130 research outputs found

    Modèles linéaires stochastiques théoriques pour la réponse des petits bassins

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    En rendant aléatoires les intrants du modèle déterministe en cascade de réservoirs linéaires de Nash-Dooge, on obtient des modèles linéaires stochastiques adaptés aux petits bassins, qui peuvent être formulés comme des systèmes dynamiques stochastiques linéaires simples représentés par des équations différentielles stochastiques (EDS). Les processus du système, la précipitation et les pertes dues à l'évapotranspiration (cette dernière étant considérée comme un intrant négatif), sont respectivement modélisés par un processus composé de Poisson et par un bruit blanc gaussien à moyenne nulle superposé à une moyenne déterministe. Pour la réponse superficielle et la réponse souterraine, on propose des modèles stochastiques en cascades de Nash-Dooge à n réservoirs linéaires égaux et à deux réservoirs en parallèle. Des travaux récents sur la genèse des débits ont conduit à mettre au point un modèle dynamique grossier, plus plausible conceptuellement, formé de régimes à réponse rapide et à réponse lente parallèles. Ce modèle est élaboré en attribuant au réservoir lent toutes les pertes d'évapotranspiration, les fluctuations de celle-ci étant modélisées par un bruit gaussien coloré à moyenne nulle et en rationalisant un modèle d'infiltration linéarisé fonction d'un écoulement à régime lent précédant une précipitation. En fait, cette contribution vise à donner une portée plus générale à la théorie déterministe de Nash-Dooge basée sur l'hydrogramme unitaire, afin de l'étendre à une théorie linéaire stochastique de réponse d'un bassin.By randomizing the inputs to the deterministic Nash-Dooge linear reservoir cascade, linear stochastic conceptual response models suitable for small catchments are formulated as simple linear stochastic dynamical systems within the formalism of stochastic differential equations (SDE’s). The system driving processes, rainfall and evapotranspiration losses, the latter regarded as a negative input, are modeled respectively as a compound Poisson process and a mean zero white Gaussian noise superposed on a deterministic mean. Elementary stochasticized Nash-Dooge cascades of n equal linear reservoirs and two reservoirs in parallel are given as potential models of surface and subsurface response. On consideration of recent discoveries concerning streamflow generation, a more conceptually plausible coarse-grained dynamical model of parallel quick and slow response regimes is developed by confining all evapotranspiration losses to the slow reservoir, modeling evapotranspiration fluctuations as mean zero colored Gaussian noise and rationalizing a linearized infiltration model dependent on slow regime outflow just prior to an event. In essence, the effort is directed towards generalizing the deterministic Nash-Dooge theory of the unit hydrograph to a linear stochastic theory of catchment response

    Studies on Zn(II) Complexes of Pyridine, 4-Ethylpyridine, 3,5-Lutidine & 3,4-Lutidine

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    664-66

    AS-322-89 Resolution on Proposal to Establish the CIM Center

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    Approves the Proposal to Establish the Computer Integrated Manufacturing Center (CIM) at Cal Poly

    Jatropha Multifida Poisoning In A Malabari Goat

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    Mixed Layer Budget Terms on Acoustic Propagation A Study based on the Butterfly Track Experiment in the South Eastern Arabian Sea

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    A butterfly type of repeat track cruise was carried out in the South Eastern Arabian Sea (off Minicoy) onboard INS Sagardhwani during July 2016 to Aug 2016. We have also made use of the data from OMNI buoy, AD09, which is about 6 km close to the centre station of butterfly track. Air sea flux, the horizontal current data from AD09 and the time series data collected from the butterfly experiment were analyzed to compute the mixed layer heat and salt budget. The short-term thermo-haline variability off Minicoy, relative contribution of heat/salt budget terms in MLD and its effects on acoustic propagation are addressed in this paper. In this study, we found that most dominating term in the mixed layer heat budget estimation is net surface heat flux followed by the advective terms. However the salinity in the mixed layer is dominated by the contribution of buoyancy mixing due to night time evaporative cooling. During the calm, sunny day, the so-called afternoon effect due to the diurnal heating restricts the sonar range. But during the windy day, the wind/wave mixing prevents the warming of the surface layer which in turn enhances the sonar range. Similarly, the night time cooling also enhance the acoustic propagation range. The presence of Arabian Sea High Salinity Watermass in the surface layer also enhances the acoustic propagation

    Anti-oxidant effect of N-acetyl cysteine in dogs with chronic kidney disease

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    The present study was carried out with the objectives of assessing oxidative stress in dogs with chronic kidney disease (CKD) and evaluating response to treatment with N-acetyl cysteine (NAC). Dogs diagnosed with stage III CKD as per the guidelines of the International Renal Interest Society (IRIS) were included in the study. The animals were divided into two groups. Animals of one group were given standard therapy for CKD and the animals of the second group were administered NAC along with standard therapy. Oxidative stress parameters such as total antioxidant status (TAS), serum malondialdehyde (MDA) level and plasma glutathione peroxidase (GSH-Px) activity were studied. On the day of presentation, a significant increase in the mean values of serum MDA and TAS were observed in diseased animals compared to healthy animals, whereas a significant decline was noted in plasma GSH-Px activity. After treatment, a significant decline in serum MDA and TAS were recorded in animals of group II receiving NAC therapy. A significant increase in plasma glutathione GSH-Px activity was recorded in this group. N-acetyl cysteine therapy was found to be effective in the management of oxidative stress in dogs with chronic kidney disease
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