Department of Physics
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Item Particulate Matter And Black Carbon Concentration Levels In Ashaiman, A Semi-Urban Area(University of Ghana, 2008-08) Dotse, S.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 ratio were determined. PM2.5 mass concentrations determined averaged 23.26 ugm-3 (3.85 - 46.43 ~gm-3 ) and that of PM10 was 96.56 ~gm-3 (37.10-293.06 ~gm-3 ). The results were compared with some literature values and World Health Organisation guideline values. The values obtained for PM2.5 to PM10 ratio and for PM10-2.5 concentrations, suggest that. the semi-urban background aerosol is not only largely made up of combustion generated carbonaceous particles but also particulate matter emissions from natural activities.Item Lightning Activity Over Legon and its Application to Rainfall Estimation(University of Ghana, 2008-08) Martey, W.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 thunderstorms. Rainfall figures during each thunderstorm were also recorded. Data was collected over a period of two and half months (from May 13 to August 2, 200S). It was observed that the number of strikes correlated with the amount of rainfall, a larger number of lightning strikes being associated with a greater amount of rainfall. Polynomials of various degrees were fit to the data and the cubic polynomial (y = 2E-05x3 - 0.0037~ + 0.42S7x - 2.3078) was found to yield the best compromise between correlation coefficient and coverage of the amount of rainfall (y) and the number of lightning strikes (x) during the study period. The experiment can be used to estimate the amount of rainfall (y) if the number of lightning strikes (x) during a thunderstonn is known assuming that there was rainfall during the period. A similar analysis perfonned on lightning flash rate and rainfall amount did not indicate a strong correlation. The maximum number of lightning strikes recorded during the study period was 200 ± 1 and this occurred on the night of May ]S, 200S when most parts of Accra were flooded. Coincidentally, a maximum of 117.3 ± 0.1 mm rain was recorded on the same day at Legon. The minimum number of lightning strikes for the study period was 15 ± occurred on June 13,2008. On that day, the amount of rainfall was 15.2 ± 0.1 mm.Item Corrosion Behaviour of Iron Steel Bars on the Ghanaian Market; Elemental Composition and Mechanical Properties Perspective(University of Ghana, 2018-07) Amesimeku, E.K.Corrosion is the main problem with structural iron steel bars. Iron steel bars undergo electrochemical reaction with its environment. The iron in the iron steel bar oxidizes to form iron (II) oxides, which is another stable form of iron. This means that the structural integrity of an iron steel bar is likely to weaken as time goes by. The aim of this research is to establish an elemental signature that will relate the mechanical properties of locally and imported 16 mm iron steel bars on the Ghanaian market to their sensitivity to corrosion to their elemental composition. Three iron steel bars brands labeled Local 1 (from Ghana), Foreign 1 (China) and Foreign 2 (Ukraine) were sampled for analyses. The samples were cut into 450 mm and their elemental composition, weight loss and mechanical properties such as ultimate tensile strength, yield strength and percentage elongation were tested at Ghana Standard Authority mechanical laboratory before and after corrosion. The Proton Induced X-ray Emission (PIXE) analytical technique method was used to analyze the samples, and the analyte sample was 16 mm iron steel bar mostly used in all building sites. The following elements, Chlorine, Potassium, Calcium, Titanium, Chromium, Manganese, Iron, Nickel, Copper, and Zinc were found present in all the three brands 16 mm iron steel. After the 60 days of immersion of the samples in 5 % NaCl solution the locally manufactured iron steel bar recorded an ultimate strength of 414.10 Nmm-2, the yield strength of 302.10 Nmm-2 and percentage elongation of 36.25 %. The Foreign 1 sample taken from China also had an ultimate tensile strength of 468.60 Nmm-2; the yield strength was 389.70 Nmm-2 and a percentage elongation of 22.50 %. The samples taken from Ukraine that was named Foreign 2, had an ultimate tensile strength of 528.60 Nmm-2, yield strength produced was 456.00 Nmm-2 and percentage elongation of 25.370 %. The results obtained showed a continuous decrease in mass of the iron steel bar samples with an increase in the immersion days. The overall results indicated that corrosion behavior of iron steel bar depends on the chloride ion concentration in the sample’s solution. The corrosion rate of the locally manufactured iron steel immersed in 5 % NaCl solution for 60 days was 0.07 mm per year and sample from China corrosion rate was 0.17 mm per year and the Ukraine sample had 0.16 mm per year. Though the locally manufactured iron steel bar recorded the lowest corrosion rate its yield strength dropped drastically as the immersion time increase. Chromium and Manganese were found to be the main elements that relate mechanical strength to corrosion rate of the iron steel bar.Item Ion Beam Energy Calibration of the 1.7 MV Tandem Accelerator At GAEC(University of Ghana, 2018-07) Berchie, E.Particle accelerators are often used for both ion implantation and ion beam analysis, therefore the accurate and precise knowledge of the energies