Unsaturated flow of soils in unsaturated soils is an important problem in geotechnical and geo-environmental engineering. Richards’ equation is often used to model this phenomenon in porous media. Obtaining appropriate solution to this equation therefore provides better means to studying the infiltration into unsaturated soils. Available 5 methods for the solution of Richards’ equation mostly f...

This case tells the true story of a university employee who suffered from color blindness and who, although he had been an exceptional employee, was terminated when he could not read the color screens displayed by the newly installed PeopleSoft system. Moral outrage on the campus initiated a process that ultimately resulted in Hal Richards being offered another position in which his talents cou...

The Richards equation is widely used as a model for the flow of water in unsaturated soils. For modelling one-dimensional flow in a homogeneous soil, this equation can be cast in the form of a specific nonlinear partial differential equation with a time derivative and one spatial derivative. This paper is a survey of recent progress in the pure mathematical analysis of this last equation. The e...

abstract spatial variability of soils makes difficult analysis of soil water flow phenomena especially in a large area such as a watershed. using scaling methods is a solution in variability problems. the objective of this study was to investigate the effect of the non-linear variability on performance of the scaling methods of richards’ equation for modeling infiltration in a watershed. the me...

and the Nature of Long-Distance Extraction Norvin Richards, MIT, August 2005 [email protected]

The parameters in Richards' equation are usually calculated from experimentally measured values of the soil-water characteristic curve and saturated hydraulic conductivity. The complex pore structures that often occur in porous media complicate such parametrization due to hysteresis between wetting and drying and the effects of tortuosity. Rather than estimate the parameters in Richards' equati...

This study compared three non-linear growth models (Richards, Gompertz, and logistic) and the spline linear regression model using BW measurements from an unselected, randombred chicken population. Based on the goodness of fit criteria, the nonlinear models (NLM) fitted the data better than the spline regression model. The four-parameter Richards model was expected to have the best overall fit;...

Spines reach out ored dendritic spines look for new challenges, say David Richards, R. Anne McKinney (in work done at the University of Zurich, Switzerland), and colleagues. Spines are small dendritic protrusions on which excitatory synapses connect to axons. Recent evidence suggested that spines are mobile even in adults. Richards et al. now suggest that this mobility allows for post-developme...

Brody's growth curve, a three-parameter function, and Richards' function, a four-parameter function, were fit to data from 233 inbred and linecross cows to study the genetic and environmental aspects of the growth curve parameters and to compare the two functions. Fitting Brody's curve was faster and less costly to compute than Richards' function, but Richards' function had smaller sums of squa...