Ecotoxicological risk assessment of agriculture intensification in Argentinean cropping lands using a fuzzy-logic based model

Current agricultural models have an increasing dependence on non-renewable resources that have significant implications for the ecosystem health. Pesticides are considered one main impact force that affects both the structure and functions of agroecosystems. In this work we presented results from the application of an environmental pesticide risk assessment of a large database of cropping systems in the Inland Pampa (Argentina) where, since 1990, the traditional mixed grazing–cropping systems were being replaced by permanent agriculture and the intensification of pesticide use has increased significantly. However, there is no clear awareness of the ecotoxicological risk associated with these land use changes. The ecotoxicological risk on both insects and mammals were assessed using a fuzzy-logic based model that links, as input variables, the amount the pesticide dose and the lethal dose (LD50) of each active ingredient use in a single crop field. Thresholds and membership functions were developed by means of expert opinion. A database, containing 29042 records of pesticide use in maize, soybean, sunflower and wheat from 1992 to 2005 were analyzed. Results showed that harvested yield increased significantly in all crops during the period studied (P<0.005). However, these higher yields were associated with higher risks over both insect and mammals as in almost all crops analyzed the fuzzy-logic ecotoxicological indicators showed negative and significant time trend in the period studied (P<0.005, Spearman rank correlation (SRC)). Summer soybean (i.e in the wheat-soybean rotation) did not show any significant tendency regarding changes in potential ecotoxicological risk during 1992-2005 interval. However, soybean (either as summer or spring crop) showed the highest ecotoxicological risk value in each one of the years analyzed (Kruskal-Wallis test, p < 0.05). Regarding the average number of pesticides applied, all crops showed a significant increment from 1992 to 2000 and a subsequent reduction from 2000 to 2005 (SRC, P < 0.05) and these reductions were higher in soybean, from 6.1 to 3.5 application/year in relation to maize, soybean and sunflower. These preliminary results indicated that higher yield in all the crops analyzed were associated to higher ecotoxicological risk of the pesticides used. However, further work has to be conducted to improve the fuzzy-logic ecotoxicological model by including variables such human toxicological risk or other chemical pesticide characteristics (i.e. soil persistence, solubility)

Simulating Nonholonomic Dynamics

This paper develops different discretization schemes for nonholonomic mechanical systems through a discrete geometric approach. The proposed methods are designed to account for the special geometric structure of the nonholonomic motion. Two different families of nonholonomic integrators are developed and examined numerically: the geometric nonholonomic integrator (GNI) and the reduced d'Alembert-Pontryagin integrator (RDP). As a result, the paper provides a general tool for engineering applications, i.e. for automatic derivation of numerically accurate and stable dynamics integration schemes applicable to a variety of robotic vehicle models

Monte Carlo-based multi-physics analysis for transients in Light Water Reactors

Die Kernreaktortechnologie ist ein ausgereiftes Feld mit mehreren Jahrzehnten Evolution und wichtigen Akteuren, die auf der ganzen Welt verteilt sind. Ein umfassendes Wissen über diese globale Technologie ist weltweit verfügbar, einschließlich gut etablierter Sicherheitsprinzipien und -praktiken, die hinsichtlich ihrer Verwendung vollständig ausgefüllt werden müssen. In diesem Rahmen ist die kontinuierliche Verbesserung der Sicherheitsstandards der Nuklearindustrie sowie der kommerziellen Ziele von Reaktordesignern und -betreibern eine treibende Kraft für die weltweite Entwicklung hochpräziser Methoden in der Reaktorphysik. Diese neuartigen Werkzeuge schlagen normalerweise ein sehr detailliertes Kopplungsschema zusammen mit einer geringeren Anzahl von Approximationen innerhalb des physikalischen Modellierungsansatzes vor. Dies ist der Treiber für die wissenschaftliche und technologische Frage, die in dieser Arbeit behandelt werden soll, die sich mit der Untersuchung fortschrittlicher Methoden zur Entwicklung gekoppelter neutronisch-thermisch-hydraulischer Berechnungen innerhalb des LWR befasst. Hier, wird ein vielseitiges gekoppeltes Werkzeug zwischen Serpent Monte Carlo-Partikeltransport und SUBCHANFLOW (SCF) -Unterkanal-Thermohydraulikcodes entwickelt, das sich auf transient-Probleme konzentriert, aber auch für stationäre und burnup Berechnungen. Es wird ein Test, Verifizierungs- und Validierungs-prozess bereitgestellt für verschiedene reale LWR-Geometrien und Betriebsbedingungen für stationäre, burnup und transient Berechnungen durchgeführt, der realistischer numerischer Benchmarks sowie experimenteller Daten berücksichtigt. Die Genauigkeit des Ansatzes wird bewertet, wobei auch ein konsistentes Verhalten aller beteiligten physikalischen Phänomene auf pin-wise-Ebene gezeigt wird. Der Schwerpunkt liegt auf der Untersuchung der damit verbundenen Funktionen des Tools, wobei seine Durchführbarkeit für weitere industrieähnliche Anwendungen aufgezeigt wird, wie z.B. die sicherheitsrelevante Analyse für Reactivity Insertion Accidents. Darüber hinaus werden potenzielle Einschränkungen und inhärente Begrenzungen analysiert und verschiedene Pfade vorgeschlagen, was beweist, dass ein MC-basierter Ansatz einen überzeugenden alternativen Pfad für die direkten pin-by-pin full-core LWR-Berechnungen darstellt

Algunos aspectos acerca de la aparición de resistencia a herbicidas en poblaciones de malezas

