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Homework answers / question archive / a system that functions without any exogenous variables generated outside the model
a system that functions without any exogenous variables generated outside the model. the system internally generates the values of all variables through time by their interactions
an origin or ending place of a flow that is outside the boundary of the system. in other words, the cloud represents an input or output of the system that is inconsequential to its behavior of interest. in a populations system, clouds might represent origin of the inflow 'birth rate' and destination of death rate that determine a 'population' stock. where babies come from and where dead bodies go may not be dynamically important and thus represented by clouds
phenomenon that occurs when the stock serves as the basis for generating its own inflow, producing exponential growth. the behavior is also said to be self-reinforcing
a set of descriptions that tell the computer how each part of the system acts. a good computer model captures the dynamic essence of the system it represents. it explicitly contains the assumptions being made about the system
the building blocks that carry information from one element in a model to another element. "Information" may be a constant, an algebraic relationship, a graphical relationship (contained by concerters or table functions), or a quantity (e.g. how many dollars in your savings account. "Information flows through connectors to converters (auxiliary variable) or flows (rates), b ut not to stocks
a flow that moves a quantity of material between two distinct stocks so that the total amount of material in that part of the system is unchanged. there is only so much material and it is divided between the two stocks. non-conserved flows, on the other hand, flow from or to a cloud that has no limit in the quantity it can supply or absorb
a term used in the STELLA software. generally known as auxiliary variables. they are usually represented in diagrams by ciricles. converters do not accumulate flows and do not have memory, but rather are recalculated from scratch each time calculations are performed. three types of converters define constants, algebra, or graphs
a type of stock that represents a space into which material flows and stays for a fixed amount of time, then exits. its associated parameters determine transit time which represents how long material stays in the conveyor. material that flows in at a given time is not mixed with material that had flowed in earlier - whatever entered first will also leave first
a surprising result of policies devised to remedy a problem. often the presumed "solutions" result in counter-productivity. thus as troubles increase, efforts are intensified which actually worsen the problem
also known as a rate equation. it is a policy statement that determines how the levels are related to the decisions (rates)
