RP-Department of Physics

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2D-Euler Deconvolution and Forward Modeling of Gravity Data of Homa-Hills Geothermal Prospect, Kenya
(2014-02-25) Ambusso, W.; Odek, A.B.; Odek, A.; Githiri, J.G.
In order to fully assess the potential of Homa Hills Geothermal prospect, the heat source which is one of the main features of a geothermal system had to be located based on its perturbation on the gravity field. Ground gravity survey was conducted in an area covering about 76 km2 and the data processed to remove all other effects which are not of geological interest. Qualitative interpretation was attempted and cross sections drawn across the anomalous areas on the complete Bouguer anomaly map. Quantitative interpretation attempted involved both Euler Deconvolution and 2‐D Forward modelling. The parameters obtained from Euler Deconvolution were used as the start up parameters for 2‐D Forward modeling. Well clustered Euler solutions were obtained at a shallow depth of approximately 200‐750 m which is consistent with the modeled shallow dike like intrusive probably of carbonatite origin.
2D-Forward Modeling of Ground Magnetic Data of Homa-Hills Geothermal Prospect Area, Kenya
(SAGE Publications, 2014) Ambusso, W.; Githiri, J.; Abuga, V.; Odek, A.; Adero, B.
Two dimensional (2D) Euler de-convolution techniques was applied on the selected profiles of reduced ground magnetic data collected in Homa Hills area. Depth estimates of causative bodies were quantitatively analysed in the an omalous areas on the residual magnetic intensity map. These depth estimates were later used as start up parameters for 2D-forward modelling using “mag2DC” software. Results of the analyses show that the magnetic anomalies in the region are caused by shallow-seated thermal intrusive structures of carbonatite origin. 2D-Euler solutions revealed subsurface faulting activities up to a depth of 250m and the presence of fluid-filled zones within the survey area which are marked by absence of magnetic sources. It is postulated from 2D-forward modelling that the heat sources are shallow intrusive bodies such as dykes, plugs and sills taping from a deeper magmatic body and that the thermal intrusive structures form along fracture zones
Advancements in Energy Storage Technologies: A Review across Canada, USA, and Africa
(GJETA, 2024-01) Chidolue, Onyinyechukwu; Ngozichukwu, Bright; Ibekwe, Kenneth Ifeanyi; Ibekwe, Kenneth Ifeanyi; Fafure, Adetomilola Victoria; Daudu, Cosmas Dominic; Illojianya, Valentine Ikenna
This research explores recent advancements in energy storage technologies across Canada, the United States, and Africa, assessing their economic and environmental impacts. In Canada, the focus is on optimizing renewable integration and grid resilience. The United States witnesses growth in utility-scale projects, influencing grid reliability and fostering economic development. In Africa, off-grid and decentralized solutions address energy access challenges. The financial implications include job creation, industry growth, and cost savings, while environmental benefits range from reduced emissions to improved air quality. Future trends highlight technological advancements, integration with electric vehicles, and regulatory support. Collaborative efforts are essential for navigating these trends and unlocking the potential of energy storage in shaping a sustainable energy future.
Advances in Silicon–Carbon Composites Anodes Derived From Agro Wastes for Applications in Lithium-Ion Battery: A Review
(Heliyon, 2024-05) Adetomilola, Victoria Fafure; Bem, Daniel Barasa; Kahuthu, Stanley Wambugu; Adediran, Adeolu Adesoji; Bodunrin, Michael Oluwatosin; Abosede, Adefunke Fabuyide; Ajanaku, Christianah
Recently, the growing demand for high-performing batteries and different environmental challenges (such include global warming and climate change) have increased the requirement and demand for Lithium-ion batteries (LIBs) used in advanced technologies (i.e., electric cars and many others). To meet this increasing demand, there is an urgent need for more advanced technologies and materials. In the pursuit of developing anode materials, silicon has emerged as the utmost favourable choice for the next generation of LIBs, aiming to substitute the commonly used graphite. Carbon is commonly used to render silicon (Si) suitable for use since Si cannot be used directly as the electrode in LIBs. One of the recently discovered techniques in the development of high-performance LIBs is the use of inexpensive, sustainable, renewable, and ecofriendly materials. Agro-waste-derived silicon and carbon are often used as long as they don’t negatively affect the LIB anode’s performance. This review paper presents the advances in the development of silicon-carbon (Si/C) composite anodes sourced from agro-waste for applications in LIBs. It provides an overview of agro-waste-derived silicon-based anode materials and techniques for extracting silica from agricultural wastes. Next, the outline explains the preparation technique of Si/C composites obtained from agricultural residues for use in LIBs. Additionally, the paper delves into recent research challenges and the potential prospects of materials derived from agro-waste in the advancement of sophisticated LIBs battery materials.
