Masters Degree Dissertations

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Investigation of radon concentration and annual effective dose in selected caves in kakumiro and fort portal, western Uganda
(Kyambogo University (Unpublished work), 2024-02) Tusiimire, Anitah
This study was conducted to determine radon concentration and annual effective dose in Amabere Ga Nyinamwiru cave and Semwama hill cave in Western Uganda using continuous radon monitor (Radon Sentinel model 1030). The radon concentration levels in Amabere caves for morning period (7:00-10:00), mid-morning period (10:00-1:00) and afternoon period (1:00- 4:00) varied from 14.27 ± 4.01 Bqm-3 to 17.70 ± 01 Bqm-3 with mean value of 15.90 ± 2.76 Bqm-3. The radon concentration in Semwama hill cave for morning period (7:00-10:00), mid-morning period (10:00-1:00) and afternoon period (1:00- 4:00) was found to vary from 447.3 ± 30.64 Bqm-3 to 507.63 ± 30.64 Bqm-3 with a mean value of 480.56 ± 30.64 Bqm-3. The annual effective dose for Amabere caves varied from 0.36 ± 0.10 mSvyr-1 to 0.44 ± 0.08 mSvyr-1 with an average value of 0.40 ± 0.07 mSvyr-1. The annual effective doses for Semwama hill cave ranged from 11.27 ± 0.77 mSvy-1 to 12.27 ± 77 mSvy-1 with mean value of 12.11 ± 0.77 mSvy-1. The Semwama Hill Cave effective dose data show that there is evidence of radon health risk to the general public and workers, as most of the values of yearly effective doses determined are more than 1 mSvy-1 as advised by United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR), International Commission on Radiological Protection (ICRP), and World Health Organization (WHO). Semwama hill cave, which has limited ventilation, has higher radon concentrations than Amabere caves. Further studies should be carried out on Semwama hill cave to ascertain the exposure levels to 222Radon gas as compared with a broad baseline measurement and future research should also look at the seasonal variations in the cave's radon concentration, equilibrium factor, and aerosol state, as well as an analysis of the tour guides' time spent there.
Investigation of mechanical properties of concrete developed from a binder composite of sugar cane bagasse ash and Portland cement
(Kyambogo University (Unpublished work), 2024-10) Nzugua, Michael Evans
Cement production has been growing over time. Statistics indicate more growth as the human population increases. However, cement production relies on natural resources such as limestone rocks. The mining of these minerals poses grave environmental hazards. Increased limestone mining and its use in cement production have led to, deforestation, soil and water contamination and greenhouse gas (GHG) emissions mostly carbon dioxide (CO2). This has led to global warming and the rising of sea levels. The East Africa Community (EAC) countries have immense sugarcane cane bagasse ash (SCBA) which remains unexploited as a supplementary-cementitious material (SCM). This study delved into using EAC SCBA as a pozzolan. SCBA investigated was collected from Kenya's coastal area. Raw SCBA, processed SCBA, Portland cement (PC) and the developed concrete were characterised by various techniques to determine the surface morphology, chemical composition, structural properties and mineralogical composition. The raw SCBA was calcinated at 600 oC to get processed SCBA (SCBA-600). SCBA-600 was then used to design the concrete mix. PC was replaced from 0 to 30 % in steps of 10 %. The flexural and compressive strengths were determined in the hardened state after twenty-eight days of concrete curing. The compressive and flexural strength of the mix containing 20 % SCBA was higher than the control mix by 9.65 and 6.51 %, respectively. The microstructural properties of the developed concrete revealed dense particle distribution, indicating good micro/nanofiller effects of the interfacial transition zone. The processed SCBA was found to meet class N and F of natural pozzolan as per ASTM –C 618. The samples were analysed using XRD, SEM, EDX, and XRF techniques. The concrete design was done following IS 10262-2009 and IS 456. The casting and curing were done as per ASTM C-192 and lastly, the mechanical strengths were done as per ASTM C-39 and ASTM C78-00 standards specifications. These positive results from the experimental investigation, technically portray the Kenya coastal SCBA as a potential SCM.
Compressive strength of concrete produced using aggregates from selected types of rocks in Uganda
(Kyambogo university (Unpublished work), 2024-05) Kawiso, Micah
This study was on determining the compressive strength of concrete made of granite, quartzite and sandstone aggregates of three aggregate sizes of 6.3 mm, 10 mm, and 14 mm and using three cement, sand and aggregate mixture ratios of 1:3:6, 1:2:4, and 1:1:2. This was to find out the effects of mixture ratios, aggregate sizes and aggregate types on compressive strength of the concrete. The samples of concrete were cured for 14 days and then a compression test machine was used to determine the compressive strength of the samples. The average compressive strength of granite concrete of mixture ratios 1:3:6, 1:2:4 and 1:1:2 were 8.56, 19.10 and 32.59 MPa respectively. The mean compressive strength of quartzite concrete of mixture ratios 1:3:6, 1:2:4 and 1:1:2 were 8.78, 17.57 and 31.22 MPa respectively. The average compressive strength of sandstone concrete of mixture ratios 1:3:6, 1:2:4 and 1:1:2 were 9.71, 20.75 and 33.58 MPa respectively. The mean compressive strength of granite concrete of aggregate sizes 6.3, 10, and 14 mm were 18.77, 19.62, and 21.87 MPa respectively. The mean compressive strength of quartzite concrete of aggregate sizes 6.3, 10, and 14 mm were 17.93, 18.95, 20.71 MPa respectively. The mean compressive strength of sandstone concrete of aggregate sizes 6.3, 10, and 14 mm were 19.49, 21.01, 23.21 MPa respectively. The results have revealed that the compressive strength of granite, quartzite and sandstone concrete increased with increase in cement aggregate ratio. Mixture ratio 1:1:2 produced the highest compressive strength of concrete and mixture ratio 1:3:6 produced the lowest compressive strength of concrete. The results have further revealed that compressive strength of the three rock types increased with increase in size of aggregate. The difference in the compressive strength for the three different types of rocks was negligible. Therefore, mixture ratios and aggregate sizes affect concrete compressive strength but rock types used did not affect the compressive strength of concrete samples. Builders and engineers who wish to construct structures should mind most about the aggregate size and mixture ratio than the granite, quartzite or sandstone aggregates used.
