A CFD-based Approach to Predict Explosion Overpressure: A Comparison to Current Methods

A CFD-based approach has been developed in this work to predict the overpressure produced during an explosion. An adiabatic exothermal reaction allows computing the explosion energy release. To validate the proposed CFD approach, overpressure predictions based on this methodology are compared with results produced with the TNObased method. It is demonstrated that the physics adopted in our model produces satisfactory predictions in the open area. The CFD simulations were carried out in the ANSYS CFX tool. The source of energy corresponds to the one produced by a stoichiometric proportion in reactants without energy generation. The explosion analysis considered that explosion occurs geometrically as a sequence of control volumes. Thus, the explosion in a volume is assumed to occur when the maximum pressure is achieved in the previous control volume. This way, the explosion is propagated and it is shown that it is equivalent to conventional predicting methods

Biological Fixation of N2 in Mono and Polyspecific Legume Pasture in the Humid Mediterranean Zone of Chile

del Pozo, A (del Pozo, Alejandro). Univ Talca, Fac Ciencias Agr, Talca, ChileDespite annual legume pasture are of great importance for dryland agricultural systems in Mediterranean environments, there are few studies of N-2 biological fixation (NBF) reported in Chile. In this study the NBF of four annual legume species: subterranean clover (Trifolium subterraneum L.), yellow serradella (Ornithopus compressus L.), arrow-leaf clover (T. vesiculosum L.), and crimson clover (T. incarnatum L.) (Experiment 1), as well as seven mixtures of these species (Experiment 2) were assessed. The NBF was measured by the N-15 natural abundance technique. The objective was to determine NBF in the legume species and in distinct mixtures used. The study was carried out in an Andisol of the Andean Precordillera located in the humid Mediterranean zone of Chile. Pasture was evaluated for biomass; and total N and natural abundance of N-15 were analyzed in plant material samples. In Experiment 1 (monospecific legume species pasture), N derived from fixation ranged between 43 and 147 kg N ha(-1) and where T. vesiculosum and T. subterraneum presented statistical differences (P <= 0.05) in connection with the other species. In the legume mixtures (Experiment 2), N derived by fixation varied between 97 and 214 kg N ha(-1) where the 50-50 mixtures (T. subterraneum and O. compressus, or T. subterraneum and T. vesiculosum, respectively) had the highest N fixation. Fixed N ranged between 12 and 25 kg N t(-1) DM, showing significant differences among mono and polyspecific legume species

Yttrium and Hydrogen Superstructure and Correlation of Lattice Expansion and Proton Conductivity in the BaZr0.9Y0.1O2.95 Proton Conductor

Bragg reflections in Y-resonant x-ray diffractograms of BaZr0.9Y0.1O2.95 (BZY10) reveal that Y is organized in a superstructure. Comparison with neutron diffraction superstructure reflections in protonated/deuterated BZY10 suggests that both superstructures are linked, and that protons move in the landscape imposed by the Y. The thermal lattice expansion decreases abruptly for protonated BZY10 at T≥648±20 K, coinciding with the onset of lateral proton diffusion and suggesting a correlation of structural changes and proton conductivity. The chemical shift in the Y L1-shell x-ray absorption spectra reveals a reduction from Y3+ toward Y2+ upon protonation

Managing Vegetation In Grassland Habitats To Enhance Livestock Or Wildlife Objectives

Sustainably stewarding grassland systems involves applying various practices to manipulate forage interactions with other plants, the environment, and grazing animals to meet resource manager objectives. These interactions can result in invasion or encroachment and increased abundance of weeds which hinder attainment of management objectives. Weeds influence the structure and function of pasture ecosystems whether forages are grown in improved pastures, rangeland, or grassland communities. They degrade pasture quality and reduce livestock performance by interfering with forage establishment, yield, and quality by competing for resources. Weeds reduce the feed value of forage, decrease pasture carrying capacity, and can be toxic or unpalatable to livestock. Managing weeds requires use of vegetation management tools that favor desirable forages. Herbicides can be a catalyst that expedite grassland renovation, improve the forage resource, and increase carrying capacity. Corteva Agriscience has a variety of herbicide products that provide superior control of herbaceous and woody weeds, while maintaining the desirable vegetation. These herbicides were designed and developed specifically for selective broadleaf weed control in rangeland, pastures, rights-of-way, non-cropland, and natural areas. Active ingredients historically used include aminopyralid, triclopyr, fluroxypyr, clopyralid, and picloram. Rinskor™ active and Arylex™ active are new herbicide active ingredients from Corteva Agriscience™ and are members of a unique synthetic auxin chemotype, the arylpicolinates (HRAC group O / WSSA group 4). Members of the arylpicolinate family demonstrate novel and differentiated characteristics in terms of use rate, spectrum, weed symptoms, environmental fate, and molecular interaction as compared to other auxin chemotypes. When applied as a stand-alone treatment or in various mixes these products are safe to desirable grass species and control key herbaceous and woody weeds in the genera Ambrosia, Acacia, Carduus, Centaurea, Cirsium, Mimosa, Prosopis, Ranunculus, Rumex, Sida, Solanum, Taraxacum, and more

Café Mesoamericano: desarrollo de una estrategia de adaptación al cambio climático

La producción de café en Mesoamérica es parte importante de la economía y la sociedad, al ser eje del bienestar de miles de familias y contribuir significativamente al PIB agrícola de diversos países. Pero las proyecciones indican que es en México y América Central donde el cambio climático tendrá los impactos más severos. Los modelos climáticos y los indicadores de aptitud climática del nicho en relación con el cultivo muestran cambios considerables, tanto en la calidad del café como en las zonas altitudinales apropiadas para la producción. Si hoy no se hacen esfuerzos para fortalecer la capacidad adaptativa, probablemente habrá grandes pérdidas económicas en toda la cadena de abastecimiento de café, así como la desaparición de importantes servicios ambientales

Hacia la evaluación del desempeño de un modelo de integración de agentes inteligentes & WSN a través de métricas

Las Redes de Sensores Inalámbricas o WSN (por su acrónimo en inglés Wireless Sensor Networks), en general, son redes inalámbricas que se componen de centenares o miles de dispositivos autónomos y compactos llamados nodos sensores. Las WSN son un área emergente de los sistemas embebidos que involucran aplicaciones de gran escala, incluyendo monitoreo, conservación ambiental y control industrial. Sin embargo, aún existen muchas limitaciones en éstas, tales como el consumo de energía, la organización de los nodos en la red, la reprogramación de la red de sensores, la confiabilidad en la transmisión de los datos, la optimización de recursos (memoria y procesamiento), etc., que requieren de investigación por parte de la comunidad científica. Investigaciones actuales incluyen el uso de técnicas de Inteligencia Artificial Distribuida (IAD), específicamente de agentes inteligentes, para hacer frente a los desafíos y limitaciones que éstas traen consigo. De esta forma, se requiere evaluar el desempeño de este modelo integrado (IAD + WSN) a través del uso de métricas. El propósito de este artículo es plantear las principales métricas que serán consideradas para evaluar el desempeño de la integración de agentes inteligentes y WSN