ABSTRACT An attempt has been made to study the effects of tensile stress and temperature on the resistivity of some metals and alloys. The specimens include; copper, constantan, manganin, tantalum and minalpha. The strain coefficient of resistivity dp , rate of increase of fractional resistivity with stress of gde resistance (gauge factor (K)) were determined for copper, constantan, manganin and tantalum. For constantan, ae is found to be highest for a sample of Qde diameter 0.19 mm and lowes...
ABSTRACT Airborne particulate matter (APM) composition has been studied at the Abuesi area. Aerosol samples in two size fractions were collected over a period of 3 months using the Gent stacked filter unit (SFU). Energy Dispersive X-ray Fluorescence Spectroscopy (EDXRF) was used to measure concentrations of up to 28 elements at the INFNAccelerator Laboratory, University of Florence, Italy for the coarse fraction which accounted for 53.84 % of PM10 aerosols in the Abuesi area. Mean values of 4...
ABSTRACT This dissertation presents the combined results of analytical, computational and experimental study of the effects of surface texture and nanoscale surface oxides on the optical and mechanical properties of silicon single crystals and MEMS thin films. The first part of this work is focused on the analytical modeling of the reflectance of flat and textured silicon substrates. The model was used to study the reflection behavior of textured silicon surfaces under non-normal incidence. ...
ABSTRACT Acoustic effects such as absorption/amplification of acoustic phonons, Acoustoelectric Effect (AE) and Acoustomagnetoelectric Effect (AME) were studied in Carbon Allotropes. In this thesis, the Carbon Allotropes considered are Graphene Nanoribbon (GNR), 2-dimensional Graphene sheet, and Carbon Nanotubes (CNT). The Boltzmann transport equation (BTE) and the phonon kinetic equation (PKE) were used. All results were analysed numerically and graphically presented. Using BTE for Armchair ...
ABSTRACT The use of High Intensity Focused Ultrasound (HIFU) in the medical treatment of cancer has attracted scientists and engineers with interest in achieving the most financially affordable but yet curative methods of curing different types of cancers. This present work considers a 2D modeling of the prostate gland without the environmental (neighbouring) tissues such as bladder, rectum, urethra and seminal vesicle. This model uses the nonlinear Westervelt equation since the propagation i...
ABSTRACT Active polar gels are a type of viscoelastic soft material formed by polar filaments which are constantly driven out of equilibrium by the consumption of chemical fuel such as ATP. Following the approach of Voituriez et al, a generic hydrodynamic theory relying on symmetry arguments only was used to study the effects of quasi one-dimensional confinement on active polar gels. The phenomenological theory based on liquid crystal hydrodynamics is motivated by the dynamics of actin filame...
ABSTRACT Wave velocities in sand stones are greatly influenced by porosity and clay contents.
ABSTRACT River sediments are known to contain natural radionuclides, the concentrations of which if beyond certain limits can cause adverse health effects. The sediments from Ogun river provide large quantities of sand for construction purposes in Nigeria. Despite this, data are scarce on the natural radionuclides: 40K, 226Ra and 232Th distribution in the river sediments. This work was aimed at determining the spatial distribution of these natural radionuclides and their concentrations in th...
ABSTRACT The Boltzmann kinetic equation was used to investigate and derived theoretically the current density characteristics of carbon nanotubes exposed simultaneously to both constant (dc) and high-frequency (ac) electromagnetic fields. Generation and amplification of terahertz radiation at room temperature was predicted. We demonstrated that this can suppress electric current instabilities while still preserving a broadband THz gain. We have further shown that THz gain in the conditions of...
ABSTRACT Ambient air inhalable particulate matter, Black Carbon (BC) and heavy metal concentration levels in the ambient air derived from combustion at a local palm kernel production site was assessed in this study. The goal of this work was to identify the effect of biomass burning from palm kernel oil production activities on ambient air quality at Akotokyir and its environs and the possible health effects. An IVL sampler and a Sierra Anderson (GAST) pump were used to sample PM10 air partic...
ABSTRACT Luminescence sensitisation is an important stage in the application of quartz in predose retrospective dosimetry and dating. The existing techniques for sensitisation in quartz are Pre-Exposure Dose (PED) and Thermal Activation (TA). Previous works were centred on combined actions of PED and TA with less attention given to the separate contributions of these techniques in pre-dose sensitisation of quartz. This work was undertaken to determine the separate contributions of PED and TA...
ABSTRACT This work considered the unsteady state drainage of fluid from a vertical column of porous material of varying porosities in an attempt to verify 'variation of drawn dawn surface with porosity and time using riverbed sand. Kerosene was used as the flowing fluid: Mathematical assumptions ware made in connection with Ducy's law.
ABSTRACT Experimental investigations have shown that variation of porosity and hydraulic gradient are responsible for the deviations from Darcy's law, which is perfectly obeyed only when the fluid flow is laminar in porous media. Previous attempts to modify this equation considered only the effects of porosity of surface-active materials such as clay in causing deviations from Darcy's law. In this study, both the effect of porosity of any porous medium and hydraulic gradient from recent exper...
ABSTRACT The prediction of Large Earthquakes (LE) constitutes a global challenge. Several methods of earthquake prediction including Pattern Recognition (PR) have been proposed but sometimes produce patterns that are not suitable. Occurrence of earthquakes is always assumed to be random when these methods produce unreliable pattern. The fact that these patterns considered to be random could be chaotic (predictable but difficult) has not been investigated. This study was designed to use chaos...
ABSTRACT Using IVL PM2.5 and PM10 particle samplers, airborne particulate matter was sampled from Ashaiman, 30 km from Accra-capital of Ghana. The airborne particles were collected on Teflon filters for a period of three months. In addition to determination of particulate mass in the two fractions by gravimetrical method, aerosol filters were analyzed to determine black carbon (BC) concentration levels using the black smoke method. BC fractions in fine and coarse, together with PM2.5 to PM10 ...