Green synthesis of copper oxide nanoparticles from pumpkin (Cucurbita maxima) dye extract: a platinum free counter electrode for dye sensitized solar cells
(Kyambogo University (Unpublished work), 2024-02) Tenywa, Stephen
Energy is a very critical requirement for all nations that boosts economic growth and development. Dye-sensitized solar cells (DSSCs), the 3rd generation photovoltaic technology which imitate the process of photosynthesis in green plants have of recent gained overwhelming attention in solar harnessing because of their simple structure, affordable cost, simple fabrication technique, little toxicity, and comparatively high efficiency of energy conversion. Currently, Platinum is used as a counter electrode for DSSCs. However, the scarcity and high cost of Pt is still a challenge. In this study, copper oxide (CuO) nanoparticles (NPs) were synthesized using Cucurbita maxima plant leaf dye extract and applied as an electrocatalytic CE in DSSCs. The CuO NPs were characterized using XRD, TEM, UV-Visible spectrophotometer and FTIR to obtain their crystal structure, surface morphology, optical properties and chemical bonds respectively. Three individual natural dyes from pumpkin leaves (P), sweet potato leaves (S) and hibiscus flowers (H), along with their composites, P:H and S:H in varying ratios were extracted, their optical properties studied and used as photosensitizers. The results indicate that the fabricated DSSC with P:H-1:3 composite dyes yielded the highest PCE of 8.7×10-4 %, a short circuit current density (Jsc) of 13.94 μA/cm2 and an open circuit voltage (Voc) of 0.29 V compared to S:H-1:3 composite and individual dyes under one-sun illumination from a solar simulator (AM1.5 100 mWcm-2).
A study of electrical insulation materials developed using selected clay minerals in Uganda
(Kyambogo University [unpublished work], 2012-06) Nasejje, Stella
This study was to investigate appropriate mixtures of different ceramic mineral ingredients needed to make electrical porcelain insulators and to determine the best method of developing the electrical insulator of slip casting, dry pressing, and wet pressing. The mixing of the clay minerals was done using percentage ratios of ball clay. kaolin, feldspar and flint of which the quantity of flint was kept constant at 20% in all compositions and that of ball clay to kaolin changed through a range of 1:1.75 , 1:2 and 1: 2.5, well as that of feldspar took up any remaining percentage. These samples were formed by slip casting. Wet, and dry pressing and then tired at a constant heating rate to a temperature of l 250°C. Then the dielectric strength was tested using the oil test set, Avo Megger foster OTS100A F/2. The mixtures of the clay minerals with a ratio of ball clay to kaolin of 1:2 showed good formability in all forming methods, but those with a ratio of 1:1.75 and 1:2.5 could not easily form good casted and wet pressed samples. The best formulation was that with 55% clay, where the ratio of ball clay to kaolin was 1:2. The sample compositions of the various, minerals were found to affect both voltage breakdown and dielectric strength. The voltage break clown. V was found to be proportional to the thickness. t of the samples according to the expression V= at + b: where a and b are constants of testing conditions like room temperature and frequency. Conversely, the values of dielectric strength; U was found to be inversely proportional to the thickness, d of the samples according to the expression; D = VB over d where VB is the breakdown voltage and d is the thickness of the sample. Values of both the voltage breakdown and dielectric strength of samples tested in air were much lower than those of samples tested in transformer oil due to generated carbon around them when in air as a result of corona discharge. The samples tested in transformer oil had values above 10kV/mm. Thus, the electrical insulation properties of the formulation of the samples developed in this study were found to match that required for international standards.
Performance of ceramic candle water filter made from selected local clays in Uganda
(Kyambogo University [unpublished work], 2016-01) Onyait, Justine
The focus of this study was to developa ceramic candle filter using local clay and mahogany saw dust and determine its filtration rate and E-coli removal efficiency. The candle filters were developed using ball clay from Ntawo mixed with mahogany saw dust of particle size less than 1mm. Five different clay- saw dust ratios were used in the production of the filters by weight of 1: 1, 5:4, 5:3, 5:2, and 5:1. The highest porosity of 48.05% was obtained in a filter sample with the highest saw dust proportion (1: 1) while the lowest porosity of 35.12% was obtained in a filter sample with the lowest saw dust proportion (5: l). Higher removal efficiencies of contaminants (99.9%) were observed in filter samples with low saw dust proportion (5:1). Ceramic candle filter (CCF) with clay to saw dust proportion of (5:1) was more effective in reducing turbidity, reduced turbidity to< 1 NTU. The candle filter with the lowest saw dust proportion (5:1) produced the lowest filtrationrate of water (196.43 ml hr-1) and the filter with highest saw dust proportion had the highest filtration rate of water (917.67ml hr-1). From this research, it can be concluded that filters with higher initial filtration rates are more porous than those with low filtration rates. It can also be concluded that the filters were capable of filtering the turbidity of the water and filter samples also decreased the concentrations of microbial contaminants, therefore making the water safe for consumption. Its recommended that further studies be carried on; the effect of grog on cohesive nature of the filter, flow rate of the water, turbidity of water, and total coliform removal of the filter. The effect of the application of colloidal silver on the adsorptive properties of the filter material and consequently on the quality of water should equally be explored.
