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Search Results: 1 - 10 of 135 matches for " Nyimvua Shaban "
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Effects of Over-Harvesting and Drought on a Predator-Prey System with Optimal Control  [PDF]
Alanus Mapunda, Eunice Mureithi, Nyimvua Shaban, Thadei Sagamiko
Open Journal of Ecology (OJE) , 2018, DOI: 10.4236/oje.2018.88028
Abstract: 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.
Formulation of Mathematical Model for TB Transmission in Zoonotic Areas with Existence of Endemic Equilibrium  [PDF]
Thomas Mwenyeheri, Nyimvua Shaban, Doroth Hove-Msekwa, Symon Bilesi Chibaya, Esther Ngadaya, Sayoki Mfinanga
Journal of Tuberculosis Research (JTR) , 2014, DOI: 10.4236/jtr.2014.23017
Abstract: A mathematical model incorporating animal TB and Human TB transmission is formulated and analysed in order to determine the role of animal TB and human TB in the overall TB transmission and also, to determine the parameters which govern the transmission of the TB disease. The model has five classes namely susceptible, exposed animal TB, and exposed human TB, infectious and recovery. The model assumed that there are two classes for infected individuals, those who acquired TB through animal and those who acquire TB from human. Qualitative results show that the model has the disease-free equilibrium and at least one endemic equilibrium that is locally asymptotically stable. The study includes numerical simulations as a way of supporting the analytical results. Graphical results indicate that animal TB has major contribution on overall TB transmission and the TB transmission can be reduced by ensuring intervention to both Animal TB and Human TB. Furthermore the equations indicate that there is at least one endemic equilibrium which translates that t animal and human have the contribution on TB transmission. This shows that both animals and humans together with fast progressors have contribution on TB transmissions.
Assessing Weather Research and Forecasting (WRF) Model Parameterization Schemes Skill to Simulate Extreme Rainfall Events over Dar es Salaam on 21 December 2011  [PDF]
Triphonia Jacob Ngailo, Nyimvua Shaban, Joachim Reuder, Michel D. S. Mesquita, Edwin Rutalebwa, Isaac Mugume, Chiku Sangalungembe
Journal of Geoscience and Environment Protection (GEP) , 2018, DOI: 10.4236/gep.2018.61003
Abstract: This paper evaluates the skills of physical Parameterization schemes in simulating extreme rainfall events over Dar es Salaam Region, Tanzania using the Weather Research and Forecasting (WRF) model. The model skill is determined during the 21 December 2011 flooding event. Ten sensitivity experiments have been conducted using Cumulus, Convective and Planetary boundary layer schemes to find the best combination and optimize the WRF model for the study area for heavy rainfall events. Model simulation results were verified against observed data using standard statistical tests. The model simulations show encouraging and better statistical results with the combination of Kain-Fritsch cumulus parameterization scheme, Lin microphysics scheme and Asymmetric Convection Model 2 (ACM2) planetary boundary scheme than any other combinations of physical parameterization schemes over Dar es Salaam region.
Geothermal Water in Lebanon: An Alternative Energy Source  [PDF]
Amin Shaban
Low Carbon Economy (LCE) , 2010, DOI: 10.4236/lce.2010.11003
Abstract: Recently, demand for energy has been increased worldwide, notably in the view of high economic value and competi-tion of fossil fuel, as well as the negative impact of fuel consumption through carbon release, and thus the consequences on human health and environment. Various aspects of energy sources into Earth’s crust have been discovered and utilized. Geothermal energy is one aspect of these sources where they have been well pronounced in many countries and proved to be a potential energy source for the future needs. Lebanon, the country with rare natural energy, the renewable energy sources are almost ignored and there is only limited utilization of hydro-power, wind and solar energy, whilst oil imports occupy a substantial portion for energy use. Yet, geothermal energy has not raised and no concern has been given to this renewable source. Meanwhile, there are several indicators showing the existence of geothermal water in different regions in Lebanon. They almost occur where basalt rocks are exposed. This was evidenced whether from water in drilled wells or from various discharging springs, as well as indications of thermal water was observed also in many localities along the Lebanese coastal water. This study shows the available information in this respect, considering the occurrence of geothermal water in Lebanon as an alternative energy source. Thus four major geothermal domains were recognized. The study introduces detailed characterization on the existing aspects of geothermal water and inducing its hydrologic regime and mechanism of groundwater heating. It would be a reconnaissance stage that may help applying further detailed assessment.
Support of Space Techniques for Groundwater Exploration in Lebanon  [PDF]
Amin Shaban
Journal of Water Resource and Protection (JWARP) , 2010, DOI: 10.4236/jwarp.2010.25054
Abstract: Lebanon is known by the availability in water resources whether on surface or among the existing rock for-mations. However, the status-quo does not reflect this availability due to a number of physical factors, as well as the mismanagement of these resources. Hence, the per capita has been reduced by about 50% in the last three decades. There are sixteen exposed rock formations in Lebanon, two of them are major aquifers and they are characterized by highly fractured and karstified carbonate rocks. Recently, challenges for groundwater in Lebanon have been developed. These are the: overexploitation, climate change and the acute geologic setting, which led to decline in rainfall rate, and thus exacerbated water demand. The existing chal-lenges resulted with a number of problems in ground water resources management, namely: quality deterio-ration, impact on springs and groundwater behavior, loss of groundwater o the sea, saltwater intrusion and exacerbated by the lack of data and mismanagement in water sector. In this respect, new technologies can be utilized as a helpful instrument in managing groundwater resources to treat the unfavorable situation. Space techniques and GIS have been recently raised in several topics on water resources management, including, mainly exploration and monitoring. They proved to be capable to extract hydrogeologic information and thus to manipulate this information in creditable approaches of analysis. This study introduced the present status on the Lebanese groundwater resources and the existing challenges and problems. Thus, it extends an appli-cation from Lebanon on the used new approaches for exploring groundwater.
