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Answers for “如何计算存量的变化率?”

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Increasing the average lifespan decreases the death rate (since Deaths=Deer/LifespanDeaths = Deer / Lifespan). If the birth rate remains constant, the inflow exceeds the outflow, resulting in a positive net growth rate and exponential population growth.

Conditions: The birth fraction parameter remains unchanged.; The lifespan parameter is increased.; The model follows the equation Deaths=Deer/LifespanDeaths = Deer / Lifespan.

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In system dynamics diagrams, stocks (also called accumulations) represent quantities that build up or deplete over time and are depicted as rectangles. Flows represent the rates of change that add to or subtract from these stocks and are depicted as arrows with valves.

Conditions: The context is introductory system dynamics modeling.; The model uses standard stock-and-flow diagram notation.

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The deer population remains constant when the inflow (births) equals the outflow (deaths). Given the equations Births=Deer⋅Birth_fractionBirths = Deer \cdot Birth\_fraction and Deaths=Deer/LifespanDeaths = Deer / Lifespan, this occurs when Birth_fraction=1/LifespanBirth\_fraction = 1 / Lifespan.

Conditions: The model uses the specific equations Births=Deer⋅Birth_fractionBirths = Deer \cdot Birth\_fraction and Deaths=Deer/LifespanDeaths = Deer / Lifespan.; Parameters are constant over the simulation period.