of the accelerated ions is essential. From the analytical point of view, the energy of the accelerated ion needs to be known with high precision which can only be achieved through calibration. Ghana Atomic Energy Commission hosts a 1.7 MV tandem accelerator, at the Accelerator Research Centre (ARC). This facility uses ion beam techniques such as Proton Induced X-ray Emission (PIXE) and Rutherford Backscattering Spectrometry (RBS) for elemental composition analysis of materials to address issues in health, biological, archaeological, forensic and other areas of science. This study was designed to calibrate the energy of alpha particle which is mainly used for RBS analysis.Item Quality Control Programme on Mammography Systems in The Republic of Benin, Assessment of Patients Dose Optimisation in Three Selected Facilities(University of Ghana, 2018-07) Geraldo, M.The Mean Glandular Dose (MGD) was estimated first using Polymethylmethacrylate (PMMA) slabs and secondly MGD was estimated per right craniocaudal (RCC) projection view and left craniocaudal (LCC) projection view. A number of 21 patients out of a total of 28 patients, undergoing breast examination in three (3) selected mammography facilities in the Republic of Benin were involved. Image quality was evaluated based on subjective analysis of images with Leeds Tests Objects and American College Radiology Mammography Accreditation Phantom (ACR MAP). Quality control (QC) tests were performed to verify if the mammography machines selected for the study were working within acceptable level of performance using International Atomic Energy Agency Human Health Series (IAEA HHS) No.2 and No.17 protocols. The QC tests showed that the mammography units were working within the acceptable performance level. For the phantom study MGD estimation for all selected mammography systems, the calculated MGD values were below the recommended values, under manual mode as well as the automatic exposure mode. From the comparison of MGD under automatic exposure control (AEC) mode and MGD under manual mode, it was observed that the difference was high. MGD under AEC mode was less than MGD under manual mode and the difference was 1.05 mGy and 1.31 mGy respectively from two (2) mammography units, namely CAR and CHUD/OP. Data collected from a total of 21 patients was used for MGD calculation. The estimated MGD of patient within the age range of [50 - 64] years with a compressed breast thickness (CBT) of 20 mm for RCC view and 18.7 mm for LCC view reported a dose of 1.10 mGy, which was slightly high compared to the recommended MGD value for CBT of 21 mm which was 1 mGy. All the remaining estimated MGD was within the recommended international levels of IAEA HHS No.17 protocol. The dose delivered by the selected mammography units were within the acceptable levels of IAEA HHS No.17 for both exposure modes. Thus the AEC mode is recommended because it delivers less MGD and this will help to achieve optimization of patient dose in mammography practices.Item Low Pressure Steam Turbine for Electricity Generation(University of Ghana, 2015-07) Minta, S.A.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 stators and rotors with the stators directing the steam at the right angle for impingement to the rotor blades. A seal was applied to the ends of the casing since the shaft of the rotor passes through the ends of the casings. Leakages were not really eliminated but merely controlled to a minimal level, the shaft of the rotors is attached two bearings, one at each end. The data obtained during the experimental operation of the turbine indicates that temperature is maximum at the beginning, that is at inlet to the first stator blade and is around 88oC and the temperature at the exit of the turbine is 59.50C. We also observed that steam velocity is maximum at the inlet to rotor blade and the velocity increases as the steam passes through the stator blades. The velocity is also maximum at the exit of the stator blade and decreases as the steam impinges over the moving blade (rotor blade), and thus satisfies condition of Impulse-reaction turbine. The maximum steam velocity at the inlet of the moving blade is 256 m/s and the velocity of steam at the exit of stage is 42 m/s. Again it was also observed that the power output and the thermal efficiency are highest when turbine inlet temperature is increased and the specific steam consumption is least with the increase in turbine inlet temperature. The satisfactory performance at low steam pressure demonstrates that this turbine may be applied in solar-thermal based power generation application where steam pressures are usually low.Item Experimental and Computational Study of Transition Metal Doped Zinc Oxide.