System Dynamics
Motion and Interaction
- The system does not change structure or function but the components interact.
- It also encompasses the Motion of a system relative to another. These systems are otherwise the same, just that they are located at a different position.
- This also includes changes in rates of interactions between subsystems due to diffusion, changes in concentration or the addition or removal of energy in the system.
Growth and Shrinkage
- Pertains to an increase or decrease in size of the system per unit time.
- Growth is sustained by a constantly increasing availability of multiple resources. Similarly for shrinkage.
- Growth dynamics are finite in practice because of scarcity.
Development and Decline
- Development pertains to a programmed change in complexity as it reaches maturation.
- It is complexity either fully realized or complexity deteriorating.
- Development and Decline are tied to Growth. They tend to require the addition or removal of material. However, unlike growth, development and decline relate to the structure of the system itself.
Adaptivity
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Involves a change in the behavior of the system using existing resources in response to an environmental change.
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Adaptation is necessary for systems that exist in an environment that can change the system.
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It involves a reallocation of material and resources within the system so that it can respond to the environment better.
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Adaptivity necessitates control systems that regulate the process.
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Adaptive Systems use information to modify their internal structures to sustain their basic overall structure and functions.
- Adaptive Systems have the emergent capacity to actively use information to anticipate future states (based on the system’s expectation of this state) of the environment.
- That is, they follow Bayesian methods (or an approximation of such), with updates dependent on the amount of information received.
- Another way to put it Adaptive systems advance to a future for which they are perfectly prepared. This is because, no new updates imply no new information received from the environment, which imply no surprise.
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For complex adaptive systems. Information is the basis for decisions. Some models for this include:
- Decision Trees - which assume perfect rationality and perfect information
- Game Theoretic Models - which need not assume perfect rationality or perfect information but may be difficult to compute
- Using Heuristics - which are only approximations and may not be optimal, but are easy to compute.
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Adaptive systems may also be Anticipatory Systems. That is, they attempt to know the future state based on what is known to be possible.
- Anticipation allows the system to alter its behavior to change future states.
- Compared to Predictive Systems, Anticipatory Systems are more proactive with regards to the future state.
- Anticipation is based on statistical models of the world.
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Adaptation implies some form of data storage and retrieval.
Dynamical States
Equilibrium
- Equilibrium pertains to a state where energy and matter are uniformly distributed throughout the interior.
- No work is accomplished internally.
- Any energy flowing in also flows out without affecting the internals.
Dissipative Systems
- Dissipative Systems are those that are subject to flows that cause the internal state to change.
- They take in, transform, and release energy flows.
- These systems are amenable to evolution since work and energy tends to go to constructive processes that create new subsystems and organizational structures.
Steady State
- Steady State Systems pertain to systems where there is energy flow but no new internal structure is being created (on average).
- The energy that flows into the system is used for maintaining the internal structure of the system.
Disturbed Systems
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All systems structurally expect conditions. Disturbances to these conditions affect the system
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The degree of adaptation or evolution required from the system to maintain itself tends to be proportional to the magnitude of the disturbance on the system’s internal structures.
- Of course, if the disturbance hits a critical subsystem, the system may deteriorate or be permanently damaged .
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Complexity tends to be directly proportional to the system’s ability to adapt to disturbances.
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A system is stable if after a small disturbance, it settles back to the state it was previously in.
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Resilience is the capacity for an active system to rebound to normal function after a disturbance or, if need be, to adapt to a modified function should the disturbance prove to be long-lived.