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Charged stellar model with three layers

Research in Astronomy and Astrophysics 2021年第12期21卷 421-432页

作者： Avirt S.Lighuda Jefta M.Sunzu Sunil D.Maharaj eunice W.mureithi Department of Mathematics University of Dar es SalaamTanzania Department of Mathematics and Statistics The University of DodomaDodomaTanzania Astrophysics Research Centre School of MathematicsStatistics and Computer ScienceUniversity of Kwa Zulu-NatalDurban 4000South Africa

We establish new charged stellar models from the Einstein-Maxwell field equations for relativistic superdense objects outfitted with three *** core layer is described by a linear equation of state(EoS)describing quark matter,while the intermediate layer is described by a Bose-Einstein condensate EoS for Bose-Einstein condensate matter and the envelope layers satisfying a quadratic EoS for the neutron *** have specified a new choice of the electric field and one of the metric *** is interesting to note that the choice of electric field in this model can be set to vanish and we can regain earlier neutral *** generated depict that the matter variables,gravitational potentials and other physical conditions are consistent with astrophysical *** interior layers and exterior boundary are also matched.

关键词： charged anisotropic stars:equations of state:layered interior

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A Mixed Convection Boundary Layer Flow over a Vertical Wall in a Porous Medium, with Exponentially Varying Fluid Viscosity

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Journal of Applied Mathematics and Physics 2014年第8期2卷 795-802页

作者： eunice mureithi Department of Mathematics University of Dar es Salaam Dar es Salaam Tanzania

This study investigates a mixed convection boundary layer flow over a vertical wall embedded in a highly porous medium. The fluid viscosity is assumed to decrease exponentially with temperature. The boundary layer equations are transformed into a non-similar form using an appropriate non-similar variable ξ and a pseudo-similar variable η. The non-similar equations are solved using an efficient local non-similarity method. The effect of viscosity variation parameter on the heat transfer, skin friction and the velocity and temperature distribution within the boundary layer is investigated. The viscosity variation parameter, the viscous dissipation parameter and non-simi-larity variable are shown to have a significant effect on velocity and thermal boundary layer and also on the skin friction coefficient and heat transfer at the wall.

关键词： Porous Medium Non-Darcy Mixed Convection Boundary Layer Temperature Dependent Viscosity

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Effects of Over-Harvesting and Drought on a Predator-Prey System with Optimal Control

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Open Journal of Ecology 2018年第8期8卷 459-482页

作者： Alanus Mapunda eunice mureithi Nyimvua Shaban Thadei Sagamiko Department of Mathematics University of Dar es Salaam Dar es Salaam Tanzania Department of Mathematics Physics and Informatics University of Dar es Salaam Dar es Salaam Tanzania

In this paper, a two species predator-prey model is developed where prey is affected by over-harvesting and drought and predator is affected by drought. The intention is to investigate the impact of over-harvesting and drought on predator-prey system, and suggest control strategies to alleviate the problem of loss of prey and predator species due to over-harvesting and drought. The control strategies suggested are creation of reserve areas with restriction of harvesting for controlling over-harvesting and construction of dams for mitigating drought effects. The results obtained from theoretical and numerical simulation of the predator-prey model with harvesting and drought without control strategies showed that, both harvesting and drought affect the predator-prey population negatively. However, the results obtained from numerical simulations of the model with control measures showed that, the use of control strategies one at a time encourages the increase of the prey and predator species to the optimal population size. Furthermore, the best result is obtained when control strategies, creation of reserve areas with restriction of harvesting and construction of dams are applied simultaneously.

关键词： Predator-Prey System Over-Harvesting Drought Optimal Control

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