Modelling of ageing, development, delays and dispersion

Abstract

In a model for a population of identical, synchronized individuals, the development stage can be treated as a single state variable. When there is a distribution of ages or of stages of development, the so-called boxcar train is a suitable method to simulate the development process of the entire population. Some dispersion (variability) may occur within the rates of development of different individuals. Three types of a boxcar train are possible, differing mainly in this dispersion of development rate. In the first type, the escalator boxcar train, dispersion is virtually absent. In the second type, the fixed boxcar train, the dispersion is quite large, and is rigidly determined by the number of boxcars. The third type, the fractional boxcar train, includes a parameter which allows the dispersion to be varied between these two extremes, and to be altered during the simulation process itself.