Spatial Inhomogenity Due to Turing Instability in a Capital-Labour Model  [PDF]
Shaban Aly
Applied Mathematics (AM) , 2012, DOI: 10.4236/am.2012.32027
Abstract: A cross-diffusion system is set up modelling the distribution of capital and labour over the land of two identical patches (cites, markets or countries) in which the per capita migration rate of each species (investment capital or labour force) is influenced not only by its own but also by the other one’s density, i.e. there is cross-diffusion present. Numerical studies show that at a critical value of the bifurcation parameter the system undergoes a Turing bifurcation and the cross-migration response is an important factor that should not be ignored when pattern emerges.
Effective Photocatalytic Reduction of Cr(VI) by Carbon Modified (CM)-n-TiO2 Nanoparticles under Solar Irradiation  [PDF]
Yasser A. Shaban
World Journal of Nano Science and Engineering (WJNSE) , 2013, DOI: 10.4236/wjnse.2013.34018
Abstract: Photocatalytic reduction of toxic Cr(VI) was successfully achieved using carbon modified titanium oxide (CM-n-TiO2) nanoparticles under natural sunlight illumination. Modification of titanium oxide by carbon significantly enhanced the photocatalytic reduction of Cr(VI) under natural sunlight irradiation. The effects of various experimental parameters such as catalyst dose, initial concentration of Cr(VI), and solution pH on the reduction rate of Cr(VI) were investigated. The highest reduction rate of Cr(VI) was obtained at the optimal conditions of pH 5 and 2.0 g·L?1 of CM-n-TiO2. Interestingly, in the presence of phenol, as a sacrificial electron donor, the rate of Cr(VI) reduction was nearly 1.7 times higher than in its absence. The solar photoreduction of Cr(VI) in aqueous solution using CM-n-TiO2 obeyed a pseudo-first order kinetics according to the Langmuir-Hinshelwood model.
Simultaneous Hydrogen Production with the Degradation of Naphthalene in Seawater Using Solar Light-Responsive Carbon-Modified (CM)-n-TiO2 Photocatalyst  [PDF]
Yasser A. Shaban
Modern Research in Catalysis (MRC) , 2013, DOI: 10.4236/mrc.2013.23A002

The simultaneous photocatalytic production of hydrogen and degradation of naphthalene in seawater was successfully achieved using carbon modified titanium oxide (CM-n-TiO2) nanoparticles under natural sunlight illumination. Compared to unmodified titanium oxide (n-TiO2), CM-n-TiO2 nanoparticles exhibited significantly higher photocatalytic efficiency. It is considered that carbon modification is responsible for the significant enhancement in the observed photoactivity. The experimental results indicated that the simultaneous production of hydrogen and degradation of naphthalene was favorable at pH 8 and optimal catalyst dose of 1.0 g.L-1. The solar photocatalytic degradation of naphthalene in seawater using CM-n-TiO2 successfully fitted using Langmuir-Hinshelwood model, and can be described by pseudo-first order kinetic model.

Finite Element Study on the Development of Damage and Flow Characteristics in Al7075 Alloy during Ex-ECAP  [PDF]
Mehdi Shaban Ghazani, Beitallah Eghbali
Modeling and Numerical Simulation of Material Science (MNSMS) , 2013, DOI: 10.4236/mnsms.2013.31004
Abstract: In the present study, 3D-finite element method was conducted to investigate the deformation characteristics of Al7075 alloy during integrated extrusion-equal channel angular pressing. Effective strain, strain rate, mean stress, and damage distributions were evaluated. Severe cracking was observed at Al7075 sample after extrusion-equal channel angular pressing. Finite element results show that cracking is due to the positive mean stress and damage accumulation at the top surface of sample.
Finite Element Analysis of the Groove Pressing of Aluminum Alloy  [PDF]
Mehdi Shaban Ghazani, Akbar Vajd
Modeling and Numerical Simulation of Material Science (MNSMS) , 2014, DOI: 10.4236/mnsms.2014.41006
In this paper, the finite element method was applied to analyze the deformation behavior of Al-1%Mg alloy during constrained groove pressing (CGP). Deformation inhomogeneity was studied in term of plastic strain distribution during deformation. It was found that after first pressing and flattening steps, the plastic strain is inhomogeneous but second pressing and flattening improve deformation distribution considerably. Also the regions between flat and inclined parts of sample receive less shear strain and consequently after four passes the deformation distribution is still inhomogeneous and doesn’t improve remarkably with more deformation steps.
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