An algorithm for simulation of a Chemical Transport Equation in an Aquifer
(2012) Ambusso, W.; Okiambe, E.; Mogwasi, R.
Dynamical systems can be predicted using mathematical models. These models are usually Partial Different Equations (PDEs). Examples include the wave equation, equations for diffusive processes, and the heat conduction equation. Numerical solution of such PDEs describing a given system and its implementation using a suitable computer code can lead to numerous predictions on the dynamical system both in space and time. In this paper, the contaminant / chemical equation and the groundwater flow equation are solved numerically using the Integrated Finite Difference Method (IFDM) and the algorithms generated are simulated using an object oriented code. Generic results generated represent important predications on the fate and transport processes of a chemical in an aquifer
Analysis of Internal Exposure Associated with Consumption of Crops and Groundwater from the High Background Radiation Area of Mrima Hill, Kenya
(Oxford University Press, 2014-09) Chege, M.; Hashim, N.; Merenga, A.; Tschiersch, J
Specific concentrations of (226)Ra, (232)Th and (40)K were measured in cassava tubers, cassava leaves and groundwater obtained from the high background radiation area of Mrima hill and used in the evaluation of the ingested dose. Cassava tubers, cassava leaves and groundwater registered average (226)Ra concentrations of 60 ± 5, 141 ± 11 and 4.3 ± 0.3 Bq kg(-1), respectively. (232)Th was not detected in cassava leaves although it was present in cassava tubers as well as in groundwater in average concentrations of 35.3±61.5 and 2.0±0.1 Bq kg(-1), respectively. (40)K was present in all samples in average concentrations of 842±539 Bq kg(-1) in cassava tubers, 1708 ± 552 Bq kg(-1) in cassava leaves and 91.4 Bq kg(-1) in groundwater. The total annual effective dose due to ingestion was found to be 7.9 mSv y(-1) of which 2.4 mSv y(-1) was due to cassava tubers, 3.8 mSv y(-1) due to cassava leaves and 1.7 mSv y(-1) due to water.
Analysis of Soil for Trace Elements along Two Highways of Kenya
(Faculty of Science Kenyatta University, 1998) Hashim, N.O.; Kinyua, A. M.; Mangala, M. J.; Rathore, I. V. S.
Energy dispersive X-ray fluorescence technique has been used to study the levels of lead and other toxic trace elements in the soil samples collected along two major highways (Mombasa and Thika) of Kenya at the various distances off the road. The soil samples from Thika road are found to have higher concentration values of the trace elements: Cr, Zr; Mn, Fe, Y; Ni, Cu, Zn, Br and Sr than those from Mombasa road. The samples from Thika and Mombasa roads have maximum concentrations of Lead, 56 ug/g and 90 ug/g respectively at the distance of 100m off the roads, which is below the admissible value of 250 Ug/g for agricultural practices.
Assessment of Levels of Natural Radioactivity in Sand Samples Collected from Ekalakala in Machakos County, Kenya
(Hindawi, 2020) Munyao, Lucia Nyiva; Ketui, Daniel Kipngetich; Otieno, Calford; Chege, Margaret Wairimu
Construction sand is naturally polluted with radionuclides of terrestrial origin. In this study, specific activities of 238U, 232+, and 40K in 30 sand samples collected along the Ekalakala River, Machakos County, Kenya, were measured using a high-purity germanium c-ray spectrometer. +e specific activities ranged between 9.7 Bqkg−1 and 24.0 Bqkg−1, 11.5 Bqkg−1 and 26.2 Bqkg−1, and 820 Bqkg−1 and 1850 Bqkg−1 for 238U, 232+, and 40K, respectively. While the mean specific activities for 238U and 232+were less than half of the world average values of 33 Bqkg−1 and 45 Bqkg−1, respectively, the average specific activity of 40K was significant since it was three times the global mean value of 420 Bqkg−1. A calculated absorbed radiation dose rate for the sand varied between 46.8 nGyh−1 and 94.2 nGyh−1 with a mean of 68.5 ± 13.3 nGyh−1. +is is not significantly different from the world average dose rate of 60 nGyh−1 for geological samples. +e AEDR and Hex had maximum values of 0.29 mSvy−1 and 0.52, respectively, both within the recommended limits of radiation exposure for members of the general public. Based on these results, the sand from Ekalakala River does not pose significant health implication to the sand harvesters as well as the inhabitants of the houses constructed using this sand.