Actualmente la mayor parte de las cosechas de grano en la Argentina están provistas por sistemas de producción agrícola permanente. Esto ha inducido el reemplazo de especies y la selección de fenotipos nuevos en las poblaciones de las malezas que acompañan los cultivos. Estos cambios se manifiestan a través de un incremento en las fallas en el control químico, debido a que las especies escapan, aumentan la tolerancia o resisten a los controles. En respuesta a estos problemas los agricultores han incrementado las dosis, la frecuencia de aplicación de herbicidas y el abanico de productos utilizados. Estas medidas, que apuntan a resolver las ineficiencias en el control de malezas, han acentuado en términos generales el problema de la reestructuración de las comunidades de malezas y el de la selección de poblaciones resistentes a los herbicidas. Ejemplos paradigmáticos de este proceso son la resistencia a glifosato y atrazina, dos de los herbicidas que se usan con mayor frecuencia.Fil: Ghersa, Claudio Marco. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Ferraro, Diego Omar. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Exergy efficiency assessment of corn-based ethanol production : a case study in the Pampas region (Argentina)

La transformación de los sistemas naturales en sistemas productivos altera no sólo su estructura sino también su funcionalidad. La necesidad de evaluar y monitorear esos cambios funcionales ha llevado al desarrollo y la aplicación de un gran número de indicadores del impacto de las actividades humanas sobre los ecosistemas. En este trabajo se presenta un marco teórico para el estudio del deterioro de los ecosistemas agrícolas a través del análisis de los flujos de energía. Se presentan los fundamentos de la evaluación del funcionamiento de los agroecosistemas a través del uso de la energía útil o exergía, y se ilustra la metodología de cálculo en un sistema agrícola de la Región Pampeana destinado a la producción de etanol sobre la base de grano de maíz. Los resultados indican que si bien el impacto potencial en términos de extracción de recursos (bajo la forma de exergía consumida) es mayor en la fase industrial, las ineficiencias en la fase agrícola son mucho más marcadas. En cuanto al ciclado interno de exergía, los resultados de este trabajo indican que 41% de la exergía utilizada para obtener 1 MJ de exergía proviene de fuentes no renovables, y se eleva a 71% si se toma en cuenta el aporte neto de exergía del combustible, después de descontarle los costos exergéticos acumulados durante los procesos de elaboración. Estos resultados indican que el sistema analizado de producción de etanol sobre la base de maíz cumple de manera parcial las condiciones deseables de baja extracción de recursos del ambiente y alta renovabilidad de la producción.Natural ecosystems transformation in agroecosystems not only alters its structure but also its functionality. The need to evaluate and monitor these functional changes has led to the development and implementation of a large number of indicators of human impact due to agricultural activities. This paper develops a theoretical framework for the assessment of agroecosystems through the analysis of energy flows. In particular, the approach is based on the use of energy or useful exergy. Also, the calculation methodology is applied to a corn-based ethanol farming system located in the Pampa Region. Results indicate that although the potential impact in terms of resource extraction from the environment, in the form of exergy consumed, is highest in the industrial stage, the inefficiencies in the agricultural phase are much more pronounced. As for the internal cycling of exergy, the results of this study indicate that 41% of the exergy used to get 1 MJ of exergy comes from non-renewable sources, rising to 71% when you take into account the contribution of net exergy fuel. These results indicate that the crop-based system analyzed for ethanol production partially meets the desirable conditions of low resource extraction from the environment and high renewability of production

Effect of energy deposition modelling in coupled steady state Monte Carlo neutronics/thermal hydraulics calculations

In coupled calculations with Monte Carlo neutronics and thermal hydraulics the Monte Carlo code is used to produce a power distribution which in practice means tallying the energy deposition. Usually the energy deposition is estimated by making a simple approximation that energy is deposited only in fission reactions. The goal of this work is to study how the accuracy of energy deposition modelling affects the results of steady state coupled calculations. For this task an internal coupling between Monte Carlo transport code Serpent 2 and subchannel code SUBCHANFLOW is used along with a recently implemented energy deposition treatment of Serpent 2. The new treatment offers four energy deposition modes each of which offers a different combination of accuracy and required computational time. As a test case, a 3D PWR fuel assembly is modelled with different energy deposition modes. The resulting effective multiplication factors are within 30 pcm. Differences of up to 100K are observed in the fuel temperatures

Geometric Integrators for Higher-Order Variational Systems and Their Application to Optimal Control

Numerical methods that preserve geometric invariants of the system, such as energy, momentum or the symplectic form, are called geometric integrators. In this paper we present a method to construct symplectic-momentum integrators for higher-order Lagrangian systems. Given a regular higher-order Lagrangian L: T( k )Q→ R with k≥ 1 , the resulting discrete equations define a generally implicit numerical integrator algorithm on T( k - 1 )Q× T( k - 1 )Q that approximates the flow of the higher-order Euler–Lagrange equations for L. The algorithm equations are called higher-order discrete Euler–Lagrange equations and constitute a variational integrator for higher-order mechanical systems. The general idea for those variational integrators is to directly discretize Hamilton’s principle rather than the equations of motion in a way that preserves the invariants of the original system, notably the symplectic form and, via a discrete version of Noether’s theorem, the momentum map. We construct an exact discrete Lagrangian Lde using the locally unique solution of the higher-order Euler–Lagrange equations for L with boundary conditions. By taking the discrete Lagrangian as an approximation of Lde, we obtain variational integrators for higher-order mechanical systems. We apply our techniques to optimal control problems since, given a cost function, the optimal control problem is understood as a second-order variational problem.Fil: Colombo, Leonardo Jesus. University of Michigan; Estados UnidosFil: Ferraro, Sebastián José. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Matemática Bahía Blanca. Universidad Nacional del Sur. Departamento de Matemática. Instituto de Matemática Bahía Blanca; ArgentinaFil: Martin de Diego, David. Instituto de Ciencias Matemáticas; España. Consejo Superior de Investigaciones Científicas; Españ