Performance of plastic-derived liquid fuel in a compression ignition engine
(Kyambogo University [unpublished work], 2023-09) Tifu, Waiswa
Fossil fuels are the major sources of energy for running engines, powering industries, and for supporting domestic activities. However, as energy-intensive activities increase, there is a need for diverse sources of energy other than petroleum-based sources. This has led to the production of alternative liquid fuels from industrial waste, residential waste, agricultural waste, and plastics. Such fuels have been characterized and compared to petroleum fuels. However, additional testing of these fuels in engines reveals more data regarding the quality of these fuels in relation to the power of the engine. This study was designed to produce fuel from two types of plastics, High-Density Polyethylene (HDPE) and Polypropylene (PP) plastics through thermal pyrolysis, characterize the obtained liquid fuels, and evaluate their performance in a diesel engine in relation to standard diesel. The density of the fuel samples were measured to be 0.830 ± 0.001, 0.790 ± 0.003 and 0.788 ± 0.001 g cm-3, ash content was 0.02 ± 0.01, 0.03 ± 0.01and0.02 ± 0.00 % (m/m), cetane index was 53, 65 and 66, copper strip corrosion was class 1 a, class 3a, and class la, kinematic viscosity of 2.71±0.04, 2.00 ± 0.04 and 2.04 ± 0.02 cSt, and calorific value was 47.59 ± 0.49, 48.65 ± 0.13 and 48.52 ± 0.00 MJ/kg for standard diesel, High-Density Polyethylene Liquid Fuel (HDPELF) and Polypropylene Liquid Fuel (PPLF) respectively. The engine tests revealed that liquid fuel from HDPE and PP plastics had 12.8 % and 10.7 % higher Brake Specific Fuel Consumption, and a lower Brake Power of 1.3 % and 2.3 % respectively than that of standard diesel. The Brake Thermal Efficiency of HDPELF and PPLF were found to be 15.2 % and 13.1 % lower than when using standard diesel. These results suggest that the liquid fuel obtained from HDPE and PP plastic can be used as fuels in diesel engines with a minimum drop in brake power.
Thermal conductivity of fired clay of varied mineral composition made from selected Uganda clay types
(Kyambogo University [unpublished work], 2016-01) Kella, Allan
The use of thermal insulators is one of the most important applications in thermal energy conservation systems. This study determined the effect of varying mineral compositions on thermal conductivity. Dry powders of kaolin, ball clay, quartz and feldspar were prepared by ball milling, sieved to particle size of 45μm and then mixed in different proportions to make 100g. For each formulation, three of the four minerals were kept in fixed proportions by mass while varying one. Eighty clay rectangular shapes of dimensions 100mm x 50mm x 20mm were compressed at a pressure of 75MPa and then fired to a maximum temperature of 1200°C. The first formulation had the proportion of Quartz varied while that of other minerals fixed. The second formulation had the proportion of Ball clay varied while that other three fixed. The third formulation had the proportion of feldspar varied while that other three fixed. The forth formulation had the proportion of kaolin varied while that other three fixed. And the fifth formulation had the proportion of all the minerals varied. The Quick thermal conductivity meter was used in the measurement of thermal conductivity at room temperature of approximately 25°C. The study showed that thermal conductivity value increased with increasing proportion of Quartz from 3.305x10-1 to 3.32x10-1 Wm-1K-1. Thermal conductivity values also increased with decreasing proportion of ball clay from 3.225x10-1 to 3.267x10-1Wm-1K- 1. The thermal conductivity value increased with increasing proportion of Feldspar from 3.313x10-1 to 3.274x10-1 Wm-lK-1. The thermal conductivity value increased with decreasing proportion of kaolin from 3.179x10-1 to 3.28x10-1 Wm-lK-1. And when all the mineral proportions was varied, The thermal conductivity value increased with decrease in proportion of kaolin and ball clay in each mixture, and ranged from 3.239x10-1 to 3.288x10-1 Wm-lK-1. From the samples studied, formulation consisting of (Quartz-15%, Ball clay-15%, Feldspar- 15%, and Kaolin-55%) was the best insulating material with thermal conductivity value of 0.3179 Wm-lK-1. The highest thermal conductivity values was due to high proportions of quarts, while the lowest thermal conductivity values was due to high proportions of kaolin. The study recommended further work to be done on thermal conductivity of clays by varying pressure, particle size, firing temperature and the impact of combustible organic wastes on the thermal conductivity.
