The System dynamics perspective Flashcards
What is a system?
Interconnected elements that are coherently organized around some purpose
Why do we make systems?
Systems are a human construct made to help try understand and order a complex reality
What is inclusive thinking?
Taking all aspects of the system into account. This includes for instance paramedics and road builders when looking at the car system.
What is important when trying to change the system?
To understand how the system and all it’s feedbacks work, and what its pros and cons are. This allows to change the system to a more desirable form when trying to transition to a different system.
What is Flow?
Flow is the input and output of a system. It is always something per time, etc.
What is Stock?
Stock is the accumulation of Flow that has entered the system and stays there either temporarily or permanently.
How can we influence stock?
In order to influence stock the inFlow and/or the outFlow need to be changed either positively or negatively.
What happens when we influence the inFlow but there is no outflow
Just like with pollution, with only an inFlow stock will accumulate. Decreasing the inFlow will not reduce the stock, it will only increase at a slower rate.
Why are Stock characteristics important?
Stock characteristics are important because it can influence how for example a policy measure works out.
Example: if there was a policy that said that all houses should be ..% efficient, this would be much easier to accomplish with newer houses then with older houses. Therefore the effectiveness of this policy is based on what the stock characteristics are.
Why do systems have inertia?
Because flow capacity can constrain the stock rate.
Three important aspects of a good model
- Feedback structures
- delays
- causal loop diagrams
What is often forgotten when one wants to change something in a system?
All parts of the system can react, either positively by supporting the change or negatively by proposing the change. This all influences how effective the change will be.
What was the general lesson Bert de Vries wanted us to learn from this lecture?
Keep in mind that when you want to change something, the whole system will react. Furthermore, changing the flow does not mean the stock will increase/decrease. Think of what you want to happen to the stock and how to do that.
The system approach is…
an abstract way of looking at what constitutes a part of reality (descriptive) and what determines its evolution in time (analysis, dynamics).
Exponential decline goes…
to a steady state
Definition on sustainability from a system perspective
get definition from pp
Positive aspects of the car system
Better mobility.
It leads to acces to education, healthcare and employment.
Negative aspects of the car system
- (Noise) pollution
- accidents
- land use
- oil use
Difficulties in making transition (car system)
1) Uncertainties about:
- cost
- efficiency
- environmental aspects
2) competing against Internal Combustion engines
3) infrastructure change
4) behavioural change
Systems consist of 3 things:
1) elements
2) interconnections
3) purpose
Interconnections are:
Flows, and law and regulations that govern the flow.
CLDs
Causual loop diagram
Stock is: (3 things)
- content where something is stored
- integrals
- state variable
Flows: (2 things)
- change in stock
- derivatives
Steady state
The system is in equilibrium
Inflow = outflow
Inertia
The stock level cannot change or be changed faster than the maximum difference between inflow and outflow
PFL
Positive fewdback loop
NFL
Negative feedback loop
Logistic growth process
A charechteristic dynamic process in which both a PFL and NFL operate
Sigmoid curve
Other name for logistic growth curve with t0 the value at which Y=1/2K
Delays occur in the system as..
Strategic/informational and physical/technical
A delay can bring a system out of
Equilibrium
Sustainability lesson delays:
Cleaning up environmental compartments or making capital stock more resource efficient will necessarily take time.
(Think of stock turnover which can take years)
Perception delay
The manufacturer uses some average of past sales instead of yesterday’s sales for decisions.
The definition of SD used in this course
“sustainable development refers to a collection of strategies for
achieving quality of life targets (including economic
development) without having adverse effects on the Earth’s
capacity to sustain such quality of life in the long run”
