# Reinforcing Loop Models

These models and simulations have been tagged “Reinforcing Loop”.

Based on a written description of why a dining hall was experiencing difficulties.

Example of the exponential decay of a Stock with the decay rate being a function of a decay constant.

My first simulation model example.

Simple reinforcing loop causal loop diagram.

Reinforcing Loop/SFD Simulation allow one to experience the explicit implications of the interactions.

Newtonian Cooling is an example of the exponential decay of a stock with the decay rate dependent on the environment.

A topical example of feedback for students about to embark on the homeostasis section of BIOL 112 at Thomas Jefferson University.
In its common usage, evolutionary design is a disaster. The design ends up being the aggregation of a bunch of ad-hoc tactical decisions, each of which makes the code harder to alter. In many ways you might argue this is no design, certainly it usually leads to a poor design. As Kent puts it, design is there to enable you to keep changing the software easily in the long term. As design deteriorates, so does your ability to make changes effectively. You have the state of software entropy, over time the design gets worse and worse. Not only does this make the software harder to change, it also makes bugs both easier to breed and harder to find and safely kill. This is the "code and fix" nightmare, where the bugs become exponentially more expensive to fix as the project goes on.
This is a simulation of exponential growth as set out by Dennis Sherwood in his book, Seeing the Forest for the Trees: A manager's guide to applying systems thinking.  The story of the frogs is this:

A colony of frogs is living happily on one side of a large pond.  At the other side of the pond is a lily pad.  One day, a chemical pollutant flows into the pond, which has the effect of stimulating the growth of the lily pad so that it doubles every 24 hours.  This is a problem for the frogs, for if the lily pad were to cover the pond entirely, the frog colony would be wiped out.

•Q1: how would you describe the growth of the lily pad?
•Q2: if the lily-pad can cover the entire pond in 50 days, on what day is the pond half covered?
•Q3: The frogs have a method of stopping the growth of the lily-pad, but it takes them 10 days to put their method into effect.  What proportion of the pond is covered at the latest possible time the frogs can take action to save themselves?

Reinforcing Loop/SFD Simulation allow one to experience the explicit implications of the interactions.

Simple reinforcing loop causal loop diagram.

"In its common usage, evolutionary design is a disaster. The design ends up being the aggregation of a bunch of ad-hoc tactical decisions, each of which makes the code harder to alter. In many ways you might argue this is no design, certainly it usually leads to a poor design. As Kent puts it, design is there to enable you to keep changing the software easily in the long term. As design deteriorates, so does your ability to make changes effectively. You have the state of software entropy, over time the design gets worse and worse. Not only does this make the software harder to change, it also makes bugs both easier to breed and harder to find and safely kill. This is the "code and fix" nightmare, where the bugs become exponentially more expensive to fix as the project goes on."
Source: Is Design Dead? by Martin Fowler
10 months ago
Savings account growing through accummulation of interest

Simple reinforcing loop causal loop diagram.

Savings account growing through accummulation of interest
This is a model which attempts to replicate a simple reinforcing loop described by Dennis Sherwood on page 75-87 of his book 'Seeing the forest for the trees - a manager's guide to applying systems thinking.

This is not a realistic model but I just wanted to reproduce it as practice of implementing causal loop models.

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