Investigation of mechanical properties of ceramic tiles developed from selected clay deposits in Uganda
(Kyambogo University [unpublished work], 2023-10) Mukwaya, George William
In this study the characteristics of Buwambo kaolin, Lunya feldspar, Ntawo ball clay and Liddo beach sand were determined. The Modulus of Rapture (MOR) and Compressive Strength (CS) of the tiles produced using kaolin:feldspar of different composition ratios were determined. The composition ratios of kaolin:feldspar used were 4:3, 3:4, 5:9 and 2:5 by mass. On the other hand, a fixed composition ratio was used for ball clay:sand of 5:1 by mass (Ochen et.al 2012). The samples were fired at 1100 0C for 8 hours. Using the scanning electron microscope (SEM), the Buwambo kaolin had a porous cellular structure of irregular-shaped particles of average size of 0.202 ± 0.131 μm. Liddo beach sand had porous particles with average particle size of 0.168 ± 0.198 μm, the Lunya feldspar had irregular confined particles with average particle size of 0.153 ± 0.105 μm and the Ntawo ball clay had fine grained uniform rounded particles of average size of 0.095 ± 0.055 μm. X-ray fluorescence (XRF) and Energy dispersive x-ray (EDX) spectroscopy were used to determine the elemental composition. The XRF on Liddo beach sand showed that it is mainly composed of 99.5 % SiO2 with trace amounts of Al2O3 and Fe2O3 each 0.2 %. The EDX revealed that Buwambo kaolin mainly had 11.15 % Aluminium and 10.83 % Silicon. The Lunya feldspar mainly had 19.53 % Silicon and 5.46 % Sodium. The Ntawo ball clay mainly had 12.91 % silicon and 4.52 % aluminium. X-ray diffraction (XRD) on Liddo beach sand showed a broad reflection peak at 2θ = 22.86 o indicating its amorphous nature. The Lunya feldspar showed major peaks at 20.69, 26.40 and 29.52 o which are within the acceptable range of sodium feldspar. The Ntawo ball clay showed major peaks at 2θ = 20.82, 26.53 and 27.35 o. For Buwambo kaolin, the major peaks were located at 2θ = 12.29 and 27.40 o. The MOR and CS were significantly dependent on composition ratios at significant levels α = 0.01 and α = 0.05 and therefore the null hypotheses that the CS and MOR of the tiles produced are not affected by the composition ratios of the clay mixture rejected at the two levels of significance. The sample with the highest kaolin-feldspar ratio of 4:3 had the highest MOR of 30.84 ± 2.67 MPa at α = 0.01 and 30.84 ± 1.60 MPa at α = 0.05. It also had the highest CS of 1.36 ± 0.06 MPa at α = 0.01 and 1.36 ± 0.04 MPa at α = 0.05. Similarly, the sample with the lowest kaolin-feldspar ratio of 2:5 had the least MOR of 18.58 ± 0.51 MPa at α = 0.01 and 18.58 ± 0.31 MPa at α = 0.05. It also had the least CS of 0.82 ± 0.03 MPa at α = 0.01 and 0.82 ± 0.02 at α = 0.05. Further investigation should be carried out using other clay deposits to find out how the variation in the amount of kaolin and feldspar in them would affect the CS and MOR of tile samples developed using these clays.
Structure and optical absorption properties of dyes extracted from selected plant materials for dye sensitized solar cells
(Kyambogo University [unpublished work], 2023-11) Tibenkana, Mohammad
Sunlight is a natural alternative renewable energy source to expensive hydroelectricity. Dye sensitized solar cells (DSSCs) are third generation solar cells which have the potential to significantly lower the cost associated with the first and second generation solar cells and they can easily be fabricated. A dye is an important component in a DSSC because it absorbs light, produces photoelectrons and facilitates processes of electron transfer to improve the efficiency of electrical energy conversion. It is important to modify the dye as an active component in DSSC for improved performance of optical absorption properties of the dye. Mixing chlorophyll and anthocyanin dyes aims to broaden the absorption wavelength range of visible light. In this study, the chemical structural and optical absorption properties of dyes extracted from selected plant materials for DSSCs were investigated. Anthocyanin dyes from hibiscus flower, chlorophyll dyes from pumpkin and sweet potato leaves and their composites were used as natural sensitizers in the fabrication of DSSCs. The extracted dye powders were characterized using Fourier Transform Infra-Red (FTIR) spectrophotometer to determine their chemical structural properties. The dye extracts and their composites were also characterized using UV-visible spectrophotometer to determine their optical absorption properties. Scanning Electron Microscopy (SEM) and Raman spectroscopy were used to determine the surface morphology and crystalline structure of TiO2 thin film respectively. The performance of the developed cells was measured under one-sun illumination using a solar simulator (AM1.5 100 mWcm-2). Keithley SMU-2450 was used to record the current-voltage (I-V) characteristics of the solar cells. The results reveal that the DSSC fabricated from sweet potato dye extracts had the best power conversion efficiency (PCE) of 0.5 % while that from a mixed dye of sweet potato leaves and hibiscus flower (SH) at a mass ratio of 1:3 gave the best PCE of 1 % with open circuit voltage (Voc) of 0.47 V and short circuit current density (Jsc) of 62 μA/cm2.
