Biomedical subjects
Peter Reichert
Publications and source records attributed to Peter Reichert.
A water resources threshold and its implications for food security.
Cereal import has played a crucial role in compensating local water deficit. A quantitative account of water deficit and cereal import relations therefore is of significance for predicting future food import demand and formulating corresponding national and international policies. On the basis of data for countries in Asia and Africa, we estimated a water resources threshold with respect to cereal import. Below the threshold, the demand for cereal import increases exponentially with decreasing water resources. There appeared to be a declining trend in the threshold, from 2000 m3/(capita year) in the early 1980s to 1500 m3/(capita year) by the end of the 1990s. Until recently, most countries below the threshold were oil-rich and thus were able to afford cereal import. However, the next 30 yr may see many poor and populous countries dropping below the threshold in association with their rapid population growth and the depletion of fossil groundwater. Water deficit-induced food insecurity and starvation could intensify because cereal import may not be affordable for these countries.
Practical identifiability of ASM2d parameters--systematic selection and tuning of parameter subsets.
In many applications, some parameters of the Activated Sludge Model No. 2d (ASM2d) need calibration. Since ASM2d usually is overparameterized with respect to the available data, the subset of calibration parameters is not unique. In practice, calibration of ASM2d (and other ASMs) is often addressed by ad hoc selecting and tuning procedures. In this paper, a more systematic approach based on parameter identifiability analysis of parameter subsets is applied. The approach consists of a preliminary prior parameter analysis and a subsequent iterative parameter subset selection and tuning procedure. The former includes the choice of suitable prior parameter values and uncertainties and a pre-selection of parameters which are reasonably estimated from the data available. The latter is based on three diagnostic measures which are simple to calculate and easy to interpret. It is demonstrated as to how these measures can be used to identify the most important model parameters and to analyze their interdependencies. In addition, it is shown how these measures facilitate the analysis of the influence of fixed parameter values on parameter estimates.