StarLogo Models
StarLogo is a programmable modeling environment for exploring the workings of decentralized systems -- systems that are organized without an organizer, coordinated without a coordinator. With StarLogo, you can model (and gain insights into) many real-life phenomena, such as bird flocks, traffic jams, ant colonies, and market economies. StarLogo Models are available for download. To run this model you need the Starlogo software.
Download StarLogo
To run the following models you will need StarLogo which can be downloaded from http://el.www.media.mit.edu/groups/el/projects/starlogo/. StarLogo only runs on the Macintosh platform.
Urban Diffusion Model
by Brian Deal
WHAT IS IT?
This project illustrates the concept of resource allocation and the growth of an urban environment
HOW TO USE IT
Select the growth rate, resources available and spread potential for your development. Then Go.
THINGS TO NOTICE
When growth potential is high and resource availablity is high the urban form spreads rapidly, although it is slow to get started if a small spread potential is used (if the spread potential is too confining growth may not occurr).
When spread potential is increased, initial growth starts sooner but the development patterns are less centralized.
As resource availabilty and growth rates are decreased the urban growth slows to a crawl.
A slow growth rate with high resource availability and a large spread coefficient will produce the largest amount of disaggregation. If the growth rate is high enough it will fill in the available space, even with a high spread coefficient.
Download this model from ftp://www.imlab.uiuc.edu/pub/smforest/urban-diffusion-model
Nee May Patch Model
by Brian Deal
WHAT IS IT?
This project simulates the spread of a fire through a forest. The fire starts on the left edge of the forest, and spreads to neighboring trees. The fire spreads in four directions: north, east, south, and west. The fire's chance of reaching the right edge of the forest depends critically on the density of trees in the forest.
HOW TO USE IT
Click the SETUP button to set up the trees (green) and fire (red). Click the GO button to start the simulation.
The DENSITY slider controls the density of trees in the forest. (Note: changes in the DENSITY slider do not take effect until the next setup.)
THINGS TO NOTICE
Set the density of trees to 55%. At this setting, there is virtually no chance that the fire will reach the right edge of the forest. Set the density of trees to 65%. At this setting, it is almost certain that the fire will reach the right edge. There is a sharp transition around 59% density. At 59% density, the fire has a 50/50 chance of reaching the right edge.
The blue "walls" prevent the fire from spreading off the edges of the screen.
EXPLORATIONS
What if the fire could spread in eight directions (including diagonals)? How would that change the fire's chances of reaching the right edge?
In this model, what "critical density" of trees is needed for the fire to propagate?
Add wind to the model so that the fire can "jump" greater distances in certain directions.
This program uses only patches to control the fire. Can you make a fire program that uses only turtles? For hint, a check out the code from fire.alt.
STARLOGO FEATURES
Each tree uses the StarLogo primitive nsum4 to determine whether any of the surrounding trees are on fire.
Notice how the program gradually decreases the patch color of the red patches to achieve the visual effect of burning.
Download this model from ftp://www.imlab.uiuc.edu/pub/smforest/neemay-patch-model