ABSTRACT Gravimetric, reflectometric and elemental analyses have been carried out on airborne particulate matter sampled in a semi-rural area of Kwabenya, near Accra-Ghana. The PM 10 aerosols were sampled using a Gent sampler, size segregating the aerosol into coarse (PM10.2.5) and fine (PM2.5) fractions. The data and derived information were generated from 216 days of sampling spanning a period of about 14 months, 28th December 2005 to 12th February 2007. The particulate matter (PM) at Kwab...
ABSTRACT Lightning is an important component in the global electric circuit of the earth. It is a leading cause of outages in electric power and telecommunication systems, of forest fires and of delays in aircraft missions. A lightning sensor operating at a radio frequency of300 kHz was constructed ~d used to study the occurrence of lightning in and around the University of Ghana campus during thunderstonns. Rainfall figures during each thunderstonn were also recorded. Data was collected ov...
Abstract Key to Escherichia coli (E-coli) bacteria survival is its ability to direct its movement to greener pasture and flee harmful environment - also known as chemotaxis. This thesis focuses on the modelling of E-coli chemotaxis in twodimensions with emphasis on trying to understand the basic physics of how such a tiny microswimmer swim up a concentration gradient despite the enormous thermal fluctuations in its environment. E-coli strategically employs near straight swimming (also known ...
Abstract The power conversion efficiency of perovskite solar cells has risen from as low as 3.8% to as high as 19.3% in just five years with yet a projected value of over 20% in the next few years by experimentalists. Such a tremendous breakthrough is one of its kind in photo-voltaic research with thin film solar cells as the only major competitor. The light harvesting layer in these new devices has a crystalline structure called the perovskite structure which is capable of absorbing photons...
Abstract The thesis presents the modeling and simulation of three types of lasers namely; Semicondoctor laser, Solid state laser and CO2 laser. The rate equations were derived and simulated to examine the dynamic behaviour of the three types of lasers under investigation. The result shows that the Semicondoctor laser has the longest latency period, highest intensity spikes and takes a longer time to come to relaxation oscillation (RO) while the CO2 laser has the shortest latency time, the lo...
Abstract Not too long ago(2008),a new pnictide Superconductor free from arsenic was discovered –LiFeP. It belongs to the family of the so called ‘111’ type iron Superconductor. It has unique characteristics in its normal state which can be useful in understanding the unusual high temperature superconductivity observed in iron pnictide compounds. In this work,we studied LiFeP from first principles. The structure was optimised,electronic structure calculations were performed yielding lat...
ABSTRACT This work presents the responses of optical properties and mechanical failure of layers of stretchable organic electronic structures under tension using analytical, simulations, and experimental techniques. The interfacial contact around dust particles was modelled. The deformation induced during stretching was also modelled before simulating the stress distributions and calculating the crack driving forces of the layers using finite element analysis. The finite element simulation o...
ABSTRACT An effect that is observed when an electron passes through a non-collinear magnetic textures such as skyrmion, the electron gets deviated as a result of the fictitious magnetic field generated by the skyrmion giving rise to Topological (spin) Hall effect. our interest is on the effect of disorder (magnetic and non-magnetic) on transport of non-trivial topological textures. In these work we carry out a thorough study of the topological Hall and topological spin Hall effects and test t...
Abstract This work presents numerical calculation of electromagnetic waves in unidirectional on-chip silicon optical diodes. An original optical diode, designed by Wang et. al. [Opt. Express. 19, 26948-26955 (2011)], is based on breaking of spatial inversion symmetry and the directional band gap difference of two 2D photonic crystals comprising a hetero-junction structure. The dimensions of our structure are however different from those of Wang et. al. The electromagnetic waves in the diode ...
ABSTRACT The basic understanding of the underlying techniques of growing Carbon Nanotubes (CNTs) with a specific chirality is still obscure and needs to be understood so as to properly harness its potentials. Using both Classical Molecular Dynamics (MD) simulation with empirical force fields and a geometry optimization based on ab initio forces, we show that the dynamics involved in the growth of CNT on iron nanoparicles is non linear but complex. For a good geometry, the growth depends on t...
Abstract We have used ab initio density functional theory to study the coadsorption of N and O on Pt(100) and Pt(111) surfaces. Our calculations show that on Pt(100) the most favourable site is the hollow site for N and the bridge site for O, while for Pt(111) there are different possible N and O coadsorption geometries. On both surfaces the interaction between N and O is repulsive in nature.
ABSTRACT Density functional theory (DFT) is a useful theoretical and computational tool for electronic structure calculations, which form the basis for the classification of materials into conductors, semiconductors or insulators. DFT started with a crude approximation by Thomas and Fermi (TF theory) which calculated the kinetic energy of electrons using the so-called local density approximation (LDA). Although TF is computationally inexpensive, it provides a poor numerical result due to a la...
ABSTRACT The study of the structures and properties of organic materials for organic photovoltaic (OPV) applications and their interrelationships is a rapidly growing field of research, involving interdisciplinary efforts at the frontiers of chemistry, solid state physics and materials science. These materials differ from the better-understood silicon solar cell based materials by the lack of long range three-dimensional translational periodicity in their atomic arrangements and also by their...
ABSTRACT In this study, Flexy energy analysis taking exergy analysis and heat recovery into account on performance has been performed. The effects of wasting heat on exhaust gas temperature and cooling engine, is analysed in terms of design paramèters. It was observed that thermal exergy from a wasting heat for Flexy energy might be used to produce cold. In the theoretical study, the achievement of heat recovered is to circulate water through the source of exhaust gas. It was found that the...
Abstract The complexity of the microstructure of the active layer in organic photovoltaics (OPVs) poses a unique challenge in improving the efficiency of OPV devices. Molecular dynamics (MD) simulation provides a direct route to determining this microstructure. However, for a donor material like poly (3- hexylthiophene), (P3HT)n, approximations made in all previous force field for MD simulation has been the neglect of explicit polarization. We looked at the morphology of (P3HT)n using MD sim...