(University of Ghana, 2016-07) Seidu, A.Pristine and transition metal (Fe, Mn, Co and Ni) doped ZnO powders were synthesised us- ing a hydrothermal method, and characterised by x-ray powder diffraction, ultraviolet-visible absorption spectroscopy, and photoluminescence (PL) emission spectroscopy. Synthesis was carried out at pH 3 and pH 5, and the powders annealed at 280 ◦C and 600 ◦C. Doping was done at concentrations of 1, 2, 4 and 8 mol %. Computational studies were also carried out on undoped and transition metal (Fe, Mn, Co and Ni) doped ZnO using the Generalized gradient Approximation (GGA) of the Density Functional Theory (DFT) implemented in the ab-initio computational suite, Quantum ESPRESSO. Doping was done at concentrations of 5.56 % and 11.11 %. X-ray diffraction spectra showed the presence of secondary phases of Fe3O4, Co3O4, Mn3O4, and NiO at higher doping concentrations. However, the results indicated that synthesis at higher pH diminished the occurrence of these secondary phases. In the experimental work, the band gap energies from the absorption edge of the ultraviolet-visible absorption spectra de- creased with doping concentration for all dopants except for nickel. The band gap energy from the near band edge of the PL spectra on the other increased. The computational results and the experimental results both showed that the band energy in- creased with doping concentration. The unit cell volume also increased for iron and manganese doping in both the experimental and computational results. However, while the computational results predicted a narrowing in the unit cell volume for cobalt and nicked doping, the experi- mental results showed an increase for coItem Neutron Activation Analysis of Soils(University of Ghana, 200-06) Osei, B.; Osae, E.K.; Agyei, G.K.A.; University of Ghana, College of Basic and Applied Sciences, School of Physical and Mathematical Sciences, Department of PhysicsInstrumental 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 Ankasa series are related to the nature of parent materials and the degree to which these materials have been altered by weathering. The low isotopic abundance, low thermal and epithermal cross-section together with the low sensitivity of 0.07 counts/pg for the 30Si nuclide with energy 1266KeV made detection of silicon in the five soils impossible. Validation of the analytical technique which was done using a Standard Reference Material SOIL-7 supplied by the International Atomic Energy Agency showed a maximum deviation of 23.9%.Item Economic Evaluation and Potential Assessment of Solar Water Heaters in Urban Ghana A Contribution to an Environmentally Sustainable Framework(University of Ghana, 1996-04) Amarvie, F.D.K.; Adanu, K.G.; Galster, G.; University of Ghana, College of Basic and Applied Sciences, School of Physical and Mathematical Sciences, Department of Physics; University of Ghana, College of Basic and Applied Sciences, School of Physical and Mathematical Sciences, Department of PhysicsThis project work describes the different methods of analyzing the economics of a solar water heating system to determine its economic viability and potential in Ghana. The economic variables in relation to cost that were considered in the analyses are the annual cost of owning the collector, storage unit and associated controls, the annualized life-cycle cost (ALCC) of operating the system, the yearly cost of maintenance, life-cycle savings (LCS), life-cycle cost (LCC), the payback period (PBP). Based on cost analysis, solar water heaters were found more economical than the use of electric water heaters. A survey conducted in parts of Accra to determine the awareness of the use of solar water heaters, and the affordability of solar water heaters in Ghana, revealed that solar water heaters can be afforded by commercial users (restaurants, hotels, hospitals) and very few private individuals in the medium and high income groups. Critical evaluation of income and expenditure patterns of potential end users revealed that the expenditure pattern of all the income groups is much higher than their corresponding income levels. A further analysis of the income and expenditure pattern revealed that if all the income is to be used in the installation of a solar water heater, for a family of four in low, medium and high income groups with average income of one hundred and twenty-five thousand, two hundred and fifty thousand, and three hundred thousand cedis respectively, it would take ten, six, and five years respectively to purchase a solar water heater. An economic and financial viability analyses (see appendices C and D) of a thermosyphon solar water heater were made using an f-chart simulation program, and technical viability using eurosol simulation program for thermal solar water heating systems. The results of the economic analyses revealed that for such a system with an economic lifetime of ten years, the marginal investment is profitable over the economic lifetime and a payback period of eight years.Item The Erodibility of some Ghanaian Soils in Relation to their Physical and Chemical Properties.(University of Ghana, 1997-09) Teye-Mensah, R.; Oduro-Afriyie, K.; University of Ghana, College of Basic and Applied Sciences, School of Physical and Mathematical Sciences, Department of PhysicsThe erodibility of soils from six different rainfall erosivity areas in Ghana were investigated. The soils were sampled and packed into wooden boxes maintained at 9% slope. Soil erosion was measured by applying simulated rainfall storms over the soil samples. The erodibility factor K for each soil type was calculated from USLE, K=A/EI30LSCP. The results showed a variability in erodibility factor values which ranged from 0.36 to 0.62. The physical and chemical properties of the soils were also measured and correlated with K values using regression techniques. The statistical analysis showed that the most important properties which related and predicted the K values for the soils studied were, permeability , pH and percentages of fine sand, clay and very fine sand.