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