ABSTRACT The thesis presents the modelling and simulation of free running semiconductor laser. The rate equations which were derived on the basis of the fact that there must be a balance between carriers that undergo transition and the photons generated and annihilated were simulated to examine what laser looks like when ran without positive optical feedback nor any optical injection. The result shows the photons get amplified due to stimulated emission but no oscillation of the output is ob...
ABSTRACT In this study, the complex interaction of surface runoff with the biomechanics of soil water transport and heat transfer rate is theoretically investigated using mathematical model that rely on the two phase flows of an incompressible Newtonian fluid (stormwater) within the soil (porous medium) and on the soil surface (runoff). The flow and heat transfer characteristics within the soil are determined numerically based on Darcy-Brinkman-Forchheimer model for porous medium coupled with...
ABSTRACT Chemical method is the most efficient and flexible method of hydrate control in offshore operations. In recent times, polymers and surfactants have been used to influence the kinetics of hydrate growth and coagulation. However, the traditional polar solvents are still relevant because of their ability to melt hydrates. Due to the large volume of polar thermodynamic inhibitors usually required in the field, this work examines the effect of hybrid hydrate inhibitors (HHI) comprising b...
ABSTRACT Density-Functional Theory (DFT) offers a simplification to electronic structure problems by using the electron density instead of the wave-function. Unlike the wavefunction which is a function of 3N variables (excluding spin) for an N-electron system, the density depends only on three variables, irrespective of the number of electrons in the system. While DFT, in principle, gives an accurate description of ground state properties, practical applications of DFT are based on approximat...
ABSTRACT A year-long campaign that accounted for seasonal differences have been conducted to examine the levels, chemical composition and sources of ambient particulate matter in multiple neighbourhoods of varying socioeconomic status in Accra, Ghana. Between September 2007 and August 2008, simultaneous measurements of PM2.5 and PM10 aerosols at five monitoring sites in four neighbourhoods (Asylum Down, East Legon, Nima and James Town/Ussher Town) were done for one 48-hour period every six d...
Abstract Graphene is an effectively two dimensional form of carbon atoms arranged in honeycomb lattice. Due to its lightweight, high electron mobility and other special electronic properties it is considered both an academically interesting and industrially promising candidate for various electronics applications. Many investigations focused on graphene require theoretical simulations to be performed over a large number of unit cells of graphene. For simulation scenarios where ab-initio meth...
Abstract We present theoretical results of the study of H2S adsorption on gold cluster Aun(n = 1, 5) using density functional theory with PerdewBurke-Ernzerhof (PBE) exchange-correlation energy functional. Minimum energy structures of the gold cluster along with their isomers are considered in the optimization process. H2S molecule is observed to adsorb on to the gold cluster. However, the adsorption energy decreases with increasing cluster size. The structure of the gold clusters are simila...
Abstract Most anticancer drugs are polar, cytotoxic and have complicated structures which cause difficulty in their penetration through the cell membrane. This presents a serious problem in chemotherapy. Is it possible to use carbon nanotubes (CNTs) as intracellular drug delivery agents to concomitantly mininmize side effects and maximize therapeutic effect? Although previous experimental and simulation studies have demonstrated that CNTs are able to translocate through cell membrane, the ce...
ABSTRACT In general, it is assumed in some non viscous flows that the flow velocity is constant at a cross-section. In this thesis, If we impose more realistic boundary conditions by, for example, introducing viscosity,and suction at walls, the net mass flow will change since the continuity equation must hold. The convective acceleration terms will be products of variables such that a nonlinear behavior will take place in the flow. The work will consist of deriving all the equations and param...
ABSTRACT This thesis deals with the control of non linear oscillations in plasma governed by a classical Van der Pol equation . The main interest devoted to such an investigation is that non linear oscillations in plasma is essential in industry. In chapter 1 , we present some generality on the dynamical systems . Chapter 2 is focussed on the analytical study of the Van der Pol equation in autonomous regime . The amplitude and the phase of the stable limit cycle are derived using the Averagin...
ABSTRACT Solar radiation is the ultimate source of energy for the planet. To predict the values of temperature and instant solar radiation when equipment are not readily available from obtained equations, a good knowledge and understanding of the disposition and distribution of solar radiation is a requirement for modelling earth’s weather and climate change variables. A pyranometer (CM3) in series with a PHYWE amplifier and a voltmeter were experimentally set up and used to study the amou...
ABTRACT Instrumental Neutron Activation Analysis has been applied in the multi-element analysis of five soils from three agro-ecological zones in Ghana, using the Single Relative Standardization Method. The analysis was carried out at the Ghana Atomic Energy Commission Research Reactor-1 (GHARR-1) Centre. Concentrations of 34 elements in deciduous forest, forest and Coastal Savanna soils were obtained. Elemental compositions and their levels in the five soils; Oda ,Bekwai, Toje, Akuse and An...
ABSTRACT This work shows the increase in surface dose caused by thermoplastic immobilizing masks used for positioning and immobilization of patients. Thermoplastics are organic materials which soften when they are heated. They can be formed after softening and retain their final shape when cooled. The use of these thermoplastic masks are relevant during patient treatment. However, it can lead to an increased skin dose. Measurements were done at source-to-suface distance of 80 cm for external ...
ABSTRACT Corrosion of mild steel used in industrial and engineering enviroments has posed a serious problem in the society. Hence, this research investigated the effects of ethanol, water and sulphuric acid extracts of Solanum melongena(SM), (garden egg) and Chrysophyllum albidum (CA), (sherry) on the corrosion of mild steel in I M HCl and 0.5 M H2S04 solutions using gravimetric and electrochemical techniques. The results obtained indicated that all studied plant extracts were adsorption typ...
ABSTRACT In this research work a low pressure steam turbine was designed, constructed and tested for the purpose of studying how electrical power can be generated using low pressure steam from concentrated solar power (CSP) sources. The turbine consist essentially of a two cylindrical casings to which stationary blades are fixed on the inside and a shaft carrying rotating blades (rotors) penetrating between the rows of stators. Steam fed into the turbine passes alternately through the stator...