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System Dynamics. Pedro Ribeiro de Andrade São José dos Campos, 2016. How to model Natural-Society systems?. Connect expertise from different fields Make the different conceptions explicit. If (... ? ) then. Desforestation?.
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System Dynamics Pedro Ribeiro de Andrade São José dos Campos, 2016
How to model Natural-Society systems? • Connect expertise from different fields • Make the different conceptions explicit If (... ? ) then ... Desforestation?
“[The] advantage of a mathematical statement is that it is so definite that it might be definitely wrong…..Some verbal statements have not this merit; they are so vague that they could hardly be wrong, and are correspondingly useless.” Lewis Fry Richardson (1881-1953) – first to apply mathematical methods to numerical weather prediction Models
A system A system is a group of different components that interact with each other Can you identify parts? Do the parts affect each other? How?
System Dynamics Any measurable part of reality can be modeled Systems are represented as stocks and flows Stocks represent energy, matter, or information Flows connect and transport stocks
Systems Theory: stocks and flows Stocks: measurable elements Flows: changes in stocks over time source: Meadows,2008
Water in the tub • Initial stock: water in tub = 40 gallons • water in tub(t) = water in tub(t – dt) – outflow x dt • t = minutes • dt = 1 minute • Runtime = 8 minutes • Outflow = 5 gal/min
Water in the tub Initial stock: water in tub = 40 gallons water in tub(t) = water in tub(t – dt) – outflow x dt t = minutes dt = 1 minute Runtime = 8 minutes Outflow = 5 gal/min Inflow = 40 gal every 10 min
Conclusions Two ways to increase stocks Stocks act as delays or buffers Stocks allow inflows and outflows to be decoupled