a. take apart the components to see how they work individually
explain each
(this is very similar in set of skills to the multiple-representations)
be able to put back together (over a limited range)
b. example: the Logistic Growth Equation
equation for each time step:
growth_rate = growth_rate_max * (K - N)/K
or
y = m *X +B growth_rate = (- growth_rate_max/K) *N + growth_rate_max*K graphical:
model behavior:
change in population = growth rate * population at any time
population vs. time
Matching the parts of the equation to the final behavior of the model.
c. That's just one simple part of a model like we've seen before
we used this as a component of a predator-prey model and recycling model
a. look at the grouping of components
closed
look for bi-flow
open
source or sink
flow control
constant, linear, MM depletion
feedback
positive or negative (can't tell from this diagram)
joint or multiplicative control
may contain "efficiency" parameter
co-flow
linked only through information, no direct flow, different units
b. open up the dialog boxes for the equations or look at the equation sheet
c. construct diagnostic outputs to determine the relationship
d. examples:
Logistic model -
make a plot of flow vs. population
make a plot of growth rate rate vs. population
this is just to check that what you put in is what you get out
watershed runoff model from ESR220
look at each component / understand the statements
immediate
STELLA diagram
equation for response
positive: rate of inflow is a positive function of stock
negative: if stock gets higher then rate in gets slower
loops
could be multiple causal steps leading to the increase or decrease of the rate of input
examples - draw on board or go to lect 15
why these are important
control-systems rely on a combination of positive and negative
short term positive or near-scale positive
longer term or larger scale negative
