Nonlinear set-membership estimation: a support vector machine approach

In this paper a support vector machine (SVM) approach for characterizing the feasible parameter set (FPS) in non-linear set-membership estimation problems is presented. It iteratively solves a regression problem from which an approximation of the boundary of the FPS can be determined. To guarantee convergence to the boundary the procedure includes a no-derivative line search and for an appropriate coverage of points on the FPS boundary it is suggested to start with a sequential box pavement procedure. The SVM approach is illustrated on a simple sine and exponential model with two parameters and an agro-forestry simulation model

Set-membership estimation from poor quality data sets: modelling ammonia volatilisation in flooded rice systems

A set-membership (bounded-error) estimation approach can handle small and poor quality data sets as it does not require testing of statistical assumptions which is possible only with large informative data sets. Thus, set-membership estimation can be a good tool in the modelling of agri-environmental systems, which typically suffers from limited and poor quality observational data sets. The objectives of the paper are (i) to demonstrate how six parameters in an agri-environmental model, developed to estimate NH3 volatilisation in flooded rice systems, were estimated based on two data sets using a set-membership approach, and (ii) to compare the set-membership approach with conventional non-linear least-squares methods. Results showed that the set-membership approach is efficient in retrieving feasible parameter-vectors compared with non-linear least-squares methods. The set of feasible parameter-vectors allows the formation of a dispersion matrix of which the eigenvalue decomposition reflects the parameter sensitivity in a region

Emergy synthesis for aquaculture: A review on its constraints and potentials.

The search for healthier protein sources and the growing demand for food by an increasing world population require aquaculture systems to not only be economically and technologically viable, but also sustainable. Among other methods, emergy synthesis is a powerful tool to assess the sustainability of production systems in a biophysical perspective.Early View - Online Version of Record before inclusion in an issue

Formation and structure of ionomer complexes from grafted polyelectrolytes

We discuss the structure and formation of Ionomer Complexes formed upon mixing a grafted block copolymer (poly(acrylic acid)-b-poly(acrylate methoxy poly(ethylene oxide)), PAA21-b-PAPEO14) with a linear polyelectrolyte (poly(N-methyl 2-vinyl pyridinium iodide), P2MVPI), called grafted block ionomer complexes (GBICs), and a chemically identical grafted copolymer (poly(acrylic acid)-co-poly(acrylate methoxy poly(ethylene oxide)), PAA28-co-PAPEO22) with a linear polyelectrolyte, called grafted ionomer complexes (GICs). Light scattering measurements show that GBICs are much bigger (~70–100 nm) and GICs are much smaller or comparable in size (6–22 nm) to regular complex coacervate core micelles (C3Ms). The mechanism of GICs formation is different from the formation of regular C3Ms and GBICs, and their size depends on the length of the homopolyelectrolyte. The sizes of GBICs and GICs slightly decrease with temperature increasing from 20 to 65 °C. This effect is stronger for GBICs than for GICs, is reversible for GICs and GBIC-PAPEO14/P2MVPI228, and shows some hysteresis for GBIC-PAPEO14/P2MVPI43. Self-consistent field (SCF) calculations for assembly of a grafted block copolymer (having clearly separated charged and grafted blocks) with an oppositely charged linear polyelectrolyte of length comparable to the charged copolymer block predict formation of relatively small spherical micelles (~6 nm), with a composition close to complete charge neutralization. The formation of micellar assemblies is suppressed if charged and grafted monomers are evenly distributed along the backbone, i.e., in case of a grafted copolymer. The very large difference between the sizes found experimentally for GBICs and the sizes predicted from SCF calculations supports the view that there is some secondary association mechanism. A possible mechanism is discussed

« Half dicht, half prose gheordineert » : vers et prose de moyen français en moyen néerlandais

In both French-speaking and Dutch-speaking literary cultures of the late Middle Ages, competition between poets produced a collective poetic expertise. To what extent, then, can such competition be identified across the two cultures, in translations of verse or prosimetrum compositions from Middle French into Middle Dutch? An examination of the Dutch translations reveals that verse is both a means to knowledge and an object of knowledge, in the target culture as well as the source culture. The diversity of translations shows that verse is not only a system that translators attempt to master, but also a formal supplement in ways that are unavailable to prose

System identification in production ecology: from theory to agroforestry practice

This paper introduces a system identification approach to agricultural ecosystems. In particular, the identification of an agroforestry system, combining trees with crops, is subject of study. Typically, for these systems N < p, where N is the number of data points and p the number of parameters in a (process-based) model. In this paper, we follow a constrained optimization approach, in which the constraints are found from literature or are given by experts. Given the limited a priori systems knowledge and very limited data sets, after decomposition of the parameter estimation problem and after model adaptation, we were able to produce an acceptable fit to validation data from a real-world agroforestry experiment

Methodological approach for the assessment of environmental effects of agroforestry at the landscape scale.

Silvoarable agroforestry, the deliberate combined use of trees and arable crops on the same area of land, has been proposed in order to improve the environmental performance of agricultural systems in Europe. Based on existing models and algorithms, we developed a method to predict the environmental effects of SAF at a farm and landscape scale. The method is comprised of an assessment of soil erosion, nitrogen leaching, carbon sequestration, and landscape diversity and allowed the comparison of the environmental performance of SAF with arable systems using these four indicators

IMPROVING LOCAL WEATHER FORECASTS FOR AGRICULTURAL APPLICATIONS

ABSTRACT For controlling agricultural systems, weather forecasts can be of substantial importance. Studies have shown that forecast errors can be reduced in terms of bias and standard deviation using forecasts and meteorological measurements from one specific meteorological station. For agricultural systems usually the forecasts of the nearest meteorological station are used whereas measurements are taken from the systems location. The objective of this study is to evaluate the reduction of the forecast error for a specific agricultural system. Three weather variables , that are most relevant for greenhouse systems are studied: temperature, wind speed, and global radiation. Two procedures are used consecutively: diurnal bias correction and local adaptive forecasting. For each of the variables both bias and standard deviation were reduced. In general, if local measurements are reliable, forecast errors can be reduced considerably