PERCOLATION (Oriented)
| Collection | International Encyclopedia of Systems and Cybernetics |
|---|---|
| Year | 2004 |
| Vol. (num.) | 2(2) |
| ID | ◀ 2523 ▶ |
| Object type | Methodology or model |
A percolation process submitted to some constraint, in space or in time.
In an abstract model, it is for instance possible to impede propagation in one or various defined directions.
Using the example of a forest fire, the direction of the wind may favour percolation in one direction and impede it in another one. It is altogether obvious that, when the percolation process implies the destruction of the affected elements, it will not be able to propagate itself again in zones where populations have already been devastated. Where the fire has raged, there are no more trees to burn and where the epidemics raged, the number of immunized or naturally resistant individuals is much higher than the one of the individuals who could yet succumb to the illness.
This phenomenon also shows up in the time dimension. A destroyed forest will need a long time to become again a combustible forest. In the case of epidemics, increasing survival of immune and immunized individuals at each resurgence of the epidemics lead normally to such a situation where the percolation threshold cannot be reached anymore, at least for long time.