Determination of thermal diffusivity of fired clay bricks produced from cow pie mixed with selected Ugandan clays
(Kyambogo University [unpublished work], 2023-05) Kansiime, Evalyne Mary
This study was designed to determine the thermal diffusivity of fired clay samples produced by mixing cow pie with clays from selected districts in Uganda. The focus of the study was to find out the effect of clay particle sizes and the ratio of kaolin clay, ball clay and cow pie on thermal diffusivity. The clay particle sizes considered were 0-74, 75-89, 90-149, 150-299 and 300-349 μm, the cow pie particle sizes considered were 75-149 and 150-299 μm and the clay-cow pie ratios considered were 9:7:4, 9:6:5 and 9:7:0. The samples used in the study were compacted by using a compression machine International, England at a pressure of 50 MPa and were fired in a heating chamber (CARBOLITE, GERO, HTF 1700) up to a temperature of 950 0C at different firing rates of 1.2 0C/s, 1.3 0C/s, 1.5 0C/s and 0.5 0C/s. Thermal conductivity was measured by using a QTM-machine, density was obtained from mass per unit volume and specific heat capacity was obtained by using a simple calorimeter and applying the method of mixtures. The average values obtained for the thermal properties in the order of increasing particle sizes were as follows; for the kaolin: ball clay: cow pie ratio 9:7:4, thermal conductivity values were 0.2254, 0.2210, 0.2214, 0.2204 and 0.2195 Wm-1K-1, density values were 1.1800, 1.1535, 1.1537, 1.1433 and 1.1490 gcm-3, specific heat capacity values were 1.0670, 1.0510, 0.9810, 1.0490 and 1.0100 Jg-10C-1, the average calculated thermal diffusivity values were 0.1924 e -6, 0.2021 e-6, 0.1883 e-6, 0.2441 e-6, and 0.2039 e-6 m2s-1, for the kaolin: ball clay: cow pie ratio 9:6:5 thermal conductivity values were 0.2237, 0.2221, 0.2188, 0.2200 and 0.2178 Wm-1K-1, density values were 1.1866, 1.1661, 1.1945, 1.1789 and 1.2002 gcm-3, specific heat capacity values were 1.0490, 1.0810, 1.0630, 1.0450 and 1.0020 Jg-10C-1, the average calculated thermal diffusivity values were 0.1919 e-6, 0.2005e-6, 0.2046 e-6, 0.2080e-6, and 0.2031 e-6 m2s-1 and for the kaolin: ball clay: cow pie ratio 9:7:0, thermal conductivity values were 0.2871, 0.2781, 0.2771, 0.2654 and 0.2654 Wm-1K-1, density values were 1.1685, 1.1578, 1.1379, 1.1450 and 1.1280 gcm-3, specific heat capacity values were 1.0690, 1.0490, 1.0460, 1.0200 and 1.0510 Jg-10C-1, the average calculated thermal diffusivity values were 0.2546 e-6, 0.2439 e-6, 0.2427 e-6, 0.2466 e-6, and 0.2254 e-6 m2s-1. From the results, thermal diffusivity increased with the decrease in particle sizes of kaolin and ball clay; however, it was lower for the ratio 9:6:5. Thermal diffusivity values for the control experiment were very high and this implies that cow dung was a good pore former and should be incorporated into clay bricks to improve on their thermal insulation.
Mechanical properties of ceramic floor tiles made from selected minerals in Uganda
(Kyambogo University [unpublished work], 2012-06) Ochen, William
This study was designed to produce porcelain floor tiles using raw materials found in Uganda and to determine mechanical properties of the tiles produced. The properties were then compared with South African National Standards. Porcelains are made of clays, kaolin, feldspar and sand. In this study, the raw materials were mixed in proportions of 40-60% clays, 30-40% feldspar and 10-30% sand. The tests carried out include shrinkage, strength, water absorption and chemical analysis. Samples were pressed at 30MPa with 12% moisture content by weight. Firing was at peak temperatures of 1050, 1100, 1150, 1200 and 12500C. Firing process involved heating dry samples from room temperature to 1050C at 1000C/hr, after 2 hrs of holding the rate was then raised to 3600 C/hr and soaked for 1 hr at peak temperatures. Samples were left to cool naturally in the kiln for 16 hrs. Chemical analysis of the minerals by XRF method revealed that kaolin had an alumina content of 24.9 (wt %) whereas sand had silica at 95.0 (wt %). Iron oxide which influences the color of samples was high in ball clay at 3.2 (wt %). Maximum strength of 34MPa was exhibited by composition 2 at 12500C with linear shrinkage of 9.1 % and water absorption of 0.0 (wt %). South African National Standards classifies tiles whose strength is above 30MPa as B1. All samples fired in the temperature range of 1100 to 12500C exhibited properties in the range recommended by SANS both in strength and water absorption for flooring as B1 to B4 tiles. Minerals from the studied deposits yielded high grade ceramic floor tiles recommended by SANS for flooring. No cracks were exhibited by samples fired at 1100 to 12500C
Gamma ray activity levels and radiological hazard indices of Radionuclides in mine tailings from selected mines in Southwestern Uganda.