Assessment of Radioactivity Concentration for Building Materials Used in Babadogo Estate, Nairobi City County, Kenya
(Oxford, 2023-12) Oborah, Kenneth A.; Hashim, Nadir O.; Migwi, Charles M.; Rotich, Charles
Assessment of Radioactivity Levels and Risks Due to Different Rock Types from the KERIO Valley “High Background Radiation Area (HBRA)” of Kenya
(IJMPSR, 2015) Agora, Jared Omari; Hashim, Nadir Omar
The goal of this study was to analyse the natural radioactivity levels and assess the contribution of different rock types to environmental dose in the Kerio Valley region of Kenya, a suspect high background radiation area (HBRA). The activity concentrations of 238U, 232Th and 40K in granite, sandstone, tuff, limestone, quartzite, gneiss, marble and conglomerate rocks were found to vary from 72.70 8.47 Bqkg-1-116.15 11.46 Bqkg-1, 40.32 14.48 Bqkg-1- 83.65 9.91 Bqkg-1 and 427.41 48.23 Bqkg-1-1397.24 65.27 Bqkg-1 respectively. Radium equivalent activity and external hazard index show that all the rock types do not exceed the recommended limit of 370 Bqkg-1 and 1, respectively. Calculated outdoor absorbed dose rate ranged from 90.585 nGyh-1 (limestone) to 159.085 nG/h (quartzite) while the indoor absorbed dose rate ranged from 66.696 nGyh-1(limestone) to 157.442 nGyh-1 (quartzite), which are above the world average value of 60nGy-1. The annual effective dose rate analysis is also presented.
Auger electron spectroscopy study and depth profile analyses of the CaS:Eu2+ pulsed laser deposited thin luminescent films
(Springer Science+Business Media, 2016) Nyenge, R.L.; Swart, H.C.; Ntwaeaborwa, O.M.
This paper presents the results of a study of the chemical composition, depth profile analyses of pulsed laser deposited CaS:Eu2? thin films grown at different substrate temperatures. Using Auger electron spectroscopy, we have shown that the thin film grown in an argon atmosphere shows sulfur deficiency as the substrate temperature is increased from 200 to 650 C.
Calculation of Cross Sections for Elastic Scattering of Electrons at Intermediate Energies by a Magnesium Atom
(The African Review of Physics, 2014) Kariuki, P. K.; Okumu, J.; Singh, C. S.
We have obtained differential and integral cross sections for elastic scattering of electrons by magnesium atom at 10 – 100 eV using a complex, local, energy-dependent, spherically-symmetric optical potential incorporating a modified semiclassical exchange potential. The results have been compared with available theoretical and experimental results. The present results are in good agreement with recent experimental results at electron impact energies E ³ 40 eV and are in qualitative agreement at lower energies. The results indicate the reliability of the modified exchange potential at higher energies in the intermediate energy range.
Calculation of linear and non-linear optical properties of amorphous Silicon
(Faculty of Science Kenyatta University, 2001) Okumu, J.; Morgan, G.J.
We have used the random phase model for the electronic wave functions to calculate the imaginary part of the dielectric function 82 (m) and the magnitude of the third harmonic generation, 11'3(OJ ~ using a model structure of a-Si containing 1728 atoms. We show that this simple calculation gives reasonable results for e(e) and furthermore the behaviour of .l. «(l). is similar to more detailed theoretical calculations
Cancer and Non-Cancer Health Risks from Carcinogenic Heavy Metal Exposures in Underground Water from Kilimambogo, Kenya
(Elsevier, 2020) Nyambura, Catherine; Hashim, Nadir Omar; Chege, Margaret Wairimu; Tokonami, Shinji; Omonya, Felix Wanjala
Water is very crucial for man, animals and plants because of its health implications in case it is polluted. Water has many uses like drinking for man and animals, domestic use and for agricultural use. The concentration levels of Cd, Ni and Pb in borehole water of Kilimambogo region were measured using the atomic absorption spectrometer (AAS). pH was measured on site using a digital pH standard meter. The use of fertilizers and chemicals from the neighboring small scale farms and the large pineapple farms could easily contaminate the water table. The mean heavy metal concentration for Cd, Ni and Pb were found to be 6.4, 6.9 and 42.0 ppm respectively. The mean hazard quotients (HQ) were 26.2, 1.4 and 57.0.for adults and 12.9, 0.69 and 27.9 for children for the corresponding elements. The mean carcinogenic risks for Cd, Ni and Pb were 4.9 × 10−2, 1.2 × 10−2 and 7.3 × 10−3 for adults and 1.1 × 10−2, 2.8 × 10−2 and 1.6 × 10−3 for children respectively. The mean metal pollution index (MPI) and heavy metal evaluation index (HEI) were 10 and 934, higher than the set critical threshold value of 100. Therefore, the borehole sources are enriched with heavy metals and should be periodically monitored.
