From Jay Forrester 1988 killian lectures youtube  video  describing system dynamics at MIT. For more detailed biography See Jay Forrester memorial  webpage  For MIT HIstory see  IM-184930  For Applications se  IM-185462
From Jay Forrester 1988 killian lectures youtube video describing system dynamics at MIT. For more detailed biography See Jay Forrester memorial webpage For MIT HIstory see IM-184930 For Applications se IM-185462
4 6 months ago
Simulating Hyperinflation for 3650 days.  If private bond holdings are going down and the government is running a big deficit then the central bank has to monetize bonds equal to the deficit plus the decrease in private bond holdings.  We don't show the details of the central bank buying bonds here,
Simulating Hyperinflation for 3650 days.

If private bond holdings are going down and the government is running a big deficit then the central bank has to monetize bonds equal to the deficit plus the decrease in private bond holdings.  We don't show the details of the central bank buying bonds here, just the net results.

See blog at http://howfiatdies.blogspot.com for more on hyperinflation, including a hyperinflation FAQ.
 Goodwin business cycle  model , modified from Keen and Blatt

Goodwin business cycle model, modified from Keen and Blatt

This is Figure 6 from Lancastle, N. (2012) 'Circuit Theory Extended: The Role of Speculation in Crises' based on Keen, S. (2010). Solving the Paradox of Monetary Profits.   http://www.economics-ejournal.org/economics/journalarticles/2012-34      Banks expand their lending, which in this model leads
This is Figure 6 from Lancastle, N. (2012) 'Circuit Theory Extended: The Role of Speculation in Crises' based on Keen, S. (2010). Solving the Paradox of Monetary Profits.

http://www.economics-ejournal.org/economics/journalarticles/2012-34

Banks expand their lending, which in this model leads to higher production, wages and spending. The result is an increase in total spending.  
 
 Adapted from Fig 12.1 p.476 of the Book James A. Forte ( 2007), Human Behavior and The Social Environment: Models, Metaphors and Maps for Applying Theoretical Perspectives to Practice; Thomson Brooks/Cole Belmont ISBN 0-495-00659-9

Adapted from Fig 12.1 p.476 of the Book James A. Forte ( 2007), Human Behavior and The Social Environment: Models, Metaphors and Maps for Applying Theoretical Perspectives to Practice; Thomson Brooks/Cole Belmont ISBN 0-495-00659-9

The simulation integrates or sums (INTEG) the Nj population, with a change of Delta N in each generation, starting with an initial value of 5. The equation for DeltaN is a version of  Nj+1 = Nj  + mu (1- Nj / Nmax ) Nj  the maximum population is set to be one million, and the growth rate constant mu
The simulation integrates or sums (INTEG) the Nj population, with a change of Delta N in each generation, starting with an initial value of 5.
The equation for DeltaN is a version of 
Nj+1 = Nj  + mu (1- Nj / Nmax ) Nj
the maximum population is set to be one million, and the growth rate constant mu = 3.
 
Nj: is the “number of items” in our current generation.

Delta Nj: is the “change in number of items” as we go from the present generation into the next generation. This is just the number of items born minus the number of items who have died.

mu: is the growth or birth rate parameter, similar to that in the exponential growth and decay model. However, as we extend our model it will no longer be the actual growth rate, but rather just a constant that tends to control the actual growth rate without being directly proportional to it.

F(Nj) = mu(1‐Nj/Nmax): is our model for the effective “growth rate”, a rate that decreases as the number of items approaches the maximum allowed by external factors such as food supply, disease or predation. (You can think of mu as the growth or birth rate in the absence of population pressure from other items.) We write this rate as F(Nj), which is a mathematical way of saying F is affected by the number of items, i.e., “F is a function of Nj”. It combines both growth and all the various environmental constraints on growth into a single function. This is a good approach to modeling; start with something that works (exponential growth) and then modify it incrementally, while still incorporating the working model.

Nj+1 = Nj + Delta Nj : This is a mathematical way to say, “The new number of items equals the old number of items plus the change in number of items”.

Nj/Nmax: is what fraction a population has reached of the maximum "carrying capacity" allowed by the external environment. We use this fraction to change the overall growth rate of the population. In the real world, as well as in our model, it is possible for a population to be greater than the maximum population (which is usually an average of many years), at least for a short period of time. This means that we can expect fluctuations in which Nj/Nmax is greater than 1.

This equation is a form of what is known as the logistic map or equation. It is a map because it "maps'' the population in one year into the population of the next year. It is "logistic'' in the military sense of supplying a population with its needs. It a nonlinear equation because it contains a term proportional to Nj^2 and not just Nj. The logistic map equation is also an example of discrete mathematics. It is discrete because the time variable j assumes just integer values, and consequently the variables Nj+1 and Nj do not change continuously into each other, as would a function N(t). In addition to the variables Nj and j, the equation also contains the two parameters mu, the growth rate, and Nmax, the maximum population. You can think of these as "constants'' whose values are determined from external sources and remain fixed as one year of items gets mapped into the next year. However, as part of viewing the computer as a laboratory in which to experiment, and as part of the scientific process, you should vary the parameters in order to explore how the model reacts to changes in them.
WIP Based on Gene's Enabling a Better Tomorrow Map  IM-2879  this is a Specific Health Care version based on the archived  Systemswiki Health Care  material. The focus is on Models and Simulation, with videos and discussion in the fullness of time. I am following Gene's   Adventures in Wonderland  f
WIP Based on Gene's Enabling a Better Tomorrow Map IM-2879 this is a Specific Health Care version based on the archived Systemswiki Health Care material. The focus is on Models and Simulation, with videos and discussion in the fullness of time. I am following Gene's  Adventures in Wonderland framework. Revised for More Complex AnyLogic transition at IM-57331
3 11 months ago
Ocean/atmosphere/biosphere model tuned for interactive economics-based simulations from Y2k on.
Ocean/atmosphere/biosphere model tuned for interactive economics-based simulations from Y2k on.
​Summary of Hermans Scale dynamics of grassroots innovations through parallel pathways of  transformative change Ecological Economics 2016  article (paywalled)  This is applied to  health in a subsequent insight
​Summary of Hermans Scale dynamics of grassroots innovations through parallel pathways of  transformative change Ecological Economics 2016 article (paywalled) This is applied to health in a subsequent insight
 Additional Research:    1. DuPont Renewably Sourced Materials Report - I learned how DuPont uses separation, fermentation and chemistry to create high performance crops.  No Author, No Date, Retrieved from:  http://www2.dupont.com/Renewably_Sourced_Materials/en_US/assets/DuPont_Renewably_Sourced.pd
Additional Research: 
1. DuPont Renewably Sourced Materials Report - I learned how DuPont uses separation, fermentation and chemistry to create high performance crops.
No Author, No Date, Retrieved from:  http://www2.dupont.com/Renewably_Sourced_Materials/en_US/assets/DuPont_Renewably_Sourced.pdf
2. The Science of Hybrid Crops - This article explains the history of hybrid crops.
Reinhart, K. (2003) Living History - Science of Hybrid Crops. Retrieved from:   http://www.livinghistoryfarm.org/farminginthe30s/crops_03.html