A simple example

• Population growth with capacity limit:
  • Population size N changes by births B and deaths D (per time)
  • given by rates b, d and a capacity N_k as
    • 
• System dynamics model:
  • 
• Fixed causality:
  • converter: output of its variable
  • flow: output of flow value (left and right)
  • reservoir: input of flow (on both sides)
  • basic scheme of Cellier's Modelica library