System Dynamics Modules

First Order Linear Positive Feedback

A first-order system contains only one stock (level or accumulator). Systems are described as linear systems when the algebraic expressions controlling rate(s) of flow into the system, that is, creating a change (at any point in time) in the state variable ‘S’ STATE OF SYSTEM are simply the product of a constant and the current value of S. Rate of change of state is the product of the current state of the system and a constant.
     A first-order positive feedback loop has the effect (each time we calculate it) of adding to S an amount (where the constant is a Fractional Growth Factor ‘g’) which is larger than the previous time we calculated it. Consider a series of calculations at times t0, t1, t2 ... tn, with the initial value of S being S0 and a Fractional Growth Factor g operating on the inflow.
     The description of the module is at
     The module coded in Powersim Studio is at .
     A PowerSim Example using this module is at .

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