Characterization of Aluminum Doped Zinc Oxide (Azo) Thin Films Prepared by Reactive Thermal Evaporation for Solar Cell Applications
(OMICS International, 2015) Mugwang’a, F. K.; Karimi, P. K.; Njoroge, W. K.; Omayio, O.
Aluminium doped Zinc Oxide (AZO) thin films have been deposited using reactive thermal evaporation technique using an Edward Auto 306 Magnetron Sputtering System. Transmittance and reflectance data in the range 300 nm-2500 nm were obtained using UV-VIS NIR Spectrophotometer Solid State 3700 DUV for all the thin films samples that were prepared. Transmittance values of above 70% were observed. The optical measurements were simulated using SCOUT 98 software to determine optical constants and optical bad gap of the thin film. The optical properties in these films were varied by varying Aluminums doping percentages. It was observed that the transmission over the visible range decreased as the concentration of Aluminum increased. This is due to free carriers coupling to the electric field hence increasing the reflection. Optical band gap for various samples of Aluminum doped thin films show a direct allowed transition and a shift in the optical absorption edge as the Aluminums concentration increased. These results show values of band gap ranging between 3.2 eV and 3.5 eV. Between 0% - 3% the optical band gap reduces. This is followed with widening of the band gap for doping between 4%- 6%. Urbach energy gradually increased with increasing band gap. The band gap reduced due to formation of localized states near the conduction band corresponding to increase in Urbach energy
Characterization of SnSe-CdO: Sn PN Junction for Solar Cell Applications
(Scientific and Academic Printing (SAP), 2015) Makori, N. E.; Njoroge, W. K.; Amatalo, A.; Karimi, P. M.
Solar energy has a great potential of meeting a large fraction of energy needs using photovoltaics. While most photovoltaic cells in use today are Silicon-based, cells of other semiconductor materials have been manufactured. Considerable research has been focused in search of thin-film photovoltaic cells with high conversion efficiency. In our early studies, we reported optimization of Tin Selenide (SnSe) and Tin doped Cadmium Oxide (CdO:Sn) thin films for solar cell applications. SnSe and CdO:Sn thin films were successfully deposited by thermal and reactive thermal evaporation respectively using Edward’s Auto 306 Magnetron Sputtering System. Their optical and electrical properties were studied using Solid Spec-3700 DUV Spectrophotometer and Four-Point-Probe respectively. Transmittance of SnSe thin films deposited had transmittance ranging 0.01% to 45% while the band gap values obtained were in the range of 1.71eV to 1.76eV. SnSe thin films showed decrease of resistivity from 181Ωcm to120Ωcm with increase in film thickness from 112nm to 148nm. The optical properties of CdO:Sn showed high transparency in the visible region which varied with Sn doping. CdO and CdO:Sn had a transmittance of 70% to 85% and 50% to 89% respectively within the visible range of the electromagnetic spectrum. Band gap energy for undoped CdO was 2.43eV while that of tin doped CdO was in the range of 3.19eV to 3.29eV for tin doping of 1% to 7%. Resistivity of CdO was 42Ωcm while that of tin doped CdO ranged between 16Ωcm to 93Ωcm. In this study, the optimized thin films were used to fabricate SnSe-CdO:Sn P-N junction. SnSe of film thickness 148nm and 3% Sn doped CdO were used in the fabrication of the junction whose parameters are; Isc = 0.993mA, Voc = 273mV, Imax = 0.905mA, Vmax = 207mV, FF = 0.69 and η = 0.59%.
