MKBA EcoLaNa grondfonds : De maatschappelijke gevolgen van de implementatie van een aantal duurzaamheidcriteria op veehouderij en akkerbouwbedrijven

Het EcoLaNa plan houdt in dat boeren overstappen op een duurzamere vorm van landbouw dan gangbare landbouw. Wat er onder duurzaamheid wordt verstaan blijkt uit de maatregelen die voor EcoLaNa zijn opgesteld. Door in te zetten op duurzame landbouw zal het EcoLaNa plan bijdragen aan het realiseren van de doelen die gesteld zijn door verschillende overheden, onder andere in het Europese Plattelandsontwikkelingsbeleid. Het gaat hierbij om doelen als het bevorderen van een sterke en dynamische agrofoodsector, instandhouding van de biodiversiteit en van landbouwsystemen met hoge natuurwaarden en uitvoering van de kaderrichtlijn water (POP2). In deze studie is middels een MKBA onderzocht of overschakeling naar duurzamere EcoLaNa landbouw voor de samenleving interessant is

Detection of contaminant plumes released from landfills

International audienceContaminant leaks released from landfills are a significant threat to groundwater quality. The groundwater detection monitoring systems installed in the vicinity of such facilities are vital. In this study the detection probability of a contaminant plume released from a landfill has been investigated by means of both a simulation and an analytical model for both homogeneous and heterogeneous aquifer conditions. The results of the two models are compared for homogeneous aquifer conditions to illustrate the errors that might be encountered with the simulation model. For heterogeneous aquifer conditions contaminant transport is modelled by an analytical model using effective (macro) dispersivities. The results of the analysis show that the simulation model gives the concentration values correctly over most of the plume length for homogeneous aquifer conditions, and that the detection probability of a contaminant plume at given monitoring well locations match quite well. For heterogeneous aquifer conditions the approximating analytical model based on effective (macro) dispersivities yields the average concentration distribution satisfactorily. However, it is insufficient in monitoring system design since the discrepancy between the detection probabilities of contaminant plumes at given monitoring well locations computed by the two models is significant, particularly with high dispersivity and heterogeneity

A decision analysis approach for optimal groundwater monitoring system design under uncertainty

International audienceGroundwater contamination is the degradation of the natural quality of groundwater as a result of human activity. Landfills are one of the most common human activities threatening the groundwater quality. The objective of the monitoring systems is to detect the contaminant plumes before reaching the regulatory compliance boundary in order to prevent the severe risk to both society and groundwater quality, and also to enable cost-effective counter measures in case of a failure. The detection monitoring problem typically has a multi-objective nature. A multi-objective decision model (called MONIDAM) which links a classic decision analysis approach with a stochastic simulation model is applied to determine the optimal groundwater monitoring system given uncertainties due to the hydrogeological conditions and contaminant source characteristics. A Monte Carlo approach is used to incorporate uncertainties. Hydraulic conductivity and the leak location are the random inputs of the simulation model. The design objectives considered in the model are: (1) maximizing the detection probability, (2) minimizing the contaminated area and, (3) minimize the total cost of the monitoring system. The results show that the monitoring systems located close to the source are optimal except for the cases with very high unit installation and sampling cost and/or very cheap unit remediation cost

Counting base phi representations

In a base phi representation, a natural number is written as a sum of powers of the golden mean φ. There are many ways to do this. Well known is the standard representation, introduced by George Bergman in 1957, where a unique representation is obtained by requiring that no consecutive powers, φn and φn+1, occur in the representation. In this paper, we introduce a new representation by allowing that the powers φ0 and φ1 may occur at the same time, but no other consecutive powers. We then argue that this representation is much closer to the classical representation of the natural numbers by powers of an integer than Bergman’s standard representation

Anisotropic Scaling in Layered Aperiodic Ising Systems

The influence of a layered aperiodic modulation of the couplings on the critical behaviour of the two-dimensional Ising model is studied in the case of marginal perturbations. The aperiodicity is found to induce anisotropic scaling. The anisotropy exponent z, given by the sum of the surface magnetization scaling dimensions, depends continuously on the modulation amplitude. Thus these systems are scale invariant but not conformally invariant at the critical point.Comment: 7 pages, 2 eps-figures, Plain TeX and epsf, minor correction

Wat noemen we verbrede landbouw? Verkenning van definities en informatiebehoeften

Het ministerie van LNV wil zich inzetten om agrarische ondernemers te faciliteren in de keuze van een (nieuwe) bedrijfsstrategie. Een belangrijk aspect daarvan behelst het inzichtelijk maken van het economische belang van de verbrede landbouw. Om de discussie rond het belang van verbreding op agrarische bedrijven zuiver te kunnen voeren is een empirische onderbouwing nodig waarmee uiteindelijk de omvang, de economische bijdrage en de ontwikkeling daarvan over de jaren heen, van de verbrede landbouw bepaald kan worden. The Dutch Ministry of Agriculture, Nature, and Food Quality (LNV) actively supports agricultural entrepreneurs in determining their business strategies. Given the increasing interest from entrepreneurs for multifunctional agriculture, there is strong demand for insights into its economic relevance. At the same time, there is a need for a robust empirical framework to understand and compare all the economic issues which are relevant to multifunctional agriculture. This framework would need to consist of indicators for market size, economic contribution to business revenue and the development of multifunctional agriculture over the years. This report is concerned with defining these indicators and looks into a preliminary design of a monitoring system which could fulfil the sector's requirements for more knowledge on the economic potential of multifunctional agriculture

Surface Magnetization of Aperiodic Ising Systems: a Comparative Study of the Bond and Site Problems

We investigate the influence of aperiodic perturbations on the critical behaviour at a second order phase transition. The bond and site problems are compared for layered systems and aperiodic sequences generated through substitution. In the bond problem, the interactions between the layers are distributed according to an aperiodic sequence whereas in the site problem, the layers themselves follow the sequence. A relevance-irrelevance criterion introduced by Luck for the bond problem is extended to discuss the site problem. It involves a wandering exponent for pairs, which can be larger than the one considered before in the bond problem. The surface magnetization of the layered two-dimensional Ising model is obtained, in the extreme anisotropic limit, for the period-doubling and Thue-Morse sequences.Comment: 19 pages, Plain TeX, IOP macros + epsf, 6 postscript figures, minor correction

Limit theorems for weakly subcritical branching processes in random environment

For a branching process in random environment it is assumed that the offspring distribution of the individuals varies in a random fashion, independently from one generation to the other. Interestingly there is the possibility that the process may at the same time be subcritical and, conditioned on nonextinction, 'supercritical'. This so-called weakly subcritical case is considered in this paper. We study the asymptotic survival probability and the size of the population conditioned on non-extinction. Also a functional limit theorem is proven, which makes the conditional supercriticality manifest. A main tool is a new type of functional limit theorems for conditional random walks.Comment: 35 page