Courses/CS 461/Winter 2006/Robert Lai/Homework 2
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[edit] Biology -- AIDS
Properties
This model simulates the spread of the human immunodeficiency virus (HIV), via sexual transmission, through a small isolated human population. It therefore illustrates the effects of certain sexual practices across a population.
Rules
INITIAL PEOPLE: How many people simulation begins with.
AVERAGE COUPLING-TENDENCY: General likelihood member of population has sex.
AVERAGE COMMITMENT: How many weeks sexual relationships typically lasts.
AVERAGE CONDOM-USE: General chance member of population uses a condom.
AVERAGE TEST-FREQUENCY: Average frequency member of population will check their HIV status in a 1-year time period.
Description
The model examines the emergent effects of four aspects of sexual behavior. The user controls the population's tendency to practice abstinence, the amount of time an average "couple" in the population will stay together, the population's tendency to use condoms, and the population's tendency to get tested for HIV. Exploration of the first and second variables may illustrate how changes in sexual mores in our society have contributed to increases in the prevalence of sexually transmitted diseases, while exploration of the third and fourth may provide contemporary solutions to the problem.
[edit] Biology -- Disease Solo
Properties
This model is a one-player version of the HubNet activity Disease. It simulates the spread of a disease through a population. One agent in the population is a person controlled by the user; the others are "androids" controlled by the computer.
Rules
SETUP/CLEAR: sets up the world and clears plots.
SETUP/KEEP: sets up the world without clearing the plot; this lets you compare results from different runs.
GO: runs the simulation.
NUM-ANDROIDS: determines how many androids are created at setup
INFECTION-CHANCE: a healthy agent's chance at every time step to become sick if it is on the same patch as an infected agent
AVOID?: when this switch is on each uninfected android checks all four directions to see if it can move to a patch that is safe from infected agents.
CHASE?: when this switch is on each infected androids checks all four directions to see if it can infect another agent.
UP, DOWN, LEFT, and RIGHT: move the person around the world.
Description
Initially, one android is infected. Sick agents are indicated by a red circle. Androids can move using a few different simple strategies. By default they simply move randomly, however, using the AVOID? and CHASE? switches you can indicate that uninfected androids should run from infected ones or infected androids should chase uninfected ones. The person may also catch the infection. However the person's movement is controlled by the buttons on the right side of the view. Healthy "agents" on the same patch as sick agents have an INFECTION-CHANCE chance of becoming ill.
[edit] Biology -- Virus
Properties
This model simulates the transmission and perpetuation of a virus in a human population. Ecological biologists have suggested a number of factors which may influence the survival of a directly transmitted virus within a population.
Rules
INFECTIOUSNESS: slider determines how great the chance is that virus transmission will occur when an infected person and susceptible person occupy the same patch. For instance, when the slider is set to 50, the virus will spread roughly once every two chance encounters.
DURATION: slider determines the percent of the average life-span (which is 1500 weeks, or approximately 27 years, in this model) that an infected person goes through before the infection ends in either death or recovery. Note that although zero is a slider possibility, it produces an infection of very short duration (approximately 2 weeks) not an infection with no duration at all.
CHANCE-RECOVERY: slider controls the likelihood that an infection will end in recovery/immunity. When this slider is set at zero, for instance, the infection is always deadly.
SETUP: resets the graphics and plots and randomly distributes 140 green susceptible people and 10 red infected people (of randomly distributed ages). The GO button starts the simulation and the plotting function.
Description
The model is initialized with 150 people, of which 10 are infected. People move randomly about the screen in one of three states: healthy but susceptible to infection (green), sick and infectious (red), and healthy and immune (gray). People may die of infection or old age. When the population dips below the environment's "carrying capacity" (set at 700 in this model) healthy people may reproduce healthy and susceptible offspring.