(Kyambogo University [unpublished work], 2016-01) Turyahabwa, Evarist Rutahweire Silver
This study was designed to determine and compare the specific activity levels and the radiological hazard indices of gamma ray emitting radionuclides in mine tailings from three selected mines in Southwestern Uganda. This was achieved by analyzing 72 soil and rock mine tailing samples using the GDM 20 Nal(TI) detector. The specific activities of the principal primordial radionucides of 238U, 232Th and 4°K in the samples were measured. The values obtained were used to determine the absorbed dose rates, the annual effective dose rates, the radium equivalent activity, external and internal hazard index and the excess lifetime cancer risk. The mean specific activities of 238U, 232Th and 4°K in mine tailings at 90% confidence level ranged from 23±14 Bqkg-1 to 59±16 Bqkg-1 for 238U, 49±39 Bqkg-1 to 244±19 Bqkg-1 for 232Th, and 226±232 Bqkg-1 to 893±167 Bqkg-1 for 4°K. The mean outdoor and indoor absorbed dose rates in air for Mashonga, Kikagati and B utare were (181±36 nGyh-1 and 338±67 nGyh-1 ), (167±23 nGyh-1 and 310±47 nGyh-1 ) and (192±16 nGyh-1 and 355±32 nGyh-1 ) respectively for waste soil samples and (67±50 nGyh-1and 127±102 nGyh-1 ), (85±37 nGyh-1 and 159±80 nGyh-1 ) and (115±33 nGyh-1 and 215±66 nGyh-1 ) respectively for waste rock samples. The ratio of the mean indoor to outdoor absorbed dose rates in all the samples was 1.9 but this was 36% higher than the world average. The total annual effective dose rates, radium equivalent activities, external and internal hazard indices for waste soil samples were above the maximum permissible limits recommended for members of the public. Potential radiological hazards on miners and the people living in the neighborhood of the sites due to external irradiation are significant. There is need to improve waste management practices in the mining sites in order to prevent health hazards associated with the radionuclides in the mine tailings.
A study of upland clay from ant-hills as a refractory material.
(Kyambogo University [unpublished work], 2016-01) Wamaholo, Elizabeth
This study was purposed to investigate the suitability of upland ant-hill clays for fabricating refractory bricks. The chemical composition of the anthill clay was determined using the Atomic Absorption Spectrophotometer (GBC SavantAA) and X-Ray Spectrometry. The chemical analysis revealed the presence of the elements which included; alumina, silica, iron oxide, titanium oxide, potassium, sodium, calcium, organic carbon, phosphate, zirconium, strontium, cranium, rubidium, magnesium, manganese, copper, zinc, yttrium and nitrogen. Wet and dry pressed samples were obtained by using the hydraulic press with a die mould (Hydraulina Laboratory Manual press- PW40) and slip casted samples were formed using a metallic brick mould. All dry pressed samples were found to be structurally inadequate due to development of strata, formation of cracks after firing. The wet pressed and slip casted samples were fired at a heating rate of 2°C/minute to a temperature of 534°C and held at this temperature for lhour then heated to 1150°C at a rate of 6°C/minute and held for 1 hour and then allowed to cool in the furnace at a rate of s°C/minute. All Samples fired at 11 S0°C were successfully retrieved and had no cracks or any other deformities. The Modulus of rupture was determined using the three point loading method (LLOYD INSTRUMENTS). Thin wet pressed fired samples had high MOR average values of 13826.08KPa for Nkombe, 1963.43KPa for Namagunga and 1510.23KPa for Kyambogo. The slip casted fired samples had an average MOR of 31.60Pa for Namagunga and 1l7.74Pa for Kyambogo. These suggested that sample forming methods have an effect on the modulus of rupture. The average MOR of the wet pressed fired samples of upland ant-hill clay was found to match that recommended by ASTM (American Society for Testing and Materials) standards for refractory materials and the percentage of the alumina in upland ant-hill clay showed quite close compliance with ASTM standards. This therefore means that based on the findings above, upland ant-hill clay is suitable for refractory materials.
Infra-red reflectance and transmittance by thin film coatings of some selected metals on glass substrate
(Kyambogo University(unpublished), 2018-11-14) Kamwasir Hellene
Reflection and transmission of light serve as key parameters in thin films coatings meant for temperature regulation in warm climates. In this study, the infrared reflectance and transmittance for three different thicknesses of thin films of palladium and platinum were determined. The thin films were made by thermally evaporating various masses of the platinum and palladium on glass substrates. A Shimadzu UV-VIS-NIR Spectrophotometer was used to determine the reflectance and transmittance of the samples from which the spectra were determined. Ex situ measurements, using Point wise Unconstrained Minimization Approach (PUMA) were made to determine the exact thicknesses of the films. Reflectance was found to vary with film thickness. The results showed that the 60 nm film of palladium had a maximum reflectance of 33%, 140 nm film, a maximum reflectance of 39% and 230 nm film, a maximum reflectance of 72%. For platinum, the 140 nm film had a maximum reflectance of 28%, 146 nm film a maximum of 35% and 395 nm film a maximum reflectance of 42%. In all the cases, the reflectance in the infrared part of the spectra (800-2500 nm) was higher than in the visible region which suggests that palladium and platinum thin films may be used as heat mirrors. The transmittances of palladium and platinum thin films were high (over 80%) an indication that the thin films probably had voids. The study also showed that for the same thickness of palladium and platinum films (Palladium film of 140 nm and platinum film of 140 nm), palladium has greater reflectance than platinum showing dependence of reflectance of thin film on material used for its fabrication.