Charge Transport Mechanism in Thin Cuticles Holding Nandi Flame Seeds
(International Journal of Biomaterials, 2009) Rathore, I. V. S.; Kipnusu, Wycliffe K; Katana, Gabriel; Migwi, C. M.; Sangoro, Joshua R
Metal-sample-metal sandwich configuration has been used to investigate DC conductivity in 4 mum thick Nandi flame [Spathodea campanulata P. Beauv.] seed cuticles. J-V characteristics showed ohmic conduction at low fields and space charge limited current at high fields. Charge mobility in ohmic region was 4.06 x 10(-5) (m(2)V(-1)s(-1)). Temperature-dependent conductivity measurements have been carried out in the temperature range 320 K < T > 450 K. Activation energy within a temperature of 320 K-440 K was about 0.86 eV. Variable range hopping (VRH) is the main current transport mechanism at the range of 330-440 K. The VRH mechanism was analyzed based on Mott theory and the Mott parameters: density of localized states near the Fermi-level N(E(F)) approximately 9.04 x 10(19) (eV(-1)cm(-3)) and hopping distance R approximately 1.44 x 10(-7) cm, while the hopping energy (W) was in the range of 0.72 eV-0.98 eV.
Consumers satisfaction in the energy sector in Kenya
(Energy Policy, 2012-09) Ngui, D.; Mutua, J.; Osiolo, H.; Aligula, E.; Gachanja, J.
This paper analyzes consumer satisfaction in the energy sector in Kenya to assess the quality and level of service delivery. By use of the European Consumer Satisfaction Index (ECSI), the paper estimates consumer satisfaction in biomass, petroleum, electricity and renewable energy subsectors. The findings are that consumer satisfaction is highest in the renewable energy sub sector at 74.7% followed by petroleum at 62.8%. The electricity sub sector has the lowest consumer satisfaction of 53.06%. Further, it is found that the image of renewable energy providers is also the highest at 72.5% followed by that of petroleum companies at 63.1%. In the electricity sub sector, perceived value scored the highest at 64.2%. The paper concludes that image of a service provider, loyalty of consumers, consumer expectations, perceived value, perceived quality and the way complains are handled are very important factors that determine consumer satisfaction levels. It is recommended that for monitoring and evaluation purposes in the performance of the energy sector, the Energy RegulatoryCommission(ERC) could use the consumer satisfaction index level to evaluate whether the regulatory policies and their implementation are bearing fruit where a high index would be associated with good performance and vice versa. Keywords Energy sector; Energy sources; Consumer satisfaction
Control Systems in Renewable Energy: A Review of Applications in Canada, USA, and Africa
(WJAETS, 2024-01) Chidolue, Onyinyechukwu; Daudu, Cosmas Dominic; Illojianya, Valentine Ikenna; Fafure, Adetomilola Victoria; Ibekwe, Kenneth Ifeanyi; Ngozichukwu, Bright
This research explores the applications of control systems in renewable energy across Canada, the United States, and Africa. It underscores their pivotal role in optimizing efficiency and reliability by examining supervisory, predictive, and adaptive control strategies. The literature review delves into global and regional renewable energy landscapes, emphasizing unique challenges and opportunities. Technological innovations, including advanced monitoring, artificial intelligence, and blockchain, are investigated, highlighting their transformative impact. The paper anticipates prospects such as quantum computing, decentralized systems, and heightened cybersecurity measures. The findings contribute to understanding the nuanced interplay between control systems and renewable energy, offering insights for policymakers, researchers, and industry stakeholders as they navigate the evolving landscape of sustainable energy solutions.
Creep and Recovery Behavior of Compression Molded Low Density Polyethylene/Cellulose Composites
(Hindawi Publishing Corporation, 2013) Riara, Martin Munene; Merenga, Abdullah S.; Migwi, C. M.
Low density polyethylene (LDPE) is an important industrial material because it is durable, light-weight, easily processed and characteristically inert, but its everyday use is hazardous to the environment. The solution to this seems to consist of incorporation of biopolymers in the structure of LDPE to form composites. Compression molded composites at different cellulose loading were subjected to creep tests at 30, 40, 50, and 60°C. The samples were displaced for 12 minutes and allowed to recover for 12 minutes. Creep behavior of the polymer composites was governed by temperature, time, and cellulose loading. Creep performance decreased with increase in temperature and improved with cellulose loading while creep modulus decreased with increase in time and temperature. Time temperature superposition was used to predict the long time (up to 106 s) creep behavior of the samples. William-Landel-Ferry (WLF) model offered a better description of the shift factors based on the short term data that was used to predict the long time behavior of the polymer composites by shifting the curves along the logarithmic time axis. The deformation was dependent on free volume.

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