Lecture D-E (2022-02-22): Midterm Review

In this lecture, the Spring 2022 midterm for SOS 212 is discussed and we review topics from Units A, B, C, and D. Some practice problems are also completed.

Lecture D4 (2022-02-17): Chapter 3, Modelling Dynamic Systems (Morecroft, 2015)

We start this lecture with very brief tutorials of building, executing, and analyzing stock-and-flow diagrams in both Vensim PLE (from Ventana Systems) and Insight Maker. We then move on to cover Chapter 3 from Morecroft (2015), which is an introduction to dynamical systems modeling (i.e., using stock-and-flow diagrams to simulate dynamical system behavior-over-time trajectories). The chapter coverage is truncated due to lack of time, but we cover the identification of stocks and how to draw links between them that help us visualize the dependencies that emerge from the flow models used.

Lecture D3 (2022-02-15): Stock-and-Flow Diagrams in Vensim and Insight Maker

In this lecture, we review how to simulate a the behavior over time of simple negative feedback dynamical system (the filling of water in a toilet tank) using spreadsheet numerical methods. We compare and contrast this with bacterial growth models simulated in similar ways and discuss two basic categories of flow equations that will be used in a variety of different models. We then pivot to discussing how to build stock-and-flow diagrams and implement them in Vensim so that behavior over time trajectories can be generated more quickly.

Lecture D2 (2022-02-10): Introduction to Numerical Simulation of Dynamical Systems, Part 2

In this lecture, we continue to discuss numerically integrating (simulating) dynamical systems in a spreadsheet tool such as Microsoft Excel or Google Sheets. We go over our previous example (bacterial growth with both reproduction and death modeled) and explore the effect of changing the time step size ("dt"). We then pivot to introducing a negative feedback example (filling of a toilet tank).

Lecture D1 (2022-02-10): Introduction to Numerical Simulation of Dynamical Systems, Part 1

In this video, we begin the discussion of using computer-based automation tools (in this case, spreadsheets) to generate numerical simulations of dynamical system behaviors over time (BOT). We start with a simplistic example of compound interest in a bank and show how the small-time scale behavior of any dynamical system can be approximated by a "bank account model" so long as each "compounding period" ("dt") is sufficiently small to assume that the variables are not changing much during that period. This is equivalent to the "secant approximation" of a derivative (where a derivative, which is strictly defined at a point, is approximated by the slope of a line connecting that point to a point just a little later in the trajectory). We close with an exercise where the exponential growth of bacteria is numerically simulated within a spreadsheet.

Lecture C2 (2022-02-03): "Applying Systems Archetypes" (Kim and Lannon, 1997)

In this lecture, we discuss how Kim and Lannon (1997) describe the four uses of Systems Archetypes for feedback systems thinking -- as structural pattern templates, lenses, dynamic theories, and for predicting future behavior. This allows us to describe several very common systems archetypes as well.

Lecture C1 (2022-02-01): Feedback Systems Thinking with CLDs

In this lecture, we start to introduce methods to embellish CLD's to form more complex models of dynamical systems with multiple feedback loops. This is an introduction to the next lecture, where we go over a wide range of systems archetypes discussed by Kim and Lannon (1997).