Determination of radiological hazard levels in soil, mine tailings and rock samples from selected gold mines in Busia district, Uganda
(Kyambogo University(unpublished), 2018-11-15) Eling, Jimmy
This study was designed to determine radiological hazard levels in soil, mine tailings and rock samples from Agata, Okame, Busia 90 and Greenstone Resource Limited Gold mines in Busia District. The specific activity of the radionuclides were determined using Nal (Ti) scintillation detector and the values were then used to determine the radiological hazard parameters due to radionuclides in the samples from the mines under study. The specific activity of 238U in soil, mine tailings and the rock samples from the four gold mines ranged from 18.7 Bqkg-1 to 27.9 Bqkg-1 , 7.4 Bqkg-1 to 13.2 Bqkg-1 and 1.7 Bqkg-1 to 27.8 Bqkg-1 respectively. The specific activity of 232Th in soil, mine tailings and rock samples from the mines ranged from 60.8 Bqkg-1 to 98.8 Bqkg-1 , 25.1 Bqkg-1 to 32.7 Bqkg-1 and 2.3 Bqkg-1 to 66.6 Bqkg-1 respectively while that of4°K in soil, mine tailings and rock samples ranged from 53.6 Bqkg-1 to 211.8 Bqkg-1 , 5.7 Bqkg-1 to 217.3 Bqkg-1 and 2.1 Bqkg-1 to 120.1 Bqkg-1 respectively. The Specific activity values of 232Th in soil sample from each of the four gold mines were above the worldwide average value of 30 Bqkg-1 . It is only Greenstone mine tailings and Okame rocks that had higher activity for 232Th than the world wide average value. The Absorbed Dose rates in soil, rock and mine tailings samples ranged from 41.7 nGyh-1 to 76.3 nGyh-1 , 13.3 nGyh-1 to 32.7 nGyh-1 and 2.3 nGyh-1 to 58.0 nGyh-1 respectively. Only Okame had a higher value for soil than the world wide average value of 60 nGyh-1 • The Annual Effective Dose rates in soil, mine tailings and rock samples ranged from 0.051 mSvy-1 to 0.093 mSvy-1 , 0.024 mSvf1 to 0.050 mSvf1 and 0.011 mSvy-1 to 0.047 mSvf1 respectively which were lower than the ICRP recommended value of 20 mSvf1 • The internal hazard indices in soil, mine tailings and rock samples ranged from 0.30 to 0.56, 0.15 to 0.27 and 0.02 to 0.43 respectively. External hazard indices of the radionuclides in the soil, mine tailings and rock samples ranged from 0.27 to 0.47, 0.10 to 0.23 and 0.01 to 0.36 respectively. They were found to be below unity as per ICRP, 2007 maximum permissible limit. The Excess Lifetime Cancer Risk (ELCR) ranged from 6.90x10-5 to 1.93x104 was lower than the ICRP maximum permissible excess lifetime cancer risk limit of 5.60x10-2 . Despite the low radiological health risk, miners need protective gears particularly at Okame and Greenstone mines and further research need to be done to validate these findings.
Gamma radiation exposure levels due to radionuclides in soils from selected gold mines in Karamoja
(Kyambogo University(unpublished work), 2016-01) Chelangat, Kadafi
The aim of this study was to determine radiation exposure levels due to gamma ray emitting radionuclides in soils from selected gold mines in Karamoja and the associated hazard indices. The people of Karamoja use poor methods of mining gold, therefore they are exposed to ionizing radiation of unknown concentrations. In this study, 60 samples from Rupa, Nakabaat, Morulem, Acerer, Nabulatuk and Morita were analysed using a Nal (TI) gamma-ray detector. The activity concentrations of natural radionuclides 226 Ra, 232 Th, 238 U and 4° K in soils were measured by gamma spectroscopy using sodium iodide detector. In addition, radiological assessment due to these radionuclides was also carried out. To ensure quality control, the samples collected from the sites were transferred to polythene bags, labeled and double-bagged. They were transported in boxes whose background radiation emissions were measured with an identifier. The average activity concentrations of 226 Ra, 232 Th, 238 U and 4° K were 49.26 ± 1.58, 44.29 ± 0.74, 16.57 ± 0.40 and 599.64 ± 7.33 Bqkg-1 respectively. The mean absorbed dose rate was 50.44 ± 1.48 nGhr-1 which is below the world average dose rate of 60 nGhr-1 • Radium equivalent values for the area studied ranged from 83 .83 ± 2.33 to 186.12 ± 3.52 Bqkg-1 with mean of 117.22 ± 2.30 Bqkg-1 which is below the world average of 370 Bqkg-1 • The mean external and internal hazard indices were both below unity. Therefore, though the results in the study indicated higher levels of natural radionuclides in soils of Karamoja region than the world average values, the mining activities pose no significant radiological hazard to the population and the soils from these areas can be safely used for construction purposes. The observed unprofessional practices such as lack of use of gas masks while working in the dust-filled mine caves could expose workers to possible risks from inhalation of respirable crystalline silica and radon gas; therefore miners must be educated and sensitized on the effects of exposure to radiation by the Atomic Energy Council of Uganda. These can be done by introducing Safety and Health awareness days. People of Nabulatuk and Acerer in Nakapiripirit district where concentrations of radionuclides are twice the world average levels must be advised to reduce on the time they spend in mines.
Intensity of secondary scattered x-rays during x-ray diagnostic procedures in selected diagnostic centres in Uganda
(Kyambogo University[unpublished work], 2014-01) Byaruhanga, Bonaventure
The purpose of the study was to investigate the intensity of secondary scattered X-rays when different body regions; the chest, the abdomen and the lower limbs were exposed to X-rays during radiography. The study used experimental design where the secondary scattered X-ray dose from three diagnostic centres in South Western Uganda were measured us.ing TLDs that were worn at the back of the radiographer. The cards were then read monthly and the process repeated for a period of six months. The number of patients exposed to X-rays for each procedure for the same period was also noted. From the study, it was found that the limb exposures constituted the highest proportion of the patients X-rayed (42%), followed by the chest· (35%) and finally the abdomen (23%). In addition, it was found that the chest exposures generally lead to the highest intensity of secondary scattered X-rays to the radiographers which was 2,670 mSv, 2,756 mSv and 2,505 mSv for Mutolere Hospital, Goodwill Imaging Centre and Mbarara Diagnostic Centre respectively. The limbs contributed the second highest intensity of secondary scattered X-rays (2,442 mSv) at Mutolere Hospital, though generally the abdomen contributed the second highest secondary scattered X-rays (1,712 and 1,294 mSv for Goodwill and Mbarara Diagnostic Centre respectively). The limbs contributed the lowest intensity of secondary scattered X-rays in Goodwill and Mbarara Diagnostic Centre i.e 1,578 and 1,236 mSv respectively. In relation to the safety standards set by the International Atomic Energy Agency ( IAEA, 2002), the predicted cumulative annual dose to radiographers from Mutolere Hospital, Goodwill Imaging Centre and Mbarara Diagnostic Centre are 13,704, 11,964 and 10,692 mSv respectively. These values are below the annual dose limit of 20 mSv for radiation worker as recommended by IAEA (IAEA, 2002). This means that the radiographers from the three diagnostic centres are at a low risk of developing stochastic health effects. However, the annual dose from the diagnostic centres could be dangerous if radiographers are exposed over many years in a lifetime.
Comparison of roki and sunflower oils as sensible heat storage materials for cooking applications
(Kyambogo University [unpublished work], 2022-07) Frank, Mndeme Sayuni
Sensible heat storage materials are cheaper than latent heat storage materials for small storage volumes. Static experiments to evaluate the thermal performances of two Ugandan locally available edible vegetable cooking oils for medium temperature thermal energy storage are presented. The two vegetable oils evaluated and compared are Sunflower oil and Roki oil (a blend of Palm oil and Sunflower oil). Temperature profiles are used to assess the thermal performances during heating cycles, cool-down cycles, energy, exergy, and heat utilization. The results show that Roki oil attains a higher maximum temperature (~ 170 ℃) compared to the Sunflower oil (~ 160 ℃) during low-temperature heating cycles. Roki oil shows higher temperatures during cooling compared to Sunflower oil, achieving a final temperature (~ 78 ℃) slightly higher than that of Sunflower oil (~ 76 ℃). Roki oil shows a maximum energy rate of 413 W compared to Sunflower oil showing a maximum energy rate of 387 W, this is possibly due to the low thermal mass (mc) of Roki oil compared to Sunflower oil. Roki oil also shows higher maximum exergy rate of ~ 129 W compared to that of Sunflower oil ~ 120 W. This occurs because of the lower thermal mass (mc) of the Roki oil which leads to a quick rise of temperature. The exergy factor of Roki oil (0.31 – 0.62) is slightly higher than Sunflower oil (0.27 – 0.59) within 1 hour and 40 minutes. This is possibly due to the higher difference in temperature of Roki oil compared to Sunflower oil. The heat utilization characteristics of the two heat storage materials are experimentally determined in water heating experiments using 1.0 kg to 3.0 kg water loads. Roki oil shows higher average heat utilization (151 – 350) kJ, and higher average heat utilization efficiency values (0.25 – 0.66) as compared to Sunflower oil (148 – 300) kJ and (0.25 – 0.60), respectively. The average heat utilization and average heat utilization efficiency values increase with the increase in the water load for both Sunflower oil and Roki oil. The best overall performance is shown by Roki oil compared to Sunflower oil. Preliminary results with parabolic dish solar cookers are also presented in this work. The results show that Roki oil performs better than Sunflower oil during heating, cooling/heat retention, and heat utilization.
Performance evaluation of amorphous silicon photovoltaic module using solar light of different wavelengths
(Kyambogo University[unpublished work], 2022-07) Seba Ackim, Sichone
The performance of amorphous silicon photovoltaic module was evaluated using solar light of different wavelengths in this study. The different wavelengths of solar light were filtered by use of colour filters. During data collection, the plane of the module was oriented perpendicular to the sun, in order to ensure that module gets the maximum irradiation. The I-V tracer was employed to obtain the module I-V curves, P-V curves and subsequently the I-V outputs of the module. The short circuit current and power output of the module varied at different wavelengths of solar light, but the module’s open circuit voltage was almost constant at different wavelengths. The highest short circuit current of 0.76 A, maximal power of 9.60 W and efficiency of 3.60 % were obtained when the module was not covered with any colour filter. Among all the used colour filters, the yellow colour of solar light gave the highest short circuit current of 0.68 A, maximal power of 8.89 W and efficiency of 3.29 %. This suggests that the yellow light is highly efficient in the amorphous silicon photovoltaic module power generation compared to the other colours of the visible light. The impact of module temperature on the module’s open circuit voltage and short circuit current for different wavelengths of solar light were also investigated. The results showed that the rise in module temperature led to the fall in the open circuit voltage and small increment in short circuit current of the module regardless the wavelength of solar light. Due to the outcomes of this research, it was recommended that more research is needed to be done by filtering solar light into single wavelengths rather than the band of wavelengths. The colors of visible light which were not considered in this study, have to be considered for future work. Manufacturers may use the findings of this study to modify the technological design of the module so as efficiently capture the wavelengths of solar light within the yellow portion of the visible spectrum.

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